Hydrostatic variable displacement axial piston machine, in particular hydrostatic variable displacement axial piston motor

Abstract

A hydrostatic axial piston machine includes a swashplate with an oblique surface formed thereon. Working pistons, which revolve and are supported by the oblique surface, are axially positioned on the swashplate with respect to a drive shaft. An adjusting cylinder, coupled to the swashplate, is configured to produce a pivoting moment and pivot the swashplate about a pivoting axis. Displacement of the working cylinders per revolution around the drive shaft is adjustable by adjusting a pivoting angle of the oblique surface. The adjustment of the pivoting angle is configured to pass beyond zero degrees, such that the direction of rotation of the drive shaft is changeable. The pivoting axis is at a distance from an axis of rotation of the drive shaft, such that an internal counter pivoting moment counteracting the pivoting moment is produced during operation of the axial piston machine when the working pistons are subjected to pressure.

Claims

1. A hydrostatic axial piston machine, comprising: a drive shaft configured to rotate about a rotation axis; a pivoting cradle; an adjustment device coupled to the pivoting cradle and configured to produce a pivoting moment that pivots the pivoting cradle about a pivoting axis in a first direction, wherein the pivoting cradle is configured to be pivoted from positive pivoting angles to negative pivoting angles through a pivoting angle of 0 degrees, the adjustment device including an adjusting piston positioned at least partially within an adjusting cylinder; a spring configured to bias the adjustment piston in a direction into the adjusting cylinder; and a cylinder drum configured to: revolve with the drive shaft such that the cylinder drum is secured against twisting; and guide working pistons supported on the pivoting cradle; wherein the pivoting axis is located at a distance from the rotation axis, such that a counter pivoting movement on the pivoting cradle is produced via support of the working pistons, and wherein a side of the pivoting cradle facing the cylinder drum defines a plane and the pivoting axis is between the plane and the cylinder drum.

2. The hydrostatic axial piston machine according to claim 1, wherein the adjusting piston is coupled to the pivoting cradle by a ball joint.

3. The hydrostatic axial piston machine according to claim 1, wherein: the adjusting piston is formed integrally with an adjusting piston rod; the adjusting piston is mounted in an articulated configuration in the adjusting cylinder; and the adjustment piston rod is mounted in an articulated configuration on the pivoting cradle.

4. The hydrostatic axial piston machine according to claim 1, wherein the hydrostatic axial piston machine is a fan motor.

5. The hydrostatic axial piston machine according to claim 1, wherein a maximum positive pivoting angle from the pivoting angle of 0 degrees is equal in magnitude to a maximum negative pivoting angle from the pivoting angle of 0 degrees.

6. The hydrostatic axial piston machine according to claim 2, wherein the spring is configured to act indirectly on the pivoting cradle via a counter piston that enters a hydrostatic counter cylinder.

7. The hydrostatic axial piston machine according to claim 6, wherein: the counter piston has an extension configured to come into contact with a bottom of the counter cylinder; and the spring surrounds the extension.

8. The hydrostatic axial piston machine according to claim 1, further comprising a restraining plate configured to hold sliding shoes articulated on the working pistons in contact with an oblique surface of the pivoting cradle, wherein each sliding shoe is encircled by a respective collar located adjacent to or on the edge of the restraining plate.

9. The hydrostatic axial piston machine according to claim 8, wherein the restraining plate includes recesses distributed around a circumference of the restraining plate; the recesses are configured to hold the sliding shoes in contact with the oblique surface; and edges of the recesses are configured as the respective collars.

10. A hydrostatic axial piston machine, comprising: a drive shaft configured to rotate about a rotation axis; a pivoting cradle; an adjustment device including an adjusting cylinder and an adjusting piston mounted in a tiltable and slidable configuration in the adjusting cylinder and formed integrally with an adjusting piston rod, the adjusting piston mounted in an articulated configuration on the pivoting cradle and configured to produce a pivoting moment that pivots the pivoting cradle about a pivoting axis in a first direction, wherein the pivoting cradle is configured to be pivoted from positive pivoting angles to negative pivoting angles through a pivoting angle of 0 degrees; and a cylinder drum configured to: revolve with the drive shaft such that the cylinder drum is secured against twisting; and guide working pistons supported on the pivoting cradle; wherein the pivoting axis is located at a distance from the rotation axis, such that a counter pivoting movement on the pivoting cradle is produced via support of the working pistons, and wherein a side of the pivoting cradle facing the cylinder drum defines a plane and the pivoting axis is between the plane and the cylinder drum.

11. A hydrostatic axial piston machine, comprising: a drive shaft configured to rotate about a rotation axis; a pivoting cradle; an adjustment device coupled to the pivoting cradle and configured to produce a pivoting moment that pivots the pivoting cradle about a pivoting axis in a first direction, wherein the pivoting cradle is configured to be pivoted from positive pivoting angles to negative pivoting angles through a pivoting angle of 0 degrees; a cylinder drum configured to: revolve with the drive shaft such that the cylinder drum is secured against twisting; and guide working pistons supported on the pivoting cradle; wherein the pivoting axis is located at a distance from the rotation axis, such that a counter pivoting movement on the pivoting cradle is produced via support of the working pistons; and a restraining plate configured to hold sliding shoes articulated on the working pistons in contact with an oblique surface of the pivoting cradle, wherein each sliding shoe is encircled by a respective collar having an outer chamfer portion proximate an outer edge of the restraining plate and an inner chamfer portion located radially inwardly from the outer chamfer portion, a first end of the inner chamfer portion separated from a first end of the outer chamfer portion by a first planar portion of the collar, and a second end of the inner chamfer portion separated from a second end of the outer chamfer portion by a second planar portion of the collar.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A number of illustrative embodiments of a hydrostatic axial piston machine according to the disclosure are shown in the drawings. The disclosure is now explained in greater detail with reference to the figures of these drawings, in which:

(2) FIG. 1 shows a first illustrative embodiment at a pivoting angle of 100% in a longitudinal section,

(3) FIG. 2 shows the illustrative embodiment according to FIG. 1 in a longitudinal section at a pivoting angle of +100%,

(4) FIG. 3 shows a restraining plate of the first illustrative embodiment in elevation,

(5) FIG. 4 shows the restraining plate according to FIG. 3 in a side view,

(6) FIG. 5 shows a detail of a second illustrative embodiment,

(7) FIG. 6 shows a detail of a third illustrative embodiment, and

(8) FIG. 7 shows a detail of a fourth illustrative embodiment.

DETAILED DESCRIPTION

(9) The illustrative embodiments shown of a hydrostatic axial piston machine according to the disclosure are designed primarily for operation as hydraulic motors. However, operation as a pump is not excluded.

(10) FIG. 1 shows a first illustrative embodiment of an axial piston motor according to the disclosure in a longitudinal section. Mounted in the housing 1 thereof is an output shaft 2. This is connected for conjoint rotation to a cylinder drum 4, which surrounds the output shaft 2 in a rotationally symmetrical manner. A plurality of working cylinders is provided uniformly on the circumference of the cylinder drum 4, of which only one working cylinder 6 is illustrated in FIG. 1. Guided in each working cylinder 6 is a working piston 8, which is articulated on a respective sliding shoe 12 via a respective piston foot 10. The sliding shoes 12 are held against an oblique surface 16 by means of a restraining plate 14, which is explained in greater detail with reference to FIGS. 3 and 4. The oblique surface 16 is formed on a pivoting cradle 18, which is mounted in the housing 1 by means of a pivot bearing. The pivot bearing is symbolized by a circle 20, and the radius of the pivot bearing is symbolized by an arrow 22. The oblique surface 16 can thus be pivoted with the pivoting cradle 18 about a pivoting axis S, which is arranged perpendicularly to the section plane and hence to the plane of the drawing of FIG. 1. The pivoting axis S has an eccentricity or a distance e from the axis of rotation 24 of the output shaft 2, on the one hand, and from a center line (not shown specifically) of the oblique surface 16, on the other. The center line extends parallel to the pivoting axis S. The pivoting axis S is furthermore situated in a plane perpendicular to the axis of rotation 24.

(11) An adjusting piston rod 28 of an adjusting cylinder 30 is articulated to the pivoting cradle 18 via a ball joint 26 on the same side of the axis of rotation 24 as that on which the pivoting axis S is also situated (the upper side in FIG. 1). Formed integrally on the adjusting piston rod 28 is an adjusting piston 32, which is guided in the adjusting cylinder 30 by means of a mechanical seal 34. The mechanical seal is advantageously preloaded outward with a radial force. As a result and owing to a spherical shaping of the adjusting piston 32, slight tilting of the adjusting piston rod 28 with the adjusting piston 32 occurring during the pivoting of the pivoting cradle 18 can be tolerated. By means of the mechanical seal 34, the leakage from the adjusting chamber behind the adjusting piston 32 into the interior of the housing is kept small.

(12) In the operating state shown in FIG. 1, the pivoting cradle 18 has been pivoted out to the maximum extent in one direction from a neutral or zero position, in which the oblique surface 16 is perpendicular to the axis of rotation 14. For this purpose, the adjusting piston rod 28 and adjusting piston have been extended to the maximum extent. Normally, pivoting out in this direction is referred to as negative, and therefore the pivoting cradle assumes the maximum negative pivoting angle (100%) in FIG. 1.

(13) On the opposite side of the axial piston motor (at the bottom in FIG. 1) in relation to the axis of rotation 24, a counter piston 36 of a counter cylinder 38 is in contact with the pivoting cradle 18. At the maximum pivoting angle of the pivoting cradle 18 shown in FIG. 1, the counter piston 36 has been pushed back and retracted to the maximum extent by the adjusting piston 32. The adjusting piston 30 and the counter cylinder 38 are set at an oblique angle to the longitudinal axis 24.

(14) To pivot the pivoting cradle 18 back to 0 (vertical in FIG. 1) or to pivot the pivoting cradle 18 through to a positive pivoting angle, pressure medium is released from the adjusting cylinder 30.

(15) FIG. 2 shows the axial piston motor according to FIG. 1 in an operating state in which the pivoting cradle 18 has been pivoted through relative to FIG. 1, with the result that the pivoting angle is +100%. For this purpose, pressure medium has been released from the adjusting cylinder 30. Owing to the eccentric mounting, the pivoting cradle has been pivoted from the position shown in FIG. 1 into the position shown in FIG. 2 via the zero position under the action of the forces in the driving mechanism, wherein the forces in the driving mechanism are assisted via the counter piston 36 by the two relaxing springs 40a and 40b, which are arranged concentrically with one another.

(16) The counter piston 36 has a radial collar 42, on which the springs 40a and 40b rest. The counter piston 36 is guided in the housing 1. An extension 44 extends in the direction of a cylinder bottom 46 on the side of the radial collar 42 facing away from the pivoting cradle 18. An intermediate spring plate 48 is guided on the extension 44. The two springs 40a and 40b are clamped between the radial collar 42 and the intermediate spring plate 48, which, in turn, is supported on the cylinder bottom 46 by two further springs, which are similar to springs 40a and 40b. The maximum negative pivoting angle is determined by abutments of the extension 44 on the cylinder bottom 46, as is apparent from FIG. 1. If the maximum negative value of the pivoting angle is to be variable, the cylinder bottom can be provided with an internal thread, making it possible to screw in an adjusting screw, against which the extension 44 strikes.

(17) The two springs 40a, 40b are accommodated concentrically with the extension 44 and concentrically with one another in the counter cylinder 38. In the operating state shown in FIG. 2, the two springs 40a, 40b are relaxed to the maximum extent and the return piston 36 is extended to the maximum extent, while the adjusting piston 32 of the adjusting cylinder 30 rests on a cap 50 screwed into said cylinder.

(18) Owing to the eccentric mounting of the pivoting cradle 18, more working pistons 8 are supported continuously on the side of the oblique surface 16 which lies on the same side as the counter cylinder 38. As a result, there is a further counter adjusting moment in addition to the force of the counter cylinder 38 or of the springs 40a, 40b thereof, said counter adjusting moment being the product of the distance e of the pivoting axis S from the axis of rotation 24 and the working pressure. At normal working pressures of 50 to 250 bar, the further counter adjusting moment is significantly greater than the moment produced by the springs.

(19) FIG. 3 shows the restraining plate 14 of the first illustrative embodiment in accordance with the two preceding figures. It has recesses 52 distributed uniformly over the circumference, into each of which a sliding shoe 12 is inserted. In this case, there is an encircling collar 53 formed at the edge of each recess 52.

(20) FIG. 4 shows the restraining plate 14 according to FIG. 3 in a side view. An encircling chamfer 54 is formed on an outer edge of the restraining plate 14 in order in this way to create space for the two maximum pivoting angles (+100% and 100%) relative to the cylinder drum 4 (cf FIG. 1 or 2).

(21) FIG. 5 shows a detail of a second illustrative embodiment of an axial piston motor according to the disclosure. Here, a further embodiment of a hydrostatic counter cylinder 138 with a corresponding hydrostatic counter piston 136 is shown. This has no extension and is retracted to the maximum extent into the cylinder 138 at the illustrated pivoting angle of 100%, while the adjusting piston (not shown) is extended to the maximum extent.

(22) As in the preceding illustrative embodiment, the counter piston 136 has a contact surface at the end, which rests on a spherical contact on the edge of the pivoting cradle 18. It is thus possible for the two contacts to slide (within narrow limits) transversely to the direction of motion of the counter piston 136 during pivoting of the pivoting cradle 18.

(23) FIG. 6 shows a detail of a third illustrative embodiment of an axial piston motor according to the disclosure. An adjusting piston 232 designed as a hollow piston is guided in the adjusting cylinder 230 inserted into the housing 1, said piston being coupled to the pivoting cradle 18 by a ball joint 226. A spring 240 acting as a counter spring is provided on the pivoting cradle 18 on the same side of the axial piston motor in relation to the axis of rotation 24 (not shown in FIG. 6). In FIG. 6, said spring is supported on the left on the housing 1 and pushes the pivoting cradle 18 in the direction of the counter pivoting moment. To receive and fix the end section of the spring 240 on the pivoting cradle side, the pivoting cradle 18 has a peg-type projection 256 on its rear side.

(24) FIG. 7 shows a detail of a fourth illustrative embodiment of an axial piston motor according to the disclosure. Here, the spring 240 and the projection 256 correspond to those in the third illustrative embodiment shown in FIG. 6. The adjusting cylinder 30 with the cap 50 corresponds to that in the first illustrative embodiment shown in FIGS. 1 and 2. As a departure from the first illustrative embodiment, the adjusting piston rod 328 and the adjusting piston 332 are not of integral design but are coupled to one another by a ball joint 26, which corresponds approximately to the ball joint 26 between the adjusting piston rod 328 and the pivoting cradle 18 for instance. No tilting of the adjusting piston 332 in the adjusting cylinder 30 is therefore necessary.

(25) A disclosure is made of a hydrostatic axial piston machine having a swashplate, on which an oblique surface is formed, on which working pistons arranged at least approximately axially with respect to a drive shaft revolve and are supported. To produce a pivoting moment and to pivot the swashplate about a pivoting axis, an adjusting piston of an adjusting cylinder is coupled to the swashplate. By adjusting the pivoting angle of the oblique surface, the displacement of the machine per revolution around the drive shaft is adjusted. The adjustment of the pivoting angle can pass via a zero position, in which the oblique surface is perpendicular to the axis of rotation of the drive shaft, thus allowing the direction of rotation of the drive shaft or the direction of delivery to be changed in a simple manner. Since the pivoting axis is arranged at a distance from the axis of rotation of a drive shaft, a counter pivoting moment counteracting the pivoting moment is produced during the operation of the axial piston machine when the working pistons are subjected to pressure.

LIST OF REFERENCE SIGNS

(26) 1 housing 2 drive shaft 4 cylinder drum 6 working cylinder 8 working piston 10 piston foot 12 sliding shoe 14 restraining plate 16 oblique surface 18 pivoting cradle 20 circle 22 arrow 24 axis of rotation 26 ball joint 28 adjusting piston rod 30 adjusting cylinder 32 adjusting piston 34 mechanical seal 36 counter piston 38 counter cylinder 40a spring 40b spring 42 radial collar 44 extension 46 cylinder bottom 48 intermediate spring plate 52 recess 53 collar 54 chamfer 136 counter piston 138 counter cylinder 226 ball joint 230 adjusting cylinder 232 adjusting piston 240 spring 256 projection 328 adjusting piston rod 332 adjusting piston S pivoting axis e distance