WO2012035932A1 - 圧電素子及び積層型圧電構造体 - Google Patents
圧電素子及び積層型圧電構造体 Download PDFInfo
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- WO2012035932A1 WO2012035932A1 PCT/JP2011/068828 JP2011068828W WO2012035932A1 WO 2012035932 A1 WO2012035932 A1 WO 2012035932A1 JP 2011068828 W JP2011068828 W JP 2011068828W WO 2012035932 A1 WO2012035932 A1 WO 2012035932A1
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- 238000006073 displacement reaction Methods 0.000 abstract description 18
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/80—Constructional details
- H10N30/87—Electrodes or interconnections, e.g. leads or terminals
- H10N30/871—Single-layered electrodes of multilayer piezoelectric or electrostrictive devices, e.g. internal electrodes
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/50—Piezoelectric or electrostrictive devices having a stacked or multilayer structure
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/80—Constructional details
- H10N30/87—Electrodes or interconnections, e.g. leads or terminals
- H10N30/872—Interconnections, e.g. connection electrodes of multilayer piezoelectric or electrostrictive devices
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/80—Constructional details
- H10N30/87—Electrodes or interconnections, e.g. leads or terminals
- H10N30/875—Further connection or lead arrangements, e.g. flexible wiring boards, terminal pins
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/80—Constructional details
- H10N30/88—Mounts; Supports; Enclosures; Casings
- H10N30/886—Additional mechanical prestressing means, e.g. springs
Definitions
- the present invention relates to a piezoelectric element and a laminated piezoelectric structure, and in particular, a laminated piezoelectric structure such as a piezoelectric actuator configured by further laminating a piezoelectric element in which a piezoelectric layer made of piezoelectric ceramics and the internal electrode layer are laminated.
- a laminated piezoelectric structure such as a piezoelectric actuator configured by further laminating a piezoelectric element in which a piezoelectric layer made of piezoelectric ceramics and the internal electrode layer are laminated.
- a multilayer piezoelectric actuator for example, a multilayer piezoelectric element described in JP-A-2005-108989 (Patent Document 1) is known.
- This multilayer piezoelectric element has a laminate in which a piezoelectric ceramic layer and an internal electrode layer are laminated, and the internal electrode layer includes a first internal electrode layer and a second internal electrode layer.
- the first internal electrode layers are alternately led to different side surfaces of the multilayer body.
- the second internal electrode layer is formed over substantially the entire cross section of the multilayer body for each predetermined length dimension in the stacking direction of the multilayer body, and is led out to at least one side surface of the multilayer body.
- protective layers serving as contact points with the object to be driven are provided on the upper and lower surfaces of the multilayer piezoelectric element.
- this type of laminated piezoelectric element first, an electric field is applied between the second internal electrode layers to perform overall polarization in which the orientation of the domain of the entire laminate is oriented in the substantially laminating direction, and then the first internal electrode Interlayer polarization in which an electric field is applied to the stacked body through the layers is performed.
- a multilayer piezoelectric element described in Japanese Patent Laid-Open No. 7-135348 (Patent Document 2) is known.
- This multilayer piezoelectric element includes a plurality of piezoelectric layers, internal electrodes that are arranged between the piezoelectric layers and drawn out on both side surfaces facing each other, and the same poles drawn out on both sides.
- Two external electrodes that are electrically connected to each internal electrode are provided, and the two external electrodes are formed so as to extend from the side surface from which the internal electrodes of the same polarity are drawn out to the upper and lower surfaces.
- the upper and lower piezoelectric layers are polarized at the ends, but are not polarized near the center.
- the present invention has been made paying attention to the above points, and according to various embodiments of the present invention, a piezoelectric element and a laminate type that can reduce displacement transmission loss and prevent cracks from occurring.
- a piezoelectric structure is provided.
- a piezoelectric element includes a first piezoelectric layer having an internal electrode drawn out to a first part, and an internal electrode drawn out to a second part different from the first part.
- a plurality of second piezoelectric layers are alternately stacked, and a cover portion made of a piezoelectric layer is formed at each end in the stacking direction, and each of the internal electrodes drawn out to the first portion is provided with a first portion.
- first and second cover part electrodes are formed on the exposed surface of the cover part, and the first cover part electrode is at least at the center of the cover part. Covering the vicinity, connecting the first cover electrode to an external electrode to which a drive voltage having a polarity different from that of the internal electrode facing the cover portion is sandwiched, and connecting the second cover electrode to the cover portion It is connected to an external electrode to which a drive voltage of the same polarity as the internal electrode opposite to the electrode is applied, and at least the vicinity of the center of the cover portion is polarized and activated by the first cover electrode and the opposing internal electrode It is characterized by that.
- One aspect of the present invention is that an insulating layer is formed around the cover electrode.
- the piezoelectric element according to any one of the above is joined to the cover electrode to which the drive voltage of the same polarity is applied, and the drive voltage of the same polarity is applied.
- a large number of external electrodes are stacked on the same surface.
- the present invention since the vicinity of the center of the cover portion is polarized into the active region, the loss of displacement transmission can be reduced well, and the occurrence of cracks can also be prevented.
- a piezoelectric element 100 includes a plurality of piezoelectric layers 12 having internal electrodes 10 formed on the surface and a plurality of piezoelectric layers having internal electrodes 20 formed on the surface.
- Cover portions 32 and 42 having cover portion electrodes 30 and 40 formed on the surface are respectively laminated on the upper and lower surfaces of a laminated structure formed by alternately laminating layers 22.
- the cover part electrodes 30 and 40 are configured in the same shape as the internal electrodes 10 and 20.
- the cover electrodes 30 and 40 are configured to have an area substantially equal to the internal electrodes 10 and 20. Further, the cover electrodes 30 and 40 are arranged so as to overlap the internal electrodes 10 and 20.
- the cover part electrode 30 is drawn out in the same direction as the internal electrode 20, and the cover part electrode 40 is drawn out in the same direction as the internal electrode 10.
- Internal electrodes 10 are formed on the surfaces of the plurality of piezoelectric layers 12, and internal electrodes 20 are formed on the surfaces of the plurality of piezoelectric layers 22. These internal electrodes 10 and 20 and cover part electrodes 30 and 40 are formed by printing, for example.
- FIG. 1B shows the appearance of the piezoelectric element 100 in which the piezoelectric layers 12 and 22 and the cover portions 32 and 42 are laminated.
- FIG. 1C shows a cross section viewed in the direction of the arrow along the line # 1- # 1 in FIG.
- the piezoelectric element 100 has a total of eight piezoelectric layers, which are composed of four piezoelectric layers 12 and four piezoelectric layers 22.
- the entire piezoelectric element 100 is simultaneously fired in a stacked state as shown in FIG.
- the upper and lower surfaces of the cover portions 32 and 42 are polished after simultaneous firing in order to ensure surface smoothness.
- FIG. 2A shows the external appearance of a piezoelectric element constituting a multilayer piezoelectric actuator according to an embodiment of the present invention.
- FIG. 2B shows a cross section viewed in the direction of the arrow along the line # 2- # 2 in FIG.
- the insulating layers 34 and 44 having the same thickness are formed around the cover part electrodes 30 and 40 of the piezoelectric element 100 shown in FIG.
- external electrodes 50 and 60 are formed in the internal electrode outlets on the side surfaces of the piezoelectric element 100, respectively.
- the external electrode 50 is connected to the lead portion of the internal electrode 10 and the cover portion electrode 40, and the external electrode 60 is connected to the lead portion of the internal electrode 20 and the cover portion electrode 30.
- the piezoelectric element 100 according to an embodiment of the present invention is obtained.
- FIG. 2C schematically shows a state where a plurality of piezoelectric elements 100 according to an embodiment of the present invention are stacked.
- FIG. 2D schematically shows a cross section of the stacked piezoelectric element 100.
- a stacked piezoelectric actuator according to an embodiment of the present invention is configured by stacking a required number of the piezoelectric elements 100 described above.
- three piezoelectric elements 100A-100C are stacked.
- a plurality of piezoelectric elements 100 are stacked in a state where every other piezoelectric element 100 is turned upside down. For example, when three piezoelectric elements 100A to 100C are stacked as shown in the drawing, the central piezoelectric element 100B is inverted and arranged.
- the plurality of piezoelectric elements 100 are arranged such that the cover part electrodes 30 and the cover part electrodes 40 face each other.
- the external electrode 50 of each piezoelectric element 100 is exposed on the same side surface of the stacked piezoelectric elements 100 in a state where the piezoelectric elements 100 are stacked.
- the external electrode 60 of each piezoelectric element 100 is also exposed on the same side surface of the stacked piezoelectric elements 100.
- the piezoelectric layers 12 and 22 are made of, for example, a piezoelectric ceramic green sheet having a layer thickness of 25 ⁇ m.
- the internal electrodes 10 and 20 are made of, for example, Ag, Ag / Pd (molar ratio is 7/3 to 95/5), Pt, Cu, Ni, or the like.
- the internal electrodes 10 and 20 are formed by printing or the like so as to cover, for example, about 50% or more of the surface of the piezoelectric layers 12 and 22.
- the piezoelectric element 100 according to an embodiment is configured by stacking 20 piezoelectric layers 12 and 22 on which internal electrodes 10 and 20 are formed.
- the cover portion 32 is configured by laminating a plurality of piezoelectric ceramic green sheets having a layer thickness of 25 ⁇ m.
- the total thickness of the cover part 32 is, for example, 200 ⁇ m.
- the cover portion 42 is configured by laminating a plurality of green sheets so that the total thickness is about 200 ⁇ m.
- the cover part electrodes 30 and 40 are configured similarly to the internal electrodes 10 and 20.
- the insulating layers 34 and 44 are made of polyimide, for example.
- the external electrodes 50 and 60 are made of, for example, Ag, and are formed by a method such as sputter deposition, adhesion using a thermosetting resin, or baking. The external electrodes 50 and 60 are formed with good adhesion on the side surface of the piezoelectric element 100 by being formed by baking.
- FIG. 3 is a diagram showing a main cross-sectional structure of the multilayer piezoelectric actuator according to one embodiment of the present invention.
- the cover electrodes 30 and the cover electrodes 40 are surfaces of a rigid adhesive (that is, an adhesive having the same degree of elasticity as the cover electrode 30 and the cover electrode 40).
- a rigid adhesive that is, an adhesive having the same degree of elasticity as the cover electrode 30 and the cover electrode 40.
- the cover part electrodes 30 and the cover part electrodes 40 can be joined using a highly elastic conductive adhesive.
- the insulating layers 34 and the insulating layers 44 are joined together by an insulating layer 72 such as epoxy in order to ensure insulation between the electrodes.
- the external electrodes 50 and the external electrodes 60 are electrically connected by a bridge 74 made of a conductive paste or the like.
- the piezoelectric layers 12 and 22 and the cover portions 32 and 42 are polarized by applying a polarization voltage between the external electrode 50 and the external electrode 60.
- a polarization voltage is applied to the external electrode 50 and a negative voltage is applied to the external electrode 60.
- the piezoelectric inactive layer is polarized and becomes an active layer.
- the state of the piezoelectric element 100 shown in FIGS. 2 (A) and 2 (B) that is, as shown in FIGS. 2 (A) and 2 (B)).
- the polarization process may be performed by applying a voltage to the external electrodes 50 and 60 in a state where the piezoelectric element 100 alone is used.
- the polarization direction of each layer is indicated by an arrow.
- the polarization direction is reversed across the internal electrodes 10 and 20.
- the piezoelectric layers 12 and 22 have a thickness different from that of the cover portions 32 and 42, but the inter-electrode applied voltage applied to the piezoelectric layers 12 and 22 and the inter-electrode applied voltage applied to the cover portions 32 and 42 during the polarization process. Therefore, the piezoelectric layers 12 and 22 and the cover portions 32 and 42 have different effective electric field strengths and different polarization states (strains). This difference in polarization state is defined by a combination of the thickness of the piezoelectric layers 12 and 22 and the thickness of the cover portions 32 and 42.
- the laminated piezoelectric actuator 110 is obtained by the above polarization treatment.
- FIG. 4A shows the appearance of the multilayer piezoelectric actuator 110 according to one embodiment of the present invention.
- a drive voltage is applied to the external electrodes 50 and 60. Due to this drive voltage, distortion corresponding to the applied electric field is generated in the piezoelectric layers 12 and 22 and the cover portions 32 and 42, and the multilayer piezoelectric actuator 110 is deformed as a whole in accordance with this distortion.
- the cover portions 32 and 42 are also displaced by the driving voltage, so that the strain difference between the piezoelectric layers 12 and 22 and the cover portions 32 and 42 is reduced, and cracks are generated. Can be suppressed.
- the cover electrodes 30 and 40 may be configured to have a larger area than the internal electrodes 10 and 20. Even when the cover part electrodes 30 and 40 are formed to have a larger area than the internal electrodes 10 and 20, the size of the polarized active region of the cover parts 32 and 42 is different from that of the cover part electrodes 30 and 40. It is almost equivalent to the case where it is configured to have the same area.
- FIG. 4B shows a piezoelectric element 120 according to another embodiment of the present invention.
- the piezoelectric element 120 is configured such that the cover electrode 30A has a smaller area than the internal electrode 10A.
- the active area of the cover part of the piezoelectric element 120 becomes narrower than that of the piezoelectric element 100, but the laminated piezoelectric structure generally tends to have a large displacement near the center of the cover part. If is polarized, it is possible to reduce the displacement transmission loss and prevent the occurrence of cracks when the coupling body is used.
- FIG. 4C shows a piezoelectric element 122 according to another embodiment of the present invention.
- the piezoelectric element 122 has a cover portion electrode 30B formed in a circular shape.
- the four corners of the internal electrode 10B do not overlap the cover portion electrode 30A, and the portions corresponding to the four corners of the internal electrode 10B of the cover portion are not polarized, but the vicinity of the center of the cover portion is polarized, so FIG.
- the displacement transmission loss is reduced, and the occurrence of cracks can be prevented.
- the cover parts electrodes 30 and 40 having the same shape as the internal electrodes 10 and 20 are formed on the cover parts 32 and 42, the cover parts 32 and 42 have an electric field effective area equal to that of the piezoelectric layers 12 and 22. Since the cover portions 32 and 42 and the piezoelectric layers 12 and 22 have an electric field effective area equal to each other, the portions having the same area become piezoelectric active layers when a driving voltage is applied, thereby reducing displacement transmission loss. Can do.
- the cover electrodes 30 and 40 do not need to be peeled off after polarization, and not only can the number of manufacturing steps be reduced, but also can be used as they are to connect the connected body, and the external electrodes 50 and 60 can be connected to each other. Later, the integrated polarization of the coupling body becomes possible.
- the difference (strain difference) between the polarization states of the two can be defined.
- the strain amount of the cover portions 32 and 42 is piezoelectric compared to the case where the cover portions 32 and 42 are piezoelectrically inactive. It approaches the strain amount of the layers 12 and 22. For this reason, it is possible to prevent or reduce cracks during displacement.
- the sample of the present invention was tested and compared with the multilayer piezoelectric element of the prior art (Patent Document 2) described above, and the results shown in the following Table 1 were obtained.
- Example 2 of the present invention will be described with reference to FIG.
- the cover electrodes were formed on both the front and back surfaces of the piezoelectric element, whereby the piezoelectric elements were easily connected to each other.
- FIG. 5A shows the appearance of the piezoelectric element 200 according to the second embodiment of the present invention.
- FIG. 5B schematically shows a state in which a plurality of piezoelectric elements 200 according to the second embodiment of the present invention are stacked.
- FIG. 5C shows an actuator obtained by stacking the piezoelectric elements 200 according to the second embodiment of the present invention.
- the external electrode 60 of the piezoelectric element 200 is connected to the cover portion electrode 230A on the upper surface side and the cover portion electrode 230B on the lower surface side.
- the external electrode 50 is connected to the lower surface side cover portion electrode 240A and the upper surface side cover portion electrode 240B, respectively.
- the cover part electrode 230A is formed on the upper surface side of the piezoelectric element 200 so as to have a larger area than the cover part electrode 240B.
- An insulating layer 234 is formed around the cover electrode 230A and the cover electrode 240B for insulation and thickness matching of both electrodes.
- the cover electrode 240A is formed to have a larger area than the cover electrode 230B.
- An insulating layer 244 is formed around the cover part electrode 240A and the cover part electrode 230B for insulation and thickness matching of both electrodes.
- the piezoelectric elements 200 as described above are laminated by inverting the top and bottom.
- a piezoelectric element 200B that is inverted up and down is disposed between the piezoelectric element 200A and the piezoelectric element 200C.
- the cover part electrodes 240A and the cover part electrodes 230B are joined, and between the piezoelectric elements 200B and 200C, the cover part electrodes 230A and the cover part electrodes 240B are respectively joined. Join.
- a region sandwiched between the cover portion electrode 230A having a large area and the internal electrode 10 and a region sandwiched between the cover portion electrode 240A having a large area and the internal electrode 20 are polarized. Therefore, although the active region is narrower than that of the first embodiment described above, since the central portion is polarized, the displacement transmission loss is reduced and cracks can be prevented from occurring as in the first embodiment.
- a lead line for applying a driving voltage can be provided on the same end face.
- the cover electrodes having different polarities are exposed on the upper and lower surfaces of the piezoelectric element 200. Therefore, by stacking the piezoelectric elements 200, it is possible to connect the external electrodes without providing a bridge between the external electrodes.
- the stacked piezoelectric elements 200A, 200B, and 200C are supported from above and below by the spring means 250, so that the stacked structure can be maintained without using an adhesive or the like.
- Spacers 252 are provided between the spring means 250 and the upper end of the piezoelectric element 200A and the lower end of the piezoelectric element 200C for insulation or the like.
- 5C can be provided with a structure that gives displacement to the outside (not shown).
- FIG. 6 shows a piezoelectric element 300 according to Embodiment 3 of the present invention.
- Each unit piezoelectric element constituting the piezoelectric element 300 includes four piezoelectric layers 12 (four internal electrodes 10) and three piezoelectric layers 22 (three internal electrodes 20). It is composed of piezoelectric layers.
- the external electrode 60 is connected to the cover portion electrode 330A on the upper surface side and the cover portion electrode 330B on the lower surface side.
- the external electrode 50 is not connected to the cover electrode, and insulating layers 334 and 344 are formed between the external electrode 50 and the cover electrodes 330A and 330B for insulation and thickness matching of both electrodes. ing.
- a stacked actuator can be obtained by stacking the piezoelectric elements 300 in the same direction.
- the connection between the cover part electrode 330A and the cover part electrode 330B and the connection between the external electrodes 50 can be performed by the same method as shown in FIG.
- Embodiment 4 of the present invention will be described with reference to FIG. Also in this embodiment, the number of stacked piezoelectric layers is an odd number.
- the external electrode 60 of the piezoelectric element 400 is connected to the cover portion electrode 430A on the upper surface side and the cover portion electrode 430B on the lower surface side.
- the external electrode 50 is connected to the upper surface side cover portion electrode 440A and the lower surface side cover portion electrode 440B, respectively.
- the cover electrode 430A, 430B connected to the external electrode 60 has an area larger than the cover electrode 440A, 440B connected to the external electrode 50 on either the upper surface or the lower surface of the piezoelectric element 400. Is set large, and insulating layers 434 and 444 for insulation and thickness matching of both electrodes are formed around them.
- a stacked actuator can be obtained by stacking the piezoelectric elements 400 in the same direction.
- the cover electrodes having different polarities are exposed on the upper and lower surfaces of the piezoelectric element 400. Therefore, by stacking the piezoelectric elements 400, it is possible to connect the external electrodes without providing a bridge between the external electrodes.
- a lead line for applying a driving voltage can be provided on the same end face.
- the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. For example, the following changes can be added.
- (1) The shape and size of each part, the material, the number of stacked piezoelectric layers, the number of stacked piezoelectric elements, etc. shown in the above embodiments are merely examples, and may be appropriately changed as necessary.
- a flexible material can be used as the protective layer.
- the multilayer piezoelectric structure of the present invention can be applied to a multilayer piezoelectric actuator, but it does not preclude application to other piezoelectric actuators.
- piezoelectric elements with an even number of piezoelectric layers or odd-numbered piezoelectric elements are laminated, respectively. However, an even-numbered piezoelectric element and an odd-numbered piezoelectric element are laminated. You may make it do. For example, instead of the piezoelectric element 100C of FIG. 3, the piezoelectric element 300 of FIG. 6 is laminated.
- At least the vicinity of the center of the cover portion is polarized and activated, so that it is possible to reduce the displacement transmission loss and prevent the occurrence of cracks when the coupling body is used.
- This is suitable for a piezoelectric actuator of a type.
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Abstract
Description
(1)カバー部32、42に内部電極10、20と同一の形状のカバー部電極30、40を形成するので、カバー部32、42が圧電層12、22と等しい電界有効面積を有する。カバー部32、42、及び、圧電層12、22は、互いに等しい面積の電界有効面積を有するので、駆動電圧の印加により互いに等しい面積を有する部分が圧電活性層となり、変位伝達損失を低減することができる。
(2)カバー部電極30、40は、分極後剥離する必要はなく、製造の工数軽減が可能であるのみならず、そのまま連結体の接続に用いることができ、外部電極50、60同士の接続後、連結体の一体分極が可能となる。
(3)圧電層12、22の厚みとカバー部32、42の厚みが互いに異なることにより、圧電層12、22の実効電界強度とカバー部32、42の実効電界強度も互いに異なるので、圧電層12、22とカバー部32、42とでは圧電活性層となった両者の分極状態が異なる。しかし、圧電層12、22の厚みとカバー部32、42の厚みを規定することで、両者の分極状態の差(歪み差)を規定することができる。
(4)カバー部32、42を圧電層12、22と同じ圧電活性層とすることで、カバー部32、42が圧電不活性の場合と比較して、カバー部32、42の歪量が圧電層12、22の歪量に近づく。このため、変位時のクラック防止ないし低減を図ることができる。
(5)本発明のサンプルについて実験を行い、上述した従来技術(特許文献2)の積層型圧電体素子と比較したところ、次の表1に示すような結果が得られた。駆動電圧ON/OFFを100万回行った後の製品100個当たりのクラック発生率について比較すると、従来技術では50個についてクラックが発生したのに対し、本発明では発生しなかった。また、カバー部を分極しない場合と比較して、相対変位量が1.25となり、変位も増大した。
(1)前記実施例に示した各部の形状・寸法、材料、圧電層の積層数、圧電素子の積層数などは、いずれも一例であり、必要に応じて適宜変更してよい。
(2)前記実施例を組み合わせることも任意である。例えば、圧電素子を複数積層した場合に、その上下両端もしくは上下どちらかの圧電素子の表面について、カバー電極構造を図5(A)のような形状とすることで、駆動電圧印加のための引き出し線を同一端面に設けることができる。
(3)カバー部電極を保護するための保護層を更に形成してもよい。保護層としては、柔軟性のある材料を用いることができる。
(4)本発明の積層型圧電構造体は、積層型の圧電アクチュエータに適用することができるが、それ以外のものに適用することを妨げるものではない。
(5)前記実施例では、圧電層の積層数が偶数の圧電素子同士、もしくは奇数の圧電素子同士を、それぞれ積層したが、圧電層の積層数が偶数の圧電素子と奇数の圧電素子を積層するようにしてもよい。例えば、図3の圧電素子100Cの代わりに、図6の圧電素子300を積層するという具合である。
12、22:圧電層
30、30A、30B、40:カバー部電極
32、42:カバー部
34、44:絶縁層
50、60:外部電極
70:接着層
72:絶縁層
74:ブリッジ
100、100A~100C:圧電素子
110:積層型圧電アクチュエータ
120、122:圧電素子
200:圧電素子
200A、200B、200C:圧電素子
230A、230B:カバー部電極
234:絶縁層
240A、240B:カバー部電極
244:絶縁層
250:バネ手段
252:スペーサ
300:圧電素子
330A、330B:カバー部電極
334、344:絶縁層
340A、340B:カバー部電極
400:圧電素子
430A、430B:カバー部電極
434、444:絶縁層
440A、440B:カバー部電極
Claims (7)
- 第1の部位に引き出された第1の内部電極を有する複数の第1の圧電層と前記第1の部位と異なる第2の部位に引き出された第2の内部電極を有する複数の第2の圧電層とを交互に積層して成る積層構造体と、
前記積層構造体の積層方向の両端部に設けられ、圧電体から成る一組のカバー部と、
前記一組のカバー部の各々の露出面に、対応するカバー部の少なくとも中央付近を覆うように設けられた一組のカバー部電極と、
前記第1の内部電極のそれぞれに第1の極性の駆動電圧を印加する第1の外部電極と、
前記第2の内部電極のそれぞれに第2の極性の駆動電圧を印加する第2の外部電極と、
を備え、
該一組のカバー部電極の各々が前記第1の内部電極と隣接する場合には、該第1の内部電極と隣接するカバー部電極を前記第2の外部電極に接続する一方、該一組のカバー部電極の各々が前記第2の内部電極と隣接する場合には、該第2の内部電極と隣接するカバー部電極を前記第1の外部電極に接続した圧電素子。 - 第1の部位に引き出された第1の内部電極を有する複数の第1の圧電層と前記第1の部位と異なる第2の部位に引き出された第2の内部電極を有する複数の第2の圧電層とを交互に積層して成る積層構造体と、
前記積層構造体の積層方向の両端部に設けられ、圧電体から成る一組のカバー部と、
前記一組のカバー部の各々の露出面に、対応するカバー部の少なくとも中央付近を覆うように設けられた一組の第1カバー部電極と、
前記露出面の各々に、対応する第1カバー部電極と電気的に絶縁するように設けられた一組の第2カバー部電極と、
前記第1の内部電極のそれぞれに第1の極性の駆動電圧を印加する第1の外部電極と、
前記第2の内部電極のそれぞれに第2の極性の駆動電圧を印加する第2の外部電極と、
を備え、
該一組の第1カバー部電極の各々が前記第1の内部電極と隣接する場合には、該第1の内部電極と隣接する第1カバー部電極を前記第2の外部電極に接続する一方、該一組の第1カバー部電極の各々が前記第2の内部電極と隣接する場合には、該第2の内部電極と隣接する第1カバー部電極を前記第1の外部電極に接続し、
該一組の第2カバー部電極の各々が前記第1の内部電極と隣接する場合には、該第1の内部電極と隣接する第2カバー部電極を前記第2の外部電極に接続する一方、該一組の第2カバー部電極の各々が前記第2の内部電極と隣接する場合には、該第1の内部電極と隣接する第2カバー部電極を前記第1の外部電極に接続した圧電素子。 - 前記カバー部電極、前記第1カバー部電極、及び前記第2カバー部電極の少なくとも一つの周囲に絶縁層を形成した請求項1又は2記載の圧電素子。
- 前記カバー部電極と、該カバー部電極と隣接する内部電極とによって、前記カバー部の少なくとも中央付近を分極して活性化した請求項1に記載の圧電素子。
- 前記第1カバー部電極と、該第1カバー部電極と隣接する内部電極とによって、前記カバー部の少なくとも中央付近を分極して活性化した請求項2に記載の圧電素子。
- 前記第1及び第2の外部電極が、前記積層構造体の側面にその積層方向に沿って延伸するように設けられた請求項1又は2に記載の圧電素子。
- 複数の圧電素子を積層して成る積層型圧電構造体であって、
前記複数の圧電素子の各々が請求項6に記載された圧電素子であり、
前記複数の圧電素子に含まれ、互いに隣接する圧電素子は、
一方の圧電素子において第1の外部電極に接続されたカバー部電極、第1カバー部電極、又は第2カバー部電極と、他方の圧電素子において第1の外部電極に接続されたカバー部電極、第1カバー部電極、又は第2カバー部電極とが接合し、且つ、
前記一方の圧電素子の第1の外部電極が前記他方の圧電素子の第1の外部電極と同一面となると共に前記一方の圧電素子の第2の外部電極が前記他方の圧電素子の第2の外部電極と同一面となるように積層される積層型圧電構造体。
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