| 摘要 |
<p>An end, which forms a spark discharge gap, of a center electrode (2) is a noble metal tip (22) having a diameter of 1.0 mm or smaller and a straight-rod part of 0.2 mm or longer in length. A grounded electrode (11) to which an angular-shaped noble-metal tip (112) is welded has a covering dimension K, where -d ≤ K ≤ 0.5 mm. The width w in a range inside the discharge surface (111A) of the grounded electrode (11) and formed by extending the end face (22B) of the noble metal tip (22) disposed on the center electrode (2) along the axix satisfies the relation W < 2.1 - K (unit: mm), where the covering dimension K is used.</p> |
