| 摘要 |
PURPOSE: To stably control the concn. of toner in a developing device. CONSTITUTION: A CPU 67 decides that a phenomenon where the differences between the image area ratios of the N(>=1)th original and originals after the (n-l)th original are >=50% respectively, consecutively occurs by the previously set number of times. When a negative decision is obtained and further, the detected toner concn. is lower than an initial toner concn., the toner of a quantity corresponding to the difference in the toner concn. is supplied from a toner supplying tank 60 to a developing chamber 9 by a carrying screw 62 and when the detected toner concn. is higher than the initial toner concn., the supplying of the toner 63 is stopped. On the other hand, when a positive decision is obtained by the CPU 67, the toner 63 is supplied from the toner supplying tank 60 to the developing chamber 9 by the carrying screw 62, until a supplied toner quantity integrated with the result of the detection of the toner concn. is larger than that obtained by integration by a counter 66, after the positive decision. |
