A liquid pressure rotary machine in which a rotation delay of a retainer with respect to a cylinder block is reduced and contact of pistons placed between the retainer and the cylinder block with peripheral members is suppressed is provided.

A piston pump includes a rotation shaft, a cylinder block, piston heads, piston rods, a retainer, a swash plate, and a tilt adjustment mechanism. When the tilt adjustment mechanism swings the swash plate, a discharge amount of the piston pump becomes variable. The retainer to be rotated together with the piston heads and the piston rods is supported by a retainer bushing provided in the rotation shaft. By engaging ball pins of the retainer bushing with spherical surface pin grooves of the retainer, the retainer and the retainer bushing are integrally rotatable about the center axis of the rotation shaft and the retainer is swung about the spherical surface center.

An axial piston pump, particularly for hydraulic systems, includes a cylinder drum (1) rotationally driven about an axis (15) in a pump housing (7). Piston cylinder units are arranged in the drum in a circle at an offset. Pistons (21) are at least indirectly supported on a swashplate (3) by their actuation end (31) accessible outside the cylinder drum (1). Between the swept volumes (19) of the piston cylinder units and a stationary fluid inlet and stationary fluid outlet of the pump housing (7), a control device (23) is arranged that has fluid channels (25, 26) for the targeted transfer of fluid from the fluid inlet into the swept volumes (19) and from the swept volumes (19) to the fluid outlet. At least one pressure compensation channel (28, 30) is provided in the control device (23), between the fluid channels (25, 26), to build or release fluid pressure in the swept volumes (19) in a targeted manner.

Hydraulic axial piston unit having a rotational group for driving or being driven by a driving shaft, and a tiltable displacement element for adjusting the displacement volume of the rotational group. The rotational group includes a rotatable cylinder block in which working pistons are mounted reciprocally moveable in cylinder bores for conveying hydraulic fluid from an inlet port to an outlet port on a valve segment. At least two control ports are located on the valve segment each between the inlet port and the outlet port. The control ports can be brought sequentially in fluid connection with the cylinder bores when the cylinder block is rotating. At least one hydraulic fluid injector is connected fluidly to one control port, for sequentially injecting pressurized hydraulic fluid via the control port into the passing cylinder bores. Via the other control port hydraulic fluid can be drained from passing cylinder bores.

Hydraulic axial piston unit having a rotational group for driving or being driven by a driving shaft, and a tiltable displacement element for adjusting the displacement volume of the rotational group. The rotational group includes a rotatable cylinder block in which working pistons are mounted reciprocally moveable in cylinder bores for conveying hydraulic fluid from an inlet port to an outlet port on a valve segment. At least two control ports are located on the valve segment each between the inlet port and the outlet port. The control ports can be brought sequentially in fluid connection with the cylinder bores when the cylinder block is rotating. At least one hydraulic fluid injector is connected fluidly to one control port, for sequentially injecting pressurized hydraulic fluid via the control port into the passing cylinder bores. Via the other control port hydraulic fluid can be drained from passing cylinder bores.

A hydrostatic axial piston pump of swashplate construction, which is also configured to be operated as a motor, has a stationary control plate against which a rotating cylinder drum is tensioned. During operation, a tilting tendency of the cylinder drum arises in the direction of that quadrant of the control plate which is operatively connected to the first part of the displacement stroke of the pistons. The control plate has a supporting device configured for the cylinder drum. The supporting device is arranged adjacent to an outer edge of the control plate in the first quadrant thereof. The supporting device is configured to be formed by a hydrostatically relieved additional field.

A swashplate-type axial piston machine includes a housing, a first pivot bearing received in the housing, a drive shaft rotatably mounted in respect of an axis of rotation, a cylinder drum, a control plate, a third control aperture in the plate, and a first channel arranged in the housing. The first pivot bearing delimits a first and second housing space from one another. The drum and the plate are arranged in the first housing space. The plate has at least a first and at least a second control aperture. The first aperture is in fluidic exchange connection with a first fluid connection on the housing. The second aperture is in fluidic exchange connection with a second fluid connection on the housing. The third aperture is arranged in the peripheral direction between a first and a second aperture. The first channel fluidically connects the third aperture to the second housing space.

A hydraulic pump assembly comprises a rotatable piston drum (20) with at least one centrifugal lever (23) pivotally attached thereto for radial movements between radial flanges (20) under the action of centrifugal force at rotation of the piston drum. The centrifugal lever (23) is arranged to control the position of a valve member, preferably a ball (22), at the opening end of a bore (21) in the piston drum (20). There is a defined friction surface (28; 32) between the lever (23) and one of the radial flanges (20), and there are spring means (29-31; 25, 33) for resiliently biasing the lever against said one of the flanges.

A hydraulic pump assembly comprises a rotatable piston drum (20) with at least one centrifugal lever (23) pivotally attached thereto for radial movements between radial flanges (20) under the action of centrifugal force at rotation of the piston drum. The centrifugal lever (23) is arranged to control the position of a valve member, preferably a ball (22), at the opening end of a bore (21) in the piston drum (20). There is a defined friction surface (28; 32) between the lever (23) and one of the radial flanges (20), and there are spring means (29-31; 25, 33) for resiliently biasing the lever against said one of the flanges.

It includes a plurality of cylinders formed on the cylinder block; a piston slidably inserted into the cylinder; a case accommodating the cylinder block; and a valve plate formed by a core member and a resin layer coating the core member, the valve plate being interposed between the cylinder block and an end cover of the case. The valve plate has a first land portion formed by the resin layer, the first land portion being in sliding contact with the cylinder block; and an outer-side non-contact portion provided closer to an outer side in a radial direction than the first land portion, the outer-side non-contact portion being separated away from the cylinder block. At least a part of the outer-side non-contact portion is an exposed portion where the core member is exposed.

A rotatable piston assembly for a reciprocating piston type hydraulic machine includes a rotatable piston configured for a controlled rotation and configured to reciprocate within a cylinder bore of the reciprocating piston type hydraulic machine.