EP0781370A1

EP0781370A1 - Internal combustion engine

Info

Publication number: EP0781370A1
Application number: EP95936122A
Authority: EP
Inventors: Lambertus Hendrik De Gooijer
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-10-19
Filing date: 1995-10-19
Publication date: 1997-07-02
Also published as: AU3816995A; JPH10509493A; NL9401729A; WO1996012870A1

Abstract

An internal combustion engine operating according to the four-stroke principle comprises a housing having a rotor space therein; preferably at least a pair of regularly circumferentially spaced combustion chambers in the rotor space; a rotor rotating truly about a rotor axis within the rotor space, said rotor having an unround shape and preferably including at least two circumferentially spaced cams; sealing means at the circumference of the rotor to form a seal between the rotor and the rotor space; inlet and outlet ducts adapted to communicate with the combustion chambers; valve means which, in cooperation with the cams of the rotor, are adapted to separate for each pair of combustion chambers four varying rooms between the rotor and the housing in which the four strokes of the four-stroke process take place.

Description

Internal combustion engine

The present invention relates to an internal combustion engine operating according to the four-stroke principle.

Despite all technical advancements, for driving non- rail-bound road vehicles, the most widely used internal combustion engine is the four-stroke crank shaft piston engine, in particular the Otto- and Diesel-engine, which is known for ages. Of course, these engines are being improved considerably through the years, but the principle involves several disadvantages which are very hard or impossible to remove. As disadvantages of the Otto-engine the following can be mentioned: a relatively low theoretical efficiency as a result of the equal compression and expansion ratios, a relatively low quality efficiency due to the ignition of the mixture before the upper dead center is reached by the piston; a relatively low quality efficiency because compression and expansion take place on the same side of the piston causing great heat and energy losses due to strong heat exchanges; a low mechanical efficiency at low loads of the engine because friction losses remain the same when the load is decreasing; and uncoupling cylinders is hard to realize while it is also difficult to combine the Otto- engine with an electric motor.

The Wankel-engine was an attempt to avoid several disadvantages of the Otto-engine, in particular those related to the reciprocating movement of the piston and relating to the valve mechanism, but also this engine has failed to replace the Otto-engine.

It is an object of the present invention to provide a new internal combustion engine in which the above disadvantages are removed or at least substantially reduced.

For this purpose the invention proposes an internal combustion engine operating according to the four-stroke principle, comprising a housing having a rotor space there¬ in, preferably at least a pair of regularly circumferentially spaced combustion chambers in the rotor space, a rotor rotating truly about a rotor axis within the rotor space, said rotor having an unround shape and preferably including at least two circumferentially spaced cams, sealing means at the circumference of the rotor to form a seal between the rotor and the rotor space, inlet and outlet ducts adapted to communicate with the combustion chambers, valve means which, in cooperation with the cams of the rotor, are adapted to separate for each pair of combustion chambers four varying rooms between the rotor and the housing in which the four strokes of the four-stroke process take place. The advantages of such combustion engine are a.o. the following:

- As a result of the use of a rotor which makes a true rotational movement and does not bare against the wall, the friction losses will be minimal. The only friction losses occurring besides those within the bearings are caused by the necessary seals and the motion and friction losses due to the movement of the valve means.

- By selecting the circumferential width of the cams of the rotor in the design stage, one is able to determine the angular rotation of the rotor during which there is created more or less a stationary UDC-condition in which an ignition and pressure building can take place within the combustion chamber without causing negative work by pushing back a piston or rotor. - By locking the valve means in the upper position, the combustion cycle of a rotor can be switched off causing the rotor to rotate only as a fly wheel . Then only the friction resistances of the seals remain as mechanical losses which are minimal, however, if there are no gas forces. If there are blank contact seals, then there is no frictional resistance of the seals at all. - The scavenging of the gasses is optimal because the timing as a result of the operation of the valve means is always optimal with any rotational speed. The gas inflow and outflow do not have to take place in the combustion chambers avoiding contact between the inlet and outlet gasses (no valve overlap, no risk of backfire) . Depending on the embodiment, it is possible to extend the inlet and outlet ducts over the whole width of the rotor thereby obtaining a proper charging of the combustion chambers. - The trend of the torque of the engine is much more regular in comparison with an Otto-engine. With a simple engine type having a single rotor and two opposite combus¬ tion chambers there is a combustion each 180° corresponding to a four cylinder four-stroke Otto-engine. - Because the rotor has a separated cold and hot side, the compression and expansion ratios can be chosen independently by giving the rotor an asymmetrical shape and/or by spacing the cams in a non-uniform manner. This offers the possibility of an increased theoretical efficiency.

- The combustion engine according to the present invention is very suitable for combining it with an electric motor resulting in a hybrid drive. In such a combination, the rotor may revolve with the electric motor as a fly wheel if the valve means are out of operation. At the time the combustion engine should take over the drive from the electric motor, the valve means are set into operation and care should be taken to ensure the proper ignition and injection causing a smooth take-over of the drive. Furthermore, the shape of the combustion engine is substantially circular just as the electric motor and also the diameter can be chosen such that it fits well to the respective electric motor.

- In the combustion engine according to the invention a further efficiency increase can be obtained during low load conditions if there is a provision to slightly lift the compression valve from the rotor during low loads so that air may be taken-in internally from the compression room, instead of taking-in air which should be sucked in with great resistance through the throttle valve which is almost closed. The invention will hereinafter be further illustrated with reference to the drawings showing embodiments of the combustion engine according to the invention by way of example.

Fig. la-h illustrate in a very schematic sectional view eight different positions of the engine during its operation.

Fig. 2a-h illustrate in the same manner eight positions of an alternative embodiment of the combustion engine according to the invention. Fig. 3 is a sectional view along the line III-III in Fig. 2a.

Fig. 4, 5, 6 are sectional views along the lines IV- IV, V-V and VI-VI, respectively, in Fig. 3.

Fig. 7 is an enlarged partial sectional view of another alternative embodiment of the combustion engine according to the invention.

Fig. 8 is a sectional view substantially corresponding to that of Fig. 7 showing still a further alternative embodiment . Fig. 9 is a sectional view along the line IX-IX in

Fig. 8.

Fig. 10 is a partially sectioned bottom view of Fig. 8 on a slightly reduced scale.

Fig. 11 is a partial sectional view of a combustion engine according to the invention in the embodiment of Fig.

8.

Fig. 12, 13 are schematical partial transverse sectional views of Fig. 11 along the lines XII-XII and XIII- XIII, respectively, shown on a reduced scale, wherein the left portion of the sectional view shows a part of the rotor which is positioned diametrically opposed to the part of the rotor shown in the right portion of the view, and wherein the right portion of the view corresponds to the sectional lines in Fig. 11.

Fig. 14 very schematically illustrates an examplary embodiment of a combustion engine according to the invention having an axial separation of the rotor in compression and expansion portions, wherein on the left side of the figure there are shown transverse sectional shapes of the respec¬ tive rotor portions.

Fig. 15 is a partial sectional view of the combustion engine in the embodiment of Fig. 14.

Fig. 16 and 17 are views corresponding to that of Fig. 14 showing alternative embodiments of the axial separation of the rotor.

Fig. 1 shows a very simple design of an internal combustion engine according to the present invention. The combustion engine comprises a housing 1 which is only very briefly indicated and which has a rotor space 2 formed therein. With the exception of two oppositely disposed combustion chambers 3, 4, the rotor space 2 is round- cylindrical in shape, the axis of which is perpendicular to the plane of the drawing. As mentioned, in this embodiment there is provided a pair of regularly circumferentially spaced combustion chambers 3, 4 in the rotor space 2, but it is very well possible to provide several pairs of combustion chambers. A rotor 5 is rotatably mounted on a rotor shaft 6 within the rotor space 2 such that the rotor shaft 6 co¬ incides with the axis of the rotor space 2. The rotor 5 is unround in shape, in this case having two cams 7, 8 reaching up to the circumference of the rotor space 2: a compression and expansion cam 7 and an inlet and outlet cam 8. The cams

7, 8 are arranged with the same distribution as the combus¬ tion chambers 3, 4 so that in this case they are diametrically opposed. The rotor 5 has then a long geometrical axis 9 and a short geometrical axis 10. The shape of the rotor does not have to be symmetrically relative to these axes 9, 10, but generally it is symmetrical upon a rotation through 180° . It is however possible to arrange the cams 7, 8 with an offset other than 180° in order to optimize the expansion and compression ratios, for which purpose also the shape of the rotor on both sides of the cams may be varied. On both sides of each long geometrical axis 9 there is arranged a sealing means 11 on each cam 7, 8, which ensures a gas tight seal between the rotor 5 and the housing 1.

As seen in the direction of rotation (see arrow) of the rotor 5, an outlet duct 12, 13 debouches a short distance before the respective combustion chamber 3, 4, said outlet ducts 12, 13 being closed and opened by a corres¬ ponding outlet valve 14, 15. Behind the combustion chamber 3, 4 an inlet duct 16, 17 debouches, which can be closed and opened by a corresponding inlet valve 18, 19, respectively. The valves 14, 15 and 18, 19 are internally operable, for example by means of cam shafts, cam tracks or the like (not shown) . The valves 14, 15 and 18, 19 are not only capable of closing and opening the respective ducts 12, 13 and 16, 17, but also serve to separate the room between the rotor 5 and the housing 1 into four rooms which are separated in a gas tight manner and in which the four strokes of the four- stroke process take place. This separation of the four rooms is of course accomplished in cooperation with the seals 11 on the cams 7, 8 of the rotor 5. In each of these rooms there is alternately obtained an inlet stroke, a compression stroke, an expansion stroke and an outlet stroke. In the drawing there is indicated with A the room of the inlet stroke, with B the room of the compression stroke, with C the room of the expansion stroke and with D the room of the outlet stroke. The circumference of the rotor 5 and the inward end of each valve 14, 15 and 18, 19 should of course be adapted to each other so that they can run in abutting fashion without too much wear and are also capable of effecting a good seal. Techniques are available for this purpose. Fig. la-h show eight different positions during half of a revolution of the rotor 5 in which the four strokes takes place completely.

In fig. la the four rooms A-D are indicated, in which it is shown that the inlet valve 18 is open for allowing the entry of a fresh gas mixture from the inlet duct 16. The inlet valve 18 also limits the room A on one side, while the other side of the inlet stroke room A is sealed by the seal 11 on the cam 8 of the rotor 5. Because the cam 8 of the rotor 5 is moving away from the inlet valve 18, the volume of room A increases and the fresh gas mixture is consequently sucked-in from the inlet duct 16. On the other side of the inlet valve 18 sealing against the rotor 5 a compression stroke takes place in room B defined there, wherein the outlet valve 14 is closed and the cam 7 of the rotor 5 moves in a direction to the combustion chamber 3 so that the volume of room B decreases and the contained fresh gas mixture is compressed. The expansion stroke takes place in room C, in which the ignition and combustion of the mixture within the combustion chamber 4 have resulted in a pressure increase of the contained gas mixture and this pressure in room C exerts a torque on the rotor 5 in a direction resulting in an increase of the volume of room C, that is in a direction according to the arrow shown. Finally it can be seen that the outlet stroke has almost ended in room D and the outlet valve 15, defining room D together with the adjacent seal 11 of the cam 8 of the rotor 5, has almost closed.

In fig. lb, the rotor 5 is rotated slightly further, wherein the volume of the outlet room D is reduced to nil and the outlet valve 15 is now closed completely.

Fig. lc and d show two further rotational positions in which in fig. Id the inlet valve 18 is almost closed.

Fig. le shows the position of the rotor in which the rooms A and C has reached their maximum volume and the rooms B and D their minimum volume. Room A has been charged with an amount of fresh gas mixture which will be compressed upon further rotation of the rotor 5. The compression stroke has just ended in room B and an ignition of the compressed gas mixture in the combustion chamber 3 can take place, said ignition being initiated by a spark not shown. The seal 11 of the leading side of the cam 7 of the rotor 5 together with the outlet valve 19 ensure sealing the combustion chamber 3 such that the high gas pressure can be resisted. The circumferential width of the cam 7 determines the angular rotation of the rotor 5 during which there is created a stationary UDC and consequently no change in volume of room B takes place upon rotation of the rotor. During this angular rotation, the ignition and combustion of the gas mixture can take place without causing a negative work on the rotor 5 by the resulting pressure. In the design stage, for a certain motor type the width of the cam 7 can be selected for optimizing the desired stationary UDC. In room C, the expansion stroke has come to an end and all pressure energy in this room has been used. Finally, room D is ready to convert into room B in which a fresh gas mixture is compressed, as will appear from the following figure.

Fig. If illustrates that rooms A-D are more or less shifted one position so that for example room A, in which first the inlet stroke took place, has now become compression room B in which the entered gas mixture will be compressed. In the position of fig. If, the inlet and compression are not really started. On the other hand, in the earlier compression room B of fig. le the expansion stroke has already been started in what is now room C of which the volume is increased by driving the rotor 5 so that the ingited gas mixture therein is allowed to expand. In what is now room D, defined by the adjacent seal 11 of the rotor cam 8 and the outlet valve 14, the outlet stroke is already taking place. In fig. lg and h the four strokes in the rooms A-D have further developed and in fig. lh the position is reached in which the rotor 5 is rotated through an angle of 180° with respect to the position of fig. la. From this position on the same developments take place as in fig. lb-lg, although with an 180° offset.

From the foregoing it is clear that on one side of the rotor 5 there is an inlet stroke and a compression stroke, while on the other side of the rotor 5 there is only the expansion stroke and the outlet stroke. This side of the rotor 5 may be called the hot side of the rotor 5, while the opposite side is the cold side of the rotor. Such separation is favourable in regard of the heat losses and the energy losses in the gas mixture. This has a favourable effect on the quality efficiency of the engine.

Fig. 2a-h show an alternative embodiment of the combustion engine of fig. 1, in which there is only one outlet duct 12 and one inlet duct 16 and they are formed not in the housing 1, but in the rotor 5 and they are always open, whereas the valves 14, 15 and 18, 19 only serve for separating the four rooms A-D, which has the effect, how¬ ever, that the outlet duct 12 and the inlet duct 16 always communicate with the proper room D or A, respectively. In this construction, the outlet duct 12 and the inlet duct 16 should extend through the rotor shaft 6 which should therefore have a hollow construction. Principally, it is of course possible to cause the housing and not the rotor 5 to rotate and to cause the rotor 5 to remain stationary. Fig. 3-6 schematically show more details of the construction of the internal combustion engine of the invention in the embodiment of fig. 2. One may recognize the housing 1, the rotor 5, the rotor shaft 6, the outlet duct 12, the inlet duct 16, the outlet valve 14 and the inlet valve 19. It can be seen that in this case the valves 14, 15 and 18, 19 are rotatably mounted on a valve shaft 20 permitting the movement of the valves. In this embodiment, the valve shaft 20 also serves to operate the valves 14, 15 and 18, 19 because the valve shafts 20 are rotationally fixed to the respective valves 14, 15, 18, 19, respectively, and these shafts are each provided on both ends with a respective cam 21 rotationally fixed to the valve shaft 20 and engaging a respective cam plate 20, 23, respectively. Both cam plates 23 operate the cams 21 of the upper inlet valve 18 on their upper side and the cams 21 of the lower inlet valve 19 (shown in fig. 3) on their lower side. Due to the symmetry of the construction, this common operation of the valves 18, 19 by the double working cam plate 23 is made possible. Such a common operation by the cam plate 22 is also possible with the outlet valves 14 and 15. Fig. 5 and 6 show the shape of the cam plate 22 and 23. Torsion springs, such as the coiled springs 24, load the valve shafts 20 in a sense for inwardly rotating the respective valves 14, 15 and 18, 19.

Fig. 3 and 4 also illustrate that on both sides of the rotor 5 there are fixed co-rotating plates 25 having a circular outer circumference. These plates together with the sealing means 26 ensure the lateral seal between the rotor 5 and the housing 1. The sealing means 26 may be attached both to the housing 1 and to the plate 25.

Fig. 3 further shows that the rotor shaft 6 is hollow and is journalled in the housing 1 by means of bearings 27. The rotor shaft 6, which is closed in its center, serves as outlet duct on one side and as inlet duct 16 on the other side.

Fig. 7 illustrates a further embodiment of the internal combustion engine according to the invention, wherein a special valve arrangement is used. In this case, the compression valve 14 and the expansion valve 18 are journalled with their valve shafts 20 on a bearing portion 28 disposed within the combustion chamber 3. Because of this bearing portion 28 there is created a duct 29 leading to the combustion chamber 3. The inlet and outlet ducts may be formed within the rotor 5 in this embodiment. Advantages of this embodiment include a very favourable flow of the compressed gasses to the combustion chamber 3, and the fact that in this manner the compressed gasses do not flow past the hot expansion valve 18. Furthermore, the very hot expansion gasses do not flow past the compression valve 14 so that the thermal load on this valve is low. This embodiment also enables the fuel to be injected in a favourable position. The nozzle directly injects fuel into the combustion chamber 3 when the compression valve 14 is open. Of course, the seals of the valves should meet high standards.

Fig. 8, 9 and 10 show a further valve structure having as first noticeable feature the bearing of both valves 14 and 18 on one shaft 31, at least they rotate about the same axis. The advantage thereof is that the passage flow duct 29 over the valves 14 and 18 to the combustion chamber 3 is as short as possible, which leads to a compact combustion chamber, a minimum of braking action on the compressed gasses and a more easy injection of the fuel directly through the duct 29 into the combustion chamber 3. There is drawn a mounting hole 30 for the fuel injector of which the nozzle head preferably should be constructed such that it injects the required petrol directly into the combustion chamber 3 during the last part of the compression stroke. Since the compression valve 14 closes off the combustion chamber 3, the fuel injector is not subjected to the high combustion pressures .

Fig. 10 shows a simplified illustration of the suspension of both valves 14 and 18 to the shaft, wherein valve 14 is carried by a inner shaft 32 which is journalled in housing parts 33 on both sides of said valve 14, and valve 18 being fixed to a hollow shaft 34 which is journalled on said inner shaft 32.

Fig. 8 and 9 further show that the expansion valve comprises a particular type of sealing structure including lateral sealing partitions 35 restricting the width of the combustion chamber 3 as much as possible in order to allow for a sufficiently high compression. Due to these sealing partitions 35 the compressed gas flows from a relatively narrow compression valve 14 into a similar relatively narrow combustion chamber 3 enabling said sufficiently high compression. On the other hand, the sealing partitions 35 ensure that, when the expansion valve 18 is opened, the combustion gasses do not immediately flow out over the whole width of the wide expansion valve 18 which would otherwise cause a rapid decrease of power from the expansion pressure. In the present case this cannot happen because transverse front wall portions 36 exclude the space 38 outside the sealing partitions 35 from the expansion room 37. These transverse wall portions 36 are guided and sealed in mating cavities 39 in the housing 1. It can also be seen in figs. 8 and 11 that the compression valve 14 and the expansion valve 18 have a concave shape on their side facing the rotor 5 and therefore have a cavity 40 such that valves 14 and 18 are permitted to engage the rotor past a seal 41 at the position of the cam 7 or 8 and to seal against the rotor 5 with their free ends so that opening and closing movements of the valves 14, 18 may be effected over the seal 41 and this seal between valve and rotor remains possible if the cams 7, 8 pass by the valves.

The seal between the rotor and the housing preferably is a blank contact seal resulting in minimal or total lack of friction losses when a rotor 5 is switched off, which could be the case in an embodiment having several rotors and in which a rotor is switched off when only little power is required. Also a hybrid embodiment is conceivable in which the rotor 5 is coupled with an electric motor which may be put into operation while the combustion engine is switched off. In both cases, the valves 14, 18 are kept in closed position.

Figs. 12 and 13 show a blank contact seal 42 between both sides of the rotor 5 and the housing 1. This seal 42 includes a gap 43 having a very close fit of 0.03-0.05 mm, for example. Near the part of the circumference of the rotor 5 where the expansion takes place (the right portion of the sectional view in the figure) , the gap 43 connects in inward direction to an air chamber 44 formed in the rotor 5 and preferably being tangentially segmented, an air duct which is formed in the housing 1 is adapted to open into the air chamber 44. This air duct 45 may for example be supplied from an air vessel to cause a pressure and an air flow in it, which are electronically controlled and cause the formation of a counter pressure and flow to the gas pressures on the outer circumference of the rotor 5. A comparison of figs. 12 and 13 show that the radial length and/or the axial depth of the air chamber 44 may be varied in circumferential direction of the rotor 5, depending on the expected local gas pressure on the rotor 5. By varying the length of the air chamber 44, variations in the length of the sealing gap 43 may be obtained with which other ratios of pressure and flow within the sealing gap 43 may be obtained. In order to prevent the bearings of the rotor shaft 6 from becoming pressurized by leakage of pressurized air from the air duct 45 in radial inward direction, there is formed a pressure release duct 53 in the housing 1 near the rotor shaft 6. The compression part of the rotor 5 (see fig. 12 and 13, left portion) does not have an air chamber 44 because there the pressure at the circumference of the rotor 5 and consequently the leakage risk is considerably lower.

With reference to fig. 11, the seal 41 on the compression and expansion cam 7 of the rotor may also include a gap 45 having a very close fit of 0.03-0.05 mm and , in order to counteract a flow past the cam, this gap 7 may include one or more wedge shaped recesses 46 directed to the expansion room in order to disturb any gas flow above the cam 7 and make it turbulent as a result of which partly any gas will be allowed to pass. Here it is also possible to supply pressurized air, in this case through the rotor 5, in order to counteract a leakage of gas. The seal on the inlet and outlet cam 8 may have a more simple construction.

Other variations of the invention may for example be a further and even complete separation of cold and hot portions by axial separation of rotor 5 and rotor space 2 into compression and expansion portions. By separation of the rotor space 2 in an inlet and compression room and an expansion and outlet room, the inlet and outlet ducts in the rotor housing may remain continuously open. The inlet duct can also be formed in the rotor and be connected to the air supply through the hollow rotor shaft 6. Fig. 14 shows an example of a rotor 5 having full axial separation of compression and expansion. In this embodiment, the central rotor portion 47 serves as expansion portion and both outer portions 48 serve as compression portions. The valves 14 and 18 extend in transverse direc- tion only through their respective expansion or compression portion 47, 48, respectively, of the rotor 5. Fig. 15 shows in which way the compressed air can be supplied to the combustion chamber 3 through ducts 49. Of course, the consequence of this arrangement is that the power generation is less in comparision with a rotor 5 without full separa¬ tion, since the compression and expansion take place in a portion of the width of the rotor only. An advantage of this construction is, however, that both the compression and expansion valves 14 and 18 may be guided in their movements by their rotor portion 48, 47, respectively, thereby avoiding the necessity of external control means .

Fig. 16 shows an examplary embodiment in which there is created a partial axial separation between expansion and compression portions. In this case there are five portions of which the extreme outer portions 50 perform only the compression, the central portion 51 only expansion and intermediate portions 52 both expansion and compression. This embodiment does not require an external operation of the valves as well because the outer portions 50 are able to control the compression valves 14 and the central portions 51 control the expansion valves 18.

Fig. 17 shows a rotor 5 in which a partial axial separation is effected in another way. The central portion 47 serves for both compression and expansion, while the outer portions 48 only effect the expansion. The outer portions 48 and therefor the expansion portions have an overlap only with the expansion valves 18 and have a circular shape in one half which is therefore ineffective (the upper half) . Contrary thereto, the central portion 47 (on the left side in the figure) is fully oval-shaped. In this embodiment, the expansion valves 18 may be guided in their movements by the rotor portions 48, but the compression valves 14 require an external control. The rotor 5 shown in figs. 12 and 13 is constructed according to the embodiment of fig. 17.

For the sake of completeness it is noted that in principle the invention also enables the use of only one combustion chamber and one rotor cam. In this case there is created a six stroke principle including two inactive strokes. In three revolutions of the rotor there is one combustion stroke. Combustion spaces having four, six, eight, etc. combustion chambers are also conceivable.

Also other changes or variations are possible. For example, the blank contact seal on the sides of the rotor may consist of a labyrinth seal of which the labyrinth outlet may be connected to the combustion gas outlet or to a pressurized duct, for example.

Claims

CLAIMS ;

1. Internal combustion engine operating according to the four-stroke principle, comprising

- a housing having a rotor space therein,

- preferably at least a pair of regularly circumferentially spaced combustion chambers in the rotor space,

- a rotor rotating truly about a rotor axis within the rotor room, said rotor having an unround shape and preferably including at least two circumferentially spaced cams,

- sealing means at the circumference of the rotor to form a seal between the rotor and the rotor space,

- inlet and outlet ducts adapted to communicate with the combustion chambers,

- valve means which, in cooperation with the cams of the rotor, are adapted to separate for each pair of combustion chambers four varying rooms between the rotor and the housing in which the four strokes of the four-stroke process take place.

2. Combustion engine according to claim 1, wherein the rotor space is substantially circular shaped in transverse section, the center of which coincides with the axis of the rotor shaft.

3. Combustion engine according to claim 1 or 2, wherein the inlet and outlet ducts are formed in the housing and may be opened and closed by the valve means.

4. Combustion engine according to claim 1 or 2, wherein the inlet and outlet ducts are formed in the rotor and the valve means are adapted to effect a seal between the rotor and the housing to selectively separate combustion chambers and inlet and outlet ducts.

5. Combustion engine according to one of the preceding claims, wherein the valve means are rotatable about a valve axis extending parallel to the rotor shaft.

6. Combustion engine according to claim 5, wherein the valve means are controlled by a cam disc mounted on the rotor shaft or by a cam shaft driven by the rotor shaft .

7. Combustion engine according to claim 5 or 6, wherein the two valves of one combustion chamber rotate about a common axis.

8. Combustion engine according to claim 5, 6 or 7, wherein the combustion chambers are each defined by the two respective valves and the housing and is adapted to communicate with the circumference of the rotor upon opening of the expansion valve.

9. Combustion engine according to claim 8, wherein the side of the valves facing the rotor are of concave shape in circumferential direction such that the valves seal against the rotor only near the free end thereof.

10. Combustion engine according to one of the preceding claims, wherein the rotor is axially separated into a central expansion and/or compression portion and two compression and/or expansion portions positioned on either side thereof.

11. Combustion engine according to claim 10, wherein the separation is complete and the compression portion is totally different from the expansion portion, the corresponding valves extending only through the width of the respective rotor portion and a duct being formed extending from the compression room in axial direction to the combustion room.

12. Combustion engine according to claim 10, wherein the separation is partial and at least a portion of the rotor is a mixed portion where both compression and expansion take place and with which both the compression valve and the expansion valve cooperate.

13. Combustion engine according to one of claims 10- 12, wherein the outlet ducts are formed within the housing and the inlet ducts within the rotor.

1 . Combustion engine according to one of the preceding claims, wherein the sealing means between rotor and housing operate through blank contacts.

15. Combustion engine according to claim 14, wherein air ducts supplied with pressurized gas are connectable to sealing points.

16. Combustion engine according to claim 14 or 15, wherein the sealing means on each cam of the rotor includes a close fit in combination with a plurality of wedge shaped recesses directed to the expansion room and formed in the rotor circumference.

17. Combustion engine according to claim 15 or 16, wherein the sealins means on the sides of the rotor includes an air chamber extending in circumferential direction, connectable to the air duct and the transverse section of the air chamber varying in circumferential direction and transforms into a close fit gap in outward direction.