| 摘要 |
PROBLEM TO BE SOLVED: To prevent bearing grease from leaking by giving large draft resistance to a hole of a housing through which a rotating shaft is passed for connecting a rotary chamber and an upper bearing. SOLUTION: The portion of about 20 mm length having a minute clearance B narrower than the clearance of about 0.2 mm between a noncontact seal 22 and a bearing inner ring 21 of an upper bearing 14 is formed by a rotating shaft 9 and a smooth cylindrical surface of a housing 11 above the upper bearing 14. By this, resistance to pressure decrease force generated by the rotation of a rotor. is formed to keep the upper bearing 14 from the effect of pressure decrease generated by the rotation of the rotor. In this way, a pressure decrease value near the upper bearing 14 is sharply reduced to enable preventing grease leakage.
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