JP2022140152A - ultrasonic transmitter and receiver - Google Patents

ultrasonic transmitter and receiver Download PDF

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JP2022140152A
JP2022140152A JP2021040845A JP2021040845A JP2022140152A JP 2022140152 A JP2022140152 A JP 2022140152A JP 2021040845 A JP2021040845 A JP 2021040845A JP 2021040845 A JP2021040845 A JP 2021040845A JP 2022140152 A JP2022140152 A JP 2022140152A
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ultrasonic sensor
cylindrical case
metal
piezoelectric element
resin
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誠 坂口
Makoto Sakaguchi
巧 重森
Takumi Shigemori
啓貴 中島
Hirotaka Nakajima
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Nippon Ceramic Co Ltd
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Nippon Ceramic Co Ltd
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Abstract

To solve a problem in which, in a conventional ultrasonic sensor, variation in the thickness of the bottom surface of a cylindrical case with a bottom affect the variation in the resonance frequency of the ultrasonic sensor, and sensor cost reduction is difficult because it is necessary to perform precision processing on the bottom surface of the cylindrical case with the bottom, and when the ultrasonic sensor is driven to perform transmission and reception, the bottom vibration of the cylindrical case with the bottom is transmitted to the side wall of the cylindrical case with the bottom, resulting in worsening of the reverberation of the ultrasonic sensor.SOLUTION: In a housing used for an ultrasonic sensor, the accuracy management of the bottom thickness of a cylindrical case with a bottom is easily realized by joining a unimorph vibrator, which consists of a plate made of resin or metal and a piezoelectric element, and a cylindrical part, which is made of resin or metal, with an elastic resin material. In addition, by suppressing the transmission of vibration from the bottom of the cylindrical case to the side walls of the cylindrical case with the bottom, unnecessary vibrations can be suppressed, the short-range detection performance of the ultrasonic sensor is improved.SELECTED DRAWING: Figure 1

Description

本発明は、圧電素子を有底筒状ケースに貼り合わせた空中用の超音波センサに関するものである。 BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aerial ultrasonic sensor in which a piezoelectric element is attached to a cylindrical case with a bottom.

超音波センサを用いた距離計ユニットを車両に取り付けて、車両に物体が接近した際に運転者に衝突の危険を知らせる安全装置が広く使用されている。特に、車両を後退させる際に後方の物体を距離計ユニットで検出し、運転手に物体の接近を知らせる安全装置がよく利用されている。（例えば特許文献１） A safety device is widely used in which a rangefinder unit using an ultrasonic sensor is attached to a vehicle to inform the driver of the risk of collision when an object approaches the vehicle. In particular, a safety device is often used that detects an object behind the vehicle with a rangefinder unit and notifies the driver of the approach of the object when the vehicle is backed up. (For example, Patent Document 1)

具体的には、物体の接近を運転手にブザーで知らせる安全装置や車両の前方に障害物があると車両が発進しないようブレーキが動作させるブレーキ連動式の安全装置が発明されている。 Specifically, a safety device that uses a buzzer to notify the driver of an approaching object and a safety device that interlocks with the brake to prevent the vehicle from starting if there is an obstacle in front of the vehicle has been invented.

ここで使用される超音波センサを用いた距離計ユニットでは、主に防滴型の超音波センサが使用されている。
防滴型の超音波センサは、例えば特許文献２で紹介されている（文献中では防滴型の超音波センサを防滴型超音波送受波器とよんでいる）。
防滴型の超音波センサは有底筒状ケースの底面に、両面に電極が施された圧電素子が接着されており、圧電素子の各電極に電気的に接続された端子は外部に取り出されており、圧電素子の上部にはスポンジ状もしくはフェルト状の吸音材をかぶせてから、シリコーンゴムなどの弾性を有する充填剤で密閉した構造である。
有底筒状ケースの開口側の背面がシリコーンゴムなどの充填剤で完全に覆われることで内部に液体が浸入しない構造になっている。前述の構造のため、超音波センサ内部にて圧電素子の各電極同士が短絡することがないため、液体がかかるような屋外でも使用できる。 A rangefinder unit using an ultrasonic sensor used here mainly uses a drip-proof ultrasonic sensor.
A drip-proof ultrasonic sensor is introduced, for example, in Patent Document 2 (the drip-proof ultrasonic sensor is called a drip-proof ultrasonic transducer in the document).
A drip-proof ultrasonic sensor has a piezoelectric element with electrodes on both sides attached to the bottom of a bottomed cylindrical case, and the terminals electrically connected to each electrode of the piezoelectric element are taken out. The piezoelectric element is covered with a sponge-like or felt-like sound absorbing material, and then sealed with an elastic filler such as silicone rubber.
The opening side of the cylindrical case with a bottom is completely covered with a filler such as silicone rubber to prevent liquid from entering inside. Due to the structure described above, the electrodes of the piezoelectric element are not short-circuited inside the ultrasonic sensor, so that the ultrasonic sensor can be used outdoors where it may be splashed with liquid.

特開２００７－１１２２９７JP 2007-112297 特開２０１０－１５４０５９JP 2010-154059

従来の超音波センサは、有底筒状ケースの内底面に接合された圧電素子の上側に、予め成形されたスポンジを配置し、その上の有底筒状ケースの開口側に封止材を配置する構造が、一般的である。
従来の超音波センサにおいては、有底筒状ケースの底面厚みのばらつきが超音波センサの共振周波数ばらつきに大きく影響しており、このばらつきを抑える為には有底筒状ケースの底面を切削による精密な加工を行う必要がある。このため従来の技術における超音波センサにおいてはセンサ筐体の低コスト化が難しい。加えて超音波センサに電圧を印可して超音波の送受信を行う際、有底筒状ケースの底面部振動が、有底筒状ケース側壁にも伝達してしまい不要な振動が発生する事で超音波センサの残響が悪化し、超音波センサの近距離検知性能が悪くなるという問題がある。
A conventional ultrasonic sensor has a preformed sponge placed on the upper side of a piezoelectric element bonded to the inner bottom surface of a cylindrical case with a bottom, and a sealing material is placed on the opening side of the cylindrical case with a bottom. Arranged structures are common.
In conventional ultrasonic sensors, variations in the thickness of the bottom surface of the cylindrical case with a bottom have a large effect on variations in the resonance frequency of the ultrasonic sensor. Precise machining is required. For this reason, it is difficult to reduce the cost of the sensor housing in the conventional ultrasonic sensor. In addition, when a voltage is applied to the ultrasonic sensor to transmit and receive ultrasonic waves, the bottom vibration of the cylindrical case with a bottom is transmitted to the side wall of the cylindrical case with a bottom, causing unnecessary vibration. There is a problem that the reverberation of the ultrasonic sensor deteriorates and the short-range detection performance of the ultrasonic sensor deteriorates.

超音波センサに用いる筐体において、樹脂又は金属から成る板と圧電素子から成るユニモルフ振動子と樹脂または金属から成る筒状部品を弾性を有する樹脂材で接合する。有底筒状ケースにおける底面の厚みは切削による加工を実施せずともプレスなどによる安価な工法で金属板厚みの精度管理が容易となる。また、樹脂又は金属から成る板と圧電素子から成るユニモルフ振動子と樹脂または金属から成る筒状部品を弾性を有する樹脂材で接合することで、超音波センサに電圧を印可して超音波の送受信を行う際の有底筒状ケースの底面部振動が弾性を有する樹脂材によって吸収され、有底筒状ケース側壁への振動伝達が遮断されて不要な振動の発生を抑制する事が出来、超音波センサ残響特性の安定化による近距離検知性能の向上が可能となる。さらに、有低筒状ケースの底面のみを振動させることが出来る為、ユニモルフ振動子の振動効率が向上し、超音波センサの出力特性が向上し、有底筒状ケースを用いた従来の超音波センサよりも超音波の音圧の帯域が広くなり、幅広い温度域での安定した送受信性能が実現できる効果もある。
In a housing used for an ultrasonic sensor, a unimorph transducer composed of a plate made of resin or metal, a piezoelectric element, and a cylindrical part made of resin or metal are joined with an elastic resin material. The thickness of the bottom surface of the cylindrical case with a bottom can be easily controlled by an inexpensive method such as pressing, without machining. In addition, by joining a unimorph transducer consisting of a plate made of resin or metal and a piezoelectric element and a cylindrical part made of resin or metal with an elastic resin material, a voltage is applied to the ultrasonic sensor to transmit and receive ultrasonic waves. The vibration of the bottom surface of the cylindrical case with a bottom is absorbed by the elastic resin material, and the transmission of vibration to the side wall of the cylindrical case with a bottom is blocked. It is possible to improve short-distance detection performance by stabilizing the reverberation characteristics of the sound wave sensor. Furthermore, since only the bottom surface of the bottomed cylindrical case can be vibrated, the vibration efficiency of the unimorph transducer is improved, and the output characteristics of the ultrasonic sensor are improved. The sound pressure band of the ultrasonic wave is wider than that of the sensor, and there is also an effect that stable transmission and reception performance can be realized in a wide temperature range.

本発明の請求項１に関わる超音波センサの構造図Structural drawing of an ultrasonic sensor related to claim 1 of the present invention 本発明の請求項２に関わる超音波センサの構造図Structural drawing of an ultrasonic sensor related to claim 2 of the present invention 従来の超音波センサの構造図Structural drawing of a conventional ultrasonic sensor 本発明に関わる超音波センサと従来の超音波センサにおける有底筒状ケース底面の振動振幅と有底筒状ケースの側壁部振動振幅Vibration amplitude of the bottom surface of the bottomed cylindrical case and the vibration amplitude of the side wall of the bottomed cylindrical case in the ultrasonic sensor according to the present invention and the conventional ultrasonic sensor 本発明に関わる超音波センサと従来の超音波センサにおける残響時間、反射感度Reverberation time and reflection sensitivity of ultrasonic sensor related to the present invention and conventional ultrasonic sensor 本発明に関わる超音波センサと従来の超音波センサにおける音圧を示したグラフGraph showing sound pressure in an ultrasonic sensor related to the present invention and a conventional ultrasonic sensor

（発明型の超音波センサの構造）
図１は本発明の請求項１に関わる超音波センサの構造図である。本発明に関わる超音波センサの構成は、 金属板１とＰＺＴ系セラミックと折り返し電極とを構成に含む圧電素子２から成るユニモルフ振動子３と、金属の筒状部品４を、弾性を有する樹脂材５で接合することによる筐体内部に、圧電素子２の表面を覆うように成形されたスポンジ材６ａまたは発泡シリコーンからなる多孔質弾性体６ｂが配置される。金属板１は密度が高く、ヤング率が大きい樹脂材を用いてもよい。また、筒状部品４は金属を用いてもよい。前述の圧電素子２上の各電極は、リード線７ａおよび７ｂで半田付けにより電気的に接続されており、有底筒状ケース２内部の開口側を非多孔質の樹脂材からなる弾性体８を充填することにより封止されている。
図２は本発明の請求項２に関わる超音波センサの構造図である。請求項２に関わる超音波センサにおいては、 金属板１とＰＺＴ系セラミックと折り返し電極とを構成に含む圧電素子２から成るユニモルフ振動子３と、樹脂または金属から成る筒状部品４を、弾性を有する樹脂材５で接合することによる筐体の内部に、圧電素子２の表面を覆うように成形されたスポンジ材６ａまたは発泡シリコーンからなる多孔質弾性体６ｂが配置される。筒状部品４には金属端子９ａおよび９ｂがインサートまたは圧入により一体化されている。前述の圧電素子２上の各電極とピン端子９ａおよび９ｂの各端子はリード線１０ａおよび１０ｂで半田付けにより電気的に接続されており、有底筒状ケース２内部の開口側を非多孔質の樹脂材からなる弾性体８を充填することにより封止されている。 (Structure of Inventive Ultrasonic Sensor)
FIG. 1 is a structural diagram of an ultrasonic sensor relating to claim 1 of the present invention. The structure of the ultrasonic sensor according to the present invention is composed of a unimorph vibrator 3 composed of a piezoelectric element 2 including a metal plate 1, a PZT-based ceramic, and folded electrodes, and a metal cylindrical part 4, which are made of an elastic resin material. A sponge material 6a or a porous elastic body 6b made of foamed silicone, which is molded so as to cover the surface of the piezoelectric element 2, is disposed inside the housing formed by bonding at 5. FIG. A resin material having a high density and a large Young's modulus may be used for the metal plate 1 . Also, the cylindrical part 4 may be made of metal. Each electrode on the piezoelectric element 2 is electrically connected by soldering with lead wires 7a and 7b. is sealed by filling with
FIG. 2 is a structural diagram of an ultrasonic sensor relating to claim 2 of the present invention. In the ultrasonic sensor according to Claim 2, a unimorph transducer 3 composed of a piezoelectric element 2 including a metal plate 1, a PZT-based ceramic, and folded electrodes, and a tubular part 4 made of resin or metal are elastically A sponge material 6a or a porous elastic body 6b made of foamed silicone, which is molded so as to cover the surface of the piezoelectric element 2, is disposed inside the housing formed by bonding with the resin material 5. As shown in FIG. Metal terminals 9a and 9b are integrated with the cylindrical part 4 by inserting or press-fitting. Each electrode on the piezoelectric element 2 and each terminal of the pin terminals 9a and 9b are electrically connected by soldering with lead wires 10a and 10b, and the opening side inside the bottomed cylindrical case 2 is made non-porous. It is sealed by filling with an elastic body 8 made of a resin material.

（従来型の超音波センサの構造） 図３は従来型の超音波センサの構造図の一例である。従来型の超音波センサの構成は、アルミ合金からなる有底筒状ケース２の内底面に、PZT系セラミックと折り返し電極とを構成に含む圧電素子１が接着されており、圧電素子1の上に成形されたスポンジ３ｂが配置され、リード線４が圧電素子上1の各電極とピン端子６の各端子とが半田付けにより電気的に接続されており、有底筒状ケース２内部の開口側を非多孔質のシリコーン樹脂からなる弾性体３ｂを充填することにより封止されている。 (Structure of Conventional Ultrasonic Sensor) FIG. 3 is an example of a structural diagram of a conventional ultrasonic sensor. A conventional ultrasonic sensor has a configuration in which a piezoelectric element 1 including a PZT-based ceramic and a folding electrode is adhered to the inner bottom surface of a bottomed cylindrical case 2 made of aluminum alloy. A molded sponge 3b is arranged, and a lead wire 4 is electrically connected to each electrode on the piezoelectric element 1 and each terminal of the pin terminal 6 by soldering. The side is sealed by filling an elastic body 3b made of non-porous silicone resin.

図４は図１の本発明に関わる超音波センサと図３の従来の超音波センサにおける有底筒状ケース底面の振動振幅と有底筒状ケースの側壁部振動振幅を比較したものである。これによると、従来の超音波センサにおける有底筒状ケース底面の振動振幅と本発明における有底筒状ケース底面の振動振幅が同等であった場合でも本発明に関わる超音波センサの有底筒状ケースの側壁部振動振幅は従来の超音波センサにおける有底筒状ケースの側壁部振動振幅に対して半分以下となっており、有底筒状ケース底面の振動が有底筒状ケース側壁部へ伝達するのを抑制出来ていることが分かる。
図５は図１の本発明に関わる超音波センサと図３の従来の超音波センサにおける残響時間、反射感度を示したグラフである。残響時間について、本発明に関わる超音波センサでは従来型の約半分になっている。これは有底筒状ケース底面の振動が有底筒状ケース側壁部へ伝達する事を抑制した効果によるものである。尚、今回の発明に関わる実施の形態において、弾性を有する樹脂材５の材質をシリコーンとした場合には、硬度30から硬度50の間で良好な特性を示すことが分かった。
図６は図１の本発明に関わる超音波センサと図３の従来の超音波センサにおける音圧を示したグラフである。音圧の周波数特性に関して、本発明に関わる超音波センサにおいては有低筒状ケースの底面のみを振動させることが出来る為、ユニモルフ振動子の振動効率が向上し、従来の超音波センサよりもより広帯域において高い音圧を示している。 FIG. 4 compares the vibration amplitude of the bottom surface of the bottomed cylindrical case and the side wall vibration amplitude of the bottomed cylindrical case between the ultrasonic sensor according to the present invention shown in FIG. 1 and the conventional ultrasonic sensor shown in FIG. According to this, even when the vibration amplitude of the bottom surface of the bottomed cylindrical case in the conventional ultrasonic sensor and the vibration amplitude of the bottom surface of the bottomed cylindrical case in the present invention are equivalent, the bottomed cylinder of the ultrasonic sensor according to the present invention The vibration amplitude of the side wall of the cylindrical case is less than half the vibration amplitude of the side wall of the bottomed cylindrical case in the conventional ultrasonic sensor. It can be seen that it is possible to suppress the transmission to
FIG. 5 is a graph showing the reverberation time and reflection sensitivity of the ultrasonic sensor according to the present invention shown in FIG. 1 and the conventional ultrasonic sensor shown in FIG. The reverberation time of the ultrasonic sensor according to the present invention is about half that of the conventional type. This is due to the effect of suppressing the transmission of the vibration of the bottom surface of the bottomed cylindrical case to the side wall of the bottomed cylindrical case. In addition, in the embodiment of the present invention, it was found that when silicone was used as the material of the resin material 5 having elasticity, good characteristics were exhibited between hardness 30 and hardness 50. FIG.
FIG. 6 is a graph showing the sound pressure in the ultrasonic sensor according to the present invention shown in FIG. 1 and the conventional ultrasonic sensor shown in FIG. Regarding the frequency characteristics of sound pressure, in the ultrasonic sensor according to the present invention, only the bottom surface of the low-low cylindrical case can be vibrated. It shows high sound pressure in a wide band.

本発明は、車両向けのバックセンサやコーナーセンサ、自動駐車システムのみならず、超音波センサが利用されている様々な分野に適用できる。
INDUSTRIAL APPLICABILITY The present invention can be applied not only to back sensors, corner sensors and automatic parking systems for vehicles, but also to various fields in which ultrasonic sensors are used.

１ 樹脂又は金属から成る板
２ 圧電素子
３ ユニモルフ振動子
４ 樹脂又は金属から成る筒状部品
５ 弾性を有する樹脂材
６ａ スポンジ材
６ｂ 発泡シリコーンからなる多孔質弾性体
７ａ リード線
７ｂ リード線
８ 非多孔質の樹脂材からなる弾性体
９ａ ピン端子
９ｂ ピン端子 1 Plate made of resin or metal 2 Piezoelectric element 3 Unimorph vibrator 4 Cylindrical part made of resin or metal 5 Elastic resin material 6a Sponge material 6b Porous elastic body made of foamed silicone 7a Lead wire 7b Lead wire 8 Non-porous Elastic body 9a made of high quality resin material Pin terminal 9b Pin terminal

Claims (2)

底部と筒状部を有する有底筒状ケースと、前記有底筒状ケースの内底面に接合された圧電素子とを備える超音波センサの構造において、樹脂又は金属から成る板と圧電素子から成るユニモルフ振動子と、樹脂または金属から成る筒状部品を、弾性を有する樹脂材で接合したことを特徴とする超音波センサ。
A structure of an ultrasonic sensor comprising a bottomed tubular case having a bottom and a tubular portion, and a piezoelectric element joined to the inner bottom surface of the bottomed tubular case, wherein the piezoelectric element comprises a plate made of resin or metal. An ultrasonic sensor comprising a unimorph transducer and a tubular part made of resin or metal joined together with an elastic resin material.
 請求項１に記載の超音波センサにおいて、筒状部品に金属製端子をインサート成型または圧入によって一体化したことを特徴とする超音波センサ。 2. The ultrasonic sensor according to claim 1, wherein the metal terminal is integrated with the cylindrical part by insert molding or press fitting.
JP2021040845A 2021-03-12 2021-03-12 ultrasonic transmitter and receiver Pending JP2022140152A (en)

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