| 摘要 |
PURPOSE:To eliminate an ineffective stroke of a booster piston so as to improve its responsibility by providing a relief port valve provided in an oil path, connected between a brake fluid pressure chamber and an oil tank, and associated with an input level in a manner wherein the valve is opened, when the input lever is retracted, and closed when the input lever is advanced. CONSTITUTION:In a tandem type master cylinder, a cylinder main unit 1 connects to its rear end part a hydraulic booster B fitting a booster piston 27 to a cylinder hole 24 in a front part sleeve 21. While a stepped inner side piston 29 is slidably fitted to a stepped cylinder hole formed in the booster piston 27, and providing a valve piston 31, input piston 33 and a reaction force mechanism or the like to be arranged in a hollow part of the inner side piston 29, an input lever 39, operated by a brake pedal, is connected to the input piston 33. Here the inner side piston 29 drills a radial relief port 62 opened to a reaction force oil pressure chamber 61, and the port 62 is opened and closed by a front part land 57 serving as the relief port valve formed in a front part of the valve piston 31. |
