JP5113354B2 - Ultrasonic flow meter - Google Patents

Description

  The present invention relates to an ultrasonic flowmeter that measures a flow rate by an ultrasonic propagation time difference method.

  Conventionally, in an ultrasonic flowmeter in a small-diameter pipe having an inner diameter of, for example, 10 mm or less, it is difficult to accurately perform the measurement.

  In the measurement using the Z-type ultrasonic transmission path shown in FIG. 3 or the V-type ultrasonic transmission path shown in FIG. 4 that is normally performed, if the diameter of the pipe line 1 is small, the ultrasonic waves from the ultrasonic transmitters / receivers 2 and 3 are transmitted. Since the distance of propagation in the fluid is short, the resolution of flow measurement is low.

  Therefore, when the distance between the ultrasonic transmitters / receivers 2 and 3 is increased as shown in FIG. 5, the number of times the ultrasonic waves are reflected by the tube wall of the pipe line 1 increases, and the intensity of the obtained signal waveform is attenuated, The SN ratio will be small.

  To solve these problems and increase the ultrasonic transmission / reception angle θ with respect to the pipeline 1 of the ultrasonic transmitters / receivers 2 and 3 to reduce the number of reflections in order to lengthen the waveguide length, transmission of ultrasonic waves into the pipeline Efficiency and reception efficiency from inside the pipe deteriorate.

  Therefore, using the U-shaped pipe 4 as shown in FIG. 6 or the crank-type pipe 5 as shown in FIG. The flow rate may be measured by sound wave propagation.

  In this type of measurement method, there is an advantage that the transmission / reception efficiency of ultrasonic waves into the pipelines 4 and 5 is improved and the reflection of ultrasonic waves by the inner walls of the pipelines 4 and 5 is small. However, the pipes 4 and 5 have a right-angle path, and there is a problem that a pressure loss in hydrodynamics is likely to occur, a fluid retention portion is generated, and sediment is easily deposited on the refraction portion.

  From such a viewpoint, it is preferable that the following conditions be provided in the flow rate measurement using ultrasonic waves in a small-diameter pipe.

  (1) In order to increase the resolution of the measurement accuracy of the transmission time in the ultrasonic transmitter / receiver in the pipeline, the propagation distance of the ultrasonic wave is increased.

  (2) Since the reflection of ultrasonic waves is accompanied by attenuation, the number of reflections on the tube wall is minimized.

  (3) Even when reflection is required, a large reflection angle is given to the normal line of the tube wall in order to reduce the transmitted wave to the outside of the tube wall in the reflection of the fluid in the pipe line.

  (4) Reduce the pressure loss of the fluid in the pipeline as much as possible.

  However, it is difficult to satisfy the conditions (1) to (4) at the same time by using only a conventional straight line.

  An object of the present invention is to solve the above-described problems and to provide an ultrasonic flowmeter having high flow measurement accuracy using a curved pipe line as a measurement pipe.

In order to achieve the above object, the technical feature of the ultrasonic flowmeter according to the present invention is that a pair of blocks made of a synthetic resin material each having a straight pipe portion with one end as an open end and the other end as a closed portion are formed therein. The body is held at a predetermined interval by a holding member, and the open ends of the straight pipe portions are connected to each other through a joint provided in each block body by an arc-shaped curved pipe portion having a length of approximately ¼ of the circumference. An ultrasonic transmitter / receiver for connecting and transmitting / receiving ultrasonic pulses in the axial direction of the straight pipe portion through the closed portion of the straight pipe portion is attached to each block body, and the straight pipe portion of each block body is attached A pair of fluid conduits are connected to the straight pipe part from the side in the vicinity of the closed part via a joint provided on the block body with the pipe axes aligned with each other, and from one ultrasonic transceiver The emitted ultrasonic pulse passes through the straight pipe portion of the one block body. Reflected by the curved pipe portion, through the straight pipe portion of the other of said block body lies in the to reach the other of the ultrasonic transducers.

  According to the ultrasonic flowmeter according to the present invention, the curved pipe portion is provided in the measurement pipe, the pressure loss is reduced, and the measurement accuracy is improved. In addition, when the fluid conduit is used in the vertical direction, deposits in the fluid are reduced.

  The present invention will be described in detail based on the embodiment shown in FIGS.

FIG. 1 shows a configuration diagram of the ultrasonic flowmeter according to the first embodiment, and both end portions of a measuring tube 12 having an arcuate curved tube portion 11 at the center are straight tube portions 13 and 14 . Curved pipe portion 11 is connected to the open end of the straight pipe sections 13 and 14, the other end of the straight pipe portion 13 and 14 is a closed section 15, 16. In addition, the magnitude | size of the curved pipe part 11 is made into the size of about 1/4 of the circumference.

  First and second ultrasonic transmitters / receivers 17 and 18 are attached to the blocking portions 15 and 16 with their transmitting / receiving directions directed to the tube axis directions of the straight tube portions 13 and 14, respectively. Further, a pair of fluid conduits 19 and 20 are connected to the straight pipe portions 13 and 14 from the side, and the tube axes of these fluid conduits 19 and 20 are on the same line.

Actually, the straight pipe portions 13 and 14 are respectively molded into block bodies 21 and 21 'in which a synthetic resin material is injection-molded . The block bodies 21 and 21' have joint portions and fluid conduits for the curved pipe portion 11, respectively. Joint portions for 19 and 20 and attachment portions for the first and second ultrasonic transceivers 17 and 18 are formed.

Then, one end of the curved pipe part 11 and the fluid conduit 19 are connected to the straight pipe part 13 of one block body 21 , and the first ultrasonic transmitter / receiver 17 is attached via the closed part 15 of the straight pipe part 14. It has been. Further, the other end of the curved pipe portion 11 and the fluid conduit 20 are connected to the straight pipe portion 14 of the other block body 21 ′ , and the second ultrasonic transmitter / receiver is further connected via the closing portion 16 of the straight pipe portion 15 . 18 is attached, and the block bodies 21 and 21 ′ are held by a metal plate 22 at a predetermined interval, for example.

The fluid to be measured flows from the fluid conduit 19 through the straight pipe portion 13 and the curved pipe portion 11 to the straight pipe portion 14 and the fluid conduit 20. At the time of measurement, the ultrasonic pulse transmitted from the first ultrasonic transmitter / receiver 17 efficiently enters the straight pipe portion 13 and the curved pipe portion 11 , and is reflected at reflection points 11 a and 11 b by the inner wall of the curved pipe portion 11. The light is reflected and incident on the second ultrasonic transmitter / receiver 18 through the straight pipe section 14 to obtain an ultrasonic signal as measurement data. Similarly, the ultrasonic pulse from the second ultrasonic transmitter / receiver 18 reaches the first ultrasonic transmitter / receiver 17 through the straight tube portion 14, the bent tube portion 11, and the straight tube portion 13 .

  Transmission of ultrasonic pulses from the first ultrasonic transmitter / receiver 17 to the second transmitter / receiver 18 and transmission of ultrasonic pulses from the second transmitter / receiver 18 to the first transmitter / receiver 17 are alternately performed. The time until the ultrasonic pulse transmitted from the first transmitter / receiver 17 is reflected by the two reflection points 11a and 11b of the curved pipe section 11 and is received by the second transmitter / receiver 18 is the same as that of the ultrasonic pulse. In order to superimpose on the progress of the fluid, the time from the second transmitter / receiver 18 to the first transmitter / receiver 17 through two reflections at the bent tube portion 11 is shorter corresponding to the flow velocity. .

  These times are measured by a measurement circuit (not shown), and the obtained time difference is related to the flow velocity of the fluid to be measured. Therefore, the flow velocity is obtained by this time difference, and the measured flow rate is obtained by multiplying the cross-sectional area of the measurement tube 12.

  In the first embodiment, the curved pipe portion 11 has an arc shape. However, as shown in FIG. In the second embodiment, the ultrasonic pulse is reflected at the reflection point 11a '. In this case, unless the bending angle is increased so much, the pressure loss of the fluid does not occur greatly.

  In the present invention, an ultrasonic flowmeter that satisfies all the conditions (1) to (4) mentioned above in the problem to be solved can be obtained.

1 is a configuration diagram of Example 1. FIG. 10 is a cross-sectional view of a main part of Example 2. FIG. It is a block diagram of the ultrasonic flowmeter of the Z type conventional example. It is a block diagram of the ultrasonic flowmeter of the V type conventional example. It is a block diagram of the ultrasonic flowmeter of the prior art example at the time of enlarging the distance between transmitter / receivers. It is a block diagram of the conventional ultrasonic flowmeter using a U-shaped pipe line. It is a block diagram of the ultrasonic flowmeter of the prior art example using a crank type pipe line.

Explanation of symbols

11, 11 'Curved tube portion 12 Measuring tube 13, 14 Straight tube portion 15, 16 Blocking portion 17, 18 Ultrasonic transmitter / receiver 19, 20 Fluid conduit

Claims (4)

A pair of block bodies made of a synthetic resin material, each having a straight pipe portion with one end as an open end and the other end as a closed portion, are held at predetermined intervals by a holding member, and have a length of approximately 1/4 of the circumference. The open ends of the straight pipe portions are connected to each other through a joint provided in each block body by an arc-shaped curved pipe portion having an ultrasonic pulse through the closed portion of the straight pipe portion. An ultrasonic transmitter / receiver that transmits and receives in the axial direction is attached to each block body, and a pair of fluid conduits are respectively provided from the side of the straight pipe portion in the vicinity of the closed portion of the straight pipe portion of each block body. of the tube axis each other to match the connected via a joint provided on the block body, the curved pipe portion through the straight tube portion of one of said ultrasonic transceiver ultrasonic pulses emitted from said one block body Reflected by the other, through the straight pipe part of the other block body, the other Ultrasonic flow meter, characterized in that serial was to reach the ultrasonic transducer. The ultrasonic flowmeter according to claim 1, wherein both ends of the bent pipe portion are straight pipes, and the straight pipes are connected to an opening end of the straight pipe portion . The ultrasonic flowmeter according to claim 1, wherein the curved pipe portion has a shape of “<” . Ultrasonic flow meter according to claim 1 or 2 or 3 wherein the holding member is characterized by being made of metal.

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