JP6051809B2 - Inspection method and driving method - Google Patents

Description

  The present invention relates to an inspection method and a driving method.

  An ink jet recording apparatus used as an image forming apparatus such as a printer, a facsimile machine, a copying apparatus, or a plotter includes a nozzle that ejects ink droplets (hereinafter also referred to as “droplet”), an ink flow path that communicates with the nozzle, A liquid ejecting head including a pressure generating unit that pressurizes ink in the ink flow path is mounted.

  In an ink jet recording apparatus, pressure fluctuation is generated in ink in a pressure chamber by supplying ejection pulses having a predetermined waveform shape to a pressure generating element, and ink droplets are ejected from nozzle openings. As described above, in a recording apparatus that causes pressure fluctuations to eject ink droplets, the magnitude and timing of pressure fluctuations at the time of ink droplet ejection are important. That is, by optimizing the magnitude and timing of this pressure fluctuation, it is possible to fly a predetermined amount of ink droplets as planned.

  High precision is required for the magnitude and timing of the pressure fluctuation, and when these magnitudes and timings are shifted, a phenomenon called “bending” occurs. This “bending” is a phenomenon in which columnar ink droplets extending obliquely with respect to the surface of the recording paper fly in the direction of the surface of the recording paper. When this bending occurs, the dots formed by the landing of the ink droplets become larger than the designed size or deform, and the image quality is impaired.

  Due to this “bending”, when the head unit of the ink jet recording apparatus is a line head, the “bending” appears as a streak in the image when the entire printed image is viewed. In addition, even when the head unit is a serial head, ink droplets ejected from other nozzles in the nearby area land, making it less noticeable than the line head type, but disturbing the printed image. End up.

  As described above, in an ink jet recording apparatus, it is necessary to discharge a low volume of ink droplets in order to obtain a high definition image. In such a driving method of the ink jet recording apparatus, the amplitude of the meniscus due to the vibration system having the period Tc is increased. Therefore, there is a problem in that the mist-like ink droplets generated when the spherical ink droplets are separated from the meniscus are likely to fly in a rod shape, resulting in a decrease in print quality.

  Japanese Patent Application Laid-Open No. 2004-133867 discloses a technique for measuring the ink droplet bending with a laser detector and adjusting the waveform of the ejection pulse to satisfy the criterion when the criterion is not satisfied. Patent Document 2 describes that a printed image is read to measure a flying bend amount and drive control is performed according to the bend amount. And the technique which reduces a curvature by changing the pressure of a pressure chamber using the 1st and 2nd drive source is disclosed. Further, Patent Document 3 discloses a technique for preventing ink droplets from flying and bending by minimizing meniscus vibration and shortening the meniscus vibration decay time.

  However, the technique described in Patent Document 1 has a problem that the bending evaluation of the ink droplet is not performed in consideration of the error factor because the ink droplet bending inspection is performed in the normal ejection pattern state. In the technique described in Patent Document 2, the amount of bending is measured with a specific printed image. However, there is a problem that it is not possible to see all the capabilities of the liquid ejecting head in an image of normal printing.

  That is, when the water-repellent film applied to the nozzle surface deteriorates and the edge peels off, the surface tension becomes low and the temperature becomes high, and the meniscus shape becomes distorted. Then, there is a problem that the ink droplet is easily bent in a high frequency region where the meniscus fluctuation is large.

  Such a phenomenon related to deterioration does not occur uniformly in all nozzles of the head, but occurs in weak nozzles. When the waveform is optimized using a strong nozzle in a state where a weak nozzle cannot be found, bending may occur due to the weak nozzle.

  Further, in the liquid ejecting head, meniscus vibration tends to change due to various error factors such as detection temperature error, ink lot difference, and deterioration of the water-repellent film adhering to the nozzle. However, the technique described in Patent Document 3 has a problem that when the meniscus vibration after ejection increases, the ink droplet to be ejected next tends to bend.

  Therefore, the present invention has been made in view of the above-described problems of the prior art, and in order to prevent image defects due to the discharge bend of the liquid ejecting head, the bend is measured in advance, and the waveform is further reduced to a reference value or less. It is an object of the present invention to provide an inspection method capable of obtaining a liquid ejecting head in which the above is adjusted.

  In order to solve the above-described problem, the inspection method according to the first aspect of the present invention is an inspection method for a liquid ejecting head in which ink droplets are ejected from nozzles, and the meniscus shakes when the ink droplets are ejected. A step of applying an excitation waveform having an amplitude that maximizes the amplitude and an inspection waveform that is normally used during printing and has a minimum amplitude, and a bending amount of an ink droplet that is ejected by applying the inspection waveform. A step of measuring, a step of determining whether or not the bending amount satisfies a predetermined criterion, and a new inspection instead of the inspection waveform when it is determined that the bending amount does not satisfy the criterion. A step of selecting a waveform from waveform candidates prepared in advance, a step of applying the excitation waveform and the new inspection waveform, and an ink droplet ejected by applying the new inspection waveform Bend Characterized in that it comprises a measuring a.

  According to the present invention, it is possible to obtain an inspection method capable of preventing an image defect due to the discharge bend of the liquid ejecting head and further reducing the discharge bend to a reference value or less.

FIG. 3 is a perspective view of a liquid ejecting head that executes the inspection method according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view of FIG. 1, which is a perspective view of a liquid jet head that performs an inspection method according to the first embodiment of the present invention, when viewed from the X direction. FIG. 3 is a cross-sectional view taken along the line AA of FIG. 2, which is a cross-sectional view of the liquid jet head that executes the inspection method according to the first embodiment of the present invention. It is a flowchart figure which shows the flow of the inspection method which concerns on the 1st Embodiment of this invention. It is a figure which shows (a) excitation waveform, a test | inspection waveform, and (b) meniscus fluctuation when the inspection method which concerns on the 1st Embodiment of this invention is performed. It is a figure which shows the (a) discharge state and (b) excitation waveform and test | inspection waveform when the test | inspection method which concerns on the 1st Embodiment of this invention is performed. It is a figure which shows the waveform which reduced the bending of the vibration waveform and test | inspection waveform when the test | inspection method which concerns on the 1st Embodiment of this invention is performed. It is a figure which shows an excitation waveform and inspection waveform when the inspection method which concerns on the 2nd Embodiment of this invention is performed. It is a figure which shows the waveform which applied the vibration waveform when the inspection method which concerns on the 4th Embodiment of this invention was performed, and the bending | flexion countermeasure of the inspection waveform. FIG. 9 is a perspective view of a liquid ejecting apparatus equipped with a liquid ejecting head that executes an inspection method according to first to fifth embodiments of the present invention.

  Next, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified thru | or abbreviate | omitted suitably. The present invention relates to an inspection method and a driving method, and further relates to prevention of deterioration in image quality due to ejection bending.

  In short, in order to prevent an image defect due to the ejection bending of the liquid ejecting head, an inspection method and a driving method capable of measuring the bending in advance and further adjusting the waveform to be equal to or less than the reference value are obtained. It is what.

  The characteristics of the present invention described above will be described in detail with reference to the drawings. First, a liquid jet head that executes the inspection method according to the first embodiment of the invention will be described. FIG. 1 is a perspective view of a liquid ejecting head that performs an inspection method according to the first embodiment of the present invention, and FIG. 2 is a liquid ejecting head that performs an inspection method according to the first embodiment of the present invention. It is sectional drawing which looked at FIG. 1 which is a perspective view of this from the X direction. FIG. 3 is a cross-sectional view taken along the line AA of FIG. 2, which is a cross-sectional view of the liquid jet head that performs the inspection method according to the first embodiment of the present invention.

  The liquid ejecting head 1 that executes the inspection method according to the first embodiment of the present invention includes a piezoelectric element that is filled with ink from a main tank through a common liquid chamber, a pressure chamber communication path, and a pressure chamber. As a result, the ink in the pressure chamber is pressurized, and ink droplets are ejected from the nozzles. The configuration of the liquid jet head 1 can be broadly divided into a flow path portion and a drive portion.

  The flow path portion includes a nozzle plate 2 having a nozzle 20, a chamber plate 3 having a pressure chamber 21 and a pressure chamber communication path 22, a diaphragm plate 4 having a diaphragm, a filter damper plate having a filter 29 and a filter damper. 6, a manifold plate 5 serving as a common liquid chamber below the filter 29, and a frame 7 having a common liquid chamber on the filter 29 and an ink supply path.

  The common liquid chambers 25, 26 are formed by the manifold plate 5 and the frame 7, and the filter damper plate 6 sets the upstream side as the filter upper common liquid chamber 26 on the frame 7 side and the downstream side as the lower filter common liquid chamber 25. The nozzle plate 2 has nozzles 20 arranged in a staggered manner with two rows arranged in a row. The material is stainless steel, in particular, SUS (Stainless Used Steel) 316 is used, and the processing method uses press working.

  The chamber plate 3 includes a pressure chamber 21 disposed so as to communicate with the nozzle 20 and a pressure chamber communication path 22 communicating with the common liquid chambers 25 and 26. In this case, stainless steel is used as the material, and SUS304 is particularly used. As a method of forming the pressure chamber 21 and the pressure chamber communication path 22, press working is used. Deformation and burrs caused by pressing are post-processed so as to be substantially flat by double-side polishing.

  The diaphragm plate 4 includes a vibration plate that forms one wall surface of the pressure chamber 21, an ink communication hole that supplies ink from the common liquid chambers 25 and 26 to the pressure chamber 21, and a vibration plate damper. The material is Ni and is formed by electroforming. The diaphragm damper is provided in a portion facing the common liquid chambers 25 and 26. The thickness of the vibration plate damper is the same as that of the vibration plate, and is arranged at substantially the same length as the nozzle row.

  The filter damper plate 6 is provided with a filter 29 that collects foreign matters contained in the ink flowing from the upstream. The material is Ni and is formed by electroforming. The filter 29 is disposed within the same range in length and width of the common liquid chambers 25 and 26. Therefore, it becomes longer than the length of the nozzle row.

  In addition, filter dampers are provided at both ends of the filter 29 in the nozzle row direction. The filter damper has a role of absorbing pressure waves propagating from the pressure chamber 21 to the common liquid chambers 25 and 26. The filter damper is formed with the same thickness as the filter 29. A frame formed by two-stage electroforming and holding the filter 29 and the filter damper in the first layer and the first layer is arranged in the second layer. Here, the first layer is 3 μm and the second layer is 10 μm.

  The manifold plate 5 has a filter damper air vent chamber 36 and an air release passage at both ends of the common liquid chamber 25 under the filter and the nozzle row direction. The common liquid chamber 25 under the filter has substantially the same length as the nozzle row. The filter damper air bleed chamber 36 is arranged approximately the same size as the filter damper. The air release passage is formed in a state where a part of the side wall of the filter damper air vent chamber 36 is recessed.

  The common liquid chamber 25 under the filter is formed by full etching, and the filter damper air vent chamber 36 and the air release passage are formed by half etching. The half etching depth is about half of the plate thickness. Here, the manifold plate 5 has a plate thickness of 0.2 mm, and the filter damper air vent chamber 36 has a depth of 0.1 mm.

  The filter damper plate 6 is disposed at a position that divides the common liquid chambers 25 and 26 into two, and is provided with a filter 29 that captures foreign matter and a filter damper that suppresses vibrations of the common liquid chambers 25 and 26. The filter 29 has an infinite number of holes smaller than the nozzle holes, and prevents foreign matters larger than the nozzle holes from flowing into the common liquid chambers 25 and 26. The filter damper suppresses vibrations of the common liquid chambers 25 and 26 in the same manner as the diaphragm damper. The material formed by electroforming is Ni.

  In the configuration, the part constituting the filter damper and the filter 29 is the first layer, and the part supporting it is the second layer. Here, the first layer is formed with 3 μm, and the second layer is formed with 10 μm. Since the filter 29 is a resistor, it is desirable to increase the number as much as possible and to make it thin. Since the filter damper is deformed, it is desirable that the filter damper is thin. However, if the filter damper is too thin, the strength becomes low, and the filter damper may be damaged beyond the limit of displacement.

  The frame 7 includes a filter common liquid chamber 26 and an ink supply path for supplying ink. The ink supply paths are respectively disposed at both ends in the longitudinal direction of the common liquid chamber 26 on the filter. The ink supply path is arranged outside the range of the filter 29. The material is SUS303, which is formed by cutting. Alternatively, it may be formed by resin injection molding.

  The drive unit is the actuator 8 using the piezoelectric element 32. The actuator 8 is formed by connecting two rows of nozzles 20 and connecting two piezoelectric elements 32 to one base. The piezoelectric element 32 is connected to a diaphragm, and an electric signal is applied by an FPC (Flexible Printed Circuits) 34 to displace the piezoelectric element, fluctuate the pressure chamber 21, and eject ink droplets from the nozzle 20.

  In these, first, the nozzle plate 2, the chamber plate 3, and the diaphragm plate 4 are joined together as a set, and then the manifold plate 5 and the filter damper plate 6 are joined. Next, the actuator 8 and the diaphragm plate 4 are joined. Finally, the liquid ejecting head 1 is formed by joining the frame 7.

  The liquid ejecting head 1 formed in this manner supplies ink from the frame 7, collects foreign matter by the filter 29, and fills the individual liquid chamber with ink, thereby ejecting ink droplets from the nozzle 20. The vibrations of the common liquid chambers 25 and 26 generated when ink droplets are ejected are absorbed by the diaphragm damper and the filter damper.

  Next, the inspection method according to the first embodiment of the present invention will be described with reference to FIG. FIG. 4 is a flowchart showing the flow of the inspection method according to the first embodiment of the present invention. The bending inspection using the inspection method according to the first embodiment of the present invention is performed in the discharge state observation apparatus.

  The inspection procedure is as shown below. In the process of step 401 (hereinafter referred to as “S”) 401 in FIG. 4, the excitation waveform and the inspection waveform are applied. The excitation waveform is obtained by combining and applying two pulses of an excitation waveform and an inspection waveform shown in FIG. 8 to be described later at a resonance timing that is a resonance frequency of a liquid chamber filled with ink. It is the one that maximizes the shaking.

  Next, in the process of S402, the bending amount of the ink droplet ejected with the inspection waveform is measured. In the process of S403, it is determined whether or not the amount of bending of the droplet is below a reference value. If the amount of bending is equal to or less than the reference value (S403: Y), the process is terminated.

  If it is equal to or greater than the reference value (S403: N), the inspection waveform is changed to a waveform that is difficult to bend in the process of S404. The inspection waveform is selected from bend countermeasure waveform candidates prepared in advance. For example, an inspection waveform that widens the pulse width or slows down the falling waveform is selected.

  In FIG. 9 to be described later, the bending is reduced by selecting the two-stage waveform as the falling waveform of the inspection waveform. That is, the inspection waveform is stepped with two stages of pulling in, and the time tw between the first pulling time and the second pulling time is adjusted to employ the one with the least amount of bending. .

  Note that the reference value indicating the bending reference is determined based on the image quality. The selection from the bend countermeasure waveform candidates varies depending on the time allowed for the waveform, the number of subsequent pulses, and the like.

  In the process of S405, the excitation waveform and the changed inspection waveform are applied again. In the process of S406, the bending amount of the changed inspection waveform is measured. In the process of S407, it is determined whether or not the bending amount is equal to or less than a reference value.

  In the process of S407, if the amount of bending is less than the reference value (S407: Y), the process is terminated. If the amount of bending is equal to or greater than the reference value (S407: N), the process returns to S403.

  By adopting this inspection method, the waveform is conventionally determined by the strength against the bending of the nozzle, whereas according to the inspection method according to the embodiment of the present invention, by applying the excitation waveform, It became possible to make it easier to bend by shaking. Even if a weak nozzle cannot be detected, it is possible to intentionally bend it easily. As a result, it was possible to find a condition that is easy to bend and to optimize the waveform in a state that is easy to bend.

  Next, the vibration waveform, the inspection waveform, and the meniscus fluctuation when the inspection method according to the first embodiment of the present invention is executed will be described. FIG. 5 is a diagram showing (a) an excitation waveform, an inspection waveform, and (b) a meniscus fluctuation when the inspection method according to the first embodiment of the present invention is executed.

  The excitation waveform 40 is a waveform when the meniscus is shaken more than in normal printing. That is, a normal waveform or a waveform that is easy to bend and is used to obtain image quality. Here, as shown in FIG. 5A, the amplitude voltage of the excitation waveform 40 is larger than the amplitude voltage of the inspection waveform 41.

  The droplet velocity at time Td between the excitation waveform 40 and the inspection waveform 41 is as shown in FIG. By inputting the vibration waveform 40, the inspection waveform 41 is easily bent, and the ability of the liquid ejecting head can be easily confirmed. Note that the inspection waveform 41 has a minimum pulse configuration used in a printing waveform during normal printing.

  In the inspection waveform 41, when the portion where Tj, which is the reciprocal of the droplet velocity shown in FIG. 5B, is small, that is, the portion where the droplet velocity is high is used, the meniscus shake becomes large, and the portion becomes easier to bend. . As the portion where Tj is small, an excitation waveform 40 that is the first pull-in of Td and an inspection waveform 41 that is the next pull-in are used.

  Next, a droplet discharge state, an excitation waveform, and an inspection waveform when the inspection method according to the first embodiment of the present invention is executed will be described. FIG. 6 is a diagram showing (a) a discharge state, and (b) an excitation waveform and an inspection waveform when the inspection method according to the first embodiment of the present invention is executed. Two droplets are ejected by the excitation waveform 40 and the inspection waveform 41, respectively. The waveform to be measured is only the inspection waveform 41.

  Here, at an average speed 1.4 mm away from the nozzle, the excitation waveform 40 is 10 m / s and the inspection waveform 41 is 7 m / s. Since the timing of the inspection waveform 41 varies depending on the liquid ejecting head, the water repellent film, the waveform, and the like, it is necessary to measure in advance at which timing it is easy to bend. Here, the measurement is performed at the timing at the peak at which the meniscus rises again after the droplet is ejected.

  The amount of bending of the droplet is measured at a point 1.4 mm away from the nozzle. Here, the reference value of the bending amount is set to 20 μm or less. If it is above the reference value, the waveform is changed to a waveform that is difficult to bend. Here, the inspection waveform that has been changed when the bending amount is equal to or greater than the reference value will be described. FIG. 7 is a diagram showing a waveform in which the excitation waveform and the bending of the inspection waveform are reduced when the inspection method according to the first embodiment of the present invention is executed.

  As shown in FIG. 7, here, it is known in advance that the droplet is difficult to bend by increasing the pull-in time of the falling portion of the inspection waveform 41, and this is adopted. However, if the pull-in time is made too long, the waveform length becomes longer, so the productivity is lowered. Therefore, it is desirable to shorten the waveform length as much as possible.

  The inspection waveform is changed and the inspection is performed again. If the amount of bending of the droplets is equal to or less than the reference value, the inspection is terminated with the liquid ejection head being passed in the new inspection waveform. The waveform that actually forms the image is a waveform that matches the inspection waveform when the image is passed. By using this inspection method, it is possible to easily carry out an inspection in a state where the droplet is most easily bent, and to select an optimum waveform.

  Next, a second embodiment of the present invention will be described. FIG. 8 is a diagram showing an excitation waveform and an inspection waveform when the inspection method according to the second embodiment of the present invention is executed. In this embodiment, the inspection is executed by combining a plurality of excitation waveforms 40, for example, two pulses. Here, the pulse interval Td is arranged according to the resonance frequency of the liquid chamber filled with the ink of the liquid ejecting head.

  Here, the resonance frequency Tc indicates a Helmholtz frequency, and in this embodiment, Tc = 3.0 us. As a result, the excitation force can be made stronger than in the case of a voltage increase of a simple pulse, and a strong stress can be applied to the liquid ejecting head due to an increase in meniscus vibration.

  Next, a third embodiment of the present invention will be described. In the present embodiment, the same waveform is used for the excitation waveform and the idle ejection waveform. As a result, the number of unnecessary waveform data can be reduced, and the excitation waveform can be input without increasing the memory capacity of the waveform control circuit. For example, by bending this into the liquid ejecting apparatus, bending verification in the apparatus state can be performed.

  Next, a fourth embodiment of the present invention will be described. FIG. 9 is a diagram illustrating an excitation waveform when the inspection method according to the fourth embodiment of the present invention is executed, and a waveform in which a countermeasure against bending of the inspection waveform is taken. Here, the inspection waveform 41 as the bending countermeasure waveform is a two-stage lead-in waveform.

  As shown in FIG. 9, the amount of bending is minimized by optimizing the time tw between the first pull-in time and the second pull-in time in two stages of the test waveform 41. Can do.

  Next, a fifth embodiment of the present invention will be described. Here, as a measurement of the amount of bending, droplets of an excitation waveform and an inspection waveform are printed on the medium, and the amount of bending is measured from the landing position of the dot. Accordingly, it is possible to measure the amount of bending even in the liquid ejecting apparatus and the like, and it is possible to perform the bending evaluation when, for example, deterioration occurs over time.

  Next, a sixth embodiment of the present invention will be described. Here, the liquid ejecting head described in the first to fifth embodiments is mounted on the liquid ejecting apparatus. FIG. 10 is a perspective view of a liquid ejecting apparatus equipped with a liquid ejecting head for executing the inspection methods according to the first to fifth embodiments of the present invention.

  Thus, high-quality printing can be performed by performing an appropriate inspection with respect to the bending amount. In addition, since the bending amount inspection and the bending amount countermeasure can be executed even in a state where the liquid ejecting head is mounted, a highly reliable liquid ejecting apparatus can be provided.

  Note that each operation flow of the inspection method in the embodiment of the present invention shown in FIG. 4 can be executed by a program on a computer. That is, a CPU (not shown) built in the droplet ejecting apparatus loads a program stored in a storage medium including a ROM, a RAM, etc. (not shown), and the processing steps of the program are sequentially executed.

  As described above, according to the present invention, it is possible to obtain an inspection method and a driving method that can prevent an image defect due to the discharge bend of the liquid ejecting head and can make the discharge bend below a reference value.

  The present invention has been described above by the preferred embodiments of the present invention. While the invention has been described with reference to specific embodiments thereof, various modifications and changes can be made to these embodiments without departing from the broader spirit and scope of the invention as defined in the claims. is there.

DESCRIPTION OF SYMBOLS 1 Liquid jet head 2 Nozzle plate 3 Chamber plate 4 Diaphragm plate 5 Manifold plate 6 Filter damper plate 7 Frame 8 Actuator 20 Nozzle 21 Pressure chamber 22 Pressure chamber communication path 25 Common liquid chamber under filter 26 Common liquid chamber on filter 29 Filter 32 Piezoelectric Element 34 FPC
35 Vibration plate damper air release chamber 36 Filter damper air release chamber 40 Excitation waveform 41 Inspection waveform 50 Ink cartridge 54 Liquid ejecting device 55 Carriage 56 Main guide lot 57 Subordinate guide lot 59 Printing mechanism section 64 Main scanning motor 65 Drive pulley 66 Drive pulley 67 Timing belt 73 Sub-scanning motor 81 Recovery device

Japanese Patent No. 4158357 JP 2006-062165 A Japanese Patent No. 3500831

Claims (6)

A method for inspecting a liquid jet head in which ink droplets are ejected from a nozzle,
Applying an excitation waveform having an amplitude that maximizes shaking of the meniscus when the ink droplets are ejected, and an inspection waveform that is used during normal printing and has the minimum amplitude;
Measuring the bending amount of the ink droplet ejected by applying the inspection waveform;
Determining whether the bending amount satisfies a predetermined criterion;
When it is determined that the amount of bending does not satisfy the criterion, a step of selecting a new inspection waveform instead of the inspection waveform from among waveform candidates prepared in advance;
Applying the excitation waveform and the new inspection waveform;
And a step of measuring a bending amount of the ink droplet ejected by applying the new inspection waveform.   Including a step of determining whether or not a bending amount of an ink droplet ejected by applying the new inspection waveform satisfies the criterion, and when the bending amount is determined not to satisfy the criterion, The inspection method according to claim 1, further comprising a step of selecting a new inspection waveform from the waveform candidates in place of the new inspection waveform. The vibration waveform, the inspection method according to claim 1 or 2, characterized in idle discharge waveform der Rukoto. 4. The inspection method according to claim 1, wherein the falling edge of the new inspection waveform is a two-stage waveform. 5. The curve amount, the inspection method according to any one of the preceding claims 4, characterized in Rukoto measured using the position of the ink droplets ejected in a point distant sauce predetermined distance from the nozzle . A method of driving a liquid jet head in which ink droplets are ejected from a nozzle,
Applying an excitation waveform having an amplitude that maximizes shaking of the meniscus when the ink droplets are ejected, and an inspection waveform that is used during normal printing and has the minimum amplitude;
Measuring the bending amount of the ink droplet ejected by applying the inspection waveform;
Determining whether the bending amount satisfies a predetermined criterion;
When it is determined that the amount of bending does not satisfy the criterion, a step of selecting a new inspection waveform instead of the inspection waveform from among waveform candidates prepared in advance;
Applying the excitation waveform and the new inspection waveform;
The driving method characterized in that it comprises a measuring a curve amount of the ink droplets ejected by the new test waveform is applied.

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