JP2016223800A - Ultrasonic flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic flowmeter which can sufficiently uniformize the flow of a measurement object fluid at the time of the large flow rate and achieve miniaturization.SOLUTION: A meter case comprises: an inlet buffer part which is formed with an opening provided adjacently in the direction substantially perpendicular to the flow direction with respect to the depth side end of an inflow passage to which measurement object fluid flows from an inflow port and communicating the inflow passage, and is sectioned in a substantial box shape so that the inlet side of the measurement passage part with the substantially rectangular cross section protrudes inward, and the measurement object fluid flows into the inlet of the measurement passage part; and an outlet buffer part which communicates the outflow port and is sectioned in the substantial box shape so that the outlet side of the measurement passage part protrudes inward and the measurement object fluid flowing out from the outlet of the measurement passage part flows out to the outside. The measurement passage part is arranged so as to cover the most of the opening in the front view by protruding into the inlet buffer part so that the side surface on the inlet side becomes substantially parallel with the inner wall of the inlet buffer part formed with the opening.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an ultrasonic flowmeter that measures the flow rate of a fluid to be measured.

Conventionally, various techniques relating to an ultrasonic flowmeter for measuring the flow rate of a fluid to be measured have been proposed.
For example, in the ultrasonic flowmeter described in Patent Document 1 below, the measurement chamber is divided into an inflow side and an outflow side by a partition wall, and a substantially rectangular cross section in which a flow path through which a fluid to be measured flows is formed. The cylindrical flow tube which has has penetrated the partition wall.

  In addition, a baffle plate that partitions both spaces between the inflow portion into which the fluid to be measured flows and the measurement chamber is provided substantially at right angles to the flow direction of the fluid to be measured that flows into the inflow portion. . The baffle plate has a circular inflow port formed at the end on the partition wall side. Therefore, the fluid to be measured hits the upper surface of the baffle plate from the inflow part, then flows along the baffle plate, enters the inlet, again hits the outer wall of the flow tube, and flows in the measurement chamber along the outer wall of the flow tube. And flow into the flow path. Therefore, since the fluid to be measured is changed in direction by 180 degrees twice and flows for a certain distance, the flow can be made uniform.

JP 2004-85210 A

  However, in the ultrasonic flowmeter described in Patent Document 1, the fluid to be measured needs to change its direction 180 degrees twice and flow for a certain distance in order to make the flow sufficiently uniform. As a result, when the flow rate of the fluid to be measured becomes a large flow rate (for example, a flow rate of about 6000 (liters / hour)), it is difficult to reduce the size of the measurement chamber. There is a problem that miniaturization is difficult.

  Therefore, the present invention has been made to solve the above-described problems, and it is possible to sufficiently equalize the flow of the fluid to be measured at the time of a large flow rate and to reduce the size. It aims at providing the ultrasonic flowmeter which becomes.

  In order to achieve the object, an ultrasonic flowmeter according to claim 1 includes a meter case in which an inlet of a fluid to be measured and an outlet of the fluid to be measured are formed, and the meter case disposed in the meter case. A flow rate measurement unit that measures the flow rate of the fluid to be measured that passes through the flow channel, and the flow rate measurement unit includes a measurement channel portion having a substantially rectangular cross section through which the fluid to be measured flows, A pair of ultrasonic transducers attached to the upstream side and the downstream side, and the meter case is substantially in the flow direction at the back end of the inflow path through which the fluid to be measured flows from the inflow port. An opening is formed adjacent to each other at right angles and communicates with the inflow path, and the inlet side of the measurement channel portion protrudes inward so that the fluid to be measured flows into the inlet portion of the measurement channel portion. Like a box A substantially box-like body that communicates with the mouth buffer portion and the outlet, and that the outlet side of the measurement channel portion protrudes inward so that the fluid to be measured that has flowed out of the outlet portion of the measurement channel portion flows out to the outside. An outlet buffer section partitioned into a shape, and the measurement flow path section has a side surface on the inlet side substantially parallel to an inner wall of the inlet buffer section in which the opening is formed. It protrudes into the inlet buffer part, and is arranged so as to substantially cover the opening part in a front view.

  An ultrasonic flowmeter according to claim 2 is the ultrasonic flowmeter according to claim 1, wherein the meter case closes the opening and supplies the fluid to be measured to the inlet buffer. A shut-off valve for shutting off, and the shut-off valve is disposed so as to face the side surface on the inlet side of the measurement flow path section through the opening, and between the shut-off valve and the opening. The first gap is arranged so that the distance between the first gap and the second gap between the opening and the side surface on the inlet side of the measurement flow path is substantially equal.

  Moreover, the ultrasonic flowmeter according to claim 3 is the ultrasonic flowmeter according to claim 1 or 2, wherein the opening is substantially equal to a height of a side surface of the opposed measurement flow path portion. The cross section is formed in a substantially circular shape having an inner diameter.

  An ultrasonic flow meter according to claim 4 is the ultrasonic flow meter according to claim 3, wherein the measurement flow path portion is protruded into the inlet buffer portion and is located on the protrusion direction side of the opening. The protrusion distance at which the end protrudes outward from the inlet portion of the measurement flow path portion is set to a predetermined value or less so that the fluid to be measured does not flow directly from the opening portion into the inlet portion of the measurement flow path portion. It is characterized by being set.

  The ultrasonic flowmeter according to claim 5 is the ultrasonic flowmeter according to any one of claims 1 to 4, wherein the meter case is sandwiched between the inlet buffer portion and the outlet buffer portion. And a central space portion in which the portion of the measurement flow path portion provided with the pair of ultrasonic transducers is disposed.

  Furthermore, an ultrasonic flowmeter according to claim 6 is a meter case in which an inlet for a fluid to be measured and an outlet for the fluid to be measured are formed, and is disposed in the meter case and passes through the meter case. A flow rate measuring unit for measuring a flow rate of the fluid to be measured, the flow rate measuring unit having a substantially rectangular cross-section of the flow channel through which the fluid to be measured flows, and upstream and downstream of the measurement flow channel unit A pair of ultrasonic transducers attached to a side of the meter case, the meter case adjacent to a rear end portion of the inflow path through which the fluid to be measured flows from the inflow port in a direction substantially perpendicular to the flow direction. In addition, an opening that is provided and communicates with the inflow path is formed, and the inlet side of the measurement channel portion protrudes inward so that the fluid to be measured flows into the inlet portion of the measurement channel portion. An inlet buffer section partitioned in a box shape In addition to communicating with the outlet, the outlet side of the measurement channel section protrudes inward, and the fluid to be measured that has flowed out of the outlet section of the measurement channel section is partitioned into a substantially box shape. An outlet buffer part, a central space part where the pair of ultrasonic transducers of the measurement flow path part is provided sandwiched between the inlet buffer part and the outlet buffer part, and the opening part. And a shutoff valve that shuts off the supply of the fluid to be measured to the inlet buffer unit, and the measurement channel unit has a side surface on the inlet side and the inlet buffer unit in which the opening is formed. Projecting into the inlet buffer part so as to be substantially parallel to the inner wall of the sensor, and the shut-off valve is disposed so as to face the side surface on the inlet side of the measurement channel part through the opening, A first gap between the shut-off valve and the opening. Is arranged so that the distance is substantially equal to the distance of the second gap between the opening and the side surface on the inlet side of the measurement flow path section, and the opening section of the measurement flow path section facing each other. An end portion on the protruding direction side of the opening in the protruding direction into the inlet buffer portion of the measurement flow path portion is formed in a substantially circular shape having an inner diameter substantially equal to the height of the side surface. The protruding distance protruding from the inlet portion of the flow path portion is set to be equal to or less than a predetermined value, and the measurement flow path portion is arranged so as to substantially cover the opening as viewed from the front.

  In the ultrasonic flowmeter according to claim 1, the inlet buffer section partitioned in a substantially box shape is substantially perpendicular to the flow direction at the back end of the inflow path through which the fluid to be measured flows from the inlet. Openings that are provided adjacent to each other and communicate with the inflow passage are formed. Further, the measurement flow path portion having a rectangular cross section of the flow rate measurement unit protrudes into the inlet buffer portion so that the side surface on the inlet side is substantially parallel to the inner wall of the inlet buffer portion in which the opening is formed, It arrange | positions so that a front view opening part may be covered substantially.

  Therefore, after the fluid to be measured flows into the inlet buffer portion at the back end portion of the inflow passage, the flow direction is bent in a substantially right angle direction, hits the side surface of the opposite measurement flow path portion, and again along the side surface. The liquid crystal is bent in a substantially right angle direction, that is, in both height directions of the side surface of the measurement flow path portion, and flows into the inlet buffer portion. Then, the fluid to be measured that has flowed into the inlet buffer portion flows while being bent in a substantially right angle direction toward the inlet portion side of the measurement channel portion along the side surface opposite to the opening portion of the measurement channel portion. Thereafter, the fluid to be measured hits the inner wall of the inlet buffer portion facing the inlet portion of the measurement flow path portion, and again changes its direction by 180 degrees and flows into the inlet portion of the measurement flow path portion.

  As a result, the flow direction is changed several times before the fluid to be measured flows into the inlet buffer portion and into the inlet portion of the measurement flow path portion, so that the flow is sufficiently uniform and a large flow rate (for example, , The flow rate of 8000 (liter / hour). In addition, the opening provided in the inner wall of the substantially box-shaped inlet buffer portion is formed in a size that is substantially covered by the measurement channel portion protruding into the inlet buffer portion. By shortening the protruding length of the inlet buffer, it is possible to reduce the size of the inlet buffer portion. As a result, it is possible to reduce the size of the ultrasonic flowmeter.

  In the ultrasonic flowmeter according to claim 2, the shut-off valve that closes the opening and shuts off the supply of the fluid to be measured to the inlet buffer is provided on the side surface on the inlet side of the measurement channel through the opening. It arrange | positions so that it may oppose. Further, the distance of the first gap between the shut-off valve and the opening is arranged so as to be approximately equal to the distance of the second gap between the opening and the side surface on the inlet side of the measurement flow path. . Thereby, the distance of the 1st clearance gap between a shut-off valve and an opening part can be narrowed, and it becomes possible to narrow the distance of the 2nd clearance gap between an opening part and the side surface by the side of the inlet of a measurement flow path part. Further, it is possible to further reduce the size of the inlet buffer section. As a result, it is possible to further reduce the size of the ultrasonic flowmeter.

  In the ultrasonic flowmeter according to claim 3, since the opening is formed in a substantially circular cross section having an inner diameter substantially equal to the height of the side surface of the opposing measurement flow path, the opening is formed. Can be easily performed. In addition, the measurement channel portion protruding into the inlet buffer portion can be easily configured so as to substantially cover the opening portion when viewed from the front.

  In the ultrasonic flowmeter according to claim 4, in the protruding direction into the inlet buffer portion of the measurement flow path portion, the end portion on the protruding direction side of the opening portion protrudes outward from the inlet portion of the measurement flow path portion. The protruding distance to be measured is set to be equal to or less than a predetermined value at which the fluid to be measured does not flow directly from the opening to the inlet of the measurement channel. As a result, the flow of the fluid to be measured is sufficiently uniform, and a large flow rate (for example, a flow rate of 8000 (liter / hour)) can be measured. As a result, it is possible to reduce the size of the inlet buffer, and thus it is possible to reduce the size of the ultrasonic flowmeter.

  In the ultrasonic flowmeter according to the fifth aspect, a portion of the measurement flow path portion where the pair of ultrasonic transducers is provided is disposed in a central space portion sandwiched between the inlet buffer portion and the outlet buffer portion. Therefore, it is possible to easily reduce the size of the outlet buffer unit. As a result, it is possible to further reduce the size of the ultrasonic flowmeter.

  In the ultrasonic flowmeter according to the sixth aspect, the inlet buffer section partitioned in a substantially box shape is substantially perpendicular to the flow direction at the back end of the inflow path through which the fluid to be measured flows from the inlet. Openings that are adjacent to each other and communicate with the inflow passage are formed. Further, the measurement flow path portion having a rectangular cross section of the flow rate measurement unit protrudes into the inlet buffer portion so that the side surface on the inlet side is substantially parallel to the inner wall of the inlet buffer portion in which the opening is formed, It arrange | positions so that a front view opening part may be covered substantially.

  Therefore, after the fluid to be measured flows into the inlet buffer portion at the back end portion of the inflow passage, the flow direction is bent in a substantially right angle direction, hits the side surface of the opposite measurement flow path portion, and again along the side surface. The liquid crystal is bent in a substantially right angle direction, that is, in both height directions of the side surface of the measurement flow path portion, and flows into the inlet buffer portion. Then, the fluid to be measured that has flowed into the inlet buffer section wraps around the outer peripheral surface of the measurement flow path section and hits the inner wall facing the opening in the inlet buffer section. Thereafter, the fluid to be measured flows to and collides with the central portion of the inlet buffer section, and is substantially perpendicular to the inlet section side of the measurement flow path section along the side surface opposite to the opening section of the measurement flow path section. Bent and flow. Thereafter, the fluid to be measured hits the inner wall of the inlet buffer portion facing the inlet portion of the measurement flow path portion, and again changes its direction by 180 degrees and flows into the inlet portion of the measurement flow path portion.

  As a result, the flow direction is changed several times before the fluid to be measured flows into the inlet buffer portion and into the inlet portion of the measurement flow path portion, so that the flow is sufficiently uniform and a large flow rate (for example, , The flow rate of 8000 (liter / hour). In addition, the opening provided in the inner wall of the substantially box-shaped inlet buffer portion is formed in a size that is substantially covered by the measurement channel portion protruding into the inlet buffer portion. By shortening the protruding length of the inlet buffer, it is possible to reduce the size of the inlet buffer portion. As a result, it is possible to reduce the size of the ultrasonic flowmeter.

  Further, the shut-off valve that closes the opening and blocks the supply of the fluid to be measured to the inlet buffer is disposed so as to face the inlet side surface of the measurement channel through the opening. Further, the distance of the first gap between the shut-off valve and the opening is arranged so as to be approximately equal to the distance of the second gap between the opening and the side surface on the inlet side of the measurement flow path. . Thereby, the distance of the 1st clearance gap between a shut-off valve and an opening part can be narrowed, and it becomes possible to narrow the distance of the 2nd clearance gap between an opening part and the side surface by the side of the inlet of a measurement flow path part. Further, it is possible to further reduce the size of the inlet buffer section. As a result, it is possible to further reduce the size of the ultrasonic flowmeter.

  Moreover, since the opening is formed in a substantially circular cross section having an inner diameter substantially equal to the height of the side surfaces of the opposing measurement channel parts, the opening can be easily formed. In addition, the measurement channel portion protruding into the inlet buffer portion can be easily configured so as to substantially cover the opening portion when viewed from the front.

  In addition, in the protruding direction of the measurement flow channel portion into the inlet buffer portion, the protruding distance at which the end portion on the protruding direction side of the opening portion protrudes outward from the inlet portion of the measurement flow channel portion is determined by the fluid to be measured. It is set so as to be equal to or less than a predetermined value that does not directly flow into the inlet portion of the measurement flow channel portion. As a result, the flow of the fluid to be measured is sufficiently uniform, and a large flow rate (for example, a flow rate of 8000 (liter / hour)) can be measured. As a result, it is possible to reduce the size of the inlet buffer, and thus it is possible to reduce the size of the ultrasonic flowmeter.

  In addition, since the portion of the measurement flow path portion where the pair of ultrasonic transducers is provided is disposed in the central space portion sandwiched between the inlet buffer portion and the outlet buffer portion, the outlet buffer portion can be easily reduced in size. It becomes possible to plan. As a result, it is possible to further reduce the size of the ultrasonic flowmeter.

It is a disassembled perspective view which shows an example of schematic structure of the ultrasonic flowmeter which concerns on this embodiment. It is a front view which shows the state which removed the cover of the meter case of an ultrasonic flowmeter. It is principal part sectional drawing of the center part of a flow measurement unit. It is X1-X1 arrow sectional drawing in FIG. 2 of a meter case. It is X2-X2 arrow sectional drawing in FIG. 2 of a meter case. It is explanatory drawing which shows an example of the flow of the fuel gas in an inlet_port | entrance buffer part. It is explanatory drawing which shows an example of the flow of the fuel gas in the X3-X3 arrow cross section of FIG. It is a figure which shows an example of the measurement result of the largest measurable flow volume measured by changing the deviation | shift amount of the entrance part and opening part edge part of a flow measurement unit.

  DETAILED DESCRIPTION Hereinafter, an ultrasonic flowmeter according to the present invention will be described in detail with reference to the drawings based on an embodiment embodying the invention.

[Schematic configuration of ultrasonic flowmeter 1]
First, a schematic configuration of the ultrasonic flowmeter 1 according to the present embodiment will be described with reference to FIGS. 1 to 5. FIG. 1 is a diagram illustrating a state in which the flow rate measurement unit 11 and the cover 3B are attached to the meter housing 3A of the meter case 3. As shown in FIG. 1, the ultrasonic flowmeter 1 according to the present embodiment is a fuel gas meter that measures the flow rate of a fuel gas (for example, city gas, LP gas, etc.) that is an example of a fluid to be measured. The meter case 3 having a substantially rectangular parallelepiped shape connected to the fuel gas pipe 2 is provided.

  The meter case 3 includes a meter housing 3A formed in a substantially rectangular parallelepiped shape whose front side is open, and a substantially box-shaped cover 3B whose inner side is recessed by a predetermined depth, which is screwed to the front side through each screw hole 3C. And the inside is kept airtight. Further, from the upper surface of the meter housing 3 </ b> A, an inflow port 5 and an outflow port 6 that are airtightly connected to the pipe 2 are provided so as to protrude from both ends in the longitudinal direction and communicate with the meter case 3. Fuel gas is supplied to the inflow port 5 through the pipe 2. Further, in the meter case 3, a flow rate measurement unit 11 that measures the flow rate of the fuel gas passing through the meter case 3 with a pair of ultrasonic transducers 12A and 12B (see FIG. 3) is provided on the front surface of the meter housing 3A. It is inserted from the side and arranged along the longitudinal direction.

  Here, a schematic configuration of the flow rate measurement unit 11 will be described with reference to FIGS. 1 to 4. As shown in FIG. 1 to FIG. 4, the flow rate measurement unit 11 includes a rectangular cylindrical measurement flow path section 15 whose flow path section is long in the vertical direction, and an upper side of the longitudinal center of the measurement flow path section 15. The circuit case 16 is formed.

  As shown in FIG. 3, in the circuit case 16, at a position facing the short side of the measurement flow path portion 15 (on the upper surface side of the measurement flow path portion 15 in FIG. 3), at both ends in the flow direction. The ultrasonic transducers 12A and 12B are arranged, and a V-shaped ultrasonic wave propagation path 17 is formed in which the ultrasonic wave is reflected by the opposing surface. In addition, a circuit board 18 on which a measurement circuit 18A to which the ultrasonic transducers 12A and 12B are electrically connected is formed is disposed above the ultrasonic transducers 12A and 12B. The flow rate measurement value of the fluid is calculated and output.

  As shown in FIGS. 1 to 4, the inlet portion 15 </ b> A and the outlet portion 15 </ b> B of the measurement flow path portion 15 are formed in curved surfaces whose inner peripheral surfaces smoothly spread outward. Further, as shown in FIGS. 3 and 4, a plurality of, for example, five flow dividing plates 19 are provided below the ultrasonic transducers 12A and 12B, on the long side of the flow channel cross section of the measurement flow channel section 15. They are provided at substantially equal intervals in the short side direction so as to be parallel (left and right direction in FIG. 4) and parallel to the flow direction. Accordingly, each flow dividing plate 19 is provided in the measurement flow path section 15 so as to be parallel to a plane including the ultrasonic wave propagation path 17 between the ultrasonic transducers 12A and 12B. Thereby, the flow direction in the measurement flow path part 15 can be stabilized by the respective flow dividing plates 19.

  Next, a schematic configuration in the meter case 3 will be described with reference to FIGS. As shown in FIGS. 1, 2 and 4, the pair of partition walls 21A and 21B are located at the front end from the rear side wall surface in the meter housing 3A at a position substantially equal to the both ends in the longitudinal direction of the meter housing 3A. It is erected in parallel to the vertical direction over the entire height to the part. The distance between the pair of partition walls 21 </ b> A and 21 </ b> B is set to a distance slightly longer (for example, about 6 mm longer) than the length of the circuit case 16 in the longitudinal direction of the measurement flow path portion 15 of the flow rate measurement unit 11. A pair of partition walls 22A and 22B are erected in parallel to the vertical direction over the entire height from the position facing the partition walls 21A and 21B on the back side wall surface portion in the cover 3B to the front end. .

  Each partition wall 21A, 21B has a slightly larger cross-sectional shape than the measurement flow path portion 15 of the flow rate measurement unit 11 from the center in the vertical direction of the front end portion toward the back side. Notch recesses 23A and 23B having a similar rectangular cross section that is long in the up-down direction and about 1 mm to about 3 mm larger than the shape are formed. In addition, two rows of ribs 25 for attaching so-called O-rings formed of elastic rubber or the like are provided on the outer peripheral portions of the measurement flow path portion 15 of the flow rate measurement unit 11 facing the partition walls 21A and 21B, respectively. It is erected over the entire circumference.

  As shown in FIGS. 1 and 2, the height in the vertical direction from the both longitudinal ends in the meter housing 3 </ b> A to the partition walls 21 </ b> A and 21 </ b> B is the inlet 15 </ b> A of the measurement flow path 15. The outlet portion 15B is formed to have a height that is slightly larger than the height in the vertical direction. Further, the distance from both longitudinal end portions in the meter housing 3A to the partition walls 21A and 21B is the distance from each rib 25 of the measurement flow path portion 15 of the flow rate measurement unit 11 to the inlet portion 15A and the outlet portion 15B. It is formed so as to be longer by a predetermined distance (for example, a distance of about 10 mm).

  Further, the height in the vertical direction between the partition walls 21A and 21B in the meter housing 3A is determined by attaching an O-ring between the ribs 25 of the measurement flow path unit 15 of the flow rate measurement unit 11 to measure the measurement flow path unit 15. When the portion to which the O-ring is attached is fitted into each of the partition recesses 23A and 23B from the front side of the meter housing 3A, the circuit case 16 is formed so that the height can be inserted.

  Accordingly, as shown in FIGS. 1, 2, and 4, the meter case 3 has an O-ring attached between the ribs 25 of the measurement flow path unit 15 of the flow rate measurement unit 11, and the O-ring of the measurement flow path unit 15 is After the attached portion is fitted into the partition recesses 23A and 23B from the front side of the meter housing 3A, the cover 3B is screwed to the front side of the meter housing 3A.

  As a result, an inlet buffer section 27 is formed in the meter case 3 in which the inlet section 15A of the measurement flow path section 15 is partitioned in a substantially box shape projecting inward from the partition walls 21A and 22A. Further, a partition is formed in a substantially box shape between the partition walls 21A and 22A and the partition walls 21B and 22B, in which a central portion sandwiched between the ribs 25 of the circuit case 16 and the measurement flow path portion 15 is disposed. A central space 28 is formed.

  Further, an outlet buffer section 29 is configured in which the outlet section 15B of the measurement flow path section 15 is partitioned in a substantially box shape protruding inward from the partition walls 21B and 22B. Accordingly, the inlet buffer unit 27, the central space unit 28, and the outlet buffer unit 29 are configured such that the inside thereof is kept airtight. Further, the inlet buffer unit 27 and the outlet buffer unit 29 are communicated with each other by a substantially rectangular measurement channel unit 15 whose section is long in the vertical direction. In addition, an external terminal 30 electrically connected to the measurement circuit 18A is airtightly attached to the wall surface of the central space 28 opposite to the cover 3B, and the flow rate of the combustion gas output from the measurement circuit 18A The measurement value can be output to the outside.

  2, 4, and 5, on the opposite side of the meter buffer 3 </ b> A to the cover 3 </ b> B of the inlet buffer portion 27, an inflow passage 5 </ b> A through which combustion gas flows from the inflow port 5 extends in the vertical direction. A substantially rectangular parallelepiped inflow chamber 31 is formed adjacent to the inlet buffer 27 at the back end of the inflow passage 5A. The cross-sectional shape along the vertical direction (inflow direction) of the inflow chamber 31 is formed substantially the same as the cross-sectional shape along the vertical direction (inflow direction) of the inlet buffer portion 27.

  Further, the wall surface portion of the inflow chamber 31 on the inlet buffer portion 27 side has a central axis perpendicular to the axis of the measurement flow channel portion 15 protruding into the inlet buffer portion 27, and the cross section of the measurement flow channel portion 15. An opening 32 having a circular cross section having a diameter substantially equal to the height H1 in the vertical direction (see FIG. 2) is opened. In addition, when viewed from the front, the end L on the opposite side of the partition wall 21A of the opening 32 is shifted to the outside from the inlet 15A of the measurement flow path section 15, that is, the partition wall of the opening 32. The distance L1 in the longitudinal direction of the measurement flow path portion 15 between the end opposite to 21A and the end face of the inlet portion 15A is a predetermined length or less (for example, 0 mm to 4.5 mm or less), as will be described later. .) (See FIG. 8).

  A shut-off valve 33 capable of closing the opening 32 is disposed on the wall surface of the inflow chamber 31 opposite to the inlet buffer 27. Therefore, the shut-off valve 33 is disposed so as to face the side surface of the measurement flow path portion 15 through the opening 32. As shown in FIG. 4, the shutoff valve 33 normally has a distance D <b> 1 between the opening 32 and the shutoff valve 33 such that the distance D <b> 1 between the opening 32 and the shutoff valve 33 is the side of the opening 32 and the measurement flow path 15. Are arranged so as to be substantially equal to the distance D2 of the gap (second gap) between and the opening 32. The shut-off valve 33 closes the opening 32 when an abnormality occurs in the supply gas flow rate, forcibly shuts off the inflow chamber 31 and the inlet buffer 27, and stops the supply of combustion gas. It is possible.

  A control unit 34 including a microcomputer or the like is electrically connected to the external terminal 30 electrically connected to the measurement circuit 18 </ b> A of the flow rate measurement unit 11, the cutoff valve 33, and the like. The control unit 34 detects an abnormality such as a supply gas flow rate based on the measured value of the flow rate of the combustion gas output from the measurement circuit 18A. If the abnormality is a predetermined gas cutoff target, the cutoff valve 33 is detected. Is driven to close the opening 32 and supply of combustion gas is stopped. Further, the control unit 34 is configured to be able to output the flow rate measurement value of the combustion gas output from the measurement circuit 18A to a personal computer (not shown) or the like.

  The flow of the combustion gas in the inlet buffer portion 27 of the meter case 3 configured as described above will be described with reference to FIGS. As shown in FIGS. 6 and 7, the combustion gas that has flowed into the inflow port 5 flows into the inflow chamber 31 through the inflow path 5 </ b> A along the vertical direction, bends substantially at right angles to the flow direction, and opens the opening 32. Into the inlet buffer 27 (see arrow 35). Then, the combustion gas that has flowed into the inlet buffer portion 27 strikes the side surface portion of the measurement flow path portion 15 facing the opening portion 32, and then in the protruding direction of the measurement flow path portion 15 along this side surface portion. It flows in the vertical direction of the orthogonal inlet buffer section 27 (see arrow 36).

  Then, the fuel gas that has flowed in the vertical direction of the inlet buffer 27 along the side surface of the measurement channel 15 wraps around the outer surface of the measurement channel 15 toward the cover 3B, It hits the inner wall surface of the cover 3B facing the side surface. Thereafter, the combustion gas flows along the inner wall surface of the cover 3 </ b> B to the central portion in the vertical direction of the inlet buffer portion 27 and collides with it, and the inlet buffer portion between the inner wall surface of the cover 3 </ b> B and the side surface portion of the measurement flow path portion 15. 27, the flow is made uniform (see arrow 36).

  Thereafter, the combustion gas further passes through the outer peripheral edge portions of the three sides of the upper and lower edge portions of the inlet portion 15A of the measurement flow path portion 15 and the edge portion on the cover 3B side, and enters the inlet portion 15A of the measurement flow path portion 15. Is then turned 180 degrees (see arrows 36 and 37). Subsequently, the combustion gas whose direction has been changed by 180 degrees flows into the measurement flow path section 15 (see the arrows 37 and 38). Then, the combustion gas that has flowed into the measurement flow path portion 15 flows from the outlet portion 15 </ b> B of the measurement flow path portion 15 into the outlet buffer portion 29, and then is discharged to the outlet 6 that communicates with the outlet buffer portion 29.

  Therefore, the combustion gas that has flowed into the inlet buffer portion 27 through the opening 32 hits the side surface portion of the measurement flow path portion 15 and the vertical wall surface portion of the inlet buffer portion 27 and then hits the inner wall surface of the cover 3B. Then, it flows and collides with the center part of the up-down direction of the inlet buffer part 27 along the inner wall face of the cover 3B. Furthermore, after the combustion gas hits the wall surface portion of the inlet buffer portion 27 facing the inlet portion 15A of the measurement flow path portion 15, the direction of the gas is changed by 180 degrees, and the flow is sufficiently uniformed. It flows into the inlet 15 </ b> A of the measurement channel 15.

  As a result, the flow rate of the combustion gas that can be measured via the flow rate measurement unit 11 is increased, a wide flow region is measured with the same meter case 3, and the flow rate of the supply gas is abnormal. When this occurs, the shutoff valve 33 can be operated reliably and the supply of combustion gas can be stopped.

  Here, the measurement which measured the maximum flow volume which can measure combustion gas (for example, city gas, LP gas, etc.) by ultrasonic flowmeter 1 at room temperature of 20 ° C using a piston probing type flow measuring device. An example of the result will be described with reference to FIG. It should be noted that the end portion of the opening 32 opposite to the partition wall 21A is shifted to the outside from the inlet 15A of the measurement flow path portion 15, that is, with respect to the partition wall 21A of the opening 32. Measurement of combustion gas by the ultrasonic flow meter 1 by changing the distance L1 (see FIG. 2) in the longitudinal direction of the measurement flow path portion 15 between the opposite end portion and the end face of the inlet portion 15A from 0 mm to 7.5 mm. The maximum possible flow rate was measured.

  As shown in FIG. 8, when the shift amount L1 between the inlet 15A of the measurement channel 15 and the end of the opening 32 opposite to the partition wall 21A is 0 mm to 4.5 mm, the ultrasonic wave The maximum flow rate of combustion gas that can be measured by the flow meter 1 was about 8000 (liters / hour). When the amount of displacement L1 between the inlet 15A of the measurement flow path 15 and the end of the opening 32 opposite to the partition wall 21A is 6.0 mm, the combustion gas is measured by the ultrasonic flowmeter 1. The maximum possible flow rate was about 6500 (liters / hour).

  Further, when the amount of deviation L1 between the inlet 15A of the measurement flow path 15 and the end of the opening 32 opposite to the partition wall 21A is 7.5 mm, measurement of combustion gas by the ultrasonic flow meter 1 is performed. The maximum possible flow rate was about 5500 (liters / hour). Therefore, the ultrasonic flowmeter is set by setting the amount of deviation L1 between the inlet 15A of the measurement flow path 15 and the end opposite to the partition wall 21A of the opening 32 from 0 mm to 4.5 mm or less. The maximum measurable flow rate of the combustion gas by 1 is about 8000 (liter / hour), and it is considered that a large flow rate can be measured.

  As described in detail above, in the ultrasonic flowmeter 1 according to the present embodiment, the inlet buffer section 27 partitioned in a substantially box shape has the inflow path 5A through which combustion gas flows from the inlet 5 along the vertical direction. An inflow chamber 31 disposed at the back end is provided adjacent to the flow direction of the combustion gas in the inflow passage 5 </ b> A in a substantially perpendicular direction, and an opening 32 communicating with the inflow chamber 31 is formed. ing. Further, in the measurement flow path portion 15 having a rectangular cross section of the flow rate measurement unit 11, the side surface portion protruding into the inlet buffer portion 27 is substantially parallel to the inner wall of the inlet buffer portion 27 in which the opening portion 32 is formed. Thus, it protrudes into the inlet buffer 27 and is arranged so as to substantially cover the opening 32 in front view.

  Therefore, after the combustion gas flows into the inlet buffer portion 27 in the inflow chamber 31 provided at the back end of the inflow passage 5A, the flow direction is bent in a substantially right angle direction and then flows into the inlet buffer portion 27, the measurement flow passage portions facing each other. 15 hits the side surface portion 15 again, is bent along the side surface in a substantially right angle direction, that is, in both height directions of the side surface of the measurement flow path portion 15 and flows into the inlet buffer portion 27. Then, the combustion gas that has flowed into the inlet buffer section 27 wraps around the outer peripheral surface of the measurement flow path section 15 and hits the inner wall surface of the cover 3 </ b> B facing the side surface section of the measurement flow path section 15.

  Thereafter, the combustion gas flows along the inner wall surface of the cover 3 </ b> B to the central portion in the vertical direction of the inlet buffer portion 27 and collides with it, and the inlet buffer portion between the inner wall surface of the cover 3 </ b> B and the side surface portion of the measurement flow path portion 15. At 27, the flow is made uniform. Then, the combustion gas further passes through the outer peripheral edge of the three sides of the upper and lower edge portions of the inlet portion 15A of the measurement flow path portion 15 and the edge portion on the cover 3B side, and enters the inlet portion 15A of the measurement flow path portion 15. Then, the direction is changed by 180 degrees and flows into the inlet 15A of the measurement flow path 15.

  As a result, the flow of the combustion gas is changed several times before flowing into the inlet buffer 27 and into the inlet 15A of the measurement flow path 15, so that the flow is sufficiently uniform and large. A flow rate (for example, a flow rate of 8000 (liter / hour)) can be measured. In addition, the opening 32 provided in the inner wall of the substantially box-shaped inlet buffer portion 27 is formed in a size that is substantially covered by the measurement flow passage portion 15 protruding into the inlet buffer portion 27. By shortening the protrusion length of the portion 15 into the inlet buffer portion 27, the inlet buffer portion 27 can be downsized. As a result, the ultrasonic flow meter 1 can be downsized.

  The shut-off valve 33 that closes the opening 32 and blocks the supply of combustion gas to the inlet buffer 27 is disposed so as to face the side surface of the measurement flow path 15 via the opening 32. . Further, the distance D1 of the gap (first gap) between the shut-off valve 33 and the opening 32 is set to the distance D2 of the gap (second gap) between the opening 32 and the side surface of the measurement flow path section 15. They are arranged to be almost equal. Thereby, the distance D1 of the clearance (first clearance) between the shut-off valve 33 and the opening 32 is narrowed, and the clearance (second clearance) between the opening 32 and the side surface of the measurement flow path portion 15 is reduced. The distance D2 can be reduced, and the inlet buffer unit 27 can be further reduced in size. As a result, the ultrasonic flow meter 1 can be further reduced in size.

  Moreover, since the opening part 32 is formed in the substantially circular cross section which has an internal diameter substantially equal to the height of the side surface of the measurement flow path part 15 which opposes, it becomes possible to form the opening part 32 easily. Become. Further, the measurement flow path portion 15 protruding into the inlet buffer portion 27 can be easily configured so as to cover the opening portion 32 substantially in a front view.

  In addition, when viewed from the front, the end L on the opposite side of the partition wall 21A of the opening 32 is shifted to the outside from the inlet 15A of the measurement flow path section 15, that is, the partition wall of the opening 32. Combustion gas is measured from the opening 32 by setting the distance L1 in the longitudinal direction of the measurement flow path portion 15 between the end opposite to 21A and the end face of the inlet portion 15A to, for example, 0 mm to 4.5 mm or less. It is possible to set so as not to directly flow into the inlet portion 15A of the flow path portion 15. As a result, the flow of the combustion gas is sufficiently uniform, and a large flow rate (for example, a flow rate of 8000 (liter / hour)) can be measured. As a result, it is possible to reduce the size of the inlet buffer unit 27, and thus it is possible to reduce the size of the ultrasonic flowmeter 1.

  A central space in which a circuit case 16 provided with a pair of ultrasonic transducers 12A and 12B is sandwiched between an inlet buffer portion 27 and an outlet buffer portion 29 on the upper side of the central portion in the longitudinal direction of the measurement flow path portion 15. Since it is disposed in the portion 28, it is possible to easily reduce the size of the outlet buffer portion 29. As a result, the ultrasonic flow meter 1 can be further reduced in size.

  In addition, this invention is not limited to the said embodiment, Of course, various improvement and deformation | transformation are possible within the range which does not deviate from the summary of this invention.

DESCRIPTION OF SYMBOLS 1 Ultrasonic flow meter 3 Meter case 5 Inlet 6 Outlet 11 Flow measurement unit 12A, 12B Ultrasonic transducer 15 Measurement flow path part 15A Inlet part 15B Outlet part 27 Inlet buffer part 28 Central space part 29 Outlet buffer part 32 Opening Part 33 Shut-off valve

Claims (6)

A meter case in which an inlet of the fluid to be measured and an outlet of the fluid to be measured are formed;
A flow rate measuring unit that is disposed in the meter case and measures the flow rate of the fluid to be measured passing through the meter case; and
With
The flow rate measuring unit is
A measurement channel portion having a substantially rectangular cross section through which the fluid to be measured flows;
A pair of ultrasonic transducers attached to the upstream side and the downstream side of the measurement channel part;
Have
The meter case is
An opening is formed at the back end of the inflow path through which the fluid to be measured flows from the inflow port, adjacent to the flow direction at a substantially right angle to communicate with the inflow path. An inlet buffer section partitioned in a substantially box shape so that the inlet side of the passage projects inward and the fluid to be measured flows into the inlet section of the measurement flow path section;
In addition to communicating with the outlet, the outlet side of the measurement channel section protrudes inward, and the fluid to be measured that has flowed out of the outlet section of the measurement channel section is partitioned into a substantially box shape. An exit buffer section;
Have
The measurement channel portion protrudes into the inlet buffer portion so that the side surface on the inlet side is substantially parallel to the inner wall of the inlet buffer portion in which the opening portion is formed. An ultrasonic flowmeter, which is arranged so as to cover. The meter case has a shut-off valve that closes the opening and shuts off the supply of the fluid to be measured to the inlet buffer.
The shut-off valve is disposed so as to face the side surface on the inlet side of the measurement flow path portion through the opening, and the distance of the first gap between the shut-off valve and the opening is The ultrasonic flowmeter according to claim 1, wherein the ultrasonic flowmeter is disposed so as to be substantially equal to a distance of a second gap between the opening and a side surface on the inlet side of the measurement flow path.   The ultrasonic wave according to claim 1 or 2, wherein the opening is formed in a substantially circular cross section having an inner diameter substantially equal to a height of a side surface of the measurement flow channel portion facing each other. Flowmeter.   In the projecting direction of the measurement channel part into the inlet buffer unit, the projecting distance at which the end of the opening on the projecting direction side projects outward from the inlet part of the measurement channel unit is the measurement target. The ultrasonic flowmeter according to claim 3, wherein the ultrasonic flowmeter is set to a predetermined value or less so that fluid does not flow directly from the opening to the inlet of the measurement flow path.   The meter case has a central space portion in which a portion where the pair of ultrasonic transducers of the measurement flow path portion is provided is disposed between the inlet buffer portion and the outlet buffer portion. The ultrasonic flowmeter according to any one of claims 1 to 4. A meter case in which an inlet of the fluid to be measured and an outlet of the fluid to be measured are formed;
A flow rate measuring unit that is disposed in the meter case and measures the flow rate of the fluid to be measured passing through the meter case; and
With
The flow rate measuring unit is
A measurement channel portion having a substantially rectangular cross section through which the fluid to be measured flows;
A pair of ultrasonic transducers attached to the upstream side and the downstream side of the measurement channel part;
Have
The meter case is
An opening is formed at the back end of the inflow path through which the fluid to be measured flows from the inflow port, adjacent to the flow direction at a substantially right angle to communicate with the inflow path. An inlet buffer section partitioned in a substantially box shape so that the inlet side of the passage projects inward and the fluid to be measured flows into the inlet section of the measurement flow path section;
In addition to communicating with the outlet, the outlet side of the measurement channel section protrudes inward, and the fluid to be measured that has flowed out of the outlet section of the measurement channel section is partitioned into a substantially box shape. An exit buffer section;
A central space portion in which the portion of the measurement flow path portion provided with the pair of ultrasonic transducers is disposed between the inlet buffer portion and the outlet buffer portion;
A shutoff valve that closes the opening and shuts off the supply of the fluid to be measured to the inlet buffer;
Have
The measurement channel portion protrudes into the inlet buffer portion such that the side surface on the inlet side is substantially parallel to the inner wall of the inlet buffer portion where the opening is formed,
The shut-off valve is disposed so as to face the side surface on the inlet side of the measurement flow path portion through the opening, and the distance of the first gap between the shut-off valve and the opening is It is arranged so as to be approximately equal to the distance of the second gap between the opening and the side surface on the inlet side of the measurement flow path portion,
The opening is formed in a substantially circular cross-section having an inner diameter substantially equal to the height of the side surface of the measurement flow channel portion facing each other, and in the protruding direction of the measurement flow channel portion into the inlet buffer unit, The projecting distance at which the end of the opening in the projecting direction side projects from the inlet of the measurement channel is set to be a predetermined value or less,
The ultrasonic flowmeter, wherein the measurement flow path portion is disposed so as to substantially cover the opening when viewed from the front.

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