| 摘要 |
PROBLEM TO BE SOLVED: To improve forward operating responsiveness of a booster piston when an atmospheric air introducing valve seat is opened, by enlarging diameter of the atmospheric air introducing valve seat and a negative pressure introducing valve seat without mutually interfering, spreading these opening ports, and reducing flow path resistance leading to an operating chamber from the atmospheric air introducing valve seat, in a negative pressure booster. SOLUTION: A front annular chamber 46 communicating with operating chambers 2b, 3b and a rear annular chamber 47 adjacent to a rear part of this front annular chamber 46 through an annular partition 48 are formed in the internal periphery of a valve cylinder 10. An atmospheric air introducing valve seat 30 appearing in the front annular chamber 46 is formed in an input plunger 18 connected to an input rod 20 and a negative pressure introducing valve seat 31 appearing in the rear annular chamber 47 is formed in the partition 48. A valve part 34a of a valve element 34 mounted in the internal periphery of the valve cylinder 10, is energized by a valve spring 36 for seating it in both the valve seats 30, 31, and seat center diameters d1, d2 of both the valve seats 30, 31 are set equal to or larger than an internal diameter d3 of the partition 48.
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