JP3796969B2 - Ultrasonic sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic sensor. In particular, the present invention relates to an ultrasonic sensor used for automobile back sonar and corner sonar.
[0002]
[Prior art]
The ultrasonic sensor performs sensing using ultrasonic waves, intermittently transmits ultrasonic pulse signals from the piezoelectric vibration element, and receives reflected waves from obstacles existing in the vicinity by the piezoelectric vibration element. Thus, the presence of an obstacle is detected, or the distance to the obstacle is calculated from the elapsed time from when the ultrasonic pulse signal is transmitted to when it is received.
[0003]
An ultrasonic sensor that operates based on such a principle is required to have a characteristic that enables detection of a long distance and reliably extracts a weak reflected wave as an electric signal without being buried in disturbance noise or the like. For this purpose, it is necessary to adopt a structure that does not hinder the vibration operation of the vibration part so that both the transmission output sound pressure and the reception sensitivity characteristic of the ultrasonic sensor can be enhanced. Specifically, it has been widely and generally used that the wiring directly connected to the piezoelectric vibration element disposed in the vibrating portion is particularly thin and soft.
[0004]
However, it is extremely difficult to stably connect and connect thin and soft wiring within the small casing of an ultrasonic sensor, which causes an increase in production cost, and the reliability of electrical connection is low, resulting in unstable sensor characteristics. It was also the cause of the transformation.
[0005]
In order to overcome the above-mentioned problems, the present inventors have disclosed in Japanese Patent Application No. 10-4882 a structure of an ultrasonic sensor capable of obtaining stable electrical connection with good workability without using thin and soft wiring. Already proposed.
[0006]
As shown in FIG. 5, the ultrasonic sensor 51 disclosed in the above application is provided with a metal plate 53 serving as a vibrating portion at a front opening of a substantially cylindrical case body 52 made of an insulating material, and the metal plate The piezoelectric vibration element 54 is joined to the inner surface of 53, and a part of a pair of conductive members 55 formed integrally with the case body 52 is electrically connected to each electrode (not shown) of the piezoelectric vibration element 54. (Description of other configurations is omitted).
[0007]
In the ultrasonic sensor 51 having the above-described configuration, one end of the conductive member 55 is electrically connected to each electrode of the piezoelectric vibration element 54 inside the case body 52 as described above. The other end of the conductive member 55 is drawn from the case main body 52 in a state of being directly exposed to the outside.
[0008]
[Problems to be solved by the invention]
However, the configuration of the ultrasonic sensor described above has the following problems.
[0009]
First, a conductive cable (hereinafter simply referred to as a cable) 56 for applying a drive voltage to the piezoelectric vibration element 54 is generally attached to the other end of the conductive member 55 by soldering or the like. However, the other end of the conductive member 55 is directly exposed to the outside as described above. For this reason, the soldered portion of the cable 56 is also exposed to the outside. As a result, there is a concern that the moisture resistance and impact resistance of the soldered portion are inferior and the reliability of electrical connection is lowered.
[0010]
By the way, as a characteristic required for an ultrasonic sensor, in addition to the above-described long-distance detection capability, a short-distance detection capability may be required. In this case, after transmitting the ultrasonic pulse signal, it is necessary to quickly converge the reverberation vibration (vibration of the case main body and the internal space) in the sensor before receiving the reflected wave (reverberation characteristics). However, in this respect, in the above-described ultrasonic sensor, the vibration of the piezoelectric vibration element 54 is transmitted through the conductive member 55, and finally the cable 56 is also vibrated, and there is a concern that the reverberation characteristics of the ultrasonic sensor are deteriorated. .
[0011]
Therefore, the present invention has been made to solve the above technical problems, and is excellent in the moisture resistance and impact resistance of the soldered portion between the conductive member and the cable, and has a structure having excellent reverberation characteristics. It is to provide an acoustic wave sensor.
[0012]
[Means for Solving the Problems]
In order to achieve the purpose of the above operation, the ultrasonic sensor of the present invention is provided with a metal plate serving as a vibration part at the front opening of a substantially cylindrical case body made of an insulating material, and the inner surface of the metal plate. A piezoelectric vibration element is joined, a part of a pair of conductive members formed integrally with the case body is electrically connected to each electrode of the piezoelectric vibration element, and a recess is formed around the entire periphery of the opening on the rear surface of the case body. The conductive member was exposed, the cable was led out from the conductive member, and the inside of the case including the concave portion was sealed with an insulating resin.
[0013]
Thus, by forming a recess in the rear surface opening of the case body and exposing the conductive member in the recess, the soldered portion between the conductive member and the cable is located in the recess. Further, by sealing the inside of the case including the recess with an insulating resin, the moisture resistance and impact resistance of the soldered portion can be improved.
[0014]
Further, when sealing the inside of the case with an insulating resin, it is desirable that the cable led out from the conductive member is routed inside the case body before sealing. In this way, the cable is routed inside the case body and then resin-sealed, so that the vibration of the piezoelectric vibration element transmitted from the conductive member to the cable can be absorbed by the sealing resin and the vibration can be suppressed. Because.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
[First embodiment, FIGS. 1 to 2]
Hereinafter, the ultrasonic sensor according to the first embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 is a cross-sectional view showing the ultrasonic sensor of this embodiment, and FIG. 2 is a plan view of the ultrasonic sensor before resin sealing when viewed from the rear opening side.
[0016]
As shown in FIG. 1, the ultrasonic sensor 1 is provided with a metal plate 3 serving as a vibrating portion at a front opening of a substantially cylindrical case body 2 made of an insulating material, and piezoelectric vibration is provided on the inner surface of the metal plate 3. The element 4 is joined, and a part of the pair of conductive members 5 formed integrally with the case body 2 is electrically connected to each electrode (not shown) of the piezoelectric vibration element 4. In general, electrodes are formed on both main surfaces of the piezoelectric vibration element. In the ultrasonic sensor 1 of the present embodiment, one end of one conductive member is connected to the electrode on the upper surface side of the piezoelectric vibration element 4 and the other conductivity. One end of the member is electrically connected to the electrode on the lower surface side of the piezoelectric vibration element 4 through the metal plate 3.
[0017]
A recess 9 is partially provided in the rear surface opening of the case body 2, and the other end of the conductive member 5 not connected to the piezoelectric vibration element 4 is drawn out to the recess 9. The cables 6 are attached to the other ends of the conductive members 5 drawn out to the recesses 9 by soldering or the like.
[0018]
Inside the case body 2, a sound absorbing material 7 made of felt or the like is inserted and disposed above the piezoelectric vibration element 4. The sound absorbing material 4 is filled and hardened with an insulating resin having elasticity such as silicon rubber, urethane rubber, foaming resin, etc., and the rear surface opening side of the case body 2 including the concave portion 9 is resin. It is sealed. The cable 6 attached to the other end of the conductive member 5 is led out of the case body 2 after being routed in the sealing resin inside the case body.
[0019]
In the ultrasonic sensor 1 according to the present embodiment, as described above, the recess 9 is formed in the rear surface opening of the case body 2, and the conductive member 5 is exposed in the recess 9. And the soldering part of the electrically-conductive member 5 and the cable 6 will also be located in the recessed part 9, and the inside of the case containing this recessed part 9 is filled with the insulating resin 8. As a result, the above-described soldered portion is also sealed with the insulating resin 8 and is not directly exposed to the outside of the case, so that moisture resistance and impact resistance can be improved.
[0020]
The cable 6 is led out of the case body 2 after being routed inside the case body 2. As a result, the vibration of the piezoelectric vibration element 4 transmitted from the conductive member 5 to the cable 6 is absorbed in the insulating resin 8, and reverberation vibration can be suppressed.
[0021]
[Other Examples]
The ultrasonic sensor of the present invention is not limited to the above-described embodiment.
[0022]
For example, in the ultrasonic sensor of the first embodiment, the recess provided in the rear opening of the case body is a part of the opening. However, the present invention is not limited to this, for example, as shown in FIG. The recess 19 may be formed over the circumference. This is because, depending on the type of material of the case main body, it is conceivable that the concave portion over the entire circumference is easier to form than the partial concave portion.
[0023]
In the ultrasonic sensor of the first embodiment, the cable attached to the conductive member is led out of the case main body after being routed inside the case main body. However, the present invention is not limited to this. For example, as shown in FIG. Furthermore, even if it leads out of the case main body from the vicinity immediately above the solder mounting portion, the moisture resistance and impact resistance of the soldered portion can be improved.
[0024]
【The invention's effect】
As is apparent from the above description, the ultrasonic sensor of the present invention has a structure in which a recess is formed in the rear surface opening of the case body and the conductive member is exposed in the recess, so that the conductive member and the cable are connected to each other. The soldered portion is located in the recess. Further, by sealing the inside of the case including the recess with an insulating resin, the moisture resistance and impact resistance of the soldered portion can be improved.
[0025]
Further, by adopting a structure in which the cable is routed inside the case main body and sealed with resin, the vibration of the piezoelectric vibration element transmitted from the conductive member to the cable can be absorbed by the sealing resin and vibration can be suppressed. . As a result, the reverberation characteristics of the ultrasonic sensor can be improved.
[0026]
Furthermore, since the cable is routed inside the case body and then resin-sealed, the tension generated in the cable can be dispersed in the sealing resin, for example, during ultrasonic sensor manufacturing or user installation work. It is possible to effectively prevent a decrease in connection reliability due to the tension generated in the cable.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing the structure of an ultrasonic sensor according to a first embodiment of the present invention.
FIG. 2 is a plan view of the ultrasonic sensor according to the first embodiment before resin sealing when viewed from the rear opening side.
FIG. 3 is a plan view of an ultrasonic sensor of another embodiment before resin sealing as viewed from the rear opening side.
FIG. 4 is a cross-sectional view showing the structure of an ultrasonic sensor according to another embodiment.
FIG. 5 is a cross-sectional view showing the structure of a conventional ultrasonic sensor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Ultrasonic sensor 2 ... Case main body 3 ... Metal plate 4 ... Piezoelectric vibration element 5 ... Conductive member 6 ... Conductive cable 7 ... Sound-absorbing material 8 ... Insulating property Resin (sealing resin)
9: Recess

Claims (2)

A metal plate serving as a vibration part is provided at the front opening of a substantially cylindrical case body made of an insulating material, a piezoelectric vibration element is joined to the inner surface of the metal plate, and a pair of conductive members integrally formed on the case body. A part is electrically connected to each electrode of the piezoelectric vibration element, a recess is formed in the rear opening of the case body over the entire circumference , the conductive member is exposed in the recess, a cable is led out from the conductive member, and the recess is An ultrasonic sensor characterized in that the inside of a case is sealed with an insulating resin.   An ultrasonic sensor, wherein the cable is routed inside the case body and led out of the case body.

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