| 摘要 |
PURPOSE:To suitably control a toner concentration even in plural reference concentrations by impressing a reference voltage in a voltage comparing means from the external part and changing the reference toner concentration of a developer. CONSTITUTION:When the type of a developer is changed and the necessity to change other toner concentration occurs, a variable resistance Rv is adjusted and the reference voltage is changed. Namely, when the toner concentration is controlled based on T1 and the variable resistance Rv is large, the reference voltage of a voltage comparing circuit 13 comes to be high, comes to be the value shown by E1 and the toner concentration can be set to the T1 of the low level. When the toner concentration is to be increased to T2, reversely, the variable resistance Rv is small and the reference voltage may be lowered to E2. The relation between the toner concentration changing width and the reference voltage changing width can be freely selected by considering the characteristic of a detecting circuit, the character of the developer and so on. |
