| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a negative pressure type booster which attains the improvement effect of responsiveness of booster action even during normal operation other than a rapid operation with a structural change to be hardly carried out. <P>SOLUTION: A chamber 27 communicated with a variable pressure chamber 14 by a valve 32 opened when inputting operational force is made to be a positive pressure chamber into which a positive pressure higher than an atmospheric pressure is introduced. A compressed air chamber 43 partitioned by annular seals 41, 42 is thereby defined between the front end cylinder part 11a of a booster shell 11 and the outer circumference of the front end part of a valve body 17. This chamber 43 is communicated with a positive pressure source through a pipe 44 and is communicated with the chamber 27 through a hole 17a in a radial direction. At the beginning when a plunger 21 moves leftward by operational force, the valve 32 is kept in a closed state through the displacement of a valve body 25 by following the plunger 21. A valve 35 is made to be in a closed state by making the valve body 25 contact with an outer circumferential valve seat 33 and an outermost circumferential valve seat 34, and thereafter the valve body 25 remains at that point. An inner circumferential valve seat 31 is separated from the valve body 25 by the further leftward movement of the plunger 21 and the valve 32 is opened, and pressure is increased at the variable pressure chamber 14 in a negative pressure state by the positive pressure in the positive pressure chamber 27, so that the booster action is carried out. <P>COPYRIGHT: (C)2009,JPO&INPIT |
