JP2010181321A - Ultrasonic flowmeter - Google Patents

Abstract

An object of the present invention is to prevent an externally reflected wave unsuitable for measurement.
An ultrasonic beam B from ultrasonic transmitters / receivers 15a and 15b is incident on a synthetic resin tube 11 through a beam transmission body 16 and is reflected on an inner surface of the tube through a fluid F. Then, it becomes an internal reflection wave Ba and again enters the other ultrasonic transducers 15a and 15b through the fluid F through the beam transmission body 16. On the other hand, since the ultrasonic beam B that has passed through the tube 11 and reached the outer surface enters the vibration absorber 13 through the viscous body 17 and is scattered and absorbed, there are few outer surface reflected waves Bb that return to the outer surface again.
Therefore, most of the ultrasonic beam B reaching the ultrasonic transmitters / receivers 15a and 15b is caused by internal reflection, so that it is easy to distinguish the external reflected wave Bb from a circuit, and the measurement accuracy is improved.
[Selection] Figure 1

Description

  The present invention relates to an ultrasonic flowmeter that measures a flow rate in a pipe by propagating an ultrasonic beam to a fluid in the pipe line.

  FIG. 3 is a principle explanatory view of the ultrasonic flowmeter. As in Patent Documents 1 to 3, the ultrasonic transducer 3a is provided on the tube body 1 through which the fluid F flows, on the outer surface on one side of the upstream side and the downstream side via the beam transmission body 2 made of synthetic resin. 3b is fixed by adhesion.

  From the ultrasonic transducers 3a and 3b, the ultrasonic beam B passes through the beam transmission body 2 and the tube body 1 and is alternately transmitted into the tube body 1 and is reflected by the inner surface of the opposite tube body 1 so as to return to the tube. It passes through the body 1 and the beam transmission body 2 and reaches the ultrasonic transducers 3b and 3a on the other side. The flow rate of the fluid F such as water flowing in the tubular body 1 can be measured by the difference in propagation time of the bidirectional ultrasonic beam B.

JP 2001-281032 A JP 2005-181268 A JP 2006-337313 A

  As shown in FIG. 3, the ultrasonic beam B emitted from the ultrasonic transducer 3 a generates an inner surface reflected wave Ba that is reflected by the inner surface of the tube body 1, and passes through the tube body 1 to pass through the outer surface of the tube body 1. The outer surface reflected wave Bb is reflected and reaches the ultrasonic transducer 3b.

  In the case where the tube 1 is made of metal, for example, since the specific acoustic impedance of the fluid F made of water and the metal are sufficiently different, the ultrasonic beam B hardly enters the tube 1 at the reflecting portion, and is often Becomes the inner surface reflected wave Ba on the inner surface of the tube 1.

  However, when the tubular body 1 is made of synthetic resin, the synthetic resin has an inherent acoustic impedance close to that of water, so that the ultrasonic beam B is incident on the tubular body 1 along with the generation of the internal reflection wave Ba. It is easy to generate an external reflection wave Bb from the external surface.

  FIG. 4 is a graph of the ultrasonic beam B obtained by the ultrasonic transducer 3b in this case, and the internal reflection wave Ba shown by a solid line and the external reflection wave Bb shown by a chain line are generated to the same extent. In order to improve the measurement accuracy, the internal reflection wave Ba and the external reflection wave Bb must be distinguished from each other in order to eliminate the external reflection wave Bb that makes measurement unstable and extract only the internal reflection wave Ba. I must.

  An object of the present invention is to provide an ultrasonic flowmeter that solves the above-described problems and that hardly generates external reflection waves and improves measurement accuracy even when the tube is made of synthetic resin.

  In order to achieve the above object, an ultrasonic flowmeter according to the present invention has a pair of ultrasonic transducers attached to an upstream side and a downstream side in a fluid flow direction of a tubular body. The ultrasonic beam transmitted from the wave generator is alternately and repeatedly received by the other ultrasonic wave transmitter / receiver through the reflection of the inner wall of the tube, and propagates in the fluid by the flow velocity of the fluid flowing through the tube. An ultrasonic flowmeter for measuring a flow rate in the tube based on a propagation time difference generated in the ultrasonic beam, wherein a vibration absorber is attached to an outer wall of an inner surface reflection portion of the tube via a viscous material. It is characterized by.

  According to the ultrasonic flowmeter of the present invention, most of the obtained ultrasonic beam reflected wave is an internally reflected wave, and therefore, accurate measurement is possible.

It is a block diagram of the ultrasonic flowmeter of an Example. It is a wave form diagram of an ultrasonic beam obtained in an example. It is a principle explanatory drawing of an ultrasonic flowmeter. It is a wave form diagram of the ultrasonic beam obtained with the conventional ultrasonic flowmeter.

  The present invention will be described in detail based on the embodiments shown in the drawings.

  FIG. 1 shows a configuration diagram of a clamp-type ultrasonic flowmeter that is used by being attached to the outside of an existing pipe body of an embodiment. A block body 12 made of synthetic resin or metal is disposed on one side of a flow path tube body 11 made of synthetic resin such as Teflon (registered trademark), and a vibration absorber 13 made of synthetic rubber, for example, on the other side of the tube body 11. Is fixed around the tube 11 by a band 14.

  A pair of ultrasonic transducers 15a and 15b are attached to the upstream side and the downstream side in the block body 12, and a beam transmission body made of synthetic resin is provided on the input and output sides of the ultrasonic transducers 15a and 15b. 16 is arranged.

  When the ultrasonic flowmeter is fixed to the tube body 11, a viscous material 17 such as grease or silicone oil is applied to the inside of the block body 12 and the vibration absorber 13 to be in close contact with the outer wall of the tube body 11. The inside of the block body 12 is formed in accordance with the outer shape of the tube body 11, and the vibration absorber 13 is deformed by using, for example, a flexible synthetic rubber plate, and the viscous body 17 is similarly applied. The block body 12 and the vibration absorber 13 may be detachably fixed by the band 14.

  The ultrasonic transducers 15a and 15b are connected to the output of the driving means 21 for supplying a pulse signal, the electrical outputs of the ultrasonic transducers 15a and 15b are connected to the arithmetic control means 22, and further the arithmetic control means. The output 22 is connected to the display means 23.

  When measuring the flow rate, an ultrasonic beam B is transmitted from one of the ultrasonic transducers 15a and 15b into the tube body 11 through the beam transmission body 16 and the viscous body 17 by a signal from the driving means 21. Further, in the other of the ultrasonic transducers 15 a and 15 b, the internal reflection wave Ba that passes through the fluid F and is reflected by the internal reflection portion of the inner wall of the tubular body 11 is received and transmitted to the calculation control means 22. As described above, the transmission and reception of the ultrasonic beam B are alternately repeated by the ultrasonic transducers 15a and 15b.

  The arithmetic control means 22 averages the propagation time difference between the time when the ultrasonic beam B reaches the downstream side from the upstream side of the fluid F and the return time when the ultrasonic beam B reaches the upstream side from the downstream side. Based on this propagation time difference, the calculation control means 22 obtains the flow velocity of the fluid F by a known method, calculates the flow value, and displays it on the display means 23.

  In this embodiment, as shown in FIG. 1, the ultrasonic beam B from the ultrasonic transducers 15 a and 15 b is incident on the tubular body 11, passes through the fluid F, and a part is reflected by the inner wall of the tubular body 11. Then, the inner surface reflected wave Ba is formed, and the other ultrasonic beam B passes through the reflecting portion of the tube body 11 and reaches the outer surface of the tube body 11. A viscous body 17 is applied to the outer surface, and the inherent acoustic impedance between the synthetic resin, which is the material of the tube body 11, and the viscous body 17 is approximated. Therefore, the ultrasonic beam B reaching the outer surface is the viscous body 17. , And enters the vibration absorber 13 whose natural acoustic impedance is similarly approximated.

  The ultrasonic beam B incident on the vibration absorber 13 is absorbed and converted into heat while being scattered in the vibration absorber 13 whose molecular structure is randomly arranged. Even if it is incident on the vibration absorber 13, scattered inside, emitted from the vibration absorber 13, returns to the tube body 11 through the viscous body 17, the direction is random, and the ultrasonic transducer There is little going to the direction of 15b.

  Therefore, as shown in FIG. 2, the level of the external reflection wave Bb is reduced, and the internal reflection wave Ba can be extracted from the obtained reflection waves Ba and Bb based on the level threshold value, thereby improving the measurement accuracy. .

  Although the clamp type ultrasonic flowmeter has been described in the embodiments, it is needless to say that an existing ultrasonic flowmeter can be applied by attaching a vibration absorber.

DESCRIPTION OF SYMBOLS 11 Channel body 12 Block body 13 Vibration absorber 14 Band 15a, 15b Ultrasonic transmitter / receiver 16 Beam transmission body 17 Viscous body 21 Driving means 22 Arithmetic control means 23 Display means

Claims (5)

  It has a pair of ultrasonic transducers attached to the upstream and downstream sides of the fluid flow direction of the tubular body, and reflects the ultrasonic beam transmitted from the one ultrasonic transducer on the inner wall of the tubular body. Then, the reception of the other ultrasonic transducer is alternately repeated, and the flow rate in the tube is determined based on the propagation time difference generated in the ultrasonic beam propagating in the fluid due to the flow velocity of the fluid flowing in the tube. An ultrasonic flow meter for measuring a vibration absorber, wherein a vibration absorber is attached to the outer wall of the inner surface reflection portion of the tubular body via a viscous material.   The ultrasonic flowmeter according to claim 1, wherein the viscous body is made of grease.   The ultrasonic flowmeter according to claim 1, wherein the vibration absorber is made of synthetic rubber.   The ultrasonic flowmeter according to claim 1, wherein the tubular body is made of a synthetic resin.   The ultrasonic flowmeter according to claim 1, wherein the pair of ultrasonic transducers is a clamp type that can be attached to and detached from the tube body.

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