| 摘要 |
PURPOSE:To suitably control a toner concentration even when the environmental conditions of a developing device are changed by changing the reference voltage in a voltage comparing means through the output signal of an external environment detecting means and changing the reference toner concentration of a developer. CONSTITUTION:A reference voltage correcting circuit 11 is connected to an external environment detecting means 12 and the external environment detecting means 12 uses, for example, a temperature sensor or respective types of the sensor such as a humidity sensor. In a certain type of the condition to use the developer, when the reference voltage is set to E0, to control a toner concentration by the signal of a detecting circuit 10 based on a reference toner concentration T0 is the same as the conventional device. When the characteristic of the developer is changed by the change of temperature or humidity, a reference voltage correcting circuit 11 is operated by the signal of the external environment detecting means 12, the reference voltage of a voltage comparing circuit 9 is changed, and the inconvenience due to the shifting of a characteristic curve (a) to a1 or a2 can be prevented beforehand. |
