Five-section variable-pitch screw assembly of screw vacuum pump and vacuum pump screw design method

The invention provides a five-section variable-pitch screw assembly of a screw vacuum pump and a vacuum pump screw design method, and belongs to the technical field of vacuum pumps. The screw vacuum pump solves the problems that a screw of an existing screw vacuum pump is narrow in adjustable range and poor in design flexibility. The five-section variable-pitch screw assembly of the screw vacuum pump comprises a cylindrical screw, a spiral groove is formed in the outer side face of the screw, an air inlet section, a first transition section, a middle section, a second transition section and a compression exhaust section which are sequentially arranged in the axial lead direction are arranged in the screw, and the first transition section and the second transition section are symmetrically arranged; the spiral grooves in the air inlet section, the middle section and the compression exhaust section are equal-pitch spiral grooves, the pitch of the spiral grooves in the air inlet section is the same as that of th