JP2002214011A - Ultrasonic flow velocity measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic flow velocity measuring apparatus which can efficiently increase the gain of a received wave and realize a smooth flow of a fluid and hence ensure a satisfactory measuring accuracy. SOLUTION: A flow velocity measuring unit 11 has inner surfaces formed symmetrically about the center point O between ultrasonic transducers 2, 3 over the entire circumference, and these symmetric inner surfaces form a part of an elliptical surface with a focus at the most close point of the peripheral edges of the transducers 2, 3. This increases the apertures of a fluid inlet and outlet 11a, 11b enough to take the almost of an ultrasonic wave transmitted from the ultrasonic transducer into the measuring unit (11) and realize a smooth flow of a fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flow velocity measuring device for measuring the flow velocity of a gas or other fluid using ultrasonic waves.

[0002]

2. Description of the Related Art When determining the flow rate of a gas or other fluid, the flow rate of the fluid is measured continuously or periodically, and the flow rate is calculated based on the measured flow rate. As one of such fluid flow velocity measuring methods, a method utilizing ultrasonic waves is known.

FIG. 4 shows the principle of such an ultrasonic flow velocity measuring method.
The following is a description of the conventional device shown in FIG. In FIG. 4, (101) is an ultrasonic flow velocity measuring tube through which a fluid such as a gas flows, and (111) is a part for measuring the flow velocity of the fluid. In the ultrasonic flow velocity measuring tube (1), ultrasonic vibrators (2) and (3) are arranged at a predetermined distance upstream and downstream in the flow direction.

The ultrasonic vibrators (2) and (3) are driven by a driving pulse from a pulse generating circuit (4) to vibrate, generate and transmit ultrasonic waves, and receive transmitted ultrasonic waves. The reception wave when the ultrasonic transducers (2) and (3) vibrate is output as an electric signal from the reception amplification circuit (5).

[0005] The propagation time until the ultrasonic wave transmitted from the upstream ultrasonic oscillator (2) in the forward direction with respect to the flow is received by the downstream ultrasonic oscillator (3); The difference between the ultrasonic wave transmitted from the downstream ultrasonic oscillator (3) in the opposite direction to the flow and the propagation time until the ultrasonic wave is received by the upstream ultrasonic oscillator (2) is related to the flow velocity. Therefore, the flow velocity of the fluid is measured by calculating the propagation time difference. In the figure, reference numeral (6) denotes a switching circuit for switching the connection between each of the ultrasonic transducers (2) and (3) and the pulse generating circuit (4) and the receiving amplifier circuit (5). After connecting the ultrasonic transducer (2) on the upstream side and the ultrasonic transducer (3) on the downstream side and the receiving amplifier circuit (5) to measure the propagation time from the upstream side to the downstream side, the switching is performed. By the operation of the circuit (6), the pulse generating circuit (4) and the downstream ultrasonic vibrator (3) are switched so that the upstream ultrasonic vibrator (2) and the receiving amplifier circuit (5) are connected. Thus, the propagation time from the downstream side to the upstream side is measured.

In such an ultrasonic flow velocity measuring apparatus, as shown in FIG. 4, an inner surface of a flow velocity measuring section (111) has an ellipse whose focal point is a center point between the ultrasonic vibrators (2) and (3). What is formed on the inner surface is known. According to this, the ultrasonic wave transmitted from one of the ultrasonic vibrators (2) and (3) is reflected only once on the inner surface of the ellipse of the flow velocity measuring unit (111), and then the other ultrasonic vibrator (3) Received in (2). Therefore, in addition to the straight ultrasonic wave transmitted from one of the ultrasonic transducers (2) and (3) in parallel with the flow direction of the fluid, the reflected ultrasonic wave reflected only once on the inner surface of the ellipse of the flow velocity measuring unit (111). Is received by the opposed ultrasonic transducers (3) and (2).

[0007]

However, if the flow velocity measuring section is structured as described above, the flow velocity measuring section (11
1) The fluid inlet (111a) at both ends and the fluid outlet (11
Since the aperture of 1b) is inevitably reduced, a part of the ultrasonic waves transmitted from the ultrasonic transducers (2) and (3) does not enter the flow velocity measuring section (111), and the gain of the received wave is reduced. There is a problem that it is difficult to increase the size. Further, since the diameters of the fluid inlet (111a) and the fluid outlet (111b) of the flow velocity measuring unit (111) are small, there is also a problem that the fluid may not flow smoothly in the flow velocity measuring unit (111). Was.

The present invention has been made in view of the above-mentioned problems, and can increase the gain of a received wave efficiently, can realize a smooth flow of fluid, and can therefore achieve a sufficient flow. It is an object of the present invention to provide an ultrasonic flow velocity measuring device capable of ensuring measurement accuracy.

[0009]

An object of the present invention is to provide an ultrasonic transducer arranged upstream and downstream of a measurement fluid flowing through a flow velocity measuring unit, and generating and transmitting ultrasonic waves from each ultrasonic transducer. While receiving the transmitted ultrasonic waves, the ultrasonic flow velocity measuring device is configured to measure the flow velocity of the measurement fluid based on the difference in the propagation time of the ultrasonic waves, the flow velocity measuring unit, All or a part of the inner surface is formed symmetrically with respect to the center point between the ultrasonic transducers, and the inner surfaces having such a symmetrical relationship constitute a part of an elliptical surface whose focal point is the peripheral portion of each ultrasonic transducer. The problem is solved by an ultrasonic flow velocity measuring device. In the present invention, the peripheral portion of the ultrasonic vibrator means all parts except the center point on the front of the ultrasonic vibrator.

According to this, the diameters of the fluid inlet and the fluid outlet are increased, and most of the ultrasonic waves transmitted from the ultrasonic vibrator can enter the flow velocity measuring section. In addition, due to the structure of the flow velocity measurement unit as described above, the ultrasonic wave that has entered the flow velocity measurement unit is reflected by one inner ellipse of the flow velocity measurement unit, and is reliably received by the ultrasonic transducer. Can be efficiently increased.

In addition, since the diameter of the fluid inlet increases, the fluid can easily flow into the flow velocity measuring section, and since the diameter of the fluid outlet increases, the fluid can easily flow out of the flow velocity measuring section. A smooth flow can be realized, and sufficient measurement accuracy can be ensured in combination with the above-described efficient increase in the gain of the received wave.

[0012]

Next, an ultrasonic flow velocity measuring apparatus according to an embodiment of the present invention will be described with reference to FIGS.

In FIG. 1, (1) is a U-shaped ultrasonic flow velocity measuring tube which is open upward and through which gas flows, and a lower horizontal portion of the ultrasonic measuring tube (1) is provided with a flow velocity measuring section (11). It has been done.

(2) and (3) are cylindrical ultrasonic vibrators for transmitting and transmitting ultrasonic waves, facing the inner wall of the ultrasonic flow velocity measuring tube (1) on the center line of the flow velocity measuring section (11). It is arranged. (4) is a generation circuit for generating a pulse for driving the ultrasonic transducers (2) and (3), and (5) is a reception amplifier for outputting a reception wave received by the ultrasonic transducers (2) and (3). A circuit (6) is a switching circuit for switching the connection between the ultrasonic vibrators (2) and (3), the drive pulse generating circuit (4) and the receiving amplifier circuit (5), which are the same as those shown in FIG. .

The flow velocity measuring section (11) has an upstream end as a fluid inlet (11a), a downstream end as a fluid outlet, and fluid flows from the fluid inlet (11a). After flowing into the flow velocity measuring section (11), the fluid outlet (11
b).

The flow velocity measuring section (11) has an inner surface formed symmetrically with respect to a center point O of each of the ultrasonic vibrators (2) and (3) over the entire circumference, and the inner surfaces having a symmetrical relationship therebetween. Specifically, each of them constitutes a part of an elliptical surface whose focal point is the closest point of the peripheral portion of each of the ultrasonic transducers (2) and (3).
In FIG. 1, the inner surfaces (EG) and (HJ) on both sides are symmetric with respect to a center point O between the ultrasonic transducers (2) and (3).
In addition, it constitutes a part of the inner surface of the ellipse whose focal point is the closest points (A) and (D) of the peripheral portions of the ultrasonic transducers (2) and (3).
On the other hand, the inner surfaces (FH) and (GI) on both sides are also symmetric with respect to the center point O between the ultrasonic transducers (2) and (3), and the peripheral ends of the ultrasonic transducers (2) and (3). Point of closest approach (B)
The same ellipse inner surface having the focus at (C) is formed. further,
In FIG. 2, the inner surface (E ′ that is symmetrical on both sides)
G ′) and (H′J ′), and (F′H ′) and (G′I ′), and the other inner surfaces on both sides have the same structure.

By forming the flow velocity measuring section (11) in the above-described structure, the fluid inlet (11) is formed.
a) and the diameter of the fluid outlet (11b) are increased, so that most of the ultrasonic waves transmitted from the ultrasonic vibrator can enter the flow velocity measuring unit (11). In addition, since the ultrasonic wave that has entered the flow velocity measuring unit (11) is reflected by one inner surface of the ellipse of the flow velocity measuring unit (11), it is reliably received by the opposed ultrasonic transducers (3) and (2). The gain of the received wave can be efficiently increased.

Further, the diameter of the fluid inlet (11a) is increased, so that the fluid easily flows into the flow velocity measuring section (11), and the diameter of the fluid outlet (11b) is increased, so that the fluid is measured for the flow velocity. It is easy to flow out of the part (11), and a smooth flow of the fluid can be realized.
Sufficient measurement accuracy can be ensured in combination with the above-described efficient increase in the gain of the received wave.

Next, the principle of ultrasonic flow velocity measurement using the ultrasonic flow velocity measuring device shown in FIG. 1 will be described.

First, as shown by a white arrow in FIG. 1, when a fluid such as a gas flows into the ultrasonic flow velocity measuring tube (1), the fluid flows from a fluid inlet (11a) of the flow velocity measuring section (11). The fluid flows into the flow velocity measuring section (11), flows in the flow velocity measuring section (11) along the longitudinal direction, and flows out from the fluid outlet (11b) of the flow velocity measuring section (11). At this time, as described above,
The larger diameter of the fluid inlet (11a) facilitates the flow of the fluid into the flow velocity measuring unit (11), and the larger diameter of the fluid outlet (11b) allows the fluid to flow from the flow velocity measuring unit (11). The fluid easily flows out, and a smooth flow of the fluid can be realized.

When a drive pulse for driving the upstream ultrasonic vibrator (2) is generated from the drive pulse generating circuit (4), the ultrasonic vibrator (2) is driven by the drive pulse to vibrate. Then, an ultrasonic wave is transmitted according to the vibration of the ultrasonic vibrator (2).

Most of the ultrasonic waves transmitted from the ultrasonic transducer (2) enter the flow velocity measuring section (11) from the fluid inlet (11a) having a large diameter, and flow therethrough. After being reflected by the inner surface of one ellipse, it is reliably received by the opposed ultrasonic transducers (3) and (2).

Next, the switching circuit (6) connects the pulse generating circuit (4) to the downstream ultrasonic vibrator (3), and connects the upstream ultrasonic vibrator (2) to the receiving amplifier circuit (5). Then, the ultrasonic wave transmitted from the ultrasonic transducer (3) is reliably received by the opposed ultrasonic transducer (2) in the same manner as described above.

Thus, the ultrasonic wave obtained above and transmitted from the upstream ultrasonic oscillator (2) in the forward direction with respect to the flow direction is received by the downstream ultrasonic oscillator (3). Between the propagation time until the ultrasonic wave transmitted from the downstream ultrasonic transducer (3) and the ultrasonic wave transmitted in the opposite direction to the flow is received by the ultrasonic transducer (2) on the upstream side. Is derived and the flow velocity of the fluid is measured.

In this embodiment, the flow velocity measuring section (11) has its inner surface formed symmetrically with respect to the center point O of each of the ultrasonic transducers (2) and (3) over the entire circumference. The inner surfaces that are in a symmetric relationship are each ultrasonic transducer (2)
Although a part of the elliptical surface having the focal point at the closest point of the peripheral edge in (3) is configured, the structure described above may be formed on a part of the inner surface.

The focal point of the inner surface of the ellipse is set to the closest point (A) (A ') of the peripheral portion of the ultrasonic transducers (2) and (3).
(B) is set to (B '), but as described above,
As shown in FIG. 3, the focal point of the inner surface of the ellipse is a point (A) at a distance equal to or more than 1/2 times the diameter R from the center point (Z) of the ultrasonic transducers (2) and (3) so that the effect is remarkable. '')
It is desirable to set (B ''). In addition, as long as the above-described functions and effects are achieved, a point that is less than half the diameter R from the center point (Z) of the ultrasonic vibrators (2) and (3) (however, the ultrasonic vibrator (2 ) (Excluding the center point of (3))
(A ''') and (B''').

Although the ultrasonic transducer has a cylindrical shape, it may have a rectangular shape or another shape.

[0028]

According to the present invention, the diameters of the fluid inlet and the fluid outlet are increased, so that most of the ultrasonic waves transmitted from the ultrasonic transducer can enter the flow velocity measuring section. In addition, due to the structure of the flow velocity measuring unit as described above, the ultrasonic wave that has entered the flow velocity measuring unit is reflected by one inner ellipse of the flow velocity measuring unit, and is reliably received by the opposed ultrasonic transducer. The wave gain can be increased efficiently.

Further, since the diameter of the fluid inlet is large, the fluid can easily flow into the flow velocity measuring section, and since the diameter of the fluid outlet is large, the fluid can easily flow out of the flow velocity measuring section. A smooth flow can be realized, and sufficient measurement accuracy can be ensured in combination with the above-described efficient increase in the gain of the received wave.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an ultrasonic flow velocity measuring device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the ultrasonic flow velocity measuring device of FIG. 1 taken along the line II.

FIG. 3 is a front view of the ultrasonic transducer.

FIG. 4 is a schematic configuration diagram of a conventional ultrasonic flow velocity measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ultrasonic flow velocity measuring tube 2, 3 ... Ultrasonic vibrator 11 ... Flow velocity measuring part

 ──────────────────────────────────────────────────の Continuing on the front page (72) Eiji Nakamura, Inventor, Kansai Gas Meter Co., Ltd., 10 at Kashida-ji, Kida-cho, Shimogyo-ku, Kyoto (72) Inventor Toshifumi Matsuda 10 Kansai Gas-meter, Kagi-daka, Shimoda-ku, Kyoto, Japan Incorporated (72) Inventor Tetsuya Yasuda 10 Kida-machi, Chudo-ji, Shimogyo-ku, Kyoto F-term (reference) 2F035 DA19 DA22

Claims (1)

[Claims] An ultrasonic transducer is arranged on each of an upstream side and a downstream side of a measurement fluid flowing through a flow velocity measuring unit, and the ultrasonic transducers generate and transmit ultrasonic waves to each other, and transmit the transmitted ultrasonic waves. Mutually, and the ultrasonic flow velocity measuring device that is configured to measure the flow velocity of the measurement fluid based on the difference in the propagation time of the ultrasonic wave, the flow velocity measurement unit, all or a part of the inner surface, each An ultrasonic flow velocity characterized in that the inner surfaces are formed symmetrically with respect to a center point between the ultrasonic transducers, and the inner surfaces having the symmetrical relationship form a part of an elliptical surface whose focal point is the peripheral portion of each ultrasonic transducer. measuring device.