| 摘要 |
A controller sets an AC voltage Vac, applies the voltage to a charging roller, and measures a DC component of a charging current flowing from the charging roller to a photosensitive drum. When it is determined that an absolute value of a measured value of the DC component in the charging current is lower than a prediction value, the controller sets an AC voltage Vac that differs from the AC voltage Vac set in step S4, and applies the voltage to the charging roller. Thereby, a charging current capable of performing sufficient charging can be flown to the photosensitive drum, and the photosensitive drum can thereby be charged to a desired surface potential. |
| 主权项 |
1. An image forming apparatus comprising:
a rotatable image bearing member; a charging member disposed proximate or in contact with the image bearing member, the charging member charging the image bearing member by applying a voltage having superimposed an AC voltage and a DC voltage as charging voltage during an image forming operation of forming an image on the image bearing member; an image forming unit forming an image on the image bearing member being charged by the charging member; a direct current detection unit capable of detecting a direct current flowing from the charging member to the image bearing member when the charging voltage is applied to the charging member; and a control unit capable of selectively executing a first mode of setting a voltage having superimposed a first AC voltage and the predetermined DC voltage as a charging voltage during an image forming operation, and a second mode of setting a voltage having superimposed a second AC voltage higher than the first AC voltage and the predetermined DC voltage as the charging voltage during the image forming operation, the control unit applying the voltage having superimposed the first AC voltage and the predetermined DC voltage to the charging member, and detecting a direct current flowing from the charging member to the image bearing member via the direct current detection unit during execution of the first mode, and if an absolute value of the detected direct current is lower than a predetermined value, switching the first mode to the second mode and executing the second mode. |
