JP6213398B2 - Image forming apparatus and cleaning member movement control method - Google Patents

Description

  The present invention relates to an image forming apparatus capable of forming an image by an electrophotographic method and a method for controlling the movement of a cleaning member provided in the image forming apparatus.

  In general, in an image forming apparatus such as a printer capable of forming an image by an electrophotographic method, the surface of an image carrier such as a photosensitive drum is charged by a charging member such as a charging roller, and the surface of the image carrier is electrostatically charged. A latent image is formed (see, for example, Patent Document 1).

  In this type of image forming apparatus, there may be a problem called image flow in which the electrostatic latent image formed on the image carrier is disturbed. It is widely known that such a problem is caused by a discharge product generated by a discharge generated between the charging member and the surface of the image carrier when the surface of the image carrier is charged. That is, the discharge product generated by the discharge adheres to the surface of the image carrier, and the discharge product absorbs moisture in the air and reduces the electrical resistance of the surface of the image carrier. It is known that the formed electrostatic latent image is disturbed.

  On the other hand, a configuration is known in which a metal oxide that functions as an abrasive is contained in a toner, and a polishing member such as a polishing roller that polishes the surface of an image carrier is provided. Also known is a configuration in which an image forming process for forming a predetermined toner image on the surface of the image carrier is performed to polish the surface of the image carrier by a polishing member at high temperatures and high humidity where image flow is likely to occur. Yes. Here, when the metal oxide contained in the toner locally adheres to the surface of the charging member, the electrical resistance of the adhered portion may increase and cause an image defect. Therefore, in these configurations, a cleaning member such as a cleaning roller for cleaning the surface of the charging member is provided.

JP 2006-47397 A

  By the way, in this type of image forming apparatus, the occurrence of image flow may be noticeable while the number of image formations after the start of use of the charging member is small. Such a phenomenon is considered to occur because components such as the conductive agent and process oil contained in the charging member contribute to the occurrence of image flow. Specifically, the contained component leaked to the surface of the charging member is transferred from the charging member to the image carrier at the contact portion between the charging member and the image carrier, thereby reducing the electrical resistance of the surface of the image carrier. Conceivable. As the number of image formations increases, the metal oxide contained in the toner gradually adheres to the surface of the charging member to prevent leakage of the contained components, so that the occurrence of image flow is gradually suppressed.

  An object of the present invention is to provide an image forming apparatus and a cleaning member movement control method capable of suppressing the occurrence of image flow while the number of times of image formation after the start of use of a charging member is small.

  An image forming apparatus according to an aspect of the present invention includes an image carrier, a charging member, an image formation control unit, a cleaning member, a movement mechanism, and a movement control unit. The image carrier carries a toner image formed by a toner containing a metal oxide. The charging member is provided in contact with the image carrier and charges the image carrier. The image forming control unit executes an image forming process for forming a predetermined toner image on the surface of the image carrier. The cleaning member removes the metal oxide attached to the surface of the charging member. The moving mechanism moves the cleaning member between a first position in contact with the charging member and a second position separated from the charging member. The movement control unit moves the cleaning member from the first position to the second position when the image forming process is executed.

  The cleaning member movement control method according to another aspect of the present invention includes an image carrier that carries a toner image formed of a toner containing a metal oxide, and an image carrier that is provided in contact with the image carrier. A charging member for charging the body, a cleaning member for removing the metal oxide adhering to the surface of the charging member, a first position for contacting the cleaning member with the charging member, and a second position for separating the cleaning member from the charging member The image forming apparatus includes a moving mechanism that moves between the first step and the second step. In the first step, an image forming process for forming a predetermined toner image on the surface of the image carrier is executed. The second step moves the cleaning member from the first position to the second position when the image forming process is executed.

  According to the present invention, an image forming apparatus and a cleaning member movement control method capable of suppressing the occurrence of image flow while the number of image formations after the start of use of the charging member is small are realized.

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing a system configuration of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a flowchart illustrating an example of a movement control process executed by the image forming apparatus according to the embodiment of the present invention.

  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: The thing of the character which limits the technical scope of this invention is not.

[Schematic Configuration of Image Forming Apparatus 10]
First, a schematic configuration of an image forming apparatus 10 according to an embodiment of the present disclosure will be described with reference to FIGS. 1 and 2. Here, FIG. 1 is a schematic cross-sectional view showing the configuration of the image forming apparatus 10.

  As shown in FIGS. 1 and 2, the image forming apparatus 10 includes an ADF 1, an image reading unit 2, an image forming unit 3, a paper feeding unit 4, a control unit 5, and an operation display unit 6. The image forming apparatus 10 is a multifunction machine having a plurality of functions such as a scan function, a facsimile function, and a copy function, in addition to a printer function for forming an image based on image data. The present invention can also be applied to image forming apparatuses such as printers, facsimile machines, and copiers.

  The ADF 1 is an automatic document feeder that includes a document setting unit, a plurality of conveyance rollers, a document pressing unit, and a paper discharge unit, and conveys a document read by the image reading unit 2. The image reading unit 2 includes a document table, a reading unit, a plurality of mirrors, an optical lens, and a CCD (Charge Coupled Device), and can execute image reading processing for reading image data from a document.

  The control unit 5 includes control devices such as a CPU, ROM, RAM, and EEPROM (not shown), and controls the operation of the image forming apparatus 10. The operation display unit 6 is a display unit such as a liquid crystal display that displays various types of information according to control instructions from the control unit 5 and an operation that inputs various types of information to the control unit 5 according to user operations. An operation unit such as a key or a touch panel is provided.

  The image forming unit 3 is an electrophotographic image forming unit capable of executing an image forming process (printing process) for forming an image based on the image data read by the image reading unit 2. The image forming unit 3 can also execute the image forming process based on image data input from an information processing apparatus such as an external personal computer.

  Specifically, as shown in FIG. 1, the image forming unit 3 includes a photosensitive drum 31, a charging device 32, an optical scanning device (LSU) 33, a developing device 34, a transfer roller 35, a cleaning device 36, and a fixing roller 37. , A pressure roller 38, and a paper discharge tray 39. In the image forming unit 3, an image is formed on a sheet supplied from a paper feed cassette that can be attached to and detached from the paper feed unit 4 according to the following procedure, and the sheet after the image formation is discharged to the paper discharge tray 39. Is done. The sheet is a sheet material such as paper, coated paper, postcard, envelope, and OHP sheet.

  First, the photosensitive drum 31 is uniformly charged to a predetermined potential by the charging device 32. Next, the optical scanning device 33 irradiates the surface of the photosensitive drum 31 with light based on image data. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 31. The electrostatic latent image on the photosensitive drum 31 is developed (visualized) as a toner image by the developing device 34. Here, the photosensitive drum 31 is an example of an image carrier in the present invention. The developing device 34 is supplied with toner (developer) from a toner container 34 </ b> A that can be attached to and detached from the image forming unit 3.

  Subsequently, the toner image formed on the photosensitive drum 31 is transferred to a sheet by the transfer roller 35. Thereafter, the toner image transferred to the sheet is heated and fixed by the fixing roller 37 when the sheet passes between the fixing roller 37 and the pressure roller 38. The toner remaining on the surface of the photosensitive drum 31 is removed by the cleaning device 36.

  Here, in an image forming apparatus such as the image forming apparatus 10, a problem called image flow in which the electrostatic latent image formed on the photosensitive drum 31 is disturbed may occur. It is widely known that such a problem is caused by a discharge product generated by a discharge generated between the charging device 32 and the surface of the photosensitive drum 31 when the surface of the photosensitive drum 31 is charged. It has been. That is, the discharge product generated by the discharge adheres to the surface of the photosensitive drum 31, and the discharge product absorbs moisture in the air to reduce the electrical resistance of the surface of the photosensitive drum 31. It is known that the electrostatic latent image formed on the surface of the photosensitive drum 31 is disturbed.

  In contrast, the image forming apparatus 10 employs a configuration in which a metal oxide that functions as an abrasive is contained in the toner and the surface of the photosensitive drum 31 is polished using the toner. . For example, the metal oxide is titanium oxide. The metal oxide may be silica, aluminum oxide, iron oxide, or the like, or a mixture of a plurality of types of metal oxides.

  Specifically, as shown in FIG. 1, the cleaning device 36 of the image forming unit 3 includes a cleaning blade 361, a polishing roller 362, and a conveying screw 363.

  The cleaning blade 361 removes the toner remaining on the surface of the photosensitive drum 31. The toner removed by the cleaning blade 361 is transported to a toner collection container (not shown) by the transport screw 363.

  Here, in the image forming apparatus 10, the photosensitive layer of the photosensitive drum 31 is formed of amorphous silicon. Accordingly, although it is difficult to remove the discharge products attached to the photosensitive drum 31 by the cleaning blade 361, it is possible to obtain high durability for the photosensitive drum 31.

  The polishing roller 362 polishes the surface of the photosensitive drum 31. Specifically, the polishing roller 362 polishes the surface of the photosensitive drum 31 using the toner remaining on the surface of the photosensitive drum 31 and the toner removed by the cleaning blade 361. Here, the polishing roller 362 is an example of a polishing member in the present invention. As a result, the discharge product adhering to the surface of the photosensitive drum 31 is removed by polishing.

  In addition, when the metal oxide contained in the toner passes through the cleaning blade 361 and locally adheres to the charging device 32, the electrical resistance of the adhered portion may increase and cause image defects. . For this reason, the image forming apparatus 10 employs a configuration in which the metal oxide attached to the charging device 32 is removed.

  Specifically, the charging device 32 includes a charging roller 321 and a cleaning roller 322 as shown in FIG.

  The charging roller 321 is provided in contact with the photosensitive drum 31 and charges the photosensitive drum 31. The charging roller 321 is an example of the charging member in the present invention. For example, the charging roller 321 is formed of a synthetic rubber such as EPDM rubber imparted with conductivity by adding a conductive material such as carbon.

  The cleaning roller 322 removes the metal oxide and the like attached to the surface of the charging roller 321. The said cleaning roller 322 is an example of the cleaning member in this invention here. As a result, local adhesion of the metal oxide that has passed through the cleaning blade 361 to the charging roller 321 is suppressed. Therefore, in the charging roller 321, it is possible to suppress the occurrence of image defects due to an increase in electrical resistance at the location where the metal oxide is attached.

  On the other hand, the control unit 5 includes a detection unit 51, an image formation control unit 52, and a movement control unit 53, as shown in FIG. Specifically, the control unit 5 functions as the detection unit 51, the image formation control unit 52, and the movement control unit 53 by executing a control program stored in the ROM using the CPU. To do. When the control unit 5 is an electronic circuit, the detection unit 51, the image formation control unit 52, and the movement control unit 53 are configured as modules included in the control unit 5.

  The detection unit 51 detects temperature and humidity. For example, in the image forming apparatus 10, the image forming unit 3 is provided with a temperature / humidity sensor 30 </ b> A (see FIG. 2) that outputs an electrical signal corresponding to the temperature and humidity inside the housing of the image forming apparatus 10. Yes. The detection unit 51 can detect the temperature and humidity inside the housing of the image forming apparatus 10 based on the electrical signal output from the temperature / humidity sensor 30A. The temperature / humidity sensor 30A may output an electrical signal corresponding to the temperature and humidity outside the image forming apparatus 10.

  The image formation control unit 52 executes an image formation process for forming a predetermined toner image on the surface of the photosensitive drum 31. Specifically, the toner image has a length in the main scanning direction corresponding to a contact area of the photosensitive drum 31 with the charging roller 321 or an image forming area in the contact area, and has a length in the sub scanning direction. 3 is a solid image having a uniform density corresponding to a contact area of the charging roller 321 with the photosensitive drum 31. FIG. The main scanning direction corresponds to the axial direction of the photosensitive drum 31, and the sub-scanning direction corresponds to the rotational direction of the photosensitive drum 31. Further, the image formation control unit 52 may form a plurality of the toner images in the image forming process.

  For example, the image formation control unit 52 controls the charging device 32 and the optical scanning device 33 to form an electrostatic latent image corresponding to the toner image on the surface of the photosensitive drum 31. Subsequently, the image formation control unit 52 controls the developing device 34 to form the toner image on the surface of the photosensitive drum 31. The image formation control unit 52 controls a power supply device (not shown) that applies a transfer bias voltage to the transfer roller 35, and has a polarity opposite to that at the time of transferring the toner image onto the sheet. A voltage is applied to send the toner image to the cleaning device 36. As a result, the toner image is supplied to the cleaning device 36 and the surface of the photosensitive drum 31 is polished by the polishing roller 362.

  Further, the image formation control unit 52 automatically executes the image formation process at a preset timing. For example, the timing may be determined when the power of the image forming apparatus 10 is turned on, when the image forming apparatus 10 returns from the power saving mode, when a predetermined specific period has elapsed, or when a predetermined specific time has elapsed. This is the case when the number of sheets is printed.

  Here, the image formation control unit 52 executes the image formation process when the temperature and humidity detected by the detection unit 51 satisfy a predetermined high-temperature and high-humidity condition. The high temperature and high humidity conditions are set in advance in consideration of the temperature and humidity at which the image flow is likely to occur. For example, the high temperature and high humidity condition is set to a temperature of 28 degrees or higher and a humidity of 80 percent or higher.

  By the way, in the image forming apparatus such as the image forming apparatus 10, the occurrence of the image flow may be noticeable while the number of times of image formation after the start of use of the charging roller 321 is small. Such a phenomenon is considered to occur because components such as a conductive agent and process oil included in the charging roller 321 contribute to the generation of the image flow. Specifically, the contained component leaked to the surface of the charging roller 321 is transferred from the charging roller 321 to the photosensitive drum 31 at the contact point of the charging roller 321 and the photosensitive drum 31, and the photosensitive member. It is considered that the electric resistance on the surface of the drum 31 is lowered. As the number of image formations increases, the metal oxide contained in the toner gradually adheres to the surface of the charging roller 321 to prevent leakage of the contained components, so that the occurrence of the image flow is gradually suppressed. Is done. On the other hand, in the image forming apparatus 10, as described below, it is possible to suppress the occurrence of the image flow while the number of times of image formation after the start of use of the charging roller 321 is small.

  Specifically, in the image forming apparatus 10, the moving mechanism that causes the image forming unit 3 to move the cleaning roller 322 between a first position that contacts the charging roller 321 and a second position that is separated from the charging roller 321. 30B (see FIG. 2) is provided. For example, the moving mechanism 30B swings a bearing portion (not shown) that rotatably supports the cleaning roller 322 using a cam member or the like, thereby moving the cleaning roller 322 to the first position and the second position. Move between.

  On the other hand, the movement control unit 53 moves the cleaning roller 322 from the first position to the second position when the image forming process is executed. Specifically, the movement control unit 53 controls the movement mechanism 30B to move the cleaning roller 322 from the first position to the second position.

  Here, the movement control unit 53 moves the cleaning roller 322 from the first position to the second position until a predetermined reference number of the printing processes are executed. For example, in the image forming apparatus 10, the control unit 5 stores the total number of printed sheets printed in the printing process in a predetermined storage area of the EEPROM. The movement control unit 53 moves the cleaning roller 322 from the first position to the second position when the total number of printed sheets stored in the EEPROM is equal to or less than the reference number. The reference number is set in advance in consideration of the number of image formations in the image forming apparatus 10 until the metal oxide layer that suppresses leakage of the component is formed on the surface of the charging roller 321. Is done. For example, the reference number is set to an appropriate number between 10,000 and 100,000.

[Move control processing]
Hereinafter, an example of the procedure of the movement control process executed by the control unit 5 according to the control program in the image forming apparatus 10 will be described with reference to FIG. Here, steps S1, S2,... Represent the numbers of processing procedures (steps) executed by the control unit 5. The movement control process is performed when the image forming apparatus 10 is turned on, when the image forming apparatus 10 returns from the power saving mode, when a preset specific period has elapsed, or is set in advance. This is executed by the control unit 5 when a specific number of sheets has been printed.

<Step S1>
First, in step S <b> 1, the control unit 5 detects the temperature and humidity inside the housing of the image forming apparatus 10. Specifically, the control unit 5 detects the temperature and humidity inside the housing of the image forming apparatus 10 based on the electrical signal output from the temperature / humidity sensor 30A. Here, the process of step S <b> 1 is executed by the detection unit 51 of the control unit 5.

<Step S2>
In step S2, the control unit 5 determines whether or not the temperature and humidity detected in step S1 satisfy the high temperature and high humidity condition.

  Here, if the said control part 5 judges that the temperature and humidity detected by said step S1 satisfy the said high temperature, high humidity conditions (Yes side of S2), it will transfer a process to step S3. If the temperature and humidity detected in step S1 do not satisfy the high-temperature and high-humidity condition (No in S2), the control unit 5 ends the movement control process. As a result, the execution of the image forming process other than the high temperature and high humidity where the image flow is likely to occur is avoided, and the consumption of the toner consumed in the image forming process is saved.

<Step S3>
In step S <b> 3, the control unit 5 determines whether the total number of printed sheets printed by the image forming apparatus 10 is equal to or less than the reference number. Specifically, the control unit 5 determines whether the total number of printed sheets stored in the EEPROM is equal to or less than the reference number.

  Here, when the control unit 5 determines that the total number of printed sheets printed by the image forming apparatus 10 is equal to or less than the reference number (Yes side of S3), the process proceeds to step S4. If it is determined that the total number of printed sheets printed by the image forming apparatus 10 exceeds the reference number (No in S3), the control unit 5 moves the process to step S31.

<Step S4>
In step S4, the control unit 5 moves the cleaning roller 322 from the first position to the second position. Specifically, the control unit 5 controls the moving mechanism 30B to move the cleaning roller 322 from the first position to the second position. Here, the process of step S4 is an example of the second step in the present invention, and the processes of step S3 and step S4 are executed by the movement control unit 53 of the control unit 5. Accordingly, it is possible to promote the fixing of the metal oxide that passes through the cleaning blade 361 and adheres to the surface of the charging roller 321 to the surface of the charging roller 321.

<Step S5>
In step S5, the controller 5 executes the image forming process. Specifically, the control unit 5 controls the charging device 32 and the like to form the toner image on the surface of the photosensitive drum 31 and sends it to the cleaning device 36. Here, the process of step S5 is an example of the first step in the present invention. Further, the processing of Step S2 and Step S5 is executed by the image formation control unit 52 of the control unit 5.

  As a result, discharge products adhering to the surface of the photosensitive drum 31 are removed, and the occurrence of the image flow is suppressed, and a part of the metal oxide contained in the toner image causes the cleaning blade 361 to move. It slips through and adheres to the charging roller 321. That is, the metal oxide can be supplied to the charging roller 321.

  The toner image formed by the image forming process has a length in the main scanning direction corresponding to a contact area of the photosensitive drum 31 with the charging roller 321 or an image forming area in the contact area. The solid image has a uniform density corresponding to the contact area of the charging roller 321 with the photosensitive drum 31 in the scanning direction. Therefore, it is possible to supply the charging roller 321 with the metal oxide distributed on the average in a contact area of the charging roller 321 with the photosensitive drum 31 or in the image forming area in the contact area. .

<Step S6>
In step S6, the controller 5 moves the cleaning roller 322 from the second position to the first position. Specifically, the control unit 5 controls the moving mechanism 30B to move the cleaning roller 322 from the second position to the first position. Here, the process of step S6 is executed by the movement control unit 53 of the control unit 5. Accordingly, when the printing process is executed, the metal oxide that locally adheres to the surface of the charging roller 321 is removed by the cleaning roller 322.

<Step S31>
On the other hand, in step S31, the control unit 5 executes the image forming process as in step S5. Thereby, when the metal oxide layer that suppresses leakage of the component is already formed on the surface of the charging roller 321, power consumption due to movement control of the cleaning roller 322 is suppressed. Is possible.

  It is conceivable that the image forming unit including the charging device 32 is replaced after the use of the image forming apparatus 10 is started. Therefore, a configuration is conceivable in which the total number of printed sheets stored in the EEPROM is reset when the image forming unit is replaced. Further, the total number of printed sheets stored in the EEPROM may be reset in response to a user operation input to the operation display unit 6.

  Thus, in the movement control process, the cleaning roller 322 is moved from the first position to the second position when the image forming process is executed. Thereby, it is possible to promote the formation of the metal oxide layer for suppressing leakage of the contained component on the surface of the charging roller 321. Therefore, the occurrence of the image flow due to the contained component while the number of image formations is small is suppressed.

  A configuration in which the image forming control unit 53 automatically executes the image forming process at the timing regardless of whether the high temperature and high humidity condition is satisfied is considered as another embodiment. According to such a configuration, since the opportunity to supply the metal oxide to the surface of the charging roller 321 increases, it is possible to further promote the formation of the metal oxide layer on the surface of the charging roller 321. It is.

  A configuration is also conceivable in which the image forming control unit 53 automatically executes the image forming process at the timing until the printing process for the reference number of sheets is executed. According to such a configuration, the metal oxide on the surface of the charging roller 321 only until the metal oxide layer that suppresses leakage of the component is formed on the surface of the charging roller 321. It is possible to increase supply opportunities. Note that after the printing process for the reference number of sheets is executed, the image forming control unit 53 may execute the image forming process when the high-temperature and high-humidity conditions are satisfied at the timing.

1: ADF
2: Image reading unit 3: Image forming unit 30A: Temperature / humidity sensor 30B: Moving mechanism 31: Photoconductor drum 32: Charging device 321: Charging roller 322: Cleaning roller 36: Cleaning device 361: Cleaning blade 362: Polishing roller 4: Paper feeding unit 5: Control unit 51: Detection unit 52: Image formation control unit 53: Movement control unit 6: Operation display unit 10: Image forming apparatus

Claims (8)

An image carrier for carrying a toner image formed by a toner containing a metal oxide;
A charging member provided in contact with the image carrier and charging the image carrier;
An image forming control unit for executing an image forming process for forming a predetermined specific toner image on the surface of the image carrier;
A cleaning member for removing the metal oxide adhering to the surface of the charging member;
A moving mechanism for moving the cleaning member between a first position contacting the charging member and a second position separating from the charging member;
Before execution of the image forming process, the cleaning member is moved to said second position from said first position, after the execution of the image formation process is moved to the first position the cleaning member from said second position A movement control unit,
A transfer roller for transferring the toner image formed on the image carrier to a sheet;
Equipped with a,
The specific toner image has a length in the main scanning direction corresponding to a contact area of the image carrier with the charging member or an image forming area in the contact area, and a length in the sub scanning direction of the charging member. A solid image having a uniform density corresponding to the contact area with the image carrier,
Said imaging control unit, the image forming apparatus Ru is application of reverse polarity voltage to the transfer roller at the time of transfer of the toner image to the sheet.   The image forming apparatus according to claim 1, wherein the image forming control unit automatically executes the image forming process at a preset timing.   The image forming apparatus according to claim 2, wherein the image forming control unit automatically executes the image forming process at the timing until a predetermined reference number of printing processes are executed. A polishing member for polishing the surface of the image carrier using the toner adhering to the surface of the image carrier;
A detection unit for detecting temperature and humidity;
The image forming apparatus according to claim 1, wherein the image forming control unit executes the image forming process when the temperature and humidity detected by the detecting unit satisfy a predetermined high temperature and high humidity condition. .   The image forming apparatus according to claim 4, wherein the movement control unit moves the cleaning member from the first position to the second position until a predetermined reference number of printing processes are executed. The image forming apparatus according to claim 1 , wherein the metal oxide includes titanium oxide. The image forming apparatus according to claim 1 , wherein the image carrier is formed of amorphous silicon. An image carrier that carries a toner image formed by a toner containing a metal oxide, a charging member that is provided in contact with the image carrier and charges the image carrier, and adheres to the surface of the charging member Formed on the image carrier, a cleaning member that removes the metal oxide, a moving mechanism that moves the cleaning member between a first position that contacts the charging member and a second position that is separated from the charging member. And a cleaning member movement control method executed in an image forming apparatus comprising a transfer roller for transferring the toner image to a sheet ,
A first step of executing an image forming process for forming a predetermined specific toner image on the surface of the image carrier;
Before execution of the image forming process, the cleaning member is moved to said second position from said first position, after the execution of the image formation process is moved to the first position the cleaning member from said second position A second step,
Only including,
The specific toner image has a length in the main scanning direction corresponding to a contact area of the image carrier with the charging member or an image forming area in the contact area, and a length in the sub scanning direction of the charging member. A solid image having a uniform density corresponding to the contact area with the image carrier,
In the first step, a cleaning member movement control method in which a voltage having a reverse polarity to the transfer of the toner image onto the sheet is applied to the transfer roller .

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