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JPH0631298

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DESCRIPTION JPH0631298
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic sensor having high reliability and stable temperature characteristics. BACKGROUND
OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic
sensor having high reliability and stable temperature characteristics.
[0002]
2. Description of the Related Art Since the mechanical impedance of air is much smaller than that
of a piezoelectric element or a metal plate, the material of the resonator on the conical has a low
mechanical impedance, for example, aluminum and plastic since mechanical matching is
conventionally achieved. Materials are used. Many of these materials are difficult to weld, and
usually the diaphragm and the resonator are bonded with an epoxy adhesive as shown in FIG. 1
of the structure. 2. Description of the Related Art The mechanical impedance of air is much
smaller than that of a piezoelectric element or a metal plate, and the mechanical impedance is
low as a conical resonator material for mechanical matching compared to the prior art.
Aluminum and plastic materials are used. Many of these materials are difficult to weld, and
usually the diaphragm and the resonator are bonded with an epoxy adhesive as shown in FIG. 1
of the structure.
[0003]
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In the conventional ultrasonic sensor, a defect occurs in the bonding surface between the
diaphragm and the resonator due to the change of the external environment temperature, and
the resonance frequency of the vibrator or the transmission / reception sensitivity largely
fluctuates. was there. An object of the present invention is to solve the conventional problems
and to provide a highly reliable ultrasonic sensor. Problems to be Solved by the Invention In a
conventional ultrasonic sensor, deterioration occurs at the bonding surface between the
diaphragm and the resonator due to the temperature change of the external environment, and
the resonance frequency of the vibrator or the transmission / reception sensitivity is large.
Because of the fluctuating defects, the present invention solves the conventional problems and
provides a highly reliable ultrasonic sensor.
[0004]
SUMMARY OF THE INVENTION In order to achieve the above object, according to the present
invention, an ultrasonic sensor on which a conical resonator is mounted is formed into a
sandwich structure using the same or similar metal diaphragm as that of a metal diaphragm. It is
characterized in that the parts are joined by welding. SUMMARY OF THE INVENTION In order to
achieve the above object, the present invention is an ultrasonic sensor on which a conical
resonator is mounted and which is made of the same or similar metal diaphragm as the
resonator. It features a sandwich structure and welds the parts.
[0005]
The ultrasonic sensor produced by this method has the same coefficient of thermal expansion at
the resonator bonding surface, and its environmental temperature change is extremely stable as
compared with the epoxy adhesive layer by the conventional method. The coefficient of thermal
expansion of the metal diaphragm in the conventional product is about 1.5E-6 / ° C, and it is
very different at about 6E-5 / ° C in the case of an epoxy adhesive. Since the thermal expansion
coefficient in the adhesive layer is equal to the mechanical stress due to the thermal factor of the
layer, stable characteristics against temperature change can be obtained. The ultrasonic sensor
produced by this method has the same coefficient of thermal expansion at the resonator bonding
surface, and its environmental temperature change is extremely stable as compared with the
epoxy-based adhesive layer produced by the conventional method. The coefficient of thermal
expansion of the metal diaphragm in the conventional product is about 1.5E-6 / ° C, and it is
very different at about 6E-5 / ° C in the case of an epoxy adhesive. Since the thermal expansion
coefficient in the adhesive layer is equal to the mechanical stress due to the thermal factor of the
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layer, stable characteristics against temperature change can be obtained.
[0006]
Embodiment 1 FIG. 2 shows a structure in which a resonator is made of the same material as that
of a metal diaphragm or a material having a low thermal expansion coefficient and which has a
welded structure, and the welded ultrasonic sensor exhibits extremely stable performance. Also,
according to the welded part enlarged view of FIG. 3 and FIG. 4, FIG. 3 makes the welded part to
be the upper layer of the resonator convex and stabilizes the welding, and FIG. 4 strengthens the
resonator joint and stabilizes the frequency. Do. Embodiment 1 FIG. 2 shows a structure in which
a resonator is made of the same material as that of a metal diaphragm or a material having a low
thermal expansion coefficient and which has a welded structure, and the welded ultrasonic
sensor exhibits extremely stable performance. Also, according to the welded part enlarged view
of FIG. 3 and FIG. 4, FIG. 3 makes the welded part to be the upper layer of the resonator convex
and stabilizes the welding, and FIG. 4 strengthens the resonator joint and stabilizes the
frequency.
[0007]
Embodiment 2 The same performance can be obtained by using a method in which a hole is
formed in the center of the resonator by pressing pressure at the time of welding without
forming a hole in the center of the above-described embodiment. Embodiment 2 The same
performance can be obtained by using a method in which a hole is formed in the center of the
resonator by pressing pressure at the time of welding without forming a hole in the center of the
above-described embodiment.
[0008]
Example 3 FIG. 4 shows the comparison of the characteristics before and after the thermal shock
(-30.degree. C..times.30 minutes to 85.degree. C..times.30 minutes, 100 cycles), and FIG. The
transmission wave frequency characteristic of the sensor is shown, and (b) shows the reception
wave frequency characteristic of the same kind. Further, (c) shows the transmission wave
frequency characteristics of the ultrasonic sensor of the present invention, and (d) shows the
same reception wave frequency characteristics. Example 3 FIG. 4 shows a comparison of
characteristics before and after a thermal shock (−30 ° C. × 30 minutes to 85 ° C. × 30
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minutes, 100 cycles), and FIG. The transmission wave frequency characteristic of the ultrasonic
sensor of (1) is shown, and (b) shows the reception wave frequency characteristic of the same
kind. Further, (c) shows the transmission wave frequency characteristics of the ultrasonic sensor
of the present invention, and (d) shows the same reception wave frequency characteristics.
[0009]
Industrial Applicability As described above, the present invention is highly reliable in ultrasonic
sensors and is intended to supply the market at the most economical price. It is a very effective
method for stabilizing the characteristics of the ultrasonic sensor in moisture resistance, thermal
shock resistance, and temperature characteristics. [00010] [Submission Date] September 3, 1993
[Procedure Amendment 2] [Name of the Amendment Document] Description [Item Name of
Amendment Item] Detailed Description of the Invention [Correction Method] Change [Detailed
Description of the Invention] As described in detail above, the present invention is highly reliable
in ultrasonic sensors, and is intended to supply the market at the most economical price. It is a
very effective method for stabilizing the characteristics of the ultrasonic sensor in moisture
resistance, thermal shock resistance, and temperature characteristics.
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