Sliding shoe for a hydrostatic axial piston machine

Abstract

A sliding shoe for supporting a piston of a hydrostatic axial piston machine against a swash plate includes a sliding face that defines a central concentric pressure pocket that is flat in order to stabilize the sliding shoe. The pressure pocket has radial supply grooves in order to ensure an optimal supply of pressure medium to the pressure pocket from a central mouth opening. The radial supply grooves extend through the pressure pocket and as far as a circumferential groove which surrounds the pressure pocket.

Claims

1. A sliding shoe, comprising: a sliding side configured to bring the sliding shoe into abutment against a swash plate, the sliding side defining (i) a central relief recess configured to form a relieving pressure field, and (ii) at least one radial groove formed in the relief recess in order to be deeper than the relief recess, wherein: the sliding side defines a central mouth opening; the at least one radial groove includes a first and a second radial groove, each of the first and second radial grooves extending radially outwardly from the central mouth opening; and the first and second radial grooves are aligned with one another.

2. The sliding shoe according to claim 1, wherein the relief recess is circular in a plane parallel to the sliding face when the sliding shoe abuts the sliding face.

3. The sliding shoe according to claim 1, wherein: the relief recess is surrounded by a first circumferential groove that is deeper than the relief recess, the first circumferential groove having an outer circumference that is surrounded by a sealing web; a second circumferential groove is arranged at an outer circumference of the sealing web, the second circumferential groove having an outer circumference that is surrounded by an outer supporting web; and the outer supporting web defines two substantially radial connecting grooves to an outer circumference of the sliding shoe, the two radial connecting grooves extending approximately at right angles to the two radial grooves.

4. The sliding shoe according to claim 3, wherein the outer supporting web is wider than the sealing web and wider than the first and second circumferential grooves.

5. The sliding shoe according to claim 4, wherein the outer supporting web defines at least one substantially radial connecting groove to an outer circumference of the sliding shoe.

6. The sliding shoe according to claim 3, wherein the outer supporting web has an outer beveled peripheral region.

7. The sliding shoe according to claim 6, wherein the peripheral region is at an angle of less than 10 degrees with respect to a sliding face.

8. A sliding shoe, comprising: a sliding side configured to bring the sliding shoe into abutment against a swash plate, the sliding side defining (i) a central relief recess configured to form a relieving pressure field, and (ii) at least one radial groove formed in the relief recess in order to be deeper than the relief recess, wherein the relief recess is surrounded by a first circumferential groove that is deeper than the relief recess, the first circumferential groove having an outer circumference that is surrounded by a sealing web.

9. The sliding shoe according to claim 8, wherein the at least one radial groove extends radially to the first circumferential groove.

10. The sliding shoe according to claim 8, wherein a second circumferential groove is arranged at an outer circumference of the sealing web, the second circumferential groove having an outer circumference that is surrounded by an outer supporting web.

11. The sliding shoe according to claim 10, wherein the outer supporting web is wider than the sealing web and wider than the first and second circumferential grooves.

12. The sliding shoe according to claim 10, wherein the outer supporting web defines at least one substantially radial connecting groove to an outer circumference of the sliding shoe.

13. The sliding shoe according to claim 10, wherein the outer supporting web has an outer beveled peripheral region.

14. The sliding shoe according to claim 13, wherein the peripheral region is at an angle of less than 10 degrees with respect to a sliding face.

15. The sliding shoe according to claim 8, wherein the relief recess is circular in a plane parallel to the sliding face when the sliding shoe abuts the sliding face.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An exemplary embodiment of a sliding shoe according to the disclosure is illustrated in the drawings. The disclosure is now explained in more detail with reference to the figures of these drawings.

(2) In the drawings:

(3) FIG. 1 shows a longitudinal section of the essential part of an axial piston machine of swash plate design, in which the exemplary embodiment of the sliding shoe according to the disclosure is installed,

(4) FIG. 2 shows a longitudinal section of the exemplary embodiment of the sliding shoe from FIG. 1,

(5) FIG. 3 shows a view of the sliding shoe according to FIGS. 1 and 2, and

(6) FIG. 4 shows a longitudinal section of a detail of the sliding shoe according to FIGS. 1 to 3.

DETAILED DESCRIPTION

(7) FIG. 1 shows a drive mechanism of an axial piston machine in longitudinal section. It has a driving shaft 1, on the outer circumference of which a cylinder drum 2 is arranged for conjoint rotation. In the cylinder drum 2, a plurality of cylinder bores 4 are distributed uniformly around the circumference, wherein only two mutually opposite cylinder bores 4 are shown in FIG. 1. A piston 6 is guided in an axially movable manner in each cylinder bore 4, wherein each piston 6 has a piston foot 8 at its end portion remote from the cylinder drum 2, said piston foot 8 being coupled pivotably via a ball joint 10 to a respective sliding shoe 12 assigned to the piston 6.

(8) Each sliding shoe 12 has, on its sliding side 14 remote from the ball joint 10, a planar sliding face 16 by way of which it revolves in a sliding manner around an inclined, planar, stationary sliding face 18 of a swash plate 20. Since the sliding shoes 12 are all held permanently in abutment against the sliding face 18 of the swash plate 20 via a holding-down means 22, the pistons 6 execute the desired stroke movement as they revolve about a central axis 24. Since the inclined position of the swash plate 20 with respect to the central axis 24 can be adjusted via an adjusting device (not shown), the stroke movement of each piston 6, and thus the swept volume of the axial piston machine, can be changed during a revolution.

(9) FIG. 2 shows a perspective longitudinal section of a sliding shoe 12 from FIG. 1. In this case, a spherical recess 26 for receiving the piston foot 8 of the associated piston 6 can be seen. Arranged concentrically in the sliding shoe 12 is a duct 28 which connects the spherical recess 26 to a central mouth opening 30 in the sliding face 16. Via the duct 28, pressure medium from the cylinder bore 4, said pressure medium being under high pressure during a portion of the revolving path, is fed to the mouth opening 30. The mouth opening 30 is surrounded by a concentric, comparatively flat relief recess 32 which is subdivided into two semicircular parts, since two radial grooves 34 extend through the middle thereof, only one radial groove 34 being illustrated in FIG. 2.

(10) FIG. 3 shows a view of the sliding side 14 and thus of the sliding face 16 of the sliding shoe 12. It can be seen that the relief recess 32 is passed through by the two grooves 34, which both extend along a common groove line 36. Both grooves 34 are thus aligned with each other, and the mouth opening 30 is arranged on the groove line 36 between them. Provided at the outer circumference of the relief recess 32 is a circumferential groove 38, which bounds the relief recess 32.

(11) In FIG. 2, it can be seen that the relief recess 32 is comparatively flat, while the two grooves 34 and the circumferential groove 38 are deeper than the relief recess 32. The two grooves 34 open into the circumferential groove 38, as a result of which the latter is connected to the mouth opening 30. The circumferential groove 38 is surrounded by a concentric sealing web 40 and thus bounded at its outer side. The sealing web 40 is in abutment against the sliding face 18 of the swash plate 20 when the axial piston machine in question is in operation (cf. FIG. 1).

(12) Provided concentrically at the outer circumference of the sealing web 40 is a second circumferential groove 42 which serves to discharge the leakage oil which passes between the sealing web 40 and the sliding face 18 of the swash plate 20. The second circumferential groove 42 is, as can be seen in FIG. 2, deeper and narrower than the first circumferential groove 38. Provided at the outer circumference of the second circumferential groove 42 is a concentrically encircling supporting web 44 which bears against the sliding face 18 of the swash plate 20 during operation of the axial piston machine in question.

(13) Provided on mutually opposite sides of the supporting web 44 at right angles to the two grooves 34 and to the first groove line 36 are two connecting grooves 46, which likewise extend along a common second groove line 48 which is arranged at right angles to the first groove line 36. Via these two connecting grooves 46, the second circumferential groove 42 is connected to the outer circumference of the sliding shoe 12 and thus to the housing interior of the axial piston machine in question.

(14) FIG. 4 shows a section through the supporting web 44, which is arranged between the outer circumference of the sliding shoe 12 and the second circumferential groove 42. It can be seen that the supporting web 44 has an inner annular region 50 which is in abutment against the sliding face 18 of the swash plate 20 during operation of the axial piston machine in question and is thus located in the sliding face 16 of the sliding shoe. Furthermore, the supporting web 44 has an outer, crowned, rounded peripheral region 52. The latter encompasses preferably about half the width of the supporting web in the radial direction. The reverse offset x at the outer periphery of the supporting web is in the region of 10 micrometers and is in particular 10 micrometers in the exemplary embodiment shown. The radius is 200 millimeters. As a result of this shaping of the supporting web 44, a waterski effect is allowed.

(15) Disclosed is a sliding shoe for supporting a piston of a hydrostatic axial piston machine against a swash plate. Formed in a sliding face of the sliding shoe is a central concentric pressure pocket which is flat in order to stabilize the sliding shoe. In order nevertheless to ensure an optimal supply of the pressure pocket with pressure medium from a central mouth opening, radial supply grooves are provided which extend through the pressure pocket and as far as a circumferential groove which surrounds the pressure pocket.

LIST OF REFERENCE SIGNS

(16) 1 Driving shaft 2 Cylinder drum 4 Cylinder bore 6 Piston 8 Piston foot 10 Ball joint 12 Sliding shoe 14 Sliding side 16 Sliding face 18 Sliding face 20 Swash plate 22 Holding-down means 24 Central axis 26 Spherical recess 28 Duct 30 Mouth opening 32 Relief recess 34 Grooves 36 First groove line 38 First circumferential groove 40 Sealing web 42 Second circumferential groove 44 Supporting web 46 Connecting groove 48 Second groove line 50 Inner annular region 52 Peripheral region R Rounding radius x Maximum distance