| 摘要 |
PURPOSE:To control the supply of toner to a developing device, by switching the polarity of bias voltage to be impressed to a roll to be detected and detecting the density of toner charged to required polarity and toner charged to reverse polarity. CONSTITUTION:The density of a developer adhered to the surface of the roll 9 to be detected is detected by a density detector 10 and inputted to a control circuit 11 and a control signal corresponding to the density signal is transmitted to a toner feeding device 13. A bias voltage impressing means 12 is constituted so as to inverted to positive and negative polarity alternately at a fixed timing, and the toner charged to required polarity and the toner charged to reverse polarity are adhered to the roller 9 to be detected alternately. A detector 10 detects the toner density and the control circuit 11 controls the toner feeding device 13 so that toner is supplied during the developer is fresh and the ratio of toner supply is reduced when the developer is deteriorated. |
