Abstract: Disclosed is an actuator that realizes reciprocal rotational motion of an electric toothbrush, for example, without utilizing a drive transmission mechanism that is separate from the drive source. In the actuator, a fixed body (120) has a coil (128) that is disposed around a magnet (160) and faces the magnetic planes with different polarities within the magnet (160) at individual prescribed distances, and an outer yoke (150) that covers the outer periphery of the coil (128). The fixed body (120) rotatably supports a movable body (110), which holds the magnet (160), via a coil spring that is an elastic member (130) made from a wire. An alternating current supplying part (140) supplies an alternating current having roughly the same resonance frequency as that of the fixed body (120) to the coil (128) to cause the movable body (110) to vibrate in a reciprocal rotational motion. The coil spring that is the elastic member (130) uniformly disperses stress generated by the vibration.

Abstract: An electric machine including a rotor (R) with a shaft (4) having a longitudinal axis (x-x) and a stator (S1; S2) with two stator units coaxially disposed one inside and the other outside the rotor (R). The inner stator (S1) having an annular part from which a plurality of teeth (D1) emerge radially and centrifugally. The external stator (S2) having an annular part from which a plurality of teeth (D2) emerge radially and centripetally. The said rotor (R) includes a rotor ring (1) formed by a plurality of parallelepiped permanent magnets (2) having predetermined width, height and length (W2, H2, P2).