A three-stage screw rotor and its twin-screw vacuum pump

Abstract

The invention discloses a three-section type screw rotor and a twin-screw vacuum pump comprising the same and belongs to the field of dry twin-screw vacuum pumps. The screw rotor comprises a gas suction section, a compression section and a gas exhaust section, wherein section profile lines of the gas suction section, the compression section and the gas exhaust section change continuously with a spiral expansion angle; the gas suction section and the gas exhaust section have profile lines with the equal pitch and equal sections, the pitch of the gas suction section is larger than that of the gas exhaust section, but the tooth top surface width of the gas suction section is smaller than that of the gas exhaust section; transition from the gas suction section to the gas exhaust section is realized by the aid of the compression section; the compression section has the profile line with the varying pitch and varying section; and tooth surfaces and spiral lines between the gas suction section and the compression section and between the compression section and the gas exhaust section are in smooth transition. The screw rotor can form the relatively large gas suction volume and the relatively small gas exhaust volume within a relatively small axial size, and the inner volume ratio and the sealing performance of the screw rotor are increased; thus, the screw rotor has the advantages of large inner volume ratio, good sealing performance, compact structure, small axial size and low machining difficulty, and the final vacuum and the pumping speed of the twin-screw vacuum pump are increased.

Description

technical field [0001] The invention relates to a dry twin-screw vacuum pump, in particular to a three-section screw rotor suitable for the dry twin-screw vacuum pump and the twin-screw vacuum pump. Background technique [0002] Dry twin-screw vacuum pump is a positive displacement vacuum pump, which has the advantages of large gas volume, compact structure, high reliability, long life and good dynamic balance. It is widely used in chemical, pharmaceutical, semiconductor and food industries; the screw rotor is a dry type The core component of the twin-screw vacuum pump, the sealing performance, efficiency, and area utilization coefficient of the screw rotor directly affect the pumping speed and ultimate vacuum of the twin-screw vacuum pump. [0003] Patent US6702558, patent CN104373347 and patent CN102937094 disclose multi-stage screw rotors, the pitch of the suction section is large, and the pitch of the exhaust section is small, which can increase the internal volume ratio...

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Problems solved by technology

[0003] Patent US6702558, patent CN104373347 and patent CN102937094 disclose multi-stage screw rotors, the pitch of the suction section is large, and the pitch of the exhaust section is small, which can increase the internal volume ratio of the screw rotor; the screw rotors proposed in the above patents are composed of a The section line shape is generated by helical expansion along the axial direction, that is, the screw rotor with equal section line shape. The width of the tooth top surface of the suction section of the screw rotor is too large, resulting in low area utilization of the section line shape; in the exhaust of the screw rotor In the section, the interstage leakage and return flow of gas is large, but the tooth top surface width of the exhaust section is too small, and the ability to block the interstage leakage and backflow is weak, which is inconsistent with the requirements of the working process; therefore, the ultimate vacuum of the twin-screw vacuum pump is reduced. speed and pumping speed

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