| 摘要 |
PROBLEM TO BE SOLVED: To form an image of good image quality at all times by applying a bias voltage having a specific current value to the roller shaft of a supply roller, and securely supplying normally-electrified toner to a developing roller. SOLUTION: A CPU 61 controls a control circuit 66 based on the value of each sensor and a program and so on stored in a ROM 62. To the roller shaft of the developing roller 27, a bias voltage, a constant voltage, is applied from a high-voltage power source circuit 67 via the control circuit 66. Also, because the toner having a positive-electrification characteristic is used, a voltage which causes the toner to move toward the developing roller 27 is applied to the toner supply roller 31. Therefore, in the process unit, constant-current control is exerted over a DC power source circuit 69, which applies the bias voltage to the roller shaft of the toner supply roller 31, so as to give a specific current value, thereby causing the specific current to flow between the toner supply roller 31 and the developing roller 27 even in case insulation films or the like are formed on the surfaces of the toner supply roller 31 and developing roller 27. |
