Vacuum pump and rotary cylindrical body included in vacuum pump

Abstract

A vacuum pump reduces a stress without reducing the rotation speed of a rotating cylindrical body. In an outlet port-side lower portion of a rotor cylindrical portion included in the vacuum pump, a smaller diameter portion having an outer diameter smaller than that of an inlet port-side portion of the rotor cylindrical portion is provided. A lowermost end portion (outlet port-side end portion) of the rotor cylindrical portion is designed longer than a thread groove exhaust element to provide an extending portion. In the extending portion, a smaller diameter portion having an outer diameter smaller than that of the inlet port-side portion of the rotor cylindrical portion which is opposed to the thread groove exhaust element is provided.

Dependencies are inferred from the claim text.