JPS61132824A - Ultrasonic flowmeter - Google Patents

Abstract

PURPOSE:To enlarge the direct receiving wave and to improve S/N of receiving waves of a transmitter-receiver by fitting a thin metal plate adherently to the external wall surface of the piping corresponding to the wall surface within the piping to which ultrasonic waves emitted to the inside of a fluid reflect. CONSTITUTION:The thin metal plate 9 with the proper quality of material and thickness is adhered to the external wall surface of the piping corresponding to the reflecting surface of the direct receiving waves on the inside wall of the piping. Further, a sound pressure level of the receiving waves is increased by an interference of the reflected ultrasonic waves by the thin metal plate 9 and the direct waves. In this case, it is desirable to select the quality of material of the same system as the piping 1 for the thin metal plate 9.

Description

[Detailed Description of the Invention] [Technical Field to Which the Invention Pertains] The present invention emits ultrasonic waves from the outer wall of a pipe into a fluid and receives them on one surface outside the pipe, and the propagation time is proportional to the flow rate or flow rate of the fluid. This article relates to an ultrasonic flowmeter based on the principle of More specifically, it is mainly for small or medium diameters, in which ultrasonic waves are emitted diagonally into the fluid from the outer wall of the pipe, reflected into the fluid by the inner wall of the pipe, and then received at the outer wall of the pipe. Regarding general ultrasonic flowmeters.

[Prior art and its problems]

A conventional ultrasonic flowmeter of this type has a configuration as shown in FIGS. 5 to 7. That is, ultrasonic transducers (hereinafter simply referred to as transducers) 2a and 2b that emit ultrasonic waves into the fluid and receive the ultrasonic waves reflected on the inner wall surface of the pipe,
They are placed on the outer wall of the pipe 1 that guides the fluid, with acoustic force and a bringing material 4 interposed therebetween, with their positions shifted from each other. Transducer/receiver 2a,
As shown in the figure, 2b is made of a material such as epoxy resin that is generally used as an ultrasonic transmitting material (hereinafter simply referred to as "shite transparent material professional") 5, and a piezoelectric element such as PZT. It has a structure in which a certain ultrasonic transducer 6 is bonded.

With this configuration, the time it takes for the ultrasonic waves emitted by the transducer 2a to reach the transducer 2b and the time taken by the transducer 2
The flow velocity or flow rate of the fluid flowing through one circle of piping is determined based on the difference in time between the ultrasonic wave emitted from b and the time it takes to reach the transducer 2a. Therefore, based on the measurement principle, ultrasonic waves (abbreviated as direct) are transmitted from a transducer through the fluid, reflected on the P131Ni surface of the pipe, propagated through the fluid again, and are received by the other transducer. The propagation time of the received wave (referred to as a received wave) is the original measurement signal of this ultrasonic flowmeter, and is proportional to the flow velocity or flow rate of the fluid.

However, in conventional ultrasonic flowmeters with such a configuration, as described later, the energy of directly received waves is weakened by reflection and transmission on the inner wall surface of the piping, and interference, and the energy of the directly received waves is weakened by Along internal and external walls or inside piping f!
! The Nt wave (hereinafter simply referred to as a wrap-around wave) propagating while undergoing multiple electrical reflections in the # section forms an X fold as noise. For this reason, the S/N ratio of the waves received by the transducers 2a and 2b decreases, and the measurement accuracy of the propagation time of the directly received waves, which is proportional to the flow velocity or flow rate of the fluid, decreases. As a result, there is a problem in that the measurement accuracy of nuclear ultrasonic flow correction is reduced.

[Eyes of invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ultrasonic transducer that improves the S/N ratio of waves received by a transducer, solves the above-mentioned problem, and improves measurement accuracy.

[Key points of the invention]

According to the present invention, this purpose is achieved by attaching a thin plate of appropriate material and thickness to the outer wall surface of the pipe corresponding to the reflection surface of the fluid on the inner wall surface of the pipe for directly receiving waves. tree(
However, this is achieved by increasing the Δ of the received 111' wave of the transducer.

[Embodiments of the invention]

An embodiment of the present invention is shown in FIG. 81 and FIG.

As shown in the figure, the configuration of the present invention is such that a thin metal plate 7 of an appropriate material and thickness is closely attached to the outer surface of the pipe corresponding to the reflection surface of the directly received wave on the inner wall of the pipe.

As a result, the above-mentioned purpose can be achieved by increasing the sound pressure level of the Ti [receiving wave] and heightening the chin.

3 and 4 illustrate the principle of the present invention, and the present invention will be explained in detail based on these figures. In the figure,
Ultrasonic waves emitted from the outer wall of the pipe 1 into the fluid by the ultrasonic transducer 6a are reflected by the inner wall 115 and the outer wall 16 of the pipe 1, propagate through the fluid 3, and pass through the thick part of the pipe 1. and is received by the ultrasonic transducer 6b. In this case, the ultrasonic wave i that has propagated through the fluid is one of the pipes 1! [i 15 and is reflected and transmitted by the outer wall surface 16 to become an ultrasonic wave amen, which interferes with the ultrasonic wave vj that propagates through the fluid and is reflected by the inner wall surface 15.

Therefore, if the phases of the ultrasonic waves m, n and the ultrasonic waves j, reflected on the inner wall surface 15 match, the sound waves will strengthen each other, so the reflected sound pressure level on the inner wall surface 15 will increase, and Ultrasonic waves m, n and reflected ultrasonic waves j at the inner wall surface 15,
If the phases of the two waves are reversed, the sound waves cancel each other out, so the reflected sound pressure on the inner wall surface 15 becomes smaller.

The present invention utilizes the interference of sound waves as described above to increase the sound pressure level of directly received waves. That is, ultrasonic waves m, n and reflected ultrasonic waves j at the inner wall surface 15.

In order to match the phase with k, a thin metal plate of an appropriate thickness is brought into close contact with the outer wall surface 16 corresponding to the reflection surface of the direct reception wave on the inner wall of the pipe, thereby increasing the reflected sound pressure level on the inner wall surface 15. This is to increase the sound pressure level of the received wave. In this case, it is preferable to select a material for the thin metal plate that has the same type of reading as the piping.

Figure 4 shows the material SGP, diameter IB, and thickness 3.2% (
7) Ultrasonic waves are applied to the pipe at an angle of 42 degrees through a transparent material made of epoxy resin, and the outer wall surface 16 of the pipe is
Experimental confirmation results of the relationship between the thin plate thickness and the sound pressure level (relative value) of the received wave when thin metal plates made of stainless steel are brought into close contact with each other, and the thickness of the thin plate and the sound pressure reflection height (relative value) at the inner wall surface 15. An example of the calculation result of the relationship between As shown in the figure, the sound pressure level 12 (relative value) of the received wave and the sound pressure reflection wheel 13 (relative value in the calculation result) on the inner wall surface 15 have the same characteristics and have a periodicity relative to the thickness of the metal thin plate. There is a thin plate thickness that has characteristics and increases the sound pressure level of the received wave. If the thickness of the thin metal plate is selected to increase the sound pressure level of the received wave, and this thin metal plate is brought into close contact with the outer wall surface of the pipe corresponding to the reflection surface on the inner wall of the pipe for direct reception, the sound pressure level of the received wave will be increased. Pressure levels can be increased.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, reception can be received simply by closely adhering a thin metal plate of an appropriate material and thickness to the outer wall surface of the pipe corresponding to the reflection surface of the direct received wave on the inner wall surface of the pipe. The sound pressure level of the waves can be increased, and as a result, the received waves have a higher quality, and the measurement accuracy can be improved.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are a side view and a radial cross-sectional view showing an ultrasonic flowmeter according to an embodiment of the present invention together with piping, respectively;
FIG. 3 is a schematic diagram schematically showing the propagation mode of ultrasonic waves in piping, FIG. 4 is a graph for explaining the present invention, and FIG.
6 are a side view and a radial cross-sectional view showing a conventional ultrasonic flowmeter together with piping, respectively, and FIG. 7 is a cross-sectional view showing the configuration of a transducer. 1: Piping, 2.2m, 2b: Transducer, 3: Fluid, 4
: Acoustic force, pulling material, 9: Metal thin plate, 15: Piping inner wall surface, 16: Piping outer wall surface.

Claims (1)

[Claims] An ultrasonic transmitting part and a receiving part are arranged at different positions on the outer wall of the pipe, and the ultrasonic waves are emitted from the outer wall of the pipe into the fluid and reflected into the fluid by the inner wall of the pipe. An ultrasonic flowmeter configured to receive ultrasonic waves on a wall surface, characterized in that a thin metal plate is attached in close contact with the outer wall surface of the pipe corresponding to the inner wall surface of the pipe where the ultrasonic waves emitted into the fluid are reflected. Flowmeter.