Patent ID: 9405249
Filing Date: 2016-08-02
CPC Classification: G03G,H05B

Claim Text:
1. A fixing device for fixing an image on a recording material, comprising: a rotatable member including an electroconductive layer; a helical coil provided inside said rotatable member, said helical coil having a helical axis direction along a generatrix direction of said rotatable member; a magnetic member extending in a helically shaped portion formed by said coil, wherein said magnetic member does not form a loop outside the electroconductive layer; a frequency setting portion configured to set the frequency of an AC current caused to flow through said coil; and a temperature detecting portion configured to detect the temperature of said rotatable member, said temperature detecting portion including a first temperature detecting member configured to detect the temperature of said rotatable member at a central portion with respect to the generatrix direction and a second temperature detecting member configured to detect the temperature of said rotatable member at an end portion with respect to the generatrix direction, wherein the electroconductive layer generates heat through electromagnetic induction heating by the magnetic flux resulting from the AC current, and the image is fixed on the recording material by the heat of said rotatable member, and wherein said frequency setting portion sets the frequency depending on a value of a difference between a detection temperature of said first temperature detecting member and a detection temperature of said second temperature detecting member.