JP2009234025A - Test print for evaluating eccentricity degree of roller and method of evaluating eccentricity degree of roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a test print for evaluating eccentricity degree of a roller, the test print facilitating the observation and evaluation of the eccentricity degree of a print conveying roller. <P>SOLUTION: In the test print TP for evaluating the eccentricity degree of the roller, a dot line extends in a main scanning direction formed by a first nozzle unit, in which a selection division area selected in order from division areas 81, 82, 83, 84, and 85 divided into a plurality of areas in the main scanning direction, is in white and the other areas are in black, and the dot line is used as a comparison dot line. The formation of this dot line is repeated by a length corresponding to a sub-scanning distance for at least one rotation of the print conveying roller while selecting the selection division area in order. Further, in the position where a comparison dot line in which the middle division area is formed in white corresponds to a specific nozzle of a second nozzle unit, a dot line extending in the main scanning direction is formed in black as an evaluation dot line by a specific nozzle at the timing of conveyance in sub-scanning. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a first nozzle unit having a number of nozzles that form dot lines in the main scanning direction with respect to a recording medium, and a second nozzle that is shifted from the first nozzle unit by a predetermined distance in the sub-scanning direction. An eccentricity of the print transport roller in a printing apparatus having a print head having a unit, a print transport roller for transporting the recording medium in a sub-scanning direction, and a drive unit for rotating the print transport roller at a predetermined pitch. The present invention relates to a roller eccentricity evaluation test print for evaluation and a roller eccentricity evaluation method.

  As a technique for preventing deterioration in image quality due to the eccentricity of the recording paper conveyance roller, a recording paper conveyance roller for reciprocating the recording paper, and when the recording paper moves forward by the recording paper conveyance roller, the same area on the recording paper is used. A recording unit that performs line-by-line print recording in different colors, a detection unit that detects a rotational angle position of the recording conveyance roller, a registration mark recording unit that records registration marks on a recording sheet at regular time intervals, and Based on the reading means for reading the registration mark, calculation means for calculating the moving speed displacement of the recording paper at each rotation angle position of the recording paper conveyance roller from the reading information of the registration mark, and based on the calculated moving speed displacement of the recording paper Data for creating correction data for line-by-line print recording timing by the recording means at each rotation angle position of the recording paper transport roller And forming means, the image recording apparatus is known which is provided and control means for controlling the printing recording by said recording means on the basis of the correction data created by said data creating means (for example, see Patent Document 1). In this image recording apparatus, first, a registration mark is created on the recording paper at the same timing as the time of image recording, and the registration mark is read, and the movement speed displacement of the recording paper at each rotational angle position of the recording paper transport roller is obtained. To create recording timing correction data for recording dots. Based on the correction data, image recording is performed by correcting the recording timing from the time of image recording of the first color. In this image recording apparatus, the eccentricity of the recording paper conveyance roller is obtained by measuring the individual intervals of the registration marks formed at regular time intervals irrespective of the conveyance speed. In order to obtain the above, it is necessary to shorten the interval between the registration marks and increase the measurement accuracy of the interval. However, in order to increase the measurement accuracy of the interval between the registration marks formed at a short interval, it is necessary to make the registration mark position detector have high performance, which is costly.

  In addition, a recording medium transport rotating body that transports the recording medium, an encoder that detects position or speed information of the recording medium transport rotating body, and a driving force that engages with the recording medium transport rotating body and transmits a driving force. A recording medium conveyance system for moving the recording medium by a predetermined amount by a transmission means and a motor engaged with the driving force transmission means is provided. A drive unit that rotates; a transport unit that transports a recording medium by adding an eccentricity detection amount to a predetermined amount of the drive unit; and a process that performs printing for each transport unit of the recording medium, Ink having means for associating the eccentricity correction value of the recording medium conveyance rotating body with the position information of the encoder by comparing the formed image on the recording medium by the printing process for each rotation of the conveyance rotating body. Jet recording apparatus is also known (e.g., see Patent Document 2). In this ink jet recording apparatus, wide print patterns obtained by performing wide printing for each divided drive amount of the recording medium transport rotator are sequentially superposed while shifting in the main scanning direction, and by eccentricity of the recording medium transport rotator. The degree of overlap of each print pattern that changes is evaluated. Since the overlapping portion of the print pattern that changes due to the eccentricity of the recording medium conveyance rotating body is a small area of the entire print pattern, it is difficult to accurately evaluate the eccentricity from the density change due to the overlap.

JP-A-8-101618 (paragraph number 0075-0104, FIG. 6) Japanese Patent Laying-Open No. 2006-192807 (paragraph numbers 0036-0042, FIG. 7)

  In view of the above-described circumstances, an object of the present invention is to provide a test print for evaluating roller eccentricity that makes it easy to observe and evaluate the eccentricity of a print conveying roller that conveys a recording medium in the sub-scanning direction. The present invention provides a technique for outputting a roller eccentricity test print and evaluating the roller eccentricity.

A first nozzle unit having a plurality of nozzles that form dot lines in the main scanning direction with respect to the recording medium; and a second nozzle unit that is arranged at a predetermined distance from the first nozzle unit in the sub-scanning direction. To evaluate the eccentricity of the print transport roller in a printing apparatus having a print head, a print transport roller that transports the recording medium in the sub-scanning direction, and a drive unit that rotates the print transport roller at a predetermined pitch. In order to solve the above-described problems, the roller eccentricity evaluation test print according to the present invention includes a plurality of comparative dots formed by the first nozzle unit and extending in the main scanning direction. Lines and a plurality of evaluation docks extending in the main scanning direction formed by the second nozzle unit. And a line,
In the comparative dot line, a portion entering a selected divided region selected from among divided regions divided in the main scanning direction is formed with a first gradation value, and the other divided regions are the first divided region. The comparison dot line is formed with a second gradation value different from the one gradation value, and the comparison dot line selects at least one rotation of the print transport roller while selecting the selected divided region in the order of the main scanning direction. Are repeatedly formed at predetermined rotation angles of the print transport roller until a length in the sub-scanning direction corresponding to the sub-scanning distance is reached,
The evaluation dot line is a second angle at a rotation angle of the print transport roller where a central divided region located in the center of the divided regions overlaps the comparative dot line formed with the first gradation value. It is formed with gradation values.
Note that the central divided region located in the center of the divided regions does not mean only the divided region located in the middle in a strict sense in the plurality of divided regions extending in the main scanning direction. Instead, it should be interpreted as a phrase representing a divided area in which there are further divided areas at least on the right and on the left.
Furthermore, the dot here is a minimum print pixel formed by a print head. For example, in the case of an ink jet printing apparatus, one dot is formed on a recording medium by one unit ink droplet ejected from an ink nozzle. Pixels. Therefore, the dot line here means a line segment created by continuously forming such dots in the main scanning direction.

  In this roller eccentricity evaluation test print, comparative dot lines, which are dot lines extending in the main scanning direction, are formed in the sub-scanning direction. In each comparative dot line, a predetermined number in the main scanning direction is formed. A portion corresponding to one divided region is a line segment having a first density (for example, a bright line segment) formed with a first gradation value, and the other portion is a second gradation value. This is a line segment (for example, a dark line segment) having the second density formed in (1). The line segments having the first density are sequentially shifted in the main scanning direction for each comparison dot line. Further, the evaluation dot line is formed so that the line segment having the first density overlaps with the specific comparison dot line in the central divided region. The comparison dot line is formed by the nozzles of the first nozzle unit, whereas the evaluation dot line is a second nozzle unit provided at a position separated by a predetermined distance in the sub-scanning direction from the first nozzle unit. Formed by a nozzle. Therefore, when the print conveying roller is not eccentric and the recording medium is conveyed with a constant sub-scan conveying length in any rotation angle range, the first density is always set, that is, in any sub-scanning direction position. The evaluation dot line overlaps immediately above the comparison dot line in which the line segment is located at the center, and the line segment having the first density becomes a line segment having the same density as the other remaining portions. As a result, the divided area located at the center appears to have a different density compared to the other divided areas. However, when the print transport roller is eccentric and the recording medium is transported with a different sub-scan transport length depending on the rotation angle range, the sub-scan position of the evaluation dot line is shifted from the target position. The evaluation dot line does not overlap directly above the comparison dot line in which the line segment having the density of 1 is located in the center, but is positioned away from the center of the other comparison dot lines. Overlap the line with the first concentration. Therefore, an area that appears to have a different density compared to the other areas is shifted in the main scanning direction due to the eccentricity. Since the eccentric behavior is repeated with one rotation of the print conveying roller as a cycle, the cycle of how to shake an area that appears darker (darker) than other regions is similarly conveyed with one rotation of the print conveying roller. This is the length in the sub-scanning direction. In other words, according to the test print for evaluating the degree of eccentricity of the roller according to the present invention, the portion that originally has the first density changes to the second density according to the degree of eccentricity of the print transport roller, and is originally Since the portion having the second density is the first density, the eccentricity of the print transport roller can be easily observed and evaluated.

  The feed pitch of the comparative dot lines in the sub-scanning direction is about 10 to several tens of microns, and considering the eccentricity of a general print conveying roller, it is sufficient to divide the divided area into several. From this, it becomes a pattern in which several comparison dot lines are repeated, but if this is too fine, after the comparison dot lines for the number of divisions of the divided area, in addition, the divided into a plurality of A configuration may be adopted in which a predetermined number of auxiliary dot lines extending in the main scanning direction over the entire divided region are formed by the first nozzle unit with the second gradation value. In this case, the pattern is such that a dot line group consisting of a comparison dot line corresponding to the number of divisions and a predetermined number of auxiliary dot lines repeats, and the required number of dot patterns for evaluation can be reduced.

  In order to make the density change based on the degree of eccentricity conspicuous as described above, the first gradation value is a gradation value that produces a low density such as white, and the second gradation value is a gradation that produces a high density such as black. Value is good. As a result, the originally white portion is filled with black, so that it is easy to confirm the shake in the main scanning direction of the blackened portion.

The present invention is not limited to the above-described test print for evaluating the degree of eccentricity of a roller, but also a technique for evaluating the degree of eccentricity of a roller by outputting such a test print. For example, a first nozzle unit having a large number of nozzles that form dot lines in the main scanning direction with respect to the recording medium, and a second nozzle unit that is shifted from the first nozzle unit by a predetermined distance in the sub-scanning direction, Evaluation of roller eccentricity of the print transport roller in a printing apparatus comprising: a print head having a print head; a print transport roller that transports the recording medium in a sub-scanning direction; and a drive unit that rotates the print transport roller at a predetermined pitch. In the method, in order to solve the above problem, in the present invention, a comparative dot line forming step in which a plurality of comparative dot lines extending in the main scanning direction by the first nozzle unit are formed on the recording medium, A plurality of evaluation dot lines extending in the scanning direction by the two-nozzle unit are formed on the recording medium. And a evaluation dot line forming step to be,
In the comparison dot line forming step, the comparison dot line is formed with a first gradation value in a portion that is included in a selected divided region selected from among divided regions divided in the main scanning direction. In addition, the other divided areas are formed with a second gradation value different from the first gradation value. At this time, the comparative dot line selects the selected divided areas in the order of the main scanning direction, It is repeatedly formed at predetermined rotation angles of the print transport roller until it reaches a length in the sub-scanning direction corresponding to the sub-scanning distance for at least one rotation of the print transport roller,
In the evaluation dot line forming step, the print dot transport is such that the central divided region located in the center of the divided regions overlaps the comparative dot line formed with the first gradation value. Formed at the second gradation value at the rotation angle of the roller;
The density of the recording medium on which the comparative dot line and the evaluation dot line are formed is measured, and the roller eccentricity is evaluated from the density distribution in the divided area. This roller eccentricity evaluation method also has the advantage that the eccentricity of the print transport roller can be easily observed and evaluated for the reasons described above.

Hereinafter, an embodiment of a printing apparatus employing an eccentricity evaluation technique according to the present invention will be described with reference to the drawings.
As shown in FIGS. 1 and 2, this printing apparatus feeds print paper P as a recording medium stored in a roll shape to a printing mechanism 2 by a feed conveyance mechanism 1 to print an image. A discharge conveyance mechanism 4 is provided that sequentially conveys the paper P to the cutting unit C, the back printing unit B, and the decurling unit D and discharges the paper P to a discharge tray 31 attached to the outside of the housing 30. The discharge / conveyance mechanism 4 includes a plurality of nipping / conveying roller pairs 40.

  Since the printing apparatus is configured as an ink jet system, the print mechanism 2 includes an ink jet print head 20 as shown in FIGS. 3 and 4 that reciprocates in the main scanning direction. Inside the housing 30, there are provided a suction unit 33, an ink storage unit IB, and a control unit 5 that are arranged at positions facing the print head 20 across the transport path of the print paper P. The suction unit 33 incorporates an electric fan (not shown) that sucks air from a large number of openings formed on the upper surface of the case-like unit and sends it out downward.

  The feed conveyance mechanism 1 includes a print conveyance roller 10 on the upstream side of the printing mechanism 2 in the conveyance direction. Two press rollers 10a and 10b are attached to the print transport roller 10, and the print paper P is sandwiched and transported by pressing the print paper P against the print transport roller 10 by the press rollers 10a and 10b. The print transport roller 10 creates the transport of the print paper P in the sub-scanning direction during printing, and the rotational displacement amount of the roller peripheral surface becomes the displacement amount of the print paper P in the sub-scanning direction. The print transport roller 10 uses a transport motor M1 formed of a DC servo motor as a drive source. A rotary encoder E is attached to the rotation shaft of the print transport roller 10 and has a resolution capable of generating 32768 pulses by one rotation of the print transport roller 10. The feed conveyance mechanism 1 is further provided with a pull-in conveyance roller pair 13, whereby the cut paper set on the manual feed tray 32 is drawn in and delivered to the print conveyance roller 10, whereby the cut paper is transferred to the print mechanism 2. Can be supplied.

  The cutting unit C includes a disk-shaped cutter 34 that cuts the print paper P, and an operating mechanism 35 that reciprocates the disk-shaped cutter in the main scanning direction. The back print unit B includes a print head 3 that prints information on the back side of the print paper P. In order to correct the curl of the print paper P, the decurling unit D is configured to convey the print paper P while curving it in a direction opposite to the winding direction of the roll-shaped print paper P, and a guide plate 42. And. A plurality of ink cartridges (not shown) are set in the ink reservoir IB, and ink sent from the ink reservoir IB is supplied from an intermediate tank (not shown) to the print head 20 via a flexible tube. .

  The print head 20 includes a carriage 21 and an ink discharge unit 23 that is connected to the carriage 21 and discharges ink onto the print paper P to print information, and has a carriage cover 22 that covers the carriage 21. Yes. The first nozzle unit 23a and the second ink nozzle unit 23b are arranged on the lower surface of the ink discharge unit 23 at two positions spaced apart in the sub-scanning direction. As shown in FIG. 5, a large number of ink nozzles 24 for ejecting ink are formed in each of the ink nozzle units 23a and 23b.

  In the print mechanism 2, a pair of guide rods 26 having a circular cross-sectional shape are arranged in a parallel posture in the main scanning direction. The carriage 21 is supported so as to be slidable with respect to the pair of guide rods 26. One side surface of the carriage 21 in the sub-scanning direction is provided with a pair of slide guides 25 in which circular holes are formed so as to be fitted on one guide rod 26, and the other guide rod 26 is provided on the other side surface. The slide block 25 is provided with a recess that is engaged with the slide block 25. A belt driving mechanism 27 including a driving pulley 27a, a driven pulley 27b, and a timing belt type driving belt 27c wound around the driving pulley 27a is arranged along the main scanning direction on the side of the carriage. The drive belt 27c and the carriage 21 are connected, and a rotational driving force is transmitted to the drive pulley 27a from the drive motor M2.

  In order to construct the linear encoder system 28 that acquires the position of the print head 20 in the main scanning direction, a belt-like linear strip 28a is fixed to the housing 30 at a position near the print head 20 in a posture parallel to the main scanning direction. A sensor unit 28b for optically acquiring scale information of the linear strip 28a is supported by the carriage 21 of the print head 20. The linear encoder system 28 is configured to specify the position of the print head 20 in the main scanning direction by counting the scale information of the linear strip 28a when the print head 20 moves.

  The control unit 5 acquires information such as images and characters to be printed and converts them into print data. The control unit 5 controls the transport motor M2 while checking the pulses from the encoder E based on the print data, thereby realizing the sub-scan transport of the print paper P by the feed transport mechanism 1 and the signal from the linear encoder system 28. By controlling the drive motor M2 based on the above, the reciprocation of the print head 20 in the main scanning direction is realized. In synchronism with these movements, the control unit 5 controls the ink discharge mechanism built in the ink discharge unit 23 based on the print data, thereby controlling the ink nozzles 24 of the first nozzle unit 23a and the second nozzle unit 23b. Ink is ejected from the ink nozzles 24 to form an image composed of dot groups on the print paper P. More specifically, the print head 20 is moved in one of the main scanning directions, and printing is performed while ejecting ink through the ink nozzles 24. As a result, when the print head 20 reaches the moving end, the print paper P is transported by a predetermined pitch in the sub-scanning direction by the feed transport mechanism 1. After this conveyance, the print head 20 is moved to the other side of the main scanning direction (in the reverse direction), and printing is performed while ejecting ink again through the ink nozzles 24 of the ink nozzles 24 of the first nozzle unit 23a and the second nozzle unit 23b. An image is formed on the paper P.

  The control unit 5 of the printing apparatus also has a function of evaluating the eccentricity of the print transport roller 10. FIG. 6 is a functional block diagram illustrating functions related to the roller eccentricity evaluation in the control unit 5. This functional block diagram includes an image data input unit 51, a memory 52 for developing input image data, an image processing unit 53 for processing input image data, and print data for generating print data from the processed image data The generation unit 54, the print head control unit 55 that controls the ink ejection mechanism of the print head 20 and the drive motor M2 that moves the print head 20 in the main scanning direction based on the print data, and the print conveyance roller that performs the sub-scan conveyance of the print paper P Some of them are also used for normal image printing such as a conveyance motor control unit 56 that controls ten conveyance motors M1 based on a pulse signal from an encoder E. A test print output management unit 57 for managing processing for outputting a roller eccentricity evaluation test print TP with this printing apparatus as shown in FIG. 7 is used for evaluating the roller eccentricity. It is included. While the output test print TP for evaluating roller eccentricity is visually observed, adjustment data for compensating for roller eccentricity may be manually input. When adopting a configuration in which adjustment data for automatically compensating for roller eccentricity is generated and the rotation of the print transport roller 10 is adjusted, an eccentricity evaluation means 58 is incorporated in the control unit 5.

  In this embodiment, the drive unit that rotates the print transport roller 10 at a predetermined pitch includes a transport motor M 1, an encoder E, and a transport motor control unit 56.

  The test print management unit 57 stores test print data for a roller eccentricity evaluation test print TP (hereinafter simply referred to as a test print TP) shown in FIG. 7, and this test print data is stored as necessary. The print data generation unit 54 outputs the test print TP. The test print TP has a strip-shaped chart portion 80 that is long in the sub-scanning direction. The chart unit 80 is equally divided into five areas in the sub-scanning direction, and from the left in the drawing, the first divided area 81, the second divided area 82, the third divided area 83, the fourth divided area 84, and the fifth divided area. This is referred to as a divided area 85. Note that the length of the chart unit 80 in the sub-scanning direction is determined to correspond to the sub-scan feed length of one or more rotations of the print transport roller 10.

  The chart unit 80 can be regarded as a collection of dot lines extending in the main scanning direction, and FIG. 8 shows a schematic diagram enlarged to such an extent that each dot (ink droplet) can be confirmed. Moreover, the schematic diagram expanded to such an extent that a dot line can be recognized as a straight line is shown by FIG. 9 and FIG. In this embodiment, the dot lines constituting the chart unit 80 can be divided into comparative dot lines 91, auxiliary dot lines 92, and evaluation dot lines 93. The comparison dot line 91 is a single dot line extending over the entire width of the chart portion 80, but is formed with the maximum gradation value (255: white) which is the first gradation value in a specific divided region. In other divided areas, the second gradation value is the minimum gradation value (0: black). The divided areas formed with the maximum gradation value are sequentially shifted in the main scanning direction. That is, if the first comparative dot line 91 is formed in the first divided area 81 with the maximum gradation value, the next comparative dot line 91 is in the second divided area 82. The portion is formed with the maximum gradation value, and further, in the next comparative dot line 91, the portion entering the third divided region 83 is formed with the maximum gradation value, and the portion formed with the maximum gradation value in that order. Will shift. When the comparative dot line 91 in which the portion in the fifth divided region 85 is formed with the maximum gradation value is formed, the auxiliary dot line 92 is formed with the minimum gradation value over the entire area. A predetermined number, here four, is formed. Thereafter, similar five comparative dot lines 91 are formed again. In this way, a pattern in which five comparison dot lines 91 and four auxiliary dot lines 92 are combined is repeated. The comparison dot line 91 and the auxiliary dot line 92 are formed by the nozzle 24 of the first nozzle unit 23a.

  The evaluation dot line 93 is a comparison dot line 91 (hereinafter referred to as this comparison dot line) in which the portion of the divided area that is in the third divided area 83 that is the central divided area located at the center is formed with the maximum gradation value. The dot line 91 is referred to as a reference dot line for comparison) at a timing when the sub-scan transport is performed at a position corresponding to the specific nozzle 24 of the second nozzle unit 23b. Are dot lines extending in the main scanning direction. In order to understand this well, FIG. 9 shows a chart portion 80 in which the evaluation dot lines 93 are not formed, and FIG. 10 shows a chart portion 80 in which the evaluation dot lines 93 are formed. It is shown. Note that the evaluation dot lines 93 in FIG. 10 are drawn out of the chart portion 80 so as to be easily distinguished from the evaluation dot lines 91.

  In this embodiment, the distance between the first nozzle unit 23 a and the second nozzle unit 23 a in the sub-scanning direction substantially corresponds to the length of the half circumference of the print transport roller 10. Accordingly, the second nozzle unit 23a is controlled so as to form the evaluation dot line 93 so as to overlap the reference dot line 91 for comparison formed by the first nozzle unit 23a. At this time, if the length of the half circumference of the print transport roller 10 is deviated from the normal length, the evaluation dot line 93 is shifted in the sub-scanning direction with respect to the reference dot line 91 for comparison. Will be. FIG. 10 shows an example in which the feed length by the print transport roller 10 is slightly shorter than normal due to the eccentricity of the print transport roller 10, and the evaluation dot line 93 is compared with the reference dot line 91 for comparison. Is shifted upward. The fact that the evaluation dot line 93 is shifted upward relative to the comparison reference dot line 91 means that the white portion of the reference dot line 91 that is one above the comparison reference dot line 91 is filled with black. As a result, the fourth divided region 84 becomes relatively dark (high density). Similarly, when the feed length by the print transport roller 10 becomes slightly longer than normal due to the eccentricity of the print transport roller 10, the evaluation dot line 93 is shifted downward with respect to the reference dot line 91 for comparison, and as a result The two-divided area 82 becomes relatively dark (high density). Of course, when there is no eccentricity, only the third divided region 83 becomes relatively dark (high density).

  As described above, because of the eccentricity of the print transport roller 10, the divided area that appears relatively dark (dark) swings from the third divided area 83 to the second divided area 82 or the fourth divided area 84. By observing the chart portion 80 of the test print TP, the eccentricity of the print transport roller 10 can be grasped. At that time, in order to specify the eccentricity portion of the print transport roller 10 from the test print TP, a marker that defines the reference rotation angle position is set on the print transport roller 10 and a marker detector MD that detects this marker is set. It is preferable that the first dot line is formed in response to the detection signal from.

  The degree of eccentricity of the print transport roller 10 can be automatically evaluated by the density distribution in the sub-scanning direction of the chart portion 80 of the test print TP. That is, the output test print TP is converted into a digital image by using an image reading device such as a flatbed scanner 60, and is developed as test print image data in the memory 52 through the image data input unit 51. The density distribution is obtained, and the eccentricity of the print transport roller 10 from the reference rotation angle position can be converted into data based on the density distribution. The eccentricity converted into data is sent to an adjustment unit 56a built in the conveyance motor control unit 56, so that the adjustment unit 56a controls the conveyance motor M1 so as to compensate the roller eccentricity of the print conveyance roller 10. can do. As a result, accurate sub-scanning conveyance is realized regardless of the roller eccentricity of the print conveyance roller 10.

A perspective view schematically showing the configuration of an ink jet printing apparatus Side view schematically showing the configuration of an ink jet printing apparatus The perspective view explaining the operation mechanism of the print head Side view explaining the configuration of the print head Bottom view showing nozzle unit and nozzle Functional block diagram showing the functions of the control unit Plan view showing test print for evaluating roller eccentricity Enlarged view of the chart part of the test print for evaluating roller eccentricity Enlarged view of the chart without the evaluation dot line Enlarged view of the chart part including the dot line for evaluation

Explanation of symbols

E Encoder P Print paper (recording medium)
TP roller eccentricity evaluation test print M1 conveyance motor MD marker detector 10 print conveyance roller 20 print head 51 image data input unit 56 conveyance motor control unit 56a adjustment unit 57 print output management unit 58 eccentricity evaluation means 80 chart unit 81 First divided area 82 Second divided area 83 Third divided area (central divided area)
84 Fourth divided area 85 Fifth divided area 91 Comparison dot line 92 Auxiliary dot line 93 Evaluation dot line

Claims (4)

A first nozzle unit having a plurality of nozzles that form dot lines in the main scanning direction with respect to the recording medium; and a second nozzle unit that is arranged at a predetermined distance from the first nozzle unit in the sub-scanning direction. To evaluate the eccentricity of the print transport roller in a printing apparatus having a print head, a print transport roller that transports the recording medium in the sub-scanning direction, and a drive unit that rotates the print transport roller at a predetermined pitch. In the test print for evaluating roller eccentricity
A plurality of comparative dot lines extending in the main scanning direction formed by the first nozzle unit, and a plurality of evaluation dot lines extending in the main scanning direction formed by the second nozzle unit;
In the comparative dot line, a portion entering a selected divided region selected from among divided regions divided in the main scanning direction is formed with a first gradation value, and the other divided regions are the first divided region. The comparison dot line is formed with a second gradation value different from the one gradation value, and the comparison dot line selects at least one rotation of the print transport roller while selecting the selected divided region in the order of the main scanning direction. Are repeatedly formed at predetermined rotation angles of the print transport roller until a length in the sub-scanning direction corresponding to the sub-scanning distance is reached,
The evaluation dot line is the second angle at the rotation angle of the print transport roller where a central divided region located in the center of the divided regions overlaps the comparative dot line formed with the first gradation value. Test print for evaluating roller eccentricity formed with gradation values   After the comparison dot lines corresponding to the number of divisions of the divided area, auxiliary dot lines extending in the main scanning direction by a predetermined number are additionally formed, and the auxiliary dot lines are all divided into a plurality of divided areas. 2. The test print for evaluating roller eccentricity according to claim 1, wherein the test print is formed by the first nozzle unit at the second gradation value.   The roller eccentricity evaluation test print according to claim 1, wherein the first gradation value is a gradation value that produces white, and the second gradation value is a gradation value that produces black. A first nozzle unit having a plurality of nozzles that form dot lines in the main scanning direction with respect to the recording medium; and a second nozzle unit that is arranged at a predetermined distance from the first nozzle unit in the sub-scanning direction. In a method for evaluating the degree of eccentricity of a print transport roller in a printing apparatus, comprising: a print head; a print transport roller that transports the recording medium in a sub-scanning direction; and a drive unit that rotates the print transport roller at a predetermined pitch. ,
A comparison dot line forming step in which a plurality of comparison dot lines extending in the main scanning direction by the first nozzle unit are formed on the recording medium, and a plurality of evaluation dot lines extending in the scanning direction by the second nozzle unit Comprises a dot line forming step for evaluation formed on the recording medium,
In the comparison dot line forming step, the comparison dot line is formed with a first gradation value in a portion that is included in a selected divided region selected from a plurality of divided regions in the main scanning direction. In addition, the other divided areas are formed with a second gradation value different from the first gradation value. At this time, the comparative dot line selects the selected divided areas in the order of the main scanning direction, It is repeatedly formed at predetermined rotation angles of the print transport roller until it reaches a length in the sub-scanning direction corresponding to the sub-scanning distance for at least one rotation of the print transport roller,
In the evaluation dot line forming step, the print dot transport is such that the central divided region located in the center of the divided regions overlaps the comparative dot line formed with the first gradation value. Formed at the second gradation value at the rotation angle of the roller;
A roller eccentricity evaluation method in which the density of the recording medium on which the comparative dot line and the evaluation dot line are formed is measured, and the roller eccentricity is evaluated from the density distribution in the divided area.