JP6237197B2 - Printing method and printing apparatus - Google Patents

Description

  The present invention relates to a printing method and a printing apparatus that perform printing by ejecting ink droplets from ink nozzles.

  In a printing apparatus that performs printing by ejecting ink from an ink nozzle, an ink nozzle that does not eject ink for a certain period of time becomes clogged due to evaporation of moisture from the nozzle tip, increasing the viscosity of the ink. For this reason, ink cannot be normally ejected from ink nozzles with low ejection frequency, and print quality may be deteriorated. Therefore, a maintenance unit is provided in the printing apparatus, and flushing is performed to discharge ink toward the maintenance unit, thereby preventing or eliminating clogging of the ink nozzles. Patent Document 1 discloses this type of printing apparatus (inkjet recording apparatus).

  In Patent Document 1, in order to suppress an increase in ink consumption and a decrease in throughput during printing due to performing flushing at regular intervals, control is performed so as not to perform flushing according to the contents of printing. For example, the time when printing is not performed for each nozzle is measured, and only the nozzles for which the time equal to or greater than the reference value has passed is flushed. However, even if such control is performed, although the frequency of flushing is reduced, the reduction in throughput due to flushing cannot be completely eliminated. Therefore, flushing that discharges ink onto a recording medium (so-called flushing on paper) is performed without using a maintenance unit to prevent or eliminate clogging of the ink nozzles. Patent Document 2 discloses this type of printing apparatus (droplet discharge apparatus).

  In Patent Document 2, a pattern in which dots are irregularly arranged (dummy jet discharge data) is stored in a memory in advance, or such a pattern is generated each time, and this pattern is combined with image data to be printed. By combining and printing, flushing is performed on the recording medium. In this way, it is not necessary to interrupt printing when performing flushing. Therefore, it is possible to prevent a decrease in print quality due to clogging of the ink nozzles without reducing the throughput.

JP 11-192729 A JP 2007-136722 A

  In Patent Document 2, in order to perform flushing on paper for ejecting ink onto a recording medium, a pattern in which dots are irregularly arranged (that is, a flushing pattern) is stored in advance, or based on a random number. Each time a flushing pattern is generated. However, if the flushing pattern is stored in advance, it is necessary to store the flushing pattern corresponding to the maximum print size in the memory, which increases the necessary storage capacity. Further, when generating a pattern each time based on a random number, it is necessary to store such a processing program, and the load of image processing is large. In addition to paper flushing, when performing regular flushing that ejects ink from the print head toward the maintenance unit at a predetermined timing such as before starting printing or during standby, in the flushing on paper depending on the frequency of regular flushing. The appropriate value of the flushing frequency for each ink nozzle is different. In other words, the necessary flushing pattern may differ depending on the frequency of the regular flushing. In such a case, the necessary storage capacity is further increased and the load of image processing is further increased.

  In view of such problems, the present invention provides a printing method and a printing apparatus that perform flushing (flushing on paper) that ejects ink toward a recording medium, and reduces the storage capacity of data necessary for performing flushing on paper. The purpose is to reduce the processing load.

In order to solve the above-described problem, the present invention provides n columns × m including flushing dots when printing is performed in the first mode in which the frequency of flushing for ejecting ink toward the maintenance unit is the first frequency. First flushing patterns in rows (n and m are integers greater than or equal to 2) are arranged in a column direction that intersects the transport direction of the recording medium and in a row direction that is the transport direction, and the first print flushing pattern is generated, when performing printing the frequency of the flushing in a second mode to said first frequency and different from the second frequency corresponds to the number of rows the first flushing pattern in said second frequency line A second flushing pattern that increases or decreases in number is generated, the second flushing pattern is arranged in the column direction and the row direction, and a second print flushing pattern is formed. And generating an over emissions.

Further, the printing apparatus of the present invention includes a print head including ink nozzles, a transport mechanism that transports a recording medium, a maintenance unit that receives ink ejected from the ink nozzles of the print head, and printing performed by the print head. The mode is a first mode in which flushing for discharging ink to the maintenance unit is executed at a first frequency, or the first mode
A mode setting unit for setting the second mode in which the flushing is executed at a second frequency different from the first frequency, and a first of n columns × m rows (n and m are integers of 2 or more) including flushing dots. A storage unit that stores a flushing pattern and a flushing dot composition table, a print dot pattern generation unit that generates a print dot pattern based on print data, and, in the first mode, records the first flushing pattern in the first mode. A first print flushing pattern is generated by arranging in a column direction intersecting a medium conveyance direction and a row direction which is the conveyance direction. In the second mode, the number of rows of the first flushing pattern is set to the first flushing pattern. A second flushing pattern that is increased or decreased to the number of rows corresponding to a frequency of 2 is generated, and the second flushing pattern is generated in the column direction. And a flushing pattern determining unit configured to generate a second printing flushing pattern arranged in the row direction, the flushing pattern for synthesizing the printing dot pattern and the first printing flushing pattern or the second printing flushing pattern. The image forming apparatus includes: a combining unit; and a print control unit that discharges ink from the print head based on data generated by the flushing pattern combining unit.

  As described above, the printing method and the printing apparatus of the present invention can suppress the thickening of the ink in the ink nozzles by the on-paper flushing. Therefore, clogging of the ink nozzles can be prevented or eliminated without reducing the throughput during printing. The flushing on paper can be generated by repeatedly arranging a reference flushing pattern (first flushing pattern) smaller than the printing flushing pattern. Accordingly, it is possible to reduce the storage capacity of data necessary for the on-paper flushing, and the load of image processing is also small. In the present invention, flushing for ejecting ink to the maintenance unit is performed separately from the flushing on paper. Therefore, even when printing is performed without using the ink nozzles outside the printing area, clogging of the ink nozzles can be prevented or eliminated by flushing the maintenance unit. Then, when the frequency of flushing to the maintenance unit is a second frequency different from the first frequency, a second flushing pattern in which the number of rows of the first flushing pattern is increased or decreased is generated. This is repeatedly arranged in the same manner as the first flushing pattern to generate a print flushing pattern. Therefore, it is possible to change the frequency of ink droplet ejection from the ink nozzles in the on-paper flushing according to the frequency of flushing to the maintenance unit. Therefore, flushing on paper can be performed at an appropriate frequency, and clogging of ink nozzles can be prevented or eliminated without consuming ink wastefully. Further, in order to perform such processing, it is not necessary to store a plurality of flushing patterns in advance. Therefore, the data storage capacity can be reduced, and the image processing load is also small.

  In the present invention, it is preferable that the first frequency of the first mode is smaller than the second frequency of the second mode. In this way, a pattern with a high ejection frequency of ink droplets from each ink nozzle in the flushing on paper, that is, a pattern with a small size in the row direction becomes the first flushing pattern. Accordingly, it is possible to reduce the storage capacity of data necessary for the on-paper flushing.

  In this case, it is desirable to add a blank line to the first flushing pattern to generate the second flushing pattern having a larger number of lines than the first flushing pattern. In this way, the frequency of ink ejection by flushing on paper can be lowered as the frequency of flushing the maintenance unit increases. Therefore, it is possible to perform flushing on paper at an appropriate frequency.

  In the present invention, it is preferable that the first flushing pattern includes one flushing dot in one row. In this way, the size of the first flushing pattern can be minimized. Accordingly, it is possible to reduce the storage capacity of data necessary for the on-paper flushing.

FIG. 2 is a schematic block diagram illustrating a control system of a printer to which the present invention is applied. FIG. 2 is an explanatory diagram schematically illustrating a print head, a maintenance unit, and a print sheet of the printer of FIG. 1. It is explanatory drawing which shows the conversion process from input data to head drive data. It is explanatory drawing of a reference | standard flushing pattern. It is explanatory drawing of an adjustment flushing pattern and its production | generation method. It is explanatory drawing of a printing flushing pattern. It is explanatory drawing which shows the condition where the printing flushing pattern and the printing dot pattern were offset for each ink color and superimposed. It is explanatory drawing of an offset position information table. It is explanatory drawing of the synthetic | combination method of a printing flushing pattern and a printing dot pattern. It is explanatory drawing of the flushing dot composition table.

  Hereinafter, embodiments of a printing apparatus and a printing method to which the present invention is applied will be described with reference to the drawings. In the following embodiments, the present invention is applied to an ink jet printer. However, the present invention is also applicable to a printing apparatus having functions such as a scanner and a facsimile. In addition, although the following embodiment includes a line head type print head, the present invention is also applicable to a printing apparatus including a serial head type print head.

(printer)
FIG. 1 is a schematic block diagram showing a control system of a printer to which the present invention is applied, and FIG. 2 is an explanatory diagram schematically showing a print head, a maintenance unit, and printing paper of the printer of FIG. As shown in FIGS. 1 and 2, the printer 1 includes a print head 2 that ejects ink droplets of four colors of cyan ink C, magenta ink M, yellow ink Y, and black ink Bk, and printing by the print head 2. A transport mechanism 3 that transports the printing paper P (recording medium) along a transport path that passes through the position, a maintenance unit 4, a control unit 5 that controls the print head 2, the transport mechanism 3, the maintenance unit 4, and the like, and printing. A communication unit 6 that receives target input data (image data, document data, etc.) is provided. In this embodiment, as the printing paper P, a label paper in which labels are attached to a long mount at regular intervals is used. In the case of label paper, the entire area of the label or a predetermined area on the label is the print area P1. Note that as the printing paper P, a continuous paper or a cut sheet without a label may be used.

  The print head 2 is a line-type inkjet head, and includes four sets of inkjet heads 2C, 2M, 2Y, and 2Bk arranged at a predetermined interval along the conveyance direction A of the printing paper P as shown in FIG. . Inkjet heads 2C, 2M, 2Y, and 2Bk all have a length in the paper width direction B that intersects the transport direction A longer than the maximum width of the printing paper P, and print by ejecting ink onto the printing paper P. Do. The inkjet head 2Bk arranged at the uppermost stream in the transport direction A of the printing paper P ejects black ink Bk, and the downstream inkjet head 2C ejects cyan ink C. The inkjet head 2M disposed on the downstream side of the inkjet head 2C ejects magenta ink M, and the downstream inkjet head 2Y ejects yellow ink Y.

  The ink jet heads 2C, 2M, 2Y, and 2Bk include four head units 21 to 24 that are arranged in the paper width direction B that intersects the transport direction A. The four head units 21 to 24 are arranged so that adjacent head units move back and forth in the transport direction A. The four head units 21 to 24 include two ink nozzle rows in which a plurality of ink nozzles 25 are arranged at a predetermined nozzle pitch in the paper width direction B. The nozzle pitch is set to 300 dpi, for example. The two ink nozzle rows are arranged by shifting the position in the paper width direction B by a dimension that is ½ of the distance between the adjacent nozzles (nozzle pitch). Further, the head units 21 and 22 adjacent in the paper width direction B are arranged so that the ink nozzles 25 at the end portions overlap when viewed in the transport direction A. Similarly, the head units 22 and 23 and the head units 23 and 24 adjacent in the paper width direction B are also arranged so that the ink nozzles 25 at the end portions overlap when viewed in the transport direction A.

  The maintenance unit 4 is disposed at a standby position of the print head 2, for example, outside in the width direction of the transport path. The print head 2 can be moved to a position facing the printing paper P on the transport path and a position facing the maintenance unit 4 by a head moving mechanism (not shown). In the standby state in which printing is not performed, the nozzle surface of the print head 2 is capped by the maintenance unit 4. Further, at a predetermined timing such as before the start of printing, the print head 2 is moved to a position facing the maintenance unit 4, and periodic flushing for discharging ink from the ink nozzles 25 toward the maintenance unit 4 is performed. In this embodiment, as will be described later, during printing, flushing that discharges ink droplets from the ink nozzles 25 located at a position facing the printing area P1 (so-called flushing on paper) is performed in parallel with the printing operation. In the regular flushing, flushing is performed on the ink nozzles 25 that are not used at the time of printing, for example, the ink nozzles 25 including the ink nozzles 25 located outside the print region P1 in the paper width direction B. Therefore, flushing can be performed also on the ink nozzles 25 located outside the printing region P1, and the clogging can be prevented or eliminated.

(Control system)
As shown in FIG. 1, the control system of the printer 1 is configured around a control unit 5 including a CPU and the like. A communication unit 6 is connected to the input side of the control unit 5. Input data (image data, document data, etc.) to be printed is supplied to the control unit 5 from an external device such as a computer via the communication unit 6. On the other hand, to the output side of the control unit 5, the print head 2, the transport mechanism 3, the maintenance unit 4 and the like are connected. The transport mechanism 3 is a known mechanism such as a paper feed roller pair that transports the printing paper P, a transport motor that is rotated by a control signal from the control unit 5, and a driving force transmission mechanism that transmits the rotation of the transport motor to the paper feed roller pair. Is provided.

  The control unit 5 includes a storage unit 51, a rendering unit 52, a color conversion processing unit 53, a binarization processing unit 54, a flushing pattern determination unit 55, a flushing pattern synthesis unit 56, a print control unit 57, a size adjustment unit 58, and regular flushing. An execution unit 59 and the like are provided. The control unit 5 includes a conveyance control unit (not shown) that controls the conveyance mechanism 3 to convey the printing paper P at a designated speed.

  The storage unit 51 stores and holds a color conversion lookup table 61, an SML table 62, a reference flushing pattern 63, an offset position information table 64, a flushing dot composition table 65, a size adjustment table 67, and the like.

(Print mode setting)
The printing mode of the printer 1 can be set to a first mode in which the above-described regular flushing is performed at a preset reference frequency and a second mode in which the regular flushing is performed at a frequency higher than the reference frequency. Note that it is possible to set a third mode in which periodic flushing is performed more frequently than the second mode, and to set three or more print modes. The setting of the printing mode and the process of controlling the print head 2 and the maintenance unit 4 according to the printing mode and performing the periodic flushing are performed by the periodic flushing execution unit 59 (mode setting unit). The print mode is set based on a control command input to the control unit 5. The control command may be included in the input data 10 or may be supplied separately from the input data 10.

(Conversion process from input data to print data)
FIG. 3 is an explanatory diagram showing a conversion process from input data to head drive data. The rendering unit 52 performs rendering processing for converting the input data 10 (print data) to be printed into image data 11 having the number of pixels corresponding to the designated print size and resolution. Specifically, the input data 10 is enlarged or reduced to a designated print size, and decomposed into pixels so as to have a designated resolution. The pixels of the image data 11 after the rendering processing are RGB color system color data (RGB multivalued data).

  The color conversion processing unit 53 (a part of the print dot pattern generation unit) refers to the color conversion lookup table 61 and converts each pixel (RGB multi-value data) of the image data 11 after the rendering processing to C, Y, M , Bk, the color conversion process for separating the ink amount data 12 (12Bk, 12C, 12M, 12Y) of the four colors. In the color conversion lookup table 61, ink amount data of four colors C, Y, M, and Bk is stored with respect to RGB multi-value data (a combination of R, G, and B) that is RGB color system color data. It is associated. The ink amount data of C, Y, M, and Bk is represented by, for example, an 8-bit gradation value (256 gradations).

  The binarization processing unit 54 (a part of the print dot pattern generation unit) forms pixel ink amount data with the ink nozzles 25 for the ink amount data 12 (12Bk, 12C, 12M, 12Y) after the color conversion processing. A process of converting into dot data of possible four gradations is performed. In the SML table 62, gradation values of C, M, Y, and Bk ink amount data are associated with the occurrence rates of four types of dots including blank dots. The four types of dots are Null (blank dots), S (small dots), M (medium dots), and L (large dots). First, the binarization processing unit 54 refers to the SML table 62 and performs a dot ratio determination process for converting the ink amount data of the pixel into the incidence data of the four types of dots. Halftone processing is performed to determine the presence or absence for each dot size. As a result, for each ink color, a print dot pattern 13 (13Bk, 13C, 13M, 13Y) in which one of four types of print dots including a blank dot is designated with respect to the pixel position is generated.

  Based on the set print mode, the size adjustment unit 58 refers to the size adjustment table 67 and adjusts the reference flushing pattern 63 to generate an adjustment flushing pattern 63B. Specific configurations of the reference flushing pattern 63 and the adjustment flushing pattern 63B will be described later.

  The flushing pattern determination unit 55 performs a flushing pattern determination process for determining the print flushing pattern 66 based on the reference flushing pattern 63 or the adjustment flushing pattern 63B and the print size of the input data 10. The print flushing pattern 66 is a pattern for designating the ink nozzles 25 for ejecting ink droplets and the timing thereof when performing printing on the print region P1 of the input data 10 and flushing on paper for ejecting ink droplets onto the print region P1. is there. A specific configuration of the print flushing pattern 66 will be described later.

  The flushing pattern synthesis unit 56 performs a flushing pattern synthesis process for synthesizing the print dot pattern 13 (13Bk, 13C, 13M, 13Y) after the halftone process and the print flushing pattern 66. As will be described later, the flushing pattern synthesis process is performed with reference to the offset position information table 64 (see FIG. 8) and the flushing dot synthesis table 65 (see FIG. 10).

  The print control unit 57 assigns each dot of the combined dot pattern 14 (14Bk, 14C, 14M, 14Y) after combining the print flushing pattern 66 to the ink nozzles 25 of the inkjet heads 2C, 2M, 2Y, 2Bk. Then, a head drive data generation process for generating head drive data 15 used for driving the print head 2 is performed. Then, the ejection of ink from the print head 2 is controlled based on the generated head drive data. Here, the ink nozzles 25 for each color overlap in the transport direction A at the end portions of the four head units 21 to 24 as described above. For this reason, in the head drive data generation process, a mask process for assigning dots to one of the overlapping ink nozzles 25 of the head unit is performed. Further, in this mask process, if the dots assigned to the ink nozzles 25 that overlap in the transport direction A are dots on paper flushing (flushing dots Df described later) or dots that are combined with printing dots, they overlap. Dots are assigned to both ink nozzles 25.

(Reference flushing pattern)
FIG. 4 is an explanatory diagram of the reference flushing pattern 63. As shown in this figure, the reference flushing pattern 63 is a dot matrix pattern of n columns × m rows, and is composed of blank dots and flushing dots Df. In FIG. 4, for the sake of simplicity, an example of a dot matrix pattern of 10 columns × 10 rows is shown, but a dot matrix pattern having a different number of rows and columns may be used. In the following description, “column alignment direction” is referred to as “column direction”, and “row alignment direction” is referred to as “row direction”. That is, the reference flushing pattern 63 is a dot matrix pattern in which n columns are arranged in the column direction and m rows are arranged in the row direction.

  The column direction V of the reference flushing pattern 63 corresponds to the arrangement direction of the ink nozzles 25. The four sets of inkjet heads 2C, 2M, 2Y, and 2Bk included in the print head 2 have the same number of arrays of ink nozzles 25 in the paper width direction B, and the number of columns in the paper width direction B is 3200 in this embodiment. The number of dot arrangements in the row direction V (that is, the number of rows n) in the reference flushing pattern 63 is set to be smaller than the number of arrangements (3200) in the paper width direction B of the ink nozzles 25 in the print head 2.

  The row direction H of the reference flushing pattern 63 corresponds to the flushing execution timing. The size in the row direction H (that is, the number of rows m) of the reference flushing pattern 63 is obtained by replacing the flushing execution cycle (that is, the generation cycle of the flushing dots Df) with the number of dots. For example, when flushing is performed once in 0.1 sec, the number of dots printed in this period (0.1 sec) (that is, the number of lines m) depends on the setting of the printing speed and resolution, but is 1000 to 10,000. The number is within the dot range. For example, when the generation period of the flushing dot Df is 5000 dots, the number of rows m is set to 5000. Note that the number of rows m may be an integral multiple of the generation cycle of the flushing dots Df, but in order to reduce the size of the reference flushing pattern 63, the number of rows m is set to the generation cycle of the flushing dots Df.

Here, when the resolution is constant and the printing speed is slow, the number of dots in one cycle decreases. Also, when the printing speed is constant and the resolution changes, the number of dots in one cycle is reduced. The printing speed is a dimension printed in a unit time (length in the conveyance direction A), for example, 300
A value such as mm / sec is applied. Since the size of the reference flushing pattern 63 in the row direction H is the number of dots in the flushing generation cycle, it is increased or decreased in proportion to the printing speed and resolution. That is, when the printing speed is low, the size of the reference flushing pattern 63 in the row direction H can be reduced. Also, when the resolution is not low, the size of the row direction H of the reference flushing pattern 63 can be reduced.

  Since the reference flushing pattern 63 is a flushing pattern of one cycle, it includes one flushing dot Df in one row. The flushing execution timing is designated by the position of the flushing dot Df in each row. The positions of the flushing dots Df are the same in some of the n columns and are different from each other in the other columns. For example, in the example of FIG. 4, the flushing dot Df is arranged in the first row in the third and tenth columns of the reference flushing pattern 63. On the other hand, in the other eight columns, the positions of the flushing dots Df are distributed in different rows (eight rows of 2-7 rows and 9-10 rows). Note that the flushing dots Df may be arranged in the same row in three or more of the n columns.

(Adjusting the size of the reference flushing pattern 63 when the print mode is different)
FIG. 5 is an explanatory diagram of the adjustment flushing pattern 63B and a generation method thereof. The size adjustment unit 58 does not perform the process of generating the adjustment flushing pattern 63B when the set print mode is the first mode, that is, the mode in which the regular flushing is performed at the reference frequency. On the other hand, when the set print mode is the second mode, that is, the mode in which the regular flushing is performed in a predetermined mode higher than the reference frequency, a blank line is added to the reference flushing pattern 63 as shown in FIG. As a result, the adjustment flushing pattern 63B in which the frequency of occurrence of the flushing dots Df in the row direction H is reduced is generated. The row of the adjustment flushing pattern 63B includes one flushing dot Df in one row, similarly to the row of the reference flushing pattern 63.

  Here, in the size adjustment table 67, a value indicating the occurrence frequency of the appropriate flushing dot Df is associated with each print mode. For example, in the example shown in FIG. 5, 10 (1 dot per 10 rows) is associated with the first mode. In addition, for the second mode, a size adjustment table 67 in which 25 (1 dot per 25 rows) is associated is created. As described above, in the second mode, the regular flushing is performed at a frequency higher than the reference frequency. Therefore, the flushing interval of the ink nozzles 25 in the on-paper flushing can be made longer than that at the reference frequency. For this reason, in the second mode, the occurrence frequency of the flushing dot Df in the row direction H is set to a low frequency.

  The size adjustment unit 58 refers to the size adjustment table 67 and calculates a size adjustment ratio Q that realizes the frequency of occurrence of the flushing dots Df associated with the set print mode. Specifically, Q = 2.5 (= 25/10) is calculated as the size adjustment ratio Q of the reference flushing pattern 63 for adjusting the first value (10) to the second value (25). A size adjustment ratio Q corresponding to each print mode may be calculated in advance, and a table in which this value is set in the print mode may be used as the size adjustment table 67. After calculating the size adjustment ratio Q, the size adjustment unit 58 enlarges the reference flushing pattern 63 in the row direction H in proportion to Q times to generate an adjustment flushing pattern 63B. The number of rows that is the size in the row direction H of the adjustment flushing pattern 63B is determined by m × Q based on the size adjustment ratio Q. That is, when m = 10 and Q = 2.5, m × Q = 25. When m × Q includes a fractional part, the number of lines is rounded down.

  Each row of the adjustment flushing pattern 63B includes one flushing dot Df per row. The position of the flushing dot Df in the column of the adjustment flushing pattern 63B is a pattern that is proportionally enlarged Q times in the row direction H with respect to the reference flushing pattern 63, and the position of the flushing dot Df in each column is proportional to Q times in the row direction H. It is determined at the enlarged position. That is, when the coordinates of the flushing dot Df in the original reference flushing pattern 63 are (g, h (g is a row number, ie, a coordinate in the row direction H, and h is a column number, ie, a coordinate in the column direction V)), g × Q And the position of the flushing dot Df in the adjustment flushing pattern 63B is determined based on this value. Specifically, a value g1 is calculated by rounding off the fractional part from g × Q. Then, the coordinates (g1, h) are determined as the position of the flushing dot Df in the adjustment flushing pattern 63B. By calculating the coordinates of the flushing dots Df in this way, the arrangement of the flushing dots Df in the adjustment flushing pattern 63B is determined. Then, an adjustment flushing pattern 63B is generated by adding a blank line to the reference flushing pattern 63 so as to realize such an arrangement.

  FIG. 5 shows a conversion example of the line number g (coordinate in the row direction H) in the size adjustment process. By the process of rounding off fractions from g × Q, the line number g (specifically, 1, 2,..., 10) of the original reference flushing pattern 63 is changed to g1 (specifically, 2, 5, 7, 10, 12, 15, 17, 20, 22, 25). Then, the flushing dot Df is moved to the post-conversion line, and as blank lines, 1, 3, 4, 6, 8, 9, 11, 13, 14, 16, 18, 29, 21, 23, and 24 lines 15 Add a line.

  The example of FIG. 5 is an example in which the line number is set and the size adjustment process is performed with the first line as the first line. However, the line number g1 is calculated with the line number of the first line as the 0th line and the size is calculated. Adjustment processing may be performed. Even in this method, the flushing dot Df can be moved to a position proportionally enlarged in the row direction H. Further, even when the size adjustment ratio Q is set to a value different from 2.5, the occurrence frequency of the flushing dot Df can be similarly adjusted. In this embodiment, g1 is calculated by rounding off the fractional part from g × Q. However, the size may be adjusted by calculating g1 by rounding up the fractional part or rounding off. good.

(Print flushing pattern)
FIG. 6 is an explanatory diagram of a print flushing pattern 66. An example of a plurality of print flushing patterns 66 used when a plurality of input data 10 are continuously printed on a plurality of print regions P1 arranged on the print paper P at a predetermined pitch. Is shown. Further, the example of FIG. 6 is a first mode in which the regular flushing is performed at the reference frequency, and the print flushing pattern 66 is generated from the reference flushing pattern 63. As shown in FIG. 6, on the printing paper P, a non-printing area is arranged between adjacent printing areas P1. The first input data 10 (1) is printed in the first print area P1 (1), and then the second input data 10 (2) is printed in the second print area P1 (2). . When three or more input data 10 are continuously printed, similarly, the input data 10 (i) is continuously printed up to the i-th (i ≧ 3) print area P1 (i).

  At this time, the flushing pattern determining unit 55 applies the print flushing pattern 66 (66 (1) of the size corresponding to the print size to the input data 10 ((1), 10 (2)... 10 (i)). ), 66 (2)... 66 (i)) are formed. That is, the first print flushing pattern 66 (1) having the same size as the print size of the first input data 10 (1) and the second print flushing having the same size as the print size of the second input data 10 (2). A pattern 66 (2) is generated. Similarly, a print flushing pattern 66 (i) having the same size as the print size of the i-th input data 10 (i) is generated. The print flushing pattern 66 (66 (1), 66 (2)... 66 (i)) is input to the input data 10 (10 (1), 10 (2). ) And the generated dot pattern 13 (13 (1), 13 (2)... 13 (i)).

  The print size of the input data 10 (10 (1), 10 (2)... 10 (i)) is the size of the image data 11 after the rendering process described above, and more specifically, the pixels are printed dots. Is the size of the printed dot pattern 13 replaced with. When the print mode is the first mode, the print flushing pattern 66 (66 (1), 66 (2)... 66 (i)) matches the row direction H of the reference flushing pattern 63 with the transport direction A. The reference flushing pattern 63 is generated by repeatedly arranging the reference flushing pattern 63 in the row direction H and the column direction V in a direction in which the column direction V coincides with the paper width direction B intersecting the transport direction A. For example, in the print flushing pattern 66 (1), the reference flushing pattern 63 is repeatedly arranged in the row direction H and the column direction V a plurality of times. In this way, a print flushing pattern 66 having the same size as an arbitrary print size is generated from the reference flushing pattern 63 that is a flushing pattern for one cycle. Here, when the printing mode is the second mode different from the first mode, the adjustment flushing pattern 63B is generated. In this case, the flushing pattern determination unit 55 similarly generates the print flushing pattern 66 using the adjustment flushing pattern 63B instead of the reference flushing pattern 63.

  In the example illustrated in FIG. 6, the first row of the first print flushing pattern 66 (1) is the first dot row of the reference flushing pattern 63. On the other hand, the last row of the first print flushing pattern 66 (1) is the k-th (k <m) dot column of the reference flushing pattern 63. Thus, when the print size in the transport direction A of the first input data 10 (1) is not an integral multiple of the size in the row direction H of the reference flushing pattern 63, the last row of the first print flushing pattern 66 (1). (K row) is a dot column different from the last row (m row) of the reference flushing pattern 63.

  When the first printing flushing pattern 66 (1) ends in the middle of the reference flushing pattern 63, that is, in a row before the m-th row, the flushing pattern determination unit 55 uses the second flushing pattern used in the next printing. The first line of the print flushing pattern 66 (2) is determined based on the last line of the first print flushing pattern 66 (1) used immediately before. Specifically, the first line of the second print flushing pattern 66 (2) is set to the line (k + 1 line) next to the last line (k line) of the first print flushing pattern 66 (1). Similarly, the first line of the i-th print flushing pattern 66 (i) is defined as the line (j + 1 line) next to the jth line (j <m) which is the last line of the immediately preceding print flushing pattern 66 (i-1). To do.

  Thus, in the case of continuous printing, the position of the reference flushing pattern 63 is offset and arranged based on the last line of the immediately preceding print flushing pattern 66 to generate the next print flushing pattern 66. As a result, the flushing dots Df are arranged so that the flushing frequency determined by the reference flushing pattern 63 is maintained over the two print flushing patterns 66 that are used continuously. Thus, the arrangement of the flushing dots Df is determined so that the flushing frequency determined by the reference flushing pattern 63 is maintained in all the steps of continuous printing on the plurality of print regions P1.

  Similarly, when the adjustment flushing pattern 63B is arranged in the row direction H and the column direction V in place of the reference flushing pattern 63 to determine the print flushing pattern 66, similarly, the first line of the print flushing pattern 66 is printed immediately before. By determining the final line of the flushing pattern 66 in consideration, the occurrence frequency of the flushing dot Df determined by the adjustment flushing pattern 63B is maintained. As a result, the flushing dots Df can be generated so as to maintain the optimum frequency in each printing mode.

(Composition of printing flushing pattern)
FIG. 7 is an explanatory diagram illustrating a state in which the printing flushing pattern 66 and the printing dot pattern 13 (13Bk, 13C, 13M, 13Y) are offset and overlapped for each ink color. FIG. 8 is an explanatory diagram of the offset position information table 64. As shown in FIG. 8, the offset position information table 64 includes, for each of four ink colors C, Y, M, and Bk, color-specific combinations that are combinations of the offset amount Dh in the row direction H and the offset amount Dv in the column direction V. Offset amounts (Dh, Dv) are associated with each other. The color-specific offset amounts (Dh, Dv) are, for example, (0, 0), (4, 1), (6, 3), (5, 5) in the order of Bk, C, M, Y. Set to The color-specific offset amount is not limited to the value shown in FIG. 8 as long as one or both of Dh and Dv are different from each other.

  In the synthesis process of the print flushing pattern 66 and the print dot pattern 13 (13Bk, 13C, 13M, 13Y), first, the same print flushing pattern is applied to the four print dot patterns 13 (13Bk, 13C, 13M, 13Y). 66 are shifted and overlapped by the specified color-specific offset amounts (Dh, Dv). Specifically, as shown in FIG. 7A, the print flushing pattern 66 is superimposed on the print dot pattern 13Bk without offset based on the color-specific offset amount (0, 0). Similarly, as shown in FIG. 7B, in the print dot pattern 13C, the print flushing pattern 66 has 4 dots in the row direction H and 1 dot in the column direction V based on the color-specific offset amount (4, 1). They are superimposed and shifted. Further, as shown in FIG. 7C, in the print dot pattern 13M, the print flushing pattern 66 is shifted by 6 dots in the row direction H and 3 dots in the column direction V based on the offset amount by color (6, 3). Are superimposed. As shown in FIG. 8D, in the print dot pattern 13Y, the print flushing pattern 66 is shifted by 5 dots in the row direction H and 5 dots in the column direction V based on the color-specific offset amount (5, 5). Are superimposed.

  As shown in FIG. 7E, the print flushing pattern 66 is superimposed with the offset position shifted depending on the ink color, and synthesized with the print dot pattern 13 (13Bk, 13C, 13M, 13Y). That is, the print dot pattern 13Bk and the print flushing pattern 66 are combined based on the offset amount (0, 0) for black ink, and the print dot pattern 13C and the print flushing pattern 66 are based on the offset amount (4, 1) for cyan ink. The print dot pattern 13M and the print flushing pattern 66 are synthesized based on the offset amount (6, 3) with respect to the magenta ink, and the print dot pattern 13Y and the print flushing pattern 66 are offset with respect to the yellow ink (5, 5). Is synthesized based on In this way, by shifting the offset position depending on the ink color, it is possible to avoid the positions of the flushing dots Df overlapping for a plurality of ink colors. Thereby, it is possible to make the change in the printing result due to the on-paper flushing (that is, the addition of dots by the flushing and the change of the dot size) inconspicuous. Accordingly, it is possible to suppress a decrease in print quality due to the flushing performed on the print area. Further, by shifting the offset position, the same print flushing pattern 66 can be used for a plurality of ink nozzles that eject a plurality of ink colors. Therefore, the processing load can be reduced and the storage capacity can be reduced.

  FIG. 9 is an explanatory diagram of a method for synthesizing the printing flushing pattern 66 and the printing dot pattern 13 (13Bk, 13C, 13M, 13Y), and shows a change in dot size at the position where the flushing dot Df is overlapped. FIG. 10 is an explanatory diagram of the flushing dot composition table 65. In the flushing dot composition table 65, the final dot size (that is, the corrected dot size) that is finally adopted when the flushing dot Df overlaps is associated with each of the four gradation dot sizes of the print dots. ing. 9 and 10 illustrate a case where the dot size of the flushing dot Df is set to M.

  The flushing dot composition table 65 is set to use the larger dot size as the final dot size when the flushing dot Df overlaps the print dot. Specifically, as shown in FIG. 10, when the flushing dot Df overlaps the printing dots D (Null) and D (S) of a size smaller than M, the dot size is converted to M dots, and the final dot Dt (M) is used. On the other hand, when the flushing dot Df overlaps the M or L size print dots D (M) and D (L), the dot size of the original print dot is applied to obtain the final dot Dt (M) or Dt (L ) Is used. By referring to the flushing dot composition table 65, as shown in FIG. 9, the composite dot pattern 14 (14Bk, 14C, 14M) is generated from the print dot pattern 13 (13Bk, 13C, 13M, 13Y) on which the print flushing pattern 66 is superimposed. , 14Y) is generated. As described above, when dots of different sizes are overlapped, an increase in ink viscosity in the vicinity of the nozzle surface can be suppressed by using a dot having a large size, that is, an ink discharge amount. Further, in such a composition method, it is possible to minimize the change in the print target data associated with the composition of the flushing dot Df as compared with the method of simply adding the flushing dot Df.

(Printing method)
When the control unit 5 of the printer 1 receives input data 10 (print data) such as image data or document data via the communication unit 6, the rendering processing, color conversion processing, and 2 described above are performed on the input data 10. A value conversion process (dot ratio determination process and halftone process) is performed, and a determination process of the above-described print flushing pattern 66 and a combination process with the print dot pattern 13 (13Bk, 13C, 13M, 13Y) are performed. 14, the head drive data 15 is generated.

  On the other hand, the control unit 5 performs a cueing operation for transporting the printing paper P toward the printing head 2 and positioning the leading portion of the printing area P1 of the printing paper P at the printing position by the printing head 2. When the cueing operation is completed, based on the generated head drive data 15, a pulse of a voltage applied to the piezoelectric element corresponding to each ink nozzle 25 is generated as a drive signal and supplied to the print head 2. As a result, the print head 2 is driven, ink droplets are ejected from the ink nozzles 25 of the ink jet heads 2C, 2M, 2Y, and 2Bk, and the contents designated by the input data 10 are printed. The control unit 5 drives the print head 2 based on the head drive data 15 to discharge ink onto the print paper P, and the print paper P by the transport amount corresponding to the print resolution specified in the head drive data 15. Performs transporting operation. In addition, periodic flushing is performed at a reference frequency or a predetermined frequency different from the reference frequency in accordance with the set print mode during a period immediately before starting printing, before standby, or after waiting for printing. .

  Since the print flushing pattern 66 is combined with the head drive data 15, by driving the print head 2 according to the head drive data 15, the ink dot forming operation for printing the input data 10 and the ink nozzle 25 are performed. Ink dots are formed for the purpose of flushing. That is, printing of an image or a document on the print area P1 and flushing (paper flushing) on the print area P1 are performed. The ejection frequency of the ink droplets from the ink nozzles 25 by the flushing on paper is adjusted according to the period of the regular flushing.

  As described above, the printer 1 according to the present embodiment performs the printing operation of the input data 10 on the printing area P1 and the flushing on paper. Therefore, the clogging of the ink nozzles 25 can be prevented or eliminated without reducing the throughput during printing, and the deterioration of the printing quality can be suppressed. In particular, in this embodiment, a print flushing pattern 66 having a size corresponding to an arbitrary print size can be generated using the reference flushing pattern 63 having a size of one flushing cycle. Therefore, the print flushing pattern 66 can be generated from the reference flushing pattern 63 having a small size by a simple process. For this reason, the storage capacity of data required for the on-paper flushing is small, and the image processing load is small.

  In the present embodiment, regular flushing for discharging ink to the maintenance unit 4 is performed separately from the flushing on paper. Therefore, even when printing is performed without using the ink nozzles 25 outside the printing area, clogging of the ink nozzles 25 can be prevented or eliminated by regular flushing. Then, when printing in the first mode in which the periodic flushing execution frequency is the reference frequency, the reference flushing pattern 63 is used as it is, but printing may be performed in the second mode in which the periodic flushing is performed at a frequency higher than the reference frequency. In this case, based on the size adjustment ratio Q, the reference flushing pattern 63 (first flushing pattern) is size-adjusted in proportion to the row direction H, and the adjusted flushing pattern 63B (second flushing pattern) ) Is generated. Then, the printing flushing pattern 66 is generated using the adjustment flushing pattern 63B instead of the reference flushing pattern 63. In this way, it is possible to perform on-paper flushing at an optimal ink droplet ejection frequency in a plurality of printing modes with different regular flushing execution frequencies. Moreover, although it is the structure which performs such frequency adjustment, it is not necessary to memorize | store a several flushing pattern. Accordingly, it is possible to reduce the storage capacity of data necessary for the on-paper flushing.

  Furthermore, in this embodiment, the arrangement pattern of the flushing dots Df for one cycle used in the first mode in which the regular flushing is performed at the lowest frequency is used as the reference flushing pattern 63. Therefore, the size of the reference flushing pattern 63 can be minimized, and the storage capacity of data necessary for the on-paper flushing can be reduced. It is also possible to set the mode in which the regular flushing is performed at a frequency lower than the reference frequency, and to generate the adjustment flushing pattern 63B by proportionally reducing the reference flushing pattern 63. However, in this case, the reference flushing pattern 63 is not the minimum size. Therefore, it is desirable to set the pattern used in the mode in which the regular flushing is performed at the lowest frequency as the reference flushing pattern 63.

(Other forms)
(1) In the above embodiment, in order to change the ejection frequency of ink droplets for each ink nozzle 25, size adjustment is performed so that the reference flushing pattern 63 is proportionally enlarged or reduced in the row direction H. However, printing is performed at different printing speeds. Is performed, the size of the reference flushing pattern 63 in the column direction changes even if the ejection frequency of the ink droplets for each ink nozzle 25 is constant. Therefore, when printing is performed at a printing speed F1 different from the reference printing speed F, the size adjustment ratio Q is determined based on the printing speed and the printing mode, and the size of the reference flushing pattern 63 is adjusted. desirable. In this case, the size adjustment ratio Q1 is determined based on the print mode as in the above embodiment, the speed ratio Q2 (Q2 = F1 / F) is set based on the print speed, and the final ratio Q = Q1 × Q2. do it.

(2) The above embodiment adjusts the ejection frequency of the ink droplets of the ink nozzle 25 in the on-paper flushing according to the printing mode, that is, the frequency of the regular flushing, based on the reference flushing pattern 63 used when the regular flushing is performed at the reference frequency. However, according to other parameters such as resolution and environmental conditions (for example, air temperature and humidity), processing for adjusting the ejection frequency of ink droplets from the ink nozzles 25 may be similarly performed. Further, the adjustment flushing pattern may be generated based on a combination of a plurality of parameters including temperature, humidity, and printing mode.

DESCRIPTION OF SYMBOLS 1 ... Printer (printing apparatus), 2 ... Print head, 2Bk, 2C, 2M, 2Y ... Inkjet head, 3 ... Conveyance mechanism, 4 ... Maintenance unit, 5 ... Control part, 6 ... Communication part, 10 ... Input data (printing) Data), 11 ... Image data, 12 (12Bk, 12C, 12M, 12Y) ... Ink amount data, 13 (13Bk, 13C, 13M, 13Y) ... Print dot pattern, 14 (14Bk, 14C, 14M, 14Y) ... Composition Dot pattern, 15 ... print data, 21-24 ... head unit, 25 ... ink nozzle, 51 ... storage unit, 52 ... rendering unit, 53 ... color conversion processing unit (part of print dot pattern generation unit), 54 ... 2 Value processing unit (part of print dot pattern generation unit), 55... Flushing pattern determination unit, 56... Flushing pattern synthesis unit, 7 ... Print control unit, 58 ... Size adjustment unit, 59 ... Regular flushing execution unit (mode setting unit), 61 ... Color conversion lookup table, 62 ... SML table, 63 ... Reference flushing pattern (first flushing pattern), 63B ... Adjustment flushing pattern (second flushing pattern), 64 ... Offset position information table, 65 ... Flushing dot composition table, 66 ... Print flushing pattern, 67 ... Size adjustment table, A ... Conveyance direction, B ... Paper width direction, D ... Print dots, Df ... Flushing dots, Dt ... Last dot, H ... Row direction, V ... Column direction, P ... Print paper (recording medium), P1 ... Print area, Q ... Size adjustment ratio

Claims (8)

When performing printing in the first mode in which the frequency of flushing for discharging ink toward the maintenance unit is set to the first frequency,
A first flushing pattern of n columns × m rows (n and m are integers of 2 or more) including flushing dots is arranged in a column direction intersecting with the conveyance direction of the recording medium and a row direction that is the conveyance direction. Generate a first print flushing pattern;
When performing printing in the second mode in which the flushing frequency is set to a second frequency different from the first frequency,
A second flushing pattern is generated by increasing or decreasing the number of rows of the first flushing pattern to the number of rows corresponding to the second frequency, and the second flushing pattern is arranged in the column direction and the row direction. Generate a second print flushing pattern ;
Generate a print dot pattern based on the print data,
Generating a composite dot pattern in which the print dot pattern and the first print flushing pattern or the second print flushing pattern are synthesized based on a flushing dot synthesis table;
A printing method , wherein the ink is ejected from a print head onto the recording medium based on the synthetic dot pattern . The printing method according to claim 1, wherein the first frequency in the first mode is smaller than the second frequency in the second mode. The printing method according to claim 2, wherein a blank line is added to the first flushing pattern to generate the second flushing pattern having a larger number of lines than the first flushing pattern. The printing method according to claim 1, wherein the first flushing pattern includes one flushing dot in one row. A print head comprising ink nozzles;
A transport mechanism for transporting the recording medium;
A maintenance unit for receiving ink ejected from the ink nozzles of the print head;
The printing mode by the print head is performed in a first mode in which flushing for discharging ink to the maintenance unit is performed at a first frequency, or the flushing is performed in a second frequency different from the first frequency. A mode setting unit for setting the second mode;
A storage unit for storing a first flushing pattern and a flushing dot composition table of n columns × m rows (n and m are integers of 2 or more) each including a flushing dot ;
A print dot pattern generation unit that generates a print dot pattern based on the print data;
In the first mode, the first flushing pattern is arranged in a column direction intersecting with a conveyance direction of the recording medium and a row direction which is the conveyance direction to generate a first print flushing pattern, and the second In this mode, a second flushing pattern in which the number of rows of the first flushing pattern is increased or decreased to the number of rows corresponding to the second frequency is generated, and the second flushing pattern is changed to the column direction and the row. A flushing pattern determination unit that generates a second print flushing pattern arranged in a direction;
A flushing pattern synthesis unit that synthesizes the print dot pattern and the first print flushing pattern or the second print flushing pattern based on a flushing dot synthesis table ;
A print control unit that ejects ink from the print head based on the data generated by the flushing pattern synthesis unit;
A printing apparatus comprising: The printing apparatus according to claim 5, wherein the first frequency in the first mode is smaller than the second frequency in the second mode. The printing apparatus according to claim 6, wherein the flushing pattern determination unit generates the second flushing pattern having a larger number of lines than the first flushing pattern by adding blank lines to the first flushing pattern. The printing apparatus according to claim 5, wherein the first flushing pattern includes one flushing dot in one row.

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