| 摘要 |
PURPOSE:To control independently of the image forming conditions, by measuring the concentration on the photoreceptor to issue a concentration signal, and performing toner replenishment by judging from this concentration signal and the specified image forming conditions. CONSTITUTION:A development bias power source 4 is formed by plural power supplies E2-E4 and a selector switch S1 thereof. An amplifier A1 creates an output e1 corresponding to the quantity of light received by a photo diode D2, and this output becomes a concentration signal depending on the concentration on a photoreceptor 1. A development bias voltage Vd from the development bias power source 4 is divided down by voltage dividers R4, R5, and added to the concentration signal e1 in an addition circuit consisting of an amplifier A2 and resistances R6-R8. The output e2 of this addition circuit is compared with the reference voltage Vref made in the power source E5 and resistance R9 in an amplifier A3, and the toner concentration is set below a certain concentration, then the necessity of the toner replenishment is judged. The output E3 of this judgment is sent to the driving part of the toner replenishing mechanism in a developing device 3, so that the toner is sent into the developer. |
