| 摘要 |
PROBLEM TO BE SOLVED: To restrict the withstanding pressure of each stage of plural stages to the limit or less by forming one or both of the opposite surfaces of a first and a second annular magnetic pole parts with a spiral group for generating the fluid carrying force in the axial direction in an annular clearance with the relative rotary movement of the opposite surfaces. SOLUTION: A surface 2a of a rotary shaft 2 facing to magnetic members 7A, 7B functions as a second magnetic pole part. Furthermore, the surface 2a of the rotary shaft 2 is formed with a spiral group 2b for generating the fluid carrying force directed from a low-pressure side L toward a high-pressure side H when the rotary shaft 2 is rotated in a direction illustraded with an arrow A1. At the time of practical use, the magnetic fluid interposed in plural stage parts ST provided in the axial direction is displaced to the high-pressure side by the fluid carrying force of the spiral group 2b, and the withstanding pressure of each stage is raised. Consequently, strength against the critical withstanding pressure in each stage part ST is obtained, and generation of accidental burst due to the agitation can be prevented.
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