JP2000147098A - Sound wave receiver and sound wave transmitting/ receiving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sound wave transmitter/receiver, wherein unwanted oscillations of a piezoelectric element adopted for an ultrasonic transducer are suppressed. SOLUTION: An ultrasonic transducer 10 transmits sound waves to a reflector through an object to be measured, based on the oscillation of a piezoelectric element 12 driven by a drive signal from a drive circuit 100 and receives reflected sound waves from the reflector S through the object, when they are reflected, to generate a received signal from the piezoelectric element 12. To suppress unwanted oscillations generated from the piezoelectric element 12 after the output stop of the drive signal from the drive circuit 100 to the piezoelectric element 12, a signal having a phase opposite to that of the unwanted oscillations is fed to the piezoelectric element 12 as a suppressing signal, thus obtaining a received signal of good accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmitting / receiving apparatus and a transmitting / receiving method for sound waves such as audible sound waves and ultrasonic waves.

[0002]

2. Description of the Related Art Conventionally, for example, the physical properties of liquid fuel in a fuel tank of a vehicle (for example, whether it is heavy gasoline,
Or a light gasoline), there is a measuring device for measuring the propagation time of ultrasonic waves through the liquid fuel. In order to perform such a measurement, as shown in FIG. 7, both the transmission of the ultrasonic wave according to the drive signal from the measuring device 1 for the propagation time and the reception of the ultrasonic wave reflected by the reflector S There is a type that employs an ultrasonic transducer 2 that performs the above.

For example, as shown in FIG. 8, the ultrasonic transducer 2 includes a case 3, a parabolic horn 4 disposed in the case 3, and a piezoelectric element 5 having a bimorph structure. There is. The piezoelectric element 5 sandwiches a common electrode plate 5c between the two piezoelectric ceramic plates 5a and 5b, and has a piezoelectric ceramic plate 5 between the two electrode plates 5d and 5e.
a, the common electrode plate 5c and the piezoelectric ceramic plate 5b are sandwiched.

Here, both piezoelectric ceramic plates 5a, 5b
Are supplied with drive signals so that they have opposite polarities in the thickness direction. For this reason, both piezoelectric ceramic plates 5a,
Since the piezoelectric expansion and contraction characteristics in the plate thickness direction of 5b are in opposite phases, the amplitude of the vibrating surface increases. Thereby, the transmission of the ultrasonic waves and the reception of the reflected ultrasonic waves are made more efficient.

[0005]

However, in the ultrasonic vibrator 2, the piezoelectric element 5 vibrates upon receiving the driving signal from the measuring device 1, and thereafter, the application of the driving signal by the measuring device 1 is stopped. Even after that, it keeps making unnecessary vibrations until it loses its kinetic energy. In response to the unnecessary vibration, the piezoelectric element 5 generates an unnecessary signal from both between the common electrode plate 5c and the electrode plate 5d and between the common electrode plate 5c and the electrode plate 5e.

For this reason, when the measuring distance H (see FIG. 7) between the ultrasonic transducer 2 and the reflector S is short, the reflector S
During the unnecessary vibration of the piezoelectric element 5, that is, during the generation of the unnecessary signal, the reflected ultrasonic wave by the piezoelectric element 5
May be received as a received wave. As a result, FIG.
As shown by, the signal received by the piezoelectric element 5 and the unnecessary signal overlap.

[0007] As described above, when the received signal and the unnecessary signal overlap with each other, an accurate signal waveform of the received wave cannot be obtained, which causes a problem that the measurement of the received signal becomes difficult. On the other hand, as shown in JP-A-8-322100, as shown in FIG.
Is disposed on the upper side of the piezoelectric element 5 via an adhesive layer 8, and a signal is applied between the two electrode plates 6 a and 6 b of the organic polymer piezoelectric element 6 to suppress unnecessary vibration of the piezoelectric element 5. There are things that I try to do.

However, the ultrasonic transducer shown in FIG.
As compared with the ultrasonic transducer shown in FIG. 8, extra members such as the organic polymer piezoelectric element 6 and the adhesive layer 8 are required. Therefore, the present inventors have considered that unnecessary vibrations can be suppressed by applying some signal to the piezoelectric element of the ultrasonic vibrator, and examined in detail the unnecessary vibrations and unnecessary signals of the ultrasonic vibrator, It has been found that the frequency of the unnecessary vibration, and hence the frequency of the unnecessary signal, is the natural frequency of the ultrasonic transducer.

[0009] According to this, the piezoelectric element unnecessarily vibrates at the above-mentioned natural frequency after the application of the drive signal by the measuring device is stopped, and generates an unnecessary signal having the above-mentioned natural frequency from between the two electrode plates. . In view of this point, the inventors have considered that unnecessary vibration can be suppressed by applying a signal having a phase opposite to that of the unnecessary signal to the piezoelectric element of the ultrasonic vibrator. After applying a drive signal between the two electrode plates, a signal having a phase opposite to that of the unnecessary signal was applied (see FIG. 11).

Here, a number of different periods are employed as the period t1 (see FIG. 11) for applying a signal having the opposite phase to the unnecessary signal, and the potential of the signal line R (see FIG. 7) is measured each time. Then, in the case where the period t1 is a certain period, the timing chart shown in FIG. 12 is obtained. In FIG. 12, the vertical axis represents voltage (V), and the horizontal axis represents time.
(μsec).

Accordingly, in the timing chart (see FIG. 13) in the case where the drive signal is applied to the piezoelectric element of the ultrasonic vibrator and the signal having the opposite phase to the unnecessary signal is not applied (see FIG. 13), the unnecessary signal is applied after the drive signal is applied. However, when a signal having a phase opposite to that of the unnecessary signal is given, the unnecessary signal is suppressed and almost disappeared as shown in FIG.

As a result, after a drive signal is applied to the piezoelectric element of the ultrasonic transducer, a signal having an opposite phase to the unnecessary signal is applied for a period t1.
It was found that unnecessary vibration of the piezoelectric element was suppressed by giving the above-mentioned fixed period. In view of the foregoing, the present invention provides a sound wave transmitting / receiving apparatus and a sound wave transmitting / receiving method that suppress unnecessary vibration without adding an extra member to a piezoelectric element employed in a sound wave vibrator. The purpose is to provide.

[0013]

In order to achieve the above object, according to the first aspect of the present invention, after the output of the drive signal to the piezoelectric element is stopped, a suppression signal for suppressing unnecessary vibration of the piezoelectric element is transmitted to the piezoelectric element. It is characterized by outputting. Accordingly, even when the acoustic transducer receives the reflected sound wave from the reflector and outputs the reception output from the piezoelectric element during the unnecessary vibration of the piezoelectric element, the suppression signal for suppressing the unnecessary vibration of the piezoelectric element is generated. Since this is output, unnecessary vibration from the piezoelectric element is suppressed. As a result, an accurate reception output can be obtained.

Further, in the invention according to claim 2,
A signal having a natural frequency of the acoustic transducer is output to the piezoelectric element as a suppression signal. As described above, even when the signal having the natural frequency of the acoustic transducer is output to the piezoelectric element as the suppression signal, unnecessary vibration of the piezoelectric element is suppressed, as in the first aspect of the present invention.

Further, according to the third aspect of the present invention,
Even if a signal having the opposite phase to the drive signal is output to the piezoelectric element as a suppression signal, unnecessary vibration of the piezoelectric element is suppressed as in the first aspect of the present invention. Further, in the invention according to claim 4, after the drive signal output means stops outputting the drive signal to the piezoelectric element, the suppression signal output means (6) for outputting a suppression signal for suppressing unnecessary vibration of the piezoelectric element to the piezoelectric element.
0, 70, 90, 100, 140).

Thus, even if the acoustic transducer receives the reflected acoustic wave from the reflector and outputs the received output from the piezoelectric element during the unnecessary vibration of the piezoelectric element, the suppression signal output means can output the signal from the piezoelectric element. Since the suppression signal for suppressing unnecessary vibration of the piezoelectric element is output to the piezoelectric element, unnecessary vibration of the piezoelectric element is suppressed. As a result, an accurate reception output can be obtained. Claim 5
In the invention described in (1), the suppression signal output means outputs a signal having a natural frequency of the acoustic transducer as a suppression signal to the piezoelectric element.

As described above, the suppression signal output means outputs the signal having the natural frequency of the sound wave transducer to the piezoelectric element as a suppression signal. Is suppressed. Furthermore, according to the invention described in claim 6, even if the suppression signal output means outputs a signal having the opposite phase to the drive signal to the piezoelectric element as the suppression signal, Unwanted vibration of the piezoelectric element is suppressed.

In the first to sixth aspects of the present invention, the sound wave may be an audible sound wave or an ultrasonic wave.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 shows a first embodiment of an ultrasonic propagation time measuring apparatus according to the present invention. This measuring device detects the physical properties of the measurement object (gasoline) existing between the ultrasonic vibrator 10 and the reflection plate S in the fuel tank of the vehicle so that the ultrasonic wave passing through the measurement object can be measured. It measures the propagation time.

The ultrasonic transducer 10 transmits an ultrasonic wave from the horn 11 to the reflection plate S through the object to be measured. The ultrasonic vibrator 10 receives the ultrasonic wave reflected by the reflection plate S through the measurement object by the horn 11 and generates a reception signal from the piezoelectric element 12. The measuring device of the propagation time is a microcomputer 2
0, frequency generator 30, counter circuit 40, gate circuit 50, frequency generator 60, inverting circuit 70, timer circuit 8
0, a gate circuit 90, a drive circuit 100, and an analog switch 110.

The microcomputer 20 executes the computer program according to the flowchart shown in FIG. 2, and performs an arithmetic process for measuring the propagation time of the ultrasonic wave passing through the measurement object during the execution of the computer program. . The frequency generator 30 is reset in response to a measurement start signal from the microcomputer 20, and sequentially generates a frequency signal having a frequency F1 in a pulse shape.

The counter circuit 40 is reset in response to a measurement start signal from the microcomputer 20.
The counting operation of the wave number of the frequency signal from the frequency generator 30 is started. The counter circuit 40 outputs an end signal to the gate circuit 50, the frequency generator 60, and the timer circuit 80 after counting a predetermined number of waves of the frequency signal (for example, after detecting the falling timing of the eighth wave). .

The gate circuit 50 connects between the frequency generator 30 and the drive circuit 100 until the end signal from the counter circuit 40 is received. Frequency generator 30 and drive circuit 7
Cut off between 0. As a result, the gate circuit 50
Only before receiving the end signal, the frequency generator 30
Is output to the drive circuit 100.

The frequency generator 60 is reset in response to an end signal from the counter circuit 40, and sequentially generates a frequency signal having a frequency F2 and starting from a phase of zero in a pulse shape. The frequency F2 corresponds to the ultrasonic transducer 1
The frequency of the unnecessary signal by the piezoelectric element 12 of 0, that is, the natural frequency of the ultrasonic transducer 10 is the same. Inverting circuit 70
Receives the frequency signal from the frequency generator 60 and converts the inverted signal (hereinafter referred to as the inverted frequency signal) of the gate circuit 9
Output to 0.

The timer circuit 80 receives the end signal from the counter circuit 40, outputs a short-circuit signal to the gate circuit 90, and starts the timer operation. This timer circuit 8
0 outputs a cutoff signal to the gate circuit 90 and outputs a switching signal to the analog switch circuit 100 after the measurement of the specified period. Note that the specified period corresponds to a certain period as the above-described period t1 (see FIG. 8).

The gate circuit 90 short-circuits the inverting circuit 70 and the driving circuit 100 only during the above-mentioned specified period from when the short-circuit signal is received from the timer circuit 80 to when the cut-off signal is received. As a result, the gate circuit 90 outputs the inverted frequency signal from the inverting circuit 80 to the driving circuit 100 only during the specified period. The drive circuit 100 is a voltage amplifying circuit, and amplifies the voltage of the frequency signal (the portion from the first wave to the fall of the eighth wave) from the gate circuit 50, and amplifies the voltage amplified signal through the analog switch 70 to the ultrasonic transducer 1
0 is applied to the piezoelectric element 12. This means that the piezoelectric element 12 of the ultrasonic vibrator 10 vibrates based on the voltage amplification signal and transmits the ultrasonic wave of the frequency F1 from the horn 11. Hereinafter, the voltage amplification signal is referred to as a drive signal.

The drive circuit 100 amplifies the voltage based on the inverted frequency signal from the inverting circuit 90, and amplifies the voltage amplified signal through the analog switch 70.
2 Incidentally, the voltage amplified signal is a signal based on the inverted frequency signal obtained by inverting the frequency signal (having the frequency F2 and starting from the state of zero phase) from the frequency generator 60 as described above. is there.
At the same time, the voltage amplification signal is added to the falling time of the eighth wave of the drive signal as described later,
0 is added.

Thus, the amplified voltage signal is applied to the piezoelectric element 12 of the ultrasonic transducer 10 as a signal having a phase opposite to that of the unnecessary signal. The amplified voltage signal plays a role of suppressing unnecessary vibration of the piezoelectric element 12. Less than,
The voltage amplification signal based on the inverted frequency signal is called a suppression signal. The analog switch 110 short-circuits the drive circuit 100 and the ultrasonic vibrator 10 and receives the ultrasonic vibrator 1 before receiving the switching signal from the timer circuit 80.
0 and the amplifier circuit 120 are shut off. On the other hand, after receiving the switching signal from the timer circuit 80, the analog switch 110 cuts off the connection between the drive circuit 100 and the ultrasonic vibrator 10 and short-circuits the ultrasonic vibrator 10 and the amplifier circuit 120. I do.

The amplifier circuit 120 receives the signal from the piezoelectric element 12 of the ultrasonic transducer 10 through the analog switch 110, amplifies the signal, and generates an amplified signal. Further, the binarization circuit 130 binarizes the amplified signal from the amplifier circuit 130 with reference to a predetermined threshold and outputs the binarized signal to the microcomputer 20 as input data. In the first embodiment configured as described above, the microcomputer 20
Starts execution of the computer program according to the flowchart of FIG.

In step 200, the count result of the internal counter CO in the microcomputer 20 is cleared. Next, at step 210, the measurement start signal from the microcomputer 20 is output to both the frequency generator 30 and the counter circuit 40. Accordingly, in step 220, the internal counter CO starts its counter operation at the measurement frequency F3.

Upon receiving the measurement start signal, the frequency generator 30 starts outputting a frequency signal having the frequency F1. Then, the gate circuit 50 outputs the frequency signal from the frequency generator 30 to the drive circuit 100.
Accordingly, the drive circuit 100 outputs a drive signal to the ultrasonic transducer 10 through the analog switch 110 in response to the frequency signal.

Therefore, the ultrasonic transducer 10 transmits an ultrasonic wave of the frequency F1 to the reflection plate S through the object to be measured in response to the drive signal. Also, the counter circuit 40
Is reset in response to the measurement start signal, and the counting operation of the wave number of the frequency signal from the frequency generator 30 is started. Then, the counter circuit 40 outputs an end signal to each of the gate circuit 50, the frequency generator 60, and the timer circuit 80 after counting eight wave numbers of the frequency signal (after detecting the falling edge of the eighth wave). I do.

Then, the gate circuit 50 cuts off the connection between the frequency generator 30 and the drive circuit 100 in response to the end signal. As a result, the gate circuit 50
The output of the frequency signal from the frequency generator 30 to 0 is stopped. In response, the ultrasonic transducer 10 stops transmitting the ultrasonic wave in response to the drive signal. Then, the timer circuit 80 receives the end signal from the counter circuit 40, outputs a short-circuit signal to the gate circuit 90, and starts the timer operation.

Next, the gate circuit 90 receives the short-circuit signal and short-circuits the inverter circuit 70 and the drive circuit 100. Thus, the frequency generator 60 has the counter circuit 4
The reset processing is performed in response to the end signal from 0, and the output of the frequency signal having the frequency F2 to the inverting circuit 70 is started.

Then, the inverting circuit 70 controls the frequency generator 6
Upon receiving the frequency signal from 0, it outputs an inverted frequency signal to the gate circuit 90. Then, the gate circuit 90 outputs the inverted frequency signal to the drive circuit 100. Accordingly, the driving circuit 100 responds to the frequency signal,
The suppression signal is output to the ultrasonic transducer 10 through the analog switch 110.

The timer circuit 80 outputs a cutoff signal to the gate circuit 90 and outputs a switching signal to the analog switch 110 after the measurement of the specified period. Therefore, the gate circuit 90 receives the cutoff signal from the timer circuit 80 and cuts off between the inverting circuit 70 and the drive circuit 100. As a result, the gate circuit 90 stops outputting the inverted frequency signal to the drive circuit 100.

The analog switch 110 cuts off the connection between the drive circuit 100 and the ultrasonic vibrator 10 in response to the switching signal from the timer circuit 80, and connects between the ultrasonic vibrator 10 and the amplifier circuit 120. Short circuit. Thereafter, when the reflected ultrasonic wave reflected by the reflection plate S passes through the measurement target and enters the horn 11 of the ultrasonic vibrator 10, the piezoelectric element 1
2 generates a received signal.

Then, the amplifier 120 receives the received signal and generates an amplified signal. Next, the binarization circuit 13
A value of 0 binarizes the amplitude of the amplified signal from the amplifier 120 with reference to a predetermined threshold to generate a binarized signal. Then, in step 230, the second
When the value signal is received as input data, it is determined as YES. In response, the measurement operation of the internal counter CO of the microcomputer 20 ends.

Then, in step 240, the propagation time T of the ultrasonic wave in the object to be measured is calculated based on the equation (1) based on both the measurement result of the internal counter CO and the measurement frequency F3.

[0040]

## EQU1 ## Propagation time T = (result of counting by internal counter CO) / (counting frequency F3) As described above, the output of the frequency signal from frequency generator 30 to drive circuit 100 is stopped by gate circuit 50. After receiving the short-circuit signal, the gate circuit 90 short-circuits the inversion circuit 70 and the drive circuit 100, while receiving the cut-off signal, the gate circuit 90 and the drive circuit 1
Cut off between 00 and 00.

Therefore, the gate circuit 90 outputs the inverted frequency signal from the inverting circuit 70 to the drive circuit 10 during the specified period from when the short circuit signal is received to when the cutoff signal is received.
0 will be output. Therefore, the driving circuit 100
After stopping the application of the frequency signal by the gate circuit 50,
In the specified period, the suppression signal based on the inverted frequency signal from the gate circuit 90 is output to the piezoelectric element 12 of the ultrasonic transducer 10 through the analog switch 110. Therefore, unnecessary vibration in the piezoelectric element 12 of the ultrasonic element 10 and thus unnecessary signal are suppressed.

Accordingly, since the measuring distance H (see FIG. 7) is short, the ultrasonic vibrator 10 receives the reflected sound wave from the reflector S while the unnecessary signal of the piezoelectric element 12 is being generated, and Even if the received signal is output from the drive signal 12, the suppression signal is output from the drive circuit 110 to the piezoelectric element 12 through the analog switch 110, so that unnecessary vibration of the piezoelectric element 12 and thus unnecessary signal are suppressed.

Therefore, a highly accurate received signal from the piezoelectric element 12 can be obtained. With this, a highly accurate amplified signal from the amplifier circuit 120 and a highly accurate binary signal from the binarization circuit 130 are obtained. As a result, the propagation time is accurately calculated by the microcomputer 20. (Second Embodiment) FIG. 3 shows a second embodiment of the present invention.

In the second embodiment, an ultrasonic oscillator 10a is used instead of the ultrasonic oscillator 10 described in the first embodiment.
Has been adopted. The piezoelectric element 12a of the ultrasonic transducer 10a is connected to the drive circuit 100 described in the first embodiment.
Unnecessary vibration is performed at a frequency F4 that is close to the frequency of the drive signal. In response, the piezoelectric element 12a has the frequency F4
Is generated.

The timer circuit 80 according to the second embodiment measures the specified period different from the specified period described in the first embodiment, and then controls the gate circuit 90 similarly to the first embodiment. It outputs a cutoff signal and outputs a switching signal to the analog switch circuit 110. In the second embodiment, the frequency generator 6 described in the first embodiment is used.
An inverting circuit 140 is employed in place of the 0 and the inverting circuit 70. The inverting circuit 140 receives the frequency signal from the frequency generator 30 described in the first embodiment and outputs an inverted frequency signal to the gate circuit 90.

In substantially the same manner as in the first embodiment, the gate circuit 90 operates in the inversion circuit 1 during the specified period from when the short circuit signal is received from the timer circuit 80 to when the cutoff signal is received.
The inversion frequency signal from 40 is output to the drive circuit 100. The drive circuit 100 applies the inversion drive signal to the piezoelectric element 12a of the ultrasonic transducer 10a via the analog switch 110 in response to the inversion frequency signal in substantially the same manner as in the first embodiment. The inversion drive signal plays a role of suppressing unnecessary vibration of the piezoelectric element 12a substantially in the same manner as the suppression signal described in the first embodiment. Other configurations are substantially the same as those of the first embodiment.

In the second embodiment configured as above, after the gate circuit 50 stops outputting the frequency signal from the frequency generator 30 to the drive circuit 100, the gate circuit 90 outputs the signal from the timer circuit 80. Upon receiving the short-circuit signal, the inverter circuit 140 and the drive circuit 100 are short-circuited. Therefore, the gate circuit 90 outputs the inverted frequency signal from the frequency generator 30 to the drive circuit 100. Accordingly, the drive circuit 100 provides the inverted drive signal to the piezoelectric element 12a of the ultrasonic transducer 10a through the analog switch 110 in response to the inverted frequency signal.

Thereafter, the timer circuit 60 outputs a cutoff signal to the gate circuit 140 after the measurement of the specified period. However, the specified period (see reference numeral t2 in FIG. 4) in the second embodiment is substantially the same as the specified period in the first embodiment, after the drive signal is applied to the piezoelectric element 10a.
This is a period during which the inversion drive signal is applied, and is determined in advance by experiments. Further, the specified period is not an integral multiple of the period of the inversion drive signal (see FIG. 4).

Thus, the gate circuit 90 cuts off between the inverting circuit 140 and the drive circuit 100 in response to the cutoff signal. Therefore, the gate circuit 90 includes the driving circuit 100
The output of the inverted frequency signal to is stopped. Other operations are substantially the same as those of the first embodiment. As described above, after the driving circuit 100 stops applying the frequency signal by the gate circuit 50, the driving circuit 100
The inversion drive signal based on the inversion frequency signal from the gate circuit 90 is passed through the analog switch 110 to the ultrasonic vibrator 1.
0a is applied to the piezoelectric element 12a.

In this case, after the drive signal is applied to the piezoelectric element 12a, unnecessary signals of the piezoelectric element 12a are suppressed as compared with the case where the inversion drive signal is not applied. For example, as shown in FIGS. 5 and 6, the unnecessary signal may be suppressed both in a period before the reception of the reception signal by the piezoelectric element 12a and in a rear period t3 after the reception of the reception signal. I understand.

As described above, suppression of the unnecessary signal by the piezoelectric element 12a means that unnecessary vibration of the piezoelectric element 12a is suppressed. Therefore, according to the second embodiment, when the frequency of the unnecessary vibration of the piezoelectric element 12a is close to the frequency of the drive signal, the inverted drive signal is used instead of the suppression signal described in the first embodiment. By doing so, substantially the same effects as in the first embodiment can be obtained.

According to the second embodiment, as described above, the inverted drive signal is employed instead of the suppression signal. The inverted drive signal is generated based on the frequency signal from the frequency transmitter 30 for the drive signal as described above. Therefore, since there is no need to provide a frequency oscillator for the inversion drive signal, the electric circuit configuration of the propagation time measuring device can be simplified as compared with the first embodiment.

In the second embodiment, the piezoelectric element 12
The case where the drive signal of the piezoelectric element 12a is close to the frequency of the unnecessary vibration of the piezoelectric element 12a has been described. However, even when the drive signal of the piezoelectric element 12a is the same as the frequency of the unnecessary vibration of the piezoelectric element 12a, Since there is no need to provide a frequency transmitter for signals, the same effects as in the second embodiment can be obtained.

In carrying out the present invention, the propagation time in the object to be measured may be measured by using various sound waves such as audible sound waves without being limited to the ultrasonic waves. An effect can be obtained. Further, in implementing the present invention, each step in the flowchart of each of the above embodiments may be executed by a hardware logic configuration as a function executing unit.

Further, in the practice of the present invention, the ultrasonic transducers 10 and 10a employ a piezoelectric element as the ultrasonic transducers 10 and 10a, regardless of whether the object to be measured is a liquid such as gasoline or water or a gas (for example, the atmosphere). If it is a vibrator, various kinds of sound wave vibrators such as a bimorph ultrasonic vibrator and a PZT ultrasonic vibrator may be employed. In implementing the present invention, for example, a conner sonar that uses a reflected ultrasonic wave of an ultrasonic wave transmitted from an ultrasonic vibrator provided in a part of a vehicle to know an obstacle around the vehicle, Others
The present invention may be applied to an apparatus using reflected ultrasonic waves transmitted from an ultrasonic transducer.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the microcomputer of FIG.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

FIG. 4 is a timing chart showing a drive signal and an inverted drive signal in the second embodiment.

FIG. 5 shows a result of measuring a potential of a signal line between the ultrasonic transducer and a propagation time measuring device when an inversion drive signal is applied to the piezoelectric element of the ultrasonic transducer according to the second embodiment. It is a timing chart shown.

FIG. 6 is a timing chart showing a result of measuring a potential of a signal line between the ultrasonic vibrator and a propagation time measuring device when an inversion drive signal is not applied to a piezoelectric element of the ultrasonic vibrator.

FIG. 7 is a block diagram showing an apparatus for measuring a propagation time and an ultrasonic transducer.

FIG. 8 is a cross-sectional view showing an ultrasonic transducer.

9 is a timing chart showing a result of measuring a potential of a signal line between the propagation time measuring device shown in FIG. 7 and the ultrasonic transducer.

FIG. 10 is a sectional view showing an ultrasonic transducer.

FIG. 11 is a timing chart showing signals of opposite phases to the drive signal and the unnecessary signal.

FIG. 12 is a timing chart showing a case where a signal having a phase opposite to that of an unnecessary signal is applied to a piezoelectric element of an ultrasonic transducer.

FIG. 13 is a timing chart showing a case where a signal having a phase opposite to that of an unnecessary signal is not applied to the piezoelectric element of the ultrasonic transducer.

[Explanation of symbols]

Reference numeral 20: microcomputer, 30, 60: frequency generator, 50, 90: gate circuit, 70, 140: inverting circuit, 100: driving circuit.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yutaka Suzuki 14 Iwatani, Shimowakaku-cho, Nishio-shi, Aichi Prefecture Inside the Japan Automobile Parts Research Institute Co., Ltd. (72) Inventor Toshimitsu Takahashi 1 Toyota Town, Toyota City, Aichi Prefecture F-term (reference) 2G047 AA01 BA02 BC02 CA01 GB11 GB35 GF11 5J083 AA02 AB20 AC19 AD08 AD30 AE10 AF01 BA01 BE30 BE33 CA15 CB01 CC01 EA05 EA10

Claims (6)

[Claims] 1. A piezoelectric element built in a sound wave vibrator is vibrated by a drive signal to transmit a sound wave from the sound wave vibrator, and a reflected sound wave of the transmitted sound wave is received by the sound wave vibrator and the piezoelectric wave is received. A sound wave transmitting / receiving method for generating a reception output from an element, comprising: after stopping output of the drive signal to the piezoelectric element, outputting a suppression signal to suppress unnecessary vibration of the piezoelectric element to the piezoelectric element. . 2. The sound wave transmitting / receiving method according to claim 1, wherein a signal having a natural frequency of the sound wave oscillator is output to the piezoelectric element as the suppression signal. 3. The sound wave transmitting / receiving method according to claim 1, wherein a signal having an opposite phase to the drive signal is output to the piezoelectric element as the suppression signal. 4. A piezoelectric element (1) having a built-in piezoelectric element.
A sound wave is transmitted based on the vibration of 2, 2a), a sound wave vibrator (10, 10a) that receives a reflected sound wave of the transmitted sound wave and generates a reception output from the piezoelectric element, and vibrates the piezoelectric element. And a drive signal output means (30, 50) for outputting a drive signal to the piezoelectric element. After the drive signal output means stops outputting the drive signal to the piezoelectric element, A sound wave transmitting / receiving device comprising a suppression signal output means (60, 70, 90, 100, 140) for outputting a suppression signal for suppressing unnecessary vibration to the piezoelectric element. 5. The sound wave transmitting / receiving device according to claim 4, wherein the suppression signal output unit outputs a signal having a natural frequency of the sound wave transducer to the piezoelectric element as the suppression signal. 6. The sound wave transmitting / receiving apparatus according to claim 4, wherein the suppression signal output unit outputs a signal having a phase opposite to the drive signal to the piezoelectric element as the suppression signal.