Patent ID: 8862007

Claim:
A fixing device comprising: a heating member; a pressurizing member that makes pressured contact with the heating member; a coil wound in a loop shape in a width direction of the heating member, wherein the coil is configured to generate a magnetic flux that inductively heats the heating member; and a magnetic core adjacent to the coil, wherein the magnetic core is configured to apply the magnetic flux to an inductive heat-generating layer of the heating member; wherein the magnetic core includes: a plurality of first core parts that are positioned to enclose the coil in a direction orthogonal to a paper conveyance direction, wherein a recording medium is conveyed in the paper conveyance direction, a plurality of second core parts that are placed in hollow areas formed by loops of the coil at both ends in the direction orthogonal to the paper conveyance direction, wherein the plurality of second core parts have a lower Curie temperature and a lower thermal capacity than the plurality of first core parts, and wherein after a first fixing process is performed on a first recording medium and a surface temperature in non-feeding areas is raised above an upper fixing-ready temperature limit, a second fixing process is performed on a second recording medium having a larger width than the first recording medium, and wherein the first recording medium has a smaller width than a maximum width for the first fixing process and the second fixing process, and wherein after the surface temperature in non-feeding areas drops to or below the upper fixing-ready temperature limit, the second recording medium is inserted into a nip part formed by the heating member and the pressurizing member.