JP2009103460A - Ultrasonic flowmeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic flowmeter which is capable of realizing stable and high-accuracy measurement across the whole flow zone without being affected by the flow velocity distribution in the width direction according to a flow zone. <P>SOLUTION: The ultrasonic flowmeter has reflective members which are formed in the shape of plates disposed respectively along a flow passage inside a flow passage forming part and partitions the section of the flow passage into a flow passage central area and areas touching internally the inner wall surfaces of the flow passage forming part, which are located on the opposite sides of the flow passage central area. A propagation time of an ultrasonic beam in a first propagation route wherein the total length of propagation through the flow passage central area is larger than that of propagation through the areas touching internally the wall surfaces and in a second propagation route wherein the total length of propagation through the flow passage central area is smaller than that of propagation through the areas touching internally the wall surfaces and which is different from the first propagation route, is measured individually. Based on the result of the measurement, the ultrasonic flowmeter calculates the information on the flow rate distribution in the section of the flow passage in the manner of dividing it into the information on the flow passage central area and that on the areas touching internally the wall surfaces, and outputs it. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ultrasonic flow meter.

  It is generally known hydrodynamically that a fluid flowing through a flow path has a different flow velocity distribution depending on its flow rate. In other words, when the flow is slow, it shows a parabolic flow velocity distribution called laminar flow in the channel width direction, the peak flow velocity and the average flow velocity are different, and conversely when the flow becomes faster, the distribution gradually The flow velocity distribution at that time becomes a flow velocity distribution called a bathtub shape in which the peak flow velocity is equal to the average flow velocity, and the flow velocity distribution is uniformly distributed in the channel width direction. . Further, in the laminar flow region, a slight difference occurs in the parabolic flow velocity distribution shape, and the flow velocity difference in the width direction is not constant. Furthermore, it is generally known that in the laminar flow region, the flow velocity distribution varies depending on the gas type, the flow channel geometry, and the like.

  Thus, if there is a difference in the flow velocity distribution in the flow channel width direction due to the flow rate region, the type of fluid, the flow channel shape dimensions, etc., the ultrasonic element transmits and receives ultrasonic waves across the flow velocity distribution, When measuring the fluid flowing in the flow path, the measured average flow velocity is affected by the flow velocity distribution described above depending on the flow rate range, and the measured flow rate includes an error. It cannot be calculated. Even if the influence of this error is corrected, the measured flow velocity distribution itself cannot be grasped, so it is extremely difficult to correct the flow velocity distribution in the flow region as the average flow velocity.

  Therefore, in order to reduce this effect and obtain an averaged flow velocity distribution in any flow region, the width direction inside the flow channel is divided into a plurality of areas, and the parabolic flow velocity distribution generated especially in the laminar flow region is obtained. A flow measuring device has been devised in which a member called a partition plate is arranged inside a flow path so as to be smoothed (see Patent Document 1). As a result, in the laminar flow region, the averaged flow velocity distribution can be measured and handled in the same manner as in the turbulent flow region, so that an accurate flow velocity can be calculated and a highly accurate flow rate can be calculated.

JP 2005-257363 A

  However, in patent document 1, pressure loss will become remarkable by inserting a partition plate in the inside of a flow path and making it generate | occur | produce resistance with respect to a flow. Even if this pressure loss can be tolerated, there is a concern that it may contribute to product stability, yield, etc. in consideration of the effects of individual differences in products, the accuracy of assembly of partition plates, variation, temperature factors, etc. In addition, it is inevitable that the cost will increase due to the addition of parts.

  Against the background of the above problems, an object of the present invention is to provide an ultrasonic flowmeter that is not affected by the flow velocity distribution in the width direction due to the flow rate region and can realize stable and highly accurate measurement over the entire flow rate region. .

Means for Solving the Problems and Effects of the Invention

  In order to solve the above problems, an ultrasonic flowmeter of the present invention is attached to a flow path forming section that forms a flow path of a fluid to be measured, and the flow path forming section, one of which is an ultrasonic wave to the fluid to be measured A first and a second ultrasonic transmission / reception unit pair each composed of a pair of ultrasonic transmission / reception units configured such that the transmission / reception function can be switched so that the other becomes a transmission unit of the beam and the reception unit of the ultrasonic beam; It is formed in a plate shape that is disposed along the flow path inside the path forming portion, and the cross section of the flow path is divided into the flow path center region and the inner wall surface of the flow path forming portion on both sides of the flow path central region. The first propagation is such that the total propagation length passing through the central region of the flow path is longer than the total propagation length passing through the wall inscribed region. Along the path, for the second ultrasound transmitter / receiver pair, The ultrasonic beam is reflected and refracted from the transmitting unit along the second propagation path different from the first propagation path whose total propagation length passing through the wall inscribed region is shorter than the total propagation length passing through the wall inscribed region. The first reflection time, which is the propagation time of the ultrasonic beam when using the reflecting member to be guided, and the first ultrasonic transmission / reception unit pair, and the propagation of the ultrasonic beam when using the second ultrasonic transmission / reception unit pair Based on the measurement results of the first propagation time and the second propagation time, the flow distribution information in the cross section of the flow path is obtained as It is characterized by having flow rate distribution information calculating means for calculating in a form divided into wall surface inscribed regions and flow rate distribution information outputting means for outputting the calculated flow rate distribution information.

  With the above configuration, it is possible to grasp and analyze the flow velocity distribution pattern due to the flow rate flowing in the flow path based on the propagation time measurement result by sending and receiving these multiple ultrasonic waves or the flow velocity result calculated and calculated from the time measurement information Therefore, the flow rate of the fluid flowing through the flow path can be calculated and calculated. In addition, by adjusting the dimensional ratio, the number and arrangement of the plurality of piezoelectric element blocks constituting the piezoelectric element in the width direction corresponding to the width direction of the flow path to the optimum dimensional ratio, number and position, Optimal flow velocity detection corresponding to the type of fluid (gas type) flowing through the channel, flow path geometry, flow rate range, and even flow velocity distribution deviation (even with a deviation from the central axis) Therefore, it is possible to realize stable and highly accurate measurement over the entire flow rate range without being affected by the flow velocity distribution in the width direction and the bias due to the flow rate range.

  Moreover, the ultrasonic flowmeter of this invention can also be comprised so that a 1st propagation path and a 2nd propagation path may be set to the same length.

  Even if the two propagation path lengths are the same, the propagation time of the ultrasonic beam passing through the region where the flow distribution is different is different. Even with the above configuration, stable and highly accurate measurement can be realized over the entire flow rate range.

  Further, the reflecting member in the ultrasonic flowmeter of the present invention has a first reflecting member located on the side closer to the transmitting unit and a second reflecting member located on the side closer to the receiving unit, and the first reflecting member Is formed with a first penetrating portion that guides the ultrasonic beam transmitted from the transmission unit of the first ultrasonic transmission / reception unit pair along the first propagation path to the central region of the flow path. A second penetrating portion is formed to guide the ultrasonic beam that has been multiple-reflected in the center region of the road into the inscribed region on the wall side on the receiving side, and the formation position of the first penetrating portion and the second penetrating portion is It can also be configured such that the number of reflections of the ultrasonic beam in the road center region is determined to be larger than the total number of reflections in each wall inscribed region.

  With the above configuration, the flow rate distribution information in the central region of the flow path can be calculated with high accuracy.

  Further, the ultrasonic flowmeter of the present invention is configured such that the formation position of the first penetrating portion and the second penetrating portion is determined so that the ultrasonic beam passes through each wall inscribed region without reflection. You can also.

  With the above configuration, the flow rate distribution information in the central region of the flow path can be calculated more accurately without being affected by the flow rate distribution in each wall inscribed region.

  Further, the reflecting member in the ultrasonic flowmeter of the present invention has a first reflecting member located on the side closer to the transmitting unit and a second reflecting member located on the side closer to the receiving unit, and the first reflecting member Is sent from the transmission unit of the second ultrasonic transmission / reception unit pair along the second propagation path, and the inner wall surface of the flow path forming unit facing the first reflection member in the wall inscribed region on the transmission unit side, A third penetrating portion is formed to guide the ultrasonic beam that has been multiple-reflected between the two to the flow path central region, and the second reflecting member has a wall inscribed region on the receiving unit side from the flow channel central region. The fourth penetration that guides the ultrasonic beam into the receiving part of the second ultrasonic transmitting / receiving part pair while performing multiple reflections between the second reflecting member and the inner wall surface of the flow path forming part facing the second reflecting member Part is formed, the formation position of the third penetration part and the fourth penetration part is the total reflection in each wall inscribed region The number can also be configured to be determined to be larger than the number of reflections of the ultrasonic beam at the middle of the channel region.

  With the above configuration, the flow distribution information in the wall inscribed region can be calculated with high accuracy.

  Moreover, the formation position of the 3rd penetration part and the 4th penetration part in the ultrasonic flowmeter of this invention can also be comprised so that an ultrasonic beam may pass through a flow-path center area | region without reflection. it can.

  With the above configuration, the flow rate distribution information in each wall inscribed region can be calculated more accurately without being affected by the flow rate distribution in the flow channel central region.

  Moreover, the ultrasonic flowmeter of this invention is provided with the requirements of Claim 3 or Claim 4, and each transmission part and receiving part of a 1st ultrasonic transmission / reception part pair and a 2nd ultrasonic transmission / reception part pair are The ultrasonic beam is disposed at the same position in the flow direction of the flow path and adjacent to each other in the width direction of the reflection member, and at the same angle with respect to each of the first reflection member and the second reflection member. The first penetrating part and the second penetrating part are applied to the transmitting part or the receiving part forming the first ultrasonic transmitting / receiving part pair with respect to the first reflecting member and the second reflecting member. Only the opposite side of the first ultrasonic transmission / reception unit of each reflecting member is allowed to allow the ultrasonic beam to pass and prevent the transmission of the ultrasonic beam to the transmission unit or reception unit forming the second ultrasonic transmission / reception unit pair. Are formed in a shape that is partially cut out in the width direction. The through part allows the transmission of the ultrasonic beam applied to the transmission unit or the reception unit forming the second ultrasonic transmission / reception unit pair with respect to the first reflection member and the second reflection member, and the first ultrasonic transmission / reception unit pair It is configured so that only the opposite side of the second ultrasonic transmission / reception unit of each reflection member is partially cut out in the width direction so as to prevent the transmission of the ultrasonic beam applied to the transmission unit or reception unit. You can also

  With the above configuration, the first propagation path and the second propagation path can be formed without complicating the structure of the reflecting member and without affecting the flow of the flow path.

  In addition, the first and second ultrasonic transmission / reception units in the ultrasonic flowmeter of the present invention are configured by one piezoelectric body, and the piezoelectric body is placed on the surface of the piezoelectric body in the flow direction of the flow path. A groove for dividing the first and second ultrasonic transmission / reception units may be provided, and each piezoelectric body divided in the groove may have an independent ultrasonic directivity characteristic.

  It is known that when one piezoelectric body is divided and a voltage is applied, an ultrasonic wave is transmitted from each of the divided piezoelectric bodies. With the above configuration, since only one voltage application unit is required, an ultrasonic transmission / reception unit can be configured at low cost. In addition, since the structure is mechanically independent by the slit, a decrease in vibration efficiency and unnecessary vibration can be suppressed, so that detection accuracy is high and stable measurement is possible. In addition, because it is composed of the same piezoelectric element and can be transmitted and received by dividing into symmetrical shapes, it can realize stable measurement with the same characteristics and no sensitivity difference due to the path, and highly accurate detection with very little error due to temperature and aging. Can be realized.

  Further, the first and second ultrasonic transmission / reception units in the ultrasonic flowmeter of the present invention are configured by independent piezoelectric bodies, and these piezoelectric bodies are separately arranged symmetrically with respect to the flow direction of the flow path, It can also be configured to have independent ultrasonic directivity characteristics.

  With the above configuration, the transmission timing of ultrasonic waves of these two piezoelectric bodies can be arbitrarily set, and the flow rate distribution information can be accurately calculated according to the gas type, the flow path shape dimension, and the like. In addition, since each piezoelectric body has a completely independent and symmetric shape, the vibration efficiency is good and the loss is small, so that an ultrasonic beam can be radiated into the flow path with improved transmission / reception sensitivity. Furthermore, since each piezoelectric body is configured in the same lot, the characteristics are relatively close, and the tendency of temperature change and change with time is uniform, resulting in a stable configuration.

  Further, the ultrasonic flowmeter of the present invention includes a flow velocity calculation means for calculating a flow velocity in the flow path central region and the wall inscribed region of the fluid to be measured based on the flow distribution information, and two calculated fluids to be measured. A flow velocity distribution correction coefficient calculating unit that calculates a flow velocity distribution correction coefficient corresponding to the flow distribution information based on the flow velocity may be provided.

  With the above configuration, the transmission time result corresponding to the flow velocity distribution can be obtained by transmitting and receiving the ultrasonic beam propagating through the two kinds of propagation paths by the two kinds of sound beams propagating through the different propagation paths. Compare the propagation time ratio values of at least two types of sound beams from the time results, estimate the flow velocity distribution pattern based on the magnitude relationship, predict the appropriate flow rate range, and at the same time, the ratio value The optimum flow velocity distribution correction coefficient can be calculated according to the above.

  The ultrasonic flowmeter of the present invention can also be configured to include a flow velocity correction unit that corrects the flow velocity of the fluid to be measured based on the calculated flow velocity distribution correction coefficient.

  With the above configuration, in order to perform optimal correction according to the flow rate range, an appropriate flow rate correction coefficient is allocated and flow rate measurement is performed to calculate the flow rate and calculate the flow rate. It is possible to cope with the difference in flow velocity distribution due to the difference in flow velocity value in the difference in viscosity and density depending on the type of fluid. In addition, even if there is a difference in the flow velocity distribution in the ultrasonic beam area depending on the flow path shape and dimensions, it is possible to separately apply a correction coefficient corresponding to this, so the propagation time measurement by ultrasonic beam transmission and reception Based on the result, the ratio value of the propagation time is compared, and the flow velocity distribution pattern in the channel width direction is estimated based on the magnitude relationship to predict an appropriate flow area, and at the same time, the optimum flow rate is determined according to the ratio value. By assigning a flow velocity distribution correction coefficient, it is possible to calculate and calculate the average flow velocity across the flow path cross section, so that it is not affected by the flow velocity distribution in the width direction due to the flow region, and is stable and highly accurate over the entire flow region. Measurement can be realized. Or, based on the flow velocity result calculated and calculated based on the time measurement result by transmission and reception, the flow rate ratio value is compared, and based on the magnitude relationship, the flow velocity distribution pattern in the flow channel width direction is estimated and the appropriate flow rate range By simultaneously assigning the optimal flow velocity distribution correction coefficient according to the ratio value, the average flow velocity across the cross section of the flow path can be calculated and calculated. Without being affected, stable and highly accurate measurement can be realized over the entire flow rate range.

  An embodiment of an ultrasonic flowmeter according to the present invention will be described with reference to the drawings. FIG. 1 shows a basic configuration of an embodiment of an ultrasonic flow meter used as a general residential gas meter or the like. The ultrasonic flowmeter 1 is provided at a position different from each other in the flow direction of the fluid GF to be measured with respect to the flow passage forming portion 3 and the flow passage forming portion 3 that form the flow path of the fluid GF to be measured. While functioning so that the measurement ultrasonic wave is sent to the measurement fluid GF and the other is the measurement ultrasonic wave reception side, each of the measurement ultrasonic waves has directivity in a predetermined direction. A pair of ultrasonic transmission / reception units 2a and 2b capable of transmitting ultrasonic beams SW2 and SW4, and a plate surface method arranged along the flow path inside the flow path forming unit 3, respectively. And a plurality of reflecting members 31 and 32 provided at predetermined intervals in the line direction. Then, the ultrasonic transmission / reception units 2a and 2b on the transmission side are subjected to multiple reflection in the flow path by using the reflecting members 31 and 32 and the ultrasonic transmission / reception unit on the reception side. It leads to 2b and 2a. The flow path forming unit 3 is made of metal, for example.

  The flow path forming unit 3 including the reflecting members 31 and 32 and the ultrasonic transmission / reception units 2a and 2b constitute a flow meter main body 1M, and the flow meter main body 1M and the control circuit unit 1E The whole is configured. The ultrasonic transmission / reception unit 2a corresponds to the first ultrasonic transmission / reception unit pair of the present invention, and the ultrasonic transmission / reception unit 2b corresponds to the second ultrasonic transmission / reception unit pair of the present invention.

  The control circuit unit 1E includes a pair of ultrasonic transmission / reception units 2a and 2b. The upstream ultrasonic transmission / reception unit 2a located on the upstream side of the flow channel serves as the transmission side, and the downstream ultrasonic transmission / reception unit located on the downstream side of the flow channel. It has an ultrasonic drive mechanism 4 that can be switched between a forward drive mode in which the 2b side is the receiving side and a reverse drive mode that is the opposite of the forward drive mode. The control circuit unit 1E corresponds to the propagation time measuring unit, the flow rate distribution information calculating unit, the flow rate distribution information output unit, the flow rate calculating unit, the flow rate distribution correction coefficient calculating unit, and the flow rate correcting unit of the present invention.

  A flow rate measurement gas (fluid) flows in the flow direction shown in the flow rate measurement flow path 3P of the ultrasonic flowmeter 1. In the flow path 3P, a downstream ultrasonic transmission / reception unit 2b is provided on the downstream side in the flow direction, and an upstream ultrasonic transmission / reception unit 2a is provided on the upstream side in the flow direction. These ultrasonic transmission / reception units 2a and 2b are ultrasonic transducers having an ultrasonic transducer such as a piezoelectric transducer, and have an ultrasonic transmission function for transmitting an ultrasonic beam by applying a drive voltage, It is combined with an ultrasonic wave reception function that outputs an electrical signal (reception signal) upon reception. The ultrasonic beam for measurement is sent out in a pulse shape having a predetermined wave number or less so as not to generate a standing wave between the ultrasonic transmission / reception units 2a and 2b in the flow path.

  In addition, when the measurement target is gas, the axial cross-sectional shape of the flow path forming portion 3 that forms the flow path 3P may be any shape that forms a space closed by the wall portion 3J. For example, a circular shape, an elliptical shape, Any of a square shape, a rectangular shape, or the like may be adopted. In the present embodiment, as shown in FIG. 1, the flow path forming portion 3 is formed in a rectangular shape, the upstream ultrasonic wave transmitting / receiving unit 2a is formed on the upper wall portion 3Ja, and the downstream ultrasonic wave transmitting / receiving unit 2b is formed on the lower wall portion 3Jb. It is attached. In other words, the paired ultrasonic transmission / reception units 2 a and 2 b are arranged so as to be distributed to the flow path forming unit 3 so as to sandwich the plurality of reflecting members 31 and 32 in the arrangement direction.

  The flow path forming unit 3 is formed by the reflecting members 31 and 32 with the flow path center area 3W, the upper wall surface inscribed area 3C in contact with the inner wall surface of the flow path forming part on both sides of the flow path center area, and the lower wall surface inscribed. It is partitioned into a region 3C ′. The reflecting member 31 corresponds to the first reflecting member of the present invention, and the reflecting member 32 corresponds to the second reflecting member of the present invention.

  FIG. 2 is a perspective view of a cross-sectional structure of the flow meter main body 1M. Of the ultrasonic beams SW4 and SW2 transmitted from the ultrasonic transmission / reception unit on the arrangement transmission side (the upstream ultrasonic transmission / reception unit 2a in the forward drive mode and the downstream ultrasonic transmission / reception unit 2b in the reverse drive mode) The ultrasonic beam SW4 is subjected to an ultrasonic transmission / reception unit (downstream ultrasonic transmission / reception in the forward drive mode) while being multiple-reflected in the flow path central region 3W formed between the pair of reflecting members 31 and 32 while being multiplexed. In the part 2b, reverse drive mode, it is guided to the upstream ultrasonic transmission / reception part 2a). That is, the propagation path of the ultrasonic beam SW4 corresponds to a first propagation path in which the total propagation length passing through the flow path center region is longer than the total propagation length passing through the wall inscribed region. Further, the ultrasonic beam SW2 is guided to the ultrasonic transmission / reception unit on the reception side while being multiple-reflected in the two wall surface inscribed regions 3C and 3C '. That is, the propagation path of the ultrasonic beam SW2 is different from the first propagation path in which the total propagation length passing through the flow path central region 3W is shorter than the total propagation length passing through the wall surface inscribed regions 3C and 3C ′. Corresponds to the route.

  In the reflection members 31 and 32, the ultrasonic beam SW4 from the ultrasonic transmission / reception units 2a and 2b facing the reflection members 31 and 32 is introduced into the flow path central region 3W, and the ultrasonic beam SW4 is supplied to the flow path central region 3W. The beam introduction opening 31h1 (first penetration part of the present invention) and 32h1 (second penetration part of the present invention) for multiple reflection are formed. The formation positions of the beam introduction openings 31h and 32h on the reflecting members 31 and 32 are determined so as to include the beam center axis of the ultrasonic beam SW4.

  Further, the reflection members 31 and 32 are arranged in the center of the flow path after the ultrasonic beam SW2 from the ultrasonic transmission / reception units 2a and 2b facing the reflection members 31 and 32 is subjected to multiple reflection at the wall inscribed regions 3C and 3C ′. Beam introduction openings 31h2 (third penetration portion of the present invention) and 32h2 (fourth penetration portion of the present invention) for introduction into the region 3W are formed. The formation positions of these beam introduction openings 31h2 and 32h2 on the reflecting members 31 and 32 are determined so as to include the beam center axis of the ultrasonic beam SW2.

  The beam introduction openings 31h1, 32h1 and 31h2, 32h2 may be rectangular or substantially semicircular cutouts or may be formed through. Moreover, the formation position of the 1st penetration part and the 2nd penetration part is the total reflection in each wall surface inscribed area | region (3C, 3C ') that the frequency | count of reflection of ultrasonic beam SW4 in a flow-path center area | region (3W). It is determined to be more than the number of times. The formation positions of the third penetration part and the fourth penetration part are determined so that the ultrasonic beam SW2 passes through the flow path central region 3W without reflection.

  In addition, when the acoustic impedance of the fluid to be measured (medium) is Z1 and the acoustic impedance of the reflective member is Z2, the reflecting members 31 and 32 have the boundaries (reflecting surfaces) as the reflecting members 31 and 32. A material having an acoustic impedance Z2 that satisfies Z1 / Z2 << 1 may be selected. In this way, the acoustic impedance Z2 of the reflecting members 31 and 32 is sufficiently larger than the acoustic impedance Z1 of the medium, so that the reflecting members 31 and 32 forming the boundary (reflecting surface) are made to be the ultrasonic beam SW (2, 4 ) Can be prevented from being transmitted and almost total reflection occurs, so that the propagation loss of the ultrasonic beam SW is reduced, and highly sensitive transmission / reception can be achieved. Specifically, the acoustic impedance ratio Z1 / Z2 may be 1/10 or less, and examples of specific materials of the reflecting members 31 and 32 include metals, ceramics, and plastics.

  In addition, it is desirable that the thickness of the reflecting members 31 and 32 is secured to 0.4 mm or more in consideration of the mechanical properties and workability of the material. If the thickness of the reflecting members 31 and 32 is equal to ½ of the ultrasonic wavelength λ, as shown in FIG. 19, the sound wave transmittance of the reflecting member increases very steeply due to resonance, and almost no reflection occurs. The thickness is preferably smaller than λ / 2 (in the example shown in FIG. 19, λ / 2 = about 1.25 mm, and the thickness of the reflecting members 31 and 32 is set to 1 mm or less. However, since λ varies depending on the material of the reflecting members 31 and 32, the upper limit of the appropriate thickness is appropriately set according to the material).

  Furthermore, the surface roughness of the reflecting surfaces of the reflecting members 31 and 32 (the arithmetic average height Ra defined in JIS B0601 (2001) is adopted) is finished to 1/10 or less of the ultrasonic wavelength λ. It is desirable. As a result, the loss of ultrasonic energy due to irregular reflection on the reflecting surface is reduced and almost total reflection is performed, so that the propagation loss of the ultrasonic beam is suppressed, and highly sensitive transmission / reception can be realized.

  FIG. 3 shows the configuration of the ultrasonic transmission / reception units 2a and 2b. Since the ultrasonic transmission / reception units 2a and 2b have the same configuration, the ultrasonic transmission / reception unit 2a will be described as an example. The piezoelectric element (piezoelectric body of the present invention) constituting the ultrasonic transmission / reception unit 2a is configured as an integrated structure separated into two piezoelectric element blocks 2a1 and 2a2 by a groove SL. Then, each of the piezoelectric element blocks 2a1 and 2a2 is driven, and the ultrasonic beams α (corresponding to SW2) and β (corresponding to SW4) are transmitted in the flow path width direction via the acoustic matching layer 2z for matching the acoustic impedance. Radiates in half.

  When a time difference is provided in the radiation timings of the ultrasonic beams α and β, the ultrasonic wave is guided to the ultrasonic wave transmitting / receiving unit 2b along different propagation paths in the flow path width direction. At this time, a certain time difference is generated. Even if the ultrasonic beams α and β are emitted at the same timing, they are received with a certain time difference if the propagation paths of the ultrasonic beams are different. Furthermore, even if the ultrasonic beams α and β are emitted at the same timing and the propagation paths of the respective ultrasonic beams have the same length, if the flow rate distribution in each region (3W, 3C) is different, a certain time difference is obtained. Will be received.

  As shown in FIG. 4, the piezoelectric element can be configured as two square-shaped piezoelectric element blocks 2a1 and 2a2 in which grooves SL are provided at positions that divide the flow path width into two as in the A pattern. As described above, the substantially disk-shaped piezoelectric element may be divided into two by the groove SL in the flow path width direction. In addition to the above, the piezoelectric elements may have a substantially elliptical shape and are separated in a shape symmetrical in the flow path width direction. 5 and 6 show examples of attachment of piezoelectric elements having respective shapes.

  FIG. 7 shows another example of the configuration of the piezoelectric elements constituting the ultrasonic transmission / reception units 2a and 2b. The piezoelectric elements are arranged symmetrically with respect to the flow path width direction and arranged side by side as piezoelectric element blocks 1 and 2 separated into two arrays, and each piezoelectric element block has a certain delay time. The ultrasonic beams α (corresponding to SW2) and β (corresponding to SW4) are transmitted and received through the acoustic matching layer 2z common to the respective blocks.

  FIG. 8 shows a block diagram of the microcomputer 11. The microcomputer 11 includes a CPU 111, a ROM 112 (nonvolatile memory: stored contents can be electrically rewritten by an EEPROM, a flash memory, or the like), a RAM 113, an input / output unit 114, and an internal bus 115. The ROM 112 stores a control program 112a, and the CPU 111 reads out and executes the control program 112a to perform flow rate calculation and the like. Further, the RAM 113 is provided with a measurement data storage area 113c for storing measurement data necessary for flow rate calculation and the like.

  The time measurement unit 10 in FIG. 1 is configured to perform forward propagation time until the ultrasonic beams SW2 and SW4 transmitted from the upstream ultrasonic transmission / reception unit 2a reach the downstream ultrasonic transmission / reception unit 2b in the forward drive mode. And the backward propagation time until the ultrasonic beams SW2 and SW4 transmitted from the downstream ultrasonic wave transmitting / receiving unit 2b in the reverse direction driving mode reach the upstream ultrasonic wave transmitting / receiving unit 2a. Further, the microcomputer 11 calculates the average flow velocity and the flow rate of the fluid flowing through the flow path 3P from the time difference between the forward propagation time and the backward propagation time. The amplifying unit 7 includes a known amplifying circuit for enabling the CPU 111 to process the level (voltage level) of the received ultrasonic beam signal.

  In the present invention, since the propagation path of the ultrasonic beam SW4 has a polygonal line shape due to quaternary reflection, the flow rate Q can be calculated as follows in the configuration of FIG. 9 (the dimensions of each part are shown in FIG. 9). This is explained by the symbols shown in the figure). First, among the spaces partitioned by the reflecting members 31, 32, the heights of the upper wall surface inscribed region 3C, the flow path center region 3W, and the lower wall surface inscribed region 3C ′ are h1, h2, h3, and the sectional area is S1. , S2, and S3. Further, the thickness of the reflecting members 31 and 32 is t, the offset length of the stagnation space 2d (see FIG. 1) is L0, and the ultrasonic wave transmitting / receiving units 2a and 2b (represented as transducers 1 and 2 in FIG. 9) are attached angles. Is θ, the propagation path length L is calculated by the following equation.

L = {(h1-t / 2) / SINθ
+ 5 · (h2−t) / SINθ + (h3−t / 2) / SINθ} + 2L0 (21)
Moreover, since the reflecting members 31 and 32 are provided in the vertical direction with respect to the flow path center axis,
h1 = h3 = h ′ (22)
S1 = S3 = S ′ (23)
And can.

Next, the flow rate cross section including the triangular part other than the flow path center region 3W, that is, the flow velocity V ′ and the instantaneous flow rate Q ′ in the upper wall side space 3C and the lower wall side space 3C ′ are calculated. First, in the propagation path, the length L ′ of the portion belonging to the upper wall side space 3C and the lower wall side space 3C ′ is:
L ′ = 2 · {h′−t / 2} / SINθ + L0} (24)
It is. Then, the forward propagation time T1 ′ is
T1 ′ = L ′ / (C + V′COSθ) (25)
(However, C is the speed of sound in the gas to be measured)
Similarly, the backward propagation time T2 ′ is
T2 ′ = L ′ / (C−V′COSθ) (26)
Therefore, the flow velocity V ′ in the upper wall side space 3C and the lower wall side space 3C ′ is
V ′ = (L ′ / COSθ) (1 / T1′−1 / T2 ′) (27)
Similarly, the instantaneous flow rate Q ′ is
Q ′ = V ′ · 2S ′ (28)

Next, when the flow velocity: V ″ and instantaneous flow rate Q ″ in the flow path center region 3W are calculated in the same manner,
Of the propagation path, the length L ″ of the portion belonging to the flow path central region 3W is:
L ″ = N · {(h2−t) / SINθ} (29)
(However, N is the reflection order (number of reflections))
It is. Then, the forward propagation time T1 ″ is
T1 ″ = L ″ / (C + V ″ COSθ) (30)
Similarly, the backward propagation time T2 ″ is
T2 ″ = L ″ / (C−V ″ COSθ) (31)
Therefore, the flow velocity V ″ in the flow path center region 3W is
V ″ = (L ″ / COSθ) (1 / T1 ″ −1 / T2 ″) (32)
Similarly, the instantaneous flow rate Q "
Q ″ = V ″ · S2 (33)

From the above, the total flow rate value Q is the sum of the flow rates of the flow path center region 3W (S2), the upper wall side space 3C, and the lower wall side space 3C ′ (S ′ + S ′ = 2S ′).
Q = Q ′ + Q ″ (V ′ · 2S ′ + V ″ · S2) (34)
Can be calculated as Both the forward propagation time T1 (T12) and the backward propagation time T2 (T22) measured are the sum of the propagation times of the two spaces (T1 ′ + T1 ″ and T2 ′ + T2 ″).

  According to the above configuration, as shown in FIG. 9, the propagation path length is increased by the number of times of reflection more than twice as compared with the case where the ultrasonic beam SW propagates straight between the ultrasonic transmission / reception units 2a and 2b. Increases in a polygonal line, which can contribute to the improvement of flow measurement accuracy or the rangeability of flow measurement. Further, even if the propagation path length is the same, the path shape becomes a polygonal line, so that the distance between the paired ultrasonic transmission / reception units 2a and 2b can be reduced, contributing to the miniaturization of the apparatus. Moreover, although the flow path 3P is divided into a plurality of parts within the axial cross section by the reflecting members 31 and 32, the reflecting members 31 and 32 also function as a rectifying element for the fluid GF to be measured. From this point of view, it contributes to the improvement of the flow rate measurement accuracy. In particular, if the flow can be sufficiently uniform in the direction of dividing the flow path by the reflecting members 31 and 32, the flow to be measured can be handled as a two-dimensional flow approximately, and further in terms of improving measurement accuracy. It will be advantageous.

  In addition, as shown in FIG. 9, in the ultrasonic transmission / reception units 2a and 2b, the attachment angle of the ultrasonic transmission / reception units 2a and 2b with respect to the flow path forming unit 3 is set large in order to cause multiple reflection. As a result, as described above, the stagnation space 2d formed in the immediate vicinity of each of the ultrasonic transmission / reception units 2a and 2b is reduced, which greatly contributes to an improvement in flow rate measurement accuracy.

  The flow distribution information output process will be described with reference to FIG. This process is included in the control program 112a and is repeatedly executed together with other processes of the control program 112a. First, an ultrasonic beam (SW2: α, SW4: β) is emitted from the ultrasonic transmitters 2a and 2b at a predetermined timing (S11). Next, when the ultrasonic beam is received by the ultrasonic receivers 2a and 2b (S12: Yes), the propagation time of each ultrasonic beam is measured (S13). Based on these propagation times, a flow velocity correction value is calculated (S14), and a final flow rate and flow velocity (flow rate distribution information) are calculated (S15).

  The radiation timing of the ultrasonic beam (SW2: α, SW4: β) will be described with reference to FIG. For example, an ultrasonic beam SW2 (α beam) is first emitted with reference to a 1 MHz clock signal included in the control circuit unit 1E and output from an oscillation circuit (not shown) including a crystal oscillator. Subsequently, the clock signal is counted by a microcomputer or a counter circuit, and an ultrasonic beam SW4 (β beam) is emitted when the counter value reaches a predetermined value (tr) such as 10 counts. .

  The ultrasonic beam SW4 is radiated tr time after the ultrasonic beam SW2 is emitted, and is received td time after the ultrasonic beam SW2 is received. Even if the propagation lengths of the ultrasonic beams SW2 and SW4 are the same, since the propagation paths are different, tr = td is not always obtained due to the influence of the flow rate and flow velocity in the flow path.

  Another example of the configuration of the ultrasonic transmission / reception unit and the reflection member will be described with reference to FIGS. 12 and 13. The ultrasonic transmission / reception units 2 a and 2 b are attached so as to be close to a right angle with respect to the flow path forming unit 3. The reflecting member 31 is provided with a beam introduction opening 31h3 so that an ultrasonic beam emitted from the ultrasonic transmission / reception unit 2a can pass therethrough. The reflecting member 32 is provided with a reflecting plate 32r whose mounting angle is adjusted so that the ultrasonic beam that has passed through the beam introducing opening 31h3 is directed toward the opening 31h. Similarly, a beam introduction opening 32h3 and a reflecting plate 31r are provided corresponding to the ultrasonic transmission / reception unit 2b.

  Also with the above configuration, the first propagation path (β) in which the total propagation length passing through the flow path central region 3W is longer than the total propagation length passing through the waveguide space 3C on the wall surface and the flow passage central region 3W are passed. A second propagation path (α) having a total propagation length shorter than the total propagation length passing through the wall surface inscribed regions 3C and 3C ′ can be formed.

  Another example of the configuration of the ultrasonic transmission / reception unit and the reflection member will be described with reference to FIGS. 14 and 15. This configuration is a modification of FIGS. 12 and 13. The reflectors 31r and 32r are divided into two in the flow path direction. The reflecting plate 31r includes a reflecting plate 31r1 having an angle θ1 that forms the second propagation path (α) and a reflecting plate 31r2 having an angle θ2 that forms the first propagation path (β). . Similarly, the reflecting plate 32r includes a reflecting plate 32r1 and a reflecting plate 32r2.

  An ultrasonic beam is simultaneously emitted from the ultrasonic transmitter 2a, reflected by the reflector 32r attached with slightly different angles θ1 and θ2, respectively, and the first propagation path (β) and the second propagation path (β) having L2 and L1 different from each other. While propagating through the two propagation paths (α) while being subjected to multiple reflections, they are separated from each other in a manner that bisects the width direction of the flow path, and are reflected by the reflection plates 31r attached with the same angles θ1 and θ2 as the reflection plates 32r. Due to the path difference ΔL, the ultrasonic wave reception unit 2b on the receiving side receives the signal with a certain time difference (delay time) Δt.

  In the configurations of FIGS. 12 to 15, the ultrasonic transmission / reception unit is perpendicular to the fluid flow direction, that is, the normal direction of the radiation surface of the ultrasonic transmission / reception unit is arranged to be orthogonal to the fluid flow direction. Since the location 2d (see FIG. 1) where the fluid stagnates can be eliminated, an accurate flow rate can be calculated and a highly accurate flow rate can be calculated.

  Then, based on the propagation time measurement result by transmitting and receiving the ultrasonic beam in the forward direction and the reverse direction received and transmitted with a certain time, or the flow velocity result calculated and calculated from the time measurement information, By grasping and analyzing the flow velocity distribution pattern according to the flowing flow rate, the flow rate of the fluid flowing through the flow path can be calculated and calculated. For example, in FIG. 15, when the propagation length L1 of the second propagation path is approximately 139.99 mm, the propagation length L2 of the first propagation path is approximately 116.15 mm, and the path difference L is approximately 22.84 mm, two ultrasonic beams are received. The time difference Δt≈67.18 μs (when the speed of sound C = 340 m / s). In addition, in this configuration, a delay circuit and a reference clock are not necessary, and the cost can be reduced.

  The calculation of the flow velocity distribution information included in the flow distribution information will be described with reference to FIG. This is the measurement result of the first propagation time that is the propagation time in the first propagation path (broken line part) of the ultrasonic beam and the second propagation time that is the propagation time in the second propagation path (solid line part) and the flow velocity information. Based on the above, the flow velocity distribution is calculated. The forward propagation time of the second propagation path is Tj1, the backward propagation time is Tg1, the forward propagation time of the first propagation path is Tj2, and the backward propagation time is Tg2. Vw (second propagation path), Vc (first propagation path) are calculated as the flow velocities calculated from the state of the ultrasonic beam propagating through each second propagation path calculated from the propagation time measurement result by the above-described method. To do. And the value of the ratio of the propagation time results obtained by propagating through the respective propagation paths: based on the magnitude relationship of Tj2 / Tj1 = α and Tg2 / Tg1 = β, or the flow velocity calculated and calculated from the propagation time measurement It is possible to compare the ratio value: Vc / Vw = ζ, estimate the flow velocity distribution pattern in the flow path height direction based on the magnitude relationship, predict the flow rate region, and calculate the flow rate.

  In FIG. 16, the values α and β of the propagation time result by the flow velocity pattern 1 (laminar basin 1) are α1 and β1, α and β by the flow velocity pattern 2 (laminar basin 2) are α2 and β2, and the flow velocity If α3 and β3 by pattern 3 (turbulent flow region) are α3 and β3, the magnitude relationship is α1 (β1)> α2 (β2)> α3 (β3) ≈1, and depending on the value of each ratio, The flow rate distribution pattern by the flow rate region can be grasped, and the flow rate can be calculated by calculating an appropriate flow rate distribution. Areas A, B, and C correspond to the upper wall surface inscribed area 3C, the flow path center area 3W, and the lower wall surface inscribed area 3C ', respectively.

The flow rate range may be grasped by using a flow velocity value calculated from the propagation times measured from the two types of beam patterns, and predicting the flow rate region from the magnitude relationship of the flow velocity. That is, in the flow velocity distribution pattern 1 (laminar flow region 1), 2 (laminar flow region 2), 3 (turbulent flow region 3), the flow velocity by the ultrasonic beam pattern 1 (first propagation path): Vc, the ultrasonic beam pattern 2 (first (Two propagation paths) Velocity: Vw
Vc = {L / (2 · cos θ)} · (1 / Tj1-1 / Tg1)
Vw = {L / (2 · cos θ)} · (1 / Tj2-1 / Tg2)
An appropriate flow rate may be determined by predicting the flow rate region based on the magnitude relationship.

That is,
When Vc> Vw, it can be estimated that the region is a laminar flow region, and an appropriate flow velocity is determined by the value of Vc / Vw at that time.
If Vc / Vw≈1, it can be estimated that the region is a turbulent region, and an appropriate flow velocity is determined. The velocity ratio in the case of the distribution pattern of the laminar basin 1 is Vc1 / Vw1, the velocity ratio in the case of the distribution pattern of the laminar basin 2 is Vc2 / Vw2, and the velocity ratio in the case of the distribution pattern of the turbulent basin 3 is Vc3 / Vw3. Then, the relationship of (Vc1 / Vw1)> (Vc2 / Vw2)> (Vc3 / Vw3) ≈1 is established, the current flow rate range can be grasped from the order of the flow rate ratio, and the current reasonable flow rate can be calculated.

  Note that the flow rate range is determined by comparing the data stored in advance, determining the flow rate range according to the value that fits the range of the data, assigning a reasonable coefficient in the flow rate range, calculating the flow velocity and calculating the flow rate. This can be done by computing. Hereinafter, the details will be described with reference to FIG.

  If the flow velocities calculated from the propagation times measured by the ultrasonic beam propagating separately in the first propagation path (broken line part) and the second propagation path (solid line part) are Vc and Vw, respectively, these Vc and Vw The flow rate range is predicted based on the magnitude relationship and the ratio value, and an appropriate flow velocity is determined. When Vc> Vw, the flow rate is a laminar flow region. By determining an appropriate flow velocity coefficient based on the value of Vc / Vw and calculating the average flow velocity, the flow rate can be calculated and the flow rate can be calculated. If Vc≈Vw, it can be understood that the region is a turbulent flow region, and the average flow velocity can be determined without a coefficient.

  Since the velocity distribution related to turbulent flow is almost the average velocity, the correction coefficient is basically not used, but by assigning a reasonable correction coefficient until switching to the turbulent flow region according to the value of Vc / Vw, Regardless of the flow rate range, it is possible to calculate the average flow velocity and calculate the flow rate.

  As shown in FIG. 17, according to the flow velocity distribution, for example, in the case of a velocity distribution pattern having a maximum center such as a solid line and a symmetric velocity distribution pattern from the center (flow velocity distribution pattern 1 in a laminar flow region), area B (flow channel central region) 3W), the flow velocity Vc calculated on the basis of the propagation time of the first propagation path that propagates while preferentially reflecting the central portion so as to contribute to the position where the flow velocity is fast at the central portion, and the wall surface of the flow path The first and second areas are propagated with multiple reflections preferentially in areas A (upper wall inscribed area 3C) and area C (lower wall inscribed area 3C ′) whose flow velocities are slower than the center (flow path center area 3W). The ratio Vc / Vw = ζ1 with the flow velocity Vw calculated based on the propagation time of the two propagation paths. In the case of the flow velocity distribution pattern in the dotted line (flow velocity distribution pattern 2 in the laminar flow region), Vc / Vw = ζ2.

  At this time, if correction coefficients proportional to the magnitudes of ζ1 and ζ2 are Φ1 and Φ2, respectively, the average flow velocity V1 in the flow velocity distribution pattern 1 in the laminar flow region is V1 = Φ1 · (Vc + Vw) / 2, The average flow velocity V2 in the flow velocity distribution pattern 2 can be calculated as V2 = Φ2 · (Vc + Vw) / 2.

Or it is also possible to calculate as V1 = Φ1 ′ · Vc and V2 = Φ2 ′ · Vc. However, Φ1 ′ and Φ2 ′ are other correction coefficients proportional to ζ1 and ζ2.
Of course, the average flow velocity may be calculated by an equation (V1 = Φ1 ′ · Vw, V2 = Φ2 ′ · Vw) in which a new correction coefficient is added to Vw.

  Note that Φ1 and Φ2 can be changed depending on the type of fluid, the shape and dimensions of the flow path, and the like.

  As described above, the distribution pattern is estimated according to the order of the flow velocity ratio by the two kinds of ultrasonic beam patterns having different propagation paths in the flow channel height direction, and an appropriate correction coefficient is determined according to the flow velocity distribution pattern. By allocating, the average flow velocity can be calculated and the flow rate can be calculated.

  Similarly, when the gas type is city gas 13A, if the correction coefficients proportional to the magnitudes of ζ1 and ζ2 are Φ5 and Φ6, respectively, the average flow velocity V1 in the flow velocity distribution pattern 1 in the laminar flow region is V1 = Φ5 · ( Vc + Vw) / 2, the average flow velocity V2 in the flow velocity distribution pattern 2 in the laminar flow area can be calculated as V2 = Φ6 · (Vc + Vw) / 2. Alternatively, V1 = Φ5 ′ · Vc and V2 = Φ6 ′ · Vc can be calculated. (However, Φ5 ′ and Φ6 ′ are other correction coefficients proportional to ζ1 and ζ2.) Of course, using another correction coefficient, the flow velocity (V1 = Φ5 ′ · Vw, V2 = Φ6 ′) is corrected for Vw. -Vw) may be calculated. In this way, by changing the correction coefficient so that it becomes an appropriate value according to the subtle difference in flow velocity distribution that changes depending on the type of gas, the average flow velocity is calculated regardless of the flow velocity distribution, and the flow rate is calculated and calculated. can do.

  Further, in the piezoelectric elements constituting the ultrasonic transmission / reception units (2a, 2b), the number of piezoelectric element blocks may be increased. FIG. 18 shows a configuration when the number of piezoelectric element blocks is three. In the example of FIG. 18, each piezoelectric element block is divided by two slits SL, but each piezoelectric element block may be configured independently.

  The ultrasonic beam α in the channel width direction radiated from the piezoelectric element block 2a1 propagates through the second propagation path (broken line). The ultrasonic beam β in the channel width direction radiated from the piezoelectric element block 2a2 propagates through the first propagation path (solid line). In addition, the channel width direction ultrasonic beam γ radiated from the piezoelectric element block 2a3 propagates through a path (two-dot chain line) that performs multiple reflections on the upper wall surface inscribed region 3C and the central channel central region 3W. In this configuration, a relatively large number of paths propagate in the upper and middle parts of the flow path, so that in the case where more uneven flow velocity distribution occurs in the upper part of the flow path, the flow distribution state is more detailed. Can be grasped.

  Then, the ratio of the propagation time of the ultrasonic beam β to the propagation time of the ultrasonic beam α, the ratio of the propagation time of the ultrasonic beam γ to the propagation time of the ultrasonic beam α, and the ultrasonic beam β Depending on the value of the ratio of three different propagation times, such as the ratio of the propagation time by the ultrasonic beam γ to the propagation time, or the value of the three flow velocity ratios calculated from these propagation times, It is also possible to calculate the average flow velocity and calculate the flow rate by estimating the distribution pattern according to the order and assigning an appropriate correction coefficient according to the flow velocity distribution pattern.

  Although the embodiments of the present invention have been described above, these are merely examples, and the present invention is not limited to these embodiments, and the knowledge of those skilled in the art can be used without departing from the spirit of the claims. Various modifications based on this are possible.

The schematic diagram which shows the whole structure which concerns on an example of the ultrasonic flowmeter of this invention. The cross-sectional perspective view which shows the internal structure of the flowmeter main body of an ultrasonic flowmeter. The figure which shows the structural example of an ultrasonic transmission / reception part. The figure which shows the structure of an ultrasonic transmission / reception part following FIG. The figure which shows the example of attachment of the ultrasonic transmission / reception part of FIG. 3, FIG. The figure which shows the example of attachment of the ultrasonic transmission / reception part of FIG. 3, FIG. The figure which shows another example of a structure of an ultrasonic transmission / reception part. The block diagram which shows the structure of a microcomputer. The figure which shows the calculation method of flow volume. The flow figure explaining flow distribution information output processing. The figure explaining the radiation timing of an ultrasonic beam. The figure which shows another example of a structure of an ultrasonic transmission / reception part and a reflection member. The figure which shows another example of a structure of an ultrasonic transmission / reception part and a reflecting member following FIG. The figure which shows another example of a structure of an ultrasonic transmission / reception part and a reflection member. The figure which shows another example of a structure of an ultrasonic transmission / reception part and a reflection member following FIG. The figure explaining calculation of the flow velocity distribution information contained in flow volume distribution information. The figure which shows the method of calculating a flow rate by calculating a flow rate by assigning a reasonable coefficient in a flow rate range. The figure which shows another example of a structure of an ultrasonic transmission / reception part. The graph which shows the result of having simulated the relationship between the thickness of a reflection part, and ultrasonic transmittance.

Explanation of symbols

1 Ultrasonic flow meter 1E Control circuit (propagation time measurement means, flow distribution information calculation means, flow distribution information output means, flow velocity calculation means, flow velocity distribution correction coefficient calculation means, flow velocity correction means)
2a Ultrasonic transmitter / receiver (first ultrasonic transmitter / receiver pair)
2b Ultrasonic transmitter / receiver (second ultrasonic transmitter / receiver pair)
2a1, 2a2 Piezoelectric element block (piezoelectric body)
3 flow path forming portion 3C upper wall inscribed area 3C 'lower wall inscribed area 3P flow path 3W flow path central area 11 microcomputer 31 reflecting member (first reflecting member)
31h1 Beam introduction opening (first penetration)
31h2 Beam introduction opening (third penetration)
31h3 Beam introduction opening 32 Reflective member (second reflective member)
32h1 Beam introduction opening (second penetration part)
32h2 Beam introduction opening (fourth penetration part)
32h3 Beam introduction opening GF Fluid to be measured

Claims (11)

A flow path forming section for forming a flow path of the fluid to be measured;
A pair of transmission / reception functions that are attached to the flow path forming unit and are configured to be interchangeable so that one is a sending part of the ultrasonic beam to the fluid to be measured and the other is a receiving part of the ultrasonic beam. A first and second ultrasonic transmission / reception unit pair consisting of ultrasonic transmission / reception units;
It is formed in a plate shape arranged along the flow path inside the flow path forming portion, and the cross section of the flow path is divided into a flow path central area and both sides of the flow path central area. The first ultrasonic transmission / reception unit pair is divided into a total propagation length that passes through the flow path central region and the total propagation length that passes through the wall inscribed region. Along the first propagation path that is longer than the length, for the second ultrasonic transmission / reception unit pair, the total propagation length that passes through the flow path central region is greater than the total propagation length that passes through the wall inscribed region. A reflecting member that guides the ultrasonic beam to the receiving unit while being reflected and refracted from the transmitting unit along a second propagation path different from the short first propagation path;
A first propagation time which is a propagation time of the ultrasonic beam when the first ultrasonic transmission / reception unit pair is used, and a propagation time of the ultrasonic beam when the second ultrasonic transmission / reception unit pair is used. A propagation time measuring means for measuring each of the second propagation times,
Based on the measurement results of the first propagation time and the second propagation time, the flow distribution information is calculated by dividing the flow distribution information in the flow channel section into the flow channel central region and the wall inscribed region. A calculation means;
A flow distribution information output means for outputting the calculated flow distribution information;
An ultrasonic flowmeter characterized by comprising:   The ultrasonic flowmeter according to claim 1, wherein the first propagation path and the second propagation path are set to have the same length. The reflection member includes a first reflection member positioned on a side close to the transmission unit and a second reflection member positioned on a side close to the reception unit, and the first reflection member includes the first propagation member. A first penetrating part that guides the ultrasonic beam transmitted from the transmitting unit of the first ultrasonic transmitting / receiving unit pair along the path to the flow path central region is formed, and the second reflecting member includes the A second penetrating portion is formed for guiding the ultrasonic beam that has been multiple-reflected in the central region of the flow channel into the wall-inscribed region on the receiving unit side;
The formation positions of the first penetrating portion and the second penetrating portion are determined so that the number of reflections of the ultrasonic beam in the central region of the flow path is greater than the total number of reflections in each wall inscribed region. The ultrasonic flowmeter according to claim 1 or 2, wherein the ultrasonic flowmeter is formed.   The ultrasonic flow rate according to claim 3, wherein the formation positions of the first penetrating portion and the second penetrating portion are determined so that the ultrasonic beam passes through the wall inscribed regions without reflection. Total. The reflective member includes a first reflective member located on a side close to the transmitting unit and a second reflective member located on a side close to the receiving unit, and the first reflective member includes the second propagation member. An inner wall surface of the flow path forming unit that is sent from the transmission unit of the second ultrasonic transmission / reception unit pair along the path and faces the first reflecting member in the wall inscribed region on the transmission unit side; A third penetrating portion is formed for guiding the ultrasonic beam that has been multiple-reflected between the flow path to the central region of the flow path, and the second reflective member has the ultrasonic beam transmitted from the flow path central region to the receiving unit side. The ultrasonic beam is introduced into the wall surface inscribed region of the second reflection member and multiple reflected between the second reflection member and the inner wall surface of the flow path forming portion facing the second reflection member. A fourth penetration is formed leading to the receiver of the pair;
The formation positions of the third penetrating portion and the fourth penetrating portion are determined so that the total number of reflections in each wall inscribed region is greater than the number of reflections of the ultrasonic beam in the flow channel central region. The ultrasonic flowmeter according to claim 1, wherein the ultrasonic flowmeter is formed.   The ultrasonic flowmeter according to claim 5, wherein the formation position of the third through portion and the fourth through portion is determined so that the ultrasonic beam passes through the flow path central region without reflection. . Comprising the requirements of claim 3 or claim 4;
The transmitting unit and the receiving unit of the first ultrasonic transmission / reception unit pair and the second ultrasonic transmission / reception unit pair are adjacent to each other in the width direction of the reflecting member at the same position in the flow direction of the flow path. And the ultrasonic beam is emitted or incident at the same angle with respect to each of the first reflecting member and the second reflecting member,
The first penetrating portion and the second penetrating portion pass through the ultrasonic beam applied to the transmitting unit or the receiving unit forming the first ultrasonic transmitting / receiving unit pair with respect to the first reflecting member and the second reflecting member. Is allowed, and only the first ultrasonic transmission / reception unit opposite side of each reflection member in the width direction so as to block the passage of the ultrasonic beam applied to the transmission unit or reception unit forming the second ultrasonic transmission / reception unit pair. Formed in a partially cutout shape,
The third penetrating portion and the fourth penetrating portion pass through the ultrasonic beam applied to the transmitting unit or the receiving unit forming the second ultrasonic transmitting / receiving unit pair with respect to the first reflecting member and the second reflecting member. Is allowed, and only the second ultrasonic transmission / reception unit opposite side of each reflection member in the width direction so as to prevent the transmission of the ultrasonic beam applied to the transmission unit or reception unit forming the first ultrasonic transmission / reception unit pair. The ultrasonic flow meter according to claim 5 or 6, wherein the ultrasonic flow meter is formed in a partially cut-out shape.   The first and second ultrasonic transmission / reception units are configured by a single piezoelectric body, and the piezoelectric body is placed on the surface of the piezoelectric body in the flow direction of the flow path. The ultrasonic flow rate according to any one of claims 1 to 7, wherein a groove for dividing the transmitter / receiver is provided, and each piezoelectric body divided in the groove has independent ultrasonic directivity characteristics. Total.   The first and second ultrasonic transmission / reception units are each composed of an independent piezoelectric body, and these piezoelectric bodies are separately arranged symmetrically with respect to the flow direction of the flow path, and have independent ultrasonic directivity characteristics. The ultrasonic flowmeter according to any one of claims 1 to 7. Based on the flow rate distribution information, a flow velocity calculating means for calculating a flow velocity in the flow path central region and the wall surface inscribed region of the fluid to be measured;
A flow velocity distribution correction coefficient calculating means for calculating a flow velocity distribution correction coefficient corresponding to the flow distribution information based on the calculated flow velocities of the two fluids to be measured;
An ultrasonic flowmeter according to claim 1, comprising:   The ultrasonic flowmeter according to claim 10, further comprising a flow velocity correction unit that corrects a flow velocity of the fluid to be measured based on the calculated flow velocity distribution correction coefficient.

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