JP2007108589A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a cleaning blade provided for a transfer roller from being turned up, while restraining wasteful toner consumption. <P>SOLUTION: By directly transferring a toner image formed on a non-image part to the transfer roller and supplying toner periodically, the cleaning blade is prevented from being turned up. By controlling the supply of toner based on printing information on the non-image part considering the supply of toner in frameless printing and the supply of toner by a control patch, the wasteful toner consumption is restrained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer and a copying machine using an electrophotographic system.

  In recent years, the demand for borderless prints that form an image on the entire surface of a recording medium has increased, and an image forming apparatus that uses an electrophotographic method is considered to be capable of this. In the case of electrophotographic printing, when performing borderless printing, an image larger than the recording medium is formed on the image carrier, and the image is transferred to reliably eliminate the margins, thereby creating a borderless image. Yes.

Conventionally, in an image forming apparatus using an electrophotographic system, a transfer roller is often used as a means for transferring an image from an image carrier to a recording medium. When borderless printing is performed as described above, there is a problem in that the toner image formed on the outside of the recording medium adheres to the transfer roller itself and stains the back surface of the recording medium. In view of this, there has been proposed an image forming apparatus that is provided with a cleaning means such as a cleaning blade that cleans the surface of the transfer roller after the transfer, and cleans the toner image transferred to the surface of the transfer roller (JP-A-8-190288, JP-A-8-290288). 8-240998).
Japanese Patent Laid-Open No. 08-190288 Japanese Patent Laid-Open No. 08-240998

  However, since the cleaning means provided on the transfer roller collects almost no toner in a normal printing operation with a margin, it is mainly compared with the cleaning means provided on the photosensitive drum or the intermediate transfer body that collects transfer residual toner. As a result, the amount of toner that is regularly collected decreases. Rubber cleaning blades that are widely used as cleaning means tend to cause blade turning when the toner staying at the edge of the blade is depleted. The risk of turning over the blade is greater than in the case of the body.

  In order to solve the above-described problems, the image forming apparatus of the present invention periodically forms a toner image on the non-image portion and collects it by the cleaning means of the transfer roller, thereby eliminating the risk of turning up the cleaning roller of the transfer roller. To reduce. Also, wasteful toner consumption can be suppressed by changing the supply amount in consideration of the amount of toner collected by the transfer roller cleaning means by printing on a non-image portion by borderless printing, a control patch, or the like. It becomes possible.

  As described above, according to the present invention, in an electrophotographic image forming apparatus, a toner image is formed on a non-image portion on an image carrier, transferred to a transfer roller, and transferred by periodically supplying toner. It is possible to prevent the cleaning blade coming into contact with the roller from turning up. In addition, in consideration of the supply of toner by borderless printing or the like, wasteful toner consumption can be suppressed by controlling the supply of toner based on the print information to the non-image portion.

  Hereinafter, the present invention will be described in detail based on examples.

  A first embodiment will be described with reference to FIGS.

  FIG. 1 is a block diagram showing a tandem color image forming apparatus employing an intermediate transfer member 30 as an example of an electrophotographic color image forming apparatus.

  The operation of the electrophotographic color image forming apparatus will be described with reference to FIG.

  As shown in FIG. 1, the color image forming apparatus includes a paper feeding unit 21, photosensitive members (hereinafter referred to as photosensitive drums) 22Y, 22M, 22C, and 22K arranged in parallel for development colors, and a charger 23Y that constitutes a charging unit. , 23M, 23C, 23K, toner cartridges 25Y, 25M, 25C, 25K, developing devices 26Y, 26M, 26C, 26K constituting the developing means, photosensitive drum cleaning means 27Y, 27M, 27C, 27K, intermediate transfer member 30, The image forming apparatus includes a primary transfer roller 31, a secondary transfer roller 32, and a fixing unit 50. An electrostatic latent image is formed by exposure controlled by an image processing unit (not shown) based on an image signal. The image is developed to form a monochromatic toner image, and the monochromatic toner images are superimposed to form a multicolor toner image. The multicolor toner image is transferred to the recording medium 11. Copy, is intended to fix the multicolor toner image on the recording medium 11.

  The photosensitive drums 22Y, 22M, 22C, and 22K are configured by applying an organic optical transmission layer to the outer periphery of an aluminum cylinder, and are rotated counterclockwise when a driving force of a driving motor (not shown) is transmitted.

  As charging means, four chargers 23Y, 23M, 23C, and 23K for charging the photosensitive drums of yellow (Y), magenta (M), cyan (C), and black (K) are provided for each station. .

  Exposure to the photosensitive drums 22Y, 22M, 22C, and 22K is sent from the scanner units 24Y, 24M, 24C, and 24K, and electrostatic latent images are obtained by selectively exposing the surfaces of the photosensitive drums 22Y, 22M, 22C, and 22K. Is formed.

  As developing means, in order to visualize the electrostatic latent image, four developing devices 26Y, 26M for developing yellow (Y), magenta (M), cyan (C), and black (K) for each station, 26C and 26K.

  The intermediate transfer member 30 is in contact with the photosensitive drums 22Y, 22M, 22C, and 22K, and a drive motor (not shown) rotates the intermediate transfer member 30 in the clockwise direction. By rotating the photosensitive drums 22Y, 22M, 22C, and 22K according to the image forming operation and applying a bias to the primary transfer rollers 31Y, 31M, 31C, and 31K, the monochrome toner images are sequentially transferred to the intermediate transfer body 30. Is transcribed. The transfer residual toner remaining on the photosensitive member is collected by the photosensitive drum cleaning means 27Y, 27M, 27C, and 27K.

  Thereafter, the intermediate transfer member 30 and the secondary transfer roller 32 provided so as to be in contact with the intermediate transfer member 30 sandwich the recording medium 11 and apply a bias to the secondary transfer roller 32, whereby the recording medium 11. Then, the multicolor toner image on the intermediate transfer body 30 is transferred.

  The fixing unit 50 melts and fixes the transferred multi-color toner image while conveying the recording medium 11, and as shown in FIG. 1, the fixing roller 51 for heating the recording medium 11 and the recording medium 11 are fixed to the fixing roller. A pressure roller 52 for press-contacting to 51 is provided. Heaters 53 and 54 are built in the fixing roller 51 and the pressure roller 52, respectively.

  The recording medium 11 after the toner image is fixed is then discharged to a discharge tray (not shown), and the image forming operation is completed.

  The intermediate transfer member cleaning means 33 is for cleaning the transfer residual toner remaining on the intermediate transfer member 30, the cleaning blade 34 for scraping off the transfer residual toner on the intermediate transfer member 30, and the scraped toner. It consists of a rake sheet 35 to be collected. The transfer residual toner after the four-color multicolor toner image formed on the intermediate transfer body 30 is transferred to the recording medium 11 is conveyed by a screw (not shown) and stored in a waste toner container 36 located on the front side of the main body. It is done.

  FIG. 2 is a cross-sectional view of the secondary transfer roller 32. As shown in FIG. 2 (a), a general transfer roller having no roller surface cleaning means is composed of a SUS cored bar 32a and an elastic layer 32b such as a sponge around it. In order to clean the surface with the cleaning blade 34, as shown in FIG. 2B, the outermost layer is covered with a resin tube made of polyimide or the like having a thickness of 20 to 100 μm. By making the outermost layer of the roller smooth, cleaning with a rubber blade becomes possible.

  FIG. 3A is an enlarged view of the secondary transfer portion of the image forming apparatus described above. The cleaning means for the secondary transfer roller is composed of a urethane rubber cleaning blade 37 having a thickness of 1 to 2 mm and a rake sheet 38 made of polyethylene terephthalate having a thickness of 20 to 75 μm. The toner adhering to the secondary transfer roller 32 is cleaned. The blade 37 is scraped off and collected.

  However, in the normal printing operation, as shown in FIG. 3A, the toner on the intermediate transfer member 30 is transferred to the recording medium 11, and therefore hardly adheres to the secondary transfer roller 32. Therefore, the cleaning blade The toner at the edge portion 37 is depleted, and the blade is likely to be turned over.

  Therefore, for each fixed number of prints (for example, every 50 sheets of A4 size), as shown in FIG. 3B, a toner image for supply to the cleaning blade is formed on the non-image portion that is not transferred to the recording medium. Then, by applying a bias having the same polarity as that in the normal image forming operation to the secondary transfer roller 32 and transferring the toner image directly from the intermediate transfer body 30 to the secondary transfer roller 32, the cleaning of the secondary transfer roller is performed. Toner is supplied to the blade 37.

  The color, shape, density, and the like of the toner image to be supplied are not limited. However, when the blade in a state where the toner is depleted cleans the solid image, there is a possibility that a cleaning failure may occur in which the toner slips through without being completely cleaned. In this case, a halftone image or the like is desirable.

  If the supply toner image is a non-image portion that is not transferred to the recording medium, it is formed in the main scanning direction with respect to the recording medium as shown in FIG. 4A, and the image is transferred to the recording medium. Even if the supplying operation is performed, the recording medium may be formed in the sub-scanning direction and supplied between the recording media as shown in FIG.

  However, if there is a bias in the toner supply with respect to the longitudinal direction of the cleaning blade, there is a possibility that an area where the toner supply is insufficient may occur, so a toner image for supply is formed in the non-image portion in the sub operation direction, It is desirable that the cleaning blade is supplied over the entire longitudinal width. However, since the supplied toner moves along the edge of the blade to some extent and spreads beyond the supplied width, it is possible to prevent the blade from being turned up even when supplying to a limited area.

  Therefore, an experiment was conducted to examine the relationship between the toner supply width and the effect of preventing blade turning. Table 1 shows the toner supply width (T1 + T2 in FIG. 4A) and T in FIG. 4B with respect to the cleaning blade longitudinal width (corresponding to W in FIGS. 4A and 4B). This is a summary of blade turnover rates when changing

表１から分かるように、クリーニングブレードの幅に対し、２０％以下の幅でトナーを供給した場合、クリーニングブレードのめくれを防止する効果が不十分となるため、２０％以上の幅を用いて供給することが必要である。したがって、記録媒体に対して主走査方向にクリーニングブレードの幅に対し２０％以上の非画像部が存在しない場合には、記録媒体に対し副走査方向の非画像部に形成することが必要となる。

As can be seen from Table 1, when toner is supplied at a width of 20% or less with respect to the width of the cleaning blade, the effect of preventing the cleaning blade from turning up is insufficient, and therefore, the toner is supplied using a width of 20% or more. It is necessary to. Accordingly, when there is no non-image portion of 20% or more with respect to the width of the cleaning blade in the main scanning direction with respect to the recording medium, it is necessary to form the non-image portion in the sub-scanning direction with respect to the recording medium. .

  As described above, according to this embodiment, it is possible to prevent the transfer blade cleaning blade from being turned up by forming a toner image for supplying toner in the non-image portion.

  A second embodiment will be described with reference to FIGS.

  This embodiment is different from the first embodiment in that printing on a non-image portion by borderless printing is considered, and the number of prints with a margin is used as print information on the non-image portion. The difference is that the timing of forming the toner image on the image portion is controlled.

  Since the basic configuration of the apparatus is the same as that of the first embodiment described above, only the control contents different from the above-described embodiment will be described here.

  As shown in the first embodiment, the toner supply itself can be performed by periodically forming a toner image on a non-image portion on the intermediate transfer member 30 and transferring it to the secondary transfer roller 32. When performing borderless printing, it is necessary to form an image about 1 to 2 mm larger than the recording medium in consideration of errors in the conveyance position of the recording medium in order to eliminate the margins. Thus, the toner image formed on the non-image portion outside the recording medium is transferred to the secondary transfer roller 32, and as a result, the same result as that when the toner is supplied to the cleaning blade 37 of the secondary transfer roller is brought about. Therefore, forming a toner image for supplying toner during borderless printing results in supplying toner more than necessary, leading to wasteful toner consumption.

  Therefore, in this embodiment, it is determined for each image whether it is borderless printing, and the number of prints with margins in which toner is not supplied to the cleaning means of the secondary transfer roller is counted, and recording is performed accordingly. By controlling the timing of printing on the non-image area in the sub-scanning direction on the medium, toner image formation for toner supply is performed only when a certain number of margins are printed, thereby reducing wasteful toner consumption. Yes.

  Hereinafter, the flow of control will be described using the flowchart of FIG.

In step 201, control is started from a print count E with margin E = 0.
In step 202, image data is transferred from a host computer (not shown) to the image forming apparatus.

  In step 203, it is determined whether the image data is borderless printing. If it is a borderless printing, the process proceeds to step 204a. If it is a printing with a margin, the process proceeds to step 204b.

  In step 204a, an image forming operation for a borderless image is performed, the print count with margins is left as it is, and the process returns to step 202 to move to determination of the next image data.

  On the other hand, in step 204b, an image forming operation for an image with a margin is performed.

  In step 205b, 1 is added to the print count with margins.

  In step 206b, it is determined whether the print count E with margin exceeds the preset upper limit value Elim. If it exceeds, the process proceeds to step 207b. If it does not exceed, the process returns to step 202b, and the next image data is determined. .

  In step 207b, a toner image for toner supply is formed in the non-image portion, and the process returns to step 201 to reset the print count E with margin.

  FIG. 6 is a printing example when the control of this embodiment is used.

  FIG. 6A shows a case where marginless printing is performed without borderless printing, and when the marginal print count E exceeds the upper limit Elim, the non-image portion between the recording media is not supplied with toner. A toner image is formed on the image portion.

  On the other hand, FIG. 6B shows a case in which borderless printing is continued, and the print count with margins does not increase. Therefore, toner image formation for toner supply is not performed, and only image data is printed.

  As described above, according to the present embodiment, by forming a toner image for supplying toner in the non-image portion, it is possible to count the number of prints with a margin while preventing the cleaning blade of the transfer roller from turning up. Thus, it is possible to suppress wasteful toner consumption.

  In this embodiment, the margin print count is incremented by 1 for each image data with margin. However, since the toner depletion state at the edge of the cleaning blade depends on the travel distance of the transfer roller, for example, it is counted for the A4 size. 1 may be added, and the count may be changed depending on the image size, such as adding 2 for the A3 size.

  A third embodiment will be described with reference to FIGS.

  This embodiment is different from the second embodiment in that the pixel count for printing on the non-image portion by borderless printing is used as print information on the non-image portion, and toner supply is performed as control for toner image formation. The difference is that the amount of toner consumed for forming the toner image on the non-image portion is changed. In the pixel count, the presence or absence of image data is determined for each pixel from the image information. If there is image data, 1 is counted per pixel, and 0 if there is no image data.

  Since the basic configuration of the apparatus is the same as that of the first embodiment described above, only the control contents different from the above-described embodiment will be described here.

  Hereinafter, the flow of control will be described using the flowchart of FIG.

  In step 301, image data is transferred from a host computer (not shown) to the image forming apparatus.

  In step 302, a non-image portion pixel count P to be printed on a non-image portion outside the recording medium is calculated from the image data.

  In step 303, the calculated non-image part pixel count P is compared with a preset non-image part pixel count upper limit value Plim. If P exceeds Plim, the process proceeds to step 304a, and if it falls, the process proceeds to step 304b. When P is higher than Plim, it can be determined that the toner is sufficiently supplied to the cleaning means of the secondary transfer roller by printing on the non-image portion by borderless printing. On the other hand, when P is lower than Plim, In addition, it is necessary to separately form a toner image on the non-image portion and supply the toner.

  In step 304a, since the non-image is sufficiently printed only by the image data, only the image data is printed.

  On the other hand, in step 304b, a toner image having a pixel count (Plim-P) is formed in the non-image portion in the sub-scanning direction with respect to the recording medium by the amount P is insufficient for Plim.

  An actual printing example by the control as described above is shown in FIG.

  FIG. 8A shows the case of image data with margins where no borderless printing is performed. At this time, since the non-image portion pixel count P is 0 (or at least P <Plim), the non-image portion for supplying toner is displayed. The toner image is formed.

  FIG. 8B shows a case where a small amount of borderless printing is performed and P <Plim. In this case, although the toner image formed on the non-image portion is collected by the cleaning means of the secondary transfer roller, it is insufficient with respect to the upper limit value Plim. The toner image is formed on the non-image portion. Therefore, the amount of toner consumed in the toner image for supplying toner is smaller than that in FIG.

  FIG. 8C shows a case where borderless printing exceeding a certain level is performed and P> Plim. In this case, since the toner is sufficiently supplied only by the image data, it is not necessary to separately form a toner image for supplying the toner.

  As described above, according to the present embodiment, by using the pixel count number as the printing information on the non-image portion, the amount of toner printed on the non-image portion is accurately grasped and consumed for printing on the non-image portion. It is possible to control the amount of toner to be finely controlled.

  In this embodiment, the toner image is formed on the non-image portion for each piece of image data. However, the toner image may be formed every certain number of times, or as described in the second embodiment, The image formation timing may be controlled.

  Further, in this embodiment, only the pixel count of printing on the non-image portion by the borderless printing is counted, but a control patch or the like formed on the image carrier for the purpose of density detection or printing position correction, It is also possible to consider the pixel count number of the toner image formed on the non-image part for other purposes.

  In this embodiment, the amount of toner consumed in the toner image for supplying toner is adjusted by changing the density of the toner image, but it may be adjusted by the area of the toner image.

  As described above, in the first to third embodiments, the color image forming apparatus using the intermediate transfer member has been described. However, the same effect can be obtained in a single color image forming apparatus that directly transfers a toner image from a photosensitive drum to a recording medium. Can be expected.

1 is a configuration diagram of a color image forming apparatus used for explaining a first embodiment of the present invention. Sectional view of the secondary transfer roller 32 1 is a configuration diagram of a secondary transfer unit in a color image forming apparatus used for explaining a first embodiment of the present invention. Example of toner image formation in the first embodiment of the present invention The flowchart which shows the control content in 2nd Example of this invention. Example of printing in the second embodiment of the present invention The flowchart which shows the control content in the 3rd Example of this invention. Example of printing in the third embodiment of the present invention

Explanation of symbols

11 Recording medium 21a, 21b Paper feed unit 22Y, 22M, 22C, 22K Photosensitive drum (photoconductor)
23Y, 23M, 23C, 23K Charger 24Y, 24M, 24C, 24K Scanner unit 25Y, 25M, 25C, 25K Toner cartridge 26Y, 26M, 26C, 26K Developer 27Y, 27M, 27C, 27K Photosensitive drum cleaning means 30 Intermediate Transfer body 31 Primary transfer roller 32 Secondary transfer roller 32a Core metal of secondary transfer roller 32 32b Elastic layer of secondary transfer roller 32 32c Cover tube of secondary transfer roller 32 33 Cleaning means for intermediate transfer body 34 Cleaning blade 35 Rake Sheet 36 Waste toner container 37 Cleaning blade 38 Rake sheet 39 Waste toner 50 Fixing means 51 Fixing roller 52 Pressure roller 53, 54 Heater

Claims (12)

  An image carrier, a transfer roller that transfers a toner image from the image carrier to a recording medium, and a cleaning unit that uses a blade that cleans the surface of the transfer roller. An image forming apparatus, wherein a toner image is formed, and the toner image for supplying toner is transferred to a transfer roller, whereby toner is supplied to a cleaning means of the transfer roller.   2. The image according to claim 1, wherein the toner image for supplying toner is formed using a region having a width of at least 20% in the main scanning direction with respect to the width of the cleaning unit of the transfer roller. Forming equipment.   The image forming apparatus according to claim 1, wherein the image carrier is an intermediate transfer member.   The image forming apparatus according to claim 1, wherein the image carrier is a photoconductor.   The image forming apparatus according to claim 1, wherein the toner image formed on the non-image portion is formed on a non-image portion in a main scanning direction of exposure with respect to a recording medium.   The toner image to be formed on the non-image portion is formed on a non-image portion in a recording medium conveyance direction between a recording medium and a next recording medium, according to any one of claims 1 to 4. The image forming apparatus described.   The image forming apparatus according to claim 1, wherein formation of a toner image formed on the non-image part is controlled by printing information on the non-image part.   The image forming apparatus according to claim 7, wherein the control changes a timing for forming a toner image in a non-image portion.   The image forming apparatus according to claim 7, wherein the control changes a toner consumption amount used for a toner image formed in a non-image portion.   The image forming apparatus according to claim 7, wherein the printing information on the non-image portion is a pixel count number for printing on the non-image portion.   Borderless printing for forming an image with no margins on the entire surface of the recording medium is possible, and the printing information on the non-image part is a ratio of normal printing with margins and borderless printing. The image forming apparatus according to claim 7.   The image forming apparatus according to claim 7, wherein the print information on the non-image portion is a number of normal prints having a margin.

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