| 摘要 |
PROBLEM TO BE SOLVED: To provide a glow plug having high durability under the impact of abnormal combustion. SOLUTION: The glow plug 1 comprises a ceramic heater 13 and an outer cylinder 12 for inserting the ceramic heater 13. An outer diameter Dc of the ceramic heater 13 and an outer diameter Ds of the outer cylinder are set so as to obtain the glow plug 1 wherein Dc/Ds is 0.8 or lower and Dc/Ds is 0.5 or more. The breakage load of the glow plug 1 is equal to or more than that of the ceramic heater wherein Dc/Ds is 0.8 in a the case where an equal velocity load is imposed, at right angle to the longitudinal direction, on a position which is 2 mm from the tip of the ceramic heater 13.
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