Liquid ejection device

Abstract

To provide a device for discharging a liquid, which can curb a liquid consumption amount.SOLUTION: Flushing is carried out for at least one of a tip margin part which is a tip part and a rear end margin part which is a rear part of a sheet which is a recording medium in a conveying direction, and a flushing pattern formed through the flushing is read by an in-line sensor which is image detection means. The increase of defective nozzles is detected on the basis of an image abnormality such as a white stripe in the read flushing pattern, and defective noise identification control for identifying the defective nozzles is executed when the defective noises have increased.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection device. [Background technology]

[0002] Conventionally, there is known a liquid ejection device that has an array of multiple nozzles, is equipped with a liquid ejection head that ejects liquid onto a recording medium, and performs flushing (also called blank ejection or purging) to eject thickened ink that has accumulated near the nozzles.

[0003] Patent Document 1 describes the following device for ejecting the liquid. Specifically, the device performs flushing on the leading edge margin, which is the leading edge in the transport direction of a recording medium that has been newly transported from a feeding device to the liquid ejection position of a liquid ejection head. Following the flushing result, which is an absolute pattern, a test pattern for identifying faulty nozzles is formed in the leading edge margin, and the device ejects liquid that detects the test pattern using an in-line sensor, which is image detection means, to identify faulty nozzles. Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Document 1, a flushing pattern and a test pattern for identifying faulty nozzles are formed on the leading edge of the recording medium every time a new recording medium is transported from the feeding device to the liquid ejection position, resulting in a problem of high liquid consumption. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, the liquid ejecting device of the present invention comprises a liquid ejection head in which a plurality of nozzles are arranged and which ejects liquid onto a recording medium, an image detection means which detects an image formed on the recording medium, and a determination means which performs flushing on at least one of a leading end portion and a trailing end portion in a transport direction of the recording medium, detects a flushing pattern formed on the recording medium by the flushing using the image detection means, and determines whether or not to execute defective nozzle identification control based on the flushing pattern detected by the image detection means; The liquid ejection during the flushing is made different from the liquid ejection during the printing operation, and one or more nozzles are skipped to set the nozzles to be used in the flushing pattern. It is characterized by the following. [Effects of the Invention]

[0006] According to the present invention, the amount of liquid consumed can be reduced. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram showing a schematic configuration of a printer according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing the configuration of an image forming unit. [Figure 3] FIG. 4 is a diagram illustrating the arrangement of a first inline sensor and a second inline sensor. [Figure 4] FIG. 4 is a control block diagram relating to control for identifying a defective nozzle. [Figure 5] 10A and 10B are diagrams showing flushing patterns formed on a sheet P during continuous printing operations. [Figure 6] An enlarged view of the K-color flashing pattern. [Figure 7] (a) is a diagram showing pixel values ​​of the read image of the flushing pattern when there is no defect in the nozzle used, and (b) is a diagram showing pixel values ​​of the read image of the flushing pattern when there is an ejection defect in the nozzle used. [Figure 8] FIG. 10 is a diagram showing a portion of a sheet of paper on which a test pattern for identifying defective nozzles is printed. [Figure 9] 6A and 6B are diagrams for explaining position detection of a nozzle check line in the main scanning direction. [Figure 10] 10 is a flowchart for identifying a defective nozzle. [Figure 11] 1 is an overall flow diagram for identifying defective nozzles in continuous printing operations. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0009] [Overall explanation] FIG. 1 is a schematic diagram showing the general configuration of a printer 1, which is an inkjet recording apparatus serving as a "liquid ejecting apparatus" according to this embodiment. The printer 1 is mainly composed of a paper feed section 100, an image forming section 200, a drying section 300, and a paper discharge section 400.

[0010] In the printer 1, an image is formed on paper P (medium, sheet material, and recording material) fed from a paper feed unit 100 using ink, which is a liquid for image formation, in an image forming unit 200. Then, after the ink adhering to the paper P is dried in a drying unit 300, the paper P is discharged from a paper discharge unit 400.

[0011] [Paper feed section] The paper feed section 100 is mainly composed of a paper feed tray 110 on which multiple sheets of paper P are stacked, a feed device 120 that separates and sends out sheets of paper P one by one from the paper feed tray 110, and a pair of registration rollers 130 that sends the sheets of paper P to the image forming section 200.

[0012] Any type of feeding device can be used for the feeding device 120, such as a device using rollers or a device using air suction. After the leading edge of the paper P sent out from the paper feed tray 110 by the feeding device 120 reaches the pair of registration rollers 130, the pair of registration rollers 130 is driven at a predetermined timing, whereby the paper is fed to the image forming unit 200.

[0013] In this embodiment, the paper feed unit 100 is not limited in configuration as long as it can feed the paper P to the image forming unit 200.

[0014] [Image forming section] The image forming unit 200 is mainly composed of a receiving drum 201, a paper transport drum 210 (transport member), an ink ejection unit 220, and a delivery drum 202. FIG. 2 is a schematic diagram showing the configuration of the image forming unit 200. As shown in FIG. The receiving drum 201 is a member that receives the fed paper P (medium) and transports it downstream. The paper transport drum 210 is a cylindrical member that carries the paper P transported by the receiving drum 201 on its outer circumferential surface and transports it. The ink ejection unit 220 is a mechanism that ejects ink toward the paper P transported by the paper transport drum 210. The delivery drum 202 is a member that delivers the paper P transported by the paper transport drum 210 to the drying unit 300.

[0015] The paper sheet P transported from the paper supply unit 100 to the image forming unit 200 has its leading edge gripped by a receiving paper gripper 201a provided on the surface of the receiving drum 201, and is transported as the surface of the receiving drum 201 moves. The paper sheet P transported by the receiving drum 201 is handed over to the paper transport drum 210 at a position opposite the paper transport drum 210.

[0016] A transport paper gripper 210a is also provided on the surface of the paper transport drum 210, and the transport paper gripper 210a grips the leading edge of the paper P delivered to the paper transport drum 210. In addition, a plurality of suction holes are formed in a dispersed manner on the surface of the paper transport drum 210, and a suction device 211 generates a suction air current inward of the paper transport drum 210 at each suction hole.

[0017] The paper P transferred from the receiving drum 201 to the paper transport drum 210 has its leading edge gripped by the transport paper gripper 210a, and is adsorbed to the surface of the paper transport drum 210 by the suction airflow, and is transported as the surface of the paper transport drum 210 moves.

[0018] The ink ejection unit 220 of this embodiment ejects four colors of ink, C (cyan), M (magenta), Y (yellow), and K (black), to form an image, and is provided with a separate liquid ejection head 230 (230C, 230M, 230Y, 230K) for each ink. The four liquid ejection heads 230 have the same configuration except for the colors of ink they eject, and therefore in the following explanation, the suffixes "C," "M," "Y," "K," etc., which indicate the colors of ink ejected, will be omitted as appropriate.

[0019] There are no limitations on the configuration of the liquid ejection head 230, and any configuration can be used as long as it ejects liquid from the ejection holes. If necessary, a liquid ejection head that ejects special ink such as white, gold, or silver ink, or a liquid ejection head that ejects a liquid that does not form an image, such as a surface coating liquid, may be provided.

[0020] The ejection operation of each of the four liquid ejection heads 230 of the ink ejection unit 220 is controlled by a drive signal corresponding to image information. When the paper P transported by the paper transport drum 210 passes through an area facing the ink ejection unit 220, ink of each color is ejected from the four liquid ejection heads 230, and an image corresponding to the image information is formed.

[0021] In this embodiment, the image forming unit 200 is not limited to a specific configuration as long as it deposits a liquid on the paper P to form an image.

[0022] [Drying section] The drying section 300 is mainly composed of a drying mechanism 301 for drying the ink adhered to the paper P in the image forming section 200, and a transport mechanism 302 for transporting the paper P transported from the image forming section 200.

[0023] After being received by the transport mechanism 302, the paper P transported from the image forming unit 200 is transported to pass through the drying mechanism 301 and delivered to the paper discharge unit 400. When passing through the drying mechanism 301, the ink on the paper P is subjected to a drying process, which evaporates the liquid content in the ink, such as water, and fixes the ink on the paper P, while suppressing curling of the paper P.

[0024] [Paper output section] The paper discharge section 400 is mainly composed of a paper discharge tray 410 on which a plurality of sheets of paper P are stacked. The sheets of paper P conveyed from the drying section 300 are stacked and held on the paper discharge tray 410 in order.

[0025] In this embodiment, the configuration of the paper discharge unit 400 is not limited as long as it can discharge the paper P.

[0026] [Other functional parts] The printer 1 of this embodiment is composed of a paper feed unit 100, an image forming unit 200, a drying unit 300, and a paper discharge unit 400, but other functional units may be added as appropriate. For example, a pre-processing unit that performs pre-processing for image formation may be added between the paper feed unit 100 and the image forming unit 200, or a post-processing unit that performs post-processing for image formation may be added between the drying unit 300 and the paper discharge unit 400.

[0027] An example of a pre-treatment unit is one that performs a treatment liquid application process in which a treatment liquid that reacts with ink to suppress bleeding is applied to the paper P, but there are no particular restrictions on the content of the pre-treatment.

[0028] Examples of the post-processing section include a paper inversion and transport process for inverting the paper P on which an image has been formed in the image forming section 200 and sending it back to the image forming section 200 to form images on both sides of the paper P, and a process for binding multiple sheets of paper P on which images have been formed. However, there are no particular limitations on the content of the post-processing.

[0029] In this embodiment, the device for ejecting liquid is described using an example of an inkjet recording device, a printer 1. The printer 1 is equipped with a liquid ejection head 230 that ejects ink, which is a liquid, onto a surface to be dried of paper P, which is a sheet material.

[0030] In this embodiment, a long liquid ejection head (line head) is formed by arranging multiple liquid ejection heads in the paper width direction (the direction perpendicular to the transport direction). Unless otherwise specified, "liquid ejection head" means "line head."

[0031] Each liquid ejection head 230 in this embodiment is a line-type liquid ejection head having a length across the width of the paper P (length in the main scanning direction), and ejects ink from each liquid ejection head 230 onto the paper P.

[0032] In this embodiment, the individual liquid ejection heads 230 are individually arranged radially around the rotation axis of the paper transport drum 210 .

[0033] A scanner unit 10 serving as an image detection means is provided downstream of the ink discharge unit 220 in the transport direction of the paper P so as to face the paper transport drum 210. The scanner unit 10 has a first inline sensor 10a and a second inline sensor 10b. As shown in FIG. 3, the first inline sensor 10a is disposed at one end in the main scanning direction (paper width direction), and the second inline sensor 10b is disposed at the other end in the main scanning direction.

[0034] In this embodiment, the first inline sensor 10a and the second inline sensor 10b are arranged at different positions in the sub-scanning direction (paper transport direction). The other end of the first inline sensor 10a in the main scanning direction and one end of the second inline sensor 10b in the main scanning direction are arranged to overlap (overlapping area). This allows the first inline sensor 10a and the second inline sensor 10b to read the image formed on the paper continuously across the entire area in the main scanning direction.

[0035] FIG. 4 is a control block diagram relating to the control of identifying defective nozzles in this embodiment. The control unit 11, which serves as a control means and a judgment means, is composed of a CPU, RAM, ROM, etc. The control unit 11 is connected to the scanner unit 10, the liquid ejection head 230, an image correction unit 12 serving as an image correction means, a memory unit 13, an operation panel 14, etc. The memory unit 13 is composed of nonvolatile memory means such as a flash memory or HDD, and stores information about defective nozzles identified by defective nozzle identification control, drive waveforms for driving the liquid ejection head, etc. The drive waveforms stored in the memory unit 13 include a printing drive waveform used when printing an image on paper P, and a flushing drive waveform used when performing flushing (also known as blank ejection or purging). The image correction unit 12 corrects input image data based on the defective nozzle information stored in the memory unit 13.

[0036] The ROM of the control unit 11 stores a judgment program that detects the presence or absence of defective nozzles and determines whether or not to perform defective nozzle identification control, a control program that performs defective nozzle identification control, etc. These control programs are read and executed by the CPU. The ROM of the control unit 11 also stores a control program that controls liquid ejection from the liquid ejection head 230 based on the drive waveforms stored in the storage unit 13, and this program is read and executed by the CPU.

[0037] The defective nozzle detection control of this embodiment detects whether or not a defective nozzle has occurred by using the scanner unit 10 to read a flushing pattern formed by flushing the leading and trailing margins of the paper P during continuous printing. The defective nozzle identification control forms a test pattern on the paper to identify defective nozzles, and then uses the scanner unit 10 to read the test pattern and identify the defective nozzles.

[0038] FIG. 5 is a diagram showing a flushing pattern formed on the paper P during a continuous printing operation. 5, a first flushing pattern 20a is formed in a leading edge margin, which is a region on the leading edge side in the paper transport direction, relative to a print image section 21 where a print image on the paper is formed. A second flushing pattern 20b is formed in a trailing edge margin, which is a region on the trailing edge side in the paper transport direction, relative to the print image section 21. Each of the flushing patterns 20a, 20b is made up of patterns in four colors: K, C, M, and Y.

[0039] Each flushing pattern 20a, 20b is formed by controlling the liquid ejection from the liquid ejection head 230 with a flushing drive waveform that is different from the printing drive waveform. The flushing drive waveform is a drive waveform that results in a faster ejection speed than the printing drive waveform. Alternatively, the flushing drive waveform is a drive waveform that ejects a larger volume of ink than the printing drive waveform. Alternatively, the flushing drive waveform may be a drive waveform that results in a faster ejection speed than the printing drive waveform and a larger volume of ink ejected than the printing drive waveform. By using the flushing drive waveform as described above, thickened ink in the nozzles can be efficiently ejected.

[0040] FIG. 6 is an enlarged view of the K color flushing pattern. In the following, the color K will be explained, but the same applies to the other colors (C, M, Y). As shown in Figure 6, the K-color flushing pattern is a pattern in which multiple line images extending in the sub-scanning direction (paper transport direction) are lined up in the main scanning direction. The K-color pattern is formed by using every other nozzle. If the resolution in the main scanning direction when all nozzles are used is 1200 dpi, the resolution of this pattern is 600 dpi. The nozzles used for the second flushing pattern 20b formed in the trailing edge margin are the nozzles that were not used when forming the first flushing pattern 20a in the leading edge margin. This allows flushing to be performed for all nozzles.

[0041] In the above example, the flushing pattern is formed by thinning out one nozzle from the nozzles in use, but two or more nozzles may be thinned out. For example, if four or more nozzles are thinned out, different nozzles are used to form the flushing patterns for the leading and trailing margins of two sheets of paper during continuous printing. This allows flushing to be performed for all nozzles.

[0042] In this way, the flushing patterns formed in the leading and trailing margins of the paper are read by the scanner unit 10 to detect whether or not a discharge defect has occurred. Figure 7(a) shows the pixel values ​​of the read image of the flushing pattern when there is no defect in the nozzles used, and Figure 7(b) shows the pixel values ​​of the read image of the flushing pattern when there is an ejection defect in the nozzles used.

[0043] As shown in FIG. 7(a), when no ejection defects occur in the nozzles being used, the image read by the scanner unit 10 has substantially the same pixel values ​​in the main scanning direction.

[0044] On the other hand, if a nozzle in use has an ejection defect, ink is not ejected from the defective nozzle, resulting in a white streak in the flushing pattern. As a result, areas with high pixel values ​​appear in the main scanning direction in the image read by the scanner unit 10. For this reason, the control unit 11 detects whether there are any areas in the flushing pattern where the pixel value exceeds a threshold, and if there are any pixels where the pixel value exceeds the threshold, it determines that there is a defective nozzle with an ejection defect.

[0045] In this embodiment, the flushing patterns 20a and 20b are formed using a flushing drive waveform, which results in a fast ejection speed and a large volume of ink being ejected when forming a print image. Therefore, the line images extending in the sub-scanning direction of the flushing patterns 20a and 20b are thick. Therefore, if the flushing patterns 20a and 20b are formed using all nozzles, adjacent line images may overlap, potentially preventing white streaks from appearing in the flushing patterns even if a defective nozzle occurs.

[0046] In contrast, in this embodiment, by thinning out one nozzle from use and forming a flushing pattern, line images do not overlap, and when a faulty nozzle occurs, a white streak appears, causing an abnormality in the flushing pattern. This makes it possible to accurately detect the presence of a faulty nozzle from the flushing pattern.

[0047] However, while the flushing pattern shown in FIG. 5 can determine whether or not there is a faulty nozzle, it cannot identify which nozzle is experiencing the ejection failure. This is because the resolution of the scanner unit 10 in the main scanning direction is low, making it difficult to accurately identify the location of white streaks from an image obtained by scanning the flushing pattern with the scanner unit 10. Furthermore, the flushing pattern has line images arranged at close intervals in the main scanning direction, and the line images of flushing patterns 20a and 20b are thick, so there is a risk that the line images will merge with adjacent line images. Furthermore, because the line images are closely spaced, it is sometimes difficult to recognize each individual line image in an image scanned by the low-resolution scanner unit 10. Therefore, it is difficult to associate pixels in the scanned image with nozzle numbers based on the line images of the flushing pattern. Therefore, to identify faulty nozzles, continuous printing operations are interrupted and faulty nozzle identification control is performed. In the defective nozzle identification control, a test pattern with sufficiently spaced line images as shown in FIG. 8 is formed on paper using the drive waveform during printing, and the test pattern is read by the scanner unit 10 to identify the defective nozzle.

[0048] FIG. 8 is a diagram showing a portion of a sheet of paper on which a test pattern for identifying defective nozzles is printed. 8, a test pattern for identifying faulty nozzles is formed on paper. The test pattern is formed by controlling the liquid ejection from the liquid ejection head 230 with a printing drive waveform. The test pattern for identifying faulty nozzles has a start mark 32, an end mark 31, and a nozzle check pattern 35.

[0049] End marks 31a and 31b are formed on both sides of the leading edge of the paper in the main scanning direction. Start mark 32 is formed in the overlapping area between first inline sensor 10a and second inline sensor 10b at the center of the paper in the main scanning direction. Start mark 32 is formed one step downstream in the paper transport direction from the end mark. Start mark 32 is also formed in the same position as the nozzle line at the center of the first check line group 34a in the main scanning direction. End mark 31a on the left side of the figure is formed in a position corresponding to the position in the main scanning direction of the nozzle at one end of the nozzle row in the main scanning direction. Meanwhile, end mark 31b on the right side of the figure is formed in a position corresponding to the position in the main scanning direction of the nozzle at the other end of the nozzle row in the main scanning direction.

[0050] A nozzle check pattern 35 for identifying faulty nozzles is formed upstream of the start mark 32 in the paper transport direction. The nozzle check pattern is made up of multiple nozzle check lines 33, each consisting of a plurality of check line groups 34a, 34b, 34c, etc., formed at predetermined intervals in the main scanning direction. The nozzle check lines 33 are line images having a predetermined length in the sub-scanning direction and formed by ejecting ink from one nozzle for a predetermined period of time.

[0051] The nozzle check lines of each check line group 34a, 34b, 34c... are formed so that every n nozzles are used, and the nozzles used in each check line group 34a, 34b, 34c... are different from each other. Specifically, if the nozzle at one end of the nozzle row in the main scanning direction (the nozzle corresponding to the left end in the figure) is numbered 1 and the number of nozzles is N, the nozzles used by the first check line group 34a, which is the most downstream in the paper transport direction, are 1, (1+n), (1+2n),..., (N-(n-1)). The nozzles used by the second check line group 34b are (2+n), (2+2n),..., (N-(n-2)). The nozzles used by the final (nth) check line group are n, 2n..., N.

[0052] The test pattern formed on the paper for identifying defective nozzles is read by the in-line sensors 10a and 10b of the scanner unit 10. The nozzle check line 33 on the left side of the start mark 32 in the drawing is detected based on the read image read by the second in-line sensor 10b. On the other hand, the nozzle check line 33 on the right side of the start mark 32 in the drawing is detected based on the read image read by the first in-line sensor 10a.

[0053] FIG. 9 is a diagram for explaining the position detection of the nozzle check line 33 in the main scanning direction. 9A and 9B, the position detection in the main scanning direction of the nozzle check line 33 on the right side of the start mark 32 in the drawing will be described, but the same applies to the left side of the start mark 32 in the drawing. First, the control unit 11 detects the main scanning direction positions of the start mark 32 and the end mark 31b from the scanned image read by the in-line sensor. Next, a nozzle check line detection range is set based on the detected main scanning direction positions of the start mark 32 and the end mark. Next, for the first row of check lines 34a, the main scanning direction position of each nozzle check line 33 is detected using the main scanning direction position of the start mark 32 as a reference. Specifically, the control unit determines whether the pixel value of each pixel in the main scanning direction is greater than a threshold value. If the pixel value is greater than the threshold value, the control unit determines the main scanning direction position of that pixel as the main scanning direction position of the nozzle check line 33. The pixel value of each pixel in the main scanning direction is the average value of the pixel values ​​of multiple pixels in the sub-scanning direction. This detection of the nozzle check line position is performed for all rows of check lines 34b, 34c,..., 34n.

[0054] FIG. 10 is a flowchart for identifying defective nozzles. First, as described above, the control unit 11 detects the positions of the start mark 32 and the end mark 31b in the main scanning direction and sets the detection range of the nozzle check line 33 (S1-S2). Next, the control unit 11 uses the start mark 32 as a reference and detects the nozzle check line positions of the check line group in each row as shown in Fig. 9 (S3).

[0055] Next, for the first row of check line group 34a, whether or not there is a missing nozzle check line 33 and whether or not there is a bend in the nozzle check line is detected (S4). Whether or not there is a bend in the nozzle check line is detected by the process described in JP 2020-146947 A.

[0056] Then, once the detection of missing nozzle check lines 33 and the presence or absence of bends in the nozzle check lines has been performed for all rows of check line groups (YES in S5), the defective nozzle identification process ends.

[0057] Note that a nozzle check line may be formed only for nozzles near the location where a white streak occurs in the flushing pattern to determine whether or not the nozzle is defective. Furthermore, if a determination is made only for nozzles near the location where a white streak occurs in the flushing pattern to determine whether or not the nozzle is defective, the length of the test pattern in the sub-scanning direction can be shortened. Therefore, a test pattern may be formed in the leading edge margin of the paper on which the image is printed without interrupting the continuous printing operation.

[0058] The control unit 11 stores the nozzle numbers of the defective nozzles identified by the defective nozzle identification process and the number of identified defective nozzles in the memory unit 13. Based on the nozzle numbers of the defective nozzles stored in the memory unit 13, the image correction unit 12 performs image correction such as changing the dither pattern so that the defective nozzles are not used, and compensates for the defective nozzles using the nozzles around the defective nozzles.

[0059] FIG. 11 is an overall flow diagram for identifying defective nozzles in a continuous printing operation. First, the control unit 11 performs flushing on the leading edge margin and trailing edge margin of the paper on which the print image is to be formed, forming the flushing patterns 20a and 20b shown in Fig. 5 (S11). In this way, by performing flushing on the leading edge margin and trailing edge margin of the paper each time a print image is formed on the paper, it is possible to form a good print image. Note that the portion of the paper on which the flushing pattern is formed is cut after printing.

[0060] Next, the control unit 11 reads the flushing patterns formed in the leading and trailing margins of the paper with the in-line sensors 10a and 10b (S12). Next, the control unit 11 checks whether the number of defective nozzles has increased since the previous defective nozzle identification control, based on the number of white stripes in the flushing patterns read by the in-line sensors 10a and 10b (S13).

[0061] When the control unit 11 determines that the number of defective nozzles is increasing (Yes in S14), it temporarily suspends the continuous printing operation and performs defective nozzle identification control. When the defective nozzle identification control is performed, the test pattern for defective nozzle identification shown in FIG. 8 is printed on paper (S15), and the test pattern printed on the paper is read by the in-line sensors 10a and 10b (S16). Next, the control unit 11 identifies the defective nozzles (S17), as described using the flow in FIG. 10.

[0062] Next, the control unit 11 stores the number of the newly identified defective nozzle in the memory unit 13 as a result of the defective nozzle identification during the continuous printing operation, thereby updating the defective nozzle (S18). Next, the image correction unit 12 determines whether the newly identified defective nozzle can be compensated for by image correction using the nozzles surrounding the defective nozzle, based on the number of the defective nozzle identified in the previous defective nozzle identification control and the newly identified defective nozzle number (S19). If the image correction unit 12 determines that the newly identified defective nozzle cannot be compensated for by image correction using the nozzles surrounding the defective nozzle, the continuous printing operation is stopped (S20). Then, head cleaning is performed to clean the liquid ejection head, thereby attempting to recover the defective nozzle (S21).

[0063] On the other hand, if image correction can be performed to compensate for the defective nozzle using the nozzles surrounding the defective nozzle (Yes in S19), continuous printing is resumed (Yes in S22).Furthermore, if the number of white streaks, which are abnormal image portions in the flushing pattern, has not increased and the number of defective nozzles has not increased (Yes in S14), continuous printing is continued (Yes in S22).

[0064] In this way, in this embodiment, defective nozzle identification control is performed only when the number of abnormalities in the flushing pattern increases. This allows defective nozzle identification control to be performed as soon as a new defective nozzle is discovered, compared to performing defective nozzle identification control periodically, such as after every specified number of sheets. As a result, good images can be maintained. Furthermore, unnecessary defective nozzle identification control is no longer performed, which reduces paper waste and ink consumption compared to performing defective nozzle identification control periodically.

[0065] Furthermore, in this embodiment, the flushing pattern is used as a pattern for detecting whether a new faulty nozzle has occurred. This allows for reduced ink consumption compared to forming a pattern for detecting whether a new faulty nozzle has occurred separately from flushing. Furthermore, compared to forming a pattern for detecting whether a new faulty nozzle has occurred in the leading or trailing margin of the paper after flushing has been performed in the leading or trailing margin of the paper, this method offers the following advantage: the leading and trailing margins can be narrowed, allowing for a wider area in which to form the print image on the cut paper.

[0066] In this embodiment, a "liquid ejection head" refers to a functional component that ejects and sprays liquid from ejection holes (nozzles). The ejected liquid may have a viscosity and surface tension that allows it to be ejected from the head. While not particularly limited, it is preferable that the viscosity of the ejected liquid be 30 mPa·s or less at room temperature and pressure, or upon heating or cooling. More specifically, the liquid may be a solution, suspension, emulsion, or the like containing a solvent such as water or an organic solvent, a colorant such as a dye or pigment, a functionalizing material such as a polymerizable compound, a resin, or a surfactant, a biocompatible material such as DNA, amino acids, proteins, or calcium, or an edible material such as a natural dye. These liquids can be used, for example, as inkjet inks, surface treatment solutions, liquids for forming components of electronic elements or light-emitting elements, or resist patterns for electronic circuits, and liquid materials for three-dimensional modeling. Energy sources for ejecting the liquid include piezoelectric actuators (laminated piezoelectric elements or thin-film piezoelectric elements), thermal actuators using electrothermal conversion elements such as heating resistors, and electrostatic actuators consisting of a diaphragm and an opposing electrode.

[0067] In this embodiment, multiple liquid ejection heads are arranged in the paper width direction (direction perpendicular to the transport direction) to form a long liquid ejection head (line head), and the liquid ejection head is configured to not move relative to the device main body. The liquid ejection head may also be configured to form a "liquid ejection unit" together with other components, and to move relative to the device main body while printing.

[0068] A "liquid ejection unit" is a collection of components related to liquid ejection, in which functional components and mechanisms are integrated with a liquid ejection head. For example, a "liquid ejection unit" includes a combination of a liquid ejection head and at least one of a supply / circulation mechanism, a carriage, a maintenance / recovery mechanism, and a main scanning movement mechanism. Here, "integration" includes, for example, a combination in which the liquid ejection head and functional components or mechanisms are fixed to each other by fastening, bonding, engaging, or the like, or a combination in which one is held movably relative to the other. The liquid ejection head, functional components, and mechanisms may also be configured to be detachable from each other.

[0069] For example, some liquid ejection units integrate a liquid ejection head and a supply / circulation mechanism. Others integrate the liquid ejection head and the supply / circulation mechanism by connecting them with a tube or the like. A filter unit can be added between the supply / circulation mechanism and the liquid ejection head of these liquid ejection units. Other liquid ejection units integrate a liquid ejection head and a carriage. Other liquid ejection units integrate a liquid ejection head and a scanning movement mechanism by movably holding the liquid ejection head on a guide member that constitutes part of a scanning movement mechanism. Other liquid ejection units integrate a liquid ejection head, carriage, and maintenance / recovery mechanism by fixing a cap member, which is part of a maintenance / recovery mechanism, to a carriage to which the liquid ejection head is attached. Other liquid ejection units integrate a liquid ejection head and a supply mechanism by connecting a tube to a liquid ejection head to which a supply / circulation mechanism or a flow path component is attached. Liquid from a liquid storage source is supplied to the liquid ejection head via this tube. The main scanning movement mechanism also includes the guide member alone. The supply mechanism also includes the tube alone and the loading unit alone.

[0070] A "liquid ejecting device" is a device that has a liquid ejection head or a liquid ejection unit and ejects liquid by driving the liquid ejection head. Liquid ejecting devices include not only devices that can eject liquid onto objects onto which the liquid can adhere, but also devices that eject liquid into air or liquid. This "liquid ejecting device" can also include means for feeding, transporting, and discharging objects onto which the liquid can adhere, as well as pre-processing devices and post-processing devices.

[0071] Examples of "liquid ejecting devices" include image forming devices that eject ink to form an image on paper, and three-dimensional modeling devices (three-dimensional modeling devices) that eject modeling liquid onto a powder layer formed with powder to form a three-dimensional object (a three-dimensional object). Furthermore, "liquid ejecting devices" are not limited to devices that visualize meaningful images such as letters and figures using the ejected liquid. For example, they also include devices that form patterns that have no meaning in themselves, and devices that form three-dimensional images.

[0072] "Something to which a liquid can be attached" means something to which a liquid can be attached at least temporarily, and to which the liquid can adhere and stick, or to which the liquid can adhere and penetrate. Specific examples include media such as paper, recording paper, film, and cloth, electronic circuit boards, electronic components such as piezoelectric elements, powder layers (powder layers), organ models, and test cells. Unless otherwise specified, the term includes all things to which a liquid can be attached. The material of the "thing to which a liquid can be attached" may be paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, or other materials to which a liquid can be attached, even if only temporarily. The shape of the "thing to which a liquid can be attached" is not limited to a sheet-like shape like paper P, and may be any shape to which a liquid can be attached. "Something to which a liquid can be attached" may be, for example, a film product, a fabric product such as clothing, a building material such as wallpaper or flooring, or a leather product.

[0073] The "liquid" may be any liquid having a viscosity and surface tension that allows it to be ejected from a head, but is not particularly limited thereto. Preferably, the viscosity of the liquid is 30 mPa·s or less at room temperature and pressure, or upon heating or cooling. More specifically, the liquid may be a solution, suspension, emulsion, or the like containing a solvent such as water or an organic solvent, a colorant such as a dye or pigment, a polymerizable compound, a resin, a surfactant, or the like, a biocompatible material such as DNA, amino acids, proteins, or calcium, or an edible material such as a natural dye. These liquids can be used, for example, in inkjet inks, surface treatment solutions, liquids for forming components of electronic devices or light-emitting elements, or resist patterns for electronic circuits, and liquid materials for three-dimensional modeling.

[0074] Furthermore, the printer 1 of this embodiment is a "liquid ejecting device" in which the liquid ejection head and an object to which the liquid can be attached move relatively. Specific examples of devices that move relatively include a line-type device in which the liquid ejection head does not move, as in this embodiment, and a serial-type device in which the liquid ejection head moves. The "liquid ejecting device" is not limited to a device in which the liquid ejection head and an object to which the liquid can be attached move relatively.

[0075] Other examples of "liquid ejecting devices" include treatment liquid application devices that eject treatment liquid onto paper to apply the treatment liquid to the surface of the paper for purposes such as modifying the surface of the paper. Also included are spray granulation devices that spray a composition liquid in which raw materials are dispersed in a solution through a nozzle to granulate the raw material into fine particles. In addition, the terms "image formation," "recording," "printing," "imaging," "printing," "shaping," and the like in this application are all synonymous.

[0076] The above description is merely an example, and each of the following aspects provides unique effects. (Aspect 1) The apparatus includes a liquid ejection head 230 having an array of nozzles that ejects liquid onto a recording medium such as paper, an image detection means such as inline sensors 10a, 10b that detects an image formed on the recording medium, and a determination means such as a control unit 11 that performs flushing on at least one of the leading edge portion in the transport direction, such as the leading margin, and the trailing edge portion, such as the trailing margin, of the recording medium, detects flushing patterns 20a, 20b formed on the recording medium by flushing using the image detection means, and determines whether or not to execute defective nozzle identification control based on any abnormality in the flushing pattern detected by the image detection means. If there is a faulty nozzle that does not eject liquid during flushing, in which the drive of liquid ejection is controlled so that thickened ink in the nozzle is ejected, an abnormality such as a white streak will appear in the flushing pattern formed by the flushing operation. Therefore, the presence or absence of a faulty nozzle can be detected from the abnormality in the flushing pattern. If a faulty nozzle is found, in order to identify the faulty nozzle, faulty nozzle identification control is required that forms a specific test pattern on the recording medium that can accurately identify the faulty nozzle, for the following reason: That is, due to the low resolution of the image detection means, it is difficult to associate each pixel in the main scanning direction of the image detected by the image detection means with the position of the nozzle, and therefore it is difficult to identify the faulty nozzle from the position of the white streak in the flushing pattern detected by the image detection means. In the first aspect, for example, during normal printing operations, flushing is performed on at least one of the leading edge portion of the recording medium in the transport direction, such as the leading margin, and the trailing edge portion, such as the trailing margin, to form only a flushing pattern. Then, when it is determined that a faulty nozzle may have occurred based on an abnormality in the flushing pattern, faulty nozzle identification control is executed. As a result, when there is no abnormality in the flushing pattern, faulty nozzle identification control can be omitted, and the formation of a test pattern on the recording medium to identify faulty nozzles can be omitted. This reduces liquid consumption compared to the device described in Patent Document 1, which forms a flushing pattern and a test pattern each time a new recording medium is transported from the feed device to the liquid ejection position of the liquid ejection head. In addition, typically, only the flushing pattern can be formed at the leading or trailing end portion of the recording medium, and the area for forming the pattern at the leading or trailing end portion can be set narrower than in a case where both the flushing pattern and the test pattern are formed at the leading or trailing end portion.

[0077] (Aspect 2) In the first embodiment, the liquid ejection during flushing is different from the liquid ejection during printing. This allows the thickened ink in the nozzles to be ejected more effectively than when the liquid ejection during flushing is the same as the liquid ejection during printing.

[0078] (Aspect 3) In the second aspect, the volume of liquid ejected from the nozzles during flushing is set to be larger than the volume of liquid ejected during printing operations. This allows the thickened ink in the nozzles to be ejected satisfactorily.

[0079] (Aspect 4) In the second or third aspect, the ejection speed of the liquid ejected from the nozzles during flushing is set to be faster than the ejection speed of the liquid during the printing operation. This allows the thickened ink in the nozzles to be ejected satisfactorily.

[0080] (Aspect 5) In any of the second to fourth aspects, the nozzles to be used in the flushing pattern are set by skipping one or more nozzles. According to this, as explained in the embodiment, by discharging the liquid during flushing differently from the liquid discharge during printing, and discharging the thickened ink in the nozzles properly, images such as line images formed with the liquid discharged from the nozzles during flushing become thicker than images formed with the liquid discharged from the nozzles during printing. As a result, images formed with the liquid discharged from the adjacent nozzles overlap, and there is a risk that abnormalities such as white streaks will not appear in the flushing pattern even if a defective nozzle occurs. Therefore, in aspect 5, by skipping one or more nozzles and setting the nozzles to be used in the flushing pattern, when a faulty nozzle occurs, it is possible to effectively produce an abnormality such as a white streak in the flushing pattern, thereby making it possible to detect whether or not a faulty nozzle has occurred from the flushing pattern.

[0081] (Aspect 6) In embodiment 5, the nozzles used in the flushing pattern are set every other nozzle, and the nozzles that perform flushing on the leading edge portion, such as the leading margin portion of the recording medium, and the nozzles that perform flushing on the trailing edge portion, such as the trailing margin portion of the recording medium, are made different from each other. According to this, flushing can be performed for all nozzles by passing one sheet of recording medium, and the presence or absence of nozzle defects can be detected for all nozzles.

[0082] (Aspect 7) In any of the first to sixth aspects, an image correction unit such as an image correction unit 12 is provided that corrects the print image formed on the recording medium based on the defective nozzle identified by the defective nozzle identification control. As a result, as described in the embodiment, the printed image is corrected by an image correction means such as the image correction unit 12, and the nozzles surrounding the defective nozzle are used to complement the defective nozzle, thereby preventing the occurrence of abnormal images caused by the defective nozzle.

[0083] (Aspect 8) In the seventh aspect, the determination means such as the control unit 11 determines to execute the defective nozzle identification control if the number of abnormal locations in the flushing pattern increases after the defective nozzle identification control is executed. This allows for faulty nozzle identification control to be executed when the number of abnormalities in the flushing pattern increases and new nozzle defects occur, forming test patterns at appropriate times and reducing unnecessary liquid consumption. [Explanation of symbols]

[0084] 1: Printer 10: Scanner unit 10a: First in-line sensor 10b: Second in-line sensor 11: Control section 12: Image correction section 13: Storage section 14: Operation panel 20a: First flushing pattern 20b: Second flushing pattern 21: Print image section 31: End mark 32:Start mark 33: Nozzle check line 34: Check lines 35: Nozzle check pattern 230: Liquid ejection head 500: Control section P:Paper [Prior art documents] [Patent documents]

[0085] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-201033

Claims

1. a liquid ejection head having a plurality of nozzles arranged therein and configured to eject liquid onto a recording medium; an image detection means for detecting an image formed on the recording medium; a determination means for performing flushing on at least one of a leading end portion and a trailing end portion in a transport direction of the recording medium, detecting a flushing pattern formed on the recording medium by the flushing with the image detection means, and determining whether or not to execute defective nozzle identification control based on the flushing pattern detected by the image detection means, A liquid ejection device characterized in that the liquid ejection during the flushing is made different from the liquid ejection during the printing operation, and the nozzles to be used in the flushing pattern are set by skipping one or more nozzles.

2. In the device for discharging the liquid according to claim 1, A liquid ejecting device, characterized in that the volume of liquid ejected from the nozzles during the flushing is set to be larger than the volume of liquid ejected during a printing operation.

3. 3. The liquid ejection device according to claim 1, A liquid ejection device, characterized in that the ejection speed of the liquid ejected from the nozzles during the flushing is set to be faster than the ejection speed of the liquid during a printing operation.

4. In an apparatus for discharging a liquid according to any one of claims 1 to 3, Set the nozzles to be used in the flushing pattern every other nozzle, A liquid ejection device, characterized in that a nozzle for flushing the leading end portion of the recording medium and a nozzle for flushing the trailing end portion of the recording medium are different from each other.

5. The liquid ejection device according to any one of claims 1 to 4, a liquid ejection device comprising: an image correction unit that corrects a print image formed on a recording medium based on the defective nozzles identified by the defective nozzle identification control;

6. 6. The liquid ejection device according to claim 5, The liquid ejection device is characterized in that the determination means determines to execute defective nozzle identification control if the number of abnormal locations in the flushing pattern increases after defective nozzle identification control is executed.

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