| 摘要 |
A spark plug (10) has a central electrode (12) and a plurality of peripheral electrodes 14. Each peripheral electrode (14) has a lower portion (25) and an upper portion (26). Each upper portion (26) has a distal-most point (28). Each distal-most point (28) is disposed in a central plane (30) within which the longitudinal axis (20) of the distal portion (18) of the central electrode (12) is wholly disposed. The cross-section of each upper portion (26) taken along its central plane (30) defines a convex outer side (32) and a non-convex inner side (34). Each convex outer side (33) has a curved surface (36) which is tangent to a plurality of tangent planes (38), all of which intersect the longitudinal axis (30) of the distal portion (18) of the central electrode (12) at points at or above the distal end (22) of the distal point of the central electrode (12). |
