| 摘要 |
PURPOSE:To permit adequate maintenance of a toner concn. in a developing chamber by detecting the toner concn. after an image area on a photosensitive drum passes a developing roller part and replenishing the toner in accordance with the result of the detection. CONSTITUTION:The toner concn. is detected after the developing area of the photosensitive drum 10 passes the developing roller 206 part at the time of replenishing the toner from a toner chamber 204 to the developing chamber 202 during the non-napping period of the toner when the developing roller 206 is rotated backward from the rotation at the time of development. Whether the prescribed toner concn. is satisfied or not is judged in accordance with the result of the detection. The speed of a toner replenishing roller at which the deficient amt. can be made up as well as the period of non-napping are calculated when the deficiency is judged. The toner replenishment is executed in accordance with the calculated value. The toner is replenished in the optimum amt. at which the target toner concn. can be obtd. in accordance with the result of the detection of the toner concn. and, therefore, the adequate toner concn. is obtd. with high accuracy.
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