JP4507631B2 - Image forming apparatus - Google Patents

Description

  According to the present invention, an electrostatic latent image is formed on an image carrier whose peripheral surface is uniformly charged with a predetermined polarity, and toner is attached to the electrostatic latent image of the image carrier based on a potential difference. The present invention relates to an image forming apparatus that forms a toner image on a body, transfers the toner image to a recording medium via an intermediate transfer body, and forms an image on the recording medium.

  2. Description of the Related Art Conventionally, an image forming apparatus such as a laser printer or an electrophotographic copying machine that forms an image by irradiating a photosensitive member with a light beam has been widely used. In such an image forming apparatus, a photosensitive drum as an image carrier is charged by a charger such as a charging roll, and an electrostatic latent image is formed by irradiating the charged photosensitive drum with a light beam from an exposure device. Toner is adhered from a developing unit to a photosensitive drum on which an electrostatic latent image is formed, and the toner is transferred onto an image recording medium such as paper by a transfer unit. Also, in an image forming apparatus such as a color laser printer, for example, a photosensitive drum is provided for each color of yellow, magenta, cyan, and black, and an electrostatic latent image is formed on each photosensitive drum, and toner of each color is attached. Then, a color toner image is formed by superimposing the toners of the respective colors on the intermediate transfer member, and the color toner image is further transferred from the intermediate transfer member to the image recording medium.

  At the time of this transfer, not all toner is transferred to the image recording medium, and there is toner that remains attached to the photosensitive drum and the intermediate transfer member. In a color laser printer, for example, when toner is transferred to an intermediate transfer member in the order of yellow, magenta, cyan, and black, other color toners that have already been transferred when transferring magenta, cyan, and black in the second and subsequent stages are transferred. (For example, when transferring black, yellow, magenta, and cyan toners) may be transferred from the intermediate transfer member to the photosensitive drum. As described above, in the image forming apparatus, toner remains on the photosensitive drum, and when the toner is transferred in reverse, a ghost or the like is generated in the printed image and the image quality is deteriorated. For this reason, a cleaner and a toner collection box for collecting the residual toner are required for each photosensitive drum, and it is difficult to downsize the image forming apparatus.

  Therefore, the present applicant has disclosed an image forming apparatus provided with a cleaning roll for temporarily collecting residual toner in Patent Document 1. This cleaning roll has brush hairs implanted on its peripheral surface, and when a voltage having a polarity opposite to the polarity of the toner is applied, the toner is adsorbed by electrostatic force, and a voltage having the same polarity as the polarity of the toner is applied. And exhale the toner. The image forming apparatus described in Patent Document 1 has an image forming mode and a cleaning mode. In the image forming mode, an image is formed on a sheet based on image data, and residual toner is temporarily collected from a photosensitive drum to a cleaning roll. In the cleaning mode, the residual toner accumulated on the photosensitive drum is discharged from the cleaning roll, and the discharged residual toner is returned to the developing unit or collected on the intermediate transfer member and collected in a batch. For this reason, it is not necessary to provide a toner collection box for each photosensitive drum, and the image forming apparatus can be downsized.

By the way, when the rotation of the cleaning roller is stopped when collecting the residual toner (image forming mode), the brush hair slides with respect to the photosensitive drum, so that the residual toner has good adsorbability (cleaning property). In addition, when the accumulated residual toner is discharged (cleaning mode), if the cleaning roll is driven to rotate relative to the photosensitive drum (the rotational speed of the cleaning roll and the photosensitive member is the same), the accumulated residual toner from the brush bristles to the photosensitive drum. Good discharge. For this reason, in the image forming apparatus, the rotation of the cleaning roll is switched between the image forming mode and the cleaning mode.
JP 2001-75448 A

  However, in order to switch the rotation of the cleaning roll between the image forming mode and the cleaning mode, it is necessary to provide a clutch mechanism on the cleaning roll. If the clutch mechanism is provided, the apparatus becomes complicated and the manufacturing cost of the image forming apparatus increases.

  SUMMARY OF THE INVENTION In consideration of the above-described facts, an object of the present invention is to provide an image forming apparatus capable of rotating (sliding) and drivenly rotating a toner collection / discharge unit with respect to an image carrier by a simple mechanism. .

According to the first aspect of the present invention, an electrostatic latent image is formed by irradiating the light beam with the exposure unit while rotating the image carrier whose peripheral surface is uniformly charged with a predetermined polarity by the charging unit. And developing the electrostatic latent image of the image carrier by the developing means to form a toner image, the residual toner adhering to the image carrier is changed to a first potential difference from the image carrier. In the cleaning mode that is tentatively collected based on a predetermined interval, the collected residual toner is transferred to the peripheral surface of the image carrier based on a second potential difference from the image carrier. An image forming apparatus having a roller-shaped toner collecting / discharging unit disposed opposite to a peripheral surface of the image carrier to be discharged , wherein the image forming apparatus is coaxially connected to a rotation shaft of the toner collecting / discharging unit, and Outside the image forming area on the peripheral surface of the carrier A touch arranged rotary body, and a voltage applying means for applying a predetermined voltage to the peripheral surface of the rotating body and the toner collecting / discharging means, said first potential difference controls the voltage by the voltage applying means The toner collection / ejection means is moved relative to the peripheral surface of the image carrier by the rotational load of the rotation shaft, and the second potential difference is controlled by controlling the voltage applied by the voltage application means. And a potential difference control means for controlling the potential difference so that the rotating body and the image carrier are adsorbed and the toner collection / discharge means is driven to rotate by the image carrier .

According to the first aspect of the present invention, the potential difference control means can change the electrostatic force by changing the potential difference between the rotating body and the image carrier by controlling the voltage applied by the voltage application means. When the electrostatic force with the image carrier is small, the rotator moves (slids) relative to the image carrier due to the rotational load of the rotator, and when the electrostatic force is large, the rotator is attracted to the image carrier and is driven to rotate. . The rotating body is connected to the toner collection / discharge unit, and rotates the toner collection / discharge unit in conjunction with each other. Therefore, the rotating body can be moved relative to the image carrier and driven to rotate by controlling the potential difference by the potential difference control means.

  According to a second aspect of the present invention, in the first aspect of the present invention, the rotating body is a pair of conductive elastic members, and is disposed so as to sandwich the toner collecting / discharging unit in the axial direction. It is characterized by that.

According to the second aspect of the present invention, since the rotating body is a conductive elastic member, the rotating body is easily attracted to the image carrier by electrostatic force and easily rotated. Further, since the pair of conductive elastic members are arranged so as to sandwich the toner collecting / discharging unit, it is possible to apply a force for bringing the toner collecting / discharging unit into uniform contact with the image carrier.

  The invention according to claim 3 is the invention according to claim 2, wherein the conductive elastic member is a conductive rubber.

  According to the third aspect of the present invention, since the conductive elastic member is a conductive rubber, it is inexpensive and the manufacturing cost can be reduced.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the toner collecting / discharging means is a brush roller in which brush hairs are planted on a peripheral surface, and the hair tip is It is in contact with the surface of the image carrier.

  According to the fourth aspect of the invention, since the toner collecting / discharging means is a brush roller, the image carrier is not damaged even if it comes into contact with the image carrier.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the potential difference control means steps down the voltage of the charged image carrier by exposure by the exposure means. A potential difference between the image carrier and the rotating body is controlled.

  According to the fifth aspect of the present invention, when the charged image carrier is exposed by the exposure means, the voltage drops. Therefore, the potential difference between the image carrier and the rotating body can be controlled also by exposure by the exposure means.

  As described above, according to the present invention, the rotating body is connected coaxially with the rotating shaft of the toner collecting / discharging means, and the toner collecting / discharging means is controlled by controlling the potential difference between the rotating body and the image carrier. It has an excellent effect that it can provide an image forming apparatus capable of relative movement (sliding) and driven rotation with respect to the image carrier.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following examples.

(overall structure)
FIG. 1 shows an image forming apparatus 10 according to the present exemplary embodiment.

  The image forming apparatus 10 is a full color type and includes four image forming units 15. These image forming units 15 are arranged at predetermined intervals along the longitudinal direction of the intermediate transfer belt 14. The intermediate transfer member belt 14 is stretched around a plurality of winding rollers 12 and has an endless belt shape that is conveyed in the direction of arrow E in FIG. 1 by driving an intermediate transfer member driving motor 80 (see FIG. 4).

  The four image forming units 15 will be described in detail. The image forming units 15 correspond to four colors of yellow (Y), magenta (M), cyan (C), and black (K), respectively ( Hereinafter, they are referred to as image forming units 15Y, 15M, 15C, and 15K). In the following, each component of the image forming unit 15 is indicated by an alphabet (Y / M / C / K) indicating each color at the end of the reference numeral, but the colors are not particularly distinguished. In the explanation, the alphabet at the end of the code is omitted.

  The image forming unit 15 is provided with a cylindrical photosensitive drum 16 as an image carrier, and is driven in a direction indicated by an arrow F or an arrow G in FIG. 1 by driving a photosensitive member driving motor 82 (see FIG. 4). Rotate. Further, a charging roll 18 is disposed around each photosensitive drum 16 as a charging unit that uniformly charges the surface of the photosensitive drum 16. Charging of the photosensitive drum 16 by the charging roll 18 is the first stage of a series of image forming processes. Further, on the downstream side of the charging roll 18 along the rotation direction of each photosensitive drum 16 (in the direction of arrow F in FIG. 1), the axial direction of the photosensitive drum 16 uniformly charged by the charging roll 18 is desired. An exposure device 20 that irradiates a light beam based on the image and forms an electrostatic latent image on the photosensitive drum 16 is disposed. In the present embodiment, an LED array 40 (light emitting diode) (see FIG. 2) arranged in a line (may be a plurality of lines) in the axial direction of the photosensitive drum 16 is applied as the exposure unit 20.

  Further, around each photosensitive drum 16, there is an electrostatic formed on the photosensitive drum 16 on the downstream side of the exposure device 20 along the rotation direction of the photosensitive drum 16 (direction of arrow F in FIG. 1). A developing unit 22 is provided that develops the latent image with toner (yellow / magenta / cyan / black), and forms a toner image. A contact point (transfer position) with the intermediate transfer belt 14 is located on the downstream side of the developing unit 22, and the first transfer unit is sandwiched between the photosensitive drum 16 and the intermediate transfer belt 14. 24 is arranged. The first transfer device 24 has a function of transferring a toner image on the photosensitive drum 16 to the intermediate transfer belt 14 by applying a predetermined voltage with a polarity opposite to the polarity of the toner. A cleaning roll 26 that temporarily collects residual toner adhering to the photosensitive drum 16 after transfer is disposed downstream of the transfer position and upstream of the charging roll 18.

  The toner images of different colors formed on the respective photosensitive drums 16 are respectively transferred to the intermediate transfer belt 14 so as to overlap each other (in the same area) on the belt surface of the intermediate transfer belt 14. As a result, a full-color toner image is formed on the intermediate transfer belt 14. In this embodiment, the toner image in which the four color toner images are transferred in a superimposed manner is referred to as a final toner image.

  A second transfer device 29 including a pair of rollers 29A and 29B is disposed on the downstream side in the transport direction (the direction of arrow E in FIG. 1) from the toner image transfer position from the photosensitive drum 16 of the intermediate transfer belt 14. Has been. The final toner image area formed on the intermediate transfer belt 14 is sandwiched between the rollers 29A and 29B of the second transfer device 29, and from the paper tray 30 in synchronism with this timing. A sheet 28 as a recording medium that is taken out by a sheet feeding roller 32 and a sheet winding means (not shown) and conveyed by two sets of conveying rollers 33 is sandwiched. The toner image is transferred to the paper 28.

  The paper 28 onto which the final toner image has been transferred is conveyed to a fixing device 34 composed of a pressure roller 34A and a heating roller 34B, and subjected to a fixing process. As a result, the final toner image is fixed, and a desired image (color image) is formed on the paper 28. The paper 28 on which the image is formed is discharged out of the apparatus by a pair of paper discharge rollers 35 disposed on the downstream side in the transport direction of the fixing device 34.

  Here, a cleaner 38 having a cleaning blade 37 is disposed downstream of the second transfer unit 29 in the transport direction of the intermediate transfer belt 14 (in the vicinity of the upstream side of the first-stage image forming unit 15C). The first purpose of the cleaner 38 is to transfer the final toner image onto the paper 28 by the second transfer device 29 and then slide the remaining toner adhering on the intermediate transfer belt 14 with the cleaning blade 37. There is to remove.

(Detailed configuration of the image forming unit 15)
Next, referring to FIG. 2, the details of the configuration of one of the four image forming units 15 will be described as a representative. Since the other image forming units 15 have the same configuration, description of the configuration is omitted.

  As shown in FIG. 2, a predetermined DC voltage (−800 V in the present embodiment) is applied to the charging roll 18 disposed below the photosensitive drum 16, and the charging roll driving motor 84 (FIG. 4) is applied. 2) so as to be synchronized with the rotation of the photosensitive drum 16 in the direction of arrow J or M in FIG. 2 to uniformly charge the surface of the photosensitive drum 16 from the charging roll 18 to about −500V. Let The predetermined voltage is preferably obtained by superimposing an AC component on a DC component. That is, -800V is applied as a DC component, and the AC component of the sine curve is superimposed with this -800V level as a reference.

  The exposure device 20 is composed of LED arrays 40 arranged in one or a plurality of rows along the axial direction of the photosensitive drum 16, and image data is supplied to the photosensitive drum 16 charged to about −500V. Then, a light beam is output from the LED array 40 and exposed. The voltage of the exposed area of the photosensitive drum 16 is lowered to about −200 V, and an electrostatic latent image is formed by the unexposed area.

  The developing unit 22 has a developing roll 42 constituting a part thereof in contact with the photosensitive drum 16. The developing roll 42 is rotated in the direction of the arrow K in FIG. 2 by the driving force of the developing roll driving motor 86 (see FIG. 4), and is electrostatically charged by a developer containing two components of negative polarity toner and positive polarity carrier. Develop the latent image. In addition to the developing roll 42, the developing device 22 includes a developer conveying member 44 that conveys the developer to the developing roll 42 and a developer agitating member 46 that agitates the developer. In this developing device 22, a negative voltage (−300 V in the present embodiment) is applied to perform reverse development, and toner that is a negative polarity component of the developer is exposed by the LED array 40 of the photosensitive drum 16. It adheres to the area that did not exist.

  The first transfer device 24 is applied with a positive voltage (in the present embodiment, +500 V) in an image forming mode in which an image is formed on a normal paper 28. In the cleaning mode in which the toner temporarily collected on the cleaning roll 26 is discharged, a negative voltage (-1000 V in this embodiment) is applied. Accordingly, in the image forming mode, the first transfer device 24 is +500 V, and the area on the photosensitive drum 16 where the developer adheres is −500 V. Therefore, toner having a negative polarity is transferred from the photosensitive drum 16 to the intermediate transfer belt. 14 is transferred.

  However, the first transfer device 24 cannot transfer all of the toner, and there is a slight amount of toner remaining on the photosensitive drum 16, and the polarity is reversed to positive when the first transfer device 24 is charged. It is known that toner (reversal toner) is present. On the photosensitive drums 16K, 16Y, and 16M (see FIG. 1), the toners of other colors that have already been transferred may be transferred from the intermediate transfer belt 14 in reverse.

The cleaning roll 26 is in contact with the photosensitive drum 16 and is rotatable by being attracted to the photosensitive drum 16 based on electrostatic force due to a potential difference with the photosensitive drum 16. The cleaning roller 26 has conductive brush hairs planted on a part of its peripheral surface (details will be described later), and residual toner adhered to the photosensitive drum 16 by rubbing the surface of the photosensitive drum 16 with the brush hairs. Has the role of adsorbing.

(Detailed configuration of the cleaning roll 26)
Next, the details of the cleaning roll 26 will be described with reference to FIG.

  The cleaning roller 26 includes a brush roller 47 serving as a toner collecting / discharging unit having conductive brush hairs implanted on the surface thereof, and a pair of conductive elastic members (for example, conductive rubber) on both ends of the brush roller 47. A conductive roller 48 as a rotating body is connected by a shaft 49 so that it can rotate about the shaft 49 as an axis. The brush roller 47 corresponds to a region (image forming region) where a toner image on the peripheral surface of the photosensitive drum 16 is formed, and the brush bristles are in contact with the image forming region. The pair of conductive rollers 48 are in contact with regions (non-image forming regions) where toner images are not formed on both ends of the image forming region.

Both the brush roller 47 and the conductive roller 48 of the cleaning roll 26 are charged to a predetermined voltage in the cleaning mode and the image forming mode. The charged conductive roller 48 is attracted to the photosensitive drum 16 by the electrostatic force based on the potential difference from the non-image forming area of the photosensitive drum 16 and rotates in a dependent manner. Since the cleaning roll 26 is connected to the conductive roller 48 by the shaft 49, the cleaning roller 26 rotates dependently when the conductive roller 48 rotates dependently. However, the shaft 49 has a rotational load that does not rotate the cleaning roll 26 when the electrostatic force is small. That is, in the cleaning mode, the potential difference of the conductive roller 48 and the non-image forming region is actively increased by increasing the electrostatic force attracted to the photosensitive drum 16, to adsorb the conductive roller 48 to the photosensitive drum 16 by the cleaning The roll 26 is driven and rotated by the photosensitive drum 16. On the other hand, in the image forming mode, the electrostatic force is reduced by reducing the potential difference between the conductive roller 48 and the non-image forming area, and the rotation of the cleaning roll 26 is stopped by the rotational load by the shaft 49. Therefore, the cleaning roll 26 can stop rotating and follow the photosensitive drum 16 without a driving device.

  Here, the non-image forming area of the photosensitive drum 1 is charged to −500 V by the above-described charging roll 18. The electrostatic force generated between the conductive roller 48 and the non-image forming area increases as the potential difference increases. However, since the discharge occurs when the potential difference becomes too large, the potential difference is preferably set to about 300V to 400V. For this reason, in this embodiment, the voltage charged to the brush roller 47 and the conductive roller 48 is set to −600 V (potential difference 100 V) in the image forming mode and −200 V (potential difference 300 V) in the cleaning mode.

  In the image forming mode, the conductive roller 48 is charged to −600 V, the potential difference from the non-image forming area (−500 V) is set to 100 V, and the rotation of the cleaning roll 26 is stopped by the rotational load of the shaft 49. Thereby, the bristle of the brush roller 47 slides on the image forming area of the photosensitive drum 16. Further, when the brush roller 47 is charged to −600 V, the residual toner can be adsorbed due to a potential difference from the image forming area.

In the cleaning mode, the conductive roller 48 is charged to −200 V, the potential difference from the non-image forming area is set to 300 V, and the conductive roller 48 is attracted to the photosensitive drum 16 to be driven to rotate. The brush roller 47 is charged to −200 V, and when driven by the photosensitive drum 16 and rotated, the residual toner accumulated in the brush hair can be discharged onto the photosensitive drum 16 due to a potential difference with the photosensitive drum 16.

  Here, when executing the cleaning mode, the photosensitive drum 16 rotates in the same direction as the rotation direction during image formation, and the developing roller 22 and the developing device 22 develop with the accumulated residual toner received from the cleaning roller 26 adhered thereto. In general, it passes through the roll 42 to reach the contact position with the intermediate transfer belt 14 and is transferred to the intermediate transfer belt 14. However, the photosensitive drum 16 can be rotated in the direction opposite to the rotation direction during image formation to reach the contact position with the intermediate transfer belt 14 without passing through the charging roll 18 and the developing device 22.

  In the present embodiment, the case where the cleaning mode is executed is described by applying the case of rotating in the direction opposite to the rotation direction at the time of image formation. However, the cleaning mode may be executed in the same direction as the rotation direction at the time of image formation.

(Detailed configuration of the control unit 50)
Next, the configuration of the control unit 50 that controls the image forming apparatus 10 will be described with reference to FIG.

  When image data is input from an external host computer (not shown) or the like, the control unit 50 controls image formation processing (image formation mode) by a print control unit 52 described later, and will be described later at predetermined intervals. The cleaning control unit 58 controls the discharge process (cleaning mode) of the accumulated toner collected on the cleaning roll 26.

  The print controller 52 includes a non-volatile memory 54, an intermediate transfer member controller 60, a second transfer device charge controller 62, a first transfer device charge controller 64, a photoreceptor rotation controller 70, a lighting controller 72, The charging roll controller 74, the developing device controller 76, and the cleaning roll controller 78 are connected.

  When image data is input, the print control unit 52 outputs the following various instructions to control the image forming process (image forming mode) on the paper 28. The photosensitive member rotation control unit 70, the lighting control unit 72, the charging roll control unit 74, the developing device control unit 76, and the cleaning roll control unit 78 are provided for each color of the image forming unit 15 as the image forming unit control unit 66. However, since the control to the four image forming units 15 is the same, the control to one image forming unit 15 will be described as a representative.

  First, the print controller 52 outputs a drive instruction to the intermediate transfer body controller 60 to drive the intermediate transfer body belt 14 in the direction of arrow E in FIG. 1 (FIG. 2).

  Next, the print control unit 52 outputs a forward rotation instruction to rotate the photosensitive drum 16 in the direction of arrow F in FIG. 2 to the photosensitive member rotation control unit 70 of the image forming unit control unit 66.

  When the photosensitive drum 16 rotates, the printing control unit 52 outputs a charging roll forward rotation charging instruction for charging the charging roll 18 to −800 V to the charging roll control unit 74 and rotating it in the direction of arrow J in FIG. The image forming area and the non-image forming area of the photosensitive drum 16 are charged to −500V. Further, a lighting instruction is output to the lighting control unit 72 based on the image data to turn on the LED array 40 of the exposure device 20, and an electrostatic latent image is formed in the image forming area on the photosensitive drum 16. Further, a developing instruction for generating a voltage of −300 V on the developing roll 42 of the developing device 22 and rotating it in the direction of the arrow K in FIG. 2 is output to the developing device controller 76, and toner is applied to the electrostatic latent image in the image forming area. Then, development is performed to form a toner image.

  Further, the print control unit 52 outputs a toner transfer instruction to the first transfer unit charge control unit 64, outputs +500 V to the first transfer unit 24, and outputs a final toner transfer instruction to the second transfer unit charge control unit 62. Then, a voltage of +1000 V is generated in the second transfer device 29B, and the toner image on the photosensitive drum 16 is transferred to the paper 28 via the intermediate transfer belt 14.

  Further, a temporary collection instruction for charging the brush roller 47 and the conductive roller 48 of the cleaning roll 26 to −600 V is output to the cleaning roll control unit 78, and the remaining adhering to the image forming area of the photosensitive drum 16 by the transfer is output. The toner is temporarily collected. When the brush roller 47 and the conductive roller 48 of the cleaning roll 26 are charged to −600 V by the provisional collection instruction, the potential difference between the conductive roller 48 and the photosensitive drum 16 charged by the charging roll 18 becomes 100 V. The rotation stops. As a result, the brush bristles of the brush roller 47 slide on the image forming area of the photosensitive drum 16, and the residual toner is collected on the bristles based on the potential difference between the brush roller 47 and the image forming area.

  Further, when the image forming process is completed, an instruction to count up the total number of sheets is output to a non-volatile memory 54 described later, and the post-cleaning total number of printed sheets stored in the non-volatile memory 54 is counted up.

  The nonvolatile memory 54 is connected to the print control unit 52, the cleaning determination unit 56, and the cleaning control unit 58. The non-volatile memory 54 stores a cleaning condition for determining the cleaning mode interval. In this embodiment, the cleaning mode is executed every time 30 sheets of cleaning conditions are printed. Further, the non-volatile memory 54 stores the cumulative number of printed sheets after cleaning since the cleaning mode was performed. The cumulative number of printed sheets after cleaning is counted up when a cumulative number count instruction is received from the print control unit 52, and is initialized to zero when a cumulative number initialization instruction is received from a cleaning control unit 58, which will be described later. That is, the cumulative number of printed sheets after cleaning stores the cumulative number of printed sheets since the most recent cleaning mode was performed.

  The cleaning determination unit 56 is connected to the cleaning control unit 58 and the nonvolatile memory 54. The cleaning determination unit 56 reads the cleaning condition and the cumulative number of printed sheets after cleaning from the nonvolatile memory 54, determines whether the cumulative number of printed sheets after cleaning is the cleaning condition as a result of performing the image forming process, and if the cleaning condition is satisfied. A cleaning instruction is output to the cleaning control unit 58 to cause the remaining toner accumulated in the brush roller 47 of the cleaning roll 26 to be discharged.

  The cleaning control unit 58 includes a nonvolatile memory 54, a cleaning determination unit 56, an intermediate transfer body control unit 60, a first transfer device charging control unit 64, a photoconductor rotation control unit 70, a charging roll control unit 74, and a cleaning roll control. The unit 78 is connected.

  When receiving a cleaning instruction from the cleaning determination unit 56, the cleaning control unit 58 outputs the following various instructions to control the cleaning mode.

  Here, in the present invention, in the cleaning mode, the cleaning control unit 58 controls the rotation of the photosensitive drum 16 in the opposite direction to the image forming mode. Since the control of each image forming unit 15 is the same, the control for one image forming unit 15 will be described as a representative.

  First, the cleaning control unit 58 outputs a driving instruction to the intermediate transfer member control unit 60 to drive the intermediate transfer member belt 14 in the direction of arrow E in FIG. 1 (FIG. 2), and the photosensitive member rotation control unit 70. A reverse rotation instruction for rotating the photosensitive drum 16 in the direction of arrow G in FIG. As a result, the photosensitive drum 16 rotates in the reverse direction.

  When the photosensitive drum 16 rotates, the cleaning control unit 58 outputs a charging roll reverse rotation charging instruction for charging the charging roll 18 to −800 V to the charging roll control unit 74 and rotating it in the direction of arrow M in FIG. The image forming area and the non-image forming area −500 V of the photosensitive drum 16 are charged.

  Next, the cleaning control unit 58 outputs a discharge instruction for charging the cleaning roll 26 to −200 V to the cleaning roll control unit 78, and discharges the accumulated residual toner onto the photosensitive drum 16 to the cleaning roll 26. When the brush roller 47 and the conductive roller 48 of the cleaning roll 26 are charged to −200 V in response to the discharge instruction, the potential difference between the conductive roller 48 and the non-image forming area of the photosensitive drum 16 becomes 300 V. 16 is driven to rotate. The brush roller 47 discharges accumulated residual toner based on the potential difference from the image forming area of the photosensitive drum 16. Since the photosensitive drum 16 rotates in the reverse direction, the residual toner discharged to the cleaning roll 26 is carried to the contact point with the first transfer unit 24 without passing through the charging roll 18 and the developing unit 22.

  Further, an accumulation residual toner transfer instruction is output to the first transfer unit charging control unit 64 to generate a voltage of −1000 V in the first transfer unit 24, and the accumulation residual toner on the cleaning roll 26 is transferred to the intermediate transfer member belt. 14 to transfer.

  When the cleaning mode is completed, an instruction to initialize the accumulated number is output to the nonvolatile memory 54, and the accumulated number of printed sheets after cleaning stored in the nonvolatile memory 54 is initialized to zero.

  The intermediate transfer body control unit 60 is connected to the print control unit 52 and the cleaning control unit 58. When the intermediate transfer member control unit 60 receives a driving instruction from the print control unit 52 and the cleaning control unit 58, the intermediate transfer member control unit 60 controls the intermediate transfer member driving motor 80 so that the intermediate transfer member belt 14 is moved to the arrow in FIG. 1 (FIG. 2). Drive in direction E.

  The second transfer unit charging control unit 62 is connected to the printing control unit 52. When receiving the final toner transfer instruction from the print control unit 52, the second transfer unit charge control unit 62 sets the voltage of the second transfer unit 29 to + 1000V.

  The first transfer unit charging control unit 64 is connected to the printing control unit 52 and the cleaning control unit 58. When receiving a toner transfer instruction from the print control unit 52, the first transfer unit charging control unit 64 generates a voltage of +500 V for the first transfer unit 24, and receives a stored residual toner transfer instruction from the cleaning control unit 58. And a voltage of -1000V is generated. Note that the first transfer unit charging control unit 64 is provided for each of the first transfer units 24Y, 24M, 24C, and 24K, and can be controlled separately.

  The photoconductor rotation control unit 70 is connected to the print control unit 52 and the cleaning control unit 58. When receiving a forward rotation instruction from the print control unit 52, the photosensitive member rotation control unit 70 controls the photosensitive member driving motor 82 to rotate the photosensitive drum 16 in the direction of arrow F in FIG. When receiving a reverse rotation instruction from the cleaning control unit 58, the photosensitive drum 16 is rotated in the direction of arrow G in FIG. In the cleaning mode, the photoconductor rotation control unit 70 receives the reverse rotation instruction from the cleaning control unit 58 and reversely rotates the photoconductor driving motor 82, so that the rotation direction of the photoconductor drum 16 is switched to the reverse of the image formation. be able to.

  The lighting control unit 72 is connected to the print control unit 52. When the lighting control unit 72 receives a lighting instruction from the print control unit 52, the lighting control unit 72 lights the LED array 40 of the exposure unit 20.

  The charging roll control unit 74 is connected to the printing control unit 52 and the cleaning control unit 58. When the charging roll control unit 74 receives the charging roll forward rotation charging instruction from the printing control unit 52, the charging roll control unit 74 charges the charging roll 18 to -800 V, and controls the charging roll driving motor 84 so that the charging roll 18 shown in FIG. When rotating in the direction of arrow J and receiving a charging roll reverse rotation charging instruction from the cleaning control unit 58, the charging roll 18 is charged to -800V, and the charging roll driving motor 84 is controlled so that the charging roll 18 is illustrated. Rotate in the direction of arrow M of 2.

  The developing device control unit 76 is connected to the print control unit 52. When the developing device controller 76 receives a development instruction from the print controller 52, the developing device controller 76 generates a voltage of −300 V on the developing roller 42, and controls the developing roller driving motor 86 to move the developing roller 42 to the arrow K in FIG. The toner is attached to the electrostatic latent image on the photosensitive drum 16 by rotating in the direction, and development is performed.

  The cleaning roll control unit 78 is connected to the print control unit 52 and the cleaning control unit 58. When receiving the provisional collection instruction from the print control unit 52, the cleaning roll control unit 78 charges the brush roller 47 and the conductive roller 48 of the cleaning roll 26 to -600 V, and performs provisional collection of the remaining toner on the photosensitive drum 16. . On the other hand, when a discharge instruction is received from the cleaning control unit 58, the brush roller 47 and the conductive roller 48 of the cleaning roll 26 are charged to -200 V, and the remaining toner accumulated on the photosensitive drum 16 is discharged.

(Function)
Next, the operation of the present embodiment will be described with reference to the flowchart of FIG.

  FIG. 5 is a flowchart showing the flow of processing when image data is input to the control unit 50.

  In step 100, when image data is input, an image forming process is started, a drive instruction is output from the print controller 52, and the intermediate transfer belt 14 is driven in the direction of arrow E in FIG. Migrate to

  In step 102, a forward rotation instruction is output from the print controller 52, and the photosensitive drums 16Y, 16M, 16C, and 16K rotate in the direction of arrow F in FIG. 6A, and the process proceeds to step 104.

  In step 104, a charging roll forward rotation charging instruction is output from the printing control unit 52, and the charging rolls 18Y, 18M, 18C, and 18K are charged to −800 V, and the photosensitive drum 16Y is moved in the direction of arrow J in FIG. , 16M, 16C, and 16K, the charging rolls 18Y, 18M, 18C, and 18K charge the image forming areas and the non-image forming areas of the photosensitive drums 16Y, 16M, 16C, and 16K to about −500 V, respectively. (See FIG. 6A), the process proceeds to step 106.

  In step 106, the print control unit 52 converts the image data into data for each color of yellow / magenta / cyan / black, and the image forming unit control units 66Y, 66M, 66C, 66K for each color are turned on based on the converted data. A lighting instruction is output to the control units 72Y, 72M, 72C, and 72K to light the LED arrays 40Y, 40M, 40C, and 40K. The photosensitive drums 16Y, 16M, 16C, and 16K are exposed to light beams from the LED arrays 40Y, 40M, 40C, and 40K, and electrostatic latent images are formed in the image forming areas of the photosensitive drums 16Y, 16M, 16C, and 16K for each color. An image is formed and step 108 is entered. Here, the voltage of the region exposed by the LED array 40 on the photosensitive drum 16 is about −200V, and the voltage of the region not exposed is −500V.

  In step 108, a development instruction is output from the print control unit 52, a voltage of -300 V is generated on the developing rolls 42Y, 42M, 42C, and 42K, and the photosensitive drum 16Y rotates in the direction of arrow K in FIG. , 16M, 16C, and 16K, the toner T1 of each color is attached to the electrostatic latent images in the image forming areas (see FIG. 6A), and development is performed.

  In step 110, a toner transfer instruction is output from the print controller 52, + 500V is generated in the first transfer devices 24Y, 24M, 24C, and 24K, and the photosensitive drum developed by the developing devices 22Y, 22M, 22C, and 22K. The toner images of different colors on 16Y, 16M, 16C, and 16K are transferred onto the intermediate transfer belt 14 so as to overlap each other on the belt surface of the intermediate transfer belt 14, thereby forming a final toner image. Migrate to

  Here, as shown in FIG. 6A, not all the toner T1 on the photosensitive drum 16 is transferred to the intermediate transfer belt 14, but the toner (transfer residual toner) T2 that is not transferred, the first transfer. In some cases, toner (reversed toner) T3 whose polarity is reversed to positive by the voltage generated in the device 24 remains on the photosensitive drum 16. Further, as in the photosensitive drums 16M, 16Y, and 16K (see FIG. 1), toner images of different colors (for example, a cyan toner image in the case of the photosensitive drum 16M) are already transferred to the intermediate transfer belt 14. In addition, when the toner T1 is transferred in an overlapping manner, the polarity of the toner T4 of a different color that has already been transferred is reversed to plus by the voltages of the first transfer devices 24M, 24C, and 24K to become the inverted toner T3. The body drums 16C, 16M, and 16Y may be transferred in reverse. That is, the reverse toner T3 includes a different color toner T4.

  In step 112, a temporary collection instruction is output from the print controller 52, and the brush roller 47 and the conductive roller 48 of the cleaning roll 26 are charged to -600V. When the conductive roller 48 is charged to −600 V, the potential difference from the non-image forming area of the photosensitive drum 16 becomes 100 V as shown in the period t1 in FIG. 7, and the rotation of the cleaning roll 26 is stopped by the rotational load by the shaft 49. On the other hand, as shown in FIG. 8A, an electrostatic latent image (exposed area-200 V, non-exposed area-500 V) is formed in the image forming area of the photosensitive drum 16, and the toner is developed and developed. This is an area where an image is formed, and is also an area where residual toner (transfer residual toner T2, reversal toner T3) is adhered. For this reason, the brush roller 47 is temporarily charged with the reverse toner T3 that is charged to −600 V and the polarity of the image forming area is reversed to positive due to the potential difference with the image forming area, and the process proceeds to step 114. Further, since the untransferred toner T2 has a negative polarity, it is not collected by the cleaning roll 26 as shown in FIG. 6B and reaches the charging roll 18 as the photosensitive drum 16 rotates. However, since the charging roll 18 is charged to −800V, the transfer residual toner T2 is not attracted to the charging roll 18 and the photosensitive drum 16 is charged to −500V again. The untransferred toner T2 that has passed through the charging roll 18 reaches the developing roll 42 and is taken into the developing roll 42 as shown in FIG. Here, since the transfer residual toner T2 is the toner T1 that has not been transferred by the first transfer unit 24 among the toner T1 attached to the developing roll 42, color mixing does not occur.

  In step 114, a final toner transfer instruction is output from the print control unit 52, the second transfer device 29 (see FIG. 1) generates a voltage of +1000 V, and the final toner image transferred to the intermediate transfer belt 14 is a roller. The paper is fed between 29A and 29B, taken out from the paper tray 30, and transferred to the paper 28 that has also been transported between the rollers 29A and 29B.

  The paper 28 onto which the final toner image has been transferred is conveyed to a fixing device 34 composed of a pressure roller 34A and a heating roller 34B, and subjected to a fixing process. As a result, the final toner image is fixed, and a desired image (color image) is formed on the paper 28. When the image forming process is completed, an instruction for counting up the total number of sheets is output from the print control unit 52, and the cumulative number of printed sheets after cleaning stored in the nonvolatile memory 54 is counted up.

  Here, the state in which the image forming process is completed is a state in which the reverse toner T3 is temporarily collected and accumulated on the cleaning roll 26 (see FIG. 9A).

  In step 116, based on the cleaning condition stored in the non-volatile memory 54 and the cumulative number of printed sheets after cleaning, it is determined whether the number of printed sheets since the previous cleaning of the cleaning roll 26 is less than 30. If the number of printed sheets is less than 30, the determination is affirmative and the process proceeds to the end without performing the cleaning mode.

  On the other hand, in step 116, a negative determination is made that the number of printed sheets will be 30, and the routine proceeds to step 118 where cleaning processing is performed.

  In step 118, a driving instruction is output from the cleaning control unit 58, and the intermediate transfer belt 14 is driven in the direction of arrow E in FIG. 9B, and the process proceeds to step 120.

  In step 120, a reverse rotation instruction is output from the cleaning control unit 58, and the photosensitive drum 16 rotates in the direction opposite to that at the time of image formation (the direction of arrow G in FIG. 9B), and the process proceeds to step 121.

  In step 121, a charging roll reverse rotation charging instruction is output from the cleaning control unit 58, the charging rolls 18Y, 18M, 18C, and 18K are charged to -800 V, and the photosensitive drums 16Y, 16M, 16C, and 16K are charged as shown in FIG. B) By rotating synchronously in the direction of arrow M, the charging roll 18 charges the image forming areas and non-image forming areas of the photosensitive drums 16Y, 16M, 16C, and 16K to about −500 V, and the process proceeds to step 122. To do.

In step 122, a discharge instruction is output from the cleaning control unit 58, and the brush roller 47 and the conductive roller 48 of the cleaning roll 26 are charged to -200V. When the conductive roller 48 is charged to −200 V, the potential difference from the non-image forming area of the photosensitive drum 16 becomes 300 V as shown in the period t2 in FIG. 7, and as shown in FIG. An electrostatic force is generated between the photosensitive drum 16 and the non-image forming area, and the cleaning roller 26 is driven to rotate following the photosensitive drum 16 by the adsorption between the conductive roller 48 and the non-image forming area (FIG. 9B). ) In the direction of arrow I).

  Further, since the reverse toner T3 on the brush roller 47 of the cleaning roll 26 has a positive polarity, when the brush roller 47 of the cleaning roll 26 is charged to −200 V, the image forming area of the photosensitive drum 16 is charged to −500. Therefore, the ink is discharged from the cleaning roll 26 and is adsorbed on the photosensitive drum 16. The reversal toner T3 adsorbed on the photosensitive drum 16 moves in the direction of arrow G in FIG. 9B as the photosensitive drum 16 rotates, reaches the first transfer unit 24, and proceeds to step 124. .

  In step 124, an accumulation residual toner transfer instruction is output from the cleaning control unit 58, the first transfer unit 24 generates a voltage of −1000 V, and the reverse toner T 3 that has reached the first transfer unit 24 is intermediated. The toner is transferred to the transfer belt 14 and removed from the photosensitive drum 16. The reverse toner T3 transferred onto the intermediate transfer belt 14 reaches the cleaner 38 (see FIG. 1) and is removed from the intermediate transfer belt 14 as the intermediate transfer belt 14 is driven.

  Also, the cleaning control unit 58 outputs a cumulative sheet number initialization instruction to the nonvolatile memory 54, initializes the cumulative number of printed sheets after cleaning stored in the nonvolatile memory 54 to zero, and shifts to the end.

  As described above, the cleaning roll 26 stops rotating in the image forming mode to collect the remaining toner, and in the cleaning mode, the remaining toner accumulated by rotating with the photosensitive drum 16 is discharged onto the photosensitive drum 16. be able to.

  As described above, the cleaning roller 26 is provided with the brush roller 47 and the conductive roller 48, and the potential difference between the non-image forming area of the photosensitive drum 16 and the conductive roller 48 is controlled, so that the cleaning roller 26 has the cleaning roller 26 in the image forming mode. The remaining toner can be collected by stopping the rotation. In the cleaning mode, the accumulated residual toner can be discharged and removed by being driven to rotate with the photosensitive drum 16.

  Therefore, it is possible to perform rotation and driven rotation for sliding the cleaning roll 26 on the photosensitive drum 16 without providing a driving device, a clutch mechanism, or the like.

  In the present embodiment, the rotation of the cleaning roll 26 in the image forming mode is stopped. However, the rotation load of the shaft is adjusted so that the cleaning roll 26 is rotated at a lower rotational speed than the photosensitive drum 16. It may be.

  The potential difference between the non-image forming area of the photosensitive drum 16 and the conductive roller 48 is controlled by applying a voltage to the charging roll 18 and the conductive roller 48, but the photosensitive drum 16 is exposed by the LED array 40. Therefore, the potential difference may be controlled by exposing the non-image forming area with the LED array 40.

  In this embodiment, the LED array 40 is used as the exposure device 20, but a light beam scanning device or the like that scans a light beam on the photosensitive drum 16 to form an electrostatic latent image may be used.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. It is a detailed block diagram of an image forming unit. It is a detailed block diagram of a cleaning roll. 2 is a block diagram illustrating a control unit of the image forming apparatus. FIG. It is the flow which shows the flow of control. FIG. 6 is a diagram illustrating a toner flow in an image forming mode. It is a graph which shows the voltage of the non-image formation area of a conductive roller and a photoreceptor drum. It is a figure which shows the voltage of the cleaning roll and photoconductor drum in image formation mode and cleaning mode. FIG. 4 is a diagram illustrating a toner flow in an image forming mode and a cleaning mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 14 Intermediate transfer belt 15, 15, 15M, 15C, 15K Image forming unit 16, 16Y, 16M, 16C, 16K Photosensitive drum (image carrier)
18, 18Y, 18M, 18C, 18K Charging roll (charging means)
20, 20Y, 20M, 20C, 20K Exposure unit 22, 22Y, 22M, 22C, 22K Developer 24, 24Y, 24M, 24C, 24K First transfer unit 26, 26Y, 26M, 26C, 26K Cleaning roll 28 Paper 29 , 29A, 29B Second transfer unit, roller 30 Paper tray 32 Paper feed roller 33 Transport roller 33
34, 34A, 34B Fixing device, pressure roller, heating roller 35 paper discharge roller 37 cleaning blade 38 cleaner 40, 40Y, 40M, 40C, 40K LED array (exposure means)
42, 42Y, 42M, 42C, 42K Developing roll (developing means)
44 Developer Conveying Member 46 Developer Stirring Member 47 Brush Roller (Toner Collection / Discharge Unit)
48 Conductive roller (rotating body)
49 Shaft 50 Control unit 52 Print control unit (potential difference control means)
54 Non-volatile memory 56 Cleaning judgment section (potential difference control means)
58 Cleaning control unit (voltage application means)
60 Intermediate transfer member control unit 62 Second transfer unit charging control unit 64, 64Y, 64M, 64C, 64K First transfer unit charging control unit 66, 66Y, 66M, 66C, 66K Image forming unit control unit 70, 70Y, 70M, 70C, 70K Photoconductor rotation control unit 72, 72Y, 72M, 72C, 72K Lighting control unit 74, 74Y, 74M, 74C, 74K Charge roll control unit 76, 76Y, 76M, 76C, 76K Developer control unit 78, 78Y, 78M, 78C, 78K Cleaning roll controller 80, 80Y, 80M, 80C, 80K Intermediate transfer member drive motor 82, 82Y, 82M, 82C, 82K Photoconductor drive motor 84, 84Y, 84M, 84C, 84K Charging Roll drive motor 86, 86Y, 86M, 86C, 86K Development roll drive motor

Claims (5)

An electrostatic latent image is formed by irradiating a light beam with an exposure unit while rotating an image carrier whose peripheral surface is uniformly charged with a predetermined polarity by a charging unit, and a developing unit forms an electrostatic latent image. During image formation in which the electrostatic latent image is developed to form a toner image, residual toner adhering to the image carrier is temporarily collected based on a first potential difference from the image carrier, In the cleaning mode performed every predetermined interval, the peripheral surface of the image carrier that discharges the collected residual toner to the peripheral surface of the image carrier based on the second potential difference with the image carrier. An image forming apparatus having a roller-shaped toner collecting / discharging unit disposed opposite to the image forming apparatus,
A rotating body that is coaxially connected to the rotation axis of the toner collecting / discharging means and that is disposed outside the image forming area on the peripheral surface of the image carrier;
Voltage applying means for applying a predetermined voltage to the peripheral surfaces of the rotating body and the toner collecting / discharging means ;
The first potential difference is obtained by controlling the voltage applied by the voltage application unit to move the toner collection / ejection unit relative to the circumferential surface of the image carrier with a rotational load of the rotation shaft. The potential difference of 2 is controlled such that the voltage applied by the voltage applying means is used to adsorb the rotating body and the image carrier with electrostatic force, and the toner collection / discharge means is driven to rotate following the image carrier. A potential difference control means to control;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the rotating body is a pair of conductive elastic members, and is arranged so as to sandwich the toner collecting / discharging unit in an axial direction.   The image forming apparatus according to claim 2, wherein the conductive elastic member is a conductive rubber.   4. The toner collection / ejection means is a brush roller having brush hairs planted on a peripheral surface thereof, and a hair tip is in contact with a surface of the image carrier. The image forming apparatus according to claim 1.   2. The potential difference control unit controls a potential difference between the image carrier and the rotating body by lowering a voltage of the charged image carrier by exposure by the exposure unit. 5. The image forming apparatus according to claim 4.

Images