Axial piston machine

Abstract

An axial piston machine is shown comprising a cylinder drum rotatable around an axis of rotation and having at least a cylinder, a piston arranged in said cylinder, a swash plate arranged in front of said cylinder drum, said piston being provided with a slipper (11) resting against said swash plate and having a pressure area (17) on a side facing said swash plate, wherein a cylinder axis of said cylinder is arranged on a circle line (27) around said axis of rotation (16). Such a machine should be made compact. To this end said pressure area (17) deviates from a circular form.

Claims

1. An axial piston machine comprising a cylinder drum rotatable around an axis of rotation and having at least a cylinder, a piston arranged in said cylinder, a swash plate arranged in front of said cylinder drum, said piston being provided with a slipper resting against said swash plate and having a pressure area on a side facing said swash plate, wherein a cylinder axis of said cylinder is arranged on a circle line around said axis of rotation, characterized in that said pressure area deviates from a circular form.

2. The axial piston machine according to claim 1, wherein said pressure area comprises a radially inner border and a radially outer border and said radially inner border has a larger distance to said circle line than said radially outer border.

3. The axial piston machine according to claim 2, wherein said radially inner border has a distance to said circle line which is larger than a distance of the circumference of the largest possible circle around said cylinder axis defined by a size of said cylinder drum and the number of cylinders of said cylinder drum.

4. The axial piston machine according to claim 3, wherein said pressure area has a wedge-like form.

5. The axial piston machine according to claim 3, wherein said pressure area is limited by a wall having straight sections, said straight sections being connected by rounded sections.

6. The axial piston machine according to claim 2, wherein said pressure area comprises in an area radially outside said circle line at least one enlargement extending in circumferential direction around said axis of rotation.

7. The axial piston machine according to claim 2, wherein said pressure area has a wedge-like form.

8. The axial piston machine according to claim 2, wherein said pressure area is limited by a wall having straight sections, said straight sections being connected by rounded sections.

9. The axial piston machine according to claim 2, wherein said pressure area is symmetric with respect to a radius line of said circle line.

10. The axial piston machine according to claim 1, wherein said pressure area comprises in an area radially outside said circle line at least one enlargement extending in circumferential direction around said axis of rotation.

11. The axial piston machine according to claim 10, wherein said pressure area has a wedge-like form.

12. The axial piston machine according to claim 10, wherein said pressure area is limited by a wall having straight sections, said straight sections being connected by rounded sections.

13. The axial piston machine according to claim 1, wherein said pressure area has a wedge-like form.

14. The axial piston machine according to claim 13, wherein said pressure area is limited by a wall having straight sections, said straight sections being connected by rounded sections.

15. The axial piston machine according to claim 1, wherein said pressure area is limited by a wall having straight sections, said straight sections being connected by rounded sections.

16. The axial piston machine according to claim 15, wherein at least two rounded sections are located radially outside said circle line and at least one rounded section is located radially inside said circle line.

17. The axial piston machine according to claim 1, wherein said pressure area is symmetric with respect to a radius line of said circle line.

18. The axial piston machine according to claim 17, wherein said pressure area has three axis of symmetry.

19. The axial piston machine according to claim 1, wherein said cylinder is connected to said pressure area by a channel running through said piston, said channel opening into said pressure area at a position on a radially inner side of said circle line.

20. The axial piston machine according to claim 19, wherein said position is located in the center of said pressure area.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A preferred example of the invention will now be described in more detail with reference to the drawing, wherein:

(2) FIG. 1 shows a schematic sectional view through an axial piston machine,

(3) FIG. 2 shows a schematic illustration of pressure areas of slippers of the axial piston machine according to FIG. 1, and

(4) FIG. 3 shows schematically a comparison between pressure areas according to the prior art and according to the present invention.

DETAILED DESCRIPTION

(5) A hydraulic axial piston machine 1 comprises a housing 2, in which a cylinder drum 3 is rotatably supported. The cylinder drum 3 is unrotatably connected to a drive shaft 4.

(6) Several cylinders 5 are located and uniformly distributed in the circumferential direction in the cylinder drum 3. A piston 6 is moveably guided in each cylinder 5. The cylinder 5 is connected to a valve plate 8 via a connecting socket 7, the valve plate 8 interacting with a control plate 9. During operation, the valve plate 8 rotates in relation to the control plate 9.

(7) In the present case, the axial piston machine 1 is a pump. To this end the drive shaft 4 is driven from the outside by applying a torque to the drive shaft 4.

(8) The drive of the piston 6 occurs via a swash plate 10. Each piston 6 is connected to a slipper 11 (which can also be termed slide shoe), the connection being made by means of a ball 12, so that the slipper 11 can be tilted in relation to the piston 6. By means of a pressure plate 13 the slippers 11 are kept to bear on the swash plate 10. The pressure plate 13 again is supported on the cylinder drum 3 via a ball joint 14 and a spring 15.

(9) When the cylinder drum 3 rotates about an axis of rotation 16 under the effect of the above mentioned torque acting upon the drive shaft 4, the pistons 6 are reciprocated, known per se, in the axial direction of the cylinder drum 3 by the slippers 11 bearing on the swash plate 10.

(10) If, on the other hand, the cylinders 5 are supplied with hydraulic fluid in the right position, the shaft 4 is rotated, and the machine works as a motor.

(11) In any case the slippers 11 are pressed against swash plate 10 by means of a pressure acting in the respective cylinder 5. This causes a corresponding friction between slipper 11 and swash plate 10 which produces wear. In order to minimize such wear and to reduce frictional losses, each slipper 11 is provided with a pressure area 17 shown in FIG. 2. Pressure area 17 is connected to the interior of cylinder 5 by means of a channel 18 in ball 12 which is connected to an opening 19 in the slipper 11.

(12) As it comes out from FIG. 2, the pressure area 17 deviates from a circular form. The pressure area 17 has a wedge-like form and is almost of triangular form.

(13) To this end the pressure area 17 is limited by a wall 20 which has three straight sections 21, 22, 23 and three rounded edge sections 24, 25, 26, wherein each of the rounded edge sections 24, 25, 26 connects two of the straight sections 21, 22, 23. The straight sections 21, 22, 23 can be slightly curved.

(14) FIG. 2 shows a circle line 27 around the axis of rotation 16. This circle line 27 represents the line along which a middle axis of cylinders 5 moves when cylinder drum 3 is rotated. It can be seen that said pressure area 17 comprises a radially inner border, i.e. rounded section 25, and a radially outer border, i.e. straight section 21, wherein said radially inner border has a larger distance to said circle line 27 than said radially outer border. In other words, rounded section 25 is further away from the circle line 27 than the straight section 21.

(15) The pressure area 17 comprises in an area radially outside said circle line 27 at least one enlargement 28, 29 extending in circumferential direction around said axis of rotation 16. This enlargement 28, 29 is basically located at the inner sides of rounded sections 24, 25.

(16) Two of the rounded edge sections 24, 26 are located radially outside said circle line 27 and one rounded edge section 25 is located radially inside said circle line 27. It is, however, possible to replace rounded edge section 25 by two edge sections connected by a straight section or even more edge sections so that more than one rounded section 25 is located on the radially inner side of circle line 27. In the same way it is possible to replace straight section 21 by some edge sections connected by other straight sections so that more than two rounded sections 24, 26 are located radially outside the circle line 27.

(17) In any case, it is preferred that the pressure area 17 is symmetric with respect to a radius line of the circle line 27. Furthermore, it is preferred that the pressure area has three axis of symmetry, i.e. corresponds to a triangle having three equal sides.

(18) The opening 19 of channel 18 is located on a radially inner side of the circle line 27. This opening 19 is located in the center of the pressure area 17. This allows for a uniform distribution of the pressure coming from the cylinder 5 in the pressure area 17.

(19) FIG. 3 shows an illustration allowing a comparison between the pressure shoes 11 described above and pressure shoes 111 according to prior art embodiments.

(20) The prior art embodiments have a pressure shoe 111 with a pressure area 117 of circular form. This circular form corresponds to the largest possible circle around the cylinder axis 16 in the cylinder drum 3. The diameter of this largest possible circle depends on the diameter of the cylinder drum 3 and the number of cylinders 5 in cylinder drum 3.

(21) It can be seen that the pressure area of the new pressure shoes 11 extends radially inwardly further than the pressure area of pressure shoe 111. On the other hand, on the radially outside of circle line 27 the pressure shoe 111 of prior art embodiments extends further than the pressure area of the new pressure shoe 111. However, the new pressure shoe 11 extends radially outside the circle line 27 further in circumferential direction than the pressure area of pressure shoe 111 of prior art embodiments.

(22) In prior art embodiments the opening 119 is located on the circle line 27. In the new slipper 11 the opening 19 is located on the radial inside of circle line 27.

(23) While the present disclosure has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this disclosure may be made without departing from the spirit and scope of the present disclosure.