JP6795343B2 - Piezoelectric actuator - Google Patents

Description

The present disclosure relates to, for example, a piezoelectric actuator used for precise positioning for correcting a displacement of a magnetic head, a shutter drive for a camera, a needle selection drive for a knitting machine or a loom, a relay switch, or the like.

Piezoelectric actuators in which a piezoelectric element and a shim are bonded together are widely used, for example, for precise positioning for correcting displacement of a magnetic head, shutter drive for a camera, needle selection drive for a knitting machine or a weaving machine, or a relay switch. Then, a piezoelectric actuator using an ultraviolet curable adhesive for bonding the piezoelectric element and the shim plate is known (see, for example, Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 2000-092876 Japanese Unexamined Patent Publication No. 7-066466

In recent years, in a piezoelectric actuator, in order to improve the displacement amount, the displacement amount is increased by driving with a high voltage. In a conventional piezoelectric actuator in which a piezoelectric element and a shim plate are bonded with an ultraviolet curable adhesive, the piezoelectric element and the shim plate may be peeled off by a long-term high voltage drive. This is because the piezoelectric element is provided with a surface electrode for applying a voltage, and the surface electrode blocks ultraviolet rays, so that it is difficult for the ultraviolet curable adhesive to be sufficiently irradiated with ultraviolet rays.

The piezoelectric actuator is provided on a plate-shaped piezoelectric body that transmits ultraviolet rays, a first surface electrode provided on the first main surface of the piezoelectric body, and a second main surface facing the first main surface of the piezoelectric body. A piezoelectric element including a second surface electrode, a shim plate bonded to the side of the piezoelectric element provided with the second surface electrode, and between them in order to bond the piezoelectric element and the shim plate. The first surface electrode has a first opening, the second surface electrode has a second opening, and the first opening and the first opening are provided with an intervening ultraviolet curable adhesive. The two openings face each other , and the peripheral edge of the second opening is outside the peripheral edge of the first opening when viewed from the direction perpendicular to the first main surface and the second main surface .

Other piezoelectric actuators include a plate-shaped laminate in which a piezoelectric body that transmits ultraviolet rays and an internal electrode are laminated, a first surface electrode provided on the first main surface of the laminate, and a first main electrode of the laminate. A piezoelectric element including a second surface electrode provided on a second main surface facing the surface, a shim plate joined to the side of the piezoelectric element provided with the second surface electrode, and the piezoelectric element and the shim plate. It is provided with an ultraviolet curable adhesive interposed between them for bonding, the first surface electrode has a first opening, the second surface electrode has a second opening, and the internal electrode layer has a second opening. It has a third opening, and the first opening, the second opening, and the third opening face each other , and the first main surface and the second main surface are viewed from a direction perpendicular to the second main surface. The peripheral edge of the two openings is outside the peripheral edge of the first opening .

According to the piezoelectric actuator of the present disclosure, peeling between the piezoelectric element and the shim plate during long-term high voltage driving is suppressed.

It is a perspective view which shows an example of the piezoelectric actuator of this embodiment. It is an exploded perspective view which shows an example of the piezoelectric actuator of this embodiment. An example of the piezoelectric actuator of this embodiment is shown, (a) is a top view, and (b) is a cross-sectional view taken along the line bb of (a). Another example of the piezoelectric actuator of this embodiment is shown, (a) is a top view, and (b) is a cross-sectional view taken along the line bb of (a). (A) to (c) are top views showing other examples of the piezoelectric actuator of this embodiment. (A) to (c) are top views showing other examples of the piezoelectric actuator of this embodiment. It is sectional drawing which shows the main part of the other example of the piezoelectric actuator of this embodiment in an enlarged manner. It is a perspective view which shows another example of the piezoelectric actuator of this embodiment. It is an exploded perspective view which shows another example of the piezoelectric actuator of this embodiment. Another example of the piezoelectric actuator of this embodiment is shown, (a) is a top view, and (b) is a cross-sectional view taken along the line bb of (a).

Hereinafter, an example of the embodiment of the piezoelectric actuator 1 will be described in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments shown below.

FIG. 1 is a schematic perspective view showing an embodiment of the piezoelectric actuator 1 of the present embodiment. FIG. 2 is an exploded perspective view which is an example of an exploded view of the piezoelectric actuator 1 of FIG. 3A and 3B show an example of the piezoelectric actuator 1 of FIG. 1, where FIG. 3A is a top view and FIG. 3B is a cross-sectional view taken along the line bb of FIG.

The piezoelectric actuator 1 of the present embodiment includes a piezoelectric element 2, a shim plate 3, and an ultraviolet curable adhesive 4. The piezoelectric element 2 is provided on the plate-shaped piezoelectric body 21, the first surface electrode 22 provided on the first main surface of the piezoelectric body 21, and the second main surface facing the first main surface with the piezoelectric body 21 interposed therebetween. The second surface electrode 23 is included. The shim plate 3 is bonded to the side of the piezoelectric element 2 where the second surface electrode 23 is provided (the second main surface of the piezoelectric body 21) with an ultraviolet curable adhesive 4. In other words, an ultraviolet curable adhesive 4 is interposed between the piezoelectric element 2 and the shim plate 3 in order to join them. Further, the first surface electrode 22 has a first opening 221 and the second surface electrode 23 has a second opening 231. The first opening 221 and the second opening 231 face each other.

In the conventional piezoelectric actuator, even if the ultraviolet rays are irradiated with the ultraviolet curable adhesive interposed between the piezoelectric element and the shim plate, the ultraviolet rays are irradiated only to the outer edge of the ultraviolet curable adhesive. Curing of the UV curable adhesive was likely to be insufficient. This is because ultraviolet rays do not pass through electrodes such as surface electrodes provided on the piezoelectric element. Therefore, in the conventional piezoelectric actuator, the piezoelectric element and the shim plate may be peeled off by high voltage driving for a long period of time.

According to the piezoelectric actuator 1 of the present embodiment, since the first surface electrode 22 provided on the first main surface of the piezoelectric body 21 has the first opening 221 the ultraviolet rays are piezoelectric from the first opening 221. It enters the inside of the body 21 and passes through the piezoelectric body 21. A second opening 231 is provided in the second surface electrode 23 provided on the second main surface facing the first main surface with the piezoelectric body 21 interposed therebetween. Then, since the first opening 221 and the second opening 231 face each other, the ultraviolet rays transmitted through the piezoelectric body 21 reach the ultraviolet curable adhesive 4 through the second opening 231. Therefore, the portion of the ultraviolet curable adhesive 4 located between the second opening 231 of the piezoelectric element 2 and the shim plate 3 and its periphery is cured. That is, in the piezoelectric actuator 1 of the present embodiment, not only the outer edge portion of the ultraviolet curable adhesive 4 but also the inner portion is cured, so that the bonding strength between the piezoelectric element 2 and the shim plate 3 is high and the bonding strength is high for a long period of time. Even in high voltage drive, the peeling between the piezoelectric element 2 and the shim plate 3 is suppressed.

Here, FIG. 4 shows another example of the piezoelectric actuator 1, (a) is a top view, and (b) is a cross-sectional view taken along the line bb of (a). As shown in the example shown in FIG. 4, the peripheral edge of the second opening 231 is outside the peripheral edge of the first opening 221 when viewed from the direction perpendicular to the first main surface and the second main surface (perspectively). There may be.

Ultraviolet rays incident on the piezoelectric body 21 from the first main surface are scattered inside the piezoelectric body 21 and proceed to the second main surface. Therefore, the ultraviolet rays incident perpendicularly to the first main surface of the piezoelectric body 21 are not limited to the region where the first opening 221 is projected onto the second main surface in the second main surface of the piezoelectric body 21. It will extend to the outside of the area. Ultraviolet rays that are obliquely incident on the first main surface and travel straight also reach the outside of this region on the second main surface. That is, on the second main surface, the ultraviolet rays are irradiated to a region wider than the first opening 221.

Here, in the piezoelectric actuator 1 as in the example shown in FIG. 4, the peripheral edge of the second opening 231 is outside the peripheral edge of the first opening 221. In other words, the second opening 231 is larger than the first opening 221. Therefore, the ultraviolet rays that have passed through the inside of the piezoelectric body 21 and spread are also irradiated to the ultraviolet curable adhesive 4, so that the cured region of the ultraviolet curable adhesive 4 increases. Therefore, in the piezoelectric actuator 1 of the present embodiment, the bonding strength between the piezoelectric element 2 and the shim plate 3 is further improved, and peeling between the piezoelectric element 2 and the shim plate 3 is suppressed even in a long-term high voltage drive.

Here, FIGS. 5 (a) to 5 (c) and 6 (a) to 6 (c) are top views showing another example of the piezoelectric actuator 1. In the example shown in FIGS. 1 to 4, the shape of the first opening 221 and the second opening 231 in a plan view, that is, the shape of the peripheral edge is circular. On the other hand, in the examples shown in FIGS. 5 and 6, the shape of the peripheral edge of the first opening 221 is a square shape, a rectangular shape, and an oval shape. Although the shape of the second opening 231 is not shown in FIGS. 5 and 6, it has the same shape as the shape of the first opening 221. The shapes of the first opening 221 and the second opening 231 are not limited to the shapes shown in FIGS. 1 to 6, and are not particularly limited to polygons such as triangles and quadrangles, circles, and ellipses. As shown in the examples shown in FIGS. 4 and 5, the second opening 231 has the same shape as the first opening 221 and is one size larger, and the peripheral edge of the second opening 231 is the first opening. It may be located on the outer side of the peripheral edge of 221 by the same distance over the entire circumference.

In FIGS. 1 to 5, the first surface electrode 22 has two first openings 221 and the second surface electrode 23 facing the first surface electrode 22 also has two second openings 231. .. The number of the first opening 221 and the second opening 231 may be one, three as in the example shown in FIG. 6 (a), and FIGS. 6 (a) and 6 (b). ) May be more than three.

If the areas of the first opening 221 and the second opening 231 are large, a wide area of the ultraviolet curable adhesive 4 can be cured, but the area of the surface electrode that applies a voltage to the piezoelectric body 21 is small, so that the piezoelectric material is piezoelectric. The amount of displacement of the element 2 becomes small. Therefore, the areas (dimensions and numbers) of the first opening 221 and the second opening 231 can be set in consideration of the balance between the curing of the ultraviolet curable adhesive 4 and the displacement amount of the piezoelectric element 2.

Since the ultraviolet rays are scattered and spread inside the piezoelectric body 21, if the first opening 221 and the second opening 231 have the same area, the ultraviolet curable adhesive 4 is spread by the longer peripheral length. The area where UV is cured becomes large. Specifically, the first opening 221 of FIG. 5A has a square shape, whereas the first opening 221 of FIG. 5B has an elongated shape such as a rectangle. Good. The area of the first opening 221 in FIG. 5 (a) and the area of the first opening 221 in FIG. 5 (b) are about the same, but the length of the peripheral edge of the first opening 221 in FIG. 5 (b). The length is longer than the length of the peripheral edge of the first opening 221 of FIG. 5 (b) of FIG. 5 (a). Further, as in the example shown in FIG. 5B, when the piezoelectric body 21 has a shape having a longitudinal direction such as a rectangle, the longitudinal direction of the first opening 221 and the second opening 231 of the piezoelectric element 2 It may be aligned in the longitudinal direction. In this way, the cured region of the ultraviolet curable adhesive 4 is unlikely to be unevenly arranged, and the piezoelectric actuator 1 is likely to be deformed uniformly, so that the reliability is high.

Also, as an example of an opening having the same area and a long peripheral edge, a plurality of small first openings 221 (and second openings) are used instead of one large first opening 221 (and second opening 231). It can also be 231). The total area of the three first openings 221 of the example shown in FIG. 6 (a) and the total area of the 21 first openings 221 of the example shown in FIG. 6 (b) are about the same. On the other hand, the total peripheral length of the 21 first openings 221 in the example shown in FIG. 6 (b) is about the total peripheral length of the three first openings 221 in the example shown in FIG. 6 (a). It is 2.7 times. Further, the 21 first openings 221 are arranged so as to be uniformly distributed in the first surface electrode 22. When a large number of first openings 221 are arranged so as to be uniformly distributed in the first surface electrode 22 in this way, the cured region of the ultraviolet curable adhesive 4 is unlikely to be unevenly arranged. Since the deformation of the piezoelectric actuator 1 tends to be uniform, the reliability is high.

If the size of each of the plurality of first openings 221 (and the second opening 231) is small, the piezoelectric material between the first opening 221 and the second opening 231 due to the wraparound of the electric field due to the edge effect. The proportion of the region where the voltage is applied in 21 increases. Therefore, it is possible to suppress a decrease in the displacement amount of the piezoelectric element 2 due to a decrease in the area of the first surface electrode 22 and the second surface electrode 23 due to the provision of the first opening 221 and the second opening 231. In order to obtain such an effect and enlarge the cured region of the ultraviolet curable adhesive 4, the shape of the first surface electrode 22 (and the second surface electrode 23) is as shown in FIG. 6 (c). May be in the form of a mesh. The line width of the mesh at this time is, for example, 0.1 mm to 1 mm, and the size of the first opening 221 (and the second opening 231) is, for example, 0.1 mm square to 1 mm square (or the diameter is 0.1 mm to 1 mm). ) Can be set.

In the examples shown in FIGS. 5 and 6, the shape of the first opening 221 (and the second opening 231) is a shape in which the corners of a square or a rectangle are rounded. As described above, both the first opening 221 and the second opening 231 may have a peripheral edge having no corners. The shape without corners includes not only a polygon with rounded corners but also a circular shape, an oval shape, an ellipse shape, and the like as shown in FIGS. 1 to 6.

Since it is difficult to apply a driving voltage to the region sandwiched between the first opening 221 and the second opening 231 of the piezoelectric body 21, it is difficult to extend even if a voltage is applied to the piezoelectric element 2. Therefore, the behavior of the piezoelectric body 21 when a voltage is applied differs between this region and the region around it. Then, stress is generated along the boundary between this region and the surrounding region, that is, the peripheral edges of the first opening 221 and the second opening 231, and this stress may cause cracks in the piezoelectric body 21. .. When both the first opening 221 and the second opening 231 have no corners, the cracks generated in the piezoelectric body 21 can be suppressed because there are no corners where the stress is concentrated.

FIG. 7 is an enlarged cross-sectional view showing a main part of an example of the piezoelectric actuator 1. The first opening 221 and the second opening 231 in the cross section perpendicular to the first main surface and the second main surface of the piezoelectric body 21 are shown. As described above, the inner peripheral surfaces of the first opening 221 and the second opening 231 may be inclined rather than perpendicular to the first and second main surfaces of the piezoelectric body 21, respectively. Specifically, in the first opening 221 and the second opening 231 both, the size of the opening on the surface of the first surface electrode 22 and the second surface electrode 23 opposite to the piezoelectric body 21 is larger. Piezoelectric body 2
It may be larger than the size of the opening on one side surface. In other words, the inner surface of the first opening 221 is inclined so that the opening on the surface of the first surface electrode 22 and the second surface electrode 23 opposite to the piezoelectric body 21 is larger than the opening on the surface in contact with the piezoelectric body 21. You may be doing it.

When the inner surface of the first opening 221 is inclined so that the opening on the surface of the first surface electrode 22 and the second surface electrode 23 opposite to the piezoelectric body 21 is large, the first principal of the piezoelectric body 21 Ultraviolet rays are likely to be incident on the first opening 221 from the direction inclined with respect to the surface, in other words, from the periphery of the first opening 221. Further, the ultraviolet rays that have passed through the piezoelectric body 21 and reached the second opening 231 spread in the peripheral direction of the second opening 231 and are irradiated from the second opening 231 to the ultraviolet curable adhesive 4. That is, the ultraviolet rays are irradiated to a wider area of the ultraviolet curable adhesive 4. Therefore, the area where the ultraviolet curable adhesive 4 is cured increases. Therefore, in the piezoelectric actuator 1 of the present embodiment, the bonding strength between the piezoelectric element 2 and the shim plate 3 is further improved, and peeling between the piezoelectric element 2 and the shim plate 3 is suppressed even in a long-term high voltage drive.

8 to 10 show an example of another embodiment of the piezoelectric actuator 1, FIG. 8 is a perspective view, FIG. 9 is an exploded perspective view, FIG. 10 (a) is a top view, and FIG. 10 (b) is a sectional view. Is. The piezoelectric element 2 of the embodiment described so far is a single plate type, whereas the piezoelectric element 2 is a laminated type. That is, the piezoelectric actuator 1 of the present embodiment includes the piezoelectric element 2, the shim plate 3, and the ultraviolet curable adhesive 4. The piezoelectric element 2 faces a plate-shaped laminate in which the piezoelectric body 21 and the internal electrode 24 are laminated, a first surface electrode 22 provided on the first main surface of the laminate, and a first main surface of the laminate. The second surface electrode 23 provided on the second main surface is included. The shim plate 3 is bonded to the side of the piezoelectric element 2 where the second surface electrode 23 is provided (the second main surface of the laminate) with an ultraviolet curable adhesive 4. In other words, an ultraviolet curable adhesive 4 is interposed between the piezoelectric element 2 and the shim plate 3 in order to join them. Further, the first surface electrode 22 has a first opening 221 and the second surface electrode 23 has a second opening 231 and the internal electrode 24 has a third opening 241. The first opening 221 and the second opening 231 and the third opening 241 face each other.

According to the piezoelectric actuator 1 of the present embodiment, ultraviolet rays enter the inside of the piezoelectric body 21 from the first opening 221 and pass through the third opening 241 and the second opening 231 to be an ultraviolet curable adhesive 4 To reach. Therefore, in the piezoelectric actuator 1 of the present embodiment, not only the outer edge portion of the ultraviolet curable adhesive 4 but also the inner portion is cured, so that the bonding strength between the piezoelectric element 2 and the shim plate 3 is high, and the bonding strength is high for a long period of time. Even in high voltage drive, the peeling between the piezoelectric element 2 and the shim plate 3 is suppressed.

Here, as in the example shown in FIG. 10, the peripheral edges of the second opening 231 and the third opening 241 are the first when viewed from the direction perpendicular to the first main surface and the second main surface (see through). 1 It may be outside the peripheral edge of the opening in the surface electrode 22. In other words, the second opening 231 and the third opening 241 are larger than the first opening 221. Therefore, the ultraviolet rays that have passed through the first opening 221 and spread through the inside of the piezoelectric body 21 are also irradiated to the ultraviolet curable adhesive 4 through the third opening 241 and the second opening 231. The area where the curable adhesive 4 is cured increases. Therefore, in the piezoelectric actuator 1 of the present embodiment, the bonding strength between the piezoelectric element 2 and the shim plate 3 is further improved, and peeling between the piezoelectric element 2 and the shim plate 3 is suppressed even in a long-term high voltage drive.

In the example shown in FIG. 10, the third opening 241 is larger than the first opening 221 and the second opening 231 is larger than the third opening 241. Further, a plurality of third openings 241 are provided, and the size of the openings increases from the first opening 221 to the second opening 231. With such a configuration, the ultraviolet rays in which the ultraviolet rays are spread in the piezoelectric body 21 between the plurality of third openings 241 and the piezoelectric body 21 between the third openings 241 and the second opening 231 are also the third openings. It becomes easier to pass through the 241 and the second opening 231. Therefore, in the piezoelectric actuator 1 of the present embodiment, the bonding strength between the piezoelectric element 2 and the shim plate 3 is further improved, and peeling between the piezoelectric element 2 and the shim plate 3 is suppressed even in a long-term high voltage drive.

The shape of the first opening 221 and the second opening 231 in a plan view, that is, the shape of the peripheral edge, is the same as in the case of the single plate type piezoelectric element 2, especially polygonal shapes such as triangles and quadrangles, circles, and ellipses. There is no limit. Further, both the first opening 221 and the second opening 231 may have a peripheral edge having no corners. The same applies to the third opening 241. If the peripheral edges of the first opening 221 and the second opening 231 and the third opening 241 all have no corners, there are no corners where stress is concentrated, so that cracks generated in the piezoelectric body 21 are suppressed. it can. The shapes, numbers, arrangements, etc. of the first opening 221 and the second opening 231 and the third opening 241 are the same as in the case where the piezoelectric element 2 is a single plate type.

The piezoelectric element 2 includes a plate-shaped piezoelectric body 21, a first surface electrode 22, and a second surface electrode 23. When the piezoelectric element 2 is of a single plate type, the first surface electrode 22 is provided on the first main surface of the plate-shaped piezoelectric body 21, and the second surface electrode 23 is the second main surface facing the first main surface. It is provided on the surface. When the piezoelectric element 2 is a laminated type, it includes a plate-shaped laminate in which a plate-shaped piezoelectric body 21 and an internal electrode 24 are laminated, a first surface electrode 22, and a second surface electrode 23. The first surface electrode 22 is provided on the first main surface of the plate-shaped laminate, and the second surface electrode 23 is provided on the second main surface facing the first main surface. The ends of the internal electrodes 24 are alternately led out to a pair of opposite side surfaces (first side surface and second side surface) of the laminated body. As shown in the examples shown in FIGS. 8 and 9, the internal electrode 24 may be led out to the first main surface, the second main surface, the first side surface, and the other pair of side surfaces surrounded by the second side surface. In the examples shown in FIGS. 8 to 10, the piezoelectric body 21 has three layers and the internal electrode 24 has two layers, but the number of layers of the piezoelectric body 21 and the internal electrode 24 is not limited to this.

In the examples shown in FIGS. 8 to 10, the laminated piezoelectric element 2 further includes a first side electrode 25 and a second side electrode 26. The first side surface electrode 25 is provided on the first side surface, and connects the internal electrode 24 led out to the first side surface and the first surface electrode 22. The second side surface electrode 26 is provided on the second side surface, and connects the internal electrode 24 led out to the second side surface and the second surface electrode 23. In the single plate type piezoelectric element 2, the first surface electrode 22 is provided on the entire surface of the first main surface of the piezoelectric body 21, and the second surface electrode 23 is provided on the entire surface of the second main surface. On the other hand, in the laminated piezoelectric element 2, the first surface electrode 22 and the second side electrode 26 are electrically insulated from each other, and the second surface electrode 23 and the first side electrode 25 are electrically insulated from each other. There is. Therefore, the first surface electrode 22 is not provided on the entire surface of the first main surface of the laminated body, and a gap is provided between the first surface electrode 22 and the second side electrode 26. Further, the second surface electrode 23 is not provided on the entire surface of the second main surface of the laminated body, and a gap is provided between the second surface electrode 23 and the first side electrode 25.

Instead of providing the first side electrode 25 and the second side electrode 26, a through conductor penetrating the piezoelectric body 21 is provided to connect the internal electrode 24 and the first surface electrode 22, and the internal electrode 24 and the second surface electrode 23. You may make a connection with. In this case, the first surface electrode 22 can be provided on the entire surface of the first main surface of the laminated body, and the second surface electrode 23 can be provided on the entire surface of the second main surface.

The shape of the piezoelectric element 2 (the shape of the piezoelectric body 21 of the single plate type piezoelectric element 2 and the shape of the laminated body of the laminated piezoelectric element 2) is a rectangular parallelepiped shape in the examples shown in FIGS. 1 and 8. Is. The shape of the piezoelectric element 2 is not particularly limited, and may be a polygonal shape other than a rectangle, a circular shape, or an elliptical shape. The dimensions of the piezoelectric element 2 can be, for example, 18 mm to 45 mm in length, 1 mm to 10 mm in width, and 0.1 mm to 1.0 mm in thickness.

The piezoelectric body 21 is made of ceramics having piezoelectric characteristics. As such ceramics, for example, perovskite-type oxide made of lead zirconate titanate (PbZrO _3- PbTIO ₃ ), lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ) and the like can be used. The thickness of one layer of the piezoelectric body 21 in the case of the laminated piezoelectric element 2 can be set to, for example, 0.01 to 0.1 mm. Further, as the piezoelectric body 21, a material having a piezoelectric d31 constant of 200 pm / V or more can be used. As a result, a large bending vibration can be obtained.

The first surface electrode 22 and the second surface electrode 23 may be a so-called thick film conductor or a thin film conductor formed by sputtering, vapor deposition, or the like. The first surface electrode 22 and the second surface electrode 23 may be formed by simultaneous firing with the piezoelectric body 21 and the internal electrode 24 in the case of a thick film conductor, or the fired piezoelectric body 21 or the laminated body. It may be formed by baking on. As the material of the first surface electrode 22 and the second surface electrode 23, in the case of a thick film conductor, for example, a conductor containing silver or a silver-palladium alloy as a main component capable of low-temperature firing, copper, platinum, or the like is used. Including conductors can be used. Further, the first surface electrode 22 and the second surface electrode 23 may contain a ceramic component and a glass component in addition to these conductor materials. In the case of a thin film conductor, for example, a conductor such as copper, chromium, or nickel can be used in addition to the above conductor material.

The internal electrode 24 is formed by simultaneous firing with the ceramics of the piezoelectric body 21. As this material, for example, a conductor containing silver or a silver-palladium alloy as a main component, which can be fired at a low temperature, or a conductor containing copper, platinum, or the like can be used. Further, the internal electrode 24 may contain a ceramic component or a glass component in addition to these conductor materials.

The first opening 221 and the second opening 231 and the third opening 241 (hereinafter, the three are collectively referred to as an opening) form the first surface electrode 22, the second surface electrode 23, and the internal electrode 24. Can be formed at the time. When these are thick-film conductors, they can be formed by printing in a pattern shape having an opening by plate making when printing the conductor paste. It can also be formed by transferring the printed pattern. In the case of a thin film conductor, a mask can be formed in a portion that becomes an opening when the thin film is formed. Further, in any case, it can be formed by forming a thick film or a thin film with a pattern having no opening and then etching with a mask or the like.

The first side surface electrode 25 and the second side surface electrode 26 can be formed in the same manner as the first surface electrode 22 and the second surface electrode 23. When a through conductor is provided instead of the first side electrode 25 and the second side electrode 26, the through conductor can be formed by simultaneous firing with the ceramics of the piezoelectric body 21, and the same material as the internal electrode 24 should be used. Can be done.

For the shim plate 3, for example, a metal such as an iron-nickel alloy or stainless steel, or a conductive material such as carbon can be used. Alternatively, an insulating material may be used, and for example, a resin material or a fiber reinforced resin which is a composite material of a resin and a fiber can be used. As the resin material, epoxy, polyimide, bismalade, polyetheretherketone, polyetherimide, polyimide and the like can be used. As the reinforcing fiber material of the fiber-reinforced resin, carbon (carbon) fiber, aramid fiber, polyethylene fiber, polyarylate fiber, alumina fiber, silicon carbide fiber, boron fiber, glass fiber and the like can be used. In either case of a conductive material or an insulating material, a plate-shaped material of these materials can be produced by forming a predetermined shape by processing such as cutting or punching.

The dimensions of the shim plate 3 can be, for example, 20 mm to 50 mm in length, 1 mm to 10 mm in width, and 0.1 mm to 3.0 mm in thickness. The shim plate 3 can have at least one of a width and a length larger than that of the piezoelectric element 2. The portion of the shim plate 3 protruding from the piezoelectric element 2 can be used as a mounting portion for the piezoelectric actuator 1. Also, shim board 3
Can also be used as a terminal electrode for connecting a lead wire or the like for applying a voltage to the piezoelectric element 2. The dimensions of the shim plate 3 may be set according to the ease of mounting the piezoelectric actuator 1 and connecting lead wires and the like.

In the examples shown in FIGS. 1 to 5 and 8 to 10, the shim plate 3 protrudes from one end of the piezoelectric element 2 in the length direction. There is no particular limitation on the direction in which the shim plate 3 protrudes from the piezoelectric element 2. As shown in the example shown in FIG. 6A, the shim plate 3 may protrude from both ends of the piezoelectric element 2 in the length direction. Further, the shim plate 3 may protrude in the width direction of the piezoelectric element 2. As shown in the examples shown in FIGS. 6 (b) and 6 (c), the shim plate 3 may protrude in both the length direction and the width direction of the piezoelectric element 2. Further, there is no particular limitation on the length of the shim plate 3 protruding from the piezoelectric element 2. As shown in the example shown in FIG. 6A, the length of protrusion from the piezoelectric element 2 is the same on both sides of the piezoelectric element 2 (in FIG. 6A, both sides in the length direction of the piezoelectric element 2). You may. Further, as shown in the example shown in FIG. 6C, the length of protrusion from the piezoelectric element 2 differs on both sides of the piezoelectric element 2 (in FIG. 6A, both sides in the length direction of the piezoelectric element 2). You may be. Further, as shown in the example shown in FIG. 6B, even if the protrusion length from the piezoelectric element 2 is the same in each of the length direction and the width direction of the piezoelectric element 2, the piezoelectric element 2 The length direction and the width direction may be different.

In the piezoelectric actuator 1, when the piezoelectric element 2 has a rectangular plate shape and is bent in the length direction of the piezoelectric element 2, the shim plate 3 may protrude from only one end of the piezoelectric element 2 in the length direction. Good. In this way, since there is no unnecessary portion in the shim plate 3, the piezoelectric actuator 1 has a large displacement and is small.

As the ultraviolet curable adhesive 4, commonly used adhesives such as epoxy type, acrylate type, and polyester type can be used. If the ultraviolet curable adhesive 4 has anaerobic curability, the cured region can be made larger.

By applying a liquid ultraviolet curable adhesive to the piezoelectric element 2 or the shim plate 3 and pressurizing it and then irradiating it with ultraviolet rays, the piezoelectric element 2 and the shim plate 3 are joined by the cured ultraviolet curable adhesive 4. It becomes the piezoelectric actuator 1. At this time, the exposed outer edge portion of the ultraviolet curable adhesive 4 is directly irradiated with ultraviolet rays and cured. The ultraviolet curable adhesive 4 directly under and around the second opening 231 passed through the first opening 221 (and the third opening 241), passed through the piezoelectric body 21, and passed through the second opening 231. It is cured by ultraviolet rays.

When a voltage is applied to the piezoelectric element 2, the piezoelectric body 21 of the piezoelectric element 2 expands and contracts. The piezoelectric actuator 1 bends because the expandable and contractible piezoelectric element 2 and the non-expandable shim plate 3 are bonded together. This is the case where the piezoelectric element 2 is a unimorph type. When the piezoelectric element 2 is a laminated type, the piezoelectric element 2 may be a bimorph type. In this case, the piezoelectric element 2 itself bends, and the piezoelectric actuator 1 also bends together with the shim plate 3. The magnitude of bending of the piezoelectric actuator 1 is the displacement amount of the piezoelectric actuator 1. The voltage is applied to the piezoelectric element 2 by using the first surface electrode 22 and the second surface electrode 23 of the piezoelectric element 2 as different electrodes.

Since the first surface electrode 22 is exposed, a voltage can be directly applied via, for example, a lead wire bonded with solder or a conductive adhesive. On the other hand, since the second surface electrode 23 of the piezoelectric element 2 and the shim plate 3 are bonded by the ultraviolet curable adhesive 4, the second surface electrode 23 is hardly exposed. Therefore, the voltage may be applied to the second surface electrode 23 via the shim plate 3.

For example, as shown in the example shown in FIG. 3B, the second surface electrode 23 can be provided with the protrusion 232 so as to be brought into contact with the conductive shim plate 3 and electrically connected. Similarly, when the shim plate 3 is conductive, if the ultraviolet curable adhesive 4 is a conductive adhesive containing conductive particles, the shim plate 3 and the second surface electrode 23 can be electrically connected. it can. Then, if a lead wire or the like is connected to the shim plate 3, a voltage can be applied to the second surface electrode 23 via the lead wire and the conductive shim plate 3.

When the shim plate 3 is insulating, an electrode may be provided on the surface of the shim plate 3 to electrically connect the electrode and the second surface electrode 23. For this electrical connection, the protrusion 232 provided on the second surface electrode 23 and the conductive ultraviolet curable adhesive 4 as described above can be used. If, for example, a lead wire or the like is connected to the electrode on the shim plate 3, a voltage can be applied to the second surface electrode 23 via the lead wire and the electrode.

If the piezoelectric element 2 is a laminated type, it may be the second side electrode 26 connected to the second surface electrode 23. Further, an electrode extending from the second side surface electrode 26 onto the first main surface of the laminated body may be provided, and a lead wire or the like may be connected to this electrode.

Up to now, one piezoelectric element 2 has been bonded to one side of the shim plate 3 as the piezoelectric actuator 1, but the piezoelectric actuator 1 has the piezoelectric elements 2 bonded to both sides of the shim plate 3 with the shim plate 3 sandwiched between them. It may be the one that has been used.

1: Piezoelectric actuator 2: Piezoelectric element 21: Piezoelectric body 22: First surface electrode 23: Second surface electrode 221: First opening 231: Second opening 24: Internal electrode 241: Third opening 25: First Side electrode 26: Second side electrode 3: Sim plate 4: UV curable adhesive

Claims (6)

A plate-shaped piezoelectric body through which ultraviolet rays are transmitted, a first surface electrode provided on the first main surface of the piezoelectric body, and a second surface provided on a second main surface facing the first main surface of the piezoelectric body. Piezoelectric elements including electrodes and
A shim plate joined to the side of the piezoelectric element provided with the second surface electrode,
An ultraviolet curable adhesive interposed between the piezoelectric element and the shim plate for joining the shim plate is provided.
The first surface electrode has a first opening, the second surface electrode has a second opening, the first opening and the second opening face each other , and the first A piezoelectric actuator characterized in that the peripheral edge of the second opening is outside the peripheral edge of the first opening when viewed from the main surface and the direction perpendicular to the second main surface . The piezoelectric actuator according to claim 1, wherein both the first opening and the second opening have a peripheral shape having no corners. The first or second aspect of the present invention, wherein the inner surface of the first opening is inclined so that the opening of the surface of the first surface electrode opposite to the piezoelectric body is large. Piezoelectric actuator. A plate-shaped laminate in which a piezoelectric body that transmits ultraviolet rays and an internal electrode are laminated, a first surface electrode provided on the first main surface of the laminate, and a first surface facing the first main surface of the laminate. 2 Piezoelectric elements including a second surface electrode provided on the main surface and
A shim plate joined to the side of the piezoelectric element provided with the second surface electrode,
An ultraviolet curable adhesive interposed between the piezoelectric element and the shim plate for joining the shim plate is provided.
The first surface electrode has a first opening, the second surface electrode has a second opening, the internal electrode has a third opening, and the first opening, the first. The two openings and the third opening face each other , and the peripheral edges of the second opening and the third opening are the first when viewed from the direction perpendicular to the first main surface and the second main surface. A piezoelectric actuator characterized in that it is outside the periphery of the opening . The piezoelectric actuator according to claim 4, wherein the first opening, the second opening, and the third opening all have a peripheral shape having no corners. The first or second aspect of the present invention, wherein the inner surface of the first opening is inclined so that the opening of the surface of the first surface electrode opposite to the piezoelectric body is large. Piezoelectric actuator.

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