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DESCRIPTION JPH08251696

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DESCRIPTION JPH08251696
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the
improvement of the structure of an ultrasonic transducer used in an ultrasonic distance
measuring device.
[0002]
2. Description of the Related Art As shown in FIG. 4 (a), for example, an ultrasonic distance
measuring apparatus has an ultrasonic transducer 1 attached to a structure 2, and an ultrasonic
pulse is directed toward an object 3 at a constant cycle. It emits an echo, receives an echo,
measures an elapsed time t from the time when an ultrasonic pulse is emitted from the ultrasonic
transducer 1 to the object 3 and the time when the echo is received. The distance x between the
transducer 1 and the device under test 3 is obtained by performing an operation of x = t × C / 2.
C is the velocity of sound.
[0003]
By the way, not all echoes reflected on the object to be measured 3 are directly received by the
ultrasonic transducer 1, but as shown in (b) of FIG. There are also devices that are received by
the ultrasonic transducer 1 after being reflected back and forth between the structure 2 and the
object 3 to be measured. Therefore, as shown in FIG. 5, for example, in addition to the first echo
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received directly, the ultrasonic transducer 1 reflects back and forth between the structure 2 and
the object 3 for one transmission. After that, a plurality of echoes, such as the second echo, the
third echo,..., The n-th echo, which are received, are received. Usually, the first echo shows the
maximum amplitude, and the echo received thereafter decreases its amplitude in order.
[0004]
By the way, in the distance measurement by an ultrasonic distance measuring device, the
distance to a measuring object may change. For example, it is the case of the measurement of the
wave height on the sea surface, and the measurement of the distance to the back wall of a
building or a garage when the vehicle moves backward. In such a case, depending on the
relationship between the speed of distance change and the ultrasonic pulse transmission period,
the second echo due to the transmission one period before may be received after the
transmission of the current period. In this case, there is a possibility that so-called erroneous
measurement may occur in which the second echo of the previous cycle is misidentified as the
first echo of the current cycle to perform distance measurement.
[0005]
Therefore, conventionally, in the case of, for example, a wave height meter, as shown in FIG. 6, a
gate (window) is set so that the first echo can be acquired with high probability. That is, the
reception time tx of the maximum amplitude of the echo received within the previous
transmission cycle is taken out ((a) of FIG. 6), the gradient of the waveform is limited by the
installation location of the wave height meter, and Set the theoretical range D in which the sea
level can be taken around the time tx in this transmission, using the fact that the amount by
which the sea level changes in the transmission cycle is theoretically limited. ((B) in FIG. 6),
generates a gate signal having such a range D as the gate width ((c) in FIG. 6), and the echo
present in this gate width among echoes for this transmission is It takes in as a measurement
echo.
[0006]
That is, although the gate to be set has a fixed width, the position of the gate in the current
transmission is changed according to the echo data acquired at the previous transmission so that
the change of the position of the object to be measured can be automatically followed. There is.
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In many cases, since the echo showing the maximum amplitude is the first echo, the distance
data acquired in this way is reliable.
[0007]
Specifically, for example, as shown in (a) of FIG. 7, the second echo (b) of the first transmission is
generated from the first echo (b) of the second transmission between the second transmission
and the third transmission. When the signal is received earlier, as shown in (b) of FIG. 7, since the
gate is set to the timing of receiving the first echo (b) by the second transmission, the first echo
(b Only) can be captured.
[0008]
As a result, as shown in FIG. 8, for example, the wave height meter reproduces the shape of the
wave by connecting each point of the height of the sea surface determined by the distance
measurement (the value of the jump calculated for each measurement repetition cycle) It will be
able to output.
Although the above is description by a wave height meter, it is the same also in the case of
guidance of a vehicle.
[0009]
However, in an actual measurement environment, sometimes the amplitude of the second echo
may be larger than that of the first echo, in which case the time at which the second echo is
received is centered. In this case, a gate is generated, and erroneous measurement is performed.
Also, the position of the object to be measured with position fluctuation is changed in various
manners, such as the position fluctuation becomes severe. Therefore, as described above, under
the method of generating a fixed width gate for current transmission using the echo reception
time of the maximum amplitude acquired at the previous transmission, for example, as shown in
(c) of FIG. It also occurs when, during the second transmission, the second echo (c) of the first
transmission and the first echo (d) of the second transmission are close together and within the
gate width.
[0010]
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In such a case, both echo data of the data relating to the second echo (c) in the first transmission
and the data relating to the first echo (d) in the second transmission become valid data. That is,
there is a problem that an erroneous measurement is performed and, for example, an erroneous
measurement result as shown by a broken line in FIG. 9 is output.
[0011]
An object of the present invention is, in view of the problems of the prior art described above,
that the structure of the ultrasonic transducer is configured such that echoes below the second
echo causing erroneous measurement are not received by the transducer An object of the present
invention is to provide an ultrasonic transducer for a distance measurement device which does
not cause erroneous measurement.
[0012]
SUMMARY OF THE INVENTION In order to achieve the above object, the present invention has
the following means configuration.
That is, the ultrasonic transducer according to the present invention is characterized in that the
surface of the structure around the transmission / reception wavefront of the transducer of the
ultrasonic transducer is inclined rearward of the transmission / reception wavefront with respect
to the transmission / reception wavefront. It is an acoustic transducer.
[0013]
Further, the mounting member of the present invention is characterized in that the transmission
/ reception wavefront of the ultrasonic transducer is exposed, and the periphery of the
transmission / reception wavefront is inclined backward with respect to the transmission /
reception wavefront. Mounting member.
[0014]
Furthermore, the cover of the present invention is characterized in that the transmission /
reception wavefront of the ultrasonic transducer is exposed, and the circumference of the
transmission wavefront is covered with a surface inclined rearward with respect to the
transmission / reception wavefront. It is a cover of
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[0015]
The operation of the present invention will be described below.
In the ultrasonic transducer according to the present invention, since the structure around the
transmission / reception wavefront is inclined backward with respect to the transmission /
reception wavefront, the sound wave transmitted from the transducer is reflected by the distance
measurement object and returned. Among the sound waves that have arrived, the sound waves
other than the sound waves that hit the transmission / reception wavefront are reflected on the
inclined surface around the transmission / reception wavefront, but the direction is reflected in
an oblique direction and does not return to the transducer again.
[0016]
In addition, since the sound wave that has hit the transmission / reception wavefront is
converted into an electric signal by the ultrasonic transducer, it is not reflected so as to cause a
problem in practical use.
Therefore, the repetition of the sound wave between the transducer and the distance
measurement object is eliminated and the occurrence of the second echo and the third echo in
addition to the first echo is prevented.
[0017]
Such a function is a mounting member in which the transmitting and receiving surface of the
ultrasonic transducer is exposed and its periphery is inclined backward with respect to the
transmitting and receiving wavefront even if the ultrasonic transducer itself does not have an
inclined surface. Can also be performed by attaching an ultrasonic transducer.
[0018]
Furthermore, as in the cover of the present invention, the transmission / reception wave front of
the ultrasonic transducer is exposed, and the circumference of the transmission / reception wave
front is covered with a cover having a surface inclined backward with respect to the transmission
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/ reception wave front. Be
[0019]
Embodiments of the ultrasonic transducer according to the present invention will be described
below with reference to the drawings.
FIG. 1 is a view showing how sound waves are reflected between an ultrasonic transducer 4 and
a distance measurement object 8 according to the present invention.
The sound wave transmitted from the transmission / reception wavefront 5 of the ultrasonic
transducer 4 is reflected by the distance measurement object 8 and returns to the ultrasonic
transducer 4. Among the returned sound waves, the sound waves that hit the transmission /
reception wavefront 5 are converted into electric signals and there is no reflection that would
cause a problem in practical use.
[0020]
On the other hand, since the sound wave striking the inclined surface 6 is reflected in a direction
different from the direction reflected from the distance measurement object 8, the sound wave is
also reflected on the distance measurement object 8 and the sound wave Can not reach the
transmitted / received wave surface 5. Therefore, the second echo, the third echo, etc. do not
occur. By this, the erroneous measurement caused by the second echo and the third echo as in
the prior art can be completely eliminated.
[0021]
Although FIG. 1 described above is an example in which the transducer itself has an inclined
surface, FIG. 2 shows that the ultrasonic transducer 9 itself does not have an inclined surface, but
the ultrasonic transducer 9 has an inclined surface. The mounting member 11 to which is
mounted has the inclined surface 6. The mounting member 11 to which the ultrasonic transducer
9 is attached is attached to the structure 2 such that the transmission / reception wavefront 10 is
directed to the distance measurement object.
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[0022]
In FIG. 3, as in the case of FIG. 2, the ultrasonic transducer 9 itself does not have an inclined
surface, but a cover having an inclined surface that is inclined backward with respect to the
transmission and reception wavefront 10 around the transmission and reception wavefront 10. It
is a figure which shows the case where it covers by 12. FIG. Also in the cases of FIG. 2 and FIG. 3,
the second echo, the third echo, etc. are not generated by the same action as in the case of FIG.
[0023]
As described above, according to the present invention, since the periphery of the transmission /
reception wavefront of the ultrasonic transducer is formed by a surface inclined backward with
respect to the transmission / reception wavefront, echoes other than the first echo There is an
advantage that no erroneous measurement due to the second echo, the third echo, etc. occurs.
[0024]
Brief description of the drawings
[0025]
1 is a diagram showing the reflection of sound waves between the ultrasonic transducer of the
present invention and the distance measurement object.
[0026]
2 is a diagram of the ultrasonic transducer attached to the mounting member having the inclined
surface of the present invention.
[0027]
FIG. 3 is a view showing a state in which the cover of the present invention is covered by the
ultrasonic transducer attached to the construction.
[0028]
4 is a general operation explanatory view of the ultrasonic distance measuring apparatus, (a) is
an explanatory view of the principle of distance measurement, (b) is an explanatory view of the
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generation of each echo after the second echo.
[0029]
5 is an explanatory view of a plurality of echoes that the ultrasonic transducer emits and receives
one ultrasonic pulse.
[0030]
6 is an explanatory view of a setting method of the gate.
[0031]
7 is an operation explanatory view of the conventional ultrasonic distance measuring device.
[0032]
<Figure 8> It is the figure which shows the measurement result (the change of sea level) of the
wave height meter as a conventional ultrasonic distance measurement device.
[0033]
FIG. 9 is a view showing the measurement result (change of sea level) in the case where the
change of the sea surface is severe and the second echo etc. is erroneously taken in the wave
height meter as the conventional ultrasonic distance measuring device.
[0034]
Explanation of sign
[0035]
Reference Signs List 1 ultrasonic transducer 2 structure 3 measured object 4 ultrasonic
transducer 5 transmission / reception wavefront 6 inclined surface 7 vibrator 8 distance
measurement object 9 ultrasonic transducer 10 transmission / reception wavefront 11 mounting
member 12 cover
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