JP2014194377A - Piezoelectric property measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric property measuring device capable of measuring piezoelectric properties without allowing a piezoelectric material sample to stand.SOLUTION: A piezoelectric property measuring device 1 includes an electrically driven stand 2, first and second sample holding parts 3A and 3B and an elastic deformation part 5. The electrically driven stand 2 has a fixed part 21 and a movable part 22 and can freely adjust an interval between the fixed part 21 and the movable part 22. The first sample holding part 3A connected with the movable part 22 is freely attached and detached to and from the upper end of a piezoelectric material sample 10. The second sample holding part 3B connected with the fixed part 21 is freely attached and detached to and from the lower end part of the piezoelectric material sample 10. The elastic deformation part 5 is connected with between the movable part 22 and the first sample holding part 3A. The measuring device 1 measures a relation between an electric charge generated in the piezoelectric material sample 10 and a tensile load applied to the piezoelectric material sample 10.

Description

  The present invention relates to a measuring apparatus for measuring piezoelectric characteristics of a piezoelectric sample.

In recent years, polylactic acid films and cellulose-based material films are sometimes used as piezoelectric bodies in piezoelectric devices. In the case of a polylactic acid film, in the manufacturing process, a stretching process is performed in which tension is applied in a direction parallel to the film surface, and the stretching direction becomes a polarization direction, and crystallization and polarization of the polylactic acid film progress. The stretched polylactic acid film has piezoelectricity that causes distortion in the shear direction when an electric field is applied in the thickness direction, and is deformed in the in-plane direction (length direction and width direction) perpendicular to the thickness direction. Occurs. The piezoelectric can be expressed by the piezoelectric tensor _{d 14.}

In order to measure the piezoelectric tensor d ₁₄ of a film-like piezoelectric body, conventionally, deformation caused by the inverse piezoelectric effect when an electric field is applied to the piezoelectric body is detected, and the piezoelectric tensor d ₁₄ is based on the electric field strength and the deformation amount. The measuring method which calculates is adopted (for example, refer to Patent Document 1).

  FIG. 9 is a diagram illustrating a schematic configuration of a measuring apparatus used in a measuring method with reference to Patent Document 1.

  The measuring apparatus 101 includes a light emitting unit 102, a fiber head 103, a movable reflector 151, a sample holding structure 110, a photometric unit 104, a calculation control unit 105, and a voltage application unit 106. The light emitting unit 102 emits light. The fiber head 103 irradiates light guided by the light emitting unit 102 and receives the reflected light. The sample holding structure 110 fixes the lower end portion of the piezoelectric sample 150 and allows the upper end portion side of the piezoelectric sample 150 to stand upright vertically. The movable reflecting plate 151 is disposed so that the lower surface thereof is in contact with the upper end portion of the piezoelectric sample 150, and reflects the irradiation light of the fiber head 103. The voltage application unit applies a voltage to the piezoelectric sample 150. The arithmetic control unit 105 detects the displacement of the movable reflector 151 due to the piezoelectric deformation of the piezoelectric sample 150 and measures the piezoelectric characteristics of the piezoelectric sample 150.

JP2012-163502A

  In the conventional measuring apparatus and measuring method, it is necessary to fix the lower end of the piezoelectric sample to be measured and make the piezoelectric sample stand upright vertically. Therefore, when the piezoelectric sample is soft or curls on the piezoelectric sample When such wrinkles are attached, it is difficult to make the piezoelectric sample stand upright vertically, and it is difficult to measure the piezoelectric characteristics.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a piezoelectric characteristic measuring apparatus that can measure piezoelectric characteristics without allowing a piezoelectric sample to stand independently.

  The piezoelectric characteristic measuring apparatus according to the present invention includes an interval adjusting unit, first and second sample holding units, an elastic deformation unit, and a measuring unit. The interval adjusting unit has a first fulcrum and a second fulcrum, and the interval between the first fulcrum and the second fulcrum is adjustable. The first sample holder is connected to the first fulcrum and is detachable from the first end of the piezoelectric sample. The second sample holder is connected to the second fulcrum and is detachable from the second end of the piezoelectric sample. The elastic deformation portion is connected to at least one between the first fulcrum and the first sample holding portion and between the second fulcrum and the second sample holding portion. The measurement unit is electrically connected to the piezoelectric sample mounted on the first and second sample holding units, and measures the relationship between the charges generated in the piezoelectric sample with respect to the tensile load applied to the piezoelectric sample.

  In this configuration, since the piezoelectric sample is connected between the first fulcrum and the second fulcrum, the interval of which can be adjusted, a soft piezoelectric sample or a piezoelectric sample with a curled wrinkle is provided. Can be held in a straight shape between the first fulcrum and the second fulcrum. However, if the piezoelectric sample is held in this manner, deformation of the piezoelectric sample is constrained, and it becomes difficult to measure the piezoelectric characteristics using the inverse piezoelectric effect from deformation that occurs when an electric field is applied. Therefore, in this configuration, the piezoelectric characteristics of the piezoelectric sample are measured from the charges generated by the piezoelectric effect when a tensile load is applied to the piezoelectric sample. Therefore, a tensile load is applied to the piezoelectric sample by adjusting the distance between the first fulcrum and the second fulcrum connected to the piezoelectric sample through the elastic deformation portion. Then, the amount of change in the distance between the first fulcrum and the second fulcrum coincides with the sum of the amount of change in elongation of the elastic deformation portion and the amount of change in elongation of the piezoelectric sample. The elastic deformation portion is subjected to a tensile load equal to the tensile load applied to the piezoelectric sample, and extends with an elongation amount that is several times or several tens of times the elongation amount of the piezoelectric sample. That is, the sensitivity of the elongation of the piezoelectric sample to changes in the distance between the first fulcrum and the second fulcrum is improved. Therefore, the elongation amount and tensile load of the piezoelectric sample can be set precisely and stably, and the adjustment accuracy required for the interval adjustment unit can be relaxed. As a result, it becomes easy to accurately measure the relationship between the charge generated in the piezoelectric sample with respect to the elongation amount and tensile load of the piezoelectric sample, that is, the piezoelectric characteristics. In addition, play such as the interval adjusting unit, the first sample holding unit, and the second sample holding unit can be absorbed by the elastic deformation unit, and the occurrence of variations in the measurement of piezoelectric characteristics due to play can be suppressed.

  In the above-described piezoelectric characteristic measuring apparatus, the measurement unit may include a storage circuit that stores charges generated in the piezoelectric sample, and may detect the amount of charge stored from the storage circuit. Further, the storage circuit includes a capacitor connected in parallel with the piezoelectric sample, and the measurement unit can detect the amount of charge stored in the storage circuit from the voltage of the capacitor and the known capacitance of the capacitor. Good.

  The piezoelectric sample generates an amount of charge according to the applied tensile load, and if the tensile load is constant, no new charge is generated. Therefore, the output voltage of the piezoelectric sample is the initial reference voltage. The voltage value instantaneously changes to a voltage value corresponding to the amount of displacement, and then instantaneously changes to the reference voltage again. Therefore, by providing an accumulation circuit in the detection unit and accumulating charges generated in the piezoelectric sample, it is possible to stably detect the amount of charge generated in the piezoelectric sample. Further, by providing a capacitor in the storage circuit and detecting the voltage, the amount of charge stored in the storage circuit can be grasped from the voltage of the capacitor and a known capacitance.

  The above-described piezoelectric characteristic measuring device may include a control unit that controls the interval adjusting unit and sets the interval between the first fulcrum and the second fulcrum.

  The above-described piezoelectric characteristic measuring device may include a load detection unit that is provided between the first fulcrum and the second fulcrum and detects a tensile load applied to the piezoelectric sample.

  In the above-described piezoelectric characteristic measuring apparatus, the control unit may control the interval adjusting unit based on a tensile load detected by the load detecting unit.

  In the above-described piezoelectric characteristic measuring apparatus, the measurement unit may calculate the piezoelectric constant based on the electric charge generated in the piezoelectric sample and the tensile load detected by the load detection unit.

  In the above-described measuring apparatus, the piezoelectric sample is preferably a long rectangular piece of a polylactic acid film that has been subjected to stretching treatment, and is cut out at an angle of 45 ° from the stretching direction as a longitudinal direction.

  According to the piezoelectric characteristic measuring apparatus of the present invention, even a very soft piezoelectric sample or a piezoelectric sample with curled wrinkles goes straight between the first fulcrum and the second fulcrum. It can be held in such a shape. Then, by applying a tensile load to the piezoelectric sample held in this way and detecting the amount of charge generated in the piezoelectric sample, the piezoelectric characteristics of the piezoelectric sample can be measured using the piezoelectric effect. In addition, since the piezoelectric sample is held between the first fulcrum and the second fulcrum via the elastic deformation portion, the sensitivity of the elongation of the piezoelectric sample with respect to the distance between the first fulcrum and the second fulcrum. In addition, the sensitivity of the tensile load applied to the piezoelectric sample is improved, and the piezoelectric characteristics can be measured with high accuracy while suppressing measurement variations.

1 is a side view of a piezoelectric characteristic measuring apparatus according to a first embodiment. It is sectional drawing which shows the holding structure of the piezoelectric material sample in the measuring apparatus of the piezoelectric characteristic which concerns on 1st Embodiment. 1 is a block diagram of an apparatus for measuring piezoelectric characteristics according to a first embodiment. It is a graph which illustrates the relationship between the tensile load and electric charge which are measured with the measuring device of the piezoelectric characteristic concerning a 1st embodiment. It is a circuit diagram of the electric charge detection part in the measurement apparatus of the piezoelectric characteristic which concerns on 1st Embodiment. It is a block diagram of the measurement apparatus for piezoelectric characteristics according to the second embodiment. It is a block diagram of the measurement apparatus for piezoelectric characteristics according to the third embodiment. It is a block diagram of the measurement apparatus of the piezoelectric characteristic which concerns on 4th Embodiment. It is a schematic diagram explaining the measuring apparatus of the piezoelectric characteristic which concerns on a prior art example.

  Hereinafter, an apparatus and a method for measuring piezoelectric characteristics according to embodiments of the present invention will be described with reference to the accompanying drawings. In each attached drawing, an X axis, a Y axis, and a Z axis of an orthogonal coordinate system are appropriately attached. The X-axis positive direction of the orthogonal coordinate system is the front direction of the measuring device, the Y-axis positive direction of the orthogonal coordinate system is the right side surface direction of the measuring device, and the Z-axis positive direction of the orthogonal coordinate system is the top surface direction of the measuring device. .

  Further, in the following description, the thickness of the piezoelectric sample is along the front direction of the measuring apparatus, that is, along the X-axis positive direction of the orthogonal coordinate system, and the short side of the main surface of the piezoelectric sample is the right side direction of the measuring apparatus, that is, Embodiment in which the piezoelectric sample is held so that the major surface of the piezoelectric sample is along the positive direction of the Y-axis of the orthogonal coordinate system, and the top surface direction of the measuring device, that is, the positive direction of the Z-axis of the orthogonal coordinate system. Indicates.

<< First Embodiment >>
FIG. 1 is a side view of the piezoelectric characteristic measuring apparatus 1 according to the first embodiment of the present invention as seen from the right side. FIG. 1A shows a state in which the tensile force is hardly applied to the piezoelectric sample 10 by the measuring apparatus 1. FIG. 1B shows a state in which the measuring device 1 applies a predetermined tensile load to the piezoelectric sample 10.

  The measuring apparatus 1 includes a motorized stand 2, a first sample holding unit 3A, a second sample holding unit 3B, a load detection unit 4, and an elastic deformation unit 5.

  The motorized stand 2 includes a fixed portion 21, a movable portion 22, and a support column portion 23, and an interval between the movable portion 22 and the fixed portion 21 can be adjusted. The motorized stand 2 corresponds to the interval adjusting portion described in the claims, the movable portion 22 corresponds to the first fulcrum described in the claims, and the second fulcrum includes The fixed part 21 corresponds.

  The fixing unit 21 is placed on the top surface of a mounting table (not shown). The column part 23 has a long columnar shape along the Z axis, and the lower end side is fixed to the fixed part 21. The movable part 22 is attached to the front side of the column part 23 so as to be movable along the Z axis, and is opposed to the fixed part 21 with a gap along the Z axis. The column part 23 has a built-in drive mechanism including a motor (not shown) and moves the movable part 22 along the Z axis.

  The load detection unit 4 is attached to the lower surface of the movable unit 22 and detects a tensile load applied along the Z axis. Here, the elastically deforming portion 5 is a coil spring that extends along the Z axis, and is attached to the lower end portion of the load detecting portion 4, has a predetermined spring constant along the Z axis, and extends along the Z axis. It is elastically deformable. The elastic deformation portion 5 is not limited to a coil spring, and other elastically deformable members such as rubber may be employed.

  The first sample holding portion 3A is attached to the lower end portion of the elastic deformation portion 5 so that the piezoelectric sample 10 can be attached and detached. The second sample holding unit 3B is attached to the upper surface of the fixed unit 21, and the piezoelectric sample 10 can be attached and detached. The first sample holder 3A and the second sample holder 3B are opposed to each other with a gap along the Z axis.

  As described above, the piezoelectric sample 10 has a thickness along the front direction, that is, along the X-axis positive direction of the orthogonal coordinate system, and a short side of the principal surface along the right side direction, that is, along the Y-axis positive direction of the orthogonal coordinate system. The major surface is held by the first and second sample holders 3A and 3B so that the long side of the main surface is along the top surface direction, that is, the positive Z-axis direction of the orthogonal coordinate system.

  Therefore, if the piezoelectric sample 10 is attached to the first and second sample holders 3A and 3B and the position of the movable unit 22 on the Z-axis is appropriately set, even if the piezoelectric sample 10 is soft, Further, even if the curled wrinkles are attached, the piezoelectric sample 10 can be formed into a straight shape up and down as shown in FIG.

  Further, as shown in FIG. 1B, the load detecting unit 4 is mounted by attaching the piezoelectric sample 10 to the first and second sample holding units 3A and 3B and moving the movable unit 22 largely upward. A predetermined tensile load having an equal size can be applied to each of the elastic deformation portion 5 and the piezoelectric sample 10. Thereby, the load detection part 4 can detect the magnitude | size of the tensile load applied to the elastic deformation part 5 and the piezoelectric material sample 10. FIG. Moreover, the piezoelectric material sample 10 and the elastic deformation part 5 respectively extend in the direction in which the tensile load is applied with an elongation amount corresponding to the magnitude of the applied tensile load.

  Here, in the state shown in FIG. 1A, the dimension of the short side of the main surface of the piezoelectric sample 10 is, for example, 10 mm, the thickness of the piezoelectric sample 10 is, for example, 65 μm, and the main surface of the piezoelectric sample 10 is The long side dimension is, for example, 80 mm, and the elastic constant is, for example, 2.5 GPa. The first and second sample holders 3A and 3B are assumed to hold positions of 5 mm from both ends of the piezoelectric sample 10 respectively. The spring constant in the direction along the major surface long side of the elastically deformable portion 5 is 1 N / mm.

  Then, from the state shown in FIG. 1A, the movable unit 22 is moved upward so that the tensile load detected by the load detection unit 4 is increased by, for example, 10 Newtons (N), and the measuring apparatus 1 is moved to FIG. ).

  Then, an extension of about 0.4 mm occurs in the dimension of the major surface long side of the piezoelectric sample 10. At this time, since the tensile load of 10 N which is the same as the tensile load applied to the piezoelectric sample 10 is also applied to the elastic deformation portion 5, the dimension of the elastic deformation portion 5 in the direction along the Z axis is 10 mm. The growth of. Therefore, the elongation (10 mm) generated in the elastically deformed portion is about 25 times the elongation (0.4 mm) generated in the piezoelectric sample 10.

  As described above, if the elongation generated in the elastically deforming portion is 25 times the elongation generated in the piezoelectric body sample 10, the load detection accuracy by the load detection unit 4 is low, and there is an error in the detected load. Even if the portion 22 is slightly deviated from the position to be originally set (for example, the position where the tensile load is actually 10 N), the error occurring in the amount of elongation of the piezoelectric sample 10 is 1 / of the position error of the movable portion 22. Only (1 + 25) will occur. For example, even if the movable part 22 is deviated by 1 mm from the position that should be originally set, an error of 0.038 mm is generated in the extension amount of the piezoelectric sample 10. Therefore, by supporting the piezoelectric sample 10 via the elastic deformation portion 5, the tensile load applied to the piezoelectric sample 10 and the elongation amount of the piezoelectric sample 10 can be set with extremely high accuracy.

  In addition, by supporting the piezoelectric sample 10 via the elastic deformation portion 5, redundancy for accurately applying a tensile load to the piezoelectric sample 10 is increased, and the positional accuracy of the movable portion 22 and the load detection portion 4 are increased. The required level of detection accuracy will be relaxed. Therefore, it is possible to adopt even a low-cost and low-performance one as the motorized stand 2 or the load detection unit 4, and the measuring apparatus 1 can be configured at a low cost as a whole. Therefore, even when the piezoelectric characteristics are measured for all devices at the time of manufacturing the piezoelectric device, the manufacturing cost of the piezoelectric device can be reduced.

  FIG. 2 is a cross-sectional view showing the first and second sample holders 3A and 3B that hold the piezoelectric sample 10. 2A is a cross-sectional view taken along the alternate long and short dash line AA in FIGS. 2B and 2C from the right side surface direction. 2B is a cross-sectional view taken along a dashed line BB in FIGS. 2A and 2C when viewed from the front. FIG. 2C is a cross-sectional view taken along the alternate long and short dash line CC in FIGS. 2A and 2B when viewed from the top surface direction.

  Each of the first and second sample holders 3A and 3B includes a fixing jig 31 and two metal rods 34. The fixing jig 31 has plate-like portions 32 and 33. The plate-like portion 32 and the plate-like portion 33 are opposed to each other, and are configured to be fixed by adjusting the interval. The two metal rods 34 are round bars each having a cross-sectional diameter of about 2 mm. A groove 32 </ b> A that is shallower than the diameter of the metal rod 34 is provided on the surface of the plate-like portion 32 facing the plate-like portion 33. In addition, a groove 33 </ b> A shallower than the diameter of the metal rod 34 is provided on the surface of the plate-like portion 33 facing the plate-like portion 32. Each of the grooves 32A and 33A is provided so as to extend along the Y axis and is opposed to each other, and a metal rod 34 is fitted into each of the grooves 32A and 33A. Accordingly, the two metal rods 34 are opposed to each other, and a part of each protrudes from the grooves 32A and 33A.

  The piezoelectric sample 10 includes a piezoelectric film 11 and detection electrodes 12 and 13.

  The piezoelectric film 11 has a long rectangular main surface shape, and is made of a piezoelectric film having a short side of the main surface and a long side of the main surface. The detection electrode 12 is formed on the entire main surface facing the front direction of the piezoelectric film 11. The detection electrode 13 is formed on the entire main surface facing in the direction opposite to the front direction (back direction) of the piezoelectric film 11. The piezoelectric film 11 generates an electric charge due to elongation in the direction along the major surface long side (Z axis), and generates a potential difference between the detection electrode 12 and the detection electrode 13.

As a material of the piezoelectric film 11, for example, a uniaxially or biaxially stretched L-type polylactic acid (PLLA) film can be employed. PLLA is a chiral polymer whose main chain has a helical structure, and is uniaxially stretched so that the molecules are oriented and have piezoelectricity. In addition, PLLA is subjected to heat treatment after stretching, whereby the crystallization of the extended chain crystal of polylactic acid is promoted and the piezoelectric constant is improved. PLLA has a piezoelectric represented by piezoelectric tensor d _14, when the angle of 0 ° with respect to the stretching direction was cut out as a longitudinally long rectangular piece is deformed to distorted into a parallelogram. Therefore, here, a long rectangular piece is cut out from the PLLA film with the angle direction of 45 ° as a longitudinal direction with respect to the stretching direction, thereby constituting the piezoelectric film 11. Therefore, the piezoelectric film 11 efficiently generates charges by being deformed so as to expand and contract along the major surface long side. As the piezoelectric film 11, in addition to the long rectangular piece cut out from the PLLA with the 45 ° angle direction of the stretching direction as the longitudinal direction, any other piezoelectric material can be used as long as charges are generated by stretching in the longitudinal direction. You may be comprised with material.

  The piezoelectric sample 10 is sandwiched between two metal rods 34 of the first sample holder 3A on the upper end side and sandwiched between the two metal rods 34 of the second sample holder 3B on the lower end side. ing. The dimension of the piezoelectric sample 10 in the direction along the Y axis, that is, the dimension of the short side of the main surface is shorter than the dimension in which the two metal rods 34 face each other along the Y axis. It is in contact with the two metal rods 34 over the entire length. Further, since the two metal rods 34 are each in the shape of a round bar, the area where the piezoelectric sample 10 and each metal rod 34 are in contact with each other is small, and the piezoelectric sample 10 is clamped with a strong clamping force. The detection electrode 12 of the piezoelectric sample 10 is electrically connected to the metal rod 34 of the first and second sample holders 3A and 3B, and the detection electrode 13 of the piezoelectric sample 10 is a metal It is electrically connected to the rod 34.

  FIG. 3 is a block diagram of the measuring apparatus 1.

  The measuring apparatus 1 includes a load control unit 6, a charge detection unit 7, and a calculation unit 8 in addition to the above-described configuration.

  The load control unit 6 corresponds to the control unit described in the claims. The load control unit 6 controls the motorized stand 2 so that the actual tensile load detected by the load detection unit 4 becomes the set value when the set value of the tensile load is set from the outside.

  The load detection unit 4 detects the magnitude of the load applied to the piezoelectric sample 10.

  The charge detection unit 7 constitutes at least a part of the measurement unit described in the claims. The charge detection unit 7 is electrically connected to the piezoelectric sample 10 via the metal rod 34 described above, and detects charges generated in the piezoelectric sample 10. As the charge detection unit 7, a device generally called an electrometer or a circuit configuration shown in FIG.

  The calculation part 8 comprises at least one part of the measurement part as described in a claim. The calculation unit 8 reads at least the predetermined value P1 and the predetermined value P2 of the tensile load applied to the piezoelectric sample 10 from the output of the load detection unit 4. Further, the calculation unit 8 determines, based on the output of the charge detection unit 7, that at least the charge Q1 generated when the tensile load applied to the piezoelectric sample 10 is a predetermined value P1 and the tensile load applied to the piezoelectric sample 10 are predetermined. Read the charge Q2 generated at the value P2. Then, the piezoelectric characteristics relating to the relationship between the predetermined values P1, P2 of the tensile load detected by the load detection unit 4 and the charges Q1, Q2 detected by the charge detection unit 7 are calculated.

Calculator 8, for example, a piezoelectric tensor _{d 14} of the piezoelectric film 11 made of PLLA, is calculated as piezoelectric properties. Here, the calculation method of the piezoelectric tensor d _14, will be described more specifically.

  FIG. 4A is a graph in which time is plotted on the horizontal axis and the magnitude of tensile load and charge is plotted on the vertical axis. FIG. 4B is a graph in which the horizontal axis indicates the load and the vertical axis indicates the charge. Here, the motorized stand 2 is driven so that the piezoelectric sample 10 is applied with a tensile load of 4N as the predetermined value P1 and a tensile load of 9N as the predetermined value P2, and the movable part 22 is moved up and down at a speed of 2 mm / sec. The example in the case of moving repeatedly is shown.

  When a tensile load is applied to the piezoelectric sample 10 so that the tensile load goes back and forth between the predetermined value P1 (= 4N) and the predetermined value P2 (= 9N), so as to follow in synchronization with the change in the tensile load, The charge detected by the charge detector 7 changes, and the amount of charge changes between a predetermined value Q1 (= 5 nC) and Q2 (= 21 nC). 4B, when the tensile load is increased by 1N, the generated charge is increased by 3.2 nC (nanocoulomb), and the change amount of the generated charge with respect to the change amount of the tensile load is , Q2-Q1 / (P2-P1) = 3.2 nC.

If the amount of change in the generated charge relative to the amount of change in the tensile load can be measured, referring to a known calculation method described in Japanese Journal of Applied Physics.vol.37 p3374-3376, 1998, etc. The tensor d ₁₄ can be calculated.

For example, the tensile and the amount of change in electric charge generated with respect to a change in load, the following relationship holds between the piezoelectric tensor d _14.

(Q2-Q1) / (P2-P1)
= ((L1 × L2) / (L3 × L4)) × d 14/2
= 3.2 [nC / N]
= ((70 [mm] × 10 [mm]) / (10 [mm] × 65 [μm])) × d 14/2
However, in the above equation, the dimension of the portion to which the tensile load of the piezoelectric sample is applied (the portion on the inner side of the sample holding portion from the major surface long side length of the piezoelectric sample) is L1, and the major surface short side of the piezoelectric sample is Are L2 and L3, respectively, and the thickness of the piezoelectric sample is L4.

Therefore, the piezoelectric characteristics of the piezoelectric sample 10, where it is possible to calculate the piezoelectric tensor d ₁₄ as follows.

d ₁₄ = 3.2 [nC / N] × (10 [mm] × 65 [μm]) × 2 / (70 [mm] × 10 [mm]) = 5.9 [pC / N]
As described above, in the measuring apparatus 1 according to the present embodiment, the piezoelectric tensor d ₁₄ of the piezoelectric body sample 10, by utilizing the piezoelectric effect of the piezoelectric body sample 10, the tensile charges produced with respect to the change amount of the load change amount of the It can be measured based on the relationship. As described above, by applying a tensile load to the piezoelectric sample 10 via the elastic deformation portion 5, the amount of change in the tensile load can be set with high accuracy. the tensor d _14, can be measured with high accuracy.

  That is, even if the error due to the load detection unit 4 is large and the load detection accuracy is low, or even if the error due to the motorized stand 2 is large and the driving accuracy is low, the extension amount of the piezoelectric sample 10 and the piezoelectric sample 10 Since the error that occurs in the actually applied tensile load is extremely small, the amount of change in the tensile load can be set stably with high accuracy, whereby the piezoelectric characteristics of the piezoelectric sample 10 can be stabilized with high accuracy. Can be measured.

  Furthermore, even if there is play in the movable part 22, the first sample holding part 3A, the second sample holding part 3B, etc., the play is absorbed by the elastic deformation part 5 and measurement variations of the piezoelectric characteristics occur. Can be suppressed.

  Next, a circuit configuration example when the charge detection unit 7 is configured without using an electrometer will be described.

  FIG. 5 is a circuit diagram of the charge detection unit 7.

  The charge detection unit 7 includes a resistor R1, a resistor R2, a capacitor C1, an operational amplifier U1, and a voltmeter V1.

  The piezoelectric sample 10 is connected to a connection point between the resistor R1 and the resistor R2 via one of the detection electrodes 12 and 13 described above. The resistors R1 and R2 are connected in series between the drive voltage application terminal Vdd and the ground. A capacitor C1 is connected to the piezoelectric sample 10 in parallel. The piezoelectric sample 10 is connected to the non-inverting input terminal of the operational amplifier U1 through the other of the detection electrodes 12 and 13 described above. The output terminal of the operational amplifier U1 is connected to the inverting input terminal of the operational amplifier U1. A driving voltage is supplied from the driving voltage application terminal Vdd to the operational amplifier U1. The output terminal of the operational amplifier U1 is connected to the voltmeter V1.

  In the charge detection unit 7 configured as described above, the operational amplifier U1 employs a CMOS type having a bias current of 1 pA and an input impedance of 1 TΩ (teraohm) class. Then, the electric charge generated in the piezoelectric sample 10 hardly leaks through the operational amplifier U1, and the electric charge stays in the capacitor C1 for a long time. That is, the operational amplifier U1 and the capacitor C1 function as an accumulation circuit described in the claims, and accumulate electric charges generated in the piezoelectric sample 10. Therefore, a potential difference due to the charge generated in the piezoelectric sample 10 exists stably between the detection electrodes 12 and 13 of the piezoelectric sample 10, and this potential difference is stably detected using the voltmeter V1. be able to. It should be noted that measurement is preferably performed in an environment in which temperature and humidity are controlled, since electric charge may leak from the capacitor C1 due to the influence of a slight leak path on the printed circuit board.

  In the charge detector 7, the charge generated in the piezoelectric sample 10 appears as a product of the capacitance of the capacitor C1 and the voltage value detected by the voltmeter V1. Therefore, the charge generated in the piezoelectric sample 10 is calculated by the charge detection unit 7 and the calculation unit 8 from the detection voltage of the voltmeter V1 detected by the charge detection unit 7 and the known capacitance of the capacitor C1. be able to. As the capacitance of the capacitor C1, when the capacitance of the piezoelectric sample is C2, the known capacitance of the capacitor C1 is appropriately about 30 to 300 times that of C2.

<< Second Embodiment >>
FIG. 6 is a block diagram of a piezoelectric characteristic measuring apparatus 41 according to the second embodiment of the present invention.

  The measurement apparatus 41 according to the present embodiment includes an interval control unit 46, a load detection unit 44, a charge detection unit 47, and a calculation unit 48 in addition to the configuration similar to the configuration shown in FIG. ing.

  The interval control unit 46 corresponds to the control unit described in the claims. The space | interval control part 46 controls the motorized stand 2 so that the moving amount in the electric stand 2 becomes a set value by setting the moving amount of the electric stand 2 from the outside. Thereby, the motorized stand 2 moves the movable part 22 by the movement amount set in the interval control part 46. Then, the tensile load applied to the elastically deformable portion 5 and the piezoelectric sample 10 changes from the predetermined value P1 to the predetermined value P2 due to the movement of the movable portion 22.

  The load detection part 44 comprises at least one part of the measurement part as described in a claim. The load detection unit 44 detects the magnitude of the load applied to the piezoelectric sample 10.

  The charge detection unit 47 constitutes at least a part of the measurement unit described in the claims. The charge detection unit 47 detects charges generated in the piezoelectric sample 10.

  The calculation part 48 comprises at least one part of the measurement part as described in a claim. The calculation unit 48 reads at least the predetermined value P1 and the predetermined value P2 of the tensile load applied to the piezoelectric sample 10 from the output of the load detection unit 44. In addition, the calculation unit 48 determines from the output of the charge detection unit 47 at least a charge Q1 generated when the tensile load applied to the piezoelectric sample 10 is a predetermined value P1 and a tensile load applied to the piezoelectric sample 10. Read the charge Q2 generated at the value P2. Then, the piezoelectric characteristics relating to the relationship between the predetermined values P1, P2 of the tensile load detected by the load detection unit 44 and the charges Q1, Q2 detected by the charge detection unit 47 are calculated.

  Therefore, the measuring apparatus 41 according to the present embodiment can also measure the piezoelectric characteristics based on the relationship between the amount of change in the generated charge with respect to the amount of change in the tensile load, using the piezoelectric effect of the piezoelectric sample 10. As described above, by applying a tensile load to the piezoelectric sample 10 via the elastic deformation portion 5, the amount of change in the tensile load can be set with high accuracy. The characteristics can be measured with high accuracy.

<< Third Embodiment >>
FIG. 7 is a block diagram of a piezoelectric characteristic measuring apparatus 51 according to the third embodiment of the present invention.

  The measurement apparatus 51 according to the present embodiment includes an interval control unit 56, a load detection unit 54, and a charge detection unit 57 in addition to the same configuration as the configuration shown in FIG.

  The interval controller 56 corresponds to the controller described in the claims. The space | interval control part 56 controls the motorized stand 2 so that the moving amount in the electric stand 2 becomes a set value by setting the moving amount of the electric stand 2 from the outside. Thereby, the motorized stand 2 moves the movable part 22 by the movement amount set in the interval control part 56. Then, the tensile load applied to the elastically deformable portion 5 and the piezoelectric sample 10 changes from the predetermined value P1 to the predetermined value P2 due to the movement of the movable portion 22.

  The load detection part 54 comprises at least one part of the measurement part as described in a claim. The magnitude of the load applied to the piezoelectric sample 10 is detected, and at least signals indicating the predetermined value P1 and the predetermined value P2 are output as data to some standard input / output means.

  The charge detection unit 57 constitutes at least a part of the measurement unit described in the claims. The charge detection unit 57 detects the charge generated in the piezoelectric sample 10, and at least when the tensile load applied to the piezoelectric sample 10 is a predetermined value P1, the charge Q1 generated in the piezoelectric film 11 of the piezoelectric sample 10 and When the tensile load applied to the piezoelectric sample 10 is a predetermined value P2, a signal indicating the charge Q2 generated in the piezoelectric film 11 of the piezoelectric sample 10 is output as data to some standard input / output means.

  As described above, the measurement device 51 according to the present embodiment uses the piezoelectric effect of the piezoelectric sample 10 to measure the relationship between the amount of change in the generated charge with respect to the amount of change in the tensile load, and outputs the measured data. To do. Therefore, it is possible to calculate various piezoelectric constants related to the piezoelectric sample by using an external device or the like using these data.

<< Fourth Embodiment >>
FIG. 8 is a block diagram of a piezoelectric characteristic measuring apparatus 61 according to the fourth embodiment of the present invention.

  The measurement apparatus 61 according to the present embodiment includes a load control unit 66 and a charge detection unit 67 in addition to the same configuration as the configuration shown in FIG.

  The load control unit 66 corresponds to the control unit described in the claims. In the load control unit 66, the correspondence relationship between the tensile load applied to the piezoelectric sample 10 and the driving amount of the motorized stand 2 is registered in advance, and the setting value of the tensile load is set from the outside, The motorized stand 2 is controlled so that the corresponding driving amount is obtained. Thereby, the motorized stand 2 moves the movable part 22 so that the tensile load set in the load control part 66 is applied to the elastic deformation part 5 and the piezoelectric sample 10. Then, the tensile load applied to the elastically deformable portion 5 and the piezoelectric sample 10 changes from the predetermined value P1 to the predetermined value P2 due to the movement of the movable portion 22.

  The charge detection unit 67 constitutes at least a part of the measurement unit described in the claims. The charge detection unit 67 detects charges generated in the piezoelectric sample 10, and at least charges Q1 generated in the piezoelectric sample 10 when the tensile load applied to the piezoelectric sample 10 is a predetermined value P1 and the piezoelectric sample 10. A signal indicating the charge Q2 generated in the piezoelectric sample 10 when the applied tensile load is a predetermined value P2 is output to some standard input / output means as data.

  As described above, the measurement apparatus 61 according to the present embodiment uses the piezoelectric effect of the piezoelectric sample 10 to measure the relationship between the change amount of the generated charge and the change amount of the tensile load, and outputs the measured data. To do. Therefore, it is possible to calculate various piezoelectric constants related to the piezoelectric sample by using an external device or the like using these data.

Although the present invention can be implemented as in each of the embodiments described above, for example, the major surface long side of the piezoelectric sample is arranged along the right side direction or the front direction of the measuring device. The piezoelectric sample may be configured to be pulled left and right or back and forth. Moreover, you may make it connect an elastic deformation part to each of the upper end part side and lower end part side of a piezoelectric material sample. Moreover, you may make it connect an elastic deformation part and a load measurement part to the lower end part side of a piezoelectric material sample. In addition, the polylactic acid film shown in each embodiment is merely an example of a piezoelectric sample, and the present invention suitably measures piezoelectric characteristics of any material as long as it is a film-like piezoelectric sample. can do. Further, even if the piezoelectric properties to be measured is not limited to the piezoelectric tensor d _14, it may measure the other piezoelectric D constants or other piezoelectric characteristics (such as a piezoelectric G constant).

DESCRIPTION OF SYMBOLS 1,41,51,61 ... Measuring apparatus 2 ... Electric stand 21 ... Fixed part 22 ... Movable part 23 ... Support | pillar part 3A ... First sample holding part 3B ... Second sample holding part 31 ... Fixing jigs 32, 33 ... plate-like part 32A, 33A ... groove 34 ... metal rod 4, 44, 54 ... load detection part 5 ... elastic deformation part 6, 66 ... load control part 7, 47, 57, 67 ... charge detection part 8, 48 ... calculation Part 10: Piezoelectric sample 11 ... Piezoelectric film 12, 13 ... Detection electrodes 46, 56 ... Interval control part

Claims (8)

An interval adjusting unit having a first fulcrum and a second fulcrum, and capable of adjusting an interval between the first fulcrum and the second fulcrum;
A first sample holder connected to the first fulcrum and detachably attached to a first end of the piezoelectric sample;
A second sample holder connected to the second fulcrum and detachably attached to a second end of the piezoelectric sample;
An elastic deformation portion connected between at least one of the first fulcrum and the first sample holder and between the second fulcrum and the second sample holder; and
Measurement that is electrically connected to the piezoelectric sample mounted on the first and second sample holders and measures the relationship between the charge generated in the piezoelectric sample and the tensile load applied to the piezoelectric sample. Part,
A piezoelectric characteristic measuring device comprising: The measurement unit includes a storage circuit that stores charges generated in the piezoelectric sample, and detects the amount of charge stored from the storage circuit.
The apparatus for measuring piezoelectric characteristics according to claim 1. The storage circuit includes a capacitor connected in parallel with the piezoelectric sample,
The measurement unit detects the amount of charge accumulated in the accumulation circuit from the voltage of the capacitor and the known capacitance of the capacitor.
The apparatus for measuring piezoelectric characteristics according to claim 2.   The piezoelectric characteristic measuring device according to claim 1, further comprising a control unit that controls the interval adjusting unit and sets an interval between the first fulcrum and the second fulcrum.   5. The apparatus according to claim 1, further comprising a load detection unit that is provided between the first fulcrum and the second fulcrum and detects a tensile load applied to the piezoelectric sample. Measuring device for piezoelectric characteristics. A control unit for controlling the interval adjusting unit and setting an interval between the first fulcrum and the second fulcrum;
A load detecting unit provided between the first fulcrum and the second fulcrum and detecting a tensile load applied to the piezoelectric sample;
The said control part is a measurement apparatus of the piezoelectric characteristic of any one of Claims 1-3 which controls the said space | interval adjustment part based on the tensile load which the said load detection part detects.   The piezoelectric characteristic according to claim 1, wherein the measurement unit calculates a piezoelectric constant based on an electric charge generated in the piezoelectric sample and a tensile load applied to the piezoelectric sample. Measuring device.   The piezoelectric sample is a long rectangular piece of a polylactic acid film that has been subjected to a stretching treatment, and is cut out at an angle of 45 ° from the stretching direction as a longitudinal direction. 2. The piezoelectric characteristic measuring device according to 1.