Ultrasonic flowmeter

Abstract

To provide an ultrasonic flowmeter capable of suppressing variation in compressive deformation in an elastic couplant.SOLUTION: The ultrasonic flow meter 101 includes ultrasonic elements 1222 and including ultrasonic transmitting and receiving sections 12a and 22a that transmit and receive ultrasonic waves to and from the fluid flowing in the pipe 31, an elastic couplant 1424 provided between the outer circumferential surface of the pipe 31 and the ultrasonic elements 1222 and, and fixing members 1525 and provided adjacent to a side portion of the elastic couplant 1424 and fixing distances between the outer circumferential surface of the pipe 31 and the ultrasonic elements 1222 and.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to ultrasonic flow meters. [Background technology]

[0002] Clamp-on type ultrasonic flowmeters have been provided that use ultrasonic waves to measure the flow rate or flow velocity of a fluid flowing through a pipe (hereinafter referred to as "fluid measurement"). Clamp-on type ultrasonic flowmeters can perform fluid measurement simply by clamping an ultrasonic element to the outer surface of a pipe. Such a clamp-on type ultrasonic flowmeter is disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-158680 Summary of the Invention [Problem to be solved by the invention]

[0004] The ultrasonic flowmeter disclosed in Patent Document 1 has an elastic couplant interposed between the piping and the ultrasonic element. The elastic couplant matches the acoustic impedance of the piping with the acoustic impedance of the ultrasonic element. The ultrasonic flowmeter disclosed in Patent Document 1 improves fluid measurement by including the elastic couplant.

[0005] Here, in order to efficiently propagate the ultrasonic waves emitted from the ultrasonic element to the fluid flowing in the pipe, it is preferable that there be no gaps between the pipe and the elastic couplant, and between the elastic couplant and the ultrasonic element. Therefore, when clamping the ultrasonic element to the pipe via the elastic couplant, it is possible to eliminate the above-mentioned gaps by clamping the ultrasonic element with a large load and causing large compressive deformation (elastic deformation) of the elastic couplant.

[0006] However, variations in the load applied during clamping or variations in the stiffness of individual elastic couplants can cause variations in the amount of compressive deformation when the elastic couplant is compressed, which can result in individual differences in measurement accuracy and measurement errors.

[0007] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide an ultrasonic flowmeter that can suppress variations in compressive deformation in an elastic couplant. [Means for solving the problem]

[0008] The ultrasonic flowmeter according to the present disclosure comprises an ultrasonic element having an ultrasonic transmitting / receiving unit that transmits and receives ultrasonic waves to and from a fluid flowing through a pipe, an elastic couplant that is provided between the outer surface of the pipe and the ultrasonic element, and a fixing member that is provided adjacent to the side of the elastic couplant and fixes the distance between the outer surface of the pipe and the ultrasonic element. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to reduce variations in compressive deformation in the elastic couplant, thereby reducing individual differences in measurement accuracy and measurement errors. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of an ultrasonic flowmeter according to a first embodiment. [Figure 2] 2A and 2B are diagrams illustrating an operation when clamping the ultrasonic flowmeter according to the first embodiment, in which Fig. 2A is a diagram before clamping and Fig. 2B is a diagram after clamping. [Figure 3] 3A and 3B are schematic diagrams of layers through which ultrasonic waves transmitted from an ultrasonic element propagate. [Figure 4] FIG. 10 is a cross-sectional view of an ultrasonic flowmeter according to a second embodiment. [Figure 5] FIG. 10 is a cross-sectional view of an ultrasonic flowmeter according to a third embodiment. [Figure 6]FIG. 10 is a cross-sectional view of an ultrasonic flowmeter according to a fourth embodiment. [Figure 7] FIG. 1 is a cross-sectional view of a conventional ultrasonic flowmeter. [Figure 8] 8A and 8B are diagrams illustrating the operation of clamping a conventional ultrasonic flowmeter. Fig. 8A shows a case where the diameter of the pipe is equal to the R shape of the inner peripheral surface of the corresponding elastic couplant. Fig. 8B shows a case where the diameter of the pipe is larger than the R shape of the inner peripheral surface of the corresponding elastic couplant. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0012] Embodiment 1 An ultrasonic flowmeter 101 according to the first embodiment will be described with reference to FIGS. 1, 2, 7, and 8. FIG.

[0013] First, the configuration of an ultrasonic flowmeter 101 according to the first embodiment will be described with reference to FIGS.

[0014] Fig. 1 is a cross-sectional view of an ultrasonic flowmeter 101 according to embodiment 1. The ultrasonic flowmeter 101 according to embodiment 1 shown in Fig. 1 is a clamp-on ultrasonic flowmeter that measures the flow rate or flow velocity of a fluid 33 flowing in a pipe 31 using ultrasonic waves.

[0015] The pipe 31 has a cylindrical shape. The inner peripheral surface of the pipe 31 forms a flow path 32. The cross section of the flow path 32 in the axial direction of the pipe is circular. The fluid 33 is, for example, a gas or a liquid.

[0016] The ultrasonic flowmeter 101 performs fluid measurement using, for example, a pair of ultrasonic transmitters and receivers 10a and 20a. The ultrasonic transmitters and receivers 10a and 20a transmit and receive ultrasonic waves between each other. Therefore, the ultrasonic flowmeter 101 performs fluid measurement of the fluid 33 flowing inside the pipe 31 based on electrical signals transmitted from the ultrasonic transmitters and receivers 10a and 20a. For example, the ultrasonic flowmeter 101 performs fluid measurement based on the difference between the propagation time of ultrasonic waves transmitted from one ultrasonic transmitter and receiver 10a to the other ultrasonic transmitter and receiver 20a and the propagation time of ultrasonic waves transmitted from the other ultrasonic transmitter and receiver 20a to the one ultrasonic transmitter and receiver 10a.

[0017] The ultrasonic flowmeter 101 includes, for example, a clamping member (not shown). This clamping member generates a clamping force from the outer peripheral surface of the pipe 31 toward its radially inward direction by clamping the pipe 31 or surrounding the outer peripheral surface of the pipe 31 in the circumferential direction. Therefore, the clamping member can detachably hold the ultrasonic transmitters and receivers 10a and 20a to the outer peripheral surface of the pipe 31. At this time, the ultrasonic transmitters and receivers 10a and 20a are arranged to face each other in the radial direction of the pipe 31.

[0018] The ultrasonic transmitter / receiver 10 a includes a substrate 11 , an ultrasonic element 12 , a wire 13 , an elastic couplant 14 , and a fixing member 15 .

[0019] The substrate 11 is a substrate for extracting electrical signals from the ultrasonic element 12. The ultrasonic element 12 is capable of transmitting and receiving ultrasonic waves. The ultrasonic element 12 is mounted on the surface of the substrate 11. The surface of the substrate 11 is the mounting surface. The substrate 11 is arranged with its mounting surface facing the piping 31. The ultrasonic element 12 has an ultrasonic transmitter / receiver unit 12a on its surface. The ultrasonic element 12 is mounted on the substrate 11 with the ultrasonic transmitter / receiver unit 12a facing the piping 31. The surface of the substrate 11 and the surface of the ultrasonic element 12 are electrically connected by a wire 13.

[0020] The elastic couplant 14 matches the acoustic impedance of the pipe 31 with that of the ultrasonic element 12. The elastic couplant 14 is formed of a soft elastic material, for example, solid polymer rubber or a solid gel-like substance. The elastic couplant 14 is provided between the ultrasonic element 12 and the outer peripheral surface of the pipe 31. In this case, the elastic couplant 14 is provided so as to cover the ultrasonic transmitting / receiving unit 12a of the ultrasonic element 12. The elastic couplant 14 is also formed so as to surround the outer peripheral surface of the pipe 31. The elastic couplant 14 is fixed while being pressed against the outer peripheral surface of the pipe 31 so that its arc-shaped inner peripheral surface is in close contact with the outer peripheral surface of the pipe 31.

[0021] The fixing members 15 are provided adjacent to both sides of the elastic couplant 14 on the surface of the ultrasonic element 12 in the radial direction of the pipe 31. The fixing members 15 are members for fixing the distance between the surface of the ultrasonic element 12 and the outer peripheral surface of the pipe 31. This distance corresponds to the height of the fixing members 15. Specifically, the fixing members 15 are members for fixing the distance between the surface of the ultrasonic element 12 and the outer peripheral surface of the pipe 31 so that the elastic couplant 14 does not become compressed beyond a preset compression state after the ultrasonic element 12 is clamped to the outer peripheral surface of the pipe 31; in other words, so that the elastic couplant 14 does not become thinner than a preset thickness.

[0022] In this way, by providing the fixing member 15, the ultrasonic transmitter / receiver 10a is structured so that when it is clamped to the piping 31, the elastic couplant 14 is only compressed (elastically deformed) up to the position determined by the fixing member 15.

[0023] The ultrasonic transmitter / receiver 20a has a substrate 21, an ultrasonic element 22, a wire 23, an elastic couplant 24, and a fixing member 25. Furthermore, the ultrasonic element 22 has an ultrasonic transmitter / receiver unit 22a. Note that the ultrasonic transmitter / receivers 10a and 20a have the same configuration and the same functions, so a description of the ultrasonic transmitter / receiver 20a will be omitted.

[0024] Furthermore, the ultrasonic transmitter / receivers 10a and 20a may have the ultrasonic elements 12 and 22 configured by MUTs (Micromachined Ultrasonic Transducers) formed using micromachining technology. Examples of such MUTs include PMUTs (Piezoelectric Micromachined Ultrasonic Transducers) and CMUTs (Capacitive Micromachined Ultrasonic Transducers).

[0025] Next, the ultrasonic flowmeter 101 according to the first embodiment and a conventional ultrasonic flowmeter 101A will be compared using Figs. 2, 7, and 8. Fig. 2 is an operation diagram when clamping the ultrasonic flowmeter 101 according to the first embodiment. Fig. 2 shows only the ultrasonic transmitter / receiver 10a. Fig. 7 is a cross-sectional view of the conventional ultrasonic flowmeter 101A. Fig. 8 is an operation diagram when clamping the conventional ultrasonic flowmeter 101A.

[0026] The conventional ultrasonic flowmeter 101A shown in Fig. 7 does not include fixing members 15, 25. Fig. 8A is a diagram showing a case where the diameter of the pipe 31 is equal to the R shape of the inner circumferential surface of the corresponding elastic couplant 14. Fig. 8B is a diagram showing a case where the diameter of the pipe 31 is larger than the R shape of the inner circumferential surface of the corresponding elastic couplant 14. As shown in Figs. 8A and 8B, when measuring fluids 33 flowing in pipes 31 having different diameters in the conventional ultrasonic flowmeter 101A, the R shape of the inner circumferential surface of the elastic couplant 14 needs to be designed according to the diameter of the pipe 31.

[0027] In contrast, in the ultrasonic flowmeter 101 according to the first embodiment, the thickness of the elastic couplant 14 is controlled by the height of the fixing members 15 and 25, and therefore the R shape of the inner peripheral surface of the elastic couplants 14 and 24 is intentionally made gentle, as shown in Figures 2A and 2B. Therefore, the ultrasonic flowmeter 101 according to the first embodiment can accommodate pipes 31 having different diameters using the same elastic couplants 14 and 24.

[0028] 3 is a schematic diagram of each layer through which ultrasonic waves transmitted from ultrasonic elements 12 and 22 propagate. In FIG. 3, three layers, Layers 1 to 3, correspond to ultrasonic elements 12 and 22, elastic couplants 14 and 24, and piping 31.

[0029] Generally, the ultrasonic propagation efficiency when propagating between different media is D = (2n-1) × λ2, where D is the thickness of Layer 2 and R1 to R3 are the acoustic impedances of Layers 1 to 3. 2 = R1 × R3, where n is an arbitrary integer equal to or greater than 1, and λ2 is the wavelength of Layer 2. That is, the ultrasonic propagation efficiency is calculated using the frequency for driving the ultrasonic elements 12 and 22 and the sound speed of Layer 2.

[0030] Assuming that the elastic couplants 14 and 24 are Layer 2 and are made of a material with an appropriate acoustic impedance R2, the optimal thickness D can be calculated based on the driving frequency of the ultrasonic elements 12 and 22 and the sound velocity of the material. In the conventional ultrasonic flowmeter 101A, the thickness of the elastic couplants 14 and 24 fluctuates during clamping, making it difficult to control the thickness to an arbitrary value. In contrast, the ultrasonic flowmeter 101 according to the first embodiment controls the thickness of the elastic couplants 14 and 24 using the height of the fixing members 15 and 25. Therefore, the ultrasonic flowmeter 101 according to the first embodiment can adjust the thickness of the elastic couplants 14 and 24 to a more appropriate value by changing the height of the fixing members 15 and 25. As a result, the ultrasonic flowmeter 101 according to the first embodiment can improve the ultrasonic transmission and reception sensitivity.

[0031] As described above, the ultrasonic flowmeter 101 according to the first embodiment includes ultrasonic elements 12 and 22 having ultrasonic transmitting and receiving units 12a and 22a that transmit and receive ultrasonic waves to and from the fluid flowing through the pipe 31, elastic couplants 14 and 24 that are provided between the outer circumferential surface of the pipe 31 and the ultrasonic elements 12 and 22, and fixing members 15 and 25 that are provided adjacent to the sides of the elastic couplants 14 and 24 and that fix the distance between the outer circumferential surface of the pipe 31 and the ultrasonic elements 12 and 22. Therefore, the ultrasonic flowmeter 101 can suppress variations in compressive deformation in the elastic couplants 14 and 24. As a result, the ultrasonic flowmeter 101 can suppress individual differences in measurement accuracy and measurement errors.

[0032] In the ultrasonic flowmeter 101 according to the first embodiment, the elastic couplants 12 and 24 are provided so as to cover the ultrasonic transmitting and receiving units 12 and 24. Therefore, the ultrasonic flowmeter 101 can match the acoustic impedance of the piping 31 and the acoustic impedance of the ultrasonic element 12 with high accuracy.

[0033] Embodiment 2 An ultrasonic flowmeter 102 according to the second embodiment will be described with reference to Fig. 4. Fig. 4 is a cross-sectional view of the ultrasonic flowmeter 102 according to the second embodiment. Note that components having the same functions as those described in the first embodiment above are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0034] As shown in FIG. 4, the ultrasonic flowmeter 102 according to the second embodiment has ultrasonic transmitters and receivers 10b and 20b.

[0035] The ultrasonic transmitter / receiver 10b includes a substrate 11, an ultrasonic element 12, a wire 13, and an elastic couplant 14.

[0036] The substrate 11 is disposed with its back surface, which is opposite to the front surface that serves as the mounting surface, facing the piping 31. The substrate 11 also has a through-hole 11a. The through-hole 11a penetrates the substrate 11 in the thickness direction and opens to the front surface and the back surface. The outer peripheral surface of the piping 31 can be fitted into this through-hole 11a.

[0037] The ultrasonic element 12 is mounted on the surface of the substrate 11 so as to cover the through-hole 11a. The ultrasonic element 12 also has a dug portion 12b. The dug portion 12b is dug into the back surface of the ultrasonic element 12, and its bottom surface contacts the ultrasonic transmitting / receiving portion 12a and communicates with the through-hole 11a.

[0038] The elastic couplant 14 is filled in the through hole 11a of the substrate 11 and the dug portion 12b of the ultrasonic element 12. The arc-shaped inner peripheral surface of the elastic couplant 14 is in close contact with the outer peripheral surface of the pipe 31.

[0039] That is, the through hole 11a of the substrate 11 corresponds to the fixing member 15, and is a portion for fixing the distance between the rear surface of the ultrasonic element 12 and the outer peripheral surface of the pipe 31. This distance corresponds to the thickness of the substrate 11, that is, the axial length of the through hole 11a.

[0040] The ultrasonic transmitter / receiver 20b has a substrate 21, an ultrasonic element 22, a wire 23, and an elastic couplant 24. Furthermore, the substrate 21 has a through-hole 21a. The ultrasonic element 22 has a recessed portion 22b. Note that the ultrasonic transmitter / receivers 10b and 20b have the same configuration and the same function, so a description of the ultrasonic transmitter / receiver 20b will be omitted. Therefore, the ultrasonic flowmeter 102 controls the thicknesses of the elastic couplants 14 and 24 using the thicknesses of the substrates 11 and 21.

[0041] As described above, the ultrasonic flowmeter 102 according to the second embodiment includes ultrasonic elements 12 and 22 having ultrasonic transmitting and receiving units 12a and 22a that transmit and receive ultrasonic waves to and from a fluid flowing through a pipe 31, substrates 11 and 21 that are disposed with their back surfaces, opposite to the surfaces on which the ultrasonic elements 12 and 22 are mounted, facing the pipe 31 and have through holes 11a and 21a into which the outer peripheral surface of the pipe 31 can be fitted, and on which the ultrasonic elements 12 and 22 are mounted so as to cover the through holes 11a and 21a, and elastic couplants 14 and 24 that are provided in the through holes 11a and 21a. Therefore, the ultrasonic flowmeter 102 can suppress variations in compressive deformation of the elastic couplants 14 and 24. As a result, the ultrasonic flowmeter 101 can suppress individual differences in measurement accuracy and measurement errors.

[0042] In the ultrasonic flowmeter 102 according to the second embodiment, the ultrasonic elements 12 and 22 are connected to the ultrasonic transmitting and receiving units 12a and 22a and have dug portions 12b and 22b that communicate with the through holes 11a and 21a, and the elastic couplants 14 and 24 are provided across the through holes 11a and 21a and the dug portions 12b and 22b. Therefore, in the ultrasonic flowmeter 102, even if the back surface of the substrates 11 and 21, which is opposite to the front surface on which the ultrasonic elements 12 and 22 are mounted, faces the piping 31, acoustic impedance matching can be performed by the elastic couplants 14 and 24.

[0043] Embodiment 3 An ultrasonic flowmeter 103 according to a third embodiment will be described with reference to Fig. 5. Fig. 5 is a cross-sectional view of the ultrasonic flowmeter 103 according to the third embodiment. Note that components having the same functions as those described in the first and second embodiments are denoted by the same reference numerals, and description thereof will be omitted.

[0044] As shown in FIG. 5, an ultrasonic flowmeter 103 according to the third embodiment has ultrasonic transmitters and receivers 10c and 20c.

[0045] The ultrasonic transmitter / receiver 10 b includes a substrate 11 , an ultrasonic element 12 , an elastic couplant 14 , and an electrode 16 .

[0046] The substrate 11 is disposed with its back surface, which is opposite to the mounting surface, facing the piping 31. The ultrasonic element 12 is mounted on the surface of the substrate 11 such that the ultrasonic transmitter / receiver unit 12a is disposed within the through-hole 11a. For this reason, the elastic couplant 14 is provided so as to cover the ultrasonic transmitter / receiver unit 12a of the ultrasonic element 12. The electrode 16 is interposed between the surface of the substrate 11 and the surface of the ultrasonic element 12, electrically connecting them.

[0047] The ultrasonic transmitter / receiver 20c has a substrate 21, an ultrasonic element 22, an elastic couplant 24, and an electrode 26. Since the ultrasonic transmitter / receivers 10c and 20c have the same configuration and the same functions, a description of the ultrasonic transmitter / receiver 20c will be omitted. Therefore, the ultrasonic flowmeter 103 controls the thicknesses of the elastic couplants 14 and 24 using the thicknesses of the substrates 11 and 21.

[0048] As described above, in the ultrasonic flowmeter 103 according to the third embodiment, the ultrasonic transmitting and receiving units 12a and 24a are arranged in the through holes 11a and 21a. Therefore, the ultrasonic flowmeter 103 can match the acoustic impedance of the piping 31 and the acoustic impedance of the ultrasonic element 12 with high accuracy.

[0049] In addition, in the ultrasonic flowmeter 103 of embodiment 3, the electrode 16 is interposed between the surface of the substrate 11 and the surface of the ultrasonic element 12, so that the ultrasonic transmitting / receiving units 12b, 24b of the ultrasonic elements 12, 24 can be made to face the piping 31.

[0050] Embodiment 4 An ultrasonic flowmeter 104 according to a fourth embodiment will be described with reference to Fig. 6. Fig. 6 is a cross-sectional view of the ultrasonic flowmeter 104 according to the fourth embodiment. Note that components having the same functions as those described in the first to third embodiments are denoted by the same reference numerals, and description thereof will be omitted.

[0051] As shown in FIG. 6, the ultrasonic transmitter / receiver 10d includes a substrate 11, an ultrasonic element 12, an elastic couplant 14, and a through electrode 17.

[0052] The substrate 11 is disposed with its back surface, which is opposite to the front surface that serves as the mounting surface, facing the pipe 31. The ultrasonic element 12 is mounted on the front surface of the substrate 11 so as to cover its through hole 11a. The elastic couplant 14 fills the through hole 11a of the substrate 11 and the recessed portion 12b of the ultrasonic element 12. The arc-shaped inner peripheral surface of the elastic couplant 14 is in close contact with the outer peripheral surface of the pipe 31.

[0053] The through electrode 17 penetrates the ultrasonic element 12 in its thickness direction. One end of the through electrode 17 is disposed on the front surface of the ultrasonic element 12, and the other end of the through electrode 17 is disposed on the back surface of the ultrasonic element 12. That is, the through electrode 17 electrically connects the front surface and the back surface of the ultrasonic element 12. Furthermore, the other end of the through electrode 17 is interposed between the back surface of the ultrasonic element 12 and the front surface of the substrate 11, electrically connecting them together.

[0054] The ultrasonic transmitter / receiver 20d has a substrate 21, an ultrasonic element 22, an elastic couplant 24, and a through electrode 27. Since the ultrasonic transmitter / receivers 10d and 20d have the same configuration and the same functions, a description of the ultrasonic transmitter / receiver 20d will be omitted. Therefore, the ultrasonic flowmeter 104 controls the thicknesses of the elastic couplants 14 and 24 using the thicknesses of the substrates 11 and 21.

[0055] As described above, the ultrasonic flowmeter 104 according to the fourth embodiment can easily connect the surfaces of the substrates 11 and 21 and the surfaces of the ultrasonic elements 12 and 24 by providing the through-holes 17 and 27 that penetrate the ultrasonic elements 12 and 24.

[0056] It should be noted that within the scope of the present disclosure, the embodiments may be freely combined, or any component in each embodiment may be modified, or any component in each embodiment may be omitted. [Explanation of symbols]

[0057] 10a, 10b, 10c, 10d Ultrasonic transmitter / receiver 11 Circuit Board 11a Through hole 12 Ultrasonic element 12a Ultrasonic transmitter / receiver 12b Excavated section 13 wires 14 Elastic Couplant 15 Fixing member 16 electrodes 17 Through electrode 20a, 20b, 20c, 20d Ultrasonic transmitter / receiver 21 PCB 21a Through hole 22 Ultrasonic element 22a Ultrasonic transmitter / receiver 22b Excavation 23 wire 24 Elastic Couplant 25 Fixing member 26 electrodes 27 Through electrode 31 Piping 32 Flow path 33 Fluid 101,101A,102,103,104 Ultrasonic flowmeter

Claims

1. an ultrasonic element having an ultrasonic transmitting / receiving unit that transmits and receives ultrasonic waves to and from a fluid flowing in a pipe; an elastic couplant provided between an outer peripheral surface of the pipe and the ultrasonic element; a fixing member provided adjacent to a side of the elastic couplant and fixing the distance between the outer circumferential surface of the pipe and the ultrasonic element; 1. An ultrasonic flow meter comprising:

2. The elastic couplant is provided so as to cover the ultrasonic transmitting and receiving unit.

2. The ultrasonic flowmeter according to claim 1.

3. an ultrasonic element having an ultrasonic transmitting / receiving unit that transmits and receives ultrasonic waves to and from a fluid flowing in a pipe; a substrate that is disposed with a back surface opposite to the front surface on which the ultrasonic element is mounted facing the piping side, has a through hole into which the outer peripheral surface of the piping can be fitted, and the ultrasonic element is mounted so as to cover the through hole; an elastic couplant provided in the through hole; 1. An ultrasonic flow meter comprising:

4. The ultrasonic element is a recessed portion connected to the ultrasonic transmitting / receiving unit and communicating with the through hole; The elastic couplant is provided across the through hole and the recessed portion.

4. The ultrasonic flowmeter according to claim 3.

5. The ultrasonic wave transmitting and receiving unit is disposed in the through hole.

4. The ultrasonic flowmeter according to claim 3.

Images