| 摘要 |
A ground electrode (30) includes a noble metal tip (38), a holder (39) having a through hole for disposing therein the noble metal tip (38), and a body (33) to which the holder is joined. At least one of the inner circumferential surface of the holder (39) which forms the through hole, and the outer circumferential surface of the noble metal tip (38) which is disposed in the through hole, continuously reduces in diameter toward the forward side. The forward end surface of the noble metal tip (38) is located on the forward side with respect to the forward end surface of the holder (39). |
