JP6141166B2 - Inkjet printing device - Google Patents

Description

  The present invention relates to an inkjet printing apparatus that performs printing by ejecting ink onto a printing medium.

  2. Description of the Related Art A line-type inkjet printing apparatus that prints by discharging ink from a fixed inkjet head onto a sheet while conveying the sheet is known.

  The ink jet head of this line type ink jet printing apparatus may be composed of a plurality of head modules arranged in a staggered manner along the main scanning direction orthogonal to the paper transport direction (sub-scanning direction).

  Further, as a head module constituting the ink jet head as described above, there is a head module having an ink chamber divided into two regions and two nozzle rows for discharging ink stored in each region. The nozzle positions in the main scanning direction of these two nozzle rows are shifted by half the nozzle pitch (half pitch).

  According to such a head module, it is possible to eject two colors of ink from one head module. Further, if the same color ink is ejected from the two nozzle rows, the printing resolution of the color can be increased.

  By the way, in an inkjet printing apparatus, in order to make the temperature of the ink at the time of printing suitable temperature, the temperature of the ink may be adjusted in an ink supply system (for example, refer patent document 1).

JP 2003-220714 A

  In an ink jet printing apparatus, when an ink ejection operation is performed, the temperature of ink rises due to the influence of heat generated by a piezo element that ejects ink from a nozzle.

  In the above head module, when two nozzle rows discharge the same color ink distributed and supplied from a common path, if there is a difference in driving rate between the two nozzle rows, the inside of the head module Thus, a temperature difference may occur in the ink in the region corresponding to each nozzle row. Then, as the continuous printing time elapses, the temperature difference widens, and the ink corresponding to one nozzle row may quickly deviate from the appropriate temperature range. For this reason, there is a possibility that the printable time may be shortened at an ink temperature within an appropriate temperature range. If the temperature of the ink deviates from the appropriate temperature range, for example, the flying state of the ink becomes unstable, and the print image quality is deteriorated.

  Even if the ink temperature is adjusted in the ink supply system as described in Patent Document 1, the above-described temperature difference of the ink in the head module cannot be suppressed.

  The present invention has been made in view of the above, and an object of the present invention is to provide an ink jet printing apparatus capable of suppressing a decrease in print image quality.

  In order to achieve the above object, a first feature of the ink jet printing apparatus according to the present invention includes a plurality of nozzles arranged at predetermined intervals along a main scanning direction orthogonal to the transport direction of the transported paper. The positions of the nozzles in the main scanning direction are shifted from each other and discharged from the first nozzle row and the first nozzle row and the second nozzle row that are spaced apart from each other along the transport direction. Is divided into a first region for storing ink to be stored and a second region for storing ink ejected from the second nozzle row, and is distributed from a common path and supplied to the first and second regions. Each of the plurality of head modules disposed along the main scanning direction, the first ejection data, and the second ejection data. A control unit that controls to eject ink from the nozzles of the first and second nozzle rows of each head module for each line to perform printing on a sheet. The first and second ejection data and the first ejection data in each head module are controlled so as to suppress an increase in the temperature difference of the ink between the first area and the second area caused by the ink ejection operation. Printing is performed by controlling the correspondence relationship between the first and second nozzle arrays, and in the printing of each page, the first and second ejection data and the first are in each joint portion between the head modules. In the printing in the original correspondence relationship with the second nozzle row, the joint portion has no continuous non-ejecting region where a plurality of nozzles continuous along the main scanning direction are non-ejecting If included, the first and second ejection data and the first ejection data in each head module of the interlocking head module group composed of a plurality of the head modules continuous through the joint portion without the continuous non-ejection area. In addition, the correspondence with the second nozzle row is controlled in conjunction with each other.

  A second feature of the ink jet printing apparatus according to the present invention is that, in each of the head modules, the control unit is configured to print the first and second nozzle arrays on the previous page or the first page up to the previous page. The print ratios of the first and second nozzle arrays between the cumulative print ratios of the first and second nozzle arrays and the print ratios of the first and second nozzle arrays on the current page. In order to reverse the relationship, the correspondence relationship between the first and second ejection data and the first and second nozzle rows is controlled, and the interlocking head module group prints the interlocking head when printing a page. One reference head module is selected from the module group, and the print ratio of the first and second nozzle arrays on the previous page in the reference head module or the first ink up to the previous page. The print ratios of the first and second nozzle arrays are reversed between the cumulative print ratios of the second and second nozzle arrays and the first and second nozzle arrays on the current page. In other words, the correspondence relationship between the first and second ejection data and the first and second nozzle rows in each head module of the interlocking head module group is controlled in conjunction with each other.

  A third feature of the ink jet printing apparatus according to the present invention is that the control unit uses a cumulative value of a total printing rate of the first and second nozzle arrays in each head module of the interlocking head module group. The reference head module is selected.

  A fourth feature of the ink jet printing apparatus according to the present invention is that the control unit determines the correspondence between the first and second ejection data and the first and second nozzle rows in all the head modules. The purpose is to perform control to replace every predetermined printing unit.

  According to a fifth aspect of the inkjet printing apparatus of the present invention, the ink jet printing apparatus further includes a temperature detection unit that detects the temperature of the ink in each of the first and second regions of each of the head modules. In the head module, when the temperature difference between the ink in the first region and the ink in the second region is equal to or greater than the threshold value, the higher the temperature of the ejected ink in the first and second nozzle rows, the higher the printing The linked head module group controls the correspondence between the first and second ejection data and the first and second nozzle rows so that the rate is low, and when the page generated by the linked head module group is printed. If one temperature difference between the ink in the first area and the ink in the second area of the reference head module is equal to or greater than the threshold value, Among the first and second nozzle rows of the reference head module, the first and second in each head module of the interlocking head module group are such that the printing rate is lower when the temperature of the ejected ink is higher. The correspondence between the discharge data and the first and second nozzle arrays is controlled in conjunction with each other.

  A sixth feature of the ink jet printing apparatus according to the present invention is that the control unit selects the reference head module using the temperature of the ink detected by the temperature detection unit in each head module of the interlocking head module group. There is to do.

  According to the first feature of the ink jet printing apparatus according to the present invention, the control unit increases the temperature difference of the ink between the first region and the second region caused by the ink ejection operation in each head module. Printing is performed by controlling the correspondence relationship between the first and second ejection data and the first and second nozzle rows in each head module so as to suppress it. Thereby, it is possible to reduce the temperature difference of the ink between the first region and the second region and the temperature of the ink deviating from the appropriate temperature range. For this reason, it is possible to suppress a reduction in the printable time at the ink temperature within the appropriate temperature range.

  In addition, in the printing of each page, when the joint portion between the head modules includes a joint portion that does not have a continuous non-ejection region, the control unit continuously passes through the joint portion that does not have a continuous non-ejection region. The correspondence relationship between the first and second ejection data and the first and second nozzle rows in each head module of the interlocking head module group including the plurality of head modules is controlled in conjunction with each other. Accordingly, it is possible to suppress a decrease in print image quality at the joint portion due to the correspondence between the first and second ejection data and the first and second nozzle rows being reversed between adjacent head modules.

  Therefore, according to the first feature of the ink jet printing apparatus, it is possible to suppress the deterioration of the print image quality due to the ink temperature deviating from the appropriate temperature range while suppressing the decrease of the print image quality at the joint portion between the head modules.

  According to the second feature of the ink jet printing apparatus according to the present invention, the control unit uses the printing rate that has a large influence on the temperature of the ink, and uses the first and second ejection data and the first and second nozzles. Controls correspondence with columns. Thereby, expansion of the temperature difference of the ink between the 1st field and the 2nd field can be controlled efficiently.

  According to the third feature of the ink jet printing apparatus according to the present invention, the control unit selects the reference head module using the cumulative value of the printing rate that has a large influence on the ink temperature. Thereby, an appropriate reference head module can be easily selected as a reference for controlling the correspondence relationship between the first and second ejection data and the first and second nozzle rows in the interlocking head module group.

  According to the fourth feature of the ink jet printing apparatus according to the present invention, the control unit determines the correspondence between the first and second ejection data and the first and second nozzle arrays in all the head modules. Control to replace each printing unit. Thereby, the expansion of the temperature difference of the ink between the first region and the second region can be suppressed by processing with a small load on the control unit.

  According to the fifth feature of the ink jet printing apparatus according to the present invention, the control unit uses the detected ink temperature and the printing rate that has a large influence on the ink temperature, and uses the first and second ejection data. And the correspondence relationship between the first and second nozzle rows. Thereby, the temperature difference of the ink between the first region and the second region can be controlled with high accuracy.

  According to the sixth aspect of the ink jet printing apparatus of the present invention, the control unit selects the reference head module using the detected ink temperature. Thereby, an appropriate reference head module can be easily selected as a reference for controlling the correspondence relationship between the first and second ejection data and the first and second nozzle rows in the interlocking head module group.

1 is a schematic configuration diagram of an inkjet printing apparatus according to a first embodiment. It is a schematic block diagram of the head module in 1st Embodiment. It is explanatory drawing of arrangement | positioning and a joint part of a head module. It is explanatory drawing of dot formation by the discharge of the ink from an upstream nozzle row and a downstream nozzle row. It is explanatory drawing of dot formation by the discharge of the ink from an upstream nozzle row and a downstream nozzle row. It is explanatory drawing of the ink discharge in a joint part. It is explanatory drawing of the ink discharge in a joint part. It is explanatory drawing of the ink discharge in a joint part. It is a flowchart for demonstrating operation | movement of the inkjet printing apparatus which concerns on 1st Embodiment. It is a figure which shows the image of the image which a continuous non-discharge area | region produces. It is a flowchart of the procedure which selects a reference | standard head module. It is a figure for demonstrating the selection method of a reference | standard head module. FIG. 6 is an explanatory diagram showing a change in ink temperature when an ink temperature difference occurs between an upstream region and a downstream region of the ink chamber. FIG. 6 is an explanatory diagram illustrating a change in ink temperature when a temperature difference of ink between an upstream region and a downstream region of the ink chamber is suppressed. (A) is a figure which shows the example of the printing rate accumulated to the previous page, (b) is a figure which shows the example of the printing rate of this page, (c) is a figure which shows the printing rate after replacement. It is a schematic block diagram of the inkjet printing apparatus which concerns on 2nd Embodiment. It is a schematic block diagram of the head module in 2nd Embodiment. 10 is a flowchart for explaining control of a correspondence relationship between ejection data and nozzle rows in the second embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same or equivalent parts and components are denoted by the same or equivalent reference numerals. However, it should be noted that the drawings are schematic and different from the actual ones. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  Further, the embodiment described below exemplifies an apparatus or the like for embodying the technical idea of the present invention, and the technical idea of the present invention includes the material, shape, structure, The layout is not specified as follows. The technical idea of the present invention can be variously modified within the scope of the claims.

(First embodiment)
FIG. 1 is a schematic configuration diagram of an ink jet printing apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic configuration diagram of the head module. FIG. 3 is an explanatory diagram of the arrangement of the head modules and the joints. In addition, the up-down direction in the following description is a vertical direction, and shall show the up-down direction of FIG.

  As illustrated in FIG. 1, the inkjet printing apparatus 1 according to the first embodiment includes an inkjet head 2, an ink circulation unit 3, and a control unit 4.

  The ink jet head 2 prints an image by ejecting ink onto the paper PA conveyed by a conveyance unit (not shown). The inkjet head 2 has six head modules 11A to 11F. In addition, the alphabetic suffixes (A to F) in the reference numerals of the head modules 11A to 11F may be omitted and collectively described.

  As shown in FIGS. 1 and 3, the head modules 11 </ b> A to 11 </ b> F are staggered along the main scanning direction orthogonal to the conveyance direction (sub-scanning direction) of the paper PA. That is, the six head modules 11A to 11F are arranged along the main scanning direction, and are alternately arranged in the sub scanning direction. Further, the head modules 11A to 11F are arranged so that a part thereof overlaps between the head modules 11 adjacent in the main scanning direction. That is, in the inkjet head 2, joint portions 12 </ b> A to 12 </ b> E that are portions where the head modules 11 adjacent in the main scanning direction overlap each other are formed.

  The joint portion 12A is a portion where the head modules 11A and 11B overlap each other. The joint portion 12B is a portion where the head modules 11B and 11C overlap each other. The joint portion 12C is a portion where the head modules 11C and 11D overlap each other. The joint portion 12D is a portion where the head modules 11D and 11E overlap each other (see FIG. 10). The joint portion 12E is a portion where the head modules 11E and 11F overlap each other (see FIG. 10). In addition, the alphabetic suffixes (A to E) in the symbols of the joint portions 12A to 12E may be omitted and collectively described.

  As shown in FIGS. 2 and 3, the head module 11 includes an ink chamber 21 and two nozzle rows 22U and 22D.

  The ink chamber 21 stores the ink supplied by the ink circulation unit 3. A partition 21 a is provided in the ink chamber 21. The partition 21a partitions the ink chamber 21 into an upstream area 31U and a downstream area 31D in the conveyance direction of the paper PA.

  The regions 31U and 31D store ink of the same color that is distributed and supplied by a distributor 55 from a later-described pipe 59 that is a common path. Piezo elements (not shown) are arranged in the regions 31U and 31D. When the piezo element is driven by a driver (not shown), ink is ejected from the nozzles 41 of the nozzle rows 22U and 22D. The upstream region 31U corresponds to a first region (or a second region) in the claims. The downstream region 31D corresponds to a second region (or first region) in the claims.

  The nozzle rows 22U and 22D are each composed of a plurality of nozzles 41 as shown in FIG. The nozzle rows 22U and 22D are arranged at intervals from each other along the conveyance direction of the paper PA. The upstream nozzle row 22U corresponds to a first nozzle row (or a second nozzle row) in the claims. The downstream nozzle row 22D corresponds to a second nozzle row (or first nozzle row) in the claims.

  The nozzle 41 ejects ink. The nozzle 41 opens on the lower surface of the head module 11. The nozzles 41 of the upstream nozzle row 22U discharge the ink stored in the upstream region 31U of the ink chamber 21. The nozzles 41 of the downstream nozzle row 22 </ b> D eject ink stored in the downstream region 31 </ b> D of the ink chamber 21. In each nozzle row 22U, 22D, the nozzles 41 are arranged at equal intervals at a predetermined pitch P along the main scanning direction. Further, the nozzles 41 of the nozzle row 22U and the nozzles 41 of the nozzle row 22D are arranged so as to be shifted by a half pitch (P / 2) in the main scanning direction. In the joint portion 12, as shown in FIG. 3, the nozzles 41 in the nozzle row 22U and the nozzles 41 in the nozzle row 22D are arranged at the same position in the main scanning direction.

  The ink circulation unit 3 supplies ink to the inkjet head 2 while circulating the ink. The ink circulation unit 3 includes an upstream tank 51, a downstream tank 52, an ink bottle 53, a pump 54, a distributor 55, a collector 56, a heater 57, a cooler 58, and pipes 59 to 62, 63a. , 63b, 64a, 64b.

  The upstream tank 51 stores the ink sent from the downstream tank 52 and supplies the ink to the inkjet head 2.

  The downstream tank 52 stores ink that has not been consumed by the ejection operation by the inkjet head 2. Further, the downstream tank 52 stores the ink supplied from the ink bottle 53.

  The ink bottle 53 holds ink used for printing in the inkjet printing apparatus 1. The ink bottle 53 supplies ink to the downstream tank 52.

  The pump 54 sends ink from the downstream tank 52 to the upstream tank 51. The pump 54 is provided in the middle of the pipe 61 between the downstream tank 52 and the upstream tank 51.

  The distributor 55 distributes the ink supplied from the upstream tank 51 via the pipe 59 to the regions 31U and 31D of the ink chamber 21 of the head modules 11A to 11F.

  The aggregator 56 collects ink that has not been consumed by the ejection operation in the head modules 11 </ b> A to 11 </ b> F from the regions 31 </ b> U and 31 </ b> D of the ink chamber 21. The ink collected by the collecting device 56 flows to the downstream tank 52 through the pipe 60.

  The heater 57 heats the ink circulated in the ink circulation unit 3. The heater 57 is provided in the middle of the pipe 59 between the upstream tank 51 and the distributor 55.

  The cooler 58 cools the ink circulated in the ink circulation unit 3. The cooler 58 has a heat sink and a fan (both not shown). The cooler 58 is provided in the middle of the pipe 61 between the downstream tank 52 and the upstream tank 51.

  The pipe 59 connects the upstream tank 51 and the distributor 55. The pipe 60 connects the collector 56 and the downstream tank 52. The pipe 61 connects the downstream tank 52 and the upstream tank 51. The pipe 62 connects the ink bottle 53 and the downstream tank 52.

  The pipe 63a connects the distributor 55 and the region 31U on the upstream side of the ink chamber 21 of the head module 11. The pipe 63 b connects the distributor 55 and the region 31 </ b> D on the downstream side of the ink chamber 21 of the head module 11. The pipe 64 a connects the region 31 U on the upstream side of the ink chamber 21 of the head module 11 and the collector 56. The pipe 64 b connects the region 31 </ b> D on the downstream side of the ink chamber 21 of the head module 11 and the collector 56. The pipes 63a, 63b, 64a, and 64b are provided for each head module 11.

  The control unit 4 controls the operation of the entire inkjet printing apparatus 1. The control unit 4 includes a CPU, a RAM, a ROM, a hard disk, and the like.

  At the time of printing, the control unit 4 discharges ink for each line from the nozzles 41 of the nozzle arrays 22U and 22D of the head modules 11A to 11F based on the discharge data for the upstream nozzle array and the discharge data for the downstream nozzle array. To control printing.

  The ejection data for the upstream nozzle array is data indicating the number of ink droplets (drop number) ejected from the nozzles 41 of the upstream nozzle array 22U to each pixel in order to form a print image. The discharge data for the upstream nozzle array corresponds to first discharge data (or second discharge data) in claims. The ejection data for the downstream nozzle array is data indicating the number of drops ejected from the nozzles 41 of the downstream nozzle array 22D to each pixel in order to form a print image. The discharge data for the downstream nozzle row corresponds to second discharge data (or first discharge data) in claims.

  As described above, the discharge data for the upstream nozzle row and the discharge data for the downstream nozzle row are generated as corresponding to the upstream nozzle row 22U and the downstream nozzle row 22D, respectively. On the other hand, the control unit 4 controls the upstream nozzle row in each head module 11 so as to suppress the expansion of the ink temperature difference between the regions 21U and 21D caused by the ink ejection operation in each head module 11. Printing is performed by controlling the correspondence between the discharge data and the discharge data for the downstream nozzle row and the nozzle rows 22U and 22D.

  Specifically, in each head module 11, the control unit 4 determines whether the nozzle row 22U is between the print rate of the nozzle rows 22U and 22D on the previous page and the print rate of the nozzle rows 22U and 22D on the current page. , 22D, the correspondence relationship between the ejection data and the nozzle rows 22U, 22D is controlled so that the magnitude relationship of the print ratios is reversed.

  However, in the printing of each page, if the joint portion 12A to 12E includes a joint portion 12 that does not have a continuous non-ejection region, which will be described later, the control unit 4 passes the joint portion 12 that has no continuous non-ejection region. The correspondence relationship between the ejection data and the nozzle rows 22U and 22D in each head module 11 of the interlocking head module group including a plurality of continuous head modules 11 is controlled in conjunction with each other.

  Specifically, the control unit 4 selects one reference head module from the interlocking head module group. Here, the control unit 4 selects the reference head module using the cumulative value of the total printing rate of the nozzle rows 22U and 22D of the head modules 11 of the interlocking head module group.

  Then, the control unit 4 prints the nozzle rows 22U and 22D between the print rate of the nozzle rows 22U and 22D of the previous page and the print rate of the nozzle rows 22U and 22D of the current page in the reference head module. The correspondence relationship between the ejection data in the reference head module and the nozzle rows 22U and 22D is controlled so that the ratio of the rates is reversed. At this time, the control unit 4 controls the correspondence relationship between the ejection data in the other head modules 11 of the interlocking head module group and the nozzle rows 22U and 22D in conjunction with the reference head module.

  Here, the control of the correspondence between the discharge data and the nozzle rows 22U and 22D is based on the correspondence between the discharge data for the upstream nozzle row and the discharge data for the downstream nozzle row and the nozzle rows 22U and 22D. This is to control whether to change the relationship or to reverse the correspondence relationship.

  If printing is performed as shown in FIG. 4 in printing with the original correspondence, printing is performed as shown in FIG. 5 with the opposite correspondence from the original.

  4 and 5, the dot 66 u indicates a dot formed on the paper PA by the ink ejected from the nozzle 41 of the upstream nozzle row 22 </ b> U. A dot 66d indicates a dot formed on the paper PA by the ink ejected from the nozzle 41 of the downstream nozzle row 22D. Since the nozzle rows 22U and 22D eject the same color ink, the dots 66u and 66d are the same color dots.

  At the time of printing, ink is ejected from the nozzles 41 of the upstream nozzle row 22U, the dot 66u for one line is formed on the paper PA, and then the dot 66d is formed on the same line as the dot 66u. Thus, ink is ejected from the downstream nozzle row 22D. In this way, a print image is formed for each line on the conveyed paper PA.

  As shown in FIGS. 4 and 5, the same print image is formed even if the correspondence relationship between the ejection data and the nozzle rows 22U and 22D is changed. However, the print image is shifted in the main scanning direction by a half pitch (P / 2). For this reason, in the inkjet printing apparatus 1, if the correspondence relationship between the ejection data and the first and second nozzle rows is reversed between the adjacent head modules 11, the print image quality may be deteriorated at the joint portion 12.

  For example, it is assumed that ink is ejected as shown in FIG. 6 at the connecting portion 12A. Here, when printing with the original correspondence (no replacement) between the ejection data and the nozzle rows 22U and 22D, it is used so that ink is not ejected from the two head modules 11 at the same position in the main scanning direction. The nozzle 41 to be determined is determined. In the example of FIG. 6, among the five columns printed by the connecting portion 12A, ink is ejected from the head module 11A in the first to third columns from the left in the drawing, and ink is ejected from the head module 11B in the fourth and fifth columns.

  On the other hand, only the ejection content of the head module 11A is shifted by changing the correspondence between the ejection data and the nozzle rows 22U and 22D only in the head module 11A. For example, as shown in FIG. 6, the discharge content of the head module 11A is shifted by a half pitch in the right direction in the figure, and the discharge content of the head module 11B is not shifted. In this case, ink is ejected from both the head modules 11A and 11B in the fourth row. For this reason, in the printing result of the fourth row, the dots are larger than when the correspondence relationship between the ejection data and the nozzle rows 22U and 22D is not changed. As a result, the print image quality is degraded.

  For example, only the head module 11B is assumed to change the correspondence between the ejection data and the nozzle rows 22U and 22D. In this case, only the ejection content of the head module 11B is shifted. For example, as shown in FIG. 7, the discharge content of the head module 11B is shifted by a half pitch in the right direction in the drawing, and the discharge content of the head module 11A is not shifted. In this case, ink is not ejected from either of the head modules 11A and 11B in the fourth row.

  For this reason, in the 3rd to 5th rows when the replacement is performed, corresponding to the portions where the continuous ejection is performed in the 2nd to 4th rows in the case where there is no replacement, the discharge in the fourth row is eliminated. As a result, the print image quality is degraded.

  As shown in FIGS. 6 and 7, if the correspondence between the ejection data and the nozzle rows 22U and 22D is changed in only one of the two adjacent head modules 11, the print image quality may be deteriorated. .

  However, when there is a continuous non-ejection region in the joint portion 12, the above-described deterioration in print image quality is reduced. The continuous non-ejection area is an area where a plurality of nozzles that are continuous along the main scanning direction are non-ejection in printing in the original correspondence relationship (no replacement) between the ejection data and the first and second nozzle rows. .

  For example, as shown in FIG. 8, when printing is performed without changing the correspondence between the ejection data and the first and second nozzle rows, the second row and the third row are non-ejection (no ejection). And This portion corresponds to a continuous non-ejection region. In addition, it is assumed that the first row is ejected by the head module 11A and the fourth row is ejected by the head module 11B.

  On the other hand, it is assumed that only the ejection content of the head module 11A is shifted by a half pitch in the right direction in the figure by switching the correspondence between the ejection data and the nozzle rows 22U and 22D only in the head module 11A. In this case, as shown in FIG. 8, in the case of no replacement, the second and second columns are the print results without discharge, whereas the replacement results in no discharge only in the third column. It has become. That is, the row without ejection is reduced by one row.

  In the example of FIG. 8, when only the head module 11 </ b> B replaces the correspondence relationship between the ejection data and the nozzle rows 22 </ b> U and 22 </ b> D, the 3rd to 2nd to 4th rows have no ejection. That is, the number of rows without ejection increases by one.

  However, even if the number of non-ejection rows is increased or decreased by one, the change is such that it cannot be discerned by human eyes, and the print image quality hardly deteriorates.

  In addition, when there is a continuous non-ejection area, even if only one head module 11 replaces the correspondence between the ejection data and the nozzle rows 22U and 22D, the occurrence of ejection overlap as shown in FIG. 6 can be suppressed.

  As described above, when there is a continuous non-ejection region in the joint portion 12, even if the correspondence relationship between the ejection data and the nozzle rows 22 </ b> U and 22 </ b> D is different between the two head modules 11 that are adjacent to each other via the joint portion 12. The effect on print quality is small. On the other hand, when there is no continuous non-ejection region in the joint portion 12, the correspondence relationship between the ejection data and the nozzle rows 22U and 22D is different between the two head modules 11 that are adjacent to each other through the joint portion 12. As shown in the examples of FIGS. 6 and 7, the print image quality is degraded.

  Therefore, as described above, the control unit 4 includes the discharge data in each head module 11 of the interlocking head module group including the plurality of head modules 11 via the joint portion 12 having no continuous non-discharge region, the nozzle row 22U, The correspondence with 22D is controlled in conjunction. On the other hand, between the head modules 11 adjacent to each other via the joint portion 12 where there is a continuous non-ejection region, the control unit 4 controls the correspondence between the ejection data and the nozzle rows 22U and 22D independently.

  Next, the operation of the inkjet printing apparatus 1 will be described.

  FIG. 9 is a flowchart for explaining the operation of the inkjet printing apparatus 1. The process of the flowchart of FIG. 9 starts when print data is input to the inkjet printing apparatus 1. The print data includes discharge data for the upstream nozzle row and discharge data for the downstream nozzle row.

  In step S <b> 1 of FIG. 9, the control unit 4 determines whether or not there is a joint portion 12 having no continuous non-ejection area in printing of the current page, based on the ejection data of the page to be printed.

  When it is determined that there is a joint portion 12 that does not have a continuous non-ejection area (step S1: YES), in step S2, the control unit 4 selects a reference head module from the interlocking head module group.

  Here, for example, it is assumed that there is no continuous non-ejection area in the joint portion 12C for a page having the print areas 70A to 70C as shown in FIG. In this case, the head modules 11C and 11D that are continuous through the joint portion 12C having no continuous non-ejection area constitute an interlocking head module group. Therefore, in this case, the control unit 4 selects the reference head module from the head modules 11C and 11D. The procedure for selecting the reference head module will be described later.

  For example, when the joint portion 12C and the joint portion 12E do not have a continuous non-ejection area, the head modules 11C and 11D constitute one interlocking head module group, and the head modules 11E and 11F constitute another interlocking head module group. To do. Further, for example, when there is no continuous non-ejection region in the joint portion 12C and the joint portion 12D, the head modules 11C, 11D, and 11E constitute an interlocking head module group.

  Next, in step S3, the control unit 4 determines the correspondence relationship between the ejection data in each head module 11 and the nozzle rows 22U and 22D.

  Specifically, for each head module 11 not included in the interlocking head module group, the control unit 4 prints the nozzle rows 22U and 22D of the previous page in the head module 11 and the nozzle row on the current page. The correspondence relationship between the ejection data and the nozzle rows 22U and 22D is determined so that the magnitude relationship between the print rates of the nozzle rows 22U and 22D is reversed between the print rates of 22U and 22D.

  If the current print is the first page, the original correspondence between the ejection data and the nozzle rows 22U and 22D is determined. That is, the correspondence relationship is such that ink is ejected from the upstream nozzle array 22U based on the ejection data for the upstream nozzle array, and ink is ejected from the downstream nozzle array 22D based on the ejection data for the downstream nozzle array. decide.

  For the interlocking head module group, the control unit 4 determines whether the nozzle row is between the print rate of the nozzle rows 22U and 22D of the previous page and the print rate of the nozzle rows 22U and 22D of the current page in the reference head module. The correspondence relationship between the ejection data in the reference head module and the nozzle rows 22U and 22D is determined so that the magnitude relationship between the printing rates of 22U and 22D is reversed. At this time, the control unit 4 also links the correspondence relationship between the ejection data in the other head modules 11 of the linked head module group and the nozzle rows 22U and 22D to the reference head module.

  For example, it is assumed that the correspondence relationship between the ejection data in the reference head module and the nozzle rows 22U and 22D is determined as a correspondence relationship opposite to the original one. That is, for the reference head module, ink is ejected from the downstream nozzle array 22D based on the ejection data for the upstream nozzle array, and ink is ejected from the upstream nozzle array 22U based on the ejection data for the downstream nozzle array. Suppose that the correspondence is determined as follows. In this case, the control unit 4 determines the correspondence relationship between the ejection data and the nozzle rows 22U and 22D as the correspondence relationship opposite to the original relationship for the other head modules in the interlocking head module group.

  If it is determined in step S1 that there is no joint portion 12 without a continuous non-ejection region, that is, there is a continuous non-ejection region in all joint portions 12 (step S1: NO), the controller 4 in step S3 The correspondence relationship between the ejection data in each head module 11 and the nozzle rows 22U and 22D is determined.

  Specifically, the control unit 4 determines, for each head module 11, between the print rate of the nozzle rows 22U and 22D of the previous page in the head module 11 and the print rate of the nozzle rows 22U and 22D on the current page. Thus, the correspondence relationship between the ejection data and the nozzle rows 22U and 22D is determined so that the magnitude relationship between the print rates of the nozzle rows 22U and 22D is reversed.

  After step S3, in step S4, the control unit 4 executes printing. Specifically, the control unit 4 conveys the paper PA by a conveyance unit (not shown), and based on the discharge data for the upstream nozzle row and the discharge data for the downstream nozzle row, the nozzle row 22U of each head module 11 is used. , 22D to eject ink. Here, the control unit 4 causes ink to be ejected from the nozzles 41 of the nozzle rows 22U and 22D according to the correspondence relationship between the ejection data in each head module determined in step S3 and the nozzle rows 22U and 22D. Thereby, an image is printed on the paper PA.

  Next, in step S5, the control unit 4 determines whether printing of all pages has been completed. If it is determined that printing of all pages has not been completed (step S5: NO), the control unit 4 returns to step S1. When it is determined that printing of all pages has been completed (step S5: YES), the control unit 4 ends the operation.

  Next, the procedure for selecting the reference head module in step S2 in FIG. 9 will be described with reference to the flowchart in FIG.

  In step S11 of FIG. 11, the control unit 4 extracts the two head modules 11 with the highest cumulative print rate from each head module 11 included in the interlocking head module group. The cumulative printing rate of the head module 11 is a cumulative value of the total printing rate of the nozzle rows 22U and 22D from the start of printing.

  Next, in step S12, the control unit 4 determines whether or not the difference in the cumulative printing rate between the two head modules extracted in step S11 is greater than or equal to a threshold value.

  When it is determined that the difference in the cumulative print ratio is equal to or greater than the threshold (step S12: YES), in step S13, the control unit 4 selects the head module 11 having the maximum cumulative print ratio as the reference head module.

  If it is determined in step S12 that the difference between the cumulative printing rates is less than the threshold value (step S12: NO), in step S14, the control unit 4 selects the current print target from the two head modules extracted in step S11. The head module 11 having the larger print rate difference between the nozzle rows 22U and 22D in the page is selected as the reference head module.

  For example, assume that the cumulative printing rate for each page in each head module 11 is as shown in FIG. Here, on the fourth page, it is assumed that there is no continuous non-ejection area at the joint portion 12C between the head modules 11C and 11D, that is, the head modules 11C and 11D constitute an interlocking head module group. Further, on the sixth page, it is assumed that there is no continuous non-ejection region at the joint portion 12E between the head modules 11E and 11F, that is, the head modules 11E and 11F constitute an interlocking head module group. Further, on the eighth page, it is assumed that there is no continuous non-ejection area at the joint portion 12A between the head modules 11A and 11B, that is, the head modules 11A and 11B constitute an interlocking head module group. Further, it is assumed that the threshold value of the difference in the cumulative printing rate is 5 (%).

  In the fourth page, the difference between the cumulative printing rate 80 (%) of the head module 11C up to the previous page (third page) and the cumulative printing rate 50 (%) of the head module 11D is not less than the threshold value 5 (%). is there. The head module 11C has a higher cumulative printing rate than the head module 11D. For this reason, the head module 11C becomes the reference head module.

  On the sixth page, the difference between the cumulative printing rate 87 (%) of the head module 11E up to the previous page (fifth page) and the cumulative printing rate 100 (%) of the head module 11F is greater than or equal to the threshold 5 (%). is there. The head module 11F has a higher cumulative printing rate than the head module 11E. For this reason, the head module 11F becomes a reference head module.

  On the 8th page, the difference between the cumulative printing rate 155 (%) of the head module 11A up to the previous page (7th page) and the cumulative printing rate 139 (%) of the head module 11B is greater than or equal to the threshold 5 (%). is there. The head module 11A has a higher cumulative printing rate than the head module 11B. For this reason, the head module 11A becomes the reference head module.

  In addition, on the ninth page (not shown), the head modules 11A and 11B constitute an interlocking head module group. In this case, the difference between the cumulative printing rate 177 (%) of the head module 11A up to the previous page (8th page) and the cumulative printing rate 176 (%) of the head module 11B is less than the threshold value 5 (%).

  In this case, the difference in printing rate between the nozzle rows 22U and 22D of the head module 11A on the ninth page is compared with the difference in printing rate between the nozzle rows 22U and 22D of the head module 11B. Here, for example, the difference in printing rate between the nozzle rows 22U and 22D of the head module 11A on the ninth page is 5 (%), and the difference in printing rate between the nozzle rows 22U and 22D of the head module 11B is 20 (%). And In this case, the head module 11B having a large difference in print rate between the nozzle rows 22U and 22D serves as a reference head module.

  Here, unlike the control of the correspondence between the ejection data and the nozzle rows 22U and 22D as described above, when printing is performed with the correspondence between the ejection data and the nozzle rows 22U and 22D fixed, printing is performed. A difference in ink temperature may occur between the areas 31U and 31D due to a difference in printing rate in 22D.

  For example, it is assumed that a large number of pages having a large printing rate deviation are continuously printed between the nozzle rows 22U and 22D. In this case, as shown in FIG. 13, the temperature difference of the ink between the regions 31U and 31D increases as the continuous printing time elapses. Then, the temperature of the ink in the upstream region 31U may exceed the upper limit temperature T2 of the appropriate temperature range (T1 to T2). If the temperature of the ink in the region 31U exceeds the upper limit temperature T2, for example, the flying state of the ink ejected from the upstream nozzle row 22U may become unstable, and the print image quality may deteriorate.

  On the other hand, as described above, the print rate of the nozzle rows 22U and 22D is larger or smaller between the print rate of the nozzle rows 22U and 22D on the previous page and the print rate of the nozzle rows 22U and 22D on the current page. If the control is performed so that the relationship is reversed, the printing rate can be distributed between the nozzle rows 22U and 22D. Accordingly, as shown in FIG. 14, there is almost no ink temperature difference between the areas 31U and 31D. Even if the temperature of the ink in the area 31U exceeds the upper limit temperature T2 in FIG. The temperatures of the 31U and 31D inks are maintained within an appropriate temperature range.

  As described above, in the inkjet printing apparatus 1, the control unit 4 controls each head module 11 so as to suppress the expansion of the ink temperature difference between the regions 21 </ b> U and 21 </ b> D caused by the ink ejection operation in each head module 11. Printing is performed by controlling the correspondence between the discharge data for the upstream nozzle row and the discharge data for the downstream nozzle row and the nozzle rows 22U and 22D.

  Specifically, in each head module 11, the control unit 4 determines whether the nozzle row 22U is between the print rate of the nozzle rows 22U and 22D on the previous page and the print rate of the nozzle rows 22U and 22D on the current page. , 22D, the correspondence relationship between the ejection data and the nozzle rows 22U, 22D is controlled so that the magnitude relationship of the print ratios is reversed.

  Thereby, it is possible to reduce the occurrence of a large ink temperature difference between the regions 31U and 31D in each head module 11 and the ink temperature deviating from the appropriate temperature range. For this reason, it is possible to suppress a reduction in the printable time at the ink temperature within the appropriate temperature range. As a result, it is possible to suppress deterioration in print image quality due to the ink temperature deviating from the appropriate temperature range.

  In addition, in the printing of each page, when the joint portion 12 having no continuous non-ejection area is included in the joint portions 12A to 12E, the control unit 4 determines the ejection data in each head module 11 of the interlocking head module group. The correspondence with the nozzle arrays 22U and 22D is controlled in conjunction with each other.

  Specifically, the control unit 4 selects one reference head module from the interlocking head module group. Then, the control unit 4 prints the nozzle rows 22U and 22D between the print rate of the nozzle rows 22U and 22D of the previous page and the print rate of the nozzle rows 22U and 22D of the current page in the reference head module. The correspondence relationship between the ejection data in the reference head module and the nozzle rows 22U and 22D is controlled so that the ratio of the rates is reversed. At this time, the control unit 4 controls the correspondence relationship between the ejection data in the other head modules 11 of the interlocking head module group and the nozzle rows 22U and 22D in conjunction with the reference head module.

  Accordingly, it is possible to suppress a decrease in print image quality at the joint portion due to the correspondence between the ejection data and the nozzle rows 22U and 22D being reversed between the adjacent head modules 11.

  Therefore, according to the inkjet printing apparatus 1, it is possible to suppress a decrease in print image quality due to the ink temperature deviating from the appropriate temperature range while suppressing a decrease in print image quality at the joint portion 12.

  Further, in the ink jet printing apparatus 1, it is possible to efficiently suppress the occurrence of the ink temperature difference between the regions 31U and 31D by using the printing rate that has a large influence on the ink temperature.

  Moreover, in the inkjet printing apparatus 1, the control part 4 selects a reference | standard head module from an interlocking head module group using a cumulative printing rate. Here, in the interlocking head module group, in the head modules 11 other than the reference head module, the correspondence between the ejection data and the nozzle rows 22U and 22D is controlled in conjunction with the reference head module. For this reason, in the head modules 11 other than the reference head module, the magnitude relationship between the print rates between the nozzle rows 22U and 22D is not always reversed between pages. For this reason, in the head modules 11 other than the reference head module, the temperature difference of the ink between the regions 21U and 21D increases, and one ink in the regions 21U and 21D may approach the upper limit temperature of the appropriate temperature range. Therefore, in the interlocking head module group, it is appropriate to use the head module 11 having the highest ink temperature as the reference head module. Therefore, in the inkjet printing apparatus 1, an appropriate reference head module can be easily selected as a reference by using a cumulative printing rate that has a large influence on the ink temperature.

  In the above embodiment, the magnitude relationship of the printing rates of the nozzle rows 22U and 22D between the printing rates of the nozzle rows 22U and 22D on the previous page and the printing rates of the nozzle rows 22U and 22D on the current page. The correspondence relationship between the ejection data and the nozzle rows 22U and 22D was controlled so that the nozzles 22U and 22D up to the previous page were changed instead of the print ratio of the nozzle rows 22U and 22D of the previous page. The cumulative printing rate of each of the above may be used.

  That is, there is a magnitude relationship between the print rates of the nozzle rows 22U and 22D between the cumulative print rates of the nozzle rows 22U and 22D up to the previous page and the print rates of the nozzle rows 22U and 22D on the current page. The correspondence relationship between the ejection data and the nozzle rows 22U and 22D may be controlled so as to be reversed.

  Control of the correspondence relationship between the ejection data and the nozzle rows 22U and 22D in this case will be described with reference to the example of FIG.

  FIG. 15A shows an example of the cumulative printing rate of each of the nozzle rows 22U and 22D up to the previous page (third page) in each head module 11. FIG. 15B shows an example of the printing rate of the discharge data for the upstream nozzle row and the discharge data for the downstream nozzle row in the current page (fourth page) for each head module 11. In FIG. 15C, the print ratios of the nozzle rows 22U and 22D on the current page are reversed with respect to the cumulative print rates of the nozzle rows 22U and 22D up to the previous page. The printing rate of this page after this is shown.

  Here, on the fourth page, it is assumed that there is no continuous non-ejection area in the joint portion 12C between the head modules 11C and 11D, that is, the head modules 11C and 11D constitute an interlocking head module group. Here, the cumulative printing rate of the head module 11C up to the third page is 70 + 68 = 138 (%). Further, the cumulative printing rate of the head module 11D up to the third page is 65 + 60 = 125 (%). The difference between them is equal to or greater than the threshold value 5 (%). For this reason, the head module 11C having a large cumulative printing rate becomes the reference head module. In this case, the head module 11C is the target of the replacement process, and the head module 11D is processed in conjunction with it.

  15A and 15B, in all the head modules 11A to 11F, the cumulative print rates of the nozzle rows 22U and 22D up to the third page are also the print rates of the nozzle rows 22U and 22D on the fourth page. In addition, the nozzle row 22U is larger than the nozzle row 22D. Therefore, on the fourth page, as shown in FIG. 15C, the correspondence relationship between the ejection data and the nozzle rows 22U and 22D is changed with respect to FIG. 15B in all the head modules 11A to 11F. .

  In addition, the control unit 4 controls to replace the correspondence relationship between the discharge data for the upstream nozzle row and the discharge data for the downstream nozzle row and the nozzle rows 22U and 22D in every head module 11 for each predetermined print unit. May be performed. The printing unit can be, for example, one page.

  If the control is performed to switch the correspondence between the ejection data and the nozzle rows 22U and 22D in a predetermined printing unit, the printing rate can be distributed among the nozzle rows 22U and 22D. Thereby, it is possible to reduce the occurrence of a large ink temperature difference between the areas 21U and 21D in the inkjet head 2 and the ink temperature deviating from the appropriate temperature range. For this reason, it is possible to suppress a reduction in the printable time at the ink temperature within the appropriate temperature range. As a result, it is possible to suppress deterioration in print image quality due to the ink temperature deviating from the appropriate temperature range.

  In addition, since the control is merely to change the correspondence between the ejection data and the nozzle rows 22U and 22D in a predetermined printing unit, the temperature difference of the ink between the regions 31U and 31D is reduced by processing with a small load on the control unit 4. Can be suppressed.

  Further, in all the head modules 11, since the correspondence relationship between the ejection data and the nozzle rows 22U and 22D is changed for each predetermined printing unit, the correspondence relationship between the ejection data and the nozzle rows 22U and 22D between the adjacent head modules 11. It is possible to avoid a decrease in the print image quality at the joint portion due to the reverse.

(Second Embodiment)
FIG. 16 is a schematic configuration diagram of an ink jet printing apparatus according to the second embodiment. FIG. 17 is a schematic configuration diagram of a head module according to the second embodiment.

  As shown in FIGS. 16 and 17, the inkjet printing apparatus 1 </ b> A according to the second embodiment has a configuration in which temperature sensors 32 </ b> U and 32 </ b> D are added to the head module 11 with respect to the inkjet printing apparatus 1 of FIG. 1.

  The temperature sensors 32U and 32D detect ink temperatures in the regions 31U and 31D of the ink chamber 21, respectively. The temperature sensors 32U and 32D correspond to a temperature detection unit in claims.

  In the inkjet printing apparatus 1A, the control unit 4 selects the reference head module using the temperature of the ink detected by the temperature sensors 32U and 32D in each head module 11 of the interlocking head module group. Specifically, the control unit 4 selects, as a reference head module, the head module 11 in which the highest temperature is detected by the temperature sensors 32U and 32D in the interlocking head module group.

  Next, control of the correspondence between the ejection data and the nozzle rows 22U and 22D in the inkjet printing apparatus 1A will be described with reference to the flowchart of FIG. The process of the flowchart in FIG. 18 is performed for each page to be printed on each head module 11.

  In step S21 of FIG. 18, the control unit 4 calculates the print ratios of the nozzle rows 22U and 22D of the head module 11 to be processed in the current page. Specifically, the control unit 4 calculates a printing rate in the ejection data for the upstream nozzle row corresponding to the processing target head module 11 in the current page and a printing rate in the ejection data for the downstream nozzle row. To do.

  Next, in step S22, the control unit 4 acquires the ink temperature Tu in the region 31U of the ink chamber 21 of the head module 11 to be processed from the temperature sensor 32U. Further, the control unit 4 acquires the ink temperature Td in the region 31D from the temperature sensor 32D.

  Next, in step S23, the control unit 4 determines whether or not the ink temperature difference | Tu−Td | between the regions 31U and 31D is equal to or greater than a threshold value.

  When it is determined that the ink temperature difference | Tu−Td | is equal to or greater than the threshold (step S23: YES), in step S24, the control unit 4 determines whether or not Tu> Td.

  When it is determined that Tu> Td is satisfied (step S24: YES), in step S25, the control unit 4 performs processing so that the upstream nozzle row 22U has a smaller printing rate than the downstream nozzle row 22D. The correspondence relationship between the ejection data in the target head module 11 and the nozzle rows 22U and 22D is determined.

  If it is determined in step S24 that Tu ≦ Td (step S24: NO), in step S26, the control unit 4 causes the upstream nozzle row 22U to have a higher printing rate than the downstream nozzle row 22D. As described above, the correspondence between the ejection data in the head module 11 to be processed and the nozzle rows 22U and 22D is determined.

  If it is determined in step S23 that the ink temperature difference | Tu−Td | is less than the threshold value (step S23: NO), in step S27, the control unit 4 associates the original ejection data with the nozzle rows 22U and 22D. Maintain a relationship.

  When the correspondence relationship between the ejection data and the nozzle rows 22U and 22D is determined for all the head modules 11A to 11F as described above, the control unit 4 executes printing based on the determined correspondence relationship.

  As described above, in the second embodiment, the control unit 4 uses the ink temperatures Tu and Td detected by the temperature sensors 32U and 32D and the print rate, and the ejection data and the nozzle rows 22U and 22D. Controls the correspondence with. Thereby, the temperature difference of the ink between the areas 31U and 31D can be controlled with high accuracy.

  Further, the control unit 4 selects the reference head module using the detected ink temperature. Here, as described above, in the interlocking head module group, it is appropriate that the head module 11 having the highest ink temperature be the reference head module. In the second embodiment, by using the detected ink temperature, an appropriate reference head module can be easily selected as a reference for controlling the correspondence between the ejection data and the nozzle rows 22U and 22D in the interlocking head module group. it can.

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

DESCRIPTION OF SYMBOLS 1,1A Inkjet printer 3 Ink circulation part 4 Control part 11A-11F Head module 12A-12E Joint part 21 Ink chamber 22U, 22D Nozzle row 31U, 31D area | region 32U, 32D Temperature sensor 41 Nozzle

Claims (6)

Each of the nozzles includes a plurality of nozzles arranged at predetermined intervals along a main scanning direction orthogonal to the transport direction of the transported paper, and the positions of the nozzles in the main scanning direction are shifted from each other and along the transport direction. First nozzle row and second nozzle row arranged at intervals, first region for storing ink ejected from the first nozzle row, and ink ejected from the second nozzle row And an ink chamber for storing ink that is distributed from a common path and supplied to the first and second regions, respectively, along the main scanning direction. A plurality of arranged head modules;
A control unit that controls to print ink on a sheet by discharging ink from the nozzles of the first and second nozzle rows of the head modules line by line based on the first discharge data and the second discharge data. And
The controller is
The first and second in each head module so as to suppress an increase in ink temperature difference between the first region and the second region caused by the ink ejection operation in each head module. Printing by controlling the correspondence between the ejection data and the first and second nozzle rows;
In the printing of each page, the main scanning direction in printing in the original correspondence between the first and second ejection data and the first and second nozzle rows in each joint portion between the head modules A plurality of the head modules that are continuous through the joint portion without the continuous non-ejection area. An inkjet printing apparatus, wherein the correspondence relationship between the first and second ejection data and the first and second nozzle rows in each head module of the interlocking head module group is controlled in conjunction with each other. The controller is
In each of the head modules, the print ratio of the first and second nozzle arrays on the previous page or the cumulative print ratio of each of the first and second nozzle arrays up to the previous page, and the current page The first and second ejection data and the print data so that the magnitude relationship of the print rates of the first and second nozzle rows is reversed between the print rates of the first and second nozzle rows. Controlling the correspondence with the first and second nozzle rows;
When printing a page in which the interlocking head module group is printed, one reference head module is selected from the interlocking head module group, and the print rate or the front of the first and second nozzle rows of the previous page in the reference head module is selected. The first and second nozzle rows are printed between the cumulative print ratios of the first and second nozzle rows up to the current page and the first and second nozzle rows on the current page. Control is performed by interlocking the correspondence relationship between the first and second ejection data and the first and second nozzle rows in each head module of the interlocking head module group so that the magnitude relationship is reversed. The inkjet printing apparatus according to claim 1, wherein:   The said control part selects the said reference | standard head module using the cumulative value of the printing rate of the sum total of the said 1st and 2nd nozzle row in each said head module of the said interlocking head module group. Item 3. The inkjet printing apparatus according to Item 2.   The control unit performs control to switch the correspondence relationship between the first and second ejection data and the first and second nozzle rows for each predetermined printing unit in all the head modules. The inkjet printing apparatus according to claim 1. A temperature detection unit for detecting the temperature of the ink in each of the first and second regions of each head module;
The controller is
In each of the head modules, when the temperature difference between the ink in the first region and the ink in the second region is equal to or greater than the threshold, the temperature of the ejected ink in the first and second nozzle rows is higher. And controlling the correspondence between the first and second ejection data and the first and second nozzle rows so that the printing rate is low,
When printing a page generated by the interlocking head module group, one reference head module is selected from the interlocking head module group, and a temperature difference between the first region ink and the second region ink of the reference head module is determined. Each head module of the interlocking head module group is configured such that when the temperature is equal to or higher than the threshold, the printing rate is lower when the temperature of the ejected ink is higher in the first and second nozzle arrays of the reference head module. 2. The inkjet printing apparatus according to claim 1, wherein a correspondence relationship between the first and second ejection data and the first and second nozzle arrays is controlled in conjunction with each other.   6. The inkjet printing according to claim 5, wherein the control unit selects the reference head module using the temperature of ink detected by the temperature detection unit in each head module of the interlocking head module group. apparatus.