Vacuum pump

Abstract

A vacuum pump exhausting gas by rotating a rotor relative to a stator includes a rotor having a ferromagnetic body provided on a rotational axis on, or near, a rotational axis of the end face of a rotational axis direction of a rotational body. The ferromagnetic body's Curie temperature is approximately equal to an allowable temperature of the rotor. A detecting portion disposed opposite the ferromagnetic body is configured to detect a change in magnetic permeability of the ferromagnetic body based upon a change in inductance. A revolution sensor target and an inductance-type revolution sensor are disposed in such a way as to detect both a revolution of the rotor and a change in the magnetic permeability of the ferromagnetic body. A control device halts rotor rotation when a change in magnetic permeability of the ferromagnetic body is detected and/or when a predetermined integrated time is exceeded.

1 . A vacuum pump configured to exhaust gas by rotating a rotor relative to a stator, comprising:
 a ferromagnetic body provided on or near a rotational axis of an end face of a rotational axis direction of a rotational body including said rotor, the ferromagnetic body having a Curie temperature approximately equal to an allowable temperature of said rotor; and   a detecting portion provided in such a way as to be opposed to the ferromagnetic body and configured to detect a change in magnetic permeability of the ferromagnetic body based upon a change in inductance.   
   
   
       2 . A vacuum pump configured to exhaust gas by rotating a rotor relative to a stator, comprising:
 a revolution sensor target provided near a rotational axis of an end face of a rotational axis direction of a rotational body including said rotor;   a ferromagnetic body provided in a position wherein a radial directional distance from the rotational axis of said rotor is approximately equal to a radial directional distance of said revolution sensor target, and a Curie temperature of the ferromagnetic body is approximately equal to an allowable temperature of said rotor; and   an inductance-type revolution sensor disposed in such a way as to be opposed to said revolution sensor target and said ferromagnetic body, said revolution sensor being configured to detect a revolution of said rotor and a change in magnetic permeability of said ferromagnetic body as a detected inductance change.   
   
   
       3 . A vacuum pump according to  claim 1 , wherein said ferromagnetic body is provided on the end face of said rotor in such a way that a detected inductance when said detecting portion and said ferromagnetic body are opposed to each other, becomes smaller than a detected inductance when said detecting portion and the end face of said rotor are opposed to each other, when the temperature of said rotor is lower than the Curie temperature. 
   
   
       4 . A vacuum pump according to  claim 1 , further comprising control means for reducing speed of rotation of said rotor or halting the rotation of said rotor when change in the magnetic permeability of said ferromagnetic body is detected. 
   
   
       5 . A vacuum pump according to  claim 1 , further comprising control means for halting rotation of said rotor when an integrated time, wherein change of the magnetic permeability of said ferromagnetic body is detected, exceeds a predetermined allowable time based on a creep life design of said rotor. 
   
   
       6 . A vacuum pump according to  claim 4 , further comprising alarm means for presenting alarm information regarding abnormality of the vacuum pump when the change of the magnetic permeability of said ferromagnetic body is detected. 
   
   
       7 . A vacuum pump configured to exhaust gas by rotating a rotor relative to a stator, comprising:
 a first ferromagnetic body provided on or near a rotational axis of an end face of a rotational axis direction of a rotational body including said rotor, the first ferromagnetic body having a Curie temperature approximately equal to an allowable temperature of said rotor;   a second ferromagnetic body provided on or near the rotational axis of the end face of the rotational axis direction of said rotor, the second ferromagnetic body having a Curie temperature higher than the Curie temperature of the first ferromagnetic body;   a detecting portion provided in such a way as to be opposed to said first and said second ferromagnetic bodies, and configured to detect a change in the magnetic permeability of said first and said second ferromagnetic bodies as an inductance changes respectively; and   control means for halting rotation of said rotor when at least one of the change in the magnetic permeability of said second ferromagnetic body is detected, and when an integrated time, wherein the change of the magnetic permeability of said first ferromagnetic body is detected, exceeds a predetermined allowable time based on a creep life design of said rotor.