Ultrasonic transmitter-receiver

Abstract

The surface of the resin film (8) is provided with a coating layer having an ultraviolet-resistant effect and impact resistance, the coating layer is used as a protective film, and the protective film is bonded to the surface of the ultrasonic sensor, so that the ultrasonic sensor can be protected from impact caused by flying stones and the like without compromising the ultrasonic transmission and reception capability of the ultrasonic sensor. Furthermore, by providing a hard coat layer (9) having an ultraviolet-resistant effect on the surface of the protective film, yellowing due to ultraviolet light can be prevented, and deterioration of sensor characteristics due to peeling of the protective film can also be prevented. In addition, the colored layer (11) is formed by overlapping a plurality of layers of ink toned to be in the same color as the vehicle exterior member, so that the appearance can be ensured.

Description

Technical Field

[0001] The present invention relates to an ultrasonic sensor for use in mid-air, in which a piezoelectric element is bonded to a bottomed cylindrical casing. Background Art

[0002] A safety device is widely used, which incorporates a rangefinder unit using an ultrasonic sensor into a vehicle and notifies the driver of a collision risk when an object approaches the vehicle. In particular, a safety device is widely used, which detects an object behind the vehicle by a rangefinder unit when the vehicle is moving backward and notifies the driver of the approaching object (for example, see Patent Document 1).

[0003] Specifically, a safety device that notifies the driver of an approaching object through a buzzer and a brake-linked safety device that applies the brakes to prevent the vehicle from starting when an obstacle is present in front of the vehicle have been invented.

[0004] In the distance measurement unit using the ultrasonic sensor used here, a drip-proof ultrasonic sensor is mainly used. The drip-proof ultrasonic sensor is introduced in, for example, Patent Document 2 (the drip-proof ultrasonic sensor is referred to as a drip-proof ultrasonic transceiver in the document). The drip-proof ultrasonic sensor has the following structure: a piezoelectric element having electrodes provided on both sides is bonded to the bottom surface of a bottomed cylindrical shell, and the terminals electrically connected to the electrodes of the piezoelectric element are led out to the outside. After covering the upper part of the piezoelectric element with a sponge-like or felt-like sound-absorbing material, it is sealed with an elastic filler such as silicone rubber. The back side of the opening side of the bottomed cylindrical shell is completely covered with a filler such as silicone rubber, thereby forming a structure in which liquid does not penetrate into the interior. Due to the above structure, the electrodes of the piezoelectric element inside the ultrasonic sensor will not be short-circuited to each other, so it can be used even outdoors where liquid may be splashed. The surface of the ultrasonic sensor assembled on the vehicle for transmitting and receiving ultrasonic waves is provided with a coating that matches the exterior color of the vehicle to improve the appearance. However, due to the low strength of the coating film, the surface of the ultrasonic sensor may be damaged by flying stones in the market. If the piezoelectric element inside is broken due to continuous corrosion or surface depression, the sensor will become unable to function. In addition, in the coating-based method, it is difficult to eliminate the defects caused by the attachment of foreign matter during manufacturing and the defects caused by scratches. There is a problem that the coating film is annularly raised on the outer periphery of the appearance surface of the ultrasonic sensor, which deteriorates the appearance. Moreover, when mounted on the vehicle, the directivity of the ultrasonic wave when it is transmitted will change due to the attachment of raindrops and snow, which may cause malfunction. In response to this, as shown in Patent Document 3, it is considered to protect the surface of the ultrasonic sensor by pasting a resin film on the surface to prevent scratches and depressions, but there is a problem that the sound pressure and sensitivity of the ultrasonic sensor are impaired. In addition, regarding the coating implemented on the aforementioned ultrasonic sensor, there are also the following problems: it will fade when exposed to ultraviolet rays in the market, or it is not resistant to liquids, acids, and alkalis such as gasoline and kerosene.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2007-112297

[0008] Patent Document 2: Japanese Patent Application Publication No. 2010-154059

[0009] Patent Document 3: Japanese Patent Application Publication No. 2005-308639 Summary of the invention

[0010] Technical problem that the invention aims to solve

[0011] In the existing ultrasonic sensor, when it is installed on the bumper of the vehicle, etc., the outer surface of the bottomed cylindrical shell is exposed to transmit and receive ultrasonic waves. If the impact caused by flying stones or the like is applied to the outer surface of the sensor during the driving of the vehicle, scratches will be generated on the vibration surface, and the piezoelectric element inside the sensor will be damaged, and there is a problem that the ultrasonic sensor will fall into malfunction. In order to prevent this situation, it is considered to stick a protective film on the outer surface, but in the existing technology, when the protective film is stuck on the outer surface of the sensor, there is a difficulty that the ultrasonic transmission and reception capabilities of the ultrasonic sensor are reduced, and it is difficult to balance the impact resistance and sensor performance. In addition, in the existing ultrasonic sensor, when a transparent protective film is stuck, yellowing caused by ultraviolet rays and heat occurs, and the appearance deteriorates. In addition, in the existing ultrasonic sensor, the film will peel off due to the deterioration of the adhesion between the protective film and the painted surface of the sensor, and the ultrasonic wave will be reflected in the gap, thereby deteriorating the reverberation performance, which may cause malfunction of the system. In addition, when the sensor surface is colored the same color as the vehicle, it is difficult to eliminate defects caused by foreign matter adhesion and damage during manufacturing in the coating method, and there is a problem that the coating film is annularly raised on the outer periphery of the appearance surface of the ultrasonic sensor, which deteriorates the appearance. Moreover, when mounted on a vehicle, the directivity of the ultrasonic transmission changes due to the adhesion of raindrops and snow, which may cause malfunctions. The coating applied to the ultrasonic sensor also has the problem of being intolerant to liquids such as gasoline and kerosene, acids, and alkalis.

[0012] In the structure of an ultrasonic sensor having a bottomed cylindrical shell having a bottom and a cylindrical portion and a piezoelectric element bonded to the inner bottom surface of the bottomed cylindrical shell, a coating having a UV resistance effect and impact resistance and a film thickness of 5 μm to 20 μm is provided on the surface of a resin film having a tensile elastic modulus of 2.0 GPa or more and a film thickness of 30 μm to 115 μm as a protective film, and is bonded to the surface of the bottomed cylindrical shell, thereby protecting the appearance surface and internal structure of the ultrasonic sensor from impact caused by flying stones, etc. without damaging the sound pressure and sensitivity characteristics of the ultrasonic sensor. In addition, by providing a hard coating having a UV resistance effect on the surface of the protective film, it is possible to prevent the appearance from being deteriorated due to yellowing caused by ultraviolet rays, and it is also possible to prevent the characteristics of the ultrasonic sensor from being deteriorated due to film peeling caused by the deterioration of the adhesion between the protective film and the sensor coating surface. In addition, in the coloring for ensuring the appearance, for the ink to be colored the same color as the vehicle exterior parts, the thickness of the coloring layer is suppressed to 10 μm or less by using a method based on printing or the like, and the total thickness of the coloring layer is suppressed by overlapping multiple layers, and the specified color tone can be achieved, thereby further achieving the stability of the performance of the ultrasonic sensor. In addition, in the ultrasonic sensor, by making the protective film joined to the bottomed cylindrical shell cover the bottomed cylindrical shell continuously from the appearance surface to the side of the bottomed cylindrical shell, the coating film is annularly raised on the outer periphery of the appearance surface of the ultrasonic sensor, thereby improving the protection and appearance of the ultrasonic sensor, and the problem of being intolerant to liquids, acids, and alkalis such as gasoline and kerosene. By applying a matte texture generated by texturing or the like on the coating or resin film layer of the above-mentioned protective film, the appearance difference with the matte black resin part used in the grille part of the vehicle disappears, and the appearance can be improved. In addition, by applying a water-repellent coating on the surface of the protective film, the problem of malfunction caused by the change of ultrasonic directivity caused by the adhesion of raindrops and snow when it is set on the vehicle can also be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a structural diagram showing one side surface of the ultrasonic sensor according to claim 1 of the present invention.

[0014] Figure 2 This is a structural diagram showing one side surface of the ultrasonic sensor according to claim 2 of the present invention.

[0015] Figure 3 This is a structural diagram showing one side surface of the ultrasonic sensor according to claim 4 of the present invention.

[0016] Figure 4 This is a diagram showing a structure of an example of a conventional ultrasonic sensor.

[0017] Figure 5 This is a graph showing an example of the thickness of the protective film of the ultrasonic sensor according to the present invention and the sound pressure of the ultrasonic sensor.

[0018] Figure 6 This is a graph showing an example of the impact resistance performance (scar depth) of the ultrasonic sensor according to the present invention and a conventional ultrasonic sensor.

[0019] Figure 7 This is a graph showing an example of the thickness of the resin film and the sound pressure after the impact test in the ultrasonic sensor according to the present invention.

[0020] Figure 8 This is a graph showing an example of the hard coat thickness and the sound pressure after the impact test in the ultrasonic sensor according to the present invention. DETAILED DESCRIPTION

[0021] Example 1

[0022] (Structure of conventional ultrasonic sensor)

[0023] Figure 4 This is an example of a structural diagram of a conventional ultrasonic sensor. In the structure of the conventional ultrasonic sensor, a piezoelectric element 6 including PZT-based ceramics and folded electrodes is bonded to the inner bottom surface of a bottomed cylindrical housing 2 made of aluminum alloy, a molded sponge 5 is arranged on the piezoelectric element 6, a lead wire 4 is electrically connected to each electrode on the piezoelectric element 6 and each terminal of the pin terminal 1 by welding, and the opening side inside the bottomed cylindrical housing 2 is sealed by filling an elastic body 3 made of non-porous silicone resin.

[0024] (Structure of the inventive ultrasonic sensor)

[0025] Figure 1 1 is a structural diagram showing one side of the ultrasonic sensor according to claim 1 of the present invention. Figure 4 The structure of the conventional ultrasonic sensor shown is the same. In the ultrasonic sensor of the mode for implementing claim 1 of the present invention, the member having the hard coating layer 9 on the resin film 8 is bonded to the surface of the bottomed cylindrical housing 2 using an adhesive. In this case, polyethylene terephthalate is used as the material of the resin film 8, and an acrylic material having ultraviolet resistance and impact resistance is used as the material of the hard coating layer 9. An epoxy adhesive is used to bond the protective film A10 to the bottomed cylindrical housing 2. Figure 21 is a structural diagram showing one side of an ultrasonic sensor according to claim 2 of the present invention. In the ultrasonic sensor according to the mode for implementing claim 2 of the present invention, the size of the protective film A10 used in claim 1 is processed to be larger than the bottomed cylindrical case 2, the bottomed cylindrical case 2 and the protective film A10 are loaded into a molding die while being heated, and epoxy adhesive is used and hardened while being pressurized, so that the bottomed cylindrical case 2 is continuously covered from the outer surface to the side of the bottomed cylindrical case 2. Figure 3 1 is a structural diagram showing one side of the ultrasonic sensor according to claim 4 of the present invention. In the ultrasonic sensor according to the mode for implementing claim 4 of the present invention, a coloring layer 11 is printed by screen printing on the surface of the resin film 8 not bonded to the hard coating layer 9 in the protective film B12, and the coloring layer 11 is colored with ink of the same color as the vehicle exterior component, and the bottomed cylindrical housing 2 and the protective film B12 are bonded via an epoxy adhesive in the same manner as the ultrasonic sensor according to claim 1. In addition, the adhesive does not necessarily have to be an epoxy adhesive, and an acrylic adhesive may also be used.

[0026] Figure 5 This is a graph showing an example of the thickness of the protective film of the ultrasonic sensor involved in the present invention and the sound pressure of the ultrasonic sensor. If the thickness of the protective film is in the range of 30 μm to 115 μm, the sound pressure reduction of the ultrasonic sensor after the protective film is bonded to the bottomed cylindrical housing can meet the level of 103 dB that does not cause performance problems. Figure 6 This is a graph showing an example of the impact resistance performance (scratch depth) of the ultrasonic sensor involved in the present invention and the existing ultrasonic sensor. In this verification, in the ultrasonic sensor involved in the present invention, the thickness of the resin film was changed between 30μm and 120μm to confirm. In the existing ultrasonic sensor, the scratch depth after the impact test was 65μm, but in the ultrasonic sensor involved in the present invention, the scratch depth was 20μm to 50μm in the range of the resin film thickness of 30μm to 120μm, and improvement was seen. Figure 7 This is a graph showing an example of the thickness of the resin film in the ultrasonic sensor involved in the present invention and the sound pressure after the impact test. The thickness of the resin film was checked from 30μm to 120μm. The result was that in the conventional ultrasonic sensor, the sound pressure drop after the impact test was -6.0dB, while in the ultrasonic sensor involved in the present invention, the sound pressure drop was greatly improved to -1.4dB to -0.4dB. Figure 5 , Figure 6 , Figure 7 As a result, the thickness of the protective film was set to 30 μm to 115 μm in consideration of the balance between the sound pressure drop before and after the protective film was bonded to the bottomed cylindrical case and the sound pressure drop after the impact resistance test. Figure 8 This is a graph showing an example of the thickness of the hard coating layer in the ultrasonic sensor involved in the present invention and the sound pressure after the impact test. In this verification, the thickness of the resin film was set to a range of 30μm to 120μm, and the thickness of the hard coating layer was changed between 2μm and 20μm to confirm the reduction in sound pressure after the impact test. The combination of the hard coating layer when the thickness of the resin film was 30μm had a significant reduction in sound pressure after the impact test. The thickness of the hard coating layer was set to 5μm to 20μm as the target to meet the sound pressure reduction level of -1.5dB required for sensor performance.

[0027] Here, the features of the connector of the present embodiment described above will be briefly summarized and listed below.

[0028] [1] An ultrasonic sensor, characterized in that:

[0029] It comprises: a bottomed cylindrical shell (2) having a bottom and a cylindrical portion; and a piezoelectric element (6) bonded to the inner bottom surface of the bottomed cylindrical shell (2). In the structure of the ultrasonic sensor, a coating having UV resistance and impact resistance and a film thickness of 5 μm to 20 μm is provided on the surface of a resin film having a tensile elastic modulus of more than 2.0 GPa and a film thickness of 30 μm to 115 μm, and the coating is used as a protective film (10, 12) and bonded to the surface of the bottomed cylindrical shell (2).

[0030] [2] The ultrasonic sensor according to [1] above, wherein:

[0031] The protective film (10, 12) joined to the bottomed cylindrical shell (2) continuously covers the bottomed cylindrical shell (2) from the exterior surface to the side surface of the bottomed cylindrical shell (2), thereby achieving both protection and aesthetics.

[0032] [3] The ultrasonic sensor according to [1] above, wherein:

[0033] A matte texture is applied to the coating layer or the resin film layer of the protective film (10, 12) by texturing, etc., thereby improving the aesthetics of the vehicle.

[0034] [4] The ultrasonic sensor according to [1] or [2], wherein:

[0035] A layer colored with ink having the same color as the vehicle exterior component is provided on the back side of the resin film (8) in the protective film (10, 12), and the colored layer is constructed by overlapping a plurality of layers having a thickness of less than 10 μm so as to suppress the deviation of the total thickness of the colored layer and achieve a predetermined color tone.

[0036] [5] An ultrasonic sensor according to any one of [1] to [3], wherein:

[0037] A water-repellent coating is applied on the surface of the protective film (10, 12).

[0038] While the present invention has been described in detail and with reference to specific embodiments, it will be apparent to one skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention.

[0039] This application is based on the Japanese patent application (Japanese Patent Application No. 2022-067891) filed on April 15, 2022, the contents of which are incorporated herein by reference.

[0040] Possibility of industrial application

[0041] The present invention can be applied not only to a reversing sensor, a corner sensor, and an automatic parking system for a vehicle, but also to various fields using an ultrasonic sensor.

[0042] Explanation of symbols

[0043] 1. Pin terminal

[0044] 2. A cylindrical shell with a bottom made of aluminum alloy

[0045] 3. Elastomer made of non-porous silicone resin

[0046] 4. Lead

[0047] 5. Sponge

[0048] 6. Piezoelectric elements

[0049] 7. Adhesive layer

[0050] 8. Resin film

[0051] 9. Hard coating

[0052] 10. Protective film A

[0053] 11. Coloring layer

[0054] 12. Protective film B

[0055] 13. Base coating

[0056] 14. Base coat

[0057] 15. Varnish

[0058] 16. Surface coating

Claims

1. An ultrasonic sensor, characterized in that: The ultrasonic sensor comprises: a cylindrical shell with a bottom, the cylindrical shell having a bottom and a cylindrical portion; and a piezoelectric element, the piezoelectric element being bonded to the inner bottom surface of the cylindrical shell with a bottom. In the structure of the ultrasonic sensor, a coating having UV resistance and impact resistance and a film thickness of 5 μm to 20 μm is provided on the surface of a resin film having a tensile elastic modulus of 2.0 GPa or more and a film thickness of 30 μm to 115 μm, and the coating is used as a protective film and bonded to the surface of the cylindrical shell with a bottom.

2. The ultrasonic sensor according to claim 1, characterized in that: The protective film joined to the bottomed cylindrical case continuously covers the bottomed cylindrical case from the outer surface to the side surface of the bottomed cylindrical case, thereby achieving both protection and aesthetics.

3. The ultrasonic sensor according to claim 1, characterized in that: A matte texture is applied to the coating layer or the resin film layer of the protective film by texturing or the like, thereby improving the aesthetics of the vehicle.

4. The ultrasonic sensor according to claim 1 or 2, characterized in that: A layer colored with ink toned to the same color as the vehicle exterior component is provided on the back side of the resin film in the protective film. The colored layer is configured to achieve a predetermined color tone while suppressing variation in the total thickness of the colored layer by stacking a plurality of layers having a thickness of 10 μm or less.

5. The ultrasonic sensor according to any one of claims 1 to 3, characterized in that: A water-repellent coating is provided on the surface of the protective film.

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