Patent ID: 6031305
Filing Date: 2000-02-29
Classification: H02K

Abstract:
A stepping motor comprising:a first annular stator comprising an inner yoke and an outer yoke for forming a magnetic path for a first annularly wound exciting coil,a second annular stator comprising an inner yoke and an outer yoke for forming a magnetic path for a second annularly wound exciting coil and laminated concentrically with the first annular stator, anda rotor rotatably supported by a rotary shaft within a hollow portion of a stator-laminated body formed by concentrically and vertically laminating the first and second annular stators with the inner yokes thereof lying adjacent to each other,wherein said rotor comprises a first and a second magnet each having a plurality of magnetic poles heteropolarly magnetized to the outer peripheral surface thereof in an alternative fashion along the rotational direction thereof and concentrically fixed to said rotary shaft,wherein two sets of pole teeth are disposed on said first and second annular stators, respectively, in an annular comb-teeth arrangement such that they extend into the hollow portion of said stator-laminated body from said inner and outer yokes along the axis of said rotor,wherein when the axial width of each of the first and second magnets is expressed by W0, the axial width of overlapping of each of the two sets of pole teeth corresponding to said first and second magnets is expressed by W1 and the width of a space between the inner surfaces of each of said inner and outer yokes making a pair sandwiching each of said sets of pole teeth therebetween is expressed by W2, W2>W0>W1; andwherein the center of said width W0 is offset towards said outer yokes with respect to the center of said width W2.