| 摘要 |
PROBLEM TO BE SOLVED: To provide a glow plug excellent in strength although a sheath tube has a small diameter in which required heat generation characteristics can be ensured easily and short circuit between a heating coil and the sheath tube is prevented. SOLUTION: In a glow plug, a sheath heater 2 secured in a main metal comprises a sheath tube 11 closed on the forward end side, a heating coil 21 arranged in the sheath tube, and a control coil 23 connected in series with the heating coil 21 on the rear side thereof and controlling conduction of the heating coil 21 by increasing electric resistance upon receiving heat therefrom. A conduction terminal shaft connected with the control coil 23 and having larger diameter than a protruding part in the main metal of the sheath tube 11 is inserted into a large diameter part. Protrusion of the sheath tube 11 is set in the range of 3.0-4.4 mm.
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