JP2007171461A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent degradation in the picture quality of an image formed after cleaning a charging part. <P>SOLUTION: When a charging roll is cleaned in a charger, potential setting-up, image density setting-up and intra-surface irregularity setting-up for correcting density irregularity in a surface are performed interlocking with the cleaning operation. In the intra-surface irregularity setting-up, irregularity correction data used for correcting intra-surface irregularity are reset after performing the cleaning of the charger. Consequently irregularity correction corresponding to charging irregularity generated by the cleaned charger can be performed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile.

  Conventionally known image forming apparatuses include a photosensitive drum, a charging device, an exposure device, a developing device, a transfer device, and the like. In such an image forming apparatus, the rotating photosensitive drum is uniformly charged by a charging device. Next, the charged photosensitive drum surface is selectively exposed by an exposure device to form an electrostatic latent image on the photosensitive drum. The electrostatic latent image formed on the photosensitive drum is developed by a developing device to be a visible image, and the obtained toner image is transferred to a recording material by a transfer device.

  Here, as the charging device, those using a corotron arranged in non-contact with the photosensitive drum and those using a charging member arranged in contact with the photosensitive drum (for example, a charging roll or a charging film) are known. ing. In the non-contact charging method using a corotron or the like, a discharge is generated between the wire and the grid, and the photosensitive drum is charged by this discharge. On the other hand, in the contact charging method using a charging roll or the like, a charging bias is applied to the contact charging member to generate a discharge in a small gap near the nip between the photosensitive drum and the contact charging member. Charge.

  In such an image forming apparatus, for example, when a halftone image for one sheet is formed, uneven density (called in-plane unevenness) may occur in the formed image. This in-plane unevenness is, for example, uneven sensitivity of the photosensitive layer provided on the photosensitive drum, uneven charging by the charging device, uneven exposure by the exposure device, uneven development due to a variation in the distance between the developing roll constituting the developing device and the photosensitive member, Further, it occurs due to uneven transfer by the transfer device. Therefore, by forming a toner image under standard image forming conditions in advance, a profile of in-plane unevenness is acquired in advance, and for example, by appropriately adjusting the intensity of light emitted from the exposure apparatus according to this profile, There is a technique for correcting in-plane unevenness (see, for example, Patent Document 1).

Among the uneven density factors, the uneven charging is caused by, for example, the charging device being inclined with respect to the photosensitive drum. In addition, uneven charging is caused by, for example, non-uniform adhesion of discharge products, toner, and the like to a wire or a charging roll constituting the corotron. Here, with respect to the latter, since the amount of dirt attached to the wire, the charging roll, etc. increases with time, the density unevenness and streaks in the formed image gradually become noticeable. .
Therefore, for example, in a charging device using a non-contact charging method, a cleaner for cleaning the wire is provided and cleaning is performed at a predetermined timing. In the charging device using the contact charging method, a cleaner for cleaning the charging roll is provided, and cleaning is performed in the same manner.

Further, in such an image forming apparatus, a patch image (toner image) having a predetermined pattern is formed at a predetermined timing in order to suppress density fluctuation of the image. Then, based on the detection result of the density (toner adhesion amount) of the formed patch image, the operation parameters of each apparatus constituting the image forming apparatus are adjusted.
However, when the density of the reference patch image, that is, the toner adhesion amount, changes, this change is due to a change in the charging potential of the photosensitive drum due to dirt adhering to the charging device, or the developing capability in the developing device. It is not possible to distinguish whether the change is due to a change in toner (for example, a decrease in toner density). Then, it becomes very difficult to determine which device operating parameter should be adjusted. For this reason, there is a possibility that an operation parameter of a device other than the device that should originally adjust the operation parameter is adjusted, and as a result, erroneous control may be executed.
Therefore, a technique has been proposed that removes the cause of unevenness in the charging device by cleaning the charging device (charging roll) before creating the patch image and setting the operation parameters of the device associated therewith. (For example, see Patent Document 2). By cleaning the charging device in this manner, it is possible to reduce the level of contamination of the charging device and reduce the effect on the formation of the reference patch image.

JP-A-5-268440 (page 6-7, FIG. 11) Japanese Patent Laying-Open No. 2004-102182 (page 3-4, FIG. 2)

  However, even if the charging device is cleaned as in Patent Document 2, it is very difficult to completely remove the dirt adhering to the wire, the charging roll, etc. and to make it the same as the initial state. That is, even after cleaning, slight dirt remains on the wire, the charging roll, and the like. In addition, the distribution of dirt attached to the wire, the charging roll, etc. before and after the cleaning is changed. Then, before and after cleaning of the charging device, the charging unevenness and the in-plane unevenness caused by the charging unevenness change. For this reason, if the in-plane unevenness correction performed before the cleaning is performed as it is after the cleaning, the in-plane unevenness may be worsened.

  The present invention has been made to solve such a technical problem, and an object of the present invention is to suppress deterioration in image quality of an image formed after cleaning of a charging portion.

  For this purpose, an image forming apparatus to which the present invention is applied includes an image carrier, a charging unit that charges the image carrier, an exposure unit that exposes the image carrier charged by the charging unit, and exposure. A developing unit that develops the electrostatic latent image formed on the image carrier at the image forming unit, a transfer unit that transfers the image developed on the image carrier at the developing unit to a recording material, and a charging unit. It includes a cleaner that cleans at a timing, and a controller that cleans the charged portion by the cleaner and corrects the uneven density of the image in conjunction with the cleaning operation of the charged portion.

In such an image forming apparatus, the image forming apparatus further includes a reading unit that reads an image formed using the charging unit, the exposure unit, and the developing unit, and the control unit performs the correction of uneven density when the charging unit, the exposure unit, and the like. And an unevenness correction image are formed using the developing unit, and density unevenness correction data is created from the reading result of the unevenness correction image by the reading unit. In this case, the reading unit can read the unevenness correction image transferred to the recording material. In addition, when the image forming apparatus further includes a fixing unit that fixes the image transferred onto the recording material, the reading unit reads the unevenness correction image fixed on the recording material by the fixing unit.
Further, the control unit can adjust the charging potential on the image carrier charged by the charging unit and the exposure potential on the image carrier exposed by the exposure unit before executing the density unevenness correction. .
Furthermore, the control unit can execute the density correction of the image formed on the image carrier after the adjustment of the charging potential and the exposure potential but before the density unevenness correction.

  From another viewpoint, the image forming apparatus to which the present invention is applied includes an image carrier, a charging unit that charges the image carrier, and an exposure unit that exposes the image carrier charged by the charging unit. A developing unit that develops the electrostatic latent image formed on the image carrier in the exposure unit, a transfer unit that transfers the image developed on the image carrier in the developing unit to a recording material, and a predetermined unit By adjusting the image forming conditions for the image carrier using the correction data, an image quality correction unit that corrects the image quality of the formed image, a cleaner that cleans the charging unit at a predetermined timing, and cleaning of the charging unit by the cleaner A setting unit that resets predetermined correction data used in the image quality correction unit in conjunction with the operation is included.

Here, the image quality correction unit can correct density unevenness in an image formed on the image carrier by the charging unit, the exposure unit, and the development unit. When the charging unit, the exposure unit, and the development unit further include a reading unit that reads an image formed, the setting unit may include the charging unit, the exposure unit, and the development unit when correcting the density unevenness. The unevenness correction image can be formed using the correction data, and the correction data can be created from the reading result of the unevenness correction image by the reading unit.
The image quality correction unit can correct the charging potential on the image carrier charged by the charging unit and the exposure potential on the image carrier exposed by the exposure unit. When the setting unit further includes a potential detection unit that detects a potential on the image carrier, the setting unit charges the image carrier with the charging unit when the charging potential is corrected, and the charged site potential is detected by the potential detection unit. Based on the result, the charging bias is determined as correction data to be applied to the charging unit, and when correcting the exposure potential, the image bearing member charged by the charging unit to which the charging bias is applied is exposed by the exposure unit to detect the potential. The exposure amount of the exposure part as correction data can be determined from the potential detection result of the exposure part by the part.
Furthermore, the image quality correction unit can correct the density of an image formed on the image carrier by the charging unit, the exposure unit, and the development unit. Here, when the image forming apparatus further includes a reading unit that reads an image formed by using the charging unit, the exposure unit, and the developing unit, the setting unit sets the charging unit, the exposure unit, and the developing unit when correcting the density. By using this, a density correction image can be formed, and correction data can be created from the reading result of the density correction image by the reading unit.

  According to the present invention, in association with the cleaning operation of the charging unit, density unevenness correction of an image formed on the image carrier is executed, or correction data for correcting the image quality of the formed image is reproduced. Since it is set, it is possible to suppress deterioration in image quality of an image formed after cleaning of the charging portion.

The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram showing an outline of the image forming apparatus according to the first embodiment. The image forming apparatus includes, for example, a plurality of (four in the present embodiment) image forming units 10 (specifically, 10Y (yellow), 10M (magenta)) on which each color component toner image is formed by electrophotography. 10C (cyan), 10K (black)). In addition, the image forming apparatus includes an intermediate transfer belt 20 that sequentially transfers (primary transfer) and holds each color component toner image formed by each image forming unit 10. Here, each image forming unit 10 as a kind of marking engine includes a yellow image forming unit (yellow unit) 10Y, a magenta image forming unit (magenta unit) 10M, and a cyan image from the upstream side in the rotation direction of the intermediate transfer belt 20. A forming unit (cyan unit) 10C and a black image forming unit (black unit) 10K are arranged in this order. The image forming apparatus further includes a secondary transfer device 30 that collectively transfers (secondary transfer) the superimposed image transferred to the intermediate transfer belt 20 onto the paper P. Furthermore, the image forming apparatus includes a fixing device 50 that fixes the second-transferred image on the paper P. A control unit 100 that controls the operation of the image forming apparatus and a user interface (UI) 110 that receives instructions from the user and displays messages and the like to the user are provided.

  Each image forming unit 10 (10Y, 10M, 10C, 10K) has the same configuration except for the color of the toner used. Accordingly, the yellow unit 10Y will be described as an example. The yellow unit 10Y includes a photosensitive drum 11 as an image carrier that has a photosensitive layer (not shown) and is rotatably arranged in an arrow A direction. Around the photosensitive drum 11, a charger 12, an exposure device 13, a developing device 14, a primary transfer roll 15, a drum cleaner 16, and a potential sensor 17 are disposed. Among these, the charger 12 as a charging unit charges the photosensitive drum 11 to a predetermined potential. An exposure unit 13 as an exposure unit selectively irradiates the photosensitive drum 11 charged to a predetermined potential by the charger 12 with the laser beam Bm to form an electrostatic latent image. The developing unit 14 as a developing unit stores corresponding color component toner (yellow toner in the yellow unit 10Y), and develops the electrostatic latent image on the photosensitive drum 11 with this toner. A primary transfer roll 15 as a transfer unit primarily transfers a toner image formed on the photosensitive drum 11 to the intermediate transfer belt 20 by an applied primary transfer bias. The drum cleaner 16 removes residues (toner and the like) on the photosensitive drum 11 after the primary transfer. The potential sensor 17 is disposed opposite to the photosensitive drum 11 downstream of the exposure device 13 in the rotation direction A of the photosensitive drum 11 and upstream of the developing device 14. A potential sensor 17 serving as a potential detection unit detects the potential of the photosensitive drum 11 that passes through the facing portion. The photosensitive drum 11 is provided with a photosensitive member rotation number counter 18 (see FIG. 5) described later. The photoconductor rotation number counter 18 counts the accumulated rotation number of the photoconductor drum 11.

The intermediate transfer belt 20 as a recording material is rotatably supported by a plurality of (five in the present embodiment) support rolls and is rotated in the direction of arrow B. Of these support rolls, the drive roll 21 stretches the intermediate transfer belt 20 and drives the intermediate transfer belt 20 to rotate. Further, the driven rolls 22 and 25 are stretched by the intermediate transfer belt 20 and rotated by the intermediate transfer belt 20 driven by the drive roll 21. The correction roll 23 is a steering roll that stretches the intermediate transfer belt 20 and restricts meandering in a direction substantially orthogonal to the conveyance direction of the intermediate transfer belt 20 (is disposed so as to be tiltable about one end in the axial direction). Function. Further, the backup roll 24 stretches the intermediate transfer belt 20 and functions as a constituent member of the secondary transfer device 30 described later.
Further, a belt cleaner 26 for removing residues (toner and the like) on the intermediate transfer belt 20 after the secondary transfer is disposed at a portion facing the drive roll 21 with the intermediate transfer belt 20 interposed therebetween. A first density sensor 27 is disposed opposite to the intermediate transfer belt 20. The first density sensor 27 as a reading unit is disposed adjacent to the black unit 10K. The first density sensor 27 reads each color toner image primarily transferred onto the intermediate transfer belt 20 and detects its density. The first density sensor 27 is a line sensor that can read the toner image primarily transferred onto the intermediate transfer belt 20 over the entire region in the main scanning direction.

  The secondary transfer device 30 includes a secondary transfer roll 31 disposed in pressure contact with the toner image carrying surface side of the intermediate transfer belt 20 and a counter electrode of the secondary transfer roll 31 disposed on the back surface side of the intermediate transfer belt 20. And a backup roll 24. A power supply roll 32 for applying a secondary transfer bias having the same polarity as the toner charging polarity is disposed in contact with the backup roll 24. On the other hand, the secondary transfer roll 31 is grounded.

The paper transport system includes a paper tray 40, a transport roll 41, a registration roll 42, a transport belt 43, and a discharge roll 44. In the paper transport system, after the paper P stacked on the paper tray 40 is transported by the transport roll 41, the paper P is temporarily stopped by the registration roll 42 and then moved to the secondary transfer position of the secondary transfer device 30 at a predetermined timing. Send it in. Further, the sheet P after the secondary transfer is conveyed to the fixing device 50 via the conveying belt 43, and the sheet P discharged from the fixing device 50 is sent out to the outside by the discharge roll 44.
A second density sensor 45 is disposed at a position facing the toner carrying surface on the paper P on the downstream side in the paper transport direction from the fixing device 50 serving as a fixing unit. The second density sensor 45 serving as a reading unit reads the density of the toner image fixed on the paper P and detects the density. The second density sensor 45 is constituted by a line sensor that can read the toner image fixed on the paper P over the entire region in the main scanning direction.

  Next, a basic image forming process of the image forming apparatus will be described. Now, when a start switch (not shown) is turned on, a predetermined image forming process is executed. More specifically, for example, when the image forming apparatus is configured as a printer, digital image signals input from the outside such as a PC (personal computer) are temporarily stored in a memory. Then, toner images of each color are formed based on the digital image signals of four colors (Y, M, C, K) stored in the memory. That is, each image forming unit 10 (specifically, 10Y, 10M, 10C, and 10K) is driven according to the digital image signal of each color. Next, in each image forming unit 10, an electrostatic latent image is formed by irradiating the photosensitive drum 11 uniformly charged by the charger 12 with laser light Bm corresponding to the digital image signal by the exposure device 13. Form. Then, the electrostatic latent image formed on the photosensitive drum 11 is developed by the developing device 14 to form toner images of each color. When the image forming apparatus is configured as a copying machine, a document set on a document table (not shown) is read by a scanner, and the obtained read signal is converted into a digital image signal by a processing circuit. Thus, the toner images of the respective colors may be formed.

  Thereafter, the toner images formed on the respective photosensitive drums 11 are sequentially primary-transferred to the surface of the intermediate transfer belt 20 by the primary transfer roll 15 at a primary transfer position where the photosensitive drum 11 and the intermediate transfer belt 20 are in contact with each other. . On the other hand, the toner remaining on the photosensitive drum 11 after the primary transfer is cleaned by the drum cleaner 16.

  The toner image primarily transferred to the intermediate transfer belt 20 in this way is superimposed on the intermediate transfer belt 20 and conveyed to the secondary transfer position as the intermediate transfer belt 20 rotates. On the other hand, the paper P is conveyed to the secondary transfer position at a predetermined timing, and the secondary transfer roll 31 nips the paper P with respect to the backup roll 24.

  Then, at the secondary transfer position, the toner image carried on the intermediate transfer belt 20 is secondarily transferred to the paper P by the action of a transfer electric field formed between the secondary transfer roll 31 and the backup roll 24. . The sheet P on which the toner image is transferred is conveyed to the fixing device 50 by the conveyance belt 43. In the fixing device 50, the toner image on the paper P is heated and pressure-fixed, and then sent out to a paper discharge tray (not shown) provided outside the apparatus. On the other hand, the toner remaining on the intermediate transfer belt 20 after the secondary transfer is cleaned by the belt cleaner 26.

By the way, in the image forming apparatus according to the present embodiment, foreign substances such as discharge products and toner adhere to the charger 12 that charges the photosensitive drum 11. Further, the foreign matter does not adhere uniformly to the charger 12 but adheres in some distributed state. For this reason, if the charger 12 is continuously used for a long period of time, the charging ability is reduced and charging unevenness occurs, resulting in in-plane unevenness and streaks extending in the sub-scanning direction in the formed toner image.
Therefore, in this embodiment, the charger 12 is cleaned at a predetermined timing. In consideration of the change in the distribution of foreign matter before and after cleaning of the charger 12, image quality adjustment operations such as in-plane unevenness correction are performed in conjunction with the cleaning operation of the charger 12. Yes. Hereinafter, cleaning of the charger 12 and image quality adjustment after cleaning will be described in detail.

  FIG. 2 is a diagram for explaining a detailed configuration of the charger 12. In the present embodiment, a contact charging method is used in which the photosensitive drum 11 is contact-charged, and the charger 12 includes a charging roll 61 and a roll cleaner 62. Here, the charging roll 61 has a metal rotating shaft 61a and a conductive rubber layer 61b formed on the peripheral surface of the rotating shaft 61a, and is rotatably arranged. On the other hand, the roll cleaner 62 as a cleaner includes a housing 62a provided above the charging roll 61 and a sponge member 62b attached to the lower surface side of the housing 62a.

  A charging power source 63 is connected to the rotating shaft 61 a of the charging roll 61, and a predetermined charging bias is supplied to the charging roll 61. The photosensitive drum 11 is grounded. A retraction mechanism 64 is connected to the charging roll 61. The retract mechanism 64 is between a charging position (shown by a solid line in the figure) where the charging roll 61 contacts the photosensitive drum 11 and a cleaning position (shown by a one-dot chain line in the figure) where it contacts the sponge member 62b. The charging roll 61 is moved. Here, the charging roll 61 is driven to rotate by the driving force of the photosensitive drum 11 when it is in a charging position where it contacts the photosensitive drum 11. On the other hand, when the charging roll 61 is in the cleaning position, it cannot be rotated as it is because it is separated from the photosensitive drum 11. Therefore, in the present embodiment, a driving mechanism 65 for rotating the charging roll 61 placed at the cleaning position is provided.

  FIG. 3 is a view for explaining the configuration of the exposure device 13 and the state in which the exposure device 13 scans and exposes the photosensitive drum 11. The exposure device 13 has a light source 71 made of a semiconductor laser, a collimator lens 72, a cylinder lens 73, for example, a rotating polygon mirror (polygon mirror) 74 formed of a regular hexagonal body. The exposure device 13 further includes an fθ lens 75, a folding mirror 76, a reflection mirror 77, and an SOS (Start Of Scan) sensor 78.

  In the exposure device 13, the divergent laser light Bm emitted from the light source 71 is converted into parallel light by the collimator lens 72, and the deflecting / reflecting surface of the polygon mirror 74 by the cylinder lens 73 having refractive power only in the sub-scanning direction. A line image that is long in the main scanning direction is formed in the vicinity of 74a. The laser beam Bm is reflected by the deflecting / reflecting surface 74a of the polygon mirror 74 that rotates at a constant speed at a high speed, and is scanned counterclockwise (in the direction of arrow C) at a constant angular velocity. Next, after the laser beam Bm passes through the fθ lens 75, the direction is changed toward the surface of the photosensitive drum 11 by the folding mirror 76, and the surface of the photosensitive drum 11 is scanned and exposed in the direction of arrow D. Here, the fθ lens 75 has a function of equalizing the scanning speed of the light spot of the laser beam Bm. Further, the above-described line image is formed in the vicinity of the deflecting / reflecting surface 74a of the polygon mirror 74, and the fθ lens 75 causes a light spot on the surface of the photosensitive drum 11 with the deflecting / reflecting surface 74a as an object point in the sub-scanning direction. Make an image. Therefore, this scanning optical system has a function of correcting the surface tilt of the deflecting / reflecting surface 74a.

  Further, the laser beam Bm is incident on the SOS sensor 78 via the reflection mirror 77 prior to scanning exposure on the surface of the photosensitive drum 11. That is, each time the laser beam Bm scans the surface of the photosensitive drum 11, the first laser beam Bm of each scanning line is incident on the SOS sensor 78. The SOS sensor 78 detects the irradiation timing for each scanning line on the surface of the photosensitive drum 11 and generates an SOS signal indicating the irradiation start timing.

The light source 71 is connected to a laser driver 79 that outputs a laser drive signal corresponding to the writing image data output from an image signal generation unit (Image Processing System: IPS) 55 at a predetermined timing. In the present embodiment, the laser driver 79 functioning as an image quality correction unit controls ON / OFF of the semiconductor laser of the light source 71 based on the writing image data from the IPS 55. As a result, the laser beam Bm corresponding to the writing image data is output from the light source 71. The IPS 55 converts an image signal input from a PC, a scanner, or the like provided outside the image forming apparatus into an image signal corresponding to the image forming apparatus and outputs the image signal.
The laser driver 79 is connected to the SOS sensor 78, and the SOS signal generated by the SOS sensor 78 is input. Then, the laser driver 79 sets timing for starting output of a laser drive signal to the semiconductor laser of the light source 71 based on the SOS signal from the SOS sensor 78. Further, the control unit 100 is connected to the laser driver 79.

  FIG. 4 is a diagram illustrating the configuration of the developing device 14. The developing device 14 has a developing housing 81 in which an opening (development opening) is formed at a portion facing the photosensitive drum 11. Further, the developing device 14 includes a developing roll 82 disposed facing the opening of the developing housing 81, a first auger 83 disposed in the developing housing 81 and on the side close to the developing roll 82, and the developing roll 82. And a trimmer 87 that regulates the thickness of the developer layer attached to the developing roll 82. Here, the developing roll 82 includes a rotatable developing sleeve 85 made of a nonmagnetic metal, and a magnet roll 86 in which a plurality of magnetic poles are arranged and enclosed in the developing sleeve 85. The developing sleeve 85 is made of, for example, a nonmagnetic aluminum pipe, and is driven to rotate while maintaining a predetermined distance from the peripheral surface of the photosensitive drum 11. In the developing housing 81 of the developing device 14, a developer including toner having a negative charging polarity and a carrier having magnetism and a positive charging polarity is accommodated.

  Further, both the first auger 83 and the second auger 84 are configured by attaching spiral blades around the rotation axis. However, in the first auger 83 and the second auger 84, the blades are formed in opposite directions. As a result, the first auger 83 stirs and conveys the developer in the developing housing 81 toward the front side in the drawing, for example, while the second auger 84 transfers the developer in the developing housing 81 to the back side in the drawing, for example. Stir and transport toward The developing housing 81 is provided with a partition wall 81 a that partitions the first auger 83 and the second auger 84, but the partition wall 81 a does not exist at both ends in the longitudinal direction of the developing housing 81. As a result, the developer in the developing housing 81 is circulated and conveyed while being stirred in the developing housing 81 by the first auger 83 and the second auger 84. For this reason, the toner having a negative charging polarity is rubbed by being agitated and conveyed together with a carrier having a positive charging polarity and magnetism, and is charged negatively. The trimmer 87 is made of, for example, a metal plate and is fixed to the developing housing 81. A predetermined gap is formed between the developing sleeve 85 and the free end of the trimmer 87 in order to obtain a preferable developer layer thickness.

  In the present embodiment, the rotation direction of the developing sleeve 85 is set in the same direction as the rotation direction of the photosensitive drum 11 at a position facing the photosensitive drum 11. The developing sleeve 85 is connected to a developing power source 88 for applying a developing bias. The developing power supply 88 applies a developing bias in which an alternating current (for example, AC 1 kV (peak to peak value)) is superimposed on a direct current (for example, DC-350 V) to the developing sleeve 85. On the other hand, the photosensitive drum 11 is grounded as described above. Further, the developing device 14 is provided with a toner replenishing device 89 that replenishes toner decreased by transferring to the photosensitive drum 11 at an appropriate timing. The toner replenisher 89 may be configured to supply a developer obtained by adding a small amount of carrier to toner.

FIG. 5 is a functional block diagram of the control unit 100 shown in FIG. In this embodiment, the control unit 100 that also functions as a setting unit controls the operation of the entire image forming apparatus. Here, only the blocks related to cleaning of the charger 12 and image quality adjustment after cleaning are shown. ing.
The control unit 100 receives a potential signal of the photosensitive drum 11 measured by the potential sensor 17 of each image forming unit 10 (10Y, 10M, 10C, 10K). The controller 100 also receives the cumulative number of rotations of the photosensitive drum 11 counted by the photosensitive member rotation number counter 18 of each image forming unit 10 (10Y, 10M, 10C, 10K). Further, the concentration detection signal measured by the first concentration sensor 27 and the concentration detection signal measured by the second concentration sensor 45 are also input to the control unit 100.
On the other hand, the control unit 100 outputs a control signal to the charging power source 63, the retract mechanism 64, and the drive mechanism 65 of the charger 12 of each image forming unit 10 (10Y, 10M, 10C, 10K). Further, the control unit 100 outputs a control signal to the laser driver 79 of the exposure unit 13 of each image forming unit 10 (10Y, 10M, 10C, 10K). Further, the control unit 100 outputs a control signal to the developing power supply 88 and the toner replenishing device 89 of the developing device 14 of each image forming unit 10 (10Y, 10M, 10C, 10K). Then, the control unit 100 also outputs a control signal to the UI 110.

The control unit 100 includes a cleaning setting unit 101, a latent image potential setting unit 102, a development bias setting unit 103, and a toner supply setting unit 104. The control unit 100 further includes a density / tone correction unit 105, an in-plane unevenness correction unit 106, and a patch data storage unit 107.
The cleaning setting unit 101 determines whether or not to perform cleaning in the charger 12 based on the cumulative rotation number of the photosensitive drum 11 input from the photosensitive member rotation number counter 18. Further, the cleaning setting unit 101 controls the charging power source 63, the retract mechanism 64, and the drive mechanism 65 when performing the cleaning in the charger 12.
The latent image potential setting unit 102 sets the charging potential of the photosensitive drum 11 by the charger 12 and the exposure potential of the photosensitive drum 11 by the exposure device 13 upon completion of cleaning in the charger 12. The charging potential and the exposure potential are collectively referred to as a latent image potential. The latent image potential setting unit 102 controls the charging power source 63 and the laser driver 79 when setting the latent image potential.

The developing bias setting unit 103 receives the density detection result by the first density sensor 27 and sets the magnitude of the developing bias by the developing device 14. The development bias setting unit 103 controls the development power supply 88 when setting the development bias.
The toner replenishment setting unit 104 receives the density detection result from the first density sensor 27 and determines whether or not to replenish toner to the corresponding developing device 14. Further, the toner replenishment setting unit 104 controls the toner replenisher 89 when the toner replenishment to the developing device 14 is executed.

The density / gradation correction unit 105 receives the density detection result from the first density sensor 27, and corrects density (0-100%) or gradation (0-255 for 8-bit) correction data (density / gradation correction). Data). Further, the density / tone correction unit 15 outputs the determined density / tone correction data to the laser driver 79 of the exposure unit 13.
The in-plane unevenness correction unit 106 receives the density detection result from the first density sensor 27 or the second density sensor 45, and sets in-plane unevenness correction data (unevenness correction data) in the image for one sheet of paper P. . Further, the in-plane unevenness correction unit 106 outputs the determined unevenness correction data to the laser driver 79 of the exposure device 13.
The patch data storage unit 107 stores density / tone correction patch data used when the density / tone correction unit 105 executes density / tone correction. Further, the patch data storage unit 107 stores unevenness correction patch data used when the in-plane unevenness correction unit 106 executes in-plane unevenness correction.

Here, FIG. 6 is a flowchart showing a processing flow in the image quality adjustment operation executed in conjunction with the cleaning operation of the charger 12 and the cleaning operation. This process is performed independently for each image forming unit 10.
In the control unit 100, the cleaning setting unit 101 first determines whether or not the cleaning time of the charging roll 61 of the charger 12 has arrived (step 101). More specifically, the cleaning setting unit 101 acquires the cumulative rotational speed of the photosensitive drum 11 input from the photosensitive member rotational speed counter 18, and the cumulative rotational speed is a predetermined rotational speed (for example, 10,000 times). ) Is determined. If it is determined that the cleaning time has not been reached, the process returns to step 101. On the other hand, when it is determined in step 101 that the cleaning time has been reached, the cleaning setting unit 101 executes a cleaning operation of the charger 12 (step 102).

  When the cleaning operation is completed, the latent image potential setting unit 102 then executes a potential setup operation (step 103). The potential setup means adjustment of the latent image potential of the photosensitive drum 11, that is, the charging potential and the exposure potential. Thereafter, when the potential setup operation is completed, the density / tone correction unit 105 next executes the image density setup operation (step 104). Note that the image density setup means correction of the overall density and gradation of the toner image formed on the photosensitive drum 11. When the image density setup operation is completed, the in-plane unevenness correction unit 106 executes the in-plane unevenness setup operation (step 105). The in-plane unevenness setup means correction of in-plane unevenness of the toner image formed on the photosensitive drum 11. When the in-plane unevenness setup operation is completed, the cleaning setting unit 101 resets the photoconductor rotation number counter 18 corresponding to the photoconductor drum 11 for which the cleaning operation and the series of set-up operations have been completed (step 106). End the process.

Now, the cleaning operation of the charger 12 in step 102 will be described in detail. FIG. 7 is a flowchart for explaining the flow of processing in the cleaning setting unit 101 that controls the cleaning operation. In the initial state, it is assumed that the charging roll 61 is disposed in pressure contact with the photosensitive drum 11.
The cleaning setting unit 101 that has determined that the cleaning time has arrived in step 101 first outputs a control signal to the charging power source 63 to stop the application of the charging bias to the charging roll 61 (step 201). Next, the cleaning setting unit 101 outputs a control signal to the retract mechanism 64, separates the charging roll 61 from the photosensitive drum 11, and presses the sponge roller 62b of the roll cleaner 62 (step 202). That is, the retract mechanism 64 moves the charging roll 61 at the charging position to the cleaning position. Then, the cleaning setting unit 101 outputs a control signal to the drive mechanism 65 and starts driving the charging roll 61 (step 203). As a result, the charging roll 61 rotates, and the foreign matter adhering to the outer peripheral surface of the charging roll 61 is removed at the pressure contact position with the sponge member 62b. Next, the cleaning setting unit 101 determines whether or not a predetermined time (for example, about 40 seconds) has elapsed since the driving of the charging roll 61 was started (step 204). If the predetermined time has not elapsed, the process returns to step 204 and waits for the elapse of the predetermined time. On the other hand, when the predetermined time has elapsed, the cleaning setting unit 101 outputs a control signal to the driving mechanism 65 and stops driving the charging roll 61 (step 205). Next, the cleaning setting unit 101 outputs a control signal to the retract mechanism 64, separates the charging roll 61 from the sponge member 62b of the roll cleaner 62, and presses the charging roll 61 against the photosensitive drum 11 (step 206). That is, the charging roll 61 in the cleaning position is moved again to the charging position, and a series of processes is completed.

  By performing such a cleaning operation, the outer peripheral surface of the charging roll 61 is cleaned, and foreign matters such as discharge products and toner are removed. However, it can be said that it is substantially impossible to completely remove the foreign matter from the charging roll 61, and a slight amount of foreign matter remains. The distribution of foreign matters remaining on the outer peripheral surface of the charging roll 61 after cleaning is likely to be different from that before cleaning. Therefore, as described with reference to FIG. 6, various setup operations are continuously performed.

Next, the potential setup operation in step 103 will be described in detail. FIG. 8 is a flowchart for explaining the flow of processing in the latent image potential setting unit 102 that controls the potential setup operation.
Upon detecting the end of the cleaning operation of the charger 12 in step 102, the latent image potential setting unit 102 outputs a control signal to the charging power source 63 and applies a reference charging bias to the charging roll 61 (step 301). Here, the reference charging bias is set to −800 V, for example. As a result, the outer peripheral surface of the photosensitive drum 11 is negatively charged by the charging roll 61. At this time, the photosensitive drum 11 and the intermediate transfer belt 20 are driven to rotate, and the potential sensor 17 detects a charged potential VH that is the potential of the photosensitive drum 11 after charging (step 302). Next, the latent image potential setting unit 102 determines the magnitude of the charging bias that becomes the target charging potential (for example, −700 V) from the detection result of the charging potential VH input from the potential sensor 17, and supplies the charging power source 63. A control signal is output and the determined charging bias is set (step 303). Thereafter, the charging power source 63 applies this charging bias (referred to as a set charging bias) to the charging roll 61. As a result, the photosensitive drum 11 is almost charged to the target charging potential.

  Next, the latent image potential setting unit 102 outputs a control signal to the laser driver 79 and causes the exposure device 13 to perform optical writing corresponding to the reference input density, thereby forming an electrostatic latent image on the photosensitive drum 11. (Step 304). For example, Cin 60% can be used as the reference input density at that time. Next, the potential sensor 17 detects the exposure potential VM, which is the potential of the photosensitive drum 11 after charging and after optical writing (step 305). Thereafter, the latent image potential setting unit 102 determines an exposure amount to be a target exposure potential (for example, −200 V in the case of an input density Cin of 60%) from the detection result of the exposure potential VM input from the potential sensor 17, and A control signal is output to the laser driver 79 to set the determined exposure amount (step 306). As described above, a series of processing is completed.

Next, the image density setup operation in step 104 will be described in detail. FIG. 9 is a flowchart for explaining the flow of processing in the density / tone correction unit 105 that controls the image density setup operation.
The density / tone correction unit 105 that has detected the end of the potential setup operation in step 103 first reads the density / tone correction patch data from the patch data storage unit 107 (step 401). Next, the density / gradation correction unit 105 outputs a control signal (light quantity data) generated based on the read density / gradation correction patch data to the laser driver 79 and causes the exposure device 13 to perform optical writing. . That is, exposure based on density / tone correction patch data is executed (step 402). At this time, the photosensitive drum 11 and the intermediate transfer belt 20 continue to rotate, and the charging power source 63 continues to apply the set charging bias to the charging roll 61. For this reason, an electrostatic latent image including the target charging potential and the exposure potential based on the density / tone correction patch data is formed on the photosensitive drum 11.

  The density / tone correction unit 105 outputs a control signal to the developing device 14 and applies a developing bias to the developing sleeve 85 from the developing power supply 88. The developing sleeve 85 is driven to rotate. As a result, the electrostatic latent image formed on the photosensitive drum 11 is developed with toner (step 403). Thereafter, the toner image (referred to as a density / tone correction patch) formed on the photosensitive drum 11 is primarily transferred onto the intermediate transfer belt 20 by the primary transfer roll 15 (step 404).

  Then, the density / tone correction patch primarily transferred onto the intermediate transfer belt 20 passes through a portion facing the first density sensor 27 as the intermediate transfer belt 20 rotates. At this time, the first density sensor 27 detects a density / tone correction patch on the intermediate transfer belt 20 (step 405). Next, based on the detection result of the density / gradation correction patch input from the first density sensor 27, the density / tone correction unit 105 sets the target density / tone and the actually formed density / Density / gradation correction data is obtained from the relationship between the gradation correction patch density / gradation (step 406). Then, the density / tone correction unit 105 outputs the obtained correction data (density / tone correction data) to the laser driver 79 (step 407). The laser driver 79 stores the input density / gradation correction data in a memory (not shown). Further, the density / gradation correction unit 105 outputs a control signal to the toner replenisher 89 as necessary, and causes the developer 14 to be replenished with toner (step 408). Further, the density / tone correction unit 105 outputs a control signal to the developing power supply 88 as necessary, adjusts the magnitude of the developing bias supplied to the developing device 14 (step 409), and ends the series of processing. .

Next, the in-plane unevenness setup operation in step 105 will be described in detail. FIG. 10 is a flowchart for explaining the flow of processing in the in-plane unevenness correction unit 106 that controls the in-plane unevenness setup operation.
The in-plane unevenness correction unit 106 that has detected the end of the image density setup in step 104 first reads the unevenness correction patch data from the patch data storage unit 107 (step 501). Next, the in-plane unevenness correction unit 106 outputs a control signal (light amount data) generated based on the read unevenness correction patch data to the laser driver 79 and causes the exposure device 13 to perform optical writing. That is, exposure based on the unevenness correction patch data is executed (step 502). At this time, the photosensitive drum 11 and the intermediate transfer belt 20 continue to rotate, and the charging power source 63 continues to apply the set charging bias to the charging roll 61. For this reason, an electrostatic latent image including a target charging potential and an exposure potential based on unevenness correction patch data is formed on the photosensitive drum 11.

  The in-plane unevenness correcting unit 106 outputs a control signal to the developing device 14 and applies a developing bias to the developing sleeve 85 by the developing power supply 88. The developing sleeve 85 is driven to rotate. As a result, the electrostatic latent image formed on the photosensitive drum 11 is developed with toner (step 503). Thereafter, a toner image (referred to as an unevenness correction patch) formed on the photosensitive drum 11 is primarily transferred onto the intermediate transfer belt 20 by the primary transfer roll 15, and is secondary transferred onto the paper P by the secondary transfer device 30. The image is transferred and fixed by the fixing device 50 (step 504).

  Then, the unevenness correcting patch fixed on the paper P is further conveyed and passes through a portion facing the second density sensor 45. At this time, the second density sensor 45 detects the unevenness correction patch on the paper P (step 505). Next, the in-plane unevenness correction unit 106 performs unevenness correction based on the detection result of the unevenness correction patch input from the second density sensor 45 (step 506). Then, the in-plane unevenness correction unit 106 outputs the obtained correction data (unevenness correction data) to the laser driver 79 (step 507), and ends a series of processing. The laser driver 79 stores input in-plane unevenness correction data in a memory (not shown).

  Here, the above-described in-plane setup operation will be described with a specific example. In the present embodiment, an unevenness correction patch (main scanning unevenness correction patch) used for correcting density unevenness in the main scanning direction is formed in the in-plane setup operation. In addition, an unevenness correction patch (subscanning unevenness correction patch) used for correcting unevenness in density in the sub-scanning direction is also formed. Then, unevenness correction data in the main scanning direction in each image forming unit 10 is determined based on the detection result of the main scanning unevenness correction patch. Further, unevenness correction data in the subscanning direction in each image forming unit 0 is also determined based on the detection result of the patch for correcting unevenness in subscanning.

  FIG. 11 shows a main scanning unevenness correction patch used in the present embodiment. Here, FIG. 11A is a patch for correcting primary scanning unevenness of a primary color (single color) composed of only yellow (Y), magenta (M), cyan (C), and black (K). 11 (b) is for correcting main scanning unevenness of a secondary color constituted by superposing two colors of yellow, magenta and cyan and a tertiary color constituted by superposing three colors of yellow, magenta and cyan. It is a patch.

  The primary color non-uniformity correction patch shown in FIG. 11A has a black toner image formed as a mark on the most upstream side (K100% (meaning input density Cin of 100%, hereinafter the same)). ing. Subsequently, a plurality of color and density toner images are sequentially arranged in the sub-scanning direction. Specifically, yellow (Y20%), magenta (M20%), cyan (20%), black (K20%) toner images, and yellow (Y60%), magenta (M60%), cyan (60%) , A black (K60%) toner image. Each toner image extends in the main scanning direction.

  On the other hand, the multi-color (secondary and tertiary) main scanning unevenness correction patch shown in FIG. 11B has a black (K100%) toner image formed as a mark on the most upstream side. . Subsequently, a plurality of color and density toner images are sequentially arranged in the sub-scanning direction. Specifically, toners of gray (3C (= Y + M + C): Y20% + M20% + C20%), red (R: Y20 + M20%), green (G: Y20% + C20%), blue (B: M20% + C20%) And a gray (3C (= Y + M + C): Y60% + M60% + C60%), red (R: Y60 + M60%), green (G: Y60% + C60%), blue (B: M60% + C60%) toner image is there. Each toner image extends in the main scanning direction.

  Here, the main scanning direction length of the patch for correcting unevenness in main scanning shown in FIGS. 11A and 11B is set to the maximum length that can be formed by this image forming apparatus. Further, the length in the sub-scanning direction of the entire main scanning unevenness correction patch excluding black (K100%) is set to the circumferential length (one round) of the photosensitive drum 11. In this embodiment, the circumference of the photosensitive drum 11 is divided into 15 equal parts, and toner images having the same contents are formed in the sub-scanning direction areas S0, S1,. ing.

  In the case of the multi-order color toner image shown in FIG. 11B, in the state of primary transfer on the intermediate transfer belt 20, the first primary transfer toner is positioned on the uppermost surface. I do not know the state. Therefore, in the present embodiment, when the in-plane unevenness correction is performed, the image on the paper P that has passed through the fixing device 50 is detected by the second density sensor 45. In the case of the primary color toner image shown in FIG. 11A, the primary transfer state on the intermediate transfer belt 20 is almost the same as the state after fixing. It is also possible to detect images on 20.

  The in-plane unevenness correction unit 106 corrects unevenness in the main scanning direction of each image forming unit 10 based on the detection results of the primary color unevenness main scanning unevenness correction patch and the multicolor primary color unevenness correction patch by the second density sensor 45. Ask for data. At this time, the in-plane unevenness correcting unit 106 divides the total length in the main scanning direction into six equal parts, and in each main scanning direction area M0, M1,..., M5 shown in FIGS. The unevenness correction data is sequentially calculated. The obtained nonuniformity correction data in the main scanning direction is stored in a memory (not shown) provided in the laser driver 79 (see FIG. 3).

  On the other hand, FIG. 12 shows a sub-scanning unevenness correction patch used in the present embodiment. Here, FIG. 12A is a sub-scanning nonuniformity correction patch composed of yellow (Y) and cyan (C), and FIG. 12B is composed of magenta (M) and black (K). This is a sub-scanning unevenness correction patch. Note that the sub-scanning unevenness is mainly caused by the eccentricity of the photosensitive drum 11 of each image forming unit 10, and therefore, even if the sub-scanning unevenness correcting patch is composed of only the primary color, there is a particular problem. Does not occur.

  The patch for correcting unevenness in the sub-scanning direction of yellow and cyan shown in FIG. 12A has a black (K100%) toner image formed as a mark on the most upstream side. Subsequently, toner images having a plurality of densities of yellow and cyan are sequentially arranged in the main scanning direction. Specifically, the toner images are yellow (Y60%), yellow (Y20%), cyan (C60%), and cyan (C20%). Each toner image extends in the sub-scanning direction.

  On the other hand, the magenta and black sub-scanning direction unevenness correction patch shown in FIG. 12B has a black (K100%) toner image formed as a mark on the most upstream side. Subsequently, toner images of a plurality of densities of magenta and black are sequentially arranged in the main scanning direction. Specifically, the toner images are magenta (M60%), magenta (M20%), black (K60%), and black (K20%). Each toner image extends in the sub-scanning direction.

  Here, the length in the main scanning direction of the sub-scanning unevenness correction patch shown in FIGS. 12A and 12B is set to the maximum length that can be formed by this image forming apparatus. Further, the length in the sub-scanning direction of the entire sub-scanning unevenness correction patch excluding black (K100%) is set to the circumferential length (one round) of the photosensitive drum 11. In this embodiment, the image formable area on the photosensitive drum 11 is divided into six equal parts so that toner images having the same contents are formed in the main scanning direction areas M0, M1,. It has become.

  The in-plane unevenness correction unit 106 obtains unevenness correction data in the sub-scanning direction of each image forming unit 10 from the detection result of the sub-scanning unevenness correction patch by the second density sensor 45. At this time, the in-plane unevenness correcting unit 106 divides the total length of the sub-scanning direction length into 15 equal parts, and in each of the sub-scanning direction areas S0, S1,..., S14 shown in FIGS. The unevenness correction data is sequentially calculated. The obtained non-uniformity correction data in the sub-scanning direction is stored in a memory (not shown) provided in the laser driver 79 (see FIG. 3).

Here, FIG. 13 shows the relationship between the main scanning direction area and the sub scanning direction area on the photosensitive drum 11, the unevenness correction data in the main scanning direction and the sub scanning direction stored in the memory (not shown) of the laser driver 79. It is a figure for demonstrating the relationship with nonuniformity correction data.
In the memory of the laser driver 79, as the main scanning direction unevenness correction data, data in which each main scanning direction area M0, M1,... M5 is associated with the corresponding light amount correction value is stored. The memory of the laser driver 79 stores sub-scanning direction unevenness correction data in which each sub-scanning direction area S0, S1,..., S14 is associated with a corresponding light amount correction value. .

  For example, when the exposure device 13 intends to expose the main scanning direction area M2 and the sub scanning direction area S13 on the photosensitive drum 11, the laser driver 79 generates a laser drive signal as follows. First, the laser driver 79 reads a light amount correction value corresponding to the main scanning direction area M2 and a light amount correction value corresponding to the sub scanning direction area S13 from a memory (not shown). Next, the laser driver 79 generates a laser drive signal while performing light amount correction on the writing image data input from the IPS 55 using these two light amount correction values. Based on the laser drive signal output from the laser driver 79, the laser beam Bm is emitted from the light source 71, and this laser beam Bm exposes the main scanning direction area M2 and the sub scanning direction area S13 on the photosensitive drum 11. Will do.

As described above, in the present embodiment, after the charger 12 is cleaned, the in-plane unevenness correction is executed. As a result, even if the foreign matter adhesion distribution on the charging roll 61 of the charger 12 fluctuates before and after the cleaning, and as a result the state of uneven charging is changed, the occurrence of uneven density can be suppressed.
In this embodiment, the charging potential and the exposure potential of the photosensitive drum 11 by the charger 12 and the exposure unit 13 are set up before the in-plane unevenness correction is performed. Thereby, the image quality of the image formed after cleaning the charger 12 can be improved.
Further, in the present embodiment, after the potential setup on the photosensitive drum 11 is performed and before the in-plane unevenness correction is performed, the density correction of the image formed on the photosensitive drum 11 is performed. did. Thereby, the image quality of the image formed after cleaning the charger 12 can be further improved.

  From another viewpoint, in the present embodiment, in the image forming apparatus that performs in-plane unevenness correction using the unevenness correction data, the state of occurrence of in-plane unevenness is changed by cleaning the charger 12. In such a case, the unevenness correction data is reset according to the cleaning operation. For this reason, in-plane unevenness in the formed image can be suppressed before and after cleaning of the charger 12.

  In the present embodiment, cleaning of the charger 12 is automatically executed in accordance with the cumulative number of rotations of the photosensitive drum 11, but the present invention is not limited to this. For example, an instruction from the user is given. You may make it perform based on. Here, FIG. 14 is a diagram showing the contents of the screen displayed on the UI 110 at that time. Here, FIG. 14A shows a screen displayed when an instruction for cleaning the charger 12 is received, and FIG. 14B shows an instruction for image quality setup after the cleaning of the charger 12 is completed. The screen displayed when receiving is shown. In this case, the control unit 100 may execute the above-described cleaning operation and image quality setup operation in accordance with the instruction received by the UI 110.

1 is a diagram illustrating an overall configuration of an image forming apparatus to which the exemplary embodiment is applied. It is a figure which shows the detailed structure of a charging device. It is a figure which shows the detailed structure of an exposure device. It is a figure which shows the detailed structure of a developing device. It is a functional block diagram of a control part. 6 is a flowchart showing a processing flow in an image quality adjustment operation executed in conjunction with a charging device cleaning operation and a cleaning operation. It is a flowchart for demonstrating the flow of a process in the cleaning setting part which controls cleaning operation | movement. It is a figure for demonstrating the flow of a process in the latent image electric potential setting part which controls electric potential setup operation | movement. 5 is a flowchart for explaining a processing flow in a density / tone correction unit that controls an image density setup operation. It is a flowchart for demonstrating the flow of the process in the in-plane nonuniformity correction | amendment part which performs in-plane nonuniformity setup operation | movement. FIG. 6A is a diagram illustrating a primary color unevenness correction patch for primary colors, and FIG. 9B is a diagram illustrating a color irregularity main scan correction patch for secondary colors (secondary color and tertiary color). FIG. 5A is a diagram illustrating a yellow and cyan sub-scanning unevenness correction patch, and FIG. 5B is a diagram illustrating a magenta and black sub-scanning unevenness correction patch. FIG. 6 is a diagram for explaining a relationship between a main scanning direction area and a sub-scanning direction area on a photosensitive drum, and unevenness correction data in the main scanning direction and unevenness correction data in the sub-scanning direction. (a), (b) is a figure for demonstrating the content of the image displayed on UI at the time of cleaning of a charger.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image forming unit, 11 ... Photoconductor drum, 12 ... Charger, 13 ... Exposure device, 14 ... Developer, 15 ... Primary transfer roll, 16 ... Drum cleaner, 17 ... Potential sensor, 18 ... Photoconductor rotation number counter , 20 ... intermediate transfer belt, 27 ... first density sensor, 45 ... second density sensor, 50 ... fixing device, 61 ... charging roll, 62 ... roll cleaner, 79 ... laser driver, 100 ... control unit, 101 ... cleaning setting , 102 ... Latent image potential setting unit, 103 ... Development bias setting unit, 104 ... Toner replenishment setting unit, 105 ... Density / tone correction unit, 106 ... In-plane unevenness correction unit, 107 ... Patch data storage unit, 110 ... User interface (UI)

Claims (13)

An image carrier;
A charging unit for charging the image carrier;
An exposure unit that exposes the image carrier charged by the charging unit;
A developing unit for developing the electrostatic latent image formed on the image carrier in the exposure unit;
A transfer unit for transferring the image developed on the image carrier in the developing unit to a recording material;
A cleaner for cleaning the charging unit at a predetermined timing;
An image forming apparatus comprising: a control unit that cleans the charging unit by the cleaner and that corrects density unevenness of the image in conjunction with a cleaning operation of the charging unit. A reading unit that reads an image formed using the charging unit, the exposure unit, and the developing unit;
When performing the density unevenness correction, the control unit forms an unevenness correction image using the charging unit, the exposure unit, and the developing unit, and a reading result of the unevenness correction image by the reading unit The image forming apparatus according to claim 1, wherein density unevenness correction data is generated from the image data.   The image forming apparatus according to claim 2, wherein the reading unit reads the unevenness correction image transferred to the recording material. A fixing unit for fixing the image transferred on the recording material;
The image forming apparatus according to claim 2, wherein the reading unit reads the unevenness correction image fixed on the recording material by the fixing unit.   The control unit adjusts the charging potential on the image carrier charged by the charging unit and the exposure potential on the image carrier exposed by the exposure unit before executing the density unevenness correction. The image forming apparatus according to claim 1, wherein:   The control unit executes density correction of an image formed on the image carrier after the adjustment of the charging potential and the exposure potential and before the density unevenness correction is executed. The image forming apparatus according to claim 1, wherein: An image carrier;
A charging unit for charging the image carrier;
An exposure unit that exposes the image carrier charged by the charging unit;
A developing unit for developing the electrostatic latent image formed on the image carrier in the exposure unit;
A transfer unit for transferring the image developed on the image carrier in the developing unit to a recording material;
An image quality correction unit that corrects the image quality of the formed image by adjusting image forming conditions for the image carrier using predetermined correction data;
A cleaner for cleaning the charging unit at a predetermined timing;
An image forming apparatus including: a setting unit that resets the predetermined correction data used in the image quality correction unit in conjunction with a cleaning operation of the charging unit by the cleaner.   8. The image forming apparatus according to claim 7, wherein the image quality correction unit corrects uneven density in an image formed on the image carrier by the charging unit, the exposure unit, and the developing unit. A reading unit that reads an image formed using the charging unit, the exposure unit, and the developing unit;
When the density unevenness is corrected, the setting unit forms an unevenness correction image using the charging unit, the exposure unit, and the developing unit, and based on a reading result of the unevenness correction image by the reading unit. 9. The image forming apparatus according to claim 8, wherein the correction data is created.   The image quality correction unit corrects a charging potential on the image carrier charged by the charging unit and an exposure potential on the image carrier exposed by the exposure unit. Image forming apparatus. A potential detector for detecting a potential on the image carrier;
When the charging unit corrects the charging potential, the charging unit charges the image carrier with the charging unit, and a charging bias as the correction data to be applied to the charging unit based on a charged portion potential detection result by the potential detecting unit. When the exposure potential is corrected, the image bearing member charged by the charging unit to which the charging bias is applied is exposed by the exposure unit, and the potential detection of the exposed part by the potential detection unit is performed. The image forming apparatus according to claim 10, wherein the exposure amount of the exposure unit as the correction data is determined from the result.   The image forming apparatus according to claim 7, wherein the image quality correction unit corrects a density of an image formed on the image carrier by the charging unit, the exposure unit, and the developing unit. A reading unit that reads an image formed using the charging unit, the exposure unit, and the developing unit;
The setting unit, when correcting the density, forms a density correction image using the charging unit, the exposure unit, and the developing unit, and based on the reading result of the density correction image by the reading unit, The image forming apparatus according to claim 12, wherein correction data is created.

Images