04-10-2016, 10:15 AM
1457594763-camlessengines121110070108phpapp02.ppt (Size: 435.5 KB / Downloads: 6)
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
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.
Main sensors
Engine load sensor Exhaust gas sensor
Valve position sensor Engine speed sensor
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
Lift, timing & duration of valve opening is varied by controlling solenoid valves
This is done by ECU when signals are sent from the sensors
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.
Reduction in size & weight
Disadvantages
Opening & closing of valves requires some power.
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.