Field of the invention

The invention relates to the field of rotary piston arrangements for rotary engines, compressors or pumps.

Background of the invention

Rotary engines are well known and have been developed in various

configurations, the most famous of which is the Wankel engine. Common to all rotary engines is the provision of two or more variable-volume chambers formed between a rotor and the walls of the stator chamber in which the rotor rotates. The volume of each chamber varies as the rotor rotates in the stator. The Wankel design defines three chambers, isolated from each other by the contact between the triangular rotor's three apexes and the oval chamber wall. All phases of the four-stroke engine cycle are implemented by the three variable-volume chambers. Disadvantages of the Wankel rotor design are its complex eccentric rotor bearing and the continuous lateral displacement of the rotor mass, which expends energy and promotes wear and vibration. Other rotary piston arrangements have been proposed with a view to providing rotary engines with simpler, balanced rotor construction and improved performance.

Prior art

American patent US4638776 describes a twin-rotor engine which has two cooperating rotors arranged adjacent to each other and communicating via a connecting channel. The first eccentric rotor rotates inside a first (compression) chamber so as to draw in a fuel/air mixture during a first part of the cycle (intake) and then compresses the mixture during a second part of the cycle (compression). The compressed mixture is then expelled into a second (combustion) rotor chamber via the connecting channel, whereupon the mixture is detonated in a third part of the cycle (power) and then expelled through an exhaust port in a fourth part of the cycle (exhaust). The rotors of US4638776 are equipped with radial vanes providing a low-friction seal between the rotor and the stator (chamber). These vanes are arranged to move radially outward and inward from the rotor, synchronised with the eccentric motion of the rotor, so as to maintain a small but constant gap distance between the vane tip and the inner peripheral wall of the chamber. This vane is moved in and out by a pin which engages in a circular slot in the side wall of the chamber. This vane drive arrangement is subject to wear, and is difficult to access for adjustment and repair. Furthermore, the vane and the drive arrangement embody an eccentric and radially-mobile mass and exert radial forces on the rotor which are complicated to compensate and contribute to an imbalance in the rotor.

Brief description of the invention

The present invention aims to overcome at least some of the above

disadvantages of prior art engines such as the one described above. To this end, the invention foresees a rotary engine as described in claim 1. Further variants of the invention are set out in the dependent claims. The inventive reciprocating vane drive (follower shaft) arrangement, with the moving vane seal effected with a predetermined (but very small) gap at the rotor surface instead of at the chamber wall, allows a rotor construction which is simpler, lighter and better balanced. It also permits easier access for maintenance, adjustment and repair of the vane seal and the reciprocating vane drive mechanism.

Brief description of the drawings

The above and other advantages of the invention will be described in detail with reference to the attached drawings, in which:

Figure 1 shows in cross-section, in the plane D-D indicated in figure 7, an example of a first (compression) rotor in a twin-rotor engine using a vane actuator according to the present invention.

Figure 2 shows in cross-section, in the plane B-B indicated in figures 7 and 9, an example of a second (combustion) rotor in a twin-rotor engine using a vane actuator according to the present invention. Figure 3 shows in cross-section, in the planes F-F indicated in figures 2 and 7, the first and second rotors of figures 1 and 2.

Figure 4 shows in cross-section, in the plane G-G indicated in figures 2 and 7, the rotary engine of figures 1 to 3.

Figure 5 shows in cross-section, in the plane C-C indicated in figure 7, the rotary engine of figures 1 to 4. Figure 6 shows in cross-section, in the plane A-A indicated in figures 7 and 9, the rotary engine of figures 1 to 5.

Figure 7 shows a plan view of the rotary engine of figures 1 to 6.

Figure 8 shows a side elevation view, in the plane indicated by E-E in figure 7, of the rotary engine of figures 1 to 7.

Figure 9 shows a variant of the tangential seal used in the engine of figures 1 to

8.

Figure 10 shows how two engines of the type illustrated in figures 1 to 8 can be arranged coaxially, back-to-back, sharing a common main shaft and vane actuator. Figures 11a to 11c show a variant with an offset arrangement of the vane actuator guides.

Figure 12 shows a variant of the vane with automatic gap adjustment.

Figure 13 shows a first longitudinal cross-section of the vane with automatic gap adjustment. Figure 14 shows a second longitudinal cross-section view and a transverse cross-sectional view of the vane with automatic gap adjustment,

Figure 15 shows a side elevation view of the vane with automatic gap

adjustment.

Figure 16 shows a first cross-sectional view of the rotor vane with automatic gap adjustment.

Figure 17 Shows a second cross-sectional view of the rotor vane with automatic gap adjustment.

Figure 18 shows a plan view of a rotor with a rotor vane with automatic gap adjustment. The figures are provided merely as an aid to understanding the principles underlying the invention, and should not be taken as limiting the scope of protection sought. Where the same reference numbers are used in different figures, these are intended to indicate similar or equivalent features. It should not be assumed, however, that the use of different reference numbers is intended to indicate any particular degree of difference between the features to which they refer. Detailed description of the invention

Figures 1 to 8 show different views of the same example implementation of a twin-rotor rotary engine employing a vane actuator according to the present invention. Reference numbers are used consistently throughout, but not all reference number are included in every view for the sake of clarity. An index of the reference numbers is provided at the end of this description.

The example implementation is a four-cycle internal combustion engine working with eccentric rotors instead of conventional reciprocating pistons. It comprises two rotor- stator assemblies; a compression rotor-stator assembly is illustrated in figure 1, and a combustion rotor-stator assembly is illustrated in figure 2. The two assemblies are arranged with coaxial stator chambers which are connected for fluid communication by means of a connecting channel A8/B14. The connecting channel is opened and closed by an opening E32 in a valve disc E23 located between the two assemblies and arranged to rotate with the main shaft C38. Each assembly comprises a stator chamber with a central main shaft and a peripheral inner wall concentric with the main shaft, and an eccentric rotor mounted on the main shaft such that the most remote part of its outer peripheral surface from the rotation axis touches or almost touches the inner peripheral wall of the stator chamber at point A9. The outer peripheral surface of the rotor, and the inner peripheral wall of the stator chamber are both cylindrical. The compression rotor A4 shown in figure 4 is shaped such that its centre of gravity coincides with the centre axis of the main shaft. Balancing may be achieved by machining one or more hollow regions in the rotor, for example. Side seals are provided between the side walls of the rotor and the side walls of the stator chamber. These are indicated by dotted lines in figures 1 and 2, and by C34 in figure 3. They are shown as being concentric with the circular shape of the rotors. Alternatively, they may preferably be arranged concentrically with the main shaft C38. According to one variant, the balancing may be achieved by shaping or configuring all of the components of the vane actuator (eg including the actuator rotor, the bearing, the follower shaft, the pivot, the vane shaft and the vane) such that their total net rotational centre of gravity coincides with the axis of rotation of the main shaft. The usable stator volume (ie the part outside the rotor periphery) is divided into two sub-volumes, Al and A7, by vane seal A6 and tangential seal A9. Vane seal A6 is formed at the tip of vane A3, which is held in almost-contact with the eccentrically-rotating surface of rotor A4 by vane actuator means which will be described in more detail below. Tangential seal A9 is formed by the close proximity between the peripheral surface of the rotor and the peripheral wall of the stator chamber. Additional seal components such as packing or a sprung seal, may be included as will be discussed below. Sub-volume Al is the air-intake volume; as the rotor rotates in the direction of the arrow, the increasing volume of sub-volume Al draws air in through the air intake channel. At the same time, air drawn in during the previous rotation is being compressed in compression volume A7 by the rotation of the rotor A4. The compressed air is allowed through the connecting channel A8 when the opening E32 in the valve disc E23 coincides with the connecting channel A8. Guide A5 and vane A3 are positioned adjacent to and rotationally after the connecting channel A8, so that the air in sub-volume A7 reaches its maximum compression at the point in the rotation cycle where the valve disc opens to allow the compressed air into the connecting channel. After the compressed air has passed through the connecting channel A8/B14 and into the enclosed subvolume B15 of the adjacent (combustion) rotor-stator assembly, fuel is sprayed or misted into the airflow.

In order to achieve satisfactory compression, the vane seal A6 is preferably maintained at a very small distance (eg less than 0.3 mm or less than 0.1 mm, or less than 0.06 mm), ie almost touching the surface of the rotor. Vane A3 is mounted so that its shaft can reciprocate radially, running in guide means A5 (eg between two pairs of rollers mounted in bearings, as shown). A fluid seal is also provided around the vane shaft A3 such that the vane shaft can move radially in and out without any fluid losses around the vane shaft. Figure 2 shows the combustion rotor-stator assembly, which operates in a similar manner to the compression assembly except that the sub-volumes B15 and B19 vary inversely with respect to their counterpart sub-volumes Al and A7 of the compression assembly. In this example, the two rotors are both rotationally fixed to the same main shaft C38, but with the combustion rotor leading the compression rotor by an offset angle of approximately 90°. Fuel is introduced (eg sprayed or atomised) into the sub-volume B15 by fuel injection nozzle B13 after the closure of the rotating valve. The vane shaft guide B17 and the vane shaft B22 which maintains the vane seal gap B16 are configured so that the vane is positioned adjacent to and rotationally before the connecting channel so that the compressed fuel-air mixture in the sub-volume B15 can then be detonated by the ignition spark B12, thereby providing drive force on the rotor B18. Meanwhile, sub- volume B19 contains the exhaust gases from the previous detonation, which are then expelled through exhaust channel B20.

In the illustrated example, the compression and combustion vanes are angularly positioned 16° before and 16° after the centre-line of the connecting channel, but other angular positions could be used. The angular separation of the two vanes is thus 32° in this example. This angular separation may preferably be less than 40°, or more preferably less than 30°, or more preferably less than 25° in order to minimise the instantaneous size of the space created temporarily by the combined volumes of the compression sub- volume A7, the detonation sub-volume B15 and the volume of the connecting channel A8/B14. The tips of the vanes A3 and B22, which form fluid-tight pressure seals A6 and

B16 by their proximity with the peripheral surface of the rotors A4 and B18 respectively, are shown as planar (flat) surfaces, in this case perpendicular to the longitudinal axis of the vane shaft. The substantially planar (flat) tip configuration allows different parts of the tip surface to come into contact or almost-contact with the rotor surface at different parts of the rotational cycle. Thanks to the flat vane tip, the vane-to-rotor gap tolerances can be kept to a minimum.

Figures 3, 6 and 8 show how the vane actuators may be configured to ensure that the vanes closely follow their respective rotor surfaces. The shaft of each vane is connected by a pivot or hinge H28 to a reciprocating follower shaft rotatably mounted on an eccentric actuator rotor, concentric with the corresponding rotor A4 or B18 and coaxial with the main shaft, so as to rotate with the main shaft. The actuator rotor H26, H27 may comprise ball or roller bearings for smooth, reliable operation. As with the rotors A4 and B18, the actuator rotors and bearings may be shaped so as to be rotationally balanced, having a centre of gravity which coincides with the axis of rotation. Note that the actuator rotor need not have the same radius as the corresponding rotor A4 or B18, however the rotors' eccentricity (distance of rotation axis from centre axis), and their rotational position on the main shaft should be the same.

The vane shaft or the follower shaft can be provided with elongation-adjustment means for adjusting or fine-tuning the radial position of the vane relative to the centre axis of the actuator rotor (and therefore relative to the outer peripheral surface of the main rotor A4, B18. The elongation adjustment means may be mechanical, for example, and may be controlled to adjust the shaft elongation in dependence on predetermined parameters such as the surface profile of the main rotor, or on dynamic parameters, such as temperature or thermal expansion eg of the rotor. While the embodiments are described here as having a finite predetermined or controllable vane seal gap, the vane shaft may alternatively be provided with a vane which is lifted from the rotor surface, in case of expansion, such that an effective seal contact, but with minimal friction, can be accomplished automatically .

Figures 3, 4 and 5 also illustrate the operation of the valve disk E23, rotationally mounted on the main shaft and provided with side faces E35 and E36 which are sealed for example mechanically, with tight tolerances, with a sealing lubricant against the outer side faces of the two stator chambers. Valve disk E23 is provided with an opening which is configured to coincide with the fluid connection channel A8/B14 for a short part of the rotation cycle to allow compressed air from the compression chamber to enter the combustion chamber. Fuel is also introduced into the compressed air through nozzle B13. Once the channel A8/B14 has been closed again by the rotation of the opening E32 past the channel, the fuel/air mixture is detonated by ignition B12. In this way, the illustrated configuration achieves one power stroke per rotor revolution.

Figure 7 also shows an arrangement in which multiple (two in this example) fuel injectors are used to achieve good mixing of air and fuel.

Figure 9 shows a variant of the compression rotor in which the tangential seal 48 (which corresponds to seals A9 and Bll) is implemented as a radially-mobile vane 44 with a radial-outward biasing spring 51 and a control pin 46 engaging with a control surface (eg the outer peripheral surface of a substantially circular groove in the side wall of the stator chamber) to maintain the desired vane seal gap distance of the tangential seal 38. As described above in relation to a variant of the vanes A3 and B22 and associated vane actuators, the radially-mobile tangential vane 48 may be moved to follow a trajectory which is not purely circular. This means that the stator periphery wall may be non-circular, for example so that the rotor's sealing edge 48 may pass under the descending vane without interference. It also means that tangential vane seal gap may be varied in dependence on dynamic parameters such as temperature, thermal expansion etc, but with an optimal gap (ie minimal gas leakage).

Figure 10 shows how two twin-rotor engine (or equivalent pump or compressor) assemblies such as that shown in figures 1 to 8 can be mechanically coupled, back to back, so as to share a common main shaft and a common actuator shaft. The first (left- hand) twin-rotor assembly comprises two vane shafts T4 and T8, while the second (right- hand) twin-rotor assembly comprises two vane shafts T5 and T9. The vane shafts T4 and T5 are connected to one common follower shaft Tl by pivots T2 and T3 respectively.

Figures 11a to 11c show how the vane guides (rollers) can be arranged for improved stability of the vane. For each vane, the lower, outer guide is positioned closer to the rotor-stator assembly than the lower, inner guide. By supporting the vane as close as possible to the rotor-stator assembly, lateral flexing of the vane can be minimised, the onset of damaging vibrations can be reduced, and the vane can be of a lighter

construction and material. Since the reciprocating action of the vane requires energy to accomplish, a lighter vane results in a reduction in overall energy losses in the

engine/pump/compressor. Figure 11a shows the implementation of this variant in the first rotor-stator assembly; figure lib shows the implementation of this variant in the first rotor- stator assembly; and figure 11c shows the twin rotor-assembly implementation.

Figures 12 to 15 relate to a variant in which the vane is provided with a mechanism for accommodating variations in diameter of the rotor and/or variations in the length of the vane. Such variations may arise during operation due to variations in temperature of the engine/pump/compressor as a whole, and/or due to variations in relative temperatures of the various components. If the stator is cooled, for example, but the rotor temperature increases significantly during operation, the radius of the rotor will increase, and the vane's radial position can be adjusted such that the vane tip moves radially outward so as to maintain a constant seal gap at the vane-tip/rotor-surface interface. The proposed solution illustrated in figures 12 to 16 includes one or more surface-tracking rods, indicated by reference 58 in figures 12 and 13. Each tracking rod comprises a foot 57 in contact with the rotor surface. The foot and rod are lightly biased against the rotor surface by biasing spring 59. The distal end of the vane is provided with a mechanism for translating a radial movement of the tracking rod into an adjustment of the vane's radial position relative to the rotor. In this way, the sealing gap at the rotor surface can be automatically adjusted in dependence on a thermal expansion or contraction of the radial dimensions of the rotor. In the example implementation illustrated in figures 12 to 15, the or each tracking rod is arranged to produce a rotation of an eccentric cam 62 which raises or lowers the vane relative to the vane actuator shaft. A fine adjustment of the sealing gap size, and/or of the movement transfer ratio between the rod and the vane can be accomplished by adjusting the position of the engagement location of the rod's distal end 61 with the cam 62, for example. Such an adjustment mechanism is not shown in the figures. Figure 15 shows a side elevation view of a vane arrangement comprising two tracking rods for translating a change in radius of the rotor into a small rotation of the cam 62, and two adjustment actuating rods for translating the rotation of the cam 62 into a change in radial position of the vane, thereby maintaining a constant, finite seal gap at the vane-tip/rotor-surface interface

Figures 16 to 18 show a variant of the implementation of figure 9 in which the rotor vane is provided with a mechanism for maintaining an optimum seal at the second rotor/stator interface, ie at the point on the rotor's circumference where the rotor outer surface is closest to the stator's interior surface, while avoiding interference with the first (stator) vane. As in figure 9, the rotor vane blade 44 is provided for making effective but low-friction sealing contact between the rotor and the stator. The rotor vane blade 44 is held in low-friction contact against the stator surface by biasing spring and vane blade rod 43. In this variant, however, the vane blade 44 is provided with one or more lateral slide elements 52 which are arranged to engage with corresponding elements at the proximal end of the vane (ie on the vane tip planar surface) so as to ensure that the vane tip of the stator vane and the vane blade of the rotor vane do not come in contact as the rotor vane blade passes the stator vane tip. As shown in figures 17 and 18, the rotor vane blade 44 may be provided with multiple (in this case two) such biasing springs with sliding elements 52. Note that the radial inner end of the vane blade biasing arrangement may follow a tracking path, as in figure 9, or it may be radially fixed, as indicated in figures 16 and 17.

Index of reference numbers used in the drawings

Al Air intake channel, first (intake) volume

A2 First stator block

A3 First vane shaft

A4 First (compression) rotor

A5 First vane shaft guide

A6 First vane seal

A7 Second (compression) volume

A8 Communication channel opening

A9 First tangential seal

BIO Second stator block

Bll Second tangential seal

B12 Ignition

B13 Fuel injection

B14 Communication channel

B15 Third (detonation) volume

B16 Second vane seal

B17 Second vane shaft guide

B18 Second (combustion) rotor

B19 Fourth (exhaust) volume

B20 Exhaust port

B22 Second vane shaft

C24 Second stator outer side wall

C25 First stator outer side wall

C34 Lateral seal between rotor and stator side-wall

C37 Coolant channel

C38 Main shaft

E23 Valve disc

E25 Key and keyway (valve disc)

E32 Valve disc opening

E35 First side face of rotating valve disc

E36 Second side face of rotating valve disc

F30 First vane actuator rotor

F32 Second vane actuator rotor

H26 Second follower shaft eccentric and bearing

H27 First follower shaft eccentric and bearing

H28 Second vane actuator connecting pivot axle

H29 First vane actuator connecting pivot axle

Tl Common first vane actuator follower

T2 First actuator pivot of first twin-rotor engine

T3 First actuator pivot of second twin-rotor engine

T4 First vane shaft of first twin-rotor engine

T5 First vane shaft of second twin-rotor engine

T6 Second vane actuator follower of first twin-rotor engine T7 Second vane actuator follower of second twin-rotor engine

T8 Second vane shaft of first twin-rotor engine

T9 Second vane shaft of second twin-rotor engine Radial rotor vane

Guide surface for control pin Tangential seal gap

Stator chamber peripheral wall Biasing spring

Slider element