Image forming apparatus that controls voltages to reduce image fogging

An image forming apparatus comprising:

• photosensitive drum that is rotatable;
• a charging roller that comes into contact with the photosensitive drum to form a charging portion and that charges a surface of the photosensitive drum at the charging portion;
• an exposure unit that exposes the photosensitive drum to form an electrostatic latent image on the surface of the photosensitive drum;
• a developing roller that bears a developer charged to have a normal polarity and supplies the developer to the electrostatic latent image formed on the surface of the photosensitive drum to form a developer image on the surface of the photosensitive drum;
• a transfer roller that comes into contact with the photosensitive drum to form a nip and transfers the developer image onto a recording material conveyed to the nip;
• a charging voltage application portion that applies a charging voltage of the normal polarity to the charging roller;
• a developing voltage application portion that applies a developing voltage to the developing roller;
• a transfer voltage application portion that applies a transfer voltage to the transfer roller;
• and
• a controller that controls the charging voltage application portion, the developing voltage application portion, and the transfer voltage application portion,
• wherein, when a region of the photosensitive drum that comes into contact with the recording material at the nip in a state in which the transfer voltage is applied to the transfer roller and the recording material is held by the nip is assumed as a first region, a region of the photosensitive drum that comes into contact with the transfer roller in a state in which the transfer voltage is applied to the transfer roller and the recording material is not held by the nip is assumed as a second region, a region of the photosensitive drum after the first region passes through the nip and before the second region passes through the nip is assumed as a third region, and the third region comes into contact with the recording material at the nip in a state in which the transfer voltage is applied to the transfer roller and the recording material is held by the nip,
• the controller controls to apply a first developing voltage to the developing roller when the first region in which a first surface potential has been formed at the charging portion to which a first charging voltage has been applied faces the developing roller and apply a second developing voltage lower than an absolute value of the first developing voltage to the developing roller when the second region in which a second surface potential has been formed at the charging portion to which a second charging voltage has been applied faces the developing roller after the recording material passes through the nip,
• the second charging voltage has a polarity that is the same as a polarity of the first charging voltage and is lower than an absolute value of the first charging voltage,
• the controller controls to apply a third charging voltage to the third region in which a third surface potential has been formed at the charging portion, and
• the third charging voltage has a polarity that is the same as a polarity of the second charging voltage and is higher than an absolute value of the second charging voltage.