| 摘要 |
<p>Enhancement of separation resistance, and the like, is sought by improving the performance for conducting heat of a noble metal tip. A spark plug 1 includes a center electrode 5 extending along an axial line CL1, a ground electrode 27, a noble metal tip 32, and the like. A center axis CL3 of the noble metal tip 32 is displaced from a center axis CL2 of the ground electrode 27 toward a base-end side in the axial line CL1. The ground electrode 27 includes an outer layer 27A and an inner layer 27B, and a distal end of the inner layer 27B is situated closer to the axial line CL1 than a base end of the ground electrode 27. An overlap area OA between the inner layer 27B and the noble metal tip 32 occupies a ratio of 25% or more in a projective plane PH, where the projective plane PH is defined by projecting, along the center axis CL2, a plane of the ground electrode 27 viewed from a distal-end face 27f on a cross section of the ground electrode 27 in which a maximum cross-sectional area of the inner layer 27B is achieved, among cross sections orthogonal to the center axis CL2.</p> |
