JP2004109635A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively avoid toner sticking to a reversely bending roll with simple configuration. <P>SOLUTION: The image forming device is provided with an image carrier 40 for carrying a toner image corresponding to image information, an endless intermediate transfer belt 10 stretched around a plurality of rolls, a primary transfer means for transferring the toner image on the image carrier onto an intermediate transfer belt, a secondary transfer means 24 for collectively transferring the toner image transferred to and held on the intermediate transfer belt onto a recording medium, and a cleaning means 17 for cleaning off remaining materials on the intermediate transfer belt after secondary transfer and has a reversely bending roll 60 which bends the intermediate transfer belt inward, and a release layer is provided on the roll surface of the reversely bending roll. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly to a transfer in a color image forming apparatus.
[0002]
[Prior art]
Conventionally, a color image forming apparatus using an intermediate transfer member has been known as an image forming apparatus. A charger, an image exposing unit, and a developing unit are arranged around the image carrier to form toner images on the image carrier, and these toner images are transferred to an intermediate transfer member (primary transfer). The transfer from the transfer body to the transfer material is performed again (secondary transfer).
[0003]
When the intermediate transfer belt is used as the intermediate transfer member, the internal space of the intermediate transfer belt tends to be large, the degree of freedom in layout is restricted, and this is an obstacle to downsizing the apparatus. There are also problems such as occurrence of image defects such as fluctuation due to meandering of the belt, adhesion of molten toner to the intermediate transfer belt, lowering of transfer efficiency, and deterioration of image quality.
[0004]
In order to reduce the internal space of the intermediate transfer belt, increase the degree of freedom of layout, and realize the miniaturization of the device, the intermediate transfer belt is wound around the belt downstream of the secondary transfer section in the reverse direction as a winding method. The following patent publication proposes that a roller be brought into contact with an outer peripheral surface of a belt to be bent.
[Patent Document 1]
Japanese Patent Application Laid-Open No. 9-222804 [Patent Document 2]
JP 2000-137386 A
These transfer the toner images on a plurality of image carriers to the intermediate transfer belt at once or sequentially, and then transfer the color toner images transferred and held on the intermediate transfer belt to the recording medium at once. The intermediate transfer belt after the batch transfer is cleaned of the residue by a cleaning device.
[0006]
[Problems to be solved by the invention]
However, since the reverse refraction roller comes into contact with the surface of the intermediate transfer belt on which the toner image is formed, even a small amount of residual toner remains on the belt despite the cleaning by the intermediate transfer belt cleaning device. In some cases, the residual toner may adhere to the reverse refraction roller. Residual toner that adheres to the reverse refraction roller due to cleaning failure will eventually accumulate and later adhere to the intermediate transfer belt again, thereby contaminating the image. In addition, as a result, the image may be disturbed.
[0007]
Therefore, it is an object of the present invention to effectively and simply solve the above problem with a simple configuration.
[0008]
[Means for Solving the Problems]
According to the present invention, there is provided an image carrier that carries a toner image corresponding to image information, an endless intermediate transfer member that is stretched over a plurality of rollers, and a toner image on the image carrier. A primary transfer unit for transferring the toner image on the transfer belt, a secondary transfer unit for collectively transferring the toner image transferred and held on the intermediate transfer belt to a recording medium, and a residue on the intermediate transfer body after the secondary transfer. In an image forming apparatus including a cleaning means for cleaning and having a reverse bending roller for bending an intermediate transfer body inward, the problem can be solved by providing a release layer on a roller surface of the reverse bending roller.
[0009]
It is preferable that the release layer is made of a fluororesin. It is more preferable that a conductive material is dispersed in the release layer.
Further, an image carrier for carrying a toner image corresponding to image information, an endless intermediate transfer body stretched over a plurality of rollers, and a primary for transferring a toner image on the image carrier onto an intermediate transfer belt A transfer unit; a secondary transfer unit that collectively transfers the toner image transferred and held on the intermediate transfer belt onto a recording medium; and a cleaning unit that cleans a residue on the intermediate transfer body after the secondary transfer. In an image forming apparatus having a reverse bending roller for bending an intermediate transfer body inward, the above-described problem is solved because the reverse bending roller is a brush roller having a surface formed of a brush.
[0010]
It is preferable to have a scraping member capable of contacting the brush of the brush roller and scraping off the toner attached to the brush. It is even more advantageous if the scraping member is made of an elastic material.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows an embodiment of the present invention, which is an electrophotographic apparatus of a tandem type indirect transfer system. In the figure, reference numeral 100 denotes a copying apparatus main body, 200 denotes a sheet feeding table on which the apparatus main body is mounted, 300 denotes a scanner mounted on the copying apparatus main body 100, and 400 denotes an automatic document feeder (ADF) further mounted thereon. It is.
[0012]
In the copying apparatus main body 100, an endless belt-shaped intermediate transfer belt 10 is provided at the center. As shown in FIG. 2, the intermediate transfer belt 10 is formed by combining a material such as fluororesin with low elongation or a rubber material with high elongation and a non-elongable material such as canvas as the base layer 11, and an elastic layer 12 is provided thereon. Make. The elastic layer is made of, for example, fluorine-based rubber or acrylonitrile-butadiene copolymer rubber. The surface of the elastic layer 12 is covered with a coat layer 13 having good smoothness, for example, by coating a fluorine resin.
[0013]
In the illustrated example, the intermediate transfer belt 10 is wound around three support rollers 14, 15, and 16 and is rotatable clockwise in the figure. In the illustrated example, an intermediate transfer body cleaning device 17 that removes residual toner remaining on the intermediate transfer belt 10 after image transfer is disposed between the second support roller 15 and the third support roller 16. On the intermediate transfer belt 10 between the first support roller 14 and the second support roller 15, four image forming means 18 of black, yellow, magenta, and cyan are provided along the transport direction. A so-called tandem image forming apparatus 20 is arranged side by side. On the tandem image forming apparatus 20, as shown in FIG.
[0014]
On the other hand, a secondary transfer device 22 is provided on the opposite side of the intermediate transfer belt 10 from the tandem image forming device 20. In the illustrated example, the secondary transfer device 22 is configured such that a secondary transfer belt 24, which is an endless belt, is stretched between two rollers 23, and a third support roller is provided via the intermediate transfer belt 10. The image on the intermediate transfer belt 10 is transferred to a sheet as a transfer material.
[0015]
A fixing device 25 for fixing a transfer image on a sheet is provided beside the secondary transfer device 22. The fixing device 25 is configured by pressing a pressure roller 27 against a fixing belt 26 which is an endless belt. The above-described secondary transfer device 22 also has a sheet conveying function of conveying the sheet after image transfer to the fixing device 25. Of course, the secondary transfer device 22 may be configured by a transfer roller or a non-contact charger, and in such a case, a transport device for transporting the sheet after the secondary transfer to the fixing device may be separately provided. become.
[0016]
In the illustrated example, below the secondary transfer device 22 and the fixing device 25, a sheet reversing device 28 for reversing the sheet in order to record an image on both sides of the sheet is provided in parallel with the tandem image forming device 20 described above. Provided.
[0017]
When making a copy using this color electrophotographic apparatus, a document is set on the document table 30 of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened, a document is set on the contact glass 32 of the scanner 300, and the automatic document feeder 400 is closed and pressed. When a start switch (not shown) is pressed, when a document is set on the automatic document feeder 400, the document is conveyed and moved onto the contact glass 32, and then when the document is set on the other contact glass 32. Drives the scanner 300 immediately and travels on the first traveling body 33 and the second traveling body 34. The first traveling body 33 irradiates light from the light source and directs the reflected light from the document surface to the second traveling body 34, and further reflects the light on the mirror of the second traveling body 34 and passes through the imaging lens 35 to the reading sensor 36. And read the contents of the original.
[0018]
As described above, when a start switch (not shown) is pressed, one of the support rollers 14, 15, and 16 is driven to rotate by the drive motor (not shown), and the other two support rollers are driven to rotate, so that the intermediate transfer is performed. The belt 10 is rotated and conveyed. At the same time, the respective photoconductors 40 are rotated by the individual image forming means 18 to form black, yellow, magenta, and cyan monochrome images on the respective photoconductors 40, respectively. Then, while the intermediate transfer belt 10 is being conveyed, the monochrome images are sequentially transferred to form a composite color image on the intermediate transfer belt 10.
[0019]
On the other hand, when the start switch is pressed, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated, and a sheet is fed out from one of the paper feed cassettes 44 provided in the paper bank 43 in multiple stages. The sheets are separated into sheet feed paths 46, conveyed by conveying rollers 47, guided to a sheet feeding path 48 in the copying machine main body 100, and abutted against registration rollers 49 to be stopped. Alternatively, the manual feed tray 51 is fed out by the paper feed roller 50, separated one by one by the separation roller 52, put into the manual feed path 53, and similarly stopped against the registration roller 49.
[0020]
Then, the registration roller 49 is rotated in synchronization with the synthesized color image on the intermediate transfer belt 10, the sheet is fed between the intermediate transfer belt 10 and the secondary transfer device 22, and the sheet is transferred by the secondary transfer device 22. Record a color image on the sheet.
[0021]
The sheet after the image transfer is conveyed by the secondary transfer device 22 and sent to the fixing device 25, where the transfer image is fixed by applying heat and pressure by the fixing device 25, and then discharged by the switching operation of the switching claw 55. The sheet is discharged onto a sheet discharge tray 57 using the rollers 56 and stacked. Alternatively, the sheet is guided to the sheet reversing device 28 by the switching of the switching claw 55, is reversed there, is again guided to the transfer position, and the image is also recorded on the back surface, and then discharged onto the discharge tray 57 by the discharge roller 56. .
[0022]
On the other hand, the intermediate transfer belt 10 after the image transfer has the residual toner remaining on the intermediate transfer belt 10 after the image transfer is removed by the intermediate transfer body cleaning device 17 and is prepared for the second image formation by the tandem image forming device 20. .
[0023]
Here, the registration roller 49 is generally often used while grounded, but it is also possible to adopt a configuration in which a bias is applied for removing paper dust from a sheet. For example, a bias is applied using a conductive rubber roller. The conductive NBR rubber having a diameter of φ18 and a surface of 1 mm thickness is used. The electric resistance is about 10E9 Ωcm in terms of volume resistance of the rubber material, and a voltage of about -800 V is applied as an applied voltage to the side (front side) where the toner is transferred. A voltage of about +200 V is applied to the back side of the sheet. In general, in the intermediate transfer method, paper dust is difficult to move to the photoconductor, so there is little need to consider paper dust transfer, and the intermediate transfer method may be grounded. In the above description, a DC bias is applied as an applied voltage, but this may be an AC voltage having a DC offset component in order to charge the sheet more uniformly.
[0024]
The sheet surface after passing through the resist roller 49 to which the bias is thus applied is slightly negatively charged. Therefore, in the transfer from the intermediate transfer belt 10 to the sheet, the transfer condition may be changed and the transfer condition may be changed as compared with the case where no voltage is applied to the registration roller 49.
[0025]
FIG. 3 shows an intermediate transfer portion in the tandem type intermediate transfer type image forming apparatus. As can be seen from a comparison with FIG. 1, the path of the intermediate transfer belt of the reverse bending roller 60 disposed in the intermediate transfer belt cleaning device is changed by a pressure spring 61, and the intermediate transfer portion is downsized. The reverse bending roller 60 is in contact with the image forming surface side of the intermediate transfer belt 10. Therefore, when the intermediate transfer belt remains dirty, the reverse bending roller 60 adheres to the roller. .
[0026]
This dirt is mainly the toner leaking from the belt cleaner 63, and when the toner continuously adheres to the roller, it causes the toner to adhere to the roller surface. If the toner sticks, the projections damage the intermediate transfer belt and cause problems such as image omission. Therefore, it is necessary to prevent the toner from sticking. Therefore, by providing a release layer on the surface of the reverse bending roller, it is possible to prevent toner from adhering to the reverse bending roller.
[0027]
Here, a fluorine resin is used as an example of a material constituting the release layer. Fluororesins include TFE (tetrafluoroethylene) resin, FEP (tetrafluoroethylene-hexafluoropropylene copolymer) resin, PFA (tetrafluoroethylene-perfluoroalkylvinyl ether copolymer) resin, and the like. Here, PTFE (polytetrafluoroethylene), which is a kind of TFE, is used, but the material is not limited to this. In the present example, the release layer is provided on the surface of the reverse bending roller by coating the periphery of the reverse bending roller with the tubular PTFE, but the method of coating the roller with the resin is not limited.
[0028]
Further, by using a tube in which a conductive member is dispersed in PTFE as a release layer, it is possible to further prevent the toner from adhering to the reverse bending roller. Generally, carbon black, which is a conductive agent, is used as the conductive member, but is not limited to this material.
[0029]
FIG. 4 shows an example in which the reverse bending roller is a brush roller. By making the surface of the reverse bending roller a brush, it is possible to prevent the toner from adhering and prevent the adhering toner from being pressed against the belt, thereby preventing the belt from being damaged. The brush roller 66 is configured by implanting a flocking fiber by electrostatic flocking on the surface of the roller, but the configuration method is not limited. The thickness of the brush fiber is 1 to 10 denier, the fiber density is 100,000 to 300,000 F / inch ² , and the length is 3 to 10 mm. However, these shapes are not limited.
[0030]
Further, the toner adhered to the brush roller 66 is scraped off by the scraping member 67, so that the adhesion of the toner to the brush roller can be further prevented. At this time, by using an elastic member as the scraping member 67, it is possible to scrape more toner adhered to the brush roller 66, and it is possible to reduce hindrance to driving of the brush roller.
[0031]
【The invention's effect】
According to the device of the first aspect, by providing the release layer on the surface of the reverse bending roller, the adhesion between the reverse bending roller and the toner can be weakened, and the adhesion of the toner to the reverse bending roller can be prevented. As a result, the toner adheres and accumulates on the reverse bending roller, and then re-adheres to the intermediate transfer member, thereby contaminating the image. Can be prevented.
[0032]
According to the apparatus according to claim 2, by using a fluororesin as a material constituting the release layer, the non-adhesiveness, lubricity, and weather resistance, which are the characteristics of the fluororesin, enable a continuously stable reverse bending roller. The toner can be prevented from adhering to the toner.
[0033]
According to the apparatus according to the third aspect, by dispersing the conductive member in the release layer, charging of the surface of the reverse bending roller is prevented, electric adhesion between the reverse bending roller and the toner is reduced, and adhesion of the toner is reduced. More preventable.
[0034]
According to the apparatus according to the fourth aspect, by making the surface of the reverse bending roller a brush, the contact area with the intermediate transfer member is reduced as compared with the case where there is no brush, and the amount of toner adhering is also reduced. Further, the toner adhering to the brush enters the space between the brushes due to the pressure from the transfer member, and it is difficult to contact the intermediate transfer member again.
[0035]
According to the apparatus according to claim 5, by attaching the scraping member to the brush roller, the toner attached to the brush is scraped off, the toner is deposited on the brush, and the deposited toner stains the image on the intermediate transfer member. Or damage to the belt.
[0036]
According to the apparatus according to claim 6, by making the scraping member an elastic member, the scraping member is deflected by being pressed by the brush, and the force applied to the brush roller in the reverse rotation direction of the brush roller is weakened. Can be prevented from being hindered.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus to which the present invention is applied.
FIG. 2 is a schematic partial cross-sectional view illustrating a configuration of an intermediate transfer belt.
FIG. 3 is a schematic diagram illustrating a configuration of an intermediate transfer unit.
FIG. 4 is a schematic view showing another configuration of the reverse bending roller.
[Explanation of symbols]
Reference Signs List 10 Intermediate transfer belts 14, 15, 16 Support roller 23 Support roller 40 for secondary transfer belt Photoconductor 60 Reverse bending roller 61 Pressure spring 62 Belt cleaner

Claims (6)

An image carrier for carrying a toner image corresponding to image information, an endless intermediate transfer body stretched over a plurality of rollers, and a primary transfer means for transferring the toner image on the image carrier onto an intermediate transfer belt A secondary transfer unit that collectively transfers the toner image transferred and held on the intermediate transfer belt onto a recording medium; and a cleaning unit that cleans a residue on the intermediate transfer body after the secondary transfer. In an image forming apparatus having a reverse bending roller that curves the transfer body inward,
An image forming apparatus, wherein a release layer is provided on a roller surface of the reverse bending roller. The image forming apparatus according to claim 1, wherein the release layer is made of a fluororesin. The image forming apparatus according to claim 1, wherein a conductive material is dispersed in the release layer. An image carrier for carrying a toner image corresponding to image information, an endless intermediate transfer body stretched over a plurality of rollers, and a primary transfer means for transferring the toner image on the image carrier onto an intermediate transfer belt A secondary transfer unit that collectively transfers the toner image transferred and held on the intermediate transfer belt onto a recording medium; and a cleaning unit that cleans a residue on the intermediate transfer body after the secondary transfer. In an image forming apparatus having a reverse bending roller that curves the transfer body inward,
The image forming apparatus, wherein the reverse bending roller is a brush roller whose surface is formed of a brush. The image forming apparatus according to claim 4, further comprising a scraping member that can abut on a brush of the brush roller to scrape off toner attached to the brush. The image forming apparatus according to claim 5, wherein the scraping member is made of an elastic material.

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