| 摘要 |
PROBLEM TO BE SOLVED: To reduce a dimensional tolerance of a spark gap in a spark plug.SOLUTION: The spark plug manufacturing method includes: an assembly step of assembling a center electrode having a first end with a main body metal fitting to which a rod-like ground electrode having a second end is jointed; and a bending step of making the first end near the second end by bending the ground electrode after the assembly step. The bending step includes: a push-in step of bending the ground electrode by pushing in the ground electrode; a measurement step of measuring a position A of the ground electrode on a virtual plane P orthogonal to an axial line direction and passing through the first end, before the push-in step; and an estimation step of calculating an estimation value estimated as a spring-back amount when the push-in step is applied to the ground electrode whose position A is measured, based on the position A. In the push-in step, the ground electrode is pushed in by a push-in amount according to the estimation value. |
