A hydraulic piston machine is described comprising a piston (1) having a hollow (2) secured by a wall (3) and an insert (4) arranged in the hollow. Such a machine should have a high efficiency at low costs. To this end the insert (4) comprises a section (29) which extends out of the hollow (2).

A hydrostatic axial piston machine includes a housing, a connection plate closing the housing, working connections formed on the connection plate, a drive shaft, a swashplate, a cylinder drum coupled to the shaft in the direction of rotation, bores formed in the drum and each including a piston, a control plate against which the drum bears, a retraction plate for removing a piston from the bores, and a retraction ball arranged in front of the first end face of the drum which surrounds a drum neck of the drum and the shaft and by which the retraction plate is loaded in the direction of the swashplate. A pressure chamber is defined by seals between the retraction ball, the drum, and the shaft, and is configured to be acted upon by a pressure above a housing pressure. The retraction ball is sealed against the drum neck and against the shaft.

A hydraulic rotary machine configured to reduce sliding resistance of a reciprocating piston and to suppress a reduction in volumetric efficiency corresponding to an amount of leakage of hydraulic oil. A piston pump includes a rotor shaft, a cylinder block, a piston head, a piston rod, a retainer, a swash plate, and a tilt regulation mechanism. When the tilt regulation mechanism rocks the swash plate, the amount of discharge from the piston pump is variably changed. The retainer which rotates with both the piston head and the piston rod is supported by a retainer bush provided to the rotor shaft. The retainer sphere section of the retainer and the retainer bush sphere section of the retainer bush have spherical shapes having the same curvature. During the regulation of tilt, the retainer rocks while the retainer bush sphere section is in sliding contact with the retainer bush.

The hydraulic piston (1) constitutes a hydraulic chamber (5) with a cylinder (4) and has a cylindrical body (6) connectedfrom the side of the chamber (5)by a link-stop valve (3) to a cooling and lubricating gasket valve (2) which is passed right through by a flow calibration opening (27), the valve (2) being able to move in longitudinal translation over a short stroke with respect to the body (6) or to be held at a distance from the body (6) by the valve link-stop (3), a valve return spring (30) tending to move the valve (2) away from the cylindrical body (6).

A hydrostatic positive-displacement machine, in particular a hydrostatic axial piston machine, having a cylinder drum with at least one cylinder, in which a longitudinally displaceable piston is received, which is supported directly or indirectly by a support portion on an inclined plane of the positive-displacement machine. An outer circumferential surface portion of the piston is in bearing contact with an inner circumferential surface portion of the cylinder.

The hydraulic piston forms a hydraulic chamber with a cylinder and has a cylindrical body which receives a seal and whose external cylindrical surface is housed with little clearance in the cylinder in such a manner as to leave an interstitial space, the cylindrical body being run through by a cooling and lubrication pipe which can be opened or closed by a cooling and lubrication valve which is moved by translation by a valve-actuator in such a manner that fluid can pass via a flow calibration opening from the hydraulic chamber to the interstitial space when the pressure existing in the hydraulic chamber is low and cannot pass when the pressure in the chamber is high.

An axial hydraulic pump-motor, in which a cylinder block having a plurality of cylinder bores on a valve plate having a high-pressure side port and a low-pressure side port for controlling an amount of reciprocation of a piston in each of the cylinder bores, the hydraulic pump-motor includes: a residual pressure release port provided on the valve plate and communicating until the cylinder bore on a top dead center side communicates with the low-pressure side port; a residual pressure acquisition portion obtaining a value of a residual pressure in the cylinder bore on the top dead center side; and a directional switching valve switching a flow path between the residual pressure release port and an hydraulic oil tank and a flow path between the residual pressure release port and the low-pressure side port.

A hydraulic rotary machine configured to reduce sliding resistance of a reciprocating piston and to suppress a reduction in volumetric efficiency corresponding to an amount of leakage of hydraulic oil. A piston pump includes a rotor shaft, a cylinder block, a piston head, a piston rod, a retainer, a swash plate, and a tilt regulation mechanism. When the tilt regulation mechanism rocks the swash plate, the amount of discharge from the piston pump is variably changed. The retainer which rotates with both the piston head and the piston rod is supported by a retainer bush provided to the rotor shaft. The retainer sphere section of the retainer and the retainer bush sphere section of the retainer bush have spherical shapes having the same curvature. During the regulation of tilt, the retainer rocks while the retainer bush sphere section is in sliding contact with the retainer bush.

A swash plate type liquid-pressure rotating device includes a movement restricting mechanism configured to restrict a movement of a spherical bushing relative to a rotating shaft toward a first side in an axial direction. The movement restricting mechanism is a restricting member such that a portion of the spherical bushing which portion is located at the first side in the axial direction contacts the restricting member. The swash plate type liquid-pressure rotating device further includes: a stopper attached to the rotating shaft; and a gap adjusting member. The gap adjusting member is inserted into a gap G3 formed between the stopper and the bearing when the spherical bushing, the retainer plate, the shoe, and the swash plate tightly contact one another in the axial direction. The gap adjusting member restricts a movement of the rotating shaft relative to the casing toward the first side in the axial direction.

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.