Stator yoke of PM type stepping motor and stator unit using the same

摘要

PROBLEM TO BE SOLVED: To secure high torque based on increase in the number of times of winding or to secure the same torque with a low-priced and large-diameter material by expanding a winding width of an excitation coil without changing an external dimension of a motor.SOLUTION: A PM-type stepping motor includes: a rotor magnet which includes a rotary shaft and is formed by magnetizing a circumferential surface of a permanent magnet alternately to different poles in a circumferential direction; a stator yoke 4 including a plurality of magnetic pole teeth surrounding the rotor magnet, and formed from a ring-shaped plate of a vertical face to the rotary axis; and the excitation coil which is wound in a space formed by making the stator yoke 4 opposite while alternately meshing the magnetic pole teeth in no contact with each other. In the stator yoke 4 forming the stator unit, over a plurality of positions on an annular surface of the stator yoke 4, a thin part 43 is formed by reducing plate thickness. Together with the thin part 43, an opening 44 is formed within an area where the thin part 43 is formed, or at a continuous position including the area.