| 摘要 |
By heating a glass sealing material (5), a center electrode (6) is sealed and fixed within an axial bore (3) of an insulator (2). Formation of a groove (8) in a head portion (7) of the center electrode (6) makes it possible to protect the head portion of the center electrode from deformation under a pressure which is applied upon filling the glass sealing material in a powder form in the axial bore. The glass sealing material is therefore assured to flow to a peripheral side wall of a flange portion (12) of the center electrode, thereby enhancing mechanical engagement between the center electrode and the insulator, that is, uniting strength for them. A spark plug (1) is hence obtained with improved impact resistance and accordingly, with sufficient durability. <IMAGE> |
