camless engines (1)

7/29/2019 Camless Engines (1)

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CAMLESSENGINES


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Introduction

CAMS

Control the breathing channels (valves) of an ICengine

Connected to camshaft which is operated bycrankshaft

Cams push open valves at proper time & guidetheir closure

But they are inflexible except VTEC & VVT-I

Engineers could not vary timing, lift & duration ofvalve opening infinitely


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CAMLESS ENGINES

Eliminated mechanical linkages

Could provide infinite variation of valveparameters

It can make engines clean, efficient &

responsive


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Working of conventionalengines

The 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


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Conventional engine valves
http://us1.webpublications.com.au/static/images/articles/i9/0910_3mg.jpg


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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


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Camless engines overview

Main sensors -

Engine load sensor Exhaust gas sensorValve position sensor Engine speed sensor

ELECTRONIC

CONTROL

UNIT

SENSORS ACTUATORS


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Sensors senseparameters & send signals to

ECU

ECU contains microprocessors withassociated software

This ECU controls the actuators to work

according to requirements


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Actuators

It is a electro-hydraulic camless valve train

(ECV)

Uses elastic property of compressedhydraulic fluid which acts like a liquid

spring, accelerates & decelerates the valves


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Hydraulic pendulum

Involves conversion of PE to KE and back

to PE with minimum energy lossDuring acceleration of valves PE is

converted to KE

During deceleration of valve energy ofmoving valve is returned to fluid


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Detailed view of HydraulicPendulum


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Operation of hydraulicpendulum


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Lift, timing & duration of valve opening is

varied by controlling solenoid valves

This is done by ECU when signals are sentfrom the sensors


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Modifier Rod

Used to impart

Unequal lift to the

paired valves

Zero motion to any

valve


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Modifier Rod Operation


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Advantages

Offers 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


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Resultant Advantages

Better fuel economy- 7 to 10 % increase

Higher torque & power- 10 to 15 %

increase

Lower exhaust emissions- EGR system is

eliminated since EGR effect occurs on its

own & thus reduces NOx

emissions

Reduction in size & weight


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Disadvantages

Opening & closing of valves requires some power-

Electromechanical- alternator

Electrohydraulic- accumulator

Sophisticated electronic control required forgentle seating of valves

Current solenoids cannot run at high rpms;

Hidden cost of microprocessor & softwarecontrols


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Conclusion

Even though some disadvantages are

present, we can expect electrohydraulic &

electromechanical valves to replace the

conventional camshaft technology.


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Thanks

camless engines (1)

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