Image-forming apparatus having charging potential control during non-image forming operation

1. An image-forming apparatus configured to execute an image-forming operation to form an image on a recording material, the image-forming apparatus comprising:

an image bearing member;

a driving portion configured to rotationally drive the image bearing member;

a charging member to be in contact with a surface of the image bearing member to form a charging portion, the charging member being configured to charge the surface of the image bearing member at the charging portion;

a developing member configured to supply the surface of the image bearing member with developer;

a charging voltage application portion configured to apply a charging voltage to the charging member; and

a control unit configured to control the driving portion and the charging voltage application portion,

wherein the control unit controls the image-forming operation and a non-image-forming operation different from the image-forming operation to be executable, the non-image-forming operation being an operation to apply the charging voltage to the charging member in a state where the image bearing member is rotated, and

wherein, in the non-image-forming operation, the control unit executes the following control processing:

i) not discharging electric charge between the charging member and the image bearing member and applying a first charging voltage having a first polarity with respect to a surface potential on the surface of the image bearing member to the charging member;

ii) after performing the processing of i), not discharging electric charge between the charging member and the image bearing member and applying a second charging voltage to the charging member, the second charging voltage having a polarity opposite to the first polarity with respect to the surface potential; and

iii) after performing the processing of ii), controlling a third charging voltage having a second polarity with respect to the surface potential to be applied to the charging member and controlling a fourth charging voltage having a polarity opposite to the second polarity with respect to the surface potential to be applied to the charging member, and controlling electric charge to be discharged between the charging member and the image bearing member in a case where at least one of the third charging voltage and the fourth charging voltage is applied as the charging voltage.

2. The image-forming apparatus according to claim 1 , wherein the developing member is configured to be in contact with the image bearing member in the non-image-forming operation.

3. The image-forming apparatus according to claim 1 , further comprising a developing container configured to contain the developer,

wherein a developer supply container is attachable to the developing container, and

wherein the control unit controls the non-image-forming operation to be executed after the developer supply container is attached to the developing container and developer is supplied into the developing container.

4. The image-forming apparatus according to claim 1 , further comprising a developing container configured to contain the developer,

wherein the developing container is detachably attached to the image-forming apparatus, and

wherein the control unit controls the non-image-forming operation to be executed after the developing container is replaced with another developing container.

5. The image-forming apparatus according to claim 1 , wherein the control unit controls the first polarity and the second polarity to be set to the same polarity.

6. The image-forming apparatus according to claim 1 , wherein the control unit controls the first polarity and the second polarity to be set to opposite polarities.

7. The image-forming apparatus according to claim 1 , wherein the control unit controls a first repetitive operation to repetitively execute the processing in i) and the processing in ii) to be executable, and controls, in the first repetitive operation, a first potential difference between the surface potential and the first charging voltage to gradually increase.

8. The image-forming apparatus according to claim 7 , wherein the control unit controls, in the first repetitive operation, a second potential difference between the surface potential and the second charging voltage to gradually increase.

9. The image-forming apparatus according to claim 1 , wherein the control unit controls a second repetitive operation to repetitively execute the processing in iii) to be executable, and controls, in the second repetitive operation, a third potential difference between the surface potential and the third charging voltage to gradually increase.

10. The image-forming apparatus according to claim 9 , wherein the control unit controls, in the second repetitive operation, a fourth potential difference between the surface potential and the fourth charging voltage to gradually increase.

11. An image-forming apparatus configured to execute an image-forming operation to form an image on a recording material, the image-forming apparatus comprising:

an image bearing member;

a driving portion configured to rotationally drive the image bearing member;

a charging member to be in contact with a surface of the image bearing member to form a charging portion, the charging member being configured to charge the surface of the image bearing member at the charging portion;

a developing member configured to supply the surface of the image bearing member with developer charged to a normal polarity;

a charging voltage application portion configured to apply a charging voltage to the charging member; and

a control unit configured to control the driving portion and the charging voltage application portion,

wherein the control unit controls the image-forming operation and a non-image-forming operation different from the image-forming operation to be executable, the non-image-forming operation being an operation to apply the charging voltage to the charging member in a state where the image bearing member is rotated, and

wherein in the non-image-forming operation, the control unit executes the following control processing:

i) not discharging electric charge between the charging member and the image bearing member and applying a first charging voltage and a second charging voltage to the charging member, the first charging voltage having a polarity opposite to the normal polarity with respect to a surface potential on the surface of the image bearing member, the second charging voltage having the opposite polarity and having a magnitude different from the magnitude of the first charging voltage; and

ii) after performing the processing of i), controlling a third charging voltage having a first polarity with respect to the surface potential to be applied to the charging member and controlling a fourth charging voltage having a polarity opposite to the first polarity with respect to the surface potential to be applied to the charging member, and controlling electric charge to be discharged between the charging member and the image bearing member in a case where at least one of the third charging voltage and the fourth charging voltage is applied as the charging voltage.