Download - Electronic Diesel Control EDC 2001

ISBN-3-934584-47-0 The Bosch Yellow Jackets Edition 2001 Technical Instruction Diesel-Engine ManagementOrder Number 1 987 722 135 AA/PDI-08.01-En

2001

The Program Order Number ISBN

Automotive electrics/Automotive electronicsBatteries 1 987 722 153 3-934584-21-7Alternators 1 987 722 156 3-934584-22-5Starting Systems 1 987 722 170 3-934584-23-3Lighting Technology 1 987 722 176 3-934584-24-1Electrical Symbols and Circuit Diagrams 1 987 722 169 3-934584-20-9Safety, Comfort and Convenience Systems 1 987 722 150 3-934584-25-X

Diesel-Engine ManagementDiesel Fuel-Injection: an Overview 1 987 722 104 3-934584-35-7Electronic Diesel Control EDC 1 987 722 135 3-934584-47-0Diesel Accumulator Fuel-Injection System Common Rail CR 1 987 722 175 3-934584-40-3Diesel Fuel-Injection Systems Unit Injector System/Unit Pump System 1 987 722 179 3-934584-41-1Radial-Piston Distributor Fuel-Injection Pumps Type VR 1 987 722 174 3-934584-39-XDiesel Distributor-Type Fuel-Injection Pumps VE 1 987 722 164 3-934584-38-1Diesel In-Line Fuel-Injection Pumps PE 1 987 722 162 3-934584-36-5Governors for Diesel In-Line Fuel-Injection Pumps 1 987 722 163 3-934584-37-3

Gasoline-Engine ManagementEmission Control (for Gasoline Engines) 1 987 722 102 3-934584-26-8Gasoline Fuel-Injection System K-Jetronic 1 987 722 159 3-934584-27-6Gasoline Fuel-Injection System KE-Jetronic 1 987 722 101 3-934584-28-4Gasoline Fuel-Injection System L-Jetronic 1 987 722 160 3-934584-29-2Gasoline Fuel-Injection System Mono-Jetronic 1 987 722 105 3-934584-30-6Spark Plugs 1 987 722 155 3-934584-32-2Ignition 1 987 722 154 3-934584-31-4M-Motronic Engine Management 1 987 722 161 3-934584-33-0ME-Motronic Engine Management 1 987 722 178 3-934584-34-9Gasoline-Engine Management: Basics and Components 1 987 722 136 3-934584-48-9

Driving and Road-Safety SystemsConventional Braking Systems 1 987 722 157 3-934584-42-XBrake Systems for Passenger Cars 1 987 722 103 3-934584-43-8ESP Electronic Stability Program 1 987 722 177 3-934584-44-6Compressed-Air Systems for Commercial Vehicles (1): Systems and Schematic Diagrams 1 987 722 165 3-934584-45-4Compressed-Air Systems for Commercial Vehicles (2): Equipment 1 987 722 166 3-934584-46-2

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ElectronicDiesel Control EDC

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• Lambda closed-loop control for passenger-car diesel engines• Functional description• Triggering signals

Published by:© Robert Bosch GmbH, 2001Postfach 30 02 20,D-70442 Stuttgart.Automotive Aftermarket Business Sector,Department AA/PDI2.Product-marketing, software products,technical publications.

Editor-in-Chief:Dipl.-Ing. (FH) Horst Bauer.

Editors:Dipl.-Ing. (BA) Jürgen Crepin,Dipl.-Ing. Karl-Heinz Dietsche.

Authors:Dipl.-Ing. Joachim Berger (Sensors),Dipl.-Ing. Johannes Feger (VE-EDC),Dipl.-Ing. Lutz-Martin Fink (Open and closed-loop control),Dipl.-Ing. Wolfram Gerwing(Lambda closed-loop control),Dipl.-Ing. Martin Grosser (Common Rail System),Dipl.-Inform. Michael Heinzelmann (UIS, UPS),Dipl.-Math. techn. Bernd Illg (Diagnosis, open and closed-loop control),Dipl.-Ing. (FH) Joachim Kurz (VP30, VP44),Dipl.-Ing. Felix Landhäußer (In-line injection pumps)Dipl.-Ing. Rainer Mayer (Torque-controlled EDC systems),Dr. rer. nat. Dietmar Ottenbacher (VP30, VP44),Dipl.-Ing. Werner Pape (Actuators),Dr. Ing. Michael Walther (Data transfer),Dipl.-Ing. (FH) Andreas Werner (Common Rail System),in cooperation with the responsible technical departments of Robert Bosch GmbH.

Translation:Peter Girling.

Unless otherwise stated, the above are all em-ployees of Robert Bosch GmbH, Stuttgart.

Reproduction, duplication, and translation of thispublication, including excerpts therefrom, is onlyto ensue with our previous written consent andwith particulars of source. Illustrations, descriptions, schematic diagrams,and other data only serve for explanatory pur-poses, and for presentation of the text. Theycannot be used as the basis for design, installa-tion, and scope of delivery. We undertake no lia-bility for conformity of the contents with nationalor local regulations. Robert Bosch GmbH is exempt from liability,and reserves the right to make changes at anytime.

Printed in Germany.Imprimé en Allemagne.

1st Edition, February 2001.English translation of the German edition dated: August 2001.(1.0)

Imprint

Robert Bosch GmbH

ElectronicDiesel Control EDC

Bosch

Robert Bosch GmbH

4 Diesel fuel-injection systems: An overview

4 Technical requirements6 Designs

12 Electronic diesel control EDC12 Technical requirements,

system overview13 System blocks14 In-line injection pumps15 Port-and-helix-controlled axial-pis-

ton distributor pumps16 Solenoid-valve-controlled axial-pis-

ton and radial-piston distributorpumps

17 Common Rail System (CRS)18 Unit Injector System (UIS) for pas-

senger cars19 Unit Injector System (UIS) and

Unit Pump System (UPS) for com-mercial vehicles

20 Sensors21 Temperature sensors22 Micromechanical pressure sensors25 Rail-pressure sensors26 Inductive engine-speed (rpm)

sensors27 Rotational-speed (rpm) sensors

and incremental angle-of-rotationsensors

28 Hall-effect phase sensors30 Half-differential short-circuiting-ring

sensors31 Nozzle holders with needle-motion

sensor32 Accelerator-pedal sensors34 Hot-film air-mass meter HFM536 Planar broad-band Lambda oxygen

sensors

38 Electronic Control Unit (ECU)38 Operating conditions, design and

construction, data processing

44 Open and closed-loop electroniccontrol

44 Open and closed-loop electroniccontrol, data processing (DP)

46 Data exchange with other systems48 Diesel-injection control57 Lambda closed-loop control for

passenger-car diesel engines63 Further special adaptations63 Port-and-helix-controlled injection

systems: Triggering66 Solenoid-valve-controlled injection

systems: Triggering73 Control and triggering of the re-

maining actuators74 Substitute functions75 Torque-controlled EDC systems

78 Electronic diagnosis78 Operating concept81 On-Board Diagnostics (OBD)

82 Data transfer between electronicsystems

82 System overview, serial data trans-fer (CAN)

87 Prospects

88 Actuators88 Electropneumatic transducers89 Continuous-operation braking sys-

tems, engine-fan control90 Start-assist systems

92 Index of technical terms92 Technical terms94 Abbreviations

Contents

Robert Bosch GmbH

Electronics is coming more and more to the forefront in the control and management

of the diesel engine, whereby the question is often raised “Is it really necessary to fill

the vehicle with so much electronics ?”

The point is though, without electronics it would be impossible to detect a large

number of important variables, such as engine speed, quickly enough for them to be

used for engine management. Electronic control is behind the modern diesel engine

having become more powerful, more efficient, quieter, cleaner, and more economical.

These facts hold true irrespective of the engine’s operating range or mode.

Electronic Diesel Control, EDC, permits the implementation of such auxiliary func-

tions as smooth-running control (SRC).

EDC is applied for all modern diesel injection systems:

In-line injection pumps, PE,

Distributor injection pumps, VE, VR,

Unit Injector System, UIS,

Unit Pump System, UPS,

Common Rail System, CRS.

Although these injection systems differ in many respects, and are installed in a wide

variety of different vehicles, they are all equipped with a similar form of EDC.

This “Technical Instruction” manual describes the Electronic Diesel Control and all

its components. The differences between the individual injection systems are shown in

tabular form (Pages 12 through 17). The manual thus provides the reader with a com-

prehensive overview of the various diesel fuel-injection systems from the point of view

of their open and closed-loop electronic control.

Robert Bosch GmbH

Diesel engines are characterized by theirhigh levels of economic efficiency. Since thefirst series-production injection pumpswere introduced by Bosch in 1927, injec-tion-system developments have continuedunceasingly.

Diesel engines are employed in a wide rangeof different versions (Figure 1 and Table 1),for example as:

The drive for mobile electric generators (up to approx. 10 kW/cylinder),

High-speed engines for passenger carsand light commercial vehicles (up to approx. 50 kW/cylinder),

Engines for construction, agricultural,and forestry machinery (up to approx. 50 kW/cylinder),

Engines for heavy trucks, buses, and trac-tors (up to approx. 80 kW/cylinder),

Stationary engines, for instance as used inemergency generating sets (up to approx. 160 kW/cylinder),

Engines for locomotives and ships (up to 1,000 kW/cylinder).

Technical requirements In line with the severe regulations coming intoforce to govern exhaust and noise emissions,and the demand for lower fuel consumption,increasingly stringent demands are beingmade on the diesel engine's injection system.

Basically speaking, depending on the partic-ular diesel combustion process (direct or in-direct injection), in order to ensure efficientA/F mixture formation the injection systemmust inject the fuel into the diesel engine’scombustion chamber at a very high pressure(today, this is between 350 and 2,050 bar),and the injected fuel quantity must be me-tered with extreme accuracy. With the dieselengine, load and speed control must takeplace using the injected fuel quantity with-out intake-air throttling.

For diesel injection systems, the mechanical(flyweight) governor is increasingly beingsuperseded by the Electronic Diesel Control(EDC). In the passenger-car and commer-cial-vehicle sector, the new diesel fuel-injec-tion systems are all EDC-controlled.

4 Diesel fuel-injection systems: An overview Technical requirements

Diesel fuel-injection systems: An overview

Figure 1M, MW, A, P, H, ZWM, CW In-line injection

pumps in order ofincreasing size;

PF Single-plunger in-jection pumps

VE Axial-piston distributor injectionpumps

VR Radial-piston dis-tributor injectionpumps

UPS Unit Pump SystemUIS Unit Injector

SystemCR Common Rail

System

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UPS

CR

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MW MW MW MW CW

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Bosch diesel fuel-injection systems. Areas of application1æ

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Diesel fuel-injection systems: An overview Technical requirements 5

Table 11 Stationary engines,

building and con-struction machines,agricultural andforestry machines

2 With two ECUs,larger numbers ofcylinders are possi-ble

2a As from EDC16: 6cylinders

3 1st generation4 Pilot injection (PI) up

to 90° cks beforeTDC; post injection(POI) possible

5 Up to 5,500 min–1

during overrun6 2nd generation7 Pilot injection (PI)

possible up to 90°cks before TDC;post injection (POI)up to 210° after TDC

8 Pilot injection (PI) upto 30° cks beforeTDC; post injection(POI) possible

The most important diesel-engine high-pressure fuel-injection systems: Properties and characteristic data1

Fuel-injection system Fuel injectionApplication Engine-related data

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In-line injection pumps

M P 60 550 – m, e IDI 4 ...6 5000 20A O 120 750 – m DI/IDI 2 ...12 2800 27MW P, O 150 1100 – m DI 4 ...8 2600 36P3000 N, O 250 950 – m, e DI 4 ...12 2600 45P7100 N, O 250 1200 – m, e DI 4 ...12 2500 55P8000 N, O 250 1300 – m, e DI 6 ...12 2500 55P8500 N, O 250 1300 – m, e DI 4 ...12 2500 55H1 N 240 1300 – e DI 6 ...8 2400 55H1000 N 250 1350 – e DI 5 ...8 2200 70ZWM S 900 850 – m DI/IDI 6 ...12 1500 150CW S 1500 1000 – m DI/IDI 6 ...10 1600 260

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Axial-piston distributor pumps

VE … F P 70 350 – m IDI 3 ...6 4800 25VE … F P 70 1205 – m DI 4 ...6 4400 25VE … F N, O 125 800 – m DI 4, 6 3800 30VP37 (VE-EDC) P 70 1250 – em DI 3 ...6 4400 25VP37 (VE-EDC) O 125 800 – em DI 4, 6 3800 30VP30 (VE-M) P 70 1400 PI e, MV DI 4 ...6 4500 25VP30 (VE-M) O 125 800 PI e, MV DI 4, 6 2600 30

Radial-piston distributor pumps

VP44 (VR) P 85 1850 PI e, MV DI 4, 6 4500 25VP44 (VR) N 175 1500 – e, MV DI 4, 6 3300 45

Single-plunger injection pumps

PF(R)… O 13... 450 ... – m, em DI/IDI Arbitrary 4000 4 ...120 1150 30

PF(R)… Large diesel P, N, O, S 150 ... 800 ... – m, em DI/IDI Arbitrary 300 ... 75 ...engines 18000 1500 2000 1000UIS P1 P 60 2050 PI e, MV DI 52, 2a 4800 25UIS 30 N 160 1600 – e, MV DI 82 4000 35UIS 31 N 300 1600 – e, MV DI 82 2400 75UIS 32 N 400 1800 – e, MV DI 82 2400 80UPS 12 N 180 1600 – e, MV DI 82 2400 35UPS 20 N 250 1800 – e, MV DI 82 3000 80UPS (PF[R]) S 3000 1600 – e, MV DI 6 ...20 1500 500

Common Rail accumulator injection system

CR3 P 100 1350 – PI, POI4 DI 3 ...8 48005 30CR6 P 100 1600 – PI, POI7 DI 3 ...8 5200 30CR N, S 400 1400 – PI, POI8 DI 6 ...16 2800 200

Robert Bosch GmbH

Injection-pump designsThe diesel engine’s injection system has thetask of injecting the diesel fuel into the en-gine’s cylinders at very high pressure, in thecorrect quantities, and at exactly the rightinstant in time.

Depending upon the particular combustionprocess, the nozzle extends into either themain or the auxilary combustion chamber.It opens at a fuel pressure which is specificto the particular injection system, and closesas soon as the pressure drops again. The ma-jor difference between the various injectionsystems is to be found in the high-pressuregeneration process.

The very high injection pressures involvednecessitate the precision manufacture of allthe injection components from high-tensilematerials. All components must be exactlymatched to each other.

Electronic closed-loop control functions en-able the inclusion of numerous auxiliaryfunctions (for instance, active surge damp-ing, Cruise Control, and boost-pressure con-trol).

In-line injection pumpsPE standard in-line injection pumpsThe standard PE in-line injection pumps(Figure 1) have a plunger-and-barrel assem-bly for each engine cylinder. As the nameimplies, this comprises the pump barrel (1)and the corresponding pump plunger (4).The pump camshaft (7) is integrated in thepump and driven by the engine, and forcesthe pump plunger in the delivery direction(in this case upwards). The plunger is re-turned by its spring (5). The individualplunger-and-barrel assemblies (also knownas pumping elements) are normally arrangedin-line, and plunger lift is invariable.

During the plunger’s upward travel, high-pressure generation starts when the inletport (2) is closed by the plunger's top edge.This instant in time is termed the start ofdelivery. The plunger continues to move be-yond this point and in doing so increases thefuel pressure to such an extent that the noz-zle opens and fuel is injected into the enginecylinder.

A helix has been mechanically machinedinto the plunger, and as soon as it opens theinlet port the fuel pressure collapses, thenozzle needle closes and injection stops.

6 Diesel fuel-injection systems: An overview Designs

Figure 1a PE standard in-line

injection pumpb Control-sleeve in-

line injection pump 1 Pump barrel2 Inlet port3 Helix4 Pump plunger5 Plunger return

spring6 Rotational travel due

to action of controlrack (injected fuelquantity)

7 Camshaft8 Control sleeve9 Adjustment travel

due to actuatingshaft (start of fueldelivery)

10 Flow of fuel to thenozzle

X Effective stroke

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The plunger travel between the closing andopening of the inlet port is termed the effec-tive stroke (X).

The pump is equipped with a control rack(6) which rotates the plunger so that the po-sition of the helix relative to the inlet port ischanged. This changes the plunger’s effectivestroke, and along with it the injected fuelquantity. The control rack is controlled byeither a mechanical (flyweight) governor oran electrical actuator mechanism.

Control-sleeve in-line injection pump The control-sleeve in-line injection pumpdiffers from a conventional in-line injectionpump by having a “control sleeve” (Figure 1,Pos. 8) which slides up and down the pumpplunger. By way of an actuator shaft (Figure1, Pos. 9), this varies the plunger lift to (in-let) port closing, and with it the start of in-jection.

Since the start of injection can be varied in-dependent of engine speed, the control-sleeve version features an additional degreeof freedom compared to the standard PE in-line injection pump.

Distributor injection pumpsThe distributor pump has only one plunger-and-barrel asembly for all the engine’s cylin-ders (Figures 2 and 3). A vane-type supplypump delivers fuel to the high-pressurechamber (6). High-pressure generation isthe responsibility of either an axial piston(Figure 2, Pos. 4) or several radial pistons(Figure 3, Pos. 4). A rotating distributorplunger opens and closes the metering slots(8) and spill ports, and in the process dis-tributes the fuel to the individual enginecylinders via the injection nozzles (7). Theduration of injection (injection time) can bevaried using a control collar (Figure 2, Pos.5) or a high-pressure solenoid valve (Figure3, Pos. 5).

Axial-piston distributor pumpThe drive for the cam plate (Figure 2, Pos. 3)comes from the vehicle’s engine. The num-ber of cams on the underside of the camplate corresponds to the number of enginecylinders. These cams ride on the rollers (2)of the roller ring with the result that a rotat-ing-reciprocating movement is imparted tothe plunger. For one revolution of the drive-shaft, the piston performs as many strokes asthere are engine cylinders.

Diesel fuel-injection systems: An overview Designs 7

Figure 21 Timing-device travel

on the roller ring2 Roller3 Cam plate4 Axial piston5 Control collar6 High-pressure

chamber7 Fuel outlet to the in-

jection nozzle8 Metering slotX Effective stroke

4 5

6

7

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Port-and-helix-controlled axial-piston distributor pump: Principle of functioning2

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On the port-and-helix-controlled VE axial-piston distributor pump with mechanical(flyweight) governor, or electronically con-trolled actuator, the control collar (5) de-fines the effective stroke and with it the in-jected fuel quantity.

The timing device adjusts the pump's startof delivery by rotating the roller ring (1).

Radial-piston distributor pumps Here, instead of the cam plate as used on theaxial-piston distributor pump, a radial-pis-ton pump with cam ring (Figure 3, Pos. 3)and two to four radial pistons (4) is respon-sible for high-pressure generation. Higherpressures can be achieved with the radial-piston pump than with the axial-piston ver-sion, although this necessitates the pumphaving to be much stronger mechanically.

The cam ring is rotated by the timing device(1). On all radial-piston distributor pumps,start of injection and duration of injection(injection time) are solenoid-valve-con-trolled.

Solenoid-valve-controlled distributorpumpsOn the solenoid-valve-controlled distributorpump, an electronically controlled high-pres-sure solenoid valve (5) is used to meter the in-jected fuel quantity and to change the start-of-injection point. With the solenoid valveclosed, pressure can build up in the high-pres-sure chamber (6). Once the valve opens, fuelescapes so that there is no fuel-pressurebuildup and no fuel is injected. The open andclosed-loop control signals are generated ineither one or two ECU’s (pump ECU and en-gine ECU, or only in the pump ECU).

Single-plunger injection pumpsPF single-plunger pumpsPF single-plunger pumps are used principallyfor small engines, diesel locomotives, marineengines, and construction machinery. Single-plunger pumps are also suitable for operationwith viscous heavy oils.

Although these pumps have no camshaft oftheir own (the F in their designation standsfor external drive) their basic operating con-cept corresponds to that of the PE in-linepumps. The cams for actuating the individualPF single-plunger injection pumps are on theengine camshaft. When used with large en-gines, the mechanical-hydraulic governor, or


Figure 31 Timing device on

roller ring2 Roller3 Cam ring4 Radial piston5 High-pressure

solenoid valve6 High-pressure

chamber7 Fuel outlet to the

injection nozzle 8 Metering slot

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Solenoid-valve-controlled radial-piston distributor pump: Principle of functioning3

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the electronic controller, is attached directly tothe engine block. The fuel-quantity adjust-ment as defined by the governor (or con-troller) is transferred by a rack integrated inthe engine. The cams for actuating the indi-vidual PF single-plunger pumps are on theengine camshaft, and this means that injectiontiming cannot be implemented by rotating thecamshaft. When used with large engines, themechanical-hydraulic governor, or the elec-tronic controller, is attached directly to the en-gine block. The fuel-quantity adjustment asdefined by the governor (or controller) istransferred by a rack integrated in the engine.Due to the direct connection to the engine’scamshaft, this cannot be turned to implementinjection timing. Instead, injection timingtakes place by adjusting an intermediate ele-ment, whereby an advance angle of several an-gular degrees can be obtained. Adjustment isalso possible using solenoid valves.

Unit-Injector System (UIS)In the Unit Injector System (UIS), injectionpump and injection nozzle form a single unit(Fig. 4). One of these units is installed in theengine’s cylinder head for each engine cylin-

der, and driven directly by tappet or indirectlyfrom the engine camshaft through a valvelifter. Compared with the in-line and distribu-tor injection pumps, considerably higher in-jection pressures (up to 2050 bar) have be-come possible due to the omission of high-pressure lines. The fuel-injection parametersare calculated by the ECU, and injection iscontrolled by opening and closing the high-pressure solenoid valve.

Unit-Pump System (UPS)The modular Unit Pump System (UPS) usesthe same operating concept as the UIS. Incontrast to the UIS, pump and nozzle holder(2) are joined by a short high-pressure deliv-ery line (3) precisely matched to the respectivecomponents. Separation of high-pressure-generation stage and nozzle holder simplifiesinstallation at the engine. The UPS system fea-tures an injection unit for each cylinder com-prised of pump, delivery line, and nozzleholder. The pump is driven from the engine’scamshaft (6).On the UPS too, injection duration and startof injection are controlled electronically by ahigh-speed high-pressure solenoid valve (4).

Diesel fuel-injection systems: An overview Designs 9

Figure 41 Actuating cam2 Pump plunger3 High-pressure

solenoid valve 4 Injection nozzle

Figure 51 Injection nozzle2 Nozzle holder3 High-pressure line4 High-pressure

solenoid valve5 Pump plunger6 Actuating cam

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High-pressure components of the Unit Injector System (UIS): Principle of functioning

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High-pressure components of the Unit Pump System (UPS): Principle of functioning

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Accumulator injection systemCommon-Rail System CRS In this system the processes of pressure gen-eration and fuel injection are decoupledfrom each other (Figure 6). Injection pres-sure is generated and controlled by a high-pressure pump (1), and is for the most partindependent of engine speed and injectedfuel quantity. It is permanently available inthe “rail” (fuel accumulator, 2) for injection.

The CRS thus provides maximum flexibil-ity in the injection-process design.

Each engine cylinder is provided with an in-jector (4) which forms the injection unit.Opening and closing the high-pressure sol-enoid valve (3) controls the injectionprocess. The instant of injection and the in-jected fuel quantity are calculated in theECU.


Figure 71 P1 Unit Injector

(passenger cars)2 CP2 Common Rail

high-pressure pump(commercial vehi-cles)

3 Rail with injectors(commercial-vehicleCRS)

4 VP30 distributorpump (passengercars)

5 RP39 control-sleevein-line pump (com-mercial vehicles)

Figure 61 High-pressure pump2 Rail (high-pressure

fuel accumulator)3 High-pressure sole-

noid valve4 Injector5 Injection nozzle

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High-pressure components of the Common Rail System (CRS): Principle of functioning

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Examples of the high-pressure components as used in Bosch diesel injection systems7

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Diesel fuel-injection systems: An overview A brief history of diesel injection 11

A brief history of diesel injection

Bosch started at the end of 1922 with thedevelopment of a fuel-injection system fordiesel engines. All technical factors werefavorable: Bosch had experience with internal-combustion engines, production engineeringwas highly developed, and above all it waspossible to apply the know-how that Boschhad accumulated in the manufacture of lubri-cation pumps. Notwithstanding these facts, forBosch there was considerable risk involved inthis development work, and numerous chal-lenges had to be surmounted.

The first injection pumps went into seriesproduction in 1927. At that time, the precisionachieved in their manufacture was absolutelyunique. They were small and of lightweightdesign, and were behind the diesel enginenow being able to run at high speeds. Thesein-line pumps were installed as from 1932 incommercial vehicles, and as from 1936 in pas-senger cars. From this point onwards, therewas not letup in the development of the diesel-engine and its injection equipment.

In 1976, the diesel engine was given a newlease of life when Bosch introduced the distribu-tor injection pump with automatic timing device.And a decade later, after years of intensivedevelopment work to bring it to the volume-pro-duction stage, Bosch brought the ElectronicDiesel Control (EDC) onto the market.

Development engineers are constantlyfaced with the need for the even more preciseinjection of minute quantities of diesel fuel, atexactly the right instant in time, and underhigher and higher injection pressures. This hasled to a number of innovative injection-systemdevelopments (see adjacent Figure).

The diesel engine is still at the forefrontregarding fuel economy and efficient utilizationof fuel.

New injection systems make even betteruse of this potential. In addition, the internal-combustion engine’s power output is continu-ously increasing, while its noise and emissionsfigures have continued to drop.

Milestones in diesel injection technology

1927First series-production in-line pump

1962First axial-piston distributor pump,the EP-VM

1986The first electronically controlled axial-piston distributor pump

1994First Unit Injector System (UIS) for commercial vehicles

1995First Unit Pump System (UPS)

1997First Common Rail accumulator injection system (CRS)

1998First Unit Injector System (UIS) for passenger cars

1996First radial-piston distributor pump

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Modern electronic diesel-engine controlpermits the precise and highly flexible defi-nition of the fuel-injection parameters. Thisis the only way to comply with the widerange of technical demands made on amodern diesel engine. The Electronic DieselControl (EDC) is subdivided into the threesystem blocks “Sensors and desired-valuegenerators”, “ECU”, and “Actuators”.

Technical requirements

The calls for reduced fuel consumption andemissions, together with increased poweroutput and torque, are the decisive factorsbehind present-day developments in thediesel fuel-injection field.

In the past years this has led to an increasein the use of direct-injection (DI) diesel en-gines. Compared to prechamber or whirl-chamber engines, the so-called indirect-in-jection (IDI) engines, the DI engine operateswith far higher injection pressures. Thisleads to improved A/F mixture formation,combustion of the more finely atomized fueldroplets is more complete, and there are lessunburnt hydrocarbons (HC) in the exhaustgas. In the DI engine, the improved mixtureformation and the fact that there are nooverflow losses between pre-chamber/whirlchamber and the main combustion chamberresults in fuel-consumption savings of be-tween 10...15% compared to the IDI engine.

In addition, the increasing requirements re-garding vehicle driveability have a markedeffect on the demands made on modern en-gines, and these are subject to increasinglymore severe requirements with regard to ex-haust-gas and noise emissions (NOX, CO,HC, particulates).

This has led to higher demands beingmade on the injection system and its controlwith respect to:

High injection pressures, Structured rate-of-discharge curve, Pilot injection and possibly post injection,

Adaptation of injected fuel quantity, boostpressure, and injected fuel quantity to thegiven operating state,

Temperature-dependent start quantity, Load-independent idle-speed control, Cruise Control, Closed-loop-controlled exhaust-gas recir-

culation (EGR), and Tighter tolerances for injected fuel quan-

tity and injection point, together withhigh accuracy to be maintained through-out the vehicle’s useful life.

Conventional mechanical (flyweight) gover-nors use a number of add-on devices to reg-ister the various operating conditions, andensure that mixture formation is of highstandard. Such governors, though, are re-stricted to simple open-loop control opera-tions at the engine, and there are many im-portant actuating variables which they can-not register at all or not quickly enough.

The increasingly severe demands it was sub-jected to, meant that the EDC developed froma simple system with electrically triggered ac-tuator shaft to become a complex engine-management unit capable of carrying outreal-time processing of a wide variety of data.

System overview

In the past years, the marked increase in thecomputing power of the microcontrollersavailable on the market has made it possiblefor the EDC (Electronic Diesel Control) tocomply with the above-named stipulations.

In contrast to diesel-engine vehicles withconventional in-line or distributor injectionpumps, the driver of an EDC-controlled ve-hicle has no direct influence, for instancethrough the accelerator pedal and Bowdencable, upon the injected fuel quantity.

12 Electronic Diesel Control (EDC) Technical requirements

Electronic diesel control EDC

Robert Bosch GmbH

On the contrary, the injected fuel quantity isdefined by a variety of actuating variables,for instance: Driver input (accelerator-pedal setting), Operating state, Engine temperature, Intervention from other systems

(e.g. TCS), Effects on toxic emissions etc.

Using these influencing variables, the ECUnot only calculates the injected fuel quantity,but can also vary the instant of injection.This of course means that an extensive safetyconcept must be implemented that detectsdeviations and, depending upon their sever-ity, initiates appropriate countermeasures(e.g. limitation of torque, or emergency(limp-home) running in the idle-speedrange). EDC therefore incorporates a num-ber of closed control loops.

EDC also permits the exchange of data withother electronic systems in the vehicle (e.g.with the traction control system (TCS), theelectronic transmission-shift control, orwith the electronic stability program (ESP).This means that engine management can beintegrated in the overall vehicle system (e.g.for engine-torque reduction when shiftinggear with an automatic gearbox, adaptationof engine torque to wheel slip, release signalfor fuel injection from the vehicle immobi-lizer, etc.).

The EDC system is fully integrated in thevehicle’s diagnostics system. It complies withall OBD (On-Board-Diagnosis) and EOBD(European On-Board Diagnosis) stipula-tions.

System blocksThe EDC system comprises three systemblocks: (Fig. 1):

1. Sensors and desired-value generators (1)for the detection of operating conditions(e.g. engine rpm) and of desired values (e.g.switch position). These convert the variousphysical quantities into electrical signals

2. Electronic control unit (ECU) (2) processesthe information from the sensors and thedesired-value generators in accordance withgiven computational processes (control al-gorithms). The ECU triggers the actuatorswith its electrical output signals and also setsup the interfaces to other systems in the ve-hicle (4) and to the vehicle diagnosis facility(5).

3. Solenoid actuators (3) convert the ECU’selectrical output signals into mechanicalquantities (e.g. for the solenoid valve whichcontrols the injection, or for the solenoid ofthe actuator mechanism).

Electronic Diesel Control (EDC) System blocks 13

Figure 11 Sensors and de-

sired-value genera-tors (input signals)

2 ECU3 Actuators4 Interface to other

systems5 Diagnosis interface

42

1

3

5

Major EDC components1

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In-line injection pumps

14 Electronic Diesel Control (EDC) In-line injection pumps

Engine rpm (crankshaft)

Fuel temperature, control-rack travelAccelerator-pedal sen-sor with low-idle switch

Boost pressure

Start of injection**(needle-motion sensor)

Vehicle speed

Engine rpm and cylinder identification (camshaft)

ECU MS 5/6.1

Signal inputs

Sensor evaluation

Ambient-pressure sensor

Signal processing

- Idle-speed control

- Intermediate-speedcontrol

- External intervention in injected fuel quantity

- Injected fuel-quantity control and limitation

- Cruise Control

- Vehicle-speed limitation

- Calculation of start-of-delivery and delivery period

- Supplementary special adaptations*

System diagnosis

Substitute functions

Engine diagnosis

Power stages

Signal outputs

CAN communication

Diagnosis communication

EoL programming

Power supply

Redundant fuel shutoff (ELAB)

***

Injected-fuel-quantity actuator

Start-of-delivery actuator*

Supplementary driver stages*

ISO interface (e.g. OBD)

CAN interface*

In-line injection pump

Switch for intermediate-speed control

Clutch switch

Door contact

Vehicle-speed-limitation lamp

+

Diagnosis lamp+

* Optional** On control-sleeve in-line injection pumps,*** Start-of-delivery actuator on control- sleeve in-line injection pumps.

Engine temperature (coolant)

Brake switch

Changeover switch for Cruise Control and vehicle-speed limitation

Communication

Actuators

Input signals

Glow-plug and starter switch

Exhaust-brake switch

Cruise Control operator unit

Multi-stage switch for maximum-speed limiter

Multi-stage switch for injected-fuel-quantity limitation, and max. rpm control

Boost-pressure actuator

Exhaust-brake triggering

Intercooler-bypass triggering

L

Input pwm signals

K

CAN+24V (12V*)

Kl. 15

Overview of the EDC components for in-line injection pumps1

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Port-and-helix-controlled axial-piston distributor pumps

Electronic Diesel Control (EDC) Axial-piston distributor pumps 15


Actuator position

Timing-device solenoid valve

ELAB

Actuator

Accelerator-pedal sen-sor with low-idle switch

Boost pressure

Intake-air temperature


Fuel temperature

Air mass

Vehicle speed (also possible via CAN) Km/h

ECU EDC 15V

Signal inputs

Sensor evaluation


Signal processing:


- Cylinder-balance control

- Active surge damper

- Externaltorque intervention

- Immobilizer

- Injected-fuel-quantitycontrol and limitation

- Cruise Control


- Calculation of start of delivery and delivery period

- Supplementary adaptations*

System diagnosis


Engine diagnosis

Power stages

Signal outputs

CAN communication

OBD communication

EoL programming

Power supply

EGR positioner



A/C compressor

Glow control unit

ISO interface (e.g. OBD)

Fuel-consumption signal (TQ signal)

CAN interface*

Brake switch

Main A/C switch

Start of injection*(needle-motion sensor)

+

+

Warning lamp

+

+

OBD lamp+

*Optional

Engine-oil temperature

Clutch switch


Communication

Actuators

Input signals

+

+

+

Multi-stage Cruise Control switch

L

Engine-speed signal (TD signal)Input for pwm signals*

K

CAN12V+

Kl. 15

Distributor pump

Overview of the EDC components for VE-EDC port-and-helix-controlled distributor pumps2

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Solenoid-valve-controlled axial-piston and radial-piston distributor pumps

16 Electronic Diesel Control (EDC) Axial-piston and radial-piston distributor pumps


Angle of rotation of the trigger wheel, timing-device setting (IWZ signal)Accelerator-pedal sen-sor with low-idle switch and kick-down switch

Boost pressure

Air temperature


Fuel temperature

Air mass


ECU EDC15 M

Signal inputsSensor evaluationAmbient-pressure sensor

Signal processing- Idle-speed control- Cylinder-balance

control- Active surge damper- External

torque intervention- Immobilizer- Injected-fuel-quantity

control and limitation- Cruise Control- Vehicle-speed limitation- Cylinder shutoff (only

for commercial vehs.)- Calculation of start of

delivery, and of delivery period

- Pilot-injection control*- Supplementary

special adaptations*

System diagnosisSubstitute functionsEngine diagnosis

Solenoid-valve driver stagesPower stagesSignal outputsCAN communicationDiagnosis communicationEoL programming

Power supply +12V

CAN-Bus

DZG

MAB

EGR positioner



A/C compressor

ISO interface (e.g. diagnostics)


CAN interface*

Distributor pumpVP 30VP 44

Main relay

Brake switch

Main A/C switch

Start of injection*(needle-motion sensor)

+

+

+12V (24V*)

Warning lamp

+

+

Diagnosis lamp+

*OptionalOn distributor pumps with pump ECU PSG16, the engine ECU is integrated in the pump ECU

Engine-oil temperature

Clutch switch


Communication

Actuators

Input signals

+

+

+


L

Engine rpm signal (TD signal)Input for pwm signals*

K

CAN

Glow control unit

Overview of the EDC components for solenoid-valve-controlled distributor pumps VE-MV, VR1

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Common Rail System (CRS)

Electronic Diesel Control (EDC) Common Rail System (CRS) 17



Rail pressure

Accelerator-pedal sen-sor, with low-idle switch and kick-down switch

Boost pressure

Charge-air pressure


Rail-pressure control valve of the high-pressure pump

Element shutoff*

Electronic shutoff or electric fuel pump

EGR positioner

Boost-pressure actuator*

Throttle-valve actuator

Auxiliary heater*

ISO interface(e.g. diagnosis)

Glow control unit (GZS)

Engine rpm signal (TD signal)Diagnosis lamp

CAN interfaceCAN

Clutch switch (or P/N contact for automatic transmissions)

Terminal 15

Multi-stage switch for maximum-speed limiter and for Cruise Control

Air mass or exhaust-gas-signal check-back

Terminal 50*

+

Communication

Actuators

Input signals

12V

ECUEDC 15 C / MS 6.3

Signal processing:- Idle-speed control- Intermediate-speed

control- Smooth-running

control (SRC)- Active surge damper- External


control and limitation- Cruise Control*- Vehicle-speed

limitation*- Cylinder shutoff- Fuel-quantity control- Fuel-pressure control- Start-of-injection control- Pilot-injection control- Post-injection control*- Supplementary special

adaptations*

Signal inputsSensor evaluationAmbient-pressure sensor

System diagnosisSubstitute functionsEngine diagnosis

Solenoid-valve driver stagesPower stagesSignal outputsCAN communicationDiagnosis communicationEoL programming

Power supply

Mainrelay

*Optional

Injectors(max. 6 per ECU)

**

Exhaust-gas temperature*

Fan control*

Starter*

Additional driver stages*

Intake-tract switch-over*

L

K

Overview of the EDC components for the Common Rail System (CRS)2

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Unit Injector System (UIS) for passenger cars

18 Electronic Diesel Control (EDC) Unit Injector System (UIS) for passenger cars


Engine rpm and cylinder recognition (camshaft)

Accelerator-pedal sensor with low-idle switch and kick-down switch (2nd sensor*)

Boost pressure

Intake-air temperature


Fuel temperature

Air mass


ECU EDC15P

Signal inputs

Sensor evaluation


Signal processing


- Cylinder-balance control

- Active surge damper

- Externaltorque intervention

- Immobilizer

- Injected-fuel-quantitycontrol and limitation

- Cruise Control

- Calculation of start of delivery and delivery period

- Start-of-delivery (BIP) correction


System diagnosis


Engine diagnosis

Solenoid-valve driver stages

Power stages

Signal outputs

CAN communication

Diagnosis communication

EoL programming

Power supply

Start of delivery, delivery period

Glow-relay control

A/C switch-off

EGR actuator


Supplementary low-power driver stages (e.g. A/C switch-off, fan, auxiliary heater)

*

ISO interface (e.g. diagnosis)

System lamp

MIL lamp (for diagnosis)

CAN interface

Engine rpm signal (TD signal)


Unit Injector (max. 5 per ECU)

Main relay

MIL request (request for MIL lamp)

Brake switch

Terminal 15

Glow-relay status

Gearbox input

Air-conditioner input

+

+12 V

+

+

*Optional

Clutch switch

Communication

Actuators

Input signals

+


L

K

CAN

Overview of the EDC components for a passenger-car unit injector system (UIS)1

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Unit Injector System (UIS) and Unit Pump System (UPS) for commercial vehicles

Electronic Diesel Control (EDC) UIS and UPS for commercial vehicles 19

+



Exhaust-gas turbocharger, rpm signal

Accelerator-pedal sensor with low-idle switch and kick-down switch*

Boost pressure

Charge-air temperature


Fuel temperature

Vehicle speed (also possible via CAN)

Km/h

Start-of-delivery, delivery period


Exhaust brake

Additional driver stages(e.g. fan control)

Diagnosis lamp

Input forpwm signals

Engine rpm signal (TD signal)


Brake contact

Clutch contact

Exhaust-brake contact

Parking-brake contact

Terminal 15

Communication

Actuators

Input signals

24V (12V*)

ECU MS 6.2

Signal inputs Sensor evaluationAmbient-pressure sensor

Signal processing:

- Idle-speed control- Intermediate-speed

control- External


control and limitation- Cruise Control- Vehicle-speed

limitation- Cylinder shutoff- Calculation of start of

delivery and delivery period

- Start-of-delivery (BIP) correction


System diagnosisCalibrationSubstitute functionsEngine diagnosis

Solenoid-valve driver stagesDriver stagesSignal outputsCAN communicationDiagnosis communic.EoL programming

Power supply

*Optional

UP* (max. 8 per ECU)

UI* (max. 8 per ECU)or

Multi-function switch

ISO interface(e.g. diagnosis)

CAN interface

Main relay

CAN

L

K

+

*

*

Overview of the EDC components for Unit Injector System (UIS) and Unit Pump Systems (UPS) for commercial vehicles2

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Sensors register operating states (e.g. enginespeed) and setpoint/desired values (e.g. ac-celerator-pedal position). They convertphysical quantities (e.g. pressure) or chemi-cal quantities (e.g. exhaust-gas concentra-tion) into electric signals.

Automotive applications

Sensors and actuators represent the inter-faces between the ECU’s, as the processingunits, and the vehicle with its complex drive,braking, chassis, and bodywork functions(for instance, the Engine Management, theElectronic Stability Program ESP, and the airconditioner). As a rule, a matching circuit inthe sensor converts the signals so that theycan be processed by the ECU.

The field of mechatronics, in which me-chanical, electronic, and data-processingcomponents are interlinked and cooperateclosely with each other, is rapidly gaining inimportance. They are integrated in modules(e.g. in the crankshaft CSWS (CompositeSeal with Sensor) module complete withrpm sensor).

Since their output signals directly affect notonly the engine’s power output, torque, andemissions, but also vehicle handling andsafety, sensors, although they are becomingsmaller and smaller, must also fulfill de-mands that they be faster and more precise.These stipulations can be complied withthanks to mechatronics.

Depending upon the level of integration,signal conditioning, analog/digital conver-sion, and self-calibration functions can allbe integrated in the sensor (Fig. 1), and infuture a small microcomputer for furthersignal processing will be added. The advan-tages are as follows:

Lower levels of computing power areneeded in the ECU,

A uniform, flexible, and bus-compatibleinterface becomes possible for all sensors,

Direct multiple use of a given sensorthrough the data bus,

Registration of even smaller measuredquantities,

Simple sensor calibration.

20 Sensors Automotive applications

Sensors

Figure 1SE Sensor(s)SA Analog signal con-

ditioning A/D Analog-digital con-

verterSG Digital ECUMC Microcomputer

(evaluation electron-ics)

SE SA A D

SE SA A D

SE SA

SEConventional

1st Integration level

2nd integration level

3rd integration level MC SG

SG

SG

SGSA A D

A D

Sensors Transmission path ECUSusceptible to interference (analog)

Resistant tointerference (analog)

Immune tointerference (digital)

Immune tointerference (digital)

Multiple tap-off

Bus-compatible

Bus-compatible

Sensor integration levels1

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Temperature sensors

ApplicationsEngine-temperature sensorThis is incorporated in the coolant circuitand measures the coolant temperature as anindication of engine temperature (Fig. 1).This information is needed for the engine-management system. The measurable tem-perature range is between – 40 and +130 °C.

Air-temperature sensorThis is installed in the engine's intake tractand measures the temperature of the intakeair. In coordination with a boost-pressuresensor, this intake-air temperature can beused to precisely measure the mass of the airdrawn into the engine. Apart from this, thesetpoint values for closed control loops (e.g.EGR, boost-pressure control) can beadapted as a function of the air temperature.The measurable temperature range is be-tween – 40 and +120 °C.

Engine-oil temperature sensorThe signal from the engine-oil temperaturesensor is used when determining the serviceinterval. The measurable temperature rangeis between – 40 and +170 °C.

Fuel-temperature sensorThis sensor is installed in the low-pressure

stage of the fuel system. The fuel tempera-ture is an important factor in preciselydefining the correct injected fuel quantity.The measurable temperature range is be-tween – 40 and +120 °C.

Exhaust-gas temperature sensorThis sensor is installed at a point in the ex-haust system which is critical with regard totemperature. It is used in the control of theexhaust-gas treatment system. Platinum isusually used for the measuring resistor. Themeasurable temperature range is between – 40 and +1000 °C.

Design and operating conceptDepending upon the particular application,these temperature sensors are available in avariety of different shapes and versions. Atemperature-dependent semiconductormeasuring resistor is mounted inside thesensor housing. This resistor is usually of theNTC (Negative Temperature Coefficient)type, or less commonly of the PTC (PositiveTemperature Coefficient) type. In otherwords, when subjected to increasing temper-ature, its electrical resistance decreases(NTC) or increases (PTC) dramatically.

The measuring resistor is part of a voltage-distributor circuit to which 5 V is applied,and the voltage measured across it is there-

Sensors Temperature sensors 21

Figure 11 Electrical

connections 2 Housing3 Seal ring4 Sensor thread5 Measuring resistor6 Coolant

1

1 cm

2 3 654

Coolant-temperature sensor1

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Characteristic curve of an NTC resistor2

-40 0 40 80 120°C102

103

104

Ω

Res

ista

nce

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Robert Bosch GmbH

fore temperature-dependent. This is in-putted to the ECU through an A/D con-verter and is a measure for the temperatureat the sensor. The engine ECU incorporatesa characteristic curve which allocates a spe-cific temperature to each output-voltagevalue or resistance (Fig. 2, Page 21).

Micromechanical pressuresensors

ApplicationsIntake-manifold sensor or boost-pressuresensorThis sensor measures the absolute pressurein the intake manifold (typically 250 kPa or2.5 bar) between the supercharger and theengine. The actual measurement is referredto a reference vacuum and not to the sur-rounding pressure. This permits precisemeasurement of the air mass so that the su-percharger can be controlled in accordancewith engine requirements.

Atmospheric-pressure sensorThe atmospheric-pressure sensor can be in-stalled in the ECU or at another location inthe engine compartment. Its signal is usedfor altitude-dependent correction of the set-point values for the closed control loops (forinstance for the EGR and the boost-pressurecontrol). This permits the differences in at-mospheric pressure encountered at differentaltitudes to be taken into account. The at-mospheric-pressure sensor measures ab-solute pressure (60...115 kPa, 0.6...1.15 bar).

Oil-pressure and fuel-pressure sensorsOil-pressure sensors are installed in the oilfilter for measuring the absolute oil pressure.This information is applied for determiningengine loading as required for the ServiceDisplay. The sensor’s pressure range is50...1000 kPa (0.5...10.0 bar). The sensor el-ement’s high resistance to the measuredmedium means that it can also be used forthe fuel-pressure measurement in the fuel-system low-pressure stage. The sensor is fit-

22 Sensors Micromechanical pressure sensors

p

1 3

2

5

R1 R1R2

4

UM U0

R1

R2

R2

R1

Sensor element of a pressure sensor with referencevacuum on the component-buildup side (schematic)

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Figure 11 Diaphragm2 Silicon chip3 Reference vacuum4 Glass (Pyrex) 5 Wheatstone bridgep Measured pressureU0 Supply voltageUM Measurement

voltageR1 Measuring resistors

(compressed) andR2 Measuring resistors

(stretched)

Figure 21, 3 Electrical connec-

tions with glass-en-closed lead-in

2 Reference vacuum4 Sensor element

(chip) with evalua-tion electronics

5 Glass base6 Cap7 Pressure connection

for measured pres-sure p

Robert Bosch GmbH

ted either in the fuel filter or on it, and itssignal is used to monitor the degree of fuelcontamination (measuring range 20...400kPa or 0.2...4 bar).

Design with the reference vacuum onthe component sideDesignThe measuring element is the heart of themicromechanical pressure sensor, and iscomprised of a silicon chip (Fig. 1, Pos. 2)into which a thin diaphragm (1) has beenetched micromechanically. Four measuringresistors (R1, R2), whose electrical resistanceschange when mechanical pressure is applied,are arranged on the diaphragm. On itsstructure side, the sensor element is sur-rounded and sealed off by a cap which en-closes the reference vacuum (Figs. 2 and 3).A temperature sensor can also be integratedin the pressure sensor (Fig. 4, Pos. 1), whosesignals can be evaluated separately. This hasthe advantage that only a single sensor hous-ing is needed when both temperature andpressure are to be measured.

Operating conceptThe sensor-element diaphragm bends byseveral µm (10...1000 µm) as a function ofthe applied pressure. The resulting mechani-cal tension causes the four measuring resis-tors on the diaphragm to change their resis-tance (piezoresistive effect).

These measuring resistors are arranged onthe silicon chip so that when the diaphragmdeforms (due to pressure application), theelectrical resistance of two of the resistorsincreases, and that of the other two de-creases. Since the resistors are part of aWheatstone bridge (Fig. 1, Pos. 5), when theresistance values change so does the voltageratio across the measuring resistors, andwith it the measurement voltage UM whichthus becomes a measure of the pressure ap-plied to the diaphragm.

Using a bridge circuit enables a highermeasurement voltage to be generated thanwould be possible with a single resistor. TheWheatstone bridge, therefore, permits a

higher level of sensor sensitivity.

The component side of the diaphragm towhich no pressure is applied is subjected to areference vacuum (Fig. 2, Pos. 2) so that thesensor measures absolute pressure.

The signal-conditioning electronics are in-tegrated on the chip and have the job of am-plifying the bridge voltage, compensating fortemperature fluctuations, and linearizing thepressure curve. Output voltage is 0...5 V andvia the sensor’s electrical plug-in connection(Fig. 4, Pos. 5) it is inputted to the ECU whichuses it to calculate the pressure curve (Fig. 5).

Sensors Micromechanical pressure sensors 23

Figure 41 Temperature sensor

(NTC),2 Housing base 3 Intake-manifold wall4 O-rings5 Electrical plug-in

connection6 Housing cover7 Sensor element

1 2 3 4 5

6

7

1 cm

Micromechanical pressure sensor with reference vacuum on the component side

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kPa250100

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olta

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Characteristic curve of a micromechanical boost-pressure sensor (example)

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Version with the reference vacuum in acavityDesignThe pressure sensor with reference vacuuminside a cavity (Figs. 6 and 8) is used as anintake-manifold or boost-pressure sensor. Itis simpler in design than the version withthe reference vacuum on the componentside. A silicon chip with etched diaphragmand four measuring resistors in a bridge cir-cuit is mounted as the sensor element on aglass base similar to the sensor version withcap and reference vacuum on the compo-

nent side. In contrast to the latter versionthough, there is no hole in the cavity-typesensor’s glass base for transmitting the mea-sured pressure from the sensor’s rear side tothe sensor element. Instead, pressure is ap-plied to the silicon chip at the side contain-ing the evaluation electronics. This sidemust therefore be sealed off with a specialgel to protect it against environmental ef-fects (Fig. 7, Pos. 1). The reference vacuum islocated in the hollow space (cavity) betweenthe silicon chip (6) and the glass base (3).The complete measuring element ismounted on the ceramic hybrid (4) which isprovided with solder surfaces for connec-tions within the sensor.

It is also possible to integrate a temperaturesensor inside the pressure sensor’s housing.This extends into the air stream and is thusable to react extremely quickly to tempera-ture changes.

Operating conceptOperating concept, signal conditioning andamplification, as well as the characteristiccurve, are all identical to those of the sensorwith cap and reference vacuum on the com-ponent side. The sole difference is that thesensor-element’s diaphragm, and with it themeasuring resistors, is deformed in the op-posite direction.

24 Sensors Micromechanical pressure sensors

Figure 61 Intake-manifold wall2 Housing3 Seal ring4 Temperature sensor

(NTC)5 Electrical plug-in

connection6 Housing cover7 Sensor element

Figure 71 Protective gel2 Gel frame3 Gass base 4 Ceramic hybrid5 Cavity with refer-

ence vacuum6 Sensor element

(chip) with evalua-tion electronics

7 Bonded connectionp Measured pressure

51

4

3

2

6

7

1 cm

Micromechanical pressure sensor with reference vacuum in a cavity

6

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Micromechanical pressure sensor with reference vacuum in a cavity and integrated temperature sensor

8

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3

4

p

6

5

7

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Sensor element with reference vacuum in a cavity

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Robert Bosch GmbH

Rail-pressure sensorsApplicationIn the Common-Rail injection system andthe gasoline direct-injection system MED-Motronic, these sensors are used to measurethe fuel pressure in the high-pressure fuelaccumulator (or rail, from which the systemtook its name). Strict compliance with thestipulated fuel pressure is of extreme impor-tance with regard to emissions, noise, andengine power. The fuel pressure is regulatedin a control loop, and deviations from thedesired pressure level are compensated forby a pressure-control valve.

The rail-pressure sensors feature very tighttolerances, and in the main measuring rangethe measuring accuracy is better than 2% ofthe measuring range.

These rail-pressure sensors are used in thefollowing engine systems:

Common-Rail diesel injection system(CRS)Maximum operating pressure pmax

(rated pressure) is 160 MPa (1600 bar).

Gasoline direct injection MED-MotronicFor this gasoline direct-injection system,operating pressure is a function of loadand rotational speed, and is 5...12 MPa(50...120 bar).

Design and operating conceptThe heart of this sensor is a steel diaphragmon which measuring resistors in the form ofa bridge circuit have been vapor-deposited(Fig. 1, Pos. 3). The sensor’s measuringrange is a function of diaphragm thickness(thicker diaphragms for higher pressures,thinner diaphragms for lower pressures). Assoon as the pressure to be measured is ap-plied to the diaphragm through the pressureconnection (Fig. 1, Pos. 4), this bends andcauses a change in the resistance of the mea-suring resistors (approx. 20 µm at 1500 bar).The output voltage generated by the bridge

is in the range 0...80 mV and is inputted tothe evaluation circuit (2) in the sensor. Thisamplifies the bridge signal to 0...5 V andtransmits it to the ECU which uses it to-gether with a stored characteristic curve tocalculate the pressure (Fig. 2).

Sensors Rail-pressure sensors 25

Figure 11 Electrical plug-in

connection2 Evaluation circuit3 Steel diaphragm

with measuring re-sistors

4 Pressure connection5 Mounting thread

2

3

4

5

p

1

2 cm

Rail-pressure sensor 1

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pmax0

4.5

0.5

Pressure

Out

put v

olta

ge

V

Rail-pressure sensor: Characteristic curve2

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Robert Bosch GmbH

Inductive engine-speed(rpm) sensorsApplicationsSuch engine-speed sensors are used for mea-suring:

Engine rpm, Crankshaft position

(for information on the position of theengine pistons).

The rotational speed is calculated from theintervals between the signals from the rpmsensor. The output signal from the rpm sen-sor is one of the most important quantitiesin electronic engine management.

Design and operating conceptThe sensor is mounted directly opposite aferromagnetic trigger wheel (Fig. 1, Pos. 7)from which it is separated by a narrow airgap. It has a soft-iron core (pole pin) (4),which is enclosed by the solenoid winding(5). The pole pin is also connected to a per-manent magnet (1), and a magnetic field ex-tends through the pole pin and into the trig-ger wheel. The level of the magnetic fluxthrough the winding depends upon whetherthe sensor is opposite a trigger-wheel toothor gap. Whereas the magnet’s stray flux isconcentrated by a tooth and leads to an in-crease in the working flux through the wind-ing, it is weakened by a gap. When the trig-ger wheel rotates therefore, this causes a

fluctuation of the flux which in turn gener-ates a sinusoidal voltage in the solenoidwinding which is proportional to the rate ofchange of the flux (Fig. 2). The amplitude ofthe AC voltage increases strongly along withincreasing trigger-wheel speed (severalmV...>100 V). At least about 30 rpm areneeded to generate an adequate signal level.

The number of teeth on the trigger wheeldepends upon the particular application. Onsolenoid-valve-controlled engine-manage-ment systems for instance, a 60-pitch triggerwheel is normally used, although 2 teeth areomitted (Fig. 1, Pos. 7) so that the triggerwheel has 60 – 2 = 58 teeth. The very largetooth gap (7) is allocated to a defined crank-shaft position and serves as a reference markfor synchronizing the ECU.

There is another version of the triggerwheel which has one tooth per engine cylin-der. In the case of a 4-cylinder engine, there-fore, the trigger wheel has 4 teeth, and 4pulses are generated per revolution.

The geometries of the trigger-wheel teethand the pole pin must be matched to eachother. The evaluation-electronics circuitry inthe ECU converts the sinusoidal voltage,which is characterized by strongly varyingamplitudes, into a constant-amplitudesquare-wave voltage for evaluation in theECU microcontroller.

26 Sensors Inductive engine-speed (rpm) sensors

Figure 21 Tooth2 Tooth gap3 Reference mark

Figure 11 Permanent magnet2 Sensor housing3 Engine block4 Pole pin5 Solenoid winding6 Air gap7 Trigger wheel with

reference-mark gap

1 2

67

3

45

S

N

2 cm

Inductive rpm sensor (principle)1

æU

MZ

0138

-2Y

Time

1

2

3Out

put v

olta

ge

Signal from an inductive rpm sensor2

æU

AE

0727

E

Robert Bosch GmbH

Rotational-speed (rpm) sen-sors and incremental angle-of-rotation sensorsApplicationThe above sensors are installed in distribu-tor injection pumps with solenoid-valvecontrol. Their signals are used for:

The measurement of the injection pump’sspeed,

Determining the instantaneous angularposition of pump and camshaft,

Measurement of the instantaneous settingof the timing device.

The pump speed at a given instant is one ofthe input variables to the distributor pump’sECU which uses it to calculate the triggeringtime for the high-pressure solenoid valve,and, if necessary, for the timing-device sol-enoid valve.

The triggering time for the high-pressuresolenoid valve must be calculated in order toinject the appropriate fuel quantity for theparticular operating conditions. The camplate’s instantaneous angular setting definesthe triggering point for the high-pressure sol-enoid valve. Only when triggering takes placeat exactly the right cam-plate angle, can it beguaranteed that the opening and closingpoints for the high-pressure solenoid valve arecorrect for the particular cam lift. Precise trig-gering defines the correct start-of-injectionpoint and the correct injected fuel quantity.

The correct timing-device setting asneeded for timing-device control is ascer-tained by comparing the signals from thecamshaft rpm sensor with those of the an-gle-of-rotation sensor.

Design and operating conceptThe rpm sensor, or the angle-of-rotationsensor, scans a toothed pulse disc with 120teeth which is attached to the distributorpump’s driveshaft. There are tooth gaps, thenumber of which correspond to the numberof engine cylinders, evenly spaced aroundthe disc’s circumference. A double differen-

tial magnetoresistive sensor is used.Magnetoresistors are magnetically con-

trollable semiconductor resistors and similarin design to Hall-effect sensors.

The double differential sensor has four re-sistors connected to form a full bridge cir-cuit. The sensor has a permanent magnet,the magnet pole face opposite the toothedpulse disc being homegenized by a thin fer-romagnetic wafer on which are mounted thefour magnetoresistors, separated from eachother by half a tooth gap. This means thatalternately there are two magnetoresistorsopposite tooth gaps and two opposite teeth(Fig. 1). The magnetoresistors for automo-tive applications are designed for operationin temperatures of ≤170°C (≤200°C briefly).

Sensors Rotational-speed (rpm) sensors and incremental angle-of-rotation sensors 27

Figure 21 Flexible conductive

strip2 Rotational-speed

(rpm)/angle-of-rota-tion sensor

3 Tooth gap4 Toothed pulse disc

(trigger wheel)5 Rotatable mounting

ring6 Driveshaft

Figure 11 Magnet2 Homogenization

wafer (Fe)3 Magnetoresistor4 Toothed pulse disc

1

2

43

5

3

3

6

3

Rotational-speed/angle-of-rotation sensor (installed) 2

æU

MK

1553

-1Y

1

N

S

2

4

3

Rotational-speed/angle-of-rotation sensor1

æU

MK

1771

Y

Robert Bosch GmbH

Hall-effect phase sensorsApplicationThe engine’s camshaft rotates at half thecrankshaft speed. Taking a given piston onits way to TDC, the camshaft‘s rotationalposition is an indication whether the pistonis in the compression or exhaust stroke. Thephase sensor on the camshaft provides theECU with this information.

Design and operating conceptHall-effect rod sensorsAs the name implies, such sensors (Fig. 2a)make use of the Hall effect. A ferromagnetictrigger wheel (with teeth, segments, or per-forated rotor, Pos. 7) rotates with thecamshaft. The Hall-effect IC (6) is locatedbetween the trigger wheel and a permanentmagnet (5) which generates a magnetic fieldperpendicular to the Hall element.

If one of the trigger-wheel teeth (Z) nowpasses the current-carrying rod-sensor ele-ment (semiconductor wafer), it changes thefield strength. This causes the electrons,which are driven by a longitudinal voltageacross the element, to be deflected perpen-dicularly to the direction of current (Fig. 1,angle α).

This results in a voltage signal (Hall volt-age) in the millivolt range, which is indepen-dent of the relative speed between sensorand trigger wheel. The evaluation-electron-ics stage integrated in the sensor’s Hall ICconditions the signal and outputs it in theform of a rectangular-pulse signal (Fig. 2b“High”/“Low”).

Differential Hall-effect rod sensorsRod sensors operating as per the differentialprinciple are provided with two Hall ele-ments. These elements are offset from eachother either radially or axially (Fig. 3, S1 andS2), and generate an output signal which isproportional to the difference in magneticflux at the element measuring points. A two-track perforated plate (Fig. 3a) or a two-track trigger wheel (Fig. 3b) are needed inorder to generate the opposing signals in the

Hall elements (Fig. 4) as needed for thismeasurement.

Such sensors are used when particularly se-vere demands are made on accuracy. Furtheradvantages are their relatively wide air-gaprange and good temperature-compensationcharacteristics.

28 Sensors Hall-effect phase sensors

Figure 2a Positioning of sensor

and single-track trig-ger wheel

b Output signal charac-teristic UA

1 Electrical plug-in con-nection

2 Sensor housing3 Engine block4 Seal ring5 Permanent magnet6 Hall-IC7 Trigger wheel with

tooth/segment (Z)and gap (L)

a Air gap, Angle of rotation

Figure 1I Wafer currentIH Hall currentIV Supply currentUH Hall voltageUR Longitudinal volt-

ageB Magnetic inductionα Deflection of the

electrons by themagnetic field

Z

L

UAL L

ϕs

ϕ

Z

High

Low

Angle of rotation ϕ

a

b

a

2 cm

7

1

SN

2

3

4

5

6

Hall-effect rod sensor 2æ

UM

K17

68E

UH

+B

UR

IV

IH

I

α

Hall element (Hall-effect vane switch)1

æU

AE

0699

-2Y

Robert Bosch GmbH

Sensors Hall-effect phase sensors 29

Figure 3a Axial tap-off

(perforated plate)b Radial tap-off

(two-track triggerwheel)

1 Electrical plug-in con-nection

2 Sensor housing3 Engine block4 Seal ring5 Permanent magnet6 Differential Hall-IC

with Hall elements S1and S2

7 Perforated plate8 Two-track trigger

wheelI Track 1II Track 2

Figure 4Output signal “Low”: Material (Z) in front ofS1, gap (L) in front ofS2;

Output signal “High”:Gap (L) in front of S1,material (Z) in front ofS2

S signal width

UA

L1 L2

Z2 Z3

ϕs

ϕ

Z4Z1

L3 L4High

Low

90°

0°

180°

270°

360°

Characteristic curve of the output signal UA from a differential Hall-effect rod sensor4

æU

MK

1770

YS2S1

ZLLZ

Z ZLL

1

7 8

8

SN

2

5

6

7

S2S1

SN

S2S11

S1a b

2

S2

3

4

Differential Hall-effect rod sensors3

æU

MK

1769

Y

Robert Bosch GmbH

Half-differential short-circuiting-ring sensorsApplicationThe above sensors are applied as positionsensors for travel or angle. They are veryprecise and very robust, and are used as

Rack-travel sensors (RWG) for measuringthe control-rack setting in in-line dieselinjection pumps, and as

Angle-of-rotation sensors in the injected-fuel quantity actuators for diesel distribu-tor pumps.

Design and operating conceptThese sensors (Figs. 1 and 2) are comprisedof a laminated soft-iron core on each limb ofwhich are wound a measuring coil and a ref-erence coil.

When the alternating current (AC) out-putted by the ECU flows through these coils,alternating magnetic fields are generated.The copper short-circuiting rings surround-ing the limbs of the soft-iron core, though,screen these against the alternating magneticfields. Whereas the reference short-circuitingrings are fixed in position, the measuringshort-circuiting rings are attached to thecontrol rack or to the control-collar shaft(in-line pumps and distributor pumps re-spectively) and are free to move (control-rack travel s, and adjustment angle ).

When the measuring short-circuiting ringmoves, the magnetic flux changes and, since

the ECU maintains the current constant(load-independent current), the voltageacross the coil also changes.

The ratio of the output voltage UA to thereference voltage URef (Fig. 3) is calculatedby an evaluation circuit. This ratio is pro-portional to the deflection of the measuringshort-circuiting ring and can be processedby the ECU. Bending the reference short-cir-cuiting ring adjusts the characteristic-curvegradient, and the basic position of the mea-suring short-circuiting ring defines the zeropoint.

30 Sensors Half-differential short-circuiting-ring sensors

Figure 11 Soft-iron core2 Reference coil3 Reference short-

circuiting ring4 Control rack5 Measuring coil6 Measuring short-

circuiting rings Control-rack travel

Figure 21 Measuring coil2 Measuring short-

circuiting ring3 Soft-iron core4 Control-collar shaft5 Reference coil6 Reference short-

circuiting ringmax Adjustment angle

for the control-col-lar shaft

Measured angle

Figure 3UA Output voltageURef Reference voltage

UA

URef

13

2

6

4

5

s

Design of the rack-travel sensor for diesel in-line injection pumps

1

A

mmControl-rack travel s

Linear range

U /

U Ref

Voltage ratio as a function of control-rack travel

3

æU

MK

0641

E

60°

0°

1

5 6

2

ϕ

ϕ max

UA

URef

43

Design of the half-differential short-circuiting-ring sensor for diesel distributor pumps

2

æU

AE

0746

Y

æU

AE

0290

-1Y

Robert Bosch GmbH

Nozzle holders with needle-motion sensor

ApplicationThe start-of-injection point is an importantparameter for optimum diesel-engine oper-ation. Its evaluation, for instance, permitsload and speed-dependent injection timing,and/or the control of the exhaust-gas recir-culation (EGR), as well as diagnosis in theECU. Here, a nozzle holder with needle-mo-tion sensor (Fig. 2) is used which outputs asignal as soon as the nozzle needle lifts off itsseat.

Design and operating conceptWhen the needle lifts, the extended pressurepin (12) enters the coil (11). The degree towhich it enters the coil (immersion length“X” in Fig. 2), determines the strength of themagnetic flux in the coil. Nozzle-needlemovement causes a change in the coil’s mag-netic flux so that a signal voltage is inducedwhich is proportional to the needle’s speedof movement but not to the distance it hastravelled. This signal is processed directly inthe evaluation circuit. When a given thresh-old voltage is exceeded (Fig. 1), the evalua-tion circuit uses this as the signal for thestart of injection.

Sensors Nozzle holders with needle-motion sensor 31

2

Y

Detail Y

X

3

1

5

4

6

7

9

10

11

13 12

8

2 cm

Two-spring nozzle holder with needle-motion sensorfor direct-injection (DI) engines

2

æU

MK

1718

-1Y

a

Start-of-injection signal

Threshold voltage

Nee

dle

lift

Sig

nal v

olta

ge

Crankshaft angle

b

Needle-motion sensor: Signal1

æU

MK

1427

-1E

Figure 1a Needle-lift curve,b Corresponding sig-

nal-voltage curve atthe coil

Figure 211 Nozzle-holder body12 Needle-motion sen-

sor13 Spring14 Guide element15 Spring16 Pressure pin17 Nozzle-retaining nut18 Connection to the

evaluation circuit19 Setting pin10 Contact lug11 Coil (sensor coil)12 Pressure pin13 Spring seat

Robert Bosch GmbH

a

1

3

b c

1 5 cm

10 cm

3

2

1

2

Accelerator-pedal sensorsApplicationIn conventional engine-management sys-tems, the driver transmits his/her wishes foracceleration, constant or lower speed, to theengine by using the accelerator pedal to in-tervene mechanically at the throttle plate(gasoline engine) or injection pump (dieselengine). Intervention is transmitted fromthe accelerator pedal to throttle plate or in-jection pump by means of a Bowden cableor linkage.

On today’s engine-management systems,the Bowden cable and/or linkage have beensuperseded and the driver’s accelerator-pedal inputs are transmitted to the ECU byan accelerator-pedal sensor. This registers

the pedal travel, or its angular setting, andsends this to the engine ECU in the form ofan electrical signal.

The accelerator-pedal module (Fig. 2band c) is available as an alternative to the in-dividual accelerator-pedal sensor (Fig. 2a).The module is a ready-to-install unit com-prising accelerator pedal and sensor. Suchmodules mean that adjustments on the vehi-cle have become unnecessary.

Design and operating conceptPotentiometer-type accelerator-pedal sensorThe heart of the accelerator-pedal sensor is apotentiometer across which there is a volt-age which is a function of the accelerator-pedal setting. In the ECU, a programmedcharacteristic curve is used to calculate theaccelerator-pedal travel or its angular settingfrom this voltage.

A second (redundant) sensor is incorpo-rated for diagnosis purposes and for use incase of malfunction. It is a component partof the monitoring system. One version ofthe accelerator-pedal sensor operates with asecond potentiometer. The voltage acrossthis potentiometer is always half that acrossthe first potentiometer. This provides twoindependent signals which are used for trou-ble-shooting (Fig. 1). Instead of the secondpotentiometer, another version uses a low-idle switch which provides a signal for theECU when the accelerator pedal is in theidle position. For automatic-transmission

32 Sensors Accelerator-pedal sensors

Figure 2a Individual accelera-

tor-pedal sensorb Top-mounted accel-

erator-pedal modulec Bottom-mounted ac-

celerator-pedal mod-ule FMP1

1 Sensor2 Vehicle-specific

pedal3 Pedal bracket

Figure 11 Potentiometer 1

(master poten-tiometer)

2 Potentiometer 2(50% of voltage)

Pedal travel approx. 25 mm

Out

put v

olta

ge

V

4.75

0.75

1

2

Characteristic curve of an accelerator-pedal sensor with redundant potentiometer

1

æU

AE

0724

E

2 Accelerator-pedal-sensor versions

æU

AE

0725

Y

Robert Bosch GmbH

vehicles, a further switch can be incorpo-rated for a kick-down signal.

Hall-effect angle-of-rotation sensorsThis Hall-effect angle-of-rotation sensor(ARS1) is based on the movable-magnetprinciple. It has a measuring range of ap-prox. 90° (Figs. 3 and 4).

A semicircular permanent-magnet rotor(Fig. 4, Pos. 1) generates a magnetic fluxwhich is returned back to the rotor via apole shoe (2), two conductive elements (3)and the magnetically soft shaft (6). In theprocess, the amount of flux which is re-turned through the conductive elements is afunction of the rotor’s angle of rotation .There is a Hall-effect sensor (5) located inthe magnetic path of each conductive ele-ment, so that is it possible to generate apractically linear characteristic curve in themeasuring range.

On the ARS2 sensor, a simpler design is usedwithout magnetically soft conductive ele-ments. Here, a magnet rotates around theHall-effect sensor. The path it takes is in theform of a circular arc. Since only a small sec-tion of the resulting sinusoidal characteristiccurve features good linearity, the Hall-effectsensor is located slightly outside the centerof the arc. This causes the characteristiccurve to deviate from its sinusoidal form sothat the linear section of the curve is in-creased to more than 180 °.

Mechanically, this sensor is highly suitablefor installation in an accelerator-pedal mod-ule (Fig. 5).

Sensors Accelerator-pedal sensors 33

Figure 5a Installation in

accelerator-pedalmodule

b Components1 Hall-effect sensor2 Pedal shaft3 Magnet

Figure 41 Rotor

(permanent mag-net)

2 Pole shoe3 Conductive ele-

ment4 Air gap5 Hall-effect sensor6 Pedal shaft

(magnetically soft) Angle of rotation

Figure 31 Housing cover2 Rotor

(permanent mag-net)

3 Evaluation electron-ics with Hall-effectsensor

4 Housing base5 Return spring6 Coupling element

(e.g. gear)

11

22

3

ba

Hall-effect angle-of-rotation sensor ARS25

æU

AE

0771

Y

a b

c d

1

2 3

6

54

4

ϕ ϕ

ϕ

Hall-effect angle-of-rotation sensor ARS1 (shown with angular settings a...d)

4

æU

AE

0770

Y

1

4

5

6

2

3

Hall-effect angle-of-rotation sensor ARS13

æU

AE

0769

Y

Robert Bosch GmbH

Hot-film air-mass meterHFM5ApplicationFor the optimal combustion as needed tocomply with the emission regulations im-posed by legislation, it is imperative thatprecisely the necessary air mass is inductedas dictated by the engine’s operating state.

To this end, part of the total air flow whichis actually inducted through the air filter orthe measuring tube is measured by a hot-filmair-mass meter. Measurement is very preciseand takes into account the pulsations and re-verse flows caused by the opening and closingof the engine’s intake and exhaust valves. In-take-air temperature changes have no effectupon measuring accuracy.

Design and constructionThe housing of the HFM5 hot-film air-massmeter (Fig. 1, Pos. 5) projects into a measur-ing tube (2) which, depending upon the en-gine's air-mass requirements, can have a va-riety of diameters (for 370...970 kg/h). This

tube is installed in the intake tract down-stream from the air filter. Plug-in versionsare also available which are installed insidethe air filter.

The most important components in thesensor are the sensor element (4), situated inthe air intake (8), and the integrated evalua-tion electronics (3).

Vapor-deposition is used to apply the sen-sor-element components to a semiconduc-tor substrate, and the evaluation-electronics(hybrid circuit) components to a ceramicsubstrate. This principle permits a verycompact design. The evaluation electronicsare connected to the ECU through the plug-in connection (1). The partial-flow measur-ing tube (6) is shaped so that the air flowspast the sensor element smoothly (withoutwhirl effects) and back into the measuringtube via the air outlet (7). This method en-sures efficient sensor operation even in caseof extreme pulsation, and in addition to for-ward flow, reverse flows are also detected(Fig. 2).

Operating conceptThe hot-film air-mass meter is a “thermalsensor” and operates according to the fol-lowing principle:

A micromechanical sensor diaphragm (Fig.3, Pos. 5) on the sensor element (3) is heatedby a central heating resistor and held at aconstant temperature. The temperaturedrops sharply on each side of this controlledheated zone (4).

The temperature distribution on the di-aphragm is registered by two temperature-dependent resistors which are attached up-stream and downstream of the heating resis-tor so as to be symmetrical to it (measuringpoints M1, M2). Without the flow of incom-ing air, the temperature characteristic (1) isthe same on each side of the heated zone (T1 = T2).

34 Sensors Hot-film air-mass meter HFM5

Figure 11 Electrical plug-in

connection2 Measuring tube or

air-filter housing wall3 Evaluation electron-

ics (hybrid circuit)4 Sensor element5 Sensor housing6 Partial-flow measur-

ing tube7 Air outlet for the par-

tial air flow QM

8 Intake for partial airflow QM

7

8

2

1

5

4

6

3

1 cm

QM

Hot-film air-mass meter HFM51

æU

MK

1713

-1Y

Robert Bosch GmbH

As soon as air flows over the sensor element,the uniform temperature distribution at thediaphragm changes (2). On the intake side,the temperature characteristic is steepersince the incoming air flowing past this areacools it off. Initially, on the opposite side(the side nearest to the engine), the sensorelement cools off. The air heated by theheater element then heats up the sensor ele-ment. The change in temperature distribu-tion leads to a temperature differential (∆T)between the measuring points M1 and M2.

The heat dissipated to the air, and thereforethe temperature characteristic at the sensorelement is a function of the air mass flow.The temperature differential is a measure ofthe air mass flow, and is independent of theabsolute temperature of the air flowing past.Apart from this, the temperature differentialis directional, which means that the air-massmeter not only registers the mass of the in-coming air but also its direction.

Due to its very thin micromechanical di-aphragm, the sensor has a highly dynamicresponse (<15 ms), a point which is of par-ticular importance when the incoming air isfluctuating heavily.

The resistance differential at the measur-ing points M1 and M2 is converted by theevaluation electronics integrated in the sen-sor into an analog signal of 0...5 V which issuitable for processing by the ECU. Usingthe sensor characteristic (Fig. 2) pro-grammed into the ECU, the measured volt-age is converted into a value representing theair mass flow [kg/h].

The shape of the characteristic curve is suchthat the diagnosis facility incorporated inthe ECU can detect such malfunctions as anopen-circuit line. A temperature sensor forauxiliary functions can also be integrated inthe HFM5. It is located on the sensor ele-ment upstream of the heated zone, and isnot required for measuring the air mass.

For applications on specific vehicles, sup-plementary functions such as improved sep-aration of water and contamination are pro-

vided for (inner measuring tube and protec-tive grid).

Sensors Hot-film air-mass meter HFM5 35

Figure 31 Temperature profile

without air flowacross sensor ele-ment

2 Temperature profilewith air flow acrosssensor element

3 Sensor element4 Heated zone5 Sensor diaphragm6 Measuring tube with

air-mass meter7 Intake-air flowM1, M2 measuring pointsT1, T2 Temperature val-

ues at the mea-suring points M1 and M2

∆T Temperature differ-ential

T2

T1

T

1

2

∆

T

0

35

4

7

76

T1 = T2

M2

M1

Hot-film air-mass meter: Measuring principle3

æU

MK

1652

Y

00

200 400 kg/h 600

5

6

4

3

2

1

VO

utpu

t vol

tage

Air-mass flow

Reverse flow

Forward flow

Output voltage of the hot-film air-mass meter as afunction of the partial air mass flowing past it

2

æU

MK

1691

E

Robert Bosch GmbH

Planar broad-band Lambdaoxygen sensor LSU4ApplicationAs its name implies, the broad-bandLambda sensor is used across a very exten-sive range to determine the oxygen concen-tration in the exhaust gas. The figures pro-vided by the sensor are an indication of theair-fuel (A/F) ratio in the engine’s combus-tion chamber. The excess-air factor λ is usedwhen defining the A/F ratio. The broad-band Lambda sensor is capable of makingprecise measurements not only at the “stoi-chiometric” point λ = 1, but also in the leanrange (λ > 1) and the rich range (λ < 1). Inthe range from 0.7 < λ < ∞ (∞ = air with21 % O2) these sensors generate an unmis-takable, clear electrical signal (Fig. 2).

These characteristics enable the broad-bandLambda sensor to be used not only in en-gine-management systems with two-stepcontrol (λ = 1), but also in control conceptswith rich and lean air-fuel (A/F) mixtures.This type of Lambda sensor is also suitablefor the Lambda closed-loop control usedwith lean-burn concepts on gasoline en-gines, as well as for diesel engines, gaseous-fuel engines and gas-powered central heatersand water heaters (this wide range of appli-

cations led to the designation LSU: LambdaSensor Universal (taken from the German),in other words Universal Lambda Sensor).The sensor projects into the exhaust pipeand registers the exhaust-gas flow from allcylinders. In a number of systems, severalLambda sensors are installed for evengreater accuracy. Here, for instance, they arefitted upstream and downstream of the cat-alytic converter as well as in the individualexhaust tracts (cylinder banks).

Design and constructionThe LSU4 broad-band Lambda sensor (Fig.3) is a planar dual-cell limit-current sensor.It features a zirconium-dioxide measuringcell (Fig. 1) which is a combination of aNernst concentration cell (sensor cell whichfunctions the same as a two-step Lambdasensor) and an oxygen pump cell for trans-porting the oxygen ions.

The oxygen pump cell (Fig. 1, Pos. 8) is soarranged with respect to the Nernst concen-tration cell (7) that there is a 10 ... 50 µm dif-fusion gap (6) between them which is con-nected to the exhaust gas through a gas-ac-cess passage (10). A porous diffusion barrier(11) serves to limit the flow of oxygen mol-ecules from the exhaust gas.

On the one side, the Nernst concentrationcell is connected to the atmosphere by a ref-

36 Sensors Planar broad-band Lambda oxygen sensors

Figure 11 Exhaust gas2 Exhaust pipe3 Heater4 Control electronics5 Reference cell with

reference-air pas-sage

6 Diffusion gap7 Nernst concentra-

tion cell8 Oxygen pump cell

with internal and ex-ternal pump elec-trode

9 Porous protectivelayer

10 Gas-access pas-sage

11 Porous diffusion bar-rier

IP Pump currentUP Pump voltageUH Heater voltageURef Reference voltage

(450 mV, corres-ponds to λ = 1)

US Sensor voltage

10

11URef

UH

US

UP

IP

2 3 4

5789

+–

6

1

Planar broad-band Lambda sensor (installation in the exhaust pipe and schematic design of the measuring cell)1

æU

MK

1260

-1Y

Robert Bosch GmbH

erence-air passage (5), and on the other, it isconnected to the exhaust gas in the diffusiongap.The sensor must have heated up to at least600 ... 800 °C before it generates a usable sig-nal. It is provided with an integral heater(3), so that the required temperature isreached quickly.

Operating conceptThe exhaust gas enters the actual measuringchamber (diffusion gap) of the Nernst con-centration cell through the pump cell’s gas-access passage. In order that the excess-airfactor λ can be adjusted in the diffusion gap,the Nernst concentration cell compares theexhaust gas in the diffusion gap with thesurrounding air in the reference-air passage.

The process as a whole functions as follows:By applying the pump voltage UP across

the pump cell’s platinum electrodes, oxygenfrom the exhaust gas can be pumpedthrough the diffusion barrier and into or outof the diffusion gap. With the help of theNernst concentration cell, an electronic cir-cuit in the ECU controls the voltage UP

across the pump cell in order that the com-position of the gas in the diffusion gap re-mains constant at λ = 1. If the exhaust gas islean, the pump cell pumps the oxygen to the

outside (positive pump current). On theother hand, if it is rich, due to the decompo-sition of CO2 and H2O at the exhaust-gaselectrode the oxygen is pumped from thesurrounding exhaust gas and into the diffu-sion gap (negative pump current). Oxygentransport is unnecessary at λ = 1 and pumpcurrent is zero. The pump current is propor-tional to the exhaust-gas oxygen concentra-tion and is thus a measure for the non-linearexcess-air factor λ (Fig. 2).

Sensors Planar broad-band Lambda oxygen sensors 37

Figure 31 Measuring cell

(combination ofNernst concentra-tion cell and oxygen-pump cell)

2 Double protectivetube

3 Seal ring4 Seal packing 5 Sensor housing6 Protective sleeve7 Contact holder8 Contact clip9 PTFE sleeve 10 PTFE shaped sleeve11 Five connecting

leads12 Seal ring

21 3 4 5 6 8 9 10 11 127

1 cm

LSU4 planar broad-band sensor3

æU

MK

1607

Y

Excess-air factor λ

Pum

p cu

rren

t Ip

1 20.7 3 4

-1

0

1

mA

-2

Pump current IP of a broad-band Lambda sensor asa function of the exhaust-gas excess-air factor λ

2

æU

MK

1266

-1E

Robert Bosch GmbH

Digital technology permits the implementa-tion of a wide range of open and closed-loop control functions in the vehicle. An ex-tensive array of influencing variables can betaken into account simultaneously so thatthe various systems can be operated at max-imum efficiency. The ECU (Electronic Con-trol Unit) receives the electrical signals fromthe sensors, evaluates them, and then calcu-lates the triggering signals for the actuators.The control program, the “software”, isstored in a special memory and imple-mented by a microcontroller.

Operating conditions

The ECU is subjected to very high demandswith respect to

Surrounding temperatures (during nor-mal operation from – 40 °C to between +60 °C and +125 °C)

Resistance to the effects of such materialsas oil and fuel etc.,

Surrounding dampness, Mechanical loading due for instance to

engine vibration.

Even when cranking the engine with a weakbattery (cold start), the ECU must operatejust as reliably as when operating voltage isat a maximum (fluctuations in on-boardvoltage supply).

To the same degree, very high demands ap-ply regarding EMC (ElectroMagnetic Com-patibility) and the limitation of HF interfer-ence-signal radiation.

More details on the severe standards apply-ing to the ECU are given in the box at theend of this Chapter.

Design and construction The pcb (printed-circuit board) with theelectronic components (Fig. 1) is installed ina metal case, and connected to the sensors,actuators, and power supply through amulti-pole plug-in connector (4). The high-power driver stages (6) for the direct trigger-ing of the actuators are integrated in theECU case in such a manner that excellentheat dissipation to the case is ensured.

When the ECU is mounted directly on theengine, an integrated heat sink is used todissipate the heat from the ECU case to thefuel which permanently flushes the ECU.This ECU cooler is only used on commercialvehicles. Compact, engine-mounted hybrid-technology ECUs are available for evenhigher levels of temperature loading.

The majority of the electronic compo-nents use SMD technology (SMD, Surface-Mounted Device). Conventional wiring isonly applied at some of the power-electron-ics components and at the plug-in connec-tions, so that a particularly space-saving andweight-saving design can be used.

Data processing

Input signalsIn their role as peripheral components, theactuators and the sensors represent the in-terface between the vehicle and the ECU inits role as the processing unit. The ECU re-ceives the electrical signals from the sensorsthrough the vehicle's wiring harness and theplug-in connection. These signals can be ofthe following type:

Analog input signalsWithin a given range, analog input signalscan assume practically any voltage value. Ex-amples of physical quantities which areavailable as analog measured values are in-take-air mass, battery voltage, intake-mani-fold and boost pressure, coolant and intake-air temperature. An analog/digital (A/D)converter in the ECU microcontroller con-

38 ECU Data processing

Electronic Control Unit (ECU)

Robert Bosch GmbH

1

2

3

4

3 cm

8

7

6

5

9

verts these values to the digital values usedby the microprocessor to perform its calcu-lations. The maximum resolution of thesesignals is in steps of 5 mV per bit (approx.1000 steps).

Digital input signalsDigital input signals only have two states.They are either “high” or “low” (logical 1and logical 0 respectively). Examples of digi-tal input signals are on/off switching signals,or digital sensor signals such as the rota-tional-speed pulses from a Hall generator ora magnetoresistive sensor. Such signals areprocessed directly by the microcontroller.

Pulse-shaped input signalsThe pulse-shaped signals from inductivesensors containing information on rota-tional speed and reference mark are condi-tioned in their own ECU stage. Here, spuri-ous pulses are suppressed and the pulse-shaped signals converted into digitalrectangular signals.

Signal conditioningProtective circuitry is used to limit the inputsignals to a permissible maximum voltage.By applying filtering techniques, the super-imposed interference signals are to a greatextent removed from the useful signalwhich, if necessary, is then amplified to thepermissible input-signal level for the micro-controller (0 ... 5 V).

Signal conditioning can take place com-pletely or partially in the sensor dependingupon the sensor’s level of integration.

Signal processingThe ECU is the system control center, and isresponsible for the functional sequences ofthe engine management (Fig. 2, next page).The closed and open-loop control functionsare executed in the microcontroller. The in-put signals from the sensors and the inter-faces to other systems serve as the inputvariables, and are subjected to a furtherplausibility check in the computer.

ECU Data processing 39

Figure 11 Atmospheric-pres-

sure sensor2 Switched-mode

power supply(SMPS) with volt-age stabilization

3 Low-power driverstage

4 Plug-in connection5 CAN interface and

general input andoutput circuitry (un-derneath the pcb,therefore not visiblehere)

6 High-power driverstages

7 ASIC for driver-stage triggering

8 Booster-voltagestore (Common Rail)

9 Microcontroller core

ECU: Design and construction1

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The output signals are calculated using theprogram.

Microcontroller The microcontroller is the ECU’s centralcomponent and controls its operative se-quence. Apart from the CPU (Central Pro-cessing Unit), the microcontroller containsnot only the input and output channels, butalso timer units, RAMs, ROMs, serial inter-faces, and further peripheral assemblies, allof which are integrated on a single micro-chip. Quartz-controlled timing is used forthe microcontroller.

Program and data memoryIn order to carry out the computations, themicrocontroller needs a program - the “soft-ware”. This is in the form of binary numeri-cal values arranged in data records andstored in a program memory.

These binary values are accessed by theCPU which interprets them as commandswhich it implements one after the other (re-fer also to the Chapter “Electronic open andclosed-loop control”).

This program is stored in a Read-OnlyMemory (ROM, EPROM, or Flash-EPROM)which also contains variant-specific data(individual data, characteristic curves, andmaps). This is non-variable data which can-not be changed during vehicle operation. ltis used to regulate the program’s open andclosed-loop control processes.The program memory can be integrated inthe microcontroller and, depending uponthe particular application, expanded by theaddition of a separate component (e.g. by anexternal EPROM or a Flash-EPROM).

ROMProgram memories can be in the form of aROM (Read Only Memory). This is a mem-ory whose contents have been defined per-manently during manufacture and there-after remain unalterable. The ROM installedin the microcontroller only has a restrictedmemory capacity, which means that an ad-ditional ROM is required in case of compli-cated applications.


Digital

Input signals:

Power supply

Actuators

Analog

Pulse-shaped

Interface to other systems

Diagnosis interface

EEPROMSignal

conditioning

Micro-controller

Driver stages

ECU

Mon

itorin

g m

odul

e

A /Dconverter

CAN

RAM

Flash-EPROM

Signal processing in the ECU2

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Robert Bosch GmbH

EPROMThe data on an EPROM (Erasable Program-mable ROM) can be erased by subjecting thedevice to UV light. Fresh data can then beentered using a programming unit.

The EPROM is usually in the form of aseparate component, and is accessed by theCPU through the Address/Data-Bus.

Flash-EPROM (FEPROM)The Flash-EPROM is often referred tomerely as a “Flash”. lt can be erased electri-cally so that it becomes possible to repro-gram the ECU in the service workshopswithout having to open it. In the process, theECU is connected to the reprogrammingunit through a serial interface.

lf the microcontroller is also equippedwith a ROM, this contains the programmingroutines for the Flash programming. Flash-EPROMs are available which, together withthe microcontroller, are integrated on a sin-gle microchip (as from EDC16).

Its decisive advantages have helped theFlash-EPROM to largely supersede the con-ventional EPROM.

Variable-data or main memorySuch a read/write memory is needed in or-der to store such variable data (variables) asthe computational and signal values.

RAMInstantaneous values are stored in the RAM(Random Access Memory) read/write mem-ory. If complex applications are involved, thememory capacity of the RAM incorporatedin the microcontroller is insufficient so thatan additional RAM module becomes neces-sary. lt is connected to the ECU through theAddress/Data-Bus.

When the ECU is switched off by turningthe “ignition” key, the RAM loses its com-plete stock of data (volatile memory).

EEPROM (also known as the E2PROM)As stated above, the RAM loses its informa-tion immediately its power supply is re-moved (e.g. when the "ignition switch " isturned to OFF). Data which must be re-tained, for instance the codes for the vehicleimmobilizer and the fault-store data, musttherefore be stored in a non-erasable (non-volatile) memory. The EEPROM is an elec-trically erasable EPROM in which (in con-trast to the Flash-EPROM) every singlememory location can be erased individually.lt has been designed for a large number ofwriting cycles, which means that the EEPROM can be used as a non-volatileread/write memory.

ASICThe ever-increasing complexity of ECUfunctions means that the computing powersof the standard microcontrollers availableon the market no longer suffice. The solu-tion here is to use so-called ASIC modules(Application Specific Integrated Circuit).These IC's are designed and produced in ac-cordance with data from the ECU develop-ment departments and, as well as beingequipped with an extra RAM for instance,and inputs and outputs, they can also gener-ate and transmit pwm signals (see “PWMsignals” below).

Monitoring moduleThe ECU is provided with a monitoringmodule. Using a “Question and Answer”cycle, the microcontroller and the monitor-ing module supervise each other, and assoon as a fault is detected one of them trig-gers appropriate back-up functions inde-pendent of the other.

ECU Data processing 41

Robert Bosch GmbH

Output signalsWith its output signals, the microcontrollertriggers driver stages which are usually pow-erful enough to operate the actuators di-rectly. The driver stages can also trigger spe-cific relays. The driver stages are proofagainst shorts to ground or battery voltage,as well as against destruction due to electri-cal or thermal overload. Such malfunctions,together with open-circuit lines or sensorfaults are identified by the driver-stage IC asan error and reported to the microcon-troller.

Switching signalsThese are used to switch the actuators onand off (for instance, for the engine fan).

PWM signalsDigital output signals can be in the form ofpwm (pulse-width modulated) signals.These are constant-frequency rectangularsignals with variable on-times (Fig. 3), andare used to shift the actuators to the desiredsetting (e.g. EGR valve, fan, heating element,boost-pressure actuator).

Communication within the ECU In order to be able to support the microcon-troller in its work, the peripheral compo-nents must communicate with it. This takesplace using an address/data bus which, forinstance, the microcomputer uses to issuethe RAM address whose contents are to beaccessed. The data bus is then used to trans-mit the relevant data. For former automo-tive applications, an 8-bit structure sufficedwhereby the data bus comprised 8 lineswhich together can transmit 256 values si-multaneously.The 16-bit address bus commonly usedwith such systems can access 65,536 ad-dresses. Presently, more complex systems de-mand 16 bits, or even 32 bits, for the databus. In order to save on pins at the compo-nents, the data and address buses can becombined in a multiplex system. That is,data and addresses are dispatched throughthe same lines but offset from each otherwith respect to time.

Serial interfaces with only a single dataline are used for data which need not betransmitted so quickly (e.g. data from thefault storage).

EoL programmingThe extensive variety of vehicle variants withdiffering control programs and data records,makes it imperative to have a system whichreduces the number of ECU types needed bya given manufacturer. To this end, the Flash-EPROM's complete memory area can beprogrammed at the end of production withthe program and the variant-specific datarecord (this is the so-called End-of-Line, orEoL, programming). A further possibility isto have a number of data variants available(e.g. gearbox variants), which can then beselected by special coding at the end of theline (EoL). This coding is stored in an EEPROM.


Figure 3a Fixed frequencyb Variable on-time

Time

Sig

nal v

olta

ge

a

b

a

b

PWM signals3

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Robert Bosch GmbH

ECU Severe demands on the ECU 43

Very severe demands are made on the ECU

Basically, the ECU in the vehicle functions thesame as a conventional PC. Data is enteredfrom which output signals are calculated. Theheart of the ECU is the printed-circuit board(pcb) with microcontroller using high-precisionmicroelectronic techniques. The automotiveECU though must fulfill a number of otherrequirements.

Real-time compatibility Systems for the engine and for road/traffic safe-ty demand very rapid response of the control,and the ECU must therefore be "real-time com-patible". This means that the control's reactionmust keep pace with the actual physicalprocess being controlled. lt must be certain thata real-time system responds within a fixed peri-od of time to the demands made upon it. Thisnecessitates appropriate computer architectureand very high computer power.

Integrated design and constructionThe equipment’s weight and the installationspace it requires inside the vehicle are becom-ing increasingly decisive. The following tech-nologies, and others, are used to make the ECUas small and light as possible:

Multilayer: The printed-circuit conductors arebetween 0.035 and 0.07 mm thick and are“stacked” on top of each other in layers.

SMD components are very small and flatand have no wire connections through holesin the pcb. They are soldered or glued to thepcb or hybrid substrate, hence SMD (Sur-face Mounted Devices).

ASIC: Specifically designed integrated com-ponent (Application-Specific Integrated Cir-cuit) which can combine a large number ofdifferent functions.

Operational reliabilityVery high levels of resistance to failure are pro-vided by integrated diagnosis and redundantmathematical processes (additional processes,usually running in parallel on other programpaths).

Environmental influencesNotwithstanding the wide range of environmen-tal influences to which it is subjected, the ECUmust always operate reliably.

Temperature: Depending upon the area ofapplication, the ECUs installed in vehiclesmust perform faultlessly during continualoperation at temperatures between –40°Cand +60...125°C. In fact, due to the heatradiated from the components, the tempera-ture at some areas of the substrate is consid-erably higher. The temperature changeinvolved in starting at cold temperatures andthen running up to hot operating tempera-tures is particularly severe.

EMC: The vehicle's electronics have to gothrough severe electromagnetic compatibilitytesting. That is, the ECU must remain com-pletely unaffected by electromagnetic distur-bances emanating from such sources as theignition, or radiated by radio transmitters andmobile telephones. Conversely, the ECUitself must not negatively affect other elec-tronic equipment.

Resistance to vibration: ECUs which aremounted on the engine must be able to with-stand vibrations of up to 30 g (that is, 30times the acceleration due to gravity).

Sealing and resistance to operating medi-ums: Depending upon installation position,the ECU must withstand damp, chemicals(e.g. oils), and salt fog.

The above factors and other requirements meanthat the Bosch development engineers are con-tinually faced by new challenges.

Hybrid substrate of an ECU

æU

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Robert Bosch GmbH

The most important assignment of the Elec-tronic Diesel Control (EDC) is the controlof the injected fuel quantity and the instantof injection. The “Common Rail” accumula-tor injection system also controls the injec-tion pressure. Furthermore, on all systems,the engine ECU also controls a number ofactuators. For all components to operate ef-fciently, it is imperative that the EDC func-tions be precisely matched to every vehicleand every engine (Fig. 1).

Open and closed-loop electronic controlIn both forms of control, one or more inputquantities influence one or more outputquantities

Open-loop controlWith open-loop control, the actuators aretriggered by the output signals which theECU has calculated using the input vari-ables, stipulated data, characteristic maps,and algorithms. The final results are notchecked (open control loop). This principleis used for instance for the glow-plug se-quence control.

Closed-loop controlOn the other hand, as its name implies,closed-loop control is characterized by aclosed control loop. Here, the actual value atthe output is continually checked against thedesired value, and as soon as a deviation isdetected this is corrected by a change in theactuator control. The advantage of closed-loop control lies in the fact that disturbancesfrom outside are detected and taken into ac-count. Closed-loop control is used for in-stance to control the engine’s idle speed.

In fact, therefore, the EDC Electronic Con-trol Unit (ECU) is really an “open andclosed-loop control unit”. The term ECU“Electronic Control Unit” has become sowidespread though, that it is still used eventhough the word “control” alone is not ex-plicit enough.

Data processing (DP)

The ECU processes the incoming signalsfrom the external sensors and limits them tothe permissible voltage level. A number ofthe incoming signals are also checked forplausibility.

Using these input data, together withstored characteristic curves, the micro-processor calculates the injection’s timingand its duration. This information is thenconverted to a signal characteristic which isaligned to the engine’s piston movements.This calculation program is termed the“ECU software”.

The required degree of accuracy togetherwith the diesel engine’s outstanding dy-namic response necessitate high-level com-puting power. The output signals are appliedto output stages which provide adequatepower for the actuators (for instance thehigh-pressure solenoid valves for fuel injec-tion, EGR positioner, or boost-pressure ac-tuator). Apart from this, a number of otherauxiliary-function components (e.g. glowrelay and air conditioner) are triggered.

Faulty signal characteristics are detected bythe output-stage diagnosis functions. Fur-thermore, signals are exchanged with othersystems in the vehicle via the interfaces. Theengine ECU monitors the complete injec-tion system within the framework of a safetyconcept.

44 Open and closed-loop electronic control Data processing (DP)

Open and closed-loop electronic control

Robert Bosch GmbH

Open and closed-loop electronic control Data processing (DP) 45

EDC ECU

Demands from the driver - Driver input,- Cruise Control (CC),- Exhaust brake ...

Exchange of data with other systems- Traction Control System (TCS),- Transmission-shift control,- Climate control ...

System for electronic cylinder-charge control- Supercharging,- Exhaust-gas recirculation (EGR).

Actuators- Electropneumatic transducer- Continuous-operation

braking system- Fans, blowers,- Glow control ...

Air

Fuel

Engine

Sensors and desired-value generators- Accelerator-pedal sensor,- Rotational-speed sensor,- Switches ...

Closed-loop control and triggering of the remaining actuators

CAN

Triggering of the fuel-injection components

- In-line injection pumps,- Distributor injection pumps,- Unit Injector / Unit Pump,- Common Rail high-pressure

pump and injectors,- Nozzles and nozzle holders.

Air control loopData and information flow

Fuel-injection components

Fuel control loop 1 (fuel-injection components)Fuel control loop 2 (engine)“Detour” by way of the driver

Closed-loop control of the fuel injection

Electronic Diesel Control (EDC): Basic sequence1

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1793

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Robert Bosch GmbH

Data exchange with othersystemsFuel-consumption signal The engine ECU (Fig. 1, Pos. 3) detects theengine fuel consumption and transmits thesignal via CAN to the instrument cluster, orto an independent on-board computer (6),where the driver is informed of the currentfuel consumption and/or the remainingrange with the fuel still in the tank. Oldersystems used pulse-width modulation(pwm) for the fuel-consumption signal.

Starter controlThe starter (8) can be triggered from the en-gine ECU. This ensures that the driver can-not operate the starter with the engine al-ready running. The starter only turns longenough for the engine to have reliablyreached self-sustaining speed. This functionleads to a lighter and thus lower-pricedstarter.

Glow control unitThe glow control unit (GZS, 5) receives in-formation from the engine ECU on whenglow is to start and for how long. It thentriggers the glow plugs accordingly andmonitors the glow process, as well as report-ing back to the ECU on any faults (diagnosisfunction). The pre-glow indicator lamp isusually triggered from the ECU.

Electronic immobilizerTo prevent unauthorized starting and drive-off, the engine cannot be started before aspecial immobilizer (7) ECU removes theblock from the engine ECU.

Either by remote control or by means ofthe glow-plug and starter switch (“Ignition”key), the driver can signal the immobilizerECU that he/she is authorised to use the ve-hicle. The immobilizer ECU then removesthe block on the engine ECU so that enginestart and normal operation become possible.

46 Open and closed-loop electronic control Data exchange with other systems

Figure 11 ESP ECU

(with ABS and TCS)2 ECU for transmis-

sion-shift control3 Engine ECU (EDC)4 A/C ECU5 Glow control unit6 Instrument cluster

with on-board com-puter

7 Immobilizer ECU8 Starter9 Alternator10 A/C compressor

1 2 3 4

9

5

6

78

10

Possible components involved in the exchange of data with the Electronic Diesel Control (EDC)1

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Robert Bosch GmbH

External torque interventionIn the case of external torque intervention,the injected fuel quantity is influenced byanother (external) ECU (for instance theECU for transmission shift, or for TCS).This informs the engine ECU whether theengine torque is to be changed, and if so, byhow much (this defines the injected fuelquantity).

Alternator controlBy means of a standard serial interface, theEDC can remotely control and remotelymonitor the alternator (9). The regulatorvoltage can be controlled, just the same asthe complete alternator assembly can beswitched off. In case of a weak battery for in-stance, the alternator’s charging characteris-tic can be improved by increasing the idlespeed. It is also possible to perform simplealternator diagnosis through this interface.

Air conditionerIn order to maintain comfortable tempera-tures inside the vehicle when it is very hotoutside, the air conditioner (A/C) coolsdown the air with the help of a refrigeratingcompressor (10). Depending upon the en-gine and the operating conditions, the A/Ccompressor can need as much as 30% of theengine’s output power.

Immediately the driver hits the acceleratorpedal (in other words he/she wishes maxi-mum torque), the compressor can beswitched off briefly by the engine ECU, sothat all the engine’s power is available at thewheels. Since the compressor is onlyswitched off very briefly, this has no notice-able effect upon the passenger-compartmenttemperature.

Open and closed-loop electronic control Data exchange with other systems 47

Where does the word “Electronics” come from?

This term really originates from the ancientGreeks. They used the word electron for "am-ber" whose forces of attraction for wool andsimilar materials had already been describedby Thales von Milet 2,500 years ago.

The term “electronics” originates directly fromthe word “electrons”. The electrons, andtherefore electronics as such, are extremelyfast due to their very small mass and theirelectrical charge.

The mass of an electron has as little effecton a gram of any given substance as a 5 gramweight has on the total mass of our earth.

Incidentally, the word “electronics” is a prod-uct of the 20th century. There is no evidenceavailable as to when the word was used forthe first time. Sir John Ambrose Fleming, oneof the inventors of the electron tube couldhave used it around 1902.

The first “Electronic Engineer” though goesback to the 19th century. He was listed in the1888 Edition of a form of “Who’s Who”, pub-lished during the reign of Queen Victoria. Theofficial title was “Kelly’s Handbook of Titled,Landed and Official Classes”. The ElectronicEngineer is to be found under the heading“Royal Warrant Holders”, that is the list of per-sons who had been awarded a Royal Warrant.

And what was this Electronic Engineer’sjob? He was responsible for the correct func-tiong and cleanliness of the gas lamps atcourt. And why did he have such a splendid ti-tle ? Because he knew that “Electrons” in an-cient Greece stood for glitter, shine, andsparkle.

Source:“Basic Electronic Terms” (“Grundbegriffe derElektronik”) – Bosch publication (reprint fromthe “Bosch Zünder” (Bosch Company News-paper))..

Robert Bosch GmbH

Fuel-injection controlAn overview of the various control func-tions which are possible with the EDC con-trol units is given in Table 1. Fig. 1 oppositeshows the sequence of fuel-injection calcula-tions with all functions, a number of whichare special options. These can be activated inthe ECU by the workshop when retrofitequipment is installed.

In order that the engine can run with opti-mal combustion under all operating condi-tions, the ECU calculates exactly the rightinjected fuel quantity for all conditions.Here, a number of parameters must be takeninto account. On a number of solenoid-valve-controlled distributor pumps, the sol-enoid valves for injected fuel quantity andstart of injection are triggered by a separatepump ECU (PSG).

48 Open and closed-loop electronic control Diesel-injection control

Table 11 Only control-sleeve

in-line injectionpumps

2 Passenger cars only3 Commercial vehicles

only

EDC variants for road vehicles: Overview of functions1

Fuel-injection system In-line injection

pumps

PE

Helix-controlled

distributor

injection pumps

VE-EDC

Solenoid-valve-

controlled

distributor

injection pumps

VE-M, VR-M

Unit Injector

System and

Unit Pump

System

UIS, UPS

Common Rail

System

CR

Function

Injected-fuel-quantity limitation

External torque intervention 3

Vehicle-speed limitation 3

Vehicle-speed control

(Cruise Control)

Altitude compensation

Boost-pressure control

Idle-speed control

Intermediate-speed control 3

Active surge damping 2

BIP control – – –

Intake-tract switch-off – – 2

Electronic immobilizer 2

Controlled pilot injection – – 2

Glow control 2 2

A/C switch-off 2

Auxiliary coolant heating 2 –

Cylinder-balance control 2

Control of injected fuel

quantity compensation 2 –

Fan (blower) triggering –

EGR control 2 2

Start-of-injection control

with sensor 1, 3 – –

Cylinder shutoff – – 3 3 3

Robert Bosch GmbH

Open and closed-loop electronic control Diesel-injection control 49

Accelerator-pedal sensor(driver input)

Inputs

Calculations

Triggering

Vehicle-speed controller(Cruise Control),

vehicle-speed limiter

Inputs from other systems

(e.g. ABS, TCS, ESP)

CAN

Start

Switch

Drive mode

Start quantity

Fuel-quantity metering(pump map)

Timing-device triggering

Solenoid-valve triggering

Pump ECU triggering

Control of start of injection, and/or start of delivery

Selection of the required injected fuel quantity

External torque intervention

Injected-fuel-quantity limit

+/-

+

+

Idle-speed controller, or controller for injected-fuel-

quantity compensation

Active surge damperSmooth-running controller

Calculation of fuel-injection process in the ECU1

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Robert Bosch GmbH

Start quantityFor starting, the injected fuel quantity is cal-culated as a function of coolant temperatureand cranking speed. Start-quantity signalsare generated from the moment the startingswitch is turned (Fig. 1, switch in “Start” po-sition) until a given minimum engine speedis reached.The driver cannot influence the start quan-tity.

Drive modeWhen the vehicle is being driven normally,the injected fuel quantity is a function of theaccelerator-pedal setting (accelerator-pedalsensor) and of the engine speed (Fig. 1,switch in “Drive” position). Calculation de-pends upon maps which also take other in-fluences into account (e.g. fuel and intake-air temperature). This permits best-possiblealignment of the engine’s output to the dri-ver’s wishes.

Idle-speed controlWhen the accelerator is not depressed, it isthe job of the idle-speed control to ensurethat a given idle speed is maintained. Thiscan vary depending upon the engine’s par-ticular operating mode. For instance, withthe engine cold the idle speed is usually sethigher than when it is warm. There are fur-ther instances when the idle speed is heldsomewhat higher. For instance when the ve-hicle‘s electrical-system voltage is too low,when the air-conditioner is switched on, orwhen the vehicle is rolling freely. When thevehicle is driven in stop-and-go traffic, to-gether with stops at traffic lights, the engineruns a lot of the time at idle. Considerationsconcerning emissions and fuel consumptiondictate therefore that idle speed should bekept as low as possible. This of course is adisadvantage with respect to smooth-run-ning and pull-away.

When adjusting the stipulated idle speed,the idle-speed control must cope with heav-ily fluctuating requirements. The inputpower needed by the engine-driven auxiliaryequipment varies extensively.

At low electrical-system voltages for in-stance, the alternator consumes far morepower than it does when the voltages arehigher. In addition, the power demandsfrom the A/C compressor, the steeringpump, and the high-pressure generation forthe diesel injection system must all be takeninto account. Added to these external loadmoments is the engine’s internal frictiontorque which is highly dependent upon en-gine temperature, and which must also becompensated for by the idle-speed control.

In order to regulate the desired idle speed,the controller continues to adapt the in-jected fuel quantity until the actual enginespeed corresponds to the desired idle speed.

Maximum-rpm controlThe maximum-rpm control ensures that theengine does not run at excessive speeds. Toavoid damage to the engine, the enginemanufacturer stipulates a permissible maxi-mum speed which may only be exceeded fora very brief period.

Above the rated-power operating point, themaximum-rpm controller reduces the in-jected fuel quantity continually, until justabove the maximum-rpm point fuel-injec-tion stops completely. In order to preventengine surge, a ramp function is used to en-sure that the drop off in fuel injection is nottoo abrupt. This becomes all the more diffi-cult the nearer the rated-power point is tothe maximum-rpm point.


Robert Bosch GmbH

Intermediate-speed controlThe intermediate-speed control is used onlyfor trucks and small commercial vehicleswith auxiliary power take-offs (e.g. for craneoperation) or for special vehicles (e.g. am-bulances with electrical power generator).With the control in operation, the engine isregulated to a load-independent intermedi-ate speed. With the vehicle stationary, the in-termediate-speed control is activated via theCruise Control operator panel.

A fixed rotational speed can be called upfrom the data store at the push of a button.In addition, this operator panel can be usedfor preselecting specific engine speeds. Theintermediate-speed control is also appliedon passenger cars with automated gearboxes(e.g. Tiptronic) to control the engine speedduring gearshifts.

Vehicle-speed controller (Cruise Control)The Cruise Control is taken into operationwhen the vehicle is to be driven at a constantspeed. It controls the vehicle speed to thatselected by the driver without him/her need-ing to press the accelerator pedal. The drivercan input the required speed either throughan operating lever or through the steering-wheel keypad. The injected fuel quantity iseither increased or decreased until the de-sired (set) speed is reached.

On some Cruise Control applications, thevehicle can be accelerated beyond the cur-rent set speed by pressing the acceleratorpedal. As soon as the accelerator pedal is re-leased again, the Cruise Control regulatesthe speed back down to the previously setspeed.

If the driver depresses the clutch or brakepedal while the Cruise Control is activated,the control is terminated. On some applica-tions, the control can be switched off by theaccelerator pedal.

If the Cruise Control has been switched off,the driver only needs to shift the lever to thereactivate setting in order to again select thelast speed which had been set.

The operator’s controls can also be used fora step-by-step change of the selected speed.

Vehicle-speed limiterVariable limitationThe vehicle-speed limiter limits the vehicle’smaximum speed to a set value even if the ac-celerator is depressed further. On very quietvehicles, in which the engine can hardly beheard, this is a particular help for the driverwho can then no longer exceed speed limitsinadvertently.

The vehicle-speed limiter keeps the injected-fuel quantity down to a limit which is in linewith the selected maximum speed. It can beswitched off by the lever or by the kick-down switch. In order to again select the lastspeed which had been set, the driver onlyneeds to shift the lever to the reactivate set-ting. The operator’s controls can also beused for a step-by-step change of the se-lected speed.

Fixed limitationIn a number of countries, fixed maximumspeeds are mandatory for certain classes ofvehicles (for instance, for heavy trucks). Thevehicle manufacturers also limit the maxi-mum speeds of their heavy vehicles by in-stalling a fixed speed limit which cannot beswitched off.

In the case of special vehicles, the driver canalso select from a range of fixed, pro-grammed speed limits (for instance, whenthere are workers on the garbage truck’s rearplatform).


Robert Bosch GmbH

Active surge dampingSudden engine-torque changes excite the ve-hicle’s drivetrain, which as a result goes intosurge oscillation. These oscillations are reg-istered by the vehicle’s occupants as unpleas-ant periodic changes in acceleration (Fig. 2,a). It it the job of the active surge damper toreduce them (b). Two separate methods areused:

In case of sudden changes in the torquerequired by the driver (through the accel-erator pedal), a precisely matched filterfunction reduces the drivetrain excitation(1).

The speed signals are used to detect drive-train oscillations which are then dampedby an active control. In order to counter-act the drivetrain oscillations (2), the ac-tive control reduces the injected fuelquantity when rotational speed increases,and increases it when speed drops.

Smooth-running control (SRC)/Controlof injected-fuel-quantity compensation(MAR)Presuming the same duration of injection,not all of the engine’s cylinders generate thesame torque. This can be due to differencesin cylinder-head sealing, as well as differ-ences in cylinder friction and in the hy-draulic injection components. These differ-ences in torque output lead to rough enginerunning and an increase in toxic emissions.

The smooth-running control (SRC), or thecontrol of injected-fuel-quantity compensa-tion (MAR), use the resulting rotational-speed fluctuations when detecting suchtorque fluctuations. By selected variation ofthe injected fuel quantities at the cylindersconcerned, they compensate for the torquevariation. Here, the rotational speed at agiven cylinder after injection is compared toa mean speed. If the particular cylinder’sspeed is too low the injected fuel quantity isincreased, and if it is too high the fuel quan-tity is reduced (Fig. 3).


Figure 2a Without active surge

damperb With active surge

damper1 Filter function2 Active correction

Time t

Inje

cted

fuel

qua

ntity

Engi

ne s

peed

n

800

20

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Actual speed:Cyl. 1 Cyl. 2 Cyl. 3 Cyl. 4800min-1 790 820 790

Injected fuel quantity

= + +

Desired (setpoint) speed:

Smooth-running control (SRC): Example3æ

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The smooth-running control is a comfortfunction, the primary object of which is toensure that the engine runs smoothly in thevicinity of idle. The injected-fuel-quantitycompensation function is aimed at not onlyimproving comfort at idle but also at reduc-ing the emissions in the medium speedranges by ensuring identical injected fuelquantities for all cylinders. On commercialvehicles, the smooth-running control is alsoknown as the AZG (adaptive cylinder equal-ization).

Injected-fuel-quantity limitThere are a number of reasons why the fuelquantity actually wished for by the driver, orthat which is physically possible, should notalways be injected. The injection of such fuelquantities could have the following effects:

Excessive emissions, Excessive soot, Mechanical overloading due to high

torque or excessive engine speed, Thermal overloading due to excessive

temperatures of the exhaust gas, coolant,oil, or turbocharger,

Thermal overloading of the solenoidvalves as a result of them being triggeredtoo long.

To avoid these negative effects, a number ofinput variables (for instance intake-airquantity, engine speed, and coolant temper-ature) are used in generating this limitationfigure. The result is that the maximum in-jected fuel quantity is limited and with it themaximum torque.

Engine-brake functionWhen a truck’s engine brake is applied, theinjected fuel quantity is either reduced tozero or the idle fuel quantity is injected. Forthis purpose, the ECU registers the setting ofthe engine-brake switch.

Altitude compensationAtmospheric pressure drops along with in-creasing altitude so that the cylinder ischarged with less combustion air. Thismeans that the injected fuel quantity mustbe reduced accordingly, otherwise excessivesoot will be emitted.

In order that the injected fuel quantity canbe reduced at high altitudes, the atmos-pheric pressure is measured by the ambient-pressure sensor in the ECU. Atmosphericpressure also has an effect upon boost-pres-sure control and torque limitation.

Cylinder shutoffIf less torque is required at high enginespeeds, very little fuel must be injected. Asan alternative, cylinder shutoff can be ap-plied for torque reduction. Here, half of theinjectors are switched off (commercial-vehi-cle UIS, UPS and CRS). The remaining in-jectors then inject correspondingly morefuel which can be metered with even higherprecision.

When the injectors are switched on andoff, special software algorithms ensuresmooth transitions without noticeabletorque changes.

Start-of-injection controlThe start of injection has a critical effect onpower output, fuel consumption, noise, andemissions. The desired value for start of in-jection depends on engine speed and in-jected fuel quantity, and it is stored in theECU in special maps. Adaptation is possibleas a function of coolant temperature andambient pressure.


Robert Bosch GmbH

Tolerances in manufacture and in the pumpmounting on the engine, together withchanges in the solenoid valve during its life-time, can lead to slight differences in the sol-enoid-valve switching times which in turnlead to different starts of injection. The re-sponse behaviour of the nozzle-and-holderassembly also changes over the course oftime. Fuel density and temperature also havean effect upon start of injection. This mustbe compensated for by some form of controlstrategy in order to stay within the pre-scribed emissions limits. The followingclosed-loop controls are employed (Table 2):

The start-of-injection control is not neededwith the Common Rail System, since thehigh-voltage triggering used in the CRS per-mits highly reproducible starts of injection.

Closed-loop control using the needle-mo-tion sensorThe inductive needle-motion sensor is fittedin an injection nozzle (reference nozzle, usu-ally cylinder 1). When the needle opens (andcloses) the sensor transmits a pulse (Fig. 4).The needle-opening signal is used by theECU as confirmation of the start of injec-tion. This means that inside a closed controlloop the start of injection can be preciselyaligned to the desired value for the particu-lar operating point.

The needle-motion sensor’s untreated signalis amplified and interference-suppressed be-fore being converted to precision square-wave pulses which can be used to mark thestart of injection for a reference cylinder.

The ECU controls the actuator mecha-nism for the start of injection (for in-linepumps the solenoid actuator, and for dis-tributor pumps the timing-device solenoidvalve) so that the actual start of injection al-ways corresponds to the desired/setpointstart of injection.

The start-of-injection signal can only beevaluated when fuel is being injected andwhen the engine speed is stable. Duringstarting and overrun (no fuel injection), theneedle-motion sensor cannot provide a sig-nal which is good enough for evaluation.This means that the start-of-injection con-trol loop cannot be closed because there isno signal available confirming the start-of-injection.


Figure 41 Untreated signal from

the needle-motionsensor (NBF),

2 Signal derived fromthe NBF signal,

3 Untreated signal fromthe inductive engine-speed sensor

4 Signal derived fromuntreated engine-speed signal,

5 Evaluated start-of-in-jection signal

1

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5Time t

Conditioning of the signal from the needle-motion sensor

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Injection system

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In-line injection pumps – –Helix-controlled distributor pumps – –Solenoid-valve-controlleddistributor pumps –Common Rail – – –Unit Injector/Unit Pump – –

Start-of-injection control2

Table 2

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Robert Bosch GmbH

1

2 3

4

5

In-line injection pumpsOn in-line pumps, a special digital currentcontroller improves the control’s accuracyand dynamic response by aligning the cur-rent to the start-of-injection controller’s set-point value practically without any delay atall.

In order to ensure start-of-injection accu-racy in open-loop-controlled operation too,the start-of-delivery solenoid in the control-sleeve actuator mechanism is calibrated tocompensate for the effects of tolerances. Thecurrent controller compensates for the ef-fects of the temperature-dependent solen-oid-winding resistance. All these measuresensure that the setpoint value for current asderived from the start map leads to the cor-rect stroke of the start-of-delivery solenoidand to the correct start of injection.

Start-of-delivery control using the incre-mental angle/time signal (IWZ)On the solenoid-valve-controlled distributorpumps (VP30, VP44), the start of injectionis also very accurate even without the help ofa needle-motion sensor. This high level ofaccuracy was achieved by applying position-ing control to the timing device inside thedistributor pump. This form of closed-loopcontrol serves to control the start of deliveryand is referred to as start-of-delivery con-trol. Start of delivery and start of injectionhave a certain relationship to each other andthis is stored in the so-called wave-propaga-tion-time map in the engine ECU.

The signal from the crankshaft-speed sensorand the signal from the incrementalangle/time system (IWZ signal) inside thepump, are used as the input variables for thetiming-device positioning control.

The IWZ signal is generated inside thepump by the rotational-speed or angle-of-rotation sensor (1) on the trigger wheel (2)attached to the driveshaft. The sensor shiftsalong with the timing device (4) which,when it changes position, also changes theposition of the tooth gap (3) relative to the

TDC pulse of the crankshaft-speed sensor.The angle between the tooth gap, or the syn-chronization pulse generated by the toothgap, and the TDC pulse is continually regis-tered by the pump ECU and compared withthe stored reference value. The difference be-tween the two angles represents the timingdevice’s actual position, and this is continu-ally compared with its setpoint/desired posi-tion. If the timing-device position deviates,the triggering signal for the timing-devicesolenoid valve is changed until actual andsetpoint position coincide with each other.

Since all cylinders are taken into account,the advantage of this form of start-of-deliv-ery control lies in the system’s rapid re-sponse. It has a further advantage in that italso functions during overrun when no fuelinjection takes place which means that thetiming device can be preset for when thenext injection event occurs.

In case even more severe demands aremade on the accuracy of the start of injec-tion, the start-of-delivery control can havean optional start-of-injection control withneedle-motion sensor superimposed uponit.


Figure 51 Rotational-

speed/angle-of-rota-tion sensor insidethe injection pump

2 Trigger wheel3 Trigger-wheel tooth

gap4 Shift due to timing

device5 Electrical plug-in

connection

Rotational-speed/Angle-of-rotation sensor for theIWZ signal

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BIP controlBIP control is used with the solenoid-valve-controlled Unit Injector System (UIS) andUnit Pump System (UPS). The start of de-livery – or BIP (Begin of Injection Period) –is defined as the instant in time in which thesolenoid closes. As from this point, pressurebuildup starts in the pump high-pressurechamber. The nozzle opens as soon as thenozzle-opening pressure is exceeded, and in-jection can commence (start of injection).Fuel metering takes place between start ofdelivery and end of solenoid-valve trigger-ing. This period is termed the delivery pe-riod.

Since there is a direct connection betweenthe start of delivery and the start of injec-tion, all that is needed for the precise controlof the start of injection is information onthe instant of the start of delivery.

So as to avoid having to apply additionalsensor technology (for instance, a needle-motion sensor), electronic evaluation of thesolenoid-valve current is used in detectingthe start of delivery. Around the expected in-stant of closing of the solenoid valve, con-stant-voltage triggering is used (BIP win-dow, Fig. 6, Pos. 1). The inductive effectswhen the solenoid valve closes result in thecurve having a specific characteristic whichis registered and evaluated by the ECU. Foreach injection event, the deviation of the so-lenoid-valve closing point from the theoreti-cal setpoint is registered and stored, and ap-plied for the following injection sequence asa compensation value.

If the BIP signal should fail, the ECUchanges over to open-loop control.

ShutoffThe “auto-ignition”principle of operationmeans that in order to stop the diesel engineit is only necessary to cut off its supply of fuel.With EDC (Electronic Diesel Control), theengine is switched off due to the ECU out-putting the signal “Fuel quantity zero”(thatis, the solenoid valves are no longer triggered,or the control rack is moved back to the zero-delivery setting).

There are also a number of redundant (sup-plementary) shutoff paths (for instance, theelectrical shutoff valve (ELAB) on the port-and-helix controlled distributor pumps).

The UIS and UPS are intrinsically safe, andthe worst thing that can happen is that onesingle unwanted injection takes place. Here,therefore, supplementary shutoff paths arenot needed.


Firgure 61 BIP window2 BIP signal3 Level of pickup cur-

rent4 Holding-current level

Time

1

2

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t

Sol

enoi

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BIP detection6æ

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Lambda closed-loop-controlfor passenger-car diesel en-ginesApplicationsThe lawmakers are continually increasingthe severity of the legislation governing theexhaust-emission limit values for diesel en-gines. Apart from the measures taken to op-timize the engine’s internal combustion, theopen and closed-loop control of those func-tions which are relevant with regard to theexhaust emissions are continuing to gain inimportance. The introduction of theLambda closed-loop control opens up im-mense potential for reducing the diesel en-gine’s exhaust emissions.

The broad-band Lambda oxygen sensor inthe exhaust pipe (Fig. 1, Pos. 7) measures theresidual oxygen in the exhaust gas. This is anindicator for the A/F ratio (excess-air-factorLambda l). A high level of signal accuracy isensured throughout the sensor’s service lifeby adapting the Lambda-sensor signal dur-ing actual operations. The Lambda-sensorsignal is used as the basis for a number ofLambda functions which will be describedin more detail in the following.

A Lambda closed-loop control circuit is im-perative for the regeneration of NOX accu-mulator-type catalytic converters.

The Lambda closed-loop-control is suitable

Open and closed-loop electronic control Lambda closed-loop control 57

Figure 11 Diesel engine2 Diesel injection com-

ponent (here Com-mon Rail injector)

3 Throttle valve4 Hot-film air-mass

meter5 Exhaust-gas tur-

bocharger (here,VTG version)

6 Engine ECU forEDC

7 Broad-band Lambdaoxygen sensor

8 EGR valve

2

3

4

5

7

8

6

λ-Control

1

System overview of Lambda closed-loop control for passenger-car engines (Example)1

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for all passenger-car diesel injection systemscontrolled by the EDC16 generation.

Basic functions

Pressure compensationThe untreated Lambda-sensor signal is afunction of the oxygen concentration in theexhaust gas and of the exhaust-gas pressureat the sensor’s installation point. The influ-ence of the pressure on the sensor signalmust therefore be compensated for.

The pressure-compensation function incor-porates two maps, one for the exhaust-gaspressure and one for the pressure-depen-dence of the lambda sensor’s output signal.These two maps are used for the correctionof the sensors output signal with referenceto the particular operating point.

AdaptationIn the overrun (trailing throttle) mode, the

Lambda sensor’s adaptation takes into ac-count the deviation of the measured oxygenconcentration from the fresh-air oxygen con-centration (approx. 21%). As a result, the sys-tem “learns” a correction value which at everyengine operating point is used to correct themeasured oxygen concentration. This leads toa precise, drift-compensated Lambda outputsignal throughout the sensor’s service life.

Lambda-based EGR control

Regarding emissions, compared with theconventional EGR method based on airmass, using the Lambda oxygen sensor tomeasure the residual oxygen in the exhaustgas permits a tighter tolerance range for thecomplete vehicle fleet. In the MNEFZ (mod-ified new European driving cycle) exhaust-gas test, therefore, from the exhaust-emis-sions viewpoint this equates to an improve-ment of 10...20% with regard to the fleet as awhole.

58 Open and closed-loop electronic control Lambda closed-loop control

Engine-rpm sensor

Lambda oxygen sensor

+

+

-

+-

Hot-film air-mass meter

EGR valve

Desired injected fuel quantity

Calculation of the actual air mass using Lambda

Lambda controller

Air-mass controller

Desired air mass

ECUEngine

Desired characteristic map for EGR

Exhaust-gas recirculation using Lamda closed-loop control (EGR cascade control): Principle of operation2

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Lambda control loop Further sensor signals

Air-mass control loop

Robert Bosch GmbH

Cascade controlWith the cascade control (Fig. 2), the con-ventional air-mass control loop as used inpresent-day series production has a Lambdacontrol loop superimposed upon it (refer tothe section “Control and triggering of theremaining actuators”).

The dynamic response is excellent when air-mass control is used (that is, the air-massmeter responds far more quickly). The ex-ternal Lambda closed-loop control circuitimproves the EGR-system accuracy.

The actual air-mass figure is calculated fromthe Lambda oxygen sensor signal and fromthe desired value for the injected fuel quan-tity. The system deviation between the cal-culated air mass and the desired air masstaken from the EGR desired-value character-istic map, is compensated for by the Lambdacontroller.

Notwithstanding the change to the calcu-lated air mass as the reference (command)variable for the EGR, in its physical effects,this control architecture acts as a Lambdaclosed-loop control (in contrast to theLambda closed-loop control used on gaso-line engines in which the fuel mass is takenas the reference (command) variable).

Fuel-quantity mean-value adaptationThe fuel-quantity mean-value adaptation(MMA) provides a precise injected-fuel-quantity signal for the setpoint generation asneeded for those control loops which arerelevant for exhaust-gas emission (e.g. EGRcontrol, boost-pressure control, and start-of-injection control). The MMA operates inthe lower part-load range and determinesthe average deviation in the injected fuelquantity of all cylinders together.

Fig. 3 shows the basic structure of the MMAand its intervention in the control loops


Engine-rpm sensor Desired air mass



EGR valve

Turbocharger

Injection system

+

+

+

-

-

+

Start-of-injection control

Desired injected fuel quantity

Adaptation characteristic map

ECUEngine

Air-mass controller

Calculating the in-jected fuel quantity from Lambda

Characteristic map for EGR desired-value

Boost-pressure control

Fuel-quantity mean-value adaptation in the "indirect control" mode: Principle of operation3æ

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Further sensor signals

Robert Bosch GmbH

ECUEngine

Engine-rpm sensor

+

-

+ +


λdesired

λactual


Injection system

Smoke-limitation quantity

Calculation of the preliminary quantity

Desired-value map for smoke limitation

Lowest value

Lambda controller

Calculation of the injected fuel quantity

which are relevant for the exhaust-gas emis-sions.

The Lambda-sensor signal and the air-masssignal are used in calculating the actually in-jected fuel mass which is then comparedwith the desired injected fuel mass. Differ-ences are then stored in an adaptation mapin defined “learning points”. This procedureensures that when the operating point ne-cessitates an injected fuel quantity correc-tion, this can be implemented without delayeven during dynamic changes of state.

These correction quantities are stored in theEEPROM of the ECU and are available im-mediately the engine is started.

Basically speaking, there are two MMA op-erating modes. These differ in the way theyapply the detected deviations in injected fuelquantity:

Operating mode: Indirect controlIn the “indirect control” mode (Fig. 3), aprecise desired injected fuel quantity is usedas an input variable in the desired-valuecharacteristic maps which are relevant forexhaust emissions. The injected fuel quan-tity is not corrected during the fuel-meter-ing process.

Operating mode: Direct controlIn the “direct control” mode, in order thatthe amount of fuel actually injected corre-sponds as closely as possible to the desiredquantity, the fuel-quantity deviation is usedto correct the injected fuel quantity duringthe fuel-metering process. In this case, this is(indirectly) a closed fuel-quantity loop.

60 Open and closed-loop electronic control Lambda closed-loop control

Full-load smoke limitation using the Lambda closed-loop control: Principle of operation

Further sensor signals

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Full-load smoke limitationFig. 4 shows the block diagram of the con-trol structure for full-load smoke limitationusing a Lambda oxygen sensor. The objec-tive here is to determine the maximumamount of fuel which may be injected with-out exceeding a given smoke value.

The signals from the air-mass meter and theengine rpm sensor are applied together witha smoke-limitation map in determining thedesired Lambda value λDESIRED. This, inturn, is applied together with the air mass inorder to calculate the preliminary value forthe maximum permissible injected fuelquantity.

This form of control is already in series pro-duction, and has a Lambda closed-loop con-trol imposed upon it. Using the differencebetween λDESIRED and the actually measuredresidual oxygen in λACTUAL the Lambda con-troller calculates the correction fuel quan-tity. The maximum full-load injected fuelquantity is the total of the preliminaryquantity and the correction quantity.

This control architecture permits a highlevel of dynamic response due to the pilotcontrol, and improved precision due to thesuperimposed Lambda control loop.

Detection of undesirable combustionDuring overrun (trailing throttle), if theLambda-sensor signal drops below a given,specially calculated threshold this indicatesthat undesirable combustion is taking place.In this case, the engine can be switched offby closing a control flap and the EGR valve.The detection of undesirable combustionrepresents an additional engine safeguardfunction.

SummaryUsing Lambda-based EGR it is possible toconsiderably reduce a vehicle fleet’s exhaust-gas emissions scatter. Here, either fuel-quan-tity mean-value adaptation (MMA) can beused or cascade control.

MMA provides a precise injected-fuel-quan-tity signal for generating the desired (set-point) values for the control loops which arerelevant for emissions (for instance, for EGRcontrol, boost-pressure control, start-of-in-jection control). The precision of these con-trol loops is increased as a result.

In addition, the application of Lambdaclosed-loop control permits the precise defi-nition of the full-load smoke quantity aswell as the detection of undesirable combus-tion in the overrun (trailing throttle) mode.

Furthermore, the Lambda sensor’s high-pre-cision signal can be used in a Lambda con-trol loop for the regeneration of NOX cat-alytic converters.


Robert Bosch GmbH

62 Open and closed-loop electronic control Engine dynamometer

1 Intake air2 Filter3 Cold-water supply4 Hot-water supply5 Fuel6 Coolant7 Heater8 Quick-change sys-

tem9 Transfer module for

coolant, water, fuel,etc.

10 Engine management(EDC)

11 Intercooler12 Injection system13 Engine14 Triggering and sen-

sor signals15 Catalytic converter16 Power supply17 Interface for mea-

surement tech-niques

18 Electrical dy-namometer

19 Accelerator-pedalactuator

20 Test-bench com-puter

21 Indicating system(high-speed angle-synchronous mea-sured-value acquisi-tion)

22 Exhaust-gas analysisequipment (e.g.Analysis equipmentfor gaseous emis-sions, opacimeter,Fourier-transformedinfrared (FTIR) spec-troscope, massspectrometer, parti-cle-counting system)

23 Dilution tunnel24 Dilution air25 Mixing chamber26 Volume meter27 Blower28 Particle sampling

system29 CVS bag sampling

system30 Change-over valve

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Engine dynamometer

Every injection system is tested using an en-gine-dynamometer setup featuring a high de-gree of engine accessibility.

By conditioning intake, air, fuel, and coolantwith respect to temperature and pressure etc.,it is possible to obtain reproducible test re-sults.

Increasingly, dynamic tests with rapid load andrpm changes must be run through in additionto steady-state tests. Here, test stands with anelectrical dynamometric brake (dynamometer)are the best solution, as they can also “drive”the test specimen (as takes place on the roadduring overrun or trailing-throttle operation ona downhill gradient). Using the appropriatesimulation software, the passenger-car ex-haust-gas tests demanded by law can then berun through on the engine dynamometer in-stead of on the roller-type test bench.

The dynamometer computer (20) is responsi-ble for the control and monitoring of the en-gine and the test equipment. It also takes overdata acquisition and data storage. Highly effi-cient application-engineering work (map mea-surements) can be carried out with the help ofautomation software.

By means of suitable quick-change systems(8), it is possible to change engine palletswithin about 20 minutes, a feature which in-creases the dynamometer’s utilization time.

Engine dynamometer: Basic design

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Further special adaptationsIn addition to those described here, EDCpermits a wide range of other functions. Forinstance, these include:

Drive recorderOn commercial vehicles, the Drive Recorderis used to record the engine’s operating con-ditions (for instance, how long was the vehi-cle driven, under what temperatures andloads, and at what engine speeds). This datais used in drawing up an overview of opera-tional conditions from which, for instance,individual service intervals can be calcu-lated.

Special application engineering forcompetition trucksOn race trucks, the 160 km/h maximumspeed may be exceeded by no more than2 km/h. On the other hand, this speed mustbe reached as soon as possible. This necessi-tates special adaptation of the ramp func-tion for the vehicle-speed limiter.

Adaptations for off-highway vehiclesSuch vehicles include diesel locomotives, railcars, construction machinery, agriculturalmachinery, boats and ships. In such applica-tions, the diesel engine(s) is/are far more of-ten run in the full-load range than is thecase with road vehicles (90% full-load oper-ation compared with 30%). The power out-put of such engines must therefore be re-duced in order to ensure an adequate servicelife.

The mileage figures which are often usedas the basis for the service interval on roadvehicles are not available for such equip-ment as agricultural or construction ma-chinery, and in any case if they were avail-able they would have no useful significance.Instead, the Drive Recorder data is usedhere.

Port-and-helix-controlled fuel-injection systems: Triggering

Electronically controlled in-line injectionpumps, PE-EDCAs with the mechanically (flyweight) gov-erned in-line fuel-injection pumps, the in-jected fuel quantity here is also a function ofthe control-rack position and the enginespeed. The control rack is shifted to the de-sired position by the linear magnet of theactuator mechanism directly attached to thepump (Fig. 1 on the next page, Pos. 3).

On the control-sleeve in-line pump, anadditional electrical actuator in connectionwith start-of-injection control can be usedto arbitrarily adjust the injected fuel quan-tity and the start of delivery. This necessi-tates an extra actuator mechanism (4).

Triggering the control-rack actuatormechanismWith the solenoid de-energized, a springforces the control rack to the stop positionand thus interrupts the fuel supply. Whenthe current through the solenoid increases,the solenoid gradually overcomes the forceof the spring and control-rack travel in-creases so that more fuel is injected.

This means that the level of current per-mits the continuous adjustment of control-rack travel between zero and maximum de-livery quantity (pwm signal = pulse-width-modulated signal).

The corresponding pump characteristic mapis programmed into the ECU. Using this map,and depending on engine speed, the control-rack travel appropriate to the desired fuelquantity is calculated. In order to improvedriveability, a control characteristic can beprovided which is familiar from the mechan-ical (flyweight) RQ and RQV governors.

Using a sensor (rack-travel sensor (RWG)),the position control in the ECU registers theactual control-rack setting so that the systemdeviation can be calculated.

Open and closed-loop electronic control Special adaptations. Port-and-helix-controlled injection systems: Triggering 63

Robert Bosch GmbH

This enables the position control to quicklyand accurately correct the rack setting.

Triggering of the control-sleeve actuatormechanismA power stage which is triggered directlyfrom the processor with a pwm signal pro-vides the power needed to energize the start-of-delivery solenoids. A low-level currentcauses minor travel of the start-of-deliverysolenoid, and retards the start of delivery orstart of injection. On the other hand, a highlevel of current advances the start-of-deliv-ery point.

The injected-fuel-quantity controls as ap-plied to the control-sleeve in-line pumpsand the conventional in-line pumps (bothwith EDC) are identical. The more extensivefunctional scope in the ECU for the control-sleeve pump results to a great extent fromexpanded programs.

Key stopThe key stop function using the “ignition”key supersedes the conventional mechanicalshutoff device. It stops the supply of fuel byinterrupting the power supply to the electri-cal shutoff valve (ELAB, redundant shutoffpath) and to the control-rack linear sol-enoids.

Port-and-helix-controlled axial-pistondistributor pumps, VE-EDCSolenoid actuator for injected-fuel-quantitycontrolThe solenoid actuator (moving-magnet ac-tuator) engages the delivery-piston controlcollar via a shaft (Fig. 2, Pos. 3). Similar tothe mechanically governed distributorpumps, the cutoff bores are exposed sooneror later depending upon the position of thecontrol collar.

The injected fuel quantity can be continuallyvaried between zero and maximum. Bymeans of an angle sensor (Hall short-cir-cuiting-ring sensor, HDK), information onthe angle of rotation of the actuator, andtherefore on the setting of the control collarwith respect to the cutoff ports, is reportedback to the ECU and used to calculate thecorrect fuel quantity as a function of enginespeed.

In the de-energized state, the fuel delivery isset to zero by return springs on the actuatormechanism.

64 Open and closed-loop electronic control Port-and-helix-controlled injection systems: Triggering

Figure 11 In-line injection

pump2 Electrical shutoff

valve (ELAB)3 Control-rack actua-

tor mechanism (in-jected fuel quantity)

4 Control-sleeve actu-ator mechanism(start of delivery)

5 Engine ECU

1

4

2

5

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PE control-sleeve in-line fuel-injection pumps: Injection-triggering components1

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Robert Bosch GmbH

Solenoid valve for start-of-injection controlThe pump’s internal pressure is proportionalto the pump speed and, similar to the me-chanical timing device, is effective at thetiming-device piston. This pressure is ap-plied to the timing-device pressure side andis modulated by the clocked timing-devicesolenoid valve (2). The on/off ratio (ratio ofthe solenoid’s open time to its closed time)for the triggering of the solenoid valve istaken from a programmed control map.

A permanently opened solenoid valve (pres-sure reduction) results in later start-of-injec-tion points, and with the solenoid valve per-manently closed (pressure increase) thestart-of-injection points take place earlier. Inbetween these two extremes, infinite varia-tion of the on/off ratio can be implementedby the ECU.

Deviations between actual and desired start-of-injection points, as detected with the helpof the needle-motion sensor, result in achange of the on/off ratio for triggering thetiming-device solenoid valve. This ratio ischanged continually until the system devia-tion is “zero”, and ensures a dynamic re-sponse which is comparable to that of themechanical start-of-injection adjustment.

ShutoffAs a rule, shutoff is by means of the in-jected-fuel-quantity actuator (“zero” fuel de-livery). The redundant electrical shutoffvalve (ELAB) provides a further degree ofsafety (4).

On the distributor pump, the redundantelectrical shutoff valve is mounted on theupper side of the pump’s distributor head.When switched on (that is, with the enginerunning), the solenoid keeps the inlet portto the high-pressure chamber open (the ar-mature with sealing cone is pulled in). Whenswitch off takes place using the "ignitionswitch", the solenoid winding is de-ener-gized and the sealing cone is forced backonto its seat by a spring so that the inlet portto the high-pressure chamber is interrupted.

On marine engines, the ELAB is open whende-energized. This means that the enginecan still run even though the on-boardpower supply has failed. Apart from this, thenumber of electrical consumers is kept to aminimum since continuous current aggra-vates the effects of saltwater corrosion.

Open and closed-loop electronic control Port-and-helix-controlled injection systems: Triggering 65

Figure 21 Distributor pump2 Timing-device sol-

enoid valve (start ofinjection)

3 Moving-magnet actu-ator (injected fuelquantity)

4 Electric shutoff valve(ELAB)

5 Engine ECU

5

2

1 3 4

VE-EDC axial-piston distributor pumps: Injection-triggering components2

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Solenoid-valve-controlled in-jection systems: Triggering

The solenoid-valve-controlled injection-sys-tem family includes the following:

Axial-piston distributor pumps,VE-M (VP30),

Radial-piston distributor pumps,VR (VP44),

Common Rail System CRS, Unit Injector System, UIS Unit Pump System, UPS

These solenoid-valve-controlled injectionsystems are all triggered by similar signals.The characteristic features of the individualsystems are described in the following sec-tions, together with the differences betweenthem and conventional injection systems.

Due to better EMC (ElectroMagneticCompatibility) characteristics, the high-pressure solenoid valves are triggered byanalog signals. Since the triggering signalmust feature steep current edges in order toensure narrow tolerances and a high degreeof reproducibility for the injected fuel quan-tity, this form of triggering makes severe de-mands on the output stages.

In addition, the triggering process mustensure a minimum of power loss in the ECUand in the high-pressure solenoid valve. Inother words, the triggering currents must beas low as possible.

Irrespective of operating range, injectioncontrol must be extremely accurate in orderthat the injection pump and solenoid injec-tor inject precisely and with a high level ofreproducibility.

The injection system must respond ex-tremely quickly to changes, which meansthat the calculations in the microcontrollerand the triggering-signal implementation inthe output stages must take place at veryhigh speed. Data processing is therefore re-ferred to as being “real-time compatible”(resolution time 1 µs).

Solenoid-valve-controlled distributorpumpsOn the distributor pumps equipped with ahigh-pressure fuel-quantity solenoid valve(VP44 and VP30), a pump ECU (PSG) at-tached to the pump housing is responsiblefor triggering the solenoid valves at the cal-culated start-of-delivery point (Fig. 1a, Pos.1a). This takes place in accordance with therequirements of the engine ECU (6) whichis responsible for the engine and vehiclefunctions. The two ECUs communicate witheach other through the CAN bus.

The latest generation of the VP44 systemfeatures only a single ECU (PSG 16) whichhas united all the EDC functions in a singleunit, and which is situated directly on thepump (Fig. 1b, Pos. 1b).

The timing-device solenoid valve (4) usedon the distributor pumps is triggered using apulse-width-modulated (pwm) signal. In or-der to avoid malfunctions due to resonanceeffects, the clock frequency is not held con-stant thoughout the complete rotational-speed range but instead, at given speedranges, it is switched to a different frequency(window technique).

The high-pressure fuel-quantity solenoidvalve is triggered via current control (Fig. 2)

66 Open and closed-loop electronic control Solenoid-valve-controlled injection systems: Triggering

Figure 1a With separate pump

and engne ECUb With integral pump

and engine ECU

1a Pump ECU (PSG5)1b Pump ECU

(PSG16)2 Distributor pump3 Timing device4 Timing-device sol-

enoid valve5 High-pressure fuel-

quantity solenoidvalve

6 Engine ECU (MSG)

a

2

34

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which subdivides the triggering process intoa pickup-current phase (a) of approx. 18 A,and a holding-current phase (c) of approx.10 A. At the beginning of the controlledholding-current phase (after 200 ... 250 µs),the BIP evaluation circuit detects the sol-enoid-valve needle closing against the valveseat (BIP = Beginning of the Injection Pe-riod).

The latest generation uses the PSG16pump ECU, and is also provided with a BIPcurrent (b) between the pickup and hold-ing-current phases which is at the optimumlevel for the BIP detection function.

In order that the pump’s injection character-istics are always reproducible irrespective ofoperating conditions, the triggering circuitryas a whole, and the current control, must beextremely accurate. Furthermore, they mustkeep the power loss in ECU and solenoidvalve down to a minimum.

Defined, rapid opening of the solenoid valveis required at the end of the injectionprocess. To this end, high-speed quenching(d) using a high quenching voltage (1) is ap-plied at the valve to dissipate the energystored in its solenoid.

The solenoid valve can also be used to con-trol pilot injection (PI) for reduction ofcombustion noise. Here, the solenoid valveis operated ballistically between the PI pointand the MI (main injection) point. In otherwords it is only partially opened, whichmeans that it can be closed again veryquickly. The resulting injection spacing isvery short so that even at high rotationalspeeds, adequate cam pitch remains for themain injection process.

The subdivision into the individual trig-gering phases is calculated by the microcon-troller in the pump ECU.

Open and closed-loop electronic control Solenoid-valve-controlled injection systems: Triggering 67

Figure 2a Pickup-current

phaseb BIP detectionc Holding-current

phased High-speed quench-

ing1 Quenching voltage

a b c

1 1

a b c

Solenoid-valvecurrent I

U

h

Pilot injection (PI) Main injection (MI)

M

Solenoid-valvevoltage M

Solenoid-valveneedle lift M

Time t

d d

High-pressure solenoid valves: Triggering sequence using current control2

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Common Rail System CRSIn the Common Rail System (CRS), the fuelpressure in the rail (Fig. 3, Pos. 3) and with itthe injection pressure, are determined by therail-pressure valve (Pos. 8), and if required bya throttle upstream of the high-pressurepump (1). The injector’s (6) high-pressuresolenoid valve (7) defines the injection pointand the duration of injection in accordancewith the various operating parameters. Thismeans, therefore, that injection pressure isdecoupled from injection point and durationof injection. Decoupling the injection pres-sure from injection point and duration of in-jection means that in addition to the main in-jection (MI), which is responsible for the gen-eration of torque, other injection processesindependent of the injection pressure canalso be triggered. On the one hand these arefor the most part pilot injections (PI) withthe principle objective of reducing the com-bustion noise, and on the other secondary in-jection processes (post injection (POI))whichserve to reduce exhaust emissions. The in-jected fuel quantity is the product of injectionpressure and duration of injection.

Post injection involves minute quantities offuel. Injection is not carried out individuallyat stipulated cylinders, but rather the minutequantities concerned are added together inthe ECU until the smallest quantity is

reached which can be handled by the injec-tor. When this is reached, it is injected at thenext possible opportunity.

Rail-pressure controlThe permanent pressure in the rail is gener-ated by a continuously operating high-pres-sure pump. The closed control loop for therail pressure comprises the rail-pressure sen-sor (4) the engine ECU (5) and the rail-pres-sure control valve (8).

The microcontroller in the engine ECUreceives the sensor signal and uses it to cal-culate the desired pressure. This is outputtedto a driver stage which triggers the rail-pres-sure control valve by means of a pwm signal.The level of the applied current correspondsto the desired pressure. The higher the trig-gering current the higher the rail pressure.The microcontroller compares the actualpressure at the sensor with the desired pres-sure and takes appropriate closed-loop con-trol action in case of deviation.

In a number of versions, at high speedsand low levels of required fuel, one of thehigh-pressure pump’s three pumping ele-ments can be switched off (element shutoff).In this case, a triggering current flowsthrough the element-shutoff solenoid valve.Switching off one of the elements reducesthe strain on the pump as well as increasingthe engine’s efficiency.


Figure 31 High-pressure pump2 Element shutoff

valve3 Rail4 Rail-pressure sensor5 Engine ECU (for

higher numbers ofcylinders, it is alsopossible to use a"master slave al-liance" with 2ECUs)

6 Injector7 High-pressure sol-

enoid valve8 Rail-pressure control

valve

2

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Injector triggeringIn the inoperative mode, the injector’s high-pressure solenoid valve is not triggered andis therefore closed.

The injector injects when the solenoidvalve opens. Solenoid-valve triggering issubdivided into five phases (Figs. 4 and 5).

Opening phase Initially, in order to ensure tight tolerancesand high levels of reproducibility for the in-jected fuel quantity, the current for openingthe valve features a steep, precisely definedflank and increases rapidly up to approx.20 A. This is achieved with a so-called“booster voltage” of up to as much as 100 Vwhich is generated in the ECU and stored ina capacitor (boost-voltage store). When thisvoltage is applied across the solenoid valve,the current increases several times faster thanit does when only battery voltage is used.

Pickup-current phase During the pickup-current phase, batteryvoltage is applied to the solenoid valve, andassists in opening it quickly. Current control

limits pickup current to approx. 20 A.

Holding-current phase In order to reduce the power loss in ECUand injector, the current is dropped to ap-prox. 12 A in the holding-current phase. Theenergy which becomes available whenpickup current and holding current are re-duced is routed to the booster-voltage store.

Switch offWhen the current is switched off in order toclose the valve, the surplus energy is alsorouted to the booster-voltage store.

RechargeBetween the actual injection events, a saw-tooth waveform is applied to the injectorswhich are not injecting (Fig. 5, f1). Maxi-mum current level is so low that there is nodanger of the injector opening. Energystored in the solenoid valve as a result isthen routed to the booster-voltage store(Fig. 5, f2), which it recharges until the origi-nal voltage is reached as required for open-ing the solenoid valve.


Figure 4a Opening phaseb Pickup-current

phasec Transition to holding-

current phased Holding-current

phasee Switch off, f Recharge

a b c d e f

Solenoid-valvecurrent IM

Q

hM

Injected fuelquantity

Solenoid-valveneedle lift

Time t

Triggering sequence of a high-pressure solenoid valve for a single injection event4

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Figure 51 Battery2 Current control3 Solenoid windings

of the high-pressuresolenoid valves

4 Booster switch5 Booster-voltage

store (capacitor)6 Free-wheeling

diodes for energy re-covery and high-speed quenching

7 Cylinder selectorswitch

I Current flow

a Opening phase

c Transition to holding-current phase

b Pickup-current phase

1

2 4

5

3

I

I

7

36

67I

I

I

I

I

I

I

I

d Holding-current phase

e Switch off

I

I

f1 Recharge

f2 Recharge to booster- voltage store

I

I

I

I

I

I

Common Rail System: Block diagram of the triggering phase in the control for a single cylinder group5

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Robert Bosch GmbH

Unit Injector Systems and Unit PumpSystems (UIS/UPS)The triggering of the high-pressure solenoidvalve places severe demands on the outputstages. Close tolerances and high repro-ducibility of the injected fuel quantity de-mand that the triggering signal features aparticularly steep edge.

The Unit Injector and Unit Pump high-pres-sure solenoid valves are triggered in a similarmanner using current control (Figs. 6through 8) which divides the triggeringprocess into the pickup-current phase (a)and the holding-current phase (c). Thisform of triggering permits very fast switch-ing times and reduces the power loss. For abrief period between these two phases, con-stant triggering current is applied to permitthe detection of the solenoid-valve closingpoint (refer to section “BIP control”, b).

In order to ensure high-speed, definedopening of the solenoid valve at the end ofthe injection event, a high voltage is appliedacross the terminals (d) for rapid quenchingof the energy stored in the solenoid valve.

The microcontroller is responsible for the

calculation of the individual triggeringphases. An ASIC module (gate array) withhigh computing power assists the microcon-troller by generating two digital triggeringsignals (MODE signal and ON signal).These triggering signals then instruct the


Figure 7a Pickup current

(commercial-vehicleUIS/UPS: 12...20 A;passenger-car UIS:20 A)

b BIP detection, c Holding current

(commercial-vehicleUIS/UPS: 8...14 A;passenger-car UIS:12 A)

d High-speed quench-ing

Figure 6a Unit Injector System

(UIS) with 2 ECUsb Unit Pump System

(UPS)1 Unit Injector (UI)2 High-pressure sol-

enoid valve3 Engine ECU4 Unit Pump (UP)

Time t

Solenoid-valvecurrent IM

Switch-on signal

Needle-motiondetection

a b c d

Solenoid-valveneedle lift hM

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Unit Injector and Unit Pump Systems (UIS/UPS):Triggering components

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Robert Bosch GmbH

output-stage drivers to generate the requiredtriggering-current sequence.

Boot-shaped injection characteristicFuture systems will provide the possibility ofa special “boot-shaped” injection character-istic (with the main injection (MI) immedi-ately following the pilot injection (PI Fig. 8).Here, the solenoid-valve current is held at aprecise intermediate level (approx. 4...6 A,c1) between the pickup-current and hold-ing-current phases. This leads to the sol-enoid valve being held in an intermediateposition so that a “boot-shaped” injectioncharacteristic is the result.

ECU couplingThe passenger-car Unit Injector System canalso be used on engines with more than 6cylinders. In order to be able to cope withthe requirement for more driver stages forinjector triggering, and for increased micro-controller computing power, such enginescan be equipped with two ECUs coupled to-gether to form a “master-slave alliance”. Sim-ilar to the Common Rail System (CRS), theECUs are coupled together by means of aninternal CAN-Bus operating at a baud rateof up to 1 Mbaud (1,000,000 bit/s).

Some of the functions are allocated to aspecific ECU which is then solely responsi-ble for their processing (for instance, the in-jected-fuel-quantity compensation). Otherassignments though can be flexiblyprocessed in this configuration by either ofthe ECUs (for instance, the registration ofsensor signals). This configuration cannotbe changed during operation.

Using this master-slave concept, it is pos-sible to implement both Biturbo control andactive exhaust-gas treatment.


Figure 8a Pickup current (com-

mercial-vehicleUIS/UPS: 12...20 A)

b BIP detectionc1 Holding current for

"boot-shaped" injec-tion characteristic

c2 Holding current(commercial-vehicleUIS/UPS: 8...14 A)

d High-speed quench-ing

Solenoid-valve current IM

hM

pE

Time t

Injection pressure

a b c d e

Solenoid-valveneedle lift

Triggering sequences of the high-pressure solenoid valves for the “boot-shaped” injection characteristic

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Control and triggering of theremaining actuatorsIn addition to the fuel-injection compo-nents themselves, EDC is responsible for thecontrol and triggering of a large number ofother actuators. These are used for cylinder-charge control, or for the control of enginecooling, or are used in diesel-engine start-assist systems. Here too, as is the case withthe closed-loop control of injection, the in-puts from other systems (such as TCS) aretaken into account.

A variety of different actuators are used,depending upon the vehicle type, its area ofapplication and the type of fuel injection.This chapter deals with a number of exam-ples, and further actuators are covered in theChapter “Actuators”.

A variety of different methods are used fortriggering:

The actuators are triggered directly froman output (driver) stage in the engineECU using appropriate signals (e.g. theEGR valve).

If high currents are involved (for instancefor fan control), the ECU triggers a relay.

The engine ECU transfers signals to an in-dependent ECU, which is then used totrigger or control the remaining actuators(for instance, for glow control).

The advantage of incorporating all engine-control functions in the EDC ECU lies in thefact that not only the injected fuel quantityand instant of injection can be taken into ac-count in the engine control concept, but alsoother engine functions such as EGR andboost-pressure control. This leads to a con-siderable improvement in engine manage-ment. Apart from this, the engine ECU has avast amount of information at its disposal asneeded for other functions (for instance, en-gine and intake-air temperature as used forglow control on the diesel engine).

Auxiliary coolant heatingHigh-performance diesel engines are veryefficient, and under certain circumstancesdo not generate enough waste heat to ade-quately heat the vehicle’s interior. One solu-tion for overcoming this problem is to installauxiliary coolant heating using glow plugs.Depending upon the power available fromthe alternator, this system is triggered in anumber of steps. It is controlled by the en-gine ECU as used for EDC.

Intake-duct switch-offIn the lower engine-rpm ranges and at idle,a flap (Fig. 1, Pos. 6) operated by an elec-tropneumatic transducer closes one of theintake ducts (5). Fresh air in then only in-ducted through the turbulence duct (2).This leads to improved air turbulence in thelower rpm ranges which in turn results inmore efficient combustion. In the higherrpm ranges, the engine’s volumetric effi-ciency is improved thanks to the open intakeduct (5) and the power output increases as aresult.

Open and closed-loop electronic control Control and triggering of the remaining actuators 73

Figure 11 Intake valve2 Turbulence duct3 Cylinder4 Piston5 Intake duct6 Flap

1

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Robert Bosch GmbH

Boost-pressure controlBoost-pressure control applied to the ex-haust-gas turbocharger improves the en-gine’s torque curve in full-load operation,and its exhaust and refill cycle in the part-load range.The optimum (desired) boostpressure is a function of engine speed, in-jected fuel quantity, coolant and fuel tem-perature, and the surrounding air pressure.This optimum (desired) boost pressure iscompared with the actual value registered bythe boost-pressure sensor and, in the case ofdeviation, the ECU either operates the by-pass valve’s electropneumatic transducer orthe guide blades of the VTG (Variable Tur-bine Geometry) exhaust-gas turbocharger(refer also to the Chapter “Actuators”).

Fan triggeringWhen a given engine temperature is ex-ceeded, the engine ECU triggers the enginecooling fan, which continues to rotate for abrief period after the engine is switched off.This run-on period is a function of thecoolant temperature and the load imposedon the engine during the preceding drivingcycle.

Exhaust-gas recirculation (EGR)In order to decrease the NOX emissions, ex-haust gas is directed into the engine’s intakeduct through a channel, the cross section ofwhich can be varied by an EGR valve. TheEGR valve is triggered by an electropneu-matic transducer or by an electric actuator.

Due to the high temperature of the exhaustgas and its high proportion of contamina-tion, it is difficult to precisely measure theexhaust-gas flow which is recirculated backinto the engine. Control, therefore, takesplace indirectly through an air-mass meterlocated in the flow of fresh intake air. Themeter’s output signal is then compared inthe ECU with the engine’s theoretical air re-quirement which has been calculated from avariety of data (e.g. engine rpm).

The lower the measured mass of the incom-ing fresh air compared to the theoretical airrequirement, the higher is the proportion ofrecirculated exhaust gas.

Currently, EGR is only used on passengercars, although work is proceeding on the de-velopment of a commercial-vehicle version.


If individual input signals should fail, theECU is without the important informationit needs for calculations. In such cases, sub-stitute functions are used. Two examples aregiven below:

Example 1: The fuel temperature is neededfor calculation of the injected fuel quantity.If the fuel-temperature sensor fails, the ECUuses a substitute value for its calculations.This must be selected so that excessive sootformation is avoided, although this can leadto a reduction of engine power in certainoperating ranges.

Example 2: Should the camshaft sensor fail,the ECU applies the crankshaft-sensor signalas a subsitute. Depending on the vehiclemanufacturer, there are a variety of differentconcepts for using the crankshaft signal todetermine when cylinder 1 is in the com-pression cycle. The use of substitute func-tions leads to engine restart taking slightlylonger.

Substitute functions differ according to ve-hicle manufacturer, so that many vehicle-specific functions are possible.

The diagnosis function stores data on allmalfunctions that occur. This data can thenbe accessed in the workshop (refer also tothe Chapter “Electronic Diagnosis (OBD)”).

74 Open and closed-loop electronic control Control and triggering of the remaining actuators

Robert Bosch GmbH

Torque-controlled EDC systemsThe engine-management system is continu-ally being integrated more closely into theoverall vehicle system. Through the CAN-Bus, vehicle dynamics systems such as TCS,and comfort and convenience systems suchas Cruise Control, have a direct influence onthe Electronic Diesel Control (EDC). Apartfrom this, much of the information regis-tered and/or calculated in or by the enginemanagement system must be passed on toother ECUs through the CAN-Bus.

In order to be able to incorporate the EDCeven more efficiently in a functional alliancewith other ECUs, and implement otherchanges rapidly and effectively, it was neces-sary to make far-reaching changes to thenewest-generation controls. These changesresulted in the torque-controlled EDC whichwas introduced with the EDC16. The mainfeature is the change over of the module in-terfaces to the parameters as commonly en-countered in practice in the vehicle.

Engine parametersEssentially, an IC engine’s output can be de-fined using the three parameters: Power P,rpm n, and torque M.

For 2 diesel engines. Fig. 1 compares typi-cal curves of torque and power as a functionof engine rpm. Basically speaking, the fol-lowing formula applies:

P = 2 ·π · n · M

In other words, it suffices to use the torqueas the reference (command) variable. Enginepower then results from the above formula.Since power output cannot be measured di-rectly, torque has turned out to be a suitablereference (command) variable for enginemanagement.

Torque controlWhen accelerating, the driver uses the accel-erator pedal (sensor) to directly demand a

given torque from the engine. At the sametime, but independent of the driver’s re-quirements, via the interfaces other vehiclesystems submit torque demands resultingfrom the power requirements of the particu-lar component (e.g. air conditioner, alterna-tor). Using these torque-requirement inputs,the engine management calculates the out-put torque to be generated by the engineand controls the fuel-injection and air-sys-tem actuators accordingly. This method hasthe following advantages:

No single system (for instance, boost pres-sure, fuel injection, pre-glow) has a directeffect upon the engine management. Thisenables the engine management to alsotake into account higher-level optimiza-tion criteria (such as exhaust emissionsand fuel consumption) when processingexternal requirements, and thus controlthe engine in the most efficient manner,

Many of the functions which do not di-rectly concern the engine managementcan be designed to function identically fordiesel and gasoline engines.

Extensions to the system can be imple-mented quickly.

Open and closed-loop electronic control Torque-controlled EDC systems 75

Figure 1a Year of manufacture

1968b Year of manufacture

1998

Pow

er o

utpu

t

0

25

50

75

kW

Torq

ue

00

Engine rpm1000 2000 3000 4000

100

200

300

N·m

a

b

a

b

min-1

Example of the torque and power-output curves as a function of engine speed for two passenger-cardiesel engines with approx. 2.2 l displacement

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Engine-management sequenceFig. 2 shows (schematically) the processingof the setpoint inputs in the engine ECU. Inorder to be able to fulfill their assignmentsefficiently, the engine management’s controlfunctions all require a wide range of sensorsignals and information from other ECUs inthe vehicle.

Propulsion torqueThe driver’s input (that is, the signal fromthe accelerator-pedal sensor), is interpretedby the engine management as the request fora propulsive torque. The inputs from theCruise Control and the Vehicle-Speed Lim-iter are processed in exactly the same man-ner.

Following this selection of the desiredpropulsive torque, should the situation arise,the vehicle-dynamics system (TCS, ESP) in-creases the desired torque value when thereis the danger of wheel lockup and decreasesit when the wheels show a tendency to spin.

Further external torque demandsThe drivetrain’s torque adaptation must betaken into account (drivetrain transmissionratio). This is defined for the most part by theratio of the particular gear, or by the torque-converter efficiency in the case of automaticgearboxes. On vehicles with an automatic-gearbox, the gearbox control stipulates thetorque requirement during the actual gearshift. Apart from reducing the load on thegearbox, reduced torque at this point resultsin a comfortable, smooth gear shift. In addi-tion, the torque required by other engine-powered units (for instance, air-conditionercompressor, alternator, servo pump) is deter-mined. This torque requirement is calculatedeither by the units themselves or by the en-gine management.

Calculation is based on unit power androtational speed, and the engine manage-ment adds up the various torque require-ments. The vehicle’s driveability remains un-changed notwithstanding varying require-ments from the auxiliary units and changesin the engine’s operating status.

Internal torque demandsAt this stage, the idle-speed control and theactive surge damper intervene.

For instance, if demanded by the situa-tion, in order to prevent mechanical dam-age, or excessive smoke due to the injectionof too much fuel, the torque limitation re-duces the internal torque requirement. Incontrast to the previous engine-manage-ment systems, limitations are no longer onlyapplied to the injected fuel-quantity, but in-stead, depending upon the required effects,also to the particular physical quantity in-volved.

The engine’s losses are also taken into ac-count (e.g. friction, drive for the high-pres-sure pump). The torque represents the en-gine’s measurable effects to the outside. Theengine management though can only gener-ate these effects in conjunction with the cor-rect fuel injection together with the correctinjection point, and the necessary marginalconditions as apply to the air-intake system(e.g. boost pressure and EGR rate). The re-quired injected fuel quantity is determinedusing the current combustion efficiency. Thecalculated fuel quantity is limited by a pro-tective function (for instance, protectionagainst overheating), and if necessary can bevaried by the smooth-running control(SRC). During engine start, the injected fuelquantity is not determined by external in-puts such as those from the driver, butrather by the separate “start-quantity con-trol” function.

Actuator triggeringFinally, the desired values for the injectedfuel quantity are used to generate the trig-gering data for the injection pump and/orthe injectors, and for defining the optimumoperating point for the intake-air system.

76 Open and closed-loop electronic control Torque-controlled EDC systems

Robert Bosch GmbH

Open and closed-loop electronic control Torque-controlled EDC systems 77

Driver input: Selection of the desired propulsion torque

Propulsion torque:

Further external torque demands

- Accelerator-pedalsensor

- Vehicle-speed control(Cruise Control)


Intake-air system- Turbocharger,- EGR ...

Injection system- Fuel-injection

pump,- Injectors ...

Inputs:

Actuator triggering

- Boost pressure- EGR rate,- ...

External inputs

Input:- Start of delivery,- Timing device,- Rail pressure,- ... (depending on system).

Input from the vehicle-dynamics systems:

Drivetrain transm.

Input from the gearbox ECU

Coordination of the drivetrain torque

Start quantity

Engine loading due to auxiliary units

Coordination of the propulsion torque

- TCS,- ESP. Data

exchange

Sensor signals

Internal sequences

Data trans-mission possible through CAN

,

Fuel-quantity input

Start Drivemode

Engine efficiency

Fuel-quantity limit

Smooth-running control

Internal torque requirements

Control of the engine torque(internal functions)

Idle-speed control

Active surge damping

Torque limitation

Engine-management sequence for torque-controlled diesel injection2

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ECU-integrated diagnostics belong to thebasic scope of electronic engine-manage-ment systems. During normal vehicle oper-ation, input and output signals are checkedby monitoring algorithms, and the overallsystem is checked for malfunctions andfaults. If faults are discovered in the process,these are stored in the ECU. When the vehi-cle is checked in the workshop, this storedinformation is retrieved through a serial in-terface and provides the basis for rapid andefficient trouble-shooting and repair.

Operating concept

Originally, it was intended that the self-diag-nosis of the engine-management system(on-board diagnostics/OBD) should merelybe a help in rapid and efficient fault-findingin the workshop. Increasingly severe legalstipulations, and the more wide-rangingfunctional scope of the vehicle’s electronicsystems though, led to the emergence of amore extensive diagnostics system withinthe engine-management system.

Input-signal monitoringHere, the analysis of the input signals is ap-plied for monitoring the sensors and theirconnection lines to the ECU (Table 1). Thesechecks serve to uncover not only sensorfaults, but also short-circuits to the batteryvoltage UBatt and to ground, as well as opencircuits in lines. The following processes areapplied:

Monitoring the sensors’ power supply. Checking that the measured values are in-

side the correct range (e.g. engine temper-ature –40 °C...+150 °C.

If auxiliary information is available, theregistered value is subjected to a plausibil-ity check (e.g. the camshaft and/or crank-shaft speed).

Important sensors (such as the accelera-tor-pedal sensor) are designed to be re-dundant which means that their signalscan be directly compared with each other.

Output-signal monitoringHere, in addition to the connections to theECU, the actuators are also monitored. Us-ing the results of these checks, open-circuitsand short-circuits in the lines and connec-tions can be detected in addition to actuatorfaults. The following processes are appliedhere:

Hardware monitoring of the output-sig-nal circuit using the driver stage. The cir-cuit is checked for open circuit, and forshort circuits to battery voltage UBatt andto ground.

The actuator’s influence on the system ischecked for plausibility. In the case of ex-haust-gas recirculation (EGR) for in-stance, a check is made whether intake-manifold pressure is within given limitsand that it reacts accordingly when the ac-tuator is triggered.

Monitoring ECU communicationAs a rule, communication with the otherECUs takes place via CAN-Bus (ControllerArea Network). The diagnostics integratedin the CAN module are described in theChapter “Data transfer between electronicsystems”. A number of other checks are alsoperformed in the ECU. Since most CANmessages are sent at regular intervals by theparticular ECUs, monitoring the time inter-vals concerned leads to the detection of ECUfailure.

In addition, when redundant informationis available in the ECU, the received signalsare checked the same as all input signals.

78 Electronic diagnosis Operating concept

Electronic diagnosis

Robert Bosch GmbH

Monitoring the internal ECU functionsIn order that the functional integrity of theECU is ensured at all times, monitoringfunctions are incorporated in the hardware(e.g. “intelligent driver-stage modules”) andin the software.

These check the individual ECU compo-nents (e.g. microcontroller, Flash-EPROM,RAM). Many of these checks are performedimmediately the engine is switched on. Dur-ing normal operations, further checks areperformed regularly so that the failure of a

component is detected immediately. Se-quences which require extensive computingcapacity (for instance for checking theEPROM), are run through immediately theengine is switched off (only possible at pre-sent on gasoline engines).

This method ensures that the other func-tions are not interfered with. On the dieselengine, the switch-off paths are checked inthe same period.

Electronic diagnosis Operating concept 79

Table 1

Monitoring the most important input signals1

Signal path Monitoring

Accelerator-pedal sensor Check of the power supply and the signal range

Plausibility with regard to a redundant signal

Plausibility with regard to the brakes

Crankshaft-rpm sensor Checking the signal range

Plausibility with the camshaft-rpm sensor

Checking the changes as a function of time (dynamic plausibility)

Engine-temperature sensor Checking the signal range

Logical plausibility as a function of rpm

and injected fuel quantity or engine load

Brake-pedal switch Plausibility with regard to redundant brake contact

Speed signal Checking the signal range

Plausibility with regard to rpm and injected fuel quantity or engine load

EGR positioner Checks for short circuits and open circuits in lines

EGR control

Checking the system's reaction to valve triggering

Battery voltage Checking the signal range

Plausibility with regard to engine rpm (at present, only possible with gasoline (SI) engines)

Fuel-temperature sensor Checking the signal range (at present, only possible with diesel engines)

Boost-pressure sensor Checking the power supply and the signal range

Plausibility with regard to ambient-pressure sensor and/or further signals

Boost-pressure actuator Checking for short circuits and open-circuit lines

Control deviation of boost-pressure control

Air-mass meter Checking the power supply and the signal range

Logical plausibility

Air-temperature sensor Checking the signal range

Logical plausibility with regard to the engine-temperature sensor for instance

Clutch-signal sensor Plausibility with regard to vehicle speed

Ambient-pressure sensor Checking the signal range

Logical plausibility of the intake-manifold-pressure sensor

Robert Bosch GmbH

Dealing with a faultFault recognitionWhen a fault remains in a signal path longerthan a defined period, the signal path is clas-sified as being defective. Until it is finallyclassified as defective, the last valid value isutilised in the system. Normally, as soon as itis classified as defective, a substitute func-tion is triggered (refer to the Chapter“Closed-loop and open-loop electronic con-trol”).

Most faults can be revoked and the signalpath classified as serviceable again providedthe signal path remains without fault for adefined period of time.

Fault storageEach fault is stored as a malfunction code inthe non-volatile area of the data memory. Inthe fault entry, each malfunction code is ac-companied by auxiliary information in theso-called “freeze-frame” containing the op-erating and environmental conditions at themoment the fault occurred (e.g. engine rpm,engine temperature). Information is alsostored on the fault type (for instance shortcircuit, conductor open circuit) and the faultstatus (in other words, permanent fault orsporadic fault).

The lawmaker has prescribed specific mal-function codes for many of the faults whichhave an effect on the vehicle’s toxic emis-sions. Further fault information not coveredby legislation can also be stored for retrievalby the vehicle workshop.

Following storage of the fault entry, thediagnosis for the system or component con-cerned continues. If the fault does not occuragain in the further course of the diagnosis(in other words it was a sporadic fault), it isthen erased from the fault memory providedthat certain conditions are complied with.

Fault retrievalThe faults can be retrieved from the faultmemory with a specified workshop testerprovided by the vehicle manufacturer, or by

using a System Tester (e.g. Bosch KTS500),or a scan tool. Once the fault informationhas been retrieved in the workshop and thefault repaired, the fault memory can becleared again using the tester.

Diagnostic interfaceA communication interface is needed for“Off-board testers” in order for them to beable evaluate the “On-Board Diagnosis”.This serial interface is mandatory and is de-fined in ISO 9141 (diagnostic interfacethrough the K-line). The interface operateswith a transfer rate (baud rate) of between10 baud and 10 kbaud, and is either a single-wire interface with common send and re-ceive lines, or a two-wire interface with sepa-rate data line (K-line) and initiate line (L-line). A number of ECUs can be connectedtogether at a single diagnostic connector.

The tester sends an initiate address to all theECUs, one of which recognises this addressand replies with a baud-rate identificationword. Using the interval between the pulseedges, the tester determines the baud rate,adjusts itself accordingly and sets up thecommunication with the ECUs.

Actuator diagnosis An actuator diagnosis facility is incorpo-rated in the ECU so that the workshops canselectively actuate individual actuators andcheck their correct functioning. This testmode is triggered by the tester and onlyfunctions with the vehicle at standstill, andwith the engine running at below a givenspeed or with it stopped. Actuator function-ing is checked either acoustically (e.g. click-ing of the valve), visually (e.g. movement ofa flap), or by other uncomplicated methods.

80 Electronic diagnosis Operating concept

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On-Board-Diagnostics (OBD)In the past years there has been a continualreduction in toxic emissions per vehicle. Inorder for the emission limits defined by thevehicle manufacturers to be maintained dur-ing continuous in-field operations, it is nec-essary that the engine and its componentsare monitored continually. This was the rea-son for the lawmaker defining specificationsto regulate the diagnosis scope for the ex-haust-gas-relevant components and systemsin the vehicle.

1988 marked the coming into force of OBDI in California, that is, the first stage ofCARB legislation (California Air ResourcesBoard). All newly registered vehicles in Cali-fornia were forced to comply with thesestatutory regulations. OBD II, that is the sec-ond stage, came into force in 1994.

Since 1994, in the remaining US States thelaws of the Federal Authority EPA (Environ-mental Protection Agency) have applied.The scope of these diagnostics comply forthe most part with the CARB legislation(OBD II), although the requirements forcompliance with the emissions limits are lesssevere.

The OBD adapted to European require-ments is known as the EOBD and is basedon the EPA-OBD. At present, the EOBDstipulations are even less severe than thoseof the EPA-OBD.

OBD IThe electrical components which are rele-vant for exhaust-gas emissions are checkedfor short circuits and breaks by the firststage of the CARB-OBD. The resulting elec-trical signals must remain within the stipu-lated plausibility limits.

When a fault/error is discovered, the dri-ver is warned by a lamp in the instrumentcluster. Using “on-board devices” (for in-stance, a diagnosis lamp which displays ablink code), it must be possible to read outwhich component has failed.

OBD IIThe diagnostic procedure for Stage 2 of theCARB-OBD is far more extensive than OBDI. Monitoring no longer stops at the check ofthe electrical signals from the components,but has been extended to include the checkof correct system functioning. For instance,it is no longer sufficient to check that thesignal from the engine-temperature sensordoes not exceed certain fixed limits. OBD IIregisters a fault if the engine temperature re-mains too low (for instance below 10 °C) fora longer period of time (plausibility check).

OBD II demands that all those systemsand components be checked which in caseof malfunction can lead to a noticeable in-crease in toxic emissions. In addition, all thecomponents which are actually used forOBD must also to be checked, and every de-tected fault must be stored. The driver mustbe warned of malfunctions by a lamp in theinstrument cluster. The stored faults arethen retrieved by testers which are con-nected for trouble-shooting.

OBD II legislation stipulates the standard-ization of the information stored in the faultmemory in accordance with the ruling ofthe SAE (Society of Automotive Engineers).The means that provided they comply withthe standards, commercially available testerscan retrieve fault information from the faultmemory (so-called “scan tools”).

Diagnosis-sequence controlAs a rule, the diagnostic functions for all thesystems and components to be tested mustbe run through at least once during each ex-haust-gas test cycle (e.g. ECE/EU test cycle).

Depending on the driving status, the diag-nostics-system management can dynami-cally change the order of the diagnosis func-tions. The target here is that all diagnosisfunctions are run through often enoughduring everyday operations.

Electronic diagnosis On-Board Diagnostics 81

Robert Bosch GmbH

Today’s vehicles are being equipped with aconstantly increasing number of electronicsystems. Along with their need for extensiveexchange of data and information in orderto operate efficiently, the data quantitiesand speeds concerned are also increasingcontinuously.

For instance, in order to guarantee perfectdriving stability, the Electronic Stability Pro-gram (ESP) must exchange data with the en-gine management system and the transmis-sion-shift control.

System overview

Increasingly widespread application of elec-tronic communications systems, and elec-tronic open and closed-loop control sys-tems, for automotive functions such as

Electronic engine-management (EDC andMotronic),

Electronic transmission-shift control(GS),

Antilock braking system (ABS), Traction control system (TCS), Electronic Stability Program (ESP), Adaptive Cruise Control (ACC), and Mobile multimedia systems together with

their display instrumentation

has made it vital to interconnect the individ-ual ECUs by means of networks.

The conventional point-to-point exchangeof data through individual data lines hasreached its practical limits (Fig. 1), and thecomplexity of current wiring harnesses andthe sizes of the associated plugs are alreadyvery difficult to manage. The limited num-ber of pins in the plug-in connectors hasalso slowed down ECU development work.

To underline this point:Apart from being about 1 mile long, thewiring harness of an average middle-classvehicle already includes about 300 plugs andsockets with a total of 2000 plug pins. Theonly solution to this predicament lies in theapplication of specific vehicle-compatibleBus systems. Here, CAN has established it-self as the standard.

Serial data transfer (CAN)

Although CAN (Controller Area Network)is a linear bus system (Fig. 2) specifically de-signed for automotive applications, it has al-ready been introduced in other sectors (forinstance, in building installation engineer-ing).

Data is relayed in serial form, that is, oneafter another on a common bus line. AllCAN stations have access to this bus, and viaa CAN interface in the ECUs they can re-ceive and transmit data through the CANbus line. Since a considerable amount ofdata can be exchanged and repeatedly ac-cessed on a single bus line, this networkingresults in far fewer lines being needed.

82 Data transfer between electronic systems System overview, serial data transfer (CAN)

Data transfer between automotive electronic systems

Transmission-shift controlStation 1

Engine managementStation 2

ABS/TCS/ESPStation 3

Instrument clusterStation 4

Conventional data transfer1

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Applications in the vehicleFor CAN in the vehicle there are four areasof application each of which has differentrequirements. These are as follows:

Multiplex applicationsMultiplex is suitable for use with applicationscontrolling the open and closed-loop controlof components in the sectors of body elec-tronics, and comfort and convenience. Theseinclude climate control, central locking, andseat adjustment. Transfer rates are typicallybetween 10 kbaud and 125 kbaud (1 kbaud =1 kbit/s) (low-speed CAN).

Mobile communications applicationsIn the area of mobile communications, CANnetworks such components as navigationsystem, telephone, and audio installationswith the vehicle’s central display and operat-ing units. Networking here is aimed at stan-dardizing operational sequences as far aspossible, and at concentrating status infor-mation at one point so that driver distrac-tion is reduced to a minimum. With this ap-plication, large quantities of data are trans-mitted, and data transfer rates are in the 125kbaud range. It is impossible to directlytransmit audio or video data here.

Diagnosis applicationsThe diagnosis applications using CAN areaimed at applying the already existing net-work for the diagnosis of the connectedECUs. The presently common form of diag-nosis using the special K line (ISO 9141)then becomes invalid. Large quantities ofdata are also transferred in diagnostic appli-cations, and data transfer rates of 250 kbaudand 500 kbaud are planned.

Real-time applications Real-time applications serve for the openand closed-loop control of the vehicle'smovements. Here, such electronic systems asengine management, transmission-shift con-trol, and electronic stability program (ESP)are networked with each other.Commonly, data transfer rates of between125 kbaud and 1 Mbaud (high-speed CAN)are needed to guarantee the required real-time response.

Bus configurationConfiguration is understood to be the layoutand interaction between the components ina given system. The CAN bus has a linearbus topology (Fig. 2) which in comparisonwith other logical structures (ring busand/or star bus) features a lower failureprobability. If one of the stations fails, thebus still remains fully accessible to all theother stations. The stations connected to thebus can be either ECUs, display devices, sen-sors, or actuators. They operate using theMulti-Master principle, whereby the stationsconcerned all have equal priority regardingtheir access to the bus. It is not necessary tohave a higher-order administration.

Data transfer between electronic systems Serial data transfer (CAN) 83

CAN

Transmission-shift controlStation 1

Engine managementStation 2

ABS/TCS/ESPStation 3

Instrument clusterStation 4

Linear bus topology2

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Content-based addressingThe CAN bus system does not address eachstation individually according to its features,but rather according to its message contents.It allocates each “message” a fixed “identi-fier” (message name) which identifies thecontents of the message in question (for in-stance, engine speed). This identifier has alength of 11 bits (standard format) or 29 bits(extended format).

With content-based addressing each sta-tion must itself decide whether it is inter-ested in the message or not (“message filter-ing” Fig. 3). This function can be performedby a special CAN module (Full-CAN), sothat less load is placed on the ECU’s centralmicrocontroller. Basic CAN modules “read”all messages. Using content-based address-ing, instead of allocating station addresses,makes the complete system highly flexible sothat equipment variants are easier to installand operate. If one of the ECUs requiresnew information which is already on thebus, all it needs to do is call it up from thebus. Similarly, provided they are receivers,new stations can be connected (imple-mented) without it being necessary to mod-ify the already existing stations.

Bus arbitrationThe identifier not only indicates the datacontent, but also defines the message’s prior-ity rating. An identifier corresponding to alow binary number has high priority andvice versa. Message priorities are a functionfor instance of the speed at which their con-tents change, or their significance with re-spect to safety. There are never two (ormore) messages of identical priority in thebus.

Each station can begin message transmis-sion as soon as the bus is unoccupied. Con-flict regarding bus access is avoided by ap-plying bit-by-bit identifier arbitration (Fig.4), whereby the message with the highestpriority is granted first access without delayand without loss of data bits (nondestruc-tive protocol).

The CAN protocol is based on the logicalstates “dominant” (logical 0) and “recessive”(logical 1). The “Wired And” arbitrationprinciple permits the dominant bits trans-mitted by a given station to overwrite the re-cessive bits of the other stations. The stationwith the lowest identifier (that is, with thehighest priority) is granted first access to thebus.

84 Data transfer between electronic systems Serial data transfer (CAN)

Figure 3Station 2 transmits,Station 1 and 4 acceptthe data.

Figure 4Station 2 gains first access (Signal on the bus = sig-nal from Station 2)

0 Dominant level1 Recessive level

Provision

Sendmessage

CANStation 1

CANStation 2

Bus

CANStation 3

CANStation 4

Accept

Selection

Reception

Accept

Selection Selection

Reception Reception

Addressing and message filtering (acceptance check)3

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Bus line1

0

Station 1loses the arbitration

Station 3loses the arbitration

Station 11

0

Station 21

0

Station 31

0

Bit-by-bit arbitration (allocation of bus access in case of several messages)

4

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The transmitters with low-priority messagesautomatically become receivers, and repeattheir transmission attempt as soon as thebus is vacant again.

In order that all messages have a chance ofentering the bus, the bus speed must be ap-propriate to the number of stations partici-pating in the bus. A cycle time is defined forthose signals which fluctuate permanently(e.g. engine speed).

Message formatCAN permits two different formats whichonly differ with respect to the length of theiridentifiers. The standard-format identifier is11 bits long, and the extended-format iden-tifier 29 bits. Both formats are compatiblewith each other and can be used together ina network. The data frame comprises sevenconsecutive fields (Fig. 5) and is a maximumof 130 bits long (standard format) or 150bits (extended format).

The bus is recessive at idle. With its domi-nant bit, the “Start of frame” indicates thebeginning of a message and synchronises allstations.

The “Arbitration field” consists of the mes-sage’s identifier (as described above) and anadditional control bit. While this field is be-ing transmitted, the transmitter accompa-nies the transmission of each bit with acheck to ensure that it is still authorized totransmit or whether another station with ahigher-priority message has accessed theBus. The control bit following the identifieris designated the RTR-bit (Remote Trans-mission Request). It defines whether themessage is a “Data frame” (message withdata) for a receiver station, or a “Remoteframe” (request for data) from a transmitterstation.

The “Control field” contains the IDE bit(Identifier Extension Bit) used to differenti-ate between standard format (IDE = 0) andextended format (IDE = 1), followed by a bit

reserved for future extensions. The remain-ing 4 bits in this field define the number ofdata bytes in the next data field. This enablesthe receiver to determine whether all datahas been received.

The “Data field” contains the actual messageinformation comprised of between 0 and8 bytes. A message with data length = 0 isused to synchronise distributed processes. Anumber of signals can be transmitted in asingle message (e.g. engine rpm and enginetemperature).

The “CRC Field” (Cyclic RedundancyCheck) contains the frame check word fordetecting possible transmission interference.

The “ACK Field” contains the acknowledge-ment signals used by the receiver stations toconfirm receipt of the message in non-cor-rupted form. This field comprises the ACKslot and the recessive ACK delimiter. TheACK slot is also transmitted recessively andoverwritten “dominantly” by the receiversupon the message being correctly received.Here, it is irrelevant whether the message isof significance or not for the particular re-ceiver in the sense of the message filtering oracceptance check. Only correct reception isconfirmed.

Data transfer between electronic systems Serial data transfer (CAN) 85

Figure 50 Dominant level,1 Recessive level.

* Number of bits

Data frame

Message frame

Start of FrameArbitration Field

Control FieldData Field

CRC FieldACK Field

End ofFrame

InterFrameSpace

1*1

012* 6* 16* 2* 7* 3* IDLEIDLE 0...64*

CAN message format5

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The “End of frame” marks the end of themessage and comprises 7 recessive bits.

The “Inter-frame space” comprises three bitswhich serve to separate successive messages.This means that the bus remains in the re-cessive IDLE mode until a station starts abus access.

As a rule, a sending station initiates datatransmission by sending a “data frame”. It isalso possible for a receiving station to call indata from a sending station by transmittinga “remote frame”.

Detecting errorsA number of control mechanisms for de-tecting errors are integrated in the CAN pro-tocol.

In the “CRC field”, the receiving stationcompares the received CRC sequence withthe sequence calculated from the message.

With the “Frame check”, frame errors arerecognized by checking the frame structure.The CAN protocol contains a number offixed-format bit fields which are checked byall stations.

The “ACK check” is the receiving stations’confirmation that a message frame has beenreceived. Its absence signifies for instancethat a transmission error has been detected.

“Monitoring” indicates that the sender ob-serves (monitors) the bus level and com-pares the differences between the bit that hasbeen sent and the bit that has been checked.

Compliance with “Bitstuffing” is checked bymeans of the “Code check”. The stuffing rulestipulates that in every “data frame” or “re-mote frame”, a maximum of 5 successiveequal-priority bits may be sent between the“Start of frame” and the end of the “CRCfield”. As soon as five identical bits have beentransmitted in succession, the sender insertsan opposite-priority bit. The receiving sta-

tion erases these opposite-polarity bits afterreceiving the message. Line errors can be de-tected using the “bitstuffing” principle.

If one of the stations detects an error, it in-terrupts the actual transmission by sendingan “Error frame” comprising six successivedominant bits. Its effect is based on the in-tended violation of the stuffing rule, and theobject is to prevent other stations acceptingthe faulty message.

Defective stations could have a derogatoryeffect upon the bus system by sending an“error frame” and interrupting faultlessmessages. To prevent this, CAN is providedwith a function which differentiates betweensporadic errors and those which are perma-nent, and which is capable of identifying thefaulty station. This takes place using statisti-cal evaluation of the error situations.

StandardizationThe International Organization for Stan-dardization (ISO) and SAE (Society of Auto-motive Engineers) have issued CAN stan-dards for data exchange in automotive appli-cations:

For low-speed applications up to125 kbit/s: ISO 11519-2, and

For high-speed applications above125 kbit/s: ISO 11898 and SAE J 22584(passenger cars) and SAE J 1939 (trucksand buses).

Furthermore, an ISO Standard on CANDiagnosis (ISO 15765 – Draft) is beingprepared.

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ProspectsAlong with the increasing levels of system-component performance and the rise infunction integration, the demands made onthe vehicle’s communication system are alsoon the increase. And new systems are con-tinually being introduced, for instance in theconsumer-electronics sector. All in all, it is tobe expected that a number of bus systemswill establish themselves in the vehicle, eachof which will be characterized by its ownparticular area of application.

In addition to electronic data transmission,optical transmission systems will also comeinto use in the multimedia area. These arevery-high-speed bus systems and can trans-mit large quantities of data as needed for au-dio and video components.

Individual functions will be combined bynetworking to form a system alliance cover-ing the complete vehicle, in which informa-tion can be exchanged via data buses. Theimplementation of such overlapping func-tions necessitates binding agreements cover-

ing interfaces and functional contents. TheCARTRONIC® from Bosch is the answer tothese stipulations, and has been developedas a priority-override and definition conceptfor all the vehicle’s closed and open-loopcontrol systems. The possible sub-division ofthe functions which are each controlled by acentral coordinator can be seen in Fig. 1.The functions can be incorporated in vari-ous ECUs.

The combination of components and sys-tems can result in completely novel func-tions. For instance, the exchange of data be-tween the transmission-shift control and thenavigation equipment can ensure that achange down is made in good time before agradient is reached. With the help of thenavigation facility, the headlamps will beable to adapt their beam of light to make itoptimal for varying driving situations andfor the route taken by the road (for instanceat road intersections). Car radios, sound-carrier drives, TV, telephone, E-mail, Inter-net, as well as the navigation and terminalequipment for traffic telematics will be net-worked to form a multimedia system.

Data transfer between electronic systems Prospects 87

Functions

ActuatorsSensorsModules

Bodywork and interior

On-board electrical system

Vehicle coordination

DriveVehicle

movement

Mobile Multimedia

CARTRONIC®: Design schematic1

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Actuators convert the electrical output sig-nals from the ECU into mechanical quanti-ties (e.g. for setting the EGR valve or thethrottle valve).

Electropneumatic transducersEGR valveWith exhaust-gas recirulation (EGR) a por-tion of the exhaust gas is led back into theengine’s intake tract with the object of re-ducing toxic emissions.

The quantity of exhaust gas directed backto the engine is controlled by an electrop-neumatic valve situated between the exhausttract and the intake tract. In future, electricvalves will be used for this purpose.

Boost-pressure actuatorIn order to provide for high engine torque atlow engine speeds, the exhaust-gas tur-bocharger is designed to generate high boostpressure in this rotational-speed range. Toprevent the generation of excessive boostpressure at high engine turbocharger speeds,the boost-pressure control’s actuator divertssome of the exhaust gas around the exhaust-gas turbocharger’s turbine by means of a so-called wastegate (Fig. 1).

Instead of the wastegate, turbines withvariable turbine geometry (VTG) can beused to adapt the turbocharger’s output. Inthe case of VTG, an electrical or electrop-neumatic valve varies the angle of the tur-bine blades in the exhaust-gas passage.

Swirl controllerIn the passenger car, swirl control is appliedto influence the swirl motion of the intakeair in the cylinder. The swirl itself is usuallygenerated by spiral-shaped intake ports.Since it determines the mixing of fuel andair in the combustion chamber, it has con-siderable influence upon combustion qual-ity. As a rule, a pronounced swirl is gener-ated at low speeds, and a weak swirl at highspeeds.

The swirl can be modified by the swirl con-troller (flap or slide valve) near to the intakevalve.

Intake-manifold flapOn the passenger-car UIS, the intake-mani-fold flap cuts off the supply of air when theengine is switched off so that less air is com-pressed and the engine stops smoothly. Theflap is controlled by an electropneumaticvalve.

Throttle valveThe throttle valve is controlled by an elec-tropneumatic valve, and in the diesel engineits function is very different to that in thegasoline engine. On the diesel engine itserves to increase the EGR rate by reducingthe overpressure in the intake manifold.Throttle-valve control is only operative inthe lower speed range.

88 Actuators Electropneumatic Transducers

Actuators

Figure 11 Boost-pressure ac-

tuator2 Vacuum pump3 Pressure actuator4 Exhaust-gas tur-

bocharger5 Bypass valve6 Exhaust-gas flow7 Intake-air flow8 Turbine9 Compressor

1

5

48

9

6

7

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3

Boost-pressure control with boost-pressure actuator1

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Robert Bosch GmbH

Continuous-operation braking systemsThese braking systems are used for reducingthe speed of heavy trucks without causingwear of the conventional braking compo-nents. They cannot stop the vehicle though.Since, in contrast to service brake systemswith friction wheel brakes, they adequatelydissipate the braking heat even when theyare applied over a long period, continuous-operation braking systems are most suitablefor slowing down the vehicle on extendeddownhill gradients. As a result, the frictionbrakes are used less and remain cool so thatthey can be applied to full effect in an emer-gency. The continuous-operation brakingsystem is controlled by the engine-manage-ment ECU.

Exhaust brakeThe injection of fuel into the engine is cutoff when the exhaust brake is switched on,and intake air which is drawn into the cylin-der is forced out again without havingmixed with fuel. An electropneumatic valveoperates a rotary valve or a flap in the ex-haust pipe which serves as an obstacle to theintake air attempting to leave the enginethrough the exhaust pipe. The resulting aircushion generated in the cylinder brakes thepiston in the compression and exhauststrokes. With the exhaust brake, there is nomeans of varying the degree of braking in-tensity.

Auxiliary engine brake When the engine is to be braked, an electro-hydraulic valve-lifting device opens the ex-haust valve at the end of the compressionstroke. The compression pressure collapsesas a result and energy is removed from thesystem. Lube oil is used as the hydraulicswitching medium.

RetarderThe retarder is an auxiliary braking systemwhich is completely independent of the en-gine. It is installed in the drivetrain down-

stream of the gearbox and is thus also effec-tive when passing through neutral duringgear changes. There are two different sys-tems:

Hydrodynamic retarderComprises a rotatable turbine wheel (brakerotor) and at the opposite end a fixed tur-bine wheel (brake stator). The rotor is me-chanically connected to the vehicle drive.When the brakes are applied, the bladechambers in the stator and rotor fill with oil.This oil is accelerated by the (rotating) rotorand decelerated by the (fixed) stator. In theprocess, the kinetic energy is converted toheat and dissipated to the engine coolant.The quantities of oil entering the rotor andstator chambers can be used for infinitevariation of the braking effect.

Electrodynamic retarderThis comprises an air-cooled soft-iron diskwhich rotates in a controllable electromag-netic field generated by the vehicle battery.The resulting eddy currents brake the disk,and with it the vehicle wheels. The brakingeffect is infinitely variable.

Engine-fan control

As a function of coolant temperature, theengine ECU switches the engine's fan onand off as required using an electromagneticclutch.

Electrically powered fans are being usedincreasingly. Since they are not driven by theengine V-belt, this permits innovative solu-tions regarding their location in the enginecompartment.

Actuators Continuous-operation braking systems 89

Robert Bosch GmbH

Start-assist systemsCompared to gasoline, diesel fuel is far moreeasily ignited. This is why the warm dieselengine starts immediately when cranked.The DI (direct injection) diesel engine evenstarts immediately at temperatures down to0 °C. When starting, the 250 °C auto-ignitiontemperature is reached when the engine iscranked at its starting speed. Prechamber en-gines (IDI – indirect injection) engines needsome form of start-assist system when start-ing “cold”. DI engines on the other hand onlyneed assistance when starting below 0 °C.The cylinders of prechamber and swirl-chamber engines are equipped with asheathed-element glow plug (GSK) in theirauxiliary combustion chamber which func-tions as a “hot spot”. On small DI engines(up to 1 l/cylinder), this “hot spot” is locatedon the combustion chamber’s periphery.Large DI truck engines on the other handhave the alternative of using air preheating inthe intake manifold (flame start), or special,easily ignitable fuel (Start Pilot) which issprayed into the intake air. Today, sheathed-element glow plugs are used practically with-out exception in start-assist systems.

Intake-air pre-heating Flame glow plugThe flame glow plug burns fuel in the intaketract to heat the incoming air. Normally, the

injection system’s supply pump delivers fuelto the flame plug through a solenoid valve.The flame plug’s connection fitting is pro-vided with a filter, and a metering devicewhich permits passage of precisely the rightamount of fuel appropriate to the particularengine. This fuel then evaporates in an evap-orator tube surrounding the tubular heatingelement and mixes with the intake air. Theresulting mixture ignites on the 1000 °Cheating element at the flame-plug tip. Theheating power is limited since the heaterflame must not consume more than a frac-tion of the oxygen needed for subsequentcombustion in the engine cylinder.

Electrical heatingA number of heater elements in the air-intakesystem are switched on and off by a relay.

Sheathed-element glow plugThe sheathed-element glow plug’s (GSK)glow element is so firmly pressed into theglow-plug shell (Fig. 1, Pos. 3) that a gas-tight seal is formed. The element is a metalglow tube (4) which is resistant to both cor-rosion and hot gases, and which contains aheater (glow) element embedded in magne-sium-oxide powder (6). This heater elementcomprises two series-connected resistors:the helical heating wire (7) in the glow-tubetip, and the control filament (5). Whereasthe helical heating wire maintains virtually

90 Actuators Start-assist systems

Figure 1 1 Electrical connector

terminal2 Insulating washer3 Glow-plug shell4 Glow tube5 Control filament6 Filling powder7 Helical heating wire8 Heater-element gas-

ket9 Double gasket10 Round nut

1 2 3 4 7

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Sheathed-element glow plug GSK21

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Robert Bosch GmbH

constant electrical resistance regardless oftemperature, the control filament is made ofmaterial with a positive temperature coeffi-cient (PTC). On newer-generation glowplugs (GSK2), its resistance increases evenmore rapidly with rising temperature thanwas the case with the conventional S-RSKglow plug. This means that the newer GSK2glow plugs are characterized by reaching thetemperature needed for ignition far morequickly (850 °C in 4 s). They also feature alower steady-state temperature which meansthat their temperature is limited to a non-critical level. The result is that the GSK2glow plug can remain on for up to 3 minutesfollowing engine start. This post-glow fea-ture improves both the warm-up and run-up phases with considerable improvementsin noise and exhaust-gas emissions.

Glow control unitThe glow control unit (GZS) uses a powerrelay for triggering the glow plugs. It receivesits start pulse from the engine ECU via atemperature sensor.

The glow control unit controls the glowduration of the glow plugs, as well as havingsafety and monitoring functions. Using theirdiagnosis functions, more sophisticatedglow control units are also able to recognisethe failure of individual glow plugs and in-form the driver accordingly. Multiple plugsare used as the control inputs to the glowcontrol units.

Functional sequenceThe diesel engine’s glow plug and starterswitch, which controls the preheat and start-ing sequence, functions in a similar mannerto the ignition and starting switch on thegasoline engine. Switching to the “ignitionon” position starts the preheating process(Fig. 3). When the glow-indicator lamp ex-tinguishes, this indicates that the glow plugsare hot enough for the engine to start, andcranking can begin. In the following startingphase, the droplets of injected fuel ignite inthe hot compressed air. The heat released as

a result leads to the initiation of the com-bustion process.

In the warm-up phase following a suc-cessful start, post-glow contributes to fault-less engine running (no misfiring) andtherefore to practically smokeless enginerun-up and idle. At the same time, when theengine is cold, pre-heating reduces combus-tion noise. A glow-plug safety switchoff pre-vents battery discharge in case the enginecannot be started.

The glow control unit can be coupled tothe ECU of the Electronic Diesel Control(EDC) so that information available in theEDC control unit can be applied for opti-mum control of the glow plugs in accor-dance with the particular operating condi-tions. This is yet another possibility for re-ducing the levels of blue smoke and noise.

Actuators Start-assist systems 91

Figure 31 Glow-plug and

starter switch2 Starter3 Indicator lamp4 To battery5 Glow plugs6 Self-sustained en-

gine operationtV Preheating timetS Ready to starttN Postheating time

Figure 21 Sheathed-element

glow plug2 Glow control unit3 Glow-plug and

starter switch4 To battery5 Indicator lamp6 Control line to the

engine ECU7 Diagnosis line

tV tS tN

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2

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4

56 Time t

Typical preheating sequence3

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EDC-controlled glow system in a direct-injection(DI) diesel engine

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Robert Bosch GmbH

Technical term

AAccelerator-pedal sensor, 32, 33Accumulator injection systemp Common Rail System (CRS)

Active surge damping control, 52Actuator diagnosis, 80Air-mass meter, 34, 35Altitude compensation, 53Analog input signals, 38Angle-of-rotation sensor (ARS)

(distributor pumps), 27Arbitration (CAN-Bus), 84ASIC (ECU), 41Auxiliary coolant heating, 73

BBIP control, 56Blower (or fan) triggering, 74, 89Boost-pressure control, 74, 88Boot-shaped injection characteristic

(Unit Pump System), 72Broad-band Lambda oxygen sensor, 36

CCascade control

(Lambda closed-loop control), 59Characteristic data for injection

systems (Overview), 5Closed-loop control, 44Closed-loop start-of-delivery control

(IWZ signal), 7Common Rail System (CRS),–, EDC triggering, 68f–, EDC overview, 17–, Principle of functioning, 10Continuous-operation braking

systems, 89 Controller Area Network (CAN), 82fCruise controlp Vehicle-speed control 49

Cylinder shutoff, 53Cylinder-balance control, 52

DData exchange with other

systems, 46, 47, 82fData processing (ECU), 38fDiagnosis interface, 80 Diagnosis, 78fDigital input signals, 39Distributor injection pumps,–, EDC overview, 15, 16–, EDC triggering (actuators), 64, 65–, EDC triggering (high-pressure

solenoid valve), 66, 67–, EDC principle of functioning, 7, 8Drive Recorder, 63

EElectronic control unit (ECU), 38fECU link-up–, Unit injector system, 72EGR–, Lambda-based closed-loop

control, 58Electronic Diesel Control (EDC),–, Functional overview, 45, 48–, Functions, 44f–, Overview, 12fEnd-of-Line (EoL) programming, 42Engine (exhaust) brake, 89Engine test bench, 62Engine-brake function, 53EPROM, EEPROM, 41Exhaust-gas recirculation

(EGR), 74, 88

FFlame glow plugs, 90Flash-EPROM, 41Fuel-quantity mean-value adaptation

(Lambda closed-loop control), 59–, Operating mode: Direct and

indirect control, 60Full-load smoke limitation

(Lambda closed-loop control), 60

GGlow control unit, 91

HHalf-differential short-circuiting-ring

sensor(Rack-travel sensor), 30

Hot-film air-mass meter, 34, 35

92 Index of technical terms

Index of Technical Terms

An arrow p indicates aterm in italics (e.g. p Common RailSystem) which is a syn-onym or related term.

Robert Bosch GmbH

IIdentifier (CAN addressing), 84Idle-speed control, 50Incremental angle/time (IWZ)

signal, 55Incremental angle-of-rotation sensor

(ARS) (Distributor injection pump), 27

Injected-fuel-quantity limit, 53In-line fuel-injection pumps–, EDC triggering, 63, 64–, EDC overview, 14f–, EDC principle of functioning, 6Intake-air pre-heating, 90Intake-duct switch-off, 73Intake-manifold flap, 88Intermediate-speed control, 51

LLambda closed-loop control, 57fLambda oxygen sensor, 36p Broad-band Lambda oxygen sensor, 36

MMain Injection (MI), 68Max. rpm control, 50Memory (ECU), 40, 41Message format (CAN), 85, 86

NNeedle-motion sensor, 31

OOn-Board-Diagnosis (OBD), 81Open-loop control, 44Oxygen pump cellp Broad-band Lambda oxygen sensor, 36

PParameters (engine), 75Phase sensor (camshaft), 28, 29Port-and-helix controlled injection

systemsp Distributor injection pumpsp In-line injection pumps

Post injection (POI), 68Pre-glow, 90, 91Pulse-shaped input signals, 39Pulse-width-modulated (pwm)

signal, 42

RRack-travel sensor, 30RAM, 41Real-time compatibility, 43Recharge, 69Retarder, 89ROM, 40

SSensors, 20f–, Accelerator-pedal, 32, 33–, Angle-of-rotation, 27–, Half-differential short-circuiting-

ring, 30–, Lambda oxygen, 36, 37–, Needle-motion, 31–, Phase (camshaft), 28, 29–, Pressure, 22f–, Rotational-speed, 26–, Temperature, 21Sheathed-element glow plug, 90, 91Single-plunger fuel-injection pumps

(Principle of functioning), 8Smooth-running control (SRC), 52Solenoid-valve-controlled injection

systemsp Common Rail System (CRS)p Distributor injection pumpsp Unit Pump System (UPS)p Unit Injector System (UIS)

Start-of-injection control(Needle-motion sensor), 54

Start-assist systems, 90, 91Start quantity, 50Substitute functions/Equivalent

functions, 74Swirl controller, 88

TThrottle valve, 88Torque control, 75fTriggering (injection system), 63f

UUnit Injector System (UIS), –, EDC triggering, 71, 72–, EDC overview, 18, 19–, Principle of functioning, 9, Unit Pump System (UPS),–, EDC triggering, 71, 72–, EDC overview, 19–, Principle of functioning, 9

VVehicle-speed control

(cruise control), 51Vehicle-speed limitation, 51

WWastegatep Boost-pressure control, 81, 88

Index of technical terms 93

Robert Bosch GmbH

Abbreviations

AABS: Antilock Braking SystemACC: Adaptive Cruise Control A/D: Analog/DigitalADF: Atmospheric-pressure sensor AGR: p Exhaust-gas recirculation

(EGR)ARD: p Active surge-damping controlARF: p Exhaust-gas recirculation

(EGR)ARS: Angle-of-rotation sensorp Accelerator-pedal sensor

ASIC: Application Specific Integrated Circuit

ASR: Traction Control System (TCS)AZG: Adaptive cylinder balancing

BBIP signal: Signal for Beginning of the

Injection Period (also known as Begin of Injection Period) p (BIP control)

CCAN: p Controller Area NetworkCO: Carbon monoxideCO2: Carbon dioxideCR System: p Common Rail System

DDI: Direct InjectionDZG: Rotational-speed sensor

(p Sensors)

EEAB: p ELABECE: Economic Commission for

EuropeEDC: Electronic Control Unit

(p Electronic Diesel Control)EG: European UnionELAB: Electrical shutoff valve

(In-line and distributor pumps)EMV: Electromagnetic compatibility

(EMC)EOBD: European p On-Board

DiagnosisEOL programming: p End-of-Line programming

ESP: Electronic Stability ProgramEU: European Union

FFGB: p Vehicle-speed limitationFGR: p Vehicle-speed control

(Cruise Control)

GGSK: p Sheathed-element glow plugGZS: p Glow control unit

HHC: Generic term for hydrocarbonsHDK: Half-differential short-circuiting-

ring sensor p SensorsHE: Main Injection p MIHFM: (p Hot-film air-mass meter)HGB: (p Vehicle-speed limitation)

IIDI: Indirect Injection

(Prechamber engines)ISO: International Organization for

StandardizationIWZ-Signal: p Incremental angle/time

signal

KKW: Crankshaft (cks)

LLDR: p Boost-pressure controlLLR: p Idle-speed controlLRR: p Smooth-running control

MMAB: Fuel shutoffMAR: p Smooth Running Control

(SRC)MI: p Main InjectionMIL: Malfuction Indicator Lamp

(diagnosis lamp)MMA: p Fuel-quantity mean-value

adaptation (Lambda closed-loop control)

MNEFZ: Modified new European driving cycle (exhaust-gas test)

MSG: Engine ECUMV: Solenoid valve

94 Index of technical terms Abbreviations

Robert Bosch GmbH

NNBF: Needle-motion sensorp Sensors

NBS: p Needle-motion sensorNE: p Post injection p POINOX: Generic term for oxides of

nitrogenNTC: Negative Temperature

CoefficientNW: Camshaft (cms)

OO2: OxygenOBD: p On-Board DiagnosisOT: Top Dead Center (TDC)

PPDE: p Unit Injector SystemPE pump: p In-line fuel-injection

pumpsPF pump: p Single-plunger fuel-

injection pumpsPI: Pilot InjectionPLD: p Unit Pump system (UPS)POI: Post InjectionPSG: Pump ECU p Distributor injection pumps

PTC: Positive Temperature CoefficientPWG: Accelerator-pedal sensor p Sensors

PWM signal: p Pulse-width-modulated (pwm) signal

RRWG: p Rack-travel sensor

SSAE: Society of Automotive Engineers SRC: p Smooth Running Control

TTCS: p (ASR)TD signal: Rotational-speed signalTQ signal: Fuel-consumption signal

UUIS: p Unit Injector SystemUPS: p Unit Pump SystemUT: Bottom Dead Center (BDC)

VVE p Distributor injection

pumpVP30: Solenoid-valve-controlled axial-

piston p Distributor injection pump

VP44: Radial-piston pumpp Distributor injection pump

VR pump: Radial-piston-p Distributor injection pump

VTG: Turbocharger with Variable Turbine Geometry

ZZDR: p Intermediate-speed control

Index of technical terms Abbreviations 95

Robert Bosch GmbH

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