Image heating device capable of controlling activation of plural heaters

摘要

Disclosed is an image heating device for a fixing device in image forming apparatus. The image heating device is provided with two heaters and an image fixing roller. The image fixing roller is heated by the two heaters, one having the heat distribution in the center and the other having the heat distribution in the end portion of the fixing roller. The heaters are alternately energized so that the power requirement is maintained limited. The energization time ratio of the heaters is suitably varied according to the sheet size in order to compensate the temperature loss in the end portions when the heating is conducted in the central portion only, or to reduce the temperature rise in the end portions, encountered when narrow sheets are consecutively passed, thereby preventing various drawbacks resulting from uneven temperature distribution on the fixing roller.