| 摘要 |
PURPOSE:To heighten the reliability by disposing a temperature sensor for controlling a current applied to a coil on the side end portion of a friction surface of a field core to be kept from an abnormal temperature rise. CONSTITUTION:By a V-belt stretched on a belt groove 4a of a rotor 4, the rotor 4 is always rotated by power of an engine, so that when an electric current is applied to a coil 7 in a U-shaped section 9, an armature 15 is attracted to a friction surface of the rotor 4 to transmit rotating motion to a main shaft 2. The slide of the armature 15 causes an abnormal rise in the temperaure of the friction surface, which results in increasing the temperature of the coil 7, increasing resistance, lowering sucking force, and increasing the slide of the armature 15. Further, the generation of heat causes grease sealed in a ball bearing 3 to flow out, and the grease is adhered to the friction surface by centrifugal force, which will cause a lowering of frictional force. As abnormal generation of heat of the friction surface is detected by a temperature sensor 10 such as a bimetal disposed on the side end portion of the rotor friction surface of the coil 7 to cut off an electric current applied to the coil 7, the armature 15 is separated from the friction surface by the restoring force of a plate spring 16, to prevent the generation of abnormal heat due to the slide between the armature 15 and the rotor friction surface. |
