Patent ID: 8229339

Claim:
A fixing device comprising: a heating member; a pressing member; the heating member and the pressing member fixing a toner image to a sheet by heat from the heating member while conveying the sheet having the toner image transferred thereto in a sandwiched state, a coil arranged along an outer surface of the heating member and generating a magnetic field to induction heat the heating member; a magnetic core arranged around the coil to form a magnetic path between the heating member and the magnetic core, and guiding the magnetic field generated by the coil to the heating member; a path switching member switching the magnetic path between a first path in which the induction heating of the heating member is promoted and a second path in which the induction heating of the heating member is inhibited; and a magnetism adjustment member fixedly arranged over a range of the magnetic field including the first path and the second path; the magnetism adjustment member being configured to allow a passage of a magnetic flux from the magnetic core towards the heating member within the magnetic field range when the magnetic path is switched by the path switching member to the first path, and to shield the magnetic flux without allowing the passage of the magnetic flux within the magnetic field range when the magnetic path is switched to the second path, wherein the magnetism adjustment member has a plurality of ring-shaped portions that are formed from a single wire material having an endless shape, and each of the ring-shaped portions extends in a longitudinal direction of the magnetic core according to a size of the sheet.