| 摘要 |
PROBLEM TO BE SOLVED: To form a high electric resistance part in the vicinity of both ends, without forming slits in a heating unit and to expand a uniform temperature region by constituting the heating unit by adding silicon particles having a purity of specified percent or higher to an insulating ceramic, so as to be the specified present based on the total volume, arranging the high resistant part having coarse silicon particles in the vicinity of both ends, and using other part as a heating part. SOLUTION: A heating unit is formed with a silicon - containing composite ceramic, and by making silicon particles partially coarse in the vicinity of both ends a uniform temperature region is expanded. Silicon particles having a purity of 90% or higher are added to the insulating ceramic, so as to be 10-40 vol.% based on the total volume to form the heating unit, and high resistance part having coarse silicon particles is formed in the vicinity of the both ends. Current supplied from a power supply part flows into the inside, is passed through the high resistance part, where generated heat quantity is increased than other part, the falling part of a temperature curve is raised up by the heat generation of the high resistance part, and the uniform temperature region is expanded. |
