Patent ID: 8355660

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 generating a magnetic field to induction heat the heating member; a fixed core made of a magnetic material and arranged around the coil to form a magnetic path between the fixed core and the heating member; a movable core made of a magnetic material and so provided between the fixed core and the heating member with respect to a direction in which the coil generates the magnetic field as to form the magnetic path together with the fixed core, the movable core having an axis intersecting with the generation direction of the magnetic field and being rotatable about the axis; a shielding member made of a nonmagnetic metal, provided on the movable core, and having a ring part capable of shielding magnetism in the magnetic field; a position switching unit rotating the movable core about the axis to move the shielding member between a shielding position where the ring part shields magnetism and a retracted position where the ring part does not shield magnetism, the shielding position being a position where the magnetic field penetrates the ring part in one direction and the retracted position being a position where the magnetic field penetrates the ring part in two directions; wherein: a first area requiring the magnetic shielding and a second area not requiring the magnetic shielding are selectively set in the heating member, the shielding member includes a first annular portion provided at a position corresponding to a boundary part between the first and second areas, and the first annular portion has a shape closed in a circumferential direction and has an insulated part disposed at a circumferential position to cut electrical connection of the shielding member in the circumferential direction.