Image fixing device

A fixing device configured to fix an image on a recording material by heating the recording material where the image is formed, comprising:na cylindrical rotary member including an electroconductive layer;a coil configured to form an alternating magnetic field which subjects the electroconductive layer to electromagnetic induction heating, the coil including a spiral shaped portion which is disposed in the rotary member so that a spiral axis of the spiral shaped portion extends along a generatrix direction of the rotary member; anda core configured to induce magnetic force lines of the alternating magnetic field, the core being disposed in the spiral shaped portion;wherein magnetic resistance of the core is, with an area from one end to the other end of the maximum passage region of the image on a recording material in the generatrix direction, equal to or smaller than 30% of combined magnetic resistance made up of magnetic resistance of the electroconductive layer and magnetic resistance of a region between the electroconductive layer and the core.

A fixing device configured to fix an image on a recording material by heating a recording material where an image is formed, comprising:na cylindrical rotary member including an electroconductive layer;a coil configured to form an alternating magnetic field which subjects the electroconductive layer to electromagnetic induction heating, the coil including a spiral shaped portion which is disposed in the rotary member so that a spiral axis of the spiral shaped portion extends along a generatrix direction of the rotary member; anda core configured to induce magnetic force lines of the alternating magnetic field, the core having a shape where a loop is not formed outside the rotary member and being disposed in the spiral shaped portion;wherein 70% or more of magnetic force lines output from one end of the core in the generatrix direction pass over the outside of the electroconductive layer and return to the other end of the core.

A fixing device configured to fix an image on a recording material by heating the recording material where the image is formed, comprising:na cylindrical rotary member including an electroconductive layer;a coil configured to form an alternating magnetic field which subjects the electroconductive layer to electromagnetic induction heating, the coil including a spiral shaped portion which is disposed in the rotary member so that a spiral axis of the spiral shaped portion extends along a generatrix direction of the rotary member; anda core configured to induce magnetic force lines of the alternating magnetic field, the core being disposed in the spiral shaped portion;wherein relative permeability of the electroconductive layer and relative permeability of a member in a region between the electroconductive layer and the core, in an area from one end to the other end of the maximum passage region of the image on a recording material in the generatrix direction, are smaller than 1.1; andwherein the fixing device satisfies a following relational expression (1) with a cross section perpendicular to the generatrix direction throughout the area:n0.06×μc×Sc≧Ss+Sa  (1)nwhere Ss represents a cross-sectional area of the electroconductive layer, Sa represents a cross-sectional area of a region between the electroconductive layer and the core, Sc represents a cross-sectional area of the core, and μc represents a relative permeability of the core.

A fixing device configured to fix an image on a recording material by heating the recording material where the image is formed, comprising:na cylindrical rotary member including an electroconductive layer;a coil configured to form an alternating magnetic field which subjects the electroconductive layer to electromagnetic induction heating, the coil including a spiral shaped portion which is disposed in the rotary member so that a spiral axis of the spiral shaped portion extends along a generatrix direction of the rotary member; anda core configured to induce magnetic force lines of the alternating magnetic field, the core being disposed in the spiral shaped portion;wherein the electroconductive layer is formed of a non-magnetic material, and the core has a shape where a loop is not formed outside the rotary member.

A fixing device configured to fix an image on a recording material by heating the recording material where the image is formed, comprising:na cylindrical rotary member including an electroconductive layer;a coil configured to form an alternating magnetic field which subjects the electroconductive layer to electromagnetic induction heating, the coil including a spiral shaped portion which is disposed in the rotary member so that a spiral axis of the spiral shaped portion extends along a generatrix direction of the rotary member; anda core configured to induce magnetic force lines of the alternating magnetic field, which is disposed in the spiral shaped portion;wherein the electroconductive layer is formed of a non-magnetic material, and thickness of the electroconductive layer is equal to or thinner than 75 μm.

A fixing device configured to fix an image on a recording material by heating the recording material where the image is formed, comprising:na cylindrical rotary member including an electroconductive layer;a coil configured to form an alternating magnetic field which subjects the electroconductive layer to electromagnetic induction heating, the coil including a spiral shaped portion which is disposed in the rotary member so that a spiral axis of the spiral shaped portion extends along a generatrix direction of the rotary member; anda core configured to induce magnetic force lines of the alternating magnetic field, the coil being disposed in the spiral shaped portion,wherein the core has a shape where a loop is not formed outside the rotary member, andwherein the rotary member is heated mainly by a current induced by the alternating magnetic field circumferentially flowing in the electroconductive layer.