To detect the angle of rotation of a rotor without using a large-scale sensor and without using a resistor not required for rotating a DC motor.
The DC motor 1 can detect the angle of rotation of the rotor 4. The DC motor 1 includes: a DC motor body 2; and a rotational-angle detector 6, and is connected to a DC power supply 3. The DC motor body 2 includes: the rotor 4; a housing 8; a magnet 9; and brushes 16/17. The rotor 4 includes: a rotating shaft 7; a rotor core 40; a coil (a); the coil (b); the coil (c); and commutator segments 31/32/33. When the DC power supply 3 applies a DC voltage between the brushes 16/17, the rotor 4 is rotated centering around the rotating shaft 7. The coil (c)<the coil (b)=the coil (a) holds in the number of turns. A resistance value between the brushes 16/17 is changed in response to contacting states among the brushes 16/17 and each commutator segment by the differences of the number of turns of the coils. The changes are detected by a rotational-angle detector 6 by using a current flowing between the brushes 16/17.
TAKEDA KENJI
NAKAMURA TSUTOMU
TOGE MASARU
DENSO CORP
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