| 摘要 |
A spark plug (100) includes a spark portion (31, 32) of an Ir-based metal and a resistor (15) disposed between a center electrode (3) and a metallic terminal (13) and adapted to establish an electric resistance of not less than 10 k OMEGA , preferably not less than 15 k OMEGA , as measured between the center electrode (3) and the metallic terminal (13). Thus, even in a system in which an ignition coil (51) is connected directly to the spark plug (100) without use of a high tension cable, an electrical discharge with a relatively weak current, such as a glow discharge, can be maintained stably, so that even at high-speed or heavy-load operation, consumption of the spark portion (31, 32) caused by volatilization of Ir through oxidation can be suppressed, thereby extending spark plug life. <IMAGE> |
