JP2017043072A - Liquid discharge device and method for adjusting liquid discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress further appropriately an influence of variation of discharge characteristics of nozzles in a discharge head.SOLUTION: The liquid discharge device, which discharges liquid droplets, comprises: an inkjet head 12, a discharge head having a plurality of nozzles and a plurality of driving elements; a driving signal output portion 18; a discharge nozzle setting portion 20; and a timing setting portion 22 that sets timing for the driving elements to receive driving signals. The driving signal output portion 18 outputs voltage-change signals whose voltages change as time passes, as at least part of the driving signals, in common to the plurality of nozzles. The timing setting portion 22 sets, with respect to periods of time during which the driving elements receive the voltage-change signals, the period individually for each driving element. Each of the nozzles discharges liquid droplets by an inkjet method according to the driving signals for which the periods of time for receiving the voltage-change signals are individually set.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 voltage applied to the drive element such as a piezo element is not directly changed individually, but the signal supplied to each drive element by indirect control. A method for adjusting the effective voltage was considered. Further, as a method thereof, more specifically, a signal that gradually changes with the passage of time is commonly used for a plurality of nozzles, and only the timing for supplying the signal to the drive element of each nozzle is determined for each nozzle. I thought about making it different. If comprised in this way, the effective 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. Selecting a discharge head, a drive signal output unit that outputs a drive signal for driving the drive element, a drive element that receives the drive signal, thereby setting a nozzle that discharges the droplet; A timing setting unit that sets a timing at which the drive element corresponding to the nozzle set as the nozzle setting unit receives the drive signal as a nozzle to be discharged, and the discharge nozzle setting unit is preset as a nozzle that discharges droplets A plurality of nozzles that discharge droplets of the same volume can be selected, and the drive signal output unit can output a plurality of droplets that discharge droplets of the same volume. In common with the nozzles, a voltage change signal that is a signal that changes in voltage over time is output as at least a part of the drive signal, and the timing setting unit receives a voltage change signal for the drive element. Each nozzle is individually set, and each nozzle discharges a droplet by an ink jet method in accordance with a drive signal in which a period for receiving a voltage change signal is individually set in the corresponding drive element.

  When configured in this way, for example, by setting the period during which each drive element receives the voltage change signal for each drive element individually, the effective voltage (effective effective) received by each drive element based on the voltage change signal is set. Voltage) can be set individually for each nozzle. 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.

  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. Accordingly, for example, the effective voltage of the drive signal can be individually set for each nozzle with a circuit scale in 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, when the same drive signal is received, the period in which the drive element receives the voltage change signal is made different for a plurality of nozzles having different droplet capacities to be discharged. Adjust so that the drop volume 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 addition, in this configuration, 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. is there. 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 configuration, the voltage change signal is, for example, a signal whose voltage changes periodically. In this case, for example, the timing setting unit sets, for each drive element, which period in the cycle is supplied to each drive element. If comprised in this way, the effective voltage which each drive element receives based on a voltage change signal can be adjusted appropriately, for example.

  In addition, the timing setting unit may be able to set a plurality of types of preset periods, for example, as periods during which the drive element receives the voltage change signal. In this case, the timing setting unit sets a period in which each drive element receives the voltage change signal, for example, by selecting one of a plurality of periods.

  The timing setting unit may change the pulse width for supplying the voltage change signal to each drive element, for example. If comprised in this way, the effective voltage which a drive element receives can be changed appropriately, for example. In addition, this makes it possible to appropriately realize, for example, a pulse width drive voltage control system operation that changes the effective voltage of the drive signal in accordance with the pulse width.

  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 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. With this configuration, for example, by setting a period during which each piezo element receives a voltage change signal, it is possible to appropriately adjust the ejection characteristics of the liquid droplets by the respective nozzles.

  (Configuration 3) 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 a 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 timing setting unit sets the timing for receiving the first pull signal, the push signal, and the second pull signal for each drive element, and changes the voltage. No. is at least one of the signal of the first pull signal, a push signal, and a second pull signal.

  When configured in this way, each drive element 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, droplet discharge in the known push-pull method. As a result, it is possible to appropriately eject the droplets from the respective nozzles. In addition, by using at least one of the first pull signal, the push signal, and the second pull signal as a voltage change signal, the droplet discharge operation can be individually adjusted for each nozzle. Therefore, with this configuration, for example, it is possible to more appropriately adjust the droplet discharge characteristics of each nozzle.

  (Configuration 4) The image forming apparatus further includes a correction data storage unit that stores correction data used for correcting the ejection characteristics of the nozzles. The correction data storage unit changes the voltage of the drive element for the nozzles that require correction of the ejection characteristics as correction data. The timing set in advance corresponding to the ejection characteristics of the nozzle is stored as the timing for receiving the signal, and the timing setting unit supplies the voltage change signal to the drive element corresponding to the nozzle that requires correction of the ejection characteristics. Is set based on the correction data. If comprised in this way, the adjustment of the discharge characteristic with respect to each nozzle can be performed more appropriately based on the correction data prepared beforehand, for example.

  (Configuration 5) The voltage change signal is a signal that is repeated in a preset cycle, and the voltage gradually changes in one direction with the passage of time within the cycle. The signal in which the voltage gradually changes in one direction in accordance with the passage of time in the cycle is, for example, a signal in which the voltage gradually increases in the cycle or a signal in which the voltage gradually decreases in the cycle. In this case, for example, the voltage may be changed stepwise at the boundary portion of the cycle.

  If comprised in this way, the voltage of a voltage change signal can be changed more appropriately, for example. This also makes it possible to more appropriately adjust the droplet ejection characteristics of each nozzle.

  (Configuration 6) The voltage change signal is a sawtooth wave whose voltage changes in a sawtooth shape. If comprised in this way, the voltage of a voltage change signal can be changed more appropriately, for example.

  (Configuration 7) The voltage change signal is a signal that is repeated in a preset cycle, and the timing setting unit reverses the polarity of the voltage change signal in the middle of the cycle and sets the timing for inverting the polarity for each drive element. By setting these individually, the period during which each drive element receives the signal is individually set for the voltage change signal before and after the inversion of the polarity. If comprised in this way, the voltage of a voltage change signal can be changed more appropriately, for example.

  (Structure 8) A method for adjusting a liquid discharge apparatus for adjusting a droplet discharge characteristic in the liquid discharge apparatus according to any one of Structures 1 to 7, wherein the drive element receives a voltage change signal for 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.

  (Configuration 9) By previously measuring the discharge characteristics of each nozzle when a preset reference drive signal is used, nozzle characteristic data indicating the discharge characteristics of each nozzle is acquired in advance, and For the corresponding driving element, the timing set based on the nozzle characteristic data is set as the timing when the driving element receives the voltage change signal, and the driving element changes the voltage based on the timing set based on the nozzle characteristic data. A period for receiving a signal is individually set for each driving element. 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 10) 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. In this case, for example, it is conceivable to switch the effective voltage received by the drive element in a direction that reduces the variation for each nozzle by the pulse width drive effective voltage control method.

  (Configuration 11) 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 the drive signal used in this example. It is a figure explaining the relationship between the capacity | capacitance of an ink droplet, and a landing position. FIG. 8A is a table showing an example of the relationship between the line width of a straight line determined according to the ink droplet volume and the amount of landing position deviation (landing deviation). FIG. 8B is a diagram showing the relationship between the line width (wire diameter) and the landing deviation in the case where ink droplets are ejected from nozzles having normal ejection characteristics. 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 simplifies and shows the equivalent circuit of the drive circuit which drives the piezoelectric element 104 in an inkjet head. 4 is a diagram more specifically showing a configuration for supplying a drive signal to a piezo element 104. FIG. It is a figure which shows the modification of a drive signal. It is a figure which shows the further modification of a drive signal. It is a figure which shows the further 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, an ejection nozzle setting unit 20, a timing setting unit 22, a correction data storage unit 24, and a control unit 26. Have. 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 nozzles 102 according to 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. The drive signals used in this example 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.

  Further, the discharge nozzle setting unit 20 may transmit a signal indicating the selected piezo element 104 to the scan driving unit 16 via, for example, the timing setting unit 22. 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 timing setting unit 22 sets the timing at which each piezo element 104 receives a drive signal. In this case, for example, the timing setting unit 22 sets a timing for receiving a drive signal at least for the piezo element 104 corresponding to the nozzle 102 set in the discharge nozzle setting unit 20 as the nozzle 102 for discharging an ink droplet.

  In addition, the timing setting unit 22 may transmit a signal indicating the set timing to the scan driving unit 16. Thereby, the scanning drive unit 16 supplies a drive signal to each piezo element 104 based on the timing set by the timing setting unit 22. In this example, the timing setting unit 22 sets the timing at which each piezo element 104 receives a drive signal based on the correction data stored in the correction data storage unit 24. In this case, the correction data stored in the correction data storage unit 24 is data used for correcting the ejection characteristics of the nozzle 102. The timing setting by the timing setting unit 22 will be described in more detail later.

  The correction data storage unit 24 is a storage unit that stores correction data. In this example, the correction data storage unit 24 stores, as correction data, the timing at which the piezo element 104 receives a voltage change signal for the nozzle 102 that requires correction of ejection characteristics. In addition, as this timing, more specifically, a preset timing corresponding to the ejection characteristics of each nozzle 102 is stored.

  The control unit 26 controls the operation of each unit of the liquid ejection device 10. The control unit 26 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.

  In addition, in the above description, the scanning drive unit 16, the drive signal output unit 18, the discharge nozzle setting unit 20, the timing setting unit 22, the correction data storage unit 24, and the like in the liquid discharge apparatus 10 are arranged outside the inkjet head 12. It was described as a configuration to be provided. However, all or a part of these parts may be disposed in the inkjet head 12.

  Next, the drive signal used in this example, timing setting by the timing setting unit 22, 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 droplet ejected from the nozzle 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 driving signal different from the conventional one and controlling the timing of supplying the driving signal to each piezo element 104, the ink droplets can be produced with a smaller practical circuit scale. Correct the capacity. Hereinafter, this point 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 timing setting unit 22 (see FIG. 1) is based on the correction data stored in the correction data storage unit 24 (see FIG. 1). 1) sets the timing for receiving the drive signal. The correction data storage unit 24 stores data used for correcting the ejection characteristics of the nozzles 102 as correction data.

  In order to perform such timing adjustment, in this example, for example, measurement is performed in advance to acquire the ejection characteristics of each nozzle 102 (see FIG. 1) in the inkjet head 12. 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, necessary correction data is generated and stored in the correction data storage unit 24.

  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 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 when using the inkjet head 12 in which 12 nozzles 102 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 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, 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. The other nozzles 102 are all normal. Therefore, in FIG. 5A, the measurement result (ΔX2c) of the line width corresponding to the line drawn by the ejection abnormal nozzle 102 is different from the measurement results (ΔX7c, etc.) for the other normal nozzles 102. Yes. 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, along with the variation in the volume of ink droplets, the line width of the straight line drawn by each nozzle also varies.

  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, ± 5% with respect 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 be within a variation range of (0.95X0 to 1.05X0) below.

  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 a defective product as it is and reduce the defect rate (for example, about 5% or less), for example, in the case shown in FIG. It is desirable to correct the ejection characteristics so that the ink jet head is a good 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. Similarly, an inkjet head having such a defective nozzle may be determined to be 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. In this example, based on the result of the variation in the ejection characteristics of the nozzles detected as the line width, for example, the ejection characteristics are adjusted for nozzles within a predetermined variation range. Further, in this case, for example, the effective received by the piezo element 104 by the pulse width drive effective voltage control method of changing the effective voltage (effective drive voltage) received by the piezo element by changing the pulse width of the signal applied to each piezo element. The voltage is switched to a direction that reduces the variation of each nozzle.

  FIG. 7 is a diagram illustrating an example of a drive signal used in this example, and illustrates an example of a drive signal when ink droplets are ejected from a nozzle by the Pull-Push-Pull method. In this example, in a configuration using a piezo-type inkjet head, basically, pulling that draws ink into the ink chamber by applying a voltage to the piezo element is basically the same as when modeled using FIG. A combination of three waveforms: a waveform for operation (waveform A), a waveform for push operation for pushing out ink from the ink chamber (waveform B), and a waveform for pull operation for returning ink to the ink chamber (waveform C). By using the drive signal, the ejection amount of ink droplets from each nozzle is controlled.

  In this case, the portion of the waveform A in the drive signal is an example of a first pull signal that is a voltage signal for displacing the piezo element so as to draw liquid (ink) into the ink chamber in the preceding stage of the nozzle. The portion of the waveform B is an example of 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. The portion of the waveform C is an example of a second pull signal that is a signal for displacing the piezo element so that a part of the liquid pushed out of the nozzle is pushed back into the nozzle in response to the push signal. In this case, in the liquid ejection apparatus 10 (see FIG. 1), the drive signal output unit 18 (see FIG. 1) outputs the first pull signal, the push signal, and the second pull signal as at least a part of the drive signal. Output. Further, the timing setting unit 22 (see FIG. 1) sets the timing for receiving the first pull signal, the push signal, and the second pull signal for each piezo element. Each piezo element sequentially receives the first pull signal, the push signal, and the second pull signal, thereby ejecting ink droplets from the corresponding nozzle.

  Further, as can be seen from the figure, in this example, the drive signal output unit 18 outputs a voltage change signal that is a signal whose voltage changes with time as at least a part of the drive signal. More specifically, in the illustrated case, the first pull signal corresponding to the waveform A is a voltage change signal.

  The drive signal shown in FIG. 7 is a drive signal for ejecting a predetermined volume of ink droplets preset in the liquid ejecting apparatus 10. In this case, the discharge nozzle setting unit 20 is, for example, a plurality of nozzles that discharge droplets of the same capacity based on image data indicating an image to be printed, for example, as nozzles that discharge ink droplets according to the drive signal. May be selected. The drive signal output unit 18 outputs a drive signal including a voltage change signal in common to the plurality of nozzles.

  Note that the plurality of nozzles that discharge droplets of the same volume are a plurality of nozzles that discharge droplets of 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 example, the timing setting unit 22 individually sets each piezoelectric element for a period in which the piezoelectric element receives the voltage change signal (waveform A, first pull signal). Each nozzle discharges a droplet by an ink jet method in accordance with a drive signal in which a period for receiving a voltage change signal is individually set in the corresponding piezoelectric element.

  More specifically, in this case, the timing setting unit 22 sets the timing at which the piezo element receives the voltage change signal, for example, for the piezo element corresponding to each nozzle. In this case, the timing setting unit 22 sets the timing at which the piezo element corresponding to the nozzle that requires correction of the ejection characteristics receives the voltage change signal based on the correction data stored in the correction data storage unit 24. . Accordingly, the timing (period) at which each piezo element receives the voltage change signal is individually set for each piezo element based on the nozzle characteristic data obtained in advance by measuring the line width or the like. If comprised in this way, the adjustment of the discharge characteristic of the ink droplet by each nozzle can be appropriately performed based on the correction data prepared beforehand, for example.

  More specifically, in the case of the drive signal shown in FIG. 7, 3 pulses having a pulse width of TA0, TB, and TC are obtained as signals of waveform A, waveform B, and waveform C, respectively, with respect to a normal nozzle. Use two waveform signals. A sawtooth wave shown as waveform a (pulse width TA) in the figure is used as a signal of waveform A that is a voltage change signal. A sawtooth wave is a signal whose voltage changes in a sawtooth shape, for example.

  In this case, the voltage change signal can be considered as a signal whose voltage changes depending on the applied pulse width. Therefore, the effective voltage received by the piezo element in accordance with the voltage change signal changes in accordance with the timing at which the piezo element receives the waveform A signal that is the voltage change signal.

  For example, when the period during which the waveform A signal is supplied to the piezo element is TA0 in the figure, the maximum voltage (absolute value) received by the piezo element is VpushA0. Further, when the period for supplying the signal of the waveform A to the piezo element is shortened and changed to TA1, the maximum voltage received by the piezo element decreases from VpushA0 to VpushA1. This also changes the amount of displacement of the piezo element in accordance with the first pull signal.

  In such a configuration, for example, the time-varying sawtooth wave (a0) is used in common for all the nozzles, and the pulse width supplied to each piezo element is individually set by the timing setting unit 22 for each nozzle. As a result, the effective voltage of the first pull signal can be changed. In addition, this makes it possible to effectively change the voltage of the drive signal with a simpler configuration, not directly.

  Therefore, according to this example, for example, the effective voltage of the drive signal supplied to the piezo element corresponding to each nozzle can be individually adjusted appropriately. Further, as described above, the variation in the capacity discharged from the nozzles of the ink jet head is often about 20% or less. In this case, the ink droplet capacity variation can be appropriately corrected by the above method. Therefore, according to this example, it is possible to appropriately correct the variation in the discharge capacity of each nozzle by using a simple method in which the circuit scale is not too complicated.

  More specifically, in this example, 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. Accordingly, for example, the effective voltage of the drive signal can be individually set for each nozzle with a circuit scale in a practical range. Therefore, according to this example, for example, it is possible to appropriately suppress the influence of the variation in the ejection characteristics of the nozzles within a range that is not problematic in practice.

  In the above description, the case where the portion of the waveform A corresponding to the first pull signal is a sawtooth wave has been described. However, when considered in a more general manner, not only the portion of the waveform A but also the other portion (for example, the portion of the waveform B or the waveform C) may be a signal whose voltage value changes with time such as a sawtooth wave. That is, the voltage change signal may be at least one of a first pull signal, a push signal, and a second pull signal.

  Also in this case, a portion using a sawtooth wave or the like is considered as a voltage change signal, and a period (pulse width or the like) in which each piezo element receives the voltage change signal is individually set for each piezo element. Based on this, the effective voltage received by each piezo element can be set individually for each nozzle. In addition, this makes it possible to individually control the ejection amount of ink droplets from the corresponding nozzles by individually changing the displacement amount of each piezoelectric element.

  In this case as well, the ink droplet capacity can be reduced by changing the period in which the piezo element receives the voltage change signal for a plurality of nozzles having different ink droplet capacities when receiving the same drive signal. 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 appropriately, for example.

  Further, when the voltage change signal is considered more generalized, it is a signal that is repeated in a preset cycle and the voltage gradually changes in one direction with the passage of time within the cycle. It can be said. In this case, a signal whose voltage gradually changes in one direction with the passage of time in the cycle is, for example, a signal in which the voltage gradually increases in the cycle or a signal in which the voltage gradually decreases in the cycle. It is. In this case, for example, the voltage may be changed stepwise at the boundary portion of the cycle. If comprised in this way, the voltage of a voltage change signal can be changed more appropriately, for example. In this case, for example, by setting for each piezo element which period of voltage in the cycle is supplied to each piezo element, the effective voltage received by each piezo element based on the voltage change signal is appropriately set. Can be adjusted. This also makes it possible to more appropriately adjust the droplet ejection characteristics of each nozzle.

  In addition, regarding the timing of supplying the voltage change signal to each piezo element, the timing setting unit 22 may be able to set a plurality of preset periods as a period during which the piezo element receives the voltage change signal, for example. In this case, the timing setting unit 22 sets a period in which each piezo element receives the voltage change signal, for example, by selecting one of a plurality of periods.

  Next, the relationship with the ink droplet landing position will be described in relation to the ejection characteristic correction performed in this example. As described above, according to this example, the volume of droplets ejected from each nozzle can be adjusted appropriately 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.

  FIG. 8 is a diagram for explaining the relationship between the ink droplet volume and the landing position. FIG. 8A is a table showing an example of the relationship between the line width of a straight line determined according to the volume of ink droplets and the displacement amount (landing displacement) of the landing position. Ink droplets are ejected from nozzles having normal ejection characteristics. In the case of ejection, the relationship between the voltage of the drive signal, the line width (wire diameter), and the landing deviation is shown.

  As shown in the table, 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 in a predetermined range corresponding to the resolution pitch. . 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, when the voltage of the drive signal is changed, the diameter and landing position of the ink dots 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. 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.

  FIG. 8B is a diagram showing the relationship between the line width (wire diameter) and landing deviation in the case where ink droplets are ejected from nozzles with normal ejection characteristics, and the effective voltage of waveform A is changed in the drive signal. When the pulse width T is changed variously, the wire diameter X, which is the thickness of a drawn straight line, and the landing position deviation amount Xp are shown. Moreover, in this figure, the straight line which attached | subjected the code | symbol A shows the relationship between the wire diameter X and the pulse width T. FIG. A straight line with a symbol B indicates a relationship between the deviation amount Xp of the landing position and the pulse width T.

  As is clear from this figure, the wire diameter X and the landing position shift amount Xp do not change independently, but change with correlation with changes in the effective voltage of the drive signal. Therefore, by changing the effective voltage of the drive signal, the wire diameter X and the landing position shift amount Xp can be changed simultaneously. More specifically, as can be seen from FIG. 8, when correction for returning the ink droplet volume (line width) to the center value X0 is performed, the deviation of the landing position also moves in a direction to return to the center value xp0. In this case, for example, if the ejection characteristics are corrected by changing the effective voltage of the drive signal by changing the pulse width T for a nozzle with poor ejection characteristics, the wire diameter (ink droplet capacity) and the landing position Can be corrected (improved) at the same time.

  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.

  In this example, for example, by adopting a pulse width drive effective voltage control method, a range that can be corrected for the effective voltage of the drive signal is about ± 25% (α = 0.25) with respect to the center voltage V0. Can be corrected. In addition, for example, the line width of the drawn straight line can be appropriately corrected in a range of about ± 25% with respect to the predetermined center value. Therefore, according to this example, at the time of manufacturing an inkjet head, for example, the number of inkjet heads that have normal ejection characteristics by correction can be appropriately increased, and the inkjet head can be manufactured more appropriately with a high yield.

  More specifically, when the drive signal shown in FIG. 7 is used, variations such as ink droplet volume 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 constant pulse width TA0 corresponding to the set center value is added to all nozzles is measured. Then, based on the measured print line width for each nozzle, a shift amount (a shift amount of the ink droplet capacity) from the set center value of the line width is calculated. Further, an applied pulse width TAn that can return the line width to the set center value X0 is obtained based on the amount of deviation of the line width in each nozzle. For example, in FIG. 8, when the position where the line width is shifted is the position indicated by the symbol k, if the pulse width is reduced by αTo, the point returns to the point k0 of the center value X0, and the line diameter, that is, the volume of ejected ink ( (Size) can be returned to the set center value.

  Then, based on the deviation amount from the center value of the line width obtained for each nozzle, an applied pulse width TAn for returning the set center value is added to each nozzle. Then, the variation in line width is measured again. 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 with a line width that exceeds a predetermined range, the same correction as described above is performed again on the nozzle, and the pulse width TXx after re-correction is added to remeasure the line width. To do. If the line width variation is below a certain value, the correction is completed.

  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.

  Next, a supplementary explanation will be given for the change in the amount of deviation of the landing position of the ink droplets. As described above, when ink droplets are ejected by the ink jet method, the influence of the air resistance received by the ink droplets varies depending on the volume of the ink droplets. As a result, the amount of deviation of the landing position also changes depending on the ink droplet capacity.

  9 and 10 are diagrams for explaining a change in the deviation amount of the landing position of the ink droplet. FIG. 9 is a diagram illustrating an example of how the landing position changes due to the change in the ink droplet volume. How the landing position shifts in the wide gap when the distance (print gap) between the inkjet head and the medium is increased. Is modeled. FIG. 10 is a diagram illustrating an example of velocity components of ink droplets during flight.

  When the volume of the ink droplet changes, for example, as shown in FIG. 9, 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 of the ink droplet change, and the average velocity Vi suitable for the ink changes. More specifically, for example, as shown in FIG. 10, 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. Therefore, for example, when the flying speed of the ink droplet is reduced, the flight curve 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.

  On the other hand, in this example, for example, by changing the effective width of the drive signal by changing the pulse width for controlling the timing for supplying the drive signal, according to the use conditions (printing conditions) of the liquid ejection device, The line width of the drawn straight line can be adjusted appropriately. This also makes it possible to appropriately correct the ink droplet volume and the landing position variation at the same time. Therefore, according to this example, for example, even when printing is performed under various conditions, it is possible to perform printing more appropriately with high accuracy.

  Next, a more specific circuit configuration for driving the piezoelectric element in this example, a modified example of the drive signal, and the like will be described. First, an example of a more specific circuit configuration for driving a piezo element in this example will be described.

  FIG. 11 is a diagram showing a simplified equivalent circuit of a drive circuit for driving the piezo element 104 in the inkjet head. In the piezo-type ink jet 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 can be considered as shown in FIG. In this example, for example, a drive signal voltage including a sawtooth waveform A having a pulse width TA as shown in FIG. 7 is applied to a common electrode of a plurality of piezo elements 104.

  In this case, the energizing time for supplying the waveform A signal to each piezo element 104 is set to any required value by the timer function in the timing setting unit 22 (see FIG. 1). In this case, for example, setting to TA0 or TA1 shown in FIG. 7 can be considered. Then, the voltage of the signal of the waveform A is applied to each piezo element 104 only during the set time (Ta). If comprised in this way, the peak voltage of a sawtooth wave can be changed continuously, for example by changing energization time.

  After the supply of the waveform A signal, the voltage of the waveform A is interrupted by the switching circuit, and the waveform B in the drive signal shown in FIG. 7 rises in synchronization with the fall and fall. Further, when the waveform B ends, the waveform C rises in synchronization with the end, and one of the waveforms shown in FIG. 7 is completed. According to this example, for example, a drive signal including a voltage change signal can be appropriately supplied to each piezo element 104.

  FIG. 12 is a diagram more specifically showing a configuration for supplying a drive signal to the piezo element 104. In this example, the drive signal output unit 18 supplies a drive signal to a common electrode with respect to the plurality of piezo elements 104. The ejection nozzle setting unit 20 includes, for example, a latch unit and a shift register unit, and selects a nozzle that should eject ink droplets in accordance with an instruction received from the control unit 26. In addition, the timing setting unit 22 has a timer function for controlling the timing for supplying the drive signal to each piezo element 104, and in accordance with an instruction from the control unit 26 based on correction data received from the correction data storage unit 24. The timing for supplying the drive signal to each piezo element 104 is controlled.

  Further, the discharge nozzle setting unit 20, the timing setting unit 22, and the like may be connected to the piezo element 104 via, for example, a circuit configuration that is the same as or similar to a known configuration that controls the operation of the piezo element 104. For example, in the illustrated case, the ejection nozzle setting unit 20 and the timing setting unit 22 are connected to the piezo element 104 via various logic circuits, switching transistors, and the like. According to this example, a drive signal can be appropriately supplied to each piezoelectric element 104.

  The circuit configuration shown in FIG. 12 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 a sawtooth wave is mainly used as the voltage change signal included in the drive signal has been described. However, the voltage change signal is not limited to the sawtooth wave, and a signal having another waveform may be used. In this case, for example, it is preferable to use a signal whose voltage peak value changes by controlling the pulse width.

  FIG. 13 is a diagram showing a modified example of the drive signal, and shows an example in which various signals other than the sawtooth wave are used for the portion of the waveform A corresponding to the voltage change signal. As shown in the drawing, as the voltage change signal, for example, various signals as indicated by reference numerals a1 to a4 in the drawing can be used. Moreover, you may use the voltage change signal which changes similarly about the part of the waveform B or the waveform C. FIG.

  As the drive signal, for example, a signal whose polarity is inverted at a predetermined timing using an inverting converter circuit or the like may be used. In this case, it is conceivable to change the effective voltage applied to the piezo element by inverting the polarity of the drive signal including the voltage change signal by, for example, an inverting converter circuit controlled by an input current. Also in this case, by changing the inversion timing for each piezo element, it is possible to individually control the pulse width of the voltage change signal and adjust the effective voltage appropriately.

  In this case, more specifically, the timing setting unit 22 (see FIG. 1), for example, inverts the polarity of the voltage change signal in the middle of the cycle, and individually sets the timing to invert the polarity for each drive element. Set. Thereby, for example, for the voltage change signal before and after the inversion of the polarity, the period during which each piezo element receives the signal is individually set. If comprised in this way, the voltage of a voltage change signal can be changed more appropriately, for example.

  FIG. 14 is a diagram showing a further modification of the drive signal, and shows an example of the drive signal when the polarity is inverted at a predetermined timing. In this case, the drive signal having the waveform shown in the figure can be obtained by inverting the polarity of the input sawtooth wave after a predetermined time using an inverting converter circuit. In this case, TA0 (line a1) or TA2 (line a2) is a timing different from TA0, where TA0 (line a0) is the initial (reference) inversion timing without correction. By reversing the polarity, it is possible to change the initial push voltage Vpush-t0 as small as Vpush-t1 or as large as Vpush-t2. Therefore, also in this case, the effective voltage of the drive signal supplied to the piezo element can be appropriately changed.

  Also in this case, a signal having a waveform other than the sawtooth wave may be used as the voltage change signal. FIG. 15 is a diagram showing a further modification of the drive signal, and shows an example of the drive signal when the polarity is inverted at a predetermined timing using a signal having a waveform other than the sawtooth waveform. In this case as well, as in the case described with reference to FIG. 14, the effective voltage of the drive signal supplied to the piezo element can be appropriately changed.

  Further, in this case, since the change in the input voltage is gentle as compared with, for example, the case where the input voltage of the sawtooth wave is inverted, the voltage can be changed more finely than when the sawtooth wave is used. Therefore, with this configuration, for example, it is possible to appropriately control a change in a voltage having a smaller width in a certain time range.

  In the above description, the signal input as the voltage change signal is mainly illustrated and described in the case where the voltage changes linearly. However, the voltage of the input signal may be changed in a curved shape, for example. The circuit that inverts the input voltage is not particularly limited, and various configurations that can switch the voltage at a predetermined timing can be used. Further, the positive / negative relationship of the voltage may be a relative relationship as long as the effective voltage applied to the electrode of the piezoelectric element is changed.

  As described above, according to this example, for example, by measuring and correcting the line width of the straight line drawn by each nozzle in the sub-scanning direction, the variation in the ink droplet capacity and the variation in the landing position are appropriately corrected. In addition, the ink droplet volume can be made uniform and landed at an appropriate position. In addition, for example, the occurrence of streaks or the like can be appropriately suppressed. Therefore, according to the present example, for example, it is possible to perform printing more appropriately by appropriately increasing the quality of printing.

  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.

  Further, for the correction of the ink droplet capacity and the like, an increase in circuit scale can be suppressed by using a method in which the effective voltage of the drive signal is individually set for each nozzle. In addition, this makes it possible to perform correction more appropriately while suppressing an increase in cost.

  Note that the correction of the ink droplet volume and the like described above may be performed, for example, at the time of factory shipment of the liquid ejection device 10 (see FIG. 1) or at the time of manufacturing the inkjet head. 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.

  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 ... Timing setting unit, 24 ... correction data storage unit, 26 ... control unit, 50 ... medium, 102 ... nozzle, 104 ... piezo element

Claims (11)

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 timing setting unit that sets a timing at which the driving element corresponding to the nozzle set in the nozzle setting unit as the nozzle that discharges a droplet receives the driving signal;
The discharge nozzle setting unit can select a plurality of nozzles that discharge droplets of the same preset volume as the nozzles that discharge droplets,
The drive signal output unit is a voltage change signal that is a signal whose voltage changes over time as at least a part of the drive signal in common with respect to the plurality of nozzles that discharge droplets of the same capacity. Output
The timing setting unit individually sets each of the driving elements for a period in which the driving elements receive the voltage change signal.
Each of the nozzles discharges a droplet by an ink jet method in accordance with the drive signal in which the period for receiving the voltage change signal is individually set in the corresponding drive element.   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 timing setting unit sets a timing for receiving the first pull signal, the push signal, and the second pull signal for each of the driving elements,
The liquid discharge apparatus according to claim 2, wherein the voltage change signal is at least one of the first pull signal, the push signal, and the second pull signal. A correction data storage unit for storing correction data used for correcting the ejection characteristics of the nozzles;
The correction data storage unit, as the correction data, for the nozzle that needs to be corrected for ejection characteristics, the timing at which the drive element receives the voltage change signal is set in advance according to the ejection characteristics of the nozzle Remember
The timing setting unit sets the timing for supplying the voltage change signal to the drive element corresponding to the nozzle that requires correction of ejection characteristics based on the correction data. The liquid discharge apparatus according to any one of the above.   The voltage change signal is a signal that is repeated at a preset cycle, and the voltage gradually changes in one direction with the passage of time within the cycle. 5. The liquid ejection device according to any one of items 1 to 4.   6. The liquid ejection apparatus according to claim 1, wherein the voltage change signal is a sawtooth wave whose voltage changes in a sawtooth shape. The voltage change signal is a signal repeated at a preset period,
The timing setting unit reverses the polarity of the voltage change signal in the middle of the cycle, and individually sets the timing for inverting the polarity for each of the driving elements, so that the voltage before and after the polarity is inverted. The liquid ejecting apparatus according to claim 5, wherein a period during which each of the driving elements receives the signal is set individually for the change signal. 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, comprising: individually setting a period during which the driving element receives the voltage change signal for each of the driving elements to adjust ejection characteristics of droplets from the nozzles. By preliminarily measuring the ejection characteristics of each nozzle when using the preset reference drive signal, nozzle characteristic data indicating the ejection characteristics of each nozzle is acquired in advance,
For the drive elements corresponding to the respective nozzles, a timing set based on the nozzle characteristic data is set as a timing at which the drive element receives the voltage change signal,
9. The liquid ejection apparatus according to claim 8, wherein a period in which the driving element receives the voltage change signal is individually set for each driving element based on a timing set based on the nozzle characteristic data. Adjustment method.   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 9, 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 8, 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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