| 摘要 |
PROBLEM TO BE SOLVED: To provide a turbomolecular pump having a DC brushless motor provided with a detecting mechanism for number of revolution of a simple structure. SOLUTION: A pickup coil 303 for detecting the magnetic flux generated by a permanent magnet 301 of a DC brushless motor 30 is incorporated in the motor. Specifically, a small-sized, low-cost, simple and sturdy pickup coil is arranged in the space between the permanent magnet (rotor) 301 of the DC brushless motor 30 and a motor drive coil (stator coil) 302. When the magnetic flux generated by the permanent magnet 301 is detected with the pickup coil 303, it is converted into the number of revolution signals of the DC brushless motor in a sequence control circuit to and monitors whether it is excessive in speed. If excess speeding is detected, a breaking command is given to a power supply breaker. By forcibly stopping the supply of electric power, the DC brushless motor is forced to stop. |
