Image forming apparatus having charging voltage and developing voltage stepwise control

An image forming apparatus comprising:

• a rotatable image bearing member;
• a charging member configured to charge a surface of the image bearing member;
• a developing member in contact with the surface of the image bearing member in a developing portion and configured to form a toner image by supplying toner to the surface of the image bearing member charged by the charging member;
• a charging voltage applying portion configured to apply a charging voltage to the charging member;
• a developing voltage applying portion configured to apply a developing voltage to the developing member;
• and
• a controller configured to control the charging voltage applying portion and the developing voltage applying portion,
• wherein the controller controls to perform a preparation operation before start of image formation in which the toner image to be transferred to a recording material is formed on the image bearing member so that rotation of the image bearing member is started in a state in which the developing member is in contact with the image bearing member, and the charging voltage and the developing voltage are changed stepwise respectively so that a potential difference between a surface potential of the image bearing member and the developing voltage in the developing portion becomes a predetermined value,
• wherein while changing stepwise the charging voltage in the preparation operation, in a state in which the developing member is rotating while in contact with the image bearing member,
• the controller controls the charging voltage applying portion so as to change the charging voltage to a first charging voltage of the same polarity as during the image formation and an absolute value thereof lower than a discharge start voltage from a state in which the charging voltage is not applied to the charging member, and then so as to change the charging voltage to a second charging voltage, of the same polarity as during the image formation and the absolute value thereof equal to or greater than the discharge start voltage, from the first charging voltage,
• wherein an absolute value of the first charging voltage is greater than a difference between the absolute value of the second charging voltage and the absolute value of the first charging voltage.