Image forming apparatus featuring a rotatable belt member adjustment roller

An image forming apparatus comprising:

• a toner image forming portion for forming a toner image;
• a rotatable belt member which bears a toner image formed by the toner image forming portion;
• a transfer portion for forming a transfer nip portion which transfers the toner image on the belt member on to a recording material;
• an adjustment roller that is located next to the transfer portion at an upstream side of the transfer portion and at a downstream side of the toner image forming portion, in a belt moving direction of the belt member, and sets up the belt member by coming into contact with an inside surface of the belt member;
• a moving unit for moving the adjustment roller so that an advancing angle of the belt member advancing into the transfer nip portion changes;
• a guide member, which is arranged at an upstream side of the transfer nip portion in a recording material conveying direction and adapted to come in contact with a face of a recording material opposite to a face to which the toner image is transferred from the belt member, to guide the recording material to the transfer nip portion;
• and
• a controller for controlling the moving unit so that a belt face advancing into the transfer nip portion when a recording material having a first thickness is conveyed to the transfer nip portion is at a position farther from the guide member than the belt face advancing into the transfer nip portion when a recording material having a second thickness, smaller than the first thickness, is conveyed to the transfer nip portion.