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 Engineers 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 engines 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

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 ELECTRONIC CONTROL UNIT SENSORS ACTUATORS

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

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

Hydraulic pendulum Involves 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

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

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

Disadvantages Opening & closing of valves requires some power- Electromechanical- alternator Electrohydraulic- accumulator Sophisticated electronic control required for gentle seating of valves Current solenoids cannot run at high rpms; Hidden cost of microprocessor & software controls

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

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