JP2014073609A - Ink jet recorder and method for maintaining ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recorder and a method for maintaining an ink jet head, for maintaining preferable discharge characteristics by suitably executing preliminary discharge in each nozzle and suppressing the entire consumption amount during dummy jetting.SOLUTION: An ink jet head (16) including a plurality of nozzles (54), and an image processing part (86) for generating image data for drawing from input image data and generating image data for preliminary discharge by reversing the magnitude relation of gradation values in image data for drawing from the input image data are provided. Ink is discharged onto a recording medium from the ink jet head on the basis of the image data for drawing during drawing, and ink is discharged from the ink jet head on the basis of dot data for preliminary discharge during preliminary discharging.

Description

  The present invention relates to an inkjet recording apparatus and an inkjet head maintenance method, and more particularly to a maintenance technique for a liquid discharge head.

  As a general-purpose image forming apparatus, an ink jet recording apparatus that discharges ink droplets from a plurality of nozzles provided in an ink jet head is known. Ink jet heads may change their discharge characteristics as the ink in the nozzles thickens over time.In addition, as the ink thickens, the ejection direction is abnormal, the ejection amount is abnormal, Non-ejection that is not ejected occurs.

  In the ink jet recording apparatus, dummy jets (preliminary ejection and flushing) for ejecting ink from all nozzles are executed after a certain period of time has elapsed since the start of use in order to prevent ejection abnormalities and non-ejections of the ink jet head.

  The occurrence of abnormal ejection and non-ejection of the ink jet head becomes conspicuous with nozzles that are used infrequently. Therefore, by preferentially performing dummy jets for nozzles that are used infrequently, the ink in the nozzles is prevented from thickening without wasting ink.

  Patent Document 1 describes a recording apparatus in which a flushing pattern is formed based on drive data in which a liquid discharge amount for forming an image on a recording medium is assigned to each of a plurality of discharge ports.

  The recording apparatus described in Patent Document 1 generates data for forming flushing dots from drive data for each nozzle so that liquid is discharged from all nozzles within a certain period.

  Patent Document 2 describes an ink jet printer in which a flushing amount during a flushing operation is determined by a printing mode (high density, low density) immediately after flushing.

  The ink jet printer described in Patent Document 2 includes a plurality of types of printing modes, and in each printing mode, based on the meniscus state of the nozzle that can eject the minimum ink droplet volume in the printing mode performed immediately after the flushing operation. Flushing is performed using waveform pulses with the maximum ink drop volume.

  In Patent Document 3, a pixel that discharges liquid and a pixel that does not discharge liquid are determined, a nozzle that needs to be flushed is determined from image data, and liquid is discharged from a nozzle that requires flushing to a non-ejection pixel adjacent to the discharge pixel. A liquid discharge apparatus that discharges water is described.

JP 2011-116138 A JP 2009-090533 A JP 2008-179011 A

  However, the method of detecting the frequency of use (number of droplet ejection) for each nozzle requires the creation of software that calculates drive information decomposed for each nozzle from an image (image data), There is a problem that the circuit scale of a PLD (Programmable Logic Device), an FPGA (Field Programmable Gate Array), and the like that control driving increases.

  The recording apparatus described in Patent Document 1 collects drive data for each ejection port, generates data for forming flushing dots for each ejection port, and stores these data. A processor that performs high-speed computation for generation and a large-capacity memory for storing flushing data are required.

  The ink jet printer described in Patent Document 2 is not a process for each nozzle but a process for the entire ink jet head, and ink is ejected from nozzles that do not require flushing, thereby suppressing ink consumption during flushing. Is difficult.

  The liquid ejecting apparatus described in Patent Document 3 needs to determine the nozzles that need to be flushed from the image data, so software used for this processing is required. Further, if a nozzle that needs to be flushed is not flushed during printing, there is a concern that the nozzle may cause ejection abnormality or non-ejection over time.

  The present invention has been made in view of such circumstances, and an ink jet recording apparatus and an ink jet head in which preliminary ejection is appropriately performed for each nozzle, the overall consumption during dummy jet is suppressed, and preferable ejection characteristics are maintained. The purpose of this is to provide a maintenance method.

  In order to achieve the above object, an inkjet recording apparatus according to the present invention includes an inkjet head having a plurality of nozzles, a drawing image processing unit that generates drawing image data from input image data, and input image data. Preliminary ejection image processing unit for generating preliminary ejection image data in which the magnitude relationship of gradation values in the rendering image data is reversed, and rendering for ejecting ink from the inkjet head onto the recording medium based on the rendering image data And an ejection control means for performing preliminary ejection by ejecting ink from an inkjet head based on preliminary ejection image data.

  According to the present invention, preliminary discharge image data for generating a preliminary discharge image in which the magnitude relationship between the gradation values in the drawing image is reversed is generated from the input image data. In this preliminary ejection image, each nozzle in the drawing image is ejected more frequently from the less frequently used nozzles, and less frequently ejected from the nozzles that are used more frequently. Therefore, it is not necessary to create dedicated software for performing this operation, and it is not necessary to secure a processing unit (PLD, FPGA, etc.) for generating the dot data, and the ink consumption during preliminary ejection is suppressed.

1 is an overall configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. Schematic configuration diagram of the maintenance processing unit Plane perspective view showing schematic configuration of inkjet head Plane perspective view showing nozzle arrangement of sub head Sectional view showing the three-dimensional structure of the inkjet head Block diagram showing the configuration of the control system of the ink jet recording apparatus 1 is a block diagram showing the configuration of an image processing unit applied to a first embodiment Explanatory drawing showing inversion coefficient Explanatory drawing showing another mode of inversion coefficient Explanatory drawing showing another mode of inversion coefficient Flow chart showing the flow of drawing Flow chart showing the flow of the dummy jet process Flow chart showing another aspect of dummy jet process Explanatory drawing when executing a dummy jet toward the blank area of the recording medium, a: explanatory diagram showing an example of dividing the dummy jet image, b: executing a dummy jet that is a part of the dummy jet image in the blank area Explanatory diagram showing an example of the case The block diagram which shows the structure of the image process part applied to 2nd Embodiment. Explanatory drawing of an inversion table. a: In case of 2 gradation expression b: Simple replacement example, c: Example in which the minimum output value is a small dot Overall configuration diagram of another aspect of the inkjet recording apparatus

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[First Embodiment: Overall Configuration of Inkjet Recording Apparatus]
FIG. 1 is an overall configuration diagram of an ink jet recording apparatus according to a first embodiment of the present invention. An ink jet recording apparatus 10 shown in the figure is an on-demand ink jet recording apparatus.

  The ink jet recording apparatus 10 holds K (black), C (cyan), M (for a recording medium conveying unit 14 that holds and conveys the recording medium 12 and the recording medium 12 held by the recording medium conveying unit 14. And a printing unit 17 including inkjet heads 16K, 16C, 16M, and 16Y that discharge color inks corresponding to magenta) and Y (yellow).

  1 is omitted, and a maintenance processing unit shown in FIG. The maintenance processing unit is a unit that performs maintenance processing such as dummy jet (preliminary ejection and flushing) and suction on the inkjet heads 16K, 16C, 16M, and 16Y.

  The recording medium conveyance unit 14 includes an endless conveyance belt 18 provided with a plurality of suction holes (not shown) in a recording medium holding area where the recording medium 12 is held, and a conveyance roller (drive) around which the conveyance belt 18 is wound. The roller 20 and the driven roller 22) and the back side of the conveyance belt 18 in the recording medium holding region (the surface opposite to the recording medium holding surface on which the recording medium 12 is held), and the non-adjustment provided in the recording medium holding region. A chamber 24 communicated with the illustrated suction hole and a vacuum pump 26 for generating a negative pressure in the chamber 24 are included.

  The carry-in unit 28 into which the recording medium 12 is carried is provided with a pressure roller 30 for preventing the recording medium 12 from floating, and the discharge roller 32 from which the recording medium 12 is discharged is also provided with a pressure roller 34. It has been.

  The recording medium 12 carried in from the carry-in section 28 is given a negative pressure from the suction hole provided in the recording medium holding area, and is sucked and held in the recording medium holding area of the transport belt 18.

  On the conveyance path of the recording medium 12, a temperature adjustment unit 36 for adjusting the surface temperature of the recording medium 12 to a predetermined range is provided on the upstream side of the printing unit 17 (upstream side in the recording medium conveyance direction). A reading device (reading sensor) 38 that reads an image recorded on the recording medium 12 is provided on the rear side of the recording medium 17 (downstream in the recording medium conveyance direction).

  The recording medium 12 carried in from the carry-in section 28 is sucked and held in the recording medium holding area of the conveyor belt 18 and subjected to temperature adjustment processing by the temperature adjustment section 36, and then image recording is performed in the printing section 17.

  As shown in FIG. 1, the inkjet heads 16K, 16C, 16M, and 16Y are arranged in this order from the upstream side in the recording medium conveyance direction. When the recording medium 12 passes directly under the ink jet heads 16K, 16C, 16M, and 16Y, each color ink of KCMY is ejected onto the recording medium 12 to form a desired color image.

  The printing unit 17 is not limited to the above-described form. For example, the inkjet heads 16LC and 16LM corresponding to LC (light cyan) and LM (light magenta) may be provided. Further, the arrangement order of the inkjet heads 16K, 16C, 16M, and 16Y can be changed as appropriate.

  The recording medium 12 on which the image has been recorded is ejected from the ejection unit 32 after the recorded image (test pattern) is read by the reading device 38.

[Maintenance processing section]
FIG. 2 is a schematic configuration diagram of a maintenance processing unit that performs maintenance processing on the inkjet head 16. In the following description, when it is not necessary to distinguish the inkjet heads 16K, 16C, 16M, and 16Y for each color, the inkjet head is represented by the reference numeral 16.

  The maintenance processing unit 40 shown in the figure is orthogonal to the conveyance direction of the recording medium 12 from the image forming position on the recording medium conveying unit 14 (the inkjet head 16 disposed at the image forming position is indicated by a broken line). In the direction in which the recording medium 12 is moved, or the position where the recording medium 12 is horizontally moved diagonally intersecting the conveyance direction.

  That is, the inkjet head 16 arranged at the image forming position temporarily moves upward (the inkjet head 16 moved upward from the image forming position is indicated by a solid line), and further moved horizontally to perform maintenance. The position (non-drawing area) is reached.

  The maintenance processing unit 40 includes a cap 42 that performs a dummy jet (preliminary discharge, flushing) or suction processing (discharge processing of ink in the nozzles) on the inkjet head 16. When the inkjet head 16 reaches the maintenance position, the cap 42 is lifted to bring the cap 42 into close contact with the nozzle surface (ink ejection surface) 16D of the inkjet head 16.

  In this state, when the pump 44 is operated to depressurize the inside of the cap 42, ink is ejected from a nozzle (not shown in FIG. 2, not shown in FIG. 2 and indicated by reference numeral 54 in FIG. 4) formed on the nozzle surface 16D of the inkjet head 16. Discharged.

  The maintenance processing unit 40 includes a drainage channel 46 having one end connected to a drainage port (not shown) of the cap 42, a drainage tank 48 connected to the other end of the drainage channel 46, When the pump 44 disposed in the drainage flow path 46 is operated, the ink discharged from the inkjet head 16 to the cap 42 is sent to the drainage tank 48.

  In addition, there may be an aspect including a cleaning liquid applying device that applies a cleaning liquid to the nozzle surface 16D and a wiping member (blade, web, or the like) that wipes the nozzle surface 16D.

  Although FIG. 1 illustrates the configuration of the maintenance processing unit 40 corresponding to one head, this configuration may be provided for the number of inkjet heads, or the maintenance processing unit 40 may be provided in a number smaller than the number of inkjet heads 16. Alternatively, the maintenance processing unit may be applied to all the inkjet heads 16 while moving the inkjet head 16 or the maintenance processing unit 40.

  As a moving mechanism for moving the inkjet head 16 in the vertical direction and the horizontal direction, a well-known horizontal conveyance mechanism and vertical conveyance mechanism (ball screw, linear actuator, etc.) can be applied.

[Description of inkjet head]
FIG. 3 is a plan perspective view showing the schematic configuration of the inkjet head 16 (a view of the recording medium 12 (see FIG. 1) viewed from the inkjet head 16). As shown in the figure, each sub head 50 has a structure in which the head main body portion 52 is supported by head covers 54A and 54B from both sides of the inkjet head 16 in the short direction.

  In the head main body 52, nozzles (not shown in FIG. 3, not shown in FIG. 4 and indicated by reference numeral 54) are formed on a nozzle surface 16D (see FIG. 2) for discharging ink. An ink reservoir and a filter (both not shown) are arranged on the opposite side of the head main body 52 from the nozzle surface 16D.

  FIG. 4 is a perspective plan view showing the nozzle arrangement of the sub head 50. As shown in the figure, each sub head 50 has a structure in which nozzles 54 are two-dimensionally arranged, and the ink jet head 16 including the sub head 50 is called a so-called matrix head.

  In the sub head 50 shown in FIG. 4, a large number of nozzles 54 are arranged along a column direction W that forms an angle α with respect to the sub scanning direction Y and a row direction V that forms an angle β with respect to the main scanning direction X. It has a structure, and the substantial nozzle arrangement density in the main scanning direction X is increased.

  In FIG. 4, the nozzle group (nozzle row) arranged along the row direction V is indicated by reference numeral 56, and the nozzle group (nozzle row) arranged along the column direction W is indicated by reference numeral 58. ing.

  Here, the “sub-scanning direction” is a term having the same technical significance as the “recording medium conveyance direction” described above. The “main scanning direction” is a term having the same technical significance as the “direction perpendicular to the conveyance direction of the recording medium” described above, and has the same technical significance as the “arrangement (arrangement) direction of the sub heads 50”. It is a term.

  The inkjet head 16 having the structure shown in FIG. 4 has a grid pattern with a fixed arrangement pattern along a row direction V that forms an angle β with the main scanning direction X and a column direction W that forms an angle α with respect to the sub-scanning direction Y. The high-density nozzle head of this example is realized by arranging a large number of the nozzle heads.

  It is also possible to configure the matrix head by arranging the nozzles in a fixed arrangement pattern along the main scanning direction in the row direction and the column direction intersecting with the main scanning direction.

  FIG. 5 is a cross-sectional view showing a three-dimensional structure of one ejection element of the inkjet head 16 (sub head 50). As shown in the figure, the inkjet head 16 is provided on the vibration plate 62, a nozzle 54 that discharges ink, a pressure chamber 60 that communicates with the nozzle 54, a vibration plate 62 that forms the ceiling surface of the pressure chamber 60, and the vibration plate 62. And a piezoelectric element 64.

  The pressure chamber 60 communicates with a common flow path 68 through a supply port (supply throttle) 66, and the common flow path 68 is ink that is disposed outside the inkjet head 16 through a flow path (not shown). It communicates with the tank.

  The piezoelectric element 64 has a structure in which a piezoelectric body 74 is sandwiched between an upper electrode 70 and a lower electrode 72. When a driving voltage is applied between the upper electrode 70 and the lower electrode 72, the piezoelectric element 64 is bent and deformed. As the pressure chamber 60 is deformed by the deformation of the element 64, the ink stored in the pressure chamber 60 is ejected from the nozzle 54.

  When the bending deformation of the piezoelectric element 64 is restored to the original state, the pressure chamber 60 is filled with ink from the common flow path 68 through the supply port 66. When a metal material is applied to the diaphragm 62, the diaphragm 62 and the lower electrode 72 may be shared.

  The inkjet head 16 shown in FIG. 5 has a structure in which a plurality of cavity plates are stacked. For example, a nozzle plate 76 in which an opening of the nozzle 54 is formed, a pressure chamber 60, a supply port 66, a flow path plate 78 in which a common flow path 68 and the like are formed, a vibration plate 62, and a piezoelectric element 64 are provided. The aspect which laminates | stacks in this order is mentioned. Note that each of the above-described plates can be further constituted by a plurality of plates.

  In this example, the aspect including the full-line type inkjet head 16 in which the nozzles 54 are disposed over the length corresponding to the entire width of the recording medium 12 is illustrated, but the inkjet head applied to the present invention is a full-line type. It is not limited to.

  For example, the present invention can be applied to an aspect including a serial type ink jet head in which a plurality of nozzles are arranged in parallel with the conveyance direction of the recording medium.

  Note that the “full width” of the recording medium 12 is the total length of the recording medium 12 in a direction orthogonal to the conveyance direction of the recording medium 12 (the direction illustrated with reference numeral Y in FIG. 4), and margins are considered. The total length in the same direction of the image forming area where the image is formed may be used.

  The term “orthogonal” used herein includes not only a direction that forms 90 ° with respect to the reference recording medium transport direction but also an oblique direction that is deviated within the range of the recording medium transport error. In this specification, unless otherwise specified, the terms “orthogonal” and “parallel” include an oblique direction that is deviated within a range of error from the reference.

[Explanation of control system]
FIG. 6 is a block diagram showing the configuration of the control system of the inkjet recording apparatus 10 shown in FIG. As shown in the figure, the inkjet recording apparatus 10 includes a communication interface 80, a system control unit 82 (ejection control means), a conveyance control unit 84, and an image processing unit 86 (drawing image processing unit, preliminary ejection image processing unit). In addition to the head drive unit 88 (discharge control means), an image memory 90 and a ROM 92 are provided.

  The communication interface 80 is an interface unit that receives raster image data sent from the host computer 94. The communication interface 80 may be a serial interface such as USB (Universal Serial Bus) or a parallel interface such as Centronics. The communication interface 80 may include a buffer memory (not shown) for speeding up communication.

  That is, the host computer 94 performs RIP (Raster Image Processing) processing for converting electronic data to be printed, for example, electronic data described in a page description language (PDL) into a raster image, RGB three primary colors. Functions as a processing means for performing color conversion processing, gradation conversion processing, and the like.

  The system control unit 82 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 10 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. Further, it functions as a memory controller for the image memory 90 and the ROM 92.

  That is, the system control unit 82 controls each unit such as the communication interface 80 and the conveyance control unit 84, performs communication control with the host computer 94, read / write control of the image memory 90 and the ROM 92, and the like. A control signal to be controlled is generated.

  The image data sent from the host computer 94 is taken into the ink jet recording apparatus 10 via the communication interface 80 and subjected to predetermined image processing by the image processing unit 86.

  The image processing unit 86 has a signal (image) processing function for performing various processing and correction processes for generating a signal for driving an inkjet head (for printing control) from input image data for each color. A control unit that supplies drive data (dot data) to the head drive unit 88.

  When the signal processing is performed in the image processing unit 86, the ejection droplet amount (droplet ejection amount) and ejection timing of the inkjet head 16 are controlled via the head driving unit 88 based on the drive data. .

  Thereby, a desired dot size and dot arrangement are realized. The head driving unit 88 shown in FIG. 6 may include a feedback control system for keeping the driving conditions of the inkjet head 16 constant.

  The conveyance control unit 84 controls the conveyance timing and conveyance speed of the recording medium 12 (see FIG. 1) based on the print data generated by the image processing unit 86. 6 includes a motor that drives the drive roller 20 (22) of the recording medium transport unit 14 that transports the recording medium 12, and the transport control unit 84 functions as a driver of the motor. Yes.

  The image memory (temporary storage memory) 90 functions as temporary storage means for temporarily storing image data input via the communication interface 80, a development area for various programs stored in the ROM 92, and a calculation work area for the CPU. (For example, a work area of the image processing unit 86). As the image memory 90, a volatile memory (RAM) capable of sequential reading and writing is used.

  The ROM 92 stores a program executed by the CPU of the system control unit 82, various data necessary for control of each unit of the apparatus, control parameters, and the like, and data is read and written through the system control unit 82. The ROM 92 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used. Alternatively, a removable storage medium that includes an external interface may be used.

  The parameter storage unit 98 stores various control parameters necessary for the operation of the inkjet recording apparatus 10. The system control unit 82 appropriately reads out parameters necessary for control, and executes update (rewrite) of various parameters as necessary.

  The program storage unit 100 is a storage unit that stores a control program for operating the inkjet recording apparatus 10. The system control unit 82 (or each unit of the device) reads a necessary control program from the program storage unit 100 when executing control of each unit of the device, and the control program is executed as appropriate.

  The maintenance control unit 102 controls the operation of the maintenance processing unit 40 in accordance with a command signal from the system control unit 82. For example, in response to a maintenance process start command for the inkjet head 16, a moving mechanism for moving the inkjet head 16 is operated, a moving mechanism for moving the cap 42 is operated, and the pump 44 is operated.

  The drawing image data storage unit 104 stores drawing image data (drawing dot data, drawing drive data) generated by the image processing unit 86. The head driving unit 88 reads the drawing image data stored in the drawing image data storage unit 104 and generates a driving voltage to be supplied to the inkjet head 16 at the time of drawing.

  The dummy jet (DJ) image data storage unit 106 stores the dummy jet image data generated by the image processing unit 86. The head drive unit 88 reads the dummy jet image data stored in the dummy jet image data storage unit 106 and generates a drive voltage supplied to the inkjet head 16 during the dummy jet.

  Although illustration is omitted, a display unit is provided as means for displaying various information sent from the system control unit 82. A general-purpose display device such as an LCD monitor is applied to the display unit. Note that lighting (flashing and extinguishing) of the lamp may be applied to the display form of the display unit. Further, sound (sound) output means such as a speaker may be provided.

  In addition, an input interface (not shown) is provided, and information input via the input interface is sent to the system control unit 82. Information input means such as a keyboard, a mouse, and a joystick are applied to the input interface.

[Detailed description of image processing unit]
FIG. 7 is a block diagram showing the configuration of the image processing unit 86 applied to this example. The image processing unit 86 shown in the figure includes a data expansion processing unit 122, an enlargement / reduction processing unit 124, a distortion correction processing unit 126, and an X registration correction processing unit 128.

  Further, a gamma correction processing unit 130 that performs gamma correction processing on the image data that has been processed by each of the above processing units, and a nonuniformity correction processing unit that corrects uneven density due to a difference in ejection characteristics for each nozzle. 132, an XY conversion processing unit 134 for performing XY conversion processing on the image data after unevenness correction processing, and halftone processing (HT processing, error diffusion method, dither method, threshold matrix method) on the image data after XY conversion processing , A density pattern method, and the like, and a nozzle mapping processing unit 138 that assigns nozzles to the image data (dot data) after the halftone process.

  In this way, drawing image data including dot position and dot size information for each nozzle is generated from the raster image data sent from the RIP data server 94.

  Further, in the inkjet recording apparatus 10 shown in this example, dummy jet image data that is drive data at the time of dummy jet (DJ) processing is generated from raster image data. The dummy jet image data is generated by performing halftone processing on density inversion data obtained by inverting the density value of each pixel (density value magnitude relationship) of input image data before halftone processing.

  For example, when the density value (gradation value) of each pixel of the input image data is represented by a value from 0 to 255, the absolute value of the value obtained by subtracting 255 from the density value becomes the density value of the density inversion data. Dummy jet image data is generated by performing halftone processing on the inverted data.

  In the ink jet recording apparatus shown in this example, “inversion of density value” means that a reference value is determined from density values and is converted into a symmetrical value with respect to the reference value. Specifically, for values larger than the reference value, the ascending order of the values is changed to descending order (descending order is ascending order) and changed to a value smaller than the reference value, and values smaller than the reference value are set to descending order of the values. It is changed to a value larger than the reference value by changing (descending order to ascending order).

  This reference value may be a center value in the entire range of density values, or may be a value shifted by a value determined from the center value. If the density value after inversion exceeds the density value range, the value exceeding the density value range may be set as the maximum value or the minimum value of the density value, or the converted density value is multiplied by a coefficient. (Compressed) may be a value within the range of the density value.

  As shown in FIG. 7, the image processing unit 86 performs inversion using the inversion coefficient recorded in the inversion coefficient storage unit 141 on the image data processed by the X registration correction processing unit 128. A processing unit 140; a non-uniformity correction processing unit 142 that performs non-uniformity correction processing on the image data after inversion processing; an XY conversion processing unit that performs XY conversion processing on the image data after non-uniformity correction processing; and an XY conversion processing. A halftone (HT) processing unit that performs halftone processing on the subsequent image data, and 146, and a nozzle mapping processing unit 148 that assigns nozzles to the image data after the halftone processing are provided.

  The image data for drawing and the image data for dummy jet generated by the image processing by each processing unit shown in FIG. 7 are sent to the head driving unit 88, and a driving voltage supplied to the inkjet head 16 is generated.

  The head driving unit 88 performs a bar position correction processing unit 150 for correcting the inclination of the inkjet head 16 on the drawing image data and the dummy jet image data, and the position error for each sub head 50 (see FIG. 3). A head position correction processing unit 152 that performs correction processing, and includes a drive waveform storage unit (drive waveform generation unit) (not shown), a drive timing signal generation unit, an amplification unit, an output circuit, and the like.

  In the above description, the image processing unit 86 is mounted on the image processing board, and the head driving unit 88 is mounted on the driving circuit board disposed in the vicinity of the inkjet head 16. Note that the relationship between each processing unit and the substrate described above can be changed.

  Note that the unevenness correction processing unit 132 and the unevenness correction processing unit 142, the XY conversion processing unit 134 and the XY conversion processing unit 144, the halftone processing unit 136 and the halftone processing unit 146, the nozzle mapping processing unit 138 and the nozzle illustrated in FIG. Since the mapping processing unit 148 has a common function, the hardware configuration of the image processing unit 86 is simplified by sharing these functions.

  7 illustrates an example in which the inversion processing is performed on the processing target data for the gamma correction processing. However, the processing target data for the inversion processing includes processing target data for the unevenness correction processing and processing target data for the XY conversion processing. Any data before halftone processing, such as data, may be used.

[Detailed description of image data generation for dummy jet]
Hereinafter, generation of dummy jet image data will be described in detail. FIG. 8 is an explanatory diagram showing the inversion coefficient. The curve shown by the solid line is the inversion coefficient 200, and the curve shown by the broken line is used for the gamma correction processing for generating the drawing image data. The gamma correction coefficient 202 used.

  The inversion coefficient 200 is a gamma correction coefficient 202 used for gamma correction processing applied to input image data when generating drawing image data, and is 180 counterclockwise around the origin (0, 0). It is generated by rotating and then geometrically turning it upside down.

  The gamma correction coefficient 202 is a correction coefficient that is determined for each head (for each color) in order to correct the ejection characteristics for each nozzle in which the actual density is nonlinear with respect to the input density value.

  Inverted image data that has been subjected to inversion processing using the inversion coefficient 200 has a density value magnitude relationship with respect to image data that has been subjected to gamma processing using the gamma correction coefficient 202 for generating drawing image data. It has been replaced.

  In other words, a pixel having a large density value in the image data subjected to gamma correction processing has a small density value in the inverted image data, and a pixel having a small density value in image data subjected to the gamma correction processing is a density value in the inverted image data. Becomes larger.

  In addition, a pixel having a density value of zero in the image data subjected to the gamma correction processing has a maximum density value in the inverted image data, and a pixel having the maximum density value in the image data subjected to the gamma correction processing is a reverse image. The concentration value is zero in the data.

  As a result, nozzles that are frequently used in drawing are less frequently used in dummy jets, and nozzles that are frequently used in drawing are frequently used in dummy jets. )It can be performed.

  Thus, it is necessary to detect the usage status of each nozzle by generating an image dedicated to the dummy jet (a virtual image obtained by inverting the density of the image to be drawn) by the same processing as the drawn image. This eliminates the need to create software for detecting the usage status of each nozzle, and further reduces the amount of data processed by the PLD or FPGA and the processing load.

  FIG. 9 is an explanatory diagram showing another aspect of the inversion coefficient 200 of FIG. The inversion coefficient 204 shown in the figure is determined so that the output value (minimum output value) is D when the input value is 255 (maximum value).

  By using the inversion coefficient 204 shown in FIG. 9, a certain amount of ink is ejected (dummy jet) even with nozzles that are frequently used in drawing. That is, the minimum output value D shown in FIG. 9 is determined in consideration of factors such as the type of ink and the environment during drawing.

  It is also possible to generate and store the inversion coefficients 204 having different values of the output minimum value D using the ink type, drawing environment, etc. as parameters, and switch them according to the ink type and drawing environment. .

  The inversion coefficient 206 shown in FIG. 10 has the most simplified linear shape. Since the image dedicated to the dummy jet (shown with reference numeral 220 in FIG. 14) does not require high-definition image quality, the purpose of the dummy jet is achieved even if the variation in ejection characteristics for each nozzle is not corrected. can do.

  Then, as shown in FIG. 10, it is also possible to use a linear inversion coefficient 206 obtained by linear approximation of the correction coefficient of FIG. That is, the density value of each pixel included in the input image data may be simply inverted (the magnitude relationship between the density values is switched).

  Also, for the inversion coefficient 206 shown in FIG. As shown in FIG. 9, the output initial value may be a value other than zero.

  When the inversion process is performed using any one of the inversion coefficients 200, 204, and 206 shown in FIGS. 8 to 10, the subsequent processes are the same as the generation of the drawing image data, and the dummy jet image Data is generated and stored in the dummy jet image data storage unit 106 (see FIG. 6).

  8 to 10 illustrate the inversion coefficient in which the output value continuously changes with respect to the input value, the inversion coefficient applied to this example uses the horizontal series as the input value and the vertical series as the output value. As long as it is expressed two-dimensionally.

  For example, at least the relationship between the high density area and the low density area in the drawing image data may be interchanged, and the intermediate area may have a flat portion, or may be stepwise (stepped). Also good.

  The “low density region” is a region where there is a high necessity for the dummy jet, and can be, for example, a region on the left side of the reference value of the input value in FIGS. The reference value of the input value may be a center value (127 when the input value is represented by an integer from 0 to 255) in the entire range of the input value, or a value less than the center value (an input value is an integer from 0 to 255). 32, 64, etc.).

  Further, the “high density region” is a region where the necessity of the dummy jet is low, and can be, for example, a region on the right side of the reference value of the input value in FIGS. The reference value of the input value may be a center value (127 when the input value is represented by an integer from 0 to 255) in the entire range of the input value, or a value exceeding the center value (an input value is an integer from 0 to 255). 159, 191 etc.).

[Description of maintenance method of inkjet head]
Next, a maintenance method for the inkjet head 16 will be described. FIG. 11 is a flowchart showing the flow of drawing control. In the inkjet recording apparatus 10, dummy jets are appropriately executed during drawing in order to avoid ejection abnormalities due to thickening (deterioration) of ink in the nozzles.

  As shown in FIG. 11, when drawing is started (step S10), drawing image data is generated based on the input image data (step S12). Also, dummy jet image data is generated based on the input image data (step S14) and stored (step S16). That is, dummy jet image data is generated and stored for each drawing image.

  When the drawing image data is generated (step S12) and the dummy jet image data is stored (step S16), drawing is performed using the drawing image data (step S18), and the set number of drawings is drawn. It is determined whether or not it has been executed (step S20).

  In step S20, when the number of drawn images is less than the set number (No determination), the determination of the end of drawing is continued (step S20). On the other hand, if the number of drawn images reaches the set number in step S20 (Yes determination), the presence / absence of a dummy jet command is determined (step S22).

  Whether or not to execute the dummy jet is determined based on information such as the operating time (or non-operating time) of the inkjet head 16 and the environmental temperature and humidity. When the conditions for executing the dummy jet are satisfied, the dummy jet is satisfied. Execution command is issued.

  If it is determined in step S22 that a dummy jet execution command has not been issued (No determination), the process proceeds to step S32 to determine whether or not the next image data exists. On the other hand, if it is determined in step S22 that a dummy jet execution command has been issued (Yes determination), dummy jet image data is read (step S24), and a dummy jet using the dummy jet image data is executed. (Step S26).

  During execution of the dummy jet, the presence / absence of an end command is monitored (step S28). When there is no end command (No determination), the dummy jet is continued (step S26), and when the end command is issued (Yes determination of step S28). ), The dummy jet is terminated (step S30).

  When the dummy jet is terminated in step S30, it is determined whether or not there is next drawing data (step S32). If there is next drawing data (Yes determination), the process proceeds to step S18 and drawing is executed.

  On the other hand, when there is no next drawing data (No determination in step S32), the drawing is ended after the end processing is performed (step S34).

  The drawing image data generation (step S12) and the dummy jet image data generation (step S14) shown in FIG. 11 are also executed in the drawing area during the steps after the drawing step (step S18). .

  That is, the generation of the drawing image data used for the next drawing and the generation of the dummy jet image data corresponding to the drawing image data used for the next drawing are performed when the previous drawing is executed. Can start.

  The dummy jet image data storage unit 106 illustrated in FIG. 6 may store a plurality of dummy jet image data. When dummy jet image data is newly generated, the latest dummy jet image data is stored. Data may be stored.

  In addition, when a plurality of dummy jet image data is stored, any of the dummy jet image data may be used. Since the previously generated dummy jet image data corresponds to the drawing image data for which drawing has already been completed, dummy jets that reflect the past use environment of the inkjet head are possible.

  On the other hand, since the dummy jet image data generated later corresponds to the drawing image data to be drawn from now on, dummy jets in anticipation of the future use environment of the inkjet head can be realized.

  FIG. 12 is a flowchart showing the flow of the dummy jet process shown in step S26 of FIG. When the dummy jet process is started (step S100), drawing is completed at a certain timing (for example, when drawing on a certain recording medium is completed) (step S102), and the inkjet head 16 is moved to the maintenance position (step S102). In step S104, the cap 42 is attached to the nozzle surface 16D of the inkjet head 16 (step S106).

  Then, the dummy jet is executed (step S108), and if the dummy jet end command is not issued (No determination in step S110), the dummy jet is continued (step S108).

  On the other hand, when a dummy jet termination command is issued (Yes in step S110), the cap 42 is separated from the nozzle surface 16D of the inkjet head 16 (step S112), and the inkjet head 16 is moved to the drawing position (step S114). The dummy jet process is ended (step S116).

  FIG. 13 is a flowchart of a mode in which a dummy jet is applied to a recording medium. In the following description, the same parts as those in FIG. 12 are denoted by the same reference numerals, and the description thereof is omitted.

  In the flowchart shown in FIG. 13, a paper feeding process (step S105) is executed instead of the head moving process (step S104) and the cap mounting process (step S106) in FIG.

  That is, when drawing is stopped (step S102), the dummy jet recording medium is fed, and the dummy jet is executed toward the dummy jet recording medium (step S108).

  When the dummy jet is finished (Yes in step S110), the dummy jet recording medium is discharged (step S113), and the dummy jet process is finished (step S116).

  A recording medium for drawing may be used as the recording medium for the dummy jet, or a recording medium dedicated to the dummy jet may be used.

  FIG. 14 is an explanatory diagram when a dummy jet is executed toward the blank areas 12B and 12C of the recording medium 12. FIG. FIG. 14A is an explanatory diagram schematically showing an example of division of the dummy jet image 220. FIG. 14B shows the dummy jet image portions 220A and 220B in the blank areas 12B and 12C. It is explanatory drawing which illustrated typically the example in the case of performing a dummy jet.

  FIG. 14A shows a case where a dummy jet is executed on the user area 12A (drawing area). In the user area 12A, a dummy jet image 220 in which the density is inverted with respect to the drawn image (the relationship between light and shade is inverted) is formed.

  A recording used to draw at least one of the divided dummy jet images 220A, 220B, 220C, and 220D obtained by dividing the dummy jet image 220 into four in the conveyance direction of the recording medium (vertical direction in FIG. 14A). You may form in the margin area | regions 12B and 12C of the medium 12. FIG.

  In the example shown in FIG. 14B, the divided dummy jet image 220A is formed in the blank area 12B on the downstream side in the recording medium conveyance direction, and the divided dummy jet image 220B is formed in the blank area 12C on the upstream side in the recording medium conveyance direction. Has been. The remaining divided dummy jet images 220C and 220D may be superimposed on the divided dummy jet images 220A and 220B, or may be formed in the blank areas 12B and 12C of the next recording medium 12. The blank areas 12B and 12C are cut after drawing and discarded.

  In the example shown in FIGS. 14A and 14B, the dummy jet image 220 is divided into four, and one of the divided dummy jet images is formed in one blank area 12B (12C). The number of divided dummy jet images 220A, 220B, 220C, 220D to be formed in one blank area 12B, 12C is determined according to the contents of the dummy jet image 220, the areas of the blank areas 12B, 12C, and the like. .

  In this manner, the dummy jet image 220 is divided and at least one of the divided dummy jet images 220A, 220B, 220C, and 220D is formed in the blank areas 12B and 12C of the recording medium 12 used for drawing. Accordingly, it is not necessary to use the recording medium every time the dummy jet is executed, and the dummy jet is executed immediately before and after the drawing, so that the ejection state of the inkjet head 16 can be stabilized.

  According to the ink jet recording apparatus 10 configured as described above, dummy jet image data for forming a dummy jet image in which the density of the drawn image is reversed by switching the magnitude relationship of the density values of the input image data is generated. The

  This dummy jet image data detects more frequently used nozzles in the drawing image because it discharges more frequently from the less frequently used nozzles in the drawn image and less frequently from the nozzles that are used more frequently in the drawn image. Rather, a dummy jet reflecting the frequency of nozzle use is executed.

  That is, by applying a process similar to the process for generating the drawing image data from the input image data, the gamma correction coefficient for generating the drawing image data is changed to the inversion coefficient for generating the dummy jet image data. Since the dummy jet image data is generated by modification, it is not necessary to create dedicated software for generating the dummy jet image data, and PLD, FPGA, etc. are used to generate the dummy jet image data. It is not necessary to secure a processing unit, and wasteful ink consumption due to a dummy jet is avoided.

[Second Embodiment: Description of Configuration of Image Processing Unit]
Next, a second embodiment of the present invention will be described with reference to FIGS. 15 and 16. In addition, in 2nd Embodiment demonstrated below, the same code | symbol is attached | subjected to the part which is the same as that of 1st Embodiment demonstrated previously, or is similar, and the description is abbreviate | omitted.

  FIG. 15 is a block diagram illustrating a configuration of an image processing unit 86 ′ applied to the second embodiment. In this example, in the nozzle mapping, dummy jet image data is generated by reversing (replacement) the size relationship of the dot size of the drawing image data.

  That is, instead of the inversion processing unit 140, the inversion coefficient storage unit 141, the correction processing unit 142, the XY conversion processing unit 144, the halftone processing unit 146, and the nozzle mapping processing unit 148 shown in FIG. A unit 141 is provided.

  FIGS. 16A to 16C are explanatory diagrams of the inversion table. FIG. 16A shows an example in which two gradations are expressed by “with dot” and “without dot” (binarization), and FIGS. 16B and 16C show “without dot”, In the case of expressing four gradations using “small size dots (small dots)”, “medium size dots (medium dots)”, and “large size dots (large dots)” (quaternization) is there.

  In FIGS. 16A to 16C, “before conversion” is dot information in the drawing image data, and “after conversion” is dot information in the dummy jet image data.

  In FIG. 16A, “no dot” is represented by “1”, and “with dot” is represented by “2”. In the two-tone representation shown in FIG. 16A, “with dot” in the drawing image data is converted to “without dot” in the dummy jet image data, and “without dot” in the drawing image data represents the dummy jet. Image data is converted to “with dot”.

  That is, if a dummy jet image is formed based on the dummy jet image data, the dummy jet image is an image obtained by inverting the black and white of the drawing image generated based on the drawing image data.

  The “dummy jet image” here is a virtual image formed on the recording medium when the recording medium is transported and ink is ejected from the ink jet head in the same manner as in the case of forming a drawn image. The dummy jet image need not be formed on the recording medium.

  In the case of the four gradation expression shown in FIGS. 16B and 16C, a dummy jet image can be formed by inverting the density of the drawn image (changing the density relationship).

  FIG. 16B is an example in which the size relationship between the dot sizes of the drawing image data is simply switched. “0” indicates no dot (for example, ink discharge amount is zero picoliter), and “1” indicates a small dot ( For example, an ink discharge amount of 2 picoliters), “2” represents a medium dot (for example, an ink discharge amount of 4 picoliters), and “3” represents a large dot (for example, an ink discharge amount of 8 picoliters).

  In the example shown in FIG. 16B, “no dot” in the drawing image data is converted to “large dot” in the dummy jet image data, and “small dot” in the drawing image data is converted into the dummy jet image data. “Medium dot”, “Medium dot” of drawing image data is converted to “Small dot” of dummy jet image data, and “Large dot” of drawing image data is converted to “No dot” of dummy jet image data .

  That is, when the conversion coefficient shown in FIG. 16B is used, the gradation value M (≦ N) is converted into the gradation value (N−M + 1) in the dot data that has been converted into N values by halftone processing. N is an integer of 2 or more and less than the input gradation value, and M is an integer from 1 to N.

  In this way, by inverting (replacing) the dot size relationship in the drawing image data, dummy jet image data corresponding to the dummy jet image in which the density of the drawing image is inverted can be generated.

  FIG. 16C shows an example of conversion when the minimum output value of dummy jet image data is “small dots”. That is, “no dot” in the drawing image data is converted to “large dot” in the dummy jet image data, and “small dot” in the drawing image data is converted into “large dot” in the dummy jet image data. .

  Further, the “medium dot” of the drawing image data is “medium dot” (or “small dot”) of the dummy jet image data, and the “large dot” of the drawing image data is “small dot” of the dummy jet image data. Is converted to

  That is, in N-valued halftone data, the gradation value M is converted into a gradation value N when M = 1, and is converted into a gradation value NM + 2 when M> 1.

  When the magnitude relationship of dots is reversed as shown in FIG. 16C, ink is ejected from all nozzles when the dummy jet is executed, and the ejection state of the inkjet head 16 can be kept better.

  16B and 16B, the dummy jet image data corresponding to the dummy jet image in which the density is inverted with respect to the drawing image is generated. If necessary, it can be changed as appropriate.

  According to the second embodiment described above, the same effects as those of the first embodiment can be obtained, and the configuration of the image processing unit 86 is further simplified.

  In this example, an example is shown in which four gradations are represented by four types of dot sizes including no dots, but the scope of application of the present invention is not limited to this example. Further, the present invention can also be applied to a mode in which one pixel is constituted by a plurality of dots (dots of the same size) and expresses two or more gradations.

[Other device configuration examples]
FIG. 17 is an explanatory diagram of another apparatus configuration. In the ink jet recording apparatus 300 shown in the figure, an impression cylinder conveyance method is used in which a recording medium (not shown) is conveyed along the outer circumferential surface of the impression cylinder 314 while the recording medium is held on the outer circumferential surface of the impression cylinder 314. The

  The recording medium transferred from the recording medium supply unit (not shown) to the transfer cylinder 328 is conveyed directly below the printing unit 317 while being held on the outer peripheral surface of the impression cylinder 314. Color ink is ejected from the inkjet heads 316K, 316C, 316M, and 316Y provided in the printing unit 317 to form a desired image on the recording medium.

  The inkjet heads 316K, 316C, 316M, and 316Y shown in the figure are disposed obliquely with respect to the horizontal plane so that the nozzle surface is orthogonal to the normal line of the outer peripheral surface of the impression cylinder 314. With this configuration, the distance (clearance) between the recording medium and the nozzle surface is kept constant.

  The recording medium on which the image is formed is transferred from the impression cylinder 314 to the transfer cylinder 332. Thereafter, after a predetermined post-process (drying process, fixing process, etc.) is performed, the sheet is discharged from the discharge unit. There may be a mode in which a pretreatment process (a treatment liquid application process, a heating process, or the like) is performed before image formation by the printing unit 317.

  The configurations of the printing unit 317, the control system, and the maintenance processing unit in the inkjet recording apparatus 300 illustrated in FIG. 17 can be the same configurations as those of the inkjet recording apparatus 10 described above.

  The above-described inkjet recording apparatus and inkjet head maintenance method can be appropriately changed, added, and deleted without departing from the spirit of the present invention.

[Invention disclosed in this specification]
As will be understood from the description of the embodiments of the invention described in detail above, the present specification includes disclosure of various technical ideas including at least the invention described below.

  (First aspect): Ink-jet head provided with a plurality of nozzles, a drawing image processing unit that generates drawing image data from input image data, and a magnitude relationship between gradation values in drawing image data from input image data A pre-discharge image processing unit that generates image data for pre-discharge, and drawing for discharging ink from an inkjet head onto a recording medium based on the image data for drawing, and the image data for pre-discharge An ink jet recording apparatus comprising: an ejection control unit that performs preliminary ejection by ejecting ink from an ink jet head based thereon.

  According to the first aspect, preliminary discharge image data for generating a preliminary discharge image in which the magnitude relationship between the gradation values in the drawing image is reversed is generated from the input image data. In this preliminary ejection image, each nozzle in the drawing image is ejected more frequently from the less frequently used nozzles, and less frequently ejected from the nozzles that are used more frequently. Therefore, it is not necessary to create dedicated software for performing this operation, and it is not necessary to secure a processing unit (PLD, FPGA, etc.) for generating the dot data, and the ink consumption during preliminary ejection is suppressed.

  It is preferable that the preliminary ejection image data is generated for each drawing image data.

  (Second Aspect): In the inkjet recording apparatus according to the first aspect, the drawing image processing unit includes a gamma correction processing unit that performs a gamma correction process using a gamma correction coefficient on the input image data, The discharge image processing unit performs an inversion process using an inversion coefficient obtained by inverting the magnitude relationship of the gamma correction coefficients with respect to the input image data.

  According to the second aspect, since the inversion coefficient is generated by inverting the magnitude relationship of the existing gamma correction coefficients, the pre-ejection for which the use frequency for each nozzle is reflected without detecting the use frequency for each nozzle. Data is generated.

  (Third Aspect): In the ink jet recording apparatus according to the first aspect, the drawing image processing unit includes a gamma correction processing unit that performs gamma correction processing using a gamma correction coefficient on the input image data. The ejection image processing unit inverts the input image data by using the inversion coefficient obtained by inverting the magnitude relationship of the gamma correction coefficients and approximating the line.

  According to the third aspect, since the reversal process using a simpler reversal coefficient is performed, the processing load of the image processing for generating the preliminary ejection image is reduced.

  (Fourth aspect): In the ink jet recording apparatus according to any one of the first to third aspects, the preliminary ejection image processing unit uses an inversion coefficient whose value exceeds 0 in the entire range of the input image data. Inversion processing is applied to the input image data.

  According to this aspect, since ink is ejected from all the nozzles in the preliminary ejection, a preferable ejection state is maintained for all the nozzles after the preliminary ejection.

  (Fifth aspect): An inkjet head provided with a plurality of nozzles, and halftone processing is performed on input image data to obtain N (where N is an integer equal to or greater than 2 and less than the gradation value of the input image data). A drawing image processing unit for generating the drawn drawing image data, a preliminary ejection image processing unit for generating preliminary ejection image data obtained by inverting the magnitude relationship of the gradation values in the drawing image data, and a drawing image And an ejection control unit that performs drawing by ejecting ink from the inkjet head on the recording medium based on the data, and performs preliminary ejection by ejecting ink from the inkjet head based on the image data for preliminary ejection. Inkjet recording device.

  According to the fifth aspect, the preliminary ejection image data is generated by inverting the magnitude relationship between the gradation values of the drawing image data. In this preliminary ejection image data, each nozzle in the drawing image is ejected more frequently from the less frequently used nozzles and less frequently ejected from the nozzles that are used more frequently. It is not necessary to create dedicated software for generation, it is not necessary to secure a processing unit (PLD, FPGA, etc.) for generating the dot data, and the ink consumption during preliminary ejection is suppressed.

  Further, the drawing image processing unit and the preliminary ejection image processing unit can also have a configuration of a processing unit that performs processing up to halftone processing.

  (Sixth Aspect): In the ink jet recording apparatus according to the fifth aspect, the preliminary ejection image processing unit converts the gradation value M of the drawing image data (where M is an integer from 1 to N) to a gradation value ( N−M + 1) to generate preliminary discharge image data.

  In the sixth aspect, the multi-tone may be expressed by modulating the size of the dots constituting one pixel, or the multi-tone may be expressed by modulating the number of dots constituting one pixel.

  (Seventh Aspect): In the ink jet recording apparatus according to the fifth aspect, the preliminary ejection image processing unit calculates the gradation value M (where M is an integer from 1 to N) of the image data for drawing, M = 1 Is converted to a gradation value N, and when M> 1, it is converted to a gradation value (N−M + 1) to generate preliminary ejection image data.

  According to the seventh aspect, since ink is ejected from all the nozzles in the preliminary ejection, a preferable ejection state is maintained for all the nozzles after the preliminary ejection.

  (Eighth Aspect): In the ink jet recording apparatus according to any one of the first aspect to the seventh aspect, the ink jet recording apparatus includes a moving unit that moves the ink jet head to the non-drawing area when the preliminary ejection is executed. Performs preliminary ejection of the inkjet head in the non-drawing area after drawing.

  As an example of the non-drawing area in the eighth aspect, the non-drawing area includes a maintenance position for performing maintenance on the inkjet head.

  (Ninth aspect): In the ink jet recording apparatus according to any one of the first aspect to the seventh aspect, the ejection control unit performs preliminary ejection of the ink jet head on the recording medium after or during the drawing at the drawing position. Let

  According to the ninth aspect, preliminary ejection of the inkjet head can be performed without moving the inkjet head to the non-drawing position.

  (Tenth aspect): In the ink jet recording apparatus according to the ninth aspect, the ejection control means causes the image based on the preliminary ejection image data to be drawn in the drawing area of the recording medium in the preliminary ejection of the inkjet head.

  According to the tenth aspect, the preliminary ejection of the ink-jet head can be executed as a series of steps in drawing, so that it is not necessary to replace the steps for preliminary ejection.

  (Eleventh aspect): In the ink jet recording apparatus according to the ninth aspect, in the preliminary ejection of the inkjet head, the ejection control means divides and draws an image based on the preliminary ejection image data in a blank area of the recording medium.

  According to the eleventh aspect, a recording medium for preliminary ejection becomes unnecessary, and wasteful consumption of the recording medium is suppressed.

  (Twelfth aspect): In an ink jet recording apparatus including an ink jet head having a plurality of nozzles, a drawing image processing step for generating drawing image data from input image data, and drawing image data from input image data Preliminary ejection image processing step for generating preliminary ejection image data in which the magnitude relationship of the gradation values is reversed, a drawing step for ejecting ink from the inkjet head onto the recording medium based on the drawing image data, and preliminary ejection And a preliminary ejection step of ejecting ink from the inkjet head based on the image data for use.

  In the twelfth aspect, the drawing image processing step includes a gamma correction processing step of performing gamma correction processing using a gamma correction coefficient on the input image data, and the preliminary ejection image processing step includes gamma correction on the input image data. It is preferable to perform an inversion process using an inversion coefficient obtained by inverting the magnitude relationship of the correction coefficients.

  The drawing image processing step includes a gamma correction processing step for performing gamma correction processing using a gamma correction coefficient on the input image data, and the preliminary ejection image processing step inverts the magnitude relationship of the gamma correction coefficients. In addition, it is preferable to perform an inversion process on the input image data using an inversion coefficient approximated by a straight line.

  Furthermore, it is preferable that the image processing step for preliminary ejection performs an inversion process on the input image data using an inversion coefficient having a value exceeding 0 in the entire range of the input image data.

  (Thirteenth aspect): In an inkjet recording apparatus including an inkjet head having a plurality of nozzles, halftone processing is performed on input image data, where N is a gradation value of input image data of 2 or more. Less than integer) drawing image processing step for generating converted drawing image data, and preliminary ejection image processing for generating preliminary ejection image data in which the magnitude relationship of the gradation values in the drawing image data is reversed A drawing process for performing drawing by ejecting ink onto a recording medium from an ink jet head based on the image data for drawing, and a preliminary for performing preliminary ejection by ejecting ink from the ink jet head based on the image data for preliminary ejection And a discharging step.

  In the thirteenth aspect, the preliminary ejection image processing step converts the gradation value M (where M is an integer from 1 to N) of the drawing image data into a gradation value (N−M + 1) and performs preliminary ejection image processing. A mode of generating data is preferred.

  In the preliminary ejection image processing step, the gradation value M (where M is an integer from 1 to N) of the image data for drawing is converted into a gradation value N when M = 1, and M> 1. In this case, it is preferable that the preliminary ejection image data is generated by converting the gradation value (N−M + 1).

  Furthermore, in the twelfth and thirteenth aspects, the preliminary ejection step includes a movement step of moving the inkjet head to the non-drawing area when the preliminary ejection is executed. A mode in which is executed is preferable.

  In addition, it is preferable that the preliminary discharge process is performed by performing preliminary discharge of the ink jet head on the recording medium after or during drawing at the drawing position.

  Furthermore, it is preferable that the preliminary ejection step is such that an image based on the preliminary ejection image data is drawn in the drawing area of the recording medium in the preliminary ejection of the inkjet head.

  Furthermore, it is preferable that the preliminary discharge step is an aspect in which an image based on the preliminary discharge image data is divided and drawn in a blank area of the recording medium in the preliminary discharge of the inkjet head.

  DESCRIPTION OF SYMBOLS 10,300 ... Inkjet recording device, 16, 16K, 16C, 16M, 16Y, 316K, 316C, 316M, 316Y ... Inkjet head, 40 ... Maintenance processing unit, 54 ... Nozzle, 82 ... System control unit, 86 ... Image processing unit , 88... Head drive unit, 106... Dummy jet image data storage unit, 140, 158... Inversion processing unit, 141 .. Inversion coefficient storage unit, 200, 204, 206.

Claims (13)

An inkjet head comprising a plurality of nozzles;
A drawing image processing unit for generating drawing image data from input image data;
A preliminary ejection image processing unit that generates preliminary ejection image data obtained by inverting the magnitude relationship of gradation values in the drawing image data from the input image data;
Discharge control means for performing drawing for discharging ink from the inkjet head onto a recording medium based on the drawing image data, and for performing preliminary discharge by discharging ink from the inkjet head based on the preliminary discharge image data; ,
An ink jet recording apparatus comprising: The drawing image processing unit includes a gamma correction processing unit that performs gamma correction processing using a gamma correction coefficient on input image data,
The inkjet recording apparatus according to claim 1, wherein the preliminary ejection image processing unit performs an inversion process using an inversion coefficient obtained by inverting the magnitude relationship of the gamma correction coefficient with respect to input image data. The drawing image processing unit includes a gamma correction processing unit that performs gamma correction processing using a gamma correction coefficient on input image data,
2. The inkjet according to claim 1, wherein the preliminary ejection image processing unit performs a reversal process on the input image data using a reversal coefficient obtained by reversing the magnitude relationship of the gamma correction coefficients and linearly approximating. Recording device.   The image processing unit for preliminary ejection performs inversion processing on input image data using an inversion coefficient whose value exceeds 0 in the entire range of input image data. Inkjet recording device. An inkjet head comprising a plurality of nozzles;
A drawing image processing unit that performs halftone processing on the input image data to generate drawing image data that has been converted to N (where N is an integer that is greater than or equal to 2 and less than the gradation value of the input image data);
A preliminary ejection image processing unit that generates preliminary ejection image data in which the magnitude relationship between the gradation values in the drawing image data is reversed;
An ejection control unit that performs drawing by ejecting ink from an inkjet head onto a recording medium based on the image data for drawing, and that performs preliminary ejection by ejecting ink from the inkjet head based on the image data for preliminary ejection When,
An ink jet recording apparatus comprising:   The preliminary ejection image processing unit generates a preliminary ejection image data by converting a gradation value M (where M is an integer from 1 to N) of the drawing image data into a gradation value (N−M + 1). An ink jet recording apparatus according to claim 5.   The preliminary ejection image processing unit converts the gradation value M of the drawing image data (where M is an integer from 1 to N) into a gradation value N when M = 1, and M> 1. The inkjet recording apparatus according to claim 5, wherein the preliminary ejection image data is generated by converting to a gradation value (N−M + 1). A moving means for moving the inkjet head to a non-drawing area when preliminary ejection is performed;
The inkjet recording apparatus according to claim 1, wherein the ejection control unit causes preliminary ejection of the inkjet head in the non-rendering region after rendering.   8. The inkjet recording apparatus according to claim 1, wherein the ejection control unit causes the inkjet head to perform preliminary ejection on a recording medium after or at the drawing position.   The inkjet recording apparatus according to claim 9, wherein the ejection control unit draws an image based on image data for preliminary ejection in a rendering area of the recording medium during preliminary ejection of the inkjet head.   The inkjet recording apparatus according to claim 9, wherein the ejection control unit divides and draws an image based on the preliminary ejection image data in a blank area of the recording medium in preliminary ejection of the inkjet head. In an inkjet recording apparatus including an inkjet head provided with a plurality of nozzles,
A drawing image processing step for generating drawing image data from input image data;
A preliminary ejection image processing step for generating preliminary ejection image data obtained by inverting the magnitude relationship of gradation values in the drawing image data from the input image data;
A drawing step of discharging ink from an inkjet head onto a recording medium based on the drawing image data;
A preliminary ejection step of ejecting ink from the inkjet head based on the preliminary ejection image data;
An inkjet head maintenance method including: In an inkjet recording apparatus including an inkjet head provided with a plurality of nozzles,
A drawing image processing step of generating drawing image data that has been subjected to halftone processing on the input image data and converted to N (where N is an integer that is greater than or equal to 2 and less than the gradation value of the input image data);
A preliminary ejection image processing step of generating preliminary ejection image data in which the magnitude relationship between the gradation values in the drawing image data is reversed;
A drawing process for drawing by discharging ink from the inkjet head onto the recording medium based on the drawing image data;
A preliminary ejection step of performing preliminary ejection by ejecting ink from an inkjet head based on the preliminary ejection image data;
An inkjet head maintenance method including:

Images