piezoelectric actuator

Abstract

A piezoelectric actuator (1) includes: a piezoelectric element (10) of a columnar shape; and an electrode plate (20) located at a side surface (10a, 10c) of the piezoelectric element (10) and electrically connected to an internal electrode layer (12) of the piezoelectric element (10). The electrode plate (20) includes: a main body portion (21) extending in a stacking direction (D) of the piezoelectric element (10); and a lead portion (22) extending in a direction intersecting the stacking direction (D) and connected to a lead terminal (30). The lead portion (22) has a recessed portion (R) recessed in a width direction of the lead portion (22) in at least one side portion (22c).

Description

Technical Field

[0001] The disclosed implementation relates to piezoelectric actuators. Background Technology

[0002] Previously, a piezoelectric actuator was known, comprising: columnar stacked piezoelectric elements; and a metal housing that houses the piezoelectric elements such that two ends of the piezoelectric elements abut against an inner wall (see, for example, Patent Document 1).

[0003] In this piezoelectric actuator, for example, an electrode plate is attached to the side of a cylindrical piezoelectric element, and a driving voltage is applied to the piezoelectric element via the electrode plate. The electrode plate includes: a main body portion attached to the side of the piezoelectric element; and a lead portion electrically connecting the main body portion and lead terminals.

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: JP 2013-211419 Summary of the Invention

[0007] One aspect of the implementation aims to provide a piezoelectric actuator capable of suppressing the detachment of the electrode plate from the piezoelectric element.

[0008] Methods for solving problems

[0009] One embodiment of the piezoelectric actuator includes: a columnar stacked piezoelectric element; and an electrode plate located on the side of the piezoelectric element and electrically connected to an internal electrode layer of the piezoelectric element. The electrode plate has: a main body portion extending in the stacking direction of the piezoelectric element; and a lead portion extending in a direction intersecting the stacking direction and electrically connected to a lead terminal. The lead portion has a recess on at least one side in the width direction of the lead portion. Attached Figure Description

[0010] Figure 1 This is a perspective view showing the overall structure of the piezoelectric actuator involved in the embodiment.

[0011] Figure 2 yes Figure 1 The cross-sectional view is shown in the direction of the arrow on line AA.

[0012] Figure 3 This is a perspective view showing the internal structure of the piezoelectric actuator involved in the embodiment.

[0013] Figure 4 This is an enlarged top view showing the structure of the electrode plate involved in the embodiment.

[0014] Figure 5This is an enlarged top view showing the shape of the recess located in the lead portion of the embodiment.

[0015] Figure 6 This is an enlarged top view showing an example of the recess in the lead portion and its surrounding structure according to the embodiment.

[0016] Figure 7 This is an enlarged top view showing another example of the recess in the lead portion and its surrounding structure according to the embodiment.

[0017] Figure 8 This is an enlarged top view showing another example of the recess in the lead portion and its surrounding structure according to the embodiment.

[0018] Figure 9 This is an enlarged top view showing another example of the recess in the lead portion and its surrounding structure according to the embodiment.

[0019] Figure 10 This is an enlarged perspective view showing another example of the recess in the lead portion and the structure around it according to the embodiment.

[0020] Figure 11 This is an enlarged perspective view showing the structure of the electrode plate involved in the embodiment.

[0021] Figure 12 This is an enlarged top view showing the structure of the electrode plate involved in Modified Example 1 of the embodiment.

[0022] Figure 13 This is an enlarged top view showing the structure of the electrode plate involved in Modified Example 2 of the embodiment.

[0023] Figure 14 This is an enlarged top view showing the structure of the electrode plate involved in the modified example 3 of the embodiment. Detailed Implementation

[0024] Hereinafter, embodiments of the piezoelectric actuator disclosed in this application will be described with reference to the accompanying drawings. However, this disclosure is not limited to the embodiments shown below. Furthermore, the drawings are schematic, and it should be noted that the dimensional relationships and ratios of the elements may sometimes differ from reality. Moreover, the drawings may sometimes contain portions with different dimensional relationships and ratios.

[0025] Previously, a piezoelectric actuator was known, comprising: columnar stacked piezoelectric elements; and a metal housing that houses the piezoelectric elements such that two ends of the piezoelectric elements abut against an inner wall.

[0026] In this piezoelectric actuator, for example, an electrode plate is attached to the side of a cylindrical piezoelectric element, and a driving voltage is applied to the piezoelectric element via the electrode plate. The electrode plate includes: a main body portion attached to the side of the piezoelectric element; and a lead portion electrically connecting the main body portion and lead terminals.

[0027] However, in the prior art, the lead portion cannot deform sufficiently relative to the telescoping action of the piezoelectric element, resulting in the problem that the main body portion may peel off from the piezoelectric element.

[0028] Therefore, we look forward to the realization of a technology that can overcome the above-mentioned problems and prevent the electrode plate from peeling off from the piezoelectric element.

[0029] <Overall Structure of a Piezoelectric Actuator>

[0030] Initially, reference Figures 1-3 The overall structure of the piezoelectric actuator 1 involved in the implementation method will be explained. Figure 1 This is a perspective view showing the overall structure of the piezoelectric actuator 1 according to the embodiment. Figure 2 yes Figure 1 The cross-sectional view is shown in the direction of the arrow along line AA. Furthermore, Figure 3 This is a perspective view showing the internal structure of the piezoelectric actuator 1 according to the embodiment.

[0031] like Figures 1-3 As shown, the piezoelectric actuator 1 according to the embodiment includes a piezoelectric element 10, a pair of electrode plates 20, a pair of lead terminals 30, and a housing 40. In addition, the pair of electrode plates 20 includes electrode plate 20A and electrode plate 20B, and the pair of lead terminals 30 includes lead terminal 30A and lead terminal 30B.

[0032] like Figure 3 As shown, the piezoelectric element 10 has a columnar shape. The piezoelectric element 10 is, for example, a tetragonal prism (cubic parallelepiped) with dimensions of 0.5 mm to 10 mm in length, 0.5 mm to 10 mm in width, and 1 mm to 100 mm in height. However, the shape of the piezoelectric element 10 is not limited to a tetragonal prism; it can also be a hexagonal prism, an octagonal prism, or a cylinder, etc.

[0033] like Figure 2 As shown, the piezoelectric element 10 has a piezoelectric body layer 11, an internal electrode layer 12, a predetermined fracture layer 13, and a pair of side electrodes 14. Furthermore, the pair of side electrodes 14 includes side electrode 14A and side electrode 14B.

[0034] The piezoelectric element 10 is constructed by stacking a piezoelectric layer 11, an internal electrode layer 12, and a predetermined fracture layer 13 in a given order along the stacking direction D. In this disclosure, the stacking direction D of the piezoelectric element 10 is aligned with the direction of its long side.

[0035] The piezoelectric layer 11 contains a piezoelectric material with piezoelectric properties, such as a piezoelectric ceramic. The piezoelectric ceramic may be, for example, a perovskite oxide containing lead zirconate titanate (PbZrO3-PbTiO3), lithium niobate (LiNbO3), or lithium tantalate (LiTaO3).

[0036] The average particle size of the piezoelectric ceramics involved is, for example, 1.6 (μm) to 2.8 (μm). In addition, the thickness of the piezoelectric layer 11 is, for example, 3 (μm) to 250 (μm).

[0037] The internal electrode layer 12 comprises a conductive material and includes a plurality of first electrode layers 12a and a plurality of second electrode layers 12b. The first electrode layers 12a are electrically connected to side electrodes 14A. The side electrodes 14A are disposed on one side 10a of the piezoelectric element 10. A given positive voltage is applied to the first electrode layers 12a via the side electrodes 14A.

[0038] The second electrode layer 12b is electrically connected to the side electrode 14B. The side electrode 14B is disposed on the side 10b of the piezoelectric element 10 opposite to the side 10a. A given negative voltage (or ground voltage) is applied to the second electrode layer 12b via the side electrode 14B.

[0039] like Figure 2 As shown, a first electrode layer 12a, a second electrode layer 12b, and a piezoelectric layer 11 are stacked inside the piezoelectric element 10, such that the piezoelectric layer 11 is disposed between the first electrode layer 12a and the second electrode layer 12b. Therefore, in the piezoelectric element 10, a driving voltage can be applied to the piezoelectric layer 11 through the first electrode layer 12a and the second electrode layer 12b.

[0040] Furthermore, the piezoelectric element 10 according to the embodiment includes: an active portion formed by alternately stacking multiple piezoelectric layers 11 and internal electrode layers 12; and an inactive portion disposed at both ends of the stacking direction D in the active portion and having piezoelectric layers 11.

[0041] The active portion is the part that stretches or contracts (hereinafter also referred to as stretching) in the lamination direction D by applying a driving voltage to the piezoelectric element 10 from the outside. On the other hand, the inactive portion is the part that does not stretch even when a driving voltage is applied to the piezoelectric element 10 from the outside.

[0042] Furthermore, in this disclosure, the end of the housing 40 on the base 41 side is designated as the base end 10e of the piezoelectric element 10, and the end of the housing 40 on the cover 43 side is designated as the front end 10f of the piezoelectric element 10.

[0043] Furthermore, in the piezoelectric actuator 1 according to the embodiment, the base end 10e (i.e., the base 41) of the piezoelectric element 10 is fixed, and the front end 10f (i.e., the cover 43) of the piezoelectric element 10 is displaced along the stacking direction D.

[0044] The material of the internal electrode layer 12 is, for example, a metal with silver, silver-palladium, silver-platinum, or copper as its main components. The internal electrode layer 12 can be formed, for example, by firing it simultaneously with the piezoelectric layer 11. The thickness of the internal electrode layer 12 is, for example, 0.1 (μm) to 5 (μm).

[0045] The predetermined fracture layer 13 is a layer used to mitigate the stress generated by the driving of the piezoelectric element 10. Examples of the predetermined fracture layer 13 include a porous metal layer that does not function as the internal electrode layer 12, or a metal layer with pre-existing cracks. Alternatively, the predetermined fracture layer 13 may be omitted in the piezoelectric element 10 according to the embodiment.

[0046] As described above, the pair of side electrodes 14 includes: a side electrode 14A located on side 10a of the piezoelectric element 10; and a side electrode 14B located on side 10b of the piezoelectric element 10. The side electrodes 14 are configured to cover the entire active portion of the piezoelectric element 10.

[0047] The side electrode 14 is made of a metal, for example, with silver or copper as the main component. The side electrode 14 can be made of a metallized layer of a sintered body comprising the aforementioned metal and glass. The thickness of the side electrode 14 is, for example, 5 μm to 500 μm.

[0048] Additionally, although not illustrated in this disclosure, it is also possible to use side 10c (see reference) located between side 10a and side 10b of the piezoelectric element 10. Figure 3 ) and side 10d (reference) Figure 3 A coating layer containing an insulator is configured. By configuring the coating layer in question on the sides 10c and 10d, surface discharge between the electrodes that occurs when a high voltage is applied during driving can be suppressed.

[0049] Ceramic materials can be cited as examples of insulators that serve as the coating. Among the ceramic materials mentioned, there are materials that can follow the expansion and contraction of the piezoelectric element 10 when the piezoelectric actuator 1 is driven, and can be deformed by stress to the point that the coating itself cannot peel off, thereby generating surface discharge.

[0050] Specifically, as a coating layer, examples include partially stabilized zirconium oxide and Ln. 1-X Si X AlO 3+0.5XCeramic materials, in which stress causes localized phase transformation and volume change, thus enabling deformation. Additionally, Ln represents any one of the following: Sn, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb, where x = 0.01 to 0.3.

[0051] Alternatively, as a coating layer, examples include piezoelectric materials such as barium titanate and lead zirconate titanate, which exhibit changes in the interionic distance within the crystal lattice to mitigate the resulting stress.

[0052] A pair of electrode plates 20 includes electrode plate 20A and electrode plate 20B, which electrically connect a pair of side electrodes 14 to a pair of lead terminals 30. Specifically, electrode plate 20A electrically connects side electrode 14A to lead terminal 30A, and electrode plate 20B electrically connects side electrode 14B to lead terminal 30B.

[0053] like Figure 3 As shown, the electrode plate 20 has a generally T-shaped form and includes a main body portion 21 and a lead portion 22. The main body portion 21 is located at the point where the piezoelectric element 10 extends in the stacking direction D and is electrically and mechanically connected to the side electrode 14 of the piezoelectric element 10.

[0054] The main body 21 has the same size as the side electrode 14 and is bonded to the side electrode 14 by a conductive bonding material. Examples of conductive bonding materials include epoxy resin or polyimide resin containing metal powders with high conductivity, such as Ag powder or Cu powder.

[0055] Furthermore, this disclosure shows an example of electrically connecting the electrode plate 20 and the inner electrode layer 12 via the side electrode 14, but the side electrode 14 can be omitted as long as the conduction between the electrode plate 20 and the inner electrode layer 12 is sufficient. In this case, the electrode plate 20 and the inner electrode layer 12 are directly connected.

[0056] On the other hand, by configuring the side electrode 14, the electrode plate 20 and the internal electrode layer 12 can be stably electrically connected. Therefore, according to the embodiment, the reliability of the piezoelectric actuator 1 can be improved.

[0057] The lead portion 22 is a portion that extends in a direction intersecting the lamination direction D, and is electrically and mechanically connected to the lead terminal 30. The lead portion 22 is wound from one side of the piezoelectric element 10 of the connecting body portion 21 to the adjacent side.

[0058] For example, such as Figure 3As shown, in the electrode plate 20A that is engaged with the side 10a of the piezoelectric element 10, the lead portion 22 is wound while bending from the side 10a to the adjacent side 10c.

[0059] also, Figure 3 Although not fully illustrated, in the electrode plate 20B that is engaged with the side 10b of the piezoelectric element 10, the lead portion 22 is wound from the side 10b to the adjacent side 10d, just like in the electrode plate 20A.

[0060] The electrode plate 20 is made of metals such as copper, iron, stainless steel, or phosphor bronze. The width of the electrode plate 20 is, for example, 0.5 mm to 10 mm, and the thickness is, for example, 0.01 mm to 1.0 mm. A tin plating or silver plating film M (see reference) is applied to the surface of the electrode plate 20 to improve electrical and thermal conductivity. Figure 10 ).

[0061] like Figure 3 As shown, a pair of lead terminals 30, including lead terminal 30A and lead terminal 30B, are respectively arranged facing each other to the sides 10c and 10d of the piezoelectric element 10. Specifically, lead terminal 30A is arranged facing each other to the side 10c of the piezoelectric element 10, and lead terminal 30B is arranged facing each other to the side 10d of the piezoelectric element 10.

[0062] Furthermore, a hole 22a1 is provided at the front end 22a of the electrode plate 20, which is wound from one side of the piezoelectric element 10 to the adjacent side. Figure 11 (See reference). Furthermore, a lead terminal 30 is inserted into the hole 22a1 at the forward end 22a and bonded by a conductive bonding material 31. Thus, the electrode plate 20 and the lead terminal 30 are electrically and mechanically connected.

[0063] In this embodiment, multiple bends 22e (see reference) are provided in the lead portion 22 of the electrode plate 20. Figure 11 This reduces vibration transmitted via the electrode plate 20. Furthermore, in this embodiment, by extending the lead portion 22 from one side of the piezoelectric element 10 to the adjacent side for an extended period, vibration transmitted via the electrode plate 20 can be further reduced.

[0064] like Figure 2 As shown, the housing 40 internally houses the piezoelectric element 10 and the electrode plate 20. The housing 40 has a base 41, a cylindrical body 42, and a cover 43. The base 41 is columnar (e.g., cylindrical), with one side ( Figure 2 The upper end has a widened portion 41a.

[0065] Furthermore, the end face 41b of the extended portion 41a is in contact with the base end face 10e of the piezoelectric element 10. Alternatively, the end face 41b of the substrate 41 and the base end face 10e of the piezoelectric element 10 can also be joined by a bonding material not shown.

[0066] Furthermore, a pair of through holes (not shown) are provided in the substrate 41 to pass between the end face 41b and the end face 41c on the opposite side of the end face 41b, and a pair of lead terminals 30 are inserted into the pair of through holes respectively.

[0067] Furthermore, the lead terminal 30 is fixed relative to the base 41 by filling the gap between the through hole in the base 41 and the lead terminal 30 with an insulating material (such as soft glass). The lead terminal 30 then penetrates the base 41 from the inside of the housing 40 and protrudes outward from the end face 41c of the base 41 (see reference). Figure 1 ).

[0068] The cylinder 42 has a cylindrical shape (e.g., a circular shape). Furthermore, the cylinder 42 has a bellows (belly-shaped) shape, and the axial direction of the cylinder is aligned with the stacking direction D of the piezoelectric element 10. Thus, the cylinder 42 can extend and retract axially in accordance with the extension and retraction of the piezoelectric element 10 in the stacking direction D.

[0069] Furthermore, the cylinder 42 has a given spring constant to allow it to follow the expansion and contraction of the piezoelectric element 10. The spring constant of the cylinder 42 can be adjusted by the thickness of the cylinder 42, the shape of the grooves in the cylinder 42, and the number of grooves in the cylinder 42. The thickness of the cylinder 42 is, for example, 0.1 mm to 0.5 mm, and the diameter of the cylinder 42 is, for example, 5 mm to 50 mm.

[0070] Furthermore, the end of the cylinder 42 on the base 41 side has a convex edge 42a that extends radially outward in a trumpet shape. The convex edge 42a of the cylinder 42 and the widened portion 41a of the base 41 are welded together, for example, while a compressive load is applied to the piezoelectric element 10.

[0071] For example, after preparing a seamless tube of a given shape, the seamless tube is processed into a bellows (belly) shape through rolling, hydrostatic pressing, etc., thereby forming the cylinder 42.

[0072] The cap 43 is a cylindrical shape (e.g., a cylindrical shape) with one end blocked. Furthermore, the outer diameter of the cap 43 is slightly smaller than the inner diameter of the end 42b of the cylindrical body 42 on the side opposite to the protruding edge 42a. The cap 43 is inserted into the end 42b, and the inner wall of the end 42b and the side wall of the cap 43 are fixed together, for example, by welding.

[0073] Furthermore, the inner bottom surface 43a of the cover 43 is in contact with the front end portion 10f of the piezoelectric element 10. Alternatively, the inner bottom surface 43a of the cover 43 and the front end portion 10f of the piezoelectric element 10 can also be joined by a bonding material not shown.

[0074] <Structure of Electrode Plates>

[0075] Next, refer to Figures 4 to 11 The detailed structure of the electrode plate 20 involved in the embodiment will be explained below. Figure 4 This is an enlarged top view showing the structure of the electrode plate 20 according to the embodiment. As described above, the electrode plate 20 has a generally T-shaped shape and has a main body portion 21 extending in the stacking direction D of the piezoelectric element 10 and a lead portion 22 extending in a direction intersecting the stacking direction D.

[0076] And, as Figure 4 As shown, in this embodiment, the main body 21 of the electrode plate 20 has a plurality of slits S. The slits S involved are, for example, cut out to extend along the width direction of the main body 21 (i.e., the direction perpendicular to the stacking direction D).

[0077] Multiple slits S are alternately cut from two sides of the main body 21 and arranged side by side 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 notch direction (i.e., the width direction of the main body 21).

[0078] Furthermore, the lengths of the multiple slits S are set such that their front ends overlap when viewed in the stacking direction D. Here, overlap means that, when viewed in the stacking direction D, adjacent slits S have mutually opposing regions.

[0079] In this embodiment, by providing a plurality of slits S in the main body 21 of the electrode plate 20, the main body 21 can be extended and retracted in the stacking direction D in accordance with the extension and retraction of the piezoelectric element 10. Therefore, according to this embodiment, it is possible to suppress the electrode plate 20 from peeling off from the piezoelectric element 10.

[0080] The lead portion 22 of the electrode plate 20 has a pair of sides 22b and 22c. Side 22b is a piezoelectric element 10 (reference). Figure 3 ) front end 10f (reference) Figure 3 The side portion 22c is the base end portion 10e of the piezoelectric element 10 (reference). Figure 3 The side of the side.

[0081] Here, in the embodiment, the lead portion 22 is on at least one side ( Figure 4The middle side portion 22c) has a recess R that is recessed in the width direction of the lead portion 22 involved. In addition, the width direction of the lead portion 22 is the direction perpendicular to the direction in which the lead portion 22 extends.

[0082] Therefore, the twisting that originates from the recess R as the piezoelectric element 10 expands and contracts in the stacking direction D makes the lead portion 22 easier to deform. Thus, according to the embodiment, since the stress generated at the base end 22d of the lead portion 22 due to the expansion and contraction of the piezoelectric element 10 can be mitigated, the peeling of the electrode plate 20 from the piezoelectric element 10 can be suppressed.

[0083] Furthermore, in one embodiment, multiple recesses R may be provided on one side of the lead portion 22. This allows the lead portion 22 to be further deformed by following the expansion and contraction of the piezoelectric element 10 in the stacking direction D.

[0084] Therefore, according to the embodiment, since the stress generated at the base end 22d of the lead portion 22 due to the expansion and contraction of the piezoelectric element 10 can be further mitigated, the peeling of the electrode plate 20 from the piezoelectric element 10 can be further suppressed.

[0085] In addition, Figure 4 The example shown illustrates two recesses R on one side. The number of recesses R on one side is not limited to two; one recess R can be configured, or more than three recesses R can be configured. Furthermore, the multiple recesses R on one side can all be approximately equal in size, or they can be of different sizes.

[0086] Furthermore, in one embodiment, a recess R may be provided on at least one of the pair of sides 22b and 22c in the lead portion 22, on the side 22c on the base end portion 10e of the piezoelectric element 10. This makes the side 22c on the end portion 10e, which is subjected to greater tensile stress when the piezoelectric element 10 is elongated, easier to deform.

[0087] Therefore, according to the embodiment, since the stress generated at the base end 22d of the lead portion 22 when the piezoelectric element 10 is elongated can be mitigated, the electrode plate 20 can be prevented from peeling off from the piezoelectric element 10.

[0088] Furthermore, in the embodiment, the recess R may be disposed at the front end portion 22a of the lead portion 22 (see reference). Figure 3 The recess R is positioned closer to the base end portion 22d of the lead portion 22. In this way, by arranging the recess R at a position close to the base end portion 22d adjacent to the main body portion 21 where peeling occurs, the lead portion 22 can be easily deformed by the stretching and contraction of the piezoelectric element 10.

[0089] Therefore, according to the embodiment, since the stress generated at the base end 22d of the lead portion 22 due to the expansion and contraction of the piezoelectric element 10 can be further mitigated, the peeling of the electrode plate 20 from the piezoelectric element 10 can be further suppressed.

[0090] Figure 5 This is an enlarged top view showing the shape of the recess R located in the lead portion 22 according to the embodiment. For example... Figure 5 As shown, the recess R in the embodiment can have a generally V-shaped form. This allows the lead portion 22 to be further easily deformed by following the expansion and contraction of the piezoelectric element 10 in the stacking direction D.

[0091] Therefore, according to the embodiment, since the stress generated at the base end 22d of the lead portion 22 due to the expansion and contraction of the piezoelectric element 10 can be further mitigated, the peeling of the electrode plate 20 from the piezoelectric element 10 can be further suppressed.

[0092] Furthermore, in the implementation method, such as Figure 5 As shown, the bottom Ra of the recess R can be R-shaped. Therefore, when the lead portion 22 deforms due to the expansion and contraction of the piezoelectric element 10, stress is concentrated at the bottom Ra of the recess R, which can prevent the lead portion 22 from breaking off from the bottom Ra or cracking.

[0093] Therefore, according to the implementation method, the reliability of the piezoelectric actuator 1 can be improved.

[0094] Furthermore, assuming that the lead portion 22 is configured with a slit S extending longer in the notch direction instead of a shallow recess R, the volume resistivity of the lead portion 22 increases, which may sometimes cause localized heat generation in the lead portion 22. That is, if the lead portion 22 is configured with a slit S extending longer in the notch direction, the reliability of the piezoelectric actuator 1 may be reduced.

[0095] On the other hand, in the embodiment, since the shallow recess R is arranged in the lead portion 22, local heating in the lead portion 22 can be suppressed, thus maintaining the reliability of the piezoelectric actuator 1 well.

[0096] Furthermore, the recess R of this disclosure can, for example, have a depth-to-width ratio of less than 2. As a result, localized heating in the lead portion 22 can be suppressed, thus maintaining the reliability of the piezoelectric actuator 1 effectively.

[0097] Furthermore, the depth of the recess R can be less than one-tenth of the width of the lead portion 22. As a result, the piezoelectric actuator 1 can be stably driven for a long time without interfering with the power supply from the lead terminal 30.

[0098] Furthermore, in the embodiments, the width of the recess R can be, for example, in the range of 0.01 to 0.1 (mm), and the depth of the recess R can be, for example, in the range of 0.05 to 1.0 (mm).

[0099] Figure 6 This is an enlarged top view showing an example of the recess R in the lead portion 22 according to the embodiment and its surrounding structure. For example... Figure 6 As shown, the side portion 22c where the recess R is located in the lead portion 22 includes: a first region 22c1 sandwiched by a pair of recesses R and a second region 22c2 other than the first region 22c1.

[0100] And, it can be like Figure 6 As shown, in the lead portion 22 of the embodiment, the first region 22c1 and the second region 22c2 are approximately flush with each other near a pair of recesses R in the side portion 22c.

[0101] Furthermore, the lead portion 22 in the embodiment is not limited to the case where the first region 22c1 and the second region 22c2 are approximately flush. Figures 7-9 This is an enlarged top view showing another example of the recess R in the lead portion 22 according to the embodiment and the structure around it.

[0102] like Figure 7 As shown, in the lead portion 22 of the embodiment, the first region 22c1 may protrude outward relative to the second region 22c2 near a pair of recesses R in the side portion 22c.

[0103] In addition, such as Figure 8 As shown, in the lead portion 22 of the embodiment, the first region 22c1 may be recessed inward relative to the second region 22c2 near a pair of recesses R in the side portion 22c.

[0104] Furthermore, in the lead portion 22 according to the embodiment, near the pair of recesses R in the side portion 22c, the lead portion is recessed to the bottom Ra of the recess R by the first region 22c1, which can be as follows: Figure 9 As shown, the recesses R are roughly trapezoidal in shape and are integrated into a pair of recesses R.

[0105] Figure 10 This is an enlarged perspective view showing another example of the recess R in the lead portion 22 according to the embodiment and its surrounding structure. As described above, a coating film M for improving electrical conductivity and thermal conductivity is disposed on the surface of the electrode plate 20 according to the embodiment, including the surface of the lead portion 22. Furthermore, in Figure 10 In the middle, dotted shadows are added to the areas where the coating M is configured.

[0106] Here, in the implementation method, such as Figure 10 As shown, the side portion 22c of the lead portion 22 may have a portion without a coating M in the first region 22c1 between adjacent recesses R. For example, it may also be as follows Figure 10 As shown, the entire first region 22c1 is a region without the coating M.

[0107] Thus, by providing a portion of the surface of the first region 22c1 where the high-hardness coating M is not disposed, the lead portion 22 can be further deformed following the stretching and contraction of the piezoelectric element 10 in the stacking direction D. Therefore, according to the embodiment, the peeling of the electrode plate 20 from the piezoelectric element 10 can be further suppressed.

[0108] Figure 11 This is an enlarged perspective view showing the structure of the electrode plate 20 according to the embodiment. For example... Figure 11 As shown, in the lead portion 22, a plurality of bent portions 22e are arranged from the base end portion 22d to the front end portion 22a.

[0109] The bend 22e1 closest to the base end 22d among the multiple bends 22e involved is along the piezoelectric element 10 (reference). Figure 3 The curved section is configured at the corners of adjacent sides in the middle.

[0110] Furthermore, the curved portion 22e2, which is located immediately following the curved portion 22e1 with reference to the base end portion 22d, is located around the hole portion 22a1 at the front end portion 22a and is a curved portion used to make the front end portion 22a involved in the case approximately horizontal.

[0111] Furthermore, the curved portion 22e3, which is located immediately following the curved portion 22e2 with reference to the base end portion 22d, is positioned around the hole portion 22a1 at the front end portion 22a, and is arranged to face the curved portion 22e2 across the hole portion 22a1.

[0112] And, as Figure 11 As shown, in this embodiment, the recess R located on the side portion 22c of the lead portion 22 can be disposed between the base end portion 22d and the bending portion 22e1. Thus, by disposing the recess R near the base end portion 22d adjacent to the main body portion 21 where peeling occurs, the stress generated in the lead, which changes directionally via the bending portion 22e1 following the stretching and contraction of the piezoelectric element 10 in the stacking direction D, can generate a torsion originating from the recess R. This alleviates the stress towards the base end portion 22d and further suppresses the electrode plate 20 from peeling off from the piezoelectric element 10.

[0113] Therefore, according to the embodiment, since the stress generated at the base end 22d of the lead portion 22 due to the expansion and contraction of the piezoelectric element 10 can be further mitigated, the peeling of the electrode plate 20 from the piezoelectric element 10 can be further suppressed.

[0114] Furthermore, in the embodiment, the curved portions 22e2 and 22e3 surrounding the hole 22a1 may have through holes 22f. This allows the lead terminal 30 to be inserted into the hole 22a1 (see reference). Figure 3 ) and through bonding material 31 (reference) Figure 3 When the connection is made, the stress around the lead terminal 30 involved can be relieved.

[0115] Therefore, according to the embodiment, the reliability of the piezoelectric actuator 1 can be improved. Furthermore, in the embodiment, the bonding material 31 may or may not enter the through-hole 22f involved.

[0116] <Variation Example 1>

[0117] Next, refer to Figures 12-14 Various variations of the implementation will be described below. Furthermore, in the various variations shown below, repeated descriptions are sometimes omitted by using the same symbols for the same parts as in the implementation.

[0118] Figure 12 This is an enlarged top view showing the structure of the electrode plate 20 according to Modified Example 1 of the embodiment. Figure 12 In the modified example 1 shown, the arrangement of the recess R differs from the embodiment described above. Specifically, in modified example 1, the recess R is not the piezoelectric element 10 disposed in the lead portion 22 (see reference). Figure 3 The base end 1oe (reference) Figure 3 Instead of the side portion 22c on the side of the piezoelectric element 10, it is disposed at the front end portion 1of (refer to) Figure 3 ) Side part 22b.

[0119] Therefore, the lead portion 22 can easily deform as it follows the expansion and contraction of the piezoelectric element 10 in the stacking direction D. Thus, according to the modified example 1, the electrode plate 20 can be prevented from peeling off from the piezoelectric element 10.

[0120] <Variation Example 2>

[0121] Figure 13 This is an enlarged top view showing the structure of the electrode plate 20 according to Modified Example 2 of the embodiment. Figure 13 As shown, in modified example 2, the lead portion 22 has recesses R on its two sides 22b and 22c.

[0122] Therefore, in Modification 2, it is easy to follow the stretching and contraction of the piezoelectric element 10 in the stacking direction D, and to generate a torsion starting from the recesses R on both sides, making the lead portion 22 even easier to deform. Therefore, according to Modification 2, it is possible to further suppress the electrode plate 20 from peeling off from the piezoelectric element 10.

[0123] Furthermore, in variation example 2, such as Figure 13 As shown, the recesses R located on the two sides 22b and 22c of the lead portion 22 can be arranged facing each other. In this way, by arranging the recesses R so that they face each other on the two sides 22b and 22c, it is easy to generate a torsion starting from the area where the opposing recesses R are connected to each other, and even a weak force can easily deform the lead portion 22 near the recesses R.

[0124] Therefore, according to Modification 2, the peeling of the electrode plate 20 from the piezoelectric element 10 can be further suppressed. Furthermore, the recesses R on the two sides 22b and 22c that face each other can be approximately equal in size, or they can be of different sizes.

[0125] <Variation Example 3>

[0126] Figure 14 This is an enlarged top view showing the structure of the electrode plate 20 according to Modified Example 3 of the embodiment. Figure 14 As shown, in Modification 3, similar to Modification 2 described above, the lead portion 22 has recesses R on its two sides 22b and 22c.

[0127] On the other hand, in variation 3, with respect to the piezoelectric element 10 (reference) Figure 3 ) front end 10f (reference) Figure 3 Compared to the recess R on the side portion 22b, the base end portion 10e of the piezoelectric element 10 (reference) Figure 3 The recess R of the side portion 22c on the base end portion 10e is deeper. As a result, the side portion 22c on the base end portion 10e, which is subjected to greater tensile stress when the piezoelectric element 10 is elongated, is further easier to deform.

[0128] Therefore, according to Modification 3, since the stress generated at the base end 22d of the lead portion 22 when the piezoelectric element 10 elongates can be further mitigated, the peeling of the electrode plate 20 from the piezoelectric element 10 can be further suppressed.

[0129] The piezoelectric actuator 1 according to the embodiment includes: a columnar stacked piezoelectric element 10; and an electrode plate 20 located on the sides 10a, 10c of the piezoelectric element 10 and electrically connected to the internal electrode layer 12 of the piezoelectric element 10. The electrode plate 20 has: a main body portion 21 extending in the stacking direction D of the piezoelectric element 10; and a lead portion 22 extending in a direction intersecting the stacking direction D and electrically connected to a lead terminal 30. The lead portion 22 has a recess R on at least one side portion 22c (22b) that is recessed in the width direction of the lead portion 22. As a result, it is possible to prevent the electrode plate 20 from peeling off from the piezoelectric element 10.

[0130] Furthermore, in the piezoelectric actuator 1 according to the embodiment, the recess R is positioned closer to the base end 22d of the lead portion 22 than the front end 22a of the lead portion 22. This further suppresses the electrode plate 20 from peeling off from the piezoelectric element 10.

[0131] Furthermore, in the piezoelectric actuator 1 according to the embodiment, the lead portion 22 has recesses R on its two sides 22b and 22c. This further suppresses the electrode plate 20 from peeling off from the piezoelectric element 10.

[0132] Furthermore, in the piezoelectric actuator 1 according to the embodiment, the recesses R on the two sides 22b and 22c of the lead portion 22 are positioned facing each other. This further suppresses the electrode plate 20 from peeling off from the piezoelectric element 10.

[0133] Furthermore, in the piezoelectric actuator 1 according to the embodiment, the recess R of the side portion 22b located on the base end portion 10e side of the piezoelectric element 10 is deeper than the recess R of the side portion 22c located on the front end portion 10f side of the piezoelectric element 10. This further suppresses the electrode plate 20 from peeling off from the piezoelectric element 10.

[0134] Furthermore, in the piezoelectric actuator 1 according to the embodiment, the recess R has a generally V-shaped form. This further suppresses the electrode plate 20 from peeling off from the piezoelectric element 10.

[0135] Furthermore, in the piezoelectric actuator 1 according to the embodiment, the bottom Ra of the recess R is R-shaped. This improves the reliability of the piezoelectric actuator 1.

[0136] Furthermore, in the piezoelectric actuator 1 according to the embodiment, the lead portion 22 has a plurality of recesses R on one side portion 22c (22b), and one side portion 22c (22b) has a portion without a coating M in the region between adjacent recesses R (first region 22c1). This further suppresses the electrode plate 20 from peeling off from the piezoelectric element 10.

[0137] Furthermore, in the piezoelectric actuator 1 according to the embodiment, the lead portion 22 has multiple bends 22e and a hole 22a1 through which the lead terminal 30 is inserted, and the bends 22e2 and 22e3 around the hole 22a1 have through holes 22f. As a result, the reliability of the piezoelectric actuator 1 can be improved.

[0138] The above describes the implementation of this disclosure, but this disclosure is not limited to the above implementation. Various changes can be made as long as they do not depart from its spirit.

[0139] Further effects and other modifications can be readily derived by those skilled in the art. Therefore, the broader aspects of this disclosure are not limited to the specific, detailed, and representative embodiments characterized and described above. Thus, various modifications can be made without departing from the spirit or scope of the invention as defined by the appended claims and their equivalents.

[0140] Symbol Explanation

[0141] 1 Piezoelectric actuator

[0142] 10 piezoelectric elements

[0143] 10a~10d side views

[0144] 10e base end

[0145] 10f front end

[0146] 11 piezoelectric layers

[0147] 12 Internal Electrode Layers

[0148] 14, 14A, 14B Side Electrodes

[0149] 20, 20A, 20B electrode plates

[0150] 21 Main body

[0151] 22 lead section

[0152] 22a front end

[0153] 22a1 Hole

[0154] 22b, 22c side

[0155] 22c1 Region 1

[0156] 22c2 Region 2

[0157] 22d base end

[0158] 22e, 22e1~22e3 curved sections

[0159] 22f through hole

[0160] 30, 30A, 30B lead terminals

[0161] 40 housing

[0162] D-stack direction

[0163] S-shaped slit.

Claims

1. A piezoelectric actuator, comprising: Piezoelectric elements, stacked in columnar layers; and The electrode plate is located on the side of the piezoelectric element and is electrically connected to the internal electrode layer of the piezoelectric element. The electrode plate has the following characteristics: The main body extends in the stacking direction of the piezoelectric element; and The lead portion extends in a direction intersecting the stacking direction and is electrically connected to the lead terminal. The lead portion has a recess on at least one side that is recessed in the same direction as the stacking direction, i.e., in the width direction of the lead portion.

2. The piezoelectric actuator according to claim 1, wherein, The recess is positioned closer to the base end of the lead portion than the front end portion of the lead portion.

3. The piezoelectric actuator according to claim 1, wherein, The lead portion has the recesses on both sides.

4. The piezoelectric actuator according to claim 3, wherein, The recesses located on the two sides of the lead portion are arranged to face each other.

5. The piezoelectric actuator according to claim 3, wherein, The recess located on the base end side of the piezoelectric element is deeper than the recess located on the front end side of the piezoelectric element.

6. The piezoelectric actuator according to claim 1, wherein, The recess has a roughly V-shaped form.

7. A piezoelectric actuator, comprising: Piezoelectric elements, stacked in columnar layers; and The electrode plate is located on the side of the piezoelectric element and is electrically connected to the internal electrode layer of the piezoelectric element. The electrode plate has the following characteristics: The main body extends in the stacking direction of the piezoelectric element; and The lead portion extends in a direction intersecting the stacking direction and is electrically connected to the lead terminal. The lead portion has a recess on at least one side that is recessed in the width direction of the lead portion. The bottom of the recess is arc-shaped.

8. A piezoelectric actuator, comprising: Piezoelectric elements, stacked in columnar layers; and The electrode plate is located on the side of the piezoelectric element and is electrically connected to the internal electrode layer of the piezoelectric element. The electrode plate has the following characteristics: The main body extends in the stacking direction of the piezoelectric element; and The lead portion extends in a direction intersecting the stacking direction and is electrically connected to the lead terminal. The lead portion has a plurality of recesses on one side that are recessed in the width direction of the lead portion. One side portion has an uncoated area in the region between adjacent recesses.

9. The piezoelectric actuator according to any one of claims 1 to 8, wherein, The lead portion has multiple bends and holes through which the lead terminals are inserted. The curved portion surrounding the hole has a through hole.

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