The invention will be described in relation to two aspects. The first aspect is directed to an inlet system design to improve volumetric efficiency at low engine speeds. The second aspect is directed to modifications designed to increase torque and/or power output and optionally to improve volumetric efficiency.

By volumetric efficiency herein is meant the extent to which the cylinder is filled during induction. Thus 100% volumetric efficiency would correspond to the induction of a volume of gas equivalent to the swept capacity of the engine. Typically the volumetric efficiency of a four-stroke engine lies in the range of 60-130%.

The two aspects of the invention will now be described separately, as follows:- First Aspect Reed valves have been used in two-stroke motorcycle engines since 1973. There have been some patents granted which use reed valves on four-stroke engines to improve cylinder filling or to prevent the reversal of gas flow within the inlet manifold at low engine speeds. An example of one use of reed valves on a four-stroke engine is given in U. K.

Patent Application GB 2134179A. The reed valve is positioned in the induction system, and during the induction period the air or fuel-air mixture that flows through it fills a cylinder in which a piston is situated, connected to the crankshaft via a connecting rod. The movement of the piston reduces the volume contained between itself and the reed valve. This forces some air or fuel-air mixture out of the cylinder and this causes a positive pressure against the reed valve. On a four-stroke engine, this forced expulsion of some of the air or fuel-air mixture out of the cylinder

past the inlet valve, against the reed valve, by definition means that maximum volumetric efficiency is not achieved.

U. K. Patent Application GB 2134179A teaches the use of a reed valve on an internal combustion engine with several intake valves per cylinder, of high specific power. Engines of high specific power, for example the engines used on Formula One cars, can be characterised in that their induction systems are short, typically 15 to 30 centimetres long, to obtain a high volumetric efficiency at high engine speeds. It is suggested that, at low rotational speeds, the volumetric efficiency can be improved by the addition of a non-return valve in the absence of any inertia induction effects.

All of the published technologies on four-stroke engines such as U. K. Patent Application GB 2134179A, rely on the reed valve being placed as close as possible to the inlet valve with which it is associated, to reduce the reversal of flow from the cylinder. This unfortunately limits the size of the reed valve that can be fitted and thus introduces a restriction to flow.

This flow restriction limits the maximum possible flow thereby reducing the volumetric efficiency at high engine speeds which consequently reduces the maximum power attainable by the engine. With the close proximity of the reed valve to the inlet valve, the velocity and pressure profiles on the back of the inlet valve may be adversely affected. This also would be detrimental to the flow past the inlet valve.

It has been suggested previously that one or more valves may be used as a flame arrestor for combustion apparatus (European Patent application 0 044 353 A1), where one or more valves are positioned in the induction system, but the application does not disclose how volumetric efficiency may be improved.

Engineers developing two-stroke engines on motorcycles with reed valves fitted, overcame the limited space for reed valves by fitting the reed valves closer to the engine, locating the reed valves directly onto the

crankcase. This allowed much larger reed valves to be fitted and the size of the transfer ports to be enlarged.

With the presence of oil ways, coolant cavities, push rod holes for valve gear and other design necessities in a cylinder head, the fitment of a larger reed valve on a four-stroke engine can only be made possible by moving it away from the inlet valve nearer the air filter. However, this repositioning of the valve destroys the original effect of stopping the reversal of flow, and thus the volumetric efficiency and torque output are no better than if there were no reed valve present.

In accordance with the first aspect of the present invention there is provided an internal combustion engine comprising at least one cylinder having at least one inlet valve through which, in operation, air or fuel-air mixture enters the cylinder, and an induction system comprising an input port for induction air, said engine being characterised by one or more non- return valves placed in the path of the air or fuel-air mixture passing to the inlet valve and in that the length of the induction system, upstream of the non-return valve or valves, is sufficiently long that, at low engine speeds, the gas retained between the inlet valve, when closed, and the non-return valve or valves is pressurised.

By low engine speeds is meant engine speeds less than 4000 r. p. m., preferably less than 3000 r. p. m.

By induction system is meant that part of the engine which is responsible for passing air or fuel-air mixture to the or each inlet valve of the engine. Generally speaking the induction system will comprise a pipe, generally referred to as a ram pipe, for passing the air/mixture from the air input port, which may be fitted with a filter, to the cylinderhead, possibly via an inlet manifold.

When the engine is operating, air flows through the induction system to the inlet valve. This moving body of air acquires a momentum due to its motion and its mass. Thus, if that part of the induction system

between the input port and the non-return valve or valves is sufficiently long, the momentum acquired at low engine speeds will be sufficient to keep the non-return valve open for a short time after the inlet valve has closed to thereby force extra volume past the non-return valve or valves to pressurise the gas retained between the closed inlet valve and the non- return valve or valves.

Preferably, the non-return valve or valves are sufficiently large as to allow an unrestricted flow of air or fuel-air mixture therethrough in the direction of filling the cylinder, so that their presence does not otherwise affect engine performance. A particularly preferred form of non-return valve is the reed valve and, for convenience, the remaining discussion assumes this type of valve.

It is believed that the present invention works by trapping the kinetic energy of the induction mixture between the inlet valve and reed valve. It can also be said that the present invention combines the use of inertia induction effects and one or more large, non-restrictive reed valves. This energy may be stored as pressure which reduces the reversal of flow at the end of the induction cycle, when the inlet valve is closing, but is still open, and the piston is ascending up the cylinder bore and acts to prevent the pumping of any large volume of the inducted air or fuel-air mixture out of the cylinder again. Any pressure that is retained in this manner after the inlet valve closes, may assist the expulsion of the exhaust gas that remains in the combustion chamber at the start of the next induction stroke when both inlet and exhaust valves are open, thus enabling the induction of air or fuel-air mixture to occur earlier than if the pressure were not present.

The upstream induction system may be made in many different forms. For example, each cylinder may have an inlet tract that is entirely separate from those of any other cylinders. Alternatively the inlet manifolds to one or more cylinders of a multicylinder engine may be joined together to form one or more plenum chambers such that, for example, the

entire induction system may form one or more Helmholtz resonators.

It is possible for engines to have one or more Heimholtz resonators with one or more plenum chambers, for example, where a multicylinder engine has some cylinders fed from one plenum chamber and the other cylinders fed from a separate plenum chamber.

Individual inlet tracts may be straight or curved, whether they function separately or as part of an induction system such as a Helmholtz resonator. It may be beneficial to have curved inlet tracts as this can be helpful with fitting constraints in a vehicle, or the curved inlet tract profile may increase the momentum or kinetic energy of the air, or fuel-air mixture, or gases, thereby reducing the total length to achieve the same effect.

Plenum chambers may be designed such that loss of momentum of the inducted air or fuel-air mixture is minimized by the plenum chamber being of a cylindrical shape, and there may be one or more inlets and one or more outlets from the plenum chamber which are perpendicular or near perpendicular to the axis of the cylinder, and tangential to the wall of the cylinder. With plenum chambers of this design, whenever the engine is running, the air or fuel-air mixture will be constantly rotating about the axis of the cylinder, and the speed of rotation of the air or fuel-air mixture will be dependent on parameters such as the engine speed and throttle position (for spark ignition engines). This may assist the filling of the cylinder, and thus improve volumetric efficiency at low engine speeds, and with a long induction length, by giving the cylinders of the engine a buffer volume of moving air or fuel-air mixture, thereby reducing induction pumping losses.

The position and design of any inlets to said plenum chambers may be such that each inlet forms a pipe inside the plenum chamber positioned so that the outlet of each pipe is into the middle of the plenum chamber.

This outlet of the pipe inside the plenum may be positioned at any point along the radius of the plenum. Any pipe may be shortened to any extent, even as far as being removed totally, such that any inlet is flush with or

recessed below the wall of the plenum chamber.

In order to achieve the required increased pressure of the gas retained between the inlet valve and the non-return valve (s), an induction system length, upstream of the non-return valve, greater than 30 centimetres is necessary, with greater than 60 centimetres being preferable. A typical preferred length is approximately 1 metre. The optimum or minimum length of the induction system required to achieve the increased pressure is dependent on several parameters. For each induction system, the cross-sectional area of any pipes, tracts or manifolds, will change the velocity or momentum of the air or fuel-air mixture, thereby for different cross-sectional areas, different lengths will be required. For example, a smaller intake area may enable the same effect to be provided with a shorter induction system length. The engine cylinder size will also determine the flow rate through the induction system, with larger engines creating a greater flow rate for specific induction system pipe cross- sectional areas.

Reed valves that may be suitable for the present invention include those from high performance two-stroke motorcycle engines, for example, Yamaha RD350 YPVS, Kawasaki KMX 125 or KR-1, Suzuki RGV250.

The reed valves mentioned here have many flaps on each valve, for example, the Yamaha RD350 YPVS reed valves have two flaps on either side, the Kawasaki KMX 125 reed valves have three flaps on either side.

The number or exact position or design of the flaps is not important, provided that they are sufficient in number, and the design is such that they do not cause a significant restriction to the flow of air or fuel-air mixture.

The flaps, which are the moving parts of reed valves, may be made of different materials, for example, spring steel, or phenolic resin. The type of material is unimportant for the functioning of the present invention provided that it is suitable for repeatedly bending open and closed, to give a reasonable service life.

The effects achieved by the invention will be reduced as the reed valve is moved away from the inlet valve in the cylinderhead or the engine.

The change can be defined in terms of the cylinder swept volume. The effect will be significantly reduced if the volume contained between the reed valve and the inlet valve that controls flow into the cylinder is increased to more than the cylinder swept volume. Another effect of the present invention is the reduction of induction noise, because induction pressure pulses (sound waves) are trapped by the reed valves and are not allowed to escape.

The present invention is particularly useful for fitting to engines or cylinderheads, where it is undesirable to modify the engine or cylinderhead. This may be because of cost, where the design and testing of new cylinderheads is expensive, and the fitment of the present invention can be done retrospectively to engines or cylinderheads of older designs, that were not originally designed to use reed valves.

High volumetric efficiency at engine speeds below 2000 r. p. m. is difficult to achieve except with very short duration camshafts, which give a very short inlet valve opening period. The present invention may enable greater volumetric efficiencies to be obtained at low engine speeds with a camshaft or inlet valve opening period that is normally used on a high specific power output engine, and that the maximum volumetric efficiency may be more constant over the engine speed range from tick-over to approximately 3000 r. p. m.. The present invention may enable an increased volumetric efficiency (torque output) to be obtained at low to medium engine speeds (<3000 r. p. m.), with no detrimental effect on maximum power at higher engine speeds (>3000 r. p. m.).

The engine speed range over which the present invention may have a beneficial effect on engine performance may be dependent on the design of engine to which the present invention is fitted. For example, a four- stroke reciprocating piston engine may produce different characteristics to

those of a Wankel rotary engine. Also the engine speed range over which the present invention may have a beneficial effect on engine performance may be dependent on other parameters of the engine design, for example, the camshaft lift, duration, or overlap, or the port flows, or some aspect of cylinderhead or valve or engine design.

The long induction system required to effect the working of the present invention, may be too long for maximum volumetric efficiency to be achieved at high engine speeds. This is because the inertia of the column of air may be large, so that the volumetric efficiency of the engine is reduced at high engine speeds. In an embodiment, this is overcome by the provision of one or more additional valves that are normally closed for the functioning of the present invention at low engine speeds, but which are opened at high engine speeds to reduce the induction system length or to change its volume or to open another inlet tract which feeds the same or a separate inlet valve or valves to provide the optimum induction system dimensions for high engine speed operation.

Thus the components of the present invention may comprise a kit of parts consisting of, for example, an electronic sensing circuit, a suitable valve or valves, and any additional air filters and manifold components to enable the construction of an inlet manifold with variable length or resonant frequencies. The electronic circuit may have an input related to, for example, engine speed or the flow of air or flow of fuel into the engine.

The electronic circuit may control a valve in the induction system either directly or indirectly. One example of a valve that can be controlled directly is a solenoid valve. Some examples of suitable valves include a butterfly valve, a poppet valve or a diaphragm valve. A valve may alternatively be opened by a stepper motor. This valve may on opening change the effective dimensions of the induction system or may itself control the opening of another secondary valve. For example, by the first valve controlling a difference of fluid or gaseous pressure, causes the

opening of the secondary valve, where the secondary valve changes the effective dimensions of the induction system on opening. Alternatively, the electronic circuit may control a mechanical device, for example a stepper motor, which directly changes the induction system length by moving ram tubes or some pipe that is part of the induction system.

Other suitable methods may for example include:- a) Tuned port induction such as on the Corvette ZR1; b) The variable Vauxhall Lotus Canton induction system; c) The Honda V-TEC system, where only one inlet valve of the two provided in the cylinderhead for each cylinder is opened at low engine speeds ; d) The variable induction system employed on the Ford V6., engine where there is an extra butterfly valve provided in one of the inlet passages for one of the two valves of each cylinder, which is closed for low speed operation, but is opened for high engine speed operation. This design was originally suggested by BL cars Ltd. in 1979 (GB 2063 362A); e) The Porsche variable length induction system.

Additional devices to increase the volumetric efficiency may be used such as variable camshaft timing devices. For example, suitable devices include the BMW Vanos system, or the Rover Variable Valve Control (WC) system or the Alfa Romeo variable camshaft timing system on which both the BMW and Rover systems are based.

The introduction of air or fuel-air mixture from a short inlet tract that is used for improving the volumetric efficiency at high engine speeds may or may not flow through the reed valve that is used in the present invention. This also includes the supply of air or fuel-air mixture from a turbocharger or supercharger if fitted.

Further embodiments of the present invention may also include the use of a turbocharger or supercharger or nitrous oxide injection as methods to provide a positive pressure between the inlet valve and the

reed valve of the present invention, to stop or reduce the inducted air or fuel-air mixture from being expelled from the cylinder thereby improving the volumetric efficiency. Any number or combination of these forced induction devices may be present.

The present invention may also be applied to other engine types where the induction process is also periodic or cyclic, where pressure pulses may be formed or changes of kinetic energy of the air or fuel-air mixture may occur within the inlet port associated with each cylinder. For example, other engine types may include two-stroke engines which for example may have rotary inlet valves, reed inlet valves or piston-port inlet valves or rotary engines such as a Wankel engine, Quadratic engine or Spherical engine (invented by M. Rodriguez), which may for example, have rotor-port inlet valves.

The present invention when applied to two-stroke engines, for example with a crankcase reed inlet valve, may benefit from the following effects. The reed inlet valve that is normally present on the two-stroke engine is closed by the pressure within the crankcase, which is caused by the reduction of the volume as the piston descends down the cylinder from top dead centre. Whilst there is pressure in the crankcase, which closes and maintains the normal reed inlet valve shut, no induction of any air or fuel-air mixture can occur from the pressure pulses or kinetic energy that exist within the induction system. These forms of energy of the air or fuel- air mixture within the induction system would therefore be dissipated to a certain extent before the next induction cycle. However, the fitment of the present invention to this engine could enable this energy to be stored as pressure in the volume between the two reed valves i. e. between the reed inlet valve and the reed valve of the present invention. This pressure on the outer surface of the reed inlet valve may enable the start of the next induction cycle to occur earlier because this pressure may be greater than that normally present.

The present invention when applied to two-stroke engines for example with a rotary inlet valve, or piston-port inlet valve may benefit from the following effects. The inlet valve that is normally present on the two-stroke engine is closed at a certain crankshaft angle from top dead centre by a rotating disc with cut outs or by the piston within the cylinder covering the inlet port in the cylinder.

Whilst these inlet valves remain shut, as the engine operation continues, no induction of any air or fuel-air mixture can occur from the pressure pulses or kinetic energy within the induction system. These forms of energy of the air or fuel-air mixture within the induction system may therefore be dissipated to a certain extent before the next induction cycle. However, the fitment of the present invention to either of these engines could enable this energy to be stored as pressure in the volume between either the rotary inlet valve, or the piston-port inlet valve and the reed valve of the present invention. This pressure on the outer surface of the rotary inlet valve, or the piston-port inlet valve may enable greater flow to occur at the start of the next induction cycle, because this pressure may be greater than that normally present.

Whilst the above has been described in relation to two-stroke engines, the present invention may be applied to any engine utilising crankcase scavenging for the induction of air or fuel-air mixture.

The present invention when applied to rotary engines for example Wankel type engines with a rotor-port inlet valve, may benefit from the effects as described above on the two-stroke engines with rotary inlet valves or piston-port inlet valves.

By the trapping of positive pressure pulses between the inlet valve or valves of the engine and the reed valve of the present invention, this may prevent the normal occurrence of large negative pressure pulses within the whole induction system. These negative pressure pulses occur when positive pressure pulses are created at the end of the induction cycle which are reflected off the closed inlet valve, or are caused by the expulsion of air or fuel-air mixture from the cylinder out past the open inlet valve, which travel back up the induction system and are reflected from the open end of the induction system, causing the large negative pressure

pulse. This may help prevent the reductions of engine torque or power output that occur at certain engine speeds when the negative pressure pulses within the induction system reduce the volumetric efficiency of the engine.

The present invention may be also be beneficial if fitted to any four- stroke engine which is already fitted with small reed valves near the inlet valve for example as described in U. K Patent Application GB 2134179A.

The positive pressure caused by the piston, which closes the reed inlet valve as described in GB 2134179A, may be so great that it prevents the reed inlet valve (GB 2134179A) from opening when a positive pressure pulse arrives at that reed inlet valve. This would prevent the energy from the positive pressure pulse from being passed through the reed inlet valve, and would therefore be reflected back down the iniet tract. This reflected positive pressure pulse would be converted to a negative pressure pulse once it is reflected from the air inlet which would give the negative effects on the engine volumetric efficiency at certain engine speeds as described above. The placement of the reed valve as disclosed in GB 2134179A allows some of the inducted air or fuel-air mixture to escape out of the larger of the two inlet valves at low engine speeds. This is no different to that which occurs in the absence of any reed valve and would limit the volumetric efficiency at low engine speeds.

There may be any number of breaks within the induction system for assembly, between the reed valve or valves and their respective inlet valve or valves of the engine.

Embodiments of the reed valve housing may be as a fuel injection throttle body, with or without throttle valve or valves. The throttle valve or valves may be of any type, for example, butterfly or slide throttle valves.

There are currently several fuel injection throttle bodies, which bolt onto, for example, Weber carburettor type manifolds. These current products are a direct replacement for Weber carburettors, giving a small

power advantage and allow the engine to which they are fitted to use electronically controlled fuel injection. Some embodiments of the present invention may be a reed valve housing designed with dimensions and proportions that enable its fitment in place of the carburettors or fuel injection throttle bodies onto the manifold designed for the carburettors.

These embodiments of present invention will be able to replace any of these throttle bodies or carburettors, and whilst the maximum power output may be unaffected, a greater torque output may be obtained at low engine speeds, when a long ram manifold is also fitted. Different embodiments may be produced which are able to be attached to specific manifolds suitable for other carburettor types for example, SU, Dellorto, or Stromberg, or other fuel injection systems, for example Bosch, Lucas, Weber.

Further embodiments of the present invention may consist of a reed valve housing designed with dimensions and proportions that enable its fitment in front of, or after, or either side of a carburettor or a fuel injection throttle body. These embodiments of the present invention may be able to be used in addition to the fuel injection throttle body or the carburettor, and whilst the maximum power output may be unaffected, a greater torque output may be obtained at low engine speeds, when a long ram manifold is also fitted. Different embodiments may be produced which may be able to be attached to a specific make or model of fuel injection throttle body or carburettor, for example, SU, Dellorto, or Stromberg, or other fuel injection systems, for example Bosch, Lucas, Weber.

The extra torque that the present invention provides may be beneficial in several applications, for example, for modified road cars where'drivability'and fuel economy are important, and for rallying or hillclimb competition vehicles, where maximum acceleration from tight hairpin bends is essential. Fuel economy may be indirectly improved by enabling the same driving force at the wheels to be obtained, but at lower

engine speeds, thus reducing friction and pumping losses when higher gearing is used. An off-road vehicle may also benefit from the fitment of an embodiment of the present invention as the gradient climbing ability may be improved if a greater torque output is available from its engine.

Another application where the present invention may be advantageous is for turbocharged vehicles. Turbocharging an engine, whilst giving a substantial increase in maximum power, is often at the expense of torque at low engine speeds. This is most noticeable at low engine speeds during acceleration, when the turbocharger is not providing any boost (positive pressure in the induction system) and this leads to the phenomenon known as turbolag. Turbolag is the delay-time between the throttle being opened, and the build up of boost. The present invention may be able to increase the torque at low engine speeds, which may reduce this turbolag, thus improving the performance of the vehicle and making it easier to drive.

The present invention may be widely adapted to two-stroke, four- stroke and rotary engine types, including diesels and this optimisation for each of these engine types can be considered to be routine and within the capability of those skilled in the art of for example engineering, automotive engineering, performance tuning.

Embodiments of the present invention fitted to diesel engines may help reduce exhaust emissions, and may increase the thermal efficiency, by increasing the volumetric efficiency at low engine speeds. Normally at very low engine speeds in some diesel engines the volumetric efficiency is low, which means that when the accelerator is pressed hard, injecting more diesel into the engine, the amount of diesel fuel may be in excess of the amount of air or oxygen available for combustion. This means that the fuel will not combust completely, leading to high emissions. The increased volumetric efficiency that may be achieved by diesel engines fitted with embodiments of the present invention, may reduce particulate carbon and

hydrocarbon emissions, and exhaust gas recirculation (EGR) may also be used to reduce emissions of nitrogen oxides.

Several different designs are shown which use fuel injection.

However, the type of fuel, its method of addition to the air drawn into the engine, or the type or positioning of any throttle valves if they are required, are not important for the functioning of the present invention.

The effect of other manifold design parameters such as volume, pipe diameter and length may be adjusted by one skilled in the art to determine their effect on the functioning of the present invention. Other engine design parameters, such as camshaft design, cylinderhead modifications and exhaust manifold design may have an effect on the effectiveness of the present invention; however, it is within the ability of one skilled in the art to determine their effects on the performance of any engine that uses the present invention.

Fuel injection throttle bodies that are manufactured by various companies, can be modified to incorporate the present invention. This modification work can be done by attaching a reed valve housing on the throttle body using any fixing method for example, bolting, or welding. Inlet manifolds that bolt directly, or with one or more spacers or adapters, onto the engine can be modified in a similar manner.

Carburettors may also be produced so that a reed valve housing is an integral part of the carburettor Compressors of, for example, air which operate and produce pressure fluctuations, or have reversed flow out passed an inlet valve may also benefit from the use of one of the many embodiments of the present invention, as described herein.

Second aspect The following are the references to items of prior art relating to engine design that are relevant to the second aspect of the present invention :-

1) An article entitled"Engine Review: Webra T4 Four Cycle" commencing at page 32 of the May 1981 issue of"Model Airplane News".

2) SAE Technical Paper Series 840423,"Torque Boosting of 4-Stroke cycle etc. ", N. Okanishi et al., Feb. 27,1984 3) SAE Technical Paper Series 940840,"Application of Crankcase- Supercharging to a 4-Stroke Cycle Compression ignition Engine", N.

Okanishi et al., Feb. 28-Mar. 3,1994 4) SAE Technical Paper Series 940841,"On-Road Tests Using Small Crankcase-Supercharged 4-Stroke Cycle Engines", N. Okanishi et al., Feb.

28-Mar. 3,1994 The references continuing below are U. S. patents relating to engine design, where crankcase scavenging is used. These are relevant to the present invention:- 5) U. S. patent 4,715,336, inventors Schindler, M. and Ficht, R., filed Feb. 26,1986, entitled"Four-stroke internal combustion piston engine".

6) U. S. patent 5,072,699, inventor Pien, P. C., filed Jan. 22,1990, entitled"Internal combustion engine".

7) U. S. patent 5,230,314, inventors Kawahara, Y., et al., filed June 19, 1992, entitled"4-Cycle engine".

8) U. S. patent 5,579,735, inventors Todero, G. P. I. and Harms, R. L., filed Apr. 1,1994, entitled"Four-stroke internal combustion engine".

All the above items of prior art disclose the use of crankcase charging to increase the volumetric efficiency of the four-stroke engine, where the fuel-air mixture is first inducted into the crankcase and then fed up to the valves in the cylinderhead.

The further references listed below are U. S. patents relating to six- stroke internal combustion engines that are relevant to the second aspect of the present invention:- 9) U. S. patent 4,924,823, inventors Ogura, Y. and Ikenoya, Y., filed Oct. 7,1988, entitled"Six stroke internal combustion engine".

The further references listed below are U. S. patents relating to inlet valves and cylinder heads that are relevant to the second aspect of the present invention:- 10) U. S. patent 4,739,737, inventor Kruger, H, filed Aug. 14,1987, entitled"Rotary valve for the control of the cylinder charge change of an internal combustion engine".

11) U. S. patent 5,154,147, inventor Muroki, T., filed Apr. 9,1991, entitled"Rotary valve".

12) U. S. patent 5,361,739, inventor Coates, G. J., filed May 12,1993, entitled"Spherical rotary valve assembly for use in a rotary valve internal combustion engine".

13) U. S. patent 5,417,188, inventor Schiattino, M., filed Dec. 23,1993, entitled"Double effect distribution sequential valve shaft assembly".

14) U. S. patent 5,526,780, inventor Wallis, A. B., filed May 3,1995, entitled"Gas sealing system for rotary valves".

Engine designs are usually based on one of three basic designs, two-stroke, four-stroke and Wankel. However more engine designs have recently been invented such as the six-stroke engine. The present invention seeks to provide the means by which the performance and efficiency of all internal combustion engines including two-stroke, Wankel and other rotary type, six-stroke and eight-stroke engines may be improved.

The number of strokes of an engine, is defined as the number of times the crankshaft turns through half a revolution between each power producing event, specifically the initiation of combustion. It is therefore suggested that the maximum power output from any given internal combustion engine will only be achieved by the engine being able to induct, combust and exhaust one cylinder volume of fuel-air mixture for each crankshaft revolution at the highest possible engine speed. As a consequence of this, for any reciprocating engine of 2n strokes (where n is

an integer), for all values of n, the volumetric efficiency must be equal to n-x 100%.

Most four-stroke engines produced for cars, motorcycles, aircraft, boats, generators, lawnmowers, etc. rely on atmospheric pressure to cause the filling of the cylinder as the piston descends on the induction stroke.

Other effects such as inertia tuning or resonance tuning utilising the pressure pulses within the induction and exhaust systems, depending on the optimisation of the valve timing as usually controlled by a camshaft, are used to improve the volumetric efficiency at various engine speeds. The torque and power output characteristics of engines are optimised using the effects described above, taking into consideration the intended application for which the engine is to be used. Four-stroke engines for road vehicles are generally designed for good drivability, low exhaust emissions, good fuel economy and reliability.

All engines are optimised by appropriate design of some or all of the engine components, especially those attached to or that are part of the cylinderhead. Examples are camshaft duration and lift, valve type, size and shape, port angles, shape and dimensions, valve guide angle, cylinderhead designs, method and design of camshaft or valve operation and, because designs of cylinderhead valves other than the poppet type have been used, rotary valves for example, spherical rotary valves as designed by G. J. Coates, or Cross rotary valve or Aspin type rotary valve.

Sleeve valves have also been used. Different valve spring arrangements have been used, mainly steel or titanium coil springs, but pneumatic springs have also been used. Other dimensions and considerations such as the bore and stroke, the design of the piston and its crown and the type, and arrangement of piston rings are usually optimised depending on the intended application, and exceptional consideration is given to these aspects depending on the type of lubrication or fuel to be combusted. For example the piston crown may contain a bowl to improve the efficiency of

combustion if diesel fuel is injected directly into the engine. Another two examples of direct fuel injection are those of the very economical Mitsubishi system, and the system designed by Dr. Merritt and developed in conjunction with Cosworth, where direct petrol injection is used. The pistons in the Mitsubishi engine have raised piston crowns. Any of these technologies mentioned herein may be used in connection with the present invention. Any of the induction systems mentioned as part of the first aspect of the invention may be used on embodiments of this second aspect.

There is one induction period for each cylinder in a four-stroke engine every two crankshaft revolutions. At high engine speeds, the time for induction to occur is reduced in an inverse proportion to the engine speed i. e. there is half the time for induction to occur at 8000 r. p. m. as there is at 4000 r. p. m.. This ultimately reduces volumetric efficiency at high engine speeds, because the time for induction is substantially reduced.

In the"Otto-cycle"engine, this effect has been overcome in three main ways, by firstly shortening the stroke of the engine whilst concomitantly increasing the bore to maintain the same engine capacity, secondly by increasing the duration for which the inlet valve is open, and thirdly by designing the four-stroke engine cylinderhead with many valves, usually two inlet and two exhaust valves although three inlet valves are used on some four-stroke engines, to increase the flow capabilities of the ports and valves. These design changes enable the volumetric efficiency to be increased at high engine speed, but the maximum engine speed is determined to some extent by the valve area and the dynamics of the valve train for example, effects such as valve float or valve bounce.

Unfortunately maintaining the inlet valve or valves open for a long duration increases the overlap with the exhaust period leading to contamination of the fresh induction charge of air or fuel-air with exhaust

gas which is detrimental to combustion and reduces torque and power output at low engine speeds. The inlet valve is also maintained open for a longer period after the piston has reached bottom dead centre, which causes flow reversals in the induction system which reduce the volumetric efficiency at low engine speeds thus reducing the torque and power output.

Variable valve timing is now used on many'Otto-cycle'engines used in cars, and the different systems, examples of which are mentioned in the first aspect of the present invention, effectively overcome the problems associated with long valve opening periods. In most of these systems, the valve timing or valve area is reduced during low engine speed operation.

High power outputs can be achieved with short duration opening period of the inlet valve by pressurising the induction system by turbocharging, or supercharging. A supercharger or turbocharger is a device that is driven either from the crankshaft, or energy from the exhaust gases from the engine respectively, or driven by both these means, that is capable of increasing the pressure of the air or fuel-air mixture that is inducted into an internal combustion engine where, if the essential moving parts of the supercharger or turbocharger were to be removed and any holes left by the essential working parts were to be blocked, or the supercharger or turbocharger were to be removed completely, then the engine would still be able to function, albeit at a lower maximum volumetric efficiency, after the fuel-air mixture and ignition timing were adjusted for the operation of the engine.

According to the second aspect of the invention, there is provided an internal combustion engine comprising one or more cylinders and a piston mounted within each cylinder for reciprocatory motion, said engine being characterised in that at least one port for the induction or exhaust of gases to or from the cylinder is formed in the wall of the cylinder, said port being positioned so as to open into the volume of the cylinder above the

piston when positioned at the bottom of its stroke, and wherein a valve is situated in such a way as to control the flow of gas through the or each said port. Preferably such port or ports are additional to the existing cylinderhead inlet and exhaust valves found on a conventional reciprocatory internal combustion engine. Such conventional valves are normally of the poppet type, although other types are found occasionally.

Where there are two or more such ports, some may be inlet ports (for induction) and some outlet ports (for exhaust). Thus, in one preferred embodiment, there is a set of inlet ports and a set of outlet ports. The inlet port or ports, if present, are connected to receive combustion gas-air, or fuel-air mixture-either from an induction system, or from a compartment below the piston. This is explained in more detail below.

The invention may be applied to any reciprocating internal combustion engine, including for example, two-stroke, four-stroke or Wankel, or six-stroke, or eight-stroke engines, or any internal combustion engine of 2n strokes, where n is an integer.

Engines of 2n strokes where n>2, i. e. with more than four-strokes, are characterised in that they have a four-stroke cycle, which constitutes the main induction, compression, expansion and exhaust events in the compartment above the piston, but they also have either additional induction and compression strokes, or induction and scavenge strokes or both. There are three types of additional two strokes that can be added to the normal four-stroke process: a) The additional induction and compression strokes can be of air or fuel-air mixture, or b) The additional induction and scavenge strokes can be of air or exhaust gasses, or c) Alternatively, the cylinder valves can remain closed and residual gases in the cylinder can undergo additional expansion and compression events as the piston moves between top and bottom dead centre.

These additional two stroke processes, may only involve the compartment above the piston, or may involve additional induction strokes utilising air or fuel-air mixture from the crankcase. For example, a six- stroke engine may have a normal four-stroke cycle, and a two stroke scavenging process, and an eight-stroke engine may have a normal four- stroke cycle, and a four stroke scavenging process.

The teaching of the present invention can be applied to 2n-stroke engines in which the feed of air or fuel-air mixture is taken wholly or partly from a compartment below the piston, whether this be from the crankcase or from a compartment which is part of the cylinder where the compartment is separated from the crankcase, or indeed from a compartment whose pressure is affected by that within said compartment below the piston, with said feed entering a cylinder operating by the principle of the four-stroke cycle. Each of the embodiments described below may be used separately or together, with one or more of the other embodiments described herein, to increase the volumetric efficiency of four-stroke engines to 100% or greater, or to increase the torque output, or to broaden the torque curve, or to increase the power output, or to increase fuel efficiency, without the use of a supercharger or turbocharger:- An embodiment of the present invention comprises a 2n-stroke engine which inducts air or fuel-air mixture into a compartment below the piston, which compartment may comprise the crankcase itself, or a compartment which is part of the cylinder, or both the crankcase and a compartment which is part of the cylinder, or indeed another compartment whose pressure is affected by that pressure within the compartment below the piston, and from where it is directed into the volume of the cylinder above the piston. The air or fuel-air mixture that is inducted into the compartment below the piston, may be directed during the induction period of the 2n-stroke cycle into that compartment of the cylinder where combustion occurs, which may be the volume above the piston of the

same cylinder, or may be one or more other volumes above the pistons in other cylinders. a) It can be arranged that there is an induction period into the compartment below each piston for every two strokes of the piston moving in the cylinder. By setting, changing or maintaining the valve timing or degree of opening of any valve controlling the air or fuel-air mixture inducted, any proportion of the air or fuel-air mixture inducted into any of the compartments below any of the pistons may be fed to one or more of the cylinders, via said inlet orifices, for induction at any time during the induction stroke of the compartment above the piston of the cylinder or cylinders. Therefore the volumetric efficiency may be increased to more than that which is achieved by an engine which is not using this effect. b) In an embodiment of the present invention, the inducted air or fuel-air mixture may be directly fed under pressure from such a compartment below the piston into the volume of the cylinder above the piston, via said inlet orifice or orifices, where combustion occurs during the induction period of the four-stroke cycle, with there being present only the normal cylinderhead valve or valves to control the feed, thus increasing the volumetric efficiency. c) Another embodiment of the present invention, may provide an additional valve or valves in a feed connection between such a compartment below the piston and the inlet valves of the cylinder or cylinders. The additional valve or valves defines a separate chamber which can be pressurised to a greater pressure. This could occur for example if a reed valve is provided in the feed connection. On the first stroke, with the piston ascending up the cylinder, fresh air or fuel-air mixture is inducted into the compartment below the piston through a suitable valve, for example a poppet valve, or a rotary valve or a reed valve. When the piston descends, pressurising the air or fuel-air mixture, the air or fuel-air mixture is forced through the reed valve in the feed

connection from the compartment below the piston into the separate chamber. This process is repeated on the next crankshaft revolution, increasing the pressure within the separate chamber. This will pressurise the air or fuel-air mixture to a pressure greater than that achieved in embodiment b) and thus may give a greater volumetric efficiency during the induction process of the four-stroke cycle of the engine. d) A further embodiment of the present invention is a multicylinder engine which has the feeds from the compartments below each of the pistons, each going through a valve to a manifold or chamber which connects all the feeds together. This would enable high volumetric efficiencies to be achieved, without the necessity to store pressurised air or fuel-air mixture in the chamber for a long period. During the induction period of each cylinder, more than one compartment below more than one of the pistons will be supplying air or fuel-air mixture to the cylinder that is inducting air or fuel-air mixture. e) In another embodiment, a second valve or valves may be positioned between the first valve, as described in embodiment (c) or (d) above, in the feed connection between the compartment below the piston, and the valve or valves which control the flow of air or fuel-air mixture into the volume of the cylinder or cylinders above the piston or pistons. This valve or valves may be controlled by the position of the crankshaft and may enable even greater volumetric efficiencies to be achieved. The start of the normal induction period of the four-stroke cycle may for example be achieved by natural aspiration or by turbocharging or supercharging, by a separate induction system attached to the cylinderhead. Towards the end of the induction process, the second valve or valves in the feed connection or connections from the compartment or compartments below the piston or pistons are opened, effectively topping-up the almost full compartment of the cylinder, where the combustion is to occur. This requires a smaller volume from the feed connection from the compartment or compartments

below the piston or pistons which would maintain a greater pressure in the feed connection from the compartment or compartments below the piston or pistons, thus achieving a greater pressure in the volume of the cylinder above the piston before the inlet valve or valves close.

In a normal four-stroke engine, working at full throttle, if there is no vacuum evacuation of the sump or crankcase, the engine wastes power by moving air and large volumes of oil under the pistons. Exhaust vacuum evacuation reduces this power loss, but does not remove it completely.

This can be considered to be a pumping loss. Some embodiments of the present invention may have this pumping loss, and this may be greater than normally incurred, as this pumping energy is used to pressurise the air or fuel-air mixture in the compartment below the piston and the feed from it. This assists the filling of the cylinder thereby reducing the pumping loss that is also incurred to fill the cylinder, which may therefore increase the power output. This is particularly important at part throttle where the cylinder is filled to below atmospheric pressure at the end of the induction process. Thus, the present invention, may have the advantage that less energy is lost due to pumping losses of air or fuel-air mixture in the compartment below each piston than that which normally occurs in the crankcase of four-stroke engines and may therefore increase the power output and reduce fuel consumption at part throttle. The use of oil-mist lubrication or direct oil injection of the precise minimum quantities of oil onto the required working surfaces such as the cylinderbore surface may substantially reduce the amount of energy expended for lubrication. g) It may be. possible to increase the fuel efficiency of road vehicles in further ways. This will be illustrated by a comparison between the'Otto- cycle'four-stroke engine designs, and embodiments of the present invention. If an engine is selected on the criteria of power and torque output, with the same number of cylinders, then the capacity of the'Otto- cycle'four-stroke engine will be approximately 50% to 100% larger than

embodiments of the present invention. The internal friction of embodiments of the present invention may be less than that of the'Otto- cycle'four-stroke engine, because of the smaller area of pistons and their rings causing friction. The same torque or power output may be able to be achieved with embodiments of the present invention at lower engine speeds, and with higher gearing on the vehicle, pumping and friction losses may be reduced thus improving fuel economy. In traffic, or during the urban cycle that is the industry standard cycle for measuring the fuel economy in traffic, the engine of the vehicle spends some of the time at tick-over. With the smaller capacity engine, the volume of air or fuel-air mixture inducted in a certain period of time may be less than that inducted by the'Otto-cycle'four-stroke engine also operating at tick-over thus embodiments of the present invention may again improve fuel economy. h) Embodiments of the present invention with either smaller cylinderhead inlet valve or valves, or with less duration of opening of these inlet valve or valves may be able to achieve the same torque or power outputs as an'Otto-cycle'four-stroke engine. This may be achieved because the pressurized feed from the compartment below the piston or pistons increases the flow in the inlet port past the inlet valve or valves.

Therefore it is possible to allow the induction of the same volume of air or fuel-air mixture into the cylinder in a shorter period of time. This may enable the engine to provide a broader spread of torque across all of the engine speed range, and a greater maximum power output than that of an 'Otto-cycle'four-stroke engine. i) Embodiments of the present invention may have one or more of said inlet ports in one or more walls of the cylinder for the induction of air or fuel-air mixture from the compartment below the piston or from the compartment below any other piston or pistons, into the cylinder during the induction period. These inlet port or ports are additional to the existing inlet port (s) in the cylinderhead. As already mentioned, the flow of air or

fuel-air mixture through this additional inlet port or ports, may be controlled by one or more valves. The type of valve is unimportant for the functioning of the present invention, for example rotary, poppet, disc, slide, butterfly, but certain valve types may be preferable. For example, an embodiment of the present invention may have a port positioned in the wall of the cylinder so that it starts to become exposed when the piston has travelled a distance from top dead centre, for example, at 60 degrees (of crankshaft turning) before bottom dead centre. The provision of a valve or valves in the port or ports, for example, a rotary valve, may be necessary to prevent the flow of high temperature and pressure exhaust gases from entering the port or ports or the compartment below the piston. The mixing of these exhaust gases with the inducted air or fuel-air mixture may at least reduce the efficiency of combustion because of the dilution effect, or at worst cause the initiation of combustion in an inappropriate part. The valve or valves if present would enhance volumetric efficiency by opening during the induction period of, for example, the four-stroke cycle, allowing the air or fuel-air mixture from the compartment below the piston or from the compartment below another piston or pistons, to flow into the cylinder through the inlet port past the valve or valves. The said valve or valves would be closed during the power and exhaust strokes of operation to prevent the flow of high temperature and pressure exhaust gases from entering the port or ports or the compartment below the piston. When induction through the cylinderhead port or ports and the port or ports in the side of the cylinder occurs, the different flows of air or fuel-air mixture impinging on each other may create more turbulence, which may assist combustion. j) A shorter duration of the opening period of the inlet valve or valves in the cylinderhead may be necessary or desirable. For example, when the additional inlet port or ports in the wall of the cylinder allows the induction of air or fuel-air mixture from the compartment below the piston or

from the compartment below any other piston or pistons, the pressure of the air or fuel-air mixture in the cylinder may be greater than that in the cylinderhead port. This may allow air or fuel-air mixture from the cylinder to flow out past the inlet valve or valves in the cylinderhead which would reduce the volumetric efficiency of the engine. This may therefore require the inlet valve or valves in the cylinderhead to close when the piston is nearer to, or is before, bottom dead centre. With a shorter duration of the opening period of the inlet valve or valves in the cylinderhead, the flow past these valves at low lift may be more important, as there may be mechanical limitations to the maximum lift that can be used as the engine speed increases. The vaive acceleration is one such mechanical consideration. The use of lightweight materials such as titanium may enable greater valve lifts and rates of acceleration than if steel was used.

The use of more, smaller valves may improve the volumetric efficiency, which require lower lifts to achieve the same flow rate. The use of an embodiment of aspect one of the present invention may be advantageous to obtain the greatest possible flow rates at low valve lifts. If there is a risk of detonation or knock at low engine speeds due to the high volumetric efficiency of the engine, it may be useful to allow some flow out of the inlet valve or valves in the cylinderhead, to keep the volumetric efficiency below a certain level. k) Embodiments of the present invention may also utilise a non- return valve or valves in the inlet port of the cylinderhead or in a manifold that is attached to it, to prevent or reduce the flow of air or fuel-air mixture out of the inlet port or ports, past their respective valves in the cyiinderhead. This may improve the volumetric efficiency at low engine speeds, or small throttle openings, or it may maintain the volumetric efficiency at low engine speeds at a level which prevents the onset of knock or detonation when a high compression ratio is used. The timing of the inlet valve or valves in the cylinderhead will be a critical factor, and will

need to be optimised. Any previously published non-return valve or system may be suitable. The first aspect of the present invention may be particularly suitable, using any of the possible effects that have been described herein.

I) Embodiments of the present invention may be provided with the means to induct air or fuel-air mixture from one or more compartments below one or more pistons, through one or more inlet ports in the cylinderhead and through one or more inlet ports positioned in the wall of the cylinder. Valves may be fitted which enable the air or fuel-air mixture to be directed, to only one or more of the cylinderhead inlet ports with their respective valves, or to only one or more of the inlet ports positioned in the side of the cylinder, or both, depending on the engine speed, the throttle position, or some other parameter. m) Embodiments of the present invention may be provided with the means to induct air or fuel-air mixture through one or more inlet ports in the cylinderhead and through one or more inlet ports positioned in the wall of the cylinder, where the air or fuel-air mixture is not supplied from one or more compartments below one or more pistons. Valves may be fitted which enable the air or fuel-air mixture to be directed, to only one or more of the inlet ports or valves in the cylinderhead, or to only one or more of the inlet ports positioned in the wall of the cylinder or both depending on the engine speed, the throttle position, or some other parameter. n) To achieve the maximum power output, the relative flow of the exhaust valve or valves and port with respect to the flow of the inlet valve or valves and port of a naturally aspirated four-stroke engine usually occurs when the exhaust is capable of a flow that is approximately 75% to 80% of the inlet flow. With an increased volumetric efficiency, giving a greater flow past the inlet valve or valves, it may be necessary to increase the size or number of the exhaust valve or valves in the cylinderhead preferentially to achieve the maximum power output from the engine, for

example, by having two inlet valves and three exhaust valves. o) It has been stated previously herein that the improved volumetric efficiency may require additional exhaust valves or increased exhaust valve size in order to obtain the maximum benefit from the efficiency gains described above. Embodiments of the present invention may have one or more of said exhaust ports provided in the wall of the cylinder for the expulsion of exhaust gases during the exhaust period. These exhaust port or ports are additional to the existing exhaust port (s) in the cylinderhead. The flow of exhaust gases or other gases such as air or fuel-air mixture through these additional port or ports, may be controlled by a valve or valves. The type of valve is unimportant for the functioning of the present invention, for example rotary, poppet, disc, slide, butterfly, but certain valve types may be preferable. For example, an embodiment of the present invention may have an exhaust positioned in the wall of the cylinder so that it becomes fully exposed when the piston has travelled a distance from top dead centre, for example, at bottom dead centre. The provision of a valve or valves in the exhaust port or ports, for example, a rotary valve, may be necessary to prevent the flow of air or fuel-air mixture from entering the port or ports and flowing out through the exhaust manifold which, in the absence of any valve or valves may reduce the volumetric efficiency, or allow the mixing of the exhaust gases with the inducted air or fuel-air mixture which may reduce the efficiency of combustion because of the dilution effect. The valve or valves if present may enhance power output by opening at or near the start of the exhaust period of the four-stroke cycle. The exhaust period usually starts during the power stroke, at a time before the piston has reached bottom dead centre. This may allow the exhaust gases to escape more rapidly from the cylinder than would be possible through the exhaust valve or valves in the cylinderhead alone. This may result in a lower pressure of exhaust gases being present in the cylinder as the piston commences the exhaust stroke

proper, when the piston has reached bottom dead centre and starts to travel towards top dead centre again. This exhaust gas pressure reduction will concomitantly reduce the energy required to pump the remaining exhaust gases out of the cylinder. The exhaust manifold may connect the port in the cylinderhead to the port or ports in the side of the cylinder, which causes the expulsion of exhaust gases through the port or ports in the side of the cylinder to create a lower pressure or partial vacuum at the exhaust valve in the cylinderhead, which may increase the flow of exhaust gases out through the cylinderhead when the piston is travelling up the bore to top dead centre. This reduction of energy expenditure, may also reduce the fuel consumption, and may increase the power output. The said valve or valves would be closed during the induction and compression periods of operation to prevent the flow of air or fuel-air mixture from entering the exhaust port or ports and flowing out through the exhaust manifold. p) In embodiments of the present invention, a shorter duration of the opening period of the exhaust valve or valves in the cylinderhead may be beneficial. For example, when additional exhaust port or ports are present in the cylinder wall, together with their respective valve or valves, there may be sufficient flow capacity through all of the exhaust valves present, and time for the exhaust process to occur without taking any extra energy from the crankshaft so much so that the exhaust period can be started later in the four-stroke cycle. This would concomitantly increase the length of the power stroke, or the degrees of crankshaft rotation, over which the high pressure of the combusted gases are exerting pressure on the piston, which may increase the power output, or may reduce fuel consumption. The amount of energy that is extracted from the expanding high temperature and pressure combusted gases is dependent on the expansion ratio. The expansion ratio, is the ratio between the minimum volume of the cylinder, usually when combustion commences, and the

maximum volume of the cylinder when the exhaust valve or valves open at the start of the exhaust process. The delay of opening of the exhaust valve or valves will concomitantly increase the expansion ratio. With a shorter duration of the opening period of the exhaust valve or valves in the cylinderhead, the flow past these valves at low lift will be more important, as there may be mechanical limitations as to the maximum lift that can be used as the engine speed increases. The valve acceleration is one such mechanical consideration. As stated above, the use of lightweight materials such as titanium may enable greater lifts and rates of acceleration than if steel was used. The use of more, smaller valves may improve the flow efficiency, which require lower lifts to achieve the same flow rate. q) In embodiments of the present invention with one or more additional exhaust ports positioned in the wall of the cylinder, the volume of high temperature exhaust gases that flow out of the cylinder past the exhaust valve or valves in the cylinderhead will be reduced. This may reduce the temperature, not only of those exhaust valves present, but also of the cylinderhead itself, which may reduce the possibility of knock or detonation, which may enable higher compression ratios to be used for a given octane rating of fuel, or more ignition timing advance in spark-ignition engines. r) Embodiments of the present invention may also benefit from less duration of overlap of inlet valve or valves and exhaust valve or valves opening. This occurs towards the end of the exhaust stroke, when the inlet valve or valves open before the piston has reached top dead centre, whilst the exhaust valve or valves are still open. This creates inertia induction effects at medium to high engine speeds, this is where the momentum of the exhaust gases is used to accelerate the air or fuel-air mixture towards the cylinder that is to be inducted for the next four-stroke cycle. Some of the air or fuel-air mixture may be lost out of the exhaust,

but this effect is one of the most important that enables Formula One engines to attain high volumetric efficiencies at high engine speeds. With the potential greater volumetric efficiency of the present invention, being provided by the induction of air or fuel-air mixture from one or more compartments below the piston or pistons, or additional ports in the wall of the cylinder providing a greater inlet port area, inertia induction effects may have a reduced significance on the ability to produce high power outputs.

This does not mean that embodiments of the present invention will not benefit from the optimisation of inertia induction effects, but that they may be able to produce a greater power output than an'Otto-cycle'four-stroke engine, in the absence of any inertia induction effects. s) The pistons may be of various different designs, depending on the presence of the ports in the wall of the cylinder. In the presence of one or more ports in the wall of the cylinder, the piston or pistons may require skirts. Where a four-stroke lubrication arrangement is used, with the presence of ports and valves in the wall of the cylinder, the oil control rings of the pistons may be arranged near the bottom of the long piston skirt, so that they do not pass over the ports as the piston travels up and down the bore of the cylinder. The design of a port in the wall of the cylinder may be such that even with the presence of a valve, there may be a gap between the valve and piston that is a greater distance than the normal clearance than is present between a piston and its cylinder wall.

During the compression, and power strokes, the pressure of gas in the volume above the piston will be greater than that in the compartment below the piston. The gap at the port in the cylinder wall may provide a passage through which gas can escape from the volume above the piston, into the compartment below the piston. Pistons with skirts may also prevent the leakage of exhaust gases, air or fuel-air mixture from the volume above the piston, into the compartment below the piston. The design of the valve or valves that control flow through the port or ports in the wall of the cylinder

may be such as to minimise the volume contained between the piston and the valve. A Scotch Yoke design consisting of a one-piece conrod and piston member the same or similar to that patented by Tresillian in about 1950 may be used, but may be disadvantageous for designs which have one or ports in the wall of the cylinder, because the piston part has virtually no skirt. The Scotch Yoke design may be in a horizontally-opposed configuration by having a second conrod shank on the other side of the slider window and another'shortened'piston, thus making a double ended piston and conrod unit, with a single window with slider and one or more bearings around one crankshaft big-end journal. t) Another factor may affect the choice of valve or valves that may be used to control the flow through either the inlet and/or exhaust ports in the wall or walls of the cylinder. If the ports are low down in the cylinder, this means that they become uncovered by the piston only at or near bottom dead centre, which in turn means these valves would be exposed to only a few atmospheres of pressure, which is lower than the extreme pressures which are present after compression and during combustion at the start of the power stroke, to which the poppet valves in the cylinderhead are exposed. This substantially reduces the sealing demands on these valves and enables simple valve designs to be used, for example rotary valves. u) Embodiments of the present invention may use rotary valves in the cylinderhead, instead of poppet valves that are normally used on four- stroke engines. This would remove the problems of valve bounce or valve float that normally limits the maximum permissible engine speed of four- stroke engines. Rotary valves are not normally used because of sealing difficulties and they can present a flow restriction. Ports in the cylinder wall for the induction and exhaust processes are not so dependent on the flow capabilities of the valves in the cylinderhead. This gives greater freedom in the choice of cylinderhead valves, and those with lower flow,

but extreme high speed capability may be suitable. For example cylinderhead rotary valves designed by G. J. Coates. Poppet type valves may still be retained in the cylinderhead, but particular attention should be paid to the camshaft, for example, reducing the maximum valve lift, reducing the maximum valve accelerations, which may enable such embodiments to work at greater engine speeds, than is possible at present, before valve bounce or valve float occur. Alternatively with the described camshaft design changes, it may be possible to reduce the valve spring pressures, to achieve the same maximum engine speed, which would also reduce the friction losses associated with opening and closing of the valves. v) Direct injection of fuel into the crankcase or compartment below the piston, when it is directed at the top or underside of the piston may assist piston cooling, improve fuel volatilisation, reduce emissions or reduce fuel consumption. w) As already mentioned, some embodiments of the present invention may not utilise a feed of air or fuel-air mixture from the compartment below the piston, when either one or more inlet ports or one or more exhaust ports or one or more of both types of ports are present in the wall of the cylinder. Instead, the inlet port or ports in the wall of the cylinder may be supplied by air or fuel-air mixture at atmospheric pressure from a conventional induction system, or by a supercharger or turbocharger or may simply provide a place for the direct injection of fuel only or fuel and nitrous oxide. The direct injection of fuel only may allow the fuel to volatilise completely using the heat from the cylinder, which may improve combustion or reduce emissions. x) Embodiments of the present invention may have valves and passages arranged such that at low engine speeds, the air or fuel-air mixture from one or more compartments below the pistons is directed to only one of the inlet valves of each cylinder in the cylinderhead, and the

other valves remain closed or flow through their ports in the cylinderhead is prevented by the presence of a valve which is closed, then when the engine speed and throttle position have reached pre-set values, the air or fuel-air mixture from one or more compartments below the pistons is directed to only the port in the wall of the cylinder and air or fuel-air mixture is supplied to both of the cylinderhead valves from another manifold. y) Embodiments where air or fuel-air mixture from one or more compartments below the pistons is directed to only one of the inlet valves of each cylinder in the cylinderhead, or to a valve in the cylinderhead which enables the air or fuel-air mixture to enter the cylinder at a tangent to the axis of the cylinder, may have more swirl in the cylinder during the induction, which may improve mixing, or improve lean-burn capability. z) Embodiments of the present invention with one or more ports in the wall of the cylinder, be they inlet, exhaust or both types, may have some exhaust gases trapped between the piston, the cylinder wall and any valves, if present in those ports. This small volume of exhaust gas may act in a similar manner to exhaust gas recirculation (EGR) devices which introduce a small volume of exhaust gas back into the cylinder during the induction period of the next four-stroke cycle. Exhaust gas recirculation can be helpful in reducing the combustion temperatures which may reduce the harmful exhaust gas emissions, such as nitrogen oxides.

In an embodiment of the present invention, there may be more than one piston and cylinder enclosing a crankcase compartment. For example, if there are two cylinders in a V-arrangement, and the air or fuel-air mixture is drawn into the crankcase compartment then the volumetric efficiency will depend on the angle between the centrelines of the bores of the cylinders, when there is a common big-end journal on the crankshaft. As the angle increases from 0 degrees to 180 degrees, the volumetric efficiency will decrease. Another embodiment of the present invention may have the big-end journals of the two cylinders set 180 degrees apart on the

crankshaft. In this case, maximum volumetric efficiency will occur when the two cylinders are arranged horizontal opposed, and the volumetric efficiency will decrease concomitantly with the reduction of the angle between the centrelines of the bores of the cylinders. In general, where the crankcase is used for the induction of air or fuel-air mixture, it is necessary that there is sufficient volume change within the crankcase, with each crankshaft revolution to be able to induct and expel air or fuel-air mixture into and out of the crankcase, and that one or more pistons may be connected to the same crankshaft journal or that there may be one or more crankshaft journals controlling different pistons in the same crankcase compartment.

These arrangements described above, with more than one piston and cylinder enclosing a crankcase compartment may also be used for multiple cylinder two-stroke engines of the V or horizontal opposed configurations.

The piston may be normal or stepped. If the piston is stepped then both two-stroke and four-stroke lubrication may be required. With a stepped piston, the primary induction and compression may occur in the volume enclose between the cylinder wall, the piston and the two sets of rings, in an identical manner to a two-stroke engine that has a stepped piston.

Lubrication may be as for a two-stroke or a four-stroke engine.

Suitable bearings are used, depending on the lubrication. Oil-mist, (two- stroke lubrication) for example requires roller bearings or bearing races.

Pressurised, (four-stroke lubrication) can use plain bearings however, a pressurised feed of oil may be directed to roller bearings or bearing races.

Embodiments of the present invention may use both types of lubrication.

The type of lubrication or bearings is unimportant for the functioning of this invention. It is important, as it is for any internal combustion engine that the lubrication is sufficient but not excessive and of the correct type, to

reduce wear, minimise oil consumption, ensure that combustion is efficient and to prevent misfiring, overheating or seizures. For those embodiments of the present invention where the crankcase is involved in the induction of air or fuel-air mixture, lubrication of the piston, small end bearing and big end bearing by oil mist (two-stroke) lubrication is preferable. For those embodiments of the present invention, where the compartment below the piston involved in the induction of air or fuel-air mixture is separate from the crankcase, only lubrication of the piston by oil mist (two-stroke) (total loss) lubrication is preferable, all other bearings being lubricated preferably by direct oil feed which may be pressurised if the bearing is plain, or at a lower pressure for example by drip feed if a roller bearing or ball bearing race is used. Oil may be directed at low pressure, to the cylinder walls through oil ways in the cylinder block to assist the lubrication of the piston, its rings and the cylinder walls.

Embodiments of the present invention that use oil mist (two-stroke) (total loss) lubrication may have greater exhaust gas emissions. Similar problems have been encountered historically with the Wankel rotary engine, and with modern two-stroke engines. The exhaust gas emissions may be reduced for example, by after-burning, by the addition of air into the exhaust manifold, or exhaust catalysts for example, dual catalysts or three-way catalysts being used in conjunction with electronic fuel injection and one or more lambda sensors.

In embodiments of the present invention where the primary induction is into the crankcase, it is desirable that there are good gas pressure seals between each crankcase compartment as there are in two- stroke engines. Embodiments of the present invention may use any embodiment of any two-stroke engine bottom ends, for example, parts including the crankshaft, connecting rod and its roller bearings (one bearing at each end), main bearings and seals. Two-stroke engines normally have the main crankshaft bearings exposed to the oil-mist and

fuel-air mixture in the crankcase ; however, embodiments are described herein which have the main crankshaft bearings separated from the crankcase by a seal, and lubrication is supplied separately from a pump.

This may help the longevity of these main crankshaft bearings, and reduce the amount of oil for lubrication of engine parts in the crankcase.

Embodiments with the main crankshaft bearings separated from the crankcase may also be suitable for other four-stroke or two-stroke engines.

The frequency of oil changes may be reduced, as the lubricating oil should not be contaminated by combustion by-products.

Embodiments of the present invention may have big-end bearings of the conrod or Skotch Yoke type which consist of two roller bearing races where one is inside the other, with a race separator in between. This may be necessary when high engine speeds are used, which normally result in a single roller bearing race sliding or skipping on the crankshaft journal, which dramatically increases the rate of wear. In one crankshaft revolution, the speed of the roller bearing accelerates and decelerates between about 0.8 and 1.2 times the engine speed. Having two bearings replace a single roller bearing, may therefore reduce the acceleration and deceleration of each bearing to between about 0.9 and 1.1 times the engine speed, thus reducing the possibility of sliding or skipping, which may allow the maximum engine speed to be increased to twice that permitted by a single roller bearing. This effect may be extended further by more bearing races. Embodiments with big-end bearings of the conrod or Skotch Yoke type which consist of two bearing races may also be suitable for other four-stroke or two-stroke engines. The bearing races may, for example, be of the roller type or ball race type.

To reduce the amount of oil drawn into the cylinder on each induction cycle. An oil separator may also be used to separate the oil from the air, when oil-mist (two-stroke) lubrication is used.

There may be one or more valves in series or parallel controlling the

induction into the compartment below the piston, and the valve or valves may be of any type, for example, reed valve, rotary valve, poppet valve or butterfly valve. The induction into the compartment below the piston may be natural or forced, by turbocharging or supercharging, or by any combination or permutation of these induction methods.

The induction into the compartment below the piston, or the pressure of the feed from that compartment, may be controlled by the absolute pressure at which the engine is operating. This would be particularly useful for aircraft. Atmospheric air pressure is dependent upon altitude. As the altitude is increased, the air pressure is reduced. When aircraft fly at higher and higher altitudes above the ground, their engines power output is reduced because the reduced air pressure decreases volumetric efficiency. If however, at higher altitudes, more air or fuel-air mixture may be allowed into the compartment below the piston, or the pressure in the feed from this compartment is allowed to increase to maintain the volumetric efficiency to compensate for the reduced atmospheric air pressure, the engines power output will be maintained.

The feed from the compartment below the piston may be directed to the cylinderhead inlet valve or valves, which controls the flow into the cylinder above the same piston. Alternatively the feed may be directed to the cylinderhead inlet valve or valves of one or more of the other cylinders in any permutation if the engine has more than one cylinder. The feed from the compartment below the piston may also be controlled by a valve or valves for example reed valve, rotary valve or poppet valve. This valve or valves may be opened depending on the position of the crankshaft, or depending on the relative pressures of the air or fuel-air mixture in the feed and of the air or fuel-air mixture in the compartment below the piston or pistons, or depending on the relative pressures of the air or fuel-air mixture in the feed and atmospheric pressure or depending on the engine speed, or the throttle position, or by any combination of these.

Controlling the feed, depending on the engine speed may be necessary if there is a risk of knock or detonation because of a high compression ratio. The feed from the compartment below the piston may then for example, only be opened at high engine speeds to maintain the volumetric efficiency as the engine speed increases.

The feed from the compartment below the piston or pistons may be directed to one or more of the cylinderhead inlet valves, which control the flow into the cylinder or cylinders above the piston or pistons of those cylinders. The same inlet valve or valves, or the other inlet valve or valves may or may not be, together or separately, connected to another induction system which is fed by natural aspiration, or by forced induction or by both.

The pressure in the feed from the compartment below the piston or pistons may be controlled by a valve or valves which release the said pressure when the throttle valve is closed when the engine is operating as a spark ignition engine. This would be useful to improve the rate at which the engine speed slows when the throttle is closed abruptly, thereby improving throttle response. The reduction of pressure of the feed from the compartment below the piston may be achieved by venting a volume of air or fuel-air mixture into any part of the induction system, or if it is only air that is pressurised in the feed from the compartment below the piston, then the valve or valves may allow the pressurised air to be vented through a non-return valve to the atmosphere or some part of the induction tract or manifold that is at atmospheric pressure.

The feed of air or fuel-air mixture from the compartment below the piston may be through a transfer port in a similar manner to that of a two- stroke engine where it is directed to a valve which controls the flow from the feed.

Different types of rotary valves may be used as inlet or exhaust valves, in the port or ports in the walls of the cylinder. Many possible different bearing and seal arrangements may be used, for example, the

rotary valve may be positioned as near as possible alongside the cylinder bore walls, the rotary valve may constantly rotate by being driven from another rotating part of the engine, for example, the crankshaft or the camshaft by, for example, a belt, chain or gear, in a similar manner to that of a camshaft. The speed of valve rotation will be dependent on the design of the valve itself. For example, a rotary valve with a cut-out in the valve which goes right through the middle of the valve will need to rotate at 0.25 times the engine speed, whereas a valve, with a cut-out on one half of the valve circumference will need to rotate at 0.5 times the engine speed.

The rotary valve lubrication seals may be of any design, which may, for example, be identical to the design of any piston ring, for example, plain and of rectangular cross-section, or the design of the sealing ring gap may be reduced by overlapping ends or another overlapping ring, for example, in a similar manner to Total SealTM piston rings. The rotary valve may be sealed by another means, for example, bearing seals. The rotary valve may be lubricated by a pressurised oil feed from an oil way, the rotary valve may be formed so that the port in each cylinder is closed or open at the appropriate time by a passage in the rotary valve. Apart from lubrication seals, the rotary valves may have gas seals, to seal against air, or fuel-air, or exhaust gas pressure, which for example may be of a design the same as or similar to Wankel engine rotor tip seals. The gas seals may also be located in the cylinder block, and bear against the rotary valve, for example, as in U. S. patent 5,154,147, Muroki, T. inventor, where the cylinderblock has a split line down the axis of the rotary valve to allow machining of slots in which the seals are located. Similar rotary valves may be used in the cylinderhead with one or more additional seals which are able to seal against the valve and in the part of the port which leads to or from the combustion chamber in the cylinderhead.

Further embodiments of the present invention may enable even greater increases in the volumetric efficiency of the engine to be achieved.

The piston may be connected solidly, with no movement, or flexibly with for example, a fixing similar to a small end bearing, to a piston rod, or piston tube, which is then connected to a connecting rod which performs the same function of those connecting rods found in modern two-stroke or four-stroke engines, which is, at the opposite end of the connecting rod (conrod), connected to a crankshaft. The piston rod, or piston tube connects the piston to the connecting rod by passing through a bearing for example, plain bearing or roller bearing, which is situated at one end of the cylinder and that end of the cylinder may effectively be closed off by the material that supports the bearing. A seal at the end of the bearing may also be present through which the piston rod or piston tube passes. There may be one or more ports with or without valves, situated around the bearing to allow the induction of air or fuel-air mixture into the compartment below the piston from the crankcase, or from another part of the induction system.

The piston tube or piston rod may be of any cross-section, but a round cross-section is preferred as this simplifies the manufacture and machining of the piston rod or piston tube and their bearing.

Embodiments of the present invention may consist of some or all of the components to enable the conversion of previous designs of four- stroke engines or two-stroke engines to one of the embodiments shown herein of high volumetric efficiency internal combustion engines. These components together would constitute a conversion kit and may consist of one or more of the following components :- i) piston tube or piston rod for each cylinder, ii) pistons and rings, iii) threaded gudgen bolts and lock nuts, iv) gudgen pins, v) a supporting block with bearings and seals, vi) a cylinder block,

vii) a cylinderhead, viii) manifolds, connectors and tubing, ix) fuei-injection components, x) any valves and their components for their operation, xi) components for additional lubrication for example, oil pipes and oil pump and components for its operation.

The components shown here may not be a comprehensive list, but represent most of the major components required for such a conversion.

Different conversion kits may enable different four-stroke engines to be converted to a high volumetric efficiency four-stroke engine or high volumetric efficiency two-stroke engine as disclosed herein. Further conversion kits may enable different two-stroke engines to be converted to a high volumetric efficiency four-stroke engine or high volumetric efficiency two-stroke engine as disclosed herein.

These conversions may retain the original crankcase block, which may be used with or without additional machining, for example, by milling of the crankcase block surface which mates against the cylinderhead or its gasket. On top of the original crankcase block will be positioned the supporting block, on top of which the new cylinder block will be positioned the cylinderhead. The cylinderhead may be the original or may be a new, different casting.

Those embodiments of the present invention which have each of its pistons connected to a piston rod or a piston tube, which is connected to the connecting rod, and then to the crankshaft, may have some operating constraints because the weight of this reciprocating mass may be greater than that of the other embodiments of the present invention, or previous four-stroke or two-stroke engine designs. If the reciprocating mass is greater, then the maximum engine speed may need to be lower because greater strains may be placed on various components, for example, the connecting rods, the main bearings, big-end bearings, small end bearings.

This may prevent these embodiments from being suitable for high speed operation, for example, for racing, unless special attention is paid to reducing the mass of each component, for example, by making the components out of titanium. These embodiments may however still be suitable for use in, for example, cars, aeroplanes, motor-mowers, diesel vehicles because the engine speeds typically used for these applications are much lower.

The addition of fuel to a cylinder can be direct into the cylinder where combustion occurs, or may be into another part of the engine or its induction system. For example, fuel may be added to the air flowing through one or more of the ports, and this may be determined by the temperature of the engine. For example, when the engine is starting and warming up to operating temperature, the fuel may only be injected into the air stream flowing through the cylinderhead. This may assist combustion because when the engine is not at operating temperature, and if fuel was to be injected into the air in the compartment below the piston, the fuel may condense or puddle in that compartment below the piston. However, when the engine has reached the correct operating temperature, the addition of fuel to only the air entering the compartment below the piston may assist cooling by the evaporation of fuel taking heat from for example, the piston. This switching of fuel injection to only the air entering the compartment below the piston would mean that no fuel is added to the air stream flowing through the cylinderhead and therefore during cylinderhead exhaust and inlet valve overlap, and only air would be involved in the scavenging of the combustion chamber, which would prevent any fuel loss out through the exhaust system.

Any suitable means may be used to open and close the valves, for example, rotary valves may be driven by, for example, a belt and sprocket, intermeshing gears, chain and sprocket, from another rotating engine component, for example, camshaft or crankshaft. Embodiments of rotary

valves shown herein may require a device to locate the rotary valve which prevents movement in the direction of the axis of the valve, without preventing the rotation of the valve, for example, a plate which fits into a machined groove in an identical manner to that which is used for camshafts.

Cooling of the engine may be by for example, air, oil, water or water anti-freeze mix. The coolant cavities for liquid cooling may be arranged for example, along the sides of the cylinder block, or between each of the cylinders.

The pistons and valves may need to have a thermal barrier coating to reduce the amount of heat absorbed by the air or fuel-air mixture. Such a coating may reduce the possibility of seizures of the pistons, because the engine may not have oil jets directed at the underside of the piston, which assist piston cooling in some four-stroke engines.

There are many interrelated factors or parameters that will affect the optimisation of any engine made in accordance with the present invention, for example, volumetric efficiency, ignition timing, compression ratio, fuel- air ratio, cylinderhead design, piston design, engine cooling.

The ignition system or method of ignition of the fuel-air mixture is dependant on the type and quality of fuel to be burned. It is within the ability of one skilled in the art to provide and position the components accordingly, by for example, providing one or more spark plugs in the cylinderhead when using petrol or any other fuel that requires spark ignition.

Embodiments of the present invention can be considered to be naturally aspirated because in the same way a two-stroke engine may use atmospheric pressure to fill the compartment below the piston during the primary induction period, so too do embodiments of the present invention.

Greater power outputs may be obtained by utilising any form of forced induction such as supercharging or turbocharging. Forced

induction may be provided by an additional device that either takes energy from the exhaust gases, or from a mechanical drive from the engine, or from any electrical output that is provided by an electricity generator for example an alternator or a dynamo. Chemical supercharging may also be used, for example by the induction of nitrous oxide and extra fuel.

A supercharger or turbocharger is a device that is driven either from the crankshaft, or by energy from the exhaust gases, or by both these means, and that is capable of increasing the pressure of the air or fuel-air mixture that is inducted into the engine, where if the essential moving parts of the supercharger or turbocharger were to be removed and any holes left by the essential working parts were to be blocked, or the supercharger or turbocharger were to be removed completely, then the engine would still be able to function, albeit at a lower maximum volumetric efficiency, after the fuel-air mixture and ignition timing were adjusted for the operation of the engine.

The engine of the present invention may have one or more cylinders. Embodiments of the present invention may have their cylinders, if there are more than one, arranged in any configuration, for example straight, V, opposed, radial, square, parallel, horizontal.

The cylinder of an internal combustion engine may be divided into two or three compartments by the piston or rotor (in the case of a Wankel engine), and the maximum specific power output achievable by natural aspiration will only be attained when combustion occurs in one of the compartments in the cylinder, one of the other compartments being used to assist the induction of the air or fuel-air mixture into that compartment of the cylinder where combustion occurs, and wherein the third compartment, if present, is used to assist the expulsion of the residual exhaust gases.

Engines that are designed in this way are theoretically able to induct, compress, ignite, burn and exhaust the equivalent of one cylinder volume of fuel-air mixture for each crankshaft revolution at the highest

possible engine speed. This is necessary to achieve the maximum possible power output from a naturally aspirated internal combustion engine.

The principles of operation and some embodiments of four-stroke engines are described and shown herein, which may be able to produce the power output per unit capacity of which some two-stroke and Wankel engines are capable. Some of the aspects of the present invention may also be used on internal combustion engines of 2n strokes where n is an integer, for example, two-stroke, Wankel, six-stroke, eight-stroke engines, to improve their volumetric efficiency.

Compressors of, for example, air which operate and produce pressure fluctuations, or have reversed flow out past an inlet valve may also benefit from the use of one of the many embodiments of the present invention.

In order that the invention may be better understood, several embodiments thereof will now be described by way of example only and with reference to the accompanying drawings in which :- Figure 1 is a cross sectional view of an induction system for an internal combustion engine according to a first embodiment of the first aspect of the invention; Figure 2 is a view similar to Figure 1, showing a second embodiment of the first aspect of the invention; Figure 3 is a cross sectional view of a valve housing for use in a third embodiment of the first aspect of the invention ; Figure 4 is a cross sectional plan view of a valve housing for use in a fourth embodiment of the first aspect of the invention; Figure 5 is a perspective view of the valve housing of Figure 4; Figures 6,7 and 8 are views similar to Figure 3, showing fifth, sixth and seventh embodiments; Figure 9 is a cross sectional view showing how the valve housing of

Figure 3 might be connected to a cylinderhead; Figures 10 to 14 are views similar to Figure 9, showing further embodiments; Figure 15 is a diagrammatic view of a complete induction system of a four valve per cylinder, four cylinder, four stroke engine; Figure 16 is a side cross section of the system of Figure 15, through one of the inlet ports; Figures 17 and 18 are diagrammatic views showing, respectively, different embodiments of turbocharged engines incorporating the first aspect of the invention; Figure 19 is a cross sectional side view of a two-stroke engine incorporating the first aspect of the invention ; Figure 20 is a cross sectional view of part of an engine induction system of the type utilising a rotary disc valve, and incorporating the first aspect of the invention; Figure 21 is a cross sectional view of a Wankel engine incorporating the first aspect of the invention; Figure 22 is a table of engine performance at various engine speeds of a Ford 2 litre OHC engine (1981) modified in accordance with the first aspect of the present invention; Figure 23 is a graph of Power/torque against engine speed drawn from the tabular results in Figure 22; Figures 24 to 27 are diagrammatic views showing, respectively, different versions of plenum chambers for use with the engine according to the first aspect of the invention; Figure 28 is a diagram showing the arrangement of a plenum chamber and inlets and outlets to form a helmholtz resonator; Figure 29 is a diagrammatic side view of the piston and cylinder assembly of an embodiment of an internal combustion engine according to the second aspect of the invention, intended to illustrate the mode of

operation; Figures 30 to 52 are views similar to those of Figure 29 illustrating further stages in operation; Figure 53 is a cross sectional view through the cylinder of a four- stroke internal combustion engine in accordance with an embodiment of the second aspect of the invention; Figures 54 to 57 are views similar to Figure 53 showing further embodiments according to the second aspect of the invention; Figure 58 is a front view in cross section of a rotary valve which may be used in connection with the second aspect of the present invention; Figure 59 is a cross sectional view through part of the valve of Figure 58, taken perpendicular to the axis of the valve; Figure 60 is a plan view in cross section of the valve of Figure 58 ; Figures 61 to 63 are views similar to Figure 53 showing still further embodiments according to the second aspect of the invention; Figures 64 and 65 are partial cross-sectional views of the piston/cylinder of an internal combustion engine, showing how the rotation of the rotary valves changes during two stages of the cycle of operation ; Figure 66 is a plan view in cross section of a piston/cylinder of an internal combustion engine according to the second aspect of the invention; Figure 67 is a view similar to Figure 66, but showing an alternative embodiment; Figure 68 is a side view, partly in cross section of a further embodiment of a rotary valve element for use in the internal combustion engine according to the second aspect of the present invention; Figures 69 and 70 show front and side views respective of the piston-ring type seal used in the valve element of Figure 68 ; Figure 71 is a lateral sectional view of the valve element shown in Figure 68;

Figures 72 and 73 are side and end views, respectively, in cross section, showing tension spring seals for use with the valve element of Figure 68 ; and Figures 74 to 76 are views similar to Figure 53, showing stiil further embodiments according to the second aspect of the invention.

In the attached drawings, it should be noted that Figures 1 to 28 are intended primarily to illustrate embodiments according to the first aspect of the invention, while Figures 29 onwards are intended to illustrate embodiments according to the second aspect of the invention.

Referring firstly to Figure 1, there is shown part of the cylinderhead 22 of an internal combustion engine. The inlet port for combustion air or fuel-air mixture is shown under reference 20. Attached directly to the cylinderhead 22 in communication with port 20 is a housing 12 which connects the port 20 to a ram pipe 23 of the engine which in turn leads to an air filter 11.

A reed valve assembly 16 is mounted within the housing 12 and controls the supply of combustion gas from the pipe 23 to the port 20. The reed valve assembly, which may be of any suitable type as discussed above, acts as a non-return valve, allowing gas to flow from right to left in Figure 1, but not in the reverse direction. In addition, the ram pipe 23 is made longer than usual, sufficiently long such that, at low engine speeds, the momentum of the combustion gas within the ram pipe 23 is sufficient to force extra volume past the valve assembly 16 so as to pressurise the gas in the space including port 20 between the valve assembly 16 and the inlet valve or valves (not shown).

It will be noted that no throttle valve, nor any method of fuel injection is shown, thus keeping the drawing general and non-specific to a particular fuel system. Thus the invention can be used with carburettor systems, or with fuel injection systems including direct injection diesel engines.

Figure 2 shows an embodiment similar to that of Figure 1 but in

which an adaptor inlet manifold 24 is fitted between the reed valve housing 12 and the cylinderhead 22.

Figure 3 is an enlarged side view of the reed valve housing 12 of Figures 1 and 2, showing the valve assembly 16 in greater detail. Figure 4 is a top view, showing a twin valve assembly 16', 16"but also serves to show upper and lower horizontal sections through the valve assembly 16.

The valve assembly comprises a pair of flaps 13 and reed valve stops 14 which are attached to a reed valve body 15 by fixing screws 25. The valve assembly 16 fits into the reed valve housing 12 and operates as a demand or non-return valve. The inherent elasticity or spring of the flaps 13 normally holds them flat, against the surface of the reed valve body 15 ; however the flaps 13 open by bending towards the reed valve stops 14, when there is positive pressure on the other side of the flaps 13, which pressure is sufficient to overcome the elasticity or spring of the flaps. The reed valve stops 14 limit the maximum possible travel of the flaps 13; if the reed valve stops 14 were not present, the service life of the flaps would be significantly reduced.

The reed valve assembly operates by defining, between the inlet valve (not shown) and itself a chamber 2 which is closed when the inlet valve is closed. When the inlet valve is open, any excess pressure within chamber 2 will result in a flow of gas from the chamber 2 past the inlet valve and into the cylinder.

During normal induction, the inlet valve is open as the piston falls, on its induction stroke, thus drawing air or fuel-air mixture into the cylinder via the inlet valve. This air enters the engine at the air filter 11 and passes along the ram pipe 23, possibly having fuel added at some point to make a fuel-air mixture. The air or mixture thence flows past the valve assembly 16 and through the chamber 2 to the inlet valve. It will be seen that the movement of this air through the induction system acquires a momentum due to the mass of air in the induction system. Thus, when the inlet valve

closes, usually at or shortly after bottom dead centre, the air or mixture will continue to flow through the valve assembly 16 for a short time, thus pressurising the chamber 2. The extent to which this happens depends upon the length of the ram pipe 23. In the longer ram pipe of the invention, the mass of moving air in the ram pipe creates sufficient momentum to overcome the spring tension of the flaps 13 of the reed valve assembly 16 and to pressurise the chamber 2, even at the low engine speeds (less than 3000 or 4000 r. p. m.) being considered.

Since the valve assembly 16 allows flow only from right to left and not vice-versa, this increased pressure is retained in the now closed chamber 2. When the inlet valve opens again, usually shortly before top dead centre at the end of the exhaust stroke, this pressure will cause a flow of gas into the cylinder from chamber 2 even though the piston may still be travelling upwards, and before the induction stroke has started.

At the relative low engine speeds being considered here, the exhaust gas has not acquired a particularly high momentum and, when the inlet valve opens shortly before the end of the exhaust stroke, there may be a tendency for exhaust gas to escape via the inlet valve into the induction system. The existence of the chamber 2 prevents this, however, and in addition provides input of new air or mixture which helps to scavenge the exhaust gases from the cylinder and at the same time providing an initial charge of air or mixture before the descending piston on the induction stroke opens the valve assembly 16 and draws air or mixture in from the induction system. The result of this in engine performance is increased power and/or torque at lower engine speeds.

Figure 4 is a twin-valve variant of the arrangement illustrated in Figure 3. In Figure 4 there are two valve assemblies 16', 16" comprising respective valve bodies 15', 15"fitted into a common reed valve housing 12. In order to more clearly illustrate the construction of valve assembly

16, the upper and lower valve assemblies 16', 16"respectively in Figure 4 are represented slightly differently. The upper valve assembly 16'is viewed as one would see a cross section through the centre line of Figure 3 and thus illustrates the valve body 15', partly in section, and one of the flaps 13 behind the windows in the valve body; the valve stop is not visible because it is behind the flap 13. The lower valve assembly is illustrated by a view taken from above (as would be seen in Figure 3), but with the housing shown in section; thus the top of the housing is notionally removed, allowing a view of the valve assembly 16"from above. In this view, the valve stops 14 are visible, together with the edge of the body 15" and its fixing flange (the latter in section).

Figure 5 shows an embodiment which is suitable for use as a fuel injection throttle body to replace a Weber DCOE or similar carburettor.

The reed valve bodies 15 are shown fitted in the reed valve housing, and the flaps 13, holes 30 for injectors, and holes 31 for bolting the housing to a manifold are visible. The twin throttle (not visible) is mounted on a shaft 100.

Figures 6 to 8 show further embodiments. In Figure 6, the housing 12 is fitted with a fuel injector 27 sealed by a sealing ring 28. A butterfly valve 26 controls the supply of combustion air through valve assembly 16.

In Figure 7, the supply of combustion gas through the valve assembly 16 is controlled by the butterfly valve 26. This arrangement is suitable for use with systems where, for example, the fuel is mixed with the incoming air upstream of the reed valve assembly 16. In Figure 8 a hole 30 for an optional fuel injector is closed by a sealing plug 29 having a sealing ring 28.

Figure 9 is a plan view showing a reed valve assembly 16 having three reed valve stops 14 for each of the flaps (not visible), fitted in the reed valve housing 12. The housing 12 is attached to the cylinderhead 22, which has two inlet valves 32,33 per cylinder where either both valves

are operated all the time, or they may be operated by the Honda V-TEC system, or this may represent a siamesed inlet port 20 in which each of the inlet valves 32,33 feeds a different cylinder. The remainder of the induction system is omitted for clarity.

Figure 10 shows an embodiment similar to that shown in Figure 9, but in which an adaptor inlet manifold 24 is positioned between the reed valve housing 12 and the cylinderhead 22. In addition, there is another passage 35 in the adaptor inlet manifold 24 which may be connected to a supercharger or turbocharger or to the crankcase or to a compartment below the piston, any of which may supply air or fuel-air mixture.

Figure 11 shows an embodiment similar to that shown in Figure 9, but in which there are three inlet valves 1,32,33 per cylinder.

Figure 12 shows an embodiment similar to that shown in figure 9, but in which the reed valve assembly 16 has two reed valve stops 14 for each of the flaps (not visible) fitted in the reed valve housing 12 which is attached to the cylinderhead 22, which has a single inlet valve 32 per cylinder.

Figures 13 and 14 show two embodiments in which a pair of inlet ports 20 each having a respective inlet valve 32,33 is provided for each cylinder. The flow to one of the inlet valves is stopped in both directions at low engine speeds by means of a butterfly valve 126. In the embodiment of Figure 13, when the butterfly valve 126 opens at high engine speed, the flow to both inlet valves comes from a common inlet manifold 8 forming part of the induction system. In the embodiment of Figure 14, when the butterfly valve 126 opens at high engine speed, then the flow to one of the inlet valves 33 comes from another passage 35 in the induction system which may be connected to a supercharger or turbocharger or to the crankcase or to a compartment below the piston. Alternatively, the engine may be naturally aspirated by the passage 35 being connected to another inlet manifold (not shown) with dimensions that may or may not be different

to those of the inlet manifold 8, any of which may supply air or fuel-air mixture. The remainder of the induction system is omitted for clarity.

Figures 15 and 16 show a complete induction system of a four valve per cylinder, four cylinder four-stroke engine. In the illustrated engine, the common reed valve housing 12 is directly positioned against the cylinderhead 22 and each pair of inlet valves 32,33 has flow of air or fuel- air mixture from one of the reed valve assemblies 16,17,18,19 which are all fitted into the reed valve housing 12. Throttling is achieved by two butterfly valves 9,26. A valve 59, leading to a second air filter 111, is normally closed for low engine speed operation so all of the inducted air flows through the long ram pipe 23. The valve 59 opens for high engine speed operation thus reducing the length and volume of the induction system. Figure 16 is a cross-section through one of the inlet ports 20 and shows the inlet manifold 8 of rectangular cross-section, from where the inducted air flows, through the reed valve assembly 16 in the reed valve housing 12 which, in this case, has a hole for an injector 30, and into the inlet port 20 of the cylinderhead 22, past the inlet valve 32 into the cylinder.

The exhaust valves are shown under reference 34.

Figures 17 and 18 show two embodiments of the invention in which turbocharging is used. In Figure 17, one of the inlet ports 20 is shown in the cylinderhead 22 fitted with a reed valve housing 12 having two reed valve assemblies 16,171. To the lower one of the reed valve assemblies 16 is attached a long ram pipe 23, while to the upper one of the reed valve assemblies 171 is attached the compressor side of a turbocharger 40.

The turbocharger comprises a driving impeller 42, rotated by the exhaust gases, and a driven impeller 41 connected to the impeller 42 by a drive shaft.

The butterfly throttle valves 9,26 which control the engine may operate so that, at low engine speeds, air is permitted to flow through the butterfly valve 9 from the long ram pipe 23 and then, at high engine

speeds, air is also permitted to flow through the butterfly valve 26 under pressure from the turbocharger. Therefore, at high engine speeds, the air may not flow through the reed valve assembly 16 associated with the long ram manifold 23.

The embodiment shown in Figure 18 is similar to that of Figure 17 except that air is permitted to flow through the butterfly valve 26 from the long ram manifold 23 through the reed valve assembly 16, at all engine speeds. At medium to high engine speed, the functioning of the turbocharger provides pressure in the induction system. At low engine speed, the arrangement operates in the manner described previously.

Figure 19 shows a side cross-section of a two stroke engine incorporating the teachings of the invention. The general construction of the engine will be recognised by those skilled in the art, and will not be described in detail. The main components of the engine are visible, namely a crankcase 45, cylinder block 44 and cylinderhead 22. A piston 46 is slidably movable within the or each cylinder and drives a crankshaft rotatably mounted within the crankcase 45 via a connection rod 48.

References 50 and 52 indicate the little end and the big end respectively.

Extending between the interior of the crankcase 45 and the volume of the cylinder above the piston are passages 60 which supply combustion gas to the cylinder. The exhaust port is shown under reference 21; the spark plug under reference 43. Combustion gas is inducted into the interior of the crankcase during upward movement of the piston from the ram pipe 23, and the remainder of the induction system (not shown), via the normal reed valve assembly 17 which is located in the wall of the crankcase 45. In accordance with the invention a further reed valve assembly 16, mounted in a housing 12, is placed upstream of the reed valve assembly 17.

Figure 20 shows the use of the first aspect of the invention in an engine in which a rotary disc valve 58 controls the normal induction

processes into the crankcase 45. The valve 58 comprises a disc which is mounted directly on the crankshaft 56. The crankshaft flywheel connects the crankshaft 56 to the big end journal 51. The crankshaft 56 is mounted in a bearing 55 and is equipped with an external oil seal 57 in the usual way. In accordance with the first aspect of the present invention, a reed valve assembly 16 in the reed valve housing 12 with a long ram manifold 23 are placed upstream of the rotary disc valve 58.

Figure 21 shows the use of the first aspect of the invention in a Wankel engine. The engine comprises a rotor 62 mounted on a crankshaft 63 within a housing. The extremities of the rotor 62 are fitted with seals 65 which bear against the inside of the housing in the known manner, and sealingly divide the interior of the housing into three separate compartments. The spark plugs are shown under reference 43; the exhaust port under reference 21. The induction system is connected to the input port 20, and comprises an air filter 11, long ram pipe 23, housing 12 having a reed valve assembly 16 and an adaptor 24. A further air filter 111 is connected via a valve 59 in order to change the effective dimensions of the induction system. The valve (59) is normally closed for low engine speed operation so all of the inducted air flows through the long ram manifold 23. The valve 59 opens for high engine speed operation thus reducing the length and volume of the complete induction system.

Figures 22 and 23 are a table and graph respectively intended to demonstrate the effect of the first aspect of the present invention on a typical internal combustion engine, in this case a Ford 2 litre overhead cam engine of 1981. The two Figures show the engine performance at various engine speeds when fitted with reed valve assemblies 16 according to the invention, and both with and without a long ram pipe 23. It will be seen that, at low engine speeds (less than about 3000 rpm) there is a significant increase in both torque and power output when a long ram pipe is used.

Figures 24 to 27 show different types of plenum chamber which may

be used with advantage in the engine according to the first aspect of the invention. The plenum chamber takes the shape of a cylinder 105 having closed ends and, in this case, having two combustion gas inlet pipes 23', 23". The plenum chamber acts as a common feed to a plurality of the cylinders of a multi-cylinder engine and has an appropriate number of outlets 106 which feed into the inlet ports 20 of the engine. In accordance with the invention, a reed valve assembly 16, fitted in a housing 12, is fitted between the output of each outlet 106 and the cylinderhead 22.

Figures 25,26 and 27 illustrate three different ways in which the inlet pipes 23', 23" are connected to the cylinder 105, the object being to achieve a rotation of the combustion gas about the longitudinal axis of the cylinder 105, as explained in greater detail above.

Figure 28 is a diagram of a more generalised form of plenum chamber, and its associated inlets and outlets, suitable for use with the engine according to the first aspect of the present invention. In such an arrangement, the whole induction system may take the form of a helmholtz resonator and the diagram shows an example of such a resonator, where there may be one or more inlets 151,152 to the plenum chamber 105 of the resonator. The inlets may be positioned in the side (151) or the end (152) of the plenum chamber. The inlet tracts 153,154,155,156 connect the plenum chamber to the respective cylinders 157,158,159,160 of the engine. These inlet tracts may feed one or more of the cylinder inlet valves, or there may be more inlet tracts tracts 161,162,163,164 feeding separate cylinder inlet valves.

The total length of a helmholtz resonator induction system may be determined by the length of the inlet tracts 153,154,155,156 to each cylinder from the plenum chamber 105 and the length of the inlets 151,152 to the plenum chamber of the resonator. Therefore, for example, embodiments of the present invention may have one or more long inlet tracts to each cylinder from the plenum chamber, or one or more long inlet

lengths to the plenum chamber, or both long inlet tract lengths to each cylinder from the plenum chamber, and one or more long inlet lengths to the plenum chamber.

Figures 29 to 51 are a series of diagrams intended to illustrate the operation of the internal combustion engine which is the subject of the second aspect of the invention. In each case, the drawing shows a single cylinder assembly comprising a piston 46, a poppet-type inlet valve 32, and a poppet-type exhaust valve 34. Situated in the side wall of the cylinder are an inlet port 69 and exhaust port 71, the flow through each of these ports being controlled by respective valves 70,72. Arrows indicate the direction of combustion and/or exhaust gases, as appropriate. The position of the ports 69,71 along the cylinder is preferably near to the top of the piston when at bottom dead centre. This position is shown, for example, in Figure 30A.

Figure 29 illustrates the initial induction of combustion gas past inlet valve 32 as the piston 46 begins its descent. The inlet valve 70 in side inlet port 69 is open ready for the piston to expose it. The exhaust valves 34 and 72 are closed.

The next stages of the cycle is illustrated in Figure 30A, but the opportunity has been taken to illustrate in Figures 30B, C and D various methods of dealing with the incoming combustion air.

In Figure 30A, the piston has reached bottom dead centre on the induction stroke and inlet valve 32 has closed. Valve 70 remains open, however, and continues to pass combustion gas into the volume of the cylinder above the piston, in this case from below the piston.

In Figures 30B, C and D, the inlet valve 32 is still open. In Figure 30B combustion gas from below the piston 46 is passed by a feed passage 73 and via inlet valves 32 and 70 into the volume above the piston. Figure 30C shows an embodiment in which there is no side inlet port, only a side exhaust port 71. Combustion air from beneath the piston 46 is passed by

feed passage 73 and via inlet valve 32 to the volume above the piston. In Figure 30D, combustion gas is being passed into the cylinder via both inlet valves 32 and 70; the feed to port 69 is from the induction system (not shown) from the exterior; there is no induction of gas from below the piston.

Continuing with the cycle of operation, Figure 31 shows the compression of air or fuel-air mixture in the cylinder as the piston 46 ascends up the cylinder. All cylinderhead and exhaust valves are closed and the valve 70 in the inlet port 69 in the side of the cylinder is open, but is starting to close. In Figure 32 the piston 46 is at top dead centre, at the start of the power stroke, when combustion of the fuel-air mixture has been initiated. All valves are closed. In Figure 33 the piston 46 is descending on the power stroke. The exhaust valve 72 in the exhaust port 71 in the side of the cylinder has opened ready for when the port is exposed by the descending piston 46. Inlet valves 32 and 70 are closed. In Figures 34A and 34B the piston 46 has descended to bottom dead centre and the exhaust gases are being released from the cylinder. Figure 34A shows an embodiment in which the exhaust gases flow through the exposed exhaust port 71 in the side of the cylinder past the open exhaust valve 72 in that exhaust port 71 and past the open exhaust valve 34 in the cylinderhead 22. By contrast, Figure 34B shows an embodiment in which the exhaust gases only flow past the open exhaust valve 34 in the cylinderhead 22, there being no exhaust port in the side of the cylinder.

Figure 35 shows the piston 46 ascending on the exhaust stroke, and exhaust gases flowing past the open exhaust valve 34 in the cylinderhead 22. The exhaust valve 72 in the exhaust port 71 in the side of the cylinder is open, but is starting to close.

Figure 36 shows the piston 46 having reach top dead centre again, at the start of the induction stroke, at which point both the inlet and exhaust valves 32,34 in the cylinderhead 22 are opened to allow the scavenging of

the combustion chamber by air or fuel-air mixture which may assist the initial induction of air or fuel-air mixture into the cylinder. Both the inlet valve 70 and exhaust valve 72 of their respective ports in the sides of the cylinder are closed.

For a four-stroke engine, the processes of the four-stroke cycle are now repeated, by returning to the position illustrated in Figure 29.

For engines of six strokes or more, there are additional induction and compression strokes, or induction and scavenge strokes or both.

There are three types of additional two strokes that can be added to the normal four-stroke process: (i) The additional induction and compression strokes can be of air or fuel-air mixture, or (ii) The additional induction and scavenge strokes can be of air or exhaust gasses, or (iii) The cylinder valves can remain closed and residual gases in the cylinder can undergo additional expansion and compression events as the piston moves between top and bottom dead centre.

These additional two stroke processes may only involve that volume of the cylinder above the piston, or may involve additional induction strokes utilising air or fuel-air mixture from the crankcase. For example, a six- stroke engine would have a normal four-stroke cycle, and a two stroke scavenging process, and an eight-stroke engine would have a normal four- stroke cycle, and a four stroke scavenging process. The operations shown in Figures 37,38,39,40 in sequence, are inserted between the operations shown in Figures 35 and 36, and show the additional two- strokes that may occur in embodiments of the present invention. All cylinder valves remain closed and residual gases in the cylinder undergo an additional expansion and compression event as the piston moves from top to bottom dead centre, and back to top dead centre, as illustrated by the arrows below the piston 46.

The operations shown in Figures 41,42,43, and 36 again, in sequence, are inserted after the operation shown in Figure 36, and show the additional two-strokes that may occur in embodiments of the present invention, where the additional induction and scavenge strokes utilise air.

Figure 41 shows the induction of air into the cylinder through the inlet valve 32 in the cylinderhead 22. Figure 42 shows the piston 46 having reached bottom dead centre, and the inlet valve 32 in the cylinderhead 22 is almost closed and the exhaust valve 34 in the cylinderhead 22 is opening. Figure 43 shows the inducted air in the cylinder being pushed out of the cylinder through the exhaust valve 34 in the cylinderhead 22 by the ascending piston 46.

The operations shown in Figures 47 in sequence, are inserted between the operations illustrated in Figures 35 and 36, and show the additional two-strokes where the additional induction and scavenge strokes are of exhaust gases, that may occur in embodiments of the present invention. Exhaust gases are inducted into the cylinder and are pushed out of the cylinder past the exhaust valve 34 in the cylinderhead 22 by the descending and ascending piston 46. All other cylinder valves remain closed as the piston moves from top to bottom dead centre, and back to top dead centre, as illustrated by the arrows below the piston.

The operations shown in Figures 48,49,50,51,52 and 30A in sequence, are inserted between Figures 36 and 31, and show the additional two-strokes that may occur in embodiments of the present invention, where the additional induction and compression strokes are of air or fuel-air mixture. Figure 48 shows the situation where the initial induction of air or fuel-air mixture into the cylinder has past an inlet valve 32 in the cylinderhead 22 and the valve 70 in the inlet port 69 in the side of the cylinder has opened ready for when the port is exposed by the descending piston 46. Figure 49 shows the situation where the induction of air or fuel-air mixture from the compartment below the piston 46 has

passed into the cylinder through the exposed inlet port 69 in the side of the cylinder past the valve 70 in that inlet port. The inlet valve 32 in the cylinderhead 22 is shown closed. Figure 50 shows the situation where the compression of air or fuel-air mixture in the cylinder is occurring as the piston 46 ascends up the cylinder. All cylinderhead and exhaust valves are closed, the valve 70 in the inlet port 69 in the side of the cylinder remains open. Figure 51 shows the piston 46 at top dead centre, when combustion of the fuel-air mixture has not been initiated. All valves are closed. Figure 52 shows the piston 46 descending from top dead centre during the induction stroke of the four-stroke cycle where the inlet valve 32 in the cylinderhead 22 has remained closed and the valve 70 in the inlet port 69 in the side of the cylinder is still open, ready for the second induction event through the inlet port 69 and valve 70 when the port becomes exposed by the descending piston 46.

The further embodiments of the present invention described below, whilst they are described as four-stroke engines, could easily operate as six-stroke or eight-stroke engines, just by the changing and re-optimisation of the valve timings, for example, in the different manners described above.

Figures 53 to 57 show embodiments of the present invention which are four-stroke engines which utilise the compartment 54 below the piston for induction, where this compartment consists of the crankcase 45.

The engine shown in Figure 53 has one or more cylinders, just one of which is shown. The engine comprises a cylinderhead 22 in which are formed an inlet port 20 for combustion gas and an exhaust port 21 for exhaust gas. Passage through the ports 20,21 is controlled by respective poppet valves 32,34 moving in valve sleeves 3 and biased by valve springs 77. The valves 32,34 are operated by respective cam shafts 74a, 74b via respective tappets 76. The cylinderhead cover is shown under reference 75.

The cylinder block is shown under reference 44 and crankcase under reference 45. Moving within the or each cylinder is a respective piston 46 connected by a connecting rod 48 to a crankshaft 51.

Combustion gas enters the engine via an inlet manifold 156 to port 20 and via an inlet manifold 8 to the compartment 54 below the piston.

Induction into the compartment 54 is via a non-return valve, such as the illustrated reed valve assembly 16.

Formed in the side wall of the cylinder, at a position immediately above the top of the piston when at bottom dead centre, is an inlet port 69.

Passage of gas through the inlet port 69 is controlled by a rotary iniet valve 82, driven by the engine via gearing or belts (not shown). A feed passage 60 enables combustion gas to pass from the compartment 54 to the volume of the cylinder above the piston, via the valve 82, when open (as shown).

Figure 54 shows an engine of similar construction to that shown in Figure 53, but in which an exhaust port 71, controlled by a rotary valve 84, is fitted in the side wall of the cylinder substantially opposite the inlet port 69. The exhaust ports 21 and 71 connect to an exhaust manifold 158.

Figure 55 illustrates an embodiment similar to Figure 54 but in which the inlet port 20 is blanked off by a plate 157. Air or fuel-air mixture is supplied to pressurise port 20 at the end of the induction cycle by reverse flow out of the cylinder.

Figure 56 shows an embodiment in which the induction into the crankcase from the inlet manifold 8 is controlled by the reed valve assembly 16, and is fed through the transfer port 60 to the inlet port 69 in the side of the cylinder. The inducted air or fuel-air mixture is also fed to the inlet valves 32 in the cylinderhead 22 through a feed passage 73.

There is also an additional passage 35 in the feed which is connected to other feeds from the crankcases of the other cylinders of a multicylinder engine. The optional reed valve assembly 17 enables a build up of

pressure of air or fuel-air mixture in the feed passage 73. Another manifold 156 also supplies air or fuel-air mixture through a reed valve assembly 18 to the inlet valves 32. Induction into the cylinder may also occur through the inlet manifold 156 and reed valve assembly 18 past the inlet valves 32 in the cylinderhead 22. Exhaust gases may flow through both the exhaust port 71 in the side of the cylinder past the rotary exhaust valve 84 and through the exhaust port 21 in the cylinderhead 22 past the exhaust valve 34.

Figure 57 shows an embodiment of a multicylinder V-configuration engine, where the two connecting rods 48,117 are connected to two pistons 46 and to a common crankshaft big end journal 51 in a single crankcase compartment, with the crankshaft rotating in the clockwise direction. Induction into the crankcase 45 from the inlet manifold 8 is controlled by the reed valve assembly 16, and the inducted air or fuel-air mixture is fed through the transfer ports 60 to the inlet ports 69 in the side of the cylinders, the flows through which are controlled by respective rotary inlet valves 82,85. Induction into the cylinder may also occur through the inlet manifold 8 and inlet ports 20 past the inlet valves 32,33 in the cylinderheads 22. Exhaust gases may flow through both the exhaust ports 71 in the side of the cylinder past the respective rotary exhaust valves 84,86 and the exhaust ports 21 in the cylinderheads 22 past the exhaust valves 34. Throttling is achieved by the butterfly valves 9,26, 159. Assuming the crankcase to be at the bottom, the cylinder with the piston at bottom dead centre is nearing the end of the induction cycle with an open inlet port 69 in the side of the cylinder, open rotary inlet valves 82, and closed rotary exhaust valves 84. The other cylinder with the piston nearing bottom dead centre is about to commence the exhaust cycle with an open rotary exhaust valve 86, and closed rotary inlet valve 85. All cylinderhead valves are closed.

Figures 58 to 60 show an embodiment of a rotary valve that may be

used as an inlet or exhaust valve to control flow through the side inlet and exhaust ports.

The rotary valve 161 is positioned as near as possible alongside the cylinder bore walls 92. The rotary valve constantly rotates by being driven from another rotating part of the engine (not shown) such as the crankshaft or the camshaft by for example a belt, chain or gear. The rotary valve sealing rings 93,94,95,96 may be identical to the design of a piston ring.

The rotary valve sealing rings 93,94,95,96 shown here are plain and of rectangular cross-section. The sealing ring may be improved by a change in the design of the rotary valve sealing ring gap, which may be reduced by overlapping ends or another overlapping ring. The rotary valve 161 is lubricated by a pressurised oil feed from oil way 100, and the oil drains away through a lower oil way 113. The rotary valve 161 is formed so that the port in each cylinder is closed or open at the appropriate time by a passage in the rotary valve, there are two such passages shown under references 162 and 163.

Figure 61 shows an embodiment similar to that of Figure 54, but in which induction into the cylinder of a four-stroke engine starts from air or fuel-air mixture being inducted from the inlet manifold 8 past the inlet valves 32 in the cylinderhead 22. Induction into the cylinder also occurs from the inlet manifold 8 through the reed valve assembly 16, which then flows through the inlet port 69 in the side of the cylinder, the flow through which is controlled by the rotary inlet valve 82. Exhaust gases may flow through both the exhaust port in the side of the cylinder 71 past the rotary exhaust valve 84 and the exhaust port 21 in the cylinderhead 22 past the exhaust valve 34. Contrary to the embodiment of Figures 54, in this embodiment there is no induction into the compartment 54 below the piston.

Figure 62 shows an embodiment in which induction into the compartment 54 below the piston 46 from the inlet manifold 8 is controlled

by the reed valve assembly 16, and is fed through the feed passage 60 to an inlet port 69 in the side of the cylinder, the flow through which is controlled by the rotary inlet valve 82. induction into the cylinder also occurs through the inlet manifold 156 past the inlet valves 32 in the cylinderhead 22. Exhaust gases may flow through both the exhaust port in the side of the cylinder 71 past the rotary exhaust valve 84 and the exhaust port 21 in the cylinderhead 22 past the exhaust valve 34. The piston 46 has a skirt, and is designed to be connected to a piston tube 87 via a female rose joint 181. The piston tube 87 is slidably movable in a guide 160 which is in turn mounted on a support 88.

Figure 63 shows an embodiment in which induction into the compartment 54 below the piston 46 from the inlet manifold 8 is controlled by the reed valve assembly 16, and is fed through the transfer port 60 to an inlet port 69 in the side of the cylinder, the flow through which is controlled by the rotary inlet valve 82. Induction into the cylinder also occurs through the inlet manifold 156 past a Coates rotary inlet valve 179 in the cylinderhead 22. Exhaust gases may flow through both the exhaust port in the side of the cylinder 71 past the rotary exhaust valve 84 and the exhaust port 21 in the cylinderhead 22 past the Coates rotary exhaust valve 180. The piston 46 has a skirt, and is designed to be connected to the conrod 48 directly.

Figures 64 and 65 show two different variations of rotary valve positions relative to piston position that may be used for the side inlet or exhaust valves. The rotary exhaust valve 84 and rotary inlet valve 82 are positioned as near as possible alongside the cylinder bore walls 92. They constantly rotate by being driven from another rotating part of the engine (not shown) such as the crankshaft or the camshaft by for example a belt, chain or gear. The rotary valves 82,84 are formed so that the port in each cylinder is closed or open at the appropriate time by means of passages in the rotary valves. There is a passage shown in each rotary valve 82,84.

The position of the rotary exhaust valve in Figure 64 is shown in one position as the piston 46 descends just before the start of the exhaust stroke, whereas, in Figure 65 the rotary exhaust valve is not completely open before the piston starts to reveal the port in the side of the cylinder.

In Figure 64 the rotary exhaust valve is completely open just as the piston 46 starts to reveal the port in the side of the cylinder. This variation of rotary valve position may be achieved by any of the known means of variable valve timing, used to change the shaft position relative to the driving sprocket or gear position, and is applicable to either inlet or exhaust rotary valves, or both.

Figure 66 is a plan view of a single cylinder and shows four rotary valves 161,82,84,85 spaced 90° apart and positioned as near as possible alongside the cylinder bore wall 92. The rotary valves constantly rotate by being driven from another rotating part of the engine (not shown), as described above. The rotary valve sealing rings 93,94,95,96 may be identical to the design of a piston ring. The rotary valve sealing rings shown here are plain and of rectangular cross-section. The sealing ring may be improved by a change in the design of the rotary valve sealing ring gap, which may be reduced by overlapping ends or another overlapping ring. The rotary valves 161,82,84,85 are lubricated by a pressurised oil feed. There are three rotary inlet valves which allow their respective inlet ports 60,173,174 in the cylinder to close or open at the appropriate time by means of passages in the rotary valves 163. Two of the rotary valves are driven by intermeshing gears 187 from the main rotary inlet valve 161. The rotary exhaust valve 84 is driven separately (not shown), and the casing split line shows the limit of the valve cover which can be removed to allow the installation of all the rotary inlet valves 161,82,85.

Figure 67 is a view similar to that of Figure 66 but showing an embodiment in which the inlet ports 69 communicate via passages 169 to

a common rotary inlet valve 161. There is thus no need for the inlet valves 82 and 85 of the embodiment illustrated in Figure 66.

Figure68 shows an embodiment of a rotary valve with a valve aperture 162 showing. The valve has machining for additional sealing means, where the grooves around the circumference of the valve 186 enable the piston ring type seal 93 shown in Figures 69 and 70 to fit. The longitudinal grooves 185, shown in Figure 71, are capable of accepting straight seals 183 with tensioning springs 184 the same as or similar to those on the rotor tips of a Wankel engine rotor (see Figures 72 and 73).

Figure 74 shows an embodiment in which induction into the cylinder of a four-stroke engine starts from air or fuel-air mixture being inducted from the inlet manifold 8 past the inlet valves 32 in the cylinderhead 22.

Induction into the cylinder also occurs from the inlet manifold 8 through the inlet ports 69 in the side of the cylinder, the flow through which is controlled by respective rotary inlet valves 82,85. Exhaust gases may only flow through the exhaust port 21 in the cylinderhead 22 past the exhaust valve 34. In this embodiment there is no induction into the compartment 54 below the piston 46. The piston has a skirt, and the oil control rings 185 are positioned at the bottom of the skirt to allow plain bottom end bearings to be used with pressurised lubrication.

Figure 75 shows an embodiment in which induction into the cylinder of a four-stroke engine starts from air or fuel-air mixture being inducted from the inlet manifold 8 past the inlet valves 32 in the cylinderhead 22.

Induction into the cylinder also occurs from the inlet manifold 8 which then flows through the inlet port 69 in the side of the cylinder, the flow through which is controlled by the rotary inlet valve 82. Exhaust gases may flow through both the exhaust port 71 in the side of the cylinder past the rotary exhaust valve 84 and the exhaust port 21 in the cylinderhead 22 past the exhaust valve 34. In this embodiment there is no induction into the compartment 54 below the piston 46. The piston has a skirt and the oil

control rings 185 are positioned at the bottom of the skirt to allow plain bottom end bearings to be used with pressurised lubrication.

Figure 76 shows an embodiment in which induction into the cylinder of a four-stroke engine only occurs from the inlet manifold 8 past the inlet valves 32 in the cylinderhead 22. Exhaust gases may flow through two exhaust ports 71 in the side of the cylinder, controlled by the rotary exhaust valves 84,86. Exhaust gases may also flow through the exhaust port 21 in the cylinderhead 22 past the exhaust valve 34. In this embodiment there is no induction into the compartment 54 below the piston 46. The piston has a skirt, and the oil control rings 185 are positioned at the bottom of the skirt to allow plain bottom end bearings to be used with pressurised lubrication.