Patent ID: 7785085
Filing Date: 2010-08-31
Classification: B60T,F04B

Abstract:
1. A piston pump comprising: a pump housing having a suction port, a discharge port, and an internal cavity; a first cylinder member having a cylinder bore and built into the internal cavity of the pump housing; a piston built into the cylinder bore of the first cylinder member to thereby form a pump chamber in the cylinder bore, the piston being axially reciprocated along a central axis of the first cylinder member so as to increase and decrease a volume of the pump chamber; a suction valve provided in the piston, the suction valve opening when the volume of the pump chamber increases, and closing when the volume decreases; and a discharge valve provided at a discharge side of the pump chamber, the discharge valve opening when the volume of the pump chamber decreases, and closing when the volume increases, wherein the piston is axially reciprocated so as to increase and decrease the volume of the pump chamber to thereby cause fluid to flow from the suction port to the discharge port, and wherein a circumferential protrusion, formed wholly around the outer circumferential surface of the first cylinder member, having a smooth exterior shape, and possessing an arc shape in a cross-sectional view of the first cylinder member along a plane containing the central axis of the first cylinder member, is formed externally at an axially intermediate portion of the first cylinder member; the first cylinder member is press-fitted, only at a whole circumference of an apex of the arc shape, into the internal cavity of the pump housing in a fluid-tight condition; and a leading end portion of the first cylinder member has a diameter smaller than that of the internal cavity of the pump housing, the leading end portion extending from the circumferential protrusion in a direction of insertion of the first cylinder member into the pump housing.