| 摘要 |
<p>This invention relates to a seal structure for a pump unit of a vacuum pump and a driving means for rotating a rotor in the pump stages (A, B) of the pump. The seal structure is provided with a narrow gap sealing means formed by a stationary member (2a) which is opposed to the portion of a shaft (4) of the driving means (5) which is between the pump unit and an upper bearing (6) supporting the same shaft (4), which narrow gap sealing means consists of first, second and third seal portions (15; 17); a means for supplying a discharge gas to the first seal portion; and a means for supplying a purge gas (11, 12, 13) to the second and third seal portions. Owing to these parts, the feed rate of the purge gas can be minimized, and the entry of the oil mist, which occurs during the lubrication of the bearing (6, 7), into the interior of the pump unit can be prevented. This enables the interior of the pump unit to be kept clean.</p> |
