WO2008059271A1

WO2008059271A1 - Engine

Info

Publication number: WO2008059271A1
Application number: PCT/GB2007/004389
Authority: WO
Inventors: Patrick Kenlock
Original assignee: Environmental Manufacturing Llp
Priority date: 2006-11-15
Filing date: 2007-11-15
Publication date: 2008-05-22
Also published as: GB0622796D0

Abstract

A rotary internal combustion engine (1) comprising a first rotor (4) and two or more piston rotors (3). The first rotor comprises at least one chamber (42) and each piston rotor comprises at least one piston (32). In use, the piston rotors are out phase for at least part of their cycle of operation. The engine (1) includes optional sealed piston channels formed by cooperating surfaces of a housing, the piston rotors along which the at least one piston passes in use. The or each piston rotor (3) may also include a central sealing member (34), for example a bush which is rotatably mounted to a core portion of the piston rotor to provide a portion of the sealed piston channel.

Description

ENGINE

The present invention relates to an engine, for example a rotary engine and specifically, but not exclusively, to a rotary internal combustion engine.

Rotary internal combustion engines are well are known in the art, and there are several designs in existence.

A well-known rotary engine is the "Wankel engine", which includes a rotor which rotates and shifts inside a combustion housing. The combustion housing comprises a cavity in the shape of a substantially oval cylinder while the rotor has a substantially triangular (Reuleux triangle) periphery. The single rigid triangular rotor is synchronised by gears with the housing and driven by a crankshaft. The corners of the rotor seal against the periphery of the housing thereby defining separate chambers of different size with the rotor. As the rotor turns, its motion, shape and the shape of the housing are such that each side of the rotor approaches and moves away from the wall of the housing, thereby compressing and expanding the air inside the combustion chamber, so as to provide a combustion cycle similar to the standard reciprocating engine.

In the so-called 'Quasiturbine' engine, an oval housing surrounds a four-sided articulated rotor which turns and moves within the housing. The sides of the rotor seal against the sides of the housing, and the corners of the rotor seal against the inner periphery, dividing it into four chambers. In contrast to the Wankel engine where the crankshaft moves the rotary piston face inward and outward, the Quasiturbine rotor face rocks back and forth with reference to the engine radius, but stays at a constant distance from the engine centre at all time, producing only pure tangential rotational forces. Because the Quasiturbine has no crankshaft, the internal volume variations do not follow the usual sinusoidal engine movement, which provides very different characteristics from the reciprocating piston engine or the Wankel engine.

As the rotor turns, its motion and the shape of the housing cause each side of the housing to get closer and further from the rotor, compressing and expanding the chambers in a manner corresponding to the "strokes" in a reciprocating engine. However, whereas a four stroke cycle engine produces one combustion stroke per cylinder for every two revolutions, that is to say one half power stroke per revolution per cylinder, the four chambers of the Quasiturbine rotor generate four combustion "strokes" per rotor revolution; this is eight times more than a four-stroke piston engine.

US3353519 discloses a further rotary petrol engine having a driving rotor and a driven rotor for engaging the driving rotor. The driving rotor includes four equidistant combustion slots extending radially inward which engage four equidistant cylinder members connected to the piston rotor.

US6877476 discloses a rotary engine design having an indexer and two opposing pin wheels for engaging the indexer. The indexer has four equidistant combustion slots extending radially inward which engage four equidistant piston pins fixedly connected to each of the pin wheels. Rotation of the pin wheels causes the pins to engage the indexer, move along the combustion slots to effect the combustion cycle and disengage the indexer as the next piston enters the next combustion chamber. Synchronisation of the pin wheels is effected using a belt. The cycles of engagement of the piston pins mounted on the opposing pin wheels are in phase with each other.

Consequently, each rotation of the indexer results in four power strokes and each power stroke is effected by opposing pin wheels, which provides a higher power output for each power stroke than the engine of US3353519.

US3472210 discloses a rotary internal combustion engine having a socket wheel and a lobe wheel. The socket wheel includes combustion sockets formed therein and the lobe wheel includes pistons mounted thereto. The engine also includes a further socket wheel and a further lobe wheel for synchronising the rotation of the piston rotor relative to the combustion rotor.

It is a non-exclusive object of the present invention to provide an improved engine. It is a further or alternative non-exclusive object of the invention to provide an alternative engine which provides improved engine balance, for example balance of power output and/or synchronisation of components.

According to a first aspect of the invention, there is provided a rotary internal combustion engine comprising a first rotor and two or more piston rotors, the first rotor comprising at least one chamber and each piston rotor comprising at least one piston, wherein the piston rotors are arranged to rotate to engage the pistons with the at least one chamber and wherein the piston rotors are out phase for at least part of their cycle of operation.

At least one piston rotor may comprise a central sealing member.

The engine may further comprise a housing. The housing and the at least one piston rotor may cooperate to provide a sealed piston channel along which the at least one piston passes in use. The central sealing member may be free to rotate with respect to the housing and with respect to the at least one piston rotor. Additionally or alternatively, the at least one piston rotor may comprise two plates. The at least one piston may be mounted between the plates and/or the sealing member may be mounted between the plates and preferably rotatable therewith.

According to a second aspect of the invention, there is provided a rotary engine comprising a housing, a first rotor and at least one piston rotor, the first rotor comprising at least one chamber, the or each piston rotor comprising a central sealing member and at least one piston, wherein the housing and the piston rotor cooperate to provide a sealed piston channel along which the at least one piston passes in use, the central sealing member being free to rotate with respect to the housing and with respect to the piston rotor.

The or each piston rotor may comprise two plates and the at least one piston may be mounted between the plates. The housing, plates and sealing member may cooperate to provide a sealed piston channel along which the at least one piston passes in use.

According to a third aspect of the invention, there is provided a rotary engine comprising a housing, a first rotor and at least one piston rotor, the first rotor comprising at least one chamber, the or each piston rotor comprising a central sealing member, two plates and at least one piston mounted between the plates, the sealing member being mounted between the plates and rotatable therewith, wherein the housing, plates and sealing member cooperate to provide a sealed piston channel along which the at least one piston passes in use.

The central sealing member may comprise a central sealing bush. The at least one piston may be rotatably mounted to the piston rotor, for example such that it contacts the central sealing member in use. The central sealing member may be arranged to rotate in response to a contacting rotation of the at least one rotatably mounted piston.

The at least one piston rotor may comprise two or more piston rotors.

Preferably, the cycle of engagement of the piston rotors with the first rotor are out of phase with respect to one another.

The first rotor may comprise a plurality of chambers. The at least one piston from a first of the two or more piston rotors may engage a first chamber and the at least one piston from a second of the two or more piston rotors may engage a further chamber. In use, at least one piston may be in engagement with one of the chambers at any given point of rotation of the first rotor.

The chambers may be located about the first rotor preferably equidistantly. The or each chamber may be mounted or formed in, on or to the first rotor. The or each chamber may be radially aligned in the first rotor.

The or each piston rotor may comprise a plurality of pistons. The engine may comprise three or more piston rotors. The piston rotors may be located around the first rotor, preferably equidistantly.

The or each piston may be in the shape of a cylinder, sphere or of frusto-spherical shape. The or each corresponding chamber may be of complementary shape to the or each piston. The or each piston rotor may comprise two plates and one of the plates may comprise a hole therethrough of size and shape slightly larger than the maximum peripheral size and shape of the piston, the piston being slideably receivable therein.

According to a fourth aspect of the invention, there is provided an engine having at least one chamber and at least one piston rotor, the piston rotor comprising at least one piston, wherein the piston rotor comprises a hole of size and shape slightly larger than the maximum peripheral size and shape of the piston, the piston being slideably receivable therein, the rotation of the rotor being arranged to cause reciprocal motion of the piston along the combustion chamber.

The at least one piston may be rotatable with respect to the at least one piston rotor. The at least one piston rotor may comprise two plates and the at least one piston may be mounted between the plates. The hole may be through one of the plates and the other of the plates comprises a further hole therethrough of size and shape slightly larger than that of the end of the piston, the piston being slideably receivable therein.

The at least one piston rotor may comprise two or more piston rotors, each piston rotor comprising a timing gear for synchronising rotation between the piston rotors.

The engine may further comprise a first gear having a first lobe portion and a second gear having a second lobe portion, the first gear being operably connected to the first rotor and the second gear being connected to at least one of the piston rotors, wherein rotation of the first rotor causes the first lobe portion to cooperate with the second lobe portion to effect rotation of the second gear. The profiles of the first and second lobe portions may be such that the mechanical advantage of the first gear with respect to the second gear varies with the angular position thereof. Additionally or alternatively, the first gear and the first rotor may be rotatable about a first axis, wherein the profiles of the first and second lobe portions are such that the radial position of the area of contact between the first and second lobe portions with respect to the first axis of rotation varies with the angular position of the first lobe portion.

The second gear and piston rotor may be rotatable about a second axis. The profiles of the first and second lobe portions may be such that the radial position of the area of contact between the first and second lobe portions with respect to the second axis of rotation varies with the angular position of the second lobe portion. In use, the angular velocity of the first gear may vary with a constant angular velocity of the second gear.

The engagement of the first and second lobe portions may be arranged to match substantially the engagement between the first rotor and the piston rotor.

The first rotor may comprise a substantially circular disc. The chamber or chambers may comprise slots through the thickness of the circular disc. The chamber or chambers may comprise slots through the thickness of the circular disc.

The engine may further comprise means to inject fuel into the or each chamber and may further comprise timing means arranged to control the fuel injection means and thereby control the injection of fuel into the or each combustion chamber.

The engine is preferably an internal combustion engine such as a compression ignition internal combustion engine. According to a further aspect of the invention, there is provided a method of checking and/or replacing a piston of a rotary engine comprising the steps of: removing a portion of the housing of the engine and removing the piston through a piston rotor.

Any combination of two or more of the individual features disclosed above and/or herein may be provided without departing from the scope of the invention.

One embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1a is a plan view of a part of an engine according to the invention showing a first piston at top dead centre in a first combustion slot;

Figure 1 b is a plan view of the engine of Figure 1 a at a different position in the combustion cycle;

/ Figure 1c is a plan view of the engine of Figure 1a at a yet a different position in the combustion cycle;

Figure 2a is a plan view of the central crankcase plate of the housing;

Figure 2b is a plan view of the lower outer crankcase plate of the housing;

Figure 2c is a plan view of the lower sealing plate of the housing; Figure 3a is a plan view of one of the piston rotors of the engine with the top piston plate omitted;

Figure 3b is a plan view of the combustion rotor of the engine;

Figure 4 is a cross-sectional view of the piston rotor in the housing along line A-

A of Figure 1c; Figure 5 is a perspective view of the engine with the outer crankcase plates, sealing plates and upper transfer valve gears removed; Figure 6a is a perspective view of the underside of the engine with the housing and lower piston plates removed;

Figure 6b is a plan view of the engine showing the profile of the lobed gears; Figure 6c is a perspective view of the lobed gears; Figure 7 is a schematic drawing showing the operation of the engine;

Figure 8 provides an acceleration curve for the engine;

Figure 8a, b and c provide indications of the movement corresponding to the acceleration curve of Figure 8.

Referring to Figures 1a, 1b and 1c there is shown a compression ignition engine 1 of the invention which includes a housing 2, three piston rotors 3, a combustion rotor 4 and three transfer valves 5.

The housing 2 includes a central crankcase plate 21 , two outer crankcase plates 22a, 22b and two sealing plates 23a and 23b (as shown in Figure 4).

The central crankcase plate 21 , shown in more detail in Figure 2a, is circular in plan with a substantially constant thickness and includes a central hole 211 , three secondary holes 212, three tertiary holes 213, three air inlet ports 214, three exhaust ports 215 and a series of bolt holes 216. The central 211, secondary 212, tertiary 213 and bolt holes 216 are all substantially circular in plan and are formed through the thickness of the central crankcase plate 21.

The secondary holes 212 are equally spaced from the centre of the central crankcase plate 21 at 120 degree intervals and overlap the central hole 211. A first of the corners 212a is formed by the overlap of each secondary hole 212 with the central hole 211 and is chamfered. The tertiary holes 213 are equally spaced from the centre of the central crankcase plate 21 at 120 degree intervals. One tertiary hole 213 overlaps each secondary hole 212. One of the corners 213a formed by the overlap of each tertiary hole 213 with its respective secondary hole 212 includes a reverse fillet or arcuate chamfer.

The air inlet ports 214 are formed on the outer circumferential surface of the central crankcase plate 21 , which can be seen in Figure 5. Each air inlet port 214 terminates at one of the aforementioned arcuate chamfered corners 213a adjacent the tertiary hole 213, as shown in Figure 2a.

The exhaust ports 215 are also formed on the outer circumferential surface of the central crankcase plate 21 as shown in Figure 5. Each exhaust port 215 terminates at one secondary hole 212 adjacent the overlap between the secondary hole 212 and the tertiary hole 213.

The bolt holes 216 are spaced apart along the edges formed by the central 211 , secondary 212 and tertiary holes 213 and offset therefrom.

The upper outer crankcase plate 22a, shown in more detail in Figure 2b, is also circular in plan and has substantially the same diameter as the central crankcase plate 21. The upper outer crankcase plate 22a also has a substantially constant thickness and includes a central hole 221 , three secondary holes 222, three tertiary holes 223, a series of bolt holes 226, three combustion chamber inlet ports 227, three combustion chamber outlet ports 228 and three injection ports 430a. All of the aforementioned holes 221 , 222, 223, 226, 227, 228, 430a are substantially circular in plan and are formed through the thickness of the outer crankcase plate. The lower outer crankcase plate 22b is of the same configuration as the upper outer crankcase plate 22a except that it does not include combustion chamber inlet ports 227, combustion chamber outlet ports 228 and injection ports 430a.

The centres of the central 221 , secondary 222, tertiary 223 and bolt holes 226 correspond to those of the central crankcase plate 21. The diameter of the central hole 221 of the upper outer crankcase plate 22a is less than that of the central hole 211 of the central crankcase plate 21. The diameter of each secondary hole 222 is greater than the diameter of the corresponding secondary hole 212 of the central crankcase plate 21. The diameter of each tertiary hole 223 is less than the corresponding tertiary hole 213 of the central crankcase plate 21. The diameter of the bolt holes 226 are substantially the same as the corresponding bolt holes 216 of the central crankcase plate 21.

None of the aforementioned holes 221, 222, 223, 226, 227, 228, 430a in the upper outer crankcase plate 22a overlap.

The upper sealing plate 23a, shown in more detail in Figure 2c, is also circular in plan and has substantially the same diameter as the central 21 and outer 22 crankcase plates. The sealing plate 23a also has a substantially constant thickness and includes a central hole 231 , three secondary holes 232, three tertiary holes 233, a series of bolt holes 236, three combustion chamber inlet ports 237, three combustion chamber outlet ports 238 and three injection ports 430b formed through its thickness. Each sealing plate 23a, 23b also includes a plurality of seal evacuation ports 239a (shown in more detail in Figure 4). The positions and diameters of the central 231 and bolt holes 236 correspond to those of the central 21 and outer crankcase plates 22. The positions of the secondary holes 232 correspond to those of the central crankcase plate 21 and outer crankcase plates 22a, 22b but their diameter is substantially less.

The housing 2 also comprises a piston channel outlet port 24 and an exhaust inlet port 25 (shown in Figure 7). The piston channel outlet port 24 is fluidly connected to the combustion chamber inlet port 227, 237 by a pipe 241 and the combustion chamber outlet port 228, 238 is fluidly connected to the exhaust inlet port 25 by a pipe 251.

Each piston rotor 3, shown in more detail in Figures 3a and 4, includes an upper piston plate 31a, a lower piston plate 31b, pistons 32, of which two pistons 32a and 32b are shown, a piston shaft 33 and a central sealing member 34.

The piston plates 31a, 31 b are circular in plan and have substantially the same thickness. Each piston plate 31a, 31 b has two piston holes (not shown) through its thickness. The piston holes (not shown) are sized and shaped slightly larger than the maximum peripheral size and shape of each piston 32 and are marginal to the circumferential edge of the piston plate 31a, 31b located at 180 degrees about its centre. The piston plates 31a, 31 b are preferably made of hardened material, for example a hardened steel.

The pistons 32 are cylindrical in shape and preferably made of hardened material, for example a hardened steel. However, the hardness of the pistons 32 should preferably be less than the hardness of the piston plates 31a, 31 b in order to ensure that any wear occurs in the pistons 32 rather than on the piston plates 31a, 31 b. Each piston 32 is slideably received in the piston holes (not shown) of the piston plates 31a, 31 b and rotatably confined therein, more of which later. The piston shaft 33 includes two gear mounting portions 331, two bearing mounting portions 332, two sealing portions 333 and a core portion 334. The gear mounting portions 331 are preferably substantially cylindrical in shape and include a male key (not shown) protruding from the peripheral (e.g. circumferential) surface thereof. The bearing mounting portions 332 are preferably substantially cylindrical in shape with a diameter which is larger than the adjacent gear mounting portion 331. The sealing portions 333 are also preferably substantially cylindrical in shape and have a diameter which is larger than the adjacent bearing mounting portion 332. The core portion 334 of the piston shaft 33 in this embodiment is integrally formed with one of the piston plates 31a. The core portion 334 also includes a bush surface at the longitudinal centre thereof and a piston plate mounting diameter slightly greater than that of the sealing portions 333. The piston shaft 33 includes undercuts adjacent the transition in diameter of each portion thereof.

In this embodiment, the central sealing member 34 is a bush or ring made of, for example phosphor bronze having a relatively small radial thickness and an axial thickness slightly less than the distance between the two piston plates in order to allow the central sealing member 34 to rotate relative to the piston rotor 3.

As shown in Figure 3b, the combustion rotor 4 is a circular plate of substantially uniform thickness and includes a shaft 41 , four combustion slots 42 and four injection ports 43.

The combustion slots 42 extend inwardly from the circumferential edge and through the thickness of the plate and terminate with a semi-circular base. The combustion slots 42 are located at 90 degree intervals about the centre of the combustion rotor 4. The depth of each combustion slot 42 is substantially the same as the width thereof. Each injection port 43 includes an arcuate channel portion 431 , a transverse portion

432 and a radial portion 433. The arcuate channel portion 431 is shaped and positioned to have a constant radial distance from the centre of the combustion rotor 4, the reason for which is discussed below. The transverse portion 432 extends from one end of the channel portion 431 into the plate substantially perpendicular to the top surface of the combustion rotor 4 to approximately half its depth. The radial portion

433 extends from the terminal end of the channel portion 431 to the semi-circular base of the combustion slot 42.

As shown more clearly in Figures 1a to 1c and Figure 5, each transfer valve 5 is substantially circular in plan and has a substantially constant thickness. Each transfer valve 5 includes a central shaft 51 and two arcuate slots 52 through its thickness.

The engine 1 also includes upper and lower main gear assemblies, each of which consists of one central gear 61 , three piston gears 62 and three valve gears 63 (the upper main gear assembly is shown in Figure 5). The engine 1 also includes and a lobed gear assembly below the lower main gear assembly (not shown), which consists of one primary lobed gear 64 and three secondary lobed gears 65 (shown in Figures 6a to 6c). The lobed gears 64, 65 in this embodiment are relatively thick plates which are substantially circular in plan, each gear 64, 65 having four lobe shaped protrusions about their circumferential edge. The lobed gears 64, 65 are profiled such that the mechanical advantage of the secondary lobed gear 65 with respect to the primary lobed gear 64 varies with the angular position thereof.

In an assembled condition, the central crankcase plate 21 is sandwiched between the two outer crankcase plates 22a, 22b and these three plates 21 , 22a, 22b are sandwiched between the sealing plates 23a, 23b. The assembly is secured together using bolts (not shown) which pass through the bolt holes 216, 226, 236 in each of the plates 21, 22a, 22b, 23a, 23b.

The combustion rotor 4 is located in the central hole 211 of the central crankcase plate 21 such that the circumferential surface of the combustion rotor 4 seals against the inner surface of the central hole 211. The outer crankcase plates 22a, 22b seal against respective upper and lower surfaces of the combustion rotor 4. The shaft 41 passes through holes 221 in the outer crankcase plates 22a, 22b and holes 231 in the sealing plates 23a, 23b. The combustion rotor 4 is rotatably secured to the sealing plates 23a, 23b by bearings (not shown).

Each piston rotor 3 is located in one of the secondary holes 212 of the central crankcase plate 21 such that the pistons 2 seal against the inner surface of the secondary hole 212 as shown more clearly in Figure 4. Each piston plate 31a, 31b is sealed within the cavity created by the difference in diameter between the secondary hole 212 of the central crankcase plate 21, the secondary hole 222 of the relevant outer crankcase plate 22a, 22b and the secondary hole 232 of the relevant sealing plate 23a, 23b. A seal 239b is provided between each of the sealing plates 23a, 23b and the sealing portion 333 of the shaft 33. Each piston rotor 3 is rotatably secured to the sealing plates 23a, 23b by bearings 35. The pistons 32 are rotatably confined in the holes (not shown) of the piston plates 31a, 31b by the sealing plates 23a, 23b and contact the central sealing member 34 in use.

It will be appreciated that this preferable arrangement facilitates replacement of the pistons 32 without completely dismantling the engine 1. For example, the lower relative hardness of the pistons 32 as compared to the piston plates 31a, 31 b encourages any wear therebetween to take place in the pistons 32. This arrangement allows for removal, checking and/or replacement of worn pistons 32 by only requiring partial dismantling of the engine 1 by removing the upper sealing plate 23a and removing the piston 32 through the piston rotor 3.

Each transfer valve 5 is located in one of the tertiary holes 213 of the central crankcase plate 21 such that the circumferential surface of the transfer valve 5 seals against the inner surface of the tertiary hole 213. The outer crankcase plates 22a, 22b seal against respective upper and lower surfaces of the transfer valve 5. The shaft 51 passes through holes 223 in the outer crankcase plates 22a, 22b and holes 233 in the sealing plates 23a, 23b. Each transfer valve 5 is rotatably secured to the sealing plates 23a, 23b by bearings (not shown).

Figure 4 shows the sealing arrangement between the housing 2, the combustion rotor 4, the piston rotors 3 and the transfer valves 5. provides An effective seal is provided by the close proximity between the stationary and moving surfaces, where any fluid (air and/or fuel) must pass through a long and difficult path to escape through the seal evacuation ports. The result is a non-contact sealing action provided by controlling the passage of fluid through a variety of chambers by centrifugal motion and by the formation of controlled fluid vortices. This arrangement reduces wearing of the aforementioned components (2, 3, 4) during operation of the engine 1.

Referring now to Figure 5, each central gear 61 is rotatably mounted on each side of the housing 2 by bearings (not shown) and rotates independently from the combustion rotor 4. Each central gear 61 is coupled to a drive shaft 7 for connecting to a load, for example the drive train of a vehicle. One piston gear 62 is fixed to each gear mounting portion 331 of each piston shaft 33 by a key way arrangement (not shown). One valve gear 63 is fixed to each end of each transfer valve shaft 51 by a key way arrangement (not shown). The gears mesh together to ensure rotation of any one of the aforementioned piston rotors 3 or transfer valves 5 effects rotation of the others.

As shown in Figures 6a to 6c, the primary lobed gear 64 is fixed to the combustion rotor shaft 41 and one secondary lobed gear 65 is fixed to one of the piston rotor shafts 33 (see also Figure 4).

The internal surfaces of the housing 2 are configured such that they act, in conjunction with piston rotors 3, to provide sealed piston channels along which the pistons 32 pass.

As shown in Figure 4, the housing 2, piston plates 31a, 31 b and sealing member 34 cooperate to provide the sealed piston channels in this embodiment. The internal surfaces of the housing 2 are configured to provide minimal clearance to the edge of the combustion rotor 4 to so that as the combustion rotor 4 rotates each combustion chamber 42 is closed or sealed.

One of each of ports 214 and 215 is formed in each of the piston channels. One piston valve 5 communicates with each of the piston channels and separates the exhaust port 215 from the air inlet port 214 and is operable to isolate the portion of the piston channel exposed to each of the ports 214 and 215.

Figures 1a to 1c show the engine 1 at different angles of rotation of the combustion rotor 4 and piston rotors 3. In this particular embodiment, the configuration of the piston rotors 3 and the combustion rotor 4 is such that, at any angle of rotation, at least one of the pistons 32 is always at least partly in communication with one of the combustion chambers 42, thus ensuring continuous cooperation between the combustion rotor 4 and piston rotors 3 during operation. In operation, the sequence is identical (although out of phase) for each piston rotor 3 and so only one such sequence will be described. Referring now to Figures 1a to 1c in conjunction with Figure 7, the engine cycle begins with both the combustion rotor 4 and the piston rotors 3 in motion with a piston 32 passing the air inlet port 214 thereby sealing off the piston channel between the piston 32 and combustion rotor 4. The rotation of piston rotor 3 in direction A causes the air in the piston channel and in the pipe 241 to compress between the piston 32 and the surfaces of combustion rotor 4.

Air inlet port 214 allows air to be drawn into the piston channel thus preventing a vacuum between the piston 32 and piston valve 5.

As a combustion chamber 42 starts to align with the combustion chamber inlet port 227, 237, the compressed air in the pipe 241 pre-charges the combustion chamber 42. Further rotation causes the piston 32 to seal off the piston outlet port 24 at substantially the same time as the combustion rotor 4 seals off the combustion chamber inlet port 237 and compression is limited to the portion of the piston channel between the piston 32 and the circumferential surface of the combustion rotor 4.

As the combustion chamber 42 starts to align with the piston channel, the compressed air enters the combustion chamber 42. The piston 32 then enters the combustion chamber 42 and the relative rotation of the two rotors 3 and 4 causes the piston 32 to approach the base of the combustion chamber 42 thereby causing further compression of the air. Maximum compression occurs when the piston 32 is closest to the base of the combustion chamber 42, which coincides with the point of radial alignment between the combustion rotor 4 and the piston rotor 3 shown in Figure 1a. The forces exerted on the pistons 32 during the final stages of compression are transmitted to the core portion 334 through the central sealing member 34. Thus each piston 32 bears against the core portion 334, thereby providing a reinforced arrangement which dissipates the forces at the point of maximum compression.

At this stage, a suitable fuel, for example diesel, is injected into the combustion chamber 42 through the aligned injection port 43. Fuel is injected into the combustion chamber 42 through the series of injection ports 430a, 430b, 43 by a stationary fuel injector (not shown) mounted to the upper sealing plate 23a. It will be appreciated that the shape of the arcuate portion 431 is required when using the stationary fuel injector due to the rotation of the combustion rotor 4.

The high pressure and temperature of the mixture causes a compression ignition and the resulting rapid expansion of burning gases forces the piston 32 away from the centre of the combustion rotor 4 in a radial direction. The resulting forces to which the pistons 32 are subjected are transmitted to the core portion 334 through the central sealing member 34 as described above.

This force drives the rotation the piston rotor 3, which in turn provides torque to the drive shafts 7 through the piston gears 62 and central gears 61. One of the piston rotors also drives the secondary lobed gear 65, which drives the combustion rotor through the primary lobed gear 64.

As the gases continue to expand and provide torque to rotors 3, 4, some of the spent air/fuel mixture is evacuated into the piston channel after the piston 32, thereby contaminating the air within the piston channel. The spent air/fuel mixture which remains in the combustion chamber 42 after it seals against the housing 2 is evacuated through the pipe 251 , which is connected to the exhaust port 215, when the combustion chamber 42 aligns with the combustion chamber outlet port 238.

Further rotation of the piston rotor 3 causes the piston 32 to move through the piston channel, thereby urging the contaminated air/fuel mixture in the piston channel from the previous cycle through the exhaust port 215. The piston 32 then passes through the transfer valve 5 past the inlet port 214 and the next cycle begins. As mentioned above, the centres of the tertiary holes 213, which house the transfer valves, are slightly offset to the centres of the secondary holes 212, which house the piston rotors, thereby to provide a longer stroke for expansion than for compression.

As the pistons 32 are free to rotate in the holes (not shown) of the piston plates 31a, 31 b, friction between the combustion chambers 42 and pistons 32 is minimised. As the pistons 32 are in contact with the rotatable central sealing member 34, friction between the pistons 32 and piston shaft 33 is also minimised whilst ensuring that the piston channel remains sealed.

As shown in Figures 1a to 1c, engagement of the piston rotors 3 with the combustion rotor 4 is sequential, wherein the piston rotors 3 are out of phase during their cycle of operation. In particular, the engagement between each piston rotor 3 and the combustion rotor 4 is out of phase with the other two piston rotors 3. Figure 1a shows a first piston 32 at the point of maximum compression in a first combustion chamber 42, just before ignition of the air/fuel mixture. Figure 1b shows the first piston 32 as it exits the first combustion chamber 42 as the gases expand, wherein a second piston 32 from a second piston rotor 3 is shown entering into a second combustion chamber 42. Figure 1c shows the second piston 32 as it exits the second combustion chamber 42, after ignition has occurred and as the gases expand, wherein a third piston 32 from the third piston rotor 3 is shown entering into a third combustion chamber 42.

This arrangement results in 12 power strokes for every rotation of the combustion rotor 4 with an alternating firing pattern. It will be appreciated by those skilled in the art that this configuration provides a balanced engine design with a smooth power output. The use of multiple piston rotors is preferred to the use of multiple combustion rotors due to the additional features associated with the combustion rotor such as the fuel injection assembly.

This arrangement is also preferred due to its inherent thermal balance. In particular, a more constant temperature is maintained in the centre of the engine 1 , which coincides with the combustion area. The temperature in the combustion chamber 42 is preferably controlled by varying the temperature of the air injected therein during the aforementioned purging operation. It will also be appreciated that the heat which is transferred to the pistons 3 during the combustion cycle is dissipated effectively since it is only subjected to every sixth combustion cycle and the temperature of the air entering the inlet port 214 is may also be controlled.

Reference is now made to Figure 8 and Figures 8a, b and c. The graph of Figure 8 shows the rotational movement of the combustion rotor (y-axis) against the rotational movement of the piston rotor (x-axis) (from the position shown in Figure 8a, through the position shown in Figure 8b to the position shown in Figure 8c). As will be appreciated, at the first position (Figure 8a), a 2° movement of the piston rotor causes a corresponding 1° movement of the combustion rotor. At the second position (Figure 8b) the 2° movement of the piston rotor causes a corresponding 0.75° movement of the combustion rotor and at the last position (Figure 8c) a 2° movement of the piston rotor cause a 1° movement of the combustion rotor. Therefore, it can be shown that a constant rotation of the piston rotor causes a non-constant rotation of the combustion rotor. It also shows that at no point of the engagement of the piston with the combustion chamber is the combustion rotor at a stand-still and, moreover, that the deceleration and acceleration lies on a smooth curve which will not cause unwanted and potentially harmful vibrations.

It will be appreciated that the aforementioned variation in angular velocity between rotors 3, 4 is the direct result of the change in radial distance of the contact point between the piston 32 and the combustion chamber 42. This variation precludes the possibility of using a simple arrangement of standard gears to synchronise rotation of the piston rotors 3 relative to the combustion rotor 4.

However, it will also be appreciated that relying on the piston 32 to drive the combustion rotor 4 by exerting a force on the surfaces of the combustion chambers 42 will result in excessive wear of these components. The lobed gears 64, 65 are profiled to cooperate with each other to match the relative motion of the cooperating piston rotors 3 and combustion rotor 4, therby in order to minimise the stresses exerted on the pistons 32 and combustion chambers 42 and reduce the wear of these components.

The exemplary embodiment of the invention disclosed herein should not be construed as the only means of carrying out the invention. In particular, several variations to the configuration of piston rotors 3 and combustion rotors 4 disclosed above are envisaged. The piston rotors 3 and/or the combustion rotor 4 may vary in size, shape or position and/or the pistons 32 may be disposed asymmetrically about the piston rotor 3 in order to provide the sequential engagement described above. Any number of piston 32 and/or piston rotor 3 geometries may be incorporated into a single engine design. Multiple combustion rotors 4 may also be incorporated into the engine without departing from the scope of the invention.

The central sealing member 34 may be fixed relative to the piston rotor 3, for example fixed and/or integrally formed with one or both of the piston plates 31a, 31 b and/or piston shaft 33. Additionally or alternatively, the central sealing member 34 may be provided by the piston shaft 33, for example the core portion 334 of the piston shaft 33 may be sized and shaped such that it performs one or more of the functions of the sealing member 34. Additionally or alternatively, the central sealing member 34 may comprise a disc rotatable relative to the piston 3, for example relative to the piston plates 31a, 31b.

The pistons 32 may be formed integrally with, or fixed to, the piston plates 31a, 31 b and/or piston shaft 33, for example the pistons 32 may comprise protrusions of, or be otherwise secured to, the core portion 334 of the piston shaft 33.

Furthermore, the lobed gearing arrangement 64, 65 may be incorporated into an engine having piston rotor 3 operating cycles which are not out of phase. Additionally or alternatively, two or more or indeed all of the piston rotors 3 may each comprise a lobed gear 65. Alternatively, the engine may simply comprise a single piston rotor 3.

For example, whilst the housing 2 of the embodiment described above is substantially flat and circular, any suitable shape is envisaged depending on the application. In particular, a more conventional shape such as a cuboid may be desired for ease of mounting into a standard vehicle chassis. The housing 2 of the engine 1 may comprise a two piece casting which houses the entire engine 1. Moreover, whilst one of the piston plates 31a is formed integrally with the piston shaft 33, separate components are envisaged. Also, the pistons 32 may be rotatably mounted to the piston plates 31a, 31b using bearings to minimise wear therebetween. The shape of the pistons may also be varied, for example they may be spherical or frustoconical or any other shape without departing from the scope of the invention. Whilst the central sealing member 34 is typically made of phosphor bronze, any suitable material may be used.

Advantageously, at least one of the pistons 32 may include at least one undersized end which is slideably received within a hole (not shown) in one of the piston plates 31a,

31b for rotatably limiting the piston 32 in one or more directions. It is further envisaged that at least one of the pistons 32 includes one such undersized end which is slideably received within a hole (not shown) in one of the piston plates 31a, 31b while the hole

(not shown) in the other piston plate 31a, 31b is of a size and shape slightly larger than the maximum peripheral size and shape of the piston 32 to allow insertion and/or removal of the piston 32 when the piston rotor 3 is in an assembled condition.

This arrangement could advantageously be configured such that the undersized end of piston 32 is received within the lower piston plate 31b such that it is not in contact with the lower sealing plate 23b. This would confine any wear between the piston 32 and the housing 2 to the upper sealing plate 23a, which could also be checked when the aforementioned checking of the pistons 32 takes place.

In a further preferred embodiment, the combustion rotor shaft 41 is hollow and the engine comprises a single drive shaft 7 passing through the hole in the combustion rotor shaft 41 and coupled to both central gears 61. Further embodiments are also envisaged wherein sequential firing is provided by mounting the piston rotors 3 such that they are not equidistant around the combustion rotor 4. Other configurations of rotors are also possible, as are other numbers of piston rotors 3, pistons 32, combustion chambers 42 and so on without departing from the scope of the invention. It should be appreciated that, whilst the configuration of the piston rotors 3 and the combustion rotor 4 provides continuous cooperation therebetween during operation, this feature is optional.

Variations to the compression stroke and/or expansion stroke are also envisaged by scaling the diameter of the secondary holes 212 and piston plates 31a, 31b and/or the diameter of the pistons 32 and/or altering the location of the piston valves 5 on the periphery of the secondary holes 212.

Simplified gear arrangements for synchronising the piston rotors 3 and transfer valves 5 are also envisaged in order to reduce the mechanical losses. For example, if the application does not require a drive shaft 7 on either side of the housing, a single gear assembly 61 , 62, 63 may be provided.

Whilst the above description discloses the driving of the piston rotors 3 and the coupling of the piston rotors 3 to the drive train of a vehicle, for example, it is possible to so-couple the combustion rotor 4.

It should be appreciated that, whilst the engine 1 is a compression ignition engine, it can be constructed as a spark ignition engine without departing from the scope of the invention. This can be achieved by altering the compression ratio, adding a spark plug to communicate with the combustion chambers 6 of the combustion rotor 2 and altering the timing of fuel injection. Furthermore, it should also be appreciated that the engine 1 may comprise a turbo charger, supercharger, or other known apparatus which enhances the power output of conventional engine designs without departing from the scope of the invention. For example, the pipe 241 connected to the combustion chamber inlet port 227 may be connected to the outlet of the turbo charger or supercharger rather than being connected to the piston channel outlet port 24. In the case of a turbo charger, the exhaust gases which exit from the combustion chamber outlet port 228 through the pipe 251 may be used to power the turbo charger rather than being connected directly to the exhaust port 215.

In further embodiments, engines of the invention may be modified so as to provide a compressor or pump. For instance, the injectors (not shown) may be replaced with a valve to permit the operation of such a device. In the case of a compressor, the valve could open shortly before the point of maximum compression between the piston 32 and the chamber 42 to release the compressed fluid. In the case of a pump, the valve could be connected to a source of fluid to allow the fluid to be drawn from the source by the piston 32 and pumped out through the exhaust port 215. Various other modifications may be necessary in order to adapt the engine to perform such functions. However, it should be appreciated that these devices are within the scope of the invention.

Claims

1. A rotary internal combustion engine comprising a first rotor and two or more piston rotors, the first rotor comprising at least one chamber and each piston rotor comprising at least one piston, wherein the piston rotors are out phase for at least part of their cycle of operation.

2. An engine as claimed in Claim 1 , wherein the cycle of engagement of the piston rotors with the first rotor are out of phase with respect to one another.

3. An engine as claimed in Claim 1 or Claim 2, wherein at least one piston rotor comprises a central sealing member.

4. An engine as claimed in Claim 3, further comprising a housing, wherein the housing and the at least one piston rotor cooperate to provide a sealed piston channel along which the at least one piston passes in use.

5. An engine as claimed in Claim 4, wherein the central sealing member is free to rotate, in use, with respect to the housing and with respect to the at least one piston rotor.

6. An engine as claimed in any one of Claims 3 to 5, wherein at least one piston rotor comprises two plates, the at least one piston being mounted between the plates, the sealing member being mounted between the plates and rotatable therewith.

7. An engine as claimed in Claim 6, wherein the housing, plates and sealing member cooperate to provide a sealed piston channel along which the at least one piston passes in use.

8. An engine as claimed in any one of Claims 3 to 7, wherein the central sealing member comprises a central sealing bush.

9. An engine as claimed in Claim 8, wherein the at least one piston is rotatably mounted to the piston rotor such that it contacts the bush, the bush being arranged to rotate in response to a contacting rotation of the at least one rotatably mounted piston.

10. An engine as claimed in any preceding Claim, wherein the first rotor comprises a plurality of chambers, the at least one piston from a first of the two or more piston rotors engaging, in use, a first chamber and the at least one piston from a second of the two or more piston rotors engaging a further chamber.

1 1. An engine as claimed in Claim 10, wherein, in use, at least one piston is in engagement with one of the chambers at any given point of rotation of the first rotor.

12. An engine as claimed in any preceding Claim, wherein the piston rotors are located equidistantly around the first rotor.

13. An engine as claimed in any preceding Claim, wherein at least one piston rotor further comprises two plates, one of the plates having a hole therethrough of size and shape slightly larger than the maximum peripheral size and shape of the piston, the piston being slideably receivable therein.

14. An engine as claimed in Claim 13, wherein the at least one piston is rotatable with respect to the at least one piston rotor.

15. An engine as claimed in any preceding Claim, wherein each piston rotor comprises a timing gear for synchronising rotation between the piston rotors.

16. An engine as claimed in any preceding Claim, further comprising a first gear having a first lobe portion and a second gear having a second lobe portion, the first gear being connected to the first rotor and the second gear being connected to at least one of the piston rotors, wherein rotation of the first rotor causes the first lobe portion to cooperate with the second lobe portion to effect rotation of the second gear.

17. An engine as claimed in Claim 16, wherein the profiles of the first and second lobe portions are such that the mechanical advantage of the first gear with respect to the second gear varies with the angular position thereof.

18. An engine as claimed in Claim 16 or Claim 17, wherein the first gear and the first rotor are rotatable about a first axis, the profiles of the first and second lobe portions being such that the radial position of the area of contact between the first and second lobe portions with respect to the first axis of rotation varies with the angular position of the first lobe portion.

19. An engine as claimed in any one of Claims 16 to 18, wherein the second gear and the at least one piston rotor are be rotatable about a second axis, wherein the profiles of the first and second lobe portions are such that the radial position of the area of contact between the first and second lobe portions with respect to the second axis of rotation varies with the angular position of the second lobe portion.

20. An engine as claimed in any one of Claims 16 to 19, wherein the engagement of the first and second lobe portions is arranged to match substantially the engagement between the first rotor and the at least one piston rotor.

21. An engine as claimed in any preceding Claim, further comprising means to inject fuel into the or each chamber.

22. An engine as claimed in Claim 21 , further comprising timing means arranged to control the fuel injection means and thereby control the injection of fuel into the or each combustion chamber.

23. An engine as claimed in any preceding Claim, wherein the engine is a compression ignition internal combustion engine.