Patent ID: 8350437

Claim:
A direct-current motor, comprising: a plurality of magnetic poles arranged in a circumferential direction; an armature core including a plurality of teeth arranged in the circumferential direction, the teeth extending in a radial pattern, distal ends of the teeth face the magnetic poles in a radial direction; plurality of armature coils wound around the teeth; a commutator, which is rotatable integrally with the armature core, the commutator including a plurality of segments arranged in the circumferential direction; and plurality of power supply brushes pressed against the segments, wherein the armature coils include a plurality of inner layer coils and a plurality of outer layer coils, each of the inner layer coils being wound around radially proximal end portions of two circumferentially adjacent teeth or a radially proximal end portion of one of the teeth, the inner layer coils being arranged in the circumferential direction without overlapping each other in the radial direction, each of the outer layer coils being wound around radially distal end portions of two circumferentially adjacent teeth by distributed winding, the outer layer coils being arranged radially outward of the inner layer coils and arranged in the circumferential direction without overlapping each other in the radial direction, and the circumferential centers of the inner layer coils and the circumferential centers of the outer layer coils are displaced in the circumferential direction, wherein each of the teeth includes an inner winding portion formed at the radially proximal end portion, and a first branched tooth portion and a second branched tooth portion, which extend from the radially distal end of the inner winding portion to separate from each other in the circumferential direction, wherein each of the inner layer coils is wound around the inner winding portion of one of the teeth by concentrated winding, and wherein each of the outer layer coils is wound around the first branched tooth portion of one of two circumferentially adjacent teeth and the second branched tooth portion of the other one of the teeth that is circumferentially adjacent to the first branched tooth portion, wherein the number of segments is equal to the sum of the number of the first branched tooth portions and the number of the second branched tooth portions.