JP5560587B2 - Method for manufacturing piezoelectric actuator - Google Patents

Description

  The present invention relates to a method for manufacturing a piezoelectric actuator having a piezoelectric layer having an active portion that deforms when an electric field is applied.

  In the ink jet printer described in Patent Document 1, a piezoelectric actuator is manufactured by laminating a plurality of piezoelectric sheets to be a piezoelectric layer having electrodes formed on the surface and firing the laminated piezoelectric sheets. The manufactured piezoelectric actuator is bonded and fixed on a cavity plate made of a metal material.

JP 2002-36568 A

  In general, a piezoelectric material such as ceramics that forms a piezoelectric layer has a small linear expansion coefficient, and an electrode, a diaphragm, a cavity plate, and the like have a larger linear expansion coefficient than the piezoelectric layer. Therefore, when the piezoelectric sheet on which the electrode is formed is fired, a compressive force acts on the piezoelectric layer due to the difference in linear expansion coefficient between the electrode and the piezoelectric layer when the piezoelectric actuator is cooled after firing. Also, when the piezoelectric actuator and the cavity plate are heated and bonded with a thermosetting adhesive or the like, when the piezoelectric actuator is cooled after bonding, due to the difference in linear expansion coefficient between the piezoelectric layer and the cavity plate. A compressive force acts on the piezoelectric layer. When such a compressive force is generated in the active portion of the piezoelectric layer, deformation of the active portion is inhibited, and apparent piezoelectric characteristics in the active portion are deteriorated.

  The objective of this invention is providing the manufacturing method of the piezoelectric actuator which can suppress the fall of the apparent piezoelectric characteristic of an active part.

  It is generally known that a compressive force acts on a piezoelectric layer when manufacturing a piezoelectric actuator. When a compressive force acts on the active portion of the piezoelectric layer, the deformation of the active portion is inhibited, and the apparent piezoelectric characteristics of the active portion are deteriorated. In the present invention, in the joining step, the active part is pulled in the direction perpendicular to the laminating direction of the plate and the base material, and the plate is joined to the base material. The compression force generated in the active portion during the manufacture of the piezoelectric actuator is relieved by the tensile force). Thereby, it is possible to suppress a decrease in the apparent piezoelectric characteristics of the active part due to the action of the compressive force.

According to a first aspect of the present invention, there is provided a method of manufacturing a piezoelectric actuator comprising: a base material; a piezoelectric layer having an active portion that is deformed by application of an electric field; and a surface of the piezoelectric layer opposite to the base material. A method of manufacturing a piezoelectric actuator having a plate-like body having a diaphragm having no active part, the plate-like body forming step for forming the plate-like body, and the plate-like body and the base material A joining step of laminating and joining, and in the joining step, in the state where the active portion is pulled in a direction perpendicular to the laminating direction of the plate-like body and the base material, The base material is joined, and the active portion is arranged to be biased toward the piezoelectric layer side in the thickness direction with respect to the neutral surface of the plate-like body, and in the plate-like body forming step, It said active portion and said active portion facing the portion, the vibration relates to the thickness direction Forming the plate-like body that is curved to be convex to the side, in the joining step, the joining to the substrate while deforming such that the flat than curved state of the curved the plate-like body It is a feature.

  According to this, when the active portion is arranged to be deviated to one side in the thickness direction with respect to the neutral surface of the plate-like body, the active portion and the portion facing the active portion are curved to the other side in the thickness direction. By forming a plate-like body and joining the curved plate-like body to the base material while deforming it so that it is flatter than the curved state, the active part can be easily placed in the laminating direction of the plate-like body and the base material. The piezoelectric layer can be bonded to the substrate while being pulled in the vertical direction.

A method of manufacturing a piezoelectric actuator according to a second aspect of the present invention is a method of manufacturing a piezoelectric actuator according to the first aspect of the present invention, wherein, in the plate-like body forming step, the curved portion is curved so that the curvature at the active portion is constant. A state in which a plate-like body is formed, and in the joining step, a moment is applied to the curved plate-like body so as to be deformed to be flatter than a curved state, and the moment is applied to the plate-like body. Then, the plate-like body and the base material are bonded together by pressing the plate-like body and the base material against each other.

  According to this, before the plate-shaped body and the base material are brought into contact with each other and pressed, the curved plate-shaped body is deformed to be flatter than the curved state so that the curvature in the active portion is constant. Therefore, a tensile force is uniformly generated in the active portion, and the compressive force in the active portion is uniformly relaxed.

  In addition, since the plate-like body held in a state where a moment for deforming it so as to be flatter than the curved state is pressed against the substrate, the plate-like body has the above moment. It is pressed against the base material in a state flatter than the state where it has not been added, and cracks and cracks are unlikely to occur in the piezoelectric layer during bonding.

A method for manufacturing a piezoelectric actuator according to a third invention is a method for manufacturing a piezoelectric actuator according to the first or second invention, wherein the piezoelectric layer includes a plurality of the active portions, and the plate-like In the body forming step, the plate-like body curved so as to have the same curvature in each of the plurality of active portions is formed.

  According to this, since the curvatures in the plurality of active portions of the curved plate-like body are the same as each other, when the plate-like body is joined to the substrate, tensile forces having the same magnitude are generated in the plurality of active portions. Therefore, the compressive force in the plurality of active portions is uniformly relaxed, and as a result, the apparent piezoelectric characteristics in the plurality of active portions are the same.

A method for manufacturing a piezoelectric actuator according to a fourth invention is a method for manufacturing a piezoelectric actuator according to any one of the first to third inventions, wherein the plate-like body is provided in the active portion. An electrode to which a voltage is applied in order to apply an electric field to the active part, and the plate-like body forming step includes the piezoelectric layer and the piezoelectric layer. An electrode forming step of forming the electrode in a region corresponding to the region to be the active portion of the piezoelectric material, and a baking step of baking the piezoelectric material on which the electrode is formed to form the piezoelectric layer. It is characterized by being.

  When an electrode made of a material having a larger linear expansion coefficient than the piezoelectric layer is formed in the active portion, and the piezoelectric material is fired after forming the electrode in the region that becomes the active portion, the piezoelectric material on which the electrode is formed is fired. After the piezoelectric layer is formed, when the piezoelectric layer and the electrode are cooled, a compressive force acts on the active part in a direction perpendicular to the stacking direction of the plate-like body and the base material due to the difference in linear expansion coefficient between them. . However, in the present invention, even in such a case, the compressive force is increased by bonding the piezoelectric layer to the base material in a state where the active portion is pulled in a direction perpendicular to the stacking direction of the plate-like body and the base material. Can be relaxed.

A method for manufacturing a piezoelectric actuator according to a fifth invention is a method for manufacturing a piezoelectric actuator according to any one of the first to fourth inventions, wherein the base material has a larger linear expansion coefficient than the piezoelectric layer. In the joining step, the plate-like body and the base material are brought into contact with each other and pressed while heating the plate-like body and the base material. It is characterized by joining.

  When the base material is made of a material having a larger linear expansion coefficient than that of the piezoelectric layer, when the plate and the base material are cooled after being joined by heating both in the joining process, the difference between the two However, a compressive force acts on the active part in a direction perpendicular to the laminating direction of the plate-like body and the base material. The compression force can be relaxed by bonding the piezoelectric layer to the base material in a state of being pulled in the direction of.

  According to the present invention, in the joining step, the active part is pulled in the direction perpendicular to the laminating direction of the plate-like body and the base material, and the active part is pulled to join the plate-like body to the base material. As a result, the compressive force acting on the active portion in the manufacture of the piezoelectric actuator is relaxed. Thereby, it is possible to suppress a decrease in the apparent piezoelectric characteristics of the active part due to the action of the compressive force.

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 the III-III sectional view taken on the line of FIG. It is the IV-IV sectional view taken on the line of FIG. It is process drawing which shows the manufacturing process of a piezoelectric actuator. FIG. 6 is a diagram corresponding to FIG. FIG. 6 is a diagram corresponding to FIG. FIG. 6 is a diagram corresponding to FIG.

  Hereinafter, preferred embodiments 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 transport roller 4, and the like. The carriage 2 reciprocates in the scanning direction (left and right direction in FIG. 1). The inkjet head 3 is provided on the lower surface of the carriage 2 and ejects ink from a plurality of nozzles 15 (see FIG. 2) formed on the lower surface. The transport roller 4 transports the recording paper P in the paper feed direction (frontward direction in FIG. 1).

  In the printer 1, printing is performed on the recording paper P by ejecting ink onto the recording paper P in the paper feeding direction from the inkjet head 3 that reciprocates in the scanning direction together with the carriage 2. Further, the recording paper P on which printing has been performed is discharged in the paper feeding direction by the transport roller 4.

  Next, the inkjet head 3 will be described. FIG. 2 is a plan view of the inkjet head 3 of FIG. 3 is a cross-sectional view taken along line III-III in FIG. 4 is a sectional view taken along line IV-IV in FIG. As shown in FIGS. 2 to 4, the inkjet head 3 applies pressure to the flow path unit 31 in which an ink flow path such as a pressure chamber 10 and a nozzle 15 described later is formed, and ink in the pressure chamber 10. The piezoelectric actuator 32 is provided.

  The flow path unit 31 is formed by stacking the cavity plate 21, the base plate 22, the manifold plate 23, and the nozzle plate 24. Of these four plates 21 to 24, the three plates 21 to 23 excluding the nozzle plate 24 are made of, for example, a metal material such as SUS430, and the nozzle plate 24 is made of a synthetic resin material such as polyimide. Yes. Or the nozzle plate 24 may also be comprised with the metal material similar to the other three plates 21-23.

  A plurality of pressure chambers 10 are formed in the cavity plate 21. The pressure chamber 10 has a substantially elliptical plane shape whose longitudinal direction is the scanning direction, and a plurality of pressure chambers 10 are arranged in the paper feed direction to form one pressure chamber row. Such pressure chamber rows are arranged in two rows in the scanning direction. In the base plate 22, a plurality of through holes 12 and 13 each having a substantially circular planar shape are formed at portions facing both end portions in the longitudinal direction of the plurality of pressure chambers 10.

  A manifold channel 11 is formed in the manifold plate 23. The manifold channel 11 extends in two rows in the paper feed direction corresponding to the two pressure chamber rows, and the portions extending in these two rows respectively constitute the pressure chamber rows on the right side of FIG. 10 and approximately the right half of the pressure chamber 10 and the substantially left half of the pressure chamber 10 constituting the left pressure chamber row. Further, the portions extending in these two rows of the manifold channel 11 are joined to each other at the lower end portion in FIG. 2, and the ink supply port 9 formed in the piezoelectric layer 41 described later is formed in this portion of the manifold channel 11. Ink is supplied from.

  In the manifold plate 23, a plurality of through holes 14 having a substantially circular planar shape are formed at portions facing the plurality of through holes 13. In the nozzle plate 24, a plurality of nozzles 15 are formed at portions facing the plurality of through holes 14.

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

  As described above, the piezoelectric actuator 32 is formed by the cavity plate 21 that is also a part of the flow path unit 31, the piezoelectric layers 41 and 42, the common electrode 43, and the plurality of individual electrodes 44. The piezoelectric layer 41 is made of a piezoelectric material mainly composed of lead zirconate titanate, which is a mixed crystal of lead titanate and lead zirconate, and is bonded to the upper surface of the cavity plate 21 so as to cover the plurality of pressure chambers 10. Yes. Note that the piezoelectric layer 41 functions as a diaphragm that deforms in accordance with deformation of an active portion 42a described later. The thickness of the piezoelectric layer 41 is about 30 μm.

  The piezoelectric layer 42 is made of the same piezoelectric material as the piezoelectric layer 41, and is continuously disposed on the upper surface of the piezoelectric layer 41 across the plurality of pressure chambers 10. The thickness of the piezoelectric layer 42 is about 30 μm, like the piezoelectric layer 41. The common electrode 43 is made of, for example, a metal material such as Ag—Pd, and extends across the entire area between the piezoelectric layer 41 and the piezoelectric layer 42. The common electrode 43 is always held at the ground potential by a driver IC (not shown).

  The plurality of individual electrodes 44 are made of the same metal material as the common electrode 43, and have a substantially elliptical planar shape that is slightly smaller than the pressure chamber 10. The plurality of individual electrodes 44 are respectively formed on portions of the upper surface of the piezoelectric layer 42 facing the substantially central portion of the pressure chamber 10. Further, the end of each individual electrode 44 on the opposite side to the nozzle 15 in the longitudinal direction extends to a portion that does not face the pressure chamber 10, and the tip thereof serves as a connection terminal 44a. The connection terminal 44a is connected to a driver IC (not shown) via a flexible wiring board (FPC) (not shown), whereby a drive potential (for example, about 20 V) is individually applied from the driver IC to the plurality of individual electrodes 44. It is possible to grant.

  The active portion 42 a sandwiched between the common electrode 43 and the individual electrode 44 of the piezoelectric layer 42 described above is polarized in the thickness direction of the piezoelectric layer 42. In the present embodiment, of the piezoelectric actuator 32, the laminated body including the piezoelectric layers 41 and 42, the common electrode 43, and the individual electrode 44 excluding the cavity plate 21 corresponds to the plate-like body according to the present invention. Moreover, the active part 42a is biased to the upper side (one side in the thickness direction) with respect to the neutral surface A1 of the laminate. Here, the neutral plane A1 is a plane in which no distortion occurs when a bending moment is applied in the laminate.

  Here, a driving method of the piezoelectric actuator 32 will be described. In the piezoelectric actuator 32, the plurality of individual electrodes 44 are previously held at the ground potential. When a driving potential is applied to one of the individual electrodes 44 by the driver IC, a potential difference is generated between the individual electrode 44 and the common electrode 43 held at the ground potential. An electric field in a direction parallel to the polarization direction is generated in 42a. Due to this electric field, the active portion 42a contracts in the horizontal direction perpendicular to the polarization direction, and accordingly, the portion of the piezoelectric layers 41, 42 facing the pressure chamber 10 is convex toward the pressure chamber 10 as a whole. It deforms and the volume of the pressure chamber 10 decreases. As a result, the pressure of the ink in the pressure chamber 10 increases (pressure is applied), and the ink is ejected from the nozzle 15 communicating with the pressure chamber 10.

  Next, a method for manufacturing the piezoelectric actuator 32 (inkjet head 3) will be described. FIG. 5 is a process diagram showing a manufacturing process of the piezoelectric actuator 32.

  When manufacturing the piezoelectric actuator 32, first, as shown in FIG. 5 (a), the surface of two green sheets of piezoelectric material to be the piezoelectric layers 41 and 42 (regions to be the active portions 42a) are respectively provided. The common electrode 43 and the individual electrode 44 are formed (electrode forming step), and the two green sheets on which the electrodes 43 and 44 are formed are stacked on each other.

  Next, as shown in FIG. 5B, the formed laminate is disposed on the jig J1 curved with a certain curvature so that the region where the active portion 42a is disposed protrudes downward. Thus, the laminate is curved so as to protrude downward, and in this state, the piezoelectric material green sheets are fired to form the piezoelectric layers 41 and 42 (firing step). The upper surface of the jig J1 may be a curved surface that is curved only in the left-right direction in FIG. 5B, or in addition to the left-right direction in FIG. Similarly, the curved surface, that is, the upper surface of the jig J1 may be a spherical surface.

At this time, the linear expansion coefficients (about 10.6 to 19.3 [10 ⁻⁶ / ° C.]) of the electrodes 43 and 44 are the same as the linear expansion coefficients (2.6 [10 ⁻⁶ / ° C.] of the piezoelectric layers 41 and 42. Therefore, when the stacked body is cooled after the firing of the piezoelectric layers 41 and 42, the active portion 42 a has a difference in linear expansion coefficient between the electrodes 43 and 44 and the piezoelectric layers 41 and 42. A compressive force S11 is generated in the surface direction.

  Then, by the above process (plate body forming process), the entire piezoelectric layers 41 and 42 including the portion extending over the plurality of active portions 42a are fixed so as to protrude downward (the other side in the thickness direction). A laminated body curved with a curvature is formed.

  Next, as shown in FIG. 5C, the laminate is placed on the cavity plate 21 coated with a thermosetting adhesive (the laminate and the cavity plate 21 are brought into contact with each other), and the heater H The laminated body is pressed toward the cavity plate 21 while heating the laminated body to about 200 ° C. or by pressing the cavity plate 21 toward the heater H, as shown in FIG. Is deformed into a flat state, and the laminate is joined to the cavity plate 21 (base material) in this state (joining step).

At this time, the linear expansion coefficient of the cavity plate 21 (about 10.4 [10 ⁻⁶ / ° C.]) is larger than the linear expansion coefficient of the piezoelectric layers 41 and 42 (about 2.6 [10 ⁻⁶ / ° C.]). Therefore, after the laminated body is bonded to the cavity plate 21, the laminated body and the cavity plate 21 are cooled, so that the piezoelectric layer 42 (active part 42 a) has a linear expansion coefficient between the piezoelectric layers 41 and 42 and the cavity plate 21. Due to the difference, a compressive force acts in the surface direction (in FIG. 5D, a combination of the compressive force and the compressive force S11 is shown as a compressive force S12).

  Here, when the compressive force S12 is generated in the active portion 42a, the deformation of the active portion 42a when the piezoelectric actuator 32 is driven is hindered by the compressive force S12, so that the apparent piezoelectric characteristics of the active portion 42a are reduced. In addition, the deformation amount of the active portion 42a when an electric field is applied is reduced. As a result, the pressure applied to the ink in the pressure chamber 10 decreases, and the amount of ink discharged from the nozzle 15 decreases.

  However, in the present embodiment, since the laminated body curved so as to protrude downward is joined to the cavity plate 21 in a state of being deformed into a flat state, it is on the upper side with respect to the neutral plane A1. The biased piezoelectric layer 42 (active portion 42a) is pulled in a direction perpendicular to the stacking direction of the laminate and the cavity plate 21 (a tensile force F11 is generated in the active portion 42a). That is, in the bonding step, the active portion 42a is bonded to the cavity plate 21 in a state where the active portion 42a is pulled in a direction orthogonal to the stacking direction of the stacked body and the cavity plate 21.

  Therefore, the compressive force S12 is relieved by the pulling force F11, thereby suppressing the apparent decrease in piezoelectric characteristics in the active portion 42a as described above.

  In addition, the active portion 42a is arranged so as to be biased upward with respect to the neutral surface A1 of the laminate, and a laminated body that is curved so as to protrude downward is formed, and the laminate is deformed into a flat state. By joining to the cavity plate 21 in such a state, the pulling force F11 can be easily generated in the active portion 42a.

  Furthermore, in the laminated body before joining, in which the entire portion including the plurality of active portions 42a is curved with a constant curvature, the curvatures in the plurality of active portions 42a are the same, and the laminated body is joined to the cavity plate 21. In some cases, tensile forces F11 having the same magnitude are generated in the plurality of active portions 42a. Thereby, the ejection characteristics of ink from the plurality of nozzles 15 when the piezoelectric actuator 32 is driven become uniform.

  Here, for example, when the laminated body of the piezoelectric layers 41 and 42 is bonded to the cavity plate 21 while being heated at 200 ° C., a compressive stress of about 0.3 Gpa is generated in the surface direction of the active portion 42a. If the laminated body curved to have a curvature radius of about 24 mm is joined to the cavity plate 21, the tensile stress caused by the tensile force F11 generated in the active portion 42a becomes almost the same as the compressive stress, and the compressive stress is completely relaxed. Is done.

  The value of the radius of curvature is calculated on the assumption that the compressive stress is caused only by the difference in linear expansion coefficient between the piezoelectric layers 41 and 42 and the cavity plate 21. That is, the radius of curvature of the laminate can be changed as appropriate in accordance with the linear expansion coefficient of each material used for the laminate, the heating conditions, and the like.

  Then, after joining the laminate to the cavity plate 21, the common electrode 43 is set to the ground potential, and the individual electrode 44 is applied with a potential higher than the drive potential (for example, about 70V), thereby polarizing the active portion 42a. . Note that the polarization of the active portion 42 a may be performed before the stacked body is bonded to the cavity plate 21.

  Next, modified examples in which various changes are made to the present embodiment will be described. However, components having the same configuration as in the present embodiment are denoted by the same reference numerals, and description thereof is omitted as appropriate.

  In one modification (Modification 1), as shown in FIG. 6D, a common electrode 43 is formed on the lower surface of the piezoelectric layer 41, and the individual electrode 44 is provided between the piezoelectric layer 41 and the piezoelectric layer 42. Is formed. An insulating layer 51 is formed on the lower surface of the piezoelectric layer 41 on which the common electrode 43 is formed to prevent the common electrode 43 from coming into contact with the ink in the pressure chamber 10.

  In this case, the active portion 41a sandwiched between the common electrode 43 and the individual electrode 44 of the piezoelectric layer 41 is polarized in the thickness direction of the piezoelectric layer 41, and the piezoelectric layer 42 functions as a vibration plate. The active portion 41a is located on the lower side (one side in the thickness direction) with respect to the neutral surface A1 of the laminated body (plate-like body) including the piezoelectric layers 41 and 42, the common electrode 43, the individual electrode 44, and the insulating layer 51. ). In this piezoelectric actuator, when a driving potential is applied to the individual electrode 44, the portion facing the pressure chamber 10 of the piezoelectric layers 41 and 42 is generally opposite to the pressure chamber 10, contrary to the above-described embodiment. Deforms so that it is convex to the side.

  When manufacturing such a piezoelectric actuator, first, as shown in FIG. 6A, a common electrode 43 and individual electrodes are respectively formed on the surface of two green sheets of piezoelectric material to be the piezoelectric layers 41 and. 44 is formed (electrode forming step), and the two green sheets on which the electrodes 43 and 44 are formed are laminated with each other. Then, as shown in FIG. 6B, the formed laminate is placed on a jig J2 that is curved with a certain curvature so that the upper surface thereof protrudes upward, so that the laminate is placed on the upper side (thickness). Then, the piezoelectric layers 41 and 42 are formed by firing the green sheet of the piezoelectric material (curing step). At this time, due to the difference in the linear expansion coefficient between the electrodes 43 and 44 and the piezoelectric layers 41 and 42, a compressive force S21 in the surface direction is generated in the active portion 41a. Through the above steps, a laminate of the piezoelectric layers 41, 42, the common electrode 43, and the individual electrodes 44, which is curved with a certain curvature so that the entire piezoelectric layers 41, 42 are convex upward, is formed.

  Next, as shown in FIG. 6C, an insulating layer 51 is formed on the lower surface of the piezoelectric layer 41 on which the common electrode 43 is formed, and then the laminate is applied to the cavity plate coated with a thermosetting adhesive. As shown in FIG. 6 (d), it is arranged on 21 and pressed against the cavity plate 21 while heating the laminate with the heater H, or pressed against the heater H with the cavity plate 21. The curved laminate is deformed into a flat state, and the laminate is joined to the cavity plate 21 in this state (joining step).

  Also at this time, as in the above-described embodiment, the compressive force acts on the active portion 41a due to the difference in linear expansion coefficient between the cavity plate 21 and the piezoelectric layers 41 and 42 (in FIG. 6D, this compressive force). And the compression force S21 is shown as a compression force S22).

  However, since the laminated body curved so as to be convex upward is bonded to the cavity plate 21 in a state of being deformed into a flat state, the laminated body also has a lower side with respect to the neutral plane A2 in this case. The piezoelectric layer 41 (active portion 41a) disposed in a biased state is pulled in the surface direction (a tensile force F21 is generated in the active portion 41a).

  Therefore, the compressive force S22 is relieved by the pulling force F21, thereby suppressing a decrease in the apparent piezoelectric characteristics of the active portion 41a due to the compressive force S22.

  Further, in the above-described embodiment, the piezoelectric layers 41 and 42 made of the same piezoelectric material are laminated with each other, and the piezoelectric layer 41 without an active portion functions as a vibration plate, but is not limited thereto.

  In another modification (Modification 2), as shown in FIG. 7D, a diaphragm 61 made of the same metal material as the plates 21 to 23 is provided instead of the piezoelectric layer 41. Further, the diaphragm 61 having conductivity also serves as a common electrode and is always held at the ground potential.

  In order to manufacture such a piezoelectric actuator, first, as shown in FIG. 7A, the piezoelectric layer 42 is formed on the upper surface of the vibration plate 61 by the aerosol deposition method (AD method). Individual electrodes 44 are formed on the upper surface of the piezoelectric layer 42. Next, as shown in FIG. 7B, the laminate of the diaphragm 61 and the piezoelectric layer 42 is cured so that the same jig J1 as in the above-described embodiment and the lower surface protrude downward. The laminated body is bent so as to protrude downward by sandwiching it with a jig J3 curved with the same constant curvature as the upper surface of the tool J1, and then the laminated body is heated at about 800 ° C. Then, an annealing process for crystallizing the piezoelectric layer 42 is performed.

  Alternatively, the piezoelectric layer 42 is formed on the upper surface of the vibration plate 61 by a sol-gel method instead of the AD method, and the laminate of the vibration plate 61 and the piezoelectric layer 42 is heated at about 600 to 700 ° C. May be removed. In Modification 2, the step of forming the piezoelectric layer 42 and the individual electrode 44 on the surface of the vibration plate 61 by the AD method or the sol-gel method, and then heating the laminate of the vibration plate 61 and the piezoelectric layer 42 is the main process. This corresponds to the plate-like body forming step according to the invention.

And the laminated body of the diaphragm 61 and the piezoelectric layer 42 curved so as to be convex downward is formed by the above process. At this time, the linear expansion coefficient of the diaphragm 61 (about 10.4 [10 ⁻⁶ / ° C.]) and the linear expansion coefficient of the individual electrode 44 (about 10.6 to 19.3 [10 ⁻⁶ / ° C.]) Since it is larger than the linear expansion coefficient of the piezoelectric layer 42 (about 2.6 [10 ⁻⁶ / ° C.]), when the vibration plate 61 and the piezoelectric layer 42 are cooled after heating, the difference between these linear expansion coefficients is A compressive force S31 is generated in the piezoelectric layer 42 (active portion 42a) in a direction perpendicular to the stacking direction of the laminate and the base material.

  Next, as shown in FIGS. 7C and 7D, similarly to the above-described embodiment, the laminate of the vibration plate 61, the piezoelectric layer 42, and the individual electrode 44 and the cavity plate 21 are heated and joined. To do. In FIG. 7D, a combination of the compressive force acting on the active portion 42a and the compressive force S31 when the laminate and the cavity plate 21 are cooled after the joining is shown as a compressive force S32. Also at the time of this joining, the active part 42a is pulled in a direction perpendicular to the stacking direction of the laminate and the base material (a pulling force F31 is generated), and the compressive force S32 is relieved by the pulling force F31. Thus, a decrease in the apparent piezoelectric characteristics in the active portion 42a is suppressed.

  In the second modification, the piezoelectric layer 42 and the individual electrodes 44 are formed on the upper surface of the flat vibration plate 61, and then the formed laminate is curved. However, the piezoelectric layer 42 is formed on the upper surface of the curved vibration plate 61. In addition, the individual electrode 44 may be formed.

  In the second modification, after the individual electrode 44 is formed on the upper surface of the piezoelectric layer 42, annealing treatment or heating for removing the solvent in the gel is performed. However, after the heating is performed, the individual electrode 44 is formed. May be.

  Further, in the above-described embodiment, a laminated body curved with a constant curvature is formed across the plurality of active portions 42a, and this laminated body is joined to the cavity plate 21, but this is not restrictive.

  In another modified example (modified example 3), as in the above-described embodiment, as shown in FIG. 8A, the common electrodes 43 and the green sheets of the two piezoelectric materials to be the piezoelectric layers 41 and 42 are provided. After the individual electrodes 44 are formed (electrode formation step), these two green sheets are laminated, and then, as shown in FIG. 8B, the laminated body is provided with portions that become the active portions 42a. Are disposed on jigs J4 that are curved with the same constant curvature so that the regions corresponding to the respective active portions 42a are convex downward, respectively, so that the stacked body is placed on each active portion 42a and each active portion 42a. The portions facing the active portion 42a are curved with the same constant curvature so as to individually protrude downward. In this state, the piezoelectric material green sheets are fired to form the piezoelectric layers 41 and 42 (baking process).

  Through the above steps, a plurality of active portions 42a and a laminated body curved with the same constant curvature are formed so that the portions facing the plurality of active portions 42a are convex downward, and thereafter, the above-described implementation is performed. Similarly to the embodiment, as shown in FIGS. 8C and 8D, the laminate and the cavity plate 21 are heated and joined in a state where the laminate is deformed into a flat state.

  Also in this case, similarly to the above-described embodiment, due to the difference in the linear expansion coefficient between the piezoelectric layer 42 and the electrodes 43 and 44, the active portion 42 a has a surface direction when the laminate is cooled after the firing step. When compressive force S41 is generated and the laminated body and the cavity plate 21 are joined and then the laminated body and the cavity plate 21 are cooled due to the difference in linear expansion coefficient between the piezoelectric layer 41 and the piezoelectric layer 42 and the cavity plate 21. A compressive force acts on the active portion 42a in a direction perpendicular to the stacking direction of the laminate and the base material (in FIG. 8D, a combination of the compressive force and the compressive force S41 is illustrated as the compressive force S42. )

  Also in this case, since the active part 42a is pulled in the direction perpendicular to the stacking direction of the laminate and the base material, the compressive force S42 is relaxed by the pulling force F41, as in the above-described embodiment. A decrease in the apparent piezoelectric characteristics of the active portion 42a due to the compressive force S42 is suppressed.

  Further, in this case, since the curvature of the plurality of active portions 42a is the same in the curved laminate before joining, the tensile force generated in the plurality of active portions 42a when the laminate is joined to the cavity plate 21. Since the magnitudes of the forces F41 are the same and the deformation amount of each active portion 42 is the same when the piezoelectric actuator 32 is driven, the ink ejection characteristics from the plurality of nozzles 15 are uniform.

  Further, in the above-described embodiment, the laminated body of the piezoelectric layers 41 and 42, the common electrode 43, and the individual electrode 44 is joined to the cavity plate 21 that constitutes the flow path unit 31, but this is not a limitation. The curved laminate may be joined to a substrate different from the cavity plate 21 in a state of being deformed into a flat state, and then the laminate and the substrate joined together may be joined to the cavity plate 21. .

  In the above description, a stacked body in which a plurality of active portions are curved with the same curvature is formed. However, a plurality of active portions may have different curvatures. In this case, the tensile forces generated in each active portion 42a are different from each other. On the other hand, the compressive force acting on each active portion 42a at the time of manufacturing the piezoelectric actuator is the same. The piezoelectric characteristics are different from each other. For example, if the magnitudes of the drive potentials applied to the plurality of individual electrodes 44 are individually changed, ink ejection characteristics from the plurality of nozzles 15 when the piezoelectric actuator is driven. Can be made uniform.

  Moreover, in the above description, each active part formed the laminated body which each curved with the fixed curvature, However, The curvature of each active part may differ for every part.

  In the above description, the curved laminated body is brought into contact with the cavity plate 21, and the laminated body is pressed toward the cavity plate 21 by the heater H, or the cavity plate 21 is pressed toward the heater H. As a result, the laminate was joined to the cavity plate 21 while being deformed into a flat state. However, the present invention is not limited to this, and the laminate is transformed into a laminate in which the active portion is curved with a certain curvature. By preliminarily holding the laminated body in a flat state by applying a moment for causing the laminated body to contact the cavity plate 21 and pressing the laminated body toward the cavity plate 21 by the heater H, Alternatively, the laminate is joined to the cavity plate 21 by pressing the cavity plate 21 toward the heater H. It may be.

  In this case, before pressing the laminate toward the cavity plate 21 or pressing the cavity plate 21 toward the heater H, the active portion is flattened into a laminate with a certain curvature. Since the moment for deforming is applied to the active portion 42a, a more uniform tensile force is generated in the active portion 42a. As a result, the compressive force acting on the active portion 42a is uniformly relaxed.

  Further, in this case, since the laminated body held in a deformed state and the cavity plate 21 are joined, the piezoelectric layers 41 and 42 are hardly cracked or cracked when pressed.

  In the above description, the heater H is brought into contact with the laminate and the laminate and the cavity plate 21 are joined. However, the heater H may be disposed on the side in contact with the cavity plate 21, and The heaters H that come into contact with both the laminate and the cavity plate 21 may be disposed.

  In the above description, the curved laminated body is deformed into a flat state without bending and joined to the cavity plate 21, but the laminated body is deformed into a flatter state than the original state. If joining to the cavity plate 21, the laminate may be joined to the cavity plate 21 in a slightly curved state.

  Further, in the above description, the active portion is arranged to be biased to one side in the thickness direction with respect to the neutral surface of the laminate, and the active portion and the portion facing the active portion are curved to the other side in the thickness direction. The laminated body was formed and joined to the base material in a state where the curved laminated body was deformed into a flat state, thereby generating a tensile force in the surface direction in the active part. When the active part is pulled in a direction perpendicular to the stacking direction of the laminate and the base material, the laminate and the base material are heated and joined to each other to generate a tensile force in the plane direction on the active part. You may let them.

  Further, in this case, the active portion is not limited to be disposed on one side in the thickness direction with respect to the neutral surface of the laminate, and the active portion sandwiches the neutral surface of the laminate. You may arrange | position symmetrically in the thickness direction. Furthermore, the laminate may be formed of only the piezoelectric layer, and the active portion may be formed in all regions in the thickness direction of the piezoelectric layer.

  Moreover, in the above description, although the laminated body and the base material were heated and joined, it is not restricted to this. For example, when a piezoelectric layer is formed by firing a piezoelectric material integrally with an electrode, or when a piezoelectric layer is formed on a diaphragm by an AD method or a sol-gel method, and then the piezoelectric layer is heated. When the compressive force is applied to the active part before joining the laminate and the substrate, the laminate and the substrate are pulled in a state perpendicular to the stacking direction of the laminate and the substrate. The materials may be joined via an adhesive that cures at room temperature. In this case, the compressive force acting on the active part before the laminate and the base material are joined is alleviated by the tensile force generated in the active part when the laminate and the base material are joined.

  In the above, the present invention is applied to the manufacture of a piezoelectric actuator used for an ink jet head that discharges ink from a nozzle, and the cavity plate is used as a base material. It is also possible to apply the present invention to the manufacture of the piezoelectric actuator used. In this case, the substrate may have a hole in the region corresponding to the active part, such as a cavity plate. Unlike the cavity plate, the substrate may be a flat plate having no hole in the region corresponding to the active part. There may be.

  Furthermore, although the piezoelectric layer has a plurality of active portions in the above, the present invention is not limited to this, and the present invention can also be applied to the manufacture of a piezoelectric actuator in which the piezoelectric layer has only one active portion.

21 Cavity plate 32 Piezoelectric actuator 41 Piezoelectric layer 41a Active part 42 Piezoelectric layer 42a Active part 43 Common electrode 44 Individual electrode 61 Diaphragm

Claims (5)

A substrate ;
Provided with a plate-like body having a piezoelectric layer having an active part deformed by application of an electric field, and a diaphragm having no active part bonded to the surface of the piezoelectric layer opposite to the base material A method for manufacturing a piezoelectric actuator, comprising:
A plate-like body forming step for forming the plate-like body;
A joining step of laminating and joining the plate-like body and the base material,
In the joining step, in a state where the active part is pulled in a direction perpendicular to the laminating direction of the plate and the base, the plate and the base are joined,
The active portion is arranged to be biased toward the piezoelectric layer with respect to the thickness direction with respect to the neutral surface of the plate-like body,
In the plate-like body forming step, the plate-like body that is curved so that the active portion and the portion facing the active portion are convex toward the diaphragm side in the thickness direction is formed,
In the joining step, the curved plate-like body is joined to the base material while being deformed so as to be flatter than the curved state. In the plate-like body forming step, the curved plate-like body is formed so that the curvature in the active portion is constant,
In the joining step, a moment for deforming the curved plate-like body so as to be flatter than a curved state is added, and the plate-like body is held in a state where the moment is applied. by pressing by contact with each other plate-like body and said substrate, method of manufacturing the piezoelectric actuator according to claim 1, characterized in that said joining said substrate and said plate-like body . The piezoelectric layer includes a plurality of the active portions,
3. The method for manufacturing a piezoelectric actuator according to claim 1, wherein, in the plate-like body forming step, the plate-like body that is curved so that the curvatures in the plurality of active portions are the same as each other is formed. The plate-like body is made of a material having a larger linear expansion coefficient than the piezoelectric layer provided in the active portion, and further includes an electrode to which a voltage is applied in order to apply an electric field to the active portion Because
The plate-like body forming step includes
An electrode forming step of forming the electrode in a region corresponding to the region to be the active portion of the piezoelectric material to be the piezoelectric layer;
Method for manufacturing a piezoelectric actuator according to claim 1, characterized in that by firing the piezoelectric material on which the electrode is formed and a firing step of forming the piezoelectric layer. The base material is made of a material having a larger linear expansion coefficient than the piezoelectric layer,
In the joining step, the plate-like body and the base material are joined by pressing the plate-like body and the base material while abutting each other while heating the plate-like body and the base material. method for manufacturing a piezoelectric actuator according to any one of claims 1 to 4, characterized in.

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