camless engines

Download CAMLESS ENGINES

Post on 25-Nov-2014

118 views

Category:

Documents

8 download

Embed Size (px)

TRANSCRIPT

CAMLESS ENGINES

Introduction

CAMS Control the breathing channels (valves) of an IC engine Connected to camshaft which is operated by crankshaft Cams push open valves at proper time & guide their closure But they are inflexible except VTEC & VVT-I VVTEngineers could not vary timing, lift & duration of valve opening infinitely

CAMLESS ENGINES Eliminated mechanical linkages Could provide infinite variation of valve parameters It can make engines clean, efficient & responsive

Working of conventional enginesThe crankshaft turns camshaft which operates valves by mechanism as in figure Spring brings back valve to initial position Timing of engine valves depends on shape of cams

Conventional engine valves

Engineers must design cams in the development stages This design compromises b/n engine power & fuel efficiency Considering this compromise automobile companies brought variable valve timing mechanisms But is effects were limited

Camless engines overview

Main sensors Engine load sensor Exhaust gas sensor Valve position sensor Engine speed sensor

SENSORS

ELECTRONIC CONTROL UNIT

ACTUATORS

Sensors sense parameters & send signals to ECU ECU contains microprocessors with associated software This ECU controls the actuators to work according to requirements

ActuatorsIt is a electro-hydraulic camless valve train electro(ECV) Uses elastic property of compressed hydraulic fluid which acts like a liquid spring, accelerates & decelerates the valves

Hydraulic pendulumInvolves conversion of PE to KE and back to PE with minimum energy loss During acceleration of valves PE is converted to KE During deceleration of valve energy of moving valve is returned to fluid

Detailed view of Hydraulic Pendulum

Operation of hydraulic pendulum

Lift, timing & duration of valve opening is varied by controlling solenoid valves This is done by ECU when signals are sent from the sensors

Modifier Rod

Used to impart Unequal lift to the paired valves Zero motion to any valve

Modifier Rod Operation

AdvantagesOffers continuously variable & independent control of all aspects of valve motion - lift, operation duration, event of opening ECV system can control valve velocity, valve acceleration and deceleration

Resultant AdvantagesBetter fuel economy- 7 to 10 % increase economy Higher torque & power- 10 to 15 % powerincrease Lower exhaust emissions- EGR system is emissionseliminated since EGR effect occurs on its own & thus reduces NOx emissions Reduction in size & weight

DisadvantagesOpening & closing of valves requires some powerpowerElectromechanicalElectromechanical- alternator ElectrohydraulicElectrohydraulic- accumulator Sophisticated electronic control required for gentle seating of valves Current solenoids cannot run at high rpms; Hidden cost of microprocessor & software controls

ConclusionEven though some disadvantages are present, we can expect electrohydraulic & electromechanical valves to replace the conventional camshaft technology.

Thanks

Q&A

View more >