JP2004205751A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device constituted so that a recording medium hardly gets wet, as for the fixing device used for an image forming apparatus. <P>SOLUTION: The fixing device is provided with a rotary driven fixing member 61, a pressure member 62 which is rotated in press contact with the fixing member 61, a peeling member 80 arranged in at least one of the fixing member 61 and the pressure member 62 so as to peel and guide the sheet-like recording medium coming after passing through a nip part N between the fixing member 61 and the pressure member 62, and the peeling member 80 is arranged above the exit N1 of the nip part or on the downstream side of an air current flowing from the exit N1 of the nip part, and a roller 83 which is rotated in the moving direction of the recording medium is arranged for the peeling member 80. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fixing device used in an image forming apparatus such as a printer, a facsimile, and a copying machine that forms an image using an electrophotographic technique. In particular, the present invention relates to a technique for improving the peeling member.
[0002]
[Prior art]
Generally, an image forming apparatus using an electrophotographic technique includes a photosensitive member having a photosensitive layer on an outer peripheral surface, a charging unit for uniformly charging the outer peripheral surface of the photosensitive member, and a uniform charging by the charging unit. Exposing means for selectively exposing the outer peripheral surface to form an electrostatic latent image, and applying a toner as a developer to the electrostatic latent image formed by the exposing means to form a visible image (toner image). Developing means, a transfer means for transferring the toner image developed by the developing means to a sheet-like recording medium such as paper to be transferred, and the toner image on the recording medium on which the toner image has been transferred by the transfer means. And a fixing device for fixing the image.
The fixing device has a fixing member (for example, a fixing roller or a fixing belt having a heat source) that is driven to rotate, and a pressing member (for example, a pressing roller) that is rotated by being pressed against the fixing member. The toner is melted and fixed on the recording medium by heating while passing the recording medium through the pressure contact portion between the member and the pressing member.
Further, the surface of the recording medium on which the toner image is formed is easily adhered to a fixing member (and also to a pressing member when images are formed on both sides of the recording medium) by an adhesive action of the toner. A peeling member is provided for peeling and guiding the sheet-like recording medium that has passed through the pressure contact portion from at least the fixing member of the pressing member.
[0003]
As a conventional fixing device, a fixing roller 1 that is driven to rotate, a pressure roller 6 that rotates while being pressed against the fixing roller 1, and a fixing roller One having a release sheet 7 that peels off and guides the sheet-shaped recording medium P that has passed through the pressing portion N from the surface of the fixing roller 1 and a support plate 12 that supports the release sheet 7 It is known (for example, see Patent Document 1).
The release sheet 7 is composed of a base material 8 made of a heat-resistant resin or metal and a fluororesin layer 9 provided on the surface thereof, and the support plate 12 is composed of metal (for example, see Patent Document 1).
[0004]
[Patent Document 1]
JP-A-11-184300 (paragraphs 0018, 0022 to 0024, FIGS. 1 and 2)
[0005]
[Problems to be solved by the invention]
In the fixing device as described above, since the recording medium is conveyed while being heated at the pressure contact portion between the fixing member and the pressure member, if the recording medium is a medium containing moisture such as paper, The moisture of the recording medium is released as steam from the outlet.
This steam flows upward or, if a blowing device (or suction device) is provided for the fixing device, toward the downstream side of the airflow by the blowing device.
For this reason, if the peeling member is provided above the outlet of the pressure contact portion or downstream of the airflow from the outlet of the pressure contact portion and the temperature of the peeling member is low (for example, in the early operation of the fixing device, the peeling member is peeled off). The temperature of the member is low, and then the temperature gradually increases due to heat from the fixing member and the like), and dew condensation occurs on the surface (guide surface of the recording medium) of the peeling member.
The moisture condensed on the surface of the peeling member wets the recording medium, forms a wet spot on the recording medium, or causes distortion of the recording medium due to the wetting.
Furthermore, when performing double-sided printing in which an image is also formed on the back side after forming an image on the front side of the recording medium, the back side of the recording medium becomes wet when the image is formed and fixed on the front side, and this wet When an image is to be formed on the back side, the electrical characteristics of the recording medium change due to the wetting of the recording medium, and the toner image cannot be transferred, or the toner is prevented from being melted by the wet moisture, and sufficient fixing cannot be performed. In some cases, significant image defects may occur.
[0006]
An object of the present invention is to solve the above-described problems and to provide a fixing device in which a recording medium is hardly wetted.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a fixing device according to the present invention includes a fixing member that is driven to rotate, a pressing member that is pressed against the fixing member and rotates, and at least one of the fixing member and the pressing member. And a peeling member that peels off and guides the sheet-shaped recording medium that has passed through the pressure contact portion between the fixing member and the pressing member from the surface of the at least one member. An apparatus provided above the outlet of the press-contact portion or downstream of the airflow from the outlet of the press-contact portion,
The peeling member is provided with a roller that rotates in a moving direction of the recording medium.
Preferably, the roller has an abacus ball shape or a star wheel shape.
Preferably, the rollers are made of synthetic resin.
Preferably, the surface of the roller has water repellency.
[0008]
[Effects]
The fixing device of the present invention is provided with respect to a fixing member that is driven to rotate, a pressing member that is pressed against the fixing member and rotates, and at least one of the fixing member and the pressing member. A peeling member that peels off and guides the sheet-shaped recording medium that has passed through the pressure contact portion between the member and the pressure member from the surface of the at least one member, and the peeling member is located above the outlet of the pressure contact portion. Alternatively, the fixing device is provided on the downstream side of the airflow from the outlet of the pressure contact portion, and the separation member is provided with a roller that rotates in the moving direction of the recording medium. The following operational effects can be obtained.
That is, since the peeling member is provided with the roller that rotates in the moving direction of the recording medium, the contact area of the recording medium with the peeling member can be reduced without hindering the movement of the recording medium.
Therefore, even if there is some condensation on the peeling member, it becomes difficult for the recording medium to come into contact with it, and as a result, the recording medium is hardly wetted, and the recording medium is stained or distorted, or during double-sided printing. The disadvantage that significant image defects occur is less likely to occur.
Further, when the rollers are in the shape of an abacus ball or a star wheel, the contact area of the rollers themselves with the recording medium can be reduced. Therefore, even if dew condensation occurs on the rollers themselves, the recording medium becomes more difficult to get wet, and the recording medium becomes less likely to have wet spots or distortion, and furthermore to cause a serious image defect during double-sided printing.
When the roller is made of synthetic resin, the surface temperature of the roller tends to increase due to the low thermal conductivity of the synthetic resin, and the surface of the roller itself is less likely to be condensed. Therefore, the recording medium becomes more difficult to get wet, so that the recording medium is less likely to have wet spots or distortion, or to have a serious image defect during double-sided printing. And
Further, when the surface of the roller has water repellency, the water repellent action makes it difficult for dew condensation to occur on the surface of the roller itself. Therefore, the recording medium becomes more difficult to get wet, so that the recording medium is less likely to have wet spots or distortion, or to have a serious image defect during double-sided printing.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic side view showing an internal structure of an example of an image forming apparatus using an embodiment of a fixing device according to the present invention.
This image forming apparatus is a color image forming apparatus capable of forming a full-color image on both sides of A3 size paper (an example of a recording medium), and includes a case 10 and an image carrier housed in the case 10. And an exposure unit 20, a developing unit 40 as a developing unit, an intermediate transfer unit 50, and a fixing unit 60 as a fixing device.
The case 10 is provided with a frame (not shown) of the apparatus main body, and each unit is attached to this frame.
[0010]
The image carrier and the exposure unit 20 include a photoconductor (image carrier) 21 having a photosensitive layer on the outer peripheral surface and a charging unit (not shown) for uniformly charging the outer peripheral surface of the photoconductor 21. The outer peripheral surface of the photoreceptor 21 uniformly charged by the charging means is selectively exposed to laser light from an exposure unit to form an electrostatic latent image, and the electrostatic latent image is developed by a developing device 40. The toner image is transferred to a visible image (toner image) by applying the toner to the intermediate transfer belt 51 of the intermediate transfer unit 50 at a primary transfer portion T1. Further, at a secondary transfer portion T2, Secondary transfer is performed on a recording medium such as a sheet to be transferred.
[0011]
In the case 10, a transport path for transporting the recording medium on which an image is formed on one side by the secondary transfer unit T <b> 2 toward a paper discharge unit (discharge tray unit) 15 on the upper surface of the case 10, and the transport path A return path (not shown) is provided for returning the sheet conveyed toward the sheet discharge unit 15 to the secondary transfer unit T2 in order to switch back the sheet and form an image on the other surface.
A lower portion of the case 10 is provided with a sheet feed tray 18 for holding a plurality of sheets stacked and a sheet feed roller 19 for feeding the sheets one by one toward the secondary transfer portion T2.
[0012]
The developing device 40 is a rotary developing device, and selectively rotates the developing roller 43 for each color on the photoconductor 21 by rotating at 90 ° pitch in the direction of the arrow to selectively develop the surface of the photoconductor 21. It is possible to do.
[0013]
The intermediate transfer body unit 50 includes a unit frame 52, a driving roller 54, a driven roller 55, a primary transfer roller 56 rotatably supported by the frame 52, and the intermediate member stretched around these rollers. A transfer belt 51 is provided, and the belt 51 is driven to circulate in the direction of the arrow in the figure. The primary transfer portion T1 is formed between the photoreceptor 21 and the primary transfer roller 56, and the secondary transfer portion T2 is formed at a pressure contact portion between the drive roller 54 and the secondary transfer roller 10b provided on the main body side. It is formed.
The secondary transfer roller 10b is capable of coming into contact with and separating from the drive roller 54 (and thus to the intermediate transfer belt 51), and forms a secondary transfer portion T2 when it comes into contact therewith.
Therefore, when forming a color image, a plurality of color toner images are superimposed on the intermediate transfer belt 51 in a state where the secondary transfer roller 10b is separated from the intermediate transfer belt 51 to form a color image. The color image (toner image) is transferred onto the recording medium by contacting the secondary transfer roller 10b with the intermediate transfer belt 51 and supplying the recording medium to the contact portion (secondary transfer portion T2). It becomes.
The recording medium onto which the toner image has been transferred passes through a fixing unit (fixing device) 60 where the toner image is melted and fixed, is conveyed by a pair of paper discharge rollers 14, and is discharged toward the paper discharge tray unit 15.
[0014]
The fixing device 60 according to this embodiment includes a fixing roller 61 as a fixing member that is rotationally driven by a driving mechanism (not shown), a pressing roller 62 as a pressing member that is pressed against the fixing roller 61 and rotates. A sheet-shaped recording medium (not shown) provided for the fixing roller 61 and the pressure roller 62 and passing through the pressure contact portion N between the fixing roller 61 and the pressure roller 62 is fixed to the fixing roller 61 or the pressure roller 62. And a pressure roller peeling member 80 as a peeling member that peels off and guides from the surface of the fixing roller.
In this embodiment, since the toner images are formed on both sides of the recording medium as described above, the peeling member (80) is also provided for the pressure roller 62. When a toner image is formed only on one side, a peeling member (a peeling member having a configuration described later) is provided only on the member on which the heat source is provided.
[0015]
As is clear from FIG. 1, the pressure roller peeling member 80 is provided above the outlet N1 of the pressure contact portion N between the fixing roller 61 and the pressure roller 62.
For example, in the case where the peeling member 80 is provided above the outlet N1 of the press-contact portion N as described above, if no measure is taken, as described above, the surface of the peeling member 80 (recording Dew condensation occurs on the medium guide surface 81 (see FIG. 2), and the problem described above occurs. Note that such a problem occurs when the peeling member 80 is provided on the downstream side of the airflow from the outlet of the press-contact portion N even if the peeling member 80 is not provided above the outlet N1 of the press-contact portion N as described above. Occurs.
[0016]
Therefore, in this embodiment, as shown in FIGS. 1 and 2, the roller 83 is provided on the peeling member 80.
2A and 2B mainly show the pressure roller peeling member 80, wherein FIG. 2A is a front view, and FIG. 2B is an enlarged cross-sectional view taken along line bb in FIG.
The pressure roller peeling member (peeling member) 80 is formed in a substantially rectangular cross section by bending a single metal plate. Further, as shown in FIG. 2A, a cutout hole 82 is partially formed in the peeling member 80. The guide surface 81 of the recording medium is coated with a synthetic resin (for example, a fluororesin such as PEA) having excellent releasability from toner and water repellency.
The notch hole 82 is formed by punching the metal plate from the guide surface 81 side to the back surface side. By performing the punching process from the guide surface 81 side to the back surface side, the guide surface 81 side becomes the press dripping side (burrs and the like by punching become the back side), so that the smoothness of the guide surface 81 is ensured.
[0017]
Reference numeral 85 denotes a support member fixed to the back side of the peeling member 80.
As shown in FIG. 2B, the roller 83 is provided with a shaft 83a, and the support member 85 is provided with a recess 85a for bearing. The roller 83 has its shaft 83 a rotatably fitted in the concave portion 85 a of the support member 85, and the peeling member 80 is fixed to the support member 85 so as to cover the concave portion 85, so that the roller 83 is fixed to the support member 85. To be rotatable (hence, rotatable in the moving direction of the recording medium).
The illustrated roller 83 has an abacus ball shape, but may have a star wheel shape.
Preferably, the roller 83 is made of a synthetic resin, and more preferably, is made of a synthetic resin (for example, a fluororesin such as PEA) having excellent releasability from the toner and water repellency. It is desirable that at least the surface of the roller 83 has water repellency. For example, the surface of the roller 83 is coated with a synthetic resin (for example, a fluororesin such as PEA) having excellent releasability from the toner and water repellency.
As shown in FIG. 2A, the roller 83 is provided on the guide surface 81 of the peeling member 80 on the downstream side in the moving direction of the recording medium, and the protrusion 84 is provided on the upstream side of the guide surface 81. Have been.
Note that both ends of the support member 85 are attached to a frame (not shown) of the fixing device 60.
[0018]
The fixing device as described above includes a fixing member 61 that is driven to rotate, a pressing member 62 that is pressed against and rotates with the fixing member 61, and a fixing member that is provided for the fixing member 61 and the pressing member 62. The separation member 80 includes separation members 70 and 80 that separate and guide the sheet-shaped recording medium that has passed through the pressure contact portion N between the pressure member 61 and the pressure member 62 from the surfaces of the fixing member 91 and the pressure member 62. Is provided above the outlet N1 of the press-contact portion N (or downstream of the airflow from the outlet of the press-contact portion), and the separation member 80 is provided with a roller 83 that rotates in the moving direction of the recording medium. Therefore, according to this fixing device, the following operational effects can be obtained.
That is, since the peeling member 80 is provided with the rollers 83 that rotate in the moving direction of the recording medium, the contact area of the recording medium with the peeling member 80 can be reduced without obstructing the movement of the recording medium. .
Therefore, even if there is some dew condensation on the guide surface 81 of the peeling member 80, the recording medium does not easily come into contact with the dew condensation, and as a result, the recording medium becomes hard to wet, and the recording medium becomes wet, stained or distorted. In addition, a problem that a remarkable image defect occurs at the time of double-sided printing is less likely to occur.
Further, by making the roller 83 in the shape of an abacus ball or a star wheel, the contact area of the roller 83 itself with the recording medium can be reduced (line contact or point contact). Therefore, even if dew condensation occurs on the roller 83 itself, the recording medium is more difficult to wet, and the recording medium is less likely to have wet spots or distortion, or a problem that a remarkable image defect is generated during double-sided printing.
In addition, since the roller 83 is made of a synthetic resin, the thermal conductivity of the synthetic resin is low, so that the surface temperature of the roller 83 is easily increased, and the surface of the roller 83 is less likely to cause dew condensation. Therefore, the recording medium becomes more difficult to get wet, so that the recording medium is less likely to have wet spots or distortion, or to have a serious image defect during double-sided printing. And
In addition, by making the surface of the roller 83 water-repellent, the water-repellent action makes it difficult for the surface of the roller 83 to form dew. Therefore, the recording medium becomes more difficult to get wet, so that the recording medium is less likely to have wet spots or distortion, or to have a serious image defect during double-sided printing.
[0019]
Further, since the hole 82 is provided in the peeling member 80, the peeling member 80 is provided above the outlet of the press contact portion N1 (or downstream of the airflow from the outlet of the press contact portion). A sufficient airflow is generated around the peeling member 80. For this reason, the water vapor released from the outlet N1 of the press contact portion N escapes from the periphery of the peeling member 80, or the density of the water vapor is reduced, and the surface 81 of the peeling member 80 is less likely to condense.
Further, since the projection 84 is provided on the guide surface 81 of the peeling member 80, the recording medium is more difficult to contact the guide surface 81 of the peeling member 80.
As a result, according to this fixing device, the recording medium is more unlikely to be wet, and the recording medium is less likely to be stained or distorted, and furthermore to cause a serious image defect at the time of double-sided printing.
[0020]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and can be appropriately modified and implemented within the scope of the present invention.
For example, the present invention is also applicable when the fixing member 61 is a belt.
[0021]
[Brief description of the drawings]
FIG. 1 is a schematic side view illustrating an internal structure of an example of an image forming apparatus using an embodiment of a fixing device according to the present invention.
FIGS. 2A and 2B are diagrams mainly showing a peeling member for a pressure roller, where FIG. 2A is a front view and FIG. 2B is an enlarged cross-sectional view taken along line bb in FIG.
[Explanation of symbols]
Reference Signs List 60 fixing device, 61 fixing roller (fixing member), 62 pressure roller (pressing member), N pressure contact portion, N1 outlet, 80 pressure roller peeling member (peeling member), 82 holes, 83 rollers.

Claims (4)

A fixing member that is driven to rotate, a pressing member that is pressed against and rotates with the fixing member, and a fixing member that is provided for at least one of the fixing member and the pressing member; A peeling member that peels off and guides the sheet-shaped recording medium that has passed through the pressure contact portion from the surface of the at least one member, and the peeling member is located above the outlet of the pressure contact portion or from the outlet of the pressure contact portion. A device provided downstream of the airflow,
A fixing device, wherein a roller that rotates in a moving direction of the recording medium is provided on the peeling member. The fixing device according to claim 1, wherein the roller has an abacus ball shape or a star wheel shape. The fixing device according to claim 1, wherein the roller is made of a synthetic resin. 4. The fixing device according to claim 1, wherein the surface of the roller has water repellency.

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