JP2015080923A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet head by which high-quality printing is possible.SOLUTION: An ink jet head of an embodiment comprises: a nozzle plate which is a nozzle plate having a plurality of nozzles arranged in fixed intervals, in which the plurality of nozzles include a plurality of normal nozzles, and a plurality of non-discharge nozzles which are located outer side than the plurality of normal nozzles in a direction where the plurality of nozzles are arranged, and diameters of the non-discharge nozzles are larger than those of the normal nozzles; a common liquid chamber which receives supply of liquid from a liquid circulation unit; a plurality of pressure chambers which are connected with the common liquid chamber on an upstream side, connected with the liquid circulation unit on a downstream side, and communicate with the plurality of nozzles, in which the liquid which is not used in the plurality of nozzles is collected by the liquid circulation unit; and a plurality of driving elements which are provided adjacent to the plurality of pressure chambers, and discharge the liquid in the plurality of pressure chambers as droplets from the plurality of normal nozzles.

Description

  Embodiments described herein relate generally to an inkjet head that can perform printing by ejecting ink.

  An ink jet head of an ink jet printer includes a drive element and a nozzle plate. The drive element is formed by bonding two piezoelectric materials, for example, and a plurality of groove-shaped pressure chambers are formed. The pillars separating the pressure chambers are deformed in a shear mode when a voltage is applied to the drive elements, and pressurize the ink in the pressure chambers. The pressurized ink in the pressure chamber is ejected from nozzles provided on the nozzle plate.

  At the time of printing, the pressure of the ink in the inkjet head is kept at a weak negative pressure (a pressure slightly lower than the atmospheric pressure). When droplets are ejected from the nozzle, the negative pressure in the inkjet head varies.

JP 2001-277503 A

  Appropriate management of the negative pressure in the ink jet head is useful for obtaining an ink jet head capable of high quality printing by preventing non-ejection during printing.

  The problem to be solved by the present invention is to provide an inkjet head capable of high quality printing.

  The inkjet head according to the embodiment is a nozzle plate having a plurality of nozzles arranged at regular intervals, and the plurality of nozzles includes a plurality of normal nozzles and the plurality of normal nozzles in a direction in which the plurality of nozzles are arranged. A plurality of non-ejection nozzles located on the outer side, the diameter of the non-ejection nozzle being larger than the diameter of the normal nozzle, a common liquid chamber that receives supply of liquid from the liquid circulation unit, A plurality of pressure chambers connected to the common liquid chamber on the upstream side and connected to the liquid circulation unit on the downstream side and communicated with the plurality of nozzles, wherein the liquid not used in the plurality of nozzles A plurality of pressure chambers recovered by the liquid circulation unit, and a liquid provided in the plurality of pressure chambers adjacent to the plurality of pressure chambers is supplied to the plurality of normal nozzles. And a plurality of driving elements for ejecting droplets, the.

FIG. 2 is a perspective view showing the inkjet head of the first embodiment. FIG. 2 is an exploded perspective view showing a head main body of the ink jet head of FIG. 1. FIG. 2 is a cross-sectional view taken along a direction parallel to the nozzle plate of the head main body of the inkjet head shown in FIG. 1. The perspective view which shows the inkjet head of 2nd Embodiment. FIG. 5 is a cross-sectional view taken along line F5-F5 of the inkjet head shown in FIG. Sectional drawing along F6-F6 line of the inkjet head shown in FIG.

[First Embodiment]
Hereinafter, a first embodiment of an inkjet head will be described with reference to FIGS. 1 to 3. The inkjet head 11 is mounted on a printing apparatus, and can receive characters (images) supplied from a liquid circulation unit 13 of the printing apparatus and print characters, images, and the like on a print target such as paper. In addition, the inkjet head 11 according to the present embodiment can perform printing on a printing target in a state where the liquid is circulated between the inside of the inkjet head 11 and the liquid circulation unit 13 of the printing apparatus 12. The liquid (ink) used in the inkjet head 11 includes various inks for forming an image and functional inks having various functions used for purposes other than forming an image.

  The inkjet head 11 is mounted on the printing apparatus 12 and connected to a liquid circulation unit 13 built in the printing apparatus 12 via a tube or the like. The liquid circulation unit 13 built in the printing apparatus 12 collects the liquid inside the tank 13A holding the liquid (ink) inside the tank 13A and the liquid inside the tank 13A to the ink jet head 11 side, and collects the liquid not used from the ink jet head 11. And a pump unit 13B. The ink jet head 11 is filled with the liquid (ink) supplied from the tank 13 </ b> A while being mounted on the printing device 12.

  The ink jet head 11 includes a head main body 14, a unit portion 15, and a pair of circuit boards 16.

  The unit portion 15 includes a manifold that forms a part of a path between the head main body 14 and the tank 13 </ b> A, and a member that is connected to the printing apparatus 12. The pair of circuit boards 16 are respectively attached to the head body 14.

  As shown in FIG. 1, each of the pair of circuit boards 16 includes a board body 17 that is a printed wiring board having a rectangular shape, and a pair of film carrier packages (FCP18). Various electronic components and connectors are mounted on the board body 17. A pair of FCPs 18 are attached to the substrate body 17.

  The pair of FCPs 18 includes a resin film on which a plurality of wirings are formed and flexibility, and an IC 21 connected to the plurality of wirings. The film is tape automated bonding (TAB). The IC 21 is a component for applying a voltage to the electrode 22. IC21 is being fixed to the film with resin.

  As shown in FIG. 2, the end portion of the FCP 18 is thermocompression-bonded to the wiring 36 on the base plate 23 by an anisotropic conductive film (ACF). The plurality of wirings of the FCP 18 are electrically connected to the wiring 36 by the ACF.

  The head main body 14 is a device for ejecting liquid droplets (ink droplets) to a printing target. As shown in FIG. 1, the head main body 14 is attached to the unit portion 15. As shown in FIG. 2, the head body 14 includes a base plate 23, a nozzle plate 24, a frame member 25, and a block 26 in which a plurality of drive elements 26 </ b> A are built.

  As shown in FIGS. 2 and 3, the base plate 23 is formed in a rectangular plate shape using ceramics such as alumina. A plurality of supply holes 31 and a plurality of discharge holes 32 are provided so as to penetrate the base plate 23.

  The supply hole 31 is provided side by side in the longitudinal direction of the base plate 23 at a substantially central portion of the base plate 23. The supply hole 31 communicates with the liquid supply part of the manifold of the unit part 15. The supply hole 31 is connected to the liquid circulation unit 13 through a liquid supply unit.

  The discharge holes 32 are provided side by side in the longitudinal direction of the base plate 23 on both sides of the supply hole 31. The discharge hole 32 communicates with the liquid discharge portion of the manifold of the unit portion 15. The discharge hole 32 is connected to the liquid circulation unit 13 through the liquid discharge unit.

  As shown in FIG. 2, the frame member 25 is formed in a square frame shape by, for example, a nickel alloy or the like. The frame member 25 is interposed between the base plate 23 and the nozzle plate 24. The frame member 25 is bonded to the mounting surface and the nozzle plate 24, respectively.

  The drive element 26A (the block 26 in which a plurality of drive elements 26A are formed) is formed by two plate-like piezoelectric bodies made of lead zirconate titanate (PZT), for example. The two piezoelectric bodies are bonded so that the polarization directions are opposite to each other in the thickness direction.

  The block 26 in which the plurality of drive elements 26 </ b> A are formed is bonded to the mounting surface of the base plate 23. As shown in FIG. 2, the block 26 is formed in a trapezoidal cross section. The top of the drive element 26 </ b> A is bonded to the nozzle plate 24.

  As shown in FIGS. 2 and 3, the block 26 is provided with a plurality of grooves. The grooves extend in the direction intersecting with the longitudinal direction of the block 26 (longitudinal direction of the inkjet head 11). The plate-like drive elements 26A are separated from each other by the grooves. A region inside the groove is a pressure chamber 33 facing (communicating with) the nozzle 37. The drive element 26A is provided adjacent to the pressure chamber 33, and can discharge droplets from a normal nozzle 37A described later. As shown in FIG. 2, a common liquid chamber 34 for supplying liquid (ink) to each pressure chamber 33 is configured by the nozzle plate 24, the portion near the supply hole 31 of the base plate 23, and the slope portion of the block 26. The The common liquid chamber 34 communicates with each pressure chamber 33 and the supply hole 31. The common liquid chamber 34 can receive liquid supply from the liquid circulation unit 13.

  Similarly, as shown in FIGS. 2 and 3, the nozzle plate 24, the portion near the discharge hole 32 of the base plate 23, the slope portion of the block 26, and the frame member 25 are used in each pressure chamber 33 (each nozzle 37). A liquid recovery path 35 for recovering the liquid (ink) that has not been formed is configured. The liquid recovery path 35 is provided as a pair on both sides with the common liquid chamber 34 interposed therebetween. The liquid recovery path 35 communicates with each pressure chamber 33 and the discharge hole 32.

  As shown in FIG. 3, each pressure chamber 33 is located upstream and connected (communication) with the common liquid chamber 34, and each pressure chamber 33 is located downstream and connected (communication) with the liquid recovery path 35. And downstream end portion 33B. The downstream end portion 33B is connected to the tank 13A of the liquid circulation unit 13 through the liquid recovery path 35, the discharge hole 32, and the liquid discharge portion.

  As shown in FIG. 3, electrodes 22 are provided on both surfaces of the drive element 26A. The electrode 22 covers the bottom of the pressure chamber 33 (groove) and the side surface of the drive element 26A. The electrode 22 is formed, for example, by laser patterning a nickel thin film.

  As shown in FIG. 2, the mounting surface of the base plate 23 is provided with a plurality of wirings 36 extending from the plurality of driving elements 26 </ b> A in a direction intersecting the longitudinal direction of the base plate 23. For example, the wiring 36 is formed by laser patterning a nickel thin film formed on the base plate 23.

  As shown in FIG. 2, the nozzle plate 24 is formed of, for example, a polyimide film and has a substantially rectangular shape. The nozzle plate 24 faces the base plate 23. The material of the nozzle plate 24 is not limited to polyimide.

  As shown in FIG. 1, the nozzle plate 24 has a plurality of nozzles 37 arranged at regular intervals in the longitudinal direction of the inkjet head 11. The plurality of nozzles 37 includes a plurality of normal nozzles 37A that actually discharge droplets (ink), and a plurality of non-ejection nozzles 37B that are positioned outside the plurality of normal nozzles 37A in the direction in which the plurality of nozzles 37 are arranged. And. The interval between the normal nozzles 37A and the interval between the normal nozzles 37A and the non-ejection nozzles 37B (intervals in the longitudinal direction of the inkjet head 11) are configured with the same length d (see FIG. 3). ). In other words, the plurality of non-ejection nozzles 37 </ b> B are provided on the end side of the nozzle row composed of the plurality of nozzles 37. The normal nozzle 37A and the non-ejection nozzle 37B are formed by, for example, laser processing, but the forming method of both nozzles is not limited to this. The normal nozzle 37A and the non-ejection nozzle 37B may be formed by, for example, press working.

  As shown in FIG. 3, the normal nozzle 37A has a circular shape, and the diameter of the normal nozzle 37A is, for example, 30 μm. The normal nozzle 37 </ b> A is provided at a position corresponding to the substantially central portion of the pressure chamber 33. The non-ejection nozzle 37B has a circular shape, and the diameter of the non-ejection nozzle 37B is, for example, 35 μm. The shape of the non-ejection nozzle 37B is not limited to a circle, and may be a quadrangle or any other shape.

  The meniscus holding pressure of the nozzle is inversely proportional to the circumferential length of the nozzle. For this reason, the magnitude of the meniscus holding pressure of the non-ejection nozzle 37B having a large diameter is smaller than the meniscus holding pressure of the normal nozzle 37A. In the present embodiment, when the meniscus holding pressure of the normal nozzle 37A is 1, the meniscus holding pressure of the non-ejection nozzle 37B is 0.857.

  In the present embodiment, the non-ejection nozzle 37 </ b> B is provided not at a position corresponding to the vicinity of the center of the pressure chamber 33 but at a position corresponding to the downstream end portion 33 </ b> B of the pressure chamber 33. And in the case of the inkjet head 11 of the type which circulates a liquid between the inside of the inkjet head 11 and the liquid circulation unit 13 of the printing apparatus 12 like this embodiment, it is downstream end part 33B rather than upstream end part 33A. There is a tendency that the pressure of the liquid in the pressure chamber 33 decreases. In the case where the non-ejection nozzle 37B is provided on the downstream side, the pressure of the liquid is reduced, and therefore the nozzle diameter may be equal to that of the normal nozzle 37A.

  Therefore, when the negative pressure in the inkjet head 11 increases during printing, the ink meniscus is destroyed first by the non-ejection nozzle 37B than by the normal nozzle 37A. When the ink meniscus is destroyed in the non-ejection nozzle 37B, bubbles enter the inkjet head 11 (in the pressure chamber 33 communicating with the non-ejection nozzle 37B) from the non-ejection nozzle 37B.

  Next, the operation of the inkjet head 11 according to the embodiment when actually mounted on the printing apparatus 12 will be described.

  When the ink jet head 11 is mounted on the printing device 12, liquid (ink) is supplied from the liquid circulation unit 13 into the ink jet head 11, and the interior of the ink jet head 11 is filled with the liquid. The initial pressure (initial negative pressure) of the liquid (ink) inside the inkjet head 11 is, for example, −1 KPa.

  When the printing apparatus 12 is operated by the user, the control unit of the ink jet printer inputs a print signal to the IC 21 connected to the wiring 36. Based on this print signal, the IC 21 applies a predetermined voltage to the electrode 22 of the pressure chamber 33 via the wiring 36. When the drive pulse voltage is applied to the electrode 22, the drive element 26A is deformed in the shear mode, and the volume of the pressure chamber 33 is expanded. Then, when the voltage applied to the electrode 22 of the pressure chamber 33 is released, the driving element 26A returns to its original shape, and the volume of the pressure chamber 33 is reduced to return to its original size. Thereby, the liquid in the pressure chamber 33 is pressurized, and the droplets are ejected vigorously from the nozzle 37. By ejecting liquid droplets from the plurality of normal nozzles 37A, an image is formed on the print target (paper).

  When image formation (droplet discharge) is continuously performed, the liquid (ink) in the inkjet head 11 is consumed, and the pressure (negative pressure) in the inkjet head 11 may change to about −4 KPa. Further, in the present embodiment, the non-ejection nozzle 37B provided at the position corresponding to the downstream end 33B of the pressure chamber 33 has a pressure lower than −4 KPa. In this state, the normal nozzle 37A is not lower than the meniscus holding pressure, but the non-ejection nozzle 37B is lower than the meniscus holding pressure. In this state, the meniscus is destroyed by the non-ejection nozzle 37 </ b> B, and bubbles enter the inkjet head 11.

  When bubbles enter the inkjet head 11 from the non-ejection nozzle 37B, the negative pressure in the inkjet head 11 decreases, and the pressure in the inkjet head 11 rises to near atmospheric pressure.

  This prevents air bubbles from being sucked from the normal nozzle 37A. The bubbles that have entered from the non-ejection nozzle 37B do not move to the normal nozzle 37A side, flow through the downstream end portion 33B, and are discharged to the discharge hole 32 via the liquid recovery path 35.

  According to the first embodiment, the inkjet head 11 is a nozzle plate 24 having a plurality of nozzles 37 arranged at regular intervals, and the plurality of nozzles 37 includes a plurality of normal nozzles 37 </ b> A and a plurality of nozzles 37. A plurality of non-ejection nozzles 37B positioned outside the plurality of normal nozzles 37A in the aligned direction, the diameter of the non-ejection nozzles 37B being larger than the diameter of the normal nozzles 37A, and a liquid circulation unit A plurality of pressure chambers 33 connected to the plurality of nozzles 37 and connected to the liquid circulation unit 13 on the downstream side. In addition, a plurality of pressure chambers 33 in which the liquid that has not been used by the plurality of nozzles 37 is collected by the liquid circulation unit 13 are provided adjacent to the plurality of pressure chambers 33. And a plurality of driving elements 26A for ejecting a droplet of the plurality of liquid in the pressure chamber 33 from a plurality of normal nozzles 37A with used.

  According to this configuration, since the ink jet head 11 is provided with the non-ejection nozzle 37 </ b> B that is liable to intrude bubbles and does not actually eject droplets, the ink jet head 11 continuously ejects droplets. When the internal negative pressure becomes large, bubbles can be actively introduced on the non-ejection nozzle 37B side. Accordingly, it is possible to manage the negative pressure in the inkjet head 11 within an appropriate range while preventing intrusion of bubbles from the normal nozzle 37A. In addition, since the non-ejection nozzle 37B is not originally used for ejecting droplets, there is no problem in printing even if bubbles are sucked and droplets cannot be ejected.

  In this case, the diameter of the non-ejection nozzle 37B is not more than 1.2 times the diameter of the normal nozzle 37A. Increasing the diameter of the non-ejection nozzle 37B makes it easy to suck bubbles, but if the diameter is too large, bubbles are sucked even in a normal printing state and printing becomes unstable. According to the above configuration, it is possible to perform printing stably by reducing the frequency with which bubbles are sucked by the non-ejection nozzle 37B.

  The non-ejection nozzle 37 </ b> B is provided at a position corresponding to the downstream end of the pressure chamber 33. According to this configuration, the liquid pressure can be further reduced (negative pressure can be increased) in the vicinity of the non-ejection nozzle 37B. Thereby, the destruction of the meniscus is promoted on the non-ejecting nozzle 37B side with respect to the normal nozzle 37A, and the non-ejecting nozzle 37B can positively allow bubbles to enter the pressure chamber 33.

  In the above embodiment, as an example, the diameter of the normal nozzle 37A is 30 μm and the non-ejection nozzle 37B is 35 μm. However, the ratio of the size of the non-ejection nozzle 37B to the normal nozzle 37A is as follows. It is not limited. The diameter of the non-ejection nozzle 37B is larger than 100% and 120% or less with respect to the diameter of the normal nozzle 37A (specifically, the diameter of the non-ejection nozzle 37B is larger than 30 μm and smaller than 36 μm). Any size).

  More preferably, the diameter of the non-ejection nozzle 37B is in the range of 110% to 120% or less with respect to the diameter of the normal nozzle 37A (specifically, the diameter of the non-ejection nozzle 37B is in the range of 33 μm to 36 μm). It is good to be. Within this range, the meniscus holding pressure of the non-ejection nozzle 37B can be made 10% to 20% smaller than the meniscus holding pressure of the normal nozzle 37A.

  In the above embodiment, the size of the non-ejection nozzle 37B is larger than that of the normal nozzle 37A. However, the non-ejection nozzle 37B is provided at a position corresponding to the downstream end of the pressure chamber 33. For example, the non-ejection nozzle 37B may be formed in the same size as the normal nozzle 37A. In this case, since the liquid pressure is lower (negative pressure is larger) at the position where the non-ejection nozzle 37B is present than at the position where the normal nozzle 37A is present, the non-ejection nozzle 37B preferentially sucks bubbles. Can be made. This prevents bubbles from entering the normal nozzle 37A and allows the negative pressure in the inkjet head 11 to be managed within an appropriate range. In this case, the non-ejection nozzle 37B can be formed at the same time as the normal nozzle 37A is formed, and the productivity can be improved.

[Second Embodiment]
Below, 2nd Embodiment of an inkjet head is described with reference to FIGS. The liquid (ink) used for the inkjet head 11 includes functional inks that exhibit various functions in addition to inks containing various pigments for forming images.

  As shown in FIG. 4, the inkjet head 11 is a so-called end shooter type (a type in which liquid is not circulated between the inside of the inkjet head 11 and the tank of the printing apparatus). The inkjet head 11 includes a base 41, a lid member 42, a pair of liquid inlets 43 provided in the lid member 42, and a nozzle plate 24. The liquid injection port 43 is connected to a tank 13A (ink tank) of the printing apparatus 12 via a tube or the like when mounted on the printing apparatus 12. The ink jet head 11 is filled with the liquid (ink) supplied from the tank 13 </ b> A while being mounted on the printing device 12. In FIG. 4, the plurality of nozzles 37 (normal nozzles, non-ejection nozzles) are greatly exaggerated than the actual inkjet head 11. FIG. 4 shows a smaller number of nozzles 37 than the actual inkjet head 11.

  As shown in FIG. 5, the lid member 42 is attached to the upper surface of the base 41. A common liquid chamber 34 that communicates with each pressure chamber 33 is provided inside the lid member 42.

  The base 41 is formed, for example, by bonding two piezoelectric plates made of lead zirconate titanate (PZT) so that their polarization directions are opposite to each other. As shown in FIG. 6, the base 41 is provided with a plurality of pressure chambers 33 arranged in the longitudinal direction L of the inkjet head 11. In addition, a plurality of column portions 44 are provided between the pressure chambers 33 of the base portion 41. The plurality of pressure chambers 33 are provided to communicate with a plurality of nozzles 37 (normal nozzles 37A and non-ejection nozzles 37B) of the nozzle plate 24 described later. That is, the plurality of pressure chambers 33 are provided to correspond to the plurality of nozzles 37 on a one-to-one basis. As shown in FIG. 5, each pressure chamber 33 is recessed from the surface of the base portion 41 into a shape including a circular arc, and is formed in a so-called groove shape.

  As shown in FIG. 6, each pressure chamber 33 is provided adjacent to the column portion 44 at a position between the pair of column portions 44. As shown in FIGS. 5 and 6, an electrode 22 is provided on the inner surface of each pressure chamber 33 (the bottom surface and the side surface of the groove constituting the pressure chamber 33). The electrode 22 is used to apply a voltage to the column portion 44 to drive the column portion 44 as the drive element 26A. The electrode 22 is formed of, for example, a nickel thin film, but is not limited thereto, and may be formed of, for example, gold or copper. The plurality of electrodes 22 are connected to the plurality of wirings 36. The column portion 44 is an example of a drive element 26A that discharges the liquid in the pressure chamber 33 as a droplet from the normal nozzle 37A.

  On the base 41, a plurality of wirings 36 connected to the electrodes 22 formed on the inner surface of the pressure chamber 33 are provided. The electrode 22 and the wiring 36 are formed, for example, by patterning a nickel thin film formed on the upper surface of the base 41 by laser processing.

  The nozzle plate 24 is attached to the front surface of the base 41 and the lid member 42. The nozzle plate 24 is formed of, for example, a polyimide film. The material of the nozzle plate 24 is not limited to polyimide.

  The nozzle plate 24 has a plurality of nozzles 37 arranged at regular intervals in the longitudinal direction L of the inkjet head 11. The plurality of nozzles 37 includes a plurality of normal nozzles 37A that actually discharge droplets (ink), and a plurality of non-ejection nozzles 37B that are positioned outside the plurality of normal nozzles 37A in the direction in which the plurality of nozzles 37 are arranged. And. The normal nozzle 37A and the non-ejection nozzle 37B are formed by laser processing. The intervals between the normal nozzles 37A, the intervals between the normal nozzles 37A and the non-ejection nozzles 37B, and the intervals between the non-ejection nozzles 37B are all configured to have the same length. In other words, the plurality of non-ejection nozzles 37 </ b> B are provided at the end portions (both end portions) of the nozzle row composed of the plurality of nozzles 37. As shown in FIG. 4, a discharge area 45 is formed in a portion corresponding to the normal nozzle 37A on the nozzle plate 24, and a portion corresponding to the non-discharge nozzle 37B on the nozzle plate 24 is not set. A discharge area 46 is configured.

  The normal nozzle 37A has a circular shape, and the diameter of the normal nozzle 37A is, for example, 30 μm. The non-ejection nozzle 37B is circular and has a diameter larger than that of the normal nozzle 37A. The diameter of the non-ejection nozzle 37B is, for example, 35 μm. The shape of the non-ejection nozzle 37B is not limited to a circle, and may be a quadrangle or any other shape.

  The meniscus holding pressure of the nozzle is inversely proportional to the circumferential length of the nozzle. For this reason, the magnitude of the meniscus holding pressure of the non-ejection nozzle 37B having a large diameter is smaller than the meniscus holding pressure of the normal nozzle 37A having a small diameter. In the present embodiment, when the meniscus holding pressure of the normal nozzle 37A is 1, the meniscus holding pressure of the non-ejection nozzle 37B is 0.857. Therefore, when the negative pressure in the inkjet head 11 increases during printing, the meniscus is first destroyed on the non-ejection nozzle 37B side. When the meniscus is destroyed in the non-ejection nozzle 37B, bubbles enter the inkjet head 11 (in the pressure chamber 33 communicating with the non-ejection nozzle 37B) from the non-ejection nozzle 37B.

  Next, the operation of the inkjet head 11 according to the embodiment when actually mounted on the printing apparatus 12 will be described.

  When the inkjet head 11 is mounted on the printing apparatus 12, a liquid (ink) is supplied from the tank 13A into the inkjet head 11, and the interior of the inkjet head 11 is filled with the liquid. The initial pressure (initial negative pressure) of the liquid inside the inkjet head 11 is, for example, −1 KPa.

  When the user operates the printing device 12, the control unit of the printing device 12 inputs a print signal to the IC 21 connected to the wiring 36. Based on this print signal, the IC 21 applies a predetermined voltage to the electrode 22 of the pressure chamber 33 via the wiring 36. When the drive pulse voltage is applied to the electrode 22, the column portion 44 is deformed in the shear mode, and the volume of the pressure chamber 33 is expanded. Then, by releasing the voltage applied to the electrode 22 of the pressure chamber 33, the column portion 44 returns to the original shape, and the volume of the pressure chamber 33 is reduced to return to the original size. As a result, the liquid (ink) in the pressure chamber 33 is pressurized, and droplets are ejected vigorously from the normal nozzle 37A toward the printing target. By ejecting droplets from the plurality of normal nozzles 37A, an image is formed on the print target (paper). It should be noted that droplets are not ejected from the non-ejection nozzle 37B.

  When images are continuously formed (droplet ejection), a large amount of liquid (ink) in the inkjet head 11 is consumed, and the supply of the liquid from the tank 13A is not in time, and the pressure (negative pressure) in the inkjet head 11 is reached. Pressure) may change to about -4 KPa. In this state, the pressure (negative pressure) in the inkjet head 11 does not normally exceed the meniscus holding pressure of the nozzle 37A, but exceeds the meniscus holding pressure of the non-ejection nozzle 37B. In this state, the meniscus is destroyed by the non-ejection nozzle 37 </ b> B, and bubbles enter the inkjet head 11. When bubbles enter the inkjet head 11 from the non-ejection nozzle 37B, the negative pressure in the inkjet head 11 decreases, and the pressure in the inkjet head 11 rises to near atmospheric pressure.

  As described above, in the present embodiment, air bubbles are prevented from being sucked from the normal nozzles 37A by positively injecting the air bubbles into the inkjet head 11 from the non-ejection nozzles 37B. The bubbles that have entered from the non-ejection nozzle 37B do not move to the normal nozzle 37A side but are held in the pressure chamber 33 facing the non-ejection nozzle 37B. If the amount of bubbles is small, the liquid (ink) ) And is moved to the common liquid chamber 34 when bubbles are large. For this reason, bubbles that have entered from the non-ejection nozzle 37B do not adversely affect other portions in the inkjet head 11.

  The inkjet head 11 of the embodiment is a nozzle plate 24 having a plurality of nozzles 37 arranged at regular intervals, and the plurality of nozzles 37 are a plurality of normal nozzles 37A and a plurality of nozzles 37 in the direction in which the plurality of nozzles 37 are arranged. A plurality of non-ejection nozzles 37B located outside the normal nozzle 37A, and the diameter of the non-ejection nozzle 37B communicates with the nozzle plate 24 and the plurality of nozzles 37, which are larger than the diameter of the normal nozzle 37A. A plurality of pressure chambers 33, a common liquid chamber 34 communicating with the plurality of pressure chambers 33, and a plurality of normal nozzles 37 </ b> A that are provided adjacent to the plurality of pressure chambers 33 and supply the liquid in the plurality of pressure chambers 33. And a plurality of driving elements 26A that are ejected as droplets.

  According to this configuration, since the ink jet head 11 is provided with the non-ejection nozzle 37 </ b> B that is liable to intrude bubbles and does not actually eject droplets, the ink jet head 11 continuously ejects droplets. When the internal negative pressure becomes large, bubbles can be actively introduced on the non-ejection nozzle 37B side. Accordingly, the negative pressure in the inkjet head 11 can be managed within an appropriate range while preventing bubbles from entering from the normal nozzle 37A with a simple structure.

  In addition, since the non-ejection nozzle 37B is not originally used for ejecting liquid droplets, there is no problem in printing even if bubbles are held in the non-ejection nozzle 37B. Normally, when air bubbles are entrapped in the nozzle 37 in this way (when the air bubbles are caught in the vicinity of the nozzle and become in a staying state), the air is not ejected from the discharge disabled state unless the air bubbles are discharged by the liquid purge / maintenance. Cannot be recovered. According to the present embodiment, it is possible to prevent bubbles from entering from the normal nozzle 37A, and to reduce the number of such purge and maintenance operations for the normal nozzle 37A.

  Further, since the plurality of nozzles 37 including the non-ejection nozzles 37B are arranged at regular intervals in the longitudinal direction L of the inkjet head 11, the non-ejection nozzles 37B are provided under the same conditions as the normal nozzles 37A in the ejection area 45. Can do. Accordingly, only the diameter of the non-ejection nozzle 37B is affected, and other factors can be made the same as those of the normal nozzle 37A. As a result, it is possible to prevent bubbles from entering the normal nozzle 37 </ b> A by preferentially causing the bubbles to enter the non-ejection nozzle 37 </ b> B as intended.

  In this case, the diameter of the non-ejection nozzle 37B is not more than 1.2 times the diameter of the normal nozzle 37A. Increasing the diameter of the non-ejection nozzle 37B makes it easier to suck bubbles, but if the diameter of the non-ejection nozzle 37B is too large, bubbles are sucked even in a normal printing state, and printing becomes unstable. According to the above configuration, it is possible to perform printing stably by reducing the frequency with which bubbles are sucked by the non-ejection nozzle 37B.

  In the above embodiment, as an example, the diameter of the normal nozzle 37A is 30 μm and the non-ejection nozzle 37B is 35 μm. However, the ratio of the size of the non-ejection nozzle 37B to the normal nozzle 37A is as follows. It is not limited. The diameter of the non-ejection nozzle 37B is larger than 100% and 120% or less with respect to the diameter of the normal nozzle 37A (specifically, the diameter of the non-ejection nozzle 37B is larger than 30 μm and smaller than 36 μm). Any size).

  More preferably, the diameter of the non-ejection nozzle 37B is in the range of 110% to 120% or less with respect to the diameter of the normal nozzle 37A (specifically, the diameter of the non-ejection nozzle 37B is in the range of 33 μm to 36 μm). It is good to be. Within this range, the meniscus holding pressure of the non-ejection nozzle 37B can be made 10% to 20% smaller than the meniscus holding pressure of the normal nozzle 37A.

  In the inkjet head 11 of the above-described embodiment, one nozzle row is disclosed, but the present invention can naturally be applied to the inkjet head 11 having a plurality of nozzle rows.

  The first embodiment and the second embodiment described above can be implemented in combination. That is, as shown in FIG. 4 of the second embodiment, two non-ejection nozzles 37 </ b> B may be provided at the end of the nozzle row composed of the plurality of nozzles 37 in the first embodiment.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 11 ... Inkjet head, 12 ... Printing apparatus, 13 ... Liquid circulation unit, 24 ... Nozzle plate, 26A ... Drive element, 33 ... Pressure chamber, 33B ... Downstream end, 34 ... Common liquid chamber, 37 ... Nozzle, 37A ... Normal Nozzle, 37B ... Non-ejecting nozzle

Claims (5)

A nozzle plate having a plurality of nozzles arranged at regular intervals, wherein the plurality of nozzles are a plurality of normal nozzles and a plurality of nozzles positioned outside the plurality of normal nozzles in the direction in which the plurality of nozzles are arranged. A non-ejection nozzle, a nozzle plate having a diameter larger than the diameter of the normal nozzle,
A common liquid chamber that receives liquid supply from the liquid circulation unit;
A plurality of pressure chambers connected to the common liquid chamber on the upstream side and connected to the liquid circulation unit on the downstream side and communicated with the plurality of nozzles, wherein the liquid not used in the plurality of nozzles A plurality of pressure chambers collected in the liquid circulation unit;
A plurality of drive elements provided adjacent to the plurality of pressure chambers and discharging liquid in the plurality of pressure chambers as droplets from the plurality of normal nozzles;
An inkjet head comprising:   The inkjet head according to claim 1, wherein a diameter of the non-ejection nozzle is 1.2 times or less of a diameter of the normal nozzle. A nozzle plate having a plurality of nozzles arranged at regular intervals, wherein the plurality of nozzles are a plurality of normal nozzles and a plurality of nozzles positioned outside the plurality of normal nozzles in the direction in which the plurality of nozzles are arranged. A non-ejection nozzle, and the non-ejection nozzle is provided at a position corresponding to the downstream end of the pressure chamber;
A common liquid chamber that receives liquid supply from the liquid circulation unit;
A plurality of pressure chambers connected to the common liquid chamber on the upstream side and connected to the liquid circulation unit on the downstream side and communicated with the plurality of nozzles, wherein the liquid not used in the plurality of nozzles A plurality of pressure chambers collected in the liquid circulation unit;
A plurality of drive elements provided adjacent to the plurality of pressure chambers and discharging liquid in the plurality of pressure chambers as droplets from the plurality of normal nozzles;
An inkjet head comprising: A nozzle plate having a plurality of nozzles arranged at regular intervals, wherein the plurality of nozzles are a plurality of normal nozzles and a plurality of nozzles positioned outside the plurality of normal nozzles in the direction in which the plurality of nozzles are arranged. A non-ejection nozzle, a nozzle plate having a diameter larger than the diameter of the normal nozzle,
A plurality of pressure chambers provided to communicate with the plurality of nozzles;
A common liquid chamber communicating with the plurality of pressure chambers;
A plurality of drive elements provided adjacent to the plurality of pressure chambers and discharging liquid in the plurality of pressure chambers as droplets from the plurality of normal nozzles;
An inkjet head comprising:   The inkjet head according to claim 1, wherein a diameter of the non-ejection nozzle is 1.2 times or less of a diameter of the normal nozzle.