15-01-2013, 02:09 PM
CAMLESS ENGINES
CAMLESS ENGINES.ppt (Size: 830 KB / Downloads: 274)
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
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
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
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
Conclusion
Even though some disadvantages are present, we can expect electrohydraulic & electromechanical valves to replace the conventional camshaft technology.