| 摘要 |
PROBLEM TO BE SOLVED: To restrain sliding sound by reducing friction force between a seal member and a valve body at an initial working stage. SOLUTION: A valve body 6 is passed through by a seal member 12 free to reciprocally move by keeping airtight on a shaft part of a center plate to partition an internal space of a tandem assistor. Though a diameter d1 of a contract part 6a to make contact with the seal member 12 at the time when the value body 6 is positioned at a non-working position is set large enough to provide sufficient sealing work, a small diametral part 6b on the rear side adjoining the contact part 6a is set as a diameter d2 which is smaller than the diameter d1 . Consequently, as the small diametrical part 6b of the valve body 6 is inserted into the seal member 12 when the valve body 6 is made to advance, friction force between the valve body 6 and the seal member 12 is reduced, and accordingly, it is possible to restrain sliding sound generated between the valve body 6 and the seal member 12. |
