Patent ID: 7235903
Filing Date: 2007-06-26
Classification: H02K

Abstract:
1. A step motor, comprising: a spindle that extends along a motor axis; a magnet unit mounted around said spindle; a stator assembly sleeved over said magnet unit and having opposite ends, and including at least one coil-and-yoke unit having a coil support, a coil wound around said coil support, and a pair of magnetic yokes mounted in said coil support, said stator assembly further including an outer tube sleeved over said coil-and-yoke unit; a fixing plate mounted to one of said ends of said stator assembly, and in which said spindle is journalled; and a cover unit mounted to another one of said ends of said stator assembly opposite to said fixing plate, and in which an end portion of said spindle is journalled; wherein said coil support includes a surrounding wall surrounding said motor axis and having an inner circumferential surface; wherein said surrounding wall includes a plurality of notches formed in said inner circumferential surface of said surrounding wall parallel to said motor axis and angularly spaced apart at equal intervals relative to said motor axis, each of said magnetic yokes including a plurality of excitation fingers inserted respectively in said notches; and wherein said excitation fingers of one of said magnetic yokes are alternately disposed with said excitation fingers of the other one of said magnetic yokes in said coil support, wherein said cover unit includes a bottom plate mounted in said outer tube, abutting against said coil support, and having a hollow center portion, a sleeve mounted in said hollow center portion of said bottom plate and in which said spindle is journalled, a seal cover secured to said outer tube, and a spring plate interposed between said bottom plate and said seal cover and providing a biasing force to said spindle along the direction of said motor axis.