| 摘要 |
PURPOSE:To improve the speed characteristic of the motor, by providing plural pairs of brushes in prescribed positions as to the magnetically neutral lines of magnets and by switching the current supply brushes depending on load conditions. CONSTITUTION:An armature 2 is rotatably supported in the hollow portion of a field body 1 comprising plural permanent magnets 5 and arc-shaped yokes. The first pair of brushes 3A are provided on the magnetically neutral lines of the permanent magnets 5. The second pair of brushes 3B are provided in positions which are displaced from the magnetically neutral lines of the magnets 5 in the circumferential direction. Under such load conditions that the acceleration and deceleration of a motor are drastically effected, currents are caused to flow through only the first brushes 3A to increase the torque constant of the motor and shorten its rising and falling time. Under such load conditions that the fluctuation in the revolution speed of the motor is small, currents are caused to flow through both the first and the second brushes 3A, 3B to decrease the torque constant of the motor and heighten its maximum angular velocity. |
