JPH01261879A - Lamination type displacement element - Google Patents

Abstract

PURPOSE:To increase the generating force of a displacement element and the change at the time of unloading, and improve the output and the efficiency of the displacement element, by making the intensity of electric field applied to a ceramic layer distant from a shim larger than that of electric field applied to a ceramic layer close to the shim. CONSTITUTION:On a shim 1, ceramic layers 9, 11, 13 sandwiched respectively by electrodes 3 are arranged. The thickness of the layer 11 is made smaller than that of the layer 9. The thickness of the layer 13 is made smaller than that of the layer 11. When the same driving voltage V1 is applied to each electrode of each layer, the layers 9, 11, 13 generate specified distortions, and the shim generates displacement. Since the thickness of the ceramic layer closer to the shim 1 becomes larger, the electric field intensity applied to the ceramic layer closer to the shim 1 becomes smaller. As a result, the distortion of the ceramic layer 18 is larger than that of the ceramic layer 11, and so displacements of the layers are effectively synthesized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a laminated displacement element, and in particular, the generated force is increased by combining a plurality of piezoelectric material layers, etc., and the displacement under no load is reduced to a large extent. <<< and relates to an actuator element with reduced displacement deterioration.

[Prior Art] FIG. 4 shows the structure of a conventional displacement element using a piezoelectric material such as ceramic. The displacement element shown in the figure consists of a ceramic layer 5 on which electrodes 3 are added on both sides of a metal plate 1 called a shim.
It has been established. By applying a voltage V1 between the electrodes 3 of such a displacement element, an electric field is applied to the ceramic layer 5, and this electric field causes the ceramic layer 5 to undergo distortion such as deflection and expansion/contraction. The driven body is then driven using this distortion. However, in the displacement element shown in FIG. 4, in order to increase the force at which the displacement becomes zero, that is, the generated force, it is necessary to increase the thickness of the ceramic layer 5 considerably, and in order to obtain a - constant displacement amount, it is necessary to increase the thickness of the ceramic layer 5. It was necessary to increase the applied voltage considerably.

For this reason, a so-called laminated displacement element has conventionally been considered in which ceramic layers 7 of the same thickness are provided on a shim 1 and sandwiched between electrodes 3, as shown in FIG. In such a displacement element, an equal voltage v1 was applied between the electrodes 3 on both sides of each ceramic layer 7. As a result, even when the same voltage V1 is applied to the displacement element shown in FIG. 4 as in the displacement element shown in FIG. 4, the electric field becomes larger because the thickness of each ceramic layer 7 is thinner, and a larger generated force is obtained. It was possible.

[Problems to be Solved by the Invention] However, although it is possible to increase the generated force in the laminated displacement element shown in FIG. 5 compared to the single-plate displacement element shown in FIG. However, the magnitude of the generated force and the displacement under no load are not sufficiently large, and therefore the efficiency as an actuator element is not very good.

SUMMARY OF THE INVENTION In view of the problems with the conventional displacement elements described above, an object of the present invention is to provide an actuator element that generates a large force and has a large displacement when no load is applied, and therefore has a high output and high efficiency.

[Means for Solving the Problem] In order to achieve the above-mentioned object, the laminated displacement element according to the present invention includes a plurality of ceramic layers added on the shim and an electrode that applies an electric field to the ceramic layer. The electric field strength applied by the shim to the ceramic layer is greater than the strength of the electric field applied to the ceramic layer closer to the shim. In addition, as another aspect,
A plurality of ceramic layers and an electrode for applying an electric field to the ceramic layers are provided on the shim, and the thickness of the ceramic layer further from the shim can be made thinner than the thickness of the ceramic layer closer to the shim.

[Function] In the laminated displacement element constructed as described above, a strong electric field is applied to the ceramic layer farthest from the shim, so that the ceramic layer expands/contracts or deflects more than the ceramic layer closer to the shim. Therefore, the displacement of each ceramic layer is effectively combined and transmitted to the shim, and each ceramic layer does not apply a force that would limit the displacement of other ceramic layers. The generated force and displacement under no load are increased, and the output and efficiency of the displacement element are improved.

[Example code] Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows the structure of a laminated displacement element according to one embodiment of the present invention. In the displacement element shown in the figure, ceramic layers 9, 11, 13 are sandwiched between electrodes 3 on shim 1, respectively.
is provided. The thickness of the ceramic layer 11 is thinner than the thickness of the ceramic layer 9, and
The thickness of the ceramic layer 3 is made thinner than that of the ceramic layer 11. That is, the displacement element shown in FIG. 1 is made by laminating and adhering three ceramic plates with electrodes, each of which has a sequentially decreasing thickness, on a shim 1.

In such a displacement element, each ceramic layer 9.11
．． For example, a drive voltage v1 of the same magnitude is applied between each of the 13 electrodes. As a result, each ceramic layer 9, 11.1
3 produces a predetermined strain and the shim 1 is displaced. In this case, since the ceramic layer near the shim 1 has a larger thickness, the electric field applied to the ceramic layer near the shim 1 becomes smaller. As a result, the distortion of the ceramic layer 11 farther away from the shim 1 is higher than the distortion of the ceramic layer 9 closer to the shim 1.
The distortion of the ceramic layer 13 becomes larger than that of the ceramic layer 11. As a result, in the displacement element shown in FIG. 1, the displacements of the respective ceramic layers are effectively combined around the shim 1. That is, the ceramic layer located farther from the shim 1 expands and contracts more greatly, and the ceramic layer closer to the shim 1 expands and contracts less. Therefore, each ceramic layer itself is less likely to be loaded with strain due to expansion and contraction of other ceramic layers, and more efficient driving force can be output.

Further, in the displacement element shown in FIG. 1, since the displacement element is of a laminated type, the total thickness of the ceramic plates can be easily increased in order to reduce the displacement due to the load (F) when zero volts are applied. Here, the magnitude of displacement (δ1) due to the load (F) when zero volts are applied is said to be proportional to the −3 power of the total plate thickness (T). That is, δ, -A-T'' Here, A is a constant. Therefore, by increasing the total plate thickness (T), the above displacement can be reduced. Conversely, the total thickness of the ceramic plate Even if we hold constant
Alternatively, even if it is made smaller, it becomes possible to reduce the thickness of each ceramic plate, and even if the drive voltage is low, the magnitude of the electric field applied to each ceramic plate can be sufficiently increased. Therefore, the displacement under no load can be increased.

Furthermore, by stacking ceramic plates with different thicknesses, compared to displacement elements made of ceramics with the same thickness,
The no-load displacement can be made larger for the same applied voltage. This is because, as mentioned above, the distortions of the ceramic plates of each layer are effectively combined and output.

FIG. 2 shows the structure of a laminated displacement element according to another embodiment of the present invention. The displacement element shown in the figure has ceramic layers 9, 11, 13 of different thickness on the shim 1, similar to the element shown in FIG.
was formed. However, instead of bonding ceramic plates with electrodes together as in the device shown in FIG. 1, the device is formed by creating a laminate with internal electrodes 15 provided so that each plate has a different thickness and sintering this. are doing. Therefore, in the structure of FIG. 2, palladium (Pd), for example, is used as the internal electrode 15. still,
The external electrode 3 is made of silver (Ag), for example.

It is clear that the displacement element shown in FIG. 2 also operates in the same way as the displacement element shown in FIG. 1, and the same effects can be obtained. Furthermore, in the structure shown in FIG. 2, it is possible to easily obtain a multilayer ceramic structure having a strong structure without requiring the labor of bonding a plurality of ceramic plates with electrodes.

FIG. 3 shows the structure of a laminated displacement element according to still another embodiment of the present invention. In the figure, each ceramic plate 7
For example, the plate thicknesses of the elements may be the same, and the structure may be the same as that of the element shown in FIG. However, in the device shown in FIG. 3, the voltage applied to each ceramic layer 7 is increased to the ceramic plate farther from the shim 1. That is, in FIG. 3, the voltage v2 applied to the ceramic plate 7 adjacent to the shim 1
The voltage v3 applied to the ceramic plate provided on the ceramic plate is made larger than this, and furthermore, the voltage v3 applied to the ceramic plate 7 furthest from the shim 1 is larger than this voltage v3. It's getting bigger. This results in
The strength of the electric field applied to each ceramic layer 7 can be reduced for ceramic layers close to the shim 1 and increased for ceramic layers far from the shim 1. Therefore, similar to the device shown in FIG. 1 or 2, the strain in the ceramic layers far from the shim 1 increases, and the strain in each ceramic layer is transmitted to the shim 1 very efficiently. Therefore, the displacement element shown in FIG. 3 can also achieve the same effect as the displacement element shown in FIG. 1 or 2.

In each of the above embodiments, a so-called unimorph type displacement element using a plurality of ceramic layers has been described, but the present invention is not limited to such a unimorph type element, but can also be applied to a laminated bimorph type element. It is applicable. However, in the case of a bimorph element, a voltage in the same direction as during polarization is applied to the ceramic layer on one side of the shim, and a voltage in the opposite direction is applied to the ceramic layer on the other side. However, if the magnitude of this applied voltage becomes a reverse voltage that exceeds one-half of the polarization process, there is a risk that the polarization will be destroyed. For this reason, in the case of a bimorph element, a very large voltage cannot be applied, and therefore there is a limit to the voltage that can be applied to obtain a large displacement. On the other hand, in the case of a unimorph type element, only a voltage in the same direction as that during the polarization process is applied, so there is no restriction on the applied voltage, and a voltage up to the dielectric breakdown voltage can be applied. Therefore, in this case, it is possible to increase the no-load displacement,
Furthermore, the thickness of the ceramic plate can be made thicker, so there are fewer restrictions on usage.

Next, the results of actually fabricating devices and measuring their characteristics for the devices of the above-mentioned Examples and Conventional Examples are shown below as specific examples and comparative examples.

(Specific Example 1) Three piezoelectric ceramic plates each having a width of 30+m and a length of 60Il1m were produced using a normal method. The thickness of each ceramic plate is
They were set to 0.18 mm, 0.23 mm, and 0.28 mm, respectively. Silver electrodes were provided on both sides of each of these ceramic plates, and polarization treatment was performed on each of them. These ceramic plates with electrodes are arranged in order from the thickest plate to 3-0 mm wide, 65 mm long,
A unimorph type element having the structure shown in FIG. 1 was produced by adhering it to a metal (Kovar) plate with a thickness of 0.1 m+s using a commercially available UV curing resin. Regarding this unimorph type element,
The following items were measured. In other words, the effective length is 5
(1) Displacement (δ1) at applied voltage Ov1 load 70 g, (2) Displacement when load OK and 200 V applied (
δ. ), and (3) the displacement (δ) in the case of a load of 70 g and an applied voltage of 200 V was determined by DI.

The results of these measurements are shown in Table 1.

(Specific example 2) Width 3011111 after sintering by normal method. length 60m
m thickness is 0. 18111% 0.23ra■
, so that it is 0.28 dragon, and the width is 30 degrees and the length is 60.
mm.

A green laminate containing palladium internal electrodes with a thickness of 0.04 m+e was produced. This was sintered using a conventional method and subjected to polarization treatment. Then, the same metal plate as in Example 1 was adhered by the same method to the thick ceramic layer side of the piezoelectric ceramic separated by the internal electrodes, and a laminated displacement element having the same structure as that shown in FIG. 2 was manufactured. Regarding this element, measurements were performed on the same items and in the same manner as in the above-mentioned specific example. The first measurement result is
Shown in the table.

(Specific Example 3) Furthermore, the following items were similarly measured for the unimorph type element shown in FIG. That is, assuming that the effective length is 50 mm, (1) displacement (δl) at applied voltage OV and load 70 g, (2) load Og, V2-160 V,
Displacement (δo) when applying V3-200V, V4-240V
, and (3) load 70g, V2-160V, V3-2
00V.

The displacement (δ) when V4-240V was applied was measured.

The measurement results are shown in Table 2 together with the measurement results of Comparative Example 1 (Table 1) below.

(Comparative Example 1) Width: 30 mm, length: 60 mm, thickness: 0°2
I made three piezoelectric ceramic plates of 311I11. From these three ceramic plates and a metal (Kovar) plate with a width of 30 mm, a length of 65 m+s, and a thickness of 0.1 mm, a unimorph type displacement element having the structure shown in FIG. was produced. Regarding this element, the same items as in Specific Example 1 were measured using the same method. The measurement results are shown in Table 1.

(Comparative Example 2) Width: 30 mm, length: 60 mm, thickness: 0°69
One mm piezoelectric ceramic plate was produced. A unimorph type element having the structure shown in FIG. 4 was produced using the same method as in Example 1 from the ceramic plate and the same metal (Kovar) plate as in the comparative example. Regarding this unimorph type element, the same items as in Example 1 were measured using the same method, and the measurement results are shown in Table 1.

As is clear from Table 1, the device of Comparative Example 1 is the same as that of Comparative Example 2.
Compared to the element shown in FIG. On the other hand, the elements of Specific Examples 1 and 2 according to the present invention have a further no-load displacement (δ0
) and displacement under load (δ) are large,
It can be seen that high output can be obtained even if the applied voltage is the same. Furthermore, as is clear from Table 2, the element of Specific Example 3 also has very large displacements under no load (δ) and displacements under load (δ) compared to the element of Comparative Example 1. I know it's impossible.

[Effects of the Invention] As described above, according to the present invention, even if a plurality of ceramic plates are laminated, the strain of each ceramic plate is effectively synthesized. This makes it possible to increase the total thickness of the ceramic plate, and to reduce displacement due to load when no voltage is applied. In addition, since the electric field strength was increased for the ceramic layers far from the shim, the displacement under no load and the displacement under load when the applied voltage was the same compared to when the same electric field was applied to each ceramic layer. The displacement can be made larger. Furthermore, by using a laminated type, the magnitude of the electric field applied to each ceramic plate can be made larger than in the case of a single ceramic plate even if the total thickness of the ceramic plates is the same. This also makes it possible to increase the displacement when no load is applied and the displacement when a load is applied, as described above. Furthermore, in the case of a unimorph type element, since no voltage is applied in the opposite direction to that during the polarization process, the polarization will not be destroyed even if the applied voltage is increased, and therefore no deterioration in displacement will occur.

[Brief explanation of the drawing]

FIGS. 1, 2, and 3 are explanatory diagrams showing the structure of a laminated displacement element according to an embodiment of the present invention, and FIGS. 4 and 5 are explanatory diagrams showing the structure of a conventional displacement element, respectively. FIG. 1: Shim, 3: Electrode, 5.7, 9.11, 13: Ceramic layer, 15: Internal electrode.

Claims (1)

[Claims] 1. A plurality of ceramic layers added on a shim, and an electrode for applying an electric field to the ceramic layers, the strength of the electric field applied by the shim to the distant ceramic layer is controlled by the A laminated displacement element characterized in that the strength of the electric field is greater than the strength of the electric field applied to the ceramic layer closer to the shim. 2. A plurality of ceramic layers added on a shim and an electrode for applying an electric field to the ceramic layers are provided, and the thickness of the ceramic layer farther from the shim is made thinner than the thickness of the ceramic layer closer to the shim. A laminated displacement element characterized by the following.