| 摘要 |
PROBLEM TO BE SOLVED: To improve ignition performance by preventing inhibition of growth of the flame kernel even at the initial stage of ignition when the discharge gap is narrow. SOLUTION: When the leg part 41 side at the opposed part 42 of the ground electrode 40 is made as a ground electrode base side and the opposite side of the leg part at the opposed part 42 of the ground electrode 40 is made as a ground electrode tip side, the precious metal tip 50 has a projection part 51 that protrudes toward orthogonal direction to the axis of the center electrode from the outer peripheral side face of the precious metal tip 50 at a part in the circumferential direction on the outer peripheral side face of the precious metal tip 50, and the projection part 51 is arranged on the ground electrode tip side. According to this, the intensity of the electric field at the discharge gap 60 is relatively stronger on the side where the projection part 51 is arranged, and the flame kernel by spark discharge is formed on the ground electrode tip side. Thereby, the flame kernel becomes to hardly receive the cooling action by the leg part or the like of the ground electrode, and the flame kernel can be grown promptly and stably. COPYRIGHT: (C)2004,JPO
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