ULTRASONIC TRANSCEIVER

Abstract

There is provided an ultrasonic sensor including: a closed-bottom tubular case including a bottom portion and a tubular portion; and a piezoelectric element joined to an inner bottom surface of the closed-bottom tubular case. A porous elastic body is in close contact with the inner bottom surface to include a portion at which an amplitude is maximum in the inner bottom surface when transmitting or receiving an ultrasonic wave in the inner bottom surface. An elastic body having a density higher than a density of the porous elastic body is in close contact to an opening side of the closed-bottom tubular case to include a portion at which vibration is transmitted from the inner bottom surface to the tubular portion of the closed-bottom tubular case.

Claims

1. An ultrasonic sensor comprising: a closed-bottom tubular case including a bottom portion and a tubular portion; and a piezoelectric element joined to an inner bottom surface of the closed-bottom tubular case, wherein a porous elastic body is in close contact with the inner bottom surface to include a portion at which an amplitude is maximum in the inner bottom surface when transmitting or receiving an ultrasonic wave in the inner bottom surface, and an elastic body having a density higher than a density of the porous elastic body is in close contact to an opening side of the closed-bottom tubular case to include a portion at which vibration is transmitted from the inner bottom surface to the tubular portion of the closed-bottom tubular case.

2. The ultrasonic sensor according to claim 1, wherein each of the porous elastic body and the elastic body is made of one kind or a plurality of kinds of materials, and is configured by a layer or a plurality of layers.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0022] Fig. 1 is a cross-sectional view of an ultrasonic sensor according to an embodiment of the present invention.

[0023] FIG. 2 is a cross-sectional view of an ultrasonic sensor of the related art.

[0024] FIG. 3 is a comparison diagram of a reverberation time, a reflection sensitivity, and a sound pressure of the ultrasonic sensor in the related-art type and the invention type.

DESCRIPTION OF EMBODIMENTS

First Embodiment

[0025] (Structure of Ultrasonic Sensor of Type of Invention)

[0026] FIG. 1 is a structural diagram of an ultrasonic sensor of the invention type. In a configuration of the ultrasonic sensor of the invention type, a piezoelectric element 1 including a PZT-based ceramic and a folded electrode is bonded to an inner bottom surface of a closed-bottom tubular case 2 formed of an aluminum alloy, a porous elastic body 3a formed of foamed silicone is applied so as to cover a surface or a periphery of a piezoelectric element 1, sealing is performed by filling an elastic body 5 formed of non-porous silicone resin and having a density higher than that of the porous elastic body 3a in a space to which the porous elastic body 3a in the closed-bottom tubular case 2 is not applied, and a lead wire 4 is electrically connected to each of electrodes of the piezoelectric element 1 and each of teiminals of a pin terminal 6 by soldering.

[0027] The foamed silicone and the silicone resin are cured by being placed in a room temperature or a high temperature environment after coating or filling. Here, a material of the porous elastic body 3a is not limited to the foamed silicone, and urethane foam or another porous elastic body material may be used, and a material of the elastic body is not limited to the silicone resin, and a urethane resin or another non-porous elastic body material may be used.

[0028] In general, when the piezoelectric element 1 is bonded to a portion at which an amplitude is maximum at a time of transmission and reception of an ultrasonic wave at the inner bottom surface of the closed-bottom tubular case 2, since a S/N ratio of the ultrasonic sensor is improved, the application of the porous elastic body 3a is performed so as to cover the surface or the periphery of the piezoelectric element 1, whereas an application range of the porous elastic body 3a is not limited to the surface or the periphery of the piezoelectric element 1, and the porous elastic body 3a may be arranged in a form including a portion at which the amplitude of the inner bottom surface of the closed-bottom tubular case 2 is maximum at the time of the transmission or the reception of the ultrasonic wave.

[0029] (Structure of Ultrasonic Sensor of Related-art Type)

[0030] FIG. 2 is an example of a structure diagram of an ultrasonic sensor of related-art type. In a configuration of an ultrasonic sensor of the related-art type, the piezoelectric element 1 including a PZT-based ceramic and a folded electrode is bonded to an inner bottom surface of the closed-bottom tubular case 2 formed of an aluminum alloy, a sponge 3b molded on the piezoelectric element 1 is arranged, the lead wire 4 is electrically connected to each of electrodes on the piezoelectric element 1 and each of terminals of the pin terminal 6 by soldering, and an opening side in the closed-bottom tubular case 2 is sealed by filling an elastic body 3b formed of a non-porous silicone resin.

[0031] FIG. 3 is a graph showing a reverberation time, a reflection sensitivity, and a sound pressure in the ultrasonic sensor of the invention type of FIG. 1 and the ultrasonic sensor of the related-art type of FIG. 2. The reverberation time is about half that of the related-art type. Meanwhile, the reflection sensitivity and the sound pressure of the related-art type having a low damping effect are higher than those of the invention type.

[0032] The invention type has lower values in terms of the reflection sensitivity and the sound pressure than that of the related-art type, and the invention type has sufficient characteristics as an ultrasonic sensor (which is equal to or greater than 1 mV that is actually used as an in-vehicle ultrasonic sensor). A short reverberation means that a short distance object can be detected, and the invention type can be said to be the ultrasonic sensor that is advantageous for the short distance detection.

INDUSTRIAL APPLICABILITY

[0033] The present invention can be applied not only to a vehicle back sensor, a corner sensor, and an automatic parking system but also to various fields in which an ultrasonic sensor is used.

[0034] REFERENCE SIGNS LIST

[0035] 1: piezoelectric element

[0036] 2: closed-bottom tubular case

[0037] 3a: porous elastic body

[0038] 3b: molded sponge

[0039] 4: lead line

[0040] 5: elastic body

[0041] 6: pin terminal