KR20050005291A - Ultrasonic sensor and manufacturing method thereof - Google Patents

Abstract

PURPOSE: An ultrasonic sensor and a method for manufacturing the same are provided to improve sensitivity of transmitting/receiving ultrasonic waves by integrating a vibration plate with a housing. CONSTITUTION: An ultrasonic sensor using a ceramic corn having piezoelectric as a vibration source includes a vibration plate(11), a housing(15), a piezoelectric ceramic(12), and rubber resin(17). The vibration plate(11) has multi-vibration modes of generating ultrasonic waves. The housing(15) is formed on the upper part of the vibration plate(11) and is coupled with the vibration plate(11). The housing(15) is cylindrical. The piezoelectric ceramic(12) is attached to the upper part of the vibration plate(11) and linked with lead wires. The piezoelectric ceramic(12) has a voltage signal applied from the bottom side of the hollow of the housing(15). The rubber resin has a step difference for preventing force above pressure of the piezoelectric ceramic(12).

Description

Ultrasonic sensor and manufacturing method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic sensor and a method of manufacturing the same, and more particularly, to narrow the beam width of the sensor and increase the detection distance by using the high frequency vibration mode.

In general, when the ultrasonic sensor applies a high frequency electrical energy using a ceramic element having piezoelectric and electrostrictive characteristics as a vibration source, a rapid vibration occurs the same number of times as the frequency. In this case, when the applied frequency is 20 [Khz] or more, the piezoelectric ceramic element generates ultrasonic waves having a specific frequency band invisible to humans by vibration.

Such a general ultrasonic sensor is widely used in a sensing device for measuring the shape or distance of an object by the transmission and reception of ultrasonic waves using a piezoelectric ceramic element as a medium. That is, when a voltage signal having the same frequency as the use frequency of the ultrasonic sensor is applied to the sensor, ultrasonic waves are generated by the vibration of the piezoelectric ceramic, and ultrasonic waves propagated in all directions of the sensor are reflected back to the object in front of the distance. Will be measured.

The following description describes the concept of a conventional ultrasonic sensor as follows. First, the resonant frequency of the ultrasonic sensor is determined by [Equation 1].

[Equation 1]

Where h is the thickness of the bottom of the metal housing, D is the cross-sectional area of the metal housing, Y is the Young's modulus of the material, ρ is the density, Is Poisson's ratio, β is Bessel function and n is dimension.

In addition, the cross-sectional area of the bottom portion of the metal housing should be larger than the cross-sectional area of the piezoelectric ceramic in consideration of the capacitance of the sensor, the allowable input voltage, the dielectric strength, and the like.

The orientation angle of the conventional ultrasonic sensor is determined by [Equation 2].

[Equation 2]

Orientation Angle:

Where D is the diameter of the diaphragm, f is the ultrasonic frequency, υ is the sound velocity in air, and λ is the wavelength.

However, in the conventional ultrasonic sensor, since the orientation angle is determined according to the orientation characteristic of the sensor and the cross-sectional area size of the bottom of the metal housing, as shown in [Equation 2], there are many restrictions in setting the cross-sectional area size of the metal housing. Accordingly, there are many difficulties in manufacturing the ratio (D / h) of the cross-sectional area D of the diaphragm of the ultrasonic sensor and the thickness h of the bottom surface of the metal housing to 20 times or more.

Conventional ultrasonic sensors using such a resonant frequency are mainly used a method of using the bending vibration mode by the metal sheet and the piezoelectric ceramic, a method using the natural frequency of the piezoelectric ceramic.

1 is an exploded perspective view of a conventional ultrasonic sensor using the bending vibration mode described above.

The conventional ultrasonic sensor 1 includes a metal housing 2, a piezoelectric ceramic 3, a lead wire 4, a sound absorbing agent 5, and a substrate 6.

The piezoelectric ceramic 3 is adhered to the bottom of the cylindrical metal housing 2, and the piezoelectric ceramic 3 is connected to the lead wire 4. The sound absorbing material 5 is inserted into the metal housing 2 to be inserted into the center groove of the metal housing 5, and the substrate 6 includes holes for connecting passages of the lead wire 4. The upper part of the housing 2 is covered.

2 shows the structure of the metal housing 2 described above.

The conventional metal housing 2 has a structure in which the upper diameter of the metal housing 2 is designed to be wider than the lower diameter as shown in FIG. 2, so that the substrate 6 is seated on the upper engaging portion. In the conventional ultrasonic sensor having such a configuration, the metal plate attached to the piezoelectric ceramic 3 is applied by applying a voltage signal having a frequency equal to the frequency determined according to the size of the diaphragm of the metal housing 2 and the characteristics of the piezoelectric ceramic 3 to the sensor. Ultrasonic waves are generated. In addition, the frequency of the conventional ultrasonic sensor will vary depending on the diameter, thickness, material characteristics of the metal plate provided on the bottom of the metal housing (2).

By the way, the ultrasonic sensor of the first vibration mode method is designed to make the diameter of the diaphragm smaller than the ultrasonic sensor using the multi-dimensional vibration mode method to generate ultrasonic waves having the same frequency by using the same metal material, the thickness of the diaphragm is thick Should be designed to Accordingly, the conventional ultrasonic sensor has a problem that the angle of the ultrasonic beam is wider, the mechanical impedance is increased, and the ultrasonic transmit / receive efficiency is lowered, making it difficult to use as a sensing sensor for remote measurement.

The present invention was created to solve the above problems, by manufacturing the ratio of the diameter and thickness of the diaphragm of the ultrasonic sensor more than 25 times, by designing by processing or bonding the diaphragm using the multi-dimensional vibration mode integrally with the housing The radiation area of the ultrasonic wave is widened to improve the directivity angle and transmit / receive sensitivity of the ultrasonic energy transmitted in all directions of the ultrasonic sensor.

1 is an exploded perspective view of a conventional ultrasonic sensor.

2 is a view showing a metal housing structure of a conventional ultrasonic sensor.

Figure 3a, 3b is a view for explaining the concept of the ultrasonic sensor according to the present invention.

4 is an exploded perspective view of the ultrasonic sensor according to the present invention;

5 is an assembled cross-sectional view of the ultrasonic sensor according to the present invention.

6a and 6b are embodiments showing a housing structure of the present invention.

7 is a perspective view showing a structure of a rubber resin of the present invention.

8 is a perspective view showing a PCB substrate structure of the present invention.

<Description of the symbols for the main parts of the drawings>

11: diaphragm 12: piezoceramic

13: Sound absorbing material 14: stepped portion

15: housing 16: step

17: rubber resin 18: wire insertion gap

19: PCB substrate 20: (+) wire

21: (-) wire 22: condenser

23: lead wire 24: soldering portion

25: substrate insertion groove

Ultrasonic sensor of the present invention for achieving the above object, the multi-dimensional vibration mode vibration plate for generating ultrasonic waves by performing a high frequency resonance; A cylindrical housing formed on an upper portion of the diaphragm and integrated with the diaphragm; A piezoelectric ceramic bonded to an upper portion of the diaphragm and connected to a lead wire, and having a voltage signal applied from a bottom surface of the hollow part of the housing; And a rubber resin inserted into the housing to prevent the piezoelectric ceramic from being subjected to a pressure higher than the pressing pressure.

In addition, the ultrasonic sensor manufacturing method of the present invention for achieving the above object comprises the steps of: integrating a cylindrical housing and a diaphragm having a multi-dimensional vibration mode; Bonding a piezoelectric ceramic having a lead wire coupled to an inner surface of the diaphragm; Inserting a sound absorbing material on an upper portion of the piezoelectric ceramic to effectively absorb ultrasonic energy generated in the rear direction of the piezoelectric ceramic; Inserting a rubber resin into an inner step of the housing to prevent ultrasonic energy from being transferred in the rearward direction and to suppress vibration of the housing; Inserting a PCB substrate to facilitate the connection of the (+) wire connected to the piezoelectric ceramic and the (-) wire electrically connected to the housing and inserted into the groove formed on the upper surface of the rubber resin; And connecting the external lead wire terminal, the positive wire, and the negative wire to the PCB substrate.

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention.

3A and 3B are views for explaining the concept of the ultrasonic sensor according to the present invention.

FIG. 3A illustrates the operation principle of the basic vibration mode method, and FIG. 3B illustrates the high frequency vibration mode method. In particular, it is possible to design the ultrasonic sensor of the multi-dimensional vibration mode by adjusting the ratio of the diameter and thickness of the diaphragm.

According to the present invention, the ratio (D / h) of the cross-sectional area D of the diaphragm of the ultrasonic sensor and the thickness h of the bottom surface of the metal housing can be manufactured at least 25 times by using the multi-dimensional high frequency vibration mode method. Accordingly, the beam angle and the transmission / reception sensitivity of the ultrasonic energy propagated in all directions of the ultrasonic sensor can be controlled efficiently.

Figure 4 is an exploded perspective view of the ultrasonic sensor according to a preferred embodiment of the present invention, Figure 5 is an assembled cross-sectional view of FIG.

As shown in Figs. 4 and 5, the present invention integrates the diaphragm 11 designed to enable high frequency vibration with the housing 15 having a cylindrical shape and processes or bonds it. The housing 15 forms a stepped groove for determining the position of the rubber resin 17 so that the rubber resin 17 is inserted therein. Then, the (-) wire 21 is connected to the inner surface of the diaphragm 11 described above by the soldering 24, the (+) wire 20 is connected to the upper surface of the piezoelectric ceramic 12, and the piezoelectric ceramic ( 12 is bonded to the upper portion of the diaphragm 11 by an adhesive. In addition, the piezoelectric ceramic 12 generates ultrasonic waves by applying a voltage signal from the bottom of the hollow portion of the housing 15.

The sound absorbing material 13 has a size of 0.5 to 1.5 times the diameter of the piezoelectric ceramic 12 and is inserted into the back of the piezoelectric ceramic 12 inside the housing 15 to be generated to the rear when the vibration plate 11 is shaken. It absorbs the ultrasonic waves and prevents the remaining ultrasonic waves from being transferred to the back of the sensor. The inner side of the housing 15 is provided with a stepped portion 14 for fixing the position of the stepped 16 of the rubber resin 17.

Then, the PCB substrate 19 is inserted into the groove 25 formed on the upper surface of the rubber resin 17, the (+) wire 20 connected to the piezoelectric ceramic 12 and the (-) wire connected to the diaphragm 11 Holes 30 for passing the 21 are provided. The PCB board 19 fixes the (+) wire 20 and the (−) wire 21 to the holes by soldering or conductive bonding. Here, after fixing the capacitor 22 for temperature compensation to the PCB substrate 19 by soldering or conductive bonding, it is assembled in the order of filling the sealing agent in the rear direction of the rubber resin 17. A gap 18 for inserting the positive wire 20 and the negative wire 21 is formed in the upper portion of the rubber resin 17.

The ultrasonic sensor of the present invention having such a configuration has a diaphragm 11 which is designed to have a high frequency vibration mode and generates ultrasonic waves in front of the ultrasonic sensor. Here, when using the same frequency as the ultrasonic sensor of the prior art, the thickness of the diaphragm 11 used in the present invention is very thin and the diameter of the diaphragm is designed large. Accordingly, when the thickness of the diaphragm 11 is thin, the mechanical impedance of the diaphragm 11 is reduced when the ultrasonic sensor is driven, so that the vibration effect is increased. Thus, the overall sensitivity of the ultrasonic wave is greatly increased. Can provide. In addition, when the width of the diaphragm 11 is widened, it is possible to reduce the angle of the beam by the above [Equation 2].

As a result, the present invention enables a long distance measurement, and because of the narrow beam characteristics it is possible to measure the distance of the area that is not applicable to the ultrasonic sensor according to the prior art.

In addition, in consideration of the economics and uniformity of the manufacturing of the ultrasonic sensor of the present invention, when the diaphragm 11 is integrally processed with the housing 15 (FIG. 6B), a predetermined thickness is produced in advance so that a predetermined frequency characteristic is output. The metal plate having the metal sheet is cut into a predetermined size and bonded to the housing 15 to produce it.

Then, the rubber resin 17 is inserted to effectively damp the vibration of the housing 15. However, the pressure applied to the sound absorbing material 13, the piezoelectric ceramics 12, and the diaphragm 11 is uneven according to the insertion height of the rubber resin 17, thereby decreasing the uniformity of the ultrasonic sensor.

Accordingly, the stepped portion 14 into which the rubber resin 17 can be inserted is formed on the inner inner wall of the housing 15. The stepped portion 14 has a size of 0.9 to 1.5 times the inner diameter of the rubber resin 17 and a hardness of 20 to 90 degrees. When the rubber resin 17 is inserted, the sound absorbing material 13, the piezoelectric ceramic 12, and the diaphragm are Uniformity may be improved by always allowing uniform pressure to be applied to (11).

6A and 6B are embodiments of the structure of the housing 15 described above.

The stepped portion 14 of the housing 15 may be designed to have a cross-sectional groove in which the rubber resin 17 is fitted by having a catch portion having a diameter larger than that of the body as shown in FIG. 6A. In addition, as shown in FIG. 6B, the double-sided groove of the step portion 14 may be provided in the middle portion of the housing 15 to design the rubber resin 17 to be bound to the grooves on both sides.

7 is a perspective view showing the configuration of the rubber resin 17 of the present invention.

The rubber resin 17 has a wire fitting gap 18 or a minute hole cut thinly enough to fit the lead wires 21 and 22 soldered from the piezoelectric ceramic 12 to the upper surface thereof. do. When the wire is inserted by cutting the wire fitting gap 18 for the passage of the wire thinly, a ringdown time of the ultrasonic sensor can be prevented because the vibration transmitted along the lead wire 23 during the vibration of the ultrasonic sensor can be prevented. The time can be reduced.

In addition, the wire fitting gap 18 connects the positive wire 20 connected to the piezoelectric ceramic 12 and the negative wire 21 connected by soldering 24 or a conductive adhesive on the inner surface of the housing 15. The connection with the wire 23 is facilitated.

Then, the PCB 25 is inserted into the grooves 25 formed on the upper portion of the rubber resin 17 so that the PCB substrate 19 can be inserted in the horizontal direction or the vertical direction. Accordingly, the efficiency of the wire work of the sensor can be improved, and the tensile or compressive force generated by the outer lead wire 23 is not directly transmitted to the inner wire, thereby reducing the change in properties and improving the tensile strength. Therefore, it is possible to manufacture a highly reliable ultrasonic sensor.

Referring to the manufacturing method of the ultrasonic sensor of the present invention having such a configuration as follows.

First, the cylindrical housing 15 is formed, and the diaphragm 11 is designed to have a multi-dimensional vibration mode in consideration of the frequency of the ultrasonic wave, the beam angle, and the physical properties of the diaphragm 11. Then, the diaphragm 11 is integrated with or adhered to the housing 15. At this time, the ratio of the diameter and thickness of the diaphragm 11 is at least 25 times or more.

Next, the piezoelectric ceramics 12 having the lead wires 20 bonded to the inner surface of the diaphragm 11 integrated with the housing 15 are bonded to each other. Then, in order to effectively absorb the ultrasonic energy generated in the rear direction of the piezoelectric ceramic 12, one or more sound absorbing material 13 is inserted 0.5 to 1.5 times the diameter of the piezoelectric ceramic 12.

In addition, the internal stepped portion 14 of the housing 15 is provided with a rubber resin 17 for preventing transfer of residual ultrasonic energy not absorbed by the sound absorbing material 13 in the rear direction and suppressing vibration of the housing 15. Insert in Here, the step portion 14 also serves to prevent a force greater than a certain pressing pressure to the piezoelectric ceramic 12 by the rubber resin (17). At this time, the rubber resin 17 to have a size of 0.9 ~ 1.5 times the size of the inner diameter of the housing.

Subsequently, a PCB substrate 19 is formed to facilitate the connection of the (+) wire 21 electrically connected to the (+) wire 20 of the piezoelectric ceramic 12 and the housing 15 by a conductive adhesive. It fits in the groove | channel 25 formed in the upper surface or upper surface of the rubber resin 17, and adhere | attaches it with the adhesive agent for resin.

Next, the external lead wire 23 terminal of the ultrasonic sensor and the (+) wire 20 and the (-) wire 21 are soldered to the PCB substrate 19. In addition, if necessary, the temperature compensation capacitor 22 is soldered to the PCB substrate 19 and the sealing agent is filled in the rear direction of the rubber resin 17.

As described above, the present invention provides the following effects.

First, by designing a metal vibrating plate that can perform high frequency resonance, it is possible to manufacture an ultrasonic sensor that has a long detection length and can adjust the detection width according to its use. That is, the thickness of the diaphragm becomes thin, so that the mechanical impedance of the diaphragm decreases when the ultrasonic sensor is driven, thereby increasing the transmission and reception sensitivity of the ultrasonic wave. In addition, since the diaphragm becomes wider, it is possible to narrowly control the size of the beam angle.

Second, by processing the housing and the diaphragm integrally, it is possible to minimize the deviation of the sensor characteristics by the machining, and furthermore to manufacture an ultrasonic sensor with high work efficiency.

Third, it is possible to make the pressing pressure of the sound absorbing material, the piezoelectric ceramic and the diaphragm constant by forming a stepped portion into which the rubber resin can be inserted into the inner wall of the housing. Accordingly, the vibration generated in the diaphragm reduces the effect of propagation to the rear of the sensor along the housing, thereby reducing the ringdown time of the ultrasonic sensor.

Claims (11)

In the ultrasonic sensor using a ceramic sora having piezoelectric and electrostrictive characteristics as a vibration source, A diaphragm of a multi-dimensional vibration mode type generating ultrasonic waves; A cylindrical housing formed on the diaphragm and coupled to the diaphragm; A piezoelectric ceramic bonded to an upper portion of the diaphragm and having a lead wire connected thereto and a voltage signal applied from a bottom surface of the hollow part of the housing; And Is inserted into the housing of the ultrasonic sensor, characterized in that it comprises a rubber resin having a step to prevent the force is applied to the piezoceramic more than the pressing pressure. The ultrasonic sensor according to claim 1, wherein the ratio of the cross-sectional area of the diaphragm and the thickness of the bottom of the housing is 25 times or more. The ultrasonic sensor according to claim 1, wherein the housing is integrally processed or adhered to the diaphragm. The ultrasonic sensor according to claim 1, further comprising a sound absorbing material provided between the housing and the piezoelectric ceramic to absorb ultrasonic energy generated in the rear direction of the piezoelectric ceramic. The ultrasonic sensor according to claim 1, wherein the rubber resin further comprises a double-sided step having a diameter larger than the diameter of the rubber resin at the center thereof to absorb vibration of the housing. The ultrasonic sensor according to claim 5, wherein the housing further comprises a stepped portion into which the two-sided step is fitted to fix the position of the rubber resin. The rubber resin of claim 1, wherein the rubber resin has thin wire-cut gaps formed on both sides thereof to form a connection passage between a negative wire connected to a diaphragm and a positive wire connected to a piezoelectric ceramic. An ultrasonic sensor, characterized in that a flaw is formed in the upper portion. The ultrasonic sensor according to claim 1, further comprising a PCB substrate having holes through which the lead wire passes, and inserted into a groove formed at an upper portion of the rubber resin horizontally or vertically. The ultrasonic sensor as claimed in claim 8, further comprising a capacitor bonded to an upper portion of the PCB to compensate for temperature. Integrating a cylindrical housing and a diaphragm having a multidimensional vibration mode; Bonding a piezoelectric ceramic having a lead wire coupled to an inner surface of the diaphragm; Inserting a flaw material on an upper portion of the piezoelectric ceramic to effectively absorb ultrasonic energy generated in the rear direction of the piezoelectric ceramic; Inserting a rubber resin into the stepped portion of the housing to prevent the ultrasonic energy from being transferred in the rearward direction and to suppress vibration of the housing; Inserting a PCB substrate in the groove formed on the upper surface of the rubber resin to facilitate the connection of the (+) wire connected to the piezoelectric ceramic and the (-) wire electrically connected to the housing and electrically connected to the housing; And And connecting an external lead wire terminal, the positive wire, and the negative wire to the PCB substrate. The method of claim 10, further comprising: connecting a temperature compensation capacitor to an upper portion of the PCB substrate, and filling a sealing agent in a rear direction of the rubber resin.