JP2004227016A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus whose cost is reduced as compared with the case of individually providing the destaticizing means and the cleaning means of an intermediate transfer belt by providing a conductive brush roller which is also used as both means. <P>SOLUTION: The image forming apparatus by which a toner image formed on a photoreceptor drum 100 is transferred to the intermediate transfer belt 501 and a toner image on the intermediate transfer belt 501 is transferred to transfer paper is provided with the conductive brush roller 514 brought into contact with the intermediate transfer belt 501 after transferring the toner image to the transfer paper and a power source 804 to apply bias voltage having a polarity reverse to the surface potential of the intermediate transfer belt 501 to the conductive brush roller 514. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly, to an image forming apparatus using an intermediate transfer member.

  Conventionally, as an image forming apparatus of this type, after transferring a toner image on an intermediate transfer member transferred from an image carrier to a transfer material, the surface potential of the intermediate transfer member is reduced by discharging the surface of the intermediate transfer member. There is known an image forming apparatus that prepares the primary transfer from the image carrier to the intermediate transfer member while preparing the toner and removing attached matter such as residual toner attached to the intermediate transfer member.

  However, in the conventional image forming apparatus, an intermediate transfer member static eliminator such as a corona discharger that eliminates the surface of the intermediate transfer member, and a cleaning device such as a cleaning blade that removes deposits on the surface of the intermediate transfer member are provided. Since they were provided separately, it was difficult to reduce costs.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a conductive brush member that can also serve as an intermediate transfer member static elimination unit and an intermediate transfer member cleaning unit, so that both units can be separately provided. An object of the present invention is to provide an image forming apparatus capable of reducing cost as compared with the case where the image forming apparatus is provided.

  In order to achieve the above object, an invention according to claim 1 is an image forming apparatus for transferring a toner image formed on an image carrier to an intermediate transfer member and transferring the toner image on the intermediate transfer member to a transfer material. A conductive brush member in contact with the intermediate transfer member after transferring the toner image to the transfer material, and a power supply for applying a bias voltage having a polarity opposite to the surface potential of the intermediate transfer member to the conductive brush member Are provided.

  In the image forming apparatus according to the first aspect, the surface potential of the intermediate transfer body is removed by the conductive brush member to which a bias voltage having a polarity opposite to the surface potential of the intermediate transfer body is applied from the power source. The surface of the intermediate transfer member is rubbed with a brush member to remove the adhered matter such as residual toner adhering to the surface of the intermediate transfer member and to perform cleaning.

  According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a rotatable conductive brush roller is used as the conductive brush member.

  In the image forming apparatus according to the second aspect, the rotatable conductive brush roller is brought into contact with the intermediate transfer member, so that the same portion of the conductive brush roller does not continuously contact the intermediate transfer member. Performance can be obtained.

  According to the first or second aspect of the present invention, static elimination and cleaning of the intermediate transfer member can be performed only by bringing one conductive brush member into contact with the intermediate transfer member. There is an effect that the cost can be reduced as compared with the case where the means are individually provided.

  In particular, according to the invention of claim 2, there is an effect that good cleaning performance can be obtained.

Hereinafter, an embodiment in which the present invention is applied to an electrophotographic color copying machine (hereinafter, referred to as a “color copying machine”) that is an image forming apparatus will be described.
FIG. 1 is a schematic configuration diagram of an image forming unit that is a main part of the color copying machine according to the present embodiment. The color copying machine includes, in addition to the image forming unit shown in FIG. 1, a color image reading unit (hereinafter, referred to as a color scanner) (not shown), a paper feeding unit, a control unit, and the like.

  The color scanner reads color image information of a document for each color separation light of, for example, Red, Green, Blue (hereinafter, referred to as “R, G, B”), and converts the read color image information into an electrical image signal. Then, based on the R, G, and B color separation image signal intensity levels obtained by the color scanner, a color conversion process is performed by an image processing unit (not shown), and Black (hereinafter, referred to as “Bk”), Cyan ( Hereinafter, color image data of “C”), Magenta (hereinafter “M”), and Yellow (hereinafter “Y”) are obtained.

  1 includes a photosensitive drum 100 as an image carrier, a charger 200 as a charging unit, a photosensitive member cleaning device 300 including a cleaning blade and a fur brush, a writing optical unit (not shown) as an exposure unit, and a developing unit. It comprises a revolver developing unit 400, an intermediate transfer unit 500, a paper transfer unit 600, and a fixing unit using a pair of fixing rollers 701 as means.

  The photoconductor drum 100 rotates in the counterclockwise direction indicated by an arrow, and around the photoconductor drum 100, a charging device 200, a photoconductor cleaning device 300, a selected developing device of the revolver developing unit 400, and an intermediate transfer member of the intermediate transfer unit 500. Are disposed.

  The writing optical unit converts the color image data from the color scanner into an optical signal, and performs optical writing corresponding to the image of the original on the surface of the photosensitive drum 100 uniformly charged by the charging charger 200, An electrostatic latent image is formed on the photosensitive drum 100. This writing optical unit can be composed of, for example, a semiconductor laser as a light source, a laser emission drive control unit, a polygon mirror and its rotation motor, an f / θ lens, a reflection mirror, and the like.

  The revolver developing unit 400 includes a Bk developing device 401 using Bk toner, a C developing device 402 using C toner, an M developing device 403 using M toner, a Y developing device 404 using Y toner, and an entire unit. It is composed of a developing revolver drive unit that rotates clockwise. Each developing device installed in the revolver developing unit 400 includes a developing sleeve as a developer carrier that rotates by contacting an ear of developer with the surface of the photosensitive drum 100 to develop an electrostatic latent image; It is composed of a developer paddle that rotates to pump up and agitate the developer, a developing roller drive unit that rotates the developing roller clockwise as indicated by an arrow, and the like.

  In the present embodiment, the toner in each developing device is charged to a negative polarity by stirring with the ferrite carrier, and a negative DC voltage Vdc (DC) is applied to each developing sleeve by a developing bias power source (not shown) as a developing bias applying unit. ) Is applied with a developing bias voltage in which an AC voltage Vac (AC component) is superimposed thereon, and the developing sleeve is biased to a predetermined potential with respect to the metal base layer of the photosensitive drum 100.

  In the standby state of the main body of the color copying machine, the revolver developing unit 400 is stopped at the home position where the Bk developing device 401 is located at the developing position. Reading of image data is started, and optical writing with laser light and formation of an electrostatic latent image are started based on the color image data (hereinafter, an electrostatic latent image based on Bk image data is referred to as “Bk electrostatic latent image”. The same applies to M and Y). Before the front end of the electrostatic latent image reaches the Bk development position so that development can be performed from the front end of the Bk electrostatic latent image, the Bk developing sleeve is started to rotate and the Bk electrostatic latent image is developed with Bk toner. I do. Thereafter, the developing operation of the Bk electrostatic latent image area is continued, but when the rear end of the Bk electrostatic latent image passes the Bk developing position, the developing operation of the next color is immediately performed until the developing device of the next color comes to the developing position. The revolver developing unit 400 rotates. This is completed at least before the leading end of the electrostatic latent image based on the next image data arrives.

  The intermediate transfer unit 500 includes an intermediate transfer belt 501 as an intermediate transfer member stretched over a plurality of rollers. Around the intermediate transfer belt 501, a pre-transfer charger (hereinafter, referred to as “PTC”) 502 as a pre-transfer charging unit, a secondary transfer belt 601 as a transfer material carrier of the paper transfer unit 600, and a secondary transfer charge A secondary transfer bias roller 605 as an applying unit, a brush roller 514 as a conductive brush member also serving as an intermediate transfer body discharging unit and an intermediate transfer body cleaning unit, a lubricant applying brush 505 as a lubricant applying unit, and the like are opposed to each other. It is arranged as follows.

  The intermediate transfer belt 501 includes a primary transfer bias roller 507 as a primary transfer charge applying unit, a belt driving roller 508, a belt tension roller 509, a secondary transfer facing roller 510, a cleaning facing roller, and a pre-primary transfer charge removing unit. Is stretched around the belt static elimination roller 512. Each roller is formed of a conductive material, and each roller other than the primary transfer bias roller 507 is grounded. The primary transfer bias roller 507 is supplied with a transfer bias controlled by a primary transfer power supply 801 controlled by a constant current or a constant voltage to a current or a voltage of a predetermined magnitude according to the number of superimposed toner images. Have been. Further, the intermediate transfer belt 501 is driven in a direction indicated by an arrow by a belt drive roller 508 that is rotated by a drive motor (not shown).

  As shown in the cross-sectional view of FIG. 2, the intermediate transfer belt 501 is formed of a belt material having a multilayer structure including a surface layer 501a, an intermediate layer 501b, and a base layer 501c. The outer peripheral surface side in contact with the photosensitive drum 100 is the surface layer 501a, and the inner peripheral surface side is the base layer 501c. Further, an adhesive layer 501d for bonding the two layers is interposed between the intermediate layer 501b and the base layer 501c.

  In a transfer unit that transfers the toner image on the photosensitive drum 100 to the intermediate transfer belt 501 (hereinafter, referred to as a “primary transfer unit”), the primary transfer bias roller 507 and the belt discharging roller 512 transfer the intermediate transfer belt 501 to the photosensitive member. A nip portion having a predetermined width is formed between the photosensitive drum 100 and the intermediate transfer belt 501 by being stretched so as to be pressed against the drum 100 side. Further, a grounded belt neutralization brush 513 as a primary transfer unit neutralization unit is brought into contact with the inner peripheral surface of the intermediate transfer belt 501 in the nip portion.

  As shown in FIG. 3, the nip width Wn of the primary transfer portion and the distance L from the downstream end of the nip portion in the belt moving direction to the contact position of the belt neutralizing brush 513 are such that predetermined transfer conditions can be obtained. Set to.

  The PTC 502 uniformly charges the toner image on the intermediate transfer belt 501 transferred from the photosensitive drum 100 in the primary transfer unit before transferring the toner image to transfer paper as a transfer material. .

  The conductive brush roller 514 removes and cleans the intermediate transfer belt 501 after the secondary transfer, and removes the DC voltage having the same polarity as the surface potential of the intermediate transfer belt 501 after the secondary transfer. Power supply 804. An AC voltage may be superimposed on this DC voltage in order to increase the static elimination efficiency. Further, the conductive brush roller 514 can switch between contact with the intermediate transfer belt 501 and separation from the belt by a separation / contact mechanism (not shown).

  The brush roller 514 is ON / OFF controlled as follows. For example, when forming one full-color image, the brush roller 514 is brought into contact at least until the intermediate transfer belt 501 makes one rotation after the completion of the secondary transfer. In the case of full-color image repeat formation, the brush roller 514 is brought into contact with the end of the next toner image until the leading end of the next toner image reaches the charge removal position and the cleaning position, respectively, after the secondary transfer. When one monocolor image is formed, the brush roller 514 is brought into contact at least until the intermediate transfer belt 501 makes one rotation after the primary transfer is completed. Further, in the case of forming a repeat of a monocolor image, the brush roller 514 is brought into contact after the end of the primary transfer until the leading end of the next toner image reaches the neutralization position and the cleaning position, respectively.

  The lubricant applying brush 505 is for polishing zinc stearate 506 as a lubricant formed in a plate shape and applying the polished fine particles to the intermediate transfer belt 501. The lubricant application brush 505 is also configured to be able to be separated from and brought into contact with the intermediate transfer belt 501, and is controlled so as to contact the intermediate transfer belt 501 at a predetermined timing.

  The paper transfer unit 600 includes a secondary transfer belt 601 and the like stretched over three support rollers 602 to 604, and a stretched portion between the support rollers 602 and 603 of the intermediate transfer belt 501 is opposed to the secondary transfer belt. It can be pressed against the roller 510. One of the three support rollers 602 to 604 is a driving roller that is rotationally driven by a driving unit (not shown), and the driving roller drives the secondary transfer belt 601 in the direction of the arrow in the drawing. The secondary transfer bias roller 605 is disposed so as to sandwich the intermediate transfer belt 501, the transfer paper and the secondary transfer belt 601 between the secondary transfer bias roller 510 and the secondary transfer opposing roller 510. A transfer bias of a predetermined current is applied by a power supply 802. Further, the support roller 602 and the secondary transfer bias roller are arranged so that the secondary transfer belt 601 and the secondary transfer bias roller 605 can take a position where the secondary transfer belt 601 presses against the secondary transfer opposing roller 510 and a position where the secondary transfer belt 601 separates. An unillustrated separation / contact mechanism for driving the 605 is provided. The secondary transfer belt 601 at the separated position is indicated by a two-dot chain line in FIG.

  A portion of the secondary transfer belt 601 wrapped around the support roller 603 on the side opposite to the fixing roller is provided with a transfer paper charge remover 606 as a transfer material charge remover and a belt charge remover 607 as a transfer material carrier charge remover. are doing. A cleaning blade 608 as a transfer material carrier cleaning unit is in contact with a portion of the secondary transfer belt 601 that is wound around the lower support roller 604 in the drawing.

  The transfer paper discharging charger 606 discharges the electric charges held in the transfer paper, so that the transfer paper can be satisfactorily separated from the secondary transfer belt 601 by the strength of the transfer paper itself. The belt static eliminator 607 eliminates the charge applied by the secondary transfer bias roller 605 and remaining on the secondary transfer belt 601. Further, the cleaning blade 608 is for removing the adhered matter on the surface of the secondary transfer belt 601 for cleaning.

  When the image forming cycle is started in the color copier having the above configuration, first, the photosensitive drum 100 is rotated in a counterclockwise direction indicated by an arrow by a drive motor (not shown), and the intermediate transfer belt 501 is driven clockwise by an arrow. Rotated. With the rotation of the intermediate transfer belt 501, Bk toner image formation, C toner image formation, M toner image formation, and Y toner image formation are performed, and finally, on the intermediate transfer belt 501 in the order of Bk, C, M, and Y. A toner image is formed overlapping.

  The formation of the Bk toner image is performed as follows. The charger 200 uniformly charges the photosensitive drum 100 with a negative charge to approximately a predetermined potential by corona discharge. Then, raster exposure is performed by the writing optical unit based on the Bk color image signal. When this raster image is exposed, in the exposed portion of the photosensitive drum 100 that is initially uniformly charged, the charge proportional to the amount of exposure light disappears, and a Bk electrostatic latent image is formed. Then, when the negatively charged Bk toner on the Bk developing roller comes into contact with the Bk electrostatic latent image, the toner does not adhere to a portion where the charge of the photosensitive drum 100 remains, and a portion without the charge, that is, the exposure is not performed. The Bk toner is adsorbed on the portion thus formed, and a Bk toner image similar to the electrostatic latent image is formed. Then, the Bk toner image formed on the photosensitive drum 100 is transferred onto the surface of the intermediate transfer belt 501 that is driven at a constant speed in contact with the photosensitive drum 100. Hereinafter, the transfer of the toner image from the photosensitive drum 100 to the intermediate transfer belt 501 is referred to as “belt transfer”.

  A small amount of untransferred residual toner remaining on the surface of the photoconductor drum 100 after the belt transfer is cleaned by the photoconductor cleaning device 300 in preparation for reuse of the photoconductor drum 100.

On the photoconductor drum 100 side, the process proceeds to the C image forming process after the Bk image forming process. At a predetermined timing, reading of C image data by a color scanner is started, and writing of a C electrostatic latent image is performed by laser light writing based on the C image data. I do. Then, after the rear end of the previous Bk electrostatic latent image has passed and before the front end of the C electrostatic latent image has arrived, the rotating operation of the revolver developing unit is performed, and the C developing device 402 is moved to the developing position. And the C electrostatic latent image is developed with C toner. Thereafter, the development of the C electrostatic latent image area is continued, but when the rear end portion of the C electrostatic latent image passes, the revolver developing unit is rotated in the same manner as in the case of the Bk developing device 401, and the next operation is performed. Is moved to the developing position. This is also completed before the leading end of the next M electrostatic latent image reaches the developing position.
In the M and Y image forming processes, the operations of reading the color image data, forming the electrostatic latent image, and developing are the same as those of the above-described processes of BK and C, and thus the description is omitted.

  The Bk, C, M, and Y toner images sequentially formed on the photosensitive drum 100 are transferred to the intermediate transfer belt 501 while being sequentially aligned on the same surface. As a result, a toner image in which a maximum of four colors are superimposed is formed on the intermediate transfer belt 501. The superimposed toner image on the intermediate transfer belt 501 is uniformly charged by the PTC 502, and is then collectively transferred to transfer paper in the next secondary transfer step.

  At the time when the image forming operation is started, the transfer paper is fed from a paper feed unit such as a transfer paper cassette (not shown) or a manual feed tray, and stands by at a nip of a pair of registration rollers (not shown). When the leading edge of the toner image on the intermediate transfer belt 501 approaches the secondary transfer portion where the nip is formed by the secondary transfer opposing roller 510 and the secondary transfer bias roller, the leading edge of the transfer paper is just The registration roller pair is driven so as to coincide with the leading end, and registration of the transfer paper and the toner image is performed. Then, the transfer paper is superimposed on the toner image on the intermediate transfer belt 501 and passes through the secondary transfer portion. At this time, the four-color superimposed toner image on the intermediate transfer belt 501 is collectively transferred onto the transfer paper by the transfer bias formed by the transfer bias applied to the secondary transfer bias roller. The transfer paper is discharged when passing through a portion opposed to a transfer paper discharging charger 606 disposed downstream of the secondary transfer portion in the secondary transfer belt moving direction, and is separated from the intermediate transfer belt 501 to fix the transfer paper. Sent toward pair 701. Then, the toner image is fused and fixed at the nip portion of the fixing roller pair 701, sent out of the apparatus main body by a discharge roller pair (not shown), and stacked face up on a copy tray (not shown) to obtain a full color copy.

  On the other hand, the surface of the intermediate transfer belt 501 after the transfer of the toner image onto the transfer paper is removed and cleaned by a brush roller 514 pressed against the intermediate transfer belt 501 by a contact / separation mechanism (not shown).

  Here, in the case of the repeat copy, the operation of the color scanner and the image formation on the photosensitive drum 100 are performed at a predetermined timing following the image formation process of the fourth sheet (Y) of the first sheet. Proceed to the image forming step (Bk). Further, the intermediate transfer belt 501 transfers the second Bk toner image to the area of the surface cleaned by the brush roller 514, following the batch transfer process of the first four-color superimposed toner image onto the transfer paper. Is transferred to the belt. Thereafter, the operation is the same as that of the first sheet.

  The above is the copy mode for obtaining a four-color full-color copy. However, in the three-color copy mode and the two-color copy mode, the same operation as described above is performed for the designated color and the number of times. In the case of the single-color copy mode, only the developing device of the predetermined color of the revolver developing unit 400 is in the developing operation state until the predetermined number of sheets is completed, and the brush roller 514 is pressed against the intermediate transfer belt 501. The copy operation is continuously performed as it is.

  As described above, according to the present embodiment, the neutralization and cleaning of the intermediate transfer belt 501 can be performed only by bringing one brush roller 514 into contact with the intermediate transfer belt 501. The cost can be reduced as compared with the case where each is provided individually.

  Further, when a corona discharger is used as the intermediate transfer member static elimination means as in the prior art, even though the surface of the intermediate transfer belt immediately after the static elimination is about 0 V, after a while, the potential of the polarity before the static elimination is removed. Is gradually observed. However, when a configuration is employed in which a voltage is applied to the brush roller 514 to remove static electricity as in the present embodiment, the polarity potential before the neutralization may appear again. And good static elimination characteristics can be obtained.

  In the above embodiment, the brush roller 514 is used as a conductive brush member for removing and cleaning the intermediate transfer belt 501. However, as shown in FIG. 4, a brush 516a extending in the axial direction of the cleaning opposing roller 511 is used. May be used. In the case of this configuration, as shown in FIG. 4, it is desirable to arrange a metal roller 517 for efficiently collecting the toner and the like attached to the brush 516a of the brush member 516 so as to contact the brush 516a. . A voltage higher than that of the brush member 516 is applied to the metal roller 517, and the toner or the like attached to the brush 516a of the brush member 516 is attracted to the metal roller 517 by electrostatic force. The deposits adhering to the surface of the metal roller 517 are collected by a blade or the like (not shown).

  Further, in the above-described embodiment, the configuration may be such that the neutralization condition by the brush roller 514 is switched according to the surface potential of the intermediate transfer belt 501 after the secondary transfer so that the intermediate transfer belt 501 can be uniformly neutralized. For example, the magnitude of the DC component of the output voltage of the power supply 804 is switched according to the number of times the toner image is superimposed on the intermediate transfer belt 501.

Next, a more specific example of the color copying machine according to the above embodiment will be described.
As the intermediate transfer belt 501, an intermediate transfer belt having a thickness of 0.15 mm, a width of 368 mm, and an inner peripheral length of 565 mm was used, and the moving speed of the intermediate transfer belt 501 was set to 200 mm / sec.

The surface layer 501a of the intermediate transfer belt 501 is formed of an insulating layer having a thickness of about 1 μm, and the intermediate layer 501b is formed of an insulating layer made of PVDF (polyvinylidene fluoride) having a thickness of about 75 μm (volume resistivity: about 10 ^13). Ωcm), and the base layer 501c was formed of a medium resistance layer (volume resistivity: 10 ⁸ to 10 ¹¹ Ωcm) made of PVDF (polyvinylidene fluoride) and titanium oxide and having a thickness of about 75 μm. When the volume resistivity of the entire intermediate transfer belt formed of such a material was measured, it was 10 ⁷ to 10 ¹² Ωcm. Each volume resistivity is measured by applying a voltage of 100 V for 10 seconds using a measuring method described in JIS K 6911. The surface resistivity of the surface of the intermediate transfer belt 501 on the surface layer 501a side was measured with a resistance meter “Hirester IP” manufactured by Yuka Denshi to be 10 ⁷ to 10 ¹² Ω / □. This surface resistivity can be measured by the surface resistance measurement method described in JIS K 6911 in addition to using the above-mentioned resistance measuring device.

  Further, a nickel-plated metal roller was used as the primary transfer bias roller 507, a metal roller was used as the belt discharging roller 512, and a metal roller or a conductive resin roller was used as the other rollers. Further, the primary transfer bias roller 507 has, for example, 1.0 kV for the first color toner image, 1.3 to 1.4 kV for the second color toner image, and 1.3 kV for the third color toner image. A DC transfer bias of an appropriate magnitude was applied, for example, from 1.6 to 1.8 kV, and from 1.9 to 2.2 kV for the fourth color toner image.

  The nip width Wn of the primary transfer portion was set to 10 mm, and the distance L from the downstream end of the nip portion in the belt moving direction to the contact position of the belt neutralizing brush 513 was set to 7 mm (see FIG. 3). As the belt neutralizing brush 513, a conductive brush having carbon-containing resin fibers implanted was used.

  As the PTC 502, a charger with a grid electrode was used. A DC bias voltage having the same polarity as the charging polarity of the toner image on the intermediate transfer belt 501 was applied to the PTC 502 by the PTC power supply 803. More specifically, a DC voltage controlled at a constant current of -500 μA was applied to the main wire 502a of the PTC 502, and a DC voltage set within a range of 0 to -3 kV was applied to the grid electrode 502b.

  As the brush roller 514 for neutralizing and cleaning the intermediate transfer belt 501 after the secondary transfer, a brush having conductive shaft fibers implanted on a metal shaft was used. A DC voltage (positive voltage) having a polarity opposite to the surface potential of the intermediate transfer belt 501 before static elimination was applied to the shaft. By using the conductive brush roller 514 to which the predetermined voltage is applied, even when the multi-layered intermediate transfer belt 501 including the high-resistance intermediate layer 501b is used as in the present embodiment, the charge once discharged is restored again. The neutralization of the intermediate transfer belt 501 after the secondary transfer was successfully performed without the phenomenon of appearing on the surface.

As the secondary transfer bias roller 605, a roller having a surface layer made of conductive sponge or conductive rubber and a core layer made of metal or conductive resin is used. This roller has a constant current of 10 to 20 μA. A controlled transfer bias was applied. As the secondary transfer belt 601, a belt material made of PVDF (polyvinylidene fluoride) having a thickness of 100 μm and a volume resistivity of 10 ¹³ Ωcm was used.

  A discharger to which only an AC voltage or an AC + DC voltage is applied by a power supply (not shown) is used as the transfer paper discharging charger 606, and a discharger to which only the AC voltage or AC + DC voltage is applied by a power supply (not shown) is used as the belt discharging charger 607. An electric device was used. In addition, the cleaning blade 608 was in contact with the portion of the secondary transfer belt 601 around the support roller 604 by a counter method.

  In the above embodiment, the example in which the photosensitive drum 100 is used as the image carrier has been described. However, the present invention can be applied to an image carrier having another shape. For example, the present invention can be applied to a photosensitive belt that is stretched between two rollers and moves endlessly.

  Further, in the above-described embodiment, an example in which the intermediate transfer belt 501 is used as the intermediate transfer body has been described. However, the present invention can be applied to an apparatus using an intermediate transfer body having another shape. The electrical characteristics (volume resistivity, surface resistivity, etc.), thickness, structure (single-layer, two-layer,...), Material, material, and the like of the intermediate transfer belt 501 are appropriate depending on image forming conditions and the like. Can be selected and adopted in various ways.

  Further, in the above-described embodiment, an example was described in which a charge elimination brush was used as the primary transfer portion charge elimination means in the nip portion of the primary transfer portion. It can also be applied to those using members of other shapes. Further, the position at which the charge is removed by the charge removing means is not limited to the position shown in the above embodiment, but may be located upstream of the primary transfer bias roller 507 in the moving direction of the intermediate transfer belt and within the nip portion of the primary transfer portion. I just need. Further, the position of static elimination in the nip portion of the primary transfer portion is not limited to one location, and static elimination may be performed at a plurality of locations. Further, in the present embodiment, the charge removing brush is grounded, but a bias having a polarity opposite to the polarity of the transfer charge may be applied in a range that does not affect the transfer charge required for transfer in the nip portion. .

  Further, in the above-described embodiment, an example in which the primary transfer bias applying roller is used as the primary transfer charge applying unit has been described. However, the present invention is also applied to an apparatus employing a primary transfer charge applying unit having another shape. be able to. Further, if it is on the downstream side of the charge removal position by the primary transfer non-charge removing means such as the charge removal brush in the moving direction of the intermediate transfer belt, the primary transfer charge may be applied within the nip of the primary transfer portion.

  In the above embodiment, the values of the voltage, current, and the like of the primary transfer bias applied to the primary transfer charge applying means such as the primary transfer bias roller 507 are not limited to the above examples. A suitable value can be set according to the image forming conditions.

  Further, in the above-described embodiment, the example in which the belt static elimination roller 512 is used as the pre-primary transfer static elimination means has been described, but the present invention uses a member having another shape such as a blade or a brush instead of this roller. Can also be applied.

  Further, in the above embodiment, the example in which the secondary transfer bias roller is used as the secondary transfer charge applying unit has been described, but the present invention uses a member of another shape such as a blade or a brush instead of this roller. It can also be applied to things.

  In the above-described embodiment, the secondary transfer belt 601 is used as a transfer material carrier for supporting the transfer material in the secondary transfer unit. However, the present invention is not limited to this belt. The present invention can be applied to those using.

  Further, in the above embodiment, the case where the charging potential of the photosensitive drum 100 is negative and the developing device adopting the reversal developing method using the two-component type developer is described. The charging potential of the body drum 100 is not limited to the one having a negative polarity, and can be similarly applied to the one using a one-component developer or the one using a regular development system.

FIG. 1 is a schematic configuration diagram of a color copying machine according to an embodiment. FIG. 2 is a cross-sectional view of an intermediate transfer belt used in the color copying machine. FIG. 2 is an enlarged view of a primary transfer section of the color copying machine. The schematic block diagram of the conductive brush member concerning a modification.

Explanation of reference numerals

Reference Signs List 100 photoconductor drum 500 intermediate transfer unit 501 intermediate transfer belt 502 pre-transfer charger (PTC)
507 Primary transfer bias roller 508 Belt drive roller 509 Belt tension roller 510 Secondary transfer facing roller 511 Cleaning facing roller 512 Belt discharging roller 513 Belt removing brush 514 Brush roller 601 Secondary transfer belt 605 Secondary transfer bias roller 801 Primary transfer Power supply 802 Secondary transfer power supply 803 Power supply for PTC 804 Power supply for static elimination

Claims (2)

An image forming apparatus for transferring a toner image formed on an image carrier to an intermediate transfer member and transferring the toner image on the intermediate transfer member to a transfer material,
A conductive brush member that is brought into contact with the intermediate transfer body after transferring the toner image to the transfer material,
An image forming apparatus, comprising: a power supply for applying a bias voltage having a polarity opposite to a surface potential of the intermediate transfer member to the conductive brush member. The image forming apparatus according to claim 1,
An image forming apparatus, wherein a rotatable conductive brush roller is used as the conductive brush member.

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