CAMLESS ENGINES Introduction CAMS Control the breathing channels

CAMLESS ENGINES

Introduction § Ø Ø Ø 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 Ø Eliminated mechanical linkages Ø Could provide infinite variation of valve parameters Ø It can make engines clean, efficient & responsive n

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

Conventional engine valves

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

Camless engines overview n 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 n ECU contains microprocessors with associated software n This ECU controls the actuators to work according to requirements n

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

§ Hydraulic pendulum Ø Involves conversion of PE to KE and back to PE with minimum energy loss Ø During acceleration of valves PE is converted to KE Ø 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 n This is done by ECU when signals are sent from the sensors n

Modifier Rod n Ø Ø 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 n ECV system can control valve velocity, valve acceleration and deceleration n

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

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 n

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

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