Patent ID: 7417398
Filing Date: 2008-08-26
Classification: F04C,F04D

Abstract:
1. A vacuum pump which exhausts gas by rotating a rotor relative to a stator, comprising: at least one magnetic body located on a circle about a rotor rotational axis, the magnetic body having a Curie temperature within a rotor temperature monitoring range; an inductance detecting portion facing the circle so as to establish a gap between the circle and the inductance detecting portion, the inductance detecting portion being configured to detect a change of magnetic permeability of the magnetic body as an inductance change when the magnetic body rotates therepast; carrier generation means generating a carrier signal for providing in the inductance detecting portion; A/D conversion means sampling a detection signal of the inductance detecting portion synchronously with a carrier generation by the carrier generation means, and converting the detection signal to a digital signal; and determination means to which a digital signal from the A/D conversion means is input, the determining means determining whether or not a temperature of the rotor exceeds a predetermined temperature, based on the change of the magnetic permeability of the magnetic body detected by the inductance detecting portion, wherein a sampling frequency fs by the A/D conversion means meets fs=fc/n relative to a frequency fc of a carrier generated by the carrier generation means, and fs≧(f rotmax) meets relative to the maximum rotational frequency f rotmax of the rotor, where n=1/2, or n=2