A hydraulic pump/motor includes: a cylinder block rotating about a rotation axis; a piston in a cylinder bore; and a valve plate facing a cylinder port. The valve plate includes: a high pressure port through which hydraulic oil discharged from the cylinder port flows; a low pressure port through which the oil to be sucked into the cylinder port flows; a region disposed between the high and low pressure ports in a circumferential direction of the rotation axis and including a top dead center position facing the cylinder port of the cylinder bore in which the piston moved to a top dead center is disposed; and a residual pressure release port between the top dead center position and the low pressure port in the region. The residual pressure release port includes first and second ports disposed at a positions different from each other in the radial direction of the rotation axis.

An axial piston device includes a cylinder block 11 rotatable integrally with a rotary shaft and having a plurality of cylinder chambers in a region surrounding the rotary shaft; a plurality of pistons 12 each contained in a corresponding one of the plurality of cylinder chambers; and a support configured to position respective protruding ends of the plurality of pistons; the cylinder block 11 has a plurality of cylinder ports 17 each continuous with a corresponding one of the plurality of cylinder chambers, and the plurality of cylinder ports 17 each have a central point T corresponding to the center of gravity in a cross section of a flow path at the cylinder port 17 and are, as viewed along the axis X, adjacent to one another along an imaginary circle C around the axis.

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).

A hydraulic piston unit including a rotational group for driving or being driven by a driving shaft, and having a tiltable displacement element for adjusting the displacement volume of the rotational group between a minimum or a maximum displacement, wherein, on t valve segment between a kidney-shaped inlet port and a kidney-shaped outlet port at respective dead end positions of reciprocally moveable working pistons first and second control ports are located in fluid connection with cylinder bores in the cylinder block, for controlling the position of the displacement element. The hydraulic piston unit further includes a control valve with a shiftable control valve spool fluidly connected via a high pressure port to a high pressure side of the hydraulic piston unit. The control valve spool is configured to conduct hydraulic fluid from the high pressure side to one of the first or the second control port.

A control plate for an axial piston machine is disclosed. The control plate includes a control face on which at least one kidney-shaped high-pressure control opening extending axially through the control plate and at least one kidney-shaped low-pressure control opening extending axially through the control plate is formed and which defines a first sealing ridge which is formed radially inside the at least one high-pressure control opening and the at least one low-pressure control opening, and a second sealing ridge which is formed radially outside the at least one high-pressure control opening and the at least one low-pressure control opening. In this case, the second sealing ridge is wider in the radial direction, preferably in some portions, than the first sealing ridge. Additionally, an axial piston machine in a swash plate design is disclosed. The axial piston machine includes a control plate which has at least one kidney-shaped high-pressure control opening and at least one kidney-shaped low-pressure control opening, by way of which piston recesses of a cylinder drum which is rotatably mounted in a housing of the axial piston machine can be connected alternately to a high-pressure connection and a low-pressure connection during rotation of the cylinder drum. In this case, a first, radially inner sealing ridge and a second, radially outer sealing ridge, which is designed to be wider in the radial direction, preferably in some portions, than the first sealing ridge, are formed on a contact face between the control plate and the cylinder drum.

There is disclosed a hydrostatic axial piston machine having a pulse reduction device. This device has a connection location or tap in the transition region in front of the high-pressure-side kidney-like elongate hole of a distributor plate. The connection location or tap is connected by means of one or two hydraulically passively controlled switching valves to a high-pressure store. It is used for precompression and consequently for the pulse reduction. In a development, the distributor plate also has a connection location or tap in the transition region behind the high-pressure-side kidney-like elongate hole. The connection location or tap is connected via one or two hydraulically passively controlled switching valves to a low-pressure store. This is used for the decompression and consequently also for the pulse reduction.

A hydraulic piston unit including a rotational group for driving or being driven by a driving shaft, and having a tiltable displacement element for adjusting the displacement volume of the rotational group between a minimum or a maximum displacement, wherein, on t valve segment between a kidney-shaped inlet port and a kidney-shaped outlet port at respective dead end positions of reciprocally moveable working pistons first and second control ports are located in fluid connection with cylinder bores in the cylinder block, for controlling the position of the displacement element. The hydraulic piston unit further includes a control valve with a shiftable control valve spool fluidly connected via a high pressure port to a high pressure side of the hydraulic piston unit. The control valve spool is configured to conduct hydraulic fluid from the high pressure side to one of the first or the second control port.

A port plate assembly of a hydraulic unit includes a port plate and a journal bearing. The port plate includes a fixed-speed interface side having a fixed-speed interface surface, and a variable-speed interface side having a variable-speed interface surface. A plurality of kidney-shaped apertures is defined at a kidney pitch diameter about a central bore of the port plate between the fixed-speed interface surface and the variable-speed interface surface. The port plate also includes control cylinder interface formed at a control cylinder radial offset from a central axis of the central bore, where a ratio of the control cylinder radial offset to the kidney pitch diameter is between 1.629 and 1.639. The journal bearing is installed in the central bore of the port plate, where the journal bearing provides an interface for a fixed-speed shaft and a variable-speed shaft of the hydraulic unit.

A valve plate of a hydraulic motor includes first and second pressure ports, and first and second oil grooves, the first and second pressure ports being alternately communicated with a cylinder bore in a cylinder block by bidirectional relative rotation in a state of being in contact with an end face of the cylinder block. Further, pad oil grooves communicating with the first oil groove and opened toward the end face of the cylinder block are provided in outer peripheral portions of the first and second pressure ports in a pad region, and the plurality of pad oil grooves is provided such that a proportion of an opening area to the end face of the cylinder block is larger at two end portions close to the second oil grooves than at a central portion separated from the second oil grooves in a circumferential direction of relative rotation.

A swashplate-type axial piston machine includes a housing and at least one working channel extending through a distributor plate. The at least one working channel opens out at an outside on the housing at an associated working port. The at least one working channel includes a first section and a second section. The first section extends over the entire distributor plate. The second section is arranged entirely in the housing. The second section directly adjoins the first section. A first rotary bearing has an outer circumferential surface that defines a circular cylindrical reference cylinder about the axis of rotation.