SPARK PLUG MANUFACTURING METHOD

摘要

A spark plug manufacturing method by which the welding strength between an electrode and a noble metal chip joined by laser welding is prevented from weakening. The center electrode (2) of a spark plug and a noble metal chip (90) joined to a ground electrode are resistance-welded to electrodes not containing any noble metal and are welded by laser so as to define a spark discharge gap. The noble metal chip (90) is exposed to a harsh environment involving spark discharge. Therefore, the fused portion (80) between the noble metal chip (90) and the electrode formed by the laser welding is likely to be separated from the non-fused portion (95) of the noble metal chip (90) along the boundary surface (83) between the fused portion (80) and the non-fuse portion (95). According to the invention, in the resistance welding, the noble metal chip (90) is pressed and a flange portion is formed at the bottom. A laser beam is applied to the flange portion. Therefore, the content of the noble metal in the fused portion (80) increases, thereby preventing separation along the boundary surface (83).