Image formation apparatus, image formation system, and program

Abstract

To accurately correct color shift in an image formed on a continuous recording medium at a start of image formation processing.SOLUTION: An image formation apparatus 20 includes: an image formation unit 22 that forms a reference image used for correcting color shift of images of respective colors in a main scanning direction; an acquisition unit (control unit 25) that acquires a first color shift amount in the main scanning direction on the basis of a read image obtained by reading the reference image formed by the image formation unit 22 during an image formation operation on a continuous recording medium (recording medium PM); and a correction unit (control unit 25) that corrects color shift at a start of image formation processing for next and subsequent jobs on the basis of the first color shift amount acquired by the acquisition unit.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] In a known conventional image forming apparatus, for example, a tandem type image forming apparatus includes image forming units of multiple colors arranged side by side, forms a monochromatic toner image of each color on the photosensitive member of each image forming unit, and sequentially transfers the monochromatic toner images of each color onto a sheet of paper to form a color image. In such a tandem type image forming apparatus, when the monochromatic toner images of each color are superimposed, the position of the images can be shifted, resulting in color shift.

[0003] In this regard, Patent Document 1 describes an image forming device in which, when correcting color misalignment in the main scanning direction, an intermediate transfer unit to which an image formed by an image forming unit is transferred and a secondary transfer unit that transfers the image transferred to the intermediate transfer unit onto paper are pressed together. Patent Documents 2 and 3 describe image forming apparatuses that can constantly monitor color misregistration during the operation of forming an output image by detecting a reference image formed outside the area on the paper where the output image is to be formed. Patent document 4 describes an image forming device in which the color shift characteristics in the sub-scanning direction of the image forming device are measured in advance before shipping and stored in a memory unit, and the color shift is corrected based on the stored color shift characteristics when the image forming device is actually used in the market. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-208154 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-008436 [Patent Document 3] Japanese Patent Publication No. 2023-40333 [Patent Document 4] Japanese Patent Application Laid-Open No. 2005-300953 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the invention of Patent Document 1, the paper on which the image is formed is a sheet of paper. On the other hand, when forming an image on continuous paper, the continuous paper is always present above the secondary transfer unit, which causes a problem that color misregistration cannot be corrected in a state where the intermediate transfer unit and the secondary transfer unit are pressed together. The inventions of Patent Documents 2 and 3 have the problem that color shift correction is not performed between the detection of the reference image formed on the paper and the start of color shift correction, that is, color shift correction is not performed at the start of the image formation process. The invention of Patent Document 4 has problems such as not correcting color shift in the main scanning direction, not correcting color shift in accordance with changes over time in the image forming device, and not correcting color shift in accordance with the user's usage conditions.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus, an image forming system, and a program that can accurately correct color misregistration in an image formed on a continuous recording medium at the start of image forming processing. [Means for solving the problem]

[0007] In order to solve the above problem, the image forming apparatus according to claim 1 comprises: an image forming unit that forms a reference image used to correct color shifts of images of each color in the main scanning direction; an acquisition unit that acquires a first color misregistration amount in a main scanning direction based on a read image obtained by reading the reference image formed by the image forming unit during an image forming operation on a continuous recording medium; a correction unit that corrects color misregistration at the start of image formation processing for a next job or later based on the first color misregistration amount acquired by the acquisition unit; Equipped with.

[0008] The invention described in claim 2 is the image forming apparatus described in claim 1, the acquiring unit acquires a second color misregistration amount in a main scanning direction based on a read image obtained by reading the reference image formed by the image forming unit before an image forming operation on the continuous recording medium; The correction unit corrects color misregistration at the start of image forming processing for the next job or later, based on the first amount of color misregistration and the second amount of color misregistration.

[0009] The invention described in claim 3 is the image forming apparatus described in claim 1, The acquisition unit acquires a read image obtained by reading the reference image formed on the continuous recording medium.

[0010] The invention described in claim 4 is the image forming apparatus described in claim 1, the image forming unit includes an intermediate transfer member onto which a toner image is transferred; The acquisition unit acquires a read image by reading the reference image formed of the toner image transferred onto the intermediate transfer body.

[0011] The invention described in claim 5 is the image forming apparatus described in claim 1, the image forming unit includes an intermediate transfer member onto which a toner image is transferred; The acquisition unit acquires a read image by reading the reference image formed from a toner image transferred onto the intermediate transfer body before the image forming operation on the continuous recording medium, and acquires a read image by reading the reference image formed on the continuous recording medium during the image forming operation on the continuous recording medium.

[0012] The invention described in claim 6 is the image forming apparatus described in claim 1, The image forming unit includes: an intermediate transfer member onto which a toner image is transferred; The reference image is formed within the image forming area on the intermediate transfer body before the image forming operation on the continuous recording medium, and the reference image is formed outside the image forming area on the continuous recording medium during the image forming operation on the continuous recording medium.

[0013] The invention described in claim 7 is the image forming apparatus described in claim 1, The correction unit corrects color misregistration at the start of image formation processing for the next job or later, based on the first amount of color misregistration within a predetermined time from the start of image formation processing.

[0014] The invention described in claim 8 is the image forming apparatus described in claim 1, When the first color misregistration amount is greater than a predetermined threshold, the correction unit changes a correction value for correcting color misregistration at the start of image forming processing for the next job or later.

[0015] The invention described in claim 9 is the image forming apparatus described in claim 1, The correction unit determines a correction value for correcting the first color misregistration amount for each specified condition, and corrects the color misregistration at the start of the image formation process for the next job or later using the correction value according to the printing conditions for the next job or later.

[0016] The invention described in claim 10 is the image forming apparatus described in claim 9, The correction unit determines the correction value corresponding to a combination of a plurality of conditions.

[0017] The invention described in claim 11 is the image forming apparatus described in claim 9, the image forming unit includes an intermediate transfer member onto which a toner image is transferred; The conditions include the transfer pressure when the toner image is transferred from the intermediate transfer member to the continuous recording medium.

[0018] The invention described in claim 12 is the image forming apparatus described in claim 9, The conditions include conditions relating to the continuous recording medium.

[0019] The invention described in claim 13 is the image forming apparatus described in claim 9, a detection unit that detects an ambient temperature inside the image forming apparatus, The conditions include the ambient temperature detected by the detection unit.

[0020] The invention described in claim 14 is the image forming apparatus described in claim 9, The conditions include conditions relating to the transport state of the continuous recording medium.

[0021] The invention described in claim 15 is the image forming apparatus described in claim 9, The conditions include the coverage of the image formed on the continuous recording medium.

[0022] The invention described in claim 16 is the image forming apparatus described in claim 1, The correction unit corrects color misregistration at the start of image forming processing for the next job or later, based on the first color misregistration amount acquired in the immediately preceding job.

[0023] The invention described in claim 17 is the image forming apparatus described in claim 1, The correction unit corrects color misregistration at the start of image forming processing for the next job or later, based on the average value of the first color misregistration amount obtained in jobs executed in the past.

[0024] The image forming system according to claim 18, an image forming apparatus according to any one of claims 1 to 17; an external device having a storage unit communicably connected to the image forming apparatus; Equipped with The correction unit stores a correction value for correcting the first amount of color misregistration in the storage unit.

[0025] The program according to claim 19 comprises: a computer of an image forming apparatus including an image forming unit that forms a reference image used to correct color shift of images of each color in the main scanning direction; an acquisition unit that acquires a first color shift amount in a main scanning direction based on a read image obtained by reading the reference image formed by the image forming unit during an image forming operation on a continuous recording medium; a correction unit that corrects color misregistration at the start of image forming processing for a next job or later, based on the first color misregistration amount acquired by the acquisition unit; Function as. [Effects of the Invention]

[0026] According to the present invention, color misregistration in an image formed on a continuous recording medium can be corrected with high precision at the start of image formation processing. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a diagram showing an example of a schematic configuration of an image forming system according to the present invention; [Figure 2] FIG. 2 is a functional block diagram showing a control configuration of the image forming system according to the present invention. [Figure 3] 10 is a flowchart showing the flow of a first color misregistration correction process. [Figure 4] 10 is a flowchart showing the flow of a second color misregistration correction process. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the scope of the invention is not limited to the illustrated examples.

[0029] (1. Configuration of Image Forming System) Fig. 1 is a diagram showing an example of a schematic configuration of an image forming system 1 according to this embodiment. Fig. 2 is a functional block diagram showing a control configuration of the image forming system 1. The image forming system 1 is a system that uses a recording medium PM (continuous recording medium) such as continuous paper such as roll paper or continuous film, and forms an image on this recording medium PM. As shown in FIG. 1, the image forming system 1 includes, from the upstream side along the conveyance direction of the recording medium PM, a paper feeding device 10, an image forming device 20, an image reading device 30, and a winding device 40.

[0030] (1-1. Paper feeder configuration) The paper feeder 10 feeds recording media PM to the image forming apparatus 20. The paper feeding device 10 includes a paper feeding section 11 and a paper feeding adjustment section 12 .

[0031] 1, for example, within the housing of the paper feed unit 11, the paper feed unit 11 winds a roll-shaped recording medium PM around a support shaft 111 and holds it rotatably. The paper feed unit 11 transports the recording medium PM wound around the support shaft 111 at a constant speed via multiple rollers to the paper feed adjustment unit 12. The multiple rollers are, for example, a delivery roller, a paper feed roller, etc. Although only one recording medium PM is shown in FIG. 1, the paper feed unit 11 may hold a plurality of continuous recording media.

[0032] The paper feed adjustment unit 12 is located downstream of the paper feed unit 11 and upstream of the image forming device 20 in the conveyance direction of the recording medium PM. The paper feed adjustment unit 12 transports the recording medium PM transported from the paper feed unit 11 to the image forming device 20. The paper feed adjustment unit 12 absorbs the speed difference between the transport speed of the recording medium PM in the paper feed unit 11 and the transport speed of the recording medium PM in the image forming device 20. Specifically, the paper feed adjustment unit 12 holds the recording medium PM with slack as shown in FIG. 1 , and adjusts the feeding of the recording medium PM to the image forming device 20.

[0033] (1-2. Configuration of Image Forming Apparatus) The image forming device 20 forms an image on a recording medium PM. The image forming device 20 is located downstream of the paper feed adjustment unit 12 and upstream of the image reading device 30 in the conveyance direction of the recording medium PM.

[0034] As shown in FIG. 2, the image forming device 20 includes a conveying unit 21, an image forming unit 22, a fixing unit 23, an operation display unit 24, a control unit 25, a memory unit 26, a communication unit 27, a second reading unit 28, a document reading unit 29, and a temperature detection unit 200.

[0035] The conveying unit 21 is a conveying mechanism for the recording medium PM inside the image forming apparatus 20. The conveying unit 21 conveys the recording medium PM conveyed from the paper feed adjustment unit 12, for example, by a plurality of rollers, to the image forming unit 22 and the fixing unit 23 in that order, and then discharges the recording medium PM.

[0036] The image forming unit 22 forms a toner image by electrophotography and transfers it onto the recording medium PM. As shown in FIG. 1, the image forming unit 22 includes photosensitive drums (Y, M, C, K) and an intermediate transfer belt B as an intermediate transfer member. The intermediate transfer belt B is an endless belt. The image forming unit 22 supports the intermediate transfer belt B by winding it around a plurality of rollers so that the belt can run. The image forming unit 22 forms toner images of each color on the photosensitive drums (Y, M, C, K) and transfers them sequentially onto the intermediate transfer belt B (primary transfer). As a result, the image forming unit 22 forms a toner image (color image) on the intermediate transfer belt B, in which layers of each color (Y, M, C, K) are superimposed. Next, the image forming unit 22 presses the transfer roller T against the intermediate transfer belt B to form a transfer nip. Next, the image forming unit 22 holds the recording medium PM in the transfer nip and applies a bias of opposite polarity to the toner to the transfer roller T. As a result, the image forming unit 22 transfers the toner image formed on the intermediate transfer belt B onto the recording medium PM (secondary transfer).

[0037] The fixing unit 23 performs a fixing process to fix the toner image transferred onto the recording medium PM. As shown in FIG. 1, the fixing unit 23 includes a pair of rollers, consisting of a heating roller 231 and a pressure roller 232, for sandwiching the recording medium PM. The fixing unit 23 heats the heating roller 231 to a predetermined temperature using a heater as a heat source. The fixing unit 23 biases the pressure roller 232 toward the heating roller 231 by an elastic member (not shown). The fixing unit 23 applies heat and pressure to the recording medium PM onto which the toner image has been transferred by passing it through a nip between a heating roller 231 and a pressure roller 232, thereby melting and fixing the toner image.

[0038] The operation display unit 24 includes a display unit 24a and an operation unit 24b. The display unit 24a has a display screen and displays various types of information on the screen. The operation unit 24b is used by the user to input various instructions.

[0039] The control unit 25 includes, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), etc. The CPU of the control unit 25 reads out various programs such as system programs and processing programs stored in the storage unit 26 and loads them into the RAM. The CPU of the control unit 25 executes various processes in accordance with the loaded programs. The control unit 25 controls the communication unit 27 to receive, for example, a print job, image data, etc. transmitted from an external device. The control unit 25 controls the image forming unit 22 to form an image on paper based on the received print job, image data, etc.

[0040] The storage unit 26 includes, for example, a hard disk drive (HDD), a semiconductor nonvolatile memory, or the like. The storage unit 26 stores various programs such as system programs and processing programs executed by the control unit 25, as well as data required for executing these programs.

[0041] The communication unit 27 includes a communication control card such as a LAN (Local Area Network) card, etc. The communication unit 27 transmits and receives various data to and from external devices connected to a communication network such as a LAN or a WAN (Wide Area Network).

[0042] The second reading unit 28 is provided downstream of the transfer nip with respect to the rotation direction (the direction of the arrow shown in FIG. 1) of the intermediate transfer belt B. The second reading unit 28 may be provided downstream of the photosensitive drums (Y, M, C, K) and upstream of the transfer nip with respect to the rotation direction of the intermediate transfer belt B. The second reading unit 28 includes a line image sensor or the like in which a plurality of image pickup elements (for example, CCDs (Charge Coupled Devices)) that perform photoelectric conversion for each pixel are arranged one-dimensionally in the width direction of the intermediate transfer belt B. The second reading unit 28 reads the toner image formed on the intermediate transfer belt B and transported without being transferred to the recording medium PM, generates a read image, and outputs it to the control unit 25. A cleaning unit (not shown) removes the toner image from the intermediate transfer belt B after it has been read by the second reading unit 28.

[0043] The document reading unit 29 includes an ADF (Auto Document Feeder) and an image reading unit such as a CCD (Charge Coupled Device). The document reading unit 29 reads an image of a document based on the setting information received by the operation unit 24b, and generates image data of the read image. Specifically, the document reading unit 29 transports a document placed on the document tray of the ADF to the contact glass, which is the reading location. Alternatively, the user places the document on the platen glass. The document reading unit 29 reads images of one or both sides of the document using the image reading unit, and generates image data thereof.

[0044] The temperature detection unit 200 detects the ambient temperature inside the image forming apparatus 20 and outputs the detection result to the control unit 25. For example, the temperature detection unit 200 detects the temperature in the vicinity of the image forming unit 22.

[0045] In this embodiment, the control unit 25 controls the entire image forming system 1 as shown in FIG. 2, but each of the paper feeding device 10, the image reading device 30, and the winding device 40 may also be provided with a control unit.

[0046] The image forming apparatus 20 may be an MFP (Multi-Function Peripheral) that has a copy function, a scan function, a facsimile function, and the like in addition to an image forming function.

[0047] (1-3. Configuration of image reading device) The image reading device 30 is installed downstream of the image forming device 20 and upstream of the winding device 40 in the conveying direction of the recording medium PM. The image reading device 30 includes a first reading unit 31 . The first reading unit 31 includes a line image sensor or the like in which a plurality of image pickup elements (for example, CCDs) that perform photoelectric conversion for each pixel are arranged one-dimensionally in the width direction of the recording medium PM. The image reading device 30 reads the upper surface of the recording medium PM transported from the image forming device 20, i.e., the image formed by the image forming device 20, using the first reading unit 31, generates a read image, and outputs it to the control unit 25.

[0048] (1-4. Configuration of the winding device) The winding device 40 is located downstream of the image reading device 30 in the conveying direction of the recording medium PM. The winding device 40 includes a winding adjustment section 41 and a winding section 42 .

[0049] The winding adjustment unit 41 is located downstream of the image reading device 30 and upstream of the winding unit 42 in the transport direction of the recording medium PM. The winding adjustment unit 41 transports the recording medium PM transported from the image reading device 30 to the winding unit 42. The winding adjustment unit 41 absorbs the speed difference between the transport speed of the recording medium PM in the image reading device 30 and the transport speed of the recording medium PM in the winding unit 42. Specifically, the winding adjustment unit 41 holds the recording medium PM with slack as shown in FIG. 1 , and adjusts the discharge of the recording medium PM from the image reading device 30.

[0050] 1, for example, inside the housing of the winding unit 42, the winding unit 42 winds the recording medium PM around a support shaft 421 and holds it in a roll. The winding unit 42 winds the recording medium PM, which has been transported from the winding adjustment unit 41, around the support shaft 421 at a constant speed via a plurality of rollers. The plurality of rollers are, for example, a feed roller, a paper discharge roller, etc.

[0051] (2. Operation of the image forming system) Next, the operation of the image forming system 1 in this embodiment will be described. 3 before the image forming apparatus 20 is shipped from a factory. The control unit 25 of the image forming apparatus 20 executes the first color misregistration correction process shown in FIG. 3 in cooperation with a program stored in the storage unit 26.

[0052] (First color misregistration correction process) The control unit 25 determines a pre-printing correction value for correcting color misregistration in the main scanning direction in an image formed by the image forming unit 22 (step S1). In step S1, the control unit 25 causes the image forming unit 22 to form a toner image of a second reference image for correcting color misregistration in the main scanning direction within the image formation area on the intermediate transfer belt B. The image formation area is an area where a job image is formed, and is a print guaranteed range in which the quality of the formed image is guaranteed. Next, the control unit 25, without pressing the transfer roller T against the intermediate transfer belt B, causes the second reading unit 28 to read the second reference image formed from the toner image transferred onto the intermediate transfer belt B to obtain a read image (second read image). Next, the control unit 25 obtains the amount of color misregistration in the main scanning direction (second color misregistration amount) based on the second read image. Next, the control unit 25 determines a pre-printing correction value for correcting the amount of color misregistration. Next, the control unit 25 stores the pre-printing correction values ​​determined in step S1 in the storage unit 26 (step S2).

[0053] Next, the control unit 25 corrects the image formation position for each color (Y, M, C, K) based on the pre-printing correction values ​​stored in step S2. The control unit 25 also controls the image forming unit 22 to execute image formation processing under the standard printing conditions (step S3). In step S3, the control unit 25 causes the image forming unit 22 to form a first standard image for color misregistration correction in the main scanning direction outside the image formation area on the recording medium PM. The area outside the image formation area is outside the guaranteed print area and is also within the image formable area.

[0054] In this embodiment, the printing conditions include information related to the recording medium PM, such as the type, basis weight, thickness, stiffness, and coefficient of friction on the surface of the recording medium PM. The printing conditions include information on the transfer pressure, which is the pressure applied when the transfer roller T is pressed against the intermediate transfer belt B during secondary transfer. The printing conditions include information on the ambient temperature inside the image forming apparatus 20 detected by the temperature detection unit 200 and the coverage of the job image. The printing conditions include conditions related to the transport state of the recording medium PM. The conditions related to the transport state of the recording medium PM include the transport direction of the recording medium PM, the difference between the transport speed of the recording medium PM during secondary transfer and the transport speed of the recording medium PM during fixing processing by the fixing unit 23, etc.

[0055] Next, during a measurement period from the start of the image forming process executed in step S3 until a predetermined time has elapsed, the control unit 25 reads the first reference image formed on the recording medium PM by the first reading unit 31 to obtain a read image (first read image). Next, the control unit 25 measures the amount of color shift in the main scanning direction of the image formed by the image forming unit 22 during the measurement period based on the obtained first read image (step S4).

[0056] Next, the control unit 25 determines a printing correction value for correcting the amount of color misregistration measured in step S4. Next, the control unit 25 associates the determined printing correction value with the reference printing conditions and stores them in the storage unit 26 (step S5). Next, the control unit 25 determines whether or not to store printing correction values ​​corresponding to printing conditions other than the standard printing conditions, based on, for example, an instruction operation by the user via the operation unit 24b (step S6). If the printing correction values ​​corresponding to printing conditions other than the reference printing conditions are not to be stored (step S6; NO), the control unit 25 ends the first color misregistration correction process.

[0057] On the other hand, the case where printing correction values ​​corresponding to printing conditions other than the reference printing conditions are stored (step S6; YES) will be described. In this case, control unit 25 corrects the formation position of each color image based on the pre-printing correction values ​​stored in step S2. Furthermore, control unit 25 controls image forming unit 22 to execute image formation processing under printing conditions other than the reference printing conditions (step S7). In step S7, control unit 25 causes image forming unit 22 to form a first reference image outside the image formation area on recording medium PM. Next, during a measurement period from the start of the image forming process executed in step S7 until a predetermined time has elapsed, the control unit 25 reads the first reference image formed on the recording medium PM by the first reading unit 31 to acquire a first read image. Next, based on the acquired first read image, the control unit 25 measures the amount of color shift in the main scanning direction of the image formed by the image forming unit 22 during the measurement period (step S8).

[0058] Next, control unit 25 determines a printing correction value for correcting the amount of color misregistration measured in step S8. Next, control unit 25 associates the determined printing correction value with the printing conditions of the image forming process executed in step S7, stores the result in storage unit 26 (step S9), and proceeds to step S6 in the first color misregistration correction process.

[0059] In step S2 of the first color misregistration correction process, the control unit 25 may store the pre-printing correction values ​​determined in step S1 in a storage unit of an external device communicatively connected to the image forming apparatus 20. In step S5, the control unit 25 may associate the printing correction values ​​with reference printing conditions and store them in a storage unit of the external device. In step S9, the control unit 25 may associate the printing correction values ​​with printing conditions other than the reference printing conditions and store them in a storage unit of the external device. In this case, the image forming system 1 includes the external device.

[0060] When the printing conditions in the image formation process change, the amount of color misregistration in the main scanning direction of the formed image changes. For example, when the transfer pressure during secondary transfer changes, the bias force applied to the intermediate transfer belt B (the force that causes the intermediate transfer belt B to meander) changes, thereby changing the amount of color misregistration. For example, when the conditions related to the recording medium PM change, the influence of the recording medium PM on the intermediate transfer belt B changes, thereby changing the amount of color misregistration. For example, when the temperature inside the image forming apparatus 20 changes, parts expand or contract, changing the alignment of the rollers that stretch the intermediate transfer belt B, thereby changing the amount of color misregistration. For example, when the conditions related to the transport state of the recording medium PM change, the influence of the recording medium PM on the intermediate transfer belt B changes, thereby changing the amount of color misregistration. For example, when the coverage of the job image changes, the influence of the recording medium PM on the intermediate transfer belt B changes, thereby changing the amount of color misregistration. Therefore, in the first color misregistration correction process, by storing the print correction value for each printing condition in the storage unit 26, color misregistration in the image formed by the image forming unit 22 can be corrected with high precision.

[0061] The degree of influence of each printing condition on the amount of color misregistration in the main scanning direction in an image formed by image forming unit 22 differs for each model of image forming device 20. Therefore, in step S9 of the first color misregistration correction process, it is preferable to store in storage unit 26, for each model of image forming device 20, printing conditions that have a relatively large influence on the amount of color misregistration in the main scanning direction and printing correction values ​​corresponding to those printing conditions. This makes it possible to accurately correct color misregistration in an image formed by image forming unit 22 in the image formation process immediately after image forming device 20 is installed at the installation location.

[0062] Next, a second color misregistration correction process (see FIG. 4) that is executed by the control unit 25 of the image forming apparatus 20, for example, after the image forming apparatus 20 is installed at an installation location, will be described. The control unit 25 executes the second color misregistration correction process in cooperation with a program stored in the storage unit 26.

[0063] (Second color misregistration correction process) The control unit 25 executes step S11, which is the same as step S1 in the first color misregistration correction process. For example, the control unit 25 executes step S11 when the image forming apparatus 20 is started up for the first time after the image forming apparatus 20 is installed at the installation location. Alternatively, for example, the control unit 25 executes step S11 when the power of the image forming apparatus 20 is turned ON after a predetermined time has passed while the power is OFF. Next, the control unit 25 updates the pre-printing correction values ​​stored in the storage unit 26 with the pre-printing correction values ​​determined in step S11 (step S12).

[0064] Next, the control unit 25 acquires the print job by receiving the print job from an external device via the communication unit 27, or by accepting an input operation of the print job by the user via the operation unit 24b (step S13). A print job includes job image data, job setting information, etc. The job setting information includes printing conditions.

[0065] Next, the control unit 25 determines whether or not the printing conditions that are associated with the printing correction values ​​and match the printing conditions (job conditions) of the print job acquired in step S13 are stored in the memory unit 26 (step S14). The following describes a case where printing conditions that are associated with the pre-printing correction values ​​and that match the job conditions are stored in the storage unit 26 (step S14; YES). In this case, the control unit 25 corrects the formation position of the image for each color based on the pre-printing correction values ​​updated in step S12 and the pre-printing correction values ​​associated with the printing conditions that match the job conditions. The control unit 25 also controls the image forming unit 22 to execute image formation processing for the print job according to the job conditions (step S15). In step S15, the control unit 25 causes the image forming unit 22 to form a job image within the image formation area on the recording medium PM, and form a first reference image outside the image formation area.

[0066] Next, during a measurement period, which is the period from the start of the image forming process executed in step S15 until a predetermined time has elapsed, the control unit 25 reads the first reference image formed on the recording medium PM by the first reading unit 31 to acquire a first read image. Next, based on the acquired first read image, the control unit 25 measures the amount of color shift in the main scanning direction of the image formed by the image forming unit 22 during the measurement period (first amount of color shift) (step S16). As a result, the control unit 25 acquires the first amount of color shift in the main scanning direction. The control unit 25 functions as an acquisition unit.

[0067] Next, the control unit 25 determines whether the amount of color misregistration measured in step S16 is equal to or less than a predetermined threshold (step S17). The predetermined threshold is set in advance and stored in the storage unit 26. The predetermined threshold is, for example, 30 μm for the average amount of color misregistration during the measurement period, or 100 μm for the maximum amount of color misregistration during the measurement period. If the amount of color misregistration measured in step S16 is equal to or less than the predetermined threshold value (step S17; YES), the control unit 25 ends the second color misregistration correction process.

[0068] On the other hand, the case where the amount of color misregistration in the main scanning direction measured in step S16 is greater than the predetermined threshold (step S17; NO) will be described. In this case, control unit 25 updates the printing correction value associated with the printing conditions that match the job conditions by adding or subtracting the amount of color misregistration in the main scanning direction measured in step S16 (step S18), and ends the second color misregistration correction process. In this case, the control unit 25 performs the following process in step S15 of the second color misregistration correction process to be executed from the next print job onwards. Specifically, the control unit 25 corrects color misregistration at the start of image formation from the next print job onwards, using the printing correction value updated based on the first color misregistration amount and the pre-printing correction value updated based on the second color misregistration amount. The control unit 25 functions as a correction unit.

[0069] The following describes a case where the printing conditions associated with the printing correction values ​​and matching the job conditions are not stored in the storage unit 26 (step S14; NO). In this case, the control unit 25 corrects the formation position of the image for each color based on the pre-printing correction values ​​updated in step S12 and the printing correction values ​​associated with the reference printing conditions. The control unit 25 also controls the image forming unit 22 to execute image formation processing for the print job according to the job conditions (step S19). In step S19, the control unit 25 causes the image forming unit 22 to form a job image within the image formation area on the recording medium PM, and form a first reference image outside the image formation area.

[0070] Next, during a measurement period from the start of the image forming process executed in step S19 until a predetermined time has elapsed, the control unit 25 reads the first reference image formed on the recording medium PM by the first reading unit 31 to acquire a first read image. Next, based on the acquired first read image, the control unit 25 measures the amount of color shift in the main scanning direction of the image formed by the image forming unit 22 during the measurement period (first amount of color shift) (step S20).

[0071] Next, the control unit 25 determines the print correction value corresponding to the job conditions by adding or subtracting the print correction value associated with the reference print condition based on the amount of color misregistration measured in step S20. Next, the control unit 25 stores the determined print correction value in the storage unit 26 in association with the job condition (step S21), and ends the second color misregistration correction process. That is, in step S21, control unit 25 determines a print correction value for correcting the first color misregistration amount for each predetermined condition (print condition). In step S15, which is executed for the next print job and thereafter, control unit 25 corrects color misregistration at the start of image formation processing for the next print job and thereafter using the print correction value according to the print condition for the next print job and thereafter. In step S21, the control unit 25 may determine a printing correction value for correcting the first color misregistration amount for each combination of a plurality of conditions (a plurality of printing conditions). The combination of a plurality of conditions is, for example, a combination of the transfer pressure during the secondary transfer and the type of recording medium PM.

[0072] In step S12 of the second color misregistration correction process, the control unit 25 may update the pre-printing correction values ​​stored in a memory unit of an external device communicatively connected to the image forming apparatus 20 with the pre-printing correction values ​​determined in step S11. In step S18, the control unit 25 may update the printing correction values ​​stored in a memory unit of the external device and associated with printing conditions that match the job conditions by adding or subtracting the amount of color misregistration in the main scanning direction measured in step S16. In step S21, the control unit 25 may store the determined printing correction values ​​in a memory unit of the external device in association with the job conditions. In this case, the image forming system 1 includes the external device.

[0073] In the second color misregistration correction process, the control unit 25 may execute step S18 after step S16 without executing step S17. That is, the control unit 25 corrects color misregistration at the start of image formation processing for the next print job onward, based on the first amount of color misregistration acquired in the immediately preceding job. This allows the print correction value to be set based on the most recent amount of color misregistration in the main scanning direction at all times, so that changes over time in the image forming apparatus 20 can be dealt with more quickly and color misregistration can be corrected with high precision.

[0074] In the second color misregistration correction process, the control unit 25 may execute the following process after step S16 without executing steps S17 and S18. Specifically, the control unit 25 averages (for example, calculates a moving average) the amount of color misregistration measured in step S16 of the second color misregistration correction process executed in the past and in step S16 of the second color misregistration correction process executed this time. Next, the control unit 25 updates the printing correction value associated with the printing conditions that match the job conditions by adding or subtracting the average value of the amount of color misregistration. That is, the control unit 25 corrects color misregistration at the start of image formation processing for the next print job onward, based on the average value of the first color misregistration amounts acquired in jobs executed in the past. This allows color misregistration to be corrected with high precision when the amount of color misregistration in the main scanning direction is not stable during the measurement period, when there is a large variation in the measurement of the amount of color misregistration in the main scanning direction, and so on.

[0075] Next, a case where the second color misregistration correction process is performed after the intermediate transfer belt B, the transfer roller T, or the fixing unit 23 is replaced in the image forming apparatus 20 will be described. When the intermediate transfer belt B is replaced in the image forming apparatus 20, the alignment of the rollers that stretch the intermediate transfer belt B may change. When the transfer roller T is replaced in the image forming apparatus 20, the transfer pressure during secondary transfer, the balance before and after the transfer pressure, and the like may change. When the fixing unit 23 is replaced in the image forming device 20, the alignment of the fixing unit 23 with respect to the recording medium PM may change, which may result in a change in the conveying direction of the recording medium PM or a change in the difference between the conveying speed during secondary transfer and the conveying speed during fixing processing. In this case, the control unit 25 may execute step S18 after step S16 of the second color misregistration correction process without executing step S17.

[0076] (3. Effects) As described above, the image forming apparatus 20 of this embodiment includes the image forming unit 22 that forms the reference images (first reference image, second reference image) used to correct color shift of images of each color in the main scanning direction. The image forming device 20 is equipped with an acquisition unit (control unit 25) that acquires a first color shift amount in the main scanning direction based on a read image obtained by reading a reference image formed by the image forming unit 22 during an image forming operation on a continuous recording medium (recording medium PM). The image forming apparatus 20 includes a correction section (control section 25) that corrects color misregistration at the start of image forming processing for the next job onward, based on the first amount of color misregistration acquired by the acquisition section. Therefore, based on the amount of color misregistration that occurs during image formation on the continuous recording medium, color misregistration can be corrected from the start of image formation processing for the next job onward, thereby enabling color misregistration in images formed on the continuous recording medium to be corrected with high accuracy at the start of image formation processing.

[0077] In the image forming apparatus 20 of this embodiment, the acquisition unit (control unit 25) acquires the second color shift amount in the main scanning direction based on the read image obtained by reading the reference image formed by the image forming unit 22 before the image forming operation on the continuous recording medium (recording medium PM). The correction section (control section 25) corrects the color misregistration at the start of image formation processing for the next job onward, based on the first color misregistration amount and the second color misregistration amount. Therefore, color misregistration in an image formed on a continuous recording medium can be corrected with high accuracy at the start of image formation processing based on the first color misregistration amount and the second color misregistration amount that occur during image formation operation on the continuous recording medium.

[0078] In the image forming apparatus 20 of this embodiment, the acquisition unit (control unit 25) acquires a read image obtained by reading a reference image formed on a continuous recording medium (recording medium PM). Therefore, it is possible to correct color misregistration that occurs in the output product, which is the recording medium PM on which the image is formed.

[0079] In the image forming apparatus 20 of this embodiment, the image forming section 22 includes an intermediate transfer member (intermediate transfer belt B) onto which a toner image is transferred. The acquisition unit (control unit 25) acquires a read image by reading a reference image formed of a toner image transferred onto an intermediate transfer body. Therefore, color misregistration can be corrected without performing a process of transferring an image onto the recording medium PM.

[0080] In the image forming apparatus 20 of this embodiment, the image forming section 22 includes an intermediate transfer member (intermediate transfer belt B) onto which a toner image is transferred. The acquisition unit (control unit 25) acquires a read image by reading a reference image formed of a toner image transferred onto an intermediate transfer body before an image forming operation on a continuous recording medium (recording medium PM). The acquisition unit acquires a read image by reading a reference image formed on the continuous recording medium during an image forming operation on the continuous recording medium. Therefore, before the image forming operation on the recording medium PM, color misregistration can be corrected without performing the process of transferring the image onto the recording medium PM. During the image forming operation on the continuous recording medium, color misregistration that occurs in the output product, which is the recording medium PM on which the image has been formed, can be corrected.

[0081] In the image forming apparatus 20 of this embodiment, the image forming section 22 includes an intermediate transfer member (intermediate transfer belt B) onto which a toner image is transferred. The image forming unit 22 forms a reference image within the image forming area on the intermediate transfer body before an image forming operation on a continuous recording medium (recording medium PM). The image forming unit 22 forms a reference image outside the image forming area on the continuous recording medium during the image forming operation on the continuous recording medium. Therefore, before the image forming operation on the recording medium PM, color misregistration within the image forming area where the job image is formed can be corrected. During the image forming operation on the continuous recording medium, color misregistration can be corrected while the job image is being formed.

[0082] In the image forming apparatus 20 of this embodiment, the correction unit (control unit 25) corrects color misregistration at the start of image forming processing for the next job onward, based on the first color misregistration amount within a predetermined time from the start of image forming processing. Therefore, color misregistration caused by changes in transfer pressure due to pressing the transfer roller T against the intermediate transfer belt B, changes in the conveyance state of the recording medium PM, and the like, which occur at the start of image formation processing, can be corrected.

[0083] In the image forming apparatus 20 of this embodiment, when the first color misregistration amount is greater than a predetermined threshold, the correction unit (control unit 25) changes the correction value for correcting color misregistration at the start of image formation processing for the next job onwards. Therefore, if the first color misregistration amount is equal to or less than a predetermined threshold value, the process of changing the correction value can be omitted.

[0084] In the image forming apparatus 20 of this embodiment, the correction unit (control unit 25) determines a correction value for correcting the first color misregistration amount for each predetermined condition. The correction unit corrects color misregistration at the start of image formation processing for the next job or later using the correction value according to the printing conditions for the next job or later. Therefore, by correcting color misregistration using a correction value according to the printing conditions of the job, color misregistration can be corrected with higher accuracy.

[0085] In the image forming apparatus 20 of this embodiment, the correction unit (control unit 25) determines a correction value corresponding to a combination of a plurality of conditions. Therefore, by correcting color misregistration using correction values ​​according to a plurality of printing conditions of a job, color misregistration can be corrected with higher accuracy.

[0086] In the image forming apparatus 20 of this embodiment, the image forming section 22 includes an intermediate transfer member (intermediate transfer belt B) onto which a toner image is transferred. The conditions include the transfer pressure when the toner image is transferred from the intermediate transfer member to the continuous recording medium (recording medium PM). Therefore, by correcting the color misregistration using a correction value according to the transfer pressure as a printing condition of the job, the color misregistration can be corrected with higher accuracy.

[0087] In the image forming apparatus 20 of this embodiment, the conditions include conditions relating to the continuous recording medium (recording medium PM). Therefore, by correcting color misregistration using a correction value according to the conditions related to the recording medium PM as the printing conditions of the job, color misregistration can be corrected with higher accuracy.

[0088] The image forming apparatus 20 of this embodiment includes a detection unit (temperature detection unit 200) that detects the ambient temperature inside the image forming apparatus 20. The conditions include the ambient temperature detected by the detection unit. Therefore, by correcting the color misregistration using a correction value according to the ambient temperature inside the image forming apparatus 20, which is a printing condition of the job, the color misregistration can be corrected with higher accuracy.

[0089] In the image forming apparatus 20 of this embodiment, the conditions include conditions relating to the conveyance state of the continuous recording medium (recording medium PM). Therefore, by correcting color misregistration using a correction value according to the conditions related to the conveyance state of the recording medium PM as the printing conditions of the job, color misregistration can be corrected with higher accuracy.

[0090] In the image forming apparatus 20 of this embodiment, the conditions include the coverage of the image formed on the continuous recording medium (recording medium PM). Therefore, by correcting color misregistration using a correction value according to the image coverage as a printing condition of the job, color misregistration can be corrected with higher accuracy.

[0091] In the image forming apparatus 20 of this embodiment, the correction unit (control unit 25) corrects color misregistration at the start of image forming processing for the next job onward, based on the first color misregistration amount acquired in the immediately preceding job. Therefore, the print correction value can always be set based on the latest amount of color misregistration in the main scanning direction, so that the image forming apparatus 20 can be adapted to changes over time more quickly and color misregistration can be corrected with high precision.

[0092] In the image forming apparatus 20 of this embodiment, the correction unit (control unit 25) corrects color misalignment at the start of image forming processing for the next job or later based on the average value of the first color misalignment amount obtained in jobs executed in the past. Therefore, when the amount of color misregistration in the main scanning direction is not stable during the measurement period, when there is a large variation in the measurement of the amount of color misregistration in the main scanning direction, or the like, the color misregistration can be corrected with high precision.

[0093] The image forming system 1 of this embodiment includes an image forming apparatus 20 and an external device having a storage unit that is communicably connected to the image forming apparatus 20. The correction unit (control unit 25) stores a correction value for correcting the first amount of color misregistration in a storage unit of the external device.

[0094] The embodiments to which the present invention can be applied are not limited to those described above, and can be modified as appropriate without departing from the spirit of the present invention. For example, in the above embodiment, the control unit 25 functions as an acquisition unit and a correction unit, but this is not limited to this. If a device other than the image forming device 20 included in the image forming system 1 includes a control unit, the control unit may function as an acquisition unit and a correction unit. [Explanation of symbols]

[0095] 1. Image forming system 10 Paper feeder 11 Paper feed section 111 Support shaft 12 Paper feed adjustment section 20 Image forming device 21 Conveyor 22 Image forming unit 23 Fixing section 231 Heated Roller 232 Pressure roller 24 Operation display section 24a Display section 24b Operation section 25 Control unit (acquisition unit, correction unit) 26 Memory section 27 Communications Department 28 Second reading unit 29 Document reading unit 30 Image reader 31 First reading unit 40 Winding device 41 Winding adjustment section 42 Winding section 421 Support shaft PM recording media

Claims

1. an image forming unit that forms a reference image used to correct color shifts of images of each color in the main scanning direction; an acquisition unit that acquires a first color misregistration amount in a main scanning direction based on a read image obtained by reading the reference image formed by the image forming unit during an image forming operation on a continuous recording medium; a correction unit that corrects color misregistration at the start of image forming processing for a next job or later based on the first color misregistration amount acquired by the acquisition unit; An image forming apparatus comprising:

2. the acquiring unit acquires a second color misregistration amount in a main scanning direction based on a read image obtained by reading the reference image formed by the image forming unit before an image forming operation on the continuous recording medium; The image forming apparatus according to claim 1 , wherein the correction section corrects color misregistration at the start of image forming processing for the next job or later, based on the first color misregistration amount and the second color misregistration amount.

3. The image forming apparatus according to claim 1 , wherein the acquisition unit acquires a read image obtained by reading the reference image formed on the continuous recording medium.

4. the image forming unit includes an intermediate transfer member onto which a toner image is transferred; The image forming apparatus according to claim 1 , wherein the acquisition unit acquires a read image by reading the reference image formed of a toner image transferred onto the intermediate transfer body.

5. the image forming unit includes an intermediate transfer member onto which a toner image is transferred; The image forming apparatus according to claim 1, wherein the acquisition unit acquires a read image by reading the reference image formed from a toner image transferred onto the intermediate transfer body before the image forming operation on the continuous recording medium, and acquires a read image by reading the reference image formed on the continuous recording medium during the image forming operation on the continuous recording medium.

6. The image forming unit includes: an intermediate transfer member onto which a toner image is transferred; 2. An image forming apparatus according to claim 1, wherein the reference image is formed within the image forming area on the intermediate transfer body before the image forming operation on the continuous recording medium, and the reference image is formed outside the image forming area on the continuous recording medium during the image forming operation on the continuous recording medium.

7. 2. The image forming apparatus according to claim 1, wherein the correction section corrects color misregistration at the start of image forming processing for the next job or later, based on the first amount of color misregistration within a predetermined time from the start of image forming processing.

8. 2. The image forming apparatus according to claim 1, wherein the correction unit changes a correction value for correcting color misregistration at the start of image forming processing for a next job or later, when the first color misregistration amount is greater than a predetermined threshold value.

9. The image forming apparatus according to claim 1, wherein the correction unit determines a correction value for correcting the first color misregistration amount for each specified condition, and corrects the color misregistration at the start of the image forming process for the next job or later using the correction value according to the printing conditions for the next job or later.

10. The image forming apparatus according to claim 9 , wherein the correction unit determines the correction value corresponding to a combination of a plurality of conditions.

11. the image forming unit includes an intermediate transfer member onto which a toner image is transferred; 10. The image forming apparatus according to claim 9, wherein the conditions include a transfer pressure when the toner image is transferred from the intermediate transfer member to the continuous recording medium.

12. The image forming apparatus according to claim 9 , wherein the conditions include a condition relating to the continuous recording medium.

13. a detection unit that detects an ambient temperature inside the image forming apparatus, The image forming apparatus according to claim 9 , wherein the conditions include the ambient temperature detected by the detection unit.

14. 10. The image forming apparatus according to claim 9, wherein the conditions include a condition relating to a conveyance state of the continuous recording medium.

15. 10. The image forming apparatus according to claim 9, wherein the conditions include coverage of the image formed on the continuous recording medium.

16. The image forming apparatus according to claim 1 , wherein the correction section corrects color misregistration at the start of image forming processing for the next job or later, based on the first amount of color misregistration acquired in the immediately preceding job.

17. The image forming apparatus according to claim 1 , wherein the correction unit corrects color misregistration at the start of image forming processing for a subsequent job onward based on the average value of the first color misregistration amount obtained in jobs executed in the past.

18. The image forming apparatus according to any one of claims 1 to 17, an external device having a storage unit communicably connected to the image forming apparatus; Equipped with The correction unit stores a correction value for correcting the first amount of color misregistration in the storage unit.

19. a computer of an image forming apparatus including an image forming unit that forms a reference image used to correct color shift of images of each color in the main scanning direction; an acquisition unit that acquires a first color shift amount in a main scanning direction based on a read image obtained by reading the reference image formed by the image forming unit during an image forming operation on a continuous recording medium; a correction unit that corrects color misregistration at the start of image forming processing for a next job or later, based on the first color misregistration amount acquired by the acquisition unit; A program that functions as a

Images