Ultrasonic flow meter

Abstract

The propagation of the temperature of the fluid to the ultrasonic element is suppressed. [Solution] An ultrasonic flowmeter measures the flow rate of a fluid in a pipe 10. The ultrasonic flowmeter includes a first ultrasonic sensor and a second ultrasonic sensor installed in the pipe 10, and each of the first ultrasonic sensor and the second ultrasonic sensor includes a rod-shaped extension portion 23 including a first end E1 and a second end E2, an ultrasonic element 21 installed at the second end E2, a protrusion portion 24 protruding from the outer peripheral surface of the extension portion 23, and a support portion 25 that supports the protrusion portion 24 with the first end E1 facing into the pipe 10, and recesses C (C1, C2) are formed on at least one of the contact surface of the protrusion portion 24 with the support portion 25 and the contact surface of the support portion 25 with the protrusion portion 24.

Description

[Technical Field]

[0001] The present disclosure relates to a technique for measuring the flow rate of a fluid using ultrasound. [Background technology]

[0002] Techniques for measuring the flow rate of a fluid in a pipe using ultrasonic elements such as piezoelectric elements have been proposed. For example, Patent Document 1 discloses a configuration in which an ultrasonic vibrator is attached to a wedge-shaped portion that protrudes from the outer surface of a measurement pipe. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-251652 Summary of the Invention [Problem to be solved by the invention]

[0004] It is assumed that the fluid to be measured may be at an extremely low or high temperature. In the configuration of Patent Document 1, the ultrasonic vibrator is installed close to the fluid in the pipe, so the temperature of the fluid is transmitted to the ultrasonic vibrator. Therefore, there is a possibility that the ultrasonic vibrator may be cooled to an excessively low temperature or heated to an excessively high temperature. In consideration of the above circumstances, one aspect of the present disclosure aims to suppress the transmission of the temperature of the fluid to the ultrasonic element. [Means for solving the problem]

[0005] An ultrasonic flow meter according to one embodiment of the present disclosure is an ultrasonic flow meter that measures the flow rate of a fluid in a pipe, and includes a first ultrasonic sensor and a second ultrasonic sensor installed in the pipe, each of the first ultrasonic sensor and the second ultrasonic sensor including a rod-shaped extension portion having a first end and a second end, an ultrasonic element installed at the second end, a protrusion protruding from the outer peripheral surface of the extension portion, and a support portion that supports the protrusion with the first end facing into the pipe, and a recess is formed on at least one of the contact surface of the protrusion with the support portion and the contact surface of the support portion with the protrusion.

[0006] An ultrasonic flow meter according to another aspect of the present disclosure is an ultrasonic flow meter that measures the flow rate of a fluid in a pipe, and includes a first ultrasonic sensor and a second ultrasonic sensor installed in the pipe, and each of the first ultrasonic sensor and the second ultrasonic sensor includes a rod-shaped extension portion having a first end and a second end, an ultrasonic element installed at the second end, a protrusion protruding from the outer peripheral surface of the extension portion, a support portion that supports the protrusion with the first end facing into the pipe, and an ultrasonic absorbing material that covers at least a portion of the outer peripheral surface of the extension portion. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a cross-sectional view of an ultrasonic flowmeter according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view of an ultrasonic sensor. [Figure 3] 3A and 3B are a plan view and a cross-sectional view of the mounting base; [Figure 4] FIG. [Figure 5] FIG. 10 is a cross-sectional view of an ultrasonic sensor according to a second embodiment. [Figure 6] FIG. 10 is a cross-sectional view of an ultrasonic sensor according to a third embodiment. [Figure 7] FIG. 10 is a cross-sectional view of an ultrasonic flowmeter according to a fourth embodiment. [Figure 8] FIG. 10 is a cross-sectional view of an ultrasonic sensor according to a fourth embodiment. [Figure 9]9 is a cross-sectional view taken along line aa in FIG. 8. [Figure 10] 10 is a graph showing the relationship between the axial position in the propagation rod and the surface temperature of the propagation rod. [Figure 11] 1 shows the waveform of a detection signal received by an ultrasonic element. [Figure 12] FIG. 10 is a plan view of a mounting base in a modified example. [Figure 13] 10A and 10B are a plan view and a cross-sectional view of a protrusion in a modified example. [Figure 14] 10A and 10B are a plan view and a cross-sectional view of a protrusion in a modified example. [Figure 15] FIG. 10 is a cross-sectional view of an ultrasonic sensor according to a modified example. [Figure 16] FIG. 10 is a cross-sectional view of an ultrasonic sensor according to a modified example. [Figure 17] FIG. 10 is a cross-sectional view of an ultrasonic sensor according to a modified example. [Figure 18] FIG. 10 is a cross-sectional view of an ultrasonic sensor according to a modified example. [Figure 19] FIG. 10 is a cross-sectional view of an ultrasonic sensor according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] The embodiments for carrying out the present disclosure will be described with reference to the drawings. Note that the dimensions and scale of each element in each drawing may differ from those of the actual product. Furthermore, the embodiment described below is an exemplary embodiment that may be envisioned when carrying out the present disclosure. Therefore, the scope of the present disclosure is not limited to the embodiment exemplified below.

[0009] A: First embodiment FIG. 1 is a cross-sectional view of an ultrasonic flowmeter 100 according to a first embodiment. The ultrasonic flowmeter 100 is a measurement system that measures the flow rate Q of a fluid (hereinafter referred to as "observation fluid") using ultrasonic waves, and includes a pipe 10, a first ultrasonic sensor 12_1, a second ultrasonic sensor 12_2, and a signal processing unit 14. The pipe 10 is a cylindrical structure made of a highly rigid material such as stainless steel. The observation fluid to be measured is a liquid or gas that flows unidirectionally inside the pipe 10. That is, the ultrasonic flowmeter 100 measures the flow rate Q of the observation fluid in the pipe 10.

[0010] Any type of observation fluid may be used to flow through the pipe 10, but in the first embodiment, liquid hydrogen is assumed to be the object of measurement. Liquid hydrogen has a boiling point of -253°C, which is a very low temperature. That is, in the first embodiment, the observation fluid flowing through the pipe 10 is at a very low temperature.

[0011] Each of the first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2 is a detector capable of transmitting and receiving ultrasonic waves. The first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2 are installed in the pipe 10. Specifically, the second ultrasonic sensor 12_2 is installed downstream of the first ultrasonic sensor 12_1 in the observation fluid.

[0012] The first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2 are installed in the pipe 10 with their central axes Z inclined at a predetermined angle θ with respect to the direction in which the observation fluid flows (the axial direction of the pipe 10). Therefore, ultrasonic waves transmitted from one of the first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2 pass through the observation fluid, are reflected by the inner wall surface of the pipe 10, and reach the other of the first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2, as illustrated in Fig. 1. Specifically, two states may occur: an ultrasonic wave transmitted by the first ultrasonic sensor 12_1 passes through the observation fluid in the pipe 10 and is received by the second ultrasonic sensor 12_2, and an ultrasonic wave transmitted by the second ultrasonic sensor 12_2 passes through the observation fluid in the pipe 10 and is received by the first ultrasonic sensor 12_1.

[0013] The signal processing unit 14 is a computer system that calculates the flow rate Q of the observed fluid according to the results of the operations of the first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2. Specifically, the signal processing unit 14 calculates the flow velocity V by the operation of the following equation (1) (transit time difference method), and calculates the flow rate Q of the observed fluid according to the flow velocity V and the cross-sectional area of ​​the pipe 10.

number

[0014] The symbol L in formula (1) represents the propagation distance of the ultrasonic waves transmitted between the first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2, and the symbol C in formula (1) represents the speed of sound. Furthermore, the symbol t1 in formula (1) represents the propagation time (i.e., forward propagation time) of the ultrasonic waves transmitted from the first ultrasonic sensor 12_1 to the second ultrasonic sensor 12_2 on the downstream side, and the symbol t2 represents the propagation time (i.e., backward propagation time) of the ultrasonic waves transmitted from the second ultrasonic sensor 12_2 to the first ultrasonic sensor 12_1 on the upstream side. The difference (t2-t1) between the propagation time t1 and the propagation time t2 is calculated from the waveforms of the ultrasonic waves received by each of the first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2. The signal processing unit 14 displays the flow rate Q calculated by the above procedure. The method by which the signal processing unit 14 calculates the flow rate Q of the observed fluid is not limited to the above example. Any method can be used to calculate the flow rate Q, such as a frequency shift method.

[0015] 2 is a cross-sectional view illustrating the configuration of each of the first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2. Note that the first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2 have substantially the same structure. Therefore, in the following description, the first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2 will be collectively referred to as "ultrasonic sensor 12," and a description of the ultrasonic sensor 12 will also serve as a description of both the first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2.

[0016] In the following description, the direction along the central axis Z of the ultrasonic sensor 12 will be referred to as the "axial direction." The axial direction is divided into the Z1 direction and the Z2 direction. The Z1 direction is one direction along the central axis Z, and the Z2 direction is the direction opposite to the Z1 direction. Furthermore, the direction along the circumference of an imaginary circle of any diameter centered on the central axis Z will be referred to as the "circumferential direction," and the direction of the radius of the imaginary circle will be referred to as the "radial direction." In the radial direction, the direction toward the central axis Z will be referred to as the "inner side," and the direction facing away from the central axis Z will be referred to as the "outer side."

[0017] As illustrated in FIG. 2, the ultrasonic sensor 12 includes an ultrasonic element 21, a transmission rod 22, and a support 25. The ultrasonic element 21 is a vibrator capable of transmitting and receiving ultrasonic waves. For example, a piezoelectric element is exemplified as the ultrasonic element 21. A drive circuit and a detection circuit (not shown) are connected to the ultrasonic element 21. The drive circuit is a transmission circuit that transmits ultrasonic waves by driving the ultrasonic element 21 using the inverse piezoelectric effect. The detection circuit is a reception circuit that generates a detection signal by detecting the voltage generated in the ultrasonic element 21 due to the piezoelectric effect.

[0018] The transmission rod 22 is a structure for propagating ultrasonic waves transmitted from the ultrasonic element 21 or ultrasonic waves to be received by the ultrasonic element 21. That is, the transmission rod 22 is formed of a highly rigid metal material (such as stainless steel) that can propagate ultrasonic waves.

[0019] The transmission rod 22 of the first embodiment includes an extension portion 23 and a protrusion portion 24. The extension portion 23 is a cylindrical portion extending along the central axis Z. The extension portion 23 is formed in an elongated shape including a first end E1 and a second end E2. The first end E1 is an end of the extension portion 23 located in the Z1 direction, and the second end E2 is an end of the extension portion 23 located in the Z2 direction. The ultrasonic element 21 is installed at the second end E2 of the extension portion 23.

[0020] The protruding portion 24 of the transmission rod 22 is a portion that protrudes radially outward from the outer peripheral surface of the extending portion 23. Specifically, the protruding portion 24 is an annular (i.e., brim-shaped) flange portion that surrounds the entire circumference of the extending portion 23. For example, the extending portion 23 and the protruding portion 24 are integrally formed by cutting a metal rod. However, the manufacturing method of the transmission rod 22 is arbitrary. For example, the extending portion 23 and the protruding portion 24 may be manufactured as separate bodies and then joined by welding or the like.

[0021] The protrusion 24 is provided on the extension 23 at a midpoint between the first end E1 and the second end E2 in the axial direction. The protrusion 24 includes a first surface F1, a second surface F2, and a side surface S. The first surface F1 is a surface facing the Z1 direction, and the second surface F2 is a surface facing the Z2 direction. In other words, the first surface F1 and the second surface F2 are perpendicular to the central axis Z. The side surface S is a cylindrical surface connecting the first surface F1 and the second surface F2.

[0022] The support 25 is a structure that supports the transmission rod 22. Specifically, the support 25 supports the transmission rod 22 with the first end E1 facing the inside of the pipe 10. That is, the first end E1 of the transmission rod 22 is exposed inside the pipe 10 and contacts the observation fluid in the pipe 10. An ultrasonic wave that has entered the second end E2 from the ultrasonic element 21 propagates in the Z1 direction inside the transmission rod 22 and is emitted from the first end E1 into the pipe 10. Furthermore, an ultrasonic wave that has entered the first end E1 from the observation fluid in the pipe 10 propagates in the Z2 direction inside the transmission rod 22 and is emitted from the second end E2 to reach the ultrasonic element 21.

[0023] As described above, in the first embodiment, the first end E1 of the extension portion 23 of the transmission rod 22 faces the inside of the pipe 10, and the ultrasonic element 21 is installed at the second end E2 of the extension portion 23. According to the above configuration, it is easier to ensure a sufficient distance between the observation fluid in the pipe 10 and the ultrasonic element 21, compared to, for example, a configuration in which the ultrasonic element 21 is close to the pipe 10. Therefore, a temperature gradient is ensured between the first end E1 and the second end E2, and the temperature difference between the first end E1 and the second end E2 can be sufficiently maintained. That is, propagation of the temperature of the observation fluid to the ultrasonic element 21 can be suppressed. As a result of suppressing temperature propagation, the possibility of the ultrasonic element 21 being cooled to an excessively low temperature can be reduced. Furthermore, for example, in a configuration in which the observation fluid in the pipe 10 has an extremely high temperature, the possibility of the ultrasonic element 21 being heated to an excessively high temperature can be reduced. As described above, the transmission rod 22 of the first embodiment is structured to protect the ultrasonic element 21 from excessive cooling or heating.

[0024] The support portion 25 of the first embodiment supports the protruding portion 24 of the transmission rod 22. That is, the support portion 25 is in contact with the protruding portion 24 of the transmission rod 22. Ultrasonic waves propagating within the transmission rod 22 are also propagated to the protruding portion 24. Therefore, there is a possibility that ultrasonic waves will propagate from the transmission rod 22 to the support portion 25 via the protruding portion 24.

[0025] As illustrated in FIG. 2, the support portion 25 of the first embodiment includes a mounting base 30 and a holder 40. The mounting base 30 and the holder 40 are configured as separate bodies. The mounting base 30 is a cylindrical portion connected to the pipe 10. That is, the internal space of the mounting base 30 is connected to the internal space of the pipe 10. The mounting base 30 is installed along the central axis Z. That is, the mounting base 30 is connected to the outer peripheral surface of the pipe 10 in an attitude inclined at a predetermined angle θ with respect to the direction in which the pipe 10 extends. The mounting base 30 is formed of a highly rigid metal material such as stainless steel, like the pipe 10.

[0026] Fig. 3 shows a plan view and a cross-sectional view of the mounting base 30. The plan view of Fig. 3 shows the mounting base 30 as viewed in the Z1 direction. As illustrated in Figs. 2 and 3, the mounting base 30 of the first embodiment includes a tip surface G. The tip surface G is an annular end surface of the mounting base 30 on the side opposite to the pipe 10 that faces the Z2 direction.

[0027] As illustrated in FIG. 2 , the first surface F1 of the protrusion 24 contacts the tip surface G of the mounting base 30. Therefore, a portion of the extension 23 of the transmission rod 22, including the first end E1, is inserted into the mounting base 30. Specifically, a portion of the extension 23 located in the Z1 direction relative to the first surface F1 of the protrusion 24 is inserted into the mounting base 30. That is, the portion of the extension 23, including the first end E1, is surrounded by the mounting base 30. The outer peripheral surface of the extension 23 and the inner peripheral surface of the mounting base 30 face each other at a predetermined interval over the entire circumference. Therefore, the portion of the extension 23 located in the Z1 direction relative to the protrusion 24 contacts the observation fluid in the mounting base 30. On the other hand, the portion of the extension 23 located in the Z2 direction relative to the protrusion 24 is exposed to the outside of the mounting base 30 and does not contact the observation fluid. As described above, in the first embodiment, the transmission rod 22 can be supported by bringing the first surface F1 of the protrusion 24 into contact with the tip surface G of the mounting base 30.

[0028] An attachment groove 32 and a recess C1 are formed in the tip surface G of the mounting base 30. The attachment groove 32 and the recess C1 overlap with the protrusion 24 when viewed in the axial direction. In other words, the attachment groove 32 and the recess C1 are formed in an area of ​​the tip surface G that faces the first surface F1 of the protrusion 24.

[0029] 2 and 3, the mounting groove 32 is a groove recessed into the tip surface G and formed in a circular ring shape centered on the central axis Z. A sealing seal 26 is installed in the mounting groove 32. The seal 26 is, for example, a circular metal seal. The seal 26 installed in the mounting groove 32 comes into contact with the first surface F1 of the protrusion 24, thereby sealing the space between the mounting base 30 and the protrusion 24. This prevents the observation fluid in the mounting base 30 from passing through the gap with the protrusion 24 and leaking to the outside.

[0030] The recess C1 is a groove recessed relative to the tip surface G and formed in an annular shape centered on the central axis Z. The recess C1 is formed outside the mounting groove 32. That is, the recess C1 is formed with a larger diameter than the mounting groove 32 and surrounds the mounting groove 32. The relationship between the groove width and depth of the mounting groove 32 and the recess C1 is arbitrary. For example, although FIGS. 2 and 3 illustrate an example in which the groove width of the recess C1 is greater than that of the mounting groove 32, a configuration in which the groove width of the recess C1 is less than that of the mounting groove 32 or a configuration in which the groove width of the recess C1 is equal to that of the mounting groove 32 is also conceivable. Furthermore, although FIGS. 2 and 3 illustrate an example in which the depth of the recess C1 is less than that of the mounting groove 32, a configuration in which the depth of the recess C1 is greater than that of the mounting groove 32 or a configuration in which the depth of the recess C1 is equal to that of the mounting groove 32 is also conceivable.

[0031] Further, a guide portion 33 is formed on the tip surface G of the mounting base 30. The guide portion 33 is a portion that protrudes in the Z2 direction from the peripheral edge of the tip surface G. The guide portion 33 in the first embodiment is formed in an annular shape that follows the outer circumferential edge of the tip surface G. In other words, the mounting groove 32 and the recess C1 are surrounded by the guide portion 33 when viewed in the axial direction.

[0032] The inner diameter of the guide portion 33 is substantially equal to the outer diameter of the protrusion 24. Therefore, the side surface S of the protrusion 24 contacts the inner peripheral surface of the guide portion 33 over the entire circumference. As described above, the side surface S of the protrusion 24 contacts the guide portion 33 at the tip surface G, thereby determining the position of the protrusion 24 in a plane perpendicular to the central axis Z. In other words, the guide portion 33 is a guide for positioning the protrusion 24 (and further the propagation rod 22) in a plane perpendicular to the central axis Z.

[0033] The height of the guide portion 33 relative to the tip surface G is less than the thickness of the protrusion 24. For example, a portion of the protrusion 24 that is approximately 1 mm to 2 mm thick contacts the inner circumferential surface of the guide portion 33. Therefore, a portion of the side surface S of the protrusion 24 that is located in the Z1 direction contacts the inner circumferential surface of the guide surface. In other words, compared to a configuration in which the entire side surface S of the protrusion 24 contacts the inner circumferential surface of the guide portion 33, the contact area between the protrusion 24 and the guide portion 33 is reduced. Therefore, the propagation of ultrasonic waves between the protrusion 24 and the guide portion 33 can be suppressed.

[0034] 2 is a structure that cooperates with the mounting base 30 to support the transmission rod 22 (specifically, the protrusion 24), and is fixed to the mounting base 30. The holding device 40 of the first embodiment is a nut that includes a mounting portion 41 and a base portion 42. The mounting portion 41 is a cylindrical portion that surrounds the mounting base 30. The base portion 42 is an annular portion that is located in the Z2 direction of the mounting portion 41.

[0035] The inner diameter of the base portion 42 is larger than the outer diameter of the extension portion 23 of the propagation rod 22. With the extension portion 23 of the propagation rod 22 inserted into the opening of the base portion 42, the holder 40 is fixed to the mounting base 30. For example, a thread groove formed on the outer peripheral surface of the mounting base 30 engages with a thread groove formed on the inner peripheral surface of the mounting portion 41, thereby fixing the holder 40 to the mounting base 30. In other words, with the extension portion 23 inserted into the opening of the base portion 42, the holder 40 is fastened to the mounting base 30 by rotating the holder 40 about the central axis Z.

[0036] The holder 40 of the first embodiment includes a holding surface H. The holding surface H is an annular surface of the base portion 42 facing the Z1 direction. The holding surface H can also be expressed as a step surface between the base portion 42 and the mounting portion 41. As illustrated in FIG. 2 , the holding surface H faces the tip surface G of the mounting base 30 at a distance. The protrusion 24 of the transmission rod 22 is supported between the tip surface G of the mounting base 30 and the holding surface H of the holder 40. Specifically, the tip surface G of the mounting base 30 contacts the first surface F1 of the protrusion 24 as described above, and the holding surface H of the holder 40 contacts the second surface F2 of the protrusion 24. As described above, with the protrusion 24 sandwiched between the mounting base 30 and the holder 40, the transmission rod 22 is supported by the support portion 25. In the first embodiment, the protrusion 24 can be supported by a simple configuration that utilizes the tip surface G of the mounting base 30 and the holding surface H of the holder 40.

[0037] 4 is a plan view of the protruding portion 24 of the transmission rod 22 as viewed in the Z1 direction. As illustrated in FIGS. 2 and 4, a recess C2 is formed in the second surface F2 of the protruding portion 24. Specifically, the recess C2 is formed in a region of the second surface F2 of the protruding portion 24 that overlaps with the holding surface H when viewed in the axial direction.

[0038] FIG. 4 illustrates the X and Y directions, which intersect with each other. The recess C2 is a lattice-shaped groove formed by a combination of multiple grooves extending in the X direction and multiple grooves extending in the Y direction. For example, the recess C2 is formed by knurling, which cuts the second surface F2 of the protrusion 24. The depth of the grooves constituting the recess C2 is selected so as to form an air layer that reflects ultrasonic waves with a wavelength of, for example, several tens of micrometers. For example, the depth of each groove is about 0.3 mm.

[0039] As can be understood from the above explanation, in the first embodiment, recesses C (C1, C2) are formed on the contact surface of the protrusion 24 with the support portion 25 (specifically, the second surface F2) and on the contact surface of the support portion 25 with the protrusion 24 (specifically, the tip surface G).

[0040] As described above, ultrasonic waves propagating through the transmission rod 22 may propagate from the protrusion 24 to the support 25. The ultrasonic waves propagating from the protrusion 24 to the support 25 may further reach the pipe 10. Therefore, in a configuration in which the recesses C (C1, C2) of the first embodiment are not formed (hereinafter referred to as the "comparative example"), ultrasonic waves may propagate between the first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2 only through the pipe 10 without passing through the fluid therein. The ultrasonic waves propagating only through the pipe 10 may be superimposed on the ultrasonic waves that have passed through the observation fluid in the pipe 10 and are intended to be detected, which may cause an error in measuring the flow rate Q of the observation fluid.

[0041] In contrast to the comparative example, in the first embodiment, recesses C (C1, C2) are formed at the locations where the protrusions 24 and the support parts 25 come into contact. That is, the contact area between the protrusions 24 and the support parts 25 (i.e., the area of ​​the region through which ultrasonic waves can propagate) is reduced by forming the recesses C. Therefore, according to the first embodiment, the propagation of ultrasonic waves between the protrusions 24 and the support parts 25 can be suppressed compared to the comparative example. That is, the propagation of ultrasonic waves between the first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2 via the pipe 10 and the support parts 25 can be suppressed. Therefore, the flow rate Q of the observation fluid can be measured with high accuracy.

[0042] Specifically, in the first embodiment, a recess C1 is formed in the tip surface G of the mounting base 30. That is, the contact area between the tip surface G of the mounting base 30 and the first surface F1 of the protrusion 24 is reduced by the formation of the recess C1. Therefore, compared to an embodiment in which the tip surface G of the mounting base 30 does not have the recess C1, the propagation of ultrasonic waves between the protrusion 24 and the mounting base 30 can be suppressed.

[0043] Furthermore, in the first embodiment, a recess C2 is formed on the second surface F2 of the protrusion 24. That is, the contact area between the holding surface H of the holder 40 and the second surface F2 of the protrusion 24 is reduced by the formation of the recess C2. Therefore, compared to an embodiment in which the second surface F2 of the protrusion 24 is a flat surface without any irregularities, the propagation of ultrasonic waves between the protrusion 24 and the holder 40 can be suppressed.

[0044] Incidentally, for example, if an elastic body such as rubber is interposed between the protrusion 24 and the support 25, the ultrasonic waves will be attenuated by the elastic body, which may potentially suppress the propagation of ultrasonic waves between the protrusion 24 and the support 25. However, as described above, if the observation fluid is very low or high temperature, the elastic body may be excessively cooled or heated by the heat propagation from the dry fluid, resulting in the deterioration of the elastic body. In the first embodiment, the formation of the recesses C1 and C2 suppresses the propagation of ultrasonic waves, so that the propagation of ultrasonic waves between the protrusion 24 and the mounting base 30 can be suppressed even in an environment where the observation fluid is very low or high temperature.

[0045] B: Second embodiment A second embodiment of the present disclosure will be described. Note that, for elements in the following exemplary aspects that have the same functions as those in the first embodiment, the same reference numerals as those in the first embodiment will be used, and detailed descriptions of each will be omitted as appropriate.

[0046] 5 is a cross-sectional view of the ultrasonic sensor 12 (first ultrasonic sensor 12_1 and second ultrasonic sensor 12_2) in the second embodiment. As illustrated in FIG. 5, the support portion 25 of the ultrasonic sensor 12 in the second embodiment includes a bushing 50 in addition to the same elements as in the first embodiment (the mounting base 30 and the holder 40).

[0047] The bushing 50 is an annular structure made of a highly rigid metal material such as stainless steel. The bushing 50 is interposed between the protrusion 24 and the holder 40. Specifically, the surface of the bushing 50 located in the Z1 direction contacts the second face F2 of the protrusion 24. The surface of the bushing 50 located in the Z2 direction contacts the holding face H of the holder 40. The bushing 50 is disposed concentrically with the protrusion 24 and the holder 40.

[0048] In the second embodiment, recesses C2 are formed in the second surface F2 of the protrusion 24 in an area that overlaps with the bushing 50 when viewed in the axial direction. That is, recesses C2 are formed on the surface of the protrusion 24 that comes into contact with the bushing 50. As in the first embodiment, recesses C2 are lattice-shaped grooves formed by, for example, knurling. The second embodiment also achieves the same effects as the first embodiment.

[0049] In the first embodiment, a recess C2 is formed on the second surface F2 of the protrusion 24, which contacts the holding surface H of the holder 40. As a result of the formation of the recess C2 on the second surface F2, the frictional force acting from the protrusion 24 to the holding surface H increases compared to the comparative example in which the second surface F2 is a flat surface without any irregularities. Therefore, the load required to rotate the holder 40 in the process of fixing the holder 40 to the mounting base 30 is large.

[0050] In the second embodiment, a bushing 50 is interposed between the protrusion 24 and the holder 40. That is, it is the bushing 50 that comes into contact with the second surface F2 of the protrusion 24 on which the recess C2 is formed. Therefore, even if the frictional force acting from the protrusion 24 to the bushing 50 increases due to the recess C2 on the second surface F2, the frictional force acting from the bushing 50 to the holding surface H of the holder 40 is reduced. Therefore, the second embodiment has the advantage of being able to reduce the load required to rotate the holder 40 in the process of fixing the holder 40 to the mounting base 30.

[0051] On the other hand, the first embodiment does not require the bush 50, which simplifies the configuration of the ultrasonic sensor 12. For example, according to the first embodiment, it is possible to reduce the number of parts in the ultrasonic sensor 12 and to make the device more compact.

[0052] C: Third embodiment 6 is a cross-sectional view of the ultrasonic sensor 12 (first ultrasonic sensor 12_1 and second ultrasonic sensor 12_2) in the third embodiment. The ultrasonic sensor 12 of the third embodiment differs from the first embodiment in the structure for supporting the transmission rod 22.

[0053] 6, the support part 25 of the third embodiment includes a mounting base 30 and a flange part 35. The flange part 35 is a part that protrudes radially outward from the outer peripheral surface of the mounting base 30 at the end of the mounting base 30 in the Z2 direction. The mounting base 30 and the flange part 35 are integrally formed. The support part 25 of the third embodiment does not include the retainer 40 and bushing 50 described above.

[0054] Moreover, the protrusion 24 of the third embodiment includes an inner circumferential portion 241 and an outer circumferential portion 242. The inner circumferential portion 241 corresponds to the protrusion 24 of the first and second embodiments. The first surface F1 of the inner circumferential portion 241 contacts the tip surface G of the mounting base 30. On the other hand, the outer circumferential portion 242 is an annular portion that protrudes radially outward from the outer circumferential surface of the inner circumferential portion 241. The thickness of the outer circumferential portion 242 is less than the thickness of the inner circumferential portion 241. Therefore, a step is formed between the inner circumferential portion 241 (first surface F1) and the outer circumferential portion 242. The step between the inner circumferential portion 241 and the outer circumferential portion 242 corresponds to a recess C2 formed on the first surface F1 of the protrusion 24. The recess C2 is an annular depression formed along the outer circumferential edge of the protrusion 24.

[0055] In the third embodiment, the transmission rod 22 is fixed to the support part 25 by a plurality of fasteners 60. The plurality of fasteners 60 are arranged at intervals from one another in the circumferential direction. Each fastener 60 is composed of a bolt 61 and a nut 62. The bolt 61 passes through the outer circumferential part 242 of the transmission rod 22 and the flange part 35 of the support part 25. The nut 62 is fixed to the tip of the bolt 61, thereby fixing the protrusion 24 of the transmission rod 22 to the support part 25 (flange part 35).

[0056] In the above configuration, the first surface F1 of the inner circumferential portion 241 of the protruding portion 24 contacts the tip surface G of the support portion 25, as in the first embodiment. On the other hand, the outer circumferential portion 242 of the protruding portion 24 does not contact the flange portion 35 of the support portion 25. In other words, due to the configuration in which the recess C2 is formed in the protruding portion 24, the outer circumferential portion 242 and the flange portion 35 face each other with a distance D in the axial direction.

[0057] As described above, in the third embodiment, the recess C2 is formed on the first surface F1 of the protrusion 24. That is, the contact area between the support portion 25 and the protrusion 24 is reduced by forming the recess C2. Therefore, compared to a configuration in which the first surface F1 of the protrusion 24 is a flat surface without any irregularities, it is possible to suppress the propagation of ultrasonic waves between the protrusion 24 and the support portion 25.

[0058] In the third embodiment, the outer periphery 242 of the protrusion 24 and the flange 35 of the support 25 are required to fix the transmission rod 22 to the support 25, which may result in an increase in the size of the ultrasonic sensor 12. Therefore, from the perspective of miniaturizing the ultrasonic sensor 12, a configuration in which the protrusion 24 of the transmission rod 22 is supported by the holder 40 and the support 25, as in the first and second embodiments, is preferable. Furthermore, in the third embodiment, the transmission rod 22 and the support 25 must be joined by a plurality of fasteners 60. On the other hand, in the first and second embodiments, the protrusion 24 of the transmission rod 22 is supported by attaching the holder 40 to the mounting base 30. Therefore, the first and second embodiments are advantageous from the perspective of ease of assembly of the ultrasonic sensor 12.

[0059] D: Fourth embodiment Fig. 7 is a cross-sectional view of an ultrasonic flowmeter 100 in the fourth embodiment. As illustrated in Fig. 7, each of the first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2 in the fourth embodiment includes an ultrasonic absorbing material 70 in addition to the same elements as in the first embodiment. Note that in the fourth embodiment, the configuration other than the ultrasonic absorbing material 70 is the same as in the first embodiment. Therefore, the fourth embodiment also achieves the same effects as in the first embodiment.

[0060] 8 is a cross-sectional view of the ultrasonic sensors 12 (12_1, 12_2) according to the fourth embodiment. As illustrated in FIG. 8, the ultrasonic absorber 70 is a cylindrical member that covers part of the outer circumferential surface of the extension portion 23 of the transmission rod 22. The outer diameter of the ultrasonic absorber 70 is smaller than the outer diameter of the protrusion 24. However, a configuration in which the outer diameter of the ultrasonic absorber 70 is equal to the outer diameter of the protrusion 24 or a configuration in which the outer diameter of the ultrasonic absorber 70 is larger than the outer diameter of the protrusion 24 is also conceivable.

[0061] 8, the ultrasonic waves transmitted from the ultrasonic element 21 include a component that travels in the axial direction within the extension portion 23 as well as a component that travels in a direction oblique to the axial direction. The ultrasonic absorber 70 absorbs the ultrasonic waves that are emitted to the outside from the outer circumferential surface of the extension portion 23 during propagation through the propagation rod 22. Note that while the above description has focused on the ultrasonic waves transmitted by the ultrasonic element 21, the ultrasonic waves directed toward the ultrasonic element 21 similarly include a component that travels in the axial direction within the extension portion 23 as well as a component that travels in a direction oblique to the axial direction.

[0062] The ultrasonic absorber 70 is formed of, for example, a rubber material containing a metal material. Examples of rubber materials that can be used as the main material of the ultrasonic absorber 70 include various rubber materials such as silicone rubber (SR), butyl rubber (IIR), ethylene propylene diene rubber (EPDM), urethane rubber (U), polyurethane rubber (PU), chloroprene rubber (CR), and fluororubber (FKM).

[0063] The metal material contained in the rubber material is, for example, a material with a high density or specific gravity in order to bring the acoustic impedance closer to that of the transmission rod 22. For example, a rubber material containing a heavy metal such as tungsten (W) is exemplified as the material for the ultrasound absorber 70. The content of the metal material is selected appropriately. For example, when tungsten is used as the metal material, it is mixed into the rubber material at a content of 20% to 70% by weight. Note that the ultrasound absorber 70 may be formed from a single rubber material that does not contain any metal material.

[0064] As described above, in the fourth embodiment, since the rubber material constituting the ultrasonic absorber 70 contains a metal material, it is easier to ensure sufficient ultrasonic wave absorption function of the ultrasonic absorber 70 compared to a configuration that does not contain a metal material. In particular, in the fourth embodiment, since the rubber material constituting the ultrasonic absorber 70 contains high-density or high-specific-gravity tungsten, it is possible to ensure sufficient ultrasonic wave absorption function of the ultrasonic absorber 70.

[0065] FIG. 9 is a cross-sectional view taken along line aa in FIG. 8. As illustrated in FIG. 9, the ultrasound-absorbing material 70 is formed by winding an ultrasound-absorbing sheet 71 made of one of the materials exemplified above around the extending portion 23. The ultrasound-absorbing sheet 71 is a layered or film-like member formed to a predetermined width. Specifically, the ultrasound-absorbing material 70 is formed by winding the ultrasound-absorbing sheet 71 around the extending portion 23 multiple times. For example, an ultrasound-absorbing sheet 71 having a thickness of 0.5 mm to 1 mm is wound two to three times around an extending portion 23 having a diameter of 10 mm to 20 mm. Thus, the ultrasound-absorbing material 70 is formed by laminating multiple layers of ultrasound-absorbing sheets 71. The number of turns of the ultrasound-absorbing sheet 71 may be changed as desired.

[0066] A filler such as grease (not shown) is filled between the ultrasonic absorber 70 and the transmission rod 22 (extension portion 23) and between each layer of the ultrasonic absorber 70. The application of the filler prevents air from remaining, thereby preventing ultrasonic waves from being reflected toward the central axis Z at the interface between the transmission rod 22 and the ultrasonic absorber 70 or inside the ultrasonic absorber 70. The filler may be omitted.

[0067] As illustrated in FIG. 8, the ultrasonic absorber 70 covers a portion of the outer peripheral surface of the extending portion 23 on the second end E2 side. Specifically, the ultrasonic absorber 70 covers a region of the outer peripheral surface of the extending portion 23 between a first position P1 and a second position P2 in the axial direction. The first position P1 is a position spaced a predetermined distance from the support portion 25 in the direction toward the second end E2 (Z2 direction). The second position P2 is a position closer to the second end E2 than the first position P1. Specifically, the second position P2 is the position of the second end E2. As illustrated in the above example, the ultrasonic absorber 70 covers a portion of the outer peripheral surface of the extending portion 23 between the second end E2 and the protruding portion 24. The total length Lz of the ultrasonic absorber 70 in FIG. 8 is the distance between the first position P1 and the second position P2 in the axial direction.

[0068] Fig. 10 is a graph showing the relationship between the axial position on the transmission rod 22 and the surface temperature of the transmission rod 22. The horizontal axis of Fig. 10 corresponds to the distance from the second end E2 of the transmission rod 22 (specifically, the installation surface of the ultrasonic element 21). As described above, the transmission rod 22 is cooled by the observation fluid in the piping 10, and therefore the surface temperature of the transmission rod 22 decreases as the position on the transmission rod 22 approaches the first end E1 in the axial direction.

[0069] The temperature Tmin in Figure 10 is the minimum usable temperature of the rubber material used to form the ultrasound absorber 70. The minimum usable temperature Tmin is the lower limit (low temperature limit) of the usable temperature range defined in the specifications of the rubber material. In other words, the minimum usable temperature Tmin is the lowest temperature at which the material can be used while maintaining mechanical properties such as flexibility or elasticity. The allowable range R in Figure 10 is the range in which the surface temperature of the transmission rod 22 exceeds the minimum usable temperature Tmin.

[0070] The ultrasonic absorber 70 is installed in a portion of the extending portion 23 within the allowable range R. That is, the total length Lz of the ultrasonic absorber 70 in the axial direction is set to a dimension less than the upper limit value Rmax of the allowable range R (Lz < Rmax). According to the above configuration, the temperature of the portion of the extending portion 23 covered by the ultrasonic absorber 70 exceeds the minimum usable temperature Tmin of the rubber material constituting the ultrasonic absorber 70. That is, it is possible to avoid the rubber material of the ultrasonic absorber 70 being cooled to a temperature below the minimum usable temperature Tmin. Therefore, the possibility that the ultrasonic absorber 70 is hardened and damaged due to excessive cooling can be reduced.

[0071] As described above, in the fourth embodiment, since at least a part of the outer peripheral surface of the extending portion 23 is covered by the ultrasonic absorber 70, the ultrasonic waves that reach the outer peripheral surface of the extending portion 23 in the process of propagating inside the extending portion 23 are absorbed by the ultrasonic absorber 70. That is, the reflection of ultrasonic waves on the outer peripheral surface of the extending portion 23 is suppressed, and as a result, the multiple reflection of ultrasonic waves inside the extending portion 23 is suppressed. Therefore, noise components caused by the multiple reflection of ultrasonic waves can be suppressed. According to the above configuration, since the quality of the detection signal (for example, the S / N ratio) is improved, the flow rate Q of the observation fluid in the pipe 10 can be measured with high accuracy.

[0072] FIG. 11 is a waveform of a detection signal received by the ultrasonic element 21 of the ultrasonic sensor 12 on the receiving side. The detection signal of the first embodiment where the ultrasonic absorber 70 is not installed and the detection signal of the fourth embodiment where the ultrasonic absorber 70 is installed are shown together.

[0073] According to the fourth embodiment, as a result of suppressing the multiple reflection of ultrasonic waves by the ultrasonic absorber 70, it can be confirmed from FIG. 11 that the S / N ratio is improved compared to the first embodiment where the ultrasonic absorber 70 is not installed. Specifically, the S / N ratio is improved by about 10 dB. Therefore, according to the fourth embodiment, the flow rate Q of the observation fluid can be measured with higher accuracy compared to the first embodiment.

[0074] Furthermore, in the fourth embodiment, since the ultrasonic absorber 70 is located between the second end E2 and the protruding portion 24, the temperature of the observation fluid can be prevented from propagating to the ultrasonic absorber 70, compared to, for example, a configuration in which the ultrasonic absorber 70 extends to a position closer to the first end E1 than the protruding portion 24. That is, excessive cooling of the ultrasonic absorber 70 is prevented. Therefore, the possibility of deterioration in the characteristics or damage of the ultrasonic absorber 70 due to excessive cooling can be reduced. In particular, in the fourth embodiment, the ultrasonic absorber 70 is located between a first position P1 spaced from the support portion 25 toward the second end E2 and a second position P2 further closer to the second end E2. That is, it is easy to ensure a sufficient distance between the observation fluid in the piping 10 and the ultrasonic absorber 70. Therefore, the aforementioned effect of reducing the possibility of deterioration in the characteristics or damage of the ultrasonic absorber 70 due to excessive cooling is particularly remarkable.

[0075] E: Modified Example Specific modified embodiments that can be added to each of the embodiments exemplified above are exemplified below. Two or more embodiments arbitrarily selected from the following examples may be appropriately combined within the scope of not being mutually contradictory.

[0076] (1) In the above-described embodiments, a configuration in which an annular recess C1 is formed on the tip surface G of the mounting base 30 has been exemplified, but the shape of the recess C1 can be changed as desired. For example, as illustrated in FIG. 12 , the recess C1 on the tip surface G may be a lattice-shaped groove formed by combining a plurality of grooves extending in the X direction and a plurality of grooves extending in the Y direction, similar to the recess C2 in the above-described embodiments. In addition, the recess C1 does not need to be formed along the entire circumference of the tip surface G. For example, the recess C1 may be formed in each of a plurality of ranges arranged in the circumferential direction of the tip surface G.

[0077] (2) In the above-described embodiments, the configuration in which the lattice-shaped recesses C2 are formed on the second surface F2 of the protrusion 24 has been exemplified, but the shape of the recesses C2 may be changed as desired. For example, as illustrated in FIG. 13, the recesses C2 of the protrusion 24 may be annular grooves formed concentrically with the protrusion 24, similar to the recesses C1 in the above-described embodiments. As illustrated in FIG. 14, a plurality of annular recesses C2 may be formed concentrically on the second surface F2. In addition, the recesses C1 do not need to be formed along the entire circumference of the protrusion 24. For example, the recesses C2 may be formed in each of a plurality of ranges arranged circumferentially on the second surface F2.

[0078] (3) In the above-described embodiments, the recess C1 is formed on the tip surface G of the mounting base 30 facing the protrusion 24. However, the location where the recess C1 is formed is not limited to the above examples. For example, as illustrated in FIG. 15, the recess C1 may be formed on the holding surface H of the holder 40 facing the protrusion 24. The recess C1 may be formed on both the tip surface G and the holding surface H. Furthermore, as illustrated in FIG. 16, the recess C1 may be formed on the surface of the bushing 50 facing the protrusion 24. As can be understood from the above examples, the recess C1 is collectively expressed as the recess C formed on the surface of the support portion 25 that contacts the protrusion 24 (specifically, the tip surface G, the holding surface H, and the surface of the bushing 50). The recess C1 is an example of a "first recess."

[0079] (4) In the above-described embodiments, the recess C2 is formed on the second surface F2 of the protrusion 24 facing the holder 40 (or bushing 50), but the location where the recess C2 is formed is not limited to the above examples. For example, as illustrated in FIG. 17, the recess C2 may be formed on the first surface F1 of the protrusion 24 facing the mounting base 30 (tip surface G). As can be understood from the above examples, the recess C2 is collectively expressed as the recess C formed on the contact surface (specifically, the first surface F1 and the second surface F2) of the protrusion 24 that contacts the support portion 25. The "recess C2" is an example of a "second recess."

[0080] (5) In the above-described embodiments, a configuration in which a recess C1 is formed in the support portion 25 and a recess C2 is formed in the protrusion 24 is illustrated, but one of the recess C1 and the recess C2 may be omitted. As can be understood from the above examples, in one aspect of the present disclosure, a recess C is formed in at least one of the contact surface of the protrusion 24 with the support portion 25 (e.g., second surface F2) and the contact surface of the support portion 25 with the protrusion 24 (e.g., tip surface G).

[0081] (6) In the fourth embodiment, an example is given of a form in which the ultrasonic absorbing material 70 is formed by wrapping the ultrasonic absorbing sheet 71 around the extension portion 23, but the method of forming the ultrasonic absorbing material 70 is not limited to the above example and may be changed as desired.

[0082] For example, an ultrasonic absorbing material 70 formed into a cylindrical shape by a molding technique such as injection molding may be placed on the extension portion 23 of the transmission rod 22. For example, the extension portion 23 is inserted into one opening of a cylindrical ultrasonic absorbing material 70 that is open at both ends. Alternatively, the ultrasonic absorbing material 70 may be formed by applying a rubber material containing a metal material to a predetermined film thickness on the outer peripheral surface of the extension portion 23.

[0083] In the fourth embodiment, the ultrasonic absorbing material 70 is formed by winding the ultrasonic absorbing sheet 71 around multiple times, so that the thickness of the ultrasonic absorbing sheet 71 can be controlled to a thickness that is easy to deform, while forming the ultrasonic absorbing material 70 with a predetermined thickness. Since rubber materials containing metal materials are difficult to deform, the configuration in which the ultrasonic absorbing material 70 is formed by winding the ultrasonic absorbing sheet 71 is particularly effective.

[0084] (7) In the above-described embodiments, the ultrasonic element 21 is installed on the end surface of the extension portion 23. However, as illustrated in FIG. 18, the ultrasonic element 21 may be installed inside an installation hole 27 formed on the end surface of the extension portion 23 in the Z2 direction. The installation hole 27 is, for example, a bottomed hole formed in a circular shape in a plan view and having a predetermined depth. The opening of the installation hole 27 in which the ultrasonic element 21 is installed is closed by, for example, a closing portion 28. As illustrated in FIG. 18, the ultrasonic absorbing material 70 may be formed to surround the ultrasonic element 21 in addition to the extension portion 23.

[0085] (8) In the fourth embodiment, the thickness of the ultrasonic absorber 70 (i.e., the distance between the inner peripheral surface and the outer peripheral surface) is constant over the entire length Lz. However, the thickness of the ultrasonic absorber 70 may vary depending on the position in the axial direction. For example, as shown in Fig. 19, a configuration is exemplified in which the thickness of the ultrasonic absorber 70 at a first position P1 is smaller than the thickness at a second position P2. Specifically, the thickness of the ultrasonic absorber 70 decreases stepwise or continuously in the Z1 direction.

[0086] (9) In the fourth embodiment, the ultrasonic absorber 70 covers a portion of the outer peripheral surface of the extension portion 23. However, the range of the outer peripheral surface of the extension portion 23 that is covered by the ultrasonic absorber 70 is not limited to the above example. For example, the entire outer peripheral surface of the extension portion 23 from the first end E1 to the second end E2 may be covered by the ultrasonic absorber 70.

[0087] (10) In the fourth embodiment, Configuration 1: A configuration in which a recess C (C1, C2) is formed on at least one of a contact surface (specifically, the second surface F2) of the protrusion 24 with the support portion 25 and a contact surface (specifically, the tip surface G) of the support portion 25 with the protrusion 24; Configuration 2: A configuration in which an ultrasonic absorbing material 70 is provided to cover at least a part of the outer peripheral surface of the extension portion 23. However, in the ultrasonic flowmeter 100 having the configuration 2, the configuration 1 is not essential and may be omitted.

[0088] (11) In the above-described embodiments, the first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2 both include the structure 1. However, only one of the first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2 may be provided with the structure 1. Furthermore, in the fourth embodiment, the first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2 both include the structure 2. However, only one of the first ultrasonic sensor 12_1 and the second ultrasonic sensor 12_2 may be provided with the structure 2 (ultrasonic absorbing material 70).

[0089] (12) The term "nth" (n is a natural number) in this application is used only as a formal and convenient label to distinguish each element in the description and does not have any substantive meaning. Therefore, there is no room for restrictive interpretation of the position of each element or the order of production, etc., based on the term "nth."

[0090] F: Notes From the above-described exemplary embodiments, the following configurations can be understood, for example.

[0091] An ultrasonic flowmeter according to one aspect (aspect 1) of the present disclosure is an ultrasonic flowmeter for measuring the flow rate of a fluid in a pipe, comprising a first ultrasonic sensor and a second ultrasonic sensor installed in the pipe. Each of the first ultrasonic sensor and the second ultrasonic sensor includes a rod-shaped extension having a first end and a second end, an ultrasonic element installed at the second end, a protrusion protruding from the outer circumferential surface of the extension, and a support supporting the protrusion with the first end facing the inside of the pipe. A recess is formed on at least one of the contact surface of the protrusion with the support and the contact surface of the support with the protrusion. In this aspect, the first end of the extension faces the inside of the pipe and the ultrasonic element is installed at the second end of the extension. This makes it easier to ensure a distance between the fluid in the pipe and the ultrasonic element compared to, for example, a configuration in which the ultrasonic element is installed in the pipe. Therefore, propagation of the temperature of the fluid to the ultrasonic element can be suppressed. Furthermore, a recess is formed on at least one of the contact surface of the protrusion with the support and the contact surface of the support with the protrusion. Therefore, it is possible to prevent ultrasonic waves from propagating between the first ultrasonic sensor and the second ultrasonic sensor via the piping and the support portion.

[0092] In a specific example (Aspect 2) of Aspect 1, the support portion includes a cylindrical mounting base connected to the pipe, a portion of the extension portion including the first end is inserted into the mounting base, and the protrusion portion includes a first surface that contacts a tip end surface of the mounting base. In the above aspect, the protrusion portion is supported by contacting the first surface with the tip end surface of the mounting base.

[0093] In a specific example (Aspect 3) of Aspect 2, the recess includes a first recess formed in a region of the tip surface facing the first surface. In this aspect, propagation of ultrasonic waves between the protrusion and the mounting base can be suppressed more effectively than in an embodiment in which no recess is formed in the tip surface of the mounting base.

[0094] In a specific example (Aspect 4) of Aspect 2 or Aspect 3, the mounting base includes a guide portion protruding from the peripheral edge of the tip end surface, and a side surface of the protrusion contacts the guide portion. In the above aspect, by contacting the side surface of the protrusion with the guide portion on the tip end surface, the protrusion can be positioned in a direction perpendicular to the central axis of the extension portion.

[0095] In a specific example (Aspect 5) of any of Aspects 2 to 4, the support portion includes a holder fixed to the mounting base, and the protrusion is supported between the tip surface of the mounting base and a holding surface of the holder that faces the tip surface. In the above aspects, the protrusion can be supported by a simple configuration that utilizes the tip surface of the mounting base and the holding surface of the holder.

[0096] In a specific example (Aspect 6) of any of Aspects 2 to 5, the recess includes a second recess formed on a second surface of the protrusion that faces the holding surface. In the above aspects, propagation of ultrasonic waves between the protrusion and the holder can be suppressed more effectively than in an embodiment in which no recess is formed on the second surface of the protrusion.

[0097] In a specific example of aspect 6, the support portion further includes a bushing interposed between the protrusion and the holder, and the second recess is formed on a surface of the protrusion that contacts the bushing. In this aspect, the frictional force acting on the holder is reduced compared to a configuration in which the holder contacts the contact surface on which the second recess is formed. Therefore, for example, when the holder is fixed to the mounting base by rotation, the load required to rotate the holder can be reduced.

[0098] In a specific example (Aspect 8) of any of Aspects 1 to 7, each of the first ultrasonic sensor and the second ultrasonic sensor further includes an ultrasonic absorbing material covering at least a portion of the outer peripheral surface of the extension portion. According to the above aspect, since at least a portion of the outer peripheral surface of the extension portion is covered with the ultrasonic absorbing material, ultrasonic waves that reach the outer peripheral surface of the extension portion while propagating inside the extension portion are absorbed by the ultrasonic absorbing material. In other words, reflection of ultrasonic waves at the outer peripheral surface of the extension portion is suppressed, and as a result, multiple reflection of ultrasonic waves inside the extension portion is suppressed. Therefore, noise components caused by multiple reflection of ultrasonic waves inside the extension portion can be suppressed. According to the above configuration, the quality of the detection signal (e.g., S / N ratio) is improved, and the flow rate of fluid in the pipe can be measured with high accuracy.

[0099] In a specific example of aspect 8 (aspect 9), the ultrasonic absorbing material covers the outer peripheral surface of the extension portion between the second end and the protruding portion. In the above aspect, since the ultrasonic absorbing material is located between the second end and the protruding portion, it is possible to suppress the temperature of the fluid in the piping from being transmitted to the ultrasonic absorbing material, compared to a configuration in which the ultrasonic absorbing material extends to a position closer to the first end than the protruding portion. In other words, excessive cooling of the ultrasonic absorbing material is suppressed. Therefore, it is possible to reduce the possibility of deterioration of the properties or damage to the ultrasonic absorbing material due to excessive cooling.

[0100] In another example (Aspect 10) of Aspect 9, the ultrasonic absorbing material covers an area of ​​the outer surface of the extension portion between a first position spaced from the support portion toward the second end and a second position closer to the second end than the first position. In the above aspect, the ultrasonic absorbing material is located between the first position spaced from the support portion toward the second end and the second position closer to the second end. In other words, it is easy to ensure a sufficient distance between the fluid in the piping and the ultrasonic absorbing material. Therefore, the aforementioned effect of reducing the possibility of deterioration or damage to the ultrasonic absorbing material due to excessive cooling is particularly significant.

[0101] In a specific example (Aspect 11) of any of Aspects 8 to 10, the ultrasonic absorbing material is formed of a rubber material containing a metal material. In the above aspects, since the rubber material constituting the ultrasonic absorbing material contains a metal material, it is easier to ensure that the ultrasonic absorbing material has a sufficient function of absorbing ultrasonic waves compared to a configuration that does not contain a metal material.

[0102] In a specific example (Aspect 12) of Aspect 11, the metal material contains tungsten. In the above aspect, the rubber material constituting the ultrasonic absorber contains tungsten, which has a high density or a high specific gravity, so that the ultrasonic absorber can sufficiently ensure its ability to absorb ultrasonic waves.

[0103] In a specific example (Aspect 13) of any of Aspects 8 to 12, the ultrasonic absorbing material is formed by winding an ultrasonic absorbing sheet around the extending portion multiple times. In the above aspects, since the ultrasonic absorbing material is formed by winding the ultrasonic absorbing sheet multiple times, it is possible to form an ultrasonic absorbing material of a predetermined thickness while restricting the thickness of the ultrasonic absorbing sheet to a thickness that is easy to deform. Because rubber materials containing metal materials are difficult to deform, a configuration in which the ultrasonic absorbing material is formed by winding an ultrasonic absorbing sheet is particularly effective.

[0104] However, there may be cases where the fluid to be measured is very low or high temperature. From the viewpoint of suppressing the propagation of the temperature of the fluid to the ultrasonic element, for example, a configuration in which the ultrasonic element is installed at the end of an extension part that protrudes from a pipe through which the fluid flows is conceivable. With this configuration, it is easy to ensure the distance between the fluid in the pipe and the ultrasonic element, so that the propagation of the temperature of the fluid to the ultrasonic element can be suppressed.

[0105] However, ultrasonic waves transmitted from the ultrasonic element may be multiple-reflected within the extension portion. Therefore, the detection signal generated by receiving the ultrasonic waves includes noise components due to multiple reflections within the extension portion. The noise components described above may reduce the accuracy of measuring the flow rate of a fluid. In consideration of the above circumstances, one aspect of the present disclosure aims to suppress a reduction in accuracy due to multiple reflections of ultrasonic waves in a configuration that measures the flow rate of a fluid using ultrasonic waves.

[0106] In order to solve the above problems, an ultrasonic flowmeter according to one embodiment of the present disclosure is an ultrasonic flowmeter that measures the flow rate of a fluid in a pipe, and includes a first ultrasonic sensor and a second ultrasonic sensor installed in the pipe, and each of the first ultrasonic sensor and the second ultrasonic sensor includes a rod-shaped extension portion having a first end and a second end, an ultrasonic element installed at the second end, a protrusion protruding from the outer peripheral surface of the extension portion, a support portion that supports the protrusion with the first end facing into the pipe, and an ultrasonic absorbing material that covers at least a portion of the outer peripheral surface of the extension portion.

[0107] According to the above-described aspect, at least a portion of the outer peripheral surface of the extension portion is covered with an ultrasonic absorbing material, and ultrasonic waves that reach the outer peripheral surface of the extension portion while propagating through the extension portion are absorbed by the ultrasonic absorbing material. That is, reflection of ultrasonic waves at the outer peripheral surface of the extension portion is suppressed, and as a result, multiple reflection of ultrasonic waves inside the extension portion is suppressed. Therefore, noise components caused by multiple reflection of ultrasonic waves inside the extension portion can be suppressed. According to the above-described configuration, the quality of the detection signal (e.g., S / N ratio) is improved, and the flow rate of the fluid in the pipe can be measured with high accuracy. [Explanation of symbols]

[0108] 100... ultrasonic flow meter, 10... piping, 12... ultrasonic sensor, 12_1... first ultrasonic sensor, 12_2... second ultrasonic sensor, 14... signal processing unit, 21... ultrasonic element, 22... transmission rod 22, 23... extension portion, 24... protrusion portion, 241... inner peripheral portion, 242... outer peripheral portion, 25... support portion, 26... seal, 30... mounting base, 32... mounting groove, 33... guide portion, 35... protrusion portion, 40... holder, 41... mounting portion, 42... base portion, 50... bushing, 70... ultrasonic absorbing material, 71... ultrasonic absorbing sheet.

Claims

1. An ultrasonic flow meter for measuring the flow rate of a fluid in a pipe, a first ultrasonic sensor and a second ultrasonic sensor installed on the piping; Each of the first ultrasonic sensor and the second ultrasonic sensor includes: a rod-shaped extension portion including a first end and a second end; an ultrasonic element disposed at the second end; a protruding portion protruding from an outer peripheral surface of the extending portion; a support portion that supports the protrusion portion with the first end facing into the pipe, A recess is formed on at least one of a contact surface of the protrusion with the support portion and a contact surface of the support portion with the protrusion. Ultrasonic flow meter.

2. The support portion is a cylindrical mounting base connected to the piping; a portion of the extension portion including the first end is inserted into the mounting base; The protrusion includes a first surface that contacts the tip surface of the mounting base.

2. The ultrasonic flowmeter of claim 1.

3. The recess includes a first recess formed in a region of the tip surface facing the first surface.

3. The ultrasonic flowmeter of claim 2.

4. the mounting base includes a guide portion protruding from a peripheral edge portion of the tip surface, The side surface of the protrusion contacts the guide portion.

4. The ultrasonic flowmeter according to claim 2 or 3.

5. The support portion is a holder fixed to the mounting base, The protrusion is supported between the tip surface of the mounting base and a holding surface of the holder that faces the tip surface.

3. The ultrasonic flowmeter of claim 2.

6. The recess includes a second recess formed on a second surface of the protrusion that faces the holding surface.

6. The ultrasonic flowmeter of claim 5.

7. The support portion is a bushing interposed between the protrusion and the retainer; The second recess is formed on the surface of the protrusion that comes into contact with the bush.

7. The ultrasonic flowmeter of claim 6.

8. Each of the first ultrasonic sensor and the second ultrasonic sensor includes: The ultrasonic wave absorbing material further includes an ultrasonic absorbing material that covers at least a part of the outer peripheral surface of the extension portion.

2. The ultrasonic flowmeter of claim 1.

9. The ultrasonic absorbing material is The outer peripheral surface of the extending portion between the second end and the protruding portion is covered.

9. The ultrasonic flowmeter of claim 8.

10. The ultrasonic absorbing material is The extension portion covers an area of ​​the outer peripheral surface between a first position spaced apart from the support portion toward the second end and a second position closer to the second end than the first position. The ultrasonic flowmeter of claim 9.

11. The ultrasonic absorbing material is Made of rubber material containing metal material 9. The ultrasonic flowmeter of claim 8.

12. The metallic material includes tungsten. The ultrasonic flow meter of claim 11.

13. The ultrasonic absorbing material is formed by wrapping an ultrasonic absorbing sheet around the extension portion multiple times. The ultrasonic flowmeter according to claim 11 or claim 12 (any of claims 8 to 10).

14. An ultrasonic flow meter for measuring the flow rate of a fluid in a pipe, a first ultrasonic sensor and a second ultrasonic sensor installed on the piping; Each of the first ultrasonic sensor and the second ultrasonic sensor includes: a rod-shaped extension portion including a first end and a second end; an ultrasonic element disposed at the second end; a protruding portion protruding from an outer peripheral surface of the extending portion; a support portion that supports the protrusion portion with the first end facing into the pipe; an ultrasonic absorbing material covering at least a portion of the outer circumferential surface of the extension portion; Ultrasonic flow meter.

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