JP2946870B2 - Method and apparatus for evaluating piezoelectric material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for evaluating a piezoelectric material, and more particularly, to a method and an apparatus for evaluating a piezoelectric material for a piezoelectric material pellet which is a single piezoelectric material.

[0002]

2. Description of the Related Art In a conventional method for evaluating a piezoelectric material, for example, a single piezoelectric material is coated with silver (Ag) paste and baked, and about 10 sheets are laminated in the thickness direction of the single piezoelectric material. The layers of the piezoelectric material (piezoelectric material stack) formed by baking and bonding the layers with an Ag paste and then electrically connecting the laminated piezoelectric materials alone in parallel are used as piezoelectric material evaluation targets. (Japan Ceramic Association 1989 Fall Symposium, Material 5-1A12, "Durability of PZT Piezoelectric Ceramics against Compressive Stress"). For example, in a durability test, a constant pressure is applied in the axial direction (thickness direction of a single piezoelectric material) of the piezoelectric material stack having the above configuration (hereinafter, simply referred to as a stack) to periodically apply a pulse-like voltage to the stack. When applied, a compressive stress is periodically generated in the stack. Then, the relationship between the number of applied pulses and the maximum generated force generated by the stack at the time of an appropriate pulse number is determined to evaluate the decrease in the maximum generated force of the stack over time, that is, the durability.

As described above, in the conventional method for evaluating a piezoelectric material, an entire stack in which a plurality of piezoelectric materials alone are stacked is to be evaluated. In general, piezoelectric materials are often used as precision actuators by increasing the displacement or generated force by laminating a plurality of piezoelectric materials as described above,
Therefore, the durability and other characteristics of the actuator can be obtained by the conventional evaluation method.

[0004]

According to the conventional method for evaluating a piezoelectric material, although the characteristics of a stack in which a plurality of piezoelectric materials alone are stacked as described above can be obtained, changes in characteristics of only the piezoelectric material alone can be grasped. It is difficult. That is, the characteristic changes in the conventional evaluation method include the shape of the entire stack, the electrode materials mounted on the upper and lower surfaces of the piezoelectric material alone,
Insulators, shims and adhesives (Ag paste etc.),
The effects of components other than the piezoelectric material alone, such as stress concentration due to misalignment during lamination and variations in temperature distribution in the stack under test, are likely to be included, making it difficult to grasp the characteristic changes of the piezoelectric material alone. is there. Therefore, there is little feedback to the development of the piezoelectric material, which is a factor that delays the development of a high-performance piezoelectric material.

Accordingly, the present invention has been made in view of the above problems, and by taking out a single piezoelectric material and testing the same with the piezoelectric material stack under the same conditions, the characteristic change of only the piezoelectric material alone in the piezoelectric material stack can be obtained. It is an object of the present invention to provide a method and an apparatus for evaluating a piezoelectric material that enable evaluation.

[0006]

According to a first aspect of the present invention, there is provided a piezoelectric material stack formed by stacking a plurality of single piezoelectric materials in the thickness direction of the single piezoelectric material, and A piezoelectric material pellet, which is a single material, is disposed so as to overlap with the central axis along the thickness direction of the single piezoelectric material, and the pressure and temperature conditions applied to the piezoelectric material stack and the piezoelectric material pellet are the same. The voltage applied to the piezoelectric material stack is periodically controlled to periodically expand and contract the piezoelectric material stack in the direction of the central axis, and the voltage applied to the piezoelectric material pellets at the same cycle as the piezoelectric material stack. By controlling, the piezoelectric material pellet is expanded and contracted periodically in the direction of the central axis, and after a predetermined number of expansions and contractions, the piezoelectric material pellet is taken out, and its characteristics are determined. Is worth configuration.

In order to realize the first aspect of the present invention, a second aspect is provided.
According to the invention, a plurality of piezoelectric materials are laminated in the thickness direction of the piezoelectric material alone, and a center along the thickness direction of the piezoelectric material with respect to the piezoelectric material pellet, which is the piezoelectric material alone. A piezoelectric material stack that is arranged to overlap the axes and vibrates the piezoelectric material pellet in the central axis direction, and periodically applies a predetermined voltage to the piezoelectric material stack to periodically apply the piezoelectric material stack to the piezoelectric material stack. A first driver circuit for expanding and contracting in the central axis direction, a second driver circuit for periodically applying a predetermined voltage to the piezoelectric material pellets to periodically expand and contract the piezoelectric material pellets in the central axis direction, A synchronization device for synchronizing voltages applied from the first driver circuit and the second driver circuit to the piezoelectric material stack and the piezoelectric material pellet, respectively; DOO is provided comprising configure.

[0008]

According to the first aspect of the present invention, the pressure and temperature conditions applied to the piezoelectric material stack and the piezoelectric material pellet are the same, so that the piezoelectric material pellet can be moved under the pressure and temperature conditions. Can be set in the same environment as a single unit. In addition, the piezoelectric material stack and the piezoelectric material pellet are overlapped with each other so that the central axes along the thickness direction of the piezoelectric material alone are aligned with each other. By expanding and contracting in the direction, the piezoelectric material pellet can be set to the same load state as the piezoelectric material alone in the piezoelectric material stack in the pressure fluctuation in the central axis direction. By taking out the piezoelectric material pellets after a predetermined number of expansions and contractions of the piezoelectric material pellets and evaluating the characteristics, the characteristics of the piezoelectric material alone in the piezoelectric stack can be accurately obtained.

According to the second aspect of the present invention, each of the first driver circuit and the second driver circuit applies a predetermined voltage to the piezoelectric material stack and the piezoelectric material pellet in a state where the respective cycles are made equal by the synchronization means. I do. Therefore, at the same period as the piezoelectric material stack vibrates the piezoelectric material pellet, the piezoelectric material pellet itself contracts in the direction of the central axis. Therefore, the load condition of the piezoelectric material pellet is the same as that of the piezoelectric material alone in the piezoelectric material stack.

[0010]

FIG. 1 is a block diagram showing an embodiment of a piezoelectric material evaluation apparatus according to the present invention.

In FIG. 1, reference numeral 1 denotes a set jig for a single piezoelectric material to be evaluated (this is referred to as a piezoelectric material pellet 2 or simply a pellet 2). As shown in FIG. Circuit 30, power supply 4
0, an amplifier 50, an oscillator 60, a charge amplifier 70, an oscilloscope 80, a control device 9 for controlling the entire evaluation device
0 together with the piezoelectric material evaluation device 100.

FIG. 2 is a front view of the jig 1 for setting piezoelectric material pellets in FIG.

In FIG. 2, reference numeral 3 denotes a frame of the set jig 1, and a clamping valve 4 is provided above the frame 3.
Are fixed by a nut 5a. A hydraulic hose 21 connected to a hydraulic pump 20 shown in FIG. 1 is connected to the clamping valve 4.
The hydraulic pressure from the hydraulic cylinder 5 the hydraulic pump 20 to the lower, movable part 5b to be displaced in the vertical direction (Z ₁ -Z ₂ direction) is provided.

A piezoelectric material stack (hereinafter, simply referred to as a stack) 6 as a vibrator is disposed below the movable portion 5b so that the axial direction thereof is aligned with the vertical direction. FIG. 3 is a diagram for explaining a configuration of a main part of the stack 6. Stack 6
As shown in FIG. 3B, electrode plates 6b- ₁ and 6b- ₂ made of stainless steel (SUS304H) are arranged on the upper and lower surfaces of a pellet 6a, which is a single piezoelectric material, and the electrode plates 6b- ₁ and 6b- _2. Insulator 6 on the opposite side of the pellet 6a
As shown in FIG. 3A, a plurality of unit laminates each having a respective c are arranged and laminated with their respective shapes interposed therebetween with a metal dummy 6d interposed therebetween. Each of the above laminated members 6a, 6
Each of b _-1 , 6b _-2 , 6c and 6d is bonded by an adhesive. Each of the plurality of electrode plates 6b- ₁ disposed above the plurality of pellets 6a of the stack 6 is electrically connected in parallel by an electric wire 6e, and the electrode plate disposed below the pellet 6a. 6b- ₂ are similarly connected in parallel by the electric wire 6f.

Therefore, when a predetermined voltage is applied to the electric wires 6e and 6f, an electric field is generated between the electrode plates 6b- ₁ and 6b- ₂ , and the pellet 6a expands in the thickness direction. The above-mentioned pellet 6a, which is a single piezoelectric material of this embodiment, is made of a multi-component piezoelectric ceramic (Pb (Zr _0.3 Ti _0.7 ) O _3.
Pb (Ni _1/3 Nb _2/3 ) O ₃ ) is used.

A connecting portion between the stack 6 having the above-described structure and the movable portion 5b of the hydraulic cylinder 5 is provided with a cylinder plate 5c, a superficial surface 7a and a superficial lower 7b. The seat prevents an uneven load on the pellet 2 provided below the stack 6.

Below the stack 6, there are provided setters 10, 11 for holding the pellets 2 via a setter upper 8, and an insulator 9 made of a zirconia sintered body. The pressure sensor 1 is provided below the lower setter 11 via an insulator 12 and a setter lower 13 formed of a zirconia sintered body similarly to the insulator 9 described above.
4 are provided. Pressure sensor 14 is setter lower 1
3 and the upper surface 3c of the lower member 3b of the frame 3. A rod-shaped guide member 13a is formed below the setter lower 13, and the guide member 13a
By There is inserted into the guide hole 3d formed in the lower member 3b of the frame 3, Settaroa 13, i.e. to prevent the lower setter 11 is displaced in the other axial direction (Z ₁ -Z ₂ direction) I have.

As described above, the pellet 2 to be evaluated is sandwiched between the setters 10 and 11 via the electrode plates 15a and 15b. The pellet 2 is made of the same material and has the same shape as the pellet 6a of the stack 6 described above.
The electrode plates 15a and 15b are also the electrode plates 6b- ₁ and 6b- _2.
The same material and the same shape as The electric wire (not shown) for applying a voltage to the pellet 2 is
0, 11 respectively, and the application of voltage and pressure to the pellet 2 is performed by the setters 10, 11 and the electrode plates 15a, 15b.
Done through. The insulators 9 and 12 are setters 10 and 11, a setter upper 8 and a setter lower 13.
It is provided to provide electrical insulation between

Here, the pellet 2 and the electrode plates 15a, 15
From the viewpoint of preventing the pellet 2 from being scratched and preventing stress concentration, the contact surface with b is important in terms of dimensional intersection, flatness, and surface roughness.
In the present embodiment, the dimension intersection of the setters 10 and 11 is ^{set to} _φ15 ^+0.05 _+0.02 , the flatness is 0.02 mm, and the surface ^{roughness is} _0.8Z , considering that the dimension intersection of the pellet 2 is φ15 ⁺⁰ _-0.05. doing. The dimension intersection of the electrode plates 15a and 15b is φ15.
It is set to ^-0.05 _-1 . Further, the electrode plates 15a, 15b
In the manufacture of, a method is employed in which a large number of electrode plates are formed from one plate at a time by etching. For this reason, the electrode plates 6b of FIG.
_As shown in FIG. ₁ , projections 6g were provided at both ends to allow tabs to be arranged there.

All members from the hydraulic cylinder 5 fixed to the frame 3 to the setter lower 13 guided and guided to the frame 3 are provided coaxially in the Z ₁ -Z ₂ direction in the figure. Therefore, when the hydraulic pressure of the hydraulic cylinder 5 is increased, compressive stress is generated in the members from the stack 6 to the setter lower 13 supported by the pressure sensor 14 along the axial direction (Z ₁ -Z ₂ direction).

The temperature of the pellet 2 is set in the pellet 2
In order to also prevent insulation along the surface, a set jig 1 is placed in a water tank (not shown) having a temperature control mechanism using silicone oil as a medium and controlled. Thereby, the pellet 2 can be set under the same temperature condition as the stack 6.

In FIG. 1, a hydraulic pump 20 applies a predetermined hydraulic pressure instructed by a control device 90 to a hydraulic cylinder 5 of a set jig 1. Thereby, the initial pressure on the pellets 2 can be set to an arbitrary value. In addition, a monitor signal is sent from the hydraulic pump 20 to the control device 90, and feedback control of the hydraulic pump 20 is performed by the control device 90.

The driver circuit 30 corresponds to the first driver circuit, and the output side is the electric wire 6 of the stack 6.
e, 6f. 0 → + 3 ~ from the oscillator 60
When a trigger of 5V is applied, a plus voltage of about twice the value set by the DC constant voltage power supply 40 is applied to the stack 6, and when a trigger of +3 to 5V → 0 is applied, a similar negative voltage is applied. Is done. The voltage is such that a plus voltage and a minus voltage are alternately applied in a predetermined cycle in the oscillator 60, and the plurality of pellets 6a in the stack 6 expand and contract in the thickness direction at a predetermined cycle by this voltage. I do. For this reason, the stack 6 vibrates in the axial direction (Z ₁ -Z ₂ direction), and acts as a vibrator for applying a pressure fluctuation of a predetermined period to the pellet 2.

The amplifier 50 corresponds to the second driver circuit, and controls an applied voltage to the pellet 2 to be evaluated. An oscillator 60 connected to the driver circuit 30 is connected to the input side of the amplifier 50. Therefore, the voltage applied to the pellet 2 can be synchronized with the trigger of the driver circuit 30, and the voltage waveform can be set to an arbitrary waveform by the oscillator 60. The output side of the amplifier 50 is the setter 1
0 and 11 are connected respectively. Therefore, the application of the voltage also causes the pellet 2 itself to expand and contract in the axial direction at the same cycle as the expansion and contraction of the stack 6.

The driver circuit 30 and the amplifier 50
Each sends a monitor signal to the control device 90, and the control device 90 performs feedback control of the applied voltage applied to the stack 6 and the pellet 2.

The initial pressure applied to the pellet 2 by the hydraulic cylinder 5, the pressure fluctuation caused by the stack 6, and the pressure fluctuation caused by the expansion and contraction of the pellet 2 itself are measured by the pressure sensor 14. The oscilloscope 80 is used as the pressure waveform shown in FIG.
You can check with. The voltage waveform of the amplifier 50 is also changed to the voltage waveform shown in FIG.
You can check with. The voltage waveform of the driver circuit 70 can be similarly confirmed by the oscilloscope 80.

The voltage waveform, pressure waveform, and temperature can be arbitrarily controlled within the setting ranges of the parameters shown in Table 1 by the piezoelectric material evaluation apparatus 100 having the above configuration.

[0028]

[Table 1]

Next, a description will be given of a test method and an evaluation method of a piezoelectric material using the apparatus having the above configuration.

First, the pellet 2 is placed on the electrode plates 15a, 1a.
5b is accurately sandwiched between the setters 10 and 11 while being sandwiched by 5b. Next, a predetermined hydraulic pressure is applied to the hydraulic cylinder 5 by the hydraulic pump 20 and the pressure sensor 1 is output from the stack 6.
An initial pressure is applied to the portion up to 4. In this embodiment, the initial pressure is set to 20 MPa.

Next, the set jig 1 is placed in the above-mentioned water tank, and the stack 6 and the pellet 2 are placed under the same temperature environment.
At a predetermined cycle to vibrate the stack 6 in the axial direction.
In this embodiment, the pressure fluctuation due to the vibration of the stack 6 is ± 10 MPa. Therefore, the pellet 2 is vibrated by periodically receiving the fluctuating pressure of 30 to 10 MPa. In addition, amplifier 5
0 and a voltage having a predetermined voltage waveform are periodically applied to the pellet 2 by the oscillator 60. This cycle is the same as the cycle of the pressure fluctuation of the stack 6 as described above. The voltage waveform in the present embodiment is, for example, as shown in FIG.
It is a waveform of. In this case, the pressure waveform in the portion of the pellet 2 has a peak value of 30 MPa as shown in FIG. 4B.

As described above, according to this embodiment, the pellet 2 to be evaluated is arranged coaxially with the stack 6 and is kept at the same temperature. Under the same environment under the conditions. Further, as described above, the pellet 2 itself is expanded and contracted by applying a voltage at the same cycle as the pressure fluctuation of the stack 6, so that the pellet 2 is set to the same load state as the pellet 6 a in the stack 6. Thus, the pellets 2 sandwiched between the setters 10 and 11 are set in the same environment as the pellets 6a constituting the stack 6 under each of the pressure condition, the temperature condition, and the load condition of the pressure fluctuation.

Therefore, after the predetermined number of vibrations and application of the voltage, the pellet 2 is taken out and a predetermined voltage is applied thereto, whereby the pellet 2 itself, that is, the characteristic of only the piezoelectric material alone in the stack 6, for example, the displacement The quantity, generated power, calorific value, power consumption, electromechanical coupling coefficient Kp, dielectric constant ε, mechanical quality factor Qm as an index of the response speed to a signal, and the like can be accurately obtained. Then, by increasing the number of vibrations and measuring the characteristics of the pellets 2 at some point as described above, it is possible to accurately change the characteristics of only the piezoelectric material alone in the stack 6 over time, durability performance, and the like. Obtainable.

In addition, according to the evaluation apparatus 100, the voltage waveform, the pressure waveform, and the temperature can be arbitrarily controlled within the setting ranges shown in Table 3, so that the characteristics of only the piezoelectric material alone in the stack 6 under a plurality of conditions are obtained. A change in characteristics over time can be obtained.

Further, by accurately grasping the characteristic change of the piezoelectric material itself, it is possible to develop a high-performance piezoelectric material with little characteristic change, and the durability and reliability of the piezoelectric actuator using the material are improved. . Therefore, there is no need to design an actuator on the premise of performance degradation, so that the design and driving conditions for ensuring only the initial performance are sufficient. As a result, the number of pellets to be laminated, the area thereof, and the applied voltage can be reduced, and the deriving effects such as low cost, compactness, and low power consumption of the actuator are great.

[0036]

As described above, according to the present invention, the piezoelectric material pellet and the piezoelectric material pellet are made to have the same conditions under the pressure condition, the temperature condition, and the load condition of the pressure fluctuation, whereby the piezoelectric material pellet is formed. Since it can be set in the same environment as the piezoelectric material alone in the inside, the characteristic change of only the piezoelectric material alone in the piezoelectric material stack can be accurately obtained. By accurately grasping the change in characteristics of the piezoelectric material alone, it is possible to develop a high-performance piezoelectric material with little change in characteristics and improved durability and reliability. Reliability can be improved. In addition, by improving the durability and reliability of the piezoelectric material, there is no need to provide a margin for product design, which greatly contributes to low cost, compact size, low power consumption, and the like of the product.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a piezoelectric material evaluation apparatus according to the present invention.

FIG. 2 is a front view of a jig for setting a piezoelectric material pellet in FIG.

FIG. 3 is a diagram illustrating a configuration of a main part of a piezoelectric material stack.

FIG. 4 is a diagram showing an example of a voltage waveform and a pressure waveform applied to a piezoelectric material pellet.

[Explanation of symbols]

 Reference Signs List 1 set jig 2 piezoelectric material pellet 5 hydraulic cylinder 6 piezoelectric material stack 10, 11 setter 14 pressure sensor 15a, 15b electrode plate 20 hydraulic pump 30 driver circuit 40 power supply 50 amplifier 60 shaker 70 charge amplifier 80 oscilloscope 90 control device 100 Apparatus for evaluating piezoelectric materials

Claims (2)

(57) [Claims] 1. A piezoelectric material stack formed by laminating a plurality of single piezoelectric materials in the thickness direction of the single piezoelectric material, and a piezoelectric material pellet as the single piezoelectric material in a thickness direction of the single piezoelectric material. The central axes along the axis are aligned and overlapped, and the pressure and temperature conditions applied to the piezoelectric material stack and the piezoelectric material pellets are the same, and the voltage applied to the piezoelectric material stack is periodically controlled to The piezoelectric material stack is periodically expanded and contracted in the central axis direction, and the applied voltage of the piezoelectric material pellet is controlled in the same cycle as the piezoelectric material stack, so that the piezoelectric material pellet is periodically expanded and contracted in the central axis direction. A method for evaluating a piezoelectric material, comprising: taking out the piezoelectric material pellets after a predetermined number of expansions / contractions and evaluating the characteristics thereof. 2. A single piezoelectric material is formed by laminating a plurality of single piezoelectric materials in the thickness direction of the single piezoelectric material, and the piezoelectric material pellets, which are the single piezoelectric materials, are arranged along the thickness direction of the single piezoelectric material. A piezoelectric material stack arranged so as to overlap with the central axis and vibrating the piezoelectric material pellet in the central axis direction; and periodically applying a predetermined voltage to the piezoelectric material stack to periodically apply the piezoelectric material stack. A first driver circuit that expands and contracts in the central axis direction; a second driver circuit that periodically applies a predetermined voltage to the piezoelectric material pellets to expand and contract the piezoelectric material pellets in the central axis direction; Synchronizing means for synchronizing voltages applied from the first driver circuit and the second driver circuit to the piezoelectric material stack and the piezoelectric material pellet, respectively. An evaluation device for a piezoelectric material comprising: