JP2005250290A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the lowering of productivity by preventing the occurrence of ghost by recovering toner left after transfer in the case of image data having the high maximum value of image density and by preventing the unnecessary discharge of recovered toner from a temporary toner recovering/discharging means in the case of image data having the low maximum value of image density. <P>SOLUTION: The number of sheets set as an interval to perform a cleaning mode is selected based on applied voltage to a cleaning roll and the cumulative number of pixels. Since the cumulative number of pixels is a value correlated to the amount of use of the toner adhering to a photoreceptor drum 16, the amount of the toner (reversal toner and toner left after transfer) left on the cleaning roll 26 becomes larger as the cumulative number of pixels gets larger. Hence, the number of sheets set as the intervals is reduced as the maximum image density gets high and the cumulative number of pixels gets large, whereby the intervals are shortened and the cleaning performance of the cleaning roll 26 is kept. <P>COPYRIGHT: (C)2005,JPO&NCIPI

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 that forms an image by irradiating a photosensitive member with a light beam such as a laser printer or an electrophotographic copying machine has been widely used. In such an image forming apparatus, for example, a negative voltage is applied to a charger such as a charging roll to negatively charge the photosensitive drum as the image carrier, and the charged photosensitive drum is irradiated with a light beam. An electrostatic latent image is formed, a toner having a negative polarity is attached to the electrostatic latent image based on a potential difference by a developing unit, a positive voltage is applied to the transfer unit, and the toner is applied to a sheet or the like via an intermediate transfer member. An image is formed by transferring to an image recording medium.

  At the time of this transfer, there is toner (reversed toner) that adheres to the photosensitive drum by reversing the polarity positively by the voltage of the transfer device, and is not transferred onto the image recording medium depending on the image density. There is toner (transfer residual toner) that remains attached to the toner. A so-called cleaner-less system that does not use a cleaning blade has been devised for collecting the residual toner on the photosensitive drum, and Patent Document 1 discloses an image forming apparatus provided with a cleaning roll.

In the image forming apparatus described in Patent Document 1, the toner attached to the photosensitive drum is temporarily collected by the cleaning roll. This cleaning roll has brush hairs implanted on its peripheral surface. When a voltage having a polarity opposite to that of the toner is applied, the cleaning roll adsorbs the toner by electrostatic force, and a voltage having the same polarity as that of the toner is applied. Then the toner is discharged. The image forming apparatus described in Patent Document 1 has an image forming mode and a cleaning mode that is executed at predetermined intervals. In the image forming mode, an image is formed on a recording medium based on image data, and a minus is applied to a cleaning roll. The positive polarity reversal toner is temporarily collected and accumulated, and the negative transfer residual toner is collected by the developing device. On the other hand, in the cleaning mode, a positive voltage is applied to the cleaning roll to discharge the accumulated reversal toner onto the photosensitive drum, and the discharged reversal toner is returned to the developing unit or collected on the intermediate transfer member and collected at once. I do.
JP 2001-75448 A

  However, when the image density of the image formed on the photosensitive drum is high, the toner density increases and the transfer residual toner on the photosensitive drum increases. Since the developing device has a first purpose of development processing, if the amount of transfer residual toner increases, it cannot be sufficiently collected, and the transfer residual toner remains on the photosensitive drum, causing a ghost. For this reason, it is sufficient to apply a positive voltage to the cleaning roll to collect the negative transfer residual toner, but the positive polarity reversal toner adheres to the charger, and the contamination increases. In order to prevent this, there is a proposal to provide two cleaning rolls to which a positive voltage and a negative voltage are applied, but the image forming apparatus becomes complicated and the manufacturing cost increases.

  Furthermore, the cleaning roller has a large amount of toner remaining on the photosensitive drum when the image density is high. Therefore, it is necessary to shorten the interval for performing the cleaning mode. However, if the interval is shortened, unnecessary discharge is performed with a small amount of collected toner when the image density is low, and productivity of forming an image in the image forming apparatus is lowered.

  In consideration of the above facts, the present invention can collect the transfer residual toner for image data having a high maximum image density to prevent the occurrence of ghosting, and the provisional toner for image data having a low maximum image density. An object of the present invention is to provide an image forming apparatus capable of preventing unnecessary discharge of the toner collected to the collection / ejection unit and preventing a decrease in productivity.

  According to the first aspect of the present invention, an electrostatic latent image is formed by irradiating a light beam to an image carrier uniformly charged with a predetermined polarity based on image data, and the electrostatic latent image is based on a potential difference. An image forming apparatus that forms a toner image by attaching toner of the predetermined polarity and transfers the toner image to a recording medium by electrostatic force, and calculates correlation data correlated with the toner usage of the toner image Temporary data that is disposed opposite to the image carrier, and that collects or discharges the transfer residual toner generated during transfer on the image carrier and the reverse toner whose polarity is reversed mainly by electrostatic force. Toner collection / discharge means, voltage application means for applying a voltage for selectively collecting or discharging the transfer residual toner or the reversal toner to the temporary toner collection / discharge means, and the phase Characterized in that on the basis of the calculation result of the data arithmetic means; and a voltage value or polarity of the changing means for changing at least one of the applied voltage of said voltage applying means.

  According to the first aspect of the present invention, the untransferred toner and the reversal toner are generated at the time of transfer of the toner image, and the amounts generated are increased or decreased according to the amount of toner used in the toner image. Since the correlation data calculation means calculates correlation data that correlates with the amount of toner used, the changing means obtains whether the transfer residual toner or the reverse toner should be collected based on the calculation result of the correlation data calculation means, and the provisional toner collection / The voltage value and polarity of the voltage applied to the ejection means can be changed optimally. Thus, the temporary toner collecting / discharging unit can selectively collect the transfer residual toner or the reversal toner by applying the voltage changed by the changing unit.

  Note that the change of the voltage value means a case where the voltage is changed with the same polarity, and the change of the polarity means, for example, inversion of the polarity with reference to 0V. In a broad sense, the change of the voltage value may be accompanied by the change of the polarity, but in the present invention, the change of the voltage and the change of the polarity are intentionally described.

  According to a second aspect of the present invention, in the first aspect of the invention, the temporary toner collecting / discharging unit executes mainly the reversal toner collection and discharges the reversal toner appropriately collected during non-image formation. It is characterized by.

  According to the second aspect of the present invention, during the formation of a general image (for example, an image in which the average value of the image density on the recording medium is gray), the temporary toner collection / discharge unit collects the reverse toner. And the discharge of the recovered toner is executed as appropriate during non-image formation. As a result, the reversal toner is stably recovered from the image carrier, so that ghosting is prevented and the image quality is improved.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the correlation data is a density of the toner image, and the change means generates the higher the density, the higher the density is at the time of transfer. The applied voltage is changed so as to increase the collecting ability of the transfer residual toner.

  According to the third aspect of the present invention, the higher the density of the toner image, the greater the amount of untransferred toner generated during transfer. For this reason, the changing means can prevent the occurrence of ghost by changing the applied voltage so as to enhance the collecting power of the residual toner and causing the temporary toner collecting / discharge means to collect the residual toner.

  According to a fourth aspect of the present invention, in the first or second aspect of the present invention, the correlation data is the maximum density of the toner image, and the change means generates more during the transfer as the maximum density is higher. The applied voltage is changed so as to enhance the collecting power of the transfer residual toner.

  According to the fourth aspect of the present invention, the higher the maximum density of the toner image, the greater the amount of residual toner that is generated during transfer. For this reason, the changing means can prevent the occurrence of ghost by changing the applied voltage so as to enhance the collecting power of the residual toner and causing the temporary toner collecting / discharge means to collect the residual toner.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, when the image data forms a multicolor image, the temporary toner collecting / discharging means is mainly used at the time of transfer. The generated transfer residual toner is collected, and the reversal toner is collected as a subsidiary.

  According to the fifth aspect of the present invention, when the image data forms a multi-color image, the amount of toner remaining after transfer increases because a plurality of color toners are used. Therefore, the provisional toner collecting / discharging means mainly collects the transfer residual toner, thereby preventing the occurrence of ghost due to the transfer residual toner.

  According to a sixth aspect of the present invention, in the first aspect of the present invention, the larger the toner collection amount of the temporary toner collection / discharge means, the shorter the interval of the discharge operation. It is characterized by that.

  According to the sixth aspect of the present invention, it is possible to prevent the transfer residual toner or reversal toner collected in the temporary toner collection / discharge means from being excessively accumulated by shortening the interval as the toner collection amount increases.

  In addition, since the interval becomes longer when the amount of toner collected is small, unnecessary ejection by the temporary toner collecting / discharging unit is prevented, and a reduction in productivity can be prevented.

  According to a seventh aspect of the invention, in the sixth aspect of the invention, the interval is converted into the number of the recording media to be image-formed.

  According to the seventh aspect of the present invention, since the interval is converted into the number of recording media on which image forming processing is performed, the transfer residual toner collected from the temporary toner collecting / discharging means for each number set as the interval or The reverse toner is discharged.

  According to an eighth aspect of the present invention, in the invention according to any one of the first to seventh aspects, the temporary toner collecting / discharging means is a brush roller having brush hairs planted on a peripheral surface thereof. The tip contacts the surface of the image carrier and scrapes off the toner on the image carrier regardless of whether a voltage is applied.

  According to the eighth aspect of the present invention, the transfer residual toner and the reversal toner can be recovered by scraping the surface of the image carrier with the bristles even if no voltage is applied to the temporary toner recovery / discharge means. Can do.

  As described above, according to the present invention, ghosting can be prevented by collecting untransferred toner in image data having a high maximum image density. In addition, it is possible to provide an image forming apparatus that can prevent an unnecessary discharge of the toner collected to the temporary toner collection / discharge unit and prevent a decrease in productivity for image data having a low maximum image density. Have.

  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-like shape conveyed in the direction of arrow E in FIG. 1 by driving an intermediate transfer member driving motor 80 (see FIG. 3).

  The four image forming units 15 will be described in detail. Each of the image forming units 15 corresponds to four colors of yellow (Y), magenta (M), cyan (C), and black (K) (hereinafter, referred to as “color”). And 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. The photosensitive drum driving motor 82 (see FIG. 3) drives the arrow F or G in FIG. 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. A cleaning roll 26 as a temporary toner collecting / discharging means for temporarily collecting the residual toner adhering to the photosensitive drum 16 after the transfer is disposed downstream of the transfer position and upstream of the charging roll 18. Has been.

  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, with reference 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. 3) is applied. 2), the surface of the photosensitive drum 16 is uniformly charged from the charging roll 18 to about −500V. 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. 3), and is electrostatically charged by a developer containing two components of a negative polarity toner and a 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. Therefore, in the image forming mode, the first transfer unit 24 is +500 V, and the toner on the photosensitive drum 16 has a negative polarity, so that it is transferred to the intermediate transfer member belt 14.

  However, the first transfer device 24 cannot transfer all the toner, and there is toner remaining on the photosensitive drum 16 (transfer residual toner), and a voltage of +500 V is applied to the first transfer device 24. As a result, it is known that there is toner (reversed toner) whose polarity is reversed to plus. 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 has conductive brush hairs implanted on the surface thereof, and can be rotated in the direction of arrow H or arrow I in FIG. 2 by driving a cleaning roll driving motor 88 (see FIG. 3). Yes. The cleaning roll 26 is relatively moved with respect to the rotation of the photosensitive drum 16 and is configured to rotate in the direction in which the brush bristles slide on the contact surface with the photosensitive drum 16, and image data for forming a toner image. A positive or negative voltage is applied in accordance with the image density calculated from the above, and the surface of the photosensitive drum 16 is rubbed with brush hairs to attract the residual toner adhering to the photosensitive drum 16. That is, when the image density is high, the toner density of the toner image formed on the photoconductive drum 16 becomes high, and the transfer residual toner remaining on the photoconductive drum 16 increases, so that a positive voltage is applied to the cleaning roll 26. Apply to collect negative transfer residual toner. Further, when the image density is low, the toner density of the toner image formed on the photosensitive drum 16 is low, and the transfer residual toner remaining on the photosensitive drum 16 is also reduced, but the reversal toner is relatively increased. Therefore, a negative voltage is applied to the cleaning roll 26 to collect the positive polarity reversal toner. In the image forming mode, since the residual toner is attracted and collected by the brush bristles of the cleaning roll 26, it is preferable that the rotational speeds of the cleaning roll 26 and the photosensitive drum 16 are different, but if the difference in rotational speed is too large. Since the adsorbed residual toner is rubbed against the surface of the photosensitive drum 16, the rotational speed difference is kept within 2%.

  Further, the cleaning roll 26 is applied with a voltage opposite to the polarity of the accumulated residual toner, and performs a process of discharging the accumulated residual toner onto the photosensitive drum 16 as a cleaning mode. In the cleaning mode, the accumulated residual toner is discharged to the cleaning roll 26 and is adsorbed to the photosensitive drum 16, so that the rotation speeds of the cleaning roll 26 and the photosensitive drum 16 are the same and rotate following the photosensitive drum 16. Yes.

  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, the sheet 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 photosensitive drum 16 is rotated in the direction opposite to the rotation direction at the time of image formation will be described when executing the cleaning mode, but the rotation direction is the same as the rotation direction at the time of image formation. May be.

  The accumulated residual toner discharged on the photosensitive drum 16 reaches the contact position with the intermediate transfer belt 14, and a voltage corresponding to the polarity of the accumulated residual toner is applied to the first transfer unit 24. Transferred to the intermediate transfer belt 14 by electrostatic force.

(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 a print instruction (image data and the number of prints) is input from an external host computer (not shown) or the like, the control unit 50 performs a voltage applied to the cleaning roll 26 and a cleaning mode by an applied voltage / interval determination unit 51 described later. An interval is obtained, and image forming processing (image forming mode) is controlled by the print control unit 52 described later. Further, the discharge control (cleaning mode) of the accumulated residual toner collected by the cleaning roll 26 is controlled by the cleaning control unit 58 described later at each interval.

  As shown in FIG. 4, the applied voltage / interval determining unit 51 includes a cleaning roll applied voltage determining unit 90, a pixel count accumulating unit 92, and an interval selecting unit 94.

  The cleaning roll application voltage determination unit 90 is connected to the pixel count accumulation unit 92, the interval selection unit 94, and the collection / discharge instruction unit 59. The cleaning roll application voltage determination unit 90 calculates the image density of the image formed from the image data of the print instruction and obtains the maximum value (maximum image density). Further, it is determined whether the image data is multicolor (image data composed of two or more colors of yellow / magenta / cyan / black) or a single color, and in the case of multicolor, based on the maximum image density, FIG. From (A), the voltage applied to the cleaning roll 26 (cleaning roll applied voltage) is obtained. In the case of a single color, the cleaning roll applied voltage is obtained from FIG. 5B based on the maximum image density. That is, a positive voltage is applied to the cleaning roll 26 when the maximum image density of the image data is high and there are multiple colors. This is because a large amount of residual toner remains on the photosensitive drum in a region where the image density is high, and in the case of multiple colors, residual toner remains on a plurality of photosensitive drums, resulting in ghosting. This is because the transfer residual toner is collected by applying a voltage. The cleaning roll application voltage determination unit 90 sends the cleaning roll application voltage to the recovery / discharge instruction unit 59 and the interval selection unit 94, and sends a print instruction (image data and the number of prints) to the pixel count accumulation unit 92.

  The pixel count accumulation unit 92 is connected to the cleaning roll applied voltage determination unit 90, the interval selection unit 94, and the print control unit 52. The pixel count accumulating unit 92 accumulates the number of pixels in the area where the toner adheres from the image data of the print instruction sent from the cleaning roll applied voltage determination unit 90, and accumulates the number of pixels in the toner adhering area (hereinafter, the accumulated number of pixels). ) Is sent to the interval selector 94. This is to obtain a value that correlates with the amount of toner used that adheres to the photosensitive drum 16. In addition, the pixel count accumulating unit 92 sends a print instruction (image data and the number of prints) to the print control unit 52.

  The interval selection unit 94 is connected to the cleaning roll applied voltage determination unit 90, the pixel count accumulation unit 92, the nonvolatile memory 54, and the cleaning determination unit 56. The interval selection unit 94 reads a lookup table (LUT) shown in FIG. 6 from the nonvolatile memory 54 described later, and sends it from the cleaning roll application voltage sent from the cleaning roll application voltage determination unit 90 and the pixel count accumulation unit 92. Based on the accumulated number of pixels, the number of intervals for performing the cleaning mode is selected. This is for obtaining an appropriate interval for discharging the remaining toner accumulated from the cleaning roll 26. In the region of the maximum image density in the image, the amount of transfer residual toner remaining on the cleaning roll 26 is the largest. For this reason, the cleaning roll applied voltage is increased as the maximum image density increases (see FIG. 5A). Further, since the cumulative number of pixels is a value that correlates with the amount of toner used that adheres to the photosensitive drum 16, the amount of toner (reversed toner and transfer residual toner) remaining on the cleaning roll 26 increases as the cumulative number of pixels increases. Therefore, in the LUT, the maximum image density is increased (the cleaning roll applied voltage is positive), and the interval number is decreased and the interval is shortened as the cumulative number of pixels increases. In the LUT shown in FIG. 6, the cleaning roll application voltage and the cumulative pixel number are shown only by representative values, and the cleaning roll application voltage and the cumulative pixel number can be set in more detail.

  The interval selection unit 94 (see FIG. 4) sends the selected number of intervals to the cleaning determination unit 56.

  The print control unit 52 (see FIG. 3) includes a pixel count accumulating unit 92 (see FIG. 4), a nonvolatile memory 54, a collection / discharge instruction unit 59, an intermediate transfer body control unit 60, a second transfer device control unit 62, The first transfer device controller 64, the photoconductor rotation controller 70, the lighting controller 72, the charging roll controller 74, and the developing device controller 76 are connected.

  When a print instruction is input from the pixel count accumulating section 92, the print control section 52 outputs the following various instructions and controls 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 applies a voltage of −800 V to the charging roll 18 to the charging roll control unit 74 and outputs a charging roll charging instruction for rotating in the arrow J direction in FIG. The photosensitive drum 16 is charged. Further, a lighting instruction is output to the lighting control unit 72 based on the image data, and the LED array 40 of the exposure device 20 is turned on to form an electrostatic latent image on the photosensitive drum 16. Further, a developing instruction for generating a voltage of −300 V on the developing roll 42 of the developing unit 22 and rotating it in the direction of the arrow K in FIG. 2 is output to the developing unit control unit 76, and the toner is attached to the electrostatic latent image. Development is performed to form a toner image.

  Further, the print control unit 52 outputs a toner transfer instruction to the first transfer unit control unit 64 (see FIG. 3), and + 500V to the first transfer unit 24, and final toner transfer to the second transfer unit control unit 62. An instruction is output to generate a voltage of +1000 V 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 is output to the collection / discharge instruction unit 59. A later-described collection / discharge instruction unit 59 causes the cleaning roller 26 to temporarily collect the remaining toner adhering to the photosensitive drum 16 (details will be described later).

  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 an interval selection unit 94 (see FIG. 4), a print control unit 52, a cleaning determination unit 56, and a cleaning control unit 58. The above-described LUT (see FIG. 6) is stored in the nonvolatile memory 54. 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 interval selection unit 94 (see FIG. 4), the cleaning control unit 58, and the nonvolatile memory 54. The cleaning determination unit 56 receives the interval number from the interval selection unit 94, reads the cumulative number of printed sheets after cleaning from the nonvolatile memory 54, and performs the image forming process. As a result, the cumulative number of printed sheets after cleaning becomes the interval number. When it is determined that the number of sheets is reached, a cleaning instruction is output to the cleaning control unit 58 to discharge the remaining toner accumulated in the cleaning roll 26.

  The cleaning control unit 58 is connected to the nonvolatile memory 54, the cleaning determination unit 56, the collection / discharge instruction unit 59, the intermediate transfer body control unit 60, and the photoconductor rotation control unit 70.

  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. 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 drive instruction to the intermediate transfer body control unit 60 to drive the intermediate transfer body belt 14 in the direction of arrow E in FIG. 1 (FIG. 2).

  Next, the cleaning control unit 58 outputs a discharge instruction to the collection / discharge instruction unit 59. A collection / discharge instruction unit 59, which will be described later, discharges the accumulated toner from the cleaning roll 26 onto the photosensitive drum 16 (details will be described later).

  Further, the cleaning control unit 58 outputs a reverse rotation instruction to rotate the photosensitive drum 16 in the direction of arrow G in FIG. As a result, the photosensitive drum 16 is rotated in the reverse direction, and 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. In the first transfer unit 24, the collection / discharge instruction unit 59 that has received the above-described discharge instruction applies a voltage having a polarity opposite to that of the accumulated toner, and the storage is carried to the contact point with the first transfer unit 24. The remaining toner is transferred to the intermediate transfer belt 14.

  In addition, when the cleaning mode is completed, the cleaning control unit 58 outputs an instruction for initializing the cumulative number of sheets to the nonvolatile memory 54 and initializes the cumulative number of printed sheets after cleaning stored in the nonvolatile memory 54 to zero.

  The collection / discharge instruction unit 59 is connected to the cleaning roll application voltage determination unit 90 (see FIG. 4), the print control unit 52, the cleaning control unit 58, the first transfer device control unit 64, and the cleaning roll control unit 78. Yes.

  When receiving a provisional collection instruction from the print control unit 52 in the image forming mode, the collection / discharge instruction unit 59 applies the cleaning roll application voltage sent from the cleaning roll application voltage determination unit 90 to the cleaning roll 26 and the cleaning roll 26. 2 is sent to the cleaning roll controller 78 to rotate the toner in the direction indicated by the arrow H in FIG. As a result, the cleaning roll 26 collects transfer residual toner when the maximum image density of the image data is high and the number of colors is high, and collects the transfer residual toner. When the maximum image density is low or single color, the cleaning roll 26 26 becomes a negative voltage to collect the reversal toner.

  On the other hand, the collection / discharge instruction unit 59 discharges the accumulated residual toner onto the photosensitive drum 16 when receiving the discharge instruction from the cleaning control unit 58 in the cleaning mode, so that the cleaning roll is applied when the applied voltage of the cleaning roll is negative or 0V. When a voltage of +500 V is applied to No. 26, when a voltage applied to the cleaning roll is positive, a voltage of -500 V is applied to the cleaning roll 26, and an instruction for discharging the accumulated residual toner that rotates the cleaning roll 26 in the direction of arrow I in FIG. Send it out. Further, the collection / discharge instruction section 59 transfers the residual toner discharged on the photosensitive drum 16 to the intermediate transfer belt 14, so that the first transfer device 24 is used when the cleaning roll applied voltage is negative or 0V. When a voltage of −500 V is applied, and a cleaning roll applied voltage is positive, a discharge toner transfer instruction for applying a voltage of +500 V to the first transfer device 24 is output.

  That is, when the cleaning roll applied voltage is negative or 0 V, the cleaning roll 26 adsorbs the positive polarity reversal toner in the image forming mode. Therefore, a voltage of +500 V is applied to discharge the reverse toner, and the first transfer. The device 24 is applied with a voltage of −500 V to transfer the reversal toner to the intermediate transfer belt 14.

  Further, when the cleaning roll applied voltage is positive, the cleaning roll 26 adsorbs negative transfer residual toner in the image forming mode. Therefore, a voltage of −500 V is applied to discharge the transfer residual toner, and the first roll is discharged. The transfer unit 24 is applied with a voltage of +500 V to transfer the transfer residual toner to the intermediate transfer belt 14.

  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 shown in FIG. Drive in direction E.

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

  The first transfer device controller 64 is connected to the print controller 52 and the collection / discharge instruction unit 59. When the first transfer device controller 64 receives a toner transfer instruction from the print controller 52, the first transfer device controller 64 generates a voltage of +500 V for the first transfer device 24. When a discharge toner transfer instruction is received from the collection / discharge instruction unit 59, a voltage of +500 V or -500 V specified by the discharge toner transfer instruction is generated, and the reverse toner or the transfer residual toner is transferred to the intermediate transfer belt 14. The first transfer device controller 64 is provided for each of the first transfer devices 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 print control unit 52. When the charging roll control unit 74 receives a charging roll charging instruction from the printing control unit 52, the charging roll control unit 74 applies a voltage of −800 V to the charging roll 18 and controls the charging roll driving motor 84 to cause the charging roll 18 to move as shown in FIG. Rotate in the direction of arrow J.

  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 collection / discharge instruction unit 59. When receiving the residual toner collection instruction from the collection / discharge instruction section 59, the cleaning roll control section 78 applies the voltage of the cleaning roll application voltage to the cleaning roll 26, and controls the cleaning roll driving motor 88 to control the cleaning roll 26. 2 is rotated in the direction of arrow H in FIG. 2 so that the difference in rotational speed with respect to the photosensitive drum 16 is within 2%, and the remaining toner on the photosensitive drum 16 is temporarily collected. On the other hand, when an instruction for discharging the remaining toner is received from the cleaning control unit 58, a voltage of + 500V or -500V is applied to the cleaning roll 26 in accordance with the instruction for discharging the remaining toner, and the cleaning roll 26 is moved in the direction of arrow I in FIG. The drum 16 is rotated so as to follow the rotation of the drum 16, and the remaining toner accumulated on the photosensitive drum 16 is discharged.

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

  FIG. 7 is a flowchart showing the flow of processing when image data is input to the control unit 50.

  In step 100, when a print instruction (image data, number of prints) is input, an image density is calculated from the image data to obtain a maximum image density. Further, it is determined whether the image data is multicolor or single color, and when it is multicolor, the cleaning roll applied voltage is obtained from FIG. 5A based on the maximum image density, and when it is single color, based on the maximum image density. The cleaning roll applied voltage is obtained from FIG.

  Here, for example, when the image data is multicolor and the maximum image density is 90%, the cleaning roll applied voltage is 500 V (Example 1) (see arrow example 1 in FIG. 5A), and the image data is When there are multiple colors and the maximum image density is 50%, the applied voltage of the cleaning roll is 0 V (Example 2) (see the arrow example 2 in FIG. 5A), and the image data is monochromatic and the maximum image density is 15 In the case of%, the applied voltage of the cleaning roll is −500 V (Example 3) (see the arrow example 3 in FIG. 5B).

  In step 102, the number of pixels in the region to which the toner adheres is accumulated from the image data, and the accumulated number of pixels is obtained, and the process proceeds to step 104. This cumulative number of pixels can be applied as a numerical value that correlates with the amount of toner used that adheres to the photosensitive drum 16 during image formation, that is, as correlation data.

  In step 104, the number of intervals is selected from the LUT (see FIG. 6) based on the maximum image density and the cumulative number of pixels, and the process proceeds to step 106. Here, as for the number of intervals, the cleaning roll applied voltage becomes positive, and the larger the cumulative number of pixels, the smaller the number of intervals and the shorter the interval.

  In step 106, an image forming process is started, a drive instruction is output from the print controller 52, the intermediate transfer belt 14 is driven in the direction of arrow E in FIG. 8A, and the process proceeds to step 108.

  In step 108, 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. 8A, and the process proceeds to step 110.

  In step 110, a charging roll charging instruction is output from the printing control unit 52, a voltage of -800V is applied to each of the charging rolls 18Y, 18M, 18C, and 18K, and is synchronized with the photosensitive drums 16Y, 16M, 16C, and 16K. By rotating, the charging roll 18 charges the surfaces of the photosensitive drums 16Y, 16M, 16C, and 16K to about −500 V (see FIG. 8A), and the process proceeds to step 112.

  In step 112, the print controller 52 converts the image data into data for each color of yellow / magenta / cyan / black, and the image forming unit controllers 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, and the LED arrays 40Y, 40M, 40C, and 40K of the image forming units 15 are turned on. The photosensitive drums 16Y, 16M, 16C, and 16K are exposed to light beams from the LED arrays 40Y, 40M, 40C, and 40K to form electrostatic latent images for the respective colors, and the process proceeds to step 114. Here, as described above, the voltage of the region exposed by the LED array 40 on the photosensitive drum 16 is about −200V.

  In step 114, a development instruction is output from the print control unit 52 to generate a voltage of -300 V 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 image (see FIG. 8A), development is performed, and the process proceeds to step 116.

  In step 116, 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. Step 118 Migrate to

  Here, as shown in FIG. 8A, 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.

  Here, the amount of residual toner T2 increases as the image density is higher and the cumulative number of pixels is larger. Therefore, the amount of each toner remaining on the photosensitive drum 16 is the amount of residual toner T2> reversal in the case of Example 1. In the case of toner T3, Example 2, transfer residual toner T2≈reverse toner T3, and in case of Example 3, transfer residual toner T2 <reverse toner T3.

  In step 118, a temporary collection instruction is output from the print control unit 52, and the collection / discharge instruction unit 59 outputs a residual toner collection instruction and applies a cleaning roll application voltage to the cleaning roll 26. Here, FIG. 8A shows the case where the cleaning roll applied voltage is +500 V (Example 1). In response to the remaining toner collection instruction, the cleaning roller 26 rotates in the direction of arrow H in FIG. 8B so that the rotational speed difference with the photosensitive drum 16 is within 2%, and collects the transfer residual toner T2 having a negative polarity. To do. On the other hand, the reverse toner T3 having a positive polarity is not collected by the cleaning roll 26 and reaches the charging roll 18 as the photosensitive drum 16 rotates. Since a voltage of −800 V is applied to the charging roll 18, the reversal toner T3 is attracted to the charging roll 18 as shown in FIG. However, in the case of Example 1, since the amount of each toner remaining on the photosensitive drum 16 is the transfer residual toner T2> the reversal toner T3, the cleaning roller 26 collects the transfer residual toner T2 and thereby the photosensitive drum 16 is recovered. The amount of toner remaining on the top can be reduced. Further, the toner contamination of the charging roll 18 is removed by a cleaning mode to be described later before the toner contamination increases because the cleaning roll applied voltage is positive and the number of intervals is small.

  FIG. 9A shows a case where the cleaning roll applied voltage is 0 V (Example 2). In the case of Example 2, since the cleaning roll 26 is 0 V, a part of the reversal toner T3 is collected by rubbing with brush hair. Further, the transfer residual toner T2 having a negative polarity due to the potential difference from the photosensitive drum 16 is also collected. In the case of this example 2, since the amount of each toner remaining on the photosensitive drum 16 is the residual transfer toner T2≈the reverse toner T3, the cleaning roller 26 collects both the residual transfer toner T2 and the reverse toner T3, thereby exposing the photosensitive drum. The amount of toner remaining on the body drum 16 can be reduced.

  Further, FIG. 9B shows a case where the cleaning roll applied voltage is −500 V (Example 3). In the case of Example 3, the reversal toner T3 has a positive polarity and is collected by the cleaning roll 26. However, the transfer residual toner T2 having a negative polarity is not collected by the cleaning roll 26, and the charging roll 18 is rotated with the rotation of the photosensitive drum 16. To reach. However, since a voltage of −800 V is applied to the charging roll 18, as shown in FIG. 9B, the transfer residual toner T 2 is not attracted to the charging roll 18 and the transfer residual toner T 2 that has passed through the charging roll 18. Reaches the developing roll 42 and is taken into the developing roll 42. In the case of Example 3, since the amount of each toner remaining on the photosensitive drum 16 is the residual transfer toner T2 <reversed toner T3, the cleaning roll 26 collects the reversed toner T3 together, and thus the toner is transferred onto the photosensitive drum 16. The amount of remaining toner can be reduced.

  In this way, the remaining toner is collected according to the applied voltage of the cleaning roll, and the process proceeds to step 120.

  In step 120, a final toner transfer instruction is output from the print controller 52, the second transfer unit 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.

  In step 122, it is determined whether or not the cumulative number of prints after cleaning stored in the nonvolatile memory 54 is equal to the interval number. If the determination is negative, the process proceeds to step 132 without performing the cleaning mode. On the other hand, if the determination in step 122 is affirmative, the process proceeds to step 124 and the cleaning mode process is performed.

  In step 124, a driving instruction is output from the cleaning control unit 58, the intermediate transfer belt 14 is driven in the direction of arrow E in FIG. 10A, and the process proceeds to step 126.

  In step 126, a reverse rotation instruction is output from the cleaning control unit 58, and the photosensitive drum 16 rotates in a direction opposite to that during image formation (in the direction of arrow G in FIG. 10A), and the process proceeds to step 128.

  In step 128, a discharge instruction is output from the cleaning control unit 58, and the collection / discharge instruction unit 59 outputs a stored residual toner discharge instruction, and the voltage is applied to the cleaning roll 26 according to the cleaning roll applied voltage in the image forming mode. Apply and rotate in the direction of arrow I in FIG.

  Here, in the case of Example 1, since the negative transfer residual toner T2 is collected in the image forming mode, a voltage of −500 V is applied to the cleaning roll 26 as shown in FIG. The toner T2 is discharged from the cleaning roll 26 and is adsorbed on the photosensitive drum 16. Further, the positive polarity reversal toner T3 attached to the charging roll 18 is attached to the photosensitive drum 16 by removing the voltage applied to the charging roll 18, and the toner contamination is removed.

  In Example 2, both the untransferred toner T2 and the reversal toner T3 are collected in the image forming mode. However, as shown in FIG. 10B, the reversal toner is applied by applying a voltage of +500 V to the cleaning roll 26. T3 is discharged from the cleaning roll 26 and adsorbed onto the photosensitive drum 16.

  Further, in the case of Example 3, since the positive polarity reversal toner T3 is collected in the image forming mode, a voltage of +500 V is applied to the cleaning roll 26 as shown in FIG. And is adsorbed on the photosensitive drum 16.

  Each toner adsorbed on the photosensitive drum 16 moves with the rotation of the photosensitive drum 16 and reaches the first transfer unit 24.

  In step 130, a discharge toner transfer instruction is output from the cleaning control unit 58, and the first transfer device 24 is applied with a voltage of +500 V in the case of Example 1 and −500 V in the case of Example 2 and Example 3. The reverse toner T3 or the transfer residual toner T2 that has reached the first transfer unit 24 is transferred to the intermediate transfer belt 14 and removed from the photosensitive drum 16. The toner 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.

  In addition, the cleaning control unit 58 outputs a cumulative sheet number initialization instruction to the nonvolatile memory 54, the post-cleaning cumulative printed sheet number stored in the nonvolatile memory 54 is initialized to zero, and the process proceeds to step 132.

  In step 132, it is determined whether the number of printed sheets according to the print instruction has been printed. When printing of the number of prints is completed, the image forming process is completed and the process proceeds to the end. On the other hand, if printing of the designated number of pages has not been completed, the process proceeds to step 110 to perform the next image forming process.

  As described above, the cleaning roller 26 can collect a large amount of toner remaining on the photosensitive drum 16 in accordance with the image density. Further, since the number of intervals changes according to the image density and the cumulative number of pixels, when the image density is high and a large amount of toner is collected by the cleaning roll 26, the interval is short, and the toner collected by the cleaning roll 26 is low and the image density is low. When the number is small, the interval can be lengthened.

  As described above, the cleaning roller 26 can collect the transfer residual toner for image data having a high maximum image density. Further, in the case of image data having a low maximum image density, since the toner collected in a long cycle is discharged, it is possible to prevent a decrease in productivity.

  In the present embodiment, the cleaning roll application voltage and the cumulative number of pixels are obtained from the image data for each print instruction, but a plurality of print instructions are received, the maximum value of the image density in the plurality of image data is obtained, A cleaning roll applied voltage may be obtained. As the cumulative pixel number, a cumulative value may be obtained for each image data, and a maximum value or an average value may be used. As a result, the number of intervals obtained from the cleaning roll applied voltage and the cumulative number of pixels becomes a value suitable for continuous processing of image data, and a reduction in productivity can be prevented as compared with the case where the number of intervals is obtained for each print instruction.

  In this embodiment, the cleaning roll application voltage is determined based on the maximum value of the image density. However, a value correlating with other toner use amount such as an average value and a maximum value of the density of the toner image may be used. Although the interval is selected from the cleaning roll applied voltage and the cumulative number of pixels, the interval may be selected from a value obtained by accumulating the density of the toner image or a value correlated with other toner usage.

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. 2 is a block diagram illustrating a control unit of the image forming apparatus. FIG. It is a detailed block diagram of an applied voltage / interval determination part. It is a figure which shows the relationship between a maximum image density and a cleaning roll applied voltage. It is a figure which shows a look-up table. It is the flow which shows the flow of control. 6 is a diagram illustrating a toner flow in an image forming mode of Example 1. FIG. 6 is a diagram illustrating a toner flow in an image forming mode of Example 1 and Example 2. FIG. 6 is a diagram illustrating a toner flow in the cleaning mode of Example 1 and Example 2. FIG. 10 is a diagram illustrating a toner flow in a cleaning mode of Example 3. FIG.

Explanation of symbols

10 Image forming apparatus 14 Intermediate transfer belt (intermediate transfer body)
15, 15Y, 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 (transfer means)
26, 26Y, 26M, 26C, 26K Cleaning roll (provisional toner collection / discharge means)
28 paper (recording medium)
29, 29A, 29B Second transfer device, roller (transfer means)
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 50 Control Unit 51 Applied Voltage / Interval Determination Unit 52 Print Control Unit 54 Non-Volatile Memory 56 Cleaning Determination Unit 58 Cleaning Control Unit (Operation Switching Unit)
59 Collection / discharge instruction part (change means)
60 Intermediate transfer member control unit 62 Second transfer unit control unit 64, 64Y, 64M, 64C, 64K First transfer unit 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 Charging roll control unit 76, 76Y, 76M, 76C, 76K Developer control unit 78, 78Y, 78M, 78C, 78K Cleaning roll controller (voltage application means)
80, 80Y, 80M, 80C, 80K Intermediate transfer member driving motor 82, 82Y, 82M, 82C, 82K Photoconductor driving motor 84, 84Y, 84M, 84C, 84K Charging roll driving motor 86, 86Y, 86M, 86C , 86K Development roll drive motor 88, 88Y, 88M, 88C, 88K Cleaning roll drive motor 90 Cleaning roll applied voltage determination unit (correlation data calculation means)
92 pixel count accumulating part (accumulating means)
94 Interval selection part (interval setting means)

Claims (8)

An image bearing member uniformly charged with a predetermined polarity is irradiated with a light beam based on the image data to form an electrostatic latent image, and the toner of the predetermined polarity is attached to the electrostatic latent image based on a potential difference. An image forming apparatus for forming a toner image and transferring the toner image to a recording medium by electrostatic force,
Correlation data calculating means for calculating correlation data correlated with the amount of toner used in the toner image;
Temporary toner collecting / discharging means that is disposed opposite to the image carrier and collects or discharges the transfer residual toner generated at the time of transfer on the image carrier and the reversed toner whose polarity is reversed mainly by electrostatic force;
Voltage application means for applying a voltage for selectively collecting or discharging the transfer residual toner or the reversal toner to the temporary toner collection / discharge means;
Changing means for changing at least one of the voltage value or polarity of the applied voltage of the voltage applying means based on the calculation result by the correlation data calculating means;
An image forming apparatus comprising:   2. The image forming apparatus according to claim 1, wherein the provisional toner collecting / discharging unit executes mainly the collection of the reverse toner and discharges the reverse toner appropriately collected during non-image formation.   The correlation data is the density of the toner image, and the changing means changes the applied voltage so that the higher the density is, the higher the recovery performance of the transfer residual toner generated at the time of transfer is. The image forming apparatus according to claim 1.   The correlation data is a maximum density of the toner image, and the changing unit changes the applied voltage so that the higher the maximum density is, the higher the recovery ability of the transfer residual toner generated at the time of transfer is. The image forming apparatus according to claim 1 or 2.   2. The provisional toner collecting / discharging means collects the transfer residual toner generated mainly at the time of transfer and collects the reversal toner as an auxiliary when the image data forms a multicolor image. The image forming apparatus according to claim 4.   6. The image forming apparatus according to claim 1, wherein the interval of the discharge operation is shortened as the toner collection amount of the temporary toner collection / discharge unit increases.   The image forming apparatus according to claim 6, wherein the interval is converted into the number of the recording media subjected to image forming processing.   The temporary toner collecting / discharging means is a brush roller having brush hairs planted on a peripheral surface thereof, and the toner on the image carrier regardless of the presence or absence of voltage application with the hair tip contacting the surface of the image carrier. The image forming apparatus according to claim 1, wherein the image forming apparatus is scraped off.

Images