JP2010217383A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having long life and high image quality, which appropriately cleans an image carrier over a long period of time. <P>SOLUTION: A color printer includes an intermediate transfer belt 12 that carries a toner image on its surface, and a belt cleaner 13 that cleans the surface, and the belt cleaner 13 includes a rotary brush 32 that rotates in contact with the surface of the intermediate transfer belt 12, a collecting roller 33 that rotates in contact with bristles of the brush of the rotary brush 32 and that is coated with a photocatalytic material 42 on the surface, a blade 35 that is arranged in contact with the surface of the collecting roller 33 and that scrapes the surface of the collecting roller 33, and a light source 34 that radiates light for making the photocatalytic material 42 cause photocatalytic reaction, on the surface of the collecting roller 33. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus. More specifically, for example, it has a brush-like cleaning member for collecting deposits from the surface of an image carrier such as an intermediate transfer belt or a photoreceptor, and a collection member for collecting deposits from the brush-like cleaning member. The present invention relates to an image forming apparatus.

  Conventionally, in an electrophotographic image forming apparatus, it is inevitable that some toner remains on the image carrier after transfer. Therefore, it often has a member for cleaning the image carrier after transfer. For example, there is an image forming apparatus having an intermediate transfer belt on which the formed toner images of respective colors are temporarily placed. Such a belt usually has a belt cleaner for cleaning / removing toner adhering to the intermediate transfer belt. For example, in Patent Document 1, as this belt cleaner, a rotating brush that contacts the surface of the belt, a collecting roller that is arranged in contact with the rotating brush, and a surface of the collecting roller are rubbed to scrape off deposits. What has a blade member is disclosed.

  Further, in the vicinity of the image carrier, a minute discharge may occur due to the charging process or the like, and in this case, discharge products such as ozone and nitrogen oxide (NOx) are generated. In order to decompose these discharge products, it has been proposed to place a photocatalytic substance in the vicinity of the image carrier. For example, Patent Document 2 discloses an image forming apparatus in which a photocatalytic substance is disposed on the surface of a cleaning blade that rubs the surface of a photoreceptor.

JP 2006-208761 A JP 2005-266277 A

  However, since the brush cleaner is a system that forms an electric field and removes residual toner on the image carrier, the discharge product adheres to the surface of the collecting roller and the like, so that other adhering matter easily adheres. Further, due to the discharge product, the deposits may stick together as a lump. For example, if a deposit lump is formed on the surface of the collecting roller, the surface roughness increases. In that case, there is a problem that toner or the like may slip through between the blades that rub the surface of the collection roller. As a result, there is a problem in that the electric field for cleaning is not properly formed in the portion, and the cleaning property may be further deteriorated.

  The present invention has been made to solve the problems of the conventional image forming apparatus described above. That is, an object of the present invention is to provide an image forming apparatus that can appropriately clean the image carrier over a long period of time and has a long life and high image quality.

  An image forming apparatus of the present invention made for the purpose of solving this problem is an image forming apparatus having an image carrier that carries a toner image on a surface thereof, and a cleaner that cleans the surface of the image carrier. , A rotating brush rotating in contact with the surface of the image carrier, rotating in contact with the brush bristles of the rotating brush, contacting the surface of the collecting roller with a recovery roller whose surface is coated with a photocatalytic substance And a blade that scrapes the surface of the collecting roller and a light source that irradiates the surface of the collecting roller with light that causes a photocatalytic reaction on the photocatalytic substance.

  According to the image forming apparatus of the present invention, the deposit on the surface of the image carrier is scraped off by the rotating brush. And the deposit | attachment adhering to the rotary brush is collect | recovered with a collection | recovery roller, and the surface is scraped off with a braid | blade. Therefore, the surface of the image carrier can be appropriately cleaned. Furthermore, since the surface of the recovery roller is coated with a photocatalytic substance and light is irradiated by a light source, a photocatalytic reaction can be caused. Therefore, the discharge products generated around the image carrier are decomposed. As a result, deposits due to discharge products are prevented from being deposited, so that the image carrier can be properly cleaned over a long period of time, and the image quality is long and the image quality is high.

Further, in the present invention, both the rotating brush and the collection roller are formed of a conductive or semi-conductive material, and a voltage on the opposite polarity side to the polarity of the toner is applied to the collection roller with reference to the ground potential. It is desirable to have a power source and a control unit that controls on / off of the power source and the light source. The control unit preferably executes an image forming mode in which a voltage is applied to the power source and light is emitted to the light source during image formation.
In this way, the residual toner can be electrically drawn and collected by the rotating brush or the collecting roller. Furthermore, since the light source is also turned on when the power is turned on, the discharge product generated by the application of voltage is decomposed by the photocatalytic reaction.

Further, in the present invention, the control unit controls the rotation of the collecting roller, and when the non-image is formed after continuous printing exceeding the predetermined number, the power source is not applied with a voltage to the light source. It is desirable to execute a cleaning mode in which light is irradiated and the collection roller is rotated.
In this way, the discharge product accumulated around the collecting roller by the continuous printing is also appropriately decomposed.

  According to the image forming apparatus of the present invention, the image carrier can be appropriately cleaned over a long period of time, and a long-life and high-quality image can be formed.

1 is a schematic configuration diagram illustrating an image forming apparatus according to the present embodiment. It is a schematic block diagram which shows the belt cleaner which concerns on this form. It is a graph which shows the experimental result which investigated the change of the surface roughness of the collection | recovery roller by durability.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the accompanying drawings. In the present embodiment, the present invention is applied to an electrophotographic image forming apparatus of a tandem type.

  As shown in FIG. 1, the color printer 10 of this embodiment is a so-called tandem type image forming apparatus capable of forming a color image. The color printer 10 has an intermediate transfer belt 12 and a belt cleaner 13 for cleaning the intermediate transfer belt 12. This embodiment is a printer that uses negatively charged toner.

  The intermediate transfer belt 12 is wound around two left and right rollers (a driving roller 14 and a driven roller 15) in FIG. At the time of image formation, the image is rotated by the drive roller 14 on the right side in the figure as indicated by an arrow in the figure. The driven roller 15 on the left side in the drawing is driven to rotate by the rotation of the intermediate transfer belt 12. The belt cleaner 13 is provided at a position facing the driven roller 15 with the intermediate transfer belt 12 interposed therebetween. A secondary transfer roller 17 is provided at a position facing the drive roller 14 with the intermediate transfer belt 12 and the printing paper P interposed therebetween.

  As shown in FIG. 1, the color printer 10 of this embodiment has four color image forming portions (yellow 20Y, magenta 20M, cyan 20C, and black 20K). They are arranged in order. Each of the image forming units 20Y, 20M, 20C, and 20K is a general electrophotographic image forming unit, and a toner image is formed on the intermediate transfer belt 12 by these. The image forming units 20Y, 20M, 20C, and 20K have substantially the same configuration for each color. Further, the specific configuration for image formation is not limited to that shown in FIG.

  An example of the yellow image forming unit 20Y will be described. As shown in FIG. 1, the image forming unit 20 </ b> Y includes a photosensitive member 21 and a charging unit 22, a developing unit 23, a primary transfer unit 24, and a cleaner 25 around it. At the time of image formation, the photoconductor 21 is rotated as indicated by an arrow in the figure, and the surface of the photoconductor 21 is charged by the charging unit 22. Then, an electrostatic latent image is formed at a position between the charging unit 22 and the developing unit 23 by receiving exposure based on the image data. The electrostatic latent image is developed by the developing unit 23 to form a toner image.

  The formed toner image is transferred to the surface of the intermediate transfer belt 12 by the primary transfer unit 24. The intermediate transfer belt 12 is rotated as indicated by an arrow in FIG. 1, and is subjected to primary transfer in order by the image forming unit of each color. Thus, the superimposed toner images are transferred onto the printing paper P by the secondary transfer roller 17. The intermediate transfer belt 12 is further rotated as shown in the figure, and the toner remaining on the surface after the secondary transfer is removed by the belt cleaner 13.

  As shown in FIG. 2, the belt cleaner 13 of this embodiment includes a pre-charging brush 31, a rotating brush 32, a collection roller 33, a light source 34, a blade 35, and a waste toner conveying screw 36. The pre-charging brush 31 is a conductive or semi-conductive fixed brush, and is disposed at a position where the tip of the brush bristles contacts the intermediate transfer belt 12 and faces the driven roller 15. A high voltage power supply 38 is connected to the pre-charging brush 31. The high-voltage power supply 38 is for applying a negative high voltage in order to charge the toner negatively.

  The rotary brush 32 is a rotary brush having conductive or semiconductive brush bristles around a metal rotary shaft. As shown in FIG. 2, the rotary brush 32 is disposed to face the driven roller 15 so that the tip of the brush bristles contacts the intermediate transfer belt 12. At the time of image formation, it is rotated in the same rotational direction as the intermediate transfer belt 12 and the driven roller 15 as indicated by arrows in the figure. Therefore, counter rotation occurs at the contact point.

  As shown in FIG. 2, the recovery roller 33 has a cylindrical roller 41 in which nickel is plated on iron, for example, and a photocatalytic substance 42 coated on the surface thereof. The material of the cylindrical roller 41 is not limited to this, but is preferably a material that is resistant to corrosion. As the photocatalytic substance 42, for example, titanium oxide is suitable. As the coating method, for example, any of wet processes such as dip coating and spray coating, and dry processes such as CVD and sputtering may be used. What is necessary is just to select suitably from well-known various methods.

  Further, as shown in FIG. 2, a high voltage power source 39 is connected to the collection roller 33. The high-voltage power supply 39 is for applying a positive high voltage. The collection roller 33 is disposed so as to come into contact with the bristles of the rotary brush 32, and is rotated in the direction opposite to the rotation of the rotary brush 32 during image formation. That is, the rotating brush 32 and the collection roller 33 are moved in the same direction at the contact portion.

  Further, a light source 34 is disposed below the collection roller 33 in FIG. As the light source 34, a light source having a wavelength capable of causing a photocatalytic reaction to the photocatalytic substance 42 coated on the collection roller 33 is selected. For example, when titanium oxide is selected as the photocatalytic substance 42, an ultraviolet LED with a wavelength of 380 nm is suitable.

  Further, as shown in FIG. 2, a blade 35 is provided in contact with the surface of the collection roller 33. The blade 35 is, for example, a flat plate member made of SUS. The material of the blade 35 may be any material having corrosion resistance. The waste toner conveying screw 36 is for conveying the waste toner scraped off by the rotating brush 32 and the blade 35 in the depth direction (axial direction) in the figure. Further, the color printer 10 of this embodiment has a control unit 45 that controls the light source 34 and the high-voltage power supplies 38 and 39. The control unit 45 also controls the rotation of the collection roller 33. The control unit 45 may be integrated with the high voltage power supply 38 or 39.

  At the time of image formation, the driven roller 15, the rotating brush 32, and the collecting roller 33 are rotated in the directions indicated by arrows in FIG. Then, the high voltage power supply 38, the high voltage power supply 39, and the light source 34 are turned on by the control unit 45. This mode is the image forming mode. Note that the light source 34 may always be turned on when a voltage is applied to the pre-charging brush 31 and the rotating brush 32, or may be turned on during a part of the voltage application time. The precharge brush 31 becomes negative potential by constant voltage control or constant current control by the high voltage power source 38. This is a potential on the same polarity side as the normal charging polarity of the toner.

  Further, the collection roller 33 becomes positive potential by constant voltage control or constant current control by the high voltage power source 39. This is a potential on the side opposite to the normal charging polarity of the toner. Further, since the rotary brush 32 is in contact with the collection roller 33, it is also at a positive potential. However, the potential of the rotating brush 32 is not as high as that of the collecting roller 33. If only these two are compared, the potential of the rotating brush 32 is on the negative polarity side of the collecting roller 33. Here, the sign of each potential is based on the potential of the driven roller 15 (usually GND), unless a reference is specified.

  During image formation, toner remaining on the intermediate transfer belt 12 after the secondary transfer is carried and includes toner charged to a reverse polarity. In this embodiment, since negatively charged toner is used, many negatively charged toners are included, but some positively charged toners are also included. Therefore, in this embodiment, the residual toner is charged to the negative polarity by the pre-charging brush 31.

  The residual toner having the negative polarity further moves on the intermediate transfer belt 12 and contacts the rotating brush 32. Since the potential of the rotary brush 32 is on the positive side with respect to the potential of the intermediate transfer belt 12 at the position of the driven roller 15, the residual toner is drawn and entangled between the brush hairs. The rotating brush 32 also mechanically removes and collects residual toner by brush bristles. Thereby, the residual toner on the intermediate transfer belt 12 is removed. Further, the residual toner comes into contact with the collection roller 33 by the rotation of the rotary brush 32. Since the potential of the collecting roller 33 is on the positive side with respect to the potential of the rotating brush 32, the toner is collected by adsorbing negative polarity toner on the surface thereof. Then, the toner adsorbed on the collecting roller 33 is scraped off by the blade 35.

  When an electric field is formed on a brush or the like, discharge products are generated around it. Therefore, in the present embodiment, when the electric field is formed on the pre-charging brush 31 and when the electric field is formed on the rotating brush 32, the light source 34 is turned on. That is, in this embodiment, when a voltage is applied by the high voltage power supply 38 or the high voltage power supply 39, the light source 34 is turned on. Then, since the photocatalytic reaction occurs in the photocatalytic material 42 of the collection roller 33, the generated discharge product is decomposed. Therefore, the discharge product is prevented from accumulating on the surface of the collection roller 33.

  As a result, an increase in the surface roughness of the collection roller 33 due to accumulation of deposits on the surface of the collection roller 33 due to discharge products is also prevented. Accordingly, slipping of the deposit between the surface of the collection roller 33 and the blade 35 is prevented. And the deterioration of the collection property in the collection roller 33 is suppressed, and the stable cleaning property can be maintained for a long time. Therefore, the life of the collection roller 33 and the blade 35 can be extended.

  In addition, when a large number of sheets are continuously printed, not all discharge products generated during the printing time can be decomposed. Therefore, during non-image formation such as between jobs, the control unit 45 performs control to rotate the collection roller 33 while turning on the light source 34. This mode is the cleaning mode. In this mode, no voltage is applied to the high voltage power supplies 38 and 39. For example, after 100 sheets are continuously printed, the collection roller 33 is rotated about 10 turns while the light source 34 is turned on. Thereby, the discharge products remaining in the belt cleaner 13 are decomposed. This further prevents the discharge products from adhering to and depositing on the surface of the collection roller 33.

  Furthermore, the inventors confirmed the degree of change in the surface roughness of the collecting roller by repeating printing, through experiments. The same test print was repeated for each of the color printer 10 (Example) using the collection roller 33 of this embodiment and the one equipped with a collection roller not coated with a photocatalytic substance (Comparative Example). In the embodiment, the light source 34 is turned on throughout the period in which the voltage is applied to the pre-charging brush 31 and the rotating brush 32. However, the cleaning mode is not executed. Then, before starting printing (when new), after collecting 50,000, 80,000, 120,000, and 250,000 sheets (examples only), the collecting rollers were taken out and their surface roughness was measured.

  The result of the experiment is shown in FIG. In the figure, the black square indicates the result of the example, and the black circle indicates the result of the comparative example. In this experiment, ten-point average roughness (Rz) was used as the surface roughness. The unit of the horizontal axis is 1000 sheets. When the product was new, the surface roughness (Rz) of the collecting roller was about 1.5 μm in both the example and the comparative example, and there was no significant difference. In the examples, the surface roughness of the collecting roller did not change much even after repeated printing, and was less than 2.0 μm even after printing 250,000 sheets.

  However, in the comparative example, the value already exceeded 2.0 μm at 50,000 sheets after the start of use. In the experiment conducted by the inventor, when the surface roughness of the collecting roller is about 2.8 μm or more, toner slippage between the collecting roller and the blade cannot be ignored. Therefore, in the comparative example, in the measurement after printing 120,000 sheets, the deterioration of the image quality due to the defective cleaning was already observed due to the toner slipping. Therefore, it was confirmed that the surface roughness of the collecting roller could be prevented by coating the surface of the collecting roller with a photocatalytic substance and causing photocatalytic reaction by light irradiation.

  As described above in detail, according to the color printer 10 of the present invention, the surface of the collection roller 33 is coated with the photocatalyst material 42, and the collection roller 33 is irradiated with light by the light source 34 during image formation. Therefore, the photocatalytic reaction can occur at the timing when the radioactive substance is generated, and the radioactive substance can be efficiently decomposed. Thereby, since the state where the surface roughness of the collection roller 33 is small can be maintained for a long time, the cleaning property is good for a long time. Therefore, the intermediate transfer belt can be properly cleaned over a long period of time, and the image forming apparatus has a long life and high image quality.

In addition, this form is only a mere illustration and does not limit this invention at all. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.
For example, the arrangement of the belt cleaner 13 is not limited to this, as long as it can properly contact the intermediate transfer belt 12. The present invention is not limited to the cleaner for the intermediate transfer belt 12 but can be applied to a cleaner for cleaning the surface of the photosensitive member. Further, the rotary brush may be bias controlled. For example, the potential may be between the driven roller and the collection roller. The present invention is not limited to a tandem type image forming apparatus, but can be applied to a 4-cycle type, a monochrome printer, and the like.

DESCRIPTION OF SYMBOLS 10 Color printer 12 Intermediate transfer belt 13 Belt cleaner 21 Photoconductor 32 Rotating brush 33 Recovery roller 34 Light source 35 Blade 38, 39 High voltage power source 42 Photocatalyst substance 45 Control part

Claims (3)

In an image forming apparatus comprising: an image carrier that carries a toner image on a surface; and a cleaner that cleans the surface of the image carrier.
The cleaner is
A rotating brush that rotates in contact with the surface of the image carrier;
A recovery roller that rotates in contact with the bristles of the rotating brush and whose surface is coated with a photocatalytic substance;
A blade disposed in contact with the surface of the collection roller and scraping the surface of the collection roller;
An image forming apparatus, comprising: a light source that irradiates light on the surface of the recovery roller that causes a photocatalytic reaction of the photocatalytic substance. The image forming apparatus according to claim 1,
Both the rotating brush and the collecting roller are made of a conductive or semiconductive material,
A power supply for applying a voltage on the opposite polarity side to the polarity of the toner with respect to the ground potential with reference to the ground potential;
A controller for controlling on / off of the power source and the light source,
The control unit executes an image forming mode in which a voltage is applied to the power source and light is emitted to the light source during image formation. The image forming apparatus according to claim 1, wherein:
The controller is
It also controls the rotation of the collection roller,
In non-image formation after continuous printing exceeding a predetermined number of sheets, a cleaning mode is executed in which the light source is irradiated with light without applying a voltage to the power source and the recovery roller is rotated. An image forming apparatus.

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