CAMLESSCAMLESS ENGINESENGINES

Presented byPresented by:: Nitesh ChowdhuryNitesh Chowdhury

IntroductionIntroduction CAMSCAMS Control the breathing channels (valves) of an IC Control the breathing channels (valves) of an IC

engineengine Connected to camshaft which is operated by Connected to camshaft which is operated by

crankshaftcrankshaft Cams push open valves at proper time & guide Cams push open valves at proper time & guide

their closuretheir closure But they are inflexible except VTEC & VVT-IBut they are inflexible except VTEC & VVT-I Engineers could not vary timing, lift & duration of Engineers could not vary timing, lift & duration of

valve opening infinitelyvalve opening infinitely

CAMLESS ENGINESCAMLESS ENGINES Eliminated mechanical linkagesEliminated mechanical linkages Could provide infinite variation of valve Could provide infinite variation of valve

parametersparameters It can make engines clean, efficient & It can make engines clean, efficient &

responsiveresponsive

Working of Working of conventional enginesconventional engines

The crankshaft turns camshaft which The crankshaft turns camshaft which operates valves by mechanism as in figureoperates valves by mechanism as in figure

Spring brings back valve to initial positionSpring brings back valve to initial position Timing of engine valves depends on shape Timing of engine valves depends on shape

of camsof cams

Conventional engine Conventional engine valvesvalves

Engineers must design cams in the Engineers must design cams in the development stagesdevelopment stages

This design is compromises between engine This design is compromises between engine power & fuel efficiencypower & fuel efficiency

Considering this compromise automobile Considering this compromise automobile companies brought variable valve timing companies brought variable valve timing mechanisms mechanisms

But its effects are limitedBut its effects are limited

Camless engines Camless engines overviewoverview

Main sensors -Main sensors - Engine load sensor Exhaust gas sensorEngine load sensor Exhaust gas sensor Valve position sensor Engine speed sensorValve position sensor Engine speed sensor

ELECTRONIC CONTROL

UNIT SENSORS ACTUATORS

Sensors senseSensors sense parameters & send signals to parameters & send signals to ECU ECU

ECU contains microprocessors with ECU contains microprocessors with associated softwareassociated software

This ECU controls the actuators to work This ECU controls the actuators to work according to requirementsaccording to requirements

ActuatorsActuators It is a electro-hydraulic camless valve train It is a electro-hydraulic camless valve train

(ECV) (ECV) Uses elastic property of compressed Uses elastic property of compressed

hydraulic fluid which acts like a liquid hydraulic fluid which acts like a liquid spring, accelerates & decelerates the valvesspring, accelerates & decelerates the valves

Hydraulic pendulumHydraulic pendulum Involves conversion of PE to KE and back Involves conversion of PE to KE and back

to PE with minimum energy lossto PE with minimum energy loss During acceleration of valves PE is During acceleration of valves PE is

converted to KEconverted to KE During deceleration of valve energy of During deceleration of valve energy of

moving valve is returned to fluidmoving valve is returned to fluid

Detailed view of Detailed view of Hydraulic PendulumHydraulic Pendulum

Operation of hydraulic Operation of hydraulic pendulumpendulum

Step 1:Step 1: The solenoid valve The solenoid valve (high- pressure) is opened, and the (high- pressure) is opened, and the high-pressure fluid enters the high-pressure fluid enters the volume above the valve piston. volume above the valve piston. The pressure above and below the The pressure above and below the piston become equal, but, because piston become equal, but, because of the difference in the pressure of the difference in the pressure areas, the constant net hydraulic areas, the constant net hydraulic force is directed downward. It force is directed downward. It opens the valve and accelerates it opens the valve and accelerates it in the direction of opening. The in the direction of opening. The other solenoid valve and the two other solenoid valve and the two check valves remain closed. check valves remain closed.

Step 2: The opening solenoid valve closes The opening solenoid valve closes and the pressure above the piston drops, but the and the pressure above the piston drops, but the engine valve continues its downward movement engine valve continues its downward movement due to momentum. Low-pressure check valve due to momentum. Low-pressure check valve opens and the volume above the piston is filled opens and the volume above the piston is filled with the low-pressure fluid. The downward with the low-pressure fluid. The downward motion of the piston pumps the high-pressure motion of the piston pumps the high-pressure fluid from the volume below the piston back into fluid from the volume below the piston back into the high-pressure rail. This recovers some of the the high-pressure rail. This recovers some of the energy that was previously spent to accelerate energy that was previously spent to accelerate the valve. The ratio of the high and low-the valve. The ratio of the high and low-pressures is selected so, that the net pressure pressures is selected so, that the net pressure force is directed upward and the valve force is directed upward and the valve decelerates until it exhausts its kinetic energy decelerates until it exhausts its kinetic energy and its motion stops. At this point, the opening and its motion stops. At this point, the opening check valve closes, and the fluid above the piston check valve closes, and the fluid above the piston is trapped. is trapped.

This prevents the return motion of the piston, and the engine valve remains fixed in This prevents the return motion of the piston, and the engine valve remains fixed in its open position trapped by hydraulic pressures on both sides of the pistonits open position trapped by hydraulic pressures on both sides of the piston.

Step 3:Step 3: which is the which is the open dwell open dwell position. The position. The engine valve engine valve remains in the open remains in the open dwell position as dwell position as long as necessary.long as necessary.

Step 4Step 4 illustrates the beginning illustrates the beginning of the valve closing. The closing of the valve closing. The closing (low-pressure) solenoid valve (low-pressure) solenoid valve opens and connects the volume opens and connects the volume above the piston with the low-above the piston with the low-pressure rail. The net pressure pressure rail. The net pressure force is directed upward and force is directed upward and the engine valve accelerates in the engine valve accelerates in the direction of closing, the direction of closing, pumping the fluid from the pumping the fluid from the upper volume back into the low-upper volume back into the low-pressure reservoir. The other pressure reservoir. The other solenoid valve and both check solenoid valve and both check valves remain closed during valves remain closed during acceleration.acceleration.

Step 5Step 5 the closing solenoid valve closes the closing solenoid valve closes and the upper volume is disconnected from and the upper volume is disconnected from the low-pressure rail, but the engine valve the low-pressure rail, but the engine valve continues its upward motion due to its continues its upward motion due to its momentum. Rising pressure in the upper momentum. Rising pressure in the upper volume opens the high-pressure check valve volume opens the high-pressure check valve that connects this volume with the high-that connects this volume with the high-pressure reservoir. The upward motion of pressure reservoir. The upward motion of the valve piston pumps the fluid from the the valve piston pumps the fluid from the volume above the piston into the high-volume above the piston into the high-pressure reservoir, while the increasing pressure reservoir, while the increasing volume below the piston is filled with fluid volume below the piston is filled with fluid from the same reservoir. Since the change from the same reservoir. Since the change of volume below the piston is only a fraction of volume below the piston is only a fraction of that above the piston, the net flow of the of that above the piston, the net flow of the fluid is into the high-pressure reservoir. fluid is into the high-pressure reservoir. Again, as it was the case during the valve Again, as it was the case during the valve opening, energy recovery takes place. opening, energy recovery takes place.

Thus, in this system the energy recovery takes place twice each valve event. Thus, in this system the energy recovery takes place twice each valve event. When the valve exhausts its kinetic energy, its motion stops, and the check valve When the valve exhausts its kinetic energy, its motion stops, and the check valve closes.closes.

Step 6:Step 6: it illustrates the it illustrates the valve seating. After that, the valve seating. After that, the closing solenoid valve is closing solenoid valve is deactivated again. For the rest deactivated again. For the rest of the cycle both solenoid of the cycle both solenoid valves and both check valves valves and both check valves are closed, the pressure above are closed, the pressure above the valve piston is equal to the the valve piston is equal to the pressure in the low-pressure pressure in the low-pressure reservoir, and the high reservoir, and the high pressure below the piston keeps pressure below the piston keeps the engine valve firmly closed.the engine valve firmly closed.

Lift, timing & duration of valve opening is Lift, timing & duration of valve opening is varied by controlling solenoid valves varied by controlling solenoid valves

This is done by ECU when signals are sent This is done by ECU when signals are sent from the sensorsfrom the sensors

Modifier RodModifier Rod Used to impart Used to impart Unequal lift to the Unequal lift to the

paired valves paired valves Zero motion to any Zero motion to any

valvevalve

To enhance the ability to vary the intake air motion in the To enhance the ability to vary the intake air motion in the engine cylinder, it is often desirable to have unequal lift of engine cylinder, it is often desirable to have unequal lift of the two intake valves, or even to keep one of the two valves the two intake valves, or even to keep one of the two valves closed while the other opens. In some cases it may also be closed while the other opens. In some cases it may also be used for paired exhaust valves. The lift modifier is then used used for paired exhaust valves. The lift modifier is then used to restrict the opening of one the paired valves. The modifier to restrict the opening of one the paired valves. The modifier is shown schematically in Figure above as a Rotating rod is shown schematically in Figure above as a Rotating rod with its axis of rotation perpendicular to the plane of the with its axis of rotation perpendicular to the plane of the drawing. The rod is installed in the cylinder head between drawing. The rod is installed in the cylinder head between the two intake valves. A cutout in the rod forms a the two intake valves. A cutout in the rod forms a communication chamber connected to the volumes below the communication chamber connected to the volumes below the hydraulic pistons of both intake valves. The communication hydraulic pistons of both intake valves. The communication chamber is always connected to the high pressure reservoir. chamber is always connected to the high pressure reservoir.

Modifier Rod OperationModifier Rod OperationIn the case A the In the case A the modifier is in the modifier is in the neutral position, and neutral position, and both valves operate both valves operate in unisonin unison

In the case B the modifier rod is shown In the case B the modifier rod is shown turned 90 degrees clockwise. The exit of turned 90 degrees clockwise. The exit of oil from the volume below the hydraulic oil from the volume below the hydraulic piston in the valve No. 1 is blocked and piston in the valve No. 1 is blocked and the valve cannot move in the direction of the valve cannot move in the direction of opening. However, the entry of oil into opening. However, the entry of oil into the volume below the hydraulic piston is the volume below the hydraulic piston is permitted by a one-way valve installed permitted by a one-way valve installed in the modifier rod. This guarantees in the modifier rod. This guarantees that, whenever deactivation takes place, that, whenever deactivation takes place, the valve No. 1 will close and remain the valve No. 1 will close and remain closed, while the valve No.2 continues closed, while the valve No.2 continues its normal operation.its normal operation.

In the case C the lift of one of the valves In the case C the lift of one of the valves is reduced relative to the second one. The is reduced relative to the second one. The rod is turned a smaller angle so that the rod is turned a smaller angle so that the exit of oil from the valve No. 1 into the exit of oil from the valve No. 1 into the communication chamber is not communication chamber is not completely blocked, but the flow is completely blocked, but the flow is significantly throttled. As a result, the significantly throttled. As a result, the motion of the valve No. 1 is slowed down motion of the valve No. 1 is slowed down and its lift is less than that of the valve and its lift is less than that of the valve No.2. Varying the angular position of the No.2. Varying the angular position of the modifier rod 26 varies the degree of oil modifier rod 26 varies the degree of oil throttling, thus varying the lift of the throttling, thus varying the lift of the valve No. 1.valve No. 1.

AdvantagesAdvantages Offers continuously variable & independent Offers continuously variable & independent

control of all aspects of valve motion - lift, control of all aspects of valve motion - lift, operation duration, event of openingoperation duration, event of opening

ECV system can control valve velocity, ECV system can control valve velocity, valve acceleration and decelerationvalve acceleration and deceleration

Resultant AdvantagesResultant Advantages Better fuel economy- 7 to 10 % increaseBetter fuel economy- 7 to 10 % increase Higher torque & power- 10 to 15 % Higher torque & power- 10 to 15 %

increaseincrease Lower exhaust emissions- EGR system is Lower exhaust emissions- EGR system is

eliminated since EGR effect occurs on its eliminated since EGR effect occurs on its own & thus reduces NOown & thus reduces NOx x emissionsemissions

Reduction in size & weightReduction in size & weight

DisadvantagesDisadvantages Opening & closing of valves requires some power- Opening & closing of valves requires some power- Electromechanical- alternatorElectromechanical- alternator Electrohydraulic- accumulatorElectrohydraulic- accumulator Sophisticated electronic control required for Sophisticated electronic control required for

gentle seating of valves gentle seating of valves Current solenoids cannot run at high rpms;Current solenoids cannot run at high rpms; Hidden cost of microprocessor & software Hidden cost of microprocessor & software

controlscontrols

ConclusionConclusion Even though some disadvantages are Even though some disadvantages are

present, we can expect electro hydraulic & present, we can expect electro hydraulic & electromechanical valves to replace the electromechanical valves to replace the conventional camshaft technology.conventional camshaft technology.

BIBLIOGRAPHY

www.machinedesign.comwww.machinedesign.com www.diedelnet.comwww.diedelnet.com www.greendieseltechnology.comwww.greendieseltechnology.com www.techwizardz.blogspot.comwww.techwizardz.blogspot.com

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