Valve plate, cylinder block, and hydraulic pump/motor

A valve plate of a hydraulic pump/motor, the valve plate comprising a high pressure-side port and a low pressure-side port on a circumference about a rotation axis, a first oil groove provided to be annular in an outer peripheral part with respect to the high pressure-side port and the low pressure-side port, and a plurality of second oil grooves extending from the first oil groove toward an outer periphery, the high pressure-side port and the low pressure-side port being alternately communicated with a cylinder bore provided in a cylinder block by relative rotation about the rotation axis in a state of being in contact with an end face of the cylinder block,

• wherein a plurality of pad oil grooves communicating with the first oil groove and opened toward the end face of the cylinder block are provided in an outer peripheral portion of the high pressure-side port, at least in a portion being on a downstream side of the relative rotation, in a pad region contacting the end face of the cylinder block between the second oil grooves, and
• wherein the plurality of pad oil grooves are provided such that a proportion of an opening area to the end face of the cylinder block is larger on the downstream side than on an upstream side of the relative rotation.