JP3016846B2 - 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 retention chamber (hereinafter, also abbreviated as a retention chamber) via a gas passage and a shutoff valve. This shutoff valve is a safety device that shuts off the flow of gas under the control of the microcomputer when a large amount of gas flows per unit time or when gas continues to flow without interruption for a long period of time. The retention chamber is a space having a fixed volume, and serves to absorb fluctuations in gas pressure and to reduce turbulence in gas flow.

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

A mesh member is attached to an upstream portion of the retention chamber or a position surrounding the retention-side opening of the nozzle portion. The gas is rectified by passing through these mesh members, and is discharged to the flow rate sensor portion. For this reason, the frequency of the gas flow in the flow sensor unit 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, in such a conventional gas meter, since the mesh member is separately installed in the retaining chamber, the number of parts increases and the number of mounting steps increases, thereby increasing the cost. Will also be higher.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a gas meter in which the number of parts and the number of mounting steps are reduced without lowering the gas flow 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. A casing, a gas inlet provided in the casing, a gas retention chamber provided in communication with the gas inlet in the casing, and a flow rate provided downstream of the gas retention chamber in the casing. A sensor portion, a gas outlet provided in the casing further downstream of the flow sensor portion, and a gas outlet provided in the casing downstream of the gas inlet and upstream of the gas retaining chamber, and the gas retaining chamber and An opening for communicating with the upstream space, a shut-off valve for closing the valve when an abnormality occurs and shutting off the communication through the opening, and the opening of the shut-off valve The point is that a porous member provided integrally with the mouth and covering the opening is provided.

<Operation> In this gas meter, the gas flowing into the casing from the gas inlet passes through the opening of the shut-off valve and the porous member integrally provided in the opening, and flows through the gas retention chamber to the flow rate sensor. After the flow rate is measured, the gas flows out of the casing through the gas outlet.

<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. 3, 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 main body 4 is provided with a gas inlet 6, and the gas flowing from the gas inlet 6 flows into the gas retaining chamber 10 through the gas passage 8. The retention chamber 10 is a space having a predetermined volume,
When the gas pressure of the inflowing gas fluctuates, there is an effect of absorbing the fluctuation.

The fluidic flow sensor 20 is located downstream of the retention chamber 10.
Is provided. A nozzle section 22 having a small passage cross-sectional area is provided at an upstream portion of the flow sensor section 20, and gas is ejected to the flow sensor section 20 via the nozzle section 22.

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 flow sensor unit 20 has the following structure.

The sensor section 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. Columns 30a and 30b are provided on both sides of the target 28.
Side surfaces of the a 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 portion 22 is deflected and flows along the side walls 32a and 32b of the cylinders 30a and 30b alternately at a constant flow rate with the assistance of the target 28, so-called gas flow. Vibration occurs. Here, assuming that the gas flow is first deflected to the left in the drawing, most of the gas flow passes through the gap 38a as shown by the arrow A in the drawing, and the gas meter 2
Spills out. 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. 3). 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 introduction paths.
Then, the piezoelectric film provided at the center thereof is formed with the small holes 54a and 54b.
Is displaced by the difference of the gas pressures. Such a displacement is converted into an electric signal, and the flow rate of the gas flowing through the gas meter 2 is measured based on the frequency.

The above-described fluid flow rate range of the fluidic flow sensor unit 20 is a large flow rate area that is equal to or more than a certain flow rate. Therefore, a thermal flow rate sensor (hereinafter, abbreviated as a thermal sensor) 70 for a small flow rate area is supplementarily used. However, as shown in FIG. 3, it is fitted and fixed in a recess 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. And, under the heating of the heater, the first,
The temperature difference generated in the second sensor is converted into an electric signal, and the gas flow rate is measured. Note that the upper surface of the thermal sensor 70 is at the same height as the bottom surfaces of the nozzle section 22 and the flow sensor section 20, so that the thermal sensor 70 does not disturb the gas flow.

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, In this case, 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 casing body 4
Alternatively, the gas flow rate is displayed on a flow rate display unit (not shown) attached to the outside of the lid 5.

A shut-off valve (solenoid valve) 80 as shown in FIGS. 1 and 2 is provided downstream of the gas passage 8 and upstream of the retention chamber 10. This is a safety device that shuts off the flow of gas when an abnormality occurs, such as when a large amount of gas flows per unit time or when gas continues to flow without interruption for a long period of time.

A flat plate 84 is fixed to one end of the valve casing 82, and an annular seat plate 88 is connected to the flat plate 84 via three legs 86.
Has been fixed. A circular opening 90 is formed at the center of the seat plate 88, and an annular projecting valve seat 92 is formed at an inner peripheral portion thereof. Also, the seat of the seat plate 88
A short cylindrical member 110 is fixed to the plate surface on the opposite side to 92, and this cylindrical member 110 is fixed to the stagnant chamber entrance 114 of the casing body 4 shown in FIG. It is fitted airtight.

A valve shaft 96 is provided movably in the axial direction through the flat plate 84, and a circular valve plate 98 is fixed to a tip of the valve shaft 96. Stem
A compression spring 100 is mounted between the projection 97 of the 96 and the flat plate 84 in a pre-compressed state, and the valve shaft 96 is urged to the left in the figure. As a result, as shown in FIG. 2, the valve plate 98 is normally opened away from the valve seat 92, and the gas flowing through the gas passage 8 (FIG. 3) flows between the legs 86, the valve plate 98 and the seat. It flows between the plate 88 and the stay chamber 10 (FIG. 3) through the opening 90 of the sheet plate 88.

As shown in FIG. 2, a solenoid 102 for driving a valve is provided in the valve casing 82, and a coil 107 is wound around a core 104 via a bobbin 106. Its core 10
4 is passed through a valve shaft 96, and an armature 108 is provided at the rear end of the valve shaft 96.
Has been fixed. Then, when the coil 107 is energized and the solenoid 102 is excited, the armature 108
4 side, and the valve shaft 96 moves to the right side in the figure.
The opening 90 close to the valve seat 92 is closed and the valve is closed, so that the above-mentioned gas flow is shut off. This valve closing operation
This is performed under the control of a microcomputer (not shown) when an abnormality occurs as described above. Note that the valve plate 98 is a rubber plate fixed to a metal plate, and the valve seat 92 is seated on the rubber plate.

On the inner wall surface of the cylindrical member 110, a mesh member 116 having an appropriate mesh interval is fixed as a porous member.
This mesh member 116 has a circular bottom 118 and cylindrical side portions.
It has a cylindrical shape with a bottom having 120 and is formed of a net made of metal or the like. The mesh member 116 functions to rectify the gas flow passing therethrough. However, if the mesh is too coarse, the rectifying effect is hardly obtained. On the other hand, if the mesh is too fine, the pressure loss of the gas when passing through the mesh is reduced. Becomes large and the rated value as a gas meter cannot be satisfied, so that an appropriate roughness is selected.

Further, if a flat mesh member is attached to the opening 90 of the sheet plate 88 having a small passage cross-sectional area, the gas pressure loss is large, and the ejection output to the flow sensor unit 20 is insufficient, so that the flow sensor unit 20 is not provided. Vibration of the gas flow at the air becomes difficult to occur. Therefore, the mesh member 116 has a bottom portion 118 and a side portion 120 as portions through which gas passes.

When the shut-off valve 80 is open, the gas from the gas passage 8 flows to the bottom 118 or the side 12 of the mesh member 116.
Since the air flow passes through 0, the rectifying action floats, and the gas flows out from the nozzle section 22 to the flow rate sensor section 20 through the retention chamber 10, so that the vibration of the gas flow in the flow rate sensor section 20 is stabilized, and the frequency of the gas flow is And the measurement accuracy is improved.

The shut-off valve 80 is usually built in this type of gas meter for ensuring safety, and the mesh member 116 is provided integrally with the seat plate 88 of the shut-off valve 80. Therefore, the assembly of the mesh member 110 is completed at the same time by the installation of the shut-off valve 80 to the gas meter 2, and the number of parts and the number of steps for mounting the gas meter 2 can be reduced.

FIG. 4 shows another embodiment. A trumpet-shaped passage 130 whose cross-sectional area increases toward the downstream side is provided in the seat plate 88 of the shut-off valve 80, and a planar mesh member 132 is attached to the downstream open end thereof. Other parts are the same as those of the previous embodiment shown in FIGS. 1 and 2, and the same reference numerals are used to indicate the corresponding relations.

In this embodiment, since the mesh member 132 through which the gas passes is a flat surface, a substantially uniform rectifying action is generated for the gas flow as compared with the previous embodiment. In addition, since the mesh member 132 exists in a portion of the passage area larger than the opening 90 of the sheet plate 88, the gas pressure loss is small.

The attachment of the mesh member to the shut-off valve 80 is not limited to the above-described embodiment, and various modes can be applied.

Further, the porous member is not limited to a mesh member in the form of a net, and various members such as a perforated plate, a rectifying grid, and a group of a plurality of tubes can be used.

Further, a porous member such as a mesh member may be further provided in 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, the flow of the gas is rectified by passing the gas through the porous member, and the porous member is provided integrally with a shut-off valve normally incorporated in the gas meter. Therefore, attaching the shut-off valve to the gas meter means that the porous member is assembled to the gas meter, and the number of parts and the number of installation steps are reduced.

[Brief description of the drawings]

FIG. 1 shows a gas meter according to an embodiment of the present invention.
FIG. 2 is a perspective view of a shutoff valve having a mesh member, and FIG. 2 is a sectional view thereof. FIG. 3 is a plan sectional view showing the entire gas meter. FIG. 4 is a plan view (partially sectional view) showing a main part of another embodiment. 2 Gas meter 4 Casing body 6 Gas inlet 10 Gas retention chamber 20 Fluidic flow sensor 80 Shutoff valve 88 Seat plate 90 Opening 116 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-4-50724 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01F 1/20 G01F 3/22

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 a gas outlet provided in the casing. An opening is provided downstream of the gas inlet and upstream of the gas retention chamber and communicates with the gas retention chamber and the upstream space. And a porous member integrally provided at the opening of the shut-off valve and covering the opening. That the gas meter.