Ultrasonic flowmeter

Abstract

[Problem] To provide a technology making it possible to increase a passable flow rate without reducing measurement accuracy as compared with the prior art. [Solution] An ultrasonic flowmeter 10A of the present embodiment includes: a housing 11 including an internal flow passage R1 through which a fluid passes; and a measurement pipe 21 disposed in the internal flow passage R1. The internal flow passage R1 comprises: a double flow passage part 11R divided into a measurement flow passage R2 inside the measurement pipe 21 and a non-measurement flow passage R3 outside the measurement pipe 21; a pair of ultrasonic sensors 70 disposed facing each other sandwiching the measurement pipe 21 in an axial direction thereof; and a flow rate calculation unit 93 for calculating the flow rate of the fluid in the entire internal flow passage R1 on the basis of the flow rate of the fluid in the measurement flow passage 21 which was obtained from the propagation time of ultrasonic waves between the pair of ultrasonic sensors 70.

Description

ultrasonic flow meter

[0001] The present disclosure relates to an ultrasonic flow meter that measures the flow rate of a fluid based on the propagation time of ultrasonic waves propagating through a fluid between a pair of ultrasonic sensors.

[0002] In general, an ultrasonic flowmeter is configured such that a pair of ultrasonic sensors are arranged so that the propagation path of ultrasonic waves between them overlaps with the measurement flow path through which the fluid passes (see, for example, Patent Documents 1 and 2).

[0003] Japanese Patent No. 6141556 (Figure 1, paragraph

[0033] ) Japanese Patent Laid-Open No. 2008-128841 (Figure 1, paragraph

[0046] ).

[0004] However, in conventional ultrasonic flow meters, the larger the cross-sectional area of ​​the measurement flow path, the less fluid resistance there is and the greater the flow rate that can pass through, but ultrasonic waves have the problem of being unable to capture the cross-sectional average flow velocity, which can easily lead to a decrease in measurement accuracy. Therefore, this application discloses a technology that can increase the flow rate that can pass through without decreasing measurement accuracy compared to conventional technology.

[0005] A first aspect of the invention of the present disclosure is an ultrasonic flow meter comprising: a housing having an internal flow path through which a fluid passes; a measuring tube arranged within the internal flow path; a double flow path section in which the internal flow path is divided into a measurement flow path inside the measuring tube and a non-measurement flow path outside the measuring tube; a pair of ultrasonic sensors arranged upstream and downstream of the measuring tube and facing each other across the measurement flow path; and a flow rate calculation section that calculates the flow rate of fluid in the entire internal flow path based on the flow rate of fluid in the measurement flow path obtained from the propagation time of ultrasonic waves between the pair of ultrasonic sensors.

[0006] 1 is a side cross-sectional view of an ultrasonic flowmeter according to a first embodiment of the present disclosure. FIG. 2 is a perspective view of the ultrasonic flowmeter. FIG. 3 is an exploded perspective view of a core assembly. FIG. 4A is a perspective view of a holder seen from the opposite side to a measuring pipe. FIG. 4B is a perspective view of the holder seen from the measuring pipe side. FIG. 5 is an enlarged side cross-sectional view of a core assembly.

[0007] [First embodiment] Hereinafter, a first embodiment of an ultrasonic flowmeter 10A according to the present disclosure will be described with reference to Figures 1 to 7. As shown in Figure 1, the housing 11 of the ultrasonic flowmeter 10A according to this embodiment has a triple-pipe structure in which an enclosing pipe 50 is provided at the center of a cylindrical case 30, and a measuring pipe 21 is provided at the center of the enclosing pipe 50.

[0008] The case 30 has a pair of pipe connection portions 43 at both ends. As shown in FIG. 2 , each pipe connection portion 43 has, for example, a plurality of threaded holes 43N on its end surface and an enlarged diameter portion 44 whose inner diameter is stepped. As shown in FIG. 1 , a pipe flange 99F provided at the end of a pipe 99 is placed on the pipe connection portion 43, and an annular protrusion 99T protruding from the inner edge of the pipe flange 99F is fitted into the enlarged diameter portion 44. Furthermore, the pipe flange 99F and the pipe connection portion 43 are screwed together with a sealing member (not shown) sandwiched between the pipe 99 and the pipe connection portion 43. This allows the ultrasonic flowmeter 10A to connect the pair of pipes 99, and fluid flowing through the pipes 99 passes through the internal flow path R1 within the housing 11. In this embodiment, the fluid to be measured by the ultrasonic flowmeter 10A is, for example, a gas primarily composed of hydrogen gas.

[0009] The case 30 is divided into three parts in the axial direction: a case main body 30H and a pair of connecting tubes 40 fitted and fixed to both ends thereof. An O-ring 80A seals the gap between the case main body 30H and the connecting tubes 40. Furthermore, multiple types of connecting tubes 40 with different sizes of pipe connection portion 43 are available, and any type of connecting tube 40 can be assembled to the case main body 30H to accommodate multiple pipes 99 with different sizes or connection structures.

[0010] The connection structure between the pipe connection portion 43 and the pipe 99 is not limited to the structure described above. Furthermore, the pipe connection portion 43 may be provided with a plurality of types that differ not only in size but also in connection structure in order to accommodate various connection structures with the pipe 99. Furthermore, although the connection tube 40 is a straight type, the invention is not limited to this and may be an elbow type. Furthermore, although the case 30 is divided into a pair of connection tubes 40 and the case main body 30H in this embodiment, the case 30 does not have to be divided.

[0011] 1, a partition wall 32 is provided in the axial center of the case 30, and the partition wall 32 divides the interior of the case 30 into a first chamber 33 on one side of the pipe connection portion 43 and a second chamber 34 on the other side of the pipe connection portion 43. Also, as shown in Fig. 2, parallel flat surfaces 31A and 31B are provided at two locations on the outer periphery of the case main body 30H, and one of the flat surfaces 31A has a cable insertion hole 39 communicating with the first chamber 33 and a cable insertion hole 39 communicating with the second chamber 34. Hereinafter, the side having the one flat surface 31A will be referred to as the upper side, and the side having the other flat surface 31B will be referred to as the lower side, and the opposing direction of the pair of flat surfaces 31A and 31B will be referred to as the up-down direction.

[0012] 1, a control box 91 is fixed to the flat surface 31A. Cables 70C extending from a pair of ultrasonic sensors 70 (described later) are passed through a pair of cable insertion holes 39 and connected to a circuit board 90 inside the control box 91. After the cables 70C have been passed through the cable insertion holes 39, the holes are sealed by being filled with, for example, a potting material.

[0013] A through hole 35 is formed in the partition wall 32 and is centered on the central axis of the case 30, and an adapter ring 53 is fitted inside the through hole 35. The adapter ring 53 has O-rings on its inner and outer peripheral surfaces and is equipped with a flange 54 that projects laterally from one end, and is overlaid on one surface of the partition wall 32 and screwed in place. The surrounding pipe 50 is fitted inside the adapter ring 53 and passes through the partition wall 32.

[0014] The surrounding tube 50 has a shape in which a flange 52 protrudes laterally from the middle part in the axial direction of a cylindrical body, and the flange 52 is placed on the end face of the adapter ring 53 on the side having the flange 54 and screwed in place. The surrounding tube 50 is arranged so that, for example, the center position in the longitudinal direction thereof overlaps the center position in the longitudinal direction of the case 30.

[0015] The surrounding pipe 50 is divided into three parts in the axial direction: a surrounding pipe main body 50H and a pair of end rings 61 fitted and fixed to both ends of the surrounding pipe main body 50H. Specifically, as shown in Fig. 3, the inner surface of each end of the surrounding pipe main body 50H is provided with an expanded diameter section 51, which is stepped and has an expanded diameter. Furthermore, a circular groove-shaped engagement groove 51M extending in the axial direction of the surrounding pipe main body 50H is formed on the inner circumferential surface of the expanded diameter section 51 (see Fig. 3).

[0016] As shown in Fig. 4B, the end ring 61 has a fitting tubular portion 62 protruding from the inner edge of one end face, and the outer peripheral surface of the fitting tubular portion 62 is provided with a semicircular cross-sectional engaging ridge 62T corresponding to the engaging groove 51M, and a plurality of linear protrusions 62J are provided at positions that divide the outer peripheral surface into a plurality of equal parts in the circumferential direction. Also, as shown in Fig. 4A, the outer peripheral portion of the end ring 61 is provided with a plurality of countersunk holes 61M that penetrate in the axial direction. The countersunk holes 61M are countersunk on the side opposite the fitting tubular portion 62. The fitting tubular portion 62 of each end ring 61 is fitted into the enlarged diameter portion 51 of the enclosing pipe body 50H, the engaging ridges 62T of the end ring 61 engage with the engaging grooves 51M of the enclosing pipe body 50H, the multiple linear projections 62J are pressed against the inner peripheral surface of the enlarged diameter portion 51, and the end ring 61 is fixed to the enclosing pipe body 50H by multiple screws passed through the multiple countersunk holes 61M. In this fixed state, the inner and outer peripheral surfaces of the end ring 61 are flush with those of the enclosing pipe body 50H, as shown in Figure 1.

[0017] 4A, a measuring pipe support ring 63 is provided at the center of the inside of the end of the end ring 61 opposite the fitting cylindrical portion 62, and a plurality of first connecting members 64 extend up, down, left, and right from positions that divide the outer peripheral surface of the measuring pipe support ring 63 into four equal parts, and are connected to the inner peripheral surface of the end ring 61. As a result, a pair of measuring pipe support rings 63 are held in the center of both ends of the enclosing pipe 50, and both ends of the measuring pipe 21 are held by the pair of measuring pipe support rings 63.

[0018] More specifically, a pair of engaging protrusions 63T protrude from two locations, one above the other, on the inner circumferential surface of the measuring pipe support ring 63. The tip surfaces of the pair of engaging protrusions 63T form arc surfaces that are included in a circle concentric with the inner surface of the measuring pipe support ring 63. Each engaging protrusion 63T extends in the direction of the central axis of the measuring pipe support ring 63, and as shown in FIG. 4B , the end on the fitting cylindrical portion 62 side has both corners chamfered in the width direction. Furthermore, as shown in FIG. 4A , the surfaces of the measuring pipe support ring 63, the multiple first connecting members 64, and the pair of engaging protrusions 63T opposite the fitting cylindrical portion 62 are arranged flush with the end surface 61A of the end ring 61.

[0019] On the other hand, as shown in Fig. 3, the measuring pipe 21 is, for example, a pipe with a circular cross section, and is provided with a pair of rectangular notches 21K in a side view at both ends. Then, both ends of the measuring pipe 21 are fitted into a pair of measuring pipe support rings 63, and a pair of engaging protrusions 63T of the measuring pipe support rings 63 are received in the pair of notches 21K at each end of the measuring pipe 21. Also, as shown in Fig. 5, both end faces of the measuring pipe 21 are arranged flush with the end faces of the respective measuring pipe support rings 63.

[0020] 4A , a plurality of second connecting members 65 extend parallel to the central axis of the end ring 61 from the boundary between the end face 61A of the end ring 61 and the outer surfaces of the plurality of first connecting members 64. The second connecting members 65 are, for example, cylindrical with a diameter substantially equal to the width of the first connecting members 64. A sensor support ring 66 is provided inside the tips of the plurality of second connecting members 65, and the tips of the plurality of second connecting members 65 are connected to the outer peripheral surface of the sensor support ring 66, so that the sensor support ring 66 is held coaxially with the measurement pipe support ring 63.

[0021] A plurality of semicircular support protrusions 66T protrude laterally from multiple positions on the outer peripheral surface of the sensor support ring 66, which are central positions between adjacent second connecting members 65. The end faces of the second connecting members 65, the end faces of the sensor support ring 66, and the end faces of the support protrusions 66T are flush with each other. A plurality of positioning protrusions 67 protrude from the boundary between the end face of the sensor support ring 66 and the pair of upper and lower second connecting members 65 and the plurality of support protrusions 66T. The cross-sectional shape of the positioning protrusions 67 is teardrop-shaped, tapering toward the central axis of the sensor support ring 66. Each pair of left and right second connecting members 65 has a screw hole 65N opening into its end face.

[0022] As shown in FIG. 5 , a pair of ultrasonic sensors 70 are fitted into the pair of sensor support rings 66 and are prevented from coming off by a pair of retaining members 73. The ultrasonic sensor 70 comprises a sensor body 71 and a vibration absorbing ring 72 fitted and fixed to its exterior. The sensor body 71 is disk-shaped and flat in the axial direction of the enclosing tube 50. It has a transmitting / receiving surface 71A on its front surface for transmitting and receiving ultrasonic waves, and a cable 70C extending from its flat rear surface. The outer periphery of the sensor body 71 is provided with a stepped large-diameter portion 71D, which engages with a fitting groove 72M formed on the inner periphery of the vibration absorbing ring 72. Furthermore, a flange 72F extends laterally from the rear end of the vibration absorbing ring 72. The ultrasonic sensor 70 is positioned in the axial direction of the enclosing pipe 50 and centered on the central axis of the enclosing pipe 50 by overlapping the flange 72F on the end face of the sensor support ring 66 and abutting against multiple positioning protrusions 67 on the peripheral surface of the flange 72F as shown in Figure 6.

[0023] 3 , the retaining member 73 includes a horizontally elongated plate portion 73A that is placed on the rear surface of the vibration absorbing ring 72, and a pair of arc-shaped projections 73H that project from the left and right outer edges of the plate portion 73A toward the sensor support ring 66. A cable insertion groove 75 extending from the center to the upper end is formed in the plate portion 73A. A pair of cylindrical portions 74 are integrally formed in the vertically intermediate portions of the outer surfaces of the pair of arc-shaped projections 73H. The pair of arc-shaped projections 73H are loosely fitted onto the outside of the flange 72F of the ultrasonic sensor 70, with their tip surfaces overlapping the end surface of the sensor support ring 66. Screws inserted through mounting holes 74N on the inside of the pair of cylindrical portions 74 are fastened to a pair of screw holes 65N in the sensor support ring 66. 5, the cable 70C extending from the rear surface of the sensor main body 71 is passed through the cable insertion groove 75 of the retaining member 73 and is routed, for example, along the upper surface of the upper second connecting member 65, toward the cable insertion hole 39, and connected to the circuit board 90. Note that in order to reduce the influence of the cable 70C on the flow of fluid, it is preferable that the cable 70C be fixed to, for example, the second connecting member 65, the surrounding tube 50, etc.

[0024] The holder 60, which is a component mainly composed of the end ring 61, measurement pipe support ring 63, and sensor support ring 66, the surrounding pipe main body 50H, the pair of ultrasonic sensors 70, and the pair of retaining members 73 are pre-assembled to form the core assembly 20, which is then assembled so that it passes through the through-hole 35. This facilitates assembly and maintenance of the ultrasonic flowmeter 10A. Furthermore, in the ultrasonic flowmeter 10A of this embodiment, as shown in FIG. 7, the multiple screws B1 to B4 that secure the components together are aligned along straight lines extending radially at positions that divide the housing 11 into four equal parts around the central axis. This also facilitates assembly of the ultrasonic flowmeter 10A. Note that symbol B1 in Figure 7 is a screw that fixes the connecting tube 40 shown in Figure 1 to the case main body 30H, symbol B2 in Figure 7 is a screw that fixes the core assembly 20 shown in Figure 1 to the adapter ring 53, symbol B3 in Figure 7 is a screw that fixes the adapter ring 53 shown in Figure 1 to the partition wall 32, and symbol B4 in Figure 7 is a screw that fixes the end ring 61 shown in Figure 1 to the enclosing pipe main body 50H.

[0025] Of the multiple components of the ultrasonic flowmeter 10A described above, the measuring pipe 21, the case body 30H, and the connecting tube 40 are made of, for example, metal, the vibration absorbing ring 72 is made of elastomer, and the remaining components, such as the surrounding pipe body 50H and the holder 60, are molded from resin. Specifically, the measuring pipe 21 is made from a metal such as aluminum, which has a smaller thermal expansion coefficient than the resin that constitutes the resin molded components, such as the surrounding pipe body 50H. The vibration absorbing ring 72 is made from an elastomer, such as urethane or vulcanized rubber, which does not easily transmit vibrations. Note that, although the materials of the multiple components of the ultrasonic flowmeter 10A of this embodiment are as described above, the materials are not limited to those described above.

[0026] This completes the description of the structure of the housing 11 of the ultrasonic flowmeter 10A of this embodiment. With the above-described configuration of the housing 11, as shown in FIG. 1 , the middle portion of the internal flow path R1 within the housing 11 forms a double flow path section 11R, which is divided into a measurement flow path R2 inside the measurement pipe 21 and a non-measurement flow path R3 outside the measurement pipe 21. All fluid passing through the housing 11 passes through either the measurement flow path R2 or the non-measurement flow path R3 in the double flow path section 11R. Furthermore, since the pair of ultrasonic sensors 70 face each other across the axial direction of the measurement pipe 21, ultrasonic waves transmitted and received between them essentially propagate only through the fluid passing through the measurement flow path R2. This allows the flow rate of the fluid in the measurement flow path R2 to be calculated from the propagation time of the ultrasonic waves between the pair of ultrasonic sensors 70 using known calculation processing similar to that used in conventional ultrasonic flowmeters. The ultrasonic flowmeter 10A then calculates the flow rate of the entire internal flow path R1 of the ultrasonic flowmeter 10A from the flow rate of the measurement flow path R2 as follows.

[0027] That is, a flow rate calculation unit 93 (see FIG. 1 ) on a circuit board 90 to which a pair of ultrasonic sensors 70 are connected calculates the flow rate of the measurement flow path R2 from the propagation time of ultrasonic waves between the pair of ultrasonic sensors 70 using a known calculation method similar to that used in conventional ultrasonic flowmeters. The flow rate calculation unit 93 also stores a diversion ratio and a correction coefficient for calculating the overall flow rate of the internal flow path R1 from the flow rate of the measurement flow path R2. These diversion ratios and correction coefficients are determined from the results of prior actual measurement experiments or simulation experiments and are stored in the memory as a data map for each flow rate of the measurement flow path R2. The flow rate calculation unit 93 then determines the diversion ratio and correction coefficient from the data map based on the flow rate of the measurement flow path R2 and multiplies them by the flow rate of the measurement flow path R2 to calculate the overall flow rate of the internal flow path R1. The ultrasonic flowmeter 10A can measure flow in both directions, and the direction of fluid flow can be determined depending on whether the flow rate calculated by the flow rate calculation unit 93 is a positive or negative value.

[0028] Alternatively, instead of using the flow division ratio and the correction coefficient, the correspondence between the flow rate of the measurement flow path R2 and the flow rate of the internal flow path R1 may be calculated from the results of a previous actual measurement experiment or simulation experiment, stored as a data map, and the flow rate of the internal flow path R1 may be calculated from the flow rate of the measurement flow path R2 based on the data map. Alternatively, the relationship between the flow rates of the measurement flow path R2 and the internal flow path R1 may be machine-learned, and the flow rate of the internal flow path R1 may be calculated from the flow rate of the measurement flow path R2 based on the results of the machine learning.

[0029] The ultrasonic flowmeter 10A of the present embodiment described above provides the following advantageous effects. Specifically, in the ultrasonic flowmeter 10A of the present embodiment, the measuring tube 21 is disposed within the internal flow path R1 of the housing 11, and the internal flow path R1 is partitioned into a measurement flow path R2 inside the measuring tube 21 and a non-measurement flow path R3 outside the measuring tube 21. The flow rate of the fluid in the measurement flow path R2 is determined by a pair of ultrasonic sensors 70 disposed opposite each other across the measurement flow path R2, and the flow rate of the fluid throughout the entire internal flow path R1 is calculated based on the determined flow rate. In this way, in the ultrasonic flowmeter 10A of the present embodiment, the internal flow path R1 of the housing 11 is partitioned by the measuring tube 21 into the measurement flow path R2 used for flow rate measurement by the pair of ultrasonic sensors 70 and the unused non-measurement flow path R3. Therefore, the overall cross-sectional area of ​​the internal flow path R1 of the housing 11 can be increased without affecting the cross-sectional area of ​​the measurement flow path R2, making it possible to increase the flow rate that can pass through without reducing measurement accuracy compared to conventional techniques.

[0030] In this embodiment, the fluid to be measured by the ultrasonic flowmeter 10A is a gas primarily composed of hydrogen gas. In such a gas, the speed of sound is significantly different from that of air. The ultrasonic wave emitted from the ultrasonic sensor 70 becomes extremely fast, the wavelength becomes long, and the directivity of the ultrasonic wave becomes low (the beam angle becomes large). This can lead to the ultrasonic wave being diffused, the received wave signal becoming smaller, and the measurement accuracy becoming more susceptible to noise. In contrast, the ultrasonic flowmeter 10A of this embodiment can narrow the measurement flow path R2 without changing the overall cross-sectional area of ​​the internal flow path R1 of the housing 11. This suppresses the diffusion of the ultrasonic wave, thereby improving detection accuracy compared to conventional methods.

[0031] Furthermore, in the ultrasonic flowmeter 10A of this embodiment, the sensor support ring 66 and the end of the measuring pipe 21 are connected by a plurality of first and second connecting members 64, 65, and the ultrasonic sensor 70 is supported by the sensor support ring 66, so that the ultrasonic sensor 70 is stably arranged coaxially with the measuring pipe 21 and measurement accuracy is stabilized. Here, the plurality of first and second connecting members 64, 65 support only both end portions of the measuring pipe 21, so that the position and attitude of the measuring pipe 21 relative to the housing 11 are stabilized and fluid resistance in the non-measurement flow path R3 is suppressed.

[0032] Furthermore, since the measuring pipe 21 is disposed at the center of the non-measurement flow path R3 and the multiple first and second connecting members 64, 65 are disposed at positions that divide the circumference of the measuring pipe 21 into multiple equal parts, the fluid flowing into the non-measurement flow path R3 tends to flow evenly throughout the non-measurement flow path R3. This increases the accuracy of the calculation result of the flow rate of the fluid throughout the entire internal flow path R1, which is calculated based on the flow rate of the fluid in the measurement flow path R2.

[0033] Furthermore, the ultrasonic flowmeter 10A of this embodiment is divided into the case 30 having a pair of pipe connection portions 43 at both ends, and the surrounding pipe 50 that is attached in a state where it penetrates the through hole 35 of the partition wall 32 that separates the inside of the case 30 and has the double flow path portion 11R on the inside including the measuring pipe 21, so that it is possible to easily accommodate a plurality of pipes 99 of different sizes by changing the size of only the case 30. Furthermore, in this embodiment, the case 30 is divided into three parts, the case main body 30H and the pair of connecting tubes 40 that are fitted and fixed to both ends of the case 30H, so that it is possible to accommodate by changing only the pair of connecting tubes 40.

[0034] In addition, since the enclosing pipe 50 is divided into an enclosing pipe main body 50H supported by the partition wall 32 and a pair of end rings 61 fixed to both end surfaces of the enclosing pipe main body 50H, it is easy to manufacture the core assembly 20, which is a single unit of the enclosing pipe 50 that incorporates the measuring pipe 21 and has a pair of ultrasonic sensors 70 at both ends.

[0035] Furthermore, while the core assembly 20 is mainly made of resin, the measuring pipe 21 is mainly made of metal, which has a smaller thermal expansion coefficient than resin, so that the manufacturing cost can be reduced while preventing a decrease in measurement accuracy.

[0036] Second Embodiment The ultrasonic flowmeter 10B of this embodiment shown in FIG. 8 differs from the ultrasonic flowmeter 10A of the first embodiment only in that an interference member 84 is provided on each of the pair of connecting tubes 40. Specifically, as shown in FIG. 8, the interference member 84 is, for example, disk-shaped and disposed at the center of each connecting tube 40. The interference member 84 is supported by the connecting tube 40 via a plurality of connecting members 84A extending radially from the interference member 84. These interference members 84 rectify the flow of fluid in the measurement flow path R2 and the non-measurement flow path R3, thereby improving measurement accuracy. Note that the interference member 84 is not limited to the above structure as long as it can rectify the flow of fluid in the measurement flow path R2 and the non-measurement flow path R3. For example, as shown in FIG. 9, the interference member 84 may have a tapered surface facing the ultrasonic sensor 70 and a dome-shaped bulge on the surface facing away from the ultrasonic sensor 70.

[0037] [Third Embodiment] The housing 11 of the ultrasonic flowmeter 10A of the first embodiment was provided with the case 30 that covered the enveloping pipe 50, but the housing 11 of the ultrasonic flowmeter 10C of this embodiment has a pair of extension pipes 50E extending from both ends of the enveloping pipe 50 while tapering in diameter, and the tips of the extension pipes 50E form pipe connecting portions 43. Note that the ultrasonic flowmeter 10C is depicted in a simplified form in Figure 10.

[0038] [Fourth Embodiment] In the first embodiment, a pair of ultrasonic sensors 70 was held at both ends of the enveloping pipe 50, but an ultrasonic flowmeter 10D of this embodiment shown in Fig. 11 has a structure in which a sensor support ring 66 to which an ultrasonic sensor 70 is attached is provided at the center of a position near both ends of the case 30, and a plurality of connecting members 68 extending radially from the sensor support ring 66 are connected to the case 30. Note that the ultrasonic flowmeter 10D is depicted in a simplified form in Fig. 11.

[0039] [Fifth Embodiment] In an ultrasonic flowmeter 10E of this embodiment shown in Fig. 12, the case 30 has a structure in which the portions facing both end faces of the enclosing pipe 50 are closed, and a pair of pipe connections 46A, 46B extend upward from both end ends. A pair of ultrasonic sensors 70 are disposed on the inner surface of the case 30, on surfaces facing both ends of the measuring pipe 21. Note that the ultrasonic flowmeter 10E is depicted in a simplified form in Fig. 12.

[0040] [Other Embodiments] In the first embodiment, the first connecting member 64 is rod-shaped with a square cross section, and the second connecting member 65 is rod-shaped with a circular cross section, but their cross-sectional shapes are not limited to those in the first embodiment. Also, a structure may be adopted in which a plurality of plate-shaped connecting members are provided, each integrating the first and second connecting members 64, 65, and the measurement pipe support ring 63, the sensor support ring 66, and the end ring 61 are connected by these plurality of plate-shaped connecting members.

[0041] Although four of each of the first and second connecting members 64, 65 are provided, the number is not limited to four and may be three or less or five or more. Also, although the first and second connecting members 64, 65 are arranged axially symmetrically with respect to the central axis of the measuring pipe 21, they do not have to be arranged axially symmetrically. The same applies to the number and arrangement of the support protrusions 66T, positioning protrusions 67, etc.

[0042] In the first embodiment, both ends of the measuring pipe 21 were fixed by the measuring pipe support rings 63 of the holder member 60, but it is also possible to fix a midpoint of the measuring pipe 21, or to fix both ends and a midpoint of the measuring pipe 21. As a configuration in which the midpoint of the measuring pipe 21 is fixed, for example, a configuration in which the outer surface of the measuring pipe 21 and the inner surface of the enclosing pipe 50 are connected by a plurality of plate-like members over the entire axial direction of the measuring pipe 21 at positions that divide the circumference of the measuring pipe 21 into a plurality of equal parts may be used.

[0043] In the first embodiment, the pair of ultrasonic sensors 70 were configured to be arranged coaxially with the measuring pipe 21, but as long as they are arranged opposite each other across the measuring flow path R2, they may be arranged opposite each other at an angle to the central axis of the measuring pipe 21 rather than being coaxial with the measuring pipe 21.

[0044] In the first embodiment, the holder 60 is provided in which the end ring 61, measuring pipe support ring 63, sensor support ring 66, etc. are integrated, but the end ring 61, measuring pipe support ring 63, and sensor support ring 66 may be separate parts. For example, the end ring 61 may be integrally formed with the surrounding pipe main body 50H, and the measuring pipe support ring 63 and sensor support ring 66 may be attached to it. In this case, the measuring pipe support ring 63 and sensor support ring 66 may be integrated or may be separate parts. Furthermore, the measuring pipe support ring 63 may be integrally formed with the measuring pipe 21, and the end ring 61 and sensor support ring 66 may be attached to it.

[0045] Although the measuring pipe 21 in the first embodiment has a circular cross section, the cross section of the measuring pipe 21 is not limited to this, and may be elliptical or polygonal.

[0046] Although the case 30 in the first embodiment is cylindrical, it is not limited to this and may be an elliptical cylindrical shape or a rectangular cylindrical shape with a polygonal cross section.

[0047] In the first embodiment, the fluid to be measured is a gas mainly composed of hydrogen gas, but it may be a gas mainly composed of helium gas, for example, and is not limited to this.

[0048] <Supplementary Notes> Below, the group of features extracted from the above embodiment will be explained, indicating, as necessary, the effects, etc. Note that, for ease of understanding, the corresponding configurations in the above embodiment will be indicated in parentheses as appropriate below, but these group of features are not limited to the specific configurations indicated in parentheses.

[0049] [Feature 1] An ultrasonic flowmeter (10A) including: a housing (11) having an internal flow path (R1) through which a fluid passes; a measuring pipe (21) arranged in the internal flow path (R1); a double flow path section (11R) in which the internal flow path (R1) is divided into a measurement flow path (R2) inside the measuring pipe (21) and a non-measurement flow path (R3) outside the measuring pipe (21); a pair of ultrasonic sensors (70) arranged opposite each other across the measuring pipe (21) in the axial direction; and a flow rate calculation section (93) that calculates the flow rate of the fluid in the entire internal flow path (R1) based on the flow rate of the fluid in the measurement flow path (R2) obtained from the propagation time of ultrasonic waves between the pair of ultrasonic sensors (70).

[0050] [Feature 2] The ultrasonic flowmeter (10A) according to Feature 1, further comprising: a pair of sensor support rings (66) that are arranged coaxially with the measuring pipe (21) and opposite each other at both ends of the measuring pipe (21) and support the pair of ultrasonic sensors (70); and a plurality of connecting members (64, 65) that are distributed around each of the sensor support rings (66) and connect each of the sensor support rings (66) to an end of the measuring pipe (21).

[0051] [Feature 3] The ultrasonic flowmeter (10A) according to Feature 2, wherein the measuring pipe (21) is supported only at both ends by the plurality of connecting members (64, 65).

[0052] [Feature 4] The ultrasonic flowmeter (10A) according to Feature 2 or 3, wherein the measuring pipe (21) is disposed in the center of the non-measurement flow path (R3), and the plurality of connecting members (64, 65) are disposed at positions that divide a circumference of the measuring pipe (21) into a plurality of equal parts.

[0053] [Feature 5] An ultrasonic flowmeter (10A) according to any one of Features 1 to 4, wherein the inner and outer surfaces of the measuring pipe (21) and the inner surface of the surrounding portion of the housing (11) surrounding the measuring pipe (21) have similar cross-sectional shapes and are arranged on a concentric axis.

[0054] [Feature 6] The ultrasonic flowmeter (10A) according to any one of Features 1 to 5, further comprising: a case (30) in which the housing (11) has a pair of pipe connection portions (43) at both ends, the pipe connection portions (43) being connected to pipes (99), and a partition wall (32) dividing the inside into a first chamber (33) on one of the pipe connection portions (43) side and a second chamber (34) on the other pipe connection portion (43) side, the case having one through hole (35) formed in the partition wall (32); and an enclosing pipe (50) attached in a state of passing through the one through hole (35) of the partition wall (32), the enclosing pipe (50) having the double flow path portion (11R) on the inside including the measuring pipe (21).

[0055] [Feature 7] The ultrasonic flowmeter (10A) according to Feature 6, wherein the enclosing pipe (50) is divided into an enclosing pipe main body (50H) attached to the partition wall (32) and a pair of end rings (61) fixed to both ends of the enclosing pipe main body (50H), and comprises: a measuring pipe support ring (63) arranged at the center of each end ring (61) and into which an end of the measuring pipe (21) is fitted; a sensor support ring (66) arranged coaxially with the measuring pipe support ring (63) and supporting the ultrasonic sensor (70); and a plurality of connecting members (64, 65) for connecting between a plurality of circumferential positions on the end rings (61), the measuring pipe support ring (63), and the sensor support ring (66).

[0056] [Feature 8] The ultrasonic flowmeter (10A) according to any one of Features 1 to 7, wherein the fluid is a gas mainly composed of hydrogen or helium.

[0057] In an ultrasonic flowmeter of Feature 1, a measuring tube is disposed within an internal flow path of a housing, and the internal flow path is divided into a measurement flow path inside the measuring tube and a non-measurement flow path outside the measuring tube. The flow rate of the fluid in the measurement flow path is determined by a pair of ultrasonic sensors disposed opposite each other across the measurement flow path, and the flow rate of the fluid in the entire internal flow path is calculated based on the determined flow rate. In this way, in the ultrasonic flowmeter of Feature 1, the internal flow path of the housing is divided by the measuring tube into a measurement flow path used for flow measurement by the pair of ultrasonic sensors and a non-measurement flow path that is not used. Therefore, the overall cross-sectional area of ​​the internal flow path of the housing can be increased without affecting the cross-sectional area of ​​the measurement flow path, and it is possible to increase the flow rate that can pass through without reducing measurement accuracy compared to conventional flow meters. Here, it is conceivable that the pair of ultrasonic sensors are arranged opposite each other in a direction that intersects diagonally with the axial direction of the measurement flow path. In this case, the pair of ultrasonic sensors would protrude from the side of the measurement pipe toward the non-measurement flow path, increasing the fluid resistance in the non-measurement flow path. However, in the ultrasonic flowmeter of Feature 1, the pair of ultrasonic sensors are arranged opposite each other across the measurement flow path, so the fluid resistance in the non-measurement flow path is reduced compared to the above-mentioned structure.

[0058] In the ultrasonic flowmeter of Feature 2, the sensor support ring, the housing, and the end of the measuring pipe are connected by a plurality of connecting members, and the ultrasonic sensor is supported on the sensor support ring, so that the ultrasonic sensor is stably arranged coaxially with the measuring pipe, and measurement accuracy is stabilized. Here, the plurality of connecting members may be rod-shaped or plate-shaped, and the connection positions of the plurality of connecting members on the measuring pipe may be, for example, a plurality of positions including both ends and an intermediate position in the axial direction of the measuring pipe, or may be only both ends of the measuring pipe as in Feature 3. According to the configuration of Feature 3, the position and orientation of the measuring pipe relative to the housing are stabilized and fluid resistance in the non-measurement flow path is suppressed. Note that the plurality of connecting members may be plate-shaped and connected over the entire axial direction of the measuring pipe.

[0059] Furthermore, if a structure is used in which the measuring pipe is placed in the center of the non-measurement flow path, and multiple connection members are placed at positions that divide the circumference of the measuring pipe into multiple equal parts, as in Feature 4, or a structure in which the cross-sectional shapes of the inner and outer surfaces of the measuring pipe and the inner surface of the surrounding portion of the housing that surrounds the measuring pipe are similar in shape and are placed on the same axis, as in Feature 5, then the fluids that flow into the measurement flow path and non-measurement flow path will each be more likely to flow evenly throughout the entire flow path. This increases the accuracy of the calculation result of the flow rate of the fluid in the entire internal flow path, which is calculated based on the flow rate of the fluid in the measurement flow path.

[0060] In addition, the ultrasonic flowmeter of Feature 6 is divided into a case having a pair of pipe connection portions at both ends, and an enclosed pipe that is attached to a through-hole in a partition wall that separates the inside of the case and has a double flow path portion including a measuring pipe on the inside, so that it can be easily accommodated for multiple pipes of different sizes by simply changing the size of the case. Furthermore, according to the structure of Feature 7, the enclosed pipe is divided into an enclosed pipe main body that is supported by the partition wall, and a pair of end rings that are overlapped and fixed to both end faces of the enclosed pipe main body, so that it is easy to manufacture a single enclosed pipe that incorporates a measuring pipe and has a pair of ultrasonic sensors at both ends.

[0061] The fluid to be measured by the ultrasonic flowmeter is arbitrary, but may also be a gas primarily composed of hydrogen or helium, as in Feature 8. In such gases whose sound speeds differ greatly from that of air, ultrasonic waves emitted from the ultrasonic sensor diffuse, reducing the received wave signal and making it susceptible to noise, which may result in a decrease in measurement accuracy. However, with the ultrasonic flowmeter disclosed herein, it is possible to narrow the measurement flow path without changing the overall cross-sectional area of ​​the internal flow path of the housing, thereby suppressing the diffusion of ultrasonic waves and achieving improved detection accuracy compared to conventional methods.

[0062] Although the present specification and drawings disclose specific examples of the technology included in the scope of the claims, the technology described in the claims is not limited to these specific examples, but also includes various modifications and variations of the specific examples, and also includes parts of the specific examples taken out alone.

[0063] 10A to 10E Ultrasonic flowmeter 11 Housing 11R Double flow path section 21 Measuring pipe 30 Case 32 Partition wall 33 First chamber 34 Second chamber 35 Through hole 40 Connection tube 43 Pipe connection section 50 Enclosure pipe 50H Enclosure pipe body 61 End ring 63 Measuring pipe support ring 64 First connection member 65 Second connection member 66 Sensor support ring 70 Ultrasonic sensor 93 Flow rate calculation section 99 Pipe R1 Internal flow path R2 Measuring flow path R3 Non-measuring flow path

Claims

1. An ultrasonic flow meter comprising: a housing having an internal flow path through which a fluid passes; a double flow path section including a measuring tube arranged within the internal flow path, the internal flow path being divided into a measurement flow path inside the measuring tube and a non-measurement flow path outside the measuring tube; a pair of ultrasonic sensors arranged opposite each other across the axial direction of the measuring tube; and a flow rate calculation section that calculates the flow rate of fluid in the entire internal flow path based on the flow rate of fluid in the measurement flow path obtained from the propagation time of ultrasonic waves between the pair of ultrasonic sensors.

2. An ultrasonic flowmeter as described in claim 1, comprising: a pair of sensor support rings that are arranged coaxially with the measuring pipe, facing each other at both ends of the measuring pipe, and that support the pair of ultrasonic sensors; and a plurality of connecting members that are distributed around each of the sensor support rings and that connect each of the sensor support rings to the end of the measuring pipe.

3. The ultrasonic flowmeter according to claim 2, wherein the measuring pipe is supported only at both ends by the plurality of connecting members.

4. An ultrasonic flowmeter according to claim 2 or 3, wherein the measuring pipe is arranged in the center of the non-measurement flow path, and the plurality of connecting members are arranged at positions that divide the circumference of the measuring pipe into a plurality of equal parts.

5. An ultrasonic flowmeter as claimed in any one of claims 1 to 4, wherein the inner and outer surfaces of the measuring pipe and the inner surface of the surrounding portion of the housing that surrounds the measuring pipe have similar cross-sectional shapes and are arranged on a concentric axis.

6. An ultrasonic flowmeter according to any one of claims 1 to 5, comprising: a case in which the housing has a pair of pipe connection parts at both ends to be connected to pipes, and a partition wall dividing the inside into a first chamber on one of the pipe connection parts and a second chamber on the other of the pipe connection parts, the partition wall having one through-hole; and an enclosing pipe attached in a state where it passes through the one through-hole of the partition wall, the inside of which forms the double flow path part including the measuring pipe.

7. An ultrasonic flowmeter as described in claim 6, wherein the enclosing pipe is divided into an enclosing pipe main body attached to the partition wall and a pair of end rings fixed to both ends of the enclosing pipe main body, and comprises: a measuring pipe support ring positioned at the center of each end ring and into which the end of the measuring pipe is fitted; a sensor support ring positioned coaxially with the measuring pipe support ring and supporting the ultrasonic sensor; and a plurality of connecting members for connecting between a plurality of circumferential positions on the end rings, the measuring pipe support ring and the sensor support ring.

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