Fixing device and image forming apparatus

Patent metadata

Field	Value
Publication number	US-9829840-B2
Application number	US-201615011886-A
Country	US
Kind code	B2
Filing date	Feb 1, 2016
Priority date	Feb 9, 2015
Publication date	Nov 28, 2017
Grant date	Nov 28, 2017

Abstract

A fixing device includes a nip formation pad that presses against a pressure rotator via an endless belt to form a fixing nip between the belt and the pressure rotator, through which a recording medium bearing a toner image is conveyed. A fixing heater is disposed opposite at least a center span of a conveyance span of the belt in an axial direction thereof where the recording medium is conveyed to heat the belt. A first lateral end heater and a second lateral end heater are mounted on the nip formation pad and disposed opposite a first lateral end span and a second lateral end span of an inner circumferential surface of the belt in the axial direction thereof, respectively, to heat the belt. The second lateral end heater is electrically connected in series to the first lateral end heater.

First claim

What is claimed is:

1. A fixing device, comprising:
a belt which is flexible and endless, and which is rotatable in a predetermined direction of rotation;
a pressure rotator disposed opposite the belt;
a nip formation pad to press against the pressure rotator via the belt to form a fixing nip between the belt and the pressure rotator, the fixing nip through which a recording medium bearing a toner image is conveyed;
a fixing heater disposed opposite at least a center span of a conveyance span of the belt in an axial direction thereof where the recording medium is conveyed to heat the belt;
a first lateral end heater mounted on the nip formation pad and disposed opposite a first lateral end span of an inner circumferential surface of the belt in the axial direction thereof to heat the belt;
a second lateral end heater mounted on the nip formation pad and disposed opposite a second lateral end span of the inner circumferential surface of the belt in the axial direction thereof to heat the belt, the second lateral end heater being electrically connected in series to the first lateral end heater; and
a reflector having a mirror finish disposed between the fixing heater and the first lateral end heater, and disposed between the fixing heater and the second lateral end heater, to reflect heat from the fixing heater toward the belt in a direction other than towards the nip formation pad,
wherein:
the fixing heater is a different type of heater and includes a different type of heat generation structure than the first lateral heater and the second lateral heater,
the fixing heater is disposed away from the fixing nip,
the nip formation pad includes a nip formation face to directly or indirectly contact the inner circumferential surface of the belt, and
the first lateral end heater, the nip formation face of the nip formation pad, and the second lateral end heater are disposed in an order of the first lateral end heater, the nip formation face of the nip formation pad, and the second lateral end heater in the axial direction of the belt.

2. The fixing device according to claim 1 ,
wherein each of the first lateral end heater and the second lateral end heater includes a belt side face disposed opposite the inner circumferential surface of the belt, the belt side face being leveled with the nip formation face of the nip formation pad in a pressurization direction in which the nip formation pad presses against the pressure rotator.

3. The fixing device according to claim 2 , further comprising a slide sheet sandwiched between the inner circumferential surface of the belt and the nip formation face of the nip formation pad.

4. The fixing device according to claim 2 , wherein the belt side face of each of the first lateral end heater and the second lateral end heater contacts the inner circumferential surface of the belt and defines an extension of the nip formation face of the nip formation pad.

5. The fixing device according to claim 1 , further comprising:
a first switch to energize the fixing heater; and
a power supply electrically connected in parallel to the fixing heater through the first switch,
wherein the fixing heater is electrically connected in series to the first lateral end heater and the second lateral end heater.

6. The fixing device according to claim 5 , further comprising:
a first contact interposed between the fixing heater and the power supply;
a second contact interposed between the first switch and the fixing heater; and
a connector connected to the second lateral end heater and selectively connected to one of the first contact and the second contact.

7. The fixing device according to claim 5 , further comprising a second switch to energize the first lateral end heater and the second lateral end heater.

8. The fixing device according to claim 7 , wherein the first switch energizes the fixing heater in accordance with temperature increase of the first lateral end heater and the second lateral end heater after the second switch energizes the first lateral end heater and the second lateral end heater.

9. The fixing device according to claim 7 , wherein the fixing heater includes:
a center heater disposed opposite the center span of the belt in the axial direction thereof; and
an outboard heater disposed outboard from the center heater and disposed opposite each lateral end span of the belt in the axial direction thereof.

10. The fixing device according to claim 9 , wherein the second switch de-energizes the first lateral end heater and the second lateral end heater and the first switch energizes the outboard heater when the first lateral end span of the belt heated by the first lateral end heater and the second lateral end span of the belt heated by the second lateral end heater are heated to a target temperature before each lateral end span of the belt heated by the outboard heater is heated to the target temperature.

11. The fixing device according to claim 9 , wherein the outboard heater partially overlaps the first lateral end heater and the second lateral end heater in the axial direction of the belt.

12. The fixing device according to claim 9 , wherein each of the first lateral end heater and the second lateral end heater is disposed outboard from the outboard heater in the axial direction of the belt.

13. The fixing device according to claim 9 , further comprising:
a temperature sensor disposed opposite an outer circumferential surface of the belt to detect a temperature of the belt; and
a thermostat disposed opposite the outer circumferential surface of the belt and disposed in proximity to the outboard heater to detect failure of the temperature sensor.

14. The fixing device according to claim 1 , wherein the first lateral end heater and the second lateral end heater are electrically connected in parallel to the fixing heater.

15. The fixing device according to claim 1 , wherein the first lateral end heater and the second lateral end heater are electrically connected to the fixing heater selectively in one of series and parallel.

16. 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 belt which is flexible and endless, and which is rotatable in a predetermined direction of rotation;
a pressure rotator disposed opposite the belt;
a nip formation pad to press against the pressure rotator via the belt to form a fixing nip between the belt and the pressure rotator, the fixing nip through which the recording medium bearing the toner image is conveyed;
a fixing heater disposed opposite at least a center span of a conveyance span of the belt in an axial direction thereof where the recording medium is conveyed to heat the belt;
a first lateral end heater mounted on the nip formation pad and disposed opposite a first lateral end span of an inner circumferential surface of the belt in the axial direction thereof to heat the belt;

a second lateral end heater mounted on the nip formation pad and disposed opposite a second lateral end span of the inner circumferential surface of the belt in the axial direction thereof to heat the belt, the second lateral end heater being electrically connected in series to the first lateral end heater; and
a reflector having a mirror finish disposed between the fixing heater and the first lateral end heater, and disposed between the fixing heater and the second lateral end heater, to reflect heat from the fixing he

Assignees

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

Inventors

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

Classifications

• G03G2215/0132

  vertical medium transport path at the secondary transfer · 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

• G03G15/2053 Primary

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