PURPOSE: To prevent damage from occurring due to everheating of an isolation film of a heater part by providing an overheat prevention circuit wherein temperature of the heater part is detected, and when the temperature reaches at least a preset value, power supply to the heater part is reduced, or stopped.
CONSTITUTION: Ceramic coating treatment is given on the metal surface of a radiation plate 16 radiating for infrared electromagnetic wave, when a heater part 17 is energized the ceramic layer is simultaneously heated to radiate for infrared electromagnetic wave to an insert 13 corresponding to that. A temperature detecting circuit 25 for the heating part detects the surface temperature of the heater part 21, sends a heater part temperature signal 24' to an overheat prevention circuit 25, which compares the heater part temperature signal 24' and a reference signal 26' corresponding to the heat-resistant temperature of the insulation film of the heater part, and when the heater part temperature 24' is greater, the output of the infrared electromagnetic wave is reduced, or stopped by controlling an infrared electromagnetic output circuit 20, and a possible damage of the insulation film due to overheating of the heater part may be prevented from occurring.
MATSUDA SHUNSUKE
KANI KAZUYOSHI
