Fixing device including mechanism for varying pressure at nip region between rotary body and pressure body

Patent metadata

Field	Value
Publication number	US-11327424-B2
Application number	US-202117211360-A
Country	US
Kind code	B2
Filing date	Mar 24, 2021
Priority date	Jun 21, 2019
Publication date	May 10, 2022
Grant date	May 10, 2022

Abstract

A fixing device includes: a rotary body; a pressure body; a frame supporting the rotary body; and a pressure varying mechanism for providing a nip pressure to a nip region formed between the rotary body and the pressure body. The pressure varying mechanism includes a first spring and a second spring for urging one of the rotary body and the pressure body. The first spring applies a first urging force, and the second spring applies a second urging force acting in an opposite direction from the first urging force. The pressure varying mechanism can vary the nip pressure between a first nip pressure and a second nip pressure smaller than the first nip pressure. The nip pressure becomes the first nip pressure while only the first urging force is applied, and becomes the second nip pressure while both of the first urging force and the second urging force are applied.

First claim

What is claimed is:

1. A fixing device comprising:
a rotary body rotatable about a rotation axis extending in an axial direction;
a frame supporting the rotary body;
a belt configured to move in a moving direction;
a first pad configured to nip the belt in cooperation with the rotary body to form a nip region between the rotary body and the belt;
a second pad configured to nip the belt in cooperation with the rotary body to form the nip region;
a holder supporting the first pad and the second pad, the holder being movable in a predetermined direction perpendicular to the axial direction and the moving direction; and
a pressure varying mechanism configured to move the holder in the predetermined direction and to provide a nip pressure to be applied to the nip region, the pressure varying mechanism being configured to vary the nip pressure to be applied to the nip region between a first nip pressure and a second nip pressure smaller than the first nip pressure,
wherein:
the first nip pressure is applied to the nip region while both of the first pad and the second pad nip the belt in cooperation with the rotary body to form the nip region,
the second nip pressure is applied to the nip region while the first pad nips the belt in cooperation with the rotary body to form the nip region but the second pad does not nip the belt in cooperation with the rotary body,
each of the first pad and the second pad has a top surface and a bottom surface opposite each other in the predetermined direction, the bottom surface of each of the first pad and the second pad being supported by the holder, and
while the second nip pressure is applied to the nip region, the top surface of the first pad is positioned closer to the rotation axis of the rotary body in the predetermined direction than the top surface of the second pad is to the rotation axis of the rotary body in the predetermined direction.

2. The fixing device according to claim 1 , wherein the holder has a support surface facing the rotary body and supporting the bottom surface of the first pad and the bottom surface of the second pad,
wherein, while the first nip pressure is applied to the nip region,
a distance between the bottom surface of the first pad and the rotation axis of the rotary body in the predetermined direction is equal to a distance between the bottom surface of the second pad and the rotation axis of the rotary body in the predetermined direction.

3. The fixing device according to claim 2 , wherein the first pad has a height from the support surface in the predetermined direction greater than a height in the predetermined direction of the second pad from the support surface.

4. The fixing device according to claim 1 , wherein the holder has a support surface facing the rotary body and supporting the bottom surface of the first pad and the bottom surface of the second pad,
wherein the support surface is perpendicular to the predetermined direction,
wherein the holder is movable linearly in the predetermined direction.

5. The fixing device according to claim 1 , wherein the first pad and the second pad are spaced apart from each other in the moving direction.

6. The fixing device according to claim 1 , wherein the first pad has an upstream end portion and a downstream end portion in the moving direction,
wherein the downstream end portion nips the belt in cooperation with the rotary body but the upstream end portion does not nip the belt in cooperation with the rotary body to provide the second nip pressure as the nip pressure.

7. The fixing device according to claim 1 , wherein the frame is formed with a through-hole elongated in the predetermined direction,
wherein the frame supports the holder through the through-hole such that the holder is movable in the predetermined direction.

8. The fixing device according to claim 7 , wherein the frame comprises:
a pair of side frames positioned at respective end portions of the rotary body in the axial direction; and
a pair of brackets each fixed to corresponding one of the side frames, the through-hole being formed in each of the brackets.

9. The fixing device according to claim 1 , wherein the pressure varying mechanism comprises an arm configured to urge the holder in the predetermined direction toward the rotary body.

10. The fixing device according to claim 9 , wherein the arm is pivotably movably supported by the frame.

11. The fixing device according to claim 9 , wherein the arm is formed with an engagement hole for engagement with the holder.

12. The fixing device according to claim 9 , wherein the pressure varying mechanism further comprises:
a cam supported by the frame; and
a cam follower supported by the arm, the cam being movable between a first cam position in separation from the cam follower and a second cam position pressing the cam follower,
wherein
the cam is in the first cam position to provide the first nip pressure as the nip pressure, and
the cam is in the second cam position to provide the second nip pressure as the nip pressure.

13. The fixing device according to claim 9 , further comprising a stay made of metal and supporting the holder, the stay being positioned opposite the rotary body with respect to the holder in the predetermined direction,
wherein the arm is configured to urge the stay.

14. The fixing device according to claim 13 , further comprising a buffer member made of resin and fitted to the stay, the arm being configured to urge the stay through the buffer member.

15. The fixing device according to claim 1 , wherein the first pad has a rectangular parallelepiped shape.

16. The fixing device according to claim 1 , wherein the second pad has a rectangular parallelepiped shape.

17. The fixing device according to claim 1 , wherein the second pad has a durometer hardness higher than a durometer hardness of the first pad.

18. The fixing device according to claim 1 , wherein the rotary body includes an elastic layer constituting an outer peripheral surface of the rotary body,
wherein the first pad has a durometer hardness higher than a durometer hardness of the elastic layer of the rotary body.

Assignees

• Brother Ind Ltd

Inventors

• Handa Hiroshi
• Tanaka Tokifumi
• Fukue Shuhei
• Watanabe Tomonori

Classifications

• G03G15/2064 Primary

  combined with pressure · CPC title

• G03G15/2053 Primary

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

• G03G15/206

  Structural details or chemical composition of the pressure elements and layers thereof · 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