| 摘要 |
In a brushless DC motor of a radial gap type, one of a pair of vertical (right and left) pole teeth (Xx, Yy) is formed in such a manner as to possess a smaller gap in a circumferential direction than the other, and the position of this pole tooth is shifted in a rotating direction of a rotor relative to an intermediate position of the other of the pole tooth. Further, a ratio (a/p) of the tooth width (a) to the pole pitch (p), a ratio (a/p) of the tooth width (a) to the tooth width (b) and a ratio (c/d) of the pole tooth pitch (c) to the pole tooth pitch (d) are stipulated to fall within predetermined ranges so that a start torque can be generated and non-uniformity of rotation can be reduced. In such a motor construction, the generation torque frequency of the cogging torque occurring between a permanent magnet rotor (2) and a stator is converted to large and small torque waves, and change-over of a current of a coil (12) is made at, or near, a position at which an absolute value of a plurality of positive peaks of the cogging torque is great. Further, change-over of the coil current is made at, or near, a position at which an excitation current generated by the coil current becomes zero. Furthermore, change-over of the coil current is made near the positive peak of the cogging torque, and the coil current is changed over at a time in which the feed of the current is interrupted. |
