| 摘要 |
<p>PURPOSE: To shorten braking time without having influence on braking release by providing in an outside pole part on a back surface side opposed to the motor main body of a direct-current electromagnet, magnetic reluctance increasing means for increasing magnetic reluctance. CONSTITUTION: A direct-current electro-magnet 10 is arranged between a motor main body 1 and a fan 3, and an exciting coil 10c is embedded between an inside pole part 10a in which a bearing 6 which is arranged inside and supports a rotary shaft 2 is mounted and an outside pole part 10b which is integrally formed outside with this inside pole part 10a and fixed to the motor main body 1. An annular slit 10d as magnetic reluctance increasing means is arranged along the circumferential direction of the back surface of the outside pole part 10b on the side opposed to the motor main body 1. Hereby, in such a condition that a pushing/pressing plate 7 is slipped off from the outside pole part 10b of the direct-current electro-magnet 10 and released, the slit 10d functions to prevent magnetic flux flow so as to increase the magnetic reluctance of a magnetic path, therefore releasing time, that is, braking time can be shortened.</p> |
