| 摘要 |
PURPOSE:To obtain an image of high quality by recovering excessive magnetic toner electrostatically from a laminar developer formed on the surface of a developing roll and holding the toner concentration of the developer supplied to a development area within the best range. CONSTITUTION:When a developing roll 4 is driven, the developer 10 consisting of magnetic toner and magnetic carriers moves attracted on the surface of the developing roll 4 to develop an electrostatic charge image carried on the surface of a carrier 1, and the excessive developer 10a is fed back into a developer tank 2. In this case, when the toner concentration measured by a toner concentration sensor 8 is large, the bias voltage of a bias voltage source 12 is increased through a control means 13 with an electric signal and a toner recovery roll 9 attracts and removes magnetic toner in the developer 10 moving attracted on the surface of the developing roll 4 electrostatically to control the toner concentration into the best range. Consequently, the image of high quality which is free from fogging and dust is obtained. |
