To provide a roots type vacuum pump that prevents the generation of an abnormal sound by a confining phenomenon of liquid between root rotors and prevents the shortening of a bearing service life caused by the infiltration of moisture into a shaft seal part.
A clearance groove 17 of a cross-sectional shape such as a shape for expanding a clearance with an inner peripheral surface 1a of a casing 1 toward the rotational direction is formed over the total length of respective lobes on a peripheral surface of a position separated by a predetermined dimension to a side in the rotational direction from the center line of the respective lobes 16 of the root rotor 15. The shaft seal part 8 fixes a moisture shake-off ring 30 arranged between a collar 26 and a bearing 9 to a rotary shaft 18 of the root rotor 15 by installing one or a plurality of housing oil seals 25 and the collar 26 in order from a place near to an installation surface 7b to the casing 1 in an inner diameter part of the housing 7. A clearance formed on an opposed surface between the collar 26 and the ring 30 is formed so as to form a labyrinth seal, and a passage 7c for returning the liquid stored in the shaft seal part 8 to a vacuum chamber is arranged at the discharge port side of the housing 7.
COPYRIGHT: (C)2010,JPO&INPIT
ITO YOSHINOBU
KATO TOSHIAKI
KATO MASAMI
YOKOI IKUTO
| JPH03130592A | 1991-06-04 | |||
| JPS55106389A | 1980-08-15 | |||
| JPH0450492A | 1992-02-19 | |||
| JPH0571487A | 1993-03-23 | |||
| JPS627991A | 1987-01-14 | |||
| JPS5458605A | 1979-05-11 |
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