JP2012019178A - Piezoelectric element and piezoelectric element manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric element having higher durability.SOLUTION: A piezoelectric element 1 includes two or more first regions 3 whose shapes change when a voltage is applied and a second region 5 whose variation of the shape when the voltage is applied is less than the variation of the shape of the first region 3 when the voltage is applied. The second region 5 is laminated so that it is positioned between the first regions 3. The first regions 3 are formed of a ceramic material sandwiched between a positive electrode and a negative electrode. The second region 5 is formed of a ceramic material sandwiched between electrodes of the same polarity.

Description

  The present invention relates to a piezoelectric element.

A piezoelectric element that deforms in accordance with the magnitude of a voltage to be applied is known.
For example, the following Patent Document 1 discloses a piezoelectric actuator having a pair of external electrodes with different polarities on the side surface, in which a plurality of piezoelectric bodies and internal electrode layers are stacked, and external electrodes connected to each internal electrode layer. A piezoelectric actuator is disclosed that is made so that the polarity is different for each layer. In this piezoelectric actuator, it is necessary to separate the internal electrode connected to one external electrode and the other external electrode. There is a region that does not deform (no potential difference occurs).

JP 2005-5680 A

However, the piezoelectric actuator of the type disclosed in Patent Document 1 has a problem that it easily breaks because, for example, pressure is applied to a boundary portion between a deforming region and a non-deforming region of the piezoelectric body.
An object of this invention is to provide a highly durable piezoelectric element.

  The piezoelectric element of the present invention includes two or more first regions whose shape changes when a voltage is applied, and a second region whose shape change amount is smaller than the first region. The one region and the second region are stacked such that the second region is located between the first regions.

In an embodiment of the present invention, the second region can be formed by laminating an inactive layer whose shape does not change even when a voltage is applied to the piezoelectric element.
In another embodiment, each of the second regions is preferably formed to a thickness of 3% or more of the thickness of the piezoelectric element. The thickness of the piezoelectric element refers to the length in the direction in which the first and second regions are stacked.
In another embodiment, it is more preferable that each of the second regions has a thickness of 4% or more of the thickness of the piezoelectric element.

In another embodiment, the second region is provided so as to divide the piezoelectric element into two equal parts, three equal parts, or four equal parts.
The piezoelectric element of the present invention includes two or more first regions whose shape changes when a voltage is applied, a second region whose shape change amount is smaller than the first region, and the second region is the first region. It is made by laminating | stacking so that it may be located between 1 area | regions, It is characterized by the above-mentioned.

  The piezoelectric element manufacturing method of the present invention includes two or more first regions whose shapes change when a voltage is applied, and a second region whose shape change amount is smaller than the first region. A piezoelectric element is formed by stacking so as to be positioned between the first regions.

  According to the present invention, by providing a second region in the piezoelectric element whose shape change amount is smaller than the first region, physical damage based on the shape change caused when a voltage is applied to the piezoelectric element is prevented. Since it can be reduced, higher durability can be realized as compared with a conventional piezoelectric element having no region corresponding to the second region.

(A) is a figure which shows typically the piezoelectric element of embodiment, (B) is a figure which expands and shows a part of piezoelectric element of embodiment. It is a figure which shows the example of the waveform measured with the impedance analyzer. It is a figure which shows the structure and test result of Example 1, Example 2, and Comparative Example 1, respectively. It is a figure which shows each structure and test result of the comparative example 2, Example 3, and Example 4. FIG. It is a figure which shows the structure and test result of each of Examples 5-11. It is a figure which shows the deformation amount at the time of the voltage application about the piezoelectric element of 4 division structure.

Hereinafter, a piezoelectric element 1 according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1A schematically shows the piezoelectric element 1, and FIG. 1B shows an enlarged part of the piezoelectric element 1.
As shown in FIG. 1A, the piezoelectric element 1 includes two or more first regions 3 whose shape changes by applying a voltage, and a second amount whose shape change amount is smaller than the first region 3. The first region 3 and the second region 5 are stacked so that the second region 5 is located between the first regions 3.
As shown in FIG. 1B, the first region 3 includes either the internal electrode 7a or the internal electrode 7b and the internal electrodes 7a and 7b so that the internal electrodes 7a and 7b having different polarities are alternately stacked. A piezoelectric body (for example, piezoelectric ceramics) 11 having external electrodes 9a and 9b connected to each other is overlapped. For example, the piezoelectric bodies 11 are all made with the same thickness (for example, 100 μm thickness).

The internal electrodes 7a and 7b and the external electrodes 9a and 9b can be formed on the surface of the piezoelectric body 11 using a printing technique. Also, for example, in the example of FIG. 1B, the left external electrode 9a and the internal electrode 7a connected to the external electrode 9a are used as the positive electrode, and the right external electrode 9b and the internal connected to the external electrode 9b. The electrode 7b is a negative electrode.
More specifically, as shown in FIG. 1 (B), the internal electrodes 7a and 7b are arranged so as not to contact the external electrodes 9b and 9a having different polarities when the piezoelectric bodies 11 are overlapped. It is formed on the surface of the piezoelectric member 11 so as to be separated from the end of the piezoelectric member 11. For example, the positive internal electrode 7a is separated from the right end (right end in the figure) of the piezoelectric body 11 so as not to contact the negative external electrode 9b when the piezoelectric bodies 11 are overlapped. In addition, the formation method of this 1st area | region 3 is the same as the manufacturing method of the conventional piezoelectric element.

The second region 5 has a smaller amount of change in shape than the first region 3, and is a region for alleviating damage based on a change in shape (for example, expansion) when a voltage is applied to the piezoelectric element 1, for example, a piezoelectric element. 1 is formed by laminating an inactive layer 13 whose shape does not change even when a voltage is applied to 1. By providing the second region 5 in the piezoelectric element 1, even when a voltage is applied to the piezoelectric element 1 and each piezoelectric element 11 is deformed, physical damage is reduced as shown in the test results described later. Can do.
As the inactive layer 13 forming the second region 5, for example, the same material as that of the piezoelectric body 11 can be used. In the illustrated example, the second region 5 is formed using a piezoelectric body. However, unlike the first region 3, the second region 5 does not have an internal electrode on its upper surface. Further, as shown in FIG. 1B, the first region 3 is formed such that internal electrodes having the same polarity (internal electrode 7a in the figure) are respectively disposed at the upper end and the lower end of the second region 5. Has been. Accordingly, the piezoelectric body (second region 5) disposed between the internal electrodes 7a having the same polarity is not affected by the voltage even when a voltage is applied to the piezoelectric element 1 (no voltage is applied). The shape does not change.

  In the example of FIG. 1A, the second region 5 is formed at three locations so as to divide the piezoelectric element 1 into four parts (for example, equally divided into four). Thickness (in the figure, the thickness in the vertical direction, which can also be called the pitch between the second regions 5) D1, the number of divisions of the piezoelectric element 1 (the number of the first regions 3), and the thickness of each of the second regions 5 Various parameters such as D2 (thickness in the vertical direction in the figure) can be appropriately changed. More preferable parameter setting values will be described later with reference to examples and test results.

  As described in the above embodiment, a voltage is applied to the piezoelectric element 1 by stacking the first region 3 and the second region 5 so that the second region 5 is located between the first regions 3. Even if the first region 3 is deformed when it is applied, the second region 5 reduces physical wear and the excellent effect that the durability of the piezoelectric element 1 is increased can be obtained.

Hereinafter, the present invention will be described in detail with reference to specific examples, comparative examples, and test results.
[Test method]
The following test was implemented with respect to the Example and comparative example of the piezoelectric element.
(1) A constant voltage (70 to 200 V) is applied for 3 seconds using a DC power supply (KENWOOD PA500-0.1A).
(2) The waveform is checked with an impedance analyzer (hp 4294A) every time the voltage application for 3 seconds is completed, and if no waveform abnormality is recognized, it is accepted and the waveform abnormality (for example, a portion surrounded by a broken line in FIG. 2) )), It is presumed that microcracks (destruction) have occurred, and is rejected.

FIG. 3 shows the configurations and test results of Example 1, Example 2, and Comparative Example of the piezoelectric element. This test was performed to verify the effect of providing an inactive layer in the piezoelectric element and the effect of increasing the total thickness of the inactive layer (thickness D2 of the second region 5).
First, the configurations of Example 1, Example 2, and Comparative Example will be described.
[Example 1]
(1) Total length = 10 mm,
(2) Number of divisions (number of first regions 3) = 2 (having one second region 5),
(3) Piezoelectric thickness = 100 μm,
(4) Total thickness of inactive layer 13 (thickness of second region 5) D2 = 400 μm (for example, 100 μm × 4 layers),
(5) Number of specimens = 10,
(6) Applied voltage = 70V, 100V, 120V, 150V.

[Example 2]
(1) Total length = 10 mm,
(2) Number of divisions (number of first regions 3) = 2 (having one second region 5),
(3) Piezoelectric thickness = 100 μm,
(4) Total thickness of inert layer 13 (thickness of second region 5) D2 = 800 μm (for example, 100 μm × 8 layers),
(5) Number of specimens = 10,
(6) Applied voltage = 70V, 100V, 120V, 150V.

[Comparative example]
(1) Total length = 10 mm,
(2) Number of divisions (number of first regions 3) = 1 (no second region 5),
(3) Piezoelectric thickness = 100 μm,
(4) Number of specimens = 10,
(5) Applied voltage = 70V, 80V, 90V, 100V, 110V, 120V.

According to the test results shown in FIG. 3, half of the piezoelectric element of Comparative Example 1 (conventional piezoelectric element) that does not have any inactive layer is broken when 80V is applied and can withstand 120V. You can see that there is nothing. The piezoelectric element of Comparative Example 1 shows a pass rate of 90% with respect to a voltage application of 70 V. Therefore, in consideration of the possibility of a sudden increase in voltage, the piezoelectric element is under a low voltage of about 50 V at most. It seems to be the limit to use.
On the other hand, each of the piezoelectric elements of Example 1 and Example 2 having an inactive layer has a pass rate of 90% with respect to a voltage application of 100 V, which is clearly higher than that of the piezoelectric element of the comparative example. It can be seen that it is highly durable against material damage (which is sometimes caused by deformations). Furthermore, when a voltage of 150 V is applied, the pass rate of the piezoelectric element of Example 1 is 50%, whereas the pass rate of the piezoelectric element of Example 2 is 80%.
By this test, the tendency that durability of a piezoelectric element increases by providing an inert layer in a piezoelectric element was confirmed. Further, it was confirmed that the durability of the piezoelectric element was further increased by increasing the total thickness of the inert layers (thickness of the second region 5).
FIG. 4 shows the configuration and test results of Comparative Example 2 (Example 1), Example 3, and Example 4 of the piezoelectric element. This test was conducted to verify the effect of increasing the number of second regions 5. The configuration and test results of Comparative Example 2 (Example 1) are the same as those described with reference to FIG.

First, the configurations of the third and fourth embodiments will be described.
[Example 3]
(1) Total length = 10 mm,
(2) Number of divisions (number of first regions 3) = 3 (having two second regions 5),
(3) Piezoelectric thickness = 100 μm,
(4) Total thickness of inactive layer 13 (thickness of second region 5) D2 = 400 μm (for example, 100 μm × 4 layers),
(5) Number of specimens = 10,
(6) Applied voltage = 100V, 120V, 150V, 200V.

[Example 4]
(1) Total length = 10 mm,
(2) Number of divisions (number of first regions 3) = 4 (having three second regions 5),
(3) Piezoelectric thickness = 100 μm,
(4) Total thickness of inactive layer 13 (thickness of second region 5) D2 = 400 μm (for example, 100 μm × 4 layers),
(5) Number of specimens = 10,
(6) Applied voltage = 100V, 120V, 150V, 200V.

  According to the test results shown in FIG. 4, the pass rate when a voltage of 150V is applied is 50% for the comparative example (Example 1), 80% for Example 3, and 100% for Example 4, and 200V. The pass rate when the voltage is applied is 70% in Example 3 and 100% in Example 4. From this test, it was confirmed that the durability of the piezoelectric element was further increased by increasing the number of the second regions 5.

FIG. 5 shows configurations and test results of Examples 5 to 11 of the piezoelectric element. In this test, it was confirmed in the test results shown in FIG. 3 that the durability of the two-part piezoelectric element increases as the thickness of the second region 5 increases. The piezoelectric element having a four-part configuration that showed the best results in the test shown was performed in order to verify the relationship between the total thickness of the inactive layer (the thickness of the second region 5) D2 and the durability. Specifically, the total thickness D2 of the inactive layer was set to 100 μm, 200 μm, 300 μm, or 400 μm, and the polarization voltage was set to 1.0 kV / mm or 1.5 kV / mm. In this test, unlike the tests in FIGS. 3 and 4, polarization was first performed, and the waveform after polarization was also confirmed by an impedance analyzer.
According to the test results shown in FIG. 5, when a polarization voltage of 1.5 kV / mm is applied, the pass rate after polarization is not high, but when a polarization voltage of 1.0 kv / mm is applied. The pass rate after polarization is 100% in all cases except Example 9 (90%). Moreover, the pass rate when a voltage of 150 V is applied is 70% in Example 9, and 100% in Example 11, and the pass rate when a voltage of 200 V is applied is 20% in Example 9. Example 11 is 100%. By this test, the tendency of increasing the durability of the piezoelectric element by increasing the thickness D2 of the second region 5 was confirmed more clearly. Moreover, according to the structure of Example 11, it can endure the voltage of 150-200V, Therefore It can utilize in the environment where the voltage of 100-150V can be applied at normal time.

FIG. 6 shows the amount of deformation when a voltage is applied to the piezoelectric element 1 having a four-part configuration. Six types of patterns were prepared for combinations of the thickness D2 of the second region 5 and the polarization voltage. As shown in this figure, it was confirmed that the deformation amount when a voltage was applied to the piezoelectric element 1 was almost the same even when the thickness D2 of the second region 5 was changed.
As described above, according to the piezoelectric element 1 of the embodiment, the two or more first regions 3 whose shape changes when a voltage is applied, and the second amount whose shape change amount is smaller than the first region 3. By laminating the region 5 so that the second region 5 is located between the first regions 3, it is more resistant to physical damage due to deformation during voltage application than the conventional piezoelectric element. High durability can be obtained.
More specifically, based on the test results described above, the second region 5 is formed to have a thickness of 3% or more, more preferably 4% or more of the thickness of the piezoelectric element 1, respectively. It can be said that the durability tends to be higher. Further, by providing the second region 5 so as to divide the piezoelectric element 1 into three equal parts, more preferably into four equal parts, it is possible to obtain higher durability.
Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above and can be applied in various modifications.

[Modification]
For example, in the embodiment, as the inactive layer 13 that forms the second region 5, the same material as that of the piezoelectric body 11 that forms the first region 3 is used. Any material that is smaller than the first region 3 can be used. Alternatively, a material that does not deform (expand) even when a voltage is applied may be used as the inactive layer 13.

  DESCRIPTION OF SYMBOLS 1 ... Piezoelectric element, 3 ... 1st area | region, 5 ... 2nd area | region, 7a, 7b ... Internal electrode, 9a, 9b ... External electrode, 11 ... Piezoelectric body, 13 ... Inactive layer

Claims (8)

Two or more first regions whose shapes change by applying a voltage;
A second region whose shape change amount is smaller than the first region;
The piezoelectric element is characterized in that the first region and the second region are stacked such that the second region is located between the first regions.   The piezoelectric element according to claim 1, wherein the second region is formed by laminating an inactive layer whose shape does not change even when a voltage is applied to the piezoelectric element. The first region is made of a ceramic material sandwiched between a positive electrode and a negative electrode,
The piezoelectric element according to claim 2, wherein the second region is made of a ceramic material sandwiched between electrodes of the same polarity.   3. The piezoelectric element according to claim 1, wherein each of the second regions has a thickness of 3% or more of the thickness of the piezoelectric element.   3. The piezoelectric element according to claim 1, wherein each of the second regions has a thickness of 4% or more of the thickness of the piezoelectric element.   6. The piezoelectric element according to claim 4, wherein the second region is provided so as to divide the piezoelectric element into two equal parts, three equal parts, or four equal parts.   Two or more first regions whose shape changes when a voltage is applied, and a second region whose shape change amount is smaller than the first region, and the second region is located between the first regions. A piezoelectric element characterized by being made by laminating so as to.   Two or more first regions whose shape changes when a voltage is applied, and a second region whose shape change amount is smaller than the first region, and the second region is located between the first regions. A piezoelectric element manufacturing method, characterized in that a piezoelectric element is formed by laminating in such a manner.

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