Low-profile stepping motor with two coils arranged flush with each other horizontally

A low-profile stepping motor comprising

• a first stator unit including:
• a first upper stator yoke having a plurality of pole teeth which are formed along its semicircular inner circumference;
• a first lower stator yoke having a plurality of pole teeth which are formed along its semicircular inner circumference and which mesh with the pole teeth of the first upper stator yoke;
• and a first coil unit fixedly sandwiched between the first upper and lower stator yokes,
• a second stator unit including:
• a second upper stator yoke punched out as one piece integrally with the first upper stator yoke so as to form an upper twin-stator yoke plate, and having a plurality of pole teeth which are formed along its semicircular inner circumference;
• a second lower stator yoke punched out as one piece integrally with the first lower stator yoke so as to form a lower twin-stator yoke plate, and having a plurality of pole teeth which are formed along its semicircular inner circumference and which mesh with the pole teeth of the second upper stator yoke;
• and a second coil unit fixedly sandwiched between the second upper and lower stator yokes and arranged horizontally flush with the first coil unit, wherein one of the upper twin-stator yoke plate and the lower twin-stator yoke plate is structured such that one half of its pole teeth partitioned in half by a predetermined datum line and open spaces each residing between two adjacent pole teeth of the other half are positioned symmetrically about the predetermined datum line, whereby the one twin-stator yoke plate can be used in common to the other twin-stator yoke plate, and
• a rotor assembly including a cylindrical magnet and rotatably disposed in a circular open space defined by the pole teeth of the first and second stator units.