| 摘要 |
A spark plug is provided which comprises a center electrode and a ground electrode having at a free end portion thereof a discharge surface which is opposite to an axial end surface of the center electrode to provide therebetween a spark gap, wherein the center electrode has a center electrode tip forming the axial end surface thereof, the center electrode tip being made of a material containing Ir as a major constituent, and wherein G<=2A+0.5 where G is a spark gap (mm) and A is the distance (mm) between a first imaginary line and a second marginal line.
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