| 摘要 |
PURPOSE:To prevent the thermal deterioration of a heat fixing device owing to overshoot by keeping a heat source off during the time since the temp. of the heat fixing device attains the prescribed temp. lower than a preset temp. until said temp. exceeds the preset temp. and decreases again to the set temp. CONSTITUTION:A comparator 22 compares a signal Sr and the signal S corresponding to the surface temp. T of a roller 12 outputted from a temp. sensor 23 and outputs a signal ''0'' when the signal Sr is larger than the signal S. The comparator outputs a signal ''1'' and applies the same to a CPU20 when said signal is smaller. A comparator 24 compares similarly the signal Ss corresponding to the set temp. Ts and the output signal S of the sensor 23 and applies the same to the CPU20. The CPU20 controls the temp. of the heat fixing device 10 in accordance with the compared output ''0'' or ''1'' from the comparators 22 and 24. The heat fixing device is thereby stopped before the surface temp. of the roller attains the set temp. The thermal deterioration of the release layer on the roller surface and stripping pawl powing to the overshoot is thus prevented. |
