A rotary displacement piston pump is disclosed having rotatable single or dual valve/port plate(s). The valve plate, being rotatable forward and/or rearward with respect to the rotation of the piston carrier, alters the phasing of the land area of the pumping action thereby altering the phasing of piston speed inasmuch as the land area can be moved to a position to accelerate the piston(s) in a pre or decompression phase. In this way, pump noise, from colliding pressure fronts within the respective high and low pressure plenums, can be tuned out of the pump by adjusting the phasing and position of the valve plate(s) and raising or lowering the pre and decompression pressure(s) as necessary. Pump volume can also be controlled by advancing or retarding the valve plate(s), either in or out of synch, so as to shorten intake/exhaust piston stroke and overlap fluid flow between respective intake/exhaust plenums.

A high pressure axial piston pump displaces high pressure, high volume fluid into a 1994-2003 7.3 liter power stroke or T444E International engine. A pump housing forms a central borehole, an intake port, and two discharge ports angled about 122 degrees from each other and in fluid communication with engine. A drive shaft rotates a cylinder block about an axis of rotation. A cam is tilted at an angle relative to axis of rotation. Multiple pistons, having a cam end and a block end, reciprocate through cylinder block. The cam end is constrained to follow surface of cam. When pistons move proximally to tilted cam, the block end restricts intake of fluid, and cam end enables discharge of fluid. When pistons move distally from tilted cam, the block end enables intake of fluid, and cam end restricts passage through discharge ports. The pump is fabricated from billet aluminum material.

A high pressure axial piston pump displaces high pressure, high volume fluid into a 1994-2003 7.3 liter power stroke or T444E International engine. A pump housing forms a central borehole, an intake port, and two discharge ports angled about 122 degrees from each other and in fluid communication with engine. A drive shaft rotates a cylinder block about an axis of rotation. A cam is tilted at an angle relative to axis of rotation. Multiple pistons, having a cam end and a block end, reciprocate through cylinder block. The cam end is constrained to follow surface of cam. When pistons move proximally to tilted cam, the block end restricts intake of fluid, and cam end enables discharge of fluid. When pistons move distally from tilted cam, the block end enables intake of fluid, and cam end restricts passage through discharge ports. The pump is fabricated from billet aluminum material.

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.

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 system includes a piston, a swash plate opposed to the piston, and a swash plate supporting member supporting the swash plate so that a tilt of the swash plate is variable. An oil reservoir portion is provided between the swash plate and the swash plate supporting member, the oil reservoir portion communicating with a pressure oil introducing passage. An area of the oil reservoir portion between the swash plate and the swash plate supporting member varies with the tilt of the swash plate.

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.

An electro hydrostatic actuator comprising a hydraulic pump driven by an electric motor to supply hydraulic fluid to a hydraulic actuator, the pump comprising an inlet and an outlet for the hydraulic fluid and an active flow path configured therebetween such that, in an active mode of operation when the pump is driven by the electric motor, hydraulic fluid is actively drawn in through the inlet and exhausted out through the outlet. The pump further comprises a bypass flow path configured to open between the inlet and outlet such that, in a damping mode of operation when the pump is not driven by the electric motor, hydraulic fluid is able to pass through the pump along the bypass flow path between the inlet and outlet. The hydraulic pump is a rotary piston pump comprising a pump barrel driven to rotate by a motor shaft.

The hydraulic apparatus is set so that the ratio of the pressure-receiving area of the respective bottom oil chambers of the boom cylinder, the arm cylinder and the bucket cylinder to the pressure-receiving area of the respective rod oil chambers matches the ratio of the extruded volume drawn into or discharged from the bottom oil chambers per single rotation by the respective extrusion members of the first hydraulic pump motor, the second hydraulic pump motor and the third hydraulic pump motor to the volume discharged from or drawn into the rod oil chambers.

A hydrostatic axial piston machine has a housing. In the housing of the hydrostatic axial piston machine, an actuating pressure cylinder is formed at an angle to the drive shaft. A control valve is inserted into the actuating pressure cylinder in a cartridge type of design. In order to enable maximum movement of an actuating piston in the direction toward the control valve, the cartridge is of shortened design. To this end, an actuating pressure port, which is arranged between a high-pressure port and a low-pressure port, and an actuating pressure passage are arranged completely inside the cartridge.