| 摘要 |
PROBLEM TO BE SOLVED: To provide a thermal fixing device capable of almost accurately grasping a change in the surface temperature of a heating member in a paper passing area even when the passing interval of a recording sheet is changed, always obtaining a fine fixed image free from defective fixing and preventing the heating member from being excessively heated. SOLUTION: The thermal fixing device is provided with a heat roller including a heater in its inside, a pressure roller for press-contacting with the heat roller, a temperature sensor for detecting the surface temperature of the heat roller by coming into contact with the heat roller on the outside of a recoding sheet passing area, a means for counting recording sheet passing time and non-passing time between the heat roller and the pressure roller, a means for predicting a difference between a temperature detected by the temperature sensor and the practical surface temperature of the heat roller in the sheet passing area on the basis of the sheet passing time and the non-passing time, and a temperature control means for controlling current supply to the heater while considering the predicted temperature difference.
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