DOUBLE-PASSAGE EXHAUST PIPE, AND MANUFACTURING METHOD THEREFOR

PROBLEM TO BE SOLVED: To prevent fatigue from being generated in the vicinity of a welded part, even when a pipe wall is vibrated by pulsation of exhaust. SOLUTION: A partitioning wall part 2 of a width W is set in one metal sheet, a flat base valley part wall 3 is bent in bent parts 3a in both sides, then a circumferential wall part 5 and end valley parts 7 are bent, a flange 8 is folded back, and a tip of the flange 8 is welded to a sideface of the adjacent valley part wall 3 to be brought into a welded part 11. Since the width W of the partitioning wall part 2 is small compared with a pipe diameter D, total pressure acting from the exhaust gets small, and bending in the wall part 2 caused by the pressure of tire exhaust is restrained thereby in a small degree. Since a bent angle of the each bent part 3a is slight, and since the flange 8 is extended over the valley part walls 3, 7, force acting on the valley part wall 3 is dispersed, and stress concentrations onto the bent part 3a and the welded part 11 are restrained to prevent the fatigue.