Abstract: A stepping motor having two stator units axially arranged. Each of the stator units includes an inner yoke and an outer yoke having a plurality of pole teeth circumferentially formed at a predetermined pitch around a rotor having magnetic poles. The outer yoke of one of the stator units is asymmetrically arranged so that the pole teeth thereof are shifted from center between the pole teeth of the inner yoke in a specific direction. As a result, a cogging torque is reduced, constant speed rotation is attained and variations in the output torque are eliminated. Variation in the generated torque are also reduced by controlling the drive pulse width, the drive voltage or the drive current during the driving operation in accordance with the number of excitation phases.

Abstract: A recorder motor with an encoder, for forming an image on a record medium in accordance with image information, has the encoder on the outside of the motor case and a plastic dust-proof cover for the encoder mounted on the case. Thus, contamination by dust or ink mist is prevented, and stable and high precision motor rotation is maintained.