JP2018105990A - Image formation apparatus, control method for the same, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a skew amount of an intermediate transfer belt in a direction orthogonal to a conveyance direction of the intermediate transfer belt before driving the intermediate transfer belt in one cycle.SOLUTION: A system control unit 101 of a printer 100 forms a first detection image on an intermediate transfer belt 87 at the time of turning-on of power supply. A detection result of the first detection image by a registration sensor 71 is stored in a memory 102. The system control unit 101 forms a second detection image on the intermediate transfer belt 87 during preparation operation, inter-sheet time and the like at the time of image formation, and determines a skew amount in a direction orthogonal to a conveyance direction of the intermediate transfer belt 87 on the basis of a detection result of the first detection image and a detection result of the second detection image, and corrects image-writing positions of a plurality of image formation units 81 on the basis of a color shift amount detected by the registration sensor 71 and the skew amount.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus, a control method for the image forming apparatus, and a program.

  2. Description of the Related Art In recent years, tandem configurations in which a plurality of image carriers are arranged side by side have become the mainstream in image forming apparatuses as the speed of image forming apparatuses increases. This image forming apparatus forms images of different colors on each of the plurality of image carriers, and transfers the images on the plurality of image carriers so that they overlap the intermediate transfer member. As a result, a full-color image is formed on the intermediate transfer member. Then, the image forming apparatus transfers the full color image on the intermediate transfer member to a recording medium and outputs a printed matter. In such an image forming apparatus, if the relative position of the image transferred onto the intermediate transfer member is shifted, the color of the image changes. Therefore, the image forming apparatus forms a detection image for each color on the intermediate transfer member, detects a shift amount (color shift amount) at a relative position of the detection image for each color using a sensor, and detects the color shift amount. And a color misregistration correction function for correcting the image forming position (image writing position) of each color image.

  Here, for example, an intermediate transfer belt is a typical example of an intermediate transfer member in an electrophotographic full-color image forming apparatus. The intermediate transfer belt is stretched by a plurality of rollers including a driving roller, and is rotationally driven by the rotation of the driving roller. There is a generally known problem that such an intermediate transfer belt stretched around a plurality of rollers approaches one of the end portions during rotation driving.

  Therefore, in the image forming apparatus described in Patent Document 1, the amount of movement of the mark provided on the intermediate transfer belt in the direction orthogonal to the conveyance direction of the intermediate transfer belt is detected by a sensor, and the intermediate transfer belt is stretched based on the detection result. The inclination of the driven roller is adjusted. When the inclination of the driven roller is adjusted, the distribution of the frictional force in the direction orthogonal to the conveyance direction of the intermediate transfer belt changes, and the intermediate transfer belt can be moved in the direction opposite to the direction in which the intermediate transfer belt moves.

JP-A-3-288167

  However, in the above-described conventional example, there is a problem that it takes time for one rotation of the belt in order to obtain the shift amount of the intermediate transfer belt.

  The present invention has been made to solve the above problems. An object of the present invention is to detect a shift amount of the intermediate transfer belt in a direction orthogonal to the conveyance direction of the intermediate transfer belt before driving the intermediate transfer belt for one round.

  The present invention provides a plurality of image forming units for forming images of different colors, an intermediate transfer belt to which the images formed by the plurality of image forming units are transferred, and driving the intermediate transfer belt to obtain the images. A driving unit that conveys; a detection unit that detects a detection image formed on the intermediate transfer belt in order to detect a color misregistration amount of the image formed by the plurality of image forming units; Before the image forming unit forms the image, the plurality of image forming units are controlled to form a first detection image, and after the plurality of image forming units form the image, the plurality of image forming units are A second detection image is formed by control, and the image on the intermediate transfer belt is conveyed based on a detection result of the first detection image and a detection result of the second detection image by the detection unit. Is The plurality of image forming units based on a determining unit that determines a shift amount in a direction orthogonal to the conveyance direction, the color misregistration amount detected by the detection unit, and the shift amount determined by the determination unit. And a correction means for correcting the image writing position.

  According to the present invention, the shift amount of the intermediate transfer belt in the direction orthogonal to the conveyance direction of the intermediate transfer belt can be detected before the intermediate transfer belt is driven for one round.

Schematic sectional view of the printer of this embodiment Schematic sectional view of the image forming unit of the printer of this embodiment 1 is a block diagram illustrating a control configuration of a printer according to a first embodiment. Color misregistration correction pattern formed to detect the color misregistration amount in the first embodiment Registration patch image for detecting the shift amount of the intermediate transfer belt FIG. 3 is a block diagram illustrating a control configuration of a printer according to a second embodiment. Color misregistration correction pattern formed to detect the amount of color misregistration in the second embodiment

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

First, an embodiment applied to a tandem color image forming apparatus (printer 100) showing an embodiment of the image forming apparatus of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view for explaining a schematic configuration of the printer 100.
FIG. 2 is a cross-sectional view for explaining a schematic configuration of the image forming unit of the printer 100.
FIG. 3 is a schematic block diagram illustrating a control configuration of the printer 100 according to the first embodiment.
FIG. 4 is a diagram illustrating a color misregistration correction pattern formed in order to detect the color misregistration amount in the first embodiment. The color misregistration correction pattern includes a registration patch image for each color.
FIG. 5 is a diagram illustrating a registration patch image for detecting the shift amount of the intermediate transfer belt. Hereinafter, the color misregistration correction is referred to as “registration correction”.

  The printer 100 includes an image forming unit 81Bk that forms a black (hereinafter “Bk”) image, an image forming unit 81C that forms a cyan (hereinafter “C”) image, and a magenta (hereinafter “M”) color. The color printer includes four image forming units (image forming units), that is, an image forming unit 81M that forms a yellow image and an image forming unit 81Y that forms a yellow (hereinafter “Y”) color image. These four image forming units 81Bk, 81C, 81M, 81Y are arranged in a line at regular intervals. The printer 100 forms a full-color image by superimposing and transferring a plurality of toner images formed by the plurality of image forming units (81Bk, 81C, 81M, 81Y) onto an endless belt-shaped intermediate transfer belt 87 described later. It is a possible image forming apparatus.

  Photosensitive drums 82a, 82b, 82c, and 82d are installed in the image forming units 81Bk, 81C, 81M, and 81Y, respectively. Around each photosensitive drum 82a, 82b, 82c, 82d, there are chargers 83a, 83b, 83c, 83d, developing devices 84a, 84b, 84c, 84d, transfer rollers 85a, 85b, 85c, 85d, a drum cleaner device 86a, 86b, 86c, 86d are respectively arranged. Further, scanning optical devices 50a, 50b, 50c, and 50d are installed below the chargers 83a, 83b, 83c, and 83d and the developing devices 84a, 84b, 84c, and 84d. The developing devices 84a, 84b, 84c, and 84d store Bk toner, C toner, M toner, and Y toner, respectively.

  Each of the photosensitive drums 82a, 82b, 82c, and 82d is a negatively charged OPC photosensitive member having a photoconductive layer on an aluminum drum base, and is driven in a direction indicated by an arrow (clockwise in FIG. 1) by a driving device (not shown). Direction) at a predetermined process speed. The chargers 83a, 83b, 83c, and 83d uniformly charge the surfaces of the photosensitive drums 82a, 82b, 82c, and 82d to a predetermined negative potential by a charging bias applied from a charging bias power source (not shown).

  The developing devices 84a, 84b, 84c, and 84d contain toner, and each color latent image formed on each photosensitive drum 82a, 82b, 82c, and 82d is attached to each color toner and developed as a toner image ( Visualization). The transfer rollers 85a, 85b, 85c, and 85d are in contact with the photosensitive drums 82a, 82b, 82c, and 82d via the intermediate transfer belt 87. In order to transfer the toner images on the photosensitive drums 82a, 82b, 82c, and 82d to the intermediate transfer belt 87 between the photosensitive drums 82a, 82b, 82c, and 82d and the transfer rollers 85a, 85b, 85c, and 85d. A primary transfer nip portion is formed. The drum cleaners 86a, 86b, 86c, and 86d are configured with a cleaning blade or the like for removing residual toner remaining on the photosensitive drum during the primary transfer from the photosensitive member.

  The intermediate transfer belt 87 is an endless belt-like intermediate transfer member, is stretched between a pair of belt drive rollers 88 and a belt transport roller 89, and rotates in the direction of arrow A (counterclockwise direction in FIG. 1) ( Moved). The intermediate transfer belt 87 is made of a dielectric resin such as polycarbonate, polyethylene terephthalate resin film, polyvinylidene fluoride resin film, or the like.

  The belt driving roller 88 is in contact with the secondary transfer roller 90 via the intermediate transfer belt 87 to form a secondary transfer nip portion. A belt cleaning device 91 that removes and collects transfer residual toner remaining on the surface of the intermediate transfer belt 87 is installed outside the intermediate transfer belt 87 and in the vicinity of the belt conveyance roller 89.

  The paper feed cassette 92 stores a sheet-like recording medium (hereinafter referred to as paper). The paper in the paper feed cassette 92 is fed one by one by the paper feed roller 93 and once transported to the registration roller pair 94, it temporarily stops and the toner image is transferred to a predetermined position at the secondary transfer nip portion. So that it is transported at the same timing. The sheet on which the toner image is transferred at the secondary transfer nip is conveyed to the fixing device 95. The fixing device 95 fixes the toner image on the paper by the heat of a heater (not shown). The paper is then transported and discharged onto a paper discharge tray 98 by a transport roller pair 96 and a paper discharge roller pair 97.

  The registration detection sensor 71 detects a color misregistration correction pattern for each color formed on the intermediate transfer belt 87. Based on the detection result of the registration detection sensor 71, the system control unit 101 measures the relative position of the registration patch image of another color with respect to the registration patch image of the reference color. The reference color is, for example, yellow (Y). Hereinafter, the registration detection sensor is referred to as “registration sensor”. As shown in FIG. 4, the registration sensor 71 has a registration sensor 71F on the front side and a registration sensor 71R on the back side, and can detect a color misregistration correction pattern at two locations on the intermediate transfer belt at the front and back. Yes. In this embodiment, yellow (Y) is used as the reference color. In this embodiment, the image forming unit 81Y is provided at the most upstream position in the moving direction of the intermediate transfer belt 87 and is farthest from the registration sensor 71. Therefore, the change in the shift amount of the intermediate transfer belt 87 is the largest. The reference color is not limited to yellow (Y).

  Here, the distance between the image forming unit 81Y and the image forming unit 81M is “L1”, the distance between the image forming unit 81M and the image forming unit 81C is also “L1”, and the distance between the image forming unit 81C and the image forming unit 81Bk is also “L1”, and the distance from the image forming unit 81Bk to the registration sensor 71 is “L2”. Then, the distance from the image forming unit 81Y to the registration sensor 71 is “L1 × 3 + L2,” the distance from the image forming unit 81M to the registration sensor 71 is “L1 × 2 + L2,” and the distance from the image forming unit 81C to the registration sensor 71. Becomes "L1 + L2".

  A system control unit 101 shown in FIG. 3 controls operations such as image formation and paper conveyance of the printer 100, and also controls the formation of the aforementioned color misregistration correction pattern. The memory 102 is a storage unit provided in the system control unit 101, and stores the total number of prints, a detection result detected (calculated) by the system control unit 101 based on a detection result by the registration sensor 71, and the like. During image formation, the system control unit 101 can perform registration correction by performing exposure control corresponding to each color based on information stored in the memory 102.

  When forming the color misregistration correction pattern, the system control unit 101 first instructs the laser drive circuit of the electric circuit board 14 (FIG. 3) of the scanning optical device 50 to control laser emission. . As a result, the scanning optical device 50 exposes the photosensitive drums 82a, 82b, 82c, and 82d and statically charges the photosensitive drums 82a, 82b, 82c, and 82d charged by the chargers 83a, 83b, 83c, and 83d. An electrostatic latent image is formed. Thereafter, each color toner that is frictionally charged in the developing devices 84a, 84b, 84c, and 84d is attached to the electrostatic latent image, whereby the color misregistration correction patterns for the respective colors are formed on the photosensitive drums 82a, 82b, 82c, and 82d. Form. Each color toner image is transferred onto the intermediate transfer belt 87 from the respective photosensitive drums 82a, 82b, 82c, and 82d at each primary transfer nip portion.

  In the color misregistration correction pattern, a plurality of registration patch images as shown in FIG. 4 are continuously formed on the intermediate transfer belt 87. Image position detection on the belt is performed by reading the registration patch image by the registration sensor 71. The relative positional relationship between the registration patch images of the respective colors is calculated from each time when the registration patch image of FIG. 4 passes through the registration sensor 71.

  For example, when each color registration patch image 711Y, 711M, 711C, 711K as shown in FIG. 4 passes through the registration sensor 71F on the front side of the registration sensor 71 (71F, 71R) at the two front backs, the detection result by the registration sensor 71 is system controlled. Input to the unit 101. The system control unit 101 detects the time from when one line of the v-shaped registration patch image is detected until the other line is detected (intervals “Y1F”, “M1F”, “C1F”, “K1F” in FIG. 4). )). The system control unit 101 can detect the amount of deviation of the writing position in the direction (main scanning direction) orthogonal to the conveyance direction of the intermediate transfer belt 87 based on this passage time. For example, when the passage time is longer than a predetermined time, the writing position is shifted to the near side. On the other hand, when the passage time is shorter than the predetermined time, the writing position is shifted to the back side. When the color registration patch images 712Y, 712M, 712C, and 712K as shown in FIG. 4 pass through the rear registration sensor 71R, the system control unit 101 detects one line of the registration patch image and then detects the other line. (Time intervals “Y1R”, “M1R”, “C1R”, “K1R” in FIG. 4) are calculated. The system control unit 101 compares the passage time calculated from the detection result of the registration sensor 71R with the passage time calculated from the detection result of the registration sensor 71F (intervals “Y1F”, “M1F”, “C1F”, “K1F”). Thus, the main scanning overall magnification is detected.

  For example, when the interval “Y1R” is longer than “Y1F” in FIG. 4, the interval between the registration patch images 711Y and 712Y is shorter than the design value, and the overall main scanning magnification of Y is small. On the other hand, when the interval “Y1R” is shorter than “Y1F” in FIG. 4, the interval between the registration patch images 711Y and 712Y is longer than the design value, and the overall main scanning magnification of Y is large. The MCK is similarly detected, and the detection result obtained in this manner is stored in a memory 102 provided in the system control unit 101. Here, as a detection result, a value stored in the memory 102, a main scanning overall magnification calculation method, and the like will be described later.

  Next, an operation for determining the registration correction amount will be described. The operation for determining the registration correction amount is controlled by the system control unit 101. Further, the operation for determining the registration correction amount is performed when the printer 100 is turned on, after printing a predetermined number of sheets, or after a predetermined time has elapsed, but is not limited thereto. Will not be described in particular.

  When starting the registration correction amount determination operation, the system control unit 101 first turns on the Y charger 83d, the M charger 83c, the C charger 83b, and the Bk charger 83a sequentially. Next, the system control unit 101 applies a primary transfer bias to the Y transfer roller 85d, the M transfer roller 85c, the C transfer roller 85b, and the Bk transfer roller 85a, and sequentially turns them ON. Next, the system control unit 101 turns on the Y developing device 84d, the M developing device 84c, the C developing device 84b, and the Bk developing device 84a. Next, based on the image data (detection image data) of the color misregistration correction pattern for each color formed on the intermediate transfer belt 87, the system control unit 101 converts the Y scanning optical device 50d to the Y photosensitive drum. 82d, M scanning optical device 50c to M photosensitive drum 82c, C scanning optical device 50b to C photosensitive drum 82b, and Bk scanning optical device 50a to Bk photosensitive drum 82a as scanning light. Perform exposure. In Y image formation, an electrostatic latent image is formed on the photosensitive drum 82d charged by the charger 83d by exposing the photosensitive drum 82d. Thereafter, under the control of the system control unit 101, the developing device 84d causes the Y-color toner frictionally charged in the developing device 84d to adhere to the electrostatic latent image on the photosensitive drum 82d, thereby forming a toner image. The formed toner image is transferred onto the intermediate transfer belt 87 from the photosensitive drum 82d at the primary transfer nip portion of the transfer roller 85d. M, C, and Bk image formation is similarly transferred at a predetermined timing onto the intermediate transfer belt 87 at the primary transfer nip portion.

  Next, the system control unit 101 detects the color misregistration correction pattern of each color formed on the intermediate transfer belt 87 with the registration sensor 71, detects the above-described passage time interval based on the detection result, and further performs a reference Color misregistration amounts for yellow, which is the color, are detected and stored in the memory 102. In this embodiment, each passing time (interval “Y1F”, “M1F”, “C1F”, “K1F”, “Y1R”, “M1R”, “C1R”) detected based on the detection of the color misregistration correction pattern. , “K1R”), Y, M, C, and Bk main scanning overall magnifications calculated from these, the difference between “Y1F” and “M1F” corrected with the respective main scanning overall magnifications, “Y1F” The difference between “C1F” and the difference between “Y1F” and “K1F” (that is, the color misregistration amount with respect to yellow as the reference color) and the like are stored in the memory 102 as detection results when determining the registration correction amount.

The main scanning overall magnification is calculated as follows.
For example, if “δY = Y1F−Y1R”, the Y main scanning overall magnification is calculated as “Y main scanning overall magnification = (design value + ΔY) / design value”. The same applies to the main scanning overall magnifications of M, C, and Bk.

Next, an operation when color image formation is performed in the printer 100 will be described with reference to FIG.
When the image data signal is input, the system control unit 101 first starts pre-rotation, turns on the Y charger 83d, and then turns on the primary transfer bias by applying it to the Y transfer roller 85d. Next, the system control unit 101 turns on the Y developing device 84d.

  Next, the system control unit 101 detects the Y-color detection image data formed on the intermediate transfer belt 87 and the detection result when determining the registration correction amount stored in the memory 102 when determining the registration correction amount (here, Y The main scanning writing timing is corrected on the basis of the main scanning overall magnification and the Y photosensitive drum 82d is exposed from the Y scanning optical device 50d using the laser beam as scanning light. In Y image formation, an electrostatic latent image is formed on the photosensitive drum 82d charged by the charger 83d by exposing the photosensitive drum 82d. Thereafter, Y-color toner frictionally charged in the developing device 84d is attached to the electrostatic latent image on the photosensitive drum 82d to form registration patch images 711Y and 712Y. The formed toner image is transferred from the photosensitive drum 82d to the intermediate transfer belt 87 at the primary transfer nip portion.

  Next, when the registration patch images 711Y and 712Y pass the registration sensor 71F on the front side and the registration sensor 71R on the back side, the system control unit 101 detects the intervals “Y1F” and “Y1R” in FIG. 5 from the passage time of the registration patch images. To do. When the interval “Y1R” is longer than the passage time “Y1F”, the interval between the registration patch images 711Y and 712Y is shorter than the design value, and the overall main scanning magnification of Y is small. On the other hand, when the interval “Y1R” is shorter than “Y1F”, the interval between the registration patch images 711Y and 712Y is longer than the design value, and the overall main scanning magnification of Y is large.

  Furthermore, the system control unit 101 calculates the Y main scanning overall magnification from the currently detected “Y1F” and “Y1R” by the above-described calculation method, and removes the influence of the main scanning overall magnification. Is recalculated (ie, “Y1F” is corrected using the Y main scanning overall magnification). When the recalculated “Y1F” is longer than the time stored in the memory 102 (“Y1F” at the time of registration correction amount determination excluding the influence of the Y main scanning overall magnification at the time of registration correction amount determination) This means that the main scanning writing position is shifted to the near side, and if it is short, the main scanning writing position is shifted to the far side.

  For example, “Y1F (Det)” is the result of removing “Y1F” detected this time, excluding the effect of the main scanning overall magnification, and “Y1F” when determining the registration correction amount stored in the memory 102. The one without the “Y1F (Mem)”. Then, the deviation amount “ΔY1” of the writing position is, for example, “ΔY1 = Y1F (Mem) −Y1F (Det)”.

  This writing position deviation “ΔY1” is the amount of deviation of the intermediate transfer belt (the amount of movement in the main scanning direction). Therefore, the system control unit 101 stores the detection result thus obtained in a memory 102 provided in the system control unit 101. Note that the influence of temperature changes in the color printer is particularly sensitive to the main scanning overall magnification. As described above, the influence of the entire main scanning magnification can be eliminated to detect the belt shift amount with high accuracy. It becomes.

  Next, the system control unit 101 sequentially turns on the M charger 83c, the C charger 83b, and the Bk charger 83a. Next, the system control unit 101 applies a primary transfer bias to the M transfer roller 85c, the C transfer roller 85b, and the Bk transfer roller 85a, and sequentially turns them ON. Next, the system control unit 101 turns on the M developing device 84c, the C developing device 84b, and the Bk developing device 84a.

  Further, the system control unit 101 determines the image data of each color formed on the intermediate transfer belt 87, the shift amount “ΔY1” of the intermediate transfer belt stored in the memory 102, and the registration correction amount in the memory 102 when determining the registration correction amount. Based on the detection result (for example, the overall magnification of Y main scanning), the writing timing of main scanning is corrected, and the Y photosensitive drum 82d is exposed from the Y scanning optical device 50d using the laser beam as scanning light.

  Next, the system control unit 101 calculates the distance M from the distance “L1 × 3 + L2” from the image forming unit 81Y to the registration sensor 71 and the distance “L1 × 2 + L2” from the image forming unit 81M to the registration sensor 71. The belt shift amount “ΔY1 × (L1 × 2 + L2) / (L1 × 3 + L2)” is calculated. Then, the system control unit 101 calculates the M belt shift amount and the detection result when determining the registration correction amount in the memory 102 (for example, the M main scanning overall magnification and the difference between “Y1F” and “M1F”). ), The M photosensitive drum 82c is exposed using the laser beam from the M scanning optical device 50c as scanning light.

  Next, the system controller 101 determines that the distance from the image forming unit 81Y to the registration sensor 71 is “L1 × 3 + L2” and the distance from the image forming unit 81C to the registration sensor 71 is “L1 + L2”. The quantity “ΔY1 × (L1 + L2) / (L1 × 3 + L2)” is calculated. Then, the system control unit 101 calculates the C belt shift amount and the detection result when determining the registration correction amount in the memory 102 (for example, the C main scanning overall magnification and the difference between “Y1F” and “C1F”). ), The C photosensitive drum 82b is exposed using the laser beam from the C scanning optical device 50b as scanning light.

  Next, the system control unit 101 calculates the belt deviation amount “Bk” from the distance “L1 × 3 + L2” from the image forming unit 81Y to the registration sensor 71 and the distance “L2” from the image forming unit 81Bk to the registration sensor 71. ΔY1 × (L2) / (L1 × 3 + L2) ”is calculated. Then, the system control unit 101 calculates the Bk belt deviation amount and the detection result when determining the registration correction amount in the memory 102 (for example, the Bk main scanning overall magnification and the difference between “Y1F” and “K1F”). The Bk photosensitive drum 82a is exposed from the Bk scanning optical device 50a using the laser beam as scanning light.

  In Y image formation, an electrostatic latent image is formed on the photosensitive drum 82d charged by the charger 83d by exposing the photosensitive drum 82d. Thereafter, the system control unit 101 attaches the Y color toner triboelectrically charged in the developing device 84d to the electrostatic latent image on the photosensitive drum 82d to form a toner image. The formed toner image is transferred onto the intermediate transfer belt 87 from the photosensitive drum 82d at the primary transfer nip portion of the transfer roller 85d. When forming M, C, and Bk images, the toner image formed in the same manner as Y is transferred onto the intermediate transfer belt 87 at the primary transfer nip portion. As described above, by correcting the image formation timing in consideration of the belt shift amount for each color, it is possible to form a good image with suppressed color shift in the main scanning direction. The registration patch image is formed at a position where the registration patch image is not transferred to the paper.

  In addition, the system control unit 101 performs the same timing correction as the formation of the registration patch image before the first image formation before the second image formation, so that the gap between the sheets (the first image and the second image is formed). Y registration patch image 721 is formed between the two images. Then, the system control unit 101 detects the interval “Y2F” in FIG. 5 from the passing time when the formed Y registration patch image 721 has passed through the registration sensor 71F on the near side. Here, the system control unit 101 uses the main scanning overall magnification obtained from “Y1F” and “Y1R” detected from the registration patch image before the first image formation as the main scanning overall magnification. Recalculate “Y2F” excluding the effect of. Further, the system control unit 101 calculates the recalculated “Y2F” from the time stored in the memory 102 (“Y1F” at the time of determining the registration correction amount) as in the case of the first image formation. The main scanning writing position deviation “ΔY2” is calculated by comparing with the above (excluding the influence of the magnification). This “ΔY2” is the shift amount of the intermediate transfer belt. Further, the system control unit 101 stores the detection result “ΔY2” thus obtained in a memory 102 provided in the system control unit 101. Even when the second image is formed, using this result, it is possible to form a good image with no color shift in the main scanning direction by correcting the image formation timing in consideration of the amount of belt deviation for each color. it can. Further, the system control unit 101 performs the same correction for the third and subsequent sheets. Note that the toner consumption fee can be reduced by setting the second and subsequent registration patch images only to the front side.

  As described above, according to the first embodiment, the detection result at the time of determining the registration correction amount is stored in the memory 102, and the registration patch image is written between sheets before image formation or when a plurality of images are formed. The registration sensor 71 detects the color misregistration amount and compares the detection result with the detection result at the time of determining the registration correction amount in the memory 102 to obtain the belt shift amount. Then, the Y writing timing (that is, the image writing position) at the time of image formation is corrected based on the belt shift amount. As for the writing start timing of other colors, the belt shift amount corresponding to the distance from the interval between the color image forming units to the registration sensor 71 is calculated, and the writing start timing is corrected based on the belt shift amount of each color. As a result, it is possible to perform good printing with the belt shift amount and color shift amount suppressed.

  It should be noted that the registration patch images are formed at two positions in the front and only during the preparatory operation before image formation, and the belt shift amount is detected with higher accuracy in order to eliminate the influence of the main scanning magnification. By forming a registration patch image only at one location on the front side, toner consumption can be suppressed. For the second and subsequent sheets, the main scanning magnification of the first sheet is used to eliminate the influence of the main scanning magnification, so that it is possible to detect the amount of belt deviation for each job while suppressing toner consumption.

  As described above, in this embodiment, the belt deviation amount detected in the preparation operation is corrected from the first image. However, when the productivity is affected, the belt shift amount may be corrected from the second image, and these do not limit the present invention.

Hereinafter, Example 2 will be described with reference to FIGS. In the second embodiment, only the configuration different from the first embodiment will be described.
FIG. 6 is a schematic block diagram illustrating a control configuration of the printer 100 according to the second embodiment.
FIG. 7 is a diagram illustrating a registration patch image for detecting the shift amount of the intermediate transfer belt according to the second embodiment.

  In the second embodiment, as shown in FIG. 6, an HP detection sensor 61 that detects the home position (hereinafter “HP”) of the intermediate transfer belt 87 is provided. The HP detection sensor 61 is an optical sensor, for example, and detects the HP of the intermediate transfer belt 87 (that is, a predetermined position in the rotation direction of the intermediate transfer belt 87) by detecting a mark attached to the intermediate transfer belt 87. . In the second embodiment, registration patch images 711Y and 712Y are created based on the HP detected by the HP detection sensor 61.

  As in the first embodiment, when the registration patch images 711Y, 711M, 711C, 711K, and 721Y pass the registration sensor 71F on the near side, the system control unit 101 determines each interval shown in FIG. 7 from the passage time of the image part of the registration patch image. “Y1F”, “M1F”, “C1F”, “K1F”, “Y2F” are detected. In the second embodiment, the system control unit 101 obtains the central position of each interval, and determines the distance between the central positions of the registration patch images 711Y and 711M, 711C, 711K, and 721Y as “YM_1F”, “YC_1F”, Calculate as “YK_1F” and “YY_1F”. The system control unit 101 performs the above operation for one rotation of the intermediate transfer belt 87. That is, the system control unit 101 forms a plurality of registration patch images (for one round of the intermediate transfer belt 87) on the intermediate transfer belt 87, detects each of the above-described intervals, and also determines the distance between the center positions of the registration patch images. Each calculation is performed, and the calculation result is stored in the memory 102 as data for one rotation of the intermediate transfer belt 87.

  At the time of image formation, the system control unit 101 performs registration correction in the transport direction between YM from the average value of all data of YM distance such as “YM_1F” stored in the memory 102, and between YC such as “YC_1F” The registration correction in the transport direction between YC is performed from the average value of all the distance data, and the registration correction in the transport direction between YK is performed from the average value of all the YK distance data such as “YK — 1F”.

  In addition, the system control unit 101 detects variations in distances between colors such as the YM distance, the YC distance, and the YK distance (for example, differences from the above average values) up to each color registration patch image from the HP of the intermediate transfer belt 87. Is stored in the memory 102 together with the distance. For example, the variation amount (difference from the average value of the YM distance) is calculated for all data of the YM distance (for example, “YM_1F”), and the calculated value is calculated from the HP of the intermediate transfer belt 87 to the corresponding registration patch image ( For example, it is stored in the memory 102 together with the distance up to 711M). This process is similarly performed for the MC distance, the YC distance, and the YK distance. As a result, the rotation unevenness component (rotation fluctuation component) for one rotation of the belt generated by driving the intermediate transfer belt 87 once can be stored in association with the distance from the HP position. Then, when calculating the belt deviation amount by measuring the registration patch image by the registration sensor 71, correction using the rotation unevenness component stored in association with the distance from the HP position is performed, so that the belt deviation is more accurately performed. The amount can be detected.

  In the second embodiment, as described above, in addition to the data stored in the memory 102 in the first embodiment, the distance between the central positions of the registration patch images for one belt of the intermediate transfer belt 87, and the central positions. Data or the like that associates the variation (difference) from the average value of the distance with the distance from the HP position is also stored in the memory 102 as a detection result during the registration correction amount determining operation.

  Next, an operation when color image formation is performed in the printer 100 will be described with reference to FIG. As in the first embodiment, the system control unit 101 corrects the main scanning write timing based on the detection result when determining the registration correction amount stored in the memory 102, and exposes and develops the Y photosensitive drum 82d. The registration patch images 711Y and 712Y are transferred onto the intermediate transfer belt 87.

  Next, when the registration patch images 711Y and 712Y pass the registration sensor 71F on the front side and the registration sensor 71R on the back side, the system control unit 101 detects the intervals “Y1F” and “Y1R” in FIG. 5 from the passage time of the image part. Then, the shift amount “ΔY1” of the Y intermediate transfer belt is calculated and stored in the memory 102 provided in the system control unit 101.

  However, in the second embodiment, when the registration patch images 711Y and 712Y pass the registration sensor 71F on the front side of the registration sensor 71 and the registration sensor 71R on the back side of the registration sensor 71, the system control unit 101 starts from the HP of the intermediate transfer belt 87 of the registration patch image. Measure with the same distance. Based on the measured distance from the HP and the data stored in the memory 102 (the rotation unevenness component of the intermediate transfer belt 87 stored in association with the distance from the HP position), the system control unit 101 Perform correction to eliminate the influence of rotation unevenness when detecting "Y1F" and "Y1R". As a result, “Y1F”, “Y1R”, etc. can be detected with higher accuracy, and as a result, the belt shift amount “ΔY” can be detected with higher accuracy. As in the first embodiment, the system control unit 101 calculates the M belt shift amount, the C belt shift amount, and the Bk belt shift amount.

  Next, the system control unit 101 exposes Y, M, C, and Bk photosensitive drums as in the first embodiment. At this time, in the second embodiment, the registration correction in the transport direction between YM is performed from the average value of all data such as “YM — 1F” stored in the memory 102 when determining the registration correction amount as described above, and YC The registration correction in the transport direction between YC is performed from the average value of all data such as “YC_1F” that is the distance between and the registration correction in the transport direction between YK is calculated from the average value of all data such as “YK_1F” that is the distance between YK. I do. Others are the same as those in the first embodiment, and the description is omitted.

  As described above, according to the second embodiment, the HP detection sensor 61 that detects the HP of the intermediate transfer belt 87 is provided, and the registration correction pattern is created based on the HP during the registration correction amount determination operation. Data for one round of the belt between the distances between the registration patch images is stored in the memory 102. Thereby, the rotation unevenness component generated by driving the intermediate transfer belt 87 once can be stored in association with the distance from the HP position. By using the rotation unevenness component associated with the distance from the HP position when calculating the belt shift amount by measuring the registration patch image by the registration sensor 71, the belt shift amount can be detected with higher accuracy. It becomes. For this reason, exposure correction of the main scanning writing timing at the time of image formation can be performed with higher accuracy, and satisfactory printing with suppressed color misregistration can be performed.

  As described above, according to each embodiment, the shift amount of the intermediate transfer belt in the direction orthogonal to the conveyance direction of the intermediate transfer belt can be detected before the intermediate transfer belt is driven for one round. As a result, the amount of deviation of the intermediate transfer belt during the preparatory operation or between sheets can be detected, and the main scanning color misregistration correction can be easily performed favorably.

In addition, the structure of the various data mentioned above and its content are not limited to this, You may be comprised with various structures and content according to a use and the objective.
Although one embodiment has been described above, the present invention can take an embodiment as, for example, a system, apparatus, method, program, or storage medium. Specifically, the present invention may be applied to a system composed of a plurality of devices, or may be applied to an apparatus composed of a single device.
Moreover, all the structures which combined said each Example are also contained in this invention.

(Other examples)
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in the computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.
Further, the present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one device.
The present invention is not limited to the above embodiments, and various modifications (including organic combinations of the embodiments) are possible based on the spirit of the present invention, and these are excluded from the scope of the present invention. is not. That is, the present invention includes all the combinations of the above-described embodiments and modifications thereof.

71 Registration detection sensor
81Bk, 81C, 81M, 81Y Image forming section
87 Intermediate transfer belt
101 System controller
102 memory

Claims (10)

A plurality of image forming means for forming images of different colors;
An intermediate transfer belt to which the image formed by the plurality of image forming means is transferred;
Driving means for driving the intermediate transfer belt to convey the image;
Detecting means for detecting a detection image formed on the intermediate transfer belt in order to detect a color shift amount of the image formed by the plurality of image forming means;
At the first timing, the plurality of image forming units are controlled to form a first detection image, and at the second timing after the first timing, the plurality of image forming units are controlled to A transport direction in which the image on the intermediate transfer belt is transported based on a detection result of the first detection image and a detection result of the second detection image by the detection unit. Determining means for determining a shift amount in a direction orthogonal to
Correction means for correcting image writing positions of the plurality of image forming units based on the color misregistration amount detected by the detection unit and the shift amount determined by the determination unit. An image forming apparatus.   2. The image forming apparatus according to claim 1, wherein the second timing is a timing during a preparatory operation when performing image formation or during the formation of a plurality of images.   The determining unit determines the shift amount based on a detection result of the first detection image and a detection result of the second detection image formed by a reference image forming unit among a plurality of image forming units. The image forming apparatus according to claim 1, wherein the image forming apparatus is determined.   The determining unit determines the shift amount corresponding to the reference image forming unit based on the detection result of the first detection image and the detection result of the second detection image, and the shift amount and the reference The image forming apparatus according to claim 3, wherein the shift amount corresponding to the other image forming unit is determined based on an interval between the image forming unit and the other image forming unit.   5. The image forming apparatus according to claim 3, wherein the reference image forming unit is an image forming unit disposed at a position farthest from the reading position of the detection image by the detection unit. . The first detection image and the second detection image include a plurality of detection images formed in a direction orthogonal to the transport direction,
The detection result of the first detection image and the detection result of the second detection image used by the determination unit to determine the shift amount are each a plurality of detection images formed in a direction orthogonal to the transport direction. 6. The image forming apparatus according to claim 1, wherein the detection result is corrected based on a magnification in a direction orthogonal to the conveyance direction, which is obtained from the detection result. Detecting means for detecting a position of the transfer belt in the transport direction;
At the first timing, the detection result of the first detection image is associated with the position of the transfer belt detected by the detection unit;
At the second timing, the detection result of the first detection image is obtained based on the rotation fluctuation component of the transfer belt obtained from the detection result of the first detection image associated with the position of the transfer belt. The image forming apparatus according to claim 1, wherein correction is performed.   The image forming apparatus according to claim 1, further comprising a storage unit that stores a detection result of the first detection image at the first timing. A plurality of image forming units that form images of different colors, an intermediate transfer belt to which the images formed by the plurality of image forming units are transferred, and a driving unit that drives the intermediate transfer belt to convey the images And a detection unit that detects a detection image formed on the intermediate transfer belt in order to detect a color shift amount of the image formed by the plurality of image forming units. There,
Controlling the plurality of image forming means to form a first detection image at a first timing;
Controlling the plurality of image forming means to form a second detection image at a second timing after the first timing;
Based on the detection result of the first detection image and the detection result of the second detection image by the detection unit, a shift amount in a direction orthogonal to the transport direction in which the image on the intermediate transfer belt is transported is calculated. A decision step to decide;
A correction step of correcting image writing positions of the plurality of image forming units based on the color misregistration amount detected by the detection unit and the shift amount determined in the determination step;
A control method for an image forming apparatus, comprising:   The program for functioning a computer as a determination means of any one of Claims 1-8.

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