In the hydraulic pump according to the present invention, a straight path among the paths, through which the fluid flows within the hydraulic pump, and a connection point on the straight path are formed to have curvatures, so that it is possible to prevent stress from being concentrated to the connection point, thereby improving durability, and it is possible to manufacture the hydraulic pump by forming a casting shape with a curvature in advance, thereby decreasing additional machining and decreasing costs of a product.

An axial piston pump has a rotor rotatable around an axis relative to a swashplate; one or more pistons movable within one or more respective sleeves; a fluid inlet port for the inflow of low pressure fluid, and a fluid outlet port for the outflow of high pressure fluid; and a floating element axially positioned between, on the one side, the inlet and outlet ports and, on the other side, a sealing surface of the rotor. Surfaces of the floating element defining an inlet chamber and the outlet chamber are configured such that, in use, the low pressure fluid and the high pressure fluid act on the defining surfaces to produce a net axial force which the axially slidable floating element applies to the rotor to seal the floating element to the sealing surface of the rotor.

A pump barrel (70) for use in a hydrostatic pump assembly includes a barrel body (88) defining a plurality of piston bores (84) that receive a plurality of pistons moveable within the bores, and a porting face (74) that defines a plurality of ports (72) in fluid communication with the piston bores and providing fluid flow paths into and out from the barrel body. Each port (72) has a leading edge surface and a trailing edge surface relative to a direction of rotation of the pump barrel, said leading and trailing edge surfaces being oriented in a first direction (along line 6-6) at non-right angles relative to the porting face (74). Each port (72) has an inner edge surface (80) and an outer edge surface (82) relative to a radial direction of the pump barrel, said inner and outer edge surfaces (80,82) being oriented in a second direction (along line 9-9) comprising a tilt angle (90,92) relative to the porting face (74) that is different from the angles in the first direction. A hydrostatic pump assembly incorporating such a pump barrel (70) is also disclosed.

A valve plate for a fluid pump includes a body having a first surface and an oppositely disposed second surface. The body defines a first kidney slot that extends through the first and second surfaces and a second kidney slot that extends through the first and second surfaces. A first notch is disposed in the first surface of the body and extends outwardly from the first kidney slot in a direction toward the second kidney slot. A second notch is disposed in the first surface and extends outwardly from the first kidney slot in a direction toward the second kidney slot. The second notch is separated from the first notch.

A valve plate of a hydraulic pump/motor, includes a high pressure-side port and a low pressure-side port, a first oil groove provided to be endless in an outer peripheral part of the high and low pressure-side ports, and a plurality of second oil grooves. Further, a plurality of pad oil grooves communicating with the first oil groove and opened toward the end face of the cylinder block is provided in an outer peripheral portion of the high pressure-side port, at least in a portion being on a downstream side of the relative rotation, in a pad region contacting the end face of the cylinder block, 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 on the downstream side than on an upstream side of the relative rotation.

A valve plate of a hydraulic pump/motor, includes a high pressure-side port and a low pressure-side port, a first oil groove provided to be endless in an outer peripheral part of the high and low pressure-side ports, and a plurality of second oil grooves. Further, a plurality of pad oil grooves communicating with the first oil groove and opened toward the end face of the cylinder block is provided in an outer peripheral portion of the high pressure-side port, at least in a portion being on a downstream side of the relative rotation, in a pad region contacting the end face of the cylinder block, 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 on the downstream side than on an upstream side of the relative rotation.

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.

A hydrostatic axial piston machine includes a cylinder drum that rotates during operation and has a plurality of cylinder bores in which displacement pistons are arranged, each of which opens out in a control opening in one end face of the cylinder drum, and having a control part against which the cylinder drum bears with the end face and on which two kidney-shaped control ports in the form of circular arcs are provided. Between the two kidney-shaped control ports, a first changeover web and a second changeover web are formed, wherein two sets of compensating openings that are able to be overlapped by control openings are located in the changeover webs with one compensating opening of each set located in each changeover web, and the compensating openings in the two sets of compensating openings are connected together via respective compensating fluid paths.

A hydrostatic axial piston machine includes a cylinder drum that rotates during operation and has a plurality of cylinder bores in which displacement pistons are arranged, each of which opens out in a control opening in one end face of the cylinder drum, and having a control part against which the cylinder drum bears with the end face and on which two kidney-shaped control ports in the form of circular arcs are provided. Between the two kidney-shaped control ports, a first changeover web and a second changeover web are formed, wherein two sets of compensating openings that are able to be overlapped by control openings are located in the changeover webs with one compensating opening of each set located in each changeover web, and the compensating openings in the two sets of compensating openings are connected together via respective compensating fluid paths.