THIS INVENTION relates to a rotary engine and more particularly to a rotary engine having a rotary piston housed in a cylindrical piston housing.

Internal combustion engines using reciprocating pistons require the reciprocating motion of the piston to be converted to rotary motion using a crank shaft and connecting rod arrangement. A rotary engine such as a Wankel engine requires gearing to be interposed between the rotating piston and the drive shaft from the engine due to the eccentric rotation of the piston itself.

It is an object of the present invention to provide a rotary piston engine which delivers direct drive to a drive shaft.

Accordingly, the present invention provides a rotary engine comprising: a cylindrical piston housing; a piston mounted for rotation within the piston housing and defining between the piston and the housing at least one space; means for dividing the space into a compression chamber and an expansion chamber; means for chanelling the compressed fuel/air mixture from the compression chamber to a combusion chamber; ignition means to ignite the fuel/air mixture in the combusion chamber; and a propulsion chamber into which the combusted fuel/air mixture expands, thereby exerting a driving force on the piston.

In order that the present invention may be more readily understood, embodiments thereof will now be

described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 shows an exploded perspective view of the component parts of a rotary piston engine embodying the present invention;

Figure 2 shows the engine of Figure 1 at the start of an induction stroke;

Figure 3 shows the engine of Figure 1 at the start of a compression stroke;

Figure 4 shows the engine of Figure 1 during the compression stroke;

Figure 5 shows the engine of Figure 1 nearing the end of the compression stroke and at the start of the power stroke;

Figure 6 shows the engine of Figure 1 during the power stroke;

Figure 7 shows the engine of Figure 1 during the exhaust stroke immediately preceeding the induction stroke shown in Figure 2;

Figures 8 and 9 show details of an expansion chamber;

Figure 10 diagramatically illustrates an assembly of four rotary pistons on a single drive shaft; and

Figure 11 is a cross-sectional view illustrating another rotary engine embodying the present invention.

Referring to Figure 1, a rotary piston engine embodying the present invention comprises a cylindrical piston housing 1 and a rotatable piston 2 mounted therein. The rotatable piston 2 comprises an oval block having an upper and a lower flat surface 3, 4 and a generally curved side wall 5 which defines the shape of the oval and presents two axially extended corners 6 defining corner lobes 6 at diametrically opposed locations of the piston 2. The piston 2 is dimensioned to fit within the piston housing such that the two opposing corner lobes 6 of the piston side wall 5 are in contact with the housing 1.

A rotatably mounted drive shaft 7 having an octagonal cross-section passes through and is a close fit within an octagonal aperture 8 formed in the centre of the piston 2. The piston 2 is thus rotatable with the drive shaft 7 about the axis of rotation of the drive shaft 7. In the present example shown in the Figures, the piston 2 rotates in a clockwise direction.

The piston housing 1 is closed at each end by an annular closure plate (not shown) , the outer periphery of which encloses all the component parts of the piston housing 1, which component parts will be described in detail below, and the inner periphery of which has a diameter which is only slightly larger than the cross- corner distance of the octagonal aperture 8 in the piston, thereby allowing free rotation of the octagonal drive shaft 7.

The rotary piston 2 is sealed against the upper and lower annular closure plates by means of brush rings 9 which act as a gasket between the piston 2 and the upper and lower annular closure plates. Lubrication of the brush rings 9 is envisaged to be by the fuel/air mixture.

Two substantially semi-cylindrical propulsion chambers 10 are formed within the piston 2 at diametrically opposite positions adjacent the respective corner lobes 6. During rotation of the piston 2, the semi-cylindrical propulsion chambers lead the respective corner lobes.

Each propulsion chamber 10 extends into the piston 2 from a rectangular aperture 11 at the surface of the side wall and terminates at an end wall 12 within the piston 2, which end wall 12 is substantially parallel to the piston side wall 5, thus defining a tongue 13 between the piston side wall 5 and the propulsion chamber end wall 12. A free edge 14 of the tongue 13 contacts the internal cylindrical wall la of the piston housing 1 in a position leading the adjacent corner lobe 6 of the piston 2.

The piston 2 within the housing 1 defines two separate spaces, the first space 15 being bounded by the upper and lower annular closure plates, the internal cylindrical wall la of the piston housing 1 and a first portion 5a (see Figure 2) of the piston side wall 5 extending from one of the corner lobes 6 to the free edge 14 of the lagging tongue 13. The second space 16 is identical to the first space 15 in shape and is bounded by the upper and lower annular closure plates, the cylindrical wall la of the piston housing and a second portion of the piston side wall 5b (see Figure 2) extending from the other corner lobe 6 to the free edge 14 of the other lagging tongue 13.

A spring loaded gate 17 is located in each semi- cylindrical propulsion chamber 10. The gate 17 is hinged along the free edge 14 of the tongue 13 for movement between the rectangular opening 11 of the propulsion chamber 10 (the closed position) and the end wall 12 of the

propulsion chamber 10 (the open position) . A bowed compression spring 18 is located between the end wall 12 and the gate 17 to bias the gate 17 toward the opening 11 of the propulsion chamber. In fact, as can be seen in Figures 8 and 9, the gate 17 is actually forced against the internal wall la of the piston housing 1 by the spring 18.

The components of the piston housing 1 comprise a pair of fuel/air mixture ports 19, a pair of exhaust valves 20, a pair of spark plugs 21 and a pair of partition rollers 22. Referring to the Figures, the components are housed within the wall of the piston housing 1 and are positioned radially around the piston housing 1 at the following angular locations: the first fuel/air mixture port 19 at 0°; the first spark plug 21 at substantially 90°; the first partition roller 22 at substantially 110°; the first exhaust valve 20 at 135°; the second fuel/air mixture port 19 at 180°; the second spark plug 21 at substantially 270°; the second partition roller 22 at substantially 290°; and the second exhaust valve 20 at 315°. The fuel/air mixture ports 19 , the spark plugs 21 and the exhaust valves 20 are all recessed back from the internal wall la of the piston housing 1 so as not to interfere with the rotation of the piston 2. Each spark plug 21 is housed in a recess 23 which constitutes a combustion chamber 23 of the engine.

The fuel/air mixture ports 19 are operable to supply into the spaces 15, 16 a fuel/air mixture for combustion, preferably by injection. The exhaust valves 20 are normally closed and are openable to exhaust a combusted fuel/air mixture. The spark plugs 21 are operable to ignite a compressed fuel/air mixture. These operations are timed to occur at predetermined moments during the rotation of the piston 2. The drive shaft 7 is provided with timing

devices (not shown) for controlling these operations such that, when the piston 2 has been rotated to the correct position, the respective timing device is triggered.

The partition rollers 22 comprise solid cylindrical blocks which are housed in recesses 24 in the piston housing 1. The partition rollers 22 are rotatable whilst being held in the recesses 24. The partition rollers 22 are biased out of the recesses 24 by compression springs (not shown) , thus pushing the partition rollers 22 into contact with the rotatable piston 2 and causing the partition rollers 22 to rotate during rotation of the piston 2 whilst maintaining a sealed contact with the rotatable piston 2. The partition rollers 22 follow the contours of the piston 2 as the piston 2 rotates.

As can be seen in Figures 3 to 5, the rollers 22 divide each of the first and second spaces 15, 16 into two chambers, namely an expansion chamber 25 leading each partition roller 22 and a compression chamber 26 lagging each partition roller 22.

The wall of the piston housing 1 is of sufficient thickness to be formed with coolant conduits 27 therein. The coolant conduits 27 are located radially around the piston housing 1 and may be filled with a coolant such as water or the like. Preferably, the coolant is continually circulated through the cooler conduits 27.

The operation of the engine is best understood with reference to Figures 2 to 7 which show a one half revolution of the piston 2. The subsequent half revolution corresponds to the first half revolution.

The engine is started by a conventional starter motor (not shown) . As shown in Figure 2, with the gates 17 in their closed positions located directly over the exhaust valves 20, the first and second spaces 15, 16 are at their maximum volumes. At this stage a fuel/air mixture is injected into the first and second spaces 15, 16, through the fuel/air mixture ports 19. The piston 2 rotates clockwise with the octagonal drive shaft 7, and the partition rollers 22 rotate following the movement of the piston 2 and move toward the respective one of the first and second spaces 15, 16.

In Figure 3 the piston 2 has rotated through 45° from its position in Figure 2. The gates 17 are now opposite the fuel/air mixture ports and the partition rollers 22 have entered the first and second spaces 15, 16 and begin to divide each of the first and second spaces 15, 16 into a respective expansion chamber 25 and a respective compression chamber 26.

Figure 4 shows the piston 2 of Figure 3 rotated through a further 45°. The partition rollers 22 now divide the first and second spaces 15, 16 equally into an expansion chamber 26 experiencing sub atmospheric pressure and a compression chamber 25 in which the fuel/air mixture is being compressed. The fuel/air mixture cannot escape under the free edges 14 of the tongues 13 which form a sealing contact with the piston housing internal wall la.

Figure 5 shows the piston 2 of Figure 4 rotated through a further 45°. The gates 17 are now directly opposite the spark plugs 21 and the compressed fuel/air mixtures are compressed into the recesses 23 in which the spark 21 plugs are mounted. These recesses 23 are separate from and not in communcation with the compression chambers

26. Figures 8 and 9 show details of the gate 17, spark plug la and partition roller configuration at two successi ve instants immediately before the position shown in Figure 5. Referring to Figures 8 and 9, as piston 2 moves from the position show in Figure 4 to the position shown in Figure 5 the compressed fuel/air mixture is channeled into the recess 23 occupied by the spark plug 21 whilst the tongue passes over the spark plug recess 23.

The spark plugs 21 are activated by a timing device on the octagonal drive shaft 7 causing ignition of the compressed fuel/air mixture in the spark plug recess 23.

Ignition of the compressed fuel/air mixture is shown in Figure 6 and, as can be seen from this drawing, the combusted fuel/air mixture rapidly expands pushing the gate 17 against the spring 18 into the open position. The opening forces on the gate 17 create a tangential force on the piston 2 at the face of the gate 17, thus exerting a torque on the drive shaft 7. The expanding gases fill the spaces at the opening 11 of the semi-cylindrical chamber 10 and rotate the piston 2 further.

In Figure 7 the piston 2 has moved through a further 45° from that shown in Figure 6 and the openings 11 of the propulsion chambers 10 are opposite the exhaust valves 20. The exhaust valves 20 are, at this stage, opened by the timing devices on the octagonal drive shaft 7 and the combusted fuel/air mixture is allowed to escape through the exhaust valves 20. This releases the pressure on the gates 17 and the springs 18 thereby return the gates 17 to their closed positions so that they come back into contact with the internal wall la of the piston housing 1. At the same time, as shown in Figures 7 & 2, the induction stroke begins again with fuel/air mixtures being injected

96/14493 PCMB95/00980

into the first and second spaces 15, 16 which are below atmospheric pressure. As previously mentioned, the subsequent half revolution of the piston 2 corresponds to the above described half revolution.

Because the octagonal aperture 8 of the rotary piston 2 keys the piston into the octagonal shaft 7, not only is low speed torque provided, but the drive shaft 7 can be used as a timing device by welding studs or the like to the faces of the shaft 7 for activating the spark plugs 21, the fuel/air mixture ports 19 and the exhaust valves 20.

The above described rotary engine is a four stroke cycle engine but can be converted to a two stroke cycle.

Only a very small portion of the working parts of the engine are exposed to the ignition of the fuel/air mixture, i.e. the recesses for the spark plugs 23 comprising the combustion chambers 23 and the cylindrical propulsion chambers 10. Thus, these areas may be specially treated, whereas reciprocating piston engines and Wankel engines combine the combustion chamber with the compression chamber, thereby creating an environment that generates nitrogen oxides (NOx) .

A four piston rotary piston engine produces sixteen power strokes in a 360° rotation of the drive shaft whilst a reciprocating piston engine produces two power strokes from a similar set up. It is, therefore, envisaged that a rotary piston engine embodying the present invention may produce 6 to 8 times the torque of a reciprocating piston engine of similar configuration.

The rotary piston engine described with reference to Figures 1 to 9 is for use in an engine comprising four such pistons (see Figure 10) so therefore an octagonal shaft is used. In engines in which two drive pistons are used, either a square or octagonal shaft may be used and in cases where three drive pistons are required an hexagonal shaft may be used. The sides of the shaft are instrumental to the timing of the induction, compression and ignition strokes.

In the case where four drive pistons are used, the power strokes of each of the four pistons are staggered such that they occur at regular intervals to one another.

In the embodiment of the invention shown in Figure 11, the combusted fuel/air mixture exhausted through the exhaust valves 20 is injected in a supercharged state to a further auxiliary rotary piston engine 30. Any fuel/air mixture which has not been fully combusted may be combusted therein so that further power may be derived from the engine and so that a final clean exhaust may be discharged from the auxiliary engine 30. The exhaust is preferably discharged through a catalytic converter 31 and silencer to the atmosphere.

As well as simply passing the combusted fuel/air mixture from the exhaust valves 20 of the main piston engine to an auxiliary piston engine 30, it is possible to re-oxygenate the exhausted mixture, prior to introduction to an auxiliary piston enginer 30.

It is envisaged that an engine embodying the present invention will have reduced vibration and exhaust problems compared to known reciprocating piston engines and rotary piston engines.