| 摘要 |
<p>In order to efficiently conduct heat from a tip to an internal layer, thereby improving resistance to wear of the tip, a spark plug (1) is provided with: an insulator (2) having an axial bore (4) that extends in the direction of an axis line (CL1); a center electrode (5) inserted in the axial bore (4); a metal shell (3) disposed on the outer periphery of the insulator (2); a ground electrode (27) that is fixed to the leading end of the metal shell (3); and a tip (32) that is joined to the leading end of the ground electrode (27), and forms a spark discharge gap (33) between the leading end of the center electrode (5) and the tip (32). The ground electrode (27) comprises an outer layer (27A), and an inner layer (27B) that is disposed inside the outer layer (27A) and comprises a metal composed mainly of copper. The tip (32) is joined to the ground electrode (27) by a fused section (35) containing a metal constituting the fused section itself and the metal constituting the outer layer (27A). The fused section (35) is in contact with the inner layer (27B) and includes a copper component.</p> |
