| 摘要 |
PROBLEM TO BE SOLVED: To provide a heat fixing device capable of detecting the temperature rise around the change pole arising when a paper sheet of which size is smaller than that of a paper sheet set at the change pole of the distributed heat of a resistor is conveyed and controlling the heat to be lower than an appropriate temperature. SOLUTION: The fixing unit has a heating roller having a heater substrate, a pressure roller brought into contact with the heating roller by a prescribed pressure, and first, second, and third temperature detecting means for detecting the temperature of the heater substrate and heat fixes the toner image on recording paper, wherein the first and second resistance heaters have at least a width corresponding to the length of the largest recording paper in a prescribed position from the center with respect to the direction orthogonal to the conveyance direction of the recording paper, and in the first heater, the resistance value is set in such a manner that the resistance value at both ends in the prescribed position from the center with respect to the direction orthogonal to the conveyance direction of the recording paper is made lower than that at the center, and in the second heater, the resistance value is set in such a manner that the resistance value at both ends in the prescribed position with respect to the direction orthogonal to the conveyance direction of the recording paper is made higher than that at the center. COPYRIGHT: (C)2006,JPO&NCIPI
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