CAMLESSCAMLESS ENGINESENGINES

IntroductionIntroduction CAMSCAMS Control the breathing channels (valves) of an IC Control the breathing channels (valves) of an IC

engineengine Connected to camshaft which is operated by Connected to camshaft which is operated by

crankshaftcrankshaft Cams push open valves at proper time & guide Cams push open valves at proper time & guide

their closuretheir closure But they are inflexible except VTEC & VVT-IBut they are inflexible except VTEC & VVT-I Engineers could not vary timing, lift & duration of Engineers could not vary timing, lift & duration of

valve opening infinitelyvalve opening infinitely

CAMLESS ENGINESCAMLESS ENGINES Eliminated mechanical linkagesEliminated mechanical linkages Could provide infinite variation of valve Could provide infinite variation of valve

parametersparameters It can make engines clean, efficient & It can make engines clean, efficient &

responsiveresponsive

Working of conventional Working of conventional enginesengines

The crankshaft turns camshaft which The crankshaft turns camshaft which operates valves by mechanism as in figureoperates valves by mechanism as in figure

Spring brings back valve to initial positionSpring brings back valve to initial position Timing of engine valves depends on shape Timing of engine valves depends on shape

of camsof cams

Conventional engine valvesConventional engine valves

Engineers must design cams in the Engineers must design cams in the development stagesdevelopment stages

This design compromises b/n engine power This design compromises b/n engine power & fuel efficiency& fuel efficiency

Considering this compromise automobile Considering this compromise automobile companies brought variable valve timing companies brought variable valve timing mechanisms mechanisms

But is effects were limitedBut is effects were limited

Camless engines overviewCamless engines overview

Main sensors -Main sensors - Engine load sensor Exhaust gas sensorEngine load sensor Exhaust gas sensor Valve position sensor Engine speed sensorValve position sensor Engine speed sensor

ELECTRONIC CONTROL

UNIT SENSORS ACTUATORS

Sensors senseSensors sense parameters & send signals to parameters & send signals to ECU ECU

ECU contains microprocessors with ECU contains microprocessors with associated softwareassociated software

This ECU controls the actuators to work This ECU controls the actuators to work according to requirementsaccording to requirements

ActuatorsActuators

It is a electro-hydraulic camless valve train It is a electro-hydraulic camless valve train (ECV) (ECV)

Uses elastic property of compressed Uses elastic property of compressed hydraulic fluid which acts like a liquid hydraulic fluid which acts like a liquid spring, accelerates & decelerates the valvesspring, accelerates & decelerates the valves

Hydraulic pendulumHydraulic pendulum Involves conversion of PE to KE and back Involves conversion of PE to KE and back

to PE with minimum energy lossto PE with minimum energy loss During acceleration of valves PE is During acceleration of valves PE is

converted to KEconverted to KE During deceleration of valve energy of During deceleration of valve energy of

moving valve is returned to fluidmoving valve is returned to fluid

Detailed view of Hydraulic Detailed view of Hydraulic PendulumPendulum

Operation of hydraulic Operation of hydraulic pendulumpendulum

Lift, timing & duration of valve opening is Lift, timing & duration of valve opening is varied by controlling solenoid valves varied by controlling solenoid valves

This is done by ECU when signals are sent This is done by ECU when signals are sent from the sensorsfrom the sensors

Modifier RodModifier Rod

Used to impart Used to impart Unequal lift to the Unequal lift to the

paired valves paired valves Zero motion to any Zero motion to any

valvevalve

Modifier Rod OperationModifier Rod Operation

AdvantagesAdvantages

Offers continuously variable & independent Offers continuously variable & independent control of all aspects of valve motion - control of all aspects of valve motion - lift, operation duration, event of openinglift, operation duration, event of opening

ECV system can control valve velocity, ECV system can control valve velocity, valve acceleration and decelerationvalve acceleration and deceleration

Resultant AdvantagesResultant Advantages

Better fuel economy- 7 to 10 % increaseBetter fuel economy- 7 to 10 % increase Higher torque & power- 10 to 15 % Higher torque & power- 10 to 15 %

increaseincrease Lower exhaust emissions- EGR system is Lower exhaust emissions- EGR system is

eliminated since EGR effect occurs on its eliminated since EGR effect occurs on its own & thus reduces NOown & thus reduces NOx x emissionsemissions

Reduction in size & weightReduction in size & weight

DisadvantagesDisadvantages

Opening & closing of valves requires some power- Opening & closing of valves requires some power- Electromechanical- alternatorElectromechanical- alternator Electrohydraulic- accumulatorElectrohydraulic- accumulator

Sophisticated electronic control required for Sophisticated electronic control required for gentle seating of valves gentle seating of valves

Current solenoids cannot run at high rpms;Current solenoids cannot run at high rpms;

Hidden cost of microprocessor & software Hidden cost of microprocessor & software controlscontrols

ConclusionConclusion

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

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