JPS63265117A - Ultrasonic wave flowmeter - Google Patents

Abstract

PURPOSE:To receive intense sound waves and to improve an S/N ratio, by attaching a horn having a slit-shaped opening part in an oscillator to a waveguide, which has an arc-shaped bottom surface with the opening part of the horn as a central axis. CONSTITUTION:A flat horn 3, to which an oscillator 2 is attached, is attached on a waveguide 1 in the flowing direction of fluid in a slant state. The width of the slit shaped opening part 4 of the horn 3 is less than the half wavelength of a sound wave used, and the length of the part 4 is more than one wavelength. An opening part 4 of the horn 3 is attached to the waveguide 1 so that the opening part is positioned at the central axis of an arc shaped bottom surface 1a. The sound wave, which is emitted from the oscillator 2, does not have directivity in a plane perpendicular to the axis of the waveguide 1. Therefore, the sound wave expands in the radial pattern. The sound wave is reflected by the bottom surface 1a and collected in the direction of the central axis. In a plane in the direction of the radius of the waveguide 1, directivity is provided. Therefore, the sound wave is reflected at the bottom surface 1a and reaches a receiver 5. Therefore, the intense sound wave is received in the receiver 5, and the S/N ratio is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ultrasonic flow meter that measures the flow velocity and flow rate of a fluid using the advection effect of ultrasonic waves.

[Conventional technology]

FIG. 7 is a configuration diagram including a block diagram of a conventional ultrasonic flowmeter described in, for example, Japanese Patent Application Laid-Open No. 58-32121. In the figure, 7 is a conduit through which fluid flows, and 8 and 9 are conduits 7. 10. A pair of oscillators and receivers are arranged diagonally.
Reference numeral 11 designates another pair of oscillator and receiver, which are also diagonally arranged. 12 is a signal generator, 13 is a modulator, 14 is a temperature sensor that detects the fluid temperature, 15 is a correction function generator that generates a correction amount using the temperature detected by the temperature sensor 2 as a correction factor, and 16 is a modulation signal generator. 17. 18 is a preamplifier connected to the receivers 9 and 11, 19.2
0 is a demodulator connected to this preamplifier 17, 18, 2
1 is a phase detector that detects a phase difference between demodulated outputs of demodulators 17 and 18, 22 is a low frequency filter, and 23 is an output terminal.

Next, the operation will be explained. The ultrasonic waves generated by the oscillators 8 and 1o are obtained by modulating the ultrasonic signals generated by the signal generator 12 with the modulator 13.

The modulation signal entering the modulator 13 changes the output of the temperature sensor 14 to 1
A correction function is generated by a correction function generator 15 as two parameters, and a correction function is generated by a modulation signal generator 16. After the modulated ultrasonic waves are emitted from the oscillator 8.10, one propagates in the same direction as the flow and the other propagates in the opposite direction to the flow and is received by the receiver 9.11. The received signals are each amplified by preamplifiers 17 and 18, demodulated by demodulators 19 and 20, and a phase detector 21 detects the phase difference between the two systems of demodulated signals. Therefore, since the flow velocity of the fluid to be measured is proportional to this phase difference, the flow velocity can be determined from the phase difference.

[Problem that the invention seeks to solve]

Since the conventional ultrasonic flowmeter is configured as described above, the sound waves directly reaching the receiver 9.11 from the oscillator 8.10 are weak, and there are reverberant waves reflected more than once on the wall of the conduit 7 and other waves. There was a problem in that noise was also received, resulting in a poor performance ratio and causing malfunctions.

This invention was made to solve the above-mentioned problems, and the purpose is to obtain an ultrasonic flowmeter that is not affected by reverberant waves or other noise and has stable performance without malfunction. shall be.

[Means for solving problems]

The ultrasonic flowmeter according to the present invention includes a horn having a slit-shaped opening in a sonic oscillator, which is attached to a conduit having an arcuate bottom surface with the opening of the horn as the center axis, and A receiver is installed in the conduit section.

[For production]

In this invention, the sound waves generated from the oscillator have directivity in the radial direction of the conduit by the horn, are reflected obliquely at the bottom of the conduit, and the strong sound waves are received by the receiver. When there is a flow in a conduit, if the direction of the flow is from the oscillator side to the receiver side, the phase of the ultrasonic wave will be advanced, and if the direction is opposite, the phase will be delayed, so the phase on the oscillating side and the receiving side The flow velocity and flow rate of the fluid can be measured by comparing the phase with the phase.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a side sectional view of the ultrasonic flowmeter according to the present invention, FIG. 2 is a plan view, and FIG. 3 is a sectional view taken along the line ■-■ in FIG. 1, where 1 is a conduit through which the fluid to be measured flows; It is formed into a substantially fan shape, consisting of an arcuate surface 1a and a side surface 1b. 2 is an oscillator that generates sound waves; 3 is a flat horn to which the oscillator 2 is attached; the oscillator 2 is mounted on the conduit 1 in an inclined manner in the flow direction of the fluid. 4 has a width less than half the wavelength of the sound wave used and a length of 1
This is the opening of a slit-shaped horn 3 whose size is longer than the wavelength, and the horn 3 is attached to the conduit 1 so that the opening 4 is located on the horizontal axis of the bottom surface 1a of the arcuate surface. Reference numeral 5 denotes a receiver attached to the conduit portion of the central axis of the bottom surface 1a on the downstream side of the oscillator 2 on the conduit 1.

The ultrasonic flowmeter of the present invention is constructed as described above, and the sound waves emitted from the oscillator 2 are emitted into the conduit 1 from the opening 4 of the horn 3. Since this sound wave has no directivity in the plane perpendicular to the axis of the conduit 1, it spreads radially as shown by the arrow in Figure 3, is reflected by the bottom surface 1a, and is collected in the direction of the central axis. However, since it has directivity within the radial plane of the conduit 1, it is reflected from the bottom surface 1a as shown by the arrow in FIG. 2 and reaches the receiver 5. Therefore, a strong sound wave is received by the receiver 5, and the S/N ratio is improved.

Thus, when there is fluid flow in the conduit 1, if the flow direction is from the oscillator 2 side to the receiver 5 side, the phase of the sound wave will be advanced;
If it is directed to the side, the phase of the sound wave will be delayed, so by comparing the phase on the oscillator side and the phase on the receiver side, the flow velocity and flow rate of the fluid can be measured.

In addition, as another embodiment of the ultrasonic flowmeter of the present invention, the fourth embodiment
By providing a horn 6 on the receiver 5 side as shown in Figures 6 to 6, only the sound waves from the oscillator 2 can be guided to the receiver 5, thereby further suppressing the influence of noise. . Furthermore, the horn 3 may be provided with a reflective surface 6 and have a bent shape.

Although not shown, two sets of oscillators and receivers may be installed in opposite directions to the flow direction to compensate for changes in the speed of sound. In this case, if the two sets are installed at the same position, they will be shifted from the center by the width of the horn opening, but this will not be a problem as long as the shift is small enough with respect to the wavelength of the sound wave.

〔Effect of the invention〕

As explained above, according to the present invention, a horn having a slit-shaped opening in a sound wave oscillator is attached to a conduit having an arcuate bottom surface with the opening of the horn as the center axis, and Since the receiver is equipped with a receiver in the downstream conduit section, the receiver can receive strong sound waves and improve the galling. This results in a highly reliable ultrasonic flowmeter that is less susceptible to reverberant waves and other noise and does not malfunction.

[Brief explanation of the drawing]

FIG. 1 is a side cross-sectional view of an ultrasonic flowmeter according to an embodiment of the present invention, FIG. 2 is a plan view of the same, and FIG.
4 to 6 are side sectional views and plan views of ultrasonic flowmeters according to other embodiments of the present invention.
FIG. 7, which is a sectional view taken along the line ■-■ in the figure, is a structural diagram of a conventional ultrasonic flowmeter. 1... Conduit, la... Bottom surface, 2... Oscillator, 3.
... Horn, 4 ... Horn opening, 5 ... Receiver,
6... Reflective surface. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (4)

[Claims] (1) A sound wave oscillator, a horn in which the oscillator has a slit-shaped opening whose width is less than half the wavelength of the sound wave used and whose length is more than one wavelength, and an arc-shaped surface whose central axis is approximately the said opening. 1. An ultrasonic flowmeter comprising: a conduit having a fan-shaped cross section having a bottom surface; and a receiver having a sound wave inlet at a conduit portion of the central axis upstream or downstream of the oscillator. (2) The ultrasonic flowmeter according to claim 1, wherein the receiver is provided with a horn having a slit-shaped opening. (3) The ultrasonic flowmeter according to claim 1 or 2, characterized in that a reflective surface is formed on the horn. (4) The ultrasonic device according to any one of claims 1 to 3, characterized in that two pairs of an oscillator and a receiver are provided in opposite directions along the flow direction of the fluid to be measured. Sonic flow meter.