JPH0610255Y2 - Ultrasonic transceiver - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic wave transmitter / receiver, and more particularly to an ultrasonic wave transmitter / receiver used in an ultrasonic flow meter for measuring a flow rate of a fluid using ultrasonic waves.

2. Description of the Related Art FIGS. 6 (A) and 6 (B) show a transmitter 1 and a receiver 2 of a conventional ultrasonic transceiver, respectively. As can be seen from both figures, the shapes of the transmitting unit 1 and the receiving unit 2 may be considered to be almost the same. In the figure, 1a and 2a are ultrasonic transducers and 1
Reference numerals b and 2b are diaphragms, 1c and 1d are terminals to which an ultrasonic wave signal is supplied from an ultrasonic oscillator, and 2c and 2d are terminals for supplying a received ultrasonic wave signal to a detector or the like in a subsequent stage.

The ultrasonic transmission / reception device including the transmission unit 1 and the reception unit 2 is used for a flow meter as shown in FIG. 7, for example. As shown in the figure, the transmitting unit 1 is disposed on the wall surface of the pipe line 3, and the receiving unit 2 is provided on the wall surface of the pipe line 3 facing the transmitting unit 1.
Is provided.

FIG. 8 is a sectional view taken along the broken line in FIG. 7, and is a schematic diagram for explaining the operation of the flowmeter. When the fluid flows from the upper side to the lower side in the figure, well-known Karman vortices are alternately generated in the left and right downstream of the vortex generator 4 provided in the center of the pipe line 3. It is known that the number of generated Karman vortices is proportional to the flow velocity of the fluid.

When an ultrasonic excitation signal is supplied from the ultrasonic signal generator (not shown) from the terminals 1c and 1d to the transmitter, the ultrasonic vibrator 1a vibrates, and this vibration is transmitted into the fluid by the diaphragm 1b. It The ultrasonic wave that has propagated through the fluid and has reached the receiving portion 2 vibrates the diaphragm 2b of the receiving portion 2 and transmits it to the ultrasonic transducer 2a, which is further detected as an ultrasonic signal at the subsequent stage. Output to a container or the like (not shown).

If the ultrasonic wave encounters the Karman vortex while propagating in the fluid, the ultrasonic wave undergoes a change in its phase. Therefore, the number of generated Karman vortices can be known by detecting the change in the phase with a detector or the like from the output ultrasonic signal of the receiving unit 2 that receives the ultrasonic wave, and the flow rate of the fluid can be obtained from this.

Problems to be Solved by the Invention However, since the diaphragms 1b and 2b of the transmitting unit 1 and the receiving unit 2 of the conventional ultrasonic transmitter / receiver are both flat, the ultrasonic waves transmitted from the diaphragm 1b into the fluid are extremely large. Among the sound waves, the wave reflected by the diaphragm 2b of the receiver 2 returns to the transmitter 1 again and interferes with the ultrasonic wave transmitted by the diaphragm 1b. This interference causes a standing wave in which the antinode and the node are repeated every λ / 4 (λ is the wavelength of the ultrasonic wave in the fluid), and the reception level depends on whether the position of the receiver is the antinode or the node. to differ greatly.

FIG. 9 shows the frequency spectrum of the reception level for each frequency when ultrasonic waves swept in the vicinity of 1 megahertz (MHz) are received in a pipe with a diameter of 50 millimeters (mm), and about every 14 KHz. The appearing peak portion indicates that the transmitted wave and the reflected wave strengthen each other (antinode portion), and the valley portion between the peaks weakens each other (node portion).

Since the sound velocity in the fluid (wavelength of the ultrasonic wave in the fluid) changes when the temperature changes, the reception level of the ultrasonic wave reflected in a certain distance section is shown in FIG. 9 even when the temperature changes. It shows the same change as when the frequency changes as shown.

From the point of view of detecting Karman vortices or other physical phenomena in the fluid, there is sufficient ultrasonic wave reception level at the peak position, but it is necessary for measurement at the valley between the peaks. The reception level is not reached. When ambient conditions such as temperature change, the speed of sound in the fluid changes. Therefore, in the conventional device of FIG. 6, even if the same frequency is used, the transmitted wave and the received wave weaken each other from the initial state in which they strengthen each other. Since the state changes, the reception level becomes lower than the level required for measurement, and there is a problem that measurement cannot be performed.

The present invention has been made in view of the above points, and an object of the present invention is to provide an ultrasonic transmitter / receiver device which can be favorably used for various measurements even when temperature changes or the like.

Means for Solving the Problems The present invention is directed to vibrating first vibrating plates, which are provided on the wall surface of a conduit through which a fluid passes and are opposed to each other with the fluid interposed therebetween, and vibrate the fluid. An ultrasonic wave transmitter that transmits an ultrasonic wave inside, and an ultrasonic wave that propagates in the fluid causes a second diaphragm to vibrate, and a vibrator that is in contact with the second diaphragm receives the ultrasonic wave. In the ultrasonic transmitting / receiving device including the ultrasonic receiver, at least one surface shape of the first and second diaphragms is a curved surface or a shape including a curved surface.

The ultrasonic waves transmitted into the fluid from the first vibrating plate of the action transmitting unit are transmitted in the normal direction of each point on the curved surface. When these transmitted waves travel substantially straight in the fluid and reach the receiver, a part of them is reflected by the second diaphragm having a curved surface. Since the reflection angle in this case is almost a finite angle, most of the ultrasonic wave reflected here is diffused in the fluid, and only a small amount of ultrasonic wave returns to the transmitter.

Since the ultrasonic wave reflected by the receiving unit and returned to the transmitting unit is also reflected by the first diaphragm on the curved surface like the reflection by the second diaphragm, the ultrasonic wave reflected here is reflected. Most of the sound waves are diffused and propagated in the fluid and hardly interfere with the ultrasonic waves that are directly transmitted from the transmission unit and reach the reception unit.

Also, in order to make only the surface shape of at least one of the first diaphragm and the second diaphragm a curved surface, instead of processing the vibrator of the ultrasonic transmitter and the ultrasonic receiver,
Not only can processing be performed easily, but since the diaphragm can be used as it is when changing to a vibrator according to the characteristics of the fluid to be measured, it is possible to easily cope with changes in the vibrator.

First Embodiment FIGS. 1 (A) and 1 (B) are cross-sectional views of a transmitter 5 and a receiver 6 of an ultrasonic transceiver according to the first embodiment of the present invention. In the figure, the same components as those in FIG. 6 are designated by the same reference numerals, and the description thereof will be omitted.

The transmitting unit 5 and the receiving unit 6 of this embodiment have the diaphragms 5a and 6a.
This is different from the conventional ultrasonic transmitter / receiver of FIG. 6 in that only the surface shape of a is spherical. In this embodiment, an ultrasonic transmitter / receiver device is attached to the conduit 3 as shown in FIG. 7 as in the conventional case, and is applied to a fluid flow meter.

The traveling direction of the ultrasonic wave transmitted into the fluid from the diaphragm 5a of the transmitter 5 is substantially the normal direction of each point on the spherical surface where the ultrasonic wave is transmitted. Therefore, of these transmitted waves, the receiving unit 6
The amount of ultrasonic waves reaching the position will be somewhat reduced, but it will not hinder the measurement of the flow rate.

The ultrasonic waves that have propagated through the fluid and undergo a phase change due to the Karman vortices and have reached the receiver 6 are received by vibrating the vibrating plate 6a, and the flow rate of the fluid is measured by detecting the number of Karman vortices generated. However, a part of it becomes a reflected wave and propagates again in the fluid. FIG. 2 schematically shows a state of ultrasonic waves reflected by the diaphragm 6a of the receiving unit 6, and ultrasonic waves other than the ultrasonic waves reflected by the spherical tip portion r are finite reflections. Reflected at the corners.
Therefore, most of the ultrasonic waves reflected by the vibrating plate 6a are diffused in the fluid, and few of the reflected waves return to the transmission unit 5 again.

Even when the reflected wave reaching the transmitting unit 5 is further reflected by the diaphragm 5a, most of them have a finite reflection angle as in the case of FIG. Very few interfere with the ultrasonic waves transmitted from.

As a result, as shown in the frequency spectrum of the reception level by the receiving unit 6 in FIG. 3, a large number of peaks as in FIG. 9 do not appear, and the center frequency (here, 1
A considerable reception level can be obtained over a relatively wide range around (MHz). This means that the reception level does not change significantly even when the temperature of the fluid changes, and the flow rate can be measured well even when the external conditions such as temperature change.

Further, in the present invention, the transducers 1a of the transmitter 5 and the receiver 6 are
2a is not processed, and only the surface shapes of the vibration plates 5a and 6a are curved, so that the processing can be performed easily and the vibrator 1 according to the characteristics of the fluid to be measured is used.
Since the vibrating plates 5a and 6a can be used as they are when changing to a or 2a, it is possible to easily deal with changing the vibrators 1a and 2a.

FIG. 4 shows a sectional view of a second embodiment of the present invention. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. The diaphragm 7a of the transmitter 7 shown in the figure is an example of a truncated cone shape. Although illustration of the receiver is omitted, the diaphragm of the receiver has the same shape.

FIG. 5 shows a sectional view of a third embodiment of the present invention. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. The diaphragm 8a of the transmitter 8 shown in the figure is different from the first and second embodiments in that it has a conical shape. The receiving unit has the same shape, and therefore the illustration is omitted.

By using the diaphragms 7a and 8a as shown in FIGS. 4 and 5, the diaphragms 5a and 6a having the shapes shown in FIG.
It is possible to achieve the same effect as the ultrasonic transmitting / receiving device having the above.

In the above embodiment, the ultrasonic transmitter / receiver is applied to detect the number of Karman vortices generated and to measure the flow rate of the fluid. However, in addition to this case, the transmission characteristics of the ultrasonic waves in the fluid are also shown. Needless to say, it can be applied to various cases in which measurement is performed by detecting a change in

Advantageous Effect of the Invention As described above, according to the present invention, only the surface shape of at least one of the first and second diaphragms in the transmitter and the receiver of the ultrasonic transmitter / receiver has a curved surface or a shape including a curved surface. By using a simple method, it is possible to prevent the interference between the transmitted wave and the reflected wave, and the reception level does not change significantly even if external conditions such as temperature change. When applied to meters, etc., good measurement is always possible. Further, the vibrators of the ultrasonic transmitter and the ultrasonic receiver are not processed, but the processing is performed so that only the surface shape of at least one of the first diaphragm and the second diaphragm is a curved surface. Not only can it be done easily,
Since the diaphragm can be used as it is when changing to a vibrator according to the characteristics of the fluid to be measured, it has a feature that it can easily cope with changes in the vibrator.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of the present invention, FIG. 2 is a schematic view showing how ultrasonic waves are reflected, and FIG. 3 is a view showing a frequency spectrum of a reception level of this embodiment, FIG. FIG. 5 is a sectional view of the second and third embodiments of the present invention, FIG. 6 is a sectional view of a conventional device, and FIGS. 7 and 8 are explanatory diagrams when the conventional device is applied to a flow meter. FIG. 9 is a diagram showing the frequency spectrum of the reception level of the conventional device. 5, 7, 8 ... Transmitter, 5a, 6a, 7a, 8a ... Diaphragm, 6 ... Receiver.

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Claims (4)

[Scope of utility model registration request] 1. An ultrasonic wave is transmitted into a fluid passage by vibrating first vibrating plates which are provided opposite to each other on the wall surface of the fluid passage through the fluid and are in contact with the vibrator. From an ultrasonic transmitter and an ultrasonic receiver in which a vibrator contacting the second diaphragm receives the ultrasonic wave by vibrating the second diaphragm by the ultrasonic waves propagating in the fluid. The ultrasonic transmission / reception device according to claim 1, wherein at least one surface shape of the first and second diaphragms is a curved surface or a shape including a curved surface. 2. The ultrasonic transceiver according to claim 1, wherein the surface shape of at least one of the first and second diaphragms is a part of a spherical surface. 3. The ultrasonic transceiver according to claim 1, wherein at least one of the first and second diaphragms has a conical surface shape. 4. The ultrasonic transceiver according to claim 1, wherein at least one of the first and second diaphragms has a conical trapezoidal surface shape.