| 摘要 |
<p>An object is to provide a spark plug which is excellent in load life performance, and a method of manufacturing the same. In a spark plug of the present invention, a connecting portion which electrically connects a center electrode and a metallic terminal within the axial hole of an insulator includes a resistor whose porosity is 5.0% or less. In a spark plug of another invention, when the length from the rear end of the center electrode to the rear end of a connecting member which constitutes the connecting portion is referred to as a charging length D and the length from the rear end of the center electrode to the forward end of the metallic terminal is referred to as a connecting portion length C, the shrinkage percentage ((D-C)/D)×100 is 35% or greater. A spark plug manufacturing method of the present invention is characterized in that, in a step of disposing the metallic terminal is the axial hole such that it comes into contact with a connecting portion forming powder for forming the connecting portion, an exposure length H and a powder portion diameter B' satisfy relational expressions (1) H ‰¥ -3.1B'+18, (2) H ‰¥ -0.85B'+11, and (3) B ‰¤ 5, where the exposure length H in an axial length (mm) from the rear end of the insulator to the forward end of a first constituent portion of the metallic terminal exposed from the axial hole, and the powder portion diameter B' represents a diameter (mm) of the axial hole at a position where the connecting portion forming powder is disposed.</p> |
