Hydraulic pump/motor

A hydraulic pump/motor comprising:

• a cylinder block that rotates about a rotation axis;
• a piston disposed in a cylinder bore of the cylinder block;
• and
• a valve plate facing a cylinder port of the cylinder bore,
• wherein the valve plate includes:
• a high pressure port through which hydraulic oil discharged from the cylinder port flows;
• a low pressure port through which hydraulic oil to be sucked into the cylinder port flows;
• a first region disposed between the high pressure port and the low pressure port in a circumferential direction of the rotation axis, the first region including a top dead center position facing the cylinder port of the cylinder bore in which the piston having moved to a top dead center is disposed;
• and
• a residual pressure release port provided between the top dead center position and the low pressure port in the first region, and
• the residual pressure release port includes a first residual pressure release port and a second residual pressure release port, the second residual pressure release port being disposed at a position different from the first residual pressure release port in a radial direction of the rotation axis,
• wherein, in the circumferential direction, a distance between the top dead center position and the first residual pressure release port is shorter than a distance between the top dead center position and the second residual pressure release port, and
• wherein a size of the first residual pressure release port is smaller than a size of the second residual pressure release port.

A hydraulic pump/motor comprising:

• a cylinder block that rotates about a rotation axis;
• a piston disposed in a cylinder bore of the cylinder block;
• and
• a valve plate facing a cylinder port of the cylinder bore,
• wherein the valve plate includes:
• a high pressure port through which hydraulic oil discharged from the cylinder port flows;
• a low pressure port through which hydraulic oil to be sucked into the cylinder port flows;
• a first region disposed between the high pressure port and the low pressure port in a circumferential direction of the rotation axis, the first region including a top dead center position facing the cylinder port of the cylinder bore in which the piston having moved to a top dead center is disposed;
• and
• a residual pressure release port provided between the top dead center position and the low pressure port in the first region, and
• the residual pressure release port includes a first residual pressure release port and a second residual pressure release port, the second residual pressure release port being disposed at a position different from the first residual pressure release port in a radial direction of the rotation axis,
• wherein, in the circumferential direction, a distance between the top dead center position and the first residual pressure release port is shorter than a distance between the top dead center position and the second residual pressure release port, and
• wherein the cylinder block rotates such that the cylinder bore is to be connected to the second residual pressure release port after being connected to the first residual pressure release port, and is to be connected to the low pressure port after being connected to the second residual pressure release port.