| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent a noble metal chip from coming off from an electrode in a spark plug having an electrode to which the noble metal chip is joined more surely than ever. <P>SOLUTION: A spark plug having an electrode to which a noble metal chip is joined directly or indirectly by using laser welding based on a laser irradiated at the axis of the noble metal chip from the outer periphery side includes a plurality of fusion sections formed by laser welding, differing in the depth fused into the noble metal chip. Out of the fusion sections, if a portion formed inside the noble metal chip is assumed to be a chip fusion part, then the distance, on a plane passing a point closest to the axis among a plurality of the chip fusion part and intersecting the axis at right angles, between a geometric center of gravity of the plurality of chip fusion parts and the axis is 0.2 D (D=diameter of a circle around the axis on plane touching the noble metal chip internally) or less. <P>COPYRIGHT: (C)2013,JPO&INPIT |
