|Publication number||US7622849 B2|
|Application number||US 11/712,511|
|Publication date||Nov 24, 2009|
|Filing date||Mar 1, 2007|
|Priority date||Mar 6, 2006|
|Also published as||CN101035394A, CN101035394B, DE102007008560A1, US20070204697|
|Publication number||11712511, 712511, US 7622849 B2, US 7622849B2, US-B2-7622849, US7622849 B2, US7622849B2|
|Inventors||Kazuaki Watanabe, Takahiko Yoshida, Makiko Sugiura, Noboru Endoh, Yasuyuki Okuda|
|Original Assignee||Denso Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (10), Referenced by (1), Classifications (5), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is based upon and claims benefit of priority of Japanese Patent Application No. 2006-59413 filed on Mar. 6, 2006, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an ultrasonic sensor having an ultrasonic vibrator mounted on a substrate.
2. Description of Related Art
An ultrasonic sensor having a piezoelectric vibrator mounted on a substrate made of such as a metallic material or a resin material has been known hitherto. The ultrasonic sensor is mounted on an automotive vehicle, and ultrasonic waves are emitted from the ultrasonic sensor toward objects in front of or around the vehicle. The objects are detected based on the ultrasonic waves reflected by the objects and received by the ultrasonic sensor. A distance to the objects and two-dimensional or three-dimensional shapes of the objects are detected in this manner.
An example of this type of ultrasonic sensor is disclosed in JP-A-2002-58097. A relevant portion of this ultrasonic sensor is shown in
Since the ultrasonic sensor is mounted on a vehicle at a position visible from outside, it is required to make it as small as possible not to destroy an ornamental design of the vehicle. However, there has been a problem that a resonant frequency of the substrate 112 becomes higher as its size becomes smaller. This results in increase in attenuation of the ultrasonic waves and worsening in directivity. It is possible to lower the resonant frequency by reducing rigidity of the substrate. For this purpose, it is conceivable to make the substrate thinner or to use a material having a lower Young's modulus. However, a strength of the substrate against an impact force is considerably reduced by reducing the rigidity of the substrate.
The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide a compact ultrasonic sensor, in which the resonant frequency is lowered while maintaining a mechanical strength against an impact force.
The ultrasonic sensor according to the present invention includes a substrate made of a material such as resin and a vibrator composed of a piezoelectric element mounted on the substrate. The ultrasonic sensor may be mounted on an automotive vehicle to detect objects positioned in front of or around the vehicle. The vibrator is vibrated by electrical signals fed thereto, and the vibrations of the vibrator are transferred to the substrate that transmits ultrasonic waves toward objects positioned in front of or around the vehicle. Ultrasonic waves reflected by the objects are received by the substrate and converted into electrical signals by the vibrator. A distance to an object from the vehicle, for example, is detected based on the reflected ultrasonic waves.
The vibrator is connected to a first surface of the substrate with adhesive, and grooves open to a second surface are formed in the substrate to reduce rigidity of the substrate. By reducing the rigidity of the substrate, its resonant frequency is lowered to a level that is desirable to obtain high directivity and sensitivity, without reducing a thickness of the substrate or enlarging its surface area. Since the thickness of the substrate is not reduced, mechanical strength of the substrate against an impact force is not reduced.
Dead-ended holes may be formed in place of or in addition to the grooves. The grooves may be formed on the first surface on which the vibrator is mounted. In this case, it is preferable not to form the grooves in an area on which the vibrator is connected in order to increase the connecting force of the vibrator to the substrate. The grooves may be formed on both surfaces. The grooves may be formed in a lattice arrangement so that the mechanical strength of the substrate becomes uniform in every direction. Through-holes may be formed in the substrate in place of or in addition to the grooves. Cutout portions may be additionally formed along side surfaces of the substrate to further reduce the rigidity of the substrate. The grooves may be filled with filler having rigidity lower than that of the substrate to prevent foreign particles from entering into the grooves.
According to the present invention, the resonant frequency of the substrate can be lowered to a desirable level without sacrificing the mechanical strength of the substrate and without enlarging a surface area of the substrate. Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiment described below with reference to the following drawings.
A preferred embodiment of the present invention will be described with reference to accompanying drawings. As shown in
The substrate 12 is made of a resin material such as engineering plastics and formed in a square plate having a thickness of 0.5 mm and a plane area of 3 mm×3 mm. The resin material can be easily shaped into the substrate 12 at a low cost by molding or machining. The ultrasonic vibrator 11 is connected to a center portion of a first surface 12 a of the substrate 12 with adhesive 13. The ultrasonic sensor 10 is fixed to a vehicle body member 20 at a predetermined position, so that the first surface 12 a of the substrate 12 faces the inside of the vehicle and the second surface 12 b faces the outside of the vehicle. The substrate 12 may be made of a material other than resin such as a semiconductor material or glass. In the case where the semiconductor material is used, other electronic elements may be formed on the substrate by using a known semiconductor manufacturing process.
The substrate is vibrated by the vibrator 11, and ultrasonic waves are transmitted from the substrate 12 toward objects to be detected. Ultrasonic waves reflected by the objects are received by the substrate 12. The objects in front of or around the vehicle are detected based on the reflected ultrasonic waves. The substrate 12 vibrates at a predetermined resonant frequency when the ultrasonic waves reflected by the objects are received. The vibrations of the substrate 12 are converted into electrical signals by the vibrator 11. The electrical signals are fed to an electronic component (not shown) connected to the vibrator 11 and then sent to an outside electronic control unit (ECU). For example, a distance from the vehicle to an object positioned in front of the vehicle is calculated based on a time difference or a phase difference between the transmitted waves and the reflected waves.
When the substrate 12 is made of a resin plate having a thickness of 0.5 mm, which is necessary to secure a sufficient mechanical strength against impact, a plane area of about 5 mm×5 mm is necessary to obtain a resonant frequency of around several-tens kHz. It is generally difficult to lower the resonant frequency without reducing the thickness of the substrate 12 or enlarging its surface area. It is possible, however, to lower the resonant frequency by reducing the rigidity of the substrate 12 because the resonant frequency is proportional to a square root of the rigidity. In the present invention, the rigidity of the substrate is reduced without changing its thickness and plane size in the following manner.
As shown in
Since the grooves 14 are made in a lattice arrangement to uniformly cover an entire first surface 12 a of the substrate 12, the mechanical strength against impact can be made uniform in every direction. The vibrations of the vibrator 11 become larger because the grooves 14 are also formed under the vibrator 11. Since no grooves are formed on the second surface 12 b, the ultrasonic waves are smoothly transmitted therefrom and received thereby without causing attenuation.
The embodiment shown in
Further, the embodiment shown in
In the ultrasonic sensor 10 described above, the resonant frequency of the substrate 12 is lowered by forming grooves 14 or holes 15 thereby to reduce the rigidity. Accordingly, the desirable resonant frequency, e.g., 60 kHz is obtained without enlarging the size of the ultrasonic sensor 10 while maintaining the mechanical strength against impact (i.e., without reducing the thickness). Therefore, the ultrasonic sensor 10 can be manufactured in a compact size at a low cost. In addition, the shape of the substrate 12 is not limited to a square shape, but it may be round, for example.
Some of variations of the embodiment described above are shown in
Variation 2 is shown in
Variation 3 is shown in
Variation 4 is shown in
Advantages attained in the present invention will be summarized below. The rigidity of the substrate can be reduced by forming the grooves 14 or holes 15 in the substrate 12 without reducing the thickness of the substrate. Therefore, the resonant frequency of the substrate 12 can be lowered to a desired level, without enlarging its plane size, while maintaining the mechanical strength of the substrate 12 against an impact force. The grooves 14 and/or the holes 15 are easily formed on the substrate 12, and the resonant frequency is lowered without using additional components.
The rigidity of the substrate 12 can be made uniform in all directions by forming the grooves 14 in a lattice arrangement. The rigidity of the substrate 12 can be further reduced by forming cutouts 16 (as shown in
In the case where the grooves 14 are filled with the filler 18 having a low rigidity (as shown in
The present invention is not limited to the embodiment and its variations described above, but it may be variously modified. For example, the grooves or the holes may be formed in the vibrator 11 in addition to those formed in the substrate 12. The resonant frequency of the ultrasonic sensor 10 can be further reduced in this manner, and the output of the vibrator 11 can be increased by lowering the rigidity of the vibrator 11 in this manner.
While the present invention has been shown and described with reference to the foregoing preferred embodiment, it will be apparent to those skilled in the art that changes in form and detail may be made therein without departing from the scope of the invention as defined in the appended claims.
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|Citing Patent||Filing date||Publication date||Applicant||Title|
|US9089872||Mar 14, 2013||Jul 28, 2015||Seiko Epson Corporation||Ultrasonic transducer element chip, probe, electronic instrument, and ultrasonic diagnostic device|
|U.S. Classification||310/334, 310/327|
|Mar 1, 2007||AS||Assignment|
Owner name: DENSO CORPORATION, JAPAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WATANABE, KAZUAKI;YOSHIDA, TAKAHIKO;SUGIURA, MAKIKO;AND OTHERS;REEL/FRAME:019033/0063;SIGNING DATES FROM 20070108 TO 20070128
|Oct 9, 2007||AS||Assignment|
Owner name: DENSO CORPORATION, JAPAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WATANABE, KAZUAKI;YOSHIDA, TAKAHIKO;SUGIURA, MAKIKO;AND OTHERS;REEL/FRAME:019958/0915;SIGNING DATES FROM 20070119 TO 20070208
|Mar 8, 2013||FPAY||Fee payment|
Year of fee payment: 4