| 摘要 |
A ground electrode (30) and a metal shell (50) are joined by welding or the like while an entire end face (35) of a base (32) of the ground electrode (30) is brought into contact with a front end constituent face (57) of the metal shell (50). The ground electrode (30) has an extending portion (36) extending forward in an axial (O) direction of the ground electrode (30). A front end portion (31) faces a noble metal tip (90) joined to a front end portion (22) of the center electrode (20) through a bending portion (37) and forms a spark discharge gap (G) therebetween. A gap (a clearance) having a sufficient space to accommodate a virtual sphere (Q) with a radius of 1.2mm is provided so that the virtual sphere (Q) being in contact with an inner face (33) of the bending portion (37) of the ground electrode (30) is neither in contact with a center electrode (20) nor an insulator (10). |
