Image forming apparatus including a plurality of heat generating elements

An image forming apparatus comprising:

• a fixing device having a heater that includes a first heat generating element, a second heat generating element having a length smaller than a length of the first heat generating element in a longitudinal direction, and a third heat generating element having a length smaller than the length of the second heat generating element in the longitudinal direction;
• a first temperature detection unit provided at a position corresponding to a center of the first heat generating element in the longitudinal direction;
• a pair of second temperature detection units provided at positions corresponding to both ends of the third heat generating element;
• a pair of first sheet-width detection units provided upstream of the fixing device in a conveyance direction of a recording material and provided at positions corresponding to both ends of the first heat generating element;
• a pair of second sheet-width detection units provided upstream of the fixing device in the conveyance direction and provided at positions corresponding to both ends of the second heat generating element;
• and
• a control unit configured to control a temperature of the heater based on a detection result of the pair of first sheet-width detection units, a detection result of the pair of second sheet-width detection units, and a detection result of the pair of second temperature detection units.