| 摘要 |
PURPOSE:To stabilize a sealing action for a long period of time, by a method wherein a driving shaft of an actuator or a valve is provided with a stopper part capable of stopping up a through-hole penetrating through the shaft by contacting an end face of the periphery of the through-hole. CONSTITUTION:The driving shaft 19 of the actuator 5 is provided with the stopper part 21a, and a compression spring 22 is provided in a negative-pressure chamber 14 of the actuator 5. When not operating, a power piston 12 and a piston rod 13 are moved leftwards as one body by the elastic force of the spring 22, a stopper part 13a is brought into contact with an end face of a bearing 21 to restrain a further leftward movement, and by this contact, the exhaust gas tending to leak through a gap between the inside peripheral surface of the through-hole 21a and the outside peripheral surface of the shaft 19 is prevented from leaking. Accordingly, since lowering of sealing performance due to sliding abrasion as encountered in a conventional device using a sealing member made of asbestos or the like can be reduced or prevented, the brake gear can be used stably for a long period of time. |
