JP2011101964A - Apparatus for inspecting ink jetting failure of line-type inkjet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for inspecting the ink jetting failure of a line-type inkjet head, in which the jetting failure state of the line-type inkjet head can quickly be inspected by a line sensor. <P>SOLUTION: The line sensor 40A for monochrome is integrally fit to the side face 30b of the most downstream side being the most downstream side of the line-type inkjet head 30 in the print paper conveying direction. Monochrome print density data by images and characters printed on print paper PA having passed through the line-type inkjet head 30 are read by the line sensor 40A for monochrome over preset m lines. M pieces of the monochrome print density data are accumulated by an accumulation circuit 74A to obtain accumulated data 74a. The accumulated data 74a from the accumulation circuit 74A are compared with preset thresholds 62a, 62b in the comparator circuit 63 of a control part 60 along the line direction to determine the ink jetting failure state of the line-type inkjet head 30. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  In the present invention, when printing an image or a character on a printing paper by ejecting ink from a line-type inkjet head, the ejection failure state of the line-type inkjet head can be quickly inspected by a line sensor, and printing processing and ejection can be performed. The present invention relates to a discharge defect inspection apparatus for a line type ink jet head capable of performing defect inspection almost simultaneously.

  In general, an ink jet printing apparatus having an ink jet head to which an ink jet method is applied prints images and characters by ejecting ink from nozzles of the ink jet head toward printing paper based on print data based on image information and character information. In addition, since print data can be printed in color on printing paper using multicolor inks, it is frequently used as a home or business printer.

  In this type of ink jet printing apparatus, the ink jet head is classified into a serial type that performs printing by moving in the main scanning direction, and a line type that simultaneously prints the entire length in the main scanning direction. The effect on the printing paper is more noticeable in the line type than in the serial type.

  Therefore, when printing images and characters on printing paper using an inkjet printing device to which a line-type inkjet head is applied, in order to prevent the occurrence of defective printed matter, a printing inspection that can inspect printing defects due to defective ink ejection, etc. There are an apparatus, a printing apparatus including the apparatus, and a print inspection method (see, for example, Patent Document 1).

  In the above-described print inspection apparatus, the printing apparatus including the print inspection apparatus, and the print inspection method described in Patent Document 1, images and characters are printed on a print sheet on a carriage, although illustration is omitted here. An inkjet head group and a line CCD for reading defective printing of images and characters printed on printing paper are attached orthogonally to each other.

  When inspecting printing defects on the printing paper, the carriage is fixed, and the test pattern is color-printed by the inkjet head group while the printing paper is conveyed in the conveyance direction, and then the line CCD is integrated with the carriage. The test pattern is read while moving in the direction perpendicular to the inkjet head group, and matching processing is performed between the read test pattern and inspection data stored in a memory (not shown) in advance to configure the inkjet head group Failure of ink ejection from each inkjet head of each inkjet head row for cyan ink (C), magenta ink (M), yellow ink (Y), and black ink (K) We are inspecting.

  Incidentally, the ejection failure of the line type ink jet head means a state in which an image or characters cannot be printed on the printing paper due to ink clogging or ink shortage.

  If the ink is ejected normally, the main printing is performed on the printing paper. On the other hand, if the ink is not ejected normally, the carriage is moved to the cleaning area and the result of the ejection defect inspection Accordingly, the inkjet head row is cleaned.

JP 2006-35727 A

  By the way, in the print inspection apparatus disclosed in Patent Document 1, the line CCD is an inkjet head when the line CCD performs an ejection failure inspection to check whether the ink is normally ejected from each inkjet head row for each ink color. A moving mechanism that moves perpendicularly to the group and moves integrally with the carriage is required, which complicates the structure and takes time to move the line CCD, and discharge after printing to an area readable by the line CCD. In order to perform the defect inspection, the printing process and the discharge defect inspection cannot be performed at the same time, which causes a problem that the processing time of the entire apparatus is significantly increased.

  Also, when an ejection failure occurs, the inkjet head group must be moved together with the carriage to the cleaning area, so when the inkjet head group is returned to the print area after the head cleaning, the inkjet head group and the printing paper There is a problem that misalignment may occur between the two, and printing cannot be started immediately after the head cleaning.

  Therefore, when an ink or ink is ejected from the line-type inkjet head to print an image or a character on the printing paper, the ejection failure state of the line-type inkjet head can be quickly inspected by a reading means using a line sensor or a camera, and Another object of the present invention is to provide a discharge failure inspection device for a line-type inkjet head capable of performing printing processing and discharge failure inspection substantially simultaneously.

The present invention has been made in view of the above problems, and the invention according to claim 1 includes a sheet conveying means for conveying a printing sheet,
The plurality of nozzles fixedly installed above the printing paper for each ink color according to at least one ink color and corresponding to a plurality of nozzles arranged in a line direction perpendicular to the conveyance direction of the printing paper. At least one line-type inkjet head that ejects ink of ink color toward the printing paper; and
An image printed on the printing paper that is installed on the most downstream side in the conveyance direction of the printing paper among the at least one or more of the linear inkjet heads and passes through the linear inkjet head arranged on the most downstream side. Reading means for reading the print density data by characters and characters line by line;
Integrating means for integrating m print density data read by the reading means over a preset number of lines m and outputting integrated data;
Comparing means for comparing the integrated data from the integrating means and a preset threshold value along the line direction to determine at least one or more ejection failure states of the line type inkjet head. This is a discharge failure inspection device for a line-type inkjet head.

According to a second aspect of the present invention, there is provided a discharge failure inspection apparatus for a line type ink jet head according to the first aspect,
In the case of printing the image or the characters on the printing paper in a single color, the line type inkjet head is one, and the reading means is a monochrome line sensor or camera. It is an ejection defect inspection device for an inkjet head.

According to a third aspect of the present invention, there is provided a discharge failure inspection apparatus for a line type ink jet head according to the first aspect,
When color printing the image and the characters on the printing paper, a plurality of the line-type inkjet heads corresponding to a plurality of ink colors are arranged in parallel along the conveyance direction of the printing paper, and 2. A discharge failure inspection apparatus for a line type ink jet head, wherein the reading means is a color line sensor or a camera.

According to a fourth aspect of the present invention, there is provided a discharge failure inspection apparatus for a line type ink jet head according to the third aspect,
In the case of color printing, the RGB integrated data obtained by integrating the RGB print density data output from the color line sensor or the camera over the number m of lines by the integrating unit is converted by the color conversion separating unit into the plurality of RGB integrated data. The integrated data of each ink color is obtained by color conversion and separation for each ink color corresponding to each ink color, and then the integrated data for each ink color is compared with the threshold value for each ink color by the comparing means. An ejection failure inspection apparatus for a line-type inkjet head, wherein the ejection failure state is inspected for each line-type inkjet head corresponding to each ink color.

Furthermore, the invention described in claim 5 is the discharge defect inspection apparatus for a line type ink jet head according to any one of claims 1 to 4,
The threshold value includes a first threshold value for inspecting a state immediately before the ejection failure of the line-type inkjet head and a first threshold value for inspecting a state of ejection failure of the line-type inkjet head. And a second threshold value that is less than
The comparison unit issues a warning when the integrated data is smaller than the first threshold, and then determines that there is a discharge defect when the integrated data is smaller than the second threshold. This is an ejection failure inspection device for a type inkjet head.

  According to the ejection failure inspection apparatus for a line-type inkjet head according to the present invention, at least one or more line-type inkjet heads provided for each ink color according to at least one or more ink colors are ejected. When printing images and characters on printing paper, the reading means is installed at the most downstream of at least one line type inkjet head in the conveyance direction of the printing paper, and is arranged at the most downstream by this reading means. After reading the print density data of images and characters printed on the printing paper that has passed through the line-type inkjet head over m lines set in advance, the print data is integrated by integrating the m print density data with the integration means. Comparing the accumulated data from the integrating means with a preset threshold value along the line direction by the comparing means Since at least one or more line-type inkjet heads are judged to be in a defective discharge state, at least one or more ink-jet heads can be quickly inspected for discharge with a simple structure, and printing processing and discharge failure inspection can be performed. Since it can be performed substantially simultaneously, the processing time of the entire apparatus can be shortened.

  In the case of monochrome printing, a monochrome line sensor or camera may be applied as the reading unit, so that the apparatus can be configured at low cost.

  In addition, when performing color printing, a color line sensor or camera is used. In this case, the RGB print density data output from the color line sensor is integrated by the integrating means over the number m of lines. After the RGB integrated data is color-converted and separated for each ink color corresponding to a plurality of ink colors by the color conversion / separation means to obtain the integrated data for each ink color, the integrated data for each ink color is obtained by the comparison means. Since the discharge failure state is inspected for each ink color corresponding to each ink color in comparison with the threshold value for each ink color, the line ink jet having a discharge failure among the line ink jet heads of each ink color Only the head can be specified.

  Further, when comparing the integrated data with the threshold value in the comparison means, the threshold value is the first threshold value for inspecting the state immediately before the line-type inkjet head discharge failure and the line-type inkjet head discharge failure. And a second threshold value that is smaller than the first threshold value for inspecting the state that has reached the first threshold value, and a warning is issued when the accumulated data is smaller than the first threshold value by the comparing means. Since it is determined that there is a discharge failure when it is smaller than the second threshold, it is possible to prompt the user to be alerted before the discharge failure increases (severely) by a warning.

It is the perspective view which showed the discharge defect inspection apparatus of the line type inkjet head of Example 1 which concerns on this invention. FIG. 3 is an enlarged bottom view showing a line type ink jet head and a line sensor in the ejection defect inspection apparatus for a line type ink jet head of Example 1 according to the present invention. It is the block diagram which showed the circuit structure of the discharge defect inspection apparatus of the line type inkjet head of Example 1 which concerns on this invention. FIG. 5 is a flowchart for inspecting an ejection failure state using a monochrome line sensor in the ejection failure inspection apparatus for a line-type inkjet head according to the first embodiment of the present invention. In the ejection defect inspection apparatus for a line-type inkjet head according to the first embodiment of the present invention, integrated data obtained by integrating monochrome print density data read for each line by a monochrome line sensor over m lines, and preset first data It is a figure for demonstrating the operation | movement which compares 1 and a 2nd threshold value. FIG. 5 is a side view for explaining the operation of cleaning the bottom side of the line type inkjet head by the head cleaning mechanism in the line type inkjet head ejection failure inspection apparatus of Example 1 according to the present invention. FIG. 5 is a perspective view illustrating a discharge defect inspection device for a line-type inkjet head according to a modification in which Example 1 is partially deformed. It is the perspective view which showed the discharge defect inspection apparatus of the line-type inkjet head of Example 2 which concerns on this invention. It is the block diagram which showed the circuit structure of the ejection defect inspection apparatus of the line type inkjet head of Example 2 which concerns on this invention. FIG. 6 is a flowchart for inspecting an ejection failure state by a color line sensor in the ejection failure inspection apparatus for a line-type inkjet head according to the second embodiment of the present invention. In the ejection failure inspection apparatus for a line-type inkjet head according to the second embodiment of the present invention, accumulated data obtained by accumulating RGB print density data read for each line by a line sensor for color over m lines is represented by C, K, M. , Y is a diagram for explaining the operation of comparing the accumulated data of each ink color obtained by color conversion and separation with the first and second threshold values set in advance. FIG. 10 is a perspective view showing a discharge defect inspection device for a line-type inkjet head according to a modification in which Example 2 is partially deformed.

  Hereinafter, an embodiment of a discharge failure inspection apparatus for a line-type inkjet head according to the present invention will be described in detail in the order of Embodiment 1 and Embodiment 2 with reference to FIGS.

  In the ejection failure inspection apparatus for a line-type inkjet head according to the present invention, printing is performed by ejecting ink of a corresponding ink color from at least one or more line-type inkjet heads provided for each ink color according to at least one or more ink colors. When printing an image or a character on a sheet, at least one or more line-type inkjet heads by a line sensor which is a reading unit installed at the most downstream in the conveyance direction of the printing sheet among at least one or more line-type inkjet heads The ejection failure state can be quickly inspected, and the printing process and the ejection failure inspection can be performed substantially simultaneously.

  Furthermore, as a modification, there is a configuration in which a camera as another reading unit is used instead of the line sensor.

  In this case, in the first embodiment, an example using a single color (single color) ink will be described, and in the second embodiment, an example using a plurality of colors of ink will be described.

  As shown in FIG. 1, the ejection failure inspection apparatus 10A for the line-type inkjet head according to the first embodiment of the present invention discharges the unprinted printing paper PA and the printed printing paper PA. It is installed between a paper discharge section and a single line type ink jet head 30 is used so that monochrome printing is possible using a single color (one color) ink.

  In the ejection failure inspection apparatus 10A for the line-type inkjet head according to the first embodiment, printing is performed by loading the unprinted printing paper PA that is moved upward in the direction of the arrow Z1 at the initial stage and is fed from the paper feeding unit while sucking air. The transported paper PA is transported to the paper discharge unit side and at the time of head cleaning, the paper air suction / conveyance mechanism 20 is provided so as to be able to move downward in the direction of the arrow Z2. One line type ink jet which is fixedly installed above the transported printing paper PA and ejects a single color ink INK onto the printing paper PA based on the print data to print the image or text on the printing paper PA in a single color. Among the head 30 and the line-type inkjet head 30, the most downstream side surface 30b which is the most downstream side in the conveyance direction (arrow X direction) of the printing paper PA. Monochrome line sensor 40A that is attached integrally and reads the print density of images and characters printed on the printing paper PA line by line, and orthogonal to the conveyance direction (arrow X direction) of the printing paper PA at the initial stage. The head cleaning mechanism 50 for moving in the direction of the arrow Y1 to retract from the line type inkjet head 30 and moving in the direction of the arrow Y2 during head cleaning to clean the line type inkjet head 30, and the line type inkjet head of Example 1 And a controller 60A for overall control of the ejection failure inspection apparatus 10A.

  Here, the main components provided in the ejection failure inspection apparatus 10A for the line type inkjet head will be described in order.

  First, the above-described sheet air suction / conveyance mechanism unit 20 is moved upward in the direction of arrow Z1 by an unillustrated moving mechanism at an initial stage to reach a position approaching below the lower surface 30a of the line-type inkjet head 30, and the head It is provided so as to allow the head cleaning mechanism 50 to move in the direction of the arrow Z2 during cleaning.

  In the paper air suction and conveyance mechanism unit 20, a belt-like belt platen 21 formed through the plurality of air suction holes 21a to convey the printing paper PA fed by the paper feeding unit while being mounted is a control unit 60A. Is driven endlessly between the drive pulley 23 and the driven pulleys 24 to 26 which are rotationally driven in the direction of the arrow by the motor 22, and printing paper is provided between the drive pulley 23 and the driven pulley 24. Air suction portions (suction boxes) 27 and 28 for sucking PA on the belt platen 21 are provided.

  When the printing paper PA is mounted on the belt-like belt platen 21, air is sucked from the plurality of air suction holes 21a formed in the belt platen 21 by the air suction portions 27 and 28, and the printing paper PA With the PA fixed on the belt platen 21, the printing paper PA is conveyed in the direction of arrow X (sub-scanning direction with respect to the head) by the rotation of the belt platen 21.

  Next, the one line-type inkjet head 30 described above is fixedly installed above the printing paper PA mounted on the belt platen 21. For example, a single color ink INK using black ink or blue ink can be applied. It is configured.

  In the line type ink jet head 30, as shown in an enlarged view in FIG. 2, the conveyance direction (arrow X direction) of the printing paper PA with a plurality of nozzles 31n on the bottom surface 30a side at a density of 300 nozzles per inch (300 dpi), for example. ), A plurality of head blocks 31 in a line direction (arrow Y direction) orthogonal to each other are arranged two-dimensionally, so that the line-type inkjet head 30 is formed long along the arrow Y direction.

  At this time, a plurality of head blocks 31 are arranged on one line along the main scanning direction (arrow Y direction), and are divided into two lines in the sub-scanning direction (arrow X direction). In addition, in the adjacent lines 1 and 2, the head blocks 31 are alternately arranged in a staggered pattern so as to partially overlap each other.

  Then, a single-color ink INK is ejected from each nozzle 31n toward the printing paper PA by driving a piezoelectric element (not shown) provided corresponding to each nozzle 31n in the line-type inkjet head 30 in accordance with the print data. It has come to be.

  Next, the monochrome line sensor (reading means) 40A lines on the most downstream side surface (right side surface) 30b that is the most downstream side in the conveyance direction (arrow X direction) of the printing paper PA in the line type inkjet head 30. The left side surface 40b of the sensor 40A is integrally attached. When monochrome printing is performed, the line sensor 40A only needs to be applied for monochrome, and thus the apparatus 10A can be configured at low cost.

  In the monochrome line sensor 40A, as shown in FIG. 2 in an enlarged manner, a light emitting element 41 that emits light toward the printing paper PA on the bottom surface 40a side, and light from the light emitting element 41 is emitted from the printing paper PA. A plurality of sets are arranged along a line direction (arrow Y direction) orthogonal to the conveyance direction (arrow X direction) of the printing paper PA. Thus, the monochrome line sensor 40 </ b> A is also formed long along the arrow Y direction, like the line-type inkjet head 30.

  The density per inch of the plurality of sets of light emitting elements 41 and light receiving elements 42 provided in the monochrome line sensor 40A can be obtained by reading the print density of images or characters printed on the printing paper PA. A coarse value smaller than the 300 dpi nozzle 31n may be used.

  A plurality of sets in which the print density of images and characters printed on the print paper PA is provided in the line sensor 40A as the print paper PA printed by the line-type inkjet head 30 moves in the arrow X direction. The printing paper PA is printed satisfactorily or defectively by reading each line along the main scanning direction (arrow Y direction) of the line-type inkjet head 30 by the light emitting element 41 and the light receiving element 42. It is possible to inspect the ejection failure of the ink INK from the line type ink jet head 30 and this will be described in detail later.

  Returning to FIG. 1, the head cleaning mechanism 50 is moved in the direction of arrow Y1 at the initial stage by a moving mechanism (not shown) and retracted from the line-type inkjet head 30, and moved in the direction of arrow Y2 during head cleaning described later. The bottom surface 30a of the line-type inkjet head 30 is provided so as to be cleaned.

  In the head cleaning mechanism 50, an ink suction nozzle 52 is mounted on a box-shaped moving table 51, and the ink suction nozzle 52 is connected to an ink suction pump 54 (shown in FIG. 6) via a hose 53. In addition, a plate-like blade 55 that is elastically displaceable behind the moving table 51 in the moving direction of the moving table 51 with respect to the movement of the moving table 51 in the arrow Y2 direction is attached.

  Then, a purge process for sucking ink clogging of each nozzle 31n (FIG. 2) is performed by the ink suction nozzle 52 on the line-type inkjet head 30, and the ink INK attached to each nozzle 31n is removed by the blade 55. A wiping process for scraping is performed.

  Here, the discharge defect inspection of the line type ink jet head 30 which is the main part of the first embodiment by the discharge defect inspection apparatus 10A for the line type ink jet head of the first embodiment configured as described above will be described with reference to FIGS. Will be described.

  As shown in FIG. 3, the monochrome data created by the personal computer 71A as print data or the monochrome data read from the original paper G using the monochrome scanner 72A is input to the image processing circuit 73A. The single-color data is processed so as to be applied to the line-type inkjet head 30 line by line within 73A.

  Thereafter, for example, when black or blue ink INK is ejected from the nozzles 31n (FIG. 2) toward the printing paper PA based on the single color data applied to the line-type inkjet head 30, one line is formed on the printing paper PA. Along with the image, characters are printed in a single color, and sequentially printed line by line as the printing paper PA is conveyed in the direction of the arrow X.

  Further, a monochrome line sensor 40A attached integrally with the line-type inkjet head 30 was used, and monochrome printing was performed on the printing paper PA by a plurality of sets of light emitting elements 41 and light receiving elements 42 provided in the line sensor 40A. Single-color print density data based on images and characters is read for each line, and the read single-color print density data is sequentially input to an integration circuit 74A serving as an integration unit.

  In the integration circuit 74A described above, the number m of lines (where m is a natural number of 2 or more) for repetitively reading monochrome print density data by the monochrome line sensor 40A is set in advance, and the line sensor 40A sets m lines. The integrated data 74a is obtained by integrating the m single-color print density data read over a period of time, and the integrated data 74a over the m lines is input to the comparison circuit 63 serving as a comparison means provided in the control unit 60A. Yes.

  The control unit 60A described above stores therein a ROM 61 that stores therein control software for the ejection failure inspection apparatus 10A for the line-type inkjet head of Example 1, and print density information for ejection failure inspection during operation of the apparatus 10A. A RAM 62 temporarily storing a first threshold 62a and a second threshold 62b having a value smaller than the first threshold 62a, and first and second thresholds 62a and 62b and an integrating circuit stored in the RAM 62 A comparison circuit 63 that performs comparison processing with the integration data 74a integrated at 74A to determine the ejection failure state of the line-type inkjet head 30 is incorporated.

  At this time, the first threshold value 62a stored in the RAM 62 is information for inspecting the state immediately before the line-type inkjet head 30 reaches the ejection failure (hereinafter referred to as before ejection failure). The threshold value 62b of 2 is information having a value smaller than the first threshold value 62a in order to inspect the state where the line-type inkjet head 30 has reached ejection failure, and the first and second threshold values 62a and 62b are set in advance. By doing so, it is possible to inspect the ejection failure state of the line-type inkjet head 30 step by step. However, the present invention is not limited to this, and only one threshold value corresponding to the second threshold value 62b is set and the line-type inkjet head is set. It is also possible to inspect 30 ejection failure states.

  In addition, an alarm processing circuit 76 and a head cleaning processing circuit 77 are provided on the output side of the comparison circuit 63. As will be described later, the alarm processing circuit 76 operates first at the time of ejection failure inspection and before ejection failure. After the warning is given by an alarm display or the like, the head cleaning processing circuit 77 is operated by detecting a defective discharge portion.

  That is, in the ejection failure inspection of the line type ink jet head in the first embodiment, as shown in FIGS. 3 and 4, in step S10, the number m of lines for integrating the print density data is set in the integration circuit 74A. .

  Next, in step S11, the monochrome print density data read for each line by the monochrome line sensor 40A in the integration circuit 74A is integrated over m lines, and m pieces of monochrome print density data are integrated over the m lines. Integration data 74a is obtained.

  Next, in step S12, the first and second threshold values 62a and 62b stored in the RAM 62 of the control unit 60A and the integration data 74a obtained in the integration circuit 74A are input into the comparison circuit 63 of the control unit 60A. To do.

  Next, in step S13, the print density is compared along the main scanning direction of the head between the integration data 74a from the integration circuit 74A and the first threshold value 62a in the comparison circuit 63, and the integration data 74a includes the first data. It is determined whether there is a portion having a value smaller than the threshold value 62a of 1. At this time, as shown in FIG. 5, the value of the first threshold value 62a is set in advance to a value smaller than the value of the portion of the integrated data 74a over m lines that has good ejection but does not print. Has been.

  If there is no portion with a value smaller than the first threshold value 62a in the integrated data 74a (in the case of NO), it is determined in step S14 that there is no ejection failure in the line-type inkjet head 30, and printing is continued. Let On the other hand, when there is a portion of the integrated data 74a having a value smaller than the first threshold 62a (in the case of YES), the line-type inkjet head 30 is before ejection failure through the alarm processing circuit 76 in step S15. An alarm is displayed to inform the user of the fact that the user is urged before there are many (severe) ejection defects. In the first embodiment, the warning that the alarm processing circuit 76 indicates that ejection failure is not occurring is displayed on a display (not shown). However, the warning sound is not limited to this, and a buzzer (not shown) is used. May be issued.

  Thereafter, it waits for a predetermined time set in advance in step S16.

  Next, in step S17, the print density is compared along the main scanning direction of the head between the integration data 74a from the integration circuit 74A and the second threshold value 62b in the comparison circuit 63, and the integration data 74a contains the first data. It is determined whether or not there is a portion having a value smaller than the threshold value 62b of 2. At this time, as shown in FIG. 5, the value of the second threshold value 62b is set to a value smaller than the value of the first threshold value 62a, and is set to a value at which it is possible to detect ejection failure. Has been.

  If there is no portion with a value smaller than the second threshold value 62b in the integrated data 74a (in the case of NO), the process returns to step S15 and a display to the effect that it is before ejection failure is displayed via the alarm processing circuit 76. Do. On the other hand, if there is a portion having a value smaller than the second threshold value 62b in the integrated data 74a (in the case of YES), it is detected that there is an ejection failure in the line-type inkjet head 30 in step S18. Cleaning is performed on the line-type inkjet head 30 that has been detected as having a discharge failure through the processing circuit 77.

  Here, when performing head cleaning on the line-type inkjet head 30, as shown in FIG. 6, the sheet air suction / conveyance mechanism 20 is moved downward in the direction of the arrow Z2 to Retreat downward away from 30a.

  Thereafter, the ink suction pump 54 is operated while moving the moving table 51 of the head cleaning mechanism section 50 in the direction of the arrow Y2 along the main scanning direction of the line-type inkjet head 30 to the moving table 51 via the hose 53. A purge process for sucking ink clogging of each nozzle 31n is performed by the attached ink suction nozzle 52, and the ink INK adhering to each nozzle 31n is scraped by a blade 55 attached to the rear end of the moving table 51 in the moving direction. The wiping process to drop is performed. As a result, a defective discharge portion is cleaned in the line-type inkjet head 30, and printing can be started immediately after the head cleaning.

  As described above, according to the ejection failure inspection apparatus 10A for the line-type inkjet head of the first embodiment, the line-type inkjet head 30 is integrated with the most downstream side surface 30b which is the most downstream side in the transport direction of the printing paper PA. The monochrome print density data by the image and the character printed on the printing paper PA that has passed through the line-type inkjet head by the attached monochrome line sensor 40A is read over m lines set in advance, and m pieces of monochrome print density data are obtained. Is integrated by the integration circuit 74A to obtain integration data 74a, and the integration data 74a obtained by the integration circuit 74A and the preset threshold values 62a and 62b are compared in the line direction by the comparison circuit 63 of the control unit 60. Since the ejection failure state of the line-type inkjet head 30 is determined, the inkjet head 3 Ejection failure state quickly can be inspected by a simple structure, and since the the printing process and the ejection failure inspection substantially can be performed simultaneously, it is possible to shorten the processing time of the whole device.

  Further, when the line-type inkjet head 30 that has been detected as having an ejection failure is cleaned, the line-type inkjet head 30 is fixed, so that a positional deviation occurs between the line-type inkjet head 30 and the printing paper PA. Since there is no worry, printing can be started immediately after the head cleaning.

  Next, a modified example in which the ejection defect inspection apparatus 10A for the line type ink jet head of Example 1 is partially deformed will be briefly described with reference to FIG.

  As shown in FIG. 7, the line-type inkjet head ejection failure inspection apparatus 10A ′, which is a modification of the first embodiment, corresponds to a single color ink above the printing paper PA conveyed in the arrow X direction. The point that the line-type inkjet head 30 is fixedly installed is the same as that of the first embodiment. Although this modified example also includes a paper air suction / conveyance mechanism and a head cleaning mechanism similar to those in the first embodiment, illustration thereof is omitted here.

  Here, different points from the first embodiment will be described. The line-type inkjet head 30 is long along the most downstream side surface 30b which is the most downstream side in the transport direction (arrow X direction) of the printing paper PA. An illumination light source 81 is attached, and the illumination light source 81 illuminates the printed printing paper PA that has passed under the most downstream side surface 30b of the line-type inkjet head 30 and the printed printing paper PA. On the upper side, a monochrome camera 82A is fixedly installed obliquely upward to the right.

  The monochrome camera (reading means) 82A described above is electrically masked on the periphery other than the one line so that the print density of one line immediately after printing on the printing paper PA can be read. ing.

  Then, the monochrome print density data is read for each line along the line immediately after monochrome printing by the line-type inkjet head 30 with the monochrome camera 82A, and is read over the preset number of lines m. Similarly, by obtaining integrated data over m lines, the ejection defect inspection is performed according to the flow shown in FIG. 4 earlier, and therefore, substantially the same effect as in the first embodiment can be obtained.

  As shown in FIG. 8, the ejection failure inspection apparatus 10B for the line-type inkjet head according to the second embodiment of the present invention discharges the unprinted printing paper PA and the printed printing paper PA. It will be explained first that it is installed between the paper discharge unit and is configured to be capable of color printing using a plurality of color inks by a plurality of line-type inkjet heads 30C, 30K, 30M, and 30Y. Therefore, the constituent members described above will be described as appropriate as necessary, and the constituent members different from those of the first embodiment will be given new reference numerals.

  In the ejection failure inspection apparatus 10B for the line-type inkjet head according to the second embodiment, unprinted printing paper PA that is moved upward in the direction of the arrow Z1 at the initial stage and is fed from the paper feeding unit side is loaded and printed while air is sucked. Since the paper air suction / conveyance mechanism unit 20 that conveys the finished printing paper PA to the paper discharge unit side and can be moved downward in the direction of the arrow Z2 at the time of head cleaning is provided with the same structure as the first embodiment. Here, the same reference numerals as in the first embodiment are used to omit the detailed description.

  A plurality of line-type inkjet heads 30C, 30K, 30M, and 30Y corresponding to a plurality of ink colors are provided above the printing paper PA transported in the direction of the arrow X in the transporting direction of the printing paper PA ( (Along arrow X direction).

  Specifically, the line-type inkjet heads 30C, 30K, 30M, and 30Y for cyan ink (C), black ink (K), magenta ink (M), and yellow ink (Y) convey the printing paper PA. Each color ink INK ejected from the line-type inkjet heads 30C, 30K, 30M, and 30Y for each ink color is fixedly installed in this order from the upstream side to the downstream side in the direction (arrow X direction). By overlaying on the PA, images and characters can be printed in full color on the printing paper PA.

  At this time, the line-type inkjet heads 30C, 30K, 30M, and 30Y for the respective ink colors all have the same structure as the line-type inkjet head 30 described above with reference to FIG. 2, and as shown in FIG. A plurality of head blocks 31 having a plurality of nozzles 31n on the 30a side are arranged on one line along the line direction (arrow Y direction), and are divided into two lines in the arrow X direction. In the adjacent lines 1 and 2, the head blocks 31 are alternately arranged in a staggered pattern so as to partially overlap each other.

  Further, among the plurality of line type ink jet heads 30C, 30K, 30M, 30Y, the most downstream side surface (right side surface) 30b of the line type ink jet head 30Y installed at the most downstream side in the transport direction (arrow X direction) of the printing paper PA. In addition, the left side surface 40b of the color line sensor 40B is integrally attached.

  This color line sensor (reading means) 40B also has the same structure as the monochrome line sensor 40A described above with reference to FIG. 2, and as shown in FIG. The light emitting element 41 that emits light toward the light source and the light receiving element 42 that receives the reflected light when the light from the light emitting element 41 is reflected by the printing paper PA, and this set is the transport direction (arrow X A plurality of sets are arranged along a line direction (arrow Y direction) orthogonal to (direction).

  Further, since the head cleaning mechanism 50 is provided with the same structure as that of the first embodiment, the same reference numerals as those of the first embodiment are used, and detailed description thereof is omitted. Moves in the X1 direction and the arrow Y1 direction, retreats from the line-type inkjet head 30C installed at the most upstream position, and moves in the arrow X2 direction and the arrow Y2 direction during head cleaning to move the line-type inkjet heads 30C, 30K for each ink color. , 30M, 30Y can be selectively cleaned.

  If four head cleaning mechanisms 50 are provided corresponding to the line-type inkjet heads 30C, 30K, 30M, and 30Y for each ink color, each head cleaning mechanism 50 moves in the directions of arrows Y1 and Y2. Furthermore, although not shown here, the width of the head cleaning mechanism is four in the direction of the arrow X so that the line-type inkjet heads 30C, 30K, 30M, and 30Y for each ink color can be cleaned together. It is also possible to adopt a structure in which the head is widened, and this structure only moves in the directions of arrows Y1 and Y2.

  Furthermore, a control unit 60B is provided for overall control of the ejection failure inspection apparatus 10B for the line-type inkjet head of the second embodiment.

  Here, the line-type inkjet heads 30C, 30K, 30M, and 30Y for the respective ink colors, which are the main parts of the second embodiment, are detected by the ejection failure inspection apparatus 10B for the line-type inkjet head of the second embodiment configured as described above. The ejection defect inspection will be described with reference to FIGS.

  As shown in FIG. 9, color data (RGB) created by the personal computer 71B as print data or color data (RGB) read from the original paper G using the color scanner 72B is input to the image processing circuit 73B. In the image processing circuit 73B, the color data (RGB) is converted into CKMY ink colors, and the CKMY data is line-type inkjet heads 30C, 30K, 30M, 30Y for each ink color for each line. To be applied.

  Thereafter, the CKMY inks INK are ejected toward the printing paper PA from the nozzles 31n (FIG. 2) based on the CKMY data applied to the line-type inkjet heads 30C, 30K, 30M, and 30Y for the respective ink colors. When superimposed, images and characters are printed in full color along one line on the printing paper PA, and sequentially printed line by line as the printing paper PA is conveyed in the arrow X direction.

  Further, a color line sensor 40B integrally attached to the line-type inkjet head 30Y installed on the most downstream side is used, and a plurality of sets of light emitting elements 41 and light receiving elements 42 provided in the line sensor 40B are used on the printing paper PA. In addition, the print density of images and characters printed in full color is read for each line, and the read RGB print density data is sequentially input to an integration circuit 74B serving as integration means.

  In the integration circuit 74B, the number of lines m (where m is a natural number of 2 or more) for repeatedly reading the RGB print density data by the color line sensor 40B is set in advance, and the line sensor 40B sets m lines. The integrated RGB data is obtained by integrating the m RGB print density data read over a period of time, and the integrated data 74b over the m lines is input to the RGB → CKMY conversion separation circuit 75 serving as a color conversion separation means. .

  In the RGB → CKMY conversion / separation circuit 75 described above, the RGB integration data 74b obtained by the integration circuit 74B is associated with the line-type inkjet heads 30C, 30K, 30M, and 30Y for each ink color for each ink color. , K, M, and Y are provided, and the integrated data 75a for each ink color is obtained and input to the comparison circuit 63 serving as comparison means provided in the control unit 60B.

  The control unit 60B described above stores therein a ROM 61 that stores therein control software for the ejection failure inspection apparatus 10B for the line-type inkjet head of Example 2, and print density information for ejection failure inspection when the apparatus 10B is in operation. The RAM 62 temporarily stores the first threshold 62a and the second threshold 62b having a value smaller than the first threshold 62a, and the first threshold 62a and the second threshold 62b stored in the RAM 62 and RGB → Comparison to determine the ejection failure state of the line-type inkjet heads 30C, 30K, 30M, 30Y for each ink color by comparing with the integrated data 75a of each ink color obtained by the CKMY conversion separation circuit 75 A circuit 63 is built in.

  At this time, the first threshold 62a stored in the RAM 62 is information for the line-type inkjet heads 30C, 30K, 30M, and 30Y for each ink color to inspect the state before ejection failure, while the second threshold The threshold value 62b is information having a value smaller than the first threshold value 62a in order to inspect the state in which the line-type inkjet heads 30C, 30K, 30M, and 30Y for each ink color have failed to discharge. By setting the second threshold values 62a and 62b in advance, it is possible to inspect the ejection failure states of the line-type inkjet heads 30C, 30K, 30M, and 30Y for each ink step by step. However, the present invention is not limited to this. In this case, only one threshold value corresponding to the second threshold value 62b is set, and the line-type inkjet heads 30C, 30K, 30M, and 30Y for each ink color are not ejected. It is also possible to check the status.

  Further, an alarm processing circuit 76 and a head cleaning processing circuit 77 are provided on the output side of the comparison circuit 63 as in the first embodiment.

  That is, in the ejection failure inspection of the line type inkjet head in the second embodiment, as shown in FIGS. 9 and 10, in step S20, the number of lines m for integrating the print density data is set in the integration circuit 74B. .

  Next, in step S21, the RGB print density data read for each line by the color line sensor 40B in the integration circuit 74B is integrated over m lines, and m pieces of RGB print density data are integrated over the m lines. Integration data 74b is obtained.

  Next, in step S22, the RGB integration data 74b obtained by the integration circuit 74B is color-converted and separated into C, K, M, and Y by the RGB → CKMY conversion separation circuit 75, and the integration data 75a for each ink color is obtained. obtain.

  Next, in step S23, the first and second threshold values 62a and 62b stored in the RAM 62 of the control unit 60B and the integrated data 75a of each ink color obtained by the RGB → CKMY conversion / separation circuit 75 are stored in the control unit 60B. Is input into the comparison circuit 63.

  Next, in step S24, the print density between the integrated data 75a of each ink color from the RGB → CKMY conversion separation circuit 75 and the first threshold value 62a in the comparison circuit 63 along the main scanning direction of the head. Comparison is made for each ink color, and it is determined whether or not there is a portion having a value smaller than the first threshold value 62a in the integrated data 75a. At this time, as shown in FIG. 11, the value of the first threshold value 62a is smaller than the value of the portion where there is a line that is good in ejection but not printed in the accumulated data 75a of each ink color over m lines. The value is preset.

  If there is no portion having a value smaller than the first threshold value 62a in the accumulated data 75a for each ink color (in the case of NO), the line-type inkjet heads 30C, 30K, and 30M for each ink color in step S25. , 30Y, it is determined that there is no ejection failure and printing is continued. On the other hand, when there is a portion having a value smaller than the first threshold value 62a in the accumulated data 75a of each ink color (in the case of YES), the line type ink jet heads 30C and 30K are passed through the alarm processing circuit 76 in step S26. , 30M, 30Y, an alarm is displayed to notify that any of the discharge failures is before the user is urged before the discharge failures increase (severely). In the second embodiment as well, the warning that the alarm processing circuit 76 indicates that ejection failure is not occurring is displayed on a display (not shown) or the like, but is not limited to this. May be issued.

  After this, it waits for a predetermined time set in advance in step S27.

  Next, in step S28, the print density is set along the main scanning direction of the head between the integrated data 75a of each ink color from the RGB → CKMY conversion separation circuit 75 and the second threshold value 62b in the comparison circuit 63. Comparison is made for each ink color, and it is determined whether or not there is a portion having a value smaller than the second threshold value 62b in the integrated data 75a. At this time, as shown in FIG. 11, the value of the second threshold value 62b is set to a value smaller than the value of the first threshold value 62a, and is set to a value that can detect the ejection failure. Has been.

  If there is no portion having a value smaller than the second threshold value 62b in the accumulated data 75a for each ink color (in the case of NO), the process returns to step S26 and before the ejection failure via the alarm processing circuit 76. Display to the effect. On the other hand, when there is a portion having a value smaller than the second threshold value 62b in the accumulated data 75a of each ink color (in the case of YES), one of the line type ink jet heads 30C, 30K, 30M, 30Y is determined in step S29. Therefore, it is possible to identify only the line-type inkjet head having the ejection failure among the line-type inkjet heads 30C, 30K, 30M, and 30Y of the respective ink colors. The line-type inkjet heads (30C, 30K, 30M, 30Y) that have been detected as having ejection defects are cleaned.

  Here, in the case where the head cleaning is selectively performed on the line type ink jet heads (30C, 30K, 30M, 30Y) that are detected to have ejection failure, substantially the same as described above with reference to FIG. Then, the sheet air suction / conveyance mechanism unit 20 is moved downward in the direction of the arrow Z2, and the moving table 51 of the head cleaning mechanism unit 50 is moved in the directions of the arrow X2 and arrow Y2, while the purge process by the ink suction nozzle 52 and the blade 55 If the wiping process is performed, the defective discharge portion is cleaned in the inkjet head (30C, 30K, 30M, 30Y) that is detected as having a defective discharge, so that printing can be started immediately after the head cleaning.

  In the second embodiment, the width of the head cleaning mechanism is widened by four heads in the arrow X direction so that the line-type inkjet heads 30C, 30K, 30M, and 30Y for each ink color can be collectively cleaned. When employed, the RGB → CKMY conversion separation circuit 75 shown in FIG. 9 is not necessary, and the RGB integration data 74b obtained by the integration circuit 74B is input to the comparison circuit 63 of the control unit 60B to cope with this. By comparing with the first and second threshold values 62a and 62b set in the RAM 62 of the control unit 60B, the ejection defects of the line-type inkjet heads 30C, 30K, 30M, and 30Y for each ink color are collectively performed. It is also possible to determine.

  As described above, according to the ejection failure inspection apparatus 10B for the line-type inkjet head of Example 2, the line-type inkjet installed at the most downstream among the line-type inkjet heads 30C, 30K, 30M, and 30Y for each ink color. RGB print density data based on images and characters printed on the printing paper PA that has passed through the line-type inkjet head installed on the most downstream side by the color line sensor 40B integrally attached to the most downstream side surface 30b of the head 30Y. The data is read over m lines set in advance, and the m pieces of RGB print density data are integrated by the integration circuit 74B to obtain integration data 74b. The integration data 74b over the m lines is converted into C, C by the RGB → CKMY conversion separation circuit 75. Integration data 75a for each ink color that has been color-converted and separated into K, M, and Y The integrated data 74b obtained in B and the preset threshold values 62a and 62b are compared along the line direction by the comparison circuit 63 of the control unit 60, and the ink jet heads 30C, 30K, 30M, and 30Y for the respective ink colors are compared. Since the ejection failure state is determined, the ejection failure states of the ink-jet heads 30C, 30K, 30M, and 30Y for the respective ink colors can be quickly inspected with a simple structure, and the printing process and the ejection failure inspection are performed almost simultaneously. Since it can be performed, the processing time of the entire apparatus can be shortened.

  Further, when the line-type inkjet heads (30C, 30K, 30M, 30Y) that are detected to have ejection defects are cleaned, the line-type inkjet heads 30C, 30K, 30M, 30Y for each ink color are fixed. For this reason, there is no fear of positional deviation between the line-type inkjet heads 30C, 30K, 30M, and 30Y for each ink color and the printing paper PA, so that printing can be started immediately after the head cleaning.

  Next, a modified example in which the ejection failure inspection apparatus 10B for the line type inkjet head of Example 2 is partially modified will be briefly described with reference to FIG.

  As shown in FIG. 12, in the ejection defect inspection apparatus 10B ′ for the line-type inkjet head, which is a modification of the second embodiment, each ink color corresponds to the upper side of the printing paper PA conveyed in the arrow X direction. The line-type inkjet heads 30C, 30K, 30M, and 30Y are fixedly installed in the same manner as the second embodiment. Although this modified example also includes a paper air suction / conveyance mechanism and a head cleaning mechanism similar to those in the second embodiment, illustration thereof is omitted here.

  Here, the differences from the second embodiment will be described. Among the line-type inkjet heads 30C, 30K, 30M, and 30Y for each ink color, the line-type inkjet installed at the most downstream in the conveyance direction of the printing paper PA. A long printed light source 81 is attached along the most downstream side surface 30b of the head 30Y, and the printed light that has passed below the most downstream side surface 30b of the most downstream line-type inkjet head 30Y is attached by the illumination light source 81. The paper PA is illuminated, and a color camera 82B is fixedly installed on the printed printing paper PA diagonally to the upper right toward the illumination location.

  The color camera (reading means) 82B described above is electrically masked on the periphery other than the one line so that the print density of one line immediately after full-color printing on the printing paper PA can be read. Has been.

  Then, the RGB print density data is read for each line along the line immediately after printing with the line-type inkjet head 30 by the color camera 82B, and is read over the preset number of lines m, which is the same as in the second embodiment. In addition, by obtaining integrated data over m lines, the ejection defect inspection is performed in accordance with the flow shown in FIG. 10 earlier, so that the same effect as in the second embodiment can be obtained.

10A ... Discharge defect inspection device for line-type inkjet head of Example 1,
10A ′: Discharge defect inspection apparatus for a line-type inkjet head according to a modification obtained by partially deforming the first embodiment,
10B ... Discharge defect inspection device for line-type inkjet head of Example 2,
10B ′: Discharge defect inspection device for a line-type inkjet head according to a modification obtained by partially deforming the second embodiment,
20 ... paper air suction and conveyance mechanism, 21 ... belt platen, 21a ... hole,
22 ... motor, 23 ... drive pulley, 24-26 ... driven pulley,
27, 28 ... Air suction part (suction box),
30, 30C, 30K, 30M, 30Y ... line type inkjet head,
30a ... bottom surface, 30b ... the most downstream side surface,
40A, 40B ... Reading means (line sensor), 40a ... bottom surface, 40b ... left side surface,
41 ... Light emitting element, 42 ... Light receiving element,
50: Head cleaning mechanism,
51 ... Moving stand, 52 ... Ink suction nozzle, 53 ... Hose, 54 ... Ink suction pump,
55 ... Blade,
60A, 60B ... control unit, 61 ... ROM, 62 ... RAM,
62a, 62b, first and second thresholds, 63, comparing means (comparing circuit),
71A, 71B ... personal computer, 72A, 72B ... scanner,
73A, 73B ... Image processing circuit,
74A, 74B ... integration means (integration circuit), 74a, 74b ... integration data,
75 ... color conversion separation means (RGB → CKMY conversion separation circuit), 75a ... integrated data,
76 ... Alarm processing circuit, 77 ... Head cleaning processing circuit,
81 ... Light source for illumination, 82A, 82B ... Reading means (camera),
INK ... ink, PA ... printing paper, G ... manuscript paper.

Claims (5)

Paper conveying means for conveying printing paper;
The plurality of nozzles fixedly installed above the printing paper for each ink color according to at least one ink color and corresponding to a plurality of nozzles arranged in a line direction perpendicular to the conveyance direction of the printing paper. At least one line-type inkjet head that ejects ink of ink color toward the printing paper; and
An image printed on the printing paper that is installed on the most downstream side in the conveyance direction of the printing paper among the at least one or more of the linear inkjet heads and passes through the linear inkjet head arranged on the most downstream side. Reading means for reading the print density data by characters and characters line by line;
Integrating means for integrating m print density data read by the reading means over a preset number of lines m and outputting integrated data;
Comparing means for comparing the integrated data from the integrating means and a preset threshold value along the line direction to determine at least one or more ejection failure states of the line type inkjet head. An ejection defect inspection device for a line-type inkjet head.   The monolithic printing of the image or the characters on the printing paper has a single line-type inkjet head, and the reading means is a monochrome line sensor or camera. The line type inkjet head ejection defect inspection apparatus according to 1.   When color printing the image and the characters on the printing paper, a plurality of the line-type inkjet heads corresponding to a plurality of ink colors are arranged in parallel along the conveyance direction of the printing paper, and 2. The ejection failure inspection apparatus for a line type ink jet head according to claim 1, wherein the reading means is a color line sensor or a camera.   In the case of color printing, the RGB integrated data obtained by integrating the RGB print density data output from the color line sensor or the camera over the number m of lines by the integrating unit is converted by the color conversion separating unit into the plurality of RGB integrated data. The integrated data of each ink color is obtained by color conversion and separation for each ink color corresponding to each ink color, and then the integrated data for each ink color is compared with the threshold value for each ink color by the comparing means. 4. A discharge failure inspection apparatus for a line type ink jet head according to claim 3, wherein a discharge failure state is inspected for each line type ink jet head corresponding to each ink color. The threshold value includes a first threshold value for inspecting a state immediately before the ejection failure of the line-type inkjet head and a first threshold value for inspecting a state of ejection failure of the line-type inkjet head. And a second threshold value that is less than
A warning is issued when the integrated data is smaller than the first threshold by the comparing means, and then it is determined that there is a discharge failure when the integrated data is smaller than the second threshold. The ejection defect inspection device for a line-type inkjet head according to any one of claims 1 to 4.

Images