| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem that failure such as curl is caused when target fixation temperature is fixed or fixation properties are spoiled because the amount of heating becomes insufficient in cold environment in an image forming apparatus equipped with a fixing device. SOLUTION: In the image forming apparatus, an ambient temperature determining means is equipped with a temperature gradient monitor part 60b for monitoring the temperature gradient of the surface 3a of a heating roller for a specified time in the case of equal temperature control that the temperature of the surface 3a of the heating roller is set to the target fixation temperature; and a calculation part 60c for calculating the total time in which the temperature gradient stays positive. If the total time in which the temperature gradient stays positive is shorter than a lower order threshold D1, the determining means determines that the ambient temperature is high, and a target temperature setting part 60a changes the set value of the target fixation temperature from T to T1. COPYRIGHT: (C)2004,JPO
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