| 摘要 |
PROBLEM TO BE SOLVED: To more surely prevent a nickel layer provided on the external surface of a ground electrode from being peeled off and cracked by heating and cooling.SOLUTION: An ignition plug 1 includes a cylindrical insulator 2 having a shaft hole 4, a center electrode 5 inserted into the tip side of the shaft hole 4, a cylindrical main metal fitting 3 provided on the periphery of the insulator 2, and a ground electrode 27 fixed to the tip part of the main metal fitting 3 while forming a spark discharge gap 28 between the center electrode 5 and itself, and a nickel layer 31 is provided on the external surface of the ground electrode 27. The nickel layer 31 contains at least one kind among carbon, phosphor, and boron, and the total concentration of carbon, phosphor, and boron at a location where the concentration of nickel is 80 at% in its thickness direction is set to be 0.1 at%-0.9 at%. Also, the thickness of the nickel layer 31 is set to be 16 μm-40 μm. |
