| 摘要 |
<p>Provided is a spark plug that achieves superior ignitability and further reliably prevents breakage of a ground electrode or the like. A spark plug 1 includes a center electrode 5, a ground electrode 27, and a ground electrode side tip 32. The tip 32 partially projects from a front end face 27F and an inner circumference-side side surface 27S of the ground electrode 27. The ground electrode 27 has a center CE of the front end face 27F. The center CE is located at a front end side in a direction of the axis CL1 with respect to a front end of the center electrode 5. L/X ‰¤ 1.28 is satisfied, where L (mm) represents a length of the ground electrode 27 along a central axis CL2 of the ground electrode 27 and X (mm) represents a projection length of the ground electrode 27 relative to a metallic shell 3. 8.4 ‰¤ (S1/S2)/A is satisfied, where S1 (mm 2 ) represents a cross section area of a portion at a base end side with respect to a portion where the tip 32 is joined to the ground electrode 27 in cross section perpendicular to a central axis CL2, S2 (mm 2 ) represents a cross section area of the tip 32 in cross section perpendicular to a projection direction of the tip 32, and A (mm) represents a projection length of the tip 32 relative to the front end face 27F.</p> |
