JP2019114960A - Ultrasonic sensor - Google Patents

Abstract

An object of the present invention is to provide an ultrasonic sensor that suppresses reverberation vibration and has excellent reverberation characteristics. SOLUTION: An ultrasonic sensor of the present disclosure includes a bottomed tubular case 1 having a bottom portion 11 and a tubular portion 12 connected to the outer circumference of the bottom portion 11, a piezoelectric element 2 attached to the bottom portion 11, a case 1 and a damping material 3 provided inside. The damping material 3 is provided along the corners from the outer circumference of the bottom portion 11 to the tubular portion 12 . With this configuration, it is possible to suppress reverberant vibration and realize an ultrasonic sensor having excellent reverberation characteristics. [Selection drawing] Fig. 3

Description

  The present disclosure relates to an ultrasonic sensor.

  For example, corner sonars and back sonars are provided for automobiles as parking assistance for cars, and ultrasonic sensors are used for the corner sonars and back sonars.

  As an ultrasonic sensor, for example, one in which a piezoelectric element is covered with a foamed elastic body and the inside of a case is filled with a silicone elastic body, and the piezoelectric element is covered with an elastic member made of silicone rubber or urethane resin and inside a case with silicone resin or urethane. What filled with the filler which consists of resin is known (refer patent document 1 and patent document 2).

JP 2002-78089 A JP, 2012-10312, A

  In an ultrasonic sensor using a piezoelectric element, reverberation vibration (ringing) occurs after the diaphragm is vibrated by a sine wave, a rectangular wave, or a burst wave. In order to suppress the reverberation vibration (ringing), in the above-described ultrasonic sensor, a filler is provided inside the case.

  In ultrasonic sensors, there is a demand to be able to measure the position of an object located closer. Here, the reverberation vibration (ringing) converges with the passage of time, but when trying to measure the position of an object at a closer distance with an ultrasonic sensor, the influence of the reverberation vibration (ringing) remains. There is a possibility that the measurement can not be performed with high accuracy because the measurement is performed in the presence state.

  This indication is made in view of the above-mentioned situation, and it aims at providing an ultrasonic sensor which controls reverberation vibration and is excellent in reverberation characteristics.

  An ultrasonic sensor according to the present disclosure includes a bottomed cylindrical case having a bottom and a cylindrical portion connected to the outer periphery of the bottom, a piezoelectric element attached to the bottom, and a damping provided inside the case. And the damping material is provided along a corner from the outer periphery of the bottom portion to the cylindrical portion.

  According to the ultrasonic sensor of the present disclosure, reverberation time can be shortened, and reverberation characteristics can be improved.

It is a schematic perspective view showing an example of an embodiment of an ultrasonic sensor. It is a longitudinal cross-sectional view of the ultrasonic sensor shown in FIG. It is a longitudinal cross-sectional view which shows the other example of embodiment of an ultrasonic sensor.

  Hereinafter, embodiments of the ultrasonic sensor will be described with reference to the accompanying drawings. Note that the present invention is not limited by the embodiments described below.

  The ultrasonic sensor of the example shown in FIGS. 1 and 2 includes a bottomed cylindrical case 1 having a bottom portion 11 and a cylindrical portion 12 connected to the outer periphery of the bottom portion 11, and a piezoelectric element 2 attached to the bottom portion 11. And a damping material 3 provided inside the case 1.

  The case 1 has a bottomed cylindrical shape having a bottom portion 11 and a cylindrical portion 12. The case 1 is made of, for example, a metal material such as aluminum, titanium, or magnesium, or a resin material such as an ABS resin, a PBT resin, or a PPS resin.

  The bottom portion 11 is attached with the piezoelectric element 2 and functions as a diaphragm that vibrates by the vibration of the piezoelectric element 2. The cylindrical portion 12 has, for example, a cylindrical shape, and functions as a support for supporting the outer periphery of the bottom portion 11. The thickness of the bottom part 11 and the cylindrical part 12 is 0.5-1.0 mm, for example. The inner diameter of the cylindrical portion 12 is, for example, 5 to 30 mm. The height (length) of the cylindrical portion 12 is, for example, 2 to 10 mm. In addition, the part to which the piezoelectric element 2 of the bottom part 11 is attached may be thinner than circumference | surroundings, and as shown in FIG. 2, the recessed part 111 may be provided. The presence of the recess 111 in the bottom portion 11 makes it possible to easily and accurately align the piezoelectric element 2.

  The piezoelectric element 2 is attached to the bottom 11 via, for example, an adhesive. The piezoelectric element 2 is a plate-like body having, for example, a rectangular shape in a plan view, a square shape, or a circular shape. The piezoelectric element 2 may be provided with a single plate piezoelectric body made of piezoelectric ceramic, and a surface electrode made of metal such as silver provided on the upper surface and the lower surface of the piezoelectric body. In addition, the piezoelectric element 2 may include, for example, a stacked body in which a piezoelectric layer and an internal electrode layer are stacked, and surface electrodes provided on the upper surface and the lower surface of the stacked body. As the adhesive, for example, an epoxy-based or acrylic-based adhesive can be used.

  The case 1 may also include a lid 13 arranged to close the opening on the side opposite to the side connected to the bottom portion 11 of the cylindrical portion 12 as necessary. The lid 13 is made of the same material as the bottom portion 11 and the cylindrical portion 12. Although the lid 13 has a hole for inserting a wire, it is omitted in the figure. Further, the wiring connecting the piezoelectric element 2 and the external circuit is also omitted in the figure.

  A damping member 3 is provided inside the case 1. The damping material 3 can be made of butyl rubber, nitrile rubber, chlorobrene rubber, acrylic resin or the like. The damping material 3 is provided along the corner from the outer periphery of the bottom portion 11 to the cylindrical portion 12. In other words, the corner from the outer periphery of the bottom 11 to the tubular portion 12 is the corner of the tubular portion 12 connected to the bottom 11 and the bottom 11, and the inner wall of the boundary between the outer periphery of the bottom 11 and the tubular 12 It is a corner located at

  With such a configuration, the damping material 3 can mainly absorb the passive vibration consisting of reverberation without inhibiting the amplitude of the active vibration transmitted from the piezoelectric element 2 to the bottom portion 11.

Since the active vibration is a single vibration, it vibrates with the outer periphery of the bottom 11 as a fixed end, but the passive vibration consisting of reverberation is reflected on the outer periphery of the bottom 11 to be the main vibration, and the bottom 11 Vibrate again. By arranging the damping member 3 along the corner from the outer periphery of the bottom portion 11 to the cylindrical portion 12, the vibration transmitted to the end portion of the bottom portion 11 is absorbed by the damping member 3, so to the bottom portion 11 Reflection is reduced, and the reverberation characteristic can be improved.

  When the cylindrical portion 12 is cylindrical, the radial width of the damping material 3 along the corner is, for example, 5 to 33 with respect to the outer diameter of the upper surface of the bottom portion 11 (inner diameter of the cylindrical portion 12). %, For example, 0.5 to 2.0 mm.

  The height of the damping material 3 along the corner is, for example, 1 to 11% of the height of the cylindrical portion 12, for example, 0.1 to 1 mm.

  The reverberation characteristic, that is, the reverberation time can be measured by a dedicated circuit for sensor measurement provided with an oscillator that oscillates a rectangular wave of a specific frequency and an amplifier that amplifies a reception signal.

  The damping material 3 is a corner from the outer periphery of the bottom 11 to the cylindrical portion 12 and may be provided over at least a half circumference or more of the outer periphery of the bottom 11, but is provided over the entire outer periphery of the bottom 11. It may be

  Since the damping material 3 is provided over the entire circumference of the outer periphery of the bottom portion 11, the passive vibration consisting of reverberation is absorbed on the entire circumference of the bottom portion 11 to suppress reflection, thereby further improving the reverberation characteristics.

  Here, as shown in FIG. 3, the damping material 3 may be applied to only a part of the upper surface of the piezoelectric element 2. Here, it is preferable that a part of the upper surface of the piezoelectric element 2 be a peripheral portion excluding the central portion. The peripheral portion means a portion of the distance from the outer periphery to 25% of the diameter when the piezoelectric element 2 is circular, and the width from the end when viewed in a cross section when the piezoelectric element 2 is rectangular It means the distance of up to 25% of the whole.

  Since the end of the bottom 11 is fixed, the piezoelectric element 2 attached to the bottom 11 of the bottomed cylindrical case 1 moves largely in the center when an electric signal is applied, and the vertical vibration occurs like an arc. Do.

  Even if the damping material 3 is applied to a part of the upper surface of the piezoelectric element 2 (peripheral part other than the central part), it hardly affects the part that vibrates up and down most, and the reverberation characteristic can be improved.

  Next, a method of manufacturing the ultrasonic sensor of the present embodiment will be described.

  For example, a bottomed cylindrical aluminum case 1 with an inner diameter of φ14 mm and a height of 9 mm is manufactured by cutting.

  Next, a piezoelectric element 2 made of lead zirconate titanate as a piezoelectric material is bonded to the upper surface of the bottom 11 located inside the case 1 with an epoxy adhesive, for example, a 5 mm long side and 0.2 mm thick.

  Next, a wire is soldered to the surface electrode of the piezoelectric element 2, and an adhesive made of butyl rubber (damping) is provided over the entire circumference of the corner portion located inside the connection portion between the bottom portion 11 of the case 1 and the cylindrical portion 12 Apply material 3).

  Finally, the lid 13 is adhered to the opening of the cylindrical portion 12 with an acrylic adhesive, and the wire is taken out of the hole of the lid 13 to the outside of the case 1.

  The ultrasonic sensor of the present embodiment can be manufactured by the above method.

DESCRIPTION OF SYMBOLS 1 Case 11 Bottom part 12 Tubular part 13 Lid 2 Piezoelectric element 3 Damping material

Claims (3)

  A bottomed cylindrical case having a bottom portion and a cylindrical portion connected to the outer periphery of the bottom portion, a piezoelectric element attached to the bottom portion, and a damping material provided inside the case, the damping material The ultrasonic sensor is characterized in that it is provided along the corner from the outer periphery of the bottom portion to the cylindrical portion.   The ultrasonic sensor according to claim 1, wherein the damping material covers only a part of the upper surface of the piezoelectric element. The ultrasonic wave according to claim 1 or 2, wherein the damping material is provided along the corner from the outer periphery of the bottom portion to the cylindrical portion along the entire outer periphery of the bottom portion. sensor.

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