Patent ID: 7183675

Claim:
A permanent magnet (PM) stepping motor, which comprises: a rotor structure, comprising: an axis; a plurality of multipolar yoke stacks, each of which includes an N multipolar yoke, a permanent magnet and an S multipolar yoke combined as a hamburger-like structure, wherein each N pole of the N multipolar yoke and each S pole of the S multipolar yoke have peripheries with a plurality of gear-shaped structures, which are alternately arranged in a staggered manner; and the magnetic poles of the plurality of multipolar yoke stacks are aligned in the pattern of N-S-S-N or S-N-N-S, wherein the N poles of one multipolar yokes stack are aligned with the S poles of another multipolar yoke stack and the S poles of one multipolar yoke stack are aligned with the N poles of another multipolar yoke stack; and at least one spacer, sandwiched between each pair of the multipolar yoke stacks; and a stator comprising a plurality of coils which respectively circumnavigate the axis and the multipolar yoke stacks and providing a magnetic field for the multipolar yoke stacks to make the axis rotating.