Abstract: A piston pump includes 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, 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. The piston pump includes a pressure wall provided at the piston and configured to contact the feed ring to axially move the feed ring, and a restriction portion provided at the feed ring and configured to engage with an outer periphery of the piston at a position approximate to the pressure wall for restricting a radial displacement of the feed ring on the piston.

Abstract: A piston pump includes 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, 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. The piston pump includes a pressure wall provided at the piston and configured to contact the feed ring to axially move the feed ring, and a restriction portion provided at the feed ring and configured to engage with an outer periphery of the piston at a position approximate to the pressure wall for restricting a radial displacement of the feed ring on the piston.