| 摘要 |
PURPOSE:To improve the degree of attained vacuum and obtain clean vacuum at all times including the time when the pump is stopped by a method wherein a bearing at a high-vacuum side is constituted by an attracting type magnetic bearing of a permanent magnet having no change of magnetic characteristics after a high-temperature treatment. CONSTITUTION:The high-vacuum side of a rotor 6 is supported by the attracting force of the permanent magnet 9 while the low-vacuum side thereof is supported by the magnetic bearings 12, 13 so as to be capable of rotating stably. When the rotor 6 is rotated by a motor 16, the molecules of gas in an apparatus to be evacuated are moved from a suction port 1A to a delivery port 3A by the effects of rotor blades 5 and stator blades 4, arranged alternately, transferred with a high compression ratio and discharged out of the delivery port 3A. Titanium alloys or stainless steels are employed for the materials of the knietic blades 5 or the rotor 6 and rare earth elements series magnetic materials, capable of receiving the high-temperature treatment, are employed for the material of permanent magnet 9 thereby enabling to increase the degree of attained vacuum since the baking temperatures thereof may be increased to a high temperature. |
