| 摘要 |
A sheathed glow plug comprising a central electrode formed by concentrically welding central shafts on the front and rear end sides, wherein the eccentricity of the central electrode is minimized and formation of burrs on the joint is suppressed. That is, the joint end (g) of one central shaft (6) of the central electrode (4) is made smaller in diameter than the joint end (f) of the other central shaft (5), with the result that the area of the abutment surface between the joint ends reduces in proportion to the diameter of the smaller-diameter side joint end; therefore, even if the joint end surface has an off-right-angle error with respect to the shaft or is roughened, its effect can be suppressed becau se of the diameter of the abutment surface being reduced, ensuring that stabilized resistance welding is performed. Further, even if burrs (X) form around the peripheral edge of the joint surface due to the resistance welding, the reduced area of the abutment surface reduces the amount of burrs, and the burring is regarded as being within the allowable range unless the burrs project beyond the main diameter of the center shaft on the larger diameter side, so that deburring can be omitted or simple deburring will do.
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