JP7035264B1 - Ultrasonic flow meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively absorb noise transmitted through a pipe body by arranging a sound deadening structure composed of a plastic substance and a metal member around the pipe body. SOLUTION: A pair of ultrasonic transmitters / receivers 3 and 4 are fixed to an outer surface of a tube body 1 along a tube body 1 via a wedge stand 5 to form a measuring tube section 2. A muffling structure 6 is installed around the measuring conduit 2, and the muffling structure 6 is provided so as to cover the periphery of the measuring conduit 2 excluding the ultrasonic transmitters / receivers 3 and 4 and the wedge stand 5. Has been done. The sound deadening structure 6 is composed of a metal member 7 and a sound wave absorbing material 8, and the metal member 7 is a plurality of long piece members made of a mold material so as to be in contact with the outer surface of the pipe body 1 along the length direction of the pipe body 1. Is located in. The sound wave absorbing material 8 is filled in the gap between the metal members 7 and the gap between the tube body 1 and the metal member 7. [Selection diagram] Fig. 2

Description

The present invention relates to an ultrasonic flow meter that absorbs noise transmitted through a tube body by a sound deadening structure, increases S / N, and improves measurement accuracy.

In the ultrasonic flow meter, an extra ultrasonic noise component transmitted through the tube is mixed in the ultrasonic receiving element, the S / N becomes small, and the measurement accuracy tends to deteriorate. Therefore, for example, as described in Patent Document 1, it is disclosed that an ultrasonic sound deadening material such as a rubber body or an adhesive gel is arranged around a tube body to absorb and reduce noise. .. Alternatively, metal particles and the like are mixed in the ultrasonic sound deadening material to improve the absorption performance.

Further, in Patent Document 2, an ultrasonic absorber made of uncrosslinked rubber or the like is arranged around the tube body, and an ultrasonic cushioning material made of a mat-shaped elastic porous body having open cells is arranged outside the ultrasonic absorber. , It is disclosed to absorb the noise transmitted through the tube.

Japanese Unexamined Patent Publication No. 6-117894 Japanese Unexamined Patent Publication No. 2018-105735

However, although the ultrasonic sound deadening material such as the rubber body used in Patent Documents 1 and 2 can absorb noise by coming into contact with the surface of the tube body, the surface area of the tube body is limited and the noise is increased. It cannot be said that the desired measurement accuracy can be obtained because the absorption is insufficient and a lot of noise remains.

In particular, when a gas is measured as a fluid, the attenuation of the ultrasonic pulse propagating in the gas is large, the influence of the noise transmitted through the tube increases, and it is about 1000 times larger than the obtained ultrasonic signal. It may result in a large amount of noise. Therefore, the signal may be buried in the noise, and the S / N ratio becomes extremely small. Unless this noise is sufficiently removed, it is difficult to secure the reliability of the measurement.

When the tube is made of synthetic resin, the transmission noise is small, so the flow velocity can be easily measured even if the removal is not sufficient, but when the tube is a metal tube, the amount of transmission noise is large and it is difficult to remove.

An object of the present invention is to solve the above-mentioned problems and to arrange a sound deadening structure composed of a metal member and a sound wave absorbing material around a measuring pipe section of a pipe body to effectively absorb transmission noise. In particular, it is an object of the present invention to provide an ultrasonic flow meter that can be applied even when a gas is a measurement target.

The ultrasonic flow meter according to the present invention for achieving the above object is a tube body around a measuring tube portion in which a pair of ultrasonic transmitters / receivers for measuring the flow velocity of a fluid in a tube by an ultrasonic pulse are arranged. An ultrasonic flow meter equipped with a sound deadening structure that absorbs noise transmitted through the sound wave, in which a plurality of metal members are arranged on the outer surface of the pipe body, and gaps between the metal members and The gap between the tube and the metal member is filled with a soft, high-density sound wave absorber having plasticity.

According to the ultrasonic flow meter according to the present invention, noise transmitted through the tube by arranging a sound deadening structure composed of a metal member and a soft high-density sound absorber around the measurement tube portion of the tube. Is effectively absorbed and the measurement accuracy in the measurement pipeline is improved.

It is a vertical cross-sectional view of the measurement pipeline part. It is an enlarged cross-sectional view of the measurement pipeline part. It is a perspective view of the state where the metal member is arranged around the tube body. It is an enlarged cross-sectional view of the measurement line part using the metal member of another shape. It is sectional drawing of the metal member of another shape.

The present invention will be described in detail with reference to the illustrated examples.

FIG. 1 is a vertical cross-sectional view of the measurement pipeline portion. A part of the pipe body 1 through which the fluid which is a gas flows is regarded as the measurement pipe portion 2. In the measuring tube portion 2, for example, a pair of ultrasonic transmitters / receivers 3 and 4 are fixed to the outer surface of a metal tube 1 having a diameter of 50 mm via a wedge base 5. The ultrasonic transmitters and receivers 3 and 4 each have a built-in vibrator, and can transmit and receive ultrasonic pulses. The wedge base 5 transmits and receives ultrasonic pulses to and from the tube 1 at a predetermined angle, and is made of a material such as titanium that easily transmits ultrasonic waves.

The ultrasonic transmitters / receivers 3 and 4 are arranged so as to be offset from the upstream side and the downstream side of the surface of the tubular body 1 along the tubular body 1, and the ultrasonic pulse P transmitted from any of the ultrasonic transmitters / receivers 3 and 4 is generated. It is a so-called V-shaped arrangement that crosses the fluid in the tube 1 in an oblique direction, is reflected by the inner wall of the tube 1, is folded back, and is received by the other ultrasonic transmitters / receivers 3 and 4. It should be noted that the ultrasonic transmitters / receivers 3 and 4 are arranged on the upstream side and the downstream side with the tube body 1 interposed therebetween, and the ultrasonic pulse P is arranged in a Z-type system so as to cross the fluid in the tube body 1 in only one diagonal direction. It can also be.

As shown in FIGS. 2 and 3, a sound deadening structure 6 for absorbing ultrasonic noise transmitted through the tube 1 is constructed around the measurement tube 2. The sound deadening structure 6 is composed of a metal member 7 and a sound wave absorbing material 8, a large number of block materials such as SUS made of a mold material are used for the metal member 7, and oil clay and a polymer material are used for the sound wave absorbing material 8. A soft high-density material having plasticity such as is used. The sound wave absorbing material 8 is not shown in the sound deadening structure 6 shown in FIG.

In the metal member 7, for example, two types of long piece members having a length of 100 mm and 50 mm are arranged in a large number of rows in the length direction of the tubular body 1 by adding them at appropriate intervals. In the embodiment shown in FIG. 2, the cross section of the metal member 7 is, for example, a square, and a recess is formed along the surface in contact with the tubular body 1. In order to improve the sound absorption efficiency of the sound wave absorbing material 8, the metal member 7 preferably has a shape having a large surface area in contact with the sound wave absorbing material 8 in its cross section.

In the measuring pipeline portion 2, two types of metal members 7 are appropriately combined and arranged, and the reason why the metal members 7 having different lengths are used is that the sound wave absorber 8 is arranged on the surface thereof. This is to increase the randomness, but there is no problem even if the metal members 7 having the same length and the same shape are used.

The sound wave absorbing material 8 is filled tightly in the gap between the metal members 7, the gap between the tube 1 and the metal member 7, and further around the metal member 7 by utilizing its plasticity.

The sound deadening structure 6 is provided so as to cover the periphery of the measuring pipeline portion 2 excluding the ultrasonic transmitters / receivers 3 and 4 and the wedge stand 5. Further, the outside of the sound deadening structure 6 is covered with, for example, a special metal cover member (not shown), and the sound deadening structure 6 can be strongly adhered to the pipe body 1 by this cover member.

At the time of measurement, ultrasonic pulse P is alternately transmitted from the vibrators built in the ultrasonic transmitters / receivers 3 and 4, and the ultrasonic pulse P crosses the fluid in the tube 1 and is reflected by the inner wall of the tube 1. It is received by the oscillators of the ultrasonic transmitters and receivers 4 and 3. The ultrasonic pulse P traveling along the flow of fluid from the upstream ultrasonic transmitter / receiver 3 toward the downstream ultrasonic transmitter / receiver 4, and the downstream ultrasonic transmitter / receiver 4 to the upstream ultrasonic transmitter / receiver 3 The flow velocity is calculated by calculation based on the arrival time difference between the flow toward and the ultrasonic pulse P going backward. The flow rate is obtained by multiplying this flow velocity by the cross-sectional area of the tube body 1, but since this measurement principle is known, further detailed description will be omitted.

Since the sound deadening structure 6 in particular, the metal member 7, is arranged around the pipe body 1 so as to be in contact with the pipe body 1, the noise transmitted through the pipe body 1 is transmitted to the metal member 7, and further, the metal member 7 is transmitted. It is effectively absorbed by the sound wave absorbing material 8 in contact with 7, and the input of noise to the ultrasonic transmitters / receivers 3 and 4 is reduced.

Explaining the reduction of noise in terms of acoustic impedance, the acoustic impedance is a value obtained by multiplying the density of the medium and the speed of sound. When a metal member 7 having an acoustic impedance having an acoustic impedance substantially equal to that of the metal tube 1 is brought into close contact with the tube 1, the noise of the tube 1 is transmitted to the metal member 7 and dispersed. Then, the noise in the metal member 7 is transmitted to the sound wave absorbing material 8 and absorbed. In this way, the noise energy transmitted to the tube body 1 and the metal member 7 is mainly converted into heat energy by the sound wave absorbing material 8 and silenced by the sound wave absorbing material 8.

When a metal cover is attached to the outside of the sound deadening structure 6 and tightened with a tightening band or the like, noise absorption is further improved. That is, since the metal cover strongly adheres the sound deadening structure 6 to the tube body 1, and the metal cover also adheres to the sound deadening structure 6, the acoustic matching state changes, and the metal member 7 and the sound wave absorption from the tube body 1. The transmission of noise to the material 8 and the transmission of noise from the metal member 7 and the sound wave absorber 8 to the metal cover are increased, and the noise is effectively absorbed. Further, by attaching the metal cover, the contact with air is reduced, and the deterioration of the sound wave absorbing material 8 is prevented.

FIG. 4 is a cross-sectional view of the measurement conduit portion 2 when the metal member 7 having a semi-arc-shaped cross section is used. , The gap between the metal members 7 is filled with the sound wave absorbing material 8.

5 (a) to 5 (d) are examples of cross-sectional shapes of the metal member 7, and by using the metal member 7 having a large surface area, the sound deadening effect of the sound deadening structure 6 is exhibited. The sound deadening structure 6 may contain metal members 7 having different shapes.

In the embodiment, it has been described that the metal member 7 is a long piece-shaped block material and is in contact with the tubular body 1 along the longitudinal direction, but the shape thereof is not limited to the embodiment, and the tubular body 1 is not limited in shape. It can also be arranged so as to be wound in the lateral direction. Further, the metal member 7 may be integrally formed around the tubular body 1 in a fin shape. That is, the surface area of the metal member 7 may be increased so that noise can be effectively transmitted to the sound wave absorbing material 8.

1 Pipe 2 Measurement pipe 3, 4 Ultrasonic transmitter / receiver 5 Wedge stand 6 Sound deadening structure 7 Metal member 8 Sound wave absorber

Claims (6)

An ultrasonic flow meter equipped with a muffling structure that absorbs noise transmitted through the tube around the measurement tube section where a pair of ultrasonic transmitters and receivers are arranged to measure the flow velocity of the fluid in the tube by ultrasonic pulses. And,
In the sound deadening structure, a plurality of metal members are arranged on the outer surface of the pipe body, and a soft, high-density sound wave absorber having plasticity in the gap between the metal members and the gap between the pipe body and the metal member. An ultrasonic flow meter characterized by being filled with. The pair of ultrasonic transmitters / receivers are attached to the upstream side and the downstream side of the outer surface of the measurement conduit portion, and the ultrasonic pulse is transmitted from one of the ultrasonic transmitters / receivers and received by the other ultrasonic transmitter / receiver. The ultrasonic flow meter according to claim 1, wherein the above is alternately repeated to measure the flow rate. The ultrasonic flow meter according to claim 1 or 2, wherein the metal member is a long piece-shaped material having a large surface area, and a part thereof is in contact with the tubular body along the longitudinal direction. The ultrasonic flow meter according to any one of claims 1 to 3, wherein the sound wave absorbing material is made of oil clay or a polymer material. The ultrasonic flow meter according to any one of claims 1 to 4, wherein the periphery of the sound deadening structure is covered with a metal cover. The ultrasonic flow meter according to any one of claims 1 to 5, wherein the metal cover can be tightened from the outside of the sound deadening structure.

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