JP2012242120A - Ultrasonic flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic flowmeter capable of saving a lot of time and effort for attachment of any probe to a pipe even when a place where two probes are arranged is narrow.SOLUTION: An ultrasonic flowmeter 1 includes a first probe 3a arranged on the peripheral surface of a pipe 33 to transmit/receive an ultrasonic wave and a second probe 3b arranged on the peripheral surface of the pipe 33 so as to be shifted from the first probe 3a in the axial direction of the pipe 33. The second probe 3b is arranged at an angle θ different from that of the first probe 3a in a range of 0 degree<θ<180 degrees in the peripheral direction of the pipe 33.

Description

  The present invention relates to a time difference type ultrasonic flowmeter.

  An ultrasonic flow meter is one of devices that measure the flow rate of fluid flowing through a pipe. There are several types of ultrasonic flowmeters, and the time difference type ultrasonic flowmeter includes two transmission / reception means (probes) for transmitting and receiving ultrasonic waves. Two probes are attached on the peripheral surface of the pipe, one probe is arranged on the upstream side, and the other probe is arranged on the downstream side. The measurement principle of the time difference type ultrasonic flowmeter is as follows.

  Ultrasound is simultaneously transmitted from the upstream probe and the downstream probe. The ultrasonic wave transmitted from the upstream probe propagates through the pipe through which the fluid flows and is received by the downstream probe. The ultrasonic wave transmitted from the downstream probe propagates through the pipe through which the fluid flows and is received by the upstream probe.

  Since the fluid flows through the pipe, the upstream probe receives the ultrasonic wave transmitted from the downstream probe until the downstream probe receives the ultrasonic wave transmitted from the upstream probe. It becomes shorter than the time until. Using the time difference and the distance between the upstream probe and the downstream probe, the flow velocity of the fluid flowing through the pipe is calculated. Using this flow velocity and the cross-sectional area of the pipe, the flow rate of the fluid flowing through the pipe is calculated.

  By the way, a part of the ultrasonic wave transmitted from each of the upstream probe and the downstream probe propagates on the surface of the pipe and is received by the downstream probe and the upstream probe. Metal pipes and small-diameter pipes are easily affected by ultrasonic waves propagating on the surface of the pipe, and in order to prevent the measurement accuracy of the flow rate from deteriorating due to this influence, the upstream probe and the downstream probe It was necessary to make the distance of a certain size. Therefore, the location where the ultrasonic flow meter can be attached is limited, and it is necessary to attach the ultrasonic flow meter to the pipe after securing the space where the two probes are arranged.

  An ultrasonic flowmeter that can secure the distance between two probes even in a narrow space by arranging the upstream probe and the downstream probe symmetrically about the axis of the pipe. Has been proposed (see, for example, Patent Document 1).

JP 2011-58883 A

  However, in the configuration in which the upstream probe and the downstream probe are arranged symmetrically about the axis of the pipe, the other probe is located behind the position of one probe on the peripheral surface of the pipe. Therefore, when the worker attaches the two probes to the pipe, one probe is located on the worker side and the other probe is located on the opposite side of the worker when viewed from the pipe. For this reason, the other probe is in a position where it is difficult to see from the operator, and in particular, in a narrow space, the range in which the hand can be moved is restricted when attaching the probe. There is.

  An object of the present invention is to provide an ultrasonic flowmeter that does not require time and effort to attach a pipe to any of the transmission / reception means even in a narrow space where two transmission / reception means for transmitting / receiving ultrasonic waves are arranged. And

  An ultrasonic flowmeter according to the present invention for achieving the above object is provided on a circumferential surface of a pipe having a circular cross section, and a first transmission / reception means for transmitting / receiving ultrasonic waves, and the pipe with respect to the first transmission / reception means. The second transmitting / receiving unit receives the ultrasonic wave transmitted from the first transmitting / receiving unit and the second transmitting / receiving unit arranged on the peripheral surface of the pipe while being shifted in the axial direction. Between the time until the first transmission / reception means receives the ultrasonic wave transmitted from the second transmission / reception means, and between the first transmission / reception means and the second transmission / reception means. And a calculation unit that calculates a flow rate of the fluid flowing through the pipe using the distance of the second transmission / reception unit, wherein the second transmission / reception unit sets an angle θ in the circumferential direction of the pipe with respect to the first transmission / reception unit. Arranged differently in the range of 0 degrees <θ <180 degrees The

  According to the ultrasonic flowmeter of the present invention, the second transmission / reception means is arranged so that the angle θ is different from the first transmission / reception means in the circumferential direction of the pipe in the range of 0 ° <θ <180 °. Therefore, the first and second transmission / reception means can be arranged on the half surface side of the peripheral surface of the pipe. For this reason, when the operator attaches the first and second transmission / reception means to the pipe, both are located on the operator side, and are easy to see and reach for the operator. Even if the place to be arranged is a narrow space, it is possible to prevent any transmission / reception means from being time-consuming to attach to the pipe.

  In the above configuration, the second transmission / reception means is arranged with respect to the first transmission / reception means at a different angle θ in the range of 0 degree <θ ≦ 90 degrees in the circumferential direction of the pipe.

  According to this configuration, when the distance between the first transmission / reception means and the second transmission / reception means is short in the axial direction of the pipe, the surface wave (super-wave propagated on the surface of the pipe is larger than the condition where the angle θ is 0 degrees). Sound wave) can be reduced. For this reason, since the place where the first and second transmission / reception means are arranged is a narrow space and the piping is short, it is possible to maintain the flow rate measurement accuracy. The range of application of possible locations can be expanded.

  Further, according to this configuration, the second transmission / reception means is arranged at a different angle θ in the range of 0 degree <θ ≦ 90 degrees in the circumferential direction of the pipe with respect to the first transmission / reception means. Any of the transmission / reception means is easier for the operator to see and reach. Therefore, even if the place where the first and second transmission / reception means are arranged is a narrow space, it is possible to prevent the effort of attaching any of the transmission / reception means to the pipe.

  In the above configuration, the second transmission / reception means is arranged with an angle θ of approximately 15 degrees different from the first transmission / reception means in the circumferential direction of the pipe.

  According to this configuration, even when the distance between the first transmitting / receiving unit and the second transmitting / receiving unit is short in the axial direction of the pipe, the received wave (the ultrasonic wave propagated in the pipe) can be made relatively large. , S (the magnitude of the received wave) / N (the magnitude of the surface wave) can be increased. Therefore, the place where the first and second transmission / reception means are arranged is a narrow space, and the flow rate can be measured with high accuracy even if the piping is short.

  The angle θ of approximately 15 degrees includes 15 degrees, and further includes an angle around 15 degrees, which includes an angle at which a high S / N ratio equivalent to the case of 15 degrees is obtained.

  ADVANTAGE OF THE INVENTION According to this invention, even if the location where the two transmission / reception means which transmit / receive an ultrasonic wave is arrange | positioned is a narrow space, it can be made not to take time and effort to attach to any piping about any transmission / reception means.

It is a figure which shows the structure of the ultrasonic flowmeter which concerns on one Embodiment of this invention. It is a figure which shows the specific example by which the 1st probe and the 2nd probe were arrange | positioned on the surrounding surface of piping. It is the figure which expanded the 1st probe and 2nd probe which are arrange | positioned at the linear part of piping shown in FIG. It is a figure which shows the state which looked at the 1st probe and 2nd probe which were shown in FIG. 3 from the cross section side of piping. It is a table | surface which shows the result of the experiment which changed the probe angle and the probe distance, and measured the echo height etc. of the surface wave signal. It is a figure which shows the received waveform of the ultrasonic wave in case a probe angle is 15 degree | times and a probe distance is 40 mm. It is a figure which shows the received waveform of the ultrasonic wave in case a probe angle is 0 degree | times and a probe distance is 40 mm.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a configuration of an ultrasonic flow meter 1 according to an embodiment of the present invention. The ultrasonic flowmeter 1 includes a first probe 3a, a second probe 3b, and a controller 5. The ultrasonic flowmeter 1 is used for measuring the flow rate of water flowing through a pipe having a circular cross section, for example, in a house.

  The first probe 3a (an example of the first transmission / reception means) and the second probe 3b (an example of the second transmission / reception means) have the same configuration, and both transmit ultrasonic waves and receive ultrasonic waves. Piezoelectric elements 7a and 7b serving as sensors are incorporated. The first probe 3a and the second probe 3b have curved surface portions 9a and 9b that come into contact with the peripheral surface of the pipe when attached to the peripheral surface of the pipe. The first probe 3a and the second probe 3b have wiring cords 11a and 11b that are electrically connected to the piezoelectric elements 7a and 7b.

  The controller 5 includes terminals 13a and 13b, a transmission / reception control unit 15, a calculation unit 17, and an operation unit 19. The wiring cord 11a of the first probe 3a is connected to the terminal 13a, and the wiring cord 11b of the second probe 3b is connected to the terminal 13b. The transmission / reception control unit 15 is electrically connected to the wiring cord 11a of the first probe 3a via the terminal 13a and the wiring cord 11b of the second probe 3b via the terminal 13b.

  The transmission / reception control unit 15 performs a transmission control function such as generating an electric signal for generating ultrasonic waves by vibrating the piezoelectric elements 7a and 7b, and an electric signal generated by vibrating the piezoelectric elements 7a and 7b with ultrasonic waves. It has a reception control function such as amplifying and converting the amplified electrical signal from analog to digital.

  The arithmetic unit 17 takes time until the second probe 3b receives the ultrasonic wave transmitted from the first probe 3a, and until the first probe 3a receives the ultrasonic wave transmitted from the second probe 3b. And the flow rate of the water flowing through the pipe using the distance between the first probe 3a and the second probe 3b (linear distance), and using this flow rate and the cross-sectional area of the pipe, Calculate the flow rate of flowing water.

  The operation unit 19 includes an operation key unit 21 and a display unit 23. The operation key unit 21 receives various settings for operating the ultrasonic flowmeter 1. The display unit 23 displays the flow rate of water calculated by the calculation unit 17.

  FIG. 2 is a diagram showing a specific example in which the first probe 3a and the second probe 3b are arranged on the peripheral surface of the pipe. A pipe 33 bent in an L shape is passed through a narrow space 31 inside a house or the like. The pipe 33 extends in the horizontal direction and is guided from the outside through the wall 35 to the space 31, bends in an L shape in the space 31, extends in the vertical direction, and is guided to the ground 37. A valve 39 for adjusting the amount of water flowing through the pipe 33 is provided at a portion extending in the vertical direction of the pipe 33.

  In the portion extending in the horizontal direction of the pipe 33, the first probe 3 a and the second probe 3 b are arranged on the peripheral surface of the pipe 33 so as to be shifted in the axial direction of the pipe 33. The second probe 3b is arranged with an angle of 90 degrees different from the first probe 3a in the circumferential direction of the pipe 33.

  In many cases, a joint of the pipe 33 and a bent portion of the pipe 33 are present at the place of the pipe 33 where the first probe 3a and the second probe 3b are arranged. The first probe 3 a and the second probe 3 b are arranged in a straight line portion of the pipe 33 like a portion extending in the horizontal direction of the pipe 33. If the location of the pipe 33 in which the first probe 3a and the second probe 3b are arranged is a narrow space 31, the length L of the straight portion of the pipe 33 can often be secured only about 10 cm. Moreover, in the water supply construction work standard, the length of the straight portion of the pipe is determined to be at least 10 cm in the meter box.

  As will be described later using experimental results, according to the ultrasonic flowmeter 1 according to the present embodiment, the length L of the straight portion of the pipe 33 in which the first probe 3a and the second probe 3b are arranged. Even when the value is about 10 cm, the flow rate measurement accuracy can be maintained.

  FIG. 3 is an enlarged view of the first probe 3a and the second probe 3b arranged in the straight portion of the pipe 33 shown in FIG. FIG. 4 is a view showing a state in which the first probe 3a and the second probe 3b shown in FIG.

  The first probe 3a includes a main body portion 41a, a base portion 43a, and a wiring cord 11a. The main body 41a contains a piezoelectric element 7a and the like, and a wiring cord 11a electrically connected to the piezoelectric element 7a is fixed.

  The base portion 43a includes a hose band mounting surface 45a, and the size of the base portion 43a is larger than that of the main body portion 41a in the axial direction of the pipe 33. The hose band attachment surface 45a is on the side opposite to the second probe 3b side. One surface of the base portion 43a is a curved surface portion 9a that comes into contact with the peripheral surface of the pipe 33, and the main body portion 41a is fixed to the other surface. Since the second probe 3b has the same configuration as the first probe 3a, description thereof is omitted.

  The first probe 3a and the second probe 3b adjust the axial position of the pipe 33 and the circumferential angle of the pipe 33, respectively, and then tighten screws (not shown) of the hose bands 47a and 47b, It is fixed to the peripheral surface of the pipe 33.

  The main effects of the ultrasonic flowmeter 1 according to this embodiment will be described. In the present embodiment, the second probe 3b is arranged with respect to the first probe 3a in the circumferential direction of the pipe 33 so that the angle θ is different in the range of 0 degree <θ <180 degrees. The first probe 3 a and the second probe 3 b can be arranged on the half surface side of the peripheral surface of 33. For this reason, when the operator attaches the first probe 3a and the second probe 3b to the pipe 33, both are located on the operator side and are easy to see and reach for the operator, so the first probe 3a And even if the location where the 2nd probe 3b is arrange | positioned is a narrow space, it can be made not to take time and effort to attach to the piping 33 in any case.

  Further, when the second probe 3b is arranged with respect to the first probe 3a in the circumferential direction of the pipe 33 so that the angle θ is different in the range of 0 ° <θ ≦ 90 °, both probes are used by the operator. This makes it easier to see and reach. Therefore, even if the place where the 1st probe 3a and the 2nd probe 3b are arrange | positioned is a narrow space, it can be made not to take much time for attachment to piping also about any probe.

  Further, when the second probe 3b is arranged with respect to the first probe 3a so that the angle θ is different in the range of 0 degree <θ ≦ 90 degrees in the circumferential direction of the pipe 33, the first probe 3a and The location where the second probe 3b is disposed is a narrow space, and even if the pipe 33 is short, the flow rate measurement accuracy can be maintained. This will be described based on experimental results. First, the experimental conditions will be briefly described.

  As shown in FIG. 3, the axis of the pipe 33 in the core part of the first probe 3a (the part where the piezoelectric element 7a is located) and the core part of the second probe 3b (the part where the piezoelectric element 7b is located). The direction distance D was set to 30 mm, 40 mm, and 50 mm. Hereinafter, the distance D is referred to as a probe distance D.

  As shown in FIG. 4, in the core portion of the first probe 3a and the core portion of the second probe 3b, the conditions of the circumferential angle θ of the pipe 33 are 0 degree, 15 degrees, 30 degrees, 45 It was 90 degrees. Hereinafter, the angle θ is referred to as a probe angle θ.

  An SUS25A steel pipe is used as the pipe 33, the pipe 33 is filled with water, all other conditions are the same, and an ultrasonic wave is transmitted from the first probe 3a and received by the second probe 3b. Was measured. As other conditions, for example, a bandpass filter having a passband of 0.5 MHz to 6 MHz was used as a filter for an electric signal generated by the second probe 3b receiving ultrasonic waves.

  FIG. 5 is a table showing the results of the experiment. FIG. 6 is a diagram showing a reception waveform of an ultrasonic wave under the condition that the probe angle θ is 15 degrees and the probe distance D is 40 mm. FIG. 7 is a graph showing the supersonic wave when the probe angle θ is 0 degree and the probe distance D is 40 mm. It is a figure which shows the received waveform of a sound wave. Each item of the table | surface shown in FIG. 5 is demonstrated using FIG.

  The surface wave signal means an electric signal generated by the second probe 3b receiving an ultrasonic wave (hereinafter referred to as a surface wave) propagated through the surface of the pipe 33. The received wave signal means an electrical signal generated by the second probe 3b receiving an ultrasonic wave (hereinafter referred to as a received wave) propagated through the pipe 33.

  The echo height of the surface wave signal means the difference between the maximum value and the minimum value of the surface wave signal. In FIG. 6, 20 mV − (− 20 mV) = 40 mV is the echo height of the surface wave signal. The echo height of the received wave signal means the difference between the maximum value and the minimum value of the received wave signal. In FIG. 6, 120 mV − (− 120 mV) = 240 mV is the echo height of the received wave signal.

  The propagation distance of the surface wave signal means a value obtained by multiplying the speed of sound of the surface wave (3600 m / s) by the time required to receive the surface wave (μs). In FIG. 6, the time required for receiving the surface wave is about 14 μs, and therefore the propagation distance of the surface wave signal is 50.25 mm. The propagation distance of the received wave signal means a value obtained by multiplying the sound speed (1500 m / s) of the received wave by the time (μs) required for receiving the received wave. In FIG. 6, the time required to receive the received wave is about 50 μs, and therefore the propagation distance of the received wave signal is 75.6.

  The S / N ratio means a value obtained by dividing the echo height of the received wave signal by the echo height of the surface wave signal.

  The echo height of the surface wave signal was smaller than the condition of 0 degree in any of the probe angles θ of 15 degrees, 30 degrees, 45 degrees, and 90 degrees. A small echo height of the surface wave signal means that the influence of the surface wave can be reduced, which is preferable for maintaining and improving the measurement accuracy of the flow rate.

  If the probe distance D is the same, the echo height of the received wave signal is 0 degree, although there are some exceptions in any of the probe angles θ of 15 degrees, 30 degrees, 45 degrees, and 90 degrees. It became smaller than the condition. In order to maintain and improve the measurement accuracy of the flow rate, it is preferable that the echo height of the received wave signal is large. As an exception, there is a condition that the echo height of the received wave signal is equal to or higher than that when the probe angle θ is 0 degree. That is, under the condition where the probe angle θ is 15 degrees and the probe distance is 30 mm, the echo height of the received wave signal is larger than the condition where the probe angle θ is 0 degrees and the probe distance is 30 mm. Also, under the condition where the probe angle θ is 15 degrees and the probe distance is 40 mm, the echo height of the received wave signal is equal to the condition where the probe angle θ is 0 degrees and the probe distance is 40 mm.

  The difference between the propagation distance of the received wave signal and the propagation distance of the surface wave signal is that there are some exceptions (probe angle θ is less than 0 degree, 15 degrees, 30 degrees, 45 degrees, and 90 degrees). There are a condition of 45 degrees and a probe distance of 30 mm, and a condition that the probe angle θ is 45 degrees and the probe distance is 40 mm. If the difference between the propagation distance of the received wave signal and the propagation distance of the surface wave signal is large, it is easy to distinguish the surface wave signal from the received wave signal, which is preferable for maintaining and improving the measurement accuracy of the flow rate.

  If the probe distance D was the same, the S / N ratio was higher than the 0 degree condition in any of the probe angle θ of 15 degrees, 30 degrees, 45 degrees, and 90 degrees. A particularly high S / N ratio was obtained when the probe angle θ was 15 degrees. Under the conditions where the probe angle θ is 15 degrees and the probe distance D is 40 mm, the highest S / N ratio is obtained in this experiment, and the probe angle θ is 0 degrees and the probe distance D is 40 mm. About 6 times.

  From the above, if the second probe 3b is arranged with respect to the first probe 3a in the circumferential direction of the pipe 33 so that the angle θ is different in the range of 0 ° <θ ≦ 90 °, the axial direction of the pipe 33 When the distance between the first probe 3a and the second probe 3b is short (for example, within 10 cm), the echo height of the surface wave signal is made smaller (reduced surface wave) than the condition where the angle θ is 0 degree. It is also possible to increase the S / N ratio. Therefore, even if the place where the first probe 3a and the second probe 3b are arranged is a narrow space, and the pipe 33 is short, it is possible to maintain the flow rate measurement accuracy. Therefore, the applicable range of the location where the ultrasonic flowmeter 1 can be attached can be expanded.

  In particular, if the second probe 3b is arranged with respect to the first probe 3a with the angle θ different by 15 degrees in the circumferential direction of the pipe 33, the first probe 3a and the first probe 3a are arranged in the axial direction of the pipe 33. Even when the distance between the two probes 3b is short (for example, within 10 cm), the echo height of the received wave signal can be made relatively large (the received wave is made relatively large). As a result, a high S / N ratio can be obtained. Therefore, even if the place where the 1st probe 3a and the 2nd probe 3b are arranged is a narrow space, and piping 33 is short, it becomes possible to measure flow volume with high accuracy.

  In addition, although water was demonstrated to the example as a fluid, this embodiment is applicable also to another liquid and gas.

  The example which fastens the 1st probe 3a and the 2nd probe 3b to the piping 33 separately with the hose bands 47a and 47b was shown above. However, the first probe 3a and the second probe 3a can be adjusted by using a jig that can adjust the circumferential phase while keeping the axial interval between the first probe 3a and the second probe 3b constant. You may make it attach 3b to the piping 33. FIG.

1 Ultrasonic flow meter 3a First probe (an example of first transmitting / receiving means)
3b Second probe (an example of second transmitting / receiving means)
33 Piping D Distance between probes θ Probe angle

Claims (3)

A first transmission / reception means arranged on the circumferential surface of the pipe having a circular cross section, for transmitting / receiving ultrasonic waves;
A second transmission / reception means arranged on the circumferential surface of the pipe and shifted in the axial direction of the pipe with respect to the first transmission / reception means;
Time until the second transmission / reception means receives the ultrasonic wave transmitted from the first transmission / reception means and until the first transmission / reception means receives the ultrasonic wave transmitted from the second transmission / reception means. A calculation unit that calculates a flow rate of the fluid flowing through the pipe using a difference between time and a distance between the first transmission / reception unit and the second transmission / reception unit;
The ultrasonic flowmeter, wherein the second transmission / reception means is arranged with an angle θ different from that of the first transmission / reception means in the circumferential direction of the pipe in a range of 0 degree <θ <180 degrees.   The said 2nd transmission / reception means is arrange | positioned with respect to the said 1st transmission / reception means by making the angle (theta) differ in the range of 0 degree <(theta) <= 90 degree | times in the circumferential direction of the said piping. Ultrasonic flow meter.   3. The ultrasonic flowmeter according to claim 2, wherein the second transmission / reception unit is arranged with the angle θ different by about 15 degrees in the circumferential direction of the pipe with respect to the first transmission / reception unit.

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