IMAGE FORMING DEVICE AND ITS METHOD

PROBLEM TO BE SOLVED: To attain stable fixation, without causing the dropping of a fixing temp. due to the passage of a paper sheet and the overrising of temp. due to the control of the fixing temp. by changing the set temp. of a fixing means to a high set temp. higher than a standard temp. as a normal set temp., at the time of forming an image. SOLUTION: When an instruction to start copying is issued from a final control element 202, a CPU 201 generates an image formation starting signal, for instructing each part to start the formation of the image. In other words, each of control parts and driving parts after receiving the image formation starting signal starts the operation of preparing to start the formation of the image. A fixing temperature control part 90C after receiving the image formation starting signal changes the set temp. in a fixing unit 90 to the high set temp. from the standard set temp. In other words, the set temp. is switched to a high set temperature of 200 deg.C from a standard set temperature of 190 deg.C, for instance, with the image formation starting signal, so that the temp. of a heater 96 in a heating roller 91 is controlled to keep the high set temp. Further, the CPU 201 sets time to keep the high set temp.