Step motor with circumferential stators on opposite sides of disc-like rotor

摘要

An electric step motor has a rotor member and a stator member aligned on a common axis with one of the two members having two pairs of interdigital pole teeth extending perpendicularly to the axis. The two pairs of pole teeth are axially spaced from each other with the inner pole teeth in each pair spaced both radially and circumferentially from the outer pole teeth in that pair. A pair of coils are associated with the two pairs of interdigital pole teeth for magnetizing the inner and outer pole teeth in each pair with opposite polarities when the corresponding coil is energized. The other member has multiple permanent magnets spaced circumferentially from each other and located axially between the two pairs of interdigital pole teeth so that energization of either coil draws the permanent magnets into register with a selected pair of interdigital pole teeth. The permanent magnets are polarized in the axial direction with each adjacent pair of the permanent magnets preferably polarized in opposite directions, and the pole teeth in one of the two interdigital pairs are preferably circumferentially offset from the pole teeth in the other pair.