| 摘要 |
A screw vacuum pump includes a gas working chamber formed by a male screw rotor and a female screw rotor respectively including unequal lead screws engaging each other and having a lead angle that continuously changes with the advance of helix and a stator receiving therein both rotors. The stator is provided with a gas inlet port and a gas outlet port that can communicate with one end portion and the other end portion of the working chamber, respectively. The male screw rotor and the female screw rotor have unequal lead screws each of which is formed into a perpendicular-to-axis cross-sectional shape that changes following a continuous change in lead angle with the advance of helix. Alternatively, one of the male screw rotor and the female screw rotor has the unequal lead screw formed into a perpendicular-to-axis cross-sectional shape that is constant. Another has the unequal lead screw formed into a perpendicular-to-axis cross-sectional shape that changes. By this, an engagement gap between the unequal lead screws from the suction side to the discharge side is made constant.
|
