JP2001289686A - Gas flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a gas flowmeter which is small, whose structure is simple and whose rangeability is wide in such a way that the hunting of a flapper valve is suppressed so as to eliminate the pulsation of a flow passage, that the durability of the flapper valve is increased and that the operation of the flapper valve is stabilized. SOLUTION: When a flow rate is at a set small flow rate or less, the flapper valve 18 comes into contact with a frame-shaped edge part 30. A gas flows into a bypass flow passage 17A from an entrance port 17a, and it flows to the downstream side of the flapper valve 18 in a main flow passage 16 from an exit port 17b. The small flow rate at this time is measured by a thermal flow sensor (not indicated in the figure) in the bypass flow passage 17A. When the flow rate is increased the flapper valve 18 is opened up to an angle B, The flapper valve 18 is situated on the downstream side of the exit port 17b, and the total flow rate is measured by an estimation-type gas flowmeter (not indicated in the figure) which communicates with the main flow passage 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gas flow meter suitable for a commercial gas meter.

[0002]

2. Description of the Related Art Commercial gas meters have a maximum flow rate of 30.
Several types of capacities from m ³ / h type to 120 m ³ / h type are used, all of which are membrane gas meters.

[0003] Current commercial membrane gas meters are very large due to their construction, and their miniaturization has been a concern of gas businesses for many years.

[0004] Regardless of whether it is for business use or for home use, the membrane gas meter has a safety (security) function such as a shut-off function such as an over-flow shut-off function and an alarm function for measuring a small flow rate such as a gas leak and issuing an alarm. For commercial use, it had a rangeability of 1: 24000 from a micro flow rate of 5 liters / h to a flow rate twice as large as the maximum use flow rate.

[0005] In recent years, small electronic flow meters such as an ultrasonic type, a vortex type, a fluidic type, and a hot wire type have been developed. It is not comparable to the rangeability of a membrane gas meter, and a so-called multi-stage flow meter, which is a parent-child flow meter, has been proposed.

For example, a fluidic oscillating element for measuring a medium to large flow rate and another fluidic element for measuring a small flow rate range are used. Japanese Patent Application Laid-Open No. Sho 61-223517 proposes a parent-child type flow meter which is used by switching over.

[0007]

In the parent-child flow meter disclosed in Japanese Patent Application Laid-Open No. 61-223517, it is difficult to measure a flow rate range 1000 times even if two fluidic elements are provided. In addition, when a switching valve is used, the movable portion of the switching valve itself causes a valve leak, and there is a defect in durability when trying to measure a minute flow rate of about 5 liter / h.

Further, since the operating force of the switching valve is determined by the area of the pressure receiving diaphragm, it is necessary to enlarge the shape of the diaphragm in order to operate with a small pressure loss as in a gas meter, and it is difficult to reduce the size of the diaphragm. In addition, since a pressure introduction path for guiding the differential pressure to both surfaces of the diaphragm, a bearing, a valve seat, and the like are required, there is a disadvantage that the mechanism is complicated and expensive.

The inventors of the present invention have two inventions relating to a gas flow meter suitable for a commercial gas meter which can cope with wide rangeability and can be formed in a small size and at a low cost by using an inferential gas flow meter. 11-183112
No. proposed. The present invention has not been disclosed.

In the first invention, a flapper valve is arranged in a flow passage so as to be opened and closed by a dynamic pressure of a gas and a valve differential pressure, and the flapper valve is closed at a small set flow rate of the gas. In the flow path, a bypass flow path that allows a small amount of gas to flow when the flapper valve is closed is provided.
The bypass flow path is a gas flow meter provided with a thermal flow sensor.

In this gas flow meter, the flapper valve closes and the gas flows through the bypass flow path when the gas is set at a small flow rate. The flow rate flowing through the bypass flow path is measured by a thermal flow sensor. If the gas flows more than the set small flow rate, the flapper valve opens due to the dynamic pressure of the gas and the valve differential pressure, and the gas flows from the flow path of the flapper valve section and the bypass flow path.

According to a second aspect of the present invention, a flapper valve is disposed in a flow passage so as to be opened and closed by a dynamic pressure of a gas and a valve differential pressure, and the flapper valve is closed at a predetermined small flow rate of the gas. In the flow path, a bypass flow path that allows a small amount of gas to flow when the flapper valve is closed is provided.
The bypass flow path includes a thermal flow sensor, and further includes a flow path on which the flapper valve is disposed and a flow path on the downstream side where the gas of the bypass flow path merges or a flow path on which a flapper valve is disposed. It is a gas flow meter in which a guess-type gas flow meter is arranged in an upstream flow path for supplying gas to a section and a bypass flow path section.

In this gas flow meter, gas flows as in the first invention. Then, at the time of the set small flow rate, it is measured by the heat flow sensor, and when a gas having a larger flow rate than the set small flow rate flows and the flapper valve is opened, the flow rate flowing from the section and the bypass flow path is determined by an estimating gas flow meter. Measured.

Specific examples of the gas flow meters according to the first and second inventions will be described below with reference to FIGS. 4, 5 and 6 presented in Japanese Patent Application No. 11-183112.

FIG. 4 is a diagram showing the configuration of the gas flow meter.
An estimating gas flow meter 3 is provided downstream thereof.

FIGS. 5 and 6 show the details of the flow path area variable mechanism 2.

The flow path forming body 4 forming the flow path area variable mechanism 2 has a cross section in a direction perpendicular to the flow direction (FIG. 6).
, One side wall 5, the other side wall 6, and the upper wall 7
And a lower wall 8, and has a channel 9 inside. The other side wall 6 is formed in a U-shape in cross section, and the flow path 9 is formed in a rectangular shape having a vertically long cross section in a direction perpendicular to the flow direction. Furthermore, the inlet 1 is located at the center of the upstream side wall 10.
0a is formed, and a main flow path 1 described later is formed at the inflow port 10a.
6 and the flow path 12 for supplying gas to the bypass flow path 17 are connected. An outlet 13 a is formed at the center of the downstream side wall 13, and an outlet 13 to which gas in a main channel 16 and a bypass channel 17, which will be described later, merge and flows out is connected to the outlet 13 a.

The flow passage 9 is divided into a large flow passage portion and a small flow passage portion by a partition plate 15, the large flow passage portion being the main passage 16 and the small flow passage portion being a bypass passage 17.
And The cross-sectional area of the flow path of these flow sections is, for example, 3
In the case of the 0-fold passage, the main passage 16 is set to 75 mm × 40 mm, and the bypass passage 17 is set to 2.5 mm × 40 mm.
In the case of a 10-fold flow path, the main flow path 16 is 40 mm × 2
5 mm, and the bypass channel 17 is 4 mm × 25 mm.

The main flow path 16 is provided with a flapper valve 18 made of a plate material, for example, a lightweight thin plate such as a foam material, so as to open and close by the dynamic pressure of flowing gas and the valve differential pressure. The flapper valve 18 is formed of a square plate having a size that can be substantially fitted into the main flow path 16, and a horizontal support shaft 19 is fixed at a position eccentric upward from a vertical center thereof,
Both ends of the support shaft 19 are rotatably fitted to the side walls 5 and 6 so that the flapper valve 18 swings about the support shaft 19.

Further, the flapper valve 18 has its spindle 1
In a state in which the lower part of the flapper 9 is located slightly downstream of the support shaft 19 and the flow path 9, the flapper valve 18
The upper end of the flapper valve 18 is provided so as to abut against a stopper 20 fixed to the upper wall 7. When the flow rate of the gas is 0 to a set small flow rate, the flapper valve 18 has its own weight and abuts against the stopper 20. As shown by the solid line in FIG. 5, the closed state is maintained at the predetermined inclination angle θ, and when the flow rate is equal to or larger than the set small flow rate, the flapper valve 18 is moved by the dashed line in FIG. They are pushed open as shown by.

The size of the flapper valve 18 is as follows.
In the case of the 30-fold passage, it is set to 72.5 mm × 39.6 mm, and in the case of the 10-fold passage, it is set to 36 mm × 24.6 mm, and the flapper valve 18 is provided between both side ends of the flapper valve 18 and both side walls 5, 6. A gap d that can be opened and closed is formed.

A thermal flow sensor 21 is provided in the bypass passage 17. In the example of the figure, it is provided at the central portion on the lower wall 8 side. The thermal type flow sensor 21 has, for example, a fluid temperature detecting section disposed upstream and downstream of a heating section on a surface of a silicon chip where a flow is applied, and detects fluid temperature on both sides of the heating section according to the flow rate. Since the electrical resistance of the part changes, this change is detected as an electrical signal, amplified,
A / D conversion is performed to obtain the flow rate by the microcomputer. Such a thermal flow sensor is disclosed in, for example, Japanese Patent No. 25
No. 95306. This thermal type flow sensor 21 can measure a small flow rate, and can arrange the small sensor part in the flow path to simplify the flow path constituent part. Further, the flow length of the measurement part is several mm. Has good features.

The estimating gas flow meter 3 is, for example, a flow meter of an ultrasonic type, a vortex type, a fluidic type, a hot wire type or the like, and is also called an electronic type flow meter. With this estimation type gas flow meter, a flow rate larger than the flow rate measured by the thermal flow sensor 21 is measured.

As described above, for example, in the 10-fold flow path as described above, the bypass flow path 17 is
When the flow path cross-sectional area is 100 mm ² and the flow rate of the gas is 0 to 200 l / h, the support shaft 19 is set so that the flapper valve 18 does not open due to the dynamic pressure of the gas and the valve differential pressure. , The weight of the flapper valve 18, and the position of the stopper 20 (the inclination angle θ of the flapper valve 18).

As a result, the flapper valve 18 is kept closed until the gas flow rate reaches 0 to 200 l / h.
The gas flows through the bypass channel 17. The flow rate at 200 liters / h is 0.055 m / s on the upstream side of the flapper valve 18 and 0.55 m / s on the bypass passage 17.
/ S, 0.055 m / s downstream of the flapper valve 18
Changes to

Then, a small flow rate of gas flowing only in the bypass passage 17 is measured by a thermal flow sensor 21 arranged in the bypass passage 17.

When the flow rate of the gas becomes 200 liters / h or more, the flapper valve 18 is pushed open by the dynamic pressure of the gas and the valve differential pressure, and the opening increases in proportion to the increase in the flow rate of the gas. Flows through the bypass passage 17 and the main passage 16. The flow rate of the gas is measured by an estimating gas flow meter 3 disposed downstream of the variable channel area mechanism 2.

The gap d on both sides of the flapper valve 18
20% of the gas leaks from the
The gap d is determined as follows, and the leakage amount is corrected and measured as necessary.

In the above specific example, the support shaft 19
Is provided in the middle of the flapper valve 18, but in FIG.
A support shaft 19 may be provided at the upper end of the flapper valve 18 to open and close the flapper valve 18 in a cantilever structure. In this case, the flapper valve 1 is attached to the partition plate 15.
8 is provided with a stopper for stopping at a predetermined angle θ. That is, the position of the fulcrum of the flapper valve 18 may be inside or outside the main flow path.

The flapper valve 18 has a structure in which the main flow path 16 is closed by its own weight at a predetermined small flow rate, and is opened when a gas dynamic pressure and a valve differential pressure are applied at a predetermined small flow rate or more. It is not always necessary that the closed state is the inclined state as in the specific example, and the fully closed state may be the vertical state.

Furthermore, the degree of opening of the flapper valve 18 with respect to the flow rate does not need to be a particular problem as long as it is within the allowable range of the pressure loss of the flow meter.

Further, in the above specific example, the estimating gas flow meter 3 is connected to the passage area variable mechanism 2, that is, the bypass passage 1.
7 and in the flow path on the downstream side of the flapper valve 18,
It may be arranged in the flow path area variable mechanism 2, that is, in the flow path on the upstream side of the bypass flow path 17 and the flapper valve 18.

Further, in the above specific example, the main flow passage 16 and the bypass flow passage 17 are divided by the partition plate 15, but without providing the partition plate 15, the flapper valve 18 is closed when the flapper valve 18 is fully closed. A bypass passage 17 may be formed between the lower end of the lower wall 18 and the inner surface of the lower wall 8, and the bypass passage may be provided on the side of the flapper valve 18 or may be located at a position completely separated from the flapper valve, for example. Perimeter wall 5
8 may be formed.

After proposing the above-mentioned gas flow meter in Japanese Patent Application No. 11-183112, the present inventor conducted intensive research to commercialize a commercial gas meter using the gas flow meter. Notices that when the valve is opened from the closed state, the differential pressure applied to the valve drops sharply, the valve tries to close again, causing unstable operation and hunting of the valve. Was. And
Such a repetition of opening and closing the valve near the open flow rate newly causes a problem that a pulsation is generated in the gas pipe.

Therefore, the present invention relates to a gas flow meter which can be formed in a small size at a low cost with wide rangeability, and which can stably open and close the flapper valve and can solve the above-mentioned problems, especially a commercial gas meter. It is an object of the present invention to provide a gas flow meter that is suitable for:

[0036]

In order to achieve the above object, according to the present invention, a flapper valve is disposed in a flow passage so as to be opened and closed by dynamic pressure of gas and a valve differential pressure, and the flapper valve is provided. The valve is closed when the set flow rate of the gas is small, and a bypass flow path is provided in the flow path for allowing a small amount of gas to flow when the flapper valve is in a closed state. Further comprising a permanent magnet interlocking with the flapper valve and a fixed permanent magnet disposed in close proximity to the permanent magnet, and assisting the closing force of the flapper valve when the valve is closed by the magnetic force of both permanent magnets. It is a gas flow meter characterized by the following.

In the present invention, when the flow rate is smaller than the set small flow rate, the flapper valve closes and gas flows through the bypass flow path. The flow rate flowing through the bypass flow path is measured by a small flow rate meter. If gas flows more than the set small flow rate,
The dynamic pressure and valve differential pressure of the gas open the flapper valve against valve closing force such as magnetic force, and the gas flows through the flow path of the flapper valve portion and the bypass flow path. The magnetic force suppresses hunting of the flapper valve.

According to a second aspect of the present invention, a flapper valve is disposed in a flow passage so as to be opened and closed by a dynamic pressure of a gas and a valve differential pressure, and the flapper valve is closed at a predetermined small flow rate of the gas. In the flow path, a bypass flow path that allows a small amount of gas to flow when the flapper valve is closed is provided.
The bypass flow path is provided with a small flow meter, and the flow path on which the flapper valve is disposed and the downstream flow path where the gas of the bypass flow path merges or the flow path on which the flapper valve is disposed Arrange a gas flow meter on the upstream side to supply gas to the section and the bypass flow path section, furthermore, a permanent magnet interlocked with the flapper valve, and a fixed permanent magnet disposed close to the permanent magnet And the magnetic force of both permanent magnets assists the closing force of the flapper valve when the valve is closed.

In the present invention, the gas flows in the same manner as in the first aspect of the present invention. When the flow rate is equal to or less than the set small flow rate, the gas is measured by the small flow rate meter, and when a large flow rate gas exceeding the set small flow rate flows and the flapper valve is opened, the gas flowing through the flow path of the flapper valve portion and the bypass flow path. Is measured by an estimating gas flow meter. The magnetic force suppresses hunting of the flapper valve.

According to a third aspect of the present invention, in the gas flow meter according to the first or second aspect, a speed-increasing gear mechanism is provided between the flapper valve and a permanent magnet interlocking with the flapper valve, and the flapper is connected via the gear mechanism. A valve and a permanent magnet are connected.

According to the present invention, when the flapper valve is opened, the permanent magnet is rotated by the flapper valve via the speed increasing gear mechanism. The magnetic force of the permanent magnet suppresses hunting of the flapper valve.

According to a fourth aspect of the present invention, a flapper valve is disposed in the flow passage so as to be opened and closed by the dynamic pressure of the gas and the differential pressure of the gas, and the flapper valve is closed at a set small flow rate of the gas. In the path, a bypass flow path that bypasses the flapper valve when the flapper valve is closed is provided with a small flow rate of gas, and the bypass flow path is provided with a small flow rate meter, and a set small flow rate of gas is provided. When the flapper valve is opened with a flow rate exceeding the above, the relative position between the outlet port of the bypass flow path and the flapper valve is determined so that the flapper valve is located downstream of the outlet port of the bypass flow path. It is a gas flow meter.

In the present invention, when the flow rate is equal to or less than the set flow rate, the flapper valve closes and the gas flows through the bypass flow path and bypasses the flapper valve. The flow rate flowing through the bypass flow path is measured by a small flow rate meter. When more gas flows than the set small flow rate, the dynamic pressure of the gas and the valve differential pressure open the flapper valve, and the flapper valve is located downstream of the outlet port of the bypass flow path. Then, the gas flowing through the bypass flow path joins the flow path of the flapper valve portion, the entire flow rate flows from the lower portion of the flapper valve, and the valve maintains an opening degree equal to or more than a certain value.

According to a fifth aspect of the present invention, a flapper valve is disposed in the flow passage so as to be opened and closed by the dynamic pressure of the gas and the differential pressure of the gas, and the flapper valve is closed at a small set flow rate of the gas. In the path, a bypass flow path that bypasses the flapper valve when the flapper valve is closed is provided with a small amount of gas, and the bypass flow path is provided with a small flow rate meter and the flapper valve is disposed. Estimated gas flow rate in the downstream flow path where the gas in the flow path part and the bypass flow path part merge or in the flow path part where the flapper valve is arranged and the upstream flow path that supplies gas to the bypass flow path part When the flapper valve is opened with a flow rate exceeding the set small flow rate of the gas, the outlet port of the bypass flow path and the flapper are positioned so that the flapper valve is located downstream of the outlet port of the bypass flow path. A gas flow meter, characterized in that defining the relative position.

In the present invention, the gas flows in the same manner as in the fourth aspect of the present invention. When the flow rate is smaller than the set small flow rate, the flow rate is measured by the small flow rate flow meter. When a large flow rate gas exceeding the set small flow rate flows and the flapper valve opens, the flapper valve is located downstream of the outlet port of the bypass flow path, and the gas flowing through the bypass flow path joins the flow path of the flapper valve section. Then, the entire flow rate flows from the lower part of the flapper valve, and the valve maintains an opening degree equal to or higher than a certain value. At this time, the total flow rate is measured by the estimation gas flow meter.

The invention of claim 6 is based on claims 1, 2, 3, 4
Alternatively, in the gas flow meter according to the fifth aspect, the small flow rate meter provided in the bypass flow path is a thermal flow sensor.

The present invention relates to claims 1, 2, 3, 4 or 5.
In addition to the above operation of the gas flow meter, the thermal type flow sensor measures the flow rate in the bypass flow path when the flow rate is equal to or smaller than the set small flow rate.

The invention of claim 7 is based on claims 1, 2,
In the gas flow meter of 3, 4, or 5, the small flow meter provided in the bypass flow path is an ultrasonic flow meter.

The present invention relates to claims 1, 2, 3, 4 or 5.
In addition to the above operation of the gas flow meter, the ultrasonic flow meter measures the flow rate in the bypass flow path when the flow rate is equal to or smaller than the set small flow rate.

[0050]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described with reference to examples.

[Embodiment 1] This embodiment is characterized in that
This corresponds to FIGS. 3 and 6, in which a control mechanism by magnetic force is added to the flapper valve 18 having the configuration shown and described in FIGS. 4, 5 and 6. A main flow path 16 as a large flow passage, a bypass flow path 17 as a small flow passage portion, a flapper valve 18 swingable about a support shaft 19, a thermal flow sensor 21 as a small flow flow meter, an estimating gas The basic configuration of the gas flow meter including the flow meter 3 is shown in FIG.
This is the same as the specific examples in FIGS.

In FIGS. 1A and 1B, a support shaft 19 of the flapper valve 18 is rotatably supported by ball bearings 22 and 23. In addition, ball bearing 2
The flow path walls supporting 2 and 23 are omitted and not shown. A large gear 24 having 60 teeth is attached to one end of the support shaft 19, and a small gear 25 having 12 teeth meshes with the large gear 24. A 16-pole permanent magnet 26 whose outer periphery is magnetized is attached to the small gear 25. Reference numeral 27 denotes a supporting shaft for rotatably holding the small gear 25. A fixed permanent magnet 28 having 16 poles is semi-fixed to a wall 29 concentrically with the supporting shaft.

The large gear 24 and the small gear 25 are the flapper valve 1
8 constitutes a speed increasing gear mechanism for interlocking the permanent magnet 26,
The speed increase ratio is set to 60/12, that is, five times.

Since the permanent magnets 26 and 28 are magnetized to 16 poles, when the permanent magnet 26 rotates in conjunction with the opening operation of the flapper valve 18, the different poles of the two magnets attract each other,
Comrades repel each other. Therefore, the control torque acting on the flapper valve by the magnetic force periodically changes every time the permanent magnet 26 rotates 45 degrees. That is, 4 of the permanent magnet 26
The control torque changes every 5 degrees, in other words, every 9 degrees of the flapper valve 18.

The control torque, that is, the magnetic force, can be adjusted by changing the angular position of the permanent magnet 26 mounted in a semi-fixed manner by the magnetic force when the valve is closed. The control torque by the magnetic force is a control torque weaker than the valve closing torque (return force) by the weight of the flapper valve 18. In this way, even when the flow rate becomes zero in the fully opened state, the flapper valve is closed by the return force due to its own weight.

The return force due to the own weight of the valve itself applied to the flapper valve is represented by the return force = W based on the own weight W of the valve, the distance L between the center of gravity of the valve and the support shaft 19, and the inclination (opening) θ of the valve.・ L ・ s
in θ, increases with the opening, and the influence of the control torque due to the magnetic force decreases.

When the flapper valve opens by overcoming the control torque by the magnetic force due to the differential pressure of a certain value or more, the flapper valve opens at a stretch to the NS portion of the magnetic pole where the next attraction force (magnetic force) is generated, and the flapper valve is opened by the magnetic force and dynamic pressure. It is fixed and overcomes the return force in the closing direction due to the weight of the flapper valve.

When the valve is closed, the closing force may be improved by slightly shifting the relative phase of the permanent magnet.

As described above, in this embodiment, the flapper valve is closed when the flow rate is smaller than the set small flow rate, and the flow rate is measured by the thermal flow sensor 21 in the bypass flow path.

When the flow rate increases, the pressure difference between the upstream side and the downstream side of the flapper valve increases, and the valve opening force becomes larger than the return force due to its own weight or the control torque due to the magnetic force, the flapper valve opens. When the valve is opened, it passes through the repulsion position by magnetic force and opens to the next suction position, where a force such as dynamic pressure is applied to stabilize.

As the flow rate further increases, the opening increases stepwise. When the flow rate decreases, the return force due to the valve's own weight overcomes the holding force due to the magnetic force, and the valve is closed.

Instead of arranging the fixed permanent magnet 28 concentrically with the movable permanent magnet 26, a fixed permanent magnet is provided as indicated by reference numeral 28 ′ which is arranged in the radial direction of the permanent magnet 26. Is also good. Note that the first embodiment
Attach packing to both sides of the flapper valve 18,
Leakage from gaps on both sides of the flapper valve 18 may be eliminated.

[Embodiment 2] This embodiment corresponds to claims 4, 5 and 6.

In the second embodiment shown in FIGS. 2A and 2B, a swingable flapper valve 18 is supported on a main shaft 16 by a support shaft 19, and the return force by its own weight causes the valve to close as shown in FIG. In state. As shown in the figure, when the flapper valve 18 is closed and the flow rate is smaller than the set small flow rate, the gas flows into the bypass passage 17A.
From the inlet port 17a, bypasses the flapper valve 18 through the bypass flow path 17A, and returns to the main flow path 16 downstream of the flapper valve 18 from the outlet port 17b.

At this time, the flow rate of the bypass passage 17A is
The measurement is performed by a thermal flow sensor (not shown) provided in the bypass passage 17A.

When the flow rate exceeds the set small flow rate, the differential pressure between the upstream side and the downstream side of the flapper valve 18 opens the flapper valve against the closing force (return force) due to the valve's own weight. When the flapper valve 18 is opened to the angle indicated by the symbol B in FIG. 3A, the flapper valve 18 is located downstream of the outlet port 17b, so that all the flow flows from the lower part of the valve, and the flapper valve has a certain degree of opening. Holds, no hunting occurs. Flapper valve 1
The total flow rate when the valve 8 is opened is measured by an estimating gas flow meter (not shown) communicating with the main flow path 16.

The frame-like edge indicated by reference numeral 30 acts to stop the flow from around the flapper valve 18 when the flapper valve 18 is closed. That is, in the closed state, the flapper valve 18 comes into contact with the frame-like edge portion 30 to stop the flow, and allows all the gas to flow into the bypass passage 17A.

At a flow rate where the flapper valve 18 has a constant opening, for example, a large opening exceeding the angle C in FIG. 2A, it is better to reduce the flow resistance by the flapper valve 18. At a valve opening degree of C or more, a part of the side wall can be eliminated so that gas flows from the valve side surface.

[Embodiment 3] This embodiment corresponds to claim 7. Embodiment 3 of FIGS. 3A and 3B is similar to that of FIG.
As compared with the second embodiment of (b), a part of the flow path shape of the bypass flow path 17A and the configuration of the small flow rate meter are different, and the other main structures are the same. The description of the parts having the same structure is omitted.

In the third embodiment, a portion having a rectangular channel cross section having a height H and a width W is provided in a part of the bypass channel 17A, and is provided upstream and downstream of the channel having the rectangular cross section. The ultrasonic transducers 21a and 21b are arranged to face each other. The ultrasonic transducers 21a and 21b constitute an ultrasonic flow meter 21A together with the flow path portion having the rectangular cross section, and the ultrasonic transducer 2
The ultrasonic pulse emitted from 1a is the downstream transducer 21b.
Based on the forward propagation time of the ultrasonic wave until the ultrasonic wave reaches the downstream side vibrator 21b and the backward propagation time of the ultrasonic pulse emitted from the downstream vibrator 21b toward the upstream vibrator 21a.・ Calculate the flow rate. That is, the ultrasonic flowmeter 21A works as a small flowmeter instead of the thermal flow sensor 21 of the second embodiment.

[0071]

Since the gas flow meter of the present invention is configured as described above, the flapper valve is closed at the time of a small flow rate, and the gas can be measured with high accuracy by the small flow rate meter in the bypass flow path. Therefore, if the flapper valve is opened at the time of a large flow rate and the measurement is performed by the estimation gas flow meter, a wide rangeability can be accommodated. Further, hunting of the flapper valve can be suppressed, pulsation of the flow rate does not occur, and the durability of the valve is improved.

Further, since a diaphragm type switching valve is not required, the size and size can be reduced, which contributes to downsizing of the flow meter.

According to the first, second and third aspects of the present invention, the valve closing force is assisted by the magnetic force, so that not only the valve closing force is stabilized, but also the mass of the flapper valve can be reduced and the valve opening flow rate can be reduced. Can be

Since the flow path area of the valve section can be enlarged,
Pressure loss is reduced. According to the third aspect of the present invention, since the magnetic force changes at each minute angle of the flapper valve, the control force by the magnetic force can be applied to the flapper valve finely. In other words, as described above, the opening of the flapper valve increases stepwise as the flow rate increases, but the step at that time is made smaller and the operation of the valve becomes smoother.

Further, according to the invention of claim 6, a small flow rate of 5 liter / h suitable for a business gas meter requiring a safety function.
A small and highly reliable gas flow meter having a wide rangeability from about 1 to about twice the maximum flow rate can be realized.

[Brief description of the drawings]

FIG. 1 is a view showing a main part of an embodiment of the present invention, wherein (a) is a partially longitudinal front view, and (b) is a side view.

FIG. 2 is a diagram showing a main part of another embodiment of the present invention.
FIG. 2 is a longitudinal side view, and FIG. 2B is a sectional view taken along line AA of FIG.

FIG. 3 is a diagram showing a main part of still another embodiment of the present invention;
(A) is a longitudinal side view, (b) is an AA sectional view of (a).

FIG. 4 is a configuration diagram of an undisclosed gas flow meter, in which a flapper valve and a bypass flow path section are substantially in section.

FIG. 5 is a longitudinal sectional side view of a main part of the gas flow meter of FIG. 4 which has not been disclosed yet.

6 is a sectional view taken along line AA of FIG.

[Explanation of symbols]

3 Inferred gas flow meter 9 Flow path 12 Upstream flow path 14 Downstream flow path 16 Flow path section (main flow path) in which flapper valve is arranged 17, 17A Bypass flow path 17a Inlet port 17b Outlet port 20 Stopper 21 Thermal flow sensor as small flow meter 21A Ultrasonic flow meter as small flow meter 24 Large gear 25 Small gear 26, 28, 28 'Permanent magnet

Claims (7)

[Claims] 1. A flapper valve is arranged in a flow passage so as to open and close by a dynamic pressure of a gas and a valve differential pressure, and the flapper valve is closed when a set small flow rate of a gas is obtained.
In the flow path, a bypass flow path for allowing a small amount of gas to flow when the flapper valve is closed is provided, and the bypass flow path section is provided with a small flow rate meter, and a permanent magnet interlocked with the flapper valve. A fixed permanent magnet disposed close to the permanent magnet, and the magnetic force of the two permanent magnets assists the closing force of the flapper valve when the valve is closed. 2. A flapper valve is arranged in the flow passage so as to be opened and closed by a dynamic pressure of a gas and a valve differential pressure, and the flapper valve is closed at a set small flow rate of the gas.
In the flow path, a bypass flow path for allowing a small amount of gas to flow when the flapper valve is closed is provided, and the bypass flow path is provided with a small flow rate meter, and further, a flow path in which the flapper valve is disposed. The estimating gas flow meter is arranged in the downstream flow path where the gas in the section and the bypass flow path merge or the flow path in which the flapper valve is disposed and the upstream flow path supplying the gas to the bypass flow path. Further, a permanent magnet interlocked with the flapper valve and a fixed permanent magnet disposed close to the permanent magnet are provided, and the magnetic force of both permanent magnets assists the closing force of the flapper valve when the valve is closed. And a gas flow meter. 3. A speed increasing gear mechanism is provided between a flapper valve and a permanent magnet interlocked with the flapper valve, and the flapper valve and the permanent magnet are connected via the gear mechanism. 2. The gas flow meter according to 2. 4. A flapper valve is arranged in the flow passage so as to be opened and closed by dynamic pressure of the gas and a valve differential pressure, and the flapper valve is closed at a small set flow rate of the gas. When the flapper valve is in a closed state, a bypass flow path that bypasses the flapper valve and allows a small amount of gas to flow is provided, and the bypass flow path is provided with a small flow rate meter, and the flapper has a flow rate exceeding a set small flow rate of the gas. The gas flow meter according to claim 1, wherein when the valve is opened, the relative position between the outlet port of the bypass flow path and the flapper valve is determined such that the flapper valve is located downstream of the outlet port of the bypass flow path. 5. A flapper valve is arranged in a flow passage so as to open and close by a dynamic pressure of a gas and a valve differential pressure, and the flapper valve is closed at a small set flow rate of the gas. When the flapper valve is closed, a bypass flow path is provided for bypassing the flapper valve and allowing a small amount of gas to flow therethrough.The bypass flow path section includes a small flow rate meter and a flow path section in which the flapper valve is disposed. Arrange the estimating gas flow meter in the downstream flow path where the gas in the bypass flow path merges with the flow path on the downstream side where the gas merges and the flow path on the upstream side that supplies the gas to the bypass flow path and the flow path where the flapper valve is arranged, When the flapper valve is opened at a flow rate exceeding the set small flow rate of gas, the relative position between the outlet port of the bypass flow path and the flapper valve is determined so that the flapper valve is located downstream of the outlet port of the bypass flow path. Gas flow meter, characterized in that the. 6. The small flow meter provided in the bypass flow path is a thermal flow sensor.
The gas flow meter according to 2, 3, 4 or 5. 7. The small flow meter provided in the bypass flow path is an ultrasonic flow meter.
The gas flow meter according to 3, 4, or 5.