Abstract: In order to develop a screw vacuum pump, which can efficiently adapt to a wide working pressure range of 0.1-100kPa and meet the expected extreme vacuum process conditions, a segmented progressive pitch screw rotor is designed. The lead of the first part,which is located at the suction end, changes from small to large, while the leads from the second part, gradually change from large to small. This lead structure ensures good dynamic balance of the screw rotor and the integrity of the tooth surface structure. The first two stages of leads determine the suction capacity of the screw vacuum pump, and the ratio of adjacent leads determines the compression capacity. The end lead pitch changes little, and the screw tooth width is large, ensuring the processing performance of the screw. The experiment show that the screw vacuum pump using a segmented gradient screw rotor can maintain a relatively high pumping speed throughout the entire working pressure range, and the pitch parameters may be optimized according to work expectations, which can greatly reduce the specific power in the set working pressure range, improve the pumping efficiency, significantly reduce the driving power and achieve good pump operation effect.

Key words: screw vacuum pump, specific power, self-balancing screw rotor, inner volume ratio