Patent ID: 6545376
Filing Date: 2003-04-08
Classification: H02K

Abstract:
A three-phase hybrid type stepping motor comprising a stator and a rotor arranged concentrically with the stator and with an air gap therebetween, said stator having an annular stator yoke, a plurality of stator poles extending radially and formed at a regular pitch on the inner peripheral surface of the annular stator yoke, and three phase stator windings each wound around each stator pole, each of-said stator poles having an even number of and at least four small stator teeth at the tip end thereof, said rotor having two split rotor elements and a permanent magnet held therebetween and magnetized so as to form N and S poles in the axial direction thereof, and a plurality of small rotor teeth formed at a regular pitch on the outer peripheral surface of each of said rotor elements, said two split rotor elements being shifted from each other in angular position by Â½ the pitch of the small rotor teeth,wherein said small stator teeth are composed of sets of two small stator teeth of the same width, and at least one pitch of adjacent teeth is different from another pitch of other adjacent teeth, so that a vector sum of the tertiary harmonic of permeances of the small stator teeth included in each of said sets becomes substantially zero.