Image forming apparatus, image forming method, and image forming program

Abstract

To provide an image forming apparatus that corrects color shift without increasing a margin between pages during printing on a continuous sheet.SOLUTION: An image forming apparatus comprises a color shift correction unit that, when executing printing related to print job data, corrects, on the print job data, a formation position of an image formation area that is a page to be printed next, for a color for which color shift occurs, based on an amount of color shift on a page to be verified one or more pages before. The color shift correction unit has: a first correction processing unit that translates the formation position of the image formation area in the page to be printed in a paper feed direction in a job of the color to be corrected in the print job data, thereby compensating for at least a part of the amount of color shift; and a second correction processing unit that inserts an additional margin area with a second width not constituting pages between the page to be printed and a page immediately before the page in the job of the color to be corrected in the print job data, thereby compensating for at least a part of the amount of color shift.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to an image forming apparatus, an image forming method, and an image forming program. [Background technology]

[0002] Image forming devices that form color images are known. Such image forming devices have four image forming units for forming toner images of the respective colors of yellow (Y), magenta (M), cyan (C), and black (K). Each image forming unit charges a photoconductor and erases the charge in accordance with the image of the original document, forming an electrostatic latent image on the photoconductor. Then, a developing unit applies toner to the electrostatic latent image on the photoconductor, forming a toner image on the photoconductor. The toner image attached to the photoconductor of each image forming unit is then primarily transferred to an intermediate transfer belt, for example, and then secondarily transferred from the intermediate transfer belt to a sheet of paper.

[0003] In this type of image forming apparatus, color misregistration may occur when overlapping toner images of different colors due to changes in the diameter of the drive roller of the intermediate transfer belt caused by temperature rises inside the apparatus during image formation operations, or changes in the speed of the intermediate transfer belt over time. For this reason, color registration correction is periodically performed in the image forming apparatus to correct color misregistration (see, for example, Patent Document 1).

[0004] Fig. 1 is a diagram for explaining a typical color shift that occurs during color image formation. Fig. 2 (Figs. 2A, 2B, and 2C) is a diagram for explaining a typical color registration correction according to the prior art.

[0005] FIG. 1 shows a state in which a typical cause of color misregistration is an increase in the temperature inside the machine due to heat from the fixing device, etc., causing the expansion of the drive roller 423 that stretches the intermediate transfer belt 421. In this case, the expansion of the drive roller 423 increases the length of the intermediate transfer belt 421, causing the rotation speed of the intermediate transfer belt 421 to fluctuate. As a result, the time it takes for the intermediate transfer belt 421 to pass between the photosensitive drums 413 of each color fluctuates, resulting in color misregistration in the paper feed direction (meaning misalignment between colors; the same applies hereinafter). The degree of such color misregistration varies over time because it depends on the temperature inside the machine.

[0006] 2A, 2B, and 2C, a method is known for performing color registration correction, in which color registration measurement patches for all colors are printed simultaneously on intermediate transfer belt 421, and a sensor (e.g., a photosensor) 430 disposed opposite intermediate transfer belt 421 reads the color registration measurement patches to calculate the amount of color registration for each color (i.e., the difference in time it takes for each color area formed on intermediate transfer belt 421 to pass through sensor 430), and the amount of color registration is fed back (corrected) to image formation. Note that color registration correction is performed, for example, by adjusting the image formation timing according to the amount of color registration, as shown in FIG. 2C. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-022439 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-079159 Summary of the Invention [Problem to be solved by the invention]

[0008] In this type of image forming device, when forming an image on each sheet of paper, printing is usually stopped temporarily, for example, when a certain number of sheets have been printed or when a change in the temperature inside the machine occurs, and color misregistration is measured and feedback is provided.

[0009] However, when forming an image on a long sheet of paper such as roll paper (hereinafter referred to as "continuous paper"), the image must be formed without any gaps on the continuous paper. Figure 3 is a diagram showing an example of how images are formed on continuous paper P. Figure 3 shows how the continuous paper P is divided into pages (P1, P2, P3, etc.) and a label image is formed on each page of the continuous paper P.

[0010] In other words, with the conventional method of periodically stopping printing to perform color registration correction, for example, in the case of a 1000-meter print job, color registration correction cannot be performed for 1000 meters, and there is a risk of color shift occurring in the latter half of the print job due to temperature changes inside the device.

[0011] The inventors of the present application have considered applying color registration correction, known as two-dimensional position correction, as a means for addressing this problem.

[0012] Fig. 4 is a diagram for explaining two-dimensional position correction in a schematic manner, where Fig. 4A shows a print job when two-dimensional position correction is not applied, and Fig. 4B shows a print job when two-dimensional position correction is applied.

[0013] Typically, print job data includes, for each page, an image formation area (meaning an area where an image to be printed is formed; the same applies below) and image content to be printed in the image formation area (i.e., the image content to be printed). In contrast, with two-dimensional position correction, as shown in Fig. 4B, print job data is generated that includes, in addition to the image formation area, a margin area (i.e., a blank area) added to the upstream and / or downstream side of the image formation area in the paper feed direction. In other words, with two-dimensional position correction, the print area of ​​each page is expanded by the margin area in addition to the image formation area.

[0014] In two-dimensional position correction, the amount of color misregistration for each color is detected before the print job is executed, and the image formation area for that color is translated within this margin area according to the amount of color misregistration for that color. This adjusts the image formation timing for each color during the print job so that the images of each color overlap on the intermediate transfer belt. Note that Figure 4B shows a state in which, because a color misregistration has occurred in the Y image formation area, the Y image formation area is translated within the margin area during the print job, resulting in the Y image formation area and the K image formation area overlapping on the intermediate transfer belt.

[0015] This two-dimensional position correction can be performed independently for each page because it only requires changing the image formation area for each color in memory through image processing. In other words, this two-dimensional position correction detects the amount of color misregistration during print job execution and provides feedback to image formation, making it possible to flexibly respond to cases where the amount of color misregistration fluctuates over time.

[0016] However, this two-dimensional position correction requires the creation of an extra margin area, which results in gaps between images on the paper that correspond to the margin area of ​​each page. In particular, when printing continuously on continuous paper without gaps, color misalignment in the paper feed direction accumulates (as will be described later with reference to Figure 9). Therefore, if the above-mentioned two-dimensional position correction were to be simply applied to continuous paper, it would be necessary to set the margin area of ​​each page considerably larger to accommodate the color misalignment.

[0017] Generally, when printing on continuous paper, there is a requirement to minimize the margins between pages (i.e., between images) to a constant distance, and considering this requirement, the above-mentioned two-dimensional position correction, which sets excessively large margin areas, is not practical.

[0018] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide an image forming device, an image forming method, and an image forming program that are capable of correcting color misalignment that occurs during continuous printing without widening the margins between pages when printing on continuous paper. [Means for solving the problem]

[0019] The present disclosure mainly solves the above-mentioned problems by: An image forming apparatus having an image forming unit that forms a color image by superimposing images of each color formed on separate photosensitive members on an intermediate transfer member, and that continuously forms color images of multiple pages on a single continuous sheet of paper in the image forming unit, a print job setting unit that manages jobs for each color and generates print job data in which a margin area of ​​a first width is set on the upstream side or downstream side of the image forming area of ​​each page in the paper feed direction; a color misregistration amount detection unit that detects, on a page-by-page basis, the amount of color misregistration of each color in the image forming area that occurs while printing related to the print job data is being performed; a color shift correction unit that corrects the formation position of the image formation area of ​​the next page to be printed on the print job data, targeting the color in which color shift has occurred, based on the amount of color shift in a verification target page one or more pages before, when printing related to the print job data is being performed; Equipped with The color misregistration correction unit a first correction processing unit that compensates for at least a part of the amount of color misregistration by shifting a formation position of the image formation area within the page to be printed in parallel in a paper feed direction within the margin area in a job of the color to be corrected in the print job data; a second correction processing unit that compensates for at least a part of the amount of color misregistration by inserting an additional margin area of ​​a second width that does not constitute a page between the page to be printed and the page immediately before it in a job of the color to be corrected in the print job data, The entire amount of color misregistration is compensated for by the processing of the first correction processing unit and the second correction processing unit. It is an image forming apparatus.

[0020] In other respects, An image forming method for continuously forming color images of multiple pages on a single continuous sheet of paper in an image forming unit that forms a color image by superimposing images of each color formed on separate photosensitive members on an intermediate transfer member, comprising: a first process for managing jobs for each color and generating print job data in which a margin area of ​​a first width is set on the upstream side or downstream side of the image forming area of ​​each page in the paper feed direction; a second process for detecting, on a page-by-page basis, the amount of color misregistration of each color in the image forming area that occurs while printing related to the print job data is being performed; a third process for correcting a formation position of the image formation area of ​​the next page to be printed on the print job data, for a color in which color shift has occurred, based on the amount of color shift in a verification target page one or more pages before, while printing related to the print job data is being performed; Equipped with In the third process, a process of compensating for at least a part of the amount of color misregistration by moving the formation position of the image formation area within the page to be printed in parallel in the paper feed direction within the margin area in a job of the color to be corrected in the print job data; and performing a process of compensating for at least a part of the amount of color misregistration by inserting an additional margin area of ​​a second width that does not constitute a page between the page to be printed and the page immediately before it in a job of the color to be corrected in the print job data, thereby compensating for all of the amount of color misregistration. It is an image forming method.

[0021] In other respects, An image forming program for continuously forming a plurality of pages of color images on a single continuous sheet of paper in an image forming unit that forms a color image by superimposing images of each color formed on separate photosensitive members on an intermediate transfer member, a first process for managing jobs for each color and generating print job data in which a margin area of ​​a first width is set on the upstream side or downstream side of the image forming area of ​​each page in the paper feed direction; a second process for detecting, on a page-by-page basis, the amount of color misregistration of each color in the image forming area that occurs while printing related to the print job data is being performed; a third process for correcting a formation position of the image formation area of ​​the next page to be printed on the print job data, for a color in which color shift has occurred, based on the amount of color shift in a verification target page one or more pages before, while printing related to the print job data is being performed; Equipped with In the third process, a process of compensating for at least a part of the amount of color misregistration by moving the formation position of the image formation area within the page to be printed in parallel in the paper feed direction within the margin area in a job of the color to be corrected in the print job data; and performing a process of compensating for at least a part of the amount of color misregistration by inserting an additional margin area of ​​a second width that does not constitute a page between the page to be printed and the page immediately before it in a job of the color to be corrected in the print job data, thereby compensating for all of the amount of color misregistration. It is an image forming program. [Effects of the Invention]

[0022] According to the image forming apparatus according to the present disclosure, when printing on continuous paper, it is possible to correct color misregistration that occurs during continuous printing without widening the margins between pages. [Brief explanation of the drawings]

[0023] [Figure 1] A diagram that explains the color misregistration that occurs when forming a color image. [Figure 2] FIG. 1 is a diagram for explaining a color registration correction according to the prior art; [Figure 3] FIG. 10 is a diagram showing an example of an embodiment in which an image is formed on continuous paper. [Figure 4] A diagram that explains two-dimensional position correction [Figure 5] 1 is a diagram showing an outline of the overall configuration of an image forming apparatus according to an embodiment of the present invention; [Figure 6] FIG. 1 is a diagram showing a main part of a control system of an image forming unit provided in an image forming apparatus according to an embodiment of the present invention. [Figure 7] FIG. 1 is a diagram showing the functional configuration of a control unit according to an embodiment of the present invention. [Figure 8] FIG. 1 is a diagram illustrating color registration correction according to an embodiment of the present invention. [Figure 9] FIG. 10 is a diagram illustrating color registration correction according to a comparative example. [Figure 10] FIG. 10 is a diagram showing an example of a formation area of ​​a color shift measurement patch according to an embodiment of the present invention. [Figure 11] 1 is a flowchart illustrating an example of processing executed by a color misregistration correction unit according to an embodiment of the present invention. [Figure 12] FIG. 10 is a diagram for explaining the process of the color misregistration amount detection unit according to Modification 1; [Figure 13] 10 is a flowchart showing an example of processing performed by a color misregistration amount detection unit according to Modification 1. [Figure 14] FIG. 10 is a diagram for explaining a color registration correction of an image forming apparatus according to a second modification; DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functions are designated by the same reference numerals, and redundant description will be omitted.

[0025] An example of the configuration of an image forming apparatus (hereinafter referred to as "image forming apparatus U") according to one embodiment of the present invention will be described below with reference to FIGS.

[0026] Fig. 5 is a diagram schematically showing the overall configuration of the image forming apparatus U according to this embodiment. Fig. 6 is a diagram showing the main parts of a control system of the image forming unit 1 provided in the image forming apparatus U according to this embodiment.

[0027] The image forming apparatus U is a system that uses continuous paper P as a recording medium and forms an image on the continuous paper P. The continuous paper P is a recording medium that has a length in its transport direction that exceeds the width of the main body of the image forming unit 1, and includes, for example, roll paper.

[0028] 5, the image forming apparatus U is configured by connecting, from the upstream side along the transport direction of the continuous paper P, a paper feed unit 2, an image forming unit 1, and a winding unit 3. The paper feed unit 2 and the winding unit 3 are used when forming an image on the continuous paper P.

[0029] The paper feed unit 2 is a device that feeds continuous paper P to the image forming unit 1. Inside the housing of the paper feed unit 2, the continuous paper P is wound in a roll around a support shaft and rotatably held. The paper feed unit 2 transports the continuous paper P wound around the support shaft to the image forming unit 1 at a constant speed via multiple transport roller pairs, such as a feed roller and a paper feed roller. The paper feeding operation of the paper feed unit 2 is controlled by a control unit 100 provided in the image forming unit 1.

[0030] Image forming unit 1 forms a color image using electrophotographic process technology. That is, image forming unit 1 primarily transfers toner images of each of the toner colors Y (yellow), M (magenta), C (cyan), and K (black) formed on photosensitive drum 413 onto intermediate transfer belt 421, superimposes the four color toner images on intermediate transfer belt 421, and then secondarily transfers the toner images onto continuous paper P fed from paper feed unit 2, thereby forming a color image on continuous paper P.

[0031] In addition, the image forming unit 1 employs a tandem system in which photosensitive drums 413 corresponding to the four colors Y, M, C, and K are arranged in series in the running direction of the intermediate transfer belt 421, and toner images of each toner color are transferred sequentially to the intermediate transfer belt 421 in a single step.

[0032] As shown in FIG. 6, the image forming unit 1 includes an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a paper conveying unit 50, a fixing unit 60, an inline scanner 70, a temperature sensor 71, a communication unit 81, a memory unit 82, and a control unit 100.

[0033] The control unit 100 includes a CPU (Central Processing Unit) 100a, a ROM (Read Only Memory) 100b, a RAM (Random Access Memory) 100c, etc. The CPU 100a reads a program corresponding to the processing content from the ROM 100b, loads it into the RAM 100c, and centrally controls the operation of each block of the image forming unit 1 in cooperation with the loaded program. At this time, various data stored in a storage unit 82 is referenced. The storage unit 82 is configured, for example, with a non-volatile semiconductor memory (so-called flash memory) or a hard disk drive.

[0034] The control unit 100 transmits and receives various data to and from an external device (for example, a personal computer (not shown)) connected to a communication network such as a LAN (Local Area Network) or WAN (Wide Area Network) via the communication unit 81. The control unit 100 receives, for example, image data (input image data) transmitted from an external device, and forms an image on the continuous paper P based on this image data. The communication unit 81 is configured, for example, by a communication control card such as a LAN card.

[0035] As shown in FIG. 5, the image reading unit 10 is configured to include an automatic document feeder 11 called an ADF (Auto Document Feeder), a document image scanning device 12 (scanner), and the like.

[0036] The automatic document feeder 11 transports the documents D placed on the document tray using a transport mechanism and sends them to the document image scanning device 12. The automatic document feeder 11 makes it possible to continuously read the images (including both sides) of multiple documents D placed on the document tray all at once.

[0037] The document image scanning device 12 optically scans a document transported from the automatic document feeder 11 onto the contact glass or a document placed on the contact glass, and forms an image of the light reflected from the document on the light receiving surface of a CCD (Charge Coupled Device) sensor 12a to read the document image. The image reading unit 10 generates input image data based on the reading result by the document image scanning device 12. This input image data is subjected to predetermined image processing in the image processing unit 30.

[0038] 5, the operation display unit 20 is configured with, for example, a liquid crystal display (LCD) with a touch panel, and functions as a display unit 21 and an operation unit 22. The display unit 21 displays various operation screens, image status, operation status of each function, information related to printing, etc. in accordance with a display control signal input from the control unit 100. The operation unit 22 has various operation keys such as a numeric keypad and a start key, and accepts various input operations by the user and outputs operation signals to the control unit 100.

[0039] The image processing unit 30 includes a circuit for performing digital image processing on input image data according to initial settings or user settings. For example, under the control of the control unit 100, the image processing unit 30 performs gradation correction based on gradation correction data (gradation correction table). In addition to gradation correction, the image processing unit 30 also performs various correction processes such as color correction and shading correction, as well as compression, on the input image data. The image forming unit 40 is controlled based on the image data that has undergone these processes.

[0040] As shown in FIG. 5, the image forming unit 40 includes toner image forming units 41Y, 41M, 41C, and 41K for forming images using color toners of Y, M, C, and K components based on input image data, and an intermediate transfer unit 42.

[0041] Toner image forming units 41Y, 41M, 41C, and 41K for the Y, M, C, and K components have the same configuration. For ease of illustration and explanation, common components are denoted by the same reference numerals, and when distinguishing between them, the reference numerals are suffixed with Y, M, C, or K. In Figure 5, only the components of toner image forming unit 41Y for the Y component are denoted by reference numerals, and the components of the other toner image forming units 41M, 41C, and 41K are not denoted by reference numerals.

[0042] The toner image forming section 41 includes an exposure device 411, a developing device 412, a photosensitive drum 413, a charging device 414, a drum cleaning device 415, a toner recovery section 200, and the like.

[0043] Photoconductor drum 413 is made of an organic photoconductor, for example, in which a photosensitive layer made of a resin containing an organic photoconductor is formed on the outer peripheral surface of a drum-shaped metal substrate. Note that control unit 100 controls the drive current supplied to a drive motor (not shown) that rotates photoconductor drum 413, thereby rotating photoconductor drum 413 at a constant peripheral speed.

[0044] The charging device 414 is, for example, a charger, and generates a corona discharge to uniformly charge the surface of the photoconductive photosensitive drum 413 to a negative polarity.

[0045] Exposure device 411 is configured with, for example, a semiconductor laser, and irradiates photosensitive drum 413 with laser light corresponding to the image of each toner color component. As a result, an electrostatic latent image of each toner color component is formed in the image area on the surface of photosensitive drum 413 irradiated with the laser light due to the potential difference with the background area.

[0046] The developing device 412 is a two-component reverse type developing device, and visualizes the electrostatic latent image by depositing the developer of each toner color component onto the surface of the photosensitive drum 413, thereby developing it into a toner image.

[0047] Developing roller 412A of developing device 412 carries a developer while rotating, and supplies the toner contained in the developer to photosensitive drum 413. Specifically, a developing bias is applied to developing roller 412A from developing bias application section 412B, and a potential difference is generated between developing roller 412A and the surface of photosensitive drum 413, thereby forming a toner image on the surface of photosensitive drum 413.

[0048] The drum cleaning device 415 is in contact with the surface of the photosensitive drum 413 and has an elastic, flat drum cleaning blade or the like, and removes toner remaining on the surface of the photosensitive drum 413 without being transferred to the intermediate transfer belt 421.

[0049] The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422, a plurality of support rollers 423, a secondary transfer roller 424, a belt cleaning device 426, and the like.

[0050] The intermediate transfer belt 421 is an endless belt that is stretched around a plurality of support rollers 423 in a loop shape. At least one of the support rollers 423 is a drive roller, and the others are driven rollers. For example, it is preferable that roller 423A, which is disposed downstream of primary transfer roller 422 for the K component in the belt running direction, be the drive roller. This makes it easier to maintain a constant running speed of the belt in the primary transfer section. As drive roller 423A rotates, intermediate transfer belt 421 runs at a constant speed in the direction of arrow A.

[0051] The intermediate transfer belt 421 is a conductive and elastic belt having a high resistance layer on its surface, and is driven to rotate by a control signal from the control unit 100.

[0052] Primary transfer rollers 422 are disposed opposite photosensitive drums 413 for the respective toner color components, on the inner peripheral side of intermediate transfer belt 421. Primary transfer rollers 422 are pressed against photosensitive drums 413 with intermediate transfer belt 421 sandwiched therebetween, thereby forming a primary transfer nip for transferring a toner image from photosensitive drum 413 to intermediate transfer belt 421.

[0053] Secondary transfer roller 424 is disposed on the outer circumferential surface side of intermediate transfer belt 421, facing backup roller 423B, which is disposed downstream of drive roller 423A in the belt running direction. Secondary transfer roller 424 is pressed against backup roller 423B with intermediate transfer belt 421 sandwiched therebetween, thereby forming a secondary transfer nip for transferring a toner image from intermediate transfer belt 421 to continuous paper P.

[0054] When intermediate transfer belt 421 passes through the primary transfer nip, the toner images on photosensitive drum 413 are sequentially superimposed and primarily transferred onto intermediate transfer belt 421. Specifically, a primary transfer bias is applied to primary transfer roller 422, and a charge of the opposite polarity to the toner is applied to the back side of intermediate transfer belt 421, that is, the side that contacts primary transfer roller 422, so that the toner images are electrostatically transferred onto intermediate transfer belt 421.

[0055] Thereafter, when the continuous paper P passes through the secondary transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred onto the continuous paper P. Specifically, a secondary transfer bias is applied to the secondary transfer roller 424, and a charge of the opposite polarity to the toner is applied to the back side of the continuous paper P, that is, the side that contacts the secondary transfer roller 424, thereby electrostatically transferring the toner image onto the continuous paper P. The continuous paper P with the transferred toner image is transported towards the fixing unit 60.

[0056] Belt cleaning device 426 removes residual toner remaining on the surface of intermediate transfer belt 421 after secondary transfer. Note that instead of secondary transfer roller 424, a so-called belt-type secondary transfer unit may be used in which a secondary transfer belt is stretched in a loop around multiple support rollers including a secondary transfer roller.

[0057] The fixing unit 60 includes an upper fixing unit 60A having a fixing surface side member that is arranged on the fixing surface of the continuous paper P, i.e., the surface on which the toner image is formed, a lower fixing unit 60B having a back surface side support member that is arranged on the back surface of the continuous paper P, i.e., the surface opposite the fixing surface, and a heating source. The back surface side support member is pressed against the fixing surface side member to form a fixing nip that sandwiches and transports the continuous paper P. The fixing unit 60 fixes the toner image to the continuous paper P by heating and pressurizing the transported continuous paper P at the fixing nip after the toner image has been secondarily transferred onto it.

[0058] The inline scanner 70 uses, for example, a built-in CCD sensor (Charge Coupled Device) or CMOS sensor (Complementary Metal Oxide Semiconductor) to capture and read images of color shift measurement patches formed on the continuous paper P. The inline scanner 70 is disposed, for example, downstream of the fixing unit 60 on the conveying path unit 53, in a position facing the continuous paper P, and captures images of the color shift measurement patches. The inline scanner 70 is capable of capturing images in each RGB wavelength band (multiple wavelength bands).

[0059] The color misregistration measurement patch is, for example, a predetermined pattern formed separately for each toner color. The color misregistration measurement patch is formed in a predetermined margin area outside the area where the document image is formed on the continuous paper P so that the amount of color misregistration in the image formation area of ​​each color that occurs during printing related to the print job data can be detected (for example, as described below with reference to FIG. 10).

[0060] It should be noted that a photosensor may be used instead of the in-line scanner 70 as a means for detecting the image of the color misregistration measurement patch.

[0061] The temperature sensor 71 is, for example, a thermistor or a radiation temperature sensor, and is disposed inside the image forming apparatus U to detect the temperature inside the image forming apparatus U. The temperature sensor 71 is disposed adjacent to the drive roller 423 that stretches the intermediate transfer belt 421 so that it can detect, for example, a change in the diameter of the drive roller of the intermediate transfer belt 421 due to a change in the temperature inside the image forming apparatus U, and thus a change in the amount of color misregistration.

[0062] The paper transport section 50 includes a paper feed section 51, a paper discharge section 52, and a transport path section 53. The transport path section 53 has a plurality of transport roller pairs, and transports the continuous paper P fed from the paper feed unit 2 to the image forming section 40 and the fixing section 60, and then sends it out to the winding unit 3. The plurality of transport roller pairs of the transport path section 53 include a registration roller pair that corrects the skew and deviation of the continuous paper P.

[0063] The paper feed section 51 is a plain paper feed section provided separately from the paper feed unit 2, and feeds paper that does not exceed the width of the main body of the image forming unit 1. The three paper feed tray units that make up the paper feed section 51 store paper identified based on basis weight, size, etc., by pre-set type.

[0064] The continuous paper P fed from the paper feed unit 2 to the image forming unit 1 is transported to the image forming unit 40 by the transport path unit 53. Then, in the image forming unit 40, the toner images on the intermediate transfer belt 421 are secondary-transferred all at once onto one side of the continuous paper P, and a fixing process is performed in the fixing unit 60. The continuous paper P on which the image has been formed is transported to the winding unit 3 by the paper discharge unit 52 equipped with a pair of transport rollers (a pair of paper discharge rollers).

[0065] The winding unit 3 is a device that winds up the continuous paper P transported from the image forming unit 1. Within the housing of the winding unit 3, for example, the continuous paper P is wound around a support shaft and held in a roll shape. To do this, the winding unit 3 winds up the continuous paper P transported from the image forming unit 1 around the support shaft at a constant speed via multiple transport roller pairs (for example, a feed roller and a paper discharge roller).

[0066] [Detailed configuration of control unit 100] Next, the functional configuration of the control unit 100 according to this embodiment will be described. The control unit 100 according to this embodiment is configured to be able to perform color registration correction while a print job is being executed (i.e., while printing on continuous paper P is being executed).

[0067] FIG. 7 is a diagram showing the functional configuration of the control unit 100 according to this embodiment.

[0068] Fig. 8 is a diagram illustrating color registration correction according to this embodiment. Fig. 9 is a diagram illustrating color registration correction according to a comparative example. Note that the color registration correction according to the comparative example is color registration correction using two-dimensional position correction according to conventional technology.

[0069] 8 and 9 show a schematic representation of print job data corrected by color registration correction when color misregistration occurs for Y color, and show how the image formation area of ​​each color (here, Y color) is corrected on the data by color registration correction. Note that in FIGS. 8 and 9, "P1" etc. represent page numbers such as page 1, "original Y (or original K)" represents the image formation area within the page, and "margin area" represents the margin area within the page. Also, the vertical width of "original Y (or original K)" and the vertical width of the "margin area" represent the respective occupied widths in the paper feed direction within the page.

[0070] The control unit 100 has the functions of a print job setting unit 101, a color misregistration amount detection unit 102, and a color misregistration correction unit 103.

[0071] The print job setting unit 101 generates print job data based on image data to be printed.

[0072] Here, the print job setting unit 101 generates print job data by converting the image data of each color of each page to be printed into a format consisting of an image formation area (the area of ​​document Y (or document K) in FIGS. 8 and 9) and a margin area (a margin area of ​​one line in FIGS. 8 and 9) of a specified width (hereinafter also referred to as the "first width") provided upstream and / or downstream in the paper feed direction from the image formation area, so that color registration correction similar to the two-dimensional position correction described with reference to FIG. 4 can be performed.

[0073] As shown in FIG. 8, the print job data generated by the print job setting unit 101 has the reference position (the top position of each page in FIG. 8) of the image formation area of ​​each page (i.e., an image formation area of ​​4 lines) set so that the image formation area of ​​each page is arranged in order along the paper feed direction with a margin area of ​​a first width (i.e., a margin area of ​​1 line) between it and the image formation area of ​​the previous page.

[0074] 8 and 9, the positions of the image formation area and margin area within a page are expressed with one line being equal to one 600 dpi unit (42 μm). In the print job data of FIG. 8, before correction, the image data of each page has an image formation area of ​​four lines from the top edge position followed by a margin area of ​​one line. On the other hand, in the print job data of FIG. 9, before correction, the image data of each page has an image formation area of ​​four lines from the top edge position followed by a margin area of ​​two lines.

[0075] The color misregistration amount detection unit 102 detects the amount of color misregistration of each color in the image formation area that occurs on a page-by-page basis while printing related to the print job data is being performed. In this case, the color misregistration amount detection unit 102 detects the amount of color misregistration without stopping the image formation operation on the continuous paper P, for example, by using one or both of the following two detection methods.

[0076] Since the amount of color misregistration is the relative positional relationship between colors, the amount of color misregistration for each color is expressed as, for example, the amount of positional misregistration with a specific color as the reference position. The color misregistration amount detection unit 102 detects the amount of color misregistration for the image formation positions of other colors, for example, with the image formation position of K as the reference.

[0077] A first method is to use a temperature sensor 71 installed inside the image forming apparatus U to sense the internal temperature of the image forming apparatus U, and to estimate the amount of color misregistration for each color from this internal temperature. This method utilizes the empirical rule that a typical cause of color misregistration is due to changes in the length of the intermediate transfer belt 421, which depend on changes in the internal temperature of the image forming apparatus U. In this method, for example, a correspondence relationship between the internal temperature of the image forming apparatus U and the amount of color misregistration is stored in advance as a data table, and the color misregistration amount detection unit 102 detects the amount of color misregistration for each color from the data table and the internal temperature of the image forming apparatus U indicated by the temperature sensor 71.

[0078] A second method is to form an image of a color shift measurement patch in a predetermined margin area set at a position shifted in the width direction (meaning the direction perpendicular to the paper feed direction; the same applies below) relative to the image formation area of ​​each page in the continuous paper P, and then detect the amount of color shift for each color by sensing the image of the color shift measurement patch with an in-line scanner 70. This makes it possible to directly detect the amount of color shift for each color in the image forming apparatus U without stopping the process of forming the image to be printed on the continuous paper P. Note that in this method, the amount of color shift may be detected using a photosensor (not shown) instead of the in-line scanner 70.

[0079] Fig. 10 shows one example of a color shift measurement patch. Fig. 10 shows a color shift measurement patch in which each of the four colors YMCK is formed in the shape of a bar (see R1 in Fig. 10). With such a color shift measurement patch, the amount of color shift is detected based on the positional deviation of each of the four color bars of YMCK.

[0080] The color shift measurement patches are formed, for example, in the margins provided at the edges of each page in the width direction. In Fig. 10, the color shift measurement patch formation areas are shown as being formed at both ends of the page, but the user may also be allowed to select either both ends, the left end, or the right end as the formation area.

[0081] When using the second method, the frequency of forming color shift measurement patches may be every few pages instead of every page. In the image forming apparatus U, a waste strip pattern may be printed in the margin area of ​​the paper when printing low coverage images. This is to ensure a certain level of toner consumption, taking into consideration that long-distance printing of low coverage images can cause the developer to deteriorate and make image formation impossible. In this case, the color shift measurement patch and the waste strip pattern cannot overlap. In this regard, color shift fluctuations are long-term, and the amount of color shift does not change in the short term. Therefore, for example, a color shift measurement patch may be formed on one of five pages, and waste strip patterns may be formed on the remaining four pages. In this case, the amount of color shift on pages where the amount of color shift was not actually detected can be estimated from the amount of color shift obtained on pages where the amount of color shift was detected.

[0082] When detecting the amount of color misregistration for each color, the color misregistration amount detection unit 102 may use a different detection method for each color. For example, when a color image is formed by overlaying five colors, Y, M, C, K, and W (white), it is preferable to detect the amount of color misregistration for the four colors, Y, M, C, and K, using the second method (detection method using the inline scanner 70) described above, and to detect the amount of color misregistration for W using the first method (detection method using the temperature sensor 71) described above. This is because W generally has a small contrast difference with the continuous paper P, making it difficult to accurately detect it using the inline scanner 70 or a photosensor. Therefore, it is preferable to apply this method to colors that do not contrast with the continuous paper P, not just W.

[0083] When printing is performed according to the print job data set in the print job setting unit 101, the color misregistration correction unit 103 corrects the formation position of the image formation area of ​​the page to be printed next (hereinafter abbreviated as the "print target page") set in the print job data, based on the amount of color misregistration in the verification target page (for example, the immediately preceding page) that is one or more pages before. In this embodiment, the page that is one page before the page to be printed is the verification target page.

[0084] More specifically, the color misregistration correction unit 103 has a first correction processing unit 103a that compensates for at least a portion of the color misregistration by shifting the formation position of the image formation area within the page to be printed for the color to be corrected in parallel in the paper feed direction from a reference position within a margin area set for each page in the print job data set in the print job setting unit 101, and a second correction processing unit 103b that compensates for at least a portion of the color misregistration by inserting an additional margin area of ​​a second width (e.g., the second width = the first width) (in this embodiment, 600 dpi (42 μm)) that does not constitute a page, upstream of the page to be printed in the paper feed direction, for the color to be corrected in the print job data set in the print job setting unit 101. The color misregistration correction unit 103 then compensates for all of the color misregistration for the page to be printed through the correction processing of the first correction processing unit 103a and the correction processing of the second correction processing unit 103b, and overlaps the images of each color on the intermediate transfer body.

[0085] Here, the correction process of the first correction processing unit 103a is a process of correcting the formation position of the image formation area within the page to be printed in the print job data, and is a process similar to two-dimensional position correction according to the prior art. Note that the range in which the first correction processing unit 103a can correct the formation position of the image formation area is within the range of the specified width (i.e., the first width) of the margin area of ​​each page.

[0086] The correction process of the second correction processing unit 103b is a correction process that shifts the start position of a page between colors in the print job data. The correction process of the second correction processing unit 103b is realized, for example, by inserting additional data of an additional margin area between the image data of the page to be printed and the image data of the page immediately before it in the print job data. However, the correction process of the second correction processing unit 103b may also be realized by changing the non-exposure time in the exposure device 411 between pages.

[0087] Note that, due to design reasons for the print job data, the correction process of the first correction processing unit 103a is capable of relatively fine position correction, but the correction process of the second correction processing unit 103b is capable of only relatively coarse position correction. Specifically, the correction resolution of the correction process of the first correction processing unit 103a according to this embodiment (i.e., shift correction of the image formation area within a page) is in units of 19200 dpi (1.3 um) (i.e., 0.03 lines), while the correction resolution of the correction process of the second correction processing unit 103b (i.e., insertion of an additional margin area between pages) is in units of 600 dpi (42 um) (i.e., 1 line).

[0088] Here, we will explain the differences between the color registration correction according to this embodiment and the color registration correction according to the comparative example. Note that the color registration correction according to this embodiment is particularly useful in that it can deal with the accumulation of color misregistration in the paper feed direction that occurs when printing continuously on continuous paper P without gaps.

[0089] As described above, color misregistration usually occurs due to factors such as an increase in the belt length of intermediate transfer belt 421, so once color misregistration occurs, the amount of color misregistration accumulates in increments of approximately the same width as the pages to be printed progress over a certain period of time until the internal temperature of image forming apparatus U returns to normal. For example, Figures 8 and 9 show a state in which the amount of color misregistration of a Y-color original relative to a K-color original accumulates by 0.5 lines as the pages to be printed progress.

[0090] In this case, in the color registration correction according to the comparative example (i.e., the two-dimensional position correction according to the conventional technology described with reference to FIG. 4), it is necessary to gradually shift the formation position of the image formation area of ​​the original (in FIG. 9, the Y-color original) where color shift has occurred within each page toward the downstream side in the paper feed direction as the pages to be printed progress.

[0091] Specifically, in the color registration correction according to the comparative example, as shown in FIG. 9, in order to accommodate the amount of color misregistration, on the second page, the image formation area of ​​the Y original is shifted downstream in the paper feed direction by 0.5 lines within the page, on the third page, the image formation area of ​​the Y original is shifted downstream in the paper feed direction by 1.0 lines within the page, and on the fourth page, the image formation area of ​​the Y original is shifted downstream in the paper feed direction by 1.5 lines within the page, and so on. In this way, the formation position of the image formation area of ​​the Y color original on each page is gradually shifted downstream in the paper feed direction as the pages to be printed progress.

[0092] It can be seen that with such a color registration correction method according to the comparative example, it becomes necessary to ensure a fairly large margin area for each page when forming color images for tens or hundreds of pages on one continuous sheet of paper P. In other words, with such a color registration correction method according to the comparative example, the margin area (blank area) of each page becomes unnecessarily long, making it impractical.

[0093] In this regard, the color shift correction unit 103 according to this embodiment compensates for the amount of color shift for each color through the correction processing of the first correction processing unit 103a and the correction processing of the second correction processing unit 103b, thereby shortening the margin area set for each page.

[0094] Fig. 11 is a flowchart showing an example of processing executed by the color misregistration correction unit 103 according to this embodiment. The flowchart shown in Fig. 11 shows processing executed by the color misregistration correction unit 103 before printing of the image of each page of the print job data is executed.

[0095] In step S1, the color shift correction unit 103 acquires the amount of color shift in the verification target page (here, the immediately preceding page) detected by the color shift amount detection unit 102. Note that here, the verification target page is the page immediately preceding the next print target page set in the print job data.

[0096] In step S2, the color shift correction unit 103, for example, by referring to past correction history data, calculates the cumulative value of the color shift amount from the time when the previous added margin area (representing the added margin area by the correction process of the second correction processing unit 103b; the same applies below) was inserted until the current correction timing.The color shift correction unit 103 then determines whether the cumulative value has increased to or greater than the specified width (here, 1 line) of the margin area set for each page.If the color shift correction unit 103 has determined that the cumulative value of the color shift amount has increased to or greater than the specified width (here, 1 line) of the margin area (step S2: YES), it proceeds to step S4.If the cumulative value of the color shift amount has not increased to or greater than the specified width (here, 1 line) of the margin area (step S2: NO), it proceeds to step S3.

[0097] In step S3, the color shift correction unit 103 corrects the print job data so as to compensate for only the amount of color shift on the page to be verified this time (here, the immediately preceding page) by moving the image formation area parallel to the paper feed direction from the reference position within the margin area set for the next page (i.e., correction processing by the first correction processing unit 103a).

[0098] In step S4, the color shift correction unit 103 corrects the print job data by inserting an additional margin area that does not constitute a page between the next page to be printed and the page immediately before it, to compensate for the cumulative amount of color shift, including the amount of color shift, on the page to be verified this time (i.e., correction processing by the second correction processing unit 103b).

[0099] In this way, in a situation where it becomes necessary to gradually shift the formation position of the image formation area of ​​the color to be corrected in the print job data in accordance with the progress of the pages to be printed, the color misalignment correction unit 103 takes measures to shift the start position of the page between colors in the print job data through correction processing by the second correction processing unit 103b.

[0100] After the correction of the print job data is performed, the color shift correction unit 103 allows the image forming unit 40 to print the image of the page to be printed. By performing the processes of steps S1 to S4 for each page to be printed, the color shift correction of each page is performed in real time.

[0101] 8, when a color shift amount is detected on the second page where the Y color original is advanced in phase by 0.5 lines relative to the K color original, the color shift correction unit 103 compensates for the color shift on the third page by delaying the formation position of the image formation area of ​​the Y color original within the page by 0.5 lines in the print job data. In this case, the cumulative value of the color shift amount from the first page to the second page has not reached 1 line, so the color shift correction unit 103 compensates for the color shift of the Y color original through the correction process of the first correction processing unit 103a.

[0102] The threshold value (here, 1 Line) for the cumulative value of this color misregistration amount is the range within which the image formation area can be moved by two-dimensional position correction, and corresponds to the specified width of the margin area set for each page.

[0103] Next, when a color shift amount is detected again on the third page where the Y color original is 0.5 line ahead in phase with respect to the K color original, the color shift correction unit 103 provides an additional margin area of ​​1.0 line for Y color between the third and fourth pages, thereby compensating for the color shift amount on the third page, and then causes the image forming unit 40 to print the fourth page (i.e., the correction process of the second correction processing unit 103b).At this time, the cumulative value of the color shift amount from the first page to the third page reaches 1 line, so the color shift correction unit 103 compensates for the color shift of Y color through the correction process of the second correction processing unit 103b.

[0104] This makes it possible to shift the page start position for Y color and the page start position for K color by 1.0 Line from the fourth page on the print job data, and on the fourth page, the image formation area for Y color can be reset to the reference position (top position) within the page.

[0105] Therefore, when a color shift is detected again on the fourth page where the Y-color original is 0.5 lines ahead in phase with respect to the K-color original, the color shift correction unit 103 can compensate for the color shift by delaying the formation position of the image formation area of ​​the Y-color original within the page on the fifth page in the print job data by 0.5 lines from the top position of the fifth page (correction processing by the first correction processing unit 103a).

[0106] As can be seen, the color misregistration correction unit 103 according to this embodiment can achieve correction processing that matches the progress of the page to be printed with only a margin area of ​​1.0 Line. This is in contrast to the correction processing according to the comparative example, which required securing an excessive margin area in order to achieve correction processing that matches the progress of the page to be printed.

[0107] As described above, the color misregistration corrector 103 compensates for the amount of color misregistration for each color through the correction process of the first correction processor 103a and the correction process of the second correction processor 103b, and overlaps the images of each color on the intermediate transfer belt 421.

[0108] In the above embodiment, the color misregistration correction unit 103 performs correction processing by the first correction processing unit 103a and / or the second correction processing unit 103b on the print job data so that the width of the margin area between the image formation area of ​​the next page to be printed and the image formation area of ​​the page immediately before it is always constant (i.e., the first width set to 1 Line in this embodiment) when overlapping images of each color on the intermediate transfer belt 421. Also, in the above embodiment, from the same perspective, the "second width" of the additional margin area inserted between pages in the correction processing by the second correction processing unit 103b is set to the same width as the specified width of the margin area of ​​each page (1 Line in this embodiment).

[0109] This is because the color misregistration correction unit 103 keeps the distance between the image formation areas of each page constant after printing, which makes it possible to omit cumbersome processing such as detecting the image formation position for each page when cutting out the image of each page from the continuous paper P.

[0110] [effect] As described above, the image forming apparatus U according to this embodiment has the following features: a print job setting unit 101 that manages jobs for each color and generates print job data in which a margin area of ​​a first width is set on the upstream side or downstream side of the image forming area of ​​each page in the paper feed direction; a color misregistration amount detection unit 102 that detects the amount of color misregistration of each color in the image forming area that occurs on a page-by-page basis while printing related to the print job data is being performed; a color shift correction unit 103 that corrects the formation position of the image formation area of ​​the next page to be printed on the print job data, targeting the color in which color shift has occurred, based on the amount of color shift in a verification target page one or more pages before, when printing related to the print job data is being performed; Equipped with The color misregistration correction unit 103 a first correction processing unit that compensates for at least a part of the amount of color misregistration by shifting the formation position of the image formation area within the page to be printed in parallel in the paper feed direction within the margin area in a job of the color to be corrected in the print job data; a second correction processing unit 103b that compensates for at least a part of the amount of color misregistration by inserting an additional margin area of ​​a second width that does not constitute a page between the page to be printed and the page immediately before it in a job of the color to be corrected in the print job data, The color misregistration amount is entirely compensated for by the processing of the first correction processing unit 103a and the second correction processing unit 103b.

[0111] This makes it possible to address color shifts that occur during continuous printing while keeping the margin area between pages (i.e., the margin area between the image formation area of ​​page n and the image formation area of ​​page n+1) to a necessary minimum.

[0112] In the above embodiment, the color shift correction unit 103 performs either the correction process of the first correction processing unit 103a or the correction process of the second correction processing unit 103b to compensate for the amount of color shift in the page to be verified. However, the color shift correction unit 103 may perform both the correction process of the first correction processing unit 103a and the correction process of the second correction processing unit 103b to compensate for the amount of color shift in the page to be verified.

[0113] In other words, the color shift correction unit 103 may allocate the amount of color shift in the verification target page to the compensation amount by the first correction processing unit 103a and the compensation amount by the second correction processing unit 103b. In this case, since the resolution at which compensation can be made by the second correction processing unit 103b is 1.0 line, a typical configuration is such that the value obtained by subtracting the amount of color shift that can be compensated by the second correction processing unit 103b from the amount of color shift in the verification target page is compensated by the first correction processing unit 103a.

[0114] (Variation 1) In the above embodiment, the color misregistration amount detection unit 102 always uses the image formation position of K as a reference and detects the color misregistration amounts of the image formation positions of the other colors. However, it is preferable that the color misregistration amount detection unit 102 expresses the color misregistration amounts of the image formation positions of the other colors as a reference, without fixing the reference color, using the image formation position of the color formed at the rearmost position in the paper feed direction among the colors.

[0115] Fig. 12 is a diagram for explaining the process of the color shift amount detection unit 102 according to Modification 1. Fig. 13 is a flowchart showing an example of the process of the color shift amount detection unit 102 according to Modification 1.

[0116] FIG. 12 shows an example in which the M image forming position is formed at the rear end in the paper feed direction on the Nth page. If the K image forming position is used as the reference, as in the above embodiment, the color misregistration of the M image forming position relative to the K image on the Nth page would be expressed as a phase delay (i.e., a color misregistration in the negative direction). However, the second correction processing unit 103b can only perform correction processing to address a phase advance (i.e., a color misregistration in the positive direction) (i.e., a shift toward the rear in the paper feed direction). Therefore, this representation method makes it impossible to compensate for the color misregistration of the M image forming position relative to the K image on the N+1th page.

[0117] From this perspective, when expressing the amount of color misregistration for a page to be verified, the color misregistration amount detection unit 102 preferably expresses the amount of color misregistration for the image formation positions of the other colors using the image formation position of the color formed at the rearmost position in the paper feed direction (M color in FIG. 12) as a reference. In other words, it is sufficient to use the color shifted furthest to the rear for each page as a reference and shift the other colors backward in the paper feed direction.

[0118] The flowchart in FIG. 13 shows a processing procedure that embodies this technical idea.

[0119] In step S11, the color shift amount detection unit 102 first obtains the color shift amount Yd of Y color based on the K color reference, the color shift amount Md of M color based on the K color reference, and the color shift amount Cd of C color based on the K color reference, and identifies the smallest value (Min=min(Yd, Md, Cd)) among these.

[0120] In step S12, the color misregistration amount detection unit 102 determines whether the minimum value (Min=min(Yd, Md, Cd)) identified in step S11 is less than zero. If the minimum value min(Yd, Md, Cd) identified in step S11 is less than zero (S12: YES), the color misregistration amount detection unit 102 proceeds to step S13, and if the minimum value min(Yd, Md, Cd) identified in step S11 is equal to or greater than zero (S12: NO), the color misregistration amount detection unit 102 proceeds to step S14.

[0121] Here, if the minimum value min(Yd, Md, Cd) identified in step S11 is less than zero (S12: YES), it means that the color formed at the rear end in the paper feed direction is not K, and if the minimum value min(Yd, Md, Cd) identified in step S11 is greater than or equal to zero (S12: NO), it means that the color formed at the rear end in the paper feed direction is K.

[0122] In step S13, the color misregistration amount detection unit 102 changes the color misregistration correction value of each color as follows, in order to change the color used as the reference for color misregistration to the color formed at the rearmost position in the paper feed direction. Y color correction value: Y=Yd-Min M color correction value: M=Md-Min C color correction value: C=Cd-Min K color correction value: K=-Min

[0123] In step S14, the color misregistration amount detection unit 102 determines the color misregistration correction value for each color as follows, since there is no need to change the color used as the reference for color misregistration from K to another color. Y color correction value: Y=Yd M color correction value: M=Md C color correction value: C=Cd K color correction value: K=0

[0124] As described above, according to the image forming apparatus U of this modified example, it is possible to execute the correction process of the color misregistration corrector 103 so as to deal with color misregistration of all colors.

[0125] (Variation 2) FIG. 14 is a diagram for explaining a color registration correction of the image forming apparatus U according to the second modification.

[0126] Normally, a time lag occurs when the amount of color misregistration is detected by the color misregistration amount detection unit 102 (inline scanner 70) and then the print job data is corrected by feeding back the amount of color misregistration by the color misregistration correction unit 103. For example, in Figure 14, when color misregistration is detected on the 1000th page of the continuous paper P, color registration correction corresponding to the color misregistration is performed and the color image is printed on the 1007th page, and the color images printed on pages 1001 to 1006 of the continuous paper P will not reflect the correction of the amount of color misregistration.

[0127] In this state, when the color shift amount detection unit 102 detects the color shift amount for pages 1001 to 1006 of the continuous paper P and the color shift correction unit 103 corrects the print job data by feeding back the color shift amount, the color shift amount is compensated for redundantly.

[0128] Therefore, the image forming apparatus U according to this modification does not perform (i.e., stops) the processing of the color shift amount detection unit 102 and / or the color shift correction unit 103 during the time lag between when the amount of color shift is detected by the color shift amount detection unit 102 and when the correction processing of the print job data to compensate for the amount of color shift is completed by the color shift correction unit 103. For example, in the aspect of Fig. 14, the image forming apparatus U according to this modification does not perform the processing of the color shift amount detection unit 102 and the color shift correction unit 103 for pages 1001 to 1006 of the continuous paper P.

[0129] The image forming apparatus U according to this modified example is useful in that it is possible to avoid overlapping correction and perform color registration correction by an appropriate amount of color misregistration.

[0130] (Variation 3) As explained in variant example 2, a time lag occurs between the time when the color shift amount detection unit 102 detects the color shift amount of the page to be verified and the time when the color shift correction unit 103 completes the correction process of the print job data to compensate for the color shift amount (i.e., the time until a color image is formed on the continuous paper P with the color shift amount compensated).

[0131] If this delay in the image forming apparatus U is on the order of several meters in terms of the paper transport distance and paper transport speed, the change in the internal temperature during this time lag can be ignored. However, if the distance from the image formation position in the image forming unit 40 to the inline scanner 70 is several tens of meters, or if the internal temperature changes drastically, the change in the internal temperature during this time lag cannot be ignored. In such a mechanical configuration, the amount of color misregistration that occurs between the time of feedback and the internal temperature difference when the color misregistration calculation page is printed can be estimated and reflected.

[0132] That is, in the image forming device U according to this modified example, the color shift correction unit 103 corrects the amount of color shift detected by the color shift amount detection unit 102 based on the difference between the internal temperature of the image forming device U when the image of the page to be verified is formed and the internal temperature of the image forming device U when the image of the next page to be printed is formed, so as to correspond to the change in the amount of color shift during the time lag.

[0133] Furthermore, the correspondence between the difference in the internal temperature of the image forming device U when the image of the page to be verified is formed and the internal temperature of the image forming device U when the image of the next page to be printed is formed, and the correction amount for the color shift amount detected by the color shift amount detection unit 102 can be obtained in advance through experiments or simulations, and stored as table data in a memory unit (e.g., ROM 100b).

[0134] The image forming device U of this modified example is useful in that it can also accommodate changes in the amount of color shift during the time lag between when the color shift amount detection unit 102 detects the amount of color shift of the page to be verified and when the color shift correction unit 103 completes the correction process of the print job data to compensate for the amount of color shift.

[0135] (Variation 4) If the difference between the internal temperature of the image forming device U at the end of the print job and the internal temperature of the image forming device U at the start of the next print job is equal to or less than a predetermined temperature, the color shift correction unit 103 may start the next print job using the amount of color shift at the end of the print job as the amount of color shift of the first page of the next print job.

[0136] In other words, the amount of color misregistration at the end of a print job is reflected as the correction value for the first page of the next print job. By doing so, when the next print job starts, it is possible to print color misregistration measurement patches on the intermediate transfer belt 421 and reduce the time it takes to calculate the amount of color misregistration for each color. However, if the fixing heater stops and the internal temperature drops when printing ends, the amount of color misregistration will change, and color misregistration correction will need to be performed again. Therefore, it is preferable to apply the correction value to the next job only if the temperature change is within a certain range after the end of a print job.

[0137] The image forming apparatus U according to this modified example is useful in that it can reduce the time required for color misregistration correction processing at the start of the next print job.

[0138] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above. [Industrial Applicability]

[0139] According to the image forming apparatus according to the present disclosure, when printing on continuous paper, it is possible to correct color misregistration that occurs during continuous printing without widening the margins between pages. [Explanation of symbols]

[0140] U Image forming device 1 Image forming unit 2 Paper feed unit 3. Winding unit 10 Image reading unit 20 Operation display section 30 Image processing section 40 Image forming unit 411 Exposure equipment 412 Developing device 413 Photosensitive drum 414 Charging device 415 Dry cleaning equipment 416 Toner supply unit 421 Intermediate transfer belt 422 Primary transfer roller 423 Support Roller 424 Secondary transfer roller 50 Paper transport section 81 Communications Department 82 Memory section 100 control section 101 Print job setting section 102 Color misregistration amount detection unit 103 Color registration correction unit 103a first correction processing unit 103b Second correction processing unit

Claims

1. An image forming apparatus having an image forming unit that forms a color image by superimposing images of each color formed on separate photosensitive members on an intermediate transfer member, and that continuously forms color images of multiple pages on a single continuous sheet of paper in the image forming unit, a print job setting unit that manages jobs for each color and generates print job data in which a margin area of ​​a first width is set on the upstream side or downstream side of the image forming area of ​​each page in the paper feed direction; a color misregistration amount detection unit that detects, on a page-by-page basis, the amount of color misregistration of each color in the image forming area that occurs while printing related to the print job data is being performed; a color shift correction unit that corrects the formation position of the image formation area of ​​the next page to be printed on the print job data, targeting the color in which color shift has occurred, based on the amount of color shift in a verification target page one or more pages before, when printing related to the print job data is being performed; Equipped with The color misregistration correction unit a first correction processing unit that compensates for at least a part of the amount of color misregistration by shifting a formation position of the image formation area within the page to be printed in parallel in a paper feed direction within the margin area in a job of the color to be corrected in the print job data; a second correction processing unit that inserts an additional margin area of ​​a second width that does not constitute a page between the page to be printed and the page immediately preceding it in a job of the color to be corrected in the print job data, thereby shifting the page start position of the page to be printed between colors in the paper feed direction and compensating for at least a part of the amount of color misregistration, the color misregistration amount is entirely compensated for by the processing of the first correction processing unit and the second correction processing unit. Image forming device.

2. the color misregistration correction unit performs correction processing of the first correction processing unit and / or the second correction processing unit on the print job data so that the width of the margin area between the image formation area of ​​the page to be printed and the image formation area of ​​the page immediately before it becomes the first width when the images of the respective colors are superimposed on the intermediate transfer body. The image forming apparatus according to claim 1 .

3. a range in which the first correction processing unit can correct the formation position of the image formation area is within the margin area of ​​each page; 3. The image forming apparatus according to claim 1.

4. The color misregistration correction unit When an accumulated value of the color misregistration amount from the time when the additional margin area was previously inserted to the time of this correction has increased to the first width or more, the correction process is performed by the second correction processing unit; If the cumulative value of the color misregistration amount from the time when the additional margin area was previously inserted to the time of this correction has not increased to the first width or more, the correction process is performed only by the first correction processing unit. The image forming apparatus according to claim 1 .

5. The second width of the additional margin area is the same as the first width of the margin area. The image forming apparatus according to claim 1 .

6. the color misregistration amount detection unit senses an internal temperature of the image forming apparatus using a temperature sensor, and detects the amount of color misregistration based on data relating to a correspondence relationship between the internal temperature of the image forming apparatus and the amount of color misregistration that is set in advance; The image forming apparatus according to claim 1 .

7. the color shift amount detection unit forms an image of a color shift measurement patch in a predetermined margin area set at a position shifted in a direction perpendicular to the paper feed direction with respect to the image formation area in the continuous paper, and detects the color shift amount by sensing the image of the color shift measurement patch with an in-line scanner or a photosensor. The image forming apparatus according to claim 1 .

8. the color misregistration amount detection unit expresses the color misregistration amounts of the other colors based on the image formation position of the color formed at the rearmost position in the paper feed direction among the colors. The image forming apparatus according to claim 1 .

9. During the time lag between when the color misregistration amount detection unit detects the color misregistration amount and when the color misregistration correction unit completes correction processing of the print job data to compensate for the color misregistration amount, processing by the color misregistration amount detection unit and / or the color misregistration correction unit is stopped. The image forming apparatus according to claim 1 .

10. the color misregistration correction unit corrects the amount of color misregistration detected by the color misregistration amount detection unit based on a difference between an internal temperature of the image forming device when the image of the page to be verified is formed and an internal temperature of the image forming device when the image of the page to be printed is formed, in order to correct additional color misregistration from the amount of color misregistration during a time lag between when the amount of color misregistration is detected by the color misregistration amount detection unit and when the correction process for the print job data to compensate for the amount of color misregistration is completed by the color misregistration correction unit; The image forming apparatus according to claim 1 .

11. When a difference between an internal temperature of the image forming apparatus at the end of a print job and an internal temperature of the image forming apparatus at the start of a next print job is equal to or smaller than a predetermined temperature, the color misregistration correction unit starts the next print job by setting the amount of color misregistration at the end of the print job as the amount of color misregistration of the first page of the next print job. The image forming apparatus according to claim 1 .

12. An image forming method for continuously forming color images of multiple pages on a single continuous sheet of paper in an image forming unit that forms a color image by superimposing images of each color formed on separate photosensitive members on an intermediate transfer member, comprising: a first process for managing jobs for each color and generating print job data in which a margin area of ​​a first width is set on the upstream side or downstream side of the image forming area of ​​each page in the paper feed direction; a second process for detecting, on a page-by-page basis, the amount of color misregistration of each color in the image forming area that occurs while printing related to the print job data is being performed; a third process for correcting a formation position of the image formation area of ​​the next page to be printed on the print job data, for a color in which color shift has occurred, based on the amount of color shift in a verification target page one or more pages before the current page, during printing related to the print job data; Equipped with In the third process, a process of compensating for at least a part of the amount of color misregistration by moving the formation position of the image formation area within the page to be printed in parallel in the paper feed direction within the margin area in a job of the color to be corrected in the print job data; and performing a process of inserting an additional margin area of ​​a second width that does not constitute a page between the page to be printed and the page immediately preceding it in a job of the color to be corrected in the print job data, thereby shifting the page start position of the page to be printed between colors in the paper feed direction and compensating for at least a part of the amount of color misregistration, thereby compensating for all of the amount of color misregistration. Image forming method.

13. An image forming program for continuously forming a plurality of pages of color images on a single continuous sheet of paper in an image forming unit that forms a color image by superimposing images of each color formed on separate photosensitive members on an intermediate transfer member, a first process for managing jobs for each color and generating print job data in which a margin area of ​​a first width is set on the upstream side or downstream side of the image forming area of ​​each page in the paper feed direction; a second process for detecting, on a page-by-page basis, the amount of color misregistration of each color in the image forming area that occurs while printing related to the print job data is being performed; a third process for correcting a formation position of the image formation area of ​​the next page to be printed on the print job data, for a color in which color shift has occurred, based on the amount of color shift in a verification target page one or more pages before the current page, during printing related to the print job data; Equipped with In the third process, a process of compensating for at least a part of the amount of color misregistration by moving the formation position of the image formation area within the page to be printed in parallel in the paper feed direction within the margin area in a job of the color to be corrected in the print job data; and performing a process of inserting an additional margin area of ​​a second width that does not constitute a page between the page to be printed and the page immediately preceding it in a job of the color to be corrected in the print job data, thereby shifting the page start position of the page to be printed between colors in the paper feed direction and compensating for at least a part of the amount of color misregistration, thereby compensating for all of the amount of color misregistration. Image formation program.

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