JPH0545190A - Fluidic flowmeter - Google Patents

Abstract

PURPOSE:To widen a flow measurement range by providing a bypass valve, detecting a flow corresponding to the oscillation of fluid in the case of a large flow, passing a narrow passage between which the reduction of the area lies in the case of a small flow and detecting its flow velocity. CONSTITUTION:Fluid such as gas is allowed to flow in an inlet part 15 of a bypass valve 5 through a passage 11 and a valve opening 14 of a shut-off valve 13 from an inlet 2 and made flow in the inlet part 16 of a fluidic element 8 from a narrow passage 6 in the case of a small flow. When the flow increases, pressure difference between the inlet parts 15, 16 of the bypass valve 5 and the element 8 increases, the valve body of the bypass valve 5 is lifted and a large part of the fluid is allowed to flow in the element 8 through a strainer 17 from the element inlet part 16. When the flow is small, the whole quantity of the fluid is allowed to flow in the narrow passage 6, the velocity of the flow is detected by the use of a hot-wire flow meter 25 and the flow is obtained by multiplying the cross section of the passage. When the flow is large, the fluid is jetted from a jet nozzle 32 to a downstream passage 29 to cause an alternating pressure wave, an oscillation frequency is detected by a piezoelectric film sensor from pressure wave introduction parts 39a, 39b and converted into the flow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow meter utilizing the fluidic phenomenon, and more particularly to a flow meter capable of measuring a minute flow rate.

[0002]

2. Description of the Related Art A fluidic flow meter for measuring the flow rate of gas, which is installed in a general household or the like, is disclosed in, for example, Japanese Patent Laid-Open No. 63-63.
It is known from JP-A-313018 and JP-A-1-250725. A fluidic flow meter utilizing this fluidic phenomenon is provided with a jet nozzle on the inlet side of the flow channel, and when a fluid is jetted from this jet nozzle into the flow channel,
The jetted fluid flows, for example, along the right sidewall by the Coanda effect. A part of the fluid that has flowed to the right side wall becomes the return fluid, the fluid energy of this return fluid is added to the jet fluid, and the jet fluid flows along the left side wall. A part of the returned fluid becomes a return fluid, the fluid energy of the return fluid is applied to the jet fluid, and the jet fluid again flows along the right side wall. That is, an alternating pressure wave is generated by the vibration phenomenon of the fluid ejected from the ejection nozzle into the flow path. This alternating pressure wave is detected by a piezoelectric film sensor or the like, the flow rate is calculated from this frequency, and the flow rate of the fluid is detected.

The fluidic flowmeter has the advantage that it has no moving parts and can be used at a medium pressure (3 kg / cm ² G), but it has the drawback that if the gas flow rate is low, no vibration phenomenon occurs. It was That is, the general gas flow meter is 1/300 to 1/400 of the maximum flow rate.
It is necessary to measure over a wide range of 00,
The measurable range of a fluidic flow meter using a piezoelectric film sensor that detects alternating pressure waves is that the pressure loss at the maximum operating flow rate is specified.
It is about 0, and measurement in a minute flow rate range below that is impossible.

Therefore, the flow rate is detected by the piezoelectric film sensor in the large flow rate region using the fluidic phenomenon, and the flow velocity is detected by the flow velocity detector attached to the jet nozzle portion in the minute flow rate region. A fluidic flow meter has been developed which is configured to multiply the cross-sectional area to detect the flow rate. As a result, the measurable range was expanded from the maximum usable flow rate to about 1/200.

[0005]

However, the flow velocity detector in the minute flow rate range of the fluidic flow meter constructed as described above is for detecting the flow velocity of the fluid, and the flow rate is the flow velocity and the cross-sectional area of the flow channel. It is a product of Therefore, in order to measure a minute flow rate, a flow velocity detector is attached to the jet nozzle portion having a narrow cross-sectional area.

However, the cross-sectional area of the jet nozzle cannot be reduced to a certain extent or less because the pressure loss at the maximum use flow rate is regulated, and therefore 1/200 of the maximum use flow rate is required.
The following minute flow rates could not be measured.

According to the present invention, a narrow passage which is smaller than the conventional jet nozzle portion is provided, and a flow velocity detector is attached to the narrow passage. When the flow rate is high, the bypass valve provided in parallel with the narrow passage is opened to measure the flow rate using the fluidic phenomenon. If the cross-sectional area of the narrow channel is set to about 1/10 to 1/200 of the jet nozzle portion, a flow rate of about 1/300 to 1 / 40,000 of the maximum use flow rate can be measured.

[0008]

The present invention includes (a) first flow rate detecting means for detecting a flow rate corresponding to vibration of a fluid whose flow rate is to be measured by utilizing a fluidic phenomenon, and (b) the first flow rate detecting means. 1 is provided on the upstream side or the downstream side of the flow rate detecting means,
A second flow rate detecting means for detecting a flow rate corresponding to the flow velocity in the fluid passage provided with a throttle.
(C) A bypass valve which is provided in parallel with the second flow rate detecting means and which is closed by the first flow rate detecting means at least when the flow rate is smaller than a range measurable by the first flow rate detecting means and which is opened when the flow rate is higher than the range. It is a Dick flow meter.

Further, the present invention is characterized in that the second flow rate detecting means is provided in two or more passages in which a fluid throttle is interposed.

[0010]

According to the present invention, when measuring a large flow rate, the fluidic element is used to detect the flow rate by the first flow rate detecting means, and when measuring a small flow rate, it is smaller than the ejection nozzle portion of the fluidic element. A narrow passage is provided, the flow rate is detected by the second flow rate detecting means for detecting the flow rate from this flow rate, the flow rate detected by either the first or second flow rate detecting means is displayed, and the bypass is provided in parallel with the narrow passage. A valve is provided and the bypass valve is closed within a flow rate range smaller than the range in which the flow rate can be measured by the fluidic element. Here, if the cross-sectional area of the narrow passage is reduced as necessary, a minute flow rate can be measured. Further, when the ratio of the cross-sectional area of the jet nozzle of the fluidic element to the narrow passage is large, the second flow rate detecting means is also provided in the jet nozzle of the fluidic element. The flow rate measurement range can be further expanded by providing two or more narrow passages and providing a second flow rate detecting means in each of them.

[0011]

EXAMPLES The fluidic flowmeter according to the present invention will be described in more detail with reference to the following examples, but the invention is not limited thereto.

FIG. 1 is a sectional view showing the structure of an embodiment of a flow meter according to the present invention, FIG. 2 is a sectional view taken along the line AA of FIG. 1, and FIG.
Is a side view, and FIG. 4 is a sectional view taken along line BB in FIG. A fluid such as gas enters the flowmeter 1 from the inlet 2, flows through the passage 11 and the valve port 14 of the shutoff valve 13 to the inlet portion 15 of the bypass valve 5. When the gas flow rate is low, the gas flows through the narrow passage 6 to the inlet portion 16 of the fluidic element 8. When the gas flow rate is high, the pressure difference between the bypass valve inlet portion 15 and the fluidic element inlet portion 16 becomes large, and the valve body 21 of the bypass valve 5 is lifted by this pressure difference, and most of the gas is discharged from the valve opening 22. It comes to flow. Gas enters the fluidic element 8 through the strainer 17 through the fluidic element inlet portion 16 and exits the flow meter 1 through the outlet 3 and is supplied to the required location.

Table 1 shows an example of the gas flow rate and the opening / closing state of the bypass valve 5. In the case of a gas flow meter with a maximum usable flow rate of 7,000 l / h, the bypass valve is closed at a flow rate of 550 l / h or less, and the differential pressure ΔP1 between the bypass valve inlet portion 15 and the fluidic element inlet portion 16 at this time is 2.1 mmH. ₂ O
Is. When the flow rate increases to 580 l / h, the differential pressure ΔP1 exceeds 2.1 mmH ₂ O, the bypass valve 5 is lifted by the differential pressure, and the distance between the valve seat 23 and the valve body 21 of the bypass valve 5 is 0. Open 3 mm. When the gas flow rate further increases, this interval increases, and at the maximum use flow rate of 7000 l / h, the interval between the valve seat 23 of the bypass valve 5 and the valve body 21 becomes 10.5 mm which is almost fully opened (see the dotted line in FIG. 1). position). As a result, the bypass valve inlet 15 and the fluidic element inlet 1
The differential pressure ΔP1 of 6 is kept constant at 2.2 mmH ₂ O. The differential pressure ΔP of the entire flow meter 1 is only the differential pressure ΔP1 between the bypass valve inlet portion 15 and the fluidic element inlet portion 16 when the flow rate is small, but when the flow rate increases, the differential pressure ΔP1 of the fluidic element portion increases. Differential pressure is applied. This differential pressure Δ
P is about 2 with a flow meter with a maximum flow rate of 7,000 l / h in the measurement method.
It is specified below ₂ mmH ₂ O (air conversion).

[0014]

[Table 1]

First, a method of measuring gas when the gas flow rate is small will be described. Since the bypass valve 5 is closed as described above, the entire amount of gas flows through the narrow passage 6. In this narrow passage, a flow velocity detector as a second flow rate detecting means,
For example, a hot wire anemometer 25 is attached. As shown in FIG. 5 (2), the hot-wire anemometer has two heaters 26 at right angles to the gas flow direction (direction of arrows), and a temperature sensor 27 in front of and behind it. When the gas is not flowing,
Although the two heaters 26 have the same temperature as indicated by the dotted line in (1), when there is a gas flow, the front heater is cooled by the gas flow and the rear heater is warmed as indicated by the solid line in FIG. 5 (2). ,
A temperature difference appears between the two heaters. Since the relationship between the temperature difference and the flow velocity has been investigated in advance, the gas flow velocity can be known, and the gas flow rate can be calculated by multiplying this by the cross-sectional area of the narrow passage 6.

Next, a method of measuring gas when the gas flow rate is high will be described. The gas flows from only the narrow passage 6 or from the gap between the narrow passage 6 and the valve body 21 of the bypass valve 5 and the valve seat 23 to the fluidic element inlet portion 16 and further enters the fluidic element 8 through the strainer 17.

1 and 6 are diagrams showing the principle of a gas measuring method using a fluidic element. When the fluid is ejected from the nozzle 32 toward the downstream flow path 29, the ejected fluid flows along the inside of the left side wall 34a by the Coanda effect, as shown in FIG. 6 (1). Most of the fluid that has flowed to the left side wall 34a is directed to the discharge passage 38a, but part of it is returned fluid, which is directed to the return passage 37a. The fluid energy of the return fluid is applied to the jetted fluid, so that the jetted fluid flows along the inside of the right side wall 34b as shown in FIG. 6 (2), and this time as shown in FIG. 6 (3). A part of the fluid that has flowed to the side wall 34b becomes a return fluid, the fluid energy of this return fluid is applied to the ejected fluid, and the ejected fluid is again returned to the left side wall 34 as shown in FIG. 6 (4).
It comes to flow along the inside of a. That is, the alternating pressure wave is generated by the vibration phenomenon of the fluid ejected from the ejection nozzle 32 into the downstream flow passage 29.

Further, the alternating pressure wave generated in the fluidic element is guided to the piezoelectric film sensor unit 31 from the pressure wave introducing units 39a and 39b provided at the symmetrical positions in the vicinity of the outlet of the injection nozzle 32, and the piezoelectric film sensor. An alternating pressure wave is transmitted to both sides of the main body 36 (see FIG. 7). The first flow rate detecting means performs measurement by utilizing the fact that the frequency of this alternating pressure wave is proportional to the gas flow rate.

As described above, the gas flow rate measured by the two flow rate detecting means is controlled by the controller 43 and displayed as a flow rate on the display 44, as shown in FIG. That is, the temperature difference measured by the hot-wire anemometer 25, which is the second flow rate detecting means, is converted into a flow rate by the hot-wire anemometer auxiliary circuit 42, and the flow rate signal is sent to the controller 43. On the other hand, the alternating pressure wave measured by the fluidic element is detected by the piezoelectric film sensor body 36 as an alternating wave which is the first flow rate detecting means, converted into a flow rate corresponding to the alternating wave by the amplification waveform shaping circuit 41, and the flow rate signal. To the control unit 43. In the controller 43, the first and second two
The flow rate signal sent from the hot wire anemometer 25 is compared with the flow rate sent from one flow rate detecting means, and the flow rate signal sent from the hot wire anemometer 25 is slightly larger than 1/20 (350 l / h) of the maximum flow rate used (eg 370 l / h) (eg 360 l / h) In h), this is switched to the flow rate signal from the piezoelectric film sensor main body 36 which is the first flow rate detecting means. If the flow rate decreases, it is slightly less than 1/20 of the maximum flow rate (eg 340 l / h).
Then, the flow rate signal from the hot wire anemometer 25 which is the second flow rate detecting means is switched to. The flow rate switched by these is displayed on the display. In addition to this, the control unit 43 incorporates a circuit for closing the shutoff valve 13 in an emergency, a circuit for remotely displaying the flow rate displayed on the display unit 44 using a communication line, or the like.

The solid line in FIG. 10 shows the instrumental error characteristic of the fluidic flowmeter using only the fluidic element. The frame shown in the figure is the allowable device error range in the measurement method. In this case, it is not possible to measure at 1/20 or less of the maximum usable flow rate, but by switching the flow rate detecting means in the vicinity of this flow rate as described above, it is possible to accurately measure up to a flow rate below this as shown by the dotted line.

Although the example in which the bypass valve and the narrow passage are provided on the inlet side of the fluidic element has been described, they may be provided on the outlet side of the fluidic element. Further, these may be provided immediately after the inlet and before the shutoff valve. The placement position does not affect the performance of the flowmeter such as instrumental error characteristics.

In addition to the narrow passage 6, the flow velocity detector 25 is attached to the jet nozzle portion 32 of the fluidic element 8,
It is also possible to measure the flow rate by further reducing the ratio of the cross-sectional area of the narrow passage 6 to the cross-sectional area of the ejection nozzle portion 32 and switching to three stages. Alternatively, two or more narrow passages 6 may be provided, a flow velocity detector 25 may be attached to each of the narrow passages 6, and a switching valve may be provided at the inlet of the narrow passage 6 to further expand the flow rate measurement range. Examples of the bypass valve 5 include those shown in FIGS. 1 and 11. The guide rod 51 is attached to the bypass valve 5 by the pin 53, and the valve body 21 is configured to move up and down in the bypass valve 5 via the guide rod 51.

Another embodiment of the bypass valve 5 is shown in FIG.
There is something like the one shown in 2. The configuration is such that the cylindrical valve body 21 is fitted into the substantially rectangular hole 54. In this embodiment, when the bypass valve 5 is opened, the cylindrical valve body 21 is in a floating state.

A third embodiment of the bypass valve is shown in FIG.
There is something like 3. It is composed of a cantilever flapper valve type valve body 21 whose one end is fixed by a hinge pin 55. When the bypass valve 5 is opened, the valve body 21 stops at a stopper 56, and when the flow rate decreases, the valve body 21 immediately Descend,
It is designed to close the bypass valve.

[0025]

As described above, according to the present invention, the measurement range of the fluidic flow meter is set to 1/3 of the maximum usable flow rate.
It can be expanded from 00 to 1/40000.

[Brief description of drawings]

FIG. 1 is a sectional view showing the configuration of an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a side view of FIG.

4 is a sectional view taken along line BB of FIG.

FIG. 5 is a principle diagram of a hot wire anemometer used in the present invention.

FIG. 6 is a principle diagram of a fluidic element used in the present invention.

FIG. 7 is a principle diagram showing a flow rate display method according to an embodiment of the present invention.

FIG. 8 is a principle diagram showing a switching range of the flow rate signal of FIG.

FIG. 9 is a principle diagram showing a switching situation of the flow rate signal of FIG. 7.

FIG. 10 is a diagram showing a device difference characteristic according to an embodiment of the present invention.

FIG. 11 is a diagram showing an embodiment of a bypass valve of the present invention.

FIG. 12 is a view showing another embodiment of the bypass valve of the present invention.

FIG. 13 is a diagram showing a third embodiment of the bypass valve of the present invention.

[Explanation of symbols]

 1 Flowmeter 2 Inlet 3 Outlet 5 Bypass valve 6 Narrow passage 8 Fluidic element 13 Shutoff valve 21 Bypass valve body 23 Bypass valve valve seat 25 Hot wire anemometer 31 Piezoelectric membrane sensor 32 Jet nozzle 34 Sidewall 36 Piezoelectric membrane sensor body 37 Return passage 39 Pressure wave inlet

 ─────────────────────────────────────────────────── --- Continuation of front page (72) Inventor Gen Onoda, 2-3 Shimura, Itabashi-ku, Tokyo Inside Kinmon Mfg. Co., Ltd. (72) Inventor, Kaichi Tomoda 4--7, Nishiiwata, Higashiosaka-shi, Osaka No. 31 Incorporated company Kinmen Manufacturing Kansai Research Institute (72) Inventor Masanari Imasaki 4-7 31 Nishi-Iwata, Higashi-Osaka City, Osaka Prefecture Inside Kinmon Manufacturing Kansai Research Institute

Claims (2)

[Claims] 1. (a) a first flow rate detecting means for detecting a flow rate corresponding to vibration of a fluid whose flow rate is to be measured utilizing a fluidic phenomenon; and (b) an upstream side of the first flow rate detecting means, or A second flow rate detecting means provided on the downstream side and provided with a fluid passage in which a throttle intervenes, and detecting the flow rate corresponding to the flow velocity in the fluid passage; and (c) the second flow rate detecting means in parallel with the first flow rate detecting means. A fluidic flow meter, comprising: a bypass valve that is closed at a flow rate that is at least smaller than a measurable range by a flow rate detection means and that is opened at a flow rate higher than that. 2. The fluidic flow meter according to claim 1, wherein the second flow rate detecting means is provided in at least two passages in which a fluid throttle is interposed.