| 摘要 |
A screw vacuum pump is designed so that it is possible to reduce the load on the pump at the time of starting and evacuation of a gas under atmospheric pressure. The screw vacuum pump has male and female rotors rotating in mesh with each other around two parallel axes, respectively, and a casing for accommodating the rotors, the casing having a suction port and a discharge port, wherein the discharge port is formed so that V1/V2 is in the range of 1.5 to 0.51, where V1 is a groove volume defined by the casing and the male and female rotors immediately after a gas has been trapped, and V2 is a groove volume immediately before the gas is discharged.
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