| 摘要 |
PROBLEM TO BE SOLVED: To provide a glow plug for improving its durability.SOLUTION: The glow plug includes a sheath heater having a tube and a heating coil. In the cross section of the sheath heater cut at a position passing through the center axis of the tube, the heating coil has a plurality of cross section parts excluding a site joined to a member different from the heating coil, out of sites appearing at positions apart from the tube. The plurality of cross section parts include a beginning cross section part located at the first place from the front end side, and a plurality of subsequent cross section parts located at the second and subsequent places from the front end side. A relationship between a cross section area A1 of the beginning cross section part and the average cross section area Am of the plurality of subsequent cross section parts satisfies 0.5≤A1/Am≤0.7.SELECTED DRAWING: Figure 3 |
