Inkjet recording device, and abnormal nozzle determination method

Abstract

To provide an inkjet recording device and an abnormal nozzle determination method that are capable of reliably determining an abnormal nozzle causing ink jetting failure, by using a simple configuration, without generating wasteful consumption of recording media such as printing paper.SOLUTION: An inkjet recording device performs: processing (S11) of reading a recording surface of a sheet including a dot image recorded at a plurality of dispersion positions by a dispersion jetting part; and processing (S14) of determining an abnormal nozzle causing ink jetting failure out of a plurality of nozzles, on the basis of a density of dispersion pixels corresponding to the plurality of dispersion positions respectively in the read reading image.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to an inkjet recording apparatus having a plurality of nozzles that eject ink, and a method for determining whether a nozzle is abnormal. [Background technology]

[0002] An inkjet recording device includes a recording head having a plurality of nozzles. In order to prevent clogging of each nozzle in the inkjet recording device, for example, a cleaning process such as flushing, in which a minute amount of ink is ejected from the nozzles while the printing process is not being performed, or wiping, in which the nozzle surface of the recording head is wiped with a cleaning member, is performed.

[0003] Even if the cleaning process is performed, the nozzles may not be cleared of clogging, resulting in poor ink ejection and reduced print quality.

[0004] Conventionally, a printing device has been disclosed in which a printed sheet with an image for checking non-ejection is mixed with multiple printed sheets of an original image in order to check for ejection failure (see Patent Document 1). Also, a method is known in which a laser and a sensor are used to check for the presence or absence of ejection droplets from the nozzles to detect clogged nozzles. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-100800 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, outputting a print sheet on which a non-discharge confirmation image is recorded not only wastes recording media such as printing paper, but also requires the troublesome task of finding the print sheet on which the non-discharge confirmation image is recorded among multiple printed matter. In addition, the above-mentioned detection method using a laser or a sensor increases the number of parts and the size of the device, and also increases the manufacturing cost.

[0007] An object of the present invention is to provide an inkjet recording device and an abnormal nozzle determination method that can reliably determine which nozzle is abnormal and causing ink ejection problems with a simple configuration, without causing unnecessary consumption of recording media such as printing paper. [Means for solving the problem]

[0008] An inkjet recording device according to one aspect of the present invention is an inkjet recording device that ejects ink from a plurality of nozzles onto a sheet to record an image on the sheet. The inkjet recording device includes an image recording processing unit, a dispersed ejection processing unit, an image reading unit, and an abnormal nozzle determination unit. The image recording processing unit performs a process of recording a predetermined image on the sheet in accordance with image data. The dispersed ejection processing unit performs a process of ejecting ink droplets from each of the plurality of nozzles at a plurality of dispersed positions determined on the sheet in parallel with the image recording process by the image recording processing unit. The image reading unit performs a process of reading a recording surface of the sheet including dot images recorded at the plurality of dispersed positions by the dispersed ejection processing unit. The abnormal nozzle determination unit performs a process of determining an abnormal nozzle among the plurality of nozzles that is causing an ink ejection failure based on the density of dispersed pixels corresponding to each of the plurality of dispersed positions in a read image read by the image reading unit.

[0009] An abnormal nozzle determination method according to one aspect of the present invention is a method applied to an inkjet recording apparatus that ejects ink from a plurality of nozzles onto a sheet to record an image on the sheet. The inkjet recording device includes an image recording processing unit that records a predetermined image on the sheet in accordance with image data, and a distributed ejection processing unit that ejects ink droplets from each of the multiple nozzles at multiple distributed positions defined on the sheet in parallel with the image recording processing by the image recording processing unit. The abnormal nozzle determination method includes an image reading step of reading a recording surface of the sheet including dot images recorded at the plurality of distributed positions by the distributed ejection processing unit; and an abnormal nozzle determination step of determining which of the plurality of nozzles is abnormal and causing an ink ejection failure based on the density of dispersed pixels corresponding to each of the plurality of dispersed positions in the read image read by the image reading step, wherein each of the steps is executed by one or more processors. Effect of the Invention

[0010] According to the present invention, it is possible to reliably determine, with a simple configuration, which nozzle is causing an ink ejection failure, without causing unnecessary consumption of recording media such as printing paper. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing the configuration of an inkjet recording apparatus according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing the configuration of an inkjet unit in the inkjet recording apparatus according to the embodiment. [Diagram 3] FIG. 3 is a block diagram of a control device in the inkjet recording apparatus according to the embodiment. [Figure 4] FIG. 4 is a diagram showing a schematic diagram of an example of processing for determining the drawing position and drawing color of a dot image in a dispersed dot ejection process executed by the inkjet recording apparatus according to the embodiment. [Diagram 5] FIG. 5 is a diagram illustrating an example of a printed matter output by the inkjet recording apparatus according to the embodiment. [Figure 6]FIG. 6 is a flowchart showing a first process example of the nozzle state determination process executed by the control device of the inkjet recording apparatus according to this embodiment. [Figure 7] FIG. 7 is a flowchart showing a second processing example of the nozzle state determination processing executed by the control device of the inkjet recording apparatus according to this embodiment. [Figure 8] FIG. 8 is a diagram illustrating another example of a printed matter output by the inkjet recording apparatus according to the embodiment. [Figure 9] FIG. 9 is a flowchart showing a third process example of the nozzle state determination process executed by the control device of the inkjet recording apparatus according to this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the following embodiment is an example of the present invention, and does not limit the technical scope of the present invention.

[0013] [Configuration of the inkjet recording device 10] The inkjet recording device 10 is a printer capable of forming an image on the recording surface of a sheet 9 by an inkjet method. In other words, the inkjet recording device 10 is a recording device that ejects ink droplets from a plurality of nozzles 30B onto the sheet 9 to record an image on the sheet 9. The sheet 9 is a sheet-like image formation medium such as paper or a resin film.

[0014] It should be noted that the inkjet recording device 10 may be a facsimile machine, a copier, a multifunction machine, or the like capable of forming an image on the sheet 9 by the inkjet method.

[0015] As shown in FIG. 1, the inkjet recording device 10 includes a sheet storage section 1, a sheet supply mechanism 2, an inkjet section 3, an ink supply section 4, a conveying device 5, a sheet discharge mechanism 6, a line sensor 8 (an example of an image reading section of the present invention), and a control device 7.

[0016] The sheet storage unit 1 can store a plurality of sheets 9. The sheet supply mechanism 2 supplies the sheets 9 stored in the sheet storage unit 1 one by one to the inkjet unit 3. For example, the sheet supply mechanism 2 includes a pickup roller 21, a pair of transport rollers 22, a sheet supply path 23, a pair of registration rollers 24, a manual feed tray 25, and the like.

[0017] The pickup roller 21 sends out the sheets 9 one by one from the sheet storage unit 1 to the transport roller pair 22. The transport roller pair 22 is composed of a drive roller and a driven roller whose roller surfaces are in pressure contact with each other. The transport roller pair 22 transports the sheet 9 along the sheet supply path 23 to the registration roller pair 24.

[0018] The pair of registration rollers 24 includes a drive roller and a driven roller whose roller surfaces are in pressure contact with each other. The pair of registration rollers 24 sends out the sheet 9 from the sheet supply path 23 to the conveying device 5 in synchronization with the processing of the inkjet unit 3.

[0019] The conveying device 5 conveys the sheet 9 in a predetermined conveying direction D0 while the recording surface (front side) of the sheet 9 faces the inkjet unit 3. The direction perpendicular to the conveying direction D0 is the main scanning direction D1, and the direction along the conveying direction D0 is the sub-scanning direction D2 (see FIGS. 1 and 2).

[0020] The inkjet unit 3 ejects ink of four colors onto a sheet 9 being transported by a transport device 5, thereby forming an image on the recording surface of the sheet 9.

[0021] The transport device 5 is disposed below the inkjet unit 3. The transport device 5 includes a circular transport belt 51, tension rollers 52 to 54, a contact roller 55, and the like.

[0022] The tension rollers 52 to 54 tension the conveyor belt 51. The tension roller 52 is driven to rotate by a motor (not shown). The rotation of the tension roller 52 rotates the conveyor belt 51. The conveyor belt 51 carries the sheet 9 and conveys it in a conveying direction D0. Furthermore, the conveyor belt 51 sends out the sheet 9 on which an image has been formed to a sheet discharge mechanism 6.

[0023] The tension roller 53 is disposed upstream of the inkjet unit 3 in the conveying direction D0. The contact roller 55 is disposed above the tension roller 53 and facing the tension roller 53. The contact roller 55 brings the sheet 9 conveyed from the sheet supply mechanism 2 into close contact with the conveyor belt 51.

[0024] The conveyor device 5 also includes a suction device (not shown) and the like. The suction device sucks air through a large number of through holes formed in the conveyor belt 51, thereby adsorbing the sheet 9 to the conveyor belt 51.

[0025] The sheet discharge mechanism 6 is provided downstream in the conveying direction D0 from the conveying device 5. The sheet discharge mechanism 6 includes a drying device 61, a sheet discharge path 62, a pair of discharge rollers 63, and a discharge tray 64, for example.

[0026] The drying device 61 dries the ink adhering to the sheet 9, for example, by blowing air onto the recording surface of the sheet 9 on which an image is formed. The conveyor belt 51 sends the sheet 9 to a sheet discharge path 62. At that time, the sheet 9 passes through the drying device 61 arranged between the conveyor belt 51 and the sheet discharge path 62.

[0027] The discharge roller pair 63 includes a drive roller and a driven roller whose roller surfaces are in pressure contact with each other. The discharge roller pair 63 discharges the sheet 9 sent to the sheet discharge path 62 onto a discharge tray 64.

[0028] The line sensor 8 reads the recording surface of the sheet 9 including the dot image g1 (see FIG. 5) recorded at a plurality of dispersed positions determined on the recording surface of the sheet 9. The line sensor 8 is provided downstream of the inkjet unit 3 in the conveying direction D0. The line sensor 8 is provided at a position facing the recording surface of the sheet 9 placed on the conveying belt 51. The line sensor 8 extends in the main scanning direction D1 (see FIG. 2). The line sensor 8 receives reflected light of light irradiated on the recording surface of the sheet 9, and outputs an electric signal according to the density of the image formed on the recording surface of the sheet 9. The line sensor 8 may be one that outputs the density of one line of the image along the main scanning direction D1 as the electric signal, or may be one that outputs the density of multiple lines of the image along the main scanning direction D1 as the electric signal. That is, the line sensor 8 may be one in which multiple image sensors are arranged in a row along the main scanning direction D1, or one in which multiple image sensors are arranged in multiple rows along the main scanning direction D1. The electrical signal includes position information of each pixel aligned in the main scanning direction D1 and density information of each pixel.

[0029] [Inkjet section 3] The inkjet unit 3 forms an image on the sheet 9 by ejecting ink onto the sheet 9 transported by the transport device 5. The inkjet unit 3 includes line heads 31, 32, 33, and 34 corresponding to the colors black, cyan, magenta, and yellow, respectively.

[0030] The four line heads 31, 32, 33, and 34 correspond to black, cyan, magenta, and yellow inks, respectively, that is, the four line heads 31, 32, 33, and 34 correspond to inks of different colors.

[0031] The four line heads 31, 32, 33, and 34 are arranged side by side in the sub-scanning direction D2 and are fixed in a predetermined positional relationship (see FIGS. 1 and 2). Note that the number of line heads provided in the inkjet unit 3 may be three or five or more.

[0032] The four line heads 31, 32, 33, and 34 are disposed at positions such that a gap of about 1 mm is formed between the ink output surfaces 30A of the heads and the upper surface of the sheet 9 on the conveyor belt 51.

[0033] 2, the line heads 31 to 34 are arranged with their longitudinal direction aligned along the main scanning direction D1. Each of the line heads 31 to 34 has a plurality of nozzles 30B arranged over an entire effective area in the main scanning direction D1 for a sheet 9 of the maximum size that the sheet storage unit 1 can accommodate.

[0034] In each of the line heads 31 to , the multiple nozzles 30B each eject ink onto a sheet 9 transported in the sub-scanning direction D2, at multiple pixel positions in one line in the main scanning direction D1.

[0035] The effective area of ​​the sheet 9 is the remaining area excluding minimum margin areas of a predetermined width at both ends in the main scanning direction D1 from the entire range of the sheet 9 in the main scanning direction D1. If the width of the minimum margin areas is zero, the entire range of the sheet 9 in the main scanning direction D1 is the effective area.

[0036] 2, each of the line heads 31 to 34 has a plurality of inkjet heads 30. Each of the plurality of inkjet heads 30 has a plurality of nozzles 30B.

[0037] In each inkjet head 30, each of the multiple nozzles 30B ejects ink onto a partial area within the effective area in the main scanning direction D1 on the sheet 9. That is, each of the multiple nozzles 30B provided in each of the line heads 31 to 34 covers a part of the effective area in the main scanning direction D1.

[0038] Each inkjet head 30 also includes a plurality of piezoelectric elements 30C (see FIG. 3) corresponding to the plurality of nozzles 30B. The plurality of piezoelectric elements 30C are operated by a plurality of drive signals Sd0 supplied from the control device 7 to eject ink from each of the plurality of nozzles 30B.

[0039] Specifically, each inkjet head 30 has a plurality of pressure chambers (not shown) corresponding to a plurality of nozzles 30B. Each piezoelectric element 30C pressurizes the ink contained in the pressure chamber by operating. As a result, the ink in the pressure chamber flows into the nozzle 30B and is ejected from the opening of the nozzle 30B toward the sheet 9.

[0040] In each of the line heads 31 to 34, the multiple nozzles 30B each eject ink for one pixel at a time onto different pixel positions in the effective area in the main scanning direction D1.

[0041] For example, each of the line heads 31 to 34 may have 7016 nozzles 30B. In this case, each of the line heads 31 to 34 can eject ink droplets to perform drawing at 7016 positions (drawing positions) for one line in the main scanning direction D1 on the sheet 9. The inkjet unit 3 has 28064 nozzles 30B corresponding to the four colors of ink.

[0042] [Control device 7] 3, the control device 7 includes a main control device 71 and a drive circuit 72. The main control device 71 includes a CPU (Central Processing Unit) 711, a RAM (Random Access Memory) 712, a storage unit 713, and the like.

[0043] The CPU 711 is a processor that executes a program that is stored in advance in the storage unit 713. The CPU 711 executes various types of arithmetic processing, data processing, and control of various types of electric devices that the inkjet recording apparatus 10 includes.

[0044] The RAM 712 is a main storage device that temporarily stores the programs executed by the CPU 711, data output and data referenced in the process of the CPU 711 executing the programs.

[0045] The storage unit 713 is a computer-readable non-volatile data storage device. The storage unit 713 can store programs and various data. For example, a combination of one or both of an SSD (Solid State Drive) and a hard disk drive may be adopted as the storage unit 713. The storage unit 713 stores various control programs, such as a program for causing the control device 7 to execute a nozzle state determination process (see FIG. 6) described below, and various data used in the nozzle state determination process.

[0046] In this embodiment, the CPU 711 included in the control device 7 executes the program to operate as an image output control unit 7111 (an example of an image recording processing unit of the present invention), a dispersed dot output control unit 7112 (an example of a dispersed jetting processing unit of the present invention), and an abnormal nozzle determination unit 7113 (an example of an abnormal nozzle determination unit of the present invention). Note that one or more processors included in the control device 7 may execute the program.

[0047] The image output control unit 7111 executes image output control. That is, the image output control unit 7111 performs an image recording process for recording a predetermined image on the sheet 9 according to the image data to be printed. The image output control is a process for controlling the amount of ink ejected from each of the multiple nozzles 30B according to multiple pixel values ​​included in the image data.

[0048] The image output control unit 7111 sets a plurality of gradation levels corresponding to the plurality of nozzles 30B according to the plurality of pixel values ​​included in the image data.

[0049] The plurality of gradation levels correspond to a plurality of stages of ink ejection amounts corresponding to each nozzle 30 B. Note that one of the plurality of gradation levels represents no ink ejection.

[0050] Furthermore, the image output control unit 7111 outputs a control signal Sc0 representing the multiple gradation levels to the drive circuit 72 through an I / O port 711x of the CPU 711. The I / O port 711x is a signal input / output interface device.

[0051] The drive circuit 72 outputs a plurality of drive signals Sd0 to the plurality of piezoelectric elements 30C in accordance with the control signal Sc0. At this time, the drive circuit 72 performs PWM (Pulse Width Modulation) control of the plurality of drive signals Sd0 in accordance with the gradation level represented by the control signal Sc0. As a result, the drive circuit 72 controls the amount of ink ejected from the plurality of nozzles by the PWM control.

[0052] Incidentally, in order to prevent clogging of each nozzle 30B, the inkjet recording device 10 may perform cleaning processes such as the flushing process in which a preset amount of ink is ejected from the nozzle 30B when no printing process is being performed, or a wiping process in which the nozzle surface of the inkjet head 30 is wiped with a cleaning member.

[0053] Even if the cleaning process is performed, clogging of the nozzle 30B may not be eliminated, resulting in ink ejection failure and a decrease in print quality. Here, the ink ejection failure refers to an abnormal state in which the nozzle 30B is clogged, and therefore no ink is ejected at all, or the amount of ink ejected is less than the reference amount, resulting in a decrease in print quality. In order to check for the ink ejection failure in the nozzle 30B, a printing device is known in which a printed sheet of an image for confirming ejection failure is mixed with multiple printed sheets of the original image. Also, a method is known in which a clogged nozzle 30B is detected by checking the presence or absence of ejected droplets from the nozzle 30B using a laser and a sensor.

[0054] However, the conventional method of outputting a print sheet on which a non-ejection confirmation image is recorded in order to detect the abnormal nozzle 30B where the ink ejection failure is occurring not only wastes recording media such as printing paper, but also forces the user to go through the troublesome task of searching for the print sheet with the non-ejection confirmation image from among multiple printed matter. In addition, the above-mentioned detection method using a laser or a sensor increases the number of parts and the size of the device, and also increases the manufacturing cost.

[0055] In this embodiment, the control device 7 executes the nozzle status determination process (see FIG. 6) described below, making it possible to reliably determine which nozzles are abnormal and causing ink ejection problems using a simple configuration, without wasting recording media such as printing paper.

[0056] The dispersed dot output control unit 7112 executes dispersed dot ejection processing in parallel with the control of the image recording processing (image output control) by the image output control unit 7111. The dispersed dot ejection processing is processing for ejecting a predetermined amount of ink droplets from each of the plurality of nozzles 30B onto a plurality of dispersed positions determined on the recording surface of the sheet 9, thereby forming a plurality of dot images g1 (see FIG. 5) on the sheet 9. The dot images g1 have a size that can be read by the line sensor 8, for example.

[0057] In this embodiment, when the image output control unit 7111 performs a process of recording the predetermined image on one sheet 9, the dispersed dot output control unit 7112 forms the dot image g1 at each of the plurality of dispersed positions determined across the single sheet 9. Also, when the image output control unit 7111 performs a process of recording the predetermined image on multiple sheets 9, the dispersed dot output control unit 7112 forms the dot image g1 at each of the plurality of dispersed positions determined across the multiple sheets 9.

[0058] Furthermore, in this embodiment, whether the specified image is recorded on one sheet 9 or on multiple sheets 9, the dispersed dot output control unit 7112 ejects ink droplets from all nozzles 30B to form the dot image g1 on the recording surface of the sheet 9.

[0059] Furthermore, in this embodiment, the multiple dispersion positions are determined in non-image recording areas on the sheet 9 where the predetermined image is not recorded. For example, if the image data is text data and the predetermined image is characters, the non-image recording areas are areas on the sheet 9 other than the characters (background areas). Also, if the image data is image data and the predetermined image is a photographic image or a solid image, the non-image recording areas are areas on the sheet 9 where the photograph or solid image is located (background areas).

[0060] The plurality of dispersion positions determined on the recording surface of the sheet 9 will be described later.

[0061] The abnormal nozzle determination unit 7113 performs a process of determining which of the plurality of nozzles 30B is an abnormal nozzle causing the ink ejection failure based on the density of a plurality of detection target pixels in the read image read by the line sensor 8. Here, the detection target pixels are pixels corresponding to the plurality of dispersed positions in the read image, and are pixels corresponding to the positions where the dot image g1 is depicted. If all the nozzles 30B are normal, the density corresponding to the dot image g1 appears in the plurality of detection target pixels. On the other hand, if one nozzle 30B is causing the ink ejection failure, the density corresponding to the dot image g1 does not appear in the detection target pixel corresponding to the nozzle 30B, and the density of the background color of the sheet 9 or a different density appears. The density in the detection target pixel is detected based on the electrical signal output from the line sensor 8. The detection target pixel in the read image corresponds to the dispersed pixel of the present invention.

[0062] In this embodiment, when the density of the detection target pixel is less than a predetermined threshold, the abnormal nozzle determination unit 7113 determines that the nozzle 30B corresponding to the detection target pixel is the abnormal nozzle. That is, the abnormal nozzle determination unit 7113 determines whether the density of the detection target pixel (hereinafter referred to as the detection density) is less than the threshold, and determines that the nozzle 30B corresponding to a low-density detection target pixel (hereinafter referred to as a low-density pixel) whose detection density is determined to be less than the threshold is the abnormal nozzle. The threshold is set to a value that can be evaluated as indicating that ink is not being ejected from the nozzle 30B, or a value that can be evaluated as indicating that a reference amount of ink is not being ejected from the nozzle 30B.

[0063] The abnormal nozzle determination unit 7113 determines whether or not each of the nozzles 30B corresponding to the plurality of dispersed positions is an abnormal nozzle. As will be described later, pixel position information (line count value LC0 and target element number EO, ​​which will be described later) indicating the plurality of dispersed positions is stored in the memory unit 713 when the dispersed dot ejection process is executed by the dispersed dot output control unit 7112. Therefore, the abnormal nozzle determination unit 7113 can refer to the pixel position information stored in the memory unit 713 to identify the plurality of dispersed positions, and further identify the nozzle 30B corresponding to the dispersed positions.

[0064] Furthermore, the dispersed dot output control unit 7112 may, for example, eject ink droplets multiple times from each of the multiple nozzles 30B at the multiple dispersed positions. In this case, the abnormal nozzle determination unit 7113 may determine whether the detection density of the detection target pixel is less than the threshold value, and determine that the nozzle 30B corresponding to the detection target pixel is the abnormal nozzle when the number of times that the detection density is determined to be less than the threshold value (low density determination number) reaches a predetermined set number of times.

[0065] Furthermore, the plurality of detection target pixels in the read image may include, for example, first dispersed pixels corresponding to the dispersed positions determined in an image recording area on the sheet 9 where a predetermined image is recorded, and second dispersed pixels corresponding to the dispersed positions determined in a non-image recording area on the sheet 9 where a predetermined image is not recorded. The first dispersed pixels are pixels corresponding to pixel positions in the read image where a dot image g2 (described later) is drawn. The second dispersed pixels are pixels corresponding to pixel positions in the read image where a dot image g1 (described later) is drawn.

[0066] In this case, the abnormal nozzle determination unit 7113 may determine that the nozzle corresponding to the first variance pixel is the abnormal nozzle when the density of the first variance pixel differs from the density of the corresponding pixel in the specified image. Also, the abnormal nozzle determination unit 7113 may determine that the nozzle corresponding to the second variance pixel is the abnormal nozzle when the density of the second variance pixel is less than a predetermined threshold value.

[0067] Below, we will explain a specific example of the dispersed dot ejection process by the dispersed dot output control unit 7112. The dispersed dot ejection process includes a dispersed position setting process that determines the multiple dispersed positions at which the dot image g1 is ejected onto the recording surface of the sheet 9, and a non-image output process that forms the dot image g1 at the multiple dispersed positions on the sheet 9.

[0068] [Dispersed dot blasting processing] The dispersed dot output control unit 7112 includes a unit line number setting unit 711c, a line identification value setting unit 711d, a color identification value setting unit 711e, an element number specification unit 711f, and a non-image output control unit 711g (see FIG. 3). In this embodiment, the dispersed position setting process is performed by the unit line number setting unit 711c, the line identification value setting unit 711d, the color identification value setting unit 711e, and the element number specification unit 711f. Also, the non-image output process is performed by the non-image output control unit 711g.

[0069] In the following description, it is assumed that the number of nozzles 30B in each of the line heads 31, 32, 33, 34 is L (hereinafter, may be referred to as the nozzle number L), and the number of the line heads 31, 32, 33, 34 is M (hereinafter, may be referred to as the head number M). For example, it is considered that the nozzle number L=7016. In this embodiment, the head number M=4. The number of line heads 31, 32, 33, 34 (head number M) is also the number of ink colors.

[0070] Furthermore, in the following description, the state before the image output control corresponding to one page of the sheet 9 by the image output control unit 7111 is started is referred to as "before page printing is started."

[0071] The unit line number setting section 711c sets the number of lines N (hereinafter sometimes referred to as the number of lines N) in accordance with a predetermined setting rule before the page printing starts. The number of lines N is equal to or less than 1 / M of the total number of lines in the sub-scanning direction D2 corresponding to the image recording area on one page of sheet 9. In the following description, it is assumed that the number of lines N is 1 / K of the total number of lines in the sub-scanning direction D2 corresponding to the image recording area. Usually, the number of lines N is smaller than the number of nozzles L.

[0072] For example, the unit line number setting section 711c may set the quotient obtained by dividing the total number of lines in the sub-scanning direction D2 corresponding to the image recording area by M or an integer multiple of M as the number of lines N.

[0073] For example, if the resolution of each of the line heads 31, 32, 33, and 34 is 600 dpi and an A4 size sheet 9 is transported landscape, the number of nozzles L=7016 (≈600×297 / 25.4), and the total number of lines in the sub-scanning direction D2 in the image recording area of ​​the sheet 9 is 4961 (≈600×210 / 25.4) lines. Also, in this embodiment, M=4. In this case, if K=M, the unit line number setting unit 711c sets the number of lines N to 1240 (≈4961 / 4).

[0074] In the following description, an area of ​​N lines from the leading edge of the image recording area of ​​one page of sheet 9 in the sub-scanning direction D2 is referred to as a band area. K=4 means that the image recording area is divided into four band areas.

[0075] Fig. 4 is a diagram showing an example of a process for determining the dispersed positions and the drawing colors at which the dot image g1 is drawn by the dispersed dot ejection process. In Fig. 4, B1 indicates the first band area from the leading edge side in the sub-scanning direction D2 in the image recording area of ​​one page of sheet 9, and B2 indicates the second band area from the leading edge side in the sub-scanning direction D2 in the image recording area.

[0076] Before the page printing starts, the line identification value setting unit 711d distributes and sets N-level line identification values ​​for identifying the N lines to the L elements of the first array variable ARY1[i] in accordance with a first distribution rule that is determined in advance, where i is an integer variable ranging from 0 to (L-1). That is, the first array variable ARY1[i] is an array variable having L elements.

[0077] For example, when the number of lines N is 1240, the line identification value setting unit 711d distributes and sets the line identification values ​​0 to 1239 to ARY1[0] to ARY1

[1239] . The line identification value setting unit 711d sets one of the N levels of line identification values ​​to all elements of the first array variable ARY1[i].

[0078] Here, a variable that identifies L elements is i, the i-th element in the first array variable is ARY1[i], and a predetermined integer constant smaller than L is C. The variable i is an integer ranging from 0 to (L-1). It is preferable that the constant C is not a divisor of L.

[0079] Moreover, ARY1[i-1] when i=0 is a positive integer. For example, it is considered that ARY1[i-1] when i=0 is a constant. Furthermore, it is assumed that the random integer number set by the line identification value setting unit 711d each time the variable i changes is R. The random number R changes within a predetermined range and is an integer that is sufficiently smaller than the constant C. For example, it is considered that the range of the random number R is about 1 / 100 of N.

[0080] For example, the first distribution rule may be a rule that sets N levels of line identification values ​​in a first array variable ARY1[i] based on the following formula (1).

number

[0081] Equation (1) indicates a rule that the remainder obtained by dividing the sum of ARY1[i-1], a constant C, and a random number R by N is set to ARY1[i]. Note that the function MOD (argument) in equation (1) is a function that calculates the remainder of the division equation set as an argument. Also, N in equation (1) is the number of lines N set by the unit line number setting unit 711c.

[0082] For the sake of convenience, Fig. 4 shows an example in which the number of nozzles L = 700, the number of heads M = 4, and the number of lines N = 100 is set by the unit line number setting unit 711c. Fig. 4 shows an example in which 100 levels of the line identification values ​​0 to 99 are distributed and set to 700 elements of the first array variable ARY1[i].

[0083] When the number of nozzles L=700 and the number of lines N=100, the line identification values ​​0 to 99 in 100 stages are distributed and set in groups of 7 across 700 elements of the first array variable ARY1[i]. Note that in Fig. 4, some of the elements of the first array variable ARY1[i] are omitted.

[0084] The color identification value setting unit 711e, at least before the start of printing the page, distributes and sets M-level color identification values ​​to the L elements of the second array variable ARY2[i] in accordance with a predetermined second distribution rule.

[0085] In this embodiment, the color identification values ​​are integers ranging from 0 to 3. In the example shown in Figure 4, the color identification values ​​0, 1, 2, and 3 indicate cyan, magenta, yellow, and black, respectively.

[0086] For example, the second distribution rule may be a circulation rule in which the color identification value changes by one step depending on the element number of the second array variable ARY2[i] and circulates in M ​​steps, and is set to the L elements of the second array variable ARY2[i].

[0087] For example, if the initial value of the color identification value is previously determined to be 0, the color identification value setting unit 711e sets the color identification values ​​circulating as 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, . . . to the second array variables ARY2[0] to ARY2[L-1].

[0088] The second distribution rule may be a rule obtained by adding the following shift rule to the circulation rule: The shift rule shifts the color identification value corresponding to the element number of the second array variable ARY2[i] by a predetermined step each time the image output control unit 7111 executes the image output control for N lines.

[0089] For example, the shift rule may be a rule that shifts the color identification value by one step every time the image output control for N lines is executed.

[0090] Fig. 4 shows two types of second array variables ARY2[i] set corresponding to the first band area B1 and the second band area B2. The example shown in Fig. 4 is an example in which the second distribution rule in which the rotation rule and the shift rule are combined is adopted.

[0091] The element number specification unit 711f specifies one or more target element numbers E0 from among all the element numbers in the first array variable ARY1[i] before the image output control for one line is started each time the image output control unit 7111 executes the image output control for one line. The pixel positions specified by the target element numbers E0 correspond to the dispersion positions where the dot images g1 are depicted.

[0092] The target element number E0 is the number of all elements in the first array variable ARY1[i] for which the line identification value equal to the line count value LC0 is set. In other words, the target element number E0 is i when ARY1[i]=LC0.

[0093] The line count value LC0 is a variable value that circulates in N stages. Each time the image output control for one line is executed, the element number identification unit 711f counts up the line count value LC0 by one before the image output control is started. However, the element number identification unit 711f initializes the line count value LC0 without counting up each time the image output control for N lines is completed, that is, each time the image output control for one of the band areas is completed. Note that the line count value LC0 that identifies the position of the line in the image recording area and the target element number EO in the line identified by the line count value LC0 are stored in the storage unit 713 as the pixel position information that identifies the dispersion position before the line count value LC0 is initialized.

[0094] In the example shown in FIG. 4, the element number identification unit 711f identifies, for each band region, the element number 4 at which ARY1[i]=LC0=0, as the target element number E0 when the line count value LC0=0.

[0095] Similarly, in the example shown in FIG. 4, when the line count value LC0=1, 2, 3, 4, 5, 6, 7, . . . , the element number determination unit 711f determines 0, 6,698, 693, 696, 2,699, . . . as the target element numbers E0 for each band region.

[0096] The non-image output control unit 711g executes the non-image output processing each time the image output control for one line is executed by the image output control unit 7111 from the start to the end of the image output control for one page of sheet 9 by the image output control unit 7111.

[0097] The non-image output process ejects the predetermined amount of ink sequentially from one or more nozzles 30B corresponding to the pixel position in the main scanning direction D1 corresponding to the target element number E0 (i.e., the dispersion position) and the color corresponding to the color identification value set for the element of the target element number E0 in the second array variable ARY2[i] among the multiple nozzles 30B. As a result, if the corresponding nozzle 30B is normal, a dot image g1 is formed on the recording surface of the sheet 9 at a position corresponding to the dispersion position in the image recording area of ​​the sheet 9.

[0098] For example, the predetermined amount may be an amount of ink that corresponds to the lowest level or the second or third lowest level among the plurality of gradation levels. The predetermined amount may also be set individually for each ink color. The predetermined amount may be any amount of ink that can form a dot image that can be read by the line sensor 8.

[0099] In FIG. 4, a plurality of squares indicate pixel positions in the image recording area, and C, M, Y, and K written in the plurality of squares indicate the ink colors cyan, magenta, yellow, and black.

[0100] In the example shown in Figure 4, when image output is performed on the 0th line (LC0 = 0) of the first band area B1, the non-image output control unit 711g ejects the specified amount of ink from nozzle 30B of the line head 32 corresponding to the 4th pixel position (dispersion position) in the main scanning direction D1 corresponding to the target element number E0 (= 4) and the cyan ink corresponding to the color identification value (= 0) set in the element of the target element number E0 (= 4) in the second array variable ARY2 [i].

[0101] Similarly, in the example shown in Figure 4, when image output of the second line (LC0 = 2) of the first band area B1 is performed, the non-image output control unit 711g ejects the specified amount of ink from nozzle 30B of the line head 34 corresponding to the sixth pixel position (dispersion position) in the main scanning direction D1 corresponding to the target element number E0 (= 6) and the yellow ink corresponding to the color identification value (= 2) set in the element of the target element number E0 (= 6) in the second array variable ARY2 [i].

[0102] However, if the image output control unit 7111 and the non-image output control unit 711g overlap in controlling the ejection of ink from the same nozzle 30B at the same time, the image output control unit 7111 will have priority in ejecting ink from nozzle 30B, and the non-image output control unit 711g will not control the ejection of ink to the dispersion position for that nozzle 30B.

[0103] In this embodiment, the image output control and the dispersed dot ejection process are executed in parallel to obtain a printed matter P1 as shown in Fig. 5. The printed matter P1 is a sheet 9 having an image g0 to be printed and a plurality of dot images g1 unrelated to the image g0 formed on its recording surface.

[0104] The image g0 is formed on the recording surface of the sheet 9 by the image output control, and the multiple dot images g1 are formed on the recording surface of the sheet 9 by the dispersed dot ejection process. Note that, in Fig. 5, a character is shown as an example of the image g0. Also, in the printed matter P1 shown in Fig. 5, the multiple dot images g1 are formed dispersedly over a wide range in the image recording area of ​​the sheet 9.

[0105] A part of the printed matter P1 is shown enlarged in Fig. 5. Although Fig. 5 is a monochrome diagram, a four-color dot image g1 is formed evenly on the sheet 9.

[0106] Meanwhile, in the dispersed dot ejection process of this embodiment, the first array variable ARY1[i] and the second array variable ARY2[i], each having L elements, are stored in the RAM 712 when the dispersed dot ejection process is performed. In addition, several other variables are also stored in the RAM 712 when the dispersed dot ejection process is performed.

[0107] That is, in the dispersed dot ejection process, the RAM 712 only needs to store variable data (variable data) of a number equivalent to the number of pixels for two lines along the main scanning direction D1, and data for a small number of other variables.

[0108] In this embodiment, each time the image output control for one line is executed, the line count value LC0 that identifies the position of the line in the image recording area and the target element number EO in the line identified by the line count value LC0 are stored in the storage unit 713 as the pixel position information that identifies the dispersion position. That is, even if the line count value LC0 temporarily stored in the RAM 712 is initialized, the pixel position information including the line count value LC0 is saved in the storage unit 713. Therefore, even if the variable data in the RAM 712 is overwritten with other variable data each time the image output control for one line is executed, the pixel position information that identifies the dispersion position for each line is stored in the storage unit 713.

[0109] The line count value LC0 and the target element number EO in the line specified by the line count value LC0 can also be said to be the pixel position information for specifying the pixel positions at which the dot image g1 is drawn by the non-image output process when the image output control for one line is executed. Therefore, if the pixel position information for each line is stored in the memory unit 713, the CPU 711 can refer to the pixel position information in the memory unit 713 to specify the dispersed positions at which the dot image g1 is drawn in the image recording area of ​​the sheet 9.

[0110] In addition, correspondence data that specifies the correspondence between the positions of all pixels in the image recording area of ​​the sheet 9 and all nozzles 30B may be stored in the memory unit 713, and the dispersion positions specified by the line count value LC0 and the target element number EO may be registered in the correspondence data.

[0111] Furthermore, when the number of lines N in the band region is set to about 1000, the line identification value, which is each element of the first array variable ARY1[i], can be represented by 10-bit data. Furthermore, when there are four ink colors, the color identification value, which is each element of the second array variable ARY2[i], can be represented by 2-bit data. That is, in the data of the number of variables equivalent to the number of pixels for the two lines, the data size of each variable is small.

[0112] With the inkjet recording device 10 configured in this manner, when the dispersed dot ejection process is performed in parallel with the image output control by the image output control unit 7111, it is possible to suppress memory usage while dispersing a large number of dot images g1 over a wide area of ​​the sheet 9.

[0113] In addition, by using formula (1) to calculate ARY1[i], two pixel positions (dispersed positions) corresponding to two adjacent pixel positions in the main scanning direction D1 are set apart by the number of lines calculated by C + R. This contributes to the dispersion of the dispersed positions where multiple dot images g1 are drawn.

[0114] Furthermore, if the dispersed positions at which the multiple dot images g1 are drawn are set regularly at regular intervals, the multiple dot images g1 may form a regular pattern. In this embodiment, in formula (1), the interval between the two pixel positions (dispersed positions) is set using a random number R. This makes it possible to prevent the multiple dot images g1 from forming a regular pattern.

[0115] It is also possible that the shift rule is not adopted in the second dispersion rule of the dispersed dot ejection process, For example, the circulation rule is adopted as the second dispersion rule.

[0116] Moreover, it is considered that the first dispersion rule of the dispersed dot ejection process is a rule that sets the line identification values ​​of N stages in a first array variable ARY1[i] based on the following formula (2).

number

[0117] Equation (2) represents a rule that sets ARY1[i] to the remainder obtained by dividing the sum of ARY1[i-1] and a constant C by the number of lines N. In equation (2), the constant C is a predetermined integer constant smaller than the number of nozzles L. It is preferable that the constant C is not a divisor of the number of nozzles L.

[0118] Also, in formula (2), ARY1[i-1] is a positive integer when i = 0. For example, ARY1[i-1] when i = 0 may be a random integer number set by the line identification value setting unit 711d before the start of page printing.

[0119] In the dispersed dot ejection process, a process may be adopted in which the drawing positions (dispersed positions) of the dot image g1 by a large number of nozzles 30B are mapped for each page of the sheet 9 as a method different from that of the present embodiment. In this case, it is necessary to specify in advance the correspondence between the positions of all pixels on one page of the sheet 9 and all the nozzles 30B, and to store in the storage unit 713 the drawing positions (dispersed positions) of the dot image g1 by each nozzle 30B.

[0120] [Nozzle status determination process] 6 to 9, an abnormal nozzle determination method executed by the control device 7 of the inkjet recording apparatus 10 will be described along with an example of the procedure of the nozzle state determination process executed by the control device 7. The present invention can be understood as an invention of a method for executing one or more steps included in the nozzle state determination process.

[0121] One or more steps included in the nozzle state determination process described below may be omitted as appropriate. Furthermore, the steps in the nozzle state determination process may be performed in a different order as long as the same operational effect is achieved.

[0122] The nozzle state determination process is mainly executed by the CPU 711 of the control device 7. For example, the nozzle state determination process is executed by the CPU 711 executing a control program stored in the storage unit 713 or the like.

[0123] In the following description, it is assumed that a print instruction is input to the inkjet recording apparatus 10, and that the image output control by the image output control unit 7111 and the dispersed dot ejection process by the dispersed dot output control unit 7112 are executed in parallel.

[0124] [First processing example] Hereinafter, the procedure of the first processing example of the nozzle state determination process will be described with reference to the flowchart in FIG.

[0125] First, in step S11, CPU 711 causes line sensor 8 to read an image of the recording surface of sheet 9, and acquires a read image of the recording surface of sheet 9. Line sensor 8 reads the image of the reading surface of sheet 9 line by line, and the read images are sequentially stored in storage unit 713. Note that step S11 is an example of an image reading step of the present invention.

[0126] In the next step S12, the CPU 711 refers to the pixel position information in the storage unit 713 and specifies the drawing positions (the dispersion positions) on the recording surface of the sheet 9 at which the dot image g1 is to be drawn.

[0127] In the next step S13, the CPU 711 determines whether a specific position (hereinafter referred to as a detection target position) corresponding to the distribution position identified in step S12 is included in a plurality of pixel positions in the image of a specific line portion in the read image, and if the detection target position is included, obtains the density (the detection density) of the drawing pixel (the detection target pixel) at the detection target position in the read image from the read image. Note that if the detection target position is not included in the plurality of pixel positions, the CPU 711 proceeds to step S16 and performs the processes from step S16 onward.

[0128] In the next step S14, the CPU 711 determines whether the detected density acquired in step S13 is less than a predetermined threshold value. If it is determined in step S14 that the detected density is less than the threshold value, the CPU 711 determines that the nozzle 30B corresponding to the detection target pixel (low density pixel) or the detection target position for which the detected density is determined to be less than the threshold value is an abnormal nozzle causing the ink ejection failure. On the other hand, if it is determined that the detected density is equal to or greater than the threshold value, the CPU 711 determines that the nozzle 30B corresponding to the detection target pixel or the detection target position is a normal nozzle causing no ink ejection failure. Note that step S14 is an example of an abnormal nozzle determination step of the present invention.

[0129] If it is determined in step S14 that the detected concentration is less than the threshold value, the CPU 711 stores in the memory unit 713 the position information of the nozzle 30B determined to be the abnormal nozzle, as well as error information indicating that the nozzle 30B is in an abnormal state (S15). Note that the position information of the abnormal nozzle can be identified from the pixel position information.

[0130] In the next step S16, the CPU 711 determines whether or not there is a read image of a next line for which the nozzle state has not yet been determined in the read image. If it is determined in step S16 that there is a next line, the CPU 711 proceeds to step S13 and performs the processes in and after step S13. On the other hand, if it is determined in step S16 that there is no next line, the CPU 711 proceeds to the next step S17.

[0131] In step S17, if it is determined that there is no next page to be printed and printing is completed, the CPU 711 reads out the error information stored in the memory unit 713 and outputs the error information as a nozzle status determination result to the display unit of the inkjet recording device 10, or to another terminal device or server device connected to the inkjet recording device 10 so as to be able to communicate with the inkjet recording device 10.

[0132] As described above, in an embodiment of the present invention, the nozzle state determination process shown in FIG. 6 is performed, making it possible to reliably determine which nozzle is abnormal and causing ink ejection problems using a simple configuration, without causing unnecessary consumption of recording media such as printing paper.

[0133] [Second processing example] Next, the procedure of a second processing example of the nozzle state determination process will be described with reference to the flowchart of Fig. 7. This second processing example is applied, for example, when ink droplets are ejected multiple times from each of the multiple nozzles 30B to the multiple dispersed positions by a dispersed ejection process performed by the dispersed dot output control unit 7112. Note that in the second processing example, the same procedures as those in the first processing example are indicated by the step numbers used in the first processing example, and descriptions of the corresponding procedures will be omitted.

[0134] When the processes from step S11 to step S14 are performed, if the detected concentration is determined to be less than the threshold in step S14, the CPU 711 performs the process of step S141. If the detected concentration is determined to be abnormal in step S14, the CPU 711 proceeds to step S16 and performs the processes from step S16 onward.

[0135] In step S141, the CPU 711 counts the number of times the detected density is determined to be less than the threshold value (the number of low density determinations) for one nozzle 30B. The number of low density determinations is linked to the nozzle 30B corresponding to the low density pixel whose detected density is determined to be less than the threshold value, and is stored in the memory unit 713. The nozzle 30B corresponding to the low density pixel can be considered a candidate for an abnormal nozzle that may be experiencing ink ejection problems.

[0136] In the next step S142, the CPU 711 determines whether the accumulated value of the low density determination count is equal to or greater than a predetermined set count. For example, if the number of times ink droplets are ejected from the nozzle 30B by the dispersed ejection process is set to N (N is a natural number equal to or greater than 2), the set count is set to a natural number equal to or greater than 2 and equal to or less than N.

[0137] If it is determined that the integrated value of the low density determination count is equal to or greater than the set count, the CPU 711 determines that the nozzle 30B corresponding to the low density pixel is an abnormal nozzle. In this case, in step S15, the CPU 711 stores in the memory unit 713 the position information of the nozzle 30B determined to be the abnormal nozzle, as well as error information indicating that the nozzle 30B is in an abnormal state. The CPU 711 then performs the processes from step S16 onward.

[0138] In this way, when the accumulated value of the number of low-density judgments is equal to or greater than the set number, the nozzle 30B corresponding to the low-density pixel is judged to be an abnormal nozzle, thereby reducing the chance of the nozzle being mistakenly judged to be an abnormal nozzle and making it possible to more reliably determine whether or not there is an abnormal nozzle.

[0139] [Third processing example] Next, the procedure of the third processing example of the setting screen display process will be described with reference to the flowchart of Fig. 9. In the third processing example, the same procedures as those in the first and second processing examples are indicated by the step numbers used in the first and second processing examples, and the description of the corresponding procedures will be omitted.

[0140] The third processing example is applied when the control of ejecting ink from the same nozzle 30B at the same time overlaps in the image output control unit 7111 and the non-image output control unit 711g, and not only the image recording process by the image output control unit 7111 but also the ejection process to the dispersed positions by the non-image output control unit 711g is performed. In this case, the printed matter P2 as shown in FIG. 8 is obtained. The printed matter P2 is a sheet 9 on whose recording surface are formed an image g0 to be printed, a plurality of dot images g1 unrelated to the image g0, and a plurality of dot images g1 on the image g0 unrelated to the image g0. The printed matter P2 differs from the printed matter P1 in that the dot image g2 is included, and the other parts are the same as the printed matter P1.

[0141] 9, when the processes of steps S11 to S13 are performed, the CPU 711 judges whether or not the rendering pixel (the detection target pixel) at the detection target position is on the image g0 to be printed (S131). For example, the CPU 711 acquires position information specified from the pixel position information stored in the memory unit 713, acquires the density (hereinafter referred to as the comparison target density) of a pixel (hereinafter referred to as the comparison target pixel) on the image data of the image g0 corresponding to the position information, and then judges whether or not the detection target pixel is on the image g0 based on the density.

[0142] If it is determined in step S131 that the detection target pixel is not on image g0, the CPU 711 proceeds to step S14, and executes the processes from step S14 onwards.

[0143] On the other hand, if it is determined in step S131 that the detection target pixel is on the image g0, the CPU 711 proceeds to step S132 and determines whether or not the density (detection density) of the drawn pixel (the detection target pixel) at the detection target position in the read image is different from the comparison target density. Note that the CPU 711 determines that the detection density is different from the comparison target density, for example, when the difference between the detection density and the comparison target density exceeds a predetermined allowable value. Note that in this embodiment, an example in which densities are compared will be described, but for example, in step S132, the CPU 711 may compare the color of the detection target pixel with the color of the comparison target pixel to determine whether the colors of these pixels are different. Also, the CPU 711 may determine whether both the density and color of each pixel are different.

[0144] If it is determined in step S132 that the detected density is not different from the comparison density, the CPU 711 determines that the nozzle 30B corresponding to the detection pixel or the detection position is a normal nozzle that is not experiencing an ink ejection failure. Then, the CPU 711 performs the process from step S16 onwards.

[0145] On the other hand, if it is determined in step S132 that the detected density is different from the comparison density, the CPU 711 determines that the nozzle 30B corresponding to the detection pixel or detection position where the detected density is determined to be different from the comparison density is the abnormal nozzle causing the ink ejection failure.Then, the CPU 711 executes the process from step S15 onwards.

[0146] In this way, by performing different judgment processes depending on whether the detection target pixel is on image g0 or not, it is possible to more reliably determine whether or not there is an abnormal nozzle, even if the detection target pixel is on image g0.

[0147] In the above-described embodiment, when a sheet shorter than the length of each of the line heads 31, 32, 33, and 34 in the main scanning direction D1 is transported, for example, a moving mechanism capable of moving the sheet in the main scanning direction D1 may be installed in the inkjet recording device 10, and the sheet may be moved in the main scanning direction D1 by the moving mechanism, so that ink droplets are ejected from all of the nozzles 30B by a dispersed ejection process by the dispersed dot output control unit 7112 during one printing operation.

[0148] It should be noted that one or more steps of each processing example in the above-described embodiment can be applied to other processing examples within the scope of having similar functions.

[0149] [Notes on the invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0150] <Appendix 1> An inkjet recording apparatus that ejects ink from a plurality of nozzles onto a sheet to record an image on the sheet, an image recording processing unit that records a predetermined image on the sheet in accordance with image data; a dispersion ejection processing unit that ejects ink droplets from each of the plurality of nozzles onto a plurality of dispersion positions determined on the sheet in parallel with the image recording processing by the image recording processing unit; an image reading unit that reads a recording surface of the sheet including a dot image recorded at the plurality of dispersed positions by the dispersed ejection processing unit; an abnormal nozzle determination unit that determines which of the plurality of nozzles is abnormal and experiencing ink ejection problems based on the density of dispersed pixels corresponding to each of the plurality of dispersed positions in a read image read by the image reading unit.

[0151] <Appendix 2> When the image recording processing unit performs a process of recording the predetermined image on a plurality of sheets, 2. The inkjet recording apparatus according to claim 1, wherein the plurality of dispersion positions are determined across the plurality of sheets.

[0152] <Appendix 3> the plurality of dispersion positions are determined in a non-image recording area on the sheet where the predetermined image is not recorded, 3. The inkjet recording apparatus according to claim 1, wherein the abnormal nozzle determination unit determines that the nozzle corresponding to the dispersed pixel is the abnormal nozzle when the density of the dispersed pixel is less than a predetermined threshold value.

[0153] <Appendix 4> the dispersed ejection processing unit ejects ink droplets from each of the plurality of nozzles at the plurality of dispersed positions a plurality of times; The inkjet recording device of claim 3, wherein the abnormal nozzle determination unit determines whether the density of the dispersed pixel is less than a predetermined threshold value, and when the number of times that the density is determined to be less than the threshold value reaches a predetermined set number of times, determines that the nozzle corresponding to the dispersed pixel is the abnormal nozzle.

[0154] <Appendix 5> the dispersed pixels include first dispersed pixels corresponding to the dispersed positions defined in an image recording area on the sheet where the predetermined image is recorded, and second dispersed pixels corresponding to the dispersed positions defined in a non-image recording area on the sheet where the predetermined image is not recorded, The abnormal nozzle determination unit When a density of the first variance pixel is different from a density of a drawing pixel of the predetermined image, the nozzle corresponding to the first variance pixel is determined to be the abnormal nozzle; 5. The inkjet recording apparatus according to claim 1, wherein, when a density of the second dispersed pixel is less than a predetermined threshold, the nozzle corresponding to the second dispersed pixel is determined to be the abnormal nozzle.

[0155] <Appendix 6> 1. A method for determining an abnormal nozzle that is applied to an inkjet recording device that ejects ink onto a sheet from a plurality of nozzles to record an image on the sheet, comprising: the inkjet recording apparatus includes an image recording processing unit that records a predetermined image on the sheet in accordance with image data, and a distributed ejection processing unit that ejects ink droplets from each of the plurality of nozzles at a plurality of distributed positions determined on the sheet in parallel with the image recording processing by the image recording processing unit; The abnormal nozzle determination method includes: an image reading step of reading a recording surface of the sheet including dot images recorded at the plurality of dispersed positions by the dispersed ejection processing unit; an abnormal nozzle determination step of determining an abnormal nozzle that is causing an ink ejection failure among the plurality of nozzles based on density of dispersed pixels corresponding to each of the plurality of dispersed positions in a read image read by the image reading step, The abnormal nozzle determination method includes one or more processors that execute each of the steps. [Explanation of symbols]

[0156] 7: Control device 8: Line sensor 9: Sheet 30: Inkjet head 31-34: Line Head 71: Main control device 72: Drive circuit 711: CPU 711c: Unit line number setting section 711d: Line identification value setting section 711e: Color identification value setting unit 711f: Element number specification part 711g: Non-image output control section 711x: I / O ports 712:RAM 713: Storage section 7111: Image output control unit 7112: Dispersed dot output control unit 7113: Abnormal nozzle detection unit

Claims

1. An inkjet recording apparatus that ejects ink from a plurality of nozzles onto a sheet to record an image on the sheet, an image recording processing unit that records a predetermined image on the sheet in accordance with image data; a dispersion ejection processing unit that ejects ink droplets from each of the plurality of nozzles onto a plurality of dispersion positions determined on the sheet in parallel with the image recording processing by the image recording processing unit; an image reading unit that reads a recording surface of the sheet including a dot image recorded at the plurality of dispersed positions by the dispersed ejection processing unit; an abnormal nozzle determination unit that determines which of the plurality of nozzles is abnormal and experiencing ink ejection problems based on the density of dispersed pixels corresponding to each of the plurality of dispersed positions in a read image read by the image reading unit.

2. When the image recording processing unit performs a process of recording the predetermined image on a plurality of sheets, The inkjet recording apparatus according to claim 1 , wherein the plurality of dispersion positions are determined across the plurality of sheets.

3. the plurality of dispersion positions are determined in a non-image recording area on the sheet where the predetermined image is not recorded, 3. The inkjet recording apparatus according to claim 1, wherein the abnormal nozzle determination unit determines that the nozzle corresponding to the dispersed pixel is the abnormal nozzle when the density of the dispersed pixel is less than a predetermined threshold value.

4. the dispersed ejection processing unit ejects ink droplets from each of the plurality of nozzles at the plurality of dispersed positions a plurality of times; 4. The inkjet recording device according to claim 3, wherein the abnormal nozzle determination unit determines whether the density of the dispersed pixel is less than a predetermined threshold value, and when the number of times that the density is determined to be less than the threshold value reaches a predetermined set number of times, determines that the nozzle corresponding to the dispersed pixel is the abnormal nozzle.

5. the dispersed pixels include first dispersed pixels corresponding to the dispersed positions defined in an image recording area on the sheet where the predetermined image is recorded, and second dispersed pixels corresponding to the dispersed positions defined in a non-image recording area on the sheet where the predetermined image is not recorded, The abnormal nozzle determination unit When a density of the first variance pixel is different from a density of a drawing pixel of the predetermined image, the nozzle corresponding to the first variance pixel is determined to be the abnormal nozzle; 3. The inkjet recording apparatus according to claim 1, wherein when the density of the second dispersed pixel is less than a predetermined threshold value, the nozzle corresponding to the second dispersed pixel is determined to be the abnormal nozzle.

6. 1. A method for determining whether a nozzle is abnormal, which is applied to an inkjet recording apparatus that ejects ink from a plurality of nozzles onto a sheet to record an image on the sheet, comprising: the inkjet recording apparatus includes an image recording processing unit that records a predetermined image on the sheet in accordance with image data, and a distributed ejection processing unit that ejects ink droplets from each of the plurality of nozzles at a plurality of distributed positions determined on the sheet in parallel with the image recording processing by the image recording processing unit; The abnormal nozzle determination method includes: an image reading step of reading a recording surface of the sheet including dot images recorded at the plurality of dispersed positions by the dispersed ejection processing unit; an abnormal nozzle determination step of determining an abnormal nozzle that is causing an ink ejection failure among the plurality of nozzles based on density of dispersed pixels corresponding to each of the plurality of dispersed positions in a read image read by the image reading step, The abnormal nozzle determination method includes one or more processors that execute each of the steps.

Images