JPH0783708A - Whistle type flowmeter - Google Patents

Abstract

PURPOSE:To obtain a compact flowmeter, which can measure the flow rate of even a non-conductive fluid, with a simple whistle structure having no moving part by arranging a sound generation unit and means for collecting and filtering sounds and for detecting and computing frequency. CONSTITUTION:A sound generation unit 1 of a whistle structure is connected in the middle of gas pipelines 10a and 10b. A microphone 2 is mounted at a part to collect sounds generated by the unit 1 while a gas is flowing. A component outside a range to be measured contained in a signal to be outputted from the microphone 2 is removed through a high cut filter 3. The signal is compared with a fixed value by a comparator 4 having a hysteresis to perform a waveform shaping. A pulse signal to be outputted from the comparator 4 is counted 5 to obtain a frequency. A flow rate is computed by a flow rate computing device 6 by a specified relational expression based on the frequency and the results of the computation is displayed 7. Since the apparatus can be made small and has a simple structure and no moving part, adaptation to any trouble is easy achieving measurement of all available fluids without demand for conductivity made by a measuring electric body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a whistle type flow meter which measures the flow rate of a fluid such as gas or liquid using a whistle structure.

[0002]

2. Description of the Related Art Conventionally, many flowmeters for measuring the flow rate of gas or liquid have been known and can be classified into various types according to the principle, structure or use. For example, a volumetric flow meter has a built-in movable part such as a rotor and a piston, so that a fixed volume of fluid is discharged from the measuring space formed by the movable part and a case in one cycle of the movable part. Therefore, the flow rate can be known by counting the number of cycles of the movable part. Turbine flow meters belong to this type. On the other hand, when an electromagnetic flowmeter applies a magnetic field at right angles to the flow direction of a conductive fluid, an electrode placed at a position orthogonal to both the flow direction of the fluid and the magnetic field is proportional to the flow velocity and the strength of the magnetic field. Since electric power is generated, if the strength of the magnetic field is kept constant, an electromotive force proportional to the flow velocity can be obtained. Since this flow amount is proportional to the flow amount, the flow amount can be measured. There are acoustic flowmeters (including ultrasonic flowmeters), thermal flowmeters, and throttle flowmeters that use orifices as flowmeters of the type that have no moving parts in such flow paths.

[0003]

By the way, since the volumetric flowmeter has a movable portion, flow resistance of fluid is generated, there is a limit to downsizing, and it is difficult to deal with a failure. There is a limit to the use. In addition, since the electromagnetic flowmeter measures only the conductive fluid, there is a limit to the fluid that can be measured. Other flow meters also have their own strengths and weaknesses.

As described above, since the flowmeters have different operation principles and structures, one type cannot satisfy all requirements, and it is important to select an appropriate flowmeter according to the application.

Then, the inventors of the present invention tried the experiment by paying attention to a whistle represented by a whistle used by a conductor of a train or a teacher of physical education, and found the following facts.

It is empirically known that this kind of whistle does not produce a desired sound unless it is blown with a certain amount of air volume or more. Therefore, in order to produce this whistle with a normal volume, the amount of air that a person blows from his mouth. It was confirmed that, in the case of the commercially available whistle investigated this time, it must be 1200 to 1500 liters or more per hour. Therefore, when the frequency of the sound emitted by the whistle when the air volume is gradually increased from 0 within the range of the air volume less than that is examined, the frequency between the air volume blown and the frequency of the generated sound is shown in FIG.
It was found that there is an almost linear relationship as shown in.

The present inventors have paid attention to this fact, and from the viewpoint of whether this characteristic can be utilized in a flow meter, the present invention has a simple whistle structure with no moving parts and can measure the flow rate of a fluid which is not conductive. It is an object of the present invention to provide a flow meter which is easy to be made compact.

[0008]

In order to achieve the above object, the present invention has a fluid inlet, a resonance space in which the fluid resonates, and an outlet in which the fluid after resonance flows out. A sound producing unit having a whistle structure in which an edge is provided at the outlet in a direction counter to the inflow direction of the fluid; sound collecting means for collecting a sound generated from the sound producing unit due to the resonance of the fluid in the resonance space of the sound producing unit; Of the frequency components of the output signal from the sound collecting means, filter means for passing the fundamental frequency component of the sound generated by the sounding unit, frequency detecting means for detecting the frequency of the fundamental frequency component, and predetermined flow rate and frequency. The flowmeter is composed of a calculating means for calculating the flow rate of the fluid based on the frequency of the fundamental frequency component from the relational expression.

[0009]

According to the present invention, when the fluid flows into the sound producing unit, the sound is emitted from the sound producing unit due to the resonance in the resonance space. Therefore, the sound is collected by the sound collecting unit and the fundamental frequency component thereof is passed through the filter unit. To detect. Then, the flow rate is calculated by the calculation means based on the detected frequency component from the relational expression of the flow rate and frequency specific to the sounding unit prepared in advance.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 shows a whistle type flow meter for measuring a gas flow rate as an embodiment of the present invention.

The whistle type flow meter is composed of a gas line 10a,
A whistle structure sounding unit 1 is connected in the middle of 10b, and a microphone 2 for collecting a sound emitted by the sounding unit 1 when gas is flowing is attached to a part of the sounding unit 1.
A comparator 4 in which a component outside the measurement target range included in the signal output from the microphone 2 is removed through the high-cut filter 3 and the signal is subjected to hysteresis (shown by a broken line in the waveform (b) shown in FIG. 1) is applied. The pulse signal output from the comparator 4 is counted by the counter / timer 5 to obtain the frequency, and the flow rate calculator 6 calculates the flow rate from a predetermined relational expression based on this frequency. The calculation result is displayed on the display unit 7.

FIG. 2 is a perspective view of the sounding unit 1, and FIG. 3 is a longitudinal sectional view of the sounding unit 1.

The sounding unit 1 of the whistle type flow meter is
As can be seen from FIGS. 1 to 3, a resin is integrally formed having a horizontally long inlet 1a for receiving gas flowing in from a pipe 10a, an outlet 1b for discharging gas to the pipe 10b, and a resonance space 1c inside. It is formed of a molded body, the inlet 1a and the resonance space 1c are connected by a flow path P, and an edge 1d is formed at the outlet 1b so as to be inclined in a direction opposite to the gas inflow direction. When the inflow port 1a is horizontally long, the flow velocity of the gas at the edge 1d is increased and a stable sound is produced from the sounding unit 1, and the rotational movement of the gas in the resonance space 1c is smoothed. The resonance space 1c is shown in FIGS.
As can be seen from the above, it is preferable to make the space substantially cylindrical. As shown in FIG. 2, when the opening height of the end portion (portion opening to the resonance space 1c) of the flow path P is D and the radius when the resonance space 1c is cylindrical is R, D ≧ R
In this case, the rotational movement of the gas in the resonance space 1c is less likely to occur, so no sound is produced from the sound producing unit 1 and measurement becomes impossible.

A circular hole 1f is formed in one side wall 1e forming the resonance space 1c of the sound producing unit 1, and a microphone 2 is hermetically attached to this position. The holes 1f are provided in order to efficiently collect the sound generated by the sounding unit 1. The microphone 2 may be of ordinary construction, since the frequency characteristics may be covered 50～3000H _Z As can be seen from FIG. 5 described above, general-purpose products can be used. The frequency of the sound emitted from the sounding unit 1 for the same gas flow rate changes depending on the volume of the resonance space 1c of the sounding unit 1, so the frequency characteristic of the microphone 2 used may be determined by the design of the sounding unit 1.

The high-cut filter 3 is provided for the purpose of noise removal and leaving only the fundamental frequency component of the frequency component of the sound generated from the sounding unit 1 by the passage of the gas, and removing the harmonic component. The upper limit value of the band is determined by the upper limit value of the gas flow rate to be measured.

The output (a) of the microphone 2 is shown in FIG.
The output (b) of the high cut filter 3 and the output (c) of the comparator 4 are shown.

The counter / timer 5 counts the number of pulse signals output from the comparator 4 within a predetermined time determined by the timer, converts the count into a count value per unit time, and generates a sound frequency f of the sound generation unit 1. Output as.

The flow rate calculator 6 is a counter based on the relational expression Q = kf (k is a proportional constant) between the gas flow rate Q and the frequency f of the sound emitted by the sounding unit 1 which is predetermined from the relationship shown in FIG. / The flow rate Q is calculated using the frequency f output from the timer 5. The flow rate calculator 6 may be composed of an electronic circuit or a microcomputer. Display 7
Is a digital or analog display of the flow rate Q calculated by the flow rate calculator 6, and a liquid crystal display or a pointer meter is used.

With the whistle type flow meter having the above structure, the flow rate of the gas flowing through the pipe lines 10a and 10b can be continuously measured.

FIG. 4 shows another embodiment of the present invention.

In the figure, the same reference numerals as those in FIG. 1 denote the same components, and the description thereof will be omitted.

In this embodiment, the same sounding unit 1 and sound collecting microphone 2 as in the embodiment of FIG. 1 are used, but the purpose of the high cut filter 3 is slightly different from the purpose of the high cut filter 3 in the embodiment of FIG. In addition to noise removal, the output signal from the microphone 2 is set to be equal to or lower than the resolution of the spectrum analyzer 11 described later.

The spectrum analyzer 11 analyzes, for each frequency, the level of the output signal from the microphone 2 set to a frequency that can be analyzed by the high-cut filter 3 or less and outputs it as digital data. The band pass filter 12 in the next stage has a function of passing only a band of the input digital data, which is a range of the fundamental frequency component of the sound generated by the sound generation unit 1, and blocking other frequency components.

FIG. 4 shows the output (a) of the microphone 2,
The output (b) of the high-cut filter 3, the output (c) of the spectrum analyzer 11, and the output (d) of the bandpass filter 12 are shown.

The peak detector 13 is a bandpass filter 1
Obtain the peak value of the digital data that passed 2
The frequency F _peak corresponding to the peak value is obtained and output.

The flow rate calculator 6 is composed of a microcomputer, and as in the case of the embodiment shown in FIG. 1, the relational expression Q = k between the gas flow rate Q and the frequency f of the sound emitted by the sounding unit 1.
The flow rate Q is calculated based on f (k is a proportional constant). For this calculation, values stored in a built-in memory as a table of the above relational expressions may be used. The calculation result is displayed on the display 7.

In this embodiment, the spectrum analyzer 1
1. Since the bandpass filter 12 and the peak detector 13 are used, it is possible to reliably remove the harmonic component in addition to the fundamental frequency component in a region where the flow rate is relatively large. Get higher

The material and structure of the whistle structure sounding unit 1 used in the present invention are not limited to those shown in the embodiments, and may be, for example, a metal or a resin laminated. Inlet 1a and outlet 1b of the sounding unit 1
The shape and position of the resonance space can be freely changed according to the shape and position of the fluid conduit to be measured.
The shape of c is not limited to the cylindrical shape (the cross-sectional shape is circular), and may be an elliptical cross-section or a rectangle with rounded corners as long as it does not disturb the gas flow inside. . However, it is necessary to consider the shape of the outlet 1b so as not to disturb the movement of fluid such as gas moving in the resonance space 1c. In the case of the embodiment, the moving direction of the gas in the resonance space 1c is limited only to the inflow direction of the gas. Therefore, if the flow velocity is constant, the frequency of the sound emitted is determined only by the sectional shape of the outlet 1b. . Therefore, unless the shape of the outlet 1b is a rectangle or a square when viewed from above, sound of a uniform frequency will not be generated, and for the same reason, the end portion of the flow path P (the portion that blows out into the resonance space 1c) will not be generated. Section S
The shape (see FIG. 2) must also be rectangular. The outer shape of the resonance space 1c may be any shape as long as it does not hinder the flow of gas inside, for example, a shape having an extension in a direction perpendicular to the gas flow direction.

Further, the lengths of the end portion of the flow path P and the edge 1d in the direction perpendicular to the gas inflow direction do not necessarily have to be the same, but both must be perpendicular to the gas inflow direction. . Furthermore, the edge 1d must be sharp enough that the gas causes oscillating development. Therefore, when the sounding unit molded body is thick, the edge processing is indispensable, but when it is thin, the thickness of the end portion of the molded body may be used without processing.

Although the flow meter of the present invention is applied to the flow rate measurement of gas in the above-mentioned embodiments, the present invention can also be applied to the flow rate measurement of liquid.

[0032]

As described above, the flowmeter of the present invention has a simple structure, can be miniaturized, can be incorporated in a narrow space, and can be used for measuring a wide range of flow rate such as measurement of a minute flow rate. it can. Also, since there are no moving parts, it has high reliability, it is easy to deal with failures, and fluid pressure loss is small. Further, from the viewpoint of the operating principle, unlike the electromagnetic flowmeter, the fluid to be measured is not required to have conductivity, so that any fluid can be measured.

[Brief description of drawings]

FIG. 1 is a block diagram of a whistle type flow meter as an embodiment of the present invention.

FIG. 2 is a perspective view of a sounding unit used in the whistle type flow meter according to the present invention.

FIG. 3 is a sectional view taken along the line AA of the sounding unit shown in FIG.

FIG. 4 is a block diagram of a whistle type flow meter as another embodiment of the present invention.

FIG. 5 shows the relationship between the amount of air blown into the whistle and the frequency of the sound generated from the whistle.

[Explanation of symbols]

 1 Sounding Unit 1a Inlet 1b Outlet 1c Resonance Space 1d Edge 2 Microphone 3 High Cut Filter 4 Comparator 5 Counter / Timer 6 Flow Rate Calculator 7 Display 10a, 10b Pipeline

Claims (4)

[Claims] 1. A fluid inlet, a resonance space in which the fluid resonates, and an outlet through which the fluid after resonance flows out, and an edge is provided at the outlet in a direction counter to the inflow direction of the fluid. Sound generating unit having a whistle structure, sound collecting means for collecting sound generated by the sound generating unit due to resonance of fluid in the resonance space of the sound generating unit, and the sound generating unit of frequency components of an output signal from the sound collecting means. Filter means for passing the fundamental frequency component of the generated sound of, the frequency detection means for detecting the frequency of the fundamental frequency component, the flow rate of the fluid based on the frequency of the fundamental frequency component from the relational expression of the predetermined flow rate and frequency A whistle type flow meter, comprising: a calculating unit that calculates a flow rate. 2. The whistle type flow meter according to claim 1, wherein the sound collecting means is mounted in the vicinity of the resonance space. 3. The whistle type flowmeter according to claim 1, wherein the frequency detecting means is a counter / timer for converting the output signal from the sound collecting means within a predetermined time into pulses and counting. 4. The whistle type flow meter according to claim 1, wherein the frequency detecting means is a peak detector.