A configuration wherein a ring-shaped groove is formed on both ends of the yoke 2 to accommodate the end portion of the heat shrinkage tube, a configuration wherein the end face of the yoke 2 to be a leading side for insertion into a motor stator is covered with an end face covering member having a decliningly tapered side face, and so on, are included. ヨー2の両端面に熱収縮チューブの端部を収容するリング状の溝を備えた形態、ヨーク2のモータ固定子への挿入先側となる端面が先細りするテーパ状側面を有する非磁性の端面覆い部材で覆われた形態、などを含む。 - 特許庁