| 摘要 |
PROBLEM TO BE SOLVED: To provide a glow plug which can achieve firm coupling without slackness after assembly, by materializing such constitution that the assembly of a heater body, a metallic outer case, a main metal fitting, etc., becomes easy, in a glow plug using a ceramic heater. SOLUTION: The glow plug is equipped with a bar-shaped ceramic heater 1 where a ceramic resistor 10 consisting of conductive ceramic is buried in a ceramic substrate 13 consisting of insulating ceramic, and it is provided with a metallic outer tube 3 which is arranged with the tip of the ceramic heater 1 projected, and a main metal fitting 4 where a mounting part to an internal combustion engine is made. The ceramic heater 1 is tight fitted inside the metallic outer tube 3, while the frictional coefficient between the engaging faces is set to be larger at the front end 101 of the metallic outer tube 3 than at the rear end 103 when defined that the tip side of the ceramic heater 1 is front side, in the case where a sliding material remains in the space (space in engagement section) made by each engaging face of the inner peripheral face of the metallic outer tube and the outer peripheral face of the ceramic heater.
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