| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a vacuum pump capable of accurately detecting the positions of the magnetic poles of the rotor. <P>SOLUTION: In this vacuum pump which discharges gas by rotating the rotor 2 by a DC brushless motor 6, a step 42b is circumferentially formed in the axial end surface of a rotating body 42 rotating integrally with the rotor 2. The vacuum pump includes: a sensor part 44 which is disposed so as to face the axial end surface of the rotating body 42, to which a predetermined carrier signal is applied, and which modulates the amplitude of the carrier signal according to a variation in impedance due to a variation in the gap between itself and the axial end surface of the rotating body 42; a demodulated wave generating means 45 which extracts an envelope from the modulated signal the amplitude of which is modulated by the sensor part 44 and generates a demodulated wave signal; and a filter means 47 allowing the demodulated wave signals with a predetermined frequency or higher to pass therethrough among the demodulated wave signals generated by the demodulated wave generating means. The vacuum pump further includes a detection means 31 for detecting the positions of the magnetic poles of the rotor 3 according to a filter signal output through the filter means 47, and a motor control means 33 for controlling the DC brushless motor 6 according to the positions of the magnetic poles detected by the detection means 31. <P>COPYRIGHT: (C)2010,JPO&INPIT |
