A piston compressor includes a housing, a drive shaft, a fixed swash plate, a plurality of pistons, a movable body, and a control valve. The housing includes a cylinder block having a plurality of cylinder bores and a plurality of first communication passages. The movable body has a second communication passage that intermittently communicates with each of the first communication passages by rotation of the drive shaft. A flow rate of refrigerant discharged from a compression chamber into a discharge chamber changes according to a position of the movable body in a direction of an axis of the drive shaft. The control valve is configured to control a control pressure. The first communication passages are connected to the second communication passage by the movable body and disconnected from the second communication passage by the drive shaft.

A piston compressor includes a housing, a drive shaft, a fixed swash plate, a plurality of pistons, a movable body, and a control valve. The housing includes a cylinder block having a plurality of cylinder bores and a plurality of first communication passages. The movable body has a second communication passage that intermittently communicates with each of the first communication passages by rotation of the drive shaft. A flow rate of refrigerant discharged from a compression chamber into a discharge chamber changes according to a position of the movable body in a direction of an axis of the drive shaft. The control valve is configured to control a control pressure. The first communication passages are connected to the second communication passage by the movable body and disconnected from the second communication passage by the drive shaft.

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.

An axial variable displacement piston pump includes a drive shaft disposed on an axis, a piston barrel comprising a plurality of pistons disposed about the drive shaft, and a swash plate disposed about the drive shaft. Each of the piston barrel and the swash plate are rotationally coupled to the drive shaft such that the drive shaft is configured to simultaneously drive rotation of each of the piston barrel and the swash plate.