Patent ID: 8860274

Claim:
A double-stator motor comprising: a rotary shaft; an annular rotor coupled with the rotary shaft so that the rotor is allowed to rotate together with the rotary shaft, the rotor having a radial direction and a circumferential direction; a first three-phase stator arranged inside the rotor in the radial direction and provided with a first winding wound at the first three-phase stator, the first winding generating a first rotating magnetic field in response to a three-phase current being supplied to the first winding; and a second three-phase stator arranged outside the rotor in the radial direction and provided with a second winding wound at the second three-phase stator, the second winding generating a second rotating magnetic field in response to the three-phase current being supplied to the second winding, wherein the rotor comprises: i) an even number of segment poles made of soft magnetic material and mutually separately arranged at positions of the rotor, the positions being equally distanced apart from the rotary shaft in the radial direction and evenly spaced apart from one another in the circumferential direction, each of the segment poles having outer and inner circumferential surfaces in the radial direction and having a concave formed at a circumferential center of each of the outer and inner circumferential surfaces or at a circumferential center of either one of the outer and inner circumferential surfaces, ii) an even number of bridges, each bridge being disposed between a mutually-adjacent two of the segment poles in the circumferential direction such that each bridge links the mutually-adjacent two segment poles, each bridge including a plurality of inner bridges and a plurality of outer bridges, the inner and outer bridges being respectively located inside and outside of the rotor in the radial direction, each inner bridge linking radially inner parts of the mutually-adjacent two segment poles, each outer bridge linking radially outer parts of the mutually-adjacent two segment poles, and iii) a plurality of permanent magnets, each of the permanent magnets being disposed between the inner and outer bridges at each of the segment poles, each of the permanent magnets having magnetic poles directed at each of the segment poles in the circumferential direction; and each of the first and second three-phase stators has poles which are the same in number as the segment poles and the poles produce magnetomotive forces whose directions are opposed to each other via the segment poles between the mutually-opposed poles of the first and second three-phase stators.