| 摘要 |
PROBLEM TO BE SOLVED: To prevent temperature from excessively rising by quickly detecting the temperature change of a fixing roller. SOLUTION: A potential detection means is composed of a terminal A in contact with the end part of a conductive substrate 6 where is not coated with a surface layer 9, a smoothing circuit consisting of a diode 15 and the like, a 1st comparator 14, a 2nd comparator 16, resistance R1, R2 and R3 and the like. Then, the potential detection means is connected to an abnormal decision means so that detected potential is transmitted to the abnormal decision means. The abnormal decision means is the OR circuit constituted so as to decide abnormality based on the outputs of the comparators 14 and 16. The decided result of the abnormal decision means is transmitted to an electricity turning off means constituted of a driving semiconductor (transistor) 19 and a breaking relay 12. Then, when the dielectric breakdown of the fixing roller 4 is caused, some potential is generated at the terminal A. Since the value of the potential is different from a reference value at the comparator, the comparator is turned on and a signal outputted from it is transmitted to the OR circuit 18. Besides, the semiconductor 19 is turned on and the relay 12 is actuated. Thus, the electricity to a resistance heating element layer 8 is turned off.
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