Patent Publication Number: US-9889668-B2

Title: Printing system, print control device, and print control method

Description:
Priority is claimed under 35 U.S.C. § 119 to Japanese Application No. 2014-057688 filed on Mar. 20, 2014, which is hereby incorporated by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a printing system, a print control device, and a print control method. 
     2. Related Art 
     Flushing is done in printers that print by ejecting ink from a printhead in order to prevent the viscosity of ink in the ink nozzles from increasing and nozzles clogging as a result of ink viscosity increasing. Flushing is typically done after moving the printhead to a position removed from the conveyance path of the recording medium. Methods of flushing by ejecting ink onto the print medium have also been proposed to reduce the drop in throughput resulting from moving the printhead away from the conveyance path. See, for example, JP-A-2007-136722. The method described in JP-A-2007-136722 flushes the nozzles in an irregular dot pattern so that the ink ejected to the print medium for flushing is not conspicuous. 
     The amount of ink that is ejected, and the number of ink nozzles that eject ink, can be reduced in order to make the ejected ink unobtrusive when flushing onto the print medium. On the other hand, increasing the amount of ink is a useful way of increasing the effectiveness of the flushing operation. Because the effectiveness of flushing onto the print medium and print quality are incompatible with each other, enabling the user of the printer to set the flushing conditions based on the printing purpose and other factors is desirable. 
     Except for printer technicians and others with sufficient technical knowledge, typical printer users have little awareness of the flushing operation used in printers. It is therefore difficult for the user to appropriately set the flushing conditions with an understanding of the effect of flushing on print quality. 
     SUMMARY 
     A printing system, print control device, and print control method according to at least one embodiment of the invention enable even users without great technical knowledge to appropriately set the flushing conditions of the printer. 
     One aspect of at least one embodiment of the invention is a printing system including a printing device and a print control device. The printing device includes: a printhead with ink nozzles; a conveyance unit that conveys a print medium; and a control unit that executes a first flushing ejecting ink from ink nozzles of the printhead into an ink receiving part, and a second flushing ejecting ink from ink nozzles of the printhead onto the print medium. The print control device includes an input reception unit that provides a user interface to select a first operating mode or a second operating mode prioritizing printer throughput more than the first operating mode; a command control unit that generates a command specifying a flushing condition of the printing device when an operating mode is selected through the user interface of the input reception unit; and a command transmission unit that transmits the command generated by the command control unit. The control unit of the printing device receives and interprets commands transmitted by the print control device, and sets a flushing condition according to a received command. 
     Thus comprised, when the user decides and inputs whether or not to prioritize printer throughput, the conditions for flushing on the conveyance path of the print medium are set appropriately to the input. The user can therefore easily and appropriately set the flushing conditions without needing technical knowledge about the effect of flushing and flushing conditions. 
     In a printing system according to another aspect of the at least one embodiment of invention, the control unit of the printing device can execute the second flushing according to plural conditions having different ink ejection volumes; and the command control unit of the print control device generates a command setting a first condition having a large ink ejection volume as the condition for the second flushing when the second operating mode is set using the user interface of the input reception unit. 
     Thus comprised, the condition of whether or not to increase the ink ejection volume when flushing on the print medium conveyance path can be set easily and appropriately. 
     Further preferably in a printing system according to another aspect of at least one embodiment of the invention, the command control unit of the print control device generates a command setting a second condition in which the ink ejection volume is a specific standard value as the condition for the second flushing when the first operating mode is set using the user interface of the input reception unit. 
     Thus comprised, the condition of whether or not to increase the ink ejection volume when flushing on the print medium conveyance path can be set easily and appropriately. 
     Further preferably in a printing system according to another aspect of at least one embodiment of the invention, the control unit of the printing device executes the first flushing at a preset flushing interval; and the flushing interval for executing the second flushing using the first condition is set to a longer time than the flushing interval for executing the second flushing using the second condition. 
     Thus comprised, throughput can be improved by increasing the ink ejection volume when flushing the ink nozzles on the print medium conveyance path. 
     In a printing system according to another aspect of at least one embodiment of the invention, the first flushing is a flushing operation that moves the printhead to the position of the ink receiving part, and ejects ink from ink nozzles of the printhead into the ink receiving part; and the second flushing is a flushing operation that ejects ink from the ink nozzles of the printhead onto the print medium while the printhead is on the conveyance path of the print medium. 
     Thus comprised, the user can easily set the conditions for flushing with the printhead on the print medium conveyance path. 
     Another aspect of the at least one embodiment of invention is a print control device that controls flushing and printing, the print control device having: an input reception unit that provides a user interface to specify selection of a first operating mode or a second operating mode prioritizing throughput of the printing operation more than the first operating mode; a command control unit that generates a command setting a condition for flushing when an operating mode is selected through the user interface of the input reception unit; and a command transmission unit that transmits the command generated by the command control unit. 
     Thus comprised, when the user decides and inputs whether or not to prioritize printer throughput, the conditions for flushing on the conveyance path of the print medium are set appropriately to the input. The user can therefore easily and appropriately set the flushing conditions without needing technical knowledge about the effect of flushing and flushing conditions. 
     Another aspect of the at least one embodiment of invention is a print control method that transmits a command and controls flushing and printing, the control method including: providing a user interface to specify selection of a first operating mode or a second operating mode prioritizing throughput of the printing operation more than the first operating mode; generating a command setting a condition for flushing when an operating mode is selected through the user interface; and transmitting the generated command. 
     Thus comprised, when the user decides and inputs whether or not to prioritize printer throughput, the conditions for flushing on the conveyance path of the print medium are set appropriately to the input. The user can therefore easily and appropriately set the flushing conditions without needing technical knowledge about the effect of flushing and flushing conditions. 
     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 side view of the inside of an inkjet printer according to some inventions. 
         FIG. 2  is a plan view showing the inside configuration of the inkjet printer. 
         FIG. 3  illustrates the configuration of the inkjet head. 
         FIG. 4  is a block diagram illustrating the functional configuration of a printing system. 
         FIG. 5  is a flow chart illustrating the operation of the printing system. 
         FIG. 6  shows an example of a user interface. 
         FIG. 7  is a flow chart illustrating the operation of the printing system. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Some embodiments of the present invention are described below with reference to the accompanying figures. 
       FIG. 1  is a side view schematically illustrating the internal configuration of an inkjet printer  1  (printing device) in a printing system  2  according to some embodiments of the present invention.  FIG. 2  is a plan view illustrating the internal construction of the inkjet printer  1 . 
     The inkjet printer  1  in this embodiment is a line inkjet printer, and prints images on a recording medium (print medium) by ejecting ink from an inkjet line head  10  (printhead) while conveying the recording medium through a conveyance path HK. 
     In the following description of the printer using  FIG. 1  and  FIG. 2 , the longitudinal axis between the front and back of the printer is indicated by the arrows in the figures. 
     As shown in  FIG. 1 , the inkjet printer  1  has a printer case  11 , and a roll paper storage compartment  12  is formed inside the back of the printer case  11 . 
     Roll paper R is held as the recording medium (print medium) inside the roll paper storage compartment  12 . The paper roll R is a continuous sheet medium wound into a roll, and may be plain paper or fine paper wound into a roll, or label paper having labels of a regular size and an adhesive backing applied to a release liner (web) and wound into a roll. 
     Below, the portion of the paper roll R that forms a roll with a hollow center is referred to as the paper roll R 1 , and the paper that is pulled from the paper roll R 1  and conveyed through the conveyance path HK is referred to as the conveyed roll paper R 2 . The conveyed roll paper R 2  is indicated in  FIG. 1  by a dotted line. 
     The paper roll R 1  is stored in the roll paper storage compartment  12 . At this time, a roll paper spindle  9  is inserted to the hollow core R 3  formed in the center of the paper roll R 1 . The roll paper spindle  9  is connected through a speed reducer mechanism not shown to the motor shaft of a spindle rotation motor  64  described below. The paper roll R 1  turns in conjunction with rotation of the roll paper spindle  9  fit into the core R 3  of the paper roll R 1 . 
     The conveyed roll paper R 2  is pulled from the paper roll R 1  in the roll paper storage compartment  12  upward and then forward in the conveyance direction F. A tension lever  13  is disposed behind the axis of the paper roll R 1 . The conveyed roll paper R 2  pulled upward contacts the tension lever  13 , curves around the tension lever  13 , and then continues to the front. 
     The tension lever  13  applies tension to the conveyed roll paper R 2  and prevents slack. The tension lever  13  is urged to pivot on a pin  14  in the direction applying tension to the conveyed roll paper R 2  (the direction indicated by arrow Y 1 ). 
     A paper guide  16  is disposed in front of the tension lever  13 . The paper guide  16  includes a lower paper guide  17  ( FIG. 1 ), upper paper guide  18  ( FIG. 1 ), and side paper guide  15  ( FIG. 2 ). The lower paper guide  17  is a platform that supports the conveyed roll paper R 2  from below. The upper paper guide  18  is positioned opposite the lower paper guide  17  with the conveyed roll paper R 2  therebetween, and prevents the conveyed roll paper R 2  from lifting away from the lower paper guide  17 . The side paper guide  15  guides the sides of the conveyed roll paper R 2  in the conveyance direction F, and suppresses the conveyed roll paper R 2  from skewing and shifting. 
     A paper detector  19  ( FIG. 1 ) is disposed at the back end of the paper guide  16 . The paper detector  19  is a transmissive optical sensor including an emitter on the upper paper guide  18  side and a photoreceptor on the lower paper guide  17  side. A detection value indicating the amount of light received by the photoreceptor of the paper detector  19  is output to a printer control unit  50  described below. The detection value from the paper detector  19  differs according to whether or not there is conveyed roll paper R 2  at the position of the paper detector  19 . Based on the detection value from the paper detector  19 , the printer control unit  50  detects when the leading end of the conveyed roll paper R 2  reaches the position where the paper detector  19  is disposed, and when the trailing end of the conveyed roll paper R 2  reaches the paper detector  19 . 
     A black mark detector  20  is disposed at the front end of the paper guide  16 . The black mark detector  20  is a reflective optical sensor including an emitter that emits light to the back side of the conveyed roll paper R 2 , and a photoreceptor that receives the reflection of light emitted by the emitter. The black mark detector  20  is used to detect when a black mark BM described below reaches the detection position T 1  (see  FIG. 2 ) of the black mark detector  20 . More specifically, a detection value indicating the amount of light received by the photoreceptor of the black mark detector  20  is output to the printer control unit  50 . The detection value from the black mark detector  20  differs according to whether or not a black mark BM is at the detection position T 1 . Based on the detection value from the black mark detector  20 , the printer control unit  50  detects if a black mark BM has reached the detection position T 1 . 
     A print unit  21  that prints images on the conveyed roll paper R 2  is disposed at the front of the paper guide  16 . The print unit  21  includes a platen  22  and the inkjet head  10 . 
     The inkjet head  10  in this embodiment ejects four colors of ink, C (cyan), M (magenta), Y (yellow), K (black), and forms dots on the printing surface of the conveyed roll paper R 2 . The inkjet head  10  includes a black head unit  24  that ejects black ink, a cyan head unit  25  that ejects cyan ink, a magenta head unit  26  that ejects magenta ink, and a yellow head unit  27  that ejects yellow ink. 
     The platen  22  has a flat surface located along the conveyance direction F. This flat surface is opposite the inkjet head  10 . The platen  22  is fixed to the frame of the inkjet printer  1 , and supports the conveyed roll paper R 2  from below. 
     A conveyor belt  30  ( FIG. 1 ) is disposed over the surface of the platen  22 . The conveyor belt  30  is a wide, endless belt that travels over the top of the platen  22  and then loops around the bottom of the platen  22 . At least the surface of the conveyor belt  30  that faces up when traveling over the top of the platen  22  is a rough surface with a high coefficient of friction. The conveyor belt  30  is further preferably made of rubber or plastic elastic material. A conveyance unit  32  including a conveyance motor  31  ( FIG. 4 ) and a drive mechanism that moves the conveyor belt  30  by means of the torque from the conveyance motor  31  is disposed below the platen  22 . The drive mechanism of this conveyance unit  32  includes a gear that engages the output shaft of the conveyance motor  31 , and a roller that moves the conveyor belt  30 . The conveyor belt  30  moves according to rotation of the conveyance motor  31 , and conveys the conveyed roll paper R 2  in the conveyance direction F. 
     A conveyance roller  34  ( FIG. 1 ) is disposed opposite the platen  22  on the upstream side of the inkjet head  10  on the conveyance path HK. The conveyance roller  34  is a driven roller supported freely rotatably on the frame of the inkjet printer  1 , and is urged toward the surface of the platen  22 . On the conveyance path HK, the conveyed roll paper R 2  is held between the conveyance roller  34  and the conveyor belt  30 , and is conveyed in the conveyance direction F in conjunction with movement of the conveyor belt  30 . Multiple rollers not shown are also disposed between the head units of the inkjet head  10  to push down on and prevent the conveyed roll paper R 2  from lifting away from the surface of the conveyor belt  30 . 
     A cutter unit  37  is disposed on the downstream side of the inkjet head  10  on the conveyance path HK. The cutter unit  37  includes a fixed knife and a movable knife on opposite sides of he conveyance path HK, and the movable knife is linked through a gear, for example, to the cutter drive motor  65  ( FIG. 4 ). When the cutter drive motor  65  turns, the movable knife moves to the fixed knife side and cuts the conveyed roll paper R 2  therebetween. The cutter unit  37  may make a partial cut leaving the conveyed roll paper R 2  uncut in part across the width, or it may cut the conveyed roll paper R 2  completely. 
     A winding unit  42  ( FIG. 1 ) is removably connected to the front of the inkjet printer  1 . Note that the winding unit  42  is omitted from  FIG. 2 . The winding unit  42  includes a take-up drum  43  onto which the conveyed roll paper R 2  discharged from the paper exit is wound, and a drive unit not shown that turns the take-up drum  43 . The take-up drum  43  is driven by torque from the conveyance motor  31  of the inkjet printer  1  transferred through a gear train not shown. The take-up drum  43  may be configured to be driven by a motor separate from the conveyance motor  31 . The take-up drum  43  turns in the direction indicated by arrow A in the figure, and rewinds the conveyed roll paper R 2 . When the winding unit  42  is used, the inkjet printer  1  does not cut the conveyed roll paper R 2  with the cutter unit  37 , and the conveyed roll paper R 2  is discharged from the paper exit as a continuous web. 
     A control board  44  is disposed toward the front on the right side of the paper guide  16 . The CPU, RAM, and other peripheral circuits of the printer control unit  50  are disposed to the control board  44 . 
     As shown in  FIG. 1  and  FIG. 2 , the inkjet head  10  is mounted on a carriage  70 . As shown in  FIG. 2 , the carriage  70  can move in a main scanning direction G 1  and a reverse scanning direction G 2 , and moves the inkjet head  10  between a printing position PP and a home position HP as shown in  FIG. 2 . The printer control unit  50  ( FIG. 4 ) drives the carriage moving motor  66  to move the carriage  70 . 
     The printing position PP is a position opposite the platen  22 , and is the position where ink is ejected to the conveyed roll paper R 2  to print an image on the printing surface. To print an image, the inkjet head  10  is moved down by a specific mechanism and set to an appropriate position at the printing position PP. 
     The home position HP is the retracted position of the inkjet head  10  disposed to a position away from the above printing position PP. A maintenance unit  90  (ink receiver part) having a cap (not shown in the figure) that covers the nozzle face of the inkjet head  10  is disposed to the home position HP. The maintenance unit  90  includes a drive unit (not shown in the figure) that moves the cap vertically to and away from the nozzle face, and seals the nozzle face of the inkjet head  10  set to the home position HP with the cap. The maintenance unit  90  also includes a pump unit  69  ( FIG. 4 ) that reduces the pressure inside the cap and suctions ink from the nozzles of the inkjet head  10 , and a waste ink tank (not shown in the figure) for holding the ink suctioned by the pump unit  69 . 
     The printer control unit  50  described below moves the carriage  70  and sets the inkjet head  10  to the home position HP when a specific event occurs, such as when the power is turned off, or when a printing process is not executed for a specific time and the standby mode is entered. The printer control unit  50  then covers the nozzle face of the inkjet head  10  with the cap of the maintenance unit  90 . As a result, the ink left in the nozzles drying and the viscosity increasing can be suppressed. 
     Flushing and cleaning processes are also performed at the home position HP. 
     In the flushing operation, the printer control unit  50  seals the nozzle face with the cap of the maintenance unit  90 , then ejects a specific amount of ink a specific number of times from the nozzles into the cap, replacing the ink left inside the nozzles with fresh ink. In the cleaning process, the printer control unit  50  seals the nozzle face with the cap of the maintenance unit  90 , drives the pump unit  69 , and suctions the ink from inside the nozzles. 
     Flushing with the inkjet head  10  set to the home position HP is referred to herein as regular flushing (first flushing). Regular flushing is executed whenever the time that the printing operation continues without interruption reaches a preset flushing interval (flushing time). In this event, the printer control unit  50  stops conveyance of the conveyed roll paper R 2 , moves the inkjet head  10  to the home position HP, and ejects ink from the nozzles into the maintenance unit  90 . The printer control unit  50  then returns the inkjet head  10  to the printing position PP, starts conveying the conveyed roll paper R 2 , and resumes printing. 
     The printer control unit  50  can also flush the nozzles while the inkjet head  10  remains at the printing position PP, that is, remains positioned above the conveyed roll paper R 2 . This flushing operation is called onto-paper flushing (second flushing). Onto-paper flushing forms dots unrelated to the image being printed while printing an image (which may be text or a picture) with the inkjet head  10 . This can prevent the ink viscosity from increasing in nozzles that are not used for a long time. 
     With onto-paper flushing, ink is discharged to the conveyed roll paper R 2  in areas where an image is not printed. As a result, if the amount of ink ejected in onto-paper flushing is great, the ink ejected for flushing may appear as random ink spray and adversely affect print quality. The inkjet printer  1  can therefore set the amount of ink ejected for onto-paper flushing to any of multiple levels. For simplicity, this embodiment can set the amount of ink to one of two levels, level 1 or level 2, where the amount of ink ejected in level 1 (first flushing condition) is great, and the amount of ink at level 2 (second flushing condition) is less than level 1. For example, the number of dots and/or the size of dots (the amount of ink per dot) that are formed by onto-paper flushing separately to the dots formed for the image being printed may differ in level 1 and level 2. 
     The printer control unit  50  performs both regular flushing and onto-paper flushing during the printing operation. The printer control unit  50  performs regular flushing at a specific flushing interval, which is a preset time, and performs onto-paper flushing between regular flushing operations. When the level for onto-paper flushing is set to level 1, which is the level ejecting the greatest amount of ink, increased ink viscosity can be prevented in more nozzles, and the frequency of regular flushing can therefore be reduced. The printer control unit  50  therefore performs regular flushing at different flushing intervals when onto-paper flushing is set to level 1 and level 2. 
     When onto-paper flushing is set to level 1, the flushing interval is set to a longer time than when set to level 2. The frequency of regular flushing can therefore be minimized according to the level of onto-paper flushing, and a drop in throughput can be prevented. 
       FIG. 3  shows the configuration of the inkjet head  10  of the inkjet printer  1  in detail. 
     The inkjet head  10  has a black head unit  24 , cyan head unit  25 , magenta head unit  26 , and yellow head unit  27 . The head units are arranged in the inkjet head  10  in the order black head unit  24 , cyan head unit  25 , magenta head unit  26 , and yellow head unit  27  in the conveyance direction F. 
     The four black heads  24   a  in the black head unit  24  are staggered to each other. A black nozzle row  24   b  is formed in each of the black heads  24   a . The black nozzle row  24   b  is a row of nozzles (not shown in the figure) that eject ink as fine ink droplets formed in a line crosswise to the conveyance direction F. Ink from a black ink cartridge is supplied to the black heads  24   a.    
     The black heads  24   a  push black ink toward the conveyed roll paper R 2 , and eject fine ink droplets from specific nozzles, by means of a piezoelectric or other type of actuator. As a result, black dots are formed on the printing surface of the conveyed roll paper R 2 . 
     The four cyan heads  25   a  of the cyan head unit  25  are likewise formed in a staggered pattern. A cyan nozzle row  25   b  that ejects droplets of cyan ink from the nozzles is formed to each of the cyan heads  25   a.    
     The four magenta heads  26   a  of the magenta head unit  26  are likewise formed in a staggered pattern. A magenta nozzle row  26   b  that ejects droplets of magenta ink from the nozzles is formed to each of the magenta heads  26   a.    
     The four yellow heads  27   a  of the yellow head unit  27  are likewise formed in a staggered pattern. A yellow nozzle row  27   b  that ejects droplets of yellow ink from the nozzles is formed to each of the yellow heads  27   a.    
     Note that for convenience, each of the heads and the nozzle row in each head are shown in  FIG. 3 , but the heads are actually formed so that ink is ejected perpendicularly down from the nozzles in each nozzle row, and other members are also provided to achieve this configuration. 
     An inkjet printer  1  prints images as a combination of dots formed by ejecting ink onto the conveyed roll paper R 2 . the inkjet printer  1  conveys the conveyed roll paper R 2  in the conveyance direction F as shown in  FIG. 3 . As conveyance of the conveyed roll paper R 2  proceeds in the inkjet printer  1  and the print area where an image is to be formed on the conveyed roll paper R 2  reaches the black nozzle row  24   b  located further upstream, black ink is ejected from the nozzles in the black nozzle row  24   b . When the print area then reaches the cyan nozzle row  25   b , cyan ink is ejected; magenta ink is ejected when the print area reaches the magenta nozzle row  26   b ; and yellow ink is ejected when the print area reaches the yellow nozzle row  27   b . Four colors of ink are thus ejected to the conveyed roll paper R 2 , and a full-color image is printed in the print area. 
       FIG. 4  is a block diagram showing the functional configuration of the inkjet printer  1 . 
     As shown in  FIG. 4 , the inkjet printer  1  is connected to communicate data with a host computer  5  (print control device), and the inkjet printer  1  and host computer  5  embody a printing system  2 . 
     The printing system  2  is a system in which the host computer  5  outputs data to be printed in response to user operations, and the inkjet printer  1  prints on the print medium based on the data to be printed. 
     An application program for controlling the inkjet printer  1  and a printer driver program are installed on the host computer  5 , and the host computer  5  sends commands to the inkjet printer  1  and controls the inkjet printer  1  by functions of these programs. 
     The host computer  5  has a host control unit  100  that controls parts of the host computer  5 . The host control unit  100  has a CPU, ROM, RAM, and other peripheral circuits as the execution unit not shown. Firmware that can be run by the CPU, and data associated with the firmware, are stored in ROM in the host control unit  100 . Data associated with the firmware run by the CPU is also temporarily stored in RAM. the host control unit  100  includes a application execution unit  101 , printer driver execution unit  102  (input receiving unit, command control unit), and print monitor unit  103  (command transmission unit). These function units are rendered by the CPU running a program, for example. 
     The application execution unit  101  runs a text editor, an image editor, a POS application, a label editor, or other type of application. When a print command is issued by a user operation, the application execution unit  101  generates and outputs data for printing the document or image that was created. 
     The printer driver execution unit  102  executes a device driver program for controlling the inkjet printer  1 . The printer driver execution unit  102  generates and outputs commands for controlling the inkjet printer  1  and data related to the commands to the inkjet printer  1 , and controls operation of the inkjet printer  1 . For example, the printer driver execution unit  102  generates and outputs a print instruction command instructing the inkjet printer  1  to print, and the data to be printed, such as image data or text data to print, based on the data output by the application execution unit  101 . In addition to the print instruction command, the printer driver execution unit  102  can also generate and output control commands for controlling the inkjet printer  1  together with data related to the control commands. 
     Note that the device driver program the printer driver execution unit  102  runs is not limited to a program optimized for the inkjet printer  1 , and may be a generic device driver program. It may also be a device driver program for a different model of printer. In this event, the inkjet printer  1  must be able to process commands and data the printer driver execution unit  102  outputs for the other model of printer. 
     The print monitor unit  103  (command transmission unit) runs a monitoring program that monitors the inkjet printer  1 . The print monitor unit  103  detects the operating status of the inkjet printer  1 , controls sending commands generated by the printer driver execution unit  102 , and controls monitoring responses to commands sent to the inkjet printer  1 . 
     More specifically, the print monitor unit  103  sequentially acquires and sends commands output by the printer driver execution unit  102  to the inkjet printer  1 . When plural commands are sent to the inkjet printer  1 , the print monitor unit  103  causes the inkjet printer  1  to execute the commands in a specific order, and adjusts the transmission sequence and the transmission timing of the commands. In this event, the print monitor unit  103  sends commands to the inkjet printer  1 , for example, and after receiving a response to the command, controls sending the next command. 
     When the application execution unit  101  outputs a command, the print monitor unit  103  acquires the command and controls transmission in the same way as transmission of commands output by the printer driver execution unit  102 . 
     When the print monitor unit  103  sends a command generated by the application execution unit  101  or printer driver execution unit  102  to the inkjet printer  1  and then receives a response from the inkjet printer  1 , it returns the received response to the unit that generated the original command. The application execution unit  101  and printer driver execution unit  102  can therefore receive the response to the generated command. The format of the responses the print monitor unit  103  receives is not specifically limited. For example, the responses may in the form of response commands, the form of status reports, or other data format, and responses can be written as expresses including any of these forms. 
     The print monitor unit  103  generally executes a program module known as a language monitor (LM) or port monitor to apply the above control. The print monitor unit  103  may be a module that is part of the host computer  5  operating system or the printer driver execution unit  102 . 
     The host computer  5  also has a host display unit  113  for displaying information, a host input unit  112  for detecting operation of the connected input devices, a host storage unit  111  for storing data, and a communication interface  110  connected to the inkjet printer  1 . The host display unit  113  and host input unit  112  are provided for user operation. The host storage unit  111  nonvolatilely stores programs such as the control program, application program, or device driver run by the host control unit  100 , and data related to these programs. 
     The inkjet printer  1  has a printer control unit  50  (control unit) that controls other parts of the inkjet printer  1 . A communication interface  51  that connects to the host computer  5 , and a printer storage unit  52 , are connected to the printer control unit  50 . The interface  51  connects to the host computer  5  by wire or wirelessly. 
     The printer control unit  50  includes a CPU as an operating unit, ROM and RAM. Firmware that can be executed by the CPU and data related to the firmware is nonvolatilely in the ROM of the printer control unit  50 . Data related to the firmware run by the CPU is also temporarily stored in RAM. 
     The printer storage unit  52  has a storage medium such as EEPROM, flash memory, or other type of semiconductor memory, or a hard disk drive, and nonvolatilely stores data rewritably. The printer storage unit  52  stores programs that are executed by the printer control unit  50 , data related to the control programs, and commands and data the inkjet printer  1  received from the host computer  5 . 
     The printer storage unit  52  in this embodiment also stores the flushing settings data  52   a  relating to regular flushing and onto-paper flushing conditions described above, and reference flushing pattern  52   b  data used for onto-paper flushing. 
     An operation detection unit  55  that detects operation of operating switches  54  disposed to a switch panel (not shown in the figure) is connected to the printer control unit  50 . The operating switches  54  includes, for example, a paper feed switch commanding the conveyance operation of the inkjet printer  1 , a cut switch commanding operation of the cutter unit  37 , and a configuration switch for making settings. A display unit such as an LCD panel or 7-segment display may be disposed to the switch panel. In this configuration, display of content by the display unit of the switch panel may be controlled by the operation detection unit  55 . 
     A sensor drive unit  56  that gets the detection values of the paper detector  19  is also connected to the printer control unit  50 . 
     The sensor drive unit  56  outputs the detection value of the paper detector  19  to the printer control unit  50 . Based on the detection value of the paper detector  19 , the printer control unit  50  then detects if the leading end or the trailing end of the conveyed roll paper R 2  reached the detection position of the paper detector  19 . 
     The sensor drive unit  56  also outputs the detection value of the black mark detector  20  to the printer control unit  50 . Based on the detection value of the black mark detector  20 , the printer control unit  50  detects if a black mark BM reached the detection position T 1 . 
     The sensor drive unit  56  also outputs the detection value of the temperature sensor  71  to the printer control unit  50 . The temperature sensor  71  is a temperature sensor disposed to a specific position of the inkjet head  10 , and detects the temperature of the inkjet head  10 . Based on the detection value of the temperature sensor  71  the printer control unit  50  detects the temperature of the inkjet head  10 . 
     Also connected to the printer control unit  50  are a conveyance motor  31 , spindle rotation motor  64 , cutter drive motor  65 , carriage moving motor  66 , and a motor driver  67  that drives the pump unit  69 . 
     The conveyance motor  31  is a brushless DC motor, for example, and conveys the recording medium by moving the conveyor belt  30 . The printer control unit  50  controls the motor driver  67  to supply drive current from the motor driver  67  to the conveyance motor  31 , and drives the conveyance motor  31 . 
     The spindle rotation motor  64  causes the paper roll R 1  to turn by rotating the roll paper spindle  9  inserted to the core R 3  of the paper roll R 1 . When the paper roll R 1  turns in the direction shown as the conveyance direction F, the conveyed roll paper R 2  is pulled from the paper roll R 1 . When the paper roll R 1  turns in the opposite direction as the conveyance direction F, the conveyed roll paper R 2  is pulled back to the paper roll R 1 . 
     The spindle rotation motor  64  is also a brushless DC motor. The printer control unit  50  controls the motor driver  67  to supply drive current from the motor driver  67  to the spindle rotation motor  64 , and drives the spindle rotation motor  64 . 
     The cutter drive motor  65  drives the movable knife of the cutter unit  37  to cut the recording medium. The carriage moving motor  66  moves the carriage  70  (inkjet head  10 ) between the printing position PP and the home position HP. The pump unit  69  has a diaphragm pump or an axial flow pump that reduces the pressure inside the cap of the maintenance unit  90 . 
     A head driver  68  that drives the inkjet head  10  is connected to the printer control unit  50 . The printer control unit  50  controls the head driver  68 , supplies voltage to the pump (not shown in the figure) that supplies ink from the ink tank (not shown in the figure) to the inkjet head  10 , and to the piezoelectric actuator (not shown in the figure) of each head of the inkjet head  10 , and thereby operates the inkjet head  10 . As a result, ink droplets are ejected from the nozzles of the heads and dots are formed. 
     While conveying the recording medium in conjunction with printing an image on the recording medium, the printer control unit  50  manages the position of the recording medium on the conveyance path HK based on the detection value output from the black mark detector  20  and the rotational angle of the conveyance motor  31 . The printer control unit  50  detects the rotational angle of the conveyance motor  31  based on the output of a rotary encoder not shown disposed according to the conveyance motor  31 . 
     The printer control unit  50  has as execution units that render functions: a command reception unit  50   a , command interpreter  50   b , configuration unit  50   c , flushing control unit  50   d , print control unit  50   e , and image processing unit  50   f . These execution units correspond to functions rendered by the CPU executing firmware. 
     A receive buffer  50   g  and print buffer  50   h , which are temporary storage areas (buffer memory), are reserved in the storage area of RAM (not shown in the figure) of the printer control unit  50 . Either or both the receive buffer  50   g  and print buffer  50   h  can be rendered in the printer storage unit  52  or in RAM externally connected to the printer control unit  50 . 
     The command reception unit  50   a  receives commands and data sent from the inkjet printer  1  through the interface  51 , and stores them in the receive buffer  50   g . The commands and data received by the command reception unit  50   a  are accumulated in the receive buffer  50   g  in the order received. 
     The command interpreter  50   b  reads and interprets the commands and data stored in the receive buffer  50   g  sequentially according to the address in the receive buffer  50   g . Because the commands and data are accumulated in the receive buffer  50   g  in the order received, the commands and data are interpreted by the command interpreter  50   b  in the order received. If the interpreted command or data is a command to be executed by the configuration unit  50   c  or data to be processed by the configuration unit  50   c , the command interpreter  50   b  passes the command or data to the configuration unit  50   c . For example, the command interpreter  50   b  passes a set level command for setting the level of onto-paper flushing to the configuration unit  50   c , and the configuration unit  50   c  executes the command. In this event, the configuration unit  50   c  overwrites the data indicating the onto-paper flushing level stored in the flushing settings data  52   a.    
     If the interpreted command or data is a command to be executed by the print control unit  50   e  or data to be processed by the print control unit  50   e , the command interpreter  50   b  passes the command or data to the print control unit  50   e . For example, the command interpreter  50   b  passes print instruction commands and data to be printed to the print control unit  50   e . Likewise, if the interpreted command or data is a command to be executed by the image processing unit  50   f  or data to be processed by the image processing unit  50   f , the command interpreter  50   b  passes the command or data to the image processing unit  50   f.    
     The print control unit  50   e  prints based on the print data received from the host computer  5 . The print control unit  50   e  acquires the image data and character data contained in the print data, and renders the image data to print in the print buffer  50   h  through the image processing unit  50   f.    
     If image data is contained in the data to be printed, the image processing unit  50   f  renders the image data as rasterized image data in the print buffer  50   h.    
     If character data is contained in the data to be printed, the image processing unit  50   f  reads the font data for the character data from the printer storage unit  52 , generates image data for the characters, and renders the character image data as rasterized image data in the print buffer  50   h . The character data contained in the data to be printed comprises, for example, data indicating the character codes and font of the characters, and by using the font data corresponding to the specified character codes of the specified font, can generate images for the characters to be printed by the inkjet head  10 . The print buffer  50   h  is a storage area created according to the print resolution of the inkjet head  10  and the size of the printable area of the inkjet printer  1 . 
     Based on a predefined lookup table (LUT) not shown stored in the printer storage unit  52 , the print control unit  50   e  converts the data generated by the image processing unit  50   f  to data indicating the amount of ink to be ejected by each nozzle of the inkjet head  10 . The image data rendered in the print buffer  50   h  is rasterized image data setting print color data for each pixel in a specific number of pixels covering the printable area of the inkjet printer  1 . Based on the lookup table, the print control unit  50   e  converts the color information for each pixel in the image data rendered in the print buffer  50   h  to the amount of each color of ink to be ejected by the inkjet head  10 . Based on the amount of ink of each color, the print control unit  50   e  generates ink volume data assigned to each nozzle of the black head unit  24 , cyan head unit  25 , magenta head unit  26  and yellow head unit  27 . The print control unit  50   e  then drives the inkjet head  10  according to the generated ink volume data, and prints the image on the conveyed roll paper R 2 . 
     While the print control unit  50   e  is printing, the flushing control unit  50   d  controls onto-paper flushing and regular flushing. The flushing control unit  50   d  monitors driving the inkjet head  10  by the print control unit  50   e , and measures the time that the inkjet head  10  is away from the home position HP. While the inkjet head  10  is away from the home position HP, the flushing control unit  50   d  executes regular flushing according to the preset flushing interval. In the event of regular flushing, the flushing control unit  50   d  pauses the printing operation of the print control unit  50   e  and moves the inkjet head  10  to the home position HP. The flushing control unit  50   d  then drives the inkjet head  10  to eject ink from the nozzles into the maintenance unit  90 . 
     The flushing control unit  50   d  then moves the inkjet head  10  back to the printing position PP and resumes printing by the print control unit  50   e . The flushing control unit  50   d  also operates the conveyance motor  31  in the indexing operation conveying and positioning the conveyed roll paper R 2  to the start printing position. When regular flushing is performed, time is therefore required to move the inkjet head  10  and for the conveyance operation positioning the conveyed roll paper R 2  to the start printing position. 
     The flushing control unit  50   d  also executes onto-paper flushing while printing with the print control unit  50   e . In the event of onto-paper flushing, the flushing control unit  50   d  reads the flushing settings data  52   a  and gets the onto-paper flushing level. The flushing control unit  50   d  also gets the reference flushing pattern  52   b  corresponding to the set flushing level, and generates and outputs a flushing pattern based on the reference flushing pattern  52   b  to the print control unit  50   e . The print control unit  50   e  merges the flushing pattern with the ink ejection volume data generated from the data in the print buffer  50   h , and updates the ink ejection volume data for each nozzle. As a result, the data related to ejecting ink to print the image, and the data related to ejecting ink for onto-paper flushing, are combined. The print control unit  50   e  then drives the inkjet head  10  to eject ink based on the merged data. As a result, flushing occurs while printing the image. 
     Commands used in this printing system  2  are described next. 
     The command used in the printing system  2  according to this embodiment includes a prefix character, command identifier, and parameter. 
     The prefix character is, for example, a single-character ASCII code that identifies the type of command. The printing system  2  uses two types of commands, formatting commands and control commands. A formatting command is a command instructing the print format for printing by the inkjet printer  1 , and a print instruction command. A control command is a command related to controlling the inkjet printer  1 . The prefix character of a formatting command is a single-byte forward slash character (/), and the prefix character of a control command is a single-byte asterisk (*). 
     The command identifier indicates the type of command, and is a 1 to 3 character ASCII code, for example. The parameter is a value controlling a function of the command, and declares the value by an ASCII code of one or more characters. The parameter may use numbers, may use letters, or may use both numbers and letters depending upon the type of command. Numeric parameters have maximum and minimum limits corresponding to the type of command. If the parameter value exceeds the maximum limit, the command interpreter  50   b  uses the maximum as the declared value. If the parameter value is less than the minimum limit, the command interpreter  50   b  uses the minimum as the declared value. If the parameter is omitted, the command interpreter  50   b  uses a default value as the declared value. For example, in the event of the set level command setting the level for onto-paper flushing, the level is declared by the parameter, and if the parameter is omitted, the level is set to an initial value (default value). 
     Commands for setting the mode of onto-paper flushing in the printing system  2  include both a formatting command and a control commands. An example of the formatting command is shown in (1) below, and an example of a control command is shown in (2) below. 
     /FDMP (parameter) (1) 
     *HDMP (parameter) (2) 
     The formatting command has a predefined syntax, and includes a group of commands starting with a start label format code and ending with an end label format code. Plural commands including a prefix character, command identifier, and parameter can be written between the start code and the end code. The host computer  5  can send plural commands to the inkjet printer  1  using this syntax. In this event, the inkjet printer  1  can be controlled to execute plural processes by sending one group of commands from the host computer  5  to the inkjet printer  1 . 
     For example, the group of commands (also called a command group) could include a print instruction command and a command sending the data to be printed in addition to the set level command for onto-paper flushing described above. In this event, the inkjet printer  1  both sets the level for onto-paper flushing and prints. 
     The order of the formatting commands in the command group between the start label format code and end label format code is not specifically limited, but the commands are preferably arranged in an execution sequence suited to the commands. When a formatting command is received, the command reception unit  50   a  stores the commands in the command group written between the start code and the end code to the receive buffer  50   g  in the order they are written in the command group. These commands are then interpreted by the command interpreter  50   b  in the order they are accumulated in the receive buffer  50   g.    
     For example, if the set level command setting the onto-paper flushing level is first, and the commands related to printing instructions follow, the inkjet printer  1  will print after setting the onto-paper flushing level. More specifically, printer operations will be set by the commands contained in one command group, and printing will then follow according to the settings. The opposite is also true. 
     That is, if the commands related to the print instructions are listed first, and the set level command for the onto-paper flushing follows, the onto-paper flushing level will be set after printing is completed. The printing operation in this event will therefore not reflect the onto-paper flushing level set by the set level command. Some embodiments of the present invention therefore lists the commands related to the print instructions after the set level command for the onto-paper flushing in the command group. 
     The control commands do not have a defined syntax, and control commands are sent individually from the host computer  5  to the inkjet printer  1 . To set the onto-paper flushing level, the command *HDMP (parameter) is sent individually from the host computer  5  to the inkjet printer  1 . In this event, the command reception unit  50   a  stores one command in the receive buffer  50   g , and the command interpreter  50   b  interprets and executes the one command. When the command interpreter  50   b  detects a *HDMP (parameter) command, it updates the flushing settings data  52   a  according to the value of the parameter in the command. 
     By thus using formatting commands in the printing system  2 , the onto-paper flushing level can be set together with a print instruction command. The onto-paper flushing level can also be set at the desired time by a control command without restricting the timing for printing. 
       FIG. 5  is a flowchart of the operation of setting the onto-paper flushing level by a command, (A) showing the operation of the host computer  5 , and (B) showing the operation of the inkjet printer  1 . 
     When printer configuration is started on the host computer  5  by the user operating an input device connected to the host input unit  112  (step SA 1 ), a configuration screen is displayed and user input is accepted by a function of the printer driver execution unit  102  (step SA 2 ). In this example, a screen for setting the onto-paper flushing level is displayed in step SA 2 . 
       FIG. 6  shows an example of a configuration screen  200  displayed on the host display unit  113  by a function of the printer driver execution unit  102 . The configuration screen  200  is a user interface enabling the user to set the onto-paper flushing level, and the printer driver execution unit  102  that displays the configuration screen  200  is an input reception unit. 
     In this example, the user interface shown in  FIG. 6  does not show the onto-paper flushing level, and instead enables inputting whether to set the operating mode called a throughput priority mode in this embodiment on or off. The inkjet printer  1  in this example enables exclusively selecting one of two operating modes, a normal operating mode (first operating mode) and this throughput priority mode (second operating mode), as the operating mode for printing. One of these two operating modes can be selected by input to the configuration screen  200 . In this example, the normal operating mode is selected when the throughput priority mode is off. 
     In the normal operating mode, the onto-paper flushing level is set to level 2. Because the ink ejection volume is low in level 2, the ink ejected by onto-paper flushing is not conspicuous in the printout on the conveyed roll paper R 2 . Because the change in print quality is therefore low, the operating mode is acceptable for the user. 
     The throughput priority mode, however, is an operating mode selected for high printer throughput. In the throughput priority mode, the onto-paper flushing level is set to level 1. Because the ink ejection volume of onto-paper flushing increases in this mode, the flushing interval is long, the frequency of regular flushing is low, and throughput is therefore improved. Because more ink is ejected by onto-paper flushing in the throughput priority mode, the ink deposited outside of the target image printed on the conveyed roll paper R 2  is obvious and the drop in print quality may be apparent to the user, but is still acceptable for an operating mode that prioritizes throughput over print quality. 
     Understanding the effect that the ink ejection volume in onto-paper flushing has on print quality and the printing operation is not necessarily easy for non-technical users to understand. Therefore, even if a setting for the onto-paper flushing level is displayed in the configuration screen  200  so that the user can set the flushing level, it will not be easy for the user to master how to use the inkjet printer  1 . However, the level of the ink ejection volume in onto-paper flushing can be easily set by enabling the user to select through a configuration screen  200  (user interface) whether to use the throughput priority mode or use the normal operating mode as shown in  FIG. 6 . 
     The configuration screen  200  has a check box  201  for selecting or cancelling the throughput priority mode, an OK button  202  for confirming the selection of the check box  201 , and a cancel button  203  for cancelling changing the selection. If the check box  201  is checked and the OK button  202  is clicked, the throughput priority mode is turned on. If the check box  201  is cleared and the OK button  202  is clicked, the throughput priority mode is turned off, that is, the normal operating mode is turned on. 
     When the OK button  202  in the configuration screen  200  is operated, the printer driver execution unit  102  generates a set level command for onto-paper flushing according to the selection in the check box  201 . This command is generated as a control command described above, for example. 
     Referring again to  FIG. 5 , when the content input through the user interface is confirmed by, for example, operating the OK button  202  (step SA 3 ), the printer driver execution unit  102  generates a command corresponding to the on/off setting of the throughput priority mode (step SA 4 ). The print monitor unit  103  then sends the command output by the printer driver execution unit  102  to the inkjet printer  1  (step SA 5 ). 
     The command reception unit  50   a  then receives and stores the command the host computer  5  sent in the receive buffer  50   g  (step SB 1 ). Next, the command interpreter  50   b  interprets the commands in the receive buffer  50   g  (step SB 2 ), and if the command is determined to be a set level command setting the onto-paper flushing level, passes the command and parameter to the configuration unit  50   c . Based on the parameter value in the command, the configuration unit  50   c  gets the level set by the command (step SB 3 ). The configuration unit  50   c  then updates and sets the flushing settings data  52   a  based on the acquired level (step SB 4 ). 
     After setting the flushing level, the printer control unit  50  sends a response command indicating that the process instructed by the command ended to the host computer  5  (step SB 5 ). The print monitor unit  103  then receives the response sent from the inkjet printer  1  (step SA 6 ). This response command is a response to the set level command generated by the printer driver execution unit  102 . The print monitor unit  103  thus recognizes the response to the command from the printer driver execution unit  102 , and may report to the printer driver execution unit  102  that the setting was successfully completed. The format of the responses generated by the printer control unit  50  is not specifically limited, and may in the form of a response command, the form of a status report, or other data format. 
     Through the operation described in  FIG. 5 , the configuration unit  50   c  updates the flushing settings data  52   a , and sets the level for onto-paper flushing to level 1 or level 2. The time until the next regular flushing is also set in the flushing settings data  52   a . When onto-paper flushing is set to level 1, the ink inside the nozzles is frequently replaced. As a result, increased viscosity can be prevented even if the frequency of regular flushing is low. However, if onto-paper flushing is set to level 2, regular flushing must be performed at the regular frequency. The flushing interval of regular flushing is therefore also set relationally to the onto-paper flushing level in the flushing settings data  52   a . As a result, when the onto-paper flushing level is set, the flushing interval corresponding to the set level is retrieved and used. 
     The printer driver execution unit  102  may therefore generate a command setting the onto-paper flushing level and a command setting the flushing interval. More specifically, when the throughput priority mode is turned on through the configuration screen  200 , the printer driver execution unit  102  may generate a command setting the onto-paper flushing level to level 1, and a command setting the flushing interval to a shorter time than the standard interval. When the throughput priority mode is turned of f through the configuration screen  200 , the printer driver execution unit  102  may generate a command setting the onto-paper flushing level to level 2, and a command setting the flushing interval to the standard interval. In this event, there is no need to relationally set the onto-paper flushing level and the flushing interval in the flushing settings data  52   a , and changing the flushing interval can be controlled by the host computer  5 . 
     When the throughput priority mode is set using the configuration screen  200 , the setting can be displayed and confirmed on the host display unit  113  of the host computer  5 . The current throughput priority mode setting may also be displayed in the display unit of the switch panel on the inkjet printer  1 . This display may also change according to operation of the operating switch  54 . Alternatively, when the configuration unit  50   c  sets the level specified by command according to the set level command for onto-paper flushing, the throughput priority mode corresponding to the set level may be displayed in the display unit. 
       FIG. 7  is a flow chart of the operation of the printing system  2  related to printing, (A) showing the operation of the host computer  5 , and (B) showing the operation of the inkjet printer  1 . 
     In this example, the application execution unit  101  of the host computer  5  generates and outputs data to be printed and print instructions to the printer driver execution unit  102  (step SA 11 ). The data generated by the application execution unit  101  may include character codes for a string, a barcode code, or image data. 
     The printer driver execution unit  102  then acquires the data and print instructions input from the application execution unit  101  (step SA 12 ), and generates a print instruction command or group of commands (step SA 13 ). The printer driver execution unit  102  outputs the command or command group generated in step SA 13  to the print monitor unit  103 , and the print monitor unit  103  passes them to the inkjet printer  1  (step SA 14 ). 
     The command reception unit  50   a  receives and stores the commands the host computer  5  sent in the receive buffer  50   g  (step SB 11 ). If the commands sent by the host computer  5  are a command group including plural formatting commands, the command reception unit  50   a  sequentially stores the plural commands in the command group in the receive buffer  50   g . The command interpreter  50   b  then sequentially interprets the commands in the receive buffer  50   g  (step SB 12 ), and passes the print instruction commands and data to be printed to the print control unit  50   e . The print control unit  50   e  then gets the print instruction commands and data to be printed (step SB 13 ), and calls the image processing unit  50   f . The image processing unit  50   f  then renders the data to be printed and stores the image data to print in the print buffer  50   h  (step SB 14 ). 
     The print control unit  50   e  then converts the color data (such as gray scale RGB data) for each pixel in the image data the image processing unit  50   f  rendered in the print buffer  50   h  to CMYK ink volume data based on a LUT stored in the printer storage unit  52 . Following this color conversion process, the print control unit  50   e  executes a digitizing process converting the ink volume data for the pixels to dot data that can be formed by the nozzles of each color of the inkjet head  10  (step SB 15 ). The nozzles of the inkjet head  10  can form four types of dots: white, small, medium and large (more specifically, no dot and three sizes of dots). The dot data for each nozzle is converted to four-level data including white (no dot). 
     The flushing control unit  50   d  references the flushing settings data  52   a  and determines the onto-paper flushing level (step SB 16 ). If set to level 1, the flushing control unit  50   d  generates a print flushing pattern using the reference flushing pattern  52   b  (step SB 17 ). 
     The reference flushing pattern  52   b  is a pattern for selecting the nozzles of the inkjet head  10  that are to eject ink, and may be a dot matrix pattern of n columns by m rows (where n and m are integers), for example. This dot matrix pattern is composed of white dots and flushing dots. A flushing dot represents a nozzle that ejects ink, and a white dot represents a nozzle that does not eject ink. The flushing control unit  50   d  applies the n-by-m reference flushing pattern  52   b  color by color to the nozzles of the black head  24   a , cyan head  25   a , magenta head  26   a , and yellow head  27   a.    
     For example, if the head of a particular color comprises p columns by q rows (where p and q are integers) of nozzle rows, the n-by-m reference flushing pattern  52   b  is scaled to p columns by q rows. This can be done by, for example, scaling the reference flushing pattern  52   b  vertically to p/n, and horizontally to q/m, discarding the remainders. This can also be done by aligning multiple reference flushing patterns  52   b , and extracting a p-by-q pattern therefrom. 
     After the reference flushing pattern  52   b  is scaled to the rows of nozzles, the flushing control unit  50   d  selects the nozzles that are also flushing dots, and selects those nozzles to eject ink. As a result of this process, the nozzles for ejecting ink in onto-paper flushing can be selected from among the numerous nozzles of the heads. The flushing control unit  50   d  generates a print flushing pattern indicating whether or not a particular nozzle ejects ink for all nozzles of the black head  24   a , cyan head  25   a , magenta head  26   a , and yellow head  27   a.    
     The ink ejection volume set by the print flushing pattern could be constant, for example. In the above example, when the ink ejection volume of the nozzles of the inkjet head  10  can be set to four levels, the print flushing pattern includes data for white dots and small, medium, and large dots. The amount of ink ejected in onto-paper flushing is preferably the smallest amount that can replace the ink inside the nozzle, and dots that are small, medium, or large are therefore selected. 
     However, if onto-paper flushing is set to level 2, the flushing control unit  50   d  generates an adjusted flushing pattern based on the reference flushing pattern  52   b  (step SB 18 ). This adjusted flushing pattern has fewer flushing dots than the reference flushing pattern  52   b . More specifically, the flushing control unit  50   d  generates the adjusted flushing pattern by a process that increases the ratio of white dots to flushing dots by, for example, inserting a specific number of white dots between the flushing dots of the reference flushing pattern  52   b.    
     The adjusted flushing pattern is a dot matrix pattern like the reference flushing pattern  52   b , but the number of rows and/or columns may be the same or different from the reference flushing pattern  52   b . The flushing control unit  50   d  then generates a print flushing pattern using the adjusted flushing pattern that was generated (step SB 17 ). More specifically, the flushing control unit  50   d  renders an adjusted flushing pattern according to the arrangement of nozzles in the inkjet head  10 , and selects the nozzles at the same locations as the flushing dots as the nozzles to eject ink. The method of rendering this adjusted flushing pattern is the same as the method for rendering the reference flushing pattern  52   b . The flushing control unit  50   d  generates a print flushing pattern indicating whether or not a particular nozzle ejects ink for all nozzles of the black head  24   a , cyan head  25   a , magenta head  26   a , and yellow head  27   a.    
     The print control unit  50   e  then generates the print data by overlaying the print flushing pattern generated in step SB 17  to the dot data generated by the digitizing process of step SB 15  (step SB 19 ). This print data is data for the ink ejection volume (in four levels including white dots, for example) of each nozzle in the inkjet head  10 , and includes dots for printing the image to be printed, and dots for onto-paper flushing. The print control unit  50   e  generates the print data by calculating the logical OR of the dot data and the print flushing pattern for each nozzle. The print data is therefore ink ejection data that forms more dots than the print flushing pattern and onto-paper flushing. 
     If a large dot, medium dot, or small dot in the dot data overlaps a dot of the print flushing pattern for any nozzle, the print control unit  50   e  determines the ink ejection volume and generates the print data for the nozzle using the data with the greater ink ejection volume. As a result, onto-paper flushing can be prevented from changing the print quality of the image to be printed. 
     In step SB 19 , the print control unit  50   e  also ignores dots in the print flushing pattern and sets the ink ejection volume of the nozzle to zero for any nozzle outside the target printing area of the conveyed roll paper R 2 . More specifically, ink is ejected in onto-paper flushing only in the target area specified as the area for printing an image on the conveyed roll paper R 2 . As a result, because ink ejected for onto-paper flushing does not land in areas of the conveyed roll paper R 2  that are intended to be blank, the effect of onto-paper flushing on print quality can be suppressed. Furthermore, the liner may be exposed on the printing side when the conveyed roll paper R 2  is label paper. If, as in this case, there are parts (such as the liner) to which ink will not adhere on the printed side, ink landing outside the targeted printing area can result in the printout being soiled after printing is completed. At least one embodiment of the present invention prevents such soiling because ink is not ejected outside the targeted printing area. 
     The print control unit  50   e  then drives the inkjet head  10  and conveyance motor  31  according to print data and prints (step SB 20 ). 
     After printing is completed, the printer control unit  50  sends a response command indicating that printing ended to the host computer  5  (step SB 21 ). The print monitor unit  103  receives the response command sent from the inkjet printer  1  (step SA 15 ). This response command is a response to the print instructions command generated by the printer driver execution unit  102 . The print monitor unit  103  may also report to the printer driver execution unit  102  that printing was completed. 
     During the operation described in  FIG. 7 , the flushing control unit  50   d  executes regular flushing according to the flushing interval set in the flushing settings data  52   a . The interval for regular flushing is determined according to the onto-paper flushing level, and is longer in the throughput priority mode than in the normal operating mode. As a result, the frequency of regular flushing can be reduced and throughput improved. 
     As described above, the printing system  2  according to this embodiment has a inkjet printer  1  and a host computer  5 . The inkjet printer  1  includes an inkjet head  10  with nozzles, and a conveyance unit  32  for conveying roll paper R 2 . 
     The printer control unit  50  executes regular flushing (first flushing) ejecting ink from the ink nozzles of the inkjet head  10  into the maintenance unit  90 . The printer control unit  50  also performs onto-paper flushing (second flushing) ejecting ink from the ink nozzles of the inkjet head  10  onto the conveyed roll paper R 2 . The host computer  5  provides a user interface for selecting a normal operating mode (first operating mode) or throughput priority mode (second operating mode) by the printer driver execution unit  102 . When the throughput priority mode is selected using the user interface, the printer driver execution unit  102  generates a command setting the conditions for flushing by the inkjet printer  1 . This command is then sent to the inkjet printer  1  by the print monitor unit  103 . 
     The printer control unit  50  of the inkjet printer  1  receives and interprets the commands sent by the host computer  5 , and sets the conditions for executing onto-paper flushing according to the received command. As a result, when the user determines and inputs whether or not to prioritize printing throughput, the conditions for flushing on the conveyance path HK of the conveyed roll paper R 2  are set according to the user input. The user can therefore easily and appropriately configure the flushing operation without having specific knowledge about the effect of flushing and conditions for flushing. 
     The printer control unit  50  can execute onto-paper flushing with the ink ejection volume set to any of plural different levels. When the throughput priority mode is selected through the user interface, the printer driver execution unit  102  generates a command setting the conditions for onto-paper flushing. As a result, whether or not the ink eject ion volume is increased when flushing is done on the conveyance path HK of the conveyed roll paper R 2  can be set easily and appropriately. 
     When the normal operating mode is set using the user interface, the printer driver execution unit  102  generates a set level command specifying level 2 (second execution condition), which is the default. As a result, whether or not the ink ejection volume is increased when flushing is done on the conveyance path HK of the conveyed roll paper R 2  can be set easily and appropriately. 
     After onto-paper flushing, the printer control unit  50  executes regular flushing according to the flushing interval, which is a preset period of time, and the flushing interval used when the onto-paper flushing level is level 1 (first execution condition) is longer than the flushing interval for level 2. Throughput can therefore be improved. 
     Regular flushing is flushing that ejects ink from the ink nozzles after moving the inkjet head  10  to the maintenance unit  90 . Onto-paper flushing is flushing that ejects ink from the ink nozzles of the inkjet head  10  onto the conveyed roll paper R 2  while the inkjet head  10  remains on the conveyance path of the conveyed roll paper R 2 . Thus comprised, the user can easily and appropriately set the conditions for onto-paper flushing by simply selecting either the normal operating mode or the throughput priority mode. 
     The present invention is described above with reference to some embodiments thereof, but the present invention is not limited thereto and can be modified and adapted in many ways without departing from the scope of the accompanying claims. 
     For example, because the ink ejection volume during onto-paper flushing differs according to the level that is set for flushing, the foregoing embodiment is described as selectively using the reference flushing pattern  52   b  and an adjusted flushing pattern created from the reference flushing pattern  52   b . More specifically, the reference flushing pattern  52   b  is used at onto-paper flushing level 1, and the adjusted flushing pattern is used at level 2. The present invention is not so limited, however, and the adjusted flushing pattern may be previously stored in the printer storage unit  52 . This configuration eliminates the need for a process to generate the adjusted flushing pattern, and reduces the processor load. 
     The ink ejection volume for onto-paper flushing can also be set in plural levels. In this event, the flushing dots of the reference flushing pattern  52   b  and adjusted flushing pattern may be configured using hierarchical ink ejection volume data. The adjusted flushing pattern can also be created as data with different ink ejection volumes for flushing dots at the same position in the reference flushing pattern  52   b . This configuration simplifies the process of creating and rendering the adjusted flushing pattern. 
     When there are three or more levels for onto-paper flushing, plural adjusted flushing patterns may be created, or adjusted flushing patterns for each level may be stored in the printer storage unit  52  as described above. 
     The operating modes for printing in the inkjet printer  1  are also not limited to a throughput priority mode and normal operating mode, and a configuration that enables selecting one operating mode from more operating modes in the configuration screen  200  is conceivable. The configuration screen  200  may also be a user interface enabling selecting more settings than just turning the throughput priority mode on or off. In this event, the printer driver execution unit  102  may generate a command group containing commands related to multiple settings configured through the configuration screen  200 . 
     The function blocks shown in  FIG. 4  can be achieved by the cooperation of hardware and software, and do not suggest a specific hardware configuration. Functions of the host computer  5  and inkjet printer  1  could also be rendered by other devices externally connected thereto. The host computer  5  and inkjet printer  1  can also operate as described above by running programs stored on an externally connected storage medium. The present invention can also be applied to a multifunction device incorporating a print unit identical to the inkjet printer  1 . 
     The disclosure being thus described, it will be apparent 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 disclosure, and all such modifications as would be apparent to one skilled in the art are intended to be included within the scope of the following claims.