JP2591173Y2 - Fluidic flow meter - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid flow meter for measuring a gas flow rate by detecting a change in an alternating pressure of a gas flowing through a fluid element.

[0002]

2. Description of the Related Art A typical prior art is disclosed, for example, in Japanese Patent Application No. 3-207015 filed by the present applicant. In this prior art, a narrow flow path having a sectional area of about 1/2 to 1/200 of a nozzle hole of a fluidic element is provided, and the flow velocity of gas flowing through the narrow flow path is detected to obtain a maximum flow rate of 1%. It is configured to measure a very small flow rate of about / 300 to 1/40000.

[0003]

In such prior art, if a narrow flow path for detecting a very small flow rate is provided in a flow path of a gas, the pressure loss at the time of measuring a large flow rate increases. The pressure loss at the maximum flow rate specified in the above greatly deviates from the allowable value. In particular, in order to detect the inner pipe leakage in the house specified by the inspection regulations of the Japan Gas Appliance Inspection Association, 3 liters It must have the ability to accurately meter minute flow rates, such as per hour, with pressure loss within tolerance. In a small gas meter, the maximum working flow rate is small, so it is possible to reduce the cross-sectional area of the flow path of the fluidic element and its nozzle hole. Although it is possible to detect a very small flow rate by the approaching flow velocity detector, in a large gas meter, the flow velocity is reduced due to the large flow passage cross-sectional area of the nozzle hole, and the minute flow rate cannot be detected by the flow velocity detector. There is.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fluidic flow meter capable of suppressing a pressure loss at the time of measuring a maximum use flow rate to an allowable value or less and detecting a minute flow rate with high accuracy without largely modifying a fluidic element. It is to provide.

[0005]

According to the present invention, there is provided a pressure detector for detecting a change in an alternating pressure of gas passing through a nozzle hole formed in a fluidic element, and a pressure detector for detecting a change in pressure of the gas at an upstream side in a gas flow direction. A rectifier for covering, a flow rate detector having a flow rate detector provided facing the nozzle hole, and a fluid flow meter for measuring a gas flow rate based on each output from the pressure detector and the flow rate detector; A first flow path in which the pressure detector faces the nozzle hole and an opening on the upstream side in the gas flow direction is closed by the rectifier, and a second flow path in which the flow velocity detector faces This is a fluidic flow meter characterized by partitioning into two.

[0006]

According to the present invention, a rectifier is provided to cover the opening of the nozzle hole of the fluidic element on the upstream side in the gas flow direction, and a partition wall is provided between the rectifier and the nozzle hole. With this partition wall, the nozzle hole is divided into a first flow path whose opening on the upstream side in the gas flow direction is closed by the rectifier, and a second flow path opening on the upstream side in the gas flow direction. Can be A pressure detector is provided at the nozzle hole outlet, and a flow velocity detector is provided in the second flow path. At the time of measuring the large flow rate, the gas flows into the first flow path and the second flow path in the nozzle hole, and the change in the alternating pressure is detected by the pressure detector to measure the gas flow rate. In addition, at the time of small flow rate measurement, since the viscosity of the gas becomes higher as the flow rate becomes smaller, the flow rate of the gas passing through the rectifier decreases, and the gas flow rate is guided to the second flow path and the gas flow rate is detected by the flow rate detector. , The gas flow is measured. In this way, the gas flow can be guided to the first or second flow path to reduce the pressure loss, and the gas flow rate flowing through the small flow path can be measured with high accuracy without complicating the configuration.

[0007]

FIG. 1 is a front view showing a fluid flow meter 1 according to an embodiment of the present invention, FIG. 2 is a rear view of the fluid flow meter 1 shown in FIG. 1, and FIG. FIG. 3 is a cross-sectional view taken along line III-III of FIG. The gas supplied to the inlet 4 of the casing 3 reaches the rectifying space 7 through the chamber 5 and the valve hole 6, passes through the nozzle hole 10 of the fluidic element 9 mounted in the measuring space 8, and forms the virtual line 1.
As shown by reference numerals 1 and 13, the Coanda effect causes vibration to the left and right, and the alternating pressure change causes two detection holes 14a,
After being detected by a piezoelectric film sensor 15 which is a pressure detector via 14b, it is discharged from an outlet 16 and supplied to a gas consuming device (not shown).

A first rectifier 17 made of, for example, a 30-mesh metal net is provided on the upstream side of the gas flow direction A of the nozzle hole 10, and further upstream of the first rectifier 17 in the flow direction A. Is provided with a second rectifier 18. The fluidic element 9 has a partition that divides the nozzle hole 10 into a first flow path 20 and a second flow path 21 over the opening 19 facing the flow direction A upstream of the nozzle hole 10 and the first rectifier 17. A wall 23 is provided. The head 25 of the hot-wire type flow rate sensor 24, which is a flow rate detector, is exposed on the back surface of the casing 3 so as to face the second flow path 21 formed in this manner. When measuring a large flow rate, the first flow path 20 and the second flow path 2
The gas flow rate flowing through the second flow path 21 is measured by the hot wire type flow rate sensor 24 when the small flow rate is measured.

FIG. 4 is an enlarged sectional view of the vicinity of the partition wall 23 of FIG. 3, FIG. 5 is an enlarged front view of the vicinity of the first rectifier 17, and FIG. 6 is a sectional view taken along line VI-VI of FIG. FIG. 7 is a perspective view showing an attached state of the partition wall 23 and the fluidic element 9. The partition wall 23 is selected to have a thickness of about Δt = 0.3 to 0.5 mm, and the shape of the distal end portion 26 facing the gas flow direction A upstream in order to minimize pressure loss is as follows: The second flow path 21 is formed in an arc shape as shown in FIG. 8 or in a wedge shape as shown in FIG. 9, and is spaced from the wall surface 27 of the casing 3 by a distance ΔL. As described above, it is covered by the first rectifier 17. Such first
The rectifier 17 is a kind of resistor, and since the viscosity of the gas increases as the flow rate decreases, the gas becomes more difficult to pass through the first rectifier 17 as the flow rate decreases, and the gas tends to flow through the second flow path 21. I do. Therefore, the present inventor sets the interval ΔL to ΔL = L, 2, 4, 6, as shown in Table 1.
The detection sensitivity of the hot-wire flow velocity sensor 24 when the interval is set to 10 mm and the interval ΔL = L is 1, and the detection sensitivity corresponding to the remaining intervals ΔL = 2, 4, 6, and 10 mm is the flow path pulse. Determined from the ratio of the numbers, `` good '' indicates that the instrumental characteristic with less change within the tolerance under the Measurement Law, and `` somewhat good '' if the instrumental characteristic is slightly larger even within the tolerance, The case where the tolerance is exceeded is indicated as "defective". In this experiment, the depth L of the nozzle hole 10 is 32 mm, and the width W is 4 mm. In this case, it has been confirmed that when the interval ΔL between the second flow paths 21 is about 0 to 6 mm, the instrumental difference is small.

[0010]

[Table 1]

As is apparent from such an experiment, there is little difference between instruments, and therefore, by providing such a second flow path 21, even if the flow rate is small, the flow rate can be accurately measured. It has been confirmed that.

As another embodiment of the present invention, as shown in FIG. 10, a first flow path component member 29 made of synthetic resin in which a partition wall 23 and a nozzle hole forming portion 28 are integrally formed.
May be fitted into a fluidic element portion formed by die-casting of aluminum or a fluidic element portion 30 formed by resin.

[0013]

As described above, according to the present invention, a partition wall is provided in the nozzle hole of the fluidic detection element to partition the first flow path and the second flow path. The gas flowing through the first flow path and the second flow path is detected by a pressure detector to obtain a gas flow rate, and when measuring a small flow rate, the gas flowing through the second flow path is detected by a flow rate detector to determine the gas flow rate. This makes it possible to detect with high accuracy a flow rate that can detect gas leakage, for example, a very small flow rate of about 3 liters / hour.

[Brief description of the drawings]

FIG. 1 is a front view showing a fluid flow meter 1 according to an embodiment of the present invention.

FIG. 2 is a rear view of the fluidic flow meter 1 shown in FIG.

FIG. 3 is a cross-sectional view taken along line III-III in FIG.

FIG. 4 is an enlarged sectional view of the vicinity of a partition wall 23 in FIG.

FIG. 5 is an enlarged front view showing the vicinity of a first rectifier 17;

FIG. 6 is an enlarged cross-sectional view taken along the line VI-VI of FIG. 5;

FIG. 7 is a perspective view showing a mounting state of the partition wall 23 and the fluidic element 9 in the embodiment shown in FIGS. 1 to 6;

FIG. 8 is an enlarged sectional view of the vicinity of a distal end portion 26 of the partition wall 23.

FIG. 9 is a front end part 2 of a partition wall 23 according to another embodiment of the present invention.
FIG. 6 is an enlarged sectional view near 6.

FIG. 10 is an exploded perspective view showing a first flow path constituting member 29 and a fluidic element portion 30 according to still another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fluidic flow meter 3 Casing 9 Fluidic element 10 Nozzle hole 15 Piezoelectric film sensor 17 1st rectifier 19 Opening 20 1st flow path 21 2nd flow path 23 Partition wall 24 Hot-wire flow velocity sensor

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor, Kazuichi Tomoda 4-73-1, Nishiiwata, Higashiosaka-shi, Osaka Inside Kansai Research Laboratory, Kinmon Works (72) Inventor Yoshihiko Saito 4, Nishiiwata, Higashiosaka-shi, Osaka No. 7-31, Kanmon Research Laboratory, Kansai Research Laboratories (58) Field surveyed (Int.Cl. ⁶ , DB name) G01F 1/20 G01F 1/00 G01F 1/68 G01F 7/00 G01F 15/12

Claims (1)

(57) [Scope of request for utility model registration] 1. A pressure detector for detecting an alternating pressure change of a gas passing through a nozzle hole formed in a fluidic element, a rectifier for covering the nozzle hole on an upstream side in a gas flow direction, A fluid flow meter having a flow rate detector provided to face and measuring a gas flow rate based on each output from the pressure detector and the flow rate detector, wherein a partition wall is provided from the nozzle hole to a rectifier, the nozzle The hole is divided into a first flow path in which the pressure detector faces and an opening on the upstream side in the gas flow direction is closed by the rectifier, and a second flow path in which the flow velocity detector faces. Fluidic flow meter.