| 摘要 |
PURPOSE: A spark plug having noble metallic or comparable tips fixed to opposed center and ground electrode is provided to shorten a length of a ground electrode to improve a heat resistance and a mechanical strength. CONSTITUTION: An axis(44) of the distal portion(42), crossing with an end surface(43) at the distal end of ground electrode(40), intersects with the center electrode axis with an acute angle. Hereinafter, the end surface(43) of ground electrode(40) is referred to as ground electrode end surface. The ground electrode(40) is made of a Ni-group alloy containing Ni as a chief material. In this case, a virtual plane is supposed as a plane including the center electrode axis and a cross-sectional centroid of a proximal end of the ground electrode(40) where the ground electrode(40) is fixed to the metallic housing(10). The axis(44) of the distal portion(42) is defined as an axis substantially crossing the ground electrode end surface(43) when the ground electrode(40) is projected on the virtual plane.
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