JP5371333B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that causes no image failure when recovering residual toner to an image carrier by uniformly scattering residual toner and conducting uniform charging, wherein secondary transfer residual toner is efficiently recovered to a photosensitive drum without causing image failure. <P>SOLUTION: The image forming apparatus includes a conductive planar toner holding member 21, which is opposed to an intermediate transfer member 9 and causes residual toner to temporarily stay on an intermediate transfer member. The conductive planar toner holding member 21 is disposed downstream of a secondary transfer position N2 and upstream of a charging member 22 in the moving direction of the intermediate transfer member 9. The surface of the conductive planar toner holding member 21 is in slide contact with an intermediate transfer member 21, and a DC voltage of polarity reverse to the normal polarity of toner is applied to the conductive planar toner holding member 21. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention transfers a toner image formed on an image carrier to a movable intermediate transfer member, such as an electrophotographic color image forming apparatus, and then transfers the toner image on the intermediate transfer member to a transfer material. The present invention relates to an intermediate transfer type image forming apparatus for transferring to an image.

  Conventionally, an electrophotographic system using an intermediate transfer system is known as an image forming apparatus that forms a color image on a transfer material such as paper.

  The intermediate transfer system is a method in which a plurality of color toners are sequentially superimposed and transferred from a photosensitive drum, which is an image carrier that carries a toner image, to an intermediate transfer belt, which is an intermediate transfer body, to perform primary transfer. This is a method for forming a toner image. As the intermediate transfer member, an intermediate transfer drum may be used instead of the intermediate transfer belt.

  Thereafter, the color toner image is collectively transferred from the intermediate transfer belt to a transfer material such as paper to form a color image.

  When the color toner images are secondarily transferred collectively by the intermediate transfer method, it is desirable that all the toner is transferred to the transfer material, but a part of the toner remains on the intermediate transfer belt. Such toner that remains on the intermediate transfer belt without being subjected to secondary transfer is hereinafter referred to as “residual toner”.

  When the next image is formed with the residual toner remaining on the intermediate transfer belt, the residual toner is secondarily transferred to the transfer material in addition to the color toner image for forming the next image, thereby improving the image quality. It will have an adverse effect.

  For this reason, it is necessary to collect the residual toner on the intermediate transfer belt.

  As a method for collecting the residual toner, a method is known in which the residual toner is charged to a polarity opposite to the normal polarity of the toner, transferred to the photosensitive drum at the primary transfer position, and collected.

  In Patent Document 1, so-called simultaneous transfer cleaning is performed in which the residual toner on the intermediate transfer belt is charged to a polarity opposite to the normal polarity by a charging unit, and is collected on a photosensitive drum in the next primary transfer process. ing.

  However, in the method in which the residual toner is collected on the photosensitive drum, if there is non-uniform residual toner on the intermediate transfer belt, the residual toner in a lump or non-uniformly charged residual toner adversely affects the next image. It is known that This is particularly noticeable during simultaneous primary transfer recovery.

In order to solve such a problem, in Patent Document 2, a bias in which a DC voltage is superimposed on an AC voltage is applied. According to this configuration, the residual toner is uniformly scattered and is uniformly charged to a polarity opposite to the normal polarity, so that it is possible to drastically reduce image defects that have been a problem in the past.
Japanese Patent Laid-Open No. 9-50167 Japanese Patent Laid-Open No. 10-49023

  However, in the configuration described in Patent Document 2 described above, toner scattering occurs as a new problem because an AC voltage is applied to residual toner whose charge state is unstable.

  In addition, repeated image formation causes toner deterioration and non-uniform residual toner. For this reason, the toner cannot be completely dispersed even by an AC voltage, causing image defects.

  Therefore, in the cleaning method for collecting the residual toner on the photosensitive drum, there is a problem of how to disperse the residual toner that comes in a non-uniform lump and uniformly charge it to collect it on the photosensitive drum. This problem appears more prominently when simultaneous primary transfer is performed.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus in which residual toner is uniformly scattered and charged uniformly, so that no image defect occurs when the residual toner is collected on the image carrier. .

The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention includes an image carrier that carries a toner image and a movable intermediate transfer member, and the toner image on the image carrier is placed on the intermediate transfer member at a primary transfer position. In an image forming apparatus that performs primary transfer and secondarily transfers a toner image on the intermediate transfer member to a transfer material at a secondary transfer position.
A planar member that contacts the intermediate transfer member without rotating with respect to the movement of the intermediate transfer member; and a power source that applies a voltage to the planar member;
The planar member is an elastic sheet supported by a rigid body, and the elastic sheet is not secondarily transferred to a transfer material when a voltage having a polarity opposite to a normal polarity of toner is applied from the power source. While the residual toner remaining on the intermediate transfer body is retained and retained on the surface of the elastic sheet upstream of the intermediate transfer body in the moving direction of the intermediate transfer body with respect to the rubbing portion to be formed, Can be scattered on the intermediate transfer member ,
In the image forming apparatus, residual toner that is not held on the elastic sheet is transferred to the image carrier at the primary transfer position.

  According to the present invention, since the toner on the intermediate transfer member can be uniformly dispersed and charged uniformly, reliable cleaning can be performed without causing image defects.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Example 1
FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to the present invention. The image forming apparatus according to the present exemplary embodiment has an effective configuration for uniform dispersion of residual toner and uniform charging.

  In this embodiment, the image forming apparatus 100 is an electrophotographic color image forming apparatus using an intermediate transfer method. The image forming apparatus 100 primarily transfers and temporarily superimposes each color toner image formed according to image information separated into yellow, magenta, cyan, and black color components onto the intermediate transfer member, and then from the intermediate transfer member, Secondary transfer is performed collectively on a transfer material such as paper.

Next, the overall configuration of the image forming apparatus 100 will be described.
(overall structure)
Referring to FIG. 1, a drum-shaped electrophotographic photosensitive member, that is, a photosensitive drum 1 is provided as an image carrier, and the photosensitive drum 1 is driven in a direction indicated by an arrow R1 by a driving means (not shown) to be charged. The charging roller 2 is uniformly charged. The charging roller 2 is connected to a high voltage power source 14.

  Next, a laser beam L according to the image information is irradiated onto the photosensitive drum 1 by an exposure device 3 which is a laser scanner device as an exposure unit, and an electrostatic latent image is formed.

  Further, when the photosensitive drum 1 advances in the direction of the arrow R1, the electrostatic latent image formed on the photosensitive drum 1 according to the image information is developed as a toner image by the developing device 4 as a developing unit.

  In this embodiment, the developing device 4 is a rotary developing device, and includes developing devices 5, 6, 7, and 8 that respectively contain yellow, magenta, cyan, and black developers. Development is performed by sequentially rotating to the development position. Since the configuration of the rotary developing device 4 is well known to those skilled in the art, further explanation is omitted.

  Further, an intermediate transfer belt 9 is disposed as an intermediate transfer member on the downstream side of the photosensitive drum 1 from the developing device 4 in the arrow R1 direction. The intermediate transfer belt 9 is a cylindrical and endless belt-like film stretched by a driving roller / secondary transfer counter roller 12 and a tension roller 13, and moves in the R3 direction at substantially the same peripheral speed as the photosensitive drum 1.

  A transfer roller 10 is disposed as a primary transfer unit at a position (primary transfer position) facing the photosensitive drum 1 with the intermediate transfer belt 9 interposed therebetween, thereby forming a primary transfer nip portion N1. As the photosensitive drum 1 and the intermediate transfer belt 9 rotate, a primary transfer bias is applied to the primary transfer roller 10 from the power source 16, so that the toner image formed on the photosensitive drum 1 is transferred onto the intermediate transfer belt 9. Perform primary transfer.

  By performing the above steps and performing primary transfer by sequentially superimposing four colors of yellow, magenta, cyan, and black, a toner image of a plurality of colors can be formed on the intermediate transfer belt 9.

At a position (secondary transfer position) facing the secondary transfer counter roller 12 with the intermediate transfer belt 9 interposed therebetween, a secondary for secondary transfer of the toner image from the intermediate transfer belt 9 onto the transfer material P such as paper. A secondary transfer roller 11 as a transfer means is disposed. The transfer material P fed by a paper feed roller (not shown) is supplied at a predetermined timing to the secondary transfer nip portion N2 where the intermediate transfer belt 9 and the secondary transfer roller 11 are rubbed. At the same time, a secondary transfer bias is applied from the power source 17 to the secondary transfer roller 11, and the toner image is secondarily transferred from the intermediate transfer belt 9 to the transfer material P. Residual toner that is not transferred to the transfer material P and remains on the intermediate transfer belt 9 is uniformly scattered by a conductive sheet toner holding member (that is, sheet member ) 21 serving as an intermediate transfer member cleaning unit, and is charged by a charging member. A charge is applied by the conductive roller 22, which is transferred to the photosensitive drum 1 and collected. The residual toner attached to the photosensitive drum 1 is scraped off by the cleaning blade 15.

  Hereinafter, the cleaning process of the intermediate transfer belt 9 will be described in detail with reference to FIGS.

(Primary transfer)
The primary transfer roller 10 uses an elastic roller having a volume resistance of 10 ⁵ to 10 ⁹ Ωcm and a rubber hardness of 30 ° (load 4.9 N Asker C hardness meter), and is connected to the photosensitive drum 1 through the intermediate transfer belt 9. It is pressed with a pressure of about 9.8 N. Further, the primary transfer roller 10 is driven and rotated with the rotation of the intermediate transfer belt 9 and can be applied with a voltage of −2.0 to +3.5 kV from the high-voltage power supply 16. .

(Intermediate transfer belt)
The intermediate transfer belt 9 is made of polyvinylidene fluoride (PVDF) having a thickness of 100 μm and a volume resistivity adjusted to about 10 ¹¹ Ωcm by mixing a conductive agent. The intermediate transfer belt 9 is stretched around two axes of a driving roller / secondary transfer counter roller 12 and a tension roller 13, and is stretched by the tension roller 13 with a total pressure of about 60N.

(Secondary transfer)
The secondary transfer roller 11 uses an elastic roller having a volume resistance of 10 ⁵ to 10 ⁹ Ωcm and a rubber hardness of 30 ° (load 4.9 N Asker C hardness meter), and the secondary transfer counter roller 12 via the intermediate transfer belt 9. On the other hand, it is pressed with a total pressure of about 39.2N. Further, the secondary transfer roller 11 is driven and rotated with the rotation of the intermediate transfer belt 9 and can be applied with a voltage of −2.0 to +4.0 kV from the high voltage power source 17. .

(Conductive surface toner holding member)
As the conductive planar toner holding member 21, a 1 mm thick NBR rubber sheet having a resistance value of 10 to 10 ⁹ Ωcm was used. The NBR rubber sheet was provided with an electrode 23 at the end opposite to the rubbing portion N3 (see FIG. 6) on the rubbing surface side, and a DC voltage was applied to the electrode 23 from the high-voltage power source 19. In FIG. 6, the free end length L in the lateral direction excluding the electrode mounting portion of the conductive planar toner holding member 21 is 5 to 20 mm, and is 10 mm in this embodiment.

  Further, the conductive planar toner holding member 21 has a tip portion (specifically, a portion corresponding to a “rubbing portion N3” described later) at an angle α in the forward direction with respect to the moving direction of the intermediate transfer belt 9. Abutment is arranged. The contact angle α is 5 ° to 60 °, and is 30 ° in this embodiment. Further, the contact tip portion 21e of the conductive planar toner holding member 21 is in contact with the intermediate transfer belt 9 at a pressure of 0.49 to 9.8N. In this embodiment, 1.96N. It was.

(Conductive roller)
The conductive roller 22 as a charging member was an elastic roller having a volume resistance of 10 ⁵ to 10 ⁹ Ωcm. In FIG. 2, the conductive roller 22 is pressed against the driving roller 12 via the intermediate transfer belt 9 and is driven to rotate as the intermediate transfer belt 9 rotates. In addition, a voltage of −2.0 to +2.0 kV is applied to the conductive roller 22 from the high-voltage power supply 20.

  In the configuration described above, a method for cleaning the intermediate transfer belt 9 will be described in detail.

(Intermediate transfer member cleaning)
In this embodiment, the toner is charged to a negative polarity (normal polarity), and the primary transfer roller 10 and the secondary transfer roller 11 are positively charged (reverse to the normal polarity of the toner) by high-voltage power supplies 16 and 17, respectively. Image formation is performed by applying a polarity voltage. The residual toner after the secondary transfer has both positive and negative polarities due to the influence of the positive bias applied to the secondary transfer roller 11 as shown in FIG. Further, under the influence of the unevenness on the surface of the transfer material, the transfer residual toner locally overlaps a plurality of layers and remains on the intermediate transfer belt 9 (A in FIG. 2). The residual toner that overlaps the plurality of layers is uniformly scattered and, if not uniformly charged, adversely affects the next image. This occurs remarkably during the simultaneous primary transfer recovery.

  First, an image defect that occurs when the residual toner is not scattered uniformly will be described.

  FIG. 3 shows a state in which the residual toner passes through the photosensitive drum 1 when the charging member 22 cannot fully charge the positive polarity (positive polarity) from the normal polarity. When the residual toner is not sufficiently charged, only the charged toner is transferred to the photosensitive drum 1 and collected during the primary transfer, and the residual toner remaining on the intermediate transfer belt 9 is transferred to the transfer material P together with the primary transfer toner. The next transfer results in an image defect.

  Further, FIG. 4 shows a case where all of the residual toner that is not scattered by the charging member 22 is charged to a polarity opposite to the normal polarity. In this case, when the residual toner is collected at the primary transfer portion N1, it is collected onto the photosensitive drum 1 together with the primary transfer toner. This is because the residual toner is agglomerated and is collected on the photosensitive drum 1 together with the primary transfer toner, and the residual toner is charged non-uniformly by the charging member 22 to a polarity opposite to the normal polarity of the toner. Therefore, the partially overcharged residual toner electrostatically attracts the primary transfer toner.

  As shown in FIG. 5, when the residual toner is uniformly dispersed and is uniformly charged with the reverse polarity by the charging member 22, the above problem does not occur at the time of collection.

  Therefore, the present invention is particularly effective when the primary transfer simultaneous cleaning is performed.

  Hereinafter, with reference to FIG. 2 and FIG. 6, the conditions under which the residual toner is uniformly scattered by the configuration of this embodiment will be described.

  Along with the start of the secondary transfer, a positive bias (a polarity opposite to the normal polarity of the toner) is applied to the conductive planar toner holding member 21 positioned upstream of the primary transfer position N1 with respect to the rotation direction of the intermediate transfer belt 9. ) Is applied.

  The manner in which the toner is scattered will be described with reference to FIG. FIG. 6 schematically shows a state in which the conductive planar toner holding member 21 is disposed on the straight portion of the intermediate transfer belt 9 and the residual toner passes through the conductive planar toner holding member 21.

  When a positive bias is applied to the conductive sheet toner holding member 21, negative toner out of the residual toner adheres to the conductive sheet toner holding member 21 and stays temporarily. When the bias applied to the conductive sheet toner holding member 21 is +0.8 kV, the temporarily staying toner is a toner rubbing region formed between the leading end portion of the conductive sheet toner holding member 21 and the transfer belt 9. (Rubbing portion) formed on N3. The rubbing portion N3 has a length of about 1 mm from the front end portion 21e of the conductive planar toner holding member 21 to the upstream side in the moving direction of the intermediate transfer belt 9 along the intermediate transfer belt 9.

  The present inventors have confirmed the following by experiments.

  That is, first, a DC voltage of +0.8 kV was applied to the conductive sheet toner holding member 21 to pass the magenta residual toner through the conductive sheet toner holding member 21. Thereafter, the cyan residual toner is passed through the position of the conductive planar toner holding member 21 and the conductive planar toner holding member 21 at that time is observed. As a result, the cyan toner adheres to the conductive planar toner holding member 21. Was. That is, the temporarily staying toner has been replaced.

Assuming that the residual toner has a charge of −30 q / g, the adhesive force of the residual toner to the intermediate transfer belt is 2.5 × 10 ⁻⁸ N, and the toner particle size is 6 μm, what amount of temporarily staying toner is present. Or estimated by calculation. As a result, at least four layers of toner adhere to the conductive planar toner holding member 21 in the range of about 1 mm of the rubbing portion N3 by the DC voltage applied to the conductive planar toner holding member 21. .

  When the conductive planar toner holding member 21 as in this embodiment is rubbed against the intermediate transfer belt 9, the conductive planar toner holding member is located at a place about 1.0 mm in the upstream direction from the tip 21e in the rubbed portion N3. Toner 21 adheres to four layers, so that the toner is densely packed in a region where the gap between conductive surface toner holding member 21 and intermediate transfer belt 9 is about 24 μm or less. Among the densely clogged residual toner, the toner that is in contact with the lowermost intermediate transfer belt 9 is more strongly contacted with the intermediate transfer belt 9 than the electric field between the conductive planar toner holding member 21 and the intermediate transfer belt 9. The adhesive force worked strongly.

  From the above results, the mechanism by which the residual toner is uniformly dispersed by temporarily retaining the residual toner in the conductive planar toner holding member 21 is as follows.

  Of the residual toner composed of a plurality of layers, the toner in contact with the intermediate transfer belt 9 has an adhesion force to the intermediate transfer belt 9 rather than the electric field between the conductive planar toner holding member 21 and the intermediate transfer belt 9. I work hard. For this reason, the toner is held on the intermediate transfer belt 9 and passes through the conductive sheet toner holding member 21 with the rotation of the intermediate transfer belt 9, but the non-contact toner adheres to the conductive sheet toner holding member 21 and is temporarily Residual toner is formed.

  Of the temporarily staying toner adhering to the conductive planar toner holding member 21, the toner that has come into contact with the intermediate transfer belt 9 is more intermediate than the electric field between the conductive planar toner holding member 21 and the intermediate transfer belt 9. Adhesion with 9 works strongly. Therefore, it is held again on the intermediate transfer belt 9 and passes through the conductive planar toner holding member 21 as the intermediate transfer belt 9 rotates.

  While applying a DC voltage to the conductive planar toner holding member 21, the above process is repeated. For this reason, the residual toner that passes through the conductive planar toner holding member 21 is scattered in approximately one layer after passing through the conductive planar toner holding member 21. Further, since the temporarily staying toner does not stay more than a certain amount by being replaced, there is no fear that the toner stays away from the conductive planar toner holding member 21. Therefore, the residual toner can be stably dispersed by the above mechanism.

  Actually, the charge of the residual toner has a distribution, and the electric field distribution changes by changing the contact angle α (see FIG. 6) of the conductive planar toner holding member 21. For this reason, a temporary staying toner similar to the above calculation result cannot be obtained, but at least the temporarily staying toner formed on the conductive surface toner holding member 21 is closely packed near the rubbing portion. As a result, the residual toner is uniformly dispersed.

  Residual toner scattered in approximately one layer moves in the rotational direction (R3) of the intermediate transfer belt 9. A positive voltage is applied to the conductive roller 22, and the residual toner on the intermediate transfer belt 9 is given a positive charge when passing through the conductive roller 22 (D in FIG. 2). The residual toner to which a positive charge is applied is transferred to the photosensitive drum 1 and collected at the primary transfer portion N1.

  In the present embodiment, the voltage applied to the conductive planar toner holding member 21 must be set to such an extent that the toner is not charged so much. This is because when a voltage that is large enough to charge the residual toner is applied, the residual toner cannot be separated from the intermediate transfer belt 9 and is not temporarily retained in the conductive planar toner holding member 21. For this reason, the residual toner scattering effect by the temporarily staying toner cannot be obtained (FIG. 7).

  The residual toner is partially scattered by the contact pressure of the conductive planar toner holding member 21 to the intermediate transfer belt 9, but is not uniformly distributed over the entire width direction of the intermediate transfer belt 9.

  Further, as shown in FIG. 8, when no voltage is applied to the conductive planar toner holding member 21, no electric field is formed between the conductive planar toner holding member 21 and the intermediate transfer belt 9. In other words, the residual toner scattering effect by the temporarily staying toner cannot be obtained. Also in this case, the residual toner is partially scattered by the contact pressure of the conductive planar toner holding member 21 to the intermediate transfer belt 9, but is not uniformly distributed over the entire width direction of the intermediate transfer belt 9.

  As described above, according to the present embodiment, by applying a predetermined direct current voltage to the conductive planar toner holding member 21 to form a temporarily staying toner, a plurality of layers of residual toner are scattered in approximately one layer, The conductive roller 22 can be uniformly charged. Therefore, even if the residual toner is simultaneously collected at the primary transfer, it can be cleaned from the intermediate transfer belt 9 without adversely affecting the primary transfer toner.

  The temporarily staying toner adhering to the conductive sheet toner holding member 21 is replaced, but remains partially adhered to the conductive sheet toner holding member 21. Therefore, a negative voltage is periodically applied to the conductive sheet toner holding member 21 to discharge the toner from the conductive sheet toner holding member 21.

  According to this embodiment, in order to disperse the residual toner uniformly, the toner must be temporarily retained. Therefore, a member that cannot retain the toner at a position opposed to the intermediate transfer belt 9, such as a roller that is driven and rotated, cannot be used. .

  In this embodiment, one conductive sheet-like toner holding member 21 is rubbed over the entire width direction of the intermediate transfer belt, but it may be divided into a plurality of pieces and rubbed.

  In addition, as shown in FIG. 9, the conductive planar toner holding member 21 may be a U-shaped member having a curvature, and the curvature portion 21 f may be applied to the intermediate transfer belt 9. As shown in FIG. 10, the same effect can be obtained by using a member having a ridge line as the conductive planar toner holding member 21 and sliding the ridge line portion 21 f against the intermediate transfer belt 9.

  As can be understood from the above description, according to the present embodiment, the toner on the intermediate transfer member can be uniformly dispersed and charged uniformly, so that it is possible to reliably perform without causing image defects. Cleaning becomes possible.

Example 2
Next, a second embodiment of the image forming apparatus of the present invention will be described. The overall configuration of the image forming apparatus according to the present embodiment is the same as that of the image forming apparatus described in the first embodiment with reference to FIG. 1, and therefore, the description of the first embodiment is used, and the description thereof is not repeated here. Omitted.

  In this embodiment, the configuration of the conductive planar toner holding member 21 has a feature, and this feature will be described below. In this embodiment, the conductive planar toner holding member 21 can be more stably in contact with the intermediate transfer belt 9, and can form a temporary stay of residual toner more stably.

  In this embodiment, as shown in FIG. 11, the conductive sheet-like toner holding member 21 has a curvature, that is, has a configuration in which an elastic sheet 21b is bonded to a U-shaped rigid body 21a. In this embodiment, a conductive sheet 21c is further attached to the elastic sheet 21b.

As the surface conductive sheet 21c, a 50 μm thick polyethylene sheet having a conductivity of about 10 ⁴ Ωcm was used. As the elastic sheet 21b, a foamed urethane sheet having a thickness of 2 mm was used. As the rigid body 21a, a Zn-coated sheet metal having a thickness of 0.8 mm and R = 12 mm was used.

  As described above, the rigid body 21a is used as the backup member, and the elastic sheet 21b is attached to the rigid body 21a. With this configuration, the contact of the conductive planar toner holding member 21 with the intermediate transfer belt 9 is stabilized. Accordingly, since the electric field between the conductive planar toner holding member 21 and the intermediate transfer belt 9 is stabilized, the temporarily staying toner is also stably formed.

  Furthermore, in this example, a polyethylene sheet having a lower friction coefficient than the foamed urethane sheet was used as the surface layer 21c. Thereby, an increase in driving torque for rotating the intermediate transfer belt due to the rubbing of the conductive planar toner holding member 21 to the intermediate transfer belt 9 can be reduced, and a stable image forming process can be obtained.

  The conductive planar toner holding member 21 having the above-described configuration was pressed at 0.98 N from each end of the member with a total pressure of 1.96 N, and slid against the intermediate transfer belt 9. Further, a DC voltage was applied from the high voltage power source 19 via the electrode 23 to the surface of the polyethylene sheet 21 c on the upstream side in the rotation direction of the intermediate transfer belt 9. The DC voltage from the high voltage power source 19 is configured to be applied with a voltage of −2.0 to +2.0 kV.

  Further, when a U-shaped planar member is used as the conductive planar toner holding member 21 as in the present embodiment, the member tip 21e can be sufficiently separated from the intermediate transfer belt 9, so that the conductive planar toner is The toner can be prevented from adhering to the back surface of the holding member 21.

In the present embodiment, the conductive sheet toner holding member 21 has a structure in which an elastic sheet 21b is bonded to a Zn-coated sheet metal 21a, and a polyethylene sheet 21c is further bonded to the elastic sheet 21b. However, any sheet may be used instead of the polyethylene sheet as long as the range of the resistance value is 10 ¹ to 10 ⁹ Ωcm. For example, PFA or PTFE can be used. Further, the elastic sheet 21b having good slidability may be directly rubbed against the intermediate transfer belt.

  In this embodiment, a Zn-coated sheet metal is used as the backup material 21a. However, since the performance required for the backup material is rigid, it is not necessary to provide conductivity, and a resin or the like can be used.

Example 3
Next, a third embodiment of the image forming apparatus of the present invention will be described. The overall configuration of the image forming apparatus according to the present embodiment is the same as that of the image forming apparatus described in the first embodiment with reference to FIG. 1, and therefore, the description of the first embodiment is used, and the description thereof is not repeated here. Omitted.

  The conductive surface toner holding member 21 has an action of scattering the residual toner substantially in one layer. The conductive planar toner holding member 21 must slidably rub against the intermediate transfer belt 9 because residual toner must be temporarily retained.

  For this reason, the driving torque for rotating the intermediate transfer belt 9 increases as the conductive planar toner holding member 21 slides on the intermediate transfer belt 9.

  Therefore, in the third embodiment, a configuration for reducing an increase in rotational driving torque of the intermediate transfer belt 9 that occurs when the conductive planar toner holding member 21 is rubbed against the intermediate transfer belt 9 will be described.

  In order to reduce the rotational driving torque, the contact area between the conductive planar toner holding member 21 and the intermediate transfer belt 9 may be reduced. In the third embodiment, the surface of the conductive sheet toner holding member used in the first embodiment is configured to have an uneven surface on the surface of the conductive sheet. With this configuration, the contact area between the conductive planar toner holding member 21 and the intermediate transfer belt is reduced to reduce an increase in driving torque, thereby enabling a stable image forming process.

  The shape of the uneven surface can be any shape as long as the contact area with the intermediate transfer belt decreases, for example, a sheet with a diamond pattern convex embossing or a sheet with a silky pattern concave embossing. Can be used.

1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus according to the present invention. It is a figure which shows a mode that a residual toner is disperse | distributed uniformly according to this invention, and is charged uniformly. FIG. 4 is a diagram illustrating a state in which residual toner with insufficient charge that has not been uniformly dispersed passes through a photosensitive drum. FIG. 6 is a diagram illustrating a state in which overcharged residual toner that has not been uniformly dispersed passes through a photosensitive drum. FIG. 4 is a diagram illustrating a state in which residual toner that is uniformly dispersed and uniformly charged passes through a photosensitive drum. FIG. 3 is an enlarged schematic view of portions A and B in FIG. 2, and shows a state in which residual toner is uniformly scattered by a conductive planar toner holding member according to the present invention. FIG. 6 is a diagram illustrating a state in which residual toner is not uniformly dispersed due to an excessive voltage applied to the conductive planar toner holding member. FIG. 6 is a diagram illustrating a state in which residual toner is not uniformly scattered by applying no DC voltage to the conductive planar toner holding member. FIG. 6 is a diagram showing a sheet as a conductive sheet-like toner holding member that is rubbed against an intermediate transfer belt by abdominal contact. FIG. 6 is a diagram in which a member having a ridge line is used as the conductive surface toner holding member, and the ridge line portion is rubbed against the intermediate transfer belt. It is a figure which shows a conductive planar toner holding member structure.

Explanation of symbols

1 Photosensitive drum (image carrier)
2 Charging roller (charging means)
3 Exposure equipment (exposure means)
4 Developing device (Developing means)
9 Intermediate transfer belt (intermediate transfer member)
10 Primary transfer roller (primary transfer means)
11 Secondary transfer roller (secondary transfer means)
12 Secondary Transfer Counter Roller 16 Primary Transfer Power Supply 17 Secondary Transfer Power Supply 19 Conductive Surface Toner Holding Member Power Supply 20 Charging Member Power Supply 21 Conductive Surface Toner Holding Member 22 Conductive Roller (Charging Member)
R1 photosensitive drum rotation direction R3 intermediate transfer belt rotation direction

Claims (7)

An image carrier that carries a toner image; and a movable intermediate transfer member. The toner image on the image carrier is primarily transferred onto the intermediate transfer member at a primary transfer position. In an image forming apparatus for secondary transfer of a toner image on a body to a transfer material at a secondary transfer position,
A planar member that contacts the intermediate transfer member without rotating with respect to the movement of the intermediate transfer member; and a power source that applies a voltage to the planar member;
The planar member is an elastic sheet supported by a rigid body, and the elastic sheet is not secondarily transferred to a transfer material when a voltage having a polarity opposite to a normal polarity of toner is applied from the power source. While the residual toner remaining on the intermediate transfer body is retained and retained on the surface of the elastic sheet upstream of the intermediate transfer body in the moving direction of the intermediate transfer body with respect to the rubbing portion to be formed, Can be scattered on the intermediate transfer member ,
The residual toner not held on the elastic sheet is transferred to the image carrier at the primary transfer position. The image forming apparatus according to claim 1, wherein residual toner not held on the elastic sheet is transferred to the image carrier simultaneously with the primary transfer. Wherein an elastic sheet, using a member having a curvature, the image forming apparatus according to curvature portion to claim 1 or 2, characterized in that rubbing causes on the intermediate transfer body. The image forming apparatus according to any one of claims of claims 1 to 3, characterized in that to have an uneven surface to the elastic sheet. In the direction of movement of the intermediate transfer member, the downstream side of the elastic sheet, and, on the upstream side of the primary transfer position, one of claims 1, characterized in that it comprises a charging member for charging the residual toner 4 The image forming apparatus according to any one of the items. Voltage the power supply is applied to the elastic sheet, the image forming apparatus according to any one of claims 1 to 5, characterized in that the residual toner at the rubbing portion is a voltage enough to dwell. The elastic sheet, by the polarity voltage of the toner normal is applied, any one of claims 1 6, characterized in that moving the residual toner which the elastic sheet is held to the intermediate transfer member The image forming apparatus described in 1.

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