| 摘要 |
PROBLEM TO BE SOLVED: To provide a control method which prevents toner concentration control from runaway in the state that electrification characteristics of developer are drastically changed, bulk density of the developer also is changed and the relation between an increase/decrease in the toner concentration and an increase/decrease in the magnetic permeability is lost. SOLUTION: In this method for controlling toner concentration, a two-component developer which is composed of carrier and toner is held in a developing device 4 of an image forming device, the magnetic permeability of the held developer is detected by a magnetic permeability sensor 10 and a means which controls the toner concentration in the developing device 4 in accordance with detection output of the magnetic permeability sensor 10 is allowed to function. The relation between a change in the toner concentration and a change in the magnetic permeability of the developer is checked beforehand and, thereby, the propriety of toner concentration control by means of the toner concentration detection at the magnetic permeability sensor 10 is judged. In the case of convincing that the output of the magnetic permeability sensor 10 is changed in the direction of lowering the magnetic permeability when the toner is forcibly fed into the developing device 4 and the developer is stirred, the toner concentration control in accordance with the detected value of the magnetic permeability sensor 10 is performed. |
