Stepping motor having at least one set of asymmetric stator pole teeth

A stepping motor comprising:

• a rotor having magnetic poles;
• an inner yoke having a plurality of pole teeth circumferentially formed at a predetermined pitch around said rotor;
• an outer yoke having a plurality of pole teeth circumferentially formed at a predetermined pitch around said rotor;
• the pole teeth of said outer yoke being located in a center position between the pole teeth of said inner yoke, respectively;
• a coil mounted between said inner yoke and said outer yoke;
• a first stator unit including said inner yoke, said outer yoke and said coil;
• a second stator unit including inner and outer yokes each having a plurality of pole teeth circumferentially formed at a predetermined pitch around said rotor and a coil mounted between said inner and outer yokes axially arranged with said first stator unit, the pole teeth of said outer yoke of said second stator unit are, respectively, in a shifted position from a center position between the pole teeth of said inner yoke of said second stator unit in a specific direction;
• the pole teeth of said inner yoke of said second stator unit being located in a middle position between the pole teeth of said outer yoke of said first stator unit and the pole teeth of said inner yoke of said first stator unit;
• and
• the pole teeth of said outer yoke of said second stator unit being located in a shifted position from a middle position between the pole teeth of said inner yoke of said first stator unit and the pole teeth of said outer yoke of said first stator unit.