INDUCTION HEATING UNIT AND FIXING DEVICE AND IMAGE FORMING APPARATUS EQUIPPED WITH THE SAME

PROBLEM TO BE SOLVED: To suppress dispersion of magnetic flux by exciting coils and suitably suppressing excessive rising of temperature in a region outside the paper width due to continuous passage of paper of a narrow width. SOLUTION: The induction heating unit has: the exciting coils 31 existing extended over a whole region of maximum heat in a heat roller 21 and generating the magnetic flux interlinking the heating roller; a plurality of arch cores 34 forming magnetic paths guiding the magnetic flux generated by these exciting coils and arranged separated in the axial direction of the heat roller ; cancel coils 35 to 37 being disposed along the arch cores in the heat suppress area in the outside of the region of minimum heat, for deteriorating the function of those arch cores as the magnetic paths; switches 41 to 43 for switching between an activated state and an inactivated state of those cancel coils by opening/closing an energizing path connecting both ends of the cancel coils; and a magnetic shielding plate 39 including conductive material for suppressing the dispersion of the magnetic flux to a side opposite to the heating roller. COPYRIGHT: (C)2010,JPO&INPIT