A nitriding layer (13) is formed on the front surface side of a base material of a cylinder block (7) including an opening side end surface (7B) and each cylinder hole (12). Then, a piston sliding surface (12A) of each cylinder hole (12) is formed as a compound layer-removed hole (17) by removing a compound layer (16) that is located on the front surface side of the nitriding layer (13) by using polishing means such as, for example, honing and so forth. Further, a compound layer-removed surface (18) is formed on a part (A) where a compound layer-removed hole (17) and a cylinder inlet side tapered surface (12B) of each cylinder hole (12) intersect by using the polishing means such as, for example, the honing and so forth. This compound layer-removed surface (18) is formed as a tapered-state inclined surface of an angle α.

A cradle bearing for supporting a swashplate of a variable hydraulic axial piston. The cradle bearing is of an angular ball bearing type or comprises, with respect to the bearing axis, a tapered inner race and/or a tapered outer race. A swashplate for a variable hydraulic axial piston unit including a first and a second cradle bearing zone spaced to each other in axial direction of a swashplate tilt axis, suitable for supporting the swashplate in a housing of a variable hydraulic axial piston unit, wherein the first cradle bearing zone is inclined with respect to the swashplate tilt axis. A variable hydraulic axial piston unit of the swashplate type including a swashplate which is supported rotatable in the housing of the variable hydraulic axial piston unit at a first bearing zone by a tapered bearing and at a second bearing zone by regular cylindrical cradle bearing or a journal bearing whose axis is aligned with the swashplate tilt axis.

An axial piston machine is capable of suppressing a sudden change in hydraulic pressure in a piston oil chamber upon start and stop to enable the axial piston machine to start and stop smoothly. The axial piston machine includes: a cylinder block including a rotation axis and a plurality of piston oil chambers disposed around the rotation axis; pistons housed in the plurality of piston oil chambers, respectively; and orifices formed in the cylinder block that allow fluid communication between each of the piston oil chambers and an outside of the cylinder block. The orifices are positioned to be opened when the movable swash plate is in the neutral position and to be closed when the movable swash plate is in the operating position. The orifices are closed by outer peripheral surfaces of the pistons when the pistons approach a top dead center position.

An axial piston machine is capable of suppressing a sudden change in hydraulic pressure in a piston oil chamber upon start and stop to enable the axial piston machine to start and stop smoothly. The axial piston machine includes: a cylinder block including a rotation axis and a plurality of piston oil chambers disposed around the rotation axis; pistons housed in the plurality of piston oil chambers, respectively; and orifices formed in the cylinder block that allow fluid communication between each of the piston oil chambers and an outside of the cylinder block. The orifices are positioned to be opened when the movable swash plate is in the neutral position and to be closed when the movable swash plate is in the operating position. The orifices are closed by outer peripheral surfaces of the pistons when the pistons approach a top dead center position.

A swash-plate type piston pump includes a cylinder block configured to be rotated with rotation of a driving shaft, a plurality of pistons accommodated in a plurality of cylinders provided in the cylinder block, a swash plate configured to reciprocate the piston so that a volume chamber of the cylinder is expanded/contracted with the rotation of the cylinder block, an biasing mechanism configured to bias the swash plate in a direction where a tilting angle is made larger, a control pin configured to drive the swash plate in a direction where the tilting angle is made smaller in accordance with a rise in a load pressure of a pressure chamber, and a discharge channel configured to discharge the load pressure of the pressure chamber.

A swash-plate type piston pump includes a cylinder block configured to be rotated with rotation of a driving shaft, a plurality of pistons accommodated in a plurality of cylinders provided in the cylinder block, a swash plate configured to reciprocate the piston so that a volume chamber of the cylinder is expanded/contracted with the rotation of the cylinder block, an biasing mechanism configured to bias the swash plate in a direction where a tilting angle is made larger, a control pin configured to drive the swash plate in a direction where the tilting angle is made smaller in accordance with a rise in a load pressure of a pressure chamber, and a discharge channel configured to discharge the load pressure of the pressure chamber.

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.

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.

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 cradle bearing for supporting a swashplate of a variable hydraulic axial piston. The cradle bearing is of an angular ball bearing type or comprises, with respect to the bearing axis, a tapered inner race and/or a tapered outer race. A swashplate for a variable hydraulic axial piston unit including a first and a second cradle bearing zone spaced to each other in axial direction of a swashplate tilt axis, suitable for supporting the swashplate in a housing of a variable hydraulic axial piston unit, wherein the first cradle bearing zone is inclined with respect to the swashplate tilt axis. A variable hydraulic axial piston unit of the swashplate type including a swashplate which is supported rotatable in the housing of the variable hydraulic axial piston unit at a first bearing zone by a tapered bearing and at a second bearing zone by regular cylindrical cradle bearing or a journal bearing whose axis is aligned with the swashplate tilt axis.