Patent ID: 7704058

Claim:
A piston pump, comprising: a pump housing including an inlet port, an outlet port, and an inner bore being in communication with the inlet port and the outlet port; a piston provided at the inner bore of the pump housing and assembled with an annular sealing member to form a pump chamber in the inner bore, the piston reciprocating in an axial direction to increase and decrease a volume of the pump chamber; an inlet valve provided at an inlet passage communicating the inlet port and the pump chamber, the inlet valve opening when the volume of the pump chamber is increased and closing when the volume of the pump chamber is decreased; and an outlet valve provided at an outlet passage communicating the outlet port and the pump chamber, the outlet valve opening when the volume of the pump chamber is decreased and closing when the volume of the pump chamber is increased; wherein a fluid flows from the inlet port into the outlet port by the increase and decrease of the volume of the pump chamber in response to the reciprocation of the piston in the axial direction; the piston is configured to slide at an inner wall of the inner bore; the annular sealing member is assembled with the piston so as to slide at the inner wall of the inner bore in the axial direction together with the piston; a sliding range of the piston relative to the inner wall of the inner bore does not overlap in the axial direction with a sliding range of the annular sealing member relative to the inner wall of the inner bore; an outer periphery of a pump chamber side end portion of the piston is slidably fitted to the inner wall of the inner bore; the annular sealing member is integrally assembled to the pump chamber side end portion of the piston; an outside diameter of a piston side end portion of the annular sealing member is defined to be smaller than an outside diameter of a pump chamber side end portion of the annular sealing member by a predetermined length; and axial length of the piston side end portion of the annular sealing member having the smaller diameter is defined to be equal to or longer than a range of reciprocation of the piston.