To prevent the crack development of a connection part between a port inner pipe and a collecting inner pipe in an exhaust manifold of hollow double pipe structure.
The respective one ends of the port inner pipes 20a, 20b, 20c are connected to a head flange 2, communicating with an exhaust hole 3, and branch pipe parts 18a, 18b, 18c of an outer pipe 10 cover the port inner pipes. The collecting inner pipe 30 of hollow structure provided with openings 36 into which the respective other ends of the port inner pipes are inserted, is held by a support mesh 38 in a collecting part 16 following the branch pipe parts of the outer pipe 10. The port inner pipe 20c largest in the discrepancy between the expansion direction based on the thermal expansion of the port inner pipe and the direction of the opening, is connected to the collecting inner pipe by welding at the insertion part into the opening 36c, and the other port inner pipes are slidable relative to the inserted openings. Since the opening 36c part is integrated with the port inner pipe 20c by welding, the force of tearing off the hollow structure is not applied.
Tetsuro Maki
Maki Reiko
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