Patent ID: 9454117
Filing Date: 2016-09-27
CPC Classification: G03G

Claim Text:
1. A fixing device comprising: a cylindrical fixing film; a backup member in contact with an inner surface of the fixing film, the backup member backing up the fixing film; a nip portion forming member in contact with an outer surface of the fixing film, the nip portion forming member and the backup member forming a fixing nip portion with the fixing film interposed therebetween; a metal plate provided on a surface on a side opposite to a surface on a side where the backup member is in contact with the fixing film, the metal plate reinforcing the backup member, a coil that forms an alternating magnetic field, which causes an electrically conductive layer to generate heat by electromagnetic induction, the coil including a spirally shaped portion of which a spiral axis is substantially parallel to a qeneratrix direction of the fixing film; and a core disposed inside the spirally shaped portion, the core directing lines of magnetic force of the alternating magnetic field, wherein a recording material carrying an unfixed image is conveyed at the fixing nip portion, and the unfixed image is fixed on the recording material by heat at the fixing nip portion, wherein the metal plate has a flat portion pressed against the backup member, wherein the fixing film includes the electrically conductive layer, and wherein the device causes a circulating current that flows in a circumferential direction of the fixing film, to flow through the electrically conductive layer of the fixing film, thereby causing the entire fixing film in the circumferential direction of the fixing film to generate heat, and wherein the current that flows through the electrically conductive layer in the circumferential direction is induced by the alternating magnetic field, thereby causing the electrically conductive layer to generate heat, and wherein the device satisfies the following equations: where R