| 摘要 |
PROBLEM TO BE SOLVED: To provide a highly reliable magnetic bearing type turbo molecular pump. SOLUTION: Three non-contact type position sensors 20 are arranged inside a face perpendicular to central axes of electromagnets 51, 52 which are an axis of a magnetic bearing. Each of the position sensors 20 is provided in a base 4 and detects a gap with an inner peripheral face of a cylindrical part 12 constituting a drag pump stage of a rotor 2. Based on a detection result of each of the position sensors 20, rotor deformation amountδwhich is change of inner diameter of the cylindrical part 12 is calculated. Based on the rotor deformation amountδ, it is determined whether or not there is a possibility of contact of the rotor 2 with a screw stator 11. When it is determined that there is the possibility, the contact is avoided by lowering the number of rotor rotations. COPYRIGHT: (C)2006,JPO&NCIPI
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