Patent ID: 7679251
Filing Date: 2010-03-16
Classification: H02K

Abstract:
1. A stepping motor comprising: a motor shaft; a plurality of stators around which coils are wound, said stators being placed in an axial direction of said motor shaft; and a rotor which is rotatably disposed such that a space is provided between said rotor and inner peripheral sides of said stators, wherein said motor shaft is disposed in a center of said rotor, wherein said rotor includes a rotor body disposed at an outer periphery of said motor shaft and a cylindrical magnet integrally provided on an outer periphery of said rotor body, said cylindrical magnet being magnetized to form multipoles in a circumferential direction, wherein said cylindrical magnet has at least an inner peripheral surface bulged inward in a diameter direction such that a portion corresponding to a central portion in an axial direction of each of said coils is thicker than the other portions, wherein said rotor body includes a large diameter portion, wherein said cylindrical magnet is integrally molded on said outer periphery of said rotor body, and wherein a plurality of projections are formed with a plurality of projected portions spaced in a circumferential direction on an outer periphery of said large diameter portion of said rotor body.