| 摘要 |
An improved structure of a spark plug is provided for improving the mechanical strength of joints between a noble metal member made of Ir-alloy and a ground electrode which withstands intense heat. The noble metal member is welded to the ground electrode through laser-fused portions. Each of the fused portion contains less than 40% by weight of Ir in a range defined inside an imaginary plane coinciding with an outer peripheral wall of the noble metal member before welded to the ground electrode, thereby enhancing the strength of the joints between the noble metal member made and the ground electrode.
|
