JP6525070B2 - Piezoelectric actuator - Google Patents

Description

  The present invention relates to a piezoelectric actuator having a structure in which a piezoelectric layer is sandwiched between individual electrodes and a common electrode.

  In Patent Document 1, a piezoelectric layer is stacked on a top plate (diaphragm) disposed at the upper end of a flow path unit, and an individual electrode opposed to a pressure chamber is disposed on one surface of these piezoelectric layers. And the other surface describes a piezoelectric actuator in which a first constant potential electrode facing substantially the center of the individual electrode and a second constant potential electrode facing both ends in the short direction of the individual electrode are disposed. It is done. In the piezoelectric actuator having such a configuration, the portion facing the individual electrode and the first constant potential electrode of the piezoelectric layer, and the portion facing the individual electrode and the second constant potential electrode are simultaneously deformed, The portion of the piezoelectric layer and the diaphragm facing the pressure chamber is deformed, whereby the deformation of the portion facing the pressure chamber with the piezoelectric layer propagates to the portion facing the other pressure chamber. It is possible to prevent cross talk.

  Further, in Patent Document 2, the piezoelectric layer is laminated on the upper surface of the diaphragm, and an individual electrode is disposed in a portion facing the pressure chambers arranged in two rows along one direction in the surface on the diaphragm side of the piezoelectric layer. And a common electrode extending continuously across a plurality of pressure chambers on the surface of the piezoelectric layer opposite to the diaphragm, and a wire connected to these electrodes is vibrated. A piezoelectric actuator is described which is drawn to the top of the plate and connected to a driver IC, which is also arranged on the top of the diaphragm. And, in the piezoelectric actuator having such a configuration, the wiring connected to a large number of individual electrodes is drawn on the same plane as the individual electrodes are arranged and connected to the driver IC. The reliability of the connection between the individual electrode and the driver IC is enhanced.

JP, 2009-96173, A (FIG. 16) Japanese Patent Application Publication No. 2006-6096

  The inventor of the present application has considered the piezoelectric actuator in which the wiring connected to the two types of common electrodes is drawn out to the upper surface of the diaphragm from the piezoelectric actuator described in Patent Documents 1 and 2 above and connected to the driver IC. . In the piezoelectric actuator having such a configuration, as described in Patent Document 1, crosstalk can also be prevented, and furthermore, the two types of common electrodes are disposed on the side opposite to the diaphragm of the piezoelectric layer. In addition, if a plurality of individual electrodes are disposed on the surface of the piezoelectric layer on the diaphragm side, the wiring connected to a large number of individual electrodes is disposed as in the case described in Patent Document 2, and the individual electrodes are disposed. Therefore, the connection between the individual electrodes and the driver IC is enhanced.

  Here, in the piezoelectric actuator, it is preferable that the potential of the common electrode be uniform in all the portions in order to equalize the drive characteristics of the portions corresponding to the respective pressure chambers. When a wire is connected to one place with respect to the common electrode, the voltage drops at the common electrode as the distance electrically connected from the portion connected to the wire increases. In order to suppress this voltage drop, in the common electrode, it is necessary to connect wires to a plurality of places separated from each other.

  Further, since the two types of common electrodes are provided corresponding to the pressure chambers (individual electrodes) arranged in two rows in one direction, at least one of the two types of common electrodes is The two parts corresponding to the individual electrodes of the column are arranged apart from each other with the other common electrode in the direction orthogonal to the one direction. Therefore, in order to equalize the potential between the two parts separated from each other, the parts need to be conducted to each other.

  When it is assumed that the common electrode having the parts separated from each other does not have a part for conducting these parts, two types of common electrodes are mutually separated on the surface on which the common electrode of the piezoelectric layer is disposed. It is possible to connect the wiring to the remote part. However, in this case, there is a possibility that the potential variation may occur between the mutually separated portions.

  An object of the present invention is to have a configuration in which two types of common electrodes held at different potentials are arranged on the same surface of the piezoelectric layer, and the potentials of the two types of common electrodes are respectively all parts It is to provide a piezoelectric actuator that can be made uniform.

  A piezoelectric actuator according to a first aspect of the present invention includes: a diaphragm; a piezoelectric layer stacked on the diaphragm; a plurality of individual electrodes disposed on one surface of the piezoelectric layer; and the plurality of piezoelectric layers A plurality of first common electrodes and second common electrodes disposed on the surface opposite to the individual electrodes and held at different potentials, and disposed on the diaphragm and connected to the first common electrodes And a plurality of first connection wires respectively connecting the first common electrode and the plurality of first wiring portions, and a plurality of wires disposed on the diaphragm and connected to the second common electrode. And a plurality of second connection wires respectively connecting the second common electrode and the plurality of second wiring portions, and the plurality of individual electrodes are arranged in two rows along one direction. The first common electrodes are arranged in the plurality of individual A plurality of first opposing portions facing a portion in each of the first and second connecting portions respectively connecting the plurality of first opposing portions to each other, and the second common electrode includes the plurality of individual electrodes A plurality of second facing portions facing each other and a second connection portion respectively connecting the plurality of second facing portions to each other, and the plurality of first connection wires The plurality of second connection wires are connected to each other at a plurality of places separated from each other in the first connection portion, and the plurality of second connection wires are connected to a plurality of places separated from each other at the second connection portion At least one of which is disposed to connect the first connection portion and the first wiring portion across the second connection portion, or at least one of the second connection wires is connected to the first connection portion. Straddle And it is characterized in that it is arranged to connect the second wiring portion and the second connecting portion.

  According to this, the first connection wiring that connects the first connection portion and the first wiring portion across the second connection portion, or the second connection portion and the second wiring portion that cross the first connection portion By providing any of the second connection wires, it is possible to connect the first and second connection wires to a plurality of mutually separated places of the first and second common electrodes disposed on the same surface of the piezoelectric layer, The potentials of the first and second common electrodes can be made uniform.

  A piezoelectric actuator according to a second aspect of the present invention is the piezoelectric actuator according to the first aspect, wherein at least one of the first connection wires straddles the second connection portion, and the first connection portion and the first wiring The first connection wiring and the second connection part are separated via an insulating material, or at least one of the second wiring members is the first connection wiring and the second connection part. It is arranged to connect the second connection portion and the second wiring portion across the connection portion, and the second wiring member and the first connection portion are separated via the insulating material. It is characterized by

  According to this, when the first connection wire straddles the second connection portion, the first connection wire and the second connection portion are separated via the insulating material, and thus the first connection wire and the second connection portion are separated. Conduction to the connection portion can be prevented, and when the second connection wire straddles the first connection portion, the first connection portion and the second connection wire are separated via the insulating material. Because of this, it is possible to prevent the first connection wiring and the second connection portion from conducting.

  A piezoelectric actuator according to a third aspect of the present invention is the piezoelectric actuator according to the second aspect, further comprising: an insulating layer disposed on the surface of the piezoelectric layer opposite to the plurality of individual electrodes, A layer covering the second connection portion, and a portion of the at least one of the plurality of first connection wirings straddling the second connection portion is a surface of the insulating layer opposite to the piezoelectric layer A portion which is disposed on the upper side or which the insulating layer covers the first connection portion and which straddles the first connection portion in the at least one of the plurality of second connection wirings It is characterized in that it is disposed on the surface of the insulating layer opposite to the piezoelectric layer.

  According to this, when the first connection wire straddles the second connection portion, the insulating layer is disposed between the first connection wire and the second connection portion, and the second connection wire is the first connection portion. Since the insulating layer is disposed between the first connection portion and the second connection wiring, the thickness of the piezoelectric actuator can be reduced.

  A piezoelectric actuator according to a fourth aspect of the present invention includes a diaphragm, a piezoelectric layer stacked on the diaphragm, a plurality of individual electrodes disposed on one surface of the piezoelectric layer, and the plurality of piezoelectric layers. A plurality of first common electrodes and second common electrodes disposed on the surface opposite to the individual electrodes and held at different potentials, and disposed on the diaphragm and connected to the first common electrodes A first wiring portion, a plurality of first connection wires connecting the first common electrode and the first wiring portion, and a plurality of second wiring portions disposed on the diaphragm and connected to the second common electrode A wiring portion, and a plurality of second connection wires connecting the second common electrode and the second wiring portion are provided, and the plurality of individual electrodes are arranged in two rows along one direction. The first common electrode is a part of each of the plurality of individual electrodes A plurality of opposing first opposing parts and two or more third connection parts respectively connecting at least two of the first opposing parts to one another are provided, and the second common electrode is a part of the plurality of individual electrodes. Each of the plurality of second opposing portions facing each other and the second connecting portion connecting the plurality of second opposing portions to each other, and each of the third connecting portions includes the second connecting portion. A first connection wiring is connected, and connection points between the plurality of first connection wirings and the two or more third connection parts are separated from each other, and the plurality of second connection wirings are the second The two or more third connection portions are connected to each other at a plurality of mutually separated places in the connection portion, and are connected to each other via a bypass wiring extending across the second common electrode. It is.

  According to this, in the first common electrode, the first connection wiring is connected to a plurality of places separated from each other, and two or more first connection parts are connected via the bypass wiring extending across the second common electrode. Because they are connected to each other, their potentials become uniform. Further, in the second common electrode, since the second connection wiring is connected to a plurality of places separated from each other, the potential becomes uniform.

  A piezoelectric actuator according to a fifth invention is the piezoelectric actuator according to the fourth invention, characterized in that the bypass wiring is isolated from the second common electrode through an insulating material. .

  According to this, since the insulating material is disposed between the bypass wiring and the second common electrode, the conduction between the bypass wiring and the second common electrode can be prevented.

  A piezoelectric actuator according to a sixth aspect of the present invention is the piezoelectric actuator according to the fifth aspect, wherein the piezoelectric actuator is disposed on the surface of the piezoelectric layer opposite to the plurality of individual electrodes, and at least one of the second common electrodes. The device further includes an insulating layer covering a portion, and the bypass wiring is disposed on the surface of the insulating layer opposite to the piezoelectric layer.

  According to this, since the insulating layer is disposed between the bypass wiring and the second common electrode, the thickness of the piezoelectric actuator can be reduced.

  A piezoelectric actuator according to a seventh aspect of the present invention is the piezoelectric actuator according to any of the first to fourth aspects, wherein the plurality of individual electrodes are disposed on the surface of the piezoelectric layer on the diaphragm side. A wiring portion connected to the plurality of individual electrodes, the first wiring portion, and the second wiring portion are connected to a driver IC disposed on the surface on the piezoelectric layer side of the diaphragm. It is said that.

  According to this, since the surface on the diaphragm side of the piezoelectric layer and the surface on the piezoelectric layer side of the diaphragm are surfaces at the same position in the stacking direction, wiring portions connected to many individual electrodes However, it will be pulled out in the same plane as the individual electrodes are formed, which will increase the reliability of the connection between the individual electrodes and the wiring.

  According to the present invention, the potentials of the first common electrode and the second common electrode disposed on the same surface of the piezoelectric layer can be made uniform.

FIG. 1 is a schematic configuration diagram of a printer according to a first embodiment. It is a top view of the ink jet head of FIG. It is a top view of the upper surface of the diaphragm in FIG. It is a top view of the upper surface of the piezoelectric layer in FIG. 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. It is a figure equivalent to FIG. 4 of the modification 1. FIG. It is a figure equivalent to FIG. 6 of the modification 2. FIG. It is a figure equivalent to FIG. 6 of the modification 3. FIG. It is a figure equivalent to FIG. 4 of the modification 4. FIG. It is a figure equivalent to FIG. 4 in 2nd Embodiment. It is a figure equivalent to FIG. 4 of the modification 5. FIG.

First Embodiment
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 first embodiment. As shown in FIG. 1, the printer 1 includes a carriage 2, an inkjet head 3, a conveyance roller 4, and the like. The carriage 2 reciprocates along a guide shaft 5 extending in the scanning direction (left and right direction in FIG. 1). The inkjet head 3 is disposed on the lower surface of the carriage 2 and ejects ink from the nozzles 15 (see FIG. 2) disposed on the lower surface. The conveyance roller 4 conveys the recording sheet P in the sheet feeding direction (front direction in FIG. 1).

  Then, in the printer 1, printing is performed on the recording sheet P by discharging the ink from the inkjet head 3 reciprocatingly moving in the scanning direction with the carriage 2 to the recording sheet P conveyed in the sheet feeding direction by the conveyance roller 4. . Further, the recording sheet P for which printing has been completed is discharged by being conveyed in the sheet feeding direction by the conveyance roller 4.

  Next, the inkjet head 3 will be described. FIG. 2 is a plan view of the ink jet head 3 of FIG. FIG. 3 is a plan view of the upper surface of a diaphragm 41 described later in FIG. FIG. 4 is a plan view of the upper surface of the piezoelectric layer 42 described later in FIG. In order to make the positional relationship easy to understand, in FIG. 3, a piezoelectric layer 42 described later is disposed, and in FIG. 4, a piezoelectric layer 42 described later is disposed on the upper surface of the through hole 46a of the insulating layer 46 and the insulating layer 46 of the wiring 47e. The respective parts are indicated by two-dot chain lines.

  The inkjet head 3 is disposed on the upper surface of the flow path unit 31 in which the ink flow path including the pressure chamber 10 and the nozzle 15 is formed, and the flow path unit 31 and applies pressure to the ink in the pressure chamber 10 And a piezoelectric actuator 32.

  The flow path unit 31 is formed by laminating four plates of the cavity plate 21, the base plate 22, the manifold plate 23 and the nozzle plate 24 as shown in FIGS. 5 and 6. Among the four plates 21 to 24, the three plates 21 to 23 excluding the nozzle plate 24 are made of a metal material such as stainless steel, and the nozzle plate 24 is made of a synthetic resin material such as polyimide. Alternatively, the nozzle plate 24 may also be made of the same metal material as the other three plates 21-23.

  In the cavity plate 21, a plurality of pressure chambers 10 and an ink supply port 9 (see FIG. 2) are disposed. The pressure chambers 10 have a substantially elliptical planar shape whose longitudinal direction is the scanning direction (left and right direction in FIG. 2), and are arranged in two rows along the paper feeding direction (one direction). In the base plate 22, substantially circular through holes 12 and 13 are disposed at portions opposed to both end portions of the plurality of pressure chambers 10 in the scanning direction. Further, the ink supply port 9 is formed at a position communicating with a manifold channel 11 described later.

  A manifold channel 11 extending in the paper feeding direction (vertical direction in FIG. 2) is formed in the manifold plate 23 so as to overlap approximately half of the through holes 12 in the scanning direction of the pressure chambers 10 in each row. Here, the ink is supplied to the manifold channel 11 from the ink supply port 9. Further, a substantially circular through hole 14 is formed in the manifold plate 23 at a portion overlapping with the through hole 13. Nozzles 15 are formed in the nozzle plate 24 at portions overlapping the through holes 14.

  In the flow path unit 31, the manifold flow path 11 communicates with the pressure chamber 10 through the through hole 12, and the pressure chamber 10 communicates with the nozzle 15 through the through holes 13 and 14. As described above, in the flow path unit 31, a plurality of individual ink flow paths extending from the outlet of the manifold flow path 11 through the pressure chamber 10 to the nozzle 15 are formed.

  The piezoelectric actuator 32 includes a diaphragm 41, a piezoelectric layer 42, a plurality of individual electrodes 43, common electrodes 44 and 45, an insulating layer 46, and a plurality of wires 47.

  The vibrating plate 41 is disposed on the upper surface of the cavity plate 21 so as to cover the plurality of pressure chambers 10. The diaphragm 41 is made of, for example, a ceramic material such as alumina, zirconia, or PZT described later, or a metal material such as stainless steel. However, when the diaphragm 41 is made of a metal material, the ceramic material is formed on the upper surface of the diaphragm 41 in order to prevent conduction between the conductive diaphragm 41 and the individual electrodes 43 and the wiring 47 described later. And the like, and the individual electrode 43 and the wiring 47 need to be arranged on the insulating layer (not shown).

  The piezoelectric layer 42 is made of a piezoelectric material (PZT) mainly composed of lead zirconate titanate which is a mixed crystal of lead titanate and lead zirconate. The piezoelectric layer 42 is disposed on the upper surface of the diaphragm, and extends continuously across the portions facing the plurality of pressure chambers 10.

  The plurality of individual electrodes 43 are disposed on the upper surface (the lower surface (one surface) of the piezoelectric layer 42) of the diaphragm 41 in correspondence with the plurality of pressure chambers 10. The plurality of individual electrodes 43 have a substantially elliptical planar shape slightly larger than the pressure chamber 10, and are disposed so as to completely cover the plurality of pressure chambers 10. Thus, the plurality of individual electrodes 43 are arranged in two rows in the paper feeding direction, as with the plurality of pressure chambers 10. The plurality of individual electrodes 43 are connected to the driver IC 50 as described later, and the driver IC 50 selectively applies either a ground potential or a predetermined positive potential (for example, about 20 V). .

  The common electrode 44 (first common electrode) is disposed on the upper surface of the piezoelectric layer 42, and is connected to the driver IC 50 as described later, and is always kept at the ground potential by the driver IC 50. In addition, the common electrode 44 includes a plurality of facing portions 44 a (first facing portions), two connection portions 44 b, and a connection portion 44 c. In the present embodiment, the combination of the two connection portions 44 b and the connection portion 44 c corresponds to the first connection portion according to the present invention.

  The plurality of facing portions 44a have a substantially elliptical planar shape which is slightly smaller than the pressure chamber 10, and are disposed to face substantially central portions (portions) of the plurality of pressure chambers 10 (individual electrodes 43) ing. Thus, the plurality of facing portions 44a are arranged in two rows in the paper feeding direction, similarly to the plurality of individual electrodes 43. The two connection portions 44b respectively extend in the paper feeding direction (one direction), and the left end portions of the plurality of facing portions 44a forming the left side row, and the plurality of facing portions forming the right side row The right ends of 44a are connected together. The connecting portion 44c extends in the scanning direction, and connects the upper ends of the two connecting portions 44b.

  The common electrode 45 (second common electrode) is disposed in a region surrounded by the two connecting portions 44 b and the coupling portion 44 c on the same upper surface of the piezoelectric layer 42 as the common electrode 44 is disposed, A plurality of facing parts 45a (second facing parts) and a connecting part 45b (second connecting parts) are provided. The plurality of facing portions 45 a are disposed to face the outer portion of the portion of the pressure chamber 10 facing the common electrode 44. The connecting portion 45 b is a portion of the common electrode 45 excluding the plurality of facing portions 45 a, and connects the plurality of facing portions 45 a to each other.

  Further, the common electrode 45 is connected to the driver IC 50 as described later, and is always held at the predetermined positive potential by the driver IC 50.

  Here, in the piezoelectric layer 42 described above, a portion sandwiched between the individual electrode 43 and the common electrode 44 (opposite portion 44a), and a portion sandwiched between the individual electrode 43 and the common electrode 45 (opposite portion 45a) Is polarized in the thickness direction of the piezoelectric layer 42.

  The insulating layer 46 is made of an insulating material such as a ceramic material such as alumina, zirconia, or PZT, or a synthetic resin material, and is disposed over substantially the entire upper surface of the piezoelectric layer 42 so as to cover the common electrodes 44 and 45 There is. The common electrode 44 and the common electrode 45 are disposed close to each other on the upper surface of the same piezoelectric layer 42, but the insulating layer 46 covering them is disposed, whereby the materials forming the electrodes cause migration. Thus, conduction between the common electrode 44 and the common electrode 45 is prevented. In the insulating layer 46, a substantially circular through hole 46a filled with a conductive material is formed in a portion facing the upper right end in the common electrode 45 of FIG.

  The plurality of wirings 47 are a plurality of wirings 47 a individually connected to the plurality of individual electrodes 43, two wirings 47 b and 47 c connected to the common electrode 44, and two wirings 47 d connected to the common electrode 45, 47e, one end of each of these wires 47 is connected to each of the electrodes 43, 44, 45, and the other end is a driver similarly disposed on the diaphragm 41 on the diaphragm 41. IC50 is connected. In FIGS. 2 to 4, only a portion in the vicinity of the connection portion with the electrodes 43-45 and a portion in the vicinity of the connection portion with the driver IC 50 among the plurality of wires 47 are illustrated. The illustration is omitted.

  More specifically, the wires 47a to 47e have one end connected to the end of the individual electrode 43 opposite to the nozzle 15 in the scanning direction, and from this portion, the individual electrode 43 is arranged The other end is connected to the driver IC 50 by drawing around the upper surface of the diaphragm 41 located on the same plane as the one shown in FIG.

  Here, among the interconnections 47, the interconnections 47a individually provided for the individual electrodes 43 have the largest number, but the interconnections 47a are routed on the same plane as the individual electrodes 43 are disposed. Because the driver IC 50 is connected, disconnection is less likely to occur and connection reliability is enhanced.

  One end of each of the two wires 47b and 47c is connected to the upper end of the left connection portion 44b and the right connection portion 44b in FIG. 2 on the upper surface of the piezoelectric layer 42, and from this connection portion Each is drawn to the upper surface of the diaphragm 41 through the left and right side surfaces in FIG. 2 of the piezoelectric layer 42, and is further drawn around the diaphragm 41, and the other end is connected to the driver IC 50. . In the present embodiment, of the two wires 47b and 47c, the portion disposed on the upper surface of the diaphragm 41 corresponds to the first wire portion according to the present invention, and the first wire portion and the connection portion 44b. And a portion connecting them to each other corresponds to a first connection wiring according to the present invention.

  The wiring 47d is connected at one end thereof to the lower left end portion (connection portion 45b) of the common electrode 45 in FIG. 2 on the upper surface of the piezoelectric layer 42, and from this connection portion to the lower side of FIG. It is drawn to the upper surface of the diaphragm 41 through the side surface of the side, and the upper surface of the diaphragm 41 is drawn around, and the other end is connected to the driver IC 50.

  The wire 47e has one end located on the upper surface (the surface opposite to the piezoelectric layer 42) of the insulating layer 46 in a portion facing the through hole 46a, with the conductive material filled in the through hole 46a. 2 and the upper surface of the insulating layer 46 is insulated from the connection portion over the connecting portion 44c of the common electrode 44 from the connection portion to the upper portion of FIG. It extends to the upper end of layer 46 in FIG.

  The wire 47e is further drawn to the upper surface of the diaphragm 41 through the side surfaces of the insulating layer 46 and the piezoelectric layer 42, as shown in FIG. Are connected to the driver IC 50.

  In the present embodiment, of the wires 47d and 47e, the portion disposed on the upper surface of the diaphragm 41 corresponds to the second wire portion according to the present invention, and the second wire portion and the common electrode 45 The portion connecting to the connecting portion 45 b) corresponds to the second connection wiring according to the present invention. In the first embodiment, as described above, the second connection wiring extends over the first connection portion.

  Here, unlike the wires 47a connected to the individual electrodes 43, the wires 47b to 47e connected to the common electrodes 44 and 45 are located at different heights from the connecting portions with the respective electrodes and the connecting portions It is drawn out to the upper surface of the diaphragm 41. In other words, the first and second connection wires connected to the first and second wiring portions have a height (the lamination of the diaphragm 41 and the piezoelectric layer 42) that the first and second wiring portions are disposed. Positions in the direction) are placed on different planes. Therefore, the connection reliability is lower than that of the wiring 47a. However, as described above, since the two wires 47 b and 47 c are connected to the common electrode 44 and the two wires 47 d and 47 e are connected to the common electrode 45, either of the two wires is temporarily Even if there is a break, the potential of the electrode will not fluctuate significantly, and the piezoelectric actuator 32 can not be driven.

  Further, it is possible to improve the connection reliability by further increasing the number of wires connected to the common electrodes 44 and 45. Even in this case, the number of wires connected to a large number of individual electrodes 43 can be increased. It is easier than increasing it.

  Here, a method of driving the piezoelectric actuator 32 will be described. In the piezoelectric actuator 32, the plurality of individual electrodes 43 are previously held at the ground potential. In this state, a potential difference is generated between the individual electrode 43 and the common electrode 45 (opposite portion 45a), and in the portion of the piezoelectric layer 42 sandwiched by these electrodes, an electric field in the direction parallel to the polarization direction It is happening. Thereby, this portion of the piezoelectric layer 42 is contracted in the horizontal direction orthogonal to the direction of the electric field, and as a result, the portion of the diaphragm 41, the piezoelectric layer 42 and the insulating layer 46 facing the pressure chamber 10 as a whole The pressure chamber 10 is deformed so as to be convex on the opposite side, and the volume of the pressure chamber 10 is larger than that in the non-deformed state.

  When driving the piezoelectric actuator 32, any potential of the plurality of individual electrodes 43 is switched from the ground potential to a predetermined positive potential. Then, the portion of the piezoelectric layer 42 sandwiched between the individual electrode 43 and the common electrode 45 returns to the state before contraction. On the other hand, an electric field in a direction parallel to the polarization direction is generated in a portion sandwiched between the individual electrode 43 of the piezoelectric layer 42 and the common electrode 44 (opposite portion 44a), and this portion of the piezoelectric layer 42 is orthogonal to the direction of the electric field. Shrink in the horizontal direction. As a result, the portion of the diaphragm 41, the piezoelectric layer 42, and the insulating layer 46 facing the corresponding pressure 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 is increased, and the ink is discharged from the nozzle 15 communicating with the pressure chamber 10. Then, after discharging the ink, the potential of the individual electrode 43 is switched from the predetermined positive potential to the ground potential, and the piezoelectric actuator 32 is returned to the initial state.

  At this time, in the piezoelectric actuator 32, when the potential of the individual electrode 43 is switched from the ground potential to a predetermined positive potential, a portion of the piezoelectric layer 42 sandwiched between the individual electrode 43 and the facing portion 44a contracts in the horizontal direction. At the same time, the portion of the piezoelectric layer 42 sandwiched between the individual electrode 43 and the facing portion 45a expands from a contracted state to a state before contraction. Thereby, the contraction and the expansion of the piezoelectric layer 42 absorb each other, and as a result, the deformation of the portion of the piezoelectric layer 42 facing the pressure chamber 10 faces the other pressure chamber 10 So-called crosstalk can be prevented.

  Here, in order to make the volume and discharge speed of ink droplets discharged from each nozzle 15 uniform when the piezoelectric actuator 32 is driven, it is necessary to make the electric field generated in the piezoelectric layer 42 uniform. For this purpose, it is necessary to make the potentials of the common electrodes 44 and 45 uniform in all parts. Assuming that each of the common electrodes 44 and 45 is connected to the wiring 47 at only one place, the common electrodes 44 and 45 are relatively large-sized provided across the plurality of pressure chambers 10 (individual electrodes 43). It is difficult to make the potential uniform in all parts of the common electrodes 44 and 45 because the That is, as the distance from the portion connected to the wiring 47 is increased, the potential of the common electrodes 44 and 45 drops. Therefore, in order to make the potential uniform, as described above, it is necessary to connect the wirings 47 (first and second connection wirings) to a plurality of places separated from each other of the common electrodes 44 and 45.

  Furthermore, with regard to the common electrode 44, since the two connection portions 44b are disposed apart from each other in the scanning direction, it is necessary to connect the two connection portions 44b to each other in order to make the potential of the common electrode 44 uniform. There is.

  However, the wirings 47 connected to a plurality of mutually separated common electrodes 44 and 45 are all connected to the common electrodes 44 and 45 on the upper surface of the piezoelectric layer 42, and the two connecting portions 44 b are formed on the upper surface of the piezoelectric layer 42 It is difficult to connect them together.

  Specifically, as in the present embodiment, the individual electrode 44 has the connecting portion 44c, and the two connecting portions 44b are connected to each other by the connecting portion 44c on the upper surface of the piezoelectric layer 42. The potential is uniform between the two connections 44b. However, in this case, since the common electrode 45 is surrounded on three sides by the two connection portions 44 b and the connection portion 44 c, the lower end portion of the common electrode 45 is the wire 47 connected to the common electrode 45. Will only connect to In this case, the potential may drop at the upper end portion of the common electrode 45 separated from the connection portion with the wiring 47.

  On the other hand, if the common electrode 44 does not have the connection portion 44c, the wiring 47 is connected to the upper end portion and the lower end portion of the common electrode 45 (connection portion 45b) on the upper surface of the piezoelectric layer 42, and the potential of the common electrode 45 is uniform. It can be However, in this case, since the two connection portions 44b are not connected to each other, there is a possibility that the potential variation may occur between the two connection portions 44b.

  On the other hand, in the present embodiment, as described above, for the common electrode 44, the two connection portions 44b are connected by the connecting portion 44c, and for the common electrode 45, the lower end portion of the connection portion 45b Since the wire 47 d is connected, and a wire 47 e (second connection wire) extending across the connection portion 44 b on the upper surface of the insulating layer 46 is connected to the upper end portion of the connection portion 45 b, the common electrode 44, The 45 potentials can be made uniform.

  In addition, since the wire 47e connected to the common electrode 45 across the connecting portion 44c is disposed on the upper surface of the insulating layer 46 covering the common electrodes 44 and 45, the wire 47c is electrically connected to the connecting portion 44c. Can be prevented.

  Next, modified examples in which various modifications are added to the first embodiment will be described. However, the same reference numerals are given to components having the same configuration as the present embodiment, and the description thereof will be omitted as appropriate.

  In one modification (Modification 1), as shown in FIG. 7, the common electrode 44 further includes a connecting portion 44 d that connects the lower end portions of the two connecting portions 44 b. The four sides are surrounded by two connecting portions 44b and two connecting portions 44c and 44d.

  In addition, a wire 47f is provided instead of the wire 47d, and one end of the wire 47f is filled in a through hole 46b formed in a portion of the insulating layer 46 facing the common electrode 45 at the lower left end in FIG. It is connected to the lower left end of the common electrode 45 via a conductive material, and extends downward from the connecting portion over the connecting portion 44 d over the upper surface of the insulating layer 46 (see FIG. 5).

  When the common electrode 45 is surrounded in four directions by the two connection portions 44b and the two connection portions 44c and 44d, wiring can not be connected to the common electrode 45 on the upper surface of the piezoelectric layer 42. Even in such a case, the wirings are connected to the mutually separated portions of the common electrode 45 by providing the wirings 47e and 47f extending across the coupling portions 44c and 44d for all the wirings connected to the common electrode 45. The potential of the common electrode 45 can be made uniform.

  In this case, in addition to the upper end portions of the two connection portions 44b being connected to each other by the connection portion 44c, the lower end portions of the two connection portions 44b are connected to each other by the connection portion 44d. The potential of the electrode 44 is further uniformed.

  Further, in the first embodiment, the insulating layer 46 disposed on the upper surface of the piezoelectric layer 42 so that the portion (second connection wire) extending across the connecting portion 44 c of the wire 47 e covers the entire common electrodes 44 and 45. It was placed on the top of the, but not limited to this.

  In another modification (Modification 2), as shown in FIG. 8, the insulating layer 81 is disposed on the upper surface of the piezoelectric layer 42 so as to cover only the connecting portion 44c, and the connecting portion 44c of the wiring 47e is formed. An extending portion is disposed on the upper surface of the insulating layer 81. Furthermore, another insulating layer 82 is disposed on the top surface of the piezoelectric layer 42 on which the above portions of the insulating layer 81 and the wiring 47 e are disposed so as to cover the common electrodes 44 and 45. The conduction of the common electrode 44 and the common electrode 45 on the upper surface of the electrode 42 is prevented.

  Even in this case, the insulating layer 81 can prevent conduction between the wiring 47 e and the coupling portion 44 c.

  In another modification (Modification 3), as shown in FIG. 9, the through hole 46a of the insulating layer 46 is not filled with a conductive material, and a portion of the common electrode 45 exposed from the through hole 46a ( One end and the other end of the wire bonding wire 91 are respectively connected to the connecting portion 45b) and the wiring 47g disposed on the upper surface of the diaphragm 41, whereby the common electrode 45 and the wiring 47g are connected. ing. Furthermore, in order to prevent peeling of the wire bonding wire 91, an insulation made of synthetic resin material or the like is formed by potting so as to cover the wire bonding wire 91 including the connection portion with the common electrode 45 and the wiring 47g. Material 92 is disposed. In this case, the wiring 47g corresponds to a second wiring portion according to the present invention, and the wire bonding wire 91 corresponds to a second connection wiring according to the present invention.

  Here, in order to connect the wire bonding wire 91 to the common electrode 45 and the wire 47g, for example, one end and the other end of the wire bonding wire 91 are respectively pressed against the portion of the common electrode 45 and the wire 47g While pressure is applied, the ultrasonic wave is applied to the abutted portion. As a result, these portions are alloyed to connect the wire bonding wire 91 to the common electrode 45 and the wiring 47g.

  Even in this case, the wire bonding wire 91 can connect the portion surrounded by the connection portion 44b (see FIG. 4) of the common electrode 45 and the connection portion 44c to the wiring 47g, as in the first embodiment. The potential of the common electrode 45 can be made uniform.

  When the insulating material 92 is formed by potting, the insulating material 92 also flows into the lower portion of the wire bonding wire 91, so the portion of the insulating layer 46 that covers the connecting portion 44c may not be present. Furthermore, since the wire bonding wire 91 is disposed in a state of being separated from the connecting portion 44c, the insulating material 92 may not be formed.

  In the first embodiment and the first to third modifications, the wires 47e, 47f, and 47g and the wire bonding wire 91 straddle the connecting portions 44c and 44d, but these straddle any of the two connecting portions 44b. It may be.

  Further, in the first embodiment, the common electrode 44 (first common electrode) is provided with two connection portions 44b provided corresponding to the arrangement of the individual electrodes 43 in two rows, and these two connection portions Although it has the connection part 44c which connects 44b, and the common electrode 45 (2nd common electrode) was surrounded by the two connection parts 44b and the connection part 44c, it is not restricted to this .

  In another modification (Modification 4), as shown in FIG. 10, common electrodes 74, 75 are disposed on the top surface of the piezoelectric layer 42 instead of the common electrodes 44, 45. The common electrode 74 (first common electrode) includes a plurality of facing portions 74 a (first facing portion) and a connection portion 74 b (first connection portion) connecting the plurality of facing portions 74 a to each other.

  The common electrode 75 (second common electrode) is disposed so as to surround the common electrode 74, and a connection portion 75b (a first common electrode) that connects the plurality of facing portions 75a (second facing portion) and the plurality of facing portions 75a to each other. 2) connection portion).

  Wirings 47h and 47i are connected to the common electrode 74 at the upper end and the lower end of the connection portion 74b, and the common electrode 75 is connected to the upper right end and the lower left end (connection portion 75b), respectively. , And the wires 47j and 47k are connected.

  The wires 47h and 47i have a conductive material filled in the through holes 46c and 46d, the ends of which are formed in portions of the insulating layer 46 (see FIG. 5) facing the upper and lower ends of the connection portion 74b. The connection portion 74b is connected to the upper end portion and the lower end portion, and the upper surface of the insulating layer 46 extends from the connection portion upward and to the left in the figure so as to straddle the common electrode 75 (connection portion). Further, it passes through the upper and left side surfaces of the insulating layer 46 and the piezoelectric layer 42 in the drawing, and is drawn to the upper surface of the diaphragm 41.

  The wires 47j and 47k have their one ends connected to the above-mentioned portion of the common electrode 75 on the upper surface of the piezoelectric layer 42 and vibrate through the right and lower side surfaces of the piezoelectric layer 42 in the figure. It is pulled out to the upper surface of the plate 41.

  Then, like the other wires in the first embodiment, the wires 47 h to 47 k drawn to the upper surface of the diaphragm 41 are drawn around the upper surface of the diaphragm 41 and the other end is connected to the driver IC 50.

  In the fourth modification, among the wires 47h and 47i, the portion disposed on the upper surface of the diaphragm 41 corresponds to the first wiring portion according to the present invention, and the first wiring portion is disposed across the common electrode 75; A portion connecting the upper end portion and the lower end portion of the connection portion 74b corresponds to a first connection wiring according to the present invention. Further, of the wires 47j and 47k, a portion disposed on the upper surface of the diaphragm 41 corresponds to a second wiring portion according to the present invention, and a piezoelectric layer 42 connecting the second wiring portion and the common electrode 45. The portion passing through the side surface of corresponds to the second connection wiring according to the present invention. And in the modification 4, as above-mentioned, the 1st connection wiring is extended over the 2nd connection part.

  Also in this case, since the wirings 47h to 47k are connected to the mutually separated portions of the common electrodes 74 and 75, the potentials of the common electrodes 74 and 75 can be made uniform.

Second Embodiment
Next, a second embodiment of the present invention will be described. However, since the second embodiment is different from the first embodiment only in part of the configuration of the piezoelectric actuator, only the differences from the first embodiment will be described below.

  FIG. 11 is a view corresponding to FIG. 4 of the second embodiment. As shown in FIG. 11, in the second embodiment, the common electrode 44 does not have the connecting portion 44c (see FIG. 4) on the piezoelectric layer 42, and the two connection portions 44b are in the scanning direction (FIG. 11). In the left-right direction) and spaced apart from each other with the common electrode 45 interposed therebetween. Further, instead of the wire 47 e (see FIG. 4), a wire 47 l is connected to the common electrode 45.

  The wiring 47 l is connected at one end thereof to the upper right end (connection portion 45 b) of the common electrode 45 on the upper surface of the piezoelectric layer 42 and passes through the side surface of the piezoelectric layer 42 at the upper side in FIG. The upper surface of the diaphragm 41 is drawn around to be connected to the driver IC 50. A portion of the wiring 47l disposed on the upper surface of the diaphragm 41 corresponds to a first wiring portion according to the present invention, and a portion of the piezoelectric layer 42 connecting the first wiring portion and the common electrode 45. The portion passing through the side surface corresponds to the first connection wiring according to the present invention.

  In addition, a bypass wire 101 is disposed on the top surface of the insulating layer 46 (see FIG. 5). The bypass wire 101 extends in the scanning direction across the common electrode 45, and one end and the other end thereof are through holes 46e formed in portions of the two connecting portions 44b of the insulating layer 46 opposed to the upper end in the drawing. , 46f are respectively connected to the upper ends of the two connection portions 44b, whereby the two connection portions 44b are connected to each other by the bypass wiring 101.

  Even in this case, as in the first embodiment, on the upper surface of the piezoelectric layer 42, the wires 47d and 47l (second connection wires) are provided at the lower left end and the upper right end (plurality) of the common electrode 45 which are separated from each other. Therefore, the potential of the common electrode 45 becomes uniform.

  Furthermore, in the scanning direction, two connection portions 44 b arranged to be separated from each other with the common electrode 45 interposed therebetween are connected to each other by the bypass wiring 101 extending across the common electrode 45. Becomes uniform.

  Next, modified examples in which various modifications are added to the second embodiment will be described. However, the same reference numerals are given to components having the same configuration as the second embodiment, and the description thereof will be omitted as appropriate.

  In the second embodiment, the two connection portions 44b arranged to be separated from each other are connected by the bypass wiring 101, but the present invention is not limited to this.

  In one modification (Modification 5), as shown in FIG. 12, the common electrode 44 further includes a connecting portion 44 f that connects substantially central portions of the two connecting portions 44 b, thereby the common electrode 45. The connection portion 45b is divided into two parts separated from each other across the connection portion 44f in the vertical direction in the drawing.

  In this case, contrary to the second embodiment, the common electrode 45 corresponds to a first common electrode according to the present invention, and the common electrode 44 corresponds to a second common electrode according to the present invention. Further, each portion of the connection portion 45 b divided into two portions corresponds to a third connection portion according to the present invention. That is, the common electrode 45 has two third connection portions.

  Further, accordingly, in the fifth modification, the portion corresponding to the first wiring portion and the portion corresponding to the second wiring portion, and the portion corresponding to the first connection wiring and the portion corresponding to the second connection wiring However, each is opposite to the second embodiment.

  Furthermore, the bypass wiring 102 is disposed on the top surface of the insulating layer 46 (see FIG. 5). The bypass wire 102 extends in a direction slightly inclined with respect to the paper feeding direction (left and right direction in FIG. 12) across the connecting portion 44 f, and one end and the other end thereof are the above-mentioned 2 of the common electrode 45 in the insulating layer 46. The two parts of the connecting portion 45b are connected to each other through the conductive material filled in the two through holes 46g and 46h respectively formed in the two parts and the parts facing each other. Thus, the two parts of the connection portion 45 b are connected to each other by the bypass wiring 102.

  Also in this case, the potentials of the common electrodes 44 and 45 can be made uniform in all parts.

  Also in the second embodiment, instead of the bypass wiring 101 disposed on the upper surface of the insulating layer 46, the two connection parts 44b may be connected to each other by a wire bonding line similar to that of the third modification described above. .

  Further, in the second embodiment, although the bypass wiring 101 connects the upper ends of the two connection parts 44b, even if the bypass wiring 101 connects the other parts of the two connection parts 44b. Good. Also, two or more bypass lines may be provided.

  Further, in the second embodiment, the common electrode 44 (first common electrode) is provided with two connection parts 44 b (first connection parts) corresponding to the row of the individual electrodes 43, but the first connection part is As long as at least two first opposing portions are connected to each other, the present invention is not limited to being provided corresponding to the row of the individual electrodes 43. Further, the number of first connection portions is not limited to two, and the first common electrode may have three or more first connection portions. In addition, when there are three or more first connection parts, for example, by providing a plurality of bypass wires connecting two different ones of the three or more first connection parts, all the first connection parts may be provided. The parts can be conducted to one another.

  In the first and second embodiments described above, the plurality of individual electrodes 43 are disposed on the lower surface of the piezoelectric layer 42, and the common electrodes 44 and 45 are disposed on the upper surface of the piezoelectric layer 42. Conversely, the common electrodes 44 and 45 may be disposed on the lower surface of the piezoelectric layer 42, and the plurality of individual electrodes 43 may be disposed on the upper surface of the piezoelectric layer 42.

  In this case, for example, an insulating layer is disposed between the piezoelectric layer 42 and the diaphragm 41, and on the lower surface of the insulating layer, the connecting portions 44c and 44d among the wires 47e, 47f, 47h and 47i, and the common electrode A portion (first connection wiring and second connection wiring) extending over 75 and the bypass wiring 101 are disposed.

  In the first and second embodiments, the common electrode 44 (opposite portion 44a) is opposed to the substantially central portion of the pressure chamber 10, and the common electrode 45 (opposite portion 45a) is substantially the center of the pressure chamber 10. Although it opposed to parts other than the part, it is not restricted to this, for example, while the 2nd opposite part is opposite to the approximate center part of pressure chamber 10 conversely to this, the 1st opposite part is pressure The facing portion of the first and second common electrodes facing the portion other than the substantially central portion of the chamber 10 may face the portion of the pressure chamber 10 different from the first embodiment. In this case, the position, the shape, and the like of the connection portion of each common electrode may be appropriately changed in accordance with the position, the shape, and the like of the facing portions of the first and second common electrodes.

  Further, in the above, in the piezoelectric actuator, a wire such as the wires 47e, 47f, 47h, 47i and the wire bonding wire 91 which are connected to one another across the two types of common electrodes, and the bypass wires 101 and 102. Although one of two types of common electrodes is straddled, and only one of the bypass wires connecting the two or more connections in the other is arranged, depending on the arrangement of the two types of common electrodes, These two types of wires may be arranged together in the piezoelectric actuator.

  In the above, the wires 47e, 47f, 47h, and 47i are disposed on the insulating layer, or the insulating material is disposed around the wire bonding wire 91 by potting, but the present invention is not limited thereto. The wire 47 and the wire bonding wire 91, and the bypass wires 101 and 102 may be formed of a coated electric wire.

  In the above, an example in which the present invention is applied to a piezoelectric actuator used for an ink jet head of a so-called serial printer that discharges ink from a nozzle while reciprocating with the carriage in the scanning direction has been described. The present invention may be applied to a piezoelectric actuator used for a so-called line head which is extended over the entire length of the recording paper in the width direction and is fixed to the printer. Furthermore, it is also possible to apply the present invention to piezoelectric actuators used in devices other than inkjet heads.

32 piezoelectric actuator 41 diaphragm 42 piezoelectric layer 43 individual electrodes 44, 45 common electrodes 44a, 45a facing parts 44b, 45b connecting parts 44c connecting parts 46 insulating layers 47 (47a to 47l) wiring 74, 75 common electrodes 74a, 75a facing parts 74b, 75b connection part 101, 102 bypass wiring

Claims (8)

A flow path unit having a plurality of pressure chambers respectively communicating with a plurality of nozzles for discharging liquid;
An insulating layer disposed on one side of the flow path unit;
A plurality of individual electrodes disposed on the side opposite to the flow path unit of the insulating layer;
A piezoelectric layer disposed on the side opposite to the flow path unit of the insulating layer and disposed to cover the plurality of individual electrodes;
A common electrode disposed on the side opposite to the flow path unit of the piezoelectric layer and having a plurality of facing portions facing the plurality of individual electrodes;
A first wiring portion which is a portion formed on the side surface of the piezoelectric layer and which is a portion of a wiring electrically connected to the common electrode;
And a first terminal disposed on the surface of the insulating layer opposite to the flow path unit and electrically connected to the first wiring portion.
The common electrode is
A first portion extending along a first direction parallel to the one surface of the flow passage unit;
A portion extending along the first direction, which is a direction parallel to the one surface of the flow path unit and separated from the first portion in a second direction intersecting the first direction. A second part, which is the part placed
A third portion extending along the second direction, the third portion connecting the first portion and the second portion;
It is a portion extending along the second direction, which connects the first portion and the second portion, and is disposed apart from the third portion in the first direction. And an extension portion having a fourth portion;
Said extending portion, said being connected to a plurality of opposing portions, the ink jet head is characterized in that it is formed so as to surround said plurality of facing portions. The first portion has a first end and a second end which are both ends in the first direction,
The first wiring portion is connected to the first portion,
The first wiring portion has a third end and a fourth end which are both ends in the first direction,
The distance from the first end to the second end in the first direction is larger than the distance from the third end to the fourth end in the first direction. The inkjet head of description.   The piezoelectric layer has a second wiring portion which is a portion formed apart from the first wiring portion and which is a part of the wiring electrically connected to the common electrode. The inkjet head according to claim 2. The plurality of individual electrodes are arranged along the first direction,
The first wiring portion is disposed between the first end and an individual electrode disposed at a position closest to the first end in the first direction among the plurality of individual electrodes in the first direction. The ink jet head according to claim 2, wherein the ink jet head is disposed. The plurality of individual electrodes are
A plurality of first individual electrodes arranged along the first direction;
A plurality of individual electrodes arranged along the first direction, the plurality of second electrodes being a plurality of individual electrodes spaced apart from the plurality of first individual electrodes in the second direction; The inkjet head according to claim 4, comprising: an individual electrode.   The piezoelectric layer has a side surface extending in the first direction, and the first wiring portion is formed on the side surface extending in the first direction. An ink jet head according to any one of claims 1 to 5.   The inkjet head according to any one of claims 1 to 6, wherein the first terminal is connected to an IC. A plurality of wires connected to the plurality of individual electrodes;
Each of the plurality of wires connected to the plurality of individual electrodes has a width greater than the width of the individual electrodes at a position overlapping the extending portion in a third direction orthogonal to the one surface of the flow path unit The ink jet head according to any one of claims 1 to 7, further comprising a portion which narrows.

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