JP5857492B2 - Image forming apparatus and program - Google Patents

Description

  The present invention relates to an image forming apparatus and a program.

  In an electrophotographic image forming apparatus, unintended unevenness may occur in an image. As a cause of unevenness, for example, when transferring an image of a secondary color or higher (that is, an image in which two or more primary colors are mixed), the toner to be transferred onto the other color toner is not sufficiently transferred. Transfer defects due to Such a transfer failure is also called retransfer (retransfer). As a specific mode of such a transfer failure, for example, there is a streak-like unevenness that occurs in a direction that intersects (typically orthogonal) the sheet moving direction.

  Patent Document 1 describes that image processing is executed using a conversion table (LUT) in order to correct “image unevenness” and “streaks” occurring in an image. More specifically, the technique described in Patent Document 1 is for correcting “image unevenness” and “streaks” occurring at a specific position.

JP 2007-88562 A

  An object of the present invention is to operate an image forming unit that operates in accordance with a predetermined condition so that a specific unevenness does not occur in an image.

An image forming apparatus according to claim 1 of the present invention operates according to determined criteria, an image forming means for forming an image by transferring a plurality of color toners on a medium, a direction perpendicular to the moving direction before Symbol medium a a width continuously or stepwise changing the secondary color or monochromatic pattern image was, said image a plurality of pattern images having different the condition for each pattern image, so as to form on said medium Formed by the control means for controlling the forming means, the detecting means for detecting the density of the plurality of pattern images formed by the image forming means in accordance with the control of the control means, over the moving direction of the medium, and the image forming means And a recording means for recording data representing the conditions when forming a pattern image whose density is detected by the detection means in a storage means, the recording means being detected by the detection means Formed by the image forming unit and a recording unit that records the correspondence between the width of the pattern image at a position where the degree is different from the density of the single color and the condition when the pattern image is formed, as the data. A direction orthogonal to the moving direction of the area in the medium when the image represented by the acquisition means and an image represented by the image data acquired by the acquisition means include an area of secondary color or more. The condition when the pattern image with the smallest variation in density detected by the detection means is formed among the data stored in the storage means by the recording means and the specifying means for specifying the width of the image, A changing means for changing the condition followed by the forming means, the width specified by the specifying means and the width represented by the data stored in the storage means If the difference between is within a predetermined range, characterized in that it comprises a changing means not using the conditions stored in correspondence with the width.

A program according to a second aspect of the present invention operates in accordance with predetermined conditions, and forms an image by transferring a plurality of colors of toner onto a medium, and the density of an image formed by the image forming means. A monochrome pattern image of a secondary color or more in which the width of a direction orthogonal to the moving direction of the medium is changed continuously or stepwise by a computer of an image forming apparatus including a detecting unit that detects the moving direction of the medium. And a control unit that controls the image forming unit to form a plurality of pattern images having different conditions for each pattern image on the medium, and the image forming unit. Recording means for recording data representing the conditions when forming a pattern image whose density is detected in a storage means, wherein the density detected by the detection means An image formed by the image forming unit, a recording unit that records the association between the width of the pattern image at a position different from the density of the single color and the condition when the pattern image is formed as the data; Width of a direction orthogonal to the moving direction of the area in the medium when the image represented by the image data acquired by the acquisition means includes an area of a secondary color or higher The image forming unit satisfies the conditions when a pattern image with the smallest variation in density detected by the detection unit is formed among the data stored in the storage unit by the recording unit. A change means for changing the condition according to the difference between the width specified by the specifying means and the width represented by the data stored in the storage means If it is within a predetermined range, characterized in that to function as changing means not using the conditions stored in correspondence with the width.

According to the first and second aspects of the present invention, it is possible to use conditions such that specific unevenness does not occur in an image for which the image forming unit is to form an image.

1 is a block diagram illustrating a functional configuration of an image forming apparatus (first embodiment). The figure which shows the specific example of an image formation means and a detection means The figure which illustrates the pattern image formed in an intermediate transfer belt The figure which illustrates the stripe retransfer which arises in a pattern image Flowchart illustrating an example of a setup operation executed by the image forming apparatus The figure which illustrates the output value of the density sensor Flowchart illustrating another example of a setup operation executed by the image forming apparatus Diagram illustrating pattern image Block diagram showing functional configuration of image forming apparatus (second embodiment) Block diagram showing functional configuration of image forming apparatus (third embodiment) The figure which shows the correlation of the width of the pattern image of the position where streak retransfer occurs, and the primary transfer current Diagram illustrating pattern image Block diagram showing the functional configuration of the control device

[Summary of the Invention]
The present invention is to suppress streak unevenness (hereinafter referred to as “streak retransfer”) that occurs in a direction intersecting the moving direction of a recording medium such as paper in an electrophotographic image forming apparatus. In the streaky retransfer, in an image area where a plurality of colors of toner is transferred (that is, an image area of a secondary color), the toner to be transferred later is not sufficiently transferred due to the influence of the previously transferred toner. Caused by For example, streak retransfer that occurs when a green image is formed by superimposing a C (cyan) toner on a Y (yellow) toner causes a transfer failure in the C toner, and thus is more yellow than the original green. Become a color. In general, the streak retransfer is perpendicular to the moving direction of the recording medium, but is not necessarily perpendicular to the moving direction and may be slightly inclined.

  The inventor of the present invention has found that the ease of occurrence of such streak retransfer has a correlation with the width of the image. The image width here is the length of the image in the direction orthogonal to the moving direction of the recording medium. When the image forming apparatus operates under a specific condition, it has been confirmed that streak retransfer is likely to occur in an image having a specific width (or a specific width portion of the image). Note that the operation conditions in the image forming apparatus relate to, for example, the potential when developing the toner and the pressure when transferring the toner, and are collectively referred to as “image forming conditions” below.

  The inventor has also found that when the image forming conditions are changed, the position where the streak retransfer is likely to occur also changes. Based on this knowledge, the present invention is mainly characterized in that the image forming apparatus is controlled so as to form an image under image forming conditions in which no streak retransfer occurs in the image. Specifically, the present invention pre-forms a pattern image formed of a single color of secondary or higher color in advance, and determines in advance the width at which streak retransfer is likely to occur and the image formation conditions at which streak retransfer is likely to occur. The image forming conditions are adjusted based on the identification.

[First Embodiment]
FIG. 1 is a block diagram showing a functional configuration of an image forming apparatus 10 according to the first embodiment of the present invention. The image forming apparatus 10 includes at least an image forming unit 100, a control unit 200, a detection unit 300, and a change unit 400. Note that the image forming apparatus 10 may further include means for optically reading a document and means for transmitting and receiving image data. That is, the image forming apparatus 10 is not limited to a so-called printer, and may be a copying machine or a facsimile machine.

  The image forming unit 100 is a unit that operates according to image forming conditions and forms an image on a recording medium. The image forming unit 100 forms a toner image using a plurality of colors of toner, and forms an image by transferring the toner image on a recording medium. The toner used in the image forming unit 100 is, for example, four colors of Y (yellow), M (magenta), C (cyan), and K (black), but may be other colors or more. Color (for example, six colors) toner may be used. Hereinafter, the color of the toner, that is, the color that is the source of the mixed color is referred to as “primary color”. The primary colors here are so-called primary colors, and are not limited to the three primary colors of subtractive color mixing.

  The control unit 200 is a unit that controls the image forming unit 100. The control unit 200 supplies image data to the image forming unit 100 or gives necessary instructions to the image forming unit 100 in order to cause the image forming unit 100 to form an image. In addition, the control unit 200 causes the image forming unit 100 to form a pattern image to be described later at an appropriate timing. The timing at which the control unit 200 forms the pattern image may be a predetermined timing (such as when the power is turned on or a periodic timing), or may be a timing designated by the user.

  The detection unit 300 is a unit that detects the density of the pattern image formed by the image forming unit 100 under the control of the control unit 200. For example, the detection unit 300 irradiates the pattern image with light and senses the reflected light to detect the density of the pattern image. The density here represents the color density of the image, and is determined, for example, by the ratio of the intensity of the irradiated light and the intensity of the sensed reflected light.

  The changing unit 400 is a unit that changes the image forming conditions applied in the image forming unit 100 in accordance with the density variation detected by the detecting unit 300. Here, the fact that the concentration detected by the detection means 300 fluctuates means that streak retransfer has occurred. In other words, the concentration variation referred to here means that the concentration changes to such an extent that it is considered that muscular retransfer has occurred (that is, significantly).

  The control means 200 and the changing means 400 are a computer having a CPU (Central Processing Unit) and a memory, a dedicated integrated circuit such as an ASIC (Application Specific Integrated Circuit) and an FPGA (Field-Programmable Gate Array), or these This is realized through collaboration.

  FIG. 2 is a diagram illustrating a device configuration of the image forming apparatus 10, and particularly illustrates specific examples of the image forming unit 100 and the detection unit 300. The image forming unit 100 includes a photosensitive drum 101, a charging roll 102, an exposure device 103, a developing device 104, an intermediate transfer belt 105, a primary transfer roll 106, a plurality of support rolls 107, and the like shown in FIG. A secondary transfer roll 108, a cleaning blade 109, and a fixing device 110 are included. The detection unit 300 includes a density sensor 301.

  The photosensitive drum 101 is a member that holds an electrostatic latent image and a toner image and rotates in a direction indicated by an arrow A1 in the drawing. The photoconductive drum 101 has a photoconductive layer formed thereon, and changes its surface potential when irradiated with light. The charging roll 102 is a member that contacts and charges the photosensitive drum 101. The means for charging the photosensitive drum 101 may be of a type that does not contact the photosensitive drum 101, such as corotron or scorotron. The exposure device 103 is a means for forming an electrostatic latent image by irradiating light to the charged photosensitive drum 101 to cause a partial potential difference.

  The developing unit 104 is a unit that stores toner of each color Y, M, C, and K together with a carrier and supplies necessary toner. The developing device 104 is a so-called rotary type developing device, and a position (angle) for supplying each color toner is determined in advance, and is configured to rotate in accordance with the color of the supplied toner. . The developing device 104 supplies toner of each color to the surface of the photoconductive drum 101, thereby forming a color toner image corresponding to the electrostatic latent image formed on the photoconductive drum 101.

  The intermediate transfer belt 105 is an endless belt-like member that moves the toner image. The intermediate transfer belt 105 is supported by a plurality of support rolls 107, and changes its position by being rotated in the direction indicated by the arrow A2 in the drawing. At least one of the support rolls 107 is driven by a driving unit such as a motor to rotate the intermediate transfer belt 105. The primary transfer roll 106 is a member that transfers the toner image formed on the photosensitive drum 101 to the intermediate transfer belt 105.

  The primary transfer roll 106 transfers the toner image from the photosensitive drum 101 to the intermediate transfer belt 105 by a current (hereinafter referred to as “primary transfer current”) for generating a desired potential difference with the photosensitive drum 101. Let The primary transfer roll 106 applies an appropriate pressure (hereinafter referred to as “nip pressure”) so as to press the intermediate transfer belt 105 against the photosensitive drum 101.

  The secondary transfer roll 108 is a means for transferring the toner image transferred to the intermediate transfer belt 105 to a recording medium conveyed along a broken arrow A3 in the drawing. The cleaning blade 109 is a means for removing a toner image (or a part thereof) that has not been transferred by the secondary transfer roll 108. The toner removed by the cleaning blade 109 includes toner that is not sufficiently transferred to the recording medium in the secondary transfer roll 108 and remains on the intermediate transfer belt 105 and toner that does not need to be transferred to the recording medium. Includes a pattern image. The fixing device 110 is a unit that applies heat and pressure to the recording medium onto which the toner image has been transferred to fix the toner on the recording medium.

  The density sensor 301 is means for detecting the density of the toner image transferred to the intermediate transfer belt 105 and outputting density information representing the density. The density sensor 301 is electrically connected to the changing unit 400 in a wired or wireless manner so that density information can be supplied to the changing unit 400.

  FIG. 3 is a diagram illustrating a pattern image formed on the intermediate transfer belt 105. Note that the direction indicated by the arrow A2 in the figure corresponds to the moving direction of the intermediate transfer belt 105, as in the case of FIG. Further, an area inside the intermediate transfer belt 105 from the broken line is an area where the toner can be transferred, and the width of this area is determined according to the maximum size of the recording medium used in the image forming apparatus 10.

  The pattern image is an image formed with a single color that is a secondary color or higher, for example, a green image in which Y toner and C toner are superimposed. Here, the single color means that the whole is a single color, and means that there is no gradation change such as gradation in the pattern image. That is, the pattern image is ideally an image that should have the same density at any position. However, when the streak retransfer occurs, the density of the pattern image changes at the position where the streak retransfer occurs.

  As shown in FIG. 3, the pattern image is an image having a determined pattern shape in which the width in the direction orthogonal to the moving direction of the intermediate transfer belt 105 continuously changes. The pattern image shown in this example is formed so that one side is an isosceles triangle parallel to a direction orthogonal to the moving direction of the intermediate transfer belt 105. The length of this side is set to be equal to the width of the area where the toner can be transferred.

  Further, the position of one vertex (vertical angle) of the pattern image is determined according to the position of the density sensor 301. In other words, the density sensor 301 is provided at a position where the pattern image can be read from the position where the width of the pattern image is minimum to the position where it is maximum over the moving direction of the intermediate transfer belt 105. However, in the case of using a line sensor having a length that allows reading up to the maximum width of the pattern image as the density sensor 301, the position of the apex angle of the pattern image is not limited.

  The pattern image need not be transferred to the recording medium. That is, the pattern image may be removed from the intermediate transfer belt 105 by the cleaning blade 109 without being transferred to the recording medium. In this case, the intermediate transfer belt 105 corresponds to the medium on which the pattern image is formed. On the other hand, when the pattern image is transferred to the recording medium, both the intermediate transfer belt 105 and the recording medium can correspond to the medium on which the pattern image is formed.

  FIG. 4 is a diagram illustrating the streak retransfer that occurs in the pattern image. In this way, the streak retransfer is long and streaks in the direction crossing the moving direction of the intermediate transfer belt 105. A typical streak retransfer occurs along the axial direction of the primary transfer roll 106. However, the streak retransfer shown in the figure is emphasized for convenience of illustration. The streak retransfer may actually occur with a width of less than 1 mm, and its length is not constant.

  Streaky retransfer is likely to occur when the image has a high density, that is, when the amount of toner (coverage) per unit area is large, as in a so-called solid image. Therefore, the pattern image is also formed with a relatively high density. A typical pattern image is an image in which the coverage of each color toner is 100%. The coverage mentioned here is an input value (input coverage) indicating a ratio of covering the recording medium with toner.

  The configuration of the image forming apparatus 10 is as described above. With this configuration, the image forming apparatus 10 forms an image according to a user instruction and an image according to acquired image data, and forms a pattern image as necessary. The image forming apparatus 10 forms a pattern image under specific image forming conditions, and changes the image forming conditions so that no streak retransfer occurs when the formed pattern image has streak retransfer. . In the following, a series of operations for forming a pattern image and changing image forming conditions as necessary is referred to as a “setup operation”.

  FIG. 5 is a flowchart illustrating an example of a setup operation executed by the image forming apparatus 10. In the setup operation, the image forming apparatus 10 first forms a pattern image according to a predetermined image forming condition (image forming condition before change) (step Sa1). At this time, in the image forming apparatus 10, the control unit 200 causes the image forming unit 100 to form a pattern image.

  When the pattern image is formed, the image forming apparatus 10 detects this by the density sensor 301 and obtains density information (step Sa2). The density information obtained at this time is information obtained by detecting the density of the pattern image from the front end side to the rear end side in the moving direction of the intermediate transfer belt 105. Further, the image forming apparatus 10 determines the variation in the density of the pattern image based on the density information, and determines whether or not the streak retransfer has occurred (step Sa3).

  FIG. 6 is a diagram illustrating the output value of the density sensor 301. The example shown in FIG. 6 is for the case where the density sensor 301 detects specularly reflected light. The output value is large at the position where the pattern image is not formed, and the output value is small at the position where the pattern image is formed. It has become. In addition, the output value at the position where the streak retransfer occurs is larger than the output value at the position where the pattern image is formed, and smaller than the output value at the position where the pattern image is not formed. Therefore, when the output value of the density sensor 301 is equal to or lower than the threshold value Th1 corresponding to the upper limit and equal to or higher than the threshold value Th2 corresponding to the lower limit, the image forming apparatus 10 has a streak shape at the position indicating the output value. Judge that transfer is occurring.

  Note that the image forming apparatus 10 may use the output value of the density sensor 301 as it is as the density information, but may use the output value subjected to signal processing as the density information. For example, the image forming apparatus 10 may execute signal processing for removing or reducing a noise component included in the output value. The noise component is, for example, a pulse-like steeply changing component. Further, when the intermediate transfer belt 105 has a step such as a joining portion, a noise component may be generated even at the position where the step is present.

  In this way, the image forming apparatus 10 determines the presence / absence of the streak retransfer, and when it is determined that the streak retransfer has occurred, the image forming condition is changed (step Sa4). A pattern image is formed again under the image forming conditions (step Sa1). The image forming apparatus 10 repeats this operation until it is determined that no streak retransfer has occurred, and when it is determined that no streak retransfer has occurred, the setup operation ends. After the setup operation is completed, the image forming apparatus 10 forms an image under the changed image forming conditions.

  The image forming conditions changed in step Sa4 are image forming conditions for changing the image density. For example, the nip pressure, the primary transfer current, the toner charge amount and toner density in the developing device 104, and the potential at the time of development. Such as conditions. When the image forming apparatus 10 determines that the streak retransfer has occurred, the image forming apparatus 10 changes the image forming conditions so that the density of the image is lighter (than that before the change). Here, the toner concentration refers to a mixing ratio of toner and carrier. The potential condition means a potential difference between the potential of the exposed portion of the photosensitive drum 101 and the potential of the non-exposed portion, or a potential difference between the potential of the exposed portion and the potential on the developing device 104 side. When the charge amount of the toner is high, streak retransfer occurs more easily than when the toner charge amount is low. In order to reduce the charge amount of the toner, it is only necessary to forcibly eject the toner and supply new toner. In this case, the forcibly discharged toner is removed by the cleaning blade 109.

  Further, the image forming apparatus 10 may change the image data itself by the LUT. In this case, changing the LUT corresponds to changing the image forming condition. For example, when the image forming apparatus 10 determines that the streak retransfer has occurred, the image forming apparatus 10 may convert the input value of the image data so as to have a low density as a whole. Further, since the streak retransfer is likely to occur in a relatively high density image, the image forming apparatus 10 changes only the relatively high density value among the input values of the image data and changes other input values. You don't have to.

  Note that the image forming apparatus 10 does not need to change all of the above-described image forming conditions, and may change at least one of them. Further, in the present embodiment, the image forming apparatus 10 changes the image forming conditions for all the colors used for forming the pattern image. As described later, some of the colors used for forming the pattern image are used. Only the image forming conditions may be changed.

  FIG. 7 is a flowchart illustrating another example of the setup operation performed by the image forming apparatus 10. The setup operation shown in FIG. 5 is to form and detect pattern images one by one and change the image formation conditions one by one. However, the setup operation in this example is a plurality of patterns with different image formation conditions. Images are continuously formed collectively and image forming conditions are set based on the detection results. Note that the image forming apparatus 10 may execute any of these setup operations as long as the image forming conditions that do not require time are changed, but change the image forming conditions that require time to change. If so, it is desirable to perform the setup operation shown in FIG.

  FIG. 8 is a diagram illustrating a pattern image formed in this example, and shows pattern images P1, P2 and P3 formed successively at appropriate intervals. The pattern images P1, P2, and P3 are images formed under different image forming conditions, for example, the potential conditions and the toner coverage are varied stepwise. Here, it is assumed that the pattern images P1, P2, and P3 are formed so that the toner coverage is 100% (P1), 98% (P2), and 96% (P3), respectively.

  In this example, the image forming apparatus 10 forms a plurality of pattern images shown in FIG. 8 (step Sb1). In addition, the image forming apparatus 10 detects a plurality of formed pattern images and obtains density information of each (step Sb2). The image forming apparatus 10 determines for each pattern image whether or not streak retransfer has occurred in the pattern image based on the density information (step Sb3).

  If the image forming apparatus 10 determines that the streak retransfer has occurred in all the pattern images, the image forming apparatus 10 changes the image forming conditions and forms a pattern image again (step Sb4). For example, when the process in step Sb4 is performed for the second time, the image forming apparatus 10 determines that the pattern image P1, the toner coverage is 94% (P1), 92% (P2), and 90% (P3). P2 and P3 are formed.

  On the other hand, if it is determined that there is a pattern image in which no streak retransfer occurs, the image forming apparatus 10 sets image forming conditions when the pattern image is formed (step Sb5), and performs subsequent image formation. Use this. Further, when there are a plurality of pattern images in which no streak retransfer occurs, the image forming apparatus 10 adopts and sets an image forming condition in which the density (that is, the coverage) is the highest.

  Note that the image forming apparatus 10 does not have to execute the process of step Sb4. For example, when the image forming apparatus 10 determines that the streak retransfer has occurred in all the pattern images, the pattern image in which the streak retransfer is most inconspicuous, that is, the detected density fluctuation is the smallest. It is also possible to specify a pattern image and set an image forming condition when the pattern image is formed. In other words, the pattern image with the least noticeable streak retransfer means that the color difference between the color of the pattern image where the streak retransfer occurs and the other position (original color position) is the smallest. It is a certain pattern image.

  The image forming condition after the setup operation is an image forming condition in which streak retransfer hardly occurs regardless of the width of the image. Therefore, the image forming apparatus after the set-up operation is less likely to cause streak retransfer in images of all widths than before the set-up operation. However, if the image forming conditions are not changed by the setup operation, there is no significant difference in the likelihood of occurrence of streak retransfer before and after the setup operation.

[Second Embodiment]
FIG. 9 is a block diagram showing a functional configuration of the image forming apparatus 20 according to the second embodiment of the present invention. In the present embodiment, the configuration described using the same reference numerals as in the first embodiment has the same features as the configuration described in the first embodiment. In the present embodiment, a duplicate description of this configuration is omitted.

  The image forming apparatus 20 includes a recording unit 500 and a storage unit 600 in addition to the image forming unit 100, the control unit 200, the detection unit 300, and the changing unit 400. That is, the image forming apparatus 20 is different from the image forming apparatus 10 of the first embodiment in that the image forming apparatus 20 includes a recording unit 500 and a storage unit 600.

  The storage unit 600 is a unit that stores data, and the recording unit 500 is a unit that records data in the storage unit 600. The storage unit 600 is realized by a storage device such as a hard disk or a flash memory. The recording unit 500 is realized as a function of a computer that implements the control unit 200 and the changing unit 400. Note that the storage unit 600 is not a component of the image forming apparatus 20 itself, but, for example, a so-called external storage device, or a component of another information processing apparatus connected to the image forming apparatus 20. May be.

  The image forming apparatus 20 does not change the image forming conditions in conjunction with the pattern image formation as in the image forming apparatus 10, but forms a pattern image in advance and records the detection result. The image forming conditions are changed when the correct timing comes. The recording unit 500 records data representing the image forming conditions when it is determined that the streak retransfer has occurred in the storage unit 600. Alternatively, the recording unit 500 may record the image forming conditions when no streak retransfer occurs. The recording unit 500 may record such data for each of a plurality of pattern images.

  When the image forming apparatus 20 forms an image other than the pattern image, the image forming condition is changed with reference to the data stored in the storage unit. That is, the image forming apparatus 20 forms an image using image forming conditions that do not cause streak retransfer. At this time, the image forming apparatus 20 may operate using the image forming conditions when the streak retransfer does not occur, or avoid the image forming conditions when the streak retransfer occurs. The image forming conditions may be changed to operate.

[Third Embodiment]
FIG. 10 is a block diagram showing a functional configuration of the image forming apparatus 30 according to the third embodiment of the present invention. In the present embodiment, the configuration described using the same reference numerals as those in the second embodiment has the same features as the configuration described in the second embodiment. In the present embodiment, a duplicate description of this configuration is omitted.

  The image forming apparatus 30 includes an acquisition unit 700 and a specifying unit 800 in addition to the image forming unit 100, the control unit 200, the detection unit 300, the change unit 400, the recording unit 500, and the storage unit 600. In other words, the image forming apparatus 30 is different from the image forming apparatus 20 of the second embodiment in that the acquiring unit 700 and the specifying unit 800 are provided.

  The acquisition unit 700 is a unit that acquires image data representing an image formed by the image forming unit 100. For example, the acquisition unit 700 may be a communication interface that receives image data from an external information processing apparatus, or may be a unit that optically reads a document, such as a so-called scanner.

  The specifying unit 800 analyzes the feature of the image based on the image data acquired by the acquiring unit 700, and when the image has a specific region, the width of the region (that is, when the image is transferred to the intermediate transfer belt 105). The length in the direction perpendicular to the moving direction) is specified. When the image represented by the image data includes an area of secondary color or more (more specifically, an area having the same color as the color forming the pattern image), the specifying unit 800 specifies the width of the area. When there are a plurality of areas that satisfy such conditions, the specifying unit 800 specifies the width for each area. In addition, when the width of the region that satisfies such a condition is not constant (for example, when the width in the movement direction changes like a pattern image), the specifying unit 800 determines the minimum value to the maximum value of the width. Identify.

  Further, in the present embodiment, when the streak retransfer occurs in the pattern image, the recording unit 500 forms the width of the pattern image at the position where the streak retransfer occurs and the image formation when the pattern image is formed. Data associated with the conditions is recorded in the storage unit 600. Here, the recording unit 500 performs the streak retransfer based on the relative positional relationship of the position where the streak retransfer occurs with respect to the length of the pattern image detected (that is, the length from the front end to the rear end). The width of the pattern image at the position where the occurrence occurs is calculated. Since the shape of the pattern image is determined in advance, the width of the pattern image at the position where the streak retransfer occurs is uniquely obtained from the position where the streak retransfer occurs.

  With this configuration, when the image to be formed includes an area of a specific color, the image forming apparatus 30 specifies the width of the area and does not cause streak retransfer at the specified width. The image is formed under image forming conditions. Specifically, the image forming apparatus 30 refers to the data stored in the storage unit 600, compares the width specified by the specifying unit 800 with the width represented by the data stored in the storage unit 600, and When the difference is within a predetermined range, the image forming conditions stored in association with the width are not used in the data, and an image is formed under other image forming conditions. . The image forming condition that the image forming apparatus 30 changes at this time is, for example, a primary transfer current.

  FIG. 11 is a diagram schematically showing the correlation between the width of the position where the streak retransfer occurs in the pattern image and the primary transfer current. In this example, it is assumed that image forming conditions other than the primary transfer current are unchanged. As shown in FIG. 11, the width of the position where the streak retransfer occurs is smaller (shorter) as the primary transfer current is larger, and larger (longer) as the primary transfer current is smaller.

  For example, in the example of FIG. 11, it is assumed that when the primary transfer current is I1, streak retransfer has occurred at the position of the width W1 of the green pattern image. In this case, when the image represented by the image data includes a green region and the width thereof is W1 (or a value close thereto), the image forming apparatus 10 sets the primary transfer current to be larger (or smaller) than I1. ) Set to the value. On the other hand, if the image represented by the image data includes a green region but the width is not W1 (or a value close to this), the image forming apparatus 10 may set I1 as the primary transfer current. There is no problem.

  That is, the image forming apparatus 30 changes the image forming condition to be applied according to the image to be formed at that time. In other words, if the image forming apparatus 30 is unlikely to cause streak retransfer in the image formed at that time, the image forming conditions that cause streak retransfer in the pattern image are set at that time. However, the image forming conditions are used without changing the image forming conditions. Therefore, in the image forming apparatus 30, it is expected that the number of times of changing the image forming conditions is reduced as compared with the image forming apparatus 10 and the image forming apparatus 20.

[Modification]
Embodiments of the present invention are not limited to the above-described embodiments, and may be, for example, the following forms. Moreover, these forms may be combined with each other by using them together or by replacing a part thereof as necessary.

(1) The shape of the pattern image need not be a triangle, and may be a circle (including a semi-elliptical shape). Further, the change in the width of the pattern image may be stepwise rather than continuous.
FIG. 12 is a diagram illustrating another example of the pattern image. In the figure, a pattern image Pa is an example of a semi-elliptical pattern image. Further, the pattern images Pb and Pc are examples of pattern images whose width changes are not continuous.

  Note that the width of the pattern image does not have to cover all the minimum value to the maximum value that can be assumed as the width of the image. It can be said that it is sufficient that the pattern image includes a width at which streak retransfer is likely to occur or a width at which streak retransfer is easily perceived by human eyes. For example, if the width of the image is very small, even if a streak retransfer occurs at that position, it is hardly perceived by the human eye. The need to change is not high. Therefore, the pattern image may be a trapezoid as shown by Pd in FIG.

(2) The streak retransfer occurs when the toner is further transferred to the surface where the toner has already been transferred. Whether or not streak retransfer occurs depends more on the amount of toner transferred earlier than on the amount of toner transferred later. Further, the change of the image forming conditions in the present invention mainly acts so that the amount of transferred toner is reduced.

  Therefore, the present invention can be effective even when the image forming conditions are changed only for the toner transferred first, instead of changing the image forming conditions for all the toners used for forming the pattern image. . For example, in the present invention, in order to suppress streak retransfer that occurs in a green image, the image forming condition when transferring the Y toner transferred first is changed, while the image when transferring the C toner is changed. The formation conditions may not be changed. If such a set-up operation is performed so that the amount of Y toner transferred is reduced, as a result, transfer failure of C toner is less likely to occur.

  However, if the image forming conditions for some colors are not changed in this way, the color balance may be lost. That is, when such a setup operation is executed, the amount of Y toner is assumed to be small even if the image should contain Y toner and C toner in the same ratio. There is a possibility that an image perceived as a color different from the original color may be formed. Therefore, when such a problem may occur, the color misregistration may be compensated for by a process different from the change of the image forming condition according to the present invention. As such processing, for example, correction of image data using an LUT can be considered.

(3) The image forming apparatus according to the present invention is not limited to one provided with a rotary type developing device. For example, the image forming apparatus according to the present invention may include a developing device for each color independently and arrange them in series along the moving direction of the intermediate transfer belt (so-called tandem system). Further, the image forming apparatus according to the present invention may be configured not to include the intermediate transfer belt but to transfer the toner directly from the photoreceptor to the recording medium.

(4) The present invention is provided not only as an image forming apparatus but also as a control apparatus that controls the image forming apparatus.
FIG. 13 is a block diagram showing a functional configuration of the control device 50 according to the present invention. The control device 50 includes a control unit 200, a changing unit 400, and a receiving unit 900. In addition, the component which attached | subjected the code | symbol same as 1st Embodiment (refer FIG. 1) in the figure is functionally common with each means demonstrated in 1st Embodiment. The accepting unit 900 is a unit that accepts information representing the concentration detected by the detecting unit 300. Such information may be the above-described density information or an output value of the density sensor 301. That is, the control device 50 may be configured to receive the output value of the density sensor 301 and perform signal processing on the output value.

  Moreover, the present invention may be provided in the form of a program for causing a computer to realize the functions of such a control device, or a recording medium on which such a program is recorded. Also, the program according to the present invention may be acquired from an external device via a network or other communication means and downloaded to a computer.

  DESCRIPTION OF SYMBOLS 10, 20, 30 ... Image forming apparatus, 50 ... Control apparatus, 100 ... Image forming means, 200 ... Control means, 300 ... Detection means, 400 ... Changing means, 500 ... Recording means, 600 ... Storage means, 700 ... Acquisition means , 800 ... identification means, 900 ... reception means

Claims (2)

An image forming unit that operates according to a predetermined condition and transfers an image of a plurality of colors to a medium to form an image;
A monochromatic pattern image of a secondary color or more in which the width in the direction orthogonal to the moving direction of the medium is changed continuously or stepwise, and a plurality of pattern images with different conditions for each pattern image, Control means for controlling the image forming means to form on the medium;
Detecting means for detecting the density of a plurality of pattern images formed by the image forming means according to the control of the control means over the moving direction of the medium;
A recording unit that records data representing the conditions when forming a pattern image formed by the image forming unit and whose density is detected by the detection unit in a storage unit, and the density detected by the detection unit is A recording unit that records, as the data, a correspondence between the width of the pattern image at a position different from the density of the single color and the condition when the pattern image is formed;
Obtaining means for obtaining image data representing an image formed by the image forming means;
A specifying unit that specifies a width in a direction orthogonal to a moving direction of the region in the medium when the image represented by the image data acquired by the acquiring unit includes an area of a secondary color or more;
Of the data stored in the storage unit by the recording unit, the condition that the image forming unit follows is changed to the condition when the pattern image with the smallest variation in density detected by the detecting unit is formed. When the difference between the width specified by the specifying means and the width represented by the data stored in the storage means is within a predetermined range, the changing means is stored in association with the width. An image forming apparatus comprising: a changing unit that does not use the condition. Operate according determined Me is condition, and an image forming means for forming an image by transferring a plurality of color toners on a medium, detecting means for detecting a density of the image formed by the image forming means across the direction of movement of the medium A computer of an image forming apparatus comprising:
A monochromatic pattern image of a secondary color or more in which the width in the direction orthogonal to the moving direction of the medium is changed continuously or stepwise, and a plurality of pattern images with different conditions for each pattern image, Control means for controlling the image forming means to form on the medium;
A recording unit that records data representing the conditions when forming a pattern image formed by the image forming unit and whose density is detected by the detection unit in a storage unit, and the density detected by the detection unit is A recording unit that records, as the data, a correspondence between the width of the pattern image at a position different from the density of the single color and the condition when the pattern image is formed;
Obtaining means for obtaining image data representing an image formed by the image forming means;
A specifying unit that specifies a width in a direction orthogonal to a moving direction of the region in the medium when the image represented by the image data acquired by the acquiring unit includes an area of a secondary color or more;
Of the data stored in the storage unit by the recording unit, the condition that the image forming unit follows is changed to the condition when the pattern image with the smallest variation in density detected by the detecting unit is formed. When the difference between the width specified by the specifying means and the width represented by the data stored in the storage means is within a predetermined range, the changing means is stored in association with the width. A program for functioning as changing means not using the above condition.

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