Piezoelectric material measuring device and piezoelectric material measuring method

Abstract

To provide a piezoelectric material measuring device and piezoelectric material measuring method that can suppress variation of measurement values.SOLUTION: A measuring device 1 includes a driving source 14, a non-contact type vibrometer 12, and a voltmeter 15. The driving source outputs an arbitrary voltage to a measuring object 2 obtained by joining two rectangular plate-shaped piezoelectric materials sheared and deformed according to the voltage in a polarization direction that is parallel and opposite. The non-contact type vibrometer measures the displacement of the measuring object. The voltmeter measures the voltage applied to the measuring object.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a piezoelectric material measuring device and a piezoelectric material measuring method. [Background technology]

[0002] Shear mode piezoelectric inkjet heads are known. In addition, to reduce the voltage and improve the performance of inkjet heads, it is desirable to use piezoelectric materials that can produce large strain. The piezoelectric constant of a piezoelectric material varies depending on the operating conditions (electric field, frequency). Therefore, when adopting a piezoelectric material, it is desirable to measure the piezoelectric constant under the operating conditions of the inkjet head in order to determine the amount of strain. However, there is a problem in that the measured values ​​vary greatly under the operating conditions of the inkjet head, which are the large electric field (e.g., several hundred V / mm) and high frequency range (e.g., several hundred kHz). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-152273 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a piezoelectric material measuring device and a piezoelectric material measuring method capable of suppressing the variation in the measured values. [Means for solving the problem]

[0005] An apparatus for measuring a piezoelectric material according to an embodiment includes: The measurement device is a measuring object in which two rectangular plate-shaped piezoelectric materials that undergo shear deformation in response to voltage are joined together with their polarization directions parallel and opposite to each other, and electrodes are formed on both main surfaces along the polarization direction, and the device measures the piezoelectric constant based on the shear strain amplitude calculated from the displacement speed of the measurement surface, which is the end surface in the polarization direction, and the electric field amplitude calculated from the voltage applied to the electrodes. The device includes a driving source, a non-contact vibrometer, and a voltmeter. The electrodes on both main surfaces of the measurement object are set based on the driving conditions of a device that uses the piezoelectric material of the measurement object. The non-contact vibrometer outputs a desired voltage. A laser beam is irradiated onto the measurement surface, and the reflected light from the measurement surface is sensed to measure the displacement speed of the measurement surface. The voltage meter measures: connected to the drive source, The object to be measured output Will be The above Measure the voltage. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is an explanatory diagram illustrating a schematic configuration of a measurement device according to an embodiment. [Diagram 2] FIG. 1 is a perspective view showing a schematic configuration of a measurement object to be measured by a measurement device according to an embodiment. [Diagram 3] FIG. 2 is an explanatory diagram illustrating a configuration of a holder of the measuring device according to the embodiment. [Figure 4] FIG. 2 is a block diagram showing the configuration of a processing device of the measurement device according to the embodiment; [Diagram 5] FIG. 2 is an explanatory diagram showing an example of measurement of a measurement object using the measurement device according to the embodiment. [Figure 6] 4 is a flowchart showing an example of a method for measuring a measurement object using the measurement device according to the embodiment. [Figure 7] FIG. 11 is an explanatory diagram showing an example of the relationship between the piezoelectric constant and the frequency, which is a result of measuring a test piece by a conventional measuring method. [Figure 8] FIG. 13 is an explanatory diagram showing the results of FEM analysis of a conventional measuring method. [Figure 9] FIG. 4 is an explanatory diagram showing the result of an FEM analysis of the measurement method according to the embodiment, illustrating the relationship between the driving frequency and the shear strain amplitude. [Figure 10] 4A to 4C are explanatory diagrams showing examples of measurement results of a soft-type PZT and a hard-type PZT measured using the measurement device and measurement method of the present embodiment. [Figure 11] FIG. 11 is an explanatory diagram in which the deviation of each measurement point from an approximation line is plotted for the measurement values ​​shown in FIG. 10. [Figure 12] 5A and 5B are explanatory diagrams showing the repeat measurement accuracy when measurements are repeatedly performed using the measurement device and measurement method of the present embodiment. [Figure 13] FIG. 13 is an explanatory diagram illustrating a schematic configuration of a holder of a measuring device according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, an example of a piezoelectric material measuring device 1 and a piezoelectric material measuring method according to an embodiment will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing a typical configuration of a measuring device 1 according to an embodiment. FIG. 2 is a perspective view showing a typical configuration of a measurement object 2 measured by the measuring device 1. FIG. 3 is an explanatory diagram showing a typical configuration of a holder 11 of the measuring device 1. FIG. 4 is a block diagram showing a configuration of a processing device 16 of the measuring device 1. FIG. 5 is an explanatory diagram showing an example of measurement of the measurement object 2 using the measuring device 1, and FIG. 6 is a flow chart showing an example of a method of measuring the measurement object 2 using the measuring device 1.

[0008] First, a measurement object 2 to be measured by the measurement device 1 will be described. As shown in FIG. 1, the measurement object 2 is an object to be measured by the measurement device 1. As shown in FIG. 2, the measurement object 2 includes, for example, two piezoelectric material pieces 4 (piezoelectric material) formed in a rectangular plate shape that shears in response to a voltage (electric field), and electrodes 5 provided on both main surfaces along the polarization direction of each piezoelectric material piece 4. The measurement object 2 is formed by joining two rectangular plate-shaped piezoelectric material pieces 4, each having electrodes 5 provided on both main surfaces along the polarization direction, so that they are polarized antiparallel. In other words, the measurement object 2 is formed by joining two piezoelectric material pieces 4 with their polarization directions parallel and opposite to each other. In FIG. 2, the polarization direction of the piezoelectric material piece 4 is indicated by an arrow.

[0009] The two piezoelectric material pieces 4 used in the measurement object 2 are made of the same material. Furthermore, the two piezoelectric material pieces 4 are set to have the same dimensions of width W, length L, and thickness t. The electrodes 5 are made of, for example, gold. However, the electrodes 5 may be made of other materials such as silver, nickel, etc. The electrodes 5 are formed on both main surfaces of the piezoelectric material piece 4 by a suitable method such as vapor deposition, baking, plating, sputtering, etc.

[0010] In this embodiment, for convenience of explanation, the direction along the polarization direction of the piezoelectric material piece 4 is defined as the longitudinal direction, and the stacking direction of the two piezoelectric material pieces 4 is defined as the thickness direction or the up-down direction. In addition, in this embodiment, the test piece including one of the piezoelectric material pieces 4 of the measurement object 2 and electrodes 5 provided on both main surfaces of the piezoelectric material piece 4 is defined as the upper test piece 6, and the test piece including the other piezoelectric material piece 4 and electrodes 5 provided on both main surfaces of the piezoelectric material piece 4 is defined as the lower test piece 7.

[0011] Next, the measuring device 1 that measures the measurement object 2 will be described. 1, the measuring device 1 includes a holder 11, a non-contact vibrometer 12, a transport device 13, a drive source 14, a voltmeter 15, and a processing device 16. The measuring device 1 drives the measurement object 2 held by the holder 11 with the drive source, and measures the displacement speed of one end face (measurement surface) in the longitudinal direction of the driven measurement object 2 at each position in the vertical direction. The measuring device 1 then finds the tilt amplitude of each piezoelectric material piece 4 from the displacement amplitude found by integrating the measured displacement speed, and finds the average value of the tilt amplitude as the strain amplitude of the piezoelectric material.

[0012] The holder 11 holds the object to be measured 2 in a position where one end face in the longitudinal direction of the object to be measured 2 faces the non-contact vibrometer 12. The holder 11 also provides electrical continuity between the electrodes 5 on both main faces of the object to be measured 2 and the driving source 14. As a specific example, the holder 11 abuts against the lower electrode 5 of the upper test piece 6 and the lower electrode 5 of the lower test piece 7 of the object to be measured 2.

[0013] 3, the holder 11 includes a pair of contact probe pins 111 that abut against the electrodes 5 on both main surfaces of the object to be measured 2 to hold the object to be measured 2. The contact probe pins 111 are made of a highly conductive metal material. The pair of contact probe pins 111 are connected to a driving source 14.

[0014] The non-contact vibrometer 12 measures the displacement of the longitudinal end face, which is the measurement face of the measurement object 2, and outputs the measured displacement value. For example, the non-contact vibrometer 12 measures the displacement speed of each measurement face of the upper test piece 6 and the lower test piece 7 of the measurement object 2. The non-contact vibrometer 12 outputs the measured displacement speed as a signal. The non-contact vibrometer 12 is, for example, a laser Doppler vibrometer.

[0015] 1, such a non-contact vibrometer 12 irradiates a measurement surface of a measurement object 2 with laser light L and measures the displacement velocity of the measurement surface by sensing the reflected light from the measurement surface. The non-contact vibrometer 12 outputs the measured displacement velocity (vibration velocity) as a vibration velocity signal of an analog voltage proportional to the vibration velocity.

[0016] For example, the non-contact vibrometer 12 is connected to a voltmeter 15 and a processing device 16. The non-contact vibrometer 12 outputs a vibration velocity signal to the voltmeter 15. In addition, the non-contact vibrometer 12 measures the displacement velocity of the measurement surface of the measurement object 2 based on a command from the processing device 16.

[0017] The transport device 13 moves the measurement object 2 and the non-contact vibrometer 12 held by the holder 11 relatively in the vertical direction. For example, the transport device 13 can move at least the vertical distance of the end face of the measurement object 2. The transport device 13 is, for example, an electric stage having a motor and a stage that moves in the vertical direction by being driven by the motor. The transport device 13 is, for example, connected to a processing device 16, and moves the measurement object 2 held by the holder 11 in the vertical direction based on a command from the processing device 16.

[0018] Driving source 14 drives object 2 to be measured by applying a voltage (electric field) to object 2 to be measured via holder 11. Driving source 14 is connected to processing device 16, for example, and applies a voltage to object 2 to be measured in response to a command from processing device 16. Driving source 14 includes, for example, a waveform generator 141 and an amplifier 142.

[0019] Waveform generator 141 generates a voltage waveform (drive waveform) of an arbitrary drive voltage. Amplifier 142 is an amplifier. Amplifier 142 amplifies the voltage waveform generated by waveform generator 141 to a voltage (electric field) or higher assumed for the drive condition of the device using the piezoelectric material of object 2 to be measured.

[0020] In this embodiment, the device using the piezoelectric material of the measurement object 2 is, for example, an actuator of an inkjet head. Note that the device using the piezoelectric material of the measurement object 2 is not limited to an actuator of an inkjet head and can be set appropriately.

[0021] In this embodiment, for example, two amplifiers 142 are used. The two amplifiers 142 apply voltage waveforms of opposite polarity to the upper test piece 6 and the lower test piece 7. In other words, by using the two amplifiers 142, the driving source 14 can apply to the measurement object 2 a potential difference that is twice as large as the voltage output specification of the amplifiers 142.

[0022] The voltmeter 15 monitors the drive voltage (voltage value) of the measurement object 2. For example, the voltmeter 15 receives a drive waveform signal as the drive voltage of the measurement object 2 and performs A / D conversion. The voltmeter 15 also monitors the vibration velocity signal output from the non-contact vibrometer 12. For example, the voltmeter 15 receives the vibration velocity signal output from the non-contact vibrometer 12 and performs A / D conversion. The voltmeter 15 also outputs data to the processing device 16 based on an instruction from the processing device 16. For example, the voltmeter 15 is connected to the processing device 16 and outputs the A / D converted drive waveform signal and vibration velocity signal to the processing device 16.

[0023] Such a voltmeter 15 is, for example, a digital oscilloscope. The voltmeter 15 outputs data such as the monitored drive waveform signal and vibration velocity signal to the processing device 16. Note that the voltmeter 15 does not have to be a measuring instrument such as an oscilloscope, and may be a processing circuit provided in the processing device 16 that can monitor the drive voltage of the measurement object 2 and the output signal of the non-contact vibrometer 12.

[0024] The processing device 16 is a control device that controls each component of the measurement device 1. As shown in Fig. 4, the processing device 16 is, for example, a processing terminal such as a personal computer or a tablet terminal. The processing device 16 includes, for example, a communication unit 21, an input unit 22, an interface 23, a display unit 24, a memory 25, and a processor 26.

[0025] The communication unit 21 is an arbitrary communication interface that is controlled by the processor 26 and can communicate with an external terminal, which is another processing device, using a wired communication technology or a wireless communication technology. The communication unit 21 may be implemented as, for example, a communication module or a communication board. The communication unit 21 can be connected to the communication unit of the external terminal using, for example, a wireless communication technology such as the BLE standard (Bluetooth (registered trademark) Low Energy standard), Wi-Fi (registered trademark), or NFC, or a wired communication technology such as USB.

[0026] The input unit 22 has a device for accepting user input, such as an operation panel including buttons, a touch panel, a keyboard, a mouse, etc. The interface 23 is a terminal or a circuit that can be electrically connected to the non-contact vibrometer 12, the motor of the conveying device 13, the driving source 14, and the voltmeter 15.

[0027] The display unit 24 has a display device such as a liquid crystal display or an organic EL display. The display unit 24 functions as a display device that displays various information. The display unit 24 may have a speaker, an LED (Light Emitting Diode) lighting unit, etc. instead of or in addition to the display device.

[0028] The memory 25 is a storage medium. Data can be read from and written to the memory 25. The memory 25 stores data used by the processor 26, various data and programs used for controlling the non-contact vibrometer 12, the transport device 13, the drive source 14, the voltmeter 15, and measuring the measurement target 2. The memory 25 also stores other components of the processing device 16 and various data and programs used for controlling external devices.

[0029] The memory 25 includes, for example, a non-volatile memory such as an Electrically Erasable Programmable Read-Only Memory (EEPROM) (registered trademark), a Read only memory (ROM), or a NAND type flash memory. The memory 25 also includes a Solid State Drive (SSD) equipped with a flash memory.

[0030] The processor 26 may be a central processing unit (CPU), a field programmable gate array (FPGA), a digital signal processor (DSP), a graphics processing unit (GPU), a microcomputer, or any other general-purpose or dedicated processor. The processor 26 performs any process, such as communication control of the communication unit 21, display control of the display unit 24, and measurement control of the measurement object 2. In addition, the processor 26 is connected to the non-contact vibrometer 12, the transport device 13, the driving source 14, the voltmeter 15, an external terminal, and the like, via the communication unit 21 and the interface 23.

[0031] The processor 26 includes, for example, a processing circuit and a memory. The processor 26 includes, for example, a storage area 261 such as a non-volatile EEPROM area or a volatile DRAM area as a memory. The processor 26 also includes a measurement control circuit 262 that controls the non-contact vibrometer 12, the transport device 13, and the drive source 14 to measure the displacement speed of the measurement surface of the driven measurement object 2, and a piezoelectric constant d 15 The circuit has an arithmetic circuit 263 for calculating the following:

[0032] That is, the processor 26 performs the functions of a measurement control circuit 262 and an arithmetic circuit 263 by executing a program or the like stored in the memory 25 or the storage area 261. The division of functions among the various parts in the processor 26 is for convenience and can be changed as appropriate.

[0033] The measurement control circuit 262 drives the object to be measured 2 , measures the displacement speed of the object to be measured 2 , and performs processing to acquire the measured displacement speed and the electric field applied to the object to be measured 2 .

[0034] As a specific example, when a command to start measurement of the object to be measured 2 is input to the input unit 22, the measurement control circuit 262 controls the drive source 14 to output a drive waveform for the object to be measured 2, which is a voltage waveform set by the input unit 22, to the object to be measured 2. The measurement control circuit 262 also controls the voltmeter 15 to output a drive waveform signal, which is data measuring the applied voltage (applied electric field) applied to the object to be measured 2. The measurement control circuit 262 also stores the drive waveform signal output from the voltmeter 15 in the memory 25 upon acquiring the drive waveform signal.

[0035] The drive waveform of the measurement object 2 is set arbitrarily based on the drive conditions of the device using the piezoelectric material. The measurement control circuit 262 controls the waveform generator 141 and the amplifier 142 of the drive source 14 to output the drive waveform.

[0036] Furthermore, the measurement control circuit 262 controls the transport device 13 to relatively move the measurement object 2 and the non-contact vibrometer 12 along the measurement direction. In this embodiment, the measurement control circuit 262 controls the transport device 13 to transport the holder 11 and move the measurement object 2 in the vertical direction (Z direction). The measurement range of the measurement object 2 is the range of the measurement surface of the measurement object 2 in the vertical direction. Furthermore, in this embodiment, since the measurement surface of the measurement object 2 is measured at multiple points in the vertical direction, the movement amount of the measurement object 2 is set in advance and stored in the memory 25.

[0037] As a specific example, the measurement control circuit 262 controls the conveying device 13 to move the measurement object 2 in the vertical direction so as to measure the displacement velocity with the non-contact vibrometer 12 at each position of the measurement points in the vertical direction on the measurement surface of the upper test piece 6 and the measurement surface of the lower test piece 7.

[0038] Various methods can be applied to detect the position of the measurement object 2 moved in the vertical direction by the conveying device 13. For example, the position of the measurement object 2 in the vertical direction may be detected by the laser light L irradiated by the non-contact vibrometer 12. For example, the ends of the upper test piece 6 and the lower test piece 7 of the measurement object 2 in the vertical direction may be estimated based on the position where the measurement object 2 cannot be detected by the non-contact vibrometer 12 or the position where the displacement speed of the measurement object 2 cannot be measured. Also, for example, the position of the measurement object 2 may be detected by providing a sensor that detects the position of the measurement object 2 (not shown) and detecting the vertical position of the measurement object 2 by the sensor, or the position of the measurement object 2 may be detected by other methods.

[0039] The measurement control circuit 262 also controls the non-contact vibrometer 12 to measure the displacement of the measurement surface of the measurement object 2. As a specific example, the measurement control circuit 262 controls the non-contact vibrometer 12 to irradiate the measurement surface of the measurement object 2 with laser light L and measure the displacement velocity with the non-contact vibrometer 12. The measurement control circuit 262 also controls the non-contact vibrometer 12 to output the measured displacement velocity as a vibration velocity signal. The measurement control circuit 262 also stores the vibration velocity signal output from the non-contact vibrometer 12 in the memory 25. The measurement control circuit 262 measures the displacement velocity at each measurement position between the measurement start position and measurement end position of the displacement velocity in the up-down direction of each of the upper test piece 6 and the lower test piece 7, and acquires the vibration velocity signal.

[0040] The arithmetic circuit 263 performs a process of calculating the piezoelectric constant of the piezoelectric material used in the object to be measured 2 from the measured displacement speed and the electric field applied to the object to be measured 2 .

[0041] As shown by the two-dot chain line in Figure 5, when a voltage (electric field) is applied to the measurement object 2, the end face in the polarization direction (longitudinal direction) is inclined by θ with respect to the end face before the application of the electric field. This inclination of the end face becomes the shear strain of each of the test pieces 6, 7. For this reason, the arithmetic circuit 263 measures the displacement velocities at multiple measurement positions in the vertical direction of the upper test piece 6 and the lower test piece 7 of the measurement object 2 using the non-contact vibrometer 12, and calculates the shear strain of the piezoelectric material used for the upper test piece 6 and the lower test piece 7 from these displacement velocities.

[0042] As a specific example, the arithmetic circuit 263 integrates the measured displacement velocity (vibration velocity signal) as a gradient amplitude analysis, and obtains the displacement amplitude at each position in the up-down direction of the upper test piece 6 and the lower test piece 7 of the measurement object 2. From the obtained displacement amplitude, the arithmetic circuit 263 obtains a gradient amplitude, which is the gradient of the displacement amplitude of the upper test piece 6 and the lower test piece 7 relative to the up-down direction.

[0043] Then, the arithmetic circuit 263 determines the average value of the tilt amplitudes of the upper test piece 6 and the lower test piece 7 as the shear strain amplitude of the piezoelectric material used in the measurement object 2 (upper test piece 6 and lower test piece 7).

[0044] The arithmetic circuit 263 also analyzes the voltage amplitude (electric field amplitude). The arithmetic circuit 263 determines the electric field amplitude of the electric field applied to the upper test piece 6 from the drive waveform signal.

[0045] The calculation circuit 263 calculates the piezoelectric constant d 15 Calculate the following.

[0046] Hereinafter, the piezoelectric constant d 15 An example of the calculation method will be described. The equation for calculating the strain S that occurs when stress T and electric field E are applied to a piezoelectric material is given by equation (1) based on the fundamental piezoelectric equations.

[0047]

number

[0048] S E : Elastic compliance (E = constant) d: Piezoelectric strain coefficient The equation for calculating the strain S5 in the case of shear mode is given by equation (2).

[0049]

number

[0050] The anti-parallel polarized measurement object 2 does not have its movement in the shear direction hindered even when the upper electrode 5 of the upper test piece 6 and the lower electrode 5 of the lower test piece 7 are restrained, so the shear stress T5 is 0 and the shear strain S5 is given by equation (3).

[0051]

number

[0052] and the shear mode piezoelectric constant d 15 is expressed by the following equation (4).

[0053]

number

[0054] Therefore, by substituting the shear strain amplitude and the electric field amplitude into this formula (4), the piezoelectric constant d 15 can be calculated.

[0055] This piezoelectric constant d 15 The calculation method is stored in the memory 25 as a program. The processor 26 executes the program to calculate the piezoelectric constant d 15 It has the function of calculating the following.

[0056] Next, as a method for measuring a piezoelectric material according to this embodiment, an example of a method for measuring a measurement object 2 using a measuring device 1 will be described with reference to the flow chart shown in Fig. 6. In the method for measuring the measurement object 2 according to this embodiment, an example is shown in which the measurement object 2 is measured in the order of the upper test piece 6 and the lower test piece 7.

[0057] As a method for measuring the measurement object 2, first, the measurement object 2 is prepared. For example, two test pieces (upper test piece 6 and lower test piece 7) made of the same piezoelectric material and having electrodes 5 formed on both main surfaces are bonded to have anti-parallel polarization. The two test pieces are bonded with thermoplastic wax so that at least partial contact between the electrodes of each test piece 6, 7 is maintained. An example of the thermoplastic wax is Electron Wax (registered trademark) H7 by Furuuchi Chemical Co., Ltd., but the thermoplastic wax is not limited to this and can be set appropriately.

[0058] As a specific example, a thin layer of thermoplastic wax is applied to a PET film heated to 90°C, and then the thermoplastic wax is transferred under heat to one surface of the opposing electrode 5 of one of the test pieces 6 and 7 to be joined. Then, after the test piece to which the thermoplastic wax has been transferred is returned to room temperature, the pair of test pieces are overlapped, lightly pressed with a small vice, and the overlapped test pieces 6 and 7 are heated to about 90°C and then cooled. By these examples, a measurement object 2 in which two test pieces 6 and 7 are joined is produced.

[0059] The dimensions of the anti-parallel polarized object 2 are preferably set to dimensions that are confirmed to have a resonance suppressing effect by FEM analysis. In particular, the thickness t of the object 2 is preferably set to 0.2 mm or less.

[0060] In addition, when measuring the displacement velocity using a laser Doppler vibrometer, the sensing of the reflected light from the measurement surface may be affected by the state of the measurement surface of the measurement object 2, and the measurement accuracy may be affected by this state. For example, when the measurement surface of the measurement object 2 is highly rough, poor sensing of the reflected light from the measurement surface may occur. Therefore, in preparing the measurement object 2, it is preferable to perform surface polishing of the measurement surface of the measurement object 2 so as to obtain sufficient reflection of the laser light L. For example, precision polishing using a wrapping film sheet is an example of surface polishing that can obtain sufficient reflection of the laser light L. As an example, when the final polishing of the measurement surface was performed using a wrapping film sheet (manufactured by 3M) with a grain size of 0.3 μm, suitable reflection of the laser light L was observed.

[0061] Next, the fabricated measurement object 2 is held by a holder 11, and the electrodes 5 on both main surfaces of the measurement object 2 are connected to a driving source 14. Next, power is supplied to the non-contact vibrometer 12, the transport device 13, the driving source 14, the voltmeter 15, the processing device 16, etc., and they are put into a standby state.

[0062] When processor 26 goes into standby state, it determines whether or not a command to start measurement of the measurement object 2 has been input to input unit 22 (ACT1), and monitors the input until a command to start measurement is received (NO in ACT1). When the person measuring operates input unit 22 and a command to start measurement of the measurement object 2 is input to input unit 22 (YES in ACT1), processor 26 starts measurement based on a signal from input unit 22. First, processor 26 controls transport device 13 to move measurement object 2 to the measurement start position of upper test piece 6 (ACT2).

[0063] Next, the processor 26 controls the drive source 14 to output a preset drive waveform to the measurement object 2 (ACT3). Next, the processor 26 controls the non-contact vibrometer 12 to measure the displacement velocity (ACT4). At this time, the non-contact vibrometer 12 irradiates the laser light L onto the measurement position on the measurement surface of the upper test piece 6 of the measurement object 2, receives the reflected light, and detects the displacement velocity. The non-contact vibrometer 12 also outputs the detected displacement velocity to the voltmeter 15 as a vibration velocity signal.

[0064] Processor 26 commands voltmeter 15 to output data such as a drive waveform signal and a vibration velocity signal. In response to the command from processor 26, voltmeter 15 outputs the drive waveform signal and the vibration velocity signal (ACT5). Specifically, voltmeter 15 receives the drive waveform signal output from drive source 14 to measurement object 2 and performs A / D conversion. Voltmeter 15 also receives the vibration velocity signal output from non-contact vibrometer 12 and performs A / D conversion. Then, voltmeter 15 outputs the A / D converted drive waveform signal and vibration velocity signal.

[0065] The processor 26 stores the drive waveform signal and the vibration velocity signal output from the voltmeter 15 in the memory 25 (ACT6). Next, the processor 26 controls the transport device 13 to change the measurement position of the measurement surface of the upper test piece 6 by the non-contact vibrometer 12, and moves the measurement object 2 a predetermined distance in the vertical direction toward the measurement end position (ACT7). The movement amount of the measurement object 2 is set in advance, for example. That is, since the measurement surface of the upper test piece 6 is measured at multiple positions in the vertical direction, the processor 26 controls the transport device 13 to move the measurement object 2 based on, for example, any measurement position, number of measurements, or movement amount of the measurement object 2 that is input in advance and stored in the memory 25 or the like.

[0066] Next, the processor 26 determines whether the measurement position of the upper test piece 6 has moved to the end position (ACT8). If the measurement position of the upper test piece 6 has not moved to the end position (NO in ACT8), the processor 26 controls the non-contact vibrometer 12 at the measurement position after the movement to measure the displacement speed (ACT4), and repeats the steps from ACT4 onwards until the measurement position of the upper test piece 6 moves to the end position. Note that, for example, in ACT4, if the drive source 14 stops outputting the drive waveform after measuring the displacement speed, and the measurement position of the upper test piece 6 has not moved to the end position (NO in ACT8), the processor 26 returns to ACT3 and repeats the steps thereafter.

[0067] When the measurement position of the upper test piece 6 has moved to the end position (YES in ACT8), the processor 26 ends the measurement of the upper test piece 6, and starts the measurement of the lower test piece 7. The processor 26 controls the transport device 13 to move the measurement target 2 to the measurement start position of the lower test piece 7 (ACT9).

[0068] Next, the processor 26 controls the driving source 14 to output a preset driving waveform to the measurement object 2 (ACT10). Next, the processor 26 controls the non-contact vibrometer 12 to measure the displacement velocity (ACT11). At this time, the non-contact vibrometer 12 irradiates the laser light L onto the measurement position on the measurement surface of the lower test piece 7 of the measurement object 2, receives the reflected light, and detects the displacement velocity. The non-contact vibrometer 12 also outputs the detected displacement velocity to the voltmeter 15 as a vibration velocity signal.

[0069] Processor 26 commands voltmeter 15 to output data such as a drive waveform signal and a vibration velocity signal. In response to a command from processor 26, voltmeter 15 outputs a drive waveform signal and a vibration velocity signal (ACT12). Specifically, voltmeter 15 receives the drive waveform signal output from drive source 14 to measurement object 2 and performs A / D conversion. Voltmeter 15 also receives the vibration velocity signal output from non-contact vibrometer 12 and performs A / D conversion. Then, voltmeter 15 outputs the A / D converted drive waveform signal and vibration velocity signal.

[0070] The processor 26 stores the drive waveform signal and the vibration velocity signal output from the voltmeter 15 in the memory 25 (ACT13). Next, the processor 26 controls the transport device 13 to change the measurement position of the measurement surface of the lower test piece 7 by the non-contact vibrometer 12, and moves the measurement object 2 by a predetermined distance along the vertical direction toward the measurement end position (ACT14). The movement amount of the measurement object 2 is set in advance, for example. That is, since the measurement surface of the lower test piece 7 is measured at multiple positions in the vertical direction, the processor 26 controls the transport device 13 to move the measurement object 2 based on any measurement position, number of measurements, or movement amount of the measurement object 2 that is input in advance and stored in the memory 25, for example. Here, the movement amount of the measurement object 2 in the measurement of the lower test piece 7 is set to be the same as the movement amount of the measurement object 2 in the measurement of the upper test piece 6.

[0071] Next, the processor 26 determines whether the measurement position of the lower test piece 7 has moved to the end position (ACT15). If the measurement position of the lower test piece 7 has not moved to the end position (NO in ACT15), the processor 26 controls the non-contact vibrometer 12 at the measurement position after the movement to measure the displacement speed (ACT11), and repeats the steps from ACT11 onwards until the measurement position of the lower test piece 7 moves to the end position. Note that, for example, if the drive source 14 stops outputting the drive waveform after measuring the displacement speed in ACT11, if the measurement position of the lower test piece 7 has not moved to the end position (NO in ACT15), the processor 26 returns to ACT3 and repeats the steps thereafter.

[0072] When the measurement position of the lower test piece 7 has moved to the end position (YES in ACT15), the processor 26 ends the measurement of the lower test piece 7. The processor 26 performs a tilt amplitude analysis and a voltage amplitude (electric field amplitude) analysis from the drive waveform signal and the vibration velocity signal stored in the memory 25 in the measurement of the upper test piece 6 (ACT16). Specifically, the processor 26 determines the tilt amplitude of the upper test piece 6 from the vibration velocity signal stored in the memory 25. The processor 26 also determines the electric field amplitude of the electric field applied to the upper test piece 6 from the drive waveform signal stored in the memory 25.

[0073] Similarly, the processor 26 performs a tilt amplitude analysis and a voltage amplitude (electric field amplitude) analysis from the drive waveform signal and the vibration velocity signal stored in the memory 25 in the measurement of the upper test piece 6 (ACT17). Next, the processor 26 performs a shear strain amplitude analysis of the piezoelectric material used in the measurement target 2 (ACT18). Specifically, the processor 26 obtains the average value of the tilt amplitude of the upper test piece 6 and the tilt amplitude of the lower test piece 7 as the shear strain amplitude.

[0074] Next, the processor 26 calculates the piezoelectric constant d 15 Specifically, the processor 26 substitutes the obtained shear strain amplitude and electric field amplitude into the formula (4) to calculate the piezoelectric constant d 15 In this manner, the piezoelectric constant of the piezoelectric material used in the measurement object 2 is measured using the measurement device 1.

[0075] According to the measurement device 1 and the measurement method configured in this manner, the tilt amplitude of each of the test pieces 6, 7 on the measurement surface of the measurement object 2, in which two test pieces made of piezoelectric materials are joined so as to have anti-parallel polarization, is obtained, and the shear strain amplitude is obtained from the tilt amplitude. Then, the piezoelectric constant of the piezoelectric material of the test pieces 6, 7 is obtained from the shear strain amplitude. Therefore, according to the measurement device 1 and the measurement method, the variation in the measured piezoelectric constant can be suppressed.

[0076] Specifically, for example, a product that is assumed to use a piezoelectric material, such as a shear mode type piezoelectric inkjet head, is assumed to operate under conditions of a large electric field (several hundred V / mm) and a high frequency range (several hundred kHz). However, as is clear from the relationship between the piezoelectric constant and frequency in FIG. 7, when the piezoelectric constant of a conventional test piece having electrodes on both main surfaces of a single piece of piezoelectric material is measured, a significant fluctuation (variation) in the value of the piezoelectric constant is observed in the frequency range of 100 kHz to 1 MHz. Note that FIG. 7 shows an example of the measurement result when an electric field of 300 V / mm is applied to a test piece having electrodes on both main surfaces of a single piece of piezoelectric material with a width W=1.43 mm, a length L=4.8 mm, and a thickness t=0.2 mm. FIG. 8 shows the results of FEM analysis using the conventional test piece and conditions at frequencies of 10 kHz and 1 MHz. As shown in Figure 8, a conventional test piece, which has electrodes on both main surfaces of a single piece of piezoelectric material, generates ideal shear deformation at 10 kHz, but at 1 MHz the test piece resonates and deforms in the thickness direction.

[0077] However, when the measurement object 2 in which the two test pieces 6 and 7 are joined so as to have antiparallel polarization is used as in this embodiment, the shear strain amplitude has flat characteristics up to a frequency range exceeding 100 kHz, and therefore, it is understood that the piezoelectric constant also has flat characteristics, as shown in Fig. 9. Note that Fig. 9 is a diagram showing the relationship between the driving frequency and the shear strain amplitude for each thickness of the test pieces 6 and 7 in the measurement object 2 with antiparallel polarization, obtained by FEM analysis. Note that the FEM analysis in Fig. 9 was performed under the conditions of an applied electric field of 5 V / mm, a width W of the test pieces of 1.5 mm, a length L of 5 mm, and thicknesses t of the test pieces 6 and 7 used in the measurement object 2 with antiparallel polarization of 0.05 mm, 0.1 mm, and 0.2 mm.

[0078] 9, by measuring the measurement target 2 in which two test pieces 6, 7 are joined so as to have antiparallel polarization, as in the measurement device 1 and measurement method of the embodiment, the fluctuation of the shear strain amplitude can be suppressed even in the high frequency range, and therefore the variance of the measured piezoelectric constant value can be suppressed. Therefore, the measurement device 1 and measurement method of the embodiment are effective for evaluating piezoelectric materials used in devices such as shear mode type piezoelectric inkjet heads that operate under large electric field and high frequency range conditions.

[0079] That is, by applying the measuring device 1 and measuring method of the embodiment, it is possible to select a piezoelectric material suitable for the actual driving conditions of the device while taking into consideration the electric field and frequency dependency of the shear strain of the piezoelectric material.

[0080] Furthermore, since the measuring device 1 and the measuring method are configured to determine the shear strain amplitude as the average value of the tilt amplitudes obtained from the two test pieces 6 and 7, the measurement accuracy can be improved compared to determining the shear strain amplitude from a single test piece.

[0081] Furthermore, in the measurement device 1 and the measurement method, the thickness of the antiparallel polarized measurement object 2 is set to 0.2 mm or less, thereby suppressing the fluctuation of the shear strain amplitude. To be more specific, the increase in the shear strain amplitude is thought to be caused by the resonance of the shear mode. Here, the frequency constant N can generally be used to calculate the resonance frequency, and since the frequency constant N is defined as the product of the length in the direction corresponding to each vibration mode and the resonance frequency, the resonance frequency f of the shear mode can be calculated. r is expressed by Equation (5) using the frequency constant N5 of the shear vibration and the thickness t of the test piece.

[0082]

number

[0083] Therefore, it is effective to take measures to shift the resonance frequency to the higher frequency side by thinning the test piece. This is also evident from the fact that, as shown in Figure 9, the increase in shear strain amplitude at frequencies above 400 kHz gradually decreases, as can be seen from the FEM analysis results when the thickness t of the measurement object 2 is thinned to 0.2 mm, 0.1 mm, and 0.05 mm, and the resonance suppression effect can be confirmed. For this reason, by setting the thickness of the measurement object 2 with antiparallel polarization to 0.2 mm or less, it is possible to prevent the fluctuation of the shear strain amplitude.

[0084] Next, the measurement results measured using the measurement device 1 and measurement method of this embodiment will be described below. First, measurement examples of soft-type PZT and hard-type PZT are shown in FIG. 10. Here, general piezoelectric ceramics can be roughly divided into soft-type materials and hard-type materials according to the mechanical quality factor Qm. Piezoelectric ceramics with relatively small mechanical quality factors Qm of 100 or less can be divided into soft-type materials, and relatively large materials with mechanical quality factors Qm of 1000 or more can be divided into hard-type materials. The piezoelectric constant d calculated from the soft-type PZT and hard-type PZT shown in FIG. 15 is 15 are 720 and 582, respectively.

[0085] In both the results for the soft-PZT and hard-PZT, no large fluctuations in the piezoelectric constant as shown in Figure 10 were observed in the range of 10 kHz to 1 MHz, and non-resonant shear strain was successfully measured. In particular, the piezoelectric constant d 15 As shown in FIG. 10 (soft-type PZT), the piezoelectric constant d of the measurement object 2 with antiparallel polarization, as shown in FIG. 11, is linearly approximated on a graph of the logarithm of the frequency for the measured values ​​shown in FIG. 10, and the deviation of each measurement point from the approximated line is plotted. As shown in FIG. 11, the deviation in the range of 10 kHz to 1 MHz is within about ±3%. This also shows that the piezoelectric constant d 15 Measurements have revealed that the resonance suppression effect is achieved.

[0086] In addition, the repeat measurement accuracy when repeat measurements were performed using the measuring device 1 and measuring method of this embodiment was obtained by the following method. Soft-type PZT was used as the piezoelectric material, and two conditions were set: an electric field of 300 V / mm and a frequency of 833 kHz and 1 MHz. The number of measurement samples of the measurement object 2 was set to 3, and for each sample, six measurements were performed, including the measurement procedure of removing and attaching the measurement object 2 from the holder 11. The repeat measurement accuracy was determined by dividing the difference between the maximum and minimum values ​​of the six measured values ​​by the average value. Here, the lower the repeat measurement accuracy, the less the measurement variation, and it can be determined that measurement with high accuracy is possible. As shown in FIG. 12, the evaluation results showed that the repeat measurement accuracy of this measurement method was 3% or less for all samples and frequencies. This also clearly shows that the measuring device 1 and measuring method of this embodiment have high measurement accuracy.

[0087] As described above, according to the piezoelectric material measuring device 1 and measuring method of the present embodiment, the measurement object 2 having antiparallel polarization is measured, so that the variation in the measurement value can be suppressed.

[0088] The measuring device 1 and the measuring method according to the embodiment are not limited to the above-mentioned example. For example, in the above-mentioned example, the example of the holder 11 for holding the measurement object 2 has been described as an example of holding the measurement object 2 by the contact probe pin 111, but the present invention is not limited to this. For example, as shown in the measuring device 1 according to another embodiment shown in FIG. 13, the holder 11 may be configured to include a pair of metal blocks 112 and a pair of conductive rubbers 113 provided on the opposing surfaces of the pair of metal blocks 112. Such a holder 11 holds the measurement object 2 by the conductive rubbers 113 between the pair of metal blocks 112.

[0089] For example, the metal block 112 is made of an aluminum material of several hundred Ω, and has a gold-plated layer of several milliΩ on its surface. The pair of metal blocks 112 is connected to the driving source 14. The conductive rubber 113 is made of, for example, a TPSPCR series material. By using a holder 11 having such a pair of metal blocks 112 and a pair of conductive rubbers 113, it becomes easy to attach a small-sized measurement target object. Furthermore, by gold-plating the surfaces of the pair of metal blocks 112, it is possible to improve the accuracy of monitoring by the voltmeter 15 at low cost.

[0090] According to at least one of the embodiments described above, it is possible to provide a piezoelectric material measuring device and a piezoelectric material measuring method capable of suppressing the variation in the measured values.

[0091] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. The following provides a description equivalent to the invention described in the original claims of this application. [1] A drive source that outputs an arbitrary voltage to a measurement object that is made of two rectangular plates of piezoelectric material that undergo shear deformation in response to voltage, with the polarization directions of the materials joined in parallel and opposite directions; a non-contact vibrometer that measures the displacement of the measurement object; A voltmeter that measures a voltage applied to the measurement object; A measuring device comprising: [2] A holder for holding the object to be measured; a conveying device that conveys the holder to a position where the measurement object is measured by the non-contact vibrometer; a storage medium for storing the displacement value measured by the non-contact vibrometer and the voltage value measured by the voltmeter; a control device that transports one of the piezoelectric materials of the measurement object to a position where the non-contact vibrometer measures the piezoelectric material of the measurement object, outputs the voltage to the measurement object, and stores the measured displacement value and voltage value of the one piezoelectric material in the storage medium, and transports the other piezoelectric material of the measurement object to a position where the non-contact vibrometer measures the piezoelectric material of the measurement object, outputs the voltage to the measurement object, and stores the measured displacement value and voltage value of the other piezoelectric material in the storage medium; The measuring device according to [1], comprising: [3] The measuring device described in [1] or [2] measures the displacement velocity of the object to be measured at multiple locations in the stacking direction of the two piezoelectric materials using the non-contact vibrator, integrates the measured displacement velocity of the object to be measured, determines the displacement amplitude of the object to be measured at multiple locations in the stacking direction, and determines the tilt amplitude with respect to the stacking direction from the multiple displacement amplitudes. [4] The measuring device described in [3], wherein the tilt amplitude of one of the piezoelectric materials of the measured object and the tilt amplitude of the other piezoelectric material of the measured object are averaged to obtain the shear strain amplitude of the measured object. [5] Two rectangular plates of piezoelectric material that undergo shear deformation in response to voltage are joined together with their polarization directions parallel and opposite to each other; outputting a voltage to the measurement object formed by bonding the two sheets of piezoelectric material by a drive source that outputs a given voltage; measuring a displacement of the object to be measured by a non-contact vibrometer while the voltage is being output to the object to be measured; Measuring a voltage applied to the measurement object with a voltmeter; A method for measuring a piezoelectric material comprising: [Explanation of symbols]

[0092] 1...measuring device, 2...measurement object, 4...piezoelectric material piece, 5...electrode, 6...upper test piece, 7...lower test piece, 11...holding device, 12...non-contact vibrometer, 13...conveying device, 14...driving source, 15...voltmeter, 16...processing device (control device), 21...communication unit, 22...input unit, 23...interface, 24...display unit, 25...memory, 26...processor, 111...contact probe pin, 112...metal block, 113...conductive rubber, 141...waveform generator, 142...amplifier, 261...memory area, 262...measurement control circuit, 263...arithmetic circuit.

Claims

1. A measuring device for measuring a piezoelectric constant based on a shear strain amplitude calculated from a displacement speed of a measurement surface, which is an end surface in the polarization direction, of a measurement object in which two rectangular plate-shaped piezoelectric materials that undergo shear deformation in response to a voltage are joined together with their polarization directions parallel and opposite to each other, and electrodes are formed on both main surfaces along the polarization direction, and the shear strain amplitude is calculated from a displacement speed of a measurement surface, which is an end surface in the polarization direction, and an electric field amplitude is calculated from a voltage applied to the electrodes, a drive source that outputs an arbitrary voltage to the electrodes on both main surfaces of the object to be measured, the voltage being set based on a drive condition of a device that uses a piezoelectric material of the object to be measured; a non-contact vibrometer that measures a displacement velocity of the measurement surface by irradiating the measurement surface of the measurement object with a laser light and sensing the reflected light from the measurement surface; a voltmeter connected to the driving source and configured to measure the voltage output to the measurement object; A measuring device comprising:

2. a holder that holds the object to be measured in such a manner that the electrodes on both main surfaces of the object to be measured are in contact with the electrodes and the measurement surface of the object to be measured faces the non-contact vibrometer; a conveying device that conveys the holder to a position where the measurement surface of the measurement object is measured by the non-contact vibrometer; a storage medium for storing the displacement value measured by the non-contact vibrometer and the voltage value measured by the voltmeter; a control device that transports one of the piezoelectric materials of the measurement object to a position where the non-contact vibrometer measures the piezoelectric material of the measurement object, outputs the voltage to the measurement object, and stores the measured displacement value and voltage value of the one piezoelectric material in the storage medium, and transports the other piezoelectric material of the measurement object to a position where the non-contact vibrometer measures the piezoelectric material of the measurement object, outputs the voltage to the measurement object, and stores the measured displacement value and voltage value of the other piezoelectric material in the storage medium; The measurement device of claim 1 , comprising:

3. 3. The measuring device according to claim 1, further comprising: a non-contact vibrometer for measuring the displacement velocity of the measurement surface of the measurement object at a plurality of locations in the stacking direction of each of the two piezoelectric materials; integrating the measured displacement velocity of the measurement object to determine displacement amplitudes of the measurement object at a plurality of locations in the stacking direction; and determining an inclination amplitude with respect to the stacking direction from the plurality of displacement amplitudes.

4. The measurement apparatus according to claim 3 , wherein the tilt amplitude of the piezoelectric material of one of the measurement objects and the tilt amplitude of the piezoelectric material of the other measurement object are averaged to determine the shear strain amplitude of the measurement object.

5. A measurement object is formed by joining two rectangular plate-shaped piezoelectric materials that undergo shear deformation in response to a voltage with their polarization directions parallel and opposite to each other, and forming electrodes on both main surfaces along the polarization direction; outputting a voltage to the electrodes on both main surfaces of the object to be measured by a drive source that outputs an arbitrary voltage set based on a drive condition of a device that uses the piezoelectric material of the object to be measured; While the voltage is being output to the measurement object, a non-contact vibrometer is used to irradiate a laser beam onto a measurement surface, which is an end surface of the measurement object in the polarization direction, and to measure a displacement speed of the measurement surface by sensing reflected light from the measurement surface; measuring the voltage output to the measurement object by a voltmeter connected to the driving source; measuring a piezoelectric constant based on a shear strain amplitude calculated from a displacement speed of the measurement surface and an electric field amplitude calculated from a voltage applied to the electrodes; A method for measuring a piezoelectric material comprising:

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