Image fixing device

Patent metadata

Field	Value
Publication number	US-9618889-B2
Application number	US-201615131876-A
Country	US
Kind code	B2
Filing date	Apr 18, 2016
Priority date	Jun 19, 2012
Publication date	Apr 11, 2017
Grant date	Apr 11, 2017

Abstract

A fixing device configured to fix an image on a recording material, includes: a rotary member including an electroconductive layer; a coil which has a spiral shaped portion and is disposed in the inside of the rotary member; and a core disposed in the spiral shaped portion; with magnetic resistance of the core being, with an area from one end to the other end of the maximum passage region of the image on the recording material regarding 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.

First claim

The invention claimed is:

1. A fixing device configured to fix an image on a recording material by heating the recording material where the image is formed, comprising:
a 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; and
a magnetic core configured to guide magnetic force lines of the alternating magnetic field, the core being disposed in the spiral shaped portion, the core having a shape where a loop is not formed outside the rotary member,
wherein the electroconductive layer generates heat mainly by an induced current in the electroconductive layer, the induced current being induced by the magnetic force lines extending from one longitudinal end of the core, through an outside of the electroconductive layer, to the other longitudinal end of the core.

2. The fixing device according to claim 1 , wherein the electroconductive layer is formed of at least one of silver, aluminum, austenitic stainless steel, and copper.

3. The fixing device according to claim 1 , wherein a frequency of alternating current to flow into the coil is equal to or greater than 21 kHz but equal to or smaller than 100 kHz.

4. The fixing device according to claim 1 , wherein the maximum passage region of the image is included in a region where the electroconductive layer and the core are overlapped in the generatrix direction.

5. The fixing device according to claim 1 , wherein the rotary member is a cylindrical film; and
wherein the fixing device has a counter member configured to form a nip portion, at which a recording material is conveying, between the film and itself.

6. The fixing device according to claim 5 , wherein the fixing device includes a nip portion forming member configured to form the nip portion, which is in contact with the inner face of the film, along with the counter member via the film.

7. The fixing device according to claim 6 , wherein the fixing device includes a reinforcing member configured to reinforce the nip portion forming member, which is long in the generatrix direction, within the film, and a material of the reinforcing member is austenitic stainless steel.

8. The fixing device according to claim 1 , wherein a longitudinal end portion of the core extends outside an end portion of the rotary member.

9. The fixing device according to claim 1 , 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.

10. The fixing device according to claim 1 , wherein 70% or more of the magnetic force lines output from the one longitudinal end of the core pass over the outside of the electroconductive layer and return to the other longitudinal end of the core.

Assignees

• Canon Kk

Inventors

• Nishizawa Yuki
• Mano Hiroshi
• Hayasaki Minoru
• Isono Aoji
• Kuroda Akira
• Miyamoto Toshio
• Uchida Michio
• Uchiyama Seiji

Classifications

• G03G15/2053 Primary

  Structural details of heat elements, e.g. structure of roller or belt, eddy current, induction heating · CPC title

• G03G15/2042

  specially for the axial heat partition · CPC title

• G03G2215/2035

  the fixing nip having a stationary belt support member opposing a pressure member · CPC title

• H05B6/365

  using supplementary conductive or ferromagnetic pieces · CPC title

• G03G15/2017 Primary

  Structural details of the fixing unit in general, e.g. cooling means, heat shielding means (G03G15/2053 takes precedence) · CPC title