JP2017064920A - Liquid ejection device and method of adjusting the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more adequately suppress influence of variation of nozzle ejection characteristics of a nozzle at an ejection head.SOLUTION: A liquid discharge device 10 comprises an ink jet head 12 which is an ejection head, a drive signal output part 18, an ejection nozzle setting part 20, and an ejection characteristic record part 22. The drive signal output part 18 includes a setting voltage output part 34 which outputs a plurality of setting voltage signal that are set at voltages different from each other, and a selective voltage supply part 36 which supplies either setting voltage signal as a drive signal to the piezo element 104 corresponding to the nozzle ejecting liquid droplets at the timing of at least a part of the period of drive signal supply to the piezo element 104. The selective voltage supply apart 36, based on the ejection characteristic recorded in the ejection characteristic record part 22, supplies the setting voltage signal which is made in advance correspond to the ejection characteristic of the nozzle to the piezo element 104 corresponding to each nozzle.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a liquid ejection device and a method for adjusting a liquid ejection device.

  Conventionally, ink jet printers that perform printing by an ink jet method have been widely used (see, for example, Non-Patent Document 1). In an inkjet printer, printing is performed by ejecting ink droplets from nozzles of an inkjet head.

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  In an ink jet head, due to the structure of ejecting ink droplets from fine nozzles, it is unavoidable that variations in ink droplet ejection characteristics will occur to some extent. For this reason, various methods for correcting variations in ejection characteristics of the ink jet head have been studied.

  For example, in the case of a serial-type inkjet printer that performs a main scanning operation (scanning operation) that ejects ink droplets while moving in a preset main scanning direction (Y-axis direction), it is necessary to correct variations in ejection characteristics. As one of the methods, conventionally, a method of performing printing by a multi-pass method is known. The multi-pass method is a method in which, for example, a main scanning operation is performed a plurality of times for each position of a printing area where printing is performed on a medium to be printed.

  In this method, for example, when the variation in the ejection characteristics of the nozzles in the inkjet head is within a certain range, the characteristics of each nozzle are not corrected, and the inkjet heads are different in a plurality of main scanning operations performed for each position. In this method, ink droplets are ejected from a portion (nozzle). In such a configuration, the same line is mixed and printed by a plurality of nozzles in the ink jet head, so that variations in the ejection characteristics of the individual nozzles can be averaged to make them unnoticeable.

  However, when printing by the multi-pass method, the printing speed decreases according to the number of passes for performing the main scanning operation on each position of the medium, and it becomes difficult to perform printing at high speed. More specifically, for example, when the number of passes in the multi-pass method is N, the printing speed is reduced to 1 / N compared to the case where printing in the multi-pass method is not performed. In addition, when printing is performed using the multi-pass method, the effect of nozzle variation is averaged and becomes difficult to see in applications where observation is performed from a distant position away from the medium. However, in the case where the printing result is visually recognized near the medium, the influence of the characteristic variation of the nozzle is seen, and the image quality may be deteriorated. In addition, for example, when printing printed wiring or the like for use in an industrial field, there is a possibility that the electrical characteristics may be adversely affected.

  Further, as a method for correcting the variation in the ejection characteristics of the nozzles, a method of performing correction in units of ink jet heads (a method of correcting head characteristics for each head unit) can be considered. In this case, for example, the variation in the nozzle ejection characteristics is measured for each inkjet head instead of each nozzle, and the central value of the variation of each inkjet head is divided into a plurality of stages. Then, for each characteristic category, determine the head group to be incorporated in one printer, or change the ejection conditions such as the pulse width and voltage of the signal (drive signal) that controls the ejection of ink droplets for each inkjet head, To suppress the variation of This also corrects variations in average discharge characteristics between inkjet heads, rather than correcting the discharge characteristics for each nozzle.

  However, in this method, since the variation in the ejection characteristics of the nozzles in the ink jet head cannot be corrected, it is necessary to use it together with another method such as a multi-pass method. As a result, the same problem as in the case of employing another method such as a multipath method occurs.

  In principle, it is also conceivable to change the signal voltage or the like for each nozzle for the drive signal for controlling the ejection of ink droplets from each nozzle. In this case, for example, in a configuration in which the ejection of ink droplets from the nozzles is controlled by the push-pull method, the voltage for controlling the push or pull operation is adjusted so that the volume of the ink droplets becomes a certain predetermined volume. It is possible.

  If comprised in this way, it will become possible to correct | amend an ejection characteristic separately about each nozzle. However, in this case, for example, voltage regulator circuits for adjusting the signal voltage are required by the number of nozzles. As a result, the circuit scale may be too large. Therefore, hitherto, this method has not been put to practical use.

  Conventionally, as a configuration of an ink jet printer, a configuration of an ink jet printer (line ink jet printer) that performs printing by a line method without performing a main scanning operation on an ink jet head is also known. As a method for suppressing the influence of variation in the discharge characteristics of the nozzles, a method applicable to a line inkjet printer is also being studied.

  For example, a method using an inkjet head with little variation in nozzle discharge characteristics, such as a Fine head developed by Canon Inc., is known. However, when such a method is used, the configuration of the inkjet head becomes complicated, and there is a possibility that miniaturization becomes difficult. In particular, it is difficult to achieve sufficient miniaturization in the case of a piezo-type inkjet head that ejects ink droplets using a piezo element instead of the thermal-type inkjet head employed in a Fine head. Conceivable.

  Also, for example, a method in which a minute heater is provided for each nozzle, the ink viscosity is adjusted by changing the temperature at the position of each nozzle, and the ejection characteristics such as ink capacity and ejection direction are adjusted (micro heater control method) Etc. are also being studied. However, in this case, since it is necessary to newly provide a large number of minute heaters, the cost of the inkjet head may be significantly increased.

  In addition, as a method for averaging discharge characteristics similar to the multi-pass method with a line ink jet printer, for example, a plurality of nozzle rows arranged in a predetermined Y-axis direction are provided for each color ink jet head used for printing. The same line extending in the Y-axis direction is mixed and printed by each nozzle (plurality of nozzles) in a plurality of nozzle rows to make the discharge variation of individual nozzles inconspicuous (multiple dot arrangement averaging method), etc. Is also possible. However, in this case, since it is necessary to provide a plurality of nozzle rows for each color, the cost may increase significantly.

  For this reason, there has been a demand for a method that more appropriately suppresses the influence of variations in the ejection characteristics of nozzles in an inkjet head. SUMMARY An advantage of some aspects of the invention is that it provides a liquid ejection apparatus and a liquid ejection apparatus adjustment method that can solve the above-described problems.

  The inventor of the present application has conducted intensive research on a method for appropriately suppressing the influence of variation in the discharge characteristics of the nozzles. In addition, more specifically, a method for reducing the influence of the variation occurring in the printing result to a level that does not cause a practical problem by eliminating or reducing the variation of the nozzle itself, instead of averaging the variation of the nozzle, We conducted intensive research.

  For the drive signal that controls the ejection of ink droplets from each nozzle, the ejection characteristics (ejection amount, etc.) are adjusted by directly changing the voltage for each drive element using a voltage regulator circuit or the like. Instead, it was considered to select a signal corresponding to the ejection characteristics from a plurality of types of voltage signals prepared in advance. As such a configuration, more specifically, for example, it was considered to classify the method of variation in ejection characteristics into a plurality of sections and prepare a voltage signal corresponding to each section in advance.

  If comprised in this way, the voltage of the signal supplied to the drive element of each nozzle can be varied for every nozzle, for example. In this case, for example, the discharge amount of each nozzle can be adjusted with a simpler circuit configuration as compared with the case where the voltage of the drive signal supplied to the drive element of each nozzle is adjusted by an individual regulator or the like. Therefore, if configured in this way, for example, it is possible to adjust the ejection characteristics of each nozzle with a practical circuit configuration.

  Such a configuration can be used not only in a printing apparatus (inkjet printer) that prints a two-dimensional image but also in various apparatuses using an inkjet head. For example, it can be considered that the present invention is applied to a liquid ejection apparatus that forms wiring by ejecting ink droplets (liquid droplets) of functional ink (liquid) from an inkjet head. Moreover, applying to the modeling apparatus etc. which model a solid thing using an inkjet head etc. is also considered. That is, the present invention for solving the above-described problems has the following configuration.

  (Configuration 1) A liquid discharge apparatus that discharges droplets by an inkjet method, and includes a plurality of nozzles that respectively discharge droplets by an inkjet method and a plurality of drive elements that respectively discharge droplets from the nozzles. An ejection head, a drive signal output unit that outputs a drive signal for driving the drive element, an ejection nozzle setting unit that sets a nozzle that ejects droplets by selecting a drive element that receives the drive signal, and each nozzle A discharge characteristic storage unit that stores the discharge characteristic of the drive signal, and the drive signal output unit outputs a plurality of set voltage signals that are a plurality of types of signals set to different voltages, and a drive element At least part of the period of supplying the drive signal to the drive element, the drive signal corresponding to the nozzle that discharges droplets as the drive signal, A selection voltage supply unit that supplies a set voltage signal of any one of the displacements, and the selection voltage supply unit sets the discharge characteristics of the nozzles stored in the discharge characteristic storage unit for the drive elements corresponding to the respective nozzles. Based on this, a set voltage signal associated in advance with the ejection characteristics of the nozzle is supplied.

  When configured in this way, for example, by setting the set voltage signal supplied to each drive element individually for each drive element, the voltage applied to each drive element at least at some timing of the drive signal Can be set individually for each drive element. This also makes it possible to individually adjust the volume of liquid droplets ejected from each nozzle in accordance with the drive signal, for each nozzle. Therefore, with this configuration, for example, the variation in the ejection characteristics of the nozzles can be appropriately reduced without averaging the variation in the ejection characteristics using a multi-pass method or the like. In addition, this makes it possible to appropriately reduce, for example, the effect of variations in ejection characteristics that occur in the printing result to a level that does not cause a problem in practice.

  In this case, for example, the required circuit configuration can be greatly reduced in scale as compared with a case where a voltage regulator circuit for adjusting the voltage of the drive signal is provided for each nozzle. In addition, this makes it possible to individually adjust the ejection characteristics of each nozzle for each nozzle, for example, with a circuit scale within a practical range. For this reason, with this configuration, for example, the influence of variations in the ejection characteristics of the nozzles can be appropriately suppressed within a practically unaffected range.

  Here, in this configuration, for example, by supplying different set voltage signals to a plurality of nozzles having different volumes of droplets that are discharged when receiving the same drive signal, the volume of the droplets is reduced. Adjust so that it is closer. If comprised in this way, the adjustment of the discharge characteristic of the droplet by each nozzle can be performed more appropriately, for example.

  In this configuration, the discharge nozzle setting unit can select, for example, a plurality of nozzles that discharge droplets having the same capacity set in advance as nozzles that discharge droplets. The plurality of nozzles that discharge droplets having the same volume set in advance are, for example, a plurality of nozzles that discharge droplets having the same volume with respect to the designed droplet volume. More specifically, for example, in the case of a configuration in which only one type of liquid droplet is ejected by a single nozzle, the same volume of liquid droplet is the one type of liquid droplet. In addition, for example, a droplet having a volume selected from a plurality of types of volumes can be ejected by a single nozzle, such as a configuration in which multiple volumes with different volumes can be set as the volume of the droplet (for example, a variable dot configuration). In the case of the configuration, the droplet having the same volume may be, for example, a droplet having any one of a plurality of volumes. In this case, the set voltage output unit outputs a plurality of set voltage signals in common to a plurality of nozzles that eject droplets of the same volume, for example. The selection voltage supply unit corresponds in advance to the discharge characteristics of the nozzles based on the discharge characteristics of the nozzles stored in the discharge characteristic storage unit for each of the plurality of nozzles that discharge the same volume of droplets. Supply the set voltage signal. If comprised in this way, the adjustment of the discharge characteristic of a nozzle can be performed more appropriately, for example.

  In this configuration, the liquid ejection device is, for example, a printing device (inkjet printer) that prints a two-dimensional image. The liquid ejection apparatus may be an apparatus that performs an operation other than image printing by ejecting functional liquid droplets. For example, the liquid discharge device may be a device that forms conductive wiring by discharging a droplet of conductive liquid. Further, the liquid ejection device may be a modeling device that models a three-dimensional object by ejecting droplets, for example. In this case, the liquid ejection device forms a three-dimensional object by an additive manufacturing method, for example, by stacking a plurality of layers formed by droplet ejection.

  (Configuration 2) The discharge characteristic storage unit classifies and stores the discharge characteristic of each nozzle in one of n preset categories (n is an integer of 2 or more), and the set voltage output unit , N kinds of setting voltage signals respectively associated with each of the n sections are output, and the selection voltage supply unit outputs the ejection characteristics of the nozzles to the ejection characteristics storage unit for the drive elements corresponding to the respective nozzles. The set voltage signal associated with the category is supplied in accordance with the category classified in FIG.

  When configured in this manner, for example, the ejection characteristics of each nozzle can be stored more appropriately in the ejection characteristics storage unit. In the selection voltage supply unit, it is possible to more appropriately supply a set voltage signal corresponding to the ejection characteristics of each nozzle to each nozzle.

  (Configuration 3) The set voltage output unit outputs signals of constant voltages having different voltages as each of the plurality of set voltage signals. If comprised in this way, the adjustment of the discharge characteristic of each nozzle can be performed more appropriately, for example.

  (Configuration 4) The drive element is a piezo element that is displaced according to a drive signal. The displacement according to the drive signal may be, for example, a displacement according to the voltage of the drive signal. If comprised in this way, the adjustment of the discharge characteristic of each nozzle can be performed appropriately, for example by setting the setting voltage signal supplied to each piezo element for every piezo element.

  (Configuration 5) The drive signal output unit includes, as at least a part of the drive signal, a first pull signal that is a voltage signal for displacing the piezo element so as to draw liquid into the ink chamber in front of the nozzle, and the first pull signal. The push signal, which is a voltage signal that displaces the piezo element so that the liquid drawn in response to the nozzle is pushed out from the nozzle, and the piezo element that pushes back part of the liquid pushed out from the nozzle in response to the push signal into the nozzle And a second pull signal that is a signal for displacing the liquid crystal, and each driving element sequentially receives the first pull signal, the push signal, and the second pull signal, thereby ejecting droplets from the corresponding nozzle, The selection voltage supply unit supplies a setting voltage signal to the driving element as at least one of the first pull signal, the push signal, and the second pull signal. That.

  When configured in this manner, the first pull signal, the push signal, and the second pull signal are sequentially received by the respective driving elements, so that, for example, the same or the same as the droplet discharge in the known push-pull method is used. Thus, droplets can be appropriately discharged from the respective nozzles. Further, by supplying the set voltage signal as at least one of the first pull signal, the push signal, and the second pull signal, for example, the ejection characteristics of each nozzle can be adjusted more appropriately.

  (Structure 6) A liquid ejection apparatus adjustment method for adjusting droplet ejection characteristics in the liquid ejection apparatus according to any one of Structures 1 to 5, wherein a set voltage signal supplied to each drive element is supplied to each drive element. By individually setting, the ejection characteristics of droplets from each nozzle are adjusted. If comprised in this way, the discharge characteristic of the droplet from each nozzle can be adjusted appropriately, for example.

  (Structure 7) The discharge characteristics of each nozzle when a preset reference drive signal is used are measured in advance, and the drive element corresponding to each nozzle is selected according to the measured discharge characteristics. And a set voltage signal selected according to the measured ejection characteristic is supplied as at least a part of the drive signal. If comprised in this way, it can adjust more appropriately based on the measurement result acquired beforehand about the discharge characteristic of each nozzle, for example.

  (Configuration 8) With respect to an operation for measuring the ejection characteristics of each nozzle in advance when a reference drive signal is used, a straight line is drawn on each nozzle using the reference drive signal, and the line width of the straight line is measured. The nozzle discharge characteristics are measured in advance.

  If comprised in this way, the capacity | capacitance of the droplet discharged from each nozzle can be indirectly detected, for example by measurement of line width. In addition, this makes it possible to easily and appropriately measure the ejection characteristics of each nozzle as compared with, for example, the case where the volume of a droplet is directly confirmed.

  The operation of drawing a straight line for each nozzle is substantially continuous by, for example, ejecting droplets continuously from the nozzle during the main scanning operation of moving the ejection head in the main scanning direction (Y-axis direction). May be an operation of printing. In this case, it is preferable to perform a plurality of main scanning operations for all the nozzles of the ejection head by using only some of the nozzles each time. In this case, based on the result of the variation in the discharge characteristics of the nozzles detected as the line width, for example, it may be possible to adjust the discharge characteristics for the nozzles within a predetermined variation range.

  (Configuration 9) For nozzles whose ejection characteristics are within a preset range, the ejection characteristics of the nozzles are adjusted, and for nozzles whose ejection characteristics are outside the preset range, the nozzles are defective nozzles It is determined that In this case, for example, with respect to the ejection characteristics of the nozzle, a deviation from a preset center value is calculated, and if the deviation is within a predetermined fixed value range, correction is performed. It can be discriminated.

  If comprised in this way, it can correct | amend appropriately with respect to the nozzle from which the discharge characteristic shifted | deviated within the range which can be correct | amended, for example. This also makes it possible to appropriately reduce the number of ejection heads that are defective. Further, in this case, for example, a nozzle whose ejection characteristics are greatly deviated is determined as a defective nozzle, thereby eliminating the need for excessive correction. If comprised in this way, it will become possible to use the structure which can correct | amend only with respect to the nozzle of the discharge characteristic within a fixed range, for example, and can correct | amend appropriately with a simpler structure.

  According to the present invention, for example, it is possible to more appropriately suppress the influence of variations in the ejection characteristics of nozzles in the ejection head.

It is a figure which shows an example of the liquid discharge apparatus 10 which concerns on one Embodiment of this invention. FIG. 1A shows an example of the configuration of the main part of the liquid ejection apparatus 10. FIG. 1B shows an example of the configuration of the inkjet head 12 in the liquid ejection apparatus 10. It is a figure which shows an example of the conventional drive signal. It is a figure which shows an example of the method of discharging the ink drop of various capacity | capacitance by the method of driving a piezo element. It is a figure explaining the measuring method (detection method) of line | wire width. FIG. 4A is a diagram showing a simplified configuration of the inkjet head 12. 4B and 4C show an example of a straight line to be measured for line width. It is a figure which shows an example of the measurement result of line | wire width. FIG. 5A shows an example of the measurement result of the line width for a plurality of straight lines drawn by the odd-numbered nozzles 102. FIG. 5B shows an example of line width measurement results for a plurality of straight lines drawn by the even-numbered nozzles 102. It is a figure which shows an example of the variation in the discharge characteristic of a nozzle. It is a figure which shows an example of a mode that a landing position changes with the change of the capacity | capacitance of an ink drop. It is a figure which shows an example of the velocity component of the ink droplet in flight. It is a figure which demonstrates in more detail about the correction | amendment operation | movement in this example. It is a figure which simplifies and shows the equivalent circuit of the drive circuit which drives the piezoelectric element 104 in an inkjet head. 4 is a diagram specifically showing a part of a drive circuit that supplies a drive signal to a piezo element 104. FIG. It is a figure which shows the modification of a drive signal.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. FIG. 1 shows an example of a liquid ejection apparatus 10 according to an embodiment of the present invention. FIG. 1A shows an example of the configuration of the main part of the liquid ejection apparatus 10. FIG. 1B shows an example of the configuration of the inkjet head 12 in the liquid ejection apparatus 10.

  In this example, the liquid ejection apparatus 10 is a printing apparatus (inkjet printer) that performs printing by an inkjet method, and prints a two-dimensional image by ejecting ink droplets onto a medium 50 that is a medium to be printed. To do. In this case, the ink droplet is an example of a droplet ejected by an inkjet method. Except as described below, the liquid ejection device 10 may have the same or similar features as a known inkjet printer. In addition to the illustrated configuration, the liquid ejection device 10 may further include various configurations necessary for the printing operation. For example, the liquid ejecting apparatus 10 may further include means for fixing the ink on the medium 50 according to the type of ink to be used.

  In this example, the liquid ejection apparatus 10 includes an inkjet head 12, a platen 14, a scanning drive unit 16, a drive signal output unit 18, a discharge nozzle setting unit 20, a discharge characteristic storage unit 22, and a control unit 24. The inkjet head 12 is an example of an ejection head that ejects droplets by an inkjet method. As the inkjet head 12, for example, a known inkjet head can be suitably used.

  In this example, the ink jet head 12 is an ink jet head that ejects ink droplets by a piezo method, and a plurality of nozzles 102 that respectively eject ink droplets by an ink jet method, and ink droplets are ejected from the respective nozzles 102. A plurality of piezo elements 104. In this case, as shown in FIG. 1B, for example, the plurality of nozzles 102 are arranged in a predetermined nozzle row direction (for example, the X direction in the drawing) to form a nozzle row. In addition, each of the plurality of piezo elements 104 is disposed at a position corresponding to each nozzle 102 inside the inkjet head 12. The piezo element 104 is an example of a drive element, and is displaced according to a drive signal received from the drive signal output unit 18 via the scanning drive unit 16, thereby ejecting ink droplets from the corresponding nozzle 102.

  Although not shown, the inkjet head 12 further includes, for example, an ink chamber (pressure chamber) that stores ink at the front stage of the nozzle 102. In this case, the piezo element 104 ejects ink from the nozzle 102 by compressing and pushing out the ink in the ink chamber by displacement. The operation of ejecting ink droplets from the nozzle 102 in accordance with the drive signal will be described in more detail later.

  Further, in FIG. 1A, only one inkjet head 12 is illustrated as a configuration of the liquid ejection apparatus 10 for the sake of simplicity. However, the liquid ejection apparatus 10 may include a plurality of inkjet heads 12. In this case, for example, it is conceivable to include a plurality of inkjet heads 12 that eject ink droplets of different colors.

  The platen 14 is a table-like member that holds the medium 50, and places the medium 50 on the upper surface at a position facing the inkjet head 12. The scanning drive unit 16 is a drive unit that moves the inkjet head 12 relative to the medium 50. In this example, the scanning drive unit 16 supplies the drive signal received from the drive signal output unit 18 to the inkjet head 12, for example, and moves the inkjet head 12 in a preset main scanning direction (for example, the Y direction in the figure). By moving, the inkjet head 12 is caused to perform a main scanning operation of ejecting ink droplets while moving in the main scanning direction. Further, for example, by moving the inkjet head 12 relative to the medium 50 in the sub-scanning direction (for example, the X direction in the figure) orthogonal to the main scanning direction between the main scanning operations, the sub-scanning operation is performed by the inkjet scanning. Let the head 12 do this. In this case, the sub-scanning operation is, for example, an operation for changing the position of the medium 50 that faces the inkjet head 12.

  The drive signal output unit 18 is a signal output unit that outputs a drive signal for driving the piezo element 104. In this example, the drive signal output unit 18 supplies a drive signal to each piezo element 104 of the inkjet head 12 via the scan drive unit 16, for example.

  In this example, the drive signal output unit 18 includes a common voltage output unit 32, a set voltage output unit 34, and a selection voltage supply unit 36. The common voltage output unit 32 and the set voltage output unit 34 are signal output units that output a signal having a preset voltage, and each output a signal that constitutes a part of the drive signal. More specifically, among these, the common voltage output unit 32 outputs a signal having a preset voltage as a signal constituting a part of the drive signal. In this case, for example, the common voltage output unit 32 may output a plurality of signals that respectively constitute different portions of the drive signal. In this case, the plurality of signals may be constant voltage signals set to different voltages.

  The set voltage output unit 34 outputs a signal constituting another part of the drive signal. In this case, the other part in the drive signal is, for example, a part of the drive signal that is different from the part configured by the signal output from the common voltage output unit 32. In this example, the set voltage output unit 34 outputs a plurality of set voltage signals which are a plurality of types of signals set to different voltages as such signals. In this case, each of the plurality of set voltage signals is a signal that is individually selected for each piezo element 104 corresponding to each nozzle 102, and constitutes a part of the drive signal supplied to each piezo element 104. .

  In this example, the set voltage output unit 34 outputs a signal having a constant voltage with a different voltage as each of the plurality of set voltage signals. More specifically, n types of preset voltage signals (n is an integer equal to or greater than 2) are output as the plurality of preset voltage signals.

  The selection voltage supply unit 36 is a signal supply unit that selects and supplies any set voltage signal to the piezo element 104 corresponding to each nozzle 102. More specifically, the selection voltage supply unit 36 is, for example, a power supply selection circuit having a function capable of selecting a plurality of n stages of applied voltages, and at least a part of a period during which a drive signal is supplied to the piezo element 104. At the timing, any set voltage signal is supplied as a drive signal to the piezo element 104 corresponding to the nozzle 102 that ejects ink droplets. In this example, the selection voltage supply unit 36 selects a set voltage signal based on the ejection characteristics of the nozzles 102 stored in the ejection characteristic storage unit 22. In this case, the selection voltage supply unit 36 supplies, to the piezo element 104 corresponding to each nozzle 102, a set voltage signal that is associated with the ejection characteristics of the nozzle 102 in advance. Further, the drive signals used in this example and the operation of each component in the drive signal output unit 18 will be described in more detail later.

  The discharge nozzle setting unit 20 selects a piezo element 104 that receives a drive signal in the inkjet head 12. In this example, the ejection nozzle setting unit 20 adjusts to the position of the pixel to eject the ink droplet based on the image data indicating the image to be printed, for example, at each timing of ejecting the ink droplet in the main scanning operation. The piezo element 104 that receives the drive signal is selected. This also sets the nozzle 102 for ejecting ink droplets based on the image data.

  In this example, the discharge nozzle setting unit 20 transmits a signal indicating the selected piezo element 104 to the scan driving unit 16. Thereby, the scanning drive unit 16 supplies the drive signal received from the drive signal output unit 18 to, for example, the piezo element 104 selected by the ejection nozzle setting unit 20.

  The discharge characteristic storage unit 22 is a storage unit that stores the discharge characteristics of each nozzle 102. For example, the discharge characteristic storage unit 22 stores the measurement results of the discharge characteristics of the nozzles 102 measured in advance in a plurality of stages. More specifically, in this example, the ejection characteristic storage unit 22 classifies the ejection characteristics of the respective nozzles 102 into any one of n categories respectively associated with each of the n types of set voltage signals. Remember.

  With this configuration, for example, the ejection characteristics of each nozzle 102 can be appropriately stored in the ejection characteristics storage unit 22. Further, in this case, the selection voltage supply unit 36, for example, with respect to the piezo element 104 corresponding to each nozzle 102, according to the classification in which the discharge characteristic of the nozzle 102 is classified in the discharge characteristic storage unit 22 A set voltage signal associated with the section is supplied. With this configuration, for example, it is possible to appropriately supply a set voltage signal corresponding to the ejection characteristics of each nozzle 102 to each nozzle 102.

  The control unit 24 controls the operation of each unit of the liquid ejection apparatus 10. The control unit 24 may be, for example, a CPU of the liquid ejection device 10. According to this example, for example, a printing operation on the medium 50 can be appropriately performed.

  Here, in the above description, an example of the configuration of the liquid ejection apparatus 10 has been described in the case where the liquid ejection apparatus 10 is a printing apparatus. However, in a modification of the configuration of the liquid ejection device 10, the liquid ejection device 10 may be a device other than an ink jet printer. For example, the liquid ejection apparatus 10 may be an apparatus that performs operations other than image printing by ejecting functional liquid droplets. More specifically, in this case, the liquid ejection device 10 may be, for example, a device that forms conductive wiring by ejecting droplets of conductive liquid. In addition, the liquid ejection device 10 may be a modeling device that models a three-dimensional object by discharging droplets, for example. In this case, the liquid ejection apparatus 10 forms a three-dimensional object by the layered modeling method, for example, by stacking a plurality of layers formed by ejecting droplets. In these cases, the liquid ejection device 10 may further include various configurations depending on the application, for example. Moreover, each part demonstrated in the above may have the characteristic changed suitably according to the use.

  Further, in the above description, the scanning drive unit 16, the drive signal output unit 18, the discharge nozzle setting unit 20, the discharge characteristic storage unit 22, and the like in the liquid discharge apparatus 10 are arranged outside the inkjet head 12. I explained. However, all or a part of these parts may be disposed in the inkjet head 12.

  Next, the drive signal used in this example, the operation of each component in the drive signal output unit 18, and the like will be described in more detail. For convenience of explanation, first, an example of a drive signal used in the conventional configuration is shown.

  FIG. 2 is a diagram showing an example of a conventional drive signal. A principle drive signal (drive voltage) in a case where an ink droplet is ejected by an operation consisting of three stages of pull, push, and pull in a piezo ink jet head. The waveform is modeled and shown. This operation is, for example, a known push-pull type operation, an operation mode in which ink is drawn into the ink chamber (pull 1 mode), and an operation mode in which ink is pushed out from the ink chamber through the nozzles (push mode). ; Push mode), operation mode (pull 2 mode) for quickly pulling back the piezo element being deformed in the push mode, and four modes of standby mode for keeping the piezo displacement constant by applying a DC voltage including zero It is made up of. In this case, as the DC voltage including zero, a voltage that is constant and does not change for a longer time than the period corresponding to the acoustic resonance frequency of the inkjet head is used.

  In FIG. 2, the horizontal center line is zero, the upper side indicates a positive voltage, and the lower side indicates a negative voltage. More specifically, in the case shown in the figure, the drive signal supplied to the piezo element corresponding to the nozzle that ejects ink droplets is composed of three waveform portions, waveform A, waveform B, and waveform C.

  In the following, in order to simplify the description, the pulses constituting the drive signal are all shown as rectangular waves that change instantaneously. However, in an actual configuration, for example, the voltage change may be completed in a time shorter than the acoustic resonance frequency period of the inkjet head. Therefore, for example, a waveform that changes over time with rising and falling edges may be used.

  When the drive signal having the waveform shown in FIG. 2 is used, in the pull 1 mode performed according to the waveform A, the piezo element is displaced in the direction of expanding and expanding the ink chamber. Further, due to this expansion, ink is drawn into the ink chamber from an ink supply path (not shown) and filled. In this case, the amount of deflection of the piezo element increases in proportion to the applied voltage VpullA.

  Moreover, it is preferable to perform this drawing operation so as not to destroy the meniscus formed by the ink at the nozzle position. More specifically, in this case, for example, an increase in the negative pressure in the ink chamber can be suppressed by supplying ink so that the negative pressure defined by the differential pressure from the atmospheric pressure does not exceed a few hundredths of atmospheric pressure. It is preferable to carry out as slowly as possible.

  Further, following this operation, the operation proceeds to a push operation (push mode) performed in accordance with the waveform B. This push operation is an operation of pushing ink from the nozzles at once. In this case, the amount of ink to be pushed out is the sum of the pull-in amount and the push-out amount. Therefore, in the illustrated case, the volume (ink volume) of the ink droplets to be ejected is determined substantially in proportion to Vpush1, which is equal to VpushB-VpullA. That is, when the drive signal shown in FIG. 2 is used, for example, VpullA (= VpushA) is changed by selecting either waveform a1 or a2 for waveform A, or either waveform b1 or b2 is selected for waveform B. If VpushB is changed, the amount of ink to be pushed out changes depending on the change in either VpullA or VpushB, so that the volume (size) of the ink droplets ejected from the nozzles changes.

  Further, following the push operation, the pull 2 mode operation performed according to the waveform C is performed. In this operation, the voltage is lowered in the pull direction in which ink is drawn, as in the examples shown as C1 and C2, for example. In this case, for example, when it is desired to reduce the amount of ink to be ejected, the pull voltage variation is reduced as in the example of C1. As a result, a small force in the direction of pulling back acts on the ink moving in the ejection direction. Further, when it is desired to increase the amount of ink to be ejected, the pull voltage variable is increased as in the example of C2. In this case, a large force in the pullback direction acts on the ink that is moving in the ejection direction. Therefore, the volume (ejection amount) of the ink droplet can be changed also by changing the voltage of the waveform C.

  As described above, even when the conventional driving signal is used, the ink droplet capacity can be changed by changing the voltages of the waveforms A, B, and C. FIG. 3 shows an example of a method for ejecting ink droplets of various capacities depending on how the piezo element is driven.

  As described with reference to FIG. 2, for example, when a conventional drive signal is used, the voltage in the pull 1 mode (VpullA = VpushA), the voltage in the push mode (Vpush1 = VpushB−VpushA), or the pull 2 mode. The volume of the ink droplet can be changed variously by changing any one of the voltages (Vpull2 = VpullB-VpullC). In FIG. 3, the change in the ink droplet volume (ink droplet size) performed in this way is shown as a model.

  As can be seen from this figure, for example, if the voltage in the pull 1 mode, push mode, and pull 2 mode can be controlled for each piezo element, the volume of ink droplets ejected from each nozzle can be controlled. In addition, for example, the ejection amount is corrected so that the volume of the ink droplets becomes a predetermined constant value even when there is a nozzle whose volume of the ejected ink droplets deviates from the standard nozzle. be able to.

  However, when using a conventional drive signal, in order to perform such correction, for example, it is necessary to provide a voltage regulator circuit for each nozzle. Therefore, it is difficult to realize such control with a realistic circuit scale.

  On the other hand, in this example, by using a drive signal different from the conventional one, the ink droplet capacity and the like are corrected with a smaller realistic circuit scale. In this case, for example, as described above, a plurality of types of setting voltage signals having different voltages are used as signals constituting a part of the drive signal, and the ejection characteristics of each nozzle 102 (see FIG. 1). By selecting the set voltage signal corresponding to the nozzle 102, the drive signal is made different for each nozzle 102 according to the ejection characteristics. This also realizes correction of ejection characteristics (ink droplet capacity, etc.) on a practical circuit scale.

  More specifically, in this example, the drive signal output unit 18 (see FIG. 1), as in the known push-pull system operation, uses the first pull signal and the push signal as at least a part of the drive signal. And the second pull signal. In this case, the first pull signal is, for example, a voltage signal for displacing the piezo element 104 (see FIG. 1) so as to draw ink into the ink preceding the nozzle 102 (see FIG. 1). The first pull signal may be a signal corresponding to the portion of the waveform A in FIG.

  The push signal is a voltage signal for displacing the piezo element 104 so as to push out the ink drawn according to the first pull signal from the nozzle 102. The push signal may be a signal corresponding to the portion of the waveform B in FIG. The second pull signal is a signal for displacing the piezo element 104 so that a part of the ink pushed out from the nozzle 102 is pushed back into the nozzle 102 in response to the push signal. The second pull signal may be a signal corresponding to the portion of the waveform C in FIG. In addition, each piezo element 104 sequentially receives the first pull signal, the push signal, and the second pull signal, thereby ejecting ink droplets from the corresponding nozzle 102.

  Further, in this case, the set voltage output unit 34 (see FIG. 1) in the drive signal output unit 18 has a plurality of signals as at least one of the first pull signal, the push signal, and the second pull signal. Outputs the set voltage signal. The selection voltage supply unit 36 (see FIG. 1) sets any one of the first pull signal, the push signal, and the second pull signal based on the ejection characteristics of each nozzle 102. Select the voltage signal. Further, the selected set voltage signal is supplied to the piezo element 104 corresponding to each nozzle 102.

  When configured in this way, each piezo element 104 receives the first pull signal, the push signal, and the second pull signal in sequence, so that it is the same as or similar to, for example, ejection of ink droplets in a known push-pull method. Thus, ink droplets can be appropriately ejected from the respective nozzles 102. In addition, by supplying a set voltage signal as at least one of the first pull signal, the push signal, and the second pull signal, for example, a set voltage signal having a voltage corresponding to the ejection characteristics of each nozzle 102 is piezoelectric. It can supply to the element 104 and the discharge characteristic of each nozzle 102 can be adjusted appropriately. Therefore, according to this example, the ejection characteristics of the respective nozzles 102 can be appropriately corrected, for example, with a realistic circuit scale.

  Subsequently, the correction operation performed in this example will be described in more detail. First, the measurement operation and the like performed prior to correction will be described.

  As described above, in this example, the selection voltage supply unit 36 corresponds to each nozzle 102 based on the ejection characteristics of each nozzle 102 stored in the ejection characteristic storage unit 22 (see FIG. 1). A setting voltage signal to be supplied to the piezo element 104 is selected. In addition, thereby, the voltage supplied to the piezo element 104 at a part of the timing of the drive signal is individually set for each nozzle 102 to adjust (correct) the ejection characteristics of each nozzle 102.

  And in order to perform such adjustment, in this example, the measurement for acquiring the ejection characteristic of each nozzle 102 in the inkjet head 12 is performed in advance. More specifically, in this case, for example, by measuring in advance the discharge characteristics of each nozzle 102 when a preset reference drive signal is used, the nozzle characteristics indicating the discharge characteristics of each nozzle 102 Data is acquired in advance. Based on the acquired nozzle characteristic data, the ejection characteristics of each nozzle 102 are classified into one of n categories and stored.

  In addition, regarding the operation of measuring the ejection characteristics of each nozzle 102 in advance when using the reference drive signal, more specifically, for example, by causing each nozzle 102 to draw a straight line using the reference drive signal, It is conceivable to measure the ejection characteristics of the nozzle 102 by measuring the line width of the straight line. If comprised in this way, the capacity | capacitance of the ink droplet discharged from each nozzle 102 can be indirectly detected, for example by measurement of line width. In addition, this makes it possible to easily and appropriately measure the ejection characteristics of the respective nozzles 102, for example, as compared with the case of directly confirming the volume of ink droplets. Therefore, the operation for measuring the ejection characteristics of the nozzle 102 by measuring the line width will be described below.

  FIG. 4 is a diagram for explaining a line width measurement method (detection method), and shows an example of a method for detecting the volume of ink droplets based on the measured line width. FIG. 4A is a diagram showing a simplified configuration of the inkjet head 12.

  In the following, for ease of explanation, an operation in the case of using the inkjet head 12 in which twelve nozzles 102 shown as N1 to N12 in the drawing are arranged in the sub-scanning direction (X direction) will be described. The inkjet head 12 is, for example, a high resolution head in which a small number of nozzles 102 are arranged at a pitch of 600 dpi (nozzle row resolution pitch) in the sub-scanning direction. In this case, the pitch in the sub-scanning direction may be, for example, an interval (pitch) between the nozzles 102 projected onto a straight line extending in the sub-scanning direction. Therefore, the plurality of nozzles 102 may be arranged in an oblique direction intersecting with the sub-scanning direction, for example, or may be arranged in a staggered structure.

  Moreover, detecting the volume of the ink droplet based on the line width may be, for example, detecting the dot size of the printed ink. In this case, the operation of detecting the dot size based on the line width may be performed by a known method, for example. Therefore, in the following, description will be made focusing on the characteristic part in this example.

  The size of the ink dots formed on the medium by the ink droplets is usually determined according to various printing conditions (printing conditions). Such conditions may include, for example, printing resolution, moving speed of the inkjet head during main scanning operation, type of medium used, ink used, environmental temperature, and the like. When these conditions are constant, it is considered that the relationship between the ink droplet volume and the width of the drawn straight line is uniquely determined. Therefore, even if the volume of the ink droplet that is difficult to measure is not directly measured, if the line width is the same value, the volume of the ink droplet is considered to be the same. In this example, the ejection characteristics of the nozzle 102 are corrected using such a relationship.

  4B and 4C show an example of a straight line to be measured for line width. In this example, for example, the inkjet head 12 having the configuration shown in FIG. 4A is moved in the main scanning direction (Y direction) so that the ink dots are continuously arranged in the main scanning direction. 12 causes ink droplets to be ejected. In this case, the interval between the ink dots in the main scanning direction is set to be smaller than the nozzle pitch in the sub scanning direction (for example, 1200 dpi). In addition, thereby, a straight line (continuous line) extending in the main scanning direction is drawn by at least some of the nozzles 102 in the inkjet head 12. In this case, the operation of drawing a straight line on each nozzle 102 is substantially performed by, for example, ejecting ink droplets continuously from the nozzle 102 during the main scanning operation of moving the inkjet head 12 in the main scanning direction (Y-axis direction). It may be an operation for printing a continuous continuity.

  In this case, it is preferable to perform a plurality of main scanning operations for all the nozzles 102 of the inkjet head 12 by using only some of the nozzles each time. More specifically, in this case, for the nozzles 102 that draw a straight line, for example, the nozzles 102 that are continuously arranged in the sub-scanning direction are not selected at the same time, so that adjacent straight lines do not touch in the sub-scanning direction. preferable. In this case, it is preferable to perform the operation of drawing a straight line a plurality of times while changing the selected nozzle 102 so that all the line widths of the drawn straight line can be measured for all the nozzles 102 in the inkjet head 12.

  For example, in FIGS. 4B and 4C, two sets of an odd-numbered nozzle 102 (odd-numbered row) and an even-numbered nozzle 102 (even-numbered row) counted from one end side of the nozzle row of the inkjet head 12 are used. In the example, the nozzle 102 is divided into two and the operation of drawing a straight line is divided into two. FIG. 4B shows a case where a line drawn by a defective (discharge failure) nozzle 102 in which the volume of the ink droplet is reduced is included. More specifically, the defective nozzle 102 is the third nozzle 102 (nozzle N3) from the top in the configuration shown in FIG.

  If the ink dot is larger than the nozzle pitch in the inkjet head 12, for example, the nozzle 102 is selected with an interval of two nozzles or n nozzles (n is an integer of 3 or more). It can be considered that a straight line extending in the main scanning direction is drawn by all the nozzles 102 by performing an operation of drawing a straight line in three or n + 1 times. If comprised in this way, a straight line can be drawn more appropriately with all the nozzles, preventing the connection, contact, etc. between the lines in a subscanning direction, for example.

  Further, after a straight line is drawn by each nozzle 102, the line width is measured (detected). In this case, for example, it is conceivable to measure the optical reflected light intensity and the density distribution at a predetermined position with respect to the drawn straight line. More specifically, for example, with respect to a plurality of straight lines drawn by the odd-numbered nozzles 102 shown in FIG. 4A, the optical reflected light intensity in the sub-scanning direction at the position indicated by the X1-X1 line in the figure. Alternatively, it is conceivable to measure the concentration distribution. In this case, for example, it is conceivable to use a reflected light distribution measurement method using a laser beam scanning type, a linear image sensor, a two-dimensional image sensor, or the like. Further, this measurement may be performed by, for example, an optical reading unit incorporated in the liquid ejection apparatus 10 (see FIG. 1), or may be performed by an external device such as an image scanner or a drum scanner. Further, for a plurality of straight lines drawn by the even-numbered nozzles 102 shown in FIG. 4B, for example, it is conceivable to perform the same measurement at the position indicated by the X2-X2 line in the drawing. .

  FIG. 5 is a diagram showing an example of the measurement result of the line width, and shows the optical reflection density curve detected by the method described above. FIG. 5A shows an example of the measurement result of the line width for a plurality of straight lines drawn by the odd-numbered nozzles 102. FIG. 5B shows an example of line width measurement results for a plurality of straight lines drawn by the even-numbered nozzles 102. In FIGS. 5A and 5B, the vertical axis indicates the relative print density.

  As described above, in FIG. 4B, the line (print line L3) drawn by the defective nozzle 102 (nozzle N3) in which the volume of the ink droplet is reduced is included. Shows the case. The other nozzles 102 are all normal. Therefore, in FIG. 5A, the peak of the reflection density indicating the measurement result corresponding to the line (print line L3) drawn by the ejection abnormal nozzle 102 (nozzle N3) is small. Accordingly, the measurement result (ΔX2c) of the line width is different from the measurement results (ΔX7c and the like) for other normal nozzles 102. Therefore, based on the measurement result of the optical reflection density distribution curve, it can be seen that the nozzle 102 in which the amount of ejected ink is insufficient is insufficient in optical reflection density as compared with other normal nozzles 102.

  In the measurement of the line width, more specifically, for example, from each distribution curve for each nozzle 102, each nozzle 102 uses a certain threshold level and the position of the half-value width of each waveform shown in the figure. Detects the line width of the drawn straight line. When the detected line width exceeds or falls below a predetermined value, it is determined that the ink droplet capacity is out of the normal range. If comprised in this way, the discharge characteristic of each nozzle 102 can be measured easily and appropriately, for example.

  Further, in this example, the ejection characteristics are corrected for at least a part of the nozzles 102 whose ink droplet volume is out of the normal range. This also corrects the dot size of the ink formed by each nozzle 102.

  FIG. 6 shows an example of variation in the ejection characteristics of the nozzles. In the case of a piezo-type inkjet head in which ink droplets are ejected from the nozzle 102 by the piezo element 104 (see FIG. 1) as in this example, the mechanical structure or material varies depending on the processing accuracy of the piezo element 104, or the nozzle or ink. Mechanical variations of the chamber will occur. As a result, even when the piezo element 104 is driven under the same driving conditions, the volume of the ink droplets ejected from the nozzles varies back and forth with respect to the central value (ejection center ejection amount V0) of the ejection design value. become. Further, as the ink droplet capacity varies, the line width of the straight line drawn by each nozzle also varies with respect to the center value X0 of the line width.

  In addition, in FIG. 6, for a line width drawn by each nozzle of each inkjet head using a large number of inkjet heads, the detected line width is shown on the horizontal axis and the number of nozzles appearing on the vertical axis is shown. ing. Further, the illustrated case shows a state where the discharge amount (line width) varies in a substantially normal distribution before and after the line width X0 corresponding to the discharge center discharge amount.

  In an actual ink jet head, the variation in the ejection characteristics of the nozzles often deviates from the normal distribution. However, since there is no hindrance in the explanation of the principle of correcting the ejection characteristics, the case where the variation is a normal distribution will be described above and below.

  Here, in order to print a clean image free from streaks caused by nozzle variations in one main scanning operation (one pass), the volume of ink droplets discharged from the nozzles is usually kept constant. There is a need. More specifically, for example, in order to realize high-quality printing, ± 3% relative to the center value of the volume (discharge amount) that becomes the center value X0 of the line width as shown by the range A in FIG. It has been experimentally confirmed that it is necessary to fall within the following (0.97X0 to 1.03X0) variation range. In this case, it is considered that the corresponding discharge amount is preferably within a variation range of ± 3% or less with respect to the center value.

  However, in an actual inkjet head, as shown in FIG. 6, many nozzles exhibit variations in ink droplet volume exceeding ± 5%. For this reason, for example, streaks appear in the nozzle scanning direction, and the image quality is greatly reduced. As a result, for example, it becomes difficult to use the printing operation in one pass or a small number of passes. Further, for example, if only a head with small variation is selected and used, in the case of an inkjet head having such variation, the defect rate of the inkjet head is extremely high at 90% or more, leading to a significant cost increase. Become.

  Therefore, in order to relieve an inkjet head that is defective as it is and reduce the defect rate to a small value (for example, about 5% or less), for example, in the case shown in FIG. 6, the nozzles in the ranges shown as ranges B1 and B2 It is desired to correct the ejection characteristics so that even an inkjet head having a non-defective product becomes a non-defective product. Further, in this case, for example, it is necessary to repair the ink jet head in which the ink droplet volume (or weight) varies at least about 20% by correction.

  Further, in this case, if correction is performed even for nozzles whose ejection characteristics are greatly deviated from the standard, for example, the configuration for correction becomes complicated and there is a possibility that correction cannot be performed appropriately. Therefore, it is preferable to adjust the ejection characteristics of only the nozzles whose ejection characteristics are within a preset range. In this case, it may be determined that the nozzles having ejection characteristics outside this range are defective nozzles. In this case, the nozzles outside the range are nozzles in the range indicated as D1 and D2 in the drawing, for example. In this case, an inkjet head having such a defective nozzle may be similarly determined as a defective inkjet head. In this case, more specifically, for example, a deviation from a preset center value is calculated for the ejection characteristics of the nozzle, and if the deviation is within a range of a predetermined constant value, correction is performed and the predetermined value is exceeded. In this case, it can be considered that the ejection and the head are defective.

  If comprised in this way, it can correct more appropriately, for example with respect to the nozzle from which the discharge characteristic has shifted | deviated within the range which can be correct | amended. This also makes it possible to appropriately reduce the number of inkjet heads that are defective. Further, in this case, for example, a nozzle whose ejection characteristics are greatly deviated is determined as a defective nozzle, thereby eliminating the need for excessive correction. In addition, this makes it possible to use a configuration that can correct only for nozzles with ejection characteristics within a certain range, and appropriate correction can be performed with a simpler configuration.

  Next, the operation for correcting the ejection characteristics in this example will be described in more detail. First, as a matter related to the operation of correcting the ejection characteristics, the relationship between the variation in the ink droplet capacity and the deviation of the landing position will be described. As described above, according to this example, by using a plurality of set voltage signals, the volume of droplets ejected from each nozzle can be adjusted individually for each nozzle. However, regarding the variation in the ejection characteristics of the nozzles, it is desirable to consider the variation in the landing position in addition to the ink droplet volume. In this regard, the variation in the landing positions of the ink droplets is not irrelevant to the variation in the volume of the ink droplets, and usually there is a correlation between the two.

  More specifically, for example, when the voltage of the drive signal supplied to the piezo element corresponding to a normal nozzle is appropriate, the diameter of the formed ink dot is set to a predetermined range according to the resolution pitch. Become. Further, when a straight line is drawn with a normal nozzle, a straight line having a predetermined normal range is drawn. The landing position is a predetermined position (set center position) set according to the resolution.

  On the other hand, for example, when the voltage of the drive signal is changed, the diameter of the ink dots and the landing position change according to the voltage of the drive signal. For example, when the voltage of the drive signal is lowered and an excessive voltage is applied, the volume of the ink droplet (droplet volume) is reduced and the drawn line width is reduced. Further, since the drop volume is easily affected by air resistance, the landing position becomes larger in the plus direction than the center setting position. In this case, the plus direction is a direction in which the direction of movement of the inkjet head during ejection of ink droplets is positive (plus). On the other hand, when an excessive voltage is applied by increasing the voltage of the drive signal, the capacity of the ink droplet increases and the drawn line width increases. In addition, since the droplet volume is less affected by air resistance, the landing position becomes smaller in the minus direction than the center setting position. As described above, the influence of the air resistance received by the ink droplet changes depending on the volume of the ink droplet. As a result, the amount of deviation of the landing position also changes depending on the ink droplet capacity.

  7 and 8 are diagrams for explaining the change in the amount of deviation of the landing position of the ink droplets. FIG. 7 is a diagram showing an example of how the landing position changes due to the change in the ink droplet volume. Is modeled. FIG. 8 is a diagram illustrating an example of velocity components of ink droplets that are flying.

  When the volume of the ink droplet changes, for example, as shown in FIG. 7, the appropriate landing position of the ink changes. This is because, for example, when the volume of the ink droplet changes, the kinetic energy and air resistance suitable for the ink change, and the average velocity Vi of the ink droplet changes. In this case, the average velocity Vi of ink droplets is the average velocity of ink droplets passing through the print gap. Further, in this case, the smaller the droplet volume, the greater the effect of air resistance, and the greater the speed drop.

  More specifically, for example, as shown in FIG. 8, when the average speed Vi changes from Vi0 to Vi1, the combined speed with the moving speed Vh in the main scanning direction (Y direction) of the inkjet head during the main scanning operation is The direction (Vh + Vi) changes from (Vh + Vi0) to (Vh + Vi1). In addition, this changes the flight direction suitable for ink and changes the landing position. Further, for example, when the flying speed of the ink droplet is reduced, the flight bend increases and the landing position is further shifted.

  The amount of change in the landing position is sufficiently small when the ink droplet velocity Vi is sufficiently larger than Vh (when Vi >> Vh). However, when the ink droplet velocity Vi decreases from the state of Vi >> Vh and approaches the condition of Vi≈Vh, the landing position deviation becomes more prominent. For this reason, the influence of the variation in the ejection characteristics of the nozzles is emphasized and appears more prominently, for example, under conditions where the print gap is large or when the moving speed of the ink jet head during the main scanning operation is large.

  Next, the correction operation performed in this example will be described in more detail. As described above, in this example, the ejection characteristics of each nozzle 102 are acquired by measuring the line width of the straight line drawn by each nozzle 102 (see FIG. 1) in the inkjet head 12. . In the step of obtaining the ejection characteristics of the nozzles 102, more specifically, for example, for each nozzle 102, a deviation from the center value is calculated for the ejection amount of the ink droplets, and the deviation amount in the plus or minus direction is calculated. Are divided into a plurality of n stages.

  In the step of correcting the ejection characteristics, for example, the set voltage output unit 34 (see FIG. 1) outputs a plurality of set voltage signals having different voltages as signals constituting a part of the drive signal. Then, the selection voltage supply unit 36 (see FIG. 1), which is a power supply selection circuit capable of selecting a plurality of n levels of applied voltages, is applied to the piezoelectric element 104 corresponding to each nozzle 102 in accordance with the measured ejection characteristics. Select one of the set voltage signals. Further, the selected set voltage signal is supplied to the piezo element 104 as a part of the drive signal. More specifically, in this example, the selection voltage supply unit 36 selects a set voltage signal for returning the ink droplet ejection amount for each nozzle 102 divided into a plurality of n stages in the direction of the center value. Accordingly, the selection voltage supply unit 36 selects the voltage to be applied to the piezo element 104 according to the amount of variation in the discharge amount for each nozzle 102.

  FIG. 9 is a diagram for explaining the correction operation in this example in more detail. A waveform A for displacing the piezo element 104 with respect to the relationship between the line width (wire diameter) of a straight line drawn by one nozzle and the landing deviation. An example of how the wire diameter X, which is the thickness of a drawn straight line, and the landing position Yp are changed when the applied voltage VpullA (= VpushA) is changed in various ways. In this case, the applied voltage VpullA of the waveform A is the applied voltage VpullA of the waveform A in the drive signal shown in FIG. In this figure, lines with a and a 'indicate the dependence of the wire diameter X (line width X) on the applied voltage V. Also, the lines with the symbols b and b 'indicate the dependency of the landing position Yp on the applied voltage V.

  In FIG. 9, range A indicates a normal range that does not require correction. More specifically, when the variation allowable range is α%, the nozzles in the range A are nozzles whose deviation of the wire diameter X is within ± α% of the center value X0.

  In this example, the ejection characteristics are corrected, for example, for the nozzles in the ranges indicated by the ranges B1 and B2. The nozzles in this range are, for example, nozzles in which an abnormality in the wire diameter X appears as a deterioration in image quality. In this example, the range (range K) that is a combination of the ranges A, B1, and B2 is a nozzle that can adjust the ejection characteristics to the normal range. Further, the nozzles in the ranges D1 and D2 that are further outside these ranges are nozzles that exceed the range in which the ejection characteristics can be corrected. Therefore, in this example, an inkjet head that includes nozzles in the regions D1 and D2 is determined to be a defective inkjet head.

  More specifically, in FIG. 9, a curve (line a) with a sign “a” is a line indicating the characteristics of a nozzle having normal characteristics corresponding to the center value, and the maximum value of the pulse voltage of the waveform A The result of having measured the change of the wire diameter X (print line width X) of the straight line drawn by changing the applied voltage V which is is shown. Like this line a, the wire diameter X changes to the right as the voltage increases. This is because the volume of ink droplets ejected from the nozzles (the amount of ejected ink droplets) rises to the right and increases substantially in proportion to the voltage. Further, in this example, for each nozzle, the voltage corresponding to the applied voltage V of the waveform A in the drive signal shown in FIG. 2 is changed, and the relationship between the applied voltage and the wire diameter X is previously shown in FIG. Measure as follows.

  Further, when the ejection characteristics of the nozzle deviate from normal characteristics, the line indicating the measurement result is deviated from the line a. For example, in the case of an ejection failure nozzle in which the discharge amount of ink becomes excessive at the set center voltage V0 and the line width becomes wide as indicated by W1, for example, the measurement result is a curve (line a ')become that way. That is, it is considered that the dependency of the wire diameter X on the applied voltage V in such a nozzle is the same as the line a ′ that shows the voltage dependency of the nozzle having normal ejection characteristics and is a line a ′ that has been translated. .

  In this case, in order to return the line width at the position of the point W1 to the X0 of the point W0 position on the line a ', it is understood that the applied voltage should be lowered by ΔV as shown in the figure. That is, in this case, the applied voltage may be lowered from V0 to (V0−ΔV). The value of ΔV is substantially equal to the value for returning the point W3 to W0 on the line a.

  Further, as described with reference to FIGS. 7 and 8, when ink droplets are ejected by the ink jet method, the deviation amount of the landing position varies depending on the volume of the ink droplets. As a result, the diameter of the straight line drawn by each nozzle and the amount of deviation of the landing position do not change independently but change with correlation. More specifically, in this case, as shown in FIG. 9, when correction is performed to return the ink droplet volume (print line width) to the center value X0, the effect of the correction is also centered on variations in landing positions. It can be seen that it works in the direction to return to the value Yp0. Therefore, it can be seen that the deviation of the straight line diameter (Yj line width, ejection amount) and the landing position in the Y-axis direction can be improved by one means by changing the applied voltage.

  In addition, as described above, in this example, the applied voltage V is not continuous but is changed in a plurality of stages according to variations in nozzle characteristics, at least at any timing in the drive signal. As a result, the line width (diameter) of the drawn straight line is corrected. In this case, as described above, the deviation of the landing position can be corrected simultaneously with the line width. Therefore, according to this example, for example, by using the applied voltage selected for each nozzle, it is possible to simultaneously correct the variation in the volume of the ink droplet and the landing position.

  In practice, in order to improve the yield of the inkjet head 12 appropriately, it is necessary to set the correction range of the variation in the diameter of the print line width to about ± 25% of the center value. It is done. On the other hand, according to the present example, correction in such a range can be easily and appropriately realized by using a method of selectively switching the voltage of the drive signal (drive voltage selection switching control method).

  More specifically, in this example, based on the relationship between the applied voltage and the wire diameter shown in FIG. 9, variations in ink droplet capacity and the like can be corrected by the following procedure. In this case, for example, the line width of a straight line (print line width for each nozzle) drawn when a pulse of a constant applied voltage V corresponding to the set center value is applied to all nozzles. Then, based on the measured print line width for each nozzle, a deviation amount (a deviation amount of the ink droplet capacity) from the set center value X0 of the line width is calculated for each nozzle. Further, based on the calculation result, the ejection characteristics of the respective nozzles are classified into any of a plurality of predetermined categories according to the distance (deviation amount) from the center value. Further, in this case, for example, as shown as a range A in FIG. 9, it is divided into a section A that does not require correction of the ejection amount, and a section B1 and B2 that require correction of the ejection amount of ink droplets. Can be considered. In this case, the category A is a category of nozzles in which the allowable range of variation is α% and the line width (diameter) is in the range of X0 ± αX0. Further, the section B1 is a nozzle section in which the line width is narrowed. For this reason, correction for increasing the line width is performed on the nozzles of the section B1. Further, the section B2 is a section of the nozzle having a thick line width. For this reason, correction for narrowing the line width is performed for the nozzles in the section B2. Further, the ranges of the sections B1 and B2 may be divided into finer sections. If constituted in this way, it will become possible to perform correction with higher accuracy, for example.

  Further, in this example, nozzles whose ink droplet capacity exceeds a predetermined range are classified into sections D1 and D2 indicating nozzles that do not require correction. Further, in this case, the ink jet head having the nozzles divided into the sections D1 or D2 is determined as a defective product.

  As described above, in this example, in order to correct the ejection characteristics of the nozzles, a plurality of settings with different voltages (voltage values) are set by the set voltage output unit 34 (see FIG. 1). Outputs a voltage signal. Further, a selection voltage signal corresponding to the ejection characteristics of the nozzle is selected by the selection voltage supply unit 36 (see FIG. 1) and supplied to the piezo element.

  In this case, as the plurality of set voltage signals, it is preferable to use signals of respective voltages that change at approximately equal intervals on both positive and negative sides of the set center voltages V0 and V0. In addition, a plurality of set voltage signals may be output by a method of dividing a predetermined power supply voltage, a method using an individual power supply circuit, or the like. In the selection voltage supply unit 36, for example, a setting voltage signal to be supplied to the piezo element corresponding to each nozzle is selected by a circuit having a function of selecting and switching the power supply voltage for each nozzle.

  Further, in this case, an applied voltage that can return the deviation of the line width in each nozzle to the value closest to the set center value X0 is obtained, and the set voltage signal having the closest voltage is connected. More specifically, in this case, the selection voltage supply unit 36 connects, for example, the piezo element corresponding to the nozzle to a power supply corresponding to the set voltage signal with the closest voltage. As a result, a voltage to be returned to the set center value is applied to the piezoelectric element corresponding to each nozzle in accordance with the deviation from the center value of the line width obtained for each nozzle.

  In this example, when adjusting the ejection characteristics, the variation in line width is measured again using the set voltage signal selected for each nozzle. Then, in this re-measurement, if the variation in line width is below a certain value, the correction is completed. If there is a nozzle whose line width is shifted beyond a predetermined range, the same correction as described above is performed again for the nozzle. In addition, the line width is measured again in the state after the second correction, and the correction is completed when the variation in the line width is equal to or less than a certain value. Also, when the line width variation is less than a certain value and the correction is completed, information indicating the set voltage signal selected for each nozzle (selected power supply information) is stored in a circuit or the like and can be automatically selected during a printing operation. Like that.

  In addition, when the correction is not completed even if the correction is repeated a predetermined number of times, it is preferable to perform a recovery operation such as cleaning of the inkjet head. If the correction is not completed even after performing the above-described correction, it may be determined that the inkjet head is defective and the correction operation may be terminated.

  In the above description, the ejection characteristic correction performed in this example has been described mainly with respect to the method of correcting the ink droplet capacity by adjusting the line width of the drawn straight line within a certain range. However, as described above, when the ink droplet volume is corrected, it is also possible to correct the deviation amount of the landing position at the same time. Therefore, when correcting the ejection characteristics, the correction may be performed in consideration of both the line width of the drawn straight line and the deviation amount of the landing position. In this case, for example, it is conceivable to perform control so that the sum or average value of the deviation amount of the line width and the deviation amount of the landing position is minimized.

  Next, a more specific circuit configuration and the like for driving the piezoelectric element in this example will be described in more detail. FIG. 10 is a diagram (equivalent circuit model of a driving voltage selection switching method) showing a simplified equivalent circuit of a driving circuit (head driving circuit) for driving the piezo element 104 in the inkjet head. For the voltage supply unit 36 and the like, an equivalent circuit is shown in a simplified manner. In this example, the head drive circuit further includes a common voltage output unit 32 and the like as described with reference to FIG. However, for convenience of illustration, the common voltage output unit 32 and the like are omitted in FIG.

  In the piezo-type inkjet head, as a drive circuit for driving the piezo element 104, an equivalent circuit in which the piezo element 104 is replaced with a capacitor as shown in FIG. 10 can be considered. Further, in the configuration shown in a simplified manner in FIG. 10, the set voltage output unit 34 outputs set voltage signals of three kinds of voltages V1 = V0 + ΔV, V2 = V0, and V3 = V0−ΔV. Further, the selection voltage supply unit 36 performs switching in three stages of V1, V2, and V3 by a selector with respect to the power supply voltage that determines the voltage applied to the piezo element 104. It should be noted that the switching stage, the change width of the switching voltage, and the like are changed depending on, for example, the degree of variation in the ejection characteristics of the nozzles in the inkjet head and the required level of image quality. Therefore, it is not limited to a specific number.

  FIG. 11 is a diagram more specifically showing a part of a drive circuit that supplies a drive signal to the piezo element 104. In the illustrated configuration, the drive signal output unit 18 outputs a plurality of set voltage signals having different voltages to a common electrode with respect to the plurality of piezo elements 104. The ejection nozzle setting unit 20 includes, for example, a shift register unit 202 and a latch unit 204, and selects a nozzle that should eject ink droplets in accordance with an instruction received from, for example, the control unit 24 (see FIG. 1). The selection voltage supply unit 36 includes a selector unit 206 and a switching circuit unit 208. For example, an instruction received from the control unit 24 and the ejection characteristics of each nozzle stored in the ejection characteristic storage unit 22 (see FIG. 1). Based on the above, a setting voltage signal to be supplied to the piezo element 104 corresponding to each nozzle is selected. In this case, the selection voltage supply unit 36 may receive, for example, data indicating a power source used for correcting nozzle variation determined in advance as the ejection characteristics of each nozzle stored in the ejection characteristic storage unit 22. Further, the data indicating the power source used for correcting the nozzle variation is more specifically, for example, data indicating a set voltage signal to be used for correcting the ejection characteristics of the nozzle. Accordingly, the selection voltage supply unit 36 determines a voltage (set voltage signal) to be connected for each nozzle. Further, the selection voltage supply unit 36 further sets a time for turning on the output by a timer function.

  In other respects, the configuration of each unit may have the same or similar features as, for example, a known configuration that controls the operation of the piezo element 104. In addition, the configuration of each unit may be connected to each other via various logic circuits, switching transistors, and the like as illustrated. With this configuration, a driving signal can be appropriately supplied to each piezo element 104. Further, by switching the set voltage signal supplied to each piezo element 104 by the switching circuit unit 208 or the like in the selection voltage supply unit 36, based on the ejection characteristics of each nozzle obtained by measuring the print line width in advance, etc. A set voltage signal corresponding to a power supply with a voltage that can reduce variations in the print line width can be appropriately selected and supplied to each piezo element 104. In addition, for example, variations such as ink droplet volume can be appropriately corrected by a combination of the measured line width and the drive voltage selection switching control method.

  The circuit configuration shown in FIG. 11 is an example of a circuit configuration used in this example by making a simple change to a known circuit configuration. In a more specific circuit configuration, it is preferable to make further changes as appropriate in accordance with the characteristics of the drive signal used, the characteristics of the piezo element 104, and the like. With this configuration, for example, a drive signal can be more appropriately supplied to each piezo element 104.

  Subsequently, a modified example of the drive signal used in this example will be described. In the above description, the case where the applied voltage of the waveform A is changed variously among the driving signals described with reference to FIG. 2 has been mainly described. However, the object whose voltage is changed using a plurality of set voltage signals is not limited to the portion of the waveform A, but may be another portion. For example, when ejecting ink droplets from a nozzle by the push-pull method, not only the voltage for the pull 1 mode corresponding to the waveform A, but also the voltage for the push mode and the pull 2 mode corresponding to the waveform B and the waveform C. May be changed in various ways. That is, when a drive signal that is the same as or similar to the drive signal described with reference to FIG. 2 is used, for example, at least one voltage value of the waveforms A, B, and C is used as the discharge characteristic (discharge state) of the nozzle. In response to this, it may be switched to a plurality of stages. Further, when considered in general terms, a configuration in which the voltage supplied to each piezo element can be switched for at least a part of the waveform of the drive signal may be used.

  Further, the drive signal to be used may be further modified. For example, it is conceivable to use a signal whose polarity is inverted at a predetermined timing using an inverting circuit or the like as the drive signal.

  FIG. 12 is a diagram illustrating a modified example of the drive signal, and illustrates an example of the drive signal in the case where a signal whose polarity is inverted at a predetermined timing is used. In this case, the waveform B0 after the predetermined timing is a waveform obtained by inverting the previous waveform A0. Therefore, when configured in this way, for example, as shown in the figure, the positive and negative applied voltages change simultaneously. As a result, for example, when the waveform A0 is changed from the waveform a1 to a2, the total pull voltage Vpush-t0 is 2 to the change ΔV from the waveform a1 to a2 in the waveform A0. Double 2ΔV. Even when such a drive signal is used, the voltage applied to the piezoelectric element corresponding to each nozzle can be appropriately changed according to the ejection characteristics of the nozzle. This also makes it possible to appropriately correct the ejection characteristics of each nozzle.

  Subsequently, further supplementary explanations will be given regarding the features and effects of this example. For example, as described above with reference to FIG. 6 and the like, in many inkjet heads, most of the defective nozzles are caused by a variation of ± 20% by weight or less in the ink discharge amount. The inventors of the present application focused on this point and considered a method of adjusting the ejection characteristics of each nozzle with a practical scale circuit configuration.

  Further, as this method, more specifically, for example, at least a part of the drive signal supplied to the piezo element corresponding to each nozzle by acquiring the ejection characteristics of each nozzle in advance by the method described with reference to FIG. For the above, a method of switching the voltage according to the ejection characteristics (driving method of the driving voltage selection switching control method) was considered. In this case, as the ejection characteristics of each nozzle, for example, the line width (print line width) of a straight line drawn by each nozzle is measured using the evaluation medium 50 and the ink used in actual printing. . In this measurement, the relationship between the voltage (drive voltage) in the drive signal that combines the switchable voltages and the change in line width is also obtained in advance. And based on these, the voltage of the drive signal supplied to the piezo element corresponding to each nozzle is determined. In order to realize such a method, more specifically, a plurality of setting voltage signals having different voltages are used, and a setting voltage signal to be supplied to each piezo element is selected according to the ejection characteristics of each nozzle. .

  When configured in this way, for example, the voltage applied to each piezo element at the timing of at least a part of the drive signal by individually setting the set voltage signal to be supplied to each piezo element for each piezo element. Can be set individually for each piezo element. Thereby, for example, the volume of ink droplets ejected by each nozzle can be individually adjusted for each nozzle in accordance with the drive signal. Therefore, with this configuration, for example, the variation in the ejection characteristics of the nozzles can be appropriately reduced without averaging the variation in the ejection characteristics using a multi-pass method or the like. In addition, this makes it possible to appropriately reduce, for example, the effect of variations in ejection characteristics that occur in the printing result to a level that does not cause a problem in practice.

  Further, in this case, by suppressing variations in the volume of ink droplets, for example, high-quality printing can be appropriately performed without performing multi-pass printing. Also, when printing is performed using the multi-pass method, the required number of passes can be appropriately reduced. Therefore, according to this example, for example, the printing speed can be increased. More specifically, in this case, for example, if printing is performed in one pass without performing printing in the multi-pass method, the printing speed is significantly increased (for example, compared with the case in which printing is performed in the conventional multi-pass method). (About 4 to 32 times).

  Further, in this case, for example, the size of the ink dots formed on the medium is made constant by suppressing variations in the volume of the ink droplets. In this case, the dot width in the sub-scanning direction is also constant, and the area where the ink dots are formed in the sub-scanning direction is also uniform. As a result, it is also possible to appropriately suppress, for example, the occurrence of streak unevenness and the like and improve the quality of printing. Further, when the volume of the ink droplet is made constant, the variation in the landing position in the main scanning direction can be appropriately suppressed as described above. Therefore, if configured in this way, for example, the accuracy of the landing position of the ink droplet in the main scanning direction can be appropriately increased, for example. This also makes it possible to improve the quality of printing in this respect.

  In this case, the voltage supplied to the piezoelectric element corresponding to each nozzle is not finely adjusted by a voltage regulator circuit or the like, but a plurality of power supply voltages (for example, n kinds of power supply voltages) are used, for example. By preparing a set voltage signal in advance and selecting a set voltage signal to be used according to the ejection characteristics of the nozzle, a configuration that achieves the same effect as adjusting the effective voltage for each nozzle is realized, The ejection characteristics of each nozzle are corrected. Therefore, for example, compared with the case where a voltage regulator circuit for adjusting the voltage of the drive signal is provided for each nozzle, the scale of the necessary circuit configuration can be greatly reduced. In addition, this makes it possible to individually adjust the ejection characteristics of each nozzle for each nozzle, for example, with a circuit scale within a practical range. For this reason, with this configuration, for example, it is possible to appropriately suppress the influence of variations in the discharge characteristics of the nozzles within a practically acceptable range while suppressing an increase in cost.

  Further, in the configuration described above, for example, a plurality of nozzles having different ejection characteristics, that is, a plurality of nozzles having different capacities of ink droplets ejected when receiving the same drive signal are different from each other. By supplying the set voltage signal, adjustment is performed so that the ink droplet capacities are closer. If comprised in this way, the adjustment of the discharge characteristic of the ink droplet by each nozzle can be performed more appropriately, for example.

  In this configuration, the ejection nozzle setting unit 20 (see FIG. 1) can select, for example, a plurality of nozzles that eject ink droplets of the same capacity set in advance as the nozzles that eject ink droplets. The plurality of nozzles that eject ink drops having the same capacity set in advance are, for example, a plurality of nozzles that eject ink drops having the same capacity with respect to the designed ink drop capacity. More specifically, for example, in the case of a configuration in which only one type of ink droplet is ejected by one nozzle, the same volume of ink droplet is the one type of ink droplet. In addition, for example, a single nozzle discharges ink droplets of a volume selected from a plurality of types of capacities, such as a configuration in which a plurality of volumes with different capacities can be set as the ink droplet capacities (for example, a variable dot configuration). In the case of the configuration, the same volume of ink droplets may be an ink droplet of any one of a plurality of volumes.

  Further, in this case, the ejection nozzle setting unit 20 is configured to eject a plurality of ink droplets having the same capacity based on, for example, image data indicating an image to be printed, for example, as a nozzle that ejects ink droplets according to a drive signal. A nozzle may be selected. Further, the set voltage output unit 34 (see FIG. 1) outputs a plurality of set voltage signals in common to a plurality of nozzles that eject ink droplets having the same capacity, for example. In addition, the selection voltage supply unit 36 (see FIG. 1) discharges the nozzles stored in the discharge characteristic storage unit 22 (see FIG. 1) for each of a plurality of nozzles that discharge ink droplets having the same capacity. Based on the characteristics, a set voltage signal associated in advance with the ejection characteristics of the nozzle is supplied. If comprised in this way, the adjustment of the discharge characteristic of a nozzle can be performed appropriately, for example.

  In addition, the correction of the ink droplet volume and the like described above may be performed at the time of shipment of the liquid ejection apparatus 10 (see FIG. 1), the manufacture of the inkjet head, or the like. It is also conceivable that the user performs it at a place where the liquid ejection device 10 is used. In addition, as the configuration of the liquid ejection apparatus 10, for example, a plurality of printing conditions (print modes) can be set, and a configuration in which the printing speed and the ink droplet capacity are changed depending on the print mode is also conceivable. In such a case, for example, the correction range and the correction value may be changed depending on the print mode. The ink used in the liquid ejection apparatus 10 is not particularly limited, and various known inks can be used. In this case, when considered more general, it is conceivable to use various liquids that can be discharged from the nozzle by a piezo element or the like.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. It is apparent from the description of the scope of claims that embodiments with such changes or improvements can be included in the technical scope of the present invention.

  The present invention can be suitably used for, for example, a liquid ejection apparatus.

DESCRIPTION OF SYMBOLS 10 ... Liquid discharge apparatus, 12 ... Inkjet head, 14 ... Platen, 16 ... Scanning drive part, 18 ... Drive signal output part, 20 ... Discharge nozzle setting part, 22 ... -Discharge characteristic storage unit, 24 ... control unit, 32 ... common voltage output unit, 34 ... set voltage output unit, 36 ... selection voltage supply unit, 50 ... medium, 102 ... Nozzle, 104 ... piezo element, 202 ... shift register unit, 204 ... latch unit, 206 ... selector unit, 208 ... switching circuit unit

Claims (9)

A liquid ejection device that ejects droplets by an inkjet method,
An ejection head having a plurality of nozzles that respectively eject droplets by an inkjet method, and a plurality of drive elements that respectively eject droplets from the nozzles;
A drive signal output unit for outputting a drive signal for driving the drive element;
A discharge nozzle setting unit for setting the nozzle for discharging droplets by selecting the drive element that receives the drive signal;
A discharge characteristic storage unit that stores discharge characteristics of each of the nozzles;
The drive signal output unit is
A set voltage output unit that outputs a plurality of set voltage signals that are a plurality of types of signals set to different voltages;
At least part of the timing of supplying the drive signal to the drive element, as the drive signal, any one of the set voltage signals is supplied to the drive element corresponding to the nozzle that ejects droplets. A selection voltage supply unit,
The selection voltage supply unit is associated in advance with the discharge characteristics of the nozzles based on the discharge characteristics of the nozzles stored in the discharge characteristic storage unit for the drive elements corresponding to the nozzles. A liquid discharge apparatus that supplies the set voltage signal. The discharge characteristic storage unit classifies and stores the discharge characteristics of each of the nozzles by classifying them into any of preset n (n is an integer of 2 or more),
The set voltage output unit outputs n types of the set voltage signals respectively associated with the n number of the sections,
The selection voltage supply unit, for the drive elements corresponding to the respective nozzles, the discharge characteristics of the nozzles corresponding to the classifications according to the classifications classified in the discharge characteristic storage unit. The liquid ejection apparatus according to claim 1, wherein a set voltage signal is supplied.   3. The liquid ejection apparatus according to claim 1, wherein the set voltage output unit outputs a signal having a constant voltage different from each other as each of the plurality of set voltage signals.   The liquid ejecting apparatus according to claim 1, wherein the driving element is a piezo element that is displaced according to the driving signal. The drive signal output unit as at least a part of the drive signal,
A first pull signal that is a voltage signal for displacing the piezo element so as to draw liquid into the ink chamber in front of the nozzle;
A push signal that is a voltage signal that displaces the piezo element so as to push out the liquid drawn in response to the first pull signal from the nozzle;
A second pull signal that is a signal for displacing the piezo element so as to push back a part of the liquid pushed out of the nozzle in response to the push signal;
Each of the driving elements sequentially receives the first pull signal, the push signal, and the second pull signal, thereby ejecting a droplet from the corresponding nozzle,
The selection voltage supply unit supplies the set voltage signal to the drive element as at least one of the first pull signal, the push signal, and the second pull signal. Item 5. The liquid ejection device according to Item 4. A method for adjusting a liquid ejection device for adjusting droplet ejection characteristics in the liquid ejection device according to claim 1,
A method for adjusting a liquid ejection apparatus, wherein the ejection characteristics of droplets from each nozzle are adjusted by individually setting the set voltage signal supplied to each of the drive elements for each of the drive elements. . Preliminarily measuring the ejection characteristics of each nozzle when using a preset reference drive signal,
For each of the drive elements corresponding to each nozzle, select one of the set voltage signals according to the measured ejection characteristics,
The method of adjusting a liquid ejection apparatus according to claim 6, wherein the set voltage signal selected according to the measured ejection characteristic is supplied as at least a part of the drive signal.   For the operation of measuring the ejection characteristics of the respective nozzles in advance when the reference driving signal is used, each nozzle is drawn with a straight line using the reference driving signal, and the line width of the straight line is set. The method for adjusting a liquid ejection apparatus according to claim 7, wherein the ejection characteristics of the nozzle are measured in advance by measurement. For the nozzles whose discharge characteristics are within a preset range, adjust the discharge characteristics of the nozzles,
The adjustment of the liquid ejection apparatus according to claim 6, wherein the nozzle is determined to be a defective nozzle with respect to the nozzle whose ejection characteristics are outside a preset range. Method.

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