| 摘要 |
PURPOSE:To prevent quickly a photosensitive body from being used if the photosensitive body is broken by providing a means which detects variation in developing bias voltage or current and detects the broken part of the photosensitive body and a means which generates an alarm on the detection. CONSTITUTION:When an H signal is sent to D3-D0, a developing bias voltage of 500V is applied and development is carried out. At this time, said 500V is divided by resistance R1 and R2 to apply 5V to the minus input of a comparator 10 unless the photosensitive drum 1 has a broken part, and the rated voltage of 5V is divided by resistances R2 and R3 to apply 2V to the plus input, so the minus input is larger than the plus input and iNT2 inputs an L signal, so that normal copy sequence control is carried out. If there is a conductive broken part at part of a photosensitive drum 1, the output of a developing bias power source 4a is short-circuited through the broken part when the part reaches a developing part 4, so the minus input to the comparator 10 drops below 2V, and consequently the plus input is larger than the minus input and the iNT2 inputs the H signal, so that a DC controller 9 which receives it turns on an alarm buzzer 12. |
