Hydraulic rotary machine

A hydraulic rotary machine in which water is used as a working fluid, comprising:

• a plurality of pistons;
• a cylinder block having a plurality of cylinders which accommodates the pistons and being rotatable;
• a shaft penetrating through the cylinder block and coupling to the cylinder block;
• a swash plate configured to reciprocate the piston in accordance with the rotation of the cylinder block so as to expand and contract a capacity chamber of the cylinder;
• a casing accommodating the cylinder block, the casing supporting one end of the shaft, the other end of the shaft being inserted through the casing;
• a supply passage provided in the casing and configured to supply the working fluid to the capacity chamber;
• a discharge passage provided in the casing and configured to introduce the working fluid discharged from the capacity chamber;
• an axial directional passage opened on an end surface of the one end of the shaft and drilled open along a shaft center of the shaft;
• a first radial directional passage drilled open along a radial direction of the shaft from the axial directional passage and configured to guide the working fluid inside the casing;
• a second radial directional passage drilled open along the radial direction of the shaft from the axial directional passage at a position closer to the one end of the shaft than the first radial directional passage and configured to guide the working fluid inside the casing;
• and
• an introduction passage configured to communicate a passage, through which the higher pressure working fluid flows, among the supply passage and the discharge passage with the axial directional passage.