JP5046824B2 - Ultrasonic flow meter - Google Patents

Description

  The present invention relates to an ultrasonic flowmeter in which a pair of ultrasonic sensors are opposed to openings at both ends of a measurement tube.

As this type of conventional ultrasonic flowmeter, one in which an ultrasonic sensor is respectively held in a pair of sensor holding portions integrally formed at both ends of a measurement tube is known (for example, see Patent Document 1). reference).
JP 2006-337059 (FIG. 1)

  However, in the above-described conventional ultrasonic flowmeter, ultrasonic waves propagated through the tube wall of the measurement tube (hereinafter referred to as “housing noise” as appropriate) can be received by the ultrasonic sensor on the receiving side. Since the housing noise is received by the ultrasonic sensor on the receiving side prior to the ultrasonic wave propagating through the fluid flowing in the measurement tube, the received signal is a superposition of the housing noise on the ultrasonic wave propagating through the fluid Thus, the reception timing of the ultrasonic wave propagating through the fluid becomes unclear. For this reason, it has been difficult to accurately measure the propagation time of the ultrasonic wave that has propagated the fluid, and thus the flow rate of the fluid.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an ultrasonic flowmeter capable of improving the measurement accuracy from the conventional level.

In order to achieve the above object, an ultrasonic flowmeter according to the invention of claim 1 is characterized in that the inside of a meter case having an inlet into which a fluid flows and an outlet from which the fluid flows out is separated from an upstream channel and a downstream by a partition wall. In an ultrasonic flowmeter that is divided into a side channel and has a pair of ultrasonic sensors facing the openings at both ends of the measurement tube that penetrates the partition wall, it has a cylindrical shape that covers the outside of the measurement tube A pair of resin cylindrical holders extending in opposite directions from the front and back surfaces of the partition wall, each tip projecting forward from the measurement tube, and holding the ultrasonic sensor away from the opening at the end of the measurement tube The pair of plastic cylindrical holders is provided with a bellows-cylindrical structure with concavities and convexities in the axial direction, and is a separate part made of a material with a different acoustic impedance from the partition wall, and is fixed to the partition wall Have

The ultrasonic flowmeter according to the invention of claim 2 divides the inside of a meter case having an inlet through which a fluid flows and an outlet through which the fluid flows into an upstream channel and a downstream channel by a partition wall, and the partition In the ultrasonic flowmeter provided with a pair of ultrasonic sensors facing each other at the openings at both ends of the measurement tube penetrating the wall, it forms a cylindrical shape that covers the outside of the measurement tube and contradicts both the front and back surfaces of the partition wall. A pair of resin cylindrical holders each extending in the direction, each tip projecting forward from the measurement tube and holding the ultrasonic sensor away from the opening at the end of the measurement tube, and the pair of resin tubes The shape holder is characterized in that it has a bellows cylinder structure with concavities and convexities in the axial direction and is arranged with a gap with respect to the measurement tube .

The invention of claim 3 is characterized in that, in the ultrasonic flowmeter according to claim 1 or 2, the partition wall is made of polyacetal resin and the resin cylindrical holder is made of urethane resin.

  According to a fourth aspect of the present invention, in the ultrasonic flowmeter according to any one of the first to third aspects, each of the resin cylindrical holders is vertically divided to provide a pair of holder components, and the partition wall Engagement protrusions that protrude from both the front and back sides and that protrude from the base end to the side are provided, and the pair of holder components move in a direction perpendicular to the axial direction on the split surface of the pair of holder components In the process, the engagement protrusions are engaged with the projections to form engagement grooves that can regulate the movement of the pair of holder components in the axial direction.

  According to a fifth aspect of the present invention, in the ultrasonic flowmeter according to any one of the first to fourth aspects, the pair of resin cylindrical holders protrudes inward from the front ends of the pair of resin cylindrical holders and are locked to both end faces of the measuring tube. It is characterized in that it has positioning protrusions.

  The invention of claim 6 is characterized in that in the ultrasonic flowmeter according to any one of claims 1 to 5, the measurement tube is made of metal.

[Invention of Claims 1 to 3 ]
According to the first and second aspects of the present invention, the inside of the meter case is partitioned by the partition wall into the upstream flow path and the downstream flow path, and is communicated by the measurement pipe penetrating the partition wall. All of the fluid that flows into the upstream flow path of the meter case from the inlet of the meter case passes through the measurement pipe and flows into the downstream flow path. Then, the flow velocity of the fluid passing through the measurement tube is calculated based on the propagation time of the ultrasonic waves transmitted and received between the pair of ultrasonic sensors, and the flow rate is calculated by multiplying the flow velocity by the cross-sectional area of the measurement tube. Is done.

Here, in the ultrasonic flowmeter of the present invention, the ultrasonic sensors are respectively held by a pair of resin cylindrical holders covering the outside of the measurement tube. Accordingly, the ultrasonic waves can propagate through the pair of resin cylindrical holders and reach the ultrasonic sensor on the receiving side. However, since each resin cylindrical holder has a bellows cylindrical structure, The propagation path length of the ultrasonic wave (casing noise) propagating through the holder is longer than before. Accordingly, the timing at which the housing noise reaches the reception-side ultrasonic sensor can be sufficiently delayed with respect to the timing at which the ultrasonic wave propagated through the fluid in the measurement tube reaches the reception-side ultrasonic sensor. In other words, since the housing noise is not superimposed when receiving the ultrasonic wave that has propagated in the fluid, the reception timing of the ultrasonic wave that has propagated in the fluid can be clarified, and the measurement accuracy of the propagation time of the ultrasonic wave that has propagated in the fluid As a result, the measurement accuracy of the flow rate can be improved as compared with the prior art. Then , as in the second aspect of the invention, a pair of resin cylindrical holders are arranged with a gap with respect to the measurement pipe so that the casing is propagated to the measurement pipe via the resin cylindrical holder. Since noise can be reduced, flow rate measurement accuracy can be further improved.

Moreover, according to the structure of Claim 1 , at the interface of the partition wall comprised with another part, and each resin cylindrical holder, housing noise reflects by the difference in those acoustic impedances. That is, the propagation of the housing noise is hindered and the housing noise can be attenuated. Here, it is preferable that the partition wall is made of polyacetal resin and the resin cylindrical holder is made of urethane resin as in the invention of claim 3. If the partition wall is made of metal (for example, aluminum) instead of resin, the difference in acoustic impedance with the resin cylindrical holder can be increased, which is more effective.

[Invention of claim 4]
According to the invention of claim 4, in the process of moving the pair of holder components in the direction orthogonal to the axial direction (method of bringing the divided surfaces close to each other) and combining them, the divided surfaces of the holder components The engaging grooves formed on the concave and convex portions engage with the engaging protrusions protruding from both the front and back surfaces of the partition wall. And the front-end | tip part of an engagement protrusion and an engagement groove | channel are latched in the axial direction of a holder structure, and the axial direction of a pair of holder structure, ie, the resin cylindrical holder formed by uniting them And the resin cylindrical holders are fixed to both the front and back surfaces of the partition wall.

[Invention of claim 5]
According to the invention of claim 5, the measuring tube accommodated inside the pair of resin cylindrical holders can be positioned in the axial direction.

[Invention of claim 6]
According to invention of Claim 6, the change of the cross-sectional area of a measuring tube by a temperature change can be prevented. In order to make the fluid flow smoothly, it is preferable to use a seamless drawn tube or extruded tube.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
Reference numeral 10 in FIGS. 1 and 2 is an ultrasonic flowmeter of the present invention, and a pipeline 100 (FIG. 2) in which a fluid (liquid or gas, specifically, hydrogen gas or helium gas having a relatively high acoustic velocity) flows. (See Fig.). The ultrasonic flow meter 10 includes a metering assembly 30 inside a meter case 20.

  The meter case 20 can be divided into a case main body 21 and case cover bodies 22 and 22 on both sides. Then, the measurement assembly 30 is inserted from one opening (the right opening in FIG. 1) of the case main body 21, and both opening ends of the case main body 21 are closed by the case lid bodies 22, 22, so that the ultrasonic flowmeter 10. Is configured. The case body 21 and the case lids 22 and 22 are fixed by a plurality of screws (not shown).

  Inside the meter case 20, a measuring assembly housing chamber 23 for storing the measuring assembly 30 is provided. The measuring assembly housing chamber 23 has a cylindrical structure as a whole, and gradually increases in diameter from the axial center to both ends.

  As shown in FIG. 2, a pair of connecting tube portions 24, 24 are provided on the side surface of the meter case 20 (specifically, the case body 21). The connecting tube portions 24, 24 slightly protrude from the side surface of the meter case 20 and are provided side by side in the axial direction of the measuring assembly housing chamber 23. Of the connecting tube portions 24, 24, the inside of one connecting tube portion 24 (the right connecting tube portion 24 in FIG. 2) is an introduction path 24 </ b> A (the main channel 24 </ b> A) through which fluid flows into the meter case 20 (the measuring assembly housing chamber 23). The fluid flows out from the inside of the meter case 20 (measuring assembly storage chamber 23) in the other connecting tube portion 24 (the left connecting tube portion 24 in FIG. 2). It is a discharge path 24B (corresponding to the “exit” of the present invention). A female spiral portion for screwing and connecting the meter case 20 to the middle of the pipeline 100 is formed on the inner peripheral surfaces of the connecting cylinder portions 24 and 24.

  As shown in FIG. 2, a partition wall 35 is provided at an intermediate portion in the axial direction of the weighing assembly housing chamber 23. The partition wall 35 partitions the measuring assembly housing chamber 23 into two chambers at an intermediate position between the pair of connecting tube portions 24, 24. That is, the measurement assembly housing chamber 23 is partitioned into an upstream flow path 25 that communicates with the introduction path 24A and a downstream flow path 26 that communicates with the discharge path 24B.

  The partition wall 35 is a molded product of resin (specifically, polyacetal resin), for example, and is provided integrally with the weighing assembly 30. The partition wall 35 has a disk shape that is smaller in diameter than the inner diameter of the intermediate portion of the measurement assembly housing chamber 23 (see FIG. 7A). A space between the outer peripheral surface of the partition wall 35 and the inner peripheral surface of the measurement assembly housing chamber 23 is sealed by an O-ring 37.

  A measurement tube insertion hole 36 is formed at the center of the partition wall 35 and the measurement tube 31 passes therethrough. The measurement tube 31 is, for example, a metal straight pipe and has a circular tube shape with a constant inner diameter and outer diameter. Specifically, it is composed of a seamless aluminum or aluminum alloy pipe that has been drawn or drawn. Since the measurement pipe 31 is made of metal, it is possible to prevent a change in the cross-sectional area of the flow path 31A of the measurement pipe 31 due to a temperature change of the fluid.

  On the other hand, as shown in FIG. 7B, the measurement tube insertion hole 36 includes a small diameter portion 36A having the same diameter as the outer diameter of the measurement tube 31, and a large diameter portion 36B larger in diameter than the small diameter portion 36A. An O-ring 38 is mounted inside the large diameter portion 36B. The O-ring 38 seals between the outer peripheral surface of the measurement tube 31 and the inner peripheral surface of the measurement tube insertion hole 36. Note that rattling between the partition wall 35 and the measurement tube 31 can be prevented by the O-ring 38.

  The measuring tube 31 penetrating the partition wall 35 extends from a position near one end in the axial direction of the measurement assembly housing chamber 23 to a position near the other end (in other words, from one opening of the case body 21 to the other opening). The upstream flow path 25 and the downstream flow path 26 are connected only by the flow path 31 </ b> A in the measurement pipe 31. That is, all of the fluid that has flowed into the upstream flow path 25 from the introduction path 24A (one connecting cylinder portion 24) of the meter case 20 passes through the measurement pipe 31 (flow path 31A) to the downstream flow path 26. It comes to flow.

  As shown in FIG. 1, a pair of ultrasonic sensors 50, 50 are arranged at both ends in the axial direction of the weighing assembly housing chamber 23. The ultrasonic sensors 50, 50 are arranged coaxially with the measurement tube 31, and are arranged opposite to each other with the flow channel 31A of the measurement tube 31 interposed therebetween as shown in FIG.

  Each of the ultrasonic sensors 50 and 50 has a transmission / reception surface 51 on the front surface, and a locking collar 52 on the rear end. In addition, the transmission / reception surface 51 of each ultrasonic sensor 50 is opposed to the opening of the measurement tube 31 by a predetermined distance. In order to position and hold the ultrasonic sensors 50, 50 at the above-described positions with respect to the measuring tube 31, the measuring assembly 30 is provided with a pair of sensor holders 40, 40 (“resin cylindrical holder of the present invention”). Is equivalent to “)”.

  The pair of sensor holders 40, 40 are arranged symmetrically across the partition wall 35 and have the same shape. The sensor holder 40 extends from the partition wall 35 along the axial direction of the measurement tube 31 and has a cylindrical shape covering the outer peripheral surface of the measurement tube 31 (see FIG. 2). The sensor holders 40, 40 are molded products of a resin (for example, urethane resin) having a different acoustic impedance from the partition wall 35.

  As shown in FIG. 3, one sensor holder 40 can be divided into a pair of holder structures 41, 41 and is configured by combining them. Specifically, the pair of holder structures 41, 41 has a structure in which the sensor holder 40 is vertically divided along the axial direction and has the same shape. By making the pair of holder constituting bodies 41, 41 into the same shape, it is possible to share a molding die.

  From the edge part of the holder structure 41, the coupling walls 42 and 42 for connecting the holder structures 41 and 41 protrude sideways. These coupling walls 42, 42 have a flat plate shape that is flush with the divided surfaces of the holder components 41, 41, and when the divided surfaces of the two holder components 41, 41 are overlapped and joined, The connecting walls 42 and 42 of 41 and 41 overlap each other. Then, as shown in FIG. 6, for example, the pair of holder structures 41 and 41 are held in the combined state by passing the tapping screws 43 and 43 through the coupling walls 42 and 42 that overlap with each other. Each coupling wall 42 is provided with a pilot hole 42A for a tapping screw 43.

  As shown in FIG. 7B, on the front and back surfaces (both side surfaces of the back-to-back) of the partition wall 35, an “L” -shaped hook 39 that protrudes in the axial direction of the measuring tube 31 and is bent at a right angle. (Corresponding to the “engagement protrusion” of the present invention) is formed so as to project, and as shown in FIG. 5, the divided surface of each holder component 41 has an “L” shape corresponding to the shape of the hook 39. An engaging groove 44 having a shape is formed. Then, as shown in FIG. 6, in the process of moving the pair of holder structures 41, 41 in a direction orthogonal to the axial direction (a direction in which the divided surfaces are brought closer to each other) and combining them, 44 and the hook 39 engage with each other (see FIG. 2), and the movement of the holder components 41 and 41 (sensor holder 40) in the axial direction is restricted. That is, the sensor holders 40 are fixed to both the front and back surfaces of the partition wall 35.

  Each part of the sensor holder 40 will be described. The sensor holder 40 includes a cylindrical body 410 that extends from the partition wall 35 along the axial direction of the measurement tube 31 and covers the outer peripheral surface of the measurement tube 31. A flange wall 420 is integrally formed at one end portion of the cylindrical body portion 410, and a sensor holding portion 430 that holds the ultrasonic sensor 50 is integrally formed at the other end portion.

  As shown in FIG. 4, the flange wall 420 protrudes laterally from an end of the cylindrical body 410 on the side of the partition wall 35 (hereinafter referred to as “proximal end” as appropriate), and from the partition wall 35. It has a large diameter disk shape. As shown in FIG. 1, the flange wall 420 is addressed to and abuts on the partition wall 35. An annular groove that accommodates the O-ring 37 is formed between the outer peripheral surface of the partition wall 35 and the flange walls 420 and 420 provided on both sides of the partition wall 35 to prevent the O-ring 37 from falling off. Yes.

  The sensor holding part 430 is separated from the end of the cylindrical body 410 opposite to the flange wall 420 (hereinafter referred to as “tip part” as appropriate) in the axial direction of the measurement tube 31 (from the opening of the measurement tube 31). Direction).

  Specifically, as shown in FIG. 4, the sensor holding portion 430 includes a pair of arm portions 431 extending from the distal end portion of the cylindrical body portion 410 in the axial direction of the measurement tube 31, and the arm portions 431. A ring portion 432 concentric with the measurement tube 31 is provided at the tip of the tube, and a plurality of (for example, four) locking protrusions 433 (specifically, snap fit) protruding from the ring portion 432 in a cantilever shape. Has a structure with. Each locking protrusion 433 extends in a direction away from the opening of the measuring tube 31 and is arranged at equal intervals in the circumferential direction of the ring portion 432. Each locking projection 433 passes through a locking hole (not shown) formed in the locking collar 52 of the ultrasonic sensor 50, and the tip protruding portion 433A is locked to the edge thereof. A plurality of locking protrusions 433 cooperate to hold one ultrasonic sensor 50.

  A plurality of positioning protrusions 411 are provided at the tip of the cylindrical body 410 of the sensor holder 40. As shown in FIG. 4, the positioning protrusion 411 protrudes inward from the opening edge of the cylindrical body 410. Then, the positioning protrusions 411 and 411 provided in the pair of sensor holders 40 and 40 are abutted against both end faces of the measuring tube 31 to position the measuring tube 31 in the axial direction (see FIG. 2).

  By the way, the intermediate part in the axial direction of the cylindrical body 410 has a bellows cylinder structure with concavities and convexities along the axial direction in order to make the propagation path length of the housing noise propagating through the sensor holder 40 longer than before. There is no. As shown in FIG. 4, the cross-section of the bellows tube has a rectangular wave shape. More specifically, a plurality of annular recesses 412 are formed at equal intervals in the axial direction on the outer peripheral surface of the cylindrical body 410, and an annular projection 413 is formed in which both sides of the annular recesses 412 are relatively convex. In addition, an annular recess 414 is formed in a portion of the inner peripheral surface of the cylindrical body 410 where the annular protrusion 413 is formed, and the annular recess 412 and the inner peripheral surface of the outer periphery of the cylindrical body 410 are formed. The annular recesses 414 in FIG. 6 are structured so as to be alternately arranged adjacent to each other in the axial direction of the sensor holder 40. In the present embodiment, the depths of the annular recesses 412 and 414 are larger than the width dimension.

  The above is the description regarding the structure of the ultrasonic flowmeter 10 of the present embodiment. This ultrasonic flow meter 10 can be assembled, for example, by the following procedure.

  The measurement assembly 30 is as follows. That is, the sensor tube 40 is passed through the measurement tube 31 with the O-ring 38 fitted in the measurement tube insertion hole 36 (large diameter portion 36 </ b> B) of the partition wall 35 so as to cover the outer peripheral surface of the measurement tube 31. Install. Specifically, as shown in FIG. 6, a pair of holder constituting bodies 41, 41 are brought close to each other from the side of the measuring tube 31 and combined. At this time, the hooks 39 of the partition wall 35 and the engaging grooves 44 of the holder constituting bodies 41 and 41 are engaged with each other. And the connecting walls 42 and 42 of each holder structure 41 and 41 are couple | bonded with the tapping screw 43. FIG. Thus, the sensor holder 40 is attached to one side of the partition wall 35 in the measurement tube 31.

  Next, the O-ring 37 is fitted to the outside of the partition wall 35, and the other sensor holder 40 is attached to the outside of the measuring tube 31 in the same procedure. Then, the ultrasonic sensors 50, 50 are attached to the sensor holding portions 430, 430 of the sensor holders 40, 40, and the assembly of the weighing assembly 30 is completed.

  Next, the completed measuring assembly 30 is mounted in the meter case 20. That is, the measuring assembly 30 is inserted into the measuring assembly housing chamber 23 from the opening on one end side (the right end in FIG. 1) of the case body 21, and the flange wall 420 of the sensor holder 40 is formed on the inner surface of the measuring assembly housing chamber 23. It is pushed in until it hits the formed step portion 23A (see FIG. 1). Then, the partition wall 35 is positioned at an intermediate position between the two connecting cylinder portions 24, 24, and the measuring assembly housing chamber 23 is partitioned into the upstream flow path 25 and the downstream flow path 26 in the axial direction. And if the case lids 22 and 22 are fixed to both ends of the case body 21 and both ends of the case body 21 are closed, the ultrasonic flowmeter 10 is completed.

  When the ultrasonic flowmeter 10 of the present embodiment is connected in the middle of the pipeline 100, the fluid flows from the upstream side of the pipeline 100 to the upstream flow path 25 of the meter case 20. All of the fluid that has flowed into the upstream flow path 25 passes through the measurement pipe 31 and flows into the downstream flow path 26, and is discharged from the downstream flow path 26 to the downstream side of the pipeline 100. At this time, transmission / reception of ultrasonic waves is performed between the pair of ultrasonic sensors 50, 50 in both the forward direction along the fluid flow and the reverse direction. That is, the propagation time in the forward direction and the reverse direction is detected by propagating ultrasonic waves using the fluid flowing through the measurement tube 31 as a propagation medium. Then, based on the propagation time (specifically, the reciprocal difference in propagation time), the flow velocity of the fluid is calculated, and the flow rate is calculated by multiplying the flow velocity by the cross-sectional area of the flow path 31A of the measurement tube 31.

  Here, when an ultrasonic wave is transmitted from one ultrasonic sensor 50, the other ultrasonic sensor 50 receives the ultrasonic wave propagated through the fluid passing through the measurement tube 31 as described above, and the ultrasonic sensors 50, 50. The housing noise propagated through the pair of sensor holders 40, 40 and the partition wall 35 is received.

  On the other hand, according to the ultrasonic flowmeter 10 of the present embodiment, the cylindrical body portion 410 of each sensor holder 40, 40 has a bellows cylinder structure, so that the propagation path length of the housing noise becomes longer than before. ing. Thereby, the timing at which the reception-side ultrasonic sensor 50 receives the housing noise can be sufficiently delayed with respect to the reception timing of the ultrasonic wave propagated through the fluid in the measurement tube 31. In other words, since the housing noise is not superimposed when receiving the ultrasonic wave that has propagated in the fluid, the reception timing of the ultrasonic wave that has propagated in the fluid can be clarified, and the measurement accuracy of the propagation time of the ultrasonic wave that has propagated in the fluid As a result, the measurement accuracy of the flow rate can be improved as compared with the prior art. In addition, the housing noise is reflected during propagation through the sensor holders 40 and 40 due to the bellows structure, and the housing noise propagation path length is extended, so that the housing noise is attenuated more than before. There is also an effect.

  Furthermore, since the sensor holders 40 and 40 and the partition wall 35 are configured as separate parts and are formed of materials having different acoustic impedances, housing noise is generated at the interface between the sensor holders 40 and 40 and the partition wall 35. Part of the reflection. That is, since the propagation of the housing noise is hindered at the interface between the sensor holders 40 and 40 and the partition wall 35, the housing noise can be further attenuated.

  Here, if the length of the propagation path of the housing noise is simply increased, a sensor holding part for holding the ultrasonic sensor may be integrally formed at both ends of the measurement pipe, and the measurement pipe has a bellows cylinder structure. In such a configuration, the flow of fluid is disturbed by the irregularities on the inner surface of the measurement tube, which may adversely affect the measurement accuracy. On the other hand, in the ultrasonic flowmeter 10 of the present embodiment, the sensor holders 40 and 40 that hold the ultrasonic sensors 50 and 50 are configured as separate parts from the measurement tube 31, and then the sensor holders 40 and 40 are configured. Since the accordion cylinder structure is used, the propagation path length of the housing noise can be extended from the conventional one without disturbing the flow of the fluid passing through the measurement tube 31, and the measurement accuracy can be improved.

[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 said embodiment, the partition wall 35 and the sensor holders 40 and 40 should just be a material from which acoustic impedance differs, and are not limited to the combination of polyacetal resin and urethane resin. For example, the partition wall 35 may be made of metal (for example, aluminum). When the partition wall 35 is made of aluminum and the sensor holder 40 is made of polyurethane resin, the transmittance of ultrasonic waves at the interface between the partition wall 35 and the sensor holder 40 is about 50%. Therefore, the sensor holder 40, the partition wall 35, and the sensor holder 40 The case noise can be attenuated to about ¼ when it propagates in this order.

  (2) As shown in FIG. 8A, the partition wall 35 may have a larger diameter than the flange wall 420 of the sensor holder 40, and an O-ring groove that accommodates the O-ring 37 may be provided on the outer peripheral surface thereof. Further, as shown in FIG. 8B, the sensor holders 40, 40 may be fixed to the partition wall 35 with screws 45 that pass through the flange walls 420, 420 and are screwed into the partition wall 35.

  (3) Further, as shown in FIGS. 8A and 8B, the outer peripheral surface of the measuring tube 31 and the inner peripheral surfaces of the sensor holders 40 and 40 may be slightly separated to provide a gap. .

  (4) As shown in FIG. 9, the arm part 431 of the sensor holding part 430 may meander to further extend the propagation path length of the housing noise.

  (5) In the above embodiment, the cross section of the bellows cylinder provided in the sensor holders 40, 40 has a rectangular wave shape, but it may have a triangular wave shape or a sawtooth shape with a slope between the peak portion and the valley portion. . Further, as shown in FIG. 10, a spiral groove 415 is formed on the outer peripheral surface of the cylindrical body 410 to form a relatively convex spiral 416, A spiral recess 417 is formed in a portion of the inner peripheral surface where the spiral convex portion 416 is formed, and the spiral recess 415 formed on the outer peripheral surface of the cylindrical barrel 410 and the cylindrical barrel. A structure in which the spiral concave portion 417 formed on the inner peripheral surface of the portion 410 is adjacently disposed in the axial direction of the sensor holder 40 may be employed.

  (6) The partition wall 35 is provided integrally with the weighing assembly 30, but may be formed integrally with the meter case 20.

  (7) In the above embodiment, the positioning projections 411 are provided on both of the pair of sensor holders 40, 40. However, the positioning projections 411 are provided only on one sensor holder 40, and the front and back of the partition wall 35 are provided. It is good also as a structure which can insert and assemble the measurement pipe | tube 31 in the state which fixed the sensor holders 40 and 40 to both surfaces. In addition, it is easier to assemble the holder constituent bodies 41 and 41 from the side of the measuring tube 31 than to insert the measuring tube 31 into the cylindrical sensor holders 40 and 40.

  (8) The cross section of the measuring tube 31 is not limited to a circle but may be an ellipse or an oval.

  (9) Both opening edges of the measurement tube 31 may be chamfered in a tapered shape so that the fluid smoothly flows in and out of the measurement tube 31 and may be expanded in a trumpet shape.

1 is a cross-sectional plan view of an ultrasonic flowmeter according to an embodiment of the present invention. Side view of ultrasonic flowmeter Exploded perspective view of sensor holder Cross section of weighing assembly Plan view of the holder structure as seen from the split surface side Side view of the process of uniting a pair of holder components (A) Front view of partition wall, (B) Side sectional view Side sectional view of ultrasonic flowmeter according to modification Sectional drawing of the sensor holder which concerns on a modification Partial sectional view of a sensor holder according to a modification

Explanation of symbols

10 Ultrasonic flow meter 20 Meter case 24A Introduction path (inlet)
24B Departure route (exit)
25 Upstream channel 26 Downstream channel 31 Measuring tube 35 Partition wall 39 Hook (engaging protrusion)
40 Sensor holder (plastic cylinder holder)
41 Holder structure 44 Engaging groove 50 Ultrasonic sensor 411 Positioning protrusion

Claims (6)

The inside of the meter case having an inlet through which the fluid flows and an outlet through which the fluid flows out is divided into an upstream flow channel and a downstream flow channel by a partition wall, and 1 is provided at the openings at both ends of the measurement tube penetrating the partition wall. In an ultrasonic flowmeter equipped with a pair of ultrasonic sensors facing each other,
Forming a cylindrical shape covering the outside of the measurement tube and extending in opposite directions from both the front and back surfaces of the partition wall, each tip protrudes forward from the measurement tube, and the ultrasonic sensor is connected to the end of the measurement tube. A pair of plastic cylindrical holders held away from the opening of the
The pair of resin cylindrical holders has a bellows cylindrical structure with concavities and convexities in the axial direction, and is fixed to the partition wall as a separate part having a material different in acoustic impedance from the partition wall. Ultrasonic flow meter. The inside of the meter case having an inlet through which the fluid flows and an outlet through which the fluid flows out is divided into an upstream flow channel and a downstream flow channel by a partition wall, and 1 is provided at the openings at both ends of the measurement tube penetrating the partition wall. In an ultrasonic flowmeter equipped with a pair of ultrasonic sensors facing each other,
Forming a cylindrical shape covering the outside of the measurement tube and extending in opposite directions from both the front and back surfaces of the partition wall, each tip protrudes forward from the measurement tube, and the ultrasonic sensor is connected to the end of the measurement tube. A pair of plastic cylindrical holders held away from the opening of the
An ultrasonic flowmeter characterized in that the pair of resin cylindrical holders has a bellows cylindrical structure with concavities and convexities in the axial direction and is provided with a gap with respect to the measurement tube. The ultrasonic flowmeter according to claim 1 or 2, wherein the partition wall is made of polyacetal resin and the resin cylindrical holder is made of urethane resin. The resin cylindrical holders are vertically divided to provide a pair of holder structures, and engaging protrusions projecting from both the front and back surfaces of the partition wall and projecting from the base end to the side. Provided,
The pair of holder components is engaged with the engaging protrusions in the process of moving the pair of holder components in a direction perpendicular to the axial direction on the split surfaces of the pair of holder components. The ultrasonic flowmeter according to claim 1, wherein an engagement groove capable of restricting movement in the axial direction is formed.   5. The supermarket according to claim 1, further comprising positioning protrusions that protrude inward from the tip end portions of the pair of resin cylindrical holders and are engaged with both end faces of the measuring tube. Sonic flow meter.   The ultrasonic flowmeter according to claim 1, wherein the measurement tube is made of metal.

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