Patent ID: 7891959

Claim:
A piston pump comprising: a pump housing having a suction port and a discharge port; a piston which is mounted in a bore of the housing and forms a pump chamber, the piston increasing and decreasing the volume of the pump chamber by reciprocating in the axial direction; a suction valve which is provided on the piston and is disposed in an inflow passage connecting the suction port with the pump chamber and which opens when the volume of the pump chamber is increasing and closes when the volume is decreasing; and a discharge valve which is provided on a discharge side of the pump chamber, the discharge side of the pump chamber being the side toward which the piston moves to decrease the volume of the pump chamber, the discharge valve being disposed in an outflow passage connecting the discharge port with the pump chamber and which opens when the volume of the pump chamber is decreasing and closes when the volume is increasing, wherein liquid flows from the suction port towards the discharge port when the piston reciprocates in the axial direction and the volume of the pump chamber increases and decreases, wherein the suction valve comprises: a retainer which is mounted on the piston and includes a valve bore which communicates with the suction port, a valve seat which is formed on the end of the valve bore closest to the pump chamber, and a valve body holding portion and a spring holding portion which are connected to and seamlessly and integrally formed with the valve seat, wherein the valve body holding portion, the spring holding portion, and the valve seat are molded out of a resin into a single piece; a valve body which is received and held by the valve body holding portion of the retainer and can seat and unseat with respect to the valve seat; and a spring which is received and held by the spring holding portion and which biases the valve body towards the valve seat; wherein the valve body holding portion and the spring holding portion of the retainer comprise a plurality of column-shaped members which extend in the axial direction of the retainer; each column-shaped member having an end portion, an end of the end portion closest to the discharge side of the pump chamber and a tapered portion which is formed on an inner periphery of the end portion and which decreases in inner diameter from a larger diameter end of the tapered portion toward the end of the column-shaped member closest to the discharge side of the pump chamber; and the spring comprising a coil spring possessing a cylindrical shape, the inner diameter of the column-shaped members as measured at the larger diameter ends of the tapered portions is smaller than the outer diameter of the end of the coil spring before the valve body and the coil spring are positioned in the retainer.