| 摘要 |
Regarding a spark plug having a ground electrode to which a noble metal tip is joined by laser welding, in order to suppress the hollow at a melted portion of a joined portion of a ground electrode main body part and the noble metal tip, to improve the resistance to oxidation at high temperatures of the ground electrode main body part and to prevent detachment of the noble metal tip, according to the invention, there is provided a spark plug comprising a cylindrical metal shell; a cylindrical insulator that is held in the metal shell; a center electrode that is held in the insulator; and a ground electrode that comprises a ground electrode main body part having one end fixedly connected to the metal shell and the other end facing the center electrode and a noble metal tip joined to the ground electrode main body part at a position facing a leading end of the center electrode, a spark discharge gap being formed between the leading end of the center electrode and the noble metal tip wherein at least a portion of the ground electrode main body part, to which the noble metal tip is joined, is made of Ni alloy containing 12 to 45 mass% of Cr, 7 mass% or less of Fe, 0.5 to 5 mass% of Al, 0.3 to 5 mass% of Si and 50 mass% or more of the balance, and wherein the joined portion and the noble metal tip are joined by laser welding or electron beam welding. |
