| 摘要 |
PURPOSE:To enable toner concentration to be adequately determined in correspondence to set concentrations by automatically detecting and displaying the stains of toner concentration detecting parts. CONSTITUTION:Since a switching circuit 13b closes only when the thin film of the developer fails to be formed in its feed channel, an FF 13c sets and lights and energizes a display device 16a when the stains of toner concentration detecting parts 1a, 1b are larger than the preset reference value or the emission light quantity of a light emitting element 1b is insufficient. Hence when the operator removes the stains of the detecting parts 1a, 1b by viewing this or when the instantaneously closes a reset switch 16b after exchanging the light emitting element 1b, the FF13c resets to put out the device 16a. Next, when a print switch 14 is closed, the input of an operational amplifier 13 has lowered and therefore its output becomes of a level ''0'' and the FF13c is not set. Thereby, the toner concentration is adequately determined in correspondence to the preset concentration. |
