| 摘要 |
PURPOSE:To eliminate use of any special pressure booster and make the construction small and light by allowing the working liquid to be pressurized at an equal area to the difference in the pressure receiving area between a minor dia. piston and a major dia. piston when the fluid pressure in the working pressure chamber is sunk by any trouble in a fluid pressure source. CONSTITUTION:In a brake device including wheel cylinder 300, master cylinder 302, and fluid pressure booster 308, a bottom-equipped cylinder bore 314 formed in a housing 312 of the master cylinder 302 is formed at a step-equipped cylinder bore 342 having a minor dia. part 340 on the bottom side. Corresponding to the step-equipped cylinder bore 342 a pressurizing piston 316 is formed provided with a minor dia. piston 346 and a major dia. piston 348. In case the level of the fluid pressure at a fluid pressure source 306 is normal, the working liquid is pressurized at an area equal to the pressure receiving area of the major dia. piston 348, while in its missing condition, a pressurizing condition altering means 350 pressurizes at an area equal to the different in the pressure receiving area between the two pistons 346, 348. |
