JP2007316145A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for improving durability of an intermediate transfer belt by suppressing the surface of the intermediate transfer belt from being damaged, while achieving miniaturization of the apparatus. <P>SOLUTION: The image forming apparatus comprises: the intermediate transfer belt 7 rotated to be supported on a plurality of rollers; a developing device 5 for forming toner images on a photoreceptor drum 1 by using a two-component developer; and a bending roller 10e for bending the intermediate transfer belt 7 from an outer peripheral face side to an inside by being arranged on the downstream side of a secondary transfer part T2 and the upstream side of a primary transfer part T1 concerning a conveying direction of the intermediate transfer belt 7. The image forming apparatus is provided with a carrier collection means 23 for collecting a carrier 30 stuck to the surface of the intermediate transfer belt 7 on the downstream side of the secondary transfer part T2 and the upstream side of the bending roller 10e concerning the conveying direction of the intermediate transfer belt 7. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus for transferring a toner image carried on an image carrier onto an intermediate transfer member and transferring the toner image on the intermediate transfer member onto a recording medium.

  In recent years, in electrophotographic apparatuses, there are increasing demands from the market for higher image quality, higher durability, lower cost, full color, and the like. In recent years, with the widespread use of color printers and color copiers, offices have become full-color, and there is an increasing demand for devices that output full-color images at the same speed as monochrome. In order to satisfy this requirement, a so-called tandem full-color image forming apparatus has attracted attention.

  A tandem type image forming apparatus includes a plurality of photoconductors arranged side by side, each having a developing device, forming a single color toner image on each photoconductor, and sequentially transferring the single color toner images. A composite color image is recorded on the superimposed recording material. In this tandem type image forming apparatus, compared with a so-called one-drum type image forming apparatus that forms a composite full-color image on a photoconductor by repeating image formation a plurality of times (usually four times) using a single photoconductor. The printing time can be greatly reduced. However, since such a tandem type image forming apparatus has a plurality of image forming units, the apparatus is likely to be large in size and high in cost.

  Some tandem type image forming apparatuses employ a direct transfer system as shown in FIG. 5, and others employ an indirect transfer system as shown in FIG. In the direct transfer method, images on the respective photosensitive drums 1 are sequentially transferred onto a sheet conveyed by the sheet conveying belt 7 by a transfer device. In the indirect transfer method, images on the respective photosensitive drums 1 are sequentially transferred to the intermediate transfer belt 7 by the primary transfer unit 2 and then transferred to a sheet by the secondary transfer units 20 and 21. Batch transfer.

  In the direct transfer method, the feeding device and the fixing device 9 must be arranged on the upstream side and the downstream side of the tandem type image forming apparatus in which a plurality of photosensitive drums 1 are arranged, and the size is further increased in the sheet conveying direction. There are drawbacks. Further, when the fixing device 9 is arranged close to the tandem type image forming apparatus so as not to increase in size as much as possible, there is not enough room for the sheet to bend. For this reason, there is a possibility that a defective image is generated at the rear end portion due to an impact when the leading edge of the sheet enters the fixing device 9 or a difference in sheet conveyance speed when passing through the fixing device 9.

  On the other hand, in the indirect transfer method, the secondary transfer position can be set relatively freely. Therefore, as shown in FIG. 6, the secondary transfer position is located away from the primary transfer position facing the photosensitive drum 1, and the size can be reduced compared to the upstream side and the downstream side of the tandem type image forming apparatus. There is. In addition, since the fixing device 9 can be disposed with a sufficient margin that allows the sheet to bend, there is no possibility of adversely affecting the image when passing through the fixing device 9. For this reason, the indirect transfer type of tandem type image forming apparatus has attracted particular attention.

  In an image forming apparatus employing an indirect transfer method, the intermediate transfer belt 7 is image-formed on the downstream side of the secondary transfer units 20 and 21 and on the upstream side of the primary transfer unit 2 with respect to the conveyance direction of the intermediate transfer belt 7. There is one provided with a bending roller 10e that bends inward from the surface side (Patent Document 1). In this image forming apparatus, an empty space is formed outside the intermediate transfer belt 7 by changing the path so that the intermediate transfer belt 7 is recessed inward by the bending roller 10e. Since another apparatus can be disposed in this empty space, the entire image forming apparatus can be further reduced in size.

  In particular, by making the hardness of the bending roller 10e harder than the hardness of the intermediate transfer belt 7, it is possible to apply a uniform tension to the surface of the intermediate transfer belt, and it is possible to form a stable running of the intermediate transfer belt 7. . Further, since the tension angle of the intermediate transfer belt 7 on the downstream side of the secondary transfer units 20 and 21 can be precisely controlled, an effect that the separation property of the sheet from the intermediate transfer belt 7 can be improved is also obtained.

JP 2003-149953 A

  However, in the configuration in which the hardness of the bending roller 10e is higher than the hardness of the intermediate transfer belt 7, the following problems occur in the case of an image forming apparatus using a two-component development system.

  The two-component developer is mainly composed of a toner and a carrier that is a magnetic material. The toner is negatively charged and the carrier is positively charged. Usually, in the developing device, only the toner flies from the developing sleeve or the carrier onto the photosensitive drum by the developing bias, and then is conveyed to the primary transfer unit and transferred onto the intermediate transfer belt. However, there is a strong force for urging the toner from the developing sleeve or carrier onto the photosensitive drum, causing a phenomenon in which not only the toner but also the carrier adheres to the photosensitive drum, which adversely affects the output image. There is. This is generally called carrier adhesion in a solid image portion.

  If a large amount of carrier adheres to the surface of the photosensitive drum, not only the toner but also the carrier is transferred onto the intermediate transfer belt in the primary transfer portion. When the carrier (about 35 to 50 μm) adhering to the intermediate transfer belt passes through the secondary transfer portion and reaches the bending roller 10e, it enters between the bending roller 10e and the intermediate transfer belt 7. At this time, the carrier is sufficiently larger than the surface unevenness (several μm) of the intermediate transfer belt 7 and has a certain degree of hardness, so that the surface of the intermediate transfer belt is scratched and the image is deteriorated. Will occur.

  However, in the image forming apparatus provided with such a bending roller 10e and the configuration in which the hardness of the bending roller 10e is harder than the hardness of the intermediate transfer belt 7, the collecting means for collecting the carrier attached on the surface of the intermediate transfer belt is provided. Not proposed.

  The present invention can reduce the size of the apparatus by providing a bending member, and can improve the durability of the intermediate transfer belt by suppressing the scratch on the surface of the intermediate transfer belt, thereby obtaining a stable image. It is an object of the present invention to provide an image forming apparatus that can be used.

  In order to solve the above problems, a typical configuration of an image forming apparatus according to the present invention is mainly composed of an intermediate transfer member supported by a plurality of rollers and driven to rotate, and a toner and a carrier that is a magnetic material. A developing device that forms a toner image on an image carrier using a component developer, a primary transfer unit that transfers the toner image formed on the image carrier onto the intermediate transfer member, and the intermediate transfer member A secondary transfer means for transferring the toner image on the recording medium; and a downstream side of the secondary transfer part and an upstream side of the primary transfer part in the transport direction of the intermediate transfer body, An image forming apparatus comprising: a bending member that bends inward from the surface side; and on the surface of the intermediate transfer member on the downstream side of the secondary transfer unit and the upstream side of the bending member with respect to the conveyance direction of the intermediate transfer member. Key to collect the carrier attached to And providing a rear collecting means.

  According to the present invention, the apparatus can be reduced in size by providing a bending member, and the durability of the intermediate transfer belt is improved by suppressing the surface of the intermediate transfer belt from being scratched, thereby obtaining a stable image. be able to.

[First embodiment]
A first embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an image forming apparatus according to the present embodiment.

(Configuration of image forming apparatus)
As shown in FIG. 1, the image forming apparatus is an electrophotographic four-color full-color laser beam printer. The image forming apparatus includes four image forming units, a scanning optical device 4, an intermediate transfer belt 7 that is an intermediate transfer body, an intermediate transfer body cleaning device 8, a bending roller 10e, and a carrier recovery means 23.

  Each image forming unit includes a photosensitive drum 1, a primary transfer roller 2, a primary charger 3, a developing device 5, and a cleaning device 6.

  The photosensitive drums 1a, 1b, 1c, and 1d are image carriers corresponding to yellow, magenta, cyan, and black toners. The developing devices 5a, 5b, 5c, and 5d form toner images on the photosensitive drum 1 using a two-component developer mainly composed of toner and a carrier 30 that is a magnetic material. The primary transfer rollers 2a, 2b, 2c, and 2d are primary transfer units that transfer the toner images formed on the photosensitive drums 1a to 1d onto the intermediate transfer belt 7.

The intermediate transfer belt 7 is in contact with the photosensitive drums 1a, 1b, 1c, and 1d to form respective primary transfer portions (primary transfer nip portions) T1. The resistance of the intermediate transfer belt 7 is preferably a volume resistivity of 10 ⁶ to 10 ¹² Ω · cm. The intermediate transfer belt 7 is made of urethane resin, fluorine resin, nylon resin, polyimide resin, elastic material such as silicone rubber or hydrin rubber, and resistance adjustment is performed by dispersing carbon or conductive powder in these materials. Can be used.

  As shown in FIG. 1, the intermediate transfer belt 7 is stretched and supported by a plurality of rollers 10c, 10d, 10e, and 20. The bending roller 10e is a bending member disposed outside the intermediate transfer belt 7, and applies tension to the intermediate transfer belt 7 by applying pressure so as to curve the intermediate transfer belt 7 inward.

  The bending roller 10e is disposed downstream of the secondary transfer portion T2 and upstream of the primary transfer portion T1 with respect to the conveyance direction of the intermediate transfer belt 7. The bending roller 10e bends the intermediate transfer belt 7 from the outer peripheral surface side to the inner side. In this embodiment, a metal roller having a diameter of 20 to 30 mm is used as the bending roller 10e, and the tension applied to the surface of the intermediate transfer belt 7 is set to be uniform.

  Further, although the magnitude of the tension applied to the plurality of rollers 10c, 10d, 20 and the bending roller 10e depends on the material of the intermediate transfer belt 7, it is possible to prevent the intermediate transfer belt 7 from being broken or permanently deformed. desirable. In this embodiment, a polyimide resin-based intermediate transfer belt 7 is used so that the intermediate transfer belt 7 is not broken or permanently deformed.

  In each primary transfer portion T1, the intermediate transfer belt 7 is sandwiched between the primary transfer rollers 2a to 2d and the photosensitive drums 1a to 1d. The primary transfer rollers 2a, 2b, 2c, and 2d are preferably made of foaming urethane or the like. A voltage of 100 to 1000 V having a polarity opposite to that of the toner is applied to the primary transfer portion T1.

  A secondary transfer outer roller 21 is disposed at a position facing the secondary transfer inner roller 20. The secondary transfer inner roller 20 and the secondary transfer outer roller 21 constitute secondary transfer means. The intermediate transfer belt 7 is sandwiched between the secondary transfer inner roller 20 and the secondary transfer outer roller 21, and a secondary transfer portion (secondary transfer nip portion) T <b> 2 is formed between the intermediate transfer belt 7. The recording medium 22 such as paper is nipped and conveyed at the secondary transfer portion T2.

  The secondary transfer inner roller 20 is preferably solid or foaming EPDM, NBR or the like, and the secondary transfer outer roller 21 is preferably NBR or the like. A voltage of 1.0 to 6.0 kV having a polarity opposite to that of the toner is applied to the secondary transfer portion T2.

(Operation of the entire image forming apparatus)
Hereinafter, the operation of the entire image forming apparatus will be described while appropriately adding a description of the configuration.

  The photosensitive drums 1a, 1b, 1c, and 1d are rotationally driven counterclockwise in FIG. 1 by a driving unit (not shown), and are uniformly charged by primary chargers 3a, 3b, 3c, and 3d. Then, the scanning optical devices 4a, 4b, 4c, and 4d modulated by the image information signal sent from the host computer irradiate the surface of the photosensitive drum 1 with laser light, and an electrostatic latent image is formed. The intensity of the laser beam and the irradiation spot diameter at this time are appropriately set according to the resolution of the image forming apparatus and the desired image density. The electrostatic latent image on the photosensitive drum 1 is formed by the potential VL of the portion (bright portion) irradiated with the laser light 4 and the potential VD of the portion not irradiated (dark portion).

  The electrostatic latent image reaches a portion facing the developing devices 5a to 5d by the rotation of the photosensitive drums 1a to 1d, and the toner charged to the same polarity (negative polarity in the present embodiment) is a bright portion of the electrostatic latent image. And is developed as a toner image.

  In the four-color full-color image formation, toner images of the respective colors are similarly formed by the photosensitive drums 1a to 1d, the primary chargers 3a to 3d, the scanning optical device 4, and the developing devices 5a to 5d corresponding to the respective colors. . These color toner images are sequentially primary-transferred onto the intermediate transfer belt 7 in each primary transfer portion T1 and superimposed on the intermediate transfer belt 7.

  In each primary transfer portion T1, an electric field formed in the primary transfer portion T1 by a voltage having a polarity opposite to that of the toner applied to the primary transfer rollers 2a, 2b, 2c, and 2d in contact with the back surface of the intermediate transfer belt 7. Thus, the toner image is primarily transferred.

  When the intermediate transfer belt 7 passes the primary transfer portion T1 with the photosensitive drums 1a to 1d, toner images of four colors are carried on the intermediate transfer belt 7, and the primary transfer process is completed. On the other hand, the surfaces of the photosensitive drums 1a to 1d after the primary transfer of the toner images are cleaned by the cleaning devices 6a, 6b, 6c, and 6d, respectively, and then prepared for the next image forming process.

  Next, one sheet of recording medium 22 such as paper is taken out from a feeding means (not shown) and inserted into the secondary transfer portion T2. At this time, a voltage having a polarity opposite to that of the toner is applied to the secondary transfer outer roller 21, whereby the four color toner images are collectively transferred from the intermediate transfer belt 7 onto the recording material medium 22. .

  The intermediate transfer belt 7 can increase the winding amount of the intermediate transfer belt 7 around the outer peripheral surface of the secondary transfer inner roller 20 at the separation portion of the recording medium 22 by the action of the curved roller 10e. For this reason, the curvature of the intermediate transfer belt 7 becomes substantially the same as the curvature of the secondary transfer inner roller 20, and the recording medium 22 can be satisfactorily separated. In the present embodiment, a roller having a diameter of 16 mm to 24 mm is used as the secondary transfer inner roller 20.

  The recording medium 22 carrying the unfixed toner image after passing through the secondary transfer portion T2 reaches a fixing device (not shown) and is fixed as a permanent image by being heated and pressurized. On the other hand, the surface of the intermediate transfer belt 7 that has finished transferring the toner image to the recording medium 22 is removed by the intermediate transfer body cleaning device 8. The intermediate transfer body cleaning device 8 brings a cleaning blade made of urethane rubber or the like into contact with the surface of the intermediate transfer belt 7 and scrapes off secondary transfer residual toner adhering to the surface of the intermediate transfer belt 7. The secondary transfer residual toner scraped off is collected in a waste toner box as waste toner. The secondary transfer residual toner refers to toner that remains on the surface of the intermediate transfer belt 7 without being secondarily transferred to the recording medium 22 during the secondary transfer.

(Carrier recovery means 23)
Next, the carrier collecting unit 23 that collects the carrier 30 attached on the intermediate transfer belt 7 will be described. FIG. 2 is an enlarged view of the carrier recovery means 23.

  The carrier recovery means 23 is disposed downstream of the secondary transfer portion T2 and upstream of the bending roller 10e with respect to the conveyance direction of the intermediate transfer belt 7. As shown in FIG. 2, the carrier recovery unit 23 includes a sleeve 24, magnets S <b> 1, N <b> 1, S <b> 2, N <b> 2, N <b> 3 and a transport unit 25.

  The sleeve (φ20-30mm) is made of a material that is aluminum alloy or plastic product, has no magnetic properties, is 0.2-1mm thick, has no thermal deformation, has excellent wear resistance, and is easy to process. . The sleeve 24 rotates in the direction opposite to the conveyance direction of the intermediate transfer belt 7 (clockwise direction in FIG. 2).

  Magnets S 1, N 1, S 2, N 2, and N 3 are magnetic field generating means disposed inside the sleeve 24. Magnets S1, N1, S2, N2, and N3 are fixed, and do not rotate even when sleeve 24 rotates. Magnets S1, N1, S2, N2, and N3 are magnets such as ferrite magnets such as barium ferrite and strontium ferrite, rubber ferrite magnets in which ferrite magnets are dispersed in rubber, and MnAl magnets.

  The magnet S1 is a carrier attracting member that attracts the carrier 30 attached on the surface of the intermediate transfer belt 7 to the surface of the rotating sleeve 24. The magnet S1 is disposed near the position where the intermediate transfer belt 7 and the sleeve 24 are close to each other. Here, the magnetic flux density in the perpendicular direction (radial direction of the sleeve 24) perpendicular to the surface of the sleeve 24 of the S1 pole located opposite to the intermediate transfer belt 7 is desirably 1500 gauss or more.

  The N2 pole and the N3 pole are repulsive magnetic poles that are opposite to the carrier 30 and are opposite to the S1 pole across the rotation center of the sleeve 24. At the position A at the center of the N2 pole and the N3 pole, the force applied to the carrier 30 from the magnetic field formed by the magnetic poles N2 and N3 on the surface of the sleeve 24 is substantially zero. At the position A, the carrier 30 drops from the sleeve 24 and prevents the carrier 30 once collected from being conveyed again to the surface of the intermediate transfer belt 7.

  In this embodiment, the same magnetic pole arrangement as that of the developing roller is adopted and the magnetic poles N1 and S2 are provided. However, the magnetic poles N1 and S2 may be omitted.

  The transport means 25 is a screw-type (φ20 to 30 mm) rotary transport member that is provided below the sleeve 24 and that rotates to transport the carrier 30 in the longitudinal direction.

  The carrier 30 adhering to the surface of the intermediate transfer belt 7 is attracted to the sleeve surface by the S1 pole, and is conveyed to the inside of the carrier recovery means 23 as the sleeve 24 rotates. Due to the positional relationship between the repulsive magnetic poles N2 and N3, the force acting on the carrier 30 is substantially zero at the position A, and the carrier 30 transported to the position A falls due to gravity. The dropped carrier 30 is transported in the longitudinal direction by the transport means 25 and is recovered in a carrier recovery box (not shown) provided on the front side of the image forming apparatus.

  In this embodiment, the carrier 30 on the surface of the intermediate transfer belt 7 is collected by the magnetic field of the magnet built in the sleeve 24. However, by applying a voltage having a polarity opposite to that of the carrier 30 to the sleeve 24, The carrier 30 can be efficiently collected.

  When the amount of the carrier 30 is large, it is preferable to install a carrier recovery coil for discharging the carrier 30 while rotating. Of course, other than the carrier recovery coil may be used to achieve the object, and the discharge mechanism is not necessary if the storage capacity of the carrier 30 is large and the discharge amount of the carrier 30 is sufficient even during periodic inspection.

(effect)
In the above configuration, the carrier 30 attached to the surface of the intermediate transfer belt 7 is collected by the carrier collecting unit 23 before reaching the curved roller 10e. Accordingly, it is possible to prevent the surface of the intermediate transfer belt from being damaged by entering between the bending roller 10e and the intermediate transfer belt 7. Therefore, the durability of the intermediate transfer belt 7 can be improved and a stable image can be obtained.

  Further, by changing the path so that the intermediate transfer belt 7 is recessed inward by the bending roller 10e, an empty space is formed on the outside thereof. Since another apparatus can be disposed in this empty space, the entire image forming apparatus can be further reduced in size.

  In addition, the cross-sectional configuration of the carrier recovery unit 23 in the present embodiment is sufficiently smaller than the peripheral length (500 to 900 mm) of the intermediate transfer belt 7, thereby making it possible to reduce the size of the entire image forming apparatus.

  Further, by making the manifestation hardness of the bending roller 10e harder than the manifestation hardness of the intermediate transfer belt 7, it is possible to apply a uniform tension to the surface of the intermediate transfer belt and to form a stable running of the intermediate transfer belt 7. It becomes. Further, since the tension angle of the intermediate transfer belt 7 on the downstream side of the secondary transfer inner roller 20 and the secondary transfer outer roller 21 can be precisely controlled, the separation property of the sheet from the intermediate transfer belt 7 can be improved. An effect is also obtained.

[Second Embodiment]
Next, a second embodiment of the image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 3 is an enlarged view of the carrier recovery means 23 in the present embodiment. About the part which overlaps with said 1st embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 3, the image forming apparatus according to the present embodiment is different from the image forming apparatus according to the first embodiment in that a carrier conveyance blocking member 26 is provided in place of the repulsion polarities N2 and N3. The carrier conveyance blocking member 26g contacts the longitudinal direction of the rotary sleeve 24, scrapes off the carrier 30, and prevents the carrier 30 once collected from being conveyed again to the surface of the intermediate transfer belt 7.

  As the carrier conveyance blocking member 26, felt, leather, artificial leather, or the like, which is fixed so that the surface thereof is in light contact with the sleeve 24, is used. It is sufficient that the surface to be contacted is about 10 mm. It is still better that the receiving part of the carrier 30 is provided with an auxiliary sheet for preventing the carrier 30 from being caught. The position where the carrier conveyance blocking member 26 and the sleeve 24 come into contact is downstream of the S1 pole and vertically below in the rotation direction of the sleeve 24.

  The magnets S1, N1, and S2 can be magnets of exciter stones instead of permanent magnets such as ferrite magnets. In this case, the magnetic force can be appropriately adjusted by adjusting the applied voltage or current. In the case of an excitation type magnet, the carrier 30 from the sleeve 24 can be dropped by interrupting energization. Even if the carrier 30 falls, there is a possibility that the carrier 30 that is physically attached is present, so the carrier transport blocking member 26 is necessary. However, since the adhesion force of the carrier 30 to the sleeve 24 is weak, the carrier 30 can be removed by bringing a member such as a conductive brush into contact with the sleeve 24.

(effect)
In the above configuration, as in the first embodiment, the bending roller 10e can be provided to reduce the size of the apparatus, and the surface of the intermediate transfer belt 7 can be prevented from being scratched and the durability of the intermediate transfer belt 7 can be reduced. And a stable image can be obtained.

[Third embodiment]
Next, a third embodiment of the image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 4 is a schematic configuration diagram of a tandem type image forming apparatus according to the present embodiment. About the part which overlaps with said 1st embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 4, the image forming apparatus according to the present embodiment replaces the carrier collecting unit 23 of the first embodiment with fur brushes 27 and 28, opposed rollers 10f and 10g, a carrier collecting container 31, 32 is provided.

  The fur brushes 27 and 28 are disposed on the downstream side of the secondary transfer portion T2 and on the upstream side of the bending roller 10e with respect to the conveyance direction of the intermediate transfer belt 7. The fur brushes 27 and 28 are in contact with the surface of the intermediate transfer belt 7. The fur brushes 27 and 28 apply a positive voltage and a negative voltage, respectively, in order to completely scrape the carrier 30 attached on the intermediate transfer belt 7.

  In this embodiment, +1.0 to 1.5 kV and -1.0 to 1.5 kV are applied to the fur brushes 27 and 28, and carrier recovery is performed by using electrostatic force in addition to mechanical force. Yes.

  Further, the fur brushes 27 and 28 not only collect the carrier 30 on the surface of the intermediate transfer belt 7 but also can remove paper dust and charge the transfer residual toner on the surface of the intermediate transfer belt 7. As a result, it becomes easy to collect the transfer residual toner on the surface of the intermediate transfer belt 7 by the cleaning blade 8 on the downstream side of the bending roller 10e.

The resistance of the intermediate transfer belt 7 is preferably a volume resistivity of 10 ⁶ to 10 ²² Ω · cm. The intermediate transfer belt 7 is made of urethane resin, fluorine resin, nylon resin, polyimide resin, elastic material such as silicone rubber or hydrin rubber, and resistance adjustment is performed by dispersing carbon or conductive powder in these materials. Can be used. In this embodiment, the intermediate transfer belt 7 is made of a material using carbon particles as a polyimide resin.

The fur brushes 27 and 28 have a density of 5 to 200,000 yarns / inch ² (7750 to 31000) of conductive yarn having a thickness of 3 to 20 deniers (D) (for example, carbon fiber dispersed and spun in a rayon resin). The hair was planted so as to be 10,000 / m ² ). The fur brushes 27 and 28 having a bristle length of 3 to 20 mm and an intrusion amount of about 0.2 to 2.5 mm give good results. In the present embodiment, the fur brushes 27 and 28 have a thread thickness of 6 denier, a flocking density of 200,000 / inch ² (31 million / m ² ), a bristle length of 5 mm, and a penetration amount of 0.1 mm. 5 mm.

  The opposing rollers 10f and 10g are disposed at positions facing the fur brushes 27 and 28 with the intermediate transfer belt 7 interposed therebetween. The opposing rollers 10f and 10g are grounded.

  The carrier recovery containers 31 and 32 are containers for storing the carrier 30 recovered by the fur brushes 27 and 28. A carrier screw or the like for transporting the carrier 30 to a large-capacity carrier recovery box (not shown) provided at another location may be provided in the carrier recovery containers 31 and 32.

(effect)
In the above configuration, as in the first embodiment, the bending roller 10e can be provided to reduce the size of the apparatus, and the surface of the intermediate transfer belt 7 can be prevented from being scratched and the durability of the intermediate transfer belt 7 can be reduced. And a stable image can be obtained.

  Further, the charge remaining on the intermediate transfer belt 7 can be easily collected by the cleaning blade 8 on the downstream side of the bending roller 10e due to the charge removal of the transfer remaining toner in the secondary transfer unit.

1 is a schematic configuration diagram of a tandem type copying machine according to a first embodiment. It is an enlarged view of the carrier collection | recovery means in 2nd embodiment. It is an enlarged view of the carrier collection | recovery means in 2nd embodiment. It is a schematic block diagram of the tandem type image forming apparatus in 3rd embodiment. It is a schematic block diagram which illustrates the intermediate transfer tandem process of the conventional direct transfer system. It is a schematic block diagram which illustrates the intermediate transfer tandem process of the conventional indirect transfer system.

Explanation of symbols

A ... Positions S1, N1, S2, N2, N3 ... Magnet T1 ... Primary transfer part T2 ... Secondary transfer part 1 ... Photosensitive drum (image carrier)
2 ... Primary transfer roller (primary transfer means)
3 ... Primary charger 4 ... Scanning optical device 5 ... Developing device 6 ... Cleaning device 7 ... Intermediate transfer belt (intermediate transfer member)
8 ... Intermediate transfer member cleaning device 9 ... Fixing device 10 ... Roller 10e ... Bending roller (bending member)
10f, 10g ... opposing roller 20 ... secondary transfer inner roller (secondary transfer means)
21 ... Secondary transfer outer roller (secondary transfer means)
22 ... Recording medium 23 ... Carrier recovery means 24 ... Sleeve 25 ... Conveyance means 26 ... Carrier transport prevention members 27, 28 ... Fur brush 30 ... Carriers 31, 32 ... Carrier recovery container

Claims (7)

A developing device that forms a toner image on an image carrier using a two-component developer mainly composed of an intermediate transfer member supported by a plurality of rollers and driven to rotate, and a carrier that is a toner and a magnetic material; A primary transfer unit that transfers a toner image formed on an image carrier onto the intermediate transfer member; a secondary transfer unit that transfers a toner image on the intermediate transfer member onto a recording medium; and the intermediate transfer member. An image forming apparatus comprising: a bending member that is disposed downstream of the secondary transfer unit and upstream of the primary transfer unit with respect to the conveying direction, and bends the intermediate transfer member from the outer peripheral surface side to the inside.
An image forming system comprising: a carrier collecting unit that collects a carrier adhering to the surface of the intermediate transfer member on a downstream side of the secondary transfer unit and an upstream side of the bending member with respect to a conveyance direction of the intermediate transfer member. apparatus.
The carrier recovery means includes a rotating sleeve that rotates in a direction opposite to the conveying direction of the intermediate transfer member, and a carrier suction member that sucks the carrier adhering on the surface of the intermediate transfer member to the surface of the rotating sleeve. The image forming apparatus according to claim 1.
The image forming apparatus according to claim 2, wherein the carrier recovery unit includes a carrier conveyance blocking member that contacts the longitudinal direction of the rotating sleeve and scrapes off the carrier.
3. The image forming apparatus according to claim 2, wherein the carrier recovery unit includes a repulsive magnetic pole having a polarity opposite to that of a carrier that drops the carrier sucked onto the surface of the rotating sleeve by the carrier suction member from the surface of the rotating sleeve.
The image forming apparatus according to claim 1, wherein the carrier recovery unit is a fur brush that contacts the surface of the intermediate transfer member.
The image forming apparatus according to claim 1, wherein a surface hardness of the bending member is harder than a surface hardness of the intermediate transfer member.
The image forming apparatus according to claim 6, wherein the bending member is a metal roller.

Images