Electric motor and reduction motor

A windshield wiper motor comprising:

• a reduction mechanism unit including an output shaft that drives a wiper device of a vehicle;
• and
• an electric motor that drives the reduction mechanism,
• wherein the electric motor comprising:
• a yoke formed in a bottomed cylindrical shape;
• four magnets arranged in a cylindrical shape on an inner surface of the yoke so that magnetic poles thereof are arranged so as to be alternate with each other;
• an armature including a rotary shaft rotatably supported by the yoke, an armature core fixed to the rotary shaft and including eighteen teeth, a commutator being fixed to the rotary shaft and including a plurality of segments insulated from each other with the same number as the number of the teeth of the armature core, an armature coil being wound so as to surround predetermined teeth of the armature core and including a plurality of winding wires having two terminals connected to the adjacent segments of the commutator, and eighteen connecting wires respectively connected to the segments arranged to face each other around the rotary shaft, and being surrounded by the four magnets and accommodated within the yoke;
• and
• a first brush, a second brush, and a third brush coming into sliding contact with the segments of the commutator,
• wherein the first brush and the second brush are arranged apart by an angle of substantially 90 degrees from each other,
• wherein the third brush is arranged apart by an angle of 90 degrees or more from the first brush and the second brush,
• wherein the first brush is connected to a common potential,
• wherein an electric current for rotating the armature at low speed is selectively supplied to the second brush,
• wherein an electric current for rotating the armature at high speed is selectively supplied to the third brush,
• wherein the width of the third brush is made smaller than the width of the first brush and the width of the second brush, and
• wherein when the second brush comes into sliding contact with a first segment of the commutator, the third brush comes into sliding contact with an adjacent segment adjacent to a first equipotential segment connected to the first segment by the connecting wire, and does not come into sliding contact with the first equipotential segment.