Single-head varying-pitch screw rotor with equal tooth top width

Abstract

The invention relates to a single-head varying-pitch screw rotor with equal tooth top width. A tooth form surface of the screw rotor is formed in a manner that a tooth root surface, an oblique tooth surface, a tooth top surface and a transition tooth surface are sequentially connected with one another, the screw lead of the rotor is linearly increased from an exhaust end to a suction end along an axial coordinate, the axial width of the oblique tooth surface is gradually increased along the screw lead, but the width of the tooth top surface always remains unchanged. Compared with various existing single-head varying-pitch screw rotors, the tooth top width of the suction end of the molded line rotor is relative narrow, thus, larger inter-stage suction volume is formed, and the molded line rotor has a larger volume utilization factor, so that the molded line rotor has a higher theoretical pumping speed under the condition of the same structural parameters; and on the other hand, the tooth top width of the exhaust end of the molded line rotor is relatively wide, thus, the molded line rotor has stronger inter-stage blocking capacity and is capable of decreasing the inter-stage gas leakage backflow volume, so that the ultimate vacuum degree and the actual effective pumping speed of a vacuum pump are beneficially improved.

Description

technical field [0001] The invention relates to the technical field of screw type oil-free vacuum pumps, in particular to a single-head variable-pitch screw rotor with equal addendum width. Background technique [0002] The oil-free screw pump has the characteristics of wide pumping speed range, simple and compact structure, no friction in the pumping chamber components, long life, low energy consumption, and no oil pollution. It is widely used in semiconductor, pharmaceutical, food, chemical and other industrial fields. The screw rotor is the most critical pumping part in the screw vacuum pump, which directly determines the working performance and service life of the pump, and its manufacturing cost accounts for nearly half of the total cost of the screw pump. The profile design of the screw rotor is the most critical technology in the whole screw pump design. Among them, the single-head variable-pitch screw rotor, because of its internal pre-compression exhaust method, ha...

AI Technical Summary

Problems solved by technology

The addendum width of the existing single-head variable-pitch screw rotor profile gradually narrows from the suction end to the exhaust end, and the ability to block inter-stage leakage becomes weaker and weaker.

However, during the working process of the screw vacuum pump, the closer to the exhaust end, the greater the gas pressure and the pressure difference between the stages. The volume utilization coefficient of the pump is relatively small; and when the pressure difference between the stages at the exhaust end is large, the width of the tooth top becomes smaller, resulting in an unreasonable increase in the gas return flow

This directly leads to the small utilization coefficient of the suction volume of the screw vacuum pump and the large overall backflow leakage, which leads to the decrease of the main performance index of the screw vacuum pump, the ultimate vacuum degree and the actual pumping rate.

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