US Patent 7477858 Image forming apparatus using a belt fixing unit

An image forming apparatus may include a belt fixing unit and a controller. The belt fixing unit includes a moving fixing belt heated by a heater, a pressure member provided inside the fixing belt, a pressure roller provided opposite to the pressure member through the fixing belt to form a nip portion, a transfer material having a toner image thereon passing the nip portion and thereby the toner image being fixed on the transfer material, and a pressing force change unit capable of changing a pressing force of the pressure member against the pressure roller. The controller controls the pressing force change unit to change the pressing force according to print information for both faces of the transfer material.