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

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 controls the charging voltage application portion to apply a first charging voltage, a second charging voltage, a third charging voltage, and a fourth charging voltage in this order such that
• i) a first electric field is formed between a surface potential formed on the surface of the image bearing member and the charging member by applying the first charging voltage,
• ii) a second electric field opposite to the first electric field is formed between the surface potential and the charging member by applying the second charging voltage,
• iii) a third electric field is formed between the surface potential and the charging member by applying the third charging voltage, and
• iv) a fourth electric field opposite to the third electric field is formed between the surface potential and the charging member by applying the fourth charging voltage, and
• wherein the control unit controls the charging voltage application portion such that
• v) electric discharge does not occur between the charging member to which the first charging voltage is applied and the image bearing member,
• vi) electric discharge does not occur between the charging member to which the second charging voltage is applied and the image bearing member, and
• vii) electric discharge occurs between the charging member and the image bearing member in a case where at least either one of the third charging voltage and the fourth charging voltage is applied.