JP2011136602A5 - - Google Patents

Claims (3)

A cylinder body into which hydraulic fluid is introduced from the reservoir;
A piston slidably fitted into the cylinder body and defining a pressure chamber in the cylinder body;
A supply passage formed in the cylinder body for supplying hydraulic fluid from the reservoir to the pressure chamber;
A bypass passage that bypasses the supply passage and communicates the reservoir and the pressure chamber;
A check valve interposed in the bypass passage and opened when a pressure in the pressure chamber is lower than a pressure in the reservoir;
With
The check valve comprises a cup seal having an annular base and a lip extending from the base,
The bypass passage has at least one hole formed on a side opposite to the extending direction of the lip portion with respect to the base portion of the cup seal.
A master cylinder, characterized in that a flexible annular plate spacer having a size covering at least the hole is fixed to the cup seal between the hole and the base. The master cylinder according to claim 1, wherein the spacer has a diameter smaller than a diameter of the cup seal. The cup seal has an outer peripheral lip portion that extends from the outer periphery of the base portion, and a groove portion that is recessed radially inward from the base portion side to an intermediate position in the axial direction on the outer peripheral surface of the outer peripheral lip portion. The master cylinder according to claim 1, wherein the master cylinder is formed.