JP3726465B2 - Ultrasonic transducer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic transducer used for, for example, an obstacle sensor of an automobile, and more specifically, an improvement of an ultrasonic transducer having a structure in which a piezoelectric vibration element is fixed in a conductive case. About.
[0002]
[Prior art]
Conventionally, ultrasonic transducers are used for obstacle sensors in automobiles. This type of ultrasonic transducer is configured using a piezoelectric vibrator, and is disclosed, for example, in Japanese Utility Model Laid-Open No. 3-42532 and Japanese Utility Model Laid-Open No. 4-116498.
[0003]
FIG. 4 is a longitudinal sectional view showing an example of the above-described conventional ultrasonic transducer. The ultrasonic transducer 51 is configured using a metal case 52 made of a metal such as aluminum. The metal case 52 has an opening 52a on the upper side and a thin portion 52b on the lower side. A piezoelectric vibrator 53 is fixed to the inner surface of the thin portion 52b. A sound absorbing material 56 made of felt or the like is disposed on the back side of the piezoelectric vibrator 53 so that an adverse effect due to vibration from the metal case 52 side is unlikely to occur.
[0004]
A lead wire 57 a is bonded to the upper surface of the piezoelectric vibrator 53. The lead wire 57a is connected to the cable 58a, and the cable 58a is drawn out of the case 52.
[0005]
On the other hand, an electrode (not shown) on the lower surface of the piezoelectric vibrator 53 is electrically connected to the metal case 52. A step 52 c is formed at an intermediate height position of the metal case 52, and a lead wire 57 b is joined by solder 59 on the step 52 c. The lead wire 57b is joined to the cable 58b.
[0006]
The space above the felt 56 is filled with a resin 60 having rubber elasticity such as silicon rubber.
[0007]
[Problems to be solved by the invention]
In the ultrasonic transducer 51, in order not to inhibit the vibration of the piezoelectric vibrator 53, that is, to reduce the load on the vibration surface of the piezoelectric vibrator 53, the lead wire 57a is a thin metal of about 0.04 mm. A lead wire composed of a plurality of wires was used. When the diameter of the lead wire 57a is increased, there is a problem that a load on a soldered portion between the piezoelectric vibrator 53 and the lead wire 57a is increased or unnecessary vibration is increased.
[0008]
However, since the thin lead wire 57a is used as described above, when the lead wire 57a is soldered to the piezoelectric vibrator 53, there is a problem that the lead wire 57a tends to be disconnected. Also, since the lead wire 57b is usually made of the same material as that of the lead wire 57a, the lead wire 57b also tends to be disconnected during soldering.
[0009]
In addition, when assembling the ultrasonic transducer 51, the lead wires 57a and 57b are damaged by an undesired external force, and the lead wires 57a and 57b are damaged when assembled or when the finally completed ultrasonic transducer 51 is actually used. Lines 57a and 57b may be disconnected.
[0010]
Further, since the thin lead wires 57a and 57b are used as described above, a skilled worker is required for assembly. In addition, since it is difficult to hold the lead wires 57a and 57b during assembly, the assembly operation cannot be mechanized. Therefore, the ultrasonic transducer 51 is not sufficiently mass-productive and it is difficult to reduce the cost.
[0011]
An object of the present invention is to provide an ultrasonic transducer that is unlikely to cause defects such as disconnection, is excellent in mass productivity, and is inexpensive.
[0012]
[Means for Solving the Problems]
The invention according to claim 1 is an ultrasonic transducer using a piezoelectric vibrator, and has a conductive case, first and second surfaces, and the inner surface of the conductive case from the first surface. A piezoelectric vibrator fixed to the first surface, a first conductive sound-absorbing material fixed to the second surface of the piezoelectric vibrator and disposed in the conductive case, and an inner surface of the conductive case And a second conductive sound absorbing material disposed in the conductive case in a state of being electrically insulated from the first conductive sound absorbing material.
[0013]
Further, the ultrasonic transducer according to the invention of claim 2 is electrically connected to the first and second conductive sound absorbing materials, respectively, and is drawn out of the conductive case. It is further characterized by further comprising first and second lead terminals.
[0014]
Furthermore, the ultrasonic transducer according to the invention of claim 3 is disposed between the first and second conductive sound absorbing materials, and the first conductive sound absorbing material and the second conductive sound absorbing material. An insulating member that electrically insulates the material is further provided.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, non-limiting examples of the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view of an ultrasonic transducer according to a first embodiment of the present invention.
[0016]
The ultrasonic transducer 1 is configured using a cylindrical conductive case 2 having an opening 2a on the upper side and a thin portion 2b on the lower side. The conductive case 2 can be made of a metal material such as aluminum or a material in which a conductive film is formed on the surface of an insulating material such as synthetic resin. In the present embodiment, the conductive case 2 is made of metal.
[0017]
A piezoelectric vibrator 3 is fixed to the thin portion 2 b of the conductive case 2. The piezoelectric vibrator 3 has a structure in which electrodes are formed on both main surfaces of a piezoelectric ceramic such as a lead zirconate titanate-based piezoelectric ceramic, and the lower electrode is joined to the thin portion 2b by the conductive adhesive. ing. However, the electrode on the lower surface of the piezoelectric vibrator 3 may be omitted.
[0018]
Further, a step 2 c is formed on the inner surface at the intermediate height position of the conductive case 2. An insulating member 5 made of an insulating material such as a synthetic resin is disposed above the step 2c. The insulating member 5 includes a base plate 5a and a cylindrical portion 5b extending downward from the lower surface of the base plate 5a. A first conductive sound absorbing material 6 is disposed in the cylindrical portion 5 b, and the first conductive sound absorbing material 6 reaches the upper surface of the piezoelectric vibrator 3. Further, the second conductive sound absorbing material 7 is disposed outside the cylindrical portion 5b.
[0019]
The first and second conductive sound-absorbing materials 6 and 7 are formed by dispersing or filling conductive powder or conductive fiber in a sound-absorbing material such as felt or sponge, and not only have an action as a sound-absorbing material. It is comprised so that it may also have electroconductivity.
[0020]
The lower surface of the first conductive sound absorbing material 6 is in contact with the upper surface of the piezoelectric vibrator 3 via the conductive paint 8a. Although the conductive paint 8a may be omitted, by using the conductive paint 8a, the conduction between the first conductive sound absorbing material 6 and the piezoelectric vibrator 3 can be made more reliable.
[0021]
Similarly, the second conductive sound absorbing material 7 is also in contact with the inner surface of the conductive case 2 through the conductive paint 8b. The conductive paint 8b may also be omitted. Therefore, the electrode on the lower surface of the piezoelectric vibrator 3 is electrically connected to the second conductive sound absorbing material 7 via the case 2, and the electrode on the upper face of the piezoelectric vibrator 3 is connected to the first conductive sound absorbing material. It is electrically connected to the material 6.
[0022]
On the other hand, first and second lead terminals 9a and 9b are attached so as to penetrate the base plate 5a. The tips of the first and second lead electrodes 9a and 9b are inserted into the first and second conductive sound absorbing materials 6 and 7, respectively. Further, the outer ends of the first and second lead terminals 9 a and 9 b are drawn out of the case 2.
[0023]
Further, a resin 10 having rubber elasticity such as silicon rubber is filled above the base plate 5 a and the first and second sound absorbing materials 6 and 7 so as to fill the opening 2 a of the conductive case 2.
[0024]
In the ultrasonic transducer 1 of the present embodiment, no lead wire is used when the piezoelectric vibrator 3 is electrically connected to the first and second lead terminals 9a and 9b. That is, the conductive sound absorbing materials 6 and 7 are used to connect the piezoelectric vibrator 3 and the first and second lead terminals 9a and 9b. Accordingly, disconnection or the like is difficult to occur and assembly is easy.
[0025]
That is, in the ultrasonic transducer according to the present invention, the sound absorbing material arranged on the back surface of the piezoelectric vibrator is made conductive, and the sound absorbing material is used to make electrical connection with the lead terminal of the piezoelectric vibrator 3. As a result, various problems caused by the use of lead terminals have been solved.
[0026]
FIG. 2 is a longitudinal sectional view showing an ultrasonic transducer according to the second embodiment of the present invention. The ultrasonic transducer 11 is configured in the same manner as the ultrasonic transducer 1 of the first embodiment except that the arrangement modes of the first and second conductive sound absorbing materials are different. Therefore, the same parts as those of the ultrasonic transducer 1 are denoted by the same reference numerals, and the description thereof is omitted.
[0027]
In the ultrasonic transducer 11, a cylindrical insulating member 15 is disposed in the conductive case 2. The cylindrical insulating member 15 is made of an appropriate synthetic resin such as polyphenylene sulfide (PPS) and has a flange portion 15a at the upper end. A first conductive sound absorbing material 16 is disposed in a cylindrical insulating member 15, and the conductive sound absorbing material 16 is joined to the upper surface of the piezoelectric vibrator 3 via a conductive paint 8 a. A second conductive sound absorbing material 17 is disposed on the outer periphery of the insulating member 15. The lower end of the conductive sound-absorbing material 17 is located above the lower end 15b of the cylindrical insulating member 15, thereby preventing a short circuit between the first and second conductive sound-absorbing materials 16 and 17. The outer peripheral side surface of the second conductive sound absorbing material 17 is in contact with the small diameter portion 2d of the case 2 via the conductive paint 8b.
[0028]
Further, first and second lead terminals 19a and 19b are joined to the first and second conductive sound absorbing materials 16 and 17, respectively. In the present embodiment, each of the lead terminals 19a and 19b is constituted by a thick lead wire having a diameter of about 0.5 mm. Therefore, although lead wires are used as the lead terminals 19a and 19b, their diameters are relatively large. Therefore, unlike the case of the conventional ultrasonic transducer 51, the lead terminals 19a and 19b are disconnected during assembly. hard. It is also easy to assemble.
[0029]
Also in the ultrasonic transducer 11, since the thin lead wire is not directly joined to the piezoelectric vibrator 3, it is difficult to cause a defect due to the disconnection of the lead wire during assembly, and the first and second conductive sound absorbing materials. Since the electrical connection with the lead terminals 19a and 19b of the piezoelectric vibrator 3 can be achieved by using 16 and 17, the reliability of the electrical connection is enhanced and the mass productivity is also enhanced.
[0030]
FIG. 3 is a longitudinal sectional view showing an ultrasonic transducer according to the third embodiment of the present invention. The same reference numerals are assigned to the same parts as those of the ultrasonic transducer 1 of the first embodiment. The description is omitted by attaching. In the ultrasonic transducer 21, an insulating member 25 is disposed in the conductive case 2. The insulating member 25 is made of a plate-shaped synthetic resin plate, and is arranged as a partition wall in the space in the case 2 so as to reach from one inner wall to the other inner wall.
[0031]
A first conductive sound absorbing material 26 is arranged inside the insulating member 25. The lower end of the first conductive sound absorbing material 26 is in contact with the piezoelectric vibrator 3 via the conductive paint 8a. On the other hand, a second conductive sound absorbing material 27 is disposed on the opposite side of the insulating member 25. The second conductive sound absorbing material 27 is in contact with the step 2c of the conductive case 2 via the conductive paint 8b.
[0032]
First and second lead terminals 29a and 29b are joined to the first and second conductive sound absorbing materials 26 and 27, respectively. The first and second lead terminals 29a and 29b are constituted by cables formed by resin coating of lead wires having relatively large diameters.
[0033]
Also in the present embodiment, the electrical connection with the first and second lead terminals 29a and 29b of the piezoelectric vibrator 3 is performed using the first and second conductive sound absorbing materials 26 and 27. In addition, when a thin lead wire is used, defects such as disconnection hardly occur and assembly can be easily performed. Therefore, similarly to the ultrasonic transducers 1 and 11, since the reliability is high and the mass productivity is high, the cost of the ultrasonic transducer can be reduced.
[0034]
In the ultrasonic transducer according to the present invention, one surface of the piezoelectric vibrator is joined to the thin portion of the conductive case, and the first conductive is provided between the lower surface of the piezoelectric vibrator and the first lead terminal. The case is characterized in that the case and the second lead-out terminal are electrically connected using the second conductive sound absorbing material using the conductive sound absorbing material. About the resin etc. which have rubber elasticity with which it fills in a case, it can change suitably and is not limited to the structure of the Example of illustration.
[0035]
【The invention's effect】
According to the first aspect of the present invention, the piezoelectric vibrator is fixed to the inner surface of the conductive case from the first surface, and the first conductive sound absorbing material is fixed to the second surface of the piezoelectric vibrator. The second conductive sound absorbing material is fixed to the inner surface of the conductive case. Therefore, it is possible to achieve electrical connection with the outside of the piezoelectric vibrator by using a conventionally used sound absorbing material in order to reduce noise by the sound absorbing action. That is, in order to electrically connect the piezoelectric vibrator to the outside, it is not necessary to join a thin lead wire directly to the piezoelectric vibrator. Therefore, disconnection and the like are unlikely to occur, the electrical connection is highly reliable, and assembly work is performed. Therefore, it is possible to provide an inexpensive ultrasonic transmitter / receiver excellent in mass productivity.
[0036]
In the invention described in claim 2, the first and second lead terminals are connected to the first and second conductive sound absorbing materials, respectively, and the first and second lead terminals are conductive cases. Since it is drawn out, it is possible to provide an ultrasonic transducer that can be electrically connected to the outside using the first and second lead terminals.
[0037]
In the invention according to claim 3, since an insulating member that electrically insulates the first and second conductive sound absorbing materials is further provided between the first and second conductive sound absorbing materials, A short circuit between the first and second conductive sound-absorbing materials can be reliably prevented.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an ultrasonic transducer according to a first embodiment of the present invention.
FIG. 2 is a longitudinal sectional view of an ultrasonic transducer according to a second embodiment of the present invention.
FIG. 3 is a longitudinal sectional view of an ultrasonic transducer according to a third embodiment of the present invention.
FIG. 4 is a longitudinal sectional view showing an example of a conventional ultrasonic transducer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Ultrasonic transducer 2 ... Conductive case 2b ... Thin part 3 ... Piezoelectric vibrator 5 ... Insulating member 6 ... 1st conductive sound-absorbing material 7 ... 2nd conductive sound-absorbing material 9a, 9b ... 1st 2nd lead-out terminal 11 ... ultrasonic transducer 15 ... insulating member 16 ... first conductive sound-absorbing material 17 ... second conductive sound-absorbing material 19a, 19b ... first and second lead-out terminals 21 ... ultrasonic wave Transceiver 25 ... insulating member 26 ... first conductive sound absorbing material 27 ... second conductive sound absorbing material 29a, 29b ... first and second lead terminals

Claims (3)

A conductive case;
A piezoelectric vibrator having first and second surfaces, fixed to the inner surface of the conductive case from the first surface;
A first conductive sound-absorbing material fixed to the second surface of the piezoelectric vibrator and disposed in the conductive case;
A second conductive sound-absorbing material that is fixed to the inner surface of the conductive case and disposed in the conductive case in a state of being electrically insulated from the first conductive sound-absorbing material; Ultrasonic transducer characterized by. The first and second conductive sound absorbing materials are further connected to the first and second conductive sound absorbing materials, respectively, and further include first and second lead terminals that are drawn out of the conductive case. The ultrasonic transducer according to claim 1. An insulating member disposed between the first and second conductive sound absorbing materials and further electrically insulating the first conductive sound absorbing material and the second conductive sound absorbing material. The ultrasonic transducer according to claim 1 or 2.

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