JP3907613B2 - Ultrasonic flow meter - Google Patents

Description

  The present invention relates to an ultrasonic flowmeter that measures the flow rate of a fluid using ultrasonic waves.

  A conventional ultrasonic flowmeter of this type is known, for example, in Japanese Patent Laid-Open No. 8-233628, and as shown in FIGS. 27A and 27B, ultrasonic vibration is generated in a part of a channel 1 having a rectangular cross section 4. The children 2 and 3 are arranged so as to face each other, and the propagation time until the ultrasonic wave transmitted from the ultrasonic vibrator 2 is received by the ultrasonic vibrator 3 and the ultrasonic wave transmitted from the ultrasonic vibrator 3 are ultrasonically vibrated. The flow rate calculation means 5 calculates the velocity of the fluid from the difference in propagation time until it is received by the child 2, and the flow velocity distribution in the flow path 1 is estimated from the Reynolds number of the fluid at that time, and the correction coefficient is obtained to calculate the flow rate. It was.

However, in the conventional ultrasonic flowmeter, since the propagation distance of the reflected wave reflected from the inner wall surface of the flow path and the direct wave propagating without being reflected is different, there is a phase difference between the reflected wave and the direct wave. As the received 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, and the period of the received wave changes. There was a problem that the range was narrowed.
JP-A-8-233628

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

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

  An ultrasonic flowmeter according to a first aspect of the present invention includes a pair of ultrasonic transducers, a measurement unit that measures the time during which ultrasonic waves propagate between the pair of ultrasonic transducers, and an output of the measurement unit. Based on the flow rate measurement unit, and the flow rate measurement unit so that the influence of the reflected wave reflected by the wall surface of the flow rate measurement unit on the measurement result is reduced. And the pair of ultrasonic transducers, the influence of the reflected wave in the flow rate measurement unit can be reduced, and a highly accurate ultrasonic flowmeter can be obtained.

  An ultrasonic flowmeter according to a second aspect of the present invention is an ultrasonic flowmeter that measures the flow rate of a fluid using ultrasonic waves, and an ultrasonic wave between a pair of ultrasonic transducers and the pair of ultrasonic transducers. A measurement unit that measures the time during which the flow is propagated, and a calculation unit that calculates the amount of fluid flowing through the flow rate measurement unit based on the output of the measurement unit, and the flow rate measurement unit reflects on the wall surface of the flow rate measurement unit The phase difference between the direct wave propagating in the fluid flowing through the flow rate measurement unit and the reflected wave reflected by the wall surface of the flow rate measurement unit affects the measurement result, and the direct wave and the reflection Since the flow measurement unit and the pair of ultrasonic transducers are configured so that the influence of the phase difference with the wave on the measurement result is reduced, the influence of the reflected wave in the flow measurement unit is reduced. A high-accuracy ultrasonic flowmeter can be obtained.

  An ultrasonic flowmeter according to a third aspect of the present invention is an ultrasonic flowmeter that measures the flow rate of a fluid using ultrasonic waves. An ultrasonic flowmeter is disposed between a pair of ultrasonic transducers and the pair of ultrasonic transducers. A measurement unit that measures the time during which the flow is propagated, and a calculation unit that calculates the amount of fluid flowing through the flow rate measurement unit based on the output of the measurement unit, and the flow rate measurement unit reflects on the wall surface of the flow rate measurement unit The phase difference between the direct wave propagating in the fluid flowing through the flow rate measurement unit and the reflected wave reflected by the wall surface of the flow rate measurement unit affects the measurement result, and the direct wave and the reflection 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 are reduced so that the influence of the phase difference with the waves on the measurement result is reduced. Characterized by combination with related parameters Because, it is possible to reduce the influence of the reflected wave at a flow rate 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 propagating along a straight line connecting the centers of the pair of ultrasonic transducers. 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 rate measuring unit, and the direct wave 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 high-accuracy ultrasonic waves 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 propagating 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 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 made shorter than the height of the flow measurement unit, the influence of reflected waves in the flow measurement unit can be reduced with a simple configuration, and a highly accurate ultrasonic flow meter can be obtained. .

 The ultrasonic flow meter according to the sixth aspect of the present invention is the ultrasonic flow meter according to the fourth or fifth aspect, wherein the frequency of the pair of ultrasonic transducers is set to a predetermined value or more, so that the flow measurement Since the influence of the reflected wave in the part 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 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 rate measuring unit, and the direct wave 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 rate measurement unit can be reduced with a simple configuration, and high-accuracy ultrasonic waves A flow meter can be obtained.

  An ultrasonic flow meter according to an eighth aspect of the present invention is the ultrasonic flow meter according to the seventh aspect, wherein the ultrasonic flow meter includes at least one or more divided plates that divide the flow rate measurement unit into a plurality of portions. Therefore, the influence of the reflected wave in the flow rate measurement unit can be reduced, and a highly accurate ultrasonic flow meter can be obtained.

  The ultrasonic flow meter according to the ninth aspect of the present invention is the ultrasonic flow meter 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 flow meter can be obtained.

 The 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 rate measurement unit is a rectangle, and the cross-sectional shape of the flow rate measurement unit 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.

  The 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 rate measurement unit is a circle, and the cross-sectional shape of the flow rate measurement unit Since the parameter related to is the diameter of the circle, 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 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 provide a propagation phase difference in reflected waves. In addition, since the straight line connecting the centers of the pair of ultrasonic transducers is arranged so as to shift with respect to the center line in the predetermined direction of the cross section of the flow rate measuring unit, the influence of the reflected wave in the flow rate measuring unit is reduced. An ultrasonic flowmeter with high accuracy can be obtained.

 An ultrasonic flow meter according to a thirteenth aspect of the present invention is the ultrasonic flow meter 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 parallel to each other, the influence of the reflected wave in the flow rate measuring unit can be reduced, and a highly accurate ultrasonic flow meter can be obtained.

  An ultrasonic flow meter according to a fourteenth aspect of the present invention is the ultrasonic flow meter 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 the cross section of the flow rate measurement unit Since it forms a predetermined angle, the influence of the reflected wave in the flow rate measuring unit can be reduced, and a highly accurate ultrasonic flow meter can be obtained.

  An ultrasonic flow meter according to a fifteenth aspect of the present invention is the ultrasonic flow meter according to the first or second aspect, wherein the ultrasonic flow meter is reflected only once by the wall surface of the flow rate measuring unit. Since the structure which prevents generation | occurrence | production of this is further provided, the influence of the reflected wave in a flow measurement part can be reduced, and a highly accurate ultrasonic flowmeter can be obtained.

  An ultrasonic flow meter according to a sixteenth aspect of the present invention is the ultrasonic flow meter 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 the cross section of the flow rate measurement unit Since it forms a predetermined angle, the influence of the reflected wave in the flow rate measuring unit can be reduced, and a highly accurate ultrasonic flow meter can be obtained.

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

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

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

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

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

  The ultrasonic flowmeter of the twenty-second aspect of the present invention is the ultrasonic flowmeter of the first or second aspect, wherein the pair of ultrasonic transducers is a line connecting the centers of the pair of ultrasonic transducers. Since the direction indicating at least one of the pair of ultrasonic transducers is arranged at a predetermined angle, the influence of the reflected wave in the flow rate measurement unit can be reduced, and the ultrasonic flow rate with high accuracy can be reduced. You can get a total.

  An ultrasonic flow meter according to a twenty-third aspect of the present invention is the ultrasonic flow meter according to any one of the first to fifth and seventh aspects, and has a rectifying means for adjusting the flow direction at least upstream of the flow rate measuring unit. Therefore, the flow direction in the flow rate measurement unit can be made uniform, and a more accurate ultrasonic flow meter can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, what attaches | subjects the same code | symbol in drawing is the same thing, and detailed description is abbreviate | omitted.

  FIG. 1 is a configuration diagram of an ultrasonic flowmeter according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the channel 6 of FIG. In FIG. 1, 6 is a flow path, 7 is a flow rate measurement unit, 8 and 9 are side wall portions of the flow path 6, and 10 and 11 are ultrasonic transducers attached to the side wall portions 8 and 9. A measurement unit 12 is connected to the ultrasonic transducers 10 and 11, and a calculation unit 13 is connected to the measurement unit 12. In FIG. 2, 14 is a lower plate portion of the flow path 6, and 15 is an upper plate portion connected to the side wall portions 8 and 9. The cross-sectional shape of the flow rate measuring unit 7 is rectangular, the width is W0, and the height is H0.

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

  The upper plate portion 15 is screwed to the end surfaces of the side wall portions 8 and 9 via a sealing material to constitute the flow rate measuring portion 7 having a rectangular cross section. Further, the ultrasonic transducers 10 and 11 are fixed to attachment ports 10a and 11a provided in the side wall portions 8 and 9 through a sealing material so that the transmission / reception surfaces face each other.

  The operation of the ultrasonic flowmeter configured as described above will be described. A distance connecting the centers of the ultrasonic transducer 10 and the ultrasonic transducer 11 is L, and an angle between the straight line and the longitudinal direction of the flow rate measuring unit 7 which is a flow direction is θ. Further, the velocity of sound in the windless state of the air to be measured is C, and the flow velocity of 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 transducer to be transmitted / received is switched, 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 Erasing the speed of sound C of air from the equation of t1 and t2,

The following equation is obtained. If L and θ are known, the flow velocity V can be obtained by measuring t1 and t2 in the measuring unit 12.

From this flow velocity V to the flow rate Q, if the cross-sectional area of the flow rate measurement unit 7 is S and the correction coefficient is K, the calculation unit 13
Q = KSV
To obtain the flow rate.

  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 of FIG.

Since the ultrasonic transducer 10 has directivity, the transmitted ultrasonic wave generally propagates through the flow rate measurement unit 7 while spreading. For this reason, the ultrasonic wave received by the ultrasonic transducer 11 is transmitted once on the inner wall surface of the upper plate 15 such as the direct wave propagating along the propagation path 17 in the flow rate measurement unit 7 and the propagation path 18, for example. There is a reflected wave that is reflected and received. Here, the propagation paths 17 and 18 are typical propagation paths, and there are direct waves other than the propagation path 17 and reflected waves other than the propagation path 18, for example, reflected waves that are reflected by the lower plate portion 14 and propagated. There is a reflected wave that is reflected not only once but also reflected twice or more. 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, there is a propagation distance difference between the direct wave and the reflected wave as indicated by the propagation paths 17 and 18. When 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 the propagation phase difference Δθ from the wavelength λ of the ultrasonic transducer,

Is obtained. Since there is a propagation phase difference in the ultrasonic wave propagating in the flow rate measuring unit 7 in this way, the received wave, which is a superposition of the direct wave and the reflected wave propagating through all propagation paths, is affected by 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 shape of the ultrasonic transducers 10 and 11 is square (constant), the distance between the ultrasonic transducers 10 and 11 is L, and the flow rate measurement unit 7 is composed of two infinitely wide parallel 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 ultrasonic wave is transmitted from the ultrasonic transducer 10 and received by the ultrasonic transducer 11. FIG. 4A and FIG. 4B show the calculation results for obtaining the propagation path distribution of ultrasonic waves. A direct wave is a solid line, a reflected wave of one reflection is a broken line, and a 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 path strength.

  The propagation path distribution of the direct wave does not change because the shape of the ultrasonic transducers 10 and 11 is constant. However, the propagation path distribution of the reflected wave once is wider than the direct wave and the propagation phase difference is wider. It shows a trend. The propagation path distribution of the reflected wave of the two-time reflection is wider than that of the one-time reflection. In addition, the distance at which the intensity of the direct wave is the largest is almost equal to the distance of the propagation path 17, and the distance at which the intensity of the reflected wave of the single reflection is the largest is also almost equal to the distance of the propagation path 18.

  Next, received waveforms calculated by adding the pulse response characteristics of the ultrasonic transducers 10 and 11 to the calculation results of FIGS. 4A and 4B are shown in FIGS. 5A and 5B. However, the frequency of the ultrasonic transducers 10 and 11 is 270 kHz, 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. The larger the propagation phase difference, the smaller the amplitude of the reflected wave once reflected. In addition, the reflected wave of the two-time reflection is smaller than the reflected wave of the one-time reflection. 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 inclination. Therefore, when considering all the propagation paths, the propagation phase difference is wide. And cancel each other due to interference between reflected waves.

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

  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. Furthermore, if the radiation surface of the ultrasonic transducer is made 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 transducers 10 and 11 is L, the effective radiation surface of the ultrasonic transducers 10 and 11 is square, the width is W0 (constant), and the height (H0 ) Is set so that the propagation phase difference between the propagation paths 17 and 18 is 0.7π to 2.2π, and experimental results using air are shown in FIGS. The frequency of the ultrasonic transducers 10 and 11 is 270 kHz.

  The horizontal axis of FIGS. 6 and 7 is the propagation phase difference between the direct wave propagation path 17 and the reflected wave propagation path 18 obtained by using (Equation 5). Note that λ is a wavelength at room temperature where the ultrasonic transducers 10 and 11 do not flow. The vertical axis in FIG. 6 is a relative received voltage of the received voltage measured by arranging the ultrasonic transducers 10 and 11 in the flow path 6 with respect to the received voltage measured by arranging in the open space. However, there is no flow. The vertical axis in FIG. 7 represents the rate of change in received voltage obtained by flowing about 6000 liters / hour with respect to the received voltage without flow.

  FIG. 6 shows that the received voltage without flow tends to be the smallest when the propagation phase difference is about π to 1.4π. As shown in FIG. 7, the rate of change in the received voltage due to the flow is the lowest in the received voltage when the propagation phase difference is about 0.8π to 1.2π, and the combination of transmission by the ultrasonic transducer 10 and reception by the ultrasonic transducer 11 is the smallest. On the other hand, the combination of transmission by the ultrasonic transducer 11 and reception by the ultrasonic transducer 10 has the highest received voltage. The phenomenon that the reception voltage increases in this way must occur if there is no phase effect in the superposition of the direct wave and the reflected wave.

  When the propagation phase difference is 3π / 2 or more, both the combination of transmission by the ultrasonic transducer 10 and reception by the ultrasonic transducer 11, the combination of transmission by the ultrasonic transducer 11 and reception by the ultrasonic transducer 10, both There is a tendency for the received voltage to decrease for both combinations. This is probably because the directivity of the ultrasonic transducer 10 and the ultrasonic transducer 11 is deflected by the flow.

  From the above results, since the influence of the reflected wave is large at the height (H0) where the propagation phase difference between the direct wave propagation path 17 and the reflected wave propagation path 18 is about 0.8π to 1.4π, it is possible to measure over a wide measurement range. It is difficult to measure the flow rate with high accuracy. On the other hand, 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 is about 3π / 2 or more, reflection is performed. The influence of waves can be reduced, and high-accuracy flow measurement over a wide measurement range is possible. Further, if the distance (L) and the height (H0) are constant, the propagation phase difference can be increased by setting the frequency of the ultrasonic transducers 10 and 11 higher, so that the flow rate can be measured with higher accuracy.

  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 path 17 and the propagation path 18 is 3π / 2 or more. By selecting the combination of the height (H0) of the flow rate measurement unit 7, the distance (L) of 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 measured over a wide range in a short time with high accuracy. Further, since the flow measuring unit 7 is not provided with a concave portion or a convex portion, the flow is not 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 the frequency of the ultrasonic transducers 10 and 11 may be selected.

  Hereinafter, Example 2 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 flowmeter according to the second embodiment of the present invention, as viewed from the side. FIG. 9 is a cross-sectional view of the flow path 6 taken along the line b-b ′. In FIG. 8, 14 and 15 are the side wall part, the lower plate part, and the upper plate part of the flow path 6, and the above is the same as the structure of FIG. In FIG. 9, reference numerals 10 and 11 denote ultrasonic transducers, which have the same configuration as that of FIG. The method for producing the flow path of the ultrasonic flowmeter configured as described above and the operating principle thereof are the same as those in the first embodiment, and are therefore omitted.

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

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

  The horizontal axes of FIGS. 10 and 11 represent the propagation phase difference between the direct wave propagation path 19 and the reflected wave propagation path 20 obtained using (Equation 5). Note that λ is a wavelength at room temperature where the ultrasonic transducers 10 and 11 do not flow. The vertical axis of FIG. 10 represents the relative received voltage of the received voltage measured by arranging the ultrasonic transducers 10 and 11 in the flow path 6 with respect to the received voltage measured by arranging them in the open space. However, there is no flow. The vertical axis in FIG. 11 represents the rate of change in received voltage obtained by flowing about 6000 liters / hour with respect to the received voltage without flow.

  In FIG. 10, the received voltage decreases as the propagation phase difference decreases. Since the effective radiation surfaces of the ultrasonic transducers 10 and 11 are constant, a part of the ultrasonic transducers 10 and 11 is blocked by the lower plate portion 14 and the upper plate portion 15 by reducing the height (H1). It is thought that it was because

  In FIG. 11, when the propagation phase difference is 0.2π or more, the transmission is performed by the ultrasonic transducer 10, the combination is received by the ultrasonic transducer 11, the transmission is transmitted by the ultrasonic transducer 11, and the combination is received by the ultrasonic transducer 10. There is a difference in the rate of change. On the other hand, when the propagation phase difference is 0: 2π or less, the transmission is transmitted by the ultrasonic transducer 10, the combination is received by the ultrasonic transducer 11, the transmission is transmitted by the ultrasonic transducer 11, and the combination is received by the ultrasonic transducer 10. The rate of change of is almost equal. The rate of change equalized in this way means that there is no phase effect on the overlap of the reflected wave with the direct wave, regardless of whether the propagation speed of the ultrasonic wave is faster or slower due to the flow. It is thought that the influence of the reflected wave on can be reduced.

  From the above results, the frequency of the ultrasonic transducers 10 and 11, the distance (L) of the ultrasonic transducers 10 and 11, and the high so that the propagation phase difference between the propagation path 19 and the propagation path 20 is about 0.2π or less. If the combination of (H1) is set, the influence of the reflected wave can be reduced, and high-accuracy flow rate measurement in a wide measurement range becomes possible. Further, if the distance (L) and the height (H1) are constant, the propagation phase difference can be made smaller by setting the frequency of the ultrasonic transducers 10 and 11 lower, so that the flow rate can be measured 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. However, 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.

  Embodiment 3 of the present invention will be described below with reference to the drawings.

  FIG. 12 is a cross-sectional view of the flow path 6 of the ultrasonic flowmeter according to the third embodiment of the present invention as seen from the side. In FIG. 12, 8, 9, 14, and 15 are the side wall part, lower plate part, and upper plate part of the flow path 6, and the above is the same as that of the structure of 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 to become divided flow rate measuring units 22a to 22c.

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

  First, an example of a method for producing the flow path 6 of the ultrasonic flowmeter will be briefly described. For example, with respect to the flow rate measuring unit 7 having an aspect ratio (W2 / H2) of 5 (height (H2) and width (W2)), SUS-made divided plates 21a and 21b having a thickness of 0.2 mm are connected to the lower plate 14. It fixes to the side wall parts 8 and 9 with an adhesive so that it may become parallel to an inner wall surface. After the divided plates 21a and 21b are fixed to the side wall portions 8 and 9, the upper plate portion 15 is screwed and fixed to the end surfaces of the side wall portions 8 and 9 through a sealing material. The height (H2a, H2b, H2c) is set so that the aspect ratio of the divided flow rate measuring units (22a, 22c) is about 20, and the aspect ratio of the divided flow rate measuring unit (22b) is about 17.

  Further, a propagation phase difference of about 0.04π is generated in the propagation path 23 and the propagation path 24 in the divided flow rate measurement unit (22b), and about 0.1π in the propagation path 25 and the propagation path 26 is generated in the divided flow rate measurement unit (22a). The distance (L) between the ultrasonic transducers 10 and 11 is selected so that a propagation phase difference of. 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 transducer to the ultrasonic flowmeter configured as described above and the operating principle thereof are the same as those in the first embodiment, and are therefore omitted.

  Next, 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 typical propagation paths, and there are propagation paths that are not shown in the same manner as in the first embodiment. FIG. 13 is a cross-sectional view of the channel 6 taken along the line b-b ′.

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

  The ultrasonic transducer 11 observes a combined wave of all direct waves and reflected waves propagating in the divided flow paths (H2a, H2b, H2c) as received waves. As shown in the second embodiment, 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 0.2π or less. The topological relationship of 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 shown in the above configuration, the flow measurement unit is divided into three parts, and the experimental result of flowing the fluid to be measured at about 6000 liters / hour shows that the ultrasonic transducer 10 transmits and the ultrasonic transducer 11 receives. It was confirmed that the rate of change of the combination and the rate of change of the combination in transmission by the ultrasonic transducer 11 and reception by the ultrasonic transducer 10 were almost equal.

 As described above, according to the present invention, by dividing the flow rate 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 measurement unit is divided into three parts. However, if the phase difference of the reflected wave with respect to the direct wave can be reduced, it may be divided into two parts or more than four parts, and the heights (H2a to H2c) are appropriately changed. You can set it. Further, although the ultrasonic wave propagates to all the divided flow rate measuring units, 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.

  Embodiment 4 of the present invention will be described below with reference to the drawings.

  FIG. 14 is a cross-sectional view of the b-b ′ line of the flow path 6 of the ultrasonic flowmeter according to the fourth embodiment of the present invention as viewed from the side. In FIG. 14, 8, 9, 14, and 15 are the side wall part, lower plate part, and upper plate part of the flow path 6, and the above is the same as the structure of FIG. 3 is different from the configuration of FIG. 3 in that the line 27 connecting the centers of the ultrasonic vibrators 10 and 11 and the center line 29 of the height (H3) are parallel and not on the same line. Is disposed on the side walls 8 and 9.

  In order to obtain a highly accurate flow meter, it is necessary to reduce the influence of the reflected wave, and it is considered to provide a propagation phase difference between the reflected wave from the inner wall surface of the lower plate portion 14 and the reflected wave from the upper plate portion 15. As one of the methods, the height (H3) of the flow rate measurement unit 28 is set so that the reflected wave from the inner wall surface of the lower plate portion 14 and the reflected wave from the upper plate portion 15 reach the ultrasonic transducer with different phases. A method of arranging the line 27 connecting the centers of the pair of ultrasonic transducers in parallel with respect to the center line 29 is selected.

  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 direct wave propagation path 27 and the reflected wave propagation path 30 at the lower plate portion 14 is 0.7π, and the propagation position between the propagation path 27 and the reflected wave propagation path 31 at the upper plate portion 15. The ultrasonic transducers 10 and 11 are screwed and fixed to the side wall portions 8 and 9 via a sealing material so that the phase difference is 2.2π. Further, the upper plate portion 15 is screwed and fixed to the end faces of the side wall portions 8 and 9 through a sealing material. 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. Since the operation principle of the ultrasonic flowmeter configured as described above is the same as that of the first embodiment, a description thereof will be omitted.

  Next, propagation of ultrasonic waves in the flow rate measuring unit 28 will be described using an example of a propagation path. The direct wave propagates along a line 27 that connects the centers, and the reflected wave has a propagation path 30 that is reflected by the inner wall surface of the lower plate portion 14 and a propagation path 31 that is reflected by the inner wall surface of the upper plate portion 15. Received in the vicinity of the center of the acoustic transducer 11. Note that the propagation paths of the direct wave and the reflected wave shown in the figure are typical propagation paths, and there are also propagation paths not shown in the same manner as in the first embodiment. When the line 27 connecting the centers and the center line 29 coincide with each other, the propagation distance between the propagation path 30 and the propagation path 31 is equal, so that no propagation phase difference occurs. However, if the line 27 connecting the centers and the center line 29 are not matched, a propagation phase difference occurs because the propagation distances of the propagation path 30 and the propagation path 31 are different. For this reason, the reflected waves are affected by interference, and the influence on the direct wave can be reduced.

  In an experiment conducted with air flowing at about 6000 liters / hour with the above 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 lower plate portion and the upper plate are arranged by shifting the line connecting the centers of the ultrasonic transducers in parallel to the center line of the height (H3) of the flow rate measuring portion. The propagation phase difference of the reflected wave reflected by the unit 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 with high accuracy in a short time.

  In the fourth embodiment, the propagation phase difference between the direct wave propagation path 27 and the reflected wave propagation path 30 at the lower plate portion 14 is 0.7π, and the reflected wave propagation path 31 at the propagation path 27 and the upper plate portion 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 arranged so as to be shifted in parallel so that the propagation phase difference between the two is 2.2π. It is not necessarily limited to the conditions, and can be appropriately changed.

  Embodiment 5 of the present invention will be described below with reference to the drawings.

  FIG. 15 is a cross-sectional view of the b-b 'line of the flow path 6 of the ultrasonic flowmeter according to the fifth embodiment of the present invention as viewed from the side. In FIG. 15, 8, 9, 14, and 15 are the side wall part, the lower plate part, and the upper plate part of the flow path 6, and the above is the same as the structure of FIG. The difference from the configuration of FIG. 3 is 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 measuring unit 36 are at a predetermined angle (θ4). The ultrasonic transducers 10 and 11 are arranged obliquely on the side wall portions 8 and 9.

  As in the fourth embodiment, in order to obtain a highly accurate flow meter, it is necessary to reduce the influence of the reflected wave, and the propagation wave from the inner wall surface of the lower plate portion 14 to the reflected wave from the upper plate portion 15 is propagated. Consider providing a phase difference. As one of the methods, the ultrasonic transducers 10 and 11 are arranged so that the line 32 connecting the centers of the pair of ultrasonic transducers and the center line 33 of the height (H4) have a predetermined angle (θ4). Selected method to do.

  Therefore, an example of a method for creating a flow path of the ultrasonic flowmeter configured as described above will be described. For example, the ultrasonic transducers 10 and 11 are placed on the side walls 8 and 9 so that 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). Secure with screws through the sealing material. Further, the upper plate portion 15 is screwed and fixed to the end faces of the side wall portions 8 and 9 through a sealing material. 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. Since the operation principle of the ultrasonic flowmeter configured as described above is the same as that of the first embodiment, a description thereof will be omitted.

  Next, propagation of ultrasonic waves in the flow rate measuring unit 36 will be described using an example of a propagation path. For example, the direct wave propagates along a line 32 connecting the centers. A propagation path 34 and a propagation path 35 radiated at the same angle 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 are considered as one of representative examples of reflected waves. Note that the propagation paths of the direct wave and the reflected wave shown in the figure are typical propagation paths, and there are also propagation paths not shown in the same manner as in the first embodiment. The ultrasonic wave propagating along the propagation path 34 is reflected by the lower plate part 14, and the ultrasonic wave propagating along the propagation path 35 is reflected by the upper plate part 15. The reflected waves propagating through the propagation path 34 and the propagation path 35 have a propagation phase difference because the propagation distances are different.

  When the line 32 connecting the centers and the center line 33 coincide with each other, the propagation distance between the propagation path 34 and the propagation path 35 is equal, so that no propagation phase difference occurs, and reception is performed 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 is generated.

  Furthermore, it is received at a different position of the ultrasonic transducer 11. For this reason, the reflected waves are affected by 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 conditions. The angle may be larger or smaller than 2.5 degrees.

  Embodiment 6 of the present invention will be described below with reference to the drawings.

  FIG. 16 is a top view of the flow path of the ultrasonic flowmeter according to the sixth embodiment of the present invention. FIG. 17 is a cross-sectional view of the flow path of FIG. 16 taken along the line c-c ′. FIG. 18 is a cross-sectional view of the flow path of FIG. 16 taken along the line d-d '. In each figure, 37 is a flow path, 38 is an upper plate portion of the flow path 37, and 39 is a mounting portion a of the ultrasonic transducer 10 provided on the upper plate portion 38. Reference numeral 40 denotes a lower plate portion of the flow path 37, 41 denotes a mounting portion b of the ultrasonic transducer 11 provided on the lower plate portion 40, 42 and 43 denote side wall portions of the flow path 37, and 44 denotes a flow rate measurement portion. is there.

  In order to obtain a highly accurate flow meter, it is necessary to reduce the influence of the reflected wave, and it is important to reduce the influence of the reflected wave of a single reflection among the reflected waves. In some cases, from the viewpoint of the flow velocity distribution, it is desired to increase the aspect ratio (W5 / H5) of the height (H5) and the width (W5). Therefore, a method of arranging a pair of ultrasonic transducers at a position where no reflection occurs once in the flow measurement unit 44 regardless of the shape of 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 with respect to the fluid to be measured.

  In this embodiment, since the fluid to be measured is air, for example, ABS resin is selected as the material. First, the attachment portion 39 is bonded and fixed to the upper plate portion 38 so that the angle (θ5) between the major axis direction of the upper plate portion 38 and the attachment direction d-d ′ of the ultrasonic transducer 10 is, for example, 30 degrees. The attachment portion 41 is bonded and fixed to the upper plate portion 40 so that the angle (θ5) between the major axis direction of the lower plate portion 40 and the attachment direction d-d ′ of the ultrasonic transducer 11 is also 30 degrees. The upper plate portion 38 is screwed to the end faces of the side wall portions 42 and 43 via a sealant to form a flow rate measuring portion 44 having a rectangular cross-sectional shape. Next, the attachment portions 39 and 41 are arranged so that the angle (θ6) 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 ′ section is 30 degrees. The ultrasonic transducers 10 and 11 are fixed via the sealing materials 45 and 46.

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

  Next, propagation of ultrasonic waves in the flow rate measurement unit 44 will be described using propagation paths 47 to 49 as shown in FIG. Propagation paths 47 to 49 are typical 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, ultrasonic waves that propagate along the propagation paths 48 and 49 also exist. However, the ultrasonic wave propagated along the propagation path 48 is reflected by the lower plate part 40 and then reflected once again by the wall surface of the flow rate measuring part 44 and cannot reach the ultrasonic transducer 11. Further, the ultrasonic wave propagated along the propagation path 49 is also reflected by the side wall portion 42 and then reflected once again by the wall surface of the flow rate measuring unit 44 and cannot reach the ultrasonic transducer 11. In the ultrasonic transducers 10 and 11 arranged in such a positional relationship, there is no reflected wave reflected and received only once by the flow rate measuring unit 44. As a result, the reflected wave that affects the direct wave is reflected twice or more, and the influence of the reflected wave that is reflected twice or more on the direct wave is considerably smaller than the reflected wave of the single reflection. Can be reduced.

  In the experimental result 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 Example 1 is equivalent to 2.2π. It was confirmed. From this result, there is a pair of angles at positions where the major axis direction of the flow path 37 and the height (H5) direction of the flow rate measurement unit 44 have angles (θ5, θ6) and no reflected wave of one-time reflection occurs. 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 measuring unit 44.

  In Example 6, the angle (θ5) between the major axis direction of the flow path 37 and the attachment direction dd ′ of the ultrasonic transducer is 30 degrees, and the height (line 47) connecting the centers of the pair of ultrasonic transducers ( Although the angle (θ6) formed with the center line of H5) is inclined by 30 degrees, it is not limited to the above conditions, and can be configured by changing to an appropriate angle.

  Embodiment 7 of the present invention will be described below 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 as viewed from the side. In FIG. 19, 8, 9, 14, and 15 are the side wall part, the lower plate part, and the upper plate part of the flow path 6, and the above is the same as the structure of FIG. 2 is that the structures 50 and 51 having dimensions that do not divide the flow rate measuring unit 52 into layers are arranged on the side wall portions 8 and 9.

 In order to reduce the influence of the reflected wave, consider a method of providing a reflecting plate 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.

  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 transducer 10 is configured so that two SUS structures 50 a and 50 b 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 part 14. It fixes to the side wall part 8 by which an adhesive is arrange | positioned with an adhesive agent. Similarly, the structural bodies 51a and 51b are also fixed to the side wall portion 9 where the ultrasonic transducer 11 is disposed with an adhesive. After the structure 50 and the structure 51 are fixed to the side wall portions 8 and 9, the upper plate portion 15 is screwed and fixed to the end surfaces of the side wall portions 8 and 9 through a sealing material. 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 transducer to the ultrasonic flowmeter configured as described above and the operating principle thereof are the same as those in the first embodiment, and are therefore omitted.

  Next, propagation of ultrasonic waves in the flow rate measuring unit 52 will be described using propagation paths 53 and 54 as shown in FIG. The propagation paths 53 and 54 are typical propagation paths, and there are also propagation paths that are not shown in the same manner as in the first embodiment. FIG. 20 is a cross-sectional view of the channel 6 taken along the line b-b ′. The direct wave propagates along the propagation path 53. Further, the reflected wave propagates while being repeatedly reflected by the structure 50 a and the lower plate portion 14 like the propagation path 54. The reflected wave propagating through the propagation path 54 has a propagation distance longer than that of the propagation path that is reflected only once by the upper plate portion 15. There is also a propagation path of a reflected wave (not shown) that is blocked by the structure 51. For this reason, it becomes possible to reduce the influence of the reflected wave on the direct wave.

  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 Example 7, the thickness of the structure is 0.2 mm, the length (L6) is 7 mm, and the product is SUS. However, the structure is not limited to the above-described conditions, and the structure and the material can be appropriately changed. . In addition, the structural bodies 50 and 51 are bonded and fixed to the side wall portions 8 and 9, but they may be disposed in places other than the side wall portions 8 and 9. Although the total number of structures is four, any number may be used as long as it is one or more.

  Embodiment 8 of the present invention will be described below with reference to the drawings.

  FIG. 21 is a cross-sectional view of the a-a ′ line of the flow channel 6 of the ultrasonic flowmeter according to the eighth embodiment of the present invention as seen from the side. In FIG. 21, 8, 9, 14, and 15 are the side wall part, the lower plate part, and the upper plate part of the flow path 6, and the above is the same as the structure 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 measurement unit 56 into layers are arranged in the lower plate unit 14 and the upper plate unit 15.

  In order to obtain a highly accurate flow meter, it is necessary to reduce the influence of the reflected wave, and a method of providing a reflector on the flow rate measuring unit 56 so that the reflected wave is difficult to receive will be considered.

  An example of a method for creating a flow path of the ultrasonic flowmeter configured as described above will be described. For example, the 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 portion 14 and the upper plate portion 15, and the width (W7). Fix it with an adhesive so that it is around the center of the. After the structural body 55 is fixed, the upper plate portion 15 is screwed and fixed to the end surfaces of the side wall portions 8 and 9 through a sealing material. 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 transducer to the ultrasonic flowmeter configured as described above and the operating principle thereof are the same as those in the first embodiment, and are therefore omitted.

  Next, propagation of ultrasonic waves in the flow rate measurement unit 56 will be described using propagation paths 57 and 58 as shown in FIG. Note that the propagation paths 57 and 58 are typical propagation paths, and there are also propagation paths not shown in the same manner as in the first embodiment. FIG. 22 is a cross-sectional view of the channel 6 taken along the line b-b ′. The ultrasonic wave transmitted from the ultrasonic transducer 10 propagates while spreading. For example, a direct wave propagates along the propagation path 57. The spread ultrasonic waves are reflected by the upper plate portion 15 and the lower plate portion 14 and are received as reflected waves by the ultrasonic transducer 11. However, by providing the structural body 55a on the upper plate portion 15, for example, the reflected wave of the propagation path 58 is inhibited from propagating by the structural body 55a. For this reason, 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, since the propagation of a part of the reflected wave can be inhibited by the structures 55a and 55b, 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. The flow rate can be measured with high accuracy in a short time.

  In Example 8, the thickness of the structural bodies 55a and 55b is 0.2 mm, the length (L7) is 1 mm, made of SUS, and is located around the center of the width (W7), but is not limited to the above conditions. The size, position, and material can be appropriately changed. Further, although the structural bodies 55a and 55b are bonded and fixed on the lower plate portion 10 and the upper plate portion 15, they may be disposed in places other than the lower plate portion 14 and the upper plate portion 15. In addition, although two structural bodies are arranged, any number may be used as long as the number is one or more.

  Embodiment 9 of the present invention will be described below with reference to the drawings.

  FIG. 23 is a cross-sectional view of the a-a ′ line of the flow channel 6 of the ultrasonic flowmeter according to the ninth embodiment of the present invention as viewed from the side. In FIG. 23, 8, 9, 14, and 15 are the side wall part, lower board part, and upper board part of the flow path 6, and the above is the same as that of the structure of FIG. The difference from the configuration of FIG. 2 is that a recess 59 is provided in the lower plate portion 14 and a mesh structure 60 is provided above the recess 59.

  In order to reduce the influence of the reflected wave while increasing the aspect ratio (W8 / H8) between the height (H8) and the width (W8) of the flow rate measuring unit 61, the flow rate measuring unit 61 is provided with a recess and further flows into the recess. Consider a method of providing a mesh structure so as not to disturb.

  An example of a method for creating a flow path of the ultrasonic flowmeter configured as described above will be described. For example, in the vicinity of the center of the lower plate part 14 of the flow rate measuring unit 61 having an aspect ratio (W8 / H8) of 5, a recess 59 is used by using a milling machine so that the propagation phase difference between the propagation path 62 and the propagation path 63 is 2.2π. Constitute. The mesh structure is fixed upward so as to cover the recess 59 so that the flow of air, which is the fluid to be measured, does not occur in the recess 59.

  For example, the mesh size is about 100 so that the ultrasonic wave can be transmitted through the mesh structure. Further, the upper plate portion 15 is screwed and fixed to the end surfaces of the side wall portions 8 and 9 with a sealing material 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 transducer to the ultrasonic flowmeter configured as described above and the operating principle thereof are the same as those in the first embodiment, and are therefore omitted.

  Next, the propagation of ultrasonic waves in the flow rate measuring 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 at the lower plate portion 14 is reflected and propagated at the bottom of the recess 59 like the propagation path 63. The reflected wave at the upper plate portion 15 is reflected and propagates like a propagation path 64. The propagation paths 62 to 64 are typical propagation paths, and there are also propagation paths that are not shown in the same manner as in the first embodiment. There are also reflected waves that do not pass through the mesh structure 60 and are reflected by the surface of the mesh structure 60.

  Since the propagation phase difference between the propagation path 62 and the propagation path 63 is 2.2π and the propagation phase difference between the propagation path 62 and the propagation path 64 is 1.2π, the propagation path distribution of each reflected wave is different, and the lower plate portion 14 and Reflected waves from the upper plate portion 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. Moreover, since the mesh structure 60 is provided in the recessed part 59, air flows through the flow rate measuring unit 61 excluding the recessed part 59, and does not disturb the flow. Further, the ultrasonic wave can propagate through the flow rate measuring unit 61 including the recess 59.

  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 size by the structure, and a stable flow velocity distribution can be realized in the measurement flow rate range. The flow rate of the fluid to be measured can be measured with high accuracy in a short time.

  In the ninth embodiment, the concave portion 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-described conditions, and can be appropriately changed. . In addition, although about 100 mesh structures 60 are provided above the recesses 59, other mesh structures may be used. If the recesses 59 do not affect the flow in terms of measurement, they need not be provided. In addition, the concave portion 59 is provided near the center of the lower plate portion 14, but it may be provided in a necessary number in a necessary place in order 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.

  Hereinafter, Example 10 of this invention is described, referring drawings.

  FIG. 25 is a cross-sectional view of the flow path 6 of the ultrasonic flowmeter according to the tenth embodiment of the present invention as viewed from above. In FIG. 25, 6 is a flow path, 8 and 9 are side walls of the flow path 6, and the above is the same as the structure of FIG. The difference from the configuration of FIG. 1 is that the center direction 66 of the ultrasonic transducer 10 is θ10 (about 5 degrees) upstream of the line 65 connecting the centers of the ultrasonic transducers 10 and 11, and the ultrasonic transducer 11 The center direction 67 is shifted from the downstream side by θ11 (about 5 degrees). Since the method for creating the flow path, the method for attaching the ultrasonic transducer, and the operating principle are the same as those in the first embodiment, the description thereof is omitted. The distance between the ultrasonic transducers 10 and 11, the radiation surface shape, and the frequency fluid to be measured are the same as those in the first embodiment.

  In general, the directivity of an ultrasonic transducer tends to be strong in the central direction of the ultrasonic transducer.

  For this reason, in the open space, when the directivities of the ultrasonic transducers 10 and 11 are made to coincide with each other, the reception voltage can be maximized. However, when ultrasonic waves are transmitted and received in a closed space such as the flow path 6, the received reflected wave is also a portion having a relatively strong directivity, so that the received voltage becomes a large reception voltage and the influence on the direct wave is increased. Therefore, the ultrasonic transducers 10 and 11 are arranged by shifting the central directions 66 and 67 by θ10 and θ11 with respect to the line 65 connecting the centers. In such an arrangement, the reception voltage of the direct wave is lowered, but the reflected wave becomes a relatively weak directivity portion, so the reception voltage of the reflected wave is also reduced, and the influence of the reflected wave can be reduced.

  In the same manner as in Example 1, the center direction 66 of the ultrasonic transducer 10 is shifted to the downstream side, and the center direction 67 of the ultrasonic transducer 11 is shifted to the upstream side by about 6000 liters / hour as in the first embodiment. In the experiment, the result that the propagation phase difference of FIG. 7 is about 2π was obtained.

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

  In Example 10, the ultrasonic transducer center directions 66 and 67 are shifted by 5 degrees with respect to the line connecting the centers of the 65 ultrasonic transducers. However, the present invention is not limited to the above conditions, and the angle is appropriately changed. Can be configured. In addition, the direction in which the center lines of the ultrasonic transducers 10 and 11 are shifted is the upstream side and the downstream side of the flow, but any combination of the lower plate direction and the upper plate portion direction may be used.

  Embodiment 11 of the present invention will be described below with reference to the drawings.

  FIG. 26 is a local cross-sectional view showing a state in which the ultrasonic flowmeter according to the eleventh embodiment of the present invention is attached to a pipe. In FIG. 26, 10a and 11a are attachment ports, 14 and 15 are the lower plate portion and upper plate portion of the flow path 6, 68 is a rectifying means, 69 is a flow rate measuring portion, and 70 and 71 are pipes. The configuration of the flow rate measuring unit 69 (not shown) is the same as that of any one of the first to tenth embodiments. The difference from the first embodiment to the tenth embodiment is that the flow measuring unit 69 is provided with a rectifying means 68. For example, the rectifying means 68 is made of an aluminum honeycomb structure, and is bonded and fixed to the lower plate portion 14 and 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 transducer, and the operating principle are the same as those in the first embodiment, and will not be described.

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

  Therefore, a rectifying means 68 having a honeycomb structure is provided to stabilize the flow of air flowing from the pipe 70 into the flow rate measuring unit 69. The flow direction of the air that has passed through the rectifying means 68 is made uniform, 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 wave in the first to tenth embodiments is reduced. By combining with the means to perform, the flow rate of the measurement fluid can be measured with high accuracy in a short time.

  In the eleventh embodiment, the rectifying means 68 is made of an aluminum honeycomb structure. However, if the rectifying effect is obtained, it may be a pipe, a mesh structure, a flat plate, or a metal, resin, or composite such as SUS. I do not care. Although the pipes 70 and 71 are attached vertically to the upper plate portion 15, they may be attached to portions other than the upper plate portion 15 or may be attached horizontally. 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 ultrasonic transducers 10 and 11 are shown to be equal, but the heights (H0, H1, H2, From H6), the height of the ultrasonic transducers 10 and 11 may be lowered or increased.

  In the first to fifth and seventh to eleventh embodiments, the ultrasonic transducers 10 and 11 are provided on the side wall portions 8 and 9 obliquely with respect to the flow. You may arrange | position and may arrange | position in the position parallel to a flow. Although the cross-sectional shape of the flow rate measuring unit is rectangular, it may be circular or elliptical if the ultrasonic transducers 10 and 11 are arranged at positions parallel to the flow.

  In the first to eleventh embodiments, the effective radiation surfaces of the ultrasonic transducers 10 and 11 are square, but are not limited to the above conditions, and may be circular, elliptical, or other polygonal shapes. Moreover, although the frequency of the ultrasonic transducers 10 and 11 is 270 kHz, it is not limited to the above condition, and may be 270 kHz or higher or lower. Moreover, although the cross-sectional shape of the flow rate measuring unit is rectangular, it is not limited to the above shape, and a shape obtained by deforming a part of the rectangle or a polygon other than the rectangle may be used. Although the fluid to be measured is air, it may be a gas other than air, such as LP gas or city gas, or a liquid such as water. In addition, although the material of the flow path 6 is ABS resin, any material can be used as long as it is not subject to chemical change by the fluid to be measured. If the fluid to be measured is LP gas, city gas, etc., metal such as SUS or aluminum die casting It doesn't matter. In order to reduce the pressure loss, the cross-sectional area of the flow rate measuring unit is generally set to be approximately the same as the inner diameter of the pipe supplying the fluid to be measured. 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 household gas meter or a flow meter for measuring the flow velocity of a fluid to be measured. Needless to say, 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 measurement unit that measures the time during which ultrasonic waves propagate between the pair of ultrasonic transducers, A calculation unit that calculates the amount of fluid flowing through the flow rate measurement unit based on the output, and the flow rate is reduced so that the influence of the reflected wave reflected by the wall surface of the flow rate 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 rate measurement unit can be reduced, and a highly accurate ultrasonic flowmeter can be obtained.

  The second ultrasonic flowmeter is an ultrasonic flowmeter that measures the flow rate of fluid using ultrasonic waves, and a time during which ultrasonic waves propagate between the pair of ultrasonic transducers and the pair of ultrasonic transducers. And a calculation unit for calculating the amount of fluid flowing through the flow rate measurement unit based on the output of the measurement unit, the flow rate measurement unit without reflecting on the wall surface of the flow rate measurement unit The phase difference between the direct wave propagating in the fluid flowing through the measurement unit and the reflected wave reflected by the wall surface of the flow rate measurement unit affects the measurement result. Since the flow measurement 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 measurement unit can be reduced, and high accuracy An ultrasonic flowmeter can be obtained.

  The third ultrasonic flowmeter is an ultrasonic flowmeter that measures the flow rate of fluid using ultrasonic waves, and a time during which ultrasonic waves propagate between the pair of ultrasonic transducers and the pair of ultrasonic transducers. And a calculation unit for calculating the amount of fluid flowing through the flow rate measurement unit based on the output of the measurement unit, the flow rate measurement unit without reflecting on the wall surface of the flow rate measurement unit The phase difference between the direct wave propagating in the fluid flowing through the measurement unit and the reflected wave reflected by the wall surface of the flow rate measurement unit affects the measurement result. Parameters related to 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 so that the influence of the phase difference on the measurement result is reduced. To be characterized by a combination of In easy Do construction can reduce the influence of the reflected wave in the flow measurement section, it is possible to obtain a high-precision ultrasonic flowmeter.

  Further, the fourth ultrasonic flowmeter is the third ultrasonic flowmeter, wherein the direct wave is a wave propagating along a straight line connecting the centers of the pair of ultrasonic transducers, 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 rate 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 flow meter can be obtained. it can.

  Further, the fifth ultrasonic flowmeter is the third ultrasonic flowmeter, wherein the direct wave is a wave propagating along a straight line connecting the centers of the pair of ultrasonic transducers, and the reflected wave is One of the effective radiation surfaces of the pair of ultrasonic transducers is a wave that is reflected only once by the wall surface of the flow rate measuring unit and has a minimum propagation time of the reflected wave longer than a propagation time of the direct wave. Since the side or diameter is made shorter than the height of the flow measurement unit, the influence of reflected waves in the flow measurement unit can be reduced with a simple configuration, and a highly accurate ultrasonic flow meter can be obtained.

  Further, the sixth ultrasonic flow meter is the fourth or fifth ultrasonic flow meter, and the frequency of the pair of ultrasonic transducers is set to a predetermined value or higher, so that the reflected wave in the flow measurement unit 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 third ultrasonic flowmeter, wherein the direct wave is a wave propagating along a straight line connecting the centers of the pair of ultrasonic transducers, and the reflected wave Is a wave propagating along the isosceles of the isosceles triangle formed by connecting the center of the pair of ultrasonic transducers and the point on the wall surface of the flow rate measuring unit, and the propagation distance of the direct wave The propagation phase difference resulting from the difference between the reflected wave and the propagation distance of the reflected wave is 0.2π or less, so that the influence of the reflected wave in the flow measurement unit can be reduced with a simple configuration, and a highly accurate ultrasonic flowmeter is obtained. be able to.

  In addition, the eighth ultrasonic flow meter is the seventh ultrasonic flow meter, and the ultrasonic flow meter further includes at least one dividing plate that divides the flow rate measuring unit into a plurality of portions. The influence of the reflected wave in the flow rate measuring unit can be reduced, and a highly accurate ultrasonic flow meter can be obtained.

  The ninth ultrasonic flowmeter is the eighth ultrasonic flowmeter, and the frequency of the pair of ultrasonic transducers is set to a predetermined value or less, so that the influence of the reflected wave in the flow measurement unit is reduced. And a high-accuracy ultrasonic flowmeter can be obtained.

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

  The eleventh ultrasonic flowmeter is any one of the first to fifth and seventh ultrasonic flowmeters, and the cross-sectional shape of the flow rate measurement unit is a circle, and the parameters related to the cross-sectional shape of the flow rate measurement unit are Since the diameter is a circle, the influence of the reflected wave in the flow rate measurement unit can be reduced with a simple configuration, and a highly accurate ultrasonic flow meter can be obtained.

  The ultrasonic flowmeter of the twelfth aspect is the ultrasonic flowmeter of any one of the first to fifth and seventh, wherein the pair of ultrasonic transducers has a line connecting the centers of the pair of ultrasonic transducers. Since it arrange | positions so that it may shift with respect to the centerline of the predetermined direction of the cross section of a flow measurement part, the influence of the reflected wave in a flow measurement part can be reduced, and a highly accurate ultrasonic flowmeter can be obtained.

  Further, the thirteenth ultrasonic flowmeter is the twelfth ultrasonic flowmeter, wherein a line connecting the centers of the pair of ultrasonic transducers and a center line in a predetermined direction of the cross section of the flow rate measuring unit are parallel to each other. Therefore, the influence of the reflected wave in the flow rate measurement unit can be reduced, and a highly accurate ultrasonic flow meter can be obtained.

  Further, the fourteenth ultrasonic flowmeter is the twelfth ultrasonic flowmeter, wherein a line connecting the centers of the pair of ultrasonic transducers and a central line in a predetermined direction of the cross section of the flow rate measuring unit form a predetermined angle. Therefore, the influence of the reflected wave in the flow rate measurement unit can be reduced, and a highly accurate ultrasonic flow meter can be obtained.

  Further, the fifteenth ultrasonic flow meter is the first or second ultrasonic flow meter, and the ultrasonic flow meter is configured to prevent generation of a reflected wave that is reflected only once by the wall surface of the flow measuring unit. Therefore, the influence of the reflected wave in the flow rate measurement unit can be reduced, and a highly accurate ultrasonic flow meter can be obtained.

  The sixteenth ultrasonic flowmeter is the fifteenth ultrasonic flowmeter, wherein a line connecting the centers of the pair of ultrasonic transducers and a central line in a predetermined direction of the cross section of the flow rate measuring unit form a predetermined angle. Therefore, the influence of the reflected wave in the flow rate measurement unit can be reduced, and a highly accurate ultrasonic flow meter can be obtained.

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

  The eighteenth ultrasonic flowmeter is the seventeenth ultrasonic flowmeter in which the at least one structure is disposed in the vicinity of the pair of ultrasonic transducers, and therefore the reflected wave in the flow measurement unit. Therefore, a highly accurate ultrasonic flowmeter can be obtained.

  Further, the 19th ultrasonic flowmeter is the 17th ultrasonic flowmeter, wherein the at least one structure is arranged on the wall surface of the flow rate measuring unit, and therefore the influence of the reflected wave in the flow rate measuring unit is reduced. An ultrasonic flowmeter with high accuracy can be obtained.

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

  The twenty-first ultrasonic flowmeter is the twentieth ultrasonic flowmeter, and the ultrasonic flowmeter further includes a mesh structure that covers the concave portion. An ultrasonic flowmeter with high accuracy can be obtained.

  The twenty-second ultrasonic flowmeter may be any one of the first to fifth and seventh ultrasonic flowmeters, and the pair of ultrasonic transducers may include a line connecting a center of the pair of ultrasonic transducers and the pair of ultrasonic transducers. Since the ultrasonic transducer is arranged so as to form a predetermined angle with the direction of directivity of at least one of the ultrasonic transducers, it is possible to reduce the influence of the reflected wave in the flow measurement unit and obtain a highly accurate ultrasonic flow meter be able to.

  Further, the 23rd ultrasonic flow meter has a rectifying means for adjusting the flow direction at least upstream of the flow rate measurement unit in the first to 22nd ultrasonic flow meters, The direction can be made uniform, and an ultrasonic flowmeter with higher accuracy can be obtained.

FIG. 1 is a configuration diagram of an ultrasonic flowmeter according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view of the flow meter as seen from the side along the line a-a ′. FIG. 3 is a cross-sectional view of a b-b ′ line of the flow meter as viewed from the side. FIG. 4A is a diagram showing a calculation result of an ultrasonic propagation path distribution in the flow rate measurement unit. FIG. 4B is a diagram showing the calculation result of the propagation path distribution of ultrasonic waves in the flow rate measuring unit. FIG. 5A is a diagram illustrating a calculation result of an ultrasonic wave. FIG. 5B is a diagram illustrating a calculation result of an ultrasonic wave reception. FIG. 6 is a characteristic diagram showing a relative received voltage in the flow meter. FIG. 7 is a characteristic diagram showing the rate of change in received voltage in the same flow meter. FIG. 8 is a cross-sectional view of the ultrasonic flowmeter according to the second embodiment of the present invention as seen from the side along the line a-a ′. FIG. 9 is a cross-sectional view of the flow meter as viewed from the b-b ′ line. FIG. 10 is a characteristic diagram showing a relative received voltage in the flow meter. FIG. 11 is a characteristic diagram showing the rate of change in received voltage in the same flow meter. FIG. 12 is a cross-sectional view of the ultrasonic flowmeter according to the third embodiment of the present invention as seen from the side along the line a-a ′. FIG. 13 is a cross-sectional view of a b-b ′ line of the flow meter as viewed from the side. FIG. 14 is a cross-sectional view of the ultrasonic flowmeter according to the fourth embodiment of the present invention as viewed from the b-b ′ line. FIG. 15 is a cross-sectional view of the ultrasonic flowmeter according to the fifth embodiment of the present invention as viewed from the b-b ′ line. FIG. 16 is a top view of the ultrasonic flowmeter according to the sixth embodiment of the present invention. FIG. 17 is a cross-sectional view of a c-c ′ line of the flow meter as viewed from the side. FIG. 18 is a cross-sectional view of the d-d ′ line of the flow meter as viewed from the side. FIG. 19 is a cross-sectional view of the ultrasonic flowmeter according to the seventh embodiment of the present invention as viewed from the side along the line a-a ′. FIG. 20 is a cross-sectional view of a b-b ′ line of the flow meter as viewed from the side. FIG. 21 is a cross-sectional view of the ultrasonic flowmeter according to the eighth embodiment of the present invention as seen from the side along the line a-a ′. FIG. 22 is a cross-sectional view of a b-b ′ line of the flow meter as viewed from the side. FIG. 23 is a cross-sectional view of the ultrasonic flowmeter according to the ninth embodiment of the present invention as viewed from the side along the line a-a ′. FIG. 24 is a cross-sectional view of the flow meter as viewed from the b-b ′ line. FIG. 25 is a cross-sectional view of the ultrasonic flowmeter according to the tenth embodiment of the present invention as viewed from above. FIG. 26 is a local cross-sectional view showing a state in which the ultrasonic flowmeter according to the eleventh embodiment of the present invention is attached to a pipe. FIG. 27A is a configuration diagram of a conventional ultrasonic flowmeter. FIG. 27B is a configuration diagram of a conventional ultrasonic flowmeter.

Explanation of symbols

7 Flow measurement unit 10 Ultrasonic transducer 11 Ultrasonic transducer 12 Measurement unit 13 Calculation unit

Claims (3)

In an ultrasonic flowmeter that measures the flow rate of fluid using ultrasonic waves,
A flow rate measurement unit through which a fluid flows; a pair of ultrasonic transducers that transmit and receive ultrasonic waves propagating in the fluid; a measurement unit that measures a time during which ultrasonic waves propagate between the pair of ultrasonic transducers; A calculation unit that calculates the amount of fluid flowing through the flow rate measurement unit based on the output of the measurement unit;
The pair of ultrasonic transducers is a received wave obtained by superimposing a direct wave propagating in the fluid without reflecting on the wall surface of the flow rate measuring unit and a reflected wave reflected on the wall surface of the flow rate measuring unit and propagating in the fluid. Is placed in a relationship to receive
In order to provide a propagation phase difference in the reflected wave, a straight line connecting the centers of the pair of ultrasonic transducers is configured to shift with respect to the center line of the cross section of the flow rate measurement unit, and at least upstream of the flow rate measurement unit With rectifying means to adjust the flow direction
The ultrasonic flowmeter which reduced the influence with respect to a direct wave by raising the interference effect of the said reflected waves .   The ultrasonic flowmeter according to claim 1, wherein a line connecting the centers of the pair of ultrasonic transducers and a center line of a cross section of the flow rate measuring unit are parallel to each other. The flow of the pair of ultrasonic transducers disposed on both side walls forming the measurement unit according to claim 1 which is a line connecting the centers mounted at a predetermined angle with respect to the height direction of the flow measuring unit The ultrasonic flowmeter described in 1.

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