| 摘要 |
PROBLEM TO BE SOLVED: To arrange an operation piston and a cut valve in the cylinder body of a secondary master cylinder by shortening the length of the secondary master cylinder as short as possible in a brake fluid pressure booster capable of boosting a wheel brake. SOLUTION: The operation piston 58 of the secondary master cylinder M2F has both ends facing to an output fluid pressure chamber 59 connected to the wheel brake and a first input fluid pressure chamber 60 connected to the proportional booster valve V, is formed with an annular second input fluid pressure chamber 61 connected to the primary master cylinder in a space relative to the internal circumference of the cylinder hole 56 provided in the cylinder body 55, and slidingly fitted to the cylinder hole 56. The cut valve 65 is provided in the operation piston 58 so as to cut off between the second input fluid pressure chamber 61 and the output fluid pressure chamber 59 according to the fluid pressure increase of the first input fluid pressure chamber 60.
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