| 摘要 |
PROBLEM TO BE SOLVED: To obtain a DC brush motor in which the rotational speed of the motor can be varied at low cost through a system generating no electromagnetic wave noise. SOLUTION: In correspondence with commutator segments 29 arranged radially around a rotary shaft 23, conduction brushes 30 and short circuit brushes 31 are arranged alternately at a pitch of 90 deg. around the rotary shaft 23. The conduction brush 30 normally slides on the commutator segment 29 and the short circuit brush 31 moves between a position sliding on the commutator segment 29 and a separated position. When the short circuit brush 31 slides on the commutator segment 29, the DC motor is operated under a state where a part of coils 25 is short-circuited and the number of turns of conduction coil of the entire motor is decreased thus increasing the rotational speed of the motor. When the short circuit brush 31 separates from the commutator segment 29, all coils 25 is conducted. Consequently, the number of turns of conduction coil of the entire motor is increased thus decreasing the rotational speed of the motor. |
