JP5205852B2 - Piezoelectric device - Google Patents

Description

  The present invention relates to a piezoelectric device.

As a technique related to this type of field, for example, there is a piezoelectric element described in Patent Document 1. Such a piezoelectric element is generally composed of a piezoelectric body, a laminated body in which internal electrodes are alternately laminated, and an external electrode provided on a side surface of the laminated body. When a voltage is applied to the external electrode, the actuator part including the part (active part) where the internal electrodes of different polarities overlap in the piezoelectric body is deformed, and a displacement corresponding to the voltage application amount is obtained.
JP 2006-173347 A

  In recent years, a piezoelectric device has been developed that improves the amount of displacement and secures the drive area by arranging a plurality of the above-described actuator units along a predetermined direction of the laminate and cooperating the plurality of actuator units. Yes. In such a piezoelectric device, there is a piezoelectric body that does not directly contribute to deformation between the plurality of actuator portions. In addition, the direction of deformation of the actuator unit may be reversed. For this reason, the deformation of each actuator unit is constrained, and the displacement amount of the entire apparatus may be limited.

  In order to avoid the restriction of the displacement amount, it is conceivable to adopt a structure in which a stress relaxation portion such as a groove is formed between the actuator portions. However, with a mechanical method, sufficient processing accuracy cannot be obtained for a piezoelectric device that is becoming smaller in size, and it has been substantially difficult to form a desired stress relaxation portion between actuator portions.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a piezoelectric device that can secure a sufficient amount of displacement.

  In order to solve the above-described problem, a piezoelectric device according to the present invention includes a multilayer body formed by alternately laminating and sintering a plurality of piezoelectric bodies and a plurality of internal electrodes including a first electrode and a second electrode, A piezoelectric device in which a plurality of actuator units each including an active portion in which a first electrode and a second electrode overlap each other in a stacking direction of a stacked body is arranged in the stacked body, The present invention is characterized in that a stress relaxation portion that is simultaneously formed during sintering is provided.

  In this piezoelectric device, the stress relieving portion provided between the actuator portions can relieve the restraining force applied to the actuator portion from the piezoelectric body that does not directly contribute to the deformation when the actuator portion is deformed. Thereby, the displacement amount of an actuator part is securable enough. In addition, the stress relaxation portion is formed at the same time when the laminate is sintered. Therefore, unlike the case where the stress relaxation portion is formed by a mechanical method, a desired stress relaxation portion can be obtained without complicating the manufacturing process.

  Moreover, it is preferable that a stress relaxation part is a slit formed by preventing the sintering reaction between the predetermined | prescribed area | regions which mutually face in the some green sheet which is a precursor of a piezoelectric material. In this case, the piezoelectric body that does not directly contribute to the deformation of the actuator portion can be deformed along with the deformation of the actuator portion, and the restraining force applied to the actuator portion can be relaxed more reliably.

The stress relaxation part is formed by sintering a green sheet in which a material containing at least one of ZrO ₂ , MgO, Nb ₂ O ₅ , Ta ₂ O ₅ , CeO ₂ , and Y ₂ O is applied to a predetermined region. It is preferable. By using such a material, when the green sheet is sintered, the sintering reaction between predetermined regions of the adjacent green sheets is sufficiently hindered, and a slit as a stress relaxation portion is more reliably formed.

  The actuator units are arranged in a direction perpendicular to the stacking direction of the laminate, and non-actuator units having no internal electrodes are provided between the actuator units and at the arrangement ends of the actuator units, respectively. Is preferably provided. In this case, in the piezoelectric device in which the actuator units are arranged orthogonal to the stacking direction of the stacked body, a sufficient amount of displacement of each actuator unit can be ensured. Further, since the stress generated by the deformation of the actuator portion is difficult to be transmitted to other adjacent actuator portions, crosstalk between the actuator portions can be reduced.

  The stress relaxation part is preferably provided in the non-actuator part so as not to be exposed on the surface of the laminate. In this case, the strength of the laminate can be ensured while relaxing the binding force applied to the actuator portion.

  In addition, it is preferable that the actuator portions are arranged in the stacking direction of the stacked body, the piezoelectric bodies are respectively provided between the actuator portions, and the stress relaxation portion is provided in the piezoelectric body. In this case, in the piezoelectric device in which the actuator units are arranged in the stacking direction of the stacked body, a sufficient amount of displacement of each actuator unit can be ensured.

  Moreover, it is preferable that an actuator part generate | occur | produces a bending displacement in the lamination direction of a laminated body. When the actuator portion generates a deflection displacement, it is easy to receive a restraining force by a piezoelectric body that does not directly contribute to the deformation. Therefore, a suitable amount of displacement can be secured by applying a stress relaxation portion between such actuator portions.

  According to the piezoelectric device according to the present invention, a sufficient amount of displacement can be secured.

  Hereinafter, preferred embodiments of a piezoelectric device according to the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a longitudinal sectional view showing a layer structure of a piezoelectric device according to a first embodiment of the present invention. FIG. 2 is a plan view of the piezoelectric device shown in FIG. As shown in FIGS. 1 and 2, the piezoelectric device 1 includes a laminated body 2 having a flat, substantially rectangular parallelepiped shape, and metal rectangular legs 3 provided on the bottom surface of the laminated body 2. ing. The piezoelectric device 1 is used as, for example, a micro pump that ejects ink droplets from nozzles in response to a predetermined signal in an inkjet printer.

  The multilayer body 2 is formed by laminating a plurality of piezoelectric bodies 4 and a plurality of internal electrodes 5A and 5B in a predetermined order and sintering them. The dimensions of the laminated body 2 are, for example, width 1.2 mm × depth 1.5 mm × height 0.2 mm.

  The piezoelectric body 4 is made of, for example, a piezoelectric ceramic material mainly composed of PZT (lead zirconate titanate). The thickness of the piezoelectric body 4 is about 80 μm to 100 μm per layer. Each piezoelectric body 4 is integrated to such an extent that the boundary cannot be visually recognized by sintering.

As a composition of PZT, the following are used, for example.
Pb0.999 [(Zn1 / 3Nb2 / 3) 0.11Ti0.425Zr0.465] O ₃ +0.2 wt% Fe ₂ O ₃ +0.2 wt% Sb ₂ O ₃

  As the powder characteristics of PZT, for example, those having a BET specific surface area of about 2.5 m 2 / g and an average particle diameter of about 0.6 μm are used. The sintering temperature of such PZT is about 950 ° C. The melting point of the PZT material is about 1300 ° C.

  The internal electrodes 5A and 5B are made of a conductive material containing Ag and Pd as main components, for example. The width dimension of the internal electrode 5A is larger than the width dimension of the internal electrode 5B, and the internal electrodes 5A and 5B are alternately stacked in pairs with the piezoelectric material 4 being sandwiched between them. Yes. As a result, the internal electrodes 5A and 5B overlap in the stacking direction of the stacked body 2. The internal electrodes 5A and the internal electrodes 5B can be connected to external terminals via through electrodes (not shown).

  In the multilayer body 2, the portion where the internal electrodes 5 </ b> A and 5 </ b> B overlap in the stacking direction is an active portion P <b> 1 where the piezoelectric body 4 is displaced when a voltage is applied to the internal electrodes 5 </ b> A and 5 </ b> B. On the other hand, portions where the internal electrodes 5A and 5B do not overlap in the stacking direction (side portions of the active portion P1) become inactive portions Q1 where the piezoelectric body 4 is not displaced when a voltage is applied to the internal electrodes 5A and 5B. ing.

  The actuator portion 11 of the piezoelectric device 1 is configured by the cooperation of the active portion P1 and the inactive portion Q1. In the actuator unit 11, when a voltage is applied, the piezoelectric body 4 of the active part P1 is displaced so as to contract in the in-plane direction, and a bending displacement is generated downward as a whole (see FIG. 4). In the laminated body 2, three such actuator portions 11 are arranged along a predetermined direction.

  Further, in the laminate 2, non-actuator portions 12 configured by laminating only the piezoelectric bodies 4 are respectively provided between the actuator portions 11 and 11 and at the arrangement end of the actuator portions 11 of the laminate 2. Yes. The non-actuator portion 12 does not have the internal electrodes 5A and 5B when viewed from the stacking direction. Therefore, the non-actuator part 12 is a part that does not directly contribute to the occurrence of bending displacement when a voltage is applied.

  The non-actuator portion 12 is provided with a slit (stress relaxation portion) S. In the plurality of green sheets 14 (see FIG. 3) that are the precursors of the piezoelectric body 4, the slits 18 simultaneously prevent the sintering reaction between predetermined regions facing each other, thereby simultaneously performing the sintering of the laminate 2. It is formed. For example, the width of the slit 18 is substantially equal to the width of the leg 3. Further, as shown in FIG. 2, the edge of the slit 18 is located on the inner side by a predetermined width than the side surface of the stacked body 2. That is, the slit 18 is not exposed on the surface of the stacked body 2 but is present only in the stacked body 2.

  Then, the manufacturing method of the piezoelectric device 1 mentioned above is demonstrated.

  FIG. 3 is an exploded perspective view showing a green laminated body produced when the piezoelectric device 1 is manufactured. As shown in the figure, first, a green sheet paste prepared by mixing an organic binder resin, an organic solvent, and the like with ceramic powder containing PZT as a main component is prepared. Next, for example, by using a doctor blade method, a green sheet paste is applied on a carrier film (not shown) to form a plurality of green sheets 14 for forming the piezoelectric body 4.

  For example, an electrode pattern paste is prepared by mixing an organic binder resin, an organic solvent, and the like with a conductive material having a ratio of Ag: Pd = 85: 15. Then, for example, by using screen printing, the electrode pattern paste is printed on the green sheet 14, and the electrode patterns 15A and 15B corresponding to the internal electrodes 5A and 5B are formed on the separate green sheets 14, respectively.

Further, to prepare a ZrO ₂ paste for example, by mixing an organic binder resin and an organic solvent such as a ceramic powder comprising ZrO _2. For example, by using a screen, in one green sheet 14 on which the electrode pattern 15B is printed, an area between the electrode patterns 15B and 15B and an area that does not overlap with the electrode patterns 15A and 15B in the upper and lower green sheets 14 Then, a ZrO ₂ paste pattern 16 is formed.

At this time, the edge of the ZrO ₂ paste pattern 16 is formed so as not to contact the end of the green sheet 14 and the adjacent electrode pattern 15B. The paste pattern can be formed using a material containing at least one of MgO, Nb ₂ O ₅ , Ta ₂ O ₅ , CeO ₂ , and Y ₂ O in addition to the above-described ZrO ₂ .

After the formation of the electrode patterns 15A and 15B and the ZrO ₂ paste pattern 16, the green sheet 14 on which the electrode pattern 15A is formed, the green sheet 14 on which the electrode pattern 15B is formed, and the electrode pattern 15B and the ZrO ₂ paste pattern 16 The formed green sheets 14 are stacked in a predetermined order. Further, the green sheet 14 without pattern formation is laminated on the outermost layer as a protective layer. Thereby, the green laminated body 17 is formed.

Next, the green laminate 17 is placed on a setter, and a binder removal process is performed at a temperature of about 400 ° C. for about 10 hours. And the green laminated body 17 after a binder removal is put in a mortar furnace, and it bakes for about 2 hours at the temperature of 950 degreeC-1000 degreeC, for example. Thus, the green sheet 14, the electrode patterns 15A, 15B, and ZrO ₂ paste pattern 16 is respectively sintered laminate 2 as a sintered body is obtained.

By the way, the ZrO ₂ paste pattern 16 described above is formed of a material having a composition system different from that of the green sheet 14. Therefore, in the region where the green sheet 14 and the ZrO ₂ paste pattern 16 are in contact, the sintering reaction is hindered, and the upper and lower green sheets 14 and 14 are not integrated. Therefore, when the green laminate 17 is sintered, the region where the ZrO ₂ paste pattern 16 is interposed becomes the slit 18 as it is, and the upper and lower green sheets 14 and 14 are separated from each other in this portion.

  Thereafter, a polarization process is performed, for example, at a temperature of 1200 ° C. for about 3 minutes so that the electric field strength in the thickness direction of the piezoelectric body 4 is about 2 kV / mm. When the leg portions 3 are bonded and fixed to the bottom surface, the piezoelectric device 1 shown in FIGS. 1 and 2 is completed.

  As described above, in the piezoelectric device 1, the slit 18 is provided between the actuator units 11 and 11 arranged in the direction orthogonal to the stacking direction of the laminate 2 and the non-actuator unit 12 existing at the arrangement end of the actuator unit 11. Is provided. Here, in the piezoelectric device 1, when a voltage is applied from the outside, the piezoelectric body 4 of the active part P <b> 1 is displaced in the in-plane direction in the actuator unit 11, and as shown in FIG. A deflection displacement occurs.

  When the slit 18 is not formed, it is conceivable that the displacement amount of the bending displacement generated in the actuator unit 11 is limited by the non-actuator unit 12 that does not directly contribute to the generation of the bending displacement. On the other hand, in the piezoelectric device 1, the non-actuator part 12 is displaced downward in conjunction with the bending displacement of the actuator part 11 by the slit 18 provided in the non-actuator part 12. For this reason, the restraining force of the bending displacement by the non-actuator part 12 is relieved, and the displacement amount of the bending displacement by the actuator part 11 can be sufficiently ensured.

  Further, since the non-actuator portion 12 is displaced by the formation of the slit 18, the stress generated in the piezoelectric body 4 when the actuator portion 11 is deflected and displaced is relieved in the non-actuator portion 12. As a result, the transmission of stress to other adjacent actuator parts 11 is suppressed, and crosstalk between the actuator parts 11 and 11 can be reduced even when the actuator parts 11 are individually driven.

Such slits 18 are formed at the same time when the laminate 2 is sintered by, for example, forming a ZrO ₂ paste pattern 16 in a predetermined region of the green sheet 14 and preventing a sintering reaction between the green sheets 14 and 14. It is formed. Therefore, unlike the case where a stress relaxation portion such as a groove is formed in the non-actuator portion 12 by a mechanical method, there is no damage to the piezoelectric body 4 due to processing, and the manufacturing process can be prevented from becoming complicated.

[Second Embodiment]
Subsequently, a second embodiment of the present invention will be described. FIG. 5 is a longitudinal sectional view showing the layer structure of the piezoelectric device according to the second embodiment of the present invention.

  As shown in FIG. 5, the piezoelectric device 20 includes a laminated body having a substantially rectangular parallelepiped shape. The piezoelectric device 20 is used for a fuel injection device of an internal combustion engine mounted on an automobile, for example. The piezoelectric device 20 is different from the first embodiment in that the arrangement direction of the actuator units 24 is arranged in the lamination direction of the laminated body 21. The material of each component is the same as in the first embodiment.

  Similar to the first embodiment, the multilayer body 21 is formed by laminating a plurality of piezoelectric bodies 22 and a plurality of internal electrodes 23A and 23B in a predetermined order and sintering them. One end of the internal electrode 23 </ b> A is exposed on one side surface 21 a of the multilayer body 21, and the other end of the internal electrode 23 </ b> A is located inside the other side surface 21 b of the multilayer body 21. Further, one end of the internal electrode 23B is exposed on the other side surface 21b of the multilayer body 21, and the other end of the internal electrode 23B is positioned on the inner side of the one side surface 21a of the multilayer body 21.

  The internal electrodes 23A, 23B are laminated as a set of the internal electrode 23A-the internal electrode 23B-the internal electrode 23A so as to sandwich the piezoelectric body 22, and the set of internal electrodes and the piezoelectric body 22 adjacent thereto are formed. One actuator unit 24 is configured. In the actuator part 24, a bending displacement occurs when a voltage is applied to the internal electrodes 23A and 23B by the cooperation of the active part P2 and the inactive part Q2. In this piezoelectric device 20, in the actuator parts 24A and 24B adjacent vertically, the arrangement of the active part P2 and the inactive part Q2 is reversed with each other, and the upward and downward deflection displacements alternate. (See FIG. 7).

  The piezoelectric body 22 existing between the actuator portions 24 and 24 is provided with a slit (stress relaxation portion) 25. The slits 25 simultaneously prevent the sintering reaction between the predetermined areas facing each other in the plurality of green sheets 31 (see FIG. 6) that are the precursors of the piezoelectric body 22, during the sintering of the stacked body 21. It is formed. The slits 25 are formed alternately in the stacked body 21.

  More specifically, the piezoelectric body 22 between the actuator portion 24A that generates the upward deflection displacement and the actuator portion 24B that generates the downward deflection displacement extends in correspondence with the position of the active portion P2. An existing slit 25A is formed, and the piezoelectric body between the actuator portion 24B that generates a downward bending displacement and the actuator portion 24A that generates an upward bending displacement includes side surfaces 21a, A slit 25B extending from each of 21b toward the center is formed.

  The slit 25 </ b> A is located at the central portion of the piezoelectric body 22, and the edge of the slit 25 </ b> A does not reach the side surfaces 21 a and 21 b of the multilayer body 21. On the other hand, the edge on the center side of the piezoelectric body 22 in the slit 25 </ b> B partially overlaps the slit 25 </ b> A when viewed from the stacking direction of the stacked body 21, but does not reach the central portion of the piezoelectric body 22. ing.

  Next, a method for manufacturing the above-described piezoelectric device 20 will be described.

FIG. 6 is an exploded perspective view showing a green laminated body produced when the piezoelectric device 20 is produced. First, as in the first embodiment, a plurality of green sheets 31 for forming the piezoelectric body 22 are formed, and electrode patterns 32A and 32B corresponding to the internal electrodes 23A and 23B are formed on the separate green sheets 31, respectively. Form. Further, ZrO ₂ paste patterns 33A and 33B corresponding to the slits 25A and 25B are formed on still another green sheet 31, respectively.

Next, the green sheet 31 on which the electrode pattern 32A is formed, the green sheet 31 on which the electrode pattern 32B is formed, the green sheet 31 on which the ZrO ₂ paste pattern 33A is formed, and the green sheet on which the ZrO ₂ paste pattern 33B is formed 31 are stacked in a predetermined order. Further, the green sheet 31 without pattern formation is laminated on the outermost layer as a protective layer. Thereby, the green laminated body 34 is formed.

After the binder removal treatment, the green laminate 34 is placed in a mortar furnace and baked at a temperature of, for example, 950 ° C. to 1000 ° C. for about 2 hours. Thereby, the green sheet 31, the electrode patterns 32A and 32B, and the ZrO ₂ paste patterns 33A and 33B are respectively sintered, and the laminate 21 as a sintered body is obtained. At this time, the regions where the ZrO ₂ paste patterns 33A and 33B are interposed become the slits 25A and 25B as they are, and the upper and lower green sheets 31 and 31 are separated from each other at the portions.

  Thereafter, when the same polarization process as in the first embodiment is performed, the piezoelectric device 20 shown in FIG. 5 is completed.

  As described above, in the piezoelectric device 20, the slit 25 is provided in the piezoelectric body 22 existing between the actuator portions 24 and 24 arranged in the stacking direction of the stacked body 21. When the slit 25 is not formed, when the actuator unit 24 is driven by applying a voltage, the actuator unit 24A that generates the deflection displacement upward and the actuator unit 24B that generates the deflection displacement downward bind each other. It is conceivable that the amount of deflection displacement generated in the entire actuator unit 24 is limited.

  On the other hand, in the piezoelectric device 20, as shown in FIG. 7, the piezoelectric body 22 between the actuator portions 24 </ b> A and 24 </ b> B and the piezoelectric body 22 between the actuator portions 24 </ b> B and 24 </ b> A are separated by the slit 25. , 24B, the restraining force of the deflection displacement is relaxed. Therefore, the displacement amount of the deflection displacement in the entire actuator unit 24 can be sufficiently ensured.

For example, the slit 25 forms ZrO ₂ paste patterns 33A and 33B in a predetermined region of the green sheet 31 and prevents a sintering reaction between the green sheets 31 and 31 so that the laminate 21 is sintered. Are formed simultaneously. Therefore, unlike the case where the stress relaxation portion is formed in the piezoelectric body 22 by a mechanical method, there is no damage caused by processing, and the manufacturing process can be prevented from becoming complicated.

It is a longitudinal section showing the layer structure of the piezoelectric device concerning a 1st embodiment of the present invention. FIG. 2 is a plan view of the piezoelectric device shown in FIG. 1. It is a disassembled perspective view which shows the green laminated body produced in the case of manufacture of the piezoelectric apparatus shown in FIG. It is the longitudinal cross-sectional view which showed the mode of the drive of the piezoelectric apparatus shown in FIG. It is a longitudinal cross-sectional view which shows the layer structure of the piezoelectric apparatus which concerns on 2nd Embodiment of this invention. It is a disassembled perspective view which shows the green laminated body produced in the case of manufacture of the piezoelectric apparatus shown in FIG. FIG. 6 is a longitudinal sectional view showing how the piezoelectric device shown in FIG. 5 is driven.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,20 ... Piezoelectric device, 2,21 ... Laminated body, 4,22 ... Piezoelectric body, 5A, 5B, 23A, 23B ... Internal electrode, 11, 24 ... Actuator part, 12 ... Non-actuator part, 14, 34 ... Green Sheet, 18, 25 ... slit (stress relieving part), P1, P2 ... active part, Q1, Q2 ... inactive part.

Claims (7)

Comprising a laminate formed by alternately laminating and sintering a plurality of piezoelectric bodies and a plurality of internal electrodes including a first electrode and a second electrode;
A piezoelectric device in which a plurality of actuator parts configured to include an active part in which the first electrode and the second electrode overlap in the stacking direction of the stacked body are arranged in the stacked body,
Between the actuator parts, there is provided a slit that is simultaneously formed when the laminate is sintered,
The actuator units are arranged in a direction orthogonal to the stacking direction of the stacked body,
A non-actuator part where the internal electrode does not exist is provided between the actuator parts and at the arrangement end of the actuator part,
Legs are provided on one surface in the stacking direction of the laminate,
The slit is provided between one piezoelectric layer corresponding to the position of the leg portion for each non-actuator portion so as not to be exposed on the surface of the laminate, and is substantially equal in width to the leg portion . A piezoelectric device characterized by extending in a direction perpendicular to the stacking direction. Said slit, said a plurality of green sheets, which is a precursor of the piezoelectric body, the piezoelectric according to claim 1, characterized in that the slit formed by preventing sintering reaction between predetermined region facing each other apparatus. The slit is formed by sintering the green sheet in which a material containing at least one of ZrO ₂ , MgO, Nb ₂ O ₅ , Ta ₂ O ₅ , CeO ₂ , and Y ₂ O is applied to the predetermined region. The piezoelectric device according to claim 2.   The piezoelectric device according to any one of claims 1 to 3, wherein the actuator section generates a flexural displacement in a stacking direction of the stacked body. Comprising a laminate formed by alternately laminating and sintering a plurality of piezoelectric bodies and a plurality of internal electrodes including a first electrode and a second electrode;
A piezoelectric device in which a plurality of actuator parts configured to include an active part in which the first electrode and the second electrode overlap in the stacking direction of the stacked body are arranged in the stacked body,
Between the actuator parts, there is provided a slit that is simultaneously formed when the laminate is sintered,
The actuator part is
A first actuator unit that generates a deflection displacement toward one side in a stacking direction of the stacked body;
A second actuator unit that generates a deflection displacement toward the other side in the stacking direction of the stack, and is alternately arranged in the stacking direction,
The slit is
A first slit extending in a direction perpendicular to the stacking direction of the stacked body corresponding to the position of the active portion in the piezoelectric body between the first actuator section and the second actuator section;
In the piezoelectric body between the second actuator portion and the first actuator portion, a second slit extending in a direction perpendicular to the stacking direction of the stacked body from the side surface of the stacked body toward the active portion And a piezoelectric device characterized by comprising: Said first slit and said second slit, a plurality of green sheets, which is a precursor of the piezoelectric body is a slit formed by preventing sintering reaction between predetermined region facing each other The piezoelectric device according to claim 5. The first slit and the second slit may be formed by applying a material containing at least one of ZrO ₂ , MgO, Nb ₂ O ₅ , Ta ₂ O ₅ , CeO ₂ , and Y ₂ O to the predetermined region. The piezoelectric device according to claim 6, wherein the piezoelectric device is formed by sintering a sheet.

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