JP2008010838A - Laminated piezoelectric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the flexibility of the connection between individual surface electrodes and interconnection electrodes, contrive the miniaturization of the contour, and reduce warp deformation. <P>SOLUTION: Between a plurality of ceramic sheets 33 and 34 between individual surface electrodes 38A to 38E and individual internal electrodes 36A to 36E, there are arranged a plurality of interconnection electrodes 42A to 42F connecting the individual surface electrodes 38A to 38E with the individual internal electrodes 36A to 36E. A plurality of individual surface electrodes 38A to 38E and a plurality of interconnection electrodes 42A to 42F that are arranged in a row are arranged oppositely and in parallel in the laminated direction. In the direction orthogonal to the arrangement directions of a plurality of individual surface electrodes 38A to 38E and a plurality of interconnection electrodes 42A to 42F, they are connected by an internal conduction electrode 52A that is filled in a through hole at mutually different positions. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multilayer piezoelectric actuator.

  Conventionally, as an inkjet head, a plurality of pressure chambers arranged in a plurality of rows at a constant arrangement pitch are provided in a cavity unit in which a plurality of sheets are stacked, and an active portion (energy generating means) corresponding to each pressure chamber is provided. The piezoelectric actuator which has is joined with the cavity unit. And as a piezoelectric actuator, between a plurality of laminated ceramic sheets, a plurality of individual internal electrodes and a common internal electrode common to the plurality of individual internal electrodes are disposed opposite each other with at least one ceramic sheet interposed therebetween, An individual surface electrode connected to the individual internal electrode and a common surface electrode connected to the common internal electrode are formed on one surface of the laminated ceramic sheets, and the individual surface electrode and the common surface An electrode is known in which a connection terminal of a signal line of a flexible flat cable that inputs a drive signal is connected to the electrode (see, for example, Patent Document 1 and Patent Document 2).

  In the device described in Patent Document 1, a plurality of relay electrodes for connecting the individual surface electrode and the individual internal electrode are further arranged between the ceramic sheets between the individual surface electrode and the individual internal electrode. Has been. In such a case, in order to connect the individual internal electrode, the relay electrode, and the individual surface electrode, and the common internal electrode, the relay electrode, and the common surface electrode, the through hole that penetrates the ceramic sheet is filled with a conductive material. Is done.

  Further, in Patent Document 2, it is possible to prevent the through-holes from being warped and deformed based on the through-holes in the firing process by arranging the through-holes so as not to be aligned in a line parallel to the arrangement direction of the individual internal electrodes. It is disclosed.

In addition, in Patent Document 1 and Patent Document 2, a large number of signal lines connected to a large number of individual surface electrodes must be arranged in a planar shape on a flexible flat cable, and interfere with the individual surface electrodes. In order to provide a gap between the signal lines without any gap, it is necessary to arrange the individual surface electrodes so that a gap exists between the individual surface electrodes as much as possible. Therefore, in the device described in Patent Document 1, the individual surface electrodes in adjacent rows are arranged in a staggered pattern shifted by a half pitch of the arrangement pitch, and in each individual surface electrode in one row, The positions connected to the lines are alternately set at both ends orthogonal to the column direction of the individual surface electrodes.
JP 2006-15539 A JP 2002-254634 A

  In the device described in Patent Document 1, the end portion of the individual internal electrode that extends outside the pressure chamber, the relay electrode, and the individual surface electrode are arranged so as to coincide with the stacking direction, and a through hole that connects them is provided for each ceramic sheet. However, the end portions of the individual internal electrodes that extend outside the pressure chambers and the relay electrodes have only the minimum necessary area for filling the through holes with the conductive material. It is. Therefore, the amount of deviation of the through holes is small, the strength of the ceramic sheet is insufficient at that location, and the firing process is similar to that in which the through holes are aligned in a row as described in the prior art of Patent Document 2. In FIG. 2, the entire actuator may be warped and deformed from the through hole as a base point. When the number of the individual internal electrodes is two rows as in the configuration of Patent Document 2, the through holes can be arranged outside the row without being aligned in one row, but the size of the actuator is increased. In the case where there are a plurality of pressure chambers as in Patent Document 1, the size is further increased. In response to the recent increase in recording speed and resolution, if the number of nozzles is increased, ceramics must be made larger, shrinkage due to firing becomes larger, and manufacturing can be performed with high accuracy. It becomes difficult.

  Therefore, the inventor uses the relay electrodes described above only for the purpose of connecting the individual surface electrodes and the individual internal electrodes, and is not restricted by the shape of the electrodes. If the individual surface electrodes are arranged opposite and parallel to each other in the stacking direction, the individual surface electrodes substantially overlap the relay electrodes in plan view. Regardless of this, the inventors have conceived that the individual surface electrodes can be connected to the relay electrodes using the through holes, and the present invention has been made.

  An object of the present invention is to provide a multilayer piezoelectric actuator that increases the degree of freedom of connection between an individual surface electrode and a relay electrode, reduces the size of the outer shape, and is less likely to warp and deform.

  According to the first aspect of the present invention, a plurality of individual internal electrodes and a common internal electrode common to the plurality of individual internal electrodes are opposed to each other with at least one ceramic sheet interposed between the plurality of laminated ceramic sheets. The individual surface electrode connected to the individual internal electrode and the common surface electrode connected to the common internal electrode are formed on one surface of the laminated ceramic sheets. A laminated piezoelectric actuator in which a connection terminal of a signal line for inputting a drive signal is connected to a surface electrode, wherein the individual surface electrode is interposed between a plurality of ceramic sheets between the individual surface electrode and the individual internal electrode. And a plurality of relay electrodes for connecting the individual internal electrodes and the plurality of individual surface electrodes and the plurality of relay electrodes in the stacking direction. Oppositely vital parallel array have, characterized in that it is connected with each other at different positions in the direction orthogonal to the array direction of the adjacent plurality of individual surface electrodes and the plurality of relay electrodes.

  According to the invention of claim 1, a plurality of relay electrodes for connecting the individual surface electrodes and the individual internal electrodes are arranged between the plurality of ceramic sheets between the individual surface electrodes and the individual internal electrodes, The individual surface electrodes and the plurality of relay electrodes are arranged opposite to and parallel to each other in the stacking direction, and mutually in a direction orthogonal to the arrangement direction of the plurality of adjacent individual surface electrodes and the plurality of relay electrodes. Since the connection positions of the relay electrode and the individual surface electrode can be dispersed regardless of the connection position of the individual internal electrode and the relay electrode, the strength of the ceramic sheet is insufficient. Or can be prevented from being deformed. In response to the recent increase in recording speed and resolution, even if the number of nozzles increases, it is necessary to ensure a wide area for connection outside the array of individual internal electrodes as in the past. Therefore, the piezoelectric actuator can be easily reduced in size.

  3. The multilayer piezoelectric actuator according to claim 1, wherein the individual surface electrode is connected to a connection terminal of the signal line at a position corresponding to a portion connected to the relay electrode. It can be.

  According to the invention of claim 2, since the individual surface electrode is connected to the connection terminal of the signal line at a position corresponding to the part connected to the relay electrode, the part connected to the relay electrode and the connection terminal of the signal line Are directly connected, and the reliability of the electrical connection is increased. In addition, since the individual surface electrodes and the connection terminals are connected to each other at different positions in the direction orthogonal to the arrangement direction of the individual surface electrodes, a large gap is secured between the connection portions, and a signal line is provided in the gap. It becomes possible to arrange more, and it is possible to increase the number of individual surface electrodes or increase the density.

  According to a third aspect of the present invention, in the stacked piezoelectric actuator according to the second aspect, the individual surface electrode and the relay electrode have a length in a direction orthogonal to the arrangement direction thereof, It can be set as the structure which has the joining electrode connected with the connection terminal of the said signal line in the position corresponding to the part connected with the said electrode for relay.

  According to the third aspect of the invention, since the junction electrode connected to the connection terminal of the signal line is provided at a position corresponding to the portion connected to the relay electrode on the individual surface electrode, the signal line is connected to the junction electrode. By connecting the terminals, the connection terminal of the signal line can be connected to the relay electrode with high reliability and easily.

  According to a fourth aspect of the present invention, in the multilayer piezoelectric actuator according to the third aspect, the joining electrodes may be arranged in a staggered manner in a direction orthogonal to the arrangement direction.

  According to the invention of claim 4, since the joining electrodes are arranged in a staggered manner in a direction orthogonal to the arrangement direction, there are gaps between the joining electrodes, and the signal lines connected to the joining electrodes The connection terminals can be spaced apart.

  According to a fifth aspect of the present invention, in the multilayer piezoelectric actuator according to the third aspect, the plurality of relay electrodes are opposed to the common internal electrode located on the opposite side to the individual surface electrode with the same area. It can be set as the structure which has.

  According to the invention of claim 5, the relay electrode has a length in a direction orthogonal to the arrangement direction thereof, and is opposed to the common internal electrode located on the side opposite to the individual surface electrode with the same area. Therefore, the capacitance generated between the relay electrode and the common internal electrode is uniform in the plurality of relay electrodes, and the characteristics as the piezoelectric actuator for each individual surface electrode can be made uniform.

  6. The multi-layer piezoelectric actuator according to claim 1, wherein the relay electrode has a length in a direction orthogonal to the arrangement direction, and the individual surface electrodes are adjacent individual surface electrodes. Can be configured such that the positions are different from each other in a direction orthogonal to the arrangement direction and are opposed to different positions in the length direction of the relay electrode.

  In this way, the individual surface electrode is located at a position different from the adjacent individual surface electrode in a direction orthogonal to the arrangement direction, and opposed to a different position in the length direction of the relay electrode. Therefore, each individual surface electrode is arranged so that a gap exists between the individual surface electrodes.

  7. The laminated piezoelectric actuator according to claim 6, wherein the junction is connected to the connection terminal of the signal line at a position corresponding to a portion connected to the relay electrode on the individual surface electrode. It can be set as the structure which has an electrode.

  If it does in this way, since it has the joining electrode connected with the connection terminal of a signal line in the position corresponding to the portion connected with the relay electrode on the individual surface electrode, the connection terminal of the signal line is connected to the joining electrode. As a result, the connection terminal of the signal line can be connected to the portion connected to the relay electrode with high reliability and easily.

  As described in claim 8, in the laminated piezoelectric actuator according to claim 7, the joining electrodes are arranged in a staggered manner in a direction orthogonal to the arrangement direction, and the individual surface electrodes are arranged in the arrangement direction. In the above, the electrode may be longer and wider than the bonding electrode.

  In this way, each individual surface electrode is longer and wider than the bonding electrode in the arrangement direction, and the individual surface electrode is formed with a large area around the bonding electrode. Therefore, when connecting the connection terminal of the signal line to the bonding electrode using a conductive brazing material such as solder, even if the brazing material flows, it is stopped on the individual surface electrode and flows to the adjacent bonding electrode. A short circuit is avoided.

  In that case, as described in claim 9, in the stacked piezoelectric actuator according to claim 8, the length in the arrangement direction of the individual surface electrodes is longer than the interval in the arrangement direction of the individual surface electrodes. It is desirable.

  In this way, the length of the individual surface electrodes in the arrangement direction is ensured as long as possible, and the allowable amount of positional deviation of the bonding electrode with respect to the individual surface electrodes in the arrangement direction can be increased.

  In addition, as described in claim 10, in the stacked piezoelectric actuator according to claim 8, the length of the individual surface electrodes in the arrangement direction is adjacent individual surface electrodes in a direction orthogonal to the arrangement direction. In addition, it is desirable that the length has a portion facing each other in a direction orthogonal to the arrangement direction.

  In this way, it is possible to increase the allowable amount of positional deviation of the bonding electrode with respect to the individual surface electrode in the arrangement direction.

  The laminated piezoelectric actuator according to claim 1, wherein the plurality of individual internal electrodes, the common internal electrode, the plurality of relay electrodes, and the plurality of individual surface electrodes And ceramic sheets each having a common surface electrode formed thereon are laminated, and the individual internal electrodes and the relay electrodes in the laminating direction, and the relay electrodes and the individual surface electrodes are between them, respectively. It can be set as the structure connected by the electrically-conductive material with which the through hole which penetrated this ceramic sheet was filled.

  According to the eleventh aspect of the present invention, the individual internal electrodes and the relay electrodes in the stacking direction, and the relay electrodes and the individual surface electrodes penetrate through the ceramic sheet therebetween, respectively. The ceramic material is easily connected by laminating ceramic sheets with the conductive material filled therein. In addition, as described above, the connection position between the relay electrode and the individual surface electrode can be freely set at different positions in the direction orthogonal to the arrangement direction, so that the interval between the through holes can be increased. The deformation of the ceramic sheet accompanying firing can be suppressed.

  The laminated ceramic actuator according to claim 11, wherein the plurality of laminated ceramics are arranged in a cavity unit having a plurality of pressure chambers corresponding to a plurality of nozzles for discharging droplets. The other surface of the sheet is joined, and the plurality of individual internal electrodes are arranged to face the plurality of pressure chambers, and a voltage is applied between the individual internal electrode and the common internal electrode. The ceramic sheet between the individual internal electrode and the common internal electrode can be displaced to give a discharge pressure to the ink in the pressure chamber.

  According to the twelfth aspect of the present invention, the individual surface electrode using the relay electrode and the individual inner part are joined to the cavity unit having a plurality of rows of pressure chambers corresponding to the plurality of nozzle rows for discharging droplets. The degree of freedom of connection with the electrodes can be increased, and even if the number of nozzles is increased in response to the demand for increased recording speed and resolution, it is connected outside the row of individual internal electrodes as in the past. Since it is not necessary to secure a large area for the cavity, the cavity unit can be easily downsized together with the piezoelectric actuator.

  The multilayer piezoelectric actuator according to claim 12, wherein the cavity unit includes a plurality of rows of the pressure chambers, and the individual internal electrodes correspond to the plurality of rows of the pressure chambers. There are a plurality of rows, the common internal electrodes are opposed to the plurality of rows of individual internal electrodes in the stacking direction and extend in the arrangement direction, and the relay electrodes and the individual surface electrodes correspond to the rows of individual internal electrodes. A plurality of rows, and the common surface electrode is formed in the same plane as the individual surface electrodes, and is formed long in the arrangement direction of the plurality of rows along an end portion orthogonal to the arrangement direction of the individual surface electrodes. be able to.

  According to the invention of claim 13, the connection between the common surface electrode and the common internal electrode can be ensured, and the degree of freedom of connection between the individual surface electrode and the individual internal electrode using the relay electrode can be increased, In response to the demand for increased speed and increased resolution, the cavity unit can be easily downsized together with the piezoelectric actuator even if the number of nozzles is increased.

  Since it comprised as mentioned above, the some relay electrode which connects an individual surface electrode and an individual internal electrode is arrange | positioned between the several ceramic sheets between an individual surface electrode and an individual internal electrode, The said some The individual surface electrodes and the plurality of relay electrodes face each other in the stacking direction and are arranged in parallel, and are mutually in a direction orthogonal to the arrangement direction of the adjacent individual surface electrodes and the plurality of relay electrodes. Since the connection is made at different positions, the connection position between the individual surface electrode and the individual internal electrode using the relay electrode can be dispersed regardless of the connection position between the individual internal electrode and the relay electrode. Insufficient strength or deformation can be suppressed. Also, in response to the recent increase in recording speed and resolution, the number of nozzles is increased, and even if the number of the individual surface electrodes is increased, the number of the individual surface electrodes is increased as in the conventional case. Since it is not necessary to secure a wide area for connection, a piezoelectric actuator can be easily realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The ink jet head using the multilayer piezoelectric actuator according to the present invention is for color recording, and although not specifically shown, a direction X (main scanning direction) orthogonal to the recording paper transport direction Y (sub scanning direction). It is mounted on a carriage that moves back and forth. The ink-jet head has four colors, for example, from an ink cartridge mounted on the carriage or from an ink tank installed in the printer body via an ink supply pipe and a damper tank mounted on the carriage. Color ink (cyan, magenta, yellow, black) is supplied.

  FIG. 1 is a perspective view showing a state in which a flexible flat cable is joined to the upper surface of an ink jet head to which the present invention is applied, FIG. 2 is a perspective view of a cavity unit, etc., and FIG. 3 is a partially enlarged perspective view of a main part of the cavity unit. is there.

As shown in FIG. 1, an inkjet head 1 includes a cavity unit 2 having a plurality of pressure chamber rows corresponding to a plurality of nozzle rows for discharging droplets, and a plate-type piezoelectric actuator 3 bonded to the upper side thereof. The flexible flat cable 4 for inputting a drive signal is joined to the upper surface side of the piezoelectric actuator 3.
(Structure of cavity unit 2)
The cavity unit 2 is a laminated structure formed by stacking and bonding eight flat plates, and as shown in FIG. 2, in order from the lower side, a nozzle plate 11, a cover plate 12, a damper plate 13, and a lower side. And the upper manifold plates 14 and 15, the lower and upper spacer plates 16 and 17, and the base plate 18 in which the pressure chambers 18a are formed.
Is provided. Except for the nozzle plate 11 made of a synthetic resin material, each of the plates 12 to 18 is formed of a 42% nickel alloy steel plate and has a thickness of about 50 μm to 150 μm.

  The nozzle plate 11 constituting the lower surface of the cavity unit 2 has five nozzle rows N (shown in FIG. 2) in which a large number of ink ejection nozzles 11a (hole diameters of about 25 μm) are arranged in a row along the Y direction. Only three rows are shown).

  The lower and upper manifold plates 14 and 15 are formed with through holes elongated in the Y direction so as to penetrate in the thickness direction corresponding to the nozzle rows N, and are sandwiched between the lower spacer plate 16 and the damper plate 13. As a result, the through holes become five manifold chambers 19a, 19b, 19c, 19d, and 19e (common ink chambers). The manifold chambers 19a, 19b, and 19c are for cyan ink (C), yellow ink (Y), and magenta ink (M), respectively, and the manifold chambers 19d and 19e are for black ink (BK). .

  In FIG. 2, four ink supply holes 21a, 21b, 21c, and 21d are provided side by side at one end of the base plate 18 in the Y direction. The ink supply holes 21a, 21b, and 21c are provided in the manifold chambers 19a, 19b, and 19c. The ink supply hole 21d supplies ink to the two manifold chambers 19d and 19e. As shown in FIG. 2, ink supply passage portions 22a, 22b, 22c and 22d whose upstream ends communicate with the ink supply holes 21a to 21d are formed in one end portions of the upper spacer plate 17 and the lower spacer plate 16. Has been. The downstream ends of the ink supply passage portions 22a, 22b, and 22c communicate with one end portions of the corresponding manifold chambers 19a, 19b, and 19c, and the downstream end of the ink supply passage portion 22d communicates with one end portions of the manifold chambers 19d and 19e, respectively. ing.

  Further, on the lower surface side of the damper plate 13, six concave grooves that open downward corresponding to the shapes of the manifold chambers 19 a to 19 e are formed in plan view, and the opening of the concave grooves is closed by the cover plate 12. As a result, the damper chamber 23 is hermetically sealed. With this configuration, a pressure wave is propagated to the pressure chamber 18 a by driving the piezoelectric actuator 3, and a retreat component of the pressure wave toward the manifold chambers 19 a to 19 e is converted into a portion where the wall thickness of each damper chamber 23 is thin. Therefore, it is possible to prevent so-called crosstalk from occurring.

  As shown in FIG. 3, the lower spacer plate 16 is formed with a throttle portion 24 corresponding to each nozzle 11 a of the nozzle row N. The narrowed portion 24 has a narrow groove shape extending in the X direction. One end of each throttle portion 24 communicates with a corresponding one of the manifold chambers 19 a to 19 e of the upper manifold plate 15, and the other end of each throttle portion 24 communicates with a communication hole 25 penetrating vertically in the upper spacer plate 17. Communicate with.

  The cover plate 12, the damper plate 13, the lower and upper manifolds 14 and 15, and the lower and upper spacer plates 16 and 17 have communication holes 25 communicating with the nozzles 11 a for each nozzle row N, respectively. Further, the damper chamber 23 is formed so as to penetrate vertically at a position that does not overlap with the damper chamber 23.

  The base plate 18 is formed with a pressure chamber 18a extending in the X direction and penetrating in the thickness direction for each nozzle row N corresponding to the number of the nozzles 11a. One end in the longitudinal direction of each pressure chamber 18a communicates with the communication hole 25 of the upper spacer plate 17, and the other end in the longitudinal direction of each pressure chamber 18a communicates with each plate 12-17. It communicates with the passage 26. The pressure chambers 18a in each row are arranged at a constant arrangement pitch P (see FIG. 3) in the Y direction via the partition walls 27. The respective pressure chambers 18a are shifted by a half pitch P / 2 in the Y direction with respect to the pressure chambers 18a in the adjacent row, and are arranged in a so-called zigzag pattern.

As a result, the ink that has flowed into the manifold chambers 19a to 19e from the ink supply holes 21a to 21d is distributed into the pressure chambers 18a through the throttle portions 24 and the communication holes 25, and then into the pressure chambers 18a. Then, the nozzle 11a corresponding to each pressure chamber 18a is reached through the communication path 26 and discharged as droplets.
(Structure of piezoelectric actuator 3)
As shown in FIG. 4, the piezoelectric actuator 3 includes a first ceramic sheet 31 on the surface of which a plurality of individual internal electrodes 36A, 36B, 36C, 36D, and 36E are formed, and a pattern of a common internal electrode 37 on the surface. A conductive dummy ceramic sheet 33 is stacked on the upper side of the portion where three second ceramic sheets 32 are alternately stacked, and the individual surface electrodes 38A, 38B, 38C, 38D, While the top ceramic sheet 34 having the surface 38E and the common surface electrodes 39A and 39B formed thereon is laminated, the entire upper surface is formed below the laminated portion of the first and second ceramic sheets 31 and 32. The common surface electrode 71 is formed and the third ceramic sheet 35 which is the lowest layer is laminated. The dummy ceramic sheet 33 and the top ceramic sheet 34 suppress the displacement to the opposite side to the pressure chamber 18a when the constraining layer, that is, the active portion of the first and second ceramic sheets 31 and 32 is displaced as will be described later. A large amount of displacement is directed toward the chamber 18a.

Each of the sheets 31 to 35 is prepared by preparing a mixed solution of ceramic powder, binder, and solvent of lead zirconate titanate (PZT (PbTiO3 / PbZrO3)) having ferroelectricity, and spreading the sheet to dry it. To form a green sheet. On these green sheets, a conductive material (a silver-palladium conductive paste) to be the above-described electrodes is formed by screen printing or the like. These green sheets are laminated and baked to be integrated. Thereafter, a high voltage for polarization treatment is applied between the individual electrode and the common electrode as is well known, and the ceramic sheet sandwiched between the two electrodes is subjected to polarization treatment, so-called piezoelectric characteristics (by applying a drive voltage). (Displacement property). Each ceramic sheet 31 to 35 has a thickness of about 30 μm. The conductive dummy ceramic sheet 33, the top ceramic sheet 34, and the third ceramic sheet 35 may be formed of other materials that do not exhibit piezoelectric characteristics, and may have electrical insulation.
-First ceramic sheet 31-
As shown in FIG. 5, five rows of individual internal electrodes 36A to 36E are arranged on the surface of the first ceramic sheet 31 corresponding to the pressure chambers 18a along the surface. The individual internal electrodes 36A to 36E have linear straight portions 36Aa to 36Ea that are substantially the same length as the pressure chambers 18a, overlap in plan view, and have a slightly narrower width than the pressure chambers 18a. In addition, conductive portions 36Ac to 36Ec having a rectangular shape in a plan view located outside the pressure chamber 18a are connected to one end portions of the straight portions 36Aa to 36Ea via bent portions 36Ab to 36Eb in a plan view, respectively. .

  The individual internal electrodes 36Ca and 36Cb constituting the central row are alternately arranged at the end portions of the straight portions 36Caa and 36Cba corresponding to the outer end portions of the pressure chambers 18a via outwardly bent portions 36Cab and 36Cbb. The conducting portions 36Cac and 36Cbc are connected so as to extend in opposite directions.

The individual internal electrodes 36B and 36D constituting the rows located outside the individual internal electrodes 36Ca and 36Cb are bent portions extending outward at the end portions of the straight portions 36Ba and 36Da corresponding to the outer end portions of the pressure chamber 18a. Conductive portions 36Bc and 36Dc are connected via 36Bb and 36Db. The individual internal electrodes 36A, 36E constituting the rows located outside the individual internal electrodes 36B, 36D are bent portions extending outward at the end portions of the straight portions 36Aa, 36Ea corresponding to the inner end portions of the pressure chamber 18a. Conductive portions 36Ac and 36Ec are connected via 36Ab and 36Eb. Then, as shown in FIG. 5, the conducting portion 36Ac and the conducting portion 36Bc, and the conducting portion 36Dc and the conducting portion 36Ec are shifted by half the arrangement pitch P of the pressure chambers 18a in the arrangement direction, and the pressure chamber 18a. , 18a are arranged corresponding to the upper part of the extended position of the partition wall 27.

  The conductive portions 36Ac to 36Ec of the individual internal electrodes 36A to 36E are conductive electrodes 41A, 41B, 41C, 41D, 41E, 41F arranged in a row on the second ceramic sheet 32 adjacent in the vertical direction, or for conduction. At least a part of each of the relay electrodes 42A, 42B, 42C, 42D, 42E, and 42F arranged in a row on the dummy sheet 33 is arranged in plan view.

Further, the first ceramic sheet 31 is a portion partially overlapping with the common internal electrode 37 (37A to 37F) in the second ceramic sheet 32 in a plan view, and on the wide surface of the first ceramic sheet 31. A dummy common electrode 43 is formed on an outer peripheral portion along the short side and the long side.
-Second ceramic sheet 32-
On the surface of the second ceramic sheet 32, as shown in FIG. 6, a common internal electrode 37 is disposed in common for each pressure chamber 18a. The common internal electrode 37 includes five first strip portions 37A, 37B, 37C, 37D, and 37E that face the plurality of rows of individual internal electrodes 36A, 36B, and 36C and extend in the arrangement direction. , And second belt-like portions 37F and 37G for connecting those end portions at the sheet end portion.

  Further, between the first belt-like portions 37A to 37E, conductive electrodes 41A to 41F are arranged in a row corresponding to the conductive portions 36Ac to 36Ec of the individual internal electrodes 36A to 36E. The common internal electrode 37 is formed so as to surround the conduction electrodes 41A to 41F arranged in a row.

The conductive electrodes 41C and 41D located in the center have an arrangement pitch in the arrangement direction that is twice the arrangement pitch of the conductive electrodes 41A, 41B, 41E, and 41F arranged on both sides. The common electrodes 41C and 41D correspond to the rows of the individual internal electrodes 36Ca and 36Cb located at the center.
-Dummy ceramic sheet 33 for conduction-
Similar to the second ceramic sheet 32, the surface of the conductive dummy ceramic sheet 33 is opposite to and parallel to the individual internal electrodes 36A to 36E in the sheet stacking direction, as shown in FIG. ˜42F are arranged in rows.

  The relay electrodes 42C and 42D located in the center have an arrangement pitch in the arrangement direction that is twice the arrangement pitch of the relay electrodes 42A, 42B, 42E, and 42F arranged on both sides, and two rows of relay electrodes 42C and 42D correspond to the columns of the individual internal electrodes 36Ca and 36Cb located at the center. The relay electrodes 42C and 42D located in the center have a rectangular shape in plan view.

  Two rows of relay electrodes 42A, 42B, 42E, and 42F located on both sides are respectively connected to the end portions of the straight portions 42Aa, 42Ba, 42Ea, and 42Fa above the partition walls 27 between the pressure chambers 18a and 18a. 42Aa, 42Ba, 42Ea, 42Fa are wider than the conductive electrodes 41A, 41B, 41E, 41F and are connected to the conductive electrodes 41A, 41B, 41E, 41F through a through-hole 53A, which will be described later. Yes.

Furthermore, the common internal electrode 37 in the ceramic sheet 32 is long in the arrangement direction of a plurality of rows along a portion along the short side of the upper surface of the dummy ceramic sheet 33 for conduction, that is, an end portion orthogonal to the arrangement direction of the relay electrodes 42A to 42F. The relay electrodes 44A and 44B for the common internal electrodes are formed at positions overlapping each other in the plan view (band portions 37F and 37G) and a part of the dummy common electrode 43 in the piezoelectric ceramic sheet 31 in plan view.
-Top ceramic sheet 34-
On the surface of the top ceramic sheet 34, as shown in FIG. 8, a plurality of individual surface electrodes 38A, 38B, 38Ca, 38Cb, 38D, and 38E are arranged along the surface corresponding to the relay electrodes 42A to 42F. The common surface electrodes 39 </ b> A and 39 </ b> B are formed long in the arrangement direction of the plurality of rows along the end portion orthogonal to the arrangement direction of the individual surface electrodes 38 </ b> A to 38 </ b> E on the surface of the top ceramic sheet 34.

  Each of the individual surface electrodes 38Ca and 38Cb located in the center includes a first portion 38Caa and 38Cba extending in the X direction, and a second portion 38Cab and 38Cbb extending in the Y direction connected to the inner end of the first portion. Is a T-shape in plan view. The individual surface electrodes 38Ca and 38Cb are arranged in a staggered manner with a half-pitch shift from the individual surface electrodes in the other rows. Bonding electrodes 38Cac and 38Cbc (see hatched portions in FIG. 8) connected to connection terminals of the flexible flat cable 4 described later are formed on the end portions of the first portions 38Caa and 38Cba.

  The individual surface electrodes 38A, 38B, 38D, and 38E located outside are linearly arranged in plan view, and are arranged in a staggered manner so as to be shifted by a half pitch from the adjacent individual surface electrodes 38A, 38B, 38D, and 38E. Yes. The individual surface electrodes 38A, 38B, 38D, and 38E in each row are connected to connection terminals of the flexible flat cable 4 to be described later so as to be alternately positioned at both ends of the individual surface electrodes in the arrangement direction, that is, in a staggered manner. The joined electrodes 38Aa, 38Ba, 38Da, 38Ea (see hatched portions in FIG. 8) are formed.

  And each individual surface electrode 38A-38E is substantially parallel to each linear part 36Aa-36Ea in each individual internal electrode 36A-36E, Comprising: Between the pressure chambers 18a and 18a adjacent to each other located in parallel below each Is located above the partition wall 27 (see FIG. 3). Therefore, the individual internal electrodes 36A to 36E are arranged at the same pitch as the arrangement pitch P in the Y direction of the pressure chambers 18a, and the individual surface electrodes 38A to 38E are arranged at a half pitch with respect to the arrangement of the pressure chambers 18a. Become. This is because the pressing force when connecting the connection terminal of the flexible flat cable 4 to the individual surface electrodes 38A to 38E is received by the partition wall 27 so that the pressing force acts on the ceramic sheet above the pressure chamber 18a and is not destroyed. is there.

  The common surface electrodes 39A and 39B are formed long on the top ceramic sheet 34 along the short side thereof, and a plurality of bonding electrodes 39Aa connected to the connection terminals of the flexible flat cable 4 along the longitudinal direction on the surface. , 39Ba (see the hatched portion in FIG. 8).

  When the piezoelectric actuator is baked as described above, the surface electrode is also processed at a high temperature, and the solderability of the connecting terminal of the flexible flat cable 4 to the surface electrode is lowered, so that the silver on the surface electrode (silver-palladium system) Bonding electrodes 38Aa, 38Ba, 38Cac, 38Cbc, 38Da, 38Ea, 39Ab, 39Bb are attached to improve the bondability with the connection terminal of the flexible flat cable 4.

  A plurality of dummy surface electrodes 51 that are not involved in electrical conduction are regularly provided between the individual surface electrodes 38Ca and 38Cb. Dummy surface electrodes 51 that are not involved in electrical continuity are also provided in the portion between the individual surface electrodes 38B and 38Ca, the portion between the individual surface electrodes 38Cb and 38D, and the outer portion of the individual surface electrodes 38A and 38E. .

The dummy surface electrode 51 described above is arranged in a well-balanced manner in the portion where the surface electrode is provided so that the pressing force is not uniformly applied and the bonding force does not decrease when pressing to integrate the sheets. The arrangement is not limited to that shown in FIG.
-Third piezoelectric ceramic sheet 35-
As described above, the common internal electrode 71 is formed over the entire upper surface (see FIG. 4). -Through hole 53A-
Except for the lowermost third ceramic sheet 35, the first and second ceramic sheets 31 and 32, the conductive dummy sheet 33, and the top ceramic sheet 34, as shown in FIGS. A plurality of through holes 53A that are filled with a conductive paste that penetrates in the sheet thickness direction and serves as the internal conductive electrode 52A are formed. The individual surface electrodes 38A to 38E, the conductive portions 36Ac to 36Ec of the individual internal electrodes 36A to 36E, the conductive electrodes 41A to 41F, and the relay electrodes 42A to 42F are electrically connected in the vertical direction. The ceramic sheets 31, 32, 33, and 34 are electrically connected through internal conduction electrodes 52 </ b> A in the through holes 53 </ b> A (see FIGS. 10 and 11).

  The ceramic sheets 31, 32, 33, and 34 include common surface electrodes 39A and 39B, common internal electrodes 37 (37A to 37E) and 71, dummy common electrodes 43, and conductive electrodes 44A and 44B for common internal electrodes. The thickness of each ceramic sheet 31, 32, 33 and 34 is similar to the above at the positions of the electrodes 39A, 39B, 37, 71, 43, 44A and 44B. Internal conductive electrodes are formed of conductive members (conductive paste) filled in a plurality of through-holes formed so as to penetrate through.

  In these cases, each internal conduction electrode 52A is formed at an appropriate distance from the top and bottom adjacent ceramic sheets 31 to 34 at positions that do not overlap vertically in plan view. This is because the through hole 53A is formed in the green sheet, which is the original material of the ceramic sheet, and then the conductive material flows into the through hole when the conductive material is screen-printed on the surface to form the internal conductive electrode 52A. Therefore, the internal conductive electrode 52A has a hollow shape with an opening on the surface side (see FIG. 10B), and when the through hole of the upper sheet overlaps the same axis, the contact area between the internal conductive electrodes 52A is increased. This is to avoid this because it decreases. The bottom of the internal conduction electrode 52A formed in a cup shape in the through hole is brought into surface contact with the planar electrode 42A (41A) of the lower layer sheet to ensure electrical conduction.

  The individual surface electrodes 38A, 38B, 38D, and 38E and the relay electrodes 42A, 42B, 42D, and 42E extend long in the direction orthogonal to the arrangement direction of the electrodes, and are opposed and arranged in parallel in the stacking direction. The individual surface electrodes 36A to 36E and the relay electrodes 42A to 42E that are adjacent to each other in a direction orthogonal to the arrangement direction are connected to each other at different positions. Specifically, as shown in FIG. 11, the individual surface electrode 38A and the relay electrode 42A facing the individual surface electrode 38A are connected by an internal conduction electrode 52A in the through hole at one end in the longitudinal direction thereof, and are adjacent to the individual electrodes. The surface electrode 38A and the relay electrode 42A are connected by the internal conduction electrode 52A at the other longitudinal end. That is, in the arrangement direction, the electrodes are alternately connected to both ends of the electrode in a staggered manner. Since they are connected to each other at different positions, a large number of through holes can be dispersedly arranged without being arranged adjacent to each other in the arrangement direction, and when firing the ceramic sheet, the ceramic sheet It is possible to suppress warping and deformation. Further, in response to the recent increase in recording speed and resolution, even if the number of nozzles is increased and the number of individual surface electrodes 38A to 38E is increased, the rows of individual internal electrodes are not changed as in the prior art. Since it is not necessary to secure a wide area for connection outside, the piezoelectric actuator can be easily downsized. Further, since the individual surface electrodes 36A to 36E and the relay electrodes 42A to 42E are opposed and arranged in parallel in the stacking direction, between the individual surface electrodes 36A to 36E and the common internal electrodes 37, 71. The capacitance not related to the displacement is also balanced.

  Further, since the plurality of relay electrodes 42A to 42E are formed so as to have the same length and width, they are opposed to each other in the stacking direction with the same area as the common electrodes 37A to 37E located therebelow. Thus, the capacitance between both electrodes becomes uniform. Since this electrostatic capacitance is located at a half-pitch shift from the straight portion 36Aa of the individual internal electrode, it does not contribute to the displacement for ejection. By making this capacitance uniform, the characteristics as piezoelectric actuators for each individual surface electrode 38A are aligned.

Incidentally, the joining electrodes 38Aa, 38Ba, 38Cac, 38Cbc, 38Da, and 38Ea on the individual surface electrodes 38A to 38E are formed so as to cover the upper end opening of the internal conduction electrode 52A, and are arranged at both ends of the electrodes 38A to 38E in the arrangement direction. Alternatingly connected in a staggered pattern. At this time, the bonding electrodes 38Aa to 38Ea are filled up to the inside of the internal conduction electrode 52A, so that even if the internal conduction electrode 52A is extremely thin in the through hole, the portion is reinforced and electrically Disconnection can be surely prevented.
-Flexible flat cable 4-
The flexible flat cable 4 is superimposed on the top surface of the top ceramic sheet 34 and is disposed so as to protrude outward in a direction (X direction) orthogonal to the nozzle row (see FIG. 1). The flexible flat cable 4 is electrically insulating and has a bonding electrode 38Aa for individual electrodes on one surface of a strip-like base material 100 made of a flexible synthetic resin material (for example, polyimide resin, polyester resin, polyamide resin). Connection terminals 48A, 48B, 48C, 48D, 48E made of copper foil and fine signal lines 46 connected thereto are provided corresponding to .about.38Ea. Further, connecting terminals 49A and 49B and strip-like (wider than wiring 46) signal wires 47 connected to the joint electrodes 39Ab and 39Bb for the common electrodes are provided on both side edges of the flexible flat cable 4. (See FIG. 9). These connection terminals and wirings are formed by a photoresist method or the like, and their surfaces are electrically insulating, and a coverlay made of a flexible synthetic resin material (for example, polyimide resin, polyester resin, polyamide resin). 102.

  The connection terminals 48A to 48E, 49A, and 49B are exposed from the base material 100 and joined to the common electrode and individual electrode joining electrodes 38Aa to 38Ea, 39Ab, and 39Bb by a conductive brazing material (for example, solder) 45. The other end of the signal line is electrically joined to a driving integrated circuit 101 mounted on the base material 100, and a driving signal can be selectively supplied to the piezoelectric actuator.

Since the connection terminals 48A to 48E are arranged in a staggered manner for each column corresponding to the joining electrodes 38Aa to 38Ea for the individual electrodes, and the adjacent terminals are also arranged in a staggered manner, the connection terminals The space between 48A to 48E can be widened, and the signal lines 46 can be wired in the space without interfering with each other.
(Function of piezoelectric actuator)
The ceramic sheets 31 and 32 between the individual internal electrodes 36A to 36E and the common internal electrodes 37 and 71 in the stacking direction of the ceramic sheets function as an active part (energy generating means). That is, by applying a voltage between any of the individual internal electrodes 36A to 36E and the common internal electrodes 37 and 71, the ceramic sheets 31 and 32 (active part) between them are displaced, so that the inside of the pressure chamber 18a. An ejection pressure is applied to the ink, and an ink droplet is ejected from the nozzle 11a.

Such active parts (energy generating means) are formed in the same number and the same number of the pressure chambers 18a in the same row. That is, the active part is the nozzle 11a (pressure chamber 18).
It is arranged along the arrangement direction (Y direction) of a) and is arranged in the X direction by the same number as the number of nozzle rows (five). In addition, each active part is formed in the X direction so as to be long in the longitudinal direction of the pressure chamber 18a, and the arrangement interval between adjacent active parts is the same as the arrangement interval of the pressure chambers 18a, and is arranged in a staggered manner. Become.

  FIG. 12 shows another embodiment. In this embodiment, the individual internal electrode 36A has a conducting portion 36Ac at an extended position of the straight portions 36Aa to 36Ea located corresponding to the pressure chamber 18a. The conducting electrode 41A and the conducting electrode portion 42Ab of the dummy ceramic sheet 33 are arranged at a position overlapping the conducting portion 36Ac in plan view. In the relay electrode 42A of the dummy ceramic sheet 33, the straight portion 42Aa is displaced from the conduction electrode portion 42Ab by a half of the arrangement pitch in the arrangement direction of the pressure chambers 18A, above the partition wall 27 between the pressure chambers 18a and 18a. It has been extended. The individual surface electrodes 38A are arranged corresponding to the upper portions of the straight portions 42Aa, and are connected to the straight portions 42Aa by the conductive electrodes 52A in the through holes alternately at both end positions of the electrodes in the arrangement direction as in the above embodiment. Has been. The connection between the other individual internal electrodes 36B to 36E and the individual surface electrodes 38B to 38E has the same configuration. Also in this embodiment, the same operational effects as the above-described embodiment can be obtained.

  FIGS. 13 and 14 (a) and 14 (b) show still another embodiment. In this embodiment, the relay electrode 42A has a length in the direction X orthogonal to the arrangement direction Y, but the individual surface electrode 38A ′ has a length in the X direction that is about half or less of the relay electrode 42A. Yes. The individual surface electrodes 38A 'are arranged at positions corresponding to the X direction both ends of the straight portion 42Aa of the relay electrode 42A in the arrangement direction of the relay electrodes 42A, that is, staggered. That is, the individual surface electrode 38A 'is displaced from the adjacent individual surface electrode 38A' in the direction X perpendicular to the arrangement direction Y, and is different from each other. Further, the individual surface electrode 38A 'is shifted in position in the length direction of the relay electrode 42A from the adjacent individual surface electrode 38A', and is opposed to a different position in the length direction.

  Then, on the individual surface electrode 38A ′, the joining electrode 38Aa connected to the connection terminals 48A to 48E of the signal line 46 at a position corresponding to the portion connected to the relay electrode 42A (conduction electrode 52A in the through hole). Is arranged. As shown in FIG. 9, the bonding electrodes 38Aa are arranged in a staggered manner in the direction X orthogonal to the arrangement direction, corresponding to the connection terminals 48A to 48E arranged in a staggered manner. Each individual surface electrode 38A 'is formed longer and wider than the bonding electrode 38Aa in the arrangement direction Y. Thus, each individual surface electrode 38A 'is formed with a large area around the bonding electrode 38Aa, so that the conductive brazing material (used to bond the connection terminals 48A to 48E of the signal line 46 to the bonding electrode 38Aa). For example, even if solder) flows out from the bonding electrode 38Aa, it is surely stopped on the individual surface electrode 38A ′.

  As shown in FIG. 14A, the length of each individual surface electrode 38A ′ in the arrangement direction Y is orthogonal to the adjacent individual surface electrode 38A ′ in the direction X perpendicular to the arrangement direction and the arrangement direction. The length has a portion that is opposed in the direction X. That is, the length in the arrangement direction Y of each individual surface electrode 38A ′ is longer than the interval in the arrangement direction of the individual surface electrodes 38A ′, and the connection terminals 48A to 48E of the signal line 46 are joined to the joining electrode 38Aa. In this case, in the arrangement direction Y, the allowable displacement of the bonding electrode 38Aa with respect to the individual surface electrode 38A ′ is increased as compared with the above-described embodiment. In this case, it is provided so that the longitudinal direction of the bonding electrode coincides with the direction in which the signal line extends, and the wiring pitch of the signal line is prevented from becoming high density. However, as shown in FIG. 38Aa ′ can also be arranged such that its longitudinal direction matches the arrangement direction Y. In this way, in FIG. 14B, there is a margin in the length difference S portion between the joining electrode 38Aa ′ and the individual surface electrode 38A ′ in the longitudinal direction of the joining electrode 38Aa ′, and the flow of the conductive brazing material is reduced. It becomes effective for the above, and it surely overlaps with the partition wall between the pressure chambers adjacent in a plan view. Therefore, the pressing force when connecting the connection terminal of the flexible flat cable 4 to the individual surface electrode 38A ′ Can be received by the partition wall 27 to prevent the ceramic sheet from cracking.

  In the embodiment of FIG. 13 as well, as in the embodiment of FIG. 12, the straight portion 36Aa and the conducting portion 36Ac of the individual internal electrode 36A are formed in a straight line, and the straight portion 42Aa of the relay electrode 42A The conductive electrode portion 42Ab can be shifted by a half pitch.

  Further, the connection between the other individual internal electrodes 36B to 36E and the individual surface electrodes 38B to 38E can be configured in the same manner as in the embodiment of FIGS.

FIG. 3 is a perspective view showing a cavity unit, a piezoelectric actuator, and a flat cable of the piezoelectric inkjet head of the present invention separately. It is a disassembled perspective view of a cavity unit. It is a partial exploded perspective view of a cavity unit. It is a disassembled perspective view of a piezoelectric actuator shown with a part omitted. It is a top view of the 1st piezoelectric ceramic sheet shown omitting some. It is a top view of the 2nd piezoelectric ceramic sheet. It is a top view which shows the dummy sheet for adjustment. It is a top view which shows a top ceramic sheet. It is a top view explaining the electrode arrangement | positioning in a flexible flat cable. (A) is sectional drawing explaining the conduction | electrical_connection relationship of an individual internal electrode-an individual surface electrode, (b) is explanatory drawing of a through hole. It is a perspective view explaining the conduction | electrical_connection relationship of a separate internal electrode-a separate surface electrode. It is a perspective view explaining the conduction | electrical_connection relationship of the separate internal electrode-separate surface electrode in other embodiment. Furthermore, it is a perspective view explaining the conduction | electrical_connection relationship of the separate internal electrode-separate surface electrode in other embodiment. (A) is a top view explaining the relationship between the joining electrode and individual surface electrode in embodiment of FIG. 13, (b) is explanatory drawing of a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet head 2 Cavity unit 3 Piezoelectric actuator 4 Flexible flat cable 11a Nozzle 18a Pressure chamber 31, 32 Ceramic sheet 34 Top ceramic sheets 36A-36E Individual internal electrodes 37, 71 Common internal electrodes 38A-38E Individual surface electrodes 38Aa-38Ea Bonding electrodes 39A, 39B Common surface electrode 39Aa, 39Ba Junction electrode 42A-42F Relay electrode 52A Internal conduction electrode 53A Through hole

Claims (13)

Between a plurality of laminated ceramic sheets, a plurality of individual internal electrodes and a common internal electrode common to the plurality of individual internal electrodes are arranged opposite to each other with at least one ceramic sheet interposed therebetween, An individual surface electrode connected to the individual internal electrode and a common surface electrode connected to the common internal electrode are formed on one surface of the ceramic sheet, and drive signals are supplied to the individual surface electrode and the common surface electrode. A laminated piezoelectric actuator to which a connection terminal of an input signal line is connected,
Between a plurality of ceramic sheets between the individual surface electrode and the individual internal electrode, a plurality of relay electrodes for connecting the individual surface electrode and the individual internal electrode are disposed,
The plurality of individual surface electrodes and the plurality of relay electrodes are opposed to and arranged in parallel in the stacking direction, and are orthogonal to the arrangement direction of the adjacent individual surface electrodes and the plurality of relay electrodes In the laminated piezoelectric actuator, the piezoelectric actuators are connected to each other at different positions.   2. The multilayer piezoelectric actuator according to claim 1, wherein the individual surface electrode is connected to a connection terminal of the signal line at a position corresponding to a portion connected to the relay electrode.   The individual surface electrode and the relay electrode have a length in a direction perpendicular to the arrangement direction, and the signal line is connected to a position corresponding to a portion connected to the relay electrode on the individual surface electrode. The multilayer piezoelectric actuator according to claim 2, further comprising a bonding electrode connected to the terminal.   The multilayer piezoelectric actuator according to claim 3, wherein the joining electrodes are arranged in a staggered manner in a direction orthogonal to the arrangement direction.   5. The stacked type according to claim 1, wherein the plurality of relay electrodes face each other with the same area as the common internal electrode located on the opposite side to the individual surface electrode. Piezoelectric actuator.   The relay electrodes have a length in a direction perpendicular to the arrangement direction, and the individual surface electrodes are different from each other in the direction perpendicular to the arrangement direction from the adjacent individual surface electrodes; and The multilayer piezoelectric actuator according to claim 1, wherein the relay electrode is opposed to a different position in the length direction of the relay electrode.   The multilayer piezoelectric actuator according to claim 6, further comprising a bonding electrode connected to the connection terminal of the signal line at a position corresponding to a portion connected to the relay electrode on the individual surface electrode. The bonding electrodes are arranged in a staggered manner in a direction orthogonal to the arrangement direction,
The multilayer piezoelectric actuator according to claim 7, wherein each individual surface electrode is longer and wider than the bonding electrode in the arrangement direction.   The multilayer piezoelectric actuator according to claim 8, wherein a length of the individual surface electrodes in the arrangement direction is longer than an interval in the arrangement direction of the individual surface electrodes.   The length of each of the individual surface electrodes in the arrangement direction is a length having an adjacent individual surface electrode in a direction orthogonal to the arrangement direction and a portion facing in the direction orthogonal to the arrangement direction. The multilayer piezoelectric actuator according to claim 8. Each of the plurality of individual internal electrodes, the common internal electrode, the plurality of relay electrodes, and each ceramic sheet formed on the surface with the plurality of individual surface electrodes and the common surface electrode are laminated,
The individual internal electrodes and the relay electrodes in the stacking direction are connected to each other, and the relay electrodes and the individual surface electrodes are connected to each other by a conductive material filled in a through hole penetrating a ceramic sheet therebetween. The multilayer piezoelectric actuator according to claim 1, wherein the multilayer piezoelectric actuator is provided. The other surface of the laminated ceramic sheets is joined to a cavity unit having a plurality of pressure chambers corresponding to a plurality of nozzles for discharging droplets,
The plurality of individual internal electrodes are arranged to face the plurality of pressure chambers, and a voltage is applied between the individual internal electrode and the common internal electrode, whereby the individual internal electrode and the common internal electrode are interposed. The multilayer piezoelectric actuator according to claim 11, wherein the ceramic sheet is displaced to apply a discharge pressure to the ink in the pressure chamber. The cavity unit includes a plurality of rows of the pressure chambers,
The individual internal electrodes have a plurality of rows corresponding to the plurality of rows of the pressure chambers,
The common internal electrode is opposed to the plurality of rows of individual internal electrodes in the stacking direction and extends in the arrangement direction,
The relay electrode and the individual surface electrode have a plurality of rows corresponding to the plurality of rows of individual internal electrodes,
13. The common surface electrode is formed in the same plane as the individual surface electrode, and is elongated in the direction in which a plurality of rows are arranged along an end portion orthogonal to the arrangement direction of the individual surface electrode. The laminated piezoelectric actuator according to 1.

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