Abstract: An image forming apparatus includes a plurality of heaters 56 for heating the fixing roller 52, a plurality of temperature sensors 57 for detecting the temperatures of the areas to be heated by the plurality of heaters 56 respectively, and a control unit 11 for turning on and off the plurality of heaters 56 on the basis of the temperatures detected by the plurality of temperature sensors 57. If one of the heaters 56 is on when the area to be heated by the other heater cools down to the ON temperature, the control unit 11 turns on the other heater with the same timing as the one heater is turned off.

Abstract: An image forming apparatus which allows a user to freely select a desired image quality is provided. The control unit 60 sets a of registration set value A1 for determining a color registration error suppression level and a dropout set value A2 for determining a dropout occurrence suppression level. Also, the control unit 60 sets a differential circumferential speed which is the difference between the circumferential speed of photoreceptor drums 1Y to 1K and the circumferential speed of an intermediate transfer belt 6 on the basis of the color registration set value A1 and the dropout set value A2. Then, the control unit 60 controls the belt drive motor 61 and the drum drive motor 62 on the basis of the differential circumferential speed which is set.

Abstract: An image forming apparatus forms decision registration mark for deciding whether or not a color registration correction for correcting color shifts in the color image carries out on an intermediate transfer belt. The decision registration mark is formed by registering four color registration marks. Color registration sensors detect a detection width of the decision registration mark along a sub scanning direction. A control portion receives the detection width of the decision registration mark and decides whether or not the color registration correction carries out based on whether or not the detection width of the decision mark detected by the detection portion exceeds the period of reference time. When the detection width of the decision mark detected by the detection portion exceeds the period of reference time, the control portion carries out the color registration correction.

Abstract: An image forming apparatus includes a plurality of heaters 56 for heating the fixing roller 52, a plurality of temperature sensors 57 for detecting the temperatures of the areas to be heated by the plurality of heaters 56 respectively, and a control unit 11 for turning on and off the plurality of heaters 56 on the basis of the temperatures detected by the plurality of temperature sensors 57. If one of the heaters 56 is on when the area to be heated by the other heater cools down to the ON temperature, the control unit 11 turns on the other heater with the same timing as the one heater is turned off.

Abstract: An image forming apparatus which allows a user to freely select a desired image quality is provided. The control unit 60 sets a of registration set value A1 for determining a color registration error suppression level and a dropout set value. A2 for determining a dropout occurrence suppression level. Also, the control unit 60 sets a differential circumferential speed which is the difference between the circumferential speed of photoreceptor drums 1Y to 1K and the circumferential speed of an intermediate transfer belt 6 on the basis of the color registration set value A1 and the dropout set value A1. Then, the control unit 60 controls the belt drive motor 1 and the drum drive motor 62 on the basis of the differential circumferential speed which is set.