CLUTCH MECHANISM

PROBLEM TO BE SOLVED: To reduce power consumption by downsizing a physical constitution of a clutch mechanism 20.SOLUTION: In a clutch mechanism 20, non-magnetic parts 90, 91 of an armature 40 and non-magnetic parts 70, 71, 72 of a pulley 30 are off-set in a radial direction of a rotary shaft 2a. Therefore, in a magnetic circuit MCa for attraction, a magnetic flux avoids the non-magnetic parts 90, 91 of the armature 40 and the non-magnetic parts 70, 71, 72 of the pulley 30 between an outside cylindrical part 31 and an inner cylindrical part 32 and passes. Thus, the magnetic flux passes a boundary between the armature 40 and the pulley 30 for six times. The number of poles of the magnetic circuit MCa for attraction increases. A physical constitution of a permanent magnet 51 can be downsized, so that a physical constitution of the clutch mechanism 20 is downsized. Accordingly, by upsizing cross sectional areas of coil parts 53a, 53b, power consumption of an electromagnetic coil 53 can be reduced.