JP2012035420A - Inkjet head and method for driving the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet head and a method for driving the same, which can achieve high quality printing.SOLUTION: The inkjet head includes an ink pressure chamber for taking in ink, an actuator for changing the volume of the ink pressure chamber, a nozzle plate having a nozzle hole communicated with the ink pressure chamber, and a pulse signal generating part for applying a driving pulse signal delivering ink droplets from the nozzle hole or a dummy pulse signal not delivering the ink droplets from the nozzle hole to the actuator. The driving pulse signal includes an expansion pulse in time t1 expanding the volume of the ink pressure chamber, and a contraction pulse in time t3 contracting the volume of the ink pressure chamber after time t2 following the expansion pulse. The dummy pulse signal includes a pulse in time t4 changing the volume of the ink pressure chamber, and the time t4 is set in the range of (t1/5)×1.4≤t4≤(t1/5)×1.6.

Description

  Embodiments described herein relate generally to an inkjet head and a driving method thereof.

  In an inkjet head that ejects ink droplets from a nozzle hole, if the pause time during which ink droplets are not ejected becomes longer after the ink droplets are ejected, the solvent contained in the ink evaporates near the nozzle holes and the viscosity of the ink increases. Phenomenon (thickening) occurs. Such thickening of the ink makes it difficult for ink droplets to be ejected from the nozzle holes, which may cause problems such as ejection delay and a decrease in ejection volume. Further, when the nozzle hole is clogged, ink droplets are not ejected, and printing may be curled.

  As a method of suppressing such ink thickening, there is a technique in which a dummy pulse signal is applied to an actuator to change the volume of the ink pressure chamber to such an extent that ink droplets are not ejected. However, even if a dummy pulse signal is applied, if the ink thickening cannot be sufficiently suppressed, the main ink droplet that should be ejected at the time of printing has a tail, and the main dot formed by the main ink droplet does not reach the main dot. In addition, minute dots (satellite) formed by minute ink droplets may be printed on the medium.

JP 2009-066867 A

  An object of this embodiment is to provide an inkjet head capable of high-quality printing and a driving method thereof.

According to this embodiment,
An ink pressure chamber for taking ink; an actuator for changing the volume of the ink pressure chamber; a nozzle plate having a nozzle hole communicating with the ink pressure chamber; and a drive pulse signal for discharging an ink droplet from the nozzle hole or the nozzle A pulse signal generation unit that applies to the actuator a dummy pulse signal that does not cause ink droplets to be ejected from the hole, and the drive pulse signal includes an expansion pulse at time t1 for expanding the volume of the ink pressure chamber, and the expansion A time t3 contraction pulse that contracts the volume of the ink pressure chamber after time t2 following the pulse, the dummy pulse signal includes a pulse at time t4 that changes the volume of the ink pressure chamber, and time t4 is (T1 / 5) × 1.4 ≦ t4 ≦ (t1 / 5) × 1.6 An inkjet head is provided.

According to this embodiment,
An ink jet head comprising: an ink pressure chamber that takes in ink; an actuator that changes a volume of the ink pressure chamber; and a nozzle plate having a nozzle hole that communicates with the ink pressure chamber. A driving pulse signal to be applied or a dummy pulse signal that does not eject an ink droplet from the nozzle hole is applied to the actuator, the driving pulse signal being an expansion pulse at a time t1 for expanding the volume of the ink pressure chamber, And a contraction pulse of time t3 for contracting the volume of the ink pressure chamber after time t2 following the expansion pulse, and the dummy pulse signal includes a pulse of time t4 for changing the volume of the ink pressure chamber, t4 is set in the range of (t1 / 5) × 1.4 ≦ t4 ≦ (t1 / 5) × 1.6. An ink-jet head driving method is provided.

FIG. 1 is an exploded perspective view schematically showing the configuration of the ink jet head in the present embodiment. FIG. 2 is a sectional view schematically showing an actuator constituting the ink jet head shown in FIG. FIG. 3 is a top view schematically showing a nozzle plate constituting the ink jet head shown in FIG. FIG. 4 is a diagram for explaining a process in which ink is ejected from a nozzle hole in the ink jet head according to the present embodiment. FIG. 5 is a dot diagram of a print pattern printed by the ink jet head in the present embodiment. FIG. 6 is a diagram illustrating a relationship between a print pattern and dots for explaining a problem caused by ink thickening. FIG. 7 is a diagram for explaining a problem that occurs when ink thickening cannot be sufficiently suppressed. FIG. 8 is a diagram for explaining an example of a driving technique that can be applied to the ink-jet head 1 according to the present embodiment and that sequentially changes the volumes of three ink pressure chambers arranged in the first direction. is there. FIG. 9 is a diagram showing experimental results for confirming whether or not satellites are generated with respect to the time of the dummy pulse signal.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings. In each figure, the same reference numerals are given to components that exhibit the same or similar functions, and duplicate descriptions are omitted.

  FIG. 1 is an exploded perspective view schematically showing the configuration of an inkjet head 1 in the present embodiment.

  The inkjet head 1 includes a main part 10, a nozzle plate 20, a mask plate 30, a holder 40, and a pulse signal generation unit 50. The main part 10 includes an insulating substrate 11, a frame 12, an actuator 13, and the like.

  The insulating substrate 11 is made of, for example, ceramics such as alumina, and is formed in a rectangular plate shape extending along the first direction X. The insulating substrate 11 has an upper surface 11A on the side facing the nozzle plate 20 and a lower surface 11B on the side facing the holder 40. Such an insulating substrate 11 has an ink supply port 11in and an ink discharge port 11out. The ink supply port 11in and the ink discharge port 11out penetrate from the upper surface 11A to the lower surface 11B.

  The frame body 12 is made of metal, for example, and is formed in a rectangular frame shape. The frame body 12 is disposed on the upper surface 11 </ b> A of the insulating substrate 11. The actuator 13 is disposed inside the upper surface 11 </ b> A of the insulating substrate 11 and surrounded by the frame body 12. Each actuator 13 extends along a second direction Y substantially perpendicular to the first direction X. These actuators 13 are arranged along the first direction X. Between the actuators 13 arranged along the first direction X, an ink pressure chamber 14 extending along the second direction Y is formed in a slit shape.

  In the illustrated example, the actuators 13 are arranged in two rows along the first direction X. The plurality of ink discharge ports 11out are arranged along the first direction X in the substantially central portion of the insulating substrate 11, that is, between the two rows of actuators 13. The plurality of ink supply ports 11 in are arranged along the first direction X in the peripheral portion of the insulating substrate 11, that is, between the frame body 12 and the actuator 13. With such a configuration, ink is supplied from each of the ink supply ports 11in toward the ink pressure chamber 14, and the ink that has passed through the ink pressure chamber 14 is discharged from each of the ink discharge ports 11out.

  The nozzle plate 20 is made of, for example, polyimide, and is formed in a rectangular plate shape extending along the first direction X. The nozzle plate 20 is disposed above the main portion 10 along a third direction Z orthogonal to the first direction X and the second direction Y. The nozzle plate 20 has an upper surface 20A on the side facing the mask plate 30 and a lower surface 20B on the side facing the main part 10. The lower surface 20B of the nozzle plate 20 is bonded to the frame body 12 and the actuator 13 with an adhesive (not shown).

  Such a nozzle plate 20 has a nozzle hole 21. Each nozzle hole 21 is formed to face the ink pressure chamber 14. In the illustrated example, the nozzle holes 21 adjacent to each other are not formed on the same straight line along the first direction X. The layout of these nozzle holes 21 will be described in detail later.

  The mask plate 30 is made of metal, for example, and is formed in a frame shape surrounding the nozzle plate 20. The mask plate 30 is disposed above the main part 10 along the third direction Z. The mask plate 30 has a rectangular opening 30 </ b> A that is substantially the same as the outer diameter of the nozzle plate 20. The mask plate 30 and the frame 12 are bonded with an adhesive (not shown).

  The holder 40 is disposed below the main part 10 along the third direction Z. The holder 40 includes an ink introduction path 41 for introducing ink toward the ink supply port 11in, and an ink collection path 42 for collecting ink discharged from the ink discharge port 11out. The ink introduction path 41 is connected to an introduction pipe P1 for introducing ink from an ink tank (not shown). A recovery pipe P <b> 2 for recovering ink to the ink tank is connected to the ink recovery path 42. The holder 40 has an upper surface 40A on the side facing the main portion 10. The upper surface 40A of the holder 40 and the lower surface 11B of the insulating substrate 11 are bonded with an adhesive (not shown).

  On the upper surface 11A of the insulating substrate 11, a terminal electrically connected to the actuator 13 is arranged outside the frame 12 although not described in detail, and the wiring substrate 15 is mounted via an anisotropic conductive film (not shown). ing. The pulse signal generation unit 50 generates a pulse signal necessary for driving the actuator 13. The pulse signal generator 50 applies a pulse signal to each actuator 13 via the wiring board 15. This pulse signal changes the volume of the ink pressure chamber 14, and includes a drive pulse signal and a dummy pulse signal described later.

  Examples of the adhesive that bonds the holder 40 and the insulating substrate 11, the adhesive that bonds the nozzle plate 20, the frame 12, and the actuator 13, and the adhesive that bonds the mask plate 30 and the frame 12 include, for example, A thermosetting resin such as an epoxy resin is applicable.

  FIG. 2 is a cross-sectional view schematically showing the actuator 13 constituting the ink jet head 1 shown in FIG.

  The actuator 13 includes piezoelectric members 131A and 131B that form the partition wall 131, and electrodes 132 and 133 that are formed on both side surfaces of the partition wall 131, respectively. The ink pressure chamber 14 is formed between two adjacent actuators 13.

  The piezoelectric members 131A and 131B are made of, for example, PZT (lead zirconate titanate). The piezoelectric member 131A is formed on the upper surface of the insulating substrate 11, and the piezoelectric member 131B is bonded onto the piezoelectric member 131A. The polarization direction of the piezoelectric member 131A is opposite to the polarization direction of the piezoelectric member 131B as indicated by the arrows in the figure.

  The electrodes 132 and 133 are formed by, for example, nickel plating or copper plating. These electrodes 132 and 133 sandwich the piezoelectric members 131A and 131B. In the actuator 13 having such a configuration, when a voltage having a reverse polarity is applied to the electrodes 132 and 133, the partition wall 131 formed by the piezoelectric members 131A and 131B is deformed to change the volume of the ink pressure chamber 14 ( That is, expand the volume or contract the volume).

  The nozzle plate 20 is bonded to the piezoelectric member 131 </ b> B constituting the actuator 13. A nozzle hole 21 formed in the nozzle plate 20 communicates with the ink pressure chamber 14.

  FIG. 3 is a top view schematically showing the nozzle plate 20 constituting the inkjet head 1 shown in FIG.

  A plurality of nozzle holes 21 are formed in the nozzle plate 20. The nozzle hole 21 is formed immediately above the ink pressure chamber 14 formed between the actuators 13 as indicated by broken lines in the drawing.

  In the example shown here, the three ink pressure chambers arranged in the first direction X are referred to as a first ink pressure chamber 14A, a second ink pressure chamber 14B, and a third ink pressure chamber 14C, respectively. Also, three nozzle holes that respectively face the first ink pressure chamber 14A, the second ink pressure chamber 14B, and the third ink pressure chamber 14C are formed as the first nozzle hole 21A, the second nozzle hole 21B, and the first nozzle hole 21B, respectively. This is referred to as a 3-nozzle hole 21C.

  The first to third nozzle holes 21 </ b> A, 21 </ b> B, and 21 </ b> C are located on the same straight line L that intersects the first direction X at an acute angle. The three nozzle holes 21 arranged in this way are repeatedly formed, and the nozzle holes 21 arranged every two are formed on the same straight line along the first direction X.

  The second direction Y is substantially parallel to the direction in which the medium moves relative to the inkjet head. In the driving period in which the first ink pressure chamber 14A (and every second ink pressure chamber from the first ink pressure chamber 14A) is selected, ink droplets can be ejected from the first nozzle hole 21A. In the driving period in which the second ink pressure chamber 14B (and every second ink pressure chamber from the second ink pressure chamber 14B) is selected, ink droplets can be ejected from the second nozzle hole 21B. Ink droplets can be ejected from the third nozzle hole 21C during the driving period in which the third ink pressure chamber 14C (and every second ink pressure chamber from the third ink pressure chamber 14C) is selected.

  FIG. 4 is a diagram for explaining a process in which ink is ejected from the nozzle hole 21 in the inkjet head 1 according to the present embodiment.

  (A) in the drawing is an example of a drive pulse signal applied to the actuator 13 that partitions the ink pressure chamber 14. This drive pulse signal includes an expansion pulse PL1 at time t1 for expanding the volume of the ink pressure chamber 14, and a contraction pulse PL2 at time t3 for contracting the volume of the ink pressure chamber 14 after time t2 following the expansion pulse PL1. Contains. The substantial drive time of this drive pulse signal corresponds to t1 + t2 + t3. The expansion pulse PL1 and the contraction pulse PL2 have the same amplitude V and different polarities. Here, the expansion pulse PL1 has a positive polarity, and the contraction pulse PL2 has a negative polarity.

  In an initial state before the expansion pulse PL1 of the drive pulse signal is applied to the actuator 13, the actuator 13 stands substantially perpendicular to the insulating substrate 11, as shown by (b) in the figure. When the expansion pulse PL1 is applied to the actuator 13, as shown by (c) in the figure, the actuator 13 is deformed, the volume of the ink pressure chamber 14 is rapidly expanded, and a negative pressure is generated in the ink pressure chamber 14. To do. This state is maintained only for time t1, and ink is filled into the ink pressure chamber.

  When the expansion pulse PL1 is not applied to the actuator 13 after the time t1 has elapsed, the actuator 13 returns to the state shown in FIG. 5B, and the volume of the ink pressure chamber 14 returns to the initial state. As a result, the pressure in the ink pressure chamber 14 increases, and the ink filled in the ink pressure chamber 14 is ejected from the nozzle hole 21 as an ink droplet. This state is maintained only for time t2.

  When the contraction pulse PL2 is applied to the actuator 13 after the time t2 has elapsed, the actuator 13 is deformed and the volume of the ink pressure chamber 14 is rapidly contracted, as shown by (d) in the figure. This state is maintained only for time t3. When the contraction pulse PL2 is not applied to the actuator 13 after the time t3 has elapsed, the actuator 13 returns to the state indicated by (b) in the figure, and the volume of the ink pressure chamber 14 returns to the initial state. Thereby, the pressure of the ink pressure chamber 14 is suppressed and residual vibration is suppressed.

  The times t1, t2, and t3 shown here are several μs, and are different from each other (t1 ≠ t2 ≠ t3), for example. Here, time t2 is the longest and time t3 is the shortest (t2> t1> t3). The time t2 is equivalent to about 1.3 times the time t1. The time t3 is equivalent to 0.4 times the time t1.

  FIG. 5 is a dot diagram of a print pattern printed by the inkjet head 1 in the present embodiment. In the drawing, the horizontal direction is the direction in which the nozzles 21 are arranged, and the vertical direction is the medium feeding direction or the moving direction of the inkjet head 1.

  In the illustrated example, ink droplets are alternately ejected from every other line from the five nozzle holes 21 located on the left side in the drawing, and dots in a staggered pattern are printed. From the five nozzle holes 21 located on the right side in the figure, ink droplets are ejected to each line, and solid pattern dots are printed. Ink droplets are not ejected from the two nozzle holes 21 located in the center in the figure, and a blank pattern is formed.

  As shown in the figure, there are a nozzle hole 21 that ejects ink droplets and a nozzle hole 21 that does not eject ink droplets depending on the print pattern, and the ink increases in viscosity as the pause time during which ink droplets are not ejected becomes longer, and ejects ink droplets. In some cases, it is difficult to eject ink droplets from the nozzle holes 21 at the timing. For this reason, in the present embodiment, a driving technique for suppressing ink thickening is applied.

  FIG. 6 is a diagram illustrating a relationship between a print pattern and dots for explaining a problem caused by ink thickening. In the drawing, the horizontal direction is the direction in which the nozzles 21 are arranged, and the vertical direction is the medium feeding direction or the moving direction of the inkjet head 1.

  In the illustrated example, ink droplets are normally ejected from each of the three nozzle holes 21 including the nozzle hole 211 located on the left side in the drawing, and uniform dots are formed. On the other hand, from the three nozzle holes 21 including the nozzle hole 212 located on the right side in the figure, it was a pause time during which ink droplets were not ejected up to the two lines shown in the figure, so that ink thickening occurred. A state in which normal dots are not formed when ink droplets are ejected from the third line shown in the drawing is shown. Specifically, due to a decrease in the ejection volume of the ink droplets ejected from the nozzle hole 212, the formed dot diameter becomes smaller than the normal dot diameter, and the ink droplet ejection speed is reduced. The dot print position is retracted from the normal dot print position. Such non-uniform dot diameters and deviations in dot printing positions can cause a reduction in print quality.

  FIG. 7 is a diagram for explaining a problem that occurs when ink thickening cannot be sufficiently suppressed.

  That is, due to the thickening of the ink, a minute ink droplet is torn off from the liquid column of the main ink droplet ejected from the nozzle hole 21 during printing, and in addition to the main dot D formed by the main ink droplet, Minute dots (satellite) D ′ formed by simple ink droplets are printed on the medium. The presence of such satellites can cause a reduction in print quality.

  Therefore, in the inkjet head 1 according to the present embodiment, the drive pulse signal for ejecting ink droplets from the nozzle holes 21 or the ink from the nozzle holes 21 in the drive period in which the ink pressure chambers 14 aligned in the first direction X are selected. A dummy pulse signal that does not cause droplets to be ejected is applied to the actuator 13.

  The drive pulse signal here is a pulse signal for changing the volume of the ink pressure chamber 14 as described with reference to FIG. By applying such a drive pulse signal to the actuator 13, the ink taken into the ink pressure chamber 14 is ejected as an ink droplet from the nozzle hole 21.

  The dummy pulse signal is a pulse signal that changes the volume of the ink pressure chamber 14 to such an extent that the ink in the ink pressure chamber 14 is not ejected from the nozzle hole 21. By applying such a dummy pulse signal to the actuator 13, it is possible to give an appropriate minute vibration to the ink in the ink pressure chamber 14 and suppress the increase in the viscosity of the ink.

  FIG. 8 is a driving technique that can be applied to the inkjet head 1 in the present embodiment, and illustrates an example of a driving technique that sequentially changes the volumes of the three ink pressure chambers 14 arranged in the first direction X. FIG.

  In the example shown here, for example, the upper stage corresponds to the first ink pressure chamber 14A and the first nozzle hole 21A, the middle stage corresponds to the second ink pressure chamber 14B and the second nozzle hole 21B, and the lower stage corresponds to the third ink. It corresponds to the pressure chamber 14C and the third nozzle hole 21C.

  That is, in the first drive period T1 in which the first ink pressure chamber 14A is selected, the drive pulse signal S1 or the dummy pulse signal S2 that changes the volume of the first ink pressure chamber 14A is applied to the actuator 13. In the illustrated example, the driving pulse signal S1 is applied to the actuator 13 in the first driving period T1. Thereby, ink droplets are ejected from the first nozzle hole 21A.

  Following the first drive period T1, in the second drive period T2 in which the second ink pressure chamber 14A is selected, the drive pulse signal S1 or the dummy pulse signal S2 for changing the volume of the second ink pressure chamber 14B is sent to the actuator 13. Applied. In the illustrated example, the dummy pulse signal S2 is applied to the actuator 13 in the second driving period T2. As a result, no ink droplet is ejected from the second nozzle hole 21B, but a minute vibration is applied to the ink in the second ink pressure chamber 14B.

  Following the second drive period T2, in the third drive period T3 in which the third ink pressure chamber 14C is selected, the drive pulse signal S1 or the dummy pulse signal S2 for changing the volume of the third ink pressure chamber 14C is sent to the actuator 13. Applied. In the illustrated example, the dummy pulse signal S2 is applied to the actuator 13 in the third drive period T3. As a result, ink droplets are not ejected from the third nozzle hole 21C, but minute vibration is imparted to the ink inside the third ink pressure chamber 14C.

  The first drive period T1, the second drive period T2, and the third drive period T3 have the same length.

  That is, when ink droplets are not ejected during the driving period, the dummy pulse signal S2 is applied instead of the driving pulse signal S1. Thereby, the viscosity increase of the ink inside the ink pressure chamber 14 can be suppressed, and when the ink droplet is ejected during the driving period, the decrease in the ejection volume of the ink droplet and the decrease in the ejection speed can be suppressed. Therefore, even if the pause time is long, the thickening of the ink is suppressed by the dummy pulse signal S2, and normal dots can be formed when the drive pulse signal S1 is next applied.

  The dummy pulse signal S2 applied in the present embodiment includes a pulse for contracting the volume of the ink pressure chamber 14. That is, the dummy pulse signal S2 has the same polarity (positive polarity) and the same amplitude (+ V) as the contraction pulse PL2 of the drive pulse signal S1. When such a dummy pulse signal S2 is applied to the actuator 13, a force acts in the direction of pushing out ink from the ink pressure chamber 14, but before that, an ink filling operation for expanding the volume of the ink pressure chamber 14 is performed. Since this is not performed, an ink droplet is not ejected from the nozzle hole 21 unless the time t4 of the dummy pulse signal S2 is too long.

  In the present embodiment, the timing at which the dummy pulse signal S2 is applied when ink is not ejected is the same as the timing at which the expansion pulse PL1 of the drive pulse signal S1 is applied at ink ejection. That is, when ink is ejected, the expansion pulse PL1 falls instantaneously during the driving period. When ink is not ejected, the dummy pulse signal S2 rises instantaneously during the driving period. The time t4 of the dummy pulse signal S2 is shorter than the time t1 of the extension pulse PL1.

Such a time t4 of the dummy pulse signal S2 has been studied by the inventor as a result of preventing the erroneous ejection, decreasing the ejection volume of ink droplets, decreasing the ejection speed, and increasing the amount of ink that causes the generation of satellites. From the viewpoint of sufficiently suppressing the viscosity, with respect to the time t1 of the expansion pulse PL1,
(T1 / 5) × 1.4 ≦ t4 ≦ (t1 / 5) × 1.6
It was confirmed that it is desirable to set the range of.

  When the time t4 is longer than (t1 / 5) × 1.6, ink droplets are erroneously ejected, resulting in a decrease in print quality. In this case, a large amount of electrical energy is required in spite of non-ejection of ink, which is not desirable from the viewpoint of energy saving.

  When the time t4 is shorter than (t1 / 5) × 1.4, the ink thickening cannot be sufficiently suppressed, the dot diameter is not uniform, the printing position of the dots is shifted, and further, the satellite. The occurrence of was confirmed.

  According to the present embodiment, by applying the dummy pulse signal S2 at the time t4 defined as described above to the actuator 13 when ink is not ejected during the driving period, the ink viscosity is suppressed and the nozzle hole is suppressed. , Ink and meniscus are kept in proper condition. For this reason, when the drive pulse signal S1 for ink discharge is applied to the actuator 13 during the drive period, the discharge volume and discharge speed of the ink droplets can be made uniform, and the generation of satellites can be suppressed. Therefore, high-quality printing is possible.

  FIG. 9 is a diagram showing an experimental result in which the presence / absence of a satellite is confirmed with respect to time t4 of the dummy pulse signal.

  Here, the number of satellites generated per line when a dummy pulse signal is applied at each time t4 during a fixed pause time during which ink is not ejected, and a drive pulse signal for ink ejection is applied immediately thereafter. Counted.

  When t4 = (t1 / 5) × 0.4, 5 satellites were confirmed per line. When t4 = (t1 / 5) × 0.6, four satellites were confirmed per line. When t4 = (t1 / 5) × 0.8, one satellite was confirmed per line. When t4 = (t1 / 5) × 1.0, two satellites were confirmed per line. When t4 = (t1 / 5) × 1.2, one satellite was confirmed per line. When t4 = (t1 / 5) × 1.4 and when t4 = (t1 / 5) × 1.6, no satellite was generated on one line.

As apparent from the experimental results, the time t4 of the dummy pulse signal is
(T1 / 5) × 1.4 ≦ t4 ≦ (t1 / 5) × 1.6
It is extremely effective to set the value within the range.

  As described above, according to this embodiment, it is possible to provide an inkjet head capable of high-quality printing and a driving method thereof.

  In addition, this invention is not limited to the said embodiment itself, In the stage of implementation, it can change and implement a component within the range which does not deviate from the summary. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

DESCRIPTION OF SYMBOLS 1 ... Inkjet head 10 ... Main part 13 ... Actuator 14 ... Ink pressure chamber 14A ... First ink pressure chamber 14B ... Second ink pressure chamber 14C ... Third ink pressure chamber 20 ... Nozzle plate 21 ... Nozzle hole 21A ... First nozzle Hole 21B ... Second nozzle hole 21C ... Third nozzle hole 30 ... Mask plate 50 ... Pulse signal generator

Claims (7)

An ink pressure chamber for taking up the ink;
An actuator for changing the volume of the ink pressure chamber;
A nozzle plate having a nozzle hole communicating with the ink pressure chamber;
A pulse signal generator for applying to the actuator a drive pulse signal for ejecting ink droplets from the nozzle holes or a dummy pulse signal for not ejecting ink droplets from the nozzle holes,
The drive pulse signal includes an expansion pulse at time t1 for expanding the volume of the ink pressure chamber, and a contraction pulse at time t3 for contracting the volume of the ink pressure chamber after time t2 following the expansion pulse,
The dummy pulse signal includes a pulse at time t4 for changing the volume of the ink pressure chamber,
(T1 / 5) × 1.4 ≦ t4 ≦ (t1 / 5) × 1.6
An inkjet head characterized by being set in a range of The ink pressure chamber includes first to third ink pressure chambers arranged in the first direction,
The pulse signal generation unit applies the driving pulse signal or the dummy pulse signal that changes the volume of the first ink pressure chamber in a first driving period, and the second driving period following the first driving period. The drive pulse signal or the dummy pulse signal for changing the volume of the two ink pressure chambers is applied, and the drive pulse signal for changing the volume of the third ink pressure chamber in the third drive period following the second drive period or The inkjet head according to claim 1, wherein the dummy pulse signal is applied. The nozzle hole includes a first nozzle hole communicating with the first ink pressure chamber, a second nozzle hole communicating with the second ink pressure chamber, and a third nozzle hole communicating with the third ink pressure chamber. ,
3. The inkjet head according to claim 2, wherein the first to third nozzle holes are located on the same straight line that intersects the first direction at an acute angle. 4. An ink jet head comprising: an ink pressure chamber that takes in ink; an actuator that changes a volume of the ink pressure chamber; and a nozzle plate having a nozzle hole that communicates with the ink pressure chamber. A driving pulse signal to be applied or a dummy pulse signal that does not cause ink droplets to be ejected from the nozzle hole is applied to the actuator,
The drive pulse signal includes an expansion pulse at a time t1 for expanding the volume of the ink pressure chamber, and a contraction pulse at a time t3 for contracting the volume of the ink pressure chamber after a time t2 following the expansion pulse.
The dummy pulse signal includes a pulse at time t4 for changing the volume of the ink pressure chamber,
(T1 / 5) × 1.4 ≦ t4 ≦ (t1 / 5) × 1.6
A method for driving an ink jet head, wherein   In the first driving period, the driving pulse signal or the dummy pulse signal for changing the volume of the first ink pressure chamber is applied, and in the second driving period following the first driving period, the first ink pressure chamber is adjacent to the first ink pressure chamber. The volume of the third ink pressure chamber adjacent to the second ink pressure chamber is applied in the third driving period following the second driving period by applying the driving pulse signal or the dummy pulse signal that changes the volume of the two ink pressure chambers. 5. The method of driving an ink jet head according to claim 4, wherein the driving pulse signal or the dummy pulse signal for changing the frequency is applied.   5. The ink jet head driving method according to claim 4, wherein the dummy pulse signal includes a pulse for contracting a volume of the ink pressure chamber.   The timing at which the dummy pulse signal is applied when an ink droplet is not ejected is the same as the timing at which the extended pulse of the drive pulse signal is applied when an ink droplet is ejected. Item 5. A method for driving an inkjet head according to Item 4.

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