| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug more reliably suppressing a rise of a ground electrode. SOLUTION: In the spark plug 100, the ground electrode 4 includes: a core part 41 extending from a base end part 4A toward a top end part 4C via a bending part 4B; a heat transmission part 42 extending from the base end part 4A toward the top end part 4C via the bending part 4B; and an outer layer 43 extending from the base end part 4A toward the top end part 4C via the bending part 4B outside the core part 41 and the heat transmission part 42. The outer layer 43 is constituted by a nickel alloy as a first metal excellent in heat resistance and corrosion resistance. The heat transmission part 42 is constituted by copper as a second metal having a higher thermal conductivity compared to the first metal. The core part 41 is constituted by pure nickel as a third metal having a higher hardness compared to the second metal. The second metal has a higher linear thermal expansion coefficient compared to the first and third metals. When the ground electrode 4 is seen in a cross section perpendicular to a direction in which the ground electrode 4 extends, at least in the middle of the bending part 4B, the center of the core part 41 is closer to a central electrode 3 than the center of the heat transmission part 42. COPYRIGHT: (C)2011,JPO&INPIT |
