JP2001197592A - Ultrasonic wave transmitter-receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic wave transmitter-receiver that is used under a corrosive gas atmosphere, adopts a structure where corrosive gas is hardly be intruded in a cylindrical case with bottom and whose characteristic is not degraded even if used at a low temperature. SOLUTION: In the ultrasonic wave transmitter-receiver consisting of a cylindrical case with bottom having an opening, a piezoelectric vibrator placed on the bottom of the cylindrical case with bottom, and an elastic body sealing the opening of the cylindrical case with bottom, a sealing material made of a silicon material with high gas barrier performance is place in duplicate onto an exposed face of the elastic body exposed to the outside of the cylindrical case with bottom.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic transducer, and more particularly, to a sealed structure of a drip-proof ultrasonic transducer used in an environment containing a large amount of corrosive gas such as exhaust gas.

[0002]

2. Description of the Related Art Ultrasonic transducers can be used for object detection, distance detection, and the like using ultrasonic waves, and are mainly used for applications such as back sonar for automobiles. The ultrasonic transducer used in such an application is assumed to be used outdoors, and the ultrasonic transducer itself is directly exposed to an external environment such as wind and rain. For this reason, in such applications, a so-called drip-proof ultrasonic transducer having a structure in which a piezoelectric vibrator used for transmitting / receiving ultrasonic waves is sealed in a case is used.

FIG. 3 is a schematic structural view of a conventional drip-proof ultrasonic transducer. FIG. 3 is a cross-sectional view showing the ultrasonic transducer 31 in which 32 is a bottomed cylindrical case made of a conductor such as aluminum, and 33 is a bottomed cylindrical case 3.
2, a piezoelectric vibrator 34 disposed at the bottom portion, a cotton-like body such as felt inserted into the bottomed cylindrical case 32 and arranged so as not to suppress the vibration of the piezoelectric vibrator 33, and 35 a cotton-like body 34 An elastic body made of silicon rubber or the like filled on the top and sealing the opening of the bottomed cylindrical case 32, 36 is a relay board embedded in the elastic body 35, and 37 is an electrode formed on the piezoelectric vibrator 33. A lead wire for electrically connecting to an external connection terminal 38 described later, and an external connection terminal 38 for inputting and outputting a signal of the piezoelectric vibrator 33 are shown. The external connection terminals 38 are fixed to the relay board 36, and are electrically connected to the lead wires 37 at the relay board portion.

[0004] The ultrasonic transducer 31 having the above-described structure operates as follows. First, when an electric signal is applied to the piezoelectric vibrator 33 via an external connection terminal, the piezoelectric vibrator 33 causes mechanical vibration and emits ultrasonic waves from the bottom surface of the bottomed cylindrical case 32. After a lapse of a predetermined time, the reflected ultrasonic wave reflected from the detection target is converted again into an electric signal via the piezoelectric vibrator 33, and the electric signal is led out from the external connection terminal 38 to the outside. Here, the distance from the ultrasonic transducer 31 to the object to be detected is measured based on the time difference from when the first electric signal is applied to when the reflected ultrasonic wave is received.

[0005]

However, the ultrasonic transducer 31 of the conventional structure shown in FIG. 3 has the following problems. That is, the ultrasonic transducer of the present structure is often used for applications such as back sonar of automobiles. In this case, a corrosive gas such as sulfur is present in a use environment in a large amount (a large amount is contained in exhaust gas and the like). Is). Therefore, this corrosive gas is transferred to the bottomed cylindrical case 32.
Of the piezoelectric vibrator 33 and the electrodes and the lead wires 37 are corroded, and the components become unusable. More specifically, the sulfur component reacts with the silver electrode to form insulating silver sulfide, and the surface of the electrode is insulated and the electricity does not pass.

In this regard, the opening of the bottomed cylindrical case 32 is sealed by an elastic body 35. However, silicon rubber having a relatively low molecular density is used for the elastic body 35 in order to ensure high elasticity. Due to the low molecular density, gas permeability is inevitably increased, and as a result, the above-mentioned corrosive gas causes deterioration of components.

As a method for solving the above-mentioned problem, for example, Japanese Patent Application Laid-Open No. 61-94496 discloses a method of opening a bottomed cylindrical case using an adhesive and a sealing material made of urethane rubber having a high molecular density. There is disclosed a structure in which a portion is sealed to prevent corrosive gas from entering a bottomed cylindrical case. However, the above-mentioned urethane rubber has a high molecular density and a high gas barrier property, but has a drawback that it is weak against a change in temperature due to its physical properties. Specifically, urethane rubber hardens in a low temperature environment,
Its elasticity deteriorates. As a result, the vibration of the bottomed cylindrical case cannot be efficiently suppressed, and the reverberation characteristics of the ultrasonic transducer are deteriorated. This becomes a particularly serious problem for ultrasonic transducers used in environments subject to severe temperature changes, such as automobile back sonars.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned technical problems, and it is an object of the present invention to provide an ultrasonic transducer used in a corrosive gas atmosphere in a cylindrical case having a bottom. It is an object of the present invention to provide an ultrasonic transducer having a structure in which a corrosive gas hardly penetrates into the apparatus and whose characteristics are not deteriorated even when used at a low temperature.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned technical problems, an ultrasonic transducer according to the present invention is provided with a bottomed cylindrical case having an opening and a bottom of the bottomed cylindrical case. A piezoelectric vibrator, and an ultrasonic transducer having an elastic body that seals the opening of the bottomed cylindrical case, on an exposed surface of the elastic body exposed to the outside of the bottomed cylindrical case. Further, a sealing material made of a silicon material having a high gas barrier property is provided in an overlapping manner.

[0010] By thus providing a silicon material having a high gas barrier property as a sealing material, it is possible to prevent corrosive gas from entering the bottomed cylindrical case. In addition, the elasticity of the silicon material hardly changes with a temperature change as compared with the urethane material. Therefore, the reverberation characteristics can be maintained at a sufficient level even in an ultrasonic transducer that is used even in a low-temperature environment in which the temperature greatly changes. Specifically, it is preferable to use a silicon material having a molecular density in the range of 1.0 to 1.5 ° as the silicon material used as the sealing material.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An ultrasonic transducer according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic structural view of a drip-proof ultrasonic transducer according to the present invention. FIG. 1 is a cross-sectional view showing an ultrasonic transducer 1, wherein 2 is a bottomed cylindrical case made of a conductor such as aluminum, and 3 is disposed on the bottom of the bottomed cylindrical case 2. The piezoelectric vibrator 4 is inserted into the bottomed cylindrical case 2 and is made of a cotton-like body such as felt arranged so as not to suppress the vibration of the piezoelectric vibrator 3. An elastic body made of silicon rubber or the like for sealing the opening of the case 2; 6 a relay board embedded in the elastic body 5;
Denotes a lead wire for electrically connecting an electrode formed on the piezoelectric vibrator 3 to an external connection terminal 8 described later, and 8 denotes an external connection terminal for inputting and outputting a signal of the piezoelectric vibrator 3. The external connection terminal 8 is fixed to the relay board 6 and is electrically connected to the lead wire 7 at the relay board portion. The present embodiment is characterized in that a silicon material having a high gas barrier property is provided as an encapsulating material 9 on the exposed surface of the elastic body 5 exposed to the outside of the bottomed cylindrical case. .

Next, a method of manufacturing the ultrasonic transducer 1 will be described. First, the bottomed cylindrical case 2 is prepared. The bottomed cylindrical case 2 is formed by a method such as cutting aluminum. Next, a piezoelectric vibrator 3 having surface electrodes made of Ag or the like formed on both main surfaces thereof is prepared, and placed and fixed on the bottom surface of the bottomed cylindrical case 2. Next, lead wires 7 are connected to the surface electrodes on the upper surface of the piezoelectric vibrator 3 and desired positions of the bottomed cylindrical case 2 by soldering or the like. The other end of the lead wire 7 is connected to an external connection terminal 8 fixed to the relay board 7. As a result, electrical connection between the electrodes on both main surfaces of the piezoelectric vibrator 3 and the external connection terminals 8 is achieved. Thereafter, the cotton-like body 7 is inserted into the bottomed cylindrical case to such an extent that the vibration of the piezoelectric vibrator 3 is not suppressed, and the cotton-like body is filled with a liquid silicone resin and solidified to form the elastic body 5.
Is configured. At this time, the relay board 6 is buried in the silicone resin. Finally, a liquid silicone resin having a high gas barrier property is filled and solidified on the elastic body 5 to form the sealing material 9, thereby obtaining a completed ultrasonic transducer 1.

The operation of the ultrasonic transducer 1 of the present embodiment is basically the same as the operation of the ultrasonic transducer of the conventional structure, and the description thereof will be omitted.

Here, a comparison experiment was conducted to verify the difference in the gas barrier property between the ultrasonic transducer obtained in the present embodiment and the ultrasonic transducer having a conventional structure having no sealing material. In the experiment (Experiment 1), a sulfidation test was performed in an environment of a temperature of 40 ° C., a humidity of 75%, and an H ₂ S concentration of 10 ppm, and the time until the electrodes on both piezoelectric vibrator surfaces stopped conducting electricity was measured. A comparison was made. FIG. 2 shows the experimental results of this experiment.
As is clear from FIG. 2, the ultrasonic transducer according to the present embodiment requires about ten times as long as the conventional product to achieve the same level of corrosion, and the corrosion resistance is improved by 10 times or more. You can confirm that you are doing.

Next, a comparative experiment was conducted to verify the difference in elasticity between a case where a silicon material was used as a sealing material and a case where a urethane material was used. In the experiment, an experiment (Experiment 2) was performed in which the elasticity of each sealing material when left in an atmosphere of −40 ° C. for 1 hour was measured and compared. The results of this experiment are shown in Table 1 below.

[0017]

[Table 1]

As is clear from the experimental results, it can be confirmed that the elasticity of the urethane material is much lower than that of the silicon material when left in a low-temperature environment compared to the silicon material.

Further, in order to study what degree of molecular density of a silicon material is suitable as a sealing material for preventing the invasion of corrosive gas, a sealing material having various molecular densities is used. And an experiment (Experiment 3) was conducted to verify the gas barrier properties and elasticity thereof. The experiment was performed under the same conditions as in Experiment 1 described above. This experimental result,
It is shown in Table 2 below.

[0020]

[Table 2]

As is apparent from the experimental results, there is a trade-off between the improvement in gas barrier properties and the elasticity. However, in order to realize desired values for both factors, the molecular density of the sealing material must be as follows. It can be understood that it is most desirable to use a silicon material in the range of 1.0 to 1.5 °.

It goes without saying that the present invention is not limited to the ultrasonic transducer of this embodiment. By forming the sealing material using a silicon material having a high gas barrier property, the point of being able to prevent the intrusion of corrosive gas even under severe temperature environment is the gist of the present invention, and it can enjoy its function. If present, the present invention can be applied irrespective of the difference in the internal sound absorbing structure, the difference in the shape of the bottomed cylindrical case, and the like.

[0023]

As is apparent from the above description, the ultrasonic transducer of the present invention seals the opening of the bottomed cylindrical case with a sealing material made of a silicon material having a high gas barrier property. Since it has a structure that is further provided on the elastic body, it is possible to effectively prevent corrosive gas from entering the bottomed cylindrical case, and use silicone rubber for the sealing material. Since the ultrasonic transducer is used, the reverberation characteristics and the like can be maintained at a desired level even when the ultrasonic transducer is used in an environment where the temperature changes drastically.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the structure of an ultrasonic transducer according to the present invention.

FIG. 2 is a diagram comparing the deterioration with time of the conduction state of the ultrasonic transducer of the present invention and the conventional ultrasonic transducer.

FIG. 3 is a schematic sectional view showing a structure of a conventional ultrasonic transducer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ultrasonic wave transmitter / receiver 2 ... Bottom cylindrical case 3 ... Piezoelectric vibrator 4 ... Cotton body 5 ... Elastic body 6 ... Relay board 7 ... Lead wire 8 ... external connection terminal 9 ... sealing material

Claims (2)

[Claims] 1. A bottomed cylindrical case having an opening, a piezoelectric vibrator disposed at the bottom of the bottomed cylindrical case, and an elastic body sealing the opening of the bottomed cylindrical case. An ultrasonic transducer, comprising: a sealing member made of a silicon material having a high gas barrier property, provided on an exposed surface of the elastic body exposed to the outside of the bottomed cylindrical case. Ultrasonic transducer. 2. The sealing material having a molecular density of 1.
2. The ultrasonic transducer according to claim 1, wherein a silicon material in a range of 0 to 1.5 [deg.] Is used.