| 摘要 |
PROBLEM TO BE SOLVED: To suppress dropping off of a noble metal tip in a spark plug in which a noble metal tip made of Pt alloy is joined to the end part of an electrode made of Ni alloy, and improve durability of the plug. SOLUTION: A ground electrode 27 and the noble metal tip 32 are joined via a melting part 42 made of the Ni alloy and the Pt alloy which are melted and mixed with each other. On the melting part 42, a plurality of needle-like or root-like minute cracks 51 are formed. In a cross-sectional view, the average length of minute cracks is 50μm or more and 500μm or less and the average aspect ratio (short side/long side) is 0.05 or less. At least one of the Ni alloy composing the ground electrode 27 and the Pt alloy composing the noble metal tip 32 contains as additional materials at least one kind out of the group 3A element and the group 4A element of the periodic table and their oxides. COPYRIGHT: (C)2009,JPO&INPIT
|
