| 摘要 |
PROBLEM TO BE SOLVED: To effectively prevent exfoliation (dropout) and deformation or the like of a chip.SOLUTION: A spark plug 1 comprises a center electrode 5 and a ground electrode 27 forming a spark discharge clearance 33 between the ground electrode 27 and the center electrode 5, and a chip 31 (32) is welded to at least one of both the electrodes 5, 27. A thermal expansion coefficient of the chip 31 (32) is smaller than that of the electrode 27 (5) to which the chip per se is welded, and a difference (A-B) between a percentage content A (mass%) of a noble metal component of the chip 31 (32) and a percentage content B (mass%) of a noble metal component of the electrode 27 (5) is 50 mass% or more. A hole 38 (39) is present in an intermediate layer 34 (35) between the chip 31 (32) and the electrode 27 (5) and when a length of a boundary between the chip 31 (32) and the intermediate layer 34 (35) is defined as L (mm) and a length of the hole 38 (39) in a direction along the boundary between the chip 31 (32) and the intermediate layer 34 (35) is defined as N (mm), 0.1≤N/L≤0.4 is satisfied. |
