JP2006150948A - Liquid transfer device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid transfer device equipped with a piezoelectric actuator which has a superior durability, and moreover has a further improved driving efficiency. <P>SOLUTION: The piezoelectric actuator of an inkjet head has a diaphragm 30 which covers pressure chambers 14 and doubles as a common electrode; a piezoelectric layer 31 arranged at the opposite side to the pressure chambers 14 of the diaphragm 30; and a plurality of discrete electrodes 32 arranged in a region that overlaps with edge parts as a region other than center parts of the plurality of pressure chambers 14 seen from a direction orthogonal to a plane where the plurality of pressure chambers 14 are set, on a face of the opposite side to the diaphragm 30 of the piezoelectric layer 31. The discrete electrode 32 extends to an outside region of the pressure chamber 14 seen from the direction orthogonal to the plane. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid transfer apparatus for transferring a liquid.

  There are various types of liquid transfer devices that apply pressure to a liquid and transfer it to a predetermined position. For example, ink is transferred to a nozzle and discharged from the nozzle onto an ejected object such as recording paper. Ink jet heads are known. Among them, for example, the ink jet head described in Patent Document 1 changes the volume of the pressure chamber and the flow path unit (cavity plate) in which a plurality of pressure chambers communicating with the nozzles and having an elongated shape in one direction are formed. And a piezoelectric actuator that applies pressure to the ink in the pressure chamber to be ejected from the nozzle.

  Furthermore, the piezoelectric actuators of this ink jet head are alternately arranged between a plurality of piezoelectric sheets made of lead zirconate titanate (PZT), which are arranged so as to cover the pressure chamber, and between the plurality of piezoelectric sheets. And an individual electrode (drive electrode) and a common electrode (common electrode). The individual electrode and the common electrode are formed in an annular shape so as to follow the peripheral edge of the pressure chamber in a region overlapping with the pressure chamber when viewed from the direction orthogonal to the surface of the piezoelectric sheet. The piezoelectric actuator is configured to be able to perform so-called striking, in which the volume of the pressure chamber is once increased to draw ink into the pressure chamber, and then the pressure chamber is decreased to apply a large pressure to the ink. Has been.

  That is, when a driving voltage is applied to the individual electrode while the common electrode is held at the ground potential, the piezoelectric sheet is annular between the individual electrode and the common electrode and along the periphery of the pressure chamber This part shrinks in a direction parallel to the surface. As a result, the plurality of piezoelectric sheets are deformed so as to protrude toward the opposite side of the pressure chamber, the volume in the pressure chamber is increased, and a pressure wave is generated in the pressure chamber. Furthermore, when the application of the drive voltage to the individual electrodes is stopped at the timing when this pressure wave turns positive in the pressure chamber, the plurality of piezoelectric sheets return to their original shape and the volume in the pressure chamber decreases. At this time, the pressure wave that accompanies the increase in volume of the pressure chamber and the pressure wave that accompanies the restoration of the piezoelectric sheet are combined to apply a large pressure to the ink. Therefore, the piezoelectric actuator of the ink jet head can apply a large pressure to the ink with a relatively low driving voltage, and the driving efficiency of the piezoelectric actuator is increased. In addition, an electric field is applied to the piezoelectric layer by applying a driving voltage to the individual electrode only at the timing of ejecting the ink, and the electric field is not applied to the piezoelectric layer except at the timing of ejecting the ink. Since the polarization deterioration hardly occurs, the durability of the actuator is high.

JP 2004-166463 A (FIGS. 5 to 7)

  As described above, in the ink jet head of Patent Document 1, the individual electrode and the common electrode are formed in an annular shape along the periphery of the pressure chamber in a region overlapping the pressure chamber in plan view. According to the studies by the authors, these electrodes are formed only in the region overlapping with the pressure chamber, so that they are close to the region outside the pressure chamber where deformation of the diaphragm is constrained, just inside the edge of the pressure chamber It has been found that the piezoelectric layer is not easily deformed in this region, and the deformation amount of the diaphragm at the position overlapping the central portion of the pressure chamber is reduced accordingly. Therefore, in order to further increase the amount of deformation of the diaphragm and further improve the driving efficiency of the actuator, it is desirable to deform the piezoelectric layer in the region immediately inside the edge of the pressure chamber more greatly, and there is room for further improvement in this respect. was there.

  An object of the present invention is to provide a liquid transfer device including a piezoelectric actuator having excellent durability and further improved driving efficiency.

Means for Solving the Problems and Effects of the Invention

  According to the present invention, a liquid transfer comprising a flow path unit having a plurality of pressure chambers arranged along a plane, and a piezoelectric actuator for changing the volume of the pressure chamber to apply pressure to the liquid in the pressure chamber. The piezoelectric actuator includes a diaphragm that covers the pressure chamber, a piezoelectric layer that is disposed on the opposite side of the diaphragm from the pressure chamber, and one surface of the piezoelectric layer that is orthogonal to the plane. A plurality of individual electrodes arranged in regions overlapping with an edge that is a region other than the central portion of the plurality of pressure chambers, and a common electrode arranged on the other surface of the piezoelectric layer And the individual electrode extends to a region outside the pressure chamber when viewed from a direction orthogonal to the plane.

  In this liquid transfer device, the individual electrodes of the piezoelectric actuator are arranged in a region overlapping the edge of the pressure chamber. Therefore, when a driving voltage is applied to the individual electrode, the portion of the piezoelectric layer that is sandwiched between the individual electrode and the common electrode and that extends along the edge of the pressure chamber contracts in a direction parallel to the surface. As a result, the diaphragm is deformed so that it protrudes on the opposite side of the pressure chamber with the portion overlapping the central portion of the pressure chamber as the apex, so that the volume of the pressure chamber increases and a pressure wave is generated in the pressure chamber. Furthermore, when the application of the drive voltage to the individual electrode is stopped at the timing when this pressure wave turns positive in the pressure chamber, the diaphragm returns to its original shape and the volume in the pressure chamber decreases. A pressure wave that accompanies the volume increase of the chamber and a pressure wave that accompanies the restoration of the diaphragm are combined to apply a large pressure to the liquid in the pressure chamber. Accordingly, it is possible to apply a high pressure to the liquid with a relatively low driving voltage, and the driving efficiency of the piezoelectric actuator is increased. In addition, since the individual electrode is applied with a driving voltage and an electric field acts on the piezoelectric layer only at the timing of transferring the liquid, polarization deterioration hardly occurs in the piezoelectric layer, and the durability is excellent.

  Furthermore, the individual electrode extends from the edge of the pressure chamber to a region outside the pressure chamber. Therefore, when the drive voltage is applied to the individual electrode, the piezoelectric layer also shrinks in the direction parallel to the surface in the region outside the pressure chamber, so that the region that is connected to this region and just inside the edge of the pressure chamber The piezoelectric layer is easily deformed, and the amount of deformation of the diaphragm increases. In this way, the diaphragm can be greatly deformed simply by forming the individual electrodes up to the area outside the pressure chamber, and the drive efficiency of the actuator can be improved without substantially increasing the manufacturing cost. become.

  In the liquid transfer device according to the aspect of the invention, the flow path unit may be located between the plurality of pressure chambers opened to the diaphragm side and the plurality of pressure chambers on a surface joined to the diaphragm. And a portion extending to a region outside the pressure chamber of the individual electrode may overlap the beam portion when viewed from a direction orthogonal to the plane. As described above, since the individual electrode extends to the region overlapping the spar portion, the piezoelectric layer is also applied to the surface of the spar portion where the deformation of the diaphragm is restricted when the drive voltage is applied to the individual electrode. Accordingly, the piezoelectric layer portion in the region immediately inside the edge of the pressure chamber is easily deformed. Therefore, the amount of deformation of the diaphragm is increased, and the driving efficiency of the piezoelectric actuator is improved.

  In the liquid transfer apparatus of the present invention, the individual electrode is located at a substantially intermediate position between a pressure chamber corresponding to the individual electrode and another pressure chamber adjacent to the pressure chamber when viewed from a direction orthogonal to the plane. Can extend to. Since the individual electrode extends to the maximum area outside the pressure chamber as long as it does not overlap with the individual electrode corresponding to the adjacent pressure chamber, the portion of the piezoelectric layer in the area immediately inside the edge of the pressure chamber is deformed. This makes it easier to deform the diaphragm more greatly.

  In the liquid transfer device of the present invention, the diaphragm may be made of a metal material and also serve as the common electrode. In this case, it is not necessary to provide a common electrode separately from the diaphragm. Alternatively, the diaphragm may have an insulating property at least on a surface opposite to the pressure chamber, and the common electrode may be formed on a surface opposite to the pressure chamber of the diaphragm. Alternatively, the diaphragm may have an insulating property at least on a surface opposite to the pressure chamber, and the plurality of individual electrodes may be formed on a surface opposite to the pressure chamber of the diaphragm.

  Furthermore, in the liquid transfer device of the present invention, the piezoelectric layer may be formed so as to cover the plurality of pressure chambers entirely. Alternatively, the piezoelectric layer may be formed in a region other than a region overlapping the central portion of the pressure chamber when viewed from a direction orthogonal to the plane.

  In the liquid transfer device of the present invention, the length of the individual electrode in the region outside the pressure chamber may be equal to or greater than the thickness of the piezoelectric layer. By adjusting the length of the individual electrode in the region outside the pressure chamber (length of the extending portion) in this way, the piezoelectric layer can be reliably deformed by overcoming the rigidity of the piezoelectric layer.

  The individual electrode may extend to a region outside the pressure chamber in a direction crossing the longitudinal direction of the pressure chamber when viewed from a direction orthogonal to the plane. Usually, the piezoelectric layer and the diaphragm are greatly deformed in a direction crossing the longitudinal direction of the pressure chamber. Therefore, in order to further increase the amount of deformation in such a direction, it is only necessary to secure the extending portion of the individual electrode in such a direction. In addition, the portion of the individual electrode that extends to the region outside the pressure chamber may be formed symmetrically with respect to the central axis of the pressure chamber that is parallel to the longitudinal direction of the pressure chamber. Note that the longitudinal direction and the intersecting direction of the pressure chamber include not only a direction orthogonal to the longitudinal direction of the pressure chamber but also a direction obliquely intersecting the longitudinal direction. For example, when the pressure chamber is elliptical, the individual electrodes are only in the minor axis direction of the ellipse or in both the minor axis direction and the major axis direction of the ellipse when viewed from the direction orthogonal to the plane. , And can extend to a region outside the pressure chamber.

  Embodiments of the present invention will be described. This embodiment is an example in which the present invention is applied to an inkjet head that ejects ink from nozzles.

  First, the ink jet printer 100 including the ink jet head 1 will be briefly described. As shown in FIG. 1, an inkjet printer 100 includes a carriage 101 that can move in the left-right direction in FIG. 1 and a serial inkjet head 1 (liquid) that is provided on the carriage 101 and discharges ink onto a recording paper P. And a transport roller 102 for transporting the recording paper P forward in FIG. The inkjet head 1 moves in the left-right direction (scanning direction) integrally with the carriage 101, and is transferred from the emission port of the nozzle 20 (see FIGS. 2 to 5) formed on the lower surface to the recording paper P. Ink is ejected. Then, the recording paper P recorded by the inkjet head 1 is discharged forward (paper feeding direction) by the transport roller 102.

  Next, the inkjet head 1 will be described. As shown in FIGS. 2 to 5, the inkjet head 1 includes a flow path unit 2 in which an ink flow path is formed, and a piezoelectric actuator 3 disposed on the upper surface of the flow path unit 2.

  First, the flow path unit 2 will be described. The flow path unit 2 includes a cavity plate 10, a base plate 11, a manifold plate 12, and a nozzle plate 13, and these four plates 10 to 13 are joined in a stacked state. Among these, the cavity plate 10, the base plate 11, and the manifold plate 12 are substantially rectangular stainless steel plates. Therefore, ink flow paths such as a manifold 17 and a pressure chamber 14 described later can be easily formed on these three plates 10 to 12 by etching. The nozzle plate 13 is formed of, for example, a polymer synthetic resin material such as polyimide, and is bonded to the lower surface of the manifold plate 12. Or this nozzle plate 13 may be formed with metal materials, such as stainless steel, similarly to the three plates 10-12.

  As shown in FIGS. 2 and 3, the cavity plate 10 has a plurality of pressure chambers 14 arranged along a plane. The plurality of pressure chambers 14 are opened upward, and the plurality of pressure chambers 14 are covered with a diaphragm 30 described later that is bonded to the upper surface of the cavity plate 10. Each pressure chamber 14 is formed in a substantially oval shape that is long in the scanning direction (left-right direction in FIG. 2) when seen in a plan view, that is, from a direction orthogonal to the plane on which the pressure chamber 14 is formed.

  Communication holes 15 and 16 are formed at positions overlapping with both longitudinal ends of the pressure chamber 14 in plan view of the base plate 11. Further, the manifold plate 12 extends in two rows in the paper feeding direction (vertical direction in FIG. 2), and overlaps the portion of the pressure chamber 14 on the side of the communication hole 15 (right side portion of the pressure chamber 14 in FIG. 2) in plan view. A manifold 17 is formed. Ink is supplied to the manifold 17 from an ink tank (not shown) through an ink supply port 18 formed in the cavity plate 10. In addition, a communication hole 19 connected to the communication hole 16 is also formed at a position overlapping the end of the pressure chamber 14 opposite to the manifold 17 in the plan view (the left side portion of the pressure chamber 14 in FIG. 2). Furthermore, as can be seen from FIG. 3, the nozzle plate 13 is formed with a plurality of nozzles 20 at positions overlapping the left end portions of the plurality of pressure chambers 14 in plan view. The nozzle 20 is formed, for example, by performing excimer laser processing on a polymer synthetic resin substrate such as polyimide.

  As shown in FIG. 4, the manifold 17 communicates with the pressure chamber 14 through the communication hole 15, and the pressure chamber 14 communicates with the nozzle 20 through the communication holes 16 and 19. In this way, the individual ink flow path 21 extending from the manifold 17 to the nozzle 20 through the pressure chamber 14 is formed in the flow path unit 2.

  Next, the piezoelectric actuator 3 will be described.

  As shown in FIGS. 2 to 5, the piezoelectric actuator 3 includes a conductive vibration plate 30 disposed on the surface of the flow path unit 2 and an upper surface of the vibration plate 30 (a surface opposite to the pressure chamber 14). And a plurality of individual electrodes 32 formed on the upper surface of the piezoelectric layer 31 so as to correspond to the plurality of pressure chambers 14, respectively. The piezoelectric layer 31 is polarized in the thickness direction and in the direction from the individual electrode 32 toward the diaphragm 30 at least in the region covered with the individual electrode 32.

  The diaphragm 30 is made of a metal material (for example, an iron-based alloy such as stainless steel, a nickel alloy, an aluminum alloy, or a titanium alloy), and has a substantially rectangular shape in plan view. The cavity plate 10 is joined so as to cover the plurality of pressure chambers 14. The diaphragm 30 also serves as a common electrode that opposes the plurality of individual electrodes 32 and applies an electric field to the piezoelectric layer 31 between the individual electrodes 32 and the diaphragm 30, and the diaphragm 30 is always at ground potential. It is in a state that is held in.

  The piezoelectric layer 31 is made of lead zirconate titanate (PZT), which is a solid solution of lead titanate and lead zirconate, and is a ferroelectric substance, and covers the plurality of pressure chambers 14 entirely on the upper surface of the diaphragm 30. It is formed as follows. The piezoelectric layer 31 can be formed by, for example, an aerosol deposition method (AD method) in which particles of a piezoelectric material are jetted and deposited on a layer forming surface. The piezoelectric layer 31 can also be formed by other known methods such as sputtering, CVD (chemical vapor deposition), sol / gel, hydrothermal synthesis, and the like. Alternatively, the piezoelectric layer 31 may be formed by cutting a piezoelectric sheet generated by firing a green sheet of PZT into a predetermined size and attaching the cut piezoelectric sheet to the vibration plate 30.

  The individual electrode 32 is formed with a hole 32a at the center thereof and has an annular shape that is long in the scanning direction (left-right direction in FIG. 2). Further, the individual electrode 32 is other than the central portion of the pressure chamber 14 in plan view. Is formed so as to surround the central portion of the pressure chamber 14. The individual electrode 32 is formed of a conductive material (for example, gold, copper, silver, palladium, platinum, or titanium). Further, the individual electrode 32 extends to the region outside the pressure chamber 14 over the entire circumference in plan view, and the portion of the individual electrode 32 extending to the outside of the pressure chamber 14 is formed on the cavity plate 10. It is located between the plurality of formed pressure chambers 14 and overlaps with the beam portion 10 a that supports the diaphragm 30. Further, a plurality of terminal portions 35 extend in the scanning direction, for example, from the right end portion in FIG. 2 of the plurality of individual electrodes 32. A driver IC (not shown) is connected to the plurality of terminal portions 35 via a flexible wiring member (not shown) such as a flexible printed circuit (FPC). A drive voltage is selectively applied from the driver IC to the plurality of individual electrodes 32 via the plurality of terminal portions 35. The individual electrodes 32 and the terminal portions 35 can be formed by screen printing, sputtering, vapor deposition, or the like.

  Next, the operation of the piezoelectric actuator 3 during ink ejection will be described.

  When a driving voltage is selectively applied to the plurality of individual electrodes 32 from the driver IC, the individual electrodes 32 on the upper side of the piezoelectric layer 31 to which the driving voltage is applied and the lower side of the piezoelectric layer 31 held at the ground potential. The potentials of the diaphragm 30 serving as the common electrode are in different states, and an electric field in the vertical direction is applied to the portion of the piezoelectric layer 31 sandwiched between the individual electrode 32 and the diaphragm 30. Then, the portion of the piezoelectric layer 31 immediately below the individual electrode 32 to which the drive voltage is applied extends in the thickness direction, which is the polarization direction, and contracts in a direction perpendicular to the polarization direction and parallel to the surface.

  Here, as described above, since the individual electrode 32 is formed in a region overlapping the edge of the pressure chamber 14 of the piezoelectric layer 31 in a plan view, as shown in FIG. A region overlapping the edge of the chamber 14 is a driving region A1 where the piezoelectric layer 31 spontaneously deforms, and a region overlapping the central portion of the pressure chamber 14 is deformed along with the deformation of the piezoelectric layer 31 in the driving region A1. It becomes area A2. The area outside the pressure chamber 14 where the diaphragm 30 is joined to the cavity plate 10 is a restrained area A3 in which the deformation of the diaphragm 30 is restrained. The piezoelectric layer 31 in the drive region A1 located on both sides in FIG. 6 contracts in a direction parallel to the surface, while the diaphragm 30 in the drive region A1 does not contract in a direction parallel to the surface. The piezoelectric layer 31 and the diaphragm 30 in the driven area A2 sandwiched between A1 are deformed. The diaphragm 30 is deformed so as to be convex on the opposite side of the pressure chamber 14 with the center of the driven area A2 as a vertex. Then, the volume in the pressure chamber 14 increases and a pressure wave is generated in the pressure chamber 14.

  Here, as is conventionally known, when the pressure wave accompanying the volume increase of the pressure chamber 14 propagates one way in the longitudinal direction of the pressure chamber 14, the pressure in the pressure chamber 14 becomes positive. Turn. Therefore, the driver IC stops applying the driving voltage to the individual electrode 32 by the driver IC at the timing when the pressure in the pressure chamber 14 turns positive. Then, the potential of the individual electrode 32 becomes the ground potential, the diaphragm 30 returns to its original shape, and the volume in the pressure chamber 14 decreases. At this time, the pressure wave accompanying the increase in the volume of the pressure chamber 14 described above Since the pressure wave generated along with the restoration of the vibration plate 30 is synthesized, a large pressure is applied to the ink in the pressure chamber 14 and the ink is ejected from the nozzle 20. Accordingly, it is possible to apply a high pressure to the ink with a low driving voltage, and the driving efficiency of the piezoelectric actuator 3 is increased. In addition, since an electric field is applied to the piezoelectric layer 31 by applying a driving voltage to the individual electrode 32 only at the timing of ejecting ink, polarization deterioration hardly occurs in the piezoelectric layer 31 and the durability is excellent.

  Furthermore, in the piezoelectric actuator 3 of the present embodiment, as shown in FIGS. 2 to 5, the individual electrode 32 extends to the region outside the pressure chamber 14 over the entire circumference in plan view. The portion of the individual electrode 32 extending to the outside of the pressure chamber 14 is located between the plurality of pressure chambers 14 formed in the cavity plate 10 and overlaps the beam portion 10 a that supports the diaphragm 30. Therefore, as shown in FIG. 6, the drive region A <b> 1 extends and overlaps to the restrained region A <b> 3 where the deformation of the diaphragm 30 is restrained, and the portion of the piezoelectric layer 31 located in the region outside the pressure chamber 14. 31a also contracts in a direction parallel to its surface. Therefore, compared to the case where the individual electrode 32 shown in FIG. 7 is formed only in the region overlapping the pressure chamber 14 (see, for example, Patent Document 1 described above), the drive region A1 is just inside the edge of the pressure chamber 14. Accordingly, the amount of deformation of the diaphragm 30 in the driven region A2 also increases. In other words, the diaphragm 30 can be deformed more greatly with the same driving voltage only by forming the individual electrode 32 up to the region outside the pressure chamber 14, and the piezoelectric actuator can be obtained without substantially increasing the manufacturing cost. 3 can be improved.

  The length of the region outside the pressure chamber 14 of the individual electrode 32 (length of the extending portion) is absolutely determined because the force required to deform the piezoelectric layer increases as the thickness of the piezoelectric layer increases. Although it is difficult to do this, it is desirable that the length is at least as large as the thickness of the piezoelectric layer. Further, since the force required to deform the diaphragm increases as the thickness of the diaphragm increases, when the diaphragm is thicker than the piezoelectric layer, the length of the extended portion of the individual electrode 32 is the thickness of the diaphragm. It is desirable to be more than that. In particular, the length of the extending portion of the individual electrode 32 is preferably equal to or greater than the sum of the thicknesses of the piezoelectric layer and the diaphragm. From the viewpoint of increasing the deformation amount of the diaphragm 30 as much as possible, the individual electrode 32 extends as wide (longest) as possible to the outside of the pressure chamber 14 within a range not overlapping with the adjacent individual electrode 32. Is preferred. Accordingly, in the spar 10a, the individual electrode 32 is located at a substantially intermediate position (in FIG. 5) between the pressure chamber 14 corresponding to the individual electrode 32 and another pressure chamber 14 adjacent to the pressure chamber 14 in a plan view. It is particularly preferable to extend to the position of the point C).

  As shown in FIG. 2, the individual electrode 32 may extend in the scanning direction so as to reach the outside of the pressure chamber to form the terminal portion 35. The individual electrode extending to the outside of the pressure chamber only for the purpose of forming such a wiring portion is referred to in the present invention as “extends to a region outside the pressure chamber as viewed from the direction perpendicular to the plane”. Not included in individual electrodes. This is because the amount of deformation of the diaphragm cannot be substantially increased even if it extends to the region outside the pressure chamber only for the purpose of forming such a wiring portion.

  Here, in order to verify that the amount of deformation of the diaphragm 30 is larger when the individual electrode 32 is formed up to the region outside the pressure chamber 14 than when the individual electrode 32 is not, the finite element method ( Structural analysis was performed using Finite Element Method (FEM). Here, the length B in the short direction (width direction) of the pressure chamber 14 shown in FIG. 5 is 419 μm, the thickness Tv of the diaphragm 30 made of stainless steel is 20 μm, and the thickness Tp of the piezoelectric layer 31 made of PZT. Was 10 μm, and the drive voltage applied to the individual electrode 32 was 20V. The combination of the value of the length L1 in the short direction (width direction) of the pressure chamber 14 in the region overlapping the pressure chamber 14 of the individual electrode 32 and the value of the length L2 in the region outside the pressure chamber 14 is mutually Four different analysis models (Model 1 to Model 4) were analyzed. The analysis results are shown in Table 1.

表１より、個別電極３２が圧力室１４の外側の領域まで延びているモデル（モデル２、モデル４）では、個別電極３２の圧力室１４と重なる領域における長さＬ１が同じで、個別電極３２が圧力室１４の内側にしか形成されていない、Ｌ２＝０のモデル（モデル１、モデル３）と比較して、それぞれ、振動板３０の最大変位量（圧力室１４の面積中心に対向する位置の変位量）が１．３倍程度になっており、個別電極３２が圧力室１４の外側の領域まで形成されている場合には、そうでない場合と比較して、振動板３０の変形量がより大きくなることがわかる。なお、表１から分かるように、圧力室１４の外側の領域における長さＬ２＝３０μｍは、圧電層Ｔｐと振動層Ｔｖの厚さの和に等しい。

According to Table 1, in the models (model 2 and model 4) in which the individual electrode 32 extends to the area outside the pressure chamber 14, the length L1 in the area overlapping the pressure chamber 14 of the individual electrode 32 is the same, and the individual electrode 32 Are formed only inside the pressure chamber 14, compared with the models of L 2 = 0 (model 1 and model 3), respectively, the maximum displacement amount of the diaphragm 30 (position facing the center of the area of the pressure chamber 14) The amount of deformation of the diaphragm 30 is smaller than that in the case where the individual electrode 32 is formed up to the region outside the pressure chamber 14. It turns out that it becomes larger. As can be seen from Table 1, the length L2 = 30 μm in the region outside the pressure chamber 14 is equal to the sum of the thicknesses of the piezoelectric layer Tp and the vibration layer Tv.

Next, modified embodiments in which various modifications are made to the embodiment will be described. However, components having the same configuration as in the above embodiment are given the same reference numerals and description thereof is omitted as appropriate.
<First modification>
The diaphragm may be made of an insulating material (for example, a silicon material whose surface is oxidized, a ceramic material such as PZT, alumina, zirconia, or a synthetic resin material such as polyimide). However, in this case, as shown in FIG. 8, in the piezoelectric actuator 3A, on the surface of the insulating diaphragm 30A opposite to the pressure chamber 14, the individual electrode 32 is opposed to the piezoelectric layer 31 therebetween. A common electrode 34 for applying an electric field is required.
<Second modification>
In the above-described embodiment, the individual electrode is formed on the opposite side of the piezoelectric layer 31 from the diaphragm 30, but the individual electrode is disposed on the diaphragm 30 side of the piezoelectric layer 31, and the piezoelectric layer 31 is opposite to the diaphragm 30. A common electrode may be disposed on the substrate. However, when the diaphragm is made of a metal material, as shown in FIG. 9, in the piezoelectric actuator 3B, in order to insulate the plurality of individual electrodes 32B, the upper surface (pressure chamber 14) of the metal diaphragm 30 is insulated. The surface of the diaphragm 30 on which the individual electrode 32B is disposed needs to have insulation properties, such as by forming the insulating material layer 40 on the surface opposite to the surface. The insulating material layer 40 is made of a ceramic material such as alumina or zirconia, and can be formed by an AD method, a sputtering method, a CVD method, a sol-gel method, or the like.
<Third modification>
When the diaphragm is made of an insulating material such as a silicon material, a ceramic material, or a synthetic resin material, as shown in FIG. 10, in the piezoelectric actuator 3C, the individual electrode 32C is disposed directly on the upper surface of the diaphragm 30C. The plurality of individual electrodes 32C are insulated from each other by the diaphragm 30C having insulating properties.
<Fourth modification>
As shown in FIG. 11, in the piezoelectric actuator 3 </ b> D, the piezoelectric layer 31 </ b> D is not formed in a region overlapping the central portion of the pressure chamber 14 in a plan view, and is formed in a region other than the region overlapping the central portion. It may be. In this case, since the driven region that overlaps the central portion of the pressure chamber 14 is configured only by the diaphragm 30, the rigidity of the driven region is reduced, compared with the piezoelectric actuator 3 of the above-described embodiment (see FIG. 5). The amount of deformation of the diaphragm 30 when the piezoelectric layer 31 in the drive region contracts increases. Table 2 shows the structural analysis results by FEM in this modified embodiment 1. In this structural analysis, the analysis conditions such as the length B of the pressure chamber 14 in the short direction, the thickness Tv of the vibration plate 30 and the thickness Tp of the piezoelectric layer 31D, and the driving voltage are the structures by the FEM in the above embodiment. Same as analysis.

表２より、個別電極３２が圧力室１４の外側の領域まで延びているモデル（モデル６、モデル８）では、個別電極３２の圧力室１４と重なる領域における長さＬ１が同じで、個別電極３２が圧力室１４の内側の領域にしか形成されていない、Ｌ２＝０のモデル（モデル５、モデル７）と比較して、振動板３０の最大変位量が１．２５倍程度となっており、この変更形態１においても、個別電極３２が圧力室１４の外側の領域まで形成されている場合には、そうでない場合と比較して、振動板３０の変形量がより大きくなることがわかる。
＜第５変更形態＞
前記実施形態のように、個別電極３２が圧力室１４の中心部を取り囲む環状に形成されている必要は必ずしもなく、例えば、図１２に示すように、個別電極３２Ｅが圧力室１４の中心部を完全に取り囲んでいなくてもよい。さらには、少なくとも、圧力室１４の中心部を挟んで両側に位置する縁部に重なる領域に個別電極が形成されていればよい。図１２に示した例では、圧力室１４の長手方向と交差する（直交する）方向においてのみ圧力室１４の外側に個別電極３２が延在している。特に、圧力室１４の長手方向と交差する（直交する）方向において振動板の変形量が大きくなるために、この方向において個別電極３２を圧力室１４の外側まで延在させることが振動板の変形量を増大させる上で有効である。それゆえ、この変形形態のように、圧力室１４の長手方向と交差する（直交する）方向においてのみ個別電極３２を圧力室１４の外側まで延在させてもよい。なお、個別電極３２の延在部は、圧力室の長手方向に平行な圧力室の中心軸に対して対称に形成されていると見ることもできる。

According to Table 2, in the models (model 6 and model 8) in which the individual electrode 32 extends to the region outside the pressure chamber 14, the length L1 in the region overlapping the pressure chamber 14 of the individual electrode 32 is the same. Is formed only in the inner region of the pressure chamber 14, and the maximum displacement amount of the diaphragm 30 is about 1.25 times as compared with the L2 = 0 model (model 5, model 7). Also in this modified embodiment 1, it can be seen that when the individual electrode 32 is formed up to the region outside the pressure chamber 14, the amount of deformation of the diaphragm 30 is larger than when the individual electrode 32 is not formed.
<Fifth modification>
The individual electrode 32 is not necessarily formed in an annular shape surrounding the central portion of the pressure chamber 14 as in the above-described embodiment. For example, as shown in FIG. It does not have to be completely surrounded. Furthermore, the individual electrode should just be formed in the area | region which overlaps the edge located on both sides across the center part of the pressure chamber 14 at least. In the example shown in FIG. 12, the individual electrode 32 extends outside the pressure chamber 14 only in the direction intersecting (orthogonal to) the longitudinal direction of the pressure chamber 14. In particular, since the amount of deformation of the diaphragm increases in a direction intersecting (orthogonal to) the longitudinal direction of the pressure chamber 14, extending the individual electrode 32 to the outside of the pressure chamber 14 in this direction causes deformation of the diaphragm. It is effective in increasing the amount. Therefore, as in this modification, the individual electrode 32 may extend to the outside of the pressure chamber 14 only in a direction intersecting (orthogonal to) the longitudinal direction of the pressure chamber 14. In addition, it can be considered that the extending part of the individual electrode 32 is formed symmetrically with respect to the central axis of the pressure chamber parallel to the longitudinal direction of the pressure chamber.

  The shape of the pressure chamber is not limited to the substantially oval shape in the embodiment, and the pressure chamber may be formed in other shapes such as a circle, a diamond, and a rectangle. However, as shown in FIG. 12, when the pressure chamber 14 has a shape that is long in one direction, the length (width) of the individual electrode in the short direction (vertical direction in FIG. 12) vibrates as described above. This greatly affects the deformation amount of the plate 30. Therefore, it is preferable that the individual electrode is formed at least in a region overlapping with two edges extending in the longitudinal direction of the pressure chamber 14 (left-right direction in FIG. 12). This will be specifically described with reference to FIGS.

  FIG. 13 shows an elliptical pressure chamber 14a as shown in FIG. 12, and the individual electrode extends outside the pressure chamber 14a in the direction perpendicular to the longitudinal direction of the pressure chamber 14a (the protruding portion). 32a. FIG. 14 shows a rhombic pressure chamber 14b, and the individual electrodes have four extended sides (protruding portions) 32b extending outside the pressure chamber 14b in the direction intersecting the longitudinal direction of the pressure chamber 14b. Have on. FIG. 15 shows a boomerang-shaped pressure chamber 14c, and each individual electrode has an extended portion (protruding portion) 32c extending outside the pressure chamber 14c in a direction intersecting the longitudinal direction of the pressure chamber 14c. On the long and short sides. FIG. 16 shows a circular pressure chamber 14d, and the individual electrode has a pair of extending portions (protruding portions) 32d that extend outside the pressure chamber 14d in the diameter direction of the pressure chamber 14d. That is, when the pressure chamber does not have a longitudinal direction, the individual electrode may have a pair of extending portions (extrusion portions) extending outward from the pressure chamber so as to face each other at least in one direction. That's fine.

  The above-described embodiment and its modification are examples in which the present invention is applied to an ink jet head that transports ink, but a liquid transport apparatus to which the present invention is applicable is not limited to an ink jet head. For example, a liquid transfer device that transfers a liquid such as a chemical solution or a biochemical solution inside a micro total analysis system (μTAS), a liquid transfer device that transfers a liquid such as a solvent or a chemical solution inside a microchemical system, etc. The present invention can also be applied to a liquid transfer device that transfers blood, for example, a medical device that transfers blood or a specific component thereof.

1 is a schematic perspective 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 a figure which shows the deformation | transformation state of a diaphragm in the piezoelectric actuator of this embodiment. It is a figure which shows the deformation | transformation state of the diaphragm in the conventional piezoelectric actuator. FIG. 6 is a cross-sectional view corresponding to FIG. FIG. 6 is a cross-sectional view corresponding to FIG. It is sectional drawing equivalent to FIG. 5 of the modification 3. FIG. It is sectional drawing equivalent to FIG. 5 of the modification 4. It is a partially expanded plan view equivalent to FIG. It is the schematic which shows the extension part of the elliptical pressure chamber and individual electrode to which this invention is applied. It is the schematic which shows the extended part of the rhombus pressure chamber and individual electrode to which this invention is applied. It is the schematic which shows the extension part of the boomerang type pressure chamber and individual electrode to which this invention is applied. It is the schematic which shows the extended part of the circular pressure chamber and individual electrode to which this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet head 2 Flow path unit 3, 3A, 3B, 3C, 3D Piezoelectric actuator 10a Girder part 14 Pressure chamber 20 Nozzle 30, 30A, 30C Diaphragm 31, 31D Piezoelectric layer 32, 32B, 32C, 32E Individual electrode 34 Common electrode

Claims (16)

A liquid transfer device comprising: a flow path unit having a plurality of pressure chambers arranged along a plane; and a piezoelectric actuator that changes the volume of the pressure chamber to apply pressure to the liquid in the pressure chamber,
The piezoelectric actuator is
A diaphragm covering the pressure chamber;
A piezoelectric layer disposed on the opposite side of the diaphragm from the pressure chamber;
A plurality of individual electrodes disposed in regions overlapping each of edges of the plurality of pressure chambers other than the central portion when viewed from a direction perpendicular to the plane of one surface of the piezoelectric layer,
A common electrode disposed on the other surface of the piezoelectric layer,
The liquid transfer apparatus according to claim 1, wherein the individual electrode extends to a region outside the pressure chamber when viewed from a direction orthogonal to the plane. The flow path unit includes a plurality of pressure chambers opened to the diaphragm side on a surface joined to the diaphragm, and a girder portion that is positioned between the plurality of pressure chambers and supports the diaphragm. Have
2. The liquid transfer device according to claim 1, wherein a portion of the individual electrode extending to a region outside the pressure chamber overlaps the beam portion when viewed from a direction orthogonal to the plane.   The individual electrode extends to a substantially intermediate position between a pressure chamber corresponding to the individual electrode and another pressure chamber adjacent to the pressure chamber when viewed from a direction orthogonal to the plane. The liquid transfer device according to claim 1 or 2.   The liquid transfer device according to claim 1, wherein the diaphragm is made of a metal material and also serves as the common electrode. The diaphragm has an insulating property at least on a surface opposite to the pressure chamber,
The liquid transfer device according to claim 1, wherein the common electrode is formed on a surface of the diaphragm opposite to the pressure chamber. The diaphragm has an insulating property at least on a surface opposite to the pressure chamber,
The liquid transfer device according to claim 1, wherein the plurality of individual electrodes are formed on a surface of the diaphragm opposite to the pressure chamber.   The liquid transfer device according to claim 1, wherein the piezoelectric layer is formed so as to entirely cover the plurality of pressure chambers.   The liquid according to claim 1, wherein the piezoelectric layer is formed in a region other than a region overlapping the central portion of the pressure chamber when viewed from a direction orthogonal to the plane. Transfer device.   The liquid transfer device according to claim 1, wherein a length of the individual electrode in a region outside the pressure chamber is equal to or greater than a thickness of the piezoelectric layer.   2. The liquid transfer according to claim 1, wherein the individual electrode extends to a region outside the pressure chamber in a direction intersecting a longitudinal direction of the pressure chamber when viewed from a direction orthogonal to the plane. apparatus.   The portion of the individual electrode that extends to a region outside the pressure chamber is formed symmetrically with respect to the central axis of the pressure chamber parallel to the longitudinal direction of the pressure chamber. Liquid transfer device.   The pressure chamber is an ellipse, and the individual electrode extends to a region outside the pressure chamber in a minor axis direction of the ellipse when viewed from a direction orthogonal to the plane. 2. The liquid transfer device according to 1.   The pressure chamber is elliptical, and the individual electrode extends to a region outside the pressure chamber in both the minor axis direction and the major axis direction of the ellipse when viewed from a direction orthogonal to the plane. The liquid transfer device according to claim 1.   2. The liquid transfer device according to claim 1, wherein a portion of the individual electrode extending to a region outside the pressure chamber is formed over the entire circumference of the pressure chamber.   The liquid transfer device according to claim 1, wherein the liquid transfer device is an ink jet printer. When the piezoelectric actuator receives a voltage applied to the individual electrode, the piezoelectric actuator is displaced in a convex shape in a direction that temporarily increases the volume of the corresponding pressure chamber, draws liquid into the pressure chamber, and then applies the voltage to the individual electrode. The liquid transfer device according to claim 1, wherein the volume of the pressure chamber is restored by releasing the pressure, and at that time, the liquid is transferred from the pressure chamber to the outside.

Images