GB2397100A

GB2397100A - I.c. engine with power and induction assemblies and two crankshafts

Info

Publication number: GB2397100A
Application number: GB0300261A
Authority: GB
Inventors: John Daborn
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-01-07
Filing date: 2003-01-07
Publication date: 2004-07-14
Anticipated expiration: 2023-01-07
Also published as: GB2397100A8; GB2397100B; GB0300261D0

Abstract

The engine has a power assembly 1 and an induction assembly 2 that share a four-stroke cycle and have respective crankshafts 15, 17 connected for rotation in the same direction 180 degrees apart. The induction assembly 2, which has induction and light compression duties only, is driven 1:1 from the power assembly 1 which has compression and power stroke duties only. The power assembly 1 is fed from two pressure chamber areas 5 and 6, containing a total air mass of about 125% of the capacity of the power assembly, that are charged with air at pressures above ambient by the induction assembly 2, allowing a stratified mode of operation. Pressure chamber 5 feeds the power assembly cylinder; the other pressure chamber 6 feeds a pre-combustion chamber 9, having a centrally-mounted sparking plug 13, in the power assembly cylinder head via a small inlet valve 8. A fuel injector 10 is located close to valve 8 in the feed duct from the pressure chamber area 6. The power assembly 1 has no exhaust valves; all the cylinder head valves are inlet valves 7, the exhaust gases exiting the cylinder via piston-controlled exhaust ports positioned near BDC. Balance masses 16 balance out the primary forces for the induction/power assembly pair at mid-stroke. The engine is intended to give low emissions, low fuel consumption and high power output.

Description

2397 1 00 Internal Combustion Engine 1 The four- stroke internal

combustion engine has been the mainstay of all types of road transport for many years. It has however, the following limitations 1. The combustion chamber of a four- stroke petrol engine with exhaust and inlet valve overlap is a compromise to give good efficiency at the most used engine speed. At other speeds emissions go up. The inlet valves are closed for a long time. This leaves the inlet gases in the ports outside each inlet valve stationary, as each valve opens.

2. The standard petrol engine in cold weather, can take up told minutes to fully warm up. Many urban cars may never warm up in the short journeys they make and many spend much of the journey during engine warm up. Emissions are excessive at warm up, and economy is poor.

3. In the past, attempts have been made, to make the four- stroke petrol engine work on the stratified charge system. It is difficult to achieve this successfully.

Nearly all the engines produced today work on the normal format.

4. The burn time for the fuel air mixture is very short and it cannot be guaranteed that full burn will occur at all revolutions of the engine. Also the volume between the piston top rim and the top ring, this mixture is seldom burnt and goes into the exhaust as unburned fuel.

5. The crankshafts of 4 and 6 in line engines are subject to torsion induced vibrations that can require a damper to make acceptable. Bending vibrations can also be present and can cause roughness problems.

A description of this invention now follows. This concept modifies the normal four- stroke cycle of a petrol engine to achieve a successful stratified charge mode of operation. This gives the following advantages.

À Emissions are much lower than that of a normal engine.

À The fuel economy can be close to that of a diesel engine.

À The engine concept also allows a high power output.

The engine concept also gives the following advantages.

À High volumetric efficiency.

À Higher compression ratio than normal without detonation or pre-ignition.

À Improved engine balance.

À Bending vibrations and torsion induced vibrations are not a problem.

À Good cold starting, and a slow reliable idling speed À Lower friction than for a normal engine À Compact engine size compared with a normal engine. Short coolant and lubrication lines. (This is an advantage for front wheel driven cars) À Warm up time is four times faster than for a normal engine.

A brief description of the engine is shown below. A 2 The engine concept successfully uses the stratified charge mode of operation. This is achieved in the following way. The four- stroke cycle is shared between a power cylinder assembly and an induction cylinder assembly. The power assembly has compression and power stroke duties only. The induction assembly has induction and light compression duties only. Both these assemblies are optimised for the duties they have to perform. The exhaust stroke has been eliminated. The induction assembly charges two separate pressure chambers, these form the outside atmosphere for the power assembly. One pressure chamber feeds the power cylinder via inlet valves in the cylinder head. This contains a larger mass of air than the other pressure chamber. The other pressure chamber feeds a pre-combustion chamber in the power assembly cylinder head, via a small inlet valve. In the dueling from the pressure chamber to the inlet valve of the precombustion chamber is a fuel injector. This injector only, if required, can control the engine power output. A second injector can be positioned in the inlet system feeding the power cylinder. The combined air mass contained by the two chambers can be designed to give the power assembly an effective volumetric efficiency greater than 120%.

The exhaust gases exit the power cylinder by means piston controlled exhaust ports.

A more detailed description now follows.

Engine Function Details The engine concept functions as described below with the help of the following drawings Fig 1. Power and induction cylinder assembly, balance system and pressure chamber areas 5 and 6 (the positions shown for areas Sand 6 are to illustrate only) Fig 2. Power and induction cylinder assemblies showing power assembly pre- combustion chamber and hemispherical type combustion chamber formed in piston crown. (Figs 1 to 3 are diagrammatic and are not to scale) All parts of this engine are to normal automotive manufacturing standards.

The power assembly 1 is described first. The power assembly is under square. The cylinder head is flat, inserted in the flat cylinder head is a pre- combustion chamber 9 with a centrally mounted sparking plug 13 and a small inlet valve 8, four inlet valves 7 are also present in the cylinder head, these give a good valve time area. The power piston 3 has a hemispherical type combustion chamber formed in its crown. The combustion chamber in the piston crown can have a protective ceramic or a stainless steel insert. The outer rim of the piston forms a squish area, (see Figs 1 & 2). The power assembly has no exhaust valves this eliminates a hot spot area in the cylinder head. Inlet valves only are used, and the sparking plug is cooled by incoming air via valve 8, this valve is off set from pre- combustion chamber centre to promote swirl. A higher than normal compression ratio can be used with this engine concept. On the power stroke, the gases expand downwards driving the piston down. As the power piston 3 approaches B.D.C. it starts to uncover two exhaust ports 21, these have a total area that exceeds four fully open exhaust valves. The downward expanding gases will freely flow into the downward sloping exhaust ports. These ports are a long way from the inlet valves 7. This fact and the engine use of the stratified charge mode of operation helps to reduce emissions. As the power piston reaches B.D.C. most of the exhaust gases have passed down the low impedance exhaust system. This exhaust system is designed to give no pulses.

As the power piston rises up from B.D.C. it starts to cut off the exhaust ports, just past B.D.C. inlet valve 8 starts to open in the procombustion chamber. Trapped behind the inlet valve, trying to push it open is air in pressure chamber area 6.

This floods into the pre- combustion chamber and purges it of exhaust fumes and cools the sparking plug, air then travels down towards the closing exhaust ports, and starts to purge the power cylinder of any exhaust remnants. When the rising power piston 3 is still near B.D.C. the four inlet valves 7, start to open. Trapped behind these valves is air in pressure chamber area 5. The air passes through these valves at high velocity with induced swirl; this purges the cylinder walls of exhaust remnants. When piston 3 is a set distance from T.D.C. the valves 7 and 8 close. As the piston 3 rises towards T.D.C.

nearly all the air originally trapped behind the valves 8 and 7 in pressure chamber areas 5 and 6, has entered into the cylinder below. The trapped air mass equals say 125% compared to the power cylinder air capacity (a small amount of air is lost to the exhaust at low engine speeds.). As the power piston rises up towards T.D.C. It starts to compress the air- fuel mixture. At T.D.C. the power piston rim is close to the flat cylinder head.

The affective pressure equals a normal 12 tot compression ratio. The high swirl rate and piston induced turbulence should give a good combustible mixture, with excess air always available. The fuel in the mixture is controlled by an injector I O mounted in the porting feeding valve 8, for idling and low throttle settings late injection takes place, the last air to pass through valve 8 is always injected into to ensure a slightly rich mixture surrounds the sparking plug 13. For medium to full throttle settings the injection starts early, but always after there is no chance of fuel-laden air being lost to the exhaust. A second fuel injector 10 can be mounted in the cylinder main inlet duct. This could control the amount of fuel in the air supplied direct to the power cylinder. For motorcycle engine and for small car engine variants and a racing version of this engine see sheet No 7. For specific example of road vehicle engine use see sheet No 8.

Cam and valve details The camshafts on this engine are driven 1 to 1 from the power crankshaft 15, all the valves can be operated by cams and rocker arms. For valves 7, 8, 14, and 1 I the springs controlling these are set to hold in the pressures in chamber areas 5 and 6, (suitable standard valve springs should be available) inlet valves 12 have normal springs. The power assembly valve timing is for inlet valves only. The cams operating these valves could be the variable timing type.

Crankshaft details The engine concept has two crankshafts. The induction assembly crankshaft 17 is more lightly loaded than the power crankshaft l 5. The power crankshaft format can be as required e.g. for a normal petrol engine or for a racing engine etc. The induction assembly crankshaft is driven one to one off the power crank by a drive that makes them rotate in the same direction (this drive can be by timing belt, or can be done by gears or by chain). To replace a four in line engine requires the two crankshafts to be only two cylinders long, to replace a six in line engine requires the crankshafts to only be three cylinders long. This makes the shorter crankshafts many times more rigid than those of the normal length. The three in line crankshaft has primary and secondary balance, with new engine concept there will be no primary couples running along it.

Engine balance On most single cylinder engines a percentage of the reciprocating mass is balanced. If all of the reciprocating mass was balanced then the side thrust of the balance mass would cause a sideways vibration equal to the now balanced vertical vibration caused by the piston and upper con rod assembly. On this engine concept the reciprocating inertia primary forces can be fully balanced. The way this is achieved is by driving the two crankshafts in the same direction, the power assembly and the induction assembly are spaced at 180 . The system balances out the reciprocating masses at T.D.C. and at B.D.C.

When at mid stroke the balance masses 16 cancel out and put no out of balance force into the engine structure. The balance masses when at the innermost positions as shown on drawing No I these masses are made to interleaf at that point. The balance shaft method to balance primary forces has been used before, but the engine concept allows this using normal engine working parts.

The power piston 3 is designed to withstand the thermal and mechanical stresses of combustion. The induction piston 4 is subject to induction and light compression loads only, the larger diameter induction piston assembly is made to have the same mass as that of the power piston assembly.

Cold starting The high volumetric effective efficiency (120%) ofthe power assembly, this will be available from low to high engine speeds. Only two power cylinder assemblies, 1 are required. (Four in line engine replacement) These each have a power stroke every 360 , these will quickly heat to aid starting. The outside atmosphere of the power assembly is pressure chamber areas 5 and 6, at pressures above the atmospheric pressure. On a cold start the induction assembly 2 inducts cold dense air, as it is lightly compressed, it is raised in temperature, when this air is allowed to expand into the power assembly via valve 8 it will more easily vaporize fuel sprayed into the high velocity air flowing past injector 10.The mixture is then compressed to a pressure equal to 12 to 1 with excess air available, via the four inlet valves 7, these induce swirl, to add to piston applied turbulence. The high volumetric efficiency and the high compression ratio will give a high compressed temperature of the mixture at low to high power outputs.

Warm up time The warm up time is short compared with a normal engine the metal work to heat up is only two cylinders long. (Four in line replacement). Each power cylinder assembly fires at every T.D.C. The induction assembly generates a small amount of heat, it has low demands on the coolant supply, the coolant mainly feeds two power cylinders only, and this gives a reduced volume of coolant in the system. This also helps to speed the warm up process.

Engine power The engine concept has a power output double that a normal engine of same capacity With a volumetric efficiency at all times greater than 120 %, each power stroke should produce more power than on a standard engine power stroke. This assumes that the power assembly swept volume is that which defines the engine capacity.

The engine concept has a power stroke every 360 for each cylinder assembly instead of the normal 720 of crankshaft rotation.

Engine economy The engine economy is improved, by means of the following engine features.

À A successful stratified charge mode of operation is used. This controls the power by the amount of fuel used. This gives good economy, the inlet system has no throttle restriction this reduces pumping losses. The engine function also allows a low idling speed to be reliably used. This also aids good economy.

À The compression ratio can be higher than for a normal engine, this improves efficiency. There are good conditions for full combustion, with excess air always available. A high temperature is achieved at every compression stroke.

À The power assembly has compression and power stroke duties only. It is designed for these functions only, and can be made more efficient than for a normal engine.

À The warm up time for the power assembly is much shorter than for the normal engine. The rich mixtures normally used during the warm up period, are not required for the new engine concept. These two factors cause less fuel to be used.

À The fact that two separate air pressure chambers supply the power assembly, this gives predictable flows of air into the power assembly. And allows more accurate metering of the fuel- air mixtures. This enables a slightly rich mixture to be accurately maintained in the pre- combustion chamber. While the mixture in the power cylinder can vary between being very weak to being near to correct.

When the mixture in the pre- combustion chamber is ignited it will have rapid combustion due to the central sparking plug and the short flame travel. This will fire into the turbulent highly compressed mixture below and will burn the weakest mixture. The volumetric efficiency of 120% ensures that excess air is available.

Engine emissions À The close control air fuel mixtures and the successful use of the stratified charge system. This gives a large reduction of emissions.

À The piston controlled exhaust ports are many times more distant from the inlet valves, than the exhaust valves of a normal engine. This arrangement gives a large reduction of emissions. Valve overlap is not required on the new engine concept.

À The volume contained between the power piston rim and the top ring, with the engine concept, this volume contains mainly air and exhaust fumes.

À The large area exhaust ports and the fact that the gas is expanding down towards them on the power stroke. These ports can open a little later than normal exhaust valves. This helps to give a more complete burn of the mixture.

Engine friction In a normal engine, the pistons, and connecting rods and crankshaft are all designed to withstand the thermal and mechanical loads of combustion. These are vastly over engineered for the induction stroke. And friction is high for this operation.

Tests have shown that if the cylinder is run at a slightly higher temperature than is normal, then piston friction is reduced due to reduced oil shear losses, but this makes it more difficult to cool the exhaust valves, also the volumetric efficiency goes down due to a less dense charge induced. With the engine concept there are only two heavily loaded piston, connecting rod and crank throw assemblies, (four in line engine replacement).

The induction assembly at near constant temperature and lightly loaded can be designed to have lower friction than normal power unit assemblies. The volumetric efficiency of the engine concept is not affected by a small temperature rise, and there are no exhaust valves.

Induction assembly 2 The induction assembly 2 is over square; the induction piston 4 is flat topped. The induction assembly swept volume can be 1.2 to 1.9 times that of the power assembly, the induction assembly 2 has the same stroke as the power assembly 1, in the flat cylinder head are five valves, two large inlet valves 12, two transfer valves 11, and one small transfer valve 14, short ducts connect these to pressure chamber areas 5 and 6. When the induction piston 4 is at T.D.C. it is very close to the cylinder head, the valves 11 and 14 have just closed. The inlet valves are slightly under Bush and are just open as the piston moves down from T.D.C. When the piston reaches the normal T.D.C for a power piston.

The induction piston has induced a low pressure above it, inducing air through the open valves 12, via a non throttled inlet system, at this point the piston 4 is gathering speed, towards B.D.C, when the piston is on the return stroke at a set distance past B.D.C. the inlet valves 12 close. Then transfer valves 11 and 14 start to open. The rising piston pushes the air through the valves into the pressure chamber areas S and 6, as the piston approaches close to T. D. C. The two valves 11 close. Valve 14 (which is under flush when closed) remains open, and closes just after T.D.C. The pressure chamber areas 5 and 6 include the ports connecting them to the valves. The air pressure trying to push the valves open will instantly flow into the power assembly 1 when the valves 7 and 8 have been opened. The induction assembly inlet valves 12 are closed for only 120 . The inlet system can be designed to ensure a rise in pressure occurs outside the inlet valves, and in the inlet ducting away from the inlet valves, air is flowing in the correct direction.

Engine smoothness Bending vibrations of the crankshaft can cause roughness problems. Primary couples along crankshafts can also give vibration problems.

Lack of good torque in low to middle engine speed ranges, and lack of smooth increase of power as accelerator is opened, can also give roughness or poor driveability.

The engine concept has a short stiff crankshaft, compared with a normal engine. Bending and torsion induced vibrations should not be a problem. The engine concept has no primary couples. The primary forces are balanced out at source. For each power assembly 1, there is a compression of 12 to I at every T.D.C. Followed by a power stroke this cushions the big end and main bearing assemblies.

The power strokes are confined to two cylinders in line only (four in line engine replacement). This gives a smoother arrangement, than for a four in line engine.

There can be a volumetric efficiency of at least 120 % available, from the very lowest engine speed to the maximum used engine speed.

This will ensure that good torque is available at low speeds and at middle range speeds, with a smooth increase of power between them. This should give good driveability. And should give a smooth further increase of power up to the top speed of the engine.

The power assembly compression ratio, the number of inlet valves, the size of the exhaust ports and the swept volume of the induction assembly, can be varied to suit any engine.

Single power cylinder engine for a ultra small car The engine concept is mainly intended to replace two in line engines, four in line engines and six in line engines.

For ultra small town cars that are starting to appear, a single power cylinder engine should be acceptable for this, the engine concept has a power stroke at every T.D.C. the engine is self- balanced for primary forces. The engine would be very compact, and of very low mass. There should be very good economy and very low emissions. See Figs 1 and 2. The capacity of this engine could be set below that which gives reduced road tax.

With a power output of an engine of twice it's capacity, the performance should be very good. A small twin power cylinder engine of the same capacity could be used.

New concept motorcycle engine The engine concept could be used to replace a normal motorcycle engine, the engine width across the flame would be halved. A full race tuned motorcycle can have a volumetric efficiency of 120% over a narrow engine speed range.

The new engine concept could give a motorcycle 120% minimum volumetric efficiency throughout it's engine speed range, (touring type of motorcycle). There is also good engine balance as described above. See Figs I and 2 (any number of these assemblies can be used to make a suitable engine) New concept high performance engine The engine described on sheets 2, 3, 4, 5, and 6 can be arranged as a very high performance petrol engine for saloon car racing and rally cars etc. As a racing engine this invention has the following advantages.

À The inlet system is not throttled, and also gives good induction conditions À The volumetric efficiency can be set for any value between say 100% and 150%.

The chosen value will prevail over a wide engine speed range.

À A higher than normal compression ratio can be successfully used.

À The engine power cylinder head has no exhaust valves all the valves are inlet.

À A high performance stratified charge system can be used.

À Engine friction is reduced.

À Engine balance is improved.

À The two piston controlled exhaust ports have a combined area greater than 4 fully open exhaust valves. As the gas expands downwards on the power stroke, it will freely flow into the downward sloping exhaust ports.

The valve timing, the fuel injection system, the compression ratio, and the induction assembly swept volume, can all be adjusted to give the maximum power.

A specific embodiment of the invention will now be described by way of example see the following drawing.

Fig 3 - Shows a replacement engine for a normal four in line petrol engine, using the engine concept. (The positions shown for areas 5 and 6 are for illustration only).

The basic engine is as described in sheets 2, 3, 4, 5 and 6, and as shown on Figs 1 and 2.

The engine size to be replaced is of 21itre capacity.

The power assembly is described first.

The engine is as shown on Fig 3. The two power cylinder assemblies 1 are spaced at 180 on power crankshaft assembly 15. If this gives an engine capacity of 1 litre nominal, the power output of this engine should equal or exceed that of the 2 litre capacity engine.

This assumes that the power assembly swept volume defines the engine capacity.

The engine concept works in the stratified charge mode. It has no exhaust valves. The downward sloping exhaust ports have an area in excess of four fully open exhaust valves.

These ports are a long way from the inlet valves. These two points help to give low emissions.

The induction assembly The induction assembly 2, the function details are described on sheet 6 and shown on Figs 1,2,and3.

The two induction cylinder assemblies 2 are spaced at 180 on induction crankshall 17.

Each induction piston assembly 4 is spaced at 180 to the power piston 3 opposite it on power crankshaft 15.

Exhaust and inlet details The exhaust pipes 18 join after a set distance into a narrow angle cone, then the exhaust gases travel in a suitable large diameter exhaust pipe, then through a low impedance silencer system. The system is arranged to give some suction but no pulses.

The inlet system has no throttle and is of a designed length and shape to suit the engine.

The system then terminates in a suitable air box and a low impedance air cleaner assembly, which has a low impedance air input.

Claims

CLAIMS q 1 An internal combustion engine having the following features;

(a) the engine has two crankshafts, these are connected by a drive that makes them rotate in the same direction; (b) one of the crankshafts is for the power assembly, the other crankshaft is for the induction assembly, the power and induction assemblies are spaced at 180 crank angle to each other, these two assemblies share the four stroke cycle, the power assembly has compression and power stroke duties only, the induction assembly has induction and light compression duties only, these two assemblies form a function related pair, this arrangement allows the engine to use a successful stratified charge mode of operation, one or more of these function related pairs may be used; (c) suitable balance masses balance out the primary forces for the power and induction assembly function related pair, at mid stroke the balance masses cancel out, the power piston and induction piston assemblies have the same mass; (d) the power assembly has no exhaust valves, all the cylinder head valves are inlet valves, the exhaust gases exit the cylinder via piston controlled exhaust ports positioned near BDC, these ports slope downwards; (e) each power and induction assembly function related pair have two separate pressure chambers, one pressure chamber feeds the power assembly cylinder via cam timed cylinder head inlet valves, this pressure chamber contains a higher mass of air than the other pressure chamber, the other pressure chamber feeds a pre-combustion chamber that is in the power assembly cylinder head, via a cam timed pre- combustion chamber inlet valve, in the duct from the pressure chamber to the inlet valve of the pre-combustion chamber is a fuel injector, this controls the engine power, the combined air mass contained by the two pressure chambers is greater than a 100% when compared to the swept volume capacity of the power assembly, a second fuel injector can be mounted in the main ducting to the power assembly cylinder; (f) the induction assembly has a larger swept volume than the power assembly, but has the same stroke, the induction assembly cylinder head has inlet and transfer valve assemblies, the induction assembly inducts air from a non throttled inlet arrangement via a cam timed inlet valve system, the induction piston then drives the air to feed two separate pressure chambers via a cam timed transfer valve system, this charges each pressure chamber with a mass of pressurised air, to suit the power assemblies two inlet systems, the air, air/ fuel mixture flowing into the power assembly from the pressure chambers, via the cam timed inlet valve systems, purges the power cylinder of exhaust fumes remaining, after the power stroke blow down. lo
2 An internal combustion engine arrangement according to claim 1, wherein the engine uses a successful stratified charge mode of operation.
3 An engine as claimed in claims 1 and 2 wherein the fuel injection is controlled such that for low throttle and idling settings, late injection of fuel takes place, the last air to pass by the pre-combustion chamber inlet valve is always injected into, to ensure a slightly rich mixture surrounds the sparking plug, for medium to full throttle settings injection of fuel starts early, but always after there is no chance of fuel laden air going down the exhaust.
4 An engine as claimed in claims 1, 2 and 3 wherein the inlet system is arranged to give some swirl of the induced air / air fuel mixture in the power assembly.
An engine as claimed in claims 1, 2, 3 and 4 wherein the power piston stroke is made greater than the cylinder bore size, the all inlet valve power cylinder head is designed to have a multi valve inlet system that ensures full cylinder filling during the cam timed inlet valve open period.
6 An engine as claimed in any of claims I to 5 wherein the induction assembly has a swept volume value that gives the power assembly a minimum volumetric efficiency of 120%.
7 An engine as claimed in claim 1, and any of claims 2 to 6 wherein the power piston has a hemispherical type depression in its crown surrounded by a squish area, above this depression in the piston is a pre-combustion chamber in the cylinder head, this has a central sparking plug, the precombustion chamber is fed an air, air / fuel mixture via the precombustion chamber inlet valve.
8 An engine as claimed in claims 6 and 7 wherein the power cylinder head has at least two inlet valves feeding the power cylinder, and has exhaust ports with a total area, equal to at least two fully open exhaust valves.
9 An internal combustion engine substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.