Valve plate assembly

Abstract

A valve plate assembly (1) of a hydraulic axial piston machine is described, the valve plate assembly comprising a wear plate (2) made of a ceramic material surrounded by a compression ring (4). Such a valve plate assembly should be produced and maintained in a cost-effective manner. To this end, the wear plate (2) is connected to a support plate (3) by means of the compression ring (4).

Claims

1. A valve plate assembly of a hydraulic axial piston machine, the valve plate assembly comprising a wear plate made of a ceramic material surrounded by a compression ring, wherein the wear plate is fixed to a support plate only by means of the compression ring, and wherein the valve plate assembly is configured to rotate with a cylinder block of the hydraulic axial piston machine.

2. The valve plate assembly according to claim 1, wherein the compression ring is fixed to the support plate by screws or bolts.

3. The valve plate assembly according to claim 1, wherein the support plate comprises an elastically deformable spring section.

4. The valve plate assembly according to claim 3, wherein the elastically deformable spring section is machined out of the support plate.

5. The valve plate assembly according to claim 1, wherein the compression ring comprises a fixation geometry accommodating fixing means connecting the compression ring to the support plate.

6. The valve plate assembly according to claim 5, wherein thrust pads are fixed in the support plate on a side opposite to the wear plate, wherein the thrust pads end in the support plate.

7. The valve plate assembly according to claim 5, wherein the support plate comprises a number of first openings and the wear plate comprises a number of second openings, wherein a form of each first opening of the number of first openings differs from a form of each second opening of the number of second openings.

8. The valve plate assembly according to claim 5, wherein the support plate comprises an elastically deformable spring section.

9. The valve plate assembly according to claim 5, wherein the fixation geometry is a threaded hole and wherein the fixation means is a screw or a bolt.

10. The valve plate assembly according to claim 1, wherein thrust pads are fixed in the support plate on a side opposite to the wear plate, wherein the thrust pads end in the support plate.

11. The valve plate assembly according to claim 10, wherein the support plate comprises a number of first openings and the wear plate comprises a number of second openings, wherein a form of each first opening of the number of first openings differs from a form of each second opening of the number of second openings.

12. The valve plate assembly according to claim 10, wherein the support plate comprises an elastically deformable spring section.

13. The valve plate assembly according to claim 10, wherein the thrust pads abut against a stop surface in the support plate.

14. The valve plate assembly according to claim 13, wherein the support plate comprises a number of first openings and the wear plate comprises a number of second openings, wherein a form of each first opening of the number of first openings differs from a form of each second opening of the number of second openings.

15. The valve plate assembly according to claim 1, wherein the support plate comprises a number of first openings and the wear plate comprises a number of second openings, wherein a form of each first opening of the number of first openings differs from a form of each second opening of the number of second openings.

16. The valve plate assembly according to claim 15, wherein each first opening of the number of first openings has a cross section which changes in an axial direction of the support plate and each second opening of the number of second openings has a constant cross section.

17. The valve plate assembly according to claim 16, wherein sealing means are arranged between the support plate and the wear plate.

18. The valve plate assembly according to claim 15, wherein sealing means are arranged between the support plate and the wear plate.

19. The valve plate assembly according to claim 18, wherein each of the sealing means is arranged in a groove surrounding a first opening of the number of first openings, wherein an area limited by each of the sealing means is of non-circular form.

20. The valve plate assembly according to claim 19, wherein the area limited by each of the sealing means is smaller than an area defined by a thrust pad on an opposite side of the support plate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

(2) FIG. 1 shows a valve plate assembly,

(3) FIG. 2 shows a support plate,

(4) FIG. 3 shows a sectional view of the valve plate assembly,

(5) FIG. 4 shows the valve plate assembly in connection with a cylinder block, and

(6) FIG. 5 shows an enlarged view of a part of the valve plate assembly.

DETAILED DESCRIPTION

(7) FIG. 1 shows a valve plate assembly 1 of a hydraulic axial piston machine. The valve plate assembly 1 comprises a wear plate 2 made of a ceramic material and a support plate 3 made of another material. The support plate 3 can be made, for example, from a metallic material like steel or stainless steel.

(8) The wear plate 2 is surrounded by a compression ring 4. The compression ring 4 preloads in compression the wear plate 2. The compression ring 4 is fitted onto the wear plate 2. The heavy preload ensures that no significant tensile stresses occur in the wear plate 2 due to pressure loads or thermal shocks.

(9) The compression ring 4 comprises a number of fixation geometries 5. The fixation geometries 5 can be in form of screw holes, i.e. holes having an inner thread. The compression ring 4 can be connected to the support plate 3 by means of screws 6. In the embodiment shown in FIG. 1 the fixation geometry 5 is a through going hole. However, this is not necessary. It can be as well a blind hole.

(10) The support plate 3 has likewise some holes 7 through which the screws 6 can be pushed. The screws 6 can be rather weak. They are necessary only to fix the combination of wear plate 2 and compression ring 4 to the support plate 3 and to correctly position the wear plate 2 relative to the support plate 3. It is not required that they withstand greater forces as will be explained below.

(11) FIG. 3 shows the valve plate assembly 1 in cross sectional view.

(12) Thrust pads 8 are fixed in the support plate 3 on a side opposite the wear plate 2. The thrust pads 8 are pressed into the support plate with interference fit. The thrust pads 8 plastically deform when pressed in and, thereby, absorb production tolerances in the thrust pads 8 and the support plate 3.

(13) As can be seen in FIGS. 4 and 5 the thrust pads 8 are inserted into a cylinder 9 which is provided in a cylinder block 10. The valve plate assembly 1 is fixed to the cylinder block 10 through the insertion of the thrust pads in the cylinders and rotates together with the cylinder block 10. A stationary part of a valve system and a housing in which the cylinder block 10 is arranged is not shown. The cylinder block 10 is connected to a shaft 11.

(14) The wear plate 2 comprises a central opening 12 and the support plate 3 comprises a central opening 13 so that the shaft 11 can be guided through the valve plate assembly 1.

(15) The thrust pads 8 are of circular form. Thus, the support plate 3 comprises first openings 14 which are of circular form on a side 15 of the support plate 3 facing away from the wear plate 2. However, as can be seen in FIG. 2, the first openings 14 have another form on a side 16 of the support plate 3 facing the wear plate 2. The form of the first openings 14 in the side 16 corresponds to a section of an annular ring. Thus, the cross section of the first openings 14 varies in axial direction, i.e. in a direction parallel to the axis of rotation of the cylinder bock 10.

(16) The wear plate 2 comprises a corresponding number of second openings 17. The form of the second openings 17 corresponds to the form of the openings 14 in the side 16 and corresponds to a section of an annular ring. The cross section of the second openings 17 is constant in axial direction, so that it is rather simple to produce the wear plate 2.

(17) As can be seen in FIG. 2, the support plate 3 comprises a groove 18 around each first opening 14. Sealing means 19, for example in form of an O-ring, are arranged in the groove 18. The sealing means 19 secure a tightness between the wear plate 2 and the support plate 3.

(18) The sealing means 19 limit a first area 20 on the side 16 of the support plate 3. This first area is slightly smaller than a second area defined by the thrust pads 8. This second area corresponds to the diameter of the cylinder 9. Thus, the thrust pads 8 generate hydraulic forces that push against the support plate 3. To this end, the support plate 3 comprises a stop 21 in each first opening 14 and the thrust pads 8 rest against the stop 21. The size of the first area 20 and of the sectional area of the cylinder 9 are designed so that the hydraulic pressure nearly balances out the forces from the thrust pads 8 onto the support plate 3. Thus, there are no separating forces between the wear plate 2 and the support plate 3. To the contrary, the support plate 3 is slightly pressed in a direction to the wear plate 2.

(19) Furthermore, the size and form of the first areas 20 is designed to achieve a uniform distribution of the contact pressure between the valve plate assembly 1 and the not illustrated stationary part of the valve system.

(20) The support plate 3 comprises a spring section 22. The spring section 22 is machined out of the support plate 3, for example by turning. The spring section 22 comprises a rim 23 resting against a protrusion 24 on the cylinder block 10. The rim 23 is connected to a radially outer part of the support plate 3 by means of a hinge section 25. The spring section 22 is integrated into the center of the support plate 3 and surrounds the shaft 11. The spring section 22 ensures that the contact force between the cylinder block 10 and the support plate 3 is transferred to the support plate 3 in a well distributed way which is nearly symmetric about the axis of rotation of the cylinder block 10, even if the cylinder block 10 has a slight misalignment relative to the stationary part of the valve system.

(21) The component that accommodates most of the functions of the rotating part of the valve system, i.e. of the valve plate assembly 1, is made from the support plate 3 which is made from a metallic material that is much easier to machine to complex geometries than a ceramic material and which is also able to withstand tensile stresses much better than the ceramic material of the wear plate 2. The wear plate 2 can have a rather simple form and can be produced in cost-effective manner.

(22) The wear plate 2 is a wear part which can easily be replaced simply by untightening the screws 6 removing the wear plate 2 together with the compressing ring 4 and mounting a new set of wear plate 2 and compression ring 4.

(23) Thus, maintenance is cost-effective as well.

(24) 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.