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DESCRIPTION JP2000023293

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DESCRIPTION JP2000023293
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic sensor used as a back sonar or corner sonar of an automobile.
[0002]
2. Description of the Related Art An ultrasonic sensor performs sensing using ultrasonic waves,
intermittently transmits an ultrasonic pulse signal from a piezoelectric vibration element, and
reflects from an obstacle present in the periphery. By detecting the presence of an obstacle by
receiving a wave with a piezoelectric vibration element, or calculating the elapsed time from
transmission to reception of an ultrasonic pulse signal with an external circuit, the distance to the
obstacle is measured. It is
[0003]
An ultrasonic sensor operating on the basis of such a principle is required to have a
characteristic capable of detecting a long distance and extracting a weak reflected wave as an
electrical signal without being buried in disturbance noise or the like. Ru.
For this purpose, it is necessary to adopt a structure that does not inhibit the vibration operation
of the vibration unit so that both the transmission output sound pressure and the reception
sensitivity characteristic of the ultrasonic sensor can be enhanced. Specifically, for the wiring
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directly connected to the piezoelectric vibrating element disposed in the vibrating portion, it is
widely and generally used to use a thin and soft one in particular.
[0004]
However, it is extremely difficult to stably connect and wire thin and soft wiring in the small case
of the ultrasonic sensor, which causes an increase in production cost, and the reliability of the
electrical connection is low and the characteristics of the sensor It was also the cause of the
destabilization of
[0005]
In order to overcome the problems described above, the applicant of the present application is a
structure of an ultrasonic sensor capable of obtaining stable electrical connection with good
workability without using thin and soft wiring in Japanese Patent Application No. 10-4882. Has
already been proposed.
Hereinafter, an ultrasonic sensor which is not a known technology but proposed by the present
applicant in Japanese Patent Application No. 10-4882 will be described based on FIG.
[0006]
As shown in the cross-sectional view of FIG. 3, the conventional ultrasonic sensor 110 has a
substantially cylindrical case main body 111 made of an insulating material and having a stepped
portion at one opening, and the steps of the case main body 111 , And a piezoelectric vibrating
element 113 joined to the inner side surface of the metal plate 112, and an input / output
member 114a. , 114b and a sound absorbing material 115 made of felt or the like.
[0007]
Electrodes are respectively formed on the front and back surfaces of the piezoelectric vibrating
element 113 (not shown), and the electrodes on the back surface are connected to the metal
plate 112 by a conductive adhesive or the like.
42The input / output members 114a and 114b made of nickel (iron-42% nickel alloy) or the like
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are integrally formed so as to be embedded in the case main body 111, and one of the input /
output members 114a is piezoelectric at one end The other input / output member 114 b is
connected to the metal plate 112 to be electrically connected to the electrode formed on the back
surface of the piezoelectric vibration element 113. The other end of each of the input / output
members 114 a and 114 b is led out of the case main body 111. Furthermore, the sound
absorbing material 115 is disposed in the case main body 111, and plays a role of absorbing a
reverberation wave when the ultrasonic sensor 110 emits an ultrasonic pulse signal.
[0008]
SUMMARY OF THE INVENTION In the conventional ultrasonic sensor, reverberation waves
remaining in the case of the ultrasonic sensor when the ultrasonic pulse signal is emitted are
absorbed, that is, the reverberation characteristics of the ultrasonic sensor. A sound absorbing
material was placed in the case body to improve the On the other hand, in order not to inhibit the
vibration of the metal plate as a vibrating portion when emitting an ultrasonic pulse signal, there
is a space on the inner side of the metal plate, that is, around the metal plate on the side to which
the piezoelectric vibration element is joined. is necessary. Furthermore, the reverberation
characteristics of the ultrasonic sensor change according to the size of the space, and the
characteristics of the ultrasonic sensor change when the size of the space is different. That is, in
order to obtain an ultrasonic sensor having good characteristics, it is necessary to make the
arrangement position of the sound absorbing material constant.
[0009]
However, in the conventional ultrasonic sensor, since the case main body has a cylindrical shape
having the same opening shape in any part, the sound absorbing material is inserted into the
case main body to fix the sound absorbing material at a desired position. Is a difficult task. For
this reason, the position of the sound absorbing material varies from one ultrasonic sensor to
another, and the reverberation characteristic of the ultrasonic sensor varies, which makes it
impossible to supply an ultrasonic sensor having certain characteristics.
[0010]
The ultrasonic sensor according to the present invention has been made in view of the above
problems, and an object thereof is to solve these problems and to provide a characteristically
stable ultrasonic sensor with no variation in reverberation characteristics. And
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[0011]
SUMMARY OF THE INVENTION In order to achieve the above object, an ultrasonic sensor
according to the present invention comprises a substantially cylindrical case main body made of
an insulating material and an electrically conductive material which is joined to the case main
body. A case comprising a vibrating portion, a piezoelectric vibrating element joined to the inner
side surface of the vibrating portion, and an input / output member embedded in the case main
body and electrically connected to the piezoelectric vibrating element; The ultrasonic sensor,
wherein the inner circumferential surface of the case body is at least partially tapered.
[0012]
Thus, the position at which the sound absorbing material is fixed in the case main body becomes
constant.
Further, since the sound absorbing material is fixed by pushing it into the case main body, a force
for pressing the case main body is added, and the reverberation characteristic is improved.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION An ultrasonic sensor according to an
embodiment of the present invention will be described below with reference to FIG.
FIG. 1 is a cross-sectional view of the ultrasonic sensor of the present embodiment. As shown in
FIG. 1, the ultrasonic sensor 10 of the present embodiment is fitted in a substantially cylindrical
case main body 11 made of an insulating material and having a stepped portion at one opening,
and the stepped portion of the case main body 11 And a case comprising a metal plate 12 as a
vibrating portion joined to the case main body 11 by an adhesive, a piezoelectric vibrating
element 13 joined to the inner side surface of the metal plate 12, members for input and output
14a, 14b, It is comprised from the sound absorbing material 15 which consists of felt etc. As the
insulating material of the case body 11, an engineering plastic excellent in heat resistance and
durability, specifically, polyphenylene sulfide, polyetheretherketone, polyethersulfone, liquid
crystal polymer and the like are used. Furthermore, for the metal plate 12 as the vibrating
portion, aluminum or the like which is lightweight and has a high elastic modulus is used.
Furthermore, high rigidity metals such as 42 nickel, nickel white, phosphor bronze, and low
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rigidity metals such as copper are used as the input / output members 14a and 14b.
[0014]
Electrodes are respectively formed on the front and back surfaces of the piezoelectric vibrating
element 13 (not shown), and the electrodes on the back surface are connected to the inner side
surface of the metal plate 12 by a conductive adhesive, solder or the like. The input / output
members 14 a and 14 b are integrally formed so as to be embedded in the case main body 11,
and one of the input / output members 14 a is conductively bonded to an electrode having one
end formed on the surface of the piezoelectric vibrating element 13. The other end of the input /
output member 14b is connected to the metal plate 12 by a conductive adhesive or the like so as
to be electrically connected to an electrode formed on the back surface of the piezoelectric
vibrating element 13. The other end of each of the input / output members 14 a and 14 b is led
out of the case main body 11.
[0015]
In ultrasonic sensors, not only long distance detection but also short distance detection may be
required. When the ultrasonic sensor measures the distance from the detected object, etc., an
ultrasonic pulse signal is sent to convert the reflected wave from the detected object into an
electric signal, and the calculated signal is sent to an external circuit. In the case of a short
distance, the vibration at the time of transmission remains in the case main body of the
ultrasonic sensor and the like, and it becomes difficult to distinguish from the reflected wave.
That is, it is necessary for the ultrasonic sensor to have a function of rapidly converging the
reverberation remaining in the case main body after transmission of the ultrasonic pulse signal,
that is, to improve the reverberation characteristics. In order to improve the reverberation
characteristics of the ultrasonic sensor 10, the sound absorbing material 15 made of felt or the
like is disposed in the case main body 11, but the inner peripheral surface of the case main body
11 in the ultrasonic sensor 10 of this embodiment is shown in FIG. As shown in the drawing, the
sound absorbing material 15 is fixed at a desired position in the case body 11 because it is
tapered. That is, if the sound absorbing material 15 is inserted from the opening on the side
opposite to the side where the metal plate 12 of the case body 11 is joined and pushed in, the
inner peripheral surface of the case body 11 is tapered. The sound absorbing material 15 stops
at a predetermined position. If the size of the sound absorbing material 15 and the shape of the
inner peripheral surface of the case main body 11 are accurately formed, the sound absorbing
material 15 can be fixed at a fixed position without any difficulty in operation. A space of a
certain size can be formed in the vicinity of 12, and variations in the reverberation characteristics
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of the ultrasonic sensor 10 and the like are eliminated. Further, since the sound absorbing
material 15 is pushed into the case main body 11, a force is applied to the case main body 11
from the sound absorbing material 15 outward. As a result, since the vibration remaining in the
case body 11 after the generation of the ultrasonic pulse signal is suppressed, the variation in the
reverberation characteristic is eliminated and the reverberation characteristic is improved.
[0016]
In the above embodiment, the taper formed on the inner peripheral surface of the case main
body 11 covers the entire inner peripheral surface of the case main body 11, but it is partially
formed, for example, in three or four parts. Even the effects of the present invention can be
obtained. Further, as shown in the cross-sectional view of FIG. 2, the present invention can be
applied to the ultrasonic sensor 10a in which the insulating resin 16 having elasticity such as
silicone rubber, urethane rubber, or foamable resin is filled and cured in the case.
[0017]
As described above, according to the present invention, the inner peripheral surface of the case
main body made of the insulating material in the ultrasonic sensor is tapered. As a result, the
position of the sound absorbing material disposed inside the case main body is fixed, the
variation in the reverberation characteristics of the ultrasonic sensor and the like is eliminated,
and the operation of arranging the sound absorbing material becomes simple. Further, by
pushing the sound absorbing material into the case main body, a force is applied from the inside
to the outside of the case main body, so that the reverberation characteristic of the ultrasonic
sensor is improved.
[0018]
Brief description of the drawings
[0019]
1 is a cross-sectional view of the ultrasonic sensor of the present invention.
[0020]
2 is a cross-sectional view of another embodiment of the ultrasonic sensor of the present
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invention.
[0021]
3 is a cross-sectional view of a conventional ultrasonic sensor.
[0022]
Explanation of sign
[0023]
10,10a ultrasonic sensor 11 case main body 12 metal plate 13 piezoelectric vibrating element
14a, 14b input / output member 15 sound absorbing material 16 insulating resin
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