| 摘要 |
PURPOSE:To improve durability and to prevent negative pressure leakage, in a hydraulic brake system for automobile, by providing a through hole and a sealing means and opening or closing the through hole according to existence of negative pressure in either operating chamber. CONSTITUTION:A diaphragm is equipped by coupling the internal part of a booster sheel 1 with a booster piston 2, a diaphragm internal peripheral bead 4a with the rear surface of the piston 2, and the external peripheral bead 4b with the shell 1. The first working chamber A which is being interconnected with a negative pressure source, from the second working chamber B which is being interconnected with the first working chamber A or the atmosphere through a control valve (not shown), a sealing means 33 and a coil spring 47 are provided in a through hole 32 of the piston 2 in which a tie rod 11 is passed through. When the first working chamber A is not under negative pressure, air is relieved through the through hole 32 so as to lighten the load, and if negative pressure is existed, it is closed so as to prevent negative pressure leakage. |
