PROBLEM TO BE SOLVED: To obtain a fixing device that can be improved in the insulating property and the actuating time of a temperature overrising preventive device and can interrupt the power conduction at a safe temperature even when temperature overrises. ;SOLUTION: This is a fixing device in an image forming device having a fixing roller 2 to be driven to rotate and a freely rotatable pressurizing roller made to abut on the fixing roller 2 with a prescribed pressure. In this case, the fixing roller consists of a hollow cylindrical metal base body, and an electrically insulated layer and a resistance heat generating layer are laminated on the inner face of a metal base body, and it possesses a thermistor 21 which abuts on the fixing roller and detects the temperature of the fixing roller, a temperature controller executing temperature control in accordance with the detected output of the thermistor 21 and the temperature overrising preventive device 27 controlling the temperature runaway of the fixing roller 2 when the thermistor 21 defectively operates, and a double insulating materials is provided outside the temperature overrising preventive device 27.;COPYRIGHT: (C)2000,JPO
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