JP2011022507A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a base image for use in the adjustment of an image forming condition in the state in which the influences of uneven density in the base image, non-uniformity in density in the base image, and a reduction in residual amount of an image forming material used for the base image are reduced. <P>SOLUTION: In case of detecting a K-color patch formed on a transfer belt by a diffusion sensor, a color satisfying the following conditions: it has the highest density, density unevenness thereof is less than a normal value, and also, the residual toner amount thereof is equal to or more than a normal value, is selected as a base color out of colors Y, M and C. With the absence of the color satisfying those conditions, two colors overlapping each other are used as the base color of the K-color patch. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  Japanese Patent Application Laid-Open No. 2004-228561 operates a process control so that the color toner image has a desired density in a method in which a color toner image is used as a reflector as a base when process control of black toner is performed on an intermediate transfer member. The function is described. In Patent Document 2, after the color toner image is created, the density of the color toner image is measured, and when the density is appropriate, the black toner image is overlaid and the density of the black toner image is detected. How to do is described. Patent Document 3 describes a configuration in which a detection toner image is formed on the intermediate transfer belt with a circumferential pitch of a developing roller in order to prevent a change in image density.

JP-A-7-168401 JP-A-11-143171 JP 2002-40726 A

  In an image forming apparatus that forms a color image by superimposing a plurality of colors, in order to form an image of each color with an appropriate density, an image for measurement is formed with each color, the density is measured, and an image is obtained according to the measurement result. Some have adjusting means for adjusting the forming conditions. As the density measuring means for the measurement image, a regular reflection type sensor that detects and measures regular reflection light by irradiating light and a diffuse reflection type sensor that detects and measures part of diffuse reflection light are appropriately used.

  When measuring the density of an image for measurement using a specular reflection sensor, the surface (for example, the surface of the intermediate transfer member) on which the image for measurement is formed depends on the ratio of the area covered with the toner or the like that forms the image for measurement. Therefore, the density of the image for measurement can be measured by measuring the amount of change.

  However, when the surface on which the measurement image is formed is not flat, specifically, for example, when a wrinkle is generated by a roll around which the intermediate transfer member is wound, the direction of the reflected light with respect to the irradiation light of the regular reflection type sensor The measurement value fluctuates as a result of fluctuations, resulting in an error in measuring the density of the measurement image. For this problem, for example, when measuring the density of a black image, first, the surface on which the image to be measured is formed is covered with a background image of a color such as yellow, cyan, magenta, etc. A method has been devised in which an image is formed and read by a diffusion type sensor so that the influence of the non-flat surface is less likely to occur. However, in this case, there is a problem that the density change of the background image affects the measurement of the density of the image for measurement originally intended to be measured.

  The present invention forms a base image in a state in which the influence of the density of the base image used for adjusting the image forming conditions, the nonuniformity of the density, and the decrease in the remaining amount of image forming material used for the base image is reduced. The purpose is to provide technology.

  According to the first aspect of the present invention, test image forming means for forming a test image using each of a plurality of types of image forming materials having a predetermined color on the intermediate transfer member, and detecting the density of the test image A density detection unit and a density determination unit for determining the density of the test image based on the density measurement value detected by the density detection unit; or the test based on the density measurement value detected by the density detection unit One of density non-uniformity determining means for determining image density non-uniformity or remaining amount determining means for determining the remaining amount of the image forming material used for the test image formed on the intermediate transfer member. Two or more determination means; a selection means for selecting a specific color based on one or more determination results among the light / dark determination means, the non-uniformity determination means or the remaining amount determination means; and the selection means Forming a background image using the specific color selected in the above, and overlaying the background image to form a measurement image for use in image formation control of a color different from the background image And an image forming apparatus.

  According to a second aspect of the present invention, in the first aspect of the present invention, the selecting unit is configured such that the density of the predetermined condition, the non-uniformity of the density of the predetermined condition, or the image of the predetermined condition A color that satisfies one or more conditions among the remaining amount of the forming material is selected.

  According to a third aspect of the present invention, in the second aspect of the present invention, the selection unit is configured such that the density of the predetermined condition, the non-uniformity of the density of the predetermined condition, or the predetermined When there is no color that satisfies one or more conditions among the remaining amount of the image forming material of the condition, a plurality of colors are selected, and an image in which the plurality of colors are superimposed is used as the base image.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus according to any one of the first to third aspects, wherein the image forming apparatus performs image formation by electrophotography using a developing device using a developing roll. The base image is created in a state where the rotation direction phase of the developing roll is aligned with the test image.

  According to the first aspect of the present invention, it is possible to create a base image necessary for accurately measuring a measurement image used for image formation control.

  According to the second aspect of the present invention, it is possible to form a base image for measuring the measurement image with a required measurement accuracy.

  According to the third aspect of the present invention, it is possible to form a base image for measuring the measurement image with necessary measurement accuracy even if there is no color that satisfies all the conditions.

  According to the invention described in claim 4, the measurement accuracy of the measurement image can be further increased.

1 is a conceptual diagram of an image forming apparatus according to an embodiment. FIG. 2 is a block diagram illustrating a configuration of a control system of the image forming apparatus in FIG. 1. 3 is a flowchart illustrating an example of an operation procedure of the image forming apparatus in FIG. 1.

(Constitution)
FIG. 1 is a conceptual diagram of an image forming apparatus according to an embodiment. FIG. 1 shows an image forming apparatus 100. The image forming apparatus 100 includes a recording paper storage device 101. The recording paper storage device 101 stores a plurality of recording papers 102 as recording sheets. The recording sheet is not limited to paper, and may be made of resin such as OHP paper.

  The recording paper is sent out from the recording paper storage device 101 to the transport path 103 by a paper feeding mechanism (not shown). Conveying roll mechanisms 104 and 105 are arranged on the conveying path 103, and convey the recording paper toward the secondary transfer unit 106.

  The secondary transfer unit 106 includes a transfer roll and a counter roll, and sandwiches the recording paper and the transfer belt 107 between them, thereby transferring the toner image formed on the transfer belt 107 onto the recording paper.

  The transfer belt 107 is an example of an intermediate transfer member, is guided by guide rolls 108 and 109, is driven by the guide roll 109, and rotates counterclockwise in the drawing. A toner image is primarily transferred from the photosensitive drums 110, 111, 112, and 113 to the transfer belt 107. That is, toner images of basic colors of Y (yellow), M (magenta), C (cyan), and K (black) are formed on each of the photosensitive drums 110 to 113, and this is applied to the transfer belt 107. Next transferred.

  Three types of images (toner images) are formed on the transfer belt 107: a test image, a measurement image, and a normal image. The test image is used to select the color of the base image that is the base of the measurement image described later. The measurement image is used to acquire correction data for the color that is the measurement target. Based on this correction data, color correction is performed when a normal image is formed. The normal image is an image formed on the recording paper, and is an image on the recording paper that is normally viewed by the user.

  Each of the photosensitive drums 110 to 113 includes a cleaning device, a charging device, an exposure device, and a developing device that performs development with toner, not shown, along the counterclockwise direction of the drawing. Each of the photosensitive drums 110 to 113 rotates counterclockwise in the figure, and at that time, the surface is cleaned by a cleaning device, the cleaned portion is charged, and the charged portion is exposed. Is performed to form an electrostatic latent image, and toner (powder of image forming material) is supplied from the developing device to the electrostatic latent image to form a toner image.

  FIG. 1 shows mag rolls 121 to 124 which are developing rolls of the developing devices. The mag rolls 121 to 124 develop the electrostatic latent images formed on the photosensitive drums 110 to 113 by rotating in the clockwise direction in the figure, and form toner images on the photosensitive drums 110 to 113.

  In the case of a normal image, each YMCK toner image formed on each of the photosensitive drums 110 to 113 is superimposed on the transfer belt 107 and primarily transferred. As a result, a color toner image is formed on the transfer belt 107. The toner image is transported toward the secondary transfer unit 106 by the rotation of the transfer belt 107, and is transferred to the recording paper transported from the left direction in the drawing by the secondary transfer unit 106.

  The recording paper onto which the toner image has been transferred in the secondary transfer unit 106 is sent to the image fixing unit 114, where toner image fixing processing is performed. The image fixing unit 114 includes a heating roll and a counter roll, applies heat and pressure to the recording paper, and fixes the toner image on the recording paper as an image. The recording paper that has passed through the image fixing unit 114 is sent from the transport roll mechanism 115 to the discharge mechanism 116 and discharged onto the recording paper discharge surface 117. Thus, a normal image is formed on the recording paper.

  When images are formed on both sides of the recording paper, the recording paper is sent from the transport roll mechanism 115 to the reversing device 118, where the recording paper is switched back and transported through the back surface image forming transport path 119. The recording sheet conveyed through the back surface image forming conveyance path 119 is supplied to the conveyance path 103 and reaches the secondary transfer unit 106 again.

  When forming a test image and a measurement image, YMCK image patterns (referred to as patch images) are sequentially formed on the transfer belt 107 on the transfer belt 107. In this case, the test image or the measurement image is not secondarily transferred onto the recording paper, but is detected by the image detection sensor 120 while being placed on the transfer belt 107, and then removed from the transfer belt 107 by a cleaning device (not shown). Is done.

  An image detection sensor 120 is arranged in the vicinity of the transfer belt 107. The image detection sensor 120 detects a test image and a measurement image formed on the transfer belt 107. The image detection sensor 120 is a diffusion sensor, and detects light in which light emitted from an irradiation light source (not shown) is diffusely reflected on the detection surface.

  The image forming apparatus 100 includes a controller 200. The controller 200 has a function as a computer, and includes a CPU, a memory, and an interface circuit, and executes functions to be described later.

  FIG. 2 is a block diagram illustrating a configuration of a control system of the image forming apparatus 100 of FIG. FIG. 2 shows the controller 200 also shown in FIG. In the controller 200, functional units to be described later are configured in software by a program stored in a memory (not shown).

  The controller 200 receives an output from a toner remaining amount detection sensor 201 (not shown in FIG. 1). The toner remaining amount detection sensor 201 detects the remaining amount of toner in the toner bottles (containers for storing toner) in the developing devices of the photosensitive drums 110 to 113. The toner remaining amount detection sensor 201 is disposed corresponding to each of the photosensitive drums 110 to 113, individually detects the remaining amount of toner of each color of YMCK, and outputs the detection result to the controller 200.

  The output of the image detection sensor 120 is input to the controller 200. The image detection sensor 120 detects a test image formed on the transfer belt 107 and inputs the image data to the controller 200.

  The controller 200 includes an image formation processing control unit 202. The image formation processing control unit 202 has a function of performing control related to image formation. In this example, the image formation processing control unit 202 includes a test image formation control unit 203, a measurement image formation control unit 204, and a normal image formation control unit 205.

  The test image formation control unit 203 controls test image formation processing. The test image is formed on the photoconductive drums 121 to 124, and is primarily transferred onto the transfer belt 107, which is optically detected by the image detection sensor 120. The detected image data of the test image is used for selecting the color of the background image of the measurement image described later. The test image formation control unit 203 controls the operation of each unit shown in FIG. 1 when forming the test image.

  The measurement image formation control unit 204 performs operation control when forming a background image of a color selected based on the above-described test image and when forming a measurement image on the background image. In forming the measurement image, first, a base image is formed on the transfer belt 107, and a measurement image is formed thereon. Thereafter, the measurement image on the transfer belt 107 is optically detected by the image detection sensor 120. The measurement image formation control unit 204 controls the operation of each unit shown in FIG. 1 when forming the measurement image.

  The normal image formation control unit 205 controls image formation on the recording paper stored in the recording paper storage device 101 described with reference to FIG.

  The controller 200 includes a density detection unit 206, a density determination unit 207, a non-uniformity determination unit 208, a toner remaining amount determination unit 209, a background color selection unit 210, and a correction data generation unit 211. The density detection unit 206 detects the density of the test image and the measurement image detected by the image detection sensor 120 based on the image data output from the image detection sensor 120.

  The density determination unit 207 processes the density data of the image detected by the density detection unit 206 using image processing software, and the degree of density (darkness) of the image detected by the image detection sensor 120 (that is, whether it is dark or light). Determine. This determination is made based on a comparison with predetermined grayscale data serving as a reference.

  The non-uniformity determination unit 208 processes the density data of the image detected by the density detection unit 206 using image processing software, and determines the degree of non-uniformity of the in-plane distribution of the image density detected by the image detection sensor 120. . This determination is made based on a comparison with data of a predetermined light and shade distribution serving as a reference.

  Based on the output of the toner remaining amount detection sensor 201, the toner remaining amount determination unit 209 determines that the remaining amount of toner (remaining amount of toner of each color of YMCK) in each developing device of the photosensitive drums 110 to 113 is greater than a specified amount. It is determined whether or not. This prescribed amount is determined as a threshold value that, if the value is less than that value, may cause a prescribed density not to be obtained during image formation.

  The base color selection unit 210 selects the base color of the measurement image based on the test image. The correction data generation unit 211 generates correction data used when forming a normal image based on the measurement image.

(Example of processing)
Hereinafter, an example of processing performed in the controller 200 will be described. For example, when a normal image is formed on a predetermined number of recording sheets, a measurement image is formed on the transfer belt 107, and correction data used to adjust the image quality of the normal image to be formed later is acquired. Is performed. Hereinafter, as an example, an example of processing for obtaining correction data relating to K color (black) will be described.

  FIG. 3 is a flowchart illustrating an example of processing performed in the controller 200. The processing shown in FIG. 3 is executed by the controller 200 in accordance with an operation program stored in a memory (not shown) in the controller 200. The operation program may be stored in an appropriate identification medium and provided from there.

  When the K color correction data acquisition process is started (step S301), YMC three-color test images are first formed in sequence on the transfer belt 107 (step S302). The test image of each color is formed so as to be a solid and uniform image without intentional light and shade distribution control. Next, the formed YMC three-color test images are detected by the image detection sensor 120, and the density of each color test image is detected by the density detection unit 206 (step S303).

  Next, the density determination unit 207 determines the density of the detected three color test images, and selects the color with the highest density (the darkest) (step S304). Then, the non-uniformity determination unit 208 determines whether or not the density non-uniformity is less than the predetermined non-uniformity for the color test image selected in step S304 (step S305). ). This processing is performed by setting a plurality of measurement points in the field of view of the image, digitizing the difference in density between them, and determining whether the result is less than a predetermined value. Is called.

  In the determination in step S305, if the density non-uniformity of the test image is less than the specified value, that is, if the density non-uniformity (density unevenness) is smaller than a predetermined value, the process proceeds to step S306. The process proceeds to step S307.

  In step S306, the toner remaining amount determination unit 209 determines whether or not the remaining amount of toner of the color selected in step S304 remains equal to or greater than a specified value. If the remaining amount of toner of the color selected in step S304 is equal to or greater than the specified value, the process proceeds to step S308. Otherwise, the process proceeds to step S307.

  In step S307, two colors in YMC are selected. In this selection, a predetermined combination is selected. After the process of step S307 ends, the process proceeds to step S308.

  In step S308, the background color selection unit 210 selects one color selected in step S304 or two colors selected in step S307 as the background color of the K measurement image (step S308). Next, a base image of the color selected in step S308 is formed on the transfer belt 107 (step S309). At this time, in the processing flow that does not go through step S307, an image of the background color of the color selected in step S304 is formed. Further, in the processing flow via step S307, the background images of the two colors selected in step S308 are sequentially superimposed.

  Next, a K color measurement image is formed on the base image formed in step S310 (step S310). The dimensional relationship between the measurement image and the background image is a dimensional relationship in which the background image is exposed around the measurement image.

  After the K color measurement image is formed, the image detection sensor 120 detects the measurement image (step S311), and the density detection unit 206 detects density information of the measurement image. Then, normalization processing is performed based on the density information of the measurement image to obtain K color correction data (step S312). In this normalization process, (measured value / reference value) is calculated, and correction data relating to K color is obtained. Thereafter, using the normalized correction data, correction processing when forming a normal image of K color is performed. After the normalization process ends, the process ends (step S313).

  In the above processing, the rotation control of the mag roll is performed so that the rotation direction phase of the mag roll when the base image is formed in step S309 and the rotation direction phase of the mag roll when the test image is formed in step S302 are aligned. In this control, the phase relationship between the test image and the angular position of the mag roll surface contributing to the formation of the test image is aligned with the phase relationship between the base image and the angular position of the mag roll surface contributing to the formation of the base image. The timing of development and the rotation of the mag roll are controlled.

(Superiority)
By using a diffusion sensor as the image detection sensor 120, the measurement image can be optically detected while suppressing the influence of curling (deformation) on the transfer belt 107. However, when a K-color measurement image is detected by a diffusion sensor, it is necessary to form a K-color measurement image on a stable background color.

  According to the above example, prior to the formation of the measurement image, the YMC having the highest density is first selected using the test image (step S304). Next, in step S305, it is determined whether or not the in-plane non-uniformity of the density of the selected color is small enough to satisfy a specified condition. Furthermore, in addition to the requirement for density non-uniformity, a determination is made in step S306 as to whether the remaining amount of toner is equal to or greater than a specified value. Then, a color that satisfies all these three requirements is selected as the background color of the K measurement image. For this reason, a background color that is suitable for detecting a K-color measurement image with diffused light, has a low density unevenness, and has a sufficient amount of remaining toner is selected, and highly accurate information about the K color is obtained. It can be obtained from diffused light. Hereinafter, this point will be described in more detail.

  When a K color measurement image is detected using diffused light, the K color itself basically has a characteristic of absorbing light. Therefore, from the diffused light from the K color measurement image and the surrounding background. Therefore, the image quality information of the measurement image for K color is acquired from the difference from the diffused light. Therefore, when the background color density is low, the amount of diffused light from the background around the K color measurement image decreases, and the error included in the image quality information related to the K color measurement image increases. For this reason, it is important that the background color around the K measurement image is dark. In the processing procedure shown in FIG. 3, since the darkest color is selected in step S304, this requirement is satisfied.

  As is clear from the above principle, the error included in the image quality information from the K measurement image also increases when the background color has in-plane density non-uniformity. Therefore, it is preferable that the density non-uniformity in the background color of the K measurement image is as small as possible. In the processing procedure shown in FIG. 3, the density non-uniformity is determined in step S305, and this requirement is satisfied.

  In addition, when the amount of toner that forms the background color of the K measurement image is low and the toner is about to run out, there is a problem that the background color becomes low density or density unevenness occurs in the background color. The possibility of doing increases. Therefore, when toner out is likely to occur, it is preferable not to select that color as the base color. In the processing procedure shown in FIG. 3, since the determination regarding the remaining amount of toner is performed in step S306, this requirement is satisfied.

  If a background color that satisfies the above three requirements cannot be selected, the background is formed by superimposing the two color images in the YMC (step S307). By superimposing two color images, the problem of density and density non-uniformity is alleviated as compared to the case of one color. For this reason, the accuracy of the image quality information in the detection of the measurement image for K color using the diffusion sensor can be improved as compared with the case of using one color that does not satisfy the above three requirements.

  Further, the rotation of the mag roll is controlled by controlling the development processing so that the rotation direction phase of the mag roll at the time of forming the background image in step S309 and the rotation direction phase of the mag roll at the time of forming the test image in step S302 are aligned. The influence of the difference in developing ability depending on the angular position is suppressed, and the reproducibility of the background image with respect to the test image can be enhanced. For this reason, the measurement accuracy of the measurement image formed on the base image can be increased.

  According to the technique exemplified here, the K-color measurement image using the diffused light can be detected with high accuracy, so that it is possible to use a transfer belt made of a material that is easily wrinkled and has an image quality adjustment function. The cost of the transfer belt can be reduced while maintaining.

(Other)
In step S307 in FIG. 3, when two colors are selected, three colors may be selected instead of two colors. In this case, images of three colors (YMC) are formed by sequentially overlapping as a base. Further, in the flowchart of FIG. 3, it is possible to first select a color with the lowest density non-uniformity and then make a determination regarding other selection conditions. Alternatively, the determination regarding the remaining amount of toner may be performed first, and then the determination regarding other selection conditions may be performed. Alternatively, the determination result regarding density density, density non-uniformity, and the remaining amount of toner may be scored, and the background color of the measurement image may be selected based on the total score. In this case, if there is no color that reaches the reference, processing for selecting two colors is performed. Further, in selecting two colors when using the scored result, two colors may be selected in order from the highest score.

  Alternatively, the background color of the measurement image may be selected by paying attention only to the density of the test image, only the uniformity of the density of the test image, or only the remaining amount of toner. In this case, the base color of the measurement image for K color is selected by paying attention to one of the three requirements.

  For example, a case where attention is paid only to the density of the test image will be described. In this case, if there is a test image having a darkness equal to or higher than a predetermined value, the color of the test image is selected as the base color of the K measurement image and has a darkness equal to or higher than the predetermined value. If there is no test image, two colors are selected, and a superposition of the images of those colors is selected as the background of the K measurement image.

  Based on the same concept, paying attention to two of the three requirements of the density of the test image, the uniformity of the density of the test image, and the remaining amount of toner, the color that satisfies these two requirements is the base of the K color. There is also a method of selecting a process in which two colors (or three colors) are overlaid when there is no color satisfying these two requirements.

  For example, the case where the density of the test image and the uniformity of the density of the test image are used as the determination conditions will be described. In this case, a color that is darker than a predetermined density and whose density in-plane uniformity is equal to or greater than a predetermined uniformity is selected as the background color of the measurement image. Then, when there is no color that satisfies this requirement, a process is selected that uses two colors (or three colors) as a base.

  In the embodiment, the case where the background color of the K measurement image is selected has been described as an example. However, the same processing can be performed on the measurement image other than the K color.

  The present invention can be used in an image forming apparatus.

  DESCRIPTION OF SYMBOLS 100 ... Image forming apparatus, 101 ... Recording paper storage apparatus, 102 ... Recording paper, 103 ... Conveyance path, 104 ... Conveyance roll mechanism, 105 ... Conveyance roll mechanism, 106 ... Secondary transfer part, 107 ... Transfer belt, 108 ... Guide Roll, 109 ... guide roll, 110 ... photosensitive drum, 111photosensitive drum, 112 ... photosensitive drum, 113 ... photosensitive drum, 114 ... image fixing unit, 115 ... conveying roll mechanism, 116 ... discharge mechanism, 117 ... recording Paper discharge surface, 118... Reversing device, 119... Backside image forming conveyance path, 120... Image detection sensor, 121 to 124.

Claims (4)

Test image forming means for forming a test image using each of a plurality of types of image forming materials having a predetermined color on the intermediate transfer member;
Density detecting means for detecting the density of the test image;
A density determination means for determining the density of the test image based on the density measurement value detected by the density detection means, or
A density non-uniformity determining means for determining a density non-uniformity of the test image based on a density measurement value detected by the density detecting means, or
One or more determination means among remaining amount determination means for determining the remaining amount of the image forming material used for the test image formed on the intermediate transfer member;
A selection unit that selects a specific color based on one or more determination results of the density determination unit, the non-uniformity determination unit, or the remaining amount determination unit;
A measurement image is formed by forming a background image using a specific color selected by the selection unit and overlaying the background image to form a measurement image for use in image formation control of a color different from the background image An image forming apparatus comprising: a forming unit.   The selection unit selects a color that satisfies one or more conditions of light and shade of a predetermined condition, non-uniformity of the density of the predetermined condition, or the remaining amount of the image forming material of the predetermined condition. The image forming apparatus according to claim 1.   The selection means is a color that satisfies one or more conditions of light and shade of the predetermined condition, density non-uniformity of the predetermined condition, or remaining amount of the image forming material of the predetermined condition. 3. The image forming apparatus according to claim 2, wherein when there is no image, a plurality of colors are selected and an image in which the plurality of colors are superimposed is used as the base image. An image forming apparatus for forming an image by an electrophotographic method using a developing device using a developing roll,
The image forming apparatus according to claim 1, wherein the base image is created in a state in which a rotation direction phase of the developing roll is aligned with respect to the test image.

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