Hydraulic machine

Abstract

A hydraulic machine is provided comprising a cylinder unit (3) having a plurality of cylinders (4a, 4b) which are located on a circle line around an axis of rotation of said cylinder unit (3), a valve plate (6) located at an axial end of said cylinder unit (3) and having a through-going opening (8) for each cylinder (4a, 4b), and a port plate, said valve plate (6) and said port plate resting against each other in sliding contact at a contact face, wherein a pressure in each cylinder (4a, 4b) acts on a pressure area on a side of said valve plate (6) opposite said port plate. In such a hydraulic machine the risk of leaking should be kept small. To this end said pressure area (17) deviates from a circular form.

Claims

1. A hydraulic machine comprising a cylinder unit having a plurality of cylinders which are located on a circle around an axis of rotation of said cylinder unit, a valve plate located at an axial end of said cylinder unit and having a through-going opening for each cylinder, a port plate, said valve plate and said port plate resting against each other in sliding contact at a contact face, and a thrust pad for each cylinder forming a pressure area acting on a side of said valve plate opposite said port plate, wherein a pressure in each cylinder acts on the pressure area of each corresponding thrust pad, wherein said pressure area deviates from a circular form, wherein a portion of each thrust pad defines a thrust pad portion area which is larger than the area within a plane oriented in a radial direction from the axis of rotation at the through-going opening, and wherein said portion of each thrust pad portion area of each thrust pad is fluidly connected to said cylinder area of each corresponding cylinder.

2. The hydraulic machine according to claim 1, wherein said port plate comprises at least a kidney-shaped opening having a radially inner border and a radially outer border and said pressure area extends radially beyond at least one of said borders.

3. The hydraulic machine according to claim 1, wherein said pressure area comprises in its radially outer half at least one enlargement in circumferential direction of said valve plate.

4. The hydraulic machine according to claim 1, wherein said pressure area has a wedge form.

5. The hydraulic machine according to claim 1, wherein said pressure area comprises outer border lines with a small curvature and rounded edges.

6. The hydraulic machine according to claim 1, wherein said thrust pad is in form of a member connected by form-fit to said valve plate.

7. The hydraulic machine according to claim 6, wherein said member comprises a first part of round shape and a second part of polygonal form, said first part and said second part being assembled together.

8. The hydraulic machine according to claim 6, wherein said member is secured against rotation relative to said valve plate.

9. The hydraulic machine according to claim 6, wherein a sealing zone sealing against an inside of one cylinder of the plurality of cylinders is formed at a circumferential wall of said member.

10. The hydraulic machine according to claim 2, wherein said pressure area comprises in its radially outer half at least one enlargement in circumferential direction of said valve plate.

11. The hydraulic machine according to claim 2, wherein said pressure area has a wedge form.

12. The hydraulic machine according to claim 3, wherein said pressure area has a wedge form.

13. The hydraulic machine according to claim 2, wherein said pressure area comprises outer border lines with a small curvature and rounded edges.

14. The hydraulic machine according to claim 3, wherein said pressure area comprises outer border lines with a small curvature and rounded edges.

15. The hydraulic machine according to claim 4, wherein said pressure area comprises outer border lines with a small curvature and rounded edges.

16. The hydraulic machine according to claim 2, wherein said pressure area is formed on a front face of one thrust pad of the thrust pad for each cylinder, said front face being located on a side opposite to said valve plate.

17. The hydraulic machine according to claim 3, wherein said pressure area is formed on a front face of one thrust pad of the thrust pad for each cylinder, said front face being located on a side opposite to said valve plate.

18. The hydraulic machine according to claim 4, wherein said pressure area is formed on a front face of one thrust pad of the thrust pad for each cylinder, said front face being located on a side opposite to said valve plate.

19. The hydraulic machine according to claim 5, wherein said pressure area is formed on a front face of one thrust pad of the thrust pad for each cylinder, said front face being located on a side opposite to said valve plate.

20. The hydraulic machine according to claim 1, wherein each thrust pad is configured such that fluid pressure at said portion of each thrust pad forces the valve plate towards the port plate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a longitudinal sectional view of a hydraulic machine,

(2) FIG. 2 shows an exploded perspective view of a cylinder unit,

(3) FIG. 3 shows a perspective view of a thrust pad, and

(4) FIG. 4 shows a partly sectional view of the thrust pad of FIG. 3,

(5) FIG. 5 shows a sectional view of an end of a cylinder,

(6) FIG. 6 shows a schematically view of circular thrust pads,

(7) FIG. 7 shows a schematically view of thrust pads according to the invention, and

(8) FIG. 8 shows a port plate according to the invention.

DETAILED DESCRIPTION

(9) FIG. 1 shows schematically in longitudinal section a hydraulic machine 1 in form of pressure exchanger which is connected to a vane cell pump 2.

(10) The hydraulic machine 1 comprises a cylinder unit 3, e.g. a cylinder drum, having a plurality of cylinders 4a, 4b. Only cylinder 4a is cut along its longitudinal middle axis. The cylinders 4a, 4b are arranged on a circle around an axis 5 of rotation.

(11) A valve plate 6 is located at an end of the cylinder unit 3 on the side facing the vane cell pump 2. A corresponding valve plate 7 is located at the opposite side. The following description focuses on the first named valve plate 6. However, it is clear that the same construction can be used in connection with the other valve plate 7.

(12) The valve plate 6 has a through-going opening 8 for each cylinder 4a, 4b.

(13) Furthermore, a port plate 9 is provided. The valve plate 6 rests against the port plate 9 in sliding contact at a contact face 10. As shown in FIG. 8, the port plate 9 comprises two kidney-shaped openings 11, 12. The first opening 11 is connected with a low pressure input 13. The second kidney-opening 12 is connected to the high pressure output 14 connecting the hydraulic machine 1 and the vane cell pump 2. The vane cell pump 2 serves as booster pump increasing the pressure of the high pressure output 14 to a higher pressure level.

(14) When the cylinder unit 3 rotates, the pressure in the high pressure opening 12 acts on the valve plate 6 in areas between the openings 8. This pressure generates a force tending to lift the valve plate 6 off the port plate 9. This causes the risk of a leakage which should be avoided.

(15) To avoid or at least reduce this risk, the valve plate 6 has, for each cylinder 4a, 4b, a thrust pad 15 of a wedge-like or triangular form. The cylinder unit 3 has, for each cylinder 4a, a corresponding recess 16 in which the thrust pad 15 can be inserted. The thrust pad 15 forms at its front face a pressure area 17 deviating from a circular form. More precisely the pressure area extends radially beyond the radially inner border of the kidney-shaped openings 11, 12. Additionally, it is possible that the pressure area 17 extends radially outwardly beyond the radially outer border of the kidney-shaped openings 11, 12. However, in most cases it will be sufficient that the pressure area is extended to the radial inside of the valve plate 6.

(16) Furthermore, as can be seen in FIGS. 2 and 3, the thrust pad 15 comprises in its radially outer half two enlargements 18, 19 in circumferential direction of said valve plate 6.

(17) It can be imagined that the cylinder unit 3 is divided in sectors, one sector for each cylinder 4a. The form of the thrust pad 15 and therefore the form of the pressure area now makes use of the form of such a sector taking into account that the width of the sector in circumferential direction increases with increasing radius.

(18) The pressure area 17 therefore can be made larger so that the pressure within a cylinder 4a, 4b is sufficient to generate a force when multiplied with the pressure area 17 which balances out the force generated by the pressure in the high pressure kidney-shaped opening 12.

(19) As can be seen in FIGS. 3 and 4, the thrust pad 15 is in form of a member separate from the valve plate 6 and connected to said valve plate by form-fit.

(20) To this end the thrust pad 15 comprises a first part 20 which is of round shape or ring shape and a second part 21 of polygonal form. The first part 20 and the second part 21 are assembled together. The thrust pad 15 can be inserted into bore 8 with the first part 20. The second part 21 rests on a surface 22 of the valve plate 6 opposite to the port plate 9. Assembling of the two parts 20, 21 can take place prior, during or after mounting the first part 20 to the valve plate 6.

(21) A protrusion 23 is provided on the surface 22 protruding into second part 21 and securing the member against rotation relative to the valve plate 6.

(22) The second part 21 comprises a circumferential face 24 which forms a sealing zone 26 acting against an inside 25 of the recess 16 of each cylinder 4a when the cylinder unit 3 and the valve plate 6 are assembled.

(23) It can be seen in FIGS. 2 and 3 that the thrust pad 15 has a wedge-like or triangular form. The circumferential face 24 is formed by three basically straight sections connected by rounded edges. The basically straight edges can be formed by straight lines or they can be slightly curved, i.e. they have a large radius of curvature. A certain curvature is preferred since this facilitates the sealing of the member against the inside 25 of the recess 16.

(24) FIG. 5 schematically shows an enlarged sectional view of an end of cylinder 4a. The thrust pad 15 is inserted into the cylinder unit 3. The circumferential face 24 of the thrust pad 15 together with the inside 25 of the recess 16 form a sealing zone 26. Therefore, the pressure within cylinder 4a can act on the pressure area 17 of the thrust pad 15.

(25) A comparison of FIGS. 6 and 7 shows the enlargement of the effective pressure area. FIG. 6 shows the conventional form in which the pressure areas are formed by a circle 27. FIG. 7 shows the new form of the pressure areas 17. It can easily be seen that the new form of the pressure area 17 is larger than just a circle. However, the same number of pressure areas 17 can be arranged on the same diameter as before.

(26) 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.