| 摘要 |
PURPOSE:To appropriately control a concentration even if one developing unit and one sensor handle developers with different characteristics by setting a reference level required for controlling the concentration of a developer according to an output that a detection means detects. CONSTITUTION:The sensor 10 consisting of a magnetic sensor, for instance, is mounted onto the interior of the developing unit. The output signal of the sensor 10 is supplied to one input terminals of 1st and 2nd comparators 12 and 13 constructing a developer concentration selection circuit 11. Reference voltages Vsh and Vsl setting the reference level for stop control are supplied to the other input terminals of the comparators 12 and 13. By adjusting a variable resistance 16, the reference voltages Vsh and Vsl required for controlling the concentration of the developer can be set according to the characteristics of the developer. If the developing unit with the same constitution, which is adjusted under the same conditions, houses developers with different characteristics, it can appropriately control their concentrations. |
