JP2007232842A - Image forming apparatus and belt cleaning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus and a belt cleaning method that can efficiently remove not only toner particles, but also external additives. <P>SOLUTION: The image forming apparatus comprises a laser unit 401 which generates a predetermined latent image on a photoreceptor drum, a development unit 103 which develops the latent image on the photoreceptor drum by a toner, a transfer roller 120 which transfers the developed latent image as a developed image to an intermediate transfer belt, a secondary transfer roller 117 which can contact and leave the intermediate transfer belt and leaves the intermediate transfer belt, in response to a signal indicating cleaning processing, and a cleaning unit 121 which cleans a developed image that is transferred to the intermediate transfer belt but is not transferred to a sheet member. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile, and more particularly, to an image forming apparatus having an improved cleaning force for a transfer belt.

In the image forming apparatus, out of the toner particles constituting the toner (developer) and the external additive (abrasive), the external additive always polishes the surface of the photoconductor drum so that the surface of the photoconductor drum is in a constant state. By maintaining this, it is possible to prevent deterioration in image quality even during long-term use. In recent years, improvement in image quality of output images has been demanded, and accordingly, the amount of external additive added has increased.
JP 2004-279902 A

  By the way, the external additive is easily detached from the surface of the toner particles. For this reason, a part of the external additive added in a large amount remains on the transfer belt at the time of transfer processing of the developed image to a sheet as a sheet member. Here, toner particles and external additives remaining on the transfer belt are removed from the transfer belt by physical (brush cleaning or the like) and electrical (bias cleaning) in the cleaning process after the transfer process. However, since the external additive has a diameter of several tenths to several hundreds smaller than that of the toner particles, the external additive is difficult to physically clean as compared with the toner particles. Further, since the charge amount of the external additive is smaller than that of the toner particles, electrical cleaning is difficult.

  When printing is continued with the external additive remaining on the transfer belt, the external additive remaining on the transfer belt changes the whitening or roughness of the surface of the transfer belt, that is, changes the surface characteristics. In particular, when a large amount of the same output image is output, the external additive on the transfer belt is localized, so that a difference in surface characteristics appears significantly. In such a state, the change in the surface characteristics causes, for example, afterimages and uneven printing, which affects the output image, that is, the image quality deteriorates.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and a belt cleaning method capable of efficiently removing not only toner particles but also external additives.

  The present invention employs the following means in order to achieve the above object. That is, an image forming apparatus according to the present invention includes a laser unit that generates a predetermined latent image on a photosensitive drum, a developing unit that develops the latent image on the photosensitive drum with toner, and the developed latent image on an intermediate transfer belt. A transfer roller for transferring the image as a developed image, a secondary transfer roller that can be pressed against and separated from the intermediate transfer belt, and separated from the intermediate transfer belt based on a signal indicating that the cleaning process is performed, and transferred to the intermediate transfer belt And a cleaning unit for cleaning the developed image that has not been transferred to the sheet member.

  In this configuration, predetermined image data is developed with predetermined toner during the cleaning process, and the developed image is cleaned. For this reason, it is possible to efficiently remove the external additive remaining on the intermediate transfer belt using the toner as a medium. As a result, partial whitening of the intermediate transfer belt and changes in surface characteristics can be prevented, and stable image output without printing unevenness can be achieved over a long period of time.

  The cleaning control unit may send the signal indicating that the cleaning process is performed to the secondary transfer roller so that the secondary transfer roller is separated even when the developed image is transferred.

  In addition, the cleaning control unit has a configuration in which an output image corresponding to the developed image last transferred to the sheet member is transmitted to the laser unit, and a signal indicating the cleaning process is transmitted to the secondary transfer roller.

  In this configuration, the same developed image as the image printed last is cleaned, and a portion with a large amount of residual toner can be efficiently cleaned, so that the amount of toner used for cleaning can be suppressed.

  The cleaning control unit combines the output images corresponding to the plurality of developed images that have been transferred to the sheet member, transmits the combined output image to the laser unit, and indicates that the cleaning process is performed. There are a configuration in which a signal is transmitted to the secondary transfer roller and a configuration in which output images corresponding to a plurality of developed images that have been transferred to the sheet member are synthesized and transmitted.

  Even with this configuration, it is possible to efficiently clean locations that are considered to have a relatively large amount of residual toner, except for locations that have been cleaned by multiple printing processes, thus achieving a wide range of cleaning while suppressing the amount of toner used for cleaning. it can.

  In addition, the cleaning control unit has a configuration in which a solid image having the entire range of the sheet member as a toner adhesion target is transmitted to the laser unit as an output image, and a signal indicating that the cleaning process is performed is transmitted to the secondary transfer roller.

  In this configuration, it is possible to surely clean the entire surface relating to printing of the intermediate transfer roller.

  Further, when the developing device includes a plurality of types of toner, the developing device receives a signal indicating that it is a cleaning process, and among the plurality of types of toner, only one toner that is determined to be used in the cleaning process in advance is used. Is used to develop the latent image on the photosensitive drum.

  This configuration is advantageous in that a toner having the best cleaning efficiency can be selected as a predetermined cleaning toner, or an inexpensive toner can be selected.

  Further, the developing device has a configuration in which the latent image on the photosensitive drum is developed at a density lower than that of the developed image last transferred to the sheet member in response to a signal indicating that the cleaning process is performed.

  As a result, the amount of toner consumed during the cleaning process can be suppressed.

  Since the predetermined image data is developed with the predetermined toner and the developed image is cleaned during the cleaning process, the external additive remaining on the intermediate transfer belt can be efficiently removed using the toner as a medium. As a result, partial whitening of the intermediate transfer belt and changes in surface characteristics can be prevented, and stable image output without printing unevenness can be achieved over a long period of time.

  In addition, by cleaning the developed image that is the same as the image printed last, it is possible to efficiently clean a portion with a large amount of residual toner, so that the amount of toner used for cleaning can be suppressed.

  Further, by performing the cleaning process with the solid image, it is possible to surely clean the entire surface relating to printing of the intermediate transfer roller.

  Furthermore, it is advantageous in that it is possible to select a toner with the highest cleaning efficiency or an inexpensive toner by predetermining the toner for the cleaning process.

  Further, the developing device receives a signal indicating that it is a cleaning process, and develops the latent image on the photosensitive drum at a density lower than the developed image transferred to the sheet member at the end, so that it is consumed during the cleaning process. The amount of toner to be reduced can be suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: It is not the thing of the character which limits the technical scope of this invention.

  FIG. 1 is a schematic diagram of the image forming apparatus 101. However, details of each part not directly related to the present invention are omitted. Specifically, the image forming apparatus 101 corresponds to a digital copying machine or a printer. Here, a color printer will be described as an example.

(Printing process and residual toner recovery process)
First, an image forming process (printing process and residual toner collecting process) in the image forming apparatus 101 will be described. When the image forming apparatus 101 is turned on, various parameters are initialized by the print control unit, and the temperature of the heating roller 108a in the fixing device 108 is sensed. When various initializations are completed and the temperature of the heating roller 108a rises to a predetermined value or higher, image forming processing in the image forming apparatus 101 becomes possible.

  In this state, when image data is input from a computer (not shown) or the like, first, the photosensitive drum 102 is charged by the charging roller 109. When the photosensitive drum 102 is charged, the laser unit 104 forms a latent image on the photosensitive drum 102 based on the image data. The laser is bent by the reflecting mirror 110 according to the position of the laser unit 104.

  When a latent image is formed on the photosensitive drum 102 by the laser unit 104, a rotating drum type developing device (rotary developing device) 103 is rotated around a rotating shaft 103a configured in a direction perpendicular to FIG. The developing unit 111 that is rotated in the direction 103 b and stores the corresponding color toner is disposed at a position facing the photosensitive drum 102. In this state, the latent image on the photosensitive drum 102 is developed with toner stored in the developing unit, and transferred to the intermediate transfer belt 107 by the transfer roller 120. The rotary drum type developing device 103 includes four developing units 111 (Y), (C), (M), and (K) that store a plurality of toner types, that is, yellow, cyan, magenta, and black toners, respectively. have. The four developing units 111 have substantially the same configuration except that the positions of the opening units at the time of toner supply are different.

  By repeating the transfer to the intermediate transfer belt 107 for each color, a full color image is formed on the intermediate transfer belt. Here, a color printer is described as an example. However, when the developing unit 103 stores only black toner and is arranged at a position facing the photosensitive drum 102 without rotating, the latent image is developed. Can be a monochrome printer. In the case of a monochrome printer, black toner is transferred to the intermediate transfer belt 107 only once, and a monochrome image is formed on the intermediate transfer belt 107.

  In synchronization with the transfer to the intermediate transfer belt 107, the paper taken out from the paper feed cassette 113 through the paper feed unit 114 is conveyed to the registration roller pair 116 through the conveyance path 115. Thereafter, the sheet is conveyed from the registration roller pair 116 to the intermediate transfer belt 107 in time with the developed image on the intermediate transfer belt 107 and guided to the secondary transfer roller 117.

  The secondary transfer roller 117 is configured to be capable of being pressed against and separated from the intermediate transfer belt 107, and is pressed against the intermediate transfer belt 107 after a full-color developed image is formed on the intermediate transfer belt 107. At the time of press contact, the developed image formed on the intermediate transfer belt 107 is transferred onto the sheet by the transfer bias applied to the secondary transfer roller 117.

  The sheet on which the developed image is transferred is guided to the fixing device 108 via the conveyance path 118, and the developed image is fixed on the sheet by the heating roller 108a and the pressure roller 108b. Thereafter, the sheet is discharged to the discharge unit 119.

  When the transfer of the developed image onto the paper is completed, the intermediate transfer belt 107 is cleaned by the cleaning unit 121. As shown in FIG. 2, the cleaning unit 121 includes a housing 206, a fixing member 208, a conductive brush roller 203, a collection roller 204, and a rubber blade 205.

  After the sheet is pressed against the intermediate transfer belt 107 by the secondary transfer roller 117 and the developed image is transferred to the sheet, the intermediate transfer belt 107 is guided between the driving roller 201 and the conductive brush roller 203.

  Here, the conductive brush roller 203 is formed by winding a long woven fabric in which resin brush fibers (filaments) such as 6 nylon are planted at high density in a spiral shape around the entire circumference of the rotating roller 207. It is bonded to form a roll.

  The conductive brush roller 203 can be pressed against and separated from the intermediate transfer belt 107 by a spring and a cam (not shown). During the cleaning process, the cam is brought into pressure contact with the intermediate belt 107.

  One of the bearings of the collection roller 204 is a conductive bearing, and a bias can be supplied to the collection roller 204 through this bearing. The bearing of the conductive brush roller 203 is non-conductive, and the bias applied to the collection roller 204 can act as a cleaning bias without loss. Further, the driving roller 201 has a conductive rubber 202 on the outer periphery thereof and is grounded, and serves as a cleaning counter electrode. That is, the cleaning current flows from the collection roller 204 to the driving roller 201 via the conductive brush roller 203 and the intermediate transfer belt 107.

  With such a configuration, when the intermediate transfer belt 107 is guided between the driving roller 201 and the conductive brush roller 203, the charged toner, that is, toner particles and external additives are electrically discharged by the cleaning bias and the conductive brush roller 203. Then, it is physically removed from the intermediate transfer belt 107 and transferred to the conductive brush roller 203. The toner transferred to the conductive brush roller 203 is physically and electrically transferred to the recovery roller 204 by the biting of the conductive brush roller 203 into the recovery roller 204 and the cleaning bias.

  The toner adhering to the surface of the collecting roller 204 is scraped off by the rubber blade 205, collected by a rotating body 209 having a spiral shape provided on the back surface of the fixing member, and collected in a waste toner box (not shown).

  Through the above processing, the toner remaining on the surface of the intermediate transfer belt 107 is removed and collected.

  The above is the main printing and residual toner collection processing in image formation of the image forming apparatus 101, which is controlled by the print control unit 401 shown in the schematic functional block diagram of FIG.

  In the image forming apparatus 101, as shown in the schematic configuration diagram of FIG. 3, a CPU (Central Processing Unit) 301, a RAM (Random Access Memory) 302, a ROM (Read Only Memory) 303, an HDD (Hard Disk Drive). 304 and a driver 305 corresponding to each drive unit in the printing process are connected via an internal bus 306. The CPU 301 uses, for example, the RAM 302 as a work area, executes a program stored in the ROM 303, the HDD 304, and the like, and exchanges data and commands with the driver 305 based on the execution result, thereby printing control unit 401. The operation of each drive unit 307 shown in FIGS. 1 and 2 is controlled.

(Cleaning process)
Next, operations of the cleaning control unit 402 and the driving units 307 according to the present invention will be described in detail.

  When the series of printing processes described above is completed, a message to that effect is sent from the print control unit 401 to the cleaning control unit 402. The cleaning control unit 402 that has received the signal indicating that the printing process has been completed performs a cleaning process subsequent to the printing process.

  That is, the cleaning control unit 402 transmits predetermined image data to the laser unit 104 and causes the photosensitive drum 102 to generate a latent image corresponding to the image data. Note that the predetermined image data transmitted to the laser unit 104 in the cleaning process is, for example, the image data last printed on the paper by the printing process.

  Further, the cleaning control unit 402 transmits a signal to the developing unit 103 to develop the latent image using a predetermined toner. The predetermined toner here is a predetermined toner, for example, yellow (Y).

  The latent image developed by the developing device 103 is transferred to the intermediate transfer belt 107 as a developed image by the transfer roller 120. At this time, the cleaning control unit 402 moves the photosensitive drum 102 or intermediate so that the moving speed (rotational speed) of the intermediate transfer belt 107 is faster or slower than the rotational speed of the photosensitive drum 102. A motor for driving the transfer belt 107 may be controlled. Here, “early” or “slow” means “early” or “slow” compared to the above-described printing process. The change in speed causes rubbing between the intermediate transfer belt 107 and the rotating drum 102, so that the external additive remaining on the intermediate transfer belt 107 forms a newly transferred developed image toner. It becomes easy to adhere to.

  Next, the developed image transferred to the intermediate transfer belt 107 and developed with yellow is guided to the secondary transfer roller 117 based on the movement of the intermediate transfer belt 107. However, the cleaning control unit 402 transmits a signal to the secondary transfer roller 117 that it is separated from the intermediate transfer belt 107 (drive roller 201) and that a transfer bias is not applied. With this signal, the developed image is guided to the cleaning unit 121 without being transferred to the paper by the secondary transfer roller 117.

The cleaning unit 121 that has received the signal indicating that the cleaning process is performed from the cleaning control unit 402 applies a larger cleaning bias to the collection roller 204 than in the above-described residual toner collection process. By the application and the conductive brush roller 203 described above, the toner that electrically and physically forms the developed image is collected as waste toner. The reason why the cleaning bias larger than that in the residual toner recovery process is applied to the recovery roller 204 is to obtain an appropriate bias for recovering a large amount of toner constituting the developed image itself, not the residual toner. .
(Cleaning process for color printing)
FIG. 5 shows the control of each drive unit 307 during the printing process and the cleaning process. FIG. 5 shows the control during color printing, and FIG. 6 shows the control of each drive unit when there is no cleaning process as a comparative example.

  First, in FIG. 5, when the detection unit detects a predetermined start position of the intermediate transfer belt, the print control unit 401 transmits a predetermined signal to the laser unit, so that the laser unit 104 is turned on. In the ON state, the laser unit 104 turns on and off the laser based on the image data (Y) corresponding to the input first color (here, yellow), thereby the latent image corresponding to the first color. Is formed on the photosensitive drum 102 (FIG. 5: S501).

  Subsequently, the developing device 103 develops the latent image with yellow toner based on a command from the print control unit 401. At the time of development, the bias from the developing unit 103 toward the photosensitive drum 102 is turned on, and development is performed with the bias (FIG. 5: S502).

  The developed image developed on the photosensitive drum 102 is transferred to the intermediate transfer belt 107 by the transfer roller 120. At the time of the transfer, the transfer bias from the photosensitive drum 102 toward the transfer roller 120 is turned ON, and transfer is performed by the bias (FIG. 5: S503).

  Since color printing is performed, the transfer to the paper by the secondary transfer roller 117 is not performed, and the residual toner collecting process is not performed, so that the bias is not applied to the secondary transfer roller 117 and the cleaning unit 121. (FIG. 5: S504, S505).

  The above processing is performed for each toner (magenta, cyan, black), so that a full-color developed image is generated on the intermediate transfer belt 107 (FIG. 5: S506).

  When the full-color developed image is generated, the secondary transfer roller 117 subsequently receives signals from the print control unit 401 that the intermediate transfer belt 107 (drive roller 201) is pressed and a transfer bias is applied. Then, the developed image is transferred to the paper (FIG. 5: S507).

  Further, the intermediate transfer belt 107 after the developed image is transferred is guided to the cleaning unit 121. Here, the cleaning unit 121 performs a residual toner collection process by applying a cleaning bias for collecting the residual toner to the collection roller 204 based on a signal from the print control unit 401 (FIG. 5: S508).

  Subsequently, the cleaning control unit 402 receives a signal from the print control unit 401 indicating that the printing process has ended, and transmits a predetermined signal to the laser unit, so that the laser unit 104 is turned on. In the ON state, the laser unit 104 forms a latent image used for the cleaning process on the photosensitive drum 102 by turning the laser on and off based on the input image data (FIG. 5: S509).

  The image data input here corresponds to, for example, image data corresponding to yellow, other image data corresponding to magenta, cyan, and black, or image data generated by combining them. Further, for example, color image data printed immediately before, or other image data generated by combining image data of a plurality of pages from the last page (for example, color image data from the fifth page to the tenth page (final page)) corresponds. . Note that the composition is performed by the cleaning control unit 402, for example. Of course, solid image data that covers the entire range of the paper may be used.

  Subsequently, the developing device 103 develops the latent image with a predetermined yellow toner, for example, based on a command from the cleaning control unit 402. At the time of development, the bias from the developing unit 103 toward the photosensitive drum 102 is turned on, and development is performed with the bias (FIG. 5: S510).

  The toner used for development is not particularly limited to yellow, and for example, black, magenta, or cyan may be selected. As the toner to be used, for example, a toner having an excellent cleaning power as compared with other toners, a toner that is advantageous in terms of price, or a toner that causes little peeling of the external additive from the toner particles is used. Alternatively, the toner amount for each toner type remaining in the developing device may be detected, and the cleaning control unit 402 may determine the toner type used for the cleaning process each time based on the remaining toner amount.

  In the cleaning process, since the developed image is not output, it is not always necessary to have the same level of density as when it is output. In other words, the bias at the time of development is lowered, or the density of the developed image at the time of the cleaning process is made lower than the density at the time of outputting to paper by controlling the photoreceptor potential, exposure amount, image processing, system speed, etc. May be. For example, the density can be 10% to 80% of normal printing. As a result, toner consumption during cleaning can be suppressed.

  The developed image developed with yellow toner on the photosensitive drum 102 is transferred to the intermediate transfer belt 107 by the transfer roller 120. At the time of the transfer, the transfer bias from the photosensitive drum 102 toward the transfer roller 120 is turned ON, and transfer is performed by the bias (FIG. 5: S511). The transfer bias during the transfer is the same as that during the printing process.

  Since the subsequent processing at the secondary transfer roller 117 is a cleaning process, no bias is applied to the secondary transfer roller 117, and the developed image is not transferred onto the paper. Naturally, neither the pressure contact of the secondary transfer roller 117 nor the conveyance of the paper used for printing to the secondary transfer roller is performed (FIG. 5: S511).

  In the cleaning unit 121, a cleaning bias for removing the developed image is applied (FIG. 5: S512). As the cleaning bias applied at this time, a cleaning bias larger than the cleaning bias in the immediately preceding residual toner recovery process (S508) is applied. This is because, in the cleaning process, it is necessary to remove more toner than the residual toner in the residual toner removal process, and thus a large cleaning bias is applied corresponding to the large amount of toner.

  As described above, by using the toner in the cleaning process (S509 to S513), that is, cleaning the external additive, the external additive remaining on the intermediate transfer belt is efficiently removed using the toner as a medium. can do. As a result, partial whitening of the intermediate transfer belt and changes in surface characteristics can be prevented, and stable image output without printing unevenness can be achieved over a long period of time.

(Cleaning process for monochrome printing)
Next, FIG. 7 shows the control of each drive unit 307 during the printing process and the cleaning process during monochrome printing (including a monochrome printer). FIG. 8 shows the control of each drive unit when there is no cleaning process as a comparative example.

  First, in FIG. 7, when the detection unit detects a predetermined start position of the intermediate transfer belt, the print control unit 401 transmits a predetermined signal to the laser unit, so that the laser unit 104 is turned on. In the ON state, the laser unit 104 turns on and off the laser based on the input image data to form a latent image corresponding to the image data on the photosensitive drum 102 (FIG. 7: S701).

  Subsequently, the developing device 103 develops the latent image with black toner based on a command from the print control unit 401. At the time of development, the bias from the developing unit 103 toward the photosensitive drum 102 is turned on, and development is performed with the bias (FIG. 7: S702).

  The developed image developed on the photosensitive drum 102 is transferred to the intermediate transfer belt 107 by the transfer roller 120. At the time of the transfer, the transfer bias from the photosensitive drum 102 toward the transfer roller 120 is turned ON, and transfer is performed by the bias (FIG. 7: S703).

  When the developed image is generated, the secondary transfer roller 117 subsequently receives a signal from the print control unit 401 that the intermediate transfer belt 107 (drive roller 201) is pressed and a transfer bias is applied. Then, the developed image is transferred to the sheet (FIG. 7: S704).

  Further, the intermediate transfer belt 107 after the developed image is transferred is guided to the cleaning unit 121. Here, the cleaning unit 121 performs a residual toner collection process by applying a cleaning bias for collecting the residual toner to the collection roller 204 based on a signal from the print control unit 401 (FIG. 7: S705).

  In monochrome printing, the above process is repeated for the number of output sheets from the first page to the last page, with the above as one cycle. The bias for collecting the residual toner is continuously applied until the end of printing.

  Subsequently, the cleaning control unit 402 receives a signal from the print control unit 401 indicating that the printing process has ended, and transmits a predetermined signal to the laser unit, so that the laser unit 104 is turned on. In the ON state, the laser unit 104 forms a latent image used for the cleaning process on the photosensitive drum 102 by turning on and off the laser based on the input image data (FIG. 7: S706).

  The image data input here is generated, for example, by combining image data of the last page printed immediately before or image data of other pages from the last page (for example, from the fifth page to the tenth page (last page)). Applicable image data. Of course, solid image data that covers the entire range of the paper may be used.

  Subsequently, the developing device 103 develops the latent image with black toner based on a command from the cleaning control unit 402. At the time of development, the bias from the developing unit 103 toward the photosensitive drum 102 is turned on, and development is performed with the bias (FIG. 7: S707).

  Further, since the developed image is not output in the cleaning process, the same level of density as that in the print output is not necessarily required as in the cleaning process at the time of color printing.

  The developed image developed on the photosensitive drum 102 is transferred to the intermediate transfer belt 107 by the transfer roller 120. At the time of the transfer, the transfer bias from the photosensitive drum 102 toward the transfer roller 120 is turned on, and transfer is performed by the bias (FIG. 7: S708). The transfer bias during the transfer is the same as that during the printing process.

  Since the subsequent processing at the secondary transfer roller 117 is a cleaning process, no bias is applied to the secondary transfer roller 117, and the developed image is not transferred onto the paper. Naturally, neither the pressure contact of the secondary transfer roller 117 nor the conveyance of the paper used for printing to the secondary transfer roller is performed (FIG. 7: S709).

  In the cleaning unit 121, a cleaning bias for removing the developed image is applied (FIG. 7: S710). The cleaning bias applied at this time is larger than the cleaning bias in the immediately preceding residual toner recovery process, for the same reason as in color printing.

  As described above, even during monochrome printing, by using toner in the cleaning process (S706 to S710), the external additive remaining on the intermediate transfer belt can be efficiently removed using the toner as a medium. it can. As a result, partial whitening of the intermediate transfer belt and changes in surface characteristics can be prevented, and stable image output without printing unevenness can be achieved over a long period of time.

Example 1
The implementation conditions and results when the cleaning process is actually performed are shown below.

  FIG. 9 shows the cleaning process conditions and results during color printing.

*conditions*
・ Intermediate transfer belt:
Conductive PVDF, film thickness 150μm, volume resistance 1E + 9Ω ・ cm, surface resistance 1E + 10Ω
・ Conductive brush roller:
Brush material 6-nylon (conductive fiber), brush diameter 14mm, filament density 37, 200 filaments / square centimeter, filament thickness 2 denier ・ Printing mode:
Color continuous printing 10 sheets, total 2500 printing (10000 images)
・ Print sample:
Print rate 20% (YMCK color print rate 5%)
・ System speed:
160mm / sec
・ Cleaning process:
Cleaning process (cleaning with yellow toner) and no cleaning process shown in FIG. 5 (corresponding to FIG. 6)
Under the above conditions, the maximum color difference of the intermediate transfer belt after the cleaning process was measured.

In addition, the color difference meter (Minolta Co., Ltd. product, CR-241) was used for the measurement. In the color difference meter, if the ΔE value in the Lab color system is less than 15, a printed matter having no afterimage due to the residue can be output, and if it is 15 or more, a printed matter in which the afterimage can be confirmed visually is output.

*result*
・ With cleaning process:
Maximum color difference on the surface of the intermediate transfer belt ΔE = 5.15
・ Results without cleaning:
Maximum color difference on the surface of the intermediate transfer belt ΔE = 15.34
Thus, it can be confirmed that the ΔE value decreased to about 33% by the cleaning process.

(Example 2)
In Example 2, the implementation conditions and results when the above-described cleaning process is performed during monochrome printing are shown below. In the monochrome printing, the same image data is continuously printed.

  FIG. 10 shows the cleaning process conditions and results during monochrome printing. Only the points where the conditions are different from those in Example 1 will be described.

*conditions*
・ Printing mode:
Monochrome continuous printing 100 sheets (same image data), total 10,000 sheets printing (10000 images)
-Print sample:
20% printing rate (K only)
・ Cleaning process:
Cleaning process and no cleaning process shown in FIG. 7 (corresponding to FIG. 8)
Under the above conditions, the maximum color difference of the intermediate transfer belt after the cleaning process was measured.

  Note that the measuring equipment and the like are the same as those in the first embodiment.

*result*
・ With cleaning process:
Maximum color difference on the surface of the intermediate transfer belt ΔE = 13.50
・ Results without cleaning:
Maximum color difference on the surface of the intermediate transfer belt ΔE = 18.16
Thus, it can be confirmed that the ΔE value decreased to about 74.3% by the cleaning process.

(Example 3)
In Example 3, the implementation conditions and results when the above cleaning process is performed during monochrome printing are shown below. The difference from the second embodiment is that the second embodiment continuously prints the same image data, but the third embodiment prints different image data.

  FIG. 11 shows the cleaning process conditions and results during monochrome printing. Only the points where the conditions are different from those in Example 1 will be described.

*conditions*
・ Printing mode:
Monochrome continuous printing 100 sheets (different image data), total 10,000 printing (10000 images)
・ Print sample:
20% printing rate (K only)
・ Cleaning process:
Cleaning process and no cleaning process shown in FIG. 7 (corresponding to FIG. 8)
Under the above conditions, the maximum color difference of the intermediate transfer belt after the cleaning process was measured.

  Note that the measuring equipment and the like are the same as those in the first embodiment.

*result*
・ With cleaning process:
Maximum color difference ΔE = 13.16 on the surface of the intermediate transfer belt
・ Results without cleaning:
Maximum color difference on the surface of the intermediate transfer belt ΔE = 16.16
Thus, it can be confirmed that the ΔE value is corrected to about 81% by the cleaning process.
(Modification)
The present invention is not limited to the above, and various changes may be made.

  In order to increase the cleaning efficiency in the cleaning process, the following conditions can be given.

  As the toner used for the cleaning process, any type of toner may be used, but it is more preferable to use a toner having the smallest toner particle diameter and high sphericity among a plurality of types. . This is because the smaller the diameter, the larger the surface area of the toner particles and the easier it is for the external additive remaining on the intermediate transfer belt to adhere to the surface. However, the smaller the toner particle diameter, the greater the non-electrostatic adhesion force. Therefore, the higher the sphericity of the toner shape, the stronger the influence of the cleaning bias, and the easier it is to remove it from the intermediate transfer belt. Because.

  In the cleaning process at the time of color printing, it is preferable to use image data corresponding to a specific color (for example, black) of the last page printed out. In the case of continuous color printing, since four types of image data corresponding to each color are developed for each page, an external additive afterimage corresponding to an image pattern of a specific color is formed on the intermediate transfer belt in a specific portion. The remaining phenomenon is unlikely to occur. For this reason, by using image data of a specific color on the last page, it is possible to perform sufficient cleaning at a low cost.

  On the other hand, in the cleaning process during monochrome printing, only black toner is used for development. For this reason, the external additive afterimage is more likely to remain on the intermediate transfer belt than during color printing. Therefore, it is preferable to combine and use at least a plurality of pages of image data from the last page of image data.

  Moreover, it is desirable that the brush fiber of the conductive brush roller has a thickness of 1 to 6 denier. As for the material of the brush fibers, nylons such as 6-nylon and 12-nylon, polyesters, and acrylics are preferably used. Moreover, it is preferable to add carbon black in order to impart conductivity.

  In the above embodiment, the amount of biting of the brush fibers into the intermediate transfer roller is set to 1 ± 0.2 mm, but there is no particular problem if it is less than half the brush hair length. It is preferable that the thickness and the amount of biting of the preferred brush fiber are set in the range of 1 to 6 denier and 0.5 to 1.5 mm, respectively.

  The conductive brush roller rotates in the reverse direction opposite to the rotation direction of the intermediate transfer belt, and the linear velocity ratio at the contact portion is set to 1.1. The linear velocity ratio value is preferably set in the range of 0.8 to 1.2.

  Since the image forming apparatus according to the present invention is excellent in removing toner particles and external additives from the belt, the image forming apparatus is useful as an image forming apparatus capable of stably outputting a good image output over a long period of time.

1 is a schematic diagram of an image forming apparatus according to the present invention. Schematic which shows the structure of a cleaning unit. 1 is a schematic configuration diagram of an image forming apparatus. 1 is a schematic functional block diagram of an image forming apparatus. 6 is a timing chart of each driving unit during color printing processing and cleaning processing. 6 is a timing chart of each driving unit during color printing processing. 6 is a timing chart of each driving unit during monochrome printing processing and cleaning processing. The timing chart of each drive part at the time of a monochrome printing process. The figure which shows the conditions and result of Example 1. FIG. The figure which shows the conditions and result of Example 2. FIG. The figure which shows the conditions and result of Example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Image forming apparatus 102 Photosensitive drum 103 Rotating drum type developing device 103a Central axis 103b Circumferential direction 104 Laser unit 105 Toner storage unit stage 106 Toner supply unit 107 Intermediate transfer belt 108 Fixing device 109 Charging roller 110 Reflection mirror 111 Development unit 113 Supply Paper cassette 114 Paper feed unit 115, 118 Conveying path 116 Registration roller pair 117 Secondary transfer roller 119 Discharge unit 120 Transfer roller 121 Cleaning unit 201 Drive roller 201
202 conductive rubber 203 conductive brush roller 204 collection roller 205 rubber blade 206 housing 207 rotating roller 208 fixed member 209 rotating body 401 print control unit 402 cleaning control unit

Claims (9)

A laser unit that generates a predetermined latent image on the photosensitive drum;
A developing unit for developing the latent image on the photosensitive drum with toner;
A transfer roller for transferring the developed latent image to the intermediate transfer belt as a developed image;
A secondary transfer roller that can be pressed against and separated from the intermediate transfer belt, and is separated from the intermediate transfer belt based on a signal indicating that it is a cleaning process;
A cleaning unit for cleaning a developed image transferred to the intermediate transfer belt and not transferred to the sheet member;
An image forming apparatus.   The image forming apparatus according to claim 1, further comprising a cleaning control unit that transmits a signal indicating a cleaning process to the secondary transfer roller. The cleaning control unit transmits an output image corresponding to the developed image finally transferred to the sheet member to the laser unit, and transmits a signal indicating the cleaning process to the secondary transfer roller,
The image forming apparatus according to claim 2, wherein the cleaning unit cleans a developed image that is the same as the developed image last transferred to the sheet member. The cleaning control unit combines output images corresponding to a plurality of developed images that have been transferred to the sheet member, transmits the combined output image to the laser unit, and indicates that the cleaning process is performed. Is sent to the secondary transfer roller,
The image forming apparatus according to claim 2, wherein the cleaning unit cleans a developed image corresponding to the synthesized output image.   The image forming apparatus according to claim 4, wherein the cleaning control unit synthesizes output images corresponding to a plurality of developed images that have been transferred to the sheet member. The cleaning control unit transmits, as an output image, a solid image in which the entire range of the sheet member is a toner adhesion target to the laser unit, and transmits a signal indicating the cleaning process to the secondary transfer roller,
The image forming apparatus according to claim 2, wherein the cleaning unit cleans a developed image corresponding to the solid image. When the developing device includes a plurality of types of toner,
The developing device receives a signal indicating that it is a cleaning process, and uses only one toner, which is determined to be used in the cleaning process in advance, among the plurality of types of toners to generate a latent image on the photosensitive drum. The image forming apparatus according to claim 1, which is developed.   2. The image forming apparatus according to claim 1, wherein the developing device develops the latent image on the photosensitive drum at a density lower than that of the developed image last transferred to the sheet member in response to a signal indicating that it is a cleaning process. apparatus. Generating a predetermined latent image on the photosensitive drum;
Developing a latent image on the photosensitive drum with toner;
Transferring the developed latent image to the intermediate transfer belt as a developed image;
Canceling the transfer of the developed image to the sheet member;
A cleaning step for cleaning the developed image transferred to the intermediate transfer belt;
A belt cleaning method comprising:

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