A bent-axis hydraulic pump motor includes: a cylinder block, a retainer plate; and a constant velocity joint, which includes an inner joint element; an outer joint element; and a plurality of balls interposed between block-side ball grooves and shaft-side ball grooves to transmit torque between the cylinder block and the retainer plate, so that all block-side groove planes, which include respective extending axial lines of the block-side ball grooves and the inclined rotation center, are inclined with respect to an axial center of a center shaft and all drive shaft-side groove planes, which include respective extending axial lines of the shaft-side ball grooves and the inclined rotation center, are inclined with respect to an axial center of a drive shaft such that loads applied to a cage in an axial direction from the balls are balanced.

A bent-axis hydrostatic axial piston machine (1) has a drive shaft (4) with a drive flange (3) rotatable around an axis of rotation (R.sub.t) and a cylinder drum (7) rotatable around an axis of rotation (R.sub.z). The cylinder drum (7) has a plurality of piston bores (8) concentric to the axis of rotation (R.sub.z) of the cylinder drum (7) and having longitudinally displaceable pistons (10) fastened in an articulated manner to the drive flange (3). Between the drive shaft (4) and the cylinder drum (7) there is a drive joint (30) (constant velocity joint) for rotationally synchronous rotation of the cylinder drum (7) and the drive shaft (4). The drive joint (30) and the cylinder drum (7) include a longitudinal bore (11) concentric to the axis of rotation (R.sub.z) of the cylinder drum, through which bore (11) the drive shaft (4) extends such that in the vicinity of the drive shaft (4) there is a torque transfer to a cylinder-drum-side end of the axial piston machine (1).

Methods and systems for a variable balancing piston motor are described. In one example, a hydraulic displacement motor includes a valve plate coupled to at least one piston of a cylinder block, the valve plate comprising a plurality of grooves fluidly coupled to a passage comprising a valve.