This master cylinder is provided with a piston seal (45) which is provided in a circumferential groove (32). The piston seal (45) is provided with: an annular base (101); an inner peripheral lip (102) which protrudes from the inner peripheral side of the base (101) and which is in sliding contact with the outer peripheral surface (18a) of a piston (18); an outer peripheral lip (103) which protrudes from the outer peripheral side of the base (101) and which is in contact with the circumferential groove (32); and an intermediate protrusion (104) which protrudes further forward from between the inner peripheral lip (102) and the outer peripheral lip (103) of the base (101) than the outer peripheral lip (103). A stepped section (107) is formed on the outer peripheral side of the base (101), the stepped section (107) being configured so as to have a greater axial length on the inner peripheral side thereof than on the outer peripheral side thereof. A step (91) with which the outer peripheral surface (101b) of the stepped section (107) is constantly in contact is formed on the circumferential wall (89) of the circumferential groove (32). A connection passage (111) which connects a replenishing passage (48) and the bottom side of the circumferential groove (32) is provided between the stepped section (107) and the step (91), the replenishing passage (48) connecting to a reservoir.
Master cylinder
2015-09-23
Patent
Electronic Resource
English