| 摘要 |
PURPOSE:To enable invariably stable and highly reliable toner concentration control by not setting an initial set value when a toner concentration target value is an upper-limit or lower-limit value at the time of the toner concentration control. CONSTITUTION:With a developer concentration signal obtained by detecting the toner concentration in a developing unit, the toner concentration is controlled to the target value between the specific upper-limit value and lower-limit value, and the target value is corrected with a pattern image density signal obtained by detecting the density of a reference pattern image formed on a photosensitive body. In this toner density control method, the pattern image density signal is generated by comparing the ratio of the detected value of the density of the reference pattern image and the detected value of the density of a ground part with the initial set value and when the target value is equal to the upper- limit or lower-limit value, setting operation for the initial set value is not performed. Consequently, abnormal image density due to improper initial value setting under the toner concentration control can be prevented. |
