Overview
Introduction
Mechanism Of Camless Engine
Types Of Camless Mechanisms
Current application of camless engine
Advantages
Limitations Of Camless Engines
Conclusion
Reference
Introduction Working Of Conventional Four Stroke IC Engine
Has four strokes. Movement of inlet and exhaust valves with the help of cam. The crankshaft turns camshaft which operates valves. Timing of engine valves depends on shape of cams. The valvetrain consists of valves, rocker arms, pushrod, lifters, and camshafts. It involves many moving parts.
Working Of Camless Engines
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Camless engine may debut on 2009 fiat 500. Could provide infinite variation of valve parameters Sensors sense parameters & send signals to ECU ECU contains microprocessors with associated software This ECU controls the actuators to work according to requirements
Valeo estimates that the efficiency of a camless engine would be be 20% greater than a comparable camshaft-operated engine .
Mechanism Of Camless Engine
Mainly five sensors are present, which senses: 1. speed of the engine. 2. load on the engine. 3. exhaust position sensor. sensor. 4. valve position sensor. sensor. 5. current sensor. sensor. microprocessors are present in ECU to issue signal and control the actuators.
Types Of Camless Mechanisms
Electromechanical Poppet Valves
Electromechanical Electro mechanical Ball Valves Valves
Electro-hydraulic Poppet Valves
Electromechanical Electromechani cal Poppet Valves
Early systems employed solenoid and magnetic attraction/repulsion attraction/repulsion was used on an iron or ferromagnetic armature
Varying air gaps which lead to high seating velocities which made varying of the lift difficult.
It is replaced with a currentcarrying armature coil.
A magnetic field is generated by a magnetic field generator and directed across the fixed air gap.
The force generated on the armature coil drives the armature coil linearly in the gap in a direction parallel with the valve stem.
Depending on the direction of the current supplied to the armature coil. The valve will be driven toward an open or closed position.
Siemens report that a special software algorithm is used to control the actuator coil currents such that the valves are decelerated to a speed near zero they land.
In conjunction with a switching time of barely three milliseconds.
The 16-valve four cylinder engines that is currently undergoing tests in Germany, Germany, by Siemens, is equipped with 16 valve actuator and corresponding armature-position sensors.
Different views of poppet valves
Electromechanic Electromec hanical al Ball Ball Valves Valves
It consists of a ball through which there is a passage passage passes.
If the ball is rotated such that passage lines up with other openings in the valve assembly, assembly, gas can pass through it.
The disc is permanently attached and indexed to the ball valve and contains permanent magnets around its perimeter.
A crank trigger sensor on the crankshaft provides information about the position of the piston relative to top dead center.
Electromechanical Electromechan ical Ball Valves Valves
Electromechanical valve train implementation would not be possible with a normal 12v electrical system.
The automotive industry has chosen a 42v electrical system as the next automotive standard.
The valve housing arrangement in a four stroke reciprocation piston engine eliminates all the independent moving parts in the valve train.
Electro-hydraulic Poppet Valves
A source of pressurized hydraulic fluid and a hydraulic actuator coupled to the poppet valve. The use of engine oil as the hydraulic fluid simplifies and lowers the cost of the design. In one design, the provision is made for a three-way electrically operated valve to control the flow of the pressurized fluid to the actuator. The valve springs that are used to reset the poppet valve.
Ricardo electro-hydraulic valve train system
Electro-hydraulic Poppet Valves
The valve actuation and control system need a manifold pressure sensor, a temperature sensor, a mass flow sensor, a coolant temperature sensor, a throttle position sensor, an exhaust gas sensor.
A valve developed by Struma industries is said to be about six times faster than conventional hydraulic valves.
Current application of camless engine •
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Camless valve trains using solenoids or magnetic system are being investigated by BMW and fiat. They are being prototyped by Valeo and Ricardo. Used in the new fiat 500.
Advantages
Offers continuously variable & independent control of all aspects of valve motion - lift, operation duration, event of opening
ECV system can control valve velocity, velocity, valve acceleration and deceleration
Better fuel economy- 7 to 10 % increase
Higher torque & powerpower- 10 to 15 % increase increase
Lower exhaust emissions- EGR system is eliminated since EGR effect occurs on its own & thus reduces NO x emissions
Reduction in size & weight
Limitations Of Camless Engines
Relatively high cost. Packaging. Power consumption. Noise and vibration.
CONCLUSION
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. Review of the benefits expected from a camless engine points to substantial improvements in performance, fuel economy, economy, and emissions over and above what is achievable in engines with camshaft-based valve trains.
3. 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.
REFERENCE
Michael M.Schechter and Michael B.Levin “Camless Engine”, SAE paper [960581] John B. Heywood, “Internal combustion engine fundamentals” www.machinedesign.com www.halfbakery.com www.deiselnet.com www.greendieseltechnology.com www.autospeed.com P. Kreuter, P. Heuser, and M. Schebitz, "Strategies to Impove SIEngine Performance by Means of Variable Variable Intake Lift, Timing and Duration", SAE paper [920449].
