| 摘要 |
PROBLEM TO BE SOLVED: To more reliably prevent the inclination and separation of a noble metal chip in spite of a thinned ground electrode. SOLUTION: This spark plug 1 includes a center electrode 5, an insulator 2, a metal shell 3, the ground electrode 27, and the noble metal chip 41 bonded to the ground electrode 27 to form a spark discharge clearance 33 between the center electrode 5 and itself. The cross section area of the ground electrode 27 along a direction perpendicular to the longitudinal direction of the ground electrode 27 is 0.5-3.0 mm<SP>2</SP>. The noble metal chip 41 is bonded to the ground electrode 27 with laser welding forming a melted portion 35 where itself and the ground electrode 27 are mixed together. On the cross section including the center axis of the noble metal chip 41 along the longitudinal direction of the ground electrode 27, the hardness of the noble metal chip 41 at its predetermined site or the hardness of the ground electrode 27 at its predetermined site satisfies a predetermined relational expression. COPYRIGHT: (C)2011,JPO&INPIT |
