| 摘要 |
In an automatic brake booster, a sleeve 18 constituting a valve mechanism 15 has a drive portion 50 disposed on the front side, a valve portion 51 forming a second valve seat 19, a mating portion 52 for mating with a valve seat portion when the drive portion is moved forward, and a conical spring 53 disposed between the drive portion and the valve seat portion and used for separating both members from each other. The conical spring is compressed during the normal braking operation so as to make the opening amount of the second valve seat greater than that during the automatic braking operation. Moreover, a plate plunger 40 for transmitting braking counterforce is relatively displaceably provided and a first member 71 and a second member 71 for mutually contacting a reaction disc 41 is also provided, so that the braking counterforce of the first member is transmitted to the sleeve during the automatic braking operation.
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