Deformation detection device

Abstract

A deformation amount detection device (1) comprises: a substrate (10) that has a first end and a second end which are two ends in a first direction, and that is fixed at the first end side and the second end side; a piezoelectric body (30) that overlaps the substrate (10) in a plan view and that is disposed between the first end and the second end; an input electrode (21) that overlaps the piezoelectric body (30) in a plan view and that inputs an input signal to the piezoelectric body (30); an output electrode (22) that overlaps the piezoelectric body (30) in a plan view and that outputs an output signal from the piezoelectric body (30); and a controller that inputs the input signal to the input electrode (21) and receives the output signal from the output electrode (22). The substrate (10) is provided with a slit (50) between the first end and the second end. The output electrode (22) is disposed at a position so as to overlap the slit (50) in a plan view. The piezoelectric body (30) resonates in the thickness direction of the piezoelectric body (30).

Description

[Technical Field]

[0001] The present invention relates to a deformation amount detection device. [Background technology]

[0002] Patent Document 1 discloses a deformation amount detection device including a first electrode, a second electrode, and a flexible transmission part.

[0003] In the configuration of Patent Document 1, when an input signal is input to a first electrode, an elastic wave is generated. The transmission unit transmits the elastic wave to a second electrode. The second electrode generates an output signal in response to the elastic wave. In the configuration of Patent Document 1, the amount of deformation of the transmission unit from a reference state can be detected based on the output signal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2022 / 030356 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of one embodiment of the present invention is to provide a deformation amount detection device that detects the amount of deformation with high sensitivity by utilizing resonance in the thickness direction. [Means for solving the problem]

[0006] A deformation detection device according to one embodiment of the present invention comprises a substrate having a first end and a second end that are opposite ends along a first direction, the first end side and the second end side being fixed, a piezoelectric body that overlaps the substrate in a planar view and is arranged between the first end and the second end, an input electrode that overlaps the piezoelectric body in a planar view and inputs an input signal to the piezoelectric body, an output electrode that overlaps the piezoelectric body in a planar view and outputs an output signal from the piezoelectric body, and a controller that inputs the input signal to the input electrode and receives the output signal from the output electrode, wherein the substrate has a slit between the first end and the second end, and the output electrode is arranged in a position that overlaps the slit in a planar view, and the piezoelectric body resonates in the thickness direction of the piezoelectric body.

[0007] The substrate and piezoelectric element are easily vibrated in the thickness direction due to the slits in the substrate. The output electrode is positioned so that it overlaps the slits in a plan view, and is therefore positioned in the piezoelectric element at the position where the deformation is greatest. Therefore, the deformation detection device can detect the deformation amount with high sensitivity by utilizing the resonance in the thickness direction. [Effects of the Invention]

[0008] According to one embodiment of the present invention, the amount of deformation can be detected with high sensitivity by utilizing resonance in the thickness direction. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a deformation amount detection device 1. [Figure 2] FIG. 2 is a cross-sectional view taken along line II in FIG. [Figure 3] FIG. 2 is a cross-sectional view taken along line II in FIG. [Figure 4] FIG. 2 is a plan view of the deformation amount detection device 1. [Figure 5] 5(A) and 5(B) are schematic diagrams showing the vibration mode of the piezoelectric body 30, and FIG. 5(C) is a cross-sectional view taken along line II-II in FIG. 5(B). [Figure 6]10 is a diagram showing the relationship between the bending angle of the substrate 10 and the resonance frequency of the piezoelectric body 30. FIG. [Figure 7] FIG. 4 is a diagram illustrating frequency characteristics of an output signal. [Figure 8] 10 is a diagram showing the relationship between the bending angle of the substrate 10 and the output signal. FIG. [Figure 9] 9(A) and 9(B) are schematic diagrams showing a state in which the deformation amount detection device 1 is fixed to a detection object 70 that may undergo minute deformation. [Figure 10] 10(A) and 10(B) are schematic diagrams showing a state in which the deformation amount detection device 1 is fixed to a detection object 70 that may undergo minute deformation. [Figure 11] 10 is a schematic diagram showing a vibration mode of a piezoelectric body 30 according to Modification 1. FIG. [Figure 12] 10 is a diagram showing the relationship between the bending angle of the substrate 10 and the resonance frequency of the piezoelectric body 30 according to the first modification. [Figure 13] 10 is a diagram showing the relationship between the bending angle of the substrate 10 and the output signal according to the first modification. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Fig. 1 is an external perspective view of the deformation amount detecting device 1. Fig. 2 and Fig. 3 are cross-sectional views taken along line II shown in Fig. 1. Fig. 4 is a plan view of the deformation amount detecting device 1.

[0011] The deformation amount detecting device 1 has a substrate 10 , a first fixed portion 15 , a second fixed portion 17 , a piezoelectric body 30 , an input electrode 21 , an output electrode 22 , a reference electrode 25 , and a controller 90 .

[0012] Substrate 10 is made of, for example, PET, polycarbonate (PC), acrylic (PMMA), stainless steel, an aluminum alloy, or a copper alloy. Substrate 10 has a first end 101 and a second end 102, which are opposite ends along a first direction. The underside of substrate 10 on the side of first end 101 is fixed to detection object 70 by first fixing portion 15. The underside of substrate 10 on the side of second end 102 is fixed to detection object 70 by second fixing portion 17. First fixing portion 15 and second fixing portion 17 are, for example, adhesive tape.

[0013] In the following description, the first direction, which is the length direction of the substrate 10, is defined as the Y direction, the thickness direction of the substrate 10 is defined as the Z direction, and the width direction of the substrate 10, which is perpendicular to the Y direction in a planar view, is defined as the X direction.

[0014] The deformation amount detection device 1 detects the amount of deformation from a reference state of a flexible substrate 10. In this embodiment, the deformation amount detection device 1 detects the angle θ when the substrate 10 is bent along the Y direction, as shown in FIG.

[0015] A reference electrode 25 is disposed on the upper surface of the substrate 10. The reference electrode 25 is disposed at a position overlapping the substrate 10 in a planar view. The reference electrode 25 has the same area as the substrate 10 in a planar view. However, the reference electrode 25 may be disposed only at a position overlapping the input electrode 21 and the output electrode 22 in a planar view. The reference electrode 25 is, for example, an inorganic electrode such as ITO (indium tin oxide) or ZnO (zinc oxide), an organic electrode such as PeDOT or conductive polyaniline, a metal film formed by vapor deposition or plating, or a printed electrode film made of silver paste.

[0016] A piezoelectric body 30 is disposed on the upper surface of the reference electrode 25. The piezoelectric body 30 is disposed at a position overlapping the substrate 10 in a plan view. The piezoelectric body 30 has the same area as the substrate 10 in a plan view. The piezoelectric body 30 deforms in accordance with the deformation of the substrate 10.

[0017] The material of the piezoelectric body 30 is polyvinylidene fluoride or a chiral polymer. An example of a chiral polymer is polylactic acid (PLA). Polylactic acid is L-type polylactic acid (PLLA) or D-type polylactic acid (PDLA). Polylactic acid made of a chiral polymer has a helical main chain structure. Polylactic acid has piezoelectricity in which the molecules are oriented when uniaxially stretched. Polylactic acid has a piezoelectric constant of d14. The uniaxial stretching direction of polylactic acid is set to form a predetermined angle (for example, approximately 45°±10°) with the Y direction or X direction when viewed in a plane.

[0018] The substrate 10 has a slit 50. The slit 50 is provided between the first end 101 and the second end 102 in plan view. In this embodiment, the slit 50 is disposed at the center of the substrate 10 in the Y direction (the dashed-dotted line shown in FIGS. 3 and 4). The center of the substrate 10 in the Y direction coincides with the center line of the bending of the substrate 10. The slit 50 makes it easier for the substrate 10 and the piezoelectric element 30 to vibrate in the thickness direction. Note that in this embodiment, the slit 50 has a rectangular shape that is long in the Y direction in plan view, but the shape of the slit 50 in plan view is not particularly limited. The slit 50 may have a shape such as a square, a diamond, a circle, or an ellipse.

[0019] An input electrode 21 and an output electrode 22 are arranged on the upper surface of the piezoelectric body 30. The input electrode 21 and the output electrode 22 are arranged at positions overlapping with the substrate 10 in a planar view. The input electrode 21 and the output electrode 22 are arranged at positions not overlapping with the first fixed portion 15 and the second fixed portion 17 in a planar view. The input electrode 21 is arranged closer to the first end 101 than the center of the Y direction of the substrate 10 (the dashed-dotted line shown in FIGS. 3 and 4). The output electrode 22 is arranged at a position overlapping with the slit 50 in a planar view. In this embodiment, the output electrode 22 is arranged at the center of the Y direction of the substrate 10 (the dashed-dotted line shown in FIGS. 3 and 4). In other words, the output electrode 22 is arranged at a position on the piezoelectric body 30 where the amount of deformation is greatest.

[0020] The input electrode 21 and the output electrode 22 are, for example, inorganic electrodes such as ITO (indium tin oxide) and ZnO (zinc oxide), organic electrodes such as PeDOT and conductive polyaniline, metal films formed by vapor deposition or plating, or printed electrode films made of silver paste.

[0021] The input electrode 21 and the output electrode 22 are each connected to a controller 90. The controller 90 inputs an input signal to the input electrode 21 and receives an output signal from the output electrode 22. The input electrode 21 inputs an input signal whose voltage changes periodically to the piezoelectric body 30. The piezoelectric body 30 vibrates in response to the input signal. The output electrode 22 outputs an output signal generated by the vibration of the piezoelectric body 30.

[0022] 5(A) and 5(B) are schematic diagrams showing the vibration of the piezoelectric body 30. FIG. 5(C) is a cross-sectional view taken along line II-II in FIG. 5(B). The piezoelectric body 30 resonates in the thickness direction of the piezoelectric body 30. Specifically, when a sine wave input signal is input from the input electrode 21, the piezoelectric body 30 has a resonance mode standing along the Y direction as shown in FIG. 5(A) and a resonance mode standing along the X direction at the center of the Y direction as shown in FIGS. 5(B) and 5(C). In the following description, the resonance mode standing along the Y direction is referred to as resonance mode A, and the resonance mode standing along the X direction is referred to as resonance mode B.

[0023] 6 shows the relationship between the bending angle of the substrate 10 and the resonance frequency of the piezoelectric body 30. The horizontal axis in FIG. 6 represents the bending angle (°) of the substrate 10, and the vertical axis represents the resonance frequency (Hz) of the piezoelectric body 30.

[0024] As shown in Fig. 6, the resonance of the piezoelectric body 30 has a plurality of resonance modes. A1 in Fig. 6 indicates the first resonance mode of resonance mode A. A2 indicates the second resonance mode of resonance mode A. A3 indicates the third resonance mode of resonance mode A. B1 indicates the first resonance mode of resonance mode B. B2 indicates the second resonance mode of resonance mode B.

[0025] For example, the controller 90 inputs a sine wave input signal with an amplitude of 5 V while sweeping the frequency, and measures the resonant frequency of each of the multiple resonant modes.

[0026] In the reference state (bending angle 0°), the piezoelectric element 30 exhibits resonant frequencies of approximately 70 Hz and approximately 330 Hz. The 70 Hz resonant frequency corresponds to the first-order resonant mode A1 of the resonant mode A. The 330 Hz resonant frequency corresponds to the second-order resonant mode A2 of the resonant mode A. As the bending angle of the substrate 10 increases, the resonant frequency of the first-order resonant mode A1 increases accordingly. When the bending angle of the substrate 10 reaches 2° and the resonant frequency reaches approximately 290 Hz, the resonant frequency of the first-order resonant mode A1 no longer changes. However, when the bending angle of the substrate 10 becomes 2° or greater, the resonant frequency of the second-order resonant mode A2 increases accordingly. When the bending angle of the substrate 10 becomes 3° and the resonant frequency reaches approximately 570 Hz, the resonant frequency of the second-order resonant mode A2 no longer changes. However, when the bending angle of the substrate 10 becomes 3° or greater, the resonant frequency of the third-order resonant mode A3 increases accordingly.

[0027] Fig. 7 is a diagram showing the frequency characteristics of the output signal. The horizontal axis in Fig. 7 is frequency (Hz), and the vertical axis is voltage (mV). The example in Fig. 7 is a graph showing the frequency characteristics of the output signal obtained from output electrode 22 when controller 90 inputs an input signal of 5V to input electrode 21 and the bending angle of substrate 10 is changed.

[0028] The example in Figure 7 shows the frequency characteristics of the output signal when the bending angle of the substrate 10 is changed in 0.2° increments from 4.2° to 5.0°. As shown in Figure 7, it can be seen that the resonant frequency corresponding to resonance mode A changes to the high frequency side depending on the bending angle of the substrate 10. It can also be seen that the resonant frequency corresponding to resonance mode B changes to the high frequency side depending on the bending angle of the substrate 10.

[0029] Therefore, the controller 90 sweeps the frequency of the input signal and detects the bending angle of the substrate 10 according to the value of the detected resonance frequency. For example, when the controller 90 detects a resonance frequency of 150 Hz, it detects the bending angle of the substrate 10 as 1°.

[0030] On the other hand, when the first resonance frequency of a first resonance mode among the multiple resonance modes exceeds a predetermined value, the controller 90 detects the bending angle according to the value of the second resonance frequency of the second resonance mode. For example, when the first resonance frequency of the first resonance mode A1, which is the first resonance mode, exceeds 290 Hz, the controller 90 detects the bending angle according to the value of the second resonance frequency of the second resonance mode A2, which is the second resonance mode. Alternatively, when the second resonance frequency of the second resonance mode A2, which is the second resonance mode, exceeds 570 Hz, the controller 90 detects the bending angle according to the value of the third resonance frequency of the third resonance mode A3, which is the third resonance mode. Alternatively, when the first resonance frequency of the first resonance mode B1, which is the first resonance mode, exceeds 900 Hz, the controller 90 detects the bending angle according to the value of the second resonance frequency of the second resonance mode B2, which is the second resonance mode.

[0031] As described above, the controller 90 can accurately detect the bending angle of the substrate 10 according to the value of the resonance frequency by changing the resonance mode of the resonance frequency associated with the bending angle.

[0032] Next, Fig. 8 shows the relationship between the bending angle of the substrate 10 and the output signal. The horizontal axis in Fig. 8 represents the bending angle (°) of the substrate 10, and the vertical axis represents the voltage (mV) of the output signal.

[0033] In this example, the controller 90 applies a sinusoidal input signal of a fixed frequency to the input electrode 21. The controller 90 receives an output signal from the output electrode 22 and measures the voltage.

[0034] 8, for example, when a sine wave input signal with a first frequency of 53 Hz is applied to input electrode 21, a voltage of approximately 10 mV is measured when substrate 10 is in the reference state (bending angle 0°). In the example of FIG. 8, it can be seen that the measured voltage drops sharply as the bending angle of substrate 10 increases.

[0035] 8, for example, when a sine wave input signal with a second frequency of 430 Hz is applied to input electrode 21, a voltage of approximately 10 mV is measured when substrate 10 is bent at an angle of 2.2°. In the example of FIG. 8, it can be seen that the measured voltage drops sharply when the bending angle of substrate 10 is made smaller or larger than 2.2°.

[0036] Therefore, the controller 90 detects the bending angle of the substrate 10 according to the magnitude of the output signal when an input signal of a constant frequency such as 53 Hz or 430 Hz is input, thereby enabling the controller 90 to detect even minute bending angles with high accuracy.

[0037] 9(A) and 9(B) are schematic diagrams showing a state in which the substrate 10 of the deformation amount detection device 1 is attached and fixed to a detection object 70. In this example, the detection object 70 is a battery. A battery may swell slightly over a long period of time, such as several months to several years, and may cause slight deformation. A general sensor has difficulty detecting such slight deformation that occurs over a long period of time.

[0038] On the other hand, as shown in FIG. 9(B), in this embodiment, when the detection object 70, which is a battery, swells, the substrate 10 of the deformation detection device 1 bends in response to the deformation of the detection object 70. Because the deformation caused by the swell of the detection object 70 is very small, the bending angle of the substrate 10 is also very small. However, as shown in FIG. 8, the controller 90 can detect a very small bending angle from the reference state by applying an input signal, for example, a 53 Hz sine wave, to the input electrode 21 and measuring the voltage of the output signal. Therefore, the deformation detection device 1 can detect even a slight swell of the detection object 70, which is a battery.

[0039] 10(A) and 10(B) are schematic diagrams showing a state in which the substrate 10 of the deformation amount detection device 1 is attached and fixed to the detection object 70. The detection object 70 in this example is also a battery.

[0040] In this example, the substrate 10 of the deformation amount detection device 1 is attached to the detection object 70 via a holding member 900 in a state where it is bent at a predetermined angle (for example, 2.2°).

[0041] 8, the controller 90 can detect a very small bending angle by applying an input signal, for example a 430 Hz sine wave, to the input electrode 21 and measuring the voltage of the output signal. Therefore, in this case as well, the deformation amount detection device 1 can detect a slight bulge in the detection object 70, which is a battery.

[0042] Fig. 11 is a schematic diagram showing the vibration mode of the piezoelectric body 30 according to Modification 1. Fig. 12 shows the relationship between the bending angle of the substrate 10 according to Modification 1 and the resonance frequency of the piezoelectric body 30. Fig. 13 shows the relationship between the bending angle of the substrate 10 according to Modification 1 and the output signal.

[0043] The deformation amount detection device according to the first modification has the same configuration as that shown in Fig. 1. However, the material of the piezoelectric body 30 is polylactic acid. The uniaxial stretching direction of the polylactic acid is set to form the same angle (for example, about 0°±10°) with the Y direction or the X direction in plan view.

[0044] Fig. 11 shows the vibration state when a sine wave with an amplitude of 5 V is applied to the input electrode 21 of the deformation amount detection device 1. As shown in Fig. 11, when the uniaxial stretching direction of the polylactic acid is at the same angle as the Y direction or the X direction in a plan view, when a sine wave input signal is input to the input electrode 21, the piezoelectric body 30 enters a resonance mode in which it vibrates mainly in the planar direction.

[0045] In this resonance mode, the resonance frequency increases as the bending angle of the substrate 10 increases, as shown in Fig. 12. Therefore, the controller 90 can accurately detect the bending angle by measuring the resonance frequency.

[0046] 13, the output voltage decreases as the bending angle of the substrate 10 increases. Therefore, the controller 90 can accurately detect the bending angle by measuring the output voltage in response to an input of a sine wave with a fixed frequency.

[0047] The description of the present embodiment should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined not by the above-described embodiments but by the claims. Furthermore, the scope of the present invention includes the scope equivalent to the claims. [Explanation of symbols]

[0048] 1: Deformation detector 10: Substrate 15: 1st fixed part 17:Second fixed part 21: Input electrode 22: Output electrode 25:Reference electrode 30: Piezoelectric material 50: Slit 70: Object to be detected 90: Controller 101 :1st end 102: 2nd end 900: Holding member

Claims

1. a substrate having a first end and a second end along a first direction; a fixing portion overlapping the first end and the second end in the thickness direction; a piezoelectric body that overlaps the substrate in a plan view and is disposed between the first end and the second end; an output electrode that is disposed on a first surface of the piezoelectric body, overlaps the piezoelectric body in a plan view, and is disposed at a position including the center in the first direction, and outputs an output signal from the piezoelectric body; an input electrode that is disposed on a first surface of the piezoelectric body, overlaps the piezoelectric body in a plan view, is disposed at a position different from that of the output electrode in a plan view, is disposed closer to the first end or the second end than the output electrode, and inputs an input signal to the piezoelectric body; a reference electrode that overlaps the input electrode and the output electrode in a plan view and is disposed on a second surface of the piezoelectric body; a controller that inputs the input signal to the input electrode and receives the output signal from the output electrode; A deformation amount detection device comprising: the substrate has a slit between the first end and the second end; the output electrode is disposed at a position that overlaps the slit in a plan view and includes a center in the first direction, the piezoelectric body resonates in the thickness direction of the piezoelectric body, The resonance has a resonance mode A standing along the first direction and a resonance mode B standing along a second direction orthogonal to the first direction, the controller measures the resonant frequencies of the resonant mode A and the resonant mode B, sweeping the frequency of the input signal; The resonance mode A has a first resonance mode A1 and a second resonance mode A2, The resonance mode B has a first resonance mode B1 and a second resonance mode B2, When the first resonance frequency of the first resonance mode A1 exceeds a first predetermined value, the bending angle is detected according to the value of the second resonance frequency of the second resonance mode A2; When the third resonance frequency of the first resonance mode B1 exceeds a third predetermined value, the bending angle is detected according to the value of the fourth resonance frequency of the second resonance mode B2. Deformation detection device.

2. The substrate is attached to the object to be detected. The deformation amount detection device according to claim 1 .

Images