JPS59188983A - Piezoelectric displacement device - Google Patents

Abstract

PURPOSE:To enable various kind of deformations by reducing the influence by the displacement due to the time delay of polarization or residual polarization by a method wherein a part of a bimorph is provided with the part displacing to the reverse direction to the main body, and the displacement is controlled by forward-reverse driving part. CONSTITUTION:Piezoelectric sheets 2 and 3 adhered on both surfaces of a metallic plate 1 so that the direction (p) of polarization becomes the same direction. The sheets 2 and 3 have the forward directional driving parts 2a and 3a and the reverse directional driving parts 2b and 3b (the direction of polarization is p'). The forward directional driving parts are provided with outside electrodes 4a and 5a, and the outside surface of the reverse directional ones with auxiliary electrodes 4b and 5b. Further, inside electrodes are formed in common to both the driving parts and earthed to the metallic plate 1. The electrode 4a and 5a are connected by means of a lead 7' and then connected to the positive terminal of a power source 9 by means of a lead wire 7. The metallic plate is connected to the movable contact of a variable resistor connected to the power source 9 by means of a lead wire 8, and the electrodes 4b and 5b to the negative terminal of the power source 9. Thus, the influence by the displacement due to the time delay of polarization or residual polarization can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric displacement device suitable for precise position control. A displacement device is obtained.

Piezoelectric materials have the property of causing mechanical strain when a voltage is applied to them, and generating voltage when a force is applied to them, making them useful as converters between mechanical and electrical energy, or as sensors and actuators. be. In particular, since the input or output is an electrical signal, it is not only easy to process the signal, but also precise and high-speed control is possible.

However, piezoelectric materials have a hysteresis phenomenon, and the strain when a voltage is applied varies depending on the direction and magnitude of the previously applied voltage.Furthermore, due to the temporal principle of polarization of piezoelectric materials, Since the strain gradually changes with the application time of
There is a large amount of heat that cannot be adjusted, which is a problem when it is desired to maintain a constant strain for a long time or when precise position control is required.

FIG. 1 is a diagram illustrating a driving situation of a conventional bimorph type piezoelectric displacement device. In the figure, 1 is a metal plate, 2.3 is a piezoelectric sheet made of lead titanate-zirconate, etc.
It is bonded to both sides of the metal plate 1 so that the polarization direction p is the same. 4.5 is an outer electrode made of silver or the like provided on the outer surface of the piezoelectric sheet, and a similar electrode is also provided on the inner surface of the piezoelectric sheet in contact with the metal plate 1. 6 is a bimorph support part. Piezoelectric sheet 2
．． The outer electrodes 4.5 of 3 are connected by a lead 7' so as to have the same potential, and are connected to the negative terminal of a power source 9 by the lead wire 7. A lead wire 8 connects the inner electrodes of the metal plate 1, that is, the piezoelectric sheets 2 and 3, to a movable contact of a variable resistance connected between the positive and negative electrodes of a power source 9.

In this figure, since a voltage with a polarity opposite to the polar direction B) is applied to the piezoelectric sheet 2, an arrow a is applied to the piezoelectric sheet 2 in the longitudinal direction of the piezoelectric material.
Elongation occurs as shown in . On the other hand, since a voltage is applied to the piezoelectric body 3 in the same direction as the polarization direction, contraction occurs in the length direction of the piezoelectric body as shown by the arrow. As a result, the tip of the bimorph bends downward (positive direction) in the figure and is displaced by S.

Figure 5 is a characteristic diagram showing how the displacement of the bimorph changes depending on the voltage and voltage application time.When the applied voltage of the bimorph is increased from O to Va, the displacement of the bimorph changes as shown by the curve 0. - increases along A, reaches point A, and S
Displaced by C. Then, when the voltage is lowered from Va to 0, the displacement decreases along curve MA-3a and reaches sa,
It will not return to 0 points immediately. Further, when the applied voltage is maintained at Va for a long time, the amount of displacement gradually increases and reaches 13 points due to the temporal irregularity of polarization and the bimorph structure. If the voltage is lowered from Va to 0 point from this state, the displacement will be curve B-
It decreases along 8b and reaches sb, and does not immediately return to Sa or 0 point.

That is, for example, even if you try to control the displacement between Sa and SC with a voltage between 0 and Va, the displacement between 5a and 3b cannot be controlled, and the voltage required to maintain the displacement at SC is from Va to vb. decreases to Therefore, in the case of a bimorph whose displacement changes more greatly over time, the voltage required to maintain the displacement Sc becomes even lower, and eventually it becomes impossible to control the displacement by voltage.

This is mainly due to the following hysteresis of the piezoelectric material. That is, in FIG. 1, the piezoelectric sheet 2
expands as shown by arrow a when voltage is applied, and tends to continue to expand over time due to the time delay in polarization, and even if the applied voltage is zero, there is residual polarization, so it tries to maintain its extended state. do. On the other hand, piezoelectric sheet 3
When a voltage is applied, it contracts as shown by the arrow, and tends to continue contracting over time, and even if the voltage is reduced to zero, residual polarization exists, so it tries to maintain its contracted state. For this reason, in this bimorph, the piezoelectric sheet 2.3
Both act to further increase the displacement S of the bimorph when voltage is applied, and -C also acts to maintain a certain displacement (Sa or sb>) when the voltage is zero.

The hysteresis phenomenon of the bimorph is not only caused by the hysteresis of the n-heavy body mentioned above, but also caused by the bimorph structure, such as variations in the performance of the piezoelectric material, the bonding state, or its non-uniformity.

The present invention is characterized in that a part of the device main body made of a piezoelectric body is provided with a part that is displaced in a direction opposite to the displacement direction of the main body, and the piezoelectric body is controlled so that it is displaced in the opposite direction to the main body. This eliminates problems caused by hysteresis phenomena such as the above-mentioned polarization time delay and residual displacement, and provides a highly reliable piezoelectric displacement device.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 2, two piezoelectric sheets 1 to 2.3 constituting a bimorph are pasted on both sides of a metal plate 1 so that the polarization direction p is in the same direction. Each has a main body consisting of forward direction drive parts 2a, 3a and reverse direction drive parts 2b, 3b, and outer electrodes 4a, 5a are on the outer surface of the part corresponding to the forward direction drive part, and the part corresponding to the reverse direction drive part. The outer surface of the auxiliary electrodes 4b and 5b
Furthermore, an inner electrode is formed in common to both drive parts and is electrically conductively connected to the metal plate 1. The outer electrodes 4a and 5a of the positive direction drive section of the piezoelectric sheet are connected by a lead 7', and are connected to the negative terminal of a power source 9 by the lead wire 7. The inner electrode of the piezoelectric sheet, ie, the metal plate 1, is connected to a movable contact of a variable resistance connected between the positive and negative electrodes of a power source 9 through a central lead wire 8. Further, the outer electrodes of the reverse direction drive parts are connected in common by a lead 10' and then connected to a positive terminal of a power source by a lead wire 10.

In the same figure, the forward direction drive section 2a of the piezoelectric sheet 2.3
, 3a act so as to be displaced in the positive direction (downward in the figure) as in FIG. At the same time, a voltage in the same direction as the polarization direction p' is applied to the reverse direction driving section 2b of the piezoelectric sheet 3, and this section contracts in the length direction as shown by arrow b', while the reverse direction driving section 2b of the piezoelectric sheet 3 contracts. Since a voltage in the opposite direction to the polarization direction is applied to 3b, it extends in the length direction as indicated by arrow a'. Therefore, the reverse direction drive section acts to displace the bimorph in the direction opposite to the forward direction drive section (upward in the figure). By connecting the wires as shown in the figure, when the center lead ls8 is at the position W of the variable resistor (positive terminal side), the entire voltage is applied to the positive drive parts 2a and 3a of the piezoelectric sheet, and the bimorph is displaced by the maximum amount in the positive direction. . When the displacement is about to move from point A to point 8 in Fig. 5 over time, the center lead llA3 is moved to the midpoint v side and the applied voltage is lowered, but at the same time as this operation, the reverse direction drive units 2b, 3b A voltage is applied to J to displace the bimorph in the opposite direction.
The effect of

In this way, when a voltage is applied to the reverse direction drive section, undesirable temporal changes in displacement due to the time delay of polarization that occur when voltage is applied for a long time will be caused by the forward direction drive section. In contrast, in the reverse direction drive part, they act in the opposite direction (in the -L direction in the figure), so they cancel each other out, and their effects are greatly reduced. The effect is particularly large near the 0 point.

When the center lead 15i18 is in the U position (negative terminal side), all voltages are applied to the reverse direction drive section, so the tip of the bimorph is moved from the 0 point to the upper position in the figure by the maximum amount only by the drive force of the reverse direction drive section. It can be displaced. In other words, by appropriately selecting the drive horns of the forward direction drive section and the reverse direction drive section, even a DC power source can be used without changing the polarity.
It can be displaced in both forward and reverse directions around the point.

In addition, in conventional bimorphs, when the voltage is reduced to zero, the displacement does not return to its original position due to the influence of residual polarization, making it impossible to control displacement by voltage, but with the present invention, a reverse driving force is forcibly applied. The displacement can be returned to its original position. Furthermore, in this case as well, the residual displacement when the voltage is zero acts in the forward direction on the forward direction drive section and in the opposite direction on the reverse direction drive section, so these effects also have the effect of canceling each other out.

FIG. 3 shows another embodiment of the present invention, in which the piezoelectric sheet 2
, 3, and piezoelectric sheets 12 and 13 are adhered to the main body, respectively, to form a reverse direction drive section. The piezoelectric sheets 12 and 13 each have an outer mold 8 made of silver or the like.
i14, 15 are provided, which are connected in common by a lead wire 10', which is connected to the negative terminal of the power supply 9.

In addition, the outer electrodes 4 and 5 of the piezoelectric bodies 2 and 3 are conductively connected to the inner electrodes of the F[electronic sheet 12 and 13], and are commonly connected by a lead 8', and are powered by a medium-heat lead wire 8. 9
It is connected to a movable contact of a variable resistor connected between the positive and negative electrodes of. Furthermore, the inner electrode of the piezoelectric sheet 2.3 is connected to the positive terminal of a power source 9 by a lead wire 7.

In this embodiment, a voltage is applied to the piezoelectric material 2 in the opposite direction to the polarization p, and extends in the length direction as indicated by the arrow a. On the other hand, since a voltage is applied to the piezoelectric sheet 3 in the same direction as the polarization p, the piezoelectric sheet 3 contracts in the length direction as shown by the arrow. All of these act to displace the bimorph in the positive direction, but
In the reverse direction drive section, a voltage is applied to the piezoelectric sheet 12 in the same direction as the polarization p', so that the arrow b
Since a voltage is applied to the piezoelectric sheet 13 in the direction opposite to the polarization direction, the piezoelectric sheet 13 expands in the length direction and acts to displace the bimorph in the opposite direction.

FIG. 4 shows another embodiment of the present invention in which a voltage is applied in series to two piezoelectric sheets and one piezoelectric sheet is glued together as a reverse drive section, and its functions and effects are as described above. This is similar to the example.

However, according to the present invention, it is possible to control the zero point in both forward and reverse directions with one type of DC power source without changing its polarity.
Therefore, the amount of displacement from the zero point becomes smaller.

Conventional bimorph control methods use power supplies with different polarities or apply a constant bias voltage to displace the bimorph in both forward and reverse directions, but the former requires two types of power supplies and has hysteresis. The disadvantage was that it became larger.

The bimorph is also displaced by 1819, and the direction of displacement is generally opposite when the temperature is raised and when the temperature is lowered. When maintaining a constant position of a bimorph with respect to a certain object, the conventional bimorph control method applies a constant bias voltage to the bimorph to give it a constant displacement, and then uses this displacement as a reference to adjust the temperature. It is necessary to compensate for the displacement caused by tCo.In such a case, compared to the method according to the present invention, the bimorph is in a state of being displaced by a voltage corresponding to the bias voltage, and in such a state, the influence of the temperature on the displacement is large. In addition, the influence of the time delay in polarization becomes large. Since the reference is set to a state with even greater displacement, the irreversibility of the bimorph's displacement may occur due to the creep phenomenon. However, according to the present invention, the displacement can be set based on the 0 point where the displacement is zero, so the above-mentioned Defects can be removed.

Furthermore, the forward drive section and reverse drive section of the bimorph have the effect of canceling out unidirectionality caused by changes in displacement due to polarization delay and residual distortion.

As explained above, the present invention is a piezoelectric body displacement device in which a piezoelectric body is provided with a forward direction drive section and a reverse direction drive section, and displacement is controlled by the magnitude relationship between the two forces, and the time delay of polarization and This reduces the influence of displacement due to residual polarity, and various modifications are possible. For example, in the embodiment described above, the reverse direction driving section is provided at the tip of the bimorph, but it may be provided at other parts, such as the center, or as shown in the embodiments of FIGS. 3 and 4. In this case, the reverse drive may be provided on the entire outer surface of the forward drive.

Furthermore, in the embodiment shown in FIG. 2, a comb-shaped electrode facing the piezoelectric sheet 2 is provided, and a comb-shaped electrode is also provided on the piezoelectric sheet 2-3, so that the two pairs of electrodes between the piezoelectric sheets 2 and 3 are connected in the positive direction. ,
It is also possible to form a reverse direction drive section and drive in both forward and reverse directions. It is also possible to adjust the magnitude of displacement due to applied voltage by reducing the thickness of the piezoelectric sheet of the reverse drive section. It can also be applied to minute displacement control devices using piezoelectric bodies such as annular or laminated bodies.

[Brief explanation of drawings]

1 and 2 are schematic diagrams showing the driving situation of a conventional bimorph, FIG. 3 is a schematic diagram showing the driving situation of the bimorph type piezoelectric displacement device of the present invention, and FIG. 4 is a schematic diagram showing the hysteresis of displacement of the conventional bimorph. FIG. 1...Metal plate 2.3...Piezoelectric body 2a
, 3a... Positive direction drive section 2b, 3b...
... Reverse direction drive section 5 ... Power supply 6 ...
...Supporting part 372 Den 4 Prisoner 5 Iconic voltage Voltage procedure Ne 11 official book (spontaneous) July 5, 1980 Commissioner of the Japan Patent Office Sir 1, Indication of matter A'1 1988 Patent application No. 64351 2. Name of the invention Piezoelectric displacement device 3. Representative Nobuo Nasu 6. Contents of the amendment 1) Scope of claims fj'f of Mei 1, page 1, lines 5 to 7 Correct the column as follows. "A piezoelectric displacement device characterized in that a part of the bimorph is provided with a part that displaces in the opposite direction to the main body, and the displacement is controlled by forward and reverse drive parts." 2) Specification page 2, 12
1st polarization direction" on page 5, line 20, is corrected to "direction of polarization."3> Specification Section, page 2, line 20, page 6, line 11, section 8
Correct "negative pole" in line 6 of the page and line 8 of page 9 to "positive pole". 4>"Polarizationdirection" on page 3, line 4 of the specification tube is corrected to r direction of polarization voltage (hereinafter referred to as polarization direction) j. 5) Correct lines 11 to 14 of page 5 of the Rōseisho as follows. rThe present invention is characterized in that a part of the bimorph body is provided with a part that is displaced in a direction opposite to the displacement direction of the body,
6) "3!)" on page 6, line 3 of the above-mentioned polarization, and "1"
3b (direction of polarization is p)),'' is corrected. 7> Correct "positive electrode" to "negative electrode" on page 6, line 16 of the Meiji M, line 9, page 7, and line 15 of page 9. 8) "Polarization direction p" on page 7, line 1 of the specification tube and page 10, line 2 of the specification tube is corrected to "polarization direction." 9) "1st polarization p" on page 9, line 15 and line 18 of the specification tube is corrected to "polarization direction." 10) "Piezoelectric material" on page 11, line 20 of the specification is corrected as "bimorph." do. 11) Figures 1 to 4 of the attached drawings are corrected as shown in the attached sheet. 7. Corrected catalog of attached documents, Figures 1 to 4> 1 or more copies 4 Bacteria 8 B" - continuation 11 ShoP (method) Commissioner of the Japan Patent Office 1. Indication of the case 1988 Patent application No. 64351 No. 2, Name of the invention Piezoelectric displacement device 3, Relationship to the amendment filer case Patent applicant address 1, Inomayo-cho, Kisshoin Nishinoshōin, Minami-ku, Kyoto Name (428> Nippon Battery Co., Ltd.) Representative: Nobu Nasu, AJl 4, Agent address: 1-7, Shonomaage-cho, Kisshoin-nishi, Minami-ku, Kyoto City, 601 Japan.This is the 1st sex diagram in line 5 of the 13th line of the detailed statement of contents of the amendment. ” is corrected as follows. FIG. 5 is a characteristic diagram showing the relationship between applied voltage and displacement of the bimorph. j or more

Claims (1)

[Claims] A piezoelectric body displacement device characterized in that a part of a main body is provided with a part that is displaced in a direction opposite to the main body, and the displacement is controlled by a forward/reverse drive section.