JP4047307B2 - Image forming apparatus and method of controlling the apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus for forming an image on a recording material and a control method for the apparatus.

  In recent years, color image forming apparatuses such as color printers and color copying machines have been required to improve the output image quality. In particular, the density gradation of the formed image and the stability of the gradation reproduction are important factors that determine the quality of the output image. However, in the image forming apparatus, the density and chromaticity of the formed image are fluctuated due to a change factor of each part of the apparatus due to a change in environment or long-term use. In particular, in the case of an electrophotographic color image forming apparatus, even a slight environmental change may cause a change in the density and chromaticity of an image to be formed, resulting in a loss of color balance. For this reason, it is necessary to always have means for maintaining a constant concentration.

  Therefore, a toner image for density detection (hereinafter referred to as a patch) is formed on an intermediate transfer member or a photosensitive member, which is an image carrier, using the toner of each color, and the density of the formed unfixed toner patch is used for the unfixed toner. It is configured to obtain a stable image by detecting with a density detection sensor (hereinafter referred to as a density sensor) and feeding back the process conditions such as exposure amount and development bias based on the detection result and performing density control. Yes. However, density control using such a density sensor is based on the density of a patch formed on an intermediate transfer member, a photosensitive drum, etc., and even changes in image color balance due to transfer to a transfer material and fixing. Cannot be controlled. That is, the density control using the above-described density sensor cannot cope with the density change in the transferred image.

Therefore, a sensor (hereinafter referred to as a color sensor) that detects the density or chromaticity of the patch on the transfer material is installed, and the color reproducibility is corrected by correcting the density and chromaticity of the toner image based on the measurement result of the color sensor. Has been proposed (Patent Document 1). This color sensor uses, for example, three or more light sources having different emission spectra such as red (R), green (G), and blue (B) as light emitting elements, or the light emitting element emits white light (W). And three or more types of filters having different spectral transmittances such as red (R), green (G), and blue (B) are formed on the light receiving element. As a result, three or more different outputs such as RGB output are obtained.
JP 2003-107833 A

  As one means for improving the accuracy of color balance correction in an image forming apparatus using this color sensor, a method of increasing the number of patches can be considered. However, a certain time is required for the color sensor to detect the density and chromaticity of one patch. For this reason, even if an attempt is made to correct the color balance by increasing the number of patches, it becomes impossible to read all the patches while the transfer material is moving, and therefore it is not possible to form all the patches on one transfer material. was there. Similarly, as the throughput of the image forming apparatus is improved, it is necessary to increase the length of one patch in the conveyance direction, so that the number of patches that can be formed per transfer material is reduced and the color balance is corrected. In addition, more transfer material and toner are consumed.

  In order to use only a single transfer material for color balance correction, it is necessary to use a transfer material that is longer in the conveyance direction than the transfer material that is normally used for color balance correction. However, such mounting of the transfer material is a troublesome operation for the user. Further, since the transfer material on which the patch for color balance correction is formed and the transfer material on which the patch is formed are unnecessary for the user, the minimum number of transfer materials are used and the patch is used. It is desirable that the consumption of toner used for forming is also minimal.

The present invention has been made in view of the above problems, characteristic of the present invention provide a depression example while the image forming apparatus and a control method thereof can be reliably measured density and chromaticity of the patch consumption of the recording material There is.

An image forming apparatus according to an aspect of the present invention has the following configuration. That is,
Image forming means for forming an image on a recording sheet, and a patch forming means for forming a patch on a recording sheet, a conveyance control means for conveying the recording paper patch was formed on the conveying means, is conveyed by said conveying means comprising a detection means for detecting the concentration or chromaticity of a formed on the recording paper patch, and a correcting means for correcting the image forming property of the image forming means on the basis of the detected density or chromaticity by said detecting means An image forming apparatus,
Means for obtaining size information of the recording paper,
When the size information of the first recording paper having the first length in the transport direction is obtained by the obtaining means, the patch forming means applies the first patch on the first recording paper to a predetermined required for correcting the image forming characteristics. When the size information of the second recording paper of the second length which is shorter than the first recording paper and cannot form the predetermined number of first patches is obtained by the obtaining means, Forming the predetermined number of second patches having a shorter length in the transport direction than the first patch on the second recording paper;
When the size information of the first recording paper is obtained by the obtaining means, the conveyance control means detects the first recording paper on which the predetermined number of first patches are formed, and detects the second patch. When the size information of the second recording paper is obtained by the obtaining means and the obtaining means obtains the size information of the second recording paper without lowering to the second speed for the detection, the predetermined number of second patches are obtained. Transporting the formed second recording paper to the transport means at the second speed slower than the first speed;
The detecting means includes density or chromaticity of the predetermined number of first patches formed on the conveyed first recording paper and the predetermined number of second patches formed on the second recording paper. Is detected .

An image forming apparatus control method according to an aspect of the present invention includes the following steps. That is,
An image forming means for forming an image on the recording paper is provided , a patch is formed on the recording paper, the recording paper on which the patch is formed is conveyed, and the density or chromaticity of the patch is detected. Is a control method of an image forming apparatus for correcting image forming characteristics in the image forming means based on chromaticity ,
Obtaining the recording paper size information;
In the obtaining step, when the size information of the first recording paper whose transport direction is the first length is obtained, a predetermined number of first patches necessary for correcting the image forming characteristics are formed on the first recording paper, In the obtaining step, when the size information of the second recording paper having the second length that is shorter than the first recording paper and in which the predetermined number of first patches cannot be formed is obtained, the second recording A patch forming step of forming the predetermined number of second patches having a shorter length in the transport direction than the first patch on paper;
When the size information of the first recording paper is obtained in the obtaining step, the first recording paper on which the predetermined number of first patches are formed is moved to the second speed for detecting the second patch. When the size of the second recording paper is obtained in the obtaining step, the second recording paper on which the predetermined number of second patches are formed is transferred from the first speed. Transporting at a slower second speed,
Detecting the density or chromaticity of the predetermined number of first patches formed on the conveyed first recording paper and the predetermined number of second patches formed on the second recording paper; , characterized by having a.

According to the present invention, according to the length of the recording material, the conveyance speed of the recording material at the time of patch detection and the length of each patch are made variable, and the density and chromaticity of the patch are reliably ensured while suppressing the consumption of the recording material Can be measured .

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing a schematic configuration of a four-drum type full-color image forming apparatus 1 that employs an electrophotographic system and uses an intermediate transfer belt as an example of an image forming apparatus according to an embodiment of the present invention. .

  In FIG. 1, a four-drum type full-color image forming apparatus 1 has a printer engine (hereinafter simply referred to as “printer engine”) 2 for forming a four-drum type full-color image. P (PY, PM, PC, PBk) includes yellow (Y: PY), magenta (M: PM), cyan (C: PC), and black (Bk: PBk) that are detachably provided on the printer engine 2. The process cartridge for each color. 31 is an intermediate transfer belt unit having an intermediate transfer belt 30 as an intermediate transfer member, and 25 is a fixing device.

  Each process cartridge P is arranged on a photosensitive drum 26 (26Y, 26M, 26C, 26Bk) which is an image carrier, and on the outer peripheral surface of each photosensitive drum 26, and the surface of the photosensitive drum is made uniform. The electrostatic latent image of each color on the surface of the photosensitive drum formed by the exposure of the laser beam from the primary charger 50 to be charged and the laser exposure device 28 (28Y, 28M, 28C, 28Bk) is converted into a corresponding yellow color. And a developing device 51 for developing using magenta, cyan, and black toners. Each process cartridge is arranged in the order of Y, M, C, and Bk from the upstream side along the moving direction of the intermediate transfer belt 30. Further, a primary transfer roller 52 that forms a primary transfer portion together with the photosensitive drum 26 is disposed opposite to the position where the intermediate transfer belt 30 is sandwiched with the photosensitive drum 26. 53 is a cleaner for removing toner remaining on the drum surface without being transferred.

  The intermediate transfer belt unit 31 includes an intermediate transfer belt 30 and three rollers: a driving roller 100 that stretches the intermediate transfer belt 30, a tension roller 105, and a secondary transfer counter roller 108. The secondary transfer roller 27 is disposed at a position that faces the secondary transfer counter roller 108 and sandwiches the intermediate transfer belt 30. A transfer conveyance unit 33 holds the secondary transfer roller 27.

  Further, the paper feeding unit 3 feeds the transfer material P to the secondary transfer unit constituted by a contact portion between the secondary transfer roller 27 and the secondary transfer counter roller 108 sandwiching the intermediate transfer belt 30. The feeding unit 3 includes a cassette 20 that stores a plurality of transfer materials P, a feeding roller 21, a retard roller pair 22 for preventing double feeding, a pair of conveying rollers 23a and 23b, a pair of registration rollers 24, and the like. . The cassette 20 is provided with a rear end regulating plate 19 for regulating the rear end of the loaded transfer material P. The rear end regulating plate 19 is configured to be movable according to the size of the transfer material P accommodated in the cassette 20, and the length in the transport direction of the transfer material P by a rear end regulating plate position detecting means (not shown). Can be detected (hereinafter, size detection).

  Further, discharge roller pairs 61, 62, 63 are provided along the conveyance path 60 in the downstream conveyance path of the fixing device 25, and the fixing device is disposed in the discharge conveyance path 60 between the discharge roller pairs 61, 62. The color sensor 90 is installed at a position separated from the roller nip portion 25 by a distance Y on the downstream side.

  FIG. 2 is a block diagram showing a control configuration of the image forming apparatus according to the embodiment of the present invention.

  The apparatus main body 1 receives an image signal (RGB signal) from an external host device 10 such as a personal computer that is communicably connected to the apparatus main body 1 or a document reading unit (not shown) provided separately in the apparatus main body 1. ). The image processing unit 11 converts the received RGB signal into a CMYK signal, corrects gradation and density, and then generates an exposure signal for the laser exposure unit 28. The image forming control unit 12 controls the image forming operation described below in an integrated manner, and controls the apparatus main body 1 at the time of color balance correction using the color sensor 90. The image forming unit 13 is a block that collectively shows elements for forming an image on the transfer material P, and is a main part of the printer engine 2 of FIG. The size detection unit 14 detects the size of the transfer material P (transfer material P accommodated in the cassette 20) used by the user for image formation. In the present embodiment, the size detection means of the transfer material P by the rear end regulating plate 19 described above is shown. The conveyance motor 15 is a driving unit that can change the conveyance speed of the transfer material P passing through the discharge conveyance path 60 that is the installation unit of the color sensor 90 at a predetermined timing according to an instruction from the image formation control unit 12. Only the transfer speed of the transfer material P in the path 60 may be changed, or the transfer speed of the transfer material P in the entire apparatus 1 may be changed. The color sensor unit 16 detects the density or chromaticity of the patch on the transfer material P using the color sensor 90 described above.

  An image forming operation of the four-drum type full-color image forming apparatus 1 configured as described above will be described.

  When the image forming operation is started, the transfer material P in the cassette 20 is first fed by the rotation of the feed roller 21, and then separated one by one by the retard roller pair 22, and then the transport roller pair 23a, Then, the sheet is conveyed to the registration roller pair 24 through 23b and the like. At this time, the registration roller pair 24 has stopped rotating, and the transfer material P is abutted against the nip of the registration roller pair 24, whereby the skew of the transfer material P is corrected.

  On the other hand, in parallel with the transfer operation of the transfer material P, in the yellow process cartridge PY, for example, the surface of the photosensitive drum 26Y is first uniformly negatively charged by the primary charger 50, and then the laser exposure unit 28Y. By performing image exposure, an electrostatic latent image corresponding to the yellow component of the image is formed on the surface of the photosensitive drum 26Y.

  Next, the electrostatic latent image is developed with a negatively charged yellow toner by the developing device 51 and visualized as a yellow toner image. The yellow toner image obtained in this way is primarily transferred onto the intermediate transfer belt 30 by the primary transfer roller 52. After the toner image is transferred, the transfer residual toner adhering to the surface of the photosensitive drum 26Y is removed by the cleaner 53. Such a toner image forming operation is performed at a predetermined timing in the other process cartridges P, and each color toner image formed on each photosensitive drum 26 is transferred onto the intermediate transfer belt 30 by the respective primary transfer portions. The primary transfer is performed in the order of YMCBk.

  The four-color toner images transferred in a superimposed manner on the intermediate transfer belt 30 are moved to the secondary transfer portion (transfer roller 27) as the intermediate transfer belt 30 rotates in the arrow direction. In parallel with this, the transfer material P whose skew has been corrected by the registration roller pair 24 is sent out to the secondary transfer portion in time with the image on the intermediate transfer belt 30. Thereafter, the toner image mixed with the four colors on the intermediate transfer belt 30 is secondarily transferred onto the transfer material P by the secondary transfer roller 27 in contact with the intermediate transfer belt 30 with the transfer material P interposed therebetween. The transfer material P onto which the toner image has been transferred in this manner is sent to the fixing device 25 where it is heated and pressed to fix the toner image. Thereafter, the paper is discharged and stacked on the upper surface tray 64 of the apparatus main body 1 by the discharge roller pairs 61 to 63.

  The intermediate transfer belt 30 that has finished the secondary transfer is subjected to removal of residual toner remaining on the surface thereof by a belt cleaner (not shown).

  In the discharge conveyance path 60 between the pair of discharge rollers 61 and 62, a color sensor 90 is installed as shown in the figure at a distance Y from the roller nip portion of the fixing device 25 on the downstream side.

  FIG. 3 is a diagram for explaining the mounting state of the color sensor 90 according to the present embodiment in more detail.

  When the patch is transferred in the same procedure as the image formation described above and the transfer material P fixed by the fixing device 25 is conveyed through the discharge conveyance path 60, the toner image fixed on the transfer material P is detected. Further, the color sensor 90 is disposed toward the image forming surface of the transfer material P being conveyed. In this way, the color sensor 90 detects the RGB value of the color of the mixed color patch array 82 after fixing formed on the transfer material P before the transfer material P is discharged out of the apparatus main body 1.

  FIG. 4 is a diagram for explaining a configuration example of the color sensor 90 according to the present embodiment.

  The color sensor 90 includes a white LED 91 and a charge storage sensor 92a with an RGB on-chip filter. Here, the light from the white LED 91 is incident on the transfer material P on which the patch 82 after fixing is formed at an angle of 45 degrees, and the intensity of diffuse reflected light in the 0 degree direction is measured by the charge storage sensor 92a with an RGB on-chip filter. To detect. In the light receiving portion of the charge storage type sensor 92a with RGB on-chip filter, as indicated by 92b, RGB are independent pixels. The charge storage sensor 92a with an RGB on-chip filter may be a photodiode, or may be a set of several RGB three-pixel sets. Further, the incident angle may be 0 degree and the reflection angle may be 45 degrees. Furthermore, you may comprise by LED which emits RGB three colors, and a sensor without a filter.

  FIG. 5 is a view showing an example of a patch pattern for density-tone characteristic control (for color balance correction) after fixing formed on the transfer material P.

  This patch pattern for density-gradation characteristic control is a gray gradation patch pattern which is the center of the color gamut and is a very important color for color balance. It is composed of gray gradation patches 80 (80a to 80f) of black (Bk) and process gray gradation patches 81 (81a to 81f) in which cyan (C), magenta (M), and yellow (Y) are mixed. , 80a and 81a, 80b and 81b, 80c and 81c, and the like, the gray gradation patch 80 of Bk having close chromaticity and the CMY process gray gradation patch 81 are arranged in pairs in a standard color image forming apparatus. It is out. Here, Lc represents the length of the patch (the length in the conveyance direction of the transfer material P), and vc represents the conveyance speed of the transfer material P when the color sensor 90 reads the patch.

  The RGB values obtained by reading the patches with the color sensor 90 are fed back to the image processing control unit 11, and color balance correction data is generated based on the detected RGB values. Thus, it is possible to control the density or chromaticity of the toner image and form a toner image with an optimum color balance.

  The patch pattern for density-tone characteristic control after fixing formed on the transfer material P is not limited to a gray patch pattern, and may be a C, M, Y, Bk single-color gradation patch pattern. If an absolute white reference is provided, absolute chromaticity can be calculated.

  Further, since the RGB value changes continuously with respect to the gradation, the detected gradation is obtained by subjecting the RGB output value of a certain gradation and the adjacent gradation to a mathematical process such as primary approximation or secondary approximation. An estimated value of the RGB output value between the furnishings can be calculated. Therefore, by increasing the number of patches, the correction accuracy of density-gradation characteristic control is increased.

  Even when absolute chromaticity cannot be calculated because there is no absolute white reference, by comparing the RGB output values of the gray gradation patch by Bk and the CMY process gray gradation patch, Bk of a certain gradation is obtained. It is possible to calculate the mixing ratio of the CMY three colors of the process gray patch obtained by mixing three colors of CMY that have substantially the same chromaticity as the gray patch.

  The color balance correction control is performed between normal printing operations. The execution timing is detected by detecting the environmental change, the number of prints, etc., and instructing the user to execute at a predetermined timing set in advance, or when the user desires to execute the control, is performed by the user's manual operation. The

  FIG. 6 is a flowchart showing control (color balance correction control) for improving the color reproducibility of the color image forming apparatus equipped with the color sensor 90 in the first embodiment of the present invention.

  Here, the length in the conveyance direction of the image formable area of the transfer material P used by the user is S, the conveyance speed of the transfer material P is v, the conveyance speed of the transfer material P during normal image formation is vp, and color. When the patch is detected by the sensor 90, the transfer speed of the transfer material P is vc, the minimum number of patches necessary for color balance correction is n, the number of patches constituting the patch row 82 on the transfer material P is nc, and the patch The length Lc in the carrying direction per one, the detection range d in the carrying direction of the color sensor 90, and the time required for the color sensor 90 to detect one patch are T. Note that, during this time T, the patch 82 is reliably detected even if there is a positional deviation from the ideal position of the patch position due to uneven speed in the conveyance direction of the transfer material P, shrinkage of the transfer material P after fixing, or the like. In order to be able to do so, a time margin is anticipated in advance.

  In the present embodiment, after the leading edge of the transfer material P on which the patch 82 is formed reaches the color sensor 90, the transfer speed vc of the transfer material P at the time of patch detection is set to the transfer material at the time of normal image formation as necessary. By making the P conveying speed slower than vp, the density and chromaticity of the patch can be reliably detected even if the patch width is smaller than the conventional one. Furthermore, since the number of patches on one transfer material P can be increased by making the patch width smaller than before, a plurality of transfer materials P are conventionally required for color balance correction. However, the number of transfer materials P can be reduced to one. In addition, since the patch width can be reduced, the amount of toner consumed at the time of color balance correction can be reduced as compared with the conventional case.

  In the present embodiment, all the patches for color balance correction are further transferred onto the transfer material P and the transfer material P from the fixing device 25 to the color sensor 90 which is the final process of image formation on the transfer material P. Therefore, the transfer speed of the transfer material P can be reduced after all patches have been formed under normal process conditions, and the color balance correction accuracy can be further improved. .

  In FIG. 6, first, in step S101, when the transfer distance of the transfer material P from the roller nip portion of the fixing device 25 to the detection portion by the color sensor 90 is Y, an image of the transfer material P used by the user can be formed. It is determined whether the conveyance direction length S of the area is larger or smaller than Y. Here, the conveyance direction length S of the image formable region of the transfer material P may be obtained from the output from the size detection means provided in the cassette 20 or is illustrated in the apparatus main body 1. It may be obtained from the size of the transfer material P input by the user from the external host device 10 or the like with respect to the transfer material P set by the user in a non-manual paper feed unit or the like. In any case, if S ≦ Y with respect to the length S in the conveyance direction of the image formable area of the transfer material P that the user intends to use for color balance correction, the transfer material P on which the patch row is formed However, since the patch at the front end reaches the region detectable by the color sensor 90 after passing through the fixing device 25, after the patch row is formed over the entire area of one transfer material P, the transfer speed of the transfer material P is increased. Change.

  On the other hand, when S> Y, since the leading edge of the transfer material P reaches the color sensor portion 16 before the trailing edge of the transfer material P passes through the fixing device 25, all patches are formed within the distance Y. Then, after fixing, it is necessary to change the conveyance speed of the transfer material P. Therefore, in step S102, the value of S is replaced with Y, and the process proceeds to step S103.

  In step S103, the color balance with respect to the length S in the conveyance direction of one image formable region of the transfer material P used by the user at the transfer material conveyance speed vp during the normal image forming operation. It is determined whether all the minimum n patches necessary for correction can be written. That is, since the detection length per patch is (vp × T + d), the length of n × (vp × T + d) is required for n patches. The conveyance direction length S is compared.

  Here, when it is determined that all the patches do not fit on one transfer material P (n (vp × T + d)> S), the process proceeds to step S104, and the number of patches to be formed is set to the minimum necessary number n ( = Nc). Accordingly, the conveyance direction length Lc per patch is Lc = S / nc. Furthermore, the conveyance speed of the transfer material P at the time of patch detection is determined to be a speed vc (vc = (Lc−d) / T) at which a patch having a length Lc can be detected (vc <vp).

  If the length Lc in the transport direction per patch is shorter than the detection range d in the transport direction of the color sensor 90, the patch 82 cannot be detected. Therefore, in order to store all the patches on one transfer material P, n <Smin, where Smin is the length of the image formable area of the transfer material P that can be passed through the shortest length in the transport direction. It is necessary to set n in advance so as to be / d. However, when Smin> Y, the value of n is set so that n <Y / d.

  On the other hand, when all the patches can be accommodated on one transfer material P (n (vp × T + d) ≦ S), the process proceeds to step S105, and the conveyance speed vc of the transfer material P at the time of patch detection is set to a normal value. A transfer speed vp of the transfer material P at the time of image formation is set, a patch length Lc that can be detected at the transfer speed vp is calculated (Lc = vc × T + d), and the number of patches nc is set to n.

  When step S104 or S105 is executed in this way, the process proceeds to step S106, where the patch length Lc and the number of patches nc calculated as described above are given to the image forming control unit 12 to form a patch row on the transfer material P. The image forming operation here is performed at a speed corresponding to the normal transfer speed P of the transfer material P. That is, the patch row 82 is formed and fixed under the same process conditions as those for normal image formation.

  When the transfer and fixing of the patch are completed in this way, in step S107, it is determined whether or not the leading end of the transfer material P on which the patch row 82 is formed has reached the color sensor unit 16. In this determination method, when there is no transfer material P in the portion to be measured of the color sensor 90, an output obtained by detecting the black conveying path 60 which is the opposite surface is obtained. Since an output obtained by detecting the blank portion at the tip of the transfer material P is obtained, it is possible to detect whether or not the transfer material P has reached from the change in the output of the color sensor 90. When it is detected that the transfer material P has arrived at the color sensor unit 16 in this way, the process proceeds to step S108, and in accordance with an instruction from the image formation control unit 12, the drive speed of the transport motor 15 is set to the transport speed of the transfer material during normal image formation. The conveyance speed vc of the transfer material P when the patch is detected by the color sensor 90 from vp is set. Next, in step S109, the color sensor 90 detects the patch row 82, and in step S110, the processing described in the section of color balance correction is performed based on the detected RGB values.

  A case where color balance correction is actually performed by the above sequence will be described below.

  In the present embodiment, the transfer speed of the transfer material during the normal image forming operation is vp = 100 mm / second, the minimum number of patches necessary for color balance correction is n = 40, and the detection direction of the color sensor 90 is detected. The range (spot diameter of the color sensor 90 at the measurement distance) is d = 2 mm, and the time required for the color sensor 90 to detect one patch is T = 0.05 seconds. Further, the conveyance distance Y of the transfer material P from the roller nip portion of the fixing device 25 to the detection position by the color sensor 90 is 360 mm.

  Here, as shown in FIG. 5, considering the case where the transfer direction length S = S1 = 420 mm of the image formable area of the transfer material P used by the user, S> Y (= 360). Therefore, the process proceeds from step S101 to step S102 and S = 360. Next, in step S103, n (vp × T + d) = 280 mm <S, so the process proceeds to step S105, where the transfer material P used by the user is used as it is, and the color without changing the transport speed vp of the transfer material P. Even if the balance correction is performed, only one sheet of transfer material P is consumed. In this case, vc = 100 mm / second, Lc (= 7 mm), and nc = 40, and the process proceeds to step S106 to form a patch.

  After the patch is formed in this way, even if it is detected in step S107 that the leading edge of the transfer material P has reached the color sensor unit 16, the patch row 82 is detected without changing the transfer speed vp of the transfer material P. Is performed (steps S108 to S109). The detection timing of the patch array 82 starts detection after a predetermined time from the timing when the leading edge of the transfer material P arrives, and then detects each patch at regular time intervals.

  FIG. 7A is a timing chart showing an outline of the sequence in this case. In this example, even after the transfer material P reaches the color sensor unit 16, patch detection is performed without changing the transfer speed of the transfer material P.

  On the other hand, consider the case where the length S in the transport direction of the image formable area of the transfer material P used by the user is 210 mm. In this case, since S <Y (= 360) in step S101, the process proceeds to step S103. Here, n (vp × T + d) = 280 mm> S2, so that the transfer material P used by the user as it is is 1 It turns out that not all necessary patches can be formed on the sheet. In this case, the process proceeds to step S104, and the patch length in the transport direction is calculated so that all necessary patches can be formed on one transfer material on the assumption that the transport speed of the transfer material P is slowed at the time of patch detection. That is, the conveyance direction length Lc = 210 ÷ 40 = 5.25 mm per patch, and the conveyance speed vc = (5.25-2) ÷ 0.05 = 65 mm / second of the transfer material P at the time of detecting the patch is obtained. It is done. In step S106, a patch row is formed on the transfer material P based on these values. In step S107, when it is detected that the leading edge of the transfer material P has reached the color sensor unit 16, the transfer speed of the transfer material P is changed from vp = 100 mm / sec to vc = 65 mm / sec. After a predetermined time has elapsed, patch detection is started (step S109).

  FIG. 7B is a timing chart showing an outline of the sequence in this case. In this example, after the transfer material P reaches the color sensor unit 16, the transfer speed of the transfer material P is decreased from vc to vc, and patch detection is executed.

  As is clear from FIGS. 7A and 7B, the time T required to detect one patch is the same in any case. In either case, when all the patches have been detected, the transfer material P is discharged out of the apparatus body by increasing the transfer material conveyance speed further than vp (for example, 200 mm / second). Thus, the color balance correction can be completed quickly.

  As described above, according to the first embodiment, it is possible to realize color balance correction control that minimizes consumption of the transfer material P and toner used.

[Embodiment 2]
In the first embodiment described above, the color balance correction with reduced toner consumption has been realized. However, by changing the color balance correction flowchart shown in FIG. 6 as shown in FIG. Can be shortened.

  FIG. 8 is a flowchart showing control (color balance correction control) for improving the color reproducibility of the color image forming apparatus equipped with the color sensor 90 in the second embodiment of the present invention. Steps for executing the same processing as in the flowchart of FIG. 6 are denoted by the same symbols, and description thereof is omitted.

  The flowchart in FIG. 9 is different from that in FIG. 6 in step S115. That is, when it is determined in step S103 that all necessary patches can be formed on one transfer material P, in step S115, the transfer speed of the transfer material P is set higher than the transfer speed vp during normal image formation. However, it is possible to finish the color balance correction control earlier by making it as early as possible. Specifically, the length obtained by subtracting the detection range d in the conveyance direction of the color sensor 90 from the length obtained by dividing the conveyance direction length S of the image formable region of the transfer material P by the number of patches nc is the time T. Therefore, vc = (S / nc−d) / T is obtained.

  As in the first embodiment, the transfer speed of the transfer material during a normal image forming operation is vp = 100 mm / second, the minimum number of patches necessary for color balance correction is n = 40, and the color sensor 90 Detection range in the conveying direction (spot diameter of sensor at measurement distance) d = 2 mm, time required for the color sensor 90 to detect one patch is T = 0.05 seconds, from the roller nip portion of the fixing device 25 to the color sensor 90, the transfer distance Y of the transfer material to the detection unit is set to 360 mm. In this case, considering the case where the conveyance direction length S of the image formable area of the transfer material P used by the user is S1 = 420 mm, since S1> Y, the process proceeds from step S101 to step S102. S = 360 (= Y) is set. In step S103, since n (vp × T + d) = 280 mm <S, the process proceeds to step S115, where the transfer speed of the transfer material at the time of detection by the color sensor 90 is vc = (S / nc−d) / T =. (360 / 40-2) /0.05=140 mm / sec, Lc = vc × T + d = 9 mm. Thus, in step S108, the conveyance speed v = vc set for patch detection is set to vc (= 140 mm / second) faster than the conveyance speed vp (= 100 mm / second) during normal image formation. .

  Thereby, the color balance correction control can be completed in a shorter time than the case of the first embodiment.

[Embodiment 3]
In the third embodiment, a method of improving the accuracy of color balance correction control by changing the color balance correction flowchart shown in FIG. 6 as shown in FIG. 9 will be described.

  FIG. 9 is a flowchart showing control (color balance correction control) for improving the color reproducibility of the color image forming apparatus equipped with the color sensor 90 in the third embodiment of the present invention. Steps common to the flowchart of FIG. 6 are denoted by the same symbols.

  The flowchart of FIG. 9 differs from FIG. 6 in step S125. If it is determined that all necessary patches can be formed on one transfer material P, the process proceeds from step S103 to step S125. By determining the number of patches nc based on the conveyance direction length S of the image formable region of the transfer material P and the patch length Lc, it is possible to improve the accuracy of color balance correction control. Specifically, it is determined by nc = int (S / Lc). Note that int () represents an integer obtained by rounding down the decimal point of the numerical value in ().

  As in the first embodiment, the transfer speed vp of the transfer material during a normal image forming operation is 100 mm / second, the minimum number of patches n required for color balance correction is 40, and the color sensor 90 is transported. Direction detection range (sensor spot diameter at measurement distance) d is 2 mm, time T necessary for the color sensor 90 to detect one patch is 0.05 seconds, and the color sensor 90 from the roller nip portion of the fixing device 25 The transfer distance Y of the transfer material to the detection unit is 360 mm. Here, considering the case where the conveyance direction length S of the image formable area of the transfer material P used by the user is 420 mm, since S> Y, the process proceeds from step S101 to step S102, and S = 360. Is set. In step S103, since n (vp × T + d) = 280 mm <S, the process proceeds to step S125, and the transfer material conveyance speed vc at the time of patch detection remains the transfer material conveyance speed vp at the time of normal image formation. The detectable patch length Lc = 100 × 0.05 + d at this transport speed vp is 7 mm. Since the patch number nc is an integer obtained by rounding down the decimals of S / Lc, it is determined that nc = 51 from 360/7 = 51.4.

  As described above, the number of patches is increased by 11 as compared with the case where the number of patches in the first embodiment is 40, and more patches can be formed. Further, even if the number of patches increases in this way, it is not necessary to reduce the transfer speed of the transfer material P for patch detection. In this way, the color balance correction accuracy can be improved.

[Embodiment 4]
The fourth embodiment shows an example in which the improvement of the color balance correction accuracy is more positively realized than in the third embodiment.

  That is, by detecting the patch density and chromaticity at the minimum detectable patch length and the minimum transfer speed of the transfer material P at which this patch can be detected, the number of patches on the transfer material P is maximized. Thus, improvement in color balance correction accuracy is realized.

  FIG. 10 shows a flowchart of color balance correction control according to the fourth embodiment.

  FIG. 10 is a flowchart showing control (color balance correction control) for improving the color reproducibility of the color image forming apparatus equipped with the color sensor 90 in the fourth embodiment of the present invention. Steps common to the flowchart of FIG. 6 are denoted by the same symbols.

  Here, the detection range (sensor spot diameter at the measurement distance) d of the color sensor 90 is 2 mm, the time T necessary for the color sensor 90 to detect one patch is 0.05 seconds, and when the patch is detected. Is 2 mm, and the conveyance distance Y of the transfer material P from the roller nip portion of the fixing device 25 to the detection portion by the color sensor 90 is 360 mm. In this case, the minimum detectable patch length Lc is Lc = d + α = 4 mm, and the transfer speed of the transfer material P that can detect this patch is vc = (Lc−d) / T = 40 mm / second. . In the fourth embodiment, the values of Lc and vc are fixed values.

  First, consider the case where the length S in the conveyance direction of the image formable area of the transfer material P used for color balance correction control is 420 mm. In step S101, since S> Y, the process proceeds to step S102, where S = 360 is set. Next, in step S133, the patch length Lc is determined as (d + α = 4 mm), and the transfer speed vc of the transfer material P that can detect this patch is determined as {= (Lc−d) / T = 40 mm / second}. Then, the number of patches nc is determined as nc = 90 from an integer (360/4 = 90) obtained by rounding down the decimal point of S / Lc.

  Since more patches can be formed than the number of patches (51) in the third embodiment, the color balance correction accuracy can be greatly improved.

  Next, considering the case where the conveyance direction length of the image formable region of the transfer material used by the user for color balance correction control is S = 210 mm, since S <Y in step S101, the process proceeds to step S102. Similarly, the patch number nc is calculated. Here, nc = 52 from 210/4 = 52.5, and even when the length of the transfer material P is short, the number of patches can be increased. Incidentally, in the above-described first embodiment, when S = 210 mm, nc = 40.

  In the fourth embodiment, since the conveyance speed of the transfer material P is reduced at the time of detecting a patch, the time required for color balance correction control increases. However, when emphasizing correction accuracy, it is a very effective means. Become.

  As described above, according to the present embodiment, when the execution of the color balance correction control is instructed, the size of the transfer material P corresponding to the paper feed port designated by the user or the size of the designated transfer material P is determined. Thus, a patch row for color balance correction is formed. At this time, the conveyance speed, patch length, and number of patches of the transfer material P at the time of patch detection are changed according to the size of the transfer material P to be used for color balance correction. Thereby, color balance correction can be performed using the transfer material P used for normal image formation.

  Further, conventionally, the color balance correction can be executed with the minimum transfer material by changing the length of the patch according to the size of the transfer material P used for the color balance correction.

  Furthermore, any one of the above-described first to fourth embodiments, or a combination thereof, can improve the correction accuracy and shorten the detection time while suppressing consumption of the transfer material P and toner. That is, it is possible to optimize the patch sequence as necessary.

  As a result, the optimum color balance correction can be performed semi-automatically using the transfer material P used for normal image formation.

  The color sensor 90 is installed in advance so that the transfer distance Y of the transfer material P from the roller nip portion of the fixing device 25 to the detection portion of the color sensor 90 is longer than the length in the transfer direction of the transfer material P that can pass the maximum sheet. As a result, the transfer speed vc of the transfer material P at the time of detecting the patch, the number of patches nc constituting the patch row, and the change width of the transport direction length Lc per patch can be widened to make it more effective. it can.

  In the present embodiment, the color balance correction using the color sensor 90 has been described. However, the present invention can also be applied to the case where the density of the fixed patch is detected by the density sensor and the density correction is performed.

  Furthermore, in this embodiment, a color image forming apparatus is taken up as an example of an image forming apparatus. However, there are various other things such as density control of a monochrome image forming apparatus and density / chromaticity correction in an inkjet image forming apparatus. The effect of the present invention is also exhibited in this image forming apparatus.

According to the embodiment described above , the recording material consumption can be reduced by optimizing the recording material conveyance speed, the length of each patch, and the number of patches according to the length of the recording material. Time required for correction or correction of image formation characteristics can be shortened. In addition, if the minimum necessary number of patches cannot be formed on one transfer material at the transfer material conveyance speed during normal image formation, the transfer material conveyance speed during patch detection is slowed down. In addition, by reducing the length in the conveyance direction per patch, it is possible to form all patches necessary for color balance correction on one transfer material.

  If the minimum necessary number of patches can be formed on a single transfer material while maintaining the transfer material conveyance speed during normal image formation, the transfer material conveyance speed during patch detection can be increased. It is also possible to shorten the time required for color balance correction by increasing the length in the transport direction per one.

  Further, according to the present embodiment, when the minimum necessary number of patches can be formed on one transfer material while maintaining the transfer material conveyance speed during normal image formation, the number of patches is further increased. As a result, the accuracy of color balance correction can be improved.

  Further, according to the present embodiment, the transfer material transport speed at the time of patch detection is set to the minimum, and the length in the transport direction per patch is also minimized, so that the transfer material used for color balance correction can be reduced. A patch row can be configured with the maximum number of patches according to the length in the transport direction, and an image forming apparatus that can improve the accuracy of color balance correction can be provided.

  Furthermore, according to the present embodiment, the first patch does not reach the color sensor until all the patches formed on the transfer material are fixed, so that all the patches are fixed and then the patch is formed. It becomes possible to change the transfer speed of the transfer material. That is, since the patch can be formed at the conveyance speed during the normal image forming operation, it is possible to provide an image forming apparatus with improved color balance correction accuracy and good color reproducibility.

  Furthermore, according to the present embodiment, it is possible to minimize the length in the transport direction of the patch row formed on the transfer material.

1 is a block diagram illustrating a schematic configuration of a four-drum type full-color image forming apparatus that employs an electrophotographic system and uses an intermediate transfer belt as an example of an image forming apparatus according to an embodiment of the present invention. 2 is a block diagram illustrating a control configuration of the image forming apparatus according to the embodiment of the present invention. FIG. It is a figure for demonstrating in detail the attachment state of the color sensor which concerns on this Embodiment. It is a figure explaining the structural example of the color sensor which concerns on this Embodiment. FIG. 5 is a diagram illustrating an example of a patch pattern for density-tone characteristic control (for color balance correction) after fixing formed on a transfer material in the present embodiment. 3 is a flowchart showing control (color balance correction control) for improving color reproducibility of a color image forming apparatus equipped with a color sensor in Embodiment 1 of the present invention. FIG. 5A is a timing diagram illustrating patch detection processing according to the first embodiment. FIG. 5A illustrates a case where the transfer material conveyance speed is not changed, and FIG. 5B illustrates a case where the transfer material conveyance speed is changed. 6 is a flowchart showing control (color balance correction control) for improving color reproducibility of a color image forming apparatus equipped with a color sensor in Embodiment 2 of the present invention. 10 is a flowchart showing control (color balance correction control) for improving color reproducibility of a color image forming apparatus equipped with a color sensor in Embodiment 3 of the present invention. 10 is a flowchart showing control (color balance correction control) for improving color reproducibility of a color image forming apparatus equipped with a color sensor in Embodiment 4 of the present invention.

Claims (4)

Image forming means for forming an image on a recording sheet, and a patch forming means for forming a patch on a recording sheet, a conveyance control means for conveying the recording paper patch was formed on the conveying means, is conveyed by said conveying means comprising a detection means for detecting the concentration or chromaticity of a formed on the recording paper patch, and a correcting means for correcting the image forming property of the image forming means on the basis of the detected density or chromaticity by said detecting means An image forming apparatus,
Means for obtaining size information of the recording paper,
When the size information of the first recording paper having the first length in the transport direction is obtained by the obtaining means, the patch forming means applies the first patch on the first recording paper to a predetermined required for correcting the image forming characteristics. When the size information of the second recording paper of the second length which is shorter than the first recording paper and cannot form the predetermined number of first patches is obtained by the obtaining means, Forming the predetermined number of second patches having a shorter length in the transport direction than the first patch on the second recording paper;
When the size information of the first recording paper is obtained by the obtaining means, the conveyance control means detects the first recording paper on which the predetermined number of first patches are formed, and detects the second patch. When the size information of the second recording paper is obtained by the obtaining means and the obtaining means obtains the size information of the second recording paper without lowering to the second speed for the detection, the predetermined number of second patches are obtained. Transporting the formed second recording paper to the transport means at the second speed slower than the first speed;
The detecting means includes density or chromaticity of the predetermined number of first patches formed on the conveyed first recording paper and the predetermined number of second patches formed on the second recording paper. An image forming apparatus characterized by detecting the above . When the predetermined number of first patches are formed on the first recording paper, the predetermined number is obtained by the predetermined number and the obtaining means so that the first speed is higher than the conveyance speed of the recording paper at the time of image formation. And determining means for determining the first speed based on the detected size information and the detection time of each patch by the detecting means, wherein the patch forming means is a recording at the time of image formation determined by the determining means. 2. The length of the first patch in the conveyance direction is determined based on the first speed faster than the paper conveyance speed and the detection time of each patch, and the first patch is formed. The image forming apparatus described in 1. An image forming means for forming an image on the recording paper is provided , a patch is formed on the recording paper, the recording paper on which the patch is formed is conveyed, and the density or chromaticity of the patch is detected. Is a control method of an image forming apparatus for correcting image forming characteristics in the image forming means based on chromaticity ,
Obtaining the recording paper size information;
In the obtaining step, when the size information of the first recording paper whose transport direction is the first length is obtained, a predetermined number of first patches necessary for correcting the image forming characteristics are formed on the first recording paper, In the obtaining step, when the size information of the second recording paper having the second length that is shorter than the first recording paper and in which the predetermined number of first patches cannot be formed is obtained, the second recording A patch forming step of forming the predetermined number of second patches having a shorter length in the transport direction than the first patch on paper;
When the size information of the first recording paper is obtained in the obtaining step, the first recording paper on which the predetermined number of first patches are formed is moved to the second speed for detecting the second patch. When the size of the second recording paper is obtained in the obtaining step, the second recording paper on which the predetermined number of second patches are formed is transferred from the first speed. Transporting at a slower second speed,
Detecting the density or chromaticity of the predetermined number of first patches formed on the conveyed first recording paper and the predetermined number of second patches formed on the second recording paper; ,
A control method for an image forming apparatus, comprising: When the predetermined number of first patches are formed on the first recording paper, the predetermined number and the obtained step are obtained so that the first speed is higher than the conveyance speed of the recording paper at the time of image formation. And determining the first speed based on the detected size information and the detection time of each patch, and the patch forming process includes a conveyance speed of the recording paper at the time of image formation determined in the determination process. 4. The image according to claim 3, wherein the first patch is formed by determining a length in a transport direction of the first patch based on the faster first speed and a detection time of each patch. 5. Control method of forming apparatus.

Images