Systems and methods for a variable displacement hydraulic motor. The hydraulic motor, in one example, includes a swash plate with a tilt angle, multiple piston assemblies configured to rotate about a drive shaft. In the motor, each of the piston assemblies includes an inner piston slideably coupled to an outer piston that mates with a cylinder in a cylinder block and a retainer device configured to inhibit axial movement of the outer piston in a first position and permit axial movement of the outer piston in a second position.

A piston motor includes a bush in the form of a curved plate held in sliding contact with a back surface of a tiltable swash plate, a supply/discharge passage formed on the casing including a swash plate port formed on the swash plate and open on the back surface of the swash plate and a bush port penetrating through the bush and provided from a piston to the swash plate, and an elastic ring interposed between the casing and the bush and surrounding an opening end of the bush port.

A hydrostatic positive displacement machine has a cylinder drum (4) located in a housing (9) and rotatable around an axis of rotation (2). During rotation of the cylinder drum (4), a piston bore (5) is placed in alternating communication with an inlet side (E) and an outlet side (A). The inlet side (E) and outlet side (A) comprise connections (21; 22) to a control plate (12). A reversing device (30) is located in a reversing area (25; 26) between the connections (21, 22) on the control plate (12). The reversing device (30) damps the pressure adjustment between a displacement chamber (V) and the pressure present in the connection (21; 22). The reversing device (30) includes at least two flow connections which are actuated simultaneously by the displacement chamber (V) as it moves along the reversing area (25; 26).

A hydraulic axial piston machine includes a drive shaft, a swashplate pivotable about a pivot axis to change inclination relative to a drive shaft axis, and an actuating piston approximately parallel to the drive shaft axis. The actuating piston has a first end which engages and adjusts the swashplate and a second end which bounds an actuating chamber. Fluid flows to the actuating chamber to pivot the swashplate one direction and is forced out of the actuating chamber when the swashplate pivots the other direction. A return element on the actuating piston incorporates a position of the actuating piston and thus the inclination of the swashplate into a control valve. The return element is positioned such that its longitudinal axis and an actuating piston longitudinal axis span a plane that differs from a plane perpendicular to the pivot axis.

A variable-displacement engine comprises an engine block, power shaft and rotating cylinder block. Pistons and connecting rods mounted in the cylinder block connect to a wobble plate having a rotating ring portion and non-rotating ring portion connected to allow relative rotation therebetween while constraining the portions to remain parallel. The wobble plate defines an inclination plane, pivot axis and wobble plate angle . A piston control mechanism includes axial lift, control lever supported by the lift and by an axially fixed anchor bearing, and links connecting the control lever to the wobble plate. Axial movement of the lift changes the axial position of the control lever pivot and changes the control lever angle, in turn changing, via the connecting links, the wobble plate angle and the axial position of the wobble plate pivot axis. This changes the piston displacement of the engine while maintaining substantially constant compression ratio.

Systems and methods for a variable displacement hydraulic motor. The hydraulic motor, in one example, includes a swash plate with a tilt angle, multiple piston assemblies configured to rotate about a drive shaft. In the motor, each of the piston assemblies includes an inner piston slideably coupled to an outer piston that mates with a cylinder in a cylinder block and a retainer device configured to inhibit axial movement of the outer piston in a first position and permit axial movement of the outer piston in a second position.

A hydraulic piston motor/pump includes a first rotor including a first cylinder, a second rotor opposing the first rotor and including a second cylinder that opposes the first cylinder, a first swashplate including a first angled face adjacent the first rotor, a second swashplate adjacent the second rotor and opposing the first swashplate. The hydraulic piston motor/pump further includes a first shoe cage including a first piston opening, a second shoe cage including a second piston opening, a piston configured to travel into and out of the first cylinder and the second cylinder, a piston shoe configured to engage the piston, the first shoe cage, and the second shoe cage, and a shaft engaging the first shoe cage and the second shoe cage. The shaft configured to rotate in response to a rotation of the first shoe cage and the second shoe cage.