| 摘要 |
PURPOSE:To lengthen the life of magnetic fluid seal and improve reliability of sealing accuracy by filling inert gas in an annular groove, and providing a seal means of inert gas between the side wall on the opposite side of magnetic fluid seal in the annular groove and a movable shaft. CONSTITUTION:At driving, the gap between a crank main shaft 31 and a casing main body part 21 is sealed with magnetic fluid seal 7, and communication between a working space 2a and a receiving space 2b is intercepted. Further, by opening a flow control valve 84, inert gas N2 is filled in an annular groove 81 on the working space 2a side of the magnetic fluid seal 7, hereby communication between the working space 2a and the magnetic fluid seal 7 is intercepted. When a scroll type hydraulic device 1 is used as a vacuum pump of a manufacturing system of semiconductor, corrosive gas such as Cl2 flows in from a suction port 44 and corrosive gas atmosphere fills in the working space 2a. In this case, the corrosive gas is not contacted with magnetic fluid 73, because the inert gas N2 is filled in the annular groove 81. |
