| 摘要 |
PROBLEM TO BE SOLVED: To improve suction performance from an atmospheric pressure chamber to a pressure chamber of brake fluid by a master cylinder.SOLUTION: A master cylinder comprises: a cylinder body which has a bottomed-cylindrical cylinder inner hole; a piston 21 which is assembled to the cylinder inner hole, forms a pressure chamber Rp1 in the cylinder body, and forms an atmospheric pressure chamber Ra1; and a piston seal ring 31 which is assembled to a seal groove 11a of the cylinder inner hole, can slide, contact an outer periphery of the piston 21 at an inner periphery, and can shield between the atmospheric pressure chamber Ra1 and the pressure chamber Rp1 by seal force to be obtained by cooperation with the seal groove 11a when the pressure chamber Rp1 becomes a positive pressure state. Seal structure S1 which is constituted of the seal groove 11a and the piston seal ring 31 is provided with a seal force losing part S1a which loses the seal force when the pressure chamber Rp1 becomes a negative pressure state, and the piston seal ring 31 moves from an end on a side of the atmospheric pressure chamber to a side of the pressure chamber of the seal groove 11a. |
