Patent ID: 7965054

Claim:
A vacuum pump designed to rotate a rotor relative to a stator so as to evacuate gas, comprising: a plurality of magnetic segments each disposed on said rotor at a position on a circumference having a center on a rotation axis of said rotor, said plurality of magnetic segments including a first magnetic segment having a Curie temperature falling within a temperature monitoring range of said rotor, and a second magnetic segment having a higher Curie temperature than an upper limit temperature of said temperature monitoring range; an inductance detection section disposed at a position opposable to said first and second magnetic segments in turn according to rotation of said rotor, and adapted to detect respective permeability changes of said first and second magnetic segments as inductance changes; a calculation-signal generation device generating a difference signal calculated based on a detection signal during a period of a time when said first magnetic segment is in opposed relation to said inductance detection section, and a detection signal during a period of time when said second magnetic segment is in opposed relation to said inductance detection section, the calculation-signal generation circuit including a wave detector circuit that detects the detection signals, a rectifier circuit that rectifies the detection signals, and a difference signal generation circuit that generates the difference signal based on a difference between the detected signals; and a temperature detection section for comparing a signal level of said calculation signal and a predetermined reference level to detect a temperature of said rotor.