Patent Publication Number: US-9895893-B2

Title: Printer and printing method

Description:
Priority is claimed under 35 U.S.C. § 120 as a continuation of U.S. application Ser. No. 14/626,133, filed Feb. 9, 2015, now U.S. Pat. No. 9,352,570, entitled “Printer and Printing Method,” and under 35 U.S.C. § 119 to Japanese Application no. 2014-023954, filed on Feb. 19, 2014 which are hereby incorporated by reference in their entireties. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a printer that prints by ejecting ink droplets from ink nozzles, and to a printing method. 
     2. Related Art 
     In printers that print by ejecting ink from ink nozzles, the ink nozzles can become clogged as a result of moisture evaporating from the ends of the nozzles and ink viscosity increasing in ink nozzles from which ink is not ejected for a particular time or longer. As a result, ink cannot be ejected normally from ink nozzles with a low ejection frequency, and print quality may drop. Ink nozzles becoming clogged can be prevented or corrected, however, by providing a maintenance unit inside the printer and ejecting ink into the maintenance unit in a flushing operation (referred to below as regular flushing). Ink may also be ejected onto the printing paper (referred to below as “onto-paper flushing”) to prevent or resolve ink nozzle clogging. 
     A drop in throughput is a problem with regular flushing because the printhead must first be moved to the maintenance unit. To suppress the drop in throughput and increased ink consumption as a result of performing the regular flushing operation at a regular time interval, JP-A-H11-192729 controls flushing according to the printed content so that flushing is not performed more than necessary. For example, when multiple copies of the same content are printed, the nozzles that were used to print the previous page are not flushed. The time for which ink was not ejected from the nozzles is also measured, and only those nozzles for which the measured time exceeds a reference value are flushed. 
     Various methods are thus used for flushing, and each method has its advantages and disadvantages. For example, regular flushing does not adversely affect print quality, but contributes to a drop in throughput. Furthermore, while the drop in throughput caused by regular flushing can be reduced by the control method described in JP-A-H11-192729, it cannot be completely eliminated. On the other hand, because the onto-paper flushing method can be used parallel the printing operation, it does not contribute to a drop in throughput. However, because ink is discharged onto the printing paper, the flush onto paper method contributes to a drop in print quality. 
     Some printers also have print modes such as a throughput-priority mode (a so-called “fast mode”) that prioritizes shortening the required printing time, and a print quality-priority mode (a so-called “clean mode”) that prioritizes maintaining print quality. The desirable flushing mode differs according to the print mode in these printers. 
     When print conditions such as the print speed and print resolution can be set in multiple levels, the desirable flushing method also differs according to the print conditions. Applying the appropriate flushing method according to the print mode or print conditions is therefore desirable. 
     SUMMARY 
     The present invention is directed to solving the foregoing problem by providing a printer and a print method that can balance throughput and print quality while suppressing ink nozzle ejection problems by combining flushing operations that eject ink into the maintenance unit, and flushing operations that eject ink onto the print medium. 
     A printer according to one aspect of the invention has a printhead with ink nozzles; a maintenance unit that receives ink ejected from the ink nozzles; a head moving mechanism that moves the printhead to a print position to print on a recording medium, and a maintenance position to eject ink to the maintenance unit; a parameter decision unit that determines a combination of first flushing conditions for ejecting ink to the maintenance unit and flushing the ink nozzles, and second flushing conditions for ejecting ink onto the recording medium and flushing the ink nozzles; a merging unit that generates merged data adding to image data a pattern of flushing dots that are formed by the second flushing based on the selected second flushing conditions; and a first flushing unit that applies the first flushing based on the selected first flushing conditions to the printhead. 
     A printing method according to another aspect of the invention includes: determining a combination of first flushing conditions for ejecting ink from ink nozzles of a printhead to a maintenance unit and flushing the ink nozzles, and second flushing conditions for ejecting ink onto a recording medium and flushing the ink nozzles; generating merged data adding to image data a pattern of flushing dots that are formed by the second flushing based on the selected second flushing conditions; ejecting ink onto the recording medium based on the merged data; and applying the first flushing based on the selected first flushing conditions. 
     The printer and printing method of the invention maintain ink nozzles using a combination of a first flushing operation that ejects ink into a maintenance unit, and a second flushing operation that ejects ink onto the recording medium. More specifically, both a first flushing that does not lower print quality, and a second flushing that does not lower throughput, can be used together and desirably combined. Ejection problems from the ink nozzles can therefore be suppressed during printing while desirably balancing print quality and throughput according to the application and conditions when printing. 
     Preferably, the printer also has a print mode setting unit that sets the print mode to either a first print mode or a second print mode that shortens the time required for printing compared with the first print mode; and the parameter decision unit determines the combination of first flushing conditions and second flushing conditions based on the set print mode. 
     The printing method preferably also includes setting the print mode to either a first print mode or a second print mode that shortens the time required for printing compared with the first print mode; and determining the combination of first flushing conditions and second flushing conditions based on the set print mode. 
     Thus comprised, when setting print modes having different priorities, the objective can be achieved by desirably combining first and second flushing operations according to the selected priority. For example, first flushing, which does not lower print quality, is primarily applied in a mode that prioritizes print quality (a second print mode), and second flushing, which does not lower throughput, is primarily used in a mode that prioritizes throughput (first print mode, a mode that shortens the time required for printing). Thus comprised, ink nozzle ejection problems can be suppressed during printing while desirably balancing print quality and throughput according to the print mode. 
     Further preferably, the printer also has a print quality setting unit that sets the print resolution; and the parameter decision unit determines the combination of first flushing conditions and second flushing conditions based on the set print resolution. 
     When the period at which flushing dots are printed is the same, this configuration changes the density of the flushing dots formed by onto-paper flushing according to the print resolution. This means the effect of second flushing on print quality is different. Therefore, by combining first and second flushing operations according to the print resolution, ink nozzle ejection problems can be suppressed during printing while desirably balancing print quality and throughput. 
     A printer according to another aspect of the invention preferably sets the frequency of the first flushing set to either a first frequency or a second frequency that is less frequent than the first frequency as a condition of the first flushing. 
     When the frequency of the first flushing operation is high, the ink nozzle recovery rate by the first flushing is high. Therefore, by combining first and second flushing operations according to the frequency of the first flushing operation, ink nozzle ejection problems can be suppressed during printing while desirably balancing print quality and throughput. 
     A printer according to another aspect of the invention preferably sets the density of flushing dots formed in the second flushing to either a first density or a second density that is less dense than the first density as a condition of the second flushing. 
     When the density of the flushing dots is high in the second flushing operation, the ink nozzle recovery rate by the second flushing is high. Therefore, by combining first and second flushing operations according to the density of the flushing dots, ink nozzle ejection problems can be suppressed during printing while desirably balancing print quality and throughput. 
     A printer according to another aspect of the invention preferably sets the strength of the first flushing to either a first strength or a second strength that ejects less ink than the first strength as a condition of the first flushing. 
     When the strength of the first flushing is high (that is, a large amount of ink is ejected), the ink nozzle recovery rate by the first flushing is high. Therefore, by combining first and second flushing operations according to the strength of the first flushing, ink nozzle ejection problems can be suppressed during printing while desirably balancing print quality and throughput. 
     Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating the control system of a printer according to the invention. 
         FIG. 2  schematically illustrates the printhead, maintenance unit, and printing paper in the printer shown in  FIG. 1 . 
         FIG. 3  illustrates the process of converting image data to print data. 
         FIG. 4  shows an example of a flushing parameter table. 
         FIGS. 5A and 5B  schematically illustrate the flushing pattern. 
         FIG. 6  shows another example of a flushing parameter table. 
         FIG. 7  is a graph showing the correlation between print speed and flushing dot density. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Preferred embodiments of a printer and a printing method according to the present invention are described below with reference to the accompanying figures. The following embodiments are described with reference to an inkjet printer, but the invention can also be applied to multifunction printing devices with scanner and facsimile machine functions, for example. Furthermore, the following embodiment is described using an inkjet line printhead, but the invention can obviously also be applied to printing devices with a serial printhead. 
     Printer 
       FIG. 1  is a basic block diagram showing the control system of a printer according to this embodiment of the invention, and  FIG. 2  schematically illustrates the relationship between the printhead, maintenance unit, and printing paper in the printer shown in  FIG. 1 . 
     As shown in  FIG. 1  and  FIG. 2 , the printer  1  has a printhead  2  that ejects ink droplets in four colors of ink, cyan ink C, magenta ink M, yellow ink Y, and black ink Bk; a conveyance mechanism  3  that conveys the printing paper P (recording medium) through a conveyance path past the position where the printhead  2  prints; a head moving mechanism  4  that moves the printhead  2  in the direction crosswise to the conveyance direction of the printing paper P by the conveyance mechanism  3 ; a maintenance unit  5 ; a control unit  6  that controls the printhead  2 , conveyance mechanism  3 , head moving mechanism  4 , and maintenance unit  5 ; and a communication unit  7  that receives input data to be printed (image data) and print settings information, for example. 
     The printhead  2  is an inkjet line head, and as shown in  FIG. 2  has four sets of inkjet heads  2 C,  2 M,  2 Y,  2 Bk arrayed at a specific interval in the conveyance direction A of the printing paper P. The inkjet heads  2 C,  2 M,  2 Y,  2 Bk are each longer in the transverse direction B intersecting the conveyance direction A than the maximum width of the printing paper P, and print by ejecting ink onto the printing paper P. The inkjet head  2 Bk located furthest upstream in the conveyance direction A of the printing paper P ejects black ink Bk, and the inkjet head  2 C on the downstream side of inkjet head  2 Bk ejects cyan ink C. The inkjet head  2 M located on the downstream side of inkjet head  2 C ejects magenta ink M, and the inkjet head  2 Y on the downstream side of inkjet head  2 M ejects yellow ink Y. 
     Each of the inkjet heads  2 C,  2 M,  2 Y,  2 Bk has four head units  21  to  24  disposed across the transverse direction B. The four head units  21  to  24  are aligned with the adjacent head units staggered in the conveyance direction A. The four head units  21  to  24  also have plural ink nozzles  25  arranged in two rows of ink nozzles disposed at a specific nozzle pitch in the transverse direction B. The nozzle pitch in this example is set to 300 dpi. The positions of the two ink nozzle rows in the transverse direction B are also offset from each other ½ the distance between adjacent nozzles (the nozzle pitch). As shown in  FIG. 2 , the head units  21 ,  22  adjacent to each other in the transverse direction B are disposed so that the ink nozzles  25  at the matching ends overlap when seen in the conveyance direction A. Each of the other head units  22 ,  23  and head units  23 ,  24  adjacent to each other in the transverse direction B are likewise disposed so that the ink nozzles  25  at the matching ends overlap when seen in the conveyance direction A. 
     The maintenance unit  5  is located outside the width of the conveyance path. The head moving mechanism  4  moves the printhead  2  between a print position C facing the printing paper P on the conveyance path, and a retracted position D opposite the maintenance unit  5 . In the standby mode when not printing, the nozzle face of the printhead  2  is capped by the maintenance unit  5 . The regular flushing operation of moving the printhead  2  to the retracted position D opposite the maintenance unit  5  and ejecting ink from the ink nozzles  25  into the maintenance unit  5  is performed at a specific timing before printing starts and while in the standby mode. 
     This embodiment of the invention also performs the onto-paper flushing operation of ejecting ink droplets from the ink nozzles  25  positioned opposite the printing paper P while printing as described below. During the regular flushing operation, the ink nozzles  25  not used for printing, such as all ink nozzles  25  including the ink nozzles  25  located Outside the printing paper P on the transverse direction B, are flushed. The ink nozzles  25  at a position separated from the printing paper P can therefore also be flushed, and clogging can be prevented or resolved. 
     Control System 
     As shown in  FIG. 1 , the control system of the printer  1  is a control unit  6  including a CPU. A communication unit  7  is connected to the input side of the control unit  6 . Input data  10  (see  FIG. 3 ) to be printed, and print settings information such as the print mode, are supplied from an external, device such as a computer through the communication unit  7  to the control unit  6 . 
     The printhead  2 , conveyance mechanism  3 , head moving mechanism  4 , and maintenance unit  5  are connected to the output side of the control unit  6 . 
     The conveyance mechanism  3  includes a paper feed roller pair that convey the printing paper P, a conveyance motor that turns as controlled by control signals from the control unit  6 , and a drive power transfer mechanism that transfers rotation from the conveyance motor to the paper feed roller pair. 
     The head moving mechanism  4  includes a carriage that carries the printhead  2 , a carriage guide rail that supports the carriage movably on the transverse direction B, a carriage motor that turns as controlled by a control signal from the control unit  6 , and a pulley and timing belt mounted thereon that rotate according to rotation from the carriage motor. 
     The control unit  6  further includes a rendering unit  62 , a color conversion processor  63 , a digitizing processor  64 , a print mode setting unit  65 , a parameter decision unit  66 , a flushing dot merging unit  67  (merging unit), a print data generating unit  68 , a print control unit  69 , and a regular flushing unit  70  (first flushing unit). The control unit  6  also has a conveyance control unit (not shown in the figure) that controls the conveyance mechanism  3  and conveys the Printing paper P at a specific speed. 
     A storage unit  61  stores a color conversion lookup table  71 , an SML table  72 , a parameter selection table  73 , and flushing patterns  74  ( 74 A,  74 B). 
     Converting Input Data to Print Data 
       FIG. 3  illustrates the process of converting input data to print data. The rendering unit  62  executes a rendering process that converts the input data  10  to be printed (such as image data) to image data  11  of a pixel count corresponding to the specified print size and resolution. More specifically, the rendering unit  62  enlarges or reduces the input data  10  to the specified print size, and then resolves the scaled input data  10  to the specified resolution. The pixels of the image data  11  resulting from the rendering process become color data in the RGB color space (binary RGB data). 
     The color conversion processor  63  then executes a color conversion process of referencing a color conversion lookup table  71  and converting the pixels (binary RGB data) in the image data  11  resulting from the rendering process to ink volume data  12  ( 12 Bk,  12 C,  12 M,  12 Y) for each of the four colors C, Y, M, Bk. The color conversion lookup table  71  stores ink volume data for the four colors C, Y, N, Bk relationally to the binary RGB data (combination of R, G, and B), which is color data in the RGB color space. In this example, the C, Y, M, Bk ink volume data is expressed as 8-bit (256 level) gray scale data. 
     The digitizing processor  64  then converts the ink volume data for each pixel in the ink volume data  12  ( 12 Bk,  12 C,  12 M,  12 Y) resulting from the color conversion process to dot data in the four levels of dots that can be formed by the ink nozzles  25 . 
     The SML table  72  stores the gray level values of the C, Y, M, Bk ink volume data relationally to the incidence of four types of dots, including white dots. The four types of dots include Null (white dot), S (small dot), M (medium dot), and L (large dot). The digitizing processor  64  first executes a dot ratio decision process that references the SML table  72  and converts the ink volume data for each pixel to incidence data for the four types of dots, and then executes a halftone process that determines for each size of dot whether or not a dot is formed for each pixel. As a result, a print dot pattern  13  ( 13 Bk,  13 C,  13 M,  13 Y) specifying if one of the four types of print dots, including null dots, is formed at each pixel position is generated for each color. Note that a BRS correction process that corrects the ink volume data based on deviation in the arrangement of the ink nozzles  25  or deviation in ink ejection may be executed before converting the ink volume data  12  to dot data after the color conversion process. 
     The print mode setting unit  65  then sets the print mode based on the print settings information supplied to the control unit  6 . In this example, two different print modes can be set: a print quality priority mode (first print mode) and a print time priority mode (second print mode). The print quality priority mode is a mode that maintains print quality. The print time priority mode is a mode that shortens the time required for printing compared with the print quality priority mode. 
     Based on the selected print mode, the parameter decision unit  66  determines the combination of regular flushing (first flushing) operations that eject ink into the maintenance unit  5 , and onto-paper flushing (second flushing) operations that eject ink onto the printing paper P. The combination of regular flushing and onto-paper flushing operations performed when printing the input data  10  is determined with reference to a parameter selection table  73 . 
       FIG. 4  shows an example of the parameter selection table  73 . As shown in the figure, the parameter selection table  73  relationally stores the content of regular flushing and the content of onto-paper flushing operations performed in each print mode. The content of the regular flushing operations is determined by the frequency and strength of the regular flushing operation. The frequency indicates the interval between regular flushing operations, and in this example is set to either of two levels, a first frequency (such as a 10-20 ms interval), or a second frequency that is less frequent than the first frequency (such as a 1200 ms interval). Note that the second frequency is set to the time required to print one roll of paper or greater, and when roll paper is used as the printing paper P, enables printing one roll of paper without interruption by the regular flushing operation. The strength indicates how much ink is ejected for flushing, and in this example may be set to either of two levels, a first strength, and a second strength at which less ink is ejected than at the first strength setting. 
     The content of onto-paper flushing is set based on the density of the ink dots formed by onto-paper flushing (referred to below as “flushing dots”), and in this example may be set in two levels, a first density (such as 1000 dots/inch 2 ), or a second density that is lower than the first density (such as 200 dots/inch 2 ). 
     As shown in  FIG. 4 , the parameter selection table  73  sets the frequency of regular flushing to the first frequency (high frequency), the strength of regular flushing to the second strength (low ink ejection volume), and the flushing dot density of onto-paper flushing to the second density (low density), in the print quality priority mode. 
     In the print time priority mode, the parameter selection table  73  sets the frequency of regular flushing to the second frequency (low frequency), the strength of regular flushing to the first strength (high ink ejection volume), and the flushing dot density of onto-paper flushing to the first density (high density). 
     The combination of regular flushing and onto-paper flushing thus increases the flushing dot density of onto-paper flushing when the frequency of regular flushing is low, and when the frequency of regular flushing is high, lowers the flushing dot density of onto-paper flushing. The strength of regular flushing is also set to increase the ink ejection volume (increase the strength) when the regular flushing frequency is low. 
     The flushing dot merging unit  67  adds the flushing dots to the print dot patterns  13  ( 13 Bk,  13 C,  13 M,  13 Y) resulting from the halftone process, and creates merged dot patterns  14  ( 14 Bk,  14 C,  14 M,  14 Y). The flushing dots are added using flushing patterns  74  (see  FIGS. 5A and 5B ). The flushing patterns  74  are patterns specifying the ink nozzles  25  that are to eject ink droplets and the ejection timing during onto-paper flushing that ejects ink droplets onto the printing paper P when printing the input data  10 . In this example, two flushing patterns  74  ( 74 A,  74 B) that differ in the density of the flushing dots are stored in the storage unit  61 . More specifically, flushing pattern  74 A is a pattern in which the density of the flushing dots is the first density (high density). Flushing pattern  74 B is a pattern in which the density of the flushing dots is the second density (low density). 
     The flushing dot merging unit  67  selects one of flushing patterns  74 A,  74 B according to the content of the onto-paper flushing selected by the parameter decision unit  66 . More specifically, the flushing dot merging unit  67  references the parameter selection table  73 , and selects flushing pattern  74 A in which the density of the flushing dots is the second density (low density) when in the print quality priority mode. When in the print time priority mode, the flushing dot merging unit  67  selects flushing pattern  74 B in which the density of the flushing dots is the first density (high density). 
       FIGS. 5A and 5B  illustrate the flushing patterns  74  ( 74 A,  74 B),  FIG. 5A  showing the flushing pattern  74 B of a first density (high density) and  FIG. 5B  showing a flushing pattern  74 A of a second density (low density). As shown in the figures, the flushing patterns  74  ( 74 A,  74 B) are dot matrix patterns of null dots and flushing dots Df. For simplicity,  FIGS. 5A and 5B  show examples of 10 row by 10 column, and 10 row by 25 column, dot matrix patterns, but dot matrix patterns of different row and column counts can obviously be used. The row direction V of the flushing patterns  74  ( 74 A,  74 B) corresponds to the direction of the ink nozzle  25  arrays (that is, the transverse direction B). The column direction H of the flushing patterns  74  ( 74 A,  74 B) corresponds to the timing of the flushing operation. The size of the row direction V of the flushing patterns  74  ( 74 A,  74 B) substitutes the number of dots for the period of the flushing operation (that is, the period at Which a flushing dot Df is formed). The flushing patterns  74  ( 74 A,  74 B) are patterns for one period. The timing of the flushing operation is determined by the positions of the flushing dots Df in each row. 
     When flushing dots Df are added to the print dot patterns  13  ( 13 Bk,  13 C,  13 M,  13 Y), the print dot patterns  13  ( 13 Bk,  13 C,  13 M,  13 Y) are superimposed with the flushing patterns  74  ( 74 A,  74 B), and the print dot at a position where there is a flushing dot Df is combined with the flushing dot Df. If the flushing pattern  74  ( 74 A or  74 B) is smaller than the print dot pattern  13  ( 13 Bk,  13 C,  13 M,  13 Y), the flushing pattern  74  ( 74 A or  74 B) may be repeated in the column direction H and row direction V. The flushing pattern  74  ( 74 A or  74 B) is superimposed with the four print dot patterns  13  ( 13 Bk,  13 C,  13 M,  13 Y) offset a certain amount determined by the ink color. The process of merging print dots with flushing dots Df is a process that makes the larger dot size the size of the dot after merging. For example, if the dot size of the flushing dot Df is M, and the flushing dot Df is merged with a print dot of a size M or smaller, the size of the merged dot is M. If the flushing dot Df is merged with a print dot of size L, the size of the merged dot is L. The merged dot patterns  14  ( 14 Bk,  14 C,  14 M,  14 Y) are created by thus merging the flushing dots Df. 
     The print data generating unit  68  executes a print data generating process that creates the print data  15  used to drive the printhead  2  by assigning the dots of the merged dot patterns  14  ( 14 Bk,  14 C,  14 M,  14 Y) to the ink nozzles  25  of the inkjet heads  2 C,  2 M,  2 Y,  2 Bk. As described above, the ink nozzles  25  overlap in the conveyance direction A at the ends of the four head units  21  to  24 . As a result, a mask process that assigns dots to the ink nozzles  25  of one of each two overlapping head units is therefore included in the print data generating process. If the dot assigned to ink nozzles  25  that overlap in the conveyance direction A is a dot combining a flushing dot Df and a print data, the mask process assigns the dot to both overlapping ink nozzles  25 . 
     The print control unit  69  controls ejection of ink from the printhead  2  based on the print data  15  that Was generated. More specifically, based on the print data  15 , the print control unit  69  generates a pulse of voltage applied to the piezoelectric device corresponding to an ink nozzle  25  as the nozzle drive signal, and supplies the pulse to the printhead  2 . As a result, the printhead  2  is driven, ink droplets are ejected from the ink nozzles  25  of the inkjet heads  2 C,  2 M,  2 Y,  2 Bk, and the content specified by the input data  10  and the print settings information is printed. 
     When ejecting ink from the ink nozzles  25  and printing the input data  10  based on the generated print data  15 , the regular flushing unit  70  executes the regular flushing operation ejecting ink from the ink nozzles  25  to the maintenance unit  5  according to the content (strength and frequency) of the regular flushing operation determined by the parameter decision unit  66 . More specifically, the regular flushing unit  70  drives the head moving mechanism  4  according to the set frequency, and moves the printhead  2  to the retracted position D opposite the maintenance unit  5 . The regular flushing unit  70  then drives the printhead  2  to eject ink into the maintenance unit  5  in the regular flushing operation. 
     Printing Method 
     A printer  1  thus comprised prints as described below. When image data or other input data  10  and print settings information are received through the communication unit  7 , the control unit  6  of the printer  1  applies the rendering process, color conversion process, and digitizing process (dot ratio decision process and halftone process) to the input data  10 . The control unit  6  also sets the print mode based on the print settings information, references the parameter selection table  73 , and determines the content of the regular flushing operation ejecting ink to the maintenance unit  5  and the onto-paper flushing operation that ejects ink onto the printing paper P. The control unit  6  then applies the merging process adding the flushing dots Df to the print dot patterns  13  ( 13 Bk,  13 C,  13 M,  13 Y) generated from the input data  10  according to the content of the onto-paper flushing operation, and generates print data  15  based on the merged dot patterns  14  ( 14 Bk,  14 C,  14 M,  14 Y). 
     The control unit  6  also drives the conveyance mechanism  3  to convey the printing paper P to the printhead  2 , and positions the beginning of the print area on the printing paper P to the print position of the printhead  2 . When positioning the printing paper P is completed, the control unit  6  supplies drive signals to the printhead  2  based on the print data  15 . As a result, the printhead  2  is driven, ink droplets are ejected from the ink nozzles  25  of the inkjet heads  2 C,  2 M,  2 Y,  2 Bk, and the content specified by the input data  10  and the print settings information is printed. 
     The control unit  6  also drives the printhead  2  based on the print data  15  to eject, ink onto the printing paper P, and drives the conveyance mechanism  3  to convey the printing paper P. 
     The control unit  6  also drives the head moving mechanism  4  at the frequency determined by the content of the regular flushing operation, and moves the printhead  2  to the retracted position D opposite the maintenance unit  5 . The control unit  6  then drives the printhead  2  to eject ink into the maintenance unit  5  in the regular flushing operation. 
     Because flushing dots Df are added to the print data  15 , the ink dot (print dot) formation operation that forms the pixels of the input data  10 , and the ink dot (flushing dot) formation operation that flushes the ink nozzles  25 , are performed by driving the printhead  2  and ejecting ink to the printing paper P based on the print data  15 . More specifically, both printing an image or other content on the printing paper P, and onto-paper flushing, are performed. 
     As described above, the printer  1  according to this embodiment executes a flushing parameter decision process that determines the combination of regular flushing that ejects ink from the ink nozzles  25  of the printhead  2  to the maintenance unit  5 , and onto-paper flushing that ejects ink onto the printing paper P, to perform when printing the input data  10  based on the print mode and other print settings information. 
     Based on the determined combination of flushing parameters, the flushing dots Df that are formed in the onto-paper flushing operation are added to the input data  10  to be printed (specifically, the print dot patterns  13  converting the pixels in the rendered image data  11  to ink dots), creating merged dot patterns  14 . The printing process that ejects ink onto the printing paper P based on the merged dot patterns  14  is executed, and regular flushing based on the selection combination of parameters is executed during the printing process. By thus combining regular flushing, which does not cause a drop in print quality, with onto-paper flushing, which does not cause a drop in throughput, according to the print mode, printing can proceed while balancing print quality and throughput according to the application or printing conditions, and ink ejection problems can be prevented in the ink nozzles  25 . 
     More specifically, this embodiment of the invention provides two print modes, a print quality priority mode and a print time priority mode. In the print quality priority mode, the frequency of regular flushing, which does not lower print quality, increases and the density of onto-paper flushing decreases. In the print time priority mode that prioritizes throughput, the density of onto-paper flushing, which does not lower throughput, increases and the frequency of regular flushing decreases. As a result, printing can proceed while balancing print quality and throughput according to the selected priority. 
     Other Embodiments 
     The combination of the regular flushing and onto-paper flushing operations is determined according to the print mode in the embodiment described above, but the combination can be determined according to print settings information other than the print mode, such as the print speed or print resolution. 
       FIG. 6  illustrates a table of combinations in another example. In this example the print speed can be set to either of two levels, and either fast printing (30 mm/s) or slow printing (150 mm/s) can be selected in the print settings. In this event, the control unit  6  has a speed setting unit, and sets the print speed based on the print speed setting supplied to the control unit  6 . In the parameter selection table  173  in this example, the content of regular flushing and the content of onto-paper flushing are set according to the print speed. 
     More specifically, in the fast print mode, the same parameter combination used in the print time priority mode above (that is, the frequency of regular flushing is the second frequency (low frequency)) the strength of regular flushing is the first strength (high ink ejection volume), and the flushing dot density of onto-paper flushing is the first density (high density)) is used. 
     In the slow print mode, the same combination used in the print quality priority mode (that is, the frequency of regular flushing to the first frequency (high frequency), the strength of regular flushing is the second strength (low ink ejection volume), and the flushing dot density of onto-paper flushing is the second density (low density)) is used. 
       FIG. 7  is a graph showing the correlation between print speed and the flushing dot density. As shown in the graph, the flushing dot density changes inversely proportionally to the print speed. However, because the print resolution (that is, the print dot density) is inversely proportional to the print speed (paper feed speed), the same flushing patterns used to add the flushing dots Df can be used. 
     Based on the print speed setting, the parameter selection table  173  is referenced to determine the combination of regular flushing and onto-paper flushing settings. As a result, the density of onto-paper flushing, which does not lower throughput, can be increased and the frequency of regular flushing decreased for fast printing. For low speed printing, the frequency of regular flushing, which does not lower print quality, can be increased and the density of onto-paper flushing decreased. As a result, printing can proceed while balancing print quality and throughput according to the print speed setting selected by the user. 
     The combination of regular flushing and onto-paper flushing parameters can also be determined according to the print resolution (quality) instead of the print speed. 
     More specifically, two print resolution (quality) settings can be selected, and high print quality with a high print resolution, or low print quality with low print resolution, can be selected according to the print Setting. In this event, the control unit  6  has a print quality setting unit, and sets the print resolution based on the print quality setting supplied to the control unit  6 . In this event, as shown in  FIG. 6 , fast printing is replaced with low print quality, and slow printing is replaced with high print quality. As a result, printing can proceed while balancing print quality and throughput according to the print quality setting selected by the user. 
     Note that in a printer in which the print mode, print speed, and print resolution can be independently adjusted, a parameter selection table setting the combination of regular flushing and onto-paper flushing parameters is compiled according to the possible combinations of these print settings, and this table can be referenced to appropriately adjust the content of the regular flushing and onto-paper flushing operations. 
     The invention being thus described, it will be obvious that it may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included Within the scope of the following claims.