Image forming apparatus including transfer roller mechanism

An image forming apparatus, comprising:

• a belt member formed in a loop, to move in a predetermined direction and bear a toner image on a surface thereof;
• a contact member disposed inside the loop formed by the belt member, to contact an inner circumferential surface of the belt member;
• a rotary pressing member disposed outside the loop, to contact the contact member through the belt member and form a nip between the contact member and the rotary pressing member via the belt member through which a recording medium bearing the toner image is conveyed;
• a transfer device to form an electric field between the contact member and the rotary pressing member to transfer the toner image formed on the belt member onto the recording medium;
• and
• a positioning mechanism that changes an amount of winding of the belt member around the rotary pressing member between a first state in which the belt member is wound around the rotary pressing member upstream from the nip in the direction of movement to the nip and a second state in which the amount of winding of the belt member around the rotary pressing member is reduced from the first state while the rotary pressing member contacts the belt member.