| 摘要 |
PURPOSE:To control toner density simply without using any special sensor, by providing an electrode member made of a magnetic material near the outer circumference of a developing sleeve, and supplementing toner so that the value of a current flowing through the electrode member is constant. CONSTITUTION:The developing sleeve 3 is impressed with a bias voltage Vg and the electrode member 7 is provided near its outer circumference as a blade for specifying the height of toner tuft; and it is grounded through a resistance 8 and a capacitor 9 and a control circuit 10 is connected. When a two-component developer 5 moves, a voltage V is developed across the resistance 8 by a current flowing between the electrode member 7 and sleeve 3. This voltage V is compared with a reference voltage by the control circuit 10 and when the voltage drops below the reference voltage, a supplement roll 12 is driven to supplement toner 14. Toner density and the voltage V have comparison relation, so the toner density is held constant without using any sensor by making the voltage V constant. |
