Patent ID: 6198888
Filing Date: 2001-03-06
Classification: G03G

Abstract:
A belt fixing device for an image forming apparatus, comprising:a fixing roller;a heating roller;an endless fixing belt spanned around the fixing roller and the heating roller;a pressing roller disposed opposing the fixing roller via the fixing belt;a heater disposed inside the heating roller for heating the fixing belt;a heating area where the fixing belt is heated by the heating roller;a fixing area where the pressing roller presses the fixing roller via the fixing belt;a temperature detector positioned to detect a surface temperature of the fixing belt in the heating area; andtemperature control means for controlling the surface temperature of the fixing belt in the heating area to a prescribed temperature when a fixing operation is repeated;wherein the fixing area includes a fixing nip portion formed between the fixing roller and the pressing roller in the fixing area, wherein the temperature at an exit of the fixing nip portion gradually rises when a fixing operation is repeated, and wherein the prescribed temperature is such that a temperature at the exit of the fixing nip portion is higher than a lowest fixing temperature that does not cause inferior fixing and lower than a highest fixing temperature that does not cause toner offsetting at the exit of the fixing nip portion during the repeated fixing operations.