ACKNOWLEDGEMENT

I would like to thank everyone who helped to see this seminar to completion. In particular, I would like to thank my seminar

coordinators Mr. K. C. Mathew and Mr. Venu P. for his moral support and

guidance to complete my seminar on time.

I would like to take this opportunity to thank Dr. E. M.

Somasekharan Nair, Head of the department Mechanical Engineering for his

support and encouragement.

I express my gratitude to all my friends and the classmates

for their support and help on this seminar.

ASHWIN JACOB

1

ABSTRACT

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.

Beside by demands for better fuel economy, more power, and less

pollution, engineers around the world are pursuing a radical camless design that

promises to deliver the internal-combustion engines 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 - 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 looks at the working of the electronically controlled

camless engine with electro-mechanical valve actuator, its general features and

benefits over conventional engine.

The engines powering todays vehicles, whether they burn gasoline or

diesel fuel, rely on a system of valves to admit fuel and air to the cylinders and

to let exhaust gases escape after combustion. Rotating camshafts with

precision-machined egg-shaped lobes, or cams 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.

2

CONTENTS

List of Figures...4

1. Introduction.....5

1.1PushRod Engine..........6

2. Camless Engine.......9

2.1 Camless Valve Train..................................................................10

2.1.1 Electromechanical Poppet Valve.....10

2.1.2 Electromechanical Ball Valve........14

2.1.3 Electrohydraulic Poppet Valve........16

3. Advantages Of Camless Engine.....18

4. Conclusion.......21

5. References22

3

LIST OF FIGURES

Figure 1: Single Cam and Valve...7

Figure 2: Conventional Valve Train Mechanism.8

Figure 3: Basic Block Diagram Of Camless Engine....9

Figure 4: Electromechanical Poppet Valve10

Figure 5: Different Views Of Poppet Valve...12

Figure 6: Assembly Of Electromechanical Ball Valve...14

Figure 7: Hardware Of Electrohydraulic Valve Train....16

Figure 8: Graph Of Stroke VS Degrees..19

1. INTRODUCTION

4

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 engines 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 theres no camshaft or connecting mechanisms

.Precise electrohydraulic camless valve train controls the valve operations, opening,

closing etc. The seminar looks at the working of the electrohydraulic camless

engine, its general features and benefits over conventional engines.

The engines powering todays 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

cams 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.

1.1PUSH ROD ENGINE

5

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.

1.1.1Crankshaft:

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.

1.1.2Camshaft:

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.

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1.1.3Working:

When the crank shaft 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, shows cam-valve arrangement in

conventional engines

Figure 1: Single cam and valve

7

Figure 2: 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 engines 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.

8

2. CAMLESS ENGINES

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. The basic block diagram of a camless engine is shown in figure 3.

Figure 3: Basic Block Diagram Of Camless Engine

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

9

ELECTRONIC CONTROL

UNITSENSORS ACTUATORS

based on this algorithm, which in turn controls the actuator, to function according to

the requirements.

2.1 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. The different types of valve trains are as follows:

2.1.1 ELECTROMECHANICAL POPPET VALVES

This type of system uses an armature attached to the valve stem. The outside

casing contains a magnetic coil of some sort that can be used to either attract or repel

the armature, hence opening or closing the valve.

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Figure 4: Electromechanical Poppet Valves

Most early systems employed solenoid and magnetic attraction/repulsion

actuating principals using an iron or ferromagnetic armature. These types of

armatures limited the performance of the actuator because they resulted in a variable

air gap. As the air gap becomes larger (ie when the distance between the moving and

stationary magnets or electromagnets increases), there is a reduction in the force. To

maintain high forces on the armature as the size of the air gap increases, a higher

current is employed in the coils of such devices. This increased current leads to

higher energy losses in the system, not to mention non-linear behaviour that makes it

difficult to obtain adequate performance. The result of this is that most such designs

have high seating velocities (i.e. the valves slam open and shut hard!) and the system

cannot vary the amount of valve lift.

The electromechanical valve actuators of the latest poppet valve design eliminate

the iron or ferromagnetic armature. Instead it is replaced with a current-carrying

armature coil. A magnetic field is generated by a magnetic field generator and is

directed across the fixed air gap. An armature having a current-carrying armature

11

coil is exposed to the magnetic field in the air gap. When a current is passed through

the armature coil and that current is perpendicular to the magnetic field, a force is

exerted on the armature. When a current runs through the armature coil in either

direction and perpendicular to the magnetic field, an electromagnetic vector force,

known as a Lorentz force, is exerted on the armature coil. The force generated on

the armature coil drives the armature coil linearly in the air 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. These

latest electromechanical valve actuators develop higher and better-controlled forces

than those designs mentioned previously. These forces are constant along the

distance of travel of the armature because the size of the air gap does not change.

The key component of the Siemens-developed infinitely variable

electromechanical valve train is an armature-position sensor. This sensor ensures the

exact position of the armature is known to the ECU at all times and allows the

magnetic coil current to be adjusted to obtain the desired valve motion.

12

Figure 5: Different views of Poppet Valves

Now referring within Figures 5, FIG. (1 to 4), an electromechanical valve actuator

of the poppet valve variety is illustrated in conjunction with an intake or exhaust

valve (22). The valve (22) includes a valve closure member (28) having a cylindrical

valve stem (30) and a cylindrical valve head (32) attached to the end of the stem

(30).The valve actuator (20) of the poppet valve system generally includes a housing

assembly (34) consisting of upper and lower tubular housing members (36) and (42).

A magnetic field generator consisting of upper and lower field coils (48) and (52), a

core (56) consisting of upper and lower core member (58) and (68), and an armature

(78) suitably connected to the valve stem (30). The armature coil is preferably made

from aluminum wire or other electrically conductive lightweight material, which is

highly conductive for its mass. Minimizing the armature mass is especially

important in view of the rapid acceleration forces placed on it in both directions.

13

The ability of the electromechanical valve actuator to generate force in either

direction and to vary the amount of force applied to the armature in either direction

is an important advantage of this design. For instance, varying the value of the

current through the armature coil and/or changing the intensity of the magnetic field

can control the speed of opening and closing of the valve. This method can also be

used to slow the valve closure member to reduce the seating velocity, thereby

lessening wear as well as reducing the resulting noise.

This system is able to operate without valve springs as shown in FIG.1 or can

equally be equipped with them as shown in FIG. (6 & 7).

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 as they land - in

conjunction with a switching time of barely three milliseconds. For the valves this

means minimal wear and minimum noise generation. The 16-valve four cylinder

engine that is currently undergoing tests in Germany, by Siemens, is equipped with

16 valve actuators and the corresponding armature-position sensors. A Siemens

ECU is used and two cable rails connect the actuators to it. A 42-volt starter-

generator provides the power.

2.1.2 ELECTROMECHANICAL BALL VALVES:

An alternative to the conventional poppet valve for use in camless valve trains is a

ball valve. This type of electromechanical valve system consists of a ball through

which a passage passes. If the ball is rotated such that the passage lines up with

other openings in the valve assembly, gas can pass through it. (Exactly like the ball

14

valves many of us use valve is accomplished by electromagnets positioned around

its exterior to control our boost).

Figure 6:Assembly Of Electromechanical Ball Valve

Referring to Figure 6, the valve housing (7) is shown in two pieces. Ball valve (8)

has two rigidly attached pivots (12). The disc (10) is permanently attached and

indexed to the ball valve and contains permanent magnets around its perimeter. The

electromagnets (11) are situated on both sides of the ball valve (8) and they are fixed

to the valve housing. The electromagnets are controlled through the ECU. A crank

trigger sensor on the crankshaft provides information about the position of the

15

pistons relative to top dead centre. Thus, at top dead centre of the power stroke, the

ECM could be used to fix the polarity of both electromagnets so that they are of

opposite polarity to the magnets in the ball valve, rotating the ball valve to the

closed position.

The substitution of a simple, efficient ball valve and valve housing arrangement in

a four stroke reciprocation piston engine eliminates all the independent moving parts

in the valve train. This may even be an improvement over the poppet valve camless

system - the ball valve needs only to rotate on its axis to achieve the desired flow

conditions, rather than be accelerated up and down in a linear fashion. A partially

open ball valve state may also be able to be used to create more turbulence.

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. Consequently, the energy demand of EMVT

can be optimally matched by a crankshaft-mounted starter-generator (KSG - in

Siemens speak) operating at 42V; it is integrated in the flywheel and designed for

the starting process as well as generator operation.

2.1.3 ELECTROHYDRAULIC POPPET VALVES:

In general terms, present designs of electrohydraulic valves comprise poppet

valves moveable between a first and second position. Used is a source of pressurized

hydraulic fluid and a hydraulic actuator coupled to the poppet valve. The motion

between a first and second position is responsive to the flow of the pressurized

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hydraulic fluid. An electrically operated hydraulic valve controls the flow of the

pressurized hydraulic fluid to the hydraulic actuator. In one design, the provision is

made for a three-way electrically operated valve to control the flow of the

pressurized hydraulic fluid to the actuator. This supplies pressure when electrically

pulsed open, and dumps actuator oil to the engine oil sump when the valve is

electrically pulsed to close. The use of engine oil as the hydraulic fluid simplifies

and lowers the cost of the design by removing the need for a separate hydraulic

system.

Figure 8: Hardware of electrohydraulic valve train

17

The basic design of the electrohydraulic valve train hardware is illustrated in

Figure 8. The engine poppet valves (22) and the valve springs (24) that are used to

reset them are shown. The poppet valves are driven by hydraulic actuators (26),

which are controlled by electrically operated electro-hydraulic valves (28) supplying

hydraulic fluid to the actuators via conduit (29). The preferred hydraulic fluid is

engine oil, supplied to the electro-hydraulic valves by the pressure rail (30). An

engine-driven hydraulic pump (32) supplies the oil pressure, receiving the oil from

the engine oil sump (34). The pump output pressure is also limited by an unloader

valve (36), as controlled by an accumulator (38) connected to the oil pressure rail.

With this design the hydraulic pump could be periodically disconnected, such as

under braking, so that the valve train would run off the stored accumulator hydraulic

pressure.

As is the trend with all modern engine systems, the camless engine has an even

greater reliance on sensors. The valve actuation and control system typically needs a

manifold pressure sensor, a manifold temperature sensor, a mass flow sensor, a

coolant temperature sensor, a throttle position sensor, an exhaust gas sensor, a high

resolution engine position encoder, a valve/ignition timing decoder controller,

injection driver electronics, valve coil driver electronics, ignition coil driver

electronics, air idle speed control driver electronics and power down control

electronics.

A valve developed by Sturman Industries is said to be about six times faster than

conventional hydraulic valves. To achieve such speeds, it uses a tiny spool

sandwiched between two electrical coils. By passing current back and forth between

the coils, a microprocessor-based controller can quickly move the spool back and

forth, thereby actuating the engine valves in accordance.

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3. 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 cylinders 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.

19

The improvement in the speed of operation valve actuation and control

system can be readily appreciated with reference to Figure 9. It shows a

comparison between valve speeds of a mechanical camshaft engine and the

camless engine valve actuation. The length of the valve stroke in inches

versus degrees of rotation of a mechanical camshaft is illustrated.

Figure 8: Graph of stroke v/s degrees

When graphed, the cycle of opening and closing of a valve driven by a

mechanical camshaft will display a shape similar to a sine curve. The opening

period (as measured in crankshaft degrees) remains constant for any engine

load or rpm. However, the cycle of opening and closing of valves driven by

the electromechanical valve actuators operates much faster. Designed to

match valve-opening rate at the maximum engine rpm, the electromechanical

valve actuators open the valve at this same rate regardless of engine operating

conditions. Because of this improved speed, greater flexibility in

20

programming valve events is possible, allowing for improved low-end torque,

lower emissions and improved fuel economy. The massive opening period for

the electromechanically driven valve can also be seen.

But in a cam less engine, any engine valve can be opened at anytime 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 conditions. The promise is less pollution, better fuel

economy and performance.

Another potential benefit is the cam less engines 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.

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4. 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. 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.

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.

22

5. REFERENCES

[1] Michael M.Schechter and Michael B.Levin Camless Engine, SAE paper [960581]

[2] John B. Heywood, Internal combustion engine fundamentals

[3] www.machinedesign.com

[4] www.halfbakery.com

[5] www.deiselnet.com

[6] www.greendieseltechnology.com

[7] www.autospeed.com

[8] 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].

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http://www.deiselnet.com/http://www.halfbakery.com/http://www.machine/

ACKNOWLEDGEMENT1.1.1Crankshaft: 1.1.2Camshaft:1.1.3Working: