Single-phase step micromotor - has ferromagnetic fixing rotor located between stator and double pole rotor providing variable gap

摘要

The single-phase step micromotor comprises a stator having a pair of pole pieces (1,2) facing each other by cylindrical surfaces (3,4). Interposed between the stator pole pieces (1,2) is a double-pole rotor (9), while arranged between the stator and rotor is a ferromagnetic ring (8) the thickness of which is less than that of the stator pole pieces (1,2). The inner diameter of the ring varies along the angular coordinate of the stator to provide a variable 'a'. The rotor poles align with an axis when no current is being applied to a winding (6). The motor can be applied to advantage in horology, such as for the manufacture of electronic/mechanical wristwatches with dial display.