| 摘要 |
PURPOSE:To remove the variance in printing density by comparing a voltage corresponding to a set toner concentration level with a voltage based upon toner cencentration to be changed in proportional to the using quantity of a developer and calculating said voltage and converting the output to a logic level and driving a toner replenishing motor in with a logic level. CONSTITUTION:A switch 10 sets the toner concentration level in accordance with the using quantity of the developer and a toner concentration sensor 8 outputs a voltage proportional to the toner concentration to be changed in accordance with the using quantity of the developer. An operational amplifier 6 adds/subtracts the output of the sensor 8 and the voltage corresponding to the toner concentration level set by the switch 10, a butter circuit 11 converts the output of the amplifier 6 into a logic level and a toner feeding means 7 is driven in accordance with the logic level. When the toner concentration in the developer is lowered lower than a previously determined toner concentration level, toner is replenished and controlled so as to coincide with the toner concentration level. Consequently, the variance in printing density can be removed. |
