JP2013125132A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation device that can appropriately reduce unevenness of concentrations for different types of images having different concentrations without consuming toner at controlling correction.SOLUTION: A first electrostatic latent image pattern is formed on a photoreceptor for detection (S11), a first image formation condition is determined based on detection results of a potential of the electrostatic latent image (S13a, S14a), and toner image formation means is controlled based on the determined first image formation condition (S15a). Further, a second electrostatic latent image pattern different from the first one is formed in a photoreceptor for detection (S12), a second image formation condition is determined based on detection results of a potential of the electrostatic latent image (S13b, S14b), and toner image formation means is controlled based on the determined second image formation condition (S15b).

Description

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

Conventionally, as this type of image forming apparatus, there are known image forming apparatuses (Patent Documents 1 to 3 and the like) that perform correction and control to reduce image density unevenness caused by potential unevenness on a latent image carrier.
Japanese Patent Application Laid-Open No. 2004-228561 periodically generates an image by controlling at least one image forming condition among a charging voltage, an exposure light amount, a developing voltage, and a transfer voltage based on periodic fluctuation data of image density. An image forming apparatus that reduces striped density unevenness is disclosed. As described above, in an image forming apparatus that performs control based on periodic fluctuation data of image density, it is necessary to form a toner image on a latent image carrier in order to measure the image density. A certain amount of toner is consumed when correction / control is performed to reduce the toner.

  Patent Document 2 discloses an image forming apparatus that measures potential unevenness of an electrostatic latent image on a latent image carrier and controls a developing bias based on the measured potential unevenness. However, in the image forming apparatus described in Patent Document 2, potential unevenness is measured in terms of toner density when an electrostatic latent image for measuring potential unevenness is developed and an image is output. For this reason, a fixed amount of toner is consumed when correction / control is performed to reduce the density unevenness of the toner image, as in Patent Document 1.

  Patent Document 3 describes a configuration in which a control electrostatic latent image pattern is formed on the surface of a latent image carrier, the potential thereof is detected, and a development bias value is determined based on the detection result. Since the development bias value is determined based on the detection result of the potential of the electrostatic latent image pattern, it is necessary to consume toner when determining the development bias value as a correction / control for reducing the density unevenness of the toner image. There is no.

However, the image forming apparatus described in Patent Document 3 has a problem in that density unevenness cannot be reduced appropriately for each of a plurality of types of images (for example, solid images and halftone images) having different image densities. .
That is, in the image forming apparatus of Patent Document 3, the electrostatic latent image pattern for control used for controlling the image forming conditions uses an electrostatic latent image pattern corresponding to image data of one type of image (for example, a solid image). Detected. However, the potential unevenness profile of the electrostatic latent image has a potential level of the electrostatic latent image (for example, the potential level of the electrostatic latent image corresponding to the solid image or the potential level of the electrostatic latent image corresponding to the halftone). May vary slightly. For this reason, in the image forming apparatus disclosed in Patent Document 3, an image corresponding to the electrostatic latent image pattern used for the measurement of potential unevenness (for example, a solid image) can correct density unevenness well, but a potential level different from that image. In such an image (for example, a halftone image), the density unevenness may not be corrected.

  The present invention has been made in view of the above problems, and an object of the present invention is to form an image that can appropriately reduce density unevenness for a plurality of types of images having different densities without consuming toner during correction control. Is to provide a device.

  In order to achieve the above object, the invention of claim 1 includes at least a latent image carrier, charging means for charging the surface of the latent image carrier, and latent image formation for forming an electrostatic latent image on the latent image carrier. A toner image forming means comprising: a developing means for supplying toner to the electrostatic latent image formed on the latent image carrier and developing the toner; and an electrostatic latent image formed on the latent image carrier An electrostatic latent image of the first electrostatic latent image pattern formed on the latent image carrier, and a detection result of the potential of the electrostatic latent image. A first image forming condition is determined based on the first image forming condition, and the toner image forming means is controlled based on the determined first image forming condition; and the first electrostatic latent image is formed on the latent image carrier. An electrostatic latent image of a second electrostatic latent image pattern different from the pattern is formed, and the potential of the electrostatic latent image is detected The second image forming condition is determined based on the result, based on the determined said second image forming condition is characterized in that and a second control means for controlling said toner image forming means.

In the present invention, the first electrostatic latent image suitable for correction control of density unevenness of one of the high density side image and the low density side image among two types of images having different densities. An electrostatic latent image of a pattern is formed on the latent image carrier. Then, based on the detection result of the potential of the electrostatic latent image, a first image forming condition that is affected by the density unevenness of the one image is determined, and toner image formation is performed based on the determined first image forming condition. Control means. By this control, density unevenness can be reduced for one of the high density side image and the low density side image.
In addition, for the other of the high density side image and the low density side image, an electrostatic latent image of a second electrostatic latent image pattern suitable for correcting the density unevenness of the other image is formed on the latent image carrier. To do. Then, based on the detection result of the potential of the electrostatic latent image, a second image forming condition that is influenced by the density unevenness of the other image is determined, and toner image formation is performed based on the determined second image forming condition. Control means. By this control, density unevenness can be reduced for the other of the high density side image and the low density side image.
Furthermore, since each image forming condition is determined based on the detection result of the potential of each electrostatic latent image pattern, it is not necessary to consume toner when performing correction / control to reduce the density unevenness of the toner image.

  According to the present invention, there is an excellent effect that density unevenness can be appropriately reduced for a plurality of types of images having different densities without consuming toner during correction control.

The flowchart of the control example 1. FIG. 1 is a schematic configuration diagram illustrating a configuration example of a copying machine to which the present invention can be applied. FIG. 3 is a schematic configuration diagram illustrating another configuration example of a copying machine to which the present invention can be applied. FIG. 5 is a schematic configuration diagram showing still another configuration example of a copying machine to which the present invention can be applied. FIG. 2 is a schematic perspective view showing the arrangement of a surface potential sensor with respect to a photoreceptor. FIG. 2 is a block diagram illustrating an example of a main part of a control system of a copying machine. FIG. 3 is an explanatory diagram illustrating an example in which a first electrostatic latent image pattern and a second electrostatic latent image pattern used for latent image potential unevenness correction control are formed on the surface of a photoreceptor. FIG. 7 is an explanatory diagram showing another example in which a first electrostatic latent image pattern and a second electrostatic latent image pattern used for correction control of latent image potential unevenness are formed on the surface of a photoreceptor. The flowchart of the control example 2. FIG. 6 is a graph simply showing an example of a potential relationship in the first embodiment. 10 is a graph simply showing an example of a potential relationship in Example 2. 6 is a graph illustrating the relationship between a rotational position detection signal (A), a latent image potential unevenness detection signal (B) by a toner image detection sensor, and a value (C) of an image forming condition (control table).

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 2 is a schematic configuration diagram showing a copying machine (hereinafter referred to as a copying machine 100) as an example of a configuration of an applicable image forming apparatus. FIG. 2 shows a configuration example of a full color machine of a quadruple tandem type intermediate transfer system as an electrophotographic image forming apparatus to which the present invention can be applied. The present invention is a quadruple tandem type which will be described later. The present invention can also be applied to other image forming apparatuses such as a direct transfer type full color machine and a one-drum intermediate transfer type full color machine. Furthermore, the present invention can also be applied to a monochrome machine such as a one-drum direct transfer system.

  In FIG. 2, a drum-shaped photosensitive member 2 (Y, M, C, K) that is a latent image carrier is formed along a stretched surface (stretching surface) of an intermediate transfer belt 1 that is an intermediate transfer member as an image carrier. ) Are arranged in parallel, and four image forming stations 40 (Y, M, C, K) are provided. In the figure, Y added to each symbol indicates yellow, M indicates magenta, C indicates cyan, and K indicates black. The four image forming stations 40 (Y, M, C, and K) have substantially the same configuration except that the colors of the toners to be used are different from each other, and hence the subscripts K, Y, M, and C are omitted below. To explain.

The image forming station 40 is arranged around the photosensitive member 2 in the order of the rotation direction indicated by an arrow α in the drawing in the order of the charging charger 3, the surface potential sensor 60, the developing unit 5, the primary transfer roller 6, the photosensitive member cleaning unit 7, and the quenching lamp. 8 etc. are arranged. The surface of the photoreceptor 2 between the charging charger 3 serving as a charging unit and the surface potential sensor 60 serving as a surface potential detecting unit is an optical writing unit serving as an exposing unit disposed above the four image forming stations 40. The writing light L emitted from the unit 4 is incident and becomes an exposure position where a latent image is formed.
A developing unit 5 as a developing unit is arranged downstream of the exposure position in the surface movement direction of the photosensitive member 2, and further, the developing unit 5 is opposed to the photosensitive member 2 with the intermediate transfer belt 1 interposed therebetween. A primary transfer roller 6 is disposed as a primary transfer unit. On the downstream side of the surface of the photosensitive member 2 in the surface movement direction with respect to the primary transfer nip where the photosensitive member 2 and the primary transfer roller 6 are opposed to each other, a photosensitive member cleaning unit 7 as a latent image carrier cleaning unit and a discharging unit. A quenching lamp 8 is arranged.

Above the optical writing unit 4, a scanner unit 9 as an image reading unit, an ADF 10 as an automatic document supply unit, and the like are provided.
In the copying machine 100, toner image forming means for forming a toner image on the intermediate transfer belt 1 as an image carrier is a photosensitive member 2, a charging charger 3, an optical writing unit 4, a developing unit 5, and a primary transfer roller 6. Etc. are constituted.

  The intermediate transfer belt 1 is rotatably supported by tension rollers (first tension roller 11, second tension roller 12, and third tension roller 13) as a plurality of tension members. A belt cleaning unit 15 is provided on the outer periphery of the intermediate transfer belt 1 at a position facing the second stretching roller 12 across the intermediate transfer belt 1. Further, a toner image on the surface of the intermediate transfer belt 1 is transferred to a recording paper 20 as a recording medium at a position on the outer periphery of the intermediate transfer belt 1 facing the third stretching roller 13 with the intermediate transfer belt 1 interposed therebetween. A secondary transfer roller 16 as a secondary transfer unit is provided and forms a secondary transfer portion.

  A plurality of paper feed trays 17 serving as a plurality of paper feed units are provided at the lower portion of the copying machine 100, and these paper feed trays 17 are pickups that feed out the uppermost sheet of recording paper 20 to be stored. A roller 21 is provided. Further, the lower part of the copying machine 100 is provided with a paper feed roller 22 that conveys the recording paper 20 sent out by the pickup roller 21 toward the paper conveyance path. A plurality of conveyance roller pairs 23 are arranged. In addition, the recording paper 20 is moved between the paper transport path in which the recording paper 20 is directed upward and the secondary transfer unit in accordance with the timing at which the toner image on the intermediate transfer belt 1 reaches the secondary transfer unit. A registration roller pair 24 is provided for feeding toward the next transfer section.

  A fixing unit 25 that is a fixing unit that fixes the toner image transferred by the secondary transfer unit on the surface of the recording paper 20 downstream of the secondary transfer unit in the conveyance direction of the recording paper 20 is provided. Alternatively, a discharge tray 26 for discharging the recording paper 20 that has passed through the fixing unit 25 is provided outside the apparatus on the right side of the copying machine 100 in the drawing. On the other hand, below the fixing unit 25, there are formed a refeed conveyance path 101 and a sheet reversing unit 102 for conveying the recording paper 20 on which the toner image is formed on one side during double-sided printing. Further, the recording paper 20 that has passed through the fixing unit 25 is transported toward the paper reversing unit 102 between the re-feed conveyance path 101 and the paper reversing unit 102, and before the trailing edge of the recording paper 20 passes. A switchback roller pair 27 is provided that conveys the recording paper 20 toward the refeed conveyance path 101 by rotating in reverse.

  The image forming operation of the copying machine 100 shown in FIG. When a print start command is input from an external device such as an operation unit (not shown) or a personal computer, the rollers in the periphery of the photoreceptor 2, the periphery of the intermediate transfer belt 1, the paper conveyance path, and the like rotate at predetermined timing. First, the recording paper 20 starts to be fed from the paper feeding tray 17 at the bottom of the copying machine 100. The recording paper 20 fed from the paper feed tray 17 is fed by the pickup roller 21 and the paper feed roller 22, transported by the transport roller pair 23, and transported to a position where it abuts against the roller nip of the two rollers of the registration roller pair 24. Is done. Then, the recording paper 20 stops at a position where the leading edge is sandwiched between the registration roller pair 24 and is sent to the secondary transfer unit at a predetermined timing described later.

  On the other hand, the surface of each photoconductor 2 is charged to a uniform potential by a charging charger 3. Further, the optical writing unit 4 receives the writing light L corresponding to the image information of each color based on the image information of the original image read by the scanner unit 9 or the image information input from an external device such as a personal computer. The surface of 2 is irradiated and exposed to form an electrostatic latent image on the surface of the photoreceptor 2. The potential pattern after the exposure is called an electrostatic latent image. By supplying toner from the developing unit 5 at the development position to the surface of the photosensitive member 2 carrying the electrostatic latent image, the photosensitive member is obtained. The electrostatic latent image carried on the surface 2 is developed to a specific color. In the copying machine 100 shown in FIG. 2, since there are four photosensitive members 2, toner images of yellow, magenta, cyan, and black (color order varies depending on the system) are developed on each photosensitive member 2. .

  The toner image developed on each photoconductor 2 is transferred to the intermediate transfer belt by a primary transfer bias and a pressing force applied to the primary transfer roller 6 in a primary transfer nip which is a contact portion between the photoconductor 2 and the intermediate transfer belt 1. 1 is primarily transferred onto 1. By repeating this primary transfer operation for four colors while matching the timing, a full-color toner image is formed on the intermediate transfer belt 1.

  The full-color toner image formed on the intermediate transfer belt 1 is transferred to the recording paper 20 conveyed at the timing by the registration roller pair 24 in the secondary transfer portion. In the secondary transfer portion, secondary transfer is performed by a secondary transfer bias and a pressing force applied to the secondary transfer roller 16. The recording paper 20 onto which the full-color toner image has been transferred passes through the fixing unit 25, whereby the toner image carried on the surface thereof is heat-fixed.

  If the input print command is single-sided printing, it is straightly conveyed and conveyed to the paper discharge tray 26. If double-sided printing is performed, the conveyance direction is changed downward and conveyed to the paper reversing unit 102. The recording paper 20 in which the leading end reaches the sheet reversing unit 102 and the vicinity of the trailing end is sandwiched between the switchback roller pair 27 is reversed in the transport direction by the reverse rotation of the switchback roller pair 27. Thereafter, the sheet reversing unit 102 is exited from the end side. This is called a switchback operation, and the front and back of the recording paper 20 can be reversed by this operation. The recording paper 20 that is turned upside down does not return to the fixing unit direction, but passes through the refeed conveyance path 101 and joins the paper conveyance path through which the recording paper 20 fed from the paper feed tray 17 passes. Thereafter, the toner image is transferred in the same manner as the front surface printing, and is discharged through the fixing unit 25. This is a double-sided printing operation.

The operation of each part will be described to the end. The primary transfer residual toner that has not been transferred to the intermediate transfer belt 1 is carried on the surface of the photoreceptor 2 that has passed through the primary transfer nip, and this is constituted by a blade, a brush, and the like. The photosensitive member cleaning unit 7 is removed. Thereafter, the surface of the photoreceptor 2 is uniformly discharged by the quenching lamp 8 to prepare for charging for the next image.
The intermediate transfer belt 1 that has passed through the secondary transfer portion also carries secondary transfer residual toner on the surface thereof, which is also removed by a belt cleaning unit 15 composed of blades and brushes. Removed and ready for transfer of next toner image. By repeating such an operation, single-sided printing or double-sided printing is performed.

  FIG. 3 is a schematic configuration diagram showing another configuration example of the copying machine 100 as an image forming apparatus to which the present invention can be applied. In FIG. 3, members and apparatuses similar to those of the copying machine 100 in FIG. 2 are assigned the same reference numerals, and descriptions thereof are omitted. The copying machine 100 in FIG. 3 is a one-drum type intermediate transfer type full-color machine, and includes a drum-shaped photosensitive member 2 and a revolver developing unit 50 facing the drum-shaped photosensitive member 2.

  The revolver developing unit 50 holds four developing devices 51 (Y, M, C, K) by a holding body that rotates about a rotation axis. These developing units 51 develop the electrostatic latent image on the photosensitive member 2 with yellow (Y), magenta (M), cyan (C), and black (K) toners. The revolver developing unit 50 rotates the holding member to move the developing device 51 of any color among Y, M, C, and K to a developing position facing the photosensitive member 2, and thereby on the photosensitive member 2. The electrostatic latent image can be developed into any color. In the case of forming a full-color image, for example, Y, M, C, and K electrostatic latent images are sequentially formed on the photoreceptor 2 in the process of rotating the endless intermediate transfer belt 1 about four times, Development is performed sequentially by four developing units 51 (Y, M, C, K) for M, C, and K. The Y, M, C, and K toner images obtained on the photoreceptor 2 are sequentially superimposed and transferred onto the intermediate transfer belt 1 to form a four-color superimposed toner image on the intermediate transfer belt 1.

  In the secondary transfer portion where the transfer facing roller 113 which is a stretch member of the intermediate transfer belt 1 and the secondary transfer roller 16 of the secondary transfer unit 28 face each other, the intermediate transfer belt 1 and the secondary transfer unit 28 A secondary transfer nip is formed by contacting the transfer conveyance belt 28a with a predetermined nip width. When a four-color superimposed toner image on the intermediate transfer belt 1 passes through the secondary transfer nip, recording as a recording medium transported by the transfer transport belt 28a of the secondary transfer unit 28 in time with the passage. The four-color superimposed toner image on the intermediate transfer belt 1 is batch-transferred onto the paper 20. When images are formed on both sides of the recording paper 20, the recording paper 20 that has passed through the fixing unit 25 is conveyed to the double-side unit 117, and the recording paper 20 that has been turned upside down by the double-sided unit 117 again becomes the above-described secondary transfer nip. The four-color superimposed toner image on the intermediate transfer belt 1 is secondarily transferred collectively onto the back surface of the recording paper 20.

  FIG. 4 is a schematic configuration diagram showing still another configuration example of the copying machine 100 as an image forming apparatus to which the present invention can be applied. In FIG. 4, members and devices similar to those of the copying machine 100 in FIG. 2 are given the same reference numerals, and descriptions thereof are omitted. The copying machine 100 in FIG. 4 is a quadruple tandem direct transfer type full-color machine, and below the four image forming stations 40 (Y, M, C, K), there are photoreceptors 2 (Y, M, A transfer unit 29 for transferring the toner image formed on C, K) to the recording paper 20 is provided. The transfer unit 29 includes an endless transfer / conveying belt 29a that is rotatably supported by stretching rollers 111 (ad) serving as a plurality of stretching members.

  The transfer conveyance belt 29a is wound around a driving roller 111a and other stretching rollers 111 (b to d) serving as driven rollers, and rotates the recording paper 20 in a counterclockwise direction in the drawing at a predetermined timing. It is carried and conveyed so as to pass the transfer position of each image forming station 40 (Y, M, C, K). Further, on the inner side of the transfer conveyance belt 29a, a transfer roller 70 (Y, Y, M) is applied to transfer toner images on the photoreceptors 2 (Y, M, C, K) to the recording paper 20 by applying transfer charges at the transfer position. M, C, K) are provided.

  In the copying machine 100 of FIG. 4, for example, when the full-color mode of four-color superposition is selected by an operation unit (not shown), the photoreceptors 2 (Y, Y) of the image forming stations 40 (Y, M, C, K) of the respective colors. An image forming process for forming toner images of each color on each of M, C, and K) is executed in synchronization with the conveyance of the recording paper 20. On the other hand, the recording paper 20 fed from the paper feed tray 17 is sent out at a predetermined timing by the registration roller pair 24 and is carried on the transfer conveyance belt 29a, and each image forming station 40 (Y, M, C, K). It is conveyed so as to pass through the transfer position. The recording paper 20 on which the toner images of the respective colors are transferred and the four-color superimposed color image is formed is discharged onto the paper discharge tray 26 after the toner image is fixed by the fixing unit 25.

Next, a configuration for correcting density unevenness based on the detection result of the potential of the electrostatic latent image pattern in the image forming apparatus having the above configuration will be described. In the image forming apparatus to which the present invention is applied, the first and second electrostatic latent image patterns are detected by the surface potential detecting means, and the surface potential detecting means in each copying machine 100 of FIGS. This is a surface potential sensor 60 shown in each figure.
As shown in FIGS. 2 to 4, the surface potential sensor 60 can detect a surface potential between the exposure position and the development position on the surface of the photoreceptor 2 regardless of the image forming engine system of the image forming apparatus. Is installed.

FIG. 5 is a schematic perspective view showing the arrangement of the surface potential sensor 60 with respect to the photoreceptor 2.
As shown in FIG. 5, the surface potential sensor 60 includes a sensor head 61 disposed at a position facing the surface of the photoreceptor 2, and a sensor cable 62 that electrically connects the sensor head 61 to a control unit 200 described later. And have.
In each copying machine 100 described above, the surface potential sensor 60 is provided with one surface potential sensor 60 for each photoconductor 2 so that the surface potential at one location on the photoconductor 2 can be measured.

Although the installation position of the surface potential sensor 60 in the main scanning direction with respect to the photoconductor 2 is illustrated at a substantially central position in the width direction of the photoconductor 2 in FIG. A toner adhesion amount detection sensor (not shown) installed at a position between the development position and the transfer position above or between the transfer position from the photoreceptor 2 and the cleaning position on the surface of the intermediate transfer belt 1. In general, the main scanning direction position is set. This is because the potential information is obtained by the surface potential sensor 60 and the adhesion amount information is obtained by the toner adhesion amount detection sensor for the same pattern image.
In FIG. 5, an image is shown in which the surface potential sensor 60 can measure the surface potential at one point on the surface of the photoreceptor 2 in the main scanning direction. However, a surface potential sensor 60 having a plurality of sensor heads 61 or a plurality of surface potential sensors 60 may be installed so that a plurality of points can be measured in the main scanning direction. It may be arranged so as to be slidable in the scanning direction and slid to obtain potential information at a plurality of points in the main scanning direction on the surface of the photoreceptor 2.

FIG. 6 is a block diagram illustrating an example of a main part of the control system of the copying machine 100.
In FIG. 6, a control unit 200 as a control unit is configured by, for example, a microcomputer, and includes a CPU (Central Processing Unit) 201 as an arithmetic processing unit, a RAM (Random Access Memory) 202 and a ROM of a nonvolatile memory as a storage unit. (Read Only Memory) 203 and the like.

An image forming station 40 (Y, M, C, K), the optical writing unit 4, the surface potential sensor 60, and the like are electrically connected to the control unit 200. And the control part 200 controls these various apparatuses based on the control program memorize | stored in RAM202.
In the RAM 202 which is a nonvolatile memory, output conversion data (conversion table), output conversion formula (algorithm), etc. as output conversion information used when calculating the surface potential from the detection value of the sensor head 61 of the surface potential sensor 60, etc. Is remembered.

  The control unit 200 also includes a first control unit and a first control unit that perform correction control to optimize the surface potential of the photoconductor 2 so as to optimize the image density of each color when the power is turned on or every time a predetermined number of prints are performed. It functions as two control means. When functioning as the first control means, an electrostatic latent image of the first electrostatic latent image pattern is formed on the photosensitive member 2 and the first image forming condition is determined based on the detection result of the potential of the electrostatic latent image. Then, based on the determined first image forming condition, the toner image forming unit configured as described above is controlled. In the case of functioning as the second control means, an electrostatic latent image having a second electrostatic latent image pattern different from the first electrostatic latent image pattern is formed on the photosensitive member 2, and the potential of the electrostatic latent image is formed. The second image forming condition is determined based on the detected result, and the toner image forming unit having the above-described configuration is controlled based on the determined second image forming condition.

  As described above, in the copying machine 100, the first electrostatic latent image pattern and the second electrostatic latent image pattern are formed on the surface of the photoreceptor 2, and the first electrostatic latent image pattern and the second electrostatic latent image pattern are formed. The first image forming condition and the second image forming condition are determined on the basis of the respective surface potential fluctuations with the image pattern. Examples of the first electrostatic latent image pattern and the second electrostatic latent image pattern formed on the surface of the photoreceptor 2 (hereinafter also referred to as “photoreceptor surface 2f”) of such an image forming apparatus are shown in FIG. And it demonstrates using FIG. 7 and 8 are image diagrams in which the surface 2f of the photosensitive member is cut out in a planar shape, and the outline of a portion having a length equal to or longer than one turn of the photosensitive member 2 is indicated by a broken line.

  FIG. 7 is an explanatory view showing an example in which the first electrostatic latent image pattern and the second electrostatic latent image pattern used for the correction control of the image density unevenness (latent image potential unevenness) are formed on the photoreceptor surface 2f. . In the example of FIG. 7, two types of electrostatic latent image patterns having different latent image potentials are formed by exposure by the optical writing unit 4 immediately below the surface potential sensor 60 in the center in the width direction of the photoreceptor 2. It is an example. In the case of this example, a strip-shaped first electrostatic latent image pattern 901 and a second electrostatic latent image pattern 902 are sequentially formed on a portion of the photosensitive member surface 2f facing the surface potential sensor 60 in the center in the width direction. Yes.

  Since it is necessary to collect potential data for one or more rounds of the photoreceptor surface 2f, the length of each electrostatic latent image pattern (901 and 902) is at least the circumference of the photoreceptor circumference Lp. Although the first electrostatic latent image pattern 901 and the second electrostatic latent image pattern 902 are sequentially formed, the shapes are the same and only the potentials are different. As shown in FIG. 7, as an example of forming two types of electrostatic latent images, the potential of the first electrostatic latent image pattern 901 is a solid portion potential, and the potential of the second electrostatic latent image pattern 902 is The halftone part potential is used.

  FIG. 8 is an explanatory view showing another example in which the first electrostatic latent image pattern and the second electrostatic latent image pattern used for the correction control of the image density unevenness (latent image potential unevenness) are formed on the photoreceptor surface 2f. It is. In the example of FIG. 8, the first electrostatic latent image pattern 901 forms an electrostatic latent image pattern by exposure by the optical writing unit 4 as in the example of FIG. In this example, the dark portion potential (background portion potential) charged by the charging means is used as it is without performing exposure by the writing unit 4. The second electrostatic latent image pattern 902 is a dark portion potential, and the potential fluctuation in only one point in the main scanning direction of the surface 2f of the photosensitive member uniformly charged by the charging charger 3 (surface moving direction of the photosensitive member 2). Is measured by the surface potential sensor 60. The first electrostatic latent image pattern 901 is formed with an electrostatic latent image pattern having a latent image potential different from the dark portion potential by exposure by the optical writing unit 4. The electrostatic latent image pattern is, for example, a solid portion potential pattern.

The two types of image forming conditions to be determined based on the surface potential fluctuations of the two types of electrostatic latent image patterns formed in this way are any of charging conditions, developing conditions, and exposure conditions. As an example, the exposure condition is determined based on the surface potential fluctuation of the first electrostatic latent image pattern 901, and the charging condition is determined based on the surface potential fluctuation of the second electrostatic latent image pattern 902.
Hereinafter, in each embodiment, an example of density unevenness (potential unevenness) correction control using the first electrostatic latent image pattern 901 and the second electrostatic latent image pattern 902 will be described.

[Control example 1]
FIG. 1 is a flowchart of a first control example (hereinafter referred to as control example 1) of density unevenness (potential unevenness) correction control using two electrostatic latent image patterns in the copying machine 100. In Control Example 1, the first image forming condition and the second image forming condition are determined independently by the surface potential fluctuation of the first electrostatic latent image pattern 901 and the surface potential fluctuation of the second electrostatic latent image pattern 902, respectively. To do.

In the control flow of the control example 1, first, the first electrostatic latent image pattern 901 is formed on the photosensitive member surface 2f, and the potential thereof is detected by the surface potential sensor 60 (S11). A second electrostatic latent image pattern 902 is formed and the potential thereof is detected by the surface potential sensor 60 (S12).
Further, after detecting the potential of the first electrostatic latent image pattern 901, analysis of the photosensitive member periodic component of potential unevenness of the first electrostatic latent image pattern 901 (S13a) and calculation of the first image forming condition (control table) (S14a) and reflection on the first control means (setting the created control table) (S15a).
Similarly, after detecting the potential of the second electrostatic latent image pattern 902, analysis of the photosensitive member periodic component of potential unevenness of the second electrostatic latent image pattern 902 (S13b) and calculation of the second image forming condition (control table) (S14a) and reflection on the second control means (setting the created control table) (S15b).

  In the control flow of FIG. 1, since there is one surface potential sensor 60, formation of an electrostatic latent image pattern and detection of its potential (S11 and S12) must be performed serially. On the other hand, the calculation process (S14a, S14b) of the image formation condition and the reflection process (S15a, S15b) on the image formation condition are performed in parallel independently of each other in the first system and the second system different from each other in the control unit 200. Executed.

That is, in the first system, after the formation and detection of the first electrostatic latent image pattern 901, based on the detection result, the photosensitive member periodic component of the potential unevenness of the first electrostatic latent image pattern 901 is analyzed (extracted). Processing (S13a), a first image formation condition calculation process (S14a) for determining a first image formation condition based on the photosensitive member periodic component, and the calculated first image formation condition as a first control unit. The first image forming condition reflecting process (S15a) to be reflected on the control unit 200 is executed.
On the other hand, in the second system, after the formation and detection of the second electrostatic latent image pattern 902, based on the detection result, the photosensitive member periodic component of potential unevenness of the second electrostatic latent image pattern 902 is analyzed (extracted). Processing (S13b), a second image formation condition calculation process (S14b) for determining a second image formation condition based on the photosensitive member periodic component, and the calculated second image formation condition as a second control unit. The second image forming condition reflecting process (S15b) to be reflected on the control unit 200 is executed.
When determining each of the two image forming conditions only from the information of the respective electrostatic latent image patterns, the control flow of the control example 1 shown in FIG. 1 is applied.

[Control example 2]
FIG. 9 is a flowchart of a second control example (hereinafter referred to as control example 2) of density unevenness (potential unevenness) correction control using two electrostatic latent image patterns in the copying machine 100. In the control example 2, the first image forming condition is determined from the surface potential fluctuation of the first electrostatic latent image pattern 901, and based on both the surface potential fluctuation of the second electrostatic latent image pattern 902 and the first image forming condition. A second image forming condition is determined.

In the control flow of the control example 2, first, the first electrostatic latent image pattern 901 is formed on the photoreceptor surface 2f, and the potential thereof is detected by the surface potential sensor 60 (S21), and then on the photoreceptor surface 2f. A second electrostatic latent image pattern 902 is formed and the potential thereof is detected by the surface potential sensor 60 (S22).
In addition, after detecting the potential of the first electrostatic latent image pattern 901, analysis of the photosensitive member periodic component of potential unevenness of the first electrostatic latent image pattern 901 (S23a), calculation of the first image forming condition (control table) (S24a) and reflection on the first control means (setting the created control table) (S25a).
Similarly, after detecting the potential of the second electrostatic latent image pattern 902, analysis of the photosensitive member periodic component of potential unevenness of the second electrostatic latent image pattern 902 is performed (S23b). The steps up to here are the same as those in the control example 1 shown in FIG. 1, but in the control example 2, the formation of the second electrostatic latent image pattern 902, the detection of the potential (S22), and the second electrostatic latent image pattern. In parallel with the step of analyzing the photosensitive member periodic component of potential unevenness 902 (S23b), analyzing the photosensitive member periodic component of potential unevenness of the first electrostatic latent image pattern 901 (S23a) and the first image. The step of calculating the formation conditions (S24a) is executed. Furthermore, in the control example 2, when the calculation of the second image forming condition (S24b) is performed thereafter, the result of the analysis of the photosensitive member periodic component (S23b) of the potential unevenness of the second electrostatic latent image pattern 902, and the first The second image forming condition is calculated (S24a) using both of the image forming conditions. Thereafter, the calculated second image forming conditions are reflected on the second control means (the created control table is set) (S25b).

  Next, an embodiment of a combination of potential patterns used as two types of electrostatic latent image patterns and correction control will be described.

[Example 1]
In Example 1, the first electrostatic latent image pattern 901 is a bright portion potential pattern (a potential pattern obtained by solid exposure from a dark portion potential), and the second electrostatic latent image pattern 902 is a dark portion potential pattern (charged by a charging unit). Only unexposed patterns). The first image forming condition is the exposure condition, and the second image forming condition is the charging condition. In such a case, the electrostatic latent image pattern described with reference to FIG. 8 is used to perform control in the control flow of the control example 1 described with reference to FIG.

FIG. 10 simply shows an example of the potential relationship in the first embodiment.
In FIG. 10, the detected values of the dark part potential and the bright part potential before the control are indicated by alternate long and short dash lines. In the example shown in FIG. The potential periodically changes during a certain photosensitive member cycle TLp, resulting in potential unevenness. Further, in the state before the control in the example shown in FIG. 10, the bright portion potential is lower in the left half of the photosensitive member cycle TLp and higher in the right half (S11, S13a), whereas the dark portion is dark. The potential is high in the left half of the photoreceptor period TLp and low in the right half (S12, S13b). As described above, the graphs of the dark portion potential unevenness (before control) and the light portion potential unevenness (before control) do not necessarily have the same shape. This is because the variation in charging characteristics on the surface of the photoreceptor 2 does not necessarily match the variation in exposure characteristics.

  In order to prevent toner image density unevenness from occurring due to the generated light portion potential unevenness, the development potential that is the difference between the developing bias and the light portion potential should be constant. When an exposure condition (exposure power) is selected as a parameter (first image forming condition) that is controlled to suppress image density unevenness due to bright portion potential unevenness, the exposure power control table is indicated by a solid line in FIG. Thus, it is sufficient to generate a periodic control table (S14a) so as to cancel out the bright part potential unevenness indicated by the alternate long and short dash line, and by reflecting this exposure power control table (S15a), the bright part potential after the control is As shown by the broken line in FIG. 10, the image becomes flat, the development potential becomes constant, and the image density unevenness due to the light portion potential unevenness can be suppressed.

  If dark portion potential unevenness occurs when the developing bias is constant, unevenness also occurs in the background potential, which is the difference between the dark portion potential and the developing bias. If the background potential becomes too small, the background becomes dirty, and if it becomes too large, problems such as carrier adhesion occur. Then, if unevenness occurs in the background potential, the background stain may be partially noticeable or the carrier may be partially attached. For this reason, it is desirable that the ground potential is constant. When the charging condition is selected as a parameter (second image forming condition) that is controlled to suppress the unevenness of the background potential due to the dark part potential unevenness, the charging bias control table is a one-dot chain line as shown by the solid line in FIG. A periodic control table may be generated (S14b) so as to cancel the dark portion potential unevenness indicated by (5). By reflecting this charging bias control table (S15b), the dark portion potential after control is indicated by a broken line in FIG. As shown, it becomes flat and the ground potential is constant.

In the example shown in FIG. 10, a first image formation condition (exposure power control table) is created based on a bright part potential detection result (bright part potential unevenness) that is a first electrostatic latent image pattern, and the second electrostatic A second image forming condition (charging bias control table) is created based on the detection result (dark part potential unevenness) of the dark part potential which is a latent image pattern.
As described above, the development potential and the background potential can be controlled to be constant by creating the control tables independently of each other for the first image forming condition and the second image forming condition, and density unevenness (latent image potential). Unevenness) can be removed.

[Example 2]
In Example 2, the first electrostatic latent image pattern 901 is a bright part potential pattern (a potential pattern obtained by solid exposure from a dark part potential), and the second electrostatic latent image pattern 902 is a dark part potential pattern (charged by a charging unit). Only unexposed patterns). The first image forming condition is a developing condition, and the second image forming condition is a charging condition. In such a case, control is performed in the control flow of the control example 2 described using FIG. 9 using the electrostatic latent image pattern described using FIG.

FIG. 11 simply shows an example of the potential relationship in the second embodiment.
In FIG. 11, the detected values of the dark part potential and the bright part potential before the control are indicated by a one-dot chain line. In the example shown in FIG. 11, both the dark part potential and the bright part potential before the control are cycled between the photoreceptor periods TLp. As a result, the potential changes and potential unevenness occurs. In the state before the control in the example shown in FIG. 11, the bright portion potential is lower in the left half of the photoreceptor period TLp and higher in the right half (S21, S23a), whereas the dark portion is dark. The potential is high in the left half of the photoreceptor period TLp and low in the right half (S22, S23b).

  In order to prevent toner image density unevenness from occurring due to the generated light portion potential unevenness, the development potential that is the difference between the developing bias and the light portion potential should be constant. In the example shown in FIG. 11, in order to select a developing bias as a parameter (first image forming condition) to be controlled in order to suppress image density unevenness due to bright portion potential unevenness, and to make the developing potential constant, As shown by the broken line on the right side of FIG. 11, the development bias control table is created periodically so as to have the same profile as the bright portion potential unevenness (before control) (S24a).

By reflecting this development bias control table (S25a), the difference between the development bias after control and the bright portion potential becomes constant, and the development potential becomes constant, so that density unevenness in the solid portion can be removed. However, when the development bias varies between the photoreceptor periods TLp, the background potential, which is the difference between the dark portion potential and the development bias, also varies.
When the ratio between the development potential and the background potential is lost, there is a problem that the density of the halftone portion mainly fluctuates. Further, the background potential needs to be controlled at an appropriate value because problems such as background contamination and carrier adhesion occur when the background potential becomes too small.

  The background potential is the difference between the development bias and the dark portion potential. In the example of FIG. 11, the development bias is varied so that the development potential is constant. Therefore, the charging condition is selected as a parameter (second image forming condition) to be controlled in order to suppress the unevenness of the background potential so that the background potential becomes constant according to the change in the developing bias, and the background potential is kept constant. Therefore, a periodic control table is created so that the charging bias control table has a profile indicated by a solid line in FIG. 11 (S24b). Reflecting this charging bias control table (S25b), the dark part potential after control varies as indicated by the broken line in FIG. 11, but the dark part potential variation after control can be made the same profile as the development bias variation. If possible, at any timing, the difference between the development bias after control and the dark portion potential is constant, and the background potential is constant.

By setting the control center value of the charging bias control table so that the background potential becomes the target value, the ratio between the development potential and the background potential can be kept constant, so that the image can be satisfactorily displayed over the entire gradation area. It is possible to remove density unevenness.
The example shown in FIG. 11 is an example of a specific control method in the case where the second image forming condition is determined based on both the surface potential fluctuation of the second electrostatic latent image pattern and the first image forming condition.

  Further, the copying machine 100 is provided with a rotational position detecting means (for example, a home position sensor or a rotary encoder) for detecting the rotational position of the photosensitive member 2 that is a rotating body that is a source of occurrence of image unevenness. The first image forming condition and the second image forming condition described above may be determined and controlled in synchronization with the detection signal of the means.

  FIG. 12 shows the rotational position detection signal (A) and the surface potential sensor 60 when determining and controlling the first image formation condition and the second image formation condition in synchronization with the detection signal of the rotational position detection means. 6 is a graph illustrating the relationship between a latent image potential unevenness detection signal (B) due to and a value (C) of an image forming condition (control table) created based on the signal. In the example shown in FIG. 12, signals for two rounds of the photosensitive member 2 are drawn.

  The latent image potential unevenness detection signal (B) fluctuates in the same cycle as that of the rotational position detection signal (A), and the image forming condition (control) is set to have an opposite phase to the latent image potential unevenness detection signal (B). Table) value. The charging bias, the developing bias, and the exposure power that can be used as actual image density control parameters (control factors) have a negative sign, or the latent image potential decreases as the absolute value increases. For this reason, it is not appropriate to uniformly express the value of the image forming condition (control table) as “reverse phase”, but here, the fluctuation of the latent image potential indicated by the latent image potential unevenness detection signal (B) is canceled. It is expressed as “reverse phase” in the sense that a control table for the direction is created, that is, a control table for creating a variation in the latent image potential amount in the opposite phase is created.

  What is the gain when determining the control table, that is, what is the variable amount of the control table with respect to the variable amount [V] of the latent image potential unevenness detection signal (B)? Is ideally calculated from theoretical values, but when installed on actual machines, it is highly likely that actual machines will be verified based on the theoretical values and ultimately determined from experimental data. The control table determined with the gain determined in this way has the timing relationship shown in FIG. 12 with the rotational position detection signal (A). Here, it is assumed that the head of the control table is the time when the rotational position detection signal (A) is generated.

If this control table is an exposure power control table, it is necessary to determine the application timing of the control table in consideration of the distance from the exposure position to the detection position by the surface potential sensor 60. That is, the exposure power control table is applied while shifting the timing by this distance.
Similarly, in the case of the development bias control table, the distance from the detection position by the surface potential sensor 60 to the development nip (development position) is considered, and in the case of the charging bias control table, the detection position by the surface potential sensor 60 from the charging position. The control table is applied in consideration of the distance up to.

  As described with reference to FIG. 11, when the development bias control table is created, the development bias control table is generated not to create the anti-phase control table as shown in FIG. Thus, a control table having the same phase according to the bright portion potential fluctuation is generated. As for the charging bias control table, if the exposure power is controlled together, a control table of the opposite phase of the dark portion potential unevenness is created. If the control is performed together with the developing bias, FIG. 11 is used. As described above, a control table that cannot be generally expressed by the term in-phase / anti-phase is created.

  Further, in the copying machine 100, the timing of determining the image forming conditions (control table creation / updating) in the image unevenness correction control described with reference to FIG. 1 and FIGS. It may be the timing immediately after the photosensitive member 2 is set (at the time of initial setting, at the time of replacement, at the time of attachment / detachment, etc.). In this case, when the photosensitive member 2 is mechanically removed, there is a high possibility that the occurrence state of the latent image potential unevenness in the rotation cycle of the photosensitive member 2 is changed. Another reason is that once the photoconductor 2 is mechanically removed, the positional relationship with the installed photoconductor home position sensor is shifted. Furthermore, when the latent image carrier (photosensitive member 2) for which no control table has been originally created is initially set, it is necessary to first create a control table by performing a series of correction controls. At the time of replacement of the photoconductor 2, since there is a difference in charging characteristics and exposure characteristics of the new photoconductor 2 compared to the photoconductor 2 used so far, a control table corresponding to the new photoconductor 2 is recreated. There is a need.

Even when the photosensitive member 2 is simply detached and attached for maintenance, the position of the charging and exposure characteristics unevenness of the photosensitive member 2 and the position of the photosensitive member home position sensor are shifted. Need to create.
For the reasons described above, it is necessary to determine the image forming conditions (create / update the control table) immediately after the photosensitive member 2 is set.

  Further, in the copying machine 100, the above-described image forming conditions may be determined (control table creation / update) at intervals of a certain number of recording sheets 20. As the number of prints of the recording paper 20 increases, the deterioration of the photosensitive member 2 progresses, and the photosensitive layer may be damaged, resulting in a change in uneven charging characteristics and exposure characteristics. In order to cancel the influence due to the characteristic variation with time, it is desirable to determine the image forming conditions (creation / update of the control table) at intervals of a certain number of recording sheets 20.

  In the copying machine 100, the image forming conditions may be determined (control table creation / update) when the environmental conditions in the apparatus change. Of the environmental conditions, especially when the temperature condition changes, the characteristics (charging characteristics, exposure characteristics) of the photosensitive layer of the photoreceptor 2 are affected. In order to cope with this change, it is desirable to determine the image forming conditions (control table creation / update) when the environmental conditions change. As a method for determining the trigger for determining the image forming conditions in this case, for example, “there is a temperature change of N [deg] or more compared to the previous determination of the image forming conditions (control table creation / update). Can be used.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
At least a latent image carrier such as the photosensitive member 2, a charging means such as a charging charger 3 that charges the surface of the latent image carrier, and a latent image such as the optical writing unit 4 that forms an electrostatic latent image on the latent image carrier. A toner image forming means comprising image forming means and developing means such as a developing unit 5 for supplying and developing toner to the electrostatic latent image formed on the latent image carrier; and a latent image carrier. In an image forming apparatus such as a copying machine 100 having surface potential detecting means such as a surface potential sensor 60 for detecting the potential of the electrostatic latent image, a first electrostatic latent image pattern 901 or the like is formed on the latent image carrier. Forming an electrostatic latent image of one electrostatic latent image pattern, determining a first image forming condition based on a detection result of a potential of the electrostatic latent image, and forming a toner image based on the determined first image forming condition; First control means such as a control unit 200 for controlling the means, and a latent image carrier. An electrostatic latent image of a second electrostatic latent image pattern such as a second electrostatic latent image pattern 902 that is different from the electrostatic latent image pattern is formed, and the second image is based on the detection result of the potential of the electrostatic latent image. Second control means such as a control unit 200 that determines the forming conditions and controls the toner image forming means based on the determined second image forming conditions. According to this, as described in the above embodiment, among the two types of images having different densities, a bright portion potential suitable for correction control of density unevenness of a high density side image such as a solid image. An electrostatic latent image of the first electrostatic latent image pattern is formed on the latent image carrier. Then, based on the detection result of the potential of the electrostatic latent image, a first image forming condition such as an exposure condition that is influenced by density unevenness of one image such as a solid image is determined, and the determined first image forming The toner image forming means is controlled based on the conditions. By this control, it is possible to reduce density unevenness in a high density image such as a solid image. In addition, an electrostatic latent image of a second electrostatic latent image pattern such as a dark portion potential suitable for correcting the density unevenness of the image is formed on the latent image carrier, such as a white image. Then, based on the detection result of the potential of the electrostatic latent image, a second image forming condition such as a charging condition that affects the density unevenness of the other image such as a white image is determined, and the determined second image forming The toner image forming means is controlled based on the conditions. By this control, it is possible to reduce density unevenness in a low density side image such as a white image. Furthermore, since each image forming condition is determined based on the detection result of the potential of each electrostatic latent image pattern, it is not necessary to consume toner when performing correction / control to reduce the density unevenness of the toner image.
Further, periodic surface potential fluctuations are detected by measuring the surface potential of the latent image carrier, and periodic image forming conditions are determined. An image formed by an electrophotographic image forming apparatus may have periodic density unevenness in the image transport direction. There are several possible causes of this density unevenness (adhesion amount unevenness), among which are photosensitive member charging characteristic unevenness and latent image potential unevenness due to photosensitive member exposure characteristic unevenness. The photosensitive member charging characteristic unevenness is not a parameter that strongly influences the image density because it is a potential unevenness of the dark portion potential, but it is a parameter related to the background potential, and may affect the halftone density. On the other hand, the latent image potential unevenness due to the photoreceptor exposure characteristic unevenness is a parameter that directly affects the solid image density because it is a bright portion potential. A configuration is known in which only a solid image or a bright part potential is detected and feedback is applied to a parameter for controlling the development potential. However, as the control width increases, the development potential greatly fluctuates. The ratio with the background potential varies, and density unevenness occurs in the halftone density region. Therefore, two image forming conditions are used to control each of the development potential and the background potential, and two electrostatic latent image patterns are used for that purpose. By controlling both the development potential and the background potential, it is possible to remove favorable latent image potential unevenness over all gradations and to suppress density unevenness.
(Aspect B)
In (Aspect A), the first image forming condition and the second image forming condition are determined independently. According to this, as described in the above embodiment, each of the two image forming conditions can be applied only when the information is determined only from the information of the respective electrostatic latent image patterns.
(Aspect C)
In (Aspect B), the first electrostatic latent image pattern is a bright portion potential pattern, the second electrostatic latent image pattern is a dark portion potential pattern, and the first image forming condition is that the latent image forming means carries the latent image. The second image forming condition is a charging condition when the charging unit charges the surface of the latent image carrier. According to this, as described in the first embodiment, the exposure condition is determined from the bright part potential pattern and the charging condition is determined from the dark part potential pattern, so that the balance between the development potential and the background potential can be maintained. It is possible to control over the removal of excellent density unevenness (latent image potential unevenness).
(Aspect D)
In (Aspect A), the second image forming condition is determined based on the detection result of the potential of the electrostatic latent image of the first electrostatic latent image pattern. This is determined based on both the detection result of the potential of the electrostatic latent image. According to this, as described in the above embodiment, the second image forming condition can be applied when it is necessary to consider the influence of the first image forming condition.
(Aspect E)
In (Aspect D), the first electrostatic latent image pattern is a bright portion potential pattern, the second electrostatic latent image pattern is a dark portion potential pattern, and the first image forming condition is that the developing means is applied to the latent image carrier. The second image forming condition is a charging condition when the charging means charges the surface of the latent image carrier. According to this, as described in the second embodiment, the ratio between the development potential and the background potential is made constant by determining the development condition based on the bright part potential pattern and the charging condition based on the dark part potential pattern and the development condition. Therefore, good density unevenness (latent image potential unevenness) removal control over all gradations becomes possible.
(Aspect F)
In (Aspect A) to (Aspect E), a rotation position detection means such as a home position sensor or a rotary encoder for detecting the rotation position of the latent image carrier is provided, and the first image is synchronized with the detection signal of the rotation position detection means. The forming conditions and the second image forming conditions are determined. According to this, as described in the above embodiment, when performing density unevenness correction control based on the determined image forming conditions, it is necessary to perform control in synchronization with the generated image density unevenness. For this purpose, it is necessary to grasp the rotation cycle of the latent image carrier that is a rotating body in which periodic potential unevenness occurs. According to the present embodiment, the latent image carrier by the rotational position detecting means is used. The relationship between the generated image density unevenness and the rotation position of the latent image carrier can be specified based on the detection result of the rotation period of the image, and the determined image forming conditions (specifically, image forming A control table that periodically changes the conditions can be applied at an appropriate timing.
(Aspect G)
In (Aspect A) to (Aspect F), formation of an electrostatic latent image pattern and potential detection and determination of image forming conditions based on the detection result of the potential are performed by attaching a latent image carrier to the main body of the image forming apparatus. After that, it is performed before the toner image formation on the latent image carrier is started. According to this, as described in the above embodiment, the latent image potential unevenness is unique to each latent image carrier, and when a new latent image carrier is set or an existing latent image carrier is removed. In such a case, the relationship between the phase of the rotation of the latent image carrier and the phase of the latent image potential becomes unclear, so determination of image forming conditions immediately after setting the latent image carrier (creation of a control table) By performing the above, an appropriate control table for the latent image carrier in the set state can be obtained, so that effective density unevenness (latent image potential unevenness) removal control can be performed.
(Aspect H)
In (Aspect A) to (Aspect G), the image forming apparatus includes a transfer unit that transfers the toner image formed on the latent image carrier by the toner image forming unit to a recording medium. The image forming conditions based on the detection result are determined at intervals of a predetermined number of recording media onto which the toner image is transferred. According to this, as described in the above embodiment, as the number of output sheets increases, the latent image carrier may deteriorate and charging characteristics and exposure characteristics may change. The effectiveness of density unevenness (latent image potential unevenness) removal control can be maintained by recreating the image forming conditions (control table of image forming conditions).
(Aspect I)
In (Aspect A) to (Aspect H), formation of an electrostatic latent image pattern, potential detection, and determination of an image forming condition based on the detection result of the potential are performed when environmental conditions in the image forming apparatus change. According to this, as described in the above embodiment, the charging characteristics and exposure characteristics of the latent image carrier are affected by environmental fluctuations (particularly temperature), and the held control table does not function effectively. The effectiveness of density unevenness (latent image potential unevenness) removal control can be maintained by recreating the control table triggered by environmental fluctuations.

DESCRIPTION OF SYMBOLS 1 Intermediate transfer belt 2 Photoconductor 2f Photoconductor surface 3 Charger charger 4 Optical writing unit 5 Development unit 6 Primary transfer roller 7 Photoconductor cleaning unit 8 Quenching lamp 9 Scanner unit 11 First stretch roller 12 Second stretch roller 13 Third tension roller 15 Belt cleaning unit 16 Secondary transfer roller 17 Paper feed tray 20 Recording paper 21 Pickup roller 22 Paper feed roller 23 Transport roller pair 24 Registration roller pair 25 Fixing unit 26 Paper discharge tray 27 Switchback roller pair 28 Secondary transfer unit 28a Transfer conveyance belt 29 Transfer unit 29a Transfer conveyance belt 40 Image forming station 50 Revolver development unit 51 Developer 60 Surface potential sensor 61 Sensor head 62 Sensor cable 70 Transfer roller 100 Copying machine 101 Refeed conveyance path 102 Paper reversing unit 111 Tension roller 111a Drive roller 113 Transfer facing roller 117 Double-sided unit 200 Control unit 901 First electrostatic latent image pattern 902 Second electrostatic latent image pattern Lp Photoconductor peripheral length TLp Photoconductor cycle

JP-A-9-62042 JP 2009-042434 A JP-A-11-174818

Claims (9)

At least a latent image carrier, charging means for charging the surface of the latent image carrier, latent image forming means for forming an electrostatic latent image on the latent image carrier, and electrostatic formed on the latent image carrier Toner image forming means comprising developing means for supplying toner to a latent image and developing the toner image;
In an image forming apparatus having surface potential detection means for detecting the potential of an electrostatic latent image formed on the latent image carrier,
An electrostatic latent image of a first electrostatic latent image pattern is formed on the latent image carrier, and a first image forming condition is determined based on a detection result of a potential of the electrostatic latent image, and the determined first image First control means for controlling the toner image forming means based on forming conditions;
An electrostatic latent image having a second electrostatic latent image pattern different from the first electrostatic latent image pattern is formed on the latent image carrier, and a second image is formed based on a detection result of a potential of the electrostatic latent image. An image forming apparatus comprising: a second control unit that determines conditions and controls the toner image forming unit based on the determined second image forming conditions. The image forming apparatus according to claim 1.
The image forming apparatus, wherein the first image forming condition and the second image forming condition are determined independently. The image forming apparatus according to claim 2.
The first electrostatic latent image pattern is a bright part potential pattern,
The second electrostatic latent image pattern is a dark potential pattern,
The first image forming condition is an exposure condition when the latent image forming unit forms an electrostatic latent image on the latent image carrier,
2. The image forming apparatus according to claim 1, wherein the second image forming condition is a charging condition when the charging unit charges the surface of the latent image carrier. The image forming apparatus according to claim 1.
The first image forming condition determined based on the detection result of the potential of the electrostatic latent image of the first electrostatic latent image pattern, and the electrostatic latent image of the second electrostatic latent image pattern An image forming apparatus that makes a determination based on both a detection result of an electric potential of an image. The image forming apparatus according to claim 4.
The first electrostatic latent image pattern is a bright part potential pattern,
The second electrostatic latent image pattern is a dark potential pattern,
The first image forming condition is a developing condition when the developing unit supplies toner to the electrostatic latent image formed on the latent image carrier and develops the toner.
2. The image forming apparatus according to claim 1, wherein the second image forming condition is a charging condition when the charging unit charges the surface of the latent image carrier. The image forming apparatus according to any one of claims 1 to 5,
A rotation position detecting means for detecting the rotation position of the latent image carrier;
An image forming apparatus, wherein the first image forming condition and the second image forming condition are determined in synchronization with a detection signal of the rotational position detecting means. The image forming apparatus according to any one of claims 1 to 6,
The formation of the electrostatic latent image pattern, the detection of the potential, and the determination of the image forming condition based on the detection result of the potential are performed after the latent image carrier is mounted on the main body of the image forming apparatus. An image forming apparatus, which is performed before toner image formation is started. The image forming apparatus according to any one of claims 1 to 7,
Transfer means for transferring the toner image formed on the latent image carrier by the toner image forming means to a recording medium;
An image forming apparatus comprising: forming the electrostatic latent image pattern, detecting a potential, and determining an image forming condition based on the detection result of the potential at intervals of a predetermined number of the recording medium onto which the toner image is transferred. The image forming apparatus according to any one of claims 1 to 8,
An image forming apparatus comprising: forming an electrostatic latent image pattern, detecting a potential, and determining an image forming condition based on a detection result of the potential when an environmental condition in the image forming apparatus changes.

Images