Fixing device and image forming apparatus

Patent metadata

Field	Value
Publication number	US-9639042-B2
Application number	US-201615063755-A
Country	US
Kind code	B2
Filing date	Mar 8, 2016
Priority date	Mar 16, 2015
Publication date	May 2, 2017
Grant date	May 2, 2017

Abstract

A fixing device includes a nip formation pad to press against a fixing rotator. A primary heater is disposed opposite the fixing rotator in a primary heating span spanning in an axial direction of the fixing rotator to heat the primary heating span of the fixing rotator from which heat is conducted to the nip formation pad with a primary conduction. A secondary heater is disposed opposite the fixing rotator in a secondary heating span that is outboard from the primary heating span in the axial direction of the fixing rotator. The secondary heater is interposed between a first nip formation portion and a second nip formation portion of the nip formation pad to heat the secondary heating span of the fixing rotator through the nip formation pad from which heat is conducted to the fixing rotator with a secondary conduction greater than the primary conduction.

First claim

What is claimed is:

1. A fixing device comprising:
a flexible fixing rotator rotatable in a predetermined direction of rotation;
an opposed rotator disposed opposite the fixing rotator;
a nip formation pad to press against the opposed rotator via the fixing rotator to form a fixing nip between the fixing rotator and the opposed rotator, the fixing nip through which a recording medium bearing a toner image is conveyed,
the nip formation pad including:
a first nip formation portion; and
a second nip formation portion layered on the first nip formation portion and sandwiched between the first nip formation portion and the fixing rotator;

a primary heater disposed opposite the fixing rotator in a circumferential span other than the fixing nip in the direction of rotation of the fixing rotator and in a primary heating span spanning in an axial direction of the fixing rotator, the primary heater to heat the primary heating span of the fixing rotator from which heat is conducted to the nip formation pad with a primary conduction; and
a secondary heater disposed opposite the fixing rotator in the fixing nip and in a secondary heating span that is outboard from the primary heating span in the axial direction of the fixing rotator, the secondary heater, interposed between the first nip formation portion and the second nip formation portion, to heat the secondary heating span of the fixing rotator through the nip formation pad from which heat is conducted to the fixing rotator with a secondary conduction greater than the primary conduction.

2. The fixing device according to claim 1 ,
wherein the second nip formation portion includes:
a primary heating span portion contacting the primary heating span of the fixing rotator and having a primary thermal conductivity; and
a secondary heating span portion contacting the secondary heating span of the fixing rotator and having a secondary thermal conductivity greater than the primary thermal conductivity of the primary heating span portion.

3. The fixing device according to claim 1 ,
wherein the second nip formation portion is made of metal.

4. The fixing device according to claim 3 ,
wherein the nip formation pad further includes a third nip formation portion being sandwiched between the second nip formation portion and the fixing rotator and having a thermal conductivity smaller than a thermal conductivity of the second nip formation portion.

5. The fixing device according to claim 4 ,
wherein each of the first nip formation portion and the third nip formation portion is made of resin.

6. The fixing device according to claim 4 ,
wherein the third nip formation portion includes:
a primary heating span portion disposed opposite the primary heating span of the fixing rotator; and
a secondary heating span portion disposed opposite the secondary heating span of the fixing rotator.

7. The fixing device according to claim 6 ,
wherein a thickness of the primary heating span portion is greater than a thickness of the secondary heating span portion.

8. The fixing device according to claim 6 ,
wherein a surface roughness of the primary heating span portion is greater than a surface roughness of the secondary heating span portion.

9. The fixing device according to claim 4 ,
wherein the third nip formation portion is made of a material that facilitates sliding of the fixing rotator over the third nip formation portion.

10. The fixing device according to claim 1 ,
wherein a contact area where the secondary heater contacts the second nip formation portion is greater than a contact area where the secondary heater contacts the first nip formation portion.

11. The fixing device according to claim 1 ,
wherein a thermal conductivity of the first nip formation portion is smaller than a thermal conductivity of the second nip formation portion.

12. The fixing device according to claim 1 ,
wherein the first nip formation portion includes a recess accommodating the secondary heater.

13. The fixing device according to claim 12 ,
wherein the secondary heater includes a fixing nip side face contacting the second nip formation portion and projecting beyond the first nip formation portion toward the second nip formation portion.

14. The fixing device according to claim 12 ,
wherein the first nip formation portion further includes:
a cavity adjoining the recess; and
a heater bearing defining the cavity.

15. The fixing device according to claim 14 ,
wherein the secondary heater includes an outer marginal portion supported by the heater bearing.

16. The fixing device according to claim 1 ,
wherein the primary heating span is a center span of the fixing rotator in the axial direction of the fixing rotator and the secondary heating span is each lateral end span of the fixing rotator in the axial direction of the fixing rotator.

17. The fixing device according to claim 1 ,
wherein the fixing rotator includes an endless belt.

18. The fixing device according to claim 1 ,
wherein the primary heater includes a halogen heater and the secondary heater includes a laminated heater.

19. The fixing device according to claim 1 ,
wherein the second nip formation portion includes a thermal equalizer.

20. An image forming apparatus comprising:
an image bearer to bear a toner image; and
a fixing device disposed 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 flexible fixing rotator rotatable in a predetermined direction of rotation;
an opposed rotator disposed opposite the fixing rotator;
a nip formation pad to press against the opposed rotator via the fixing rotator to form a fixing nip between the fixing rotator and the opposed rotator, the fixing nip through which the recording medium bearing the toner image is conveyed,
the nip formation pad including:
a first nip formation portion; and
a second nip formation portion layered on the first nip formation portion and sandwiched between the first nip formation portion and the fixing rotator;

a primary heater disposed opposite the fixing rotator in a circumferential span other than the fixing nip in the direction of rotation of the fixing rotator and in a primary heating span spanning in an axial direction of the fixing rotator, the primary heater to heat the primary heating span of the fixing rotator from which heat is conducted to the nip formation pad with a primary conduction; and
a secondary heater disposed opposite the fixing rotator in the fixing nip and in a secondary heating span that is outboard from the primary heating span in the axial direction of the fixing rotator, the secondary heater, interposed between the first nip formation portion and the second nip formation portion, to heat the secondary heating span of the fixing rotator through the nip formation pad from which heat is conducted to the fixing rotator with a secondary conduction greater than the primary conduction.

Assignees

• Ishii Kenji
• Matsusaka Susumu
• Ogino Yasuhiko
• Kobashigawa Shohta
• Kishi Kazuhito
• Seto Takashi
• Fujimoto Ippei
• Sawada Kazunari
• Yoshinaga Hiroshi
• Takagi Hiromasa
• Hase Takamasa
• Ricoh Co Ltd

Inventors

• Ishii Kenji
• Matsusaka Susumu
• Ogino Yasuhiko
• Kobashigawa Shohta
• Kishi Kazuhito
• Seto Takashi
• Fujimoto Ippei
• Sawada Kazunari
• Yoshinaga Hiroshi
• Takagi Hiromasa
• Hase Takamasa

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

• G03G15/2082

  Physics · mapped topic