Patent ID: 7055322

Claim:
A master cylinder comprising a cylinder body, a cup supported on an inner wall of said cylinder body, and a piston inserted in said cylinder body so as to be in sliding contact with a radially inner periphery of said cup, said piston defining a pressure chamber in said cylinder body, and being formed with piston ports through which said pressure chamber is adapted to communicate with a reservoir while said piston is in an inoperative position, said piston ports comprising first ports for ensuring communication between said pressure chamber and said reservoir, and second ports through which brake fluid in said reservoir is sucked into said pressure chamber during automatic brake control, said second ports being greater in number than said first ports and being provided forwardly of said first ports with respect to a direction in which said piston advances, wherein said first ports overlap with said second ports as viewed from a direction perpendicular to an axis of said piston.