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

Patent metadata

Field	Value
Publication number	US-10969719-B2
Application number	US-202016898035-A
Country	US
Kind code	B2
Filing date	Jun 10, 2020
Priority date	Jun 21, 2019
Publication date	Apr 6, 2021
Grant date	Apr 6, 2021

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;
a pressure body configured to form a nip region in cooperation with the rotary body;
a frame supporting the rotary body; and
a pressure varying mechanism configured to provide a nip pressure to be applied to the nip region formed between the rotary body and the pressure body, the pressure varying mechanism comprising:
a first spring configured to apply a first urging force to one of the rotary body and the pressure body, the first urging force acting in a first urging direction; and
a second spring configured to apply a second urging force to the one of the rotary body and the pressure body, the second urging force acting in a second urging direction opposite to the first urging direction,

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,
the first nip pressure being applied to the nip region while the first urging force of the first spring is applied to the one of the rotary body and the pressure body without application of the second urging force of the second spring to the one of the rotary body and the pressure body, and
the second nip pressure being applied to the nip region while both of the first urging force of the first spring and the second urging force of the second spring are applied to the one of the rotary body and the pressure body.

2. The fixing device according to claim 1 , wherein the first spring has one end connected to the frame.

3. The fixing device according to claim 2 , further comprising an arm pivotably movably supported by the frame,
wherein the first spring is configured to apply the first urging force to the one of the rotary body and the pressure body through the arm, and
wherein the second spring is configured to apply the second urging force to the one of the rotary body and the pressure body through the arm.

4. The fixing device according to claim 3 , wherein the pressure varying mechanism further comprises a cam supported by the frame, the cam being configured to shift a state of the second spring between a first deformed state and a second deformed state more deformed than the first deformed state,
the second urging force of the second spring being not applied to the one of the rotary body and the pressure body in the first deformed state, and
the second urging force of the second spring being applied to the one of the rotary body and the pressure body in the second deformed state.

5. The fixing device according to claim 4 , wherein the arm comprises:
an arm body connected to another end of the first spring; and
a cam follower movably supported by the arm body, the cam follower being configured to make contact with the cam, the second spring being disposed between the arm body and the cam follower.

6. The fixing device according to claim 5 , wherein the arm further comprises a restricting member configured to restrict the cam follower from moving toward the cam,
wherein the cam follower is in contact with the restricting member while the second spring is in the first deformed state.

7. The fixing device according to claim 6 , wherein the second spring is deformed from a state thereof having a natural length in the first deformed state.

8. The fixing device according to claim 5 , wherein the cam is further configured to shift the state of the second spring from the second deformed state to a third deformed state more deformed than the second deformed state, and
wherein a portion of the cam follower is nipped between the cam and the arm body while the second spring is in the third deformed state.

9. The fixing device according to claim 8 , wherein:
the arm body is in a first posture while the second spring is in the first deformed state;
the arm body is in the first posture while the second spring is in the second deformed state; and
the arm body is in a second posture different from the first posture while the second spring is in the third deformed state.

10. The fixing device according to claim 9 , wherein the pressure body comprises:
a belt configured to move in a moving direction;
a first pad configured to nip the belt in cooperation with the rotary body;
a second pad positioned to be spaced apart from the first pad in the moving direction and configured to nip the belt in cooperation with the rotary body; and
a supporting member supporting the first pad and the second pad, the supporting member being supported by the arm body,
wherein, while the arm body is in the first posture, both of the first pad and the second pad nip the belt in cooperation with the rotary body, and
wherein, while the arm body is in the second posture, the first pad nips the belt in cooperation with the rotary body but the second pad does not nip the belt in cooperation with the rotary body.

11. The fixing device according to claim 5 , wherein the arm body comprises a guide protrusion protruding toward the cam, and
wherein the cam follower comprises a cylindrical portion coupled over the guide protrusion.

12. The fixing device according to claim 11 , wherein the second spring is a coil spring providing an internal space therein, the second spring being disposed between the cylindrical portion and the arm body with the guide protrusion extending through the internal space.

13. The fixing device according to claim 4 , wherein the arm comprises:
a first portion in contact with the first spring; and
a second portion supporting the one of the rotary body and the pressure body, the cam being positioned between the first portion and the second portion in a direction from the first portion toward the second portion.

14. The fixing device according to claim 4 , further comprising a heater configured to heat the rotary body, the rotary body extending in an axial direction,
wherein the frame comprises a pair of side frames and a connecting frame connected to each of the pair of side frames, the side frames being positioned at respective end portions of the rotary body in the axial direction, the connecting frame having a portion positioned between the heater and the cam.

15. The fixing device according to claim 4 , wherein the pressure varying mechanism further comprises:
a cam drive mechanism configured to rotate the cam
in a first prescribed direction to shift the state of the second spring from the first deformed state to the second deformed state, and
in a second prescribed direction opposite to the first prescribed direction to shift the state of the second spring from the second deformed state to the first deformed state; and

a braking mechanism configured to apply a prescribed resisting force to the cam in a case where the cam is rotated in the second prescribed direction, the prescribed resisting force being greater than a resisting force to be applied to the cam while the cam is rotated in the first prescribed direction.

16. The fixing device according to claim 15 , wherein the braking mechanism comprises:
a shaft portion; and
a spring clutch comprising a tightening portion disposed over the shaft portion, the tightening portion having one of a coiled shape and an arcuate shape, the shaft portion and the tightening portion being rotatable relative to each other in accordance with a rotation of the cam, the tightening portion being configured to tighten the shaft portion to apply the prescribed resisting force to the cam while the cam is rotated in the second prescribed direction.

17. The fixing device ac

Assignees

• Brother Ind Ltd

Inventors

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

Classifications

• G03G15/2064 Primary

  combined with pressure · 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

• G03G15/2053 Primary

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