Image forming apparatus with cleaning mode using AC voltage

1. An image forming apparatus, comprising:

an image bearing member;

a charging member configured to charge the image bearing member;

a voltage applying device configured to apply a voltage to the charging member; and

a control unit configured to control the voltage applying device so as to perform a cleaning mode for applying an AC voltage to the charging member with the voltage applying device while moving a surface of the image bearing member during non-image formation of the image forming apparatus,

wherein a period of time during which the cleaning mode is performed includes a first time-period during which a first AC voltage is applied and a second time-period during which a second AC voltage is applied, and a period of the first AC voltage is different from a period of the second AC voltage,

wherein a peak-to-peak voltage value of the first AC voltage is the same as a peak-to-peak voltage value of the second AC voltage, and

wherein the first and second AC voltages are non-sinusoidal.

2. An image forming apparatus according to claim 1 ,

wherein the second time-period is provided after the first time-period, and the period of the first AC voltage is longer than the period of the second AC voltage.

3. An image forming apparatus according to claim 2 , wherein a negatively charged particle is mainly transferred from the charging member onto the image bearing member during the first time-period, and a positively charged particle is mainly transferred from the charging member onto the image bearing member during the second time-period.

4. An image forming apparatus, comprising:

an image bearing member;

a charging member configured to charge the image bearing member;

a voltage applying device configured to apply a voltage to the charging member; and

a control unit configured to control the voltage applying device so as to perform a cleaning mode for applying an AC voltage to the charging member with the voltage applying device while moving a surface of the image bearing member during non-image formation of the image forming apparatus,

wherein a period of time during which the cleaning mode is performed includes a first time-period during which a first AC voltage is applied and a second time-period during which a second AC voltage is applied, and a period of the first AC voltage is different from a period of the second AC voltage, and

wherein a moving speed of the surface of the image bearing member during the first time-period is different from a moving speed of the surface of the image bearing member during the second time-period.

5. An image forming apparatus according to claim 2 , wherein a moving speed of the surface of the image bearing member during the first time-period is lower than a moving speed of the surface of the image bearing member during the second time-period.

6. An image forming apparatus, comprising:

an image bearing member;

a charging member configured to charge the image bearing member;

a voltage applying device configured to apply a voltage to the charging member; and

a control unit configured to control the voltage applying device so as to perform a cleaning mode for applying an AC voltage to the charging member with the voltage applying device while moving a surface of the image bearing member during non-image formation of the image forming apparatus,

wherein a period of time during which the cleaning mode is performed includes a first time-period during which a first AC voltage is applied and a second time-period during which a second AC voltage is applied, and a duty ratio of the first AC voltage is different from a duty ratio of the second AC voltage.

7. An image forming apparatus according to claim 6 ,

wherein the second time-period is provided after the first time-period, and the duty ratio of the second AC voltage is larger than the duty ratio of the first AC voltage.

8. An image forming apparatus according to claim 7 , wherein a negatively charged particle is mainly transferred from the charging member onto the image bearing member during the first time-period, and a positively charged particle is mainly transferred from the charging member onto the image bearing member during the second time-period.