Patent ID: 7773929

Claim:
A fusing device comprising: a pressure member; a heating member, positioned with an outer surface thereof in contact with an outer surface of the pressure member, for heating a sheet that is being passed in a first direction through a contact area between the pressure member and the heating member; and an external heating member for heating a predetermined area of the surface of the heating member from outside, wherein: the predetermined area along a second direction that is perpendicular to the first direction is equal to a maximum-size sheet to be passed through the contact area in length along the second direction, the heating member is a cylindrical heat roller having first and second internal heater lamps positioned along a direction of an axis thereof, the first and second internal heater lamps respectively heating first and second areas, the first area being a central section of the heat roller, the second area being only opposite ends of the heat roller, the pressure member is a cylindrical pressure roller with an axis parallel to the axial direction of the heat roller, and the external heating member is shorter than each of the heat member and the pressure member in length along the second direction, the external heating member being a cylindrical external heat roller with an axis parallel to the axial direction of the heat roller, the external heat roller being positioned with an outer surface thereof in contact with the predetermined area, the external heat roller including an internal heater lamp positioned along an axial direction thereof, the internal heater lamp having a heating element.