| 摘要 |
PROBLEM TO BE SOLVED: To prevent a curburization phenomenon such that carbon is dissolved in a lead wire at a connection between a carbonaceous heating element and an internal lead wire. SOLUTION: Coating layers 9, 10 are formed on the surfaces of a carbonaceous heating element 2 in an energizing coil portion 5 and a lead wire. In this structure, there is no direct contact between both of them because of the coating layers 9, 10 held therebetween. This prevents carbon from being dissolved in the lead wire, the lead wire from being made brittle into pieces because of no carburization, the carbonaceous heating element 2 from being thinner and less in diameter resulting in a gap in the energizing coil portion 5 which increases contact resistance and the lead wire from being dissolved and the heating element from being broken resulting from abnormal heating.
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