| 摘要 |
<p>PURPOSE:To increase the attractive force and at the same time reduce the dimension of the captioned apparatus by making the area of either or both of the friction surfaces at the center part smaller than that of the inside and the outside friction surfaces respectively. CONSTITUTION:When the area S of a friction surface, the magnetic-flux density Bg of the friction surface, and the permeability muo are set, an attractive force P is shown by the following equation: P=Bg<2>.S/muo, and the attractive force increases more when the magnetic-flux density Bg is increased rather than when the area S is increased. Therefore, on the friction surfaces 44 and 45, the attractive force is reduced, since the magnetic-flux density Bg is reduced by the influence of the leakage of magnetic-flux. Therefore, the magnetic-flux density Bg can be increased by reducing the areas of the friction surfaces 44 and 45 to about 60-80% of the friction surfaces 43 and 46 respectively, and the attractive force can be increased. Thus, the overall outside diameter can be reduced by reducing each area of the friction surfaces 44 and 45, and the dimension of the apparatus can be reduced.</p> |
