Flow meter

Abstract

To provide a flow meter including a plurality of measurement units, which is capable of suppressing a decrease in measurement accuracy.SOLUTION: The flow meter 100 includes a plurality of measurement units 20A to 20D. The plurality of measurement units 20A to 20D are arranged in the chamber with an extension direction of a measurement flow path 26 facing in a direction intersecting the direction in which a discharge surface 96 of a side wall 92 faces, spaced a predetermined distance apart in the direction intersecting the direction in which the discharge surface 96 faces, and arranged in the direction in which the discharge surface 96 faces.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a flowmeter that measures the flow rate of a fluid to be measured. [Background technology]

[0002] Patent Document 1 describes a flow meter that includes a main body case having a main body inlet and a main body outlet, and a plurality of measurement units disposed inside the main body case for measuring the flow rate of a fluid to be measured. In the flow meter, each measurement unit measures the flow velocity of the fluid to be measured that flows in from the main body inlet of the main body case, and calculates the flow rate over a predetermined time period using the average velocity of the measured flow velocities. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-208583 Summary of the Invention [Problem to be solved by the invention]

[0004] In a flowmeter having the above configuration, variations in the flow rate of the fluid to be measured flowing into each measuring unit may occur. For example, the flow rate of the fluid to be measured flowing into each measuring unit may vary depending on the shape of the chamber in the main body case in which each measuring unit is placed and the flow of the fluid to be measured within this chamber, which may result in a decrease in measurement accuracy.

[0005] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a flow meter that is equipped with a plurality of measurement units and that is capable of suppressing a decrease in measurement accuracy. [Means for solving the problem]

[0006] In order to solve the above problems, the flow meter disclosed in this embodiment comprises a main body case having a ceiling portion in which a main body inlet and a main body outlet are formed, a bottom portion facing the ceiling portion, and a side wall extending between the ceiling portion and the bottom portion, and in which a chamber which is a space surrounded by the ceiling portion, the side wall, and the bottom is formed, a plurality of measuring units arranged within the chamber of the main body case for measuring the flow rate of the measured fluid flowing within the chamber, and a discharge flow path which discharges the measured fluid flowing in from the main body inlet into the chamber, and which discharges the measured fluid toward a discharge surface which is the inner surface of the side wall within the chamber. The multiple measurement units each have a measurement flow path extending in a predetermined direction, a measurement inlet located on one side of the extension direction of the measurement flow path, and a measurement outlet located on the other side of the extension direction of the measurement flow path, and a sensor that measures a value corresponding to the flow rate of the fluid to be measured flowing through the measurement flow path, and the multiple measurement units are arranged in the chamber with the extension direction of the measurement flow path facing in a direction intersecting the direction in which the release surface faces, away from the release surface in a direction intersecting the direction in which the release surface faces, and in the direction in which the release surface faces.

[0007] In the above configuration, the measured fluid discharged from the discharge flow path is reflected by the discharge surface, which is part of the side wall of the main body case, and diffuses within the chamber. Within the chamber, multiple measurement units are arranged with the extension direction of the measurement flow path facing a direction intersecting the direction of the discharge surface from which the measured fluid is discharged, away from the discharge surface in a direction intersecting the direction of the discharge surface. Therefore, the measured fluid that has diffused within the chamber easily reaches the measurement inlet of each measurement unit, thereby suppressing variations in the flow rate of the measured fluid flowing into each measurement unit. As a result, even when multiple measurement units are used, it is possible to suppress a decrease in the measurement accuracy of the measured fluid.

[0008] The plurality of measurement units are arranged in the chamber with their measurement inlets facing the emission surface. In the above configuration, the measurement inlets of the multiple measurement units face the discharge surface, so that the measurement target fluid that is reflected and diffused by the discharge surface can easily reach the measurement inlets, thereby suppressing variations in the flow rate of the measurement target fluid flowing into the measurement inlets of each measurement unit and, ultimately, suppressing a decrease in measurement accuracy.

[0009] The main body case has chambers, an inlet chamber connected to the main body inlet and an outlet chamber connected to the main body outlet, and the measurement unit forms a flow path between the main body inlet and the main body outlet by connecting the measurement flow path and the inlet chamber on the measurement inlet side and connecting the measurement flow path and the outlet chamber on the measurement outlet side, and the discharge surface is the inner surface of the side wall forming the inlet chamber, and the multiple measurement units are arranged in the inlet chamber with the measurement inlet facing the discharge surface. In the above configuration, in a configuration in which the inlet chamber and the outlet chamber are provided separately, it is possible to suppress a decrease in measurement accuracy for the fluid to be measured flowing in the forward direction into the inlet chamber.

[0010] The main body case includes an outflow-side chamber forming section that is disposed within the main body case and forms an outflow-side chamber, the main body case having, as side walls, a first side wall having a discharge surface on its inner surface, a second side wall that faces the first side wall in the direction in which the discharge surface faces, and a third side wall and a fourth side wall that are positioned between the first side wall and the second side wall and face each other in a direction intersecting with the direction in which the discharge surface faces, the discharge surface being positioned on the first side wall side in the direction intersecting with the direction in which the discharge surface faces, and the outflow-side chamber forming section is positioned within the inflow-side chamber in a direction intersecting with the direction in which the discharge surface faces. The measurement units are positioned closer to the fourth side wall than the discharge surface in the direction of the discharge, and are arranged in the inlet chamber at a predetermined first distance from the discharge flow path in the direction intersecting the direction of the discharge surface, with the measurement outlet side ends inserted into multiple mounting openings in the outlet chamber forming portion, so that the extension direction of the measurement flow path is directed in a direction intersecting the direction of the discharge surface, and the outlet chamber forming portion is arranged at a predetermined second distance from the fourth side wall in the direction intersecting the direction of the discharge surface. With the above configuration, in the inlet-side chamber, the measurement unit is located a first distance away from the discharge flow path in a direction intersecting the direction in which the discharge surface faces, and the outlet-side chamber forming portion is located a second distance away from the fourth side wall in a direction intersecting the direction in which the discharge surface faces. As a result, the fluid to be measured that is reflected by the discharge surface and diffuses can be diffused by convection in a space according to the first distance and the second distance in the inlet-side chamber, thereby suppressing variations in the flow rate of the fluid to be measured that flows into the measurement inlets of the measurement units in the inlet-side chamber, and ultimately suppressing a decrease in measurement accuracy.

[0011] The device is provided with a shut-off valve unit that switches between an open state that allows the measured fluid to flow from the main body inlet into the chamber and a shut-off state that blocks the measured fluid from flowing from the main body inlet into the chamber depending on the flow rate of the measured fluid measured by the measuring unit, and a discharge flow path is formed within the shut-off valve unit. In the above configuration, an existing shutoff valve unit can be used to provide the discharge flow path, so that an increase in the number of parts in the flow meter can be suppressed. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. [Figure 2] FIG. [Figure 3] FIG. 2 is a diagram showing the inside of a flow meter. [Figure 4] FIG. 2 is a plan view showing the inside of the flow meter. [Figure 5] FIG. 2 is a cross-sectional view of the measurement unit. [Figure 6] FIG. 2 is a diagram illustrating a measurement flow path in a measurement unit. [Figure 7] FIG. 2 is a schematic diagram illustrating the arrangement of each measurement unit. [Figure 8] FIG. 10 is a schematic diagram illustrating the arrangement of each measurement unit in the second embodiment. [Figure 9] FIG. 10 is a schematic diagram illustrating the arrangement of each measurement unit in the third embodiment. [Figure 10]FIG. 10 is a schematic diagram illustrating the arrangement of each measurement unit in the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] (First embodiment) A flow meter according to this embodiment will be described below with reference to the drawings. The flow meter is a city gas meter that measures the flow rate of city gas, which is an example of a fluid to be measured. The flow meter is used by being connected to a pipe (not shown) through which the city gas flows.

[0014] FIG. 1 is an external view of flowmeter 100. FIG. 2 is a plan view of flowmeter 100. FIG. 3 is a diagram showing the interior of flowmeter 100. FIG. 4 is a plan view showing the interior of flowmeter 100. Hereinafter, when flowmeter 100 is in use, the up-down direction will be referred to as up-down direction D1, and the direction along the width of flowmeter 100 (the direction in which a main body inlet 93 and a main body outlet 94, which will be described later, are aligned) will be referred to as width direction D2. Furthermore, the direction along the depth of flowmeter 100 will be referred to as depth direction D3. The width direction D2 and the depth direction D3 are also directions that intersect with each other in the horizontal direction.

[0015] 1 to 4, the flowmeter 100 mainly includes an upper case 90, a lower case 80, an exhaust pipe 70, an internal unit case 75, a measurement unit 20, and a shutoff valve unit 40. In this embodiment, the upper case 90 and the lower case 80 are examples of a main body case.

[0016] The upper case 90 is a container that is open downward when in use. Specifically, the upper case 90 has a ceiling portion 91 that is substantially rectangular in plan view and side walls 92 that extend downward from four sides of the ceiling portion 91. The ceiling portion 91 is formed with a main body inlet 93 and a main body outlet 94, which are openings facing upward. The main body inlet 93 and the main body outlet 94 are formed side by side in the ceiling portion 91, separated by a predetermined distance in the width direction D2.

[0017] The sidewall 92 is a wall surrounding the opening in the upper case 90, and has a flange portion 95 that protrudes outward on the downward side. As shown in FIG. 2 , the sidewall 92 has a first sidewall 92A, a second sidewall 92B, a third sidewall 92C, and a fourth sidewall 92D that extend downward from four sides of the ceiling portion 91. The first sidewall 92A has a discharge surface 96 (described later) on its inner surface. The second sidewall 92B is a wall that faces the first sidewall 92A in the depth direction D3. The third sidewall 92C and the fourth sidewall 92D are walls that face each other in the width direction D2 between the first sidewall 92A and the second sidewall 92B. In this embodiment, the depth direction D3 is an example of a direction in which the discharge surface faces, and the width direction D2 is an example of a direction that intersects with the direction in which the discharge surface faces.

[0018] An inlet-side nozzle 14 for connecting the upper case 90 to a pipe is attached to a main body inlet 93 of the upper case 90. An outlet-side nozzle 15 for connecting the upper case 90 to a pipe is attached to a main body outlet 94 of the upper case 90.

[0019] The lower case 80 is a shielding member that shields the opening of the upper case 90. The lower case 80 has a flange portion 81, and this flange portion 81 is used to screw the lower case 80 to a flange portion 95 of the upper case 90. By screwing the lower case 80 to the upper case 90, the lower case 80 is fixed with its top surface facing the ceiling portion 91 of the upper case 90. By screwing the lower case 80 to the upper case 90, the interior of the upper case 90 is made airtight, and an inlet-side chamber 16 through which the city gas convects is formed. In this embodiment, the lower case 80 is an example of a bottom.

[0020] The exhaust pipe 70 and the inner unit case 75 are components that form the outlet chamber 17, which is part of the chamber. The exhaust pipe 70 is a component that is open at the bottom when in use. The exhaust pipe 70 has an exhaust port 71 at the top and a flange portion 72 at the bottom that protrudes outward from the edge of the opening. The exhaust port 71 is inserted into the main body outlet 94 and is connected to the piping via the outlet-side nozzle 15 attached to the main body outlet 94.

[0021] The inner unit case 75 is a member that is open upward in an in-use state and has a flange portion 76 on the edge of the opening. In an in-use state, the inner unit case 75 has an attachment side surface 78 that faces the third side wall 92C and has a plurality of unit attachment openings 77 formed therein. In the attachment side surface 78, each measurement unit 20 can be held in the inner unit case 75 by inserting the outflow side end (a measurement outlet 25 described later) of the measurement unit 20 into each unit attachment opening 77. In this embodiment, four unit attachment openings 77 corresponding to the number of measurement units 20 are formed in the attachment side surface 78 of the inner unit case 75. Specifically, the four unit attachment openings 77 are formed side by side in the depth direction D3. As a result, the inner unit case 75 can arrange the four measurement units 20A to 20D side by side in the depth direction D3 within the inflow-side chamber 16.

[0022] The exhaust pipe 70 and the inner unit case 75 are screwed together at the flanges 72, 76 with their openings facing each other, thereby forming an outlet chamber 17 through which the city gas flowing out of the measurement units 20A to 20D flows. This outlet chamber 17 is a space that is connected to the inlet chamber 16 via the plurality of measurement units 20, as will be described later, and is connected to piping via a main body outlet 94 of the upper case 90. In this embodiment, the exhaust pipe 70 and the inner unit case 75 are an example of an outlet chamber forming portion.

[0023] In the upper case 90, a shutoff valve unit 40 is attached to the third side wall 92C side of the inlet-side chamber 16. The shutoff valve unit 40 is a device that switches between an open state, which allows city gas to flow into the inlet-side chamber 16 from the main body inlet 93, and a shutoff state, which shuts off the flow of city gas from the main body inlet 93 into the inlet-side chamber 16.

[0024] The shut-off valve unit 40 has a discharge flow path forming portion 41, a valve body 42, and a drive portion not shown, and is mounted within the inlet side chamber 16 with the inlet side of the discharge flow path 43 connected to the main body inlet 93 of the upper case 90 and the outlet side of the discharge flow path 43 facing the first side wall 92A.

[0025] The discharge flow path forming portion 41 has therein a curved flow path, the discharge flow path 43. The discharge flow path 43 is a flow path that discharges the city gas that has flowed in from the main body inlet 93 toward the inner surface of the side wall 92. In this embodiment, the discharge flow path 43 is a flow path that extends while bending at approximately 90 degrees from the inlet side to the outlet side, and discharges the city gas toward the inner surface of the first side wall 92A (a discharge surface 96 described later).

[0026] The valve element 42 is mounted within the discharge flow path forming portion 41 so as to be displaceable between an open position in the open state and a blocked position in the blocked state. When the valve element 42 is in the open position, the city gas that flows in from the main body inlet 93 of the upper case 90 passes through the discharge flow path 43 and is discharged toward a first side wall 92A (a discharge surface 96 described below) within the inlet-side chamber 16. On the other hand, when the valve element 42 is in the blocked position, a portion of the discharge flow path 43 is blocked, and therefore the city gas is not discharged from the discharge flow path 43 into the inlet-side chamber 16.

[0027] Inside the inflow side chamber 16, four measurement units 20A to 20D are attached to the four unit mounting openings 77 of the inner unit case 75 via packings 18, which are elastic members. The measurement units 20A to 20D are devices that measure the flow rate (liters / hour) of the city gas that has flowed into the inflow side chamber 16 or the outflow side chamber 17.

[0028] Here, the configuration of measurement unit 20A will be described. Note that measurement units 20B, 20C, and 20D have the same configuration as measurement unit 20A, so their description will be omitted. As shown in Fig. 5, measurement unit 20A mainly includes a measuring instrument case 21, ultrasonic vibrators 27A and 27B as sensors, and a partition plate 29.

[0029] The meter case 21 has a measurement flow path forming section 22 and a sensor accommodating section 23. The measurement flow path forming section 22 is a square-tube-shaped section having a measurement inlet 24, which is a rectangular opening, and a measurement outlet 25. In the measurement flow path forming section 22, a measurement flow path 26 through which city gas flows is formed between the measurement inlet 24 and the measurement outlet 25. The measurement flow path 26 is a flow path that has a substantially rectangular opening shape and extends linearly. Hereinafter, the extension direction of the measurement flow path 26 will also be referred to as the extension direction DA. In this embodiment, the measurement unit 20 is attached to the inner machine case 75 with the extension direction DA of the measurement flow path 26 oriented substantially parallel to the width direction D2 of the flowmeter 100, and therefore the extension direction DA is also a direction along the width direction D2.

[0030] 6, partition plates 29 that divide measurement flow path 26 into a plurality of partial flow paths 30 are arranged inside measurement flow path forming section 22. Specifically, the plurality of partition plates 29 are arranged inside measurement flow path 26 with their surfaces facing each other in intersecting direction DB that intersects with extension direction DA on a horizontal plane, thereby dividing measurement flow path 26 into a plurality of partial flow paths 30 arranged in intersecting direction DB.

[0031] In this embodiment, eight partial flow paths 30A, 30B, 30C, 30D, 30E, 30F, 30G, and 30H are formed in the measurement flow path 26. Hereinafter, when distinguishing between the partial flow paths 30 separated by the partition plate 29, the letters "A, B, C, D, E, F, G, and H" are added to the reference numerals. The inner widths of the partial flow paths 30 in the cross direction DB are the same, but this is not limited thereto. For example, the inner width of the partial flow paths 30D and 30E located in the center in the cross direction DB may be larger than the inner widths of the other partial flow paths 30A to 30C and 30F to 30H. The number of partial flow paths 30 is not limited to eight, and may be two or more but less than eight, or more than eight.

[0032] Ultrasonic vibrators 27A and 27B, which serve as sensors, are disposed in sensor housing 23. By disposing ultrasonic vibrators 27A and 27B above measurement flow path 26, a V-shaped ultrasonic propagation path is formed in which ultrasonic waves from one ultrasonic vibrator 27A and 27B are reflected by the bottom surface of measurement flow path 26 and transmitted to the other ultrasonic vibrator 27A and 27A. This makes it possible to measure the flow velocity of city gas flowing through measurement flow path 26 according to the ultrasonic wave reception period.

[0033] Ultrasonic vibrators 27A and 27B measure the flow velocity of city gas using as their measurement range some of all partial flow paths 30A to 30H formed in measurement flow path 26. Specifically, measurement unit 20 uses only partial flow paths 30D and 30E of partial flow paths 30A to 30H as its measurement range, and does not use partial flow paths 30A, 30B, 30C, 30F, 30G, and 30H as its measurement range.

[0034] In the sensor housing 23, a measurement circuit 28 to which the ultrasonic vibrators 27A, 27B are electrically connected is disposed above each of the ultrasonic vibrators 27A, 27B. In this embodiment, only the measurement unit 20A has the measurement circuit 28, and this measurement circuit 28 is electrically connected to the ultrasonic vibrators 27A, 27B of the other measurement units 20B to 20D. However, the other measurement units 20B to 20D may each have a measurement circuit 28 electrically connected to the ultrasonic vibrators 27A, 27B, and the measurement circuits 28 may be electrically connected to each other.

[0035] Measurement circuit 28 calculates an average flow velocity, which is the average value of the flow velocities of the city gas flowing through measurement flow path 26 measured by ultrasonic vibrators 27A, 27B of each measurement unit 20A to 20D. Then, measurement circuit 28 can calculate the flow rate of the city gas per unit time by multiplying the calculated average flow velocity by the average cross-sectional area of ​​measurement flow path 26. Then, measurement circuit 28 can calculate the integrated flow rate of the city gas for a predetermined time as a measurement value by adding up the flow rates per unit time for the measurement time.

[0036] In the flowmeter 100 configured as described above, city gas that flows in through the main body inlet 93 of the upper case 90 flows into the discharge flow path 43 of the shutoff valve unit 40. When the shutoff valve unit 40 is in an open state, the city gas in the discharge flow path 43 is discharged from the main body inlet 93 toward the first side wall 92A in the inlet-side chamber 16, tilted at approximately 90 degrees. Then, in the inlet-side chamber 16, the city gas flows into the measurement flow path 26 from the measurement inlet 24 of each of the measurement units 20A to 20D. As already explained, the measurement circuit 28 calculates the flow rate from the average flow velocity of the city gas flowing through the measurement flow path 26 of each of the measurement units 20A to 20D, and calculates the integrated flow rate by integrating the calculated flow rate over a predetermined period of time.

[0037] The city gas flowing out from the measurement outlet 25 of each of the measurement units 20A to 20D flows into the outlet chamber 17. The city gas flowing into the outlet chamber 17 passes through the main body outlet 94 of the upper case 90 and is discharged into the piping.

[0038] Although not shown, the flowmeter 100 is equipped with a control board equipped with a microcomputer or the like, and this control board is electrically connected to the measurement circuit 28 and the shutoff valve. The control board detects abnormalities in the supply gas flow rate, etc. based on the integrated flow rate of the city gas over a predetermined period of time measured by the measurement circuit 28, and if an abnormality is detected in a predetermined gas shutoff target, it drives the valve element 42 of the shutoff valve unit 40 to the shutoff position to stop the supply of city gas. The control board is also configured to be able to output the city gas flow rate output from the measurement unit 20 to a personal computer or the like (not shown).

[0039] In the flowmeter 100 configured as described above, if the flow rate of the city gas flowing into each of the measurement units 20A to 20D varies greatly, the measurement accuracy of the city gas flow rate may decrease. Therefore, by devising the arrangement of each of the measurement units 20A to 20D within the inlet-side chamber 16, the flow rate of the city gas flowing into each of the measurement units 20A to 20D is made uniform.

[0040] Specifically, as shown in FIG. 4, each of measurement units 20A-20D is disposed in inflow-side chamber 16 by inner case 75 such that the end of each measurement unit 20A-20D on the measurement inlet 24 side is spaced a predetermined first distance LA1 in width direction D2 from the outlet of discharge flow path 43 in shutoff valve unit 40. Furthermore, each of measurement units 20A-20D is disposed in depth direction D3 with extension direction DA of measurement flow path 26 facing width direction D2, which intersects with the direction in which discharge surface 96 faces (depth direction D3). Therefore, as shown in the schematic diagram of FIG. 7, measurement inlet 24 of each of measurement units 20A-20D is located spaced a predetermined second distance LA2 from discharge surface 96 of first side wall 92A in width direction D2. Within inflow-side chamber 16, each of exhaust pipe 70 and inner case 75 has its end in width direction D2 spaced a predetermined second distance LA2 from fourth side wall 92D in width direction D2.

[0041] 7, within the inlet-side chamber 16, a separation space 19A corresponding to the first separation distance LA1 is formed in the width direction D2 between the end of the measurement inlet 24 of each of the measurement units 20A to 20D and the end of the shutoff valve unit 40. Furthermore, within the inlet-side chamber 16, a separation space 19B corresponding to the second separation distance LA2 is formed in the width direction D2 between the fourth side wall 92D and the exhaust pipe 70 and the inner unit case 75.

[0042] The city gas released from the shutoff valve unit 40 is released onto the discharge surface 96 of the side wall 92. The city gas reflects off the discharge surface 96 and diffuses within the inlet-side chamber 16. At this time, the city gas reflected off the discharge surface 96 convects within the separated space 19A formed between the shutoff valve unit 40 and each of the measurement units 20A to 20D, and a portion of the city gas convects within the separated space 19B formed between the inner unit case 75 and the fourth side wall 92D. This makes it easier for the city gas in the inlet-side chamber 16 to diffuse by convection within each of the separated spaces 19A, 19B.

[0043] Next, the variation in the flow rate flowing into the measurement flow path 26 of each of the measurement units 20A to 20D was evaluated using the split flow ratio. Here, the "split flow ratio" is a value calculated using the following (Equation 1), and is a value indicating how much the flow rate flowing through the measurement flow path 26 of the target measurement unit among the measurement units 20A to 20D differs from the average flow rate of the four measurement units 20A to 20D. The value of the split flow ratio is expressed in "percentage."

[0044] Diversion ratio = (Rn-Vave)÷Vave×100…(Formula 1)

[0045] Here, "Rn" is the flow velocity of the fluid to be measured flowing through the measurement flow path 26 of the target measuring units 20A to 20D. "n" is an identifier that identifies each measuring unit 20A to 20D, and in this embodiment, it is one of the values ​​"20A, 20B, 20C, 20D". "Vave" is the average flow velocity, which is the average value of the flow velocities measured by the four measuring units 20A to 20D.

[0046] In the four measurement units 20A to 20D, when the variation in the split flow ratio was "±5.0", it was evaluated as good, and in all other cases it was evaluated as unacceptable.

[0047] Example 1 In Example 1, the flow division ratio was calculated by arranging the measurement units 20A to 20D in the same manner as in this embodiment. That is, in Example 1, the measurement units 20A to 20D were arranged in the depth direction D3 within the inlet chamber 16, and the flow rate flowing through the measurement flow path 26 of each measurement unit 20A to 20D was measured. In Example 1, each measurement unit 20A to 20D was also attached to the internal unit case 75 with the measurement inlet 24 facing the discharge surface 96 of the first side wall 92A. Table 1 shows the flow division ratios of the four measurement units 20A to 20D in Example 1.

[0048] [Table 1]

[0049] As can be seen from Table 1, the flow division ratio was "-0.6" in the measurement units 20B and 20D, which was the minimum value. The flow division ratio was "1.2" in the measurement unit 20A, which was the maximum value. That is, the flow division ratios in the four measurement units 20A to 20D were within the range of "±5.0", and it can be evaluated that the arrangement of each of the measurement units 20A to 20D in the inlet-side chamber 16 was good.

[0050] <Example 2> FIG. 8 is a schematic diagram showing the arrangement of the measurement units 20A to 20D in Example 2. As shown in FIG. 8, four measurement units 20A to 20D were arranged two by two in each of the depth direction D3 and the up-down direction D1. The difference from Example 1 is that a set of measurement units 20A and 20C arranged in the depth direction D3 and a set of measurement units 20B and 20D were arranged side by side in the up-down direction D1. The other conditions were the same as in Example 1. Table 2 shows the flow division ratios of the four measurement units 20A to 20D in Example 2.

[0051] [Table 2]

[0052] As can be seen from Table 2, the flow division ratio for measurement unit 20B was "-1.6", the minimum value. The flow division ratio for measurement unit 20C was "2.4", the maximum value. That is, the flow division ratios for the four measurement units 20A to 20D were within the range of "±5.0", and it can be evaluated that the arrangement of each of measurement units 20A to 20D within the inlet chamber 16 was good.

[0053] Next, the number of measurement units arranged in the inlet chamber 16 was changed from four to two, and an evaluation was performed. In this example, too, when the variation in the flow division ratio was "±5.0", it was evaluated as good, and in other cases it was evaluated as unsatisfactory.

[0054] Example 3 9 is a schematic diagram showing the arrangement of the measurement units 20A to 20D in Example 3. As shown in FIG. 9, the two measurement units 20A and 20B were arranged in the depth direction D3 in the inlet chamber 16. The other conditions were the same as in Example 1. Table 3 shows the flow division ratio of the two measurement units 20A and 20B in Example 3.

[0055] [Table 3]

[0056] From Table 3, the flow division ratio for the measurement unit 20B was "-0.5", which was the minimum value. The flow division ratio for the measurement unit 20A was "0.5", which was the maximum value. That is, the flow division ratios for the two measurement units 20A and 20B were within the range of "±5.0", and it can be evaluated that the arrangement of each measurement unit 20A and 20B in the inlet chamber 16 was good.

[0057] Example 4 Fig. 10 is a schematic diagram showing the arrangement of the measurement units 20A to 20D in Example 4. As shown in Fig. 10, two measurement units 20A and 20B were arranged in the up-down direction D1 in the inlet chamber 16. The other conditions were the same as in Example 1. Table 4 shows the flow division ratio of the two measurement units 20A and 20B in Example 4.

[0058] [Table 4]

[0059] As can be seen from Table 4, the flow division ratio for the measurement unit 20B was "-2.8," which was the minimum value. The flow division ratio for the measurement unit 20A was "2.8," which was the maximum value. That is, the flow division ratios for the two measurement units 20A and 20B were within the range of "±5.0," and it can be evaluated that the arrangement of each measurement unit 20A and 20B within the inlet chamber 16 was good. On the other hand, when Example 3 and Example 4 were compared, the variation in the flow division ratio for Example 3 was smaller than that for Example 4.

[0060] Comparison with Examples 3 and 4 reveals that arranging the two measurement units 20A and 20B in the depth direction D3 results in smaller variations in the flow division ratio than arranging them in the vertical direction D1.

[0061] The present embodiment described above can achieve the following effects. In the flowmeter 100, the city gas discharged from the discharge flow path 43 is reflected off a discharge surface 96, which is the inner surface of the first side wall 92A of the upper case 90, and diffuses within the inlet-side chamber 16. Within the inlet-side chamber 16, the plurality of measurement units 20A-20D are arranged in the width direction D2, away from the discharge surface 96, with the extension direction DA of the measurement flow path 26 facing in a depth direction D3 that intersects with the direction in which the discharge surface 96 faces. Therefore, the city gas that has diffused within the inlet-side chamber 16 easily reaches the measurement inlet 24 of each of the measurement units 20A-20D, which makes it possible to suppress variations in the flow rate flowing into the measurement flow path 26 of each of the measurement units 20A-20D and thereby suppress a decrease in measurement accuracy.

[0062] The plurality of measurement units 20A to 20D are arranged in the inlet-side chamber 16 with the measurement inlet 24 facing the discharge surface 96 of the first side wall 92A. This makes it easier for the city gas that reflects off the discharge surface 96 and diffuses to reach the measurement inlet 24, suppressing variations in the flow rate flowing into the measurement flow path of each measurement unit 20A to 20D and ultimately suppressing a decrease in measurement accuracy.

[0063] The plurality of measurement units 20A to 20D are arranged in the inlet chamber 16 with the measurement inlets 24 facing the discharge surface 96. This makes it possible to suppress a decrease in measurement accuracy for the city gas flowing forward into the inlet chamber 16 in a configuration in which the inlet chamber 16 and the outlet chamber 17 are provided as separate parts with different volumes and shapes.

[0064] The discharge surface 96 is located on the third side wall 92C side of the first side wall 92A in the width direction D2, and the exhaust pipe 70 and the inner unit case 75 are located on the fourth side wall 92D side of the discharge surface 96 in the width direction D2 within the inlet-side chamber 16. The measurement units 20A-20D are spaced a predetermined first distance LA1 from the shutoff valve unit 40 in the width direction D2, and the exhaust pipe 70 and the inner unit case 75 are spaced a predetermined second distance LA2 from the fourth side wall 92D in the width direction D2. This allows the city gas reflected by the discharge surface 96 to circulate and diffuse within each of the separated spaces 19A, 19B within the inlet-side chamber 16, thereby suppressing variations in the flow rate of the fluid to be measured flowing into the measurement inlets 24 of each of the measurement units 20A-20D within the inlet-side chamber 16 and thereby suppressing a decrease in measurement accuracy.

[0065] The discharge flow path 43 is formed inside the shutoff valve unit 40. This makes it possible to provide the discharge flow path 43 by reusing an existing shutoff valve unit 40, thereby suppressing an increase in unnecessary parts in the flow meter 100.

[0066] (Other embodiments) The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified into various forms without departing from the spirit thereof, for example, the following modifications are also possible. In the above-described embodiment, the measurement circuit 28 of the flowmeter 100 calculates the flow rate of the city gas by multiplying the average flow velocity, which is the average value of the flow velocities measured by each of the measurement units 20A to 20D, by the average cross-sectional area of ​​the measurement flow path 26. Alternatively, the measurement circuit 28 may calculate the flow rate by multiplying the flow velocity measured by each of the measurement units 20A to 20D by the cross-section of the measurement flow path in each of the measurement units 20A to 20D, and calculate the flow rate of the city gas from the average value of these flow rates.

[0067] In the above-described embodiment, the flow meter 100 includes four measurement units 20A to 20D. Alternatively, the flow meter 100 may include two, three or fewer measurement units, or five or more measurement units.

[0068] In the above-described embodiment, the discharge flow path 43 is formed inside the shutoff valve unit 40. Alternatively, the flow meter 100 may include a discharge flow path 43 formed by a member separate from the shutoff valve unit 40.

[0069] In the above-described embodiment, the ultrasonic vibrators 27A and 27B are used as sensors in the flowmeter 100. The sensors are not limited to ultrasonic vibrators as long as they can measure the flow rate of the fluid to be measured.

[0070] In the above embodiment, the fluid to be measured is city gas, but the fluid to be measured may be LP gas instead. [Explanation of symbols]

[0071] 16...inlet chamber, 17...outlet chamber, 20A to 20D...measurement unit, 21...measurement instrument case, 24...measurement inlet, 25...measurement outlet, 26...measurement flow path, 27A, 27B...ultrasonic vibrator, 40...shutoff valve unit, 43...discharge flow path, 80...lower case, 90...upper case, 91...ceiling portion, 92...side wall, 93...main body inlet, 94...main body outlet, 96...discharge surface, 100...flow meter

Claims

1. a main body case having a ceiling portion in which a main body inlet and a main body outlet are formed, a bottom portion facing the ceiling portion, and a side wall extending between the ceiling portion and the bottom portion, the main body case defining a chamber which is a space surrounded by the ceiling portion, the side wall, and the bottom portion; a plurality of measurement units disposed in the chamber of the main body case for measuring a flow rate of a fluid to be measured in the chamber; a flow path that discharges the measurement target fluid flowing in from the main body inlet into the chamber, the flow path discharging the measurement target fluid toward a discharge surface that is an inner surface of the side wall in the chamber; Equipped with The plurality of measurement units include a measuring instrument case having a measurement flow path extending in a predetermined direction, a measurement inlet located on one side of the measurement flow path in the extension direction, and a measurement outlet located on the other side of the measurement flow path in the extension direction; a sensor that measures a value corresponding to a flow rate of the measurement target fluid flowing through the measurement flow path, The plurality of measurement units include The measurement flow path is spaced from the emission surface in a direction intersecting the direction of the emission surface when the measurement flow path is oriented in a direction intersecting the direction of the emission surface, and A flow meter comprising: a first flow meter and a second flow meter arranged in the chamber in a direction in which the emission surface faces.

2. The plurality of measurement units include 2. The flow meter of claim 1, wherein the measurement inlet is disposed within the chamber toward the discharge surface.

3. The main body case includes: The chambers include an inlet side chamber communicating with the main body inlet and an outlet side chamber communicating with the main body outlet, The measuring unit includes: The measurement flow path communicates with the inlet side chamber on the measurement inlet side, and the measurement flow path communicates with the outlet side chamber on the measurement outlet side, thereby forming a flow path between the main body inlet and the main body outlet, the discharge surface is an inner surface of the sidewall that defines the inlet chamber; The plurality of measurement units include 3. The flow meter according to claim 1, wherein the measurement inlet is disposed in the inlet chamber with the measurement inlet facing the discharge surface.

4. an outflow side chamber forming portion disposed in the main body case and forming the outflow side chamber, The side wall of the main body case is a first side wall having the emission surface on an inner surface thereof, a second side wall facing the first side wall in a direction in which the emission surface faces, and a third side wall and a fourth side wall positioned between the first side wall and the second side wall and facing each other in a direction intersecting the direction in which the emission surface faces; the emission surface is located on the first side wall toward the third side wall in a direction intersecting a direction in which the emission surface faces, The outlet side chamber forming portion is In the inlet side chamber, the discharge surface is located closer to the fourth side wall in a direction intersecting with a direction in which the discharge surface faces, The plurality of measurement units include the end of the measurement outlet side is inserted into a plurality of mounting openings of the outlet side chamber forming portion, so that the measurement flow path is arranged in the inlet side chamber, separated from the discharge flow path by a predetermined first distance in the direction intersecting the direction intersecting the direction in which the discharge surface faces, and arranged in the direction in which the discharge surface faces; The outlet side chamber forming portion is 4. The flow meter of claim 3, wherein the discharge surface is spaced from the fourth side wall by a second predetermined distance in a direction transverse to the direction in which the discharge surface faces.

5. a shutoff valve unit that switches between an open state that allows the measurement target fluid to flow from the main body inlet into the chamber and a shutoff state that shuts off the flow of the measurement target fluid from the main body inlet into the chamber according to a flow rate of the measurement target fluid measured by the measuring unit, 2. The flow meter of claim 1, wherein the discharge passage is formed within the shutoff valve unit.

Images