JP2014048302A - Image forming device and calibration method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device configured to improve accuracy of color registration.SOLUTION: An image forming device 1 includes: base density acquiring means 404 that acquires base density for one turn of an intermediate transfer belt B1 during color calibration; stained portion detecting means 405 that compares the acquired base density with a predetermined set threshold, to detect a portion of the intermediate transfer belt B1 corresponding to the position acquiring the base density exceeding the threshold, as a stained portion; and color registration means 406 that forms a color registration patch pattern in a portion of the intermediate transfer belt B1, which is different from the detected stained portion and allows the color registration patch pattern to be formed, to executed color registration.

Description

  The present invention relates to an image forming apparatus and a calibration method, and more particularly to an image forming apparatus and a calibration method capable of improving the accuracy of color registration.

  In recent years, the creation of documents in offices has been rapidly colorized, and accordingly, copiers, printers, facsimiles and other devices are required to support colorization. Further, when the colorization of these devices is advanced, it is required to improve the image quality of the output image and increase the output speed.

  However, when trying to increase the output speed, it becomes difficult to maintain the high quality of the output image due to the deterioration of the color registration. Here, color registration is a type of calibration, which measures the position of the patch for each color formed in a predetermined shape, corrects the positional deviation of the patch for each color, and performs color printing between colors. This is a calibration that prevents misalignment. Also, the position of the unit for forming the image of each color or the position of the parts inside each unit due to the temperature change inside the device, the impact when replenishing recording paper, the external force when a person hits the device etc. If this is slightly changed, this slight change in position causes deterioration in color registration when attempting to increase the speed.

  Therefore, in the prior art, a technique for measuring the amount of color registration error and correcting it to improve the image quality is disclosed. This is because a color registration pattern corresponding to each color is formed on the image carrier, these color registration patterns are optically read by a reading means, and an interval between the color registration patterns of each color is calculated based on the read signal. The position of each color image forming unit and the image formation start timing are corrected so that this becomes equal to the reference value.

  However, the conventional image forming apparatus has the following problems. That is, after the image forming apparatus is used for a long period of time, the environment for measuring the color registration error amount deteriorates, resulting in a problem that the measurement accuracy is lowered. In particular, an image carrier that forms a color registration pattern is easily deteriorated and is likely to be stained or scratched.

  In order to solve the above problem, Japanese Patent Laying-Open No. 2006-268052 (Patent Document 1) discloses a pattern generating means for generating a color registration pattern for measuring a color registration error, and an image of the color registration pattern. An image forming means for forming an image on the carrier, a reading means for optically reading a color registration pattern formed on the image carrier and converting it into an electrical signal, and an electrical signal obtained by the reading means. An image forming apparatus having error detection means for obtaining an error amount of color registration based on the above is disclosed. In the image forming apparatus, the error detection unit calculates a barycentric position of an area exceeding a preset threshold for the waveform of the electrical signal obtained from the reading unit, and obtains the position of the color registration pattern from the barycentric position. As a result, when measuring color registration errors, even if the image carrier is soiled or scratched, the color registration pattern can be reliably detected without being affected by the soiling or scratching with a simple and inexpensive configuration. It is possible to recognize the position of. In addition, by detecting the width of dirt and scratches on the image carrier and setting the line width of the color registration pattern according to this, the dirt and scratches that change as the image forming apparatus is used can be reduced. Correspondingly, it is possible to measure color registration errors.

  Japanese Patent Application Laid-Open No. 2007-225818 (Patent Document 2) discloses a patch that represents an image forming apparatus that represents data for determining whether or not an abnormality has occurred in the image forming apparatus. An image forming unit to be formed, a patch detecting unit for detecting the patch, the data is recognized from the detected patch, and whether or not an abnormality has occurred in the image forming unit based on the recognized data An image forming apparatus comprising: a determination unit configured to determine whether the recording material is conveyed; and a timing adjustment unit configured to adjust a conveyance timing of the recording material based on the detection timing of the patch when the abnormality has not occurred. It is disclosed. As a result, the conveyance timing of the recording material can be suitably adjusted by using a patch expressed as an image of data for determining an abnormality occurring in the image forming apparatus.

JP 2006-268052 A JP 2007-225818 A

  However, the techniques described in Patent Documents 1 and 2 cannot sufficiently prevent the image carrier (intermediate transfer body) on which the color registration pattern is formed, and improve the accuracy of the color registration. There is a problem that it cannot be done.

  Further, when the surface of the image carrier is contaminated over a wide area or a plurality of times due to aging, etc., it is necessary to notify the user of the fact and replace the image carrier. There is no forming device.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and a calibration method capable of improving the accuracy of color registration.

  In order to solve the above-described problems and achieve the object, an image forming apparatus according to the present invention is based on an image forming apparatus that performs color calibration and color registration, and adopts the following configuration.

  That is, the image forming apparatus compares the background density acquisition unit that acquires the background density for one round of the intermediate transfer body with the acquired threshold value and a preset threshold value during color calibration. A stain portion detecting means for detecting a portion of the intermediate transfer member corresponding to the acquisition position of the background density exceeding the threshold value as a stain portion, a portion of the intermediate transfer member other than the detected stain portion, and a color resist A color registration unit configured to form a color registration patch pattern on a pattern formable portion, which is a portion on which a color patch pattern can be formed, and perform color registration.

  Further, the color registration means compares the length in the rotation direction of the pattern-formable portion with the length in the rotation direction of a preset color registration patch pattern, and as a result of the comparison, the pattern can be formed. When the length of the portion in the rotation direction exceeds the length of the color registration patch pattern in the rotation direction, the color registration patch pattern is formed in the pattern formable portion.

  Further, as a result of the comparison, if the length in the rotation direction of the pattern-formable portion is less than the length in the rotation direction of the color registration patch pattern, the color registration means may stain the intermediate transfer member. Warning screen is displayed on the touch panel.

  The present invention can be provided as a calibration method for an image forming apparatus that performs color calibration and color registration. That is, in the color calibration, the calibration method compares the acquired background density with a preset threshold value by comparing the step of acquiring the background density for one turn of the intermediate transfer member. And detecting a portion of the intermediate transfer body corresponding to the acquisition position of the background density exceeding the above as a dirty portion, and forming a color registration patch pattern in the intermediate transfer body portion other than the detected dirty portion. Forming a color registration patch pattern in a pattern formable portion, which is a possible portion, and performing color registration. Even with this configuration, the same effect as described above can be obtained.

  Further, the present invention can be provided as a program for causing a computer to circulate individually via a telecommunication line or the like. In this case, the central processing unit (CPU) realizes the control operation in cooperation with each circuit other than the CPU according to the program of the present invention. Each means realized by using the program and the CPU can also be configured by using dedicated hardware. The program can also be distributed in a state where it is recorded on a computer-readable recording medium such as a CD-ROM.

  According to the image forming apparatus and the calibration method of the present invention, it is possible to improve the accuracy of color registration.

1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows an example of the developing unit which concerns on embodiment of this invention. 1 is a schematic configuration diagram of control system hardware of an image forming apparatus according to an embodiment of the present invention. 1 is a functional block diagram of an image forming apparatus according to an embodiment of the present invention. It is a flowchart for showing the execution procedure of the embodiment of the present invention. FIG. 6 is a schematic diagram (FIG. 6A) of the background density of the intermediate transfer belt B1 according to the embodiment of the present invention, and a diagram showing an example of the background density table according to the embodiment of the present invention (FIG. 6B). . FIG. 7A is a schematic diagram of a patch pattern for color calibration of the intermediate transfer belt B1 according to the embodiment of the present invention (FIG. 7A), and FIG. 7B is a diagram illustrating an example of a patch density table according to the embodiment of the present invention. )). Schematic diagram (FIG. 8A) of the dirt portion of the intermediate transfer belt B1 according to the embodiment of the present invention and schematic diagram of the color registration patch pattern of the intermediate transfer belt B1 according to the embodiment of the present invention (FIG. 8). (B)). It is a figure which shows the relationship between the acquisition density which concerns on embodiment of this invention, and the patch pattern for color registration. It is a figure which shows the acquisition density of the patch pattern for color registration which does not have a stain | pollution | contamination part concerning embodiment of this invention. It is a figure which shows the acquisition density | concentration of the patch pattern for color registration with a stain | pollution | contamination part which concerns on embodiment of this invention. FIG. 13 is a schematic diagram (FIG. 12A) of a dirty portion of the intermediate transfer belt B1 according to the embodiment of the present invention and a diagram (FIG. 12B) showing an example of a warning screen according to the embodiment of the present invention.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not. In addition, the alphabet “S” added in front of the numbers in the flowcharts means steps.

<Image forming apparatus>
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present embodiment. As shown in FIG. 1, the tandem type image forming apparatus to which the present invention is applied includes image forming units FM, FC, FY, and FK for forming color printing toner images. The image forming unit FM-FK is in contact with the intermediate transfer belt B1 along the moving direction of the intermediate transfer belt B1, and a cleaning unit B2 for cleaning the surface of the intermediate transfer belt B1. Magenta, cyan, yellow, and black photosensitive drums 10M, 10C, 10Y, and 10K are provided.

  The magenta photosensitive drum 10M includes a developing device HM for developing an electrostatic latent image formed on the peripheral surface of the photosensitive drum 10M with toner, an exposure device 12M for forming an electrostatic latent image, and the related device. A charger 11M for charging the peripheral surface of the photosensitive drum 10M is provided next to the charger 11M. Similarly, the developing device HC-HK, the exposure device 12C-12K, and the charger 11C- for charging the peripheral surfaces of the photosensitive drums 10C-10K to the cyan, yellow, and black photosensitive drums 10C-10K. 11K is provided. Further, in order to transfer the respective toner images carried on the peripheral surfaces of the respective photosensitive drums 10M-10K to the intermediate transfer belt B1, the peripheral surfaces of the respective photosensitive drums 10M-10K are separated by the intermediate transfer belt B1. Transfer rollers 20M, 20C, 20Y, and 20K are arranged.

  The intermediate transfer belt B <b> 1 is stretched between the driving roller 21 and the driven roller 22, and is given a predetermined tension by the tension roller 23. The intermediate transfer belt B1 moves in the direction of the arrow, so that the four photosensitive drums 10M-10K rotate counterclockwise in FIG.

  As shown in FIG. 2, each of the photosensitive drums 10M-10K is charged to a predetermined potential by the charger 11M-11K, and an image corresponding to the original image is written by the exposure device 12M-12K. Thereby, an electrostatic latent image is formed. The electrostatic latent images are respectively developed into different color toner images by the developing device HM-HK. The toner images of the respective colors are transferred onto the intermediate transfer belt B1 by the transfer rollers 20M-20K, and the toner images are superimposed on the intermediate transfer belt B1.

  The toner remaining on the surface of the photosensitive drum 10M-10K after the transfer as described above is wiped off by the blade 35 and discharged to a predetermined container by the discharge roller 31, and then the photosensitive drum 10M-10K. The surface is neutralized by the static eliminator 13.

  On the other hand, the paper P is transported from the cassette 2 that can store a plurality of paper P by the transport unit 6 toward the image forming unit FM-FK at a predetermined interval. The toner image transferred to the intermediate transfer belt B1 is transferred by the secondary transfer unit 3 to the paper P conveyed to the image forming unit FM-FK.

  The control unit 30 controls the operation of each image forming member in the image forming unit FM-FK including each photoconductor drum 10M-10K, each developing device HM-HK, each charger 11M-11K, and each transfer roller 20M-20K. To control. Also, the operation control of the transport mechanism including the transport rollers 21-23 is performed.

  Next, the configuration of the developing device HM will be described. Note that the configurations of the developing devices HC-HK for the respective colors are the same and are omitted.

The developing device HM includes a developing container 40 and a developing roller 40a, and the developing container 40 stores therein a powder developer composed of yellow toner particles and a carrier.
The developing roller 40a is in contact with the photosensitive drum 10M, and responds to an image instructed to be formed by a host device by the potential difference between the electrostatic latent image on the surface of the photosensitive drum 10M and the developing bias applied to the developing roller 40a. A toner image is formed on the surface of the photosensitive drum 10M (development operation).

  Under such a configuration, the image forming apparatus 1 that has received an instruction to form an image from a higher-level device such as a personal computer uses the image forming unit FM-FK and uses the image forming unit FM-FK for each color toner image corresponding to the received image data. Form. The toner images formed by the image forming units FM-FK are transferred to the intermediate transfer belt B1, and are superimposed on the intermediate transfer belt B1 to form a color toner image.

  In synchronism with the formation of the color toner image, the paper stored in the paper storage unit 2 is taken out from the paper storage unit 2 one by one by a paper feeding device (not shown) and transported on the paper transport unit 6. Then, the sheet is sent to the secondary transfer unit 3 in synchronization with the primary transfer to the intermediate transfer belt B1, and the color toner image on the intermediate transfer belt B1 is secondarily transferred to the sheet by the secondary transfer unit 3. The The sheet on which the color toner image has been transferred is further conveyed to the fixing unit 4 where the color toner image is fixed by heat and pressure. Further, the paper is discharged by a paper discharge device 5 to a paper discharge tray portion 7 provided on the outer periphery of the image forming apparatus 1. The toner remaining on the intermediate transfer belt B1 after the secondary transfer is removed from the intermediate transfer belt B1 by the cleaning unit B2 of the intermediate transfer belt.

  The density detection sensors 400a and 400b for detecting the patch density of the patch (test image, test patch) formed on the intermediate transfer belt B1 at a predetermined timing and the background density of the intermediate transfer belt B1 are used for black image formation. It is provided at a predetermined position between the unit FB and the secondary transfer unit 3. The black image forming unit FB is located on the most downstream side with respect to the rotation direction of the intermediate transfer belt B1 as compared with the other image forming units FY, FM, and FC. Therefore, the density detection sensors 400a and 400b detect the patch density of any of the plurality of image forming units FY, FM, FC, and FB even if the patch is formed on the intermediate transfer belt B1. It is configured to be able to. Further, the density detection sensors 400a and 400b are usually provided in advance at positions corresponding to the positions of the intermediate transfer belt B1 on which patches are formed.

  In the embodiment of the present invention, two density detection sensors 400a and 400b (ID sensors) are provided in the vicinity of both ends of the intermediate transfer belt B1. The density detection sensors 400a and 400b may be in any form as long as they can detect the patch density or background density of the patch for each color. For example, the background on the patch or the intermediate transfer belt B1 is obtained from the light source. A reflection type density detection sensor is used that irradiates with the light of the light, detects the intensity of the reflected light with the light receiving sensor, and converts the light intensity information into the density.

  The intermediate transfer belt B1 is preliminarily provided with a position detection member 50 (for example, a metal film, a metal piece, a notch, etc.) that indicates a specific position of the intermediate transfer belt B1, and the image forming apparatus 1 includes A detection unit 51 (for example, a photosensor) is disposed at a position where the position detection member 50 can be detected. When the detection unit 51 detects the position detection member 50 of the intermediate transfer belt B1, a specific position of the rotating intermediate transfer belt B1 is determined.

  In the embodiment of the present invention, a touch panel 60 for displaying a screen is provided for the user to input and confirm color printing conditions.

  FIG. 3 is a hardware configuration diagram of the control unit 30 of the image forming apparatus 1 according to the present embodiment.

  The image forming apparatus 1 includes a CPU (Central Processing Unit) 301, a RAM (Random Access Memory) 302, a ROM (Read Only Memory) 303, a HDD (Hard Disk Drive) 304, and a driver 305 corresponding to each driving unit in the printing. They are connected via an internal bus 306. The CPU 301 uses, for example, the RAM 302 as a work area, executes a program stored in the ROM 303, the HDD 304, or the like, and exchanges data and commands with the driver 305 based on the execution result, as shown in FIG. The operation of each drive unit is controlled. Furthermore, each means (shown in FIG. 4) described later other than the driving unit also operates as each means when the CPU 301 executes a program.

<Embodiment of the present invention>
Next, an execution procedure according to the embodiment of the present invention will be described with reference to FIGS. 4 and 5. FIG. 4 is a functional block diagram of the image forming apparatus of the present invention. FIG. 5 is a flowchart for illustrating the execution procedure of the present invention.

  First, when the user turns on the power of the image forming apparatus 1 to cause the image forming apparatus 1 to perform color printing, the control unit 401 controls the drive roller 21 and the like to rotate the intermediate transfer belt B1 by a predetermined rotation. Rotate at speed. Then, the start detection unit 402 monitors the control unit 401, detects a predetermined time point, for example, a power-on time point (FIG. 5: S101), and notifies the color calibration unit 403 to that effect. Upon receiving the notification, the color calibration unit 403 executes color calibration (FIG. 5: S102).

  Here, in addition to the time when the power is turned on, for example, the time point when a thermistor (temperature detection sensor) provided inside the image forming apparatus 1 detects an environmental change, and the drive time of the developing device has passed a predetermined time. When the predetermined number of prints are completed, when the number of printed sheets exceeds a predetermined threshold, when the printing rate exceeds a predetermined threshold, when the drive unit required for image formation is warmed up, It may be the time when the instruction is input via the touch panel 60.

  When the color calibration is performed, specifically, first, the color calibration unit 403 notifies the background density acquisition unit 404 of an instruction to acquire the background density of the intermediate transfer belt B1. Upon receiving the notification, the background density acquisition unit 404 activates the detection unit 51 provided near the intermediate transfer belt B1, as shown in FIG. 6A, and the detection unit 51 causes the intermediate transfer belt B1 to be activated. The position detection member 50 is detected.

  Next, when the detection of the position detection member 50 of the intermediate transfer belt B1 is completed, the background density acquisition unit 404 activates two density detection sensors 400a and 400b installed near both ends of the intermediate transfer belt B1. Then, using the detection position of the position detection member 50 as the background density acquisition start position, the background density 600 for one round of the intermediate transfer belt B1 is acquired (read) (FIG. 5: S103).

  Here, when the background density acquisition unit 404 acquires the background density 600, from the elapsed time (sec) from the acquisition start position of the background density 600 and the rotation time (mm / sec) of the intermediate transfer belt B1. The acquisition position (mm) of the background density 600 is calculated. As shown in FIG. 6B, the acquisition position (mm) 602 of the background density 600 and the rotation position of the intermediate transfer belt B1 on the left side are calculated. The background density (%) 603 by the density detection sensor 400a and the background density (%) 604 by the density detection sensor 400b on the right side with respect to the rotation direction of the intermediate transfer belt B1 are associated as a background density table 601 and stored in a predetermined memory. Remember.

  Here, under normal circumstances, the background density acquisition unit 404 only acquires a background density having a length corresponding to the length in the rotation direction of a color calibration patch pattern to be described later. The background density acquisition means 404 acquires a background density 600 for one turn of the intermediate transfer belt B1 (described later).

  Further, when the background density acquisition unit 404 acquires the background density, for example, when a plurality of background densities are acquired with the length in the rotation direction of the patch of the color calibration patch pattern formed subsequently as one unit, The background density is preferable because it can be used for both color calibration and color registration.

  When the background density acquisition unit 404 detects the position detection member 50 by the detection unit 51 while acquiring the background density 600, the acquisition of the background density 600 for one rotation of the intermediate transfer belt B1 is terminated. This is notified to the color calibration means 403. Receiving the notification, the color calibration means 403 forms the color calibration patch pattern with the detection position of the position detection member 50 as the color calibration patch pattern formation start position (FIG. 5: S104).

  In the color calibration patch pattern, as shown in FIG. 7A, predetermined strip-like patches formed in positions corresponding to the two density detection sensors 400a and 400b are arranged in parallel for each color. Pattern 700. One patch 700a is formed by applying a predetermined developing bias value (V) corresponding to a predetermined target density (%), and an actual measured density (%) by the density detection sensors 400a and 400b is obtained. By feedback, an appropriate development bias value (V) is determined and used for the next color image forming process.

  Next, the color calibration unit 403 activates the two density detection sensors 400a and 400b, and acquires the patch density (%) for each patch in the formed color calibration patch pattern 700. (Reading) (FIG. 5: S105).

  Here, when the color calibration unit 403 acquires the patch density, as described above, the elapsed time (sec) from the formation start position of the color calibration patch pattern 600 and the rotation of the intermediate transfer belt B1. The acquisition position (mm) for each patch is calculated from the time (mm / sec). As shown in FIG. 7B, the patch density acquisition position (mm) 702 and the rotation direction of the intermediate transfer belt B1 are calculated. The patch density (%) 703 by the density sensor 400a on the left side, the patch color (any one of black, magenta, cyan, and yellow) 704 of the patch density and the rotation direction of the intermediate transfer belt B1 The patch density (%) 705 by the right density detection sensor 400b and the patch color 706 of the patch density are represented by the patch density. Associating a Buru 701 is stored in a predetermined memory.

  Further, when the color calibration unit 403 acquires the patch density (%) of the last patch of the color calibration patch pattern 700, the background density table coincides with the acquisition position (mm) 702 of the patch density table 701. The background density (%) 603 and 604 associated with the acquisition position (mm) 602 of 601 is acquired. Next, the color calibration unit 403 obtains the background density (%) 603, 604 from the patch density (%) 703, 705 corresponding to the matched acquisition position (mm) 702 of each density detection sensor 400a, 400b. The value subtracted for each position is calculated as the patch absolute density (%). Then, the color calibration unit 403 determines an appropriate development bias value (V) based on the patch absolute density (%), the corresponding colors 704 and 706, the target density (%), and the development bias value (V). ) Is calculated (FIG. 5: S106). The color calibration unit 403 performs such processing by dividing the patch densities (%) 703 and 705 of the patch density table 701 into the respective colors 704 and 706, whereby the color calibration is completed.

  When the color calibration is completed, the color calibration unit 403 notifies the dirty part detection unit 405 to that effect, and the dirty part detection unit 405 that has received the notification notifies the acquired background density (%). A predetermined threshold value (%) is compared, and the portion of the intermediate transfer belt B1 corresponding to the background density acquisition position that exceeds the threshold value is detected as a dirty portion (FIG. 5: S107).

  Specifically, the dirt portion detection unit 405 acquires the background density (%) 603 and 604 of the background density table 601 for each acquisition position (mm) 602 and the background density (%) 603 and 604. And the threshold value (%). The threshold value (%) is set in advance as a density at which the position of a color registration patch (to be described later) cannot be detected by the density detection sensors 400a and 400b.

  If the background density (%) does not exceed the threshold value (%) as a result of the comparison, the dirt portion detection unit 405 determines that the intermediate transfer belt B1 corresponding to the acquisition position (mm) of the background density (%). It is determined that the part is not dirty.

  On the other hand, as a result of the comparison, when the background density (%) exceeds the threshold value (%) (for example, 2%), the dirt portion detection unit 405 determines that the background density (%) exceeds the threshold value (%). ) Is determined to be dirty, and as shown in FIG. 8A, the portion 800 of the intermediate transfer belt B1 is detected as a dirty portion.

  By performing such a detection on the background skin density 603 and 604 of the background density table 601 by the soiled part detection means 405, it is clear where the dirt part exists in one round of the intermediate transfer belt B1. become. The soiled portion is a unit of one background density.

  When the contamination portion detection unit 405 completes the detection of the contamination portion 800 for one rotation of the intermediate transfer belt B1, the color registration unit 406 is notified of this and the color registration unit 406 that has received the notification. Is a portion of the intermediate transfer belt B1 other than the detected dirt portion 800 and a portion where a color registration patch can be formed (referred to as a pattern-formable portion). Then, color registration is performed (FIG. 5: S108).

  Specifically, the color registration unit 406 first calculates the pattern formable portion 801 as shown in FIG. Here, the pattern formable portion 801 means a portion where a predetermined portion at both ends of the intermediate transfer belt B1 is not detected as the dirty portion 800. This is because the color registration patch pattern is simultaneously formed in parallel on both ends of the intermediate transfer belt B1.

  For example, as shown in FIG. 8A, when a predetermined portion 800a at one end of the intermediate transfer belt B1 is detected as a dirty portion, the other end facing the predetermined portion 800a at the one end. Even if the predetermined portion 800b at one end of the other is not detected as a dirty portion, it is calculated that the predetermined portion 800a at one end and the predetermined portion 800b at the other end are not the pattern formable portion 801.

  Such calculation is repeated to calculate the pattern formable portion 801 of the intermediate transfer belt B1. As shown in FIG. 8A, a plurality of the pattern formable portions 801 may exist in the intermediate transfer belt B1 depending on the appearance of the dirt portion 800.

  Then, the color registration means 406 compares the length T1 of the pattern formable portion 801 in the rotation direction with a preset length T2 of the rotation direction of the color registration patch pattern.

  As a result of the comparison, when the length T1 in the rotation direction of the pattern-formable portion 801 exceeds the length T2 in the rotation direction of the color registration patch pattern 802 (FIG. 5: S108 YES), the color registration means In step 406, it is determined that the color registration can be performed with high accuracy, and the patch pattern for color registration is formed in the pattern formable portion 801 (FIG. 5: S109).

  As shown in FIG. 8B, the color registration patch pattern 802 is a predetermined oblique line-shaped patch (an oblique patch) formed at a position corresponding to each of the two density detection sensors 400a and 400b. ) And horizontal linear patches in the direction perpendicular to the rotation direction (referred to as horizontal patches) are arranged in parallel for each color.

  Here, when the color registration unit 406 forms the color registration patch pattern 802, when there are a plurality of the pattern formable portions 801 and both T1 exceeds the T2, Since the color registration patch pattern 802 is formed on the pattern formable portion 801 close to the detection position on the basis of the detection position of the position detection member 50, the time required for the color registration can be shortened. preferable.

  Next, the color registration unit 406 activates the two density detection sensors 400a and 400b, and acquires the position (mm) for each patch in the formed color registration patch pattern 802. .

  Here, since the color registration patch pattern 802 is formed at a portion other than the dirt portion 800, the position (mm) for each patch is accurately obtained.

  As an example showing the above-described effect, FIG. 9 shows that when the color registration unit 406 obtains the density of the color registration patch pattern 802 by using predetermined density detection sensors 400a and 400b. As described above, the density 900 is uneven corresponding to the length of the patch in the rotation direction at the detection positions of the density detection sensors 400a and 400b. The convex 901 with the density 900 mainly corresponds to a magenta, cyan, and yellow patch, and the concave 902 with the density 900 mainly corresponds to a black patch. The density 903 located in the middle of the unevenness corresponds to the background density of the intermediate transfer belt B1.

  Here, since the position of the center of the patch is required in the execution of the color registration, the position of the center of the patch is calculated based on the following procedure. That is, first, a first reference density (%) 904 that is higher than the background density 903 and lower than the highest density of the convex 901 is provided for the convex 901 having the density 900, and the concave 902 having the density 900 is provided. On the other hand, a second reference density (%) 905 that is lower than the background density 903 and higher than the lowest density of the concave 902 is provided. As shown in FIG. 10, when the density 900 is convex 901, the color registration means 406 determines that the position 1000 where the density 900 exceeds the first reference density (%) 904 is the patch detection start position. The position 1001 where the density 900 is less than the first reference density (%) 904 is calculated as the patch detection end position. The color registration unit 406 calculates the center of the patch detection start position 1000 and the patch detection end position 1001 as the center position 1002 of the patch. The same applies to the case where the density 900 is concave 902.

  Here, if the color registration patch pattern 802 is formed on the dirt portion 800 of the intermediate transfer belt B1, the density 900 obtained by the density detection sensors 400a and 400b is the density of the dirt portion 800. The density is obtained by adding the density and the density of the patch pattern 802. Then, as shown in FIG. 11, a density 900 obtained by adding the density of the dirt portion 800 is obtained (solid line). It is understood that the solid line 900 is greatly different in shape from the broken line indicating the density 1100 when the density of the dirt portion 800 is not present.

  Therefore, as shown in FIG. 11, the patch detection start position 900a calculated by the solid line 900 is completely different from the patch detection start position 1100a calculated by the broken line 1100, and the patch detection end calculated by the solid line 900 is completed. The position 900b is completely different from the patch detection end position 1100b calculated by the broken line 1100. As a result, it is understood that the finally calculated center position 900c of the solid line 900 is greatly different from the center position 1100c of the patch at the appropriate (exact) broken line 1100.

  In the present invention, since the position (mm) for each patch is acquired based on the color registration patch pattern 802 formed on the pattern formable portion 801 other than the stain portion 800, the stain portion 800 described above is obtained. Since the patch detection start position and the patch detection end position do not fluctuate, the position (mm) for each patch can be obtained accurately.

  Further, the color registration unit 406 executes color registration based on the acquired position (mm) for each patch (FIG. 5: S110).

  Specifically, the color registration unit 406 performs correction of the image writing position in the main scanning direction based on the distance between the oblique patch and the horizontal patch for each color, and between the horizontal patches for each color. Correction of image drawing timing in the sub-scanning direction (rotation direction) is executed according to the distance.

  Here, since color registration is executed based on an accurate position (mm) for each patch, the accuracy of the color registration can be improved. In the subsequent processing, for example, the color registration unit 406 notifies the control unit 401 that the execution of the color registration is completed, and the control unit 401 performs image forming processing as usual.

  On the other hand, in S108, as a result of the comparison, as shown in FIG. 12A, the length T1 in the rotation direction of the pattern formable portion 801 is less than the length T2 in the rotation direction of the color registration patch pattern 802. (FIG. 5: S108 NO), the color registration unit 406 determines that the color registration cannot be performed with high accuracy, and notifies the display unit 407 to that effect. Upon receiving the notification, the display unit 407 displays a warning screen 1200 on the touch panel 60 indicating that the intermediate transfer belt B1 is dirty as shown in FIG. 12B (FIG. 5: S111). Thereby, it is possible to prompt the user to replace the intermediate transfer belt B1.

  In this case, the color registration unit 406 completely stops the execution of the color registration. As a result, the time required for calibration can be shortened.

  When there are a plurality of the pattern formable portions 801 as shown in FIG. 8A, the color registration unit 406 performs the comparison for all the pattern formable portions 801, When the length T1 in the rotation direction of the pattern formable portion 801 is less than the length T2 in the rotation direction of the color registration patch pattern (FIG. 5: S108 NO), the display means 407 displays the warning screen. It is displayed on the touch panel 60.

  As described above, in the present invention, the background density acquisition unit 404 that acquires the background density of one rotation of the intermediate transfer belt B1 is compared with the acquired background density and a preset threshold value at the time of color calibration. Then, a dirt portion detecting means 405 that detects a portion of the intermediate transfer belt B1 corresponding to the background density acquisition position that exceeds the threshold as a dirty portion, and a portion of the intermediate transfer belt B1 other than the detected dirt portion. And a color registration unit 406 for performing color registration by forming the color registration patch pattern in a portion where the color registration patch pattern can be formed.

  Thereby, the accuracy of color registration can be improved. In particular, accurate color registration can be achieved by using the background density used when executing color calibration, which has been performed in the past, without adding special control for detecting contamination on the intermediate transfer belt B1. Can be executed. As a result, it is possible to prevent erroneous detection of the position of the color registration and reliably prevent color misregistration for each color of the color image. In addition, it is possible to detect a large dirt portion in the intermediate transfer belt B1 due to deterioration over time and to prompt the user to replace the intermediate transfer belt B1.

  In the embodiment of the present invention, color calibration and color registration have been described. However, other calibration, for example, I / O calibration may be further performed as necessary.

  In the embodiment of the present invention, the stain portion detection unit 405 is configured to compare the acquired background density with the threshold value during color registration. However, other configurations may be used. For example, the stain portion detection unit 405 may compare the background density with the threshold immediately after the background density acquisition by the background density acquisition unit 404 is completed.

  In the embodiments of the present invention, the case of a tandem type image forming apparatus has been described as an example. However, the present invention is not limited to this, and an image forming apparatus using a rotary developing device can perform all of the printing of a plurality of colors. Needless to say, the present invention can be applied to an image forming apparatus.

  In the embodiment of the present invention, the image forming apparatus 1 is configured to include each unit. However, a program that realizes each unit may be stored in a storage medium, and the storage medium may be provided. . In this configuration, the above-described program is read by the multifunction peripheral, and the image forming apparatus implements the above-described units. In that case, the program itself read from the recording medium exhibits the effects of the present invention. Furthermore, it is also possible to provide a step executed by each means as a calibration method. The program can be distributed in a state where it is recorded on a computer-readable recording medium such as a CD-ROM.

  As described above, the image forming apparatus and the calibration method according to the present invention are useful for color copiers, color printers and the like as well as color multifunction peripherals, and image formation capable of improving the accuracy of color registration. It is effective as an apparatus and a calibration method.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus FY, FM, FC, FB Image forming unit 400a, 400b Density detection sensor 401 Control means 402 Start detection means 403 Color calibration means 404 Background density acquisition means 405 Dirt portion detection means 406 Color registration means 407 Display means

Claims (6)

In an image forming apparatus that performs color calibration and color registration,
A background density acquisition means for acquiring the background density for one round of the intermediate transfer member during color calibration;
A soiled part detection unit that compares the acquired background density with a preset threshold value and detects a part of the intermediate transfer body corresponding to the acquired position of the background density that exceeds the threshold as a dirty part;
The color registration patch pattern is formed on a portion of the intermediate transfer member other than the detected soiled portion and a pattern formable portion which is a portion where the color registration patch pattern can be formed. An image forming apparatus comprising: a color registration unit that executes image registration. The color registration means compares the length of the pattern formable portion in the rotation direction with a preset length of the color registration patch pattern in the rotation direction. The image formation according to claim 1, wherein when the length in the rotation direction exceeds the length in the rotation direction of the color registration patch pattern, the color registration patch pattern is formed on the pattern formable portion. apparatus. In the color registration means, as a result of the comparison, if the length in the rotation direction of the pattern formable portion is less than the length in the rotation direction of the color registration patch pattern, the intermediate transfer member is dirty. The image forming apparatus according to claim 2, wherein a warning screen to the effect is displayed on the touch panel. In a calibration method of an image forming apparatus that performs color calibration and color registration,
A step of acquiring a background density of one turn of the intermediate transfer member during color calibration;
Comparing the acquired background density with a preset threshold value and detecting a portion of the intermediate transfer body corresponding to the acquisition position of the background density exceeding the threshold value as a dirt portion;
The color registration patch pattern is formed on a portion of the intermediate transfer member other than the detected soiled portion and a pattern formable portion which is a portion where the color registration patch pattern can be formed. A calibration method comprising the steps of:   A program for causing a computer to execute the calibration method according to claim 4. A computer-readable storage medium storing the program according to claim 5.

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