| 摘要 |
PURPOSE:To facilitate removal of an externally operated fan by making an axial diameter near a hole which is drilled by means of a self tapping screw accompanied by elastic deformation, smaller than an axial diameter of other portion. CONSTITUTION:An annular groove 3c is formed by plastic working to make an axal diameter D3 of the area near a drilled hole 3a smaller than a diameter D2 of a portion where a fan boss 2 is fitted around an axis 3. Also, a width l of the axis 3, where this groove 3c is formed, should be set so that the width L, which represents the shaft length excluding the width of the fan 1 itself and the fan boss 2 fitting around the axis 3, and the outer diameter d of the self tapping screw 4 are relatively arranged to satisfy the relation d<l<L. A convex portion 3d is formed around the drilled hole 3a of the axis 3 when the fan boss 2 is fitted around the axis 3 and the self tapping screw 4 is screw up, but, the outer diamete of the convex portion 3d on groove 3c can stay smaller than the axial diameter D2 of a portion where the fan boss 2 is fitted around the axis, consequently the fan 1 itself and the fan boss 2 can be removed. |
