JP4698255B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a color image forming apparatus using an electrophotographic process in a copying machine, a facsimile, a printer, or the like.

  Conventionally, as a color image forming apparatus, each color toner image is firstly transferred onto an intermediate transfer member sequentially from a photosensitive member as a latent image carrier to form a full color image, which is recorded from the intermediate transfer member. Those that are secondarily transferred onto the body are known. As a secondary transfer of this type of image forming apparatus, a transfer electric field is formed between the intermediate transfer member and the recording member that moves in contact with the intermediate transfer member, so that the toner image on the intermediate transfer member is transferred onto the recording member. Some employ an electrostatic transfer system for transfer. In such an apparatus, secondary transfer residual toner remains on the surface portion of the intermediate transfer member after transfer. If this secondary transfer residual toner remains on the intermediate transfer member, it may adversely affect the next image formation. Therefore, a cleaning device is provided at a position facing the surface of the intermediate transfer member to remove the secondary transfer residual toner. It was. Conventionally, the secondary transfer residual toner removed by the cleaning device is collected in a waste toner tank and periodically discarded by the user.

  However, in recent years, there has been an increasing demand for eliminating waste toner and recycling secondary transfer residual toner from the viewpoint of environmental problems. Thus, Patent Documents 1 and 2 describe an image forming apparatus that collects secondary transfer residual toner on an intermediate transfer member with a developing device containing black toner. By collecting the secondary transfer residual toner on the intermediate transfer member in this manner in the developing device, the secondary transfer residual toner can be reused and waste toner can be eliminated.

JP 2003-173061 A JP 2003-149899 A

  However, in the case of the image forming apparatuses disclosed in Patent Documents 1 and 2, since the secondary transfer residual toner in which a plurality of toner colors are mixed is collected by the black developing apparatus, toner other than black is mixed in the developing apparatus. . As a result, there is a problem that black color reproducibility deteriorates and a high-quality image cannot be obtained.

  The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus capable of reusing secondary transfer residual toner and obtaining a high-quality image with good color reproducibility. Is to provide.

In order to achieve the above object, the invention of claim 1 contains one or a plurality of latent image carriers and toners of colors corresponding to the respective image colors including black , and the toner is used as a developer carrier. A plurality of developing devices that carry the toner and convey it to a portion facing the latent image carrier and supply the toner to the latent image formed on the latent image carrier to form a toner image; and a transfer bias is applied. the toner image of each color on the latent image image bearing member and toner Zoka the toner in each developing device, a first transfer means for sequentially transferring the first image bearing member, the color toner images are sequentially transferred And a second transfer means for transferring the first synthesized toner image on the first image carrier obtained by the transfer onto the recording medium, and applying a reverse transfer bias having a reverse polarity to the transfer bias. is applied to one transfer means, the first image bearing member surface after the transfer by the second transfer means The retained secondary transfer residual toner is electrostatically attached to the latent image carrier, and a bias for recovering the secondary transfer residual toner attached to the latent image carrier is applied to the developer carrier. In the image forming apparatus in which the secondary transfer residual toner attached to the latent image carrier is electrostatically attached to the developer carrier and the secondary transfer residual toner is collected by the development device, One of these is a recovery developing device that mainly stores the same black toner as the black developing device that stores only black toner, and collects secondary transfer residual toner in which toners of at least two colors are mixed. Yes , a black residual toner temporary holding roller for temporarily holding black secondary transfer residual toner consisting only of black toner , and a color for temporarily holding color secondary transfer residual toner in which at least two or more colors of toner are mixed The remaining toner A secondary transfer residual toner that is temporarily held by the temporary color toner holding roller and is collected by the collecting developer and held by the black residual toner temporary holding roller. The residual toner is collected by the black developing device .
Further, the invention of claim 2, the image forming apparatus according to claim 1, the surface of each temporarily storing rollers, is characterized in that the polarity control agent is contained.
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the linear velocity of each temporary holding roller is different from the linear velocity of the first image carrier. is there.
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, each temporary holding roller has a holding bias for holding the secondary transfer residual toner on the temporary holding roller or the secondary holding roller. An application bias selection unit is provided for selectively applying a discharge bias for discharging the transfer residual toner from the temporary holding roller to the temporary holding roller.
The invention of claim 5, when in any of the image forming apparatus according to claim 1 to 4, and when a color picture is formed by using the collecting developer device is formed, the black residual toner The temporary holding roller is separated from the first image carrier, and the color residual toner temporary holding roller is brought into contact with the first image carrier.
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects , when the image is formed using only the black developing device, the color remaining toner temporary holding roller is used as the first image. is separated from the carrier, it is characterized in that is brought into contact with the black Irozan toner temporary storage roller to the image carrier of the first.
According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, a plurality of the latent image carriers are provided, and a latent image of a color corresponding to each latent image carrier is formed. A plurality of first transfer means for sequentially transferring the toner images of the respective colors on the latent image carrier to the first image carrier on which the toner images of the corresponding colors are formed on the image carrier. be one having, if the image using only the black developing device is formed, is characterized in that to separate the latent image bearing member other than the black color from the image bearing member of the first.
According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the image forming apparatus further comprises a toner concentration sensor that detects a toner concentration in the collecting and developing device, and based on a detection result of the toner concentration sensor. The recovery developing device is replenished with black toner .
According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the image carrier and at least each temporary holding roller are integrally configured to be detachable from the main body of the image forming apparatus. A process cartridge is provided.
According to a tenth aspect of the present invention, in the image forming apparatus according to the ninth aspect , the process cartridge includes a charging device and a developing device.

  According to the first to thirteenth aspects of the present invention, one of the plurality of developing devices is a collecting developing device that collects secondary transfer residual toner in which toners of at least two colors are mixed. Therefore, if image formation is performed using this developing device for collection, the secondary transfer residual toner can be reused and waste toner can be eliminated. Further, the color of the toner mainly accommodated in the developing device for collection is the same color as one of the colors of toner accommodated in the other developing devices. That is, another developing device that contains toner of the same color as the toner color that the collecting developing device mainly contains is provided. This other developing device contains only the intrinsic color toner. Therefore, when it is desired to obtain a high-quality image with high color reproducibility, if the image is formed with the other developing device without forming an image with the collecting developing device, a high-quality image with high color reproducibility can be obtained. An image can be obtained.

  An embodiment in which the present invention is applied to an electrophotographic printer (hereinafter simply referred to as “printer”) as an image forming apparatus will be described below. In this printer, yellow (hereinafter referred to as “Y”), cyan (hereinafter referred to as “C”), magenta (hereinafter referred to as “M”), black (hereinafter referred to as “K”). ) Is used to form a color image.

First, the basic configuration of the printer will be described.
FIG. 1 is a schematic configuration diagram of a printer according to the present embodiment. The printer includes four photosensitive members 1Y, 1C, 1M, and 1K as latent image carriers. Here, a drum-shaped photoconductor is taken as an example, but a belt-shaped photoconductor can also be adopted. In the present embodiment, each of the photoconductors 1Y, 1C, 1M, and 1K is rotationally driven in the direction of the arrow in the drawing while being in contact with the intermediate transfer belt 10 as a first image carrier. Each of the photoreceptors 1Y, 1C, 1M, and 1K is obtained by forming a photosensitive layer on a relatively thin cylindrical substrate and further forming a protective layer on the photosensitive layer, and its outer diameter is 30 [mm]. The inner diameter is 28.5 [mm].
In the present embodiment, an organic photoconductor is used from the viewpoints of cost reduction, freedom of photoconductor design, non-pollution, and the like.

FIG. 2 is a diagram showing a schematic configuration around each of the photoreceptors 1Y, 1C, and 1M. 3A and 3B are diagrams showing a schematic configuration around the K-color photosensitive member 1K. The basic configuration around the photoconductor 1K for K color is the same as that of the configuration around the other photoconductors 1Y, 1C, and 1M, except that there is one more developing device. is there. In the following description, a common configuration around each of the photoconductors 1Y, 1C, 1M, and 1K will be described based on FIG. 2, and a different configuration around the K-color photoconductor 1K will be described later. In the following description, since the basic configuration around each of the photoreceptors 1Y, 1C, 1M, and 1K is the same, the symbols Y, C, M, and K for color classification are omitted.
Around the photoreceptor 1, a toner holding device 40, a charging device 3, and a developing device 5 are arranged in this order along the surface movement direction. A space is secured between the charging device 3 and the developing device 5 so that light emitted from the exposure device 4 can pass to the photoreceptor 1.

  The charging device 3 uniformly charges the surface of the photoreceptor 1 to a negative polarity. The charging device 3 in the present embodiment includes a charging roller 3a as a charging member that performs a charging process by a so-called contact method. That is, the charging device 3 uniformly charges the surface of the photosensitive member 1 by bringing the charging roller 3a into contact with the surface of the photosensitive member 1 and applying a negative bias from the charging device power supply 130 to the charging roller 3a. To do. In this embodiment, a DC charging bias of about − (minus) 1000 [V] is applied from the charging device power supply 130 to the charging roller so that the surface potential of the photoreceptor 1 is uniformly − (minus) 500 [V]. 3a is applied. Note that a charging bias in which an AC bias is superimposed on a DC bias can also be used. However, in this case, since an AC power supply is required, the apparatus becomes large, which is not preferable from the viewpoint of downsizing the apparatus. Further, the charging device 3 of the present embodiment is provided with a cleaning brush 3b for cleaning the surface of the charging roller 3a.

  An electrostatic latent image corresponding to each color is formed on the surface of the photoreceptor 1 thus uniformly charged by exposure by the exposure device 4. The exposure device 4 writes an electrostatic latent image corresponding to each color on the photoreceptor 1 based on image information corresponding to each color. The exposure apparatus 4 of the present embodiment is a laser type exposure apparatus, but other types of exposure apparatuses such as an exposure apparatus including an LED array and an image forming unit may be employed.

  Further, in the developing device 5, the developing roller 5a as the developer carrying member is partially exposed from the opening of the casing. In the developing device 5 used in the present embodiment, a two-component developer including a toner and a carrier is used, but a one-component developer not including a carrier may be used. The developing device 5 receives toner of the corresponding color from the toner bottles 31Y, 31C, 31M, and 31K shown in FIG. The toner bottles 31Y, 31C, 31M, and 31K are configured to be attachable to and detachable from the printer body so that they can be replaced individually. With such a configuration, only the toner bottles 31Y, 31C, 31M, and 31K may be replaced at the time of toner end. Therefore, other components that have not yet reached the end of their life when the toner ends can be used as they are, and the user's expense can be reduced.

  The toner replenished into the developing device 5 from the toner bottles 31Y, 31C, 31M, and 31K is conveyed while being agitated with the carrier by the agitating and conveying screw 5b, and is carried on the developing roller 5a. The developing roller 5a is composed of a magnet roller as magnetic field generating means and a developing sleeve that rotates coaxially therearound. The carrier in the developer is transferred to the developing area facing the photosensitive member 1 in a state where it stands on the developing roller 5a by the magnetic force generated by the magnet roller. Here, the developing roller 5a moves in the same direction at a linear velocity faster than the surface of the photoreceptor 1 in the developing region. Then, the carrier spiked on the developing roller 5 a supplies the toner adhering to the carrier surface to the surface of the photoreceptor 1 while rubbing the surface of the photoreceptor 1. At this time, a developing bias of −300 [V] is applied to the developing roller 5a from a power source (not shown), whereby a developing electric field is formed in the developing region. Then, between the electrostatic latent image on the photoreceptor 1 and the developing roller 5a, an electrostatic force directed toward the electrostatic latent image side acts on the toner on the developing roller 5a. As a result, the toner on the developing roller 5 a adheres to the electrostatic latent image on the photoreceptor 1. By this adhesion, the electrostatic latent image on the photoreceptor 1 is developed into a corresponding color toner image.

  As shown in FIG. 1, the intermediate transfer belt 10 is stretched around three support rollers 11, 12, and 13 and is configured to endlessly move in the direction of the arrow in the figure. On the intermediate transfer belt 10, the toner images on the photoreceptors 1Y, 1C, 1M, and 1K are transferred so as to overlap each other by an electrostatic transfer method. Although there is a configuration using a transfer charger in the electrostatic transfer system, in this embodiment, a configuration using a transfer roller that generates less transfer dust is adopted. Specifically, primary transfer rollers 14Y, 14C, 14M, and 14K as first transfer units are disposed on the back surface of the portion of the intermediate transfer belt 10 that contacts the photoreceptors 1Y, 1C, 1M, and 1K, respectively. ing. In the present embodiment, a primary transfer nip portion is formed by the portion of the intermediate transfer belt 10 pressed by the primary transfer rollers 14Y, 14C, 14M, and 14K and the photoreceptors 1Y, 1C, 1M, and 1K. . When the toner images on the photoreceptors 1Y, 1C, 1M, and 1K are transferred onto the intermediate transfer belt 10, a positive bias of 500 to 600 [V] is applied to each primary transfer roller 14. The As a result, a transfer electric field is formed at each primary transfer nip, and the toner images on the photoreceptors 1Y, 1C, 1M, and 1K are electrostatically attached to the intermediate transfer belt 10 and transferred.

  Further, a secondary transfer roller 16 as a second transfer unit is disposed in contact with the portion of the intermediate transfer belt 10 stretched around the support roller 13. A secondary transfer nip portion is formed between the intermediate transfer belt 10 and the secondary transfer roller 16, and a transfer sheet as a second image carrier is fed into this portion at a predetermined timing. Yes. The transfer paper is accommodated in a paper feed cassette 20 on the lower side of the exposure device 4 in the drawing, and is conveyed to the secondary transfer nip portion by a paper feed roller 21, a registration roller pair 22, and the like. Then, the toner images superimposed on the intermediate transfer belt 10 are collectively transferred onto the transfer paper at the secondary transfer nip portion. At the time of the secondary transfer, a positive bias is applied to the secondary transfer roller 16, and the toner image on the intermediate transfer belt 10 is transferred onto the transfer paper by the transfer electric field formed thereby.

  The secondary transfer residual toner remaining on the intermediate transfer belt 10 without being transferred to the transfer paper is held by either the K-color residual toner holding roller 50 or the color residual toner holding roller 60 as a temporary holding roller. The K-color residual toner holding roller 50 temporarily holds secondary transfer residual toner (hereinafter referred to as K-color residual toner) consisting of only K color. The color residual toner holding roller 60 temporarily holds secondary transfer residual toner (hereinafter, color residual toner) in which two or more colors of toner are mixed. The K-color residual toner holding roller 50 and the color residual toner holding roller 60 will be described later.

  A heat fixing device 23 as a fixing unit is disposed downstream of the secondary transfer nip portion in the transfer paper conveyance direction. The heat fixing device 23 includes a heating roller 23a with a built-in heater and a pressure roller 23b for applying pressure. The transfer paper that has passed through the secondary transfer nip is sandwiched between these rollers and receives heat and pressure. As a result, the toner on the transfer paper is melted and the toner image is fixed on the transfer paper. Then, the fixed transfer paper is discharged by a paper discharge roller 24 onto a paper discharge tray on the upper surface of the apparatus.

  On the other hand, the primary transfer residual toner not transferred to the intermediate transfer belt 10 and remaining on the photosensitive member is temporarily held by the toner holding device 40 shown in FIG. FIG. 4 is a schematic configuration diagram of the toner holding device 40. The toner holding device 40 includes a magnetic brush roller 41. The magnetic brush roller 41 includes a magnetic carrier and a rotating sleeve 41a and a magnet roller 41b fixedly disposed inside the rotating sleeve 41a. The rotating sleeve 41a is made of a conductive / non-magnetic material, and has a V-shaped groove on the outer peripheral surface thereof. The rotating sleeve 41a is rotated in the clockwise direction in the drawing at a higher speed than the photosensitive member 1 by a driving device (not shown) in the same manner as the photosensitive member 1. Inside the magnet roller 41b, N-pole magnets and S-pole magnets are alternately arranged. Further, the toner holding device 40 includes a casing 46 that houses magnetic particles (carriers) 47.

  A bias is applied to the magnetic brush roller 41 from either the first power supply 43 or the second power supply 44. Specifically, a changeover switch 45 is provided between the power supplies 43 and 44 and the brush roller 41, and the power supply connected to the brush roller 41 is selected by the operation of the changeover switch 45. The operation of the changeover switch 45 is controlled by the control unit of the printer. In the present embodiment, the first power source 43 applies a holding bias such that the potential of the surface portion of the brush roller 41 is −50 [V], and the second power source 44 has a potential of −−. An emission bias of 350 [V] is applied. Further, the toner holding device 40 includes a blade 42 that regulates the layer thickness of the magnetic brush.

The carrier 47 of the holding device 40 is the same as the carrier accommodated in the developing device 5.
The carrier 47 accommodated in the casing 46 is carried on the rotating sleeve 41 a and conveyed to the photoreceptor 1. At this time, the carrier 47 is raised by the magnetic field of the magnet roller 41b to form a magnetic brush. In this magnetic brush, the layer thickness is adjusted uniformly by the blade 42 in the axial direction of the rotary sleeve 41a. The magnetic brush slidably contacts the surface of the photoconductor to hold the primary transfer residual toner attached to the photoconductor without being transferred to the intermediate transfer belt. At this time, a holding bias is applied to the magnetic brush from the first power supply unit 43. As the holding bias, substantially the same voltage as the photoreceptor surface potential (-50 to -100 V) after transfer is applied. As a result, no potential difference occurs between the photoreceptor 1 and the magnetic brush roller 41. Therefore, the electrostatic transfer force generated by the potential difference between the photosensitive member and the magnetic brush roller 41 does not act on the primary transfer residual toner. As a result, the primary transfer residual toner can be held by the frictional force of the magnetic brush regardless of the polarity of the primary transfer residual toner.

  When the primary transfer residual toner is held on the magnetic brush from the surface of the photoreceptor, the primary transfer residual toner is frictionally charged by the magnetic brush, and the reversely charged toner charged positively of the primary transfer residual toner is negatively charged normally charged. Polarized to toner. Similarly, the negatively charged regular toner of the primary transfer residual toner also increases the negative charge amount due to friction with the magnetic brush. As a result, the negative charge amount of the primary transfer residual toner held on the magnetic brush increases as compared with the charge amount of the primary transfer residual toner after transfer.

  Thus, the primary transfer residual toner held by the magnetic brush is returned to the surface of the photoreceptor at a predetermined timing. Specifically, the changeover switch 45 is switched from the first power supply unit 43 to the second power supply unit 44 at a predetermined timing, and a discharge bias of −350 V is applied to the magnetic brush roller 41. As a result, a potential difference is generated between the photosensitive member 1 (about −50 V) and the magnetic brush roller 41 (−350 V). As a result, the primary transfer residual toner that is normally charged negatively by frictional charging is electrostatically adsorbed to the photosensitive member having a higher potential than the magnetic brush. As a result, the primary transfer residual toner held by the magnetic brush is returned to the surface of the photoreceptor again.

The changeover switch 45 is switched at a timing such that a latent image is not formed when the primary transfer residual toner returned from the magnetic brush to the photoreceptor 1 passes through the latent image formation region.
In addition, a cleaning mode may be provided at the time of starting the apparatus, at the end of the image forming operation, or after a certain number of image forming operations, and the changeover switch 45 may be switched to the second power supply unit 44 in this cleaning mode. In this cleaning mode, since no image is formed, the primary transfer residual toner released from the magnetic brush does not form an unexposed portion.

  The primary transfer residual toner returned from the magnetic brush roller 41 to the surface of the photosensitive member passes through a contact area with the charging roller 3a. The primary transfer residual toner at this time is a regular charged toner having the same polarity as the charging bias. Further, since the charging roller 3a is charged to about −1000 [V] and the surface of the photoreceptor 1 is about −50 [V], it is electrostatically attracted toward the photoreceptor without adhering to the charging roller 3a. Passes through the charging roller 3a. The primary transfer residual toner that has passed through the contact area with the charging roller 3a passes through the latent image forming area. At this time, the exposure device 4 is not operating, and no latent image is formed on the surface of the photoreceptor. The primary transfer residual toner moves to the development area. The developing roller 41 is applied with a bias having a polarity opposite to the developing bias necessary for image formation, that is, a bias of + 200V. As a result, the primary transfer residual toner charged negatively has an electrostatic force acting toward the developing roller in the developing region. As a result, the primary transfer residual toner is electrostatically attracted to the carrier on the developing roller and collected by the developing device 4. The primary transfer residual toner collected inside the developing device 4 by the developing roller is stirred and conveyed inside and then contributes to development again.

  In the present embodiment, as shown in FIG. 1, each of the photoconductors 1Y, 1C, 1M, and 1K, parts such as a developing device arranged around the photoreceptors, the charging device 3, the intermediate transfer belt 10, and the intermediate transfer belt 10 are provided. Temporary holding rollers 50 and 60 for temporarily holding the secondary transfer residual toner are configured as an integrated process cartridge 30. The process cartridge 30 is detachable from the printer body. Therefore, when the life of a component housed in the process cartridge 30 reaches the end of its life or when maintenance is required, the process cartridge 30 can be replaced, which improves convenience. In the present embodiment, the toner bottles 31Y, 31C, 31M, and 31K described above are configured to be detachable from the printer main body separately from the process cartridge 30.

  Next, a schematic configuration around the K-color photoconductor 1K will be described in detail. As shown in FIG. 3, a first developing device 5Ka and a second developing device 5Kb as a collecting developing device are provided around the K-color photoconductor 1K. The first developing device 5Ka is used when forming a high-quality image that requires K color reproducibility. On the other hand, the second developing device 5Kb is a secondary transfer residual toner (color residual toner) in which Y, M, C, and K toners remaining on the intermediate transfer belt 10 without being secondary transferred onto the paper at the time of image formation are mixed. The developing device collects toner. This second developing device 5Kb does not require accurate color reproducibility, for example, simple printing of provisional documents such as circulars, layout of drawings created by a personal computer, typographical omission and rough color scheme Used for printing for confirmation. Further, it is used for printing on transfer paper having relatively poor color reproducibility such as backing paper or recycled paper that is not completely bleached.

  Switching between a state in which a high-quality image is formed using the first developing device 5Ka and a state in which a low-quality image is formed using the second developing device 5Kb can be performed by an operation unit (not shown) of the image forming apparatus, for example. It has become. The user can select whether to form an image with high quality or an image with low quality in accordance with the application. Further, it may be possible to select whether to form an image with high quality or an image with low quality from printer driver software on a personal computer.

  The first developing device 5Ka and the second developing device 5Kb are configured to be able to approach and separate from the K-color photoconductor 1K by a swing mechanism (not shown) provided with a clutch or the like. When a high-quality image is formed, or when secondary transfer residual toner (K-color residual toner) generated when a black and white image is formed by using the first developing device 5Ka is collected (see FIG. 3). As shown in a), the first developing device 5Ka is brought close to the second developing device 5Kb. On the other hand, when forming an image that does not require accurate color reproducibility or when collecting the color residual toner, the first developing device 5Ka is separated as shown in FIG. Make 5 Kb close.

  The first developing device 5Ka and the second developing device 5Kb are respectively replenished with toner of K color from the toner bottle 31K. Specifically, density sensors for detecting the density of toner in the first developing device 5Ka and the second developing device 5Kb are provided. The density of the toner in the first developing device 5Ka is detected by a density sensor, and K-color toner is supplied from the toner bottle 31K according to the density in the first developing device 5Ka. Further, the density of the toner in the second developing device 5Kb is detected by a density sensor, and K-color toner is supplied from the toner bottle 31K according to the density in the second developing device 5Kb. Thereby, the toner density in the second developing device 5Kb is kept constant. Thus, since the K color toner is supplied in accordance with the density in the second developing device 5Kb, the proportion of the K color toner is overwhelming in the second developing device 5Kb with respect to the collected color residual toner. To be more. For this reason, the toner characteristics in the second developing device 5Kb are close to the toner characteristics of only the K color, and a good image can be formed without changing image conditions such as charging conditions. Further, even in an image formed using the second developing device 5Kb, the color shade of K can be brought close to the color tone when using toner from only the K color.

  Further, the K primary transfer roller 14K is configured to be biased from either the first transfer power supply 141 or the second transfer power supply 142. A changeover switch 143 is provided between the transfer power supplies 142 and 143 and the primary transfer roller 14K, and the transfer power supply connected to the primary transfer roller 14K is selected by the operation of the changeover switch 143. The operation of the changeover switch 143 is controlled by the control unit of the printer. The first transfer power supply 141 is a transfer bias for transferring the toner image formed on the photoreceptor 1K to the intermediate transfer belt 10, and applies a positive bias of 500 to 600 [V] to the transfer roller 14K. The second transfer power supply 141 is a reverse transfer bias for reversely transferring the color residual toner and K color residual toner of the intermediate transfer belt 10 to the photosensitive member 1K, and has a negative polarity of 600 to 700 [V] to the transfer roller 14K. Apply a bias.

Next, the K-color residual toner holding roller 50 and the color residual toner holding roller 60 will be described in detail.
FIG. 5 is a schematic configuration diagram showing a K-color residual toner holding roller 50 that temporarily holds the K-color residual toner and a color residual toner holding roller 60 that temporarily holds the color residual toner. FIG. 5A is a diagram illustrating a state in which the K-color residual toner holding roller 50 is separated from the intermediate transfer belt 10 and the color residual toner holding roller 60 is in contact with the intermediate transfer belt 10. FIG. 5B is a diagram illustrating a state in which the K-color residual toner holding roller 50 is in contact with the intermediate transfer belt 10 and the color residual toner holding roller 60 is separated from the intermediate transfer belt 10.

  The color residual toner holding roller 60 and the K color residual toner holding roller 50 are disposed around the support roller 11 and can be brought into and out of contact with the intermediate transfer belt 10 by a swing mechanism (not shown) provided with a clutch or the like. It is configured. When forming a black and white image with the first developing device 5Ka, the color residual toner holding roller 60 is separated from the intermediate transfer belt 10 as shown in FIG. It is brought into contact with the intermediate transfer belt 10. As a result, it is possible to prevent the color residual toner held on the color residual toner holding roller 60 from dropping off due to the movement of the intermediate transfer belt 10 and being held on the K color residual toner temporary holding roller 50. Further, in the case of an image formed using the second developing device 5Kb or a color image, as shown in FIG. 5A, the color residual toner holding roller 60 is brought into contact with the intermediate transfer belt 10, and K The color residual toner holding roller 50 is separated from the intermediate transfer belt 10. Thereby, it is possible to suppress the color residual toner from being held by the K-color residual toner holding roller.

Next, the K-color residual toner holding roller 60 will be described. The K-color residual toner holding roller 50 includes a metal core 50b and a surface layer 50a such as resin or rubber.
Examples of the surface layer 50a of the K-color residual toner holding roller 50 include acrylic resin, polyethylene resin, polyester resin, polyurethane resin, polysulfonic acid resin, epoxy resin, phenol resin, styrene resin, nylon resin, polyvinyl chloride, alkyd resin, Resins such as silicone resin, urea resin, melamine resin, fluorine resin, polybutadiene, butadiene styrene rubber, butadiene acrylonitrile rubber, polychloroprene, polyisoprene, chlorosulfonated polyethylene, polyisobutylene, isobutylene isoprene rubber, acrylic rubber, urethane rubber, There are synthetic rubbers such as polysulfide-based synthetic rubber, fluororubber, silicone rubber, etc., as well as these alone, and those obtained by copolymerizing the constituent components of these resins in monomer units, It can be used in combination of two or more like a polymeric material comprising a combination of urethane and acrylic. These surface layers 50a can be formed by a method of dissolving and dispersing in a suitable solvent and coating the cored bar as a coating material, or a method of covering the cored bar with a tube formed using an extruder or the like.

  Further, when the K-color residual toner having a reverse (positive) polarity due to charge injection or discharge during the secondary transfer is held on the K-color residual toner holding roller 50, it is frictionally charged with the intermediate transfer belt 10. A polarity control agent may be included in the surface layer 50a so as to be a negatively charged normally charged toner.

Examples of the polarity control agent contained in the surface layer include coupling agents, resins modified with coupling agents, ionic dyes and pigments, organometallic compounds, resins, and modified silicone oils. Among them, a coupling agent having a stable long-term charge control property is preferable.
Examples of the coupling agent include silane coupling agents, titanate coupling agents, and aluminum coupling agents. Examples of the silane coupling agent include trimethylsilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, and the like. .

  The K-color residual toner holding roller 50 is configured to be biased from either the first holding power source 53 or the first discharge power source 52. Specifically, a changeover switch 51 as a bias selection unit is provided between the power sources 53 and 52 and the K-color residual toner holding roller 50, and is connected to the K-color residual toner holding roller 50 by the operation of the changeover switch 51. Select the power source to be used. The operation of the changeover switch 51 is controlled by the control unit of the printer. In the present embodiment, the first holding power source 53 applies a holding bias such that the potential of the surface portion of the K-color residual toner holding roller 50 is slightly higher than at least the potential of the intermediate transfer belt 10. . The discharge power source 52 applies a discharge bias such that the potential of the surface portion of the K-color residual toner temporary holding roller 50 is significantly lower than the potential of the intermediate transfer belt 10.

  Further, the K-color residual toner holding roller 50 is rotated by a driving unit (not shown) so that the linear velocity ratio between the K-color residual toner holding roller 50 and the intermediate transfer belt 10 is 1.05 to 2.00. When the linear velocity ratio is less than 1.05, the effect of frictionally charging the K-color residual toner on the intermediate transfer belt 10 becomes small. For this reason, the K-color residual toner charged to the positive polarity in the secondary transfer cannot be reversed to the negative polarity before passing through the nip between the intermediate transfer belt 10 and the holding roller 50, and the K-color residual toner temporarily There is a possibility that it cannot be held by the holding roller 50. Further, when the linear velocity ratio exceeds 2.00, toner filming occurs. Further, the contact between the intermediate transfer belt 10 and the holding roller 50 becomes unstable, and there is a possibility that the K-color residual toner cannot be satisfactorily charged by friction and the like may occur.

  The color residual toner holding roller 60 has the same configuration as the K color residual toner holding roller 50. That is, similarly to the above, it consists of a metal core 60b and a surface layer 60a made of rubber or resin. Further, either one of a second holding power source 63 for applying a holding bias and a second emitting power source 62 for applying a discharging bias is connected to the roller by a changeover switch 61. The color residual toner holding roller 60 is also rotated by a driving unit (not shown) so that the linear speed ratio with the intermediate transfer belt is 1.05 to 2.00. By setting such a linear velocity ratio, the color residual toner can be favorably frictionally charged, and the color residual toner charged to the positive polarity can be favorably reversed to the negative polarity. The material of the surface layer 60a is the same as that of the K-color residual toner temporary holding roller 50 described above, and is made of rubber or resin containing a polarity control agent.

  Next, recovery of K-color residual toner and color residual toner remaining on the intermediate transfer belt 10 without transferring the transfer paper will be described. In the present embodiment, the K-color residual toner including only the K color remaining on the intermediate transfer belt 10 is collected by the first developing device 5Ka, and the color residual toner in which Y, M, C, and K colors are mixed is the first. (2) Recovery is performed by the developing device 5Kb.

First, recovery of the K-color residual toner will be described. When a black-and-white image is formed using the first developing device 5Ka described above, the K-color residual toner holding roller 50 is brought into contact with the intermediate transfer belt 10 as shown in FIG. The holding roller 60 is separated from the intermediate transfer belt 10. A holding bias is applied to the K-color residual toner holding roller 50 from the first holding power source 53 so that the surface of the K-color residual toner holding roller 50 is slightly higher than the potential of the intermediate transfer belt 10. As a result, the K-color secondary transfer residual toner, which is normally (negatively) charged on the intermediate transfer belt 10, is electrostatically adsorbed to the K-color residual toner holding roller 50 and is temporarily applied to the K-color residual toner holding roller 50. Retained.
Further, the K-color residual toner charged positively by charge injection or discharge during the secondary transfer is triboelectrically charged between the intermediate transfer belt 10 and the K-color residual toner holding roller 50 and is held in a negative polarity. The

  The K-color residual toner held by the K-color residual toner holding roller 50 is returned to the intermediate transfer belt 10 at a predetermined timing, for example, at the end of the image forming operation, and is then transferred from the intermediate transfer belt 10 to the K-color photosensitive member. It is returned to 1K and collected by the first developing device 5Ka. Specifically, first, the switch 51 is switched from the first holding power supply 53 to the first discharge power supply 52 at a predetermined timing such as at the end of the image forming operation. When switching to the first discharge power supply 52, a discharge bias of about −600 [V] to −700 [V] is applied from the first discharge power supply 52 to the K-color residual toner holding roller 50. When the discharge bias is applied to the K-color residual toner holding roller 50, a potential difference is generated between the intermediate transfer belt 10 and the K-color residual toner holding roller 50, and the K color held on the K-color residual toner holding roller 50 is generated. Residual toner adheres electrostatically to the intermediate transfer belt 10. The K-color residual toner electrostatically attached to the intermediate transfer belt 10 is conveyed by the intermediate transfer belt 10 to the K-color primary transfer roller 14K. At this time, the changeover switch 143 switches the first transfer power supply 141 to the second transfer power supply 142, and a reverse transfer bias of −600 to −700 [V] is applied to the K primary transfer roller 14K. By this reverse transfer bias, the K-color residual toner on the intermediate transfer belt 10 is returned to the K-color photoconductor 1K. At this time, the first developing device 5Ka is close to the photoreceptor 1K, and the second developing device 5Kb is separated from the photoreceptor 1K. Further, a discharge bias of about −350 [V] is applied to the magnetic brush roller 41 of the holding device 40. The K-color residual toner on the photosensitive member is a negatively charged regular charged toner, and the potential on the surface of the photosensitive member is about −50 [V]. For this reason, the K-color residual toner on the photosensitive member that passes through the magnetic brush roller 41 does not adhere to the magnetic brush roller 41 because it is electrostatically attracted to the surface of the photosensitive member. Further, since the charging roller is charged to about −1000 [V] and the surface of the photoconductor is about −50 [V], the K-color residual toner on the photoconductor is electrostatically attracted to the photoconductor and charged. Passes the roller 3a. Since the surface of the photosensitive member that has passed through the charging roller is charged to −500 [V], applying a bias of −350 [V] to the first developing device 5Ka statically removes the K-color residual toner on the photosensitive member. It can be electrically collected in the first developing device 5Ka.

  Thus, only the K color toner is collected in the first developing device 5Ka, and the other color toners are not mixed. Therefore, if an image is formed using the first developing device 5Ka, the K secondary transfer residual toner can be reused without deteriorating the K color reproducibility.

  Next, recovery of the color residual toner will be described. When a black and white image is formed using the second developing device 5Kb described above, or when a color image of Y, M, C, or K is formed, as shown in FIG. The holding roller 50 is separated from the intermediate transfer belt 10, and the color residual toner holding roller 60 is brought into contact with the intermediate transfer belt 10. The color residual toner mixed with Y, M, C, and K on the intermediate transfer belt 10 that has not been secondarily transferred from the intermediate transfer belt 10 to the recording medium is primarily held by the color residual toner holding roller 60. Specifically, a holding bias is applied to the color residual toner holding roller 60 from the second holding power source 63 so that the potential of the roller surface is slightly higher than the potential of the intermediate transfer belt 10. The negatively charged toner on the intermediate transfer belt 10 is electrostatically attracted to the color residual toner holding roller 60 by this holding bias. On the other hand, the color residual toner charged to the positive polarity by the secondary transfer bias or the like is reversed to the negative polarity by frictional charging with the color residual toner holding roller 60. Then, the color residual toner that has been reversed to the negative polarity is held by the color residual toner holding roller 60. In this way, the color residual toner holding roller 60 holds the color residual toner charged negatively.

  At a predetermined timing such as when image formation is completed, the changeover switch 61 is switched to apply a discharge bias of about −600 [V] to −700 [V] from the second discharge power supply 62 to the color remaining toner holding roller 60. . When this discharge bias is applied, the color residual toner held on the color residual toner holding roller 60 is electrostatically moved to the intermediate transfer belt 10. The color residual toner that has moved to the intermediate transfer belt 10 is moved by the intermediate transfer belt 10 to the K primary transfer roller 14K. The primary transfer roller 14K for K color is switched from the first transfer power supply 141 to the second transfer power supply 142 by the changeover switch 143 when the color residual toner is discharged from the temporary holding roller 60, and the primary transfer roller 14K A reverse transfer bias of 600 to −700 [V] is applied. The color residual toner on the intermediate transfer belt 10 conveyed to the primary transfer roller 14K is reversely transferred to the K color photoreceptor 1K by the reverse transfer bias. Then, the color remaining toner reversely transferred to the K-color photoreceptor 1K passes through the toner holding device 40 and the charging roller 3a and is conveyed to the second developing device 5Kb. When the color remaining toner is discharged from the temporary holding roller 60, the second developing device 5Kb approaches the photoconductor 1K and the first developing device 5Ka is separated from the photoconductor 1K by a clutch (not shown). Then, a bias is applied to the developing roller 5a of the second developing device 5Kb so that the surface potential is higher than the surface potential of the photoconductor, and the color residual toner on the photoconductor 1K is collected in the second developing device 5Kb.

  As described above, in this embodiment, the secondary transfer residual toner on the intermediate transfer belt 10 is electrostatically returned to the photosensitive member, and further returned from the photosensitive member to the developing device. Therefore, the secondary transfer residual toner can be returned to the developing device without providing a conveyance member for returning the secondary transfer residual toner on the intermediate transfer belt 10 to the developing device, and the image forming apparatus can be saved in space. can do. Of the residual toner on the intermediate transfer belt 10, the residual color toner in which Y, M, C, and K are mixed is collected by the second developing device 5Kb, and the residual K color toner of only the K color is the first. Collected in the developing device 5Ka. Therefore, since the first developing device 5Ka is not mixed with toner of other colors, if an image is formed using the first developing device 5Ka, a high-quality image with excellent color reproducibility can be obtained. it can. Further, the color residual toner in which Y, M, C, and K are mixed is collected by the second developing device 5Kb. The second developing device 5Kb is used as the K color when forming an image that does not require color reproducibility. Therefore, the color residual toner can be reused, and the waste toner can be eliminated.

  Further, when forming a monochrome image using the first developing device 5Ka, the C, M, and Y color photoreceptors 1 may be separated from the intermediate transfer belt 10. As described above, by separating the C, M, and Y color photoconductors from the intermediate transfer belt 10, it is possible to prevent toner from adhering to the intermediate transfer belt 10 from these photoconductors. Therefore, it is possible to prevent the toner of a color other than K from being held on the K-color residual toner holding roller 50. As a result, it is possible to prevent the toner other than the K color from being mixed in the first developing device 5Ka.

  In the present embodiment, the temporary holding roller that temporarily holds the secondary transfer residual toner on the intermediate transfer belt 10, the color residual toner holding roller 60 that holds the color residual toner, and the K color residual toner are held. Two of the color residual toner holding roller 50 are provided. Then, the K color residual toner is collected by the first developing device 5Ka, and the color residual toner is collected by the second developing device 5Kb. However, the present invention is not limited to this, and there is one holding roller that temporarily holds the transfer residual toner on the intermediate transfer belt 10, and this holding roller holds the color residual toner and the K color residual toner on the intermediate transfer belt 10. May be. In this case, the secondary transfer residual toner is collected only by the second developing device 5Kb.

  FIG. 6 shows a temporary holding roller 70 that temporarily holds the secondary transfer residual toner. This temporary holding roller has the same configuration as the K-color residual toner holding roller 50 and the color residual toner holding roller 60 described above. That is, it consists of a core bar 70b and a surface layer 70a made of resin or rubber, and the surface layer 70a contains a polarity control agent. The material of the surface layer and the polarity control agent are the same as those of the K-color residual toner holding roller and the color residual toner holding roller. Then, it is rotated by a driving means (not shown) so that the linear speed ratio with the intermediate transfer belt is 1.05 to 2.00. The temporary holding roller 70 includes a holding power source 73 that applies a holding bias to the temporary holding roller 70 and a discharge power source 72 that applies a discharge bias to the temporary holding roller 70. A switch 71 for switching between the holding power source 73 and the discharge power source 72 is provided.

  The temporary holding roller 70 in FIG. 6 is not configured to be in contact with or separated from the intermediate transfer belt 10 unlike the K-color residual toner holding roller 50 and the color residual toner holding roller 60 described above, and is not always attached to the intermediate transfer belt 10. It abuts and holds both the color residual toner and the K color residual toner. Then, the holding power source 73 is switched to the discharge power source 72 at a predetermined timing, and the secondary transfer residual toner held on the temporary holding roller 70 is released. As described above, the untransferred toner that has been reversely transferred to the photosensitive member by the K primary transfer roller and reversely transferred is collected by the second developing device 5Kb.

  Also in the configuration shown in FIG. 6, toners of other colors are not mixed in the first developing device 5Ka. Therefore, if an image is formed using the first developing device 5Ka, a high-quality image with excellent K color reproducibility can be obtained. Further, the secondary transfer residual toner is collected by the second developing device 5Kb, and the waste toner can be reused by using the second developing device 5Kb when the image does not require color reproducibility. Therefore, it is possible to suppress waste toner from the image forming apparatus.

  In the present embodiment, the temporary holding rollers (50, 60, 70) for temporarily holding the secondary transfer residual toner are constituted by a metal cored bar and a rubber or resin surface layer containing a polarity control agent. However, it is not limited to this. For example, as a brush roller, the secondary transfer residual toner may be primarily held on the brush roller. Further, the temporary holding roller may be a magnetic brush roller, and the secondary transfer residual toner may be held on the magnetic brush roller.

  In the above description, an image forming apparatus that performs full-color development with a plurality of photoconductors has been described. However, the present invention is not limited to this, and an image forming apparatus that performs full-color development with one photoconductor as shown in FIG. Can be applied. In the image formation by the color image forming apparatus shown in FIG. 7, first, the electrostatic latent image of one to four colors necessary for the image formation designated in advance by the charging device 3 and the exposure device 4 is applied to the photoreceptor 1 for each color. To form. Next, the electrostatic latent image is obtained for each color by using a developing device of a color corresponding to the electrostatic latent image in each of the color developing devices 5 that individually accommodates toners of four colors of yellow, magenta, cyan, and black. Develop. Then, the toner images of one to four colors developed on the photosensitive member 1 are sequentially superimposed and superimposed on the intermediate transfer member 10 that rotates in synchronization with the photosensitive member 1 for primary transfer. Next, the one- to four-color toner images sequentially superimposed and transferred on the intermediate transfer member 10 are transferred to a transfer material 22 conveyed in synchronization with the rotation of the intermediate transfer member 10 as a secondary transfer unit. Secondary transfer is performed by the secondary transfer bias roller 14 collectively. Thereafter, the toner images of 1 to 4 colors that are collectively transferred onto the transfer paper are fixed by a fixing device 17 as a fixing unit (not shown) to obtain a print image of 1 to 4 colors specified in advance. The image forming apparatus shown in FIG. 7 also includes a recovery developing device 5Kb mainly containing K-color toner, and a temporary holding roller 70 for temporarily holding the secondary transfer residual toner on the intermediate transfer belt 10. Is provided. Then, the secondary transfer residual toner held by the temporary holding roller 70 is discharged to the intermediate transfer belt 10 at a predetermined timing, and the discharged secondary transfer residual toner is returned to the photoreceptor 1. The transfer residual toner returned to the photoreceptor 1 is recovered by the recovery developing device 5Kb. At this time, the other developing devices 5Y, 5M, 5C, and 5Ka are separated from the photoconductor. In the color image forming apparatus shown in FIG. 7 as well, high-quality images with high color reproducibility can be obtained by performing image formation using the first developing device 5Ka. Further, when printing an image that does not require color reproducibility, the secondary transfer residual toner can be reused by forming the image using the recovery developing device 5Kb.

(1)
As described above, according to the image forming apparatus of the present embodiment, the second developing device as a collecting developing device that collects the secondary transfer residual toner mainly containing K toner and mixed with two or more toners. And a developing device (first developing device) containing only K-color toner. If image formation is performed using the second developing device, the secondary transfer residual toner can be reused, and waste toner can be eliminated. If an image is formed with the first developing device instead of the second developing device, a high-quality image with high color reproducibility can be obtained.
(2)
Further, according to the image forming apparatus of the present embodiment, the secondary transfer residual toner on the intermediate transfer belt as the first image carrier is returned to the photosensitive member as the latent image carrier and collected by the developing device. The Therefore, in order to reuse the secondary transfer residual toner, it is possible to collect the secondary transfer residual toner in the developing device without providing a recycled toner transport path for transporting the secondary transfer residual toner to the developing device. As a result, it is not necessary to provide an extra conveyance path such as a recycled toner conveyance path for recovery to the developing device, and the space of the apparatus can be saved.
(3)
Further, according to the image forming apparatus of the present embodiment, the temporary holding roller that temporarily holds the secondary transfer residual toner is provided, and the surface layer of the temporary holding roller contains the polarity control agent. When the secondary transfer residual toner charged to the positive polarity by charge injection or discharge at the time of the secondary transfer is held by the temporary holding roller, it can be frictionally charged with the intermediate transfer belt and charged to the negative polarity. Thereby, the polarity of the secondary transfer residual toner held by the temporary holding roller can be made negative. When the polarity of the secondary transfer residual toner held on the temporary holding roller varies, the secondary transfer residual returned from the temporary holding roller to the intermediate transfer belt even if the potential of the primary transfer roller is lower than the potential of the photosensitive member. Only the negative polarity toner is returned to the photosensitive member, and the positive polarity toner cannot be returned to the photosensitive member. However, if the potential of the primary transfer roller is made lower than the potential of the photosensitive member by making the polarity of the secondary transfer residual toner held by the temporary holding roller negative, the secondary transfer residual toner on the intermediate transfer belt It can be returned to the photoconductor without leaving. Further, since the polarity of the secondary transfer residual toner returned to the photoconductor is uniform in negative polarity, if the surface potential of the charging roller is made lower than the potential of the photoconductor, the secondary transfer residual toner on the photoconductor is set. The secondary transfer residual toner can be collected in the second developing device without the toner adhering to the charging roller.
(4)
Further, according to the image forming apparatus of the present embodiment, the linear velocity of the temporary holding roller is different from the linear velocity of the intermediate transfer belt. Accordingly, the secondary transfer residual toner on the intermediate transfer belt is brought into sliding contact with the temporary holding roller, and the secondary transfer residual toner can be frictionally charged by the temporary holding roller. Further, by setting the linear velocity ratio between the temporary holding roller and the intermediate transfer belt to 1.05 to 2.00, the secondary transfer residual toner can be favorably frictionally charged and toner filming can be suppressed.
(5)
Further, according to the image forming apparatus of the present embodiment, a holding bias for holding the secondary transfer residual toner on the temporary holding roller or a discharge bias for discharging the secondary transfer residual toner from the temporary holding roller is selected. In addition, a changeover switch is provided as an application bias selection means for applying to the temporary holding roller. In this embodiment, since the secondary transfer residual toner is triboelectrically charged to a negative polarity by the temporary holding roller, a temporary holding bias is applied so that the surface potential of the temporary holding roller is higher than the surface potential of the intermediate transfer belt. By applying to the holding roller, the secondary transfer residual toner can be surely temporarily held by the temporary holding roller. In addition, by switching from the holding bias to the discharge bias at a predetermined timing, such as at the end of the image forming operation, the secondary transfer residual toner held on the temporary holding roller can be reliably discharged electrostatically to the intermediate transfer belt. Can do.
(6)
Further, according to the image forming apparatus of the present embodiment, the K-color residual toner holding roller as the individual colored residual toner temporary holding roller that temporarily holds only the K-color toner among the secondary transfer residual toner, and the color residual toner. And a color residual toner holding roller for temporarily holding. Then, the K-color residual toner including only the K color held by the K-color residual toner holding roller is collected by the first developing device containing only the K-color toner. Therefore, consumption of K-color toner can be suppressed. Further, since the K-color residual toner consisting only of the K-color toner is collected by the first developing device, other color toners are not mixed in the first developing device. Therefore, an image formed using the first developing device can be a black image with high color reproducibility. Further, the color residual toner held by the color residual toner holding roller is collected by the second developing device and reused. Thereby, it is possible to suppress the waste toner from being emitted.
(7)
Further, according to the image forming apparatus of the present embodiment, the K-color residual toner holding roller is separated from the intermediate transfer belt when an image is formed using the second developing device and when a color image is formed. The color residual toner holding roller is in contact with the intermediate transfer belt. When an image is formed using the second developing device and when a color image is formed, the K-color residual toner holding roller is separated from the intermediate transfer belt. , K can be prevented from adhering to the color residual toner mixed with K color.
(8)
Further, according to the image forming apparatus of the present embodiment, when an image is formed using only the first developing device, the color residual toner holding roller is separated from the intermediate transfer belt, and the K color residual toner holding roller is intermediate transferred. Make contact with the belt. By separating the color residual toner holding roller from the intermediate transfer belt, it is possible to prevent the color residual toner held by the color residual toner holding roller from coming off due to sliding contact with the intermediate transfer belt. Therefore, it is possible to suppress the K-color residual toner holding roller from holding the color residual toner.
(9)
Further, according to the image forming apparatus of the present embodiment, when an image (monochrome image) is formed using only the first developing device 5Ka, the other color photosensitive members (Y, M, C) are removed from the intermediate transfer belt. Separated. As a result, it is possible to prevent the toner of a color different from the K color adhering to the other color photoreceptors (Y, M, C) from adhering to the intermediate transfer belt and temporarily held by the K color residual toner holding roller. can do.
(10)
Further, according to the image forming apparatus of the present embodiment, the toner density sensor for detecting the toner density in the second developing device is provided, and the K color toner is replenished based on the detection result of the toner density sensor. As described above, since the K color toner is supplied in accordance with the density in the second developing device, the ratio of the K color toner is overwhelming in the second developing device than the recovered secondary transfer residual toner. To be more. For this reason, the toner characteristics in the second developing device 5 are close to those of only the K color, and a good image can be formed without changing image conditions such as charging conditions. Further, even in an image formed using the second developing device 5Kb, the color shade of K can be brought close to the color tone when using toner from only the K color.
(11)
Further, according to the image forming apparatus of the present embodiment, the color remaining toner in which colors such as Y, M, and C are mixed is collected by setting the toner color mainly contained in the second developing device to K color. However, the color tone is hardly affected. Therefore, it is possible to suppress deterioration in color reproducibility of an image created using the second developing device.
(12)
In addition, according to the image forming apparatus of the present embodiment, the photosensitive member and at least the temporary holding roller are integrally configured, and the process cartridge is detachable from the image forming apparatus, so that the photosensitive member accommodated in the process cartridge is provided. When the life of the temporary holding roller is reached or maintenance is required, the process cartridge can be replaced, which improves convenience.
(13)
Further, according to the image forming apparatus of the present embodiment, when the process cartridge includes the charging device and the developing device, when the life of the charging device or the developing device is reached or maintenance is required, the process cartridge Can be exchanged, and convenience is improved.

1 is a schematic configuration diagram of a printer according to an embodiment. FIG. 2 is a schematic configuration diagram illustrating a configuration around a Y, M, and C color photoreceptor. FIG. 5A is a schematic configuration diagram showing a configuration around a K-color photoconductor showing a state in which the first developing device approaches the photoconductor and the second developing device is separated from the photoconductor. FIG. 5B is a schematic configuration diagram showing a configuration around the K-color photoconductor showing a state in which the second developing device approaches the photoconductor and the first developing device is separated from the photoconductor. FIG. 3 is a diagram illustrating a toner holding device that holds primary transfer residual toner. FIG. 6A is a diagram illustrating a state in which the color residual toner holding roller is in contact with the intermediate transfer belt and the K color residual toner holding roller is separated from the intermediate transfer belt. FIG. 6B is a diagram illustrating a state in which the K-color residual toner holding roller is in contact with the intermediate transfer belt and the color residual toner holding roller is separated from the intermediate transfer belt. FIG. 10 is a diagram illustrating another example of a temporary holding roller that temporarily holds secondary transfer residual toner. FIG. 2 is a main part configuration diagram of an image forming apparatus that performs full-color development with one photoconductor.

Explanation of symbols

1Y, 1C, 1M, 1K Each photosensitive drum 3 Charging device 4 Exposure device 5 Developing device 10 Intermediate transfer belt 14Y, 14C, 14M, 14K Primary transfer roller 16 Secondary transfer roller 30 Process cartridge 31Y, 31C, 31M, 31K Toner bottle 40 Toner holding device 41 Magnetic brush roller 50 K color residual toner holding roller 60 Color residual toner holding roller 70 Temporary holding roller

Claims (10)

One or more latent image carriers;
A toner of a color corresponding to each image color including black is accommodated, the toner is carried on a developer carrying member, and conveyed to a portion facing the latent image carrying member, and formed on the latent image carrying member. A plurality of developing devices for supplying the toner to a latent image to form a toner image;
First transfer means for sequentially transferring the toner images of the respective colors on the latent image carrier on which the transfer bias is applied and formed into a toner image with toner in each developing device onto the first image carrier;
A second transfer means for transferring a first synthetic toner image on the first image carrier obtained by sequentially transferring toner images of each color onto a recording body;
A reverse transfer bias having a polarity opposite to the transfer bias is applied to the first transfer unit, and the secondary transfer residual toner remaining on the surface of the first image carrier after being transferred by the second transfer unit is transferred to the first transfer unit. A bias for electrostatically adhering to the latent image carrier and recovering secondary transfer residual toner adhering to the latent image carrier is applied to the developer carrier and attached to the latent image carrier 2 In the image forming apparatus in which the secondary transfer residual toner is electrostatically attached to the developer carrying member and the secondary transfer residual toner is collected in the developing device.
One of the plurality of developing devices mainly stores the same black toner as the black developing device that stores only black toner, and collects secondary transfer residual toner in which at least two colors of toner are mixed. A developing device for collection,
A black residual toner temporary holding roller for temporarily holding black secondary transfer residual toner consisting of only black toner;
A color residual toner temporary holding roller for temporarily holding a color secondary transfer residual toner in which toners of at least two colors are mixed;
The color secondary transfer residual toner temporarily held by the color residual toner temporary holding roller is collected by the recovery developing device, and the black secondary transfer residual toner held by the black residual toner temporary holding roller is black. An image forming apparatus collected by a developing device. The image forming apparatus according to claim 1.
An image forming apparatus, wherein a polarity control agent is contained in a surface layer of each temporary holding roller. The image forming apparatus according to claim 1 or 2,
An image forming apparatus, wherein a linear velocity of each temporary holding roller is different from a linear velocity of the first image carrier. The image forming apparatus according to any one of claims 1 to 3,
Each temporary holding roller is selectively temporarily held with a holding bias for holding the secondary transfer residual toner on the temporary holding roller or a discharge bias for discharging the secondary transfer residual toner from the temporary holding roller. An image forming apparatus provided with an application bias selection means for applying to a roller. The image forming apparatus according to claim 1,
When an image is formed using the recovery developing device and when a color image is formed, the black residual toner temporary holding roller is separated from the first image carrier and the color residual toner temporary holding roller is separated. An image forming apparatus, wherein the first image carrier is brought into contact with the first image carrier. The image forming apparatus according to claim 1,
When an image is formed using only the black developing device, the color residual toner temporary holding roller is separated from the first image carrier, and the black residual toner temporary holding roller is attached to the first image carrier. An image forming apparatus that is brought into contact with the image forming apparatus. The image forming apparatus according to claim 1.
A plurality of latent image carriers are provided, a latent image of a color corresponding to each latent image carrier is formed, and a toner image of a color corresponding to each latent image carrier is formed, and each latent image carrier is formed. A plurality of first transfer means for sequentially transferring toner images of respective colors on the body onto the first image carrier, and when an image is formed using only the black developing device, An image forming apparatus, wherein a latent image carrier other than black is separated from the first image carrier. The image forming apparatus according to claim 1,
An image forming apparatus comprising: a toner density sensor for detecting a toner density in the collecting developing device, and supplying black toner to the collecting developing device based on a detection result of the toner density sensor. The image forming apparatus according to claim 1,
An image forming apparatus comprising a process cartridge in which the image carrier and at least each temporary holding roller are integrally formed and detachable from the main body of the image forming apparatus. The image forming apparatus according to claim 9 .
The process cartridge includes an image forming apparatus including the latent image carrier, a charging device and a developing device arranged around the latent image carrier .

Images