| 摘要 |
The present invention is directed to a vacuum servo unit which is characterized in that the negative pressure controlling valve seat is arranged in a position spaced from the atmosphere controlling valve seat in an axial direction, and the atmosphere and the negative pressure controlling seal portions of the control valve are spaced in the axial direction to cooperate with the atmosphere and the negative pressure controlling valve seats. The control valve is in air tightly engagement with an internal surface of the movable power piston at an external surface thereof, and the control valve has a path provided between the atmosphere controlling seal portion and the negative pressure controlling seal portion. Accordingly, when the brake operating member is operated, large quantities of the atmosphere can be introduced to the variable pressure chamber through the clearance between the atmosphere controlling valve seat and the atmosphere controlling seal portion. Therefore, the operation response of the vacuum servo unit can be improved.
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