JP2007176166A - Measuring method of recording medium conveyance amount and inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring method of recording medium conveyance amount which correctly detects the sub-scanning feed amount. <P>SOLUTION: The measuring method of the recording medium conveyance amount comprises the steps of: recording a first test pattern having two straight lines including at least one straight line which is not parallel with respect to a conveyance direction of a recording medium and a direction orthogonal to the conveyance direction, onto the recording medium; conveying the recording medium in the conveyance direction; recording a second test pattern having two straight lines including at least one straight line which is not parallel with respect to the conveyance direction of the recording medium and the direction perpendicular to the conveyance direction, onto the recording medium; and reading in the first and second test patterns and calculating a conveyance amount of the recording medium. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a recording medium conveyance amount measuring method and an inkjet recording apparatus, and in particular, a recording medium conveyance amount measurement for measuring and calculating a feed amount deviation in a sub-scanning direction of a recording medium in a serial type (shuttle type) inkjet recording apparatus. The present invention relates to a method and an ink jet recording apparatus using the method.

  2. Description of the Related Art Conventionally, an image recording apparatus has an inkjet head in which a large number of nozzles that eject ink as droplets are arranged, and the inkjet head and the recording medium are moved relative to each other while moving from the nozzle to the recording medium. An ink jet recording apparatus that records an image on a recording medium by ejecting ink is known.

  As a printing method of the ink jet recording apparatus, there is a printing method called a serial method or a shuttle method. This is because ink is ejected while reciprocating the inkjet head in a direction perpendicular to the conveyance direction of the recording medium (recording medium width direction) to print an image for one band in the recording medium width direction. The image is recorded on the recording medium by repeatedly printing the image for the next band while transporting the band and moving the inkjet head back and forth again.

  Therefore, in such an ink jet recording apparatus, if there is an error (sub-scan feed amount deviation) in the transport amount of the recording medium, a gap is formed at the joint of the bands, and white stripes occur, or the joints overlap to increase the density. For example, streak unevenness occurs in the width direction (main scanning direction) of the recording medium. For this reason, in order to adjust the conveyance amount of the recording medium, it is important to accurately detect the conveyance error (sub-scan feed amount deviation) of the recording medium.

On the other hand, for example, a linear image extending along the scanning direction (main scanning direction) of the print head (inkjet head) is conventionally recorded before and after the sub-scan feed of the printing material (recording medium). When detecting a sub-scan feed deviation based on the degree of coincidence of edges in the sub-scan direction of a recorded image, a recording medium that is easily detected by performing sub-scan feed a plurality of times to increase the deviation amount. A conveyance deviation detection printing pattern printing method and an inkjet image forming apparatus that can recognize a sub-scan feed amount deviation are known (see, for example, Patent Document 1).
JP 2004-17526 A

  However, in the case described in Patent Document 1, when a sub-scan feed shift is detected using a linear image extending in the main scanning direction, the edge portion that is important for detection is ejected by one nozzle. Therefore, if the nozzle has an ejection failure such as an abnormality in directionality or size or non-ejection, there is a problem that an error occurs in the detection result with respect to the original shift amount.

  In addition, when the amount of deviation is automatically detected using a sensor array attached to the carriage, the sensor for detecting the edge portion is one element. Therefore, the amount of deviation is accurately affected by the sensitivity variation of the sensor. May not be measured. Here, the sensitivity unevenness is calibrated by reading the white plate. However, when the white plate itself gets dust or dirt, the sensitivity unevenness often occurs.

  Further, the one described in Patent Document 1 attempts to facilitate detection by performing sub-scan feed a plurality of times and enlarging the shift amount. Since it is required to increase the scanning feed amount to reduce the number of multiple writings as much as possible, for example, when the feed amount at one time is set to ½ of the head length, a plurality of feed amounts at the time of test pattern printing are set. The amount of deviation cannot be enlarged by setting the time.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a recording medium conveyance amount measuring method and an inkjet recording apparatus that can accurately detect a sub-scan feed amount using a sensor. To do.

  In order to achieve the above object, the invention described in claim 1 includes a second straight line including at least one straight line that is not parallel to either the transport direction of the recording medium or the direction orthogonal thereto. One test pattern is recorded on the recording medium, the recording medium is transported in the transport direction, and includes at least one straight line that is not parallel to either the transport direction of the recording medium or a direction perpendicular thereto. A recording medium conveyance amount, wherein a second test pattern having two straight lines is recorded on the recording medium, the first and second test patterns are read, and the conveyance amount of the recording medium is calculated. Provide a measuring method.

  This makes it possible to accurately measure the conveyance amount of the recording medium.

  According to a second aspect of the present invention, the transport amount of the recording medium is calculated by calculating the intersection of the two straight lines constituting the first test pattern and the two pieces constituting the second test pattern. An intersection of the straight lines is calculated and calculated from the distance in the transport direction between the two points.

  By calculating the intersection of the straight lines in this way and calculating the transport amount, the measurement accuracy of the transport amount is further improved.

  Similarly, in order to achieve the above-mentioned object, the invention according to claim 3 comprises a conveying means for conveying a recording medium, and a liquid on the recording medium while scanning in a direction perpendicular to the conveying direction of the recording medium. A first test pattern having two straight lines including at least one straight line that is not parallel to either the transport direction of the recording medium or the direction perpendicular to the transport direction of the recording medium; Test pattern generating means for generating a test pattern, reading means for reading the first test pattern and the second test pattern formed on the recording medium, and the first test pattern and the second by the reading means Feed deviation amount calculating means for calculating a feed deviation amount in the transport direction of the recording medium based on the result of reading the test pattern, After forming a strike pattern on the recording medium, the recording medium is conveyed in the conveyance direction, and the second test pattern is formed on the recording medium, and the first test pattern and the second test pattern are formed. An ink jet recording apparatus is provided that calculates a feed shift amount of the recording medium in the transport direction based on a result of reading a pattern.

  As a result, it is possible to accurately calculate the conveyance shift amount of the recording medium in the ink jet recording apparatus.

  Further, according to a fourth aspect of the present invention, the feed deviation amount calculation means configures the first test pattern from the result of reading the first test pattern and the second test pattern by the reading means. The intersection of the two straight lines is calculated, the intersection of the two straight lines constituting the second test pattern is calculated, and the feed deviation amount is calculated from the distance in the transport direction of the two intersections. It is characterized by.

  Thereby, the calculation accuracy of the transport feed deviation amount can be further improved.

  Further, as shown in claim 5, the ink jet recording apparatus according to claim 3 or 4, further comprising a medium type specifying means for specifying the type of the recording medium, and a print mode setting means for setting a print mode. And a conveyance amount setting means for setting the conveyance amount of the recording medium based on the type and print mode of the recording medium and the calculation result of the feed deviation amount calculation means.

  As a result, the recording medium can be accurately transported in consideration of the transport feed deviation amount and the like, so that the image can be recorded with high accuracy.

  As described above, according to the present invention, it is possible to accurately measure the conveyance amount of the recording medium.

  Hereinafter, a recording medium conveyance amount measuring method and an ink jet recording apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is an overall configuration diagram showing an outline of an embodiment of an ink jet recording apparatus using a recording medium conveyance amount measuring method according to the present invention.

  As shown in FIG. 1, the inkjet recording apparatus 10 includes a printing unit 12 that includes a plurality of printing heads provided for each ink color and performs shuttle-type printing, and ink supplied to each printing head of the printing unit 12. An ink storage / loading unit 14 for storing the recording paper, a paper feeding unit 18 for supplying the recording paper 16, a decurling unit 20 for removing curling of the recording paper 16, and a nozzle surface of each print head of the printing unit 12 The suction belt transport unit 22 that is disposed opposite to the (ink ejection surface) and transports the recording paper 16 while maintaining the flatness of the recording paper 16 and the printed recording paper (printed matter) are discharged to the outside. A paper discharge unit 26.

  In FIG. 1, a magazine for rolled paper (continuous paper) is shown as an example of the paper supply unit 18, but a plurality of magazines having different paper widths, paper quality, and the like may be provided side by side. Further, instead of the roll paper magazine or in combination therewith, the paper may be supplied by a cassette in which cut papers are stacked and loaded.

  In the case of an apparatus configuration using roll paper, a cutter 28 is provided as shown in FIG. 1, and the roll paper is cut into a desired size by the cutter 28. The cutter 28 includes a fixed blade 28A having a length equal to or greater than the conveyance path width of the recording paper 16, and a round blade 28B that moves along the fixed blade 28A. The fixed blade 28A is provided on the back side of the print. The round blade 28B is arranged on the print surface side with the conveyance path interposed therebetween. Note that the cutter 28 is not necessary when cut paper is used.

  When multiple types of recording paper are used, an information recording body such as a barcode or wireless tag that records paper type information is attached to the magazine, and the information on the information recording body is read by a predetermined reader. Therefore, it is preferable to automatically determine the type of paper to be used and perform ink ejection control so as to realize appropriate ink ejection according to the type of paper.

The recording paper 16 delivered from the paper supply unit 18 retains curl due to having been loaded in the magazine. In order to remove this curl, heat is applied to the recording paper 16 by the heating drum 30 in the direction opposite to the curl direction of the magazine in the decurling unit 20. At this time, it is more preferable to control the heating temperature so that the printed surface is slightly curled outward.

  After the decurling process, the cut recording paper 16 is sent to the suction belt conveyance unit 22. The suction belt conveyance unit 22 has a structure in which an endless belt 33 is wound between rollers 31 and 32, and is configured such that at least a portion facing the nozzle surface of the printing unit 12 forms a flat surface (flat surface). Has been.

  The belt 33 has a width that is wider than the width of the recording paper 16, and a plurality of suction holes (not shown) are formed on the belt surface. As shown in FIG. 1, a suction chamber 34 is provided at a position facing the nozzle surface of the printing unit 12 inside the belt 33 spanned between the rollers 31 and 32, and the suction chamber 34 is connected to the fan 35. The recording paper 16 on the belt 33 is sucked and held by suctioning to negative pressure. The power of a motor (not shown) is transmitted to at least one of the rollers 31 and 32 around which the belt 33 is wound, so that the belt 33 is driven in the clockwise direction in FIG. The recording paper 16 is conveyed from left to right in FIG.

  Since ink adheres to the belt 33 when a borderless print or the like is printed, the belt cleaning unit 36 is provided at a predetermined position outside the belt 33 (an appropriate position other than the print area). Although details of the configuration of the belt cleaning unit 36 are not shown, for example, there are a method of niping a brush roll, a water absorbing roll, etc., an air blowing method of spraying clean air, or a combination thereof. In the case where the cleaning roll is nipped, the cleaning effect is great if the belt linear velocity and the roller linear velocity are changed.

  Although a mode using a roller / nip transport mechanism instead of the suction belt transport unit 22 is also conceivable, when the print area is transported by a roller / nip, the roller comes into contact with the print surface of the paper immediately after printing, so that the image blurs. There is a problem that it is easy. Therefore, as in this example, suction belt conveyance that does not contact the image surface in the printing region is preferable.

  A heating fan 40 is provided on the upstream side of the printing unit 12 on the paper conveyance path formed by the suction belt conveyance unit 22. The heating fan 40 heats the recording paper 16 by blowing heated air onto the recording paper 16 before printing. Heating the recording paper 16 immediately before printing makes it easier for the ink to dry after landing.

  The printing unit 12 includes each print head corresponding to each color ink that reciprocates in the direction (main scanning direction) orthogonal to the conveyance direction (sub-scanning direction) of the recording paper 16 and performs shuttle-type printing. The printing unit 12 will be described in detail later.

  As shown in FIG. 1, the ink storage / loading unit 14 has tanks that store color inks corresponding to the print heads of the printing unit 12, and each tank is connected to each of the lines via a pipe line (not shown). It is in communication with the print head. Further, the ink storage / loading unit 14 includes notifying means (display means, warning sound generating means, etc.) for notifying when the ink remaining amount is low, and has a mechanism for preventing erroneous loading between colors. is doing.

  A post-drying unit 42 is provided following the printing unit 12. The post-drying unit 42 is means for drying the printed image surface, and for example, a heating fan is used. Since it is preferable to avoid contact with the printing surface until the ink after printing is dried, a method of blowing hot air is preferred.

When printing on porous paper with dye-based ink, the weather resistance of the image is improved by preventing contact with ozone or other things that cause dye molecules to break by blocking the paper holes by pressurization. There is an effect to.

  A heating / pressurizing unit 44 is provided following the post-drying unit 42. The heating / pressurizing unit 44 is a means for controlling the glossiness of the image surface, and pressurizes with a pressure roller 45 having a predetermined uneven surface shape while heating the image surface to transfer the uneven shape to the image surface. To do.

  The printed matter generated in this manner is outputted from the paper output unit 26. It is preferable that the original image to be originally printed (printed target image) and test print (test pattern) to be described later are discharged separately. The ink jet recording apparatus 10 is provided with a selecting means (not shown) for switching the paper discharge path in order to select the printed matter of the main image and the printed matter of the test print and send them to the respective discharge portions 26A and 26B. ing. Note that when the main image and the test print are simultaneously formed in parallel on a large sheet, the test print portion is separated by a cutter (second cutter) 48. The cutter 48 is provided immediately before the paper discharge unit 26, and cuts the main image and the test print unit when the test print is performed on the image margin. The structure of the cutter 48 is the same as that of the first cutter 28 described above, and includes a fixed blade 48A and a round blade 48B.

  Although not shown, the paper output unit 26A for the target prints is provided with a sorter for collecting prints according to print orders.

  FIG. 2 is an enlarged plan view showing the periphery of the printing unit 12 of the inkjet recording apparatus 10 of the present embodiment.

  As shown in FIG. 2, the print unit 12 includes a print head 12Y that discharges yellow (Y) ink, a print head 12M that discharges magenta (M) ink, and a print head 12C that discharges cyan (C) ink. And a print head 12K that discharges black (K) ink. Each print head 12Y, 12M, 12C, 12K has a longitudinal direction substantially parallel to the conveyance direction of the recording paper 16 (indicated by an arrow A in the figure). Are arranged side by side on the head carriage 13.

  The head carriage 13 reciprocates on a guide rail 15 installed in the width direction (main scanning direction) of the recording paper 16 substantially perpendicular to the conveyance direction (sub-scanning direction) of the recording paper 16 as indicated by an arrow B in the figure. It is movable. The print heads 12Y, 12M, 12C, and 12K are shuttle type heads that perform image recording while reciprocating in the width direction of the recording paper 16 (the direction indicated by arrow B in the drawing) as the carriage 13 moves.

  At this time, the print heads 12Y, 12M, 12C, and 12K perform image recording only when moving in one direction from the left end to the right end of the recording paper 16 in the drawing. When returning to the end, image recording is not performed.

  Further, the recording paper 16 moves from one end in the width direction of the recording paper 16 to the other end (in the example shown in the drawing, from the left end to the right end) while the print heads 12Y, 12M, 12C, and 12K perform recording. When you are stationary. When the print heads 12Y, 12M, 12C, and 12K have finished recording from one end in the width direction of the recording paper 16 to the other end, and return to this one end again, the recording paper 16 is printed. The heads 12Y, 12M, 12C, and 12K are transported in the sub-scanning direction indicated by the arrow A in the figure by an amount corresponding to the width of the band-like image recording area in the width direction of the recording paper 16 that has just been recorded.

A scanner unit 17 for reading an image recorded on the recording paper 16 is provided on the left side (in the drawing) of the carriage 13. The scanner unit 17 is a line sensor in which sensor rows are arranged along the conveyance direction of the recording paper 16. The sensor cover range of the scanner unit 17 is slightly wider than the nozzle row length of each print head 12Y, 12M, 12C, 12K. Thereby, even if there is an attachment error of the scanner unit 17, all the nozzles can be covered.

  FIG. 3 is a principal block diagram showing the system configuration of the inkjet recording apparatus 10.

  As shown in FIG. 3, the inkjet recording apparatus 10 of the present embodiment includes a communication interface 70, a system controller 72, an image memory 74, a motor driver 76, a heater driver 78, a print control unit 80, an image buffer memory 82, and a head driver 84. Etc.

  The communication interface 70 is an interface unit that receives image data sent from the host computer 90. As the communication interface 70, a serial interface such as USB, IEEE 1394, Ethernet (registered trademark), a wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory for speeding up communication may be mounted.

  Image data sent from the host computer 90 is taken into the inkjet recording apparatus 10 via the communication interface 70 and temporarily stored in the image memory 74. The image memory 74 is a storage unit that temporarily stores an image input via the communication interface 70, and data is read and written through the system controller 72. The image memory 74 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The system controller 72 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 10 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. . That is, the system controller 72 controls each part such as the communication interface 70, the image memory 74, the motor driver 76, the heater driver 78, etc., performs communication control with the host computer 90, read / write control of the image memory 74, etc. A control signal for controlling the motor 77 and the heater 89 of the transport system is generated.

  Note that programs executed by the CPU of the system controller 72 and various data necessary for control are stored in a ROM (not shown) or the like. The image memory 74 is used as a temporary storage area for image data, and is also used as a program development area and a calculation work area for the CPU.

The motor driver 76 is a driver (drive circuit) that drives a conveyance system motor 77 that conveys the recording paper 16 in accordance with an instruction from the system controller 72. The heater driver 78 is a driver that drives the heater 89 such as the post-drying unit 42 in accordance with an instruction from the system controller 72.

  The print control unit 80 has a signal processing function for performing various processing and correction processing for generating a print control signal from the image data in the image memory 74 according to the control of the system controller 72, and the generated print It is a control unit that supplies data (dot data) to the head driver 84.

The print controller 80 includes an image buffer memory 82, and the print controller 8
Data such as image data and parameters is temporarily stored in the image buffer memory 82 during image data processing at 0. In FIG. 3, the image buffer memory 82 is shown in a mode associated with the print control unit 80, but can also be used as the image memory 74. Also possible is an aspect in which the print controller 80 and the system controller 72 are integrated and configured with one processor.

  Image data to be printed is input from the outside via the communication interface 70 and stored in the image memory 74. At this stage, for example, RGB image data is stored in the image memory 74.

  The image data stored in the image memory 74 is sent to the print control unit 80 via the system controller 72, and the print control unit 80 performs dot data for each ink color by a halftoning technique such as a dither method or an error diffusion method. Is converted to In the ink jet recording apparatus 10, a pseudo continuous tone image is formed by changing the droplet ejection density and dot size of fine dots with ink (coloring material) to the human eye. It is necessary to convert to a dot pattern that reproduces the gradation (shading of the image) as faithfully as possible.

  That is, the print control unit 80 performs processing for converting the input RGB image data into dot data of four colors Y, M, C, and K. Further, the print controller 80 discriminates the treatment liquid droplet ejection area (the area on the recording surface where the treatment liquid droplet ejection is necessary) based on the dot data of each color, and generates the treatment liquid droplet ejection dot data. . In this way, the dot data (for the treatment liquid and for each color) generated by the print control unit 80 is stored in the image buffer memory 82.

  The head driver 84 generates drive control signals for the print heads 12Y, 12M, 12C, and 12K for the respective color inks based on the print data (that is, dot data stored in the image buffer memory 82) given from the print control unit 80. To do.

  The drive control signal generated by the head driver 84 is applied to the ink ejection actuators of the print heads 12Y, 12M, 12C, and 12K, so that ink is ejected from the corresponding nozzles of the print heads 12Y, 12M, 12C, and 12K. .

  As described above, the recording paper 16 is stopped and the print heads 12Y, 12M, 12C, and 12K are moved from one end in the width direction of the recording paper 16 toward the other end while the print heads 12Y, 12M, and 12K are moved. Ink is ejected from 12C and 12K (see FIG. 2). Thereafter, the recording paper 16 is conveyed by the nozzle length in the sub-scanning direction (the range in which the nozzles are formed in the sub-scanning direction of each print head), and the print heads 12Y, 12M, 12C, and 12K are moved to the other side. Returning from one end to the other end, the recording paper 16 is stopped again, and ink is ejected while the print heads 12Y, 12M, 12C, and 12K are moved toward the other end. By repeating this, an image is formed on the recording paper 16.

  In this embodiment, the print controller 80 also determines the sub-scan feed deviation amount in order to accurately detect the error (sub-scan feed deviation amount) of the recording paper 16 in the sub-scan direction. A test pattern generation unit 92 that generates print data of a test pattern for detection; a sub-scan feed deviation amount calculating unit 94 that calculates a sub-scan feed deviation amount from a result of reading the printed test pattern by the scanner unit 17; Sub-scan feed amount setting means (conveyance amount setting means) 96 for setting the sub-scan feed amount (conveyance amount) based on the sub-scan feed deviation amount.

As will be described in detail later, the test pattern is composed of, for example, two straight lines that are not parallel to either the main scanning direction or the sub-scanning direction. The intersection of the two straight lines is obtained, and the amount of sub-scan feed deviation from the position of the intersection is obtained. Is calculated. Therefore, the sub-scan feed deviation amount calculation means 94 has a linear equation calculation unit 94a, an intersection calculation unit 94b, and a sub-scan feed deviation amount calculation unit 94c.

  Further, since the sub-scan feed amount setting means 96 is used when setting the sub-scan feed amount, a medium type specifying means 98 for specifying the type of the recording paper 16, a print mode setting means 99, and a reference sub-scan feed amount table 100 are provided. The print controller 80 is provided.

  Next, a sub-scan feed deviation amount calculation method as a recording medium conveyance amount measurement method according to the present invention will be described.

  FIG. 4 is a flowchart showing a rough flow of the sub-scan feed deviation amount calculation method according to this embodiment.

  First, in step S100 in FIG. 4, the first test pattern is printed. The print data of the first test pattern is generated by the test pattern generation unit 92.

  FIG. 5 shows an example of the first test pattern. As shown in FIG. 5, the first test pattern 102 is not parallel to any of the sub-scanning direction parallel to the conveyance direction of the recording paper 16 and the main scanning direction that is the moving direction of the head carriage 13 orthogonal thereto. The first straight line (first line) 102a and the second straight line (second line) 102b are constituted by two straight lines.

  Briefly explain why such test patterns are used. First, in order to obtain a sub-scan feed error, a test pattern is recorded, a sub-scan feed is performed, a test pattern is recorded again, and a recording paper 16 at a position where each test pattern is recorded before and after the sub-scan feed. It is necessary to obtain the relative position (coordinates) in the y direction (sub-scanning direction) above.

  At this time, as shown in FIG. 6, scanning is performed by moving the printed test pattern in parallel with the main scanning direction of the scanner unit 17 in which sensor elements (detection elements) are arranged in a line in the sub-scanning direction.

  Here, for example, as shown in (1) of FIG. 6, in the case of a pattern consisting of one line printed in the main scanning direction by one nozzle, since it is one nozzle, there is a discharge failure such as landing position deviation in this nozzle. And the y-direction coordinate of the pattern cannot be measured accurately.

  Further, for example, in the case of a test pattern made of a rectangle having sides parallel to the main scanning direction as shown in (2) of FIG. 6, the edge positions of the two sides parallel to the main scanning direction are obtained by a sensor. However, only the two patterns of (1) are used, and as in the case of (1), if there is a discharge failure in the nozzle that prints the edge portion, the y-direction coordinates of the pattern can be accurately measured. Can not.

  Further, since the scanning direction of the line sensor of the scanner unit 17 and the edge direction of the pattern coincide with each other, the edge portion is specified by approximately one detection element of the sensor. In this case, the threshold value of the edge that is blurred and scanned due to flare or the like is shifted, and the coordinates in the edge y direction cannot be measured accurately.

On the other hand, in the case of a test pattern composed of two straight lines that are not parallel to either of the main and sub scanning directions as shown in FIG. 6 (3), the coordinates of the intersection point are obtained by reading these two straight lines and calculating them. Thus, the coordinates of the intersection can be accurately obtained. Two such test patterns are recorded before and after the sub-scan feed, and by comparing the coordinates of their intersections, the sub-scan feed deviation amount can be accurately obtained.

  The test pattern is not limited to a pattern composed of two straight lines that are not parallel to either the main scanning direction or the sub-scanning direction as shown in FIG. It is not an essential condition that it is not parallel to either the main scanning direction or the sub-scanning direction, and it is only necessary to include two straight lines that are not parallel to each other.

  Another example of the test pattern is shown in FIG. For example, the example of FIG. 7A is two straight lines that intersect with each other, and the example of FIG. 7B is two straight lines that intersect when not extending but extending each other. The example of FIG. 7C is similar to the pattern of FIG. 5, but one straight line is parallel to the sub-scanning direction. Furthermore, the example of FIG. 7D is a figure having at least one set of edges that are not parallel to the main scanning direction and having a solid interior. Also in this case, if a set of edges that are not parallel to each other are detected, they can be handled in the same manner as a pattern composed of straight lines. It is assumed that the edge of the figure with the solid inside is also included in the straight line.

  The pattern described above is printed on the recording paper 16 as the first test pattern. That is, as shown in FIG. 8, the print head (12Y, 12M, 12C, or 12K) is moved in the width direction of the recording paper 16 (direction orthogonal to the conveyance direction (sub-scanning direction) of the recording paper 16). However, a pattern as shown in FIG. 5 is recorded on the recording paper 16 as the first test pattern 102-1. As described above, the first test pattern 102-1 is composed of two line segments each having an angle of 45 ° and −45 ° with respect to the main scanning direction, and the line segments intersect with each other at the end points.

  At this time, nozzles 51 are arranged in a line along the sub-scanning direction in the print head 12K (or any one of 12Y, 12M, and 12C). Further, the nozzles 51 are numbered 1, 2,..., N,... From the upper side of the drawing, and the first test pattern 102 is formed by m + 1 nozzles 51 from the nth to the n + mth. It is assumed that -1 is ejected.

  Next, in step S110 of FIG. 4, as shown in FIG. 9, the recording paper 16 is sub-scan fed by the length (height) in the y direction of the first test pattern 102-1, that is, m + 1 nozzles ( Conveyed in the sub-scanning direction).

  Next, in step S120, as shown in FIG. 10, while moving the print head 12K (12C, 12M, 12Y) in the width direction of the recording paper 16, nozzles from nm-1 to n-1 are used. 51, the second test pattern 102-2 is printed on the right side of the first test pattern 102-1.

  The first test pattern 102-1 and the second test pattern 102-2 are not necessarily the same pattern, but in the example shown here, the second test pattern 102-2 is the first test pattern 102-2. This is the same pattern as the pattern 102-1.

  Each pattern is printed while the print head 12K (12C, 12M, 12Y) performs one scan from one end to the other end in the width direction of the recording paper 16. This is because when reciprocal printing or printing using a plurality of passes is performed, a shift occurs in each pass in the x direction (main scanning direction), and an error occurs in the coordinate calculation of the intersection of two straight lines.

  Further, the line width of the straight lines constituting each pattern may be one dot, but when measurement by a sensor using flare is difficult, the line width may be constituted by several dots.

Next, in step S130, the first test pattern 102-1 and the second test pattern 102-2 are scanned with the sensor array of the scanner unit 17. As described above, since the scanner unit 17 is installed on the head carriage 13, each pattern can be scanned simultaneously with the recording of the second test pattern 102-2 while moving the head carriage 13.

  The data read by the scanner unit 17 is sent to the sub-scan feed deviation amount calculation means 94 of the print control unit 80.

  In step S140, as shown in FIG. 11, the sub-scanning direction positions y1 and y2 of the intersections P1 and P2 of the two straight lines constituting the first test pattern 102-1 and the second test pattern 102-2, respectively. Is calculated. In step S150, the sub-scan feed shift amount is calculated by comparing the sub-scanning direction positions y1 and y2 of the intersections P1 and P2.

  Next, how to find the intersection of two straight lines will be described. FIG. 12 is a flowchart showing how to obtain the intersection point. Since both the first test pattern 102-1 and the second test pattern 102-2 are obtained in the same way, the method for obtaining the intersection of the first test pattern 102-1 will be described.

  First, in step S200 of FIG. 12, the scanning image of the first test pattern 102-1 sent from the scanner unit 17 to the sub-scan feed deviation amount calculation means 94 of the print controller 80 is binarized.

Next, in step S210, the equation of the first straight line (first line) 102-1a constituting the first test pattern 102-1 is calculated in the linear equation calculation unit 94a. The calculation method of the straight line equation is not particularly limited. For example, as the simplest example, there is known a method of obtaining a straight line equation by the least square method by inputting each coordinate of the binarized scanning image. It has been. At this time, if there is a dot that deviates greatly from the straight line, the equation of the straight line may be obtained by excluding the dot. Further, since it is difficult to determine which of the two straight lines data is an error, an image in the vicinity of the intersection of the two straight lines has an error, so it is better to exclude it when calculating the intersection. The calculated first straight line equation is set as y = α ₁ x + β ₁ .

Next, in step S220, the linear equation calculation unit 94a calculates the equation of the second straight line (second line) 102-1b constituting the first test pattern 102-1 in the same manner as above. The calculated equation of the second straight line is y = α ₂ x + β ₂ .

Next, in step S230, the two straight line equations calculated above are solved to calculate the coordinates of the intersection of the two straight lines. The coordinates (x ₁ , y ₁ ) of the intersection of these two straight lines are obtained as follows by solving simultaneous equations.

x ₁ = (β ₂ −β ₁ ) / (α ₁ −α ₂ )
y ₁ = (α ₁ β ₂ -α ₂ β ₁ ) / (α ₁ -α ₂ )
In the same manner as described above, the coordinates (x ₂ , y ₂ ) of the intersection of the two straight lines constituting the second test pattern 102-2 are calculated.

  At this time, since there are a plurality (sufficient number) of nozzles for ejecting dots constituting each line of the test pattern, even if ejection failure nozzles are mixed, the influence is very small. When the droplet ejection positions vary randomly, the central linear equation can be obtained without any influence. Thus, even if there are variations in the discharge amount and non-discharge nozzles are mixed, it is possible to accurately obtain a linear equation without being affected by them. Furthermore, even if there are variations in sensor sensitivity, the dots constituting each line are measured by a plurality of sensor elements, so that a linear equation can be accurately obtained without being affected by variations in sensor sensitivity. it can. Therefore, since the straight line equation can be obtained with high accuracy, the coordinates of the intersection of these straight lines can be obtained with high accuracy.

Returning to step S150 in FIG. 4 again, the sub-scan feed deviation amount calculation unit 94c compares the y-coordinates y ₁ and y ₂ of the two intersections that have just been obtained, thereby obtaining the sub-scan feed deviation amount y ₂ -y ₁ . calculate.

At this time, if the sub-scan feed shift amount y ₂ -y ₁ is 0, y ₂ = y _{1 and} there is no shift in the sub-scan feed amount. Also, as shown in FIG. 11, when the sub-scan feed deviation amount y ₂ -y ₁ > 0, the difference between the y coordinates becomes the sub-scan feed deviation amount.

  In the example described above, when there is no deviation in the sub-scan feed, the y-coordinates of the intersections of the straight lines constituting the two test patterns recorded before and after the sub-scan feed match, but the sub-scan feed deviation is calculated. Is not limited to such an example.

  FIG. 13 shows another method for calculating the sub-scan feed deviation amount.

  This also uses the same test pattern as in the above example (see FIG. 5). However, when the length (height) in the y direction (sub-scanning direction) of the test pattern corresponds to m nozzles, the first pass The sub-scan feed amount after printing the test pattern in the sub-scan feed is m + 1 nozzles, and the same test pattern is again used in the second pass using the m nozzles in which the test pattern is printed in the first pass. May be printed.

In this case, as shown in FIG. 13, y-coordinate _{y 1} and, m + 1 from the y-coordinate _{y 2} of the test pattern 104-2 that has been printed by the second pass of the test pattern 104-1 that has been printed in the first pass By comparing the y coordinate y ₂ ′ obtained by subtracting the nozzle length, the sub-scan feed deviation amount can be obtained.

  Further, as in these examples, the test patterns printed in the first pass and the second pass before and after the sub-scan feed need not be the same pattern.

  For example, in the example shown in FIG. 14, the test pattern printed in the first pass and the test pattern printed in the second pass after the sub-scan feed are patterns reversed in the sub-scan direction.

  In the example shown in FIG. 14A, after first printing the V-shaped first test pattern 106-1 in the first pass, the nozzle corresponding to the length (height) of the test pattern 106-1. The second test pattern 106- in which the sub-scan feed is performed by the amount of -1 nozzle, and then the V-shaped first test pattern 106-1 is reversed in the sub-scanning direction by the same nozzle as before in the second pass. 2 is printed.

  In the example shown in FIG. 14A, the intersection point P1 of the two straight lines 106-1a and 106-1b constituting the first test pattern 106-1 and 2 constituting the second test pattern 106-2. This coincides with the intersection P2 of the straight lines 106-2a and 106-2b. In this case, the sub-scan feed deviation amount is 0, and there is no sub-scan feed deviation.

In the example shown in FIG. 14B, the V-shaped first test pattern 108-1 is similarly printed in the first pass, and then the length (height) of the test pattern 108-1 is printed. The second test pattern 108-in which the V-shaped first test pattern 108-1 is inverted in the sub-scanning direction by the same nozzle as before in the second pass. 2 is printed.

In the example shown in FIG. 14B, the intersection point P1 of the two straight lines 108-1a and 108-1b constituting the first test pattern 108-1 and 2 constituting the second test pattern 108-2. It is deviated from the intersection P2 of the straight lines 108-2a and 108-2b, and the difference y ₁ -y ₂ between the y coordinates is the sub-scan feed deviation amount.

  In this way, in the example shown in FIG. 14, since it is possible to visually recognize whether the intersections of the two straight lines of each test pattern are coincident or separated, using such a pattern allows not only automatic measurement by a sensor, Whether or not there is a deviation in the sub-scan feed can be determined visually.

  In the above embodiment, the sub-scan feed amount is an integral multiple of the nozzle pitch. However, even when the sub-scan feed amount is not an integral multiple of the nozzle pitch, the sub-scan feed deviation amount is similarly obtained. Needless to say, you can.

  Hereinafter, further effects using the sub-scan feed deviation amount calculation method (recording medium conveyance amount measurement method) of the present embodiment and applications that make use of this will be described.

  As described above, since a straight line composed of a plurality of nozzle droplets is measured by a plurality of sensor elements to calculate a straight line equation, this straight line passes through an ideal droplet ejection center regardless of the droplet ejection size. Since it is a straight line, and the intersection coordinates and the sub-scan feed deviation amount of the straight line obtained from this are also based on the center of droplet ejection, the sub-scan feed deviation amount can be obtained with high accuracy.

  In other words, the droplet ejection size changes depending on the medium type on which the test pattern is printed, but if the sub-scan feed deviation amount calculation method of this embodiment is used, the accuracy is not dependent on the medium type on which the test pattern is printed. A high sub-scan feed shift amount can be calculated.

  FIG. 15 is a block diagram related to sub-scan feed of the inkjet recording apparatus 10 to which the sub-scan feed deviation amount calculation method of this embodiment is applied. This is a part extracted from the control block diagram shown in FIG. 3 regarding the application of the sub-scan feed deviation amount calculation method.

  As shown in FIG. 15, first, the medium type specifying means 98 specifies whether the recording paper 16 is plain paper, photographic paper, ink jet dedicated paper, or the like. Further, the print mode setting means 99 sets a print mode such as a print mode in which printing speed is emphasized or a print mode in which fine printing is emphasized.

  On the other hand, using the reference sub-scan feed amount table 100 in which the reference sub-scan feed amount including the correction amount is previously set as a matrix by combining the print medium type and the print mode, the specified or set print medium type and print are set. Select the reference sub-scan feed amount from the mode.

  Using the selected reference sub-scan feed amount and the sub-scan feed deviation amount calculated by the sub-scan feed deviation calculating unit 94 of the above-described embodiment, the sub-scan feed amount setting unit 96 determines the sub-scan feed amount. Is set.

Based on the set sub-scan feed amount, a predetermined sub-scan feed is executed by a sub-scan feed means 110 including a motor 77 that drives the suction belt conveyance unit 22 and a motor driver 76 that controls the motor 77. As a result, no matter what medium type is used for test pattern printing, all medium types are sub-scan fed without sub-scan feed deviation, and there is no occurrence of streak unevenness due to sub-scan feed deviation. Image recording can be performed.

  The recording medium conveyance amount measuring method and the ink jet recording apparatus of the present invention have been described in detail above, but the present invention is not limited to the above examples, and various improvements and modifications can be made without departing from the gist of the present invention. Of course, you may also do.

1 is an overall configuration diagram showing an outline of an embodiment of an ink jet recording apparatus using a recording medium conveyance amount measuring method according to the present invention. It is a top view which expands and shows the printing part periphery of the inkjet recording device of this embodiment. It is a principal part block diagram which shows the system configuration | structure of the inkjet recording device of this embodiment. It is a flowchart which shows the flow of the sub-scan feed deviation | shift amount calculation method which concerns on this embodiment. It is explanatory drawing which shows the example of a test pattern. It is explanatory drawing which shows the effect of the test pattern of this embodiment. (A)-(d) It is explanatory drawing which shows the example of another test pattern. It is a top view which shows a mode that a 1st test pattern is printed. It is a top view which shows the sub-scan feed of 1st test pattern printing. It is a top view which shows a mode that the 2nd test pattern is printed after subscanning feeding. It is explanatory drawing which shows the calculation method of sub-scan feed deviation | shift amount. It is a flowchart which shows the procedure which calculates | requires the intersection of the 2 straight lines which comprise a test pattern. It is explanatory drawing which shows the other method of calculating | requiring a sub-scan feed deviation | shift amount. Furthermore, it is explanatory drawing which shows the other method of calculating | requiring the amount of sub-scan feed deviations. FIG. 4 is a block diagram related to sub-scan feed of an inkjet recording apparatus to which the sub-scan feed deviation amount calculation method of the present embodiment is applied.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device 12 ... Printing part, 12Y, 12M, 12C, 12K ... Print head, 13 ... Head carriage, 14 ... Ink storage / loading part, 15 ... Guide rail, 16 ... Recording paper, 17 ... Scanner unit, DESCRIPTION OF SYMBOLS 18 ... Paper feed part, 20 ... Decal processing part, 22 ... Adsorption belt conveyance part, 26 ... Paper discharge part, 28 ... Cutter, 30 ... Heating drum, 31, 32 ... Roller, 33 ... Belt, 34 ... Adsorption chamber, 35 DESCRIPTION OF SYMBOLS ... Fan, 36 ... Belt cleaning part, 40 ... Heating fan, 42 ... Post-drying part, 44 ... Heating / pressurizing part, 45 ... Pressure roller, 48 ... Cutter, 70 ... Communication interface, 72 ... System controller, 74 ... Image memory 76 ... Motor driver 78 ... Heater driver 80 ... Print control unit 82 ... Image buffer memory 84 ... Headed , 89 ... heater, 90 ... host computer, 92 ... test pattern generation unit, 94 ... sub-scan feed deviation amount calculation means, 94a ... linear equation calculation unit, 94b ... intersection calculation unit, 94c ... sub-scan feed deviation amount calculation unit 96 ... Sub-scan feed amount setting means, 98 ... Media type specifying means, 99 ... Print mode setting means, 100 ... Reference sub-scan feed amount table, 102 ... First test pattern

Claims (5)

Recording on the recording medium a first test pattern having two straight lines including at least one straight line that is not parallel to either the transport direction of the recording medium or the direction perpendicular thereto;
Transport the recording medium in the transport direction;
Recording on the recording medium a second test pattern having two straight lines including at least one straight line that is not parallel to either the transport direction of the recording medium or a direction perpendicular thereto;
A method for measuring a conveyance amount of a recording medium, wherein the conveyance amount of the recording medium is calculated by reading the first and second test patterns.   The transport amount of the recording medium is calculated by calculating an intersection of the two straight lines constituting the first test pattern and an intersection of the two straight lines constituting the second test pattern. 2. The recording medium conveyance amount measuring method according to claim 1, wherein the calculation is performed from a distance in the conveyance direction between points. Conveying means for conveying the recording medium;
Discharge means for discharging liquid toward the recording medium while scanning in a direction perpendicular to the conveyance direction of the recording medium;
Test pattern generation for generating a first test pattern and a second test pattern having two straight lines including at least one straight line that is not parallel to either the transport direction of the recording medium or the direction perpendicular thereto Means,
Reading means for reading the first test pattern and the second test pattern formed on the recording medium;
A feed deviation amount calculating means for calculating a feed deviation amount in the transport direction of the recording medium based on the result of reading the first test pattern and the second test pattern by the reading means;
And forming the first test pattern on the recording medium, transporting the recording medium in the transport direction, forming the second test pattern on the recording medium, and An ink jet recording apparatus, wherein a feed shift amount of the recording medium in the transport direction is calculated based on a result of reading a test pattern and the second test pattern.   The feed deviation amount calculating means calculates an intersection of the two straight lines constituting the first test pattern from a result of reading the first test pattern and the second test pattern by the reading means. 4. The point of intersection of the two straight lines constituting the second test pattern is calculated, and the feed deviation amount is calculated from the distance of the two points of intersection in the transport direction. 5. Inkjet recording device.   5. The ink jet recording apparatus according to claim 3, further comprising: a medium type specifying unit that specifies the type of the recording medium; a print mode setting unit that sets a print mode; and the type and print mode of the recording medium. An inkjet recording apparatus comprising: a conveyance amount setting unit that sets a conveyance amount of the recording medium based on a calculation result of the feeding deviation amount calculation unit.

Images