JP2003069101A - Piezoelectric actuator and its driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric actuator that is small in displacement even when its service condition, such as the temperature, electric field, and compressive stress is wide. SOLUTION: This piezoelectric actuator 1 uses a piezoelectric material 11 which is displaced when a voltage is impressed upon the material 11 as a driving source. When the actuator 1 is used under the condition of the minimum temperature, minimum electric field, and maximum compressive stress, the crystal structure of the piezoelectric material 11 is substantially on the tetragonal system side than the crystal phase boundary (MPB) between the tetragonal system and the rhombohedral system.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a piezoelectric actuator used in a high electric field, a high compressive stress and a wide temperature range, and a driving method thereof.

[0002]

2. Description of the Related Art Since a piezoelectric actuator having a piezoelectric body as a drive source has an accurate displacement amount, its use as a drive source for driving a valve body of a liquid ejecting apparatus such as an injector has been studied. As a conventional piezoelectric body, for example, as shown in Japanese Patent Laid-Open No. 9-55549, A
A PZT (lead zirconate titanate) -based oxide having a BO ₃ type perovskite structure is known.

It has been found that the above-mentioned piezoelectric material has tetragonal crystal and rhombohedral crystal depending on the composition, and also has a crystal phase boundary (MPB (Morophotropic Phase Boundary)) between them. There is. It is also known that piezoelectric characteristics such as dielectric constant and piezoelectric strain constant are maximized on the MPB.

In Japanese Patent Laid-Open No. 9-55549, the crystal phase boundary between the tetragonal crystal and the rhombohedral crystal (MP
It is described that the temperature dependence of displacement and dielectric constant with respect to temperature can be reduced by selecting a material that becomes tetragonal at a higher temperature in the vicinity of B). According to this, the temperature characteristics can be improved under a low electric field and a low compressive stress.

[0005]

[Problems to be Solved] However, recent actuators are required to have a small change in displacement in a high electric field, a high compressive stress, and a wide temperature range. I can't.

The present invention has been made in view of the above conventional problems, and provides a piezoelectric actuator and a driving method thereof in which a change in displacement is small even under a wide range of use conditions such as temperature, electric field, and compressive stress. It is what

[0007]

According to a first aspect of the present invention, in a piezoelectric actuator that uses a piezoelectric body that is displaced by the application of a voltage as a drive source, the piezoelectric body has a minimum temperature during use,
A piezoelectric actuator is characterized in that the crystal structure is substantially on the tetragonal side of a crystal phase boundary (MPB) between a tetragonal crystal and a rhombohedral crystal under the conditions of the minimum electric field and the maximum compressive stress. Item 1).

In the piezoelectric actuator of the present invention,
A piezoelectric body having a specific crystal structure under the specific conditions is used as a driving source. That is, the crystal structure of the piezoelectric body is changed under the three specific conditions of the lowest temperature in the temperature range where the piezoelectric actuator is used, the lowest electric field in the electric field range used, and the maximum compression stress in the compression stress range used. Stipulate.

As described above, the crystal structure of the piezoelectric body is defined as a crystal phase boundary (MPB) between a tetragonal crystal and a rhombohedral crystal.
The crystal structure is substantially on the tetragonal side. As a result, the piezoelectric actuator does not always change the crystal structure of the piezoelectric body to a rhombohedral crystal even if the operating temperature, electric field, or compressive stress changes, and always maintains a tetragonal crystal state. Further, in the piezoelectric body, the tetragonal crystal is more reliable than the rhombohedral crystal.

Therefore, the piezoelectric body remains tetragonal without changing its crystal structure even if the operating conditions such as temperature, electric field and compressive stress of the piezoelectric actuator change, and maintains relatively stable characteristics. can do. Further, in the present invention, the crystal structure of the piezoelectric body is close to the crystal phase boundary (MPB) between the tetragonal crystal and the rhombohedral crystal in the state where the above three specific conditions are satisfied, and substantially more tetragonal than MPB. Set so that it is on the crystal side. As a result, even if the usage conditions change, the tetragonal crystal in a state relatively close to MPB is maintained, and the characteristics of the piezoelectric body can be maintained in a good state.

Therefore, according to the present invention, it is possible to obtain a piezoelectric actuator having a small change in displacement even when the range of use conditions such as temperature, electric field and compressive stress is wide.

Next, a second invention is a method for driving a piezoelectric actuator using a piezoelectric body which is displaced by the application of a voltage as a drive source, wherein the piezoelectric body has a minimum temperature and a minimum temperature during use. Under the conditions of electric field and maximum compressive stress, the crystal structure is arranged to be substantially on the tetragonal side of the crystal phase boundary (MPB) between the tetragonal crystal and the rhombohedral crystal. A piezoelectric actuator driving method is characterized in that the piezoelectric actuator is driven under conditions of a minimum temperature or higher, the minimum electric field or higher, and the maximum compressive stress or lower (claim 9).

In the method for driving the piezoelectric actuator of the present invention, as described above, the piezoelectric body having the above-mentioned specific crystal structure is used under the condition that the three specific conditions for using the piezoelectric actuator are satisfied. The piezoelectric body can always maintain a tetragonal crystal structure by driving the piezoelectric body under the conditions of the minimum temperature or higher, the minimum electric field or higher, and the maximum compressive stress or lower.

Even if the use conditions change, the MP
The tetragonal crystal in a state close to B is maintained, and the characteristics of the piezoelectric body can be maintained in a good state. Therefore, according to this driving method, even when the range of use conditions such as temperature, electric field, and compressive stress is wide, it is possible to reduce the change in displacement of the driven piezoelectric body.

[0015]

DETAILED DESCRIPTION OF THE INVENTION In the first invention (claim 1), the piezoelectric body is preferably a PZT-based oxide having an ABO ₃ type perovskite structure (claim 2). The above PZT (PbZr _x Ti _y O ₃ , x + y = 1,
x> 0, y> 0) -based materials are known to have maximum values of dielectric constant and other characteristics in MPB.
The crystal structure of the PZT material is an ABO ₃ type perovskite type structure, and although it can be a material near MPB depending on the type, amount, and ratio of the constituent elements of the A and B sites, Zr that constitutes the B site is composed. And Ti molar ratio (Zr /
It is most common to adjust the Ti ratio).

Usually, when referring to a composition near MPB, room temperature,
A composition in which tetragonal crystals and rhombohedral crystals coexist under low electric field and no stress. When the Zr / Ti ratio dependence of displacement etc. is graphed, the Zr / Ti ratio, which is the maximum value, is minus or minus. It means less than 10%. That is, a composition having a smaller Zr / Ti ratio than the Zr / Ti ratio at which the displacement or the like has a maximum value is substantially referred to as a tetragonal crystal side. MP at room temperature, low electric field and no stress
It was found by experiments that the Zr / Ti ratio in the vicinity of MPB changes due to the electric field and the compressive stress even if the material composition is determined so that it is in the vicinity of B.

In the present invention, as described above, the temperature, the electric field, and the compressive stress as the use conditions are all taken into consideration, and the material composition of PZT is determined, so that the change in displacement is extremely small under the use environment conditions. A body is obtained, and an excellent piezoelectric actuator using the body can be obtained.

The temperature range in which the piezoelectric actuator is used is preferably -40 to 200 ° C (claim 3). If this temperature range can be covered, the usage range of the piezoelectric actuator can be almost covered. -4
A temperature of 0 ° C. or higher is a general piezoelectric actuator operating temperature. On the other hand, when the temperature exceeds 200 ° C., the Curie temperature of the PZT-based oxide approaches and the displacement decreases.

Further, it is preferable that the range of compressive stress using the piezoelectric actuator is more than 0 and 40 MPa or less (claim 4). The maximum value of the compressive stress range is 40 MPa for general use.

The electric field range in which the piezoelectric actuator is used is 4 k from the negative coercive electric field at the operating temperature.
It is preferably in the range of V / mm (Claim 5). Here, the coercive electric field will be briefly described. When an electric field E is applied to a polarized piezoelectric body in a direction opposite to that of polarization, depolarization occurs. The negative electric field E when polarization = 0 is called the negative coercive electric field Ec.

The range of the electric field in which the piezoelectric actuator is used by using the negative coercive electric field thus obtained is, as described above, that the range is 4 kV / mm from the negative coercive electric field at the operating temperature. Is preferred. When the electric field range is lower than the negative coercive electric field at the temperature used, there is a problem in that the displacement of the piezoelectric actuator decreases due to depolarization. On the other hand, when it exceeds 4 kV / mm, the stress generated by the strain of the material becomes large, and for example, in the case of the integrally fired piezoelectric actuator, it may be destroyed.

The temperature range in which the piezoelectric actuator is used is preferably -40 ° C. to the Curie temperature of the PZT-based oxide (claim 6). As described above, the lower limit of the temperature used is generally -40 ° C. on the other hand,
When the temperature exceeds the Curie temperature, the crystal structure becomes cubic and the displacement decreases drastically.

Further, it is preferable that the range of compressive stress using the piezoelectric actuator is more than 0 and 40 MPa or less (claim 7). The maximum value of the compressive stress range is 40 MPa for general use.

The electric field range in which the piezoelectric actuator is used may be in the range of 0 to 4 kV / mm (claim 8). In this case, by using under the condition that the electric field range is 0 kV / mm or more, depolarization will not occur, and since it will be constantly polarized during driving, it can be used up to near the Curie temperature of the PZT-based oxide. it can.
On the other hand, when the voltage exceeds 4 kV / mm, similar to the above,
The stress generated by the strain of the material becomes large, and for example, in the case of an integral firing type piezoelectric actuator, it may be destroyed.

Also in the second invention (claim 9), the piezoelectric body is preferably a PZT-based oxide having an ABO ₃ type perovskite structure (claim 1).
0). For the same reason as above, the temperature range in which the piezoelectric actuator is used is preferably -40 to 200 ° C (claim 11).

The compressive stress range using the piezoelectric actuator is preferably greater than 0 and not more than 40 MPa using the piezoelectric actuator (claim 12). For the same reason as above, the electric field range for using the piezoelectric actuator is preferably within the range of 4 kV / mm from the negative coercive electric field at the operating temperature (claim 13).

For the same reason as above, the temperature range in which the piezoelectric actuator is used is -40 ° C to PZ.
It is preferably the Curie temperature of the T-based oxide (claim 14). As mentioned above, the lower limit of the operating temperature is -4
0 ° C is common. On the other hand, when the temperature exceeds the Curie temperature, the crystal structure becomes cubic and the displacement decreases drastically.

Further, it is preferable that the compressive stress range using the piezoelectric actuator is more than 0 and not more than 40 MPa (claim 15). The maximum value of the compressive stress range is
40 MPa is sufficient for general use.

The electric field range in which the piezoelectric actuator is used may be in the range of 0 to 4 kV / mm (claim 16). In this case, the electric field range is 0 kV / mm
By using it under the above conditions, it is not depolarized, and it is constantly polarized during driving.
It can be used up to near the Curie temperature of the system oxide. On the other hand, when it exceeds 4 kV / mm, the stress generated by the strain of the material becomes large as in the above case, and for example, in the case of the integral firing type piezoelectric actuator, it may be destroyed.

[0030]

Example 1 In this example, P was used as the piezoelectric body.
When a ZT-based ABO ₃ type perovskite compound is used, the crystal structure is a tetragonal and rhombohedral crystal phase boundary (MPB) under the conditions of the minimum temperature, the minimum electric field, and the maximum compressive stress during use. The composition was determined so as to be substantially closer to the tetragonal side.

First, P of ABO ₃ type perovskite structure
In the ZT crystal, the Pb position of the A site is Sr = 9mo
1% substitution, and the (Zr, Ti) position of the B site is (Y: 1
/ 2, Nb: 1/2) = 1 mol% substitution, Zr / Ti
PZT having different (molar ratio) is prepared.

Zr / Ti (molar ratio) is 48 / 52,4
9/51, 50/50, 51/49, 52/48, 53
/ 47, 54/46, 55/45, 56/44, 57 /
There are 10 types of 43. Then, PbO and SrC, which are raw material powders, are added so that Mn is added to these perovskite compositions in an amount of 0.2 wt% in terms of Mn ₂ O _3.
O ₃ , ZrO ₂ , TiO ₂ , Y ₂ O ₃ , Nb ₂ O ₅ , Mn ₂ O ₃
Was weighed. Then, after mixing these raw materials with a wet ball mill or the like, the mixture is heated at 700 to 900 ° C.
It was calcined for 5 hours.

The obtained calcined product was pulverized by a ball mill or the like, then water, an adhesive such as polyvinyl alcohol was added and further mixed, and granulated by an apparatus such as a spray dryer. 300-1000 kgf / c of the obtained granulated powder
After pressure molding at a pressure of m ² , main firing was performed at 1000 to 1200 ° C. for 0.5 to 4 hours to obtain a fired body as a piezoelectric body.

Each of the obtained fired bodies was processed into a disk having a diameter of 10 mm and a thickness of 0.2 mm, and electrodes made of a conductive material such as silver were formed on both end faces by a known method. Further, a voltage of 2 to 4 kV / mm was applied to this disk at a temperature of 20 to 150 ° C. for 10 to 60 minutes to perform polarization treatment.

After that, it is left to stand for 24 hours and 0-40 MPa.
Capacitance was measured under the condition that the compressive stress, the bias voltage of 0 to 200 V (1 kV / mm), and the temperature of 0 to 200 ° C. were applied. Here, the capacitance was measured with an impedance analyzer at a frequency of 1 kHz (sin wave) and an amplitude of ± 1V. The measurement results are shown in FIGS.

In FIG. 1, the horizontal axis indicates temperature (° C.) and the vertical axis indicates Zr.
(Mol%), the compressive stress is kept constant at 0 MPa, and the mol% of Zr at which the electrostatic capacitance has a maximum value when three types of bias voltages are applied is plotted at each temperature. In Fig. 2, the horizontal axis is temperature (° C) and the vertical axis is Zr.
(Mol%), the voltage was kept constant at 0 V, and the mol% of Zr at which the electrostatic capacitance had a maximum value when three types of compressive stress were applied at each temperature was plotted.

As is known from FIG. 1, when the bias electric field is increased, the Zr amount that becomes MPB shifts to the larger one. Further, as is known from FIG. 2, it was found that when the compressive stress becomes higher, the amount of Zr which becomes MPB shifts to the smaller one.

Further, as is known from FIGS. 1 and 2, when the temperature rises, the Zr amount which becomes the crystal phase boundary (MPB) between the tetragonal crystal and the rhombohedral crystal is irrespective of the values of the compressive stress and the bias electric field. I found that I would shift to more people. From the above, the tetragonal side (MPB
It can be seen that in order to obtain a crystal structure in a region where the amount of Zr is smaller than that of the above), the composition should be close to MPB under the conditions of the minimum temperature, the minimum voltage and the maximum compressive stress used.

Here, the reason why the tetragonal side is better than MPB will be briefly described. When driving a piezoelectric actuator made of a PZT-based oxide (hereinafter appropriately referred to as a PZT actuator), self-heating becomes a problem. The displacement of the PZT actuator is due to the inverse piezoelectric effect and the domain rotation effect, and the latter causes self-heating. The electric field at which the domain rotation effect begins to appear is near the coercive electric field described above, and it is preferable that the coercive electric field be farther from zero in order to suppress self-heating. PZT exhibits a piezoelectric effect when its crystal structure is either tetragonal or rhombohedral, and generally tetragonal has an Ec of about twice that of rhombohedral.
Indicates. Therefore, it is desirable that the crystal structure of PZT is always tetragonal rather than rhombohedral.

(Embodiment 2) In this embodiment, the operating temperature is -40.
~ 200 ° C range, compressive stress range 0-40MPa, electric field range 0-4kV / mm at the lowest operating temperature
Assuming that it is within the range, we prepared a piezoelectric actuator optimal for this. That is, as shown in FIG. 3, the piezoelectric actuator 1 of this example is a piezoelectric actuator that uses the piezoelectric body 11 that is displaced by the application of a voltage as a drive source. The piezoelectric body 11 has a minimum temperature when used,
Under the conditions of the lowest electric field and the maximum compressive stress, the crystal structure is substantially on the tetragonal side of the crystal phase boundary (MPB) between the tetragonal crystal and the rhombohedral crystal.

As the above-mentioned piezoelectric body 11, the minimum operating temperature-
At 40 ° C., the lowest Pias electric field of 0 kV / mm was applied under a maximum compressive stress of 40 MPa, and PZT having a composition in the vicinity of MPB was prepared and applied. The PZT is
The Pb position of the A site was replaced with Sr = 9 mol%, and the (Zr, Ti) position of the B site was replaced with (Y: 1/2, Nb: 1 /
2) = 1 mol% substitution, Zr / Ti (molar ratio) = 53 /
47. Further, Mn is added to these perovskite compositions in an amount of 0.2 wt% in terms of Mn ₂ O _3.
Was added.

PZT having this composition was processed into a plate having a diameter of 10 mm and a thickness of 0.2 mm by the same process as in Example 1. As shown in FIG. 3, a piezoelectric laminate 11 made of PZT and internal electrode layers 21 and 22 are alternately laminated, and a side electrode 3 and an external electrode arranged on the side surface of the ceramic laminate 10. A piezoelectric actuator 1 composed of 4 was manufactured. Various manufacturing methods can be adopted. In this example, a structure in which the piezoelectric body 11 has a barrel shape is adopted. This is designated as sample E2.

In this example, for comparison, a PZT having a composition which is in the vicinity of MPB at a temperature of 20 ° C. under a low electric field and under no stress, and a laminated piezoelectric actuator assembled using the same as the above were prepared ( Sample C1). The specific composition of PZT in sample C1 is Sr = 9mo at the position of Pb.
1% substitution, the (Zr, Ti) position of the B site is (Y: 1
/ 2, Nb1 / 2) = 1 mol% substitution and Zr / Ti (molar ratio) = 51.5 / 48.5. Furthermore, Mn is added to these perovskite compositions in an amount of 0.2 wt% in terms of Mn ₂ O _3.
% Addition.

Next, in this example, the sample E2 and the sample C1
About, the temperature range of -40 ℃ ~ 165 ℃, compressive stress:
40 MPa, electric field: 0 to 2 kV / mm, frequency: 0.1
The displacement in Hz was measured. The result is shown in FIG.
In this figure, the horizontal axis represents temperature (° C.) and the vertical axis represents displacement (μm).

As can be seen from the figure, the sample E2, which is an embodiment of the present invention, has a smaller change in displacement and a flatter temperature characteristic than the case of the sample C1 which is a comparative example. It turned out to be good.

(Third Embodiment) In this embodiment, an injector to which the piezoelectric actuator 1 of the second embodiment can be applied will be described. The injector 5 shown in this example is, as shown in FIG. 5, applied to a common rail injection system of a diesel engine. This injector 5 is, as shown in the figure, the above-mentioned piezoelectric actuator 1 as a drive unit.
Has an upper housing 52 and a lower housing 53 fixed to the lower end thereof and having an injection nozzle portion 54 formed therein.

The upper housing 52 has a substantially cylindrical shape, and the piezoelectric actuator 1 is housed in a vertical hole 521 eccentric to the central axis.
Is inserted and fixed. A high-pressure fuel passage 522 is provided in parallel to a side of the vertical hole 521, and an upper end portion of the high-pressure fuel passage 522 communicates with an external common rail (not shown) via a fuel introduction pipe 523 protruding to an upper portion of the upper housing 52. .

A fuel outlet pipe 525 communicating with the drain passage 524 projects from the upper portion of the upper housing 52, and the fuel flowing out from the fuel outlet pipe 525 is returned to a fuel tank (not shown). The drain passage 524 has a vertical hole 52.
1 through the gap 50 between the piezoelectric actuator 1 and
Further, a passage (not shown) extending downward from the gap 50 in the upper and lower housings 52, 53 communicates with a three-way valve 551 described later.

The injection nozzle portion 54 has a piston body 53.
1, a nozzle needle 541 that slides in the vertical direction, and a fuel pool 54 that is opened and closed by the nozzle needle 541.
The injection hole 543 for injecting the high-pressure fuel supplied from 2 into each cylinder of the engine is provided. The fuel reservoir 542 is provided around the middle portion of the nozzle needle 541, and the lower end portion of the high-pressure fuel passage 522 opens here. The nozzle needle 541 receives the fuel pressure in the valve opening direction from the fuel reservoir 542, and the back pressure chamber 54 provided facing the upper end surface.
When the fuel pressure in the valve closing direction is received from No. 4 and the pressure in the back pressure chamber 544 drops, the nozzle needle 541 lifts, the injection hole 543 is opened, and fuel injection is performed.

The pressure in the back pressure chamber 544 is increased / decreased by the three-way valve 551. The three-way valve 551 is configured to selectively communicate with the back pressure chamber 544 and the high pressure fuel passage 522 or the drain passage 524. Here, it has a ball-shaped valve element that opens and closes a port communicating with the high-pressure fuel passage 522 or the drain passage 524. This valve body is based on the drive unit 1
Thus, it is driven via the large-diameter piston 552, the hydraulic chamber 553, and the small-diameter piston 554 arranged below it.

The injector 5 having such a structure is arranged in an automobile equipped with a diesel engine and used in a wide temperature range. Further, since the displacement accuracy of the piezoelectric actuator 1 in the injector 5 has a great influence on the performance of the diesel engine, it is desired to be accurate in any temperature range. On the other hand, the piezoelectric actuator 1 according to the second embodiment is optimal for an injector, exhibits excellent characteristics, and can greatly contribute to improving the performance of the injector 5.

In the second and third embodiments, the piezoelectric actuator having a barrel-shaped cross section is shown. However, as shown in FIG. 6, the cross-sectional shape may be octagonal.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the Zr amount in MPB when the temperature and the bias voltage are changed in the first embodiment.

FIG. 2 is an explanatory diagram showing the Zr amount in MPB when the temperature and the compressive stress are changed in Example 1.

FIG. 3 is an explanatory diagram showing a structure of a piezoelectric actuator according to a second embodiment.

FIG. 4 is an explanatory diagram showing changes in displacement with respect to temperature in the second embodiment.

FIG. 5 is an explanatory view showing the structure of the injector in the third embodiment.

FIG. 6 is an explanatory view showing an example in which the shape of the piezoelectric actuator is changed in Examples 2 and 3.

[Explanation of symbols]

1. ． ． Piezoelectric actuator, 11. ． ． Piezoelectric body, 21,22. ． ． Internal electrode layer, 3. ． ． Side electrode,

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3G066 AA07 AB02 AC09 AD12 BA00                       CC06T CC08T CC08U CC14                       CC64T CC64U CC66 CC67                       CC68U CC69 CC70 CD18                       CD28 CE27 CE31

Claims (16)

[Claims] 1. In a piezoelectric actuator using a piezoelectric body as a drive source that is displaced by the application of a voltage, the piezoelectric body has a crystal structure under the conditions of a minimum temperature, a minimum electric field and a maximum compressive stress during use. A piezoelectric actuator, which is substantially on the tetragonal side of a crystal phase boundary (MPB) between a tetragonal crystal and a rhombohedral crystal. 2. The piezoelectric body according to claim 1, wherein the piezoelectric body is AB
A piezoelectric actuator comprising a PZT-based oxide having an O ₃ type perovskite structure. 3. The piezoelectric actuator according to claim 2, wherein the temperature range in which the piezoelectric actuator is used is −40 to 200 ° C. 4. The compressive stress range according to claim 2 or 3, wherein the piezoelectric actuator is used, is greater than 0 and 40.
A piezoelectric actuator having a pressure of MPa or less. 5. The method according to any one of claims 2 to 4,
A piezoelectric actuator, wherein the electric field range in which the piezoelectric actuator is used is within a range of 4 kV / mm from a negative coercive electric field at a temperature in which it is used. 6. The piezoelectric actuator according to claim 2, wherein a temperature range in which the piezoelectric actuator is used is −40 ° C. to Curie temperature of PZT-based oxide. 7. The compressive stress range according to claim 2 or 6, wherein the piezoelectric actuator is used, is greater than 0 and 40.
A piezoelectric actuator having a pressure of MPa or less. 8. The electric field range in which the piezoelectric actuator is used according to claim 2, 6 or 7,
A piezoelectric actuator having a range of 4 kV / mm. 9. A method for driving a piezoelectric actuator using a piezoelectric body that is displaced by the application of a voltage as a drive source, wherein the piezoelectric body has a minimum temperature, a minimum electric field, and a maximum compressive stress when used. Below, the crystal structure is configured to be substantially on the tetragonal side of the crystal phase boundary (MPB) between the tetragonal and rhombohedral crystals, and the piezoelectric body is set to have the above-mentioned minimum temperature or more and the above-mentioned minimum electric field. As described above, the piezoelectric actuator driving method is characterized in that the piezoelectric actuator is driven under the condition that the maximum compressive stress is not more than the above. 10. The piezoelectric body according to claim 9, wherein the piezoelectric body is A
A method for driving a piezoelectric actuator, which is a PZT-based oxide having a BO ₃ type perovskite structure. 11. The method of driving a piezoelectric actuator according to claim 10, wherein a temperature range in which the piezoelectric actuator is used is −40 to 200 ° C. 12. The method for driving a piezoelectric actuator according to claim 10, wherein the compressive stress range in which the piezoelectric actuator is used is greater than 0 and 40 MPa or less. 13. The electric field range in which the piezoelectric actuator is used according to any one of claims 10 to 12,
A method for driving a piezoelectric actuator, which is in a range of 4 kV / mm from a negative coercive electric field at a temperature used. 14. The method for driving a piezoelectric actuator according to claim 10, wherein a temperature range in which the piezoelectric actuator is used is in a range of −40 ° C. to Curie temperature of PZT-based oxide. 15. The method of driving a piezoelectric actuator according to claim 10, wherein the compressive stress range in which the piezoelectric actuator is used is greater than 0 and 40 MPa or less. 16. One of claims 10, 14 and 15
2. The method for driving a piezoelectric actuator according to the item 1, wherein the electric field range using the piezoelectric actuator is in the range of 0 to 4 kV / mm.