JP2005331693A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep the cleaning force of a cleaning brush for a long period, by making the increase of toner amount accumulated on the cleaning brush gentle. <P>SOLUTION: The image forming apparatus is constituted so that voltage to prevent residual toner, having a negative polarity from adhering is applied to the cleaning brush 78, and voltage to make the residual toner having the negative polarity adhere is applied to a cleaning roll 76, in a toner consuming mode in which a large amount of toner is discharged. Thus, a large amount of toner is prevented from adhering to the cleaning brush 78. As a result, a large amount of residual toner is prevented from adhering to the cleaning brush 78, so that the increase in the accumulated toner amount is made gentle, and the cleaning force of the cleaning brush 78 is kept for a long period. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to control of a cleaning device that collects residual toner on an image carrier or intermediate transfer member of an image forming apparatus.

  Conventionally, in an image forming apparatus such as a full-color printer, a drum-shaped photoconductor as an image carrier is provided for each color of yellow (Y), magenta (M), black (K), and cyan (C), and uniformly. Exposure is performed while rotating the charged photosensitive member to form an electrostatic latent image corresponding to each color of Y, M, K, and C on each photosensitive member, and the electrostatic latent image of each color is developed as developing means. Each color toner is attached from the container and development is performed, and a full color toner image formed by superimposing the developed color toner images on the intermediate transfer member is transferred to a recording medium. At the time of transfer to this recording medium, since there is residual toner that remains without being transferred to the photosensitive member and the intermediate transfer member, a cleaning device is provided on at least one of the photosensitive member and the intermediate transfer member to collect the residual toner. ing.

  Some of the cleaning devices include a cleaning roll as a residual toner collecting unit and a cleaning brush as a temporary residual toner holding unit. The cleaning roll attaches the residual toner on the photoreceptor or intermediate transfer body by applying a voltage having a predetermined potential difference in the positive or negative direction with the voltage applied to the photoreceptor or intermediate transfer body as a reference voltage, The adhered residual toner is scraped off by a blade that comes into contact with the surface of the cleaning roll and collected in a collecting container. The cleaning brush has brush hairs implanted on the surface thereof, a predetermined voltage is applied thereto, and residual toner is attached to the brush hair and temporarily held based on a potential difference from the reference voltage. The cleaning brush discharges the remaining toner held on the photosensitive member or intermediate transfer member at the time of non-image formation, rotates the photosensitive member or intermediate transfer member, conveys it to the cleaning roll, adheres to the cleaning roll, and It is discharged into a collection container. Patent Document 1 discloses an image forming apparatus using a cleaning brush as a cleaning device.

On the other hand, some image forming apparatuses perform development by loading a cartridge filled with a two-component developer composed of toner and carrier into a developing device in order to form a high-quality image. In the developing device using the two-component developer, development is performed by charging the toner and the carrier by stirring the toner and adjusting the density of the toner image when developing the electrostatic latent image on the photosensitive member. The toner is discharged from the developing device during non-image formation. In this way, the discharged toner may be collected by a cleaning device composed of the above-described cleaning brush or the like.
Japanese Patent Laid-Open No. 11-184244

  However, if residual toner adheres to the cleaning brush, even if it is ejected during non-image formation, all the residual toner that has adhered cannot be ejected, and the residual toner is accumulated little by little.

  Further, the developing device discharges a large amount of toner when adjusting the toner density, and when this large amount of toner adheres to the cleaning brush, the amount of accumulated residual toner also increases.

  When the amount of accumulated residual toner increases, the cleaning brush reduces the amount of residual toner that can be held thereafter, and thus causes a cleaning failure.

  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 maintaining the cleaning power of a temporary residual toner holding unit for a long period of time by gradually increasing the amount of toner accumulated in the temporary residual toner holding unit. And

  According to the first aspect of the present invention, the electrostatic latent image formed on the image carrier is developed with toner discharged from the developing means, and the developed toner image is directly or via an intermediate transfer member onto a recording medium. An image forming apparatus for transferring, which is provided corresponding to at least one of the image carrier and the intermediate transfer member, and is not required for image formation, on the image carrier or the intermediate transfer member A cleaning device that collects residual toner remaining in at least one of the cleaning devices, and the cleaning device includes a residual toner recovery unit that finally recovers the residual toner, and a predetermined voltage difference in a positive or negative direction with respect to a reference voltage. A temporary residual toner holding unit that temporarily collects and holds the residual toner by electrostatic force; and at least the temporary residual toner when the toner is discharged from the developing unit during non-image formation. It characterized by having a a prohibiting means for prohibiting the recovery of the residual toner by chromatography holding means.

  According to the first aspect of the present invention, the residual toner remaining on the image carrier or the intermediate transfer member is collected by the residual toner collecting unit, and is temporarily collected and held by the temporary residual toner holding unit. The

  Here, when toner is discharged from the developing unit during non-image formation, the prohibiting unit prohibits at least the collection of the residual toner by the temporary residual toner holding unit. As a result, the toner discharged from the developing unit during non-image formation does not adhere to the temporary residual toner holding unit, and the residual toner can be prevented from accumulating in the temporary residual toner holding unit. Therefore, the increase in the amount of residual toner accumulated in the temporary residual toner holding unit can be moderated and the cleaning power of the temporary residual toner holding unit can be maintained for a long time.

  According to a second aspect of the present invention, in the first aspect of the present invention, the prohibiting unit is configured such that the prohibiting unit has a potential difference in a direction opposite to a polarity direction of a potential difference with respect to the reference voltage when the residual toner is collected with respect to the temporary residual toner holding unit. By using the repulsion of electrostatic force.

  According to the second aspect of the present invention, when the toner is ejected from the developing unit during non-image formation, the prohibiting unit has a potential difference with respect to the reference voltage at the time of collecting the remaining toner with respect to the temporary residual toner holding unit. A potential difference in the direction opposite to the polarity direction is formed. By forming the potential difference in the opposite direction, a repulsive force of electrostatic force is generated, and the residual toner can be prevented from adhering to the temporary residual toner holding unit.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the residual toner collecting unit is a residue whose collection is prohibited by the temporary residual toner holding unit by the prohibiting unit at least in a normal environment. The toner is collected.

  According to the third aspect of the present invention, when toner is discharged from the developing unit during non-image formation, the prohibiting unit prohibits the collection of the residual toner by the temporary residual toner holding unit. In this case, it is possible to prevent the residual toner from remaining on the image carrier or the intermediate transfer member by collecting the residual toner whose collection is prohibited by the temporary residual toner holding unit.

  As described above, according to the present invention, it is possible to provide an image forming apparatus that can moderately increase the amount of toner accumulated in the temporary residual toner holding unit and maintain the cleaning power of the temporary residual toner holding unit for a long period of time. It has an excellent effect.

  FIG. 1 shows an outline of an image forming apparatus 10 according to an embodiment of the present invention. The image forming apparatus 10 includes an image forming apparatus main body 12, and a paper feeding unit 14 is provided below the image forming apparatus main body 12.

  The paper feed unit 14 includes a paper tray 22 on which paper is stacked and a paper feed roll 24 that sends out the paper from the paper tray 22. The paper passes through the paper feed path 30 through the paper 26 and 28, and is conveyed to a transfer roll 74 described later.

  After the toner image is transferred onto the paper by the transfer roll 74 and fixed by the fixing unit 32, the toner image is provided on the upper portion of the image forming apparatus main body 12 by the discharge roll 36 or the discharge roll 38 depending on the position of the switching claw 34. The paper is discharged to the first discharge tray 16 or the second discharge tray 18.

  Here, in the case of double-sided printing, after the printing of the front surface is completed in the order as described above, before the paper is completely discharged to the first discharge tray 16, the discharge roll 36 is reversed and the paper is reversed. Supplied to the line 40. The paper is then returned to the paper feed path 30 through the transport rolls 42, 44, 46, and 48, and the back side of the paper is printed. In the case of manual printing, by placing paper on the manual feed tray 20, the paper is transported from the manual feed roll 49 to the paper feed path 30 via the transport roll 48 and printed.

  Meanwhile, on the right side of FIG. 1 of the image forming apparatus 10, four developer cartridges 64 filled with developer for each color (consisting of toner and carrier) are arranged. The developer cartridge 64 is connected to developing units 60Y, 60M, 60K, and 60C, which will be described later, arranged in order from the top of FIG. 1 through a developer supply path 65, and the developer in the developer cartridge 64 is stored in the developer cartridge 64. Supplied to developing devices 60Y, 60M, 60K, and 60C.

  An exposure unit 62 is arranged on the left side of the developer cartridge 64 in FIG. 1, and the exposure unit 62 emits four laser beams L (Y), L (M), L (K), and L (C). The light is output toward the photoconductor 52 constituting the photoconductor unit 50 arranged on the left side of the exposure unit 62 in FIG.

  The exposure unit 62 has laser beams L (Y), L (M), L (K), and L (C) modulated in accordance with the colors Y, M, C, and K of the image to be formed (hereinafter collectively referred to as “collection”). A light source (not shown) for outputting laser light L), a modulation processing part (not shown) for modulating the laser light L based on an image to be formed, and the laser light L on each photoconductor 52. A polygon mirror 62A for scanning and a mirror group 62B composed of a plurality of mirrors are included.

  The photoconductor unit 50 includes four photoconductors 52 (52Y, 52M, 52K, and 52C) arranged in the vertical direction. From the top, for example, yellow (52Y), magenta (52M), black (52K), and cyan. The laser beam L emitted from the light source unit and modulated by the modulation processing unit is converted into scanning light by the polygon mirror 62A, and the photoconductor 52 corresponding to each color is arranged by the mirror group 62B. Reflected in the direction and imaged on each photoconductor 52.

  As shown in FIG. 2, the photoconductor unit 50 includes a charging roll 56 and a refresh roll 54 corresponding to each photoconductor 52, and is provided so as to rotate in contact with the photoconductor 52. . The charging roll 56 applies a negative voltage (for example, −800 V) to uniformly charge the photosensitive member 52 to the negative polarity. Each of the uniformly charged photoreceptors 52 is subjected to scanning exposure with the laser beam L to form an electrostatic latent image, and toner is discharged from a magnet roll 80 provided in a developing unit 58 described later. It adheres to the surface of the photoreceptor 52. On the other hand, the refresh roll 54 discharges the photoconductor 52 to remove the residual toner adhering to the surface of the photoconductor 52, thereby preventing ghosts and the like caused by the residual toner remaining on the surface of the photoconductor 52.

  Here, the developing device unit 58 is disposed on the lower right side of FIG. 2 of each photoconductor unit 50 and corresponds to each photoconductor 52 (52Y, 52M, 52K, 52C). 60Y, 60M, 60K, 60C) are arranged in the vertical direction.

  As shown in FIG. 2, the developing device unit 58 includes four developing devices 60, and each developing device 60 includes a box-shaped housing 110 and a lid 120 that closes the housing 110. In this method, a magnet roll 80 (developer carrier) for supplying toner to the photosensitive member 52 and a developer (toner and carrier) in the developing device 60 are agitated to charge the toner negatively and the carrier positively. A spiral auger 114 and a spiral auger 112 for supplying developer to the magnet roll 80 are rotatably supported.

  Each developing device 60 can move between a position where the magnet roll 80 abuts on the photoconductor 52 and a position where the magnet roll 80 is retracted from the photoconductor 52. When the toner is discharged, the magnet roll 80 contacts the photoconductor 52. It comes to touch. As a result, the toner adheres to the photosensitive member 52 corresponding to the electrostatic latent image formed on the photosensitive member 52. However, when the toner is not discharged, the developing unit 58 is in contact with the photosensitive member 52. Evacuates from.

  As shown in FIG. 3, each developing device 60 is provided with a metal layer thickness regulating member 124 in the vicinity of the magnet roll 80 along the axial direction of the magnet roll 80. The layer thickness of the developer supplied to is regulated. The layer thickness regulating member 124 has a substantially L-shaped cross section made of sheet metal or the like, and a filling member 126 made of synthetic resin or the like is accommodated in the layer thickness regulating member 124 and fixed to the layer thickness regulating member 124.

  The clogging member 126 can guide the developer to the gap between the layer thickness regulating member 124 and the magnet roll 80. Then, a magnetic brush having a predetermined height is formed by passing through the layer thickness regulating member 124 and rubs the photoreceptor 52 (see FIG. 2) as the magnet roll 80 rotates. A developing bias voltage in which a negative direct current component is superimposed on an alternating current component is applied to the magnet roll 80, whereby negative toner is applied only to the electrostatic latent image (image portion) of the photoreceptor 52 by electrostatic force. A toner image is formed by adhering.

Here, the toner of this developer has an average particle diameter of 3 μm or more and 10 μm or less, and a shape defined by the following formula (1) from the maximum straight diameter (absolute maximum length) of one particle and the projected area of the particle. The coefficient (MLS2) is a substantially spherical shape with 100 to 140. Thereby, the transfer efficiency of the toner image is good and a high-quality image can be obtained.
MSL2 = (absolute maximum length × 2) / (projection area of particle × π × 1/4 × 100) (1)
As shown in FIG. 2, an intermediate transfer unit 66 is disposed on the left side of the photoreceptor unit 50, and three drum-shaped intermediate transfer bodies 68, 70, and 72 are provided. The two first intermediate transfer members 68 and 70 are arranged vertically in the vertical direction, and the upper first intermediate transfer member 68 is arranged on the two photoconductors 52Y and 52M arranged at the upper portion of the photoconductor 52. The lower first intermediate transfer member 70 rotates in contact with the two photoconductors 52K and 52C disposed in the lower portion. A positive voltage (details will be described later) is applied to the first intermediate transfer members 68 and 70 in order to transfer negative toner, and the toner images on the photoconductors 52Y and 52M are transferred to the first intermediate transfer member 68. The toner images on the photoconductors 52K and 52C are transferred to the first intermediate transfer body 70, respectively. Further, the second intermediate transfer member 72 rotates in contact with both the first intermediate transfer members 68 and 70, and the first intermediate transfer member 72 transfers the negative toner on the first intermediate transfer members 68 and 70. A positive voltage (details will be described later) higher than the voltage applied to the intermediate transfer member is applied, and the two color toner images on the first intermediate transfer members 68 and 70 are superimposed on the second intermediate transfer member 72. Thus, a full-color toner image is formed, and the full-color toner image is transferred onto a sheet by the transfer roll 74 (see FIG. 1).

  Further, first cleaning devices 75A and 75B are disposed in the vicinity of the first intermediate transfer bodies 68 and 70, respectively, and residual toner remaining on the surfaces of the first intermediate transfer bodies 68 and 70 after the transfer of the toner image. The second cleaning device 75C is disposed in the vicinity of the second intermediate transfer member 72, and the remaining toner remaining on the surface of the second intermediate transfer member 72 is recovered. Here, since the first cleaning devices 75A and 75B and the second cleaning device 75C have the same configuration, they are referred to as the cleaning device 75 unless otherwise distinguished.

  In the image forming apparatus 10, the toner images of the respective colors are transferred from the photosensitive member 52 to the first intermediate transfer members 68 and 70 and from the first intermediate transfer members 68 and 70 to the second intermediate transfer member 72. As a result, the residual toner generated on the intermediate transfer bodies 68, 70, and 72 is affected by the negative polarity toner, charge injection due to the positive polarity voltage applied at the time of transfer, or slight discharge generated when the paper is peeled off. As a result, a positive residual toner having a reversed polarity is generated. The cleaning device 75 collects negative-polarity residual toner and positive-polarity residual toner generated by transfer as an image forming mode by two rolls of a cleaning roll 76 and a cleaning brush 78, respectively.

  By the way, the charge injection and the minute discharge are generated when the temperature and humidity at which the image forming apparatus 10 is installed are from a low temperature and low humidity (10 ° C., 15%) to a normal (22 ° C., 55%) environment. It is easy to do and hardly occurs at high temperature and high humidity (28 ° C, 85%). In other words, the generation ratio of the positive polarity residual toner varies depending on the installation environment. Therefore, the image forming apparatus 10 is provided with a temperature / humidity sensor 90 (see FIG. 1) on the back side of the first discharge tray 16 in order to measure temperature and humidity.

  As shown in FIGS. 4 and 5, in the cleaning device 75, a cleaning roll 76 and a cleaning brush 78 are rotatably fixed in the cover housing 130, and each rotate about an axis. The cleaning roll 76 is a metal rigid body, and is applied with a predetermined voltage (described later in detail) to adhere negative residual toner or positive residual toner on the intermediate transfer bodies 68, 70, 72 based on a potential difference. . A metal blade 132 is in contact with the circumferential surface of the cleaning roll 76, and the adhered residual toner is carried into the temporary storage chamber 134 as the cleaning roll 76 rotates, and is brought into the temporary storage chamber 134 by the edge of the blade 132. It is scraped off. The temporary storage chamber 134 is provided with an auger 136 wound in a spiral shape around a predetermined axis, and rotates around the axis in conjunction with a cleaning roll 76 and a cleaning brush 78 by a gear (not shown). The residual toner can be discharged from the discharge port 138 (see FIG. 5) provided on the side by a certain amount. The discharge port 138 is inserted into a collection container (not shown), and the discharged residual toner is held in the collection container. Here, since the blade 132 is made of metal, the scraping performance is better than that of a conventional synthetic resin. Also, since both the cleaning roll 76 and the blade 132 are made of metal, both are made of synthetic resin. Less wear.

  On the other hand, the brush bristles are implanted on the surface of the cleaning brush 78, and a predetermined voltage (details will be described later) is applied, thereby adhering negative residual toner on the intermediate transfer bodies 68, 70, 72 and temporarily. The negative-polarity residual toner held and discharged every time a certain number of images (for example, 100 sheets) are formed is ejected onto the intermediate transfer bodies 68, 70, 72, and the intermediate transfer bodies 68, 70, 72 are rotated. Then, the toner is conveyed to the cleaning roll 76, and the negative polarity residual toner is adhered and collected by the cleaning roll 76.

  Here, FIGS. 6A, 6 </ b> B, and 6 </ b> C show the installation environment and applied voltage of the image forming apparatus 10. The first cleaning devices 75A and 75B use the applied voltage to the first intermediate transfer bodies 68 and 70 as a reference voltage, and the second cleaning device 75C uses the applied voltage to the second intermediate transfer body 72 as a reference voltage, respectively. On the other hand, a high (positive) or low (negative) voltage is applied to attach or discharge residual toner.

  In the image forming mode, the voltage shown in FIG. 6A is applied to the first intermediate transfer members 68 and 70 and the second intermediate transfer member 72 according to the temperature and humidity of the environment where the image forming apparatus 10 is installed. The Here, in the low temperature and low humidity and normal environment, positive residual toner is generated by the positive voltage applied to the first intermediate transfer bodies 68 and 70 and the second intermediate transfer body 72 as described above. Therefore, in the case of low temperature and low humidity and a normal environment, a voltage lower than the applied voltage of the first intermediate transfer bodies 68 and 70 is applied to the cleaning roll 76 of the first cleaning devices 75A and 75B, and the first intermediate transfer is performed based on the potential difference. A positive toner on the bodies 68 and 70 is attached, and a voltage higher than the applied voltage of the first intermediate transfer bodies 68 and 70 is applied to the cleaning brush 78 of the first cleaning devices 75A and 75B. 1 Negative toner on the intermediate transfer members 68 and 70 is adhered. In addition, a voltage lower than the voltage applied to the second intermediate transfer body 72 is applied to the cleaning roll 76 of the second cleaning device 75C to attach the positive residual toner on the second intermediate transfer body 72, and the second cleaning is performed. A voltage higher than the voltage applied to the second intermediate transfer member 72 is applied to the cleaning brush 78 of the device 75C to adhere negative residual toner on the second intermediate transfer member 72.

  On the other hand, in a high-temperature and high-humidity environment, since positive toner hardly occurs, the cleaning roller 76 and the cleaning brush 78 of the first cleaning devices 75A and 75B have a voltage higher than the applied voltage of the first intermediate transfer bodies 68 and 70. Is applied to the negative intermediate toner on the first intermediate transfer bodies 68 and 70 based on the potential difference, and the second intermediate transfer body 72 is attached to the cleaning roll 76 and the cleaning brush 78 of the second cleaning device 75C. A voltage higher than the applied voltage is applied, and the negative residual toner on the second intermediate transfer body 72 is adhered based on the potential difference.

  By the way, when the image forming mode is executed, the cleaning brushes 78 of the cleaning devices 75A, 75B, and 75C adhere and hold the negative-polarity residual toner as described above. A brush cleaning mode for discharging residual toner is performed. In this brush cleaning mode, as shown in FIG. 6B, the cleaning brush 78 of the first cleaning devices 75A and 75B has a first intermediate transfer member in any of a low temperature and low humidity environment and a normal high temperature and high humidity environment. A voltage lower than the applied voltage of 68 and 70 is applied, and a voltage higher than that of the first intermediate transfer bodies 68 and 70 is applied to the cleaning roll 76 of the first cleaning devices 75A and 75B. As a result, the negative residual toner is discharged from the cleaning brush 78 of the first cleaning devices 75A and 75B onto the first intermediate transfer bodies 68 and 70, and the first intermediate transfer bodies 68 and 70 are rotated along with the rotation of the first intermediate transfer bodies 68 and 70. It is conveyed to the cleaning roll 76 of the cleaning devices 75A and 75B and collected.

  Similarly, the voltage shown in FIG. 6B is applied to the cleaning brush 78 and the cleaning roll 76 of the second cleaning device 75C, and negative residual toner is supplied from the cleaning brush 78 of the second cleaning device 75C to the second. The ink is discharged onto the intermediate transfer member 72 and is conveyed to the cleaning roll 76 of the second cleaning device 75C as the second intermediate transfer member 72 rotates, and is collected.

  Here, with the cleaning brush 78, as described above, the negative residual toner is adhered and held, and the residual toner is discharged by performing the brush cleaning mode every time a certain number of images are formed. Even if the ejection is performed, the remaining toner cannot be completely ejected and is gradually accumulated on the brush bristles. In the cleaning brush 78, when the amount of accumulated residual toner increases, the amount of residual toner that can be adhered and held decreases, which causes a cleaning failure. Therefore, the cleaning brush 78 is replaced when the amount of accumulated residual toner increases.

  By the way, in the image forming apparatus 10 of the present embodiment, in order to reduce the size of the apparatus, the spiral auger 112 and the spiral auger 114 of the developing device 60 (60Y, 60M, 60K, 60C) are the same as the developing device driving motor (not shown). The developer (toner and carrier) for each color is agitated in the same manner. Here, for example, when monotone continues to an image formed by the image forming apparatus 10, the developer 60K consumes black developer, but the developers 60Y, 60M, and 60C develop yellow, magenta, and cyan colors. The agent is not consumed. For this reason, in the developing devices 60Y, 60M, and 60C, when the developer becomes excessive, the density of the toner of each color that adheres to the electrostatic latent image on the photosensitive member 52 is adjusted. A toner consumption mode is performed in which the amount of developer discharged inside the body 52 is adjusted. The discharged toner may be ejected more than the amount of toner of the solid image in the image formation, and from the first intermediate transfer bodies 68 and 70 to the second intermediate transfer body 72 in the same manner as the toner image at the time of image formation. The toner is collected as residual toner by the cleaning device 75 mainly in contact with the second intermediate transfer member 72.

  The cleaning device 75 collects the toner discharged from each developing device 60 as a residual toner in the toner consumption mode, but the amount of toner discharged for toner density adjustment may be larger than that during normal image formation. In addition, since transfer onto a sheet is not performed, the amount of residual toner to be collected becomes larger than that at the time of image formation. If the residual toner in the toner consumption mode adheres to the cleaning brush 78, even if the attached residual toner is discharged, it cannot be completely discharged, and a large amount of residual toner is accumulated in the cleaning brush 78. For this reason, in the image forming apparatus according to the present embodiment, in the toner consumption mode, a voltage for prohibiting the adhesion of the residual toner is applied to the cleaning brush 78 to moderately increase the amount of residual toner accumulated in the cleaning brush 78. I have to.

  In the toner consumption mode, as shown in FIG. 6C, the remaining toner of the negative electrode was collected by the cleaning brush 78 of the first cleaning devices 75A and 75B in all of the low temperature and low humidity, normal environment, and high temperature and high humidity environment. Applying a voltage lower than the applied voltage of the first intermediate transfer bodies 68 and 70 opposite to that in the image forming mode to generate a repulsive force of electrostatic force based on the potential difference and prohibit the adhesion of negative-polarity residual toner, A voltage higher than the applied voltage of the first intermediate transfer bodies 68 and 70 is applied to the cleaning rolls 76 of the first cleaning devices 75A and 75B, and negative toner is adhered and collected based on the potential difference.

  Similarly, a voltage lower than the applied voltage of the second intermediate transfer body 72 is applied to the cleaning brush 78 of the second cleaning device 75C to inhibit the adhesion of negative residual toner, and the cleaning roll of the second cleaning device 75C is used. A voltage higher than the voltage applied to the second intermediate transfer member 72 is applied to 76, and negative toner is adhered and collected.

  That is, in the toner consumption mode, all the remaining toner is collected only by the cleaning roll 76.

  Here, FIGS. 6 (A), (B), and (C) show one record each as an example of high temperature and high humidity, normal, and low temperature and low humidity, but it is determined in more detail according to temperature and humidity. It has been.

  In FIG. 7, every time 100 images are formed, toner for 4 solid images (100% density) is discharged as toner density adjustment, and when the toner discharged by the cleaning device 75 is collected, the toner consumption mode is used. The amount of residual toner accumulated in the cleaning brush 78 when it is used and when it is not used is shown. As shown in FIG. 7, the increase in the residual toner accumulated can be moderated by using the toner consumption mode when a large amount of toner adheres.

  By the way, the blade 132 of the cleaning device 75 scrapes off the positive and negative residual toner adhering to the cleaning roll 76, but is slightly separated from the cleaning roll 76 by the residual toner. And the wear of the edge of the blade 132 can be suppressed. However, if image formation with a low image density continues, the amount of toner discharged from each developing device 60 decreases, so the amount of residual toner also decreases, and there is insufficient residual toner between the cleaning roll 76 and the blade 132 and contact. There will be more parts and wear will occur. Therefore, in the image forming apparatus 10 of the present embodiment, when image formation with a low image density continues, a constant amount of toner is discharged from the developing device 60 during non-image formation, and the cleaning roll 76 and the cleaning roll 76 of the cleaning device 75 By applying the same voltage to the cleaning brush 78 as in the toner consumption mode and intentionally adhering residual toner to the cleaning roll 76 of the cleaning device 75, cleaning assist is performed to adjust the lubricant so that it is properly separated and lubricated. ing. It should be noted that the image density is as low as 2 to 5% for a character image, the image density is as high as 90 to 100% for a solid image in the entire image area, and the average image density is 50% for a general image. It is known that each color is adjusted so that

  Next, the configuration of the control unit that controls the applied voltage based on the temperature and humidity in the image forming mode, the brush cleaning mode, and the toner consumption mode of the image forming apparatus 10 will be described with reference to FIG.

  The image formation control unit 150 is connected to the toner amount calculation unit 153, the brush cleaning determination unit 151, and the applied voltage selection unit 164. The image formation control unit 150 controls image formation processing on paper. When image data is input, the image formation control unit 150 sends a voltage application instruction to an application voltage selection unit 164 described later, and the installation environment (temperature, humidity). Accordingly, a voltage as an image forming mode is applied to the first intermediate transfer members 68 and 70, the second intermediate transfer member 72, the first cleaning devices 75A and 75B, and the second cleaning device 75C. Further, while rotating the photoreceptors 52Y, 52M, 52K, and 52C, they are uniformly charged by the charging roll 56, and laser light L (Y), L (M), L (based on the image data from the exposure unit 62 is obtained. K) and L (C) are scanned and exposed to form electrostatic latent images on the photoconductors 52Y, 52M, 52K, and 52C, and each color of Y, M, K, and C is developed by the developing devices 60Y, 60M, 60K, and 60C. Development is performed by attaching toner, and toner images of respective colors are formed. Since the voltage of the image forming mode is applied to the first intermediate transfer bodies 68 and 70 and the second intermediate transfer body 72 by the voltage application instruction being sent, the toner image can be transferred, so the image formation control unit 150 is formed. The toner images on the photoconductors 52Y and 52M are transferred so as to be superimposed on the first intermediate transfer body 68 that rotates in contact with each other, and the toner images on the photoconductors 52K and 52C are rotated in contact with each other. Then, the toner image on the first intermediate transfer bodies 68 and 70 is transferred so as to overlap the second intermediate transfer body 72 that rotates in contact with each other, thereby forming a full-color toner image. Further, the formed full-color toner image is sent out from the paper tray 22 and transferred to the paper reaching the transfer roll 74 so as to be conveyed through the paper feed path 30 and synchronized, thereby forming an image on the paper.

  In addition, the image formation control unit 150 sends the image data subjected to the image formation process to the toner amount calculation unit 153 and the number of sheets on which the image has been formed to the brush cleaning determination unit 151.

  The brush cleaning determination unit 151 is connected to the image formation control unit 150 and the brush cleaning control 152. The brush cleaning determination unit 151 stores a counter m therein, and adds the number of sheets sent from the image formation control unit 150 to the counter m for storage. Further, when the value of the counter m reaches a predetermined value (for example, 100) as a result of the addition, a remaining toner discharge instruction is sent to the brush cleaning control 152. This is because the brush cleaning mode is performed every time 100 images are formed on the paper. The brush cleaning determination unit 151 initializes the counter to 0 when a residual toner discharge instruction is sent.

  The brush cleaning control 152 is connected to the brush cleaning determination unit 151 and the applied voltage selection unit 164. The brush cleaning control 152 sends a voltage application instruction to an applied voltage selection unit 164 to be described later, and the first intermediate transfer bodies 68 and 70, the second intermediate transfer body 72, the first cleaning devices 75A and 75B, and the second cleaning device 75C. A voltage in the brush cleaning mode is applied to the first cleaning devices 75A and 75B and the second cleaning device 75C to discharge residual toner. In addition, the photosensitive members 52Y, 52M, 52K, and 52C, the first intermediate transfer members 68 and 70, and the second intermediate transfer member 72 are rotated in the same manner as in the image formation, and the discharged residual toner is respectively discharged to the first cleaning device 75A. , 75B and the cleaning roller 76 of the second cleaning device 75C for recovery.

  The toner amount calculation unit 153 is connected to the image formation control unit 150, the cumulative toner amount storage unit 154, and the cleaning assist determination unit 158. The toner amount calculation unit 153 counts the number of pixels of yellow (Y), magenta (M), black (K), and cyan (C) of the image formed based on the image data sent from the image formation control unit 150. Thus, the toner amount of each color discharged from each developing device 60 in the image forming process is calculated. The toner amount calculation unit 153 sends the calculated toner amount of each color to the cumulative toner amount storage unit 154 and the cleaning assist determination unit 158.

  The cumulative toner amount storage unit 154 is connected to the toner amount calculation unit 153, the toner density adjustment determination unit 156, and the toner consumption mode control unit 160. The total toner amount storage unit 154 stores the toner amount of each color sent from the toner amount calculation unit 153 for each color. When an initialization instruction is received from a toner consumption mode control unit 160, which will be described later, the stored total toner amount for each color is initialized, and a new total is started.

  The toner density adjustment determination unit 156 is connected to the cumulative toner amount storage unit 154 and the toner consumption mode control unit 160. The toner density adjustment determination unit 156 reads the accumulated toner amount of each color stored in the accumulated toner amount storage unit 154, and calculates the difference between the accumulated toner amount of the color having the largest accumulated amount and the accumulated toner amounts of the other three colors. When each added value becomes a predetermined value, a toner discharge instruction is sent to the toner consumption mode control unit 160. This is because, for example, when the image formed by the image data is monotone, only the black (K) toner is consumed, and the yellow, magenta, and cyan toners are not consumed. Therefore, the developing devices 60Y, 60M, and 60C This is because the toner density is adjusted by discharging the toner.

  The cleaning assist determination unit 158 is connected to the toner amount calculation unit 153 and the toner consumption mode control unit 160. The cleaning assist determination unit 158 stores a counter n, and the total amount of toners of each color sent from the toner amount calculation unit 153 is a toner amount having a constant density (for example, an image density of 5%) as the entire image. It is determined whether or not it is less than or equal to a certain density. When the toner amount of each color is larger than a certain density, the counter n is initialized. That is, the counter stores how many times the image forming process of a certain density or less has been continuously performed. When the counter n reaches a predetermined value (for example, 50), the cleaning assist determination unit 158 sends a toner discharge instruction to the toner consumption mode control unit 160. This is because, when image forming processing with a low toner density continues, a shortage of residual toner occurs between the cleaning roll 76 and the blade 132 of the cleaning device 75 and wear occurs. This is because the separated state is adjusted by discharging the gas and collecting it by the cleaning device 75.

  The toner consumption mode control unit 160 is connected to the cumulative toner amount storage unit 154, the toner density adjustment determination unit 156, the cleaning assist determination unit 158, and the applied voltage selection unit 164. When the toner consumption mode control unit 160 receives a toner discharge instruction from the toner density adjustment determination unit 156, the total toner amount storage unit 154 reads the total toner amount of each color, and determines the total toner amount of the color having the largest total amount and the other toner amount. The amount of toner discharged from each developing device 60 is calculated according to the difference from the total amount of toner of the three colors, and the amount of toner calculated from each developing device 60 is discharged. Also, when a toner discharge instruction is received from the cleaning assist determination unit 158, the amount of toner discharged from each developing device 60 is set to a constant value, and each developing device 60 discharges a constant amount of toner. In addition, a voltage application instruction is sent to an applied voltage selection unit 164, which will be described later, and a toner consumption mode is sent to the first intermediate transfer members 68 and 70, the second intermediate transfer member 72, the first cleaning devices 75A and 75B, and the second cleaning device 75C. Is applied. Further, the toner consumption mode control unit 160 rotates each photoconductor 52, the first intermediate transfer bodies 68 and 70, and the second intermediate transfer body 72 to perform transfer in the same manner as when forming an image, and discharges each color toner. Are conveyed to the first cleaning devices 75A and 75B and the second cleaning device 75C, and the remaining toner is collected by the cleaning rolls 76 of the first cleaning devices 75A and 75B and the second cleaning device 75C.

  In addition, the toner consumption mode control unit 160 sends an initialization instruction to initialize the accumulated toner amount stored in the accumulated toner amount storage unit 154.

  The applied voltage storage unit 162 is connected to the applied voltage selection unit 164. The applied voltage storage unit 162 includes an image forming mode applied voltage setting table (see FIG. 6A), a brush cleaning mode applied voltage setting table (see FIG. 6B), and a toner consumption mode applied voltage setting table (see FIG. 6). (See (C)), and each table can be read from the applied voltage selection unit 164.

  The applied voltage selection unit 164 includes an image formation control unit 150, a brush cleaning mode control unit 152, a toner consumption mode control unit 160, a temperature / humidity sensor 90, an applied voltage storage unit 162, a first intermediate transfer body voltage application unit 170, and a second. The intermediate transfer body voltage application unit 172, the first cleaning device voltage application unit 174, and the second cleaning device voltage application unit 178 are connected. The applied voltage selection unit 164 sets a voltage value to be applied to the first intermediate transfer bodies 68 and 70, the second intermediate transfer body 72, the first cleaning devices 75A and 75B, and the second cleaning device 75C according to temperature and humidity. Is going. When a voltage application instruction is sent from the image formation control unit 150, the application voltage selection unit 164 reads the image formation mode application voltage setting table from the application voltage storage unit 162 and detects the temperature and humidity detected by the temperature / humidity sensor 90. The voltage values to be applied to the first intermediate transfer members 68 and 70, the second intermediate transfer member 72, the first cleaning devices 75A and 75B, and the second cleaning device 75C are selected, and the selected first intermediate transfer member voltage value is selected. The first intermediate transfer member voltage applying unit 170, the second intermediate transfer member voltage value to the second intermediate transfer member voltage applying unit 172, the cleaning roll voltage value and the cleaning brush voltage value of the first cleaning device to the first cleaning device voltage. The application unit 174 sends the cleaning roll voltage value and the cleaning brush voltage value of the second cleaning device to the second cleaning device voltage. And sends it to the application section 178.

  Similarly, the application voltage selection unit 164 reads the brush cleaning mode application voltage setting table when a voltage application instruction is sent from the brush cleaning control 152, and sends a voltage application instruction from the toner consumption mode control unit 160. Then, the toner consumption mode application voltage setting table is read, a voltage value to be applied is selected based on the temperature and humidity detected by the temperature / humidity sensor 90, and each selected voltage value is transmitted.

  The first intermediate transfer body voltage application unit 170 and the second intermediate transfer body voltage application unit 172 are connected to the application voltage selection unit 164. The first intermediate transfer member voltage application unit 170 applies the voltage of the sent first intermediate transfer member voltage value to the first intermediate transfer members 68 and 70, and the second intermediate transfer member voltage application unit 172 sends the voltage. A voltage having a second intermediate transfer member voltage value is applied to the second intermediate transfer member 72.

  The first cleaning device voltage application unit 174 and the second cleaning device voltage application unit 178 are connected to the application voltage selection unit 164. The first cleaning device voltage application unit includes a cleaning roll voltage application unit 175 and a cleaning brush voltage application unit 176, and the second cleaning device voltage application unit 178 includes a cleaning roll voltage application unit 179. And a cleaning brush voltage application unit 180. The cleaning roll voltage application unit 175 of the first cleaning device voltage application unit 174 applies the voltage of the sent cleaning roll voltage value to the cleaning roll 76 of the first cleaning devices 75A and 75B, and the cleaning brush voltage application unit 176 sends it out. The voltage of the cleaning brush voltage value thus applied is applied to the cleaning brush 78 of the first cleaning devices 75A and 75B. Further, the cleaning roll voltage application unit 179 of the second cleaning device voltage application unit 178 applies the voltage of the sent cleaning roll voltage value to the cleaning roll 76 of the second cleaning device 75C, and the cleaning brush voltage application unit 180 sends it out. The voltage of the cleaning brush voltage value thus applied is applied to the cleaning brush 78 of the second cleaning device 75C.

  Next, the effect | action of this Embodiment is demonstrated using the flow shown in the flow of FIG.

  In step 200, image data is input to the image formation control unit 150, and the laser light L (Y (Y) based on the image data from the exposure unit 62 on the photoreceptors 52 Y, 52 M, 52 K, and 52 C uniformly charged by the charging roll 56. ), L (M), L (K), and L (C) are scanned to form an electrostatic latent image, and each color toner is discharged from the developing devices 60Y, 60M, 60K, and 60C, and development is performed. A toner image of each color is formed.

  In addition, the image formation control unit 150 sends a voltage application instruction to the first intermediate transfer bodies 68 and 70, the second intermediate transfer body 72, the first cleaning devices 75A and 75B, and the second cleaning device 75C. The voltage of the image forming mode according to the humidity is applied. As a result, the formed toner images on the photoconductors 52Y and 52M are transferred onto the first intermediate transfer member 68, and the toner images on the photoconductors 52K and 52C are transferred onto the first intermediate transfer member 70. Further, the toner images on the first intermediate transfer bodies 68 and 70 are transferred so as to be superimposed on the second intermediate transfer body 72 to form a full-color toner image. Further, the formed full-color toner image is sent out from the paper tray 22, transferred to the paper feed path 30, and transferred to the paper that has reached the transfer roll 74 so as to be synchronized, and an image is formed on the paper. Migrate to

  In step 202, when the installation environment of the image forming apparatus 10 is low temperature and low humidity or normal, positive residual toner and negative electrode are formed on the first intermediate transfer bodies 68 and 70 and the second intermediate transfer body 72 by the image formation in step 200. Since a residual toner remains, a voltage lower than the applied voltage of the first intermediate transfer bodies 68 and 70 is applied to the cleaning roll 76 of the first cleaning devices 75A and 75B to adhere the positive residual toner. A voltage higher than the applied voltage of the first intermediate transfer bodies 68 and 70 is applied to the cleaning brush 78 of the first cleaning devices 75A and 75B to adhere and hold negative residual toner. Similarly, a voltage lower than the voltage applied to the second intermediate transfer body 72 is applied to the cleaning roller 76 of the second cleaning device 75C, and the positive residual toner on the second intermediate transfer body 72 is adhered and collected. Then, a voltage higher than the applied voltage of the second intermediate transfer member 72 is applied to the cleaning brush 78 of the second cleaning device 75C to adhere and hold the negative toner remaining on the second intermediate transfer member 72. . When the remaining toner is collected by the first cleaning devices 75A and 75B and the second cleaning device 75C, the process proceeds to step 204.

  Further, when the installation environment of the image forming apparatus 10 is high temperature and high humidity, there is not much positive transfer residual toner on the first intermediate transfer members 68 and 70 and the second intermediate transfer member 72, and the negative polarity is mainly used. The remaining toner is present. For this reason, a voltage higher than the voltage applied to the first intermediate transfer bodies 68 and 70 is applied to the cleaning roll 76 and the cleaning brush 78 of the first cleaning devices 75A and 75B, and negative residual toner is removed by the cleaning roll 76. The toner is adhered and collected, and negative toner is adhered and held by the cleaning brush 78 of the first cleaning devices 75A and 75B. The same applies to the cleaning roller 76 and the cleaning brush 78 of the second cleaning device 75C, and a voltage higher than the applied voltage of the second intermediate transfer member 72 is applied to adhere negative residual toner.

  In step 204, the toner amount of each color ejected in the image forming process is calculated based on the image data, the toner amount for each color is accumulated, and the number of formed images is added to the counter m, and the process proceeds to step 206. Transition.

  In step 206, it is determined from the counter m whether a predetermined number of images have been formed. If the counter m is 100, the determination in step 206 is affirmative, and the process proceeds to step 208 to perform the brush cleaning mode.

  On the other hand, if the counter m is less than 100, a negative determination is made in step 206 and the process proceeds to step 210.

  In step 208, a voltage in a brush cleaning mode corresponding to temperature and humidity is applied to the first intermediate transfer members 68 and 70, the second intermediate transfer member 72, the first cleaning devices 75A and 75B, and the second cleaning device 75C. The residual toner is discharged from the cleaning brush 78 of the first cleaning devices 75A and 75B and the second cleaning device 75C onto the first intermediate transfer members 68 and 70 and the second intermediate transfer member 72, and the first intermediate transfer members 68 and 70 and 2 With the image formation and rotational driving of the intermediate transfer body 72, the discharged residual toner is conveyed to the cleaning rollers 76 of the first cleaning devices 75A and 75B and the second cleaning device 75C and collected. When the collection is completed, the process proceeds to the end.

  In step 210, if the sum of the difference between the cumulative toner amount of the color with the largest cumulative toner amount accumulated in step 204 and the cumulative toner amount of the other three colors is equal to or greater than a predetermined value, Since only the color toner is consumed and the toner density needs to be adjusted, an affirmative determination is made and the routine proceeds to step 214.

  On the other hand, if the value obtained by adding the difference between the cumulative toner amount of the color with the largest cumulative toner amount and the cumulative toner amount of the other three colors is less than a predetermined value, the adjustment of the toner density is unnecessary. If a negative determination is made, the process proceeds to step 212.

  In step 212, when the image density formed by the image forming process is 5% or less, 1 is added to the value of the counter n stored in the cleaning assist determination unit 158. As a result of addition, the value of the counter n is 50. At step 210, an affirmative determination is made and the routine proceeds to step 214. When the counter n is incremented by 1, but the value is less than 50, a negative determination is made at step 212 and the routine proceeds to the end. Further, if the density of the image formed by the image forming process is greater than 5%, a negative determination is made in step 212, the value of the counter n is initialized to 0, and the process proceeds to the end.

  In step 214, the amount of toner discharged from each color is calculated from the total amount of toner for each color, and the amount of toner calculated from the developing devices 60Y, 60M, 60K, and 60C is discharged. Further, the photosensitive member 52, the first intermediate transfer members 68 and 70, and the second intermediate transfer member 72 are rotated to perform transfer in the same manner as in the image formation, and the discharged toner of each color is discharged to the first cleaning devices 75A and 75B. And a toner consumption mode voltage corresponding to the temperature and humidity is applied to the cleaning roll 76 and the cleaning brush 78 of the first cleaning devices 75A, 75B and the second cleaning device 75C. The negative cleaning residual toner is prohibited from adhering to the cleaning brush 78 of the first cleaning devices 75A and 75B and the second cleaning device 75C, and only the cleaning roller 76 of the first cleaning devices 75A and 75B and the second cleaning device 75C is negative. The remaining toner is attached and collected. When collection ends, the process moves to the end.

  As described above, according to the image forming apparatus 10 of the present embodiment, in the toner consumption mode in which a large amount of toner is discharged, the cleaning brush 78 is applied with a voltage that inhibits adhesion of negative-polarity residual toner to the cleaning roll. By applying a voltage for adhering negative residual toner to 76, it is possible to prevent a large amount of toner from adhering to the cleaning brush 78. As a result, the increase in the amount of toner accumulated in the cleaning brush 78 can be moderated, so that the cleaning power of the cleaning brush 78 can be maintained for a long time.

  In the present embodiment, when a large amount of residual toner is generated, the toner density adjustment of the developing device 60 and cleaning assist are performed. However, a conveyance failure (so-called jam) occurs in a recording medium such as paper. When the toner image remains without being transferred, the toner consumption mode may be performed. This is because when a conveyance failure occurs, a larger amount of residual toner remains than when the toner is normally transferred onto the first intermediate transfer bodies 68 and 70 and the second intermediate transfer body 72, so that the residual toner adheres to the cleaning brush 78. By prohibiting, an increase in the residual toner accumulated in the cleaning brush 78 can be suppressed.

  In this embodiment, the first cleaning devices 75A and 75C and the second cleaning device 75C are provided on the intermediate transfer members 68, 70, and 72. However, the remaining toner may be collected by providing each of the photosensitive members 52. .

1 is a side view of an image forming apparatus according to an embodiment of the present invention. 1 is an enlarged view of a main part of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view of a developing device according to an embodiment of the present invention. It is an enlarged view of the cleaning apparatus which concerns on embodiment of this invention. It is a perspective view of the cleaning device concerning the embodiment of the present invention. It is an applied voltage setting table of each mode concerning the embodiment of the present invention. FIG. 10 is a diagram illustrating a remaining toner accumulation amount when the toner consumption mode according to the embodiment of the present invention is used and not used. It is a block diagram of the structure of the control part of each mode which concerns on embodiment of this invention. It is a flow which shows the flow of control which concerns on embodiment of this invention.

Explanation of symbols

Image forming apparatus 10
Photoconductor 52, 52Y, 52M, 52K, 52C (image carrier)
Developer 60, 60Y, 60M, 60K, 60C (developing means)
Intermediate transfer member 68, 70, 72
Cleaning device 75, 75A, 75B, 75C
Cleaning roll 76 (remaining toner collecting means)
Cleaning brush 78 (temporary residual toner holding means)
Applied voltage selection unit 164 (prohibiting means)

Claims (3)

An image forming apparatus that develops an electrostatic latent image formed on an image carrier with toner discharged from a developing unit, and transfers the developed toner image to a recording medium directly or via an intermediate transfer body,
Residual toner that is provided corresponding to at least one of the image carrier and the intermediate transfer member and is unnecessary for image formation and remains on at least one of the image carrier and the intermediate transfer member is collected. Equipped with a cleaning device,
The cleaning device includes:
A residual toner collecting means for finally collecting the residual toner;
Temporary residual toner holding means for temporarily attaching and collecting the residual toner as a predetermined voltage difference in a positive or negative direction with respect to a reference voltage by electrostatic force;
A prohibiting unit that prohibits at least the collection of the residual toner by the temporary residual toner holding unit when toner is discharged from the developing unit during non-image formation;
An image forming apparatus comprising:   The prohibiting unit utilizes repulsion of electrostatic force by setting the potential difference in a direction opposite to the polarity direction of the potential difference with respect to the reference voltage at the time of collecting residual toner to the temporary residual toner holding unit. Item 2. The image forming apparatus according to Item 1.   3. The image forming apparatus according to claim 1, wherein the residual toner collecting unit collects residual toner whose collection is prohibited by the temporary residual toner holding unit by the prohibiting unit at least in a normal environment. .

Images