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JPH10290495

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DESCRIPTION JPH10290495
[0001]
The present invention relates to a method and apparatus for transmitting a sound wave signal
used for a sensor or the like for obtaining various information such as the presence or absence,
position or velocity of an object by sound wave, and a sound wave signal reception method. The
present invention relates to an acoustic signal transmission / reception processing system using
these devices.
[0002]
2. Description of the Related Art Conventionally, various types of sensors have been proposed in
which sound waves are emitted into various propagation media such as gas, liquid, solid and the
like, and information on the object to be measured is obtained by measuring the propagation
state. (See, for example, JP-A-7-218477, JP-A-4-313999, JP-A-4-313998, JP-A-5-49649, JP-A-2269914, etc.).
[0003]
For example, the sound wave is transmitted to the object to be measured, the reflected wave from
the object to be measured is received, and the delay time from the start of the transmission to the
start of the reception is measured. A sensor that measures the distance to the object to be
measured, a sensor that detects the presence or absence of an object by the presence or absence
of a reflected wave as this application, and that the sound wave transmitted into the solid is
reflected by scratches in the solid Using a flaw detector that nondestructively inspects a flaw in a
solid, and the fact that the transmission frequency and the reception frequency change according
to the movement speed of the object (Doppler effect), based on both frequencies A sensor that
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measures the moving speed of an object, or a sensor that measures the barrier of the internal
structure of the living body by receiving the reflected sound wave transmitted inside the living
body and reflected at the reflectance boundary, and detecting the state Etc.
[0004]
By the way, the sound wave signal in the above-mentioned various conventional sensors is
transmitted by the method of propagating vibration to a sound wave propagation medium by
mechanically resonating and vibrating the diaphragm with a piezoelectric element or the like.
In this case, the electric signal for driving the piezoelectric element or the like is only a signal for
giving a trigger for mechanical resonance, and transmission and reception of the sound wave
signal are performed with large amplitude generated by mechanical resonance. Therefore, the
essential part controlling transmission and reception of the sound wave signal is mechanical
control.
[0005]
Examples of the circuit configuration for transmitting the sound wave signal by the resonance
method as described above include one as shown in FIG. 14 or FIG.
In the configuration shown in FIG. 14, the transmission circuit 22 drives the transmission
element 20 based on the fixed frequency signal output from the oscillation circuit 24, and
transmits the sound wave signal into the propagation medium, and is reflected by the object.
Received reflected signal (sound wave signal) by the wave receiving element 21, converted into
an electric signal in the wave receiving circuit 23, and processed by the post-processing circuit
25 by various signal processing Etc. are required. Note that FIG. 15 shows that the wave
transmitting element and the wave receiving element are shared by one wave transmitting /
receiving element 26, and the switching circuit 27 is switched and connected to the wave
transmitting circuit 22 and the wave receiving circuit 23. It has become so.
[0006]
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FIG. 16 (a) shows the structure of a piezoelectric ultrasonic transducer that is conventionally
used frequently as a transmitting element or receiving element. The bottom of the bottomed
cylindrical aluminum case 30 is thin (thickness: about 0.65 [mm]), and a thin plate of
piezoelectric ceramic 31 (thickness: about 0.25 [mm]) is adhered It is fixed. A terminal 32 for
applying a voltage from the outside to the piezoelectric ceramic 31 is provided so as to protrude
from the substrate 33, and is connected to the piezoelectric ceramic 31 by a lead wire 34.
Further, reference numeral 35 denotes a holding member for holding the lead wire 34, and
reference numeral 36 denotes a member (cotton) for reducing the vibration inside the aluminum
case 30. The substrate 33 is disposed in the opening of the aluminum case 30, and the terminal
32 is sealed by the epoxy adhesive 37 in a state where the terminal 32 is protruded to the
outside of the aluminum case 30. When the voltage V is applied as shown in FIG. 6B, the
piezoelectric ceramic 31 vibrates in the lateral direction, and the vibration is converted to the
vibration in the longitudinal direction of the bottom of the aluminum case 30, and the sound
wave (super Sound waves are transmitted. The resonance frequency at this time is determined by
the frequency constant to be described later and the dimensions of the aluminum case 30 and
the like, and is generally about 40 [kHz].
[0007]
Other than this, there are also devices that vibrate a case or the like by distortion
(magnetostriction) by an applied magnetic field to emit a sound wave. In general, materials
frequently used for sound wave generation include ferrite or nickel which is a magnetostrictive
material, or piezoelectric ceramic (PZT = lead zirconate titanate etc) or a piezoelectric rubber
(PVDF = polyvinyl fluoride) which is an electrostrictive material. . However, since a large amount
of energy is required to forcibly vibrate the materials to generate sound waves, mechanical
resonance is used as described above to obtain a vibration amplitude amount in order to save the
supplied energy. It is. The vibration amplitude amount corresponds to the sound pressure of the
transmission sound wave, and greatly affects the output voltage at the time of reception.
[0008]
As described above, conventionally, a structure in which both the electrostrictive system and the
magnetostrictive system mechanically resonate is adopted. The frequency of the sound wave in
such a resonant system is determined by the fundamental standing wave which is determined
from its structural dimensions and the acoustic velocity inside the material. For example, in the
case of the ultrasonic transducer using the piezoelectric ceramic 31, since the frequency constant
is 1600 [mHz], if there is a length of 16 [mm], the vibration in the thickness direction of the
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piezoelectric ceramic 31 is It resonates at a resonance frequency of 100 kHz. The frequency
constant is a numerical value indicating the relationship between the size of the piezoelectric
ceramic 31 and the resonant frequency.
[0009]
Further, the energy required when utilizing resonance may be 1 / Q of energy when vibrating at
non-resonance (Q is a Q factor indicating resonance sharpness). That is, by adopting a
transmission method using resonance, it is possible to transmit a sound wave efficiently. The Q
factor varies depending on the material, but is about 1000 in the case of piezoelectric ceramic.
Also in the case of the magnetostrictive method, the material length is a half wavelength, and the
frequency that can be calculated from the sound velocity inside the material is the fundamental
frequency of resonance. In general, in addition to the electrostriction method and the
magnetostriction method, in the sound wave generator based on the above-mentioned resonance
method, it can be used simultaneously as a wave receiving element other than being used as a
wave transmitting element. This is because a voltage or current is generated in the material by
applying an external vibration equal to the mechanical resonance frequency.
[0010]
As described above, since sound waves are conventionally transmitted and received by the
resonance method, the frequency corresponding to the resonance frequency of the element until
stable resonance as shown in FIG. 17, for example, the period 25 corresponding to the resonance
frequency 40 [kHz] The pulse signal of [μs] is continuously applied to the element over a
plurality of cycles. This is due solely to the requirements of the transmitting element or receiving
element. Furthermore, in the case of transmission, even if the electric signal for transmission is
stopped or in the case of reception, even if the sound wave is stopped, the vibration due to
mechanical resonance remains (this is called "reverberation". It takes a considerable amount of
time to stop completely. Therefore, after transmitting a sound wave, after waiting for a
considerable time, the next operation such as signal processing is performed.
[0011]
By the way, in general, the Doppler effect refers to a phenomenon in which the frequency of the
sound wave reflected by the object moving to the observer is different from the frequency of the
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transmission sound wave. On the other hand, since transmission and reception of sound waves in
the above-described conventional example are performed by mechanical resonance, even if a
signal of a predetermined frequency is applied to the transmission element to transmit sound
waves, reflected sound waves reflected by the object In some cases, the receiving element can not
receive the reflected sound wave by shifting the frequency of (1) from the frequency of the
transmission sound wave. That is, although depending on the frequency shift amount of the
sound wave signal, the sound wave is received by the wave receiving element at a frequency
other than the resonance frequency, and the efficiency of converting the wave reception signal
into the electric signal is extremely reduced. Therefore, when the moving velocity of the object is
measured using the Doppler effect, the measurable velocity range is largely limited by the
resonant frequency of the wave receiving element, and the measurement accuracy is low.
[0012]
Also, in the conventional transmission and reception methods using mechanical resonance, for
example, even if an amplitude-modulated signal is applied to a transmission element, the
amplitude of the resonant vibration changes as the applied modulation signal. do not do.
Therefore, in the above-mentioned conventional resonance method, the sound wave signal
transmitted from the transmission element can not be controlled by the electric signal applied to
the transmission element. Therefore, there has been no idea itself of applying an analogmodulated signal to a transmitting element to transmit the signal, and receiving an acousticallymodulated sound wave with a receiving element.
[0013]
By the way, in order to make the directivity characteristics of the transmitting element and the
receiving element have desired characteristics, in the conventional resonance method, there has
been a method of changing the shapes of the transmitting wavefront and the receiving wavefront
of the transmitting element and the receiving element. It is not a practical way from having to
change the structure itself. Therefore, conventionally, as shown in FIG. 18, a horn 38 is disposed
in front of transmitting and receiving waves to obtain a desired directivity, and when the
directivity is changed, the shape conforms to the directivity. I was trying to replace it with a horn.
That is, as shown in FIG. 19, when the horn is not wired in front of the transmitting surface or
the receiving surface, the sound wave is spread in a wide space, so the spread of the sound wave
is suppressed by using the horn 38. The sound wave transmission direction can be concentrated
in the front direction.
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[0014]
By the way, in the case of the above-mentioned conventional resonance system, there are the
following problems. First, since only sound waves having a frequency substantially equal to the
resonance frequency determined in terms of structure can be transmitted and received, the
structure of the element itself must be changed to transmit and receive sound waves of other
frequencies. You must.
[0015]
Also, as shown in FIG. 17 (b), it takes about several ms for mechanical resonance to reach the
stable region, and even if the signal for sending the sound wave is stopped, As shown in (c) of the
figure, it takes about several ms until the sound wave is actually stopped due to the
reverberation, and so on, the electric signal giving the transmission element the timing of the
transmission start and end of the sound wave. In some cases, it can not be controlled in the order
of μs. In addition, in the case of the system configuration which has a transmitting element and
a receiving element independently, it is necessary to make the resonant frequency of each
element correspond. For example, it is necessary to measure the resonance frequency of a single
element to adjust the physical structure 100%, which causes an increase in the cost of parts.
Furthermore, the temperature and humidity change the dimensions including the element, which
affects the resonance frequency, and the change of the resonance frequency changes the size of
the output of the element. And since it is a resonance system, the amount of output change with
respect to environmental change, ie, frequency change, is very large.
[0016]
Furthermore, since only the resonant frequency at which the frequencies of the transmitted and
received sound waves are determined by the structure, if sound waves of the same frequency are
generated by another sound wave generator, whether sound waves from the own device or sound
waves from other devices A great deal of effort is required to distinguish them, and various
devices have been tried as described in, for example, Japanese Patent Application Laid-Open Nos.
60-91281 and 58-122482. Measures have not been made.
[0017]
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On the other hand, it is conceivable to avoid the problems of the above-mentioned resonance
method by driving the magnetostrictive material, the piezoelectric material, etc. used in the
conventional resonance method in a non-resonance manner. There is.
For example, assuming that the amount of forced vibration displacement of the piezoelectric
ceramic 31 shown in FIG. 16 is Δt = dV (d: piezoelectric constant = 200 × 10 −12 [m / V]), a
displacement of 1 μm is temporarily obtained. Therefore, about 5000 [V] is required for the
applied voltage, and it becomes necessary to provide a booster circuit for the conventional device
(see FIG. 20). In addition, even if the shape is set so that the vibration in the desired direction
becomes non-resonant, depending on the shape and dimensions of the material and the
frequency of the signal voltage to be applied, resonance vibration may occur in the undesired
direction. If sound waves due to this vibration leak in an undesired direction, they become noise
sources. Therefore, there is a problem that the dimension design of the element itself becomes
very complicated in order not to resonate in all shape directions in the wide frequency band
used.
[0018]
Also, in the case of a magnetostrictive element (ferrite, nickel, etc.) generally used, a material
length of at least 50 [mm] in order to displace 1 [μm] as shown in FIG. Is required. However,
since the sound velocity in the magnetostrictive element is about 5000 m / s in the case of
ferrite, and the frequency at which the material length becomes equal to the half wavelength of
the sound becomes the basic resonance frequency in this case, The frequency becomes 50 [kHz],
and a resonance point is present around a little beyond the audible range. Therefore, when
transmitting a sound wave non-resonantly using a conventional magnetostrictive element, there
is a disadvantage that a structural resonance frequency exists in the ultrasonic wave region of
the transmission sound wave. Moreover, using the magnetostrictive element in a region where
the relationship between the magnetic field and the distortion is not linear means that the sound
pressure of the sound wave does not change in a sine wave even if the magnetic field is changed
in a sine wave, and It has the disadvantage of being complicated. However, if the
magnetostrictive element is to be used in a portion where the relationship between the magnetic
field and the distortion is linear, the material length is further increased and the structural
resonance frequency is further reduced, which causes a problem.
[0019]
In the above 1 [μm] vibration displacement, when the propagation medium is air at normal
temperature and normal humidity, the sound pressure is at a distance of 30 [cm] when vibrating
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with a point sound source at a vibration frequency of 40 [kHz]. It corresponds approximately to
the vibration amplitude of 120 [dB] (0 [dB] = 0.00002 [Pa]), and a resonant type transmission
element and receiver using a piezoelectric ceramic which has been marketed conventionally for
air ultrasonic waves. It is almost equal to the wave element.
[0020]
By the way, when measuring the distance to the object by the time delay from the transmission
of the sound wave signal to the reception of the sound wave signal reflected, the basic expression
of the distance between the transmission element-the object-the reception element Is expressed
by the distance L = VT (V: sound velocity in the propagation medium, T: time from the start of
transmission to the start of reception), but the time until the stable resonance mentioned above
and the reverberation time after the sound wave stop command If the same element is used for
both transmission and reception at a distance corresponding to the added time, measurement
becomes impossible.
A method for reducing such reverberation is proposed in JP-A-4-70585, JP-A-64-44876, etc., and
a method for improving the above-mentioned short-distance measurement area is actually used.
Japanese Patent Application Laid-Open Nos. 59-149071 and 63-168875, etc. are proposed.
However, in the case of transmitting and receiving sound waves in the air, even if the various
measures are taken at the resonance frequency of 40 [kHz], the area within 30 [cm] becomes
substantially unmeasurable.
[0021]
As described above, in the past, only sound waves of a single frequency were transmitted by
mechanical resonance, so there was no idea itself to modulate sound waves. Therefore, the signal
processing method measures the delay time from the start of transmission to the start of
reception, and obtains the distance from the transmission time. On the other hand, in the
application of sensors, there are objects that can only be measured by sound waves. For example,
when trying to obtain information on an optically transparent object such as glass or liquid, it
can not be measured with a commonly used optical sensor, and in such fields, sensing with
acoustic waves is important It can be a scheme.
[0022]
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Also, conventionally, when it is intended to make the directivity characteristic of the sound wave
a desired characteristic, members other than the wave transmitting element such as the horn 38
as shown in FIG. 18 and the wave receiving element are required. There is a problem that the
wave device becomes structurally large. Furthermore, in order to change directivity
characteristics, there is a problem that member replacement is required and it is troublesome.
The inventions of claims 1 to 12 are made in view of the above problems, and the object of the
invention is to make it possible to transmit or receive a sound wave signal with non-resonance,
less noise, and electrically It is an object of the present invention to provide a sound wave signal
transmission method and apparatus which can be easily controlled, a sound wave signal
reception method and apparatus, and a sound wave signal transmission / reception processing
system using them.
[0023]
The inventions of claims 13 to 17 are made in view of the above problems, and the object of the
invention is to obtain information on an object according to a signal processing method different
from the conventional one by modulating a sound wave signal. It is an object of the present
invention to provide an acoustic wave signal transmitting method and apparatus therefor, an
acoustic wave signal receiving method and apparatus thereof, and an acoustic wave signal
transmission / reception processing system using these methods.
[0024]
The inventions of claims 18 and 19 have been made in view of the above problems, and the
object of the invention is to provide a method and apparatus for transmitting an acoustic wave
signal whose directivity characteristics can be easily set and changed, and acoustic wave signal
reception. It is an object of the present invention to provide a method, an apparatus therefor, and
an acoustic wave signal transmission / reception processing system using the same.
[0025]
In order to achieve the above object, the invention of claim 1 transmits a magnetostrictive
element formed of a giant magnetostrictive material composed of a binary alloy of a rare earth
element and an iron group element. A magnetostrictive element formed of a giant
magnetostrictive material having a large displacement amount, characterized in that the pressure
change is generated in the sound wave propagation medium by driving the wave transmission
element in a non-resonance manner to generate an acoustic wave signal. By using it as a
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transmission element, it is possible to transmit a sound wave signal with an appropriate amount
of energy, and by setting the size of the transmission element to an appropriate size, the
mechanical resonance frequency is in the audible range or ultrasonic range. Can be absent.
As a result, it is possible to electrically control the transmission of the sound wave signal, and the
responsiveness of the sound wave signal is improved.
[0026]
According to a second aspect of the present invention, there is provided a transmission element
formed of a giant magnetostrictive material comprising a binary alloy of a rare earth element and
an iron group element to achieve the above object, and driving the transmission element nonresonantly Driving means for driving the wave transmitting element by the driving means to
cause a pressure change in the sound wave propagation medium to transmit the sound wave
signal, and is formed of a giant magnetostrictive material having a large displacement amount. By
using a magnetostrictive element as a wave transmission element, it is possible to transmit a
sound wave signal by driving with an appropriate energy amount by the drive means, and to
make the size of the wave transmission element appropriate for the machine. Resonant
frequencies can be absent in the audible and ultrasonic regions.
As a result, transmission of the sound wave signal can be controlled by the electrical drive signal
from the drive means, and the responsiveness of the sound wave signal is improved.
[0027]
According to the invention of claim 3, in order to achieve the above object, a magnetostrictive
element formed of a giant magnetostrictive material composed of a binary alloy of a rare earth
element and an iron group element is used as a receiving element, and an acoustic wave
propagation medium by acoustic signals. Is characterized in that the pressure change of the
sensor is detected non-resonantly by the wave receiving element and converted into an electric
signal, and a magnetostrictive element formed of a giant magnetostrictive material having a large
displacement is used as the wave receiving element. Can be converted to an electric signal of an
appropriate level and output, and if the dimensions of the wave receiving element are made
appropriate, a mechanical resonance frequency exists in the audible area or the ultrasonic area.
You can lose it. As a result, it is possible to electrically control the reception of the sound wave
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signal, and the response of the sound wave signal is improved.
[0028]
In order to achieve the above object, the invention according to claim 4 is a receiving element
formed of a giant magnetostrictive material composed of a binary alloy of a rare earth element
and an iron group element, and the receiving element not resonating with the receiving element.
And a signal conversion means for converting a pressure change of the sound wave propagation
medium by the detected sound wave signal into an electric signal, and using a magnetostrictive
element formed of a giant magnetostrictive material having a large displacement amount as a
wave receiving element. A sound wave signal received by the wave receiving element can be
converted into an electric signal of an appropriate level by the signal conversion means and
output, and mechanical size can be obtained if the size of the wave receiving element is made
appropriate. Resonant frequencies can be absent in the audible or ultrasonic range. As a result, it
is possible to electrically control the reception of the sound wave signal, and the response of the
sound wave signal is improved.
[0029]
In order to achieve the above object, the invention according to claim 5 is a transmission element
formed of a giant magnetostrictive material composed of a binary alloy of a rare earth element
and an iron group element, and the transmission element is driven with non-resonance. A sound
wave signal transmission apparatus comprising a driving means, and a pressure change of a
sound wave propagation medium by a sound wave signal which is formed of the super
magnetostrictive material and is transmitted from the transmission element and reflected by an
object is detected non-resonantly Sound wave receiving device, a sound wave signal receiving
device comprising signal converting means for converting a pressure change of the sound wave
propagation medium detected by the wave receiving device into an electric signal, and at least
signal conversion provided by the sound wave signal receiving device Means for performing
processing for obtaining information on the object based on the electric signal converted by the
means, and the sound wave signal transmitting apparatus and the sound wave signal receiving
apparatus are provided with a displacement amount Made of large giant magnetostrictive
material Since the magnetostrictive element is used in the wave transmitting device and wave
receiving element, it is possible to electrically control the transmit and reception of the acoustic
signal, the response of the acoustic signal is improved.
[0030]
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The invention according to claim 6 is characterized in that, in the invention according to any one
of claims 1 to 5, the sound wave signal comprises sound wave in an audible area.
The invention according to claim 7 is characterized in that, in the invention according to any one
of claims 1 to 5, the sound wave signal comprises a sound wave in an ultrasonic wave region.
The invention according to claim 8 relates to the invention according to any one of claims 1 or 2
or 5 to 7, wherein the drive means drives an electric signal having a predetermined periodic
waveform to the transmission element. It features.
[0031]
The invention of claim 9 is characterized in that, in the invention of claim 8, the drive means
drives the transmission element by applying the electric signal of one cycle. The invention
according to claim 10 is the invention according to any one of claims 3 to 7, wherein the signal
conversion means is an electrical signal for a pressure change of a sound wave propagation
medium having a predetermined periodic waveform detected by the wave receiving element. To
convert.
[0032]
The invention of claim 11 is characterized in that, in the invention of claim 10, the signal
conversion means converts a pressure change of the sound wave propagation medium having the
waveform for one period into an electric signal. The invention according to claim 12 is the
transmission apparatus according to any one of claims 5 to 11, wherein the drive means applies
an electric signal having a predetermined periodic waveform to the transmission element to drive
the transmission element. Transmits a sound wave signal from the light source, and converts the
reflected sound wave signal of the sound wave signal reflected by the moving or stationary object
into an electrical signal by the wave receiver, and the reflected sound wave by the signal
processing means The frequency of the signal is determined, and information of the moving
speed of the object is obtained from the frequency of the sound wave signal transmitted from the
transmission device and the frequency of the reflected sound wave signal. It is not necessary to
adjust the characteristics of the transmitting element and the receiving element between the
signal receiving devices, and moreover, the level fluctuation of the sound wave signal received
against environmental changes such as temperature and humidity can be suppressed, and the
conventional resonance method Object transfer with high accuracy Speed of information can be
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obtained.
[0033]
The invention of claim 13 relates to the invention according to claim 5, wherein the drive means
transmits an acoustic signal from the transmission device by applying to the transmission
element an electric signal obtained by analog modulation of a carrier wave with a modulation
wave to drive the transmission element. And the reflected wave signal of the sound wave signal
reflected by the moving or stationary object is converted into an electric signal by the wave
receiving device, and from the modulated wave component of the reflected sound wave signal by
the signal processing means It is characterized in that the information on the object is obtained,
and the information on the object can be obtained by a method different from the conventional
method, and the information on the object is obtained accurately and quickly without being
influenced by the acoustic noise from the outside. Be
[0034]
In the invention of claim 14, according to the invention of claim 13, the signal processing means
includes a modulation component of a sound wave signal transmitted from the transmission
apparatus and a modulation component of a reflection sound wave signal received by the
reception apparatus. Calculating the time interval in the same phase of the signal, and
multiplying the time interval by the medium propagation velocity of the sound wave signal to
obtain information on the distance to the moving or stationary object, in a method different from
the prior art The distance information to the object can be obtained, and the distance information
to the object can be obtained with high accuracy and quick response without being influenced by
the acoustic noise from the outside.
[0035]
According to the invention of claim 15, in the invention of claim 13, the signal processing means
comprises a modulation component of a sound wave signal transmitted from the transmission
device and a modulation component of a reflection sound wave signal received by the reception
device. The time interval in the same phase of is calculated, and the time interval is multiplied by
the medium propagation velocity of the sound wave signal to calculate the distance to the
moving or stationary object, and the calculation is made multiple times with a predetermined
time difference. The difference between the distances is divided by the time difference to obtain
information on the moving speed of the object, and information on the moving speed of the
object can be obtained by a method different from the conventional method, and from the
outside The information on the moving speed of the object can be obtained with high accuracy
and quick response without being influenced by the acoustic noise of.
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[0036]
In the invention of claim 16 according to the invention of claim 13, the signal processing means
comprises a modulation component of a sound wave signal transmitted from the transmission
apparatus and a modulation component of a reflection sound wave signal received by the
reception apparatus. And obtaining information on the moving speed of the object from the
frequency of the modulation component of the sound wave signal transmitted from the
transmission device and the frequency of the modulation component of the reflection sound
wave signal, The information on the moving speed of the object can be obtained by a method
different from the above, and the information on the moving speed of the object can be obtained
accurately and quickly without being influenced by the acoustic noise from the outside.
[0037]
The invention according to claim 17 relates to the invention according to claim 15 or 16,
wherein the signal processing means divides the difference between the moving speeds obtained
for a plurality of times with a predetermined time difference divided by the time difference to
obtain the target object. It is characterized by obtaining information of movement acceleration,
and it is possible to obtain information of movement acceleration of the object by a method
different from the conventional method, and movement of the object with high accuracy and
quick response without being influenced by acoustic noise from the outside. Information on
acceleration can be obtained.
[0038]
The invention according to claim 18 is determined according to the invention according to any
one of claims 1 or 2 or 5 to 17 from the wavelength of the sound wave signal transmitted from
the transmission element and the shape of the sound wave transmission surface of the
transmission element. From the directivity characteristics, a sine wave signal of a frequency at
which a desired directivity characteristic can be obtained is provided from the drive means to the
transmission element, and is characterized in that the directivity characteristics when
transmitting a sound wave signal can be easily set and It can be changed.
[0039]
The invention according to claim 19 is the invention according to any one of claims 3 to 17 in
which the shape of the sound wave signal receiving wavefront of the wave receiving element
with respect to the wavelength of the sound wave signal is obtained so as to obtain desired
directivity characteristics of the wave receiving element. It is characterized in that it is
characterized in that the directivity characteristic when receiving the sound wave signal can be
easily set and changed.
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[0040]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be
described in detail by embodiments with reference to the drawings.
(Embodiment 1) As shown in FIG. 1, in the sound wave signal transmission apparatus according
to this embodiment, the magnetostrictive element formed of a super magnetostrictive material is
the transmission element 1, and the drive coil 3a is elongated around the transmission element 1.
It is wound along a direction, and a bias power supply 3b and a signal source 3c are connected in
series at both ends of the drive coil 3a.
Further, as shown in FIG. 2, in the sound wave signal receiving apparatus, the magnetostrictive
element similarly formed of a super magnetostrictive material is used as the wave receiving
element 2, and the detection coil 4a is wound around the wave receiving element 2 along the
longitudinal direction. The bias power supply 4b and the detection transformer 4c are connected
in series to both ends of the drive coil 4a.
[0041]
The super magnetostrictive material forming the transmission element 1 and the reception
element 2 includes rare earth elements such as Tb (terbium), Sm (samarium), Dy (dysprosium), Fe
(iron), Co (cobalt), Ni (cobalt). 4) having a magnetic field-magnetostriction characteristic as
shown in FIG. 4 ( industrial material , October, 1996 issue (Vol. 44, No.) 11) pp. 48-53, see
Nikkan Kogyo Shimbun Publishing Co., Ltd.).
As applications of the magnetostrictive element formed of such a giant magnetostrictive material,
a low frequency actuator is usually assumed.
[0042]
In general, the magnetostrictive element has Joule effect and billy effect.
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The Joule effect is a phenomenon in which when a magnetic field H is applied to the
magnetostrictive element, a change in dimension (magnetostriction Δl / l) corresponding to the
magnitude of the magnetic field H occurs.
Then, utilizing this Joule effect, the magnitude of the magnetic field H applied to the
magnetostrictive element (transmission element 1) is changed by changing the amount of current
flowing through the drive coil 3a, whereby the magnetostriction Δl / An acoustic wave signal is
transmitted as the magnetostriction causes a pressure change of air as a propagation medium.
That is, as shown in FIG. 3, a bias magnetic field HDC is applied to the transmission element 1 by
flowing a bias current IDC from the bias power supply 3c to the drive coil 3a, and a signal
current of, for example, a sine wave centering on the bias current IDC. When IAC flows from the
signal source 3c to the drive coil 3a, the magnetic field HAC applied to the transmission element
1 also changes in a sine wave according to the signal current IAC.
As a result, a displacement (magnetostriction) that changes in a sine wave corresponding to the
signal current IAC is generated in the transmission element 1, and by transmitting the
displacement into the air, a sine wave sound signal is transmitted. .
[0043]
On the other hand, the billy effect is a phenomenon in which when the dimension of the
magnetostrictive element changes due to the application of force, the amount of magnetization of
the magnetostrictive element changes in proportion to the change in the dimension. Thus, when
the amount of magnetization of the magnetostrictive element (the wave receiving element 2)
changes, an induced voltage EAC is generated in the detection coil 4a according to the amount of
change. That is, since the sound wave signal is a pressure change of air as a propagation medium,
when the wave receiving element 2 composed of a magnetostrictive element receives a sound
wave signal, the wave receiving element 2 is displaced by the pressure change, and the
magnetization amount is Change. As a result, the received sound wave signal can be converted
into the signal current IAC flowing to the detection coil 4 a through the change of the
magnetization amount of the wave receiving element 2.
04-05-2019
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[0044]
Here, the basic relational expressions in the magnetostrictive element forming the transmission
element 1 and the reception element 2 are as follows. S = sH · T d d · H ... B = d · 10 μ T · H
where S: magnetostriction, H: magnetic field strength, sH: reciprocal of Young's modulus, T:
mechanical stress, B: magnetic flux density, μT : It is permeability. In addition, the giant
magnetostrictive material has a magnetic field-magnetostrictive characteristic as shown in FIG. 4
as described above. As described above, in a state where the bias magnetic field H1 is applied to
the magnetostrictive element using the bias power supply 3b or the permanent magnet, when the
alternating current (signal current) IAC flows through the drive coil 3a, the alternating magnetic
field H2 is applied to the magnetostrictive element Ru. The inclination of the curve of the
magnetic field-magnetostrictive characteristic when the bias magnetic field H1 is applied is d,
and the length of the magnetostrictive element is l = 2 mm, H1 = 250 Oe, H2 = 250 Oe pp,
mechanical The stress T = 0. Here, the magnetostriction generated in the magnetostrictive
element is S = d · H 2 from the above equation, and the distortion amount Δl is obtained by Δl =
l · S. Specifically, according to FIG. 4, since the slope d is 2 × 10 −8 [m / A], the distortion
amount Δl ≒ 1 [μm]. Then, if the frequency of the alternating magnetic field H2 is set to, for
example, about 50 kHz, a sound wave in the ultrasonic region of 50 kHz is output. That is, the
frequency of the sound wave signal transmitted from the transmission element 1 is not
determined by the structural factor of the transmission element 1 as in the conventional
resonance method, but the signal current flowing from the signal source 3c to the drive coil 3a It
can be determined electrically by the frequency of IAC. That is, by changing the frequency of the
signal current IAC, it is possible to transmit a sound wave signal of an arbitrary frequency, which
is apparent from the above principle.
[0045]
In addition, the acoustic wave velocity in the giant magnetostrictive material in the present
embodiment is 2500 [m / s], and the mechanical resonance frequency of the transmission
element 1 when the length dimension of the transmission element 1 is 5 [mm]. Since f0 has a
wavelength of 10 [mm], f0 = 625 [kHz]. The resonance frequency f0 is one digit larger than that
of an ultrasonic transducer using a piezoelectric ceramic generally used at present, which is
about 40 [kHz], and the signal current supplied to the drive coil 3a It is obvious that the
transmission element 1 can be driven non-resonantly without mechanical resonance if the
frequency band of IAC is appropriately selected.
[0046]
04-05-2019
17
On the other hand, in the wave receiving element 2 in the present embodiment, it is possible to
receive a sound wave signal as follows. First, when both ends of the detection coil 4a are shortcircuited, the magnetic flux density B = 0 from the above equation from the above equation, so
the magnetic field H = -dT / .mu.T0. Further, the relation of H = n · I (n = N / l, N: total number of
turns of detection coil 4a) is established between current I and magnetic field H generated in
detection coil 4a. It becomes d / μT × l / N × T. Here, μT = 4π × 10−7 × relative
permeability, relative permeability = 8. Therefore, it is obvious from the above principle that the
wave receiving element 2 can also receive waves regardless of the frequency of the sound wave
signal.
[0047]
A basic configuration of a sound wave signal transmission / reception processing system using
the transmission element 1 and the reception element 2 is shown in FIG. A continuous signal
current is supplied from the continuous oscillation circuit 5 to the transmission circuit 3
provided with the drive coil 3a and the bias power supply 3c, and an acoustic wave signal is
transmitted from the transmission element 1. Then, the sound wave signal transmitted from the
wave transmission element 1 and reflected back to the object is received by the wave reception
element 2, converted into an electric signal by the wave reception circuit 4 including the
detection coil 4a and the like, and signal processing It is output to the circuit 6. The oscillation
frequency in the continuous oscillation circuit 5 can be varied by the transmission frequency
setting unit 7, and information on the transmission frequency is also given to the signal
processing circuit 6.
[0048]
In the signal processing circuit 6, for example, the difference between the transmission start time
of the sound wave signal from the transmission element 1 and the reception start time of the
reflected sound signal by the wave reception element 2 is determined, and the difference is a
propagation medium (for example, air The distance to the object is determined by multiplying the
propagation velocity of the sound wave signal in. Note that the information on the object
obtained by the signal processing circuit 6 is not limited to the above information on the
distance, and appropriate signal processing may be performed, for example, to detect the
presence or absence of the object or the moving speed or moving acceleration of the object. And
various other information can be obtained.
04-05-2019
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[0049]
As described above, according to the present embodiment, the wave transmitting element 1 and
the wave receiving element 2 are formed using magnetostrictive elements made of a super
magnetostrictive material whose displacement amount is larger than that of a piezoelectric
element or the like. Since the sound wave signal is transmitted by driving at resonance and the
sound wave signal is received non-resonantly at the wave receiving element 2, the energy
suitable for driving the wave transmission element 1 to transmit the sound wave signal It is
possible to transmit in quantity, and if the dimensions of the transmission element 1 are made to
be appropriate, mechanical resonance frequencies do not exist in the audible area or the
ultrasonic area. In addition, even if the amount of energy of the sound wave signal is too large for
the wave receiving element 2, the received sound wave signal can be converted into an electric
signal of an appropriate level and output. As a result, it becomes possible to electrically control
transmission and reception of the sound wave signal, and for example, it is possible to easily set
or change the sound wave signal of an arbitrary frequency by changing the frequency of the
signal current supplied to the drive coil 3a. If the filter is connected to the detection coil 4a and
the filter's pass band is made variable by volume etc., the frequency of the sound wave signal
received by the wave receiving element 2 can be easily set and changed. It becomes possible.
Thus, since the sound wave signal of an arbitrary frequency can be transmitted and received by
electrical control such as adjustment of the signal current, the structures of the transmission
element 1 and the reception element 2 are adjusted as in the conventional resonance method.
There is no such need, and moreover, the change in the output level of the wave transmitting
element 1 and the wave receiving element 2 with respect to the change in temperature and
humidity is not so large as in the conventional resonance system and is negligible.
[0050]
By the way, when the transmitting wavefront of the transmitting element 1 and the receiving
wavefront of the receiving element 2 are substantially circular of radius a, the directions of
transmitting and receiving are defined by the angle θ from the normal direction of the
transmitting wavefront and the receiving wavefront. Assuming that the sound velocity is v0, the
sound frequency is fa, and the wavelength of the sound signal is λ, k = 2π · fa / v0 = 2π / λ,
the directivity characteristics D of the transmission element 1 and the reception element 2 are as
follows It is expressed by a formula (however, J1 (x) is a first-order Bessel function). In addition,
since this is obvious in the field of acoustic engineering, the detailed description is omitted.
04-05-2019
19
[0051]
D (θ) = ¦ 2J1 (k × a × sin (θ)) / (k × a × sin (θ)) ¦ ... Various types of radius a of transmitting
wavefront and receiving wavefront and wavelength λ of sound signal according to the above
equation The directivity characteristics obtained for the combinations of the above are shown in
FIGS. 6 (a) to 6 (d). That is, as shown in (a) of the figure, in the case of a / λ = 0.2, it becomes
almost non-directional, and as shown in (b) to (d) of the figure, it becomes stronger as the value
of a / λ increases. It will show directional characteristics. In the case of transmitting a sound
wave signal, in practice, the wavelength λ of the sound wave signal is changed by setting the
frequency of the signal current flowed to the drive coil 3a appropriately to easily change and
adjust it to a desired directivity characteristic. be able to.
[0052]
(Embodiment 2) FIG. 7 is a block diagram of a sound wave signal transmission / reception
processing system according to Embodiment 2 of the present invention. However, the same
reference numerals as in the first embodiment denote the same parts as in the first embodiment,
and a description thereof will be omitted. The present embodiment is characterized in that a
single pulse sound wave signal is output by outputting a signal of an arbitrary waveform such as
a triangular wave, a rectangular wave or a sine wave to the drive coil 3a for one period. That is,
as shown in FIG. 7, the single oscillation circuit 8 is provided instead of the continuous oscillation
circuit 5 in the configuration of the first embodiment, and the start of signal output is instructed
from the transmission start instruction unit 9. By outputting a drive signal for one cycle of a
rectangular wave as shown in FIG. 8A to the drive coil 3a from the circuit 8 through the
transmission circuit 3, the rectangular wave as shown in FIG. 8B. The sound wave signal of one
cycle of is transmitted.
[0053]
Also in the present embodiment, as in the first embodiment, since the wave transmitting element
1 is driven with non-resonance to transmit the sound wave signal, the wave transmitting element
1 immediately transmits the driving signal from the wave transmitting circuit 3. In response, it
transmits a sound wave signal. Therefore, it is not necessary to repeatedly input the drive signal
having the same waveform for a plurality of times until the sound signal is stabilized as in the
conventional resonance method. That is, in the conventional resonance method, it was necessary
04-05-2019
20
to continuously output any number of pulses of a rectangular wave signal having a pulse width
of 25 μs to the resonance frequency of 40 kHz (see FIG. 17A). In the case of this embodiment, a
sound wave signal can be transmitted only by applying a pulse signal for one cycle. Moreover,
since transmission of the sound wave signal from the wave transmission element 1 is
immediately stopped when the input of the drive signal is stopped, the conventional
reverberation does not occur without any particular measures, and the sound wave from the
beginning There is no conventional latency because the signal is stable. Therefore, there is an
advantage that the response speed of the system is faster than that of the conventional system
that performs transmission and reception of resonance method.
[0054]
On the other hand, since a sound wave signal stabilized from the beginning is transmitted and no
reverberation occurs, the wave receiving element 2 can also receive a single sound wave signal
as shown in FIG. In the case where the detection speed (the detection distance recently) of the
moving speed of the object or non-existence etc. can be greatly reduced compared to the case
where the transmission element 1 and the reception element 2 are shared by one element. Even
if there is, it is possible to receive a wave immediately after the end of the wave transmission, so
the detection distance can be shortened significantly recently.
[0055]
(Third Embodiment) FIG. 9 is a block diagram of a sound wave signal transmission / reception
processing system according to a third embodiment of the present invention.
However, the same components as in the first embodiment will be assigned the same reference
numerals and descriptions thereof will be omitted. In the signal processing circuit 10 of the
present embodiment, the frequency of the sound wave signal to be transmitted and received is
measured, and the moving velocity of the object is obtained from the measured frequency using
the Doppler effect, and the frequency is measured. A frequency counter or a frequency-voltage
conversion circuit is provided, and an arithmetic circuit such as a DSP (digital signal processor) is
provided for arithmetic processing for determining a moving speed. However, even if the
frequency of the sound wave signal to be transmitted is not measured intentionally, frequency
data provided from the transmission frequency setting unit 7 may be used.
[0056]
04-05-2019
21
For example, the frequency of the sound wave signal to be transmitted (the frequency of the
signal current fed to the drive coil 3a) is fa, the velocity of the sound wave signal in the
propagation medium is v0, the frequency of the received sound wave signal (output from the
wave receiving circuit 4) Assuming that the frequency of the signal) is fb and the moving velocity
v1 of the object, the frequency shift due to the Doppler effect is expressed by the following
equation. The moving speed v1 of the object is such that the direction in which the object moves
away from the wave receiving element 2 is positive, and the direction in which the object
approaches is negative.
[0057]
fb = (v0 + v1) / (v0-v1) x fa ... From the above equation, the moving velocity v1 of the object can
be obtained by the following equation. v1 = (fb-fa) / (fa + fb) x v0 ... Note that for the difference
between the transmitting direction or receiving direction of the sound wave signal and the
moving direction of the object, the above equation and a little correction It is possible, and
detailed explanation is omitted.
[0058]
(Embodiment 4) FIG. 10 is a block diagram of a sound wave signal transmission / reception
processing system according to Embodiment 4 of the present invention. However, the same
components as in the first embodiment will be assigned the same reference numerals and
descriptions thereof will be omitted. In this embodiment, the modulated sound wave signal is
transmitted and the modulated wave component is extracted from the received sound wave
signal, and the distance from the modulated wave component of the transmitted wave and the
received wave to the object is determined by the signal processing circuit 15. It is made to
calculate. Therefore, the carrier wave signal input from the carrier wave generation circuit 12 by
the carrier wave generation circuit 12 generating the carrier wave signal, the modulation wave
generation circuit 13 generating the modulation wave signal, and the modulation wave signal
input from the modulation wave generation circuit 13 A modulation circuit 11 that modulates
and outputs to the transmission circuit 3 and a modulation wave extraction circuit 14 that
extracts the component (modulation wave component) of the modulation wave signal from the
output signal from the wave reception circuit 4 are provided. However, the outputs of the carrier
wave generation circuit 12 and the modulation wave generation circuit 13 are also given to the
modulation wave extraction circuit 14, and the modulation wave component is extracted based
on this. In this embodiment, amplitude modulation is performed in the modulation circuit 11 with
04-05-2019
22
the frequency fc = 50 [kHz] of the carrier wave signal and the frequency fm = 100 [Hz] of the
modulation wave signal.
[0059]
In FIG. 11, the modulation wave signal output from the modulation wave generation circuit 13
and the modulation wave component signal extracted by the modulation wave extraction circuit
14 from the sound wave signal received by the wave receiving element 2 are on the same time
axis. Is represented in. The signal processing circuit 15 measures a time interval when both
signals have the same phase. For example, the signal processing circuit 15 performs a process of
recording the time for each zero cross of each signal and determining the time interval t from the
difference between the zero cross time of transmission and the zero cross time of reception.
Assuming that the velocity of the sound wave signal in the propagation medium is c, the distance
L to the object A can be obtained by L = ct / 2 as shown in FIG. For example, since the speed of
sound c at normal temperature is c = 340 [m / s], if the frequency of the modulation wave is 100
[Hz] and the above time interval t is 2 [ms], the target at that time is The distance L to the object
A is L = 0.34 [m]. Further, as shown in FIG. 13, the measurement of the distance L to the object A
is repeated and the difference L2-L1 of the distance is divided by the time interval T2-T1 of the
measurement, so that the moving speed v of the object A is It can obtain ¦ require from the
formula of v = (L2-L1) / (T2-T1). Furthermore, the moving acceleration of the object A can also
be determined by temporally differentiating the determined moving velocity v. In this
embodiment, the distance to the object A is obtained from the time interval of the zero crossing,
but the moving velocity of the object A can be calculated from the frequency shift due to the
Doppler effect by measuring the frequency of the modulated wave besides that. It is also possible
to ask.
[0060]
As described above, according to the present embodiment, it is possible to obtain information on
the distance to the object A and the moving speed in a method different from the conventional
one, and to perform accurate and fast response without being affected by external acoustic noise.
The information on the distance and the moving speed of the object A can be obtained by
[0061]
According to the first aspect of the present invention, a magnetostrictive element formed of a
giant magnetostrictive material composed of a binary alloy of a rare earth element and an iron
group element is used as a transmission element, and the transmission element is driven nonresonantly By causing pressure change in the sound wave propagation medium and transmitting
04-05-2019
23
the sound wave signal, the sound wave signal can be generated with an appropriate amount of
energy by using a magnetostrictive element formed of a super magnetostrictive material having a
large displacement amount as the wave transmission element. Can be transmitted, and if the
dimensions of the transmission element are appropriately sized, mechanical resonance
frequencies can be eliminated from the audible region and the ultrasonic region, and as a result,
the acoustic wave signal It is possible to electrically control transmission, and the response of the
sound wave signal is improved.
[0062]
The invention of claim 2 comprises a transmission element formed of a giant magnetostrictive
material composed of a binary alloy of a rare earth element and an iron group element, and a
driving means for driving the transmission element in a non-resonant manner. Since the
transmission element is driven by the driving means to cause pressure change in the sound wave
propagation medium and the sound wave signal is transmitted, the magnetostrictive element
formed of a super magnetostrictive material having a large displacement amount is used as the
transmission element. The acoustic wave signal can be transmitted by driving with an
appropriate amount of energy by the driving means, and the mechanical resonance frequency is
in the audible range or the ultrasonic range if the dimensions of the transmitting element are
made appropriate. As a result, transmission of the sound wave signal can be controlled by an
electrical drive signal from the drive means, and the response of the sound wave signal is
improved.
[0063]
The invention according to claim 3 uses a magnetostrictive element formed of a super
magnetostrictive material composed of a binary alloy of a rare earth element and an iron group
element as a wave receiving element, and the pressure change of the sound wave propagation
medium by the sound wave signal is said wave receiving element Since non-resonance detection
and conversion to an electrical signal are performed at the same time, the received acoustic wave
signal is converted to an electrical signal of an appropriate level by using a magnetostrictive
element formed of a giant magnetostrictive material having a large displacement amount as a
wave receiving element. It is possible to convert and output, and by setting the dimensions of the
wave receiving element to a suitable size, it is possible to make the mechanical resonance
frequency not exist in the audible area or the ultrasonic wave area, and as a result, the sound
wave signal It is possible to electrically control the reception of the wave, and the response of the
sound wave signal is improved.
[0064]
According to a fourth aspect of the present invention, there is provided a receiving element
04-05-2019
24
formed of a giant magnetostrictive material composed of a binary alloy of a rare earth element
and an iron group element, and an acoustic wave propagation medium based on an acoustic
signal detected non-resonantly by the receiving element. And the signal conversion means for
converting the pressure change into an electric signal, so by using a magnetostrictive element
formed of a giant magnetostrictive material having a large displacement amount as a wave
receiving element, the sound wave signal received by the wave receiving element is The signal
conversion means can convert to an electric signal of an appropriate level and output it, and if
the size of the wave receiving element is made appropriate, a mechanical resonance frequency
exists in the audible area or the ultrasonic wave area As a result, it is possible to electrically
control the reception of the sound wave signal, and the response of the sound wave signal is
improved.
[0065]
The invention according to claim 5 is a transmission element formed of a giant magnetostrictive
material comprising a binary alloy of a rare earth element and an iron group element, and an
acoustic signal transmission comprising driving means for driving the transmission element in a
non-resonant manner. A wave device, and a wave receiving element for detecting non-resonant
pressure change of a sound wave propagation medium by a sound wave signal which is formed
of the super magnetostrictive material and is transmitted from the wave transmitting element
and reflected by the object; A sound wave signal reception apparatus comprising signal
conversion means for converting a pressure change of the sound wave propagation medium
detected by the element into an electric signal, and at least an electric signal converted by the
signal conversion means provided in the sound wave signal reception apparatus Since the signal
processing means for performing processing to obtain information on the object based on the
above is provided, the acoustic wave signal transmitting apparatus and the acoustic wave signal
receiving apparatus are provided with magnetostrictive elements formed of a giant
magnetostrictive material having a large displacement amount. Transmitting element and
receiving element Because they used, it is possible to electrically control the transmit and
reception of the acoustic signal, there is an effect that the responsiveness of the acoustic signal is
improved.
[0066]
According to the invention of claim 12, the acoustic wave signal is transmitted from the wave
transmitting device by driving the electric wave having a predetermined periodic waveform to
the wave transmitting element by the driving means, thereby moving or stationary. The reflected
wave signal of the sound wave signal reflected by the target object is converted into an electric
signal by the wave receiving device, and the frequency of the reflected sound wave signal is
determined by the signal processing means, and transmitted from the wave transmitting device
Since information on the moving speed of the object is obtained from the frequency of the wave
04-05-2019
25
sound wave signal and the frequency of the reflected sound wave signal, a wave transmission
element and a wave reception element are provided between the sound wave signal transmission
device and the sound wave signal reception device. It is not necessary to adjust the
characteristics, and moreover, the level fluctuation of the sound wave signal received to the
environmental change such as temperature and humidity can be suppressed, and the information
on the moving speed of the object can be obtained more accurately than the conventional
resonance method. effective.
[0067]
According to the invention of claim 13, the driving means transmits an acoustic signal from the
transmission device by driving the electric wave in which the carrier wave is analog-modulated
by the modulation wave to the transmission element to drive, and moves or rests. The reflected
wave signal of the sound wave signal reflected by the target object is converted into an electric
signal by the wave receiving device, and the information on the target object is obtained from the
modulated wave component of the reflected sound wave signal by the signal processing means
Therefore, the information of the object can be obtained by a method different from the
conventional method, and the information of the object can be obtained with high accuracy and
quick response without being influenced by the acoustic noise from the outside.
[0068]
According to the invention of claim 14, in the signal processing means, the time interval in the
same phase of the modulation component of the sound wave signal transmitted from the
transmission apparatus and the modulation component of the reflection sound wave signal
received by the reception apparatus Since information on the distance to the moving or
stationary object is obtained by multiplying the time interval by the medium propagation velocity
of the acoustic signal, the distance information on the object can be obtained by a method
different from the conventional method. Thus, the distance information to the object can be
obtained with high accuracy and quick response without being influenced by the acoustic noise
from the outside.
[0069]
In the invention of claim 15, the signal processing means is configured to generate a time
interval in the same phase of the modulation component of the sound wave signal transmitted
from the transmission device and the modulation component of the reflection sound wave signal
received by the reception device. The time interval is multiplied by the medium propagation
velocity of the sound signal to calculate the distance to the moving or stationary object, and the
difference between the distances obtained a plurality of times with a predetermined time
difference is calculated. Since the information on the moving speed of the object is obtained by
04-05-2019
26
dividing by the time difference, the information on the moving speed of the object can be
obtained by a method different from the conventional method, and accurate without being
influenced by acoustic noise from the outside. And there is an effect that the information on the
moving speed of the object can be obtained with a quick response.
[0070]
In the invention of claim 16, the signal processing means determines the respective frequencies
of the modulation component of the sound wave signal transmitted from the transmission device
and the modulation component of the reflection sound signal received by the reception device,
Since the information on the moving speed of the object is obtained from the frequency of the
modulation component of the sound wave signal transmitted from the wave transmission device
and the frequency of the modulation component of the reflected sound signal, the movement
speed of the object is different from the conventional method The present invention has the
effect of being able to obtain information on the moving speed of an object with high accuracy
and quick response without being influenced by external acoustic noise.
[0071]
According to the invention of claim 17, since the signal processing means divides the difference
between the moving speeds obtained a plurality of times with a predetermined time difference by
the time difference to obtain information on the moving acceleration of the object, It is possible
to obtain information on the movement acceleration of the object in a manner different from that
of the object, and to obtain information on the movement acceleration of the object with high
accuracy and quick response without being influenced by acoustic noise from the outside.
[0072]
According to the eighteenth aspect of the present invention, there is provided a sine wave signal
of a frequency at which a desired directivity characteristic can be obtained from the directivity
characteristic determined from the wavelength of the sound wave signal transmitted from the
transmission element and the shape of the sound wave transmission surface of the transmission
element. Since the driving unit applies the driving signal to the transmission element for driving,
there is an effect that the directivity characteristic when transmitting the sound wave signal can
be easily set and changed.
[0073]
The invention according to claim 19 receives the sound wave signal because the shape of the
sound wave signal reception wavefront of the wave reception element with respect to the
wavelength of the sound wave signal is determined so as to obtain desired directivity
04-05-2019
27
characteristics of the wave reception element. There is an effect that the directivity characteristic
of the case can be easily set and changed.
[0074]
Brief description of the drawings
[0075]
1 is a circuit diagram showing a sound wave signal transmission apparatus according to the first
embodiment.
[0076]
2 is a circuit diagram showing a sound wave signal reception device in the same as the above.
[0077]
3 is an explanatory view for explaining the operation of transmission and reception of the sound
wave signal in the same as the above.
[0078]
4 is a diagram showing the magnetic field-magnetostriction characteristics of the transmission
element and the reception element in the same as the above.
[0079]
5 is a block diagram showing the system configuration of the same.
[0080]
FIGS. 6 (a) to 6 (d) are diagrams showing the directivity characteristics of the transmission
element and the reception element at the same time.
[0081]
7 is a block diagram showing a system configuration of the second embodiment.
[0082]
04-05-2019
28
8 is an explanatory view for explaining the operation of the same.
[0083]
9 is a block diagram showing a system configuration of the third embodiment.
[0084]
10 is a block diagram showing a system configuration of the fourth embodiment.
[0085]
11 is a signal waveform diagram for explaining the operation of the same.
[0086]
12 is a diagram for explaining the operation of the same.
[0087]
13 is a diagram for explaining the operation of the same.
[0088]
14 is a block diagram showing a conventional system configuration.
[0089]
15 is a block diagram showing another conventional system configuration.
[0090]
16A and 16B show the piezoelectric ultrasonic transducer in the same as above, in which (a) is a
side sectional view and (b) is a schematic circuit diagram.
[0091]
17 is a waveform diagram for explaining the operation of the same.
[0092]
04-05-2019
29
18 is a cross-sectional view showing a structure for obtaining a desired directional characteristic
in FIG.
[0093]
19 is a cross-sectional view showing a structure for obtaining a desired directional characteristic
in FIG.
[0094]
FIGS. 20 (a) and 20 (b) are explanatory diagrams for explaining the operation of the ultrasonic
transducer in the above.
[0095]
21 is a diagram showing the magnetic field-magnetostrictive characteristics of the conventional
magnetostrictive material.
[0096]
Explanation of sign
[0097]
DESCRIPTION OF SYMBOLS 1 transmit element 2 receive element 3 transmit circuit 3a drive coil
3b bias power supply 3c signal source 4 transmit circuit 4a detection coil 4b bias power supply
4c detection transformer
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