JP5046330B2 - Ultrasonic flowmeter and ultrasonic transducer unit - Google Patents

Description

  The present invention propagates ultrasonic waves transmitted and received between a pair of measurement ultrasonic transducers to a fluid flowing in the flow path of the measurement housing, and measures the flow rate of the fluid based on the propagation time. The present invention relates to an ultrasonic flowmeter and an ultrasonic transducer unit attached to the ultrasonic flowmeter.

As a conventional ultrasonic flowmeter of this kind, by fixing a pair of ultrasonic transducers to the measurement tube via a rubber vibration isolator, from the ultrasonic transducer to the tube wall of the measurement tube There are known ones in which propagating ultrasonic waves (so-called housing noise) are reduced (see, for example, Patent Documents 1 and 2).
JP-A-61-25021 (page 4, line 7 to page 5, line 6, FIG. 1) Japanese Patent Laid-Open No. 11-23332 (paragraphs [0008], [0009], FIG. 2)

  However, the above-described conventional ultrasonic flowmeter has a problem that when the temperature is lowered and the rubber is cured, the housing noise cannot be sufficiently reduced and the measurement accuracy is deteriorated.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an ultrasonic flowmeter and an ultrasonic transducer unit that can accurately measure a flow rate.

  In order to achieve the above object, an ultrasonic flowmeter according to the first aspect of the present invention provides a measurement housing having a flow path through which a fluid flows, and a pair of transmission / reception divided into an upstream side and a downstream side of the flow path. A pair of ultrasonic transducers for measurement are fixed on the opposing surfaces of the pair of fixed transducers and a pair of ultrasonic transducers for transmission / reception are provided. In an ultrasonic flowmeter that propagates waved ultrasonic waves to the fluid in the flow path and measures the flow rate of the fluid based on the propagation time, it is opposite to the opposing surface of the pair of transducer fixed walls Ultrasonic waves that are fixed to the side surfaces and that transmit ultrasonic waves that are opposite in phase to the ultrasonic waves that are transmitted by the measurement ultrasonic transducer and propagate from the measurement ultrasonic transducer to the transducer fixed wall. Features a pair of noise canceling ultrasonic transducers for canceling sound waves To.

  According to a second aspect of the present invention, in the ultrasonic flowmeter according to the first aspect, the noise canceling ultrasonic transducer is configured to be able to receive an ultrasonic wave propagating to the transducer fixed wall, and to measure the ultrasonic flowmeter. Measurement signal received and output by ultrasonic transmitter / receiver, and noise canceling ultrasonic transmitter / receiver fixed to the same transmitter / receiver fixed wall as the measurement ultrasonic transmitter / receiver on the receiving side. Based on the received signal for noise cancellation that is output by the wave receiving device, the ultrasonic wave received by the measuring ultrasonic transducer through the fixed wall of the measuring device is received. It is characterized in that it includes a received signal processing unit that cancels received noise components due to sound waves.

  The invention according to claim 3 is the ultrasonic flowmeter according to claim 1 or 2, wherein the ultrasonic transducer for measurement and the ultrasonic transducer for noise cancellation have the same structure and the same size. It is characterized by being a vessel.

  According to a fourth aspect of the present invention, in the ultrasonic flowmeter according to any one of the first to third aspects, the measurement housing has a linearly extending tube structure, and a fluid inflow portion and a fluid are formed on side surfaces near both ends. A measuring tube portion having an outflow portion and a pair of end blocking walls that close both ends of the measuring tube portion are provided, and the pair of transducer fixed walls are connected to the fluid inflow portion and the end of the measuring tube portion. It is characterized in that it is arranged between the part closing wall and between the fluid outflow part and the end closing wall and fixed inside the measuring pipe part.

  A fifth aspect of the invention is the ultrasonic flowmeter according to the fourth aspect, wherein the pair of transducer fixing walls is formed into a flat plate shape, and the transducer fixing wall and the end blocking wall are formed at both ends of the measurement pipe portion. A pair of end section regions sandwiched between two regions, penetrating a pair of transducer fixed walls, a region between the pair of transducer fixed walls in the measurement tube section, and a pair of ends It is characterized in that it has a communication path that communicates with the partial section area.

The ultrasonic transducer unit according to the invention of claim 6 is attached in pairs to a measurement housing having a flow path through which a fluid flows in an ultrasonic flowmeter, and transmits and receives ultrasonic waves to measure the flow rate of the fluid. An ultrasonic transducer unit used for measurement, which is directed to a transducer fixed wall whose outer edge is fixed to a measurement housing, and a fluid that is fixed to the front side of the transducer fixed wall and flows through a flow path An ultrasonic transducer for measurement that can transmit ultrasonic waves, and an ultrasonic wave that is fixed to the back side of the fixed wall of the transducer and that is opposite in phase to the ultrasonic wave transmitted by the ultrasonic transducer for measurement. A noise canceling ultrasonic transducer for canceling the ultrasonic wave transmitted from the measuring ultrasonic transducer to the transducer fixing wall is characterized.

[Inventions of Claims 1 and 6 ]
According to the inventions according to claims 1 and 6 configured as described above, when ultrasonic waves are transmitted / received between a pair of ultrasonic transducers for measurement, ultrasonic transmission / reception for measurement on the transmission side is performed. Since the ultrasonic transducer for noise cancellation fixed to the same transmitter / receiver fixed wall as the transmitter transmits ultrasonic waves in the opposite phase to the ultrasonic wave transmitted by the ultrasonic transducer for measurement on the transmission side The ultrasonic wave propagating from the measurement ultrasonic transducer to the transducer fixed wall is canceled (cancelled). That is, it is possible to reduce or eliminate the ultrasonic wave (so-called housing noise) propagating to the measurement housing through the transducer fixed wall as the ultrasonic wave is transmitted from the measurement ultrasonic transducer. . Thereby, the flow rate can be accurately measured.

[Invention of claim 2]
According to the invention according to claim 2, when the ultrasonic wave propagates through the measurement housing and the transducer fixed wall, the ultrasonic transducer for measurement on the wave receiving side includes the ultrasonic wave propagated in the fluid and the measurement. Both the ultrasonic waves propagated through the housing and the transducer fixed wall are received. In addition, the noise canceling ultrasonic transducer fixed to the same transducer fixed wall as the measurement-side ultrasonic transducer on the reception side receives only the ultrasonic waves propagated through the measurement housing and the transducer fixed wall. To wave. Measurement is performed based on the measurement reception signal received and output by the measurement ultrasonic transducer and the noise cancellation reception signal received and output by the noise cancellation ultrasonic transducer. Among the received signals, the measurement ultrasonic transmitter / receiver cancels the received noise component (ie, housing noise) received through the transmitter / receiver fixed wall. Even when the ultrasonic wave propagating from the ultrasonic transducer to the measurement housing through the transducer fixed wall cannot be sufficiently reduced, the influence can be eliminated and the flow rate can be accurately measured.

[Invention of claim 3]
According to the invention of claim 3, since the ultrasonic transducer for measurement and the ultrasonic transducer for noise cancellation can be constituted by a common ultrasonic transducer, the labor of parts procurement and parts management is reduced. Can be reduced.

[Invention of claim 4]
According to the invention of claim 4, the ultrasonic transducer for noise cancellation is unnecessary from the outside of the measurement housing because the side and the ultrasonic transmission / reception surface are covered by the measurement tube portion and the end blocking wall. It is possible to prevent reception of various ultrasonic waves.

[Invention of claim 5]
According to invention of Claim 5, the fluid which flowed in from the fluid inflow part flows into the area | region between a pair of transducer fixing wall among a measurement pipe part, and a pair of edge part division area | region has, Each of them accommodates an ultrasonic transducer for noise cancellation. And since a part of fluid which flows through a measurement pipe part flows in into a pair of end section area through a communicating passage, it is the ultrasonic transducer for noise cancellation under the same conditions as an ultrasonic transducer for measurement. Can transmit and receive ultrasonic waves.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
Reference numeral 11 in FIG. 1 is a measurement housing in the ultrasonic flowmeter 10 (see FIG. 2), and is attached in the middle of a feed pipe through which fluid (for example, gas) flows.

  The measurement housing 11 includes a linear measurement tube section 12 whose both ends are closed by a pair of end block walls 15, 15, and a flow path 12 </ b> A through which a fluid flows is formed inside the measurement tube section 12. Yes. 12 A of flow paths are comprised from the large diameter parts 13 and 13 with which the both ends of the longitudinal direction were equipped, and the small diameter part 14 diameter-reduced by the step shape with respect to the large diameter parts 13 and 13, and a small diameter part The inner diameter of 14 is constant.

  Two cylindrical portions 19 and 19 stand upright at right angles to the longitudinal direction from the positions near the both ends in the longitudinal direction of the measuring tube portion 12. Of the cylindrical portions 19, 19, the inner region of one cylindrical portion 19 (the right cylindrical portion 19 in FIG. 1) is a fluid inflow passage 19 </ b> A for introducing fluid into the flow passage 12 </ b> A, and is one of the flow passages 12 </ b> A. The large diameter portion 13 is communicated with. Further, the inner region of the other cylindrical portion 19 (left cylindrical portion 19 in FIG. 1) is a fluid outflow passage 19B for discharging the fluid that has passed through the flow path 12A, and communicates with the other large-diameter portion 13. is doing. When a feed pipe (not shown) is connected to both cylindrical portions 19 and 19, as shown by an arrow in FIG. 1, from one end side to the other end side in the longitudinal direction (left-right direction in FIG. 1) of the flow path 12A. Fluid flows toward it. One cylindrical portion 19 corresponds to the “fluid inflow portion” of the present invention, and the other cylindrical portion 19 corresponds to the “fluid outflow portion” of the present invention.

  Ultrasonic transducer units 60 and 60 according to the invention of claim 7 of the present application are fixed inside the large diameter portions 13 and 13 in the flow path 12A. The ultrasonic transmitter / receiver units 60, 60 are arranged on the transmitter / receiver fixing plate 18 (corresponding to the “transmitter / receiver fixing wall” of the present invention) and the ultrasonic transducer 20 for measurement and the ultrasonic transmitter / receiver for noise cancellation. 30 is fixed back to back.

  In the ultrasonic transducer unit 60, the transducer fixing plate 18 has a disk shape that is larger in diameter than the inner diameter of the large-diameter portion 13 and flat in both sides in the plate thickness direction. And the annular | circular shape formed in the inner peripheral surface of the large diameter parts 13 and 13 at the position near both ends (end part closed walls 15 and 15) of the measurement pipe part 12 rather than the internal opening of both cylindrical parts 19 and 19 was formed. The outer peripheral edge portions of the transducer fixing plates 18 and 18 are fitted into the fitting grooves 17 and 17.

  The ultrasonic transducers 20 for measurement are respectively disposed on the opposing surfaces 18A and 18A (corresponding to the “front side surface” in claim 7 of the present application) facing each other across the flow path 12A among the transducer fixing plates 18 and 18. , 20 are fixed. The ultrasonic transducers 20 and 20 for measurement are arranged on the axis of the flow path 12A and have a flat cylindrical structure as a whole. Specifically, the front end portion of the measurement ultrasonic transducer 20 has a truncated cone shape, and the front end surface is an ultrasonic transmission / reception surface 20A.

  Of the transducer fixing plates 18 and 18, surfaces 18B and 18B opposite to the opposing surfaces 18A and 18A to which the measurement ultrasonic transducers 20 and 20 are fixed (corresponding to the “back side surface” in claim 7 of the present application). ), Noise canceling ultrasonic transducers 30 and 30 having the same structure and the same size as the measurement ultrasonic transducers 20 and 20 are fixed. That is, the noise canceling ultrasonic transducer 30 is fixed back-to-back with the measurement ultrasonic transducer 20 with the transducer fixing plate 18 sandwiched therebetween, whereby the measurement ultrasonic transducers 20, 20 are fixed. The noise canceling ultrasonic transducers 30 and 30 are arranged side by side on the axis of the flow path 12A.

  Further, in the measuring tube section 12, between the transducer fixing plates 18 and 18 and the end blocking walls 15 and 15, the transducer fixing plates 18 and 18 are disconnected from the flow path 12A and blocked. End section regions 16 and 16 are formed, and noise canceling ultrasonic transducers 30 and 30 fixed to the respective transducer fixing plates 18 and 18 are accommodated therein. Since the noise canceling ultrasonic transducers 30 and 30 are accommodated in the end section regions 16 and 16, the noise canceling ultrasonic transducers 30 and 30 transmit unnecessary ultrasonic waves from the outside of the measurement housing 11. The reception is prevented.

  Note that the end partition regions 16 and 16 are filled with the same fluid (gas in this embodiment) as the fluid flowing in the flow path 12A (the fluid whose flow rate is to be measured).

  As shown in FIG. 2, the ultrasonic transducers 20 and 20 for measurement are controlled by a switching signal from the transmission / reception switching unit 41, and when one is connected to the transmission drive circuit 42 to become a transmitter, the other receives It is connected to the detection circuit 43 to become a receiver, and the transmitter and receiver are switched at a predetermined timing.

  When receiving a transmission command from the calculation unit 45, the transmission drive circuit 42 excites the measurement ultrasonic transducer 20 on the transmission side to transmit ultrasonic waves. Specifically, as shown in FIG. 3, a drive pulse is generated by the drive wave generation unit 42 </ b> A, and ultrasonic waves are transmitted from the measurement ultrasonic transducer 20 by the drive pulse.

  The reception detection circuit 43 detects the time measurement unit 44 when a measurement reception signal output by receiving and outputting an ultrasonic wave from the reception-side measurement ultrasonic transducer 20 reaches a predetermined value. Output a signal.

  The time measurement unit 44 propagates from the time when the transmission-side measurement ultrasonic transducer 20 transmits ultrasonic waves to the time when the reception-side measurement ultrasonic transducer 20 receives ultrasonic waves. Measure time. Specifically, the timer of the time measuring unit 44 starts when a transmission command is output from the arithmetic unit 45 to the transmission drive circuit 42, and the timer stops when a detection signal is input from the reception detection circuit 43. .

  The calculation unit 45 takes in the propagation time of the ultrasonic wave measured by the time measurement unit 44. And the propagation time when transmitting and receiving ultrasonic waves from one of the pair of ultrasonic transducers 20 and 20 for measurement toward the other, and the propagation time when transmitting and receiving ultrasonic waves from the other to the other Based on the difference, the flow velocity and flow rate of the fluid are calculated by a known calculation formula. For example, the flow velocity and the flow rate are calculated based on the principle that the difference in the reciprocal of the propagation time is proportional to the flow velocity.

  In the ultrasonic flowmeter 10 of the present invention, not only the measurement ultrasonic transducers 20 and 20 but also the noise canceling ultrasonic transducers 30 and 30 are controlled by signals from the transmission / reception switching unit 41. Specifically, when one of the measurement ultrasonic transducers 20 is connected to the transmission drive circuit 42, one of the ultrasonic transducers 20 fixed to the same transducer fixing plate 18 as the one of the measurement ultrasonic transducers 20 is fixed. The noise canceling ultrasonic transducer 30 is also connected to the transmission drive circuit 42. At this time, the other measurement ultrasonic transducer 20 on the receiving side is connected to the reception detection circuit 43, but is fixed to the same transducer fixing plate 18 as the measurement ultrasonic transducer 20. The other noise canceling ultrasonic transducer 30 is not connected to either the transmission drive circuit 42 or the reception detection circuit 43.

  Then, when the measurement ultrasonic transducer 20 on the transmission side transmits the ultrasonic wave, the noise canceling ultrasonic transducer fixed to the same transducer fixing plate 18 as the measurement ultrasonic transducer 20 is used. An ultrasonic wave having a phase opposite to that of the ultrasonic wave transmitted by the measurement ultrasonic transducer 20 is transmitted from the instrument 30 (see FIG. 3).

  Here, when the measurement ultrasonic transducer 20 transmits an ultrasonic wave, for example, the waveform shown in FIG. 4A is transmitted from the measurement ultrasonic transducer 20 to the transducer fixing plate 18. Ultrasound propagates.

  On the other hand, when the noise canceling ultrasonic transducer 30 fixed to the same transducer fixing plate 18 as the measuring ultrasonic transducer 20 on the transmission side transmits ultrasonic waves, the noise canceling ultrasonic transducer For example, ultrasonic waves having a waveform shown in FIG. 4B propagate from the acoustic transducer 30 to the transducer fixing plate 18. That is, ultrasonic waves having opposite phases propagate from both the measurement ultrasonic transducer 20 and the noise canceling ultrasonic transducer 30 to the transducer fixing plate 18.

  Thereby, the ultrasonic wave propagated from the measurement ultrasonic transducer 20 on the transmission side to the transducer fixing plate 18 is fixed to the same transducer fixing plate 18 as the measurement ultrasonic transducer 20. Further, it can be canceled (cancelled) by the ultrasonic wave propagating from the noise canceling ultrasonic transducer 30 to the transducer fixing plate 18.

  The same applies to the case where ultrasonic waves are transmitted from the other measurement ultrasonic transducer 20 toward one measurement ultrasonic transducer 20, and the other measurement ultrasonic transducer is the same. The noise canceling ultrasonic transducer 30 fixed to the same transducer fixing plate 18 as 20 transmits ultrasonic waves having a phase opposite to that of the ultrasonic wave transmitted by the measuring ultrasonic transducer 20.

  As described above, according to the present embodiment, when ultrasonic waves are transmitted and received between the pair of measurement ultrasonic transducers 20 and 20, the same as the measurement ultrasonic transducer 20 on the transmission side. The noise canceling ultrasonic transducer 30 fixed to the transducer fixing plate 18 transmits ultrasonic waves having a phase opposite to that of the ultrasonic wave transmitted by the transmitting ultrasonic transducer 20. Then, the ultrasonic wave propagating from the measurement-side ultrasonic transducer 20 on the transmission side to the transducer fixing plate 18 is canceled (cancelled). That is, the ultrasonic wave (so-called housing noise) propagating to the measurement housing 11 through the transducer fixing plate 18 as the ultrasonic wave is transmitted from the measurement ultrasonic transducer 20 is reduced or eliminated. be able to. Thereby, the flow rate can be accurately measured. Further, since the end plates 16 and 16 and the flow path 12A are disconnected from each other by making the transducer fixing plates 18 and 18 flat, the waves are transmitted from the noise canceling ultrasonic transducers 30 and 30. It is possible to prevent the ultrasonic waves reflected on the end blocking walls 15 and 15 from entering the flow path 12A.

[ Second Embodiment]
In the second embodiment, the connection state between the ultrasonic transducers 30 and 30 for noise cancellation when transmitting and receiving ultrasonic waves, the transmission drive circuit 42 and the reception detection circuit 43, and the processing in the reception detection circuit 43 are as follows. Different from the first embodiment.

Specifically, as shown in FIG. 5 , when ultrasonic waves are transmitted and received between a pair of measurement ultrasonic transducers 20 and 20, the measurement ultrasonic transducer 20 on the reception side and The noise canceling ultrasonic transducer 30 fixed to the same transducer fixing plate 18 is connected to the reception detection circuit 43 and the same transducer fixing plate as the measuring ultrasonic transducer 20 on the transmission side. The noise canceling ultrasonic transducer 30 fixed to 18 is connected to the transmission drive circuit 42.

  When the measurement ultrasonic transducer 20 on the transmission side transmits an ultrasonic wave, for example, the waveform shown in FIG. 4A from the measurement ultrasonic transducer 20 to the transducer fixing plate 18. The ultrasonic wave propagates.

  On the other hand, when the noise canceling ultrasonic transducer 30 fixed to the same transducer fixing plate 18 as the measuring ultrasonic transducer 20 on the transmission side transmits ultrasonic waves, the noise canceling ultrasonic transducer For example, ultrasonic waves having a waveform shown in FIG. 4B propagate from the acoustic transducer 30 to the transducer fixing plate 18. That is, ultrasonic waves having opposite phases propagate from both the measurement ultrasonic transducer 20 and the noise canceling ultrasonic transducer 30 to the transducer fixing plate 18.

  As a result, the ultrasonic waves transmitted from the measurement-side ultrasonic transducer 20 on the transmission side to the transducer fixing plate 18 are fixed to the same transducer fixing plate 18 as the measurement ultrasonic transducer 20. It can be canceled by the ultrasonic wave transmitted from the noise canceling ultrasonic transducer 30 to the transducer fixing plate 18. Therefore, it is possible to reduce or eliminate ultrasonic waves (so-called housing noise) propagating through the measurement housing 11 and the transmitter / receiver fixing plates 18 and 18 accompanying the transmission of ultrasonic waves from the measurement ultrasonic transducer 20. it can.

  If the ultrasonic wave (casing noise) propagating from the measuring ultrasonic transducer 20 on the transmission side to the transducer fixing plate 18 cannot be sufficiently reduced, the following is performed.

  That is, the receiving-side measurement ultrasonic transducer 20 includes both the ultrasonic wave propagated in the fluid flowing through the flow path 12A and the ultrasonic wave propagated through the measurement housing 11 and the transducer fixing plates 18 and 18. Receive. FIG. 7A shows an example of a reception signal for measurement output by receiving and outputting the measurement ultrasonic transducer 20 on the transmission side. On the other hand, in the noise canceling ultrasonic transducer 30 fixed to the same transducer fixing plate 18 as the measuring ultrasonic transducer 20 on the receiving side, the ultrasonic wave propagated in the fluid is received. Instead, only the ultrasonic wave propagated through the measurement housing 11 and the transducer fixing plates 18 and 18 is received. FIG. 7B shows an example of a noise canceling reception signal received and output by the noise canceling ultrasonic transducer 30.

  As shown in FIG. 6, the reception detection circuit 43 takes in a measurement reception signal from the measurement ultrasonic transducer 20 and a noise cancellation reception signal from the noise cancellation ultrasonic transducer 30 and outputs them. The signal is amplified and subtracted by the subtractor 43A from the received signal for measurement from the received signal for measurement. As a result, of the received signal for measurement, a received noise component (receiver for noise cancellation) by the ultrasonic wave received by the measurement ultrasonic transducer 20 via the measurement housing 11 and the transducer fixing plates 18 and 18 is received. Wave signal). FIG. 7C shows an example of a reception signal for measurement after the reception noise component is canceled.

  Then, the reception point detection unit 43B determines whether or not the measurement reception signal after canceling the reception noise component has reached a predetermined value. When it is determined that the reception signal has reached the predetermined value, reception detection is performed. The circuit 43 outputs a detection signal to the time measuring unit 44. As a result, the timer of the time measuring unit 44 is stopped, and the propagation time of the ultrasonic wave propagated in the fluid between the pair of ultrasonic transducers 20 and 20 for measurement is measured. The reception detection circuit 43 corresponds to the “received signal processing unit” of the present invention.

  Since other configurations are the same as those in the first embodiment, the same reference numerals are given to the same configurations, and duplicate descriptions are omitted.

  As described above, according to the present embodiment, when ultrasonic waves are transmitted and received between the pair of measurement ultrasonic transducers 20 and 20, the same as the measurement ultrasonic transducer 20 on the transmission side. The noise canceling ultrasonic transducer 30 fixed to the transducer fixing plate 18 transmits ultrasonic waves having a phase opposite to that of the ultrasonic wave transmitted by the transmitting ultrasonic transducer 20. Then, the ultrasonic wave propagating from the measurement-side ultrasonic transducer 20 on the transmission side to the transducer fixing plate 18 is canceled (cancelled). That is, the ultrasonic wave (so-called housing noise) propagating to the measurement housing 11 through the transducer fixing plate 18 as the ultrasonic wave is transmitted from the measurement ultrasonic transducer 20 is reduced or eliminated. be able to. Thereby, the flow rate can be accurately measured.

  Even if the ultrasonic wave propagating from the measurement ultrasonic transducer 20 on the transmission side to the measurement housing 11 via the transducer fixing plate 18 cannot be sufficiently reduced, the measurement ultrasonic transducer is not provided. A reception signal for measurement (see FIG. 7 (A)) that is received and output by 20 and a reception signal for noise cancellation (FIG. 7 (B) that is received and output by the ultrasonic transducer 30 for noise cancellation). ))), The received noise component (that is, the housing noise) received by the measurement ultrasonic transducer 20 via the transducer fixing plate 18 is canceled out of the measurement received signal. Therefore, the flow rate can be measured with high accuracy.

[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.

(1) As shown in FIG. 8 , a communication path 18C is formed through both the transducer fixing plates 18 so that the end section regions 16 and 16 and the flow path 12A are communicated with each other and pass through the flow path 12A. A part of the fluid to flow may flow into the end section regions 16 and 16 from the communication path 18C. In this way, the fluid flowing through the flow path 12A flows into the end partition regions 16 and 16 and under the same conditions (for example, concentration, pressure, and temperature) as the measurement ultrasonic transducers 20 and 20. The ultrasonic wave can be transmitted and received by the noise canceling ultrasonic transducers 30 and 30. The communication path 18 </ b> C may be formed by cutting out a part of the outer edge portion of the transducer fixing plate 18.

  (2) Although the transducer fixing plate 18 and the measurement housing 11 are separate parts, they may be integrally formed.

(3) As shown in FIG. 9 , the measurement tube portion 12 of the measurement housing 11 has a cylindrical structure with both ends open, and both openings 12B and 12B (only one opening 12B is shown in FIG. 9 ). ), By fitting or screwing cap members 50, 50 which are separate parts from the measurement tube portion 12, both the openings 12B, 12B are closed, and the ultrasonic transducer units 60, 60 are connected to the measurement housing. It is good also as a structure fixed in 11. More specifically, the cap member 50 includes a cylindrical wall 50A that fits or is screwed into the inside of the opening 12B, and an end closed wall 50B that closes one end of the cylindrical wall 50A and projects sideways. The ultrasonic transducer unit 60 is inserted and fitted through the opening 12B of the measurement tube unit 12, and then the cylindrical wall 50A of the cap member 50 is fitted or screwed inside the opening 12B. It is good also as a structure which clamps the outer edge part of the waver fixing board 18 between the front-end | tip of 50 A of cylinder walls, and the internal surface level | step-difference part 12C of the measurement pipe part 12. In this case, a seal member (not shown) is sealed between the outer peripheral surface of the cylindrical wall 50A and the inner peripheral surface of the opening 12B or between the end blocking wall 50B and the end surface of the measuring tube portion 12. It is preferable.

  (4) In addition, the fitting groove 17 formed in one of the measurement tube components of the pair of measurement tube components formed by dividing the measurement tube part 12 in a vertically divided manner (on a plane parallel to the axial direction). The ultrasonic transducer unit 60, 60 is fitted into the measurement housing by fitting the transducer fixing plate 18 of the ultrasonic transducer unit 60 to each other and combining the measurement tube components together in this state. 11 may be fixed inside.

(5) In the first to second embodiments, the measurement ultrasonic transducers 20 and 20 and the noise canceling ultrasonic transducers 30 and 30 are arranged side by side on the axis of the flow path 12A. However, as shown in FIG. 10 , they may be arranged side by side in a direction that obliquely intersects the axis of the flow path 12A.

(6) transducer fixing plate 18 and 18 has been fitted to the entire circumference of the inner peripheral surface of the measurement pipe section 12, only a portion of the inner peripheral surface of the measurement pipe section 12 as shown in FIG. 11 May be fitted.

Sectional drawing of the measurement housing of the ultrasonic flowmeter concerning a 1st embodiment of the present invention. Ultrasonic flow meter block diagram Block diagram of transmission drive circuit (A) Waveform of ultrasonic wave leaking from measurement ultrasonic transducer to transmitter / receiver fixed wall, (B) Waveform of ultrasonic wave leaking from ultrasonic transducer for noise cancellation to transducer fixed wall Block diagram of an ultrasonic flowmeter according to the second embodiment Block diagram of reception detection circuit (A) Graph of received signal for measurement, (B) Graph of received signal for noise cancellation, (C) Graph of received signal for measurement with canceled received noise component Partial sectional view of a measurement housing according to another embodiment (1) Sectional drawing of the measurement housing which concerns on other embodiment (3) Sectional drawing of the measurement housing which concerns on other embodiment (5) Sectional drawing of the measurement pipe part which concerns on other embodiment (6).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Ultrasonic flowmeter 11 Measurement housing 12 Measurement pipe part 12A Flow path 15 End blockage wall 16 End part division area | region 18 Transmitter / receiver fixing plate (transmitter / receiver fixed wall)
18A Opposing surface (front side)
18B Opposite side and opposite side (back side)
19 Cylindrical part (fluid inflow part, fluid outflow part)
20 Ultrasonic transducer for measurement 30 Ultrasonic transducer for noise cancellation (Ultrasonic transducer for reception noise cancellation)
43 Reception detection circuit (received signal processor)
50B End blockage wall 60 Ultrasonic transducer unit

Claims (6)

A measurement housing having a flow path through which a fluid flows is provided with a pair of transducer fixed walls separately on the upstream side and the downstream side of the flow path, and the opposing surfaces of the pair of transducer fixed walls A pair of ultrasonic transducers for measurement are fixed to
In the ultrasonic flowmeter for propagating ultrasonic waves transmitted and received between the pair of ultrasonic transducers for measurement to the fluid in the flow path and measuring the flow rate of the fluid based on the propagation time,
An ultrasonic wave having a phase opposite to that of the ultrasonic wave transmitted by the ultrasonic transducer for measurement is transmitted to each of the pair of transducer fixed walls fixed to a surface opposite to the opposing surface. An ultrasonic flowmeter comprising a pair of noise canceling ultrasonic transducers for canceling ultrasonic waves propagating from the measurement ultrasonic transducers to the transducer fixed wall. The noise canceling ultrasonic transducer is configured to be able to receive ultrasonic waves propagating to the transducer fixed wall,
The measurement ultrasonic transducer receives and outputs an ultrasonic wave, and is fixed to the same transducer fixed wall as the measurement ultrasonic transducer on the reception side. Based on the noise canceling reception signal that is output by receiving and outputting the ultrasonic wave from the noise canceling ultrasonic transmitter / receiver, the measurement ultrasonic transducer is the transmitter / receiver of the measurement reception signals. The ultrasonic flowmeter according to claim 1, further comprising: a received signal processing unit that cancels a received noise component due to the ultrasonic wave received through the fixed wall.   The ultrasonic flow rate according to claim 1 or 2, wherein the ultrasonic transducer for measurement and the ultrasonic transducer for noise cancellation are ultrasonic transducers having the same structure and the same size. Total. The measurement housing has a tube structure that extends in a straight line and has a fluid inflow portion and a fluid outflow portion on side surfaces near both ends, and a pair of ends that close both ends of the measurement tube portion. And an obstruction wall
The pair of transmitter / receiver fixed walls are arranged between the fluid inflow portion and the end closing wall and between the fluid outflow portion and the end closing wall in the measurement pipe portion. The ultrasonic flowmeter according to any one of claims 1 to 3, wherein the ultrasonic flowmeter is fixed inside the measurement tube portion. The pair of transducer fixing walls is formed into a flat plate shape, and a pair of end partition regions sandwiched between the transducer fixing wall and the end blocking wall are provided at both ends of the measurement tube portion,
A communication path that penetrates through the pair of transducer fixed walls and communicates the region between the pair of transducer fixed walls in the measurement tube section and the pair of end section regions. The ultrasonic flowmeter according to claim 4, wherein the ultrasonic flowmeter is provided. An ultrasonic transducer unit that is attached in pairs to a measurement housing having a flow path through which a fluid flows, and is used to measure the flow rate of fluid by transmitting and receiving ultrasonic waves,
A transducer fixing wall whose outer edge is fixed to the measurement housing;
An ultrasonic transducer for measurement capable of transmitting ultrasonic waves toward the fluid flowing through the flow path fixed to the front side surface of the transducer fixed wall;
It is fixed to the back side of the transducer fixing wall, and transmits ultrasonic waves having a phase opposite to that of the ultrasonic waves transmitted by the ultrasonic transducer for measurement, from the ultrasonic transducer for measurement. An ultrasonic transducer unit comprising: a noise canceling ultrasonic transducer for canceling ultrasonic waves propagating to a transducer fixed wall.

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