The present invention relates to improvements in relation to engines and more particularly to compact rotary piston engines which can be implemented in a much smaller size for mounting, for example, directly on a vehicle axle to drive an individual wheel.

Spark ignition reciprocating engines are well known for use in many applications such as propelling vehicles. The engine is located in an engine compartment and rotary motion produced by the engine is transmitted to the required driven members, such as the wheels of a vehicle, by suitable drive shafts and gear box(es). Whilst widely utilised, these known engines have the drawback that they are usually very heavy and located remote from the driven members such that the length of the drive shafts introduce additional friction losses and thereby reduction in efficiency.

Applicants own earlier UK patent application GB2494392 provides an improvement to the conventional engine discussed above by teaching a rotary piston engine comprised of a rotor and a stator. The rotor has a rotor body and a rotor element moveably mounted on the rotor body. The stator has a stator body and a stator element moveably mounted on the stator body. The rotor is rotatable relative to the stator such that, as the rotor rotates the rotor element moves towards the stator element, compressing fuel between the two elements. As the two elements come together, they each rotate relative to their respective body so as to allow the rotor element to move past the stator element, during the course of which movement the compressed fuel is ignited so as to propel the rotor element away from the stator element and hence drive the rotation of the rotor.

The rotary piston engine concept taught in GB'392 has the potential for a significant advancement in engine technology and propulsion systems but there are many practical implementation issues which need to be addressed in order for the concept to be realised into a practical working engine. The present invention seeks to address those implementation issues.

According to the present invention there is provided an engine comprising one of a fixed stator and a rotor having a circular opening formed therein, the other of the stator and rotor mounted concentrically within the circular opening such that a circular radial space exists between the rotor and the stator , and at least one piston member engaged in the radial space between the rotor and stator, the or each piston members being movable along said space relative to one of the rotor and the stator and being a sealing fit between said rotor and stator so as to be a fluid tight fit therewith, the other of the rotor and the stator further including a plurality of chambers, each of which opens into the radial space and which form combustion and/or exhaust chambers for the engine, each chamber housing a rotary member which is a fluid tight seal across the radial space, whereby as the or each piston moves along the radial space, fuel is compressed by the piston into one of the chambers against the rotary member housed therein as the piston moves towards the chamber, igniting means being associated with each combustion chamber such that compressed fuel is ignited in the combustion chamber as the piston passes therethrough, applying a pressure to the back of the piston and thereby driving the rotational movement thereof, characterised in that each rotary member operates to rotate the piston as it passes through the chamber such that the leading face of the piston, which compresses the fuel into the chamber, becomes the trailing face as the piston moves away from the chamber, upon which the combustion pressure acts to transmit torque between the rotor and the stator.

An engine in accordance with the invention has the advantage that it provides a practical solution for implementing the rotary piston engine of the prior art in a manner which maintains the compact design. Furthermore, the engine of the invention can be realised into a design that is easily to manufacture and assemble, and preferably is of modular construction so as to enable more than one engine to be mounted in series on a shaft and/or to have the ability to have further expansion of the combustion products in units mounted in series so as to increase the thermal efficiency of the system. It will be understood that whilst described above and hereinafter in connection with an engine, the system may also be implemented as a compressor with rotational drive being used to move the pistons to compress gas as required.

The shape of the engine lends itself to hybrid applications in particular where packaging on the same axis as an electric motor would be easier than with a reciprocating engine. However the shape may also offer advantages for other applications such as unmanned aerial vehicles (UAVs) and small generator sets.

Furthermore, the configuration of the engine means that the expansion period of the engine is not limited in the same way as a reciprocating engine so there is potential to extract more energy from the expanding gases before they are released to the atmosphere, hence increasing thermal efficiency.

The chambers should be equi-angularly distributed around the rotor/stator and preferably, an even number if chambers is provided in the engine which alternate as combustion and exhaust chambers. In a particularly preferred embodiment, four chambers are provided spaced at 90 degree intervals around the engine so that each piston goes through two combustion events per revolution. Three pistons may then be provided distributed around the engine such that 6 combustion events occur per cycle.

Preferably the rotary member operates to rotate the piston through 180 degrees as it passes through the chamber.

In one particularly preferred embodiment, each rotary member includes a camming surface which is engaged by a cam follower provided on the each piston as a piston approaches the chamber, the engagement between the cam and cam follower automatically causing the rotary member to rotate as the piston approaches the chamber and to further rotate as the piston moves away from the chamber. According to a further aspect of the invention there is provided An engine comprising one of a fixed stator and a rotor having a circular opening formed therein, the other of the stator and rotor mounted concentrically within the circular opening such that a circular radial space exists between the rotor and the stator , and at least one piston member engaged in the radial space between the rotor and stator, the or each piston members being movable along said space relative to one of the rotor and the stator and being a sealing fit between said rotor and stator so as to be a fluid tight fit therewith, the other of the rotor and the stator further including a plurality of chambers, each of which opens into the radial space and which form combustion and/or exhaust chambers for the engine, each chamber housing a rotary member which is a fluid tight seal across the radial space, whereby as the or each piston moves along the radial space, fuel is compressed by the piston into one of the chambers against the rotary member housed therein as the piston moves towards the chamber, igniting means being associated with each combustion chamber such that compressed fuel is ignited in the combustion chamber as the piston passes therethrough, applying a pressure to the back of the piston and thereby driving the rotational movement thereof, characterised in that each rotary member includes a camming surface which is engaged by a cam follower provided on the each piston as a piston approaches the chamber, the engagement between the cam and cam follower automatically causing the rotary member to rotate as the piston approaches the chamber and to further rotate as the piston moves away from the chamber.

In either invention, the rotary member advantageously includes a plurality of arms, each of which has a slot extending radially from its end towards the centre of the rotary member, the slot receiving a pin carried on the piston as the piston moves towards the chamber, whereby upon engagement of the pin in the slot, the rotary member is caused to rotate as the piston moves towards the chamber and to continue to rotate in the same direction as the piston moves away from the chamber following combustion. It has been found to be particularly preferred for the rotary member to include 3 pockets equi-angularly located around the rotary member, each pocket being sized to receive the piston during its passage through the chamber. Each pocket then has an arm associated with it for effecting movement of the rotary member as the piston moves into that pocket. In this way, each pocket in turn receives a piston with the next pocket being left in position for the next combustion event as the piston disengages from the slot in the arm.

Preferably, the stator has the circular opening formed therein and the rotor is mounted in the stator, the chambers then being formed in the stator.

Ignition means is preferably associated with alternate chambers for igniting the compressed fuel and exhaust means such as an exhaust port is associated with the other chambers for exhausting combustion gases from behind each piston after the combustion pressure has subsided.

Preferably, said one of the rotor and stator of the engine which provides the output has at least one drive dog extending axially from or drive recess formed axially in an output face and the other of the rotor and stator has a complementary recess of drive dog formed in an input face. In this way, a pair of engines may be connected in series with the rotor or stator of the first engine drivingly engaged with the stator or rotor of the second engine so that the second engine is caused to rotate with the first engine before any additional drive is added by the secondary engine itself. In this was the output speed of the second engine is increased.

To that end, the present invention further provides at least two engines, each according to the invention, arrange with one of the rotor or stator of a first engine drivingly connected to the other of the rotor or stator of a second engine in a series relationship such that the second engine is caused to rotate with the first engine. In order that the invention may be well understood, there will now be described an embodiment thereof, given by way of example, reference being made to the accompanying drawings, in which:

Figure 1 is a schematic view of part of an engine according to the invention at the start of a compression phase of operation;

Figure 2 is an enlarged view of part of the engine of Figure 1 approaching the end of the compression phase;

Figure 3 is an enlarged view corresponding to Figure 2 at the end of the compression phase;

Figure 4 is an enlarged view corresponding to Figure 2 with a piston member moving away from a combustion chamber as part of an expansion phase of operation;

Figure 5 is a reduced scale view corresponding to Figure 4

Figure 6 is an enlarged view corresponding with Figure 1 showing a rotary mechanism which cooperates with the piston member to rotate it during engine cycle; Figure 7 is a view corresponding with Figure 6 with the piston in a second position; Figure 8 is a view corresponding with Figure 6 with the piston in a third position; Figure 9 is a schematic view of the engine of Figure 1 showing an arrangement for inlet and outlet ports;

Figure 10 is alternative views of the arrangement of Figure 9;

Figure 11 is a perspective view of a pair of engines according to the invention arranged in series to provide a step up in output speed;

Figure 12 is an illustrative section view through the pair of engines of Figure 11 showing the series connection between the two engines; and

Figure 13 is a detailed sectional view of a series interconnection between a pair of engines of the invention.

Referring first to Figure 1, where is shown a schematic representation of a rotary piston engine according to the invention. The engine is comprised of a rotor 1 which is concentrically mounted in a generally circular opening 3 formed in a stator 2, the rotor 1 being configured to be rotatable about its centre la relative to the stator 2. The rotor 1 is smaller than the size of the circular opening 3 in the stator 2 such that a radial space 4 exists between the rotor 1 and the stator 2 about the entire outer periphery of the rotor 1, which space 4 forms a track for piston members 5 to travel around. One such piston member 5 is shown in the Figures but it will be understood that multiple pistons will typically be utilised. Each piston 5 is carried along the track in a radial pocket la formed in the outer surface of the rotor, the engagement of the piston with both the rotor and the stator being a close tolerance fit such that fluid, in particular fuel for combustion, may be compressed ahead of the piston as it travels around the track 4 as described below. Each piston furthermore has a pin 5a extending axially from at least one face as shown in Figure 7, the purpose of which is described below.

Distributed around the stator 2 are a plurality of pockets 7a, 7b, 7c. In the illustrated embodiment, three such pockets are shown with the fourth being located diametrically opposite the upper pocket 7b. It will, however, be understood that other numbers of pockets are possible, although if following the principle of the illustrated embodiment in which pockets alternate been ignition pockets and exhaustion pockets, an even number of pockets would be necessary.

As mentioned above, each pocket 7a, 7b, 7c is either an ignition pocket 7b or an exhaust pocket 7a, 7c. The ignition pocket 7b has a rotary member 8 mounted therein which is rotatable about the centre of the pocket 7b and which extends across the track 4 so as to form a fluid tight barrier in the track. Each rotary member 8 further has a series of recesses 8a distributed equi-angularly around its circumference - 3 in the illustrated embodiment, each recess 8a being sized such that the piston 5 is a close tolerance fit therein. The rotary member 8 is furthermore connected in a rotationally fast manner to star shaped rotary guide member 9 which is located axially adjacent the rotary member 8 and has a series of arms 9a which extend behind the rotor, stator and track. In the illustrated embodiment the rotary guide member 9 has three arms 9a to corresponds with the three recesses 8a formed in the rotary member 8. Each arm furthermore has a guide slot 10 formed therein which extends radially from the end of the arm 9a towards the centre of the rotary guide member 9, each slot being size to complement the pin 5a formed on the piston such that the pin 5a engages in one of the slots 10 as it moves along the track and travels therealong, causing the rotary guide member 9 to rotate through a camming action with the pin 5 a as the piston approaches the rotary member 7b as illustrated in Figures 2 to 4.

The ignition portion of the cycle operates as follows:

Fuel and air are introduced into the track 4 ahead of the piston 5 via an inlet port 10 located between the exhaust pocket 7a and the next ignition pocket 7b as illustrated in Figure 10. As the piston moves along the track 4 as the rotor 1 rotates, the fuel/air mixed is compressed ahead of the piston against the facing recess 8a of the rotary member 8. The rotary member 8 is oriented such that the open end of the slot 10 of one of the arms 9a of the rotary guide member 9 is aligned with the track 4 such that as the piston 5 approaches the ignition pocket 7b, the pin 5a on the piston automatically engages in with the open end of the slot 10 and starts to travels along the slot as it continues to move towards the rotary member 8. The spaced apart centres of rotation of the piston 5 and the rotary guide member 9 develop a camming action between the pin 5 a and slot 10 which caused the rotary guide member 9 to rotate about its centre, rotating the rotary member 8 with it. The piston 5 is also caused to rotate about the pin 5 a as illustrated in Figure 2, and the slot is configured such that as piston 5 reaches the ignition pocket 7b, one of the recesses 8a of the rotary member 8 is in exactly the right position for the piston to engage therein and complete the compression of the air/fuel mixture.

As the rotor continues to rotate, the piston and rotary member move together allowing the piston to move past the ignition pocket 7b without compromising the pressure built up in the air/fuel mixture. During the course this movement, the compressed air/fuel mixture is ignited using a spark plug or other suitable ignition means. The combusted air/fuel mixture thereby begins to expand as the piston moves past the rotary member, and the resulting pressure which is developed between the recess 8a and the now back of the piston 5 pushes the piston away from the ignition pocket and thereby drives the continued rotary motion of the rotor.

The pin 5 a travels back along the slot 10 away from the centre of the rotary guide member 9 as the piston 5 moves away from the pocket 7b, continuing to rotate the rotary guide member 9 until it finally exits the slot 10, leaving the rotary guide member 9 in position ready for the next piston to engage in the slot 10 of the next arm 9a as it approaches the pocket 7b.

Once the pin 5a disengages from the rotary guide member, the rotary guide member and, therefore, also the rotary member 8 are both locked in position so as to ensure that they are correctly orientated to receive the next member during the next piston and associated pin 5a. Following the ignition portion of the cycle, the piston 5 continues to travel along the track 4 towards the next exhaust pocket 7c, the pressure of the expanding fuel driving the movement which, in turn, drives the rotation of the rotor 1 so as to power the movement of other pistons 5 (not shown) during the ignition phase of their cycle. The exhaust pocket 7c includes an exhaust port 11 which allows the exhaust gases to vent when expansion has completed, thereby preventing any back drag reducing efficiency as the piston 5 moves on to its next ignition phase. The exhaust gasses are fully evacuated due to the action of the following piston which drives the exhaust gasses towards and then out of the exhaust port.

The exhaust pocket 7c includes a rotary guide member 12 similar to that of the ignition pocket 7b which operates to guide the movement of the piston as it travels past the exhaust pocket 7c.

The pistons 5 may take the form of separate cylindrical roller seals or may be formed by features integral with the rotor 1. In the illustrated embodiment, each piston goes through two combustion events per revolution, giving a total of six combustions events per revolution if three pistons are present.

The rotary guide member 9 provide sealing between the rotor 1 and stator 2 during compression and expansion of the gases and also rotate intermittently to allow the pistons 5 to pass whilst still maintaining a gas seal. They also transfer compressed gases from ahead of each piston to behind each piston prior to ignition.

It will be understood that, although the invention has been described in connection with a spark ignition type engine, it may also be implemented with a compression ignition, diesel type engine.

Referring now to Figures 11 to 13, there is shown a series configuration of a pair of engines according to the invention which allows the output speed to be increased without the need for a separate gear box, thereby saving space.

The arrange of Figure 11 has a primary engine 20 and a secondary engine 30. The configuration of each engine is in accordance with the description above of Figures 1 to 10, with each engine having a rotor and a stator. AS illustrated in Figure 12, however, the rotor 21 of the primary engine 20 is drivingly connected to the stator 32 of the secondary engine, so that the drive of the primary engine causes the stator of the secondary engine to rotate with the rotor 21 of the primary engine. As a result, the rotor 31 of the secondary engine 30, which is itself cause to rotate relative to the secondary stator 32, rotates at a faster speed than the rotor of the primary engine, due to the fact that the drive from each of the engines 20, 30 is added together.

Figure 13 shows one possible configuration for the interconnection between the two engines. The rotor 21 of the primary engine 20 is provided with drive pins or dogs 23, which extend axially from the output face of the rotor. The stator 32 of the secondary engine 30 is then provided with complementary axial recesses 34 in its input face in which the dogs 23 of the primary engine 20 are engageable to effect a rotationally fast connection between the primary rotor 21 and the secondary stator 22, thereby effecting a series drive connection therebetween.

The secondary rotor 31 is also provided with dogs 33 by means of which it may be connected to the stator of a tertiary engine. From this, it can be seen that, although the system has been illustrated with just two engines, a cascade series arrange of engines can be made to meet any particular drive requires without the need for a separate gearbox.

It will further be understood that the output speed may be controlled either controlling the drive or power produced by each engine in the cascade, and in particular by selective operation of each engine - when can engine is not being operated it will effectively just allow 1: 1 pass through.