JP2010164891A - Control method for image forming and fixing conditions, image forming apparatus, program, and storage medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic image forming apparatus capable of controlling image forming and fixing conditions with high precision by utilizing color information after fixing a primary color patch. <P>SOLUTION: In the control method for the image forming and fixing conditions, a single color toner image having area rate of 100% is formed by an image forming means and is transferred, the color of the toner image after it is fixed by a fixing means is measured, and the image forming conditions are set to optimize amount of adhered toner based on color space coordinate of the color and color space coordinate of the predetermined target color to be reproduced (S201, S202-S209). A single color toner image having area rate of 100% is formed by the image forming means based on the image forming conditions and is transferred, the color of the toner image after it is fixed by the fixing means is measured, and the fixing conditions are controlled based on the color space coordinate of the color and the color space coordinate of the predetermined target color to be reproduced (S201, S210-S213). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as an electrophotographic color copying machine, a color printer, and a color facsimile apparatus, and more particularly to control of image forming conditions and fixing conditions in an electrophotographic image forming apparatus.

  As a color correction method in an electrophotographic color image forming apparatus such as a color copying machine, a color complex machine, or a color printer, conventionally, toner adhesion amount control for each single color has been performed. Since the electrophotographic system uses electrostatic phenomena, changes in the environment where the device is placed, such as temperature and humidity, and deterioration over time of the photoconductor, developer, transfer belt, fixing device, etc. This is because the image output state of the apparatus itself changes and the image reproducibility changes.

  Therefore, in an electrophotographic image forming apparatus, feedback control is used to keep the quality of an output image optimal. In general, in the control of the apparatus itself, that is, the controller, a patch is created with input data having a toner area ratio of 100%. However, an unfixed toner image patch is used to control image forming conditions in the development process, and the fixing process. In the control of fixing conditions, a patch of a fixing toner image formed on a recording medium such as paper is used.

  As a specific example of controlling the image forming conditions, the amount of toner image on the transfer belt is measured by a sensor, an error from the target amount of adhesion is obtained, and this is multiplied by a feedback gain to control the amount of adhesion. There is a way. The reason for controlling the amount of adhesion is that the color reproduction changes depending on the amount of adhesion. The reason why the control patch for the unfixed toner image is used is that the creation and erasure are simpler than the transfer image and the fixed image formed on the paper.

  On the other hand, the reason why the patch after fixing is used in the control of the fixing condition is the image itself finally obtained by the user as the image form, and the image quality can be evaluated including the variation factors in the transfer process and the fixing process. Because. In addition, even if the toner image after fixing has the same adhesion amount, the color reproducibility changes depending on the uneven state of the surface of the toner layer, so even if the fixing condition is controlled to obtain a uniform uneven state. is there. Thus, in order to obtain a stable color reproduction, it is necessary to control both the adhesion amount and the fixing conditions.

  In addition, as an example of the related art related to the present invention, even if the density variation or color variation of the patch after fixing is measured, it is possible to determine whether the variation is due to the variation in the adhesion amount or the variation in the fixing state. Because of the difficulty, the specular reflection light and diffused light on the intermediate transfer belt before fixing are measured with a built-in sensor to control the amount of adhesion, and the gloss of the output patch after fixing is measured to control the fixing conditions. A technique (see Patent Documents 1 and 3) and a technique (see Patent Documents 2 and 3) that read the density or color information of a patch after fixing and control the toner adhesion amount are known.

  However, in the case of the technique disclosed in Patent Document 1, the adhesion amount detection range is narrow with the built-in sensor, or the adhesion amount on the paper changes depending on the transfer efficiency. Therefore, the measured adhesion amount on the intermediate transfer belt is not necessarily the adhesion amount on the paper. There is a problem that they are not equivalent and have low reliability.

  In the case of the technique of Patent Document 2, the toner adhesion amount is controlled using the density value of the patch after fixing. However, since the density does not include information on the entire visible light range, it is highly accurate even when used as a control factor. There is a problem that accurate color reproduction cannot be controlled. In addition, although the patch after fixing is used, since the control factor is used for control other than the fixing condition, there remains a problem that the color reproducibility changes due to fixing fluctuation. Patent Document 2 does not have a specific description using color information as a control factor.

  In the case of the technique disclosed in Japanese Patent Application Laid-Open No. 2003-260260, the color information of the post-fixing patch is used to determine transfer failure or insufficient fixing, but the secondary color is limited. For secondary colors, for example, the cause of fluctuations in the amount of adhesion is not necessarily the same as that of the primary color, such as reverse transfer phenomenon that occurs when colors are superimposed. There is a need to do.

  The present invention has been made in view of the above, and in an electrophotographic image forming apparatus, it will be possible to control image forming conditions and fixing conditions with high accuracy using color information of samples after fixing primary colors. It is what.

The invention of claim 1
An image forming apparatus comprising: an image forming unit that forms a toner image and transfers the toner image to a recording medium; and a fixing unit that fixes the toner image transferred to the recording medium.
A single color toner image having an area ratio of 100% is formed by the image forming unit, transferred to a recording medium, fixed by the fixing unit, and based on the color of the toner image after the fixing and the color space coordinates of a predetermined reproduction target color. An image forming condition control procedure for controlling an image forming condition for determining the toner adhesion amount of the image forming means;
A monochromatic toner image having an area ratio of 100% is formed by the image forming means under the image forming conditions set so that an appropriate toner adhesion amount is obtained by the image forming condition control procedure, and is transferred to a recording medium, and the fixing means And a fixing condition control procedure for controlling the fixing condition of the fixing unit based on the color of the toner image after fixing and the color space coordinates of the predetermined reproduction target color. This is a method for controlling the conditions and fixing conditions.

  According to a second aspect of the present invention, in the image forming condition and fixing condition control method according to the first aspect of the present invention, the color space coordinates of the color of the toner image after the fixing are a white point and a reproduction target by the image forming condition control procedure. The image forming condition is such that the toner adhesion amount is on a straight line connecting the color space coordinates of the colors and close to a predetermined range with respect to the color space coordinates of the reproduction target color.

  According to a third aspect of the present invention, in the image forming condition and fixing condition control method according to the first aspect of the invention, the saturation of the color of the toner image after fixing is more than the saturation of the reproduction target color by the fixing condition control procedure. The fixing condition is controlled to make the toner layer surface smoother when the toner is low, and the fixing condition is controlled to make the toner layer surface more uneven when not.

The invention of claim 4
An image forming apparatus comprising: an image forming unit that forms a toner image and transfers the toner image to a recording medium; and a fixing unit that fixes the toner image transferred to the recording medium.
Colorimetric means for measuring the color of the toner image fixed by the fixing means;
A monochrome toner image having an area ratio of 100% is formed by the image forming means, transferred to a recording medium, fixed by the fixing means, and the reproduced color measured by the color measuring means of the toner image after fixing and a predetermined color Means for executing an image forming condition control procedure for controlling an image forming condition for determining the toner adhesion amount of the image forming means based on the color space coordinates of the reproduction target color of
A monochromatic toner image having an area ratio of 100% is formed by the image forming means under the image forming conditions set so that an appropriate toner adhesion amount is obtained by the image forming condition control procedure, and is transferred to a recording medium, and the fixing means A fixing condition control procedure for controlling the fixing condition of the fixing unit based on the reproduced color measured by the color measuring unit of the toner image after fixing and the color space coordinates of the predetermined reproduction target color And an image forming apparatus.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect of the invention, the color space coordinates of the reproduced color are on a straight line connecting the white point and the color space coordinates of the reproduced target color by the image forming condition control procedure. In addition, the image forming condition is set such that the toner adhesion amount is close to a predetermined range with respect to the color space coordinates of the reproduction target color.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fourth aspect of the present invention, when the saturation of the reproduced color is lower than the saturation of the reproduction target color by the fixing condition control procedure, the toner layer surface is made smoother. The fixing conditions are controlled so that the fixing conditions are controlled so as to make the toner layer surface more uneven.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the fourth aspect of the present invention, the optical condition of the measurement by the color measuring means is 0/45 degrees.

  According to an eighth aspect of the present invention, in the image forming apparatus according to the fifth aspect of the present invention, the color space coordinates of the white point and the reproduction target color are held for each type of a plurality of types of recording media.

  According to a ninth aspect of the present invention, in the image forming apparatus according to the fourth aspect of the present invention, the image forming apparatus has a table holding means for holding a table for associating the toner adhesion amount and its control factor, and the table depends on the result of the image forming condition control procedure. It can be rewritten.

  According to a tenth aspect of the present invention, in the image forming apparatus according to the fourth aspect of the present invention, the image forming apparatus has table holding means for holding a table associating a fixing condition with a control factor thereof, and the table is rewritten by the result of the fixing condition control procedure. It is characterized by that.

  The invention of claim 11 is a program for causing a computer to execute an image forming condition control procedure and a fixing condition control procedure of the control method according to any one of claims 1 to 3.

  According to a twelfth aspect of the present invention, there is provided a computer-readable storage medium storing a program for causing a computer to execute the image forming condition control procedure and the fixing condition control procedure of the control method according to any one of the first to third aspects. is there.

  According to the first to sixth aspects of the present invention, in the image forming apparatus, it is possible to control the image forming conditions and the fixing conditions with respect to the primary color with high accuracy and obtain uniform color reproducibility. In particular, according to the second and fifth aspects of the invention, it is possible to easily control the image forming conditions so that an appropriate toner adhesion amount is obtained by using a straight line connecting the white point and the reproduction target color in the color space. According to the third and sixth aspects of the invention, the fixing conditions can be easily controlled by using the saturation values of the reproduction target color and the reproduction color in the color space. According to the seventh aspect of the present invention, since the color measurement of the toner image after fixing is performed under the same optical conditions as in the case of evaluating the color, it is possible to control the color reproducibility with high accuracy. According to the invention described in claim 8, since the white point (paper white) and the color space coordinates of the reproduction target color are held for each type of recording medium (for example, paper), various types of recording media are stored. It is possible to achieve effects such as control of image forming conditions and fixing conditions corresponding to the recording medium.

1 is a schematic diagram for explaining an overall configuration of an image forming apparatus according to an embodiment of the present invention. It is the schematic for demonstrating the various sensors provided in the image forming apparatus. It is a figure for demonstrating the colorimetric optical conditions of the patch after fixing. FIG. 5 is a block diagram for explaining a configuration related to control of image forming conditions and fixing conditions. 6 is a flowchart illustrating a procedure for controlling image forming conditions and fixing conditions. FIG. 6 is a diagram for explaining a method of controlling a toner adhesion amount and fixing conditions. 6 is a flowchart for explaining a specific example of a procedure for controlling a toner adhesion amount and fixing conditions. It is a figure for demonstrating the process of FIG. It is explanatory drawing of the table which relates exposure light quantity and toner adhesion amount, and its rewriting.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the overall configuration of an image forming apparatus according to an embodiment of the present invention. This image forming apparatus is a so-called tandem type digital color printer, and conveys an image processing system 10 for forming an image corresponding to gradation data of each color and a recording medium (a sheet member such as paper) to the main body 1. A sheet conveying system 40, an image processing apparatus 50 and a controller 55, which are connected to a personal computer, an image reading apparatus, and the like and perform predetermined image processing on the received image data, And an image reading device 60 for reading a document image from a single-sided document. Further, a control unit 80 for controlling operations of the image process system 10 and a fixing device 29 described later is provided.

  The image process system 10 constitutes image forming means for forming a color toner image and transferring it to a recording medium. The image processing system 10 shown here is an image forming unit of four colors of yellow (Y), magenta (M), cyan (C), and black (K) that are arranged in parallel at regular intervals in the horizontal direction. 11Y, 11M, 11C, 11K and the toner images of the respective colors formed on the photosensitive drums 12 of these image forming units 11Y, 11M, 11C, 11K are transferred onto the intermediate transfer belt 21 by multiple transfer. A transfer unit 20 that secondarily transfers a toner image to a recording medium, and a ROS (Raster Output Scanner) 30 that is an optical system unit that irradiates the image forming units 11Y, 11M, 11C, and 11K with laser light. .

  Each of the image forming units 11Y, 11M, 11C, and 11K includes a developing device 13 and a small charger 14 (refer to FIG. 2) called a BCR (Bias Charge Roll). In addition, toner cartridges 19Y, 19M, 19C, and 19K are provided for supplying toner of each color to the developing device 13 of the image forming units 11Y, 11M, 11C, and 11K. Each color toner supplied to the toner cartridges 19Y, 19M, 19C, and 19K is manufactured by melting, kneading, and crushing, classifying, or polymerizing a polyester resin, a colorant, a charge control material, and the like. Further, in order to transfer the toner image formed on the image bearing member onto the intermediate transfer member or the recording medium, an external additive having releasability is added.

  The transfer unit 20 includes an intermediate transfer belt 21 that is an intermediate transfer member, a drive roller 22 that drives the intermediate transfer belt 21, a tension roller 23 that applies a certain tension to the intermediate transfer belt 21, and a toner of each color that is superimposed and transferred to the intermediate transfer belt 21. A backup roller 24 for secondary transfer of the image to the recording medium and a cleaning device 25 for removing residual toner and the like existing on the intermediate transfer belt 21 are provided. The intermediate transfer belt 21 is wound around the drive roller 22, the tension roller 23, and the backup roller 24 with a constant tension, and is rotationally driven by a dedicated drive motor (not shown) excellent in constant speed. The drive roller 22 circulates at a predetermined speed in the direction of the arrow. As the intermediate transfer belt 21, for example, a belt whose resistance is adjusted with a belt material (rubber or resin) that does not cause charge-up is used. The cleaning device 25 includes a cleaning brush 25a and a cleaning blade 25b, and removes residual toner, paper dust, and the like from the surface of the intermediate transfer belt 21 after the toner image transfer process is completed, and performs the next image forming process. It is comprised so that it may prepare for.

  In addition to a semiconductor laser and a modulator (not shown), the ROS 30 includes a polygon mirror 31 that deflects and scans laser light emitted from the semiconductor laser.

  The sheet conveyance system 40 includes a sheet feeding device 41 that loads and supplies a recording medium (hereinafter referred to as “paper”) on which an image is recorded, a nudger roller 42 that picks up and supplies paper from the sheet feeding device 41, and a nudger roller 42. A feed roller 43 that separates and conveys the supplied paper one by one, and a conveyance path 44 that conveys the paper separated by the feed roller 43 toward the image transfer unit. In addition, a registration roller 45 that conveys the paper conveyed through the conveyance path 44 in a timely manner toward the secondary transfer position, and a backup roller 24 that is provided at the secondary transfer position and press-contacts the image on the paper. A secondary transfer roller 46 for secondary transfer is provided. The paper on which the toner image is secondarily transferred by the transfer unit 20 is sent to the fixing device 29. The fixing device 29 fixes the toner image on the paper using heat and pressure by the heat fixing roller 29a and the pressure roller 29b. The paper on which the toner image is fixed by the fixing device 29 is discharged to the discharge tray and accumulated.

  FIG. 2 is a schematic diagram for explaining various sensors built in the main body 1 of the image forming apparatus. In each of the developing devices 13 of the image forming units 11Y, 11M, 11C, and 11K, 91 for detecting the toner concentration is attached in order to keep the internal toner concentration (mixing ratio of the toner and the magnetic carrier) constant. A patch sensor 92 that measures an unfixed toner image on the intermediate transfer belt 21 is attached to the downstream side of the image forming unit 11K and the upstream side of the tension roller 23. A patch sensor 94 for measuring the color of the toner image fixed on the paper is provided between the fixing device 29 and the discharge tray.

  The optical condition for colorimetry by the patch sensor 94 is 0/45 degrees. That is, as schematically shown in FIG. 3, the illumination light is incident on the sample surface at an angle of 0 degrees with respect to the normal to the sample surface, and the reflected light from the sample surface is received at an angle of 45 degrees. Done. This is the same optical condition that is generally applied when measuring paper or sample patches for color evaluation.

  The normal operation of this image forming apparatus is generally as follows. Yellow (Y), magenta (M), cyan (C), and black (K) color gradation data corresponding to the image data input from the personal computer or the image reading device 60 is generated by the image processing unit 50 and the ROS 30. Is input. In the ROS 30, for example, a laser beam modulated by corresponding color gradation data is emitted from a semiconductor laser (not shown) corresponding to each color of Y, M, C, and K, and this laser beam is emitted from an f-θ lens (not shown). The photosensitive drum 12 of the image forming units 11Y, 11M, 11C, and 11K is scanned and exposed through an imaging lens (not shown) and a plurality of mirrors. On the photosensitive drums 12 of the image forming units 11Y, 11M, 11C, and 11K, the surface charged by the charger 14 is scanned and exposed with a laser beam, whereby an electrostatic latent image of each color is formed. The formed electrostatic latent images of the respective colors are developed into toner images of the respective colors Y, M, C, and K by the developing device 13. The toner images of the respective colors formed on the photosensitive drums 12 of the image forming units 11Y, 11M, 11C, and 11K are transferred onto an intermediate transfer belt 21 that is an intermediate transfer member.

  On the other hand, in the sheet conveying system 40, the nudger roller 42 rotates in synchronization with the image formation timing, and a predetermined size of paper is supplied from the paper feeding device 41. The paper separated one by one by the feed roller 43 is conveyed to the registration roller 45 through the conveyance path 44 and is temporarily stopped. Thereafter, the registration roller 45 rotates in accordance with the movement timing of the intermediate transfer belt 21 on which the toner image is formed, and the paper is conveyed to the secondary transfer position formed by the backup roller 24 and the secondary transfer roller 46. On the paper conveyed from the lower side to the upper side at the secondary transfer position, the toner images in which the four colors are multiplexed are sequentially transferred in the sub-scanning direction using the press contact force and a predetermined electric field. The paper on which the toner image has been transferred undergoes a fixing process with heat and pressure by the fixing device 29 and is then discharged to a discharge tray.

  Next, control of image forming conditions and fixing conditions will be described. FIG. 4 is a block diagram for explaining an apparatus configuration related to control of image forming conditions and fixing conditions. The apparatus configuration shown in FIG. 4 is incorporated in the control unit 80. FIG. 5 is a flowchart for explaining a procedure for controlling image forming conditions and fixing conditions.

  Reference is first made to FIG. In FIG. 4, a color information acquisition unit 801 is means for converting a colorimetric value obtained by the patch sensor 94 into color information (color space coordinates) of a predetermined color space. Here, for example, the colorimetric value output from the patch sensor 94 is a spectral reflectance, and this is converted into coordinates (L *, a *, b *) in the CIELab space by the color condition acquisition unit 801.

  The image forming condition control unit 804 is a means for setting image forming conditions in the image process system 10 which is an image forming means. The image forming condition is a condition for determining or controlling the toner adhesion amount of the toner image. The table storage unit (1) 805 is a means for storing the setting result by the image forming condition control unit 804. Specifically, the set image forming condition is associated with the toner adhesion amount and its control factor (described later). Remembered as a table. The toner adhesion amount may be simply referred to as an adhesion amount. When the image forming condition setting is changed by the image forming condition control unit 804, the image forming condition control unit 804 causes the table in the table storage unit (1) 805 to reflect the change in the setting of the image forming condition. Rewritten. The fixing condition control unit 806 is a means for setting the fixing conditions of the fixing device 29 which is a means for fixing the toner image on the paper. The table storage unit (2) 807 is a means for storing the setting result by the fixing condition control unit 806. Specifically, the set fixing condition is a table associating the fixing condition with its control factor (described later). I remember it. When the setting of the fixing condition is changed by the fixing condition control unit 806, the table in the table storage unit (2) 807 is rewritten by the fixing condition control unit 806 to reflect the change of the setting of the fixing condition. The determination unit (1) 802 is a means for determining whether or not a change in image formation condition setting (adhesion amount control) is necessary, and the determination unit (2) 803 requires a change in fixing condition setting. It is means for determining whether or not there is. The patch output control unit 808 generates control patch data for outputting a monochromatic toner image having an area ratio of 100%, which is a control patch for controlling the image forming condition or the fixing condition, and inputs this to the ROS 30. , Means for instructing the output. Here, the single color is a primary color, that is, three colors of yellow (Y), magenta (M), and cyan (C), and the control patch data is primary color solid image data. The procedure control unit 809 is means for controlling each unit such as 804, 806, and 808 according to the procedure of FIG.

  Next, the procedure for controlling the image forming conditions and fixing conditions shown in FIG. 5 will be described in association with the apparatus configuration shown in FIG. The control mode procedure as shown in FIG. 5 is started by an instruction from an operation panel (not shown) of the image forming apparatus or an external personal computer, for example.

  When entering the control mode, the procedure control unit 809 instructs the patch output control unit 808 to output the control patch, and the patch output control unit 808 generates control patch data and inputs it to the ROS 30 to output the control patch. , The toner image of the control patch is formed by the image process system 10 and transferred to paper, and is fixed on the paper by the fixing device 29 (step S101). When this control patch is output, the image processor 10 forms an image under the image forming conditions stored in the table storage unit (1) 805 in the form of a table, and the fixing device 29 uses the table storage unit ( 2) Fixing is performed under fixing conditions stored in the form of a table in 907.

  In the present invention, the image forming conditions are controlled, and the fixing conditions are controlled after that. Since the preceding image forming conditions are controlled for each of the colors Y, M, and C, a control patch for each color is output. At this time, these three color control patches may be output simultaneously, or the control patches may be output one color at a time. In any case, image forming conditions are controlled for each color by using control patches for each color of Y, M, and C. On the other hand, since the control of the fixing condition performed after the control of the image forming condition is performed for one primary color, for example, magenta (M), it is sufficient to output only the control patch for that color.

  Now, the fixing patch 29 measures the color of the control patch after fixing by the patch sensor 94 (step S102). Colorimetric values obtained by the patch sensor 94 are converted into color information by the color information acquisition unit 801 (step S103). The determination unit (1) 802 determines whether it is necessary to change the setting of image forming conditions based on the color information (step S104).

  When it is determined that the image forming condition setting needs to be changed, the procedure control unit 809 activates the image forming condition control unit 804, and the image forming condition control unit 804 changes the setting of the image forming condition based on the color information. Then, the table in the table storage unit (1) 805 is rewritten (step S106). Then, the patch output control unit 808 is operated by the procedure control unit 809, control patch data is generated again and input to the SOP 30 to instruct the output of the control patch, and the control patch is output (S101). . At this time, image formation is performed under the changed image forming conditions stored in the table storage unit (1) 805 in the form of a table, and the changes stored in the table storage unit (2) 807 in the form of a table. Fixing is performed under subsequent fixing conditions (S101).

  The output control patch after fixing is colorimetrically measured (S102), the colorimetric value is converted into color information (step S103), and the determination unit (1) 802 needs to change the setting of image forming conditions. It is determined whether or not (step S104). When it is determined that the setting change is necessary, the image forming condition control unit 804 changes the setting of the image forming condition again (step S106), and the control patch is output under the changed image forming condition (step S101). .

  By controlling the image forming conditions in this way, the control of the image forming conditions ends when it is determined that it is not necessary to change the setting of the image forming conditions for all the colors Y, M, and C. The subsequent procedure flow is controlled according to the determination result of the determination unit (2) 803.

  That is, the determination unit (2) 803 determines whether or not the fixing condition setting needs to be changed (step S105). This determination is made only for color information obtained by measuring one primary color, here, the magenta (M) control patch. When it is determined that the fixing condition setting needs to be changed, the procedure control unit 809 activates the fixing condition control unit 806. The fixing condition control unit 806 measures the magenta (M) control patch, changes the setting of the fixing condition based on the acquired color information, and rewrites the table in the table storage unit (2) 807 (step S107). The patch output control unit 808 is activated by the procedure control unit 809, magenta (M) control patch data is generated and input to the SOP 30 to instruct the output of the control patch, and the image processing system 10 controls the control patch. The toner image is formed and transferred to the paper, and the toner image is fixed on the paper by the fixing device 29 (step S101). The patch for control after fixing is measured by the patch sensor 94 (step S102), the measured color value is converted into color information (step S103), and the setting of the fixing condition needs to be changed by the determination unit (2) 803. Is determined (step S105). If it is determined that the fixing condition setting needs to be changed, the fixing condition control unit 806 changes the fixing condition setting based on the color information and rewrites the table in the table storage unit (2) 807 (step S107). The patch output control unit 808 generates magenta (M) control patch data and inputs it to the SOP 30 to instruct the output of the control patch and output the control patch (step S101).

  When the fixing conditions are controlled in this way and the determination unit (2) 803 determines that there is no need to change the setting of the fixing conditions, the control mode ends.

  Up to this point, the procedure for controlling the image forming conditions and the fixing conditions and the related apparatus configuration have been described. Hereinafter, specific contents of the control of the image forming conditions and the control of the fixing conditions will be described.

  With reference to FIG. 6, a method of controlling the adhesion amount and fixing conditions will be described. FIG. 6 shows the relationship between saturation and lightness in a certain monochromatic hue, with the horizontal axis representing saturation and the vertical axis representing lightness.

  The inventors' experiments have shown that when the amount of adhesion is changed by changing the thickness of the toner layer, the reproduced color moves on the locus of Line A. That is, as the toner layer is made thicker, it passes through the highest saturation point SP where the saturation is maximum so as to draw an arc from WP (white point) which is paper white. When the maximum saturation point SP is exceeded, the saturation does not increase even if the adhesion amount is increased further, and the saturation and lightness decrease as if the arc is drawn again. The surface shape of the toner layer is constant. In the example of FIG. 6, the surface shape of the toner layer moving on Line A is a mirror surface. The mirror surface has the maximum gloss and the highest saturation color reproduction with the same adhesion amount.

  Next, the relationship between the uneven shape on the toner layer surface and color reproduction will be described. If the surface of the toner layer is uneven, diffused light from the surface increases and white light is added to the reproduced color. In other words, when the surface of the toner layer is a mirror surface and the coordinates of the reproduced color are point SP, if the toner layer surface is uneven, the reproduced color moves on Line B connecting point SP and point WP toward point WP. To do. More precisely, the reproduced color moves on the line connecting the point SP and the “arbitrary white point” toward the “arbitrary white point”, but the “arbitrary white point” is substituted with paper white. I do not care. This is because, generally, a reproduction target color with an area ratio of 100% is set near a mirror surface (that is, Line A), and thus the distance from the white point becomes sufficiently large. If the toner layer surface is a mirror surface and the toner adhesion amount is such that the reproduced color coordinates are at point P in FIG. 6, the reproduced color coordinates are pointed on Line C connecting points P and WP when the toner layer surface is uneven. Move towards WP. As described above, if the adhesion amount and the uneven state (that is, the fixing condition) of the toner layer surface are uniquely determined, the reproduction color on the saturation lightness coordinate is determined.

  Therefore, when it is desired to reproduce the color coordinate point O in FIG. 6, first, an appropriate amount of adhesion, that is, an appropriate image forming condition is determined, and then a fixing condition is determined. The condition for the proper adhesion amount is that the reproduction color coordinate point exists on a straight line (ie, Line B) connecting the point O and the point WP when the surface shape of the toner layer is arbitrary but close to a mirror state. When the shape of the toner layer surface changes depending on the fixing conditions, the reproduced color moves on a line connecting the coordinate points O and WP. Accordingly, the fixing conditions may be controlled so that the coordinate point O of the reproduction target color can be reproduced under the condition of an appropriate amount of adhesion.

  Based on the above understanding, the specific contents of steps S104, S105, S106, and S107 in FIG. 5 will be described. FIG. 7 is a flowchart for explaining this, and FIG. 8 is a view similar to FIG. 6 for explaining FIG.

  7, steps S202 and S206 are steps corresponding to step S104 in FIG. 5, and steps S203, S204, S205, S207, S208, and S209 are steps corresponding to step S106 in FIG. 5, and step S210. Are steps corresponding to step S105 in FIG. 6, and steps S211, S212, and S213 are steps corresponding to step S107 in FIG. Steps S101, S102, and S103 in FIG. 5 are shown in a form summarized in one step S201 in FIG. As described above, in steps S202, S203, S206, and S207, the color information acquired for yellow (Y), magenta (M), and cyan (C) is targeted, but in steps S210 and S211, about magenta (M). Only acquired color information is targeted.

Reproduction color coordinate points O _i : (L ^* _oi , a ^* _oi , b ^* _oi ) obtained by measuring the control patch, and reproduction target color coordinate points O: (L ^* _o , a ^* _o , It is determined whether or not the color difference ΔE _i with respect to b ^* _o ) is equal to or smaller than the threshold Th (step S202).

ΔE _i = sqrt ((L ^* _o− L ^* _oi ) ^ 2 + (a ^* _o− a ^* _oi ) ^ 2
^{_{+ (B * o -b * oi}} ) ^ 2)
Here, the threshold value Th will be described. In order to control the amount of adhesion, as described above, the reproduced color must be present on Line B in the saturation lightness coordinate plane (see FIG. 8). However, as the amount of adhesion decreases, the reproduced color approaches WP, which is paper white. That is, even when the adhesion amount is extremely small, the reproduced color may exist on Line B. Therefore, the reproduction color must be close to the reproduction target color to some extent and on Line B. Since the determination in step S202 is a determination for such a purpose, the threshold Th does not have to be as small as a general human perception limit. Specifically, Th can be a value in the range of 5.0 to 7.0.

If it is determined in step S202 that the color difference ΔE _i between the two points is not less than or equal to the threshold Th, the image forming conditions are changed, that is, the adhesion amount is increased or decreased (steps S203 to S205). First, the comparison between the lightness ^L _{* oi} the reproduced color lightness ^L _{* o} a reproduction target color (step S203). When L ^* _oi > L ^* _o , the image forming condition is changed so as to increase the adhesion amount (step S204), and otherwise, the image forming condition is changed so as to reduce the adhesion amount (S205). Then, i is incremented and the process returns to step S201.

On the other hand, if the two-point color difference ΔE _i is equal to or smaller than the threshold Th in step S202, it is determined whether or not the reproduced color exists on Line B (step S206). Various methods can be used for this determination. Here, for example, a linear equation that passes through the coordinate point O of the reproduction target color and the coordinate point WP of the paper white is derived on the saturation lightness coordinate plane, and the equation is derived. A method of checking whether or not the reproduction color coordinate point O _i exists above is used.

  If it is determined that the reproduced color is not on Line B, the image forming condition is changed, that is, the adhesion amount is increased or decreased (steps S207 to S209). Please refer to FIG. As described above, in FIG. 8, the horizontal axis is the saturation and the vertical axis is the lightness, as in FIG. 6, and Line A and Line B are written in the same manner as in FIG.

Since the locus of the reproduced color follows Line A in FIG. 8 according to the amount of adhesion, the lightness L ^* _oi of the reproduced color and the lightness L ^* of the coordinate point O _{i ′} that exists on Line B and has the same saturation as the reproduced color ^. Comparison with _{oi ′} is performed (step S207). If it is determined that L ^* _oi > L ^* _{oi ′} , the image forming condition is changed so as to increase the adhesion amount (step S208), and if not, the image forming condition is changed so as to reduce the adhesion amount ( Step S209). Then, i is incremented and the process returns to step S201.

By repeating the operation of changing the image forming conditions and outputting the control patch as described above, the adhesion amount is controlled to be an appropriate adhesion amount, that is, the color difference between the reproduction color and the reproduction target color is equal to or less than the threshold Th. next, and the coordinate point O _i of reproduced color glue on LineB, end the control of the image forming conditions, so that the control of the original in fixing conditions of the image forming condition is performed.

That is, the color difference evaluation Delta] E _i of the coordinate point O of the reproduction target color coordinate point _{O i} reproduction colors riding on LineB of whether or not another threshold Th1 or less (step S202).

  Here, in step S210, since it is determined whether or not the reproduction color and the reproduction target color are substantially the same, the threshold value Th1 is different from the threshold value Th used in step S202 and is similar to a general human perception limit. Must be small. Specifically, the threshold value Th1 is selected as a value in the range of 1.0 to 3.0.

Next, when it is determined that the color difference between the reproduced color and the target reproduced color is not equal to or less than the threshold Th1, the fixing conditions are changed (steps S211 to S213). That is, it is determined whether the saturation C _i of the reproduction color is smaller than the saturation C of the reproduction target color (step S211). Here, the saturation C _i of the reproduced color is expressed by the following equation.
^{_{C i = sqrt ((a *}} o -a * oi) ^ 2 + (b * o -b * oi) ^ 2)
If C> C _i , the fixing condition is changed so that the uneven shape of the toner layer surface is close to the mirror surface (step S212). Conversely, if the saturation of the reproduced color is higher than the target color, the surface of the toner layer The fixing conditions are changed so as to be more uneven than the current state (step S213). After changing the fixing conditions, i is incremented and the process returns to step S201. A control patch (only a cyan patch may be used) is output under the changed fixing condition, and the processing of steps S210 to S213 is performed on the reproduced color obtained by the color measurement. By repeating such a process, an appropriate fixing condition is determined under an appropriate amount of adhesion.

  As described above, by measuring the color of the toner image after fixing and comparing the reproduction color with the reproduction target color to control the image forming condition and the fixing condition, it is appropriate to obtain the target color reproduction. The toner adhesion amount and the fixing state can be ensured.

  The correspondence between the claims and FIGS. 4, 5, and 7 will be briefly described. The processing loop of S101 → S102 → S103 → S104 → S106 → S101 in FIG. 5 and the processing loop of S201 → S202 → S203 → S204 / S205 → S201 or S201 → S206 → S207 → S208 / S209 → S201 in FIG. This corresponds to a forming condition control procedure. Further, the processing loop of S101 → S102 → S103 → S105 → S107 → S101 in FIG. 5 and the processing loop of S201 → S210 → S211 → S212 / S213 → S201 in FIG. 7 correspond to the fixing condition control procedure. In FIG. 4, the means for executing the image forming condition control procedure is realized by a color information acquisition unit 801, a determination unit (1) 802, a procedure control unit 809, an image forming condition control unit 804, and a patch output control unit 808. The means for executing the fixing condition control procedure is realized by the color information acquisition unit 801, the determination unit (2) 803, the procedure control unit 809, the fixing condition control unit 806, and the patch output control unit 808.

  Such an image forming condition control procedure or its execution means, a fixing condition control procedure or its execution means may be realized by hardware, but a microcomputer having a general configuration including a microprocessor and a memory is used. It can also be realized by a program. Such a program and various computer-readable storage media such as a semiconductor memory, various memory cards, a magnetic disk, an optical disk, and a magneto-optical disk in which the program is recorded are also included in the present invention.

  In general, the image forming conditions and the fixing conditions, particularly the fixing conditions, vary depending on the type of paper. Therefore, the present invention also includes a mode in which these conditions are controlled for each paper type. For example, the paper space used as a white point and the color space coordinates of the reproduction target color are stored for each paper type in a storage device (not shown) in the control unit 80 and supplied from the sheet conveying system 40. The control according to the above-described procedure may be performed using information on paper white and reproduction target color corresponding to the type of paper to be printed. Naturally, the present invention also includes a mode for performing control suitable for such a paper type.

  Here, the control factor of the toner adhesion amount will be described. The control factors of the adhesion amount are toner density in the developing unit 13, developing bias, exposure light amount of the photosensitive drum 12 by the ROS 30, charging voltage of the photosensitive drum 12 by the charger 14, image digital signal, before being transferred to paper. This is the amount of adhesion of the control patch. As described above, the table storage unit (1) 805 holds a table for associating the toner adhesion amount with its control factor. When the image formation condition control unit 804 controls the image formation condition, that is, the toner adhesion amount, Rewrite the table to reflect the result in the table.

  The table and the rewriting thereof will be described with reference to FIG. 9, taking the exposure light quantity as an example of the control factor. 9A shows a table before rewriting, FIG. 9B shows a table after rewriting, the horizontal axis represents the toner adhesion amount, and the vertical axis represents the toner exposure light amount. Here, it is desirable that the exposure light amount and the toner adhesion amount have a linear relationship. The toner adhesion amount of the control patch for which an output instruction is issued by the patch output control unit 808 (FIG. 4) is originally 0.4 (Mg / cm ^ 2). In this case, the exposure light amount is α from the table shown in FIG. 9A, and the reproduction color coordinate point should be on Line B in FIG. However, it is assumed that the amount of exposure light for obtaining a reproduction color in FIG. That is, since the exposure light amount necessary to obtain the original deposition amount of 0.4 (Mg / cm ^ 2) is α ′, a table showing the relationship between the deposition amount and the exposure light amount is shown in FIG. Rewritten as a solid line.

  Further, examples of the control factors for the fixing conditions include the fixing temperature of the fixing device 29, the fixing speed, and the fixing pressure. As described above, the table storage unit (2) 807 holds a table for associating the fixing conditions with their control factors, and when the fixing conditions are controlled by the fixing condition control unit 806, the control result is reflected. The table is rewritten.

DESCRIPTION OF SYMBOLS 10 Image process system 11 Image forming unit 20 Transfer unit 29 Fixing device 30 ROS (Raster Output Scanner)
80 control unit 94 patch sensor for measuring the color of a toner image after fixing 801 color information acquisition unit 802 803 determination unit 804 image forming condition control unit 805 table storage unit 806 fixing condition control unit 807 table storage unit 808 patch output control unit 809 Procedure control unit

JP 2006-267165 A JP-A-10-63048 JP 2006-259142 A

Claims (12)

An image forming apparatus comprising: an image forming unit that forms a toner image and transfers the toner image to a recording medium; and a fixing unit that fixes the toner image transferred to the recording medium.
A single color toner image having an area ratio of 100% is formed by the image forming unit, transferred to a recording medium, fixed by the fixing unit, and based on the color of the toner image after the fixing and the color space coordinates of a predetermined reproduction target color. An image forming condition control procedure for controlling an image forming condition for determining the toner adhesion amount of the image forming means;
A monochromatic toner image having an area ratio of 100% is formed by the image forming means under the image forming conditions set so that an appropriate toner adhesion amount is obtained by the image forming condition control procedure, and is transferred to a recording medium, and the fixing means And a fixing condition control procedure for controlling the fixing condition of the fixing unit based on the color of the toner image after fixing and the color space coordinates of the predetermined reproduction target color. Control method of conditions and fixing conditions.   According to the image forming condition control procedure, the color space coordinates of the color of the toner image after fixing are on a straight line connecting the white point and the color space coordinates of the reproduction target color, and predetermined with respect to the color space coordinates of the reproduction target color. 2. The method of controlling image forming conditions and fixing conditions according to claim 1, wherein the image forming conditions are such that the toner adhesion amount is close to the range of the above.   According to the fixing condition control procedure, when the saturation of the color of the toner image after fixing is lower than the saturation of the reproduction target color, the fixing condition is controlled so as to make the toner layer surface smoother. 2. The image forming condition and fixing condition control method according to claim 1, wherein the fixing condition is controlled to make the toner layer surface more uneven. An image forming apparatus comprising: an image forming unit that forms a toner image and transfers the toner image to a recording medium; and a fixing unit that fixes the toner image transferred to the recording medium.
Colorimetric means for measuring the color of the toner image fixed by the fixing means;
A monochrome toner image having an area ratio of 100% is formed by the image forming unit, transferred to a recording medium, fixed by the fixing unit, and the reproduced color measured by the colorimetric unit of the toner image after fixing and a predetermined color Means for executing an image forming condition control procedure for controlling an image forming condition for determining the toner adhesion amount of the image forming means based on the color space coordinates of the reproduction target color of
A monochromatic toner image having an area ratio of 100% is formed by the image forming means under the image forming conditions set so that an appropriate toner adhesion amount is obtained by the image forming condition control procedure, and is transferred to a recording medium, and the fixing means A fixing condition control procedure for controlling the fixing condition of the fixing unit based on the reproduced color measured by the color measuring unit of the toner image after fixing and the color space coordinates of the predetermined reproduction target color And an image forming apparatus.   According to the image forming condition control procedure, the color space coordinates of the reproduction color are on a straight line connecting the white point and the color space coordinates of the reproduction target color, and are close to a predetermined range with respect to the color space coordinates of the reproduction target color. The image forming apparatus according to claim 4, wherein the image forming condition is such that the toner adhering amount is set.   According to the fixing condition control procedure, when the saturation of the reproduced color is lower than the saturation of the reproduction target color, the fixing condition is controlled so as to make the toner layer surface smoother. The image forming apparatus according to claim 4, wherein the fixing conditions are controlled so as to be more uneven.   5. The image forming apparatus according to claim 4, wherein an optical condition of measurement by the color measuring unit is 0/45 degrees.   6. The image forming apparatus according to claim 5, wherein the color space coordinates of the white point and the reproduction target color are held for each type of recording medium.   5. The image forming apparatus according to claim 4, further comprising a table holding unit that holds a table associating a toner adhesion amount and a control factor thereof, and the table is rewritten according to a result of the image forming condition control procedure.   5. The image forming apparatus according to claim 4, further comprising table holding means for holding a table associating a fixing condition with a control factor thereof, wherein the table is rewritten according to a result of the fixing condition control procedure.   A program for causing a computer to execute the image forming condition control procedure and the fixing condition control procedure of the image forming condition and fixing condition control method according to any one of claims 1 to 3.   A computer-readable storage medium storing a program for causing a computer to execute the image forming condition control procedure and the fixing condition control procedure of the image forming condition and fixing condition control method according to any one of claims 1 to 3.

Images