WO2000049276A1

WO2000049276A1 - Rotary piston machine

Info

Publication number: WO2000049276A1
Application number: PCT/EP2000/001519
Authority: WO
Inventors: Jürg SCHIFFMANN
Original assignee: Ecole Polytechnique Federale De Lausanne (Epfl)
Priority date: 1999-02-19
Filing date: 2000-02-21
Publication date: 2000-08-24
Also published as: AU3806200A; SE9900632D0; WO2000049276A9

Abstract

A rotary piston machine having a housing (1) provided with a cavity (2) comprising a rotor (6', 6) rotating around a first axis and a compression plate (16) dividing said cavity into separate volumes, the machine further being provided with at least one inlet port and one outlet port. Said cavity (2) is provided with a spherical wall portion (3) and is closed by means of a top cover (13). The rotor is provided with a conical part (6) reaching into said cavity (2) which conical part is provided with a slot (15) through the virtual tip of the cone perpendicular to the base of the same. The compression plate (16) is provided with a circular edge portion having essentially the same radius as the spherical wall portion (3) of said cavity and is arranged sliding in a pivoting movement in said slot (15). The plate (16) has further a straight edge portion (22) arranged at the level of the virtual tip of the cone and is arranged for rotation in said cavity in a plane parallel to the top cover (13) which compression plate during operation is thus rotating at the same speed as the cone around said first axis while simultaneously pivoting around a second axis perpendicular to said first axis.

Description

Title

ROTARY PISTON MACHINE

Technical field This invention relates to a rotary piston machine. The designation "machine" is in this context comprising both the concept of an "engine", i.e. a device for converting fluid energy into mechanical power, and the concept of a "pump", that is e.g. a device for compressing or exhausting fluid by mechanical means, in the following the description of the invention will be made in terms of a compressor and a pump, in view of the above it should be perfectly clear that this does not limit the concept of the invention.

Background art

The Swiss patent No. 571646 describes a rotating motor/pump having a housing provided with a cylindrical cavity comprising the rotor. The rotor comprises two opposite, symmetrical parts having the form of cones between which cones a circular co-rotating disc is arranged having a fixed angle less than 90 degrees in relation to the rotational axis of the motor/pump. This type of motor/pump has an important leakage-flow due to the large opening in the oblique disc. Additionally the torque at the driving motor will be varying due to the oscillating angular velocity of the oblique disc. In compression mode the discharge of the compressed fluid through the cone results in an important dead volume. The most important disadvantage is however the leakage-flow through the large opening in the oblique disc.

Brief description of the invention One object of the present invention is to provide a rotary piston machine having a co-rotating disc without any opening which can create a leakage. The new design also allows a favourable arrangement of the discharge port or ports so that a very small dead volume is created. The advantages in relation to prior art will be very low leakage flow, high volumetric efficiency and a small number of moving parts.

These objects are achieved by means of an apparatus having the following characteristics.

-a main housing provided with a cavity having a spherical wall portion. In an advantageous embodiment the cavity has the form of a half-sphere.

-the cavity being closed by means of a cover. In one embodiment this cover is flat on the side facing the cavity.

-a rotating cone reaching into said cavity. In an advantageous embodiment the cone is straight-sided. The virtual top of the cone being arranged at the virtual centre of the cavity. The cone being in contact with the inner side of the cover at least along a generatrix of the cone. In an advantageous embodiment the cover of the cavity is provided with a grove corresponding to the envelop surface of the cone on the side facing the cavity. The cover and the cone being in contact over the full surface of this grove.

Brief description of the figures

Other objects, uses and advantages of this invention will be apparent from the reading of this description which proceeds with reference to the accompanying drawings forming part thereof and wherein: Figure 1 shows an exploded view of one embodiment of the invention.

Figure 2 shows in section the same embodiment assembled.

Figure 3 - 5 show in perspective the embodiment according to figure 1 in three different phases of a compression cycle.

Figure 6 shows in a schematic view an assembly of two synchronised compressors with common geometrical axis.

Figure 7 shows in a schematic view another assembly of two synchronised compressors.

Figure 8 schematically shows an outlet port arrangement and the junction between the valve disc and the compression plate.

Figure 9 shows in section a detail of another arrangement of the junction between the valve disc and the compression plate.

Figure 10-11 shows a detail of an embodiment of the compression plate and its arrangement in the cone.

Figure 12 shows in a schematic form an arrangement for adjusting the discharge angle. Figure 13 shows in section an embodiment of the invention implemented as a pump.

Figure 14 shows in section a further embodiment of the invention implemented as a pump.

Figure 15 illustrates the arrangement of a channel for feeding fluid down under the rotating cone.

Figure 16 illustrates a further embodiment of the invention.

Detailed description of the invention

As mentioned above the following description of the invention will for the sake of simplicity be limited to one implementation of the concept in the form of a compressor and one in the form of a pump. However, as the title indicates the invention concerns a rotary piston machine which means that the same inventive concept could also be implemented as e.g. an engine. It will be well understood by the man skilled in the art that the description in this way will not limit the concept of the invention or the scope of protection.

Figure 1 shows an exploded view of one embodiment of the invention. The main housing 1 is provided with a cavity 2 having a spherical wall portion 3. From the lower side of the housing a cylindrical hole 4 communicates with the cavity and on one side of the housing a triangular opening 5 constituting the inlet port for the working fluid is arranged. This port could also have other forms. The cavity which has the general form of a segment of a sphere could correspond to exactly half a sphere or be smaller than half a sphere. In the following an embodiment is described in which the cavity corresponds to half a sphere.

A rotating part comprising a cylindrical body 6', a top in the form of a straight cone 6 fixed to the cylindrical body or forming an integral part of the same and a co-axial drive shaft 7 is arranged rotating in the cylindrical hole 4 in the wall of the main housing 1. The shaft 7 is journalled in an appropriate bearing here schematically represented by the bearing support plate 8 provided with a simple hole 9.

The geometrical axis of the hole 4 and the corresponding axis of the cavity form an angle of 45° and the axis of the hole 4 goes through the centre of the sphere in this embodiment. This means that with a top angle of the cone 6 of 90° one generatrix of the cone will always be parallel to the plane defining the opening of the cavity. Other angles between the geometrical axises could be envisaged which then correspond to other top angles of the cone.

The opening of the cavity is in this embodiment covered by a valve disc 10 provided with two valve openings 11 , 12. On top of this valve disc the housing is closed by means of a top cover 13 provided with an outlet port 14 for the working fluid co-operating with said valve openings. It should be noted that other types of outlet valves, e.g. check valves or synchronised active valves can be used. In that case these valves will advantageously be arranged in the top cover 13 and there will be no valve disc 10.

The cone is provided with a slot 15 symmetrically through the tip of the cone and perpendicular to the base of the cone. A compression plate 16 having the genera! form of a half circular segment is arranged sliding in a pivoting movement in this slot. The plate 16 has in principle the same radius as the spherical cavity which allows the plate to freely rotate and pivot inside the cavity in contact with the cavity walls. The straight edge 22 of the compression plate 16 is arranged at the level of the tip of the cone.

The rotating part including the cylindrical body 6', the cone 6 and the cooperating compression plate 16 is mounted in the main housing in such a way that the tip of the cone coincides with the centre of the cavity which means that a generatrix on the cone and the straight edge of the compression plate will be in sealing contact with the lower side of the valve disc 10. This disc 10 and the straight edge of the compression plate are designed in such a way that the rotation of the compression plate by means of the cone will also bring the valve disc 10 to rotate. Details of examples of such a design can be seen in figures 8 and 9.

Figure 2 shows in section the same embodiment assembled. Corresponding units have been given the same designations.

Figures 3 - 5 show in perspective view the embodiment according to figures 1 and 2 without the co-operating valve disc 10 and the top cover 13 for different angle positions of the compression plate 16.

The rotating part 6', 6, 7 is rotated by means of a drive motor so that the compression plate, seen from the opening of the cavity, is moving counter clock wise inside the cavity. In principle the machine could also work with a clock wise rotation with an appropriate repositioning of the inlet and outlet ports.

For reference the main housing has on figures 3, 4 and 5 been marked with an index 0° corresponding to the contact line between the envelop surface of the cone 6 and the lower side of the valve disc 10 in this embodiment. The angle ex mentioned below is measured between this index and the marked end portion of the straight edge of the compression plate 16.

The spherical wall portion 3 of the cavity, the envelop surface of the cone 6, the compression plate 16 and the lower surface of the co-rotating valve disc 10 are together defining three separate volumes A, B and C inside the main housing which will be created, expanded and compressed during the cycle covering a rotation of 540° of the drive shaft and consequently the compression plate 16.

At α = 0 the volume A does not exist. At the beginning of the cycle, 0°<α<90°, the volume A is created and is then growing larger and larger in the first quadrant. During this part of the cycle the volume B according to figure 3 is a previously created volume still expanding. The volume C is a volume under compression. It should be noted that the volumes B and C represent later stages of the volume A during the cycle. For the understanding of the working principle of the machine it is thus sufficient to follow the creation and development of one volume. The volume A is in this interval in communication with the inlet port 5 and sucks working fluid from that port.

Between 90°<α<180° the volume A continues to grow still in communication with the inlet port 5. At α=180° the volume A is occupying the first and second quadrants. Due to the tilting of the compression plate in the interval 180°<α<270° the volume A continues to grow still in communication with the inlet port 5. At α=270°, cf. Figure 4, the volume A has its maximum and the compression plate has now cut off the communication with the inlet port 5. Thus, the interval between 0° and 270° represents the suction phase for the compressor. It should be noted that in the interval 180°< <270° a new suction phase has started for the volume A'.

In the interval 270°<α<540° the volume A gets smaller and smaller. The fluid in the volume being compressed. At α=360° the volume A occupies the third and the fourth quadrants. When the valve opening 11 or 12 coincides with the outlet port in the top cover the compressed fluid will be discharged. The angular position of the outlet port in the top cover preferably in the fourth quadrant and the angular position of the valve openings in the valve disc will thus define the outlet pressure (with all other parameters of the system fixed). In the embodiment according to figures 1 to 5 these angular positions have been shown as fixed but adjustable angle positions are also possible. One example of a system for adjusting the angular positions of the valves will be described below with reference to figure 12. Figure 5 shows an angle position of the compression plate of about 520°, thus at the end of the cycle and the volume A which is occupying part of the fourth quadrant is now very small.

If the machine is used for pumping a generally incompressible fluid like a liquid the outlet port has to be open in the interval 270°<α<540° or in other words cover the full fourth quadrant of the cavity. Otherwise the rotational movement would be blocked if no emergency system is arranged, e.g. in the form of a spring loaded auxiliary valve. In general, if the working fluid is a mixture of gas and liquid, an appropriate position for the outlet port has to be found in the fourth quadrant, e.g. by means of a system according to figure 12.

So far an embodiment of the machine has been described which includes a co- rotating valve disc 10 provided with two valve openings 11 , 12 which co-operate with the outlet port 14 in the top cover 13 to allow the discharge of the working fluid at an appropriate angle position of the compression plate 16. Other arrangements of the outlet port could however be envisaged. If the compression plate 16 and the cone are arranged rotating with direct contact against the lower side of the top cover 13, i.e. without an intermediate valve disc 10, the discharge could be arranged through appropriately positioned check valves preferably in the fourth quadrant. This check valve will be set to open at a certain pressure. Figure 6 shows in a schematic view an assembly of two synchronised compressors with common geometrical axis. In certain applications such an assembly could be very advantageous. It could e.g. be implemented as a two- stage compressor of the type generally used in refrigeration and heat-pump cycles. As can be seen from the figure the assembly could be made very compact. The machines could be of the type having top cover and a cooperating valve disc or the type without a valve disc but with check-valves in the top cover.

If we consider that the system is driven by the lower shaft 7 fixed to the lower cone 6 then the upper compressor is driven by a torque transferring system comprising co-operating gears 17, 18, 17', 18' and two shafts 19, 19' connecting the two gears 18, 18'. If no further compressor stage is connected in cascade the upper shaft 7' will be redundant. If on the other hand further compressor stages are connected on top a suitable connection to the next cone will be made by means of the shaft 7'.

Figure 7 shows in a schematic view another assembly of two synchronised machines. In this case the upper compressor is driven by means of the co- rotating valve discs 10 and 10'. Therefore a coupling between the valve discs 10, 10' and the respective compression plates 16, 16' has to be so designed that it can transfer the appropriate torque. An advantageous embodiment of such a coupling is shown in figure 9.

Figure 8 shows in section an arrangement of the outlet port 14 and the junction between the valve disc 10 and the compression plate 16. The lower side of the top cover 13 has been provided with a circular ridge 20 co-operating with a corresponding groove 21 in the upper surface of the valve disc 10. This arrangement obviously gives a very small dead volume for the machine. The straight edge 22 of the compression plate 16 has a rounded form cooperating with a straight groove 23 along a diameter of the valve disc. The contact surface between the plate 16 and the disc 10 which defines the leakage path has a width which in this case corresponds to less than half a circle with a diameter equal to the thickness of the plate 16. This arrangement transfers the torque from the rotating compression plate to the valve disc and creates the sealing between the different volumes inside the machine.

Figure 9 shows in section a detail of another embodiment of the junction between the valve disc 10 and the compression plate 16. In this case the leakage path has been made longer and corresponds to more than half a circle with a diameter equal to the thickness of the plate 16. It should be noted that said diameter could be both smaller and greater than the thickness of the plate 16. This arrangement can transfer greater torque from the rotating compression plate to the valve disc and has also a more favourable sealing characteristic.

Figure 10-11 show a detail of an embodiment of the compression plate 16 and its arrangement in the cone 6. The circular edge of the plate has been made wider by means of an edge element 39 essentially perpendicular to the plate and reaching symmetrically on both sides of the plate.

This edge element 39 could be used for the arrangement of a bearing 40 of the ball bearing type between the plate and the cone as shown in figure 10. But more essential is the fact that this edge element will give the plate an increased stiffness and improve the sealing between the plate and the spherical wall portion 3 of the cavity. The external surface 41 of the edge element could be given a spherical form co-operating with the surface 3 of the cavity. One or several separate sealing elements (not shown) could additionally or as an alternative be arranged in suitable grooves along the circular edge of the plate 16.

In an embodiment without valve disc, i.e. in which the straight edge of the compression plate is sliding against the lower side of the top cover 13 this straight edge could of course also be provided with sealing elements e.g. arranged in a groove along that edge.

As has been described above in certain embodiments the compression plate 16 is transferring torque to a co-rotating valve disc 10. The arrangement of an edge element 39 gives for those embodiments the possibility to increase the grip between the plate and the disc at the periphery of the disc 10. The edge element 39 could reach beyond the straight edge 22 of the compression plate 16 forming gripping elements 42 co-operating with appropriate grooves in the valve disc 10.

The compression plate 16 does not have to be flat. A radial section of the plate could, as illustrated in figure 10, be given other forms in order to increase the stiffness or sealing characteristics of the plate.

Figure 12 shows in a schematic form an arrangement for adjusting the discharge angle. Between the co-rotating valve disc 10, provided with valve openings 11 , 12 as before, and the top cover 13 fixed to the main housing 1 and provided with an outlet port 14, an auxiliary control disc 43 is arranged co-axially with the valve disc 10. This auxiliary disc is provided with a discharge slot 45 with the same radius and general form as the outlet port 14 and the valve openings 11 , 12. Said disc can be rotated by means of a suitable mechanism e.g. a stepping motor or similar but is here illustrated as a simple control lever 44.

It should be clear that discharge of fluid from the machine could only take place when the valve opening 11 , 12, the discharge slot 45 and the outlet port 14 are overlapping. By turning the control disc 43 it will thus be possible to change the discharge angle and consequently the discharge pressure from the machine. A blocking member 46 fixed to the lower side of the top cover 13 could be arranged to close the aperture between the high and the low pressure chambers.

Figure 13 shows in section an embodiment of the invention implemented as a pump. The necessary torque for the rotation of the pump is transferred by means of magnetical means 29, 30. These means are illustrated as permanent magnets 30 embedded in the lower part of the cylindrical rotating body 6' and cooperating permanent magnets 29 carried by a drive disc 31 fixed to the drive shaft 7 on the other side of a partition wall 32 closing the cavity 2 under the cylindrical body. This means that no rotating drive shaft is entering the cavity 2. Such an arrangement could be advantageous e.g. at the realisation of small pumps for pumping sensitive fluids in e.g. medical laboratory equipment. A tap 28 having a conical or any other suitable form could be arranged at the centre of the partition wall co-operating with a corresponding cavity at the centre of the cylindrical body 6'. There are only two moving parts 6', 6 and 16 inside the cavity 2. The top cover 13, not shown in figure 15, could be fixed to the main housing 1 in such a way that it is easily removable for cleaning purposes.

This pump could be made very small for pumping small quantities of e.g. biological liquids in laboratory equipment. The outlet port 14 is advantageously arranged in the top cover as an opening without any valve arrangement in the interval between 270° and about 360°. In this case at least one chamber is always discharging fluid through the outlet port and at least one chamber is always in contact with the inlet port. This means that for constant rotational speed there will be a continuous flow of fluid from the pump with very low pulsation. Figure 14 shows in section a further embodiment of the invention implemented as a pump. This embodiment is a variant of the embodiment illustrated in figure 15. The contact point 33 between the rotating cone and the partition wall 32 is very small which gives low friction. Additionally the volume under the rotating cone is smaller than in the embodiment according to figure 15 which could be of interest in certain applications.

Figure 15 illustrates the arrangement of a channel for feeding fluid down under the rotating body. A groove 34 is arranged essentially diametrically in the lower surface of the rotating body communicating with an inlet 35 and an outlet 36 on the upper surface of the rotating body, close to the compression plate and on the same side of this plate. At the lower area the groove has two branches 37, 38 one on each side of the contact point 33. This channel will be feeding liquid in small quantities in the form of pulses from a high pressure region of the pump to a low pressure region during the working cycle of the pump. During half a turn the two openings are in the same chamber so there will be no pressure difference but during .the rest of a full turn the openings are in different chambers, one in the loading phase and the other in the discharge phase.

The decrease of the efficiency of the pump could be controlled by means of the dimensions of the channel. These pulses of liquid will flow in one direction through the channel constituted by the groove and the wall of the cavity. The liquid is sweeping the wall of the cavity during the rotation. This means on one hand that a static volume of liquid under the rotating body could be avoided when pumping and on the other hand that a cleaning liquid will efficiently clean the cavity also under the rotating body.

To increase the effect an opening angle between 270 and somewhat less than 360 degrees could be arranged to create a pocket of liquid which will not be able W „

14

to escape through the outlet port. The pressure will quickly increase in this pocket and push the liquid through the channel under the cone into a volume which at the moment is filling up with new liquid.

Arranging the channel openings on different sides of the compression plate will give the possibility to have a larger part of the surface under the rotating body swept by cleaning liquid.

Figure 16 illustrates a further embodiment of the invention. The same designations have been used for corresponding or similar parts. The rotating part is arranged inside an external housing 51 having a cover 52 fixed to the same. The conical part 6 of the rotor here forms an integral part of the housing 1' with the cavity 2 having a spherical wall portion as before. The compression plate 16 of the same type as described above is arranged in a slot 15 in the conical part 6.

A shaft 7 provided with suitable bearing elements 50 is arranged extending through the wall of the external housing. For increased stability a second bearing element 57 could be arranged around the upper part of the rotating body 1',2, 3, 6, 15.

As described above the co-operation of the straight edge portion 22 and a grove on the lower side of the valve disc 10 causes said co-rotation. The disc 10 is sealed against the spherical wall portion 3 by means of some suitable sealing means 58. Two co-axial bushings 53 and 54 are arranged in a circular hole 59 in the cover 52. By means of a first spring element 55 a flange 60 on the first bushing 53 is pressed against the valve disc 10 in sealing relation. By means of a second spring element 56 acting between the first 53 and the second 54 bushing a flange 61 on the second bushing is also pressed against the valve disc 10 in sealing relation. Thus, the axial position of the two bushings will be automatically adjusted in order to create the sealing relation against the disc 10.

Inlet ports 5' and outlet ports 14 are created by holes in the rotating disc 10 and coinciding recesses 62 and 63 in the first and second bushings respectively. Typically the outlet from the machine is arranged coaxially in the second bushing 54. An inlet could e.g. be arranged through the cover 52.

Each bushing could be independently rotated by means of some adjustment means, not shown, in order to adjust the position of the respective recess in relation to the corresponding hole in the disc 10. In this way the timing of the effective inlet and outlet of working fluid to and from the machine can be controlled.

One of the advantages of this embodiment of the invention is that in general the leakage between the volumes of different pressure in the machine during the working cycle will be easier to control. There will for instance be no leakage at all between the conical part 6 and the wall of the cavity because they are forming one integral part. Additionally, the circular edge of the compression plate 16 will not be sliding against the spherical wall portion 3 creating problems of wear and sealing. In this embodiment the compression plate 16 is only pivoting relative to the spherical wall portion 3 which means that the plate can be arranged moving in a groove in the spherical wall portion 3 increasing the possibilities to get a good sealing.

Claims

1. A rotary piston machine having a housing (1) provided with a cavity (2) comprising a rotor (6', 6) rotating around a first axis and a compression plate (16) dividing the cavity into separate volumes, the machine further being provided with at least one inlet port and one outlet port, characterised in that said cavity (2) has a spherical wall portion (3) and is closed by means of a top cover (13) said rotor is provided with a conical part (6) reaching into said cavity (2) which conical part is provided with a slot (15) through the virtual tip of the cone perpendicular to the base of the cone, said compression plate (16) is provided with a circular edge portion having essentially the same radius as the spherical wall portion (3) of said cavity and is arranged sliding in a pivoting movement in said slot (15), said plate has further a straight edge portion (22) arranged at the level of the virtual tip of the cone and is arranged for rotation in said cavity in a plane parallel to the top cover (13) which compression plate during operation is thus rotating at the same speed as the cone around said first axis while simutaneously pivoting around a second axis perpendicular to said first axis.

2. A rotary piston machine according to claim 1 , characterised in that said top cover (13) is provided with an outlet port (14) and that a valve disc (10) provided with two valve openings (11 , 12) is arranged between said top cover and said straight edge portion (22) co-rotating with said plate (16).

3. A rotary piston machine according to claim 1 or 2, characterised in that said cavity (2) has the form of a half-sphere.

4. A rotary piston machine according to any of the claims 1 to 3, characterised in that said cone is straight-sided and that the envelop surface of the cone (6), the compression plate (16) and the lower surface of the co-rotating valve disc (10) or the top cover are together defining separate volumes inside the main housing which will be created, expanded and compressed during the cycle covering a rotation of 540° of the drive shaft and concequently the compression plate (16).