Patent ID: 7756459

Claim:
A fixing device, comprising: a fixing member having an outer peripheral face with which a sheet to be transported is brought into pressure contact; a coil placed along the outer peripheral face of the fixing member and made of a conductor coiled to form an elongated shape with respect to a width direction of the sheet to be transported for induction heating of a heat generating layer of the fixing member; and a magnetic substance core placed in such a way as to cover the coil at a position opposite to the fixing member with respect to the coil, wherein a magnetic flux generated by the coil passes a magnetic circuit made of the heat generating layer of the fixing member and the magnetic substance core, the magnetic substance core includes a plurality of main cores each having an elongated form along a circumferential direction of the fixing member and arrayed at intervals along the width direction of the sheet, the plurality of main cores are divided into central row main cores placed in a central section with respect to the width direction of the sheet and end row main cores placed in end sections with respect to the width direction of the sheet, and the end row main cores have a second shape effectively closer to the outer peripheral face of the fixing member compared to a first shape possessed by the central row main cores so as to enhance density of the magnetic flux, which passes the magnetic circuit, more in the end sections than in the central section with respect to the width direction of the sheet, wherein intervals between the end row main cores are smaller than intervals between the central row main cores.