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7/29/2019 Camless Engines (1)
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CAMLESSENGINES
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Introduction
CAMS
Control the breathing channels (valves) of an ICengine
Connected to camshaft which is operated bycrankshaft
Cams push open valves at proper time & guidetheir closure
But they are inflexible except VTEC & VVT-I
Engineers could not vary timing, lift & duration ofvalve opening infinitely
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CAMLESS ENGINES
Eliminated mechanical linkages
Could provide infinite variation of valveparameters
It can make engines clean, efficient &
responsive
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Working of conventionalengines
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
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Conventional engine valves
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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
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Camless engines overview
Main sensors -
Engine load sensor Exhaust gas sensorValve position sensor Engine speed sensor
ELECTRONIC
CONTROL
UNIT
SENSORS ACTUATORS
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Sensors senseparameters & send signals to
ECU
ECU contains microprocessors withassociated software
This ECU controls the actuators to work
according to requirements
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Actuators
It is a electro-hydraulic camless valve train
(ECV)
Uses elastic property of compressedhydraulic fluid which acts like a liquid
spring, accelerates & decelerates the valves
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Hydraulic pendulum
Involves conversion of PE to KE and back
to PE with minimum energy lossDuring acceleration of valves PE is
converted to KE
During deceleration of valve energy ofmoving valve is returned to fluid
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Detailed view of HydraulicPendulum
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Operation of hydraulicpendulum
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Lift, timing & duration of valve opening is
varied by controlling solenoid valves
This is done by ECU when signals are sentfrom the sensors
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Modifier Rod
Used to impart
Unequal lift to the
paired valves
Zero motion to any
valve
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Modifier Rod Operation
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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
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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
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Disadvantages
Opening & closing of valves requires some power-
Electromechanical- alternator
Electrohydraulic- accumulator
Sophisticated electronic control required forgentle seating of valves
Current solenoids cannot run at high rpms;
Hidden cost of microprocessor & softwarecontrols
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Conclusion
Even though some disadvantages are
present, we can expect electrohydraulic &
electromechanical valves to replace the
conventional camshaft technology.
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Thanks