JP5974598B2 - Piezoelectric unit - Google Patents

Description

  The present invention relates to a piezoelectric element unit. More specifically, the present invention relates to a piezoelectric element unit that can prevent characteristic deterioration due to the pyroelectric effect.

  A piezoelectric element is an element that mutually converts mechanical displacement and electrical displacement using a piezoelectric effect and an inverse piezoelectric effect. Such a piezoelectric element is manufactured, for example, by forming and firing piezoelectric ceramics to obtain an element body, forming an electrode on the element body, and further performing a polarization treatment.

  Since the mechanical displacement obtained by the piezoelectric element is relatively small, the piezoelectric element is suitably used as an actuator that requires precise and accurate control, for example. More specifically, it can be used for lens driving, HDD head driving, inkjet printer head driving, fuel injection valve driving, and the like.

  For example, as a piezoelectric actuator using a piezoelectric element, one having a structure in which a guide member and a weight are bonded to both ends of the piezoelectric element is disclosed (see Patent Document 1, etc.).

  On the other hand, when it is assumed that the piezoelectric element is exposed to a temperature change, the piezoelectric element has a problem of deterioration of the polarization degree due to the pyroelectric effect. Particularly in the process of temperature decrease, the piezoelectric element is applied with a voltage in the opposite direction to that during the polarization process due to the charge due to the pyroelectric effect, so if the voltage is too high, the degree of polarization of the piezoelectric element is reduced. There is a risk of letting you. Since the degree of polarization thus lowered can hardly be recovered in the course of the temperature rising again, the degree of polarization gradually decreases each time the temperature change is repeated. There has been a problem that the characteristics of the piezoelectric element are deteriorated such that it cannot be obtained.

  In order to cope with such a problem, Patent Document 2 discloses that in a multilayer piezoelectric element, an internal electrode exposed on the side surface is covered with a migration preventing exterior material, and further conductive particles are dispersed in the exterior material. The technology is described.

  Further, Patent Document 2 describes that an exterior material in which conductive particles are dispersed can suppress a decrease in polarization degree due to the pyroelectric effect.

JP 2007-282372 A International Publication No. 2007/052599

  However, in the conventional technology in which the exposed surface of the internal electrode is covered with an exterior material, a process for forming the exterior material on the surface of the element body is required after the element body is formed. The manufacturing process is lengthened and the production efficiency is lowered. Further, when the piezoelectric element assembly is cut after firing, the internal electrode may extend along the direction in which the cutting blade enters, so in the conventional technique in which the cut surface is covered with an exterior material containing conductive particles, There is a possibility that a large manufacturing variation may occur in the resistance value of the path formed through the material.

  Further, the conventional exterior material containing conductive particles has a problem that a portion having a low resistance value is locally formed due to aggregation of the conductive particles and the like, and there is a possibility of causing a short circuit between the internal electrodes through the portion. there were. In particular, this problem becomes more prominent as the distance between the internal electrodes (thickness of the piezoelectric layer) becomes smaller.

  Furthermore, in the conventional technology that attempts to achieve the prevention of migration and the suppression of the decrease in the degree of polarization with a single exterior material, the exterior material is required to fulfill both functions described above. There is a problem that it is difficult to adjust the resistance and the resistance value of the exterior material is difficult to adjust.

  The present invention has been made in view of such a situation, and can surely suppress the deterioration of characteristics due to the pyroelectric effect, and the piezoelectric layer can be easily thinned and has excellent productivity. An object is to provide an element unit.

In order to achieve the above object, a piezoelectric element unit according to the present invention includes a piezoelectric layer, a first internal electrode and a second internal electrode that are stacked substantially parallel to each other with the piezoelectric layer interposed therebetween, and the first A laminated piezoelectric element having a first external electrode electrically connected to the internal electrode and a second external electrode electrically connected to the second internal electrode;
A resin portion that connects at least one end surface in the stacking direction of the multilayer piezoelectric element and an attachment surface of a connection member connected to the one end surface;
The resin portion includes conductive particles, has an electric resistance lower than that of the piezoelectric layer, and is formed so as to be in contact with the first external electrode and the second external electrode.

  The piezoelectric element unit according to the present invention has a resin portion that connects one end surface of the multilayer piezoelectric element and the attachment surface of the connection member, and the resin portion is provided on both the first external electrode and the second external electrode. It is formed to contact. Here, since the resin portion contains conductive particles and has an electric resistance value lower than that of the piezoelectric layer, the electric charge generated due to the pyroelectric effect moves through the resin portion and is excessive in the piezoelectric layer. A voltage can be prevented from being applied. As a result, the piezoelectric element unit according to the present invention can suppress characteristic deterioration caused by the pyroelectric effect.

  Further, the resin portion has a function of connecting the piezoelectric element unit and the connection member, and is not provided only for eliminating the pyroelectric effect. That is, the resin portion according to the present invention includes a conductive particle in a resin having another function of coupling the laminated piezoelectric element and the connecting member, and lowers the electric resistance value than that of the piezoelectric layer. A new function has been added to prevent a decrease in the degree of polarization of the piezoelectric element due to electrical effects. Therefore, the piezoelectric element unit according to the present invention achieves suppression of characteristic deterioration caused by the pyroelectric effect only by changing the conductive particles in the constituent material of the resin portion. Compared with the prior art which additionally attempts to suppress characteristic deterioration, it can be manufactured by a simple process and is excellent in productivity.

  In addition, since the resin portion is electrically connected by contacting the first external electrode and the second external electrode, the electrical resistance value of the path formed by the resin portion has little manufacturing variation. Therefore, the piezoelectric element unit according to the present invention can suitably control the electric resistance value of the resin portion, and while ensuring the basic characteristics such as mechanical displacement accompanying voltage application, the pyroelectric effect It is possible to prevent the characteristic deterioration due to.

  Furthermore, in the piezoelectric element unit according to the present invention, even if electrical properties are uneven in the resin portion, a fatal problem such as short-circuiting between the internal electrodes does not occur, so that stable performance is achieved. It is easy to manufacture. Moreover, since the resin part can tolerate a bias of electrical characteristics in the inside thereof relatively widely, manufacturing conditions such as selection of a constituent material and a blending ratio can be determined relatively freely. Furthermore, the piezoelectric element unit according to the present invention is advantageous in reducing the thickness of the piezoelectric layer because there is no risk that the resin portion short-circuits the internal electrodes even if the piezoelectric layer is thinned. .

  Further, for example, the multilayer piezoelectric element may further include an insulating layer that covers at least a part of the surface where the first internal electrode and the second internal electrode are exposed.

  Such a piezoelectric element unit has particularly good reliability because migration can be prevented by the insulating layer and a decrease in polarization degree can be suppressed by the resin portion. In addition, the insulating layer in this case does not need to have a function of releasing charges generated by the pyroelectric effect, and may be formed of a highly insulating material, so that it is highly reliable and easy to manufacture. In addition, the insulating layer covers the exposed portions of the first internal electrode and the second internal electrode, and thus has an effect of preventing the resin portion from coming into direct contact with the exposed portions.

  For example, the resin part may be a thermosetting adhesive curing part formed by curing a thermosetting adhesive containing the conductive particles.

  The piezoelectric element unit in which the resin part is a thermosetting adhesive curing part has a process of adhering the laminated piezoelectric element and the connection member with the thermosetting adhesive without adding other processes in particular. Since a path for releasing electric charges generated by the pyroelectric effect is formed, the manufacturing is easy and the productivity is excellent. In addition, such a resin portion can function as a path for releasing the electric charge due to the pyroelectric effect in the cooling process immediately after the thermosetting adhesive is cured, so that it is reasonable from the viewpoint of the manufacturing process.

FIG. 1 is a conceptual diagram showing a piezoelectric actuator using a piezoelectric element unit according to an embodiment of the present invention and its peripheral members. FIG. 2 is an enlarged cross-sectional view in which the periphery of the piezoelectric element unit in FIG. 1 is enlarged. FIG. 3 is an enlarged cross-sectional view of the piezoelectric unit shown in FIG. 2 cut along the line III-III. FIG. 4 is a conceptual circuit diagram illustrating the electrical resistance values of the piezoelectric layer and the resin portion. FIG. 5 is a flowchart showing an example of the manufacturing process of the piezoelectric element unit.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a conceptual diagram showing a piezoelectric actuator unit 50 using a piezoelectric element unit 30 according to an embodiment of the present invention and its peripheral members. The piezoelectric actuator unit 50 includes a piezoelectric element unit 30, a shaft 40 and a weight 42. The shaft 40 is connected to one end of the piezoelectric element unit 30, and the weight 42 is connected to the other end of the piezoelectric element unit 30, and the driving force generated by the piezoelectric element unit 30 is transmitted.

  A moving member 70 is movably engaged with the shaft 40 at the tip portion of the shaft 40. Although not shown, the moving member 70 holds an optical system and the like, and the moving member 70 and the optical system held by the moving member 70 have a shaft as shown by an arrow 80 by the driving force of the piezoelectric actuator unit 50. 40 can be displaced.

  The piezoelectric element unit 30 is deformed by applying a voltage by the drive circuit 60, and the shaft 40 connected to one end of the piezoelectric element unit 30 is displaced as the piezoelectric element unit 30 is deformed. The weight 42 connected to the other end of the piezoelectric element unit 30 functions as an inertia body for giving displacement to the shaft 40, but the weight 42 may be connected to another member.

  The drive circuit 60 is electrically connected to the first external electrode 15 and the second external electrode 16 (see FIG. 2) of the piezoelectric element unit 30, and is connected via the first external electrode 15 and the second external electrode 16. Then, a voltage is applied to the piezoelectric layer 12 (see FIG. 2). The voltage waveform output by the drive circuit 60 is not particularly limited. For example, the drive circuit 60 outputs a voltage waveform having a sawtooth waveform, so that the displacement exceeding the deformation amount of the piezoelectric element unit 30 and the displacement amount of the shaft 40 associated therewith is output. Can be generated in the moving member 70.

  As shown in FIG. 2, the piezoelectric element unit 30 according to the present embodiment includes a laminated piezoelectric element 10 and resin portions 18 and 19. The laminated piezoelectric element 10 has a substantially rectangular parallelepiped shape, and the resin portions 18 and 19 are provided on both end faces of the laminated piezoelectric element 10.

  The multilayer piezoelectric element 10 includes an element body 11, a first external electrode 15, and a second external electrode 16. The element body 11 has a substantially rectangular parallelepiped shape slightly smaller than the multilayer piezoelectric element 10, and the first external electrode 15 and the second external electrode 16 are provided on the first side surface 11 a and the second side surface 11 b of the element body 11, respectively. Is formed. As shown in FIG. 3, the multilayer piezoelectric element 10 further includes an insulating layer 17 formed on the third side surface 11 c and the fourth side surface 11 d of the element body 11.

  As shown in FIGS. 2 and 3, the element body 11 has an internal structure in which a piezoelectric layer 12, a first internal electrode 13, and a second internal electrode 14 are stacked along the stacking direction Z. At both ends of the element body 11, there are lid portions where the first internal electrode 13 and the second internal electrode 14 do not exist. However, at the central portion of the element body 11 excluding both ends, the first internal electrode 13 and the second internal electrode Electrodes 14 are alternately stacked with the piezoelectric layers 12 interposed therebetween.

  The first internal electrode 13 and the second internal electrode 14 extend substantially parallel to each other along a direction perpendicular to the stacking direction. As shown in FIG. 11 is interrupted before the second side surface 11b, and the second internal electrode 14 is interrupted before the first side surface 11a facing in the opposite direction to the second side surface 11b.

  As shown in FIG. 2, the first external electrode 15 is formed on the first side surface 11a where the second internal electrode 14 is not exposed and only the first internal electrode 13 is exposed. The first external electrode 15 and the first internal electrode 13 are electrically and physically connected. Since the first external electrode 15 and the first internal electrode 13 are both made of a conductive material, they are always substantially the same. It becomes a potential.

  On the other hand, the second external electrode 16 is formed on the second side surface 11b where the first internal electrode 13 is not exposed and only the second internal electrode 14 is exposed. The second external electrode 16 and the second internal electrode 14 are electrically and physically connected. Since the second external electrode 16 and the second internal electrode 14 are both made of a conductive material, they are always substantially the same. It becomes a potential.

  Examples of the conductive material constituting the first internal electrode 13 and the second internal electrode 14 include noble metals such as Ag, Pd, Au, and Pt and alloys thereof (Ag—Pd, etc.), or base metals such as Cu and Ni. Although these alloys etc. are mentioned, it is not specifically limited. The conductive material constituting the first external electrode 15 and the second external electrode 16 is not particularly limited, and the same material as the conductive material constituting the internal electrode can be used. Furthermore, the above-mentioned various metal plating layers and sputter layers may be formed outside the first external electrode 15 and the second external electrode 16.

  As shown in FIG. 2, the piezoelectric layer 12 in the central portion of the element body 11 has a piezoelectric active portion 12 a sandwiched between the first internal electrode 13 and the second internal electrode 14. The piezoelectric active portion 12a is a portion that is mechanically displaced when a voltage is applied via the first internal electrode 13 and the second internal electrode 14 having different polarities.

The thickness of the piezoelectric layer 12 is not particularly limited, but is preferably about 5 to 50 μm in this embodiment. The material of the piezoelectric layer 12 is not particularly limited as long as it is a material exhibiting a piezoelectric effect or an inverse piezoelectric effect, and examples thereof include PbZr _x Ti _1-x O ₃ and BaTiO ₃ . Moreover, the component for characteristic improvement etc. may contain, The content should just determine suitably according to a desired characteristic.

  As described above, among the side surfaces of the element body 11 extending along the stacking direction Z, only the first internal electrode 13 is exposed on the first side surface 11a, and the second internal electrode is exposed on the second side surface 11b. 14 is exposed, but both the first internal electrode 13 and the second internal electrode 14 are exposed on the third side surface 11c and the fourth side surface 11d that connect the first side surface 11a and the second side surface 11b. (See FIG. 3).

  As shown in FIG. 3, an insulating layer 17 is formed on the third side surface 11 c and the fourth side surface 11 d of the element body 11. The insulating layer 17 according to the present embodiment covers the entire third side surface 11c and fourth side surface 11d. However, the insulating layer 17 is a portion of the surface of the third side surface 11c and the fourth side surface 11d where the first internal electrode 13 and the second internal electrode 14 facing the piezoelectric active portion 12a shown in FIG. 2 are exposed. Covering is particularly important, and other parts may be uncovered.

The material of the insulating layer 17 is not particularly limited as long as it is highly insulating, prevents moisture from entering, and prevents migration between internal electrodes. Specific examples of the material include resin and glass. Further, the electric resistance value of the insulating layer 17 is not particularly limited as long as the insulating property can be ensured, but in the present embodiment, it is preferably 10 ⁹ Ω or more. The thickness of the insulating layer 17 is not particularly limited, but is about 1 to 20 μm, for example.

  As shown in FIG. 2, the resin portion 18 connects one end surface 10 a in the stacking direction Z of the multilayer piezoelectric element 10 and the mounting surface 40 a of the shaft 40 connected to the one end surface 10 a. As shown in FIGS. 2 and 3, the resin portion 18 extends to the outer peripheral portion of the one end face 10 a and is in contact with the first external electrode 15 and the second external electrode 16 disposed on the outer peripheral portion. .

  The resin portion 19 connects the other end surface 10b in the stacking direction Z of the multilayer piezoelectric element 10 and the attachment surface 42a of the weight 42 connected to the other end surface 10b. As shown in FIGS. 2 and 3, the resin portion 19 extends to the outer peripheral portion of the other end face 10 b similarly to the resin portion 18, and the first external electrode 15 and the second external electrode disposed on the outer peripheral portion. 16 is in contact. 2 and 3, part of the resin portions 18 and 19 may extend to the side surface of the multilayer piezoelectric element 10.

  The resin parts 18 and 19 have resin and conductive particles dispersed in the resin. Although it does not specifically limit as resin contained in the resin parts 18 and 19, An epoxy resin, a phenol resin, a fluororesin, an acrylic resin, etc. are mentioned. The material of the conductive particles contained in the resin parts 18 and 19 is not particularly limited as long as the material can be dispersed in the resin parts 18 and 19 and the resistivity of the resin parts 18 and 19 can be reduced. Carbon particles and metal particles And metal oxide particles.

  The resin portions 18 and 19 may be adhesive cured portions formed by curing an adhesive that bonds the laminated piezoelectric element 10 and the shaft 40 or the weight 42 as described in the manufacturing method described later. preferable. The connection between the laminated piezoelectric element 10 and the shaft 40 and the weight 42 is simple by bonding, which contributes to the productivity improvement of the piezoelectric element unit 30 or the piezoelectric actuator unit 50. Examples of the adhesive that can be used for forming the resin portions 18 and 19 include, but are not particularly limited to, a thermosetting adhesive, an ultraviolet curable adhesive, and a moisture curable adhesive.

Furthermore, the resin portions 18 and 19 have a lower electrical resistance value than the piezoelectric layer 12. As shown in FIG. 4, the two polar electrodes of the multilayer piezoelectric element 10 are electrically composed of a resistor R1 constituted by the piezoelectric layer 12 and a resistor R2 constituted by the resin portions 18 and 19. Can be thought of as being connected in parallel. The electric resistance value of the resistor R2 corresponding to the resin portions 18 and 19 is lower than the electric resistance value of the resistor R1 corresponding to the piezoelectric layer 12, and for example, the electric resistance value (Ω) of the piezoelectric layer 12 (resistor R1) is In the case of 10 ⁹ order, the electrical resistance value (Ω) of the resin portions 18 and 19 (resistor R2) can be 10 ⁶ to 10 ⁹ order.

The electric resistance values of the resin portions 18 and 19 may be set as appropriate according to the piezoelectric layer 12 (resistance R1). For example, in order to appropriately move charges generated by the pyroelectric effect, the piezoelectric layer 12 (resistance R1) is preferably about 1/100 or less of the electric resistance value. Further, the lower limit value of the electric resistance value of the resin portions 18 and 19 is not particularly limited, but is preferably at least about 10 ⁴ Ω so that the piezoelectric active portion 12a generates a desired mechanical displacement. Here, the electrical resistance values of the resin parts 18 and 19 are the material and content of the conductive particles contained in the resin parts 18 and 19, the thickness of the resin parts 18 and 19, or the number of the resin parts 18 and 19 (in the embodiment, 2) etc.

  Below, an example of the manufacturing method of the piezoelectric element unit 30 is demonstrated using FIG.

  FIG. 5 is a flowchart showing a manufacturing process of the piezoelectric element unit 30. In the method for manufacturing the piezoelectric element unit 30, first, the multilayer piezoelectric element 10 is prepared (step S001). In step S001, first, a green sheet on which an internal electrode paste film having a predetermined pattern to be the first internal electrode 13 and the second internal electrode 14 after baking and a green sheet having no internal electrode paste film are prepared. .

  The green sheet is produced by the following method, for example. First, the raw materials of the material constituting the piezoelectric layer 12 are uniformly mixed by means such as wet mixing and then dried. Next, calcination is performed under appropriately selected calcination conditions, and the calcination powder is wet pulverized. Then, a binder is added to the pulverized calcined powder to form a slurry. Next, the slurry is formed into a sheet by means such as a doctor blade method or a screen printing method, and then dried to obtain a green sheet having no internal electrode paste film. Furthermore, by applying the internal electrode paste containing the above-described conductive material onto the green sheet by means such as a printing method, a green sheet on which an internal electrode paste film having a predetermined pattern is formed is obtained. The raw material of the material constituting the piezoelectric layer 12 may contain inevitable impurities.

  After preparing each green sheet, the prepared green sheets are superposed, pressure is applied and pressure-bonded, a necessary process such as a drying process is performed, and then cut to obtain an assembly of green element bodies.

  Next, after the obtained laminated body is fired under a predetermined condition to obtain a sintered body, the sintered body is cut into a strip shape using a dicing saw or the like. Further, the first external electrode 15 and the second external electrode 16 are formed in portions corresponding to the first side surface 11a and the second side surface 11b in the sintered body, and a DC voltage is applied to these electrodes to polarize the piezoelectric layer 12. Process. Thereafter, the strip-shaped sintered body after the polarization treatment is cut into individual element bodies, and external electrodes 15 and 16 are formed on the first side surface 11a and the second side surface 11b, and the third side surface 11c and the fourth side surface 11d. Thus, the element body 11 is exposed (see FIG. 1). In addition, it is also preferable to carry out barrel grinding | polishing to the obtained element main body 11, and to make the corner | angular part and ridgeline part of the element main body 11 into R surface.

  Finally, an insulating layer 17 as shown in FIG. 3 is formed on the third side surface 11c and the fourth side surface 11d of the element body 11, and the side surfaces 11c, from which the first internal electrode 13 and the second internal electrode 14 are exposed, 11d is covered. In the present embodiment, an insulating resin 17 is applied to form the insulating layer 17. Through such steps, the multilayer piezoelectric element 10 is manufactured.

  In step S002 shown in FIG. 5, an adhesive for bonding the laminated piezoelectric element 10 to the shaft 40 and the weight 42 is applied to the bonding surface. The surface to which the adhesive is applied may be the mounting surfaces 40a and 42a of the shaft 40 and the weight 42, the end surfaces 10a and 10b of the multilayer piezoelectric element 10, or both surfaces. good. However, in any case, the adhesive is applied so that the resin portions 18 and 19 formed after the adhesive is cured are in contact with both the first external electrode 15 and the second external electrode 16. .

  As the adhesive applied in step S002, a mixture of the conductive particles contained in the resin portions 18 and 19 described above is used. Note that the type of adhesive used in step S002 is not particularly limited, but in the description of the manufacturing method, description will be made assuming that a thermosetting adhesive is applied.

  In step S003 shown in FIG. 5, the bonding surfaces are bonded to each other via an adhesive. More specifically, the mounting surface 40a of the shaft 40 shown in FIG. 2 and one end surface 10a of the multilayer piezoelectric element 10 are joined, and the mounting surface 42a of the weight 42 and the other end surface 10b of the multilayer piezoelectric element 10 are joined. To do. In addition, after the laminated piezoelectric element 10, the shaft 40, and the weight 42 are joined via an adhesive, these members are held with a jig or the like as necessary.

  In step S004 shown in FIG. 5, the adhesive applied in step S002 is cured to form the resin portions 18 and 19. When the adhesive applied in step S002 is a thermosetting adhesive, the resin parts 18 and 19 are formed by heating the adhesive in step S004.

  Thus, the piezoelectric element unit 30 shown in FIGS. 2 and 3 can be manufactured by the manufacturing process shown in steps S001 to S004.

  The piezoelectric element unit 30 according to the present embodiment includes resin portions 18 and 19 that connect the end faces 10a and 10b of the multilayer piezoelectric element 10 to the mounting surfaces 40a and 42a of the shaft 40 and the weight 42. , 19 are formed in contact with both the first external electrode 15 and the second external electrode 16. As described above, since the resin portions 18 and 19 include conductive particles and the electric resistance value is lower than that of the piezoelectric layer 12, the charges generated due to the pyroelectric effect are passed through the resin portions 18 and 19. It is possible to prevent the excessive voltage from being applied to the piezoelectric layer 12 by moving. As a result, the piezoelectric element unit 30 can suppress characteristic deterioration caused by the pyroelectric effect.

  The resin portions 18 and 19 have a function of connecting the piezoelectric element unit 30, the shaft 40, and the weight 42, and are not provided only for eliminating the pyroelectric effect. That is, the resin parts 18 and 19 contain conductive particles in a resin having another function of connecting the laminated piezoelectric element 10 to the shaft 40 and the weight 42 and have an electric resistance value lower than that of the piezoelectric layer 12. Thus, a new function of preventing a decrease in the degree of polarization of the piezoelectric element due to the pyroelectric effect is added. Therefore, the piezoelectric element unit 30 achieves prevention of characteristic deterioration caused by the pyroelectric effect with only a slight change in the manufacturing process, and is excellent in productivity.

  In addition, the piezoelectric element unit 30 can suitably control the electric resistance value by adjusting the shape and number of the resin portions 18 and 19, and has basic characteristics such as mechanical displacement accompanying voltage application. It is possible to prevent characteristic deterioration due to the pyroelectric effect while ensuring the above. The resin parts 18 and 19 including conductive particles may be formed only on one end surface 10a or the other end surface 10b. In this case, a resin not including conductive particles is formed on the other side. can do.

  Further, the piezoelectric element unit 30 is advantageous in reducing the thickness of the piezoelectric layer 12 because there is no risk that the resin portions 18 and 19 short-circuit the internal electrodes even if the piezoelectric layer 12 is thinned. Suitable for miniaturization. In addition, the piezoelectric element unit 30 has particularly good reliability because the insulating layer 17 can prevent migration and the resin portions 18 and 19 can suppress a decrease in the degree of polarization.

  The thermosetting adhesive is suitable as an adhesive for connecting the laminated piezoelectric element 10 to the shaft 40 and the weight 42 from the viewpoint of adhesive strength and the like, but the piezoelectric element unit 30 is cooled after the adhesive is cured. Therefore, there is a concern about the influence of the pyroelectric effect on the piezoelectric layer 12. However, since the resin portions 18 and 19 of the piezoelectric element unit 30 can function as a path for releasing charges due to the pyroelectric effect in the cooling process immediately after the thermosetting adhesive is cured, countermeasures against the pyroelectric effect in the manufacturing process are possible. It is also effective.

Other Embodiments Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and can be implemented in various modes without departing from the scope of the present invention. Of course.

  For example, the shape of the element body is not limited to a rectangular parallelepiped, and may be a polygonal column shape or a cylindrical shape. In addition, as long as the first and second external electrodes are electrically connected to the corresponding first and second internal electrodes, the place where they are formed is not particularly limited. It may be formed. Furthermore, a plurality of external electrodes having the same polarity may be formed on the same surface, or a plurality of external electrodes having different polarities may be formed.

  The target to which the piezoelectric element unit is applied is not limited to the piezoelectric actuator, and may be applied to other devices such as a temperature sensor.

DESCRIPTION OF SYMBOLS 10 ... Laminated piezoelectric element 10a ... One end surface 10b ... The other end surface 11 ... Element main body 11a ... 1st side surface 11b ... 2nd side surface 11c ... 3rd side surface 11d ... 4th side surface 12 ... Piezoelectric layer 12a ... Piezoelectric active part DESCRIPTION OF SYMBOLS 13 ... 1st internal electrode 14 ... 2nd internal electrode 15 ... 1st external electrode 16 ... 2nd external electrode 17 ... Insulating layer 18, 19 ... Resin part R1, R2 ... Resistance 30 ... Piezoelectric element unit 40 ... Shaft 42 ... Weight 40a, 42a ... mounting surface 50 ... piezoelectric actuator unit 60 ... drive circuit 70 ... moving member

Claims (4)

A piezoelectric layer, a first internal electrode and a second internal electrode stacked substantially parallel to each other with the piezoelectric layer interposed therebetween, a first external electrode electrically connected to the first internal electrode, A laminated piezoelectric element having a second external electrode electrically connected to the second internal electrode;
A resin portion that connects at least one end surface in the stacking direction of the multilayer piezoelectric element and an attachment surface of a connection member connected to the one end surface;
The first external electrode and the second external electrode are formed on side surfaces extending along the stacking direction of the stacked piezoelectric element,
The resin part includes conductive particles, has an electric resistance lower than that of the piezoelectric layer, and is formed so as to be in contact with the first external electrode and the second external electrode,
Charges generated by pyroelectric effect in the multilayer piezoelectric element, the inside of the resin portion connecting the one end surface and the mounting surface of the other of the external electrode from one of the external electrode to which the resin part is in contact A piezoelectric element unit that moves toward the surface.   2. The piezoelectric element unit according to claim 1, wherein the multilayer piezoelectric element further includes an insulating layer covering at least a part of a surface where the first internal electrode and the second internal electrode are exposed. .   3. The piezoelectric element unit according to claim 1, wherein the resin portion is a thermosetting adhesive curing portion formed by curing a thermosetting adhesive including the conductive particles. 4. .   The first internal electrode and the first external electrode are composed of a resistor R1 formed of the piezoelectric layer and a resistor R2 formed of the resin portion with respect to the second external electrode and the second internal electrode. 4. The piezoelectric element according to claim 1, wherein the piezoelectric elements are connected in parallel, and an electric resistance value of the resistor R <b> 2 is 1/100 or less of an electric resistance value of the resistor R <b> 1. unit.

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