Camless Engine
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07-04-2009, 09:35 PM


The cam has been an integral part of the IC engine from its invention. The cam controls the €œbreathing channels of the IC engines, that is, the valves through which the fuel air mixture (in SI engines) or air (in CI engines) is supplied and exhaust driven out The cam has been an integral part of the IC engine from its invention. The cam controls theœbreathing channelsof the IC engines, that is, the valves through which the fuel air mixture (in SI engines) or air (in CI engines) is supplied and exhaust driven out The aim of all this effort is liberation from a constraint that has handcuffed performance since the birth of the internal-combustion engine more than a century ago. Camless engine technology is soon to be a reality for commercial vehicles. In the Camless valve train, the valve motion is controlled directly by a valve actuator - theres no camshaft or connecting mechanisms. Precise electronic circuit controls the operation of the mechanism, thus bringing in more flexibility and accuracy in opening and closing the valves. The seminar and presentation looks at the working of the electronically controlled camless engine with electro-mechanical valve actuator, its general features and benefits over conventional engine
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14-07-2009, 09:11 PM

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28-08-2009, 11:49 PM


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Most piston engines today employ one or more camshafts to operate poppet valves. The lobes on the camshafts operate cam followers which in turn open the poppet valves. A camless (or, free valve engine) uses electromagnetic, hydraulic, or pneumatic actuators to open the poppet valves instead. Actuators can be used to both open and close the valves, or an actuator opens the valve while a spring closes it.

As a camshaft normally has only one lobe per valve, the valve duration and lift is fixed. In the case of a four stroke engine, the camshaft runs at half the engine speed. Although many modern engines use camshaft phasing, adjusting the lift and valve duration in a working engine is more difficult. Some manufacturers use systems with more than one cam lobe, but this is still a compromise as only a few profiles can be in operation at once. This is not the case with the camless engine, where lift and valve timing can be adjusted freely from valve to valve and from cycle to cycle. It also allows multiple lift events per cycle and, indeed, no events per cycle”switching off the cylinder entirely.

Camless engines are not without their problems though. Common problems include high power consumption, accuracy at high speed, temperature sensitivity, weight and packaging issues, high noise, high cost, and unsafe operation in case of electrical problems.

Camless valve trains have long been investigated by several companies, this includes Renault, BMW, Fiat, Valeo, General Motors, Ricardo, Lotus Engineering, Ford and Cargine. Some systems are commercially available, although not in production car engines

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me.sc.edu/research/AARG/camless.html
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CAMLESS ENGINE
INTRODUCTION

The cam has been an integral part of the IC engine from its invention. The cam controls the breathing channels of the IC engines, that is, the valves through which the fuel air mixture (in SI engines) or air (in CI engines) is supplied and exhaust driven out. Besieged by demands for better fuel economy, more power, and less pollution, motor engineers around the world are pursuing a radical camless design that promises to deliver the internal “ combustion engine™s biggest efficiency improvement in years. The aim of all this effort is liberation from a constraint that has handcuffed performance since the birth of the internal-combustion engine more than a century ago. Camless engine technology is soon to be a reality for commercial vehicles. In the camless valve train, the valve motion is controlled directly by a valve actuator “ there™s no camshaft or connecting mechanisms .Precise electrohydraulic camless valve train controls the valve operations, opening, closing etc. The seminar and presentation looks at the working of the electrohydraulic camless engine, its general features and benefits over conventional engines. The engines powering today™s vehicles, whether they burn gasoline or diesel fuel, rely on a system of valves to admit fuel and air to the cylinders and let exhaust gases escape after combustion. Rotating steel camshafts with precision-machined egg-shaped lobes, or cams, are the hard-tooled brains of the system. They push open the valves at the proper time and guide their closure, typically through an arrangement of pushrods, rocker arms, and other hardware. Stiff springs return the valves to their closed position. In an overhead-camshaft engine, a chain or belt driven by the crankshaft turns one or two camshafts located atop the cylinder head.
A single overhead camshaft (SOHC) design uses one camshaft to move rockers that open both inlet and exhaust valves. The double overhead camshaft (DOHC), or twin-cam, setup does away with the rockers and devotes one camshaft to the inlet valves and the other to the exhaust valves.
WORKING OF PUSH ROD ENGINE
Pushrod engines have been installed in cars since the dawn of the horseless carriage. A pushrod is exactly what its name implies. It is a rod that goes from the camshaft to the top of the cylinder head which push open the valves for the passage of fuel air mixture and exhaust gases. Each cylinder of a pushrod engine has one arm (rocker arm) that operates the valves to bring the fuel air mixture and another arm to control the valve that lets exhaust gas escape after the engine fires. There are several valve train arrangements for a pushrod.
Crankshaft
Crankshaft is the engine component from which the power is taken. It receives the power from the connecting rods in the designated sequence for onward transmission to the clutch and subsequently to the wheels. The crankshaft assembly includes the crankshaft and bearings, the flywheel, vibration damper, sprocket or gear to drive camshaft and oil seals at the front and rear.
Camshaft
The camshaft provides a means of actuating the opening and controlling the period before closing, both for the inlet as well as the exhaust valves, it also provides a drive for the ignition distributor and the mechanical fuel pump.
The camshaft consists of a number of cams at suitable angular positions for operating the valves at approximate timings relative to the piston movement and in the sequence according to the selected firing order. There are two lobes on the camshaft for each cylinder of the engine; one to operate the intake valve and the other to operate the exhaust valve.
Working

When the crank shat turn the cam shaft the cam lobs come up under the valve lifter and cause the lifter to move upwards. The upward push is carried by the pushrods through the rocker arm. The rocker arm is pushed by the pushrod, the other end moves down. This pushes down on the valve stem and cause it to move down thus opening the port. When the cam lobe moves out from under the valve lifter, the valve spring pulls the valve back upon its seat. At the same time stem pushes up on the rocker arm, forcing it to rock back. This pushes the push rods and the valve lifter down, thus closing the valve. The figure-1,2 shows cam-valve arrangement in conventional engines
Figure-1 Figure-2
Single cam and valve conventional valve train mechanism
Since the timing of the engine is dependent on the shape of the cam lobes and the rotational velocity of the camshaft, engineers must make decisions early in the automobile development process that affect the engineâ„¢s performance. The resulting design represents a compromise between fuel efficiency and engine power. Since maximum efficiency and maximum power require unique timing characteristics, the cam design must compromise between the two extremes.
This compromise is a prime consideration when consumers purchase automobiles. Some individuals value power and lean toward the purchase of a high performance sports car or towing capable trucks, while others value fuel economy and vehicles that will provide more miles per gallon.
Recognizing this compromise, automobile manufacturers have been attempting to provide vehicles capable of cylinder deactivation, variable valve timing (VVT), or variable camshaft timing (VCT). These new designs are mostly mechanical in nature. Although they do provide an increased level of sophistication, most are still limited to discrete valve timing changes over a limited range.
AN OVERVIEW OF CAMLESS ENGINE
To eliminate the cam, camshaft and other connected mechanisms, the
Camless engine makes use of three vital components “ the sensors, the electronic control unit and the actuator

Mainly five sensors are used in connection with the valve operation. One for sensing the speed of the engine, one for sensing the load on the engine, exhaust gas sensor, valve position sensor and current sensor. The sensors will send signals to the electronic control unit.
The electronic control unit consists of a microprocessor, which is provided with a software algorithm. The microprocessor issues signals to the solid-state circuitry based on this algorithm, which in turn controls the actuator, to function according to the requirements.
Camless valve train
In the past, electro hydraulic camless systems were created primarily as research tools permitting quick simulation of a wide variety of cam profiles. For example, systems with precise modulation of a hydraulic actuator position in order to obtain a desired engine valve lift versus time characteristic, thus simulating the output of different camshafts. In such systems the issue of energy consumption is often unimportant. The system described here has been conceived for use in production engines. It was, therefore, very important to minimize the hydraulic energy consumption.
Hydraulic pendulum
The Electro hydraulic Camless Valve train, (ECV) provides continuously variable control of engine valve timing, lift, and velocity. It uses neither cams nor springs. It exploits the elastic properties of a compressed hydraulic fluid, which, acting as a liquid spring, accelerates and decelerates each engine valve during its opening and closing motions. This is the principle of the hydraulic pendulum. Like a mechanical pendulum," the hydraulic pendulum involves conversion of potential energy into kinetic energy and, then, back into potential energy with minimal energy loss". During acceleration, potential energy of the fluid is converted into kinetic energy of the valve. During deceleration, the energy of the valve motion is returned to the fluid. This takes place both during valve opening and closing. Recuperation of kinetic energy is the key to the low energy consumption of this system.. Figure 7 illustrates the hydraulic pendulum concept. The system incorporates high and low-pressure reservoirs. A small double-acting piston is fixed to the top of the engine valve that rides in a sleeve. The volume above the piston can be connected either to a high- or a low-pressure source. The volume below the piston is constantly connected to the high-pressure source. The pressure area above the piston is significantly larger than the pressure area below the piston. The engine valve opening is controlled by a high-pressure solenoid valve that is open during the engine valve acceleration and closed during deceleration. Opening and closing of a low-pressure solenoid valve controls the valve closing. The system also includes high and low-pressure check valves.
Figure 7. Hydraulic Pendulum.
During the valve opening, the high-pressure solenoid valve is open, and the net pressure force pushing on the double-acting piston accelerates the engine valve downward. When the solenoid valve closes, pressure above the piston drops, and the piston decelerates pushing the fluid from the lower volume back into the high-pressure reservoir. Low-pressure fluid flowing through the low-pressure check valve fills the volume above the piston during deceleration. When the downward motion of the valve stops, the check valve closes, and the engine valve remains locked in open position. The process of the valve closing is similar, in principle, to that of the valve opening. The low-pressure solenoid valve opens, the pressure above the piston drops to the level in the low pressure reservoir, and the net pressure force acting on the piston accelerates the engine valve upward. Then the solenoid valve closes, pressure above the piston rises, and the piston decelerates pushing the fluid from the volume above it through the high-pressure check valve back into the high-pressure reservoir. The hydraulic pendulum is a spring less system. Figure 8 shows idealized graphs of acceleration, velocity and valve lift versus time for the hydraulic pendulum system. Thanks to the absence of springs, the valve moves with constant acceleration and deceleration. This permits to perform the required valve motion with much smaller net driving force, than in systems which use springs. The advantage is further amplified by the fact that in the spring less system the engine valve is the only moving mechanical mass. To minimize the constant driving force in the hydraulic pendulum the opening and closing accelerations and decelerations must be equal (symmetric pendulum).
Figure 8. Dynamic characteristics of hydraulic pendulum.
Valve opening and closing
A more detailed step-by-step illustration of the valve opening and closing process is given in Figure 9. It is a six-step diagram, and in each step an analogy to a mechanical pendulum is shown. In Step 1 the opening (high-pressure) solenoid valve is opened, and the high-pressure fluid enters the volume above the valve piston. The pressure above and below the piston become equal, but, because of the difference in the pressure areas, the constant net hydraulic force is directed downward. It opens the valve and accelerates it in the direction of opening. The other solenoid valve and the two check valves remain closed. In Step 2 the opening solenoid valve closes and the pressure above the piston drops, but the engine valve continues its downward movement due to its momentum. The low-pressure check valve opens and the volume above the piston is filled with the low-pressure fluid. The downward motion of the piston pumps the high-pressure fluid from the volume below the piston back into the high-pressure rail. This recovers some of the energy that was previously spent to accelerate the valve. The ratio of the high and low-pressures is selected so, that the net pressure force is directed upward and the valve decelerates until it exhausts its kinetic energy and its motion stops. At this point, the opening check valve closes, and the fluid above the piston is trapped. 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 piston. This situation is illustrated in Step 3, which is the open dwell position. The engine valve remains in the open dwell position as long as necessary. Step 4 illustrates the beginning of the valve closing. The closing (low-pressure) solenoid valve opens and connects the volume above the piston with the low-pressure rail. The net pressure force is directed upward and the engine valve accelerates in the direction of closing, pumping the fluid from the upper volume back into the low-pressure reservoir. The other solenoid valve and both check valves remain closed during acceleration. In Step 5 the closing solenoid valve closes and the upper volume is disconnected from the low-pressure rail, but the engine valve continues its upward motion due to its momentum. Rising pressure in the upper volume opens the high-pressure check valve that connects this volume with the high-pressure reservoir. The upward motion of the valve piston pumps the fluid from the volume above the piston into the high-pressure reservoir, while the increasing volume below the piston is filled with fluid from the same reservoir. Since the change of volume below the piston is only a fraction of that above the piston, the net flow of the fluid is into the high-pressure reservoir. Again, as it was the case during the valve opening, energy recovery takes place. 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 closes. Ideally, this should always coincide with the valve seating on its seat. This, however, is difficult to accomplish. A more practical solution is to bring the valve to a complete stop a fraction of a millimeter before it reaches the valve seat and then, briefly open the closing solenoid valve again. This again connects the upper volume with the however, is difficult to accomplish. A more practical solution is to bring the valve to a complete stop a fraction of a millimeter before it reaches the valve seat and then, briefly open the closing solenoid valve again. This again connects the upper volume with the low-pressure reservoir, and the high pressure in the lower volume brings the valve to its fully closed position. Step 6 illustrates the valve seating. After that, the closing solenoid valve is deactivated again. For the rest of the cycle both solenoid valves and both check valves are closed, the pressure above the valve piston is equal to the pressure in the low-pressure reservoir, and the high pressure below the piston keeps the engine valve firmly closed.
Valve motion control
Varying the activation timing of both solenoids varies the timing of the engine valve opening and closing. This, of course, also vanes the valve event duration. Valve lift can be controlled by varying the duration of the solenoid voltage pulse. Changing the high pressure permits control of the valve acceleration, velocity, and travel time. The valve can be deactivated during engine operation by simply deactivating the pair of solenoids which control it. Deactivation can last any number of cycles and be as short, as one cycle.
Increasing the number of valves in each cylinder does not require a corresponding increase in the number of solenoid valves. The same pair of solenoid valves, which controls a single valve, can also control several valves running in-parallel. Thus, in a four-valve engine a pair of solenoid valves operates two synchronously running intake valves, and another pair runs the two exhaust valves.
UNEQUAL LIFT MODIFIER - In a four-valve engine an actuator set consisting of two solenoid valves and two check valves controls the operation of a pair of intake or a pair of exhaust valves. Solenoids and check valves are connected to a common control chamber serving both valves (Figure 10). In a four-cylinder engine there is a total of eight control chambers connected to eight pairs of valves. For each pair, the volumes below the hydraulic pistons are connected to the high pressure reservoir via a device called the lift modifier. In a neutral position the modifier does not affect the motion of the valves, and activation of the solenoid valves moves both engine valves in unison
.
Figure 10. Paired valves with unequal lift control.
To enhance the ability to vary the intake air motion in the engine cylinder, it is often desirable to have unequal lift of 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 used for paired exhaust valves. The lift modifier is then used to restrict the opening of one the paired valves. The modifier is shown schematically in Figure 11 as a Rotating rod with its axis of rotation perpendicular to the plane of the drawing. The rod is installed in the cylinder head between the two intake valves. A cutout in the rod forms a communication chamber connected to the volumes below the hydraulic pistons of both intake valves. The communication chamber is always connected to the high pressure reservoir. In the case A the modifier is in the neutral position, and both valves operate in unison. In the case B the modifier rod is shown turned 90 degrees clockwise. The exit of oil from the volume below the hydraulic piston in the valve No. 1 is blocked and the valve cannot move in the direction of opening. However, the entry of oil into the volume below the hydraulic piston is permitted by a one-way valve installed in the modifier rod. This guarantees that, whenever deactivation takes place, the valve No. 1 will close and remain closed, while the valve No.2 continues its normal operation. If the modifier rod is turned 90 degrees counter-clockwise (from the position shown in the case A), the valve No.2 is deactivated, while the valve No. 1 would continue normal operation. In the case C the lift of one of the valves is reduced relative to the second one. The rod is turned a smaller angle so that the exit of oil from the valve No. 1 into the communication chamber is not completely blocked, but the flow is significantly throttled. As a result, the motion of the valve No. 1 is slowed down and its lift is less than that of the valve No.2. Varying the angular position of the modifier rod 26 varies the degree of oil throttling, thus varying the lift of the valve No. 1.
Figure 11. Unequal lift control.
DESIGN APPROACH FOR CAMLESS ENGINE
The camless engine was created on the basis of an existing four-cylinder, four-valve engine. The original cylinder head with all the valves, springs, camshafts, etc. was replaced by a new cylinder head assembly fully integrated with the camless valvetrain. The camshaft drive was eliminated, and a belt-driven hydraulic pump was added. There was no need for lubrication, and the access for engine oil from the engine block to the cylinder head was closed off. No other changes to the engine have been made.
Cylinder head
Two cross sections of the cylinder head are shown in Figure 12. The aluminum casting is within the original confines and contains all hydraulic passages connecting the system components. The high- and low-pressure hydraulic reservoirs are integrated into the casting. The reservoirs and the passages occupy the upper levels of the cylinder head and are part of the hydraulic system. The hydraulic fluid is completely separated from the engine oil system. A finite element analysis was used to assure the cylinder head integrity for fluid pressures of up to 9 MPa. The lower level of the head contains the engine coolant.
Figure 12. Cross sections of cylinder head.
The engine valves, the check valves and the modifiers are completely buried in the body of the head. The solenoid valves are installed on the top of the cylinder head and are kept in their proper locations by a cylinder head cover. Hydraulic and electric connections leading to the hydraulic pump and the electronic controller, respectively, are at the back end of the cylinder head. The height of the head assembly is approximately 50 mm lower than the height of the base engine head. Figure 13 is a photograph of the head on the engine with the head cover removed. 27
COMPONENTS OF CAMLESS ENGINE
Main components of a camless engine are-Engine valve, solenoid valve, high pressure pump, low pressure pump, cool down accumulator, etc.
Engine valve “ A cross section of the engine valve assembly is shown in Figure 14. The valve piston is attached to the top of the valve, and both the valve and the piston can slide inside a sleeve. The sleeve openings above and below the valve piston allow the hydraulic fluid to enter and exit. A seal in the lower part of the sleeve prevents leakage of fluid into the intake or exhaust port. A leak-off (not shown) unloads the seal from excessive pressure, which otherwise increases friction. There is a tight hydraulic clearance between the valve and the sleeve. However, the clearance between the sleeve and the cylinder head is relatively large, which improves the centering of the valve in its seat Circulation of hydraulic fluid through the chambers above and below the valve piston cools and lubricates the valve. All the forces acting on the valve are directed along its axis. Absence of side forces reduces stresses, friction and wear.
Figure 14. Engine valve
Solenoid valve “ Figure 15 shows a cross section of the solenoid valve. The solenoid has conically shaped magnetic poles. This reduces the air gap at a given stroke. The normally-closed valve is hydraulically balanced during its movement. Only a slight unbalance exists in the fully-open and the fully-closed positions. A strong spring is needed to obtain quick closing time and low leakage between activations. The hydraulic energy loss is the greatest during the closing of either the high- or the low-pressure solenoid, because it occurs during the highest piston velocity. Thus, the faster the solenoid closure, the better the energy recovery. The valve lift and the seat diameter are selected to minimize the hydraulic loss with a large volume of fluid delivered during each opening. Both high-pressure and low-pressure solenoid valves are of the same design.
Figure 15. Solenoid valve.
Lift modifier - The design of the lift modifier permits a simultaneous hydraulic control of a group of modifiers with a single pulse-width modulated solenoid-valve that adjusts the pressure in a control gallery.
Hydraulic system
A diagram of the hydraulic system is shown in Figure 16. An engine-driven variable-displacement pump automatically adjusts its output to maintain the required pressure. The high-pressure and the low-pressure reservoirs are connected to all corresponding locations serving the high- and the low-pressure solenoids and the check valves.
Figure 16. Hydraulic System.
High pressure pump: the quantity of fluid delivered by the high pressure pump with the actual needs of the system at various engine speeds and loads is critical to assuring low energy consumption. To conserve the mechanical power needed to drive the pump, its hydraulic output should closely match the needs. A variable displacement, high efficiency, axial plunger-type pump was initially selected for that reason. Taking into account the prohibitively high cost of such pump for automotive applications, a low-cost variable capacity pump was conceived. A cross section of the pump is shown in Figure 17. The pump has a single eccentric-driven plunger and a single normally-open solenoid valve. During each down stroke of the plunger the solenoid valve is open, and the plunger barrel is filled with hydraulic fluid from the low pressure branch of the system. During the upstroke of the plunger, the fluid is pushed back into the low pressure branch, as long as the solenoid valve remains open. Closing the solenoid valve causes the plunger to pump the fluid through a check valve into the high pressure branch of the system. Varying the duration of the solenoid voltage pulse varies the quantity of the high-pressure fluid delivered by the pump during each revolution.
Figure 17. High pressure pump.
Low pressure pump - A small electrically driven pump picks up oil from the sump and delivers it to the inlet of the main pump. Only a small quantity of oil is required to compensate for the leakage through the leak-off passage, and to assure an adequate inlet pressure for the main pump. Any excess oil pumped by the small pump returns to the sump through a low-pressure regulator. A check valve 1 assures that the inlet to the main pump is not subjected to pressure fluctuations that occur in the low-pressure reservoir.
Cool down accumulator - The system also includes a cool-down accumulator that, during normal operation, is fully charged with oil under the same pressure as in the inlet to the main pump. When the engine stops running, the oil in both the high- and the low-pressure branches cools off and shrinks. As the system pressure drops, the accumulator discharges oil into the system, thus compensating for the shrinkage and preventing formation of pockets of oil vapor. The high-pressure branch is fed from the accumulator through a check valve 2 that is installed in-parallel to the main pump. The low-pressure branch is fed through an orifice that is installed in-parallel to the check valve 1. The orifice is small enough to prevent pressure wave propagation through it during each engine cycle, but sufficient to permit slow flow of oil from the accumulator to the reservoir. In some applications, the orifice can be incorporated directly in the check valve. After the oil in the system has cooled off, the accumulator maintains the system at above atmospheric pressure by continuously replenishing the oil that slowly leaks out through the leak-off passage. When the engine is restarted, the accumulator is recharged again. If the engine is not restarted for a very long time, as it is the case when a vehicle is left in a long-term parking, the accumulator will eventually become fully discharged. In that case, the pressure in the accumulator drops to an unacceptable level, and a pressure sensor, that monitors the accumulator pressure, sends a signal to the engine control system which reactivates the electric pump for a short period of time to recharge the accumulator. This process can be repeated many times, thus maintaining the system under a low level of pressure until the engine is restarted. After the engine restarts it takes less than one revolution of the main pump to restore the high pressure. Operating the hydraulic system in a closed loop contributes to low energy consumption. The amount of hydraulic power consumed by the system is determined by the flow of fluid from the high- to the low-pressure reservoir times the pressure differential between the outlet from and the inlet to the high pressure pump. A small loss is also associated with leakage. There are good reasons to use high hydraulic pressure in the system, one of them being the need to maintain a high value of the bulk modulus of the oil. In a closed-loop system the pressure in the low-pressure reservoir can also be quite high, although lower than in the high-pressure reservoir (thus the pressure in the low-pressure rail is low only in relative terms). Hence, the system can operate with very high hydraulic pressure, and yet the energy consumption remains modest due to a relatively low pressure differential. The ratio of high pressure to low pressure must be sufficiently higher than the ratios of the pressure areas above and below the valve piston to assure reliable engine valve closure.
ADVANTAGES OF CAMLESS ENGINE
` Electro hydraulic camless valve train offers a continuously variable and independent control of all aspects of valve motion. This is a significant advancement over the conventional mechanical valve train. It brings about a system that allows independent scheduling of valve lift, valve open duration, and placement of the event in the engine cycle, thus creating an engine with a totally uncompromised operation. Additionally, the ECV system is capable of controlling the valve velocity, perform selective valve deactivation, and vary the activation frequency. It also offers advantages in packaging. Freedom to optimize all parameters of valve motion for each engine operating condition without compromise is expected to result in better fuel economy, higher torque and power, improved idle stability, lower exhaust emissions and a number of other benefits and possibilities. Camless engines have a number of advantages over conventional engines.
In a conventional engine, the camshaft controls intake and exhaust valves. Valve timing, valve lift, and event duration are all fixed values specific to the camshaft design. The cams always open and close the valves at the same precise moment in each cylinderâ„¢s constantly repeated cycle of fuel-air intake, compression, combustion, and exhaust. They do so regardless of whether the engine is idling or spinning at maximum rpm. As a result, engine designers can achieve optimum performance at only one speed. Thus, the camshaft limits engine performance in that timing, lift, and duration cannot be varied.
But in a cam less engine, any engine valve can be opened at any time to any lift position and held for any duration, optimizing engine performance. The valve timing and lift is controlled 100 percent by a microprocessor, which means lift and duration can be changed almost infinitely to suit changing loads and driving 0conditions. The promise is less pollution, better fuel economy and performance.
Another potential benefit is the cam less engineâ„¢s fuel savings. Compared to conventional ones, the cam less design can provide a fuel economy of almost 7- 10% by proper and efficient controlling of the valve lifting and valve timing. The implementation of camless design will result in considerable reduction in the engine size and weight. This is achieved by the elimination of conventional camshafts, cams and other mechanical linkages. The elimination of the conventional camshafts, cams and other mechanical linkages in the camless design will result in increased power output.
The better breathing that a camless valve train promotes at low engine speeds can yield 10% to 15% more torque. Camless engines can slash nitrogen oxide, or NOx, pollution by about 30% by trapping some of the exhaust gases in the cylinders before they can escape. Substantially reduced exhaust gas HC emissions during cold start and warm-up operation.
CONCLUSIONS
1. An electro hydraulic camless valve train was developed for a camless engine. Initial development confirmed its functional ability to control the valve timing, lift, velocity, and event duration, as well as to perform selectively variable deactivation in a four-valve multicylinder engine.
2. The system employs the hydraulic pendulum principle, which contributes to low hydraulic energy consumption.
3. The electro hydraulic valve train is integral with the cylinder head, which lowers the head height and improves the engine packaging.
4. Review of the benefits expected from a camless engine points to substantial improvements in performance, fuel economy, and emissions over and above what is achievable in engines with camshaft-based valve trains.
5. The development of a camless engine with an electro hydraulic valve train described in this report is only a first step towards a complete engine optimization. Further research and development are needed to take full advantage of this system exceptional flexibility.
BIBLIOGRAPHY
¢ Michael M.Schechter and Michael B.Levin Camless Engine
SAE paper 960581
¢ P. Kreuter, P. Heuser, and M. Schebitz, "Strategies to Impove SI-Engine Performance by Means of Variable Intake Lift, Timing and Duration", SAE paper 920449.
¢ K. Hatano, k. Lida, H. Higashi, and S. Murata, Development of a New Multi-Mode Variable Valve Timing Engine,SAE paper930878
¢ J-C. Lee, C-W. Lee, and J. Nitkiewitz, The Application of a Lost Motion VVT System to a DOHC SI Engine,SAE paper 950816
¢ John B. Heywood, Internal combustion engine fundamentals
¢ William H. crouse. Automotive mechanics.
¢ John Steven Brader ,A Thesis on Development of a Piezoelectric Controlled Hydraulic Actuator for a Camless Engine
¢ mmachinedesign.com
¢ halfbakery.com
¢ deiselnet.com
¢ greendieseltechnology.co
¢ me.sc.edu
¢ SEMINAR TOPICS FROM edufiveseminar and presentationtopics.html
¢
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To know more about camless engine please follow the link:
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CAMLESS ENGINE
INTRODUCTION


The cam has been an integral part of the IC engine from its invention. The cam controls the “breathing channels” of the IC engines, that is, the valves through which the fuel air mixture (in SI engines) or air (in CI engines) is supplied and exhaust driven out. Besieged by demands for better fuel economy, more power, and less pollution, motor engineers around the world are pursuing a radical “camless” design that promises to deliver the internal – combustion engine’s biggest efficiency improvement in years. The aim of all this effort is liberation from a constraint that has handcuffed performance since the birth of the internal-combustion engine more than a century ago. Camless engine technology is soon to be a reality for commercial vehicles. In the camless valve train, the valve motion is controlled directly by a valve actuator – there’s no camshaft or connecting mechanisms .Precise electrohydraulic camless valve train controls the valve operations, opening, closing etc. The seminar and presentation looks at the working of the electrohydraulic camless engine, its general features and benefits over conventional engines. The engines powering today’s vehicles, whether they burn gasoline or diesel fuel, rely on a system of valves to admit fuel and air to the cylinders and let exhaust gases escape after combustion. Rotating steel camshafts with precision-machined egg-shaped lobes, or cams, are the hard-tooled “brains” of the system. They push open the valves at the proper time and guide their closure, typically through an arrangement of pushrods, rocker arms, and other hardware. Stiff springs return the valves to their closed position. In an overhead-camshaft engine, a chain or belt driven by the crankshaft turns one or two camshafts located atop the cylinder head.
A single overhead camshaft (SOHC) design uses one camshaft to move rockers that open both inlet and exhaust valves. The double overhead camshaft (DOHC), or twin-cam, setup does away with the rockers and devotes one camshaft to the inlet valves and the other to the exhaust valves.


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.pptx   Camless Engines.pptx (Size: 1.97 MB / Downloads: 213)
Presented By- Ashwin Jacob.
CAMLESS ENGINES



What Is Cam???
Cam is a rotating machine element which gives reciprocating motion to the follower.

The motion of the follower is pre-determined and accordingly the Cam is designed.

The cams are normally placed on a fixed camshaft which is then geared to the crankshaft.

Working Of Conventional Four Stroke IC Engine



Has four strokes.


Movement of inlet and exhaust valves with the help of Cam.

Conventional Valve train

The valvetrain consists of valves, rocker arms, pushrods, lifters, and camshafts.
It involves many moving parts.





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Abstract
Presented within is a synopsis of the working and conceptual development of a piezoelectric controlled hydraulic actuator. This actuator was developed for use as a replacement for the camshaft in an internal combustion engine (ICE). Its development results in a new device; called the camless engine (CLE).
The objective of the seminar and presentation is to study about the working, literature review, and conceptual development a device that proved the concept of a CLE. More specifically, it is an electro/hydraulic device capable of producing engine valve displacement at typical automotive demands. The goals for maximum displacement and frequency are 10 mm and 50 Hz, respectively. In general, the unit must be capable of varying engine valve displacement and valve timing.
The system design utilized a customized piezoelectric stack and hydraulic spool valve combined with an in-house designed hydraulic amplifier. Control is facilitated by a function generator, and feedback is monitored with an oscilloscope.


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Contents
Acknowledgement ii
Abstract iii
Chapter One : Introduction 1
Chapter Two : Introduction to camshaft technology 2
Chapter Three: Working of camless engine 6
Chapter Four : Literature Review 7
Chapter Five : Conceptual Development 13
Chapter Six : Assembly of the Hydraulic System 18
Chapter seven: Conclusion 21
Reference: 22
List of figures 23
Definitions and Abbreviations 24

Chapter One: Introduction
Automobile manufacturers have recognized the compromises associated with engines that are governed by the rotation of a camshaft. This rotation, the speed of which is proportional to the engine speed, determines the timing of the engine valves. For this reason, automotive engineers must make a decision early in the design process that dictates the performance of the automobile. The engine will either have powerful performance or increased fuel economy, but with the existing technology it is difficult to achieve both simultaneously.
In response to the needs of improved engines, some manufacturers have designed mechanical devices to achieve some variable valve timing. These devices are essentially camshafts with multiple cam lobes or engines with multiple camshafts. For example, the Honda VTEC uses three lobes, low, mid, and high to create a broader power band. This does represent an increased level of sophistication, but still limits the engine timing to a few discrete changes.
The concept of variable valve timing has existed for some time. Unfortunately, the ability to achieve truly variable valve timing has eluded automotive manufacturers. Most variable timing mechanisms were created as tools for the automotive engineer. Their use was limited to the laboratory as a means of testing multiple, “virtual” cam profiles. These early Camless engines allowed for the designers to choose the best cams for the engine under scrutiny, but were less than energy efficient. Furthermore, they were one laboratory machines and were not capable of being mass produced or utilized in an automobile




Chapter Two: Introduction to Camshaft Technology
Since the origination of the automobile, the internal combustion engine has evolved considerably. However, one constant has remained throughout the decades of ICE development. The camshaft has been the primary means of controlling the valve actuation and timing, and therefore, influencing the overall performance of the vehicle.
The camshaft is attached to the crankshaft of an ICE and rotates relative to the rotation of the crankshaft. Therefore, as the vehicle increases is velocity, the crankshaft must turn more quickly, and ultimately the camshaft rotates faster. This dependence on the rotational velocity of the crankshaft provides the primary limitation on the use of camshafts.
As the camshaft rotates, cam lobes, attached to the camshaft, interface with the engine’s valves. This interface may take place via a mechanical linkage, but the result is, as the cam rotates it forces the valve open. The spring return closes the valve when the cam is no longer supplying the opening force. Figure 1 shows a schematic of a single valve and cam on a camshaft.

Figure 1: Single Cam and Valve
Since the timing of the engine is dependent on the shape of the cam lobes and the rotational velocity of the camshaft, engineers must make decisions early in the automobile development process that affect the engine’s performance. The resulting design represents a compromise between fuel efficiency and engine power. Since maximum efficiency and maximum power require unique timing characteristics, the cam design must compromise between the two extremes.
This compromise is a prime consideration when consumers purchase automobiles. Some individuals value power and lean toward the purchase of a high performance sports car or towing capable trucks, while others value fuel economy and vehicles that will provide more miles per gallon.
Recognizing this compromise, automobile manufacturers have been attempting to provide vehicles capable of cylinder deactivation, variable valve timing (VVT), or variable camshaft timing (VCT). These new designs are mostly mechanical in nature. Although they do provide an increased level of sophistication, most are still limited to discrete valve timing changes over a limited range.
Early in the development of variable engines, Cadillac introduced its V-8-6-4 engine. This 1981 engine was based on a 6.0 liter V-8, but was capable of operating as a 4.5 liter V-6 or a 3.0 liter V-4. The engine changes were made while running and were controlled by the on-board computer’s determination of power requirements. The engine changed the number of active cylinders by adjusting the position of the rocker-arm fulcrum. To disable a cylinder, the fulcrum was moved via a hydraulic solenoid valve to the contact point of the rocker-arm and engine valve stem. This prevented the rotating camshaft from supplying enough force to open the engine valve. The computer then made adjustments to the fuel injection rates to compensate for the change in fuel requirements.
The Cadillac V-8-6-4 was the standard engine for all 1981 Cadillac models, but the engine experienced a short production run. Due to consumer complaints about the engine response and operation, especially when changing from one mode to another, Cadillac discontinued its variable engine.
As an update to the short lived Cadillac V-8-6-4, GM introduced its “Displacement on Demand” engines in their 2004 models. The concept is similar to the earlier Cadillac attempt, but this design limits the engine to operate either as a V-8 or a V-4. With the increase of computing power, GM states the design is more sophisticated, and they promise that the change from 8 to 4 to 8 cylinders will be virtually unnoticeable to the driver.
The new GM engine incorporates a special valve lifter, designed by Eaton Corporation. This lifter is a multi-shaft component capable of telescoping. A hydraulically actuated locking pin, when engaged, prevents the lifter from collapsing. This allows the cam to open the engine valve. When the locking pin is hydraulically removed, the cam simply collapses the lifter and cannot actuate the engine valve.
Instead of the cylinder operating changes offered by the new GM engine, Honda has introduced its VTEC engines to address the need for greater levels of engine sophistication. This design incorporates three cam lobes and three rocker-arms for each engine valve; see figure 2 for a schematic of the Honda VTEC. The unit locks the rocker-arms together as engine demands change. One rocker-arm is in contact with the engine valve stem and is directly responsible for the actuation of the engine valve. As engine demands change due to increased engine speed, the adjacent rocker-arms are linked, so the valve timing becomes a function of the second cam and rocker-arm pair. This process is repeated for higher rpm’s, so the third cam controls the timing of the engine valve. A hydraulic spool valve connects the rocker arms together by driving a pin through the units. The three cam lobes are designated for low, mid, and high rpm requirements. There use generates more consistent torque output and increase fuel efficiency by providing better valve timing at three different operating ranges.

Figure 2: Honda VTEC Schematic
As another approach to VVT, Lexus has developed a “variable valve timing, intelligent” (VVT,i) system for its engines. They claim to have produced the next level of sophistication by introducing continuously VVT. The on-board computer monitors the engine demands and continuously adjusts the timing and overlap of the intake and exhaust valves.
Regardless of the VVT technology differences among the leading automotive manufacturers, the prime similarity of a camshaft remains. Therefore, limitations continue, since the timing is still a function of engine speed.
These limitations have initiated research into Camless engine technology. The following section outlines some recent accomplishments of other researchers in an attempt to develop truly independent VVT.
Chapter Three: Working of Camless Engine
Engine valve actuation is achieved through the following procedure. An electric impulse from the control hardware will cause the piezoelectric stack to expand. This linear expansion will be transferred into movement of a hydraulic spool valve. The slight movement of the spool valve will divert hydraulic fluid and pressure to one side of a hydraulic amplifier. The sudden increase of pressure in the hydraulic amplifier will be transmitted into linear motion by means of a piston. The movement of the piston acts as the actuator and is directly attached to an engine valve.
Variable valve timing is achieved by varying the input voltage signal to the piezoelectric stacks. This variance alters the speed of response and deflection of the stacks. Therefore, the movement of the spool valve is varied and alters the flow of hydraulic fluid. It is this combination that allows for the independent control of valves, their displacement, and their opening and closing velocity.
The system outlined above is required to overcome the displacement limitations of the piezoelectric stack, while exploiting its efficiency and ease of accurate control. The piezoelectric will offer the needed response for precise rapid changes in direction, but it cannot deliver the force over the required displacement needed for use as an engine valve actuator. Therefore, hydraulics is introduced as a proven technology, capable of actuating the engine valves.





Chapter Four: Literature Review
Originally, camless engines were developed for use as a design aide to automotive engine manufacturers. The use of a camless engine allowed the engineer to experiment with valve timing as a means of designing cam profiles. These early units were not limited by dimensional or power consumption restraints. Instead, they were solely developed for laboratory use as a design tool.
Aside from laboratory use, history shows that the idea of a camless internal combustion engine had its origins as early as 1899, when designs of variable valve timing surfaced. It was suggested that independent control of valve actuation could result in increased engine power. More recently, however, the focus of increased power has broadened to include energy savings, pollution reduction, and reliability.
To provide the benefits listed above, researchers throughout the previous decade have been proposing, prototyping, and testing new versions of valve actuation for the internal combustion engine. Their designs have taken on a variety of forms, from electro-pneumatic to electro-hydraulic. These designs are based on electric solenoids opening and closing either pneumatic or hydraulic valves. The controlled fluid then actuates the engine valves. Much of the remaining documentation deals with either the control of the solenoids or the computer modeling of such control systems. The research on the control of the solenoids is crucial since their precision and response is a limiting factor to the development of earlier camless valve actuators.
A comprehensive project and implimentation using solenoid control of pneumatic actuators was completed in 1991. This research included the development of the actuators, a 16 bit microprocessor for control, and comparative testing between a standard Ford. 1.9liter, spark ignition, port fuel injected four cylinder engine and the same engine modified for camless actuation. Testing compared the unmodified engine to that of the same engine, altered to include eight pneumatic actuators in place of the standard camshaft.
The actuators used during the research required an off-engine power source because an engine mounted compressor was not feasible. The researches found that for engine operation at 1500 rpm, the eight actuators used a total of 2.5 kW of power. This compares very high to the 140 watts of power consumed by comparable production engines. As Gould et al. states, their work cannot be considered feasible for implementation due to the high power requirements of the actuator.
For their project and implimentation, pneumatic actuators were chosen after running comparison tests among different methods. Pressurized air was chosen due to its low mass, allowing fast response and stability over a broad temperature range. The researchers found that hydraulic systems had sluggish response, especially at low temperatures.
The pressurized air was controlled by electromagnetic valves. All flow path distances were minimized to increase the response time of the actuator by reducing the volume of air required for actuation. The pressurized air opened the engine valves based on the timed electrical signal input to the “electromagnetic latch.” Residual air was compressed during valve seating and provided a means of slowing the valve for a soft seat.
The researchers concluded that the test engine produced approximately 11% greater torque at low engine speeds (below 2000 rpm) compared to a conventional engine. Furthermore, the camless engine was capable of reducing emission gasses, specifically “brake specific nitrous oxide emissions” (bsNOx), but only by degrading the combustion process.
In 1996 the next generation of camless engine was completed at the Ford Research Laboratory by, principally, Michael Schechter and Michael Levin. Ford’s work has taken a detailed look at the plethora of parameters associated with consistent, reliable engine operation. The first half of the paper describing their work is focused on the base parameters of valve timing and overlap. This data will serve as beneficial information during the further development of the prototype at the University of South Carolina.
Beyond the basics, Schechter and Levin introduce a new concept of the hydraulic pendulum. It is stated that the use of a hydraulic pendulum decreases the system’s energy consumption by converting the kinetic energy of a closing valve into potential energy stored in the pressurized fluid. This reduces the energy required for pumping the hydraulic fluid. Through this conversion of energy, the authors predict that a 16-valve, 2.0 L engine will consume about 125 W to operate at light loads.
The hydraulic pendulum also allows for the solenoid-based-system to slow valve velocity. This results in soft seating the valve and is a favorable attribute of the new system. Another benefit is the ability to vary the opening and closing velocity of the valve. This allows for increased variation to engine valve parameters.
A schematic of the hydraulic pendulum is shown in Figure 3. High and low pressure hydraulic reservoirs are connected to the engine valve’s actuating piston. The control of this fluid is accomplished by means of two solenoids and two check valves. High pressure fluid is always in contact with the lower side of the piston, and either high or low pressure fluid is in contact with the upper side of the piston. The difference in pressure contact area is utilized in conjunction with the hydraulic pressure to vary the actuating forces.

Figure 3: Hydraulic Pendulum Schematic
The authors provide a detailed description of the valve actuation cycle. This is summarized as follows. To open the engine valve, the high pressure solenoid opens to allow high pressure hydraulic fluid into the upper chamber. Due to the difference in pressure contact area, the valve opens. Next, the high pressure solenoid closes, but the valve’s momentum continues to open the engine further. This causes a reduction of pressure in the upper chamber and allows the low pressure check valve to open. The engine valve decelerates as it pumps the high pressure fluid from the lower cavity back to the high pressure reservoir. This process both slows the valves and recovers some energy by converting the kinetic energy of the engine valve into potential energy in the high pressure fluid. Once the upper cavity pressure equalizes with the low pressure reservoir, the check valve closes and the upper cavity fluid is static. This allows the engine valve to be held open.
Closing the valve is initiated by the opening of the low pressure solenoid valve. The engine valve accelerates toward its closed position based on the force differential between the high pressure lower cavity and the low pressure upper cavity. The upper cavity fluid is pumped back toward the low pressure reservoir. Energy is again recovered and the engine valve is soft-seated through a similar deceleration process. By closing the low pressure solenoid valve, the upward momentum of the engine valve pressurizes the upper cavity fluid. This increase in pressure opens the high pressure check valve and allows the upper cavity fluid to be pumped back to the high pressure reservoir. Again, energy is converted from kinetic to potential and the valve is decelerated.
The best timing of this process would allow for the kinetic energy of the engine valve to be exhausted exactly when it closes. However, the researchers provide an alternative to such precision. Instead, they suggest stopping the engine valve just prior to contact with the seat, and then briefly opening the high pressure solenoid to complete the cycle.
Through the use of a hydraulic pendulum, a complete four cylinder ICE was produced and found some success. However, the system is complicated and requires multiple components. The use of a hydraulic pendulum requires two solenoids and two check valves per engine valve and both a high pressure and low pressure hydraulic fluid supply. (Schechter et al. state that two solenoids can run a pair of valves as-long-as the pair is synchronized. However, this detracts from the concept of independent valve control.)
The camless engine developed by Ford and described above was then enhanced at the University of Illinois at Urbana-Champaign. The focus of the project and implimentation was to advance the hydraulic-pendulum-based CLE actuator by developing an adaptive feedback control. Their research is focused on the electronics and algorithms of data acquisition and control and extends beyond the scope of the current phase of research here at the University of South Carolina. However, as a comparison, some of the results are presented here. The complete system was limited to operating at 3000 rpm. Valve lift greater than 5 mm could not be consistently controlled.
There have been a few attempts at developing production models of Camless engines, most notably by Ford, but the use of solenoids has impeded their implementation. Using solenoids to control hydraulic fluid and ultimately the opening and closing of the engine valves introduces its own limitations. The solenoids consume considerable energy and are a binary control device – they are either on or off. Therefore the hydraulic fluid, controlled by the solenoids, is either flowing or blocked. This design allows for some variance of valve timing, but is still limited by the response capabilities of the solenoids. Furthermore, it cannot directly address valve velocity or displacement changes.
The development of the Camless engine overcomes these limitations through the use of piezoelectric stacks, a spool valve, and a hydraulic amplifier instead of solenoids. This combination results in a device capable of nearly infinitely variable valve timing, altered valve displacement, and controllable valve velocity.

Chapter Five: Conceptual Development
The concept was to use piezoelectric stacks to provide the displacement of a hydraulic spool valve. The movement of the spool valve would control the flow of hydraulic fluid. To utilize the hydraulic fluid flow from the spool valve, a hydraulic amplifier would be required. This would create the needed force and displacement for actuating an ICE valve. The original anticipation of design requirements presented during the conceptual development phase was stated as follows.
• ICE valve travel requires 8 mm. Design the system for 10 mm.
• Forces encountered will be due to internal pressure within the ICE cylinder and from the valve closure spring. Design for 8 bar acting on a valve head diameter of 28 mm and a spring rate of 35 N/mm.
• ICE speed of 6000 rpm. This equates to valve actuation of 50 Hz.
• Develop control for the system that can vary valve displacement velocity and timing.
As the ICE valve opens, the forces due to pressure reduce dramatically while the spring force increases linearly. This is shown pictorially in Figure 4.

Figure 4: Resistive Engine Forces vs. Valve Displacement
The spring is designed to close the ICE valve when no force is being applied to open it. This is similar to existing engine valves, but ultimately may prove to be an obstacle to overcome. Even during the conceptual development, the replacement of spring-return with hydraulic-return was discussed. Figure 5 shows a schematic of the engine valve with a spring return. This is similar to the valve used on the test rig.

Figure 5: Engine Valve Schematic
The use of a compression spring, as shown in Figure 2, allows for thermal expansion of valve components while maintaining valve closure. If the spring is to be removed, the control system must be able to monitor the seal integrity and accommodate any displacement changes due to thermal expansion. During proof of concept testing, a spring return was maintained, as to not introduce further control complexity.
Aside from the provided spring return valve accompanying the test rig, the other major design constraint was the hook-up requirements for connecting to the spool valve. The existing spool valve had a four port interface based on ISO 4401: Hydraulic Fluid Power – Four Port Directional Control Valves – Mounting Surfaces. Figure 6 represents a schematic of the four port interface.

Figure 6: Four Port Directional Control Valve Mounting Surface
From Figure 6, it can be seen that there are four bolt holes and the four hydraulic ports labeled A, B, P, and T. These represent the following.
• Ports A and B are the output ports for hydraulic fluid. Fluid flow is directed to A or B depending on the position of the spool. For the Camless engine application, ports A and B provide hydraulic pressure to the top and bottom of the hydraulic amplifier’s piston, respectively.
• Port P is the input port. It is connected to the output of a hydraulic pump.
• Port T is the return port. It is connected to the input of a hydraulic fluid reservoir.
The concept develops a hydraulic actuator that would connect to ports A and B of the provided spool valve. By creating a hydraulic actuator based on a piston – cylinder arrangement, hydraulic fluid from ports A or B would cause displacement of the piston. This is shown schematically in Figure 7.

Figure 7: Hydraulic Actuator Schematic
As shown in Figure 7, if hydraulic pressure is introduced through port A from the spool valve, the piston will move down. Hydraulic pressure applied to port B will cause the piston to move up. Furthermore, hydraulic fluid must be able to drain out of the cylinder through the port opposite of that being pressurized. For example, as hydraulic pressure and fluid is applied through port A, the piston moves down. Since the hydraulic fluid is essentially incompressible, the fluid must be able to drain through port B.
Considering this concept, the ICE valve would simply be attached to the end of the piston. This would create linear actuation. Length of stroke would only be dependent on the piston surface area in contact with the hydraulic fluid, the pressure of the fluid, and the resistive forces associated with opening the ICE valve. The major components that make-up the camless engine actuator are two bore plates, one cylinder block, one piston, and the piezoelectric controlled spool valve. Additional elements include the fasteners, o-rings, and PTFE lip seals. The result of the camless engine actuator assembly is shown below in Figure 8.
Figure 8: Hydraulic Actuator and Mounting Block Assembly
Figure 8 shows a cutaway view of the camless engine actuator assembly. Because it is cutaway, the spool valve and the ISO 4401 port connections are not visible. In this view, the spool valve would be coming out of the paper toward the reader. The camless engine actuator assembly and mounting block were then attached to the hydraulic system. Hydraulic connections and layout are addressed in the next section.
Chapter Six: Assembly of the Hydraulic System
The camless engine actuator assembly outlined in the previous section was mounted onto the hydraulic system. Hydraulic connections were made via the standard hydraulic threaded connection ¼ - 19 BSP (British Straight Pipe). The system flows hydraulic fluid from a pump and back to a reservoir and is a self contained scheme.
Hydraulic fluid is pumped through a ball valve and into the side port of the cylinder block. This connection is directly routed to the P port of the spool valve. From there, the position of the spool valve determines where the pressurized fluid goes. In the neutral position, the fluid is dead-headed, and aside from any leakage past the spool, the fluid is static. See Figure 9.

Figure 9: Hydraulic Amplifier Schematic
When the spool valve translates up, fluid flows through the B port and pressurizes the upper cavity of the cylinder block. This pressurization results in the downward translation of the piston. In turn, the engine valve is being opened as the piston translates down. This is shown in Figure 10.

Figure 10: Hydraulic Amplifier – Spool Valve Up
The opposite occurs as the spool valve translates down. Fluid flows through the A port and pressurizes the lower cavity of the cylinder block. This pressure causes the piston to rise and allows the engine valve to close. See Figure 11.
Figure 11: Hydraulic Amplifier – Spool Valve Down
Drainage of fluid from the cylinder block takes place through the A or B port, whichever is not being pressurized by the spool valve. As the piston translates toward the non-pressurized port, hydraulic fluid is forced back into the spool valve. This fluid is then routed directly to the T port (drain) and returns to the reservoir. From the reservoir, the fluid is pumped back into the system, and the process repeats.

Conclusion
It is the ability to vary valve timing that will provide tremendous improvements to the next generation of internal combustion engines. An engine will be capable of providing increased power when needed, increased fuel efficiency when allowable, and overall reduced emissions. For example, when entering onto a busy expressway, the onboard computer will sense the need for greater power. This results in valve timing changes to alter the overlap between intake and exhaust valves. Doing so will momentarily sacrifice efficiency for power. Then, once the automobile is cruising on the expressway, the computer will alter the timing again to reduce power and increase fuel efficiency. Furthermore, the timing can be optimized for a more complete burn; therefore the engine will produce fewer emissions. Fuel economy can further be increased by shutting down unneeded cylinders. When an automobile is cruising at a constant speed, it does not require all cylinders to be operational. With this newly developed piezoelectric controlled camless technology, complete cylinders can be removed from the timing cycle.
It is this combination of hydraulics and piezoelectric stacks that constitutes a leap in automotive engine technology. A working prototype to actuate a single valve has been completed, and testing has proven that the system is a viable alternative to a camshaft.
The overall results of a complete Camless engine will provide the consumer with a vehicle that performs to expectations, but facilitates increased fuel economy. This combination is essential, since evidence shows consumers are not prepared to compromise on performance, while at the same time fuel prices continue to escalate.



References
Dobson, N. and Muddell, G., 1993, “Active Valve Train System Promises to Eliminate Camshafts,” Automotive Engineer February/March 1993.
General Motors – GM and the Environment. May 21, 2001. General Motors. June 13, 2001.
Ladd, D; Camless Engine is Gaining Momentum. September 13, 1999. Siemens Automotive. July 4, 2000 <media.siemensautomediacenter2/queries/releasefull.phtml?prjob_num=1195>.
Lexus – Variable Valve Timing a First in an SUV. Autoworld. June 18, 2001 <autoworldRX300.htm>.
Mori, Kaz. Honda’s High-Output LEV Engine Home Page. Honda. June 13, 2001 <s2000.vtecjdmhtml/high-output-lev.htm>.
<eetimesstory/industry/system_and_software_news/OEG20000414S0050.htm>.
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18-04-2011, 04:15 PM

Submitted by:
Shivam. A. Pandey

CAMLESS ENGINE
Presented within is a synopsis of the conceptual development and design analysis of a piezoelectric controlled hydraulic actuator. This actuator was developed for use as a replacement for the camshaft in an internal combustion engine (ICE). Its development results in a new device; called, the CAMLESS ENGINE (CLE).
The objective of the presentation is to design and manufacture a device that proves the concept of a CLE. More specifically, it is an electro/hydraulic device capable of producing engine valve displacement at typical automotive demands. The first objective for maximum displacement and frequency are 10 mm and 50 Hz, respectively. But resulting system was capable of producing valve displacement of 11mm at 500Hz.
Our second objective is to get as good valve displacement efficiency as that of traditional camshaft engine. The main drawbacks of camshaft mechanism are
1. Power consumption
2. Noise
3. Friction
All these limitations are rectified by the simple hydraulic actuator, which is noiseless, frictionless and saves engine power by eliminating camshaft-gear mechanism.
Our third objective is to get good valve timing efficiency with comparison to VVT, the present scenario.
The high performance which we get through the present VVT’s can also be obtained through piezoelectric hydraulic actuator, but only the difference is eliminating the complex mechanism of VVT.
The system design utilizes a customized piezoelectric stack and hydraulic spool valve combined with an in-house designed hydraulic amplifier. Control is facilitated by a function generator, and feedback is monitored with an oscilloscope.
The sensors provided sends the signal to piezoelectric material which helps in deciding the valve timing according to the need. After this the signal sent to piezoelectric material, causes linear expansion which is furthermore transmitted to spool valve which amplifies the displacement of piezoelectric material through displacement of fluid in assembly.
This causes the flow of fluid in the piston assembly, which act as a hydraulic actuator. This movement of piston causes the operation of valve.
Positive sides of Camless:
1. Noise reduction
2. No engine power required
3. Reduction in weight
4. Infinite ratios for VVT
The proof of concept can be considered successful, as it demonstrates the ability of piezoelectric control of hydraulics for use as an ICE valve actuator. Furthermore, the device has demonstrated potential areas of improvement that can be implemented in a second generation camless engine.
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06-07-2011, 07:57 PM

thanks.. i was searching for camless engines and it was very useful.. thank u all for the information
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16-08-2011, 06:12 PM

I'm trying to do a report on Camless engine design and i'm having a hard time getting information.Can you help me?
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17-08-2011, 10:19 AM

hi friend you can refer these pages to get the details on Camless engine

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