| 摘要 |
<p>PURPOSE:To inexpensively and accurately detect the deterioration of a photosensitive body by comparing an image density with the control reference value indicating the min. required image density and making judgement that the photosensitive body reaches the time for conversion when the image density as a result of the above-mentioned comparison is below the control reference value and when the presence of a toner is confirmed by a means for detecting the residual amt. of the toner. CONSTITUTION:The toner end signal by a density detecting sensor 7 of a reflected light type is outputted when the image density falls below the control reference value and the photosensitive body deteriorates (the electrostatic charge potential drops), but the toner in a toner hopper 10 is not always empty at this time and a piezoelectric sensor is in an ordinary mode and the toner end signal is not outputted if the toner exists in the toner hopper 10. The exchange of the photosensitive drum is displayed in a mechanical operating section at this time to urge the exchange of the photosensitive drum 4 to an operator. The deterioration of the photosensitive body is judged when the image density is degraded before the toner ends in such a manner, by which the deterioration of the photosensitive body is inexpensively and accurately detected.</p> |
