JP2004138628A - Ultrasonic wave flowmeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic wave flowmeter in which the influence of a phase difference between direct wave and reflected wave exerted on a result of measurement is reduced. <P>SOLUTION: The ultrasonic wave flowmeter comprises a pair of ultrasonic vibrators 10 and 11, an instrument section 12 which measures a time of ultrasonic wave transfer across the pair of ultrasonic vibrators 10 and 11, and a computation section 13 which calculates a volume of a fluid flowing through a flow measurement section 7 based on an output from the instrument section 12. The flow measuring section 7 and the pair of ultrasonic vibrators 10 and 11 are composed so as to reduce the influence exerted on the result of measurement by a reflected wave reflected from a wall surface of the flow measuring section 7. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to an ultrasonic flowmeter for measuring a flow rate of a fluid by ultrasonic waves.

A conventional ultrasonic flow meter of this type is known, for example, from Japanese Patent Application Laid-Open No. Hei 8-233628. As shown in FIGS. 27A and 27B, an ultrasonic vibration meter The transducers 2 and 3 are arranged so as to face each other, the propagation time until the ultrasonic wave transmitted from the ultrasonic transducer 2 is received by the ultrasonic transducer 3 and the ultrasonic wave transmitted from the ultrasonic transducer 3 The flow velocity calculating means 5 calculates the velocity of the fluid from the difference in the propagation time until the signal is received by the child 2, and also estimates the flow velocity distribution in the flow path 1 from the Reynolds number of the fluid at that time to obtain a correction coefficient and calculate the flow rate. I was
JP-A-8-233628

However, in the conventional ultrasonic flowmeter, since the propagation distance between the reflected wave reflected on the inner wall surface of the flow path and the direct wave propagating without being reflected is different, a phase difference occurs between the reflected wave and the direct wave. Because the combined wave of the direct wave and the direct wave is observed as the received wave, the amplitude of the received wave increases or decreases due to the phase difference between the reflected wave and the direct wave, or the period of the received wave changes, resulting in measurement accuracy and measurable flow rate. There was a problem that the range became narrow.

In order to solve the above-mentioned problems, the present invention comprises a flow rate measuring unit and a pair of ultrasonic vibrators so that the effect of a phase difference between a direct wave and a reflected wave on a measurement result is reduced. It is.

According to the above invention, the influence of the reflected wave in the flow path measurement unit can be reduced, so that the measurement accuracy can be improved over a wide range.

An ultrasonic flowmeter according to a first embodiment of the present invention includes a pair of ultrasonic transducers, a measuring unit that measures the time that ultrasonic waves propagate between the pair of ultrasonic transducers, and an output of the measuring unit. A calculation unit for calculating the amount of fluid flowing through the flow measurement unit based on the flow measurement unit, so that the effect of the reflected wave reflected by the wall surface of the flow measurement unit on the measurement result is reduced. And the pair of ultrasonic transducers, the influence of the reflected wave in the flow measuring unit can be reduced, and a high-accuracy ultrasonic flow meter can be obtained.

An ultrasonic flowmeter according to a second embodiment of the present invention is an ultrasonic flowmeter for measuring a flow rate of a fluid using ultrasonic waves, wherein an ultrasonic wave is transmitted between a pair of ultrasonic vibrators and the pair of ultrasonic vibrators. A measuring unit that measures the time that the light propagates, and a calculating unit that calculates the amount of fluid flowing through the flow measuring unit based on the output of the measuring unit, wherein the flow measuring unit reflects off the wall surface of the flow measuring unit The phase difference between the direct wave propagating in the fluid flowing through the flow measurement unit and the reflected wave reflected by the wall surface of the flow measurement unit without affecting the measurement result, wherein the direct wave and the reflection Since the flow rate measuring unit and the pair of ultrasonic transducers are configured so that the phase difference between the wave and the effect on the measurement result is reduced, the influence of the reflected wave in the flow measuring unit is reduced. Can obtain a high-accuracy ultrasonic flowmeter .

An ultrasonic flowmeter according to a third embodiment of the present invention is an ultrasonic flowmeter for measuring a flow rate of a fluid using ultrasonic waves, wherein an ultrasonic wave is transmitted between a pair of ultrasonic vibrators and the pair of ultrasonic vibrators. A measuring unit that measures the time that the light propagates, and a calculating unit that calculates the amount of fluid flowing through the flow measuring unit based on the output of the measuring unit, wherein the flow measuring unit reflects off the wall surface of the flow measuring unit The phase difference between the direct wave propagating in the fluid flowing through the flow measurement unit and the reflected wave reflected by the wall surface of the flow measurement unit without affecting the measurement result, wherein the direct wave and the reflection As the effect of the phase difference with the wave on the measurement result is reduced, the frequency of the pair of ultrasonic transducers, the distance between the pair of ultrasonic transducers, and the cross-sectional shape of the flow rate measurement unit Characterized by combination with related parameters Is therefore possible to reduce the influence of the reflected wave in the flow measurement portion with a simple configuration, it is possible to obtain a high-precision ultrasonic flowmeter.

An ultrasonic flowmeter according to a fourth aspect of the present invention is the ultrasonic flowmeter according to the third aspect, wherein the direct wave is a wave that propagates along a straight line connecting the centers of the pair of ultrasonic transducers. The reflected wave is a wave that propagates along the isosceles of an isosceles triangle formed by connecting the center of the pair of ultrasonic transducers and a point on the wall surface of the flow rate measurement unit, Since the propagation phase difference resulting from the difference between the propagation distance of the wave and the propagation distance of the reflected wave is 3π / 2 or more, the influence of the reflected wave in the flow measurement unit can be reduced with a simple configuration, and a highly accurate ultrasonic wave A flow meter can be obtained.

An ultrasonic flowmeter according to a fifth aspect of the present invention is the ultrasonic flowmeter according to the third aspect, wherein the direct wave is a wave that propagates along a straight line connecting the centers of the pair of ultrasonic transducers. The reflected wave is a wave that is reflected only once by the wall surface of the flow rate measurement unit, and the pair of ultrasonic vibrators are arranged such that the shortest propagation time of the reflected wave is longer than the propagation time of the direct wave. Since one side or diameter of the effective radiation surface is shorter than the height of the flow measurement unit, the influence of the reflected wave in the flow measurement unit can be reduced with a simple configuration, and a high-accuracy ultrasonic flow meter can be obtained. .

An ultrasonic flowmeter according to a sixth aspect of the present invention is the ultrasonic flowmeter according to the fourth or fifth aspect, wherein the frequency of the pair of ultrasonic transducers is set to a predetermined value or more. Since the influence of the reflected waves in the section can be reduced and the time resolution can be improved, a more accurate ultrasonic flowmeter can be obtained.

An ultrasonic flowmeter according to a seventh aspect of the present invention is the ultrasonic flowmeter according to the third aspect, wherein the direct wave is a wave propagating along a straight line connecting the centers of the pair of ultrasonic transducers. The reflected wave is a wave that propagates along the isosceles of an isosceles triangle formed by connecting the center of the pair of ultrasonic transducers and a point on the wall surface of the flow rate measurement unit, Since the propagation phase difference resulting from the difference between the propagation distance of the wave and the propagation distance of the reflected wave is 0.2π or less, the influence of the reflected wave in the flow measurement unit can be reduced with a simple configuration, and a highly accurate ultrasonic wave A flow meter can be obtained.

An ultrasonic flowmeter according to an eighth aspect of the present invention is the ultrasonic flowmeter according to the seventh aspect, wherein the ultrasonic flowmeter has at least one or more dividing plates that divide the flow measuring unit into a plurality of parts. Is further provided, the influence of the reflected wave in the flow measurement unit can be reduced, and a highly accurate ultrasonic flowmeter can be obtained.

An ultrasonic flowmeter according to a ninth aspect of the present invention is the ultrasonic flowmeter according to the eighth aspect, wherein the frequency of the pair of ultrasonic transducers is set to a predetermined value or less. The influence of the reflected wave can be reduced, and a highly accurate ultrasonic flowmeter can be obtained.

An ultrasonic flowmeter according to a tenth aspect of the present invention is the ultrasonic flowmeter according to any one of the first to fifth and seventh aspects, wherein the cross-sectional shape of the flow measuring unit is rectangular, and the cross-sectional shape of the flow measuring unit is rectangular. Since the parameter related to is the height of the rectangle, the influence of the reflected wave in the flow measurement unit can be reduced with a simple configuration, and a highly accurate ultrasonic flowmeter can be obtained.

An ultrasonic flowmeter according to an eleventh aspect of the present invention is the ultrasonic flowmeter according to any one of the first to fifth and seventh aspects, wherein the cross-sectional shape of the flow measuring unit is a circle, and the cross-sectional shape of the flow measuring unit is Is related to the diameter of the circle, the influence of the reflected wave in the flow measuring unit can be reduced with a simple configuration, and a high-accuracy ultrasonic flow meter can be obtained.

An ultrasonic flowmeter according to a twelfth aspect of the present invention is the ultrasonic flowmeter according to any one of the first to fifth and seventh aspects, wherein the pair of ultrasonic vibrators is arranged such that the center of the pair of ultrasonic vibrators is at the center. Since the connecting line is arranged so as to be shifted with respect to the center line in a predetermined direction of the cross section of the flow measurement unit, the influence of the reflected wave in the flow measurement unit can be reduced, and a highly accurate ultrasonic flow meter can be obtained. Can be.

An ultrasonic flowmeter according to a thirteenth aspect of the present invention is the ultrasonic flowmeter according to the twelfth aspect, wherein a line connecting the centers of the pair of ultrasonic transducers and a center line in a predetermined direction of a cross section of the flow rate measurement unit are provided. Are parallel to each other, the influence of the reflected wave in the flow measurement unit can be reduced, and a highly accurate ultrasonic flowmeter can be obtained.

An ultrasonic flowmeter according to a fourteenth aspect of the present invention is the ultrasonic flowmeter according to the twelfth aspect, wherein a line connecting the centers of the pair of ultrasonic transducers and a center line in a predetermined direction of a cross section of the flow measurement part are provided. Is at a predetermined angle, the influence of the reflected wave in the flow measuring unit can be reduced, and a highly accurate ultrasonic flow meter can be obtained.

An ultrasonic flowmeter according to a fifteenth aspect of the present invention is the ultrasonic flowmeter according to the first or second aspect, wherein the ultrasonic flowmeter is a reflected wave reflected only once by a wall surface of the flow measurement unit. Is further provided, so that the influence of the reflected wave in the flow measuring unit can be reduced, and a highly accurate ultrasonic flowmeter can be obtained.

An ultrasonic flowmeter according to a sixteenth aspect of the present invention is the ultrasonic flowmeter according to the fifteenth aspect, wherein a line connecting the centers of the pair of ultrasonic transducers and a center line in a predetermined direction of a cross section of the flow rate measurement unit are provided. Is at a predetermined angle, the influence of the reflected wave in the flow measuring unit can be reduced, and a highly accurate ultrasonic flow meter can be obtained.

An ultrasonic flowmeter according to a seventeenth aspect of the present invention is the ultrasonic flowmeter according to the first or second aspect, wherein the ultrasonic flowmeter further includes at least one structure provided in the flow rate measurement unit. Since it is provided, the influence of the reflected wave in the flow rate measuring unit can be reduced, and a high-accuracy ultrasonic flow meter can be obtained.

An ultrasonic flowmeter according to an eighteenth aspect of the present invention is the ultrasonic flowmeter according to the seventeenth aspect, wherein the at least one structure is disposed near the pair of ultrasonic transducers. The influence of the reflected wave in the measuring section can be reduced, and a highly accurate ultrasonic flowmeter can be obtained.

An ultrasonic flowmeter according to a nineteenth aspect of the present invention is the ultrasonic flowmeter according to the seventeenth aspect, wherein the at least one structure is disposed on a wall surface of the flow measurement unit. The effect of the reflected wave can be reduced, and a highly accurate ultrasonic flowmeter can be obtained.

An ultrasonic flowmeter according to a twentieth aspect of the present invention is the ultrasonic flowmeter according to the first or second aspect, wherein at least one concave or convex part is provided on a wall surface of the flow rate measuring unit. Therefore, the influence of the reflected wave in the flow measuring unit can be reduced, and a high-accuracy ultrasonic flow meter can be obtained.

An ultrasonic flowmeter according to a twenty-first aspect of the present invention is the ultrasonic flowmeter according to the twentieth aspect, wherein the ultrasonic flowmeter further includes a mesh structure that covers the concave portion. The effect of the reflected wave can be reduced, and a highly accurate ultrasonic flowmeter can be obtained.

An ultrasonic flowmeter according to a twenty-second aspect of the present invention is the ultrasonic flowmeter according to the first or second aspect, wherein the pair of ultrasonic vibrators are connected to a line connecting centers of the pair of ultrasonic vibrators. Since the direction indicating the directivity of at least one of the pair of ultrasonic transducers is arranged so as to form a predetermined angle, it is possible to reduce the influence of the reflected wave in the flow measurement unit, and to achieve a high-precision ultrasonic flow rate. You can get a total.

An ultrasonic flowmeter according to a twenty-third aspect of the present invention is the ultrasonic flowmeter according to any one of the first to fifth and seventh aspects, further comprising a rectifying means for arranging a flow direction at least upstream of the flow measuring unit. As a result, the direction of the flow in the flow measurement unit can be made uniform, and a more accurate ultrasonic flowmeter can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that components denoted by the same reference numerals in the drawings are the same, and detailed description thereof will be omitted.

(Example 1)
FIG. 1 is a configuration diagram of an ultrasonic flowmeter according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view of the flow path 6 in FIG. In FIG. 1, reference numeral 6 denotes a flow path, 7 denotes a flow rate measuring unit, 8 and 9 denote side walls of the flow path 6, and 10 and 11 denote ultrasonic vibrators attached to the side walls 8 and 9. Reference numeral 12 denotes a measurement unit connected to the ultrasonic transducers 10 and 11, and reference numeral 13 denotes a calculation unit connected to the measurement unit 12. In FIG. 2, reference numeral 14 denotes a lower plate portion of the flow path 6, and 15 denotes an upper plate portion connected to the side wall portions 8 and 9. The cross-sectional shape of the flow measuring unit 7 is rectangular, the width is W0, and the height is H0.

例 An example of a method for manufacturing the flow path of the ultrasonic flowmeter configured as described above will be described with reference to FIGS. The material used for the side walls 8 and 9, the lower plate 14, and the upper plate 15 constituting the flow path 6 is a material that does not cause a chemical change to the fluid to be measured. In this embodiment, since the fluid to be measured is, for example, air, the material is ABS resin.

上 The upper plate portion 15 is screwed on the end surfaces of the side wall portions 8 and 9 via a sealing material to form the flow measuring section 7 having a rectangular cross section. The ultrasonic vibrators 10 and 11 are fixed to mounting holes 10a and 11a provided in the side walls 8 and 9 via a sealing material so that the transmitting and receiving surfaces face each other.

The operation of the ultrasonic flowmeter configured as described above will be described. Let L be the distance connecting the centers of the ultrasonic vibrator 10 and the ultrasonic vibrator 11, and let θ be the angle between this straight line and the longitudinal direction of the flow measuring unit 7, which is the direction of flow. The sound velocity of the air to be measured in a windless state is C, and the flow velocity of the air in the flow rate measuring unit 7 is V. The ultrasonic wave transmitted from the ultrasonic transducer 10 arranged on the upstream side of the flow path 6 obliquely crosses the flow rate measuring unit 7 and is received by the ultrasonic transducer 11 arranged on the downstream side. The propagation time t1 at this time is

Indicated by Next, the ultrasonic transducers to be transmitted and received are switched, and ultrasonic waves are transmitted from the ultrasonic transducer 11 and received by the ultrasonic transducer 10. The propagation time t2 at this time is

Indicated by Eliminating the sound velocity C of air from the equations of t1 and t2,

Is obtained. If L and θ are known, the flow rate V can be obtained by measuring t1 and t2 with the measuring unit 12.

か ら From the flow velocity V, the flow rate Q can be obtained by calculating Q = KSV in the calculation section 13 assuming that the sectional area of the flow rate measurement section 7 is S and the correction coefficient is K.

(4) The propagation of ultrasonic waves in the flow rate measuring unit 7 of the ultrasonic flow meter that measures the flow rate based on the above operation principle will be described with reference to FIG. FIG. 3 is a cross-sectional view of the flow path 6 in FIG. 1 taken along the line b-b ′.

(4) Since the ultrasonic vibrator 10 has directivity, the transmitted ultrasonic wave generally propagates through the flow measurement unit 7 while spreading. For this reason, the ultrasonic wave received by the ultrasonic vibrator 11 is, for example, a direct wave propagating along the propagation path 17 in the flow rate measuring unit 7 and one time on the inner wall surface of the upper plate 15 like the propagation path 18. There is a reflected wave that is reflected and received. Here, the propagation paths 17 and 18 are representative propagation paths, and there are direct waves other than the propagation path 17 and reflected waves other than the propagation path 18, such as reflected waves reflected by the lower plate portion 14 and propagated. The number of reflections is not only one, but there are also reflected waves that are reflected and received two or more times. As a result, the received wave received by the ultrasonic transducer 11 is observed as a combined wave of the direct wave and the reflected wave. Here, a difference in propagation distance occurs between the direct wave and the reflected wave as indicated by the propagation paths 17 and 18. Assuming that the propagation distance difference between the propagation path 17 and the propagation path 18 is ΔL,

Indicated by When the propagation distance difference between the representative propagation paths 17 and 18 is converted into a propagation phase difference Δθ from the wavelength λ of the ultrasonic transducer,

Is obtained. As described above, since the ultrasonic wave propagating inside the flow rate measuring unit 7 has a propagation phase difference, the received wave which is a superposition of the direct wave and the reflected wave propagating in all the propagation paths is affected by the interference due to the propagation phase difference. It is thought to receive.

Therefore, in order to estimate the influence of the reflected wave on the direct wave, the propagation path distribution of the direct wave and the reflected wave and the respective waveforms were calculated. In this calculation, it is assumed that the radiation surface shapes of the ultrasonic vibrators 10 and 11 are square (constant), the distance between the ultrasonic vibrators 10 and 11 is L, and the flow measuring unit 7 is composed of two infinitely wide parallel flat plates. It is assumed that there is no flow of the fluid to be measured.

When the height (H0) is changed so that the propagation phase difference between the propagation paths 17 and 18 is, for example, 0.7π to 2.2π, the signal is transmitted from the ultrasonic transducer 10 and received by the ultrasonic transducer 11. FIGS. 4A and 4B show calculation results of obtaining the propagation path distribution of the ultrasonic wave. The direct wave is a solid line, the reflected wave of one reflection is a broken line, and the reflected wave of two reflections is a one-dot chain line. 4A and 4B, the horizontal axis represents the propagation distance of each propagation path, and the vertical axis represents the relative intensity for each path.

The propagation path distribution of the direct wave does not change because the shapes of the ultrasonic transducers 10 and 11 are constant, but the propagation path distribution of the once reflected wave is wider than that of the direct wave, and the propagation phase difference is larger when the propagation phase difference is larger. Shows the trend. The propagation path distribution of the reflected wave of the twice reflection is wider than that of the single reflection. The distance at which the intensity of the direct wave by the path becomes the largest is substantially equal to the distance of the propagation path 17, and the distance at which the intensity of the once-reflected reflected wave by the path becomes the largest is also substantially equal to the distance of the propagation path 18.

Next, FIGS. 5A and 5B show reception waveforms calculated by adding the pulse response characteristics of the ultrasonic transducers 10 and 11 to the calculation results of FIGS. 4A and 4B. However, the frequency of the ultrasonic transducers 10 and 11 is 270 kHz, the direct wave is a solid line, the reflected wave once reflected is a broken line, and the reflected wave twice reflected is a one-dot chain line. The larger the propagation phase difference, the smaller the amplitude of the reflected wave once reflected. The reflected wave of the double reflection is even smaller than the reflected wave of the single reflection. This is because, as shown in FIGS. 4A and 4B, the larger the propagation phase difference between the representative propagation paths 17 and 18, the wider the propagation path distribution and the gentler the slope. And cancel each other due to interference between reflected waves.

5A and FIG. 5B, the larger the propagation phase difference, the longer the rise time of the reflected wave with respect to the direct wave tends to be.

From the above calculation results, if the height (H0) is set so that the propagation path distribution of the reflected wave becomes wide, or if the height (H0) is set so that the propagation phase difference between the propagation paths 17 and 18 becomes large, , The influence on the direct wave can be reduced. Further, if the radiation surface of the ultrasonic transducer is smaller than the height (H0), the influence of the reflected wave on the direct wave can be further reduced.

In order to confirm the influence of the reflected wave on the direct wave, the distance between the ultrasonic vibrators 10 and 11 is L, the effective radiation surface of the ultrasonic vibrators 10 and 11 is square, the width is W0 (constant), and the height (H0 ) Are set so that the propagation phase difference between the propagation paths 17 and 18 is 0.7π to 2.2π, and the results of experiments performed using air are shown in FIGS. The frequency of the ultrasonic transducers 10 and 11 is 270 kHz.

6 and 7 represent the propagation phase difference between the propagation path 17 of the direct wave and the propagation path 18 of the reflected wave obtained by using (Equation 5). Note that λ is a wavelength at room temperature where there is no flow of the ultrasonic transducers 10 and 11. The vertical axis in FIG. 6 is a relative reception voltage of the reception voltage measured by arranging the ultrasonic transducers 10 and 11 in the flow path 6 with respect to the reception voltage measured by arranging the ultrasonic transducers 10 and 11 in the open space. However, there is no flow. The vertical axis in FIG. 7 is the rate of change of the reception voltage obtained by flowing at about 6000 liter / hour with respect to the reception voltage without flow.

6. From FIG. 6, the reception voltage without flow tends to be the smallest when the propagation phase difference is about π to 1.4π. The rate of change of the received voltage due to the flow is as shown in FIG. 7. When the propagation phase difference is about 0.8π to 1.2π, the combination of transmission by the ultrasonic transducer 10 and reception by the ultrasonic transducer 11 has the lowest reception voltage. On the contrary, in the combination of transmission by the ultrasonic transducer 11 and reception by the ultrasonic transducer 10, the reception voltage is the highest. The phenomenon that the reception voltage increases as described above must occur unless the direct wave and the reflected wave are superposed on each other without a phase influence.

When the propagation phase difference is 3π / 2 or more, both the combination of transmission by the ultrasonic transducer 10 and the reception by the ultrasonic transducer 11 and the combination of transmission by the ultrasonic transducer 11 and reception by the ultrasonic transducer 10 are both There is a tendency that the reception voltage decreases in each combination. This is probably because the directivity of the ultrasonic transducers 10 and 11 was deflected by the flow.

From the above results, at the height (H0) where the propagation phase difference between the propagation path 17 of the direct wave and the propagation path 18 of the reflected wave is about 0.8π to 1.4π, the influence of the reflected wave is large, so that the measurement is performed over a wide measurement range. It is difficult to measure the flow rate with high accuracy. Conversely, if the combination of the frequency of the ultrasonic transducers 10 and 11, the distance (L) and the height (H0) of the ultrasonic transducers 10 and 11 is set so that the propagation phase difference becomes about 3π / 2 or more, reflection occurs. The effect of waves can be reduced and high-precision flow measurement over a wide measurement range is possible. Distance (L), height (H0)
If is kept constant, it is possible to increase the propagation phase difference by setting the frequency of the ultrasonic transducers 10 and 11 to be higher, so that a more accurate flow rate measurement can be performed.

As described above, according to the present invention, in the ultrasonic flowmeter in which the propagation phase difference between the direct wave and the reflected wave affects the measurement result, the propagation phase difference between the propagation paths 17 and 18 is 3π / 2 or more. By selecting a combination of the height (H0) of the flow rate measuring unit 7, the distance (L) between the ultrasonic transducers 10 and 11, and the frequency so that the influence of the reflected wave can be reduced with a simple configuration, the fluid to be measured can be reduced. Can be measured in a short time with high accuracy over a wide range. Further, since no concave portion or convex portion is provided in the flow rate measuring section 7, the flow is hardly disturbed and the pressure loss is rarely increased.

In the first embodiment, the height (H0) at which the propagation phase difference between the propagation paths 17 and 18 is 0.7π to 2.2π is selected, but the propagation phase difference between the propagation paths 17 and 18 is 2.2π or more. The height (H0) may be selected, or the distance (L) and frequency of the ultrasonic transducers 10 and 11 may be selected.

(Example 2)
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS.

FIG. 8 is a cross-sectional view of the flow path 6 of the ultrasonic flow meter according to the second embodiment of the present invention, taken along the line a-a ′. FIG. 9 is a cross-sectional view of the flow path 6 taken along line b-b ′. In FIG. 8, reference numerals 14 and 15 denote side walls, a lower plate, and an upper plate of the flow path 6, which are the same as those shown in FIG. In FIG. 9, reference numerals 10 and 11 denote ultrasonic vibrators which have the same configuration as that of FIG. The manufacturing method and operation principle of the flow path of the ultrasonic flowmeter configured as described above are the same as those in the first embodiment, and thus description thereof is omitted.

In order to reduce the pressure loss, the cross-sectional area of the flow rate measuring unit 7 is generally set to be substantially the same as the inner diameter of the pipe for supplying the fluid to be measured, and the aspect ratio of the height (H1) and the width (W1) from the viewpoint of the flow velocity distribution. (W1 / H1) may be desired to be large. In such a case, a combination of the distance (L), the height (H1), and the frequency of the ultrasonic transducers 10 and 11 such that the propagation phase difference between the propagation path 19 and the propagation path 20 becomes 3π / 2 or more cannot be selected. There are cases. Therefore, means for reducing the influence of the reflected wave while increasing the aspect ratio will be considered.

In order to confirm the influence of the reflected wave on the direct wave, as in the first embodiment, the distance between the ultrasonic vibrators 10 and 11 is L, the effective radiation surface of the ultrasonic vibrators 10 and 11 is square, and the width is W1 (constant). The height (H1) is set such that the propagation phase difference between the propagation paths 19 and 20 is 0.05π to 0.7π, and the results of experiments performed using air are shown in FIGS. The frequency of the ultrasonic transducers 10 and 11 is 270 kHz.

、 The horizontal axes in FIGS. 10 and 11 represent the propagation phase difference between the propagation path 19 of the direct wave and the propagation path 20 of the reflected wave obtained using (Equation 5). Note that λ is a wavelength at room temperature where there is no flow of the ultrasonic transducers 10 and 11. The vertical axis in FIG. 10 is a relative reception voltage of the reception voltage measured by arranging the ultrasonic transducers 10 and 11 in the flow path 6 with respect to the reception voltage measured by arranging the ultrasonic transducers 10 and 11 in the open space. However, there is no flow. The vertical axis in FIG. 11 represents the rate of change of the reception voltage obtained by flowing the same at about 6000 liters / hour with respect to the reception voltage when there is no flow.

で は In FIG. 10, the smaller the propagation phase difference, the smaller the received voltage. This is because the effective radiating surfaces of the ultrasonic transducers 10 and 11 are fixed, so that the height (H1) is reduced, so that the lower and upper plate parts 15 and 15 partially block the ultrasonic transducers 10 and 11. It is thought that it was done.

In FIG. 11, when the propagation phase difference is 0.2π or more, the combination of transmission by the ultrasonic transducer 10 and reception by the ultrasonic transducer 11 and the combination of transmission by the ultrasonic transducer 11 and reception by the ultrasonic transducer 10 are shown. There is a difference in the rate of change. On the other hand, when the propagation phase difference is 0: 2π or less, a combination of transmission by the ultrasonic transducer 10 and reception by the ultrasonic transducer 11 and a combination of transmission by the ultrasonic transducer 11 and reception by the ultrasonic transducer 10 Are almost equal. The fact that the rate of change became equal in this way means that there is no phase effect on the superposition of the reflected wave on the direct wave in the direction in which the propagation speed of the ultrasonic wave increases or decreases due to the flow. It is considered that the influence of the reflected wave on the light was reduced.

From the above results, the frequencies of the ultrasonic vibrators 10 and 11, the distance (L) between the ultrasonic vibrators 10, 11 and the height of the ultrasonic vibrators 10 and 11 are set so that the propagation phase difference between the propagation paths 19 and 20 becomes approximately 0.2π or less. If the combination of the height (H1) is set, the influence of the reflected wave can be reduced and the flow rate can be measured with high accuracy in a wide measurement range. Further, if the distance (L) and the height (H1) are constant, the propagation phase difference can be reduced by setting the frequency of the ultrasonic transducers 10 and 11 to be low, so that the flow rate measurement can be performed with higher accuracy.

In the second embodiment, the height (H1) at which the propagation phase difference between the propagation paths 19 and 20 is 0.05π to 0.7π is selected, but the propagation phase difference between the propagation paths 19 and 20 is 0.05π or less. The height (H1) may be selected, or the distance (L) and frequency of the ultrasonic transducers 10 and 11 may be selected.

(Example 3)
Hereinafter, a third embodiment of the present invention will be described with reference to the drawings.

FIG. 12 is a cross-sectional view of the flow path 6 of the ultrasonic flow meter according to the third embodiment of the present invention, taken along line a-a 'of FIG. In FIG. 12, reference numerals 8, 9, 14, and 15 denote side walls, a lower plate, and an upper plate of the flow path 6, which are the same as those in FIG. The difference from the configuration of FIG. 2 is that the cross section of the flow rate measuring unit is divided into three by the dividing plates 21a and 21b, and divided into flow rate measuring units 22a to 22c.

If the height (H2) and the aspect ratio (W2 / H2) of the width (W2) are increased while keeping the cross-sectional area of the flow rate measuring section 7 and the inner diameter of the pipe for supplying the fluid to be measured, the flow path 6 can be reduced in size. It may be difficult. Therefore, a means for dividing the cross section of the flow rate measuring section 7 into a plurality of sections and increasing the aspect ratio of the height and width of each divided flow rate measuring section will be considered.

First, an example of a method of manufacturing the flow path 6 of the ultrasonic flowmeter will be briefly described. For example, for the flow rate measurement unit 7 in which the aspect ratio (W2 / H2) between the height (H2) and the width (W2) is 5, the SUS split plates 21a and 21b having a thickness of 0.2 mm are attached to the lower plate unit 14. It is fixed to the side walls 8 and 9 with an adhesive so as to be parallel to the inner wall surface. After fixing the divided plates 21a and 21b to the side walls 8 and 9, the upper plate 15 is screwed and fixed to the end surfaces of the side walls 8 and 9 via a sealing material. The heights (H2a, H2b, H2c) are set so that the aspect ratio of the divided flow rate measuring sections (22a, 22c) is about 20, and the aspect ratio of the divided flow rate measuring section (22b) is about 17.

In the divided flow rate measuring section (22b), a propagation phase difference of about 0.04π occurs between the propagation paths 23 and 24. In the divided flow rate measuring section (22a), the propagation path 25 and the propagation path 26 have a propagation phase difference of about 0.1π. The distance (L) between the ultrasonic transducers 10 and 11 is selected so that the propagation phase difference of (1) is generated. The effective radiation surfaces of the ultrasonic transducers 10 and 11 are square and the frequency is 270 kHz. The method of attaching the ultrasonic vibrator to the ultrasonic flowmeter configured as described above and the principle of operation are the same as those in the first embodiment, and will not be described.

Next, the propagation of ultrasonic waves in the divided flow rate measuring unit 22 will be described using propagation paths 23 to 26 as shown in FIG. The propagation paths 23 to 26 are representative propagation paths, and there are propagation paths (not shown) as in the first embodiment. FIG. 13 is a cross-sectional view of the flow path 6 taken along the line b-b ′.

In the divided flow rate measuring unit 22b, the direct wave propagates along the propagation path 23, and the reflected wave propagates while being reflected by the dividing plate 21b as the propagation path 24. Further, in the divided flow rate measuring unit 22a, the direct wave propagates along the propagation path 25, and the reflected wave propagates while being reflected by the upper plate 15 as the propagation path 26. Since the height (H2c) of the divided flow rate measuring unit 22c is set equal to the height (H2a) of the divided flow rate measuring unit 22a, the relationship between the direct wave and the reflected wave is the same as that of the divided flow rate measuring unit 22a.

で は The ultrasonic transducer 11 observes, as a reception wave, a combined wave of all direct waves and reflected waves propagating in the divided flow paths (H2a, H2b, H2c). As described in the second embodiment, since the heights of the divided flow rate measuring units (22a to 22c) are set so that the propagation phase difference between the direct wave and the reflected wave is equal to or less than 0.2π, each of the divided flow rate measuring units 22a to 22c is set. The topological relationship between the superposition of the direct wave and the reflected wave in 22c is not affected by the flow. As a result, the influence of the reflected wave on the direct wave can be reduced.

As a result of an experiment in which the flow rate measuring unit was divided into three parts as described above and air as a fluid to be measured was flowed at about 6000 liters / hour, the ultrasonic vibrator 10 transmitted and the ultrasonic vibrator 11 received. It was confirmed that the change rate of the combination was almost equal to the change rate of the combination in transmission by the ultrasonic transducer 11 and in reception by the ultrasonic transducer 10.

As described above, according to the present invention, by dividing the flow measurement unit into a plurality of parts by the dividing plate, the influence of the reflected wave can be reduced, the flow can be stabilized, and the flow rate of the fluid to be measured can be reduced for a short time. Can be measured with high accuracy.

In the third embodiment, the flow rate measuring unit is divided into three, but if the phase difference of the reflected wave with respect to the direct wave can be reduced, it may be divided into two or more than four, and the height (H2a to H2c) may be changed as appropriate. You can set it. Also, it is assumed that the ultrasonic wave propagates to all the divided flow rate measuring units, but it is not necessary to propagate the ultrasonic wave to all the divided flow rate measuring units if the accuracy of the flow rate measurement can be satisfied.

(Example 4)
Hereinafter, a fourth embodiment of the present invention will be described with reference to the drawings.

FIG. 14 is a cross-sectional view of the flow path 6 of the ultrasonic flowmeter according to the fourth embodiment of the present invention, taken along line b-b 'of FIG. In FIG. 14, reference numerals 8, 9, 14, and 15 denote side walls, a lower plate portion, and an upper plate portion of the flow channel 6, which are the same as those in FIG. The difference from the configuration of FIG. 3 is that the ultrasonic transducers 10, 11 are arranged so that the line 27 connecting the centers of the ultrasonic transducers 10, 11 and the center line 29 of the height (H3) are parallel and not co-linear. Are disposed on the side wall portions 8 and 9.

に は In order to obtain a high-precision flowmeter, it is necessary to reduce the influence of the reflected wave, and consider providing a propagation phase difference between the reflected wave from the inner wall surface of the lower plate 14 and the reflected wave from the upper plate 15. As one of the methods, the height (H3) of the flow measurement unit 28 is set so that the reflected wave from the inner wall surface of the lower plate 14 and the reflected wave from the upper plate 15 reach the ultrasonic vibrator with different phases. A method was selected in which a line 27 connecting the centers of a pair of ultrasonic transducers was shifted in parallel to the center line 29 of FIG.

の 一 An example of a method for creating a flow path of the ultrasonic flowmeter configured as described above will be described. For example, the propagation phase difference between the propagation path 27 of the direct wave and the propagation path 30 of the reflected wave at the lower plate part 14 is 0.7π, and the propagation position between the propagation path 27 and the propagation path 31 of the reflected wave at the upper plate part 15. The ultrasonic vibrators 10 and 11 are screwed and fixed to the side walls 8 and 9 via a sealing material so that the phase difference becomes 2.2π. Further, the upper plate 15 is screwed and fixed to the end surfaces of the side walls 8 and 9 via a sealing material. Note that the distances between the ultrasonic transducers 10 and 11, the effective radiation surface shape, the frequency, and the fluid to be measured are the same as those in the first embodiment. The principle of operation of the ultrasonic flowmeter configured as described above is the same as that of the first embodiment, and will not be described.

Next, the propagation of the ultrasonic wave in the flow measuring unit 28 will be described using an example of a propagation path. The direct wave propagates along a line 27 connecting the centers, and the reflected wave has a propagation path 30 reflected on the inner wall surface of the lower plate part 14 and a propagation path 31 reflected on the inner wall surface of the upper plate part 15. It is received near the center of the acoustic transducer 11. Note that the illustrated propagation paths of the direct wave and the reflected wave are representative propagation paths, and a propagation path that is not illustrated also exists as in the first embodiment. When the line 27 connecting the centers coincides with the center line 29, the propagation path 30 and the propagation path 31 have the same propagation distance, so that there is no propagation phase difference. However, if the line 27 connecting the centers and the center line 29 do not match, a propagation phase difference occurs because the propagation distance between the propagation path 30 and the propagation path 31 is different. Therefore, the reflected waves are affected by the interference, and the influence on the direct wave can be reduced.

実 験 In an experiment in which air was flowed at about 6000 liters / hour with the above-described configuration, it was confirmed that the propagation phase difference in FIG. 8 was almost the same as the result of 2.2π.

As described above, according to the present invention, the line connecting the center of the ultrasonic vibrator is shifted in parallel with the center line of the height (H3) of the flow measurement unit, so that the lower plate unit and the upper plate are arranged. The propagation phase difference of the reflected wave reflected by the section can be changed, the influence of the reflected wave on the direct wave can be reduced, and the flow rate of the fluid to be measured can be measured in a short time with high accuracy.

In the fourth embodiment, the propagation phase difference between the propagation path 27 of the direct wave and the propagation path 30 of the reflected wave at the lower plate 14 is 0.7π, and the propagation path 31 of the reflected wave at the propagation path 27 and the upper plate 15. The line 27 connecting the centers of the ultrasonic transducers and the center line 29 of the height (H7) of the flow rate measurement unit are shifted and arranged in parallel so that the propagation phase difference between the two becomes 2.2π. The configuration is not limited to the conditions, and may be changed as appropriate.

(Example 5)
Hereinafter, a fifth embodiment of the present invention will be described with reference to the drawings.

FIG. 15 is a cross-sectional view of the ultrasonic flow meter according to the fifth embodiment of the present invention, taken along line b-b 'of the flow path 6. In FIG. 15, reference numerals 8, 9, 14, and 15 denote side walls, a lower plate, and an upper plate of the flow path 6, which are the same as those in FIG. 3 is different from the configuration of FIG. 3 in that the line 32 connecting the centers of the ultrasonic transducers 10 and 11 and the center line 33 of the height (H4) of the flow rate measurement unit 36 have a predetermined angle (θ4). The ultrasonic transducers 10 and 11 are arranged obliquely on the side walls 8 and 9.

As in the case of the fourth embodiment, it is necessary to reduce the influence of the reflected wave in order to obtain a high-accuracy flowmeter, and the propagation position of the reflected wave from the inner wall surface of the lower plate portion 14 and the reflected wave from the upper plate portion 15 is reduced. Consider providing a phase difference. As one of the methods, the ultrasonic transducers 10 and 11 are arranged so that a line 32 connecting the centers of a pair of ultrasonic transducers and a center line 33 of a height (H4) have a predetermined angle (θ4). I chose how to do it.

(4) An example of a method of creating a flow path of the ultrasonic flowmeter configured as described above will be described. For example, the ultrasonic vibrators 10 and 11 are attached to the side walls 8 and 9 such that the line 32 connecting the centers of the ultrasonic vibrators 10 and 11 is inclined by about 2.5 degrees with respect to the center line 33 of the height (H4). Screw it in and fix it via the sealing material. Further, the upper plate 15 is screwed and fixed to the end surfaces of the side walls 8 and 9 via a sealing material. Note that the distances between the ultrasonic transducers 10 and 11, the effective radiation surface shape, the frequency, and the fluid to be measured are the same as those in the first embodiment. The principle of operation of the ultrasonic flowmeter configured as described above is the same as that of the first embodiment, and will not be described.

Next, the propagation of the ultrasonic wave in the flow measurement unit 36 will be described using an example of a propagation path. For example, a direct wave propagates along a line 32 connecting the centers. A propagation path 34 and a propagation path 35 radiated from the vicinity of the center of the ultrasonic transducer 10 in the respective directions of the lower plate portion 14 and the upper plate portion 15 at the same angle are considered as one representative example of the reflected wave. Note that the illustrated propagation paths of the direct wave and the reflected wave are representative propagation paths, and a propagation path that is not illustrated also exists as in the first embodiment. The ultrasonic waves propagating along the propagation path 34 are reflected by the lower plate portion 14, and the ultrasonic waves propagating along the propagation path 35 are reflected by the upper plate portion 15. The reflected waves propagating through the propagation path 34 and the propagation path 35 have different propagation distances, so that a propagation phase difference occurs.

When the line 32 connecting the centers coincides with the center line 33, the propagation distance between the propagation path 34 and the propagation path 35 is equal, so that no propagation phase difference occurs, and the signal is received at the same position of the ultrasonic transducer 11. . However, since the line 32 connecting the centers and the center line 33 are inclined by 2.5 degrees, the propagation distance between the propagation path 34 and the propagation path 35 is different and a propagation phase difference occurs.

Further, it is received at a different position of the ultrasonic transducer 11. Therefore, the reflected waves are affected by the interference, and the influence on the direct wave can be reduced.

In the fifth embodiment, the line 32 connecting the centers of the ultrasonic transducers 10 and 11 is inclined by about 2.5 degrees with respect to the center line 33 of the height (H4). However, the present invention is not limited to the above condition. , May be larger or smaller than 2.5 degrees.

(Example 6)
Hereinafter, a sixth embodiment of the present invention will be described with reference to the drawings.

FIG. 16 is a top view of the flow path of the ultrasonic flow meter according to the sixth embodiment of the present invention. FIG. 17 is a cross-sectional view of the flow channel in FIG. 16 taken along the line c-c '. FIG. 18 is a cross-sectional view of the flow path of FIG. 16 taken along line d-d '. In each of the drawings, reference numeral 37 denotes a flow channel, 38 denotes an upper plate portion of the flow channel 37, and 39 denotes a mounting portion a of the ultrasonic vibrator 10 provided on the upper plate portion 38. Reference numeral 40 denotes a lower plate portion of the flow channel 37, 41 denotes a mounting portion b of the ultrasonic vibrator 11 provided in the lower plate portion 40, 42 and 43 denote side walls of the flow channel 37, and 44 denotes a flow rate measuring portion. is there.

In order to obtain a high-precision flowmeter, it is necessary to reduce the influence of the reflected wave, and it is important to reduce the influence of the once-reflected reflected wave among the reflected waves. Further, from the viewpoint of the flow velocity distribution, there is a case where it is desired to increase the aspect ratio (W5 / H5) of the height (H5) and the width (W5). Therefore, regardless of the shape of the flow measurement unit 44, a method of arranging a pair of ultrasonic transducers at a position where no single reflection occurs in the flow measurement unit 44 will be considered.
An example of a method for creating a flow path of the ultrasonic flowmeter configured as described above will be described. The material used for the upper plate portion 38, the lower plate portion 40, the mounting portions 39 and 41, and the side wall portions 42 and 43 constituting the flow path 37 is a material that does not cause a chemical change to the fluid to be measured.

In this example, since the fluid to be measured was air, for example, ABS resin was selected as the material. First, the mounting portion 39 is bonded and fixed to the upper plate portion 38 such that the angle (θ5) between the major axis direction of the upper plate portion 38 and the mounting direction d-d ′ of the ultrasonic transducer 10 is, for example, 30 degrees. The mounting portion 41 is bonded and fixed to the upper plate portion 40 such that the angle (θ5) between the major axis direction of the lower plate portion 40 and the mounting direction d-d ′ of the ultrasonic transducer 11 is also 30 degrees. The upper plate 38 is screwed to the end surfaces of the side walls 42 and 43 via a sealant to form a flow measuring unit 44 having a rectangular cross section. Next, the mounting portions 39 and 41 are attached to the mounting portions 39 and 41 such that the angle (θ6) formed between the line 47 connecting the centers of the ultrasonic transducers 10 and 11 and the center line of the height (H5) of the dd ′ cross section is 30 degrees. The ultrasonic vibrators 10 and 11 are fixed via sealing materials 45 and 46.

The distance, effective radiation surface shape, and frequency of the ultrasonic transducers 10 and 11 are the same as those in the first embodiment. The operation principle of the ultrasonic flowmeter configured as described above is the same as that of the first embodiment, and the description is omitted.

Next, the propagation of the ultrasonic wave in the flow rate measuring unit 44 will be described using propagation paths 47 to 49 as shown in FIG. The propagation paths 47 to 49 are representative propagation paths, and there are also propagation paths not shown. The direct wave transmitted from the ultrasonic transducer 10 propagates along the propagation path 47 to the ultrasonic transducer 11. Since ultrasonic waves transmitted from the ultrasonic transducer 10 generally propagate while spreading, there are also ultrasonic waves that propagate along the propagation paths 48 and 49. However, the ultrasonic wave that has propagated along the propagation path 48 is reflected by the lower plate portion 40 and then reflected again by the wall surface of the flow rate measuring portion 44 and cannot reach the ultrasonic vibrator 11. Also, the ultrasonic wave propagated along the propagation path 49 is reflected by the side wall portion 42 and then reflected again by the wall surface of the flow measuring section 44 and cannot reach the ultrasonic vibrator 11. In the ultrasonic transducers 10 and 11 arranged in such a positional relationship, there is no reflected wave that is reflected once and received by the flow rate measuring unit 44. As a result, the reflected wave that affects the direct wave is more than twice reflected, and the effect of the reflected wave that is more than twice reflected on the direct wave is considerably smaller than that of the once reflected wave. Can be reduced.

In the experimental results obtained by using the flow rate measuring unit 44 configured as described above and flowing air as the fluid to be measured at about 6000 liters / hour, the propagation phase difference of the first embodiment is equivalent to 2.2π. It was confirmed. According to this result, the angle (θ5, θ6) is set in each of the long axis direction of the flow path 37 and the height (H5) direction of the flow rate measuring unit 44, and a pair of reflected waves is generated at a position where a single reflection does not occur. If the ultrasonic transducers 10 and 11 are arranged, the flow rate of the fluid to be measured can be measured over a wide range with high accuracy without depending on the cross-sectional dimension of the flow rate measurement unit 44.

In the sixth embodiment, the angle (θ5) between the long axis direction of the flow path 37 and the mounting direction dd ′ of the ultrasonic vibrator is 30 degrees, and the line 47 connecting the centers of the pair of ultrasonic vibrators and the height ( Although the angle (θ6) between the center line of H5) and the center line is inclined by 30 degrees, the present invention is not limited to the above conditions, and the angle may be changed to an appropriate angle.

(Example 7)
Hereinafter, a seventh embodiment of the present invention will be described with reference to the drawings.

FIG. 19 is a cross-sectional view of the flow path 6 of the ultrasonic flowmeter according to the seventh embodiment of the present invention, taken along line a-a 'of FIG. In FIG. 19, 8, 9, 14, and 15 are a side wall, a lower plate, and an upper plate of the flow path 6, and the above is the same as the configuration of FIG. The difference from the configuration of FIG. 2 is that structures 50 and 51 having dimensions that do not divide the flow measurement unit 52 into layers are arranged on the side walls 8 and 9.

方法 In order to reduce the influence of the reflected wave, consider a method of providing a reflector in the flow rate measuring unit 52 so as to set the propagation phase difference between the reflected wave and the direct wave to a desired magnitude.

の 一 An example of a method for creating a flow path of the ultrasonic flowmeter configured as described above will be described. For example, with respect to the flow rate measuring unit 52, the ultrasonic vibrator 10 is configured such that two SUS structures 50a and 50b each having a thickness of 0.2 mm and a length (L6) of 7 mm are parallel to the inner wall surface of the lower plate portion 14. Is fixed with an adhesive to the side wall portion 8 where is disposed. Similarly, the structures 51a and 51b are fixed to the side wall 9 on which the ultrasonic vibrator 11 is arranged by an adhesive. After the structures 50 and 51 are fixed to the side walls 8 and 9, the upper plate 15 is screwed and fixed to the end surfaces of the side walls 8 and 9 via a sealing material. Note that the distances between the ultrasonic transducers 10 and 11, the effective radiation surface shape, the frequency, and the fluid to be measured are the same as those in the first embodiment. The method of attaching the ultrasonic vibrator to the ultrasonic flowmeter configured as described above and the principle of operation are the same as those in the first embodiment, and will not be described.

Next, the propagation of ultrasonic waves in the flow rate measuring section 52 will be described using propagation paths 53 and 54 as shown in FIG. The propagation paths 53 and 54 are representative propagation paths, and there are also propagation paths (not shown) as in the first embodiment. FIG. 20 is a cross-sectional view of the flow path 6 taken along the line b-b ′. The direct wave propagates along the propagation path 53. The reflected wave propagates while repeating reflection at the structure 50a and the lower plate portion 14 as in the propagation path 54. The reflected wave propagating in the propagation path 54 has a longer propagation distance than the propagation path reflected only once by the upper plate 15. In addition, there is a propagation path of a reflected wave (not shown) that is inhibited from being received by the structure 51. For this reason, the influence of the reflected wave on the direct wave can be reduced.

As described above, according to the present invention, the propagation phase difference between the direct wave and the reflected wave can be set to a desired magnitude by the structure, so that the influence of the reflected wave can be reduced and the flow rate of the fluid to be measured can be increased in a short time. It can be measured with accuracy.

In the seventh embodiment, the thickness of the structure is 0.2 mm, the length (L6) is 7 mm, and it is made of SUS. However, the structure is not limited to the above conditions, and the structure and the material can be appropriately changed. . In addition, although the structures 50 and 51 are bonded and fixed to the side walls 8 and 9, they may be arranged in places other than the side walls 8 and 9. In addition, the number of structures is four in total, but any number of one or more may be used.

(Example 8)
Hereinafter, an eighth embodiment of the present invention will be described with reference to the drawings.

FIG. 21 is a cross-sectional view of the flow path 6 of the ultrasonic flowmeter according to the eighth embodiment of the present invention, taken along line a-a 'of FIG. 21, reference numerals 8, 9, 14, and 15 denote side walls, a lower plate, and an upper plate of the flow path 6, which have the same configuration as that of FIG. The difference from the configuration of FIG. 2 is that the structures 55 a and 55 b that do not divide the flow rate measuring unit 56 into layers are arranged on the lower plate 14 and the upper plate 15.

に は In order to obtain a high-precision flow meter, it is necessary to reduce the influence of the reflected wave, and a method of providing a reflector in the flow measuring unit 56 so that the reflected wave is hardly received will be considered.

の 一 An example of a method for creating a flow path of the ultrasonic flowmeter configured as described above will be described. For example, with respect to the flow rate measuring unit 56, SUS structures 55a and 55b having a thickness of 0.2 mm and a length (L7) of 1 mm are perpendicular to the inner wall surfaces of the lower plate 14 and the upper plate 15 and have a width (W7). Is fixed with an adhesive so as to be in the vicinity of the center. After the structure 55 is fixed, the upper plate 15 is screwed and fixed to the end surfaces of the side walls 8 and 9 via a sealing material. Note that the distances between the ultrasonic transducers 10 and 11, the effective radiation surface shape, the frequency, and the fluid to be measured are the same as those in the first embodiment. The method of attaching the ultrasonic vibrator to the ultrasonic flowmeter configured as described above and the principle of operation are the same as those in the first embodiment, and will not be described.

Next, the propagation of the ultrasonic wave in the flow measuring unit 56 will be described using propagation paths 57 and 58 as shown in FIG. The propagation paths 57 and 58 are representative propagation paths, and there are also propagation paths (not shown) as in the first embodiment. FIG. 22 is a cross-sectional view of the flow path 6 taken along the line b-b ′. The ultrasonic wave transmitted from the ultrasonic transducer 10 propagates while spreading, and, for example, a direct wave propagates along the propagation path 57. The spread ultrasonic wave is reflected by the upper plate portion 15 and the lower plate portion 14 and received by the ultrasonic vibrator 11 as a reflected wave. However, by providing the structure 55a on the upper plate 15, for example, the reflected wave of the propagation path 58 is inhibited from propagating by the structure 55a. Therefore, the reflected wave on the propagation path 58 is not received by the ultrasonic transducer 11. Although the propagation path of the reflected wave exists in addition to the propagation path 58, the propagation of a part of the reflected wave can be inhibited by the structures 55a and 55b, so that the influence of the reflected wave on the direct wave can be reduced.

As described above, according to the present invention, since the propagation of a part of the reflected wave can be inhibited by the structure, the influence of the reflected wave can be reduced by appropriately selecting the position and the number of the structures to be arranged, so that the influence of the fluid to be measured can be reduced. The flow rate can be measured in a short time with high accuracy.

In the eighth embodiment, the structures 55a and 55b are made of SUS and have a thickness of 0.2 mm, a length (L7) of 1 mm, and are located near the center of the width (W7), but are not limited to the above conditions. Instead, it can be configured by appropriately changing the size, position, and material. Although the structures 55a and 55b are bonded and fixed on the lower plate 10 and the upper plate 15, the structures 55a and 55b may be arranged in places other than the lower plate 14 and the upper plate 15. Although two structures are arranged, any number of one or more may be used.

(Example 9)
Hereinafter, a ninth embodiment of the present invention will be described with reference to the drawings.
FIG. 23 is a cross-sectional view of the ultrasonic flow meter according to the ninth embodiment of the present invention, taken along line aa ′ of the flow path 6. In FIG. 23, reference numerals 8, 9, 14, and 15 denote side walls, a lower plate, and an upper plate of the flow channel 6, which have the same configuration as that of FIG. 2 in that a concave portion 59 is provided in the lower plate portion 14 and a mesh structure 60 is provided above the concave portion 59.

In order to reduce the influence of the reflected wave while increasing the height ratio (H8) and the width (W8) aspect ratio (W8 / H8) of the flow measurement unit 61, a concave portion is provided in the flow measurement unit 61, and the flow is further flowed into the concave portion. Consider a method of providing a mesh structure so as not to disturb.

の 一 An example of a method for creating a flow path of the ultrasonic flowmeter configured as described above will be described. For example, a concave portion 59 is formed using a milling machine near the center of the lower plate portion 14 of the flow rate measuring section 61 having an aspect ratio (W8 / H8) of 5 so that the propagation phase difference between the propagation paths 62 and 63 becomes 2.2π. Constitute. The mesh structure is fixed upward so as to cover the recess 59 so that the flow of the air to be measured is not generated in the recess 59.

(4) The mesh structure has a mesh size of about 100, for example, so that ultrasonic waves can be transmitted. In addition, the upper plate portion 15 is screwed and fixed to the end surfaces of the side wall portions 8 and 9 via sealing materials so that the propagation phase difference between the propagation path 62 and the propagation path 64 becomes 1.2π.

The distance between the ultrasonic transducers 10 and 11, the effective radiation surface shape, the frequency, and the fluid to be measured are the same as those in the first embodiment. The method of attaching the ultrasonic vibrator to the ultrasonic flowmeter configured as described above and the principle of operation are the same as those in the first embodiment, and will not be described.

Next, the propagation of the ultrasonic wave in the flow measurement unit 61 will be described using an example of a propagation path as shown in FIG. FIG. 24 is a cross-sectional view of the flow path 6 taken along the line b-b '. The direct wave propagates along the propagation path 62. On the other hand, the reflected wave from the lower plate portion 14 is reflected at the bottom of the concave portion 59 and propagates like the propagation path 63. The reflected wave from the upper plate 15 is reflected and propagates along a propagation path 64. The propagation paths 62 to 64 are representative propagation paths, and there are also propagation paths (not shown) as in the first embodiment. There are also reflected waves that do not pass through the mesh structure 60 and are reflected on the surface of the mesh structure 60.

Since the propagation phase difference between the propagation path 62 and the propagation path 63 was 2.2π, and the propagation phase difference between the propagation path 62 and the propagation path 64 was 1.2π, the propagation path distributions of the respective reflected waves were different, and the lower plate portion 14 The reflected waves from the upper plate 15 are affected by interference. Thus, by making the configuration of the lower plate portion 14 and the configuration of the upper plate portion 15 asymmetric, the influence on the direct wave can be reduced. Further, since the mesh structure 60 is provided in the concave portion 59, the air flows through the flow rate measuring section 61 except the concave portion 59, so that the flow does not disturb. Further, the ultrasonic waves can be transmitted through the flow rate measuring section 61 including the concave portion 59.

As described above, according to the present invention, the structure can make the propagation phase difference between the direct wave and the reflected wave a desired value, and can realize a stable flow velocity distribution in the measurement flow rate range. And the flow rate of the fluid to be measured can be measured in a short time with high accuracy.

In the ninth embodiment, the recess 59 is provided so that the propagation phase difference between the propagation path 62 and the propagation path 63 is 2.2π. However, the present invention is not limited to the above conditions, and can be appropriately changed. . Although the mesh structure 60 of about 100 is provided above the concave portion 59, another mesh structure may be used, and it is not necessary to provide the mesh structure 60 if the concave portion 59 does not affect the flow on the measurement. In addition, the concave portions 59 are provided near the center of the lower plate portion 14. However, the concave portions 59 may be provided in a required number in necessary places to reduce the influence of the reflected wave, and may be provided in the upper plate portion 15, Not only the concave portion 59 but also a convex portion may be provided.

(Example 10)
Hereinafter, a tenth embodiment of the present invention will be described with reference to the drawings.
FIG. 25 is a cross-sectional view of a flow path 6 of an ultrasonic flowmeter according to Embodiment 10 of the present invention as viewed from above. In FIG. 25, reference numeral 6 denotes a flow path, and reference numerals 8 and 9 denote side wall portions of the flow path 6, which are the same as those in FIG. The difference from the configuration of FIG. 1 is that the center direction 66 of the ultrasonic vibrator 10 is θ10 (about 5 degrees) upstream with respect to a line 65 connecting the centers of the ultrasonic vibrators 10 and 11, The point is that the center direction 67 is shifted to the downstream side by θ11 (about 5 degrees). The method for forming the flow path, the method for attaching the ultrasonic vibrator, and the operation principle are the same as those in the first embodiment, and thus will not be described. The distance between the ultrasonic transducers 10 and 11, the radiation surface shape, and the fluid to be measured are the same as those in the first embodiment.

Generally, the directivity of an ultrasonic transducer tends to be strong toward the center of the ultrasonic transducer.

For this reason, in the open space, when the ultrasonic transducers 10 and 11 face each other with the directivity thereof being matched, the received voltage can be maximized. However, when transmitting and receiving ultrasonic waves in a closed space such as the flow path 6, the received reflected wave also has a relatively strong directivity and therefore has a large reception voltage, and the influence on the direct wave increases. Therefore, the ultrasonic transducers 10 and 11 are arranged with the center directions 66 and 67 shifted from the line 65 connecting the centers by θ10 and θ11. In such an arrangement, the received voltage of the direct wave is reduced, but the reflected wave is a relatively weak directional part, so that the received voltage of the reflected wave is also reduced and the influence of the reflected wave can be reduced.

In a configuration in which the center direction 66 of the ultrasonic vibrator 10 is shifted to the downstream side and the center direction 67 of the ultrasonic vibrator 11 is shifted to the upstream side by about 5 degrees, air is flowed at about 6000 liter / hour as in the first embodiment. In the experiment, the result that the propagation phase difference of FIG. 7 was about 2π was obtained.

As described above, according to the present invention, by displacing the line connecting the center of the ultrasonic oscillator and the center line of the ultrasonic oscillator, the influence of the reflected wave on the direct wave can be reduced, and the flow rate of the fluid to be measured can be reduced. Can be measured in a short time with high accuracy.

In the tenth embodiment, the center directions 66 and 67 of the ultrasonic vibrator are shifted by 5 degrees with respect to a line connecting the centers of the 65 ultrasonic vibrators. However, the present invention is not limited to the above conditions, and the angles are appropriately changed. Can be configured. Also, the directions in which the center lines of the ultrasonic transducers 10 and 11 are shifted are the upstream and downstream sides of the flow, but may be any combination of the lower plate portion and the upper plate portion, or any combination of the directions.

(Example 11)
Hereinafter, an eleventh embodiment of the present invention will be described with reference to the drawings.
FIG. 26 is a local cross-sectional view showing a state where an ultrasonic flowmeter is attached to a pipe according to Embodiment 11 of the present invention. 26, reference numerals 10a and 11a denote attachment ports, 14 and 15 denote lower and upper plate portions of the flow path 6, 68 denotes a rectifying means, 69 denotes a flow rate measuring unit, and 70 and 71 denote pipes. The configuration of the flow rate measuring unit 69 (not shown) is the same as the configuration of any of the first to tenth embodiments. The difference from the first embodiment to the tenth embodiment is that a rectifying unit 68 is provided in the flow rate measuring unit 69. For example, the rectifying means 68 is made of an aluminum honeycomb structure, and is bonded and fixed to the lower plate portion 14, the upper plate portion 15, and a side wall portion (not shown) with an adhesive so as not to move due to the flow of air. The method of assembling the flow path of the ultrasonic flowmeter, the method of attaching the ultrasonic vibrator, and the operation principle are the same as those in the first embodiment, and thus will not be described.

Next, the operation of the rectifier will be described. Generally, in flow measurement, in order to stabilize the flow velocity distribution and the flow direction, a straight pipe portion sufficiently long (about 10 times) in diameter is provided upstream of the flow measurement portion. However, it is difficult to provide a sufficiently long straight pipe portion with respect to the diameter on the upstream side of the flow rate measuring section 69 due to the miniaturization of the ultrasonic flow meter and the limitation of the installation place. is there. In such a configuration, the air flows through the flow measurement unit 69 in a state where the flow direction is disturbed, and affects the measurement accuracy.

Therefore, rectifying means 68 having a honeycomb structure is provided in order to stabilize the flow of the air flowing from the pipe 70 into the flow measuring unit 69. The air flowing through the rectifying means 68 has a uniform flow direction, and is substantially parallel to the lower plate portion 14 and the upper plate portion 15.

As described above, according to the present invention, the flow direction can be stabilized by providing the rectifying means 68 on the upstream side of the flow rate measuring unit 69, and the influence of the reflected waves in the first to tenth embodiments is reduced. In combination with the means for performing the measurement, the flow rate of the measurement fluid can be measured in a short time with high accuracy.

In the eleventh embodiment, the rectifying means 68 is made of an aluminum honeycomb structure. However, if a rectifying effect can be obtained, a pipe, a mesh structure, a flat plate, a metal such as SUS, a resin, or a composite may be used. I do not care. Although the pipes 70 and 71 are vertically attached to the upper plate 15, they may be attached to a portion other than the upper plate 15, or may be horizontally attached. Although the rectifying means 68 is provided on the upstream side, it may be provided on both the upstream side and the downstream side.

In the first to third and seventh embodiments, the heights (H0, H1, H2, H6) and the heights of the ultrasonic transducers 10, 11 are shown to be equal, but the heights (H0, H1, H2, The height of the ultrasonic transducers 10 and 11 may be lower or higher than H6).

In the first to fifth and seventh to eleventh embodiments, the ultrasonic transducers 10 and 11 are provided obliquely to the side walls 8 and 9 with respect to the flow. It may be arranged, or may be arranged at a position parallel to the flow. Further, although the cross-sectional shape of the flow rate measuring section is rectangular, it may be circular or elliptical as long as the ultrasonic transducers 10 and 11 are arranged at positions parallel to the flow.

In the first to eleventh embodiments, the effective radiating surfaces of the ultrasonic transducers 10 and 11 are square. However, the present invention is not limited to the above conditions, and may be a circle, an ellipse, or another polygon. Further, the frequency of the ultrasonic transducers 10 and 11 is set to 270 kHz, but is not limited to the above condition, and may be equal to or higher than 270 kHz. Further, although the cross-sectional shape of the flow rate measuring unit is rectangular, the shape is not limited to the above shape, and a shape obtained by partially deforming the rectangle or a polygon other than the rectangle may be used. Although the fluid to be measured is air, a gas other than air, for example, a gas such as LP gas or city gas, or a liquid such as water may be used. Although the material of the flow path 6 is made of ABS resin, any material may be used as long as the material is not chemically changed by the fluid to be measured. If the fluid to be measured is LP gas, city gas, or the like, a metal such as SUS or aluminum die casting is used. But it doesn't matter. In general, the cross-sectional area of the flow rate measuring section is set to be approximately the same as the inner diameter of the pipe for supplying the fluid to be measured in order to reduce the pressure loss. However, the cross-sectional area may be increased or decreased as necessary. Absent.

The ultrasonic flow meter of the present invention may be used for an ultrasonic gas meter assuming a home gas meter or a flow meter for measuring the flow velocity of a fluid to be measured. It goes without saying that the configurations of a plurality of embodiments may be combined.

As described above, the first ultrasonic flowmeter of the present invention includes a pair of ultrasonic transducers, a measuring unit that measures the time that ultrasonic waves propagate between the pair of ultrasonic transducers, A calculation unit for calculating the amount of fluid flowing through the flow measurement unit based on the output, so that the effect of the reflected wave reflected by the wall surface of the flow measurement unit on the measurement result is reduced. Since the measurement unit and the pair of ultrasonic transducers are configured, the influence of the reflected wave in the flow measurement unit can be reduced, and a high-accuracy ultrasonic flowmeter can be obtained.

The second ultrasonic flowmeter is an ultrasonic flowmeter that measures the flow rate of a fluid using ultrasonic waves. In the ultrasonic flowmeter, a time period during which ultrasonic waves propagate between the pair of ultrasonic vibrators and the pair of ultrasonic vibrators is used. And a calculating unit for calculating the amount of fluid flowing through the flow measuring unit based on the output of the measuring unit, wherein the flow measuring unit reflects the flow rate without reflecting on the wall surface of the flow measuring unit. In a configuration in which the phase difference between the direct wave propagating in the fluid flowing through the measuring unit and the reflected wave reflected by the wall surface of the flow measuring unit affects the measurement result, the position of the direct wave and the reflected wave is Since the flow rate measuring unit and the pair of ultrasonic transducers are configured so that the influence of the phase difference on the measurement result is reduced, the influence of the reflected wave in the flow measuring unit can be reduced, and high accuracy can be achieved. A simple ultrasonic flowmeter can be obtained.

A third ultrasonic flowmeter is an ultrasonic flowmeter that measures the flow rate of a fluid using ultrasonic waves. In the ultrasonic flowmeter, a time period during which ultrasonic waves propagate between the pair of ultrasonic vibrators and the pair of ultrasonic vibrators is used. And a calculating unit for calculating the amount of fluid flowing through the flow measuring unit based on the output of the measuring unit, wherein the flow measuring unit reflects the flow rate without reflecting on the wall surface of the flow measuring unit. In a configuration in which the phase difference between the direct wave propagating in the fluid flowing through the measuring unit and the reflected wave reflected by the wall surface of the flow measuring unit affects the measurement result, the position of the direct wave and the reflected wave is As the effect of the phase difference on the measurement result is reduced, the frequency of the pair of ultrasonic transducers, the distance between the pair of ultrasonic transducers, and parameters related to the cross-sectional shape of the flow rate measurement unit. To be characterized by a combination of Can reduce the influence of the reflected wave in the flow measurement portion with a simple configuration, it is possible to obtain a high-precision ultrasonic flowmeter.

In a fourth ultrasonic flowmeter, in the third ultrasonic flowmeter, the direct wave is a wave that propagates along a straight line connecting the centers of the pair of ultrasonic transducers, and the reflected wave is A wave that propagates along the isosceles of an isosceles triangle formed by connecting the center of the pair of ultrasonic transducers and a point on the wall surface of the flow measurement unit, and the propagation distance of the direct wave and the Since the propagation phase difference resulting from the difference from the propagation distance of the reflected wave is 3π / 2 or more, the influence of the reflected wave in the flow measurement unit can be reduced with a simple configuration, and a highly accurate ultrasonic flowmeter can be obtained. it can.

In a fifth ultrasonic flowmeter, in the third ultrasonic flowmeter, the direct wave is a wave that propagates along a straight line connecting the centers of the pair of ultrasonic transducers, and the reflected wave is One of the effective radiating surfaces of the pair of ultrasonic transducers is a wave that is reflected only once by the wall surface of the flow measurement unit, and the shortest propagation time of the reflected wave is longer than the propagation time of the direct wave. Since the side or diameter is shorter than the height of the flow measurement unit, the influence of the reflected wave in the flow measurement unit can be reduced with a simple configuration, and a high-accuracy ultrasonic flow meter can be obtained.

In the sixth ultrasonic flowmeter, in the fourth or fifth ultrasonic flowmeter, since the frequency of the pair of ultrasonic transducers is set to a predetermined value or more, the reflected wave in the flow measurement unit is Since the influence can be reduced and the time resolution can be improved, a more accurate ultrasonic flowmeter can be obtained.

An ultrasonic flowmeter according to a seventh aspect is the ultrasonic flowmeter according to the third aspect, wherein the direct wave is a wave that propagates along a straight line connecting the centers of the pair of ultrasonic vibrators, and the reflected wave Is a wave propagating along the isosceles of an isosceles triangle formed by connecting the center of the pair of ultrasonic transducers and a point on the wall surface of the flow measurement unit, and the propagation distance of the direct wave And the propagation phase difference resulting from the difference between the propagation distance of the reflected wave and the propagation distance of the reflected wave is 0.2π or less. Therefore, the influence of the reflected wave in the flow measuring unit can be reduced with a simple configuration, and a high-accuracy ultrasonic flowmeter is obtained. be able to.

The eighth ultrasonic flowmeter is the seventh ultrasonic flowmeter, since the ultrasonic flowmeter further includes at least one or more dividing plates that divide the flow measuring unit into a plurality of parts. In addition, the influence of the reflected wave in the flow measuring unit can be reduced, and a high-accuracy ultrasonic flow meter can be obtained.

In the ninth ultrasonic flow meter, the frequency of the pair of ultrasonic vibrators is set to a predetermined value or less in the eighth ultrasonic flow meter, so that the influence of the reflected wave in the flow measuring unit is reduced. It is possible to obtain a high-accuracy ultrasonic flowmeter.

In a tenth ultrasonic flowmeter according to any one of the first to fifth and seventh ultrasonic flowmeters, a cross-sectional shape of the flow measuring unit is rectangular, and a parameter related to a cross-sectional shape of the flow measuring unit is Since it has a rectangular height, the influence of the reflected wave in the flow measuring unit can be reduced with a simple configuration, and a highly accurate ultrasonic flow meter can be obtained.

An eleventh ultrasonic flow meter is the ultrasonic flow meter according to any one of the first to fifth and seventh aspects, wherein a cross-sectional shape of the flow measuring unit is a circle, and a parameter related to a cross-sectional shape of the flow measuring unit is Because of the diameter of the circle, the influence of the reflected wave in the flow measuring unit can be reduced with a simple configuration, and a high-accuracy ultrasonic flow meter can be obtained.

An ultrasonic flowmeter according to a twelfth aspect is the ultrasonic flowmeter according to any one of the first to fifth and seventh aspects, wherein the pair of ultrasonic transducers has a line connecting the centers of the pair of ultrasonic transducers. Since it is arranged so as to be shifted with respect to the center line in a predetermined direction of the cross section of the flow measurement unit, the influence of the reflected wave in the flow measurement unit can be reduced, and a high-accuracy ultrasonic flow meter can be obtained.

In a thirteenth ultrasonic flow meter, in the twelfth ultrasonic flow meter, a line connecting the centers of the pair of ultrasonic transducers and a center line in a predetermined direction of a cross section of the flow measuring unit are parallel to each other. Therefore, the influence of the reflected wave in the flow measuring unit can be reduced, and a high-accuracy ultrasonic flow meter can be obtained.

In a fourteenth ultrasonic flowmeter, in the twelfth ultrasonic flowmeter, a line connecting the centers of the pair of ultrasonic transducers and a center line in a predetermined direction of a cross section of the flow measuring unit have a predetermined angle. Because of this, it is possible to reduce the influence of the reflected wave in the flow measuring unit, and to obtain a high-accuracy ultrasonic flow meter.

A fifteenth ultrasonic flowmeter is the first or second ultrasonic flowmeter, wherein the ultrasonic flowmeter prevents generation of a reflected wave that is reflected only once by a wall surface of the flow measurement unit. Is further provided, the influence of the reflected wave in the flow measurement unit can be reduced, and a highly accurate ultrasonic flowmeter can be obtained.

In a sixteenth ultrasonic flowmeter, in the fifteenth ultrasonic flowmeter, a line connecting a center of the pair of ultrasonic transducers and a center line in a predetermined direction of a cross section of the flow rate measurement unit have a predetermined angle. Because of this, it is possible to reduce the influence of the reflected wave in the flow measuring unit, and to obtain a high-accuracy ultrasonic flow meter.

A seventeenth ultrasonic flowmeter is the first or second ultrasonic flowmeter, wherein the ultrasonic flowmeter further includes at least one structure provided in the flow measurement unit. The influence of the reflected wave in the measuring section can be reduced, and a highly accurate ultrasonic flowmeter can be obtained.

An eighteenth ultrasonic flowmeter is the seventeenth ultrasonic flowmeter, wherein the at least one structure is disposed near the pair of ultrasonic vibrators, so that the reflected wave in the flow measurement unit is provided. Can be reduced, and a highly accurate ultrasonic flowmeter can be obtained.

A nineteenth ultrasonic flowmeter is the seventeenth ultrasonic flowmeter, wherein the at least one structure is disposed on a wall surface of the flow measurement unit, so that an influence of a reflected wave in the flow measurement unit is reduced. A high-accuracy ultrasonic flowmeter can be obtained.

An ultrasonic flowmeter according to a twentieth aspect of the present invention is the ultrasonic flowmeter according to the first or second aspect, wherein at least one concave or convex part is provided on a wall surface of the flow rate measuring unit. Therefore, the influence of the reflected wave in the flow measuring unit can be reduced, and a high-accuracy ultrasonic flow meter can be obtained.

A twenty-first ultrasonic flowmeter is the twentieth ultrasonic flowmeter, wherein the ultrasonic flowmeter further includes a mesh structure that covers the concave portion, so that an influence of a reflected wave in the flow measurement unit is reduced. A high-accuracy ultrasonic flowmeter can be obtained.

A twenty-second ultrasonic flow meter is the ultrasonic flow meter according to any one of the first to fifth and seventh aspects, wherein the pair of ultrasonic vibrators is a line connecting a center of the pair of ultrasonic vibrators and the pair of ultrasonic vibrators. Since at least one of the directivities of the ultrasonic transducers is arranged so as to form a predetermined angle with the direction indicating the directivity, it is possible to reduce the influence of the reflected wave in the flow measuring unit, and obtain a high-accuracy ultrasonic flow meter. be able to.

The twenty-third ultrasonic flow meter has a rectifier for adjusting a flow direction at least upstream of the flow measurement part in the first to twenty-second ultrasonic flow meters, and has a flow rectifier inside the flow measurement part. The direction can be made uniform, and a more accurate ultrasonic flowmeter can be obtained.

FIG. 2 is a configuration diagram of an ultrasonic flowmeter according to the first embodiment of the present invention. It is sectional drawing which looked at the a-a 'line in the same flow meter from the side. It is sectional drawing which looked at the b-b 'line in the same flow meter from the side. It is a figure showing a propagation path distribution calculation result of an ultrasonic wave in a flow measurement part. It is a figure showing a propagation path distribution calculation result of an ultrasonic wave in a flow measurement part. It is a figure showing a calculation result of a reception wave of an ultrasonic wave. It is a figure showing a calculation result of a reception wave of an ultrasonic wave. It is a characteristic view which shows the relative reception voltage in the same flowmeter. It is a characteristic view which shows the rate of change of the reception voltage in the same flowmeter. It is sectional drawing which looked at the a-a 'line of the ultrasonic flowmeter in Example 2 of this invention from the side. It is sectional drawing which looked at the b-b 'line in the same flow meter from the side. It is a characteristic view which shows the relative reception voltage in the same flowmeter. It is a characteristic view which shows the rate of change of the reception voltage in the same flowmeter. It is sectional drawing which looked at the a-a 'line of the ultrasonic flowmeter in Example 3 of this invention from the side. It is sectional drawing which looked at the b-b 'line in the same flow meter from the side. It is sectional drawing which looked at the b-b 'line of the ultrasonic flowmeter in Example 4 of this invention from the side. It is sectional drawing which looked at the b-b 'line of the ultrasonic flowmeter in Example 5 of this invention from the side. It is a top view of the ultrasonic flowmeter in Example 6 of this invention. It is sectional drawing which looked at the c-c 'line in the same flow meter from the side. It is sectional drawing which looked at the d-d 'line in the same flow meter from the side. It is sectional drawing which looked at the a-a 'line of the ultrasonic flowmeter in Example 7 of this invention from the side. It is sectional drawing which looked at the b-b 'line in the same flow meter from the side. It is sectional drawing which looked at the a-a 'line of the ultrasonic flowmeter in Example 8 of this invention from the side. It is sectional drawing which looked at the b-b 'line in the same flow meter from the side. It is sectional drawing which looked at the a-a 'line of the ultrasonic flowmeter in Example 9 of this invention from the side. It is sectional drawing which looked at the b-b 'line in the same flow meter from the side. It is sectional drawing which looked at the ultrasonic flowmeter in Example 10 of this invention from the top. It is a local sectional view showing the attachment state to the piping of the ultrasonic flowmeter in Example 11 of the present invention. It is a block diagram of the conventional ultrasonic flowmeter. It is a block diagram of the conventional ultrasonic flowmeter.

Claims (9)

In an ultrasonic flowmeter that measures the flow rate of a fluid using ultrasonic waves, a cross-sectional shape is rectangular, and a flow rate measurement unit through which the fluid flows, and a pair of ultrasonic transducers that transmit and receive ultrasonic waves propagating in the fluid And, a measuring unit that measures the time that ultrasonic waves propagate between the pair of ultrasonic transducers, and a calculating unit that calculates the amount of fluid flowing through the flow rate measuring unit based on the output of the measuring unit, The measurement result resulting from the difference between the propagation distance of the direct wave propagating in the fluid without being reflected on the wall surface of the flow measurement unit and the propagation distance of the reflected wave propagating in the fluid reflected by the wall surface of the flow measurement unit The flow rate measuring unit and the pair of ultrasonic transducers are arranged so that the influence thereof is reduced, the frequency of the pair of ultrasonic transducers, the distance between the pair of ultrasonic transducers, and the flow rate measuring unit. Related to the cross-sectional shape of The reflected wave is a wave that is reflected and propagated only once on the wall surface of the flow rate measuring unit, and the propagation phase difference is 3π / 2 or more. Total. In an ultrasonic flowmeter that measures the flow rate of a fluid using ultrasonic waves, a cross-sectional shape is rectangular, and a flow rate measurement unit in which the fluid flows, and an ultrasonic wave that is provided on a side wall of the flow path and propagates in the fluid. A pair of ultrasonic transducers to transmit and receive, a measuring unit that measures the time that ultrasonic waves propagate between the pair of ultrasonic transducers, and the amount of fluid flowing through the flow rate measuring unit based on the output of the measuring unit. And a calculating unit for calculating, the propagation distance of the direct wave propagating in the fluid without being reflected on the wall surface of the flow measurement unit and the propagation distance of the reflected wave propagating in the fluid reflected by the wall surface of the flow measurement unit. So as to increase the propagation phase difference resulting from the difference between the flow rate measurement unit and the pair of ultrasonic transducers, the flow rate in a direction perpendicular to the direction of transmitting and receiving ultrasonic waves and substantially parallel to the wall surface of the side wall part. Set the section height of the measuring section With, ultrasonic flow meter the pair of the frequency of the ultrasonic vibrator is set to a predetermined value or more. 3. The ultrasonic flowmeter according to claim 2, wherein the reflected wave is a wave that is reflected only once on the wall surface of the flow measurement unit and propagates, and the propagation phase difference is 3π / 2 or more. 4. The ultrasonic flowmeter according to claim 2, wherein the flow measurement unit includes at least one structure that sets the propagation phase difference to a desired magnitude. The ultrasonic flowmeter according to claim 4, wherein the structure is disposed near the pair of ultrasonic transducers. The ultrasonic flowmeter according to claim 4, wherein the structure is disposed on a wall surface of the flow measurement unit. The ultrasonic flowmeter according to claim 2, wherein at least one concave portion or convex portion is provided on a wall surface of the flow rate side portion. The ultrasonic flowmeter according to claim 7, further comprising a mesh structure that covers the recess. 3. The ultrasonic flowmeter according to claim 2, further comprising a rectification means for adjusting a flow direction at least on an upstream side of the flow measurement unit.

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