Patent ID: 6987340
Filing Date: 2006-01-17
Classification: H02K

Abstract:
1. A DC motor comprising: a stator having a plurality of poles arranged in a circumferential direction of the stator; a rotor including a plurality of cores, a plurality of coils wound around respective cores, and a plurality of commutator segments electrically connected to respective coils; and a plurality of brushes arranged and constructed to repeatedly start and interrupt a supply of current to the coils via respective commutator segments in order to rotate the rotor, wherein: the poles have surfaces opposing to the rotor and the surfaces of two circumferentially adjoining poles have different polarities from each other, so that the polarities of the pole surfaces opposing to each coil alternate during each period of supply of the current to the coil; each pole defines a reduced density area and an increased density area with respect to a magnetic flux density, the reduced density area extends along an angular range from a first position, where the supply of current to the coils is initiated, to a second position, where the polarities of the pole surfaces opposing to each coil alternate; the increased density area extends along an angular range from the second position to a third position where the supply of the current to the coils is interrupted; and the magnetic flux density produced around each coil by a magnetic force of each pole when each coil is positioned within at least a part of the angular range of the increased density area is smaller than the magnetic flux density produced around each coil by a magnetic force of each pole when each coil is positioned within at least a part of the angular range of the reduced density area.