| 摘要 |
PURPOSE:To cool a bearing part, by exposing a driving shaft end face in the atmosphere through a magnetic seal and providing a pipe which integrally forms a cavity hole with the axial center in a condition that the pipe holds a clearance of the cavity hole provided in the axial center. CONSTITUTION:A turbo molecular pump provides a shaft cover 18 arranging magnetic fluid 19 in the bottom part of a magnetic material rotary shaft 7 in a condition that the shaft cover interposes a permanent magnet 17 therebetween. A pipe 20, accurately supported through a cover 21, is inserted to the rotary shaft 7 in a condition that a clearance is provided in a cavity hole provided in the shaft center from the bottom end to the position of an upper part ball bearing. A flow of air is generated as shown by an arrow head in the drawing by vacuumizing the inside of the pipe 20, and heat, generated in bearings 8, 9 and a driving motor 21, can be effectively cooled from a side of the rotary shaft 7.
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