JPH09148647A - Polarizing method and polarizing equipment of piezoelectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain a current due to charges stored in other piezoelectric elements from instantaneously flowing in a dielectric-brokendown piezoelectric element, at the time of dielectric breakdown of at least the piezoelectric element, by using a suppressing means for restraining instantaneous current flow, between a power supply and the respective piezoelectric elements. SOLUTION: A plurality of piezoelectric elements 1 (1A, 1B, 1C, 1D...1K) are held in parallel in a piezoelectric element holder 2. A plurality of the elements 1 have basically the same capability, and further a power supply 3 for applying a DC voltage is installed. The respective elements 1 are connected in parallel with the power supply 3, through lead wires 3a, 3b. Resistors 4 for restraining instantaneous current flow are connected between the power supply 3 and the respective elements 1, so that the number of the resistor 4 is equal to that of the elements 1. When the resistors 4 are connected with the positive side or the negative side of the power supply 3, the same action and effect can be obtained. Each of the resistors 4 and each of the elements 1 are electrically connected in series.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric body polarization method and polarization device. The present invention includes, for example, PbZrO ₃ P
It can be used to polarize a PZT-based piezoelectric body containing bTiO ₃ as a main component, but is not limited to this and can be widely applied to piezoelectric bodies in general.

[0002]

2. Description of the Related Art Piezoelectric materials must be polarized in order to obtain the required piezoelectric characteristics. For polarization, as shown in FIG. 7, a technique of electrically connecting a power supply 100 capable of applying a DC voltage and the piezoelectric body 200 and applying a DC voltage to the piezoelectric body 200 is adopted. However, according to this technique, the piezoelectric bodies 200 are polarized one by one, which is not sufficient in terms of productivity.

Conventionally, in Japanese Unexamined Patent Publication No. 6-77550, a half-ring split electrode film is formed on one surface of a disk-shaped piezoelectric body, and a ring-shaped full-area electrode film is formed on the other surface of the piezoelectric body. However, there is disclosed a technique in which one surface and the other surface are laminated differently from each other, and the divided electrode films are made conductive in the stacking direction, and the polarization is performed in a state where the entire surface electrode films are made conductive.

Further, conventionally, as shown in FIG. 8, a technique has been developed in which a plurality of piezoelectric bodies 200 are electrically connected in parallel to a power source 100 and a DC voltage is applied to each piezoelectric body 200. According to this method, a plurality of piezoelectric bodies 200 can be collectively polarized at the same time.

[0005]

However, as shown in FIG. 8, according to the polarization technique in which a plurality of piezoelectric bodies 200 are electrically connected in parallel to the power source 100 to polarize, the piezoelectric bodies 200 can be formed.
Dielectric breakdown easily occurs, and the polarization yield is not sufficient. The reason is that when dielectric breakdown occurs in one piezoelectric body 200, dielectric breakdown is easily induced in the other piezoelectric bodies 200.

The reason why the dielectric breakdown is induced in other piezoelectric bodies is that when a dielectric breakdown, that is, a short circuit occurs in a certain piezoelectric body, a large current instantaneously flows through the dielectric breakdown body and the voltage drops. When the voltage drops below a certain value, the short-circuited piezoelectric body becomes insulating again, and at that moment, the voltage of the other piezoelectric body rises sharply and exceeds the breakdown voltage, causing dielectric breakdown in the other piezoelectric body. It is considered that it is done. Piezoelectric body 10
This is because 0 is also a dielectric material and is electrically charged.

It is also conceivable that the rest of the piezoelectric bodies may cause dielectric breakdown due to the expansion and contraction of the piezoelectric bodies due to the abrupt voltage change described above. Note that FIG. 9 schematically shows the waveform of the terminal voltage of the piezoelectric body observed with an oscilloscope when dielectric breakdown occurs, and the peak Pa indicates a short circuit,
The trigger pulse-like peak Pb shows a rapid voltage increase.

According to the above-mentioned polarization method, there is a problem that dielectric breakdown of the piezoelectric body is likely to be induced and the polarization yield is not always sufficient. The present invention has been made in view of the above problems, and by using the suppressing means for suppressing the instantaneous flow of current, it is advantageous to reduce or avoid the induction of dielectric breakdown in other piezoelectric bodies. Therefore, it is an object of the present invention to provide a piezoelectric body polarization method and polarization device which are advantageous in improving the polarization yield.

[0009]

The inventor of the present invention has made extensive efforts to develop polarization of a piezoelectric body, and a plurality of piezoelectric bodies are electrically connected in parallel to a power source for applying a DC voltage to obtain a DC voltage. By applying a suppressor to suppress the instantaneous flow of current between the power source and the piezoelectric body when applying and polarization to each piezoelectric body, it is possible to reduce the induction of dielectric breakdown in other piezoelectric bodies. The inventors have found that it can be avoided and that the yield of polarization is improved, and confirmed by a test to develop the method of the present invention and the apparatus of the present invention.

That is, the piezoelectric body polarization method according to the present invention is such that a plurality of piezoelectric bodies are electrically connected in parallel to a power source for applying a direct current voltage, and a direct current voltage is applied to each piezoelectric body. Is a method of polarizing the piezoelectric element, and by using a suppressing means for suppressing the instantaneous flow of current between the power source and each piezoelectric body, at the time of dielectric breakdown of at least one piezoelectric body The present invention is characterized in that the current based on the accumulated charges is instantaneously suppressed from flowing into the dielectric breakdown piezoelectric body.

In the piezoelectric polarization device according to the present invention, a plurality of piezoelectric bodies are arranged side by side, and a piezoelectric body holding portion for electrically connecting the piezoelectric bodies in parallel to a power source capable of applying a DC voltage. And a suppression unit that is provided between the piezoelectric body holding unit and the power supply and that suppresses instantaneous flow of current to the piezoelectric body that has undergone dielectric breakdown when at least one piezoelectric body undergoes dielectric breakdown. It is what

[0012]

DETAILED DESCRIPTION OF THE INVENTION A first embodiment according to the present invention will be described. (First Embodiment) FIG. 1 schematically shows the first embodiment.
The piezoelectric body 1 is a ceramics piezoelectric body, specifically a PZT system, and has a disk shape. Electrode films are laminated on both surfaces of the piezoelectric body 1 in the thickness direction. The electrode film can be generally formed by coating / baking a silver paste, electroless plating of nickel, or the like.

As can be understood from FIG. 1, a plurality of piezoelectric bodies 1 (1A, 1B, 1C, 1D ... 1K) are arranged and held in parallel with a piezoelectric body holding portion 2. Basically, the plurality of piezoelectric bodies 1 have the same ability and exhibit the same piezoelectric characteristics. Further, a power supply 3 for applying a DC voltage is provided. Each piezoelectric body 1 is electrically connected in parallel to the power source 3 via the conductive wires 3a and 3b.

Further, a resistor 4 is connected between the power source 3 and each piezoelectric body 1 as a suppressing means for suppressing the instantaneous flow of current. Therefore, the number of piezoelectric bodies 1 and the number of resistors 4 are the same. As can be understood from FIG. 1, the resistor 4 is connected to the positive electrode side of the power source 3, but the same action and effect can be obtained by connecting it to the negative electrode side. The resistor 4 and the piezoelectric body 1 are electrically connected in series with each other.

When the piezoelectric body 1 is polarized, the switch 3x is turned on and a predetermined DC voltage (for example, about 3 to 5 kV / mm) higher than the coercive electric field is applied to each piezoelectric body 1 for a predetermined time. Thereby, the polarization process of each piezoelectric body 1 is executed in a predetermined atmosphere. The application time can be about 2 to 30 minutes. As the atmosphere, silicone oil of about 100 to 200 ° C. can be adopted.

By the way, for some reason, dielectric breakdown may occur in any one of the plurality of piezoelectric bodies 1 and the piezoelectric body 1 may be short-circuited. For example, assume that the piezoelectric body 1K is short-circuited due to dielectric breakdown. Then, the short-circuited piezoelectric body 1K
The electric charges charged in the piezoelectric bodies 1 (1A, 1B, 1C, 1D ...) Other than the above instantly move to the short-circuited piezoelectric body 1K. That is, a large current is about to flow in the short-circuited piezoelectric body 1K. At this time, according to the present embodiment, since the resistor 4 is connected, it is possible to prevent a large amount of electric charge from instantaneously moving to the piezoelectric body 1K that has undergone dielectric breakdown. That is, it is possible to prevent a large current from flowing through the piezoelectric body 1K that has undergone insulation breakdown.

As a result, even if dielectric breakdown occurs in any one of the piezoelectric bodies 1, the induction of dielectric breakdown in the remaining other piezoelectric bodies 1 is reduced and avoided. (Test Example) A polarization test was performed based on the first embodiment described above. In this polarization test, a PZT element (outer diameter: 15 mm, wall thickness: 0.35 mm, capacitance:
7.5 to 8.3 nF, resonance resistance 4:20 to 30 Ω), a high-voltage DC stabilized power supply (PHS35K-3, manufactured by Kikusui Electronics Co., Ltd.) as a power supply 3, and a silicon oil bath atmosphere at 150 ° C. , The piezoelectric body 1 was polarized.

According to the above polarization test, the piezoelectric body 1 has 1 to 1
In the case of 0 pieces, 100% could be polarized satisfactorily and it was a good product. When the number of piezoelectric bodies 1 was 20, it was 100%, and when it was 40, it was 99% good. In case of 80 pieces, 9 are good products
9%. Further, as a comparative example, the polarization treatment was performed in the case where the resistor 4 was not connected, although the conditions were basically the same as those of the configuration shown in FIG. In the comparative example, when the number of the piezoelectric bodies 1 was 1 to 10, it was possible to polarize 100% satisfactorily and it was a good product, but when the number of the piezoelectric bodies 1 was 20, it was 90%.
In the case of 40 pieces, only 50% were non-defective. In the case of 80 pieces, the quality was 0%. 1st according to this test result
According to the embodiment, the remaining piezoelectric bodies 1 (1A, 1B, 1
It can be seen that the dielectric breakdown induced in C, 1D ...) can be reduced and avoided, and the polarization yield is improved.

(Second Embodiment) FIG. 2 schematically shows the second embodiment. The second embodiment has the same configuration as that of the above-described first embodiment and has the same operation and effect. The piezoelectric body 1 used in this embodiment is of the same type as that used in the first embodiment. Also in the second embodiment, as can be understood from FIG. 2, the power supply 3 for applying the DC voltage is provided. Then, the respective piezoelectric bodies 1 are electrically connected in parallel to the power source 3 via conducting wires 3a and 3b. Further, a coil 5 is connected between the power source 3 and each piezoelectric body 1 as a suppressing means for suppressing an instantaneous current flow. As can be understood from FIG. 1, the coil 5 and the piezoelectric body 1 are electrically connected to each other in series. Although the coil 5 is connected to the positive electrode side of the power source 3, the same action and effect can be obtained by connecting it to the negative electrode side.

When the piezoelectric body 1 is polarized, the switch 3x is turned on in the same manner as described above, and a DC voltage equal to or higher than the coercive electric field is applied to each piezoelectric body 1 for a predetermined time. Thereby, the polarization process of each piezoelectric body 1 is executed. However, due to some circumstances, one of the plurality of piezoelectric bodies 1 may suffer a dielectric breakdown, causing the piezoelectric body 1 to be short-circuited. For example, assume that the piezoelectric body 1K is short-circuited. Then, the piezoelectric body 1 (1
The electric charges that have been charged in A, 1B, 1C, 1D ...) Instantly move to the short-circuited piezoelectric body 1K. That is, a large current is about to flow in the piezoelectric body 1K that has undergone insulation breakdown. At this time, since the coil 5 is connected, the instantaneous movement of a large amount of charges, that is, the flow of a large current is suppressed.

This is because the counter electromotive force is generated in the coil 5 by self-induction in the direction in which the current change is prevented. Here, when the induced counter electromotive force is e and the inductance of the coil 5 is L, it is basically expressed by e = -L (dI / dt).
It should be noted that (dI / dt) means the amount of change over time of the charge, that is, the amount of change in the current. Therefore, also in the second embodiment,
Even if dielectric breakdown occurs in any one of the piezoelectric bodies 1, it is possible to prevent a large current from instantaneously flowing to the piezoelectric body 1 that has undergone dielectric breakdown. As a result, it is possible to reduce or avoid the induction of dielectric breakdown in the other piezoelectric body 1, and it is possible to improve the yield during polarization.

(Third Embodiment) FIG. 3 schematically shows a third embodiment. The third embodiment has the same configuration as that of the above-described first embodiment and has the same operation and effect. The piezoelectric body 1 used in this embodiment is of the same type as that used in the first embodiment. In the third embodiment as well, as can be understood from FIG. 3, the power supply 3 for applying the DC voltage is provided. Then, the respective piezoelectric bodies 1 are electrically connected in parallel to the power source 3 via conducting wires 3a and 3b. Further, between the power source 3 and each piezoelectric body 1, a resistor 4 and a capacitor 6 (6A, 6B, 6C, 6D) as a suppressing means for suppressing an instantaneous flow of current.
...... 6K) are connected respectively. As can be understood from FIG. 3, the resistor 4 and the capacitor 6 are connected to the positive electrode side of the power source 3, but the same action and effect can be obtained even if they are connected to the negative electrode side. The resistor 4 and the capacitor 6 are electrically parallel to each other. The resistor 4 is electrically connected to the piezoelectric body 1 in series. The capacitor 6 is also electrically in series with the piezoelectric body 1.

When the piezoelectric body 1 is polarized, the switch 3x is turned on and a DC voltage equal to or higher than the coercive electric field is applied to each piezoelectric body 1 for a predetermined time as described above. Thereby, the polarization process of each piezoelectric body 1 is executed. By the way, due to some circumstances, one of the plurality of piezoelectric bodies 1 suffers a dielectric breakdown, and
May short circuit. For example, assume that the piezoelectric body 1K is short-circuited. Then, the piezoelectric body 1 other than the short-circuited piezoelectric body 1K
The electric charges charged in A, 1B, 1C, 1D ... Try to move to the short-circuited piezoelectric body 1 instantly, but at this time,
As in the case of the embodiment, the resistor 4 is connected in series, so that a large amount of electric charge is instantaneously transferred, that is, a large current flows through the short-circuited piezoelectric body 1K.

Further, the electric charge that is about to move to the piezoelectric body 1K is charged in the capacitor 6K, and accordingly, a time delay of the current flow occurs. Therefore, also in the third embodiment, even if dielectric breakdown occurs in the piezoelectric body 1K,
Instantaneous flow of a large current through the piezoelectric body 1K is suppressed. As a result, the remaining other piezoelectric bodies 1 (1A, 1B, 1
Induction of dielectric breakdown in C, 1D ...) can be reduced or avoided, and the polarization yield can be improved.

In the third embodiment, assuming that the capacitance of each capacitor 6 is C1 and the capacitance of each piezoelectric body 1 is C2 (when the piezoelectric body is equivalent to a capacitor), C1 is made larger than C2. It is possible (C1> C2). It takes longer time to charge the capacitor 6 in case of dielectric breakdown,
This is because a time delay is secured and it is advantageous to suppress the instantaneous movement of a large amount of charges.

(Fourth Embodiment) FIG. 4 schematically shows a fourth embodiment. The third embodiment has the same configuration as that of the above-described first embodiment and has the same operation and effect. The piezoelectric body 1 used in this embodiment is of the same type as that used in the first embodiment. In the fourth embodiment, as can be understood from FIG. 4, an appropriate number of piezoelectric body holding portions 2 (for example, 3 to 1).
The piezoelectric bodies 1 of 0 to 20) are grouped together into one group. A resistor 4 is electrically connected in series between the power source 3 and each piezoelectric body holding portion 2.

In this embodiment, since the resistors 4 are connected to each group, it is advantageous to reduce the number of the resistors 4. In addition, according to the test example described above,
Since no dielectric breakdown occurred even if polarization was carried out collectively for about a few pieces, there is no special problem even if the resistors 4 are connected for each group. (Fifth Embodiment) FIGS. 5 and 6 schematically show a fifth embodiment. FIG. 5 is a physical wiring diagram. 6 is a main part of the circuit diagram of FIG. The fifth embodiment has the same configuration as that of the fourth embodiment shown in FIG. 4 and has the same effects. Hereinafter, the different parts will be mainly described.

An appropriate number of piezoelectric body holding portions 2 (for example, 3 to
10 to 20) piezoelectric bodies 1 are collectively held, and a base portion 20 formed of an electrically insulating material, and a base portion 20.
First conductive member 21 formed of a conductive material held by
A second conductive member 22 made of a conductive material held by the base 20, a first terminal portion 23 made of a conductive material held by the first conductive member 21, and a second conductive member 22 The second terminal portion 24 formed of the conductive material and the biasing spring 25 that secures electrical contact with the piezoelectric body 1 are provided.

Each piezoelectric body 1 is sandwiched between the first terminal portion 23 and the second terminal portion 24. The urging spring 25 has an extremely weak urging force of the same level as the spring characteristic under no load. This is to ensure the amount of strain of the piezoelectric body 1 during polarization while ensuring electrical contact. As can be understood from FIGS. 5 and 6, the piezoelectric body holding portion 2 includes an appropriate number of piezoelectric bodies 1.
Are held together as a group. And power supply 3
A variable resistor 4 is electrically connected in series between the and each piezoelectric body holding portion 2. The power supply 3 is controlled by the control 35.

(Others) In the above embodiment, the piezoelectric body 1
Is a PZT type, but a PLZT type and other piezoelectric materials may be used. The coil 5 may be equipped with an iron core to increase the inductance. The capacitor 6 may be a variable capacitance type. In the embodiment shown in FIG. 3, a coil may be used instead of the capacitor 6, and a coil may be used instead of the resistor 4.

(Supplementary Note) The following technical idea can be understood from the above-described embodiments. In Claims 1 and 2, the suppressing means is a resistor, a coil,
A polarization method and a polarization device, which are constituted by at least one of capacitors. In Claims 1 and 2, the suppressing means is a resistor, a coil,
A polarization method and a polarization device which are formed of at least one of capacitors and are electrically connected in series to each piezoelectric body.

[0032]

According to the method of the present invention and the device of the present invention, between the power source for applying a DC voltage to the piezoelectric body and each piezoelectric body,
Since the suppression means for suppressing the instantaneous flow of current is used, even if dielectric breakdown occurs in one piezoelectric body and a short circuit occurs, the electric charge accumulated in the other piezoelectric body is stored in the piezoelectric body subjected to the dielectric breakdown. It is possible to suppress instantaneous movement, that is, a large current instantaneously flowing to the piezoelectric body that has undergone dielectric breakdown. Therefore, it is advantageous in reducing or avoiding that dielectric breakdown is induced in another piezoelectric body, and is advantageous in improving the polarization yield.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram according to a first embodiment.

FIG. 2 is a circuit configuration diagram according to a second embodiment.

FIG. 3 is a circuit configuration diagram according to a third embodiment.

FIG. 4 is a circuit configuration diagram according to a fourth embodiment.

FIG. 5 is a configuration diagram according to a fifth embodiment.

FIG. 6 is a main part of a circuit configuration diagram according to a fifth embodiment.

FIG. 7 is a circuit configuration diagram according to a conventional technique.

FIG. 8 is a circuit configuration diagram according to another conventional technique.

FIG. 9 is a graph showing a voltage waveform of a piezoelectric body by an oscilloscope.

[Explanation of symbols]

In the figure, 1 is a piezoelectric body, 2 is a piezoelectric body holding portion, 3 is a power source, 4 is a resistance (suppressing means), 5 is a coil (suppressing means), and 6 is a capacitor (suppressing means).

Claims (2)

[Claims] 1. A method of electrically connecting a plurality of piezoelectric bodies in parallel to a power source for applying a DC voltage, and applying a DC voltage to each of the piezoelectric bodies to polarize the piezoelectric bodies. By using a suppressing means for suppressing the instantaneous flow of current between the power source and each of the piezoelectric bodies, at the time of dielectric breakdown of at least one of the piezoelectric bodies, the charge accumulated in the other piezoelectric body is stored. A method of polarizing a piezoelectric body, characterized in that a current based on the current is instantaneously suppressed from flowing into the piezoelectric body that has undergone dielectric breakdown. 2. A piezoelectric body holding section for arranging a plurality of piezoelectric bodies in parallel and electrically connecting the respective piezoelectric bodies in parallel to a power source capable of applying a DC voltage, and the piezoelectric body holding section. A piezoelectric body, which is provided between a power source and at least one of the piezoelectric bodies, and which suppresses an instantaneous current flow through the dielectric body when the dielectric breakdown occurs. Polarization device.