| 摘要 |
In a vacuum booster in which a reaction force mechanism is interposed between an input rod and a valve cylinder connected integrally with a booster piston, and an output rod, a valve piston is fitted onto an input piston connecting the input rod and the reaction force mechanism to be slidably movable forward from a predetermined retreat position with respect to the input piston, the valve piston is biased to the retreat position by a set spring, and locking device is provided between the valve piston and the valve cylinder to lock the valve piston at the valve cylinder thereby holding an atmosphere introduction valve seat in an open state at the time of emergency braking when the input piston moves forward by a predetermined number of strokes ahead of the valve cylinder. Thus, while a delay in atmosphere introduction into the operating chamber is eliminated irrespective of normal braking or emergency braking, the output is allowed to reach a servo limit point earlier and held at the time of emergency braking.
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