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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

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Presentation Transcript
introduction
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
slide3
CAMLESS ENGINES
  • Eliminated mechanical linkages
  • Could provide infinite variation of valve parameters
  • It can make engines clean, efficient & responsive
working of conventional engines
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
slide6
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

ELECTRONIC CONTROL UNIT

ACTUATORS

SENSORS

Camless engines overview
  • Main sensors -
  • Engine load sensor Exhaust gas sensor
  • Valve position sensor Engine speed sensor
slide8
Sensors senseparameters & send signals to ECU
  • ECU contains microprocessors with associated software
  • This ECU controls the actuators to work according to requirements
actuators
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
slide10
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
slide15
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
Modifier Rod
  • Used to impart
  • Unequal lift to the paired valves
  • Zero motion to any valve
advantages
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
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
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
Conclusion

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