Fixing device and image forming apparatus

Patent metadata

Field	Value
Publication number	US-9733600-B2
Application number	US-201615069457-A
Country	US
Kind code	B2
Filing date	Mar 14, 2016
Priority date	Apr 17, 2015
Publication date	Aug 15, 2017
Grant date	Aug 15, 2017

Abstract

A fixing device includes a fixing belt looped over a first roller and a second roller and rotatable in a predetermined direction of rotation and a pressure rotator to press against the first roller via the fixing belt to form a fixing nip between the fixing belt and the pressure rotator. A separation aid, disposed downstream from the fixing nip in the direction of rotation of the fixing belt, contacts an inner circumferential surface of the fixing belt to decrease a radius of curvature of the fixing belt. A polishing roller, disposed downstream from the separation aid and upstream from the second roller in the direction of rotation of the fixing belt, contacts an outer circumferential surface of the fixing belt. An opposed roller, disposed opposite the polishing roller via the fixing belt, forms a polishing nip between the polishing roller and the fixing belt.

First claim

What is claimed is:

1. A fixing device comprising:
a first roller;
a second roller;
a fixing belt looped over the first roller and the second roller and rotatable in a set direction of rotation;
a pressure rotator configured to be pressed against the first roller via the fixing belt to form a fixing nip between the fixing belt and the pressure rotator, the fixing nip through which a recording medium bearing a toner image is conveyed;
a separation aid in proximity to and downstream from the fixing nip in the direction of rotation of the fixing belt, the separation aid contacting an inner circumferential surface of the fixing belt to decrease a radius of curvature of the fixing belt;
a polishing roller downstream from the separation aid and upstream from the second roller in the direction of rotation of the fixing belt, the polishing roller contacting an outer circumferential surface of the fixing belt; and
an opposed roller opposite the polishing roller via the fixing belt to form a polishing nip between the polishing roller and the fixing belt,
wherein a length of the polishing roller in an axial direction of the polishing roller is greater than a length of the opposed roller in an axial direction of the opposed roller.

2. The fixing device according to claim 1 , further comprising a tension roller, downstream from the separation aid in the direction of rotation of the fixing belt, to exert tension to the fixing belt,
wherein the polishing roller is interposed between the tension roller and the second roller in the direction of rotation of the fixing belt.

3. The fixing device according to claim 2 ,
wherein the opposed roller and the polishing roller contact the fixing belt at a position at a half of a circumferential span of the fixing belt defined by the tension roller and the second roller in the direction of rotation of the fixing belt.

4. The fixing device according to claim 2 ,
wherein the opposed roller bends the fixing belt to form a bend angle defined by the opposed roller, the tension roller, and the second roller.

5. The fixing device according to claim 4 ,
wherein the bend angle is a crossing angle defined by a first straight line bridging an outer circumferential surface of the tension roller and an outer circumferential surface of the opposed roller in a tangential direction along a trajectory of the fixing belt and a second straight line bridging an outer circumferential surface of the second roller and the outer circumferential surface of the opposed roller in the tangential direction.

6. The fixing device according to claim 1 ,
wherein the opposed roller bends the fixing belt at a bend angle smaller than 180 degrees.

7. The fixing device according to claim 1 , further comprising a first mover coupled with the polishing roller to move the polishing roller to come into contact with and separate from the fixing belt.

8. The fixing device according to claim 1 , further comprising a second mover coupled with the opposed roller to move the opposed roller to come into contact with and separate from the fixing belt.

9. The fixing device according to claim 1 ,
wherein the separation aid includes a curved outer circumferential face contacting the inner circumferential surface of the fixing belt.

10. The fixing device according to claim 9 ,
wherein the fixing belt includes a curved projection projecting beyond an outer circumferential surface of the first roller in a radial direction of the first roller.

11. The fixing device according to claim 10 ,
wherein the projection of the fixing belt is contoured from an exit of the fixing nip along the outer circumferential face of the separation aid in the direction of rotation of the fixing belt.

12. The fixing device according to claim 1 , wherein the pressure rotator includes a pressure roller.

13. The fixing device according to claim 1 , further comprising a stationary bracket being concentric with the first roller and mounting the separation aid.

14. The fixing device according to claim 13 ,
wherein the bracket mounts the separation aid to project beyond the first roller in a radial direction of the first roller.

15. A fixing device comprising
a first roller;
a second roller;
a fixing belt looped over the first roller and the second roller and rotatable in a set direction of rotation;
a pressure rotator configured to be pressed against the first roller via the fixing belt to form a fixing nip between the fixing belt and the pressure rotator, the fixing nip through which a recording medium bearing a toner image is conveyed;
a separation aid in proximity to and downstream from the fixing nip in the direction of rotation of the fixing belt, the separation aid contacting an inner circumferential surface of the fixing belt to decrease a radius of curvature of the fixing belt;
a polishing roller downstream from the separation aid and upstream from the second roller in the direction of rotation of the fixing belt, the polishing roller contacting an outer circumferential surface of the fixing belt;
an opposed roller opposite the polishing roller via the fixing belt to form a polishing nip between the polishing roller and the fixing belt; and
a stationary bracket being concentric with the first roller and mounting the separation aid.

16. The fixing device according to claim 15 ,
wherein the bracket mounts the separation aid to project beyond the first roller in a radial direction of the first roller.

17. An image forming apparatus comprising:
an image bearer to bear a toner image; and
a fixing device downstream from the image bearer in a recording medium conveyance direction to fix the toner image on a recording medium,
the fixing device including:
a first roller;
a second roller;
a fixing belt looped over the first roller and the second roller and rotatable in a set direction of rotation;
a pressure rotator to press against the first roller via the fixing belt to form a fixing nip between the fixing belt and the pressure rotator, the fixing nip through which the recording medium bearing the toner image is conveyed;
a separation aid in proximity to and downstream from the fixing nip in the direction of rotation of the fixing belt, the separation aid contacting an inner circumferential surface of the fixing belt to decrease a radius of curvature of the fixing belt;
a polishing roller downstream from the separation aid and upstream from the second roller in the direction of rotation of the fixing belt, the polishing roller contacting an outer circumferential surface of the fixing belt; and
an opposed roller opposite the polishing roller via the fixing belt to form a polishing nip between the polishing roller and the fixing belt,

wherein a length of the polishing roller in an axial direction of the polishing roller is greater than a of the opposed roller in an axial direction of the opposed roller.

Assignees

• Nozawa Kenji
• Okamoto Masami
• Kikushima Yuuki
• Kubota Keisuke
• Yuasa Shuutaroh
• Hemmi Kaori
• Ricoh Co Ltd

Inventors

• Nozawa Kenji
• Okamoto Masami
• Kikushima Yuuki
• Kubota Keisuke
• Yuasa Shuutaroh
• Hemmi Kaori

Classifications

• G03G2215/0129

  horizontal medium transport path at the secondary transfer · CPC title

• G03G2215/2032

  the belt further entrained around additional rotating belt support members · CPC title

• G03G15/2053 Primary

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