| 摘要 |
PROBLEM TO BE SOLVED: To conduct optimum control by regular position detection without any interference with rotation control even in case of being unable to detect a position of a rotor in a brushless motor. SOLUTION: The voltage of an armature winding in a brushless motor 4 is compared with the reference voltage by a position detection part 10 to obtain a position detection signal D, which is inputted into a control circuit 11 to detect the position of a rotor. Based on the position detection, current-carrying of the winding voltage is switched. The control circuit 11 counts time between position detection intervals, and based on the counted time, the time corresponding to phase angle 30 is predicted from the position detection and position detection at the predicted time is checked. In case of no position, present current-carrying is conducted based on that at the earlier time than previous switching time of current-carrying. The voltage and number of revolutions which control the brushless motor 4 are decreased for every prescribed hour by a prescribed value until position detection is conducted and the present number of revolutions is maximum in position detection to limit the number of revolutions of the brushless motor 4 to its maximum value for a prescribed time. |
