CN113710893B

CN113710893B - Reciprocating piston compressor

Info

Publication number: CN113710893B
Application number: CN202080028292.3A
Authority: CN
Inventors: 彼得·吉泽
Original assignee: OET GmbH
Current assignee: OET GmbH
Priority date: 2019-04-12
Filing date: 2020-04-06
Publication date: 2023-08-08
Anticipated expiration: 2040-04-06
Also published as: CN113710894A; DE102019112245A1; JP2022528446A; JP7358501B2; DE102019112237A1; JP2022527608A; WO2020207937A1; WO2020207936A1; CN113710893A; CN113710894B

Abstract

The invention relates to a reciprocating piston compressor having a drive shaft (10), a wobble plate (30) and a drive plate (20), which is connected to the drive shaft (10) in a rotationally fixed manner and has a sliding surface (21), wherein the wobble plate (30) comprises a cam (31, 32) having a curved cam tip (33), which rests against the sliding surface (21) of the drive plate (20) and whose curvature lies in a first contact circle (11), which is arranged in a plane parallel to the longitudinal axis (14) of the drive shaft (10), and wherein the wobble plate (30) is coupled to at least one reciprocating piston (25) guided in a cylinder (26). The invention is characterized in that the sliding surface (21) of the drive disk (20) has a curved contour, the curvature of which lies in a second contact circle (12) which is arranged in a plane parallel to the longitudinal axis (14) of the drive shaft (10), wherein the first contact circle (11) has a smaller radius than the second contact circle (12) and the root mean square value RMS of all dead zone distances d i between the end face (27) of the cylinder (26) and the dead point of the reciprocating piston (25) near the end face is at most 0.28mm, in particular at most 0.02mm, at each full angle of inclination of the wobble disk (30) in the angle of inclination range between 0 DEG and 23 deg.

Description

Reciprocating piston compressor

The present invention relates to reciprocating piston compressors (hubkolbenkompresor). Such a reciprocating piston compressor is known, for example, from EP 1 148 241 A2.

The known reciprocating piston compressor has a drive shaft to which a drive disc (mitnehmercheibe) is connected in a rotationally fixed manner. Furthermore, a wobble plate (tauxelscheibe) is provided, which is connected to a plurality of reciprocating pistons via sliding bearings. The wobble plate has a shaft hole through which the drive shaft is guided. A cam (Nocken) is provided on the wobble plate, which cam comprises a curved cam tip which abuts against the sliding surface of the drive plate. The curvature of the cam tip (kremmung) is located within a contact circle which is arranged in the same plane as the longitudinal axis of the drive shaft. On the other hand, the sliding surface on which the cam tip slides to adapt to the angle of attack (Anstellwinkel) of the wobble plate is designed to be straight or to form a flat plane, which is however set to be inclined with respect to the drive shaft.

In the known reciprocating piston compressors it has been shown that the piston stroke changes considerably when the angle of attack of the wobble plate changes. In particular, this results in a reduction of the reciprocating piston volume, resulting in a higher dead volume or dead volume (schadraum volume). This is particularly manifested in that the distance between the top dead center of the reciprocating piston and the cylinder end face (dead zone distance) is relatively large in all operating states. Thus, the efficiency of the known reciprocating piston compressors is overall impaired.

The object of the present invention is therefore to provide a reciprocating piston compressor with improved efficiency.

According to the invention, this object is achieved by the following aspects.

In particular, the invention is based on the basic idea of providing a reciprocating piston compressor having a drive shaft, a wobble plate and a drive plate, wherein the drive plate is connected to the drive shaft in a rotationally fixed manner and has a sliding surface. The wobble plate includes a cam having a curved cam tip that abuts a sliding surface of the drive plate. The curvature of the cam tip is located in a first contact circle arranged in a plane parallel to the longitudinal axis of the drive shaft. The wobble plate is coupled to at least one reciprocating piston guided in a cylinder. According to the invention, the sliding surface of the transmission disk has a curved contour, wherein the curvature of the contour is located in a second contact circle which is arranged in a plane parallel to the longitudinal axis of the drive shaft.

The first contact circle has a smaller radius than the second contact circle. At each full inclination angle in the inclination angle range of the wobble plate between 0 DEG and 23 DEG, the root mean square value RMS of all dead zone distances between the end face of the cylinder and the dead point of the reciprocating piston near the end face is at most 0.28mm, in particular at most 0.02mm.

In the present invention, it is therefore proposed that, in addition to the curvature of the cam tip, the sliding surface of the transmission disk can also be designed to be curved, so that the change in the piston stroke which is achieved when the pivot angle of the wobble plate is changed is greater than what can be achieved with the aid of the straight, flat sliding surfaces in the prior art. Tests have shown that in this way the dead volume or the kinematic dead volume of the reciprocating piston compressor is reduced.

In particular, the present invention achieves improved efficiency of a reciprocating piston compressor by: the curvature of the sliding surface of the drive disk is predefined by a second contact circle having a radius greater than the contact circle of the cam tip. Here, the radius of the contact circle is selected such that the root mean square of the dead zone distance does not exceed a value of 0.28.

To derive the root mean square value, all dead zone distances are squared, summed over squares, divided by the number of all angles at all angles (natural values including "0") in the tilt angle range of 0 ° to 23 °, and finally rooted from this result. In other words, the root mean square value RMS is calculated as follows:

where "d" represents the dead zone distance and "n" represents the number of discrete tilt angle values. The dead zone distance corresponds to the distance or pitch between the end face of the cylinder and the (top) dead center of the reciprocating piston near the end face. The tilt angle range describes the amount of all tilt angles that a wobble plate can exhibit in operation. Preferably, in operation the wobble plate is flipped between a minimum tilt angle of 0 ° (wobble plate perpendicular to the drive shaft) and a maximum tilt angle of 23 ° (wobble plate oriented obliquely with respect to the drive shaft).

In the present invention, it is particularly preferred that the dead zone distance is at most 0.3mm, in particular at most 0.06mm, at each angle within the tilt angle range of the wobble plate. It is therefore generally proposed that the dead space remains small in all operating states of the wobble disc. It is thereby achieved that the reciprocating piston compressor according to the invention achieves a high utilization of the stroke volume in all operating states and thus a particularly high efficiency. In particular, the reduction of dead volume achieves high compression performance with less energy input compared to the prior art. This is particularly advantageous for operation of reciprocating piston compressors in vehicle air conditioning systems of hybrid electric or pure electric motor vehicles, in particular automobiles, as less energy requirements increase the electric range of travel of the vehicle.

In the reciprocating piston compressor according to the invention, it can be provided in a preferred embodiment that a line contact (Linienber u hrung) exists between the cam tip and the sliding surface, which line contact is converted into a contact radius R as a result of the load _Hertz In Hertz surface pressure, where contact radius R _Hertz At least 1mm and up to 10mm. In particular, the contact radius may be between 1mm and 8mm, preferably between 1.5mm and 5mm, further preferably between 1.5mm and 3mm. It has been shown that at such a contact radius, on the one hand, there is good contact between the wobble cam and the sliding surface, and on the other hand, the friction force for the wobble plate to roll over is not too high. This compromise results in a further increase in efficiency of the reciprocating piston compressor.

A particularly preferred embodiment of the invention provides that the sliding surface has a convexly curved contour toward the cam tip. The sliding surface is thus curved outwards from the central plane of the drive disc. In other words, it is preferably proposed that the first contact circle and the second contact circle are arranged concave to each other or that the respective curved portions are arranged in opposite directions. Therefore, the contact surface between the cam and the sliding surface is minimized. In this way, the displacement of the intersection point between the centre plane of the wobble plate and the longitudinal axis of the at least one reciprocating piston in the longitudinal axial direction can be reduced. Thereby, a particularly small dead zone distance is obtained and thus a high efficiency of the reciprocating piston compressor is obtained.

The profile of the sliding surface can be converted into a straight sliding surface section, in particular starting tangentially from the aforementioned curvature. In particular, the sliding surface can have a curved upper sliding surface section and a straight lower sliding surface section, wherein the straight sliding surface section starts tangentially from the curved sliding surface section. The sliding surface may consist of only curved sliding surface sections and straight sliding surface sections. It has been shown that such a two-part sliding surface is very suitable for reducing the dead space over the whole range of inclination angles and thus contributes to the high efficiency of the reciprocating piston compressor.

In a further embodiment of the invention, it is furthermore provided that the wobble plate is guided by the drive shaft using a shaft bore, wherein the contact contour between the shaft bore and the drive shaft has a circular cross-sectional contour. In other words, the wobble plate has a shaft hole. The drive shaft extends through the shaft hole of the wobble plate, thereby forming a guide for the wobble plate.

It is preferably provided that the shaft bore is formed by two cylindrical through bores intersecting in the wobble plate.

In particular, the shaft hole may be manufactured by obliquely guiding two through holes through the same center. This results in the resulting shaft bore having an oval cross-sectional shape. Thus, the shaft hole has two recesses that taper toward the inside of the wobble plate. The through hole may be made by a drill or a milling cutter. Alternatively, the wobble plate may also be cast, wherein the shaft bore is made during the casting process. In this respect, the term "hole" is not necessarily to be understood in the context of the present application as a description of the manufacturing process, but generally refers to a recess or through opening in a component.

It is preferably provided that the shaft bore has a curved inner surface which abuts the drive shaft and whose curvature lies on a third contact circle which is arranged in the same plane as the longitudinal axis of the drive shaft. In particular, curved inner surfaces may be provided in the region of intersecting through holes. Thus, the inner contour of the shaft bore does not form a straight contact line between the shaft bore and the drive shaft, but rather forms a curved contact surface or contact contour. This results in an improved pivoting behaviour of the wobble plate. The curved inner contour may be produced by post-machining the shaft bore (for example by milling, grinding or milling) or may be formed directly in the manufacture, in particular in the case of wobble discs manufactured by casting.

The invention is explained in more detail below on the basis of examples and with reference to the attached schematic drawings. In the drawings:

fig. 1 shows a longitudinal section of a reciprocating piston compressor according to the present invention according to a preferred embodiment;

fig. 2 shows a side view of a drive train of a reciprocating piston compressor according to the present invention having a wobble plate, a drive plate and a drive shaft according to a preferred embodiment;

FIG. 3 shows a detailed view of the drive train according to FIG. 2;

fig. 4 shows a graph for comparing dead zone distances of a reciprocating piston compressor according to the present invention and a prior art reciprocating piston compressor; and

fig. 5 shows a longitudinal section through the shaft bore of the wobble plate according to fig. 2.

In fig. 1, a reciprocating piston compressor is shown with a housing 15. The drive shaft 10 is mounted in a housing 15. The drive shaft 10 carries a drive disk 20, which drive disk 20 is connected in a rotationally fixed manner to the drive shaft 10. Further, a wobble plate 30 is provided, the wobble plate 30 including a shaft hole 34, the drive shaft 10 being guided through the shaft hole 34. The wobble plate 30 is in force-transmitting engagement with a plurality of reciprocating pistons 25 via slide bearings 23.

The wobble plate 30 has a cam 31, which cam 31 includes a cam tip 33. The cam tips 33 bear against the sliding surface 21, which sliding surface 21 is covered in fig. 1 by the counter cam 22 of the drive disk 20. The sliding surface 21 is formed integrally with the drive disk 20.

In general, it may be provided that the swing disk 30 has a total of two cams 31. The drive disk 20 may also have two mating cams 22. The cams 31 of the wobble plate 30 each rest with their inner surfaces against the counter cams 22 of the drive plate 20. Thus, the two mating cams 22 of the driving disk 20 can extend between the two cams 31 of the wobble plate 30.

Preferably, each cam 31 abuts a respective sliding surface 21 of the driving disk 20. The size of the contact surface between the corresponding sliding surface 21 and the cam 31 may be different. In particular, it is possible to provide the cams 31 with different wall thicknesses, so that the contact surfaces between the respective cams 31 and the sliding surface 21 are different. Preferably, the cam 31 that absorbs the greatest forces is designed with a greater wall thickness. The less loaded cam 31 may have a smaller wall thickness and thus help reduce the mass of the reciprocating piston compressor.

For clarity, fig. 2 shows a longitudinal section through a drive train of a preferred embodiment of a reciprocating piston compressor according to the invention. The drive train comprises a drive shaft 10, a drive disc 20 and a wobble disc 30. It is clear from fig. 2 how the driving disc 20 and the wobble disc 30 are arranged relative to each other. The wobble plate 30 has a shaft hole 34 formed by two through holes 35, 36 intersecting inside the wobble plate 30. Thereby allowing the wobble plate 30 to change the pivot angle or tilt angle within a predetermined angular range. This is preferably achieved based on back pressure in the reciprocating piston. As the wobble plate 30 pivots, the cam tips 33 slide along the sliding surfaces 21, which also affects the stroke of each of the reciprocating pistons 25.

In the enlarged view according to fig. 3, which shows "detail a" according to fig. 2, it can be clearly seen that the cam 31 has a cam tip 33, which comprises a curvature. Specifically, the cam tip 33 has a front surface curved along the radius of the circle or the first contact circle 11. For the sake of clarity, the first contact circle 11 is marked in fig. 3 by a dashed line.

As best seen in fig. 3, the drive disk 20 has a sliding surface 21 on which the cam tips 33 slide. The sliding surface 21 has a curved portion extending along the second contact circle 12. The second contact circle 12 also lies in a plane oriented parallel to the longitudinal axis 14 of the drive shaft 10.

Specifically, the sliding surface 21 includes a curved sliding surface section 21a. The curved sliding surface section 21a forms an upper portion of the sliding surface 21. In the direction of the drive shaft 10, a lower portion of the sliding surface 21, which is formed by a straight sliding surface section 21b, is connected to an upper portion of the sliding surface 21 or a curved sliding surface section 21a. The straight sliding surface section 21b starts tangentially from the curved sliding surface section 21a and extends obliquely with respect to the central plane of the drive disk 20. In particular, the straight sliding surface section 21b is oriented at a sliding surface angle α (denoted "alfa" in the figures) with respect to the central plane of the drive disk 20. Preferably, the sliding surface angle is at most 45 °.

The cam tip 33 moves substantially upward or downward along the sliding surface 21 when the swing disk 30 pivots. In this case, a different effect is achieved on the piston stroke of the respective reciprocating piston 25 as compared to the case of a straight sliding surface 21 known from the prior art, due to the curvature of the sliding surface 21 or due to the curved sliding surface section 21a.

As is also clearly visible in fig. 3, the radius R of the second contact circle 12 ₂ Is significantly larger than the radius R of the first contact circle 11 ₁ . In particular, it may be provided that the radius R of the second contact circle 12 is ₂ Radius R of the first contact circle 11 ₁ At least 8 times, in particular at least 9 times, in particular at least 10 times greater. In any case, the curved portions of the slide surface 21 and the cam tip 33 are matched to each other so that the dead zone distance d is set as small as possible over the entire inclination angle range of the wobble plate 30.

Preferably, the contact between the cam tip 33 and the sliding surface 21 generates a Hertz surface pressure that forms the contact radius, i.e. the radius of the pressed surfaces that overlie one another. Preferably, the radius of the Hertz surface pressure (i.e., the contact radius R _Hertz ) Radius R from first contact circle 11 and second contact circle 12 ₁ 、R ₂ Correlation and calculation are as follows:

preferably, the contact radius R _Hertz Up to 20mm, in particular up to 10mm, in particular up to 5mm, in particular up to 4.8mm.

In fig. 4, a graph showing the dead zone distance d in the tilt angle range of the wobble plate 30 is shown graphically. The Dead zone distance, i.e., the distance between a Dead point near the end face or upper part (Top Dead center-TDC) and the end face of the cylinder 26, is plotted on the vertical axis. The horizontal axis shows the tilt angle of the wobble plate 30. The graph compares the curve of dead space in a reciprocating piston compressor according to the present invention (solid line) with the curve of dead space in two reciprocating piston compressors of the prior art (dash-dot line or broken line). It is clearly visible that the reciprocating piston compressor according to the invention has a significantly smaller dead space and thus a significantly smaller dead volume over the entire tilt angle range of 0 deg. to 23 deg. compared to previously known reciprocating piston compressors.

In particular, it can be seen that the dead zone distance is less than 0.1, in particular less than 0.05, over the entire tilt angle range of 0 ° to 23 °. It is also understood that the RMS value of the dead zone distance is smaller over the entire tilt angle than in the prior art. The root mean square value RMS is obtained by: the squares of the respective dead zone distances at discrete tilt angles (tilt angles represented by natural values (including 0), i.e., tilt angles 0 °, 1 °, 2 °,. 22 °) are added, divided by the number of tilt angle values, and finally rooted from the result. Expressed mathematically, all dead zone distances d _i The RMS value of RMS is calculated as follows:

fig. 5 shows a longitudinal section of the shaft bore 34, only an enlarged view of this section being shown. The wobble plate 30 has a shaft hole 34 formed by two through holes 35, 36 intersecting inside the shaft hole 34. Specifically, the shaft hole 34 is preferably formed by intersecting two cylindrical through holes 35, 36. In particular, the two cylindrical through bores 35, 36 are each introduced obliquely into the wobble plate at a bore angle relative to the longitudinal axis 14 of the drive shaft 10 and intersect within the wobble plate 30. Here, each through-hole 35, 36 is oriented at a different hole angle. The first through bore 35 has a bore angle β (denoted "beta" in the figures) with respect to the longitudinal axis 14 of the drive shaft 10. The second through bore 36 has a bore angle gamma (indicated as "gamma" in the figures) with respect to the longitudinal axis 14 of the drive shaft 10. The hole angle γ of the second through hole 36 may be larger than the hole angle β of the first through hole 35. The two obliquely oriented through-holes 35, 36 result in the shaft bore 34 having its smallest cross-sectional diameter in the center plane.

The shaft bore 34 need not be manufactured by drilling, milling or any other subtractive, particularly cutting, method. The shaft hole 34 may also be formed within the scope of a casting method for manufacturing the wobble plate 30, in which the above-described inner profile is generated.

It may be generally provided that the interior profile of the shaft bore 34 has an interior surface 37 that tapers toward the interior of the wobble plate 30. In the region of the central plane, the inner surface 37 preferably forms a contact contour with a curvature, which extends in the longitudinal direction of the shaft bore 34, in particular parallel to the longitudinal axis 14 of the drive shaft 10. Here, the curvature of the inner surface 37 is located on the circular line of the third contact circle 13. The third contact circle 13 may have a radius R ₃ Which radius essentially corresponds to the radius R of the first contact circle 11 ₁ 。

As is clearly visible in fig. 5, the pivoting or tilting of the wobble plate 30 up to a predetermined angle is achieved by the inner contour of the shaft bore 34. Because of the curved inner surface 37, tilting or pivoting takes place very smoothly. The curved inner surface 37 may be created directly during the casting process when casting the wobble plate 30. This can be achieved by the mould predefining a corresponding circular arc-shaped bend. If the shaft bore 34 of the wobble plate 30 is manufactured by means of a cutting machining method, in particular by drilling or milling two through bores 35, 36, it is advantageous to create a curved inner surface 37 by post-treating the shaft bore 34. This may be done, for example, by a grinding process, a milling process or a milling process.

In order to define the bending direction within the scope of the present application, it is provided that the first contact circle 11 and the second contact circle 12 each lie in a plane oriented parallel to the longitudinal axis 14 of the drive shaft 10. The third contact circle 13 is located in the longitudinal section of the drive shaft 10.

List of reference marks

10. Driving shaft

11. First contact circle

12. Second contact circle

13. Third contact circle

14. Longitudinal axis

15. Shell body

20. Transmission disc

21. Sliding surface

21a curved sliding surface section

21b straight sliding surface section

22. Pairing cam

23. Sliding bearing

25. Reciprocating piston

26. Cylinder body

27. End face

30. Swinging disc

31. Cam

33. Cam tip

34. Shaft hole

35. First through hole

36. Second through hole

37. Inner surface

Alpha sliding face angle

Hole angle of beta first through hole 35

Hole angle of gamma second through hole 36

d dead zone distance

R ₁ Radius of the first contact circle 11

R ₂ Radius of the second contact circle 12

R ₃ Radius of the third contact circle 13.

Claims

1. Reciprocating piston compressor having a drive shaft (10), a wobble plate (30) and a transmission plate (20), which is connected to the drive shaft (10) in a rotationally fixed manner and has a sliding surface (21), wherein the wobble plate (30) comprises a cam (31) having a curved cam tip (33), which rests against the sliding surface (21) of the transmission plate (20) and the curvature of which lies in a first contact circle (11), which is arranged in a plane parallel to the longitudinal axis (14) of the drive shaft (10), and wherein the wobble plate (30) is coupled to at least one reciprocating piston (25) guided in a cylinder (26),

it is characterized in that the method comprises the steps of,

the sliding surface (21) of the drive disc (20) has a curved contour, the curvature of which lies in a second contact circle (12) which is arranged in a plane parallel to the longitudinal axis (14) of the drive shaft (10), wherein the first contact circle (11) has a smaller radius than the second contact circle (12) and the root mean square value RMS of all dead space distances between the end face (27) of the cylinder (26) and the dead point of the reciprocating piston (25) near the end face is at most 0.28mm at all inclination angles of each natural value, including 0 ° and 23 °, of the wobble disc (30) in an inclination angle range between 0 ° and 23 °.

2. Reciprocating piston compressor according to claim 1, characterized in that the root mean square value RMS of all dead space distances between the end face (27) of the cylinder (26) and the dead point of the reciprocating piston (25) near the end face is at most 0.02mm.

3. A reciprocating piston compressor according to claim 1 or 2, characterized in that the dead zone distance is at most 0.3mm.

4. A reciprocating piston compressor according to claim 3, characterized in that the dead zone distance is at most 0.06mm.

5. A reciprocating piston compressor according to any one of claims 1-2 and 4, characterized in that between the cam tip (33) and the sliding surface (21) there is presentA line contact which, due to a load, is transformed into a contact radius R _Hertz Wherein the contact radius R _Hertz At least 1mm and up to 10mm.

6. A reciprocating piston compressor according to claim 3, characterized in that there is a line contact between the cam tip (33) and the sliding surface (21), which line contact is transformed into a contact radius R due to a load _Hertz Wherein the contact radius R _Hertz At least 1mm and up to 10mm.

7. Reciprocating piston compressor according to any one of claims 1-2, 4 and 6, characterized in that the sliding surface (21) has a convexly curved profile towards the cam tip (33).

8. A reciprocating piston compressor according to claim 3, characterized in that the sliding surface (21) has a convexly curved profile towards the cam tip (33).

9. Reciprocating piston compressor according to claim 5, characterized in that the sliding surface (21) has a convexly curved profile towards the cam tip (33).

10. Reciprocating piston compressor according to claim 7, characterized in that the contour of the sliding surface (21) is transformed into a straight sliding surface section (21 b).

11. Reciprocating piston compressor according to claim 8 or 9, characterized in that the contour of the sliding surface (21) is transformed into a straight sliding surface section (21 b).

12. Reciprocating piston compressor according to any of claims 1-2, 4, 6 and 8-10, characterized in that the wobble plate (30) is guided by the drive shaft (10) by means of a shaft hole (34), wherein the contact profile between the shaft hole (34) and the drive shaft (10) has a circular cross-sectional profile.

13. A reciprocating piston compressor according to claim 3, characterized in that the wobble plate (30) is guided by the drive shaft (10) by means of a shaft hole (34), wherein the contact profile between the shaft hole (34) and the drive shaft (10) has a circular cross-sectional profile.

14. Reciprocating piston compressor according to claim 5, characterized in that the wobble plate (30) is guided by the drive shaft (10) by means of a shaft hole (34), wherein the contact profile between the shaft hole (34) and the drive shaft (10) has a circular cross-sectional profile.

15. Reciprocating piston compressor according to claim 7, characterized in that the wobble plate (30) is guided by the drive shaft (10) by means of a shaft hole (34), wherein the contact profile between the shaft hole (34) and the drive shaft (10) has a circular cross-sectional profile.

16. Reciprocating piston compressor according to claim 11, characterized in that the wobble plate (30) is guided by the drive shaft (10) by means of a shaft hole (34), wherein the contact profile between the shaft hole (34) and the drive shaft (10) has a circular cross-sectional profile.

17. Reciprocating piston compressor according to claim 12, characterized in that the shaft bore (34) is formed by two cylindrical through bores (35, 36) intersecting in the wobble plate (30).

18. Reciprocating piston compressor according to any of claims 13-16, characterized in that the shaft bore (34) is formed by two cylindrical through bores (35, 36) intersecting in the wobble plate (30).

19. Reciprocating piston compressor according to claim 17, characterized in that the shaft bore (34) has a curved inner surface (37) which abuts the drive shaft (10) and whose curvature lies on a third contact circle (13) which is arranged in the same plane as the longitudinal axis (14) of the drive shaft (10).

20. Reciprocating piston compressor according to claim 18, characterized in that the shaft bore (34) has a curved inner surface (37) which abuts the drive shaft (10) and whose curvature lies on a third contact circle (13) which is arranged in the same plane as the longitudinal axis (14) of the drive shaft (10).

21. Reciprocating piston compressor according to claim 19 or 20, characterized in that the shaft bore (34) has the curved inner surface (37) in the region of the intersecting through bores (35, 36).