JP2019008139A - Image forming apparatus - Google Patents

Abstract

To prevent the occurrence of scratches on a belt and paper powder filming to form a high-quality image.SOLUTION: An image forming apparatus 100 transfers, to a sheet P, a toner image formed on an intermediate transfer belt 17 having an elastic layer on its surface to form an image, and comprises: cleaning means 21 that is in contact with the intermediate transfer belt 17 after transfer of the toner image to the sheet P to remove an attachment attached to the surface of the intermediate transfer belt 17; and a brush member 22 that is provided upstream of the cleaning means 21 in a revolving direction of the intermediate transfer belt 17, and in contact with the intermediate transfer belt 17 after transfer of the toner image to the sheet P before the cleaning means 21 to clean the surface of the intermediate transfer belt 17. The brush member 22 is a loop brush in which brush fibers are provided in a loop shape.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus.

2. Description of the Related Art Conventionally, there is known an image forming apparatus that forms a toner image on a photosensitive member, transfers the toner image to an intermediate transfer belt, and transfers the toner image on the intermediate transfer belt onto a sheet.
In addition, as an intermediate transfer belt, an intermediate transfer belt having an elastic layer made of a rubber material or the like on a base material layer of a resin material can be used to improve the adhesion to the paper by utilizing the elasticity of the belt. It is known that efficiency can be improved.

In such an image forming apparatus, in order to adjust the image density, it is widely performed that an image density is optically detected by an IDC (Image Density Control) sensor on the intermediate transfer belt.
Image density detection uses the difference between the reflectance of the belt surface and the reflectance of the toner image, so scratches and filming (attachment of paper dust etc.) occur on the belt surface, and the reflectance of the belt surface is reduced. If unevenness occurs, it may lead to erroneous detection of image density. In particular, if there are streaks or density steps in the sub-scanning direction (FD direction), it may lead to erroneous detection of toner density when the belt meanders during detection.

  However, since the intermediate transfer belt provided with the elastic layer has a characteristic that the surface is soft and easily scratched, and foreign matters such as paper dust are likely to adhere to the intermediate transfer belt. An IDC sensor is likely to be erroneously detected due to filming, and image processing such as gradation correction is performed based on the detection result, which may cause an image defect such that a desired color tone cannot be obtained. .

  Therefore, in the image forming apparatus, a configuration is known in which a cleaning brush is provided on the downstream side in the circumferential direction of the intermediate transfer belt provided with the elastic layer so as to contact the intermediate transfer belt with respect to the transfer position to the sheet. (For example, refer to Patent Document 1).

JP 2004-198593 A

However, the above-mentioned patent document 1 is a technique for suppressing the occurrence of abnormal images by selecting an intermediate transfer belt having a property that the transfer material additive is difficult to be fixed, and does not consider the cleaning performance of the cleaning brush.
For this reason, depending on the performance of the cleaning brush and the installation conditions of the brush, belt scratches and paper dust filming may occur, resulting in image defects.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of suppressing generation of belt scratches and paper dust filming and forming a high-quality image. .

In order to solve the above problems, according to the present invention,
An image forming apparatus for forming an image by transferring a toner image formed on an intermediate transfer member having an elastic layer on a surface onto a sheet,
Cleaning means for cleaning a deposit adhered to the surface of the intermediate transfer member in contact with the intermediate transfer member after the toner image is transferred to a sheet;
Provided upstream of the cleaning means in the circumferential direction of the intermediate transfer body, and before the cleaning means, contact the intermediate transfer body after the toner image is transferred to a sheet to contact the surface of the intermediate transfer body. A brush member to be cleaned;
With
The brush member is a loop brush in which brush fibers are provided in a loop shape.

  According to the present invention, it is possible to suppress the occurrence of belt scratches and paper dust filming and to form a high-quality image.

1 is a schematic configuration diagram of an image forming apparatus in an embodiment of the present invention. 3 is a functional block diagram illustrating a control configuration of the image forming apparatus. FIG. It is a figure which shows the structure of the belt cleaning part in 1st Embodiment. It is an expansion schematic diagram of a brush member. It is a graph which shows the generation | occurrence | production situation of the belt damage | wound of a straight hair brush and a loop brush. It is a graph which shows the generation | occurrence | production situation of the paper dust filming of a straight hair brush and a loop brush. It is a figure which shows the structure of the belt cleaning part in 2nd Embodiment. It is a graph which shows the recoverability of the external additive of a straight hair brush and a loop brush. It is a graph which shows the discharge property of the external additive of a straight hair brush and a loop brush. It is a figure which shows the structure of the belt cleaning part in 3rd Embodiment. It is a graph which shows an example of the control pattern of the rotation speed of a brush. It is a graph which shows an example of the control pattern of the bias applied to a brush.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

<First Embodiment>
[Configuration of Image Forming Apparatus]
First, the configuration of the image forming apparatus according to the first embodiment will be described.
The image forming apparatus 100 in the present embodiment is a so-called tandem color printer.

FIG. 1 is a schematic configuration diagram of the image forming apparatus 100. FIG. 2 is a block diagram illustrating a functional configuration of the image forming apparatus 100.
1 and 2, the image forming apparatus 100 includes an image forming unit 10, a sensor S, a belt cleaning unit 20, a paper feeding unit 30, a control unit 41, an operation unit 42, a display unit 43, a storage unit 44, and a communication. The unit 45 includes a unit 45 and the like, and each unit is connected by a bus.

  The image forming unit 10 includes photosensitive drums 11Y, 11M, 11C, and 11K corresponding to yellow (Y), magenta (M), cyan (C), and black (K) colors, and charging units 12Y, 12M, 12C, and 12K. , Exposure units 13Y, 13M, 13C, 13K, developing units 14Y, 14M, 14C, 14K, primary transfer rollers 15Y, 15M, 15C, 15K, photoconductor cleaning units 16Y, 16M, 16C, 16K, and an intermediate transfer member An intermediate transfer belt 17, a secondary transfer roller 18, and a fixing unit 19 are provided.

The charging units 12Y, 12M, 12C, and 12K uniformly charge the photosensitive drums 11Y, 11M, 11C, and 11K.
The exposure units 13Y, 13M, 13C, and 13K are composed of laser light sources, polygon mirrors, lenses, and the like, and scan and expose the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11K with laser beams based on the image data of each color. An electrostatic latent image is formed.
The developing units 14Y, 14M, 14C, and 14K cause each color toner to adhere to the electrostatic latent images on the photosensitive drums 11Y, 11M, 11C, and 11K and perform development.

The primary transfer rollers 15Y, 15M, 15C, and 15K sequentially transfer the toner images of the respective colors formed on the photosensitive drums 11Y, 11M, 11C, and 11K onto the intermediate transfer belt 17 (primary transfer). That is, a color toner image is formed on the intermediate transfer belt 17 by superimposing four color toner images.
The photoconductor cleaning units 16Y, 16M, 16C, and 16K remove the toner remaining on the peripheral surfaces of the photoconductor drums 11Y, 11M, 11C, and 11K after the transfer.

  The intermediate transfer belt 17 is an endless belt member having conductivity, is stretched by a plurality of rollers (a driving roller, a tension roller, a driven roller), and is driven in a direction indicated by an arrow A in FIG. Details of the configuration of the intermediate transfer belt 17 will be described later.

  The secondary transfer roller 18 collectively transfers the color toner image formed on the intermediate transfer belt 17 onto one surface of the paper P supplied from the paper supply unit 30 (secondary transfer).

  The fixing unit 19 fixes the toner transferred on the paper P onto the paper P by heating and pressing.

For example, an optical sensor such as an IDC (Image Density Control) sensor is used as the sensor S, and is installed downstream of the secondary transfer position in the circumferential direction of the intermediate transfer belt 17.
The sensor S is arranged as a detection means so as to face the belt surface in order to detect the surface of the intermediate transfer belt 17 and optically detects the amount of toner on the intermediate transfer belt 17.
Then, a toner patch is formed on the surface of the belt by the image forming unit 10 during non-image formation under the control of the control unit 41 as a correction unit, and the image forming unit 10 determines whether the toner patch is detected by the sensor S. The imaging conditions are corrected periodically. As a result, for example, when a change in density occurs in the formed image due to a change in temperature or humidity with time or replacement of parts, this is corrected, and the image density can be stabilized.

  The belt cleaning unit 20 removes residual toner, paper dust, and other deposits that are not transferred to the paper P from the intermediate transfer belt 17 after the color toner image is transferred to the paper P by the secondary transfer roller 18. Then, the intermediate transfer belt 17 is cleaned. Details of the configuration of the belt cleaning unit 20 will be described later.

  The paper feed unit 30 is provided in the lower part of the image forming apparatus 100 and includes a detachable paper feed cassette 31. The paper P stored in the paper feed cassette 31 is sent out from the uppermost one by one to the transport path by the paper feed roller 32.

  The control unit 41 is configured by a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and comprehensively controls the processing operation of each unit of the image forming apparatus 100. The CPU reads various processing programs stored in the ROM, expands them in the RAM, and executes various processes according to the expanded programs.

  The operation unit 42 includes a touch panel formed to cover the display screen of the display unit 43 and various operation buttons such as numeric buttons and a start button, and outputs an operation signal based on a user operation to the control unit 41.

  The display unit 43 is configured by an LCD (Liquid Crystal Display), and displays various screens according to instructions of display signals input from the control unit 41.

  The storage unit 44 includes a storage device such as a nonvolatile semiconductor memory or a hard disk, and stores data related to various processes.

  The communication unit 45 transmits / receives data to / from an external device connected to a network such as a LAN (Local Area Network).

[Configuration of intermediate transfer belt]
Next, the configuration of the intermediate transfer belt 17 will be described.
The intermediate transfer belt 17 is an elastic intermediate transfer belt including at least one elastic layer.
Specifically, the intermediate transfer belt 17 is made of, for example, an acrylonitrile / butadiene copolymer rubber (NBR) or chloroprene rubber on a base material layer made of a resin such as polyimide (PI) or polyphenylene sulfide (PPS). An elastic belt formed with an elastic layer made of rubber such as (CR) can be used.
At this time, in order to improve the transportability of the intermediate transfer belt 17 and the workability at the time of replacement, the base layer has a thickness of about 50 to 100 μm and the transferability to the paper P having an uneven surface such as embossed paper is improved. The thickness of the elastic layer is preferably about 100 to 500 μm.
In order to reduce tackiness, it is also preferable to provide a surface layer having a higher hardness than the elastic layer on the surface of the elastic layer. For example, an oxidation treatment layer of about 2 to 20 μm is provided on the surface of the elastic layer, or 2 to 20 μm. It is also preferable to provide a coating layer such as a fluororesin.
The intermediate transfer belt 17 only needs to have a desired transfer property, and the material and thickness are not limited to those described above.

The surface hardness (surface hardness of the elastic layer or surface layer) of the intermediate transfer belt 17 is preferably set to 400 MPa or less in the measurement of the surface layer hardness by the nanoindentation method.
This is because if it exceeds 400 MPa, it becomes strong against filming of paper dust and scratches on the belt surface, but the unevenness of the paper P cannot be secured and the effect of the elastic layer is lost.
The nanoindentation method refers to the test force (force applied to the indenter) and the indentation depth (displacement amount of the indenter) in the process of forming a dent by pushing an indenter loaded with a predetermined load onto the surface of the sample. ) Is measured continuously, and the obtained indentation curve is analyzed to determine the mechanical properties of the material.

[Configuration of belt cleaning section]
Next, the configuration of the belt cleaning unit 20 will be described.
FIG. 3 is a schematic configuration diagram of the belt cleaning unit 20.
Each part of the belt cleaning unit 20 is elongated along the width direction intersecting the circumferential direction of the intermediate transfer belt 17.

As shown in FIG. 3, the belt cleaning unit 20 includes a casing CA, and includes, for example, a cleaning unit 21, a brush member 22, a flicker member 23, and the like.
A blade facing roller 24 is provided at a position facing the casing CA (cleaning means 21) via the intermediate transfer belt 17.
A brush facing roller 25 is provided at a position facing the brush member 22 via the intermediate transfer belt 17.

  The cleaning means 21 includes, for example, a rubber blade 21a, a blade holding member 21b, and an urging spring 21c.

  The rubber blade 21a is a rubber plate, and the tip of the rubber blade 21a is brought into contact with the rotating intermediate transfer belt 17 to scrape and remove the adhering matter attached to the intermediate transfer belt 17. It is. The rubber blade 21a is held rotatably about the rotation fulcrum G by a blade holding member 21b.

  The blade holding member 21b is configured to hold the rubber blade 21a at one end thereof and to be rotatable about the rotation fulcrum G. An urging spring 21c is engaged with the other end of the blade holding member 21b, and a pressure contact force (contact pressure) of the rubber blade 21a against the intermediate transfer belt 17 is obtained by the force of the spring. ing.

The urging spring 21c is, for example, a tension coil spring. The urging spring 21c gives a force for rotating the blade holding member 21b and the rubber blade 21a counterclockwise, and the rubber blade 21a contacts the intermediate transfer belt 17 with constant pressure. Will be.
By adopting such a constant pressure contact method (spring load method), the contact pressure can be properly maintained regardless of the environment. In addition to the tension coil spring, a compression coil spring or the like may be used as long as the constant pressure welding method can be realized.

The brush member 22 is provided in contact with the intermediate transfer belt 17 on the upstream side of the rubber blade 21 a in the circumferential direction of the intermediate transfer belt 17.
The brush member 22 is a brush body that rotates in a counter direction with respect to the circumferential direction of the intermediate transfer belt 17, removes paper dust adhering to the intermediate transfer belt 17, and rubber when the paper dust passes through the rubber blade 21 a. It plays a role of avoiding being buried in the intermediate transfer belt 17 by the contact pressure of the blade 21a. In other words, the brush member 22 is for removing paper dust entering the rubber blade 21a on the intermediate transfer belt 17 and reducing paper dust filming on the rubber blade 21a.
Further, the brush member 22 also plays a role of collecting a part of the residual toner adhered on the intermediate transfer belt 17 and a part of the external additive detached therefrom.

FIG. 4 is an enlarged schematic view showing a part of the brush member 22.
As shown in FIG. 4, as the brush member 22, a loop bra in which both ends of a pile (fiber) of the brush are fixed to a base material to form a loop is used.
Examples of the material for the pile of the brush member 22 include polyester, acrylic, and nylon materials.
Moreover, as the fineness of the pile of the brush member 22, a thing of 2-10d (denier) is used preferably, for example. If the fineness is lower than 2d, the frictional force between the intermediate transfer belt 17 is too low and the recoverability is insufficient. If the fineness is higher than 10d, the frictional force with the intermediate transfer belt 17 becomes too high, leading to a torque increase.
Moreover, as a density of the pile of the brush member 22, a thing of 80-200 kF / inch ² is used preferably, for example. When the density is lower than 80 kF / inch ^2, the frictional force between the intermediate transfer belt 17 is too low and the recoverability is insufficient. If the density is higher than 200 kF / inch ^2, the frictional force between the intermediate transfer belt 17 becomes too high, leading to a torque increase.
Moreover, the pile length of the brush member 22 can use a thing about 2-5 mm, for example. Further, the pushing amount of the brush member 22 to the intermediate transfer belt 17 is preferably about 0.1 to 3 mm, for example, though it depends on the pile length.

Returning to FIG. 3, the flicker member 23 is provided at a position where it can contact the brush member 22, rotates in the counter direction with respect to the rotation direction of the brush member 22, and the paper collected by the brush member 22 from the intermediate transfer belt 17. This is for separating the collected material such as powder, toner, and external additive from the brush member 22 so that the amount of collected material on the surface of the brush member 22 is always kept below a certain reference value.
As the flicker member 23, for example, a roller whose surface is made hard by plating the surface of an aluminum roller can be used. However, as long as it has a predetermined flickering function, the material and physical properties of the flicker member 23 The setting is not particularly limited.
In addition, a scraper 23 a is in contact with the flicker member 23, and the collected material collected from the brush member 22 is sequentially scraped to keep the collected material not attached to the surface of the flicker member 23.

  Further, a screw (not shown) is provided in the vicinity of the bottom of the casing CA to discharge the removed matter removed from the intermediate transfer belt 17 by the rubber blade 21a and the brush member 22 to the outside of the casing CA.

The blade facing roller 24 is disposed at a position facing the cleaning unit 21 via the intermediate transfer belt 17.
The blade facing roller 24 is preferably arranged slightly shifted from the tip of the rubber blade 21a at a position about 1 mm downstream in the circumferential direction of the intermediate transfer belt 17.
With this arrangement, the rubber blade 21a is lifted by the minute unevenness of the blade facing roller 24 or the minute unevenness of the intermediate transfer belt 17, and a so-called staple-like slip-through occurs in which the left and right of the minute unevenness part slips. Can be suppressed.

  The brush facing roller 25 is disposed at a position facing the brush member 22 with the intermediate transfer belt 17 interposed therebetween, and maintains the deposit removal function of the brush member 22 well.

[Operation of belt cleaning section]
Next, the operation of the belt cleaning unit 20 in the present embodiment will be described.

In the belt cleaning unit 20 of the present embodiment, first, the brush member 22 rotates counter to the intermediate transfer belt 17 to remove deposits such as paper powder and residual toner on the intermediate transfer belt 17. Next, deposits on the intermediate transfer belt 17 are scraped off and removed by the rubber blade 21a.
Thus, the deposits on the intermediate transfer belt 17 are removed by the brush member 22 and the rubber blade 21a.

Here, in this embodiment, a loop brush is used as the brush member 22. Thereby, compared with the case where a general straight hair brush is used, generation | occurrence | production of a belt damage and paper dust filming can be suppressed. Therefore, since unevenness in the reflectance of the belt surface is unlikely to occur, erroneous detection of image density by the sensor S is unlikely to occur, and a high-quality image can be formed.
Hereinafter, differences in the occurrence of belt scratches and paper dust filming between a general straight hair brush and a loop brush will be described.
In addition, the straight hair brush and the loop brush used for comparison in the following description have the same material, fineness, and density.

FIG. 5 is a graph showing the occurrence of belt scratches on each of the straight hair brush and the loop brush. In FIG. 5, the degree of belt damage by the brush when the frictional force between the belt and the brush is changed is evaluated by the difference in glossiness. The alternate long and short dash line indicates a level at which the belt scratch is considered not to affect the sensor output (gloss difference 2.5 degrees).
The glossiness difference is the glossiness difference between the 0% portion and the 100% portion of the belt surface after 20 sheets of images are formed. Also, coated paper that does not generate paper dust was used, and the gloss difference due to scratches was evaluated by removing the influence of paper dust filming.

FIG. 6 is a graph showing the occurrence of paper dust filming in each of the straight brush and the loop brush. In FIG. 6, the degree of paper dust filming when the frictional force between the belt and the brush is changed is evaluated by the difference in glossiness. The alternate long and short dash line indicates a level at which paper dust filming is considered not to affect the sensor output (gloss difference 2.5 degrees).
The difference in glossiness is the difference in glossiness between the 0% portion and the 100% portion of the belt surface after three images are formed. Further, using high-quality paper that easily generates paper dust, the gloss difference due to paper dust filming was evaluated at the time of forming a three-sheet image with little influence of a belt scratch by a brush.

As shown in FIG. 5, the belt damage due to the brush is more likely to occur as the frictional force between the belt and the brush becomes higher. Therefore, from the viewpoint of belt scratches, it is desirable to bring the brush into contact with the frictional force between the belt and the brush being small.
On the other hand, as shown in FIG. 6, the paper dust filming is more likely to occur as the frictional force between the belt and the brush decreases. This is presumably because the paper dust collecting ability by the brush is weakened as the frictional force between the belt and the brush is lowered. Therefore, from the viewpoint of paper dust filming, it is desired to bring the brush into contact with a large frictional force between the belt and the brush.
Therefore, it is necessary to set the frictional force between the belt and the brush for simultaneously satisfying both the belt scratch and the paper dust filming.

In the case of a straight-hair brush, as shown in FIG. 5, in order to suppress damage to the belt, the frictional force between the belt and the brush needs to be approximately 12 N / m or less, and as shown in FIG. In order to suppress filming, the frictional force between the belt and the brush needs to be approximately 15 N / m or more.
Therefore, in the case of a straight-hair brush, it is impossible to satisfy both belt scratches and paper dust filming at the same time, and it is impossible to avoid erroneous detection of the sensor S.

On the other hand, in the case of the loop brush, as shown in FIG. 5, in order to suppress the belt scratches, it is sufficient that it is suppressed to at least 20 N or less, and it is expected that there is a margin even for a larger frictional force. The Further, as shown in FIG. 6, in order to suppress paper dust filming, the frictional force between the belt and the brush may be approximately 8 N / m or more.
Therefore, in the case of the loop brush, in order to satisfy both the belt scratch and the paper dust filming at the same time, it should be between 8 and 20 N, and it can be expected that a higher frictional force can be allowed with respect to the upper limit. Detection can be avoided.
Further, in the case of a loop brush, by setting the frictional force between the belt and the brush to 15 N / m or more, the occurrence of paper dust filming can be substantially suppressed, and the occurrence of brush scratches can be substantially eliminated. More preferred.

As described above, according to the present embodiment, the image forming apparatus 100 is configured to transfer the toner image formed on the intermediate transfer belt 17 having the elastic layer on the surface thereof to the paper P to form an image. A cleaning unit 21 that contacts the intermediate transfer belt 17 after the toner image has been transferred to the paper P and cleans deposits attached to the surface of the intermediate transfer belt 17, and a circumferential direction of the intermediate transfer belt 17 rather than the cleaning unit 21. A brush member 22 provided upstream of the cleaning unit 21 and contacting the intermediate transfer belt 17 after the toner image is transferred to the paper P to clean the surface of the intermediate transfer belt 17. 22 is a loop brush in which brush fibers are provided in a loop shape.
For this reason, compared with the case where a general straight hair brush is used, generation | occurrence | production of a belt damage and paper dust filming can be suppressed. Therefore, since unevenness in the reflectance of the belt surface is unlikely to occur, erroneous detection of the image density by the sensor S hardly occurs, and a high-quality image can be formed.

Further, according to the present embodiment, the cleaning unit 21 includes the rubber blade 21 a that contacts the intermediate transfer belt 17, and the frictional force between the brush member 22 and the intermediate transfer belt 17 is 15 N / m or more.
For this reason, generation | occurrence | production of a belt damage and paper dust filming can be suppressed more reliably.

Further, according to the present embodiment, the intermediate transfer belt 17 has a surface hardness of 400 MPa or less.
For this reason, the unevenness | corrugation followability of the paper P is securable.

Further, according to the present embodiment, the sensor S that optically detects the amount of toner on the intermediate transfer belt 17, the correction unit that corrects the image forming condition of the toner image based on the detection value by the sensor S,
Is provided.
Therefore, a desired color tone can be obtained by correcting the image forming condition of the toner image based on the detection value by the sensor S.

<Second Embodiment>
Next, a second embodiment of the present invention will be described focusing on differences from the first embodiment. In addition, about the same structure, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

FIG. 7 is a diagram showing a configuration of the belt cleaning unit 20A in the present embodiment.
In the belt cleaning unit 20A of the present embodiment, a blade (hereinafter referred to as a rigid blade) 21d made of an inelastic material such as metal is used instead of the rubber blade 21a in the first embodiment.
As the rigid blade 21d used in the present embodiment, for example, a metal piece of iron or SUS (stainless steel) having a thickness of about several tens to several hundreds μm can be used.
Similar to the first embodiment, the rigid blade 21d is held by the blade holding member 21b, and is configured such that a pressing force against the intermediate transfer belt 17 is obtained by the biasing spring 21c.

  When the rubber blade is combined with the intermediate transfer belt having the elastic layer as in the belt cleaning unit 20 of the first embodiment, the frictional force between the belt and the blade increases particularly in a high temperature and high humidity environment. There is a possibility that the driving torque of the belt may be increased or the blade may be connected to the blade. By using a rigid blade as in this embodiment, the above-described problems particularly in a high-temperature and high-humidity environment can be avoided. Become.

Here, when the rigid blade is combined with an intermediate transfer belt having an elastic layer, particularly when the amount of toner or external additive entering the blade is large, aggregates of external additive grow upstream of the blade. It is generally known that it may impair cleaning properties.
In this regard, in the present embodiment, since the loop brush is provided as the brush member 22, it is possible to suppress aggregation of the external additive when using the rigid blade described above.
Hereinafter, the ability to suppress aggregation of the external additive by the loop brush will be described.
Note that the straight hair brush and the loop brush used for comparison in the following description have the same material, fineness and density.

  FIG. 8 is a graph showing the recoverability of the external additive from the intermediate transfer belt 17 for each of the straight hair brush and the loop brush. In FIG. 8, the external additive was supplied to the intermediate transfer belt 17 at three levels of supply, and the amount of the external additive attached to each of the straight hair brush and the loop brush was measured.

  FIG. 9 is a graph showing the discharge performance of the external additive for each of the straight hair brush and the loop brush. In FIG. 9, each of the straight brush and the loop brush is pre-added with an external additive at a three-stage supply amount, and the residual amount of the external additive after being rubbed with the flicker member for a certain time is measured. . The measurement of the remaining amount was evaluated by the amount of the external additive attached to the filter by sucking a certain area of the brush with a pump through the filter.

The rotational speed of the brush member was set so that the surface speed ratio was 1.0 with the counter direction relative to the belt. The rotational speed of the flicker member was set so that the surface speed ratio was 1.5 in the counter direction with respect to the brush member.
Further, in each of the straight hair brush and the loop brush, the frictional force between the belt and the brush was almost the same.

It can be seen from FIG. 8 that the loop brush has better recoverability than the straight brush.
Further, FIG. 9 shows that the remaining amount of the loop brush is smaller than that of the straight brush.
That is, under conditions where the frictional force against the belt is almost the same, the loop brush has higher recoverability of the external additive than the straight hair brush, and can quickly discharge the recovered external additive to the flicker member. I understand that I can do it.

For this reason, since the brush surface is kept relatively clean, reattachment of the external additive from the brush to the belt can be avoided while maintaining the recoverability of the external additive. In addition, the amount of the external additive that enters the rigid blade 21d can be effectively reduced.
Therefore, by using the loop brush, it is possible to make it difficult to generate wiping residue due to aggregation of the external additive, which is likely to occur when a rigid blade is combined with the elastic intermediate transfer belt.
In addition, the use of the loop brush is more preferable from the viewpoint of suppressing the occurrence of belt scratches because the aggregation of the external additive can be avoided with a low torque.

  As described above, according to this embodiment, the same effect as that of the first embodiment can be obtained, and the loop member is provided as the brush member 22, and the cleaning means 21 is the intermediate transfer belt. 17 is provided with the rigid blade 21d that abuts on the belt 17, and suppresses the aggregation of external additives that are likely to occur when the rigid blade is used, while the drive torque of the belt increases or the blade is swollen in a high temperature and high humidity environment. Occurrence can be suppressed.

<Third Embodiment>
Next, a third embodiment of the present invention will be described focusing on differences from the second embodiment. In addition, about the same structure, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

FIG. 10 is a diagram showing a configuration of the belt cleaning unit 20B in the present embodiment.
In the belt cleaning unit 20B according to the present embodiment, the rigid blade 21d according to the second embodiment is provided with a coat layer 21e.
The coat layer 21e is a material harder than the metal piece serving as the base material of the rigid blade 21d. For example, diamond-like carbon (DLC), silicon carbide (SiC), metal plating such as galvanization or chrome plating, or the like is used. be able to.
The coat layer 21e may be provided so as to cover the entire surface of the base material, but may be provided at a contact portion of the rigid blade 21d that contacts at least the intermediate transfer belt 17.
By providing such a coat layer 21e, the wear of the blade is reduced and the life of the blade can be extended.

  Here, when such a coat layer 21e is provided on the rigid blade 21d, it is common that an edge shape is formed at the edge, and aggregation of external additives is more likely to occur at the edge than when the coat layer 21e is not provided. Known to. For this reason, in this Embodiment, generation | occurrence | production of the aggregate is avoided by performing either of the following three controls to the brush member 22 by the control part 41. FIG.

As a first control, a bias voltage in the direction of collecting the toner and the external additive is applied to the brush member 22 in order to increase the recovery force of the toner and the external additive from the intermediate transfer belt 17 by the brush member 22.
As a result, even when the amount of residual toner on the intermediate transfer belt 17 is large, in addition to the high recoverability of the original brush member 22 (loop brush), the toner and external additives that enter the blade after passing through the brush member 22 are added. The amount of the agent can be sufficiently reduced, and the generation of aggregates can be avoided.

Further, as a second control, a bias voltage in the direction of collecting the toner and the external additive is applied to the flicker member 23 in order to increase the collecting power of the toner and the external additive from the brush member 22 by the flicker member 23.
Thereby, in addition to the high dischargeability of the original brush member 22 (loop brush), the state of the surface of the brush member 22 is maintained in a more recoverable state, and the recoverability of the brush member 22 is reduced. Thus, the amount of toner and external additives that enter the blade after passing through the brush member 22 can be sufficiently reduced, and the generation of aggregates can be avoided.

As the third control, the bias voltage applied to the brush member 22 and the bias voltage applied to the flicker member 23 are used in combination.
In this case, the bias voltage applied to the flicker member 23 is set so as to form an electric field that attracts toner with respect to the bias applied to the brush member 22. For example, when the toner is negative, a positive voltage is applied to the brush member 22, and a positive voltage larger than the voltage applied to the brush member 22 is applied to the flicker member 23.

As described above, according to the present embodiment, the same effect as in the first and second embodiments can be obtained, and the abutting portion of the rigid blade 21d with the intermediate transfer belt 17 can be obtained. Is provided with a coat layer 21e, and a bias in a direction in which the toner is collected from the intermediate transfer belt 17 is applied to the brush member 22.
For this reason, it is possible to extend the life of the blade while avoiding the aggregation of the external additive.

Further, according to the present embodiment, the flicker member 23 is in contact with the brush member 22, and the brush member 22 discharges the toner collected from the intermediate transfer belt 17 from the brush member 22. A bias voltage in the direction of collecting toner from the member 22 is applied.
For this reason, it is possible to extend the life of the blade while more reliably avoiding the aggregation of the external additive.

<Modification>
The aggregation of the external additive in the rigid blade 21d or the rigid blade 21d provided with the coat layer 21e described in the second and third embodiments is caused by the rounded shape of the edge. As the rounded shape of the edge wears with the endurance time (accumulated time used), it becomes less likely to occur with this.
For this reason, it is also preferable that the control unit 41 performs control to change the driving condition of the brush member 22 in the direction of relaxation as the durability time increases.
Specifically, for example, the rotational speed of the brush member 22 is decreased as the durability time increases. As a result, the rubbing between the brush member 22 and the intermediate transfer belt 17 can be reduced, and the life of the brush member 22 and the intermediate transfer belt 17 can be extended.
Further, the bias voltage applied to the brush member 22 is lowered as the durability time increases. As a result, the discharge between the brush member 22 and the intermediate transfer belt 17 can be suppressed, and the belt's ozone deterioration caused by the ozone generated by the discharge can be suppressed.

Hereinafter, specific control will be described.
FIG. 11 is a graph showing an example of the control pattern described above.
In FIG. 11, the horizontal axis represents the belt drive distance from the time of blade replacement, and the vertical axis represents the number of rotations of the brush member.
In such control, the driving distance of the intermediate transfer belt 17 from the installation time of the blade is stored in the storage unit 44 as storage means.
Then, the control unit 41 gradually increases until the driving distance of the intermediate transfer belt 17 stored in the storage unit 44 reaches a belt driving distance (presumed wear value) that is set in advance and is expected to wear out the rounded shape. Change the brush rotation speed so that the frictional force with the intermediate transfer belt 17 is reduced, and when the expected wear value is reached, maintain the minimum rotation speed (minimum rotation speed) necessary for removing paper dust. Control.
Specifically, as shown in FIG. 11, immediately after blade replacement (at the time of installation), since the edge has a large round shape, the number of rotations of the brush is set high enough to avoid aggregation of external additives even in the initial state. .
As the belt drive distance increases, the rounded shape of the edge wears, and the brush rotational speed as required at the beginning is no longer necessary, so the rotational speed is gradually reduced.
Also, after the rounded edge shape is worn out, the brush member only has to play the role of removing paper dust, so after reaching the expected wear value, the minimum rotation required for removing paper dust Maintained in numbers.

FIG. 12 is a graph showing an example of another control pattern.
In FIG. 12, the horizontal axis represents the belt driving distance after blade replacement, and the vertical axis represents the applied bias (absolute value) applied to the brush member.
In such control, the driving distance of the intermediate transfer belt 17 from the installation time of the blade is stored in the storage unit 44 as storage means.
Then, the control unit 41 gradually applies a bias voltage to the brush member 22 until the driving distance of the intermediate transfer belt 17 stored in the storage unit 44 reaches a preset predicted wear value. Then, the force for collecting the deposits is changed in a direction in which the force decreases, and when the expected wear value is reached, control to stop applying the brush bias is performed.
Specifically, as shown in FIG. 12, immediately after blade replacement (at the time of installation), since the edge round shape is large, the absolute value of the brush bias is set high enough to avoid aggregation of external additives even in the initial state. ing.
As the belt drive distance increases, the rounded shape of the edge wears, and the brush bias that is necessary at the beginning is no longer necessary, so the bias is gradually reduced.
Also, after the rounded shape of the edge is worn out, the brush member only needs to play the role of removing paper dust, so the brush bias is not necessary, so after reaching the expected wear value, apply the brush bias. Stop.
When the toner polarity is negative, a positive bias voltage is applied to the brush member in order to collect the toner and external additives. Therefore, a positive high voltage is first applied as the bias, and the positive voltage is gradually increased. Will be lowered.

Further, in the control of FIG. 11 and FIG. 12, the belt driving distance is used as a control criterion. This is because the driven belt distance is desirable because it mainly determines the wear of the rigid blade 21d.
However, as a substitute value that is considered to be approximately proportional to the belt driving distance, for example, a belt driving time or the number of prints may be used.
Further, since the wear of the rigid blade 21d depends on the amount of toner that enters the blade, it also depends on the image portion ratio included in the image pattern. For this reason, a value obtained by multiplying the belt driving distance or the substitute value of the belt driving distance by a correction coefficient considering the printed image portion ratio may be prepared as a substitute value and controlled based on the value.

  Examples of the present invention will be described below. In addition, although an Example demonstrates this invention concretely, this invention is not limited to these.

<Examples 1-12 and Comparative Examples 1-12>
As Examples 1 to 12, image formation was performed by an image forming apparatus using a polyurethane rubber blade and a loop brush having the brush conditions shown in Table I. The occurrence of belt scratches and paper dust filming and sensor detection failure The occurrence situation was evaluated and the results are shown in Table I.
Further, as Comparative Examples 1 to 12, image formation was performed in the same manner as in Examples 1 to 12 using straight hair brushes having the brush conditions shown in Table I, and belt scratches and paper dust were in the same manner as in Examples 1 to 12. The filming occurrence and sensor detection failure occurrence were evaluated and the results are shown in Table I.

The paper used was npi fine paper (manufactured by Nippon Paper Industries).
Also, as the image pattern, a YMCK vertical band pattern along the sub-scanning direction (FD direction) is used, and the vertical band is arranged so that the boundary of the vertical band pattern corresponds to the detection position of the sensor, resulting in a gloss level difference. It was made easy to lead to the detection failure of the sensor.
Further, as the intermediate transfer belt, a belt having a two-layer structure in which an NBR elastic layer is provided on a PI base material layer was used. The volume resistivity of the intermediate transfer belt is 10 ⁶ to 10 ¹⁴ Ω · cm, and the thickness of the intermediate transfer belt is 80 μm for the base material layer, 250 μm for the elastic layer, and 330 μm as a whole. Using. In order to give the belt appropriate conductivity, a suitable amount of a conductive agent such as carbon black or an ionic conductive agent was contained in the resin.

  The frictional force between the intermediate transfer belt and each brush was changed by changing the pushing amount of the brush against the belt between 0.5 and 1.1 mm. The frictional force was converted to a unit of N / m, which is the frictional force per unit length, by dividing the torque value of the drive motor of the intermediate transfer belt by the contact length in the longitudinal direction of the brush.

  Evaluation of paper dust filming was performed by measuring the difference in glossiness between 0% and 100% of the belt surface at the time when three images were formed at a measurement angle of GM-268Plus (manufactured by Konica Minolta) at 60 degrees. As a standard that leads to false detection of the sensor, “x” when the gloss difference is 2.5 degrees or more, “◯” when less than 2.5 degrees and 0.5 degrees or more, and less than 0.5 degrees In this case, “◎” is given.

The evaluation of the belt scratch was made by measuring the difference in glossiness between 0% and 100% of the belt surface when 20 images were formed at a measurement angle of GM-268Plus (manufactured by Konica Minolta) at 60 degrees. As a standard that leads to false detection, when the difference in glossiness is 2.5 degrees or more, “×”, when less than 2.5 degrees and 0.5 degrees or more, “○”, when less than 0.5 degrees “◎”.
When a gloss difference of 2.5 degrees or more occurs due to paper dust filming at the time of three-sheet image formation, it is difficult to evaluate the gloss level difference of only the belt scratch at the time of the 20-sheet image formation. Only in that case, 20 sheets of images were formed separately by changing the paper to coated paper, and the result was the result of gloss reduction due to belt scratches.

  The sensor detection failure is evaluated when patch density detection by the IDC sensor is performed 20 times on the intermediate transfer belt after 20 sheets of images are formed, and the detected γ curve inclination variation is ± 5% or more of the average value. “X” was given as a detection failure occurrence.

From Table I, when a straight-hair brush is used, either paper dust filming or belt damage always occurs, and sensor detection failure occurs accordingly.
On the other hand, when the loop brush is used, belt scratches and paper dust filming do not occur under any condition, and sensor detection failure can be avoided. In particular, under conditions where the belt-brush friction force is set to exceed 15 N / m, the gloss difference due to belt scratches and paper dust filming is suppressed to a level that has almost no gloss difference of 0.5 degrees or less. It is considered that there is almost no adverse effect on the detection by the sensor.

<Examples 13 to 24 and Comparative Examples 13 to 24>
As Examples 13 to 24, a rigid blade made of a SUS (stainless steel) leaf spring material having a thickness of 100 μm was used, and image formation was performed by an image forming apparatus using a loop brush having the brush conditions shown in Table II. The number of occurrences of wiping residue and the occurrence of external additive aggregation at the time of evaluation of wiping residue were evaluated, and the results are shown in Table II.
Further, as Comparative Examples 13 to 24, image formation was performed in the same manner as in Examples 13 to 24 using straight hair brushes having the brush conditions shown in Table II, and belt scratches and unwiped areas were left in the same manner as in Examples 13 to 24. The occurrence number of the additive and the state of occurrence of aggregation of the external additive at the time of evaluation of the remaining wiping were evaluated, and the results are shown in Table II.

As the paper, OK top coat paper (manufactured by Oji Paper) was used.
Also, as the image pattern, up to 20 sheets, a YMCK vertical band pattern along the sub-scanning direction (FD direction) was used, and after completion of the 20 sheets, the entire surface was switched to a blue solid (cyan and magenta solid two-color overlay) pattern. . By switching the image pattern, the amount of residual toner increases, and the amount of toner / external additive that enters the rigid blade increases.

  The evaluation of belt scratches was made by measuring the difference in glossiness between 0% and 100% of the belt surface at the end of 20 sheets at a measurement angle of GM-268Plus (manufactured by Konica Minolta Co., Ltd.) of 60 degrees, and erroneous detection of the sensor. As a standard that leads to, “X” when the gloss difference is 2.5 degrees or more, “◯” when it is less than 2.5 degrees and 0.5 degrees or more, and when it is less than 0.5 degrees “◎”.

  The evaluation of the number of remaining wiping was performed by counting the number of remaining wiping at the time when 1000 continuous blue solid patterns were continuously formed.

  Evaluation of the occurrence of external additive aggregation at the time of unwiping evaluation is based on the observation that the nip portion of the rigid blade is observed with a microscope and the aggregates of the external additive can be confirmed when 1000 continuous blue solid patterns are formed continuously. Was marked with “× (occurrence)”, and when it could not be confirmed, it was marked with “◯ (none)”.

From Table II, when using a straight-hair brush, either a belt scratch at the end of the vertical belt pattern or a wiping residue at the time of continuous printing of blue solids always occurs. Proves difficult.
On the other hand, when a loop brush is used, no belt scratches or wiping remains have occurred under any condition, and various image patterns can be obtained by using a loop brush in a configuration in which a rigid blade is combined with an elastic belt. It can be seen that image formation can be performed without any trouble even when the image is continuously printed.

<Examples 25-27 and Comparative Example 25>
As Example 25, a rigid blade made of a SUS (stainless steel) leaf spring material having a thickness of 100 μm was used, and an image was formed by an image forming apparatus using a loop brush having the brush conditions shown in Table III. , And the state of occurrence of aggregation of external additives at the time of evaluation of unwiping was evaluated, and the results are shown in Table III.
Further, as Examples 26 and 27, a rigid blade made of a SUS (stainless steel) leaf spring material having a thickness of 100 μm and a coating layer of a DLC film having a thickness of 1 μm was used, and the brush conditions shown in Table III were used. Using a loop brush, a bias was applied under the conditions shown in Table III, image formation was performed, and the number of occurrences of wiping residue and the occurrence of external additive aggregation during evaluation of wiping residue were evaluated, and the results were It is shown in Table III. In Example 26, the flicker bias was set to the same potential as the brush. In Example 27, the brush bias was set to the same potential as the brush facing roller.
Further, as Comparative Example 25, image formation was performed in the same manner as in Examples 26 and 27 except that no bias was applied to the brush or flicker, and the number of wiping residues generated and the aggregation of external additives during evaluation of wiping residues were evaluated. The state of occurrence was evaluated and the results are shown in Table III.

As the paper, OK top coat paper (manufactured by Oji Paper) was used.
Further, as the image pattern, a blue solid pattern (overlapping two colors of cyan and magenta) was used.

  The number of remaining wiping was determined by counting the number of remaining wiping when 3,000 continuous blue solid patterns were continuously formed.

  The evaluation of the state of occurrence of external additive agglomeration at the time of unwiping evaluation is performed when the 3,000 parts of the blue solid pattern are continuously formed on the entire surface, and the nip portion of the rigid blade is observed with a microscope, and the aggregates of the external additive can be confirmed. Was marked with “× (occurrence)”, and when it could not be confirmed, it was marked with “◯ (none)”.

From Table III, when there was no coating layer (Example 25), no wiping residue occurred, but the blade (Comparative Example 25) coated on the same blade was externally added at the stage where about 2000 sheets were continuously printed. Wiping residue that was thought to be caused by agent aggregation occurred.
On the other hand, even when a blade with a coating is used, unwiping remains are not generated under the condition where the brush bias is applied with +200 V (Example 26) or the condition where the flicker bias is applied with 800 V (Example 27). Absent.
As a result, the recovery of toner and external additives from the belt to the brush increases due to the effect of bias application, the amount of external additives entering the rigid blade decreases, and aggregation of external additives at the nip portion of the blade is avoided. It was confirmed that it was made.

100 Image forming apparatus 10 Image forming unit 17 Intermediate transfer belt (intermediate transfer member)
20, 20A, 20B Belt cleaning section 21 Cleaning means 21a Rubber blade 21b Blade holding member 21c Biasing spring 21d Rigid blade 21e Coat layer 22 Brush member 23 Flicker member 23a Scraper 24 Blade facing roller 25 Brush facing roller 41 Control section (correction means) )
44 storage unit (storage means)
S sensor (detection means)
P paper

Claims (9)

An image forming apparatus for forming an image by transferring a toner image formed on an intermediate transfer member having an elastic layer on a surface onto a sheet,
Cleaning means for cleaning a deposit adhered to the surface of the intermediate transfer member in contact with the intermediate transfer member after the toner image is transferred to a sheet;
Provided upstream of the cleaning means in the circumferential direction of the intermediate transfer body, and before the cleaning means, contact the intermediate transfer body after the toner image is transferred to a sheet to contact the surface of the intermediate transfer body. A brush member to be cleaned;
With
The image forming apparatus, wherein the brush member is a loop brush in which brush fibers are provided in a loop shape. The cleaning means includes a rubber blade that contacts the intermediate transfer member,
The image forming apparatus according to claim 1, wherein a frictional force between the brush member and the intermediate transfer member is 15 N / m or more.   The image forming apparatus according to claim 1, wherein the cleaning unit includes a rigid blade that contacts the intermediate transfer member. The contact portion of the blade with the intermediate transfer member is provided with a coat layer,
The image forming apparatus according to claim 3, wherein a bias voltage is applied to the brush member in a direction in which the deposit is collected from the intermediate transfer member. A flicker member that abuts against the brush member and causes the brush member to discharge the deposit collected from the intermediate transfer member from the brush member;
The image forming apparatus according to claim 4, wherein a bias voltage is applied to the flicker member in a direction to collect deposits from the brush member. Storage means for storing a driving distance of the intermediate transfer member from the time of installation of the blade or a substitute value thereof;
A control unit that changes the rotational speed of the brush member in a direction in which the frictional force with the intermediate transfer member is reduced in accordance with the driving distance of the intermediate transfer member stored in the storage unit or a substitute value thereof; ,
The image forming apparatus according to claim 3, further comprising: Storage means for storing a driving distance of the intermediate transfer member from the time of installation of the blade or a substitute value thereof;
The bias voltage applied to the brush member is changed in a direction in which the force for collecting the deposits from the intermediate transfer member is reduced in accordance with the driving distance of the intermediate transfer member stored in the storage unit or a substitute value thereof. A control unit;
The image forming apparatus according to claim 3, further comprising:   The image forming apparatus according to claim 1, wherein the intermediate transfer member has a surface hardness of 400 MPa or less. Detection means for optically detecting the amount of toner on the intermediate transfer member;
Correction means for correcting the image forming condition of the toner image based on the detection value by the detection means;
The image forming apparatus according to claim 1, further comprising:

Images