# US 12,724,367 B2 · Fixing device

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- Number: US 12,724,367 B2
- Document ID: US12724367B2
- Status: Granted
- Kind: B2
- Application number: 19/069,043
- Filed: 2025-03-03
- Published: 2025-09-11
- Granted: 2026-09-01
- Earliest claimed: 2024-03-11
- Assignees: Canon Kabushiki Kaisha
- Applicants: Canon Kabushiki Kaisha
- Inventors: Yasuharu Toratani; Suguru Takeuchi; Hiroshi Miyamoto; Kengo Koyama; Akiyoshi Shinagawa; Kiyonori Sotome; Ayano Saito; Masaki Suda
- Web page: https://patentgrep.com/patent/US12724367B2

## CPC

- G03G 15/2028: {with means for handling the copy material in the fixing nip, e.g. introduction guides, stripping means}
- G03G 15/2053: {Structural details of heat elements, e.g. structure of roller or belt, eddy current, induction heating}
- G03G 15/206: {Structural details or chemical composition of the pressure elements and layers thereof}
- G03G 15/2064: {combined with pressure}
- G03G 2215/2022: the fixing nip having both a stationary and a rotating belt support member opposing a pressure member
- G03G 2215/2038: the belt further entrained around one or more rotating belt support members
- G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY

## Abstract

A fixing device includes an endless belt, a rotating member, a pad disposed inside the belt so as to nip the belt between itself and the rotating member and form a nip, and a sliding member disposed between the pad and the belt. The pad includes a curved portion which is curved so as to directly contact the belt in a downstream side of the nip in a conveyance direction of the recording material. The curved portion includes a first portion positioned in a downstream side, in the conveyance direction, of a passing through region where a recording material with a maximum size passes through the nip and a second portion positioned in a downstream side of a non-passing through region outside of the passing through region in a widthwise direction. A radius of curvature of the second portion is larger than a radius of curvature of the first portion.

## Claims

### Claim 1

A fixing device for fixing a toner image carried on a recording material to the recording material, the fixing device comprising:
an endless and rotatable belt;
a rotating member configured to rotate in contact with an outer peripheral surface of the belt;
a pad member disposed inside the belt so as to nip the belt between itself and the rotating member and form a nip portion for nipping and conveying the recording material between the belt and the rotating member;
a sliding member disposed between the pad member and the belt, and configured to contact and slide together with an inner peripheral surface of the belt in the nip portion; and
a heating roller disposed inside the belt and configured to heat the belt,
wherein the pad member includes a curved portion which is curved so as to directly contact the belt in a downstream side of the nip portion with respect to a conveyance direction of the recording material and curves the belt so as to separate the recording material passed through the nip portion from the belt, and
wherein the curved portion includes a first portion positioned in a downstream side, with respect to the conveyance direction, of a passing through region where a recording material with a maximum size passes through the nip portion and a second portion positioned in a downstream side, with respect to the conveyance direction, of a non-passing through region outside of the passing through region with respect to a widthwise direction, of the recording material, crossing the conveyance direction, and
wherein a radius of curvature of the second portion is larger than a radius of curvature of the first portion.

### Claim 2 (depends on 1)

The fixing device according to claim 1, wherein the curved portion is formed so that the radius of curvature is continuously increased from the first portion toward the second portion.

### Claim 3 (depends on 1)

The fixing device according to claim 1, wherein the belt includes a base layer, and
wherein when a thickness of the base layer is defined as t, the radius of curvature of the curved portion is defined as R and a bending strain expressed by a following formula is defined as E,
E
=
t
R
×
1
⁢
00
[
%
]
,
a bending strain E of the second portion is smaller than a bending strain E of the first portion.

### Claim 4 (depends on 1)

The fixing device according to claim 1, wherein the sliding member includes a plurality of projections provided on a side of sliding with the belt so as to project toward the inner peripheral surface of the belt, and
wherein the plurality of projections are distributed in the widthwise direction.

### Claim 5 (depends on 4)

The fixing device according to claim 4, wherein the plurality of projections are distributed in the passing through region and the non-passing through region with respect to the widthwise direction.

### Claim 6 (depends on 1)

The fixing device according to claim 1, further comprising a tension applying member configured to apply a tension to the belt.

### Claim 7 (depends on 6)

The fixing device according to claim 6, wherein the tension applying member is a steering roller provided inside the belt and configured to stretch the belt and control a position of the belt with respect to the widthwise direction.

### Claim 8

A fixing device for fixing a toner image carried on a recording material to the recording material, the fixing device comprising:
an endless and rotatable belt;
a rotating member configured to rotate in contact with an outer peripheral surface of the belt;
a pad member disposed inside the belt so as to nip the belt between itself and the rotating member and form a nip portion for nipping and conveying the recording material between the belt and the rotating member; and
a sliding member disposed between the pad member and the belt, and configured to contact and slide together with an inner peripheral surface of the belt in the nip portion; and
a heating roller disposed inside the belt and configured to heat the belt,
wherein the pad member includes a curved portion which is curved so as to directly contact the belt in a downstream side of the nip portion with respect to a conveyance direction of the recording material and curves the belt so as to separate the recording material passed through the nip portion from the belt,
wherein the curved portion includes a first portion positioned in a downstream side, with respect to the conveyance direction, of a passing through region where a recording material with a maximum size passes through the nip portion and a second portion positioned in a downstream side, with respect to the conveyance direction, of a non-passing through region outside on the passing through region with respect to a widthwise direction, of the recording material, crossing the conveyance direction,
wherein the pad member includes a contact portion which is provided in a downstream side of the nip portion with respect to a conveyance direction of the recording material so as to be discontinuous to a downstream end of the nip portion, and
wherein when a direction perpendicular to each of the conveyance direction and the widthwise direction is defined as a pressing direction in which the recording material is pressed by the nip portion and a distance from a downstream end of the nip portion to the contact portion is defined as a distance in the pressing direction, a distance of the second portion in the pressing direction is shorter than a distance of the first portion in the pressing direction.

### Claim 9

A fixing device for fixing a toner image carried on a recording material to the recording material, the fixing device comprising:
an endless and rotatable belt;
a rotating member configured to rotate in contact with an outer peripheral surface of the belt;
a pad member disposed inside the belt so as to nip the belt between itself and the rotating member and form a nip portion for nipping and conveying the recording material between the belt and the rotating member; and
a sliding member disposed between the pad member and the belt, and configured to contact and slide together with an inner peripheral surface of the belt in the nip portion; and
a heating roller disposed inside the belt and configured to heat the belt,
wherein the pad member includes a contact portion which is provided in a downstream side of the nip portion with respect to a conveyance direction of the recording material so as to be discontinuous to a downstream end of the nip portion, and brings the sliding member into contact with belt or directly contacts the belt,
wherein a separation portion which curves the belt so as to separate the recording material passed through the nip portion from the belt is constituted by the downstream end of the nip portion and the contact portion,
wherein the separation portion includes a first portion positioned in a downstream side, with respect to the conveyance direction, of a passing through region where a recording material with a maximum size passes through the nip portion and a second portion positioned in a downstream side, with respect to the conveyance direction, of a non-passing through region outside on the passing through region with respect to a widthwise direction, of the recording material, crossing the conveyance direction, and
wherein when a direction perpendicular to each of the conveyance direction and the widthwise direction is defined as a pressing direction in which the recording material is pressed by the nip portion and a distance from a downstream end of the nip portion to the contact portion is defined as a distance in the pressing direction, a distance of the second portion in the pressing direction is shorter than a distance of the first portion in the pressing direction.

### Claim 10 (depends on 9)

The fixing device according to claim 9, wherein when a distance from a downstream end of the nip portion to the contact portion with respect to the conveyance direction is defined as a distance in the conveyance direction, a distance of the second portion in the conveyance direction is same as a distance of the first portion in the conveyance direction.

### Claim 11 (depends on 9)

The fixing device according to claim 9, wherein the separation portion is formed such that the distance in the pressing direction is continuously shortened from the first portion toward the second portion.

### Claim 12 (depends on 9)

The fixing device according to claim 9, wherein the belt includes a base layer, and
wherein when a thickness of the base layer is defined as t, the distance in the pressing direction is defined as ΔZ, a distance in the conveyance direction from a downstream end of the nip portion to the contact portion with respect to the conveyance direction is defined as ΔX, and a bending strain expressed by a following formula is defined as E,
E
=
t
×
Δ
⁢
X
Δ
⁢
Z
⁢
Δ
⁢
X
2
+
Δ
⁢
Z
2
×
1
⁢
00
[
%
]
a bending strain E of the second portion is smaller than a bending strain E of the first portion.

### Claim 13 (depends on 12)

The fixing device according to claim 12, wherein the sliding member includes a plurality of projections provided on a side of sliding with the belt so as to project toward the inner peripheral surface of the belt, and
wherein, of the plurality of projections, the downstream end of the nip portion is a downstream end of the projection that is further downstream with respect to the conveyance direction.

### Claim 14 (depends on 9)

The fixing device according to claim 9, wherein the sliding member includes a plurality of projections provided on a side of sliding with the belt so as to project toward the inner peripheral surface of the belt, and
wherein the plurality of projections are distributed in the widthwise direction.

### Claim 15 (depends on 14)

The fixing device according to claim 14, wherein the plurality of projections are distributed in the passing through region and the non-passing through region with respect to the widthwise direction.

### Claim 16 (depends on 14)

The fixing device according to claim 14, wherein the sliding member includes a sliding layer configured to cover a surface, on a side of sliding with the belt, including the plurality of projections, and the distance in the pressing direction is a distance from the sliding layer which covers the projections positioned in the downstream end of the nip portion to the contact portion.

### Claim 17 (depends on 14)

The fixing device according to claim 14, wherein the sliding member includes a sliding layer configured to cover a surface, on a side of sliding with the belt, including the plurality of projections, and the distance in the pressing direction is a distance from the projections positioned in the downstream end of the nip portion to the contact portion.