JP2002072718A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device and an image forming apparatus having a constitution by which faulty transport is avoided and the flatness of a recording sheet is prevented from being spoiled by securely preventing deformation at a pressure part used for holding and transporting the recording sheet. SOLUTION: In this fixing device, a welding part carried on sheet material is heated and fixed by heating the sheet material while pinching and transporting the sheet material. The fixing device is equipped with a heating member incorporating a heat source for heating the sheet material and a pressure member capable of pinching and carrying the sheet material while pressing the sheet material against the heating member. The pressure member is equipped with an elastic body capable of pressing the sheet material against the heating member, and the elastic body is constituted so that deformation to a downstream side in the moving direction of the sheet material is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device and an image forming apparatus using the same, and more particularly, to a pressing mechanism for holding a sheet material to be fixed.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer or a facsimile machine, there is a step of fixing a visible image transferred from a latent image carrier. In the fixing step, for example, an operation of heating and melting the toner used for the visible image processing and fusing it to a recording sheet carrying an image is performed. An apparatus for performing the fixing process has a configuration in which a heating member having a roller structure is combined with a pressing member that presses a recording sheet against the heating member and nips and conveys the recording sheet. In this configuration, a nip portion that sandwiches and conveys the recording sheet is formed at a position where the heating roller and the pressure roller face each other, and heat from the heating roller is supplied to the recording sheet at the nip portion.

Conventionally, a pressing member used in a fixing device is:
In some cases, a roller is used to convey the recording sheet, and as a configuration, a silicon rubber layer forming an elastic layer is provided on the outer peripheral surface of a metal cored bar, and a release agent as a release agent is further provided on the surface. A configuration in which a Teflon (registered trademark) tube is wound has been proposed.

However, in this configuration, there is a problem that the configuration of the roller itself including the core metal becomes large, and it takes a long time to rise to a predetermined temperature because of a large heat capacity.
To solve this problem, see, for example, Japanese Patent Application Laid-Open No. 8-123.
A configuration that can improve the thermal efficiency as disclosed in Japanese Patent Publication No. 225/225 has been proposed. This publication discloses a configuration in which a silicon sponge is placed in a container-like support, and a layer of a tetrafluoroethylene film having a large number of micropores is provided on the surface thereof, and the surface of the tetrafluoroethylene layer is formed on the peripheral surface of the heating roller. Abutting. In this configuration, the contact position between the heating roller and the surface of the tetrafluoroethylene layer becomes a nip portion that constitutes the nipping and transporting portion of the recording sheet, and at that position the micropores having silicon oil from inside the silicon sponge in the tetrafluoroethylene layer. It is made to exude from.

[0005]

In the structure disclosed in the above publication, the friction coefficient between the pressure side structure and the recording sheet becomes larger than that between the heating roller side and the recording sheet. Although there is an advantage that it is possible to suppress the occurrence of conveyance failure, there are the following problems.

[0006] The tetrafluoroethylene layer, which is a member on the pressure side that comes into contact with the recording sheet, may not only sandwich the recording sheet but also directly contact the heating roller. For this reason, the tetrafluoroethylene layer receives the rotational force of the heating roller.

[0007] The tetrafluoroethylene layer is attached to the silicon sponge by being adhered thereto. However, the adhesive strength is low, and there is a possibility that the tetrafluoroethylene layer is peeled off from the surface of the silicon sponge due to the rotational force when directly contacting the heating roller. There is. Therefore, in order to prevent such peeling, the surface of the tetrafluoroethylene layer may be covered with a tube using a fluororesin.

However, when a tube made of a fluororesin is coated, when the heating roller is in direct contact, the tube made of a fluororesin that is merely coated in contact with the surface of the tetrafluoroethylene layer is heated. In some cases, it is not possible to prevent the recording sheet from being deformed by receiving a force downstream of the recording sheet in the conveyance direction due to the rotational force. Accordingly, when the recording sheet comes into contact with the tube surface in the deformed state, the recording sheet may be wrinkled when being conveyed while being nipped between the heating roller and the pressing side, and the conveyance failure of the recording sheet may be caused. In some cases, functions such as flatness as a recording sheet may not be achieved.

SUMMARY OF THE INVENTION In view of the above-mentioned problems in the conventional fixing device and image forming apparatus, it is an object of the present invention to reliably prevent deformation of a pressurizing section used for nipping and transporting a recording sheet, thereby preventing defective transport and occurrence of a recording sheet. An object of the present invention is to provide a fixing device and an image forming apparatus having a configuration that can prevent the flatness from being impaired.

[0010]

According to the first aspect of the present invention,
A fixing device that heats and fixes a fused portion carried on a sheet material by heating while nipping and conveying the sheet material, wherein a heating member having a built-in heat source for heating the sheet material, A pressurizing member capable of pressing and holding the sheet material to pinch and convey it; the pressurizing member includes an elastic body capable of pressing the sheet material toward the heating member; It is characterized in that a structure for preventing deformation of the sheet material downstream in the moving direction is provided.

According to a second aspect of the present invention, in the fixing device according to the first aspect, the pressing member includes the elastic body and a supporting portion for supporting the elastic body, and the surface of the elastic body has It is characterized in that a deformation suppressing layer is provided.

According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the pressing member is provided with a screen-shaped deformation preventing portion on a surface on the downstream side in the moving direction of the sheet material. It is characterized by having.

According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects, the deformation preventing portion is provided integrally with a supporting portion of the elastic body. It is characterized by.

According to a fifth aspect of the present invention, in the fixing device according to any one of the first to third aspects, the deformation preventing portion uses a part of a housing in which the elastic body is installed. It is characterized by.

According to a sixth aspect of the present invention, there is provided a fixing device according to one of the first to fifth aspects.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus using a fixing device according to an embodiment of the present invention.
Although the image forming apparatus shown in FIG. 1 is a copying machine, the present invention is not limited to this, and includes a printer, a facsimile machine, and the like. In FIG. 1, a copying machine 1 includes a drum-shaped photoconductor 3 in an image forming unit 2 disposed in a housing 1A.

In the image forming unit 2, a charging device and a developing device (both not shown) are arranged around the photosensitive member 3. In the image forming unit 2, after the photosensitive member 3 is charged,
An electrostatic latent image is formed by a writing device (for convenience, a writing optical path is indicated by a symbol L) provided in the vicinity of the image forming unit 2, and after a visible image processing of the electrostatic latent image by development,
The visible image is transferred by the transfer device 4 to a recording sheet, which is a sheet material. The recording sheet is fed to the transfer device 4 from a sheet cassette 5A provided in the sheet feeding device 5, but the recording sheet may be carried on the photoconductor 3. After the transfer start timing (registration timing) with the visual image is set, it is fed to the transfer position and the visible image is transferred. The recording sheet on which the visible image has been transferred is heated and fused with the developer in the visible image serving as a fusion portion in the fixing device 6 and is discharged toward the paper discharge tray 7. In FIG. 1, reference numeral 8 denotes a document discharge table.

FIG. 2 is a schematic diagram showing the structure of the fixing device 6. In FIG. 2, the fixing device 6 has a built-in heat source 9A,
The apparatus includes a heating roller 9 corresponding to a rotatable heating member, and a pressing member 10 capable of abutting against the heating roller. As shown in FIG. 2B, the pressing member 10 is an elastic body 12 formed of a molded product using a silicon sponge mounted and fixed on a sheet metal supporting member 11 attached to the housing 1A side. And a coating layer 13 is provided on the outer surface thereof by a tube made of a fluororesin. Coating layer 13
The outer surface of the elastic body 12 is covered with the coating layer 13 so that the elastic body 12 is prevented from being separated from the support portion 11 and deformed. The support member 11 is
It is not limited to sheet metal, but a resin molded product can be used.

In FIG. 2B, a deformation preventing portion 14 is provided on a side surface of the elastic body 12 on the downstream side in the recording sheet conveyance direction (moving direction: the direction indicated by the arrow). The deformation preventing portion 14 is a screen-shaped high-rigidity member, and in the case of the present embodiment, a sheet metal member is used. Deformation prevention part 14
The length of the elastic body 12 is such that it can abut almost the entire surface of the recording sheet on the downstream side in the transport direction of the recording sheet, and is arranged upright along the surface. The elastic body 12 is prevented from being deformed toward the downstream side in the conveying direction of the recording sheet by the rotational force from the heating roller 9 received when the recording sheet comes into contact with the recording medium. That is,
When the surface of the coating layer 13 that is in contact with the heating roller 13 is deformed by the rotation force of the heating roller 9 toward the downstream side in the conveyance direction of the recording sheet, the elastic body 12 facing the deformation preventing unit 14 is subjected to a shearing force to perform recording. Although the surface on the downstream side in the sheet conveyance direction tends to be deformed in the conveyance direction of the recording sheet, the surface is locked by the deformation prevention unit 14, so that the deformation is suppressed. As described above, the height of the deformation preventing portion 14 is set to a height in contact with substantially the entire surface of the elastic body 12 on the downstream side in the transport direction of the recording sheet. It is desirable not to protrude from the upper surface of the coating layer 13.

Since the present embodiment has the above configuration,
When the recording sheet moves in the fixing device 6, the recording sheet is nipped and conveyed in a nip portion formed by the heating roller 9 and the pressing member 10, and is carried on the recording sheet by heat from the heating roller 9 in the process. The developer is fused and fixed to the recording sheet.

When the recording sheet is not present in the nip, the pressing member 10 comes into direct contact with the heating roller 9. For this reason, when the rotational force of the heating roller 9 acts on the coating layer 13 of the pressing member 10, a force in the shearing direction acts on the elastic body 12, and the elastic body 12 moves in a direction along the rotational force of the heating roller 9. Tries to deform. However, the deformation prevention unit 1
Since the surface of the elastic body 12 to be deformed is locked by 4, the deformation is suppressed. As a result, the elastic body 12 can keep its original shape, so that the occurrence of shear distortion can be prevented, and the flatness of the recording sheet and the occurrence of wrinkles when the recording sheet passes are prevented. can do.

Next, another embodiment according to the embodiment of the present invention will be described. The embodiment shown in FIG. 3 is characterized in that the deformation preventing portion is integrated with the support member. In FIG. 3, the deformation preventing portion 14 ′ is integrated with the surface of the support member 11 on the downstream side in the transport direction of the recording sheet and stands upright to form a screen.

Since the present embodiment has the above configuration,
As in the configuration shown in FIG. 2, the deformation of the elastic body 12 is suppressed by the deformation preventing portion 14 ′ integrated with the support member 11.
In this embodiment, the deformation preventing portion 14 ′ is integrated with the support member 11.
Is provided, so that there is no need to prepare individual components unlike the case shown in FIG. For this reason, the component cost and the assembly cost can be reduced, and the bending rigidity of the support member 11 in the direction perpendicular to the recording sheet conveyance direction can be increased, so that the deformation of the elastic body 12 hardly occurs. You can do so.

Next, another embodiment according to the embodiment of the present invention will be described. The embodiment shown in FIG. 4 is characterized in that the deformation preventing portion is constituted by the housing 1A to which the supporting portion of the elastic body 12 is attached.

In FIG. 4, the deformed support portion (for convenience, reference numeral 1
A ′) is formed by a recess formed in the housing 1A to which the support member 11 of the pressing member 10 is attached.

The deformation preventing portion 1A 'composed of a concave portion is configured such that the surface on the downstream side in the transport direction of the recording sheet can oppose the wall surface of the concave portion by dropping the support member 11 therein. Deformation prevention unit 1 composed of a recess
A ′ is a state in which the movement of the recording sheet is not hindered,
2 is substantially the same as the height of the surface on the downstream side in the transport direction of the recording sheet.

Since the present embodiment has the above configuration,
The pressing member 10 is formed by dropping the support member 11 and the elastic body 12 into the deformation preventing portion 1A 'formed by the concave portion. When the pressing member 10 comes into direct contact with the heating roller 9, the elastic body 12 tends to deform toward the downstream side in the conveying direction of the recording sheet due to the rotational force of the heating roller 9. Blocked by the 'wall. Accordingly, no shear distortion is generated in the elastic body 12, and wrinkles and poor conveyance of the recording sheet that occur when the recording sheet is nipped and conveyed while the shear distortion is generated can be prevented.

According to this embodiment, a part of the housing 1A can be used as the deformation preventing portion 1A ', so that the strength of the housing 1A is used without preparing any special deformation preventing parts. Only with this, it is possible to reliably prevent the deformation of the elastic body 12.

[0029]

According to the first aspect of the present invention, since the elastic member is provided with a structure for preventing deformation, the elastic member is deformed toward the downstream side in the moving direction of the sheet material by the rotational force of the heating roller. Can be prevented. As a result, it is possible to prevent the function of the pressing member from deteriorating due to the deformation of the elastic body, and it is possible to optimize the nipping and conveying of the sheet material, thereby preventing poor conveyance and deterioration of the flatness of the sheet material.

According to the second aspect of the invention, since the deformation suppressing layer is provided on the elastic body itself, the deformation rigidity of the elastic body itself is increased to improve the peel strength between the elastic body and the support portion. Deformation can be reduced.

According to the third aspect of the present invention, since the screen-like deformation preventing portion for preventing deformation is provided on the surface on the side where the elastic body is going to deform, deformation of the elastic body is prevented,
It is possible to prevent the sheet material from wrinkling due to deformation.

According to the fourth aspect of the present invention, since the deformation preventing portion is integrated with the supporting portion, it is possible to reduce the number of parts and the number of assembling steps.

According to the fifth aspect of the present invention, since a part of the housing is configured as a deformation preventing portion, there is no need to provide a deformation preventing member, and the structure for preventing deformation of the elastic body is simplified. It becomes possible to do.

According to the sixth aspect of the present invention, the elastic member is prevented from being deformed by the pressing member of the fixing device. And the function as a sheet material is not impaired.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus using a fixing device according to an embodiment of the present invention.

FIGS. 2A and 2B are schematic diagrams illustrating a configuration of a main part of a fixing device for explaining an example according to an embodiment of the present disclosure; FIG.
FIG. 2 is an enlarged view of a part indicated by reference numeral (B) in FIG.

FIG. 3 is a schematic diagram illustrating a configuration of a main part of a fixing device for explaining another example according to the embodiment of the present invention;
FIG. 2 is an enlarged view of a part indicated by reference numeral (B) in FIG.

FIG. 4 is a schematic diagram showing a main configuration of a fixing device for explaining another example according to the embodiment of the present invention;
FIG. 2A is an enlarged view of the entire configuration, and FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copier 1 which is one of image forming apparatuses 1A housing | casing 2 Image forming unit 3 Photoconductor 6 Fixing device 9 Heating roller corresponding to a heating member 9A Heat source 10 Pressurizing member 11 Supporting member 12 Elastic body 13 Coating layer 1A ', 14, 14 'deformation prevention part

Continued on the front page (72) Inventor Kota Takenaka 1-3-6 Nakamagome, Ota-ku, Tokyo Fico term in Ricoh Co., Ltd. 2H033 AA14 AA21 BA11 BA12 BB01

Claims (6)

[Claims] 1. A fixing device for heating and fixing a fused portion carried on a sheet material by heating the sheet material while nipping and conveying the sheet material, comprising: a heating member having a built-in heat source for heating the sheet material; A pressurizing member capable of pressing the sheet material against the heating member so as to pinch and convey the sheet material; the pressurizing member includes an elastic body capable of pressing the sheet material toward the heating member; A fixing device, wherein the body is provided with a configuration for preventing the sheet material from being deformed downstream in the movement direction. 2. The fixing device according to claim 1, wherein the pressing member includes the elastic body and a supporting portion that supports the elastic body, and a deformation suppressing layer is provided on a surface of the elastic body. A fixing device. 3. The fixing device according to claim 1, wherein the pressing member is provided with a screen-shaped deformation preventing portion on a surface on the downstream side in the moving direction of the sheet material. Fixing device. 4. The fixing device according to claim 1, wherein the deformation preventing portion is provided integrally with a supporting portion of the elastic body. . 5. The fixing device according to claim 1, wherein a part of a housing in which the elastic body is installed is used as the deformation preventing unit. . 6. An image forming apparatus using the fixing device according to claim 1. Description: