| 摘要 |
PROBLEM TO BE SOLVED: To suppress vibration displacement of a valve member, and ensure a prescribed fine valve opening by engaging a stopper device with a valve shaft, and inhibiting the displacement, when the valve member is displaced from a set opening position by reducing a valve opening and increasing a pressure difference between the upstream and downstream sides of the valve member. SOLUTION: When control negative pressure is supplied to a negative pressure chamber 60 of a valve actuator 38 bypassing a leading-in pipe 64 from a control negative pressure source 66 according to an operating condition of an engine, a valve shaft 26 and a valve member 28 fall down against a spring 62 by a first diaphragm 46 to form a valve passage having a small area. In this time, control negative pressure is supplied from the negative pressure source 66 to a control chamber 114, and a spool valve 94 is displaced on a raising position. Negative pressure induced to a negative pressure chamber 88 of a stopper device 70, and a stopper member 68 falls down and so as to abut on an upper end surface of a valve shaft 26. Even if large pressure difference exceeding a setting value between the upstream and downstream sides of the valve member 28 is generated, raising of the valve member 28 is obstructed by the pressure difference, and its opening can be held constantly.
|
