Rotary piston machine

Abstract: A rotary piston and cylinder device (1) comprising a rotor (11) and a stator (7), the stator (7) at least partially defining an annular cylinder space (9), the rotor (11) comprising a rotor body and at least one piston (13) fixedly depending from the rotor body and which is moved circumferentially through the annular cylinder space (9) on rotation of the rotor (11) relative to the stator (7), the rotor body being sealed relative to the stator (7), and a cylinder space shutter means (3) which is capable of being moved relative to the stator to a closed position in which the shutter means partitions the annular cylinder space (9), and to an open position in which the shutter means (3) permits passage of the at least one piston. The rotary piston and cylinder device (1) can be arranged to operate as an internal combustion engine, a fluid pump, an hydraulic motor/actuator or a turbine replacement.

Description: This invention relates to rotary piston and cylinder devices which may be, for example, in the form of an internal combustion engine, or a pump such as a supercharger or fluid pump, or as an expander such as a hydraulic motor or turbine replacement. The term 'piston' is used herein in its widest sense to include, where the context admits, a partition capable of moving relative to a cylinder wall, and such partition need not generally be of substantial thickness in the direction of relative movement but can often be in the form of a blade. FR 2660364 discloses a rotary piston and cylinder device in which radially inwardly extending pistons are caused to move through an annular cylinder space. A shutter disc is provided which serves to partition the annular cylinder space twice. Such an arrangement is in practice difficult to realise so as to avoid the rotating disc impeding the passage of the pistons. According to one aspect of the invention there is provided a rotary piston and cylinder device comprising a rotor and a stator, the stator at least partially defining an annular cylinder space, the rotor is in the form of a ring, and the rotor comprising at least one piston which extends generally radially inwardly from the rotor ring into the annular cylinder space, the stator being positioned internally of the ring, in use the at least one piston is moved circumferentially through the annular cylinder space on rotation of the rotor relative to the stator, the rotor body being sealed relative to the stator, and the device further comprising cylinder space shutter means which is capable of being moved relative to the stator to a closed position in which the shutter means partitions the annular cylinder space, and to an open position in which the shutter means permits passage of the at least one piston, the cylinder space shutter means comprising a shutter disc, the device being characterised in that the shutter disc passes through the cylinder space only once. The stator may have portions which extend generally radially outwardly beyond the ring if desired. Preferably the shutter disc presents a partition which extends substantially radially of the annular cylinder space. Although in theory the shutter means could be reciprocable, it is much preferred to avoid the use of reciprocating components, particularly when high speeds are required, and the shutter means is preferably at least one rotary shutter disc provided with at least one aperture which in the open condition of the shutter means is arranged to be positioned substantially in register with the circumferentially-extending bore of the annular cylinder space to permit passage of the at least one piston through the shutter disc. Preferably the at least one aperture is provided radially in the shutter disc. Preferably the rotor is adapted to receive the shutter disc. The shutter disc is preferably driven from the rotor through a suitable transmission means. Preferably the axis of rotation of the rotor is not parallel to the axis of rotation of the shutter disc. Most preferably the axis of rotation of the rotor is substantially orthogonal to the axis of rotation of the shutter disc. Preferably the piston is so shaped that it will pass through an aperture in the moving shutter means, without balking, as the aperture passes through the annular cylinder space. The rotor body is preferably rotatably supported by the stator rather than relying on co-operation between the pistons and the cylinder walls to relatively position the rotor body and stator. It will be appreciated that this is distinct from a conventional reciprocating piston device in which the piston is maintained coaxial with the cylinder by suitable piston rings which give rise to relatively high friction forces. The rotor ring is preferably rotatably supported by suitable bearing means carried by the stator. The annular cylinder space maybe divided into a plurality of annular cylinder spaces. Preferably there is at least one piston in each cylinder space. Preferably the communication means is provided between the cylinder spaces which comprises at least one transfer passage. The transfer passage or passages may be provided internally or externally of the stator, or internally or externally of the rotor. At least one of the transfer passages may be valved by the shutter means. In one embodiment the annular cylinder space is divided into two annular cylinder spaces by the inclusion of a circumferentially-extending central wall in the stator. A respective piston is provided in each cylinder space. One annular cylinder space defines an induction/compression space, and the other cylinder space defines a combustion/exhaust space. The central wall has formed therein a transfer passage which provides a communication means between one annular cylinder space on one side of the shutter disc and the other annular cylinder space on the other side of the shutter disc. The transfer passage is shaped so that as the aperture of the shutter disc passes through the transfer passage, the aperture acts as a valve therein. There are many advantages to such an engine design. The lack of a complex valve train and the fact that it has only two moving parts should reduce frictional losses. Since the induction/compression and combustion/exhaust stages are physically separated it is possible that the former could be cooled to a greater extent, and energy would be returned to the gas from the walls of the combustion side once the compressed gas had been transferred between the cylinder spaces. Primarily this would increase the efficiency of the cycle, but it would also assist with combustion side cooling. A relatively narrow transfer passage may act as a venturi, allowing direct injection of fuel into the compressed gas (from an injector on the combustion side of the transfer passage) at a lower pressure than would otherwise be necessary. Direct injection may allow a higher compression ratio to be used (and hence increase the engine efficiency). The energy expended in fuel pressurisation may be reduced by having a split injection system in which part of the fuel is injected into the inlet port (in which the gas that is injected into is around atmospheric pressure) and the rest of the fuel needed to form a combustible mixture is injected into the compressed gas in the transfer passage. This may improve fuel mixing and would still allow a high compression ratio to be used without the risk of pre-ignition that would occur if all of the fuel was added to the inlet port. The circular geometry of the engine may cause fuel to be centrifuged outwards. In the combustion side, this could possibly be controlled with an injector design, or an aerodynamic device by the injector to control amount of mixing. This would allow variable charge stratification (and hence allow power output to be varied without throttling). There are of course many modifications which could be introduced without deviating from the scope of the invention. For example, we may also provide one or more transfer passages extending externally of the stator. Such a transfer passage could be valved alternatively by, or in combination with, a suitable opening in the shutter disc. Yet a further possibility is that of providing a transfer passage in the rotor which would periodically come in to register with two static ports, the static ports providing communication between the different cylinder spaces. Another possible modification would be the introduction of a second port on the induction/compression side to allow part of the induced air to be rejected. Control of the amount of air rejected would allow throttling of the device without the pumping losses associated with conventional throttles. Using this form of throttling, the compression ratio is effectively reduced, but the expansion ratio remains the same. Preferably the stator comprises at least one inlet port and at least one outlet port. Preferably at least one of the ports is substantially adjacent to the shutter means. Preferably at least one of said ports is continuously open. Alternatively at least one of said ports may be valved. Said ports maybe valved by the shutter means. Alternatively the ports may be valved by pressure-controlled valving means or other valving means. Preferably each piston comprises sealing means. Preferably the sealing means comprises at least one sealing strip. Preferably each such sealing strip is attached to the piston by means of at least one resilient member. The sealing means may, alternatively, comprise a spring seal. Preferably the sealing strip and the piston device define a recess. Preferably the piston and the sealing strip comprise angled front portions which encourage the accumulation of pressure in that region of the annular cylinder space which is adjacent to said front angled portions. Preferably the ratio of the angular velocity of the rotor to the angular velocity of the shutter disc is 1:1. In one preferred configuration the rotary piston and cylinder device is an internal combustion engine. In another preferred configuration the rotary piston and cylinder device is a fluid pump. In a further preferred configuration the rotary piston and cylinder device is a hydraulic motor/actuator. The rotary piston and cylinder device may be a turbine replacement. The rotary piston and cylinder device may be a compressor or expander. The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of an embodiment of a rotary piston and cylinder device in accordance with the invention in which the stator has been omitted for clarity, Figure 2 is a front elevation of the embodiment illustrated in Figure 1 in which the stator is shown, Figure 3 is a cross-sectional view of the embodiment illustrated in Figure 1 in which the piston has been omitted for clarity, Figure 4 is a front elevation of the outer ring and piston for the embodiment illustrated in Figures 1 to 3, and Figure 5 is a perspective view of another embodiment of a rotary piston and cylinder device in accordance with the invention in which the piston and stator have been omitted for clarity. A rotary piston and cylinder device is shown in Figures 1 to 4. The device 31 illustrated comprises an outer ring 56, a shutter disc 58 and stator 60. The stator 60 comprises a roof 62 and walls 64a and 64b. Said roof and said walls extend circumferentially around an axis of rotation Y-Y. The walls 64a and 64b comprise two ports 80 and 81, respectively, which are located adjacent to the shutter disc 58. The inlet port and the outlet port may equally be provided in the roof 62. The outer ring 56 is rotatably mounted to said stator 60 by suitable bearing means. The outer ring 56 is provided with an inner surface 68 which is substantially arcuate in outline so as to accommodate the shutter disc 58. The inner surface 68 and stator 60 define an annular cylinder space 70. Said annular cylinder space is sealed by means of sealing rings (not shown). Said outer ring further comprises a piston 72 which extends generally inwardly of the outer ring 56. The piston 72 is provided with inner surface portion 72a and is shaped so as to allow for the movement of said inner surface portion on the roof 62. The shutter disc 58 is provided with an aperture 76 and the shutter disc is mounted within the outer ring 56 so that the shutter disc passes once through the annular cylinder space 70 as illustrated. The shutter disc has an axis of rotation X-X. Suitable transmission means are provided (not illustrated) between the outer ring 56 and the shutter disc 58 so that they both rotate at the same angular velocity. The piston is so shaped that when both the ring and the shutter disc rotate at (substantially) the same angular speed the piston is able to pass through the aperture without prohibiting interference. The effective size of the aperture is dependent on the thickness of the piston. However, the ratio of the angular velocities of the rotor to that of the shutter disc may be 1:2 if two diametrically opposed pistons were provided. The embodiment described may be used as a pump with an inlet port 80 and an outlet port 81. In this case, the outer ring 56 would be driven by suitable driving means (not shown). During operation the outer ring 56 and the shutter disc 58 would rotate and the stator 60 would remain stationary. As an alternative embodiment (not shown), the inlet and outlet ports may be provided in outer ring 56 and may be valved by openings provided in a static outer housing. As a further alternative one or more of the inlet or outlet ports may be valved by a modification to the shutter disc 58. However other suitable valving means may be used. As yet a further alternative the inlet and outlet ports may be provided in the outer ring 56 so that more conventionally the outer ring 56 remains stationary and the rotating shutter disc 58 and the stator 60 rotate inside the outer ring 56. One advantage of the inventive rotary piston and cylinder is that of compactness. The lack of reciprocating motions means that acceleration forces impose less of an rpm limit on the device. The fact that there are only two moving parts may reduce frictional losses (increasing efficiency) and wear (increasing working life). The rotary piston and cylinder device 31 could be adapted to be used as an hydraulic motor. Alternatively, if appropriate communication means were provided between different parts of the annular cylinder space 70, the device could be used as a combustion engine. A further embodiment in accordance with the invention is shown in Figure 5. In this case the angle between the axis Y-Y of rotation of the rotor ring and the axis B-B of rotation of the shutter disc is 45°. One advantage of this is that the piston attached to the outer ring is less angled with respect of the axis of rotation of the outer ring which reduces the side thrust on the outer ring. Another advantage of the embodiment shown in Figure 5 is that the external dimensions are further reduced compared to the rotary piston and cylinder device 31. The device could be used as a pump or hydraulic motor/actuator or as a compressor or expander with the addition of valving means. As a further alternative, a number of the devices set forth could be combined, or the cylinder space divided to form multi-stage machines. These could take the form of a combustion engine, if appropriate valving and communication means were provided, or other machines such as multi-stage compressors.

Claims: A rotary piston and cylinder device (31) comprising a rotor and a stator (60), the stator (60) at least partially defining an annular cylinder space (70), the rotor is in the form of a ring (56), and the rotor comprising at least one piston which extends generally radially inwardly from the rotor ring (56) into the annular cylinder space (70). the stator (60) being positioned internally of the ring (56), in use the at least one piston (72) is moved circumferentially through the annular cylinder space (9) on rotation of the rotor relative to the stator (60), the rotor body being sealed relative to the stator, and the device further comprising cylinder space shutter means (58) which is capable of being moved relative to the stator to a closed position in which the shutter means partitions the annular cylinder space, and to an open position in which the shutter means permits passage of the at least one piston, the cylinder space shutter means comprising a shutter disc and the device being characterised in that the shutter disc passes through the cylinder space only once. A rotary piston and cylinder device (31) according to claim 1 in which the shutter disc (58) presents a partition which extends substantially radially of the annular cylinder space (70). A rotary piston and cylinder device (31) according to any preceding claim in which the shutter disc (58) is a rotary shutter disc provided with at least one aperture (76) which in the open condition of the shutter means is arranged to be positioned substantially in register with the circumferentially extending bore of the annular cylinder space (70) to permit passage of the piston (72) through the shutter disc. A rotary piston and cylinder device (31) according to claim 3 in which the at least one aperture (76) is provided radially in the shutter disc (58). A rotary piston and cylinder device (31) according to claim 4 in which the axis of rotation of the rotor is not parallel to the axis of rotation of the shutter disc (58). A rotary piston and cylinder device (31) according to claim 5 in which the axis of rotation of the rotor is substantially orthogonal to the axis of rotation of the shutter disc (58). A rotary piston and cylinder device (31) according to any preceding claim in which the annular cylinder space (70) is divided into a plurality of annular cylinder spaces. A rotary piston and cylinder device (31) according to claim 7 in which there is at least one piston in each cylinder space. A rotary piston and cylinder device (31) according to either claim 7 or claim 8 in which communication means is provided between the annular cylinder spaces. A rotary piston and cylinder device (31) according to claim 9 in which the communication means comprises at least one transfer passage. A rotary piston and cylinder device (31) according to claim 10 in which the at least one transfer passage is provided internally of the stator (60). A rotary piston and cylinder device (31) according to claim 10 in which the at least one transfer passage is provided externally of the stator (60). A rotary piston and cylinder device (31) according to any one of claims 10 to 12 in which the at least one transfer passage is valved by the shutter means (58). A rotary piston and cylinder device (31) as claimed in any preceding claim, which comprises an inlet port (80) and an outlet port (81) which are provided in the rotor ring (56). A rotary piston and cylinder device (31) as claimed in claim 14, in which at least one of the inlet port (80) and the outlet port (81) are valved by openings in the stator. A rotary piston and cylinder device (31) as claimed in any of claims 1 to 13, in which the device comprises a valved port.

Inventors: LINDSEY STEPHEN FRANCIS, LINDSEY, STEPHEN FRANCIS
Applicants: LINDSEY STEPHEN FRANCIS, LINDSEY, STEPHEN FRANCIS
Application year: 1999
Main classification: F01C3
IPC codes: F01C3