A pump operation piston biased by a neutral spring mechanism and a larger volume operation spring biased by a larger volume operation spring in a larger volume direction operatively move pump and motor volume adjusting members, respectively, is provided. A first pressure control valve commonly controls supply-discharge of pressure oil that presses the pump operation piston in a first slide direction and the motor operation piston in a smaller volume direction. A second pressure control valve controls supply-discharge of pressure oil that presses the pump operation piston in a second slide direction. Biasing forces of the neutral spring mechanism and the larger volume operation spring are so set that, after the pump operation piston is moved in the first slide direction by a predetermined distance, the motor operation piston starts moving.

A hydrostatic piston machine unit, which is in particular designed as a hydrostatic axial piston machine unit, comprises at least two driving mechanisms that can be driven synchronously and have displacement pistons which each perform a reciprocating motion in operation and are provided for delivery into a common pressure line. The hydrostatic piston machine unit has a jointly assigned precompression volume for the at least two driving mechanisms.

A hydrostatic piston machine unit, which is in particular designed as a hydrostatic axial piston machine unit, comprises at least two driving mechanisms that can be driven synchronously and have displacement pistons which each perform a reciprocating motion in operation and are provided for delivery into a common pressure line. The hydrostatic piston machine unit has a jointly assigned precompression volume for the at least two driving mechanisms.

A hydraulic pump includes a cylinder block, a plurality of pistons, a swash plate, a first pressing unit, and a second pressing unit. The cylinder block has a plurality of cylinder bores and is disposed so as to be rotatable. Each of the plurality of pistons is retained in associated one of the cylinder bores so as to be movable. The swash plate is configured for controlling the amount of movement of the plurality of pistons in accordance with the size of the tilt angle. The first pressing unit is configured for pressing the swash plate in such a direction as to reduce the tilt angle of the swash plate. The second pressing unit is configured for pressing the swash plate in such a direction as to increase the tilt angle of the swash plate by a pressure supplied from the outside of the hydraulic pump.

A hydraulic machine includes a housing interior space and a group of hydrostatic working chambers which are mounted in said housing interior space so as to be rotatable about an axis of rotation and which, as the group rotates, are connectable alternately to a high pressure and to a low pressure of the hydraulic machine and exhibit leakage into the housing interior space. A heat exchanger device is accommodated in the housing interior space. The hydraulic machine may be associated with a hydraulic assembly and a hydraulic axle.

The present disclosure discloses a swashplate-type axial plunger pump with multi-channel oil feed and full-flow self-cooling and double-end-face flow distribution. The cooling oil suctioned by the plunger pump firstly cools the friction pair of the cylinder block and the plunger; then, one part of the cooling oil passes through a gap between the pump case and the cylinder block and enters the control chamber by passing by the friction pair of the oil distribution plate and the cylinder block to cool the friction pair of the oil distribution plate and the cylinder block; and the other part of the cooling oil passes through a gap between the pump case and the cylinder block and enters the control chamber by passing by the friction pair of the slipper and the swashplate to cool the friction pair of the slipper and the swashplate.

One object is to provide a hydraulic pump that allows a drive source to be started with a small torque. The hydraulic pump includes: a cylinder block having a plurality of cylinder bores and disposed so as to be rotatable; pistons each retained in associated one of the cylinder bores so as to be movable; a swash plate for controlling the amount of movement of the pistons in accordance with the size of the tilt angle; a first pressing unit for pressing the swash plate in such a direction as to reduce the tilt angle of the swash plate; and a second pressing unit for pressing the swash plate in such a direction as to increase the tilt angle of the swash plate by the pressure supplied from the outside.

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 hydraulic machine with oscillating axial cylinders includes a plurality of oscillating axial cylinders, put in synchronous rotation between a first rotating element, a rotating disc, which supports one end of the cylinder, bottom or piston, and a second rotating element, a rotating barrel, which supports the opposite end of the cylinder; each cylinder is connected to said rotating elements with a ball joint towards each of them; each ball joint is holed to allow for the passage and the feeding/discharge through it of the hydraulic liquid. At least the bottom or the piston is connected to the respective rotating element with a ball joint having a spherical surface with a diameter equal to or greater than the cylinder bore.