Axial piston machine with retraction plate for high speeds

Abstract

The invention relates to an axial piston machine in swashplate construction, with a retraction plate (50) whose first openings (53) are penetrated by a respective associated sliding shoe (30). According to the invention, the joint section (34) of the sliding shoe (30) deviates from a circular cylindrical shape in such a way that it has a maximum diameter (36) which is arranged at a distance from the web section (33), wherein it has a reduced diameter between the maximum diameter (36) and the web section (33) compared to the maximum diameter (36), wherein in a reference state the joint section (34) contacts an inner circumferential surface (55) of the associated first opening (53) in such a way that a minimum distance results between the web section (33) and the spherical outer surface section (81), wherein the inner circumferential surface (55) of the first opening (53) is adapted to the non-circular cylindrical joint section (34) of the sliding shoe (30) in such a way that the said inner circumferential surface (55) and the joint section (34) contact each other in the reference state away from the maximum diameter (36) of the joint section (34).

Description

[0001] The invention relates to an axial piston machine according to the preamble of claim 1.

[0002] An axial piston machine with a swash plate design is known from US Pat. No. 3,382,793. During intake, the pistons are withdrawn from the cylinder bores by means of a retraction plate. The piston slide shoes are supported by an annular surface on a completely flat first end face of the retraction plate. The retraction plate is supported by a retraction ball, which in turn is supported on the cylinder drum via a spring. The retraction plate is thicker radially on the inside than radially on the outside. This achieves the required rigidity of the retraction plate, with the maximum possible pivot angle being minimally affected by the thin outer retraction plate.

[0003] Another comparable retraction plate in an axial piston machine with a swash plate design is known from US 9 856 851 B2.

[0004] EP 1 561 031 B1 discloses a slightly differently shaped retraction plate, in which an annular projection is provided on the retraction plate in the area of ​​the retraction ball. This projection serves, among other things, to stiffen the retraction plate. This annular projection is not intended to be used in the context of the present invention because, contrary to the objective of the present invention explained below, it requires sliding blocks that extend radially further outward.

[0005] From DE 10 2020 202 316 A1 and DE 10 2015 208 886 A1, tapered sliding shoes are known in which the rotationally symmetrical joint section adjacent to the web section is not circularly cylindrical, but rather tapered. Accordingly, the joint section has a largest diameter, while the area between the web section and the largest diameter is designed with a smaller diameter.

[0006] The present invention seeks to create an axial piston machine with a swash plate design that can be operated at high speeds. The pistons are subjected to high centrifugal forces. Accordingly, the unsupported length, by which a fully extended piston protrudes from the cylinder barrel, should be particularly small, so that the centrifugal forces occurring during operation result in a low bending moment on the piston. Furthermore, the diameter over which the centers of the ball joints between the guide shoe and the piston run should be particularly small, so that the centrifugal forces acting on the guide shoes are small.

[0007] According to claim 1, it is proposed that the joint section of the sliding shoe deviates from a circular cylindrical shape in such a way that it has a largest diameter which is arranged at a distance from the web section, wherein between the largest diameter and the web section it has a diameter which is reduced compared to the largest diameter, wherein in a reference state the joint section touches an inner circumferential surface of the associated first opening in such a way that a minimal distance results between the web section and the spherical outer surface section, wherein the inner circumferential surface of the first opening is adapted to the non-circular cylindrical joint section of the sliding shoe in such a way that the said inner circumferential surface and the joint section touch each other in the reference state away from the largest diameter of the joint section.

[0008] The control surface is preferably flat. It can be fixedly arranged on a housing of the axial piston machine. Preferably, a separate pivoting cradle is provided which can be pivoted relative to the housing, the control surface being arranged on the pivoting cradle. The said distance between the first and second end faces preferably changes continuously, most preferably decreasing monotonically from the inside to the outside, although regions with a constant distance can be present. A smallest diameter of a first opening is preferably larger than the largest diameter of the joint section. All sliding shoes are preferably identical to one another. All first openings are preferably identical to one another and are arranged uniformly distributed over the circumference of the retraction plate.In the reference state, in particular, the annular surface of the sliding shoe rests against the flat first end face of the retraction plate, with the spherical outer surface portion of the retraction ball resting against the second opening in the retraction plate. At the largest diameter of the joint portion, contact with the inner peripheral surface of the first opening may be present in the reference state. However, a small distance is preferably present to create a defined contact location located away from the largest diameter.

[0009] Advantageous further developments and improvements of the invention are specified in the dependent claims.

[0010] It can be provided that the joint section of the sliding block comprises a first circular cylindrical section whose diameter is smaller than the largest diameter of the joint section, wherein the first circular cylindrical section is arranged between the web section and the said largest diameter, wherein the inner circumferential surface of the first opening comprises a second circular cylindrical section, wherein the first and second circular cylindrical sections touch each other in the reference state. This means that in the fully assembled axial piston machine, the smallest gap between the first and second circular cylindrical sections can be made very small, while still there is no risk of contact. The sliding blocks can therefore be arranged close to the axis of rotation, which is why the centrifugal forces acting on the sliding blocks are minimized.

[0011] It can be provided that the second circular-cylindrical section forms a corner with the first end face, which may be rounded or chamfered if desired. The first circular-cylindrical section is accordingly arranged directly adjacent to the first end face. It is thus also present radially on the outside of the first opening, even though the retraction plate has a small thickness there.

[0012] It can be provided that the inner peripheral surface of the first opening is funnel-shaped and widened away from the second circular-cylindrical section. This accommodates the largest diameter of the joint section. The exact shape of the funnel-shaped widening is not important within the scope of the invention, as long as it is ensured that the contact as claimed is present away from the largest diameter in the reference state.

[0013] It can be provided that the variable distance between the first and second end faces is designed such that the funnel-shaped extension is present at a radially inner edge of the first opening, with only the second circular-cylindrical section being present at a radially outer edge of the first opening. The thickness of the retraction plate at the radially outer edge determines the maximum length by which the pistons can protrude from the associated cylinder bore. With the proposed design, this length can be minimized, so that the bending moments on the pistons caused by centrifugal forces are also minimized.

[0014] The axial piston machine can be designed in such a way that the reference state can only be reached when at least part of the axial piston machine is disassembled and / or when the axial piston machine is not pressurized in a ready-to-use state, so that during normal operation of the axial piston machine, there is always at least some distance between the sliding block and the associated first opening. Such contact would cause noise and / or wear during operation, which is undesirable.

[0015] It can be provided that an inner circumferential surface of the second opening comprises a first and a second rotationally symmetrical section which are directly adjacent to one another, wherein the first rotationally symmetrical section is arranged adjacent to the first end face and is designed such that it can contact the spherical outer surface section of the retraction ball over its entire circumference, wherein at the same time the second rotationally symmetrical section is arranged at a distance from said spherical outer surface section. The retraction plate is preferably thick on the radial inside in order to ensure the required rigidity. With the above design, it can be achieved that the contact between the retraction plate and the retraction ball nevertheless occurs very close to the first end face, so that undesirable tilting moments on the retraction plate are avoided.

[0016] It can be provided that the second rotationally symmetrical section is spherical, with the corresponding spherical radius being larger than a spherical radius of the spherical outer surface section of the retraction ball. This allows the desired distance between the aforementioned surfaces to be reliably achieved.

[0017] It can be provided that the first rotationally symmetrical section is circularly conical. This results in a defined linear contact along the entire circumference of the retraction ball. The distance between the first end face and said contact preferably has a small dimension other than zero.

[0018] It can be provided that the second rotationally symmetrical section is circularly conical, wherein an angle of inclination between the first rotationally symmetrical section and a central axis of the second opening is greater than an analogous angle of inclination at the second rotationally symmetrical section. This can simplify the production of the second opening by approximating the ideal spherical shape of the second rotationally symmetrical section with a circular conical shape.

[0019] It can be provided that the spherical outer surface section extends to an end of the retraction ball facing the cylinder drum, so that the retraction plate can be pivoted over said end, wherein the variable distance between the first and second end faces of the retraction plate is designed such that, when the retraction plate is in a pivoted position, a gap of constant width results between the second end face of the retraction plate and the cylinder drum. Said pivoting position preferably corresponds to the maximum pivoting angle of the pivoting cradle provided for during operation. It is understood that the pivoting cradle could be pivoted out further until the retraction plate touches the cylinder drum. The preferably present end stops for the pivoting cradle are most preferably set such that the claimed pivoting position results as the end position.With this design, the pistons protrude only slightly from the cylinder drum even at maximum displacement, so that the centrifugal forces explained above cause a low bending moment on the pistons.

[0020] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0021] The invention is explained in more detail below with reference to the accompanying drawings. They show: Fig. 1 shows a longitudinal section of an axial piston machine according to the invention; Fig. 2 a longitudinal section of a cylinder drum with a retraction plate according to the invention; Fig. 3 a perspective sectional view of the retraction plate according to Fig. 2; and Fig. 4 an enlarged section of a Fig. 2 analog sectional view in the area of ​​the retraction ball.

[0022] Fig. 1 shows a longitudinal section of an axial piston machine 10 according to the invention. The axial piston machine 10 comprises a housing 12 in which a drive shaft 14 is rotatably mounted relative to a rotational axis 11. The two corresponding pivot bearings 15 are designed as tapered roller bearings. Inside the housing 12, the drive shaft 14 is surrounded by a cylinder drum 20 and is connected to it via a splined shaft for rotational drive. Several pistons 22 are accommodated in the cylinder drum 20 for linear movement. Each piston 22, together with the cylinder drum 20, defines a cylinder chamber 21, the volume of which changes periodically as the cylinder drum 20 rotates.

[0023] On in Fig. At its right end, the cylinder drum 20 rests against a separate distribution plate 16, which is firmly connected to the housing 12. The distribution plate 16 has two kidney-shaped control openings, each permanently connected to a respective associated working port 13. The cylinder chambers 21 each have a mouth opening, which can be brought into alignment with the kidney-shaped control openings such that the rotation of the cylinder drum 20 is accompanied by a fluid flow between the two working ports 13. The corresponding pressure fluid is preferably a liquid and most preferably hydraulic oil.

[0024] On the side of the cylinder drum 20 facing away from the distribution plate 16, a separate pivoting cradle 70 is arranged, which can be pivoted relative to the housing 12 with respect to a pivot axis 71. The corresponding pivoting movement is brought about by means of an actuating cylinder, which Fig. 1 is not visible. In this case, the pivot axis 71 intersects the rotation axis 11 at a right angle. However, it is also conceivable that the pivot axis 71 intersects the rotation axis 11 at a distance. The pivot cradle 70 has a flat control surface 72, the inclination of which relative to the rotation axis 11 determines the displacement volume of the axial piston machine 10.

[0025] Each piston 22 is connected via a ball joint 23 to an associated sliding block 30, with the sliding block 30 slidingly abutting the control surface 72. A hydrostatic pressure field is provided between the sliding block 30 and the control surface 72, which is supplied with pressure from the associated cylinder chamber 21.

[0026] To retract the pistons 22 from the cylinder drum 20 during suction, a separate retraction plate 50 is provided, which is supported on the cylinder drum 20 via a separate retraction ball 80. When adjusting the pivoting cradle 70, an axial relative movement can occur between the retraction ball 80 and the cylinder drum 20, which is why these parts are designed separately from each other.

[0027] Fig. Figure 2 shows a longitudinal section of a cylinder drum 20 with a retraction plate 50 according to the invention. Shown is a position of the retraction plate 50 in which the pivoting cradle (No. 70 in Fig. 1) assumes the maximum swivel angle that occurs during operation. In order to achieve the desired high speed stability, the Fig. 2 lower pistons 22 protrude as little as possible from the cylinder drum 20, since the corresponding overhang length determines the bending moment which acts on the piston 22 due to the centrifugal forces occurring during operation. As a result, the sliding shoes 30 on the opposite side of the axis of rotation 11 penetrate into the cylinder bore 26 into which the associated piston 22 runs. The largest diameter 36 of the joint region 34 of a sliding shoe 30 is therefore preferably smaller than the diameter of the aforementioned cylinder bore 26. Because of the tilting of the sliding shoes 30, a first circular-cylindrical section 37 is also provided on the joint section 34 of a sliding shoe 30, the diameter of which is smaller than the largest diameter 36 in order to avoid a collision between the cylinder bore 26 and the sliding shoe 30.

[0028] The retraction ball 80 has a spherical outer surface section 81, the center of which preferably coincides with the rotation axis 11. The spherical outer surface section 81 extends in the direction of the rotation axis 11 over the entire length of the retraction ball 80. The two ends of the spherical outer surface section 81 pointing in the direction of the rotation axis 11 are designed such that the central second opening 54 of the retraction plate 50 can move over the end of the spherical outer surface section 81, as shown in Fig. 2 above. This enables a large axial mobility of the retraction ball 80. Within the scope of this mobility, the retraction ball 80 is supported on the cylinder drum 20 in the direction of the axis of rotation 11, for example via the pressure pins 83 known from EP 1 604 113 B1 and a helical spring 82. It is also conceivable to install disc springs in the space marked with number 84 between the retraction ball 80 and the cylinder drum 20, in particular if only a small axial mobility of the retraction ball 80 is required. The retraction ball 80 is preferably pot-shaped, wherein it engages around a circular-cylindrical extension on the cylinder drum 20 pointing in the direction of the axis of rotation 11.

[0029] The ball diameter of the spherical outer surface section 81 is selected to be as large as possible, while still reliably preventing a collision between the retraction ball 80 and the pistons 22. At the same time, the pistons 22 should be arranged as close as possible to the rotational axis 11 in order to minimize the centrifugal forces occurring during operation. The retraction plate 50 according to the invention is designed to optimally meet the conflicting requirements explained above.

[0030] The rotationally symmetrical outer circumferential surface 32 of a sliding block 30 comprises a web section 33 and a joint section 34. The joint section 34 forms the ball socket 31 of the ball joint 23 on the inside. The outer diameter of the web section 33 is larger than the largest diameter 36 of the joint section 34. At the transition between the web section 33 and the joint section 34, an annular surface 35 is thus formed, which is preferably flat and perpendicular to the axis of rotational symmetry of the sliding block 30. The annular surface 35 bears against a flat first end face 51 of the retraction plate 50. The web section 33 is preferably circularly cylindrical.

[0031] The retraction plate 50 does not have any contours that project beyond the flat first end face 51 toward the pivoting cradle 70. In particular, no annular reinforcing projection is arranged around the central second opening 54. This design makes it possible to move the web section 33 very close to the spherical outer surface section 81, for example, when, contrary to the illustration in Fig. 2, the displacement volume is set to zero. In this state, the joint section 54 of the sliding shoe is arranged very close to the radially inner edge of the associated first opening 53 in the retraction plate 50.

[0032] It should be noted that the diameter of a first opening 53 is considerably larger than the largest diameter 36 of the joint section 34. As a result, a sliding shoe 30 can move within the first opening 53 in order to maintain the distance between the sliding shoe 30 and the rotational axis 11, which varies during one revolution of the cylinder drum 20, measured in a direction parallel to the control surface (No. 72 in Fig. 1). At zero displacement, this distance is constant and smallest.

[0033] Within the scope of the invention, in particular the cross-sectional shape of the first openings 53 is adapted to the non-circular cylindrical shape of the respectively associated joint section 34 in order to enable the smallest possible minimum distance between the web section 33 and the spherical outer surface section 81.

[0034] In the present retraction plate 50, the required rigidity is achieved by the fact that the second end face 52 facing away from the first end face 51 is not flat. Rather, the distance between the first and second end faces 51; 52, or the thickness of the retraction plate 50, is significantly greater radially inward than radially outward. The corresponding thickness profile is selected such that Fig. 2, a gap 25 of constant width results between the retraction plate 50 and the cylinder drum 20. The corresponding end face 27 of the cylinder drum 20 is in any case flat around the pistons 22 and perpendicular to the axis of rotation 11 so that the pistons 22 are optimally supported by the respective associated cylinder bore 26.

[0035] At the radially outer edge, the retraction plate 70 has a region of constant thickness, wherein the cylinder drum 20 is adapted in the sense of a constant width of the gap 25.

[0036] Fig. 3 shows a perspective sectional view of the retraction plate 50 according to Fig. 2. The corresponding section plane contains the central axis 59, with respect to which the second opening 54 is rotationally symmetrical. The first end face 51 is flat and perpendicular to this central axis 59. In this case, nine first openings 53 are arranged around the central axis 59. These openings are identical to one another, being evenly distributed on a common pitch circle whose center coincides with the central axis 59.

[0037] Each first opening 53 is rotationally symmetrical with a constant cross-sectional shape, whereby this cross-sectional shape is not completely present radially outward due to the variable thickness of the retraction plate 50. The cross-sectional shape is composed of a second circular-cylindrical section 57, which is arranged adjacent to the first end face 51. Adjoining this is a funnel-shaped extension 58, which is designed so large that the associated sliding shoe does not strike there when it strikes the second circular-cylindrical section 57. It should be noted that this reference state preferably does not occur during operation of the axial piston machine. However, it can easily be brought about for an individual sliding shoe by Fig. 2, the displacement volume is set to zero, whereby the retraction plate 50 is displaced radially relative to the rotation axis. Due to the variable thickness of the retraction plate 50, the funnel-shaped extension 58 is only present at the radially inner edge of a first opening 53, where it is precisely needed.

[0038] In Fig. 3 further shows that the central second opening 54 comprises a first and a second rotationally symmetrical section 61; 62, which in the present case are separated from one another by an edge.

[0039] Fig. 4 shows an enlarged section of a Fig. 2 analog sectional view in the area of ​​the retraction ball 80. The cutting plane is opposite Fig. 2 is slightly rotated around the axis of rotation so that the sliding block 30 does not fall into the cutting plane. The second opening 54 of the retraction plate 50 comprises a first and a second rotationally symmetrical section 61; 62, which are oriented in the direction of the central axis (No. 59 in Fig.3) directly adjacent to one another. The contact between the retraction plate 50 and the spherical outer surface section 81 occurs in the first rotationally symmetrical section 61, which adjoins the first end face 51. The first rotationally symmetrical section 61 is circular conical in shape, resulting in linear contact over the entire circumference of the retraction ball 80. The second rotationally symmetrical section 62 is spherical in the present case, with the corresponding sphere radius being larger by a predetermined gap than the sphere radius of the spherical outer surface section 81. However, the corresponding spherical shape can also be approximated by a circular cone without resulting in any significant disadvantages.

[0040] This design ensures that the distance between the aforementioned linear contact and the first end face 51 is small but reliably different from zero. Disturbing tilting moments on the retraction plate are thus minimized, while there is no risk of excessive wear on the inner circumferential surface 56 of the second opening 54. Reference symbol 10 axial piston machine 11 axis of rotation 12 housings 13 Working connection 14 Drive shaft 15 pivot bearings 16 Distribution plate 20 cylinder drum 21 Cylinder chamber 22 pistons 23 ball joint 24 ball head 25 Gap between retraction plate and cylinder drum 26 cylinder bore 27 Front side of the cylinder drum 30 sliding shoe 31 ball socket 32 Outer peripheral surface of the sliding shoe 33 footbridge section 34 Joint section 35 ring area 36 largest diameter of the joint section 37 first circular cylindrical section 50 retraction plate 51 first frontal surface 52 second frontal surface 53 first breakthrough 54 second breakthrough 55 Inner peripheral surface of the first opening 56 Inner peripheral surface of the second opening 57 second circular cylindrical section 58 funnel-shaped extension 59 Central axis of the first breakthrough 61 first rotationally symmetric section 62 second rotationally symmetric section 63 Corner between first opening and first front face 64 Corner between second opening and first face 70 swivel cradle 71 Swivel axis 72 control surface 80 retraction ball 81 spherical outer surface section 82 coil spring 83 push pins 84 Space for disc springs QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 3,382,793

[0002] US 9 856 851 B2

[0003] EP 1 561 031 B1

[0004] DE 10 2020 202 316 A1

[0005] DE 10 2015 208 886 A1

[0005] EP 1 604 113 B1

[0028]

Claims

[1] Axial piston machine (10) with a cylinder drum (20) rotatable with respect to a rotational axis (11), in which a plurality of pistons (22) are accommodated in a linearly movable manner, so that together with the cylinder drum (20) they each delimit an associated cylinder chamber (21) with a variable volume, wherein each piston (22) is connected to a sliding block (30) via a ball joint (23), wherein the sliding block (30) bears slidably against a control surface (72), wherein the control surface (72) can be arranged inclined at an angle other than 90° to the rotational axis, wherein a retraction plate (50) is provided which has a first opening (53) for each sliding block (30), wherein the retraction plate (50) has a flat first end face (51), wherein an outer peripheral surface (32) of the sliding block (30) is rotationally symmetrical, wherein it consists of a web section (33) and a joint section (34). is composed,wherein a diameter of the web section (33) is greater than a largest diameter (36) of the joint section (34), so that at the transition between the web section (33) and the joint section (34) an annular surface (35) is formed, which bears against the first end face (51), wherein a retraction ball (80) is provided, which has a spherical outer surface section (81), wherein the retraction plate (50) has a central second opening (54), the inner circumferential surface (56) of which bears against the spherical outer surface section (81), wherein it forms with the flat first end face a corner (64), which is rounded or chamfered if desired, wherein the retraction ball (80) is supported on the cylinder drum (20) in the direction of the axis of rotation (11) in such a way that the sliding shoes (30) can be pressed by the retraction plate (50) against the control surface (72), wherein the retraction plate (50) has a second end face (52) facing away from the first end face (51),which is rotationally symmetrical, wherein a distance between the first and the second end face (52; 52) is radially outside smaller than radially inside, , characterized byin that the joint section (34) of the sliding block (30) deviates from a circular cylindrical shape in such a way that it has a largest diameter (36) which is arranged at a distance from the web section (33), wherein between the largest diameter (36) and the web section (33) it has a diameter which is reduced compared to the largest diameter (36), wherein in a reference state the joint section (34) touches an inner circumferential surface (55) of the associated first opening (53) in such a way that a minimal distance results between the web section (33) and the spherical outer surface section (81), wherein the inner circumferential surface (55) of the first opening (53) is adapted to the non-circular cylindrical joint section (34) of the sliding block (30) in such a way that the said inner circumferential surface (55) and the joint section (34) touch each other in the reference state away from the largest diameter (36) of the joint section (34). [2] Axial piston machine (10) according to claim 1, wherein the joint section (34) of the sliding block (30) comprises a first circular cylindrical section (37) whose diameter is smaller than the largest diameter (36) of the joint section (34), wherein the first circular cylindrical section (37) is arranged between the web section (33) and said largest diameter (36), wherein the inner peripheral surface (55) of the first opening (53) comprises a second circular cylindrical section (57), wherein in the reference state the first and the second circular cylindrical section (37; 57) touch each other. [3] Axial piston machine (10) according to claim 2, wherein the second circular cylindrical section (57) forms a corner (63) with the first end face (51), which corner may be rounded or chamfered if desired. [4] Axial piston machine (10) according to claim 2 or 3, wherein the inner peripheral surface (56) of the first opening (53) is widened in a funnel shape (58) away from the second circular-cylindrical section (57). [5] Axial piston section (10) according to claim 4, wherein the variable distance between the first and the second end face (51; 52) is designed such that the funnel-shaped extension (58) is present at a radially inner edge of the first opening (53), wherein only the second circular-cylindrical section (57) is present at a radially outer edge of the first opening (53). [6] Axial piston machine (10) according to one of the preceding claims, wherein the axial piston machine (10) is designed such that the reference state can only be reached when at least part of the axial piston machine (10) is dismantled and / or when the axial piston machine (10) is not pressurized ready for operation, so that during the intended operation of the axial piston machine (10) there is always at least some distance between the sliding shoe (30) and the associated first opening (51). [7] Axial piston machine (10) according to one of the preceding claims, wherein an inner circumferential surface (56) of the second opening (54) comprises a first and a second rotationally symmetrical section (61; 62) which are directly adjacent to one another, wherein the first rotationally symmetrical section (61) is arranged adjacent to the first end face (51), wherein it is designed such that it can contact the spherical outer surface section (81) of the retraction ball (80) over the entire circumference, wherein at the same time the second rotationally symmetrical section (62) is arranged at a distance from said spherical outer surface section (81). [8] Axial piston machine (10) according to claim 7, wherein the second rotationally symmetrical portion (62) is spherical, the corresponding spherical radius being greater than a spherical radius of the spherical outer surface portion (81) of the retraction ball (80). [9] Axial piston machine (10) according to claim 7 or 8, wherein the first rotationally symmetrical section (61) is circular conical. [10] Axial piston machine (10) according to claim 9, wherein the second rotationally symmetrical section (62) is circular conical, wherein an angle of inclination between the first rotationally symmetrical section (61) and a central axis of the second opening (52) is greater than an analogous angle of inclination at the second rotationally symmetrical section (62). [11] Axial piston machine according to one of the preceding claims, wherein the spherical outer surface section (81) extends to an end of the retraction ball (80) facing the cylinder drum (20), so that the retraction plate (50) can be pivoted over said end, wherein the variable distance between the first and the second end face (51; 52) of the retraction plate (50) is designed such that in a pivoted position of the retraction plate (50) a gap (25) of constant width results between the second end face (52) of the retraction plate (50) and the cylinder drum (20).

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