Image forming apparatus with brush that collects material adhered to surface of image bearing member and that includes brush portion including threads having specified thread density

An image forming apparatus comprising:

• a rotatable image bearing member;
• a charging unit that contacts the image bearing member to form a charging portion, and that charges a surface of the image bearing member in the charging portion;
• an exposure unit that exposes the surface of the image bearing member charged in the charging portion to form an electrostatic latent image;
• a developing roller that contacts the surface of the image bearing member to form a developing portion and that supplies a one-component toner charged to have a predetermined polarity to the electrostatic latent image formed on the surface of the image bearing member to form a toner image;
• a transfer unit that contacts the image bearing member to form a transfer portion, and that transfers the toner image formed on the surface of the image bearing member onto a recording material in the transfer portion;
• a brush that has conductivity and that collects an adhering material adhered to the surface of the image bearing member downstream of the transfer portion and upstream of the charging portion in the rotating direction of the image bearing member and that comprises a brush portion which comprises threads;
• a voltage application unit that applies a voltage of the predetermined polarity to the brush;
• and
• a controller that controls the voltage application unit,
• wherein the developing roller collects residual toner on the surface of the image bearing member after the toner image has been transferred onto the transfer material in the transfer portion,
• wherein the controller controls the voltage application unit such that a potential difference between a voltage of the predetermined polarity applied to the brush and a surface electric potential of the image bearing member on the surface of the image bearing member is not more than a discharge threshold, and
• wherein the threads have a thread density of 110 to 300 kF/inch2.