| 摘要 |
PURPOSE:To surely recognize the exchange time of developer by judging the exchange of the developer and resetting a developer exchange counter when toner concentration is lower than a reference value which is set lower than standard concentration. CONSTITUTION:A toner concentration detecting device 37, for example, a light emitting part 38 and a light receiving part 39 are arranged in a developer tank 21, and light is projected from the light emitting part 38, for example, a lamp to the light receiving part 39, for example, CdS so as to detect the liquid concentration, for example, the toner concentration of the developer passing between the light emitting part 38 and the light receiving part 39. When the developer concentration becomes equal to or under a specified value, the toner is supplied by a supply means, so that the appropriate concentration is always kept. Namely, when the toner concentration detected by the means 37 is lower than the reference value which is set lower than the standard concentration, the developer exchange counter is reset by judging that the developer is exchanged. Therefore, a developer exchange counter is automatically reset, and the exchange time of the developer is surely recognized. |
