| 摘要 |
<p>A spark plug (1) includes an insulator (2), a terminal electrode (6), a center electrode (5), a resistor (7), and a glass seal layer (8). The terminal electrode (6) has: a recess part (6D) opened to the front end side and having a depth in a center axis (CL2) direction of the terminal electrode (6); and a flat part (6E) neighboring the recess part (6D) at its outer circumference side. A (mm 2 ) which represents an area of a region surrounded by an outline of an outer circumference surface of the terminal electrode (6), and B (mm 2 ) which represents an area of a region of the terminal electrode (6) surrounded by an outline of an inner surface of the recess part (6D) in a cross section orthogonal to the center axis (CL2) and located 0.1 mm away from a front end along the center axis (CL2) to the rear end side, satisfies 0.52 ‰¤ B/A ‰¤ 0.91.</p> |
