Patent ID: 8491287

Claim:
A piston pump, comprising: a pump mechanism configured to compress fluid sucked from an inlet port by increasing or decreasing a volume of a pump chamber which faces a front end of a piston by reciprocating the piston housed in a housing, the pump mechanism configured to discharge the compressed fluid from an outlet port; a feed mechanism including a feed ring mounted to an annular groove provided at an outer periphery of the piston and following a motion of the piston, a feed chamber formed between the feed ring and the housing, and a valve portion selectively opening and closing an inlet side passage of the feed chamber by selectively contacting and separating the feed ring and the piston; the feed mechanism provided at an intake passage which is configured to communicate the intake port with the pump chamber, a portion of the intake passage being formed between an inner peripheral surface of the feed ring and a bottom of the annular groove, the valve portion being closed and the volume of the feed chamber being reduced to pressure-feed the fluid in the feed chamber into the pump chamber during an intake stroke by the piston; a surface of the annular groove being an axially facing pressure wall provided at the piston and configured to contact the feed ring to axially move the feed ring; a restriction portion comprising plural pawls protruding axially from an annular base portion of the feed ring the plural pawls being arranged at intervals in a circumferential direction; a base end of the plural pawls possessing a width in a radial direction, and a base end of the annular base portion also possessing a width in a radial direction, the width of the base end of the plural pawls being smaller than the width of the base end of the annular base portion; a radial inner surface of each of the pawls including, at an intermediate portion in an axial direction of the pawl, a wall to be pressured which is positioned in the annular groove and which is configured to be pressed by the pressure wall provided at the piston so that the feed ring follows movement of the piston in response to the pressure wall pressing the wall to be pressured; each of the pawls possessing a radial inner surface, a portion of the radial inner surface of each pawl which is positioned distal of the wall to be pressured being configured to contact an outer peripheral surface of the piston other than the annular groove to restrict radial displacement of the feed ring; and wherein an axial length of the portion of the radial inner surface of each pawl which is configured to contact the outer peripheral surface of the piston other than the annular groove is greater than a maximum axial moving stroke length which the feed ring is allowed to stroke in the annular groove.