| 摘要 |
PURPOSE:To improve seal performance in a low differential pressure region and restrain pressure vibration at high differential pressure by providing a thin portion of the outer contour of a rotor to be elastically deformed by its rotation. CONSTITUTION:When a pair of rotors 1 in a pump casing 4 rotate synchronously, a transfer medium is taken in from an intake port 5 and discharged by a shift of space formed between respective rotors. Particularly when small differential pressure is provided for high vacuum, only a centrifugal force due to the high speed rotation of the rotor 1 acts on a thin portion 3 to reduce clearances between the rotor and housing and the rotors themselves and minimize leakage by the deformation of the rotors 1. Further, in-high differential pressure provided by running to bring about high differential pressure, a clearance in a seal portion is expanded to reduce a counter flow and noises.
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