Master cylinder

Abstract

An object of the present invention is to reduce the work cost of a piston, and to decrease the resistance of flow in a communicating passage between a pressure chamber and a reservoir, and to reduce the ineffective stroke, too, and the means is as flows: a small outside diameter portion (28) whose outside diameter is reduced by forming a step surface (27) on the periphery of a piston (24) and a sleeve (30) to be fitted onto the periphery of the small outside diameter portion (28) are provided; and a radial passage groove (32) formed along the radial direction between the step surface (27) and the end surface of the sleeve (30) opposite to the step surface (27) and an axial passage groove (33) formed along a direction crossing the radial passage groove (32) between the inner surface of the sleeve (30) and the peripheral surface of the small outside diameter portion (28) are provided; and the radial passage groove (32) and the axial passage groove (33) are used as a communicating hole. Then, the size of continuous length in the circumferential direction of the radial passage groove (32) is set larger and the size of depth of the axial passage groove (33) is set smaller than the size of a step of the step surface (27).

Dependencies are inferred from the claim text.