GB2415746A - High performance i.c. engine with contrarotating crankshafts - Google Patents

Abstract

The engine concept is mainly intended to be a high performance Four - Stroke engine. Two - Stroke engines can also be constructed using the concept. The engine concept has two crankshafts geared together. The two crankshafts drive yokes that are constrained to move in a straight line. The yokes drive piston assemblies via bearing supported drive rods. The pistons have no side loads. The engine concept allows a naturally aspirated volumetric efficiency of at least 140%. The exhaust gases leave the engine cylinders more effectively than is normal.

Description

24 1 5746 High performance internal combustion engine Sheet I The standard

piston crank engine can have a maximum naturally aspirated volumetric efficiency of 90%. A naturally aspirated fully tuned racing car engine can have a maximum volumetric efficiency of 1 10%, over a narrow engine speed range. A fully tuned racing motorcycle engine can have a maximum volumetric efficiency of 120%, over a narrow engine speed range. At engine speeds outside the maximum power band, the engine power is low.

The engine concept is a naturally aspirated high performance internal combustion engine.

The engine concept is mainly for four- stroke engines, but can be used for two - stroke engines see below. Listed below are some of the advantages of the engine concept.

( I) A two - stroke petrol or diesel engine, with normal four - stroke lubrication and bearings.

(2) A four - stroke petrol or diesel engine, with an easily obtained volumetric efficiency of at least 140% over a wide engine speed range.

(3) A four - stroke engine that is able to have high volumetric efficiency at high engine speeds, and have high volumetric efficiency at low engine speeds.

(4) The engine mechanism has a straight - line piston drive, this eliminates all piston side thrust, reduces friction and increases engine efficiency.

(5) The straight - line piston travel ensures that piston rings stay square to the bore this improves sealing, and reduces wear.

(6) The pistons have only axial forces their construction can be lighter than is normal. The pistons are made from alloy steel, this allows them to have a lower cylinder bore clearance, which improves sealing and reduces wear.

Aluminium alloy pistons can be used.

(7) The engine balance is improved compared with a normal engine (X) The extraction of exhaust gases from the four -stroke engines, is far better than for normal or racing type engines.

(9) The engine concept with the two crankshafts driving yoke assemblies. The cranks can operate at a more favourable torque position, compared with cranks of normal engines.

( 10) The concept four- stroke petrol engine allows a successful stratified charge system to be used. This gives good fuel economy and low emissions.

Sheet 2 (11) The engine concept has air purging to help the extraction of exhaust gases.

The air purging includes the overlap period, giving a reduction of emissions.

The exhaust valves will be at a lower temperature than is normal.

( 12) The engine concept allows the induction of air to above and below the pistons.

Thus giving a very high volumetric efficiency. Very high performance is possible, for road high performance vehicles, rally and racing cars.

Patent applications exist for four- stroke engines having inlet valves in the cylinder head, and under piston induction and compression. The air is compressed in the crankcase.

The four in line four- stroke engine is the most common engine produced all over the world. Such an engine needs each crank throw area sealed. The oil drainage to the sump would be a serious problem, even if a dry sump type lubrication system were used.

The four- stroke engine has a large amount of oil flying around in the crankcase, due to oil returning to the crankcase sump from pistons, camshaft and crankshaft lubrication.

Two- Stroke engines solve this problem by mixing lubricating oil with the fuel and having no other lubricating system.

The four- stroke normal lubrication system cannot be used successfully for crankcase air induction, compression and feeding to each cylinder by transfer ports. The mixture fed to each cylinder will contain an unacceptable amount of oil this will give high emissions, and will have an adverse affect on combustion and oil consumption, hence the lubrication method used by two-stroke engines, which have special bearings to suit.

Four- stroke type lubrication is needed to enable the lubrication of four stroke type big end bearings, main bearings, pistons and camshafts. If the oil supply is reduced to these components to reduce the oil flying around, the engine will over heat and will break down.

The concept engine does not use the crankcase to induct and compress air. The shared sealed area under each set of pistons for inducing and compressing air is sealed from the crankcase. Normal four stroke lubrication is used, the feeding of oil to and from each piston set, is through the tubular piston drive rods. The oil in the under piston sealed areas, can be controlled, to give a very small amount of oil.

Sheet 3 A brief description of the engine concept now follows.

The concept is mainly intended as a high performance four- stroke engine. It has two identical crankshafts that have a suitable gear mounted on each. The two gears in mesh drive the crankshafts in opposite directions. In line connecting rods from each crankshaft drive yoke assemblies. In this example each yoke drives four straight line driven piston assemblies, each yoke is guided in a straight line by a yoke location shaft that is a close fit in a bore that is in the centre of each piston set. The shared sealed area below the pistons is used to induce and compress air. The air is used for two- stroke engines, and to purge and charge the cylinders of four- stroke engines.

Above the pistons is a shared cylinder head for each set of pistons.

A detailed description now follows, with the aid of the following drawings.

Fig I Shows general details of two - stroke petrol or diesel engines.

Fig 2 Shows general details of four - stroke diesel or petrol engines.

Fig 3 Showing details of the induction stroke.

Fig 4 Showing details of the engine power stroke and exhaust gas purging.

Fig 5 Shows details of a stratified charge mode four- stroke petrol engine.

Figs 1 to5 are diagrammatic and are not to scale, and are arranged to show engine functions, etc. The concept engine has two identical crankshafts I that are connected by a gear drive.

Each crankshaft has a suitable gear wheel 2 fixed to it, the gears in mesh drive the cranks in opposite directions. Each two in line crank throws drive a yoke assembly 3, the yoke assembly bearings for the connecting rods, can have any suitable spacing, as the connecting rods are in free space. Each yoke assembly can drive any number of pistons.

In this example each yoke assembly drives four straight line driven pistons 4. Each yoke has tubular piston drive rods 13 fixed to it, at right angles to the yoke. The yoke drives the four piston assemblies via the tubular drive rods, the low mass piston drive rods are supported by bearings 5 and are sealed by seals 6, in the plate sealing the lower piston shared area The yoke has a tubular location rod fixed to it, at right angles to the yoke body. The rod 7 is a close fit in a bore that is at the centre ofthe four pistons. When the yoke is driven by the connecting rods 18. The yoke rod moves in the bore and runs in close fit lubricated bearings, thus the yoke is constrained to move in a straight line. The opposite rotation ofthe crankshafts makes the forces F1 equal and opposite, see (Fig 2), and thus puts no side loads on the yoke assembly 3 or on the yoke support rod 7. The system gives a straight line drive to each set of pistons. The primary forces F2 are balanced by the two masses ' 19. These masses cancel out at mid stroke. The straight line driven pistons allows the shared area under each set of pistons to be sealed, the sealed area is made to have a volume slightly greater, than the swept volume of all the pistons of a set. Air is induced in the area via suitable automatic valves 10, as the pistons rise.

Sheet 4 The air is compressed as the pistons descend. The sealed areas give an improved induction and compression when compared with a normal two - stroke engine crankcase assembly.

The pistons have seal plates on their drive rod ends, to ensure effective compression of the air. The pistons are lubricated via oil that is fed and returned via each piston tubular drive rod. The sealed area is thus kept almost free of oil. The compressed air is used to purge two stroke engine exhaust gases, and charge each set of cylinders. The air is also used to charge and help purge the cylinders of exhaust gases on four - stroke concept engines. The compressed air also allows a successful stratified charge system to be used for four- stroke petrol engines.

When on the compression stroke as the mixture is compressed, squish areas 22 of the pistons drives the mixture towards the cylinder head centre. Each cylinder head is shared by each set of pistons. At the centre of each set of four cylinders 25 is a sparking plug 15 or diesel fuel injector 17, in a combustion chamber 26, depending on the engine type.

The area over each of the four cylinders is clear. Inlet and exhaust valves can have any suitable arrangement.

Any arrangement of valves may be used. Any number of pistons can be used per yoke assembly. The latest computer controlled systems of ignition and fuel control can be used.

The pistons, piston drive rods and the yoke assemblies are designed to have the required strength for each engine type and to have minimum mass. The concept engine has short crank throws, improved balance, high volumetric efficiency and reduced engine friction, this allows the engine to have a high power output at high engine speeds. The engine concept also allows a good power output at low engine speeds.

Concept engine crankshaft detail compared with a normal crankshaft The normal engine crankshaft has poor torque conditions after mid stroke on the power stroke. Each connecting rod angle is less favourable after mid stroke.

The concept engine crankshafts I can have the yoke connecting rod bearings offset from the crankshaft centre towards power side of the stroke. The offset will be a selected fraction of the crank radius. Any suitable offset will give the concept engine crankshaft improved torque characteristics compared with a normal engine. The concept engine allows a longer power stroke than is normal. Thus taking advantage of the improved crank arrangement after mid stroke.

Four- stroke engines Seefigs2,3,4,and5 Each set of cylinder assemblies will have a suitable exhaust valves 8 area, and have a suitable inlet valves 9 area in the shared cylinder head. In the shared cylinder head is a central combustion chamber 26. On the compression stroke piston squish areas 22 will drive the mixture towards the combustion chamber. When combustion takes place, the expanding gases will drive the pistons of a set towards BDC.

Sheet 5 Near 13DC in each cylinder assembly are transfer ports 11. The transfer ports connect between the top of each piston, with the shared sealed area below each set of pistons. The concept engine can have no sealed area under each piston set, and inducts air through the normal valves only.

Induction arrangement for natural aspirated petrol and diesel engines (See Fig 3) The engine concept has a very high volumetric efficiency at all used engine speeds.

The air into each cylinder set during induction comes from two areas as listed below ( 1) Air is inducted into each the shared cylinder head and each set of four cylinders through the inlet valves 9, in each shared cylinder head.

(2) When each piston set rises on the exhaust stroke, air is induced in the shared area under each piston set through suitable automatic inlet valves l 0. As each piston set moves down on the induction stroke near BDC the air is compressed and travels into each cylinder, via suitable transfer ports 1 l, and thus also charges each cylinder. The ports 11 can be set to give some swirl to the air passing through to each cylinder. The inlet valves 9 close early, improving the compression stroke, of diesel and petrol engines.

The combined induction arrangement allows a volumetric efficiency of at least 140% to be easily obtained over a wide range of engine speeds. Thus resulting in a very powerful engine with good drivability. The concept engine can be used for high performance road vehicles, and also for rally and racing cars.

The power and exhaust stroke for petrol and diesel engines (See Fig 4) As each piston set travels down on the power stroke towards BDC, when it is near BDC the exhaust valves 8 open, and blow down takes place, the exhaust valves can open later than those on normal or racing engines. ADer blow down each piston uncovers transfer ports l l, air under pressure from ports l 1, expands and displaces the exhaust fumes upwards, through the open exhaust valves 8. The air chasing the exhaust fumes through valves 8 will cool these valves. The air expanding into each cylinder will cool the pistons, the cylinders, the shared cylinder head, sparking plug and the exhaust valves. The air enters each cylinder through the transfer ports when each set of pistons speed is low near BDC, the air will purge most of the remaining exhaust fumes at this time. The remaining combustion exhaust gas will be purged by each piston set and air on the exhaust stroke.

The load on each piston on the exhaust stroke will be lower than for a normal engine.

When each piston rises to TDC on the exhaust stroke, no exhaust fumes should remain.

On the induction stroke the high volumetric efficiency, the early inlet valve closing, and a pure mixture, allows a better compression stroke than that of a normal engine. The power stroke of each set of cylinders will be more even than that of a normal engine The exhaust valves and sparking plugs will be cooler than is normal. The combustion pressure will be higher than that of normal engines, and with the favourable crank torque arrangement, the reduced piston friction, and the later exhaust valve opening, all these advantages will give improved thermal efficiency, and a high power output. All the concept engine functions described need development to achieve the best results.

Sheet 6 Four- stroke petrol engine using the stratified charge system See fig 5 (one set of cylinders only is shown) The engine arrangement has a small central doughnut shaped pre- combustion chamber 12 in each shared cylinder head.

A port 20 feeds pressurised air from the underside of the piston set shared area, to the pre-combustion chamber 12, via a small cam controlled valve 21, each valve 21 is offset from each pre-combustion chamber centre line, this promotes swirl as the air fuel mixture is pushed through the valve when each piston is near BDC on the induction stroke. A low -pressure fuel injector 16 is positioned in the ducting close to each small valve. Each pre combustion chamber has a central sparking plug 15, and has a short central bore connecting to the shared cylinder head below. The first air to flow into each pre combustion chamber purges exhaust fumes and cools the sparking plug, this occurs during the exhaust gas purging. The inlet air into each pre- combustion chamber has fuel injected into it to give a slightly rich mixture. The mixture swirl in the doughnut shaped combustion chamber helps to retain the slightly rich mixture, during the compression stroke, and is aided by piston squish action at TDC. Each piston crown has a squish area 22 that directs gas towards the pre-combustion chamber. The fuel to air ratio in each cylinder, is controlled by a second low-pressure injector 16 that is in an inlet port that feeds each set of cylinders.

A volumetric efficiency of at least 140% is possible over a wide engine speed range. The mixture in each cylinder set can vary from being very weak to having the correct fuel air ratio. Each pre - combustion chamber has a slightly rich mixture and a short flame travel, very fast combustion will occur, the ignited gas will enter the hot compressed mixture in the shared cylinder head below, and will fire the weakest mixture.

The sparking plugs and exhaust valves, will all be at a lower temperature than that of a normal engine. There will be, no throttling losses, low emissions and good fuel economy.

Two - stroke diesel or petrol engine. (See Fig I) The two- stroke engines are similar to the four- stroke diesel or petrol engines described above, except there are no inlet valves 9 fitted. Each cylinder set assembly shared cylinder head has a large exhaust valves 8 area, and has a central diesel fuel injector 17 or sparking plug 15 depending on engine type.

The petrol version of the engine has a low- pressure fuel injector 16. The compressed air from the piston set underside is used to purge the exhaust fumes, and to charge the cylinders. As the exhaust valves 8 are closing fuel is injected in the air passing through selected transfer ports 11. Then compression occurs and the power stroke takes place.

The two stoke engines have normal four - stroke type lubrication.

Engine arrangements Straight- line driven pistons sets of a concept fourstroke engine can replace any normal type of four- stroke engine. The diesel engine and the stratified charge petrol engine will each have a volumetric efficiency of at least 140%, over a wide engine speed range.

Sheet 7 Straight- line driven pistons sets of a two -stroke concept engine, can be used to replace any two or four- stroke engines. The twostroke engine concept will have lower emissions and better fuel economy than that of a normal two- stroke engine.

The concept engine can have any number of pistons per yoke assembly. The valves in each shared cylinder head can have any suitable arrangement. The inlet valves to induct air into the under each piston set sealed area, can be any suitable two - stroke engine type valve. The crankshaft stroke can be any suitable value to suit each piston set.

Racing engines The concept is a naturally aspirated four- stroke engine with a very high volumetric efficiency. The engine concept has straight line driven pistons, eliminating piston side thrust, this reduces friction and gives better sealing.

The engine concept balance is improved compared with a normal engine.

The engine concept can be incorporated into any type of racing fourstroke engine design. An engine of this type would have an easily obtained volumetric efficiency of 150% at full throttle, over a wide engine speed range. The yoke piston drive system allows short crankshaft throws. The engine speed can be high with good induction and exhaust extraction at elevated engine speeds. See sheets 4 and 5.

On the exhaust stroke, air is used to help purge the remaining exhaust fumes this ensures an exhaust fume free compression stroke, giving more even efficient combustion. The purging air reduces negative torque on each exhaust stroke. The air also cools the exhaust valves, cylinder head, and sparking plug. The cool air chasing the exhaust gases through the exhaust system will leave a vacuum behind it. The cylinder head inlet gases will start moving before those of normal engines.

The exhaust gas purging takes place near BDC where each piston set speed is low. This allows later exhaust valve opening than for normal or racing engines. This gives a longer more effective power stroke than is normal.

The inlet valves close early compared with normal or racing engines, giving a more effective compression stroke than is normal. The concept crankshaft arrangement gives a better torque output than for normal engines (see sheet 4). The late exhaust valve opening takes advantage of the concept engines improved crank conditions after mid stroke.

The engine concept allows normal and racing engines to have alloy steel pistons The steel pistons can run at a closer clearance, giving better sealing, and the pistons also have better heat resistance than normal pistons. Aluminium alloy pistons can be used.

The high volumetric efficiency of the engine concept is easily obtained, over a wide engine speed range, and is higher than that of a full race tuned engine.

The racing engine concept can use a stratified charge arrangement. Power is controlled by the amount of fuel used. A racing car would have better fuel economy and would travel further between fuel stops.

Sheet 8 There would be no throttling losses, and a volumetric efficiency of 150% over a wide engine speed range. The computer controlled fuel system will give rapid acceleration.

(See fig 5 and sheet 6).

The very high volumetric efficiency, the early inlet valve closing, the late exhaust valve opening, the exhaust gas free compression mixture, the favourable crank arrangement, the reduced exhaust stroke piston loading, the better piston sealing, and the reduced piston friction. All these points should result in an efficient very powerful engine.

A specific embodiment of the concept will now be described by way of example See Figs 2, 3, and 4, and sheets 1, 2, 3, 4 and 5 The engine type to be replaced by the engine concept is a four - stroke diesel engine with an exhaust driven turbocharger.

The engine concept is a naturally aspirated four - stroke diesel engine. The concept engine has a volumetric efficiency of at least 140% from very low engine speeds up to the maximum engine speed. The concept engine can reliably idle at half the engine speed of the normal diesel engine. Engine starting is easily achieved due to the high volumetric efficiency at cranking speeds.

The concept engine pistons are driven in a straight line, this eliminates all side thrust, and gives lower engine friction. The engine pistons can be made from alloy steel giving closer clearance and better sealing, and better heat resistance, than normal pistons.

The crankshafts have better torque characteristics than normal crankshafts.

(See sheet 4).

The inlet valves close early on the compression stroke giving a more effective compression stroke. The exhaust valves open later than is normal on the power stroke, thus giving a longer more effective power stroke. The performance of the engine concept should be superior to any type of equal capacity diesel engine with an exhaust driven turbocharger.

Claims (1)

1. CLAIMS Sheet at 1 An internal combustion engine having the following

   features (a) The engine in this claim is for a petrol driven four- stroke high performance engine for high performance road vehicles and racing cars, the engine has two identical crankshafts, each crankshaft has a gear fixed to it, the two gears in mesh drive the two crankshafts in opposite directions, in line connecting rods from each crankshaft drive yoke assemblies, each yoke assembly drives any number of pistons, the multi piston drive of each yoke allows the crankshafts to have a short stroke allowing high engine speeds.

   (b) each yoke has tubular piston drive rods fixed at right angles to it, the pistons driven by each yoke are termed a piston set, the cylinders that the pistons slide in is termed a cylinder set, the oil feed to and from the pistons is through the piston tubular drive rods, each yoke has a tubular location rod fixed at right angles to it.

   The rod locates in lubricated bearings a bore in the centre of the piston set, as the connecting rods drive each yoke, the rod slides in the bearings in the bore, this makes each yoke move in a straight line, the opposite rotation of the crankshafts driving the connecting rods puts no side loads on the yokes, or on their location rods, (c) each yoke gives a straight line drive to each piston set, above each piston set is a shared cylinder head with a central sparking plug, each piston set at top dead centre on the compression stroke have squish areas, that drive the compressed mixture towards a central combustion chamber, when the mixture is fired the expanding gases will drive the piston set towards bottom dead centre, each shared cylinder head has any suitable arrangement of inlet and exhaust valves, (d) under each piston set is a sealed shared area, the piston rods pass through seals and support bearings in the plate that seals each shared area, each under piston set sealed area has suitable automatic air inlet valves and has suitable transfer ports connecting the shared under piston set sealed area, with each cylinder bore, when each piston set travels towards top dead centre, air is induced in the shared sealed under each piston set, when each piston set travels towards bottom dead centre, the induced air is compressed, the compressed air is used to purge exhaust gases after blow down on each power- exhaust stroke, and to charge each cylinder set during the induction stroke, the straight line piston drive gives only axial piston loading the pistons can be of lighter build than those of normal engines, the pistons are made from alloy steel, the underside of the pistons have seal plates to aid good under piston sealed area induction and compression.

   Sheet lid An engine as claimed in claim 1, wherein a diesel fuel injector is fitted to the 2 shared cylinder head, to replace the sparking plug, and the engine having a suitable compression ratio, these changes make the concept into a diesel fuel driven engine An engine as claimed in claim 1, wherein each shared cylinder head has exhaust 3 valves only, each cylinder has a low pressure fuel injector that sprays fuel into air flowing through the transfer ports, the changes make the concept into a two stroke engine with four- stroke type lubrication.

   4 An engine as claimed in claiml, wherein aluminium alloy pistons are used instead of alloy steel pistons An engine as claimed in claim 3, wherein the cylinder head mounted sparking plugs, are replaced by diesel fuel injectors, the engine having a suitable compression ratio, the changes make the concept into a diesel driven two - stroke engine.

   6 An engine as claimed in claim 1, wherein the crankshafts driving each yoke assembly, have the crank driven connecting rods able to be at any chosen angle to the cylinder set central axis, as they drive the yoke, the connecting rods and their driving crankshafts are spaced to give a favourable crankshaft torque and power output position, on each power stroke.

   7 An engine as claimed in claim 1, wherein the engine operates in the stratified charge mode of operation, above each piston set in the centre of each shared cylinder head, is a pro- combustion chamber, that has a central sparking plug and a central bore that connects to a shared cylinder head central combustion chamber, air is fed to each precombustion via a small valve that controls a port from the under piston sealed area, a fuel injector in each port controls the air fuel ratio in the pre - combustion chamber, a second fuel injector in the main inlet port of each cylinder set controls the air fuel ratio in each cylinder set.

   8 An internal combustion engine substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

   Amendments to the claims have been filed as follows CLAIMS Sheet I l 1 An internal combustion engine having the following features (a) The engine in this claim is for a petrol driven four- stroke engine for high performance road and racing vehicles, the engine has two identical crankshafts, each crankshaft has a gear fixed to it, the two gears in mesh drive the two crankshafts in opposite directions, in line connecting rods from each crankshaft drive yoke assemblies, each yoke assembly drives three or more pistons in cylinders that are arranged in a circle set about a yoke location rod, the multi piston drive of each yoke allows the crankshafts to have a short stroke allowing high engine speeds, the circular cylinder arrangement allow a circular shared combustion chamber, this gives the minimum moment of any differential forces, and the minimum combustion chamber area, any other cylinder format gives a very high area shared combustion chamber thus preventing combustion on the power stroke, and higher differential forces that can cause an engine to lock up.

   (b) each circular yoke has tubular piston drive rods fixed at right angles to it arranged in a circle, the pistons driven by each yoke are termed a piston set, the cylinders that the pistons slide in is termed a cylinder set, the oil feed to and from the pistons is through the piston tubular drive rods, each yoke has a central tubular location rod fixed at right angles to it, the rod locates in lubricated bearings a bore in the centre of the circular piston set, as the connecting rods drive each yoke, the rod slides in the bearings in the bore, this makes each yoke move in a straight line, the circular cylinder arrangement and the location rod, control the yoke at all positions, when the assembly is near top dead centre where the connecting rods angles can become different, the location rod controlling the yoke assembly to maintain straight line motion near top dead centre also controls the connecting rod angles and protects the assembly from locking up at this position, the opposite rotation of the crankshafts and the location rod controlled connecting rods angles, ensures no side loads on the yokes, or on their location rods, at bottom dead centre the risk of lock up is less than at top dead centre, the circular cylinder arrangement with the central location rod ensuring the yoke and pistons always move in a straight line gives the best protection from locking up, any similar multi piston drive without a similar location rod risks the chance of locking up, (c) each yoke and location rod ensures a straight line drive to each piston set that is in a circular arrangement about each yoke location rod, above each piston set is a circular shared cylinder head with a central sparking plug, each piston set at top dead centre on the compression stroke have squish areas, that drive the compressed mixture towards a central combustion chamber, when the mixture is fired the expanding gases will drive the piston set towards bottom dead centre, each shared cylinder head has any suitable arrangement of inlet and exhaust valves, (d) under each piston set is a circular sealed shared area, the piston rods pass through seals and support bearings in the plate that seals each shared area, each under piston set sealed area has suitable automatic air inlet valves and has suitable transfer ports connecting the shared under piston set sealed area, with each Sheet 1 cylinder bore, when each piston set travels towards top dead centre, air is induced in the shared sealed under each piston set, when each piston set travels towards bottom dead centre, the induced air is compressed, the compressed air is used to purge exhaust gases after blow down on each power- exhaust stroke, and to charge each cylinder set during the induction stroke, the straight line piston drive gives only axial piston loading the pistons can be of lighter build than those of normal engines, the pistons are made from alloy steel, the underside of the pistons have seal plates to aid good under piston sealed area induction and compression.

   2 An engine as claimed in claim 1, wherein a diesel fuel injector is fitted to the shared circular cylinder head, to replace the sparking plug, and the engine having a suitable compression ratio, these changes make the concept into a diesel fuel driven engine 3 A engine as claimed in claim 1, wherein each shared circular cylinder head has exhaust valves only, each cylinder has a low pressure fuel injector that sprays fuel into air flowing through the transfer ports, the changes make the concept into a two - stroke engine with four - stroke type lubrication 4 An engine as claimed in claims, wherein aluminium alloy pistons are used instead of alloy steel pistons An engine as claimed in claim 3, wherein the circular cylinder head mounted sparking plugs, are replaced by diesel fuel injectors, the engine having a suitable compression ratio, the changes make the concept into a diesel driven two - stroke engine.

   6 An engine as claimed in claim 1, wherein the crankshafts driving each circular yoke assembly, have the crank driven connecting rods able to be at any suitable angle to the circular cylinder set central axis, as they drive the yoke, location rod and pistons, the connecting rods and their driving crankshafts are spaced to give a favourable crankshaft torque and power output position, on each power stroke.

   7 An engine as claimed in claim 1, wherein the engine operates in the stratified charge mode of operation, above each circular arranged piston set in the centre of each shared circular cylinder head, is a precombustion chamber, that has a central sparking plug and a central bore that connects to a shared cylinder head central combustion chamber, air is fed to each pre-combustion via a small valve that controls a port from the under piston sealed area, a fuel injector in each port controls the air fuel ratio in the pre - combustion chamber, a second fuel injector in the main inlet port of each cylinder set controls the air fuel ratio in each circular arranged cylinder set.

   8 An internal combustion engine substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.