JP4815864B2 - Image forming apparatus - Google Patents

Description

The present invention is a copying machine, a printer, a facsimile, and relates to a picture imaging apparatus using an electrophotographic system having these functions, and in particular an intermediate transfer member, a color toner image on the intermediate transfer member The present invention relates to a color image forming apparatus which is superposed.

  In an electrophotographic color image forming apparatus using an intermediate transfer member, a toner image formed on an image carrier as a photosensitive member is transferred onto the intermediate transfer member, and the toner image on the intermediate transfer member is transferred to a transfer material ( Those which are transferred onto recording paper (also called recording paper or paper) are known. In such a color image forming apparatus, a toner image, which is sequentially formed on an image carrier and charged to a predetermined polarity, is transferred onto an intermediate transfer member by using a primary transfer unit by using electrostatic force, and then the intermediate transfer is performed. The toner image on the body is collectively transferred onto the transfer material by the secondary transfer means using electrostatic force.

  Since the charge amount per toner particle is almost uniform, the potential on the intermediate transfer member is determined by the toner adhesion amount within a predetermined area, and in the color image forming apparatus, a plurality of colors of the toner image on the intermediate transfer member are formed. The charged potential of the portion where the toner is superimposed becomes larger than the charged potential of the portion where only one color toner is attached.

  If the variation in potential on the intermediate transfer member after primary transfer is large, various image defects are likely to occur during secondary transfer. In Patent Documents 1 and 2, the toner image on the intermediate transfer member is AC, It has been proposed to perform uniform secondary transfer by making the charge amount of the toner on the intermediate transfer member uniform by charging by corona discharge such as DC.

  In this proposal, the charge amount of the toner on the intermediate transfer member is made uniform to a large value. However, when the toner layer potential is high, uneven density due to insufficient transfer charge is likely to occur, and when the transfer charge is increased, image disturbance due to discharge is likely to occur. Therefore, the present inventors have made the charge amount uniform by discharging the toner image on the intermediate transfer member before the secondary transfer.

  The toner layer on the intermediate transfer member may vary from one layer to multiple layers. In all cases, the present inventors performed uniform charge removal by scorotron discharge in order to obtain an appropriate charge without excessive charge removal. Is going.

  In the scorotron discharge, a grid to which a voltage is applied with an interval of about 1 mm is disposed with respect to the intermediate transfer member (belt), and discharge is performed from behind by a discharge electrode using a wire or the like. A counter electrode is disposed on the back surface of the intermediate transfer belt on which the grid is disposed.

Is a counter electrode, a grounded roller or the like for winding the intermediate transfer belt, it is excellent in terms of reducing the load of the intermediate transfer belt, when the linear velocity of the intermediate transfer belt is large in a high speed machine In order to obtain a discharge effect, it is necessary to increase the grid width facing the intermediate transfer belt. However, when the counter electrode is a part with a curvature like a roller, there is a limit to increasing the width of the electrode while keeping the distance between the intermediate transfer belt and the grid within a certain range, and the toner charge is controlled. There is a problem that it cannot be done.

  Therefore, a counter electrode that is grounded is disposed opposite to the plane portion of the rotating intermediate transfer belt.

Although Patent Documents 1 and 2 disclose a technique for making the charge amount uniform, there is no description regarding the counter electrode.
JP-A-10-274892 Japanese Patent Laid-Open No. 11-143255

  When the counter electrode is installed facing the planar portion of the rotating intermediate transfer belt, the counter electrode is fixed and the counter electrode rubs the belt surface from the back surface of the intermediate transfer belt. For the counter electrode, a conductive brush or conductive sponge is used. In order to conduct electricity through the counter electrode, it is necessary to apply a certain amount of load and press the back of the belt in order to improve the contact state. is there.

  Conventionally, when the counter electrode is fixed and a brush material is used as the counter electrode, the flexible brush bristles are pressed and bent, and when the sponge material is used as the counter electrode, it is pressed in an elastically deformed state. Has been made. However, when such a pressing means is used, it is fatigued by long-term use, the pressing force gradually decreases, the balance is lost, and the static elimination performance also decreases.

The present invention is pressed against the intermediate transfer belt of the counter electrode, it is maintained for a long term in the same pressing conditions, and an object thereof is to provide a stable image imaging apparatus neutralization performance Ru maintained a.

In order to solve the above-described problems and achieve the object, the present invention is configured as follows.
(Claim 1)
An image carrier;
An image forming unit for forming a toner image on the image carrier;
An intermediate transfer belt stretched by a plurality of rollers;
Primary transfer means for transferring the toner image formed on the image carrier onto the intermediate transfer belt;
Secondary transfer means for transferring the toner image on the intermediate transfer belt to a transfer material;
A neutralization unit disposed opposite to the intermediate transfer belt at a predetermined interval, and neutralizing the toner on the intermediate transfer belt by discharging on the downstream side of the primary transfer unit and upstream of the secondary transfer unit;
An elastic electrode in contact with the back surface of the intermediate transfer belt facing the static eliminating means;
Pressing means for pressing the elastic body electrode against the intermediate transfer belt so that the elastic body electrode uniformly contacts the intermediate transfer belt with respect to the moving direction of the intermediate transfer belt;
I have a,
The pressing means includes a shaft supporting member that pivotally supports the elastic body electrode, and a pressing force that causes the elastic body electrode to contact the intermediate transfer belt by applying a pressing force to the shaft supporting member against the intermediate transfer belt. An image forming apparatus comprising: an imparting unit .
( Claim 2 )
2. The image forming apparatus according to claim 1 , wherein the elastic body electrode has a rigidity closer to a rotation fulcrum of the shaft support member than a rigidity farther from the rotation support point.
(Claim 3 )
The image formation according to claim 2 , wherein the elastic body electrode is a brush member, and the stiffness is set by any one of a difference in brush density, a difference in hair length, and a difference in wire diameter. apparatus.
(Claim 4 )
The image forming apparatus according to claim 2 , wherein the elastic body electrode is a sponge member, and the rigidity is set by a difference in hardness of the foam material.
(Claim 5 )
The image forming apparatus according to any one of claims 1 to 4 , wherein the pressing force applying unit is performed using a weight.
(Claim 6 )
The pressing force applying unit, an image forming apparatus according to any one of claims 1 to 4, characterized in that is carried out using a pressing force of the spring member.

According to the first aspect of the present invention, an elastic electrode is used as the counter electrode of the static elimination unit, and the elastic electrode is uniformly pressed by being applied to the intermediate transfer belt by the pressing unit, pressing state long term over stable, is a good neutralization to maintain good transfer image is obtained that images forming device is to be provided.

According to the invention described in claim 4 , by using a conductive brush material as the elastic body electrode, the contact to the contact portion of the intermediate transfer belt is uniformly applied to the entire surface by the brush bristles, and a good pressing state Will be maintained.

According to the invention of claim 5 , by using a conductive sponge material as the elastic electrode, the pressing to the contact portion of the intermediate transfer belt is uniformly performed on the entire surface by the elastically deformed sponge material. A pressing state will be maintained.

According to the sixth aspect of the present invention, by using the weight as the pressing means, the elastic electrode is kept pressed against the intermediate transfer belt without changing the pressing force at all.

According to the seventh aspect of the invention, the elastic electrode is maintained in a stable pressing state of the intermediate transfer belt for a long time by the pressing force of the spring material from the back by performing the pressing force of the spring material. The Rukoto.

  The present invention will be described below with reference to embodiments, but the present invention is not limited to the embodiments described below.

  FIG. 1 is a sectional view showing a schematic configuration of a color image forming apparatus according to an embodiment of the present invention.

  This color image forming apparatus is called a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 20Y, 20M, 20C, and 20K, an intermediate transfer unit, a sheet feeding and conveying apparatus, and a fixing apparatus 8.

  The image forming unit 20Y that forms a yellow image includes a charging device 2Y, an exposure device 3Y, a developing device 4Y, a primary transfer unit 5Y, and a cleaning unit 6Y disposed around a photoreceptor 1Y as an image carrier. The image forming unit 20M that forms a magenta image includes a charging device 2M, an exposure device 3M, a developing device 4M, a primary transfer unit 5M, and a cleaning unit 6M arranged around a photoconductor 1M as an image carrier. The image forming unit 20C that forms a cyan image includes a charging device 2C, an exposure device 3C, a developing device 4C, a primary transfer unit 5C, and a cleaning unit 6C, which are arranged around a photoconductor 1C as an image carrier. The image forming unit 20K that forms a black image includes a charging device 2K, an exposure device 3K, a developing device 4K, a primary transfer unit 5K, and a cleaning unit 6K arranged around a photoconductor 1K as an image carrier.

  The semi-conductive and belt-shaped intermediate transfer body 7 is wound around a plurality of rollers 701a, 701b, 701c, 701d, 71, etc., and is supported so as to be able to circulate. In the present embodiment, the intermediate transfer member 7 is supported between the primary transfer unit 5K and the roller 71 in a planar shape.

  The image forming means including the charging device 2Y, the exposure device 3Y, and the developing device 4Y charges, exposes, and develops the photoconductor 1Y, thereby forming a yellow toner image on the photoconductor. Similarly, a magenta toner image is formed on the photosensitive member 1M by the image forming unit including the charging device 2M, the exposure device 3M, and the developing device 4M, and the image forming unit including the charging device 2C, the exposure device 3C, and the developing device 4C. A cyan toner image is formed on the photoreceptor 1C, and a black toner image is formed on the photoreceptor 1K by image forming means including the charging device 2K, the exposure device 3K, and the developing device 4K. These single color toner images are transferred to the intermediate transfer body 7 by the transfer rollers 5YR, 5MR, 5CR, and 5KR, and are superimposed to form a multicolor toner image.

  As the photosensitive member 1, a well-known one such as an OPC photosensitive member or an aSi photosensitive member is used. An OPC photosensitive member is preferable, and a negatively charging OPC photosensitive member is particularly preferable. OPC is used.

  As the charging device 2, a corona discharge device such as a scorotron or a corotron is used, and a scorotron discharge device is preferably used.

  As the exposure apparatus, a light emitting element that emits light according to image data, such as a laser or an LED array, is used.

  As the developing device 4, a developing device using a two-component developer mainly composed of a carrier and toner or a developing device using a one-component developer mainly containing a toner without including a carrier is used. A component developing device is preferred. In addition, a developing device that performs normal development or a reversal development can be used in the developing device. However, a developing bias having the same polarity as the charging of the photosensitive member 1 is applied to the developing sleeve 4a, and the charging of the photosensitive member is the same. Reversal development in which development is performed with toner charged to polarity is preferable. In this embodiment, development is performed by reversal development using negatively charged toner.

  From the viewpoint of maintaining high image quality and preventing the occurrence of fogging, the toner preferably has a volume average particle diameter of 3 to 6 μm.

  The volume average particle diameter is an average particle diameter based on volume, and is a value measured by “Coulter Counter TA-II” or “Coulter Multisizer” (both manufactured by Coulter, Inc.) equipped with a wet disperser.

  With such a toner, a high-quality image having high resolution can be formed.

  Further, in the present invention, spherical toner is desirable, and the degree of spheroidization is 0.94 or more and 0.98 or less that does not receive strong stress in the developing device, hardly causes fogging or toner scattering, and can maintain high cleaning performance. Is preferred.

  The degree of spheroidization is obtained by the following formula.

Degree of spheroidization = (perimeter of a circle with the same area as the particle projection image) / (perimeter of the particle projection image)
The degree of spheroidization was obtained by taking a picture of resin particles enlarged 500 times with a scanning electron microscope or a laser microscope for 500 resin particles, and using an image analyzer “SCANNING IMAGE ANALYSER” (manufactured by JEOL Ltd.) Then, the photographic image is analyzed, the circularity is measured, and the arithmetic average value can be obtained. Moreover, as a simple measuring method, it can measure with "FPIA-1000" (made by Toa Medical Electronics Co., Ltd.).

  For the toner having a small particle diameter and a high sphericity as described above, it is desirable to use a polymerized toner.

  The polymerized toner means a toner obtained by forming a binder resin for toner and forming the toner shape by polymerization of a raw material monomer or prepolymer of the binder resin and subsequent chemical treatment. More specifically, it means a toner obtained through a polymerization reaction such as suspension polymerization or emulsion polymerization and, if necessary, a step of fusing particles between them. In a polymerized toner, a raw material monomer or prepolymer is uniformly dispersed in an aqueous system and then polymerized to produce a toner, so that a toner having a uniform toner particle size distribution and shape can be obtained.

  Specifically, a polymer is produced by emulsion polymerization of a monomer in a liquid of an aqueous medium to which an emulsion is added or a suspension polymerization method, and then an organic solvent, agglomeration is produced. It can manufacture by the method of adding an agent etc. and making it associate. A method of preparing by mixing with a dispersion liquid of a release agent or a colorant necessary for the constitution of the toner at the time of association, or a toner component such as a release agent or a colorant dispersed in a monomer Examples thereof include emulsion polymerization. Here, the association means that a plurality of resin particles and colorant particles are fused.

  Reference numeral 5A denotes secondary transfer means, which includes a transfer roller 5AR composed of a conductive rubber roller and a power source 5AE.

  6A is an intermediate transfer member cleaning means for cleaning the intermediate transfer member 7, and 8 is a fixing device for fixing the toner image on the transfer material P.

The intermediate transfer member 7 is a single layer or multilayer belt having a belt width of 320 mm made of polyamide or polyimide, and has a volume resistivity of 10 ⁷ to 10 ¹² Ωcm, 10 ⁹ Ωcm in this embodiment, and a surface resistance of 10 ¹¹ Ω. Things are used.

  On the other hand, after the secondary transfer to the transfer material P by the transfer roller 5A, the intermediate transfer body 7 passes through the intermediate transfer body cleaning means 6A and is cleaned.

  In the present embodiment, a scorotron that is a secondary pre-transfer neutralizing unit is disposed between the primary transfer unit 5K and the secondary transfer unit 5A along the intermediate transfer unit 7 at a position where the intermediate transfer unit is supported in a planar shape. A static eliminator 9 is provided. Details of the scorotron static eliminator 9 will be described with reference to FIG.

  FIG. 2 is a cross-sectional view showing a schematic configuration of the scorotron static eliminator 9 of FIG. The scorotron static eliminator 9 is composed of a discharge electrode 91, a grid 92, and a side plate 93. The grid 92 is opposed to the belt surface of the intermediate transfer member 7 with an interval of 1 mm in this embodiment, and the side plate 93 is a circuit not shown. Is connected to the same potential as the grid 92.

  As the grid 92, a wire grid, a plate-like grid patterned on a sheet metal by etching or the like can be used, and in this embodiment, a plate-like grid subjected to gold plating is adopted. Further, the grid 92 has a width of 30 mm in this embodiment in the moving direction of the intermediate transfer body 7 (in the direction indicated by the arrow X).

  The discharge electrode 91 may be made of a wire material such as tungsten, stainless steel, or gold having a diameter of 20 to 150 μm, but the surface is particularly preferably formed of gold. The wire itself may be made of gold, or the surface of a base material such as stainless steel or tungsten may be coated with gold. The thickness of the gold coating is preferably 1 μm to 5 μm in terms of average film thickness from the viewpoints of removal efficiency of discharge products such as ozone, manufacturing cost, and discharge efficiency.

  Further, the discharge electrode 91 may be a needle-like electrode in addition to an electrode using a wire.

  On the back side of the intermediate transfer member facing the scorotron static eliminator 9 is disposed a counter electrode 12 composed of a conductive brush 12a as an elastic electrode and a support member 12b for supporting the conductive brush 12a. The conductive brush 12a The pressing means described later contacts the back side of the intermediate transfer member, and the counter electrode 12 is grounded via a resistor 12c.

The conductive brush 12a is made of conductive resin material such as acrylic, nylon, polyester, etc., and the wire diameter is 0.111 tex to 0.778 tex (unit of measurement) according to the numbering method proposed by ISO. Is 0.33 tex), the brush density is 12000 / cm ^{2 to} 77000 / cm ² (31000 / cm ^{2 in} this embodiment), and the yarn resistance is 10 ^{0 to} 10 ⁵ Ωcm (in this embodiment). 10 ² Ωcm).

The same effect can be obtained by using a conductive sponge as the counter electrode 12 instead of the conductive brush. For the conductive sponge, urethane rubber such as ether polyurethane mixed with carbon black, ethylene / propylene rubber, hydrin rubber, silicon rubber, etc. can be used, and the volume resistivity is 10 ³ to 10 ⁹ Ω · cm. For example, a thickness of 5 mm is used.

  In the present embodiment, the discharge electrode 91 can be applied with a DC bias voltage of 0 to +5 kV that discharges with a polarity opposite to that of the toner, and the grid 92 can be applied with a voltage of 0 to −300 V. Yes.

  In this embodiment, a voltage of +4 kV is applied to the discharge electrode 91 of the scorotron static eliminator 9, and a voltage of −50 V is applied to the grid 92.

  The operation of the scorotron static eliminator 9 will be described.

  FIG. 2 is a schematic diagram showing changes in the toner layer potential on the intermediate transfer body 7 before and after passing through the scorotron static eliminator 9 to which a voltage is applied. In addition, the same code | symbol is attached | subjected to the structure same as what was shown in FIG. 1, and description is abbreviate | omitted.

  The potential V1 of the full color portion F1 having a high toner adhesion amount potential decreases to V3 by passing through the static eliminator 9, but the potential V2 of the halftone portion H1 having a low toner adhesion amount potential is maintained as it is.

  FIG. 2 also shows that the first embodiment uses a heavy iron as a pressing means for pressing the conductive brush 12a, which is an elastic electrode of the counter electrode 12, against the back surface of the intermediate transfer body 7. FIG. 3 shows the state in a perspective view.

  The support member 12b that supports the conductive brush 12a has a rotation fulcrum 12c at both end portions thereof, and the conductive brush 12a is moved by a torque load of a heavy rod 12d provided on the support member 12b with the rotation fulcrum 12c as a rotation center. The back surface of the intermediate transfer body 7 is pressed.

  With this configuration, the entire pressing force of the conductive brush 12a is determined by the torque load of the heavy rod 12d and is extremely stable. However, within the contact range of the conductive brush 12a, the side closer to the rotation fulcrum 12c Since a difference arises with a far side, it is preferable to set it as the flexible member whose rigidity on the near side from the rotation fulcrum 12c is larger than that on the far side. Here, the difference in rigidity is caused by any one of a difference in brush density, a difference in hair length, and a difference in wire diameter. When the elastic electrode is a sponge material, the difference in rigidity is determined by the difference in hardness of the foam material.

  The attachment position of the weight 12d to the support member 12b is determined by the position of the counter electrode 12 facing the belt-shaped intermediate transfer body 7. FIG. 2 shows the intermediate transfer that is stretched and moved in the vertical direction. The attachment position of the heavy rod 12d pressed against the body 7 is shown.

  In the color image forming measure shown in FIG. 4, the image forming portions 20Y, 20M, 20C, and 20K are arranged in parallel below the belt with respect to the intermediate transfer member 7 that rotates in the direction indicated by the arrow with a flat portion in the left-right direction. , M, C, and K toner images are formed on the intermediate transfer member 7 so that the formed toner images are neutralized by the scorotron static eliminator 9, and then secondary transfer is performed after static elimination. ing.

  Therefore, since the counter electrode 12 of this embodiment is disposed so as to face the upper surface side of the belt and contact from the upper side, the pressing force to the belt by the conductive brush 12a is the same as the weight of the conductive brush 12a. It is determined by the weight 12d provided so as to be added thereto.

  The color image forming apparatus shown in FIG. 5 has image forming portions 20Y, 20M, 20C, and 20K arranged in parallel on the upper surface of the belt with respect to the intermediate transfer body 7 that rotates in the direction of the arrow with a flat portion in the left-right direction. A structure in which toner images of four colors Y, M, C, and K are formed on the intermediate transfer member 7 so that the formed toner image is neutralized by a scorotron neutralizer 9 and then secondary transfer is performed after neutralization. It has become.

  Therefore, since the counter electrode 12 of this embodiment is disposed so as to face the lower surface side of the belt and contact from the lower side to the upper side, the conductive material of the support member 12b provided with the rotation fulcrum 12c interposed therebetween. By providing the heavy rod 12d on the opposite side of the conductive brush 12a, the pressing force to the belt of the conductive brush 12a is generated by the torque load of the heavy rod 12d.

  FIG. 6 is a cross-sectional view showing an embodiment in which a spring material is used as means for pressing the conductive brush 12a, which is an elastic electrode, to the intermediate transfer body 7.

  In this embodiment, the pressing of the conductive brush 12a against the intermediate transfer member 7 by the plurality of compression springs 12f from the back of the support member 12b to which the conductive brush 12a is attached seems to be uniform over the entire contact range. The guide member 12g is a member that regulates the position so that the conductive brush 12a pressed by the compression spring 12f does not move or vibrate as the belt moves in the traveling direction. The unit 100 is fixed. With this configuration, a stable static elimination state is maintained over a long period of time.

  FIG. 7 is a cross-sectional view showing an embodiment in which pressing is performed using the elasticity of the support member 12b that supports the conductive brush 12a as a pressing means to the intermediate transfer body 7 of the conductive brush 12a that is an elastic electrode. .

  For example, a thin metal plate such as SUS material is used as the support member 12b, the conductive brush 12a is attached to one end of the thin metal plate, and the other end of the thin metal plate is attached to the main body mounting portion 100 in a shape that stores the elastic force by bending. Thus, the conductive brush 12a presses the intermediate transfer body 7 that is moved by the elasticity of the support member 12b. Since the conductive brush 12a may vibrate as the belt moves, it is also effective to apply a cloth or the like as a vibration absorbing material on one surface of the support member 12b. Thus, a stable static elimination state is maintained.

  The present inventors have conducted the following tests in order to confirm the effects of the present invention.

  As an example, a test was performed under the condition in which the back surface of the intermediate transfer body 7 was brought into contact with the conductive brush 12a described with reference to FIGS. On the other hand, as a comparative example, the conductive brush 12a was fixed and rubbed against the back surface of the intermediate transfer body 7 with a bending amount of brush hair of 1.5 mm.

  On the intermediate transfer member 7, a solid image in which magenta and cyan are superimposed is formed, and the potential after neutralization by the scorotron static eliminator 9 is applied to the both end positions and the center in the brush longitudinal direction where the conductive brush 12a abuts. The position was measured by the potential sensor 11.

  In the test, the potential of both was measured in a new state at the beginning of the setting and in a state after leaving the conductive brush 12a in contact with the conductive brush 12a for one month in an environment of 10 ° C. and RH 20%. The table below shows the test results.

  The toner layer potential before static elimination at the time of the test was about −170 V, and when the potential after static elimination was −140 V (absolute value) or less, a good transfer image was obtained. Was found to cause uneven transfer. In the comparative example, it was found that good transfer images could not be obtained at both ends after the brush durability, whereas in the examples, good transfer images could be obtained through the durability.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to the present invention (Example 1). FIG. 4 is a cross-sectional view showing a schematic configuration of a scorotron static eliminator and a counter electrode according to the present invention, and a schematic diagram showing a change in toner layer potential before and after passing through the scorotron static eliminator. It is a perspective view which used a heavy iron as a pressing means of a counter electrode. It is sectional drawing which shows the other structure of a color image forming apparatus. It is sectional drawing which shows the other structure of a color image forming apparatus. It is sectional drawing of the Example which used the spring material as a pressing means of a counter electrode. It is sectional drawing of the Example which used the elasticity of the supporting member as a pressing means of a counter electrode.

Explanation of symbols

1Y, 1M, 1C, 1K Photoconductor 5A Secondary transfer means 7 Intermediate transfer body 9 Scorotron static eliminator 11 Surface potential meter 91 Discharge electrode 92 Grid 12 Counter electrode 12a Conductive brush 12b Support member 12c Rotation fulcrum 12d Weight 12e 12f compression spring

Claims (6)

An image carrier;
An image forming unit for forming a toner image on the image carrier;
An intermediate transfer belt stretched by a plurality of rollers;
Primary transfer means for transferring the toner image formed on the image carrier onto the intermediate transfer belt;
Secondary transfer means for transferring the toner image on the intermediate transfer belt to a transfer material;
A neutralization unit disposed opposite to the intermediate transfer belt at a predetermined interval, and neutralizing the toner on the intermediate transfer belt by discharging on the downstream side of the primary transfer unit and upstream of the secondary transfer unit;
An elastic electrode in contact with the back surface of the intermediate transfer belt facing the static eliminating means;
Pressing means for pressing the elastic body electrode against the intermediate transfer belt so that the elastic body electrode uniformly contacts the intermediate transfer belt with respect to the moving direction of the intermediate transfer belt;
I have a,
The pressing means includes a shaft supporting member that pivotally supports the elastic body electrode, and a pressing force that causes the elastic body electrode to contact the intermediate transfer belt by applying a pressing force to the shaft supporting member against the intermediate transfer belt. An image forming apparatus comprising: an imparting unit . 2. The image forming apparatus according to claim 1 , wherein the elastic body electrode has a rigidity closer to a rotation fulcrum of the shaft support member than a rigidity farther from the rotation support point. The image formation according to claim 2 , wherein the elastic body electrode is a brush member, and the stiffness is set by any one of a difference in brush density, a difference in hair length, and a difference in wire diameter. apparatus. The image forming apparatus according to claim 2 , wherein the elastic body electrode is a sponge member, and the rigidity is set by a difference in hardness of the foam material. The image forming apparatus according to any one of claims 1 to 4 , wherein the pressing force applying unit is performed using a weight. The pressing force applying unit, an image forming apparatus according to any one of claims 1 to 4, characterized in that is carried out using a pressing force of the spring member.

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