Image forming system and program

Abstract

To suppress partial positional deviation within a single sheet between images formed by two image forming units. When aligning the position of an image printed on paper PP by image forming unit 30 with the position of an image printed on paper PP by image forming unit 50, CPU 81, which is a processor, causes one image forming unit selected from the four image forming units of image forming unit 30 and one image forming unit selected from the four image forming units of image forming unit 50 to form images at the same position on the paper. Then, CPU 81 reduces the amount of misalignment by partially changing the image write cycle of either image forming unit 30 or image forming unit 50 depending on the amount of relative misalignment between the two formed images.

Description

[Technical Field]

[0001] The present disclosure relates to an image forming system and a program. [Background technology]

[0002] Patent Document 1 discloses an image forming apparatus that can form high-quality images that can be used in place of a printing press by correcting the amount of misregistration correction, such as the position in the main scanning direction and sub-scanning direction, lead skew, and side skew, even if there is an error in the mounting position of the detection means that detects the misregistration detection pattern.

[0003] Patent document 2 discloses an image forming device having a selection means for selecting a reference edge of a sheet, a generation means for generating adjustment conditions for adjusting the printing position on the sheet based on the reading results of a scanner unit and the selected reference edge, and a CPU for performing image processing on image data based on the generated adjustment conditions and causing an exposure device or the like to form an image based on the image data that has been subjected to image processing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-274919 [Patent Document 2] Japanese Patent Application Publication No. 2018-101093 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, in order to expand the color gamut of images formed by image forming apparatuses, images have begun to be formed using not only toners of the basic colors CMYK but also toners of special colors other than CMYK. Such image forming apparatuses sometimes use a configuration in which toner images are formed on paper using two image forming units, each equipped with multiple image forming sections that form toner images. Each image forming unit performs a primary transfer of the toner images formed by the multiple image forming sections onto an intermediate transfer body, and the toner images on the intermediate transfer body are then secondary transferred onto paper transported along a paper transport path. In other words, when a toner image is formed on paper using two image forming units, secondary transfer is performed at two secondary transfer positions. Therefore, paper fed from a paper feed tray passes through two secondary transfer positions via a paper feed roll and a registration roll.

[0006] However, when forming an image on a sheet of paper using this configuration, if the rear edge of the paper passes through the paper feed roll or registration roll, the paper transport speed may change partially while the image is being formed on the sheet of paper. If the paper transport speed changes partially, partial positional misalignment occurs between the images formed on the sheet of paper by the two image forming units.

[0007] An object of the technique of the present disclosure is to provide an image forming system and program that can suppress partial positional misalignment within a single sheet of paper between images formed by two image forming units. [Means for solving the problem]

[0008] The image forming system of the first aspect of the present disclosure includes a first image forming unit having a plurality of first image forming sections and a first intermediate transfer body onto which toner images formed by the plurality of first image forming sections are primarily transferred; a second image forming unit provided downstream of the first image forming unit in a paper transport direction, the second image forming unit having a plurality of second image forming units and a second intermediate transfer body onto which toner images formed by the plurality of second image forming units are primarily transferred; a paper transport unit that transports paper to a secondary transfer position where the toner image formed on the first intermediate transfer body of the first image forming unit and the toner image formed on the second intermediate transfer body of the second image forming unit are second-transferred, respectively; a processor, When aligning the position of an image printed on paper by the first image forming unit with the position of an image printed on paper by the second image forming unit, the processor causes one first image forming unit selected from the plurality of first image forming units of the first image forming unit and one second image forming unit selected from the plurality of second image forming units of the second image forming unit to form images at the same position on the paper, and suppresses the amount of misalignment by partially changing the image write cycle of either the first image forming unit or the second image forming unit depending on the amount of relative misalignment between the two formed images.

[0009] An image forming system of a second aspect of the present disclosure is the image forming system of the first aspect, wherein the processor forms a test pattern image consisting of a plurality of straight lines at a predetermined interval at the same position on the paper using one first image forming unit selected from the plurality of first image forming units of the first image forming unit and one second image forming unit selected from the plurality of second image forming units of the second image forming unit, detects the start and end points of a speed change in the paper transport speed from the amount of positional deviation between each of the formed straight lines, and suppresses the amount of positional deviation by partially changing the image writing period between the detected start and end points.

[0010] In a third aspect of the image forming system of the present disclosure, in the image forming system of the second aspect, the processor uses a linear image formed by a selected image forming section in either the first image forming unit or the second image forming unit as a reference position, and if the position of the linear image formed by a selected image forming section in the other image forming unit is shifted backward in the paper transport direction, partially shortens the image writing cycle in the other image forming unit, and if the position is shifted forward in the paper transport direction, partially lengthens the image writing cycle in the other image forming unit, thereby suppressing the amount of positional deviation.

[0011] An image forming system of a fourth aspect of the present disclosure is the image forming system of the first aspect, wherein the processor causes one first image forming unit selected from the plurality of first image forming units of the first image forming unit and one second image forming unit selected from the plurality of second image forming units of the second image forming unit to form images on a reference position of paper, for which an absolute reference position has been set in advance, and suppresses the amount of positional deviation by partially changing the image writing period in each of the first image forming unit and the second image forming unit depending on the amount of positional deviation between the two formed images and the reference position.

[0012] An image forming system of a fifth aspect of the present disclosure is the image forming system of the fourth aspect, wherein the paper on which an absolute reference position is set in advance is paper on which a plurality of reference lines are set at preset intervals; The processor uses the position of the reference line as a reference position, detects the start and end points of the speed change in the paper transport speed from the amount of positional deviation between the reference line and the straight-line images formed by the selected image forming sections in the first image forming unit and the second image forming unit, and suppresses the amount of positional deviation of the first image forming unit and the second image forming unit, respectively, by partially changing the image writing period between the detected start and end points.

[0013] A sixth aspect of the present disclosure provides a program for an image forming apparatus including: a first image forming unit having a plurality of first image forming units and a first intermediate transfer body onto which toner images formed by the plurality of first image forming units are primarily transferred; a second image forming unit provided downstream of the first image forming unit in a paper transport direction and having a plurality of second image forming units and a second intermediate transfer body onto which toner images formed by the plurality of second image forming units are primarily transferred; and a paper transport unit that transports paper to a secondary transfer position where the toner images formed on the first intermediate transfer body of the first image forming unit and the toner images formed on the second intermediate transfer body of the second image forming unit are second-transferred, respectively; when aligning a position of an image printed on paper by the first image forming unit and a position of an image printed on paper by the second image forming unit, the program includes the steps of: forming images at the same position on paper by one first image forming unit selected from the plurality of first image forming units of the first image forming unit and one second image forming unit selected from the plurality of second image forming units of the second image forming unit; and a step of suppressing the amount of positional deviation by partially changing the image writing cycle of either the first image forming unit or the second image forming unit depending on the amount of relative positional deviation between the two formed images. [Effects of the Invention]

[0014] According to the image forming system of the first aspect of the present disclosure, it is possible to suppress partial positional deviation within one sheet of paper between images formed by two image forming units.

[0015] According to the image forming system of the second aspect of the present disclosure, by simply forming a test pattern image consisting of multiple straight lines at a predetermined interval using a first image forming unit and a second image forming unit, respectively, it is possible to detect the start and end points of a speed change in the paper transport speed and suppress partial positional misalignment within a single sheet of paper between the images formed by the two image forming units, respectively.

[0016] According to the image forming system of the third aspect of the present disclosure, it is possible to suppress relative misalignment between images formed by two image forming units without using special paper for misalignment correction.

[0017] According to the image forming system of the fourth aspect of the present disclosure, it is possible to suppress positional deviation between the absolute reference positions of the images formed by the two image forming units.

[0018] According to the image forming system of the fifth aspect of the present disclosure, by simply forming a test pattern image consisting of multiple straight lines at a predetermined interval on a sheet of paper having multiple reference lines at this interval using a first image forming unit and a second image forming unit, respectively, it is possible to suppress positional deviation between the absolute reference positions of the images formed by the two image forming units.

[0019] According to the program of the sixth aspect of the present disclosure, it is possible to suppress partial positional deviation within one sheet of paper between images formed by two image forming units. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a diagram illustrating a configuration of an image forming apparatus 10 according to an embodiment of the present disclosure. [Figure 2] 10A and 10B are diagrams for explaining the configuration of image forming units 32P, 32S, 32G, and 32Gr, and the configuration of image forming units 52Y, 52M, 52C, and 52K. [Figure 3]FIG. 2 is a diagram illustrating the configuration of a control device 80 that controls the operation of the image forming apparatus 10. [Figure 4] 10 is a diagram showing the state (speed fluctuation point 1) immediately after the rear end of the paper PP passes through the paper feed roll 14. FIG. [Figure 5] 10 is a diagram showing the state (speed fluctuation point 2) immediately after the rear end of the paper PP passes through the registration roll 15. FIG. [Figure 6] 10 is a flowchart for explaining the overall operation when correcting misalignment between two image forming units 30 and 50. [Figure 7] FIG. 10 is a diagram showing an example of a reference paper on which a plurality of reference lines perpendicular to the paper transport direction are printed in advance at 20 mm intervals. [Figure 8] FIG. 10 is a diagram showing an example of an adjustment chart generated by printing straight lines at 20 mm intervals in K and Gr colors in correspondence with the positions of reference lines on a reference sheet. [Figure 9] 9 is a diagram showing an example of a detection when a speed change point of a paper transport speed is detected from the adjustment chart shown in FIG. 8. FIG. [Figure 10] FIG. 10 is a diagram showing an example of an adjustment chart generated by printing straight lines at 20 mm intervals in K and Gr colors on ordinary printing paper. [Figure 11] 11 is a diagram showing an example of a detection when a speed change point of a paper transport speed is detected from the adjustment chart shown in FIG. 10. FIG. [Figure 12] 10A and 10B are diagrams illustrating an image printed when positional deviation correction is performed based on absolute positions using a reference paper. [Figure 13] 10A and 10B are diagrams illustrating an image printed when positional deviation correction based on relative position is performed. DETAILED DESCRIPTION OF THE INVENTION

[0021] Next, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0022] FIG. 1 is a diagram showing a configuration of an image forming apparatus 10 according to an embodiment of the present disclosure.

[0023] As shown in FIG. 1, the image forming device 10 includes a paper storage section 12 in which paper PP is stored, a transport section 11 that transports the paper PP along a transport path 19, image forming units 30 and 50 that form toner images to be transferred onto the paper PP, and a control device 80.

[0024] The paper storage section 12 can be pulled out from the image forming apparatus main body 10A, which is the main body of the image forming apparatus 10, and stores paper PP.

[0025] The transport section 11 includes, in order from the upstream side in the transport direction, a delivery roll 13, a paper feed roll 14, a registration roll 15, a transport device 20, a fixing section 18, and a discharge roll 17, and functions as a paper transport section.

[0026] The delivery roll 13 delivers the paper PP stored in the paper storage unit 12 to a transport path 19 that constitutes the transport unit 11. The paper feed roll 14 feeds the paper PP stored in the paper storage unit 12 along the transport path 19 to the registration roll 15.

[0027] The registration rolls 15 increase the transport speed of the sheet PP fed by the paper feed rolls 14 and transport it to a secondary transfer position TJ2, which will be described later. The registration rolls 15 sandwich the sheet PP and transport it downstream in the transport direction. In this way, the registration rolls 15 are paper position adjustment rolls that transport the sheet PP fed from the paper storage unit 12 to the secondary transfer position TJ2, where secondary transfer is performed by the secondary transfer unit 74, at a predetermined timing.

[0028] The transport device 20 transfers the toner images formed by the image forming units 30 and 50 onto the paper PP, and transports the paper PP downstream in the transport direction along the transport path 19. Details of the transport device 20 will be described later.

[0029] The fixing unit 18 has two fixing rolls 16, and as the paper PP passes between the two fixing rolls 16, the paper PP onto which the toner image has been transferred is heated and pressurized, thereby fixing the toner image to the paper PP. The position where the toner image is fixed to the paper PP by the two fixing rolls 16 is called the fixing position.

[0030] The discharge rollers 17 discharge the paper PP onto which the toner image has been fixed by the fixing unit 18 to the discharge unit 9.

[0031] The image forming unit 30 and the image forming unit 50 are arranged side by side in the vertical direction. In this embodiment, the image forming unit 50 is arranged above the image forming unit 30. From another perspective, the image forming unit 50 is arranged downstream of the image forming unit 30 in the paper transport direction.

[0032] The image forming unit 50 forms toner images of the basic colors of yellow (Y), magenta (M), cyan (C), and black (K).

[0033] The image forming unit 30 then forms toner images in special colors other than the basic colors. The image forming unit 30 includes four image forming sections 32 and an endless intermediate transfer belt 40, which serves as an intermediate transfer body. The toner images formed by the four image forming sections 32 are transferred to the intermediate transfer belt 40, which is mounted so as to be rotatable counterclockwise when viewed from the front in FIG. 1.

[0034] Image forming units 32 include image forming unit 32P that forms a fluorescent pink (P) toner image, image forming unit 32S that forms a silver (S) toner image, image forming unit 32G that forms a gold (G) toner image, and image forming unit 32Gr that forms a fluorescent green (Gr) toner image. These four image forming units 32 are arranged in the following order from the upstream side in the rotation direction of intermediate transfer belt 40 (the side closer to support roll 44, described later). Image forming units 32P, 32S, 32G, and 32Gr have photoconductors 33P, 32S, 32G, and 32Gr, respectively.

[0035] In addition, when there is no need to distinguish between P, S, G, and Gr, they will be omitted.

[0036] Furthermore, primary transfer rolls 37P, 37S, 37G, and 37Gr are disposed opposite the photoconductors 33 with the intermediate transfer belt 40 interposed therebetween, and transfer the toner images formed by the image forming unit 32 onto the intermediate transfer belt 40. The intermediate transfer belt 40 is wound around a support roll 44 that supports the intermediate transfer belt 40 and a backup roll 42 that is disposed in a secondary transfer unit 74 on the upstream side, which will be described later. The photoconductors 33, the primary transfer rolls 37, and the intermediate transfer belt 40 form a primary transfer unit 70. The positions between the photoconductors 33P, 33S, 33G, and 33Gr and the intermediate transfer belt 40 are designated as primary transfer positions TP1, TS1, TG1, and TGr1, respectively.

[0037] The image forming unit 50 has the same configuration as the image forming unit 30 described above, except that the color of the image formed is different.

[0038] The image forming unit 50 includes four image forming sections 52 and an intermediate transfer belt 60, which is an intermediate transfer body. The toner images formed by the four image forming sections 52 are transferred to the intermediate transfer belt 60, which is mounted so as to be rotatable counterclockwise when viewed from the front in FIG. 1.

[0039] The image forming section 52 has the same configuration as the image forming section 32 of the image forming unit 30, except for the color of the image formed. The intermediate transfer belt 60 and the primary transfer roll 57, which will be described later, also have the same configuration as the intermediate transfer belt 40 and the primary transfer roll 37 of the image forming unit 30. The other components of the image forming unit 50 are also the same as those of the image forming unit 30.

[0040] The image forming unit 52 includes an image forming unit 52Y that forms a yellow toner image, an image forming unit 52M that forms a magenta toner image, an image forming unit 52C that forms a cyan toner image, and an image forming unit 52K that forms a black toner image. The four image forming units 52 are arranged in the following order from the upstream side in the rotation direction (the side closest to the support roll 64, which will be described later): image forming unit 52Y, image forming unit 52M, image forming unit 52C, and image forming unit 52K. In other words, within the image forming unit 52, image forming unit 52K is arranged furthest downstream in the rotation direction. The image forming units 52Y, 52M, 52C, and 52K have photoconductors 53Y, 53M, 53C, and 53K, respectively.

[0041] It should be noted that when there is no need to distinguish between Y, M, C, and K, they will be omitted.

[0042] Additionally, primary transfer rolls 57Y, 57M, 57C, and 57K are disposed at positions facing each photoconductor 53 with the intermediate transfer belt 60 interposed therebetween. The intermediate transfer belt 60 is wound around a support roll 64 and a backup roll 62 disposed in a downstream secondary transfer unit 76, which will be described later. The photoconductors 53, primary transfer rolls 57, and intermediate transfer belt 60 constitute a primary transfer unit 72. The positions between the photoconductors 53Y, 53M, 53C, and 53K and the intermediate transfer belt 60 are designated primary transfer positions TY1, TM1, TC1, and TK1, respectively.

[0043] Next, the configuration of image forming sections 32P, 32S, 32G, and 32Gr will be described with reference to Fig. 2. The configuration of image forming sections 52Y, 52M, 52C, and 52K in image forming unit 50 will also be described.

[0044] 2, the image forming unit 32 includes a photoconductor 33, a charging member 34 that charges the surface of the photoconductor 33, an exposure device 35 that irradiates the charged photoconductor 33 with light, and a developing device 36 that develops the electrostatic latent image formed by the exposure light and visualizes it as a toner image. The developing device 36 has a developing roll 39, and a developing bias is applied to it.

[0045] 2, the image forming unit 52 includes a photoconductor 53, a charging member 54, an exposure device 55, and a developing device 56. The developing device 56 has a developing roll 59, and a developing bias is applied to the developing roll 59.

[0046] Next, the transport device 20 will be described in detail.

[0047] As shown in FIG. 1, the conveying device 20 includes an endless conveying belt 21, support rolls 22 and 23 that support the conveying belt 21, and secondary transfer rolls 24 and 25 that are positioned opposite the backup rolls 42 and 62 across the intermediate transfer belts 40 and 60.

[0048] The secondary transfer roll 24 sandwiches the paper PP and the conveyor belt 21 between itself and the backup roll 42, and transfers the toner image formed on the intermediate transfer belt 40 of the image forming unit 30 onto the paper PP. Similarly, the secondary transfer roll 25 sandwiches the paper PP and the conveyor belt 21 between itself and the backup roll 62, and transfers the toner image formed on the intermediate transfer belt 60 of the image forming unit 50 onto the paper PP.

[0049] The backup roll 42, the secondary transfer roll 24, and the intermediate transfer belt 40 constitute a secondary transfer unit 74. The backup roll 62, the secondary transfer roll 25, and the intermediate transfer belt 60 constitute a secondary transfer unit 76.

[0050] A transfer bias is applied to each of the secondary transfer rolls 24 and 25.

[0051] Further, the space between the intermediate transfer belt 40 of the image forming unit 30 and the conveyor belt 21 is defined as a secondary transfer position TJ2, and the space between the intermediate transfer belt 60 of the image forming unit 50 and the conveyor belt 21 is defined as a secondary transfer position TK2. The secondary transfer position TK2 is the most downstream secondary transfer position.

[0052] As described above, the image forming unit 30 includes four image forming sections 32P, 32S, 32G, and 32Gr, and an intermediate transfer belt 40 onto which the toner images formed by the four image forming sections 32 are primarily transferred. The image forming unit 50 is located downstream of the image forming unit 30 in the paper transport direction. The image forming unit 50 also includes four image forming sections 52Y, 52M, 52C, and 52K, and an intermediate transfer belt 60 onto which the toner images formed by the four image forming sections 52 are primarily transferred. The secondary transfer section 74 is located corresponding to the image forming unit 30 and performs a second transfer of the toner image formed on the intermediate transfer belt 40 onto the paper PP transported on the transport path 19. The secondary transfer section 76 is located corresponding to the image forming unit 50 and performs a second transfer of the toner image formed on the intermediate transfer belt 60 onto the paper PP transported on the transport path 19.

[0053] As configured as described above, the conveying section 11 conveys the paper PP to secondary transfer positions TJ2 and TK2 where the toner images formed on the intermediate transfer belt 40 of the image forming unit 30 and the toner images formed on the intermediate transfer belt 60 of the image forming unit 50 are secondarily transferred, respectively.

[0054] Next, the control device 80 that controls the operation of the image forming apparatus 10 will be described with reference to FIG.

[0055] As shown in FIG. 3, the control device 80 is electrically connected to the image forming unit 30, the image forming unit 50, the conveying section 11, the communication section 90, and the like.

[0056] 3, the control device 80 has a CPU (Central Processing Unit) 81, a ROM (Read Only Memory) 82, a RAM (Random Access Memory) 83, a storage device 85 such as a hard disk drive, and an input / output interface (abbreviated as I / O) 84 that inputs and outputs data to and from each device via a network. These components are connected to one another via a control bus.

[0057] The ROM 82 stores an image formation control program (not shown) to be executed by the CPU 81. The CPU 81 then reads the image formation control program (not shown) from the ROM 82 and loads it into the RAM 83 to execute a printing process in accordance with the image formation control program (not shown). While the present embodiment describes the CPU 81 reading and executing the image formation control program stored in the ROM 82, this is not limiting. The image formation control program may be provided in a form recorded on a computer-readable recording medium. For example, the image formation control program may be provided in a form recorded on an optical disc such as a CD (Compact Disc)-ROM or a DVD (Digital Versatile Disc)-ROM, or in a semiconductor memory such as a USB (Universal Serial Bus) memory or a memory card. The image formation control program may also be acquired from an external device via a communication line connected to the input / output interface 84. The image formation control program may be provided as standalone application software, or may be incorporated into the software of each device of the image forming apparatus 10 as a function of the image forming apparatus 10.

[0058] In addition, the image forming unit 30, the image forming unit 50, the conveying unit 11, the communication unit 90, etc. are connected to the I / O 84. The communication unit 90 is an interface for mutual data communication between the image forming apparatus 10 and a terminal device such as a personal computer.

[0059] The control device 80 performs various controls to form a toner image on the intermediate transfer belt 40 by the image forming section 32 of each color of the image forming unit 30. Similarly, the control device 80 performs various controls to form a toner image on the intermediate transfer belt 60 by the image forming section 52 of each color of the image forming unit 50.

[0060] The control device 80 also controls the developing biases applied to the developing rolls 39 and 59 of the developing devices 36 and 56. The control device 80 also controls the transfer biases applied to the secondary transfer rolls 24 and 25.

[0061] The control device 80 also controls the timing, time, and amount of toner supplied from the toner cartridges of each color to the developing devices 36 and 56 .

[0062] [Speed ​​fluctuation point] Next, speed fluctuation points during transport of paper in the image forming apparatus 10 will be described.

[0063] In the image forming apparatus 10 of the present embodiment described above, a toner image is formed on a sheet of paper PP using two image forming units 30, 50. Each of the two image forming units 30, 50 performs primary transfer of a toner image formed by a plurality of image forming sections 32, 52 onto intermediate transfer belts 40, 60, and the toner image on the intermediate transfer belts 40, 60 is then secondary transferred onto the sheet of paper PP transported along the transport path 19. In other words, when a toner image is formed on the sheet of paper PP using the two image forming units 30, 50, secondary transfer is performed at two secondary transfer positions TJ2, TK2. Therefore, the sheet of paper PP fed from a paper storage section 12, such as a paper feed tray, passes through the two secondary transfer positions TJ2, TK2 via the paper feed roll 14 and the registration roll 15.

[0064] However, when an image is formed on a sheet of paper PP using this configuration, the paper transport speed may change partially while an image is being formed on the sheet of paper PP if the rear edge of the sheet passes through the paper feed roll 14 or the registration roll 15. If the paper transport speed changes partially, partial positional misalignment occurs between the images formed on the sheet of paper by the two image forming units 30 and 50.

[0065] The two speed fluctuation points that occur during paper transport will be described with reference to FIGS.

[0066] Fig. 4 is a diagram showing one of the two speed fluctuation points, speed fluctuation point 1. Specifically, Fig. 4 is a diagram showing the state immediately after the rear end of the paper PP has passed the paper feed roll 14. Referring to Fig. 4, it can be seen that the transport load is released when the rear end of the paper PP has passed the paper feed roll 14, and the transport speed of the paper PP at the secondary transfer position TJ2 increases.

[0067] 5 is a diagram showing the other of the two speed fluctuation points, speed fluctuation point 2. Specifically, Fig. 5 is a diagram showing the state immediately after the rear end of the sheet of paper PP has passed through the registration roll 15. Referring to Fig. 5, it can be seen that the rear end of the sheet of paper PP has passed through the registration roll 15, and is thus released from the pressure exerted by the registration roll 15, and the conveyance speed of the sheet of paper PP at the secondary transfer positions TJ2 and TK2 is decelerating.

[0068] In this way, when an image is formed on a single sheet of paper PP, the paper transport speed may fluctuate each time the rear end of the paper PP passes the paper feed roll 14 or the registration roll 15. Therefore, even if the misalignment of the image formation positions on the intermediate transfer belts 40 and 60 is completely eliminated by adjusting the misalignment of the image formation positions between the image forming sections 32 and 52 in the two image forming units 30 and 50, the fluctuation in the transport speed of the paper PP at the secondary transfer position TJ2 will cause a misalignment in the position of the image formed on the paper PP.

[0069] Therefore, in the image forming apparatus 10 of this embodiment, the method described below is used to suppress partial positional misalignment within a single sheet of paper PP between the images formed by the two image forming units 30 and 50.

[0070] When aligning the position of an image printed on paper PP by image forming unit 30 with the position of an image printed on paper PP by image forming unit 50, CPU 81, which is a processor, causes one image forming unit 32 selected from the four image forming units 32 of image forming unit 30 and one image forming unit 52 selected from the four image forming units 52 of image forming unit 50 to form images at the same position on paper PP. Then, CPU 81 reduces the amount of misalignment by partially changing the image write cycle of either image forming unit 30 or image forming unit 50 depending on the amount of relative misalignment between the two formed images.

[0071] Specifically, the CPU 81 causes one image forming section 32 selected from the four image forming sections 32 of the image forming unit 30 and one image forming section 52 selected from the four image forming sections 52 of the image forming unit 50 to form test pattern images consisting of multiple straight lines spaced at preset intervals at the same position on the paper PP. The CPU 81 then detects the start and end points of a change in the paper conveyance speed from the amount of misalignment between the formed straight lines. The CPU 81 then reduces the amount of misalignment by partially changing the image writing cycle between the detected start and end points.

[0072] More specifically, the CPU 81 uses the linear image formed by the selected image forming section 32 or image forming section 52 in either image forming unit 30 or image forming unit 50 as a reference position, and if the position of the linear image formed by the selected image forming section 32 or 52 in the other image forming unit is shifted backward in the paper transport direction, the CPU 81 partially shortens the image writing period in the other image forming unit, and if the position is shifted forward in the paper transport direction, the CPU 81 suppresses the amount of positional deviation by partially lengthening the image writing period in the other image forming unit.

[0073] It should be noted that instead of correcting the relative positional deviation between the image forming units 30 and 50 as described above, it is also possible to correct the absolute positional deviation between the image forming units 30 and 50, respectively.

[0074] In this case, the CPU 81 causes one image forming unit 32 selected from the four image forming units 32 of the image forming unit 30 and one image forming unit 52 selected from the four image forming units 52 of the image forming unit 50 to form images on a reference position of a reference sheet for which an absolute reference position has been set in advance. Then, the CPU 81 reduces the amount of positional deviation by partially changing the image writing cycles of the image forming units 30 and 50, respectively, depending on the amount of positional deviation between the two formed images and the reference position.

[0075] Specifically, a sheet of paper on which a plurality of reference lines are provided at preset intervals is used as a sheet of paper for which an absolute reference position is previously set. Then, CPU 81 uses the positions of the reference lines as the reference positions and detects the start and end points of a speed change in the paper conveyance speed from the amount of misalignment between the reference lines and the linear images formed by selected image forming sections 32 and 52 in image forming units 30 and 50, respectively. CPU 81 then reduces the amount of misalignment between image forming units 30 and 50 by partially changing the image writing cycle between the detected start and end points.

[0076] The overall operation for correcting the misalignment between the two image forming units 30 and 50 described above will be described with reference to the flowchart of FIG.

[0077] First, in step S101, the CPU 81 outputs an adjustment chart using one image forming section 32 selected from the image forming unit 30 and one image forming section 52 selected from the image forming unit 50.

[0078] Then, in step S102, the output adjustment chart is read by a scanner or the like provided in a device other than the image forming apparatus 10 of this embodiment.

[0079] Then, in step S103, the CPU 81 calculates the correction amount for adjusting the print position based on the image of the adjustment chart that has been read. Then, in step S104, the CPU 81 performs positional deviation correction by setting the calculated correction amount as a parameter for printing.

[0080] It should be noted that the processing of step S103 in the overall operation described above may not be performed by the CPU 81, but may be performed outside the image forming apparatus 10, and only the obtained correction amount may be fed back to the image forming apparatus 10.

[0081] Next, the above-described operation of correcting positional deviation will be described in detail using a specific example image.

[0082] [Position error correction based on absolute position] First, of the above-described positional deviation correction based on the relative position and positional deviation correction based on the absolute position, positional deviation correction based on the absolute position will be described.

[0083] This positional deviation correction based on absolute position uses a reference paper as shown in Fig. 7. Fig. 7 shows an example of a reference paper on which multiple reference lines perpendicular to the paper transport direction are printed in advance at 20 mm intervals.

[0084] In the following description, it is assumed that image forming unit 30 selects image forming unit 32Gr as the reference image forming unit among four image forming units 32P, 32S, 32G, and 32Gr. Also, it is assumed that image forming unit 50 selects image forming unit 52K as the reference image forming unit among four image forming units 52Y, 52M, 52C, and 52K. In other words, it is assumed that image forming unit 30 selects Gr as the reference color, and image forming unit 50 selects K as the reference color.

[0085] When adjusting misalignment using these settings, the CPU 81 generates an adjustment chart by printing straight lines in K and Gr at 20 mm intervals, corresponding to the positions of the reference lines on the reference paper shown in Figure 7. An example of an adjustment chart generated in this way is shown in Figure 8. In Figure 8, the K straight lines are shown as solid lines, and the Gr straight lines are shown as dashed lines. The reference lines are also shown as dotted lines to make them easier to distinguish. Furthermore, because overlapping two straight lines makes them difficult to see in the drawing, they are intentionally shown with a small gap between them even when they overlap.

[0086] If the paper transport speed is constant and there is no positional deviation on the transport path 19 where the paper PP sent from the paper storage section 12 is discharged by the discharge roll 17, the straight line of K color and the straight line of Gr color will be printed on the reference line.

[0087] However, referring to the adjustment chart shown in Figure 8, it can be seen that the K line and the Gr line are misaligned from their respective reference lines, causing misalignment from the correct print position. It can also be seen that the amount of misalignment varies across parts of a single sheet of paper.

[0088] Therefore, the CPU 81 detects the speed change points of the paper conveyance speed from the amount of positional deviation of the K and Gr color straight lines from the reference line in the image data obtained by reading the adjustment chart with a scanner.The CPU 81 then calculates the amount of correction for correcting the positional deviation based on the detected speed change points.

[0089] FIG. 9 shows an example of detection of a speed change point of the paper transport speed from the adjustment chart shown in FIG.

[0090] 9, it can be seen that in image forming unit 30, the paper transport speed increases and misalignment begins at time T1 due to the influence of speed fluctuation point 1 shown in Fig. 4, and the paper transport speed becomes constant at the increased speed at time T2. When correcting misalignment based on this detection example, CPU 81 changes the image writing cycle in image forming unit 30 at time T1, and fixes the changed image writing cycle at time T2.

[0091] 9, it can be seen that in image forming unit 30, when the paper transport speed starts to decrease at time T3 due to the influence of speed fluctuation point 2 shown in Fig. 5, the positional deviation also starts to decrease, and at time T4 the paper transport speed becomes constant in the decreased state. When correcting positional deviation based on this detection example, CPU 81 changes the image writing cycle of image forming units 30, 50 at time T3, and fixes the changed image writing cycle at time T4.

[0092] [Relative position correction] Note that when performing the above-described positional deviation correction based on absolute positions, it is necessary to prepare a reference paper as shown in Fig. 7 in advance. Therefore, if a reference paper is not available, positional deviation correction cannot be performed. Therefore, positional deviation correction based on relative positions is performed as a method for adjusting positional deviation without using a reference paper.

[0093] Next, the correction of positional deviation based on such relative positions will be described.

[0094] When performing such misregistration adjustment based on relative position, the CPU 81 generates an adjustment chart by printing straight lines in K and Gr at 20 mm intervals on ordinary printing paper. An example of an adjustment chart generated in this manner is shown in Fig. 10. Note that in Fig. 10, the K straight lines are shown as solid lines and the Gr straight lines are shown as dashed lines.

[0095] If the paper transport speed is constant and there is no positional deviation on the transport path 19 where the paper PP sent from the paper storage section 12 is discharged by the discharge roll 17, the straight line of K color and the straight line of Gr color will be printed overlapping each other.

[0096] However, when referring to the adjustment chart shown in Figure 10, it can be seen that the printing positions are misaligned between image forming unit 30 and image forming unit 50 because the straight line for K color and the straight line for Gr color are printed out of alignment.

[0097] Therefore, the CPU 81 detects the speed change point of the paper conveyance speed by reading the relative positional deviation amount of the K and Gr lines from the image data obtained by reading this adjustment chart with a scanner.The CPU 81 then calculates the correction amount for correcting the positional deviation based on the detected speed change point.Note that here, a case will be described in which K in the image forming unit 50 is used as the reference color, and positional deviation correction is performed to align the printing position of the Gr image in the image forming unit 30 with the printing position of the K color.

[0098] FIG. 11 shows an example of detection of a speed change point of the paper transport speed from the adjustment chart shown in FIG.

[0099] 11, it can be seen that the speed difference in the relative paper transport speed between image forming unit 30 and image forming unit 50 begins to increase and misalignment begins at time T1 due to the influence of speed fluctuation point 1 shown in Fig. 4, and the speed difference becomes constant at time T2. When performing misalignment correction based on this detection example, CPU 81 changes the image write cycle of image forming unit 30 at time T1, and fixes the changed image write cycle at time T2.

[0100] 11, it can be seen that the speed difference in the relative paper transport speed between image forming unit 30 and image forming unit 50 begins to decrease at time T3 due to the influence of speed fluctuation point 2 shown in Fig. 5, and becomes constant at time T4 after the speed difference has decreased. When performing positional deviation correction based on this detection example, CPU 81 changes the image writing cycle of image forming unit 30 at time T3, and fixes the changed image writing cycle at time T4.

[0101] Here, by partially changing the image writing cycle, the image to be printed will be partially expanded or contracted on one sheet of paper.

[0102] Therefore, how the print position of the corrected image is corrected by performing the above-described positional deviation correction will be described with reference to FIGS.

[0103] Fig. 12 shows an image printed when misregistration is corrected based on absolute positions using a reference paper, and Fig. 13 shows an image printed when misregistration is corrected based on relative positions.

[0104] 12(A) and 13(A) show example images before misalignment correction. Referring to FIGS. 12(A) and 13(A), it can be seen that in the images before misalignment correction, the shape of the upper part of the Gr star-shaped image is elongated compared to the normal shape. Furthermore, in the K image, it can be seen that the shape of the central part of the star-shaped image is elongated compared to the normal shape.

[0105] An example of the corrected image when absolute position correction is performed in a state where such a misalignment has occurred is shown in Fig. 12(B). Referring to Fig. 12(B), it can be seen that by performing absolute position correction using the reference paper, both the Gr image and the K image have become images with normal shapes.

[0106] In contrast, Fig. 13(B) shows an example of a corrected image when misalignment correction based on relative position is performed. Referring to Fig. 13(B), it can be seen that misalignment correction based on relative position is performed to align the Gr image with the K image. Specifically, the shape of the upper part of the Gr star-shaped image has been corrected to a normal shape, just like the K star-shaped image, but it can be seen that the shape of the normal central part of the Gr star-shaped image has become elongated compared to the normal shape due to alignment with the K image.

[0107] However, whether the correction method is absolute position misalignment correction or relative position misalignment correction, the misalignment between the Gr color image and the K color image is suppressed, and the misalignment between the image printed by image forming unit 30 and the image printed by image forming unit 50 on the paper is suppressed.

[0108] In each of the above embodiments, the term "processor" refers to a processor in a broad sense, and includes general-purpose processors (e.g., CPU: Central Processing Unit, etc.) and dedicated processors (e.g., GPU: Graphics Processing Unit, ASIC: Application Specific Integrated Circuit, FPGA: Field Programmable Gate Array, programmable logic device, etc.).

[0109] Furthermore, the operations of the processor in each of the above embodiments may be performed not only by a single processor but also by multiple processors located at physically separate locations working together. Furthermore, the order of the operations of the processor is not limited to the order described in each of the above embodiments and may be changed as appropriate.

[0110] In this embodiment, the term "system" includes both a system made up of multiple devices and a system made up of a single device.

[0111] The present disclosure is also applicable to programs and program products.

[0112] [Note] (((1))) a first image forming unit having a plurality of first image forming sections and a first intermediate transfer body onto which the toner images formed by the plurality of first image forming sections are primarily transferred; a second image forming unit provided downstream of the first image forming unit in a paper transport direction, the second image forming unit having a plurality of second image forming units and a second intermediate transfer body onto which toner images formed by the plurality of second image forming units are primarily transferred; a paper transport unit that transports paper to a secondary transfer position where the toner image formed on the first intermediate transfer body of the first image forming unit and the toner image formed on the second intermediate transfer body of the second image forming unit are second-transferred, respectively; a processor, When aligning the position of an image printed on paper by the first image forming unit and the position of an image printed on paper by the second image forming unit, the processor causes one first image forming unit selected from the plurality of first image forming units of the first image forming unit and one second image forming unit selected from the plurality of second image forming units of the second image forming unit to form images at the same position on paper, and suppresses the amount of misalignment by partially changing the image write cycle of either the first image forming unit or the second image forming unit depending on the amount of relative misalignment between the two formed images. Imaging system. (((2))) the processor causes one first image forming unit selected from the plurality of first image forming units of the first image forming unit and one second image forming unit selected from the plurality of second image forming units of the second image forming unit to form a test pattern image consisting of a plurality of straight lines at a preset interval at the same position on the paper, detects a start point and an end point of a speed change in the paper conveyance speed from the amount of positional deviation between the formed straight lines, and suppresses the amount of positional deviation by partially changing the image writing cycle between the detected start point and end point; The image forming system according to (((1))). (((3))) the processor uses a linear image formed by a selected image forming section in either the first image forming unit or the second image forming unit as a reference position, and when the position of the linear image formed by the selected image forming section in the other image forming unit is shifted rearward in the paper transport direction, it partially shortens the image writing cycle in the other image forming unit, and when the position of the linear image formed by the selected image forming section in the other image forming unit is shifted forward in the paper transport direction, it suppresses the amount of positional deviation by partially lengthening the image writing cycle in the other image forming unit. The image forming system according to (((2))). (((4))) the processor causes one first image forming unit selected from the plurality of first image forming units of the first image forming unit and one second image forming unit selected from the plurality of second image forming units of the second image forming unit to form images on a reference position of a sheet of paper, the absolute reference position of which has been set in advance, and suppresses the amount of positional deviation by partially changing the image writing cycle of each of the first image forming unit and the second image forming unit according to the amount of positional deviation between the two formed images and the reference position; The image forming system according to (((1))). (((5))) The paper on which an absolute reference position is set in advance is a paper on which a plurality of reference lines are set at predetermined intervals, the processor detects a start point and an end point of a speed change of a paper conveyance speed from the amount of positional deviation between the reference line and a linear image formed by each selected image forming section in the first image forming unit and the second image forming unit, using the position of the reference line as a reference position, and suppresses the amount of positional deviation of the first image forming unit and the second image forming unit by partially changing the image writing cycle between the detected start point and end point. The image forming system according to (((4))). (((6))) an image forming apparatus including a first image forming unit having a plurality of first image forming units and a first intermediate transfer body onto which toner images formed by the plurality of first image forming units are primarily transferred; a second image forming unit provided downstream of the first image forming unit in a paper transport direction and having a plurality of second image forming units and a second intermediate transfer body onto which toner images formed by the plurality of second image forming units are primarily transferred; and a paper transport unit that transports paper to a secondary transfer position where the toner images formed on the first intermediate transfer body of the first image forming unit and the toner images formed on the second intermediate transfer body of the second image forming unit are second-transferred, respectively; suppressing the amount of misregistration by partially changing an image writing cycle of either the first image forming unit or the second image forming unit in accordance with the amount of relative misregistration between the two formed images; A program that causes a computer to execute the following.

[0113] According to the image forming system (((1))), it is possible to suppress partial positional deviation within one sheet of paper between images formed by two image forming units. According to the image forming system of (((2))), by simply forming a test pattern image consisting of a plurality of straight lines at a preset interval by the first image forming unit and the second image forming unit, respectively, it is possible to detect the start and end points of the speed change in the paper transport speed and suppress partial positional misalignment within a single sheet of paper between the images formed by the two image forming units. According to the image forming system (((3))), it is possible to suppress relative positional deviation between images formed by two image forming units without using special paper for positional deviation correction. According to the image forming system of (((4))), it is possible to suppress positional deviation between the absolute reference positions of the images formed by the two image forming units. According to the image forming system of (((5))), by simply forming a test pattern image consisting of a plurality of straight lines at predetermined intervals on a sheet of paper having a plurality of reference lines at these intervals using a first image forming unit and a second image forming unit, respectively, it is possible to suppress positional deviation between the absolute reference positions of the images formed by the two image forming units. According to the program (((6))), it is possible to suppress partial positional deviation within one sheet of paper between images formed by two image forming units. [Explanation of symbols]

[0114] 9 Discharge section 10 Image forming device 10A Image forming device main body 11 Conveyor 12 Paper storage section 13 Sending Roll 14 Paper feed roll 15 Resist Roll 16 Fixing roll 17 Ejection roll 18 Fixing section 19 Transport Route 20. Conveyor 21 Conveyor belt 22, 23 Support roll 24, 25 Secondary transfer roll 30 Image forming unit 32, 32P, 32S, 32G, 32Gr Image forming section 33, 33P, 33S, 33G, 33Gr photoconductor 34 Charging member 35 Exposure equipment 36 Developing device 37, 37P, 37S, 37G, 37Gr Primary transfer roll 39 Developing Roll 40 Intermediate transfer belt 42 Backup Roll 44 Support Roll 50 Image forming unit 52, 52Y, 52M, 52C, 52K Image forming section 53, 53Y, 53M, 53C, 53K photoconductor 54 Charging member 55 Exposure equipment 56 Developing device 57, 57Y, 57M, 57C, 57K Primary transfer roll 59 Developing Roll 60 Intermediate transfer belt 62 Backup Roll 64 Support Roll 70, 72 Primary transfer section 74, 76 Secondary transfer section 80 Control device 81 CPU 82 ROM 83 RAM 84 I / O (input / output interface) 85 Storage device 90 Communications Department 100 Paper feeder PP paper TJ2, TK2 secondary transfer position TP1, TS1, TG1, TGr1 primary transcription position TY1, TM1, TC1, TK1 primary transcription position

Claims

1. a first image forming unit having a plurality of first image forming sections and a first intermediate transfer body onto which the toner images formed by the plurality of first image forming sections are primarily transferred; a second image forming unit provided downstream of the first image forming unit in a paper transport direction, the second image forming unit having a plurality of second image forming units and a second intermediate transfer body onto which toner images formed by the plurality of second image forming units are primarily transferred; a paper transport unit that transports paper to a secondary transfer position where the toner image formed on the first intermediate transfer body of the first image forming unit and the toner image formed on the second intermediate transfer body of the second image forming unit are second-transferred, respectively; a processor, When aligning the position of an image printed on paper by the first image forming unit and the position of an image printed on paper by the second image forming unit, the processor causes one first image forming unit selected from the plurality of first image forming units of the first image forming unit and one second image forming unit selected from the plurality of second image forming units of the second image forming unit to form images at the same position on paper, and suppresses the amount of misalignment by partially changing the image write cycle of either the first image forming unit or the second image forming unit depending on the amount of relative misalignment between the two formed images. Imaging system.

2. the processor causes one first image forming unit selected from the plurality of first image forming units of the first image forming unit and one second image forming unit selected from the plurality of second image forming units of the second image forming unit to form a test pattern image consisting of a plurality of straight lines at a preset interval at the same position on the paper, detects a start point and an end point of a speed change in the paper conveyance speed from the amount of positional deviation between the formed straight lines, and suppresses the amount of positional deviation by partially changing the image writing period between the detected start point and end point; The image forming system according to claim 1 .

3. the processor uses a linear image formed by a selected image forming section in either the first image forming unit or the second image forming unit as a reference position, and when the position of the linear image formed by the selected image forming section in the other image forming unit is shifted rearward in the paper transport direction, it partially shortens the image writing cycle in the other image forming unit, and when the position of the linear image formed by the selected image forming section in the other image forming unit is shifted forward in the paper transport direction, it suppresses the amount of positional deviation by partially lengthening the image writing cycle in the other image forming unit; The image forming system according to claim 2 .

4. the processor causes one first image forming unit selected from the plurality of first image forming units of the first image forming unit and one second image forming unit selected from the plurality of second image forming units of the second image forming unit to form images on a reference position of a sheet of paper, the absolute reference position of which has been set in advance, and suppresses the amount of positional deviation by partially changing the image writing cycle of each of the first image forming unit and the second image forming unit according to the amount of positional deviation between the two formed images and the reference position; The image forming system according to claim 1 .

5. The paper on which an absolute reference position is set in advance is a paper on which a plurality of reference lines are set at predetermined intervals, the processor detects a start point and an end point of a speed change of a paper conveyance speed from the amount of positional deviation between the reference line and a linear image formed by each selected image forming section in the first image forming unit and the second image forming unit, using the position of the reference line as a reference position, and suppresses the amount of positional deviation of the first image forming unit and the second image forming unit by partially changing the image writing period between the detected start point and end point. The image forming system according to claim 4 .

6. an image forming apparatus including a first image forming unit having a plurality of first image forming units and a first intermediate transfer body onto which toner images formed by the plurality of first image forming units are primarily transferred; a second image forming unit provided downstream of the first image forming unit in a paper transport direction and having a plurality of second image forming units and a second intermediate transfer body onto which toner images formed by the plurality of second image forming units are primarily transferred; and a paper transport unit that transports paper to a secondary transfer position where the toner images formed on the first intermediate transfer body of the first image forming unit and the toner images formed on the second intermediate transfer body of the second image forming unit are second-transferred, respectively; suppressing the amount of misregistration by partially changing an image writing cycle of either the first image forming unit or the second image forming unit in accordance with the amount of relative misregistration between the two formed images; A program that causes a computer to execute the following.

Images