JP2000023290A - Ultrasonic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an applying position of an elastic adhesive where the reverberant vibrations are effectively suppressed and also can facilitate the adhesive applying job when the adhesive is applied and the reverberant characteristic of an ultrasonic sensor is improved. SOLUTION: A disk-shaped diaphragm 15 is adhered at the front end opening of an almost cylindrical case main body 14, and a piezoelectric vibrating element 12 is bonded onto the inner surface of the diaphragm 15. The conductive members 18 and 19 are inserted into the body 14. The front end part of the member 18 is protruding over the inner circumference surface of the body 14 and the tip of this front end part is soldered to an electrode 20b of the element 12. The member 19 is bonded to the diaphragm 15 and conducts to the electrode 20a. An elastic adhesive 21 of silicone resin, etc., is applied to the base of a part that is exposed over the body 14 at the front end part of the member 18. Thus, the adhesive 21 is adhered onto the inner circumference surfaces of the member 18 and the body 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an ultrasonic sensor. In particular, the present invention relates to a drip-proof ultrasonic sensor used for a back sonar or a corner sonar of an automobile.

[0002]

2. Description of the Related Art An ultrasonic sensor performs sensing using an ultrasonic wave, intermittently transmits an ultrasonic pulse signal from a piezoelectric vibrating element, and reflects a reflected wave from an object to be detected present in the vicinity. The object is detected by receiving the signal by the piezoelectric vibrating element. As this type of ultrasonic sensor, a sensor having the structure shown in FIG. 1 has been conventionally used. That is, in the ultrasonic sensor 1, the bottom surface of the bottomed cylindrical case 2 formed of metal is the diaphragm 3, and the element electrodes 4 a and 4 b are formed on both main surfaces inside the diaphragm 3. The piezoelectric vibrating element 5 is attached. Electrical extraction from the element electrodes 4a and 4b formed on the piezoelectric vibration element 5 to the outside of the case 2 is performed by lead wires 6 and 6 serving as input / output terminals. One lead wire 6 is connected to the element electrode 4 a of the piezoelectric vibration element 5 on the side not in contact with the vibration plate 3 by soldering. The other lead wire 6 is soldered to a predetermined position of the metal case 2, and is electrically connected to the other (the side in contact with the diaphragm 3) element electrode 4 b of the piezoelectric vibrating element 5 through the metal case 2. are doing. An elastic adhesive 7 is applied to the entire outer periphery of the inner surface of the diaphragm 3 outside the piezoelectric vibration element 5.

[0003] The ultrasonic sensor 1 having such a configuration operates as follows. That is, a driving voltage is applied to the lead wires 6 and 6 to vibrate the piezoelectric vibration element 5. In conjunction with this vibration, the diaphragm 3 of the bottomed cylindrical case 2 undergoes film vibration, and FIG.
Emit ultrasonic waves in the direction of the arrow. After a lapse of a predetermined time, the ultrasonic wave reflected from the object reaches the piezoelectric vibrating element 5 via the diaphragm 3 and is converted into a reflected signal.
6 is output. Here, the elapsed time from transmission (application of drive voltage) to reception (detection of a reflected signal) is measured,
From this detection result, the distance to the object is measured.

[0004]

The detection range of the ultrasonic sensor having the above-described structure is determined by sensitivity, reverberation characteristics, and directional characteristics. Sensitivity is related to the detection range. When the sensitivity of the ultrasonic sensor is increased, a weak reflected wave can be detected, and as a result, the detection range is widened. The directional characteristics determine the detection range, and only the object to be detected located in a desired azimuth can be detected by widening or narrowing the directional characteristics. In addition, if the reverberation characteristics are improved by suppressing the reverberation vibration and shortening the duration of the reverberation vibration, the time from when the ultrasonic wave is emitted to when it can be received becomes shorter, so that the reflection from a short distance is obtained. Waves can be identified, and as a result, detection at a short distance can be performed accurately.

[0005] In the conventional ultrasonic sensor 1, in order to suppress the reverberation vibration, as shown in FIG. 1, a ring is elastically attached to the inner peripheral portion of the diaphragm 3 outside the piezoelectric vibration element 5 by a dispenser. Agent 7 is applied and adhered. When the elastic adhesive 7 is applied to the outer peripheral portion of the inner surface of the diaphragm 3 as described above, when the elastic adhesive 7 spreads to the inner peripheral side of the diaphragm 3 and adheres to the piezoelectric vibrating element 5, the vibration of the diaphragm 3 Since the amplitude becomes small and a weak reflected wave cannot be detected and the sensitivity of the ultrasonic sensor 1 is reduced, it is necessary to take care not to attach the elastic adhesive 7 to the piezoelectric vibration element 5. Further, in order to effectively suppress reverberation vibration so that a reflected wave from a short distance can be identified, the elastic adhesive 7 must be applied so as to be in close contact with both the bottom surface and the inner peripheral side surface of the case 2. Must.

However, the inside of the bottomed cylindrical case 2 does not adhere to the element electrodes 4 a and 4 b of the piezoelectric vibrating element 5, and is completely adhered to the inner surface of the diaphragm 3 and the inner peripheral surface of the case. There is a problem that the operation of applying the elastic adhesive 7 over the circumference is very difficult.

Next, as a wire material of the lead wires 6 and 6, in the conventional ultrasonic sensor 1, a thin wire such as soft Cu is used. The use of wires having high rigidity as the lead wires 6 and 6 facilitates handling and improves workability, and reduces variations in characteristics such as resonance frequency and sensitivity. However, when wires having high rigidity are used as the lead wires 6, 6, the ends of the wires are brought into contact with the piezoelectric vibration element 5 for electrical connection. 5, the vibration of the piezoelectric vibrating element 5 leaks into the case 2 through the lead wires 6, that is, a so-called “vibration leak” occurs, which causes deterioration of the reverberation characteristic of the ultrasonic sensor 1. For these reasons, soft thin wires have conventionally been used for the input and output leads 6,6.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and has as its object to improve the reverberation characteristics of an ultrasonic sensor to enable short-distance detection and to provide an ultrasonic sensor. The purpose is to facilitate manufacture.

[0009]

DISCLOSURE OF THE INVENTION In an ultrasonic sensor according to the present invention, a bottom of a cylindrical case having a bottom is formed as a diaphragm, a piezoelectric vibrating element is joined to an inner surface of the diaphragm, and a part is fixed to the case. Connecting the first conductive member to one electrode of the piezoelectric vibration element,
A second conductive member different from the first conductive member is conducted to the other electrode of the piezoelectric vibrating element, and the first conductive member is provided with a second conductive member in the middle of a portion fixed to the case and a portion connected to the piezoelectric vibrating element. An elastic material is adhered to the first conductive member. Here, examples of the elastic material include an elastic adhesive, an elastic resin, a foamed resin, and a rubber material.

As described above, when the elastic material is attached between the fixed portion of the first conductive member to the case and the connection portion to the piezoelectric vibration element, the vibration of the piezoelectric vibration element causes the first conductive member to vibrate. Since it is transmitted and absorbed by the elastic member, reverberation vibration can be rapidly attenuated, and the reverberation characteristics of the ultrasonic sensor can be improved. For this purpose, the first conductive member needs to have sufficient rigidity to transmit reverberation vibration, and needs to have a moderately higher rigidity than a conventionally used soft thin wire.
For example, it is necessary to use a conductive member made of a highly rigid wire or a conductive member punched from a thin plate. But,
If the rigidity of the first conductive member is too large, even the excitation vibration at the time of transmission for the detection operation is suppressed. Therefore, the first
The conductive member needs to have an appropriate rigidity.

Therefore, according to the present invention, it is possible to improve the reverberation characteristics of the ultrasonic sensor and accurately measure not only long distances but also short distances. Moreover, as compared with the conventional method of applying an elastic adhesive to the outer peripheral portion of the diaphragm, it is only necessary to attach an elastic material to a part of the first conductive member, which simplifies the manufacture of the ultrasonic sensor. be able to.

Further, according to the present invention, the reverberation characteristics of the ultrasonic sensor can be improved even if the first conductive member having a relatively high rigidity is used, so that the first conductive member having a relatively high rigidity is used. By using, the handling in the manufacturing process is easy, the workability is improved, and the variation in characteristics such as resonance frequency and sensitivity can be reduced.

A first conductive member is insert-molded in a substantially cylindrical case body made of an insulating material, and a diaphragm is fixed to one opening of the case body to form a case. The ultrasonic sensor in which the end of the conductive member is connected to the electrode of the piezoelectric vibration element simplifies the production of the ultrasonic sensor.However, in the conventional method of applying an elastic adhesive to the outer peripheral portion of the diaphragm, The first conductive member hinders the application of the elastic adhesive. However, even with the ultrasonic sensor having such a structure, the method of attaching an elastic material to the first conductive member as in the present invention can improve the reverberation characteristics of the ultrasonic sensor by a simple operation.

From the viewpoint of suppressing the reverberation vibration of the ultrasonic sensor, it is particularly preferable to attach an elastic material to the first conductive member and the case near the fixed portion of the first conductive member. Also, if you apply an elastic material to this part,
This is also advantageous in that the elastic material is unlikely to adhere to the piezoelectric vibrating element.

Further, in addition to the method of the present invention, if an elastic material is adhered to the diaphragm in a region on the outer peripheral side of the piezoelectric vibrating element as conventionally performed, reverberation vibration can be further suppressed. To improve the reverberation characteristics.

[0016]

(First Embodiment) FIG. 3 (a)
(B) is the top view and sectional view which show the structure in the middle of the manufacturing process of ultrasonic sensor 11 by one embodiment of the present invention. The structure of the ultrasonic sensor 11 will be described including an assembly procedure. Sensor case 13 for housing piezoelectric vibration element 12
The sensor case 13 has a substantially cylindrical case main body 14 made of an insulating resin such as engineering plastic such as polyphenylene sulfide (PPS) or liquid crystal polymer, and a disc-shaped aluminum or the like. And a diaphragm 15 made of metal. An annular shallow recess 16 is recessed in the inner periphery of the front end opening of the case body 14, and an annular deep recess 17 is recessed in the inner periphery of the rear end opening of the case body 14. A diaphragm 15 that generates vibration and receives a reflected wave is fitted into the recess 16 to form a bottomed cylindrical sensor case 13. Conductive members 18 and 19 made of a metal material such as nickel-white or 42 nickel are inserted into the case main body 14, and one of the conductive members 18 has a front end projecting from the inner peripheral surface of the case main body 14 and a rear end. The end is exposed to the rear end face of the case body 14, and the other conductive member 19 has the front end exposed in the shallow depression 16 and the rear end exposed in the deep depression 17.

The piezoelectric vibrating element 12 has electrodes 20a,
20b is formed, and one electrode 20a of the piezoelectric vibrating element 12 is joined to the center of the inner surface of the diaphragm 15 by a conductive adhesive. Thus, the case body 14
Is integrally formed with the conductive members 18 and 19 and the diaphragm 15
After the piezoelectric vibration element 12 is integrated with the piezoelectric vibration element 12,
The outer peripheral portion of the vibration plate 15 to which is joined is fitted into the concave portion 16 of the case main body 14 and adhered with an adhesive, whereby the sensor case 13 is assembled and the piezoelectric vibration element 12 is placed in the sensor case 13. Then, one conductive member 18
Is soldered to the electrode 20b of the piezoelectric vibration element 12. The tip of the other conductive member 19 is in pressure contact with the diaphragm 15 and is electrically connected to the electrode 20a of the piezoelectric vibrating element 12 (the tip of the conductive member 19 and the diaphragm 15 may also be joined with a conductive adhesive or the like). Therefore, the two conductive members 18 and 19 conduct to both electrodes 20a and 20b of the piezoelectric vibration element 12. In addition, at the front end of the conductive member 18, the case body 1
An elastic adhesive 21 such as a silicone resin is applied to the base of a portion protruding from the conductive member 1.
8 and the inner peripheral surface of the case body 14. The elastic adhesive 21 may be applied after the conductive member 18 is soldered to the electrodes 20 b of the piezoelectric vibrating element 12, or may be applied before attaching the diaphragm 15 to the case body 14.

The conductive members 18 and 19 inserted into the case body 14 are lead wires formed by stamping a metal plate and have appropriate rigidity. In particular, the conductive member 18 directly connected to the electrode 20b of the piezoelectric vibrating element 12 suppresses the excitation vibration of the piezoelectric vibrating element 12 when the rigidity is too high, and transmits the reverberation vibration to the elastic adhesive 21 when the rigidity is too soft. Therefore, it is necessary to have appropriate rigidity. The required degree of rigidity depends on the distance between the portion fixed to the case and the portion connected to the piezoelectric vibrating element 12, so that the conductive member 1 suitable for suppressing reverberation vibration can be used.
The stiffness of 8 is desirably determined experimentally. In addition, by using a metal material such as nickel silver or 42 nickel as the conductive members 18 and 19, the strength of the conductive members 18 and 19 is improved, and the possibility of disconnection as in the case of using a soft signal line is reduced.

Thereafter, the ends of the signal lines (not shown) are soldered to the rear ends of the conductive members 18 and 19. If necessary, a chip capacitor for temperature compensation may be fixed in the concave portion 17 at the rear end, and the chip capacitor may be connected in parallel with the piezoelectric vibration element 12. After the components are mounted and connected in this manner, a sound absorbing material (not shown) such as felt is put into the case main body 14 to cover the vicinity of the piezoelectric vibrating element 12 with the sound absorbing material.
The inside is filled with an elastic insulating resin (not shown) such as silicon rubber or urethane rubber and cured. As the insulating resin, a synthetic resin foam may be used.

In the ultrasonic sensor 11, an AC voltage is applied to the piezoelectric vibrating element 12 via the conductive members 18, 19 and the vibrating plate 15 to cause the vibrating plate 15 to vibrate and generate sound waves. . Conversely, the piezoelectric vibrating element 12 converts the distortion generated when the diaphragm 15 is deformed by the received reflected sound wave into an electric signal, and the conductive member 18,
A signal is taken out through 19 or the like, and an object such as an obstacle is detected.

Further, since the elastic adhesive 21 is applied to and adhered to the base of the front end of the conductive member 18 which is exposed from the case body 14, the mechanical Q of the case is reduced and the reverberation vibration is reduced. Can be suppressed. On the other hand, since the elastic adhesive 21 does not adhere to the vibrating surface or the piezoelectric vibrating element 12, it does not affect the excitation vibration of the diaphragm 15 and almost changes the resonance frequency and sensitivity of the ultrasonic sensor 11. Without reverberation vibration. Therefore, it is possible to shorten the duration of the reverberation vibration and accurately measure not only a long distance but also a short distance. Moreover,
Since it is only necessary to attach the elastic adhesive 21 to a part of the conductive member 18, the operation of applying the elastic adhesive 21 can be easily performed. Further, since the amount of the elastic adhesive 21 used is reduced, the cost is reduced.

Here, the reverberation characteristics of the conventional example and the reverberation characteristics of this embodiment will be compared. The solid line in FIG. 2 shows the reverberation characteristics of the conventional ultrasonic sensor 1 (FIG. 1) in which the elastic adhesive 7 is applied to the entire outer periphery of the diaphragm 15. That is, the horizontal axis represents the elapsed time t after the excitation of the piezoelectric vibrating element 12 is stopped.
, And the vertical axis indicates the intensity of reverberation vibration by voltage. FIG. 4 shows the reverberation characteristics of the ultrasonic sensor 11 (FIG. 3) of the present invention in which the elastic adhesive 21 is attached to a part of the conductive member 18. Comparing the reverberation characteristics of FIGS. 2 and 4, it can be seen that the ultrasonic sensor 11 of the present invention can obtain the same degree of reverberation characteristics as the conventional ultrasonic sensor 1. However, in the conventional ultrasonic sensor 1, it is difficult to apply the elastic adhesive because the elastic adhesive 7 must be applied to the entire circumference of the vibration plate 3 (especially because the conductive members 18 and 19 prevent the application of the elastic adhesive). On the other hand, in the ultrasonic sensor 11 of the present invention, it is only necessary to apply the elastic adhesive 21 to the conductive member 18, and the operation of applying the elastic adhesive is simplified.

The broken line in FIG.
5 shows reverberation characteristics of an ultrasonic sensor in which an elastic adhesive is applied to one point on the outer peripheral portion of the ultrasonic sensor. In this ultrasonic sensor, since the elastic adhesive is applied only to one point, the operation of applying the elastic adhesive can be simplified similarly to the ultrasonic sensor 11 of the present invention, but the reverberation characteristic shown by the broken line in FIG. As can be seen from FIG. 7, the reverberation duration is longer and the reverberation characteristics are degraded.

(Second Embodiment) FIG. 5 is a sectional view showing an ultrasonic sensor 31 according to another embodiment of the present invention in the middle of a manufacturing process. In this embodiment, the conductive member 18
In addition to applying and attaching an elastic adhesive 21 to the base of the front end exposed from the case body 14, the piezoelectric vibrating element 1 is used as in a conventional ultrasonic sensor.
An elastic adhesive 32 such as a silicone resin is also applied to the outer peripheral portion of the inner surface of the diaphragm 15 outside the outer surface 2.

FIG. 6 shows the reverberation characteristics of the ultrasonic sensor 31. In this embodiment, the work of applying the elastic adhesive 32 is troublesome, but as can be seen from the reverberation characteristics in FIG. 6, the duration of the reverberation vibration is shorter, and the reverberation characteristics are better. Therefore, it is possible to accurately detect even closer distances,
The detection range can be extended to a short distance.

(Third Embodiment) FIG. 7 is a sectional view showing an ultrasonic sensor 41 according to still another embodiment of the present invention. In each of the embodiments described so far, the case body 14 and the diaphragm 15 are separately formed. However, in the present invention, the bottomed cylindrical case 13 is integrally formed of a metal material such as aluminum. Can be applied to That is, in this embodiment, the case main body 14 and the vibration plate 15 are manufactured as a single body with a metal material such as aluminum, and the conductive member 42 is adhered to the inner peripheral surface of the case main body 14. The end portion remote from the case body 14 is soldered to the electrode 20b of the piezoelectric vibration element 12. The elastic adhesive 21 such as silicon is applied to the conductive member 42 at the end of the fixed part of the conductive member 42 to the inner peripheral surface of the case body 14.

The conductive member 42 and the case 13 are electrically insulated from each other.
The portion in contact with 3 may be covered with an insulating coating, or the inner peripheral surface of the case may be subjected to insulation treatment. One lead wire 43 is connected to the conductive member 42, the other lead wire 43 is connected to the case 13, and both lead wires 43 are connected to the respective electrodes 20 a of the piezoelectric vibrating element 12 through the conductive member 42 and the case 13. , 20b
It is conducting.

Also in the ultrasonic sensor 41 having such a structure using the integral type case, reverberation vibration can be suppressed by the elastic adhesive 21.

(Others) In each of the above embodiments, the elastic adhesive is applied to the portion of the conductive member exposed from the case body. However, the elastic adhesive is applied to the portion of the conductive member fixed to the case body and the piezoelectric member. It may be applied to an arbitrary position with a connection portion to the vibration element. However, from the viewpoint of the effect of suppressing reverberation vibration, a position where the conductive member and the case main body adhere to each other as shown in FIG. 3 is desirable. The elastic material applied to the conductive member is not limited to the elastic adhesive, but may be an elastic resin, a foamed resin,
A rubber material or the like may be used.

[0030]

As described above, according to the ultrasonic sensor of the present invention, the operation of applying the elastic adhesive can be simplified without lowering the reverberation characteristics, and the productivity of the ultrasonic sensor can be reduced. Can be enhanced. Alternatively, the reverberation characteristics can be made better than conventional ultrasonic sensors.
Therefore, it is possible to manufacture an ultrasonic sensor capable of measuring accurately up to a short distance.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a structure of a conventional ultrasonic sensor.

FIG. 2 is a reverberation characteristic diagram of the ultrasonic sensor according to the first embodiment.

FIGS. 3A and 3B are a plan view and a cross-sectional view illustrating a structure of an ultrasonic sensor according to an embodiment of the present invention.

FIG. 4 is a reverberation characteristic diagram of the ultrasonic sensor according to the first embodiment;

FIG. 5 is a cross-sectional view illustrating a structure of an ultrasonic sensor according to another embodiment of the present invention.

FIG. 6 is a reverberation characteristic diagram of the ultrasonic sensor according to the first embodiment;

FIG. 7 is a cross-sectional view illustrating a structure of an ultrasonic sensor according to still another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Piezoelectric vibration element 13 Case 15 Vibration plate 18, 19, 42 Conductive member 21, 32 Elastic adhesive

Continuation of the front page (72) Inventor Junichi Koshino 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto F-term in Murata Manufacturing Co., Ltd. (reference) 5D019 AA11 AA22 AA26 BB09 BB28 FF01 GG12 HH03

Claims (4)

[Claims] A bottom portion of a cylindrical case having a bottom is formed as a vibration plate, a piezoelectric vibration element is joined to an inner surface of the vibration plate, and a first conductive member partially fixed to the case is formed of a piezoelectric vibration element. And a second conductive member different from the first conductive member is conducted to the other electrode of the piezoelectric vibration element, and the first conductive member is fixed to the case and connected to the piezoelectric vibration element. An ultrasonic sensor, wherein an elastic material is attached to a first conductive member at an intermediate position between the first conductive member and the connecting portion. 2. The case comprises a substantially cylindrical case main body made of an insulating material and a diaphragm fixed to one opening of the case main body. The ultrasonic sensor according to claim 1, wherein an end of the first conductive member exposed from the case main body is insert-molded in the case main body and connected to an electrode of the piezoelectric vibration element. 3. The case according to claim 1, wherein the elastic material is attached to the first conductive member and the case in the vicinity of a fixed portion of the first conductive member. Ultrasonic sensor. 4. The ultrasonic sensor according to claim 1, wherein an elastic material is attached to a region of the diaphragm closer to the outer periphery than the piezoelectric vibration element.