Nip forming device and image forming apparatus

Patent metadata

Field	Value
Publication number	US-12038705-B2
Application number	US-202218060566-A
Country	US
Kind code	B2
Filing date	Nov 30, 2022
Priority date	Dec 9, 2021
Publication date	Jul 16, 2024
Grant date	Jul 16, 2024

Abstract

A nip forming device includes an endless belt that is flexible and rotates and a nip former that is disposed opposite an inner circumferential face of the endless belt. A pressure rotator presses against the nip former via the endless belt to form a nip between the endless belt and the pressure rotator, through which a conveyed object is conveyed. A separator is disposed downstream from the nip in a conveyance direction of the conveyed object. The separator separates the conveyed object from the endless belt. The separator includes a non-contact portion separated from the endless belt and a contact portion that contacts the endless belt. The contact portion retains a gap having a predetermined size between the non-contact portion and the endless belt.

First claim

The invention claimed is:

1. A nip forming device comprising:
an endless belt that is flexible, the endless belt configured to rotate;
a nip former disposed opposite an inner circumferential face of the endless belt;
a pressure rotator configured to press against the nip former via the endless belt to form a nip between the endless belt and the pressure rotator, the nip through which a conveyed object is conveyed; and
a separator disposed downstream from the nip in a conveyance direction of the conveyed object, the separator configured to separate the conveyed object from the endless belt,
the separator including:
a non-contact portion separated from the endless belt; and
a contact portion configured to contact the endless belt, the contact portion configured to retain a gap having a predetermined size between the non-contact portion and the endless belt; and

a flange to support both lateral ends of the endless belt in axial direction of the endless belt,
wherein a slack rate Sr, which is defined as [Sa/Di]×100, is in a range of 0.1% to 10%, wherein Sa represents a difference in height coordinate of a top of the fixing belt before and after the top of the fixing belt is pressed against the flange, and Di represents a diameter of the fixing belt.

2. The nip forming device according to claim 1 , further comprising a guide configured to guide each lateral end of the endless belt in a longitudinal direction of the endless belt.

3. The nip forming device according to claim 1 ,
wherein the separator is configured to move toward the endless belt in an approach direction and separate from the endless belt in a separation direction.

4. The nip forming device according to claim 3 , further comprising a motion restrictor including:
a first restricting portion configured to restrict motion of the separator in the approach direction; and
a second restricting portion configured to restrict motion of the separator in the separation direction.

5. The nip forming device according to claim 4 ,
wherein the second restricting portion is configured to restrict motion of the separator in the separation direction at a position where the separator does not come into contact with the pressure rotator.

6. The nip forming device according to claim 5 , further comprising a biasing structure to bias the separator in the approach direction.

7. The nip forming device according to claim 6 ,
wherein the nip former is configured to move with respect to the pressure rotator between a pressurization position where the pressure rotator presses against the nip former via the endless belt at the nip and a separation position where the pressure rotator releases pressure applied at the nip, and
wherein the nip former is configured to move to the separation position in a state in which the first restricting portion restricts motion of the separator.

8. The nip forming device according to claim 6 ,
wherein the separator includes a separation plate configured to move.

9. The nip forming device according to claim 8 , further comprising a side plate configured to support the separation plate.

10. The nip forming device according to claim 9 ,
wherein the motion restrictor is interposed between the separation plate and the side plate.

11. The nip forming device according to claim 10 ,
wherein the side plate has a motion restricting hole defined by the first restricting portion and the second restricting portion disposed opposite the first restricting portion, and
wherein the motion restrictor further includes a motion restricted tab mounted on a lateral end of the separation plate in a longitudinal direction of the separation plate, the motion restricted tab inserted into the motion restricting hole.

12. The nip forming device according to claim 10 , further comprising a support shaft projecting from the side plate,
wherein the separation plate is configured to pivot about the support shaft.

13. The nip forming device according to claim 9 ,
wherein the biasing structure includes a tension spring interposed between the side plate and the separation plate.

14. The nip forming device according to claim 9 ,
wherein the side plate includes a recess configured to support the pressure rotator.

15. The nip forming device according to claim 1 ,
wherein the contact portion is disposed outboard from a conveyance span in a longitudinal direction of the endless belt, the conveyance span where the conveyed object is conveyed over the endless belt.

16. The nip forming device according to claim 1 ,
wherein the nip former includes:
a center heater disposed opposite a center span of the endless belt in a longitudinal direction of the endless belt, the center heater configured to heat the center span of the endless belt; and
a plurality of lateral end heaters disposed opposite both lateral end spans of the endless belt in the longitudinal direction of the endless belt, respectively, the plurality of lateral end heaters configured to heat the lateral end spans of the endless belt, respectively.

17. The nip forming device according to claim 1 ,
wherein the nip former includes a pad.

18. The nip forming device according to claim 1 ,
wherein the nip former includes a heater configured to heat the endless belt.

19. An image forming apparatus comprising:
an image forming device configured to form an image; and
a nip forming device through which a conveyed object bearing the image is conveyed,
the nip forming device including:
an endless belt that is flexible, the endless belt configured to rotate;
a nip former disposed opposite an inner circumferential face of the endless belt;
a pressure rotator configured to press against the nip former via the endless belt to form a nip between the endless belt and the pressure rotator, the nip through which the conveyed object is conveyed;
a separator disposed downstream from the nip in a conveyance direction of the conveyed object, the separator configured to separate the conveyed object from the endless belt,
the separator including:
a non-contact portion separated from the endless belt; and

a contact portion configured to contact the endless belt, the contact portion configured to retain a gap having a predetermined size between the non-contact portion and the endless belt,

a flange to support both lateral ends of the endless belt in the axial direction of the endless belt,
wherein a slack rate Sr, which is defined as [Sa/Di]×100, is in a range of 0.1% to 10%, wherein Sa represents a difference in height coordinate of a top of the fixing belt before and after the top of the fixing belt is pressed against the flange, and Di represents a diameter of the fixing belt.

Assignees

• Furuichi Yuusuke
• Shimada Hiroyuki
• Someya Yukimichi
• Ricoh Co Ltd

Inventors

• Furuichi Yuusuke
• Shimada Hiroyuki
• Someya Yukimichi

Classifications

• G03G15/2028 Primary

  with means for handling the copy material in the fixing nip, e.g. introduction guides, stripping means · CPC title

• G03G2215/2038

  the belt further entrained around one or more rotating belt support members · CPC title

• G03G15/2064

  combined with pressure · CPC title

• G03G2215/2035

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

• G03G15/2042

  specially for the axial heat partition · CPC title