JP2014157071A - Ultrasonic flow meter, and ultrasonic sensor for ultrasonic flow meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an ultrasonic flow meter capable of accurately measuring a flow rate of gas; and an ultrasonic wave absorbing material for the ultrasonic flow meter.SOLUTION: An ultrasonic flow meter includes: a first ultrasonic sensor 20A; a second ultrasonic sensor 20B; and a body part which measures a flow rate of a fluid on the basis of the time from transmission of an ultrasonic wave from the first ultrasonic sensor 20A to reception in the second ultrasonic sensor 20B and the time from transmission of an ultrasonic wave from the second ultrasonic sensor 20B to reception in the first ultrasonic sensor 20A. Each of the first ultrasonic sensor 20A and the second ultrasonic sensor 20B includes an ultrasonic transmitter-receiver 22 and includes a wedge 21 which causes an ultrasonic wave transmitted from the ultrasonic transmitter-receiver to be incident to a surface of the fluid at a prescribed angle, and the wedge 21 has a notch 21c.

Description

  Some embodiments according to the present invention relate to an ultrasonic flowmeter that measures a flow rate of a fluid flowing through a pipe using ultrasonic waves, and an ultrasonic sensor for the ultrasonic flowmeter.

  Conventionally, as this type of ultrasonic flowmeter, one or more ultrasonic transducers constituted by an ultrasonic transducer and a bevel wedge are installed on the outer periphery of a pipe through which fluid flows, and the flow direction of the fluid and It is known that when each ultrasonic wave is propagated in the forehead direction, the respective propagation times are measured, and the measurement control unit calculates the flow rate of the fluid based on the propagation time and generates a circumferential force (see, for example, Patent Document 1). .

Japanese Patent No. 3216769

  By the way, the ultrasonic wave emitted from the ultrasonic transducer is divided into a fluid propagation wave propagating through the fluid flowing through the pipe and a pipe propagation wave reflecting off the pipe wall of the pipe and propagating through the pipe. In the conventional ultrasonic flowmeter, the fluid propagation wave is a signal (signal component) to be detected, and the pipe propagation wave is noise (noise component) with respect to the signal.

  However, the conventional ultrasonic flowmeter cannot sufficiently reduce the energy (magnitude or strength) of the pipe propagation wave relative to the energy (magnitude or intensity) of the fluid propagation wave. It was difficult to distinguish from waves. Therefore, there is a possibility that the conventional ultrasonic flowmeter erroneously measures the flow rate of the fluid.

  Some aspects of the present embodiment have been made in view of the above-described problems, and provide an ultrasonic flowmeter capable of accurately measuring a fluid flow rate and an ultrasonic sensor for the ultrasonic flowmeter. Is one of the purposes.

  An ultrasonic flowmeter according to the present invention includes a first ultrasonic sensor provided on an upstream outer periphery of a pipe through which fluid flows, and includes an ultrasonic transceiver that transmits and receives ultrasonic waves, and the pipe described above. A second ultrasonic sensor provided on an outer periphery on the downstream side and including an ultrasonic transceiver for transmitting and receiving ultrasonic waves, and an ultrasonic wave transmitted from the first ultrasonic sensor is a second ultrasonic sensor A main body for measuring the flow rate of the fluid based on the time until the first ultrasonic sensor receives the ultrasonic wave transmitted from the second ultrasonic sensor, and the time until the ultrasonic wave transmitted from the second ultrasonic sensor is received by the first ultrasonic sensor; Each of the first ultrasonic sensor and the second ultrasonic sensor is provided with an ultrasonic transmitter / receiver, and makes ultrasonic waves transmitted from the ultrasonic transmitter / receiver enter the fluid at a predetermined angle. Further comprising a wedge, Rust, has a notch.

  According to such a configuration, each of the first ultrasonic sensor and the second ultrasonic sensor is provided with the ultrasonic transceiver, and the ultrasonic wave transmitted from the ultrasonic transceiver is transmitted through the pipe at a predetermined angle. A wedge for entering the flowing fluid is provided, and the wedge has a notch 21c. As a result, the pipe propagation wave incident on the wedge is blocked by the notch and is difficult to reach the ultrasonic transmitter / receiver, so that the energy (magnitude or strength) of the pipe propagation wave reaching the ultrasonic transmitter / receiver is propagated through the fluid. It is possible to reduce the wave energy (magnitude or intensity), that is, to improve the SN ratio.

  Preferably, the notch is formed around a propagation path to the ultrasonic transmitter / receiver in a wedge of a fluid propagation wave in which the ultrasonic wave propagates through the fluid.

  According to such a configuration, the notch is formed around the propagation path to the ultrasonic transceiver in the wedge of the fluid propagation wave. As a result, the notch efficiently inhibits the pipe propagation wave that can reach the ultrasonic transceiver, and is not formed on the propagation path of the fluid propagation wave to the ultrasonic transceiver, so that the fluid incident on the wedge The propagating wave reaches the ultrasonic transceiver without being blocked by the notch. Therefore, the notch further increases the energy (magnitude or intensity) of the pipe propagating wave reaching the ultrasonic transceiver without reducing (maintaining) the energy (magnitude or intensity) of the fluid propagating wave. Since it can be reduced, the SN ratio can be further improved.

  Preferably, the aforementioned notch is filled with a predetermined member.

  According to this configuration, the predetermined member is filled in the notch included in the wedge. Thereby, the pipe propagation wave incident on the wedge is hindered by a predetermined member filled in the notch and hardly reaches the ultrasonic transmitter / receiver, so that the SN ratio can be improved.

  In addition, since the notch is filled with a predetermined member, the wedge can suppress a decrease in strength even if it has the notch.

  Preferably, the predetermined member is a member having a different acoustic impedance from the material of the wedge.

  According to such a configuration, the predetermined member is a member made of a material having an acoustic impedance different from that of the wedge material. As a result, the greater the difference in acoustic impedance with respect to the wedge material is, the easier it is for the predetermined member to reflect the pipe propagation wave that reaches the notch. Can inhibit waves. Therefore, since the predetermined member can further reduce the energy (magnitude or strength) of the pipe propagation wave that reaches the ultrasonic transceiver, the SN ratio can be further improved.

  Preferably, the aforementioned wedge includes an elastic body provided on the outer periphery.

  According to this configuration, the wedge includes the elastic body provided on the outer periphery. Thereby, since the pipe propagation wave that has reached the outer periphery of the wedge is easily absorbed by the elastic body, a part of the pipe propagation wave incident on the wedge can be attenuated. Therefore, since the elastic body can further reduce the energy (magnitude or strength) of the pipe propagation wave that can reach the ultrasonic transceiver, the SN ratio can be further improved.

  The ultrasonic sensor for the ultrasonic flowmeter according to the present invention is based on the time until the ultrasonic wave transmitted from the outer periphery of the pipe through which the fluid flows is received at the outer periphery of the pipe. An ultrasonic sensor for an ultrasonic flowmeter that measures a flow rate, and includes an ultrasonic transmitter / receiver that transmits and receives ultrasonic waves, and an ultrasonic transmitter / receiver. And a wedge for making the sound wave incident on the fluid at a predetermined angle, and the wedge has a notch.

  According to such a configuration, the ultrasonic transmitter / receiver that transmits and receives ultrasonic waves and the ultrasonic transmitter / receiver are provided, and the ultrasonic waves transmitted from the ultrasonic transmitter / receiver are converted into fluid flowing through the pipe at a predetermined angle. A wedge for incidence, and the wedge has a notch 21c. As a result, the pipe propagation wave incident on the wedge is blocked by the notch and is difficult to reach the ultrasonic transmitter / receiver, so that the energy (magnitude or strength) of the pipe propagation wave reaching the ultrasonic transmitter / receiver is propagated through the fluid. It is possible to reduce the wave energy (magnitude or intensity), that is, to improve the SN ratio.

  According to the ultrasonic flowmeter of the present invention, the pipe propagation wave incident on the wedge is blocked by the notch and is difficult to reach the ultrasonic transmitter / receiver. Or strength) can be reduced with respect to the energy (magnitude or strength) of the fluid propagation wave, that is, the SN ratio can be improved. Therefore, the ultrasonic flowmeter can easily discriminate between the fluid propagation wave and the pipe propagation wave, and can accurately measure the fluid flow rate.

  Further, according to the ultrasonic sensor for an ultrasonic flowmeter of the present invention, the pipe propagation wave incident on the wedge is blocked by the notch so that it does not easily reach the ultrasonic transmitter / receiver, and therefore reaches the ultrasonic transmitter / receiver. The energy (magnitude or intensity) of the pipe propagation wave can be reduced relative to the energy (magnitude or intensity) of the fluid propagation wave, that is, the SN ratio can be improved. Therefore, the ultrasonic flowmeter can easily discriminate between the fluid propagation wave and the pipe propagation wave, and can accurately measure the fluid flow rate.

It is a block diagram which shows an example of schematic structure of an ultrasonic flowmeter. It is a side view for demonstrating an example of a structure of the 1st ultrasonic sensor shown in FIG. It is a top view for demonstrating an example of a structure of the 1st ultrasonic sensor shown in FIG. FIG. 4 is a cross-sectional view taken along the line II-II shown in FIG. 3. It is a top view explaining the other example of a structure of the 1st ultrasonic sensor shown in FIG. FIG. 6 is a top view for explaining still another example of the configuration of the first ultrasonic sensor shown in FIG. 1. It is a sectional side view for demonstrating the calculation method of the flow volume of the gas which flows through the inside of piping. It is sectional drawing for demonstrating a mode that the ultrasonic wave transmitted from the 1st ultrasonic sensor is received by the 2nd ultrasonic sensor. It is a sectional side view for demonstrating a mode that the ultrasonic wave which reached the 1st ultrasonic sensor propagates a wedge. It is a table | surface which shows the S / N ratio of an ultrasonic absorber. It is a graph of the received signal of a virtual ultrasonic flowmeter. 3 is a graph of a reception signal output from the reception circuit unit illustrated in FIG. 1. It is the graph which expanded a part of received signal shown in FIG. It is the graph which expanded a part of received signal shown in FIG. FIG. 10 is a side sectional view for explaining a modification of the first ultrasonic sensor shown in FIG. 9. It is a top view explaining the modification of the 1st ultrasonic sensor shown in FIG. It is a block diagram which shows the other example of schematic structure of the ultrasonic flowmeter shown in FIG.

  Embodiments of the present invention will be described below. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic. Therefore, specific dimensions and the like should be determined in light of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings. In the following description, the upper side of the drawing is referred to as “upper”, the lower side as “lower”, the left side as “left”, and the right side as “right”.

  1 to 16 show an embodiment of an ultrasonic flowmeter and an ultrasonic sensor for an ultrasonic flowmeter according to the present invention. FIG. 1 is a configuration diagram illustrating an example of a schematic configuration of the ultrasonic flowmeter 100. As shown in FIG. 1, the ultrasonic flowmeter 100 is for measuring a flow rate of a fluid, for example, a gas (gas) or a liquid flowing inside the pipe A. The fluid that is the measurement target of the ultrasonic flowmeter 100 flows in the direction indicated by the white arrow in FIG. 1 (the direction from left to right in FIG. 1). The ultrasonic flowmeter 100 includes a first ultrasonic sensor 20A, a second ultrasonic sensor 20B, and a main body 50.

  The first ultrasonic sensor 20A and the second ultrasonic sensor 20B are provided on the outer periphery of the pipe A, respectively. In the example illustrated in FIG. 1, the first ultrasonic sensor 20 </ b> A is disposed on the upstream side in the pipe A, and the second ultrasonic sensor 20 </ b> B is disposed on the downstream side in the pipe A. The first ultrasonic sensor 20A and the second ultrasonic sensor 20B transmit and receive ultrasonic waves to each other. That is, the ultrasonic wave transmitted by the first ultrasonic sensor 20A is received by the second ultrasonic sensor 20B, and the ultrasonic wave transmitted by the second ultrasonic sensor 20B is received by the first ultrasonic sensor 20A.

  2 is a side view for explaining an example of the configuration of the first ultrasonic sensor 20A shown in FIG. 1, and FIG. 3 is for explaining an example of the configuration of the first ultrasonic sensor 20A shown in FIG. 4 is a cross-sectional view taken along the line II-II shown in FIG. It is a front view explaining an example of composition of the 1st ultrasonic sensor 20A. As shown in FIGS. 2 to 4, the first ultrasonic sensor 20 </ b> A includes a wedge 21 and an ultrasonic transmitter / receiver 22.

  The wedge 21 is provided with an ultrasonic transceiver 22 and is, for example, a resin or metal member. The wedge 21 is installed such that the bottom surface 21 a contacts the outer peripheral surface of the pipe A. Further, the wedge 21 is formed with a slope 21b having a predetermined angle with respect to the bottom surface 21a. An ultrasonic transmitter / receiver 22 is installed on the slope 21b.

  In the present embodiment, an example in which the bottom surface 21a is in contact with the outer peripheral surface of the pipe A is shown, but the present invention is not limited to this. A contact medium (coplant) may be interposed between the bottom surface 21a and the outer peripheral surface of the pipe A.

  The ultrasonic transmitter / receiver 22 transmits and receives ultrasonic waves. The ultrasonic transmitter / receiver 22 can be composed of, for example, a piezoelectric element. A lead wire (not shown) is electrically connected to the ultrasonic transceiver 22. When an electric signal having a predetermined frequency is applied via the lead wire, the ultrasonic transmitter / receiver 22 vibrates at the predetermined frequency and emits an ultrasonic wave. Thereby, an ultrasonic wave is transmitted from the ultrasonic transceiver 22. As indicated by broken arrows in FIG. 4, the ultrasonic waves transmitted with the dimensions (vertical and horizontal lengths) of the ultrasonic transmitter / receiver 22 propagate through the wedge 21 at an angle of the inclined surface 21b. The ultrasonic wave propagating through the wedge 21 is refracted at the interface between the wedge 21 and the outer wall of the pipe A to change the incident angle, and is further refracted and incident at the interface between the inner wall of the pipe A and the fluid flowing through the pipe A. The angle changes and propagates through the fluid. Since the refraction at the interface follows Snell's law, the wedge 21 is set by setting the angle of the inclined surface 21b in advance based on the ultrasonic velocity when propagating through the pipe A and the ultrasonic velocity when propagating through the fluid. Can make the ultrasonic wave incident on the fluid flowing in the pipe A at a desired angle.

  On the other hand, when the ultrasonic wave reaches the ultrasonic transmitter / receiver 22, the ultrasonic transmitter / receiver 22 vibrates at the frequency of the ultrasonic wave to generate an electric signal. Thereby, the ultrasonic wave is received by the ultrasonic wave transmitter / receiver 22. An electric signal generated in the ultrasonic transmitter / receiver 22 is detected by a main body 50 described later via a lead wire.

  The wedge 21 has a notch 21 c obtained by cutting a part of the wedge 21. As shown in FIG. 3, the wedge 21 has a total of eight notches 21 c, each having four rectangular notches 21 c having a predetermined angle with respect to each side surface. The wedge 21 further has three notches 21c near the center of the upper surface. Each notch 21 c is formed around the propagation path in the ultrasonic wedge 21 that is transmitted and received with the dimensions (length and width) of the ultrasonic transmitter / receiver 22. That is, each notch 21c is arranged and its dimension (depth) is determined so as not to reach (not reach) the ultrasonic wave propagation path indicated by the broken-line arrow in FIGS. Each notch 21c is formed, for example, by cutting the wedge 21.

  The second ultrasonic sensor 20B has the same configuration as the first ultrasonic sensor 20A. That is, the second ultrasonic sensor 20 </ b> B also includes a wedge 21 and an ultrasonic transmitter / receiver 22. Therefore, the detailed description of the second ultrasonic sensor 20B is omitted with the description of the first ultrasonic sensor 20A.

  In the present embodiment, an example in which the wedge 21 has eleven rectangular cutouts 21c is shown, but the present invention is not limited to this. The number of the cutouts 21c may be one or a plurality of other cutouts, and the shape of the cutouts 21c may be a shape other than a rectangular shape.

  FIG. 5 is a top view for explaining another example of the configuration of the first ultrasonic sensor 20A shown in FIG. As shown in FIG. 5, the wedge 21 has six notches 21c in total, three rectangular notches 21c perpendicular to each side surface. As in the example shown in FIGS. 2 to 4, each notch 21 c shown in FIG. 5 is also around the propagation path in the ultrasonic wedge 21 that is transmitted and received with the dimensions (length and width) of the ultrasonic transmitter / receiver 22. Formed.

  FIG. 6 is a top view for explaining yet another example of the configuration of the first ultrasonic sensor 20A shown in FIG. As shown in FIG. 6, the wedge 21 has two circular notches 21 c in the vicinity of the upper side and the lower side on the upper surface, for a total of four notches 21 c. Similar to the example shown in FIGS. 2 to 4, each notch 21 c shown in FIG. 6 is also around the propagation path in the ultrasonic wedge 21 that is transmitted and received with the dimensions (length and width) of the ultrasonic transmitter / receiver 22. Formed.

  In the example shown in FIGS. 2 to 6, each notch 21c is symmetric with respect to the ultrasonic propagation path. However, the present invention is not limited to this, and the notch 21c is asymmetric with respect to the ultrasonic propagation path. Also good. Furthermore, the wedge 21 of the first ultrasonic sensor 20A and the wedge 21 of the second ultrasonic sensor 20B may be the same or different. Therefore, the notch 21c of the wedge 21 of the first ultrasonic sensor 20A and the notch 21c of the wedge 21 of the second ultrasonic sensor 20B are the same, different in shape, number, arrangement and the like. Also good.

  The main body 50 shown in FIG. 1 is for measuring the flow rate of the gas based on the time during which the ultrasonic wave propagates the fluid flowing inside the pipe A. The main body unit 50 includes a switching unit 51, a transmission circuit unit 52, a reception circuit unit 53, a timer unit 54, a calculation control unit 55, and an input / output unit 56.

  The switching unit 51 is for switching between transmission and reception of ultrasonic waves. The switching unit 51 is connected to the first ultrasonic sensor 20A and the second ultrasonic sensor 20B. The switching unit 51 can be configured to include, for example, a changeover switch. The calculation switching unit 51 switches the changeover switch based on a control signal input from the calculation control unit 55 and connects one of the first ultrasonic sensor 20A and the second ultrasonic sensor 20B to the transmission circuit unit 52. The other of the first ultrasonic sensor 20A and the second ultrasonic sensor 20B is connected to the receiving circuit unit 53. Accordingly, one of the first ultrasonic sensor 20A and the second ultrasonic sensor 20B transmits an ultrasonic wave, and the other of the first ultrasonic sensor 20A and the second ultrasonic sensor 20B receives the ultrasonic wave. can do.

  The transmission circuit unit 52 is for causing the first ultrasonic sensor 20A and the second ultrasonic sensor 20B to transmit ultrasonic waves. The transmission circuit unit 52 can include, for example, an oscillation circuit that generates a rectangular wave with a predetermined frequency, a drive circuit that drives the first ultrasonic sensor 20A, and the second ultrasonic sensor 20B. Based on the control signal input from the arithmetic control unit 55, the transmission circuit unit 52 uses the rectangular wave generated by the oscillation circuit as a drive signal based on the control signal, of the first ultrasonic sensor 20A and the second ultrasonic sensor 20B. To one of the ultrasonic transceivers 22. Thereby, one ultrasonic transmitter / receiver 22 of the first ultrasonic sensor 20A and the second ultrasonic sensor 20B is driven, and the ultrasonic transmitter / receiver 22 transmits ultrasonic waves.

  In general, an ultrasonic wave means a sound wave having a frequency band of 20 [kHz] or higher. Therefore, the ultrasonic wave transmitted by the ultrasonic transceiver 22 is a sound wave having a frequency band of 20 [kHz] or higher. Preferably, the ultrasonic wave transmitted by the ultrasonic transceiver 22 is an ultrasonic wave having a frequency band of 100 [kHz] or more and 2.0 [MHz] or less. More preferably, the ultrasonic wave transmitted by the ultrasonic transceiver 22 is an ultrasonic wave having a frequency band of 0.5 [MHz] or more and 1.0 [MHz] or less. In any case, the ultrasonic wave transmitted by the ultrasonic transceiver 22 of the first ultrasonic sensor 20A and the ultrasonic wave transmitted by the ultrasonic transceiver 22 of the second ultrasonic sensor 20B have the same frequency. It may be a different frequency.

  The receiving circuit unit 53 is for detecting the ultrasonic waves received by the first ultrasonic sensor 20A and the second ultrasonic sensor 20B. The receiving circuit unit 53 can include, for example, an amplifier circuit that amplifies a signal with a predetermined gain (gain), a filter circuit that extracts an electric signal with a predetermined frequency, and the like. Based on the control signal input from the arithmetic control unit 55, the receiving circuit unit 53 receives the electrical signal output from one ultrasonic transmitter / receiver 22 of the first ultrasonic sensor 20A and the second ultrasonic sensor 20B. Amplify, filter and convert to received signal. The reception circuit unit 53 outputs the converted reception signal to the calculation control unit 55.

  The timer 54 is for measuring time in a predetermined period. The timer unit 54 can be constituted by, for example, an oscillation circuit. Note that the oscillation circuit may be shared with the transmission circuit unit 52. The timer 54 measures the time by counting the number of reference waves of the oscillation circuit based on the start signal and stop signal input from the arithmetic control unit 55. The time measuring unit 54 outputs the measured time to the calculation control unit 55.

  The calculation control unit 55 is for calculating the flow rate of the fluid flowing through the pipe A by calculation. The arithmetic control unit 55 can be configured by, for example, a CPU, a memory such as a ROM or a RAM, an input / output interface, or the like. The arithmetic control unit 55 controls each part of the main body unit 50 such as the switching unit 51, the transmission circuit unit 52, the reception circuit unit 53, the time measuring unit 54, and the input / output unit 56. The method by which the arithmetic control unit 55 calculates the fluid flow rate will be described later.

  The input / output unit 56 is for a user (user) to input information and to output information to the user. The input / output unit 56 can be configured by, for example, input means such as operation buttons, output means such as a display display, and the like. When the user operates an operation button or the like, various types of information such as settings are input to the arithmetic control unit 55 via the input / output unit 56. Further, the input / output unit 56 displays information such as the fluid flow rate, the fluid velocity, the accumulated flow rate during a predetermined period, and the like calculated by the arithmetic control unit 55 on a display display.

FIG. 7 is a side cross-sectional view for explaining a method for calculating the flow rate of the gas flowing inside the pipe A. As shown in FIG. 7, the velocity (hereinafter referred to as the flow velocity) of the fluid flowing in the predetermined direction (the direction from the left side to the right side in FIG. 7) inside the pipe A is V [m / s], and exceeds the inside of the fluid. The velocity at which the sound wave propagates (hereinafter referred to as the sound velocity) is C [m / s], the propagation path length of the ultrasonic wave propagating through the fluid is L [m], and the pipe axis of the pipe A and the ultrasonic wave propagation. Let θ be the angle formed with the path. Here, the first ultrasonic sensor 20A installed on the upstream side of the pipe A (left side in FIG. 7) transmits ultrasonic waves, and the second ultrasonic wave installed on the downstream side of the pipe A (right side in FIG. 7). When the sensor 20B receives the ultrasonic wave, a propagation time t _{ab in} which the ultrasonic wave propagates through the fluid inside the pipe A is expressed by the following equation (1).
t _ab = L / (C + V cos θ) (1)

On the other hand, when the second ultrasonic sensor 20B installed on the downstream side of the pipe A transmits ultrasonic waves and the first ultrasonic sensor 20A installed on the upstream side of the pipe A receives the ultrasonic waves, A propagation time _{tba in} which the ultrasonic wave propagates through the fluid inside the pipe A is expressed by the following equation (2).
t _ba = L / (C−V cos θ) (2)

From the equations (1) and (2), the fluid flow velocity V is expressed by the following equation (3).
V = (L / 2 cos θ) · {(1 / t _ab ) − (1 / t _ba )} (3)

In the equation (3), the propagation path length L and the angle θ are known values before the flow rate is measured. Therefore, the flow velocity V is obtained by measuring the propagation time t _ab and the propagation time t _ba to obtain the equation (3). It can be calculated from

The flow rate Q [m ³ / s] of the fluid flowing inside the pipe A is determined using the flow velocity V [m / s], the complement coefficient K, and the cross-sectional area S [m ³ / s] of the pipe A. It is represented by the following formula (4).
Q = KVS (4)

Therefore, the arithmetic control unit 55 stores the propagation path length L, the angle θ, the complement coefficient K, and the cross-sectional area S of the pipe A in a memory or the like in advance. Then, the arithmetic control unit 55 measures the propagation time t _ab and the propagation time t _ba based on the reception signal input from the reception circuit unit 53, thereby calculating the equation (3) and the equation (4). The flow rate Q of the fluid flowing in the pipe A can be calculated.

  In the present embodiment, the example in which the flow rate of the fluid is calculated by the reciprocal propagation time method using FIG. 7 and equations (1) to (4) is shown, but the present invention is not limited to this. The arithmetic control unit 55 may calculate the flow rate of the fluid by another method, for example, a known propagation time difference method.

  In the present embodiment, the ultrasonic waves transmitted by one of the first ultrasonic sensor 20A and the second ultrasonic sensor 20A are propagated through the fluid inside the pipe A, and the first ultrasonic sensor 20A and the second ultrasonic sensor 20A are transmitted. Although the example which receives directly with the other of the sound wave sensor 20A was shown, it is not limited to this. The ultrasonic wave propagating through the fluid inside the pipe A can be reflected by the inner wall of the pipe A. Therefore, the other of the first ultrasonic sensor 20A and the second ultrasonic sensor 20A may receive the ultrasonic wave reflected 2n times (n is a positive integer) on the inner wall of the pipe A.

FIG. 8 is a cross-sectional view for explaining how the ultrasonic waves transmitted from the first ultrasonic sensor 20A are received by the second ultrasonic sensor 20B. As shown in FIG. 8, for example, ultrasonic waves transmitted from the first ultrasonic sensor 20A includes a fluid propagating wave W ₁ which passes through the pipe A (transmitted) to propagate the fluid inside the pipe A, the pipe A And the pipe propagation wave W ₂ that propagates through the pipe A after being reflected by the pipe wall. The fluid propagation wave W ₁ again passes through the pipe A and reaches the second ultrasonic sensor 20B. On the other hand, the pipe propagation wave W ₂ can also reach the second ultrasonic sensor 20B while reflecting the inner wall and the outer wall of the pipe A a plurality of times. Although illustration and detailed description thereof are omitted, as in the case of the ultrasonic wave transmitted from the first ultrasonic sensor 20A, the ultrasonic wave transmitted from the second ultrasonic sensor 20A is also connected to the fluid propagation wave W ₁ and the piping. The propagation wave W ₂ is divided into the propagation wave W ₂ , the fluid propagation wave W ₁ passes through the pipe A and reaches the first ultrasonic sensor 20 A, and the pipe propagation wave W ₂ also reflects the inner wall and the outer wall of the pipe A a plurality of times. The first ultrasonic sensor 20A can be reached.

  In general, whether a sound wave propagating through one medium is transmitted (passed) or reflected at an interface with the other medium is determined by a difference in acoustic impedance between the one medium and the other medium. In other words, the smaller the difference in acoustic impedance, the more the sound wave propagating in one configuration is transmitted to the other medium, and the greater the difference in acoustic impedance, the more acoustic wave propagating in one configuration is at the interface with the other medium. There is a tendency to reflect.

In particular, when the fluid flowing inside the pipe A is, for example, a gas, the acoustic impedance of the gas is smaller than the acoustic impedance of the liquid. Therefore, the difference between the acoustic impedance of the gas and the acoustic impedance of the pipe material, for example, a metal such as stainless steel (SUS) or a polymer compound such as synthetic resin is relatively large. The proportion (transmittance) of the gas passing through (passing) and propagating through the inside is small (small), that is, the proportion (reflectance) reflected by the pipe wall of the pipe A is large (large), and the pipe propagation wave W ₂ The energy (magnitude or strength) is relatively large.

Here, in the ultrasonic flowmeter that receives the ultrasonic fluid propagation wave W ₁ and measures the propagation time and measures the flow rate based on the propagation time, the fluid propagation wave W ₁ is a signal to be detected (new synthesis) The pipe propagation wave W ₂ is noise (noise component) with respect to the signal. Therefore, the fluid propagating wave W ₁ of the energy (size or strength) pipe propagating wave W ₂ of the energy (size or strength) with respect to the is not sufficiently small, fluid propagating wave W ₁ and the pipe propagating wave W Discrimination from ₂ becomes difficult. As a result, there is a possibility that the fluid propagation wave W ₁ and the pipe propagation wave W ₂ will be mistaken and the propagation time will be measured incorrectly, and the fluid flow rate will be measured based on the incorrect propagation time.

FIG. 9 is a side sectional view for explaining a state in which the ultrasonic wave reaching the first ultrasonic sensor 20 </ b> A propagates through the wedge 21. As shown in FIG. 9, the fluid propagation wave W ₁ is refracted at the interface between the fluid flowing inside the pipe A and the inner wall of the pipe A, and further refracted at the interface between the outer wall of the pipe A and the wedge 21. 21 is incident. The fluid propagating wave W ₁ incident on the wedge 21 reaches the ultrasonic transmitter / receiver 22 within the range of the propagation path indicated by the dashed arrow in FIG. 9 and is received. On the other hand, a part of the pipe propagation wave W ₂ incident on the wedge 21 is reflected by the notch 21c as shown by a dashed line arrow in FIG. Further, the other part of the pipe propagation wave W ₂ incident on the wedge 21 is changed in the direction along the notch 21c as shown by the two-dot chain line arrow in FIG. Thus, since the wedge 21 has the notch 21 c, the pipe propagation wave W ₂ incident on the wedge 21 is blocked by the notch 21 c and does not easily reach the ultrasonic transceiver 22. energy (size or strength) of the pipe propagating wave W ₂ to reach the smaller to the fluid propagating wave W ₁ of the energy (size or strength), i.e., it is possible to improve the SN ratio.

Each notch 21c is indicated by broken line arrow in FIG. 9, it is formed in the periphery of the propagation path of the ultrasonic transducer 22 in the wedge 21 of the fluid propagation wave W _1. Thereby, each notch 21c efficiently inhibits the pipe propagation wave W ₂ that can reach the ultrasonic transceiver 22 and is formed on the propagation path of the fluid propagation wave W _{1 to} the ultrasonic transceiver 22. Therefore, the fluid propagation wave W ₁ incident on the wedge 21 reaches the ultrasonic transmitter / receiver 22 without being blocked by the notches 21c.

Although illustration and a detailed description thereof are omitted, the ultrasonic wave reaching the second ultrasonic sensor 20B is wedged as in the case where the ultrasonic wave reaching the first ultrasonic sensor 20A shown in FIG. 9 propagates through the wedge 21. even when propagating 21, part of the piping propagating wave W ₂ incident on the wedge 21 is reflected by the notch 21c, also, in addition to some notch 21c of the pipe propagating wave W ₂ incident on the wedge 21 The direction can be changed along the direction.

FIG. 10 is a graph of the reception signal of the virtual ultrasonic flowmeter, and FIG. 11 is a graph of the reception signal output from the reception circuit unit 53 shown in FIG. 10 and 11, the horizontal axis represents time, and the vertical axis represents voltage (amplitude of received signal). Moreover, gas was used as the fluid flowing inside the pipe. For comparison with the ultrasonic flowmeter 100, the virtual ultrasonic flowmeter whose received signal graph is shown in FIG. 10 includes a first ultrasonic sensor and a second ultrasonic sensor having a wedge without a notch. The ultrasonic flowmeter includes a sonic sensor, and other configurations such as a main body are the same as those of the ultrasonic flowmeter 100. As shown in FIG. 11, the received signal of the ultrasonic flowmeter 100 has a smaller voltage as a whole than the received signal of the virtual ultrasonic flowmeter shown in FIG. . Thus, it can be seen that the energy (magnitude or strength) of the pipe propagation wave W ₂ is reduced by the notch 21c of the wedge 21 provided in the first ultrasonic sensor 20A and the second ultrasonic sensor 20B.

12 is an enlarged graph of a part of the received signal shown in FIG. 10, and FIG. 13 is an enlarged graph of a part of the received signal shown in FIG. 12 and 13, as in FIGS. 10 and 11, the horizontal axis is time, and the vertical axis is voltage (amplitude of received signal). As shown in FIG. 13, the ultrasonic flow meter 100, a time zone between time t ₁₃ and time t _14, which receives a signal of a relatively large voltage, the calculation control unit 55, this detected as a fluid propagating wave W _1, it can identify the fluid propagation wave W ₁ and pipe propagating waves W _2. Further, since the energy (magnitude or strength) of the pipe propagation wave W ₂ in the vicinity of the fluid propagation wave W ₁ between the time t ₁₃ and the time t ₁₄ is reduced, the ultrasonic flowmeter An S / N ratio of 100 is increased. In contrast, in the virtual ultrasonic flowmeter shown in FIG. 12, in addition to the time zone between the time t ₁₃ and time t _14, O started the time zone between time t ₁₀ and the time t ₁₁ many in the time zone that has received a signal of a relatively large voltage, these signals are due to piping propagating waves W _2. In this way, in the reception signal of the virtual ultrasonic flow meter, the energy (magnitude or strength) of the pipe propagation wave W ₂ is large, so that the calculation control unit can determine which signal in any time zone is the fluid propagation wave W ₁ is either, it is difficult to identify with the fluid propagating wave W ₁ and the pipe propagating waves W _2. Further, if the pipe propagating waves W in the vicinity of the time period between the even correctly recognize the fluid propagation wave W _1, the time t ₁₃ and time t ₁₄ between the arithmetic control unit time t ₁₃ and time t _{14 Since} the energy (size or intensity) of 2 is large, the SN ratio of the virtual ultrasonic flowmeter is smaller than that of the ultrasonic flowmeter 100.

  In the present embodiment, the notch 21c included in the wedge 21 is an example of a gap (gap) obtained by cutting a part of the wedge 21, but the present invention is not limited to this. The notch 21c may be filled with a filler, for example.

FIG. 14 is a side cross-sectional view for explaining a modification of the first ultrasonic sensor 20A shown in FIG. The same components as those of the first ultrasonic sensor 20A shown in FIG. 9 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. In addition, components similar to those of the first ultrasonic sensor 20A illustrated in FIG. 9 are denoted by similar symbols, and detailed description thereof is omitted. Further, the components not shown are the same as those of the first ultrasonic sensor 20A shown in FIG. As shown in FIG. 14, the notch 21c of the wedge 21A is filled with a filler 23. As in the case of the wedge 21 shown in FIG. 9, the fluid propagation wave W ₁ incident on the wedge 21 </ b> A reaches the ultrasonic transmitter / receiver 22 through the propagation path indicated by the dashed arrow in FIG. 14 and is received. On the other hand, a part of the pipe propagation wave W ₂ incident on the wedge 21A is reflected by the filler 23 in the notch 21c, as shown by the one-dot chain line arrow in FIG. Further, the other part of the pipe propagation wave W ₂ incident on the wedge 21A is changed in the direction along the notch 21c as shown by the two-dot chain line arrow in FIG. In this manner, similarly to the case of the notch 21c of the wedge 21 shown in FIG. 9, when the filler 23 is filled in the notch 21c of the wedge 21A, the pipe propagation wave W ₂ incident on the wedge 21 is The S / N ratio can be improved because the filler 23 of the notch 21c is obstructed to reach the ultrasonic transmitter / receiver 22.

  Moreover, since the notch 21c is filled with the filler 23, the wedge 21A can suppress a decrease in strength even if it has the notch 2c.

The filler 23 is preferably a member made of a material having an acoustic impedance different from that of the wedge 21A. As a result, the more the filler 23 is made of a material having a larger difference in acoustic impedance than the material of the wedge 21A, the more easily the pipe propagation wave W ₂ reaching the notch 21c is reflected. The pipe propagation wave W ₂ heading for 22 can be inhibited.

  Although FIG. 14 shows an example in which the filler 21A is filled in the notches 21c on the side surfaces of the wedge 21A, the present invention is not limited to this. For example, all of the notches 21c of the wedge 21A may be filled with the filler 23, or at least one of the notches 21c of the wedge 21A may be filled with the filler 23. Also good.

  In the present embodiment, an example in which the wedge 21 includes only the ultrasonic transmitter / receiver 22 has been described. However, the present invention is not limited to this. The wedge 21 may include an elastic body provided on the outer periphery, for example.

FIG. 15 is a top view for explaining a modification of the first ultrasonic sensor 20A shown in FIG. The same components as those of the first ultrasonic sensor 20A shown in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. In addition, components similar to those of the first ultrasonic sensor 20A illustrated in FIG. 3 are denoted by similar symbols, and detailed description thereof is omitted. Further, the components not shown are the same as those of the first ultrasonic sensor 20A shown in FIG. As shown in FIG. 15, the wedge 21B includes an elastic body 24 provided on each of the upper surface and both side surfaces of the inclined surface 21b. Each elastic body 24 is a material having elasticity, for example, rubber (rubber) such as natural rubber or synthetic rubber, and is a material having high ability (absorbing performance) to absorb vibration in the ultrasonic frequency band. Each elastic body 24 is attached to the side surface through an adhesive, for example, after the notches 21c are formed in the wedge 21B. Thus, since the wedge 21B includes the elastic body 24 provided on the outer periphery, the pipe propagation wave W ₂ reaching the outer periphery of the wedge 21B is easily absorbed by the elastic body 24, so that the pipe propagation incident on the wedge 21B is performed. A part of the wave W ₂ can be attenuated.

  In addition, although the example which provided the elastic body 24 in each side of the wedge 21B was shown in FIG. 15, the example was shown, However, It is not limited to this. The elastic body 24 may be provided on the inclined surface 21 b as long as it does not interfere with the ultrasonic transceiver 22. Further, the number of elastic bodies 24 is not limited to two, and may be one or may be three or more.

  Further, in FIG. 1, the first ultrasonic sensor 20 </ b> A is arranged on the upper side of the pipe A in FIG. 1 so that the first ultrasonic sensor 20 </ b> A and the second ultrasonic sensor 20 </ b> B face each other. Although the example which arrange | positions the 2nd ultrasonic sensor 20B was shown, it is not limited to this. The first ultrasonic sensor 20A and the second ultrasonic sensor 20B may be provided on the outer circumferences of the upstream side and the downstream side of the pipe A.

FIG. 16 is a configuration diagram illustrating another example of a schematic configuration of the ultrasonic flowmeter 100 illustrated in FIG. 1. The same components as those of the ultrasonic flow meter 100 shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted as appropriate. As shown in FIG. 16, the first ultrasonic sensor 20A is on the outer periphery on the upstream side (left side in FIG. 16), and the second ultrasonic sensor 20B is on the outer periphery on the downstream side (right side in FIG. 16). , Respectively. The first ultrasonic sensor 20A and the second ultrasonic sensor 20B are both arranged on a straight line parallel to the pipe axis of the pipe A on the upper side of the pipe A in FIG. In the case of such an arrangement, for example, the ultrasonic fluid propagation wave W ₁ transmitted from the first ultrasonic sensor 20A is reflected by the inner wall of the pipe A and reaches the second ultrasonic sensor 20B (V method). ).

Thus, according to the ultrasonic flowmeter 100 in the present embodiment, each of the first ultrasonic sensor 20A and the second ultrasonic sensor 20B is provided with the ultrasonic transmitter / receiver 22 and transmits from the ultrasonic transmitter / receiver 22. Wedges 21, 21A, 21B that allow the ultrasonic waves to enter the fluid flowing inside the pipe A at a predetermined angle are provided, and the wedges 21, 21A, 21B have a notch 21c. Thus, the wedge 21, 21A, since the piping propagating waves W ₂ incident on 21B hardly reach is inhibited notch 21c to the ultrasonic transceiver 22, piping propagating waves W ₂ that reaches the ultrasonic transducer 22 Can be made smaller than the energy (magnitude or intensity) of the fluid propagation wave W ₁ , that is, the SN ratio can be improved. Therefore, the ultrasonic flowmeter 100 can easily identify the fluid propagation wave W ₁ and the pipe propagation wave W _2, and can accurately measure the fluid flow rate.

Further, according to the ultrasonic flowmeter 100 of this embodiment, notches 21c are formed around the propagation path of the fluid propagating wave W ₁ of the wedges 21, 21A, the ultrasonic transducer 22 in 21B. Thereby, the notch 21c efficiently inhibits the pipe propagation wave W ₂ that can reach the ultrasonic transceiver 22 and is not formed on the propagation path of the fluid propagation wave W _{1 to} the ultrasonic transceiver 22. Therefore, the fluid propagation wave W ₁ incident on the wedge 21 reaches the ultrasonic transmitter / receiver 22 without being inhibited by the notch 21c. Therefore, the notch 21c does not reduce (maintains) the energy (magnitude or strength) of the fluid propagation wave W ₁ (while maintaining it), but the energy (magnitude) of the pipe propagation wave W ₂ that reaches the ultrasonic transceiver 22. , Or strength) can be further reduced, so that the SN ratio can be further improved.

Further, according to the ultrasonic flowmeter 100 in the present embodiment, the filler 23 is filled into the notch 21c of the wedge 21A. As a result, similarly to the case of the notch 21c of the wedge 21 shown in FIG. 9, the pipe propagation wave W ₂ incident on the wedge 21 is blocked by the filler 23 of the notch 21c and reaches the ultrasonic transmitter / receiver 22. Therefore, the SN ratio can be improved.

  Further, since the notch 21c is filled with the filler 23, the wedge 21A can suppress a decrease in strength even if the wedge 21A has the notch 21c.

Moreover, according to the ultrasonic flowmeter 100 in the present embodiment, the filler 23 is a member made of a material having an acoustic impedance different from that of the wedge 21A. As a result, the more the filler 23 is made of a material having a larger difference in acoustic impedance than the material of the wedge 21A, the more easily the pipe propagation wave W ₂ reaching the notch 21c is reflected. The pipe propagation wave W ₂ heading for 22 can be inhibited. Therefore, the filler 23 can further reduce the energy (magnitude or strength) of the pipe propagation wave W ₂ reaching the ultrasonic transmitter / receiver 22, so that the SN ratio can be further improved.

Moreover, according to the ultrasonic flowmeter 100 in the present embodiment, the wedge 21B includes the elastic body 24 provided on the outer periphery. As a result, the pipe propagation wave W ₂ reaching the outer periphery of the wedge 21B is easily absorbed by the elastic body 24, so that a part of the pipe propagation wave W ₂ incident on the wedge 21B can be attenuated. Therefore, since the elastic body 24 can further reduce the energy (magnitude or strength) of the pipe propagation wave W ₂ that can reach the ultrasonic transceiver 22, the SN ratio can be further improved.

In addition, each of the first ultrasonic sensor 20A and the second ultrasonic sensor 20B for the ultrasonic flowmeter 100 in the present embodiment includes an ultrasonic transmitter / receiver 22 that transmits and receives ultrasonic waves, and an ultrasonic transmitter / receiver 22. And wedges 21, 21A, 21B that allow the ultrasonic waves transmitted from the ultrasonic transmitter / receiver 22 to enter the fluid flowing through the pipe A at a predetermined angle, and the wedges 21, 21A, 21B are notched. 21c. Thus, the wedge 21, 21A, since the piping propagating waves W ₂ incident on 21B hardly reach is inhibited notch 21c to the ultrasonic transceiver 22, piping propagating waves W ₂ that reaches the ultrasonic transducer 22 Can be made smaller than the energy (magnitude or intensity) of the fluid propagation wave W ₁ , that is, the SN ratio can be improved. Therefore, the ultrasonic flowmeter 100 can easily identify the fluid propagation wave W ₁ and the pipe propagation wave W _2, and can accurately measure the fluid flow rate.

  Note that the configurations of the above-described embodiments may be combined, or some components may be replaced. Further, the configuration of the present embodiment is not limited to the above-described embodiment, and various modifications may be made without departing from the scope of the present embodiment.

20A ... 1st ultrasonic sensor 20B ... 2nd ultrasonic sensor 21, 21A, 21B ... Wedge 21a ... Bottom 21b ... Slope 21c ... Notch 22 ... Piezoelectric element 23 ... Filler 24 ... Elastic body 50 ... Main part 51 ... Switching part 52 ... transmission circuit unit 53 ... reception circuit section 54 ... time measuring portion 55 ... calculation control unit 56 ... input-output unit 100 ... ultrasonic flowmeter A ... pipe W ₁ ... fluid propagating wave W ₂ ... pipe propagating wave

Claims (6)

A first ultrasonic sensor provided on an outer periphery on the upstream side in a pipe through which a fluid flows, and including an ultrasonic transceiver that transmits and receives ultrasonic waves;
A second ultrasonic sensor provided on the outer periphery of the downstream side of the pipe, and comprising an ultrasonic transceiver for transmitting and receiving ultrasonic waves;
The time until the second ultrasonic sensor receives the ultrasonic wave transmitted from the first ultrasonic sensor, and the ultrasonic wave transmitted from the second ultrasonic sensor is the first ultrasonic sensor. A main body that measures the flow rate of the fluid based on the time until it is received by the ultrasonic sensor, and
Each of the first ultrasonic sensor and the second ultrasonic sensor is provided with the ultrasonic transmitter / receiver, and has a wedge for allowing the ultrasonic wave transmitted from the ultrasonic transmitter / receiver to enter the fluid at a predetermined angle. In addition,
The wedge has a notch;
Ultrasonic flow meter. The notch is formed around a propagation path to the ultrasonic transceiver in the wedge of a fluid propagation wave in which the ultrasonic wave propagates through the fluid.
The ultrasonic flowmeter according to claim 1. The notch is filled with a predetermined member,
The ultrasonic flowmeter according to claim 1 or 2. The predetermined member is a member having an acoustic impedance different from that of the wedge material.
The ultrasonic flowmeter according to claim 3. The wedge includes an elastic body provided on the outer periphery,
The ultrasonic flowmeter according to any one of claims 1 to 4. An ultrasonic sensor for an ultrasonic flowmeter that measures the flow rate of the fluid based on the time until the ultrasonic wave transmitted from the outer periphery of the pipe through which the fluid flows is received at the outer periphery of the pipe,
An ultrasonic transceiver for transmitting and receiving the ultrasonic wave;
The ultrasonic transmitter / receiver is provided, and includes a wedge for allowing the ultrasonic wave transmitted from the ultrasonic transmitter / receiver to enter the fluid at a predetermined angle,
The wedge has a notch;
Ultrasonic sensor for ultrasonic flowmeter.

Images