| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a technique for improving welding strength of a center electrode and a noble metal chip. <P>SOLUTION: A spark plug comprises: a center electrode having an electrode base material and an inner layer provided inside the electrode base material and mainly made of copper; a noble metal chip provided at a tip of the center electrode; and a fusion part formed across the noble metal chip, the electrode base material and the inner layer. The fusion part is in contact with the inner layer, and contains a component of the noble metal chip, a component of the electrode base material, and a copper component forming the inner layer. On a cross section parallel to a center shaft of the center electrode and passing through the center shaft and the fusion part, when a contact point of a contour line of the fusion part and an outer peripheral line of the inner layer is designated as a point P1, a straight line parallel to the center shaft is designated as a straight line L1, an intersection point of the straight line L1 and the contour line of the fusion part on the noble metal chip side is designated as a point P2, and an intermediate point of the point P1 and the point P2 is designated as a point P3, a content of the copper component at the point P3 of the fusion part is 50 weight% or less. <P>COPYRIGHT: (C)2013,JPO&INPIT |
