| 摘要 |
PROBLEM TO BE SOLVED: To improve the ignitability and durability of a spark plug.SOLUTION: A spark plug comprises: a center electrode extending in an axial line direction; an insulator which has an axial hole extending in the axial line direction and in which the center electrode is disposed in the axial hole; a main metal fitting disposed at the outer periphery of the insulator; a first ground electrode having a first face forming a first gap while opposing the side face of the center electrode in the radial direction; and a second ground electrode having a second face forming a second gap while opposing the side face of the center electrode in the radial direction. When viewed from the front end side toward the rear end side in the axial line direction, a smaller angle &thetas; out of angles formed by a first line segment connecting the axial line and the center of the first face and a second line segment connecting the axial line and the center of the second face satisfies 60°≤&thetas;≤150°. The spark plug has a specific plane which is a plane including the axial line and which halves the main metal fitting so that all ground electrodes are disposed on one side. |
