| 摘要 |
PURPOSE:To enable a rotor to be easily rotated for starting, by a method wherein a concave groove is provided for the outer periphery of a rotor shaft of a permanent magnet rotor, and wherein a hole is formed on the side of a bearing unit confronting the concave groove, while a spherical body, is provided to be rotated between the concave groove and the hole. CONSTITUTION:Due to a spherical body 8 provided between a lower concave groove 2b of a rotor shaft 2a of a permanent magnet rotor 2 and a hole 7b formed in a shellsection 7a for a bearing unit 7, a resistance load to the concave groove 2b of the rotor shaft 2a of the permanent magnet rotor 2 is negligible at the time of starting because of the very small frictional resistance, and the rotor shaft 2a is rotationally vibrated easily with the A.C. magnet field due to a driving coil 4 and is shifted to a synchronous rotation. The displacement in the thrust direction of the rotor shaft 2a is regulated at the concave groove 2b via the spherical body 8, and therefore the rotor shaft 2a can be always rotationally retained at a given position during the syncronous rotation including the starting time. |
