| 摘要 |
PROBLEM TO BE SOLVED: To provide an ignition plug that is able to achieve extremely satisfactory airtightness, and to provide a manufacturing method therefor.SOLUTION: An ignition plug 1 comprises: an insulator 2; and a main-body metal fitting 3 having a projection part 21 projecting radially inside. The projection part 21 has a reduced diameter part 21A, the insulator 2 has a lock part 14, and the lock part 14 is locked in the reduced diameter part 21A via a lock member 22. In a cross-section including an axial line CL1, if the angle of the lock part 14 is &thetas;p(°) and the angle of the reduced diameter part 21A is &thetas;s(°), &thetas;s≤&thetas;p is satisfied. If the Vickers hardness of the lock member 22 at the center point CP1 of a first line segment SL1 is Hvo(Hv), the Vickers hardness of the lock member 22 at the center point CP2 of the second line segment is Hvi(Hv), and the Vickers hardness of the lock member 22 at the center point CP3 of the third line segment SL3 is Hvm(Hv), Hvi>Hvm>Hvo and (Hvi-Hvm)/(Hvi-Hvo)≤0.5 are satisfied. |
