Piezoelectric element

Abstract

To reduce the possibility of peeling of an electrode plate.SOLUTION: A piezoelectric element comprises a laminate, a conductor layer, an electrode plate, and a fixing material. The laminate is obtained by laminating a plurality of piezoelectric substances and internal electrodes. The conductor layer is connected with the internal electrode and located along a lamination direction of the laminate. The electrode plate has a body part joined to the conductor layer with a conductive joint material therebetween, and a projecting part projecting in the lamination direction of the laminate from one end of the body part and opposite to the laminate. The fixing material fixes the electrode plate and the laminate. The piezoelectric element has a first gap surrounded by the fixing material, projecting part, and laminate.SELECTED DRAWING: Figure 4

Description

【Technical field】 【0001】 The disclosed embodiments relate to piezoelectric elements. 【Background art】 【0002】 A piezoelectric element is known that includes a laminate in which a plurality of piezoelectric bodies and internal electrodes are laminated, a conductor layer located on a side surface of the laminate and connected to the internal electrodes, and an electrode plate joined to the conductor layer via a conductive bonding material (see, for example, Patent Document 1). 【Prior art documents】 【Patent documents】 【0003】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 2008-130842 【Summary of the invention】 【Problems to be solved by the invention】 【0004】 However, in the prior art, due to the stress generated in the electrode plate accompanying the expansion and contraction operation of the laminate concentrating at the end of the joint portion between the electrode plate and the conductor layer, there is a problem that the electrode plate peels off from the conductor layer. 【0005】 One aspect of the embodiment has been made in view of the above, and an object thereof is to provide a piezoelectric element capable of reducing the possibility of peeling of the electrode plate. 【Means for solving the problems】 【0006】 A piezoelectric element according to one embodiment comprises a laminate, a conductor layer, an electrode plate, and a fixing material. The laminate consists of multiple piezoelectric elements and internal electrodes stacked on top of each other. The conductor layer is connected to the internal electrodes and is positioned along the stacking direction of the laminate. The electrode plate has a main body joined to the conductor layer via a conductive bonding material, and a projection that protrudes from one end of the main body in the stacking direction of the laminate and faces the laminate. The fixing material fixes the electrode plate and the laminate. The piezoelectric element has a first void between the fixing material, the projection, and the laminate. [Effects of the Invention] 【0007】 According to one embodiment, the possibility of electrode plate peeling can be reduced. [Brief explanation of the drawing] 【0008】 [Figure 1] Figure 1 is a perspective view showing the overall configuration of the piezoelectric element according to this embodiment. [Figure 2] Figure 2 is a cross-sectional view taken along the line II-II shown in Figure 1. [Figure 3] Figure 3 is an enlarged plan view showing an example of the configuration of the electrode plate and its surrounding area according to the embodiment. [Figure 4] Figure 4 is a cross-sectional view taken along the line IV-IV shown in Figure 3. [Figure 5] Figure 5 is a cross-sectional view taken along the VV line shown in Figure 3. [Figure 6] Figure 6 is an enlarged plan view showing an example of how the protruding portion is fixed by the fixing material according to the embodiment. [Figure 7] Figure 7 is an enlarged plan view showing another example of how the protruding portion is fixed by the fixing material according to the embodiment. [Figure 8] Figure 8 is an enlarged plan view showing another example of how the protruding portion is fixed by the fixing material according to the embodiment. [Figure 9] Figure 9 is an enlarged plan view showing another example of how the protruding portion is fixed by the fixing material according to the embodiment. [Figure 10] Figure 10 is a cross-sectional view showing an example of the configuration of the electrode plate and its surrounding area according to another embodiment 1. [Figure 11] FIG. 11 is a cross-sectional view showing an example of an electrode plate and its peripheral configuration according to another Embodiment 1. [Figure 12] FIG. 12 is an enlarged plan view showing an example of an electrode plate and its peripheral configuration according to another Embodiment 2. [Figure 13] FIG. 13 is a cross-sectional view taken along the arrow XIII-XIII line shown in FIG. 12. [Figure 14] FIG. 14 is a cross-sectional view showing an example of an electrode plate and its peripheral configuration according to another Embodiment 3. [Figure 15] FIG. 15 is an enlarged plan view showing an example of an electrode plate and its peripheral configuration according to another Embodiment 4. [Figure 16] FIG. 16 is a cross-sectional view taken along the arrow XVI-XVI line shown in FIG. 15. [Figure 17] FIG. 17 is a cross-sectional view showing an example of an electrode plate and its peripheral configuration according to another Embodiment 5. [Figure 18] FIG. 18 is an enlarged plan view showing an example of an electrode plate and its peripheral configuration according to another Embodiment 6. [Figure 19] FIG. 19 is a cross-sectional view showing an example of an electrode plate and its peripheral configuration according to another Embodiment 7. 【Mode for Carrying Out the Invention】 【0009】 Hereinafter, embodiments of the piezoelectric element disclosed in the present application will be described with reference to the accompanying drawings. Note that the present disclosure is not limited by the embodiments shown below. Also, the drawings are schematic, and it is necessary to note that the dimensional relationships between elements, the ratios of the elements, etc. may be different from reality. Furthermore, there may be parts where the dimensional relationships and ratios are different between the drawings. 【0010】 <Overall Configuration of Piezoelectric Element> First, the overall configuration of the piezoelectric element 1 according to the embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view showing the overall configuration of the piezoelectric element 1 according to the embodiment. FIG. 2 is a cross-sectional view taken along the arrow of line II-II shown in FIG. 1. 【0011】 As shown in FIGS. 1 and 2, the piezoelectric element 1 according to the embodiment includes a laminate 10, a pair of conductor layers 20, a pair of electrode plates 40, and a fixing material 50. The pair of conductor layers 20 includes a conductor layer 20A and a conductor layer 20B, and the pair of electrode plates 40 includes an electrode plate 40A and an electrode plate 40B. 【0012】 As shown in FIG. 1, the laminate 10 has a columnar shape. The laminate 10 is, for example, a square columnar (cuboid) shape with a length of 0.5 (mm) to 10 (mm), a width of 0.5 (mm) to 10 (mm), and a height of 1 (mm) to 100 (mm). Note that the shape of the laminate 10 is not limited to a square columnar shape, and may be a hexagonal columnar shape, an octagonal columnar shape, or a cylindrical shape. 【0013】 As shown in FIG. 2, the laminate 10 has a piezoelectric body 11, an internal electrode 12, and a planned fracture layer 13. The laminate 10 is formed by laminating the piezoelectric body 11, the internal electrode 12, and the planned fracture layer 13 in a predetermined order along the lamination direction D. In the present disclosure, the lamination direction D of the laminate 10 coincides with the longitudinal direction of the laminate 10. 【0014】 The piezoelectric body 11 is made of a piezoelectric material having piezoelectric characteristics, and is, for example, made of piezoelectric ceramics. The material of such piezoelectric ceramics is, for example, a perovskite-type oxide made of lead zirconate titanate (PbZrO3 - PbTiO3), lithium niobate (LiNbO3), or lithium tantalate (LiTaO3). 【0015】 The average particle size of such piezoelectric ceramics is, for example, 1.6 (μm) to 2.8 (μm). Also, the thickness of the piezoelectric body 11 is, for example, 3 (μm) to 250 (μm). 【0016】 The internal electrode 12 is made of a conductive material and includes a plurality of first electrodes 12a and a plurality of second electrodes 12b. The first electrodes 12a are electrically connected to a conductor layer 20A located on one side surface 10a of the laminate 10. A predetermined positive voltage is applied to the first electrodes 12a through the conductor layer 20A. 【0017】 The second electrode 12b is electrically connected to a conductor layer 20B located on the side 10b of the laminate 10 opposite to the side 10a. A predetermined negative voltage (or ground voltage) is applied to the second electrode 12b via the conductor layer 20B. 【0018】 As shown in Figure 2, inside the laminate 10, the first electrode 12a, the second electrode 12b, and the piezoelectric element 11 are stacked such that the piezoelectric element 11 is positioned between the first electrode 12a and the second electrode 12b. This allows the laminate 10 to apply a driving voltage to the piezoelectric element 11 using the first electrode 12a and the second electrode 12b. 【0019】 Furthermore, the laminate 10 according to the embodiment is composed of an active portion formed by alternately stacking a plurality of piezoelectric bodies 11 and internal electrodes 12, and an inactive portion arranged at both ends of the stacking direction D in the active portion, which has piezoelectric bodies 11 but does not have internal electrodes 12. 【0020】 The active portion is the part that expands or contracts (hereinafter also referred to as "expansion or contraction") in the lamination direction D when a driving voltage is applied to the laminate 10 from the outside. On the other hand, the inactive portion is the part that does not expand or contract even when a driving voltage is applied to the laminate 10 from the outside. 【0021】 Furthermore, in this disclosure, the lower end of Figures 1 and 2 is defined as the base end 10e of the laminate 10, and the upper end of Figures 1 and 2 is defined as the tip end 10f of the laminate 10. 【0022】 In the piezoelectric element 1 according to this embodiment, the base end portion 10e of the laminate 10 is fixed, and the tip portion 10f of the laminate 10 is displaced along the lamination direction D. 【0023】 The material of the internal electrode 12 is a metal mainly composed of, for example, silver, silver-palladium, silver-platinum, or copper. The internal electrode 12 can be formed, for example, by co-firing with the piezoelectric body 11. The thickness of the internal electrode 12 is, for example, 0.1 (μm) to 5 (μm). 【0024】 The pre-fractured layer 13 is a layer that relieves the stress generated by the driving of the laminate 10. Examples of the pre-fractured layer 13 include a porous metal layer that does not function as an internal electrode 12, or a metal layer that has pre-cracked. In the laminate 10 according to this embodiment, the pre-fractured layer 13 may be omitted. 【0025】 As described above, the pair of conductive layers 20 include a conductive layer 20A located on side surface 10a of the laminate 10 and a conductive layer 20B located on side surface 10b of the laminate 10. The conductive layers 20 are arranged to extend across the entire active portion of the laminate 10. The conductive layers 20 are located along the lamination direction D of the laminate 10. 【0026】 The material of the conductive layer 20 is, for example, a metal mainly composed of silver or copper. For example, a metallized layer made of a sintered body of the above-mentioned metal and glass can be used for the conductive layer 20. The thickness of the conductive layer 20 is, for example, 5 (μm) to 500 (μm). 【0027】 The pair of electrode plates 40 includes electrode plate 40A and electrode plate 40B, and are electrically connected to a pair of conductor layers 20, respectively. Specifically, electrode plate 40A is electrically connected to conductor layer 20A, and electrode plate 40B is electrically connected to conductor layer 20B. 【0028】 As shown in Figure 1, the electrode plate 40 is a plate-shaped member extending in the stacking direction D of the laminate 10, and has a main body portion 41 and a protruding portion 42. The main body portion 41 is the part that extends in the stacking direction D of the laminate 10 and is electrically connected to the conductor layer 20. 【0029】 The main body 41 is joined to the conductor layer 20 via a conductive bonding material 30. As such bonding material 30, for example, epoxy resin or polyimide resin containing highly conductive metal powder such as Ag powder or Cu powder is used. 【0030】 The protruding portion 42 is a part that protrudes from one end 41a of the main body portion 41 in the stacking direction D of the laminate 10. As shown in Figure 2, the protruding portion 42 faces the laminate 10. 【0031】 The electrode plate 40 is made of a metal such as copper, iron, stainless steel, or phosphor bronze. The width of the electrode plate 40 is, for example, 0.5 mm to 10 mm, and the thickness of the electrode plate 40 is, for example, 0.01 mm to 1.0 mm. The surface of the electrode plate 40 may be coated with a plating film such as tin plating or silver plating to improve electrical and thermal conductivity. 【0032】 The fixing material 50 fixes the electrode plate 40 and the laminate 10. For example, the fixing material 50 fixes at least the protruding portion 42 of the electrode plate 40 to the laminate 10. 【0033】 The fixing material 50 is made of, for example, an insulating material that is heat-resistant and flexible. Examples of insulating materials that make up the fixing material 50 include epoxy resin, glass, ceramics, or composite materials of epoxy resin and ceramics. When ceramics or a composite material of epoxy resin and ceramics is used as the insulating material for the fixing material 50, the material of the ceramics may be the same as the material of the piezoelectric ceramic that makes up the piezoelectric body 11. 【0034】 <Configuration of electrode plates and fixing materials> Next, the detailed configuration of the electrode plate 40 and fixing material 50 according to the embodiment will be described with reference to Figures 3 to 9. Figure 3 is an enlarged plan view showing an example of the configuration of the electrode plate 40 and its surroundings according to the embodiment. Figure 4 is a cross-sectional view taken along the line IV-IV shown in Figure 3. Figure 5 is a cross-sectional view taken along the line VV shown in Figure 3. 【0035】 As described above, the electrode plate 40 is a plate-shaped member extending in the stacking direction D of the laminate 10, and has a main body portion 41 joined to the conductor layer 20 via a conductive bonding material 30, and a protruding portion 42 that protrudes from one end 41a of the main body portion 41 in the stacking direction D and faces the laminate 10. 【0036】 The main body portion 41 has a first portion 411 that is in contact with the bonding material 30, and a second portion 412 located on both sides of the first portion 411 in the width direction (i.e., the direction intersecting the lamination direction D), which faces the conductor layer 20 without being in contact with the bonding material 30. 【0037】 As shown in Figure 3, in this embodiment, the main body 41 of the electrode plate 40 has a plurality of slits S. These slits S are cut out, for example, so as to extend along the width direction of the main body 41 (i.e., the direction intersecting the stacking direction D). 【0038】 Multiple slits S are alternately cut out from both sides of the main body 41 (i.e., the sides of the pair of second parts 412) and are arranged at approximately equal intervals along the stacking direction D. Furthermore, all of the multiple slits S have approximately equal lengths. The length of a slit S refers to its length in the direction of its cutout (i.e., the width direction of the main body 41). 【0039】 Furthermore, the lengths of multiple slits S are set so that their tips overlap when viewed in the stacking direction D. Here, overlapping means that, when viewed in the stacking direction D, adjacent slits S have regions that face each other. 【0040】 In this embodiment, by arranging multiple slits S in the main body portion 41 of the electrode plate 40, the main body portion 41 can be made to expand and contract in the stacking direction D in accordance with the expansion and contraction of the laminate 10 in the stacking direction D. Therefore, according to this embodiment, the possibility of the electrode plate 40 peeling off from the laminate 10 or the conductor layer 20 can be reduced. 【0041】 The protruding portion 42 of the electrode plate 40 faces the laminate 10 across the first void G1. The fixing material 50 fixes at least the protruding portion 42 of the electrode plate 40 to the laminate 10. 【0042】 Here, as shown in Figures 4 and 5, in this embodiment, the fixing material 50 fixes at least the protruding portion 42 of the electrode plate 40 to the laminate 10 while maintaining the first air gap G1 between the protruding portion 42 and the laminate 10. In other words, in this embodiment, the piezoelectric element 1 has a first air gap G1 between the fixing material 50, the protruding portion 42, and the laminate 10. 【0043】 As a result, the protrusion 42 on the first gap G1 expands and contracts along the lamination direction D in accordance with the expansion and contraction of the laminate 10, and the stress generated at the end of the joint between the electrode plate 40 and the conductor layer 20 (near one end 41a) can be released to the interface between the fixing material 50 and the laminate 10. Therefore, according to this embodiment, the stress generated at the end of the joint between the electrode plate 40 and the conductor layer 20 (near one end 41a) due to the expansion and contraction of the laminate 10 in the lamination direction D can be dispersed, and the possibility of the electrode plate 40 peeling off from the conductor layer 20 can be reduced. 【0044】 Figure 6 is an enlarged plan view showing an example of how the protrusion 42 is fixed by the fixing material 50 according to the embodiment. As shown in Figure 6, the fixing material 50 according to the embodiment may fix the entire circumference of the periphery of the protrusion 42 (i.e., the periphery on the tip side 42a and the periphery on the side side 42b) to the laminate 10. This allows stress generated at the end of the joint between the electrode plate 40 and the conductor layer 20 (near one end 41a) to efficiently dissipate at the interface between the fixing material 50 and the laminate 10 as the laminate 10 expands and contracts in the lamination direction D. 【0045】 Therefore, according to the embodiment, the stress generated at the edges of the joint between the electrode plate 40 and the conductor layer 20 due to expansion and contraction of the laminate 10 in the lamination direction D can be distributed more efficiently, and the possibility of the electrode plate 40 peeling off from the conductor layer 20 can be further reduced. 【0046】 In another embodiment, the fixing material 50 may be fixed to the laminate 10 around the entire circumference of the periphery of the protrusion 42, while leaving a predetermined area surrounded by the periphery of the protrusion 42 on the protrusion 42. This allows the predetermined area left on the protrusion 42 to be used as an area for joining lead terminals that supply power to the electrode plate 40. 【0047】 In this embodiment, the fixing material 50 does not necessarily have to fix the entire circumference of the periphery of the protruding portion 42 to the laminated body 10. In short, it is sufficient that at least a portion of the periphery of the protruding portion 42 is fixed to the laminated body 10 by the fixing material 50. Figures 7 to 9 are enlarged plan views showing another example of how the protruding portion 42 is fixed by the fixing material 50 according to this embodiment. 【0048】 As shown in Figure 7, the fixing material 50 according to this embodiment may be fixed to the laminate 10 only at the peripheral edge on the tip 42a side of the protruding portion 42. 【0049】 Furthermore, as shown in Figure 8, the fixing material 50 according to this embodiment may be fixed to the laminate 10 only on the peripheral edge of the side portion 42b of the protruding portion 42. 【0050】 Furthermore, as shown in Figure 9, the fixing material 50 according to this embodiment may have a portion that fixes the peripheral edge of the tip 42a side of the protrusion 42 to the laminate 10 and a portion that fixes the peripheral edge of the side 42b side of the protrusion 42 to the laminate 10, with these portions separated from each other. 【0051】 Thus, in this embodiment, the fixing material 50 may have at least a portion of the periphery of the protruding portion 42 fixed to the laminate 10. In this case, the protruding portion 42 may have an exposed region inside the periphery of the protruding portion 42. Here, the exposed region is the region on the protruding portion 42 where the fixing material 50 is not located. By providing an exposed region on the protruding portion 42, the exposed region can be used as a region for joining lead terminals that supply power to the electrode plate 40. 【0052】 <Another Embodiment 1> Next, various other embodiments will be described with reference to Figures 10 to 19. In the various other embodiments shown below, the same reference numerals are used for parts that are the same as in the embodiments, and redundant explanations may be omitted. 【0053】 Figures 10 and 11 are cross-sectional views showing an example of the configuration of the electrode plate 40 and its surroundings according to another embodiment 1. Figure 10 corresponds to the cross-sectional view taken along the line IV-IV shown in Figure 3, and Figure 11 corresponds to the cross-sectional view taken along the line VV shown in Figure 3. 【0054】 In the other embodiment 1 shown in Figures 10 and 11, the configuration of the fixing member 50 differs from that of the embodiment described above. Specifically, in the other embodiment 1, the fixing member 50 has an overhang 51. The overhang 51 is positioned to protrude inward from the periphery of the projection 42 and is in contact with the laminate 10. Here, "inward from the periphery of the projection 42" can also be rephrased as the direction approaching the central axis of the projection 42 (electrode plate 40). The overhang 51 is an example of a first overhang. 【0055】 In another embodiment 1, by providing an overhang 51 on the fixing material 50, the stress generated at the end of the joint between the electrode plate 40 and the conductor layer 20 (near one end 41a) can be efficiently relieved at the interface between the fixing material 50 and the laminate 10 as the laminate 10 expands and contracts in the lamination direction D. Therefore, according to the other embodiment 1, the stress generated at the end of the joint between the electrode plate 40 and the conductor layer 20 due to the expansion and contraction of the laminate 10 in the lamination direction D can be distributed more efficiently, and the possibility of the electrode plate 40 peeling off from the conductor layer 20 can be further reduced. 【0056】 <Another Embodiment 2> Figure 12 is an enlarged plan view showing an example of the configuration of the electrode plate 40 and its surroundings according to another embodiment 2. Figure 13 is a cross-sectional view taken along the line XIII-XIII shown in Figure 12. 【0057】 As shown in Figures 12 and 13, in another embodiment 2, the fixing member 50 fixes the main body portion 41 and the conductor layer 20 to the laminate 10 at one end of the conductor layer 20 located on the side of one end 41a of the main body portion 41. 【0058】 As a result, in the other embodiment 2, the stress generated at the end of the joint between the electrode plate 40 and the conductor layer 20 (near one end 41a) in response to the expansion and contraction of the laminate 10 in the lamination direction D can be efficiently relieved by the interface between the fixing material 50 and the laminate 10. Therefore, according to the other embodiment 2, the stress generated at the end of the joint between the electrode plate 40 and the conductor layer 20 due to the expansion and contraction of the laminate 10 in the lamination direction D can be distributed more efficiently, and the possibility of the electrode plate 40 peeling off from the conductor layer 20 can be further reduced. 【0059】 <Other Embodiment 3> Figure 14 is a cross-sectional view showing an example of the configuration of the electrode plate 40 and its surroundings according to another embodiment 3. Figure 14 corresponds to the cross-sectional view taken along the line XIII-XIII shown in Figure 12. 【0060】 As described above, the main body 41 has a first portion 411 that is in contact with the bonding material 30, and a second portion 412 located on both sides of the first portion 411 in the width direction (i.e., the direction intersecting the lamination direction D), which faces the conductor layer 20 without being in contact with the bonding material 30. The second portion 412 faces the conductor layer 20 across the second void G2. 【0061】 In the other embodiment 3 shown in Figure 14, the configuration of the fixing member 50 differs from that of the other embodiment 2 described above. Specifically, in the other embodiment 3, the fixing member 50 has a protruding portion 52. The protruding portion 52 is positioned to protrude inward from the side of the second portion 412 and is in contact with the conductor layer 20. Here, "inward from the side of the second portion 412" can also be rephrased as the direction approaching the central axis of the protruding portion 42 (electrode plate 40). The protruding portion 52 is an example of a second protruding portion. 【0062】 In another embodiment 3, by providing an overhang 52 on the fixing material 50, the adhesion between the fixing material 50 and the conductor layer 20 is improved compared to the case where the overhang 52 is not provided, and therefore the adhesion between the fixing material 50 and the laminate 10 is improved. Accordingly, according to the other embodiment 1, the possibility of the conductor layer 20 peeling off from the laminate 10 can be reduced. 【0063】 <Other Embodiments 4> Figure 15 is an enlarged plan view showing an example of the configuration of the electrode plate 40 and its surroundings according to another embodiment 4. Figure 16 is a cross-sectional view taken along the line XVI-XVI shown in Figure 15. 【0064】 As shown in Figure 15, in another embodiment 4, the covering layer 60 that covers the main body 41 and the conductor layer 20 is located on the side surface 10a of the laminate 10 (an example of a surface located along the lamination direction D of the laminate 10). Although not shown in Figure 15, the covering layer 60 that covers the main body 41 and the conductor layer 20 is also located on the side surface 10b of the laminate 10 (an example of a surface located along the lamination direction D of the laminate 10). By arranging such covering layers 60 on the side surfaces 10a and 10b, the main body 41 and the conductor layer 20 can be protected. 【0065】 The coating layer 60 is composed of, for example, an insulator. Examples of insulators that make up this coating layer 60 include fluororesins, silicone resins, epoxy resins, and nylon resins. 【0066】 In another embodiment 4, as shown in Figures 15 and 16, the end of the covering layer 60 covers the end of the fixing material 50 located on one end 41a side of the main body portion 41. 【0067】 As a result, in the other embodiment 4, the stress generated at the end of the joint between the electrode plate 40 and the conductor layer 20 (near one end 41a) in accordance with the expansion and contraction of the laminate 10 in the lamination direction D can be released to the interface between the fixing material 50 and the laminate 10 and the interface between the coating layer 60 and the laminate 10. Therefore, according to the other embodiment 4, the stress generated at the end of the joint between the electrode plate 40 and the conductor layer 20 due to the expansion and contraction of the laminate 10 in the lamination direction D can be distributed more efficiently, and the possibility of the electrode plate 40 peeling off from the conductor layer 20 can be further reduced. 【0068】 <Another Embodiment 5> Figure 17 is a cross-sectional view showing an example of the configuration of the electrode plate 40 and its surroundings according to another embodiment 5. Figure 17 corresponds to the cross-sectional view taken along the line XVI-XVI shown in Figure 15. 【0069】 In the other embodiment 5 shown in Figure 17, the configuration of the coating layer 60 differs from that of the other embodiment 4 described above. Specifically, in the other embodiment 5, the coating layer 60 is located around the entire circumference of the side surface of the laminate 10, including side surface 10a. That is, the coating layer 60 is located not only on side surfaces 10a and 10b of the laminate 10, but also on side surfaces 10c (see Figure 1) and 10d (see Figure 1), which are located between side surfaces 10a and 10b. 【0070】 As a result, in the other embodiment 5, the stress generated in the coating layer 60 in response to the expansion and contraction of the laminate 10 in the lamination direction D can be distributed to the entire circumference of the side surface of the laminate 10. 【0071】 <Other Embodiments 6> Figure 18 is an enlarged plan view showing an example of the configuration of the electrode plate 40 and its surroundings according to another embodiment 6. As described above, the laminate 10 is composed of an active portion 10A formed by alternately stacking multiple piezoelectric bodies 11 and internal electrodes 12, and an inactive portion 10B arranged at both ends of the stacking direction D in the active portion, which has piezoelectric bodies 11 but does not have internal electrodes 12. 【0072】 As shown in Figure 18, in another embodiment 6, the electrode plate 40 has a wider portion 43 that is wider than the other portions, at least at the protruding portion 42, at a position that overlaps with the inert portion 10B in a plan view. In another embodiment 6, the fixing material 50 may fix the wider portion 43 to the laminate 10. 【0073】 As a result, in the other embodiment 6, the stress generated at the end of the joint between the electrode plate 40 and the conductor layer 20 (near one end 41a) in accordance with the expansion and contraction of the laminate 10 in the lamination direction D can be efficiently relieved by the interface between the fixing material 50 and the laminate 10. Therefore, according to the other embodiment 6, the stress generated at the end of the joint between the electrode plate 40 and the conductor layer 20 due to the expansion and contraction of the laminate 10 in the lamination direction D can be distributed more efficiently, and the possibility of the electrode plate 40 peeling off from the conductor layer 20 can be further reduced. 【0074】 <Other Embodiments 7> Figure 19 is a cross-sectional view showing an example of the configuration of the electrode plate 40 and its surroundings according to another embodiment 7. Figure 19 corresponds to the cross-sectional view taken along the line XIX-XIX shown in Figure 15. 【0075】 In another embodiment 7 shown in Figure 19, the protrusion 42 is inclined such that the distance between the protrusion 42 and the laminate 10 narrows towards the tip 42a of the protrusion 42. In other words, the protrusion 42 is sloped downwards towards the tip 42a of the protrusion 42. 【0076】 As a result, in the other embodiment 7, a portion of the uncured fixing material 50 is adequately filled into the gap between the tip 42a of the protrusion 42 and the laminate 10, thereby improving the adhesion strength between the tip 42a of the protrusion 42 and the laminate 10 after the fixing material 50 has cured. 【0077】 <Manufacturing method for piezoelectric elements> Next, a method for manufacturing an example of the piezoelectric element 1 of this embodiment will be described. First, a ceramic green sheet, which will become the piezoelectric layer (piezoelectric 11), is prepared. Specifically, a ceramic slurry is prepared by mixing calcined piezoelectric ceramic powder, a binder having an organic polymer such as acrylic or butyral, and a plasticizer. Then, a ceramic green sheet is prepared from this ceramic slurry by using a tape molding method such as the well-known doctor blade method or calender roll method. As for the piezoelectric ceramic, any material having piezoelectric properties is acceptable, and for example, a perovskite-type oxide having PbZrO3-PbTiO3 can be used. As for the plasticizer, dibutyl phthalate (DBP) or dioctyl phthalate (DOP) can be used. 【0078】 Next, a conductive paste to serve as the internal electrode 12 is prepared. Specifically, the conductive paste is prepared by adding and mixing a binder and a plasticizer to a silver-palladium alloy metal powder. This conductive paste is printed onto the ceramic green sheet using a screen printing method. Then, multiple ceramic green sheets with the conductive paste printed on them are stacked, and multiple ceramic green sheets without the conductive paste printed on them are stacked on both ends in the stacking direction to obtain a laminated molded body. After debinding this laminated molded body at a predetermined temperature, the laminated body 10 is obtained by firing it at 900 to 1200°C. 【0079】 Subsequently, a conductive paste made of silver and glass is applied to the side surface of the laminate 10 and baked to form a conductive layer 20. The conductive paste is made by adding and mixing a binder, plasticizer, glass powder, etc., to a metal powder mainly consisting of silver, and the conductive layer 20 can be formed by printing it on the side surface of the laminate 10 using a screen printing method or the like and baking it at 600 to 800°C. 【0080】 Next, the bonding material 30 is applied to the upper surface of the conductor layer 20, the electrode plate 40 is bonded to it, dried at a temperature of 100-140°C, and then cured at a temperature of 180-220°C to bond the electrode plate 40. After that, the fixing material 50 is placed on top of the electrode plate 40. 【0081】 The method for fixing the electrode plate 40 is described below. The fixing material 50 is applied using a mask by screen printing. At this time, the fixing material 50 is a resin having a viscosity sufficient to form a first void G1 between the protruding portion 42 of the electrode plate 40 and the laminate 10. This prevents the fixing material 50 from flowing directly beneath the electrode plate 40, thereby fixing the electrode plate 40 and forming the first void G1. 【0082】 Alternatively, by providing a dam-like projection at a desired location on the laminate 10 that overlaps with the electrode plate 40 in planar projection, screen printing using a resin with lower viscosity than described above becomes possible, and the first void G1 can be formed. While thermosetting resins are commonly used here, photocurable resins can also be used. Voids may form within the fixing material 50 that secures the electrode plate 40, but these voids are surrounded by the fixing material 50 and are different from the first void G1 surrounded by the fixing material 50, the protrusion 42, and the laminate 10. The piezoelectric element 1 of this example is fabricated using the above method. 【0083】 As described above, the piezoelectric element according to the embodiment (for example, piezoelectric element 1) comprises a laminate (for example, laminate 10), a conductor layer (for example, conductor layer 20), an electrode plate (for example, electrode plate 40), and a fixing material (for example, fixing material 50). The laminate has multiple piezoelectric elements (for example, piezoelectric element 11) and internal electrodes (for example, internal electrodes 12) stacked on top of each other. The conductor layer is connected to the internal electrodes and is located along the stacking direction of the laminate (for example, stacking direction D). The electrode plate has a main body (for example, main body 41) joined to the conductor layer via a conductive bonding material (for example, bonding material 30), and a projection (for example, projection 42) that protrudes from one end of the main body (for example, one end 41a) in the stacking direction of the laminate and faces the laminate. The fixing material fixes the electrode plate and the laminate. The piezoelectric element has a first void (for example, first void G1) between the fixing material, the projection, and the laminate. This reduces the possibility of electrode plate delamination. 【0084】 Further effects and modifications can be readily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the specific details and representative embodiments expressed and described above. Accordingly, various modifications are possible without departing from the spirit or scope of the overall concept of the invention as defined by the appended claims and their equivalents. [Explanation of symbols] 【0085】 1. Piezoelectric element 10 Laminate 10A active part 10B Inactive part 10a,10b,10c,10d Side 10e Proximal end 10f tip 11 Piezoelectric material 12 Internal electrode 12a 1st electrode 12b 2nd electrode 13. Planned Fault Line 20, 20A, 20B Conductor Layers 30 Bonding material 40,40A,40B electrode plate 41 Main body 41a one end 42 Protrusion 42a Tip 42b Side 43 Wide section 50 Fixing material 51,52 Overhang 60 Covering layer 411 Part 1 412 Part 2 D Stacking direction G1 1st void G2 second void S-slit

Claims

[Claim 1] A laminate in which multiple piezoelectric materials and internal electrodes are stacked, A conductive layer connected to the internal electrode and positioned along the stacking direction of the laminate, An electrode plate having a main body portion bonded to the conductor layer via a conductive bonding material, and a protruding portion that extends from one end of the main body portion in the lamination direction of the laminate and faces the laminate, A fixing material for fixing the electrode plate and the laminate Equipped with, A first void is provided between the fixing material, the protruding portion, and the laminate. The fixing material is fixed to the laminate at least to a portion of the periphery of the protruding portion. The aforementioned protrusion is a piezoelectric element having an exposed region located inward from the periphery. [Claim 2] A laminate comprising a plurality of piezoelectric elements and internal electrodes stacked together, A conductive layer connected to the internal electrode and positioned along the stacking direction of the laminate, An electrode plate having a main body portion bonded to the conductor layer via a conductive bonding material, and a protruding portion that extends from one end of the main body portion in the lamination direction of the laminate and faces the laminate, A fixing material for fixing the electrode plate and the laminate Equipped with, A first void is provided between the fixing material, the protruding portion, and the laminate. The fixing material is a piezoelectric element having a first protruding portion that extends inward from the periphery of the protruding portion and is in contact with the laminate. [Claim 3] A laminate comprising a plurality of piezoelectric elements and internal electrodes stacked together, A conductive layer connected to the internal electrode and positioned along the stacking direction of the laminate, An electrode plate having a main body portion bonded to the conductor layer via a conductive bonding material, and a protruding portion that extends from one end of the main body portion in the lamination direction of the laminate and faces the laminate, A fixing material for fixing the electrode plate and the laminate Equipped with, A first void is provided between the fixing material, the protruding portion, and the laminate. The fixing material fixes the main body and the conductor layer to the laminate at one end of the conductor layer located on one end side of the main body, The main body portion has a first portion that contacts the joining material, and a second portion located on both sides in the width direction of the first portion and facing the conductor layer without contacting the joining material. The fixing material has a piezoelectric element that is positioned to protrude inward from the side of the second portion and has a second protruding portion that is in contact with the conductive layer. [Claim 4] A laminate comprising a plurality of piezoelectric elements and internal electrodes stacked together, A conductive layer connected to the internal electrode and positioned along the stacking direction of the laminate, An electrode plate having a main body portion bonded to the conductor layer via a conductive bonding material, and a protruding portion that extends from one end of the main body portion in the lamination direction of the laminate and faces the laminate, A fixing material for fixing the electrode plate and the laminate Equipped with, A first void is provided between the fixing material, the protruding portion, and the laminate. The aforementioned protrusion is a piezoelectric element, wherein the protrusion slopes downward toward the tip of the protrusion. [Claim 5] A covering layer covering the main body and the conductor layer is located on the surface of the laminate that is located along the stacking direction of the laminate. The piezoelectric element according to any one of claims 1 to 4, wherein the end of the covering layer covers the end of the fixing material located on one end side of the main body. [Claim 6] The piezoelectric element according to claim 5, wherein the coating layer is located around the entire circumference of a surface located along the lamination direction of the laminate. [Claim 7] The laminated body is An active section in which the piezoelectric material and the internal electrodes are alternately stacked, Located on both ends of the stacking direction of the active portion, the inert portion has the piezoelectric material but does not have the internal electrode. It has, The electrode plate has a wider portion than the other portions at least at the position where it overlaps with the inert portion in a plan view, in the protruding portion. The piezoelectric element according to any one of claims 1 to 4, wherein the fixing material fixes the wide portion to the laminate. [Claim 8] A laminate in which multiple piezoelectric materials and internal electrodes are stacked, A conductive layer connected to the internal electrode and positioned along the stacking direction of the laminate, An electrode plate having a main body portion bonded to the conductor layer via a conductive bonding material, and a protruding portion that extends from one end of the main body portion in the lamination direction of the laminate and faces the laminate, A fixing material for fixing the electrode plate and the laminate Equipped with, The aforementioned protruding portion is the part that is joined to the lead terminal, A piezoelectric element having a first void between the fixing material, the protruding portion, the laminate, the joining material, and the conductor layer.

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