Duty-ratio corrected control of fixing roller power

An image forming apparatus that forms an image on a paper sheet, comprising:

• a developing unit in which a toner-developed image is formed onto a paper sheet;
• a width-information acquisition unit that acquires information of a width of the paper sheet;
• an environmental-condition detecting unit that detects environmental conditions at a time of image formation on the paper sheet;
• a heat roller that has a cylindrical shape, the heat roller contacting the paper sheet on which the toner image is formed by the developing unit, so as to fix the toner image on the paper sheet;
• an end-portion-temperature-detecting unit that detects a temperature of an end portion of the heat roller in the heat roller's longitudinal direction;
• a first heater located inside the heat roller, the first heater heating a center portion of the heat roller in its longitudinal direction;
• a second heater located inside the heat roller, the second heater heating the end portion of the heat roller in its longitudinal direction;
• a first control unit that controls electric power supplied to the first heater according to a first duty ratio, the first duty ratio being a duty ratio of the electric power supplied to the first heater;
• a storage unit that plurally stores paper-sheet-width conditions based on the width of the paper sheet detected by the width-information acquisition unit, stores temperature conditions corresponding to a difference between the temperature of the end portion detected by the end-portion-temperature-detecting unit and a predetermined target temperature, and stores second-duty-ratio data for second duty ratios, being duty ratios of electric power supplied to the second heater, derived based on the first duty ratio;
• a correction-value derivation unit that based on the environmental conditions detected by the environmental-condition detecting unit derives a temperature-conditions correction value;
• an extracting unit that, from among second-duty-ratio data, stored in the storage unit, in which the extracting unit reflects the temperature-conditions correction value derived by the correction-value derivation unit, extracts post-correction second-duty-ratio data;
• and
• a second control unit that controls the electric power supplied to the second heater according to the post-correction second-duty-ratio data extracted by the extracting unit.