JP4669169B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fixing device and an image forming apparatus applied to an electrophotographic apparatus such as a facsimile machine, a printer, a copying machine, or a multifunction machine having these functions.
[0002]
[Prior art]
FIG. 5 is a side view showing an internal configuration of a facsimile apparatus having a conventional fixing device and image forming apparatus. 1 is a main body of the facsimile apparatus, 2 is configured to be detachable from the main body 1, and is formed by an electrophotographic process. A process cartridge containing various process devices for image formation, 3 is a photoconductor provided in the process cartridge 2, and 4 is an optical writing device that scans the photoconductor 3 with laser light modulated based on image data. 5 is a paper feed cassette for storing recording paper, 6 is a paper feed roller for feeding recording paper from the paper feed cassette 5, and 7 is toner formed on the photoconductor 3 on the recording paper in contact with the photoconductor 3. A transfer roller 8 for transferring an image, a fixing device 9 having a fixing roller 9 and a pressure roller 10 for fixing a toner image on recording paper, 11 a paper discharge roller, and 12 a contact sensor 13 shows the original table, which is formed on the upper surface of the main body 1.
[0003]
The document set on the document table 13 passes through the contact sensor 12 by the transport system and is discharged to the outside. When the document passes through the contact sensor 12, an image of the document is optically read by the contact sensor 12. Image data read by the contact sensor 12 or image data input from the outside is sent to the optical writing device 4, and the photoconductor 3 uniformly charged with laser light modulated by the optical writing device 4 based on the image data. By irradiating the surface, an electrostatic latent image is formed on the surface of the photoreceptor 3. Toner is attached to the electrostatic latent image to form a toner image, and the toner image is transferred onto a recording sheet by the transfer roller 7. Then, the toner image is fixed on the recording paper by passing through the nip portion between the fixing roller 9 and the pressure roller 10 in the fixing device 8 and is discharged to the outside by the paper discharge roller 11.
[0004]
By the way, conventionally, the fixing device employs an infrared heater or a halogen heater as a fixing heater, and is constituted by a pair of a fixing roller and a pressure roller. However, the pressure roller has a structure in which a silicon rubber layer is formed on the core metal and a release layer such as a Teflon (registered trademark) tube is formed on the pressure roller. The pressure roller does not readily warm up, causing a fixing failure. In addition, there was a demerit that the parts cost was high. Further, in order to ensure an appropriate nip width at the nip portion between the fixing roller and the pressure roller, a large pressing force is required, which causes stress on the recording paper and causes fixing wrinkles.
[0005]
Therefore, a fixing device that forms a nip by pressing a sheet-like pressure member against the fixing roller instead of the pressure roller, and fixes the unfixed image on the recording paper by passing the recording paper through the nip portion. Has been studied. With such a configuration, since it is a sheet-like pressurizing member, it is easy to warm up, it is possible to ensure a nip width, and it is possible to increase the thermal efficiency from the conventional machine.
[0006]
[Problems to be solved by the invention]
In a fixing device in which a sheet-like pressure member is applied instead of the pressure roller, the surface of the sheet-like pressure member, particularly the surface of the nip portion is uniform in the longitudinal direction when the sheet-like pressure member is fixed. It is necessary to make sure that there is no undulation. For this purpose, it is desirable that the surface of the sheet-like pressure member is flat.
[0007]
However, in the manufacturing process, in order to reduce the installation place or storage place of the belt-like sheet material that becomes the sheet-like pressure member, the belt-like sheet material is wound into a cylindrical shape. May occur. Alternatively, curling may occur due to expansion and contraction after the resin is poured into the mold during molding. In this case, it is desirable that at least the sheet-like pressure member is not curled in the longitudinal direction.
[0008]
The present invention solves such problems and provides a fixing device and an image forming apparatus that prevent the sheet-like pressure member from wavy when the fixing roller is pressed against the sheet-like pressure member. The purpose is to do.
[0012]
[Means for Solving the Problems]
The invention according to claim 1 includes a cylindrical fixing roller having a heating source therein, and a sheet-like pressure member in contact with the fixing roller, and the recording paper onto which the toner image is transferred is the fixing roller. A fixing device for fixing a toner image on a recording paper by applying pressure / heating when passing between the sheet-like pressure member, wherein the sheet-like pressure member is made of a resin, The longitudinal direction of the pressure member is set so as to be along the growth direction of the resin crystal. With this configuration, the resin becomes stretchable in a direction perpendicular to the crystal growth direction. Therefore, even if curling occurs in the sheet-like pressure member, the resin curls along the recording paper conveyance direction. This makes it easier to keep the pressure applied by the sheet-like pressure member at each position in the longitudinal direction of the fixing roller in a stable state.
[0013]
According to a second aspect of the present invention, an image forming apparatus includes the fixing device according to the first aspect. With such a configuration, it is possible to provide an image forming apparatus capable of maintaining stable fixing properties.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0015]
1 is a side view showing a configuration of a fixing device according to an embodiment of the present invention, FIG. 2 is a front view of FIG. 1, 20 is a fixing roller, 21 is a heating source provided inside the fixing roller 20, 22 Is a bearing provided at both ends of the fixing roller 20, 23 is a fixing member for supporting the bearing 22, 24 is a base, 25 is a sheet-like pressure member, 26 is a mounting portion for the sheet-like pressure member 25, and 27 is fixed. A screw for fixing the member 23 to the base 24 is shown.
[0016]
The sheet-like pressure member 25 is made of a heat-resistant member having resistance at a fixing temperature, for example, a heat-resistant resin such as fluororesin (PFA, PTFE, FEP, etc.) or polyimide.
[0017]
A concave portion 24a is formed in a portion of the base 24 that faces the fixing roller 20, and a step-shaped attachment portion 26 is formed at an edge of the concave portion 24a on the upstream side in the recording paper conveyance direction. The lower guide portion for guiding the lower surface of the recording paper from the transfer roller to the fixing roller 20, the concave portion 24 a and the attachment portion 26 are formed when the base 24 is molded.
[0018]
Then, one end of the sheet-like pressure member 25 is brought into contact with the stepped portion of the attachment portion 26, and one end portion of the sheet-like pressure member 25 is closely fixed to the attachment plane 26a with a double-sided adhesive tape. The sheet-like pressurizing member 25 is fixed to the mounting portion 26 in a cantilevered manner so that the other end of 25 can move up and down as a free end.
[0019]
In addition, fixing members 23 and 23 are fixed on the base 24 on the downstream side in the recording paper conveyance direction with respect to the mounting portion 26 by screws 27 and 27. As shown in FIG. The fixing roller 20 is installed in the main body of the image forming apparatus by supporting between the bearings 22 and 22 in FIG. Here, the mounting portion 26 is formed on the base 24 so that a plane including the mounting plane 26 a crosses the lower portion of the fixing roller 20, and the sheet-like pressure member 25 is fixed and fixed to the mounting portion 26. The sheet-like pressure member 25 is cantilevered along the plane A including the mounting plane 26a. In the present embodiment, the mounting plane 26a is formed so that the sheet-like pressure member 25 faces obliquely upward.
[0020]
Therefore, when the fixing roller 20 is installed, the fixing roller 20 comes into contact with and presses the sheet-like pressure member 25, and the fixing roller 20 and the sheet-like pressure member 25 are in pressure contact with each other. . At this time, the pressure applied from the sheet-like pressure member 25 to the fixing roller 20 is the nip pressure. Since the leaf spring property varies depending on the thickness or material of the sheet-like pressure member 25, the fixing position of the fixing roller 20 is set so that a desired nip pressure can be obtained in accordance with the characteristics of the sheet-like pressure member 25. . Further, when the fixing roller 20 is installed, the free end portion of the sheet-like pressure member 25 approaches or contacts the step portion of the concave portion 24a on the recording paper conveyance direction side with respect to the nip portion.
[0021]
In FIG. 1, the free end portion is inclined downward when the fixing roller 20 is installed, but the position may be set so as to be horizontal.
[0022]
1 and 2 is installed in place of the fixing device 8 of the conventional image forming apparatus shown in FIG.
[0023]
FIG. 3 is an explanatory view showing a part of the manufacturing process of the sheet-like pressure member. First, resin is poured into a mold to form a cylindrical body. At this time, the mold is designed so that the axial direction of the cylindrical body matches the inflow direction to the mold (hereinafter referred to as the MD direction). Next, as shown in FIG. 3 (a), the surface of the cylindrical body is spirally peeled toward the center (so-called Katsura peeling) to form a belt-like sheet material as shown in FIG. 3 (b). Furthermore, this sheet material is wound up to form a roll body as shown in FIG. Hereinafter, this roll body is set in a cutting device, the roll body is divided into the width in the longitudinal direction of the sheet-like pressure member 25, the sheet material is pulled out to the width in the recording paper conveyance direction of the sheet-like pressure member 25, The sheet-like pressure member 25 is manufactured by cutting the roll body along the axial direction.
[0024]
In the sheet-like pressure member 25 manufactured in this way, as shown in FIG. 3, the MD direction is the axial direction of the cylindrical body that is the raw material in manufacturing the sheet-like pressure member 25, and the belt-like sheet It comes to correspond with the axial direction of the roll body which winds up material. Therefore, the longitudinal direction of the fixing roller 20 is arranged along the MD direction.
[0025]
Here, in the manufacturing process of the sheet-like pressurizing member 25, the processes that may cause the sheet-like pressurizing member 25 to curl are shown in FIG. This is a winding process shown in the figure, and curls in a direction rotating with respect to the axis of the cylindrical body or roll body, that is, in a direction perpendicular to the MD direction. Accordingly, since the sheet-like pressure member 25 is not curved at least in the longitudinal direction, the sheet-like pressure member 25 can be uniformly pressed against each portion of the fixing roller 20 in the longitudinal direction.
[0026]
In addition, resin crystals grow in the MD direction during the formation of the cylindrical body as the raw material. Here, since the resin becomes highly stretchable in a direction perpendicular to the crystal growth direction, the resin tends to bend in a direction perpendicular to the MD direction when formed into a sheet. Therefore, it coincides with the curl direction generated in the Katsura peeling process shown in FIG. 3A or the winding process shown in FIG. Therefore, when the fixing roller 20 and the sheet-like pressure member 25 are assembled to the main body, the longitudinal direction of the fixing roller 20 is arranged along the MD direction as shown in FIG. The sheet-like pressure member 25 can be uniformly pressurized with respect to each part. In addition, even if the sheet-like pressure member 25 expands and contracts, the sheet-like pressure member 25 uniformly presses each part in the longitudinal direction of the fixing roller 20 because the sheet-like pressure member 25 expands and contracts in the direction perpendicular to the MD direction. Will be able to maintain.
[0027]
In addition, about the manufacturing method of a sheet-like pressurization member, it is not restricted to the manufacturing method mentioned above. In the manufacturing method described above, the cylindrical body is peeled off to form a sheet material. However, the sheet material may be formed by injection molding, and the sheet material may be wound to form a roll body. In this case, it is necessary to match the injection direction with the axial direction of the roll body.
[0028]
【The invention's effect】
According to the present invention configured as described above, when the fixing roller is pressed against the sheet-like pressure member, it is possible to prevent the sheet-like pressure member from being rippled. It is possible to stably fix the recording paper.
[Brief description of the drawings]
FIG. 1 is a side view showing a configuration of a fixing device according to an embodiment of the present invention. FIG. 2 is a front view of FIG. 1. FIG. 3 is an explanatory view showing a part of a manufacturing process of a sheet-like pressure member. FIG. 5 is a side view showing the internal configuration of a conventional facsimile apparatus having a fixing device and an image forming apparatus.
20 Fixing roller 21 Heat source 25 Sheet-like pressure member

Claims (2)

A cylindrical fixing roller having a heating source inside, and a sheet-like pressure member abutting on the fixing roller, and a recording sheet on which a toner image has been transferred between the fixing roller and the sheet-like pressure member A fixing device for fixing a toner image on a recording paper by applying pressure / heating when passing between the recording paper,
A fixing device, wherein the sheet-like pressure member is made of resin, and the longitudinal direction of the sheet-like pressure member is set along the growth direction of resin crystals.   An image forming apparatus comprising the fixing device according to claim 1.

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