PISTON PUMP MOTOR

摘要

Heat generation and seizure caused by sliding friction of a piston and a cylinder in inclined shaft type and swash plate type hydraulic pumps can be prevented even at high speeds. A piston pump motor comprises a cylinder block (20) rotatably supported in a casing (32), having suction and exhaust ports (21) on one end surface side of a cylindrical shape and provided with a plurality of cylinder bores (22) which are connected to the suction and exhaust ports and arranged uniformly on an inside circumference, and pistons (11) adapted to be rotated by a drive shaft (31), slide liquid-tightly in the cylinder bores and to partly enter and leave the other end surface side of the cylinder block. Provided on either that portion of an outer periphery of each piston, which enters and leaves the other end surface side of the cylinder block, or that portion of an inner periphery of each cylinder bore, where a portion of the associated piston enters and leaves the other end surface side of the cylinder block, is an oil introduction groove (13) communicating with the inside of the casing.