JPH0563196U - Ultrasonic sensor - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To provide a high-sensitivity ultrasonic sensor that can keep costs down and is free from reverberation. [Structure] In an ultrasonic sensor using a piezoelectric element, in order to improve the influence of electromagnetic noise as well as acoustic matching characteristics,
The ultrasonic sensor of the present invention is provided with a case (1) made of a plastic material, a piezoelectric element (3) mounted on the bottom surface of the case (1), and surrounding the piezoelectric element (3). Insulator layers (7a, 14a) on the inside and conductor layers (7a, 14a) on the outside
b, 14b) and a shield member (7, 14) made of a flexible substrate, respectively.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an ultrasonic sensor using a piezoelectric element.

[0002]

[Prior Art]

 As an ultrasonic sensor of this type, for example, as proposed in Utility Model Registration No. 1778125, a piezoelectric element is attached to the center of the inner bottom surface of a case made of foamable plastic material, and it is provided on both upper and lower surfaces of the piezoelectric element. There is known a type in which an electrode is connected to a connection terminal which communicates with the outside and an opening of a case is closed by a lid member. A similar type is also disclosed in Japanese Utility Model Application Laid-Open No. 1-41279. In such a known device, by using a foamed plastic material having a low Q value for the case, a high acoustic attenuation effect can be obtained, and as a result, the reverberation time can be significantly shortened and a sensor having high sensitivity can be provided. I can do it. In addition to the reverberation problem, there is a problem of noise caused by electromagnetic waves from the outside, as is well known that affects the sensitivity of the sensor. This problem can be solved by making the case metallic and magnetically shielding the internal piezoelectric element.However, in addition to the reverberation problem described above, the metal part is exposed on the outer peripheral surface of the case. There is also a problem from the viewpoint of electric shock prevention.

An example of solving the problem of electric shock associated with a device using such a metal case is disclosed in Japanese Utility Model Publication 2-27676. In the one disclosed in this publication, the case body is made of an insulating material, and a metal coating for electromagnetic shielding is formed on the entire inner peripheral surface thereof.

[0004]

[Problems to be solved by the device]

 By the way, in the structure using an insulating material case in which a metal coating for an electromagnetic shield is applied to the entire inner peripheral surface as described in Japanese Utility Model Publication No. 27676/1990, the influence of noise due to electromagnetic waves from the outside The problem of electric shock and electric shock can be solved, but the effect of reverberation cannot be virtually eliminated. In addition, this type of sensor is usually very small, and since the metal coating on the inner surface of the case body made of insulating material is usually formed by sputtering or vapor deposition, an expensive film forming apparatus must be used. There is also the problem that the cost of the sensor is high. Furthermore, in the structure in which a metal coating is formed on the inner surface of the case body, in order to ensure electrical insulation from the sensor body, leave a sufficient gap between the periphery of the piezoelectric element of the sensor body and the metal coating. The size of the case must be designed larger than the size of the piezoelectric element.

Therefore, the present invention solves such conventional problems, and provides a high-sensitivity ultrasonic sensor which can keep costs down and is free from the effects of reverberation and external electromagnetic noise. The purpose is to

[0006]

[Means for Solving the Problems]

 In order to achieve the above object, the ultrasonic sensor according to the present invention mounts a piezoelectric element having electrodes on both upper and lower surfaces on the inner bottom surface of a case made of plastic material, and connects both electrodes of this piezoelectric element. A shield member consisting of a flexible substrate with a conductor layer and an insulator layer, which is connected to the terminals and guided to the outside of the case, surrounds the piezoelectric element between the piezoelectric element and the inner peripheral surface of the case, and It is characterized in that the insulating layer side is placed so as to face the piezoelectric element, and the conductor layer of the shield member is connected to the ground. The shield member may be formed by forming a belt-shaped flexible substrate into an annular shape. Alternatively, the shield member may be formed by integrally punching an annular side peripheral portion and a circular lid portion from a flexible substrate. Further, a part of the conductor layer of the shield member may be pressed against one electrode of the piezoelectric element.

[0007]

[Action]

 In the ultrasonic sensor according to the present invention having such a configuration, since the shield member is made of the flexible substrate, it can be easily mounted in the case and can be easily assembled. Also, since the shield member has an insulator layer on the inside facing the outer peripheral surface of the piezoelectric element, the insulation between the piezoelectric element does not cause any problem, and therefore the gap between the piezoelectric element and the shield member does not work. It is enough to leave the vibration of the piezoelectric element so as not to interfere with it, and the size of the case can be minimized. Moreover, since the case body is made of a plastic material, a high acoustic damping effect can be obtained and the influence of reverberation during operation can be substantially prevented. Furthermore, when the shield member is formed by punching and molding an annular peripheral side portion and a circular lid portion integrally from a flexible substrate, the entire outer periphery of the piezoelectric element can be covered, and the shield effect is further improved. Can be increased.

[0008]

【Example】

 Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an embodiment of the present invention. In the illustrated apparatus, 1 is a cylindrical case, and this case 1 is made of a foamable plastic material, for example, a material in which glass microballoons are dispersed and mixed in epoxy resin. Made of The outer central part 2 of the bottom of the case 1 is bulged, and the thickness of the case including this bulged portion is dimensioned so that it is approximately equal to the wavelength of 1/4 of the sound velocity of the case material used. It is decided so that the loss at the bottom of Case 1 is reduced. A disk-shaped piezoelectric element 3 is fixed to the central portion of the inner bottom surface of the case 1, and the piezoelectric element 3 is provided with electrodes 4 and 5 on both upper and lower surfaces thereof as shown in the figure. These electrodes 4, 5 are connected to the respective conductors 6a, 6b of the connection cord 6. Around the piezoelectric element 3, there is arranged a shield member 7 in which a band-shaped flexible substrate as shown in FIG. 2 is formed in an annular shape as shown in FIG. 3, and the shield member 7 is made of an insulating material such as polyamide. It has a structure in which the body layer 7a and the conductor layer 7b such as a copper foil are bonded together by an appropriate means such as thermocompression bonding. As shown in FIG. 3, the insulator layer 7a is curved inside and both edges are polymerized. To form a ring. As a result, when mounted in the case 1, the insulating layer 7a is positioned inside the piezoelectric element 3 so as to face the periphery of the piezoelectric element 3 and ensure insulation from the piezoelectric element 3. The shield member 7 also includes a lead terminal 7c, and the lead terminal 7c is connected to the ground. As a result, the shield member 7 serves to prevent the influence of noise from electromagnetic waves from the outside on the piezoelectric element 3. Alternatively, both ends of the shield member 7 may be inserted into the case 1 in a curved state without being fixed, and then loosened so that the shield member 7 is elastically attached to the inner surface of the case 1 by the restoring force of the shield member itself. After mounting the piezoelectric element 3 and the shield member 7 in the case 1, the opening of the case 1 is sealed with a molding material 8 such as urethane resin or silicon rubber, and the connection cord 6 connected to each electrode of the piezoelectric element 3 and The lead terminal 7c of the shield member 7 is extended to the outside through the molding material 8.

FIG. 4 shows another embodiment of the present invention, and parts corresponding to the embodiment of FIG. 1 are designated by the same reference numerals. In this embodiment, the case 1 has a flat structure with no protrusions on the bottom, and the electrodes 4 and 5 of the piezoelectric element 3 extend to the outside implanted in the sealing plate 13 via the lead wires 9 and 10. Connected to terminal pins 11 and 12, respectively. The other structure is the same as that of the embodiment of FIG.

FIG. 5 shows still another embodiment, and in this case also, parts corresponding to those of the embodiment shown in FIG. This embodiment differs from the embodiment of FIG. 1 in the configuration and arrangement of the shield member 14. That is, in this embodiment, as shown in FIG. 6, the shield member 14 is formed by punching out a flexible substrate in which an insulating layer 14a made of polyamide or the like and a conductor layer 14b made of copper foil or the like are bonded together by an appropriate means such as thermocompression bonding. The circular lid portion 15, the side peripheral portion 16 and the ground terminal portion 17 are integrally formed by molding, and the side peripheral portion 16 is bent into an annular shape so that the insulating layer 14a is inside as shown by the phantom line, and the lid is closed. It is configured by bending the portion 15 toward the side peripheral portion 16 that is bent in an annular shape, and further by folding the ground terminal portion 17 with respect to the side peripheral portion 16. A hole 18 through which the connection cord 6 is passed is provided in the center of the lid portion 14, and the conductor layer 14b of the ground terminal portion 17 is pressed against the extended portion 4a of the electrode 4 provided on the upper surface of the piezoelectric element 3 during assembly. To be done. After the shield member 14 is mounted around the piezoelectric element 3, the outside is sealed with a molding material 8 such as urethane resin or silicon rubber as shown in the figure. In this embodiment, since the conductor layer 14b of the ground terminal portion 17 provided on the shield member 14 is brought into pressure contact with the electrode 4 provided on the upper surface of the piezoelectric element 3, that is, the negative electrode, as shown in FIGS. It is not necessary to provide a ground connection terminal that communicates with the outside to the shield member 14, and the electrical connection work can be simplified. Further, in the configuration of this embodiment, since the shield member 14 covers the entire outer circumference of the piezoelectric element 3, it is recognized that the shield effect against radio waves can be further enhanced.

By the way, in the embodiment of FIG. 1, the connection cord is used as the connection terminal for the electrode of the piezoelectric element, but instead, the connection terminal composed of the lead wire and the terminal pin as shown in FIG. 4 is used. Similarly, in the embodiment shown in FIG. 4, the electrode of the piezoelectric element can be connected to the outside by using the connecting cord as in the case of FIG. Further, the shape of the case, the shape and size of the shield member, etc. can be arbitrarily changed according to the piezoelectric element used. Further, in the embodiment shown in FIG. 1 or 4, the lead terminal of the shield member may be bent as in the embodiment of FIG. 5 and brought into pressure contact with the electrode 4 of the piezoelectric element 3.

[0012]

[Effect of the device]

 As described above, in the ultrasonic sensor of the present invention, the case is made of a plastic material and the shield member made of a flexible substrate is provided around the piezoelectric element. It is possible to obtain the desired high sensitivity, and since the shield member is only inserted into the case, compared with the conventional structure in which a metal coating for shielding is applied to the inner surface of the case, the device manufacturing The cost can be significantly reduced, and since the periphery of the piezoelectric element is surrounded by the insulator layer of the shield member, the gap around the piezoelectric element is as small as that required for vibration during its operation. Space is enough, the size of the case can be reduced, and the sensor can be downsized.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an ultrasonic sensor according to an embodiment of the present invention.

2 is a schematic perspective view showing a strip-shaped flexible substrate used in the apparatus of FIG.

3 is a schematic perspective view showing a shield member in which the strip-shaped flexible substrate of FIG. 2 is formed in an annular shape.

FIG. 4 is a vertical sectional view showing another embodiment of the present invention.

FIG. 5 is a vertical sectional view showing an ultrasonic sensor according to still another embodiment of the present invention.

6 is a schematic perspective view showing a stamped and formed flexible substrate which constitutes a shield member used in the apparatus of FIG.

[Explanation of symbols]

 1: Case 2: Outer central part 3: Piezoelectric element 4: Electrode 5: Electrode 6: Code 7: Shield member 8: Mold material 14: Shield member

Claims (4)

[Scope of utility model registration request] 1. A piezoelectric element having electrodes on both upper and lower surfaces is attached to an inner bottom surface of a case made of a plastic material, and both electrodes of the piezoelectric element are connected to connection terminals to lead to the outside of the case. Enclose the piezoelectric element between the element and the inner surface of the case, insert a shield member consisting of a flexible substrate with an insulator layer inside and a conductor layer outside, and ground the conductor layer of the shield member. An ultrasonic sensor characterized by being connected. 2. The ultrasonic sensor according to claim 1, wherein the shield member comprises a belt-shaped flexible substrate formed in an annular shape. 3. The ultrasonic sensor according to claim 1, wherein the shield member is formed by punching and molding an annular side peripheral portion and a circular lid portion integrally from a flexible substrate. 4. The ultrasonic sensor according to claim 1, wherein a part of the conductor layer of the shield member is pressed against one electrode of the piezoelectric element.