WO2018193863A1 - Piezoelectric actuator - Google Patents

Piezoelectric actuator Download PDF

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Publication number
WO2018193863A1
WO2018193863A1 PCT/JP2018/014562 JP2018014562W WO2018193863A1 WO 2018193863 A1 WO2018193863 A1 WO 2018193863A1 JP 2018014562 W JP2018014562 W JP 2018014562W WO 2018193863 A1 WO2018193863 A1 WO 2018193863A1
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WIPO (PCT)
Prior art keywords
electrode
internal electrode
internal
thickness
piezoelectric
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PCT/JP2018/014562
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French (fr)
Japanese (ja)
Inventor
靖行 佐藤
克己 山内
勝也 稲葉
阿部　陽子
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Tdk株式会社
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Publication of WO2018193863A1 publication Critical patent/WO2018193863A1/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
    • H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
    • H02N2/02—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing linear motion, e.g. actuators; Linear positioners ; Linear motors
    • H02N2/04—Constructional details
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
    • H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
    • H02N2/10—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing rotary motion, e.g. rotary motors
    • H02N2/12—Constructional details
    • 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
    • H10N30/20—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators
    • 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
    • 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

Definitions

  • the present invention relates to a piezoelectric actuator.
  • the piezoelectric actuator described in Patent Document 1 is a piezoelectric actuator that generates a vibration mode in which a longitudinal vibration mode and a bending vibration mode are combined by an applied voltage, and includes four fourth actuators arranged on the same piezoelectric layer.
  • positioned facing each other on both sides of a piezoelectric material layer, and a voltage is applied between 1st internal electrodes are comprised.
  • four first internal electrodes are arranged on the surface of the piezoelectric layer that is the outermost layer, and the first internal electrodes are exposed to the outside.
  • An object of one aspect of the present invention is to provide a piezoelectric actuator capable of improving drive characteristics while suppressing the occurrence of migration.
  • a piezoelectric actuator is a piezoelectric actuator that generates a vibration mode in which a longitudinal vibration mode and a bending vibration mode are synthesized by an applied voltage, and includes a plurality of piezoelectric layers that are rectangular.
  • an element body having a pair of main surfaces facing each other in the stacking direction of the plurality of piezoelectric layers, a plurality of internal electrodes disposed in the element body, and an outer surface of the element body, A plurality of external electrodes electrically connected to the corresponding internal electrodes, the plurality of internal electrodes being four first internal electrodes and four first internal electrodes disposed on the same piezoelectric layer And a second internal electrode disposed opposite to each other with a piezoelectric layer interposed therebetween, to which a voltage is applied between the first internal electrode and the four first internal powers in the element body.
  • the four first internal electrodes are arranged in the element body. That is, the first internal electrode is covered with the piezoelectric layer. Therefore, in the piezoelectric actuator, it is possible to suppress the occurrence of migration between the first internal electrodes.
  • the region between the main surface of the element body and the first internal electrode is an inactive region
  • the region between the first internal electrode and the second internal electrode is an active region
  • the stacking direction The thickness of the inactive region is smaller than the thickness of the active region.
  • the thickness of the inactive region is preferably 1 ⁇ 2 or less of the thickness of the active region. In this configuration, it is possible to further suppress displacement restraint due to the inactive region.
  • the thickness of the inactive region may be 1/5 or more and 1/2 or less of the thickness of the active region. In this configuration, since the thickness of the inactive region is secured to 1/5 or more of the thickness of the active region, in the configuration in which the external electrode is disposed on the main surface of the element body, the space between the external electrode and the first internal electrode is Withstand voltage can be secured.
  • two first internal electrodes are located at a first diagonal, and the other two first internal electrodes intersect with the first diagonal.
  • the two first internal electrodes located at the first diagonal or the second diagonal may be electrically connected by the connecting member. In this configuration, since the two first internal electrodes are electrically connected in the element body, it is not necessary to electrically connect the two internal electrodes by the external electrode. This increases the degree of freedom in designing the piezoelectric actuator.
  • FIG. 1A and FIG. 1B are perspective views of a piezoelectric actuator according to one embodiment.
  • FIG. 2 is a diagram illustrating a cross-sectional configuration of the piezoelectric actuator.
  • FIG. 3 is an exploded perspective view of the piezoelectric element.
  • FIG. 4A and FIG. 4B are diagrams illustrating the operation of the piezoelectric actuator.
  • FIG. 5 is a diagram showing the relationship between the thickness of the inactive region and the amplitude of the vibration mode.
  • FIG. 6 is an exploded perspective view of a piezoelectric element in a piezoelectric actuator according to another embodiment.
  • FIG. 7 is an exploded perspective view of a piezoelectric element in a piezoelectric actuator according to a modification.
  • the piezoelectric actuator 1 includes a piezoelectric element 3 and a friction portion 10.
  • the piezoelectric actuator 1 has a function of moving the driven body 100 (for example, a rotor or the like (see FIGS. 4A and 4B)) by being displaced by applying an AC voltage.
  • the piezoelectric element 3 includes a laminated body (element body) 2.
  • the laminate 2 has a rectangular parallelepiped shape.
  • the laminate 2 has a pair of end faces 2a, 2b facing each other, a pair of main faces 2c, 2d facing each other, and a pair of side faces 2e, 2f facing each other. .
  • the main surfaces 2c and 2d have a rectangular shape.
  • the facing direction of the pair of end surfaces 2a and 2b that face each other in the long side direction of the pair of main surfaces 2c and 2d is the longitudinal direction of the multilayer body 2 (piezoelectric element 3).
  • the facing direction in which the pair of main surfaces 2c and 2d are facing is the height direction of the multilayer body 2 (piezoelectric element 3).
  • the facing direction of the pair of side surfaces 2e and 2f facing each other in the long side direction of the pair of main surfaces 2c and 2d is the width direction of the multilayer body 2 (piezoelectric element 3).
  • the pair of end surfaces 2a and 2b extend so as to connect the pair of main surfaces 2c and 2d.
  • the pair of end surfaces 2a and 2b also extend in the short side direction of the pair of main surfaces 2c and 2d.
  • the pair of side surfaces 2e and 2f extend so as to connect the pair of main surfaces 2c and 2d.
  • the pair of side surfaces 2e and 2f also extend in the long side direction of the pair of end surfaces 2a and 2b.
  • the laminate 2 is made of a piezoelectric ceramic material.
  • the piezoelectric ceramic material include PZT [Pb (Zr, Ti) O 3 ], PT (PbTiO 3 ), PLZT [(Pb, La) (Zr, Ti) O 3 ], or barium titanate (BaTiO 3 ).
  • the laminate 2 is formed by laminating piezoelectric layers 20a to 20h (see FIG. 3) having a rectangular shape, which are sintered ceramic green sheets containing a piezoelectric ceramic material.
  • the stacking direction of the plurality of piezoelectric layers 20a to 20h coincides with the facing direction of the pair of main surfaces 2c and 2d.
  • the piezoelectric layers 20a to 20h are integrated so that the boundaries between the piezoelectric layers 20a to 20h cannot be visually recognized.
  • the outer surface of the piezoelectric layer 20a constitutes the main surface 2c of the multilayer body 2
  • the outer surface of the piezoelectric layer 20h constitutes the main surface 2d of the multilayer body 2.
  • the piezoelectric element 3 includes a first internal electrode 22, a second internal electrode 24, a third internal electrode 26, a fourth internal electrode 28, and a fifth internal electrode 30.
  • the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, the fourth internal electrode 28, and the fifth internal electrode 30 are electrically conductive materials (for example, Ag) that are normally used as internal electrodes of stacked electronic devices. , Au, Ni, Pt or Pd).
  • the 1st internal electrode 22, the 2nd internal electrode 24, the 3rd internal electrode 26, the 4th internal electrode 28, and the 5th internal electrode 30 are comprised as a sintered compact of the electrically conductive paste containing the said electrically conductive material.
  • the 1st internal electrode 22, the 2nd internal electrode 24, the 3rd internal electrode 26, and the 4th internal electrode 28 comprise the four 1st internal electrodes as described in a claim.
  • the fifth internal electrode 30 constitutes a second internal electrode described in the claims.
  • the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 are disposed on the piezoelectric layer 20b.
  • the first internal electrode 22 and the second internal electrode 24 are electrically insulated (separated) from each other on the piezoelectric layer 20b.
  • the third internal electrode 26 and the fourth internal electrode 28 are electrically connected to each other on the piezoelectric layer 20b.
  • the first internal electrode 22 is disposed on the piezoelectric layer 20b on the corner side formed by the end surface 2a and the side surface 2f of the multilayer body 2.
  • the first internal electrode 22 has a main electrode portion 22a and a connection portion 22b.
  • the main electrode portion 22a and the connection portion 22b are integrally formed.
  • the connection portion 22b extends from the main electrode portion 22a to the other side surface 2f of the multilayer body 2 and is exposed to the side surface 2f of the multilayer body 2. Specifically, the connecting portion 22b is exposed to the side surface 2f at a position near the one end surface 2a side of the laminate 2.
  • the second internal electrode 24 has a corner portion and a diagonal portion (first diagonal portion) where the first internal electrode 22 is disposed, that is, the end surface 2b and the side surface 2e of the multilayer body 2. Is arranged on the corner portion side.
  • the second internal electrode 24 has a main electrode portion 24a and a connection portion 24b.
  • the main electrode portion 24a and the connection portion 24b are integrally formed.
  • the connection portion 24 b extends from the main electrode portion 24 a to the side surface 2 e of the stacked body 2 and is exposed on the side surface 2 e of the stacked body 2. Specifically, the connection portion 24b is exposed to the side surface 2e at a position near the other end surface 2b side of the stacked body 2.
  • the 3rd internal electrode 26 is arrange
  • the third internal electrode 26 has a main electrode portion 26a and a connection portion 26b.
  • the main electrode part 26a and the connection part 26b are integrally formed.
  • the connection portion 26b extends from the main electrode portion 26a to the other side surface 2f side of the multilayer body 2 and is exposed to the side surface 2f of the multilayer body 2. Specifically, the connection portion 26b is exposed to the side surface 2f at a position near the other end surface 2b side of the stacked body 2.
  • the fourth internal electrode 28 includes, on the piezoelectric layer 20b, a corner that is diagonally opposite to the corner where the third internal electrode 26 is disposed (second diagonal), that is, the end surface 2a and the side surface 2e of the multilayer body 2. Is arranged on the corner portion side.
  • the fourth internal electrode 28 has a main electrode portion 28a and a connection portion 28b.
  • the main electrode portion 28a and the connection portion 28b are integrally formed.
  • the connection portion 28b extends from the main electrode portion 28a to the one side surface 2e side of the multilayer body 2 and is exposed to the side surface 2e of the multilayer body 2. Specifically, the connection portion 28b is exposed to the side surface 2e at a position near the one end surface 2a side of the laminate 2.
  • a fifth internal electrode 30 is disposed on the piezoelectric layer 20c.
  • the fifth internal electrode 30 has a main electrode portion 30a and connecting portions 30b and 30c.
  • the main electrode portion 30a has a rectangular shape in which the longitudinal direction of the multilayer body 2 is the longitudinal direction of the main electrode portion 30a.
  • the main electrode portion 30a includes a first internal electrode 22 (main electrode portion 22a), a second internal electrode (main electrode portion 24a), a third internal electrode 26 (main electrode portion 26a), and a first internal electrode 22 through the piezoelectric layer 20b. 4 faces the internal electrode (main electrode portion 28a).
  • the connecting portion 30b extends from one side surface along the longitudinal direction of the main electrode portion 30a to the other side surface 2f side of the multilayer body 2 and is exposed to the side surface 2f of the multilayer body 2. Specifically, the connection portion 30 b is exposed to the side surface 2 f at the center position in the longitudinal direction of the stacked body 2.
  • the connection portion 30c is exposed to the side surface 2e of the multilayer body 2 so as to extend from the other side surface along the longitudinal direction of the main electrode portion 30a to the one side surface 2e side of the multilayer body 2. Specifically, the connection portion 30 c is exposed to the side surface 2 e at the center position in the longitudinal direction of the stacked body 2.
  • the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 are disposed on the piezoelectric layer 20d, the piezoelectric layer 20f, and the piezoelectric layer 20h.
  • a fifth internal electrode 30 is disposed on the piezoelectric layer 20e and the piezoelectric layer 20g.
  • the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 are positions closest to the pair of main surfaces 2 c and 2 d in the stacked body 2. Is arranged. That is, the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 are located on the outermost side in the stacking direction.
  • the piezoelectric element 3 includes a first external electrode 4, a second external electrode 5, a third external electrode 6, a fourth external electrode 7, It has.
  • the first external electrode 4 has a first electrode portion 4a, a second electrode portion 4b, a third electrode portion 4c, a fourth electrode portion 4d, and a fifth electrode portion 4e.
  • the first electrode portion 4 a is disposed on the other side surface 2 f of the stacked body 2. Specifically, the first electrode portion 4a is disposed on the one end surface 2a side on the side surface 2f.
  • the first electrode portion 4a is formed from one main surface 2c to the other main surface 2d.
  • the first electrode portion 4a is directly connected to the connection portion 22b exposed on the side surface 2f. Thereby, the first external electrode 4 is electrically connected to the first internal electrode 22.
  • the second electrode portion 4b is disposed on one side surface 2e of the laminate 2. Specifically, the second electrode portion 4b is disposed on the side of the other end surface 2b on the side surface 2e. The second electrode portion 4b is formed from one main surface 2c to the other main surface 2d. The second electrode portion 4b is directly connected to the connection portion 24b exposed on the side surface 2e. Thereby, the first external electrode 4 is electrically connected to the second internal electrode 24.
  • the third electrode portion 4 c is disposed on one main surface 2 c of the multilayer body 2.
  • the third electrode portion 4c electrically connects the first electrode portion 4a and the second electrode portion 4b.
  • the fourth electrode portion 4d is disposed on the other main surface 2d.
  • the 4th electrode part 4d is electrically connected with the edge part by the side of the main surface 2d of the 1st electrode part 4a.
  • the fifth electrode portion 4e is disposed on the other main surface 2d.
  • the fifth electrode portion 4e is electrically connected to the end portion on the main surface 2d side of the second electrode portion 4b.
  • the second external electrode 5 has a first electrode portion 5a, a second electrode portion 5b, a third electrode portion 5c, a fourth electrode portion 5d, and a fifth electrode portion 5e.
  • the first electrode portion 5 a is disposed on the other side surface 2 f of the stacked body 2. Specifically, the first electrode portion 5a is disposed on the side of the other end surface 2b on the side surface 2f.
  • the first electrode portion 5a is formed from one main surface 2c to the other main surface 2d.
  • the first electrode portion 5a is directly connected to the connection portion 26b exposed on the side surface 2f. Thereby, the second external electrode 5 is electrically connected to the third internal electrode 26.
  • the second electrode portion 5b is disposed on one side surface 2e of the laminate 2. Specifically, the second electrode portion 5b is disposed on the side of the other end surface 2a on the side surface 2e. The second electrode portion 5b is formed from one main surface 2c to the other main surface 2d. The second electrode portion 5b is directly connected to the connection portion 28b exposed on the side surface 2e. Thereby, the second external electrode 5 is electrically connected to the fourth internal electrode 28.
  • the third electrode portion 5c is disposed on one main surface 2d of the laminate 2.
  • the third electrode portion 5c electrically connects the first electrode portion 5a and the second electrode portion 5b.
  • the fourth electrode portion 5d is disposed on one main surface 2c.
  • the 4th electrode part 5d is electrically connected with the edge part by the side of the main surface 2c of the 1st electrode part 5a.
  • the fifth electrode portion 5e is disposed on one main surface 2c.
  • the fifth electrode portion 5e is electrically connected to the end portion on the main surface 2c side of the second electrode portion 5b.
  • the third external electrode 6 has a first electrode portion 6a, a second electrode portion 6b, and a third electrode portion 6c.
  • the first electrode portion 6 a is disposed on the other side surface 2 f of the stacked body 2. Specifically, the first electrode portion 6a is disposed in the central portion in the longitudinal direction of the stacked body 2 on the side surface 2f. That is, the first electrode portion 6 a is disposed between the first electrode portion 4 a of the first external electrode 4 and the first electrode portion 5 a of the second external electrode 5 in the longitudinal direction of the stacked body 2.
  • the first electrode portion 6a is formed from one main surface 2c to the other main surface 2d.
  • the first electrode portion 6a is directly connected to the connection portion 30b exposed on the side surface 2f. Thereby, the third external electrode 6 is electrically connected to the fifth internal electrode 30.
  • the second electrode portion 6b is disposed on one main surface 2c.
  • the second electrode portion 6b is electrically connected to the end portion on the main surface 2c side of the first electrode portion 6a.
  • the third electrode portion 6c is disposed on one main surface 2d.
  • the third electrode portion 6c is electrically connected to the end portion on the main surface 2d side of the first electrode portion 6a.
  • the fourth external electrode 7 has a first electrode portion 7a, a second electrode portion 7b, and a third electrode portion 7c.
  • the first electrode portion 7 a is disposed on one side surface 2 e of the stacked body 2. Specifically, the first electrode portion 7a is disposed in the central portion in the longitudinal direction of the stacked body 2 on the side surface 2e. That is, the first electrode portion 7 a is disposed between the second electrode portion 4 b of the first external electrode 4 and the second electrode portion 5 b of the second external electrode 5 in the longitudinal direction of the stacked body 2.
  • the first electrode portion 7a is formed from one main surface 2c to the other main surface 2d.
  • the 1st electrode part 7a is directly connected with the connection part 30c exposed to the side surface 2e. Thereby, the fourth external electrode 7 is electrically connected to the fifth internal electrode 30.
  • the second electrode portion 7b is disposed on one main surface 2c.
  • the second electrode portion 7b is electrically connected to the end portion on the main surface 2c side of the first electrode portion 7a.
  • the third electrode portion 7c is disposed on one main surface 2d.
  • the third electrode portion 7c is electrically connected to the end portion on the main surface 2d side of the first electrode portion 7a.
  • the friction portion 10 is disposed on one end face 2a of the laminate 2.
  • the friction part 10 has a cylindrical shape, for example.
  • the friction part 10 is made of zirconia, alumina, or the like.
  • the friction part 10 is provided by, for example, adhering a cylindrical member to the end surface 2a.
  • a region between the main surface 2 c of the multilayer body 2 and the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 is formed. Inactive region.
  • a region between the main surface 2 d of the multilayer body 2 and the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 is an inactive region.
  • a region between the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, the fourth internal electrode 28 and the fifth internal electrode 30 is an active region. The active region is displaced when a voltage is applied.
  • the thickness T1 of the inactive region in the stacking direction is smaller than the thickness T2 of the active region. That is, the distances between the main surfaces 2c and 2d of the multilayer body 2 and the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 are the first internal electrode 22, The distance between the internal electrode 24, the third internal electrode 26 and the fourth internal electrode 28 and the fifth internal electrode 30 is shorter.
  • the thickness T1 of the inactive region is preferably 1/5 or more and 1/2 or less of the thickness T2 of the active region. The thickness of the inactive region and the active region can be adjusted by changing the thickness of the piezoelectric layers 20a to 20h.
  • the thickness of the piezoelectric layer 20a and the piezoelectric layer 20h is made smaller than the thickness of the piezoelectric layers 20b to 20g.
  • the thickness T1 of the inactive region can be set to 1/5 or more and 1/2 or less of the thickness T2 of the active region.
  • the piezoelectric actuator 1 having the above configuration has two resonance modes when driven. Specifically, the piezoelectric actuator 1 vibrates by superimposing (combining) a longitudinal vibration mode that vibrates in the longitudinal direction of the piezoelectric element 3 and a bending vibration mode in the height direction of the piezoelectric element 3.
  • the third external electrode 6 and the fourth external electrode 7 are connected to the ground, and a voltage whose phase is shifted by 90 ° is applied to the first external electrode 4 and the second external electrode 5.
  • a voltage whose phase is shifted by 90 ° is applied to the first external electrode 4 and the second external electrode 5.
  • an elliptical motion is generated in the friction portion 10.
  • FIGS. 4A and 4B a frictional force acts between the friction portion 10 and the driven body 100, and the driven body 100 moves (rotates). It becomes.
  • the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 are disposed in the multilayer body 2. . Therefore, in the piezoelectric actuator 1, it can suppress that a migration generate
  • the region between the main surfaces 2 c and 2 d of the multilayer body 2 and the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 is an inactive region.
  • a region between the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, the fourth internal electrode 28, and the fifth internal electrode 30 is an active region.
  • the thickness T1 of the inactive region is smaller than the thickness T2 of the active region. Therefore, in the piezoelectric actuator 1, the drive characteristics can be improved.
  • the thickness T1 of the inactive region is 1/5 or more and 1/2 or less of the thickness T2 of the active region.
  • FIG. 5 is a diagram showing the relationship between the thickness of the inactive region and the amplitude of the vibration mode.
  • the horizontal axis indicates the thickness of the inactive region, and the vertical axis indicates the amplitude.
  • the amplitude of the longitudinal vibration mode and the amplitude of the bending vibration mode are set. There is a difference.
  • the thickness T1 of the inactive region is 1 ⁇ 2 of the thickness T2 of the active region (in the case of “1 ⁇ 2” in FIG. 5)
  • the amplitude of the longitudinal vibration mode and the amplitude of the bending vibration mode And the amplitude in the bending vibration mode is particularly large as compared with the case where the thickness T1 of the inactive region and the thickness T2 of the active region are the same.
  • both the amplitude of the longitudinal vibration mode and the amplitude of the bending vibration mode are both inactive region.
  • the thickness of the active region and the thickness of the active region are larger than in the same case. Therefore, when the thickness T1 of the inactive region is set to 1 ⁇ 2 or less of the thickness T2 of the active region, the displacement restriction in the inactive region is suppressed, and the drive characteristics of the piezoelectric actuator 1 are improved.
  • the first external electrode 4 is formed on the main surfaces 2c and 2d of the multilayer body 2 by setting the thickness T1 of the inactive region to 1/5 or more of the thickness T2 of the active region.
  • the first external electrode 4 the second external electrode 5, the third external electrode 6, the fourth external electrode 7, and the first external electrode 4.
  • the voltage resistance among the internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 can be ensured.
  • the stacked body 2 is formed by stacking the piezoelectric layers 20a to 20h has been described as an example.
  • the number of stacked piezoelectric layers is not limited to this, and is appropriately set according to the design.
  • the thickness T1 of the inactive region is 1/2 or less of the thickness T2 of the active region has been described as an example. However, it is sufficient that at least the thickness of the inactive region is smaller than the thickness of the active region.
  • the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 of the piezoelectric element 3 have been described as an example in the configuration shown in FIG.
  • the configuration of the internal electrode is not limited to this.
  • the internal electrode may have the following configuration.
  • the piezoelectric element 3A includes a first internal electrode 22, a second internal electrode 24, a third internal electrode 26, a fourth internal electrode 28, a fifth internal electrode 30, and a sixth internal electrode.
  • An internal electrode 32, a seventh internal electrode 34, an eighth internal electrode 36, and a ninth internal electrode 38 are provided.
  • the sixth internal electrode 32, the seventh internal electrode 34, the eighth internal electrode 36, and the ninth internal electrode 38 are the same as the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28. It has the composition of.
  • the third internal electrode 26 and the fourth internal electrode 28 are electrically connected by a connection member 29.
  • the main electrode portion 26 a of the third internal electrode 26 and the main electrode portion 28 a of the fourth internal electrode 28 are electrically connected by the connection member 29.
  • the connection member 29 is disposed between the first internal electrode 22 and the second internal electrode 24 that are disposed diagonally at a predetermined interval.
  • the connection member 29 is made of a conductive material (for example, Ni, Pt or Pd).
  • the connection member 29 is configured as a sintered body of a conductive paste containing the conductive material.
  • the sixth internal electrode 32 and the seventh internal electrode 34 are electrically connected by a connection member 40.
  • connection member 40 is disposed between the eighth internal electrode 36 and the ninth internal electrode 38 that are disposed diagonally at a predetermined interval.
  • the third internal electrode 26 and the fourth internal electrode 28 are electrically connected by the connecting member 29, and the sixth internal electrode 32 and the seventh internal electrode 34 are connected by the connecting member 40. Therefore, in the piezoelectric element 3A, the third internal electrode 26 and the fourth internal electrode 28, and the sixth internal electrode 32 and the seventh internal electrode 34 may not be electrically connected by the external electrode. Therefore, the degree of freedom in designing the piezoelectric actuator is increased.
  • the configuration in which the internal electrodes are exposed on the side surfaces 2 e and 2 f of the multilayer body 2 has been described as an example.
  • the internal electrode may be configured to be exposed on the end faces 2 a and 2 b of the multilayer body 2.
  • the first external electrode 4, the second external electrode 5, the third external electrode 6, and the fourth external electrode 7 have the configuration shown in FIG. 1A and FIG.
  • the configuration of the external electrode is not limited to this.
  • the external electrode may be appropriately designed according to the configuration of the internal electrode.
  • the piezoelectric element may have the configuration shown in FIG. As shown in FIG. 7, the piezoelectric element 3B has piezoelectric layers 20a to 20f laminated in this order.
  • a fifth internal electrode 30 is disposed on the piezoelectric layer 20b, the piezoelectric layer 20d, and the piezoelectric layer 20f, and the first internal electrode 22, the second internal electrode 24, and the like are disposed on the piezoelectric layer 20c.
  • the third internal electrode 26, the fourth internal electrode 28, and the connection member 29 are disposed, and the sixth internal electrode 32, the seventh internal electrode 34, the eighth internal electrode 36, and the ninth internal electrode 38 are disposed on the piezoelectric layer 20e.
  • the connection member 40 is arrange
  • the fifth internal electrode (second internal electrode) 30 is disposed in the stacked body 2 at a position closest to the pair of main surfaces 2c and 2d.
  • the region between the main surfaces 2c, 2d and the fifth internal electrode 30 is an inactive region
  • the fifth internal electrode 30, the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the region between the fifth internal electrode 30 and the fourth internal electrode, and the region between the fifth internal electrode 30, the sixth internal electrode 32, the seventh internal electrode 34, the eighth internal electrode 36, and the ninth internal electrode 38 are active. It is an area. Also in this configuration, the thickness of the inactive region in the stacking direction is smaller than the thickness of the active region.
  • SYMBOLS 1 Piezoelectric actuator, 2 ... Laminated body (element body), 10 ... Friction part, 22 ... 1st internal electrode, 24 ... 2nd internal electrode (1st internal electrode), 26 ... 3rd internal electrode (1st internal electrode) , 28 ... fourth internal electrode, 29 ... connecting member, 30 ... fifth internal electrode (second internal electrode), 32 ... sixth internal electrode (first internal electrode), 34 ... seventh internal electrode (first internal electrode) Electrode), 36... Eighth internal electrode (first internal electrode), 38... Ninth internal electrode (first internal electrode).

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  • General Electrical Machinery Utilizing Piezoelectricity, Electrostriction Or Magnetostriction (AREA)

Abstract

This piezoelectric actuator (1) is provided with: an element body (2); a plurality of internal electrodes (22, 24, 26, 28, 30) which are arranged within the element body; and a plurality of external electrodes (4, 5, 6, 7) which are arranged on the outer surface of the element body, and which are electrically connected to corresponding internal electrodes. The plurality of internal electrodes include: four first internal electrodes (22, 24, 26, 28) which are arranged on a same piezoelectric layer; and a second internal electrode (30) which is arranged so as to face the four first internal electrodes, with the piezoelectric layer being sandwiched therebetween, while having a voltage applied between itself and the first internal electrodes. The four first internal electrodes are arranged in positions closest to a pair of main surfaces (2c, 2d) within the element body; the regions between the main surfaces of the element body and the first internal electrodes are inactive regions; the regions between the first internal electrodes and the second internal electrode are active regions; and the thickness (T1) of the inactive regions is smaller than the thickness (T2) of the active regions in the lamination direction.

Description

圧電アクチュエータPiezoelectric actuator
　本発明は、圧電アクチュエータに関する。 The present invention relates to a piezoelectric actuator.
　従来の圧電アクチュエータとして、例えば、特許文献１に記載されたものが知られている。特許文献１に記載の圧電アクチュエータは、印加される電圧によって縦振動モードと屈曲振動モードとが合成された振動モードを発生させる圧電アクチュエータであり、同一の圧電体層上に配置された４つの第１内部電極と、４つの第１内部電極と圧電体層を挟んで対向して配置され、第１内部電極との間に電圧が印加される第２内部電極と、を含んで構成されている。特許文献１に記載の圧電アクチュエータでは、最外層となる圧電体層の表面に４つの第１内部電極が配置されており、第１内部電極が外部に露出して設けられている。 As a conventional piezoelectric actuator, for example, the one described in Patent Document 1 is known. The piezoelectric actuator described in Patent Document 1 is a piezoelectric actuator that generates a vibration mode in which a longitudinal vibration mode and a bending vibration mode are combined by an applied voltage, and includes four fourth actuators arranged on the same piezoelectric layer. 1 internal electrode, 4 1st internal electrodes, and the 2nd internal electrode which are arrange | positioned facing each other on both sides of a piezoelectric material layer, and a voltage is applied between 1st internal electrodes are comprised. . In the piezoelectric actuator described in Patent Document 1, four first internal electrodes are arranged on the surface of the piezoelectric layer that is the outermost layer, and the first internal electrodes are exposed to the outside.
特表２００３－５０１９８８号公報Special table 2003-501988 gazette
　従来の圧電アクチュエータのように、内部電極が露出している構成では、外部に露出する内部電極間において、マイグレーションが生じ得る。マイグレーションが発生すると、瞬間的に内部電極の極性が反転することがあるため、圧電アクチュエータの駆動に不具合が生じ得る。そのため、圧電アクチュエータでは、マイグレーションの発生を抑制するために、内部電極を圧電体層（絶縁体層）で覆う構成が採用され得る。しかしながら、圧電体層を最上層に設けると、圧電体層が変位を拘束し、圧電アクチュエータの振動を阻害するおそれがある。 In a configuration in which internal electrodes are exposed as in a conventional piezoelectric actuator, migration can occur between internal electrodes exposed to the outside. When migration occurs, the polarity of the internal electrode may be instantaneously reversed, which may cause problems in driving the piezoelectric actuator. Therefore, in the piezoelectric actuator, in order to suppress the occurrence of migration, a configuration in which the internal electrode is covered with a piezoelectric layer (insulator layer) can be employed. However, if the piezoelectric layer is provided as the uppermost layer, the piezoelectric layer may restrain displacement and inhibit vibration of the piezoelectric actuator.
　本発明の一側面は、マイグレーションの発生を抑制しつつ、駆動特性の向上が図れる圧電アクチュエータを提供することを目的とする。 An object of one aspect of the present invention is to provide a piezoelectric actuator capable of improving drive characteristics while suppressing the occurrence of migration.
　本発明の一側面に係る圧電アクチュエータは、印加される電圧によって縦振動モードと屈曲振動モードとが合成された振動モードを発生させる圧電アクチュエータであって、矩形状を呈する複数の圧電体層を積層することによって形成されると共に、複数の圧電体層の積層方向において対向する一対の主面を有する素体と、素体内に配置された複数の内部電極と、素体の外表面に配置され、対応する内部電極と電気的に接続された複数の外部電極と、を備え、複数の内部電極は、同一の圧電体層上に配置された４つの第１内部電極と、４つの第１内部電極と圧電体層を挟んで対向して配置され、第１内部電極との間に電圧が印加される第２内部電極と、を有し、４つの第１内部電は、素体内において、一対の主面に最も近い位置に配置されており、素体の主面と第１内部電極との間の領域が不活性領域であり、第１内部電極と第２内部電極との間の領域が活性領域であり、積層方向における不活性領域の厚みは、活性領域の厚みよりも小さい。 A piezoelectric actuator according to one aspect of the present invention is a piezoelectric actuator that generates a vibration mode in which a longitudinal vibration mode and a bending vibration mode are synthesized by an applied voltage, and includes a plurality of piezoelectric layers that are rectangular. And an element body having a pair of main surfaces facing each other in the stacking direction of the plurality of piezoelectric layers, a plurality of internal electrodes disposed in the element body, and an outer surface of the element body, A plurality of external electrodes electrically connected to the corresponding internal electrodes, the plurality of internal electrodes being four first internal electrodes and four first internal electrodes disposed on the same piezoelectric layer And a second internal electrode disposed opposite to each other with a piezoelectric layer interposed therebetween, to which a voltage is applied between the first internal electrode and the four first internal powers in the element body. Located closest to the main surface A region between the main surface of the element body and the first internal electrode is an inactive region, a region between the first internal electrode and the second internal electrode is an active region, and an inactive region in the stacking direction. Is less than the thickness of the active region.
　本発明の一側面に係る圧電アクチュエータでは、４つの第１内部電極は、素体内に配置されている。すなわち、第１内部電極は、圧電体層により覆われている。そのため、圧電アクチュエータでは、第１内部電極間においてマイグレーションが発生することを抑制できる。また、圧電アクチュエータでは、素体の主面と第１内部電極との間の領域が不活性領域であり、第１内部電極と第２内部電極との間の領域が活性領域であり、積層方向における不活性領域の厚みは、活性領域の厚みよりも小さい。これにより、圧電アクチュエータでは、不活性領域が変位を拘束することを抑制できる。したがって、圧電アクチュエータでは、駆動特性の向上が図れる。 In the piezoelectric actuator according to one aspect of the present invention, the four first internal electrodes are arranged in the element body. That is, the first internal electrode is covered with the piezoelectric layer. Therefore, in the piezoelectric actuator, it is possible to suppress the occurrence of migration between the first internal electrodes. In the piezoelectric actuator, the region between the main surface of the element body and the first internal electrode is an inactive region, the region between the first internal electrode and the second internal electrode is an active region, and the stacking direction The thickness of the inactive region is smaller than the thickness of the active region. Thereby, in a piezoelectric actuator, it can suppress that an inactive area restrains displacement. Therefore, the drive characteristics can be improved in the piezoelectric actuator.
　一実施形態においては、不活性領域の厚みは、活性領域の厚みの１／２以下であることが好ましい。この構成では、不活性領域による変位の拘束をより一層抑制できる。 In one embodiment, the thickness of the inactive region is preferably ½ or less of the thickness of the active region. In this configuration, it is possible to further suppress displacement restraint due to the inactive region.
　一実施形態においては、不活性領域の厚みは、活性領域の厚みの１／５以上１／２以下であってもよい。この構成では、不活性領域の厚みが活性領域の厚みの１／５以上確保されるため、素体の主面に外部電極が配置される構成において、外部電極と第１内部電極との間の耐電圧性を確保できる。 In one embodiment, the thickness of the inactive region may be 1/5 or more and 1/2 or less of the thickness of the active region. In this configuration, since the thickness of the inactive region is secured to 1/5 or more of the thickness of the active region, in the configuration in which the external electrode is disposed on the main surface of the element body, the space between the external electrode and the first internal electrode is Withstand voltage can be secured.
　一実施形態においては、４つの第１内部電極のうち、２つの第１内部電極が第１の対角に位置し、他の２つの第１内部電極が第１の対角に交差する第２の対角に位置しており、第１の対角又は第２の対角に位置する２つの第１内部電極が接続部材によって電気的に接続されていてもよい。この構成では、素体内において２つの第１内部電極が電気的に接続されるため、２つの内部電極を外部電極によって電気的に接続することが不要となる。そのため、圧電アクチュエータの設計の自由度が高まる。 In one embodiment, of the four first internal electrodes, two first internal electrodes are located at a first diagonal, and the other two first internal electrodes intersect with the first diagonal. The two first internal electrodes located at the first diagonal or the second diagonal may be electrically connected by the connecting member. In this configuration, since the two first internal electrodes are electrically connected in the element body, it is not necessary to electrically connect the two internal electrodes by the external electrode. This increases the degree of freedom in designing the piezoelectric actuator.
　本発明の一側面によれば、マイグレーションの発生を抑制しつつ、駆動特性の向上が図れる。 According to one aspect of the present invention, it is possible to improve drive characteristics while suppressing the occurrence of migration.
図１（ａ）及び図１（ｂ）は、一実施形態に係る圧電アクチュエータの斜視図である。FIG. 1A and FIG. 1B are perspective views of a piezoelectric actuator according to one embodiment. 図２は、圧電アクチュエータの断面構成を示す図である。FIG. 2 is a diagram illustrating a cross-sectional configuration of the piezoelectric actuator. 図３は、圧電素子の分解斜視図である。FIG. 3 is an exploded perspective view of the piezoelectric element. 図４（ａ）及び図４（ｂ）は、圧電アクチュエータの動作を示す図である。FIG. 4A and FIG. 4B are diagrams illustrating the operation of the piezoelectric actuator. 図５は、不活性領域の厚みと振動モードの振幅との関係を示す図である。FIG. 5 is a diagram showing the relationship between the thickness of the inactive region and the amplitude of the vibration mode. 図６は、他の実施形態に係る圧電アクチュエータにおける圧電素子の分解斜視図である。FIG. 6 is an exploded perspective view of a piezoelectric element in a piezoelectric actuator according to another embodiment. 図７は、変形例に係る圧電アクチュエータにおける圧電素子の分解斜視図である。FIG. 7 is an exploded perspective view of a piezoelectric element in a piezoelectric actuator according to a modification.
　以下、添付図面を参照して、本発明の好適な実施形態について詳細に説明する。なお、図面の説明において同一又は相当要素には同一符号を付し、重複する説明は省略する。 Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted.
　図１（ａ）及び図１（ｂ）に示されるように、圧電アクチュエータ１は、圧電素子３と、摩擦部１０と、を備えている。圧電アクチュエータ１は、交流電圧が印加されて変位することによって、被駆動体１００（例えば、ローター等（図４（ａ）及び図４（ｂ）参照））を移動させる機能を有している。 As shown in FIGS. 1A and 1B, the piezoelectric actuator 1 includes a piezoelectric element 3 and a friction portion 10. The piezoelectric actuator 1 has a function of moving the driven body 100 (for example, a rotor or the like (see FIGS. 4A and 4B)) by being displaced by applying an AC voltage.
　圧電素子３は、積層体（素体）２を備えている。積層体２は、直方体形状を呈している。積層体２は、互いに対向している一対の端面２ａ，２ｂと、互いに対向している一対の主面２ｃ，２ｄと、互いに対向している一対の側面２ｅ，２ｆと、を有している。主面２ｃ，２ｄは、長方形状を呈している。本実施形態では、一対の主面２ｃ，２ｄの長辺方向で互いに対向する一対の端面２ａ，２ｂの対向方向が、積層体２（圧電素子３）の長手方向である。一対の主面２ｃ，２ｄが対向している対向方向が、積層体２（圧電素子３）の高さ方向である。一対の主面２ｃ，２ｄの長辺方向で互いに対向する一対の側面２ｅ，２ｆの対向方向が、積層体２（圧電素子３）の幅方向である。 The piezoelectric element 3 includes a laminated body (element body) 2. The laminate 2 has a rectangular parallelepiped shape. The laminate 2 has a pair of end faces 2a, 2b facing each other, a pair of main faces 2c, 2d facing each other, and a pair of side faces 2e, 2f facing each other. . The main surfaces 2c and 2d have a rectangular shape. In the present embodiment, the facing direction of the pair of end surfaces 2a and 2b that face each other in the long side direction of the pair of main surfaces 2c and 2d is the longitudinal direction of the multilayer body 2 (piezoelectric element 3). The facing direction in which the pair of main surfaces 2c and 2d are facing is the height direction of the multilayer body 2 (piezoelectric element 3). The facing direction of the pair of side surfaces 2e and 2f facing each other in the long side direction of the pair of main surfaces 2c and 2d is the width direction of the multilayer body 2 (piezoelectric element 3).
　一対の端面２ａ，２ｂは、一対の主面２ｃ，２ｄの間を連結するように延びている。一対の端面２ａ，２ｂは、一対の主面２ｃ，２ｄの短辺方向にも延びている。一対の側面２ｅ，２ｆは、一対の主面２ｃ，２ｄの間を連結するように延びている。一対の側面２ｅ，２ｆは、一対の端面２ａ，２ｂの長辺方向にも延びている。 The pair of end surfaces 2a and 2b extend so as to connect the pair of main surfaces 2c and 2d. The pair of end surfaces 2a and 2b also extend in the short side direction of the pair of main surfaces 2c and 2d. The pair of side surfaces 2e and 2f extend so as to connect the pair of main surfaces 2c and 2d. The pair of side surfaces 2e and 2f also extend in the long side direction of the pair of end surfaces 2a and 2b.
　積層体２は、圧電セラミック材料からなる。圧電セラミック材料としては、ＰＺＴ［Ｐｂ（Ｚｒ、Ｔｉ）Ｏ３］、ＰＴ（ＰｂＴｉＯ３）、ＰＬＺＴ［（Ｐｂ、Ｌａ）（Ｚｒ、Ｔｉ）Ｏ３］、又はチタン酸バリウム（ＢａＴｉＯ３）などが挙げられる。本実施形態では、積層体２は、圧電セラミック材料を含むセラミックグリーンシートの焼結体である、矩形状を呈する圧電体層２０ａ～２０ｈ（図３参照）が積層されて構成されている。積層体２では、複数の圧電体層２０ａ～２０ｈの積層方向が一対の主面２ｃ，２ｄの対向方向と一致する。実際の積層体２では、各圧電体層２０ａ～２０ｈは、各圧電体層２０ａ～２０ｈの間の境界が視認できない程度に一体化されている。本実施形態では、圧電体層２０ａの外表面が積層体２の主面２ｃを構成しており、圧電体層２０ｈの外表面が積層体２の主面２ｄを構成している。 The laminate 2 is made of a piezoelectric ceramic material. Examples of the piezoelectric ceramic material include PZT [Pb (Zr, Ti) O 3 ], PT (PbTiO 3 ), PLZT [(Pb, La) (Zr, Ti) O 3 ], or barium titanate (BaTiO 3 ). Can be mentioned. In the present embodiment, the laminate 2 is formed by laminating piezoelectric layers 20a to 20h (see FIG. 3) having a rectangular shape, which are sintered ceramic green sheets containing a piezoelectric ceramic material. In the stacked body 2, the stacking direction of the plurality of piezoelectric layers 20a to 20h coincides with the facing direction of the pair of main surfaces 2c and 2d. In the actual laminate 2, the piezoelectric layers 20a to 20h are integrated so that the boundaries between the piezoelectric layers 20a to 20h cannot be visually recognized. In the present embodiment, the outer surface of the piezoelectric layer 20a constitutes the main surface 2c of the multilayer body 2, and the outer surface of the piezoelectric layer 20h constitutes the main surface 2d of the multilayer body 2.
　図３に示されるように、圧電素子３は、第１内部電極２２と、第２内部電極２４と、第３内部電極２６と、第４内部電極２８と、第５内部電極３０と、を備えている。第１内部電極２２、第２内部電極２４、第３内部電極２６、第４内部電極２８及び第５内部電極３０は、積層型の電子素子の内部電極として通常用いられる導電性材料（例えば、Ａｇ、Ａｕ、Ｎｉ、Ｐｔ又はＰｄなど）からなる。第１内部電極２２、第２内部電極２４、第３内部電極２６、第４内部電極２８及び第５内部電極３０は、上記導電性材料を含む導電性ペーストの焼結体として構成される。なお、第１内部電極２２、第２内部電極２４、第３内部電極２６及び第４内部電極２８は、特許請求の範囲に記載の４つの第１内部電極を構成している。第５内部電極３０は、特許請求の範囲に記載の第２内部電極を構成している。 As shown in FIG. 3, the piezoelectric element 3 includes a first internal electrode 22, a second internal electrode 24, a third internal electrode 26, a fourth internal electrode 28, and a fifth internal electrode 30. ing. The first internal electrode 22, the second internal electrode 24, the third internal electrode 26, the fourth internal electrode 28, and the fifth internal electrode 30 are electrically conductive materials (for example, Ag) that are normally used as internal electrodes of stacked electronic devices. , Au, Ni, Pt or Pd). The 1st internal electrode 22, the 2nd internal electrode 24, the 3rd internal electrode 26, the 4th internal electrode 28, and the 5th internal electrode 30 are comprised as a sintered compact of the electrically conductive paste containing the said electrically conductive material. In addition, the 1st internal electrode 22, the 2nd internal electrode 24, the 3rd internal electrode 26, and the 4th internal electrode 28 comprise the four 1st internal electrodes as described in a claim. The fifth internal electrode 30 constitutes a second internal electrode described in the claims.
　圧電体層２０ｂ上には、第１内部電極２２、第２内部電極２４、第３内部電極２６及び第４内部電極２８が配置されている。第１内部電極２２及び第２内部電極２４は、圧電体層２０ｂ上において、互いに電気的に絶縁されている（離間している）。第３内部電極２６及び第４内部電極２８は、圧電体層２０ｂ上において、互いに電気的に接続されている。 The first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 are disposed on the piezoelectric layer 20b. The first internal electrode 22 and the second internal electrode 24 are electrically insulated (separated) from each other on the piezoelectric layer 20b. The third internal electrode 26 and the fourth internal electrode 28 are electrically connected to each other on the piezoelectric layer 20b.
　第１内部電極２２は、圧電体層２０ｂ上において、積層体２の端面２ａと側面２ｆとが形成する角部側に配置されている。第１内部電極２２は、主電極部２２ａと、接続部２２ｂと、を有している。主電極部２２ａと接続部２２ｂとは、一体に形成されている。接続部２２ｂは、主電極部２２ａから積層体２の他方の側面２ｆ側に延在し、積層体２の側面２ｆに露出している。具体的には、接続部２２ｂは、積層体２の一方の端面２ａ側寄りの位置において側面２ｆに露出している。 The first internal electrode 22 is disposed on the piezoelectric layer 20b on the corner side formed by the end surface 2a and the side surface 2f of the multilayer body 2. The first internal electrode 22 has a main electrode portion 22a and a connection portion 22b. The main electrode portion 22a and the connection portion 22b are integrally formed. The connection portion 22b extends from the main electrode portion 22a to the other side surface 2f of the multilayer body 2 and is exposed to the side surface 2f of the multilayer body 2. Specifically, the connecting portion 22b is exposed to the side surface 2f at a position near the one end surface 2a side of the laminate 2.
　第２内部電極２４は、圧電体層２０ｂ上において、第１内部電極２２が配置された角部と対角（第１の対角）の角部、すなわち積層体２の端面２ｂと側面２ｅとが形成する角部側に配置されている。第２内部電極２４は、主電極部２４ａと、接続部２４ｂと、を有している。主電極部２４ａと接続部２４ｂとは、一体に形成されている。接続部２４ｂは、主電極部２４ａから積層体２の一方の側面２ｅ側に延在し、積層体２の側面２ｅに露出している。具体的には、接続部２４ｂは、積層体２の他方の端面２ｂ側寄りの位置において側面２ｅに露出している。 On the piezoelectric layer 20b, the second internal electrode 24 has a corner portion and a diagonal portion (first diagonal portion) where the first internal electrode 22 is disposed, that is, the end surface 2b and the side surface 2e of the multilayer body 2. Is arranged on the corner portion side. The second internal electrode 24 has a main electrode portion 24a and a connection portion 24b. The main electrode portion 24a and the connection portion 24b are integrally formed. The connection portion 24 b extends from the main electrode portion 24 a to the side surface 2 e of the stacked body 2 and is exposed on the side surface 2 e of the stacked body 2. Specifically, the connection portion 24b is exposed to the side surface 2e at a position near the other end surface 2b side of the stacked body 2.
　第３内部電極２６は、圧電体層２０ｂ上において、積層体２の端面２ｂと側面２ｆとが形成する角部側に配置されている。第３内部電極２６は、主電極部２６ａと、接続部２６ｂと、を有している。主電極部２６ａと接続部２６ｂとは、一体に形成されている。接続部２６ｂは、主電極部２６ａから積層体２の他方の側面２ｆ側に延在し、積層体２の側面２ｆに露出している。具体的には、接続部２６ｂは、積層体２の他方の端面２ｂ側寄りの位置において側面２ｆに露出している。 3rd internal electrode 26 is arrange | positioned on the piezoelectric material layer 20b at the corner | angular part side which the end surface 2b and the side surface 2f of the laminated body 2 form. The third internal electrode 26 has a main electrode portion 26a and a connection portion 26b. The main electrode part 26a and the connection part 26b are integrally formed. The connection portion 26b extends from the main electrode portion 26a to the other side surface 2f side of the multilayer body 2 and is exposed to the side surface 2f of the multilayer body 2. Specifically, the connection portion 26b is exposed to the side surface 2f at a position near the other end surface 2b side of the stacked body 2.
　第４内部電極２８は、圧電体層２０ｂ上において、第３内部電極２６が配置された角部と対角（第２の対角）の角部、すなわち積層体２の端面２ａと側面２ｅとが形成する角部側に配置されている。第４内部電極２８は、主電極部２８ａと、接続部２８ｂと、を有している。主電極部２８ａと接続部２８ｂとは、一体に形成されている。接続部２８ｂは、主電極部２８ａから積層体２の一方の側面２ｅ側に延在し、積層体２の側面２ｅに露出している。具体的には、接続部２８ｂは、積層体２の一方の端面２ａ側寄りの位置において側面２ｅに露出している。 The fourth internal electrode 28 includes, on the piezoelectric layer 20b, a corner that is diagonally opposite to the corner where the third internal electrode 26 is disposed (second diagonal), that is, the end surface 2a and the side surface 2e of the multilayer body 2. Is arranged on the corner portion side. The fourth internal electrode 28 has a main electrode portion 28a and a connection portion 28b. The main electrode portion 28a and the connection portion 28b are integrally formed. The connection portion 28b extends from the main electrode portion 28a to the one side surface 2e side of the multilayer body 2 and is exposed to the side surface 2e of the multilayer body 2. Specifically, the connection portion 28b is exposed to the side surface 2e at a position near the one end surface 2a side of the laminate 2.
　圧電体層２０ｃ上には、第５内部電極３０が配置されている。第５内部電極３０は、主電極部３０ａと、接続部３０ｂ，３０ｃと、を有している。主電極部３０ａは、積層体２の長手方向を当該主電極部３０ａの長手方向とする長方形状を呈している。主電極部３０ａは、圧電体層２０ｂを介して、第１内部電極２２（主電極部２２ａ）、第２内部電極（主電極部２４ａ）、第３内部電極２６（主電極部２６ａ）及び第４内部電極（主電極部２８ａ）と対向している。 A fifth internal electrode 30 is disposed on the piezoelectric layer 20c. The fifth internal electrode 30 has a main electrode portion 30a and connecting portions 30b and 30c. The main electrode portion 30a has a rectangular shape in which the longitudinal direction of the multilayer body 2 is the longitudinal direction of the main electrode portion 30a. The main electrode portion 30a includes a first internal electrode 22 (main electrode portion 22a), a second internal electrode (main electrode portion 24a), a third internal electrode 26 (main electrode portion 26a), and a first internal electrode 22 through the piezoelectric layer 20b. 4 faces the internal electrode (main electrode portion 28a).
　接続部３０ｂは、主電極部３０ａの長手方向に沿う一方の側面から積層体２の他方の側面２ｆ側に延在し、積層体２の側面２ｆに露出している。具体的には、接続部３０ｂは、積層体２の長手方向の中央の位置において側面２ｆに露出している。接続部３０ｃは、主電極部３０ａの長手方向に沿う他方の側面から積層体２の一方の側面２ｅ側に延在に、積層体２の側面２ｅに露出している。具体的には、接続部３０ｃは、積層体２の長手方向の中央の位置において側面２ｅに露出している。 The connecting portion 30b extends from one side surface along the longitudinal direction of the main electrode portion 30a to the other side surface 2f side of the multilayer body 2 and is exposed to the side surface 2f of the multilayer body 2. Specifically, the connection portion 30 b is exposed to the side surface 2 f at the center position in the longitudinal direction of the stacked body 2. The connection portion 30c is exposed to the side surface 2e of the multilayer body 2 so as to extend from the other side surface along the longitudinal direction of the main electrode portion 30a to the one side surface 2e side of the multilayer body 2. Specifically, the connection portion 30 c is exposed to the side surface 2 e at the center position in the longitudinal direction of the stacked body 2.
　圧電体層２０ｄ、圧電体層２０ｆ及び圧電体層２０ｈ上には、第１内部電極２２、第２内部電極２４、第３内部電極２６及び第４内部電極２８が配置されている。圧電体層２０ｅ及び圧電体層２０ｇ上には、第５内部電極３０が配置されている。図２に示されるように、第１内部電極２２、第２内部電極２４、第３内部電極２６及び第４内部電極２８は、積層体２内において、一対の主面２ｃ，２ｄに最も近い位置に配置されている。すなわち、第１内部電極２２、第２内部電極２４、第３内部電極２６及び第４内部電極２８は、積層方向において最も外側に位置している。 The first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 are disposed on the piezoelectric layer 20d, the piezoelectric layer 20f, and the piezoelectric layer 20h. A fifth internal electrode 30 is disposed on the piezoelectric layer 20e and the piezoelectric layer 20g. As shown in FIG. 2, the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 are positions closest to the pair of main surfaces 2 c and 2 d in the stacked body 2. Is arranged. That is, the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 are located on the outermost side in the stacking direction.
　図１（ａ）及び図１（ｂ）に示されるように、圧電素子３は、第１外部電極４と、第２外部電極５と、第３外部電極６と、第４外部電極７と、を備えている。 As shown in FIGS. 1A and 1B, the piezoelectric element 3 includes a first external electrode 4, a second external electrode 5, a third external electrode 6, a fourth external electrode 7, It has.
　第１外部電極４は、第１電極部分４ａと、第２電極部分４ｂと、第３電極部分４ｃと、第４電極部分４ｄと、第５電極部分４ｅと、を有している。第１電極部分４ａは、積層体２の他方の側面２ｆに配置されている。具体的には、第１電極部分４ａは、側面２ｆ上において、一方の端面２ａ側に配置されている。第１電極部分４ａは、一方の主面２ｃから他方の主面２ｄにわたって形成されている。第１電極部分４ａは、側面２ｆに露出する接続部２２ｂと直接的に接続されている。これにより、第１外部電極４は、第１内部電極２２と電気的に接続されている。 The first external electrode 4 has a first electrode portion 4a, a second electrode portion 4b, a third electrode portion 4c, a fourth electrode portion 4d, and a fifth electrode portion 4e. The first electrode portion 4 a is disposed on the other side surface 2 f of the stacked body 2. Specifically, the first electrode portion 4a is disposed on the one end surface 2a side on the side surface 2f. The first electrode portion 4a is formed from one main surface 2c to the other main surface 2d. The first electrode portion 4a is directly connected to the connection portion 22b exposed on the side surface 2f. Thereby, the first external electrode 4 is electrically connected to the first internal electrode 22.
　第２電極部分４ｂは、積層体２の一方の側面２ｅに配置されている。具体的には、第２電極部分４ｂは、側面２ｅ上において、他方の端面２ｂ側に配置されている。第２電極部分４ｂは、一方の主面２ｃから他方の主面２ｄにわたって形成されている。第２電極部分４ｂは、側面２ｅに露出する接続部２４ｂと直接的に接続されている。これにより、第１外部電極４は、第２内部電極２４と電気的に接続されている。 The second electrode portion 4b is disposed on one side surface 2e of the laminate 2. Specifically, the second electrode portion 4b is disposed on the side of the other end surface 2b on the side surface 2e. The second electrode portion 4b is formed from one main surface 2c to the other main surface 2d. The second electrode portion 4b is directly connected to the connection portion 24b exposed on the side surface 2e. Thereby, the first external electrode 4 is electrically connected to the second internal electrode 24.
　第３電極部分４ｃは、積層体２の一方の主面２ｃに配置されている。第３電極部分４ｃは、第１電極部分４ａと第２電極部分４ｂとを電気的に接続している。第４電極部分４ｄは、他方の主面２ｄに配置されている。第４電極部分４ｄは、第１電極部分４ａの主面２ｄ側の端部と電気的に接続されている。第５電極部分４ｅは、他方の主面２ｄに配置されている。第５電極部分４ｅは、第２電極部分４ｂの主面２ｄ側の端部と電気的に接続されている。 The third electrode portion 4 c is disposed on one main surface 2 c of the multilayer body 2. The third electrode portion 4c electrically connects the first electrode portion 4a and the second electrode portion 4b. The fourth electrode portion 4d is disposed on the other main surface 2d. The 4th electrode part 4d is electrically connected with the edge part by the side of the main surface 2d of the 1st electrode part 4a. The fifth electrode portion 4e is disposed on the other main surface 2d. The fifth electrode portion 4e is electrically connected to the end portion on the main surface 2d side of the second electrode portion 4b.
　第２外部電極５は、第１電極部分５ａと、第２電極部分５ｂと、第３電極部分５ｃと、第４電極部分５ｄと、第５電極部分５ｅと、を有している。第１電極部分５ａは、積層体２の他方の側面２ｆに配置されている。具体的には、第１電極部分５ａは、側面２ｆ上において、他方の端面２ｂ側に配置されている。第１電極部分５ａは、一方の主面２ｃから他方の主面２ｄにわたって形成されている。第１電極部分５ａは、側面２ｆに露出する接続部２６ｂと直接的に接続されている。これにより、第２外部電極５は、第３内部電極２６と電気的に接続されている。 The second external electrode 5 has a first electrode portion 5a, a second electrode portion 5b, a third electrode portion 5c, a fourth electrode portion 5d, and a fifth electrode portion 5e. The first electrode portion 5 a is disposed on the other side surface 2 f of the stacked body 2. Specifically, the first electrode portion 5a is disposed on the side of the other end surface 2b on the side surface 2f. The first electrode portion 5a is formed from one main surface 2c to the other main surface 2d. The first electrode portion 5a is directly connected to the connection portion 26b exposed on the side surface 2f. Thereby, the second external electrode 5 is electrically connected to the third internal electrode 26.
　第２電極部分５ｂは、積層体２の一方の側面２ｅに配置されている。具体的には、第２電極部分５ｂは、側面２ｅ上において、他方の端面２ａ側に配置されている。第２電極部分５ｂは、一方の主面２ｃから他方の主面２ｄにわたって形成されている。第２電極部分５ｂは、側面２ｅに露出する接続部２８ｂと直接的に接続されている。これにより、第２外部電極５は、第４内部電極２８と電気的に接続されている。 The second electrode portion 5b is disposed on one side surface 2e of the laminate 2. Specifically, the second electrode portion 5b is disposed on the side of the other end surface 2a on the side surface 2e. The second electrode portion 5b is formed from one main surface 2c to the other main surface 2d. The second electrode portion 5b is directly connected to the connection portion 28b exposed on the side surface 2e. Thereby, the second external electrode 5 is electrically connected to the fourth internal electrode 28.
　第３電極部分５ｃは、積層体２の一方の主面２ｄに配置されている。第３電極部分５ｃは、第１電極部分５ａと第２電極部分５ｂとを電気的に接続している。第４電極部分５ｄは、一方の主面２ｃに配置されている。第４電極部分５ｄは、第１電極部分５ａの主面２ｃ側の端部と電気的に接続されている。第５電極部分５ｅは、一方の主面２ｃに配置されている。第５電極部分５ｅは、第２電極部分５ｂの主面２ｃ側の端部と電気的に接続されている。 The third electrode portion 5c is disposed on one main surface 2d of the laminate 2. The third electrode portion 5c electrically connects the first electrode portion 5a and the second electrode portion 5b. The fourth electrode portion 5d is disposed on one main surface 2c. The 4th electrode part 5d is electrically connected with the edge part by the side of the main surface 2c of the 1st electrode part 5a. The fifth electrode portion 5e is disposed on one main surface 2c. The fifth electrode portion 5e is electrically connected to the end portion on the main surface 2c side of the second electrode portion 5b.
　第３外部電極６は、第１電極部分６ａと、第２電極部分６ｂと、第３電極部分６ｃと、を有している。第１電極部分６ａは、積層体２の他方の側面２ｆに配置されている。具体的には、第１電極部分６ａは、側面２ｆ上において、積層体２の長手方向の中央部に配置されている。すなわち、第１電極部分６ａは、積層体２の長手方向において、第１外部電極４の第１電極部分４ａと第２外部電極５の第１電極部分５ａとの間に配置されている。第１電極部分６ａは、一方の主面２ｃから他方の主面２ｄにわたって形成されている。第１電極部分６ａは、側面２ｆに露出する接続部３０ｂと直接的に接続されている。これにより、第３外部電極６は、第５内部電極３０と電気的に接続されている。 The third external electrode 6 has a first electrode portion 6a, a second electrode portion 6b, and a third electrode portion 6c. The first electrode portion 6 a is disposed on the other side surface 2 f of the stacked body 2. Specifically, the first electrode portion 6a is disposed in the central portion in the longitudinal direction of the stacked body 2 on the side surface 2f. That is, the first electrode portion 6 a is disposed between the first electrode portion 4 a of the first external electrode 4 and the first electrode portion 5 a of the second external electrode 5 in the longitudinal direction of the stacked body 2. The first electrode portion 6a is formed from one main surface 2c to the other main surface 2d. The first electrode portion 6a is directly connected to the connection portion 30b exposed on the side surface 2f. Thereby, the third external electrode 6 is electrically connected to the fifth internal electrode 30.
　第２電極部分６ｂは、一方の主面２ｃに配置されている。第２電極部分６ｂは、第１電極部分６ａの主面２ｃ側の端部と電気的に接続されている。第３電極部分６ｃは、一方の主面２ｄに配置されている。第３電極部分６ｃは、第１電極部分６ａの主面２ｄ側の端部と電気的に接続されている。 The second electrode portion 6b is disposed on one main surface 2c. The second electrode portion 6b is electrically connected to the end portion on the main surface 2c side of the first electrode portion 6a. The third electrode portion 6c is disposed on one main surface 2d. The third electrode portion 6c is electrically connected to the end portion on the main surface 2d side of the first electrode portion 6a.
　第４外部電極７は、第１電極部分７ａと、第２電極部分７ｂと、第３電極部分７ｃと、を有している。第１電極部分７ａは、積層体２の一方の側面２ｅに配置されている。具体的には、第１電極部分７ａは、側面２ｅ上において、積層体２の長手方向の中央部に配置されている。すなわち、第１電極部分７ａは、積層体２の長手方向において、第１外部電極４の第２電極部分４ｂと第２外部電極５の第２電極部分５ｂとの間に配置されている。第１電極部分７ａは、一方の主面２ｃから他方の主面２ｄにわたって形成されている。第１電極部分７ａは、側面２ｅに露出する接続部３０ｃと直接的に接続されている。これにより、第４外部電極７は、第５内部電極３０と電気的に接続されている。 The fourth external electrode 7 has a first electrode portion 7a, a second electrode portion 7b, and a third electrode portion 7c. The first electrode portion 7 a is disposed on one side surface 2 e of the stacked body 2. Specifically, the first electrode portion 7a is disposed in the central portion in the longitudinal direction of the stacked body 2 on the side surface 2e. That is, the first electrode portion 7 a is disposed between the second electrode portion 4 b of the first external electrode 4 and the second electrode portion 5 b of the second external electrode 5 in the longitudinal direction of the stacked body 2. The first electrode portion 7a is formed from one main surface 2c to the other main surface 2d. The 1st electrode part 7a is directly connected with the connection part 30c exposed to the side surface 2e. Thereby, the fourth external electrode 7 is electrically connected to the fifth internal electrode 30.
　第２電極部分７ｂは、一方の主面２ｃに配置されている。第２電極部分７ｂは、第１電極部分７ａの主面２ｃ側の端部と電気的に接続されている。第３電極部分７ｃは、一方の主面２ｄに配置されている。第３電極部分７ｃは、第１電極部分７ａの主面２ｄ側の端部と電気的に接続されている。 The second electrode portion 7b is disposed on one main surface 2c. The second electrode portion 7b is electrically connected to the end portion on the main surface 2c side of the first electrode portion 7a. The third electrode portion 7c is disposed on one main surface 2d. The third electrode portion 7c is electrically connected to the end portion on the main surface 2d side of the first electrode portion 7a.
　図１（ａ）及び図１（ｂ）に示されるように、摩擦部１０は、積層体２の一方の端面２ａに配置されている。摩擦部１０は、例えば、円柱状を呈している。摩擦部１０は、ジルコニア、アルミナなどから構成されている。摩擦部１０は、例えば、円柱部材を端面２ａに接着することにより設けられている。 1 (a) and 1 (b), the friction portion 10 is disposed on one end face 2a of the laminate 2. The friction part 10 has a cylindrical shape, for example. The friction part 10 is made of zirconia, alumina, or the like. The friction part 10 is provided by, for example, adhering a cylindrical member to the end surface 2a.
　図２に示されるように、圧電素子３では、積層体２の主面２ｃと第１内部電極２２、第２内部電極２４、第３内部電極２６及び第４内部電極２８との間の領域が、不活性領域である。圧電素子３では、積層体２の主面２ｄと第１内部電極２２、第２内部電極２４、第３内部電極２６及び第４内部電極２８との間の領域が、不活性領域である。圧電素子３では、第１内部電極２２、第２内部電極２４、第３内部電極２６及び第４内部電極２８と第５内部電極３０との間の領域が、活性領域である。活性領域は、電圧が印加されたときに変位する。 As shown in FIG. 2, in the piezoelectric element 3, a region between the main surface 2 c of the multilayer body 2 and the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 is formed. Inactive region. In the piezoelectric element 3, a region between the main surface 2 d of the multilayer body 2 and the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 is an inactive region. In the piezoelectric element 3, a region between the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, the fourth internal electrode 28 and the fifth internal electrode 30 is an active region. The active region is displaced when a voltage is applied.
　圧電素子３では、積層方向における不活性領域の厚みＴ１は、活性領域の厚みＴ２よりも小さい。すなわち、積層体２の主面２ｃ，２ｄと第１内部電極２２、第２内部電極２４、第３内部電極２６及び第４内部電極２８との間の距離は、第１内部電極２２、第２内部電極２４、第３内部電極２６及び第４内部電極２８と第５内部電極３０との間の距離よりも短い。不活性領域の厚みＴ１は、活性領域の厚みＴ２の１／５以上で且つ１／２以下であることが好ましい。不活性領域及び活性領域の厚みは、圧電体層２０ａ～２０ｈの厚みを変更することにより調整できる。具体的には、圧電体層２０ａ及び圧電体層２０ｈの厚みを、圧電体層２０ｂ～２０ｇの厚みよりも小さくする。これにより、不活性領域の厚みＴ１を、活性領域の厚みＴ２の１／５以上で且つ１／２以下とすることができる。 In the piezoelectric element 3, the thickness T1 of the inactive region in the stacking direction is smaller than the thickness T2 of the active region. That is, the distances between the main surfaces 2c and 2d of the multilayer body 2 and the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 are the first internal electrode 22, The distance between the internal electrode 24, the third internal electrode 26 and the fourth internal electrode 28 and the fifth internal electrode 30 is shorter. The thickness T1 of the inactive region is preferably 1/5 or more and 1/2 or less of the thickness T2 of the active region. The thickness of the inactive region and the active region can be adjusted by changing the thickness of the piezoelectric layers 20a to 20h. Specifically, the thickness of the piezoelectric layer 20a and the piezoelectric layer 20h is made smaller than the thickness of the piezoelectric layers 20b to 20g. Thereby, the thickness T1 of the inactive region can be set to 1/5 or more and 1/2 or less of the thickness T2 of the active region.
　上記構成を有する圧電アクチュエータ１は、駆動時においては２つの共振モードを有している。具体的には、圧電アクチュエータ１は、圧電素子３の長手方向に振動する縦振動モードと、圧電素子３の高さ方向への屈曲振動モードとの重ね合わせ（合成）によって振動する。 The piezoelectric actuator 1 having the above configuration has two resonance modes when driven. Specifically, the piezoelectric actuator 1 vibrates by superimposing (combining) a longitudinal vibration mode that vibrates in the longitudinal direction of the piezoelectric element 3 and a bending vibration mode in the height direction of the piezoelectric element 3.
　圧電アクチュエータ１では、第３外部電極６及び第４外部電極７をグランドに接続すると共に、第１外部電極４と第２外部電極５とに、位相を９０°ずらした電圧をそれぞれ印加して圧電素子３を駆動させると、摩擦部１０に楕円運動が生じる。これにより、図４（ａ）及び図４（ｂ）に示されるように、摩擦部１０と被駆動体１００との間に摩擦力が作用して、被駆動体１００が移動（回転）することとなる。 In the piezoelectric actuator 1, the third external electrode 6 and the fourth external electrode 7 are connected to the ground, and a voltage whose phase is shifted by 90 ° is applied to the first external electrode 4 and the second external electrode 5. When the element 3 is driven, an elliptical motion is generated in the friction portion 10. As a result, as shown in FIGS. 4A and 4B, a frictional force acts between the friction portion 10 and the driven body 100, and the driven body 100 moves (rotates). It becomes.
　以上説明したように、本実施形態に係る圧電アクチュエータ１では、第１内部電極２２、第２内部電極２４、第３内部電極２６及び第４内部電極２８は、積層体２内に配置されている。そのため、圧電アクチュエータ１では、内部電極間においてマイグレーションが発生することを抑制できる。また、圧電アクチュエータ１では、積層体２の主面２ｃ，２ｄと第１内部電極２２、第２内部電極２４、第３内部電極２６及び第４内部電極２８との間の領域が不活性領域であり、第１内部電極２２、第２内部電極２４、第３内部電極２６及び第４内部電極２８と第５内部電極３０との間の領域が活性領域である。この構成において、圧電アクチュエータ１では、不活性領域の厚みＴ１は、活性領域の厚みＴ２よりも小さい。これにより、圧電アクチュエータ１では、不活性領域が変位を拘束することを抑制できる。したがって、圧電アクチュエータ１では、駆動特性の向上が図れる。 As described above, in the piezoelectric actuator 1 according to this embodiment, the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 are disposed in the multilayer body 2. . Therefore, in the piezoelectric actuator 1, it can suppress that a migration generate | occur | produces between internal electrodes. In the piezoelectric actuator 1, the region between the main surfaces 2 c and 2 d of the multilayer body 2 and the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 is an inactive region. A region between the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, the fourth internal electrode 28, and the fifth internal electrode 30 is an active region. In this configuration, in the piezoelectric actuator 1, the thickness T1 of the inactive region is smaller than the thickness T2 of the active region. Thereby, in the piezoelectric actuator 1, it can suppress that an inactive area restrains displacement. Therefore, in the piezoelectric actuator 1, the drive characteristics can be improved.
　本実施形態に係る圧電アクチュエータ１では、不活性領域の厚みＴ１は、活性領域の厚みＴ２の１／５以上１／２以下である。図５は、不活性領域の厚みと振動モードの振幅との関係を示す図である。図５では、横軸が不活性領域の厚みを示し、縦軸が振幅を示している。 In the piezoelectric actuator 1 according to the present embodiment, the thickness T1 of the inactive region is 1/5 or more and 1/2 or less of the thickness T2 of the active region. FIG. 5 is a diagram showing the relationship between the thickness of the inactive region and the amplitude of the vibration mode. In FIG. 5, the horizontal axis indicates the thickness of the inactive region, and the vertical axis indicates the amplitude.
　図５に示されるように、不活性領域の厚みＴ１と活性領域の厚みＴ２とが同じ場合（図５の「１」の場合）には、縦振動モードの振幅と屈曲振動モードの振幅とに差が生じている。これに対して、不活性領域の厚みＴ１を活性領域の厚みＴ２の１／２とした場合（図５の「１／２」の場合）には、縦振動モードの振幅と屈曲振動モードの振幅との差が小さくなると共に、不活性領域の厚みＴ１と活性領域の厚みＴ２とが同じ場合に比べて、屈曲振動モードでの振幅が特に大きくなっている。更に、不活性領域の厚みＴ１を活性領域の厚みＴ２の１／３、１／４及び１／５とした場合には、縦振動モードの振幅及び屈曲振動モードの振幅の両方が、不活性領域の厚みと活性領域の厚みとが同じ場合に比べて大きくなっている。したがって、不活性領域の厚みＴ１を活性領域の厚みＴ２の１／２以下とした場合には、不活性領域における変位の拘束が抑制され、圧電アクチュエータ１の駆動特性が向上する。 As shown in FIG. 5, when the thickness T1 of the inactive region and the thickness T2 of the active region are the same (in the case of “1” in FIG. 5), the amplitude of the longitudinal vibration mode and the amplitude of the bending vibration mode are set. There is a difference. On the other hand, when the thickness T1 of the inactive region is ½ of the thickness T2 of the active region (in the case of “½” in FIG. 5), the amplitude of the longitudinal vibration mode and the amplitude of the bending vibration mode And the amplitude in the bending vibration mode is particularly large as compared with the case where the thickness T1 of the inactive region and the thickness T2 of the active region are the same. Further, when the thickness T1 of the inactive region is 1/3, 1/4, and 1/5 of the thickness T2 of the active region, both the amplitude of the longitudinal vibration mode and the amplitude of the bending vibration mode are both inactive region. The thickness of the active region and the thickness of the active region are larger than in the same case. Therefore, when the thickness T1 of the inactive region is set to ½ or less of the thickness T2 of the active region, the displacement restriction in the inactive region is suppressed, and the drive characteristics of the piezoelectric actuator 1 are improved.
　また、本実施形態に係る圧電アクチュエータ１では、不活性領域の厚みＴ１を活性領域の厚みＴ２の１／５以上とすることにより、積層体２の主面２ｃ，２ｄに第１外部電極４、第２外部電極５、第３外部電極６及び第４外部電極７が配置される構成において、第１外部電極４、第２外部電極５、第３外部電極６及び第４外部電極７と第１内部電極２２、第２内部電極２４、第３内部電極２６及び第４内部電極２８との間の耐電圧性を確保できる。 In the piezoelectric actuator 1 according to this embodiment, the first external electrode 4 is formed on the main surfaces 2c and 2d of the multilayer body 2 by setting the thickness T1 of the inactive region to 1/5 or more of the thickness T2 of the active region. In the configuration in which the second external electrode 5, the third external electrode 6, and the fourth external electrode 7 are arranged, the first external electrode 4, the second external electrode 5, the third external electrode 6, the fourth external electrode 7, and the first external electrode 4. The voltage resistance among the internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 can be ensured.
　以上、本発明の実施形態について説明してきたが、本発明は必ずしも上述した実施形態に限定されるものではなく、その要旨を逸脱しない範囲で様々な変更が可能である。 As mentioned above, although embodiment of this invention has been described, this invention is not necessarily limited to embodiment mentioned above, A various change is possible in the range which does not deviate from the summary.
　上記実施形態では、圧電体層２０ａ～２０ｈが積層されることで積層体２が形成される形態を一例に説明した。しかし、圧電体層の積層数はこれに限定されず、設計に応じて適宜設定される。 In the above embodiment, an example in which the stacked body 2 is formed by stacking the piezoelectric layers 20a to 20h has been described as an example. However, the number of stacked piezoelectric layers is not limited to this, and is appropriately set according to the design.
　上記実施形態では、不活性領域の厚みＴ１が活性領域の厚みＴ２の１／２以下である形態を一例に説明した。しかし、少なくとも、不活性領域の厚みが活性領域の厚みよりも小さければよい。 In the above-described embodiment, an example in which the thickness T1 of the inactive region is 1/2 or less of the thickness T2 of the active region has been described as an example. However, it is sufficient that at least the thickness of the inactive region is smaller than the thickness of the active region.
　上記実施形態では、圧電素子３の第１内部電極２２、第２内部電極２４及び第３内部電極２６及び第４内部電極２８が、図３に示される構成である形態を一例に説明した。しかし、内部電極の構成はこれに限定されない。内部電極は、以下の構成であってもよい。 In the above embodiment, the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28 of the piezoelectric element 3 have been described as an example in the configuration shown in FIG. However, the configuration of the internal electrode is not limited to this. The internal electrode may have the following configuration.
　図６に示されるように、圧電素子３Ａは、第１内部電極２２と、第２内部電極２４と、第３内部電極２６と、第４内部電極２８と、第５内部電極３０と、第６内部電極３２と、第７内部電極３４と、第８内部電極３６と、第９内部電極３８と、を備えている。第６内部電極３２、第７内部電極３４、第８内部電極３６及び第９内部電極３８は、第１内部電極２２、第２内部電極２４、第３内部電極２６及び第４内部電極２８と同様の構成を有している。 As shown in FIG. 6, the piezoelectric element 3A includes a first internal electrode 22, a second internal electrode 24, a third internal electrode 26, a fourth internal electrode 28, a fifth internal electrode 30, and a sixth internal electrode. An internal electrode 32, a seventh internal electrode 34, an eighth internal electrode 36, and a ninth internal electrode 38 are provided. The sixth internal electrode 32, the seventh internal electrode 34, the eighth internal electrode 36, and the ninth internal electrode 38 are the same as the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the fourth internal electrode 28. It has the composition of.
　圧電素子３Ａでは、第３内部電極２６と第４内部電極２８とは、接続部材２９により電気的に接続されている。具体的には、第３内部電極２６の主電極部２６ａと第４内部電極２８の主電極部２８ａとが、接続部材２９により電気的に接続されている。接続部材２９は、所定の間隔をあけて対角に配置された第１内部電極２２と第２内部電極２４との間に配置されている。接続部材２９は、導電性材料（例えば、Ｎｉ、Ｐｔ又はＰｄなど）からなる。接続部材２９は、上記導電性材料を含む導電性ペーストの焼結体として構成される。第６内部電極３２と第７内部電極３４とは、接続部材４０により電気的に接続されている。具体的には、第６内部電極３２の主電極部３２ａと第７内部電極３４の主電極部３４ａとが、接続部材４０により電気的に接続されている。接続部材４０は、所定の間隔をあけて対角に配置された第８内部電極３６と第９内部電極３８との間に配置されている。 In the piezoelectric element 3 </ b> A, the third internal electrode 26 and the fourth internal electrode 28 are electrically connected by a connection member 29. Specifically, the main electrode portion 26 a of the third internal electrode 26 and the main electrode portion 28 a of the fourth internal electrode 28 are electrically connected by the connection member 29. The connection member 29 is disposed between the first internal electrode 22 and the second internal electrode 24 that are disposed diagonally at a predetermined interval. The connection member 29 is made of a conductive material (for example, Ni, Pt or Pd). The connection member 29 is configured as a sintered body of a conductive paste containing the conductive material. The sixth internal electrode 32 and the seventh internal electrode 34 are electrically connected by a connection member 40. Specifically, the main electrode portion 32 a of the sixth internal electrode 32 and the main electrode portion 34 a of the seventh internal electrode 34 are electrically connected by the connection member 40. The connection member 40 is disposed between the eighth internal electrode 36 and the ninth internal electrode 38 that are disposed diagonally at a predetermined interval.
　圧電素子３Ａでは、第３内部電極２６と第４内部電極２８とが接続部材２９で電気的に接続され、第６内部電極３２と第７内部電極３４とが接続部材４０されている。そのため、圧電素子３Ａでは、第３内部電極２６と第４内部電極２８、及び、第６内部電極３２と第７内部電極３４とを、外部電極によって電気的に接続しなくてもよい。したがって、圧電アクチュエータの設計の自由度が高まる。 In the piezoelectric element 3A, the third internal electrode 26 and the fourth internal electrode 28 are electrically connected by the connecting member 29, and the sixth internal electrode 32 and the seventh internal electrode 34 are connected by the connecting member 40. Therefore, in the piezoelectric element 3A, the third internal electrode 26 and the fourth internal electrode 28, and the sixth internal electrode 32 and the seventh internal electrode 34 may not be electrically connected by the external electrode. Therefore, the degree of freedom in designing the piezoelectric actuator is increased.
　また、図３及び図６に示される例では、内部電極が積層体２の側面２ｅ，２ｆに露出する形態を一例に説明した。しかし、内部電極は、積層体２の端面２ａ，２ｂに露出する構成であってもよい。 Further, in the example shown in FIGS. 3 and 6, the configuration in which the internal electrodes are exposed on the side surfaces 2 e and 2 f of the multilayer body 2 has been described as an example. However, the internal electrode may be configured to be exposed on the end faces 2 a and 2 b of the multilayer body 2.
　上記実施形態では、第１外部電極４、第２外部電極５、第３外部電極６及び第４外部電極７が、図１（ａ）及び図１（ｂ）に示される構成を有する形態を一例に説明した。しかし、外部電極の構成はこれに限定されない。外部電極は、内部電極の構成に応じて適宜設計されればよい。 In the above embodiment, an example in which the first external electrode 4, the second external electrode 5, the third external electrode 6, and the fourth external electrode 7 have the configuration shown in FIG. 1A and FIG. Explained. However, the configuration of the external electrode is not limited to this. The external electrode may be appropriately designed according to the configuration of the internal electrode.
　本発明の他の例として、圧電素子は、図７に示される構成を有していてもよい。図７に示されるように、圧電素子３Ｂは、圧電体層２０ａ～２０ｆがこの順番に積層されている。圧電素子３Ｂでは、圧電体層２０ｂ、圧電体層２０ｄ及び圧電体層２０ｆ上に、第５内部電極３０が配置されおり、圧電体層２０ｃ上に第１内部電極２２、第２内部電極２４、第３内部電極２６、第４内部電極２８及び接続部材２９が配置されており、圧電体層２０ｅ上に第６内部電極３２、第７内部電極３４、第８内部電極３６、第９内部電極３８及び接続部材４０が配置されている。 As another example of the present invention, the piezoelectric element may have the configuration shown in FIG. As shown in FIG. 7, the piezoelectric element 3B has piezoelectric layers 20a to 20f laminated in this order. In the piezoelectric element 3B, a fifth internal electrode 30 is disposed on the piezoelectric layer 20b, the piezoelectric layer 20d, and the piezoelectric layer 20f, and the first internal electrode 22, the second internal electrode 24, and the like are disposed on the piezoelectric layer 20c. The third internal electrode 26, the fourth internal electrode 28, and the connection member 29 are disposed, and the sixth internal electrode 32, the seventh internal electrode 34, the eighth internal electrode 36, and the ninth internal electrode 38 are disposed on the piezoelectric layer 20e. And the connection member 40 is arrange | positioned.
　圧電素子３Ｂでは、第５内部電極（第２内部電極）３０は、積層体２内において、一対の主面２ｃ，２ｄに最も近い位置に配置されている。圧電素子３Ｂでは、主面２ｃ，２ｄと第５内部電極３０との間の領域が不活性領域であり、第５内部電極３０と第１内部電極２２、第２内部電極２４、第３内部電極２６及び第４内部電極との間の領域、及び、第５内部電極３０と第６内部電極３２、第７内部電極３４、第８内部電極３６及び第９内部電極３８との間の領域が活性領域である。この構成においても、積層方向における不活性領域の厚みは、活性領域の厚みよりも小さい。 In the piezoelectric element 3B, the fifth internal electrode (second internal electrode) 30 is disposed in the stacked body 2 at a position closest to the pair of main surfaces 2c and 2d. In the piezoelectric element 3B, the region between the main surfaces 2c, 2d and the fifth internal electrode 30 is an inactive region, and the fifth internal electrode 30, the first internal electrode 22, the second internal electrode 24, the third internal electrode 26, and the region between the fifth internal electrode 30 and the fourth internal electrode, and the region between the fifth internal electrode 30, the sixth internal electrode 32, the seventh internal electrode 34, the eighth internal electrode 36, and the ninth internal electrode 38 are active. It is an area. Also in this configuration, the thickness of the inactive region in the stacking direction is smaller than the thickness of the active region.
　１…圧電アクチュエータ、２…積層体（素体）、１０…摩擦部、２２…第１内部電極、２４…第２内部電極（第１内部電極）、２６…第３内部電極（第１内部電極）、２８…第４内部電極、２９…接続部材、３０…第５内部電極（第２内部電極）、３２…第６内部電極（第１内部電極）、３４…第７内部電極（第１内部電極）、３６…第８内部電極（第１内部電極）、３８…第９内部電極（第１内部電極）。 DESCRIPTION OF SYMBOLS 1 ... Piezoelectric actuator, 2 ... Laminated body (element body), 10 ... Friction part, 22 ... 1st internal electrode, 24 ... 2nd internal electrode (1st internal electrode), 26 ... 3rd internal electrode (1st internal electrode) , 28 ... fourth internal electrode, 29 ... connecting member, 30 ... fifth internal electrode (second internal electrode), 32 ... sixth internal electrode (first internal electrode), 34 ... seventh internal electrode (first internal electrode) Electrode), 36... Eighth internal electrode (first internal electrode), 38... Ninth internal electrode (first internal electrode).

Claims (4)

  1. 　印加される電圧によって縦振動モードと屈曲振動モードとが合成された振動モードを発生させる圧電アクチュエータであって、
    　矩形状を呈する複数の圧電体層を積層することによって形成されると共に、複数の前記圧電体層の積層方向において対向する一対の主面を有する素体と、
    　前記素体内に配置された複数の内部電極と、
    　前記素体の外表面に配置され、対応する前記内部電極と電気的に接続された複数の外部電極と、を備え、
    　複数の前記内部電極は、同一の前記圧電体層上に配置された４つの第１内部電極と、４つの前記第１内部電極と前記圧電体層を挟んで対向して配置され、前記第１内部電極との間に電圧が印加される第２内部電極と、を有し、
    　４つの前記第１内部電は、前記素体内において、一対の前記主面に最も近い位置に配置されており、
    　前記素体の前記主面と前記第１内部電極との間の領域が不活性領域であり、前記第１内部電極と前記第２内部電極との間の領域が活性領域であり、
    　前記積層方向における前記不活性領域の厚みは、前記活性領域の厚みよりも小さい、圧電アクチュエータ。     A piezoelectric actuator that generates a vibration mode in which a longitudinal vibration mode and a bending vibration mode are combined by an applied voltage,
    An element body formed by laminating a plurality of piezoelectric layers having a rectangular shape and having a pair of main surfaces facing each other in the laminating direction of the plurality of piezoelectric layers;
    A plurality of internal electrodes disposed in the element body;
    A plurality of external electrodes disposed on the outer surface of the element body and electrically connected to the corresponding internal electrodes;
    The plurality of internal electrodes are arranged to be opposed to each other with four first internal electrodes arranged on the same piezoelectric layer, the four first internal electrodes and the piezoelectric layer interposed therebetween, and A second internal electrode to which a voltage is applied between the internal electrode and
    The four first internal electric powers are arranged at positions closest to the pair of main surfaces in the element body,
    A region between the main surface of the element body and the first internal electrode is an inactive region, and a region between the first internal electrode and the second internal electrode is an active region,
    The piezoelectric actuator, wherein a thickness of the inactive region in the stacking direction is smaller than a thickness of the active region.
  2. 　前記不活性領域の厚みは、前記活性領域の厚みの１／２以下である、請求項１に記載の圧電アクチュエータ。 2. The piezoelectric actuator according to claim 1, wherein the thickness of the inactive region is ½ or less of the thickness of the active region.
  3. 　前記不活性領域の厚みは、前記活性領域の厚みの１／５以上１／２以下である、請求項２に記載の圧電アクチュエータ。 The piezoelectric actuator according to claim 2, wherein a thickness of the inactive region is 1/5 or more and 1/2 or less of a thickness of the active region.
  4. 　４つの前記第１内部電極のうち、２つの前記第１内部電極が第１の対角に位置し、他の２つの前記第１内部電極が前記第１の対角に交差する第２の対角に位置しており、
    　前記第１の対角又は前記第２の対角に位置する２つの前記第１内部電極が接続部材によって電気的に接続されている、請求項１～３のいずれか一項に記載の圧電アクチュエータ。     Of the four first internal electrodes, two first internal electrodes are located at a first diagonal, and the other two first internal electrodes intersect with the first diagonal. Located in the corner,
    The piezoelectric actuator according to any one of claims 1 to 3, wherein the two first internal electrodes located at the first diagonal or the second diagonal are electrically connected by a connecting member. .
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