JP2008271439A - Ultrasonic sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic sensor capable of preventing generation of a noise signal and preventing extension of a reverberation period. <P>SOLUTION: An ultrasonic sensor comprises: an approximately cylindrical case 1 with a bottom having a plate-like vibrator part 1a; a piezoelectric vibrating element 2 that is abutted to the vibrator part 1a and vibrates the vibrator part 1a; a holder 3 that is provided on an upper surface of the vibrator part 1a so as to cover the outer circumference of the piezoelectric vibrating element 2; and a sound absorber 4 that is housed within the case 1 and disposed on the holder 3 while being spaced apart from the piezoelectric vibrating element 2 at a predetermined interval in a direction of thickness, wherein a surface of the piezoelectric vibrating element 2 facing the sound absorber 4 is covered with an elastic adhesive film 2a made of an elastic material. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ultrasonic sensor.

  2. Description of the Related Art Conventionally, an ultrasonic sensor that is installed in a vehicle bumper or the like and detects an obstacle around the vehicle is known. Hereinafter, a conventional example of this type of ultrasonic sensor will be described with reference to the drawings. In the following description, the vertical direction in FIG. 5B is defined as the vertical direction.

  As shown in FIG. 5, this conventional example includes a piezoelectric vibration element 2 for generating ultrasonic waves, a sound absorbing material 4 for absorbing ultrasonic waves, a holding material 3 for holding the sound absorbing material 4, and a piezoelectric vibration element 2. And a case 1 that houses the sound absorbing material 4, a piezoelectric vibration element 2, and a case 1 that is connected to the case 1 and transmits a drive signal for driving the piezoelectric vibration element 2 to the piezoelectric vibration element 2. A positive lead wire 6a and a negative lead wire 6b for transmitting signals to an external electric circuit (not shown), an elastic adhesive 7 for suppressing reverberation vibration of ultrasonic waves, and a case 1 for sealing the inside of the case 1 And a sealing material 8.

  The case 1 has a substantially cylindrical shape with a bottom, and as shown in FIG. 5B, a substantially circular piezoelectric vibration element 2 is attached to the inner bottom portion of the case 1 with a resin adhesive. The bottom vibrates when the piezoelectric vibration element 2 is driven to transmit ultrasonic waves, and the bottom is vibrated by a reflected wave from an object to be detected (not shown) to drive the piezoelectric drive element 2 to reflect the reflected wave. It plays the role of the vibrating body portion 1a that receives.

  A ring-shaped holding member 3 is disposed on the vibrating body portion 1 a so as to cover the outer periphery of the piezoelectric vibration element 2. The holding material 3 is made of silicone resin, and the thickness dimension thereof is set larger than the thickness dimension of the piezoelectric vibration element 2. Thus, when a substantially circular sound absorbing material 4 made of polyester fiber is placed on the upper surface of the holding material 3, a space is formed between the sound absorbing material 4 and the piezoelectric vibration element 2. 4 does not directly contact the piezoelectric vibration element 2. Further, the elastic adhesive 9 is applied over the entire surface excluding the holding material 3 on the upper surface of the vibrating body portion 1a. The elastic adhesive 9 is made of, for example, a silicone resin and suppresses the propagation of vibration to the case 1.

  One end of a plus lead wire 6a is soldered to the upper surface of the piezoelectric vibration element 2 with solder 10, and the other end is a substrate 5 described later through a substantially semicircular cutout 4a provided in the sound absorbing material 4. It is connected to the. Further, one end portion of the minus lead wire 6b is soldered to the inner peripheral surface of the upper portion of the case 1 with solder 10, and the other end portion is connected to a substrate 5 described later.

  An elastic adhesive 7 made of silicone resin or the like is filled from the bottom of the case 1 to a substantially center in the vertical direction, and an upper surface of the elastic adhesive 7 is connected to an external electric circuit (not shown). A substrate 5 to which one end of a connector cable 5a is connected is disposed. The substrate 5 is connected to the other end of the plus lead 6a whose one end is connected to the piezoelectric vibration element 2 and the other end of the minus lead 6b whose one end is connected to the case 1. The connector cable 5a is electrically connected to the plus lead wire 6a and the minus lead wire 6b through the substrate 5. Thus, a drive signal is supplied to the piezoelectric vibration element 2 via the connector cable 5a, and a reflection signal received by the vibration body portion 1a and converted into an electric signal by the piezoelectric vibration element 2 is transmitted to the electric circuit. It has become. Further, a sealing material 8 made of silicone resin or the like is filled from the approximate center in the vertical direction of the case 1 to the opening surface.

  Hereinafter, a method for assembling the above ultrasonic sensor will be described. First, one end portion of the negative lead wire 6b is soldered to the inner peripheral surface of the upper portion of the case 1 with the solder 10, and the piezoelectric vibration element 2 is attached to the upper surface of the bottom portion of the case 1, which is the vibrating body portion 1a, with a resin adhesive. Then, one end portion of the plus lead wire 6 a is soldered to the upper surface of the piezoelectric vibration element 2 with the solder 10. Next, the holding material 3 is applied to the upper surface of the bottom of the case 1 in a ring shape so as to cover the outer periphery of the piezoelectric vibration element 2, and further elastically bonded to the entire bottom of the case 1 except for the piezoelectric vibration element 2 and the holding material 3. Agent 9 is applied. Thereafter, the sound absorbing material 4 is placed on the upper surface of the holding material 3, and the elastic adhesive 7 is filled to the approximate center in the vertical direction of the case 1 and cured. Finally, the substrate 5 is placed on the upper surface of the cured elastic adhesive 7, and the other end portion of the plus lead wire 6a and the other end portion of the minus lead wire 6b are soldered to the substrate 5, and the sealing material 8 is attached. It is completed by filling up to the opening surface of the case 1 and curing.

As described above, the ring-shaped holding material 3 is disposed so as to cover the outer periphery of the piezoelectric vibration element 2, and the sound absorbing material 4 is disposed on the upper surface of the holding material 3. By providing a space between them, the reverberation time is reduced by preventing direct contact between the piezoelectric vibration element 2 and the sound absorbing material 4.
JP-A-2005-39688

  However, in the above conventional example, when a foreign object such as a metal fragment is present on the upper surface of the piezoelectric vibration element 2, the foreign object moves to apply stress to the piezoelectric vibration element 2, except for the reflected wave from the detected object. There was a problem that a noise signal was generated. In addition, the sound absorbing material 4 is bent by the weight of the elastic adhesive 7, and there is a problem that the reverberation time is extended due to contact with the piezoelectric vibration element 2.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an ultrasonic sensor capable of preventing generation of a noise signal and preventing the reverberation time from extending.

  In order to achieve the above object, a first aspect of the present invention provides a bottomed cylindrical case having a vibrating body portion comprising a flat bottom plate, and a piezoelectric vibration that abuts on the vibrating body portion to vibrate the vibrating body portion. An element, a holding material provided on the vibrating body so as to cover the outer periphery of the piezoelectric vibration element, and a sound absorbing material housed in the case and disposed on the holding material at a predetermined interval from the piezoelectric vibration element The surface of the piezoelectric vibration element facing the sound absorbing material is covered with an elastic adhesive film made of an elastic material.

  In order to achieve the above object, a second aspect of the invention provides a bottomed cylindrical case having a vibrating body portion made of a flat bottom plate, and a piezoelectric vibration that abuts the vibrating body portion and vibrates the vibrating body portion. An ultrasonic sensor comprising an element, wherein the surface of the piezoelectric vibration element opposite to the surface in contact with the vibration body part and the entire surface of the vibration body part excluding the piezoelectric vibration element in the case are made of an elastic material. It is characterized by being covered with an adhesive film.

  The invention of claim 3 is characterized in that, in the invention of claim 1 or 2, the elastic adhesive film is covered over the entire inner surface of the case.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the case is sealed with an insulating material made of an insulating material, and the elastic adhesive film is bonded to the case and the insulating material. It is characterized by comprising a mediating material for improving the performance.

  The invention of claim 5 is the invention of any one of claims 1 to 3, wherein the elastic adhesive film is made of a film material.

The invention of claim 6 is the invention according to any one of claims 1 to 3, wherein the elastic adhesive film is made of a sealing material. The invention of claim 7 is an elastic film according to the invention of claim 6. The adhesive film is formed by spraying a sealing material with a spray.

  According to the first aspect of the present invention, since the surface of the piezoelectric vibration element facing the sound absorbing material is covered with the elastic adhesive film, even if a foreign object such as a metal fragment exists on the piezoelectric vibration element, the piezoelectric vibration element is Can be prevented from being stressed, and therefore generation of a noise signal can be prevented. Further, even if the sound absorbing material is bent, it can be prevented from coming into direct contact with the piezoelectric vibration element because it is in contact with the elastic adhesive film, and therefore, the reverberation time can be prevented from being extended.

  According to the second aspect of the present invention, since the surface of the piezoelectric vibration element facing the sound absorbing material is covered with the elastic adhesive film, even if foreign matter such as metal fragments is present on the piezoelectric vibration element, the piezoelectric vibration element is caused by the foreign matter. Can be prevented from being stressed, and therefore the generation of noise signals can be reduced. Also, since no holding material and sound absorbing material are required, the number of parts can be reduced and the assembly process can be simplified, and the reverberation time can be prevented from being extended without considering the contact between the sound absorbing material and the piezoelectric vibration element. can do.

  According to the third aspect of the present invention, since the entire surface of the case is covered with the elastic adhesive film, the propagation of vibration to the case can be suppressed, and therefore reverberation can be reduced.

  According to the invention of claim 4, since the elastic adhesive film is made of a mediating material that improves the adhesion between the case and the insulating material, the adhesion of the insulating material to the case can be improved, and therefore vibration of the case can be prevented. Reverberation can be reduced by suppressing propagation.

  In the invention of claim 6, since the elastic adhesive film is made of a sealing material, workability when applying the elastic adhesive film to the piezoelectric vibration element can be improved.

  According to the seventh aspect of the invention, since the elastic adhesive film is applied to the piezoelectric vibration element by spraying the sealing material by spraying, workability can be improved.

(Embodiment 1)
Hereinafter, an ultrasonic sensor according to a first embodiment of the present invention will be described with reference to the drawings. However, since the basic configuration of this embodiment is the same as that of the conventional example, common portions are denoted by the same reference numerals and description thereof is omitted. In this embodiment, as shown in FIG. 1B, the upper surface of the piezoelectric vibration element 2 is covered with an elastic adhesive film 2a made of an elastic material such as a silicone resin. Hereinafter, the result of the experiment which measured the reverberation characteristic of this embodiment and a prior art example is demonstrated using Fig.2 (a), (b). In each figure, the horizontal axis represents the elapsed time t after the vibration of the piezoelectric vibration element 2 is stopped, and the vertical axis represents the output voltage V from the lead wires 6a and 6b, that is, the strength of reverberation vibration. .

  In the conventional example, as shown in FIG. 2B, after the reverberation vibration is settled, a noise signal is generated as if there is a reflected wave from the detected object. This is because a foreign object (not shown) such as a metal fragment existing on the upper surface of the piezoelectric vibration element 2 moves to give stress to the piezoelectric vibration element 2. In contrast, in this embodiment, the upper surface of the piezoelectric vibration element 2 is covered with the elastic adhesive film 2a, so that the stress applied to the piezoelectric vibration element 2 by the elastic adhesive film 2a even if the foreign matter moves on the piezoelectric vibration element 2. Therefore, as shown in FIG. 2A, the generation of the noise signal after the reverberation vibration is stopped is prevented.

  In the conventional example, as shown by the broken line in FIG. 2A, the reverberation vibration continues until time t2 due to the influence of the vibration caused by the sound absorbing material 4 coming into direct contact with the piezoelectric vibration element 2, but this embodiment Then, since the sound absorbing material 4 is prevented from coming into direct contact with the piezoelectric vibration element 2 by the elastic adhesive film 2a, the reverberation vibration is contained at time t1 (t1 <t2) as shown by the solid line in FIG.

  As described above, since the upper surface of the piezoelectric vibration element 2 is covered with the elastic adhesive film 2a made of an elastic material, even if foreign matter such as metal fragments exists on the piezoelectric vibration element 2, the piezoelectric vibration element is caused by the foreign matter. 2 can be prevented from being stressed, and therefore a noise signal can be prevented from being generated after the reverberation vibration has subsided. Further, even if the sound absorbing material 4 is bent, it can be prevented from coming into direct contact with the piezoelectric vibration element 2 because it is in contact with the elastic adhesive film 2a, and therefore, the reverberation time can be prevented from being extended.

(Embodiment 2)
Hereinafter, an ultrasonic sensor according to a second embodiment of the present invention will be described with reference to the drawings. However, since the basic configuration of this embodiment is the same as that of the conventional example, common portions are denoted by the same reference numerals and description thereof is omitted. In the present embodiment, as shown in FIG. 3B, the holding material 3, the sound absorbing material 4, and the elastic adhesive 9 are excluded, and the piezoelectric vibration element 2 on the upper surface of the piezoelectric vibration element 2 and the upper surface of the vibration body portion 1a is excluded. The entire surface is covered with the elastic adhesive film 2a.

  By configuring in this manner, similarly to the first embodiment, even if foreign matters such as metal fragments are present on the piezoelectric vibration element 2, it is possible to prevent the piezoelectric vibration element 2 from being stressed by the foreign substances, Therefore, it is possible to prevent a noise signal from being generated after the reverberation vibration has subsided. In addition, since the sound absorbing material 4 is not provided, it is not necessary to consider the contact of the sound absorbing material 4 with the piezoelectric vibration element 2, and therefore it is possible to prevent the reverberation time from being extended. Furthermore, by not providing the holding material 3, the sound absorbing material 4, and the elastic adhesive 9, the number of parts can be reduced and the assembling process can be simplified.

  As shown in FIGS. 4B and 4C, the entire inner periphery of the case 1 may be covered with an elastic adhesive film 2a. In this case, propagation of vibration to the case 1 can be suppressed, and therefore reverberation can be reduced.

  By the way, as the elastic adhesive film 2a in each of the above embodiments, a mediating material for improving the adhesiveness of the elastic adhesive 7 and the sealing material 8 to the case 1 may be used. In this case, since the adhesiveness of the elastic adhesive 7 and the sealing material 8 to the case 1 is improved, propagation of vibration to the case 1 can be suppressed, and therefore reverberation can be reduced.

  Moreover, you may use a film material as a material of the elastic adhesive film 2a. Further, a sealing material such as Humiseal (registered trademark) may be used as the material of the elastic adhesive film 2a. In this case, the work of applying the elastic adhesive film 2a by spraying the sealing material with a spray or the like becomes easy, and the workability can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the ultrasonic sensor of Embodiment 1 of this invention, (a) is a whole schematic diagram, (b) is an AA 'line cross-sectional arrow view, (c) is a BB' line cross-sectional arrow. FIG. It is a figure which shows a signal waveform same as the above, (a) is a wave form diagram of this invention, (b) is a wave form diagram in case a noise signal generate | occur | produces in a prior art example. It is a figure which shows the ultrasonic sensor of Embodiment 2 of this invention, (a) is a whole schematic diagram, (b) is an AA 'line sectional arrow view, (c) is a BB' line sectional arrow. FIG. It is a figure which shows the case where the case inner peripheral surface same as the above is covered with an elastic adhesive film, (a) is an overall schematic diagram, (b) is a cross-sectional view taken along the line AA ′, and (c) is BB. 'It is a sectional view taken along the line. It is a figure which shows the conventional ultrasonic sensor, (a) is a whole schematic diagram, (b) is an A-A 'line sectional arrow view, (c) is a B-B' line sectional arrow view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case 1a Vibrating body part 2 Piezoelectric vibration element 2a Elastic adhesive film 3 Holding material 4 Sound absorbing material

Claims (7)

  A bottomed cylindrical case having a vibrating body portion formed of a flat bottom plate, a piezoelectric vibrating element that abuts on the vibrating body portion and vibrates the vibrating body portion, and a vibrating body that covers the outer periphery of the piezoelectric vibrating element An ultrasonic sensor comprising: a holding material provided in a portion; and a sound absorbing material housed in a case and disposed on the holding material at a predetermined interval, the sound absorbing material of the piezoelectric vibrating element An ultrasonic sensor, wherein a surface facing a material is covered with an elastic adhesive film made of a material having elasticity.   An ultrasonic sensor comprising a bottomed cylindrical case having a vibrating body portion made of a flat bottom plate and a piezoelectric vibrating element that abuts on the vibrating body portion and vibrates the vibrating body portion. An ultrasonic sensor characterized in that a surface opposite to a surface in contact with the vibrating body portion and the entire surface of the vibrating body portion excluding the piezoelectric vibrating element in the case are covered with an elastic adhesive film made of an elastic material.   The ultrasonic sensor according to claim 1, wherein the elastic adhesive film covers the entire inner surface of the case.   The inside of the case is sealed with an insulating material made of an insulating material, and the elastic adhesive film is made of a mediating material for improving the adhesiveness between the case and the insulating material. The ultrasonic sensor according to any one of the above.   The ultrasonic sensor according to claim 1, wherein the elastic adhesive film is made of a film material.   The ultrasonic sensor according to claim 1, wherein the elastic adhesive film is made of a sealing material.   The ultrasonic sensor according to claim 6, wherein the elastic adhesive film is formed by spraying a sealing material with a spray.

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