| 摘要 |
In an image forming apparatus employing a two-component developing system, there are provided print-sheet number counting means; developing-device drive time integrating means for integrating time during which a developing device drives; and a toner replenishing motor drive time integrated drive time integrating means for integrating time during which a toner replenishing motor drives. Integrated drive time of the developing device and integrated drive time of the motor toner replenishing motor every fixed printed-sheet number, and the toner consuming quantity per drive time of the developing device is calculated from the extracted data. The toner charge quantity in a developer is predicted on the basis of the calculated data, and a developing bias voltage applied to the developing device is changed to thereby revised an image density.
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