Rotary piston machine

Abstract

A rotary piston machine including a rotary piston (6), which is mounted oil the crank pin (5, 5′) of a crankshaft accommodated in a stationary housing (1) and held by a holding device (8, 9, 10, 11) in a manner that prevents significant change of the angular position of the rotary piston relative to the housing. The rotary piston forms, on its periphery, at least one pair of concave and convex surfaces (12, 13; 12′, 13′) that engage with an associated pair of convex and concave surfaces (14, 15; 14′, 15′) located on a peripheral surface (3) of the housing surrounding the rotary piston. The pairs of concave and convex surfaces engage one another over the angular range of the rotation of the crankshaft while forming a chamber and while altering the size of the chamber over this angular range. The holding device has a bearing device (9, 10, 11), which is situated at a distance from the crankshaft (M1) and with which the rotary piston (6) is mounted on the housing (1) in a manner that enables it to rotate around an arbor (9) that is parallel to the crankshaft (M1) and to be displaced toward the crankshaft. The distance between the crankshaft (M1) and the pivot bearing (9) of the hearing device (9, 10, 11) is adjustable.

Description

[0001] The present invention relates to a rotary piston machine.

[0002] A rotary piston machine with the features of group a of claim 1 is known from EP 0644981 B1. To understand the generic machine type, reference is made to the complete contents of said publication.

[0003] As disclosed by said publication, this machine type comprises a piston that is mounted on the crank pin of a crankshaft accommodated in a housing and, at the same time, makes a parallel rotation, while maintaining its angular position with regard to the housing. This type of rotation is called parallel rotation below.

[0004] As is also described in detail in said publication, the piston comprises, on its periphery, one or more pairs of convex and concave surfaces, which engage with and disengage from associated concave and convex surfaces of a peripheral wall of the housing, while forming a chamber. During this chamber-forming engagement, the convex surface of the piston extends on the concave surface of the peripheral wall and the concave surface of the piston extends on the convex surface of the peripheral wall, both in a sealing manner, thus enclosing a chamber that is also sealed laterally, by sidewalls of the housing in the case of the publication named. While the rotation during the chamber-forming engagement is in progress, the volume of the chamber changes, and this at a compression ratio that is, to advantage, very high.

[0005] As is described in said publication, a machine of such type can be used for a plurality of purposes, for example as a pump, as a combustion engine and, in particular, as a gas compressor that is able to achieve a very high compression in one stage, that is in one chamber.

[0006] If the piston is mounted on a crankshaft, the angular position of the piston in relation to the crankshaft is, initially, not defined. Hence, a holding device is required that prevents the angular position of the piston with regard to the housing from changing on rotation of the crankshaft. To achieve this, the known construction mentioned provides one or more additional eccentric shafts on which the piston is mounted and which are rotating in an angle-synchronized manner.

[0007] The necessary several crankshafts that are mounted in the piston are disadvantageous in the known construction. Said crankshafts must be spaced apart, thus involving high space requirements inside the piston and limiting the constructive possibilities to a considerable degree. Moreover, the crank pin bearings in the piston, since being spaced apart, must be arranged at the edge of the piston, that is near the chambers formed on the latter's periphery where they are subject to a high thermal load. This causes problems in connection with the durability of the machine.

[0008] A rotary piston machine with the features of group b of claim 1 is known from DE 32 31 756 A1. This publication discloses a machine comprising a helical piston that is driven to make parallel rotations, as in the aforementioned known construction. As is shown in FIGS. 3 and 4 of this publication, a bearing device that is spaced apart from the crankshaft is provided as holding device for parallel arrangement of the piston. The construction of this bearing device is essentially simpler than that provided in the publication first mentioned, which comprises additional crankshafts. In addition, it results in a rotary motion that is parallel only approximately and has a minor tendency to tilt that can, however, be tolerated if the distance between the crankshaft and the bearing device is selected to be accordingly wide or can be compensated by minor changes in the shape of the chamber-forming surfaces on the piston and/or the peripheral wall, so that there will not be any leakage problems. The resultant constructive possibilities of arranging the chamber-forming wall regions are considerably more numerous. Moreover, the machine can be designed smaller while ensuring the same output, and it also has thermal benefits. The bearing device can be formed according to the alternatives shown in FIGS. 3 and 4 of DE 32 31 756 A1, wherein the piston is either rotatively mounted on a parallel slide block, or displaceable in longitudinal direction in a pivoted slide block.

[0009] All of the known constructions mentioned have the disadvantage that the kinematics of the piston movement is defined and can not be changed.

[0010] The invention aims at providing a rotary piston machine having the advantages of the two known constructions mentioned, however with piston motion kinematics that can be changed.

[0011] On the basis of the features of group c of claim 1, the running kinematics of the piston can be readjusted by changing the distance between the crankshaft and the pivot bearing of the bearing device such that, with the distance being greater, the running motion rather approximates the strict parallel rotation where no tilting occurs and, with the distance being shorter, the tilting motion increases. Stronger tilting motion and/or any deviation from a standard length, respectively, to which the chamber surfaces are adjusted will result in leaks in the chambers. Of this fact advantage can be taken, for example, by having the machine run at idle speed with a high degree of leakage, that is with low power consumption and rotund running.

[0012] The features of claim 2 are provided advantageously. With this construction, the piston can be designed in the known manner and according to the aforementioned publication. The holding rod is attached at an appropriate point and extends to the bearing device that is arranged at a distance.

[0013] Preferably, the crank pins are arranged in the piston at a point that is subject to a low thermal load, that is to say at a point that is spaced apart from the chamber-forming walls. For that reason, the features of claim 3 that are, as such, known from DE 195 00 774 A1 are preferably provided. As a result, the crank pin bearing is entirely taken out of the piston and is arranged next to it. Thereby, the thermal problems arising at the crank pin bearing can be solved in an extremely efficient manner if the crank pin bearing is, for example, arranged at a point that is passed by fresh air.

[0014] Preferably, the features of claim 4 are provided. A piston/cylinder arrangement enables the displacement capability required for the bearing device. With such a construction, the pivot bearing can be provided in a simple manner, either by mounting the holding rod in the piston on a pivot bearing in the manner of a connecting-rod bearing or by mounting the cylinder to the housing on a pivot bearing. This results to the advantage, that the piston/cylinder arrangement can be used as a further compression or expansion chamber, for example as a recompression stage of a compressor.

[0015] The only figure of the drawing shows a sectional view in transverse direction to the crankshaft of a rotary piston machine according to the invention.

[0016] The rotary piston machine shown comprises a stationary housing 1 that encloses an interior region 2 with in internal peripheral wall 3. In parallel to the plane of the drawing, the interior region 2 is closed by a plane lateral wall 4 that is positioned below the plane of the drawing. A lateral wall that is not shown and is positioned above the plane of the drawing is arranged in parallel to the lateral wall 4.

[0017] A crankshaft with center point M1 that comprises a radially offset crank pin 5 with center point M2 is mounted in the lateral wall 4 and the other lateral wall that is arranged in parallel thereto. On rotation of the crankshaft, the crank pin 5 rotates with its center point M2 on the broken circular line about the center point M1 of the crankshaft.

[0018] A rotary piston 6 is mounted on the crank pin 5. A holding pin 8 is mounted in a hole 7 within said rotary piston 6. The free end of the holding rod 8 is mounted via a pivot bearing 9, with an axis in parallel to the crankshaft, in a reciprocating piston 10 that is running in a cylinder 11 attached to the housing 1, with its cylinder axis oriented towards the region of the crankshaft.

[0019] While the crank pin 5 is rotating about M1, it is obvious that, as a result, the reciprocating piston 10 is moving in the cylinder 11 in a reciprocating manner, with the holding rod 8 slightly rotating about the pivot bearing 9 in the reciprocating piston 10. Thus, the piston/cylinder arrangement 10, 11 forms a bearing device for the rotary piston 6 which, in essence, holds the latter in its angular position with regard to the housing 1, with only a slight tilting motion when it carries out its parallel rotation. This tilting motion depends on the distance between the crankshaft and the bearing device 9, 10, 11. With the distance being great, the tilting motion is so small that it can be neglected, resulting in an approximately genuine parallel rotation.

[0020] A first pair of surfaces comprising a convex surface 12 and a neighboring concave surface 13 is provided on the periphery of the rotary piston 6. An associated first pair of surfaces comprising a concave surface 14 and a convex surface 15 is arranged on the peripheral surface 3 of the housing 1. In the shown angular position of the crank pin 5, wherein the crank pin rotates about the crankshaft in clockwise direction, a chamber has just been closed between the surface pairs 12, 13 and 14, 15, by sealing the convex surface 12 on the concave surface 14 (at point A) and by sealing the concave surface 13 on the convex surface 15 (at point B) as well as by the lateral walls 4. While rotation of the crank pin 5 continues, the convex surface 12 of the rotary piston is running across the concave surface 14 of the peripheral wall in a sealing manner. Likewise, the concave surface 13 of the rotary piston is running across the convex surface 15 of the peripheral wall. The chamber formed between the walls is constantly reducing its volume because the sealing points A and B are approaching one another. After a specific rotational angle of the crank pin 5, the rotary piston 6 lifts from the peripheral wall 3 and opens the chamber and then, in the position shown in the figure, closes the chamber again, with the chamber now having a large volume.

[0021] With the illustrated sense of rotation of the crank pin 5 about the crankshaft in clockwise direction, this results in a chamber that repeatedly closes when having a large volume, then reduces its volume and then opens. This construction can be used as a compressor. In this case, gas flows through an inlet opening 16 into the interior region 2 of the housing 1 at low pressure, is enclosed while the chamber is closing and compressed while the rotary piston 6 continues its rotation. The chamber reaches its smallest volume at a point where an outlet valve 17 is provided, which can be provided as a simple check valve that opens to the outside and which is connected to a high-pressure duct 18, through which the compressed gas via appropriate connection devices is discharged.

[0022] In the example shown, a further pair of surfaces forming a second chamber in like manner is provided each on the rotary piston 6 and on the housing 1. The description above is also applicable to this chamber. The parts of this chamber are provided with the reference marks of the chamber described above, with these reference marks being identified by a prime. In the example, the second chamber operates phase-delayed. If one chamber closes and compresses, the other chamber is open, thus being able to suck in fresh gas through the inlet opening 16′.

[0023] As regards possible constructive variants of the rotary piston 6 and the chamber-forming details as well as the possibilities of using this construction as a compressor, combustion engine or the like, reference is made to the contents of EP 0644981 B1. Any variant illustrated there can also be executed here.

[0024] In the shown example of the present invention, the bearing device 9, 10, 11 is designed with a reciprocating piston 10 and a cylinder 11, in order to ensure that the rotary piston 6 is mounted on a pivot bearing. This piston/cylinder arrangement can be used as compression or expansion chamber; to achieve this, the cylinder chamber below the reciprocating piston 10 must be formed to comprise inlet and outlet ducts with the appropriate valves, none of which are shown here. If the construction shown is used as a compressor, the two chambers that are formed on the rotary piston 6 by the surface pairs can, for example, be designed with different sizes and can operate as precompression or recompression stage, while the piston/cylinder arrangement 10, 11 is used as a third recompression stage.

[0025] The bearing device at the free end of the holding rod 8, however, can be formed in an entirely different manner, wherein it must only be ensured that both a tilting motion and a reciprocating motion in direction towards the crankshaft M1 is permitted. For example, in a simple alternative of the shown piston/cylinder arrangement 10, 11, the holding rod 8 is attached to the reciprocating piston 10 in a rigid manner and the cylinder 11 is mounted on the housing 1 in a pivoting manner. The bearing device can also be formed to comprise the same kinematics, but without a piston/cylinder unit being formed.

[0026] Since, in the construction according to the invention, the rotary piston 6 is only mounted on a crank pin 5, in contrast to the known constructions, said crank pin can be arranged at any point in the piston. It is, in particular, possible that it is arranged at a very far distance from the chamber-forming surfaces 12, 13 or 12′, 13′ respectively. This reduces the heat transfer from the very hot chambers to the bearings of the crank pin 5 and the crankshaft, so that these are subject to a lower thermal load. In a constructive variant, the crankshaft can be arranged outside of the rotary piston 6 at a point that is thermally well protected. This variant is shown by broken lines in the figure. The crankshaft is mounted at M1′ in a lateral bulging 3′ of the peripheral wall 3. The crank pin 5′ is mounted in a bearing eye 19 that is attached to the rotary piston 6 by means of an arm 20 or a similar projection of the rotary piston 6. At this point, i.e. in the region of fresh air and far away from the chamber-forming surfaces, the crankshaft is arranged at a point thermally well protected.

[0027] The crank pin can also be arranged at a different point that is not illustrated here and is situated far away from the thermally loaded region of the rotary piston 6. Preferrably, the distance between the crank pin bearing 19 and the bearing device 9, 10, 11 should be selected as great as possible, in order to minimize the tilting motion of the rotary piston 6. For that reason, the crankshaft bearing should, preferrably, be provided on that side of the rotary piston that points away from the bearing device.

[0028] As already mentioned, the shown rotary piston machine according to the invention results in an approximate parallel rotation of the rotary piston 6 which is, however, superimposed by a slight cyclic tilting motion. The chamber-forming surfaces 12, 13; 14, 15 of the one chamber that are formed almost in the shape of a circular arc in the plane of the drawing and the corresponding surfaces of the other chamber that are identified by a prime must, in comparison with the exact circular shape known from EP 06449081 B1, be varied to a minor degree, in order to ensure that the chamber is always closed in a sealing manner in case of the parallel rotation with superimposed tilting motion according to the invention. The curve shapes to be calculated result at a specific distance of the center point M1 of the crankshaft from the bearing device 9, 10, 11. Then the machine illustrated operates with the chamber being sealed in an optimum manner.

[0029] It is, however, possible to vary the distance between the crankshaft and the bearing device 9, 10, 11. To achieve this, the holding rod 8 in the hole 7 of the rotary piston 6 can, for example, be formed to be adjustable so that it can, for example, be readjusted from the end position 8′ to 8″. A readjustment from position 8′ to position 8″ results in a reduced distance between the bearing device and the crankshaft and, thus, in an increased tilting motion. If the chamber-forming surfaces at the rotary piston 6 and at the peripheral wall 3 are calculated for position 8′, they cannot seal completely at position 8″ any longer.

[0030] However, this can be used to advantage for specific purposes. If the chambers are sealing only incompletely, the power consumption of the compressor decreases, this resulting in more rotundic running. Hence, such a setting is, for example, suitable to be used as setting in the idle mode.

Claims

1. A rotary piston machine, comprising:

a) a rotary piston (6), said rotary piston being rotatably mounted on a crank pin (5, 5′) of a crankshaft accommodated in a stationary housing (1) and being held by a holding device (8, 9, 10, 11) for preventing an angular position of the rotary piston, relative to the housing, from significantly changing, said rotary piston forms, on its periphery, at least one pair of concave and convex surfaces (12, 13; 12′, 13′), said at least one pair of concave and convex surfaces engaging an associated pair of convex and concave surfaces (14, 15; 14′, 15′) located on a peripheral surface (3) of the housing, said housing peripheral surface surrounding the rotary piston, the pairs of concave and convex surfaces engage one another over an angular range of crankshaft rotation while forming a chamber and while altering the size of the chamber over this angular range,

b) wherein the holding device has a bearing device (9, 10, 11), said bearing device being situated a distance from the crankshaft (M1) and serving to mount the rotary piston (6) on the housing (1) in a manner that enables the rotary piston to rotate around an axis (9) that is parallel to the crankshaft (M1) and to be displaced toward the crankshaft,

c) wherein a distance between the crankshaft (M1) and a pivot bearing (9) of the bearing device (9, 10, 11) is adjustable.

2. The rotary piston machine according to claim 1, wherein the rotary piston (6) is connected to the bearing device (9, 10, 11) via a holding rod (8).

3. The rotary piston machine according to claim 1, wherein the rotary piston (6) carries the crank pin bearing (19) that is spaced apart via an arm (20).

4. The rotary piston machine according to claim 1, wherein the bearing device (9, 10, 11), as a device for displaceable bearing, comprises a piston/cylinder arrangement (10, 11).