JP2011212865A - Piezoelectric actuator - Google Patents

Abstract

In a piezoelectric actuator having two types of common electrodes, variation in potential is prevented from occurring in each common electrode.
In a piezoelectric actuator 32, a plurality of first common electrodes 43a disposed between a piezoelectric layer 40 and a piezoelectric layer 41 among piezoelectric layers 40 to 42 stacked on each other are connected by a first common wiring 43b. Are connected to each other. The first common wiring 43b includes four first extending portions 43b1 and through holes 51 and 53 formed so as to face the first connecting portions 43b2, respectively. It is pulled out to the upper surface. The plurality of second common electrodes 44a arranged between the piezoelectric layer 41 and the piezoelectric layer 42 are connected to each other by a second common wiring 44b. The second common wiring 44b is drawn to the upper surface of the piezoelectric layer 42 by through holes 54 and 55 formed so as to face the four second extending portions 44b1 and the second connecting portion 44b2.
[Selection] Figure 2

Description

  The present invention relates to a piezoelectric actuator having a piezoelectric layer and electrodes arranged on the surface of the piezoelectric layer.

  In the piezoelectric actuator described in Patent Document 1, of the two piezoelectric layers (piezoelectric material layers) stacked on each other, the upper surface of the upper piezoelectric layer (first layer) and the space between the two piezoelectric layers (second layer) And a plurality of individual electrodes, a second common electrode (second constant potential electrode), and a first common electrode (first constant potential electrode) on the lower surface (third layer) of the lower piezoelectric layer, respectively. ) Is arranged.

  The second common electrode is provided for each of the plurality of second portions facing the both ends of the individual electrode in the recording sheet conveyance direction and the individual electrode rows, and extends in the recording sheet conveyance direction. A first portion connecting the second portions to each other. The first portion of the second layer is connected to both ends of the second layer, and is drawn to the four corners of the third layer. Furthermore, each of these four corners is led out to a connection terminal formed on the upper surface of the upper piezoelectric layer by a through hole formed in the piezoelectric layer. The connection terminal is connected to the flexible wiring board, and a voltage is applied from the flexible wiring board via the connection terminal.

  On the other hand, the first common electrode is provided for each column of the individual electrodes, and has a third portion extending in the recording sheet conveyance direction so as to face the plurality of individual electrodes. The third portion of the third layer is connected to each other at both ends of the third layer and is drawn out to both ends in the scanning direction (direction perpendicular to the recording paper conveyance direction). Further, through the through holes formed in the piezoelectric layer from both ends in the scanning direction, the connection terminals formed on the upper surface of the upper piezoelectric layer are drawn. The connection terminal is connected to the flexible wiring board, and a voltage is applied from the flexible wiring board via the connection terminal.

JP 2009-96173 A (FIGS. 66 and 67)

  Here, in the piezoelectric actuator described in Patent Document 1, there is a portion where the first common electrode and the second common electrode face each other. In this portion, the first common electrode, the second common electrode, Since only one thin piezoelectric layer is interposed between them, an unintended deformation occurs due to the electric field between the first common electrode and the second common electrode.

  Therefore, the inventors of the present invention considered arranging the first common electrode and the second common electrode so as not to face each other. However, in this case, since the second common electrode inevitably faces the first common electrode when both ends of the first portion are connected to each other, the first portion is connected only to one end. Can not do it.

  On the other hand, with respect to the first common electrode, a portion of the third portion that is opposed to the first portion of the second common electrode is eliminated, a plurality of portions that are opposed to the individual electrodes that are separated from each other, and It is necessary to have a portion (connected portion) that is provided for each row and extends in the recording paper conveyance direction to connect the plurality of portions to each other. As a result, the connection portion inevitably faces the second common electrode, and therefore, the connection portion can be connected only to one end portion.

  The common electrode maintains a constant potential, but as the distance from the connection terminal increases, a voltage drop occurs, and the potential of the portion facing the individual electrode varies. Further, as the number of individual electrodes increases, the first and third portions extending in the recording sheet conveyance direction become longer, and the variation in potential becomes particularly remarkable. If such potential variations occur, the drive characteristics of the piezoelectric actuator may vary.

  An object of the present invention is to provide a piezoelectric actuator in which a common electrode does not vary in potential without causing unintended deformation in a piezoelectric layer.

  A piezoelectric actuator according to a first aspect of the present invention is disposed between a piezoelectric body composed of a plurality of stacked piezoelectric layers and any two piezoelectric layers of the plurality of piezoelectric layers, and is maintained at a predetermined first potential. A plurality of first common electrodes and two piezoelectric layers in which the first common electrodes are arranged, connected to the plurality of first common electrodes, and in one direction parallel to the surface of the piezoelectric body A first common wiring having a plurality of first extending portions extending in the direction, a connecting portion connecting the plurality of first extending portions, and any two piezoelectric layers of the plurality of piezoelectric layers A plurality of second common electrodes held at a second potential different from the first potential, and two piezoelectric layers in which the second common electrode is disposed, A plurality of second extending portions connected to the second common electrode and extending in the one direction , A second common wiring having a second connection portion that connects the plurality of second extending portions, and a part of the second common wiring overlaps the first common electrode when viewed from the stacking direction of the piezoelectric layer, A plurality of individual electrodes partially overlapping the second common electrode and a plurality of connection terminals arranged on the surface of the piezoelectric body and connected to the respective electrodes, via the plurality of connection terminals A piezoelectric actuator that is electrically connected to a wiring member that applies a voltage to each of the electrodes, wherein the first common wiring and the second common wiring are arranged so as not to overlap each other when viewed from the stacking direction. In the piezoelectric layer, a plurality of through holes are formed in a portion facing at a plurality of positions separated from each other in at least one of the first common wiring and the second common wiring. The plurality The through-hole includes a plurality of first extending portions and a plurality of second extending portions that are opposed to a plurality of extending portions constituting the at least one common electrode, At least one common electrode of the first common electrode and the second common electrode is drawn out to the surface of the piezoelectric body by the at least one common wiring and the plurality of through holes at the plurality of positions, and then connected. It is connected to a terminal.

  In a configuration having a plurality of types of common electrodes that are held at different potentials, the same type of common electrode is held at the same potential, and the common electrodes are connected to each other so that potential variations do not occur. Is desirable. However, a plurality of first common wires and second common wires connected to the first common electrode and the second common electrode, respectively, extend in one direction parallel to the surface of the piezoelectric body, and In the case of having the second extending portion, when the first extending portions are connected to each other at one end side of the piezoelectric body in one direction, the second extending portions are connected to each other at the other end side. Will be.

  If the first extending portions are connected to each other also on the other end side, the influence of the voltage drop in the first common electrode can be reduced, but if the first extending portions are connected to each other on the other end side, the first A region where the common wiring and the second common wiring overlap is formed. The same applies to the case where the second extending portions are connected on one end side in order to reduce the influence of the voltage drop. For this reason, the first common wiring and the second common wiring cannot be arranged on the same surface, and if they are arranged on different surfaces, an electric field is generated between the first common wiring and the second common wiring. And the piezoelectric layer in the meantime will deform | transform unintentionally.

  However, in the present invention, the first common wiring and the second common wiring are disposed so as not to face each other, and at least one of the first common wiring and the second common wiring in the piezoelectric layer is provided. A plurality of through holes are formed in portions facing a plurality of locations separated from each other. Furthermore, the plurality of through-holes include a plurality of first extending portions and a plurality of second extending portions that face a plurality of extending portions constituting at least one common electrode. Then, at least one of the first common electrode and the second common electrode is led out to the surface of the piezoelectric body by the at least one common wiring and the plurality of through holes at the plurality of locations. Therefore, the common electrodes of the same type can be connected to each other after being drawn out, and potential variation does not occur among the plurality of common electrodes. In addition, since the first common wiring and the second common wiring do not overlap inside the piezoelectric body, no electric field is generated between the first common wiring and the second common wiring.

  A piezoelectric actuator according to a second aspect of the present invention is disposed between a piezoelectric body composed of a plurality of stacked piezoelectric layers and any two piezoelectric layers of the plurality of piezoelectric layers, and is maintained at a predetermined first potential. A plurality of first common electrodes and two piezoelectric layers in which the first common electrodes are arranged, connected to the plurality of first common electrodes, and in one direction parallel to the surface of the piezoelectric body And a plurality of second common wires arranged between any two piezoelectric layers of the plurality of piezoelectric layers and held at a second potential different from the first potential. A plurality of second common wirings disposed between the common electrode and the two piezoelectric layers on which the second common electrode is disposed, connected to the plurality of second common electrodes and extending in the one direction; A part of the piezoelectric layer as viewed from the stacking direction is the first common electrode. And another part is provided with an individual electrode overlapping the second common electrode and a plurality of connection terminals arranged on the surface of the piezoelectric body and connected to each electrode, and the plurality of connection terminals A piezoelectric actuator that is electrically connected to a wiring member that applies a voltage to each of the electrodes, and the first common wiring and the second common wiring do not overlap each other when viewed from the stacking direction. In the piezoelectric layer, a plurality of through holes are formed in a portion of at least one of the first common wiring and the second common wiring facing a plurality of locations separated from each other. And at least one of the first common electrode and the second common electrode is connected to the at least one common wiring and the plurality of through holes at the plurality of locations. Ri wherein the are connected to the connection terminals on drawn on the surface of the piezoelectric body.

  In the present invention, the first common electrode and the second common electrode are arranged so as not to oppose each other, and the piezoelectric layer includes the first common wire and the second common wire in the common wire. A plurality of through holes are formed in a portion facing a plurality of separated locations. Then, at least one of the first common electrode and the second common electrode is led out to the surface of the piezoelectric body by the at least one common wiring and the plurality of through holes at the plurality of locations. Accordingly, the common electrodes of the same type can be connected to each other after being drawn out, so that there is no potential variation among the plurality of common electrodes. In addition, since the first common wiring and the second common wiring do not overlap inside the piezoelectric body, no electric field is generated between the first common wiring and the second common wiring.

  In the first and second inventions, the first common wiring and the second common wiring are arranged so as not to overlap each other because the first common electrode and the second common wiring are different surfaces of the piezoelectric layer. And the first common wiring and the second common wiring are arranged on the same surface of the piezoelectric layer, and the first common wiring and the second common wiring are arranged in different regions on the surface. Including both.

  A piezoelectric actuator according to a third invention is the piezoelectric actuator according to the first or second invention, wherein the first common wiring and the second common wiring are arranged on different surfaces of the plurality of piezoelectric layers. It is characterized by being.

  According to the present invention, the first common wiring and the second common wiring are arranged on different surfaces of the piezoelectric layer, and the first common wiring and the second common wiring are not opposed to each other across the piezoelectric layer. Therefore, it is possible to further suppress the occurrence of migration between the first common wiring and the second common wiring.

  A piezoelectric actuator according to a fourth invention is the piezoelectric actuator according to any one of the first to third inventions, wherein the first common electrode is the first common electrode of the two common electrodes of the piezoelectric body. The first common wiring and a plurality of through holes are led out to the first surface on the side, and the second common electrode is connected to the second surface of the piezoelectric body facing the first surface, It is drawn out by the second common wiring and a plurality of through holes.

  According to the present invention, the first common electrode is drawn out to the first surface of the piezoelectric body on the side where the first common electrode is disposed, and the second common electrode is opposed to the first surface of the piezoelectric body. Therefore, when connecting the wiring to the first common electrode or the second electrode drawn out, the degree of freedom of wiring is higher than when the wiring is drawn out on the same surface. Become.

  A piezoelectric actuator according to a fifth invention is the piezoelectric actuator according to any one of the first to fourth inventions, wherein the plurality of connection terminals are provided on the surface of the piezoelectric body at positions facing the plurality of through holes. Is arranged.

  According to the present invention, it is possible to easily connect the common wiring (connection terminal) drawn to the surface of the piezoelectric body and the wiring member.

  In addition, since the connection terminal is arranged in the portion facing the through hole on the surface of the piezoelectric body, it is assumed that the common electrode drawn out by the through hole and the connection terminal are connected to one surface of the piezoelectric body. If wiring is arranged, migration may occur between the wirings, but migration does not easily occur because there is no wiring for connecting the common electrode and the connection terminal.

  A piezoelectric actuator according to a sixth aspect of the present invention is the piezoelectric actuator according to any one of the first to fifth aspects, wherein the at least one common electrode is drawn out by the through hole on the surface of the piezoelectric layer. A surface wiring for connecting the holes to each other is disposed, and the plurality of connection terminals are disposed on the surface wiring.

  According to the present invention, since the surface wiring for connecting the drawn common electrodes to each other is arranged on the surface of the piezoelectric body, the potential between the common electrodes does not vary.

  According to the present invention, since at least one of the first and second common electrodes is drawn out to the surface of the piezoelectric body by the plurality of through holes, it is drawn out without causing unintentional deformation in the piezoelectric layer. If a plurality of portions are connected to each other, variation in potential of the common electrode can be prevented.

1 is a schematic configuration diagram of a printer according to an embodiment of the present invention. It is a top view of the inkjet head of FIG. It is a top view of each piezoelectric layer of the piezoelectric actuator with which the piezoelectric layer was laminated | stacked. It is the elements on larger scale of Drawing 3 (a)-(c). It is the VV sectional view taken on the line of FIG. It is the VI-VI sectional view taken on the line of FIG. (A) is the VIIa-VIIa sectional view taken on the line of FIG. 2, (b) is the VIIb-VIIb sectional view taken on the line of FIG. It is a figure equivalent to Drawing 3 (a)-(c) of modification 1. FIG. 8 is a diagram corresponding to FIG. It is a figure equivalent to Drawing 8 (a) and (b) of modification 2. FIG. 10 is a diagram corresponding to FIG.

  Hereinafter, a preferred first embodiment of the present invention will be described. FIG. 1 is a schematic configuration diagram of a printer according to the present embodiment. As shown in FIG. 1, the printer 1 includes a carriage 2, an inkjet head 3, a paper transport roller 4, and the like.

  The carriage 2 reciprocates in the scanning direction (left and right direction in FIG. 1) along the guide shaft 5. The inkjet head 3 is disposed on the lower surface of the carriage 2 and ejects ink from a plurality of nozzles 15 formed on the lower surface. The paper transport roller 4 transports the recording paper P in the paper feed direction (front side in FIG. 1).

  In the printer 1, printing is performed on the recording paper P when the ink jet head 3 ejects ink while reciprocating in the scanning direction together with the carriage 2 onto the recording paper P conveyed by the paper conveying roller 4 in the paper feeding direction. Do.

  Next, the inkjet head 3 (recording head) will be described in detail. FIG. 2 is a plan view of the inkjet head 3. FIG. 3 is a plan view of a piezoelectric layer to be described later. (A) is the upper surface of the piezoelectric layer 42, (b) is the upper surface of the piezoelectric layer 41, (c) is the upper surface of the piezoelectric layer 40, and (d) is the piezoelectric layer 40. The lower surface of each is shown. FIG. 4 is a partially enlarged view of FIGS. 3 (a) to 3 (c). 5 is a cross-sectional view taken along line VV in FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. Fig.7 (a) is the VIIa-VIIa sectional view taken on the line of FIG. FIG. 7B is a sectional view taken along line VIIb-VIIb in FIG.

  In order to make the drawing easier to understand, in FIG. 2, through holes 51 to 55 described later are shown larger than FIG. In FIG. 2, the illustration of the ink flow path excluding the pressure chamber 10 and the nozzle 15 of the flow path unit 31 described later is omitted. In FIGS. 2 and 3, conductive patterns 43 and 44 and individual 45, connection terminals 46 to 49, and surface wirings 61 and 62, which will be described later, are hatched. Further, in FIG. 6, illustration of a portion below the pressure chamber 10 of the flow path unit 31 is omitted.

  As shown in FIGS. 2 to 7, the inkjet head 3 includes a flow path unit 31 and a piezoelectric actuator 32. The flow path unit 31 is formed by stacking a plurality of plates 21 to 27, and a manifold flow path 11 to which ink is supplied from the ink supply port 9 and a manifold flow path 11 are provided therein. An ink channel having a plurality of individual ink channels from the outlet to the pressure chamber 10 through the aperture channel 12 and from the pressure chamber 10 to the nozzle 15 through the descender channel 14 is formed.

  The plurality of pressure chambers 10 have a substantially elliptical planar shape with the scanning direction (left-right direction in FIG. 2) as the longitudinal direction, and are arranged along the paper feed direction (up-down direction in FIG. 2). A pressure chamber row 8 is configured. Then, four such pressure chamber rows 8 are arranged along the scanning direction. The plurality of nozzles 15 are also arranged in the same manner as the plurality of pressure chambers 10.

  Then, black, yellow, cyan, and magenta ink droplets are ejected from the nozzles 15 constituting the four pressure chamber rows 8 in order from the nozzles 15 arranged on the right side of FIG. The configuration of other portions of the ink flow path is the same as that of the conventional one, and therefore detailed description thereof is omitted here.

  The piezoelectric actuator 32 includes piezoelectric layers 40 to 42, a first conductive pattern 43, a second conductive pattern 44, and a plurality of individual electrodes 45. The piezoelectric layers 40 to 42 are made of a piezoelectric material mainly composed of lead zirconate titanate, which is a mixed crystal of lead titanate and lead zirconate, and cover the plurality of pressure chambers 10 in a stacked state. Further, it is disposed on the upper surface of the flow path unit 30. Here, among the piezoelectric layers 40 to 42, the piezoelectric layer 40 functions as a diaphragm. In the present embodiment, the laminated body of the piezoelectric layers 40 to 42 corresponds to the piezoelectric body according to the present invention. The piezoelectric layer 40 is bonded to the upper surface of the flow path unit 30 by an adhesive, and an adhesive layer (adhesive layer 39) is interposed between the flow path unit 30 and the piezoelectric layer 40.

  The first conductive pattern 43 includes a plurality of first common electrodes 43 a and first common wires 43 b and is disposed between the piezoelectric layer 40 and the piezoelectric layer 41.

  The plurality of first common electrodes 43a are disposed so as to face both ends of the pressure chamber 10 in the paper feeding direction. The first common wiring 43b includes four first extending portions 43b1 and one first connecting portion 43b2. The first extending portion 43b1 is provided individually for each of the four pressure chamber rows 8, and extends in the paper feeding direction to form the first common electrode 43a corresponding to the pressure chamber 10 constituting each pressure chamber row 8. The right end portions in FIG. 3 are connected to each other. The first connection portion 43b2 extends in the scanning direction, and connects the upper ends of the four first extension portions 43b1 in FIG. 3 to each other.

  Here, a through hole 51 filled with a conductive material such as a metal is formed in a portion of the first extending portion 43b1 of the first common wiring 43b of the piezoelectric layer 40 facing the lower end portion in FIG. This portion of the first extending portion 43b1 is led out to the lower surface of the piezoelectric layer 40 (the first surface on the first common electrode 43a side of the piezoelectric body) by the through hole 51.

  Furthermore, a surface wiring 61 is disposed on the lower surface of the piezoelectric layer 40. The surface wiring 61 extends in the scanning direction so as to straddle the four through holes 51 and connects the through holes 51, and is bent at the right end in FIG. 3 and extends in the vertical direction in the figure. Further, in the piezoelectric layers 40 to 42, three through holes 52 are formed in a portion facing a portion extending in the vertical direction of the surface wiring 61, and this portion of the surface wiring 61 is formed by the through holes 52. The top surface of the piezoelectric layer 42 is drawn out. On the upper surface of the piezoelectric layer 42, a connection terminal 46 having a substantially rectangular planar shape is disposed at the lower right end portion in FIG. 3 facing the through hole 52, whereby the surface wiring 61 is connected by the through hole 52. It is connected to the terminal 46. The connection terminal 46 is connected via a land 56 to a COF (Chip On Film) 70 disposed above the piezoelectric actuator 32.

  On the other hand, the first connection portion 43b2 extending in the scanning direction is bent downward in FIG. Three through holes 53 filled with a conductive material such as metal are formed in the portions of the piezoelectric layers 41 and 42 facing the bent portions, and this portion of the first common wiring 43b is It is drawn out to the upper surface (surface of the piezoelectric body) of the piezoelectric layer 42 through the through hole 53. On the upper surface of the piezoelectric layer 42, a connection terminal 47 having a substantially rectangular planar shape is disposed at the upper left end portion in FIG. 3 facing the through hole 53, whereby the first drawn out by the through hole 53. The connection portion 43b2 is connected to the connection terminal 47. The connection terminal 47 is connected to the COF 70 via the land 57.

  As described above, in the present embodiment, the plurality of first common electrodes 43a are formed in through holes 51 and 53 formed in portions of the piezoelectric layers 40 and 42 facing the plurality of spaced apart portions of the first common wiring 43b. And pulled out to the lower surface of the piezoelectric layer 40 and the upper surface of the piezoelectric layer 42, respectively, and connected to the connection terminals 46 and 47.

  The second conductive pattern 44 includes a plurality of second common electrodes 44 a and second common wirings 44 b, and is disposed between the piezoelectric layer 41 and the piezoelectric layer 42.

  The plurality of second common electrodes 44 a have a substantially rectangular planar shape, and are disposed so as to face the substantially central portion of the pressure chamber 10. The second common wiring 44b includes four second extending portions 44b1 and one second connection portion 44b2. The second extending portion 44b1 is provided individually for each of the four pressure chamber rows 8, and extends in the paper feed direction to form the second common electrode 44a corresponding to the pressure chamber 10 constituting each pressure chamber row 8. The left end portions in FIG. 3 are connected to each other. The second connection portion 44b2 extends in the scanning direction, and connects the lower ends of the four second extension portions 44b1 in FIG. 3 to each other.

  Here, in the piezoelectric layer 42, through holes 54 each filled with a conductive material such as metal are formed in portions of the four second extending portions 44b1 facing the upper end portions in FIG. This portion of the second extending portion 44b1 is drawn out to the upper surface of the piezoelectric layer 42 (the second surface facing the first surface of the piezoelectric body) by the through hole 54.

  Further, a surface wiring 62 is disposed on the upper surface of the piezoelectric layer 42. The surface wiring 62 extends in the scanning direction so as to straddle the four through holes 54 and connects the through holes 54 to each other. The right end in FIG. 3 is the upper right end in FIG. The connection terminal 48 having a substantially rectangular planar shape is disposed and connected. The connection terminal 48 is connected to the COF 70 via the land 58.

  On the other hand, the second connection portion 44b2 extending in the scanning direction is bent upward in the drawing at the left end portion in FIG. Three through holes 55 filled with a conductive material such as metal are formed in a portion of the piezoelectric layer 42 facing the bent portion of the second connection portion 44b2, and the second connection portion 44b2 This portion is drawn out to the upper surface of the piezoelectric layer 42 through the through hole 55. On the upper surface of the piezoelectric layer 42, a connection terminal 49 having a substantially rectangular planar shape is arranged at the lower left end portion in FIG. 3 facing the through hole 55, whereby the second drawn out to the through hole 55. The connection portion 44b2 is connected to the connection terminal 49. The connection terminal 49 is connected to the COF 70 via the land 59.

  As described above, in the present embodiment, the plurality of second common electrodes 44a are provided through the through holes 54 and 55 formed in the piezoelectric layer 42 at portions facing the plurality of spaced apart portions of the second common wiring 44b. Then, after being pulled out to the upper surface of the piezoelectric layer 42, it is connected to the connection terminals 48 and 49.

  In the present embodiment, as described above, three through holes 52, 53, and 55 are provided, but three through holes 52, three through holes 53, and three through holes 55 are provided. Since each plays the same role, at least one through hole 52, 53, and 55 is sufficient.

  Each of the plurality of individual electrodes 45 has a substantially rectangular planar shape, and is disposed so as to face the entire area of the plurality of pressure chambers 10 on the upper surface of the piezoelectric layer 42. The individual electrode 45 is opposed to the first common electrode 43a at both end portions in the paper feeding direction, and is opposed to the second common electrode 44a in a substantially central portion in the paper feeding direction. That is, a part of the individual electrode 45 overlaps the first common electrode 43a, and another part overlaps the second common electrode 44a.

  Each individual electrode 45 extends to a portion that does not face the pressure chamber 10, and this portion serves as a connection terminal 45a. The connection terminal 45 a is connected to the COF 70 via the land 60.

  In the piezoelectric actuator 32 having the above-described configuration, the first common electrode 43a is held at the ground potential (first potential) by the driver IC (not shown) mounted on the COF 70, and the second common electrode 44a is It is held at a predetermined drive potential (for example, 20 V, second potential) different from the ground potential. Further, either the ground potential or the driving potential is selectively applied to the plurality of individual electrodes 45 by the driver IC.

  Further, in the piezoelectric actuator 32 having such a configuration, a portion (active portion R1) sandwiched between the individual electrode 45 and the second common electrode 44a is polarized in the thickness direction. In addition, the portion (active part R2) sandwiched between the individual electrode 45 and the first common electrode 43a of the piezoelectric layers 41 and 42 is polarized in the thickness direction, like the active part R1.

  Here, the operation of the piezoelectric actuator 32 will be described. In the standby state before the piezoelectric actuator 32 performs the operation of ejecting ink, as described above, the first common electrode 43a and the second common electrode 44a are always held at the ground potential and the drive potential, respectively. The potential of the individual electrode 45 is previously held at the ground potential.

  Therefore, a potential difference is generated between the individual electrode 45 and the second common electrode 44a, and an electric field in a direction parallel to the polarization direction is generated in the active part R1. As a result, the active portion R1 contracts in the direction orthogonal to the electric field, that is, the surface direction orthogonal to the thickness direction, so-called unimorph deformation occurs, and the pressures of the piezoelectric layers 41 and 42 and the piezoelectric layer 40 as the diaphragm The portion facing the chamber 10 is deformed so as to be convex toward the pressure chamber 10 as a whole. In this state, the volume of the pressure chamber 10 is smaller than when the piezoelectric layers 40 to 42 are not deformed.

  When the piezoelectric actuator 32 is driven to eject ink, the potential of a certain individual electrode 45 is once switched to the drive potential, and after a predetermined time has elapsed, the potential is returned to the ground potential. When the potential of the individual electrode 45 is switched to the driving potential, the contraction of the active part R1 is restored, and at the same time, due to the potential difference between the individual electrode 45 and the first common electrode 43a, the active part R2 is parallel to the polarization direction. By generating an electric field in a different direction, the active portion R2 contracts in the surface direction. As a result, the portions of the piezoelectric layers 41 and 42 and the piezoelectric layer 40 as a vibration plate facing the pressure chamber 10 as a whole are deformed so as to protrude toward the opposite side of the pressure chamber 10, and the volume of the pressure chamber 10 is increased. To increase.

  Thereafter, when the potential of the individual electrode 45 is returned to the ground potential, the contraction of the active portion R2 returns to the original and the active portion R1 contracts in the surface direction, and the pressure of the piezoelectric layers 40 to 42 is the same as described above. The portion facing the chamber 10 is deformed so as to be convex toward the pressure chamber 10 as a whole, and the volume of the pressure chamber 10 is reduced. As a result, the pressure of the ink in the pressure chamber 10 rises, and the ink is ejected from the nozzle 15 communicating with the pressure chamber 10.

  When the piezoelectric actuator 32 is driven in this way, the contraction of the active part R1 and the extension of the active part R2 absorb each other when the piezoelectric layers 41 and 42 are deformed, and the extension of the active part R1 and the active part R2 are absorbed. The deformation of the piezoelectric layer 41, 42 is transmitted to a portion facing the other pressure chamber 10 and affects the deformation of the portion. So-called crosstalk can be prevented.

  Here, as in the present embodiment, in the piezoelectric actuator 32 having a plurality of first common electrodes 43a and a plurality of second common electrodes 44a, a plurality of first common electrodes 43a and a plurality of It is preferable that all the first common electrodes 43a are connected to each other and all the second common electrodes 44a are connected to each other so that there is no variation in potential between the second common electrodes 44a.

  Therefore, in this embodiment, the first common electrodes 43a are connected to each other by the first common wiring 43b, and the second common electrodes 44a are connected to each other by the second common wiring 44b.

  However, if the first common wiring 43b and the second common wiring 44b are opposed to each other in any part, the piezoelectric layer 41 is provided between the first common wiring 43b and the second common wiring 44b. Therefore, the piezoelectric layer 41 is unintentionally deformed due to a potential difference between the first common wiring 43b and the second common wiring 44b.

  Therefore, in the present embodiment, by arranging the first common wiring 43b and the second common wiring 44b as described above, the first common wiring 43b and the second common wiring 44b are, as shown in FIG. They are not facing each other. Therefore, it is possible to prevent the unintentional deformation as described above from occurring in the piezoelectric layer 41.

  Further, since the first common wiring 43b and the second common wiring 44b are arranged on different surfaces of the piezoelectric layer and are not opposed to each other, migration is performed between the first common wiring 43b and the second common wiring 44b. Can be prevented from occurring.

  In addition, if there is no through hole 51, 54, the potential is applied to the first common wiring 43b only through the connection terminal 47 and the through hole 53, and the second common electrode 44b is applied only through the connection terminal 49 and the through hole 55. Assuming that a potential is applied to the potential, a voltage drop occurs in the potential of the first extending portion 43b1 according to the distance from the connection terminal 47. Similarly, a voltage drop occurs in the potential of the second extending portion 44b1 according to the distance from the connection terminal 49. As a result, potential variation occurs between the plurality of first common electrodes 43a connected to the first common wiring 43b and between the plurality of second common electrodes 44a connected to the second common wiring 44b. End up.

  The influence of this voltage drop becomes particularly noticeable when the number of the first common electrode 43a and the second common electrode 44a is large and the first extension portion 43b1 and the second extension portion 44b1 are long. .

  On the other hand, in the present embodiment, in the first common wiring 43b, the first connection portion 43b2 is drawn out to the upper surface of the piezoelectric layer 42 by the through hole 53 and connected to the connection terminal 47. The lower end portion of the first extending portion 43b1 in FIG. 2 is drawn out to the lower surface of the piezoelectric layer 40 through the through hole 51, and further drawn out to the upper surface of the piezoelectric layer 42 through the surface wiring 61 and the through hole 52. 46.

  On the other hand, in the second common wiring 44b, in addition to the second connection portion 44b2 being drawn out to the upper surface of the piezoelectric layer 42 by the through hole 55 and connected to the connection terminal 49, the second extension portion 44b1 is illustrated. 2 is drawn out to the upper surface of the piezoelectric layer 42 by the through hole 54 and is further connected to the connection terminal 48 via the surface wiring 62.

  Accordingly, if the portions drawn out by the through holes 51 to 53 of the first common wiring 43b and the portions drawn by the through holes 54 and 55 of the second common wiring 44b are connected to each other, the first common wiring 43b and The influence of the voltage drop on the second common wiring 44b can be suppressed, and variation in potential between the plurality of first common electrodes 43a and between the plurality of second common electrodes 44a can be suppressed. can do.

  Furthermore, in the present embodiment, the through holes 51 are connected to each other by the surface wiring 61 disposed on the lower surface of the piezoelectric layer 40, and the through holes 55 are connected to each other by the surface wiring 62 disposed on the lower surface of the piezoelectric layer 42. Are connected, the variation in potential of the first common wiring 43b and the second common wiring 44b can be more reliably suppressed, and between the first common electrodes 43a and between the second common electrodes 44a, respectively. It is possible to more effectively suppress the occurrence of potential variation.

  Furthermore, since the surface wiring 61 is disposed on the lower surface of the piezoelectric layer 40 (the first surface on the first common wiring side of the piezoelectric body), there are two wirings between the surface wiring 61 and the second conductive pattern 44. Piezoelectric layers 40 and 41 are interposed. On the other hand, since the surface wiring 62 is disposed on the upper surface of the piezoelectric layer 42 (second surface facing the first surface of the piezoelectric body), there are two wirings between the surface wiring 61 and the second conductive pattern 44. Piezoelectric layers 41 and 42 are interposed.

  That is, the distance between the surface wiring 61 and the second conductive pattern 44 and the distance between the surface wiring 62 and the first conductive pattern 43 are the first common wiring 43b and the second common wiring with only one piezoelectric layer 41 interposed therebetween. 44b is larger than the distance between the first common wiring 43b and the second common wiring 44b when facing each other, even if an electric field is generated between the surface electrodes 61 and 62 and the conductive patterns 44 and 43, The deformation of the piezoelectric layer sandwiched between the two can be a small deformation that does not hinder the deformation of the piezoelectric actuator.

  Further, since the adhesive layer 39 that joins the piezoelectric layer 40 and the flow path unit 31 does not have a very large thickness, the surface wiring 61 arranged on the lower surface of the piezoelectric layer 42 is connected to the flow path unit 31. Although it may be possible to conduct, the plates 21 to 27 constituting the flow path unit 31 are connected to the surface wiring 61 (first common electrode 43a) in order to prevent charging of the ink in the ink flow path. They are held at the same ground potential. Therefore, even if the surface wiring 61 and the flow path unit 31 become conductive, the potential of the first common electrode 43a does not fluctuate.

  Next, modified examples in which various changes are made to the present embodiment will be described. However, description of components having the same configuration as in this embodiment will be omitted as appropriate.

  In the above-described embodiment, the first common wiring 43b is drawn out to the lower surface of the piezoelectric layer 40 through the through hole 51, and the second common wiring 44b is drawn out to the upper surface of the piezoelectric layer 42 through the through hole 54. It is not limited to.

  For example, on the contrary, the first extending portion 43b1 is led out to the upper surface of the piezoelectric layer 42 (surface on the second common wiring 44b side of the piezoelectric body) by the through hole, and the second extending portion 44b1 is connected to the piezoelectric body. It may be drawn out to the lower surface of the piezoelectric layer 40 which is the surface opposite to the above surface.

  Furthermore, the first common wiring 43b and the second common wiring 44b are not limited to being drawn out on different surfaces of the piezoelectric body.

  In one modified example (Modified Example 1), as shown in FIGS. 8 and 9, the lower end portion of the first extending portion 43 b 1 in FIG. 8 is piezoelectric by a through hole 81 formed in the piezoelectric layers 41 and 42. It is pulled out to the upper surface of the layer 42. Further, a connection terminal 82 is individually arranged on a portion of the upper surface of the piezoelectric layer 42 facing the through hole 81, and the first extending portion 43 b 1 drawn out by the through hole 81 is connected to the connection terminal 82. Yes.

  In addition, a connection terminal 84 is individually arranged on the portion of the upper surface of the piezoelectric layer 42 facing the through hole 54, and the second extending portion 44 b 1 drawn to the upper surface of the piezoelectric layer 42 by the through hole 54 is connected. The terminal 84 is connected. The connection terminals 82 and 84 are connected to the COF 70 via lands 85 and 86, respectively.

  In the above-described embodiment, the first common wiring 43 b drawn to the lower surface of the piezoelectric layer 40 by the through hole 51 is further drawn to the upper surface of the piezoelectric layer 42 through the surface wiring 61 and the through hole 52, so that the piezoelectric layer 42 Although it was necessary to connect to the connection terminal 46 disposed on the upper surface, in the first modification, both the first common wiring 43b and the second common wiring 44b are connected to the piezoelectric layer 42 by the through holes 81, 53, 54, and 55. Since it is drawn out to the upper surface and connected to the connection terminals 47, 49, 82, 84, it is possible to easily connect the drawn-out first common wiring 43b and second common wiring 44b to the COF 70.

  In this case, if the same wiring as the surface wiring 61 is arranged on the upper surface of the piezoelectric layer 42 and the drawn first common wirings 43b are connected to each other, this wiring is connected to only one piezoelectric layer 42. The piezoelectric layer 42 is unintentionally deformed due to the electric field generated between the first common wiring 43b and the first common wiring 43b.

  However, in the first modification, the first extending portion 43b1 and the second extending portion 44b1 are provided by disposing the connection terminals 82 and 84 in the portions facing the through holes 54 and 81 on the upper surface of the piezoelectric layer 42, respectively. Are connected to the connection terminals 82 and 84 at positions where they are drawn to the upper surface of the piezoelectric layer 42, respectively, and thus the first common wiring 43b and the second common wiring 44b and the connection terminals 82 which are drawn on the upper surface of the piezoelectric layer 42 are connected. , 84 are not required, and the above-described deformation is unlikely to occur.

  Furthermore, when such a wiring is provided, migration may occur between the wirings. However, in the first modification, since there is no such wiring, migration is unlikely to occur.

  In the above-described embodiment, the first conductive pattern 43 (first common wiring 43b) and the second conductive pattern 44 (second common wiring 44b) are disposed on different surfaces of the piezoelectric layer. This is not a limitation.

  In another modification (Modification 2), as shown in FIG. 10, the first conductive pattern 43 and the second conductive pattern 44 are both disposed between the piezoelectric layer 41 and the piezoelectric layer 42. In this case, the first common wiring 43b and the second common wiring 44b are arranged in different regions on the upper surface of the piezoelectric layer 41, and the first common wiring 43b and the second common wiring 44b face each other. Not.

  In the first common wiring 43b, the lower end portion of the first extension portion 43b1 in FIG. 10 is drawn out to the upper surface of the piezoelectric layer 42 by the through hole 91 formed in the piezoelectric layer 42 and connected to the connection terminal 82. The first connection portion 43 b 2 is drawn out to the upper surface of the piezoelectric layer 42 through a through hole 92 formed in the piezoelectric layer 42 and connected to the connection terminal 47.

  On the other hand, in the second common wiring 44b, the upper end portion in FIG. 10 of the second extending portion 44b1 is drawn out to the upper surface of the piezoelectric layer 42 by the through hole 54 and connected to the connection terminal 84, as in the first modification. The second connection portion 44 b 2 is drawn out to the upper surface of the piezoelectric layer 42 through the through hole 55 and connected to the connection terminal 49.

  When the first common wiring 43b and the second common wiring 44b are disposed on the same surface of the piezoelectric layer, the lower ends of the four first extending portions 43b1 in FIG. It is difficult to connect each other and to connect the upper ends of the four second extending portions 44b1 in FIG.

  Therefore, in Modification 2, the lower end portion of the first extension portion 43b1 in FIG. 10 and the upper end portion of the second extension portion 44b1 in FIG. 10 are drawn out and connected to the upper surface of the piezoelectric layer 42 through the through holes 54 and 91. Terminals 82 and 49 are connected. As a result, by connecting the same power source to these connection terminals, the parts drawn out by the through holes of the first common wiring 43b and the parts drawn out by the through holes of the second common wiring 44b are connected. This can prevent variations in potentials of the first common wiring 43b and the second common wiring 44b.

  In the above-described embodiment, the first common wiring 43b includes the four first extending portions 43b1 and the first connecting portions 43b1 that connect the first extending portions 43b1 to each other. The two common wirings 44b are composed of the four second extending portions 44b1 and the second connecting portions 44b2 that connect the second extending portions 44b1 to each other, but are not limited thereto.

  In another modification (Modification 3), as shown in FIG. 11, between the piezoelectric layer 40 and the piezoelectric layer 41, a plurality of first common electrodes 43a and the four first extending portions 43b1 described above. A first conductive pattern 103 having a planar shape similar to that of (see FIG. 3) and comprising four first common wirings 103b respectively connecting a plurality of first common electrodes 43a corresponding to each pressure chamber row 8 is provided. Has been placed. In addition, between the piezoelectric layer 41 and the piezoelectric layer 42, each of the pressure chambers has a planar shape similar to the plurality of second common electrodes 44a and the four second extending portions 44b1 (see FIG. 3) described above. A second conductive pattern 104 including four second common wirings 104b that respectively connect a plurality of second common electrodes 44a corresponding to the column 8 is disposed.

  The lower end of the first common wiring 103b in FIG. 11 is drawn out to the lower surface of the piezoelectric layer 40 by the through hole 51, and the piezoelectric layer 42 is further formed by the surface wiring 61 and the through hole 52. It is pulled out to the upper surface of the connection terminal 46 and connected to the connection terminal 46.

  Further, the upper ends of the four first common wires 103b in FIG. 11 are drawn out to the lower surface of the piezoelectric layer 40 through the through holes 111 formed in the piezoelectric layer 40. Furthermore, a surface wiring 121 extending in the scanning direction and connecting the through holes 111 is disposed on the lower surface of the piezoelectric layer 40, and the left end portion of the surface wiring 121 in the figure is formed in the piezoelectric layers 40 to 42. It is drawn out to the upper surface of the piezoelectric layer 42 through the through hole 112 and connected to the connection terminal 47.

  On the other hand, the upper ends of the four second common wires 104b in FIG. 11 are drawn onto the piezoelectric layer 42 through the through holes 54 and connected to the connection terminals 48, as in the above-described embodiment.

  Further, the lower ends of the four second common wirings 104b in FIG. 11 are led out to the upper surface of the piezoelectric layer 42 through the through holes 114 formed in the piezoelectric layer 42. Furthermore, a surface wiring 122 extending in the scanning direction is disposed on the upper surface of the piezoelectric layer 42, and the surface wiring 122 connects the through holes 114 to each other, and the left end portion in FIG. It is connected to the.

  Even in this case, the potential of the first common wiring 103b and the potential of the second common wiring 104b do not vary, and the potential between the first common electrode 43a and the second common electrode 44a is different. Variations can be prevented from occurring. Also in this case, deformation is unlikely to occur between the surface wirings 61 and 121, the second conductive pattern 104, the surface wirings 62 and 122, and the first conductive pattern 103.

  Further, in this case, the first common wiring 103b is drawn out to the lower surface of the piezoelectric layer 40 through the through holes 51 and 111, and the second common wiring 104b is drawn out to the upper surface of the piezoelectric layer 42 through the through holes 54 and 114. Therefore, the surface wirings 61 and 121 and the surface wirings 62 and 122 are arranged on different surfaces of the piezoelectric body, and the wiring is routed more than when these surface wirings are arranged on the same surface of the piezoelectric body. The degree of freedom increases.

  In the above example, the through hole is formed so as to face the end portions of the first extending portion 43b1, the second extending portion 44b1, the first common wiring 103b, and the second common wiring 104b. However, the present invention is not limited to this, and the through hole may be formed so as to face the middle part of these.

  In the above, one common electrode is drawn out to the lower surface of the piezoelectric layer 40 through a through hole, and then drawn out to the upper surface of the piezoelectric layer 42 through another through hole. However, the present invention is not limited to this. The common electrode may be connected to the COF 70 on the lower surface of the piezoelectric layer 40 and the other common electrode may be connected to the COF 70 on the upper surface of the piezoelectric layer 42 without being drawn out to the upper surface of the piezoelectric layer 42 by another through hole. . Further, in this case, the common electrode drawn out on the lower surface of the piezoelectric layer 40 is an electrode held at the ground potential. The common electrode and the flow path unit 31 are connected on the lower surface of the piezoelectric layer 40, and the flow path unit 31. And the COF 70 may be connected.

  Further, the number of through holes is not limited to that described above, and the common wiring may be drawn to the surface of the piezoelectric body by more through holes.

  In the above description, the first extension portion 43b1, the second extension portion 44b1, the first common wiring 103b, and the second common wiring 104b are arranged in accordance with the four pressure chamber rows 8 provided. Although four each are provided, when the number of the pressure chamber rows 8 is different, two, three, or five or more may be provided according to the number.

  Further, in the above example, both the first common electrode 43a and the second common electrode 44a are led out to the surface of the piezoelectric body by the common wiring and the through hole at a plurality of locations separated from each other. Only one of the first common electrode 43a and the second common wiring 44a may be pulled out. Even in these cases, it is possible to prevent variation in potential between the one common electrode.

  In the above, an example in which the present invention is applied to a piezoelectric actuator of an ink jet head that ejects ink droplets from nozzles has been described. However, the present invention is not limited to this, and individual electrodes used in various devices other than an ink jet head can be connected to each other. The present invention can be applied to a piezoelectric actuator having two types of common electrodes held at different potentials.

32 Piezoelectric actuators 40, 41, 42 Piezoelectric layer 43a First common electrode 43b First common wire 43b1 First extending portion 43b2 First connecting portion 44a Second common electrode 44b Second common wire 44b1 Second extending portion 44b2 Second Connection part 45 Individual electrode 46-49 Connection terminal 51-55 Through hole 61, 62 Surface wiring 81 Through hole 82, 84 Connection terminal 91 Through hole 103b First common wiring 104b Second common wiring 111, 112, 114 Through hole 121, 122 Surface wiring

Claims (6)

A piezoelectric body comprising a plurality of stacked piezoelectric layers;
A plurality of first common electrodes disposed between any two piezoelectric layers of the plurality of piezoelectric layers and held at a predetermined first potential;
A plurality of first extensions arranged between two piezoelectric layers where the first common electrode is arranged, connected to the plurality of first common electrodes and extending in one direction parallel to the surface of the piezoelectric body. And a first common wiring having a connecting portion that connects the plurality of first extending portions,
A plurality of second common electrodes disposed between any two piezoelectric layers of the plurality of piezoelectric layers and held at a second potential different from the first potential;
The second common electrode is disposed between the two piezoelectric layers, and is connected to the plurality of second common electrodes and extends in the one direction, and the plurality of second extensions. 2nd common wiring which has the 2nd connection part which connects 2 extension parts,
A plurality of individual electrodes, one part of which overlaps with the first common electrode and another part of which overlaps with the second common electrode, as viewed from the stacking direction of the piezoelectric layers;
A plurality of connection terminals disposed on the surface of the piezoelectric body and connected to the respective electrodes, and electrically connected to a wiring member for applying a voltage to the respective electrodes via the plurality of connection terminals. A piezoelectric actuator comprising:
The first common wiring and the second common wiring are arranged so as not to overlap each other when viewed from the stacking direction,
In the piezoelectric layer, a plurality of through holes are formed in a portion facing at a plurality of locations separated from each other in at least one common wiring of the first common wiring and the second common wiring,
The plurality of through holes include a plurality of first extending portions and a plurality of second extending portions that face a plurality of extending portions constituting the at least one common electrode. ,
At least one common electrode of the first common electrode and the second common electrode is drawn to the surface of the piezoelectric body by the at least one common wiring and the plurality of through holes at the plurality of locations. A piezoelectric actuator connected to the connection terminal. A piezoelectric body comprising a plurality of stacked piezoelectric layers;
A plurality of first common electrodes disposed between any two piezoelectric layers of the plurality of piezoelectric layers and held at a predetermined first potential;
A plurality of first common wires arranged between two piezoelectric layers where the first common electrode is arranged, connected to the plurality of first common electrodes and extending in one direction parallel to the surface of the piezoelectric body. When,
A plurality of second common electrodes disposed between any two piezoelectric layers of the plurality of piezoelectric layers and held at a second potential different from the first potential;
A plurality of second common wirings disposed between two piezoelectric layers in which the second common electrode is disposed, connected to the plurality of second common electrodes, and extending in the one direction;
A plurality of individual electrodes, one part of which overlaps with the first common electrode and another part of which overlaps with the second common electrode, as viewed from the stacking direction of the piezoelectric layers;
A plurality of connection terminals disposed on the surface of the piezoelectric body and connected to the respective electrodes, and electrically connected to a wiring member for applying a voltage to the respective electrodes via the plurality of connection terminals. A piezoelectric actuator comprising:
The first common wiring and the second common wiring are arranged so as not to overlap each other when viewed from the stacking direction,
In the piezoelectric layer, a plurality of through holes are formed in a portion facing at a plurality of locations separated from each other in at least one of the first common wiring and the second common wiring,
At least one common electrode of the first common electrode and the second common electrode is drawn to the surface of the piezoelectric body by the at least one common wiring and the plurality of through holes at the plurality of locations. A piezoelectric actuator connected to the connection terminal.   3. The piezoelectric actuator according to claim 1, wherein the first common wiring and the second common wiring are arranged on different surfaces of the plurality of piezoelectric layers. 4. The first common electrode is led out to the first surface on the first common electrode side of the two common electrodes of the piezoelectric body by the first common wiring and a plurality of through holes,
The said 2nd common electrode is withdraw | derived by the said 2nd common wiring and the several through hole in the 2nd surface facing the said 1st surface among the surfaces of the said piezoelectric material. 4. The piezoelectric actuator according to any one of 3.   5. The piezoelectric actuator according to claim 1, wherein the plurality of connection terminals are arranged on the surface of the piezoelectric body at positions facing the plurality of through holes. On the surface of the piezoelectric layer from which the at least one common electrode is drawn by the through hole, a surface wiring for connecting the through holes is disposed,
The piezoelectric actuator according to claim 1, wherein the plurality of connection terminals are arranged on the surface wiring.

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