Swash-plate hydraulic motor or swash-plate hydraulic pump

A swash-plate hydraulic motor or a swash-plate hydraulic pump comprising:

• a main body casing;
• a rotation axis housed in the main body casing;
• a cylinder block attached to the rotation axis;
• cylinder holes formed in the cylinder block;
• pistons slidably inserted into the cylinder holes;
• shoes attached to leading ends of the pistons;
• a swash plate including a slope on which the shoes slide and a supported surface which is formed on the side opposite to the slope and is supported by the main body casing via two pivots;
• a tilt piston which is in contact with the supported surface of the swash plate and is configured to tilt the swash plate by pressing the swash plate toward the pistons;
• and
• a cylinder hole for the tilt piston, the cylinder hole being formed in the main body casing and into which the tilt piston is slidably inserted, a spherical surface member being formed at an end face on the swash plate side of the tilt piston in an integrated manner, a recess with which the spherical surface member is slidably engaged, the recess being formed in the supported surface of the swash plate,
• wherein a bottom surface of the recess is formed to be arc-shaped in a direction connecting the two pivots with each other, and
• wherein the bottom surface of the recess is formed to be flat in a direction orthogonal to the direction connecting the two pivots with each other over an entire length of the recess, and
• wherein the tilt piston is configured to be movable between an extended position in which the tilt piston presses the swash plate towards the pistons and a retracted position,
• wherein, as the tilt piston moves between the extended position and the retracted position and the swash plate pivots about the two pivots, the spherical surface member of the tilt piston is configured to engage the bottom surface of the recess at different positions of the recess, and
• wherein the different positions are spaced apart longitudinally in the direction orthogonal to the direction connecting the two pivots with each other.