JP4701905B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, and a FAX, and more particularly to an image forming apparatus having a cleaning unit that applies a bias voltage to a brush roller that cleans an intermediate transfer member.

  Conventionally, as an electrophotographic image forming apparatus using an intermediate transfer belt, a toner image formed on a photoconductor as an image carrier is primarily transferred to the intermediate transfer belt, and the toner image on the intermediate transfer belt is transferred to a sheet. A material that is secondarily transferred onto a transfer material such as (recording paper) is known. That is, after a toner image formed on a photoconductor charged to a predetermined polarity is transferred to an intermediate transfer belt using electrostatic force, the toner image on the intermediate transfer belt is transferred to the transfer material using electrostatic force. Transfer on top.

  In such an image forming apparatus using an intermediate transfer belt, electrostatic images are used to sequentially superimpose toner images formed on the respective photoreceptors on the intermediate transfer belt, and further, the superimposed toner images are used as a transfer material. Since it is possible to perform batch transfer, it is widely used as a color image forming apparatus.

  Here, a small amount of toner remains on the intermediate transfer belt after the secondary transfer, and if this is left as it is, image smearing due to the residual toner occurs when the next image is formed.

  Therefore, in order to remove the residual toner on the intermediate transfer belt after the transfer, a plate-like cleaning blade made of synthetic rubber such as polyurethane (hereinafter also simply referred to as a blade) is used, and this edge portion is provided on the surface of the intermediate transfer belt. A blade system is used that presses against the toner and blocks the toner to remove it.

  However, the friction coefficient between the photosensitive member and the blade increases, the blade is turned over, and foreign matter is caught between the photosensitive member and the blade. Therefore, a method for preventing the above inconvenience (for example, see Patent Document 1) by disposing a firing lubrication roll that reapplies the toner remaining on the surface of the image carrier as a lubricant to the upstream side of the blade. The toner is further collected on the surface opposite to the surface of the blade in contact with the photosensitive member, and the tip protrudes forward from the edge portion of the blade and is scraped off from the image carrier. A method of applying to the surface of the image carrier as a lubricant (see, for example, Patent Document 2), scraping off the toner on the intermediate transfer belt with a blade, and intermediate transfer again with a brush roller for a part of the scraped toner There has been proposed a technique that uses toner as a lubricant and avoids the inconvenience as described above, such as a method of applying to a belt surface (see, for example, Patent Document 3).

  In recent years, polymerized toners and small-diameter toners have begun to be used for image improvement, and a so-called bias cleaning method in which toner is electrostatically collected by a brush roller to which a bias voltage is applied can be considered as an alternative to blades.

  For example, the toner remaining on the intermediate transfer belt is cleaned with a brush roller (hereinafter also simply referred to as a brush). For example, the toner remaining on the intermediate transfer belt after normal transfer has positive and negative polarities. In many cases, it is difficult to remove all the transfer residual toner by applying a bias voltage to one brush. Therefore, a method is known in which two brushes are used in combination, and positive and negative voltages are applied to each.

  In the cleaning device using a brush, the cleaning performance deteriorates when the brush is contaminated with toner. Therefore, in order to always obtain good cleaning performance, it is necessary to remove the toner from the brush.

To remove toner from the brush, first, the toner is electrostatically moved from the conductive brush to which the bias voltage is applied to the flicker roller that is a toner collecting roller, and the toner is removed from the surface of the flicker roller by a scraper member such as metal. A mechanical scraping configuration is common.
Japanese Patent Laid-Open No. 7-181856 JP-A-9-16046 JP 2005-43504 A

  However, when the toner is mechanically scraped off from the surface of the flicker roller by the scraper, there is a problem of wear of the tip portion of the scraper, and there is a problem that the scraping performance by the scraper cannot be maintained through durability. That is, when scraping with the scraper is insufficient, the toner of the brush at that portion cannot be removed, so that the cleaning performance by the brush is deteriorated and defective cleaning on the image occurs.

  An object of the present invention is to provide an image forming apparatus having a cleaning unit that prevents the tip of the scraper from being worn and has improved cleaning performance.

  The above object is achieved by the following configuration.

The electrostatic latent image formed on the image bearing member is visualized as a toner image by a developing unit, and the toner image is transferred to an intermediate transfer belt and further transferred to a transfer material, and then remains on the intermediate transfer belt. the toner, in the image forming apparatus is removed by a cleaning means having a plurality of brush rollers which a bias voltage is applied, a plurality of flicker roller for removing the toner from each of the plurality of the brush roller, each of the plurality of the flicker roller A scraper that scrapes off the toner by contacting the toner and a flicker roller that removes the toner from the brush roller that collects a small amount of cleaned toner, and a toner retention member is installed upstream of the scraper that contacts the flicker roller An image forming apparatus.

  By applying toner as a lubricant to the flicker roller from the toner storage member which is a fixing member, wear of the scraper can be avoided and the cleaning performance is improved.

  First, the image forming apparatus of the present invention will be described with reference to FIG.

  In the description of the embodiment of the present invention, the technical scope is not limited by the terms used in this specification.

  FIG. 1 is a schematic diagram illustrating an example of the overall configuration of the image forming apparatus.

  In FIG. 1, 10 is a photoconductor as an image forming body, 11 is a scorotron charger as charging means, 12 is a writing device as digital image exposure means, 13 is a developing device as developing means, and 14 is a photoconductor. Reference numeral 10 denotes a cleaning device for cleaning the surface 10, reference numeral 15 denotes a blade for cleaning the photoconductor 10, reference numeral 16 denotes a developing sleeve, and reference numeral 20 denotes an intermediate transfer belt (hereinafter also simply referred to as a belt) as an intermediate transfer body.

  The image forming unit 1 includes a photoconductor 10, a scorotron charger 11, a developing unit 13, a cleaning device 14, and the like. Since the mechanical configuration of the image forming unit 1 for each color is the same, Y ( Reference numerals are given to the configuration of only the yellow (yellow) series, and reference symbols are omitted for the constituent elements of M (magenta), C (cyan), and K (black).

  The arrangement of the image forming means 1 for each color is in the order of Y, M, C, K with respect to the running direction of the intermediate transfer belt 20, and each photoconductor 10 contacts the stretched surface of the intermediate transfer belt 20. The contact point rotates in the same direction as the traveling direction of the intermediate transfer belt 20 and at the same linear speed.

  The intermediate transfer belt 20 is stretched around a driving roller 21, an earth roller 22, a tension roller 23, a static elimination roller 27, a driven roller 24, and an auxiliary roller 29. These rollers and the intermediate transfer belt 20, a transfer roller 25 as a transfer means, The belt unit 3 is constituted by the cleaning device 28 or the like which is a cleaning means. The driven roller 24 is a conductive aluminum roller having an aluminum background and is grounded.

  The photosensitive member 10 is formed by forming a photosensitive layer such as a conductive layer, an a-Si layer, or an organic photosensitive member (OPC) on the outer periphery of a cylindrical metal base formed of, for example, an aluminum material, and the conductive layer is grounded. It rotates in the counterclockwise direction indicated by the arrow in the figure.

  An electrical signal corresponding to the image data from the reading device 80 is converted into an optical signal by the image forming laser, and is projected onto the photoconductor 10 by the writing device 12.

  The developing device 13 has a developing sleeve 16 formed of a cylindrical nonmagnetic stainless steel or aluminum material that maintains a predetermined interval with respect to the peripheral surface of the photoconductor 10 and rotates in a direction opposite to the rotation direction of the photoconductor 10. ing.

The intermediate transfer belt 20 is driven by rotation of the driving roller 21 by a driving motor (not shown). The material of the intermediate transfer belt 20 is an endless belt having a volume resistivity of 10 ⁶ to 10 ¹² Ω · cm, such as modified polyimide, thermosetting polyimide, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, and nylon alloy. Two layers in which a conductive material is dispersed in an engineering plastic, and a fluorine coating having a thickness of 5 to 50 μm is preferably applied to the outside of a semiconductive film substrate having a thickness of 0.04 to 0.10 mm, preferably as a toner filming prevention layer. It is a seamless belt of the configuration. In addition to this, a semiconductive rubber belt having a thickness of 0.5 to 2.0 mm in which a conductive material is dispersed in silicon rubber, urethane rubber, or the like can also be used.

  A direct current having a polarity opposite to that of the toner is applied to the transfer roller 25 and has a function of transferring a toner image formed on the photosensitive member 10 onto the intermediate transfer belt 20. For the transfer function, a corona discharger can be used in addition to the transfer roller.

  A transfer roller 26 can be brought into contact with and released from the ground roller 22 via a belt. The toner image formed on the intermediate transfer belt 20 is re-transferred to the transfer material P at the nip portion S that is a transfer region formed by the transfer roller 26 and the earth roller 22.

  An AC voltage in which a DC voltage having the same polarity or opposite polarity as that of the toner is superimposed is applied to the charge removal roller 27, and the charge of the toner remaining on the intermediate transfer belt 20 is weakened after the toner image is transferred to the transfer material P.

  The cleaning device 28 is a means for cleaning the intermediate transfer belt 20 according to the present invention, and details will be described later.

  A fixing device 40 includes a heating roller 41 and a pressure roller 42.

  The heating roller 41 has a cylindrical shape made of thin aluminum and has a halogen heater 47 and the like for heating from the inside to a predetermined temperature. The temperature is a contact (not shown) installed on the heating roller 41. It is detected and controlled by a temperature sensor.

  The control unit B performs image forming process control, fixing temperature control, transfer material conveyance control, voltage application control to the brush roller, and the like.

  Next, the image forming process will be described with reference to FIG.

  Simultaneously with the start of image recording, the photoconductor drive motor (not shown) starts to rotate the photoconductor 10 of the color signal Y in the counterclockwise direction indicated by the arrow, and at the same time, a potential is applied to the photoconductor 10 by the charging action of the scorotron charger 11. Is started.

  After the photoconductor 10 is applied with a potential, writing of an image corresponding to the Y image data is started by the writing device 12, and an electrostatic latent image corresponding to the Y image of the original image is formed on the surface of the photoconductor 10. It is formed.

  The electrostatic latent image is reversely developed in a non-contact state by a Y developing unit 13, and a Y toner image is formed on the photoconductor 10 as the photoconductor 10 rotates.

  The Y toner image formed on the photoreceptor 10 is primarily transferred onto the intermediate transfer belt 20 by the action of the Y transfer roller 25.

  After that, the photoreceptor 10 is cleaned of residual toner by a cleaning blade 15 and enters the next image forming cycle (hereinafter, the same applies to the M, C, and K cleaning processes, and the description is omitted).

  Next, the writing device 12 performs image writing corresponding to an M (magenta) color signal, that is, M image data, and an electrostatic latent image corresponding to the M image of the original image is formed on the surface of the photosensitive member 10. The The electrostatic latent image is converted into an M toner image on the photosensitive member 10 by the M developing unit 13, and is synchronized with the Y toner image on the intermediate transfer belt 20 by the M transfer roller 25. Is superimposed on the toner image.

  By a similar process, the Y and M superimposed toner images are synchronized, and the C (cyan) toner image is superimposed on the Y and M superimposed toner images by the C transfer roller 25. . Next, the Y, M, and C superimposed toner images that have already been formed are synchronized, and the K toner image is transferred onto the Y, M, and C superimposed toner images by the K transfer roller 25. And a superimposed toner image of Y, M, C, and K is formed.

  The intermediate transfer belt 20 carrying the superimposed toner image is fed clockwise as indicated by the arrow, and the transfer material P is fed from the paper cassette 72 by the paper feed roller 70, passes through the transport roller 73, and then the timing roller 71. Then, the timing roller 71 is driven to synchronize with the superimposed toner image on the intermediate transfer belt 20, and a transfer roller 26 (intermediate) to which a DC voltage having a polarity opposite to that of the toner is applied. The superposed toner image on the intermediate transfer belt 20 is secondarily transferred onto the transfer material P. The nip portion S is in contact with the transfer belt 20.

  Thereafter, the intermediate transfer belt 20 travels, the charge of the residual toner is weakened by the neutralizing roller 27, the residual toner on the belt is cleaned by the brush rollers 281 and 283 by the cleaning device 28, and the next image forming cycle starts.

  The toner scraped off is collected in the cleaning device 28, conveyed in the axial direction (from the paper surface to the paper back surface in the drawing) by the rotation of the conveying screw 287, and collected in a storage box via a waste pipe (not shown). .

  The transfer material P onto which the superimposed toner image has been transferred is further sent to the fixing device 40, and is sandwiched and pressed between the heating roller 41 and the pressure roller 42 to be fixed. The transfer material P on which the toner image is fixed is conveyed to a paper discharge tray 82 by a paper discharge roller 81.

  As described above, when the scraper member mechanically scrapes off the surface of the flicker roller to which the toner transferred from the brush roller is scraped, the scraper wears at the tip, and the scraper scrapes through the durability. There is a problem that the performance cannot be maintained and the cleaning is poor.

  The present invention has been devised to avoid the above-described problems.

  The intermediate transfer belt cleaning process according to the present invention will be described below with reference to FIG.

  FIG. 2 is an enlarged view of the cleaning device for the intermediate transfer belt in FIG.

  In FIG. 2A, the cleaning device 28 includes conductive brush rollers 281 and 282 that rotate in the direction of an arrow with power from a drive source (not shown), a conductive flicker roller 283 to which a positive voltage is applied, The configuration includes a flicker roller 284 to which a negative voltage is applied, scrapers 285 and 286, a conveying screw 287, a fixed toner retaining member 30 attached to a cleaning device frame (not shown), and the like.

  After the secondary transfer process is completed at the nip portion S, toners having positive and negative polarities remain mixed on the intermediate transfer belt 20 and are sent to the cleaning device 28. First, the negative toner is removed by the brush roller 281, adheres to the flicker roller 283, is scraped off by the scraper 285, and falls. A part of the positive toner is also mechanically scraped off by the brush roller 281 and dropped. Thereafter, the remaining positive toner is removed by the brush roller 282 and adheres to the flicker roller 284. The adhering toner is sent to the toner retaining member 30, and a small amount of the toner is collected by the auxiliary brush 30A and retained in the toner receiving member 302, and the remaining toner is scraped off by the scraper 286 and dropped. The toner staying on the toner receiving member 302 adheres to the flicker roller 284 via the auxiliary brush 30A even when the amount of toner collected by the brush is small.

  Since the toner staying member 30 is installed on the flicker roller on the brush side where the amount of collected toner is small, there is no problem that the toner overflows from the toner receiving member 302.

  The toner retaining member 30 has an effect of applying the retained toner to the flicker roller 284 again. When the amount of toner collected by the brush roller 282 is originally small, the toner applied from the toner retaining member 30 is used as a lubricant. It is particularly effective, and is particularly effective in suppressing scraper friction. With this configuration, the friction coefficient between the flicker roller 284 and the scraper 286 can be reduced, and the friction of the scraper 286 can be reduced.

  In the case of the blade cleaning described above, at least all the transfer residual toner reaches the cleaning portion. For example, if the transfer rate is 90%, the toner for 10% of the formed image is supplied to the blade. However, in the case of the cleaning according to the present invention, only some percentage of the transfer residual toner is supplied to one scraper. The ratio of the toner that reaches the two scrapers is determined by the charge amount distribution of the untransferred toner. The toner having the same polarity as the toner in the developer can be supplied by performing the same control as that usually performed in the photoconductor cleaning, such as sending the toner without transferring the secondary transfer. It is impossible for a toner having a reverse polarity to the toner in the developer, and it is indispensable to maintain lubricity with a small amount of untransferred toner.

  Hereinafter, an experiment for confirming the effect of scraper wear and cleaning performance by applying the toner retention member was performed under the following conditions.

<Experimental conditions>
Experimental machine: Tandem color image forming device (see Fig. 1)
Intermediate transfer belt: PI (polyimide), volume resistance of 10 ⁹ Ω, surface resistance
Is 10 ¹¹ Ω
Brush roller: Conductive acrylic wire diameter 6d, density 15.5 kf / cm ²
The upstream brush travels in contact with the intermediate transfer belt.
Forward direction, downstream brush rotates in reverse direction, linear velocity is 22
0mm / sec, the amount of biting with the belt is 1mm, both
The potential of the lash roller is the driven roller (ground) on the back side of the belt
From the outside so as to be the potential between the roller and the flicker roller
Configuration to apply voltage Flicker roller: Stainless steel roller, upstream side (positive voltage applied), downstream side
(Negative voltage applied) Both are square at the contact point with the brush roller.
Rotation in the direction, bite amount with brush roller 1mm
Scraper: Stainless steel plate (thickness 0.05mm, free length 8mm, tip
Counter of end deformation (1.5mm) on each flicker roller
Contact toner retention member: Installed on the downstream brush roller (on the side where the amount of toner reached is small,
Confirmed during actual shooting), conductive nylon brush 6d, 7.75k
f / cm ² , hair length 6 mm, hair width 3 mm × length 320 mm
<Printing and measurement>
The actual shooting test of continuous 100 prints of the original with 20% coverage is performed, and after completion, the toner slipping state on the flicker roller is visually confirmed.

  That is, a scraper that was worn when a toner retention member was installed on the flicker roller and a case where nothing was installed were prepared, and the wear amount d (see FIG. 3) and the cleaning performance of the scraper were compared.

  FIG. 3 is a diagram showing a measuring part for attaching the scraper and for the amount of wear.

<Experimental result>
As shown in Table 1, by installing the toner retaining member upstream of the scraper contact portion where the amount of toner reaching the flicker roller is small, the wear of the scraper can be reduced, and good cleaning performance can be obtained due to the effect. In Table 1, ◯ indicates good and × indicates poor.

  The effects of the present invention were verified also from the results of the above confirmation experiment.

  It should be noted that the same effect can be obtained by using the toner retaining member in the form of the collection brush roller 30B instead of the auxiliary brush 30A as shown in FIG.

1 is a schematic diagram illustrating an example of an overall configuration of an image forming apparatus. FIG. 2 is an enlarged view of an intermediate transfer belt cleaning device in FIG. 1. It is a figure which shows the measurement part of attachment of a scraper, and wear amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming means 10 Photoconductor 13 Developing device 20 Intermediate transfer belt 21 Drive roller 24 Driven roller 28 Cleaning device 281, 282 Brush roller 283, 284 Flicker roller 285, 286 Scraper 30 Toner staying member 302 Toner receiving member 30A Auxiliary brush 30B Recovery Brush roller

Claims (2)

The electrostatic latent image formed on the image bearing member is visualized as a toner image by a developing unit, and the toner image is transferred to an intermediate transfer belt and further transferred to a transfer material, and then remains on the intermediate transfer belt. the toner, in the image forming apparatus is removed by a cleaning means having a plurality of brush rollers which a bias voltage is applied, a plurality of flicker roller for removing the toner from each of the plurality of the brush roller, each of the plurality of the flicker roller A scraper that scrapes off the toner by contacting the toner and a flicker roller that removes the toner from the brush roller that collects a small amount of cleaned toner, and a toner retention member is installed upstream of the scraper that contacts the flicker roller An image forming apparatus. The image forming apparatus according to claim 1, wherein the toner staying member is a fixing member that contacts the flicker roller .

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