JP2005106726A - Gas meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas meter which assures precision of a cross section area of a path of a flow channel to be measured in which a fluid flows, and precision of a flow rate of the fluid measured by an ultrasonic flow measuring means, with reduced cost. <P>SOLUTION: In the gas meter, a pair of ultrasonic transmit-receive means are located to face each other in a flow channel to be measured. The flow channel to be measured comprises a body case, and a straight measuring tube for flow rate measurement stored in the body case. The measuring tube is connected using two L-shape members (52a and 52b) whose cross section in the vertical direction against the flow direction is L-shaped so as to make the cross section of the tube is rectangular. At the position where the ultrasonic transmit-receive means is located, an opening (52c) is provided. In addition, a turbulent flow suppression member (54) which has micropore to pass through ultrasonic waves is provided at the opening. The measuring tube also comprises a member whose coefficient of linear expansion is not greater than a prescribed value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a gas meter for measuring a gas flow rate, and more particularly to a structure of an ultrasonic gas meter.

Conventionally, various ultrasonic flow measurement devices that measure the flow rate of a fluid such as gas or liquid using ultrasonic transmission / reception means have been proposed (see, for example, Patent Document 1).
In the example of Patent Document 1, in order to improve the measurement accuracy, an opening window for ultrasonic transmission / reception means is provided in the measurement channel, and an inflow suppressor having fine holes is provided in the opening window. For example, a flow stabilizing means is provided on the inflow side to suppress vortices and turbulent flow to improve measurement accuracy.
In the ultrasonic flow measurement device, the fluid flow rate is measured by the ultrasonic flow rate measurement means, and the flow rate (volume) is calculated based on the measured velocity and the cross-sectional area inside the measurement channel (the area of the passage through which the fluid flows). To do. Therefore, the accuracy of the flow rate is greatly influenced by the accuracy of the detected speed and the accuracy of the area of the measurement flow path.
Japanese Patent Laid-Open No. 2003-202254

In the conventional ultrasonic flow rate measuring device, the measurement channel is formed by die casting or the like, and in order to ensure the accuracy of the cross-sectional area of the channel through which the fluid flows in the measurement channel, the dimensional accuracy of the channel inner wall and the channel High-precision cutting and surface finishing are required after forming by die casting, such as the surface finishing accuracy of the inner wall, and a great deal of cost is required.
Further, when the fluid velocity is measured by the ultrasonic flow rate measuring means, if a subtle turbulent flow occurs in the measurement unit, the accuracy of the velocity may be affected.
The present invention was devised in view of such points, and ensures the accuracy of the cross-sectional area of the passage through which the fluid flows in the measurement flow path and the accuracy of the velocity of the fluid measured by the ultrasonic flow rate measuring means. In addition, an object is to provide a gas meter that can further reduce the cost.

As means for solving the above-mentioned problems, the first invention of the present invention is a gas meter as described in claim 1.
The gas meter according to claim 1 is a gas meter in which a pair of ultrasonic transmission / reception means is provided opposite to a measurement channel for measuring a gas flow rate, and the measurement channel includes a main body case and the main body. It is composed of a measuring tube having a straight shape for flow rate measurement housed in a case (a double structure consisting of a main body case and a measuring tube).

Moreover, the 2nd invention of this invention is a gas meter as described in Claim 2.
A gas meter according to a second aspect is the gas meter according to the first aspect, wherein the measurement tube is composed of two L-shaped members having a L-shaped cross section perpendicular to the gas flow direction. It joins and comprises so that it may become a rectangular cylinder shape.

Moreover, the 3rd invention of this invention is a gas meter as described in Claim 3.
A gas meter according to a third aspect is the gas meter according to the first or second aspect, wherein an opening is provided at a location where the ultrasonic transmission / reception means faces in the measurement tube, and the ultrasonic wave is passed through the opening. A turbulent flow suppression member having a hole is provided.

Moreover, the 4th invention of this invention is a gas meter as described in Claim 4.
A gas meter according to a fourth aspect is the gas meter according to any one of the first to third aspects, wherein the measuring tube is formed of a member having a linear expansion coefficient equal to or less than a first predetermined value.

The fifth aspect of the present invention is a gas meter as set forth in the fifth aspect.
A gas meter according to a fifth aspect is the gas meter according to any one of the first to fourth aspects, wherein the measurement flow path for measuring the flow rate of the gas includes a pair of ultrasonic transmission / reception means. The pair of ultrasonic transmission / reception means is arranged so that the traveling direction of the ultrasonic waves transmitted / received by the ultrasonic transmission / reception means has a predetermined angle with respect to the gas flow direction, and the ultrasonic waves cross the gas flow. The gas meter is parallel to the gas flow direction between one ultrasonic transmission / reception means and the other ultrasonic transmission / reception means in the measurement channel, and parallel to the direction of the ultrasonic waves transmitted from the ultrasonic transmission / reception means. Provide a straightening plate.

The sixth aspect of the present invention is a gas meter as set forth in the sixth aspect.
A gas meter according to a sixth aspect is the gas meter according to the fifth aspect, wherein the thickness of the rectifying plate is set to a second predetermined value or less.

If the gas meter of Claim 1 is used, a main body case will be formed by die-casting and a measuring tube will be formed with resin, for example. In this case, the accuracy of the cross-sectional area of the passage through which the fluid flows in the measurement flow path may be ensured by the measurement tube instead of the main body case (in order to flow the fluid into the measurement tube). Therefore, it is not necessary to cut and surface finish the inner wall of the die cast (main body case), and the accuracy can be increased by forming the resin (measurement tube).
Thereby, the required accuracy can be easily secured in the area of the cross section of the passage through which the fluid flows, and the cost can be further reduced.

Moreover, according to the gas meter of Claim 2, it is still easier to ensure the accuracy of the area of the cross section of the channel through which the fluid flows. For example, when the measuring tube is made of resin, the "U" shape requires a draft, and the accuracy of the cross-sectional area decreases due to the slope, but the "L" shape can be molded without a draft. Since it is possible, the fall of the precision of the cross-sectional area by a gradient can be suppressed.
Thereby, it is possible to ensure the necessary accuracy in the area of the cross section of the passage through which the fluid flows, and to further reduce the cost.

  According to the gas meter of the third aspect, since the turbulent flow of the portion where the ultrasonic waves come and go can be suppressed by the turbulent flow suppressing member, the velocity of the fluid measured by the ultrasonic flow rate measuring means. Accuracy can be further improved.

Moreover, according to the gas meter of Claim 4, the dimensional change of the measurement pipe accompanying a temperature change can be suppressed, and the fluctuation | variation of the cross-sectional area of the channel | path through which a fluid flows can be suppressed.
Thereby, it is possible to ensure the necessary accuracy in the area of the cross section of the passage through which the fluid flows, and to further reduce the cost.

According to the gas meter of claim 5, when the ultrasonic wave is transmitted from one ultrasonic transmission / reception unit to the other ultrasonic transmission / reception unit in the passage through which the fluid flows, the transmitted ultrasonic wave is rectified. It travels along the plate and reaches the other ultrasonic transmission / reception means.
As described above, the flow straightening plate regulates the gas flow and appropriately guides the ultrasonic waves, so that it is effective for ensuring the accuracy of the fluid velocity measured by the ultrasonic flow rate measuring means.

  Moreover, according to the gas meter of Claim 6, the influence on the area of the cross section of the channel | path through which the fluid in a measuring tube flows can be suppressed.

The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a schematic external view of a gas meter 1 of the present invention.
● [Appearance of gas meter (Fig. 1)]
The external appearance of the gas meter 1 of this Embodiment is demonstrated using FIG. 1A shows a perspective view including a front surface, and FIG. 1B shows a perspective view including a back surface. In addition, the X-axis, Y-axis, and Z-axis in each figure are axes in which the X-axis and Y-axis indicate the horizontal direction, and the Z-axis is an axis that indicates the vertical direction. The surface including the display unit 1c is the front.
The upper part of the gas meter 1 is provided with a supply source inlet 1a through which gas supplied from a gas supply source (gas company or the like) flows and a facility outlet 1b through which gas flows out to a facility using the gas. . Further, the gas meter 1 is provided with a measurement flow path 50 for measuring the flow rate of gas (see FIG. 2), and gas that flows in from the supply source inlet 1a and flows out of the facility outlet 1b. Measure the flow rate.

A display means 1c is provided on the front face of the gas meter 1, and an integrated value of gas can be displayed. A display operation unit (display switch or the like) for switching display contents is provided near the display unit 1c, and the display contents on the display unit 1c can be switched by operating the display operation unit. .
Further, when the terminal cover 1e is removed, a communication terminal (not shown) to which a communication device can be connected appears. If a communication line and a communication device are connected to this communication terminal, communication can be performed between the gas meter 1 and the communication device.

● [Internal structure (Fig. 2)]
Next, the internal structure of the gas meter 1 will be described with reference to FIG. The gas flowing in from the supply source inlet 1a is, for example, the supply source inlet 1a—the first flow path forming member 40 (including the shutoff valve 60) —the measurement flow path 50—the second flow path forming member 48 (the pressure sensor 62). Pass through the path of the facility outlet 1b.
The measurement channel 50 is provided with a pair of ultrasonic transmission / reception sensors (ultrasonic transmission / reception means), and the flow rate of the gas passing through the measurement channel 50 is detected based on the signal of the ultrasonic transmission / reception sensor. Is done. The gas flow path GR in the measurement flow path 50 has a rectangular cross section S (see FIG. 3) perpendicular to the gas flow direction (the direction from left to right in FIG. 2). It is formed with high accuracy so that the error of the area of the cross section S becomes very small. This is because the gas flow rate is calculated based on the gas velocity measured by the ultrasonic transmission / reception sensor and the area of the cross section S.
Further, the pressure sensor 62 detects the pressure of the gas passing through the second flow path forming member 48. For example, when the detected pressure deviates from a predetermined pressure range, the control means (a control means having a CPU or the like, not shown) drives the shut-off valve 60 so that the inside of the first flow path forming member 40 Is closed to shut off the gas flowing in from the supply source inlet 1a.

The first flow path forming member 40 communicates the supply source inlet 1a and the measurement inlet 50a, and the second flow path formation member 48 communicates the equipment outlet 1b and the measurement outlet 50b.
Moreover, the measurement flow path 50 is arrange | positioned substantially horizontal, and the 1st flow path formation member 40 and the 2nd flow path formation member 48 are arrange | positioned substantially perpendicularly. The first flow path forming member 40, the measurement flow path 50, and the second flow path forming member 48 are substantially U-shaped.

● [Measurement channel structure (Fig. 2, Fig. 3, Fig. 4)]
As shown in FIG. 2, the measurement flow path 50 is configured by a double structure of an outer main body case 51 and a measurement tube 52 having a straight shape for flow rate measurement accommodated in the main body case 51. The main body case 51 is formed of a member having high rigidity such as die casting. A pair of ultrasonic transmission / reception sensors are assembled to the main body case 51 so as to face each other with a predetermined angle θ with respect to the gas flow direction (assembled in the sensor hole 51c in FIG. 4).
The measurement tube 52 is assembled in the main body case 51 so that at least a part thereof is in close contact with the inner wall of the main body case 51. Thereby, all the gas whose flow rate is to be measured flows in from the measurement inlet 50a of the measurement pipe 52, passes through the inside of the measurement pipe 52, and flows out of the measurement outlet 50b. Inside the measurement tube 52 is parallel to the gas flow direction (the direction from the left to the right in FIG. 2) and the direction of the ultrasonic wave transmitted from the ultrasonic transmission / reception sensor (the front (or back) of FIG. 2). ) From the back of the paper surface (or the direction from the front) to the back of the paper).

Next, FIG. 3 shows an example of the structure of the measurement channel 50. In the measurement flow channel 50, a substantially rectangular parallelepiped measurement tube 52 is accommodated in a main body case 51 constituted by main body case members 51a and 51b.
FIG. 4 is a cross-sectional view of the measurement channel 50 cut along a horizontal plane (XY plane) when viewed from below. A sensor hole 51c for inserting an ultrasonic transmission / reception sensor is provided on a side surface of the main body case member 51a. Furthermore, in the measurement tube 52, an opening 52c for allowing ultrasonic waves to pass is provided at a location where the opposing ultrasonic transmission / reception sensor faces.
Further, as shown in FIG. 4, the opening 52c of the measurement tube 52 is provided with a turbulent flow suppressing member 54 that is substantially flush with the inner wall of the measurement tube 52 and provided with fine holes through which ultrasonic waves can pass. ing.

● [Measurement tube structure (Fig. 5)]
Next, FIG. 5 shows an example of the structure of the measuring tube 52. The measuring tube 52 is joined by two measuring tube members 52a and 52b (L-shaped members) whose cross section perpendicular to the gas flow direction is an “L” shape so that the cross section is a rectangular tube. Has been configured. In addition, the current plate 53 is accommodated in the inside at the time of joining. A groove 52z for supporting the rectifying plate 53 is provided at a contact portion of the inner walls of the measurement tube members 52a and 52b with the rectifying plate 53, and the rectifying plate 53 is positioned in the groove 52z.
Further, in the measurement tube members 52a and 52b, the protrusions 52x or the recesses 52y are respectively provided in the contact portions when they are joined in a rectangular cylindrical shape, and are positioned by the protrusions 52x and the recesses 52y. The

Here, when the measurement tube members 52a and 52b are formed in a “U” shape, a draft is indispensable. Therefore, each of the cross sections S (see FIG. 3) of the measurement tube 52 by a plane perpendicular to the gas flow direction. There is a possibility that the angle is not a right angle and the accuracy of the cross section S varies. Further, when the rectifying plate 53 is insert-molded into the measuring tube 52, since a draft is required, a problem may occur in the accuracy of the cross section S (the required accuracy cannot be satisfied).
However, in this embodiment, since the measurement tube members 52a and 52b are formed in an “L” shape, no draft is necessary. For this reason, it is possible to make each angle of the cross section S a right angle. For example, even if the measurement tube members 52a and 52b are formed using resin, the accuracy of the area S can be sufficiently secured. Moreover, when forming with resin, not only can cost be reduced, but it is easy to ensure the flatness of the inner wall, and turbulence can be further suppressed.
The opening 52c is provided with a turbulent flow suppressing member 54 on the inner wall side.

In addition, although general resin has a large thermal deformation, in order to suppress the fluctuation | variation with the temperature of the area of the cross section S, the measurement pipe members 52a and 52b have a linear expansion coefficient below 1st predetermined value (for example, 10 * 10 < ^- >). ⁵ [cm / cm · ° C.] or less) is used. For example, an ABS resin (about 10 * 10 ⁻⁵ [cm / cm · ° C.]) or a member in which about 30% glass fiber is mixed in ABS resin (about 2.8 * 10 ⁻⁵ [cm / cm · ° C.]) Phenol resin (about 5 * 10 ⁻⁵ [cm / cm · ° C.]), stainless steel (about 1.7 * 10 ⁻⁵ [cm / cm · ° C.]), aluminum (about 2.4 * 10 ^{− 5} [cm / cm · ° C.]) or the like.

In addition, other materials whose linear expansion coefficient can be equal to or less than the first predetermined value and the linear expansion coefficient of the material are: Polycarbonate (mixed with glass fiber 30%): about 7.0 * 10 ⁻⁵ [cm / cm · ° C] (about 3.5 * 10 ⁻⁵ [cm / cm · ° C.]), polyacetal (mixed with 20% glass fiber): 8.1 to 9.0 * 10 ⁻⁵ [cm / cm · ° C.] (4 to 7.0 * 10 ⁻⁵ [cm / cm · ° C.]), polyamide (mixed with 30% glass fiber): 8.0 to 10 * 10 ⁻⁵ [cm / cm · ° C.] (2 to 4 * 10 ⁻⁵ [ cm / cm · ° C.), polybutylene terephthalate: 7.0 to 9.5 * 10 ⁻⁵ [cm / cm · ° C.], polystyrene (mixed with 30% glass fiber): 7.0 to 10.0 * 10 ^{− 5 [cm / cm · ℃]} (2~7 * 10 -5 [cm / cm · ℃]), high density polyethylene: 1 ^{~15 * 10 -5 [cm / cm} · ℃], ^{polypropylene: 6~11 * 10 -5 [cm /} cm · ℃], diallyl phthalate 30% glass fiber mixed: 1 to 3.5 * 10 ^-5 [ cm / cm · ° C.] and the like.

● [Structure of turbulent flow suppression member (Fig. 6)]
Next, the turbulent flow suppressing member 54 will be described with reference to FIG. The turbulent flow suppressing member 54 is provided with a fine hole EH in a substantially two-dimensional manner within the range of the width EHh and the height EHv. The width EHh and the height EHv are substantially the same dimensions as the opening 52c of the measurement tube 52.
The turbulent flow suppressing member 54 shown in the present embodiment uses stainless steel attached to a magnet, and the thickness (width in the Y-axis direction) is about 0.1 [mm]. For example, the fine hole EH of the turbulent flow suppressing member 54 is formed by photoetching. Then, the turbulent flow suppressing member 54 is attached to the magnet, the resin is poured into the mold, and the measuring tube member 52a or 52b and the turbulent flow suppressing member 54 are integrally formed.
As for the shape and diameter of the micro holes EH, and the horizontal pitch Ph and the vertical pitch Pv of the micro holes EH, optimum shapes and dimensions are required by various experiments. The inventor conducted various experiments to make the shape of the microhole EH “circular”, the diameter of the microhole EH “about 0.16 [mm]”, and the horizontal pitch Ph “about 0.248 [mm]”. The vertical pitch was set to “about 0.212 [mm]”. However, these values may differ from each other due to various factors such as the type of fluid to be measured, the dynamic range of the flow rate, and the usage environment.

Here, when a mesh in which metal fibers are knitted is used as the turbulent flow suppressing member 54, when viewed microscopically, since each fiber is knitted alternately on the front and back, the surface has irregularities, and the gas flow As a result, a fine turbulent flow is likely to occur and the detection accuracy of the ultrasonic transmission / reception sensor is relatively large. However, in the case of the turbulent flow suppression member 54 shown in the present embodiment having the fine hole EH, there is almost no surface irregularity even when viewed microscopically, and the generation of turbulent flow due to the gas flow is suppressed, and ultrasonic transmission / reception is performed. The influence on the detection accuracy of the sensor is relatively small.
In the case of a mesh, unnecessary gaps are formed in various directions other than the direction in which the ultrasonic waves are desired to pass between the fibers and the gaps between the fibers, and fine dust or the like is likely to adhere. However, in the case of the turbulent flow suppressing member 54 shown in the present embodiment having the fine holes EH, since there is no gap in the direction other than the direction in which the ultrasonic waves are desired to pass, adhesion of dust and the like can be suppressed and more stable accuracy can be maintained. can do.

● [Arrangement and effect of current plate (Fig. 7)]
Next, the current plate 53 will be described with reference to FIG. As shown in FIGS. 5 and 7, a rectifying plate 53 is disposed in the measurement tube 52 in parallel with the gas flow direction, and rectifies the gas (suppresses turbulent flow) to transmit and receive an ultrasonic wave. The detection accuracy is improved.
The rectifying plate 53 not only rectifies the gas but also has an effect of appropriately guiding the ultrasonic wave transmitted from one ultrasonic transmission / reception sensor to the other ultrasonic transmission / reception sensor. As shown in FIG. 7, the ultrasonic wave is transmitted from one opening 52 c in the measurement tube 52 toward the opening 52 c facing the ultrasonic wave. Here, the rectifying plate 53 is arranged so as to be parallel to the gas flow direction and parallel to the direction of the ultrasonic wave transmitted from the ultrasonic transmission / reception sensor. Note that the length of the rectifying plate 53 (the length with respect to the gas flow direction) may be longer than the length including the pair of openings 52c, from at least one ultrasonic transmission / reception sensor to the other ultrasonic transmission / reception sensor. What is necessary is just to be arrange | positioned between.
Thereby, the ultrasonic wave transmitted from one ultrasonic transmission / reception sensor can be appropriately guided to the other ultrasonic transmission / reception sensor, and the S / N of the ultrasonic transmission / reception sensor is improved, and the detection accuracy is improved. Yes.

  Next, the thickness of the rectifying plate 53 (the thickness in the Z-axis direction in FIG. 7) will be described. If the rectifying plate 53 is thicker than necessary, the reception level of the ultrasonic signal from the ultrasonic transmission / reception sensor is affected (the reception level tends to decrease as the rectifying plate 53 is thicker). When the reception level is smaller than a predetermined value, amplification is performed by an electronic circuit. However, the smaller the reception level is, the larger the amplification is, the larger the noise component is, and the measurement accuracy is deteriorated (S / N is lowered). However, there is a limit to thinness as well as assembly strength and vibration resistance. As a result of various experiments, the inventors have confirmed that it is possible to obtain good measurement accuracy by using a stainless steel plate having a thickness of 0.3 [mm] or less (second predetermined value or less). In addition, from the viewpoint of strength, vibration resistance, and reception level, it was experimentally confirmed that about 0.2 [mm] was desirable, and more preferable measurement accuracy could be obtained. The material is not limited to stainless steel, and various materials can be used. Needless to say, if the strength is higher than that of the stainless steel plate, it may be 0.2 [mm] or less.

● [Effects of the present embodiment (FIGS. 8 and 9)]
In FIG. 8, the example of an experimental result is shown about the precision of the flow volume measured with the gas meter 1 shown to this Embodiment.
The example shown in FIG. 8 compares the mesh type 54z (before improvement) and the fine hole type 54a (after improvement) by photoetching in the structure of the turbulent flow suppressing member 54 (see FIG. 8A). Portions other than the structure of the turbulent flow suppressing member 54 (the structure of the measurement channel 50, the characteristics of the ultrasonic transmission / reception sensor, etc.) are the same (both are ambient temperature 23 [° C.]). In the experiment shown in FIG. 8, the contents described in the present embodiment are adopted, and the accuracy of the area of the cross section S (see FIG. 3) of the measurement tube 52 and the detection of the ultrasonic transmission / reception sensor by the rectifying plate 53 are adopted. Accuracy and the like have been improved compared to the prior art.

FIG. 8B shows the instrumental error (vertical axis direction) at each flow rate (horizontal axis direction) of air and 13A (measurement alternative gas) when the mesh type 54z (before improvement) is used. . FIG. 8C shows the instrumental difference (vertical axis) at each flow rate (horizontal axis direction) of air and 13A (alternative gas for measurement) when the fine hole type 54a (after improvement) by photoetching is used. Direction).
The “instrument difference” is obtained by subtracting the “value to be shown” from the “value shown by the measuring device” and converting it to the ratio.
In the case of the mesh type 54z (before improvement) (FIG. 8B), the instrumental difference tends to be biased toward the plus side in air, and tends to be biased toward the minus side in 13A. Further, the difference in instrumental difference between air and 13A is slightly large even at the same flow rate. Moreover, even if the air is the same, the fluctuation of the instrumental difference due to the difference in flow rate is relatively large. Normally, the flow rate of “air” is measured to check the accuracy, etc., and the flow rate of gas that is close in characteristic to “13A” is actually measured. Is not preferred.
On the other hand, in the case of the micro-hole type 54a (after improvement) by photoetching (FIG. 8C), both air and 13A are within the vicinity of “vessel difference 0 [%]” without any bias. In addition, there is almost no difference in instrumental difference between air and 13A (particularly the difference is very small when the flow rate is L1 or more), and very good characteristics are shown.

FIG. 9 is a graph of the fine hole type 54a by photoetching when the material of the measuring tube members 52a and 52b is changed. (Before improvement) is a material with a linear expansion coefficient of about 10 * 10 ⁻⁵ [cm / cm · ° C.] (After improvement) is a material with about 2.8 * 10 ⁻⁵ [cm / cm · ° C.] It is a test result when using it.
As can be seen from the graph shown in FIG. 9, both (before improvement) and (after improvement) are within the instrumental error frame, but (after improvement) has a smaller deviation from instrumental error of 0%. In addition, the margin to the instrument frame is wide. For this reason, it was confirmed that (after improvement) the flow rate measurement accuracy was higher, the instrumental difference variation with temperature change was smaller, and more favorable characteristics could be realized.

The gas meter 1 of the present invention is not limited to the configuration, structure, appearance, shape, material, and the like described in the present embodiment, and various modifications, additions, and deletions can be made without changing the gist of the present invention.
In this embodiment, three rectifying plates 53 are used. However, an appropriate number of rectifying plates may be used according to the type of fluid to be measured, the size of the cross section S, the dynamic range of the flow rate, and the like.
Further, the above (≧), the following (≦), the larger or larger (>), the smaller or smaller (<), or the like may or may not include an equal sign.
The numerical values used in the description of the present embodiment are examples, and are not limited to these numerical values.

  The gas meter 1 of the present invention can be applied to a flow rate measuring device that measures the flow rates of various fluids in addition to a business gas meter and a general household gas meter.

It is a schematic external view of one embodiment of the gas meter 1 of the present invention. It is a figure explaining the internal structure of the gas meter. It is a figure explaining the structure of the measurement flow path. It is a figure which shows the cross section (horizontal direction cross section) of the measurement flow path. It is a figure explaining the structure of the measurement pipe | tube 52. FIG. It is a figure explaining the structure of the turbulent flow suppression member. It is a figure explaining the arrangement position and effect of the baffle plate 53. FIG. It is a figure which shows the experimental result which actually measured the flow volume of the fluid. It is a figure which shows the experimental result which measured the flow volume of the fluid at each temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas meter 1a Supply source inlet 1b Equipment outlet 40 1st flow path formation member 48 2nd flow path formation member 50 Measurement flow path 51 Main body case 51a, 51b Main body case member 51c Sensor hole 52 Measurement pipe 52a, 52b Measurement pipe member 52c Opening 53 Current plate 54 Turbulence suppressing member

Claims (6)

A gas meter provided with a pair of ultrasonic transmission / reception means facing a measurement channel for measuring the flow rate of gas,
The measurement channel is composed of a main body case and a measurement tube having a straight shape for flow rate measurement accommodated in the main body case.
A gas meter characterized by that. The gas meter according to claim 1,
The measurement tube is configured by joining two L-shaped members having a L-shaped cross section perpendicular to the gas flow direction so that the cross section is a rectangular tube.
A gas meter characterized by that. The gas meter according to claim 1 or 2,
An opening is provided at a place where the ultrasonic transmission / reception means faces in the measurement tube, and a turbulent flow suppression member having a fine hole through which the ultrasonic wave passes is provided in the opening.
A gas meter characterized by that. The gas meter according to any one of claims 1 to 3,
Forming a measuring tube with a member having a linear expansion coefficient equal to or less than a first predetermined value;
A gas meter characterized by that. A gas meter according to any one of claims 1 to 4,
A pair of ultrasonic transmission / reception means is provided in the measurement flow path for measuring the gas flow rate, and the traveling direction of the ultrasonic waves transmitted / received by the pair of ultrasonic transmission / reception means has a predetermined angle with respect to the gas flow direction. And a gas meter in which a pair of ultrasonic transmission / reception means is arranged so that the ultrasonic wave crosses the gas flow,
Between the one ultrasonic transmission / reception means and the other ultrasonic transmission / reception means in the measurement flow path, a rectifying plate is provided that is parallel to the gas flow direction and parallel to the direction of the ultrasonic waves transmitted from the ultrasonic transmission / reception means,
A gas meter characterized by that. The gas meter according to claim 5, wherein
The thickness of the current plate is set to a second predetermined value or less,
A gas meter characterized by that.

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