Vibration sensor

Abstract

To solve the problem that vibration reflected by a strained diaphragm is propagated in a direction different from a direction toward an interdigital electrode for detecting vibration and hence a vibration sensor may not be capable of detecting vibration since the conventional vibration sensor may be strained because of the deformation of the diaphragm when force operating on a projection section due to the vibration of an inspected object is applied obliquely.SOLUTION: A vibration sensor includes: an input section; an elastic wave propagation section; gel or liquid that is disposed between the elastic wave propagation section and an inspected object, propagates elastic waves from the other surface to a boundary surface, reflects elastic waves on the boundary surface, and propagates the reflected elastic waves from the boundary surface to the other surface; a stretchable section that is disposed between the elastic wave propagation section and an inspected object, is adhered to the outside of the gel or liquid and surrounds it, and stretches in a direction for changing the distance between the other surface of the elastic propagation section and the boundary surface in synchronization with the vibration of the inspected object; an output section; and an amplification section.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to vibration sensors. [Background technology]

[0002] A conventional vibration sensor includes an ultrasonic device, a non-piezoelectric substrate, and a diaphragm. The ultrasonic device includes a piezoelectric thin plate and at least two pairs of interdigital electrodes. The at least two pairs of interdigital electrodes T and R are provided on one side of the piezoelectric thin plate. The other side opposite to the one side of the piezoelectric thin plate is in contact with one side of the non-piezoelectric substrate. The non-piezoelectric substrate has one side in contact with the piezoelectric thin plate and the other side opposite to the other side. A liquid is filled between the other side of the non-piezoelectric substrate and the diaphragm. The diaphragm has a protrusion for contacting the test object.

[0003] Interdigital transducer T excites a surface acoustic wave at the interface between the non-piezoelectric substrate and the thin piezoelectric plate. The non-piezoelectric substrate converts the surface acoustic wave into a bulk wave and radiates it into the liquid. The radiated bulk wave is reflected by the diaphragm. The reflected bulk wave is converted into an electrical signal and output from interdigital transducer R via the non-piezoelectric substrate. When inspecting a solid object under test, the vibration sensor brings the protrusions on the diaphragm into contact with the object under test (see, for example, Patent Document 1).

[0004] Another conventional vibration sensor includes a sensor shell, a piezoelectric substrate, a deformation layer, a weight, and an amplifier. The sensor shell is in surface contact with the object to be inspected. The piezoelectric substrate is fixed inside the sensor shell and vibrates in synchronization with the sensor shell. The piezoelectric substrate includes, on one surface, a first terminal and a first interdigital electrode for inputting an electric signal, and a second terminal and a second interdigital electrode for outputting an electric signal.

[0005] When an electrical signal is input, the piezoelectric substrate excites ultrasonic waves. The excited ultrasonic waves are irradiated onto one surface of the deformation layer that is in contact with the piezoelectric substrate. The ultrasonic waves irradiated onto one surface of the deformation layer are reflected by the other surface opposite to the one surface of the deformation layer. The ultrasonic waves reflected by the other surface of the deformation layer are transmitted toward the one surface of the deformation layer. In other words, the deformation layer forms a transmission path for the ultrasonic waves. The ultrasonic waves reflected by the other surface of the deformation layer and transmitted toward the one surface of the deformation layer are converted into an electrical signal via a second terminal and a second interdigital electrode provided on one surface of the piezoelectric substrate, and are output. The output electrical signal is amplified by an amplifier (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Unexamined Patent Publication No. 7-19845 [Patent Document 2] Patent No. 6945765 Summary of the Invention [Problem to be solved by the invention]

[0007] The protrusion of the vibration sensor disclosed in Patent Document 1 is shaped such that a part of the other surface of the diaphragm is raised and the raised part becomes thinner toward the tip. When the thin tip is brought into contact with a solid test object, if a force acting on the tip due to the vibration of the test object is applied obliquely, the diaphragm may be deformed and distorted. As a result, the bulk wave reflected by the distorted diaphragm propagates in a direction different from the direction toward the interdigital electrode R for detecting the bulk wave, which causes a problem that the vibration sensor may not be able to detect the vibration of the test object.

[0008] In the vibration sensor disclosed in Patent Document 2, the vibration of the test object is transmitted to the piezoelectric substrate by a sensor shell that is in surface contact with the test object. A deformation layer, one side of which is bonded to the other side of the piezoelectric substrate, deforms in a direction that changes the distance between one side of the deformation layer and the other side of the deformation layer, i.e., in the thickness direction of the deformation layer, in response to the movement of the piezoelectric substrate. Therefore, the vibration sensor disclosed in Patent Document 2, which has a sensor shell that is in surface contact with the test object, can solve the problems that occurred in Patent Document 1.

[0009] However, the deformation layer of the vibration sensor disclosed in Patent Document 2 had to be made of a deformable solid (such as rubber) because it had a heavy object bonded to the other side of the deformation layer. If a deformable solid is used to configure the path through which the ultrasonic waves are transmitted, the ultrasonic waves will be attenuated. For this reason, the vibration sensor disclosed in Patent Document 2 requires a large amplification factor when amplifying the electrical signal output from the terminals and interdigital transducers, which is converted into an electrical signal via a piezoelectric substrate, and the amplifier must increase the amplification factor, resulting in a problem of large amplifiers.

[0010] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a vibration sensor that can stably detect vibrations even when the vibration of the object being tested applies a force to the vibration sensor from an oblique direction, and that can use an amplifier that is smaller than conventional ones by reducing the amplification factor. [Means for solving the problem]

[0011] The vibration sensor according to the present disclosure includes an input section that converts an electrical signal into an elastic wave and inputs it, an elastic wave propagation section that is provided on one surface of the input section and that propagates an elastic wave in a direction from one surface to another surface opposite the one surface, and a gel that is disposed between the elastic wave propagation section and the test object and has a boundary surface opposite to the surface that contacts the other surface that is directly or indirectly connected to the test object, propagates the elastic wave in a direction from the surface that contacts the other surface to the boundary surface, reflects the elastic wave at the boundary surface, and propagates the reflected elastic wave in a direction from the boundary surface to the surface that contacts the other surface. Or a vibration sensor comprising: an elastic wave propagation part that is arranged between the liquid, the elastic wave propagation part, and the object under test, and that is shaped to closely surround the outside of the gel or liquid, and that expands and contracts in a direction to change the distance between the other side of the elastic wave propagation part and the boundary surface in synchronization with the vibration of the object under test; an output part that is arranged on one side of the elastic wave propagation part, receives the elastic wave that has been reflected at the boundary surface and propagated through the gel or liquid and the elastic wave propagation part, and converts it into an output signal; and an amplifier that receives the output signal from the output part, amplifies it, and transmits the amplified output signal to the input part as an electrical signal. Effect of the Invention

[0012] The vibration sensor disclosed herein is configured to include a gel or liquid that is disposed between an elastic wave propagation section and an object under test, and has a boundary surface opposite to the surface in contact with the other surface of the elastic wave propagation section that is directly or indirectly connected to the object under test, and that propagates elastic waves in a direction from the surface in contact with the other surface of the elastic wave propagation section toward the boundary surface, reflects the elastic waves at the boundary surface, and propagates the reflected elastic waves in a direction from the boundary surface toward the surface in contact with the other surface of the elastic wave propagation section, and an expansion and contraction section that is disposed between the elastic wave propagation section and the object under test, has a shape that closely surrounds the outside of the gel or liquid, and expands and contracts in a direction that changes the distance between the other surface of the elastic wave propagation section and the boundary surface in synchronization with the vibration of the object under test.

[0013] Therefore, even if a force acts from the test object on the vibration sensor from an oblique direction, the expandable section expands and contracts in a direction that changes the distance between the elastic wave propagating section and the test object, so that when the elastic wave is reflected, it is possible to prevent the elastic wave from being reflected in a direction different from the direction toward the output section. In addition, the elastic wave is propagated through a gel or liquid, which can suppress the attenuation of the elastic wave more than a solid that is easily deformed. Therefore, even if the vibration of the test object acts on the vibration sensor from an oblique direction, it is possible to obtain a vibration sensor that can stably detect the vibration and can use an amplifier that is smaller than conventional ones. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a configuration diagram of a vibration sensor according to the first embodiment. [Diagram 2] FIG. 2 is a schematic diagram of a vibration sensor according to the first embodiment. [Diagram 3] FIG. 2 is a schematic diagram showing a case where the vibration sensor 1 is used. [Figure 4] 3 is a schematic diagram showing a state of a vibration sensor and a vibrator in the first embodiment. FIG. [Diagram 5] 4 is a measurement result showing an oscillation frequency in the first embodiment. [Figure 6] 4 is a schematic diagram showing how the FM demodulator in the first embodiment converts an oscillation frequency into a voltage. FIG. [Figure 7] 4 is a schematic diagram showing how an oscilloscope converts the time variation of a voltage converted by an FM demodulator in the first embodiment into a frequency domain. FIG. [Figure 8] FIG. 4 is a diagram showing a measurement result when a vibration exciter is vibrated using an excitation signal from a signal generator as a continuous wave in the first embodiment. [Figure 9] 13 is a schematic diagram of a vibration sensor in a modification of the first embodiment when viewed from above. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the embodiments will be described with reference to the drawings. In each drawing, the same reference numerals are used to denote common or corresponding elements, and the description is simplified or omitted. The configurations shown in the embodiments below are examples of the technical ideas of the present disclosure, and may be combined with other known technologies, or multiple technical ideas described in the present disclosure may be combined. In addition, it is also possible to omit or modify a part of the configuration without departing from the gist of the present disclosure.

[0016] Embodiment 1 1 is a configuration diagram of a vibration sensor 1 in embodiment 1. The vibration sensor 1 is a device for inspecting a vibrating object 2 to be inspected. The vibration sensor 1 includes an input section 11, an elastic wave propagation section 12, an expansion section 13, a fixed plate 14, an output section 15, an amplifier 16, and an external device connection section 17.

[0017] The input unit 11 converts an electric signal into an elastic wave and inputs it. The input unit 11 is composed of a terminal 111, an electrode 112, and a piezoelectric element 113. The terminal 111 inputs an electric signal having periodicity to the electrode 112. The electrode 112 is connected to the terminal 111 at one end and is arranged on one surface of the piezoelectric element 113. The electrode 112 is, for example, an interdigital electrode having a plurality of electrode pairs. The electrode 112 is provided on one surface of the piezoelectric element 113. The piezoelectric element 113 converts the electric signal input from the electrode 112 into an elastic wave. Here, an elastic wave is a type of vibration that propagates through a solid or liquid. The elastic wave that the piezoelectric element 113 converts from an electric signal is, for example, an ultrasonic wave. An ultrasonic wave refers to a sound wave of 20 kHz or more.

[0018] The elastic wave propagation section 12 propagates the elastic waves converted by the piezoelectric element 113. The elastic wave propagation section 12 is made of, for example, a resin material having elasticity. The elastic wave propagation section 12 is not limited to a resin material as long as it is made of a material capable of transmitting elastic waves. The elastic wave propagation section 12 includes a division section 121 that divides the elastic wave propagation section 12. The division section 121 is provided so that the elastic wave oscillated from the input section 11 and the elastic wave propagating toward the output section 15 described later do not interact with each other.

[0019] The stretchable portion 13 is disposed between the elastic wave propagation portion 12 and the object under test 2. The stretchable portion 13 is in contact with the elastic wave propagation portion 12. The stretchable portion 13 is in direct or indirect contact with the object under test 2. In this embodiment, the fixed plate 14 described later comes into surface contact with the object under test 2, so the stretchable portion 13 is indirectly in contact with the object under test 2. The stretchable portion 13 expands and contracts in synchronization with the vibration of the object under test 2. The direction in which the stretchable portion 13 expands and contracts is the direction in which the distance between the elastic wave propagation portion 12 and the object under test 2 is changed. The stretchable portion 13 is annular. The stretchable portion 13 is, for example, an O-ring. The inside of the ring shape of the stretchable portion 13 is filled with gel or liquid.

[0020] The gel or liquid may be any material that is easily deformed and does not attenuate the elastic waves propagated from the elastic wave propagation portion 12. The gel is, for example, a jelly-like material. The liquid is, for example, water. The gel or liquid is covered, for example, with an O-ring on the side, the elastic wave propagation portion 12 on either the top or bottom, and a fixing plate 14 (described later) on the other of the top or bottom, and is sealed in so as not to leak.

[0021] The fixed plate 14 is provided between the stretchable portion 13 and the object to be inspected 2. The fixed plate 14 comes into surface contact with the object to be inspected 2 and transmits vibrations of the object to be inspected 2 to the stretchable portion 13. The fixed plate 14 is, for example, a metal plate. The fixed plate 14 is positioned so that no gap is created between the stretchable portion 13 and the gel or liquid filled inside the ring of the stretchable portion 13, so as to keep it from leaking out.

[0022] The output unit 15 includes a piezoelectric element 151, an electrode 152, and a terminal 153. The piezoelectric element 151 receives the elastic waves that propagate through the gel or liquid filled inside the annular shape of the elastic wave propagation unit 12 and the expandable unit 13, are reflected at the boundary between the fixed plate and the gel or liquid, and propagate through the gel or liquid filled inside the annular shape of the expandable unit 13 and the elastic wave propagation unit 12. The piezoelectric element 151 converts the received elastic waves into an output signal. The electrode 152 transmits the output signal converted by the piezoelectric element 151 to the terminal 153. The terminal 153 transmits the output signal to the amplifier 16.

[0023] The amplifier 16 receives the output signal converted by the output unit 15. The amplifier 16 amplifies the received output signal and transmits the amplified output signal to the input unit 11 as an electrical signal to be converted into an elastic wave by the input unit 11. The amplifier 16 transmits a portion of the electrical signal to the terminal 111 and transmits the remaining electrical signal to the external device connection unit 17.

[0024] The external device connection unit 17 outputs the electrical signal received from the amplifier 16 to an external device such as an FM demodulator (not shown in FIG. 1).

[0025] Next, the operation of the vibration sensor 1 will be described. An electric signal is applied to the electrode 112 from the terminal 111. When the electric signal is applied to the electrode 112, the piezoelectric element 113 converts it into an elastic wave. FIG. 2 is a schematic diagram showing the propagation path of the elastic wave of the vibration sensor 1. The converted elastic wave propagates through the elastic wave propagating section 12 and the gel or liquid, and is reflected at the boundary between the gel or liquid and the fixed plate 14. The reflected elastic wave propagates through the gel or liquid and the elastic wave propagating section 12 to reach the piezoelectric element 151. The elastic wave that reaches the piezoelectric element 151 is output as an output signal by the electrode 152. The output signal output by the electrode 152 is input as an output signal to the amplifier 16 via the terminal 153.

[0026] As described above, the amplifier 16 amplifies the output signal. A part of the amplified output signal is sent to the terminal 111. The remaining output signal is sent to the external device connection unit 17. In this manner, an oscillation loop is formed by the terminal 111, the electrode 112, the piezoelectric element 113, the elastic wave propagation unit 12, the gel or liquid, the elastic wave propagation unit 12, the piezoelectric element 151, the electrode 152, the terminal 153, and the amplifier 16.

[0027] Here, an oscillation loop refers to a path along which an elastic wave or an electrical signal propagates. The oscillation loop is formed when the amplification factor of amplifier 16 is sufficiently large. The length of the path of the oscillation loop is called the oscillation loop length. Also, the frequency when an oscillation loop is formed is called the oscillation frequency. When the oscillation loop length is shorter, the oscillation frequency is higher. Also, when the oscillation loop length is longer, the oscillation frequency is lower.

[0028] Next, an experiment using the vibration sensor 1 of the present invention will be described. Fig. 3 is a schematic diagram showing a case where the vibration sensor 1 is used. The vibration sensor 1 is vibrated by a vibrator 3 that comes into contact with the surface of a fixed plate 14. Here, the vibrator 3 corresponds to a vibrating inspection object 2. The vibrator 3 is connected to a signal generator 4. The vibration that the vibrator 3 imparts to the vibration sensor 1 is controlled using an excitation signal that the signal generator 4 outputs to the vibrator 3.

[0029] The input unit 11 and the amplifier 16 are connected to an FM demodulator 5 via an external device connection unit 17. The FM demodulator 5 is connected to an oscilloscope 6. The oscilloscope 6 is connected to a PC 7.

[0030] FIG. 4 is a schematic diagram showing the state of the vibration sensor 1 and the vibrator 3. In FIG. 4, external devices such as the FM demodulator 5 shown in FIG. 3 are not shown. FIG. 4(a) is a schematic diagram showing the state of the vibration sensor 1 and the vibrator 3 in a steady state. Here, the steady state refers to a state in which the vibration sensor 1 is simply installed on the vibrator 3. In addition, the oscillation frequency in the steady state is f0. FIG. 4(b) is a schematic diagram showing the state of the vibration sensor 1 and the vibrator 3 when a force acts from the vibrator 3 in a direction pushing the vibration sensor 1 up. FIG. 4(c) is a schematic diagram showing the state of the vibration sensor 1 and the vibrator 3 when a force acts from the vibrator 3 in a direction pushing the vibration sensor 1 down.

[0031] Fig. 5 shows the measurement results showing the oscillation frequency. Fig. 5(a) is a schematic diagram showing the oscillation frequency in a steady state. Fig. 5(b) is a schematic diagram showing the oscillation frequency when a force acts from the vibrator 3 in a direction pushing the vibration sensor 1 up. Fig. 5(c) is a schematic diagram showing the oscillation frequency when a force acts from the vibrator 3 in a direction pushing the vibration sensor 1 down.

[0032] When the vibration sensor 1 and the vibrator 3 are in a steady state as shown in Fig. 4(a), the oscillation frequency is f0 as shown in Fig. 5(a). In other words, when no force is exerted to push the vibration sensor 1 up or down, the vibration sensor 1 exhibits a specific value as the oscillation frequency.

[0033] As shown in FIG. 4(b), when a force is applied from the vibrator 3 in a direction pushing up the vibration sensor 1, the expandable portion 13 is elastic and therefore deforms. Specifically, the expandable portion 13 deforms in a direction in which it is crushed. Note that FIG. 4(b) shows the expandable portion 13 in a state in which it is crushed to the maximum extent. When the expandable portion 13 deforms in a direction in which it is crushed, the propagation path of the elastic wave propagating through the gel or liquid becomes shorter, and the oscillation loop length becomes shorter. When the oscillation loop length becomes shorter, the oscillation frequency becomes higher, and as shown in FIG. 5(b), the oscillation frequency changes from f0 to f u f u is the oscillation frequency when the expandable portion 13 is maximally compressed. In other words, when the oscillation loop length is shortened, the vibration sensor 1 exhibits an oscillation frequency of a specific value that is changed from the steady state.

[0034] As shown in FIG. 4(c), when a force is applied from the vibrator 3 to the vibration sensor 1 in a direction pushing it down, the expandable portion 13 is elastic and therefore deforms. Specifically, the expandable portion 13 deforms in the expanding direction. Note that FIG. 4(c) shows the expandable portion 13 in its maximally expanded state. When the expandable portion 13 deforms in the expanding direction, the propagation path of the elastic wave propagating through the gel or liquid becomes longer, and the oscillation loop length becomes longer. When the oscillation loop length becomes longer, the oscillation frequency becomes lower, and as shown in FIG. 5(c), the oscillation frequency changes from f0 to f d f d is the oscillation frequency when the expandable portion 13 is maximally expanded. In other words, when the oscillation loop length becomes longer, the vibration sensor 1 exhibits an oscillation frequency of a specific value that is changed from the steady state.

[0035] As shown in FIG. 4, when the vibrator 3 pushes up and down the vibration sensor 1, the length of the oscillation loop changes, and as shown in FIG. 5, the oscillation frequency of the elastic wave changes.

[0036] FIG. 6 is a schematic diagram showing how the FM demodulator 5 converts an oscillation frequency into a voltage. The FM demodulator 5 receives a part of the electric signal from the amplifier 16. The FM demodulator 5 converts the electric signal, which is the converted oscillation frequency, into a voltage. The vibration of the vibrator 3 changes periodically over time. For this reason, the oscillation frequency varies from f0 to f100, with a steady-state frequency f0 as the center. u From f d The oscillation frequency changes periodically within a range. The period of this change in oscillation frequency is hereinafter referred to as period T. Even if the change in oscillation frequency is converted into a voltage change, the period T does not change. FM demodulator 5 performs FM demodulation on the output signal sent from amplifier 16, converts the oscillation frequency into a voltage, and sends it to oscilloscope 6.

[0037] FIG. 7 is a schematic diagram showing how the oscilloscope 6 converts the time change of the voltage converted by the FM demodulator 5 into the frequency domain. The oscilloscope 6 has an FFT function. The time change of the voltage converted by the FM demodulator 5 is converted into the frequency domain by the FFT function of the oscilloscope 6. This process results in a diagram showing the vibration frequency at f=1 / T. f is the vibration frequency indicating the vibration of the vibrator 3 measured by the vibration sensor 1. The oscilloscope 6 converts the time change of the voltage converted by the FM demodulator 5 into the frequency domain by the FFT function and transmits it to the PC 7. The PC 7 stores the information transmitted from the oscilloscope 6.

[0038] Fig. 8 is a diagram showing the measurement results when the vibration exciter 3 is vibrated using the excitation signal from the signal generator 4 as a continuous wave. Fig. 8 shows the measurement results when the vibration exciter 3 in Fig. 3 is vibrated. The signal generator 4 vibrates the vibration exciter 3 using the excitation signal as a sine wave of 20 Hz, 30 Hz, 50 Hz, and 70 Hz. As shown in Fig. 8, the vibration sensor 1 has a characteristic that shows peaks at frequencies corresponding to the excitation signal.

[0039] As described above, the vibration sensor 1 in embodiment 1 comprises an elastic wave propagation section 12, a gel or liquid that is arranged between the elastic wave propagation section 12 and the object under test 2, and whose boundary surface opposite the surface in contact with the other surface of the elastic wave propagation section 12 is directly or indirectly connected to the object under test 2, and that propagates elastic waves in a direction from the surface in contact with the other surface of the elastic wave propagation section 12 toward the boundary surface, reflects the elastic waves at the boundary surface, and propagates the reflected elastic waves in a direction from the boundary surface toward the surface in contact with the other surface of the elastic wave propagation section 12, and an expansion / contraction section 13 that is arranged between the elastic wave propagation section 12 and the object under test 2, has a shape that closely surrounds the outside of the gel or liquid, and expands and contracts in a direction that changes the distance between the other surface of the elastic wave propagation section 12 and the boundary surface in synchronization with the vibration of the object under test 2.

[0040] Therefore, even if a force acts from the object under test 2 on the vibration sensor 1 in an oblique direction, the expandable section 13 expands and contracts in a direction that changes the distance between the elastic wave propagation section 12 and the object under test 2, so that it is possible to prevent the elastic wave from being reflected in a direction different from the direction toward the output section 15. Therefore, the vibration sensor 1 can detect vibration even if the vibration of the object under test 2 acts as a force on the vibration sensor 1 in an oblique direction.

[0041] In the present disclosure, the piezoelectric element 113 is used to convert an electric signal into an elastic wave, but a magnetostrictive element may be used instead of the piezoelectric element 113 as long as it can convert an electric signal into an elastic wave. The same applies to the piezoelectric element 151.

[0042] In the present disclosure, the elastic wave converted from the electric signal by the piezoelectric element 113 is not limited to an ultrasonic wave, but may be a sound wave. In this case, the amplifier 16 needs to be appropriately modified.

[0043] Moreover, a weight may be placed on the vibration sensor 1 of the present disclosure. By placing a weight on the vibration sensor 1, the sensitivity of the vibration sensor 1 can be increased at frequencies of, for example, 20 Hz or less.

[0044] Variations. Fig. 9 is a schematic diagram of the vibration sensor 1 as viewed from above. When the inside of the expandable part 13 has a portion not covered by the elastic wave propagation part 12 as shown in Fig. 9, the vibration sensor 1 may be configured to add gel or liquid required for detecting the vibration of the test object 2 from the portion not covered by the elastic wave propagation part 12. The gel or liquid may be added from a container such as a cup, or may be added through a tube or the like. In this case, since it is not necessary to prevent the gel or liquid from leaking from the expandable part 13 and the fixing plate 14, the fixing plate 14 may not be required.

[0045] According to the configuration of the modified example, even if the gel or liquid leaks out, it is possible to add gel or liquid. Also, since the fixing plate 14 is not required, the weight of the vibration sensor can be reduced.

[0046] Various aspects of the present disclosure are summarized below as appendices.

[0047] (Appendix 1) an input unit that converts an electrical signal into an elastic wave and inputs the elastic wave; The input unit is provided on one surface, and an elastic wave propagating unit propagates the elastic wave in a direction from the one surface to the other surface opposite to the one surface; a gel or liquid that is disposed between the elastic wave propagation unit and the object to be inspected, the boundary surface opposite to the surface in contact with the other surface being directly or indirectly connected to the object to be inspected, the gel or liquid propagating the elastic wave in a direction from the surface in contact with the other surface toward the boundary surface, reflecting the elastic wave at the boundary surface, and propagating the reflected elastic wave in a direction from the boundary surface toward the surface in contact with the other surface; an elastic portion that is disposed between the elastic wave propagation portion and the test object, has a shape that closely surrounds the outside of the gel or the liquid, and expands and contracts in a direction that changes the distance between the other surface of the elastic wave propagation portion and the boundary surface in synchronization with the vibration of the test object; an output section that is disposed on the one surface of the elastic wave propagation section, receives the elastic wave that is reflected at the boundary surface and propagates through the gel or the liquid and the elastic wave propagation section, and converts the elastic wave into an output signal; an amplifier that receives the output signal from the output section, amplifies the output signal, and transmits the amplified output signal to the input section as the electrical signal; A vibration sensor comprising: (Appendix 2) The elastic part is an O-ring. 2. The vibration sensor of claim 1. (Appendix 3) The test object further includes a fixing plate fixed to the stretchable portion, the fixing plate being in surface contact with the test object. 3. The vibration sensor according to claim 1 or 2. (Appendix 4) The gel or liquid is sealed so as not to leak, with the side surface covered by the stretchable portion, either the upper surface or the lower surface covered by the elastic wave propagating portion, and the other of the upper surface or the lower surface covered by the fixed plate. 4. The vibration sensor according to claim 1, [Explanation of symbols]

[0048] 1 vibration sensor, 2 test object, 3 vibrator, 4 signal generator, 5 FM demodulator, 6 oscilloscope, 7 PC, 11 input section, 12 elastic wave propagation section, 13 expansion section, 14 fixed plate, 15 output section, 16 amplifier, 17 external device connection section, 111 terminal, 112 electrode, 113 piezoelectric element, 121 division section, 151 piezoelectric element, 152 electrode, 153 terminal

Claims

1. an input unit that converts an electrical signal into an elastic wave and inputs the elastic wave; The input unit is provided on one surface, and an elastic wave propagating unit propagates the elastic wave in a direction from the one surface to the other surface opposite to the one surface; a gel or liquid that is disposed between the elastic wave propagating unit and the object to be inspected, the boundary surface opposite to the surface in contact with the other surface being directly or indirectly connected to the object to be inspected, the gel or liquid propagating the elastic wave in a direction from the surface in contact with the other surface toward the boundary surface, reflecting the elastic wave at the boundary surface, and propagating the reflected elastic wave in a direction from the boundary surface toward the surface in contact with the other surface; an elastic portion that is disposed between the elastic wave propagation portion and the test object, has a shape that closely surrounds the outside of the gel or the liquid, and expands and contracts in a direction that changes the distance between the other surface of the elastic wave propagation portion and the boundary surface in synchronization with the vibration of the test object; an output section that is disposed on the one surface of the elastic wave propagation section, receives the elastic wave that is reflected at the boundary surface and propagates through the gel or the liquid and the elastic wave propagation section, and converts the elastic wave into an output signal; an amplifier that receives the output signal from the output section, amplifies the output signal, and transmits the amplified output signal to the input section as the electrical signal; A vibration sensor comprising:

2. The elastic part is an O-ring. The vibration sensor according to claim 1 .

3. The test object further includes a fixing plate that comes into surface contact with the test object. The vibration sensor according to claim 1 or 2.

4. The gel or liquid is sealed so as not to leak, with the side surface covered by the stretchable portion, either the upper surface or the lower surface covered by the elastic wave propagating portion, and the other of the upper surface or the lower surface covered by the fixed plate. The vibration sensor according to claim 3 .

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