JP2020099105A - Measurement device - Google Patents

Abstract

To apply measurement of a physical amount such as temperature, pressure, and vibration to an IoT-related technology.SOLUTION: A measurement device comprises a vibration power generation element 101, a radiation portion 102, a receiving portion 103, a detection portion 104, and a calculation portion 105. The vibration power generation element 101 has a vibrator composed of a piezoelectric single crystal body. The radiation portion 102 radiates electromagnetic waves of a frequency swept in a set range to the vibration power generation element 101. The receiving portion 103 receives the electromagnetic waves radiated from the vibration power generation element 101 vibrated by receiving the electromagnetic waves radiated from the radiation portion 102. The detection portion 104 detects the frequency in which the strength of the electromagnetic wave received by the receiving portion 103 is the highest.SELECTED DRAWING: Figure 1

Description

The present invention relates to a measuring device, and more particularly, to a measuring device using a vibration power generating element.

In recent years, all things have been connected via the Internet, and the development of IoT (Internet to Things) technology that creates new value by exchanging information between things or between people and things is remarkable. As IoT-related devices, there are sensors that measure physical quantities such as temperature, pressure, and acceleration. A power source is indispensable for driving such a sensor, and conventionally, power is supplied to the device from a storage battery such as a button battery. Although the battery life has been extended due to the reduction in power consumption of the circuit that configures the sensor, periodic charging and battery replacement are extremely troublesome, which hinders the spread of the IoT technology.

Under such circumstances, energy harvesting (environmental power generation), which extracts electric power from energy existing in the environment, is drawing attention. Various technologies for converting energy such as vibration, heat, light, and electromagnetic waves existing in the environment into electric power have been proposed. For example, vibration power generation that utilizes mechanical energy due to vibration in the environment has been proposed.

As a power generation technique using vibration, a method using a piezoelectric body is well known (see Patent Documents 1 and 2). The piezoelectric body has a characteristic of generating an electric charge when it is distorted, so that the electric charge can be recovered by vibrating the piezoelectric body to distort it, and can be used as a power source. A pipe inspection device using vibration power generation or wireless power supply has been proposed (see Patent Document 3).

JP, 2013-243821, A JP 2012-005192 A JP, 2008-109649, A

By the way, in a vibration power generation element that generates power using vibration, generally, the motion of a person or the vibration of a bridge, a building, a vehicle, or the like is used. In these cases, the vibration frequency obtained from the environment is often a low frequency of less than several hundreds Hz, so in order to generate a sufficient amount of power to use it as a power source for a conventionally used sensor, the vibration power generation It is necessary to match the natural frequency of the element to the vibration frequency obtained from the environment.

However, in order to match the natural frequency of the vibration power generation element to the low vibration frequency obtained from the environment as described above, it is necessary to lengthen the element shape into a rod shape, which hinders the miniaturization of the vibration power generation element. It is difficult to apply the vibration power generation element to a IoT-related device as a power source of a conventionally used sensor. In addition, since vibration power generation using a piezoelectric body does not provide sufficient power for wireless communication, vibration power generation using a piezoelectric body is also applied to IoT-related devices in this respect in combination with conventional sensors. Difficult to make

It is possible to increase the amount of electric power that can be obtained by combining it with other energy harvesting, but this has the adverse effect of increasing the size of the device. In addition, when other energy harvesting is used, the installation location is limited to an environment where environmental energy such as light and heat other than vibration can be obtained at the same time, which is also difficult to apply to the IoT related device.

As described above, the measurement of physical quantities such as temperature, pressure, and vibration by the conventional technique using the small vibration power generation element as a power source has a problem that it is not easy to apply to the IoT-related technique.

The present invention has been made to solve the above problems, and an object of the present invention is to apply the measurement of physical quantities such as temperature, pressure, and acceleration using a small vibration power generation element to IoT-related technology. And

The measuring apparatus according to the present invention includes a vibration power generation element having a vibrator made of a piezoelectric single crystal body, a radiation unit that radiates an electromagnetic wave having a frequency swept within a set range to the vibration power generation element, and a radiation unit. The receiving unit receives the electromagnetic wave emitted from the vibration power generation element that vibrates by receiving the electromagnetic wave emitted from the detector, the detecting unit that detects the frequency at which the intensity of the electromagnetic wave received by the receiving unit is the highest, and the detecting unit detects And a calculation unit that obtains a physical quantity related to the environment in which the vibration power generation element is placed based on the frequency.

In one configuration example of the above-described measuring device, a capacitor that is electrically connected to the vibration power generation element and that accumulates charges generated in the vibration power generation element is further included.

In one configuration example of the above-mentioned measuring device, a capacitor that stores electric charges is driven as a power supply, and a measurement unit that measures a physical quantity related to the environment in which the vibration power generation element is placed, and a vibration power generation corresponding to the physical quantity measured by the measurement unit. And a load changing unit that changes at least one of a load resistance and a load capacitance connected to the element.

In one configuration example of the above-described measuring apparatus, the vibrator includes a first electrode formed on the − surface of the polarization axis of the piezoelectric single crystal body, and a second electrode formed on the + surface of the polarization axis of the piezoelectric single crystal body. Is further provided.

In one configuration example of the measuring device, the vibrator is a coil spring.

In one configuration example of the above measuring device, the piezoelectric single crystal body constituting the coil spring has the same crystal state in a cross section of a plane parallel to the axis of the coil spring in the power generation region of the coil spring.

In one configuration example of the above-described measuring device, the polarization axis of the piezoelectric single crystal body and the direction of the axial center of the coil spring are the same.

In one configuration example of the above measuring device, the piezoelectric single crystal body is composed of LiTaO ₃ or LiNbO ₃ .

As described above, according to the present invention, the change in the resonance frequency of the vibration power generation element is radiated from the vibration power generation element that has received the electromagnetic wave radiated from the radiation section, and is detected by the detection section from the electromagnetic wave received by the reception section. Since detection is performed, measurement of physical quantities such as temperature, pressure, and acceleration using a small vibration power generation element can be applied to IoT-related technology.

FIG. 1 is a configuration diagram showing a configuration of the measuring apparatus according to the first embodiment. FIG. 2 is a perspective view showing the configuration of the vibration power generation element 101. FIG. 3 is a cross-sectional view showing a partial configuration of the vibration power generation element 101. FIG. 4 is a configuration diagram showing the configuration of the measuring device according to the second embodiment. FIG. 5 is a configuration diagram showing the configuration of the measuring device according to the third embodiment.

Hereinafter, a measuring device according to an embodiment of the present invention will be described.

[Embodiment 1]
First, a measuring device according to the first embodiment of the present invention will be described with reference to FIG. This measuring device includes a vibration power generation element 101, a radiation unit 102, a reception unit 103, a detection unit 104, and a calculation unit 105.

The vibration power generation element 101 has a vibrator made of a piezoelectric single crystal body. The vibration power generation element 101 is composed of, for example, a coil spring of a piezoelectric single crystal body 111 as shown in FIG. The piezoelectric single crystal body 111 is made of, for example, LiTaO ₃ or LiNbO ₃ . The cross section of the piezoelectric single crystal body 111 is, for example, a substantially rectangular shape having a thickness of 0.8 mm and a width of 2 mm in the axial direction.

The coil spring spirally extends from the fixed end 112 in the axial direction. The fixed end 112 is fixed to a pedestal (not shown) using an adhesive agent or solder. A weight 114 made of brass or the like is fixed to the free end 113 of the coil spring. The polarization axis of the piezoelectric single crystal body 111 and the expansion/contraction direction (axial center direction) of the coil spring are the same. When the piezoelectric single crystal body 111 is composed of LiTaO ₃ or LiNbO ₃ , the Z axis of the piezoelectric single crystal body 111 and the expansion/contraction direction of the coil spring are the same. When vibration is applied in the axial direction, the coil spring vibrates so as to expand and contract in the axial direction.

In addition, as shown in the cross-sectional view of FIG. 3, the vibration power generation element 101 includes a piezoelectric single crystal body 111, a first electrode 131 formed on the − surface (in the case of LiTaO ₃ −Z axis surface) of the polarization axis, The second electrode 132 formed on the + plane (+Z axis plane in the case of LiTaO ₃ ) of the polarization axis of the single crystal body 111. The first electrode 131 and the second electrode 132 are provided to sandwich the piezoelectric single crystal body 111 in the axial direction of the coil spring. Further, the first electrode 131 and the second electrode 132 are provided over the entire area of the piezoelectric single crystal body 111 that is a coil spring. The first electrode 131 and the second electrode 132 are formed to have a thickness of 0.4 μm, for example. The same applies to the case of LiNbO ₃ .

Each electrode is provided for charge collection. At least one electrode is provided. The electrode is best formed on a surface that is substantially perpendicular to the piezoelectric polarization axis direction. Further, each electrode can be made of, for example, a metal such as Ag or Cu deposited using a vacuum film forming apparatus. The electrodes can also be a multi-layered metal composed of a plurality of metals. The electrodes can also be made of a conductor such as a conductive paste.

Further, the crystal state such as the crystal orientation, composition, and physical characteristics of the piezoelectric single crystal body 111 of the vibration power generation element 101 in the cross section of the plane parallel to the plane passing through the axis of the coil spring of the piezoelectric single crystal body 111 used as the coil spring It is the same (constant) in the power generation area. The power generation region is a region that substantially contributes to power generation of the vibration power generation element 101. The power generation region may be the entire area of the vibration power generation element 101 or may be a part of the vibration power generation element 101. For example, crystal orientations at both ends such as the fixed end 112 serving as the base point of the coil spring of the vibration power generating element 101 and the free end 113 serving as the end point may be different from the power generation region.

The spiral structure (coil spring) made of the piezoelectric single crystal body 111 having the above structure can be formed by growing the structure by the micro-pulling-down method. The micro-pulling-down method is a crystal growing method in which a molten material is gradually pulled down from a die provided at a lower end of a crucible to grow a crystal. Normally, it is only pulled down, but by controlling the pulling direction three-dimensionally, a spiral structure like a coil spring can be obtained. The cross section of the spiral structure formed by the grown piezoelectric single crystal body 111 can have any shape such as a rectangle, a circle, or an ellipse by changing the shape of the die. As another method of forming the spiral structure, a rod-shaped single crystal body can be formed by using an NC machine or laser processing. The polarization direction of the piezoelectric single crystal body 111 is set parallel to the axial center direction of the coil spring, but it can be changed as necessary.

Generally, a single crystal material has crystal axes represented by X, Y and Z. In the piezoelectric single crystal body 111 that is a coil spring, the crystal axis is oriented in substantially the same direction regardless of the portion of the spiral structure. This is because the spiral structure is formed by gradually pulling down the seed crystal in the pulling direction and moving the seed crystal in a circle in a plane perpendicular to the pulling direction to form a spiral structure. Is because it coincides with the crystal axis of the seed crystal. It is also possible to change the crystal axis at an arbitrary position of the spiral structure by applying a rotation motion when moving the seed crystal.

When vibration having a period close to the natural frequency of the vibration power generation element 101 is applied, resonance occurs and the vibration power generation element 101 vibrates greatly. The natural frequency is determined by the material of the piezoelectric single crystal body 111 used as the coil spring, the size of the cross section, the spiral diameter of the coil spring, the pitch of the spiral, and the number of turns. Further, by adding the weight 114, the force applied to the coil spring is increased, and the vibration power generation element 101 can obtain larger vibration.

Since the vibration power generation element 101 is composed of the piezoelectric single crystal body 111, surface charges are generated in the piezoelectric single crystal body 111 due to strain or the like generated in the vibration power generation element 101 due to the inverse piezoelectric effect. The generated charges are collected by the first electrode 131 and the second electrode 132. Since the generated electromotive force becomes an alternating current, it can be stored in, for example, a power storage circuit connected via a predetermined rectifying circuit. The electric power thus stored can be supplied to necessary circuits at a predetermined timing.

The production of the coil spring of the piezoelectric single crystal body 111 will be described using more specific numbers. A coil spring made of a piezoelectric single crystal body 111 made of LiTaO ₃ is grown by a micro pulling down method. The spiral radius is 1.5 cm, the number of turns is 8 and the pitch is 1 cm. The fixed end 112 of the coil spring is fixed on a predetermined pedestal with an epoxy resin adhesive, and the free end 113 is fixed with a weight 114 made of brass and having a weight of 5 g.

The piezoelectric single crystal body is not limited to LiTaO ₃ , but may be a single crystal piezoelectric material such as LiNbO ₃ , KNbO ₃ , Langasite-based piezoelectric body, or single crystal ceramics.

The radiating unit 102 has a sweep circuit 121, an output circuit 122, and an antenna 123, sweeps a frequency within a range set by the sweep circuit 121, and radiates an electromagnetic wave to the vibration power generation element 101 by the output circuit 122 and the antenna 123. .. For example, the radiating unit 102 radiates electromagnetic waves to the vibration power generation element 101 while sweeping the frequency at predetermined frequency intervals around the predetermined value of the resonance frequency of the vibration power generation element 101 in the 900 MHz band. Further, the radiating unit 102 radiates electromagnetic waves having a plurality of frequencies at predetermined time intervals. The radiated electromagnetic wave is received by the vibration power generation element 101. For example, the electromagnetic wave received with the resonance frequency of 920 MHz of the vibration power generation element 101 as the central wavelength is re-excited and radiated from the vibration power generation element 101.

The receiving unit 103 receives the electromagnetic wave emitted from the vibration power generation element 101 when the electromagnetic wave is emitted from the emitting unit 102. The receiving unit 103 starts the receiving operation after the emitting unit 102 emits the electromagnetic wave described above. For example, after the radiating unit 102 radiates an electromagnetic wave of one frequency, the receiving unit 103 starts the receiving operation, and the receiving unit 103 stops the receiving operation before the radiating unit 102 radiates the electromagnetic wave of the next frequency. To do. The receiving unit 103 starts and stops the above-described receiving operation according to the electromagnetic wave emission interval of the emitting unit 102 until the emitting unit 102 finishes emitting electromagnetic waves of all frequencies.

When the vibration power generation element 101 receives an electromagnetic wave having a resonance frequency, the vibration power generation element 101 emits the electromagnetic wave after a predetermined time has elapsed. Therefore, as described above, when the radiation unit 102 radiates electromagnetic waves of different frequencies at predetermined time intervals, when an electromagnetic wave of a resonance frequency is radiated, this electromagnetic wave radiates an electromagnetic wave of the next frequency. The signal is received by the receiving unit 103 before being emitted from the unit 102.

The detection unit 104 detects the frequency of the electromagnetic wave having the highest intensity among the electromagnetic waves received by the reception unit 103. The calculation unit 105 calculates the physical quantity received by the vibration power generation element 101 based on the frequency detected by the detection unit 104.

For example, when the temperature changes, the resonance frequency of the vibration power generation element 101 changes. This change appears as a change in the frequency detected by the detection unit 104. Based on the resonance frequency of the vibration power generation element 101 detected in this way, the temperature of the place where the vibration power generation element 101 is arranged can be obtained. Therefore, this measuring device can measure the temperature as the physical quantity received by the vibration power generation element 101.

The measuring apparatus according to the first embodiment described above can obtain the physical quantity received by the vibration power generation element 101 in a contactless (wireless) manner without supplying power to the vibration power generation element 101, and is applied to the IoT-related technology. be able to. As described above, according to the first embodiment, the intensity of the electromagnetic wave emitted from the vibration power generation element that radiates the electromagnetic wave having the frequency swept within the range set by the radiation unit and vibrates in response to the electromagnetic wave. Since the highest frequency is detected and the physical quantity related to the environment in which the vibration power generation element is placed is calculated based on the resonance frequency of the vibration power generation element, changes in the resonance frequency of the vibration power generation element cause changes in temperature, pressure, acceleration, etc. Can be measured and can be applied to IoT related technology.

[Second Embodiment]
Next, a measuring device according to the second embodiment of the present invention will be described with reference to FIG. This measuring device includes a vibration power generation element 101, a radiation unit 102, a reception unit 103, a detection unit 104, and a calculation unit 105. These are the same as those in the first embodiment. In the second embodiment, the capacitor 106 that is electrically connected to the vibration power generation element 101 and stores the charge generated in the vibration power generation element 101 is provided. The capacitor 106 is connected to the first electrode 131 and the second electrode 132 of the vibration power generation element 101.

When the vibration power generation element 101 receives the vibration of the mechanical resonance frequency of the vibration power generation element 101, a strain is generated, and a surface charge is generated (power is generated) by the inverse piezoelectric effect due to this strain. The generated charges are collected by the first electrode 131 and the second electrode 132. Since the electric power generated by the vibration of the vibration power generation element 101 is an alternating current, the capacitor 106 is connected to the first electrode 131 and the second electrode 132 of the vibration power generation element 101 via the rectifier circuit 107.

For example, the vibration power generation element 101 is formed so as to resonate with mechanical vibration in the vicinity of 400 Hz, which is significantly different from the electromagnetic wave frequency for detection. The vibration power generation element 101 thus formed is fixed to a vibration structure such as a motor that generates vibration. When the vibrating structure vibrates at a frequency of about 400 Hz, the vibration power generation element 101 generates power and the electric charge is stored in the capacitor 106, as described above. In the vibration power generation element 101, the resonance frequency changes due to the electric charge accumulated in the capacitor 106.

The change in the resonance frequency of the vibration power generation element 101 described above is radiated from the vibration power generation element 101 that has received the electromagnetic wave radiated from the radiation unit 102 and is received by the reception unit 103, as in the above-described first embodiment. Therefore, it is detected by the detection unit 104. Based on the change in the resonance frequency detected in this way, the calculation unit 105 determines the magnitude of vibration, which is a physical quantity received by the vibration power generation element 101.

As described above, according to the second embodiment, it is possible to wirelessly monitor the vibration state of the vibrating structure. For example, if a range in which the magnitude of vibration calculated by the calculation unit 105 can be determined to be normal is set in advance, if the magnitude of vibration determined by the calculation unit 105 deviates from the range that can be determined to be normal, the vibration structure It can be determined that an abnormality has occurred in the. In addition, the determination of this abnormality can be made at a location away from the vibrating structure. Note that it is possible to connect a circuit that discharges when the charge accumulated in the capacitor 106 exceeds a certain amount. Further, when the electric charge accumulated in the capacitor 106 reaches a certain amount, the vibration power generating element 101 may be provided with a mechanism to which a load element other than the capacitor 106 is further connected.

[Third Embodiment]
Next, a measuring device according to Embodiment 3 of the present invention will be described with reference to FIG. This measuring device includes a vibration power generation element 101, a radiation unit 102, a reception unit 103, a detection unit 104, a calculation unit 105, and a capacitor 106. These are the same as those in the second embodiment described above. In the third embodiment, the capacitor 106 in which electric charges are accumulated is driven as a power source and is connected to the measurement unit 108 that detects a physical quantity, and the vibration power generation element 101 corresponding to the physical quantity detected (measured) by the measurement unit 108. A load changing unit 109 that changes at least one of the load resistance and the load capacitance is further included.

The measuring unit 108 measures, for example, pressure. The load changing unit 109 changes the load resistance connected to the vibration power generation element 101 in response to the change in pressure measured by the measuring unit 108. When the load resistance connected to the vibration power generation element 101 is changed, the resonance frequency changes with this change.

The change in the resonance frequency of the vibration power generation element 101 described above is radiated from the vibration power generation element 101 that has received the electromagnetic wave radiated from the radiation unit 102 and is received by the reception unit 103, as in the above-described first embodiment. Therefore, it is detected by the detection unit 104. Based on the change in the resonance frequency detected in this way, the calculation unit 105 obtains the magnitude of the pressure measured by the measurement unit 108. As described above, according to the third embodiment, by using the measurement unit 108, it is possible to wirelessly obtain a change in a physical quantity other than the physical quantity received by the vibration power generation element 101.

As described above, according to the present invention, the change in the resonance frequency of the vibration power generation element is radiated from the vibration power generation element that has received the electromagnetic wave radiated from the radiation section, and is detected by the detection section from the electromagnetic wave received by the reception section. Since it is detected, measurement of physical quantities such as temperature, pressure, and acceleration using a small vibration power generation element can be applied to IoT-related technology.

The present invention is not limited to the embodiments described above, and many modifications and combinations can be implemented by a person having ordinary knowledge in the art within the technical idea of the present invention. That is clear.

101... Vibration power generation element, 102... Radiating section, 103... Receiving section, 104... Detecting section, 105... Calculating section.

Claims (8)

A vibration power generation element having a vibrator composed of a piezoelectric single crystal body,
A radiation unit that radiates an electromagnetic wave having a frequency swept in a set range to the vibration power generation element,
A receiving unit that receives an electromagnetic wave emitted from the vibration power generation element that vibrates by receiving an electromagnetic wave emitted from the emitting unit;
A detection unit that detects a frequency at which the intensity of the electromagnetic wave received by the reception unit is highest,
And a calculation unit that obtains a physical quantity related to the environment in which the vibration power generation element is placed, based on the frequency detected by the detection unit. The measuring device according to claim 1,
The measuring apparatus further comprising a capacitor electrically connected to the vibration power generation element and storing a charge generated in the vibration power generation element. The measuring device according to claim 2,
A measurement unit that drives the capacitor storing electric charge as a power source and measures a physical quantity related to the environment in which the vibration power generation element is placed,
And a load changing unit that changes at least one of a load resistance and a load capacitance connected to the vibration power generation element according to the physical quantity measured by the measuring unit. The measuring device according to any one of claims 1 to 3,
The oscillator is
A first electrode formed on the negative surface of the polarization axis of the piezoelectric single crystal;
A second electrode formed on the + surface of the polarization axis of the piezoelectric single crystal body. The measuring device according to any one of claims 1 to 4,
The measuring device, wherein the vibrator is a coil spring. The measuring device according to claim 5,
In the piezoelectric single crystal body forming the coil spring, the crystal state of the piezoelectric single crystal body in a cross section of a plane parallel to the axis of the coil spring is the same in the power generation region of the coil spring. measuring device. The measuring device according to claim 6,
The measuring device, wherein the polarization axis of the piezoelectric single crystal body and the direction of the axis of the coil spring are the same. The measuring device according to any one of claims 1 to 7,
The piezoelectric single crystal body, measuring device characterized in that it is composed of LiTaO ₃ or LiNbO _3.