Turbo-molecular pump

Abstract

In a turbomolecular pump, in connection with a dimensionless number X that is the ratio of an inter-vane distance S to a chord length C for moving vane blades of rotor impeller (4B) and stationary vane blades of stator impeller (2B), with dimensionless numbers at the outer circumferential portion and the inner circumferential portion of a first vane stage being termed Xo(R) and Xi(R) and dimensionless numbers at the outer circumferential portion and the inner circumferential portion of a second vane stage being termed Xo(S) and Xi(S), and with respect to vane stages that are adjacent along the direction of the rotational shaft, at least one vane stage is provided that satisfies a first relational equation “Xo(R)>Xo(S)” and a second relational equation “Xi(R)<Xi(S)”. As a result it is possible to enhance the evacuation performance, in particular the evacuation performance in the high flow rate region, as compared to a prior art turbomolecular pump in which the vane design has been performed according to a two-dimensional cross sectional vane model.

Dependencies are inferred from the claim text.