| 摘要 |
PURPOSE:To make constant a picture density regardless of the history of a developing agent by detecting the number of copies from the time of the exchanging of the developing agent and correcting the picture density in the device to detect the toner concn. and control the supply of the toner. CONSTITUTION:The toner concn. is detected by a sensor 2 of the inductance, and the signal is inputted to an oscillating device 3 and a frequency-voltage converting device 4. Next, a toner supply judging circuit 7 compares the toner concn. detecting signal with the reference voltage, when the density is lower, the signal is inputted to a toner supply member driving circuit 8 and the toner is supplied. When the number of times of agitating is increased for the toner, the signal level is decreased as well as the toner concn. is decreased. Then, a copy counter 10 detects the number of the copies from the time of the exchanging of the toner, counts 9 the developing unit driving time, inputs the correcting signal to a reference voltage adjusting device 6, and corrects the level of the reference voltage for the changing part only due to the number of the times of agitating the toner. Consequently, since the picture density is corrected by the history of the developing agent, the constant density can be obtained. |
