JP6751898B2 - Laminates, ultrasonic transmitters and receivers and ultrasonic flowmeters - Google Patents

Description

The present disclosure relates to a laminate including a piezoelectric body and an acoustic matching layer, an ultrasonic transmitter / receiver, and an ultrasonic flow meter.

In recent years, an ultrasonic flow meter that measures the time for ultrasonic waves to propagate in a propagation path, measures the moving speed of a fluid, and measures the flow rate is being used for gas meters and the like. An ultrasonic flow meter generally includes a piezoelectric vibrator, and detects ultrasonic waves by the piezoelectric vibrator. When the fluid is a gas, the difference in acoustic impedance between the gas and the piezoelectric vibrator is large, so that the ultrasonic waves propagating in the gas are easily reflected at the interface with the piezoelectric vibrator. Therefore, in order to efficiently inject ultrasonic waves into the piezoelectric vibrator, an acoustic matching layer may be provided at the interface between the piezoelectric vibrator and the gas.

Patent Document 1 discloses a material that can be used as an acoustic matching layer. Patent Document 2 discloses an ultrasonic wave transmitter / receiver having two acoustic matching layers.

Japanese Patent No. 2559144 Japanese Patent No. 3552054

For conventional ultrasonic transmitters and receivers, high sensitivity cannot be obtained because the acoustic impedance matching between the acoustic matching layer and the ultrasonic radiation medium is not sufficient. The present disclosure provides a laminate, an ultrasonic transmitter / receiver, and an ultrasonic flow meter including an acoustic matching layer having appropriate acoustic characteristics.

The laminate of the present disclosure is a first acoustic matching layer that is arranged in contact with the piezoelectric body and the piezoelectric body directly or via another layer, and is a plastic closed cell foam containing a plurality of closed pores. It includes a body, and includes a first acoustic matching layer having an average pore diameter of 1 μm or more and 100 μm or less and a density of 10 kg / m ³ or more and 100 kg / m ³ or less.

According to the laminate, the ultrasonic wave transmitter and the ultrasonic flow meter of the present disclosure, a highly sensitive ultrasonic wave transmitter and the ultrasonic flow meter can be realized because the acoustic matching layer having appropriate acoustic characteristics is included.

FIG. 1 is a block diagram showing an ultrasonic flow meter of the present disclosure. FIG. 2 is a schematic end view showing a first embodiment of the laminated body and the ultrasonic wave transmitter / receiver of the present disclosure. FIG. 3A is a process sectional view showing a method of manufacturing the ultrasonic wave transmitter / receiver according to the first embodiment. FIG. 3B is a process sectional view showing a method of manufacturing the ultrasonic wave transmitter / receiver according to the first embodiment. FIG. 4 is a schematic end view showing a second embodiment of the laminated body and ultrasonic wave transmission / reception of the present disclosure. FIG. 5 is an electron micrograph of the surface of the plastic closed cell foam. The left side of FIG. 6 is an electron micrograph of the surface of the plastic closed-cell foam, and the right side is a part of the soybean to be written.

The outline of the laminate, the ultrasonic wave transmitter / receiver, and the ultrasonic flow meter of the present disclosure is as follows.

[Item 1]
Piezoelectric and
A first acoustic matching layer that is arranged in contact with the piezoelectric body directly or via another layer.
Contains plastic closed-cell foam containing multiple closed pores,
The average pore diameter of the closed pore is 1 μm or more and 100 μm or less.
A first acoustic matching layer having a density of 10 kg / m ³ or more and 100 kg / m ³ or less is provided.
Laminated body.

[Item 2]
The laminate according to item 1, wherein the acoustic impedance of the first acoustic matching layer is in the range of 5 × 10 ³ kg / s ・ m ² or more and 350 × 10 ³ kg / s ・ m ² or less.

[Item 3]
The laminate according to item 1 or 2, wherein the average distance between adjacent closed pores is 50 nm or more and 1 μm or less.

[Item 4]
The laminate according to any one of items 1 to 3, wherein the sound velocity of the first acoustic matching layer is 500 m / s or more.

[Item 5]
The laminate according to any one of items 1 to 4, wherein the plastic closed-cell foam is a polymethacrylicimide foam.

[Item 6]
The laminate according to any one of items 1 to 5, wherein the thickness of the first acoustic matching layer is approximately 1/4 of the wavelength λ of the sound wave propagating in the first acoustic matching layer.

[Item 7]
A second acoustic matching layer located between the piezoelectric body and the first acoustic matching layer is further provided.
The laminate according to any one of items 1 to 6, wherein the second acoustic matching layer is 50 kg / m ³ or more and 1500 kg / m ³ or less, and has a density higher than that of the first acoustic matching layer.

[Item 8]
The laminate according to item 7, wherein the relationship between the acoustic impedance Za of the first acoustic matching layer and the acoustic impedance Zb of the second acoustic matching layer is Za <Zb.

[Item 9]
Item 7. The laminate according to item 7 or 8, wherein the thickness of the second acoustic matching layer is approximately 1/4 of the wavelength λ of the sound wave propagating in the second acoustic matching layer.

[Item 10]
The laminate according to any one of items 1 to 6, wherein the first acoustic matching layer is directly bonded to the piezoelectric body.

[Item 11]
Item 7. The laminate according to item 7, wherein the second acoustic matching layer is arranged in direct contact with the first acoustic matching layer and the piezoelectric body.

[Item 12]
Item 7. The laminate according to item 7, further comprising a structural support layer having a density of 1000 kg / m ³ or more between the first acoustic matching layer and the second acoustic matching layer.

[Item 13]
The laminate according to item 12, wherein the thickness of the structural support layer is less than 1/8 of the wavelength λ of the sound wave propagating in the structural support layer.

[Item 14]
An ultrasonic wave transmitter / receiver comprising the laminate according to any one of items 1 to 13.

[Item 15]
With the laminate according to any one of items 1 to 6.
A main body having a convex shape having a top plate and a case having a lid plate covering the convex opening are further provided.
The piezoelectric body is located in the convex shape and is fixed to the inner surface of the top plate.
An ultrasonic wave transmitter / receiver in which the first acoustic matching layer is fixed to the outer surface of the top plate.

[Item 16]
With the laminate according to any one of items 7 to 9.
A main body having a convex shape having a top plate and a case having a lid plate covering the convex opening are further provided.
The piezoelectric body is located in the convex shape and is fixed to the inner surface of the top plate.
The second acoustic matching layer is fixed to the outer surface of the top plate,
The first acoustic matching layer is an ultrasonic wave transmitter / receiver in contact with the second acoustic matching layer.

[Item 17]
The ultrasonic wave transmitter / receiver according to item 15 or 16, wherein the case is made of a metal material.

[Item 18]
The flow path through which the fluid to be measured flows and
A pair of ultrasonic wave transmitters / receivers arranged in the flow path for transmitting / receiving ultrasonic signals, the ultrasonic wave transmitter / receiver according to any one of items 14 to 16.
A time measuring unit that measures the ultrasonic wave propagation time between the pair of ultrasonic wave transmitters and receivers,
A calculation unit that calculates the flow rate of the flow path based on the signal from the time measurement unit, and
Ultrasonic flowmeter equipped with.

Hereinafter, embodiments of the laminate, ultrasonic wave transmitter / receiver, and ultrasonic flow meter of the present disclosure will be described in detail with reference to the drawings.

(First Embodiment)
Hereinafter, an example of the ultrasonic wave transmitter / receiver and the ultrasonic flow meter of the present embodiment will be described in detail.

[Configuration of ultrasonic flowmeter]
FIG. 1 shows a schematic configuration of the ultrasonic flowmeter of the present disclosure. As shown in FIG. 1, the ultrasonic flowmeter includes a flow path through which the fluid to be measured flows, a pair of ultrasonic wave transmitters and receivers 11 and 12 arranged in the flow path, a time measurement unit 31, and a calculation unit 32. , Equipped with. A fluid flows in the direction shown in the figure at a flow velocity V in the flow path defined by the pipe wall 13. The flow rate of the fluid flowing through this flow path is measured. A pair of ultrasonic wave transmitters / receivers (first and second ultrasonic wave transmitters / receivers) 11 and 12 are installed facing each other on the tube wall 13. The ultrasonic transmitters and receivers 11 and 12 include a piezoelectric vibrator such as a piezoelectric ceramic which is an electric energy / mechanical energy conversion element, and exhibit resonance characteristics similarly to a piezoelectric buzzer or a piezoelectric oscillator. First, the ultrasonic wave transmitter / receiver 11 is used as an ultrasonic wave transmitter, and the ultrasonic wave transmitter / receiver 12 is used as an ultrasonic wave receiver. When the time measuring unit 31 applies an AC voltage having a frequency near the resonance frequency to the piezoelectric vibrator of the ultrasonic wave transmitter / receiver 11, the ultrasonic wave transmitter / receiver 11 moves into the propagation path shown by L1 in the figure in the fluid in the tube. Emit ultrasonic waves along. The ultrasonic wave transmitter / receiver 12 receives the ultrasonic waves propagating in the fluid and converts them into a voltage. Subsequently, on the contrary, the ultrasonic wave transmitter / receiver 12 is used as the ultrasonic wave transmitter, and the ultrasonic wave transmitter / receiver 11 is used as the ultrasonic wave receiver. When the time measuring unit 31 applies an AC voltage having a frequency near the resonance frequency of the ultrasonic transmitter / receiver 12 to the piezoelectric vibrator, the ultrasonic transmitter / receiver 12 propagates in the fluid in the tube as shown by L2 in the figure. Ultrasonic waves are emitted along the path, and the ultrasonic wave transmitter / receiver 11 receives the propagating ultrasonic waves and converts them into a voltage. As described above, the ultrasonic wave transmitters and receivers 11 and 12 serve as a receiver and a transmitter.

In such an ultrasonic flow meter, when an AC voltage is continuously applied, ultrasonic waves are continuously radiated from the ultrasonic transmitter / receiver, making it difficult to measure the propagation time. Therefore, a pulse signal is usually used as a carrier wave. The burst voltage signal is used as the drive voltage. When the time measuring unit 31 applies a burst voltage signal for driving to the ultrasonic transmitter / receiver 11 and emits an ultrasonic burst signal from the ultrasonic transmitter / receiver 11, the ultrasonic burst signal has a propagation path L1 having a distance of L. And reaches the ultrasonic transmitter / receiver 12 after t hours. The ultrasonic wave transmitter / receiver 12 can convert only the transmitted ultrasonic burst signal into an electric burst signal with a high S / N ratio. The time measuring unit 31 electrically amplifies the electric burst signal and applies it to the ultrasonic wave transmitter / receiver 11 again to radiate the ultrasonic burst signal. This device is called a sing-around device, and the time required for an ultrasonic pulse to be radiated from an ultrasonic wave transmitter / receiver 11 and propagate through a propagation path to reach the ultrasonic wave transmitter / receiver 12 is called a sing-around period. The inverse number is called the singing around frequency. In FIG. 1, the flow velocity of the fluid flowing through the tube is V, the velocity of ultrasonic waves in the fluid is C, and the angle between the flow direction of the fluid and the propagation direction of the ultrasonic pulse is θ. When the ultrasonic transmitter / receiver 11 is used as a transmitter and the ultrasonic transmitter / receiver 12 is used as a receiver, the ultrasonic pulse emitted from the ultrasonic transmitter / receiver 11 reaches the ultrasonic transmitter / receiver 12. Assuming that the sing-around period, which is the ultrasonic propagation time, is t1 and the sing-around frequency is f1, the following equation (1) is established.
f1 = 1 / t1 = (C + Vcosθ) / L ... (1)

On the contrary, when the ultrasonic wave transmitter / receiver 12 is used as a transmitter and the ultrasonic wave transmitter / receiver 11 is used as a receiver, the sing-around period, which is the ultrasonic wave propagation time, is t2, and the sing-around frequency is f2. Then, the relationship of the following equation (2) is established.
f2 = 1 / t2 = (C-Vcosθ) / L ... (2)

Therefore, the frequency difference Δf between the two singing around frequencies is given by the following equation (3), and the flow velocity V of the fluid can be obtained from the distance L of the ultrasonic propagation path and the frequency difference Δf.
Δf = f1-f2 = 2Vcosθ / L ... (3)

That is, the flow velocity V of the fluid can be obtained from the distance L of the ultrasonic propagation path and the frequency difference Δf, and the flow velocity can be investigated from the flow velocity V.

The ultrasonic flowmeter includes a time measuring unit 31 and a calculation unit 32. The time measuring unit 31 includes a drive circuit that generates a burst voltage signal that drives the ultrasonic transmitters and receivers 11 and 12, and a receiving circuit that electrically amplifies the electric burst signal converted by the ultrasonic transmitters and receivers 11 and 12. Including, the sing-around periods t1 and t2, which are ultrasonic propagation times, are obtained by the procedure described above. The calculation unit 32 calculates the flow velocity and the flow rate of the fluid from the relationship between the obtained single-around periods t1 and t2 and the equation (3). The time measurement unit 31 and the calculation unit 32 are composed of, for example, a microcomputer, a memory, and a program stored in the memory and defining a procedure for performing the above-mentioned calculation. A part of the time measurement unit 31 and the calculation unit 32 may be configured by an electronic circuit or the like.

[Ultrasonic wave transmitter / receiver]
FIG. 2 is a cross-sectional view showing an example of an ultrasonic wave transmitter / receiver 11 used in the ultrasonic flow meter of the present disclosure. The ultrasonic wave transmitter / receiver 12 also has the same structure as the ultrasonic wave transmitter / receiver 11. The ultrasonic wave transmitter / receiver 11 includes a laminated body 28 and a case 29.

The laminate 28 includes a piezoelectric body 21 and a first acoustic matching layer 26. The first acoustic matching layer 26 is in contact with the piezoelectric body 21 directly or through another layer. The piezoelectric body 21 is made of piezoelectric ceramics or a single crystal, and is polarized in the thickness direction. Further, the piezoelectric body 21 has electrodes on the upper and lower surfaces in the thickness direction, and ultrasonic vibration is generated by applying a voltage to the electrodes.

The case 29 includes a main body 22 having a convex shape having a top plate 22u and a lid plate 23. The main body 22 and the lid plate 23 are made of a conductive material, for example, a material such as a metal that can ensure reliability with respect to an external fluid. The piezoelectric body 21 is located in the convex shape of the main body 22 and is attached to the inner surface 22a of the top plate 22u. The opening located at the bottom of the convex shape of the main body 22 is covered with the lid plate 23, and the inner space of the main body 22 is sealed. Therefore, the case 29 has a gas shielding property, and even if the ultrasonic wave transmitter / receiver 11 is exposed to various fluids, the internal piezoelectric body 21 does not deteriorate and has high reliability. Drive terminals 24a and 24b are attached to the lid plate 23. Of the two drive terminals 24a and 24b, one drive terminal 24a is electrically connected to the upper surface electrode of the piezoelectric body 21 via the lid plate 23 and the main body 22. The other drive terminal 24b is electrically insulated from the lid plate 23 by the insulating material 25, and is electrically connected to the lower surface electrode of the piezoelectric body 21 in the main body 22.

The first acoustic matching layer 26 sends ultrasonic waves to the fluid or receives ultrasonic waves propagating in the fluid. The first acoustic matching layer 26 efficiently outputs the mechanical vibration of the piezoelectric body 21 excited by the driving AC voltage to an external medium as ultrasonic waves, and efficiently outputs the reached ultrasonic waves as vibrations to the piezoelectric body 21. Tell. As a result, the voltage is efficiently converted into ultrasonic waves, and the ultrasonic waves are efficiently converted into voltage. The first acoustic matching layer 26 is attached to the outer surface 22b of the top plate 22u of the main body 22.

Assuming that the acoustic impedances of the piezoelectric body 21 and the fluid are Z1 and Z2, respectively, and the ideal acoustic impedance required for the first acoustic matching layer 26 is Z3, the acoustic impedance Z3 is obtained by Z3 = √ (Z1 and Z2). Be done. The acoustic impedance of the piezoelectric body 21 is about 30 × 10 ⁶ kg / m ² · s, and the acoustic impedance of hydrogen is about 110 kg / m ² · s. By substituting the above-mentioned numerical value into this equation, Z3 = 57 × 10 ³ (kg / m ² · s) can be obtained. The acoustic impedance is defined by the following equation (4).
Acoustic impedance = (density) x (sound velocity) ... (4)

In the present embodiment, the first acoustic matching layer 26 has a density of 10 kg / m ³ or more and 100 kg / m ³ or less. The speed of sound propagating in the first acoustic matching layer 26 is 500 m / s or more, and preferably 500 m / s or more and 3500 m / s or less. By appropriately selecting the density and sound velocity in this range, the acoustic impedance of the first acoustic matching layer 26 is within the range of 5 × 10 ³ kg / s ・ m ² or more and 350 × 10 ³ kg / s ・ m ² or less. Can take a value.

Examples of materials suitable for the first acoustic matching layer 26 having such physical properties include hard micropores. For example, the first acoustic matching layer 26 is a hard plastic closed cell foam. Examples of hard plastic closed cell foams include polymethacrylicimide foams. The polymethacrylicimide foam is, for example, sold by Roehm GmbH & Co KG under the trade name ROHACELL (R), and can be purchased from Daicel Evonik Industries, Ltd. in Japan. It is published in the catalog that the density of ROHACELL is in the range of 10 kg / m ³ or more and 100 kg / m ³ or less.

FIGS. 5 and 6 show an example of a SEM (scanning electron microscope) photograph of the surface of a plastic closed cell foam. In this photo, the holes, that is, closed pores, appear relatively white, and the partition walls (plastic) appear relatively black between the closed cells. is there. Therefore, the distance between adjacent closed pores corresponds to the thinnest part of the partition wall.

It is desirable that the average pore diameter of the closed pores in the polymethacrylicimide foam is 1 μm or more and 100 μm or less. Here, the pore diameter is defined by the diameter of each inscribed circle of the closed pores in the field of view observed by an electron microscope (see FIG. 5). Further, the average pore diameter is defined by the average value of the pore diameters of the closed pores in the field of view observed by an electron microscope including at least 100 closed pores.

Further, the average distance between adjacent pores is measured by measuring the distance between adjacent neighbors in an observation field of view with an electron microscope including at least 10 closed pores and averaging them (see FIG. 6). It is desirable that the distance between adjacent closed pores is uniformly distributed within the range of 50 nm or more and 1 μm or less.

According to the computational simulation and the experimental results described below, the average pore diameter of the closed pores and the distance between the adjacent closed pores affect the acoustic propagation characteristics. It is desirable that these values are in the above range in order to achieve good acoustic propagation characteristics. The distance between adjacent closed pores corresponds to the average thickness of the closed cell bulkhead.

Further, since the polymethacrylicimide foam has a rigid and strong molecular structure, it is superior in mechanical strength and workability as compared with other hard foams.

It is desirable that the first acoustic matching layer 26 has a thickness of approximately 1/4 of the wavelength λ of the sound wave propagating in the first acoustic matching layer 26. As a result, the sound waves reflected between the two main surfaces of the first acoustic matching layer 26 and incident on the piezoelectric body 21 are weakened by being out of phase by 1/2. Therefore, the intensity of the sound wave incident on the piezoelectric body 21 delayed by unnecessary reflection can be reduced, and the influence of the reflected wave can be suppressed.

In the present embodiment, the top plate 22u of the case 29 functions as a structural support layer that supports the laminated body 28. The top plate 22u preferably has a density of 1000 kg / m ³ or more. Further, the thickness of the top plate 22u is 1/8 or less of the wavelength λ of the sound wave propagating in the top plate 22u. When the top plate 22u satisfies this condition, the reflection of sound waves on the top plate 22u is suppressed.

The ultrasonic wave transmitter / receiver of the present embodiment can be manufactured by, for example, the following procedure. First, as shown in FIG. 3A, the case 29, the piezoelectric body 21, and the first acoustic matching layer 26 are prepared. The first acoustic matching layer 26 is processed in advance so as to have a desired thickness. The piezoelectric body 21 is attached to the inner surface 22a of the top plate 22u in the main body 22 of the case 29 with an adhesive or the like. Further, the first acoustic matching layer 26 is attached to the outer surface 22b of the top plate 22u. After that, as shown in FIG. 3B, the piezoelectric body 21 and the drive terminal 24b or the like are connected. Finally, the ultrasonic wave transmitter / receiver is completed by closing the opening of the main body 22 with the lid plate 23 using an adhesive or the like.

According to the laminate of the present embodiment, the first acoustic matching layer 26 has a density of 10 kg / m ³ or more and 100 kg / m ³ or less, so that the acoustic impedance difference between the piezoelectric body that emits ultrasonic waves and the gas It is possible to suppress the reflection of ultrasonic waves due to the above and efficiently make the ultrasonic waves incident on the piezoelectric body. Therefore, a highly sensitive ultrasonic wave transmitter / receiver and ultrasonic flow meter can be realized. In particular, the first acoustic matching layer 26 is composed of a structure having closed cells, the average pore diameter of the closed pores is 1 μm or more and 100 μm or less, and the distance between adjacent closed pores is within the range of 50 nm or more and 1 μm or less. Therefore, excellent acoustic characteristics can be realized. Therefore, a more sensitive ultrasonic wave transmitter / receiver and ultrasonic flow meter can be realized. Further, the structure having closed cells of the first acoustic matching layer 26 contains a polymethacrylicimide foam. Since the polymethacrylicimide foam has a feature of low density and high elasticity, it has resistance to impact in the manufacturing process, and is excellent in mechanical strength and workability. Therefore, it is possible to manufacture the laminate and the ultrasonic wave transmitter / receiver with a high yield. Therefore, since the acoustic matching layer is relatively easy to handle, it is possible to obtain a laminated body which is excellent in productivity, has small variation in characteristics, and can efficiently inject sound waves from the fluid into the piezoelectric body. .. Further, by using such a laminated body, an ultrasonic wave transmitter / receiver and an ultrasonic flow meter capable of detecting a fluid with high sensitivity can be realized.

(Second Embodiment)
FIG. 4 schematically shows the structure of the ultrasonic wave transmitter / receiver used in the ultrasonic flow meter of the present embodiment. In FIG. 4, the same or similar configurations as those in the first embodiment shown in FIG. 1 are designated by the same reference numerals. The description of the same or similar configuration as that of the first embodiment may be omitted. The ultrasonic wave transmitter / receiver shown in FIG. 4 differs from the first embodiment in that it includes a laminate 28'including a piezoelectric body 21, a first acoustic matching layer 26, and a second acoustic matching layer 27.

The second acoustic matching layer 27 is located between the piezoelectric body 21 and the first acoustic matching layer 26. In the present embodiment, the second acoustic matching layer 27 is attached to the outer surface 22b of the top plate 22u, and the first acoustic matching layer 26 is in contact with the second acoustic matching layer 27. The second acoustic matching layer 27 has a density of 50 kg / m ³ or more and 1500 kg / m ³ or less. Further, the density of the second acoustic matching layer 27 is higher than the density of the first acoustic matching layer. Assuming that the acoustic impedance of the first acoustic matching layer 26 is Za and the acoustic impedance of the second acoustic matching layer 27 is Zb, the relationship of Za <Zb is satisfied. Zb is smaller than the acoustic impedance of the piezoelectric body 21. By further including the second acoustic matching layer 27 having such acoustic characteristics in the laminated body 28', the sound waves incident on the first acoustic matching layer 26 can be more efficiently incident on the piezoelectric body 21. Become.

The second acoustic matching layer 27 is a material having closed pores. For example, the second acoustic matching layer 27 is made of a foamed resin such as polymethacrylicimide or a composite material. The composite material may be, for example, a glass balloon (a hollow minute glass ball) or a material obtained by solidifying a plastic balloon with a resin material. Further, these foamed resins and composite materials may have a structure in which the surface thereof is covered with a gas barrier film. It is desirable that the thickness of the second acoustic matching layer 27 also has a thickness of 1/4 of the sound wave propagating in the second acoustic matching layer 27 for the same reason as in the first embodiment.

In the present embodiment, the first acoustic matching layer 26 and the second acoustic matching layer 27 are in direct contact with each other. The second acoustic matching layer 27 is in contact with the outer surface 22b of the top plate 22u of the case 29. The top plate 22u of the case 29 functions as a structural support layer that supports the laminated body 28'. The top plate 22u preferably has a density of 1000 kg / m ³ or more. Further, the thickness of the top plate 22u is 1/8 or less of the wavelength λ of the sound wave propagating in the top plate 22u. When the top plate 22u satisfies this condition, the reflection of sound waves on the top plate 22u is suppressed.

According to the laminated body of the present embodiment, since the laminated body 28'includes the second acoustic matching layer 27, sound waves propagating in the fluid can be incident on the piezoelectric body with higher efficiency. Therefore, in addition to the features described in the first embodiment, an ultrasonic wave transmitter / receiver and an ultrasonic flow meter capable of detecting a fluid with higher sensitivity can be realized.

(Example)
Hereinafter, the results of manufacturing the ultrasonic wave transmitter / receiver and the ultrasonic flow meter of the first and second embodiments and examining their characteristics will be described.

1. Preparation of sample [Reference example (A)]
(A) Production of Second Acoustic Matching Layer (Silica Porous) After mixing spherical acrylic resin with a diameter of several tens of μm and sintered silica powder with a diameter of 1 μm or less, pressure molding was performed. After the molded body was dried, it was fired at 900 ° C. to form a porous silica body. Then, the thickness of the silica porous body was adjusted to be 1/4 of the ultrasonic oscillation wavelength, and a second acoustic matching layer was obtained. The sound velocity of the ultrasonic wave propagating in the second acoustic matching layer at about 500 kHz was 1500 m / s. The density was 570 kg / m ³ and the thickness was 750 μm.

(B) Lamination of 2nd Acoustic Matching Layer and 1st Acoustic Matching Layer A gel raw material solution prepared by mixing tetramethoxysilane, ethanol, and an aqueous ammonia solution (specified in 0.1) in a molar ratio of 1: 3: 4. The second acoustic matching layer, which had been previously cleaned by plasma cleaning so that the hydroxyl groups were exposed on the surface, was coated with a thickness of 90 μm. Then, the applied gel raw material liquid was solidified to obtain a silica wet gel layer. The second acoustic matching layer on which the silica wet gel layer was formed was hydrophobized in a 5 wt% hexane solution of trimethylethoxysilane, and then supercritical dried with carbon dioxide (12 MPa, 50 ° C.) to carry out silica. An acoustic matching layer in which the dried gel and the second acoustic matching layer were laminated was obtained. Since the hydroxyl group on the second acoustic matching layer reacts with the alkoxy group of tetramethoxysilane to form a chemical bond, the first acoustic matching layer having good adhesion was obtained. The sound velocity of the ultrasonic wave propagating in the first acoustic matching layer of about 500 kHz was 180 m / s, and the density was 200 kg / m ³ .

(C) Joining the acoustic matching layer with the case and the piezoelectric layer After temporarily bonding epoxy adhesive sheets to both sides of the top plate 22u of the main body 22 of the case 29, the piezoelectric body 21 and the second acoustic matching layer 27 are used. The top plate 22u was sandwiched and heated while pressurizing to cure and bond.

(D) Formation of Ultrasonic Wave Transmitter / Receiver A lid plate 23, drive terminals 24a, 24b and the like were assembled to the main body 22 to obtain an ultrasonic wave transmitter / receiver.

[Example (B)]
(A) Processing of First Acoustic Matching Layer As the first acoustic matching layer 26, polymethacrylicimide rigid plastic foam ROHACELL (R) (density 30 kg / m ³ ) was used. This material was processed into a cylindrical shape having an average pore size of 60 μm, an average wall thickness of 80 nm, and a diameter of 10.8 mm. The speed of the ultrasonic wave propagating in the first acoustic matching layer 26 at about 500 kHz was 1200 m / s. The thickness of the first acoustic matching layer 26 was adjusted to 600 μm.

(B) Joining the acoustic matching layer with the case and the piezoelectric layer After temporarily bonding epoxy adhesive sheets to both sides of the top plate 22u of the main body 22 of the case 29, the piezoelectric body 21 and the first acoustic matching layer 26 are used. The top plate 22u was sandwiched and heated while pressurizing to cure and bond.

(C) Formation of Ultrasonic Wave Transmitter / Receiver A lid plate 23, drive terminals 24a, 24b and the like were assembled to the main body 22 to obtain an ultrasonic wave transmitter / receiver.

[Example (C)]
(A) Processing of First Acoustic Matching Layer As the first acoustic matching layer 26, polymethacrylicimide rigid plastic foam ROHACELL (R) (density 50 kg / m ³ ) was used. This material was processed into a cylindrical shape having an average pore size of 40 μm, an average wall thickness of 200 nm, and a diameter of 10.8 mm. The speed of the ultrasonic wave propagating in the first acoustic matching layer 26 at about 500 kHz was 2000 m / s. The thickness of the first acoustic matching layer 26 was adjusted to 1000 μm.

(B) Joining the acoustic matching layer with the case and the piezoelectric layer After temporarily bonding epoxy adhesive sheets to both sides of the top plate 22u of the main body 22 of the case 29, the piezoelectric body 21 and the first acoustic matching layer 26 are used. The top plate 22u was sandwiched and heated while pressurizing to cure and bond.

(C) Formation of Ultrasonic Wave Transmitter / Receiver A lid plate 23, drive terminals 24a, 24b and the like were assembled to the main body 22 to obtain an ultrasonic wave transmitter / receiver.

[Example (D)]
(A) Processing of First Acoustic Matching Layer As the first acoustic matching layer 26, polymethacrylicimide rigid plastic foam ROHACELL (R) (density 70 kg / m ³ ) was used. This material was processed into a cylindrical shape having an average pore size of 25 μm, an average wall thickness of 400 nm, and a diameter of 10.8 mm. The speed of the ultrasonic wave propagating in the first acoustic matching layer 26 at about 500 kHz was 3000 m / s. The thickness of the first acoustic matching layer 26 was adjusted to 1500 μm.

(B) Joining the acoustic matching layer with the case and the piezoelectric layer After temporarily bonding epoxy adhesive sheets to both sides of the top plate 22u of the main body 22 of the case 29, the piezoelectric body 21 and the first acoustic matching layer 26 are used. The top plate 22u was sandwiched and heated while pressurizing to cure and bond.

(C) Formation of Ultrasonic Wave Transmitter / Receiver A lid plate 23, drive terminals 24a, 24b and the like were assembled to the main body 22 to obtain an ultrasonic wave transmitter / receiver.

[Reference example (E)]
(A) Processing of First Acoustic Matching Layer As the first acoustic matching layer 26, polymethacrylicimide rigid plastic foam ROHACELL (R) (density 70 kg / m ³ ) was used. This material was processed into a cylindrical shape having an average pore size of 200 μm, an average wall thickness of 2000 nm, and a diameter of 10.8 mm. The speed of the ultrasonic wave propagating in the first acoustic matching layer 26 at about 500 kHz was 400 m / s. The thickness of the first acoustic matching layer 26 was adjusted to 200 μm.

(B) Joining the acoustic matching layer with the case and the piezoelectric layer After temporarily bonding epoxy adhesive sheets to both sides of the top plate 22u of the main body 22 of the case 29, the piezoelectric body 21 and the first acoustic matching layer 26 are used. The top plate 22u was sandwiched and heated while pressurizing to cure and bond.

(C) Formation of Ultrasonic Wave Transmitter / Receiver A lid plate 23, drive terminals 24a, 24b and the like were assembled to the main body 22 to obtain an ultrasonic wave transmitter / receiver.

[Reference example (F)]
(A) Processing of First Acoustic Matching Layer As the first acoustic matching layer 26, polymethacrylicimide rigid plastic foam ROHACELL (R) (density 70 kg / m ³ ) was used. This material was processed into a cylindrical shape having an average pore size of 300 μm, an average wall thickness of 3250 nm, and a diameter of 10.8 mm. The speed of the ultrasonic wave propagating in the first acoustic matching layer 26 at about 500 kHz was 460 m / s. The thickness of the first acoustic matching layer 26 was adjusted to 230 μm.

(B) Joining the acoustic matching layer with the case and the piezoelectric layer After temporarily bonding epoxy adhesive sheets to both sides of the top plate 22u of the main body 22 of the case 29, the piezoelectric body 21 and the first acoustic matching layer 26 are used. The top plate 22u was sandwiched and heated while pressurizing to cure and bond.

(C) Formation of Ultrasonic Wave Transmitter / Receiver A lid plate 23, drive terminals 24a, 24b and the like were assembled to the main body 22 to obtain an ultrasonic wave transmitter / receiver.

[Example (G)]
(A) Production of second acoustic matching layer (glass epoxy) 27 Organic polymer, fibrous body of inorganic material, foam body, sintered porous body, material obtained by solidifying glass balloon or plastic balloon with resin material, glass balloon is heated A compressed material or the like can be used. Here, the jig was filled with a glass balloon, then impregnated with an epoxy solution, and thermoset at 120 ° C. The thickness of the cured molded body was cut so as to be 1/4 of the ultrasonic oscillation wavelength to obtain a second acoustic matching layer 27. The sound velocity of the ultrasonic wave propagating in the second acoustic matching layer 27 at about 500 kHz was 2500 m / s. The density was 520 kg / m ³ and the thickness was 1250 μm.

(B) Joining the second acoustic matching layer with the case and the piezoelectric layer After temporarily bonding epoxy adhesive sheets to both sides of the top plate 22u of the main body 22 of the case 29, the piezoelectric body 21 and the second acoustic matching layer The top plate 22u was sandwiched between 27 and heated while pressurizing to cure and bond.

(C) Lamination of Second Acoustic Matching Layer 27 and First Acoustic Matching Layer 26 As the first acoustic matching layer 26, polymethacrylicimide rigid plastic foam ROHACELL (R) (density 30 kg / m ³ ) was used. This material was processed into a cylindrical shape having an average pore size of 60 μm, an average wall thickness of 80 nm, and a diameter of 10.8 mm. The sound velocity of the ultrasonic wave propagating in the first acoustic matching layer 26 at about 500 kHz was 1200 m / s, and the thickness was 600 μm. An epoxy resin was applied to the surface of the second acoustic matching layer 27 to a thickness of about 50 μm, and the first acoustic matching layer 26 was placed on the epoxy resin and bonded by heat pressurization.

(D) Formation of Ultrasonic Wave Transmitter / Receiver A lid plate 23, drive terminals 24a, 24b and the like were assembled to the main body 22 to obtain an ultrasonic wave transmitter / receiver.

[Example (H)]
(A) Production of second acoustic matching layer (glass epoxy) 27 Organic polymer, fibrous body of inorganic material, foam body, sintered porous body, material obtained by solidifying glass balloon or plastic balloon with resin material, glass balloon is heated A compressed material or the like can be used. Here, the jig was filled with a glass balloon, then impregnated with an epoxy solution, and thermoset at 120 ° C. The thickness of the cured molded body was cut so as to be 1/4 of the ultrasonic oscillation wavelength to obtain a second acoustic matching layer 27. The sound velocity of the ultrasonic wave propagating in the second acoustic matching layer 27 at about 500 kHz was 2500 m / s. The density was 520 kg / m ³ and the thickness was 1250 μm.

(B) Joining the second acoustic matching layer with the case and the piezoelectric layer After temporarily bonding epoxy adhesive sheets to both sides of the top plate 22u of the main body 22 of the case 29, the piezoelectric body 21 and the second acoustic matching layer The top plate 22u was sandwiched between 27 and heated while pressurizing to cure and bond.

(C) Lamination of Second Acoustic Matching Layer 27 and First Acoustic Matching Layer 26 As the first acoustic matching layer 26, polymethacrylicimide rigid plastic foam ROHACELL (R) (density 30 kg / m ³ ) was used. This material was processed into a cylindrical shape having an average pore size of 60 μm, an average wall thickness of 80 nm, and a diameter of 10.8 mm. The sound velocity of the ultrasonic wave propagating in the first acoustic matching layer 26 at about 500 kHz was 1200 m / s, and the thickness was 600 μm. An epoxy resin was applied to the surface of the second acoustic matching layer 27 to a thickness of about 150 μm, and the first acoustic matching layer 26 was placed on the epoxy resin and bonded by heat pressurization.

(D) Formation of Ultrasonic Wave Transmitter / Receiver A lid plate 23, drive terminals 24a, 24b and the like were assembled to the main body 22 to obtain an ultrasonic wave transmitter / receiver.

[Example (I)]
(A) Production of second acoustic matching layer (glass epoxy) 27 Organic polymer, fibrous body of inorganic material, foam body, sintered porous body, material obtained by solidifying glass balloon or plastic balloon with resin material, glass balloon is heated A compressed material or the like can be used. Here, the jig was filled with a glass balloon, then impregnated with an epoxy solution, and thermoset at 120 ° C. The thickness of the cured molded body was cut so as to be 1/4 of the ultrasonic oscillation wavelength to obtain a second acoustic matching layer 27. The sound velocity of the ultrasonic wave propagating in the second acoustic matching layer 27 at about 500 kHz was 2500 m / s. The density was 520 kg / m ³ and the thickness was 1250 μm.

(B) Joining the second acoustic matching layer with the case and the piezoelectric layer After temporarily bonding epoxy adhesive sheets to both sides of the top plate 22u of the main body 22 of the case 29, the piezoelectric body 21 and the second acoustic matching layer The top plate 22u was sandwiched between 27 and heated while pressurizing to cure and bond.

(C) Lamination of 2nd Acoustic Matching Layer 27 and 1st Acoustic Matching Layer 26 As the 1st acoustic matching layer 26, polymethacrylicimide rigid plastic foam ROHACELL (R) (density 50 kg / m ³ ) was used. This material was processed into a cylindrical shape having an average pore size of 40 μm, an average wall thickness of 200 nm, and a diameter of 10.8 mm. The sound velocity of the ultrasonic wave propagating in the first acoustic matching layer 26 at about 500 kHz was 2000 m / s, and the thickness was 100 μm. An epoxy resin was applied to the surface of the second acoustic matching layer 27 to a thickness of about 50 μm, and the first acoustic matching layer 26 was placed on the epoxy resin and bonded by heat pressurization.

(D) Formation of Ultrasonic Wave Transmitter / Receiver A lid plate 23, drive terminals 24a, 24b and the like were assembled to the main body 22 to obtain an ultrasonic wave transmitter / receiver.

[Example (J)]
(A) Production of second acoustic matching layer (glass epoxy) 27 Organic polymer, fibrous body of inorganic material, foam body, sintered porous body, material obtained by solidifying glass balloon or plastic balloon with resin material, glass balloon is heated A compressed material or the like can be used. Here, the jig was filled with a glass balloon, then impregnated with an epoxy solution, and thermoset at 120 ° C. The thickness of the cured molded body was cut so as to be 1/4 of the ultrasonic oscillation wavelength to obtain a second acoustic matching layer 27. The sound velocity of the ultrasonic wave propagating in the second acoustic matching layer 27 at about 500 kHz was 2500 m / s. The density was 520 kg / m ³ and the thickness was 1250 μm.

(B) Joining the second acoustic matching layer with the case and the piezoelectric layer After temporarily bonding epoxy adhesive sheets to both sides of the top plate 22u of the main body 22 of the case 29, the piezoelectric body 21 and the second acoustic matching layer The top plate 22u was sandwiched between 27 and heated while pressurizing to cure and bond.

(C) Lamination of Second Acoustic Matching Layer 27 and First Acoustic Matching Layer 26 As the first acoustic matching layer 26, polymethacrylicimide rigid plastic foam ROHACELL (R) (density 70 kg / m ³ ) was used. This material was processed into a cylindrical shape having an average pore size of 25 μm, an average wall thickness of 400 nm, and a diameter of 10.8 mm. The sound velocity of the ultrasonic wave propagating in the first acoustic matching layer 26 at about 500 kHz was 3000 m / s, and the thickness was 1500 μm. An epoxy resin was applied to the surface of the second acoustic matching layer 27 to a thickness of about 50 μm, and the first acoustic matching layer 26 was placed on the epoxy resin and bonded by heat pressurization.

(D) Formation of Ultrasonic Wave Transmitter / Receiver A lid plate 23, drive terminals 24a, 24b and the like were assembled to the main body 22 to obtain an ultrasonic wave transmitter / receiver.

[Reference example (K)]
(A) Production of second acoustic matching layer (glass epoxy) 27 Organic polymer, fibrous body of inorganic material, foam body, sintered porous body, material obtained by solidifying glass balloon or plastic balloon with resin material, glass balloon is heated A compressed material or the like can be used. Here, the jig was filled with a glass balloon, then impregnated with an epoxy solution, and thermoset at 120 ° C. The thickness of the cured molded body was cut so as to be 1/4 of the ultrasonic oscillation wavelength to obtain a second acoustic matching layer 27. The sound velocity of the ultrasonic wave propagating in the second acoustic matching layer 27 at about 500 kHz was 2500 m / s. The density was 520 kg / m ³ and the thickness was 1250 μm.

(B) Joining the second acoustic matching layer with the case and the piezoelectric layer After temporarily bonding epoxy adhesive sheets to both sides of the top plate 22u of the main body 22 of the case 29, the piezoelectric body 21 and the second acoustic matching layer The top plate 22u was sandwiched between 27 and heated while pressurizing to cure and bond.

(C) Lamination of Second Acoustic Matching Layer 27 and First Acoustic Matching Layer 26 As the first acoustic matching layer 26, polymethacrylicimide rigid plastic foam ROHACELL (R) (density 70 kg / m ³ ) was used. This material was processed into a cylindrical shape having an average pore size of 200 μm, an average wall thickness of 2000 nm, and a diameter of 10.8 mm. The sound velocity of the ultrasonic wave propagating in the first acoustic matching layer 26 at about 500 kHz was 400 m / s, and the thickness was 200 μm. An epoxy resin was applied to the surface of the second acoustic matching layer 27 to a thickness of about 50 μm, and the first acoustic matching layer 26 was placed on the epoxy resin and bonded by heat pressurization.

(D) Formation of Ultrasonic Wave Transmitter / Receiver A lid plate 23, drive terminals 24a, 24b and the like were assembled to the main body 22 to obtain an ultrasonic wave transmitter / receiver.

[Reference example (L)]
(A) Production of second acoustic matching layer (glass epoxy) 27 Organic polymer, fibrous body of inorganic material, foam body, sintered porous body, material obtained by solidifying glass balloon or plastic balloon with resin material, glass balloon is heated A compressed material or the like can be used. Here, the jig was filled with a glass balloon, then impregnated with an epoxy solution, and thermoset at 120 ° C. The thickness of the cured molded body was cut so as to be 1/4 of the ultrasonic oscillation wavelength to obtain a second acoustic matching layer 27. The sound velocity of the ultrasonic wave propagating in the second acoustic matching layer 27 at about 500 kHz was 2500 m / s. The density was 520 kg / m ³ and the thickness was 1250 μm.

(B) Joining the second acoustic matching layer with the case and the piezoelectric layer After temporarily bonding epoxy adhesive sheets to both sides of the top plate 22u of the main body 22 of the case 29, the piezoelectric body 21 and the second acoustic matching layer The top plate 22u was sandwiched between 27 and heated while pressurizing to cure and bond.

(C) Lamination of Second Acoustic Matching Layer 27 and First Acoustic Matching Layer 26 As the first acoustic matching layer 26, polymethacrylicimide rigid plastic foam ROHACELL (R) (density 70 kg / m ³ ) was used. This material was processed into a cylindrical shape having an average pore size of 300 μm, an average wall thickness of 3250 nm, and a diameter of 10.8 mm. The sound velocity of the ultrasonic wave of about 500 kHz propagating in the first acoustic matching layer 26 was 460 m / s, and the thickness was 230 μm. An epoxy resin was applied to the surface of the second acoustic matching layer 27 to a thickness of about 50 μm, and the first acoustic matching layer 26 was placed on the epoxy resin and bonded by heat pressurization.

(D) Formation of Ultrasonic Wave Transmitter / Receiver A lid plate 23, drive terminals 24a, 24b and the like were assembled to the main body 22 to obtain an ultrasonic wave transmitter / receiver.

2. Evaluation of characteristics The sensitivity of the manufactured ultrasonic wave transmitter / receiver was measured. A pair of manufactured ultrasonic wave transmitters and receivers were opposed to each other, and one was used as a transmitter and the other was used as a receiver to transmit and receive ultrasonic waves. A standardized value was obtained based on the measurement result according to the reference example (A). In addition, the brittleness and workability of the first acoustic matching layer were evaluated by the volume elastic modulus. Specifically, the volume elastic modulus shown in the catalog of the material used for the first acoustic matching layer was normalized by the volume elastic modulus of the material of Reference Example (A). Table 1 summarizes these values and the characteristics of the first acoustic matching layer 26 and the second acoustic matching layer 27.

The symbols ×, Δ, 〇, and ◎ in the performance evaluation column in Table 1 are classified according to the following range.
(sensitivity)
×: Less than 1 Δ: 1 or more and less than 1.5 ○: 1.5 or more and less than 2 ◎: 2 or more (brittleness / workability)
×: 1 or less Δ: 2 or more and less than 5 ○: 5 or more and less than 30 ◎: 30 or more

3. Discussion of Results As shown in Table 1, it can be seen that the polymethacrylicimide foam is superior in brittleness and workability as compared with the porous silica. Further, from the relationship between the average cell diameter and the sensitivity of Examples B to F, it can be seen that the sensitivity is better when the average cell diameter is 100 μm or less and the average thickness of the partition wall is 1 μm or less. According to the results of detailed experiments by the inventor of the present application, the sensitivity of the ultrasonic transmitter / receiver is improved when the average cell diameter is 1 μm or more and 100 μm or less and the average thickness of the partition wall is 50 nm or more and 1 μm or less. Further, it can be seen that higher sensitivity can be obtained when the sound velocity of the first acoustic matching layer is higher than 500 m / s.

From the comparison between Examples G to L and Examples B to F, the sensitivity is further improved by further providing the second acoustic matching layer 27 as compared with the case where the laminated body includes only the first acoustic matching layer 26. I understand.

The laminate and ultrasonic wave transmitter / receiver of the present disclosure are suitably used for flow meters for measuring various fluids. Further, it is suitably used for various devices having sonar performance, such as a detection device for detecting a target object and a distance measuring device for measuring a distance to a target object.

11, 12 Ultrasonic wave transmitter / receiver 22 Main body 22u Top plate 22a Inner surface 22b Outer surface 23 Lid plate 24a, 24b Drive terminal 25 Insulation material 26 1st acoustic matching layer 27 2nd acoustic matching layer 28, 28'Laminated body 29 Case 31 hours Measurement unit 32 Calculation unit

Claims (18)

Piezoelectric and
A first acoustic matching layer that is arranged in contact with the piezoelectric body directly or via another layer.
Contains plastic closed-cell foam containing multiple closed pores,
The average pore diameter of the closed pore is 1 μm or more and 100 μm or less.
A first acoustic matching layer having a density of 10 kg / m ³ or more and 100 kg / m ³ or less is provided.
Laminated body. The laminate according to claim 1, wherein the acoustic impedance of the first acoustic matching layer is in the range of 5 × 10 ³ kg / s ・ m ² or more and 350 × 10 ³ kg / s ・ m ² or less. The laminate according to claim 1 or 2, wherein the average distance between adjacent closed pores is 50 nm or more and 1 μm or less. The laminate according to any one of claims 1 to 3, wherein the sound velocity of the first acoustic matching layer is 500 m / s or more. The laminate according to any one of claims 1 to 4, wherein the plastic closed-cell foam is a polymethacrylicimide foam. The laminate according to any one of claims 1 to 5, wherein the thickness of the first acoustic matching layer is approximately 1/4 of the wavelength λ of the sound wave propagating in the first acoustic matching layer. A second acoustic matching layer located between the piezoelectric body and the first acoustic matching layer is further provided.
The laminate according to any one of claims 1 to 6, wherein the second acoustic matching layer is 50 kg / m ³ or more and 1500 kg / m ³ or less, and has a density higher than that of the first acoustic matching layer. The laminate according to claim 7, wherein the relationship between the acoustic impedance Za of the first acoustic matching layer and the acoustic impedance Zb of the second acoustic matching layer is Za <Zb. The laminate according to claim 7 or 8, wherein the thickness of the second acoustic matching layer is approximately 1/4 of the wavelength λ of the sound wave propagating in the second acoustic matching layer. The laminate according to any one of claims 1 to 6, wherein the first acoustic matching layer is directly bonded to the piezoelectric body. The laminate according to claim 7, wherein the second acoustic matching layer is arranged in direct contact with the first acoustic matching layer and the piezoelectric body. The laminate according to claim 7, further comprising a structural support layer having a density of 1000 kg / m ³ or more between the first acoustic matching layer and the second acoustic matching layer. The laminate according to claim 12, wherein the thickness of the structural support layer is less than 1/8 of the wavelength λ of the sound wave propagating in the structural support layer. An ultrasonic wave transmitter / receiver comprising the laminate according to any one of claims 1 to 13. The laminate according to any one of claims 1 to 6 and
A main body having a convex shape having a top plate and a case having a lid plate covering the convex opening are further provided.
The piezoelectric body is located in the convex shape and is fixed to the inner surface of the top plate.
An ultrasonic wave transmitter / receiver in which the first acoustic matching layer is fixed to the outer surface of the top plate. With the laminate according to any one of claims 7 to 9.
A main body having a convex shape having a top plate and a case having a lid plate covering the convex opening are further provided.
The piezoelectric body is located in the convex shape and is fixed to the inner surface of the top plate.
The second acoustic matching layer is fixed to the outer surface of the top plate,
The first acoustic matching layer is an ultrasonic wave transmitter / receiver in contact with the second acoustic matching layer. The ultrasonic wave transmitter / receiver according to claim 15 or 16, wherein the case is made of a metal material. The flow path through which the fluid to be measured flows and
The ultrasonic wave transmitter / receiver according to any one of claims 14 to 16, which is a pair of ultrasonic wave transmitters / receivers arranged in the flow path for transmitting / receiving ultrasonic signals.
A time measuring unit that measures the ultrasonic wave propagation time between the pair of ultrasonic wave transmitters and receivers,
A calculation unit that calculates the flow rate of the flow path based on the signal from the time measurement unit, and
Ultrasonic flowmeter equipped with.

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