Oil leak prevention structure for vacuum pump

摘要

A Roots pump rotates a plurality of rotors by a pair of rotary shafts to draw gas. Each rotary shaft extends through a rear housing member of the Roots pump. A plurality of stoppers are located on each rotary shaft to integrally rotate with the corresponding rotary shaft, and prevent oil from entering a fifth pump chamber of the Roots pump. Stoppers have a circumferential surface, respectively. Annular oil chambers collect oil. The oil chambers are located about an axis of the rotary shaft to surround the circumferential surface of the stopper. This effectively prevents oil from entering the pump chamber of the Roots pump.