piezoelectric element

Abstract

A piezoelectric element includes: a laminate in which an internal electrode and a piezoelectric layer are stacked; and a surface electrode that is located on a side surface of the laminate and is electrically connected to the internal electrode. A second electrode shown in FIG. 3B includes a first conductor having a strip portion extending in a length direction and a lead-out portion having one end connected to the strip portion and the other end exposed on the side surface of the laminate and connected to the surface electrode. The piezoelectric element includes a second conductor between a portion of the side surface of the laminate on the opposite side from the portion where the other end of the lead-out portion is exposed and the lead-out portion.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a piezoelectric element. BACKGROUND

[0002] One example of the related art is described in Patent Literature 1.

[0003] PRIOR ART LITERATURE

[0004] PATENT LITERATURE

[0005] Patent Literature 1: JP Patent No. 4249472 SUMMARY

[0006] The piezoelectric element of the present disclosure includes:

[0007] a laminated body, an internal electrode, and a piezoelectric layer; and

[0008] a surface electrode, which is located on a side surface of the laminated body and is electrically connected to the internal electrode,

[0009] the internal electrode includes:

[0010] a first electrode that applies a voltage to the piezoelectric layer to bend the laminated body in a first direction orthogonal to a length direction of the laminated body; and

[0011] a second electrode that applies a voltage to the piezoelectric layer to bend the laminated body in a second direction orthogonal to the length direction and the first direction,

[0012] at least one of the first electrode and the second electrode includes a first conductor having a strip portion extending along the length direction and a lead-out portion having one end connected to the strip portion and the other end exposed on the side surface of the laminated body and connected to the surface electrode,

[0013] the piezoelectric element includes a second conductor between a portion of the side surface opposite to the portion where the other end of the lead-out portion is exposed and the lead-out portion. BRIEF DESCRIPTION OF DRAWINGS

[0014] The object, features, and advantages of the present disclosure will become more apparent from the following detailed description and accompanying drawings.

[0015] Figure 1A is a plan view showing the appearance of the piezoelectric element.

[0016] Figure 1B is a side view showing the appearance of the piezoelectric element.

[0017] Figure 2A is a cross-sectional view of the piezoelectric element taken along the line A-A of Figure 1A .

[0018] Figure 2B is a sectional view at section line B-B of Figure 1A

[0019] Figure 2C is a sectional view at section line C-C of Figure 1A

[0020] Figure 3A is a diagram showing a pattern shape of an internal electrode.

[0021] Figure 3B is a diagram showing a pattern shape of an internal electrode.

[0022] Figure 3C is a diagram showing a pattern shape of an internal electrode.

[0023] Figure 3D is a diagram showing a pattern shape of an internal electrode.

[0024] Figure 3E is a diagram showing a pattern shape of an internal electrode.

[0025] Figure 3F is a diagram showing a pattern shape of an internal electrode.

[0026] Figure 4 is a diagram showing another shape of a second conductor. DETAILED DESCRIPTION

[0027] As a structure underlying the piezoelectric element of the present disclosure, a piezoelectric actuator is used, which is made of a laminated piezoelectric body layer and internal electrodes and performs bending displacement by applying a voltage to the internal electrodes. The piezoelectric actuator can achieve a minute displacement with high precision.

[0028] The piezoelectric actuator described in Patent Literature 1 has a tip end that is elongated along the Z axis and can move in the XY plane.

[0029] In order to enable the tip end of the piezoelectric actuator to move in the XY plane, a plurality of patterns of internal electrodes are provided so as to be exposed at the side surface of the laminated body respectively and connected to the surface electrode. Each internal electrode has a lead-out portion for exposing the end portion thereof at a given position of the side surface. The internal electrode shown in FIG. 16 of Patent Literature 1 reduces the electrode width so as not to cause the piezoelectric body layer to expand and contract through the lead-out portion. Thus, in the laminated body, a non-uniformity occurs due to the difference in thickness between the region where the lead-out portion of the internal electrode is provided and the region where it is not provided, and the precision of the bending displacement decreases.

[0030] Figure 1A is a plan view showing an external appearance of a piezoelectric element, Figure 1B is a side view showing an external appearance of a piezoelectric element.​​Figure 2A is a sectional view at cut line A-A of Figure 1A Figure 2B is a sectional view at cut line B-B of Figure 1A Figure 2C is a sectional view at cut line C-C of Figure 1A The piezoelectric element 100 according to the present embodiment is a piezoelectric actuator that bends and displaces the laminated piezoelectric layers 4 by applying a voltage to the internal electrodes 3 via the surface electrodes 2. As shown in the sectional views of FIGS. 8A to 8C, the piezoelectric element 100 according to the present embodiment is, for example, a rectangular parallelepiped or a quadrangular prism, and is capable of moving the tip of the one end side in the length direction or the axis direction by bending and displacing. The surface electrodes 2 are provided on the two side surfaces of the other end side opposite to the movable tip. The surface electrodes 2 include the surface electrodes 2A provided on the two side surfaces of the other end side and the surface electrodes 2B provided on the two side surfaces of the central side of the surface electrodes 2A. Hereinafter, the length direction or the axis direction is referred to as the Z-axis direction, the direction orthogonal to the Z-axis direction and connecting the two side surfaces on which the surface electrodes 2 are provided is referred to as the X-axis direction, and the laminating direction of the internal electrodes 3 and the piezoelectric layers 4 is referred to as the Y-axis direction. Figure 1A Figure 1B As shown in the sectional views of FIGS. 8A to 8C, the piezoelectric element 100 according to the present embodiment is, for example, a rectangular parallelepiped or a quadrangular prism, and is capable of moving the tip of the one end side in the length direction or the axis direction by bending and displacing. The surface electrodes 2 are provided on the two side surfaces of the other end side opposite to the movable tip. The surface electrodes 2 include the surface electrodes 2A provided on the two side surfaces of the other end side and the surface electrodes 2B provided on the two side surfaces of the central side of the surface electrodes 2A. Hereinafter, the length direction or the axis direction is referred to as the Z-axis direction, the direction orthogonal to the Z-axis direction and connecting the two side surfaces on which the surface electrodes 2 are provided is referred to as the X-axis direction, and the laminating direction of the internal electrodes 3 and the piezoelectric layers 4 is referred to as the Y-axis direction.

[0031] As shown in the sectional views of FIGS. 8A to 8C, the piezoelectric element 100 according to the present embodiment is, for example, a rectangular parallelepiped or a quadrangular prism, and is capable of moving the tip of the one end side in the length direction or the axis direction by bending and displacing. The surface electrodes 2 are provided on the two side surfaces of the other end side opposite to the movable tip. The surface electrodes 2 include the surface electrodes 2A provided on the two side surfaces of the other end side and the surface electrodes 2B provided on the two side surfaces of the central side of the surface electrodes 2A. Hereinafter, the length direction or the axis direction is referred to as the Z-axis direction, the direction orthogonal to the Z-axis direction and connecting the two side surfaces on which the surface electrodes 2 are provided is referred to as the X-axis direction, and the laminating direction of the internal electrodes 3 and the piezoelectric layers 4 is referred to as the Y-axis direction. Figure 2A

[0032] ​​​​Details will be described later, the internal electrode 3 includes: a first electrode 31 that applies a voltage to the piezoelectric layer 4 to bend the laminate 1 in a first direction (X-axis direction) orthogonal to a length direction (Z-axis direction) of the laminate 1; and a second electrode 32 that applies a voltage to the piezoelectric layer 4 to bend the laminate 1 in a second direction (Y-axis direction) orthogonal to the length direction and the first direction. For example, the laminate 1 is roughly divided into three regions in the stacking direction (Y-axis direction). A central region 1M of the three regions is a region for bending displacement of the piezoelectric element 100 in the X-axis direction (left-right direction), and the first electrode 31 is located in the central region 1M. Further, upper and lower regions 1U and 1L of the three regions are regions for bending displacement of the piezoelectric element 100 in the Y-axis direction (up-down direction), and the second electrode 32 is located in these regions 1U and 1L.

[0033] For example, in the case of bending displacement in the X-axis direction, in the central region 1M, if a voltage is applied to the first electrode 31 so that the right side portion is elongated and the left side portion is contracted, it bends to the left, and if a voltage is applied to the first electrode 31 so that the right side portion is contracted and the left side portion is elongated, it bends to the right. Similarly, for example, in the case of bending displacement in the Y-axis direction, if a voltage is applied to the second electrode 32 so that the upper region 1U is elongated and the lower region 1L is contracted, it bends downward, and if a voltage is applied to the second electrode 32 so that the upper region 1U is contracted and the lower region 1L is elongated, it bends upward.

[0034] In Figures 3A-3F An example of the pattern shape of the internal electrode 3 of the present embodiment is shown. They show an example of the pattern shape of the second electrode 32 of the upper region 1U, the first electrode 31 of the central region 1M, and the second electrode 32 of the lower region 1L. Figure 3A and Figure 3B The pattern shown constitutes the second electrode 32 of the upper region 1U. Figure 3C and Figure 3D The pattern shown constitutes the first electrode 31 of the central region 1M. Figure 3E and Figure 3F The pattern shown constitutes the second electrode 32 of the lower region 1L. In this way, the internal electrode 3 of either region has two kinds of pattern shapes, and the two kinds of internal electrodes 3 are alternately arranged in the Y-axis direction with the piezoelectric layer 4 interposed therebetween. At the time of operation of the piezoelectric element 100, a voltage is applied from the outside via the surface electrode 2 to generate a potential difference between the two kinds of internal electrodes 3, and bending displacement in the X-axis direction and the Y-axis direction can be performed as described above. Further, by changing the voltage applied to the surface electrode 2, it is possible to control the displacement amount and the bending direction of the bending displacement, and the like.

[0035] The second electrode 32 in the upper region 1U is Figure 3A The second electrode 32a shown and Figure 3B The second electrode 32b shown is of two types. The second electrode 32 in the lower region 1L is... Figure 3E The second electrode 32c shown and Figure 3F The second electrode 32d shown is one of these two types. Figure 3B The second electrode 32b shown includes a first conductor 321, which has a strip-shaped portion 321a extending along the length direction; and an outlet portion 321b, one end of which is connected to the strip-shaped portion 321a, and the other end is exposed on the side of the laminate 1 and connected to the surface electrode 2A. Figure 3B The second electrode 32b shown and Figure 3F The second electrode 32d shown has the same pattern shape and also includes the first conductor 321. The lead-out portion 321b, for example, has a generally L-shaped form, with one end connected to the central portion of the strip portion 321a, extending linearly in the Z-axis direction, and the other end bent at a right angle towards the side of the laminate 1, thus protruding from the side of the laminate 1. The generally L-shaped lead-out portion 321b includes a wiring portion 321b1 with a width smaller than that of the strip portion 321a and a rectangular portion 321b2 connected to the wiring portion 321b1. On the other end side of the laminate 1, a plurality of leads 321b are stacked in the Y-axis direction on the exposed side side of the lead-out portion 321b. In this embodiment, the piezoelectric element 100 includes a second conductor 5 located on the side of the laminate 1 opposite to the exposed side of the other end of the lead-out portion 321b and between the lead-out portion 321b. In this embodiment, the second conductor 5 is rectangular, and its length along the Z-axis is set to be the same as the length of the rectangular portion 321b2 of the lead-out portion 321b.

[0036] In the structure that forms the basis of the piezoelectric element of this disclosure, there is no second conductor 5 between the side of the laminate 1 and the lead-out portion 321b. Therefore, on the other end of the laminate 1, the thickness of the side where the lead-out portion 321b is located is thicker than the thickness of the side opposite in the X-axis direction, resulting in thickness non-uniformity and reduced accuracy of the bending displacement of the piezoelectric element 100. In this embodiment, the thickness non-uniformity of the laminate 1 can be reduced by the second conductor 5, thus suppressing the reduction in accuracy of the bending displacement of the piezoelectric element 100.

[0037] Furthermore, the dimensions of the piezoelectric element 100 are not limited; for example, the length in the X direction can be set to 1–3 mm, the length in the Y direction to 1–2 mm, and the length in the Z direction to 20–50 mm. Additionally, the thickness of the internal electrode 3 can be 0.1–5 μm, and the thickness of the piezoelectric layer 4 can be 0.01–0.1 mm. The dimensions of the second conductor 5 can, for example, have a width (X-direction length) of 1–2.5 mm and a length (Z-direction length) of 1–3 mm.

[0038] The first electrode 31 in the central region 1M is Figure 3C The first electrode 31a shown and Figure 3D The first electrode 31b shown has two types of patterns. The first electrode 31b has a pattern shape that is symmetrical about the Z-axis direction to the pattern shape of the second electrode 32b. That is, in this embodiment, Figure 3D The first electrode 31b includes and Figure 3B The first conductor 321' of the second electrode 32b is symmetrical about the Z-axis, and similarly to the upper region 1U, the central region 1M also has a second conductor 5. Furthermore, in this embodiment, Figure 3F The second electrode 32d includes and Figure 3B The second electrode 32b has the same first conductor 321 as the upper region 1U, and the lower region 1L also has a second conductor 5.

[0039] and then, Figure 3A The second electrode 32a shown and Figure 3E The second electrode 32c shown includes a first conductor 321 and a first conductor 321' with a shape similar to the first conductor 321 and the first conductor 321'. The upper region 1U and the lower region 1L also have a second conductor 5.

[0040] As described above, in this embodiment, a second conductor 5 is provided in the upper region 1U, the central region 1M, and the lower region 1L. However, it is not necessary to provide it in all regions. As long as one or more second conductors 5 are provided, the non-uniformity of the thickness of the laminate 1 can be reduced compared with a piezoelectric element with a structure that does not form the basis of the piezoelectric element of this disclosure.

[0041] Furthermore, in this embodiment, the second conductor 5 is exposed on the side of the laminate 1 and connected to the surface electrodes 2A and 2B. This increases the number of conductors exposed on the side of the laminate 1, improving the wettability of the surface electrodes 2 on the side of the laminate 1, and thus increasing mechanical strength. As described above, the effect of the second conductor 5 is to reduce the thickness non-uniformity of the laminate 1, therefore it is not necessarily required to be electrically connected to the surface electrodes 2. For example, the second conductor 5 may not be exposed on the side of the laminate 1, but may be entirely embedded in the interlayer of the piezoelectric layer 4.

[0042] The first conductor 321 and the second conductor 5 can obtain the effect of reducing unevenness of the thickness of the laminate 1 even if they are not made to have the same electrical characteristics and the like, and therefore, for example, the materials of the first conductor 321 and the second conductor 5 can be the same material or different materials. By making the materials of the first conductor 321 and the second conductor 5 the same material, the difference in the thickness of the two conductors can be further reduced, and the unevenness of the thickness of the laminate 1 can be further reduced.

[0043] Next, other embodiments will be described. The second conductor of the present embodiment is different only in shape, and the structures other than this are the same as those of the aforementioned embodiments, and therefore, in the drawings and the description, the same reference numerals are used for the same structures as those of the aforementioned embodiments. Figure 4 The second conductor 5A of the present embodiment is rectangular, and the corner portion close to the lead-out portion 321b of the first conductor 321 is R-shaped. As in the aforementioned embodiments, in the case where the corner portion of the second conductor 5 is not R-shaped but pointed, discharge or the like occurs between the second conductor 5 and the lead-out portion 321b, and short-circuiting can occur. In order to prevent this, a gap is provided between the second conductor 5 and the lead-out portion 321b. The area of the second conductor 5 provided in correspondence with the amount of the gap is small. By making the corner portion of the second conductor 5A R-shaped, the distance between the second conductor 5A and the lead-out portion 321b can be narrowed. Thus, the second conductor 5A can be increased, the gap can be reduced, and the unevenness of the thickness of the laminate 1 can be further reduced.

[0044] The operation of the piezoelectric element 100 will be described. First, the electrical connection of the surface electrode 2 and the internal electrode 3 will be described. One of the surface electrodes 2A is electrically connected to the second electrode 32b of the upper region 1U and the second electrode 32d of the lower region 1L. The other of the surface electrodes 2A is electrically connected to the first electrode 31b of the central region 1M. One of the surface electrodes 2B is electrically connected to the second electrode 32a of the upper region 1U and the first electrode 31a (one side) of the central region 1M. The other of the surface electrodes 2B is electrically connected to the first electrode 31a (the other side) of the central region 1M and the second electrode 32c of the lower region 1L. With respect to the polarization direction of the piezoelectric layer 4, one side of the upper region 1U and the central region 1M is the first direction, and the other side of the lower region 1L and the central region 1M is the second direction opposite to the first direction. For example, the surface electrode 2A is made to have a ground potential, -64 V is applied to one of the surface electrodes 2B, and +64 V is applied to the other, and the piezoelectric layer 4 is polarized as described above.

[0045] The same voltage as in the operation is applied to one side and the other side of the surface electrode 2B, respectively. As an example of the applied voltage, +11 V is applied to one side and +61 V is applied to the other side of the surface electrode 2B. By applying a voltage of 0 to +72 V to one side and the other side of the surface electrode 2A, respectively, the piezoelectric element 100 can be bent and displaced in a desired direction. For example, by applying +72 V to one side and +36 V to the other side of the surface electrode 2A, the piezoelectric element 100 is bent and displaced (maximum) in one side (upper side) of the Y-axis direction. By applying 0 V to one side and +36 V to the other side of the surface electrode 2A, the piezoelectric element 100 is bent and displaced (maximum) in the other side (lower side) of the Y-axis direction. That is, by applying a constant voltage of +36 V to the other side of the surface electrode 2A and a voltage of 0 to +72 V to one side of the surface electrode 2A, the amount of bending displacement in the Y-axis direction can be adjusted. For example, by applying +36 V to one side and +72 V to the other side of the surface electrode 2A, the piezoelectric element 100 is bent and displaced (maximum) in one side (right side) of the X-axis direction. By applying +36 V to one side and 0 V to the other side of the surface electrode 2A, the piezoelectric element 100 is bent and displaced (maximum) in the other side (left side) of the X-axis direction. That is, by applying a constant voltage of +36 V to one side of the surface electrode 2A and a voltage of 0 to +72 V to the other side of the surface electrode 2A, the amount of bending displacement in the X-axis direction can be adjusted. By changing one side and the other side of the surface electrode 2A within a range of 0 to +72 V, bending displacement in the tilt direction can be performed.

[0046] The present disclosure can perform the following embodiments.

[0047] The piezoelectric element of the present disclosure includes:

[0048] a laminate, an internal electrode, and a piezoelectric layer; and

[0049] a surface electrode, which is located on a side surface of the laminate and is electrically connected to the internal electrode,

[0050] the internal electrode includes:

[0051] a first electrode, which applies a voltage to the piezoelectric layer to bend the laminate in a first direction orthogonal to a length direction of the laminate; and

[0052] a second electrode, which applies a voltage to the piezoelectric layer to bend the laminate in a second direction orthogonal to the length direction and the first direction,

[0053] at least one of the first electrode and the second electrode includes a first conductor having a strip portion extending along the length direction and a lead-out portion having one end connected to the strip portion and the other end exposed on the side surface of the laminate and connected to the surface electrode,

[0054] The piezoelectric element has a second conductor between a portion of the side surface on the opposite side from the portion of the side surface from which the other end of the lead-out portion is exposed and the lead-out portion.

[0055] According to the piezoelectric element of the present disclosure, by having the second conductor, it is possible to reduce unevenness in the thickness of the laminate, and to suppress a decrease in the precision of the bending displacement.

[0056] The above, the embodiments of the present disclosure are described in detail, in addition, the present disclosure is not limited to the above-mentioned embodiments, in the range without departing from the gist of the present disclosure, can be made various changes, improvements, etc. Of course, can be respectively constitute all or part of the above-mentioned embodiments in the range without contradicting appropriately combined.

[0057] - Symbol Explanation -

[0058] 1 Laminate

[0059] 1L Lower region

[0060] 1M Central region

[0061] 1U Upper region

[0062] 2, 2A, 2B Surface electrode

[0063] 3 Internal electrode

[0064] 4 Piezoelectric layer

[0065] 5, 5A Second conductor

[0066] 31, 31a, 31b First electrode

[0067] 32, 32a, 32b, 32c, 32d Second electrode

[0068] 100 Piezoelectric element

[0069] 321, 321' First conductor

[0070] 321a Band portion

[0071] 321b Lead-out portion

[0072] 321b1 Wiring portion

[0073] 321b2 Rectangular portion

Claims

1. A piezoelectric element comprising: a laminated body in which a plurality of piezoelectric layers and a plurality of internal electrodes are alternately stacked, and a surface electrode on a side surface of the laminated body, the surface electrode being electrically connected to the internal electrodes, wherein the internal electrodes include: a first electrode for applying a voltage to the piezoelectric layers to bend the laminated body in a first direction orthogonal to a length direction of the laminated body; and a second electrode for applying a voltage to the piezoelectric layers to bend the laminated body in a second direction orthogonal to the length direction and the first direction, wherein at least one of the first electrode and the second electrode includes a first conductor having a strip portion extending along the length direction and a lead portion having one end connected to the strip portion and the other end exposed on the side surface of the laminated body and connected to the surface electrode, and the piezoelectric element includes a second conductor between a portion of the side surface opposite to the other end of the lead portion and the lead portion, wherein the second conductor is rectangular, and an angle portion of the second conductor close to the lead portion is R-shaped. A laminate, an internal electrode and a piezoelectric layer; 2. The piezoelectric element according to claim 1, wherein the first conductor and the second conductor are made of the same material.

3. The piezoelectric element according to claim 1 or 2, wherein the second conductor is exposed on the portion of the side surface opposite to the other end of the lead portion.

4. The piezoelectric element according to claim 1 or 2, wherein the first electrode and the second electrode each include the first conductor, and a portion of the side surface on which the lead portion of the first conductor included in the first electrode is exposed is located on an opposite side of a portion of the side surface on which the lead portion of the first conductor included in the second electrode is exposed.

5. The piezoelectric element according to claim 1 or 2, wherein the lead portion includes a wiring portion including the one end and having a smaller width than the strip portion, and a rectangular portion including the other end and connected to the wiring portion. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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