HEAT-FIXING DEVICE

摘要

A fixing device includes: a rotatable member including an electroconductive layer; a helical coil having a helical axis direction along a generatrix direction of said rotatable member; a magnetic member not forming a loop outside the electroconductive layer; a frequency setting portion for setting a frequency of an AC current caused to flow through said coil; and a temperature detecting portion for detecting a temperature of said rotatable member, including a first temperature detecting member and a second temperature detecting member. The electroconductive layer generates heat through electromagnetic induction heating by magnetic flux resulting from the AC current, and an image is fixed on a recording material by heat of said rotatable member. The 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.

主权项

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 from a loop outside the electroconductive layer; a frequency setting portion for setting a frequency of an AC current caused to flow through said coil; and a temperature detecting portion for detecting a temperature of said rotatable member, said temperature detecting portion including a first temperature detecting member for detecting the temperature of said rotatable member at a central portion with respect to the generatrix direction and a second temperature detecting member for detecting 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 magnetic flux resulting from the AC current, and the image is fixed on the recording material by 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.