BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates to a rotary combustion engine.

2. Brief Description of the Prior Art

Research into improved engine design has been accelerated by the combination of the sharp increases in crude oil prices following the 1973/74 OPEC oil crisis, the demand for improved fuel comsump- tion and stricter exhaust emission levels. This research has been carried out in respect of gas turbines, diesels and petrol engines (the latter both in respect of rotary and reciprocating-piston type engines) .

To complement this research, research has also been carried out to develop improved transmission systems which complement the engines so that the engines can be operated in their most efficient work- ing range. However, these new transmission systems are proving to be fairly complex, adding to their cost and having higher maintenance requirements than the transmissions systems previously available.

SUMMARY OF THE PRESENT INVENTION it is an object of the present invention to provide an improved type of rotary combustion engine. It is a preferred object to provide an engine where the air/fuel mixture is ignited in an external combustion chamber which may be of the type used in gas turbines.

It is a further preferred object to provide an engine where the air is partially compressed in the engine before it is fed to the combustion chamber.

It is a still further preferred object to provide an engine where the work or power is extracted by

expansion of the combustion gases in cylinders in the rotor and by directing the combustion gases as they enter the engine against the rotor to drive the latter as a turbine. It is a still further preferred object to provide a variable speed transmission system which enables the engine to operate within its most efficient operating band, the output speed of the transmission system being determined by the load applied to the transmission system.

Other preferred objects of the present invention will become apparent from the following description.

In one aspect the present invention resides in a rotary combustion engine including: a housing; a rotor rotatably mounted in the housing; a plurality of substantially radial cylinders in the rotor; a shaft offset from the axis of rotation of the rotor; a piston in each cylinder operatively connected to the shaft; an air intake in the housing; an air exhaust downstream of the air intake; an external combustion chamber; means interconnecting the air exhaust to the combustion chamber; means to supply fuel to the combustion chamber; means to ignite the air/fuel mixture in the combustion chamber to geherate combustion gases; a combustion gas inlet in the housing downstream of the air exhaust; means to convey the combustion gases to the combustion gas inlet; and

a gas exhaust in the housing downstream of the combustion gas inlet; so arranged that: air entering the air intake is at least partially pressurized by the cylinders intermediate the air intake and the air exhaust before being fed to the combustion chamber; fuel is mixed with the air and the resultant air/fuel mixture is ignited in the combustion chamber to form combustion gases; and the combustion gases are fed into the housing through the combustion gas inlet, the rotor being driven by expansion of the gases in the cylinders intermediate of the combustion gas inlet and the gas exhaust, and/or by the gases being directed against the rotor in the manner of a turbine.

(Conventional turbines are heat engines and rely on the heat and speed of the combustion gases for their operation. The invention piston engine is a volumetric engine. This invention relies on the volume, not the heat and speed, of the combustion gases and so could be considered to be a "volumetric turbine") .

Preferably pair of opposed pistons are inter¬ connected to respective crank pins on the shaft so that a piston at Bottom Dead Centre (BDC) adjacent the air intake will be connected to a piston at or past Top Dead Centre (TDC) adjacent the combustion gas inlet. Prefer¬ ably each piston will approach TDC adjacent the air exhaust and will approach BDC adjacent the gas exhaust. Preferably the rotor is mounted concentrically in the housing on a rigid centre shaft and the shaft, having a plurality of offset crank throws will be mounted offset from axis of the rotor (and centre shaft) .

Preferably the air is fed to the engine under at least partial pressurization by a turbo charger or super charger.

Preferably the fuel is supplied directly to the combustion chamber, although it may be pre-mixed with the air in the housing. Preferably only a percentage of the air is mixed with the fuel (the fuel being injected into the combustion chamber by one or more nozzles) , the remaining air bypassing the inner section of the combustion chamber and being mixed with the combustion gases.

At low speeds, only one fuel nozzle be used, additional nozzles being brought into operation at higher speeds or under load.

The ignition of the air/fuel mixture in the combustion chamber may be either cycle or continuous or may switch from one to the other. Preferably the output shaft is connected to the rotor and reduction gears may be provided inter¬ mediate the rotor and the output shaft to reduce the speed of the latter.

Preferably a variable speed transmission system has its input shaft operatively connected to the output shaft of the engine. Preferably a first planetary gear- set is driven by the input shaft, this gearset driving a secondary planetary gearset which drives the output shaft for the transmission system. Preferably a speed sensing differential assembly is connected to the out¬ put shaft and is operatively connected to the first planetary gearset, which acts as a torque control, to vary the ratio of the first planetary gearset. Prefer¬ ably the differential assembly is also operatively connected to the input of the second planetary gearset to co-operate with the output from the first planetary gearset to control the speed of the input to the second¬ ary planetary gearset.

BRIEF DESCRIPTION OF THE VIEWS OF THE DRAWINGS / To enable the invention to be fully understood,

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a preferred embodiment will now be described with respect to the accompanying drawings, in which:

FIG. 1 is a sectional end view of the engine; FIG. 2 is a side view of the engine shown in part-section and the transmission in section; FIG. 3 is a sectional side view taken on line 3-3 on FIG. 1; and

FIG. 4 is a perspective view of a section of a modified form of the rotor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The engine has a main cylindrical housing 10 of steel or other suitable material, with a peri¬ pheral wall 11 between end plates 12 and 13. Cooling fins 14 are provided around the peripheral wall 14 and a cooling blower (not shown) may be provided to main¬ tain the engine in its correct operating temperature range.

A pair of inclined legs 15 support the forward end of the engine above a base 16, while the rearward end of the engine is supported by the housing 17 of a variable speed transmission system 18, the housing 17 having a common wall 19 with a rear extension 20 on the engine.

A fixed centre shaft is provided" concentrically with the peripheral wall 11 and formed by a pair of stub shafts 21, 22 keyed into sockets formed in the front end plate 12 and common wall 19, respectively.

The inner end of each stub shaft 21, 22 is provided with a socket 23 offset from the axis of the housing and the centre shaft.

A crankshaft 24 has its respective ends rotat- ably journalled in the sockets 23 and is provided, in this embodiment, with four offset crank throws 25, each provided with a ball bearing 26. The rotor 27 has eight radially directed (and

equally spaced) combustion cylinders 28, the cylinders being provided in opposed pairs with the pairs of cylinders being rearwardly offset. End plates 29 on the rotor are rotatably journalled on the stub-shafts 21, 22 to support the rotor concen¬ trically in the housing 10.

The peripheral and end faces of the rotor 27 are smooth and suitable spring loaded seals 30 bear against the rotor to seal the latter to the housing 10. As shown in FIGS. 1 and 2, the cylinders 28 are circular in plan and each cylinder is provided with a ^" piston 31 having a crown profile conforming to the inner wall of the housing, conventional piston rings 32 sealing the pistons in their cylinders. Opposed pairs of pistons 31 are interconnected by conrods 33 having a common lug-end 34 journalled on a bearing 26 on a respective crankpin 25, the ends of the conrods being fixed in the pistons by fixed pins 35. An air intake passage 36 adjacent the base of the housing 10 is connected to the air exhaust 36a of a turbocharger 37 mounted on the base 16, the turbo- charger having an air intake 38 provided with an air filter (not shown) .

An air exhaust passage 39 is spaced from the air intake passage 36 and is connected to the inlet end of an external combustion chamber 40 via a connecting manifold 41, fitted with an adjustable non-return valve 42 which prevents air being forced from the combustion chamber 40 back through the air exhaust passage 39. The manifold 41 may also be provided with an air cooler to cool the air entering the combustion chamber and thereby increase the efficiency of the engine.

The combustion chamber 40 has a tubular outer chamber 43 closed at one end by a removable cap 44, through which passes a fuel line 45 ^" connected to a source

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of fuel by a flow valve 46 which may be controlled by an acceleration linkage (not shown) . An inner firing chamber 47 is separated from the outer chamber 43 by a perforated wall 48 which is provided with a perforated conical end wall 49 adjacent the cap 44, a plurality of fuel nozzles 50 being mounted in a block in the centre of the end wall 49. A fuel igniter (e.g. a sparking plug) (not shown) is provided in the firing chamber 47 to ignite the air/fuel mixture in that chamber.

A combustion gas pipe 51 conveys the combustion gases from the combustion chamber 40 to a combustion gas inlet passage 52 in the housing downstream of the air exhaust passage 39, the inlet passage having an inner nozzle inclined relative to the peripheral wall 11 of the housing.

A combustion gas exhaust passage 53 is provided adjacent the air intake passage 36 and is connected to the exhaust turbine of the turbocharger 37 to drive the latter.

An annular extension shaft 54 is fixed on the rear of the rotor 27 and is provided with a driving gear 55 to drive a reduction driven gear 56 fixed on the forward end of the input shaft 57 of the variable speed transmission system 18, that shaft being journalled in the common wall 19 between the engine and the transmission system.

An oil pump (not shown) and a fuel pump (for liquid fuels) (not shown) are driven from the driven gear 56 to provide lubrication and fuel under pressure, respectively, for the engine.

The transmission system 18 has a housing with the common wall 19 as its front wall, a central wall 58 and a rear wall 59 in which is journalled the output shaft 60.

A first planetary gearset 61 has its sun gear 62 fixed to the input shaft 57. The pinion carrier 63 provided with gear teeth, is rotatably journalled on the input shaft, and has a number of pinions 64 meshing with the sun gear and the internal teeth of the ring gear 65 which is fixed at one end of an intermediate shaft 66 journalled in the central wall 58.

The sun gear 67 of a second planetary gearset 68 being fixed to the other end of the input, shaft 57. The pinion carrier 69, of the second gearset 68, is provided with gearteeth and is fixed on the intermediate shaft 66, the pinions 70 on the pinion carrier 69 mesh¬ ing with the sungear 67 and the internal teeth of the ring gear 71 fixed to the output shaft 60. A driven gear 72 is fixed on the output shaft

60 and meshes with a driven gear 73, having a spring- loaded hub 74 mounted on a pinion shaft 75 journalled in one end of a differential ^* cage 76 (the pinion shaft being journalled in suitable support bearings (not shown) in the housing 17) . A bevel pinion 77 is fixed to the inner end of the pinion shaft 75 and meshes with a pair of crown wheels 78 fixed on respective crown shafts 79 journalled in opposite sides of the cage 76. These crown wheels 78, in turn, mesh with a second pinion wheel 80 which is fixed to the inner end of a pinion shaft.81 journalled in the cage 76 (and housing 17) which drives a driving gear 82, having a spring loaded hub 83, in mesh with the teeth on the pinion carrier 63 of the first planetary gear set 61. An annular gear 84 is gixed around the cage 76 and meshes with the teeth on the pinion carrier 69 of the second planetary gearset 68.

The operation of the engine will now be described. The turbocharger 37 draws in air through its

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air intake 38 and feeds partially pressurized air through its air exhaust 36a into the air intake passage 36. Adjacent this passage, the pistons are at or near Bottom Dead Centre (BDC) and as the rotor 27 rotates (in a clockwise direction in FIG. 1) , the air is compressed (and further pressurized) by the pistons 31 as they approach Top Dead Centre (TDC) . The pressurized air is exhausted from the housing through the air exhaust passage 39 and is fed via the connecting manifold 41 to the combustion ' chamber 40, passing through the one-way valve 42.

A portion of the air e.g. 18% is fed into the firing chamber 47, where it is mixed with fuel supplied by one or more of the nozzles 50. The air/fuel mixture is ignited and the burning gases pass through the perforated wall 48 to be mixed with the remaining air in the outer chamber 43. The burning combustion gases are then conveyed back into the housing 10 through the combustion gas inlet passage 52 which is directed to create a "water-wheel" effect with the rotor 27.

The combustion gases drive the rotor 27 in two ways. Firstly, the expansion of the gases in the cylinders 28 push the pistons 31 towards Bottom Dead Centre (BDC) , rotating the rotor. Simultaneously, the gas engages the sides of the cylinders to drive the rotor in the manner of a turbine. (In a modified form of the rotor - see FIG. 4 - teeth 85 are formed around the rotor 27 and these combine with holes 86 in the rotor (which create turbulence) to "key" the rotor to the gases to assist in driving in the manner of a turbine) .

At or near Bottom Dead Centre (BDC) , when the energy from the gases has been obtained to drive the rotor, the gases are exhausted through the gas exhaust passage 53 to the turbocharger 37 to drive the latter to pressurize further air entering the engine. (For a short

portion of the rotation of the rotor, each cylinder 28 will be in communication with both air intake passage 36 and the gas exhaust passage 52 to enable the incoming pressurized air to purge the remaining combustion gases out of the cylinder.)

As the pistons are opposed, the force required for one piston of the pair to compress the incoming air will be provided by the expansion of the combustion gases acting against the other piston of the pair. The rotary motion of the rotor, which is at half the speed of the crankshaft 24, is transmitted to the input shaft 57 of the transmission system 18 via the gears 55, 56 which provide a 2:1 reduction ratio. (For example, when the input shaft 57 is rotating at 6000rpm. the rotor 27 is rotating at 12000 rpm. and the crankshaft 24 is rotating at 24000 rpm.) .

The operation of the variable speed transmission assembly will now be described, assuming that the engine is running at a constant speed e.g. the input shaft 57 is being driven at 2000 rpm. At rest, both sun gears 62, 67 are driven by the shaft.

The minimum speed at which driving gear 72 can rotate is determined by the stepdown ration of the second planetary gear set 67 (being determined by the relative number of teeth on the sungear 67, ring gear 71) , the rotation of the ring gear 65 causing pinion carrier 69 of the second planetary gear set 68 to rotate to provide drive between the sungear 67 and ring gear 71. When driving gear 72 begins to rotate, it drives the driven gear 73, which due to its spring coupling 74, begins to drive the pinions 77 and 80 (interconnected by crown wheels 78) . The spring loaded hub 83 provides a further delay before driving gear 82 starts to drive the pinion carrier 63. At the same time,

annular gear 84, supporting the cage 76, begins to turn. As the rotational speed of the driving gear 72, and output shaft 60, is increased to the rotational speed of the input shaft 57, the rotational speed of the pinion carrier 63 increases until the first planetary gear set 61 is locked to provide direct drive to the pinion carrier 69. Simultaneously the annular gear 84 reaches the same speed to combine with the ring gear 65 to rotate the pinion carrier 69 at the same speed as the sun gear 67 to lock the second planetary gear set 68. The input and output shafts 57, 60 now rotate at the same speed.

When a load is applied to the output shaft 60 which is sufficient to slow the latter, the reduced rotation speed of the driving gear 72 is sensed by the differential assembly and so annular gear 84 and driving gear 82 rotate more slowly, releasing the planetary gearsets to enable them to operate at stepped down ratios to provide the higher output torque required to satisfy the load. As the load is reduced, the rotational speed of the output shaft 60 increases until the planet¬ ary gearsets are again locked up.

This variable speed transmission system is particularly suitable for applications in heavy vehicle or locomotives, or where the engine is set to operate at a fixed speed e.g. at a high speed in the almost purely turbine mode. (In the latter application, the rotor 27 would have the outer profile shown in FIG. 4) .

The embodiment shown is by way of illustrative example only. For example the engine may be water cooled and have oil cooling for the rotor and the cylinders 28 may be aligned about the rotor 27, the connecting rods 33 of each piston pair being offset. In the transmission system, the spring-loaded hub 74 may be provided to connect the ring gear 68 and the driving gear 72 to the

output shaft 60.

Various other changes and modifications may be made to the embodiment described and illustrated without departing from the scope of the present invention.