WO2015068789A1

WO2015068789A1 - Image formation device

Info

Publication number: WO2015068789A1
Application number: PCT/JP2014/079543
Authority: WO
Inventors: 浩二宇野; 佑太北林; 聡植村
Original assignee: 京セラドキュメントソリューションズ株式会社
Priority date: 2013-11-08
Filing date: 2014-11-07
Publication date: 2015-05-14

Abstract

This image formation device is provided with an image formation unit, an intermediate transfer belt, a brush roller, a drive unit, and an operation control unit. A toner image is transferred from the image formation unit to the outer surface of the intermediate transfer belt. The brush roller contacts said outer surface so as to recover residual toner therefrom. The drive unit rotationally drives the brush roller. The operation control unit has a cleaning-operation mode in which, when an image is not being formed, the image formation device is controlled such that the brush roller is cleaned. In said cleaning-operation mode, the drive unit is made to rotationally drive the brush roller at a rotational speed that is higher than the rotational speed of the brush roller when an image is being formed.

Description

Image forming apparatus

The present invention relates to an image forming apparatus, and more particularly to a technique for collecting residual toner remaining on an outer peripheral surface of an intermediate transfer belt.

An image forming unit of each color is arranged in parallel at a position facing the intermediate transfer belt, and a color image is formed by superimposing the toner images of each color on the intermediate transfer belt, and the color image is transferred onto a recording sheet by a secondary transfer roller. Thus, an image forming apparatus that forms an image on a recording sheet is known. In this image forming apparatus, a brush roller that collects residual toner remaining on the outer peripheral surface of the intermediate transfer belt after transfer of a color image onto a recording sheet is provided (see, for example, Patent Document 1).

JP 2012-220634 A

The toner collected by the brush roller is collected by a collecting roller provided in contact with the outer peripheral surface of the brush roller. However, if the amount of residual toner remaining on the outer peripheral surface of the intermediate transfer belt is large or if the residual toner has a low charge amount, the toner cannot be recovered by the recovery roller or the like, and the toner accumulates in the brush roller. There is a case. When the amount of toner accumulated in the brush roller increases, the toner may fall from the brush roller to the outer peripheral surface of the intermediate transfer belt during image formation, and the image may be soiled, so that the image formation quality deteriorates.

The present invention has been made in view of the above circumstances, and the brush roller can be more efficiently and satisfactorily cleaned than before, and toner is dropped from the brush roller onto the outer peripheral surface of the intermediate transfer belt during image formation. An object of the present invention is to provide an image forming apparatus that is less likely to contaminate.

An image forming apparatus according to one aspect of the present invention includes an image forming unit, an intermediate transfer belt, a brush roller, a driving unit, and an operation control unit. The image forming unit forms a toner image. In the intermediate transfer belt, a toner image is transferred from the image forming unit to the outer peripheral surface. The brush roller contacts the outer peripheral surface of the intermediate transfer belt and collects toner remaining on the outer peripheral surface. The drive unit rotates the brush roller. The operation control unit has a cleaning operation mode for performing control to clean the brush roller during non-image formation, and in the cleaning operation mode, the drive unit has a higher rotation speed than the brush roller during image formation. The brush roller is rotationally driven at a rotational speed.

According to the image forming apparatus according to one aspect of the present invention, the brush roller can be more efficiently and satisfactorily cleaned than before, and toner is dropped from the brush roller to the outer peripheral surface of the intermediate transfer belt during image formation. There is little possibility of getting dirty.

1 is a cross-sectional view illustrating a structure of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating a structure around an intermediate transfer belt of the image forming apparatus according to the embodiment of the present invention. It is sectional drawing which shows the cleaning apparatus concerning one Embodiment of this invention, and the structure around it. 1 is a functional block diagram schematically showing a main internal configuration of an image forming apparatus according to an embodiment of the present invention. The movement of toner collected by the cleaning device during image formation according to an embodiment of the present invention will be described. It is a figure which shows the motion of the toner at the time of the cleaning operation | movement of the fur brush concerning one Embodiment of this invention. 3 is a flowchart showing a flow of operations of the image forming apparatus according to the embodiment of the present invention. It is a figure which shows the relationship between the rotation speed which rotated the fur brush in cleaning operation mode, and the accumulation amount of the toner accumulate | stored in the fur brush. FIG. 6 is a diagram illustrating a relationship between the number of recording sheets on which image formation has been performed and the accumulated amount of toner accumulated in a fur brush. FIG. 10 is a diagram illustrating an experimental result obtained by performing an image forming operation for forming a toner image on a recording sheet a plurality of times and examining whether or not toner dropping occurs.

Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

<Embodiment 1>
FIG. 1 is a cross-sectional view showing the structure of the image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view showing a structure around the intermediate transfer belt 125 of the image forming apparatus according to the first embodiment of the present invention.

The image forming apparatus 1 according to the first exemplary embodiment of the present invention is a multifunction machine having a plurality of functions such as a copy function, a printer function, a scanner function, and a facsimile function. The image forming apparatus 1 includes an apparatus main body 11 including an operation unit 47, an image forming unit 12, a fixing unit 13, a paper feeding unit 14, a document feeding unit 6, a document reading unit 5, and the like.

The operation unit 47 receives instructions such as an image forming operation execution instruction and a document reading operation execution instruction from the operator for various operations and processes that can be executed by the image forming apparatus 1.

When the image forming apparatus 1 performs a document reading operation, the document reading unit 5 optically reads a document fed by the document feeding unit 6 or a document placed on the document placing glass 161, Generate image data. Image data generated by the document reading unit 5 is stored in a built-in HDD or a computer connected to a network.

When the image forming apparatus 1 performs an image forming operation, based on image data generated by a document reading operation, image data received from a computer connected to a network, image data stored in a built-in HDD, or the like, The image forming unit 12 forms a toner image on a recording paper P as a recording medium fed from the paper feeding unit 14. The

image forming units

12M, 12C, 12Y, and 12Bk of the image forming unit 12 include a photosensitive drum 121, a developing device 122, a toner cartridge (not shown) that contains toner, a charging device 123, and an exposure device 124. A primary transfer roller 126 and a toner recovery device 128 are provided.

When performing color printing, the magenta image forming unit 12M, the cyan image forming unit 12C, the yellow image forming unit 12Y, and the black image forming unit 12Bk of the image forming unit 12 each receive image data. A toner image is formed on the photosensitive drum 121 by charging, exposure, and development processes based on the image composed of the respective color components, and the toner image is driven by the primary transfer roller 126 by the driving roller 125A and the driven roller 125B. The image is transferred onto the intermediate transfer belt 125 that is stretched around the belt.

The intermediate transfer belt 125 is driven by a driving roller 125 A in a state in which an image carrying surface on which a toner image is transferred is set on the outer circumferential surface and is in contact with the circumferential surface of the photosensitive drum 121. The intermediate transfer belt 125 travels endlessly between the driving roller 125A and the driven roller 125B while being synchronized with each photosensitive drum 121.

The toner images of the respective colors transferred onto the intermediate transfer belt 125 are superimposed on the intermediate transfer belt 125 with the transfer timing adjusted to become a color toner image. The secondary transfer roller 210 conveys the color toner image formed on the surface of the intermediate transfer belt 125 from the sheet feeding unit 14 through the conveyance path 190 at the nip N between the intermediate transfer belt 125 and the driving roller 125A. The recording sheet P is transferred. Thereafter, the fixing unit 13 fixes the toner image on the recording paper P to the recording paper P by thermocompression bonding. The recording paper P on which the color image has been formed after completion of the fixing process is discharged to a discharge tray 151.

A cleaning device 70 is provided on the intermediate transfer belt 125 stretched around the driven roller 125B. The cleaning device 70 collects the toner remaining on the outer peripheral surface of the intermediate transfer belt 125.

Further, a charging brush (charging member) 80 is provided on the upstream side of the cleaning device 70 in the traveling direction of the intermediate transfer belt 125. The charging brush 80 imparts electric charge to the toner remaining on the outer peripheral surface of the intermediate transfer belt 125.

FIG. 3 is a cross-sectional view showing the cleaning device 70 according to the first embodiment of the present invention and the structure around it.

The charging brush 80 is a fixed brush, and is arranged so that the brush surface contacts the outer peripheral surface of the intermediate transfer belt 125. The charging brush 80 is connected to a charging bias application unit (power supply device) 801. The operation of the charging bias application unit 801 is controlled by an operation control unit 101 (see FIG. 4) described later, and applies a bias having the same polarity as the normal charging polarity to the charging brush 80 during an image forming operation. On the other hand, the driven roller 125B at a position facing the charging brush 80 is grounded. Here, the charged charge of the residual toner remaining on the outer peripheral surface of the intermediate transfer belt 125 after the transfer of the color image onto the recording paper P is not uniform. For example, residual toner charged to a polarity opposite to the normal charge polarity (plus in the present embodiment) (minus in the present embodiment) due to peeling discharge or the like generated when the recording paper P is separated from the intermediate transfer belt 125 Exists. The charging brush 80 applies a charge having the same polarity as the normal charging polarity to the remaining toner by applying a bias having the same polarity as the normal charging polarity from the charging bias applying unit 801. Thereby, the charged charge of the residual toner can be made uniform, and the recoverability of the residual toner in the cleaning device 70 can be improved.

Further, the operation control unit 101 causes the charging bias applying unit 801 to apply a bias having the same polarity as the normal charging polarity to the charging brush 80 even during a cleaning operation for cleaning the fur brush 71 of the cleaning device 70 described later. . Details thereof will be described later.

The cleaning device 70 includes a fur brush (brush roller) 71, a recovery roller 72, a cleaning blade 74, a toner reservoir 75, and a toner transport screw 76.

The fur brush 71 is in contact with the outer peripheral surface of the intermediate transfer belt 125 stretched around the driven roller 125B, and collects toner remaining on the outer peripheral surface during image formation. The fur brush 71 is composed of a rotating shaft 711 and a plurality of raised brushes erected on the peripheral surface of the rotating shaft 711. A rotation shaft 711 of the fur brush 71 extends in the rotation shaft direction of the driven roller 125 B and is pivotally supported by the casing 77. The fur brush 71 is rotated in the same direction as the rotation direction of the driven roller 125 B about the rotation shaft 711 by a drive unit 712 (see FIG. 4) described later.

Further, the fur brush 71 is applied with a bias having a polarity opposite to the normal charging polarity via a recovery roller 72 from a recovery bias application unit (power supply device) 722 to be described later. Thereby, the toner remaining on the outer peripheral surface of the intermediate transfer belt 125 can be electrically adsorbed and collected.

The collection roller 72 contacts the surface of the fur brush 71 and collects the toner collected by the fur brush 71 during image formation from the fur brush 71. A rotation shaft 721 of the collection roller 72 extends in the rotation shaft direction of the fur brush 71 and is pivotally supported by the casing 77. The collection roller 72 rotates in the direction opposite to the rotation direction of the fur brush 71 around the rotation shaft 721 as a rotation center.

The recovery roller 72 is connected to a recovery bias applying unit 722, and a bias having a polarity opposite to the normal charging polarity of the toner is applied during image formation. For this reason, since the potential of the collection roller 72 is lower than the potential of the fur brush 71, the toner collected by the fur brush 71 can be electrically adsorbed and collected.

The cleaning blade 74 is made of a flat plate member and extends in the direction of the rotation axis of the collection roller 72. The cleaning blade 74 is attached to the casing 77 so that the tip portion contacts the surface of the collection roller 72. The cleaning blade 74 scrapes off the toner collected by the collection roller 72 from the surface of the collection roller 72. The scraped toner falls and accumulates in the toner reservoir 75.

The toner storage unit 75 is provided with a toner conveying screw 76. The toner conveying screw 76 extends in the direction of the rotation axis of the collection roller 72, and the rotation shaft 761 is pivotally supported by the casing 77. A toner conveying blade 762 is spirally provided on the circumferential surface of the rotation shaft 761 of the toner conveying screw 76, and the toner in the toner storage unit 75 is moved to a predetermined position in the direction of the rotating shaft 761 by the toner conveying blade 762. To be collected. As a result, the residual toner on the outer peripheral surface of the intermediate transfer belt 125 is collected.

Next, the internal configuration of the image forming apparatus 1 will be described. FIG. 4 is a functional block diagram schematically illustrating a main internal configuration of the image forming apparatus 1 according to the first embodiment.

The image memory 32 is an area for temporarily storing image data to be subjected to image formation by the image forming unit 12.

The HDD (hard disk drive) 92 is a large-capacity storage device that stores image data received from a computer connected to the image forming apparatus 1 via a network.

The drive unit 712 includes a motor, a gear, a driver, and the like, and functions as a drive source that applies a rotational drive force to the fur brush 71 and the collection roller 72.

The transfer bias applying unit 1261 includes a power supply device connected to the primary transfer roller 126 and applies a predetermined bias to the primary transfer roller 126.

The image forming apparatus 1 includes a control unit 10. The control unit 10 includes a CPU (Central Processing Unit), a RAM, a ROM, a dedicated hardware circuit, and the like. The control unit 10 functions as the control unit 100 and the operation control unit 101 when a program stored in the ROM or the HDD 92 is executed by the CPU.

The control unit 100 controls the overall operation of the image forming apparatus 1. The control unit 100 includes a document feeding unit 6, a document reading unit 5, an image forming unit 12, a fixing unit 13, an image memory 32, an HDD 92, an operation unit 47, a driving unit 712, a recovery bias applying unit 722, and a charging bias applying unit 801. The transfer bias applying unit 1261 and the like are connected. The control unit 100 controls the operation of each connected mechanism and transmits / receives a signal or data to / from each mechanism.

The operation control unit 101 controls the operation of the image forming unit 12 and the like, and in addition to an image forming operation mode for forming a toner image on the recording paper P, a cleaning operation mode for performing control for cleaning the fur brush 71 during non-image formation. have.

In the cleaning operation mode, the operation control unit 101 causes the drive unit 712 to rotationally drive the fur brush 71 at a rotational speed higher than the rotational speed of the fur brush 71 during the image forming operation. Further, the operation control unit 101 causes the charging bias applying unit 801 to apply a bias having the same polarity as the normal charging polarity to the charging brush 80 in the cleaning operation mode. Since the fur brush 71 is rotationally driven at a rotational speed higher than the rotational speed of the fur brush 71 during the image forming operation, the toner accumulated in the fur brush 71 can be efficiently and satisfactorily discharged during the image forming operation. it can. Hereinafter, the cleaning operation mode will be described in detail.

First, the movement of toner collected by the cleaning device 70 during image formation will be described with reference to FIG.

As indicated by T1 in the figure, on the outer peripheral surface of the intermediate transfer belt 125 after the color image is transferred to the recording paper P, in addition to the toner charged to the same polarity as the normal charge polarity, the reverse of the normal charge polarity There is toner that is charged to polarity. When the remaining toner reaches a position facing the charging brush 80, the charging brush 80 applies a charge having the same polarity as the normal charging polarity, and the charged charge is made uniform (see T2 in the figure).

The operation control unit 101 causes the drive unit 712 to rotationally drive the fur brush 71 at the rotation speed Va. Further, a bias having a polarity opposite to the normal charging polarity is applied to the fur brush 71 from the collection bias applying unit 722 via the collection roller 72. Therefore, as indicated by T3 in the figure, the residual toner that has reached the position facing the fur brush 71 is electrically adsorbed and collected.

A bias having a polarity opposite to the normal charging polarity is applied to the collection roller 72, and the potential of the collection roller 72 is lower than the potential of the fur brush 71. For this reason, as indicated by T4 in the figure, the toner collected by the fur brush 71 is electrically attracted and collected by the collection roller. The toner collected by the collection roller 72 is scraped off by the cleaning blade 74 as indicated by T5 in the figure, and the scraped toner falls and accumulates in the toner storage unit 75.

As described above, the toner collected by the fur brush 71 is collected by the collecting roller 72 provided in contact with the outer peripheral surface of the fur brush 71 and having a potential lower than that of the fur brush 71. When the amount of residual toner remaining on the outer peripheral surface of the intermediate transfer belt 125 is large or when the residual toner has a low charge amount, the recovery of the toner by the recovery roller 72 may not be in time. In this case, toner is accumulated in the fur brush 71 as indicated by T6 in the figure. When image formation is performed continuously for a long time, the amount of toner accumulated in the fur brush 71 increases, and as a result, the toner drops from the fur brush 71 to the outer peripheral surface of the intermediate transfer belt 125 during image formation. May become dirty (toner drop).

FIG. 6 is a diagram illustrating the movement of the toner during the cleaning operation of the fur brush 71. The operation control unit 101 causes the drive unit 712 to rotationally drive the fur brush 71 at a rotational speed (Vb) higher than the rotational speed (Va) of the fur brush 71 during the image forming operation during the cleaning operation of the fur brush 71. ing. As a result, as indicated by T7 in the figure, the toner accumulated in the fur brush 71 moves in the outer peripheral direction of the fur brush 71 by centrifugal force. As a result, the toner accumulated in the fur brush 71 is discharged from the fur brush 71 as indicated by T8 in the drawing.

The toner discharged from the fur brush 71 is a toner having a low charge amount even if it is a toner charged to a polarity opposite to the normal charge polarity or a toner charged to the same polarity as the normal charge polarity. These toners are conveyed by the intermediate transfer belt 125 (see T9 in the drawing), and when the toner reaches the position facing the charging brush 80, the charging brush 80 gives a charge having the same polarity as the normal charging polarity. As a result, as indicated by T10 in the figure, the toner discharged from the fur brush 71 is charged with the same polarity as the normal charging polarity.

Thereafter, the toner is electrically adsorbed and collected by the fur brush 71 as indicated by T11 in the figure. As a result of the charge having the same polarity as the normal charging polarity applied by the charging brush 80, the toner discharged from the fur brush 71 is a toner charged to a polarity opposite to the normal charging polarity or a toner charged to the same polarity as the normal charging polarity. However, since the toner is not weak in the charge amount, it is not accumulated in the fur brush 71 but is electrically attracted and collected by the collection roller 72 as indicated by T12 in the figure. Then, the toner collected by the collection roller 72 is scraped off by the cleaning blade 74, and the scraped toner falls and accumulates in the toner storage unit 75.

Next, the operation of the image forming apparatus 1 having the above configuration will be described. FIG. 7 is a flowchart illustrating an operation flow of the image forming apparatus 1 according to the first embodiment.

As shown in FIG. 7, the control unit 100 determines whether an instruction to start a print job has been received (step S10).

When an instruction to start a print job is received (YES in step S10), the operation control unit 101 sets the rotation speed of the fur brush 71 to Va, and causes the drive unit 712 to move the fur brush 71 at the rotation speed Va. It is rotated (step S11).

Thereafter, the operation control unit 101 controls the operation of the image forming unit 12 and the like to form a toner image on the recording paper P (step S12 to step S14). The operation control unit 101 forms an image for one recording sheet P (step S12), and then increments the count value C by one (step S13). The control unit 100 determines whether or not the print job is completed (step S14). If the print job is not completed (NO in step S14), the control unit 100 returns to the process of step S12.

When the print job is completed (YES in step S14), the operation control unit 101 compares the count value C with a predetermined cleaning operation mode start threshold (for example, 1000) (step S15).

If the count value C is smaller than the cleaning operation mode start threshold value (NO in step S15), the operation control unit 101 does not execute the cleaning operation mode and returns to the process of step S10.

If the count value C is equal to or greater than the cleaning operation mode start threshold value (YES in step S15), the operation control unit 101 executes the cleaning operation mode (steps S16 to S18). The operation control unit 101 sets the rotation speed of the fur brush 71 to Vb (Vb> Va) (step S16).

Then, the operation control unit 101 executes the cleaning operation mode (step S17). Specifically, the operation control unit 101 causes the drive unit 712 to rotationally drive the fur brush 71 at the rotation speed Vb. Further, the operation control unit 101 drives the driving roller 125 A and the driven roller 125 B to drive the intermediate transfer belt 125 in order to convey the toner discharged from the fur brush 71. Further, the operation control unit 101 applies a bias having the same polarity as the normal charging polarity to the charging brush 80 in order to charge the toner discharged from the fur brush 71 to the same polarity as the normal charging polarity, and a charging bias applying unit 801. To be applied. Further, the operation control unit 101 causes the drive unit 712 to rotationally drive the collection roller 72 in order to collect the toner discharged from the fur brush 71, and causes the collection bias application unit 722 to normally charge the collection roller. A bias having a polarity opposite to the polarity is applied. Further, the operation control unit 101 rotates the toner conveying screw 76 in order to collect the toner collected by the collecting roller 72 at a predetermined position in the toner storage unit 75.

Each control in the above-described cleaning operation mode is executed for a predetermined time (for example, 40 seconds). After the cleaning operation mode ends, the operation control unit 101 resets the count value C (step S18) and returns to the process of step S10.

(Discussion)
FIG. 8 is a diagram illustrating the relationship between the number of rotations of the fur brush 71 rotated in the cleaning operation mode and the accumulated amount of toner accumulated in the fur brush 71. In the figure, the vertical axis indicates the amount of toner accumulated in the fur brush 71, and the horizontal axis indicates the rotational speed of the fur brush 71. Further, K shown on the vertical axis is a threshold value indicating the amount of toner that may cause toner drop in the fur brush 71. This threshold value is determined by the material of the fur brush 71, the viscosity of the toner, and the like.

As shown in FIG. 8, when the fur brush 71 is rotated at a high speed (Vb), the amount of toner accumulated in the fur brush 71 is decreased more quickly than when the fur brush 71 is rotated at a low speed (Va). I understand. For this reason, since the number of rotations of the fur brush 71 necessary for eliminating toner drop is reduced, the fur brush 71 can be efficiently cleaned, and the time required for the cleaning operation mode can be shortened. it can.

FIG. 9 is a diagram illustrating the relationship between the number of recording sheets on which image formation has been performed and the accumulated amount of toner accumulated in the fur brush 71. In FIG. 9, the example shows the transition of the toner accumulation amount in the image forming apparatus 1 according to the first embodiment, and the comparative example shows the transition of the toner accumulation amount in the image forming apparatus that does not have the cleaning operation mode. In FIG. 9, the vertical axis indicates the amount of toner accumulated in the fur brush 71, and the horizontal axis indicates the number of recording sheets on which image formation has been performed.

As shown in FIG. 9, in the image forming apparatus according to the comparative example that does not have the cleaning operation mode, the accumulated amount of toner accumulated in the fur brush 71 increases as the number of recording sheets on which the image is formed increases. While the toner drop occurs, in the image forming apparatus 1 according to the first embodiment having the cleaning operation mode, the increase amount of the toner accumulated in the fur brush 71 is low and the toner does not fall off. I understand.

(Experiment)
In order to confirm the effect of the cleaning operation mode of the image forming apparatus 1 according to the first embodiment, the inventors form two patterns of images of the image forming apparatus 1 according to the first embodiment and the image forming apparatus according to the comparative example. In the apparatus, the image forming operation for forming the toner image on the recording paper P was performed a plurality of times while changing the printing rate, and it was examined whether or not the toner drop occurred. The image forming apparatus according to the comparative example is an image forming apparatus that does not have a cleaning operation mode. The experimental results are shown in FIG. In FIG. 10, a circle indicates that no toner drop occurred during 3000 image forming operations. A triangular mark indicates that one toner drop occurred during the image forming operation of 100 to 3000 sheets. The cross mark indicates that one or more toner drops occurred during 100 image forming operations.

As shown in FIG. 10, in the image forming apparatus according to the comparative example that does not have the cleaning operation mode, when the printing rate is 20%, toner drop occurs when the number of formed images exceeds 200K (200,000 sheets). On the other hand, in the image forming apparatus 1 according to the first embodiment, the toner drop starts to occur at the time when it exceeds 600K (600,000 sheets). As described above, in the image forming apparatus 1 having the cleaning operation mode, compared with the image forming apparatus according to the comparative example that does not have the cleaning operation mode, the toner falls from the brush roller to the outer peripheral surface of the intermediate transfer belt during image formation. It can be seen that there is little risk of smearing the image.

<Embodiment 2>
In the image forming apparatus 1 according to the first embodiment, the toner discharged from the fur brush is collected by the cleaning device 70 in the cleaning operation mode, whereas in the image forming apparatus according to the second embodiment, the fur is The toner discharged from the brush 71 is recovered by the toner recovery device 128 of the image forming unit 12 in addition to being recovered by the cleaning device 70.

As shown in FIG. 2, the toner discharged from the fur brush 71 in the cleaning operation mode is conveyed by the intermediate transfer belt 125 and reaches a position facing the primary transfer roller 126 of the image forming unit 12M. In the image forming apparatus according to the second embodiment, in the cleaning operation mode, the operation control unit 101 biases the primary transfer roller 126 with the same polarity as the polarity of the toner discharged from the fur brush 71. Is applied to the transfer bias applying unit 1261. Since the toner discharged from the fur brush 71 in the cleaning operation mode is mainly toner charged to a polarity opposite to the normal charging polarity, the operation control unit 101 sets the normal charging polarity to the primary transfer roller 126. Applies a reverse bias to the transfer bias applying unit 1261.

Since a bias having the same polarity as the charged polarity of the toner discharged from the fur brush 71 is applied to the primary transfer roller 126, an electric repulsive force acts on the toner discharged from the fur brush 71. The toner moves to the outer peripheral surface of the photosensitive drum 121 of the image forming unit 12M. Of the toner discharged from the fur brush 71, the toner that has not moved to the outer peripheral surface of the photosensitive drum 121 of the image forming unit 12 M is conveyed by the intermediate transfer belt 125 and collected by the cleaning device 70.

The toner that has moved to the outer peripheral surface of the photosensitive drum 121 is conveyed according to the rotation of the photosensitive drum 121 and is collected by the toner collecting device 128 when it reaches a position facing the toner collecting device 128. As shown in FIG. 2, the toner recovery device 128 includes a cleaning blade 1281, a toner storage unit 1282, and a toner conveying screw 1283. The cleaning blade 1281 is made of a flat plate member and extends in the direction of the rotation axis of the photosensitive drum 121. The cleaning blade 1281 is provided so that the tip thereof is in contact with the surface of the photosensitive drum 121, and removes toner remaining on the surface of the photosensitive drum 121 from the surface of the photosensitive drum 121. The removed toner falls and accumulates in the toner storage unit 1282. The toner storage unit 1282 is provided with a toner conveying screw 1283. A toner conveying blade (not shown) is spirally provided on the peripheral surface of the rotation shaft of the toner conveying screw 1283, and the toner in the toner storage unit 1282 is collected at a predetermined position by the toner conveying blade.

As described above, the toner ejected from the fur brush 71 is collected by the toner collecting device 128 of the image forming unit 12 in addition to being collected by the cleaning device 70. Many can be recovered.

The operation control unit 101 operates the photosensitive drum 121, the primary transfer roller 126, and the toner recovery device 128 of the image forming unit 12M in the cleaning operation mode, but the other developing device 122, charging device 123, and The exposure device 124 is not operated. This is because charging, exposure and development steps are not necessary in the cleaning operation mode.

<Modification>
The present invention is not limited to the configuration of the above embodiment, and various modifications can be made.

For example, in the first embodiment, the operation control unit 101 compares the count value with the cleaning operation mode start threshold value, and executes the cleaning operation mode when the count value C is equal to or greater than the threshold value. Although the case has been described, the present invention is not necessarily limited to this case. The operation control unit 101 may execute the cleaning operation mode when receiving an instruction to clean the fur brush 71 from a user, a serviceman, or the like.

Further, the operation control unit 101 controls the recovery bias applying unit (power supply device) 722 so that a bias stronger than the bias applied to the fur brush 71 at the time of image formation is applied in the cleaning operation mode. Good. In addition to rotating the fur brush 71 at a rotational speed higher than the rotational speed of the fur brush 71 during image formation, a bias stronger than the bias applied to the fur brush 71 during image formation is applied. The brush 71 can be cleaned more efficiently and satisfactorily.

In the second embodiment, the case where a bias having the same polarity as the polarity of the toner discharged from the fur brush 71 is applied to the primary transfer roller 126 of the image forming unit 12M has been described. However, a bias having the same polarity as the polarity of the toner discharged from the fur brush 71 may be applied to the primary transfer rollers 126 of the other

image forming units

12C, 12Y, and 12Bk.

In the second embodiment, the case where the toner discharged from the fur brush 71 is recovered by the toner recovery device 128 of the image forming unit 12 in addition to the recovery by the cleaning device 70 has been described. The configuration may be such that the toner discharged from the fur brush 71 is collected only by the toner collecting device 128 of the image forming unit 12 without operating the collecting roller 72 and the toner conveying screw 76 of the device 70.

Claims

An image forming unit for forming a toner image;
An intermediate transfer belt on which a toner image is transferred from the image forming unit to the outer peripheral surface;
A brush roller that contacts the outer peripheral surface of the intermediate transfer belt and collects toner remaining on the outer peripheral surface;
A drive unit that rotationally drives the brush roller;
The brush roller has a cleaning operation mode for performing control to clean the brush roller during non-image formation, and in the cleaning operation mode, the brush roller is rotated at a rotational speed higher than the rotational speed of the brush roller during image formation. And an operation control unit that rotationally drives the image forming apparatus.
A first power supply unit that applies a bias having a polarity opposite to the normal charging polarity of the toner to the brush roller;
The image forming unit includes a photosensitive drum, a transfer roller disposed opposite to the photosensitive drum via the intermediate transfer belt, a second power supply unit that applies a bias to the transfer roller, and the photosensitive drum A toner recovery unit that recovers toner remaining on the outer peripheral surface of the body drum,
The image forming apparatus according to claim 1, wherein the operation control unit causes the second power supply unit to apply a bias having a polarity opposite to a normal charging polarity of the toner in the cleaning operation mode.
A collection roller that contacts the outer peripheral surface of the brush roller and collects the toner collected by the brush roller from the brush roller;
A cleaning blade that contacts the outer peripheral surface of the collection roller and scrapes off the toner collected by the collection roller;
The first power supply unit is connected to the collection roller,
The image forming apparatus according to claim 2, wherein a bias having a polarity opposite to a normal charging polarity of the toner is applied to the brush roller via the collection roller.
The operation control unit causes the first power supply unit to apply a bias stronger than a bias applied to the brush roller to the first power supply unit during image formation to the brush roller in the cleaning operation mode. The image forming apparatus according to claim 2.
A charging member that is disposed upstream of the brush roller in the traveling direction of the intermediate transfer belt and imparts a charge having the same polarity as the normal charging polarity to the toner remaining on the outer peripheral surface of the intermediate transfer belt in the cleaning operation mode. The image forming apparatus according to claim 1, further comprising:
The operation control unit counts the number of recording sheets on which image formation has been performed after executing the cleaning operation mode, and executes the cleaning operation mode at the time of non-image formation after the number of sheets exceeds a predetermined number. The image forming apparatus according to claim 1.