Patent ID: 8750774

Claim:
A fixing device comprising: a heating member; a pressure member pressed to the heating member; a nip portion formed by pressure between the heating member and the pressure member so as to sandwich a recording medium carrying an unfixed toner image for melting and fixing the unfixed toner image on the recording medium; a coil wound in a loop shape in a longitudinal direction of the heating member so as to generate a magnetic flux for induction heating of the heating member; a cooling mechanism for cooling the coil; a magnetic core disposed close to the coil in a direction perpendicular to a conveying direction of the recording medium so as to guide the magnetic flux to an induction heating layer of the heating member; and a support member which is opposed to a surface of the heating member and has a mounting surface opposite to a surface opposed to the heating member, on which the coil and the magnetic core are mounted, wherein the magnetic core includes a plurality of first core portions arranged to surround the coil in the direction perpendicular to the conveying direction of the recording medium, and a second core portions disposed closer to the heating member than the first core portion on both end portions in the direction perpendicular to the conveying direction of the recording medium in a hollow portion formed by the coil loop, and the second core portion has a thermal capacity smaller than that of the first core portion, and Curie temperature of the second core portion is a temperature of the second core portion or higher when a temperature of the heating member becomes a fixable temperature and is a cooling set temperature of the coil or lower.