JP4943825B2 - Ultrasonic flow meter - Google Patents

Description

  The present invention relates to an ultrasonic flowmeter provided with a pair of ultrasonic sensors facing each other at both ends of a measurement tube.

  The conventional ultrasonic flowmeter shown in FIG. 8 has a structure in which a measuring tube 2 and a pair of ultrasonic sensors 3 and 3 are assembled to a resin holder 1 fixed inside a meter case (not shown). It was. The measuring tube 2 is formed by mounting resin guide pipes 4 and 4 for guiding a fluid to both ends of the metal pipe 2a. In addition, the resin holder 1 includes sensor support protrusions 1b and 1b that protrude from both ends of the base plate 1a, and measurement tube support protrusions 1c and 1c that protrude from both ends of the base plate 1a. . The ultrasonic sensor 3 is fixed to the sensor support protrusions 1b and 1b, and both ends of the measurement tube 2 are supported by the measurement tube support protrusions 1c and 1c, whereby both ultrasonic sensors 3 and 3 are supported. However, they were held in a state of facing each other through the internal space of the measuring tube 2.

  However, in the conventional ultrasonic flowmeter described above, the sensor support projection 1b, the measurement tube support projection 1c, and the like are integrally formed on one surface of the front and back of the base plate 1a of the resin holder 1. Due to the sink when the resin holder 1 is molded, the base plate 1a is warped, or the sensor support protrusion 1b and the measurement tube support protrusion 1c are deformed to be inclined with respect to the base plate 1a. For this reason, the distance L2 between the ultrasonic sensors 3 and 3 and the distance L1 between the ultrasonic sensor 3 and the opening of the tube 2 vary, and the measurement performance is not stable. In addition, prior art documents related to the present invention could not be found.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an ultrasonic flowmeter having more stable measurement performance than before.

In order to achieve the above object, an ultrasonic flowmeter according to the invention of claim 1 includes a meter case, a measurement tube that is accommodated in the meter case and in which a fluid flows, and ends of both ends of the measurement tube. In an ultrasonic flowmeter provided with a pair of ultrasonic sensors arranged apart from the opening and facing each other across the inner region of the measurement tube, the measurement tube has a resin cylindrical shape on the outer peripheral surface of the metal pipe Covered with a holder, integrally formed at the end of the resin cylindrical holder, and extending along the axial direction of the measuring tube and having a sensor holding part holding an ultrasonic sensor at the tip , the resin cylindrical holder is The plurality of holder structures can be divided vertically, and the sensor holding portions are provided in the plurality of holder structures, respectively, and are configured to hold the ultrasonic sensors in cooperation with each other. Have

The invention according to claim 2 is characterized in that, in the ultrasonic flowmeter according to claim 1, the sensor holding portion is composed of a plurality of sensor holding arms extending in a cantilever shape from the end of the holder structure. Have.

The invention of claim 3 is characterized in that, in the ultrasonic flowmeter according to claim 1 or 2 , the plurality of holder structural bodies are formed into the same shape.

According to a fourth aspect of the present invention, in the ultrasonic flowmeter according to any one of the first to third aspects, the resin cylindrical holder is connected to both ends of the metal pipe and extends on an extension line of the metal pipe. Is characterized in that it is provided with a mouth pipe portion that expands toward the tip.

The invention according to claim 5 is the ultrasonic flowmeter according to claim 4 , wherein the opening edge of the mouth pipe portion of the resin cylindrical holder is configured with a rounded curved surface, and the inner surface of the mouth pipe portion Is characterized by being continuous with the opening edge and flush with the inner surface of the metal pipe.

According to a sixth aspect of the present invention, in the ultrasonic flowmeter according to any one of the first to third aspects, the resin cylindrical holder is connected to both ends of the metal pipe and extends on an extension line of the metal pipe, and the inner diameter is the metal pipe. A mouth pipe portion having the same diameter as the inner diameter of the metal pipe is provided, and the inner surface of the mouth pipe portion is flush with the inner surface of the metal pipe.

The invention according to claim 7 is the ultrasonic flowmeter according to any one of claims 4 to 6 , wherein between the inner surface of the portion where the metal pipe is fitted and the inner surface of the mouth pipe portion of the resin cylindrical holder. It is characterized in that the end of the metal pipe is abutted against the stepped portion.

The invention according to claim 8 is the ultrasonic flowmeter according to any one of claims 1 to 7 , wherein the meter case is connected to a measuring tube housing room containing the measuring tube and one end side of the measuring tube housing room. A fluid inflow passage and a fluid outflow passage communicated with the other end of the measurement tube storage chamber. The measurement tube is fitted between the outer surface of the metal pipe and the inner surface of the measurement tube storage chamber. An intermediate wall is provided to divide the measurement tube storage chamber into a fluid inflow path side and a fluid outflow path side, and resin cylindrical holders are provided in pairs on both sides of the intermediate wall and fixed to the intermediate wall respectively. Have.

The invention according to claim 9 is characterized in that, in the ultrasonic flowmeter according to claim 8 , a seal member is provided between the outer surface of the intermediate wall and the inner surface of the measurement tube housing chamber.

According to a tenth aspect of the present invention, in the ultrasonic flowmeter according to the eighth or ninth aspect , the meter case is divided into a case main body and a case lid at at least one end of the measurement tube housing chamber, and the divided surface is opened. As a result, the measuring tube can be inserted and assembled in the measuring tube storage room.

The invention according to an eleventh aspect is the ultrasonic flowmeter according to any one of the eighth to tenth aspects, wherein the fluid inflow passage and the fluid outflow passage are formed in the case body so as to be orthogonal to the measurement tube housing chamber, and It is characterized by being open toward the side of the measuring tube in the accommodation room.

The invention of claim 12 is characterized in that in the ultrasonic flowmeter according to any one of claims 1 to 11 , the metal pipe is formed by drawing or extruding.

[Inventions of Claims 1 and 2]
According to another aspect of the ultrasonic flowmeter of the present invention , the resin cylindrical holder includes a plurality of holder structures , and the resin cylindrical holder including the plurality of holder structures covers the outer peripheral surface of the metal pipe. It has become. Thereby, the shape of the resin cylindrical holder can be made substantially uniform around its central axis, and deformation due to sink marks during molding can be suppressed. The sensor holding portions are integrally formed at the end portions of the plurality of holder structures, and the plurality of sensor holding portions cooperate when the plurality of holder structures are combined to complete the resin cylindrical holder. Since one ultrasonic sensor is held , variations in the distance between the ultrasonic sensors and the distance between the ultrasonic sensors and the end opening of the measurement tube can be suppressed. Moreover, since the sensor holding part extends along the axial direction of the measuring tube from the end of the resin cylindrical holder, even if the sensor holding part itself is inclined due to sink marks, the distance between the ultrasonic sensors is In addition, there is little influence on the variation in the distance between the ultrasonic sensor and the end opening of the measurement tube. Thus, according to the ultrasonic flowmeter of the present invention, the measurement performance is more stable than before.

  Here, the sensor holding portion may be constituted by a plurality of sensor holding arms extending like a cantilever from the end of the resin cylindrical holder, as in the configuration of claim 2.

[Invention of claim 3 ]
According to the configuration of the third aspect , since the plurality of holder structural bodies are formed into the same shape, it is possible to share a molding die, which is preferable in terms of manufacturing cost and component management.

[Inventions of Claims 4 and 5 ]
According to the fourth aspect of the present invention, the resin cylindrical holder is provided with a mouth pipe portion that is connected to both ends of the metal pipe, extends on the extension line of the metal pipe, and has an inner diameter that expands toward the tip. As a result, the fluid can smoothly flow into or out of the metal pipe. According to the fifth aspect of the present invention, the opening edge of the mouth pipe portion of the resin cylindrical holder is formed with a rounded curved surface, and the inner surface of the mouth pipe portion is made continuous with the opening edge, and the metal pipe By making it flush with the inner surface, it is possible to prevent the occurrence of turbulent fluid flow.

[Invention of claim 6 ]
As in the invention of claim 6 , the resin cylindrical holder is provided with a mouth pipe portion connected to both ends of the metal pipe and extending on an extension line of the metal pipe and having an inner diameter equal to the inner diameter of the metal pipe. The inner pipe may have an inner surface flush with the inner surface of the metal pipe.

[Invention of Claim 7 ]
According to the structure of Claim 7 , since the level | step-difference part formed in the inner surface of the resin cylindrical holder contact | abuts the edge part of a metal pipe, and is positioned in an axial direction, the dispersion | variation in the full length of a measurement pipe | tube can be suppressed. .

[Inventions of Claims 8 and 9 ]
According to the configuration of the eighth aspect , the fluid flows from the fluid inflow path into the measuring tube housing chamber, and all the fluid passes through the inside of the measuring tube. Then, the fluid that has passed through the inside of the measuring tube passes through the measuring tube housing chamber and is discharged from the fluid outflow path to the outside of the meter case. In addition, since the intermediate wall is fitted between the outer surface of the metal pipe and the inner surface of the measurement tube housing chamber, the measurement tube in the meter case is prevented from rattling. Further, the pair of resin cylindrical holders provided on both sides of the intermediate wall are fixed to the intermediate wall, so that each resin cylindrical holder is prevented from being detached from the metal pipe. Here, as in the invention of claim 9 , if a sealing member is provided between the outer side surface of the intermediate wall and the inner surface of the measuring tube housing chamber, the fluid can be reliably circulated through other than the inside of the measuring tube. Can be prevented.

[Invention of Claim 10 ]
According to the configuration of the tenth aspect, the measuring tube can be inserted and assembled from the opening of the measuring tube housing room opened to the dividing surface of the case body.

[Invention of Claim 11 ]
According to the configuration of the eleventh aspect, the fluid that has flowed into the measurement tube storage chamber collides with the side surface of the measurement tube before flowing into the measurement tube, so that the fluid flow state in the measurement tube flows into the measurement tube storage chamber. It becomes hard to be influenced by the state of the flow of time. Thereby, the flow of the fluid in a measuring tube can be stabilized.

[Invention of Claim 12 ]
In the structure of the twelfth aspect , since the metal pipe is formed by drawing or extruding, the inner peripheral surface becomes smooth and the fluid flow is stabilized.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
Reference numeral 10 in FIG. 1 is an “ultrasonic flow meter” of the present invention, and is attached, for example, in the middle of a gas pipe through which a gas as a fluid (specifically, hydrogen gas) flows. The ultrasonic flow meter 10 includes a metering assembly 30 inside a meter case 20.

  First, the meter case 20 will be described. The meter case 20 has a cylindrical structure with bottoms at both ends, and a measurement assembly storage chamber 23 (in the “measurement tube storage chamber” of the present invention) for storing the measurement assembly 30 therein. Equivalent). The meter case 20 can be divided into a case main body 21 and a pair of case lid bodies 22 and 22 at positions near both ends in the longitudinal direction (left-right direction in FIG. 1). The case main body 21 has a cylindrical shape with both ends open and shorter in length than the weighing assembly 30, and the inner diameters on both end portions 21 </ b> A and 21 </ b> A side are increased stepwise.

  The case lids 22 and 22 have a cylindrical structure with one end, and a flange 22F projects from the outer peripheral surface to the side. The end surface of the case body 21 is abutted against the flange 22F. In addition, an O-ring 63 is fitted to the outer peripheral surface of the portion of the case lid 22 that is fitted inside the end 21 </ b> A of the case main body 21, and the O-ring 63 is pushed between the inner surface of the case main body 21. It is crushed and stuck. The case lids 22 and 22 are fixed to the case main body 21 by a plurality of screws 64 penetrating the flange 22F.

  A pair of connecting pipes 24, 24 are provided side by side in the longitudinal direction on the side surface of the case body 21 of the meter case 20. Specifically, a male spiral portion is formed on the outer peripheral surface on the proximal end side of the connection pipes 24, 24, and the male spiral portion is screwed into a spiral hole formed through the side surface of the case body 21. Yes. Of the connecting pipes 24, 24, the inside of one connecting pipe 24 is a gas inflow path 24 </ b> A (corresponding to the “fluid inflow path” of the present invention) for introducing gas into the measuring assembly housing chamber 23. The inside of the other connecting pipe 24 is a gas outflow path 24B (corresponding to the “fluid outflow path” of the present invention) for discharging gas from the measuring assembly housing chamber 23. When a gas pipe (not shown) is connected to both the connecting pipes 24, 24, as shown by an arrow in FIG. 1, the inside of the measuring pipe 31 provided in the measuring assembly 30 is one end side in the longitudinal direction (axial direction). Gas flows from the other end side (from the right side to the left side in FIG. 1).

  Here, as shown in FIG. 1, the gas inflow passage 24 </ b> A and the gas outflow passage 24 </ b> B are orthogonal to the measurement assembly storage chamber 23 and open toward the side surface of the measurement assembly 30 in the measurement assembly storage chamber 23. . As a result, the gas flowing into the measurement assembly housing chamber 23 from the gas inflow path 24 </ b> A hits the side surface of the measurement assembly 30, so that the state of gas flow in the measurement tube 31 of the measurement assembly 30 is changed to the measurement assembly storage chamber 23. It becomes hard to be influenced by the state of the flow when it flows in. In addition, since the gas flows along the side surface of the measuring assembly 30 after it hits the side surface of the measuring assembly 30 and flows into the measuring tube 31, the gas flow is further stabilized during that time. The above is the description regarding the meter case 20.

  As shown in FIG. 1, the measurement assembly 30 integrally includes a measurement tube 31 and a pair of ultrasonic sensors 40 and 40, and these ultrasonic sensors are located at positions away from the openings at both ends of the measurement tube 31. 40 and 40 are held. The measuring assembly 30 protrudes laterally from the openings of the both end portions 21A and 21A of the case main body 21, and the protruding portions are received inside the case lids 22 and 22, respectively.

  In the measuring assembly 30, the measuring tube 31 extends from a position closer to one end to a position closer to the other end in the longitudinal direction of the meter case 20, and the inside is a flow path 31 </ b> A having a circular cross section.

  An intermediate wall 60 is provided at an intermediate portion in the longitudinal direction (axial direction) of the measuring tube 31. As shown in FIG. 5, the intermediate wall 60 has a flat disk shape corresponding to the cross-sectional shape of the measuring assembly housing chamber 23, and the measurement tube 31 (in detail, a metal pipe 32 to be described later) at the center. Has penetrated. The outer peripheral surface of the intermediate wall 60 is fitted to the inner surface of the weighing assembly housing chamber 23.

  As shown in FIG. 1, the intermediate wall 60 is fitted to the inner surface of the portion between the gas inflow passage 24 </ b> A and the gas outflow passage 24 </ b> B of the measuring assembly housing chamber 23, and the inner surface of the measuring assembly housing chamber 23 and the measuring assembly. The region between the outer surface of the inflow chamber 25 communicates with one opening of the measuring tube 31 and the gas inflow passage 24A, and the outflow chamber 26 communicates with the other opening of the measuring tube 31 and the gas outflow passage 24B. And is isolated. Thereby, all the gas that has flowed into the inflow chamber 25 from the gas inflow path 24 </ b> A passes through the inside of the measurement pipe 31 and flows into the outflow chamber 26. Here, an O-ring groove 60M (see FIG. 3) is formed on the outer peripheral surface of the intermediate wall 60, and an O-ring 61 (corresponding to the “seal member” of the present invention) fitted thereto is a weighing assembly. It is crushed and in close contact with the inner surface of the storage chamber 23. An O-ring 62 is also sandwiched between the inner surface of the through hole penetrating the central portion of the intermediate wall 60 and the outer surface of the measurement tube 31 (metal pipe 32). These O-rings 61 and 62 reliably prevent the gas from flowing outside the flow channel 31 </ b> A of the measurement tube 31.

  The measuring tube 31 is configured by fitting a pair of resin cylindrical holders 33 and 33 on the outside of the metal pipe 32. The metal pipe 32 is made of a seamless aluminum alloy pipe material that has been subjected to extrusion drawing or drawing processing in order to suppress variations in shape and dimensions. Further, the metal pipe 32 has dimensions such as an outer diameter, an inner diameter, a wall thickness, and a bend which are not more than a predetermined tolerance defined in “JIS H4080: 2006”, for example.

  On the other hand, the resin cylindrical holders 33 and 33 are, for example, resin molded products having the same shape, and are provided in pairs on both sides of the metal pipe 32 with the intermediate wall 60 interposed therebetween. The resin cylindrical holders 33 and 33 include a cylindrical portion 36 that covers the outer peripheral surface of the metal pipe 32 as a main portion, and has a structure in which the cylindrical portion 36 and sensor holding arms 50 and 50 described later are integrally provided. ing. As shown in FIG. 5, the resin cylindrical holders 33 and 33 are configured by combining two holder structural bodies 33 </ b> A and 33 </ b> A that are vertically divided in parallel with the longitudinal direction.

  The holder constituting bodies 33A, 33A are provided with laterally extending walls 38, 38 extending in the longitudinal direction of the measuring tube 31 in the plate thickness direction, extending laterally from positions 180 degrees apart from each other on the outer peripheral surface of the cylindrical portion 36. The resin cylindrical holder 33 is divided into two parts on a plane that bisects. Since these holder structures 33A and 33A have the same shape, the molds can be shared, and the manufacturing cost and parts management are excellent.

  As shown in FIG. 5, a plurality of screw holes 38 </ b> A, 38 </ b> A are formed side by side in a portion of the holder structure 33 </ b> A that is obtained by dividing the laterally extending wall 38 in the thickness direction. Then, when the two holder structural bodies 33A and 33A are joined, screws 66 (tapping screws) are screwed into the screw holes 38A and 38A communicating in the joining direction, so that the two holder structural bodies 33A and 33A are engaged. A cylindrical portion 36 is formed by being fixed in the combined state, and one resin cylindrical holder 33 is completed. More specifically, the screw holes 38A and 38A communicating in the direction in which the holder structural bodies 33A and 33A are combined have different diameters, and the screw 66 is screwed into the screw hole 38A having the smaller diameter.

  Here, as shown in FIG. 1, protrusions 38T, 38T are formed on the side surfaces of the laterally extending walls 38, 38, respectively, and these protrusions 38T, 38T are steps on the inner surface of the weighing assembly housing chamber 23. It is abutted against a protruding wall 23T that is screwed to the portion and protrudes inward. The projection 38T and the intermediate wall 60 prevent the weighing assembly 30 from rattling in the meter case 20.

  As shown in FIG. 2, a flange portion 37 is integrally formed at the proximal end portion of the resin cylindrical holder 33 (cylindrical portion 36). The flange portion 37 is directed to the side surface of the intermediate wall 60, and a plurality of screws 65 penetrating the flange portion 37 are fastened to the side surface of the intermediate wall 60. In this way, the two resin cylindrical holders 33, 33 are fixed on both sides of the intermediate wall 60.

  An extension pipe part 35 (corresponding to the “mouth pipe part” of the present invention) is formed at the tip of the cylindrical part 36 of the resin cylindrical holder 33 on the side opposite to the flange part 37. The extension pipe part 35 forms a flow path 31 </ b> A of the measurement pipe 31 together with the metal pipe 32 and constitutes an inlet or an outlet of the measurement pipe 31. The extension pipe part 35 extends from the end part of the metal pipe 32 to the ultrasonic sensor 40 side, and the tip part of the extension pipe part 35 extends in a so-called trumpet shape. Specifically, the inner diameter of the extension pipe portion 35 is constant until the middle, and the diameter is increased as the portion closer to the tip approaches the ultrasonic sensor 40. Further, the opening edge 35A on the distal end side of the extension pipe part 35 is chamfered (R chamfered) so as to be rounded, and the opening edge 35A is continuous with the inner surface of the extension pipe part 35. As described above, the extension pipe portions 35 and 35 are connected to both ends of the metal pipe 32, and the extension pipe portions 35 and 35 are used as an inlet and an outlet of the measuring pipe 31, thereby performing extrusion processing or drawing processing. Compared with the case where the metal pipe 32 is used as it is as a measurement pipe, the inflow or outflow of gas to the measurement pipe 31 becomes smooth.

  As shown in FIG. 3, a stepped portion 34 is formed on the inner surface of the cylindrical portion 36 of the resin cylindrical holder 33 near the extension pipe portion 35. The step of the step 34 has the same dimension as the thickness of the metal pipe 32, and the end surface of the metal pipe 32 abuts on the step 34. That is, the metal pipe 32 is sandwiched between the step portions 34 and 34 of the two resin cylindrical holders 33 and 33 that are fitted and fixed to the outside of the metal pipe 32, so that movement in the longitudinal direction is prohibited. Since the inner surface of the extension pipe part 35 and the inner surface of the metal pipe 32 are continuous and flush with each other, the gas flow is not disturbed at the joint between the metal pipe 32 and the extension pipe part 35, and the measurement pipe The gas flow in 31 is stabilized.

  In the measurement assembly 30, the ultrasonic sensors 40, 40 face each other at a predetermined distance from the openings at both ends of the measurement tube 31 (openings on the distal ends of the extension tube portions 35, 35), and face the measurement tube 31. Are arranged side by side in a direction parallel to the longitudinal direction (fluid flow direction, left-right direction in FIG. 1). The ultrasonic sensors 40, 40 have a substantially dome-shaped transmission / reception surface 41 on the front surface, and a flange 42 is formed at the rear end portion on the opposite side of the transmission / reception surface 41. Then, the time until the ultrasonic wave transmitted from one ultrasonic sensor 40 is received by the other ultrasonic sensor 40 (propagation time) and the ultrasonic wave transmitted from the other ultrasonic sensor 40 are converted into the ultrasonic sensor 40. The difference from the time until reception (propagation time) is obtained, and the flow velocity / flow rate of the gas flowing in the measuring tube 31 is detected based on the difference. Here, the openings (extension tube portions 35, 35) at both ends of the measurement tube 31 are formed in a so-called trumpet shape as described above, thereby efficiently measuring the ultrasonic waves transmitted from the ultrasonic sensors 40, 40. It can be introduced into the tube 31.

  Incidentally, as described above, in order to hold the ultrasonic sensors 40, 40 at positions separated from the openings at both ends of the measurement tube 31 by a predetermined distance, the resin cylindrical holders 33, 33 are respectively provided with sensor holding arms. 50 and 50 are integrally formed. As shown in FIG. 2, the sensor holding arms 50, 50 are provided in pairs at positions that are 180 degrees apart from each other in the circumferential direction of the cylindrical portion 36.

  Specifically, the sensor holding arms 50 and 50 are arranged so that the outer portions of the laterally extending walls 38 and 38 that protrude to the side of the cylindrical portion 36 are separated from the opening of the measuring tube 31 (extension tube portion 35). The structure extends in the longitudinal direction (see FIG. 4). As shown in FIG. 2, the sensor holding arms 50, 50 are connected to each other by semicircular arc-shaped arch walls 51, 51 that cover the side surfaces of the ultrasonic sensor 40, and the sensor holding arms 50, 50 are connected to each other. 50, a groove portion 50M that is engaged with the flange 42 of the ultrasonic sensor 40 is formed in a portion that protrudes forward from the arch wall 51 (see FIG. 4).

  Further, auxiliary locking pieces 52 and 52 are integrally formed in the middle portions of the arch walls 51 and 51, respectively. The auxiliary locking piece 52 is provided at an intermediate position 90 degrees apart from each of the sensor holding arms 50 and 50, and a groove portion that is engaged with the flange 42 of the ultrasonic sensor 40 at the tip portion protruding from the arch wall 51. 52M is formed (see FIG. 3). That is, the two sensor holding arms 50 and 50 integrally formed with the resin cylindrical holder 33 and the two auxiliary locking pieces 52 and 52 cooperate to hold one ultrasonic sensor 40 from four directions. . The sensor holding arms 50 and 50 and the auxiliary locking pieces 52 and 52 correspond to the “sensor holding portion” of the present invention.

  This is the end of the description of the configuration of the ultrasonic flowmeter 10 of the present embodiment. Next, a method for manufacturing the ultrasonic flowmeter 10 having the above configuration will be described.

  The weighing assembly 30 is manufactured as follows, for example. That is, first, the ultrasonic sensors 40 and 40 are assembled to the resin cylindrical holders 33 and 33, respectively. Specifically, the ultrasonic sensor 40 is held by the sensor holding arm 50 and the auxiliary locking piece 52 provided in the holder structure 33A with the split surface of one holder structure 33A facing upward. Next, the two holder constituent bodies 33A and 33A are united by overlapping the split surface of the other holder constituent body 33A with the split surface of the one holder constituent body 33A. In this state, the holder structural bodies 33A and 33A are coupled by the screws 66 penetrating the lateral projecting walls 38 and 38 so as not to be disassembled. Thereby, the ultrasonic sensor 40 is held at the tip of the resin cylindrical holder 33. At this time, the screw 66 may be temporarily tightened loosely enough that the ultrasonic sensor 40 is not detached from the resin cylindrical holder 33.

  Next, the metal pipe 32 to which the intermediate wall 60 is attached in advance is inserted from the proximal end side opening of the cylindrical portion 36 of the resin cylindrical holder 33. Then, the flange portion 37 of the resin cylindrical holder 33 is abutted against the side surface of the intermediate wall 60, and the screw 65 penetrating the flange portion 37 is fastened to the intermediate wall 60. In this state, if the screws 66 that have been temporarily tightened are finally tightened, the resin cylindrical holder 33 is fixed in a state where the outer peripheral surface on one end side of the metal pipe 32 is covered with the cylindrical portion 36. The resin cylindrical holder 33 is also fixed to the other end of the metal pipe 32 by the above-described procedure. Thus, the weighing assembly 30 is completed. That is, the measuring pipe 31 is completed in which the outer peripheral surface of the metal pipe 32 is covered with the resin cylindrical holders 33 and 33 and the extension pipe portions 35 and 35 are extended in opposite directions from both ends. A pair of ultrasonic sensors 40, 40 are held at positions separated by a predetermined distance from the openings at both ends (extension pipe portions 35, 35).

  Next, the completed measuring assembly 30 is mounted in the meter case 20. Specifically, one protruding wall 23T is inserted into the case main body 21 and temporarily fixed to the inner surface step portion with a screw, and then one end portion 21A (the left end portion 21A in FIG. 1) of the case main body 21 is fixed. The measuring assembly 30 is inserted into the measuring assembly housing chamber 23 from the opening, and is pushed in until the outer edge portion of the intermediate wall 60 hits a step portion 23A (see FIG. 1) formed on the inner surface of the measuring assembly housing chamber 23. Then, the intermediate wall 60 is fitted to the inner surface of the weighing assembly housing chamber 23 at an intermediate position between the two connecting pipes 24, 24, and both end portions of the weighing assembly 30 are opened from the openings of both end portions 21 A, 21 A of the case body 21. Protruding. In this state, the other protruding wall 23T is inserted into the case body 21 and screwed.

  When the case lids 22 and 22 are fixed to both end portions 21A and 21A of the case main body 21 with screws 64, the entire measurement assembly 30 is accommodated in the measurement assembly storage chamber 23, and the ultrasonic flowmeter 10 is completed.

  When the measuring assembly 30 is taken out from the meter case 20, the case lid fixed to the end 21 </ b> A (the left end 21 </ b> A in FIG. 1) of the case main body 21 into which the measuring assembly 30 is inserted. What is necessary is just to remove 22 and pinch the edge part of the measurement assembly 30 which protruded from the opening and pull it out.

Thus, in the ultrasonic flowmeter 10 of this embodiment, since the resin cylindrical holder 33 has a cylindrical shape covering the outer peripheral surface of the metal pipe 32, the shape of the resin cylindrical holder 33 is changed. A substantially uniform structure can be obtained around the central axis, and deformation due to sink marks during molding can be suppressed. Since the sensor holding arm 50 is integrally formed at the end of the resin cylindrical holder 33, the distance between the ultrasonic sensors 40 and 40, or the end opening of the ultrasonic sensor 40 and the measuring tube 31 is opened. Variation in the distance between the two is suppressed. In addition, since the sensor holding arm 50 extends from the end of the resin cylindrical holder 33 along the axial direction of the measurement tube 31, even if the sensor holding arm 50 itself is inclined due to sink marks, the ultrasonic sensor 40 is used. , 40 and the variation in the distance between the ultrasonic sensor 40 and the end opening of the measuring tube 31 is small. Thus, according to the ultrasonic flowmeter 10 of the present embodiment, the measurement performance is more stable than before. Further, since the resin cylindrical holder 33 is composed of two holder structural bodies 33A and 33A obtained by vertically dividing the resin cylindrical holders 33 and 33, the inner surface of the extension pipe portion 35 can be easily processed. .
[Other Embodiments]

  The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.

  (1) In the above embodiment, gas is exemplified as the fluid to be measured by the ultrasonic flowmeter 10, but a liquid may be used.

  (2) In the above embodiment, one ultrasonic sensor 40 is held in cooperation by the two sensor holding arms 50 and the two auxiliary locking pieces 52, but is held only by the two sensor holding arms 50. May be. Further, instead of the auxiliary locking piece 52, a sensor holding arm 50 extending from the cylindrical portion 36 may be provided and held by the four sensor holding arms 50. Further, the number of sensor holding arms 50 may be five or more.

  (3) In the above embodiment, the resin cylindrical holder 33 is composed of the two holder structural bodies 33A and 33A, but may be composed of three or more holder structural bodies.

  (4) In the above embodiment, the opening edge 35A of the extension pipe portion 35 of the resin cylindrical holder 33 is chamfered (R chamfering) so as to be rounded, but the opening edge 35A has a conical taper. It may be a surface.

  (5) In the above embodiment, the manufacturing method of first joining the holder structural bodies 33A and 33A to complete the resin cylindrical holder 33 and inserting the resin cylindrical holder 33 into the metal pipe 32 is exemplified. The following may be used. That is, after fixing one holder structure 33A to the intermediate wall 60, the holder structure 33A holds the ultrasonic sensor 40, and the other holder structure 33A is merged therewith to hold the holder structure 33A, 33A may be fixed with screws 66, and the other holder structure 33A may be fixed with respect to the intermediate wall 60 with screws 65.

  (6) The sensor holding arms 50 provided at both ends of the weighing assembly 30 are abutted against the inner surface of the bottom wall 22A of the case lid 22 so that the weighing assembly 30 is fixed in the axial direction in the meter case 20. Also good.

  (7) The cross section of the measurement pipe 31 (the metal pipe 32 and the extension pipe part 35) is not limited to a circle but may be an ellipse or an oval.

  (8) In the above embodiment, the resin cylindrical holders 33 and 33 are provided on both sides of the intermediate wall 60 of the metal pipe 32, respectively, but the following configuration may be used. That is, extension pipe portions 35 and 35 extending in opposite directions and a plurality of sensor holding arms 50 and 50 are integrally formed at both ends in the longitudinal direction of one resin cylindrical holder covering the entire metal pipe 32. Further, the resin cylindrical holder may be formed by combining two holder structural bodies formed by vertically dividing the resin cylindrical holder in parallel with the longitudinal direction. Further, an intermediate wall 60 that fits into the inner surface of the measuring assembly housing chamber 23 may be integrally formed at an intermediate portion in the longitudinal direction of the resin cylindrical holder.

  (9) In the above-described embodiment, the distal end portions of the extension pipe portions 35, 35 are spread in a trumpet shape. However, as shown in FIG. 6, the straight pipe (straight pipe) structure having the same inner diameter as the inner diameter of the metal pipe 32 can be used. Good.

  (10) In the above embodiment, the resin cylindrical holders 33, 33 are provided with the extension pipe portions 35, 35 extending on the extension line of the metal pipe 32. However, as shown in FIG. 35, the both ends of the metal pipe 32 may protrude from the distal ends of the resin cylindrical holders 33, 33 to the ultrasonic sensors 40, 40 side. In this case, the metal pipe 32 may be positioned with respect to the resin cylindrical holders 33 and 33 with the positioning pins 70.

1 is a side sectional view of an ultrasonic flowmeter according to an embodiment of the present invention. Perspective view of the weighing assembly without the ultrasonic sensor Cross section of weighing assembly Side view of weighing assembly Exploded perspective view of measuring assembly Side sectional view of an ultrasonic flowmeter according to another embodiment (9) Side sectional view of an ultrasonic flowmeter according to another embodiment (10) Side view of conventional ultrasonic flowmeter

Explanation of symbols

10 Ultrasonic flow meter 20 Meter case 21 Case body 22 Case lid 23 Measuring assembly storage chamber (measuring tube storage chamber)
24A Gas inlet (fluid inlet)
24B Gas outflow path (fluid outflow path)
31 Measurement pipe 32 Metal pipe 33 Resin cylindrical holder 33A, 33A Holder structure 34 Step part 35 Extension pipe part (mouth pipe part)
35A Opening edge 36 Cylindrical part 40, 40 Ultrasonic sensor 50 Sensor holding arm (sensor holding part)
52 Auxiliary locking piece (sensor holding part)
60 Intermediate wall 61 O-ring (seal member)

Claims (12)

A meter case, a measurement tube that is accommodated in the meter case, and a fluid flows inside, and is arranged away from the openings at both ends of the measurement tube, facing each other across the inner region of the measurement tube In an ultrasonic flowmeter with a pair of ultrasonic sensors,
The measuring tube is formed by covering the outer peripheral surface of a metal pipe with a resin cylindrical holder,
A sensor holding part that is integrally formed at the end of the resin cylindrical holder, extends along the axial direction of the measuring tube, and holds the ultrasonic sensor at the tip ,
The resin cylindrical holder is configured to be vertically divided into a plurality of holder structures,
The ultrasonic flowmeter according to claim 1, wherein the sensor holding part is provided in each of the plurality of holder structures and holds the ultrasonic sensors in cooperation with each other . The ultrasonic flowmeter according to claim 1, wherein the sensor holding portion is configured by a plurality of sensor holding arms extending in a cantilever shape from an end of the holder structure . The ultrasonic flowmeter according to claim 1 or 2, wherein the plurality of holder constituent bodies are formed into the same shape. The resin cylindrical holder includes a mouth pipe portion that is connected to both ends of the metal pipe, extends on an extension line of the metal pipe, and has an inner diameter that expands toward the tip. Item 4. The ultrasonic flowmeter according to any one of Items 1 to 3. Of the resin cylindrical holder, the opening edge of the mouth pipe portion is configured with a rounded curved surface, and the inner surface of the mouth pipe portion is continuous with the opening edge and is flush with the inner surface of the metal pipe. The ultrasonic flowmeter according to claim 4, wherein the ultrasonic flowmeter is provided. The resin cylindrical holder includes a mouth pipe portion connected to both ends of the metal pipe so as to extend on an extension line of the metal pipe and having an inner diameter equal to the inner diameter of the metal pipe. The ultrasonic flowmeter according to claim 1, wherein an inner surface of the metal pipe is flush with an inner surface of the metal pipe. The end portion of the metal pipe is abutted against a step portion between an inner surface of a portion of the resin cylindrical holder where the metal pipe is fitted and an inner surface of the mouth pipe portion. The ultrasonic flowmeter according to any one of 4 to 6. The meter case includes a measuring tube housing chamber that houses the measuring tube, a fluid inflow passage that communicates with one end of the measuring tube housing chamber, and a fluid outflow that communicates with the other end of the measuring tube housing chamber. Road and
The measuring pipe is provided with an intermediate wall that fits between the outer surface of the metal pipe and the inner surface of the measuring pipe housing chamber and divides the measuring pipe housing chamber into the fluid inflow path side and the fluid outflow path side. And
The ultrasonic flowmeter according to any one of claims 1 to 7, wherein the resin cylindrical holders are provided in pairs on both sides of the intermediate wall and fixed to the intermediate wall, respectively. The ultrasonic flowmeter according to claim 8, wherein a seal member is provided between an outer surface of the intermediate wall and an inner surface of the measurement tube housing chamber. The meter case is divided into a case main body and a case lid at at least one end portion of the measurement tube housing room, and the measurement tube can be inserted and assembled into the measurement tube housing room by opening the divided surface. The ultrasonic flowmeter according to claim 8 or 9, wherein The fluid inflow path and the fluid outflow path are formed in the case body, are orthogonal to the measurement tube accommodation chamber, and open toward the side surface of the measurement tube in the measurement tube accommodation chamber. The ultrasonic flowmeter according to claim 8. The ultrasonic flowmeter according to claim 1, wherein the metal pipe is formed by drawing or extrusion.