Patent ID: 7835680

Claim:
An image forming apparatus, comprising: an image forming unit for transferring a toner image to a sheet; and a fixing unit including a heating member and a pressing member and adapted to convey the sheet while holding the sheet between the heating member and the pressing member and to fix the toner image to the sheet by heat at least from the heating member in a conveying process, wherein: the heating member has a first area where a sheet does not come into contact with the heating member when the sheet being conveyed by the fixing unit passes the heating member, and a second area where the sheet comes into contact with the heating member when the sheet being conveyed by the fixing unit passes the heating member, the first area and the second area set according to the size of the sheet, and the fixing unit further includes: a coil for forming a magnetic field by generating magnetism for induction heating the heating member, a core made of a magnetic material to form a magnetic path near the coil, a magnetism adjusting member made of a nonmagnetic material, arranged on the magnetic path and having a closed frame having a hollow at an inside thereof, and a switcher capable of switching the magnetism adjusting member between a first state where the magnetism adjusting member generates an induction current resulting from the magnetic field to shield, inside the hollow, the magnetism in the first area, and a second state where the magnetism adjusting member generates no induction current and the magnetism is not shielded in the first area.