| 摘要 |
PROBLEM TO BE SOLVED: To achieve the precise control of toner concentration and improvement in image quality by controlling the toner concentration, based on the peak value of the output ripple of a magnetic permeability sensor. SOLUTION: The toner concentration is controlled, based on the top (peak value) of the output ripple of the magnetic permeability sensor 14. By using the peak value of the output ripple as control data in such a way, it does not drop below a reference value even if the level of developer in a developing device 5 becomes low due to a temporary toner concentration decrease, therefore toner is supplied from a toner bottle 16 and proper toner concentration is maintained. Where the number of the rotations of a carrying member 10 is (r), (rpm), the data of the magnetic permeability sensor 14 divided at regular intervals, equal to or longer than 60/r(sec), is the peak value of each interval, and it is preferable that an average value in a fixed period of time be used as the control data. Thus, the toner concentration can be controlled more precisely. |
