JP5799691B2 - Cleaning device, image forming apparatus, and control method of cleaning device - Google Patents

Description

  The present invention relates to a cleaning device, an image forming apparatus, and a cleaning device control method.

  An electrophotographic image forming apparatus includes an intermediate transfer belt and a secondary transfer belt for secondary transfer of a toner image onto a recording medium. A cleaning brush and a collection roller are used to remove residual deposits such as untransferred toner and paper dust adhered on the intermediate transfer belt and the secondary transfer belt. The cleaning brush contacts and rotates against the intermediate transfer belt or the secondary transfer belt, thereby picking up and removing residual deposits from the belt surface. The collection roller removes residual deposits accumulated on the cleaning brush by rotating in contact with the cleaning brush.

  However, the cleaning brush or the collection roller cannot completely remove the residue. Some residue remains in the cleaning brush without being removed from the transfer belt such as the intermediate transfer belt. It is known to use a bias voltage in order to remove residues remaining in the cleaning brush or on the transfer belt. By applying a bias voltage to the cleaning brush or the collection roller, the residue charged on the positive electrode or the negative electrode is attracted to the cleaning brush and the collection roller applied to the opposite polarity, and the residue is removed more efficiently.

  As a technique related to this, there is a technique for reversing the polarity of the voltage applied to each of the cleaning brush and the collection roller (for example, Patent Document 1). According to this technique, by reversing the polarity of the bias voltage applied every predetermined period, the residual toner of both polarities on the photosensitive drum can be collected by only one set of cleaning brush and collection roller.

  As another technique using a bias voltage, there is a technique in which a voltage having a polarity opposite to that during normal cleaning is applied to a cleaning brush (for example, Patent Document 2). By applying a bias voltage having a polarity opposite to that during normal cleaning to the cleaning brush, the residual toner remaining on the cleaning brush is moved to the intermediate transfer belt. That is, contrary to the normal cleaning in which the residual toner is removed from the intermediate transfer member, the toner is once discharged to the intermediate transfer member, and the residual toner is collected by using the photosensitive drum cleaning mechanism.

  However, in the techniques described in Patent Documents 1 and 2, the cleaning brush always remains in contact with the photosensitive drum or the intermediate transfer member. Therefore, even if a bias voltage having a reverse polarity is used, residual toner staying on the cleaning brush may be reattached on the photosensitive drum or the intermediate transfer member. In this case, sticking or filming due to residual toner on the photosensitive drum or intermediate transfer member occurs, which causes image defects.

JP-A-5-1079888 JP 2002-72697 A

  The present invention has been made based on the above problems, and can reliably prevent the residue remaining on the cleaning brush from reattaching to the transfer belt and causing sticking or filming on the transfer belt. An image forming apparatus and a cleaning apparatus control method are provided.

  The above object of the present invention is achieved by the following means.

  (1) A cleaning brush configured to remove a residue having polarity on the rotating body by rotating in contact with the rotationally driven rotating body, and to be separated from the rotating body; and the cleaning brush By rotating in contact with the cleaning brush, the residue is removed from the cleaning brush, the recovery roller configured in combination with the cleaning brush is separable together with the cleaning brush, and the voltage adjustment for applying a voltage to the recovery roller And the voltage adjusting means reverses the polarity of the voltage applied to the collection roller while the pair of the cleaning brush and the collection roller is separated from the rotating body.

  (2) The cleaning device according to (1), wherein the voltage adjusting unit reverses the polarity of the voltage applied to the collection roller and simultaneously connects the cleaning brush to the ground.

  (3) The distance between the pair of the cleaning brush and the collection roller is a value calculated by integrating the number of sheets on which an image is formed and a printing rate that is a ratio of the printed area to the area of the sheet, Alternatively, the cleaning device according to (1) or (2), which is executed based on the number of sheets on which the image is formed.

  (4) A plurality of sets of the cleaning brush and the collection roller are arranged, and among the plurality of sets in contact with the rotating body, the polarity of the voltage applied to the group positioned at the most upstream in the rotating direction of the rotating body is The cleaning device according to any one of (1) to (3), wherein the polarity is opposite to the polarity of the residue.

  (5) The plurality of sets of the cleaning brush and the collection roller are divided into a group that is simultaneously separated from the state of contact with the rotating body and a group that is simultaneously contacted from the state of being separated from the rotating body. The cleaning device according to (4), wherein the timing at which the two groups are separated or abutted is synchronized with the timing at which the other group is abutted or separated, and the period in which each group is separated and abutted is alternately repeated.

  (6) The cleaning device according to (4) or (5), wherein at least two of the cleaning brush and the collection roller are always in contact with the rotating body.

  (7) While the pair of the cleaning brush and the collection roller is separated from each other, the rotation direction of the cleaning brush is opposite to the rotation direction when the cleaning brush and the collection roller are not separated from each other. The cleaning device according to any one of the above.

  (8) The cleaning device according to any one of (1) to (7), further including a scraper that removes the residue on the collection roller.

  (9) The rotating body according to any one of (1) to (8), wherein the rotating body is an intermediate transfer belt on which a toner image is formed or a secondary transfer belt that transfers the toner image to a recording medium. Cleaning device.

  (10) An image forming apparatus comprising the cleaning device according to any one of (1) to (9).

  (11) A cleaning brush that removes the polar residue on the rotating body, a recovery roller that contacts the cleaning brush and removes the residue from the cleaning brush, and a voltage adjustment that applies a voltage to the recovery roller And a step of rotating the cleaning brush in contact with the rotating body in a state where a unipolar voltage is applied to the recovery roller; and the cleaning brush and the recovery roller. A pair is separated from the rotating body, and the voltage adjusting means applies a voltage having a polarity opposite to the polarity of the voltage applied before the separation to the separated collection roller. A method for controlling a cleaning device.

  According to the present invention, a set of a cleaning brush and a recovery roller for cleaning the surface of a transfer body or the like is configured to be separable from the transfer body, and at the time of separation, the polarity of the bias voltage to be applied is reversed, thereby efficiently cleaning Residue remaining on the brush can be removed.

1 is a cross-sectional view schematically showing a configuration of an image forming apparatus according to an embodiment. It is a figure which shows the aspect of the structure of the cleaning apparatus provided with 2 sets of cleaning brushes and collection | recovery rollers based on this embodiment, and the separation control. It is a figure which shows the aspect of the structure of the cleaning apparatus provided with 3 sets of cleaning brushes and collection | recovery rollers which concern on this embodiment, and the separation control. It is a figure which shows the structure of a cleaning apparatus provided with 4 sets of cleaning brushes and collection | recovery rollers based on this embodiment, and the aspect of the separation control.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the following description does not limit the technical scope and terminology described in the claims. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may differ from the actual ratios.

  FIG. 1 is a cross-sectional view schematically showing a configuration of an image forming apparatus according to the present embodiment.

  The image forming apparatus A shown in FIG. 1 is also called a tandem type color image forming apparatus, and performs color image formation by four sets of image forming units. The image forming apparatus A forms an image of image data on a sheet such as an image forming sheet (recording medium) using an electrophotographic image forming process.

  The image forming apparatus A performs color image formation by four sets of image forming units. The four image forming units include an image forming unit 10Y that forms a yellow (Y) image, an image forming unit 10M that forms a magenta (M) image, and an image forming unit that forms a cyan (C) color image. The unit 10C is an image forming unit 10K that forms a black (K) color image.

  The image forming unit 10Y includes a photosensitive drum 1Y as an image carrier, and a charging unit 2Y, an optical writing unit 3Y, a developing device 4Y, and a photosensitive drum cleaning device 5Y disposed around the photosensitive drum 1Y. Similarly, the image forming unit 10M includes a photosensitive drum 1M as an image carrier, and a charging unit 2M, an optical writing unit 3M, a developing device 4M, and a photosensitive drum cleaning device 5M disposed around the photosensitive drum 1M. . The image forming unit 10C includes a photosensitive drum 1C as an image carrier, and a charging unit 2C, an optical writing unit 3C, a developing device 4C, and a photosensitive drum cleaning device 5C arranged around the photosensitive drum 1C. The image forming unit 10K includes a photosensitive drum 1K as an image carrier, and a charging unit 2K, an optical writing unit 3K, a developing device 4K, and a photosensitive drum cleaning device 5K disposed around the photosensitive drum 1K. The photosensitive drums 1Y, 1M, 1C, and 1K of the image forming units 10Y, 10M, 10C, and 10K, the charging units 2Y, 2M, 2C, and 2K, the optical writing units 3Y, 3M, 3C, and 3K, and the photosensitive units, respectively. The body drum cleaning devices 5Y, 5M, 5C, and 5K have the same functions. Therefore, in the following description, symbols Y, M, C, or K are not used unless otherwise specified.

  In the image forming process of the present embodiment, the photosensitive drum 1 and the intermediate transfer belt 6 are used as the image carrier.

  The intermediate transfer belt 6 is an endless belt, is constructed by a plurality of rollers, and is supported so as to be able to run. The toner images of the respective colors formed on the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred onto the intermediate transfer belt 6 traveling by the primary transfer units 7Y, 7M, 7C, and 7K, and each color (Y, M, C , K) are overlaid on the intermediate transfer belt 6 by a primary transfer.

  The paper transport unit 20 transports the paper S. The paper S is accommodated in the paper feed trays 291, 292 and 293, fed by the first paper feed unit 21, conveyed to the secondary transfer unit 7 A through the loop forming roller pair 22 and the registration roller pair 23. The In the secondary transfer portion 7A, the color image formed on the intermediate transfer belt 6 is secondarily transferred onto the paper S. The toner image on the sheet S is melted and fixed on the sheet S on which the color image is transferred by applying heat and pressure at the nip portion N of the fixing device 50. Then, the paper S is discharged out of the apparatus by the paper discharge roller 25.

  The secondary transfer device 30 is disposed in contact with the intermediate transfer belt 6 in the secondary transfer portion 7A. The secondary transfer device 30 includes a plurality of drive rollers 32 for constructing and rotating the secondary transfer belt 31. As the sheet S passes through the nip formed between the secondary transfer belt 31 and the intermediate transfer belt 6 of the secondary transfer device 30, the toner image on the intermediate transfer belt 6 is secondarily transferred to the sheet S. Is done.

  A secondary transfer belt cleaning device (hereinafter simply referred to as a cleaning device) 40 is disposed in the vicinity of the secondary transfer belt 31 of the secondary transfer device 30 and residual toner, paper dust, etc. adhering to the secondary transfer belt 31. Remove any residual deposits. In the present embodiment, the secondary transfer belt 31 is an example of a rotating body that is cleaned by the cleaning device 40.

  Further, the image forming apparatus A includes a voltage adjusting device for applying a bias voltage to the driving roller 32 of the secondary transfer device 30 and the cleaning brush and the collection roller of the cleaning device 40. The voltage adjusting device as the voltage adjusting means applies a predetermined voltage to the collection roller. Details of the cleaning device 40 and the voltage adjustment device will be described later.

  Each unit of the image forming apparatus A is connected to the control unit 90 and is appropriately controlled by the control unit 90. A CPU (not shown) configured as a part of the control unit 90 counts and accumulates the number of pixels of an image formed image, or counts and accumulates the number of sheets S subjected to image formation processing. Etc. Details of these processes will be described later. A program corresponding to these processes is stored in a storage unit (not shown) included in the control unit 90. Each function of the above-described units of the image forming apparatus A is exhibited by the CPU executing a corresponding program.

  Note that the image forming apparatus A may include components other than the components described above, or may not include some of the components described above.

  Next, an electrophotographic process for forming an image on a sheet by the image forming apparatus A will be described.

  First, a document is placed on a document table having a slit SL on the top, and the placed document is scanned and exposed by an optical system of a scanning exposure device of the image reading device SC, and reflected light from the document is reflected by a mirror. Via a line image sensor and photoelectrically converted. The image information signal for each color generated by photoelectric conversion is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like by an image processing unit (not shown), and then image formation of the corresponding color is performed. Input to the optical writing unit 3 of the unit 10.

  The optical writing unit 3 of the image forming unit 10 writes an image information signal to the photosensitive drum 1 and forms a latent image on the photosensitive drum 1 based on the image information signal. Specifically, the photosensitive drum 1 has a photosensitive layer made of a resin such as polycarbonate including an organic photoconductor (OPC) on a metal substrate. The surface of the photosensitive drum 1 is charged by ions generated by a charging unit 2 formed of a corona discharge electrode such as a scorotron type, and the optical writing unit 3 scans and exposes the photosensitive drum 1 based on an image information signal. To do. The exposed portion of the charged photosensitive drum 1 has a reduced potential, and an electrostatic latent image corresponding to the image information signal is formed on the photosensitive drum 1. The developing device 4 uses an electrostatic force to develop the electrostatic latent image formed on the photosensitive drum 1 with toner, and a toner image corresponding to each color is formed.

  Here, the toner for development is charged on the same electrode as the photosensitive drum 1. For example, the photosensitive drum 1 is charged to the negative electrode. Of the region on the photosensitive drum 1 charged to the negative electrode, the toner charged to the negative electrode is attached only to the latent image portion whose potential has been lowered by the optical writing unit 3, and the electrostatic latent image is formed on the photosensitive drum 1. Can be formed. The electrostatic latent image on the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 6, and a toner image can be formed on the intermediate transfer belt 6. At this time, by charging the intermediate transfer belt 6 to the positive electrode, the transfer of the toner charged to the negative electrode to the intermediate transfer belt 6 can be promoted. On the intermediate transfer belt 6, patches that are not transferred to the paper S are formed for the purpose of correcting the printing density, color, or image forming position. The toner for forming the patch is charged to the negative electrode like the toner for forming the electrostatic latent image. Then, the toner image formed on the intermediate transfer belt 6 is secondarily transferred onto the paper S in the secondary transfer portion 7A. At this time, by charging the sheet S to the negative electrode, the transfer of the toner image charged to the positive electrode by the intermediate transfer belt 6 onto the sheet S can be promoted.

  In the intermediate transfer belt 6 and the secondary transfer belt 31, the toner that could not be transferred onto the paper S is removed by the cleaning device, but depending on the conditions, residual toner may remain on the belt. As described above, since the sheet S is charged to the negative electrode, most of the residual toner is charged to the negative electrode similarly to the sheet S. Therefore, after the image formation, a large amount of negative polarity toner remains on the secondary transfer belt 31 and a relatively small amount of positive polarity toner remains. A large amount of positive polarity toner remains on the intermediate transfer belt 6 and a relatively small amount of negative polarity toner remains.

  Next, the configuration of the cleaning device and the voltage adjusting device according to the present embodiment will be described in detail with reference to FIG.

  FIG. 2 is a diagram illustrating a configuration of a cleaning device including two sets of cleaning brushes and a collection roller according to the present embodiment, and a mode of separation control thereof.

  As shown in FIG. 2, the cleaning device 40 includes cleaning brushes 41 a and 42 a, collection rollers 41 b and 42 b, and a scraper 49.

  The cleaning brushes 41 a and 42 a rotate in contact with the secondary transfer belt 31 that is driven around by the driving roller 32 to remove residual toner and paper dust adhering to the secondary transfer belt 31. On the metal cores of the cleaning brushes 41a and 42a, electric-resistant brush fibers made of acrylic carbon or the like are planted around at a desired pile density, pile diameter and pile length. Or you may wind and paste the sheet | seat which planted the said brush fiber around a metal core. The rotation directions of the cleaning brushes 41a and 42a may be rotationally driven so that the outer peripheral portions of the contact portions of the cleaning brushes 41a and 42a and the secondary transfer belt 31 are moved in the opposite directions (this rotation direction). Is referred to as reversal). Alternatively, the cleaning brushes 41a and 42a and the secondary transfer belt 31 may be rotationally driven so that the outer peripheral portions thereof are relatively moved in the same direction (this rotational direction is referred to as forward rotation). The contact force of the cleaning brushes 41a and 42a against the secondary transfer belt 31 can be set as appropriate. In addition, the cleaning brushes 41a and 42a have recovery rollers 41b and 42b, respectively, for removing residues remaining in the brushes from the brushes. The cleaning brushes 41a and 42a are configured to be separated from the secondary transfer belt 31 together with the recovery rollers 41b and 42b. As will be described later, the cleaning brushes 41a and 42a are connected to the ground while being separated from the secondary transfer belt 31 in pairs with the collection rollers 41b and 42b.

  The collection rollers 41b and 42b rotate in contact with the cleaning brushes 41a and 42a, respectively, thereby removing residues in the cleaning brushes 41a and 42a from the cleaning brushes 41a and 42a. The collection rollers 41b and 42b are connected to voltage adjusting devices 45 and 46, respectively, and a bias voltage having a predetermined potential is applied thereto. When the cleaning brush is in contact with the secondary transfer belt 31 for cleaning, a positive bias voltage is applied to the collection roller 41b located on the upstream side in the rotation direction of the secondary transfer belt 31, and located on the downstream side. A negative bias voltage is applied to the collection roller 42b. Further, since the drive roller 32 is connected to the ground, a current flows between the collection rollers 41 b and 42 b and the drive roller 32 via the cleaning brushes 41 a and 42 a and the secondary transfer belt 31. For example, the voltage adjusting device 45 applies a positive bias voltage to the collection roller 41b so that a current of 50 to 55 μA flows between the collection roller 41b and the drive roller 32. The voltage adjusting device 46 applies a negative bias voltage to the collection roller 42b so that a current of 25 to 30 μA flows between the collection roller 42b and the drive roller 32. By applying a bias voltage to the collection roller so that a current flows, the residue on the secondary transfer belt 31 charged to one polarity is induced in either the positive electrode side or the negative electrode side of the generated current. Thus, it can be picked up by the cleaning brush and moved to the collection roller.

  As shown in FIG. 2A, the collection roller 41b to which the positive bias voltage is applied and the cleaning brush 41a serving as a passage point for the current generated by the bias voltage are used to clean the toner charged on the negative electrode. It can be picked up by the brush 41a and collected on the collecting roller 41b. Further, by providing the pair of the cleaning brush 41a and the collection roller 41b on the upstream side of the secondary transfer belt 31, the toner charged on the negative electrode can be efficiently removed from the secondary transfer belt 31 on the upstream side. . The collection roller 42b to which the negative bias voltage is applied and the cleaning brush 42a serving as a passage point for the current generated by the bias voltage are picked up by the cleaning brush 42a with toner or the like charged to the positive electrode. Can be recovered. By providing the pair of the cleaning brush 42a and the collection roller 42b on the downstream side of the secondary transfer belt 31, positive toner that is assumed to be a relatively small amount for toner images and the like is transferred from the secondary transfer belt 31 on the downstream side. Can be removed. Also, as shown in FIG. 2A, the electrical balance on the secondary transfer belt 31 is maintained by bringing the collection roller and the cleaning brush applied to the positive electrode and the negative electrode into contact with each other. Meanwhile, the residue of both the positive electrode and the negative electrode can be removed.

  As shown in FIG. 2B, the cleaning device 40 according to the present embodiment is configured such that a set of a cleaning brush and a collection roller can be separated from the secondary transfer belt 31. While the pair of the cleaning brush and the collection roller is separated from the secondary transfer belt 31, a bias voltage having a polarity opposite to that when rotating in contact with the secondary transfer belt 31 is applied to the collection roller. The Specifically, a positive bias voltage is applied to the collection roller 41b in the operation mode in contact with the secondary transfer belt 31, but a negative bias voltage having a reverse polarity is applied when the recovery roller 41b is separated from the cleaning mode. Is applied. Similarly, the negative bias voltage is applied to the recovery roller 42b in the operation mode, but a positive bias voltage having a reverse polarity is applied when the recovery roller 42b is separated after entering the cleaning mode. Further, simultaneously with reversing the polarity of the bias voltage applied to the collection rollers 41b and 42b, the voltage adjusting devices 45 and 46 connect the cleaning brushes 41a and 42a to the ground. By doing so, a current passing through the cleaning brushes 41a and 42a and the collection rollers 41b and 42b can be generated.

  As described above, the pair of the cleaning brush and the collection roller is separated from the secondary transfer belt 31 and the reverse polarity voltage is applied, so that the residue staying on the cleaning brush is not returned to the secondary transfer belt 31. Can be removed. That is, in the operation mode, as described above, the cleaning brushes 41a and 42a pick up the residue having the opposite polarity to the applied voltage from the secondary transfer belt 31 and absorb it. Among the residues picked up by the cleaning brush, the residues that could not be collected by the collecting roller stay in the cleaning brushes 41a and 42a, and the staying residue is applied to the applied voltage while staying in the cleaning brush. Is charged. For example, since the positive electrode voltage is applied to the cleaning brush 41a shown in FIG. 2A, the residue staying on the cleaning brush 41a is charged to the positive electrode. After that, as shown in FIG. 2B, after the cleaning brush 41a and the recovery roller 41b are separated from the secondary transfer roller, a negative negative voltage is applied to the recovery roller 41b, and the cleaning brush 41a is grounded. Is connected to generate a current. As a result, the residue charged on the positive electrode while staying on the cleaning brush 41a is drawn toward the recovery roller 41b applied to the negative polarity downstream of the generated current, and the residue staying on the cleaning brush 41a. An object can be discharged to the collection roller 41b. Here, since the pair of the cleaning brush 41a and the collection roller 41b are both separated from the secondary transfer belt 31, the residue staying on the cleaning brush 41a returns to the secondary transfer belt 31, and is fixed or filmed. It does not cause or.

  The period of the cleaning mode in which the cleaning brush and the collection roller are separated from the secondary transfer belt 31 is set to 1 minute, for example. Further, when there are only two sets of the cleaning brush and the collection roller as shown in FIG. 2, the two sets must be separated at the same time during the cleaning mode. Therefore, the image forming process using the secondary transfer belt 31 is interrupted during the cleaning mode of the cleaning brush.

  Next, with reference to FIG. 3, when there are three sets of the cleaning brush and the collection roller provided in the cleaning device according to the present embodiment, an aspect of controlling the set will be described in detail.

  FIG. 3 is a diagram illustrating a configuration of a cleaning device including three sets of cleaning brushes and a collection roller according to the present embodiment, and a mode of separation control thereof. In addition, the same code | symbol is used for the structure similar to the structure mentioned above, and the description is abbreviate | omitted in order to avoid duplication.

  As shown in FIG. 3, the cleaning device 40 includes three sets of cleaning brushes 41a to 43a and collection rollers 41b to 43b. When three sets of cleaning brushes and recovery rollers are provided, in order to maintain the electrical balance on the secondary transfer belt 31 as described above, two sets of cleaning brushes and recovery rollers applied to each polarity, either positive or negative, are provided. Control is performed so as to contact the secondary transfer belt 31. Further, as described above, the positive bias voltage is applied to the collection roller located upstream of the two sets, and the negative bias voltage is applied to the collection roller located downstream. . For example, as shown in FIG. 3A, while the pair of the cleaning brush 42a and the collection roller 42b is separated from the secondary transfer belt 31, the two sets of the cleaning brush 41a, 43a and the collection rollers 41b, 43b are It is in contact with the secondary transfer belt 31. A positive bias voltage is applied to the collection roller 43b of the set located on the upstream side in the rotation direction of the secondary transfer belt 31 in the set. Further, a negative bias voltage is applied to the pair of collection rollers 41b located on the downstream side. Of the pair of the cleaning brush 42a and the collection roller 42b in the cleaning mode, a positive bias voltage having a polarity opposite to that of the negative bias voltage applied in the operation mode is applied to the collection roller 42b. At the same time, the cleaning brush 42a is connected to the ground. By doing so, the residue staying on the cleaning brush 42a and charging the negative electrode in the operation mode is discharged to the collecting roller 42b to which the positive bias voltage is applied in the cleaning mode.

  Subsequently, the other cleaning brush and collection roller pairs are controlled to shift to the cleaning mode. For example, as shown in FIG. 3B, the set of the cleaning brush 41 a and the collection roller 41 b is separated from the secondary transfer belt 31. Therefore, there are two sets in contact with the secondary transfer belt 31: the cleaning brushes 42a and 43a and the collection rollers 42b and 43b. In the set, a positive bias voltage is applied to the collection roller 43b located upstream, and a negative bias voltage is applied to the collection roller 42b located downstream. That is, the bias voltage of the collection roller 42b that has been the positive electrode in the cleaning mode is switched to the negative electrode when the cleaning mode ends and the secondary transfer belt 31 comes into contact. In addition, the bias voltage of the collection roller 41 b that was the negative electrode before being separated is switched to the positive electrode when separated from the secondary transfer belt 31. At the same time, the cleaning brush 41a is connected to the ground. Therefore, in the operation mode, the residue staying on the cleaning brush 41a and charged on the negative electrode is discharged to the collection roller 41b to which the positive bias voltage is applied in the cleaning mode.

  Subsequently, the other cleaning brush and collection roller pairs are controlled to shift to the cleaning mode. For example, as shown in FIG. 3C, the set of the cleaning brush 43 a and the collection roller 43 b is separated from the secondary transfer belt 31. Accordingly, there are two sets in contact with the secondary transfer belt 31: the cleaning brushes 41a and 42a and the collection rollers 41b and 42b. In the set, a positive bias voltage is applied to the collection roller 41b located upstream, and a negative bias voltage is applied to the collection roller 42b located downstream. That is, in the collection roller 41b that is the positive electrode in the cleaning mode, the positive bias voltage is maintained as a set on the upstream side when the cleaning mode is ended and the secondary transfer belt 31 comes into contact. The pair of the cleaning brush 41a and the collection roller 41b starts cleaning the secondary transfer belt 31 without switching the applied bias voltage. Further, the bias voltage of the collection roller 43b that was the positive electrode before the separation is switched to the negative electrode after the separation. At the same time, the cleaning brush 43a is connected to the ground. Accordingly, the residue staying on the cleaning brush 43a during the operation mode and charged to the positive electrode is discharged to the collection roller 43b to which the negative bias voltage is applied during the cleaning mode.

  Subsequently, the separation control is continued in the state shown in FIG. When the state of FIG. 3C is shifted to the state of FIG. 3A, the pair of the cleaning brush 41a and the collection roller 41b is not separated but is in contact with the secondary transfer belt 31. Therefore, the polarity of the bias voltage applied to the collection roller 41b is reversed. That is, the pair of the cleaning brush 41a and the collection roller 41b is located on the upstream side when in the state of FIG. 3C, but is positioned on the downstream side when the state of FIG. Become. Therefore, the bias voltage applied to the collection roller 41 b is switched to the reverse polarity while being in contact with the secondary transfer belt 31. At this time, as for the residue staying on the cleaning brush 41a charged to the positive electrode at the time of FIG. 3C, the bias voltage applied to the recovery roller 41b is switched to the negative electrode after shifting to the state of FIG. 3A. Therefore, it is drawn to the collection roller 41b on the negative electrode side. Therefore, even if the electrode is reversed while the collection roller 41b is in contact with the secondary transfer belt 31, it is possible to suppress the residue in the cleaning brush 41a from moving from the cleaning brush 41a to the secondary transfer belt 31 as much as possible. Can do.

  As described above, when three sets of the cleaning brush and the collection roller are configured, one of the three sets is controlled to shift to the cleaning mode. In this way, all the cleaning brushes can be cleaned evenly and efficiently while maintaining the electrical balance on the secondary transfer belt 31 without interrupting the secondary transfer process.

  Next, with reference to FIG. 4, when the cleaning brush and the collection | recovery roller with which the cleaning apparatus which concerns on this embodiment is provided with 4 sets, the aspect which carries out separation control of the said set is demonstrated in detail.

  FIG. 4 is a diagram illustrating a configuration of a cleaning device including four cleaning brushes and a collection roller according to the present embodiment, and an aspect of the separation control thereof. In addition, the same code | symbol is used for the structure similar to the structure mentioned above, and the description is abbreviate | omitted in order to avoid duplication.

  As shown in FIG. 4, the cleaning device 40 includes four sets of cleaning brushes 41a to 44a and collection rollers 41b to 44b. As shown in FIG. 4A, while the two sets of the cleaning brushes 42a, 43a and the collection rollers 42b, 43b are separated from the secondary transfer belt 31, the cleaning brushes 41a, 44a and the collection rollers 41b, 44b The two sets are controlled to contact the secondary transfer belt 31. The bias voltage applied to the pair of the cleaning brush 44a and the collection roller 44b located on the upstream side, and the bias voltage applied to the pair of the cleaning brush 41a and the collection roller 41b located on the downstream side among the abutting sets. The relationship with this electrode is as described above.

  Subsequently, the two sets of the cleaning brush and the collection roller that are in the operation mode are controlled to shift to the cleaning mode, and the two sets that are in the cleaning mode are controlled to contact the secondary transfer belt 31. . As shown in FIG. 4B, two sets of cleaning brushes 41a and 44a and recovery rollers 41b and 44b are separated from the secondary transfer belt 31, and two sets of cleaning brushes 42a and 43a and recovery rollers 42b and 43b are provided. Are controlled to contact the secondary transfer belt 31.

  As described above, when four sets of the cleaning brush and the collection roller are configured, they are divided into a group that contacts the secondary transfer belt 31 simultaneously from the separated state and a group that separates simultaneously from the contacted state. For example, in FIG. 4, one group consists of two sets of cleaning brushes 41a and 44a and collection rollers 41b and 44b, and the other group consists of two sets of cleaning brushes 42a and 43a and collection rollers 42b and 43b. Each group is controlled to repeat contact and separation alternately for a certain period. Also, the timing at which each group abuts or separates is controlled to be synchronized. In this way, all the cleaning brushes can be cleaned evenly and efficiently while maintaining the electrical balance on the secondary transfer belt 31 without interrupting the image forming process.

  Next, a process for executing control for shifting to the cleaning mode based on the number of sheets S or the printing rate of the sheet S on which an image is formed by the image forming apparatus A will be described in detail.

  When the cleaning device 40 is provided with two sets of cleaning brushes and recovery rollers, the cleaning mode is suitably controlled based on the number of sheets S on which an image is formed and the printing rate. Specifically, the cleaning mode is executed when the value obtained by integrating the cumulative number of sheets on which images have been formed and the printing rate for one sheet S exceeds a predetermined value. The printing rate can be calculated as the ratio of the area printed in the past 15 seconds after the start of the image forming process to the total area of the printed paper, based on the total number of pixels of the image formed image, for example. . The predetermined integrated value is set to 300,000, for example, and stored in the storage unit of the control unit 90 or the like. The control unit 90 performs a calculation at the time of image formation or the like, refers to the set value, and determines whether or not the calculation result has reached a predetermined integrated value. For example, when the number of sheets S on which an image is formed is 15,000 and the printing rate is 20%, it is determined that the integrated value has reached 300,000 (15,000 × 20 = 300,000). The control unit 90 performs control so as to shift to the cleaning mode.

  When the cleaning device 40 is provided with three or more sets of cleaning brushes and collection rollers, the cleaning mode is suitably executed based on the cumulative number of sheets S on which images have been formed. For example, the cleaning mode is controlled to be executed every time an image is formed on 10,000 sheets of paper S.

  In this way, by controlling the transition to the cleaning mode based on the number of sheets on which images are formed and the printing rate, the cleaning brush is kept clean when it is assumed that a large amount of residue remains on the cleaning brush. Image defects can be prevented. In addition, by executing the cleaning mode every time an image is formed on a predetermined number of sheets, the amount of wear of the cleaning brush can be controlled to be uniform among the plurality of cleaning brushes.

  As described above, in the present embodiment, the pair of the cleaning brush and the collection roller can be separated from the secondary transfer belt 31 in the cleaning mode. Therefore, the residue staying on the cleaning brush during the cleaning mode can be separated from the secondary transfer belt 31. Can be reliably prevented from re-adhering. Accordingly, sticking and filming due to the residue on the secondary transfer belt 31 can be prevented.

  In addition, the polarity of the bias voltage applied to the recovery roller is controlled to the opposite polarity in the operation mode and the cleaning mode, so that the residue staying on the cleaning brush and charged in one polarity is reversed. It can be absorbed efficiently by the applied collection roller and removed. In addition, a positive bias voltage is applied to a group located upstream of the secondary transfer belt 31 and a negative bias voltage is applied to a group located downstream of the plurality of pairs of cleaning brushes and collection rollers. Therefore, the toner charged on the negative electrode can be efficiently removed on the upstream side.

  When three or more sets of cleaning brushes and collection rollers are configured, at least two sets are always brought into contact with the secondary transfer belt 31 and cleaning can be continued without stopping the image forming process. Cleaning can be performed efficiently. Further, since the cleaning mode is executed based on a predetermined printing rate and the number of sheets subjected to image processing, it is possible to keep the cleaning brush clean and at the same time make the cleaning brush wear uniform.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims.

  For example, the rotation direction of the cleaning brush 41a and the like has been shown to be reversed with respect to the rotation direction of the secondary transfer belt 31, but is not limited thereto. It may be rotationally driven in the forward direction. Further, the collection roller 41b and the like may be driven to rotate in the forward or reverse direction with respect to the cleaning brush.

  Further, the rotation direction of the cleaning brush in the cleaning mode may be controlled to be opposite to the rotation direction in the operation mode.

  In the above embodiment, the cleaning device 40 has been described with respect to the configuration provided in the secondary transfer belt 31. However, it is not limited to this. The cleaning device 40 according to the present invention can be used for other belt-like members and cylindrical rotating bodies. For example, the intermediate transfer belt 6 may be used. In this case, since the intermediate transfer belt 6 is charged to the positive electrode, the residual toner on the belt is charged to the positive electrode. Therefore, a negative bias voltage is applied to the pair of the cleaning brush and the collection roller disposed on the upstream side. It is preferable to set so as to.

  In the above-described embodiment, the mode in which the photosensitive drum 1 is charged to the negative electrode and the electrostatic latent image is made visible by the negative toner has been described. However, it is not limited to this. The polarities for charging the photosensitive drum 1 and the toner can be combined in any way. Moreover, according to the combination, the electrode of the bias voltage applied to each set of the cleaning brush and the collection roller on the upstream side and the downstream side of the rotating body can be appropriately determined. For example, when the photosensitive drum 1 is charged with the positive electrode and an image to be developed is exposed, positive toner can be used. Positive polarity toners can also be used for patches. Here, the intermediate transfer belt 6 is charged to the negative electrode, and the secondary transfer belt 31 is charged to the positive electrode. Therefore, since it is assumed that there is a lot of toner charged on the positive electrode on the secondary transfer belt 6, the cleaning device 40 of the secondary transfer belt 31 has an upstream cleaning brush that contacts the secondary transfer belt 31 and A negative bias voltage is applied to the set of collecting rollers. The opposite positive bias voltage is applied to the abutting downstream group.

  Moreover, in the said embodiment, the voltage regulators 45 and 46 were each shown as a different component. However, it is not limited to this. One voltage adjusting device may be configured to apply bias voltages of a plurality of collecting rollers. Further, the voltage may be adjusted by the control unit 90 without configuring the voltage adjusting device.

  Further, the rotation speeds of the cleaning brush and the collection roller are appropriately set. For example, as compared with the secondary transfer belt 31, it is controlled to be 0.5 to 1.5 times.

  Further, the number of sets of the cleaning brush and the collection roller is not limited to 2 to 4 sets. A larger number of sets may be configured.

A image forming apparatus,
S paper,
SC image reader,
SL slit,
1Y, 1M, 1C, 1K photosensitive drum,
2Y, 2M, 2C, 2K charging unit,
3Y, 3M, 3C, 3K optical writing unit,
4Y, 4M, 4C, 4K developing device,
5Y, 5M, 5C, 5K photosensitive drum cleaning device,
6 Intermediate transfer belt,
7A Secondary transfer part,
7Y, 7M, 7C, 7K primary transfer part,
10Y, 10M, 10C, 10K image forming unit,
20 Paper transport section,
21 Paper feed unit,
22 Loop forming roller pair,
23 Registration roller pair,
24 Double-sided conveyance path,
25 Paper discharge roller,
291, 292, 293 paper feed trays,
30 Secondary transfer device,
31 Secondary transfer belt,
32 Drive roller,
40 Secondary transfer belt cleaning device (cleaning device),
45, 46 voltage regulator,
49 Scraper,
50 fixing device,
80 operation display section,
90 Control unit.

Claims (14)

A cleaning brush configured to remove a residue having polarity on the rotating body by rotating in contact with the rotating body that is driven to rotate, and to be separated from the rotating body;
A collection roller configured in combination with the cleaning brush so as to remove the residue from the cleaning brush by rotating in contact with the cleaning brush and to be separated from the cleaning brush;
Voltage adjusting means for applying a voltage to the recovery roller,
While the set of the cleaning brush and the collection roller is separated from the rotating body, the voltage adjusting means reverses the polarity of the voltage applied to the collection roller and at the same time connects the cleaning brush to the ground. cleaning device that. The distance between the pair of the cleaning brush and the collection roller is a value calculated by integrating the number of sheets on which an image is formed and a printing rate that is a ratio of the printed area to the area of the sheet, or the image The cleaning device according to claim 1, wherein the cleaning device is executed based on the number of sheets formed. A plurality of sets of the cleaning brush and the collection roller are arranged, and a polarity of a voltage applied to a group located at the most upstream in the rotation direction of the rotating body among the plurality of sets contacting the rotating body is the residual The cleaning device according to claim 1, wherein the cleaning device has a polarity opposite to that of the object. A cleaning brush configured to remove a residue having polarity on the rotating body by rotating in contact with the rotating body that is driven to rotate, and to be separated from the rotating body;
A collection roller configured in combination with the cleaning brush so as to remove the residue from the cleaning brush by rotating in contact with the cleaning brush and to be separated from the cleaning brush;
Voltage adjusting means for applying a voltage to the recovery roller,
A plurality of sets of the cleaning brush and the collection roller are arranged, and the plurality of sets are separated from the rotating body at the same time from a state of being in contact with the rotating body,
The timing at which one group separates or abuts is synchronized with the timing at which the other group abuts or separates, and the period in which each group separates and abuts is alternately repeated. is the among the plurality of sets in contact with the rotating body, the polarity of the voltage applied to the set located at the most upstream of the rotational direction of said rotary body, I polarity opposite der of the residue, the The cleaning device reverses the polarity of the voltage applied to the recovery roller while the set of the cleaning brush and the recovery roller is separated from the rotating body . The cleaning device according to claim 4, wherein at least two sets of the plurality of sets of the cleaning brush and the collection roller always come into contact with the rotating body. A cleaning brush configured to remove a residue having polarity on the rotating body by rotating in contact with the rotating body that is driven to rotate, and to be separated from the rotating body;
A collection roller configured in combination with the cleaning brush so as to remove the residue from the cleaning brush by rotating in contact with the cleaning brush and to be separated from the cleaning brush;
Voltage adjusting means for applying a voltage to the recovery roller,
Set of cleaning brushes and the collection rollers are a plurality of sets disposed among the plurality of sets, always at least two pairs come into contact with the rotary body, among the plurality of sets in contact with the rotating body, the rotation of the rotating body The polarity of the voltage applied to the pair located in the uppermost stream in the direction is opposite to the polarity of the residue, and while the pair of the cleaning brush and the collection roller is separated from the rotating body, The voltage adjusting means is a cleaning device that reverses the polarity of the voltage applied to the recovery roller . A cleaning brush configured to remove a residue having polarity on the rotating body by rotating in contact with the rotating body that is driven to rotate, and to be separated from the rotating body;
A collection roller configured in combination with the cleaning brush so as to remove the residue from the cleaning brush by rotating in contact with the cleaning brush and to be separated from the cleaning brush;
Voltage adjusting means for applying a voltage to the recovery roller,
While the set of the cleaning brush and the collection roller is separated from the rotating body, the voltage adjusting means reverses the polarity of the voltage applied to the collection roller, and the rotation direction of the cleaning brush is separated. reverse der torque cleaning apparatus to the rotation direction of when not in.   The cleaning device according to claim 1, further comprising a scraper that removes the residue on the collection roller.   The cleaning device according to claim 1, wherein the rotating body is an intermediate transfer belt on which a toner image is formed or a secondary transfer belt that transfers the toner image to a recording medium.   An image forming apparatus comprising the cleaning device according to claim 1. A cleaning brush that removes the polar residue on the rotating body, a collection roller that contacts the cleaning brush to remove the residue from the cleaning brush, and a voltage adjusting means that applies a voltage to the collection roller; In a cleaning device comprising:
In a state where a unipolar voltage is applied to the collection roller, the cleaning brush rotates in contact with the rotating body;
A set of the cleaning brush and the collection roller is separated from the rotating body;
Connecting the cleaning brush to the ground at the same time that the voltage adjusting means applies a voltage having a polarity opposite to the polarity of the voltage applied before the separation to the separated collection roller;
A control method for a cleaning device including: A cleaning brush that removes the polar residue on the rotating body, a collection roller that contacts the cleaning brush to remove the residue from the cleaning brush, and a voltage adjusting means that applies a voltage to the collection roller; A plurality of sets of the cleaning brush and the collection roller are arranged, and the plurality of sets are a group that is simultaneously separated from a state of being in contact with the rotating body and a group of being simultaneously contacted from a state of being separated from the rotating body. In the cleaning device divided into
The timing at which one group separates or abuts is synchronized with the timing at which the other group abuts or separates, and the period in which each group separates and abuts is alternately repeated, and
A step of rotating the cleaning brush of the same set as each of the collection rollers in contact with the rotating body in a state where a unipolar voltage is applied to the collection rollers of each of the groups belonging to one group;
Applying a voltage having a polarity opposite to the polarity of the residue to a group located at the most upstream in the rotation direction of the rotating body among a plurality of sets in contact with the rotating body;
A set of the cleaning brush and the collection roller belonging to the other group is separated from the rotating body;
The voltage adjusting means applying a voltage having a polarity opposite to the polarity of the voltage applied before the separation to the separated collection rollers;
A control method for a cleaning device including: A cleaning brush that removes the polar residue on the rotating body, a collection roller that contacts the cleaning brush to remove the residue from the cleaning brush, and a voltage adjusting means that applies a voltage to the collection roller; In a cleaning device in which a plurality of sets of the cleaning brush and the collection roller are arranged,
Of the plurality of sets, at least two sets always rotate in contact with the rotating body in a state where a unipolar voltage is applied to the collection roller;
Applying a voltage having a polarity opposite to the polarity of the residue to a group located at the most upstream in the rotation direction of the rotating body among a plurality of sets in contact with the rotating body;
A set of the cleaning brush and the collection roller is separated from the rotating body;
The voltage adjusting means applying a voltage having a polarity opposite to the polarity of the voltage applied before the separation to the separated collection rollers;
A control method for a cleaning device including: A cleaning brush that removes the polar residue on the rotating body, a collection roller that contacts the cleaning brush to remove the residue from the cleaning brush, and a voltage adjusting means that applies a voltage to the collection roller; In a cleaning device comprising:
In a state where a unipolar voltage is applied to the collection roller, the cleaning brush rotates in contact with the rotating body;
A set of the cleaning brush and the collection roller is separated from the rotating body;
While the set of the cleaning brush and the collection roller is separated, the rotation direction of the cleaning brush is rotated in the direction opposite to the rotation direction when not separated.
The voltage adjusting means was applied to the separated collection roller before separating.
Applying a voltage having a polarity opposite to the polarity of the voltage;
A control method for a cleaning device including:

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