JP4054570B2 - Color image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus using an electrophotographic process in a copying machine, a facsimile machine, a printer or the like, and more specifically, includes an image carrier and an image carrier cleaning device, and is collected by the image carrier cleaning device. The present invention relates to a color image forming apparatus that reuses toner.
[0002]
[Prior art]
In recent years, a large amount of color documents have been handled in offices, and the demand for color image forming apparatuses such as color printers and color copiers is increasing.
[0003]
Conventionally, as a full-color image forming apparatus, a plurality of developing devices are arranged so as to come into contact with a photosensitive member as one image carrier, and a toner image of each color is created every rotation of the photosensitive member. There is a so-called one-drum configuration in which a color toner image is created by transferring onto a transfer material such as paper or an OHP sheet. Further, in this one-drum color image forming apparatus, an intermediate transfer system in which the toner images of the respective colors on the photosensitive member are primarily transferred and superimposed on the intermediate transfer member and then collectively transferred onto the transfer material. And a direct transfer type in which a color toner image is formed by sequentially transferring toner images of respective colors on a photoconductor onto a transfer sheet held on a transfer drum or the like. There is also a configuration using two photosensitive members.
In addition to the full-color image forming apparatus having the above-described 1 or 2 drum configuration (hereinafter referred to as 1 drum configuration, etc.), in order to cope with high speed, a developing device and a photoconductor are provided for each color, and these are used as an intermediate transfer body or transfer A so-called tandem color image forming apparatus is known which is arranged in a straight line in the moving direction of the material surface. In this type of color image forming apparatus, latent images of images corresponding to different colors formed individually for each photoconductor are individually converted into toner images by a developing device, and the toner images of these colors are transferred onto an intermediate transfer member or transfer material. In this way, a color image is obtained by transferring the images while sequentially superimposing them.
[0004]
By the way, in a color image forming apparatus using two or more types of color toner, there are more types of toner used than in a monochrome image forming apparatus, and the image area ratio like a photographic document is larger than a monochrome image. Since many images are often output, the amount of toner consumed for each color is relatively large. However, in recent years, there has been a movement to reduce the size and weight of the apparatus, and it has become difficult to secure a large storage space that can sufficiently accommodate each color toner. From the viewpoint, it is being demanded to collect the residual toner remaining on the surface of the photoreceptor so that the collected toner can be recycled.
[0005]
[Problems to be solved by the invention]
However, there are some problems in making the collected toner recyclable. In the case of the former one-drum configuration or the like among the various color image forming apparatuses as described above, toner images of a plurality of colors are sequentially formed on the surface of one photoconductor. The collected toner has a high color mixing ratio, and it is very difficult to completely separate it and return it to each developing device. Therefore, the collected toner is usually discarded as it is. On the other hand, the latter tandem system has a photoconductor for each color, and therefore, recycling using the collected toner by each photoconductor cleaning device and reusing the collected toner for image formation is easier than the former system. it is conceivable that. However, even in the latter case, there are problems in carrying out actual recycling. That is the color mixing of the upstream color to the downstream color process.
[0006]
For example, toner images are formed on four photoconductors using four developing units each containing four color toners, and each color toner image formed on the photoconductor is After the primary transfer, the toner images on the intermediate transfer member are transferred onto the transfer material in a batch, and then transferred onto the transfer material. Consider a case in which residual toner is collected separately for each color toner by four cleaning devices corresponding to the residual toner of each color. However, here, it is assumed that no toner remains on the intermediate transfer body after the secondary transfer.
[0007]
In such a case, toner of other colors does not mix with the residual toner on the photoconductor after the first color toner image is primarily transferred to the intermediate transfer body. Therefore, with respect to the residual toner of the first color, the collected toner can be reused as a recycled toner.
However, toners of other colors may be mixed with the residual toner on the photoconductor after the toner images of the second and subsequent colors are sequentially primary transferred to the intermediate transfer body. That is, in this type of color image forming apparatus, when the second color toner image is primarily transferred to the intermediate transfer member, the first color toner that has already been primarily transferred onto the intermediate transfer member is transferred to the photosensitive member. The toner of the first color that is reversely transferred may be mixed with the residual toner composed of the toner of the second color that is reversely transferred to the surface and remains on the photoconductor. Similarly, the residual toner composed of the third color toner on the photosensitive member is mixed with the first and second color toners reversely transferred to the photosensitive member, and the residual toner composed of the fourth color toner on the photosensitive member is included in the residual toner. The first color, the second color, and the third color reversely transferred to the photoconductor may be mixed. For this reason, regarding the residual toners of the second and subsequent colors, there is a problem in reusing the collected toner as a recycled toner as it is.
[0008]
Here, some countermeasures for preventing color mixture of the collected toner have been proposed. For example, in the “color image forming apparatus” disclosed in Japanese Patent Application Laid-Open No. 2000-242152, the toner previously transferred onto the intermediate transfer member due to discharge when the toner image is transferred from the image bearing member to the intermediate transfer member. A part of the charge polarity is opposite to the normal charge polarity, and the toner with this reverse charge polarity will be transferred back to the image carrier when transferring the next color toner. By providing a reversely charged toner removing means for collecting the toner using the reverse charge polarity of the toner, color mixture on the image bearing member is prevented.
[0009]
However, in such a color image forming apparatus, the toner having a reverse polarity charge has a stable regular charge polarity from the beginning, and the charge amount of the reverse polarity toner is not stable. Furthermore, since the toner reversely transferred to the photosensitive member is often a toner whose electric charge is almost “0”, the reversely charged toner removing means as described above cannot completely collect the mixed color toner. Therefore, with such a method, the color mixture of the collected toner cannot be reliably prevented.
[0010]
In addition, the “image forming apparatus” disclosed in Japanese Patent Laid-Open No. 10-293432 is not a tandem apparatus, but in order to prevent reverse charging of the toner that causes reverse transfer of the toner to the photoconductor, A method is used to neutralize the ground potential. Here, it is assumed that the toner image before transfer does not scatter by adjusting the degree of charge removal, but in reality the charge is suddenly reduced by light removal by light irradiation, so the toner in the image area moves to the periphery and the image I'm blurred. Also, if the background potential before the transfer is low, the toner image is discharged when it is transferred from the image bearing member to the intermediate transfer member, and the reversely charged toner is reversely transferred to the photosensitive member due to the discharge. It is impossible to prevent the color mixture of the collected toner due to the reverse transfer of the reversely charged toner to the photoreceptor. As described above, in this image forming apparatus, it is very difficult to completely prevent the mixed color of the collected toner.
[0011]
In addition, in the “image forming apparatus” disclosed in JP-A-8-63067 and JP-A-2000-267366, as problems of the toner collected by cleaning, toner aggregation and a decrease in charging characteristics are raised. It proposes to determine the supply ratio and optimize the process conditions. However, in this image forming apparatus, focusing on the color mixture state of the collected toner as described above, the color mixture state of the collected toner cannot be detected or predicted. Therefore, when the collected toner is reused as the recycled toner, The change in color due to the color mixture of the toner cannot be taken into consideration, and the image quality deterioration cannot be suppressed.
[0012]
As a prior application that considers the change in color, there is an “image forming apparatus” disclosed in Japanese Patent Laid-Open No. 9-6201. In this publication, by combining magnetic toner and non-magnetic toner, it is possible to detect the color mixing degree of the collected toner from the ratio of the magnetic toner and the non-magnetic toner, and discarding the collected toner whose color mixing level exceeds a certain level. is suggesting. According to this apparatus, it is possible to avoid an increase in the degree of color mixing in the developing device, but it is not possible to recycle and use the collected toner mixed in a certain level or more.
[0013]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described background, and an object of the present invention is to make it possible to effectively recycle the collected toner that has been mixed, and to reduce image quality due to toner mixing even when the collected toner is recycled. It is an object of the present invention to provide a color image forming apparatus that can be suppressed.
[0014]
[Means for Solving the Problems]
  In order to achieve the above object, a color image forming apparatus according to claim 1 comprises:Four colorsCorresponding to each color of the imageDiveAn image is formedpluralAn image carrier, a plurality of developers for supplying a unique color toner corresponding to each image color to visualize each latent image formed on the image carrier, and a unique color in each developer Transfer means for sequentially superimposing and transferring the toner images of the respective colors on the image carrier that has been visualized with toner onto the transfer target, and residual toner remaining on the image carrier after the transfer of the toner image to recoverpluralImage carrier cleaning meansAndIn the color image forming apparatus, the specific color that is one specific color among the toners is composed of magnetic toner or non-magnetic toner, and all the remaining colors other than the specific color are composed of magnetic toner. If the specific color is composed of non-magnetic toner, it is composed of magnetic toner.The transfer order of the toner images formed by the respective color developing devices from the image carrier to the transfer target is configured such that the toner image of the specific color is first or second, and the second or later in the transfer order. About the image carrierRecovered toner collected by image carrier cleaning meansThe magnetRecovered toner separating means for separating the toner into the non-magnetic toner and the non-magnetic tonerThe magnetic toner and the non-magnetic toner separated by the collected toner separating means for the second image carrier in the transfer order are respectively supplied to the first collected toner supply means for supplying to the developing unit used, and in the transfer order. Second recovered toner supply for supplying the magnetic toner and the non-magnetic toner separated by the collected toner separating means for the third and subsequent image carriers to a specific color developing unit which is a developing unit for forming the specific color toner image, respectively. And a supply amount adjusting means for adjusting a supply amount of the recovered toner having a magnetic characteristic different from that of at least the specific color toner among the recovered toner to the specific color developing device when the second recovered toner is supplied.Is provided.
  Claim2The color image forming apparatus of claim1In the color image forming apparatus, a color mixing state detection unit that detects a mixed state of a color different from the specific color in the toner in the specific color developing device is provided, and the toner of the specific color and the magnetic force adjusted by the supply amount adjusting unit are provided. The supply amount of the collected toner having different characteristics to the specific color developing device is determined based on the detection result by the color mixture state detection means.
  Claim3The color image forming apparatus of claim2In the color image forming apparatus, the color mixture state detection unit is configured to detect a color mixture state using image data of an already formed image..
  Claim4The color image forming apparatus of claim 1, 2.Or 3In the color image forming apparatus, the specific color is black.
  Claim5The color image forming apparatus according to claim 1, 2, 3.Or 4In this color image forming apparatus, a magnetic filter is used as the collected toner separating means.
  Claim6The color image forming apparatus according to claim 1, 2, 3, 4.Or 5In this color image forming apparatus, a magnetic roller is used as the collected toner separating means.
  Claims 1 to6In such a color image forming apparatus, the image carrier is not transferred to the transfer member but remains on the image carrier, or remains on the image carrier by reverse transfer from the transfer member to the image carrier. The remaining toner is collected by the cleaning unit, and separated by the collected toner separation unit using the magnetic characteristics (magnetic / nonmagnetic) of the toner. Of the plurality of color toners, only one specific color has magnetic characteristics different from those of all the other remaining colors. Therefore, the collected toner is separated by the magnetic characteristics (magnetic / non-magnetic) and the specific color It can be separated from other than a specific color. Further, by returning at least the collected toner of a specific color to the developing device of the color by the collected toner supply means, the collected toner can be recycled without increasing the color mixing ratio of the specific color toner.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a color printer which is an image forming apparatus of a tandem type intermediate transfer system will be described.
FIG. 1 is a schematic configuration diagram of a printer to which the present invention is applicable. In the figure, reference numeral 100 is a copying apparatus main body, 200 is a paper feed table on which the copying apparatus is placed, 300 is a scanner mounted on the copying apparatus main body 100, and 400 is an automatic document feeder (ADF) mounted thereon. The copying machine main body 100 is provided with an intermediate transfer belt 10 as a transfer belt in the center.
[0016]
As shown in FIG. 1, the intermediate transfer belt 10 is wound around three support rollers 14, 15, and 16 so as to be able to rotate and convey clockwise in the drawing. In this illustrated example, an intermediate transfer body cleaning device 17 for removing residual toner remaining on the intermediate transfer belt 10 after image transfer is provided on the left of the second support roller 15 among the three. Of the three, four images of yellow, magenta, cyan, and black are arranged on the intermediate transfer belt 10 stretched between the first support roller 14 and the second support roller 15 along the conveyance direction. The tandem image forming unit 20 is configured by arranging the forming units 18Y, 18M, 18C, and 18B side by side. However, these four color orders are merely examples, and the present invention is not limited to these.
[0017]
FIG. 2 is a partially enlarged view of the tandem image forming unit 20. In the tandem image forming unit 20, the image forming units 18Y, 18M, 18C, and 18B, which are individual toner image forming units, are photosensitive drums 40Y, 40M, 40C as drum-shaped image carriers as shown in FIG. , B, charging devices 60Y, M, C, B, developing devices 61Y, M, C, B, primary transfer devices, photoconductor cleaning devices 63Y, M, C, B, static elimination devices 64Y, M, C, B and so on.
[0018]
The charging device 60 is a roller charging roller 60Y, M, C, or B in the illustrated example, and contacts the photosensitive drums 40Y, 40M, 40C, 40B, and applies voltages to the photosensitive drums 40Y, 40Y, 40M, 40B, and 40D. C and B are charged. Of course, charging can be performed with a non-contact scorotron charger.
[0019]
An exposure device 21 is further provided on the tandem image forming unit 20 as shown in FIG. On the other hand, a secondary transfer device 22 as a secondary transfer unit is provided on the opposite side of the intermediate transfer belt 10 from the tandem image forming unit 20. In the illustrated example, the secondary transfer device 22 includes a secondary transfer belt 24, which is an endless belt, spanned between two rollers 23, and is pressed against the third support roller 16 via the intermediate transfer belt 10. The image on the intermediate transfer belt 10 is secondarily transferred to a sheet S as an image holding member. A fixing device 25 for fixing the transferred image on the sheet S is provided beside the secondary transfer device 22. The fixing device 25 is configured by pressing a pressure roller 27 against a fixing roller 26 as a fixing member.
[0020]
The secondary transfer device 22 described above is also provided with a sheet transport function for transporting the sheet S after image transfer to the fixing device 25. Of course, a transfer roller or a non-contact charger may be arranged as the secondary transfer device 22, and in such a case, it is difficult to provide this sheet conveyance function together. In the illustrated example, under such a secondary transfer device 22 and a fixing device 25, a sheet reversal that inverts the sheet S to record images on both sides of the sheet S in parallel with the tandem image forming unit 20 described above. A device 28 is provided.
[0021]
Now, 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 by it.
When a start switch (not shown) is pressed, when the document is set on the automatic document feeder 400, the document is transported and moved onto the contact glass 32, and then the document is set on the other contact glass 32. At that time, the scanner 300 is immediately driven to travel the first traveling body 33 and the second traveling body 34. Then, the first traveling body 33 emits light from the light source and further reflects the reflected light from the document surface toward the second traveling body 34 and is reflected by the mirror of the second traveling body 34 and passes through the imaging lens 35. The document is placed in the reading sensor 36 and the original content is read.
[0022]
Then, the photosensitive drums 40Y, M, C, and B are rotated by the individual image forming units 18Y, 18M, 18C, and 18B, and first, with the rotation of the photosensitive drums 40Y, M, C, and B, first, the charging devices 60Y and M , C, and B uniformly charge the surfaces of the photosensitive drums 40Y, 40M, 40C, and 40B, and then from the above-described exposure devices 21Y, 21M, 21C, and 21B with lasers, LEDs, and the like according to the reading contents of the scanner 300 Irradiation with the writing light L forms an electrostatic latent image on the photosensitive drums 40Y, 40M, 40C, and 40B.
Thereafter, the toner is attached by the developing devices 61Y, 61M, 61C, and 61B, and the electrostatic latent images are visualized to form cyan, magenta, yellow, and black on the photosensitive drums 40Y, 40M, 40C, and 40B, respectively. The monochrome image is formed. A drive motor (not shown) drives one of the support rollers 14, 15, 16 to rotate the other two support rollers, and rotates and conveys the intermediate transfer belt 10 to primarily transfer the visible image. The image is sequentially transferred onto the intermediate transfer belt 10 by the apparatus. As a result, a composite color image is formed on the intermediate transfer belt 10. The surfaces of the photoconductive drums 40Y, M, C, and B after image transfer are cleaned by removing residual toner with photoconductor cleaning devices 63Y, M, C, and B, which will be described later, and discharging devices 64Y, M, C, and B. To remove the charge and prepare for the image formation again.
[0023]
On the other hand, when a start switch (not shown) is pressed, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated, the sheet S is fed out from one of the paper feed cassettes 44 provided in multiple stages in the paper bank 43, and the separation roller The sheet is separated one by one at 45 and put into the sheet feeding path 46, conveyed by the conveying roller 47, guided to the sheet feeding path 48 in the copying machine main body 100, abutted against the registration roller 49 and stopped. Alternatively, the sheet feeding roller 50 is rotated to feed out the sheets S on the manual feed tray 51, separated one by one by the separation roller 52, put into the manual feed path 53, and abutted against the registration roller 49 and stopped.
[0024]
Then, the registration roller 49 is rotated in synchronization with the composite color image on the intermediate transfer belt 10, the sheet S is fed between the intermediate transfer belt 10 and the secondary transfer device 22, and transferred by the secondary transfer device 22. A color image is recorded on the sheet S. The sheet S after the image transfer is conveyed by the secondary transfer device 22 and sent to the fixing device 25, and the fixing device 25 applies heat and pressure to fix the transferred image, and then is switched by the switching claw 55 and discharged. The paper is discharged by a roller 56 and stacked on a paper discharge tray 57. Alternatively, it is switched by the switching claw 55 and put into the sheet reversing device 28, where it is reversed and guided again to the transfer position, and an image is recorded also on the back surface, and then discharged onto the discharge tray 57 by the discharge roller 56. On the other hand, the intermediate transfer belt 10 after image transfer is removed by the intermediate transfer body cleaning device 17 to remove residual toner remaining on the intermediate transfer belt 10 after image transfer, and is prepared for re-image formation by the tandem image forming unit 20.
[0025]
The photoconductor cleaning device 63 includes a cleaning blade 75 made of polyurethane rubber, for example, with its tip pressed against the photoconductor 40. In order to improve the cleaning property, a brush whose outer periphery contacts the photoreceptor 40 is used in combination. In this explanatory diagram, the outer periphery is provided on the photosensitive member 40 and a contact conductive fur brush 76 is rotatably provided in the direction of the arrow. Then, residual toner on the photoconductor 40 is removed by a fur brush 76 that rotates in the counter direction with respect to the photoconductor 40. The removed toner is returned to the developing device by the toner conveying device 80 connecting the photoconductor cleaning device 63 and the developing device, and used again for development.
[0026]
By the way, when the residual toner on the photoreceptor is recycled, a problem of toner color mixing occurs.
In the case of the present embodiment, for example, toner of other colors does not mix with the residual toner on the photoreceptor 40Y after the yellow toner image of the first color is primarily transferred to the intermediate transfer belt 10. . Therefore, with respect to the residual toner of the first color, the collected toner can be reused as a recycled toner.
However, toners of other colors may be mixed with the residual toner on the photoreceptors 40M, C, and B after the toner images of the second and subsequent colors are sequentially primary transferred to the intermediate transfer belt 10. That is, when the toner image of the second color and thereafter is primarily transferred to the intermediate transfer belt 10, since the toner image already transferred on the upstream side exists on the intermediate transfer belt 10, this toner image is the photosensitive member 40M. , C, and B are reversely transferred to the surface of the photosensitive member, and the toner is mixed in color. For this reason, there is a problem in reusing the collected toner as the recycled toner as it is with respect to the residual toner of the second and subsequent colors. For example, when the second color magenta toner image is primarily transferred from the photoreceptor 40M to the intermediate transfer belt 10, the yellow toner image of the first color already transferred on the intermediate transfer belt 10 is already supported. To enter the primary transfer nip. The magenta toner image is primarily transferred onto the intermediate transfer belt 10 at the nip portion between the photoreceptor 40M and the intermediate transfer belt 10, and at the same time, the yellow toner forming the yellow toner image on the intermediate transfer belt 10 is photosensitive. It is reversely transferred onto the body 40M. For this reason, the residual toner collected by the photoconductor cleaning device 63M of the photoconductor 40M is simultaneously collected in a state where the magenta transfer residual toner and the yellow reverse transfer toner are mixed. This is a color mixture. If the mixed color toner is supplied to the developing device as it is and reused, a small amount of color mixture has little effect on the image quality, but if a large amount of color is mixed, the color change, that is, the color difference becomes large and the color reproducibility deteriorates. End up.
[0027]
The color change due to the color mixture varies depending on the combination of colors to be mixed as well as the degree of color mixture (hereinafter referred to as the color mixture level).
FIG. 3 is a graph showing a result of measuring a difference from the original color (hereinafter referred to as a color difference) when the color mixing degree is changed. The horizontal axis indicates the toner color mixture degree (%), and the vertical axis indicates the color difference. A is assumed to be an allowable value of the color difference fluctuation. Also, B in the graph indicates that when each color toner is mixed with black toner, D indicates when black toner is mixed with cyan or magenta toner, E indicates when yellow toner is mixed with yellow toner, and C group indicates other colors. The combination of is shown.
[0028]
The image forming process and various conditions when the above data was taken were as follows. All the photoconductors 40Y, 40M, 40C, and 40B were charged by a non-contact roller charging system at a non-image portion to −700 V and exposed by LD. Each color toner image was formed by a post-development apparatus. The developed toner image on the photoreceptor is primarily transferred to the intermediate transfer belt 10, but in this experiment, the intermediate transfer belt 10 has a surface elastic layer on the resin layer and a volume resistance of 8 × 10.⁹A Ωcm type was used, and the primary transfer bias was 1300 V under low voltage control. However, it goes without saying that the bias value varies depending on the belt material. The residual toner on the photoconductor 40 was collected using a blade-type photoconductor cleaning device 63 whose tip is in contact with the photoconductor 40 and removes toner on the surface of the photoconductor.
[0029]
From FIG. 3, it can be seen that there is a difference in the state of color difference depending on the degree of color mixture depending on the combination of colors to be mixed. In particular, when compared with other colors, the black toner is less affected by the color mixture because of less change from the original color due to the color mixture. Therefore, conventionally, the collected toners collected by the photoreceptor cleaning devices 63Y, 63M, 63C, 63B for each color are not returned to the developing device 61 of the original color, but are all returned to the black developing device 61B for recycling. There was also a thing. However, as shown in FIG. 3, even with black toner, the occurrence of a color difference cannot be avoided with the progress of the degree of color mixture. For this reason, most of the apparatuses discard all the toner collected by the photoconductor cleaning apparatuses 63Y, 63M, 63C, and B without reusing them. Therefore, in the present embodiment, a color printer that enables the collected toners that have been mixed colors to be effectively recycled can be suppressed, and even when the collected toners are recycled, image quality deterioration due to color differences due to the color mixture of toners can be suppressed.
[0030]
In this embodiment, a magnetic toner and a non-magnetic toner are used in combination with four types of color toners. Specifically, black is selected as one specific color, magnetic toner is used for this black toner, non-magnetic toner is used for three colors other than black, yellow, magenta, and cyan, and each is used as a one-component developer. Yes. The developing device 61 employs a system that does not use magnetic force for toner conveyance so that toner in which non-magnetic toner and magnetic toner are mixed can be developed.
[0031]
Here, the relationship between the magnetic characteristics of the toner and the developing method will be described. For example, as a developing method for developing magnetic toner, a toner that is charged in both polarities in advance by frictional charging between toners is developed by rotating a mag roller and a sleeve. BMT (Bipolar, Magnet, Toner) system that transports to the area, jumping system that forms a thin toner layer on the developing sleeve, and places the toner layer close to the photoconductor 40 to develop the toner by flying with an AC bias. is there. On the other hand, what is known as a developing system for developing a non-magnetic toner is NSP (Non-Magnetic Single--) which transports toner to a developing region by attaching the toner to a conductive or surface insulating developing roller. There are a Component, Development, Process) method, a non-magnetic toner jumping method, and a two-component toner, a magnetic brush developing method.
[0032]
In each of the developing devices 61Y, 61M, 61C, and 61B of the color printer according to the present embodiment, a mixed color toner may be reused for development. Must be used. As a developing method capable of developing both magnetic toner and non-magnetic toner, an NSP method, a non-magnetic toner jumping method, or the like that does not use magnetic force for toner conveyance can be considered. Therefore, in this embodiment, an NSP developing device is used.
[0033]
In the present embodiment, as shown in FIG. 2, the toner transport is performed as a recovered toner supply means for supplying the recovery and the toner recovered by the photosensitive member cleaning device 63B of the photosensitive member 40B carrying the black toner image to the black developing device 61B. An apparatus 80B is provided so that the collected toner can be used again for development. Further, a magnetic filter is provided as a collected toner separating means for separating the toner collected by the photoreceptor cleaning device 63B of the photoreceptor 40B carrying the black toner image into a magnetic toner and a non-magnetic toner.
[0034]
The toner conveying device 80B has a toner conveying path so that the recovered toner can be supplied from the photoconductor cleaning device 63B to the developing device 61B. Further, a magnetic filter is provided in the middle of the toner conveyance path, where only the magnetic toner is trapped and separated into magnetic toner, that is, black recycled toner and non-magnetic toner. As a configuration for separating toners having different magnetic pole characteristics with a magnetic filter, a magnetic gradient may be generated. As a method for generating a large magnetic gradient, there is a method using a stainless fine wire for the filter. Specifically, a fine stainless steel wire is formed in a mesh shape and placed in a magnetic field, and the collected toner in which magnetic toner and non-magnetic toner are mixed is allowed to pass and only the magnetic toner is attached to the filter to be separated ( High gradient magnetic separation). Further, air or the like may be blown from above the mesh on which the toner is placed in order to assist the separation. Thereby, it can isolate | separate more effectively. In this way, after the collected toner of the black developing device 61B is separated into the black recycled toner and the non-magnetic recycled toner, they are stored in different storage units.
[0035]
Here, the black recycled toner is a pure black toner with no color mixture, so there is no problem even if it is supplied to the black developing device 61B as it is. However, as described above, if the nonmagnetic recycled toner is continuously supplied to the black developing device 61B as it is, the color of black changes. However, it is desirable to avoid discarding non-magnetic recycled toner without using it from the viewpoint of saving resources and reducing running costs. Therefore, the supply amount of the recycled toner to the black developing device 61B is adjusted by the supply amount adjusting means between the black recycled toner and the non-magnetic recycled toner. The details of the supply amount adjusting means will be described below.
[0036]
FIG. 4 is a flowchart relating to replenishment of recycled toner that can suppress image quality deterioration called color difference due to toner color mixing. A toner consumption amount M of black toner is calculated from the image data (step 1). Further, since the toner consumption amount M is supplied, the supply amounts of the black recycled toner and the nonmagnetic recycled toner to the black developing device 61B are stored, so that the color mixture of the nonmagnetic toner at that time is stored. The degree P can also be calculated. This is color mixture state detection means for detecting a color mixture state using image data. Further, from the data of FIG. 3, the limit mixing rate Plimit as an allowable limit of the degree of color mixing of the nonmagnetic recycled toner to the black developing device 61B can be obtained. From the toner consumption amount M, the nonmagnetic toner mixing rate P, and the limit mixing rate Plimit, the maximum supplyable amount Mmax of nonmagnetic recycled toner that can be supplied to the developing device 61B is calculated (step 2). When M <Mmax (Y in Step 3), the toner consumption amount M is smaller than the maximum supplyable amount Mmax of the nonmagnetic recycled toner, so the nonmagnetic recycled toner corresponding to the consumption amount is supplied to the developing device 61B (Step Step). 4). On the other hand, when M <Mmax is not satisfied (N in Step 3), the nonmagnetic recycled toner is replenished by the maximum supplyable amount Mmax (Step 5), and the remaining is replenished with black recycled toner (Step 6). Thereafter, the current color mixing degree is calculated from the type and amount of the recycled toner replenished in Step 4 or Steps 5 and 6, and is set as P. In this way, by adjusting the replenishment amount of the black magnetic toner and the nonmagnetic recycled toner based on the color mixing degree P or the like, the recycled toner can be used for development while suppressing image quality deterioration such as a color difference due to the color mixing of the toner. become able to.
[0037]
The limit mixing rate Plimit, which is an allowable limit of the color mixture degree, may be set in advance. However, as another method, for example, the user may be able to selectively set it again appropriately. . By selecting the limit mixing rate Plimit on the user side, for example, when a completely black image is required, the supply of non-magnetic recycled toner is stopped and the color may change, so that the recycled toner can be used up. It is possible to supply all non-magnetic recycled toner and use it up.
[0038]
At present, many color printers and color copying machines are widely used, and there are many opportunities to see color documents. However, since the text is often output in black basically, the consumption of each color toner in a color printer or copying machine is overwhelmingly large. In this embodiment, black is selected as a specific color for recycling the toner, but this has a great effect in terms of resource saving even if only the black toner is reused.
[0039]
In this embodiment, the order in which the toner images are superimposed on the intermediate transfer belt 10 is in the order of yellow, magenta, cyan, and black. As shown in FIG. 3, the order is such that the change in color when the colors are mixed is as small as possible. That is, yellow that is greatly affected by the mixing of multiple colors is arranged on the most upstream side, and black that is relatively less susceptible to the mixed colors is arranged on the most downstream side as much as possible. As a result, it is possible to reduce the influence of image quality degradation due to color mixing in all colors.
[0040]
[Modification]
Next, a modification of this embodiment will be described. In the above embodiment, the primary transfer order on the intermediate transfer belt 10 is in the order of yellow, magenta, cyan, and black, but this order can be changed. This is because only black toner is used as a magnetic toner different from the magnetic characteristics of other colors, so that the degree of freedom in color order is also possible.
[0041]
In this modification, the primary transfer order is yellow for the first color, black for the second color, magenta for the third color, and cyan for the fourth color. Further, all the collected toner is returned to the black developing device 61B for recycling as in the first embodiment.
FIG. 5 is an explanatory diagram of the photoconductor cleaning device 63B according to the modification, and is an explanatory diagram illustrating the photoconductor cleaning device 63B for the black photoconductor 40B as an example. In the present modification, unlike the magnetic filter of the above embodiment, a magnetic roller 77B is used as a collected toner separating means for separating the toner collected by the photoconductor cleaning device 63B into a magnetic toner and a non-magnetic toner. .
Here, it is sufficiently possible to separate and capture only the magnetic toner from the mixed color toner in which the magnetic toner and the non-magnetic toner are mixed simply by passing it through the cylindrical magnet together with air. However, in order to be able to recycle toners having different magnetic characteristics, it is required that the separated toner can be easily recovered from the separation member. This enables highly efficient toner recycling for the first time.
Therefore, in this modification, a magnetic roller cleaning blade 78B for scraping and collecting toner from the surface of the magnetic roller is brought into contact with the surface of the magnetic roller. Further, a magnetic toner storage portion for storing the toner scraped off by the magnetic roller cleaning blade 78B is provided inside the photoconductor cleaning device 63B.
[0042]
In the above configuration, the residual toner scraped off from the photoconductors 40B, M, and C by the photoconductor cleaning blades 75B, M, and C accumulates in the photoconductor cleaning devices 63B, M, and C as they are. The magnetic rollers 77B, M, and C that are magnetized in the vicinity of the toner reservoir are rotated to attract only the magnetic toner by magnetic force, and only the magnetic toner, that is, the black recycled toner is pumped from the collected toner reservoir to the surface of the magnetic rollers 77B, M, and C. . The black recycled toner pumped up is scraped off by the magnetic roller cleaning blades 78B, M, and C, and stored in the magnetic toner storage unit, whereby only the black recycled toner is extracted. As a result, the collected toner can be separated into black recycled toner and non-magnetic recycled toner and stored in the photoreceptor cleaning devices 63B, M, and C.
[0043]
Here, although the magnetic rollers 77B, M, and C are used, for example, a developing sleeve used in a magnetic brush developing system in a two-component developing system can be used. In this case, a magnet is provided in the sleeve, and only the sleeve rotates. As described above, the advantage of using only the magnetic rollers 77B, M, and C that rotate only the sleeve is that the magnetic pole position can be fixed because the internal magnet is not rotated. In the case of this modification, the collection load on the blade can be reduced by weakening the magnetic force using the contact portions of the magnetic roller cleaning blades 78B, M, and C as toner separation poles.
[0044]
The black recycled toner and the non-magnetic recycled toner collected and separated by the photoreceptor cleaning devices 63B, M, and C for the second and subsequent colors as described above are supplied to the black developing device 61B in the same manner as in the above embodiment. Control the amount. This makes it possible to effectively use the recycled toner for development while suppressing deterioration in image quality such as color difference due to toner color mixing.
[0045]
In this modification, since the black developing device 61B is provided for the second color, only two types of recovered toner collected from the surface of the black photoreceptor 40B are the first color yellow reverse transfer toner and the black transfer residual toner. It is in a mixed color state. Therefore, the only non-magnetic recycled toner obtained as a result of separating the collected toner is the yellow toner. If a toner conveyance path is formed so that the nonmagnetic recycled toner is returned to the yellow developing device 61Y again, the yellow toner reversely transferred to the black photoreceptor 40B can be recycled and used again for developing the yellow toner image. Consumption can also be reduced. Therefore, only the nonmagnetic recycled toner of the black photoconductor cleaning device 63B may be supplied to the yellow developing device 61Y.
[0046]
As described above, in the embodiment and the modification, the black developing device 61B is arranged in the fourth color or the second color. However, since only the black toner is a magnetic toner, the black toner can be completely separated from the collected toner. Therefore, the black developing device 61B may be arranged for the first color or the third color. Among these, when the black developing device 61B is provided for the first color and the collected toner collected by the photoconductor cleaning device 63 of the photoconductor 40 arranged for the second color is separated by magnetic characteristics, the non-magnetic recycled toner becomes the second color. Only single color toner. If the single-color toner is configured to be supplied to the developing device 61 for the second color as it is, the consumption amount of the toner can be suppressed while suppressing color mixing in the developing device 61 for the second color.
[0047]
As described above, in the embodiment and the modified example, the black toner is used as the magnetic toner, and the other color toner is used as the nonmagnetic toner. However, the black toner can be made nonmagnetic and the other color toner can be used as the magnetic toner. It is. Further, although an example in which the present invention is applied to a tandem type color image forming apparatus having a photoreceptor 40 for each color has been described, a color printer to which the present invention is applicable is not limited thereto. The present invention can also be applied to a color printer or the like that sequentially forms a plurality of color toner images on the same photoreceptor 40.
[0048]
As described above, in this embodiment, among the four color toners consisting of yellow, magenta, cyan, and black, only the black toner as the specific color toner is composed of the magnetic toner and the rest is composed of the non-magnetic toner. The collected collected toner is separated into magnetic toner and non-magnetic toner, and after separation, the toner can be supplied to the black developing device 61B by a toner conveying device 80B serving as collected toner supply means. Therefore, it is possible to recycle the collected black toner, and even if the recycled toner is used in the black developing device 61B, image quality deterioration due to color mixing can be suppressed. Further, even when the color mixture rate of the collected toner is high, the toner can be separated and reused, so that the toner discard rate can be reduced.
Further, the supply amount adjusting means can adjust the supply amount of at least non-recycled recycled toner having a magnetic characteristic different from that of the black toner to the black developing device 61B. Each recycled toner can be used while adjusting the mixing ratio of the black recycled toner and the non-magnetic recycled toner, and image quality deterioration can be reliably suppressed.
Further, the color mixture state of the toner in the developing device 61 is detected using the image data as the color mixture state detection means, and the supply amount of the black recycled toner and the nonmagnetic recycled toner is determined based on the result. Recycled toner can be used for development while suppressing image quality deterioration called color difference. As a result, the mixed color toner is not discarded, and the collected toner can be effectively used. This is because which toner is replenished is controlled according to the degree of color mixing of the toner in the black developing device 61B, so that it is possible to prevent excessive supply of nonmagnetic recycled toner into the black developing device 61B. .
Further, the color mixture state is detected using image data of an already formed image. This eliminates the need for a separate sensor for detecting the color mixture state. This is because the printer is originally provided with a sensor for image data detection, and the detection result can be used.
Further, the transfer order to the intermediate transfer belt 10 is configured such that the black toner image comes last. As a result, the load of separating the collected toner can be reduced. This is because the photosensitive member cleaning device 63B is provided only on the black photosensitive member 40B, and only the collected toner is separated into magnetic toner and non-magnetic toner and recycled. In general, since the consumption of black toner is overwhelmingly large, it is effective to save resources just by recycling the toner collected from the black photoreceptor 40B.
Also, black is selected as the specific color. This is effective in saving resources as compared with the case where the other color toner is used as the specific color. This is because, as shown in FIG. 3, black is relatively less susceptible to color mixing than other colors, can recycle more non-magnetic recycled toner, and consumes more than other colors. This is because the amount is large.
Further, a magnetic filter is used as the collected toner separating means. Thereby, magnetic toner and non-magnetic toner can be separated efficiently.
Further, in the above modification, the black toner image is arranged in the second order in the transfer order to the intermediate transfer belt 10. As a result, it is possible to obtain a collected toner having no color mixture for the yellow toner of the first color, and it is possible to recycle it to the yellow developing device 61Y. Alternatively, if the black toner image is configured to be the first, it is possible to obtain a collected toner that is not mixed with respect to the second color toner, and can be recycled to the developing device 61 for the second color. .
Further, in the above modification, the magnetic roller 77B is used as the collected toner separating means. As a result, the magnetic toner and the non-magnetic toner can be separated efficiently, and the magnetic toner can be easily collected from the magnetic roller by scraping the blade 78B against the magnetic roller 77B.
[0049]
【The invention's effect】
  Claims 1 to6According to this color image forming apparatus, since the mixed color collected toner can be separated into a specific color and a color other than the specific color, at least the specific color toner can be recycled for use in the developing device of the specific color. Accordingly, it is possible to reduce the amount of exhaust gas that is discarded without being used for development, and the collected toner can be effectively recycled. Further, there is an excellent effect that the collected toner can be recycled while suppressing deterioration in image quality due to toner color mixing.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a main part of a color image forming apparatus according to an embodiment.
FIG. 2 is a partially enlarged view of a tandem image forming unit in the color image forming apparatus of the present embodiment.
FIG. 3 is a graph showing a result of measuring a difference from an original color of an image according to a degree of color mixture (hereinafter referred to as a color difference).
FIG. 4 is a flowchart regarding supply of recycled toner according to the embodiment.
FIG. 5 is an explanatory diagram of a developing device according to a modified example.
[Explanation of symbols]
10 Intermediate transfer belt
18C, M, Y, B Image forming means
20 Tandem image forming unit
22 Secondary transfer device
25 Fixing device
26 Fixing roller
26 Fixing belt
29 Transfer conveyor belt
40C, M, Y, B Photosensitive drum
60C, M, Y, B Charging device
61C, M, Y, B Development device
63C, M, Y, B Photoconductor cleaning device
65 Development sleeve
66C, M, Y, B Stirrer
67C, M, Y, B Development section
69C, M, Y, B Metal nip roller
70 Development Case
75B, M, C Photoconductor cleaning blade
77B, M, C Magnetic roller
80 Toner transport device
100 Copier body
200 Feeding table
300 scanner
400 Automatic document feeder

Claims (6)

A plurality of image担時which a latent image that corresponds to each color images of four colors are formed, each latent image formed on the image bearing member by supplying a specific color toner corresponding to each image color A plurality of developing units to be visualized, and transfer means for sequentially superimposing and transferring the toner images of the respective colors on the image carrier developed by the inherent color toner in each developing unit onto the transfer target; in the color image forming apparatus having a plurality of image carrier cleaning means for recovering residual toner remaining on the image bearing member after transferring the toner image,
Among the above toners, a specific color that is one specific color is composed of a magnetic toner or a non-magnetic toner, and all the remaining colors other than the specific color are non-printed when the specific color is composed of a magnetic toner. If it is composed of magnetic toner and the specific color is composed of non-magnetic toner, it is composed of magnetic toner ,
The transfer order of the toner image formed by each color developing device from the image carrier to the transfer target is configured so that the toner image of the specific color is first or second,
And recovering the toner separating means for separating the collected toner collected by Kizo carrier cleaning means on the on the image carrier of the second and subsequent in the transfer order of the magnetic toner and non-magnetic toner,
A magnetic toner and a non-magnetic toner separated by the collected toner separating means for the second image carrier in the transfer order;
A magnetic toner and a non-magnetic toner separated by the collected toner separating means for the third and subsequent image carriers in the transfer order are respectively supplied to a specific color developing unit which is a developing unit for forming the specific color toner image. 2 recovered toner supply means;
Supplying by the second recovered toner supply includes a supply amount adjusting means for adjusting the supply amount of the recovered toner having a magnetic characteristic different from that of at least the specific color toner to the specific color developing unit. A color image forming apparatus . In the color image forming apparatus 請 Motomeko 1,
There is provided a color mixture state detecting means for detecting a mixed state of a color different from the specific color in the toner in the specific color developing device, and the collected toner having a magnetic characteristic different from that of the specific color toner adjusted by the supply amount adjusting means. A color image forming apparatus, characterized in that a supply amount to a specific color developing unit is determined based on a detection result by the color mixture state detection means. The color image forming apparatus according to claim 2 .
A color image forming apparatus, wherein the color mixture state detecting means is configured to detect a color mixture state using image data of an already formed image . In the color image forming apparatus 請 Motomeko 1, 2 or 3,
A color image forming apparatus, wherein the specific color is black. In the color image forming apparatus according to claim 1, 2, 3, or 4 ,
A color image forming apparatus using a magnetic filter as the collected toner separating means. The color image forming apparatus according to claim 1, 2, 3, 4 or 5 ,
A color image forming apparatus using a magnetic roller as the collected toner separating means.

Images