| 摘要 |
A spark plug without any noble metal chip on a ground electrode and capable of enhancing the ignition property, prolonging the life and ensuring a sufficiently high strength of the ground electrode is provided. The spark plug 1 includes a center electrode 5, an insulator 2, a metal shell 3, and a ground electrode 27. Spark discharge is provided substantially along a direction of an axis CL1 of the spark plug in a spark discharge gap 33 defined between the center electrode 5 and the ground electrode 27. The ground electrode includes a narrowed width portion 42 which has a substantially uniform width smaller than an outer diameter of a tip end surface 5F of the center electrode 5, and a widened width portion 41 having a width larger than the width of the narrowed width portion 42. When viewed from a tip end side of the spark plug in the direction of the axis CL1, a base end of the narrowed width portion 42 is located offset from the tip end surface 5F of the center electrode 5 toward the root side of the ground electrode 27. The base end of the narrowed width portion 42 is located offset from a center of the spark discharge gap toward the tip end side of the spark plug in the axial direction of the spark plug.
|
