Patent ID: 7449805
Filing Date: 2008-11-11
Classification: H02K

Abstract:
1. A stepping motor comprising: a rotor including a cylindrical permanent magnet that is multipole magnetized in a circumferential direction; ring-shaped first and second yoke units that are arranged so as to be mutually stacked along an axis of the rotor while surrounding a periphery of the rotor; and a pair of lid members that enclose the first and second yoke units from both sides thereof along the axis, and support the rotor so as to be rotatable around the axis, each of the first and second yoke units including: a ring-shaped exciting coil; an outer yoke that includes an outer cylindrical section that is formed in a cylindrical shape around the axis and accommodates therein the exciting coil, a back face section that bends at an angle of 90 degrees over a predetermined distance toward the axis from an outer edge of one side of the outer cylindrical section, and a plurality of magnetic pole teeth that bend at an angle of 90 degrees from the back face section substantially parallel with the axis and are arranged at fixed intervals in the circumferential direction; and an inner yoke that is combined with the outer yoke and includes a ring-shaped ring section formed around the axis, and a plurality of magnetic pole teeth that bend at an angle of 90 degrees from an inner peripheral face of the ring section substantially parallel with the axis and are arranged at fixed intervals in the circumferential direction of the exciting coil while alternating at equal intervals in a noncontacting state with respect to the magnetic pole teeth of the outer yoke, wherein the first and second yoke units are stacked while the back face sections thereof are in a mutual surface contact state.