| 摘要 |
PURPOSE:To detect abnormal lighting securely even before a warm-up of the device is finished, and to prevent the abnormal lighting in advance, by outputting an abnormality detecting signal when the lighting is decided from the current to feed to a heater when a finishing signal of a selected timer means is output. CONSTITUTION:The threshold value voltage of a comparison circuit 45, that is, the counting time from the lighting of a lamp to an abnormality detecting, is converted in the period from the time when a main switch is turned on, and the heat lamps 15a and 15b of a heat fixation device 13 are lighted, to the time the worm-up of the preparation operation to raise the surface temperature of the heat rolls 14 and 17 up to a specific temperature is finished, and in the waiting time of a copying operation after the warm-up is finished, and an abnormal lighting is detected. And, before the warm-up is completed, the threshold value voltage of the circuit 45 is converted according to the surface temperature of the rolls 14 and 17 at the on-edge of lighting of the lamps 15a and 15b to set an optimum threshold value voltage, so as to detect the abnormal lighting of lamps. |
