JP6155707B2 - Liquid ejection device - Google Patents

Description

  The present invention relates to a liquid ejection device that ejects liquid.

  Patent Document 1 discloses an ink jet head that ejects ink droplets from nozzles as a liquid ejecting apparatus. The inkjet head described in Patent Document 1 includes a flow path unit and a piezoelectric actuator. In the flow path unit, an ink flow path including a plurality of nozzles and a plurality of pressure chambers communicating with the plurality of nozzles is formed. The piezoelectric actuator includes a piezoelectric layer that covers a plurality of pressure chambers, a plurality of individual electrodes that are respectively disposed on the upper surface of the piezoelectric layer so as to correspond to the plurality of pressure chambers, and a common electrode that is disposed on the lower surface of the piezoelectric layer. Have.

  When a potential difference is generated between the individual electrode and the common electrode from the state where the individual electrode and the common electrode are at the same potential, the active portion of the piezoelectric layer sandwiched between the individual electrode and the common electrode contracts in the surface direction. Along with this, in a region facing the pressure chamber corresponding to the individual electrode, the flat piezoelectric layer is deformed so as to protrude toward the pressure chamber. In addition, there is a potential difference between the individual electrode and the common electrode, and when the individual electrode and the common electrode have the same potential from the state where the piezoelectric layer is convex toward the pressure chamber, the piezoelectric layer becomes convex. It transforms from a state to a flat state. As a method for ejecting ink using such deformation of the piezoelectric layer, there are a so-called pulling method and a pushing method. In the striking method, the pressure chamber volume is temporarily increased and then the pressure chamber volume is decreased to superimpose the pressure waves generated when the volume is increased and decreased, and the superimposed pressure waves are applied to the ink in the pressure chamber. This is a method of applying discharge energy. The pushing method is a method in which ejection energy is applied to ink in a pressure chamber by a pressure wave generated by reducing the volume of the pressure chamber.

JP 2011-212901 A

  In the inkjet head as disclosed in Patent Document 1, the ejection amount of each nozzle when ink is ejected simultaneously from a plurality of adjacent nozzles is greater than the ejection amount when ink is ejected from a specific nozzle. It is known to decrease.

  For example, when performing solid printing at a high density in an ink jet printer, it is desired to increase the amount of ink discharged from each nozzle. When solid printing is performed, ink is ejected simultaneously from a large number of nozzles, so the amount of ink ejected from each nozzle is reduced. On the other hand, when printing a fine pattern such as a thin line, it is desired to reduce the amount of ink discharged from each nozzle. However, when printing a fine pattern, ink is often not ejected from adjacent nozzles, and the amount of ink ejected from each nozzle increases.

  An object of the present invention is to improve the problem that the discharge amount of each nozzle when discharging liquid simultaneously from a plurality of adjacent nozzles is smaller than the discharge amount when discharging liquid from one nozzle. .

In a first aspect , the liquid ejection device of the present invention includes a plurality of nozzles that eject liquid, a plurality of pressure chambers that communicate with the plurality of nozzles, and the plurality of pressure chambers arranged in a predetermined direction. A flow channel structure that is adjacent to the end in the predetermined direction of the pressure chamber row formed by the hole and is formed with a hole that is the same size as the pressure chamber and that does not communicate with the nozzle ; and the flow channel structure A piezoelectric actuator provided on a body, wherein the piezoelectric actuator is disposed so as to cover the plurality of pressure chambers and the hole , and extends along a plane in which the plurality of pressure chambers are disposed. A plurality of drive electrodes disposed in the piezoelectric layer and corresponding to the plurality of pressure chambers, respectively , a hole electrode disposed in the piezoelectric layer and corresponding to the hole, and the plurality of drive electrodes and changes the potential of the hole for the electrode Each of the plurality of drive electrodes is adjacent to the corresponding pressure chamber and a first portion that overlaps the corresponding pressure chamber in a direction orthogonal to the surface direction of the piezoelectric layer. A second portion that overlaps with the pressure chamber in the orthogonal direction, and the hole electrode has a corresponding third hole that overlaps with the corresponding hole and a direction orthogonal to the surface direction of the piezoelectric layer. A fourth portion that overlaps the pressure chamber adjacent to the first chamber in the orthogonal direction, and the piezoelectric layer includes a plurality of first active portions that overlap the plurality of first portions in the orthogonal direction, and a plurality of first active portions. wherein a second portion and a plurality of second active portion that overlaps in each direction the perpendicular, the third active portion that overlaps the third portion and the orthogonal direction, a direction odor the perpendicular to the fourth portion of the And having a fourth active portions overlapping, the.
Further, according to a second aspect, the liquid ejection device of the present invention includes a flow channel structure in which a plurality of nozzles that eject liquid and a plurality of pressure chambers that respectively communicate with the plurality of nozzles are formed. A piezoelectric actuator provided on the path structure, wherein the piezoelectric actuator is disposed so as to cover the plurality of pressure chambers, and extends along an arrangement plane of the plurality of pressure chambers. A plurality of drive electrodes disposed in the piezoelectric layer and corresponding to the plurality of pressure chambers, respectively, and a drive device that changes the potential of the plurality of drive electrodes, and the plurality of drive electrodes includes: Each has a first portion that overlaps with the corresponding pressure chamber in a direction orthogonal to the surface direction of the piezoelectric layer, and a second portion that overlaps with the pressure chamber adjacent to the corresponding pressure chamber in the orthogonal direction. And before The piezoelectric layer has a plurality of first active portions that overlap with the plurality of first portions in the orthogonal direction, and a plurality of second active portions that overlap with the plurality of second portions in the orthogonal direction, respectively. The plurality of pressure chambers are arranged such that a plurality of pressure chamber rows formed by arranging a plurality of pressure chambers in a predetermined direction are arranged in a direction intersecting the predetermined direction, and the second portion Is overlapped in the direction orthogonal to the pressure chamber belonging to the pressure chamber row to which the corresponding pressure chamber belongs and adjacent to the corresponding pressure chamber in the predetermined direction, and the pressure chamber is orthogonal to the predetermined direction It is characterized by extending.

According to the first aspect of the liquid ejection device of the present invention , when liquid is ejected from a nozzle corresponding to one pressure chamber among a plurality of adjacent pressure chambers, the first pressure chamber overlaps in the orthogonal direction. The first active part is deformed, but the second active part remains as it is. When liquid is ejected from nozzles corresponding to a plurality of adjacent pressure chambers, both the first active portion and the second active portion that overlap the pressure chamber in the orthogonal direction are deformed. Since the second active part is deformed, the amount of change in the volume of each pressure chamber is larger than in the previous case. That is, the amount of change in the volume of the pressure chamber when the liquid is discharged from the nozzles corresponding to one pressure chamber is smaller than when the liquid is simultaneously discharged from a plurality of nozzles corresponding to the plurality of adjacent pressure chambers. . For this reason, the problem that the discharge amount of each nozzle when simultaneously discharging liquid from a plurality of adjacent nozzles is smaller than the discharge amount when discharging liquid from one nozzle can be improved.
Moreover, the hole electrode corresponding to the hole adjacent to the end of the pressure chamber row is provided. The hole electrode has a fourth portion overlapping with the pressure chamber adjacent to the corresponding hole in the thickness direction. For this reason, the pressure chamber at the end of the pressure chamber row overlaps the first portion, the second portion, and the fourth portion in the thickness direction. Accordingly, the pressure chamber at the end of the pressure chamber row has the same electrode arrangement as the other pressure chambers overlapping in the thickness direction with the first portion, the second portion arranged on both sides of the first portion, and the other pressure chambers. And the conditions for ejecting ink are the same.
According to the second aspect of the liquid ejection apparatus of the present invention, when a liquid is ejected from a nozzle corresponding to one pressure chamber among a plurality of pressure chambers adjacent in a predetermined direction, the pressure chamber is orthogonal to the one pressure chamber. The first active part that overlaps in the direction to be deformed is deformed, but the second active part remains as it is. When liquid is ejected from nozzles corresponding to a plurality of pressure chambers adjacent in a predetermined direction, both the first active portion and the second active portion that overlap the pressure chamber in the orthogonal direction are deformed. Since the second active part is deformed, the amount of change in the volume of each pressure chamber is larger than in the previous case. That is, compared with the case where liquid is simultaneously discharged from a plurality of nozzles corresponding to a plurality of pressure chambers belonging to the same pressure chamber row and adjacent in a predetermined direction, the pressure when liquid is discharged from nozzles corresponding to one pressure chamber The amount of change in the chamber volume is reduced. For this reason, the problem that the discharge amount of each nozzle when simultaneously discharging liquid from a plurality of nozzles adjacent in a predetermined direction is smaller than the discharge amount when discharging liquid from one nozzle can be improved. .

1 is a schematic plan view of an ink jet printer according to an embodiment of the present invention. It is a top view of an inkjet head. FIG. 3 is a partially enlarged view of FIG. 2. FIG. 4 is a sectional view taken along line IV-IV in FIG. 3. It is the VV sectional view taken on the line of FIG. It is operation | movement explanatory drawing of the piezoelectric actuator by the conventional striking method. It is operation | movement explanatory drawing of the piezoelectric actuator by a pulling method. It is operation | movement explanatory drawing of the piezoelectric actuator by the conventional pushing method. It is operation | movement explanatory drawing of the piezoelectric actuator by a pushing method. It is a figure for demonstrating the piezoelectric actuator which concerns on a modification.

  Hereinafter, embodiments of the present invention will be described. This embodiment is an example in which the present invention is applied to an ink jet printer as a liquid ejection apparatus. FIG. 1 is a schematic plan view of the ink jet printer according to the present embodiment. When the inkjet printer 1 is installed along the horizontal direction, the near side in the vertical direction on the paper surface is the upper side, and the far side in the vertical direction on the paper surface is the lower side. Hereinafter, the ink jet printer 1 in a state of being installed along the horizontal direction will be described. The left-right direction and the front-rear direction are described as the illustrated directions, and the left-right direction and the front-rear direction are parallel to the horizontal direction. As shown in FIG. 1, the inkjet printer 1 includes a printer unit 2 that records an image or the like on a recording paper 100, a maintenance unit 3 that performs maintenance of an inkjet head 5 (to be described later) of the printer unit 2, and the like.

  The printer unit 2 conveys a carriage 4 that can reciprocate in a predetermined scanning direction, in this case, a left and right direction, an inkjet head 5 mounted on the carriage 4, and a recording paper 100 perpendicular to the predetermined scanning direction along the horizontal direction. It has the conveyance mechanism 6 etc. which convey to a direction, ie, the front. A platen 8 that supports the recording paper 100 is installed in the printer housing 7 along the horizontal direction. Two guide rails 9 and 10 extending in parallel with the scanning direction are provided above the platen 8. The carriage 4 is moved in the scanning direction along the two guide rails 9 and 10 in a region facing the recording paper 100 on the platen 8 by being driven by a carriage drive motor (not shown).

  The inkjet head 5 is attached along the horizontal direction to the lower part of the carriage 4 with a gap between the inkjet head 5 and the platen 8. The lower surface of the inkjet head 5 is a droplet discharge surface in which a plurality of nozzles 20 shown in FIG. 2 are opened. The ink jet head 5 mounted on the carriage 4 is connected to the ink cartridge holder 11 by a tube (not shown). Black, magenta, cyan, and yellow inks respectively stored in the four ink cartridges 12a, 12b, 12c, and 12d mounted on the ink cartridge holder 11 are supplied to the inkjet head 5 through the tubes. .

  The ink jet head 5 moves together with the carriage 4 not only in a range facing the recording paper 100 conveyed on the platen 8 but also to a position outside the left and right sides from the facing range. The position on the right side of the range facing the recording paper 100 is a standby position where the carriage 4 stands by when the inkjet head 5 is not used. When the inkjet head 5 reaches the standby position, the inkjet head 5 faces a later-described maintenance unit 3 disposed on the lower side.

  The transport mechanism 6 includes two transport rollers 13 and 14 arranged in the front and rear so as to sandwich the platen 8 and the carriage 4. The conveyance rollers 13 and 14 are respectively driven by a conveyance motor (not shown), and convey the recording paper 100 in the conveyance direction between the inkjet head 5 and the platen 8.

  The printer unit 2 described above discharges ink from the inkjet head 5 while moving the carriage 4 in the scanning direction on the recording paper 100 on the platen 8, while recording by the two transport rollers 13 and 14. By transporting the paper 100 in the transport direction, a desired image or character is recorded on the recording paper 100.

  The maintenance unit 3 is disposed at a position on the right side of the platen 8, that is, a position facing the inkjet head 5 waiting at the standby position. The maintenance unit 3 includes a wiper 15, a cap 16, a suction pump 17, and the like.

  The cap 15 is driven up and down by a cap drive unit (not shown) configured by a drive source such as a motor and a power transmission mechanism such as a gear. The cap 15 is moved upward by the cap drive unit, and performs capping to cover the openings of the plurality of nozzles 20 by being in close contact with the droplet discharge surface of the inkjet head 5. The suction pump 16 is connected to the cap 15. The suction pump 16 performs suction suction for forcibly discharging ink from the plurality of nozzles 20 into the cap 15 by sucking air in the cap 15 and reducing the pressure inside the cap 15 in the capped state. By the suction purge, bubbles and dust mixed in the ink or ink having increased viscosity is discharged. As a result, the occurrence of a discharge abnormality of the nozzle 20 is prevented, and when a discharge abnormality occurs, the discharge performance is recovered. The wiper 17 is provided on the left side of the cap 15. The wiper 17 performs wiping to wipe off ink adhering to the droplet discharge surface when the inkjet head 5 moves from the standby position to the platen 8 side after the suction purge.

  Next, the inkjet head 5 will be described. FIG. 2 is a plan view of the inkjet head 5. FIG. 3 is a partially enlarged view of FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. As shown in FIGS. 2 to 4, the inkjet head 5 applies pressure to the ink in the pressure chamber 21 and the flow path unit 18 in which the ink flow paths such as the plurality of nozzles 20 and the plurality of pressure chambers 21 are formed. And a piezoelectric actuator 19 for performing the above operation.

  As shown in FIG. 4, the flow path unit 18 includes a cavity plate 22, a base plate 23, a manifold plate 24, and a nozzle plate 25 in which a part of the ink flow path is formed. The flow path unit 18 has a structure in which four plates 22 to 25 are stacked one above the other. The four plates 22 to 25 are joined together by an adhesive. The three plates 22 to 24 excluding the lowermost nozzle plate 25 are each formed of a metal material such as stainless steel or nickel alloy steel. The lowermost nozzle plate 25 is formed of a synthetic resin material such as polyimide.

  As shown in FIG. 2, the flow path unit 18, which is a laminate of four plates 22 to 25, is connected to the ink supply ports 26 and the ink supply ports 26 connected to the ink cartridges 12a to 12d by tubes, respectively. Each has a manifold 27 that communicates with each other and extends in a predetermined direction, here, in the transport direction, and a large number of individual ink flow paths 28 from the manifold 27 to the nozzles 20 through the pressure chambers 21. Black, magenta, cyan, and yellow inks are supplied to the manifold 27 from the left side through the ink supply port 26. Black ink is ink containing a pigment. Magenta ink, cyan ink, and yellow ink are inks containing a dye.

  In the lowermost nozzle plate 25 of the flow path unit 18, a plurality of nozzles 20 are formed at a predetermined pitch in the transport direction. The plurality of nozzles 20 form four nozzle rows side by side in the scanning direction orthogonal to the transport direction. A plurality of pressure chambers 21 arranged at a predetermined pitch are formed in the cavity plate 22 located in the uppermost layer, like the nozzle 20. The plurality of pressure chambers 21 constitute four rows of pressure chambers 37. That is, the ink flow path is formed by arranging the plurality of pressure chambers 21 in the transport direction, and has a plurality of pressure chamber rows 37 arranged in the scanning direction orthogonal to the transport direction. Here, “a plurality of pressure chambers 21 arranged in the transport direction” means that the plurality of pressure chambers 21 constituting one pressure chamber row 37 overlap in the transport direction. The pressure chamber 21 extends in the scanning direction.

  Holes 38 having the same size as the pressure chambers 21 are formed at both ends of the pressure chamber row 37 in the transport direction. Since the hole 38 is not in communication with the nozzle 20, ink is not ejected from the hole 38 through the nozzle 20.

  As shown in FIG. 4, a communication channel 29 that connects the pressure chamber 21 and the nozzle 20 is formed in the two plates 23 and 24 between the cavity plate 22 and the nozzle plate 25. As shown in FIG. 2, an ink supply port 26 is formed at one end in the conveyance direction of the cavity plate 22, here the rear end, connected to the ink cartridges 12 a to 12 d via tubes. .

  As shown in FIG. 4, the manifold plate 24 is formed with a long hole 30 that penetrates the manifold plate 24 in the thickness direction and extends in the transport direction. The long hole 30 is blocked by the upper base plate 23 and the lower nozzle plate 24 from the thickness direction of the plates 22 to 25, that is, the vertical direction, thereby forming the manifold 27.

  As shown in FIG. 2, the manifold 27 extends in the transport direction along the nozzle row, and communicates with the pressure chambers 21 belonging to the one pressure chamber row 37. That is, the manifold 27 supplies ink to one pressure chamber row 37, that is, one nozzle row.

  As shown in FIG. 4, the base plate 23 located between the cavity plate 22 and the manifold plate 24 communicates the manifold 30 and the pressure chambers 21 belonging to one row of pressure chambers 37 corresponding thereto. For this purpose, a communication channel 31 is formed.

  By joining the four plates 22 to 25 described above in a stacked state, as shown in FIG. 4, an ink flow path from the ink supply port 26 to the manifold 27, and a manifold in the flow path unit 18. A large number of individual ink flow paths 28 are formed from 27 to the nozzle 20 via the pressure chamber 21. In other words, the flow path unit 18 is formed with an ink flow path that includes a plurality of nozzles 20 that eject ink droplets and a plurality of pressure chambers 21 that respectively communicate with the plurality of nozzles 20. The plurality of pressure chambers 21 are planarly arranged by being formed in the plate-like cavity plate 22.

  Next, the piezoelectric actuator 19 will be described. FIG. 5A is a cross-sectional view taken along line IV-IV in FIG. FIG. 5B is a partially enlarged view of FIG. As shown in FIGS. 2 to 5, the piezoelectric actuator 19 is provided in the flow path unit 18. Specifically, it is heat bonded to one surface, here the upper surface, of the flow path unit 18. The piezoelectric actuator 19 includes a diaphragm 32, piezoelectric layers 33 and 34, a common electrode 35, an individual electrode 36, a hole electrode 49, and a driver IC 40. Although details will be described later, the piezoelectric actuator 19 causes the individual layers 36 to deform the piezoelectric layers 33 and 34 to discharge ink from the nozzles 20 corresponding to the pressure chambers 21.

  The diaphragm 32 is bonded to the upper surface of the cavity plate 22 constituting the flow path unit 18 with an adhesive. The diaphragm 32 is a substantially rectangular metal plate in plan view, and is made of, for example, an iron-based alloy such as stainless steel, a copper-based alloy, a nickel-based alloy, or a titanium-based alloy. The diaphragm 32 is bonded to the upper surface of the flow path unit 18 so as to cover the plurality of pressure chambers 21.

  The upper surface of the diaphragm 32, that is, the surface opposite to the pressure chamber 21, is composed mainly of lead zirconate titanate (PZT), which is a solid solution and ferroelectric material of lead titanate and lead zirconate. A piezoelectric layer 33 made of a piezoelectric material is bonded with an adhesive. On the upper surface of the piezoelectric layer 33, a piezoelectric layer 34 having a plurality of first active portions 44, a plurality of second active portions 45 and 46, a third active portion 53, and a fourth active portion 54, which will be described later, is disposed. The piezoelectric layers 33 and 34 are disposed so as to cover the plurality of pressure chambers 21, and extend along the plane in which the plurality of pressure chambers 21 are disposed.

  The common electrode 35 is disposed over the entire surface of the piezoelectric layers 33 and 34 between the piezoelectric layer 33 and the piezoelectric layer 34. Although not shown, the common electrode 35 is connected to the driver IC 40. The common electrode 35 is always kept at the ground potential by the driver IC 40.

  The plurality of individual electrodes 36 are respectively disposed on the upper surface of the piezoelectric layer 34. The plurality of individual electrodes 36 are respectively provided in the same number as the plurality of pressure chambers 21 corresponding to the plurality of pressure chambers 21. Here, “the plurality of individual electrodes 36 respectively correspond to the plurality of pressure chambers 21” means that one individual electrode 36 and one pressure of an ejection target that causes one individual electrode 36 to eject ink. It means that the chamber 21 forms one set. The individual electrode 36 is made of a conductive material such as gold, copper, silver, palladium, platinum, or titanium.

  The individual electrode 36 includes a first portion 41 that overlaps the corresponding pressure chamber 21 and a direction perpendicular to the surface direction of the piezoelectric layer 34 (hereinafter also referred to as “thickness direction”), and a pressure chamber adjacent to the corresponding pressure chamber 21. 21 and second portions 42 and 43 overlapping in the thickness direction. In other words, the first portion 41 is opposed to the pressure chamber 21 to which the individual electrode 36 belongs, with the diaphragm 32 and the piezoelectric layers 33 and 34 interposed therebetween. The second portions 42 and 43 are opposed to the pressure chambers 21 adjacent to the pressure chambers 21 to which the individual electrodes 36 belong, with the diaphragm 32 and the piezoelectric layers 33 and 34 interposed therebetween. The pressure chamber 21 where the first portion 41 overlaps the center C in the transport direction in the thickness direction is the pressure chamber 21 to which the individual electrode 36 corresponds. In FIG. 3, the thickness direction orthogonal to the surface direction of the piezoelectric layer 34 is the direction perpendicular to the paper surface of FIG.

  The first portion 41 overlaps in the thickness direction with the center C in the transport direction of the pressure chamber 21 to which the individual electrode 36 belongs. The first portion 41 extends in the scanning direction orthogonal to the transport direction. The second portion 42 overlaps in the thickness direction with the pressure chamber 21 adjacent to the corresponding pressure chamber 21 in front of the corresponding individual electrode 36. The second portion 42 extends in the scanning direction orthogonal to the transport direction. The second portion 43 is overlapped in the thickness direction with the pressure chamber 21 to which the individual electrode 36 to which the second portion 43 belongs corresponds to the pressure chamber 21 adjacent to the rear. The second portion 43 extends in the scanning direction orthogonal to the transport direction. One pressure chamber 21 overlaps the first portion 41 and the second portions 42 and 43 in the thickness direction. Specifically, the pressure chamber 21 is connected to the first portion 41 of the corresponding individual electrode 36, the second portion 43 of the individual electrode 36 corresponding to the pressure chamber 21 adjacent to the front, and the pressure chamber 21 adjacent to the rear. It overlaps with the second portion 42 of the corresponding individual electrode 36 in the thickness direction. The first portion 41 includes a second portion 43 of the individual electrode 36 corresponding to the pressure chamber 21 adjacent to the corresponding pressure chamber 21 and the second portion 42 of the individual electrode 36 corresponding to the pressure chamber 21 adjacent to the rear. Are sandwiched in the transport direction.

  The first portion 41 and the front second portion 42 are connected by a connecting portion 47 that connects these left ends. The first portion 41 and the rear second portion 43 are connected by a connecting portion 48 that connects these right ends. That is, the first portion 41 and the second portion 42 are connected by the connection portion 47 on one surface, here, the upper surface of the piezoelectric layer 34. The first portion 41 and the second portion 43 are connected by a connecting portion 48 on the upper surface. The first portion 41 and the second portion 42 connected by the connection portion 47 are electrically connected. The first portion 41 and the second portion 43 connected by the connection portion 48 are electrically connected. Here, “conduction” means a state of being electrically connected. The individual electrode 36 has a substantially S-shape that is point-symmetrical due to the first portion 41, the second portions 42 and 43, and the connection portions 47 and 48.

  A plurality of contact portions 39 each extending from the end of the first portion 41 of each of the plurality of individual electrodes 36, that is, the end opposite to the nozzle 20 in a plan view, to a region not facing the pressure chamber 21 are provided. Yes. A flexible printed circuit (Flexible Printed Circuit (FPC)) (not shown) is connected to the plurality of contact portions 39.

  The hole electrodes 49 correspond to the holes 38 formed at both ends of the pressure chamber row 37 in the transport direction. The hole electrode 49 is disposed on the piezoelectric layer 34. 3 and 5A, the hole 38 formed at the rear end in the transport direction of the pressure chamber row 37 and the hole electrode 49 corresponding to the hole 38 are shown. The hole electrode 49 includes a third portion 50 that overlaps the corresponding hole 38 in the thickness of the piezoelectric layers 33 and 34, and a fourth portion 51 that overlaps the pressure chamber 21 adjacent to the corresponding hole 38 in the thickness direction. ing.

  The fourth portion 51 of the hole electrode 49 corresponding to the hole 38 at the rear end overlaps the pressure chamber 21 adjacent to the front in the thickness direction. The fourth portion 51 of the hole electrode 49 corresponding to the hole 38 at the front end overlaps the pressure chamber 21 adjacent in the rear in the thickness direction. The third portion 50 overlaps the center in the transport direction of the corresponding hole 38 in the thickness direction. The third portion 50 extends in the scanning direction orthogonal to the transport direction. The fourth portion 51 overlaps the corresponding hole 38 in the thickness direction with the pressure chamber 21 adjacent frontward or rearward. The fourth portion 51 extends in the scanning direction orthogonal to the transport direction. The third portion 50 and the front fourth portion 51 are connected by a connecting portion 52 that connects these left ends. The third portion 50 and the rear fourth portion 51 are connected by a connecting portion 52 that connects these right ends. That is, the third portion 50 and the fourth portion 51 are connected by the connecting portion 52 on one surface, here, the upper surface of the piezoelectric layer 34. The third part 50 and the fourth part 51 connected by the connection part 52 are electrically connected.

  A contact portion 39 is provided that extends from the end of the third portion 50 of the hole electrode 49, that is, the end opposite to the nozzle 20 in plan view, to a region that does not face the pressure chamber 21. An FPC (not shown) is connected to the contact portion 39.

  The driver IC 40 is mounted on the FPC and is controlled by a control device (not shown). The driver IC 40 changes the potentials of the plurality of individual electrodes 36 and the hole electrodes 49 via the contact points 39. Specifically, the driver IC 40 changes the potential of the individual electrode 36 and the hole electrode 49 to a ground potential and a predetermined potential that is a predetermined potential difference from the ground potential. Since the first portion 41 and the second portions 42 and 43 of the individual electrode 36 are conductive, the potential changes at the same timing by the driver IC 40. Since the third portion 50 and the fourth portion 51 of the hole electrode 49 are conductive, the potential changes at the same timing by the driver IC 40.

  As shown in FIG. 5, the piezoelectric layer 34 sandwiched between the plurality of individual electrodes 36 and the common electrode 35 includes a plurality of first active portions 44, a plurality of second active portions 45 and 46, and a third active portion 53. And a fourth active part 54. “Active portion” refers to a portion where piezoelectric deformation occurs. The plurality of first active portions 44 respectively overlap with the plurality of first portions 41 in the thickness direction. The plurality of second active portions 45 respectively overlap the plurality of second portions 42 in the thickness direction. The plurality of second active portions 46 respectively overlap with the plurality of third portions 43 in the thickness direction. The third active portion 53 overlaps with the third portion 50 in the thickness direction. The fourth active portion 54 overlaps the fourth portion 51 in the thickness direction. In other words, the first active portion 44 faces the first portion 41. The second active portion 45 faces the second portion 42. The second active part 46 faces the second part 43. The third active portion 53 faces the third portion 50. The fourth active part 54 faces the fourth part 51. The first active part 44 and the third active part 53 are polarized in the thickness direction.

  The driver IC 40 causes piezoelectric deformation in the first active portion 44 by changing the potentials of the plurality of individual electrodes 36. The driver IC 40 causes the third active portion 53 to undergo piezoelectric deformation by changing the potential of the hole electrode 49. That is, the driver IC 40 is flat from the state in which the first active part 44 is convex toward the pressure chamber 21 by making the first active part 44 contracted in the surface direction or not contracting. It is deformed to a state or a state where it is convex from the flat state to the pressure chamber 21 side. The driver IC 40 is configured such that the third active portion 53 is contracted in the surface direction or is not contracted, so that the third active portion 53 is in a flat state from a state in which the third active portion 53 is convex toward the hole 38 side. Or it is made to deform | transform from the flat state to the state which became convex to the hole 38 side.

  The first active part 44 is a main active part for deforming the piezoelectric layers 33 and 34 that overlap the pressure chamber 21 to be ejected in the thickness direction. The second active portions 45 and 46 are active portions for assisting deformation of the piezoelectric layers 33 and 34 that overlap the pressure chamber 21 to be ejected in the thickness direction. The second active portions 45 and 46 are polarized in the thickness direction. The second active portions 45 and 46 cause piezoelectric deformation by the second portions 42 and 43 as the potential of the first portion 41 is changed. Similarly to the second active portions 45 and 46, the fourth active portion 54 is also an active portion for assisting the deformation of the piezoelectric layers 33 and 34 that overlap with the pressure chamber 21 to be ejected in the thickness direction. The fourth active part 54 is polarized in the thickness direction. The fourth active portion 54 causes piezoelectric deformation by the fourth portion 51 as the potential of the third portion 50 is changed.

  In a conventional inkjet printer, the ejection amount when ink is ejected from the nozzles corresponding to one pressure chamber rather than the ejection amount of each nozzle when ink is ejected simultaneously from nozzles corresponding to a plurality of adjacent pressure chambers There is a problem that there are many.

  FIG. 6 is a diagram for explaining the operation of a conventional pulling-type piezoelectric actuator. FIG. 6A shows a state in which the flat piezoelectric layers 103 and 104 are convex at portions facing the three pressure chambers 102a, 102b, and 102c, respectively. The individual electrode 101 is disposed on the upper surface of the piezoelectric layer 103. The common electrode 105 is disposed between the piezoelectric layer 103 and the piezoelectric layer 104. The common electrode 105 is kept at the ground potential. The active portions 106 a, 106 b and 106 c are portions sandwiched between the individual electrode 101 and the common electrode 105. When the individual electrode 101 is set to a predetermined potential having a predetermined potential difference from the ground potential, the active portions 106a, 106b, and 106c are convex toward the pressure chambers 102a, 102b, and 102c. In FIG. 6A, all of the individual electrodes 101 corresponding to the pressure chambers 102a, 102b, and 102c are set to a predetermined potential. Accordingly, since the active portions 106a, 106b, and 106c are convex toward the pressure chambers 102a, 102b, and 102c, the portions of the piezoelectric layers 103 and 104 that face the pressure chambers 102a, 102b, and 102c are formed in the pressure chamber 102a. , 102b and 102c are convex. In FIG. 6B, only the individual electrode 101 corresponding to one pressure chamber 102b is set to the ground potential. Therefore, since the active portion 106b facing the pressure chamber 102b is in a flat state, the piezoelectric layers 103 and 104 in a portion facing the pressure chamber 102b are in a flat state. In FIG. 6C, all of the individual electrodes 101 corresponding to the pressure chambers 102a, 102b, and 102c are set to the ground potential. Accordingly, since the active portions 106a, 106b, 106c facing the pressure chambers 102a, 102b, 102c are in a flat state, the portions of the piezoelectric layers 103, 104 facing the pressure chambers 102a, 102b, 102c are in a flat state. is there. In FIG. 6, the letter “V” below the symbol indicates that the corresponding individual electrode 101 has a predetermined potential. The letters “GND” below the reference sign indicate that the corresponding individual electrode 101 is at the ground potential.

  As shown in FIG. 6A, from the state in which the piezoelectric layers 103 and 104 facing the three adjacent pressure chambers 102a, 102b, and 102c are convex, as shown in FIG. A case where the individual electrodes 101 corresponding to 102a, 102b, and 102c are switched from a predetermined potential to a ground potential will be described. The portions of the piezoelectric layers 103 and 104 facing the pressure chambers 102a, 102b, and 102c are deformed into a flat state. As shown in FIG. 6A, from the state in which the piezoelectric layers 103 and 104 facing the pressure chambers 102a, 102b, and 102c are convex, as shown in FIG. A case where the corresponding individual electrode 101 is switched from a predetermined potential to a ground potential will be described. The portions of the piezoelectric layers 103 and 104 facing the pressure chamber 102b tend to be deformed into a flat state. However, at this time, portions of the piezoelectric layers 103 and 104 facing the adjacent pressure chambers 102a and 102c are convex toward the pressure chambers 102a and 102c. For this reason, the piezoelectric layers 103 and 104 are deformed around the girders 107 and 108 as fulcrums, and the portions of the piezoelectric layers 103 and 104 facing the pressure chambers 102b are not flat and are opposite to the pressure chambers 102b. It becomes a slightly convex state. Accordingly, the deformation amounts of the piezoelectric layers 103 and 104 when ink is ejected from the nozzles corresponding to one pressure chamber 102b, compared to the case where ink is ejected simultaneously from the nozzles corresponding to the adjacent pressure chambers 102a, 102b, and 102c. That is, the amount of change in the volume of the pressure chamber 102b increases. That is, the discharge amount of each nozzle when ink is simultaneously discharged from the nozzles corresponding to the adjacent pressure chambers 102a, 102b, and 102c is larger than the discharge amount when ink is discharged from the nozzle corresponding to one pressure chamber 102b. Less.

  Hereinafter, in this embodiment, the operation of the piezoelectric actuator 19 when ink is ejected from the nozzle 20 will be described. In the present embodiment, ink is ejected from the nozzles 20 by a pulling method.

  FIG. 7 is a diagram for explaining the operation of the piezoelectric actuator 19. FIG. 7A shows a standby state in which ink is not ejected from the nozzle 20. In the standby state, the individual electrode 36 is set to a predetermined potential. The first active part 44 and the second active parts 45 and 46 are convex toward the pressure chambers 21a, 21b and 21c. Therefore, the portions of the piezoelectric layers 33 and 34 that overlap the pressure chambers 21a, 21b, and 21c in the thickness direction are convex toward the pressure chambers 21a, 21b, and 21c. FIG. 7B shows a state in which the individual electrode 36 corresponding to one pressure chamber 21b is set to the ground potential. FIG. 7C shows a state in which the three individual electrodes 36 corresponding to the three adjacent pressure chambers 21a, 21b, and 21c are set to the ground potential. In FIG. 7, the letter “V” below the symbol indicates that the corresponding first portion 41 and second portions 42 and 43 are at a predetermined potential. The letters “GND” below the symbol indicate that the corresponding first portion 41 and second portions 42 and 43 are at ground potential.

  An operation of simultaneously ejecting ink from the nozzles 20 corresponding to the pressure chambers 21a, 21b, and 21c will be described. As shown in FIG. 7A, from the state where the individual electrode 36 is set to a predetermined potential, as shown in FIG. 7C, the potential of the individual electrode 36 corresponding to the pressure chambers 21a, 21b, and 21c is changed. The driver IC 40 once switches to the same ground potential as the common electrode 35. Focusing on the pressure chamber 21b, the individual electrodes 36 corresponding to the adjacent pressure chambers 21a and 21c are also switched to the ground potential. The first active portion 44 and the second active portions 45 and 46 that overlap the pressure chamber 21b in the thickness direction are deformed from a state of being convex toward the pressure chamber 21b to a state of being flat toward the opposite side of the pressure chamber 21b. For this reason, the piezoelectric layers 33 and 34 that overlap with the pressure chamber 21b in the thickness direction are deformed from a convex shape toward the pressure chamber 21b to a flat state opposite to the pressure chamber 21b. At this time, the volume in the pressure chamber 21b increases compared to the standby state. Thereafter, when the individual electrode 36 is set to a predetermined potential again by the driver IC 40, the state is changed to the state shown in FIG. 7A, and the volume of the pressure chamber 21b is reduced. By appropriately setting the switching timing between the volume increase and the volume decrease of the pressure chamber 21b, the pressure wave generated when the volume is increased and the pressure wave generated when the volume is decreased are superimposed. As a result, a large pressure wave is generated in the pressure chamber 21b, and ink is pushed out from the nozzle 20 communicating with the pressure chamber 21b and discharged. The same applies to the pressure chambers 21a and 21c.

  An operation of ejecting ink from the nozzle 20 corresponding to the pressure chamber 21b will be described. As shown in FIG. 7A, from the state in which the individual electrode 36 is at a predetermined potential, the potential of the individual electrode 36 corresponding to the pressure chamber 21b is changed by the driver IC 40 as shown in FIG. 7B. Once switched to the same ground potential as the common electrode 35. The first active portion 44 that overlaps the pressure chamber 21b in the thickness direction is deformed from a convex shape toward the pressure chamber 21b to a flat state opposite to the pressure chamber 21b. For this reason, the piezoelectric layers 33 and 34 that overlap the pressure chamber 21b in the thickness direction tend to be deformed from a state in which it protrudes toward the pressure chamber 21b to a state in which it is flat toward the opposite side of the pressure chamber 21b.

  The pressure chamber 21b overlaps in the thickness direction with the second portions 42 and 43 of the individual electrodes 36 corresponding to the pressure chambers 21a and 21c adjacent in the front-rear direction. Since the individual electrodes 36 corresponding to the pressure chambers 21a and 21c adjacent to the pressure chamber 21b are set to a predetermined potential, the second portions 42 and 43 remain at the predetermined potential. Accordingly, the first active portion 44 is deformed from a state of being convex toward the pressure chamber 21b to a state of being flat toward the opposite side of the pressure chamber 21b, while the second active portions 45 and 46 are convex toward the pressure chamber 21b. It remains. Accordingly, when the piezoelectric layers 33 and 34 that are convex toward the pressure chamber 21b are to be deformed into a flat state opposite to the pressure chamber 21b, the second is convex toward the pressure chamber 21b. The active portions 45 and 46 suppress deformation of the piezoelectric layers 33 and 34 that are to be deformed to the opposite side to the pressure chamber 21b. That is, an increase in the volume in the pressure chamber 21 from the standby state is suppressed. After that, when the individual electrode 36 is set to a predetermined potential again by the driver IC 40, the state returns to the state shown in FIG. As a result, the ink is pushed out from the nozzle 20 communicating with the pressure chamber 21 and discharged.

  Among the adjacent pressure chambers 21a, 21b, and 21c, when the potential of the individual electrode 36 corresponding to one pressure chamber 21b is changed and ink is ejected from the nozzle 20 corresponding to the pressure chamber 21b, the pressure chamber 21b The potential of the corresponding first portion 41 of the individual electrode 36 is changed. The potentials of the second portions 42 and 43 of the individual electrode 36 corresponding to the pressure chambers 21a and 21c adjacent to the pressure chamber 21b are not changed. For this reason, the first active portion 44 that overlaps the pressure chamber 21b in the thickness direction is in a state where it protrudes toward the pressure chamber 21b and is flat toward the opposite side of the pressure chamber 21b, or from the flat state to the pressure chamber 21b. Deforms to a convex side. The 2nd active parts 45 and 46 remain in the state where it became convex to the pressure chamber 21b side.

  On the other hand, when ink is ejected from the nozzles 20 corresponding to the pressure chambers 21a, 21b, 21c by changing the potential of the individual electrode 36 corresponding to the adjacent pressure chambers 21a, 21b, 21c, the pressure chambers 21a, 21b, 21c. The potentials of the first portion 41 and the second portions 42 and 43 that overlap in the thickness direction are changed. For this reason, both the first active part 44 and the second active parts 45 and 46 that overlap the pressure chambers 21a, 21b, and 21c in the thickness direction are deformed. In other words, compared to the case where ink is ejected from the nozzle 20 corresponding to the pressure chambers 21a, 21b, and 21c, the area of the electrode whose potential is changed when the ink is ejected from the nozzle 20 corresponding to the pressure chamber 21b. It is substantially smaller. For this reason, in the case where ink is ejected from the nozzle 20 corresponding to the pressure chamber 21b, compared with the case where ink is ejected from the nozzle 20 corresponding to the pressure chamber 21a, 21b, 21c, the inside of the pressure chamber 21 from the standby state. The decrease in volume is reduced, and the amount of ink discharged is reduced. That is, the ejection amount when ejecting ink from the nozzle 20 corresponding to the pressure chamber 21b is smaller than the ejection amount of each nozzle 20 when ejecting ink simultaneously from the nozzle 20 corresponding to the pressure chamber 21a, 21b, 21c. Become.

  Further, as described above, when ink is ejected from the nozzle 20 corresponding to one pressure chamber 21b, the second active portions 45 and 46 suppress an increase in the volume in the pressure chamber 21b from the standby state. Further, the discharge amount is reduced.

  As described above, in the present embodiment, when ink is ejected from the nozzle 20 corresponding to one pressure chamber 21b among the plurality of adjacent pressure chambers 21a, 21b, 21c, the pressure chamber 21b overlaps in the thickness direction. The first active part 44 is deformed, but the second active parts 45 and 46 are left as they are. When ink is ejected from the nozzles 20 corresponding to the pressure chambers 21a, 21b, and 21c, both the first active portion 44 and the second active portions 45 and 46 that overlap the pressure chambers 21a, 21b, and 21c in the thickness direction are deformed. Each of the cases in which ink is ejected from the nozzles 20 corresponding to the pressure chambers 21a, 21b, and 21c, compared to the case where ink is ejected from the nozzles 20 corresponding to the pressure chambers 21b, as the second active portions 45 and 46 are deformed. The amount of change in the volume of the pressure chambers 21a, 21b, 21c increases. In other words, the amount of change in the volume of the pressure chamber 21b when ink is ejected from the nozzle 20 corresponding to the pressure chamber 21b is smaller than when ink is ejected simultaneously from the nozzle 20 corresponding to the pressure chamber 21a, 21b, 21c. Become. Therefore, when the ink is ejected simultaneously from the nozzles 20 corresponding to the pressure chambers 21a, 21b, and 21c, the ink ejection amount of each nozzle 20 is the ejection amount when the ink is ejected from the nozzle 20 corresponding to the pressure chamber 21b. The problem of being less than can be improved.

  Further, as described above, in the present embodiment, ink is ejected from the nozzle 20 corresponding to one pressure chamber 21b, compared to the case where ink is ejected from the nozzle 20 corresponding to the adjacent pressure chambers 21a, 21b, 21c. In this case, the area of the electrode where the potential is changed is substantially reduced. For this reason, the ejection amount when ejecting ink from the nozzle 20 corresponding to the pressure chamber 21b is larger than the ejection amount of each nozzle 20 when ejecting ink simultaneously from the nozzle 20 corresponding to the pressure chamber 21a, 21b, 21c. Less.

  Note that “deformation of the active portion” means that the active portion is deformed from a flat state to a convex state, and the active portion is deformed from a convex state to a flat state. Further, “deformation of the piezoelectric layer” means that the piezoelectric layer is deformed from a flat state to a convex state, and the piezoelectric layer is deformed from a convex state to a flat state.

  In the present embodiment, the width of the pressure chamber 21 in the transport direction is 160 μm. The width of the first portion 41 in the transport direction is 160 μm. The widths in the transport direction of the second portions 42 and 43 are each 20 μm. The distance in the transport direction between the first portion 41 and the second portions 42 and 43 is 10 μm. In this case, the deformation area of the piezoelectric layer 34 when the ink is ejected from the nozzles 20 corresponding to all the pressure chambers 21 included in one pressure chamber row 37 / one pressure included in one pressure chamber row 37. When the ink is ejected from the nozzle 20 through the chamber 21, the deformation area of the piezoelectric layer 34 (hereinafter referred to as “in-column crosstalk”) is in the range of 5 to 10%. Intra-column crosstalk should have a large difference from the viewpoint of density increase when printing solid images and sharp edges when printing fine patterns. However, it is not desirable to change significantly from the ink ejection stability and the ink landing accuracy. For this reason, it is ideal that it is within 5 to 10%, which has little effect on ink ejection stability and ink landing. The width of the first portion 41 in the transport direction, the width of the second portions 42 and 43 in the transport direction, the distance in the transport direction between the first portion 41 and the second portions 42 and 43, the width of the pressure chamber 21, and the piezoelectric layer 33. , 34 and the like, it is possible to change the in-column crosstalk.

  The pressure chambers 21 at both ends in the pressure chamber row 37 have only one pressure chamber 21 adjacent to the front or rear in the pressure chamber row 37. For this reason, the pressure chamber 21 at the front end overlaps only the second portion 42 of the individual electrode 36 corresponding to the pressure chamber 21 adjacent to the rear in the second portion 42, 43 in the thickness direction. The pressure chamber 21 at the rear end overlaps only the second portion 43 of the individual electrode 36 corresponding to the pressure chamber 21 adjacent to the front among the second portions 42 and 43 in the thickness direction. That is, the number of the second portions 42 and 43 of the individual electrodes 36 that are not positioned at the end in the pressure chamber row 37 and overlap in the thickness direction with the other pressure chambers 21 is different, and the electrode arrangement with the other pressure chambers 21 is different. Is different.

  In the present embodiment, hole electrodes 49 corresponding to the holes 38 adjacent to both ends of the pressure chamber row 37 are provided. The hole electrode 49 has a fourth portion 51 that overlaps the pressure chamber 21 adjacent to the corresponding hole 38 in the thickness direction. For this reason, the pressure chambers 21 at both ends in the pressure chamber row 37 overlap the first portion 41, the second portion 42 or the second portion 43, and the fourth portion 51 in the thickness direction. Therefore, the pressure chambers 21 at both ends in the pressure chamber row 37 have the same electrode arrangement as the other pressure chambers 21 that overlap the first portion 41 and the second portions 42 and 43 in the thickness direction. And the conditions for ejecting ink are the same.

  When ink is ejected only from the nozzles 20 corresponding to the pressure chambers 21 positioned at the end of the pressure chamber row 37, the driver IC 40 keeps the hole electrodes 49 corresponding to the holes 38 at a predetermined potential. Therefore, the fourth portion 51 that overlaps the pressure chamber 21 located at the end of the pressure chamber row 37 adjacent to the hole 38 in the thickness direction remains at a predetermined potential. For this reason, as in the case of ejecting ink from the nozzle 20 corresponding to the other one pressure chamber 21, the ink is ejected from the nozzle 20 by the deformation of the first active portion 44.

  When ink is simultaneously ejected from the nozzles 20 corresponding to a plurality of adjacent pressure chambers 21 including the pressure chambers 21 positioned at the end of the pressure chamber row 37, the driver IC 40 has individual electrodes 36 corresponding to these pressure chambers 21. The potential of the hole electrode 49 is changed at the same timing. Therefore, as in the case where ink is ejected from the plurality of nozzles 20 corresponding to the plurality of adjacent pressure chambers 21 including the other pressure chambers 21, the first active unit 44, the second active unit 45, or the second active unit 46, the ink is ejected from the nozzle 20 by the deformation of the fourth active portion 54. Since the hole 38 is not used for discharging ink, the hole electrode 49 is not used for discharging ink from the hole 38.

  In the present embodiment, when the ink is simultaneously ejected from the plurality of nozzles 20 corresponding to the plurality of adjacent pressure chambers 21, the first active portion 44 and the second active portion 44 are formed by the first portion 41 and the second portions 42 and 43. The parts 45 and 46 are deformed simultaneously. For this reason, the potential of the first portion 41 and the second portions 42 and 43 needs to change simultaneously. As described above, the first portion 41 and the second portions 42 and 43 are electrically connected to each other, so that the first portion 41 and the second portions 42 and 43 have the same potential while the first portion 41 and the second portions 42 and 43 are kept in the same state. And the electric potential of the 2nd parts 42 and 43 can be changed simultaneously. Thereby, it is not necessary to connect the wiring etc. for changing an electric potential separately from the driver IC 40 to each of the first portion 41 and the second portions 42 and 43, and the electrical connection configuration is simplified. Also, the circuit inside the driver IC 40 can be simplified.

  As described above, the first portion 41 and the second portions 42 and 43 are on one surface of the piezoelectric layer 34. The connecting portions 47 and 48 are also on one surface of the piezoelectric layer 34. The first portion 41 and the second portions 42 and 43 are electrically connected by connecting portions 47 and 48. Therefore, the individual electrode 36 on one surface of the piezoelectric layer 34 can be formed on the one surface of the piezoelectric layer 34 at a time by printing.

  In the present embodiment, the connecting portions 47 and 48 are formed in a region of the piezoelectric layer 34 that does not overlap with the pressure chamber 21 in the thickness direction. Accordingly, since the connecting portions 47 and 48 do not overlap with the pressure chamber 21 in the thickness direction, the change in potential of the connecting portions 47 and 48 when the potential of the individual electrode 36 changes does not affect ink ejection. .

  The second portions 42 and 43 overlap the corresponding pressure chambers 21 in the thickness direction with the pressure chambers 21 adjacent in the transport direction. Accordingly, between the adjacent pressure chambers 21 in the pressure chamber row 37, when the ink is simultaneously discharged from the plurality of nozzles 20 corresponding to the plurality of adjacent pressure chambers 21, the discharge amount of each nozzle 20 is one pressure chamber. Thus, the problem that the ejection amount is smaller than the ejection amount when ejecting ink from the nozzle 20 corresponding to 21 can be improved.

  In order to change the volume of the pressure chamber 21 effectively by largely deforming the piezoelectric layers 33 and 34, it is preferable to dispose an active portion in the center of the pressure chamber 21. As described above, the first portion 41 overlaps the center C of the pressure chamber 21 in the transport direction in the thickness direction and extends in the scanning direction. For this reason, the piezoelectric layers 33 and 34 can be greatly deformed by the first active portion 44 to effectively change the volume of the pressure chamber 21.

  One pressure chamber 21 is sandwiched from both sides by two pressure chambers 21 adjacent in the transport direction. When the second portions 42 and 43 are disposed only on one side of the first portion 41, when ink is simultaneously ejected from the nozzles 20 corresponding to one pressure chamber row 37, the pressure adjacent on the other side The effect of crosstalk with the chamber 21 remains. In the present embodiment, the second portions 42 and 43 are disposed on both sides of the first portion 41 in consideration of crosstalk with the pressure chambers 21 on both sides.

  In the present embodiment, “ink” corresponds to “liquid” of the present invention. The “ink channel” corresponds to the “liquid channel” of the present invention. The “flow path unit 18” corresponds to the “flow path structure” of the present invention. The “individual electrode 36” corresponds to the “drive electrode” of the present invention. The “driver IC 40” corresponds to the “drive device” of the present invention. The “thickness direction” corresponds to the “direction perpendicular to the surface direction” of the present invention. The “conveying direction” corresponds to the “predetermined direction” of the present invention. The “scanning direction” corresponds to the “direction intersecting the predetermined direction” of the present invention.

  As mentioned above, although embodiment of this invention was described, the form which can apply this invention is not restricted to the above-mentioned embodiment, As suitably illustrated in the range which does not deviate from the meaning of this invention so that it may illustrate below. It is possible to make changes.

  In the above-described embodiment, the ink ejection method is exemplified as the ink ejection method. Even in the pushing method, the case where ink is ejected from the nozzle corresponding to one pressure chamber is more than the amount of ink ejected from each nozzle when ink is ejected simultaneously from nozzles corresponding to a plurality of adjacent pressure chambers. There is a problem that the discharge amount is large.

  FIG. 8 is a diagram for explaining the operation of a conventional push-type piezoelectric actuator. The structure of the piezoelectric actuator is the same as in FIG. As shown in FIG. 8A, from the state where the piezoelectric layers 103 and 104 facing the three adjacent pressure chambers 102a, 102b, and 102c are flat, as shown in FIG. 8C, the pressure chambers 102a and 102b. , 102c, the case where the individual electrode 101 corresponding to the predetermined potential is described. The active portions 106a and 106c facing the pressure chambers 102a and 102c adjacent to the pressure chamber 102b are contracted in the surface direction. For this reason, the stress of the direction pulled by the active part 106a, 106c side acts on the part facing the pressure chamber 102b of the piezoelectric layer 103. FIG. Since this stress is in a direction that inhibits the contraction of the active portion 106b facing the pressure chamber 102b, the deformation amount of the piezoelectric layers 103 and 104 facing the pressure chamber 102b is reduced. As shown in FIG. 8 (a), the piezoelectric layers 103 and 104 facing the pressure chambers 102a, 102b and 102c are flat, and as shown in FIG. 8 (b), an individual corresponding to one pressure chamber 102b. A case where the electrode 101 is set to a predetermined potential will be described. The active portions 106a and 106c facing the pressure chambers 102a and 102c adjacent to the pressure chamber 102b are not contracted in the surface direction. For this reason, the stress as described above does not occur in the piezoelectric layers 103 and 104 in the portion facing the pressure chamber 102b. Accordingly, the deformation amount of the piezoelectric layers 103 and 104 when ink is ejected from the nozzles corresponding to one pressure chamber 102b, compared to the case where ink is ejected simultaneously from the nozzles corresponding to the adjacent pressure chambers 102a, 102b, and 102c. That is, the amount of change in the volume of the pressure chamber 102b increases. That is, the discharge amount of each nozzle when ink is simultaneously discharged from the nozzles corresponding to the adjacent pressure chambers 102a, 102b, and 102c is larger than the discharge amount when ink is discharged from the nozzle corresponding to one pressure chamber 102b. Less.

  The present invention can also be applied to a pushing method. FIG. 9 is a diagram for explaining the operation of the piezoelectric actuator 19. FIG. 9A shows a standby state in which ink is not ejected from the nozzle 20. In the standby state, the individual electrode 36 is set to the ground potential. For this reason, the portions of the piezoelectric layers 33 and 34 that overlap the pressure chambers 21a, 21b, and 21c in the thickness direction are flat. FIG. 9B shows a state in which the individual electrode 36 corresponding to one pressure chamber 21b is set to a predetermined potential. FIG. 9C shows a state in which the three individual electrodes 36 corresponding to the three adjacent pressure chambers 21a, 21b, and 21c are set to a predetermined potential.

  An operation of ejecting ink from the nozzle 20 corresponding to the pressure chamber 21b will be described. As shown in FIG. 9A, from the state in which the individual electrode 36 is at the ground potential, as shown in FIG. 9B, the potential of the individual electrode 36 corresponding to the pressure chamber 21b is changed by the driver IC 40. Set to a predetermined potential. The first active portion 44 that overlaps the pressure chamber 21b in the thickness direction is deformed from a flat state to a convex shape toward the pressure chamber 21b. Therefore, the portions of the piezoelectric layers 33 and 34 that overlap the discharge target pressure chamber 21b in the thickness direction are deformed from a flat state to a convex shape toward the pressure chamber 21b. Thereby, pressure is generated in the pressure chamber 21b, and ink is pushed out from the nozzle 20 communicating with the pressure chamber 21b and discharged.

  An operation of simultaneously ejecting ink from the nozzles 20 corresponding to the pressure chambers 21a, 21b, and 21c will be described. As shown in FIG. 9A, the potential of the individual electrode 36 corresponding to the adjacent pressure chambers 21a, 21b, and 21c as shown in FIG. Is set to a predetermined potential by the driver IC 40. Focusing on the pressure chamber 21b, the individual electrodes 36 corresponding to the adjacent pressure chambers 21a and 21c are also set to a predetermined potential. The 1st active part 44 and the 2nd active part 45 and 46 deform | transform from the flat state to the state which became convex toward the pressure chamber 21b side. For this reason, the part which overlaps with the pressure chamber 21b of the piezoelectric layers 33 and 34 in the thickness direction deform | transforms into the state which protruded from the flat state to the pressure chamber 21b side. At this time, the volume in the pressure chamber 21b decreases compared to the standby state. Thereby, pressure is generated in the pressure chamber 21b, and ink is pushed out from the nozzle 20 communicating with the pressure chamber 21b and discharged. The same applies to the pressure chambers 21a and 21c.

  Among the pressure chambers 21a, 21b, and 21c, when the potential of the individual electrode 36 corresponding to the pressure chamber 21b is changed and ink is ejected from the nozzle 20 corresponding to the pressure chamber 21b, the individual electrode corresponding to the pressure chamber 21b The potential of the first portion 41 of 36 is changed. The potentials of the second portions 42 and 43 of the individual electrode 36 corresponding to the pressure chambers 21a and 21c adjacent to the pressure chamber 21b are not changed. For this reason, the 1st active part 44 which overlaps with the one pressure chamber 21b of discharge object in the thickness direction deform | transforms into the state which became convex from the flat state to the pressure chamber 21b side. The second active parts 45 and 46 remain flat.

  On the other hand, when the potential of the individual electrode 36 corresponding to the pressure chambers 21a, 21b, and 21c is changed and ink is ejected from the nozzles 20 corresponding to the pressure chambers 21a, 21b, and 21c, the thicknesses of the pressure chambers 21a, 21b, and 21c are the same. The potentials of the first portion 41 and the second portions 42 and 43 that overlap in the direction are changed. For this reason, both the first active part 44 and the second active parts 45 and 46 that overlap the pressure chambers 21a, 21b, and 21c in the thickness direction are deformed. In other words, compared with the case where ink is ejected from the nozzles 20 corresponding to the adjacent pressure chambers 21a, 21b, and 21c, the potential when ink is ejected from the nozzles 20 corresponding to one pressure chamber 21b is changed. The area of the electrode is substantially reduced. For this reason, in the case where ink is ejected from the nozzle 20 corresponding to the pressure chamber 21b, compared with the case where ink is ejected from the nozzle 20 corresponding to the pressure chamber 21a, 21b, 21c, the inside of the pressure chamber 21 from the standby state. The decrease in volume is reduced, and the amount of ink discharged is reduced. That is, the ejection amount when ejecting ink from the nozzle 20 corresponding to the pressure chamber 21b is smaller than the ejection amount of each nozzle 20 when ejecting ink simultaneously from the nozzle 20 corresponding to the pressure chamber 21a, 21b, 21c. Become.

  When ink is ejected from the nozzle 20 corresponding to one pressure chamber 21b, the individual electrode 36 corresponding to the pressure chamber 21b is set to a predetermined potential. For this reason, the 2nd parts 42 and 43 which overlap with the pressure chambers 21a and 21c adjacent to the pressure chamber 21b in the thickness direction become a predetermined electric potential like the 1st part 41. The second active portions 45 and 46 that overlap the pressure chambers 21a and 21c in the thickness direction are deformed from a flat state to a convex shape toward the pressure chambers 21a and 21c. Therefore, the second active portions 45 and 46 that are deformed so as to protrude toward the pressure chambers 21a and 21c pull the piezoelectric layer 34 in the portion facing the pressure chamber 21b, and the piezoelectric layer in the portion facing the pressure chamber 21b. Deformation of 33 and 34 is suppressed. Thereby, the decrease in the volume of the pressure chamber 21b is further reduced, and the discharge amount is reduced.

  In the above-described embodiment, the individual electrode 36 has a point-symmetric shape. However, the shape is not limited to this, and the shape may be symmetrical with respect to the first portion 41 as shown in FIG. In this case, the second portions 42 and 43 are connected to either one end of the first portion 41 by connection portions 47 and 48, respectively. Further, the adjacent individual electrodes 36 may be arranged so that the directions in the scanning direction are opposite. Further, as shown in FIG. 10B, the length of the first portion 41 in the scanning direction is shortened and the length of the second portions 42 and 43 is made shorter than that of the individual electrode 36 shown in FIG. It can also be made longer.

  In the above-described embodiment, the individual electrode 36 has two second portions 42 and 43. Not only this but the 2nd part may be one. For example, as shown in FIG. 10C, the individual electrode 36 has a second portion 42 that overlaps with the pressure chamber 21 adjacent to the front side of the pressure chamber 21 corresponding to the individual electrode 36 in the thickness direction. Also good. As shown in FIG. 10D, in the individual electrode 36 having the second portion 42, the adjacent individual electrodes 36 may be arranged so that the directions in the scanning direction are opposite. Moreover, when the individual electrode 36 has the 2nd part 42 which overlaps with the pressure chamber 21 adjacent ahead of the corresponding pressure chamber 21, the pressure chamber 21 is excluded except the pressure chamber 21 of the rear end which does not have the pressure chamber 21 adjacent behind. The chamber 21 overlaps the first portion 41 and the second portion 42. For this reason, the hole 38 need only be adjacent to the pressure chamber 21 at the rear end. The hole electrode 49 is also only required to correspond to the hole 38 adjacent to the pressure chamber 21 at the rear end.

  In the above-described embodiment, the piezoelectric actuator 19 has two piezoelectric layers 33 and 34. Not only this but you may have three or more piezoelectric layers. FIG. 10E is an enlarged plan view of the piezoelectric actuator 19 having three piezoelectric layers 61 to 63. FIG. 10F is a sectional view taken along line VIII-VIII in FIG. As shown in FIGS. 10E and 10F, the individual electrode 36 is disposed between the upper piezoelectric layer 63 and the middle piezoelectric layer 62. A first common electrode 64 is disposed on the upper surface of the upper piezoelectric layer 63 so as to overlap the plurality of individual electrodes 36 in the thickness direction. The first common electrode 64 has a comb shape in plan view. Between the middle piezoelectric layer 62 and the lower piezoelectric layer 61, the second common electrode 65 is disposed over the entire surface of the piezoelectric layers 61 and 62. A portion of the piezoelectric layers 62 and 63 sandwiched between the first portion 41 and the first common electrode 64 and between the first portion 41 and the second common electrode 65 is the first active portion 44. A portion of the piezoelectric layers 62 and 63 sandwiched between the second portion 42 and the first common electrode 64 and between the second portion 42 and the second common electrode 65 is the second active portion 45. A portion of the piezoelectric layers 62 and 63 sandwiched between the second portion 43 and the first common electrode 64 and between the second portion 43 and the second common electrode 65 is the second active portion 46. The upper piezoelectric layer 63 is provided with a through hole 66 for connecting the individual electrode 36 to the driver IC 40.

  The second common electrode 65 is always kept at the ground potential by the driver IC 40. The first common electrode 64 is always kept at a predetermined potential that is a predetermined potential difference from the ground potential by the driver IC 40. The individual electrode 36 is changed to a ground potential and a predetermined potential by the driver IC 40. The state in which the individual electrode 36 is set to the ground potential and the piezoelectric layers 61 to 63 are convex toward the pressure chamber 21 due to the potential difference with the first common electrode 64 is a standby state. When the individual electrode 36 is set to a predetermined potential from the standby state, the piezoelectric layers 61 to 63 are deformed in a convex shape on the side opposite to the pressure chamber 21 due to a potential difference with the second common electrode 65. Thereafter, the individual electrode 36 is set to the ground potential, and the piezoelectric layers 61 to 63 are set to a standby state in which they protrude toward the pressure chamber 21 side. As a result, the volume of the pressure chamber 21 decreases and then increases, and ink is ejected from the nozzle 20 via the pressure chamber 21.

  In the above-described embodiment, the individual electrode 36 is connected to the driver IC 40, and the first portion 41 and the second portions 42 and 43 of the individual electrode 36 are electrically connected. Not limited to this, the first portion 41 and the second portions 42 and 43 may not be electrically connected, and the first portion 41 and the second portions 42 and 43 may be connected to the driver IC 40, respectively. In this case, at the same timing as the first portion 41 of the individual electrode 36 corresponding to the discharge target pressure chamber 21, the potentials of the second portions 42 and 43 that overlap the pressure chamber 21 adjacent to the discharge target pressure chamber 21 in the thickness direction are set. Change it.

  In the above-described embodiment, the first portion 41 and the second portions 42 and 43 have substantially the same potential value. For example, a resistor other than the connection portions 47 and 48 may be provided between the first portion 41 and the second portions 42 and 43 so that the value of the changing potential is different.

  In the above-described embodiment, the first portion 41 and the second portions 42 and 43 of the individual electrode 36 are electrically connected on one surface of the piezoelectric layer 34. However, the present invention is not limited to this, and when there is a member or the like that prevents connection on one surface, for example, conduction may be established between the piezoelectric layers 33 and 34.

  In the embodiment described above, the number of the plurality of individual electrodes 36 is the same as the number of the plurality of pressure chambers 21. However, the number of the individual electrodes is not limited to the number of the plurality of pressure chambers. For example, this is a case where the individual electrodes are not in one layer but in multiple layers. When the individual electrodes are in two layers across the common electrode, the number of the plurality of individual electrodes is twice the number of the plurality of pressure chambers.

  In the above embodiment, the recording method of the ink jet printer 1 is a serial ink jet recording method in which the ink jet head 5 moves. However, the recording method of the ink jet printer 1 may be a line type ink jet recording method in which the ink jet head does not move. Also, the present invention can be applied to liquid ejection devices other than ink jet printers.

DESCRIPTION OF SYMBOLS 1 Inkjet printer 5 Inkjet head 18 Flow path unit 19 Piezoelectric actuator 20 Nozzle 21 Pressure chamber 33, 34, 61-63 Piezoelectric layer 35 Common electrode 36 Individual electrode 37 Pressure chamber row 38 Hole 40 Driver IC
41 1st part 42, 43 2nd part 44 1st active part 45, 46 2nd active part 47, 48, 52 Connection part 49 Hole electrode 50 3rd part 51 4th part 53 3rd active part 54 4th activity Part 64 first common electrode 65 second common electrode

Claims (8)

A plurality of nozzles for discharging liquid, a plurality of pressure chambers respectively communicating with the plurality of nozzles, and an end in the predetermined direction of a pressure chamber row formed by arranging the plurality of pressure chambers in a predetermined direction A flow path structure that is adjacent and formed with a hole that is the same size as the pressure chamber and does not communicate with the nozzle ;
A piezoelectric actuator provided in the flow path structure,
The piezoelectric actuator is
A piezoelectric layer disposed so as to cover the plurality of pressure chambers and the hole , and extending along a plane in which the plurality of pressure chambers are disposed;
A plurality of drive electrodes disposed in the piezoelectric layer and corresponding to the plurality of pressure chambers;
A hole electrode disposed in the piezoelectric layer and corresponding to the hole;
A drive device that changes the potential of the plurality of drive electrodes and the hole electrode ;
Each of the plurality of drive electrodes overlaps with the corresponding pressure chamber in a direction orthogonal to the surface direction of the piezoelectric layer, and in a direction orthogonal to the pressure chamber adjacent to the corresponding pressure chamber. A second part,
The hole electrode includes a third portion that overlaps the corresponding hole and a direction perpendicular to the surface direction of the piezoelectric layer, a fourth portion that overlaps the pressure chamber adjacent to the corresponding hole, and the fourth portion. Have
The piezoelectric layer includes a plurality of first active portion that overlaps the plurality of the first portion and the direction of the perpendicular, respectively, and a plurality of second active portion that overlaps the plurality of the second portion and the direction of the perpendicular, respectively, wherein A liquid ejecting apparatus comprising: a third active portion that overlaps with a third portion in the orthogonal direction; and a fourth active portion that overlaps with the fourth portion in the orthogonal direction . The driving device is configured to supply liquid from the nozzle corresponding to the first pressure chamber located at an end of the pressure chamber row and the second pressure chamber adjacent to the first pressure chamber. The liquid ejection apparatus according to claim 1, wherein the potential of the hole electrode is changed according to the presence or absence of ejection. In the case where the driving device discharges liquid from the nozzle corresponding to the first pressure chamber and does not discharge liquid from the nozzle corresponding to the second pressure chamber, the driving device moves the electrode for the hole to the second pressure chamber. The liquid ejection apparatus according to claim 2, wherein the liquid ejection apparatus is held at the same potential as the driving electrode corresponding to the pressure chamber. When the driving device simultaneously discharges liquid from the nozzle corresponding to the first pressure chamber and the nozzle corresponding to the second pressure chamber, the driving electrode corresponds to the second pressure chamber. The liquid discharge apparatus according to claim 3, wherein the potential is changed at the same timing as the driving electrode. In the case where the driving device discharges liquid from the nozzle corresponding to the first pressure chamber and does not discharge liquid from the nozzle corresponding to the second pressure chamber, the driving device moves the electrode for the hole to the second pressure chamber. In the case where liquid is simultaneously discharged from the nozzle corresponding to the first pressure chamber and the nozzle corresponding to the second pressure chamber while being held at the same potential as the drive electrode corresponding to the pressure chamber, The liquid ejection apparatus according to claim 2, wherein the potential is changed at the same timing as that of the drive electrode corresponding to the second pressure chamber. A flow path structure in which a plurality of nozzles for discharging liquid and a plurality of pressure chambers respectively communicating with the plurality of nozzles are formed;
A piezoelectric actuator provided in the flow path structure,
The piezoelectric actuator is
A piezoelectric layer disposed so as to cover the plurality of pressure chambers and extending along an arrangement plane of the plurality of pressure chambers;
A plurality of drive electrodes disposed in the piezoelectric layer and corresponding to the plurality of pressure chambers;
A drive device that changes the potential of the plurality of drive electrodes,
Each of the plurality of drive electrodes overlaps with the corresponding pressure chamber in a direction orthogonal to the surface direction of the piezoelectric layer, and in a direction orthogonal to the pressure chamber adjacent to the corresponding pressure chamber. A second part,
The piezoelectric layer includes a plurality of first active portions that overlap with the plurality of first portions in the orthogonal direction, and a plurality of second active portions that overlap with the plurality of second portions in the orthogonal direction, respectively. Have
The plurality of pressure chambers are arranged such that a plurality of pressure chamber rows formed by arranging a plurality of the pressure chambers in a predetermined direction are arranged in a direction intersecting the predetermined direction,
The second portion belongs to the pressure chamber row to which the corresponding pressure chamber belongs, and overlaps the corresponding pressure chamber in the direction orthogonal to the pressure chamber adjacent in the predetermined direction,
The liquid ejection device, wherein the pressure chamber extends in a direction orthogonal to the predetermined direction. The second part is disposed on both sides of the first part in the predetermined direction ,
The liquid ejecting apparatus according to claim 6, wherein the first portion and the second portion disposed on both sides of the first portion overlap in the predetermined direction . The second portion, in the extending direction of the pressure chamber, the liquid ejecting apparatus according to claim 6 or 7, characterized that you have overlapped in the direction perpendicular to the central portion of the pressure chamber and said predetermined direction.

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