| 摘要 |
PROBLEM TO BE SOLVED: To prevent compounds extruded inside the pressure welding surface from entering a catalyst side by forming a trap groove capable of housing the compounds extruded by friction welding inside the pressure welding surface, in a connecting structure in which an exhaust manifold and a catalyst case are connected by friction welding on the pressure welding surface. SOLUTION: A trap groove M is formed into a recessed shape inside the outer wall 2a of a catalyst case 2 connected to the lower end of an exhaust manifold 1 by friction welding, and a flange part 2b is integrally formed inside the trap groove M into an erected shape. In this case, the bottom surface of the trap groove M is set so as to be lower than the lower end of the approach margin (b) of the outer wall 2a. Therefore, when the upper end of the outer wall 2a of the catalyst case 2 and the lower end of the exhaust manifold 1 are brought into contact with each other and frictionally welded, the parts of the approach margins (a), (b) are pressed and joined, and oxidized compounds are respectively extruded inside and outside the pressure welding surface P. However, since the inside oxidized compounds are housed in the trap groove M, they are prevented from entering a catalyst 3 side.
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