US 6,184,640 B2 · DC brushless motor, magnetic bearing device and turbomolecular pump device

Abstract

A turbomolecular pump device having a DC brushless motor provided with a simplified rpm detection mechanism is provided. A pickup coil for detecting a magnetic flux produced by a permanent magnet of the DC brushless motor is built in the motor. Namely, a small size, low cost, simple and strong pickup coil is disposed in a space between the permanent magnet (rotor) of the DC brushless motor and the motor drive coil (stator coil). The magnetic flux produced by the permanent magnet in the pickup coil is detected. This is converted into an rpm signal of the DC brushless motor by a sequence controlling circuit. It is supervised whether or not the overspeed is performed. Then, when the overspeed is detected, an interruption command is fed to the power source breaker so that the supply of the power is forcibly interrupted to thereby stop the DC brushless motor.

Claims14

Dependent claims

A magnetic bearing device comprising:

a DC brushless motor comprised of a rotor having a permanent magnet and a rotary shaft, a stator coil for generating a magnetic field to rotate the rotor and disposed opposite to and spaced-apart from the permanent magnet, and a sensor for detecting a change in a polarity of the permanent magnet, the sensor being disposed between the rotor and the stator coil and in a non-contact state with the permanent magnet;
drive control means for controlling the rotation of the rotor of the DC brushless motor;
and a magnetic bearing having an electromagnet for magnetically supporting the rotary shaft of the DC brushless motor and for controlling a magnetic force of the electromagnet to support the rotary shaft at a preselected position.

Dependencies are inferred from the claim text.

DC brushless motor, magnetic bearing device and turbomolecular pump device

Life of this patent

DC brushless motor, magnetic bearing device and turbomolecular pump device

Life of this patent

Abstract

Claims14