| 摘要 |
PURPOSE:To prevent rust from being caused on a yoke when it is sterilized and disinfected frequently by a method wherein a rustproof metal thin layer is formed on the surface of the yoke. CONSTITUTION:A yoke 29 is assembled so as to be brought into nearly close contact with the inside of a casing, and it is formed by stacking a plurality of ring-shaped silicon steel plates 29a to be a cylindrical shape. Its outside diameter, its inside diameter and its wall thickness are set at 20mm, 18mm and 0.5mm, respectively. In addition, electroless nickel-plate layers 29a as rustproof metal thin layers are formed respectively on the surface of the individual silicon steel plates 29a, and their thickness is set within a range of 1 to 20mum. Then, as a result of an auotclave test and a pyrogenic test with a dental grinding apparatus in which a yoke which is not provided with any rustproof metal thin layer, it is confirmed that the surface of the yoke 29 is in a surely protected state. As a result, it is possible to obtain a brushless motor in which rust is not caused on the yoke even when the yoke is sterilized and disinfected frequently. |
