| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of bending a special shaped tube excellent in the bending accuracy by which the generation of buckling is suppressed regardless of the size in thickness even when the tube has high strength and working limit can be remarkably improved. SOLUTION: In the method of bending the special shaped tube the circumference of which is gradually increased or decreased from one side to the other side in the axial direction, the bending work is performed by controlling tensile stress imparted in accordance with the cross-sectional area of the special shaped tube by moving the end to be worked while fitting the special shaped tube into a rotary bending die having approximately the same groove as a shape after the bending work by holding both ends composed of an end to be worked of the special shaped tube and a feeding end in the opposite position of the end to be worked, performing the bending work while forming a pointed part in a part or the whole of the inner peripheral side of the bending work of the special shaped tube, or performing the bending work by combining them. The automotive parts obtained by the working method are used in the base material of a body or the frame member of the body. COPYRIGHT: (C)2008,JPO&INPIT
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