JP4131100B2 - Ultrasonic transducer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic transducer used in a detector that performs sensing using ultrasonic waves.
[0002]
[Prior art]
The piezoelectric ultrasonic transducer is filled in a vibration case having a space inside a bottomed cylindrical body, a piezoelectric vibration element attached to the bottom of the space, and a space inside the vibration case. And a lead wire connected to the piezoelectric vibration element. The ultrasonic detector using the ultrasonic transducer performs sensing using ultrasonic waves, intermittently transmits ultrasonic pulse waves from the ultrasonic transducer, and is surrounded by the ultrasonic transducer. Mainly used for vehicles that detect objects by receiving reflected waves from existing obstacles.
[0003]
The ultrasonic detector using the piezoelectric ultrasonic transducer as described above applies an ultrasonic pulse signal generated intermittently to the piezoelectric transducer of the ultrasonic transducer, and vibrates the vibration case. Send a pulse wave. Then, the reflected wave from the obstacle is received through the vibration case and the piezoelectric vibration element and amplified. If the reflected wave (reception pulse) is received within a time corresponding to a predetermined distance range, detection display is performed. An ultrasonic transducer is arranged at the rear or corner of the vehicle, monitors obstacles around the vehicle, and alerts the driver. Conventionally, an ultrasonic transducer using one piezoelectric vibration element. Was placed at each site. 4 and 5 show the obstacle horizontal detection areas 70a and 70b and the vertical detection area 70c when the ultrasonic transducers are disposed at positions 60a and 60b behind the vehicle 50, respectively.
[0004]
6 is a side sectional view of the first conventional ultrasonic detector, FIG. 7 is a top view, and FIG. 8 is an arrow view as seen from A of FIG. 6 (however, the electronic circuit 3, lead wires 4a and 4b, The ultrasonic transducer 101 includes a vibration case 1 ′, a piezoelectric vibration element 2, a buffer material 5, and lead wires 4 a and 4 b. . The vibration case 1 ′ having a cylindrical shape with a bottomed cylindrical shape has an inner cylindrical space portion 11 having a large-diameter cylindrical shape on the opening side, and the inner side of the vibration case 1 ′ is seen in a cross-sectional view perpendicular to the axial direction. It is formed in a bottomed cylindrical shape having a substantially rectangular shape, and the piezoelectric vibration element 2 is bonded to the inside of the bottom. Further, the space 11 is filled with the buffer material 5.
[0005]
The ultrasonic transducer 101 is mounted inside a bottomed cylindrical housing 8 ′ via a bottomed cylindrical holding rubber 9 ′ mounted so as to close the open end of the space portion 11. A cylindrical circuit case 10 ′ whose both ends are closed is mounted on the outer side of the bottom of “′, and the electronic circuit 3 is accommodated in the circuit case 10 ′.
[0006]
The piezoelectric vibration element 2 is made of, for example, PZT-based piezoelectric ceramics, has electrodes on both sides, connects the signal electrode (positive electrode) to one end of the lead wire 4a, and connects the ground electrode (negative electrode) to the vibration case 1 ′. The vibration case 1 'is connected to one end of the lead wire 4b. The other ends of the lead wires 4a and 4b are connected to the electronic circuit 3 through insertion holes formed on the bottom surfaces of the holding rubber 9 ', the housing 8', and the circuit case 10 '. The ultrasonic pulse signal is applied to the positive electrode of the piezoelectric vibration element 2 via the lead wire 4a and to the negative electrode via the lead wire 4b and the vibration case 1 ′. A signal received by the piezoelectric vibration element 2 is also transmitted to the electronic circuit 3 via the lead wire 4 a, the vibration case 1 ′, and the lead wire 4 b, and is amplified by the electronic circuit 3.
[0007]
Next, the operation of the ultrasonic detector of this conventional example will be described with reference to the waveform diagrams of FIGS. 9 (a), (b), and (c). First, the ultrasonic vibration signal is intermittently applied to the piezoelectric vibration element 2 by the electronic circuit 3 (FIG. 9A), and the ultrasonic vibration is transmitted by vibrating the bottom of the vibration case 1 ′. And the space part 11 inside vibration case 1 'is filled with the buffer material 5, and the buffer material 5 plays the role for converging the reverberation vibration generated after application of an ultrasonic pulse signal, On the basis of the detection operation principle, reverberation vibration remains even when the application is terminated by the applied ultrasonic pulse signal (FIG. 9B).
[0008]
Therefore, the reflected wave from the object and the reverberation vibration cannot be distinguished during the time t1 from the application of the ultrasonic pulse signal to the completion of the reverberation vibration. That is, the reflected wave 80 from the object existing at a distance away from the ultrasonic transducer can be distinguished from the reverberation vibration waveform, and the presence of the object can be determined, but the reflected wave from the object present at a short distance from the ultrasonic transducer. No. 81 has a problem that it cannot be distinguished from the reverberation vibration waveform and the existence of the object cannot be determined (FIG. 9C).
[0009]
Therefore, as a means for overcoming the above problems, an ultrasonic detector using two piezoelectric vibration elements, that is, using two ultrasonic transducers has been proposed. FIG. 10 is a side sectional view of the ultrasonic detector according to the second conventional example, and FIG. 11 is a top view, respectively. Two ultrasonic transducers 101a and 101b (the ultrasonic detector described in the first conventional example) The same configuration as that of the acoustic wave transducer 101 is provided. The ultrasonic transducers 101a and 101b are provided with a bottomed cylindrical holding rubber 9 'so as to close the open end of the space 11, and a housing 8''which is a column having a substantially oval cross-sectional shape. The cylindrical concave portions formed in the axial direction are juxtaposed in the long side direction, and the ultrasonic transducers 101a and 101b are mounted in the concave portions via the holding rubber 9 '. A cylindrical circuit case 10 '"having a substantially oval cross-sectional shape and closed at both ends is mounted on the outside of the bottom of the housing 8"'. The electronic circuit 3 is accommodated in the circuit case 10 "'. Yes. Then, a total of four lead wires, that is, two lead wires 4 a connecting each piezoelectric vibration element 2 and the electronic circuit 3 and two lead wires 4 b connecting each vibration case 1 ′ and the electronic circuit 3 are connected. Prepare.
[0010]
This ultrasonic detector intermittently applies an ultrasonic pulse signal to the piezoelectric vibration element 2 of the ultrasonic transducer 101a to transmit an ultrasonic pulse wave, and receives an reflected wave from an object by the ultrasonic transducer 101b. Therefore, the operation of the ultrasonic detector of this conventional example will be described with reference to the waveform diagrams of FIGS. 12 (a), (b), and (c). First, even if an ultrasonic pulse signal is intermittently applied to the piezoelectric vibration element 2 of the ultrasonic transducer 101a that performs transmission and the bottom of the vibration case 1 ′ is vibrated to transmit an ultrasonic pulse wave (FIG. 12 ( a)) In the ultrasonic transducer 101b that performs reception, since no ultrasonic pulse signal is applied, reverberation vibration after application occurs during time t2 (t2 <t1), but is completed immediately (FIG. 12 ( b)) The ultrasonic transducer 101b not only reflects the reflected wave 82 from the object existing at a distance away from the ultrasonic transducer, but also the reflected wave 83 from the object present at a short distance from the ultrasonic transducer. Thus, it can be distinguished from the reverberation vibration waveform, and the presence of the object can be determined (FIG. 12C).
[0011]
However, in this second conventional example, since a plurality of (two) piezoelectric vibration elements, that is, a plurality of ultrasonic transducers, are required in one ultrasonic detector, the cost is greatly increased. There is a fundamental problem that it will end up, and it has not been put into practical use.
[0012]
As a third conventional example, in recent years, by applying the principle of triangulation, two piezoelectric vibration elements, that is, two ultrasonic transducers, are provided, and one ultrasonic transducer is intermittently superposed. Ultrasonic detection that detects the distance and direction (angle) of an object by applying an ultrasonic pulse signal and transmitting an ultrasonic pulse wave and receiving the reflected wave from the object with both ultrasonic transducers Devices have been devised and disclosed in Japanese Patent Application No. 10-365420 and Japanese Patent Application No. 11-145744.
[0013]
The operation of the conventional ultrasonic detector will be described with reference to the detection principle diagram of FIG. 13 and the waveform diagrams of FIGS. 14 (a), 14 (b), and 14 (c). The ultrasonic detector includes two ultrasonic transducers 101c and 101d, and the object 51 is present at a distance L away. First, when an ultrasonic pulse signal is intermittently applied to the transmitting ultrasonic transducer 101c and an ultrasonic pulse wave 84 is transmitted (FIG. 14A), the ultrasonic transducer 101c reflects after time t3 seconds. The ultrasonic transducer 101d receives the wave 85 (FIG. 14B), and receives the reflected wave 86 after time t4 seconds after the ultrasonic transducer 101c receives the reflected wave 85 (FIG. 14C). )).
[0014]
Then, the distance L between the objects 51 is detected from the time t3 until the reflected wave 85 returns, and the object 51 exists from the time difference t4 between the reflected waves 85 and 86 received by the ultrasonic transducers 101c and 101d. The direction (angle) θ to be detected can be detected. That is, as shown in FIG. 15, when the ultrasonic transducer of this conventional example is arranged at positions 60c and 60d behind the vehicle 50, the position (distance) of the object 51 existing in the obstacle detection areas 70d and 70e. Direction), and can predict whether there is a risk of colliding with the object 51, or whether it can be avoided, and ultrasonic conversion that is more useful than previous ultrasonic transducers. Can be realized.
[0015]
However, this third conventional example also requires a plurality of (two) piezoelectric vibration elements, that is, a plurality of ultrasonic transducers, in one ultrasonic detector, so that the cost is greatly increased. There is a fundamental problem.
[0016]
[Problems to be solved by the invention]
The present invention has been made in view of the above-mentioned reasons, and an object thereof is to provide an inexpensive ultrasonic transducer that can improve short-range performance or can be employed in a triangulation ultrasonic detector. It is in.
[0017]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a vibration case having a plurality of cylindrical space portions having one end opened and the other end closed, and a continuous space portion continuously connecting the plurality of cylindrical space portions, and the plurality of tubes. A plurality of piezoelectric vibration elements attached to the bottom of each other end of the space and connecting each ground electrode to the vibration case, and one end of each signal electrode paired with the ground electrode of the plurality of piezoelectric vibration elements. A plurality of first lead wires that are connected to each other and lead out the vibration case to the vibration case; a second lead wire that connects one end to the vibration case and leads the other end to the vibration case; A plurality of cylindrical space portions and a buffer material filled in the continuous space portion at the same time , and the one second lead wire is connected to the ground of the plurality of piezoelectric vibration elements having the vibration case as a common potential. It is a line .
[0018]
According to a second aspect of the present invention, in the first aspect of the invention, the cylindrical space portion of the vibration case has a cross-sectional view shape perpendicular to the axial direction having different dimensions in the longitudinal direction and the short direction. And
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0020]
1 is a side sectional view of an ultrasonic detector using the ultrasonic transducer of the present embodiment, FIG. 2 is a top view, and FIG. 3 is an arrow view as viewed from A of FIG. The ultrasonic transducer 100 includes a vibration case 1, two piezoelectric vibration elements 2, lead wires 4a and 4b, and a buffer material 5. It consists of and.
[0021]
The vibration case 1 having the appearance of a column having a substantially oval cross-sectional view perpendicular to the axial direction includes a space portion having one end opened, and one end side is formed from a space in a large-diameter substantially oval cylindrical shape. The cylindrical space portion 6 having one end opened at the bottom of the space in the substantially oval cylindrical shape, closed at the other end, and substantially rectangular in cross-sectional view is formed in the major axis direction of the ellipse. The piezoelectric vibration elements 2 are bonded to each other inside the bottom portion of each cylindrical space portion 6. The space in the substantially oval cylindrical shape becomes a continuous space portion 7 that connects the spaces of the two cylindrical space portions 6 in the vibration case 1 to each other, and the two cylindrical space portions 6 are the continuous space portions 7. It is a continuous space through. Furthermore, although the cylindrical space part 6 and the continuous space part 7 are filled with the buffer material 5, the two cylindrical space parts 6 and the continuous space part 7 are continuous spaces, and at the same time, the buffer material 5 Since it is filled, the work for this filling may be performed once.
[0022]
The ultrasonic transducer 100 has a substantially cross-sectional view shape through the holding rubber 9 that is a bottomed cylindrical shape having a substantially oval cross-sectional view that is mounted so as to close the open end of the continuous space portion 7. A cylindrical circuit case 10 having a substantially elliptical shape with both ends closed is mounted on the outside of the bottom of the housing 8, and an electronic circuit is mounted in the circuit case 10. The circuit 3 is accommodated.
[0023]
The piezoelectric vibration element 2 is made of, for example, PZT-based piezoelectric ceramic, has electrodes on both sides, connects each signal electrode (positive electrode) to each end of the lead wire 4a, and vibrates each ground electrode (negative electrode). The vibration case 1 is bonded to the case 1 and connected to one end of one lead wire 4b. That is, the lead wires 4a are drawn out from the positive electrodes of the two piezoelectric vibrating elements 2, but only one lead wire 4b needs to be drawn out from the vibrating case 1 having a common potential (ground). The other ends of the two lead wires 4a and one lead wire 4b are connected to the electronic circuit 3 through insertion holes formed on the bottom surfaces of the holding rubber 9, the housing 8, and the circuit case 10. The ultrasonic pulse signal from the electronic circuit 3 is applied to each positive electrode of the piezoelectric vibration element 2 via the lead wire 4 a and to each negative electrode via the lead wire 4 b and the vibration case 1. A signal received by the piezoelectric vibration element 2 is also transmitted to the electronic circuit 3 via the lead wire 4 a and the vibration case 1 and the lead wire 4 b and amplified by the electronic circuit 3.
[0024]
In the conventional ultrasonic detector using two ultrasonic transducers 101 (FIGS. 10 and 11), the material cost for two vibration cases 1 ′ is required. However, the ultrasonic transducer 100 according to this embodiment is used. The material cost of the vibration case 1 can be reduced to the cost of about 1.5 vibration cases 1 ′. Further, in this embodiment, the number of lead wires 4a and 4b can be reduced from a total of four to three compared to the conventional ultrasonic transducer 101 (FIGS. 10 and 11), and the filling time of the buffer material 5 can be reduced. The time can be reduced from two times to one time. Further, the time required for bonding the ultrasonic transducer 100, the housing 8, and the holding rubber 9 is reduced from the time required for bonding the conventional ultrasonic transducer 101: 1.5 to the time for bonding 1.5. Further, other processing time can be reduced from the time of processing the conventional ultrasonic transducer 101: 2 to the time of processing 1.5.
[0025]
Therefore, in order to improve the distance performance or to use the two piezoelectric vibrating elements 2 in order to employ the triangulation system that detects the distance and direction (angle) where the object exists, conventional ultrasonic detection Compared to the cost of two ultrasonic transducers 101, the ultrasonic transducer 100 of the present embodiment has 1.2 to 1.5 ultrasonic transducers 101. The cost can be reduced.
[0026]
In addition, the cross-sectional view perpendicular to the axial direction of each cylindrical space 6 is substantially rectangular, and has different dimensions in the longitudinal direction and the lateral direction. The acoustic pulse wave has different directivities, and wide directivity in the short direction (horizontal direction) and narrow directivity is realized in the long direction (vertical direction). Furthermore, the same effect as described above can be obtained even when the shape of the cylindrical space portion 6 in a cross-sectional view is not only a rectangular shape but also an oval shape.
[0027]
As for the operation of this embodiment, as in the second conventional example, an ultrasonic pulse signal is intermittently applied to one ultrasonic transducer 100 to transmit an ultrasonic pulse wave, and the other ultrasonic wave is transmitted. The transducer 100 receives the reflected wave from the object to improve short-range performance, or intermittently applies an ultrasonic pulse signal to one ultrasonic transducer 100 as in the third conventional example. Then, an ultrasonic pulse wave is transmitted, and a reflected wave from the object is received by both ultrasonic transducers 100, thereby adopting a triangulation system that detects the distance and direction (angle) where the object exists. be able to.
[0028]
【The invention's effect】
According to a first aspect of the present invention, there is provided a vibration case having a plurality of cylindrical space portions having one end opened and the other end closed, and a continuous space portion continuously connecting the plurality of cylindrical space portions, and the plurality of tubes. A plurality of piezoelectric vibration elements attached to the bottom of each other end of the space and connecting each ground electrode to the vibration case, and one end of each signal electrode paired with the ground electrode of the plurality of piezoelectric vibration elements. A plurality of first lead wires that are connected to each other and lead out the vibration case to the vibration case; a second lead wire that connects one end to the vibration case and leads the other end to the vibration case; A plurality of cylindrical space portions and a buffer material filled in the continuous space portion at the same time , and the one second lead wire is connected to the ground of the plurality of piezoelectric vibration elements having the vibration case as a common potential. since a line, and once the work for cushioning material filling, Lee Reduce the cost by reducing the number of wires to a total of three, improve the short-range performance using a plurality of piezoelectric vibration elements, and adopt an inexpensive ultrasonic transducer that can be used in the triangulation method There is an effect that it can be provided.
[0029]
According to a second aspect of the present invention, in the first aspect of the invention, the cylindrical space portion of the vibration case has a shape in which the cross-sectional view perpendicular to the axial direction has mutually different dimensions in the longitudinal direction and the lateral direction. There is an effect that the ultrasonic pulse wave can exhibit different directivities in the direction and the short direction.
[Brief description of the drawings]
FIG. 1 is a side sectional view showing an ultrasonic detector using an embodiment of the present invention.
FIG. 2 is a top view showing an ultrasonic detector using an embodiment of the present invention.
FIG. 3 is a partially omitted arrow view as viewed from FIG. 1A of the embodiment of the present invention.
FIG. 4 is a diagram illustrating a horizontal detection area of a first conventional example.
FIG. 5 is a diagram showing a vertical detection area of a first conventional example.
FIG. 6 is a side sectional view showing a first conventional ultrasonic detector.
FIG. 7 is a top view showing an ultrasonic detector of a first conventional example.
FIG. 8 is a partially omitted arrow view as viewed from A of FIG. 6 of the first conventional example.
FIGS. 9A, 9B and 9C are waveform diagrams for explaining the operation of the first conventional ultrasonic detector. FIGS.
FIG. 10 is a side sectional view showing an ultrasonic detector of a second conventional example.
FIG. 11 is a top view showing an ultrasonic detector of a second conventional example.
FIGS. 12A, 12B, and 12C are waveform diagrams for explaining the operation of the ultrasonic detector of the second conventional example.
FIG. 13 is a diagram illustrating a detection principle of an ultrasonic detector according to a third conventional example.
FIGS. 14A, 14B, and 14C are waveform diagrams for explaining the operation of the third conventional ultrasonic detector.
FIG. 15 is another diagram for explaining the operation of the third conventional ultrasonic detector.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vibration case 2 Piezoelectric vibration element 3 Electronic circuit 4a, 4b Lead wire 5 Buffer material 6 Cylindrical space part 7 Continuous space part

Claims (2)

A vibration case having a plurality of cylindrical space portions with one end opened and the other end closed, and a continuous space portion for continuously connecting the plurality of cylindrical space portions to each other, and each other end of the plurality of cylindrical space portions A plurality of piezoelectric vibration elements attached to the bottom, each ground electrode connected to the vibration case, and one end connected to each signal electrode paired with the ground electrode of the plurality of piezoelectric vibration elements, the other end of the A plurality of first lead wires led out of the vibration case, one second lead wire having one end connected to the vibration case and the other end led out of the vibration case, and the plurality of cylindrical spaces And the buffer material filled in the continuous space portion at the same time , and the one second lead wire is a ground wire of the plurality of piezoelectric vibration elements having the vibration case as a common potential. Ultrasonic transducer. 2. The ultrasonic transducer according to claim 1, wherein the cylindrical space portion of the vibration case has dimensions different from each other in a longitudinal direction and a lateral direction in a cross-sectional view perpendicular to the axial direction.

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