Patent ID: 8424839

Claim:
A direct-current motor control device comprising: a direct-current motor including: a core equipped with three or more teeth arranged in a circumferential direction at a predetermined distance; an armature winding including three or more phase coils respectively wound around the three or more teeth; a commutator including three or more segments connected with the armature winding; and at least one pair of brushes configured to supply an electric current through the armature winding to the commutator; and a rotation angle detection device including: a direct-current power source configured to supply a direct current from one of the brushes through the commutator to the armature winding; an alternating-current power source configured to supply an alternating current from the one brush through the commutator to the armature winding; a current detection unit configured to detect an electric current flowing through the one brush to the direct-current motor, the electric current being caused by superimposing the direct current, which flows from the direct-current power source, on the alternating current, which flows from the alternating-current power source; an extracting unit configured to extract an alternating-current component from the electric current detected by the current detection unit; a rotation angle detection unit configured to detect a rotation angle of the direct-current motor according to the alternating-current component extracted by the extracting unit; and a rotative direction detection unit configured to detect a rotative direction of the direct-current motor according to a change pattern of the alternating-current component extracted by the extracting unit, wherein the core has three or more slots each defined between two of the teeth adjacent to each other in a circumferential direction of the core, the three or more slots respectively accommodate the three or more phase coils, and turns of the phase coils respectively accommodated in the slots of the core are different from each other, wherein the direct-current motor further includes: a rotor including a shaft extending in an axial direction; and a tubular stator surrounding a circumference of the rotor in a circumferential direction, the rotor further includes the core, the armature winding, the commutator, and the brushes, the stator has at least two magnetic poles, each of the teeth is equipped with: a tooth winding portion projecting from an outer circumferential periphery of the core outward in a radial direction of the rotor; and a tooth magnetic pole portion extending from an outer circumferential periphery end of the tooth winding portion toward both sides in the circumferential direction, each of the phase coils is wound by a predetermined turns to surround a circumference of corresponding one tooth winding portion of the tooth, and widths of the tooth winding portions of the three or more teeth are different from each other in consideration of a difference in weight of the phase coils.