JP7721099B2 - Deformation detection device - Google Patents

Description

Article 30, paragraph 2 of the Patent Act applies. (1) Publication name: Proceedings of the 2022 Spring Meeting of the Acoustical Society of Japan. Publication date: February 23, 2022. (2) Meeting name and venue: 2022 Spring Meeting of the Acoustical Society of Japan. Online (http://www.mtg.acoustics.jp). Publication date: March 9 to 11, 2022.

The present invention relates to a deformation amount detection device.

Patent document 1 discloses a deformation detection device having a first electrode, a second electrode, and a flexible transmission part.

In the configuration of Patent Document 1, when an input signal is input to the first electrode, an elastic wave is generated. The transmission unit transmits the elastic wave to the second electrode. The second electrode generates an output signal from the elastic wave. In the configuration of Patent Document 1, the amount of deformation of the transmission unit from its reference state can be detected based on the output signal.

International Publication No. 2022/030356

The object of one embodiment of the present invention is to provide a deformation detection device that detects deformation with high sensitivity by utilizing resonance in the thickness direction.

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; 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.

The slits in the substrate make it easier for the substrate and piezoelectric element to vibrate in the thickness direction. The output electrode is positioned so that it overlaps the slits in a planar view, and is therefore positioned at the position on the piezoelectric element where the deformation is greatest. Therefore, the deformation detection device can detect the deformation amount with high sensitivity by utilizing resonance in the thickness direction.

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.

FIG. 1 is a perspective view of a deformation amount detection device 1. 2 is a cross-sectional view taken along line II shown in FIG. 1. 2 is a cross-sectional view taken along line II shown in FIG. 1. FIG. 2 is a plan view of the deformation amount detection device 1. 5A and 5B are schematic diagrams showing the vibration mode of the piezoelectric body 30, and FIG. 5C is a cross-sectional view taken along line II-II in FIG. 5B. 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. FIG. 4 is a diagram illustrating frequency characteristics of an output signal. 10 is a diagram showing the relationship between the bending angle of the substrate 10 and the output signal. FIG. 9A and 9B 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. 10A and 10B 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. 10 is a schematic diagram showing a vibration mode of a piezoelectric body 30 according to Modification 1. FIG. 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 Modification 1. FIG. 10 is a diagram showing the relationship between the bending angle of the substrate 10 and the output signal according to Modification 1. FIG.

Figure 1 is an external perspective view of the deformation amount detection device 1. Figures 2 and 3 are cross-sectional views taken along line II shown in Figure 1. Figure 4 is a plan view of the deformation amount detection device 1.

The deformation amount detection 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.

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

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 when viewed in a plane, is defined as the X direction.

The deformation amount detection device 1 detects the amount of deformation of the flexible substrate 10 from a reference state. 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 Figure 3.

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.

A piezoelectric body 30 is disposed on the upper surface of the reference electrode 25. The piezoelectric body 30 is disposed in a position that overlaps the substrate 10 in a planar view. The piezoelectric body 30 has the same area as the substrate 10 in a planar view. The piezoelectric body 30 deforms in accordance with the deformation of the substrate 10.

The material of the piezoelectric element 30 is polyvinylidene fluoride or a chiral polymer. An example of a chiral polymer is polylactic acid (PLA). Polylactic acid is either L-type polylactic acid (PLLA) or D-type polylactic acid (PDLA). Polylactic acid, which is made of a chiral polymer, has a helical main chain structure. Polylactic acid exhibits piezoelectricity when uniaxially stretched, orienting the molecules. 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 or X direction when viewed in a plane.

The substrate 10 has a slit 50. The slit 50 is located between the first end 101 and the second end 102 in a planar view. In this embodiment, the slit 50 is positioned at the center of the substrate 10 in the Y direction (the dashed-dotted line shown in Figures 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 a planar view, but the shape of the slit 50 in a planar view is not particularly limited. The slit 50 may have a shape such as a square, diamond, circle, or ellipse.

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 in positions that overlap with the substrate 10 in a planar view. The input electrode 21 and the output electrode 22 are arranged in positions that do not overlap 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 Figures 3 and 4). The output electrode 22 is arranged in a position that overlaps 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 Figures 3 and 4). In other words, the output electrode 22 is arranged at the position of the piezoelectric body 30 that experiences the greatest deformation.

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.

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.

Figures 5(A) and 5(B) are schematic diagrams showing the vibration of the piezoelectric body 30. Figure 5(C) is a cross-sectional view taken along line II-II in Figure 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 that is stationary along the Y direction as shown in Figure 5(A), and a resonance mode that is stationary along the X direction at the center of the Y direction as shown in Figures 5(B) and 5(C). In the following description, the resonance mode that is stationary along the Y direction will be referred to as resonance mode A, and the resonance mode that is stationary along the X direction will be referred to as resonance mode B.

Figure 6 shows the relationship between the bending angle of the substrate 10 and the resonant frequency of the piezoelectric body 30. The horizontal axis in Figure 6 represents the bending angle (°) of the substrate 10, and the vertical axis represents the resonant frequency (Hz) of the piezoelectric body 30.

As shown in Figure 6, the resonance of the piezoelectric body 30 has multiple resonance modes. A1 in Figure 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.

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

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 primary resonant mode A1 of the resonant mode A. The 330 Hz frequency corresponds to the secondary resonant mode A2 of the resonant mode A. As the bending angle of the substrate 10 increases, the resonant frequency of the primary 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 primary resonant mode A1 no longer changes. However, when the bending angle of the substrate 10 is 2° or greater, the resonant frequency of the secondary resonant mode A2 increases accordingly. When the bending angle of the substrate 10 reaches 3° and the resonant frequency reaches approximately 570 Hz, the resonant frequency of the secondary resonant mode A2 no longer changes. However, when the bending angle of the substrate 10 is 3° or more, the resonant frequency of the third-order resonance mode A3 increases in proportion to the bending angle of the substrate 10.

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

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 shifts toward higher frequencies depending on the bending angle of the substrate 10. It can also be seen that the resonant frequency corresponding to resonance mode B shifts toward higher frequencies depending on the bending angle of the substrate 10.

The controller 90 then sweeps the frequency of the input signal and detects the bending angle of the substrate 10 according to the value of the detected resonant frequency. For example, when the controller 90 detects a resonant frequency of 150 Hz, it detects the bending angle of the substrate 10 as 1°.

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 in accordance with 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 exceeds 290 Hz, the controller 90 detects the bending angle in accordance with the value of the second resonance frequency of the second resonance mode A2. Alternatively, when the second resonance frequency of the second resonance mode A2 exceeds 570 Hz, the controller 90 detects the bending angle in accordance with the value of the third resonance frequency of the third resonance mode A3. Alternatively, when the first resonance frequency of the first resonance mode B1 exceeds 900 Hz, the controller 90 detects the bending angle in accordance with the value of the second resonance frequency of the second resonance mode B2.

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

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

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.

As shown in Figure 8, for example, when a sine wave input signal with a first frequency of 53 Hz is applied to the input electrode 21, a voltage of approximately 10 mV is measured when the substrate 10 is in its reference state (bending angle 0°). Furthermore, in the example of Figure 8, it can be seen that the measured voltage drops sharply as the bending angle of the substrate 10 is increased.

Furthermore, as shown in Figure 8, when a sine wave input signal with a second frequency of 430 Hz is applied to the input electrode 21, a voltage of approximately 10 mV is measured when the bending angle of the substrate 10 is 2.2°. In the example of Figure 8, it can be seen that the measured voltage drops sharply when the bending angle of the substrate 10 is made smaller or larger than 2.2°.

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. This allows the controller 90 to detect even minute bending angles with high accuracy.

Figures 9(A) and 9(B) are schematic diagrams showing the substrate 10 of the deformation detection device 1 attached and fixed to the detection object 70. In this example, the detection object 70 is a battery. Batteries can swell slightly over a long period of time, from several months to several years, causing slight deformation. Conventional sensors have difficulty detecting such slight deformations that occur over such long periods of time.

On the other hand, as shown in Figure 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 bulging of the detection object 70 is very small, the bending angle of the substrate 10 is also very small. However, as shown in Figure 8, the controller 90 can detect very small bending angles 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 slight bulges in the detection object 70, which is a battery.

Next, Figures 10(A) and 10(B) are schematic diagrams showing the 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.

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

As shown in Figure 8, the controller 90 can detect very small bending angles 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 too, the deformation amount detection device 1 can detect slight bulges in the detection object 70, which is a battery.

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

The deformation amount detection device according to Variation 1 has the same configuration as that shown in Figure 1. However, the material of the piezoelectric element 30 is polylactic acid. The uniaxial stretching direction of the polylactic acid is set to form the same angle (e.g., approximately 0°±10°) with the Y direction or X direction when viewed in a plane.

Figure 11 shows the vibration behavior when a sine wave with an amplitude of 5 V is applied to the input electrode 21 of the deformation detection device 1. As shown in Figure 11, when the uniaxial stretching direction of polylactic acid is at the same angle as the Y direction or X direction when viewed in a plane, when a sine wave input signal is input to the input electrode 21, the piezoelectric element 30 enters a resonant mode in which it vibrates mainly in the planar direction.

In this resonance mode, as shown in Figure 12, the resonance frequency increases as the bending angle of the substrate 10 increases. Therefore, the controller 90 can detect the exact bending angle by measuring the resonance frequency.

Furthermore, in this resonant mode, as shown in Figure 13, the output voltage decreases as the bending angle of the substrate 10 increases. Therefore, the controller 90 can detect the exact bending angle by measuring the output voltage in response to an input of a sine wave at a fixed frequency.

The description of this embodiment should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims, not by the above-described embodiments. Furthermore, the scope of the present invention includes the scope equivalent to the claims.

1: deformation amount detection device 10: substrate 15: first fixed portion 17: second fixed portion 21: input electrode 22: output electrode 25: reference electrode 30: piezoelectric body 50: slit 70: detection object 90: controller 101: first end 102: second end 900: holding member

Claims (2)

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