| 摘要 |
PROBLEM TO BE SOLVED: To provide a fixing device in which high-temperature offset or curling of recording paper, which are caused by a partial temperature increase of a heat roller after the passage of image formation paper of a small size, is prevented and power can be saved, and to provide an image forming apparatus using the fixing device. SOLUTION: A main heater 391a and a sub-heater 391b are disposed in a heating roller. Control is exerted so as to shut off power supplied to the sub-heater, in the case of an instruction to print on recording paper of a large size after the passage of image formation paper P' of a small size in a paper passage range D narrower than a paper passage range F that corresponds to the heat distribution characteristics of the main heater in the axial middle section of the heating roller. Also, the control is exerted such that when the temperature of the axial middle section of the heating roller has become almost uniform, power is supplied to the sub-heater so that the axial middle section reaches a predetermined temperature for fixing. On the other hand, in the case of an instruction to successively print on image formation paper of a small size, the control is exerted so as to shut off power to the sub-heater. COPYRIGHT: (C)2005,JPO&NCIPI
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