Normal spiral type screw rotor of double-screw vacuum pump

The utility model discloses a normal spiral type screw rotor of a double-screw vacuum pump. The screw rotor is composed of a pair of screw rotors which are assembled in parallel and engaged with eachother. The section molded lines of the left screw rotor (1) and the right screw rotor (2) are each composed of only two curves. The left section molded line (101) of the left screw rotor (1) is composed of a left normal spiral ACB curve and a left cycloid BDA curve which are connected end to end. A right section molded line (201) of the right screw rotor (2) is formed by connecting a right normalspiral envelope line acb and a right cycloid bda end to end; in the working process, the left screw rotor and the right screw rotor can be correctly meshed; according to the screw rotor, the tooth crest, the tooth root and the transition section part can be freely adjusted, so that the design of the screw rotor is more flexible, the parameterized design of the screw rotor is facilitated, meanwhile, the screw rotor has the