The present disclosure relates to an axial piston machine, such as a pump or motor. The axial piston machine, in on example, includes a pivotable displacement adjustment plate, the displacement adjustment plate having a first side supported by a first hydrostatic support arrangement and a second side supported by a second hydrostatic support arrangement. Further, in the axial piston machine one or both of the hydrostatic support arrangements include a large area support and a small area support which can be fluidly separated from each other.

A variable positive displacement pump actuator system for a variable positive displacement pump can include a supply line configured to provide a supply pressure, a main pump line configured to provide a pump pressure greater than the supply pressure from the variable positive displacement pump, and at least one electro-hydraulic servo valve (EHSV) in fluid communication with the supply line and the main pump line to receive the supply pressure and the pump pressure. The at least one electro-hydraulic servo valve can be configured to output a first regulated pressure and a second regulated pressure. The system can include a first control line in fluid communication with at least one of the at least one EHSV to receive the first controlled pressure, a second control line in fluid communication with at least one of the at least one EHSV to receive the second controlled pressure, a first hydraulic actuator configured to connect to and/or otherwise actuate a lever arm of the variable positive displacement pump, the first hydraulic actuator in fluid communication with the first control line and the supply line to receive the first control pressure and the supply pressure to control a position of the first hydraulic actuator, and a second hydraulic actuator configured to connect to and/or otherwise actuate the lever arm of the variable positive displacement pump, the second hydraulic actuator in fluid communication with the second control line and the supply line to receive the second control pressure and the supply pressure to control a position of the second hydraulic actuator.

A control arrangement for a variable displacement pump includes a pressure control unit and a separate mechanical control unit, each mounted on a housing of the variable displacement pump. The pressure control unit provides pressure control for the variable displacement pump and the mechanical control unit provides rotary feedback control for the variable displacement pump.

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.

A piston pump includes: a tilting mechanism configured to bias a swash plate in accordance with a control pressure; a support spring configured to support the swash plate; and a regulator configured to control a control pressure guided to the tilting mechanism in accordance with a self-pressure of the piston pump. The regulator has an outer spring and an inner spring configured to be extended and compressed by following tilting of the swash plate; and a control spool configured to be moved in accordance with a biasing force from the outer spring and the inner spring, the control spool being configured to regulate the control pressure, and the outer spring and the inner spring and the support spring are provided adjacent to each other and in parallel with respect to the swash plate.

An electronic control valve for an HVAC system of a vehicle may include, in the electronic control valve configured to control the angle of a swash plate (angle with respect to the surface perpendicular to a rotation shaft of a compressor) in the compressor in an HVAC system, a solenoid, a plunger coupled to the solenoid member and configured to slid according to whether the solenoid is magnetized, a valve body formed integrally with the plunger, and configured to open or close a supply flow path through which a fluid flows into the compressor, a discharge flow path through which a fluid is discharged from the compressor, and a control flow path through a fluid flows to control the angle of the swash plate mounted inside the compressor, a diaphragm configured to operate the plunger by the pressure of refrigerant, and a return spring configured to return the plunger, and the solenoid is applied with power according to a vehicle target cooling load.

A reciprocating compressor-expander according to the present invention comprises a cylinder, a piston, a crankshaft connected to the piston, a first valve for a low pressure compressible fluid, a second valve for a high pressure compressible fluid, and a valve drive mechanism for driving the first valve and the second respectively such that, during a compression process, the low-pressure compressible fluid is sucked into the cylinder from the first valve in synchronization with the rotation of the crankshaft and the high-pressure compressible fluid compressed in the cylinder is discharged from the second valve, and that, during an expansion process, the high-pressure compressive fluid is introduced from the second valve into the cylinder, and the low-pressure compressible fluid expanded in the cylinder is discharged from the first valve.

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.

A hydrostatic travel drive includes a hydraulic pump for the purpose of supplying pressure medium to a hydraulic motor of the travel drive that can be coupled to an output, which pump can be coupled to a drive machine. The hydraulic pump has an actuating cylinder with at least one cylinder chamber and a swept volume which can be adjusted via the actuating cylinder, and at least one electrically activatable pressure valve via which the cylinder chamber can be charged with an adjustingly active actuating pressure. The travel drive further includes device via which a pressure of the hydraulic pump can be limited by means of influencing the actuating pressure.

A hydrostatic piston machine has an adjustment element that is adjustable for varying a displacement volume, and a rotating cylinder part having a plurality of cylinder bores with pistons that are supported on the adjustment element and delimit a displacement chamber. Each displacement chamber is moved in an alternating manner by a connecting opening to overlap a low-pressure control opening situated on a low-pressure side of a stationary control part and a high-pressure control opening situated on a high-pressure side of the control part. Two switching regions are situated between the low-pressure control opening and the high-pressure control opening, the pistons changing direction at a dead center within the switching regions. The position of the adjustment element is determined from a pressure profile which is a function of the variable size of the displacement chambers in a switching region, the variable size depending on the position of the adjustment element.