JP3020581B2 - Gas meter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas meter, such as a fluidic gas meter, for measuring a flow rate of a gas based on a uniform gas flow.

2. Description of the Related Art Conventionally, a gas meter that measures the flow rate of a gas based on a uniform gas flow, for example, a fluid gas meter has the following structure.

Gas flowing from a gas inlet provided in the casing flows into a gas retaining chamber (hereinafter, also abbreviated to a retaining chamber) via a gas passage, where gas flow turbulence is reduced and gas pressure fluctuations are absorbed. .

Thereafter, the gas is ejected through a nozzle portion to a fluidic flow sensor portion (hereinafter abbreviated as a flow sensor portion), and the gas flows alternately along two side walls provided symmetrically there. Oscillation of the gas flow occurs. In addition,
Such flow of gas along one side wall is generally called the Coanda effect.

From the retention chamber side opening of the nozzle portion, a cylindrical gas introduction passage projecting into the retention chamber is provided.
By passing through this gas introduction passage, it is subjected to a rectifying action and is ejected to the flow rate sensor section. Therefore, the vibration frequency of the gas flow in the flow sensor is substantially proportional to the gas flow. Then, the gas flow rate is measured based on the vibration of the gas flow.

<Problems to be solved by the invention> However, even in the conventional gas meter described above,
The vibration of the gas flow is not completely proportional to the gas flow, which is a bottleneck in improving the accuracy of the gas meter.

Here, if the gas flow flowing into the flow rate sensor unit is more regular, the gas flow will vibrate more accurately in proportion to the gas flow rate, and the accuracy of the gas meter will be further improved. .

In view of the above points, an object of the present invention is to provide a gas meter with further improved measurement accuracy.

<Means for Solving the Problems> The present invention has been made to solve the above problems, and is characterized by a gas meter that measures the flow rate of a gas based on a uniform gas flow. And a casing, a gas inlet provided in the casing, a gas retaining chamber provided in communication with the gas inlet in the casing, and a flow rate provided downstream of the gas retaining chamber in the casing. A nozzle portion having a sensor portion, a gas outlet provided in the casing further downstream of the flow rate sensor portion, and a retention chamber side opening in the gas retention chamber, and ejecting gas from the gas retention chamber to the flow rate sensor portion. And a gas introduction passage which is provided to protrude from the retention chamber side opening of the nozzle portion into the gas retention chamber and has a passage cross-sectional area larger than that of the nozzle portion. Is provided with a porous member for rectifying the gas flow.

Here, as the porous member, a mesh member having a net shape, a member obtained by assembling a plurality of tubes, or the like can be appropriately selected.

<Operation> In this gas meter, the gas flowing into the gas retaining chamber from the gas inlet passes through the gas introduction passage and the porous member and is jetted from the nozzle to the flow sensor. The gas undergoes double rectification when passing through the gas introduction passage and through the porous member, and then the gas flow rate is measured by the flow sensor, and then the gas flows out of the casing through the gas outlet. I do.

<Example> Hereinafter, an example of a fluidic gas meter which is an example of the present invention will be described with reference to the drawings.

As shown in the plan view of FIG. 2, a casing 3 of the gas meter 2 has a box-shaped casing body 4 having one opening.
And a lid 5 hermetically covered with the opening.

The casing body 4 is provided with a gas inlet 6, from which gas flowing in passes through a gas passage 8 to a gas retaining chamber 10.
Flows into. On the way, a shutoff valve 12 is provided. This shuts off the gas flow under the control of a microcomputer (not shown) when an abnormality occurs, such as when the gas flow rate per unit time exceeds the set value or the gas flow does not stop for a certain long period. Safety device. This shutoff valve 12 has an opening 13 in the center and an annular valve seat
A seat plate 15 having a valve plate 16 and an opposite valve plate 16
The valve plate 16 moves and comes into close contact with the valve seat 14 to perform a valve closing action.

The stagnation chamber 10 is a space having a predetermined volume. In this case, the gas flow once becomes gentler, so that the turbulence of the gas flow generated while flowing in the upstream portion is reduced. It also has the effect of absorbing fluctuations in gas pressure generated in the upstream part.

The fluidic flow sensor 20 is located downstream of the retention chamber 10.
Is provided. A nozzle portion 22 having a small passage cross-sectional area is provided on the upstream side portion of the flow sensor portion 20, and gas flows through the nozzle portion 22 through the nozzle portion 22.
Spouted at 20.

A gas outlet 11 is provided further downstream of the flow sensor unit 20, and after the gas flow rate is measured by the flow sensor unit 20, the gas flows out of the casing 3 from the gas outlet 11.

The bottom surface of the flow sensor unit 20 (including the nozzle unit 22) is higher than the bottom surface of the retention chamber 10. Therefore, the tenant room 10
The gas is temporarily stored in the gas sensor, and the gas flow to the flow sensor unit 20 becomes more stable.

 The flow sensor unit 20 has the following structure.

The sensor section inner wall surface 24 forms a space having a volume that is rapidly increased as compared with the passage sectional area of the nozzle section 22. A small columnar target 28 is provided at a central portion of the nozzle portion 22 immediately downstream of the sensor portion-side opening portion 26. Cylinders 30a and 30b are provided on both sides of the target 28, and side surfaces of the cylinders 30a and 30b facing each other form side walls 32a and 32b for guiding a gas flow ejected from the nozzle portion 22.

On the downstream side of the flow sensor unit 20, a rear wall 34 having symmetrical arc-shaped wall surfaces on both sides is provided substantially across the flow sensor unit 20, and a gap is provided between both ends and the sensor unit inner wall surface 24. Parts 38a and 38b are formed.

The gas flow (main flow) ejected from the nozzle part 22 is also provided at each constant flow rate with the aid of the target 28, and the respective cylinders 30a, 30b
The gas flows so as to be deflected alternately along the side walls 32a and 32b, and so-called vibration occurs in the gas flow. Here, assuming that the beam is first deflected to the column 30a, most of the gas flow is indicated by an arrow A in the figure.
As described above, the gas flows out of the gas meter 2 from the gas outlet 11 through the gap 38a. Then, a part of the main flow flows as a feedback flow to the vicinity of the sensor-side opening 26 of the nozzle 22 as indicated by an arrow B in the drawing. At this time, the main flow deflecting to the left in the drawing and pushing it to the right in the drawing is pushed to the right in the drawing, so that the main flow sways from the left to the right in the drawing, and if the main flow deflects to the column 30b side, it is symmetrical to the above. Flow occurs.

A piezoelectric film sensor is provided on the back side of the casing body 4 (not shown in FIG. 2). The piezoelectric film sensor has a container shape, and communicates with the small holes 54a and 54b in the vicinity of the sensor-side opening 26 of the nozzle portion 22 by the respective introduction paths. Then, the piezoelectric film provided at the center thereof is displaced by a difference in gas pressure between the small holes 54a and 54b. The frequency of the gas flow is calculated by converting such displacement into an electric signal, and the gas flow rate passing through the gas meter 2 is measured based on the frequency.

Since the above-described measurement flow rate range of the fluidic flow rate sensor unit 20 is a large flow rate area of a certain flow rate or more, a thermal flow rate sensor (hereinafter abbreviated as a thermal sensor) 70 for a small flow rate area is supplementarily provided. As shown in FIG. 2, the nozzle 22 is fitted and fixed in a concave portion at the bottom of the nozzle portion 22. A first temperature sensor, a heater, and a second temperature sensor are arranged on the upper surface (the surface in contact with the gas flow) of the thermal sensor 70 in order from the upstream side. Then, the temperature difference generated in the first and second sensors according to the gas flow rate under the heating of the heater is converted into an electric signal, and the gas flow rate is measured. The upper surface of the thermal sensor 70 is located at the nozzle 2
2, at the same height as the bottom surface of the flow sensor unit 20, a thermal sensor
70 ensures that the gas flow is not disrupted.

The electric signals from the piezoelectric film sensor 50 and the thermal sensor 70 are both input to a microcomputer (not shown), and based on the electric signal from the piezoelectric film sensor 50 when the gas flow rate is large, and when the gas flow rate is small, The gas flow rate is measured based on the electric signal from the thermal sensor 70. The measured gas flow rates are integrated, and the gas flow rate is displayed on a flow rate display unit (not shown) attached to the outside of the casing body 4 or the lid 3.

From the retention chamber side opening 56 of the nozzle part 22, the retention chamber 10
A gas introduction passage 60 protruding to the side is provided. As shown in FIG. 1, the gas introduction passage 60 has a gutter-shaped passage main body.
By covering 64 openings with a part of the lid 5 described above,
It has a quadrangular cylindrical shape and has a passage cross-sectional area larger than that of the nozzle portion 22. In addition, the bottom 64a is
It is located higher than the bottom surface of 0 and at the same height as the lower part of the flow sensor unit 20 to enhance the effect of the "reservoir" of the staying chamber 10.

A mesh member 62 having an appropriate mesh interval is attached as a porous member to an opening end of the gas introduction passage 60 on the side of the retention chamber 10. This mesh member 62
For example, it is formed of a metal net. This mesh member
62 acts to rectify the gas flow passing here, but if the eyes are too coarse, the effect of rectification is hardly obtained, while if the eyes are too fine, the pressure loss of the gas when passing through it is large. This tends to make it impossible to satisfy the rated value of the gas meter.

Also, if the mesh member 62 is provided directly on the nozzle portion 22 having a small passage cross-sectional area, the gas pressure loss is large, the ejection output to the flow sensor portion 20 is insufficient, and the gas flow in the flow sensor portion 20 is reduced. Vibration is less likely to occur. Therefore, a gas introduction passage having a passage cross-sectional area larger than that of the nozzle portion 22
A mesh member 62 is attached to 60.

Then, the gas from the retaining chamber 10 passes through the gas introduction passage 60 via the mesh member 62,
Rectification by both the gas inlet passage 60 and the gas introduction passage 60, and the gas is ejected from the nozzle portion 22 to the flow sensor portion 20, so that the vibration of the gas flow in the flow sensor portion 20 is stabilized, and the frequency is well proportional to the gas flow rate. Measurement accuracy is increased.

FIG. 5 shows an output waveform output from the flow rate sensor unit 20 with respect to the gas flow passing through the rectifying mesh unit 62. If the waveform is compared with the waveform of FIG. It can be seen that the waveform is almost uniform and stable.

FIG. 3 shows another embodiment. In this example, the gas introduction passage
60 gutter-shaped passage body 64 itself is a fine mesh member 84
It is composed of That is, the bottom part and both side parts are constituted by mesh parts 84a, 84b and 84c which are integral with each other, and the upper opening is covered with the above-mentioned lid body 5 to form a square tubular introduction passage. A mesh member 62 is provided at the end on the side of the stagnation chamber 10, and the mesh member 62 is coarser than the mesh portion 84 constituting the gas introduction passage 60. Other parts are the same as those of the previous embodiment shown in FIG.

In this embodiment, the gas from the stagnation chamber 10 mainly passes through the mesh member 62 at the upstream end, and flows to the nozzle portion 22 through the gas introduction passage 60 surrounded by the three portions by the mesh portions 84a to 84c.
Some can pass through the mesh portions 84a-c and flow into the nozzle portion 22. Therefore, the pressure loss of the gas as a whole is reduced. In other words, the mesh member 62 can be made finer and the rectifying action can be increased. The mesh portions 84a to 84c also provide a rectifying effect on a part of the gas passing therethrough.

Another embodiment is shown in FIG. In this example,
At the opening of the shutoff valve 12 on the side of the retention chamber 10, a bottomed cylindrical mesh member 82 is provided so as to cover the opening. That is, the short cylindrical member 80 is fixed to the seat plate 15 of the shutoff valve 12, and the mesh member 82 is fixed inside the opening at the opening. Other parts are the same as those in the embodiment of FIG. Here, the shut-off valve 12 is usually incorporated in the gas meter 2 for safety reasons. Since the mesh member 82 is integrated with the shut-off valve 12, the shut-off valve 12 is assembled to the gas meter 2. Thereby, the assembly of the mesh member 82 is completed at the same time, and the assembly is facilitated. In addition, the mesh member 82, the gas introduction passage 60, and the mesh member 62 are combined, so that a further gas rectifying effect can be obtained. As a modified example, there is also a mode in which a gas passage that expands in a tapered shape as it extends to the downstream side is provided in the sheet plate, and a planar mesh member is fixed to an open end thereof in advance.

In FIGS. 2 and 4, the mesh member 62 is provided at the upstream end of the gas introduction passage 60.
It may be provided in a downstream portion or the like. Also, mesh members
Two or more 62 may be provided.

Further, the porous member is not limited to the mesh members 62 and 82, and various members such as a porous plate and a rectifying grid can be used.

Further, as the gas introduction passage 60, various passages such as those having a passage cross-sectional area that increases as the gas introduction passage extends from the retention chamber side opening 56 of the nozzle portion 22 into the retention chamber 10 can be used.

In addition, a suitable porous member such as a mesh member may be further provided in the retaining chamber 10 instead of or together with the mesh member 82 in a form that partitions the retaining chamber 10.

In addition, the present invention is not limited to a fluid gas meter, but can be applied to other gas meters (for example, a vortex flow meter or the like) as long as the gas meter measures the flow rate of the gas based on a uniform gas flow. .

In addition, it is needless to say that the present invention can be carried out in aspects in which various changes are made based on the knowledge of those skilled in the art.

<Effect of the Invention> In the gas meter according to the present invention, when the gas passes through the gas introduction passage provided with the porous member, the gas is subjected to a synergistic rectification action by the porous member and the gas introduction passage, and the flow sensor section is provided. Therefore, the accuracy and reliability of the gas meter are improved. Moreover, since the porous member is provided in the gas introduction passage having a passage cross-sectional area larger than that of the nozzle portion, the pressure loss of the gas can be suppressed to be small.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a gas introduction passage taken out in one embodiment of the present invention, and FIG. 2 is a plan sectional view showing the entire gas meter. FIG. 3 is a perspective view showing a main part of another embodiment of the present invention, and FIG. 4 is a plan sectional view of still another embodiment. FIG. 5 is a graph showing an output waveform in the gas meter shown in FIG. 2, and FIG. 6 is a graph showing an output waveform in the conventional gas meter having no mesh member shown in FIG. 2 Gas meter 4 Casing body 6 Gas inlet 10 Gas storage chamber 20 Fluidic flow sensor 22 22 Nozzle 56 Opening on the storage chamber side 60 Gas introduction passage 62 Mesh member

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Fujio Hori 2975 Motoe, Shinminato-shi, Toyama Toyo Gas Meter Co., Ltd. (56) References JP-A-4-62427 (JP, A) Patent 2806602 (JP, B2) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01F 1/00 G01F 1/20 G01F 15/12

Claims (1)

(57) [Claims] 1. A gas meter for measuring a gas flow rate based on a uniform gas flow, comprising: a casing; a gas inlet provided in the casing; and a gas inlet provided in the casing in communication with the gas inlet. A gas retention chamber provided in the casing, a flow sensor part provided downstream of the gas retention chamber in the casing, a gas outlet provided in the casing further downstream of the flow sensor part, and the gas retention chamber. A nozzle portion for ejecting gas from the gas retention chamber to the flow rate sensor portion, and a nozzle protruding from the retention chamber side opening of the nozzle portion into the gas retention chamber, the nozzle A gas introduction passage having a passage cross-sectional area larger than the portion, and a porous member provided in the gas introduction passage for rectifying a gas flow. Gas meter.