JP2004069535A

JP2004069535A - Strain sensor

Info

Publication number: JP2004069535A
Application number: JP2002229754A
Authority: JP
Inventors: Takanori Matsukawa; 松川　恭範; Toshiharu Motofusa; 本房　敏治; Yasunobu Kobayashi; 小林　康展; Akira Matsuura; 松浦　昭
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 2002-08-07
Filing date: 2002-08-07
Publication date: 2004-03-04

Abstract

<P>PROBLEM TO BE SOLVED: To provide a strain sensor with a stable property for generating no output signal when no external force is applied to the strain sensor. <P>SOLUTION: A fixing member 28 is constructed of an upper washer 29 and a lower washer 30. When a sensor board 11 is clamped between the the upper washer 29 and the lower washer 30, the fixing member 28 is fixed to the sensor board 11. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、人間の体重や、自動車等の車両の重量等により生じる外力により発生する歪をセンサ基板に設けた歪検出素子により検出する歪センサに関するものである。
【０００２】
【従来の技術】
従来のこの種の歪センサとしては、実願平４−２６５号（実開平５−５７６０５号）のマイクロフィルムに開示されたものが知られている。
【０００３】
以下、従来の歪センサについて図面を参照しながら説明する。
【０００４】
図８は従来の歪センサの斜視図である。
【０００５】
図８において、１は金属からなるセンサ基板で、このセンサ基板１は一端側に第１の固定孔２を設けるとともに、他端側に第２の固定孔３を設け、かつ上面に歪ゲージからなる歪検出素子４を設けている。また、センサ基板１における歪検出素子４は素子部５と、この素子部５と電気的に接続されるとともに外方へ向かって突出するリード線６とを有している。
【０００６】
以上のように構成された従来の歪センサについて、次にその動作を図面を参照しながら説明する。
【０００７】
図９に示すように、予め一対の雌ネジ７を設けた被検出部材８における一対の雌ネジ７にセンサ基板１を介して雄ネジ９を螺合することにより、センサ基板１を被検出部材８に固着する。このとき、被検出部材８に設けた一対の雌ネジ７のピッチの変動を考慮して、センサ基板１を被検出部材８に確実に取り付けできるように、第１の固定孔２および第２の固定孔３の内径は雌ネジ７の外径よりも大きめの寸法となっている。そして、この状態において、被検出部材８に外力が作用すると、被検出部材８が歪を生じ、この歪に伴い、センサ基板１が変形することになる。そしてこのセンサ基板１の変形を、センサ基板１の上面に設けた歪検出素子４の抵抗値の変化による電圧の変化としてリード線６から外部に取り出すことによって、被検出部材８に生じる外力を検出するものであった。
【０００８】
【発明が解決しようとする課題】
しかしながら、上記従来の構成においては、雄ネジ９を雌ネジ７に螺合することによりセンサ基板１を被検出部材８に固着する際、雄ネジ９の捩じり力が働くため、この捩じり力によりセンサ基板１に内部応力が生じることになり、これにより、歪検出素子４が歪んでしまって、センサ基板１に外力が加わらない状態においても、出力信号が発生してしまうことになり、その結果、歪センサの出力信号が不安定になってしまうという課題を有していた。
【０００９】
本発明は上記従来の課題を解決するもので、歪センサに外力が加わらない状態においては、出力信号が発生することのない特性の安定した歪センサを提供することを目的とするものである。
【００１０】
【課題を解決するための手段】
上記目的を達成するために、本発明は以下の構成を有するものである。
【００１１】
本発明の請求項１に記載の発明は、特に、固定部材、検出部材をそれぞれ上側ワッシャと下側ワッシャで構成するとともに、この上側ワッシャと下側ワッシャでセンサ基板を挟持することにより、固定部材および検出部材をセンサ基板に固定したもので、この構成によれば、上側ワッシャと下側ワッシャでセンサ基板を挟持することにより発生するセンサ基板の板厚と垂直方向の力によって、固定部材および検出部材はセンサ基板に固着されることになるため、センサ基板における固定孔および検出孔の周辺に捩じりによる内部応力が発生することはなくなり、これにより、歪検出素子に応力が加わることがなくなるため、歪センサの出力信号は安定するという作用効果が得られるものである。
【００１２】
本発明の請求項２に記載の発明は、特に、固定部材と検出部材における上側ワッシャと下側ワッシャにそれぞれ挿入部を設けるとともに、これらの挿入部のいずれか一方をセンサ基板における固定孔および検出孔との間に間隙を設けた状態でセンサ基板における固定孔および検出孔に挿入し、さらに前記固定部材と検出部材における上側ワッシャと下側ワッシャにそれぞれ設けた挿入部のいずれか一方の挿入部にいずれか他方の挿入部を圧入することにより、固定部材および検出部材をセンサ基板に固定したもので、この構成によれば、センサ基板に内部応力が加わらない状態で、固定部材および検出部材をセンサ基板に固定することができるとともに、固定部材および検出部材がセンサ基板から外れることもなくなるという作用効果が得られるものである。
【００１３】
本発明の請求項３に記載の発明は、特に、固定部材と検出部材における上側ワッシャにセンサ基板の上面と当接する当接部を設けるとともに、下側ワッシャにセンサ基板の下面と当接する当接部を設け、かつこれらの当接部はそれぞれ円形形状に構成したもので、この構成によれば、上側ワッシャがセンサ基板の上面で周方向に回転するとともに、下側ワッシャがセンサ基板の下面で周方向に回転したとしても、上側ワッシャおよび下側ワッシャにおけるセンサ基板との当接部の位置がセンサ基板における長手方向でずれるということはなくなり、これにより、歪検出素子に加わる曲げ応力が変動してしまうということはないため、歪センサの出力特性は安定するという作用効果が得られるものである。
【００１４】
本発明の請求項４に記載の発明は、特に、固定部材と検出部材における上側ワッシャに挿入部を設けるとともに、固定部材と検出部材における下側ワッシャに孔を設け、前記上側ワッシャにおける挿入部を下側ワッシャの孔に圧入嵌合させることにより、固定部材および検出部材をセンサ基板に固定したもので、この構成によれば、下側ワッシャ全体が上側ワッシャとの圧入に関与することになるとともに、上側ワッシャにおける挿入部の厚みを大きくすることできるため、固定部材および検出部材の強度が向上するという作用効果が得られるものである。
【００１５】
本発明の請求項５に記載の発明は、特に、固定部材と検出部材における下側ワッシャに挿入部を設けるとともに、固定部材と検出部材における上側ワッシャに孔を設け、前記下側ワッシャにおける挿入部を上側ワッシャの孔に圧入嵌合させることにより、固定部材および検出部材をセンサ基板に固定したもので、この構成によれば、上側ワッシャ全体が下側ワッシャとの圧入に関与することになるとともに、下側ワッシャにおける挿入部の厚みを大きくすることができるため、固定部材および検出部材の強度が向上するという作用効果が得られるものである。
【００１６】
【発明の実施の形態】
（実施の形態１）
以下、実施の形態１を用いて、本発明の特に請求項１〜３に記載の発明について説明する。
【００１７】
図１は本発明の実施の形態１における歪センサの上面図、図２は同歪センサの側断面図、図３は同歪センサにおける第１の固定部材をセンサ基板に固着する前の状態を示す分解斜視図、図４は同歪センサにおけるセンサ基板の上面図である。
【００１８】
図１〜図４において、１１はセンサ基板で、このセンサ基板１１は、図２に示すように、一端部側に上面から下面にわたって第一の固定孔１２を設け、かつ略中央に上面から下面にわたって第２の固定孔１３を設け、さらに前記第１の固定孔１２と第２の固定孔１３との間の略中央に位置して上面から下面にわたって検出孔１４を設けている。また、センサ基板１１の他端部側には電源電極１５を設けており、この電源電極１５は第１の歪検出素子１６の一端および第２の歪検出素子１７の一端に回路パターン１８により電気的に接続し、かつ前記第１の歪検出素子１６の他端は第１の出力電極１９に電気的に接続している。そしてまた、前記第２の歪検出素子１７の他端は第２の出力電極２０に電気的に接続するとともに、第３の歪検出素子２１の一端に電気的に接続し、さらにこの第３の歪検出素子２１の他端はＧＮＤ電極２２に電気的に接続している。
【００１９】
また、センサ基板１１の上面には第４の歪検出素子２３を設けており、この第４の歪検出素子２３は一端を第１の歪検出素子１６の他端および第１の出力電極１９に電気的に接続し、かつ他端をＧＮＤ電極２２に電気的に接続している。そして、前記した第１の歪検出素子１６、第２の歪検出素子１７、第３の歪検出素子２１、第４の歪検出素子２３、電源電極１５、第１の出力電極１９、第２の出力電極２０、ＧＮＤ電極２２および回路パターン１８によりブリッジ回路を構成している。そしてまた、センサ基板１１の他端部側の上面にはＩＣ２４を設けており、このＩＣ２４は、第１の出力電極１９および第２の出力電極２０の電圧の差動電圧を増幅し、センサ基板１１の他端部側に設けたコネクタ２５より外部に出力するものである。
【００２０】
さらに、センサ基板１１の他端部側の上面には外部電源電極２６を設けており、この外部電源電極２６は電源電極１５に電気的に接続している。また、センサ基板１１の上面には外部ＧＮＤ電極２７を設けており、この外部ＧＮＤ電極２７はＧＮＤ電極２２に電気的に接続している。
【００２１】
２８は第１の固定部材で、この第１の固定部材２８は、図３に示すように、センサ基板１１の上面に当接する金属製の第１の上側ワッシャ２９と、センサ基板１１の下面に当接する金属製の第１の下側ワッシャ３０とにより構成されている。そして、第１の固定部材２８における第１の上側ワッシャ２９は、センサ基板１１の上面と当接する円形形状の当接部３１と、センサ基板１１における第１の固定孔１２に挿入される挿入部３２を備えている。また第１の固定部材２８における第１の下側ワッシャ３０も、上記第１の上側ワッシャ２９と同様、センサ基板１１の下面と当接する円形形状の当接部３３と、センサ基板１１における第１の固定孔１２に挿入される挿入部３４を備えているもので、前記第１の上側ワッシャ２９における挿入部３２の外周部を第１の下側ワッシャ３０における挿入部３４の内周部に圧入することにより、第１の固定部材２８をセンサ基板１１に固定している。この場合、前記第１の下側ワッシャ３０における挿入部３４は、センサ基板１１における第１の固定孔１２に、第１の固定孔１２との間に間隙を設けた状態で挿入されるもので、この状態で、前記第１の上側ワッシャ２９における挿入部３２の外周部を第１の下側ワッシャ３０における挿入部３４の内周部に圧入すると、センサ基板１１に内部応力が加わらない状態で、センサ基板１１は、第１の固定部材２８を構成する第１の上側ワッシャ２９と第１の下側ワッシャ３０とにより挟持されるものである。このような構造とすることにより、センサ基板１１に内部応力が加わらない状態で、第１の固定部材２８をセンサ基板１１に固定することができるとともに、第１の固定部材２８がセンサ基板１１から外れることもなくなるという効果を有するものである。
【００２２】
３５は第２の固定部材で、この第２の固定部材３５も、上記第１の固定部材２８と同様に、金属製の第２の上側ワッシャ３６と、金属製の第２の下側ワッシャ３７とにより構成されている。３８は検出部材で、この検出部材３８は、金属製の検出部上側ワッシャ３９と、金属製の検出部下側ワッシャ４０とにより構成されている。
【００２３】
上記本発明の実施の形態１においては、検出部材３８におけるセンサ基板１１と当接する端部３８ａに外力を作用させるとともに、第１の固定部材２８におけるセンサ基板１１と当接する端部２８ａおよび第２の固定部材３５におけるセンサ基板１１と当接する端部３５ａには反力を作用させるようにしている。
【００２４】
以上のように構成された本発明の実施の形態１における歪センサについて、次にその組立方法を説明する。
【００２５】
まず、予め準備した金属のベース基材（図示せず）に、第１の固定孔１２、第２の固定孔１３、検出孔１４をプレス加工により形成する。
【００２６】
次に、ベース基材（図示せず）の上面にガラスペースト（図示せず）を印刷した後、約８５０℃で約４５分間焼成し、センサ基板１１を形成する。
【００２７】
次に、センサ基板１１の上面に位置してメタルグレーズ系のカーボンのペーストを印刷し、約８５０℃で約４５分間焼成し、センサ基板１１の上面に第１の歪検出素子１６、第２の歪検出素子１７、第３の歪検出素子２１および第４の歪検出素子２３を形成する。
【００２８】
次に、電源電極１５、第１の出力電極１９、第２の出力電極２０、ＧＮＤ電極２２および回路パターン１８を設ける位置に、銀のペーストを印刷し、約８５０℃で約４５分間焼成し、電源電極１５、第１の出力電極１９、第２の出力電極２０、ＧＮＤ電極２２および回路パターン１８を形成する。
【００２９】
次に、センサ基板１１の上面にＩＣ２４を実装する。
【００３０】
次に、センサ基板１１における第１の固定孔１２の下側から第１の下側ワッシャ３０における挿入部３４を挿入した後、第１の固定孔１２の上側から第１の上側ワッシャ２９における挿入部３２を挿入する。そして、第１の下側ワッシャ３０における当接部３３の上面をセンサ基板１１の下面に当接させるとともに、第１の上側ワッシャ２９における当接部３１の下面をセンサ基板１１の上面に当接させる際に、第１の上側ワッシャ２９における挿入部３２の外周部を、第１の下側ワッシャ３０における挿入部３４の内周部に圧入することにより、第１の固定部材２８をセンサ基板１１に固定する。
【００３１】
このように、第１の上側ワッシャ２９と第１の下側ワッシャ３０でセンサ基板１１を挟持することにより、第１の固定部材２８をセンサ基板１１に固定した場合、第１の上側ワッシャ２９と第１の下側ワッシャ３０でセンサ基板１１を挟持することにより発生するセンサ基板１１の板厚と垂直の方向の力によって、第１の固定部材２８がセンサ基板１１に固着されることになるため、センサ基板１１における第１の固定孔１２の周辺に捩じりによる内部応力が発生することはなくなり、これにより、第１の固定孔１２の近傍に位置する第３の歪検出素子２１に応力が常に加わることはなくなるため、歪センサの出力信号は安定するという効果を有するものである。
【００３２】
次に、第１の固定部材２８と同様に、第２の上側ワッシャ３６と第２の下側ワッシャ３７とにより構成される第２の固定部材３５をセンサ基板１１における第２の固定孔１３の近傍に位置して固定する。
【００３３】
最後に、検出部上側ワッシャ３９と検出部下側ワッシャ４０とにより構成される検出部材３８をセンサ基板１１における検出孔１４の近傍に位置して固定する。
【００３４】
以上のように構成し、かつ製造された本発明の実施の形態１における歪センサについて、次にその動作を図面を参照しながら説明する。
【００３５】
図５は本発明の実施の形態１における歪センサが動作する状態を示す側断面図である。
【００３６】
図５に示すように、検出部材３８に上方より外力Ｆが作用すると、この外力Ｆによりセンサ基板１１は変形する。このとき、検出部材３８におけるセンサ基板１１と当接する端部３８ａに外力が作用するとともに、第１の固定部材２８におけるセンサ基板１１と当接する端部２８ａおよび第２の固定部材３５におけるセンサ基板１１と当接する端部３５ａには反力が作用する。そして、センサ基板１１の上面に設けた第１の歪検出素子１６および第３の歪検出素子２１に引張応力が加わって、第１の歪検出素子１６および第３の歪検出素子２１の抵抗値が大きくなるとともに、第２の歪検出素子１７および第４の歪検出素子２３には圧縮応力が加わって、第２の歪検出素子１７および第４の歪検出素子２３の抵抗値は小さくなる。そして、第１の歪検出素子１６、第２の歪検出素子１７、第３の歪検出素子２１および第４の歪検出素子２３によりブリッジ回路が構成されているため、第１の出力電極１９および第２の出力電極２０の電位差をＩＣ２４により差動電圧としてコネクタ２５から出力する。
【００３７】
ここで、第１の固定部材２８に加わる反力は第１の固定部材２８を周方向に回転させるベクトルを含んでいるため、第１の固定部材２８が回転することが考えられるが、本発明の実施の形態１における歪センサにおいては、図３に示すように、第１の固定部材２８における第１の上側ワッシャ２９にセンサ基板１１の上面と当接する当接部３１を設けるとともに、第１の下側ワッシャ３０にセンサ基板１１の下面と当接する当接部３３を設け、かつこれらの当接部３１，３３はそれぞれ円形形状に構成しているため、第１の上側ワッシャ２９がセンサ基板１１の上面で周方向に回転するとともに、第１の下側ワッシャ３０がセンサ基板１１の下面で周方向に回転したとしても、第１の上側ワッシャ２９および第１の下側ワッシャ３０におけるセンサ基板１１との当接部の位置がセンサ基板１１における長手方向でずれるということはなくなり、これにより、第１の固定部材２８の近傍に設けた第３の歪検出素子２１に加わる曲げ応力が変動してしまうということはないため、歪センサの出力特性は安定するという効果を有するものである。
【００３８】
なお、上記本発明の実施の形態１においては、センサ基板１１における第１の固定孔１２の下側から第１の固定部材２８を構成する第１の下側ワッシャ３０における挿入部３４を挿入した後、第１の固定孔１２の上側から第１の固定部材２８を構成する第１の上側ワッシャ２９における挿入部３２を挿入し、そして第１の下側ワッシャ３０における当接部３３の上面をセンサ基板１１の下面に当接させるとともに、第１の上側ワッシャ２９における当接部３１の下面をセンサ基板１１の上面に当接させる際に、第１の上側ワッシャ２９における挿入部３２の外周部を、第１の下側ワッシャ３０における挿入部３４の内周部に圧入することにより、第１の固定部材２８をセンサ基板１１に固定するようにしていたが、この実施の形態１とは逆に、センサ基板１１における第１の固定孔１２の下側から第１の固定部材２８を構成する第１の上側ワッシャ２９における挿入部３２を挿入した後、第１の固定孔１２の上側から第１の固定部材２８を構成する第１の下側ワッシャ３０に挿入部３４を挿入し、そして第１の上側ワッシャ２９における当接部３１の上面をセンサ基板１１の下面に当接させるとともに、第１の下側ワッシャ３０における当接部３３の下面をセンサ基板１１の上面に当接させる際に、第１の下側ワッシャ３０における挿入部３４の内周部を、第１の上側ワッシャ２９における挿入部３２の外周部に圧入することにより、第１の固定部材２８をセンサ基板１１に固定するようにした場合でも、上記本発明の実施の形態１と同様の効果を有するものである。
【００３９】
（実施の形態２）
以下、実施の形態２を用いて、本発明の特に請求項４および５に記載の発明について説明する。
【００４０】
図６は本発明の実施の形態２における歪センサの側断面図、図７は同歪センサにおける第１の固定部材をセンサ基板に固着する前の状態を示す分解斜視図である。
【００４１】
なお、この本発明の実施の形態２においては、上記本発明の実施の形態１の構成と同様の構成を有するものについては、同一符号を付しており、その説明は省略する。
【００４２】
図６，図７において、本発明の実施の形態２における歪センサは、第１の固定部材４１を、図７に示すように、センサ基板１１の上面に当接する金属製の第１の上側ワッシャ２９と、センサ基板１１の下面に当接する金属製の第１の下側ワッシャ４２とにより構成している。そして、第１の上側ワッシャ２９はセンサ基板１１の上面と当接する円形形状の当接部３１と、センサ基板１１における第１の固定孔１２に挿入される挿入部３２を備えている。また、第１の下側ワッシャ４２は上面がセンサ基板１１の下面と当接するとともに、上面から下面にわたって孔４３を設けており、そしてこの孔４３に第１の上側ワッシャ２９における挿入部３２を圧入嵌合させることにより、第１の上側ワッシャ２９および第１の下側ワッシャ４２からなる第１の固定部材４１をセンサ基板１１に固定している。また、この第１の固定部材４１と同様に、第２の固定部材４４も、金属製の第１の上側ワッシャ３６と、金属製の第２の下側ワッシャ４５とにより構成されている。さらに、検出部材４６も、金属製の検出部上側ワッシャ３９と、金属製の検出部下側ワッシャ４７とにより構成されている。
【００４３】
上記本発明の実施の形態２においては、第１の固定部材４１における第１の上側ワッシャ２９に挿入部３２を設けるとともに、第１の固定部材４１における第１の下側ワッシャ４２に孔４３を設け、そして第１の上側ワッシャ２９における挿入部３２を第１の下側ワッシャ４２の孔４３に圧入嵌合させることにより、第１の固定部材４１をセンサ基板１１に固定するようにしているため、第１の下側ワッシャ４２の全体が第１の上側ワッシャ２９との圧入に関与することになるとともに、第１の上側ワッシャ２９における挿入部３２の厚みを大きくすることができ、その結果、第１の固定部材４１の強度が向上するという効果が得られるものである。
【００４４】
なお、上記本発明の実施の形態２における歪センサにおいては、第１、第２の固定部材４１，４４および検出部材４６における第１、第２の上側ワッシャ２９，３６および検出部上側ワッシャ３９に挿入部を設けるとともに、第１、第２の固定部材４１，４４および検出部材４６における第１、第２の下側ワッシャ４２，４５および検出部下側ワッシャ４７に孔を設け、前記第１、第２の上側ワッシャ２９，３６および検出部上側ワッシャ３９における挿入部を、第１、第２の下側ワッシャ４２，４５および検出部下側ワッシャ４７における孔に圧入嵌合させることにより、第１、第２の固定部材４１，４４および検出部材４６をセンサ基板１１に固定する構成としていたが、これとは逆に、第１、第２の固定部材４１，４４および検出部材４６における第１、第２の下側ワッシャ４２，４５および検出部下側ワッシャ４７に挿入部を設けるとともに、第１、第２の固定部材４１，４４および検出部材４６における第１、第２の上側ワッシャ２９，３６および検出部上側ワッシャ３９に孔を設け、前記第１、第２の下側ワッシャ４２，４５および検出部下側ワッシャ４７における挿入部を、第１、第２の上側ワッシャ２９，３６および検出部上側ワッシャ３９における孔に圧入嵌合させることにより、第１、第２の固定部材４１，４４および検出部材４６をセンサ基板１１に固定する構成にした場合でも、上記本発明の実施の形態２における歪センサと同様の効果を有するものである。
【００４５】
【発明の効果】
以上のように本発明によれば、固定部材、検出部材をそれぞれ上側ワッシャと下側ワッシャで構成するとともに、この上側ワッシャと下側ワッシャでセンサ基板を挟持することにより、固定部材および検出部材をセンサ基板に固定しているため、上側ワッシャと下側ワッシャでセンサ基板を挟持することにより発生するセンサ基板の板厚と垂直方向の力によって、固定部材および検出部材はセンサ基板に固着されることになり、これにより、センサ基板における固定孔および検出孔の周辺に捩じりによる内部応力が発生することはなくなるため、歪検出素子に応力が常に加わることはなくなり、その結果、出力信号の安定した歪センサを提供することができるという優れた効果を有するものである。
【図面の簡単な説明】
【図１】本発明の実施の形態１における歪センサの上面図
【図２】同歪センサの側断面図
【図３】同歪センサにおける第１の固定部材をセンサ基板に固着する前の状態を示す分解斜視図
【図４】同歪センサにおけるセンサ基板の上面図
【図５】同歪センサが動作する状態を示す側断面図
【図６】本発明の実施の形態２における歪センサの側断面図
【図７】同歪センサにおける第１の固定部材をセンサ基板に固着する前の状態を示す分解斜視図
【図８】従来の歪センサの斜視図
【図９】従来の歪センサを被検出部材に固着した状態を示す側断面図
【符号の説明】
１１　センサ基板
１２　第１の固定孔
１３　第２の固定孔
１４　検出孔
１６　第１の歪検出素子
１７　第２の歪検出素子
２１　第３の歪検出素子
２３　第４の歪検出素子
２８　第１の固定部材
２９　第１の上側ワッシャ
３０　第１の下側ワッシャ
３１　当接部
３２　挿入部
３３　当接部
３４　挿入部
３５　第２の固定部材
３６　第２の上側ワッシャ
３７　第２の下側ワッシャ
３８　検出部材
３９　検出部上側ワッシャ
４０　検出部下側ワッシャ
４１　第１の固定部材
４２　第１の下側ワッシャ
４３　孔
４４　第２の固定部材
４５　第２の下側ワッシャ
４６　検出部材
４７　検出部下側ワッシャ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a strain sensor that detects a strain generated by an external force caused by the weight of a human or a vehicle such as an automobile by a strain detecting element provided on a sensor substrate.
[0002]
[Prior art]
As a conventional strain sensor of this type, there is known a strain sensor disclosed in Japanese Patent Application No. 4-265 (Japanese Utility Model Application No. 5-57605).
[0003]
Hereinafter, a conventional strain sensor will be described with reference to the drawings.
[0004]
FIG. 8 is a perspective view of a conventional strain sensor.
[0005]
In FIG. 8, reference numeral 1 denotes a sensor substrate made of metal. The sensor substrate 1 has a first fixing hole 2 on one end side, a second fixing hole 3 on the other end side, and a strain gauge on the upper surface. Is provided. The strain detecting element 4 in the sensor substrate 1 has an element portion 5 and a lead wire 6 which is electrically connected to the element portion 5 and protrudes outward.
[0006]
Next, the operation of the conventional strain sensor configured as described above will be described with reference to the drawings.
[0007]
As shown in FIG. 9, the male member 9 is screwed into the pair of female screws 7 of the detection member 8 provided with the pair of female screws 7 via the sensor substrate 1 so that the sensor substrate 1 is connected to the detection member. 8 At this time, the first fixing hole 2 and the second fixing hole 2 are secured so that the sensor substrate 1 can be securely attached to the detected member 8 in consideration of a change in the pitch of the pair of female screws 7 provided on the detected member 8. The inner diameter of the fixing hole 3 is larger than the outer diameter of the female screw 7. When an external force acts on the detected member 8 in this state, the detected member 8 is distorted, and the sensor substrate 1 is deformed in accordance with the distortion. The deformation of the sensor substrate 1 is taken out from the lead wire 6 as a voltage change due to a change in the resistance value of the strain detecting element 4 provided on the upper surface of the sensor substrate 1, thereby detecting an external force generated in the detected member 8. Was to do.
[0008]
[Problems to be solved by the invention]
However, in the above-described conventional configuration, when the male screw 9 is screwed into the female screw 7 to fix the sensor substrate 1 to the detected member 8, the torsion force of the male screw 9 acts. As a result, an internal stress is generated in the sensor substrate 1 by the force, and the strain detection element 4 is distorted, so that an output signal is generated even when no external force is applied to the sensor substrate 1. As a result, there is a problem that the output signal of the strain sensor becomes unstable.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a strain sensor having stable characteristics in which no output signal is generated when no external force is applied to the strain sensor.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has the following configuration.
[0011]
The invention according to claim 1 of the present invention is particularly advantageous in that the fixing member and the detecting member are respectively constituted by an upper washer and a lower washer, and the sensor substrate is sandwiched between the upper washer and the lower washer. According to this configuration, the fixing member and the detecting member are fixed by the force in the vertical direction and the thickness of the sensor substrate generated by sandwiching the sensor substrate between the upper washer and the lower washer. Since the member is fixed to the sensor substrate, no internal stress due to torsion is generated around the fixing hole and the detection hole in the sensor substrate, and thus, no stress is applied to the strain detecting element. Therefore, the effect of stabilizing the output signal of the strain sensor can be obtained.
[0012]
The invention according to claim 2 of the present invention particularly provides an insertion portion on each of the upper washer and the lower washer of the fixing member and the detection member, and one of these insertion portions is provided with a fixing hole and a detection hole on the sensor substrate. Inserting into the fixed hole and the detection hole in the sensor substrate in a state where a gap is provided between the hole, and one of the insertion portions provided in the upper washer and the lower washer in the fixed member and the detection member, respectively. The fixing member and the detecting member are fixed to the sensor substrate by press-fitting one of the other inserting portions to the fixing member and the detecting member according to this configuration in a state where the internal stress is not applied to the sensor substrate. The effect of being able to be fixed to the sensor substrate and preventing the fixing member and the detection member from coming off the sensor substrate is obtained. Is shall.
[0013]
In the invention according to claim 3 of the present invention, in particular, the upper washer of the fixed member and the detection member is provided with a contact portion that is in contact with the upper surface of the sensor substrate, and the lower washer is in contact with the lower surface of the sensor substrate. Parts, and these contact portions are each configured in a circular shape. According to this configuration, the upper washer rotates in the circumferential direction on the upper surface of the sensor substrate, and the lower washer is formed on the lower surface of the sensor substrate. Even if it rotates in the circumferential direction, the position of the contact portion of the upper washer and the lower washer with the sensor substrate does not shift in the longitudinal direction of the sensor substrate, whereby the bending stress applied to the strain detecting element fluctuates. Therefore, the effect of stabilizing the output characteristics of the strain sensor can be obtained.
[0014]
The invention according to claim 4 of the present invention provides, in particular, an insertion portion in the upper washer in the fixed member and the detection member, a hole in the lower washer in the fixed member and the detection member, and the insertion portion in the upper washer. The fixing member and the detection member are fixed to the sensor substrate by press-fitting into the hole of the lower washer. According to this configuration, the entire lower washer is involved in press-fitting with the upper washer. In addition, since the thickness of the insertion portion of the upper washer can be increased, the effect of improving the strength of the fixing member and the detection member can be obtained.
[0015]
The invention according to claim 5 of the present invention particularly provides an insertion portion in the lower washer of the fixed member and the detection member, and a hole in the upper washer of the fixed member and the detection member, and further includes an insertion portion in the lower washer. Is fixed to the sensor substrate by press-fitting into the hole of the upper washer. According to this configuration, the entire upper washer is involved in press-fitting with the lower washer. Since the thickness of the insertion portion of the lower washer can be increased, the effect of improving the strength of the fixing member and the detection member can be obtained.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
(Embodiment 1)
Hereinafter, the first embodiment of the present invention will be described with reference to the first to third embodiments.
[0017]
FIG. 1 is a top view of a strain sensor according to Embodiment 1 of the present invention, FIG. 2 is a side sectional view of the strain sensor, and FIG. 3 shows a state before a first fixing member of the strain sensor is fixed to a sensor substrate. FIG. 4 is an exploded perspective view, and FIG. 4 is a top view of a sensor substrate in the same strain sensor.
[0018]
1 to 4, reference numeral 11 denotes a sensor substrate. As shown in FIG. 2, the sensor substrate 11 has a first fixing hole 12 on one end side from the upper surface to the lower surface, and a substantially central portion from the upper surface to the lower surface. A second fixing hole 13 is provided, and a detection hole 14 is provided substantially at the center between the first fixing hole 12 and the second fixing hole 13 from the upper surface to the lower surface. A power supply electrode 15 is provided on the other end side of the sensor substrate 11, and the power supply electrode 15 is electrically connected to one end of the first strain detection element 16 and one end of the second strain detection element 17 by a circuit pattern 18. And the other end of the first strain detecting element 16 is electrically connected to a first output electrode 19. Further, the other end of the second strain detecting element 17 is electrically connected to the second output electrode 20 and also electrically connected to one end of the third strain detecting element 21. The other end of the strain detecting element 21 is electrically connected to the GND electrode 22.
[0019]
A fourth strain detecting element 23 is provided on the upper surface of the sensor substrate 11, and one end of the fourth strain detecting element 23 is connected to the other end of the first strain detecting element 16 and the first output electrode 19. It is electrically connected, and the other end is electrically connected to the GND electrode 22. Then, the first distortion detecting element 16, the second distortion detecting element 17, the third distortion detecting element 21, the fourth distortion detecting element 23, the power supply electrode 15, the first output electrode 19, and the second The output electrode 20, the GND electrode 22, and the circuit pattern 18 form a bridge circuit. Further, an IC 24 is provided on the upper surface on the other end side of the sensor substrate 11, and the IC 24 amplifies the differential voltage of the voltages of the first output electrode 19 and the second output electrode 20, and The signal is output to the outside from a connector 25 provided on the other end side of the connector 11.
[0020]
Further, an external power supply electrode 26 is provided on the upper surface on the other end side of the sensor substrate 11, and the external power supply electrode 26 is electrically connected to the power supply electrode 15. Further, an external GND electrode 27 is provided on the upper surface of the sensor substrate 11, and the external GND electrode 27 is electrically connected to the GND electrode 22.
[0021]
Reference numeral 28 denotes a first fixing member. As shown in FIG. 3, the first fixing member 28 includes a first upper washer 29 made of metal that abuts on the upper surface of the sensor substrate 11, and a lower surface of the sensor substrate 11. The first lower washer 30 made of metal is in contact with the first lower washer 30. The first upper washer 29 of the first fixing member 28 includes a circular contact portion 31 that contacts the upper surface of the sensor substrate 11 and an insertion portion that is inserted into the first fixing hole 12 of the sensor substrate 11. 32. Similarly to the first upper washer 29, the first lower washer 30 of the first fixing member 28 also has a circular contact portion 33 that contacts the lower surface of the sensor substrate 11, and the first lower washer 30 of the sensor substrate 11 The outer peripheral portion of the insertion portion 32 of the first upper washer 29 is press-fitted into the inner peripheral portion of the insertion portion 34 of the first lower washer 30. By doing so, the first fixing member 28 is fixed to the sensor substrate 11. In this case, the insertion portion 34 of the first lower washer 30 is inserted into the first fixing hole 12 of the sensor substrate 11 with a gap provided between the first fixing hole 12 and the first fixing hole 12. In this state, when the outer peripheral portion of the insertion portion 32 of the first upper washer 29 is pressed into the inner peripheral portion of the insertion portion 34 of the first lower washer 30, the internal stress is not applied to the sensor substrate 11. The sensor substrate 11 is sandwiched between a first upper washer 29 and a first lower washer 30 that constitute a first fixing member 28. With such a structure, the first fixing member 28 can be fixed to the sensor substrate 11 in a state where internal stress is not applied to the sensor substrate 11, and the first fixing member 28 This has the effect that it does not come off.
[0022]
Reference numeral 35 denotes a second fixing member. Like the first fixing member 28, the second fixing member 35 also includes a second upper washer 36 made of metal and a second lower washer 37 made of metal. It consists of: Reference numeral 38 denotes a detection member. The detection member 38 includes a metal detection unit upper washer 39 and a metal detection unit lower washer 40.
[0023]
In the first embodiment of the present invention, an external force is applied to the end 38a of the detection member 38 that contacts the sensor board 11, and the end 28a of the first fixing member 28 that contacts the sensor board 11 and the second A reaction force is applied to an end 35a of the fixing member 35 abutting on the sensor substrate 11.
[0024]
Next, a description will be given of a method of assembling the strain sensor configured as described above according to the first embodiment of the present invention.
[0025]
First, a first fixing hole 12, a second fixing hole 13, and a detection hole 14 are formed in a prepared metal base material (not shown) by press working.
[0026]
Next, after printing a glass paste (not shown) on the upper surface of the base substrate (not shown), the glass paste is baked at about 850 ° C. for about 45 minutes to form the sensor substrate 11.
[0027]
Next, a metal glaze-based carbon paste is printed on the upper surface of the sensor substrate 11, baked at about 850 ° C. for about 45 minutes, and the first strain detecting element 16 and the second The strain detecting element 17, the third strain detecting element 21, and the fourth strain detecting element 23 are formed.
[0028]
Next, a silver paste is printed at a position where the power electrode 15, the first output electrode 19, the second output electrode 20, the GND electrode 22, and the circuit pattern 18 are provided, and baked at about 850 ° C. for about 45 minutes. The power supply electrode 15, the first output electrode 19, the second output electrode 20, the GND electrode 22, and the circuit pattern 18 are formed.
[0029]
Next, the IC 24 is mounted on the upper surface of the sensor substrate 11.
[0030]
Next, after inserting the insertion portion 34 of the first lower washer 30 from below the first fixing hole 12 in the sensor substrate 11, inserting the insertion portion in the first upper washer 29 from above the first fixing hole 12. The part 32 is inserted. Then, the upper surface of the contact portion 33 of the first lower washer 30 is brought into contact with the lower surface of the sensor substrate 11, and the lower surface of the contact portion 31 of the first upper washer 29 is brought into contact with the upper surface of the sensor substrate 11. At this time, the outer periphery of the insertion portion 32 of the first upper washer 29 is pressed into the inner periphery of the insertion portion 34 of the first lower washer 30 so that the first fixing member 28 is attached to the sensor substrate 11. Fixed to.
[0031]
As described above, when the first fixing member 28 is fixed to the sensor substrate 11 by sandwiching the sensor substrate 11 between the first upper washer 29 and the first lower washer 30, the first upper washer 29 The first fixing member 28 is fixed to the sensor substrate 11 by the force in the direction perpendicular to the thickness of the sensor substrate 11 generated by sandwiching the sensor substrate 11 with the first lower washer 30. In addition, internal stress due to torsion does not occur around the first fixing hole 12 in the sensor substrate 11, so that the third strain detecting element 21 located near the first fixing hole 12 Is not always added, so that the output signal of the strain sensor has an effect of being stabilized.
[0032]
Next, similarly to the first fixing member 28, the second fixing member 35 including the second upper washer 36 and the second lower washer 37 is connected to the second fixing hole 13 in the sensor substrate 11. Position and fix near.
[0033]
Lastly, the detection member 38 constituted by the detection unit upper washer 39 and the detection unit lower washer 40 is positioned near the detection hole 14 in the sensor substrate 11 and fixed.
[0034]
The operation of the strain sensor configured and manufactured as described above according to the first embodiment of the present invention will now be described with reference to the drawings.
[0035]
FIG. 5 is a side sectional view showing a state in which the strain sensor according to Embodiment 1 of the present invention operates.
[0036]
As shown in FIG. 5, when an external force F acts on the detection member 38 from above, the sensor substrate 11 is deformed by the external force F. At this time, an external force acts on the end 38a of the detection member 38 that contacts the sensor board 11, and the end 28a of the first fixing member 28 that contacts the sensor board 11 and the sensor board 11 of the second fixing member 35. A reaction force acts on the end 35a that comes into contact with the end portion. Then, a tensile stress is applied to the first strain detecting element 16 and the third strain detecting element 21 provided on the upper surface of the sensor substrate 11, and the resistance value of the first strain detecting element 16 and the third strain detecting element 21 is increased. Increases, compressive stress is applied to the second strain detecting element 17 and the fourth strain detecting element 23, and the resistance values of the second strain detecting element 17 and the fourth strain detecting element 23 decrease. Since the first distortion detecting element 16, the second distortion detecting element 17, the third distortion detecting element 21, and the fourth distortion detecting element 23 form a bridge circuit, the first output electrodes 19 and The potential difference of the second output electrode 20 is output from the connector 25 as a differential voltage by the IC 24.
[0037]
Here, since the reaction force applied to the first fixing member 28 includes a vector for rotating the first fixing member 28 in the circumferential direction, the first fixing member 28 may be rotated. In the strain sensor according to the first embodiment, as shown in FIG. 3, the first upper washer 29 of the first fixing member 28 is provided with a contact portion 31 that contacts the upper surface of the sensor substrate 11, and The lower washer 30 is provided with a contact portion 33 for contacting the lower surface of the sensor substrate 11, and the contact portions 31, 33 are each formed in a circular shape. Even if the first lower washer 30 rotates in the circumferential direction on the upper surface of the sensor substrate 11 and the first lower washer 30 rotates in the circumferential direction on the lower surface of the sensor substrate 11, the first lower washer 29 and the first lower washer 30 The position of the contact portion with the sensor substrate 11 does not shift in the longitudinal direction of the sensor substrate 11, whereby the bending stress applied to the third strain detecting element 21 provided near the first fixing member 28 is reduced. Since there is no fluctuation, the output characteristic of the strain sensor has an effect of being stabilized.
[0038]
In the first embodiment of the present invention, the insertion portion 34 of the first lower washer 30 forming the first fixing member 28 is inserted from below the first fixing hole 12 in the sensor substrate 11. Thereafter, the insertion portion 32 of the first upper washer 29 constituting the first fixing member 28 is inserted from above the first fixing hole 12, and the upper surface of the contact portion 33 of the first lower washer 30 is removed. The outer peripheral portion of the insertion portion 32 of the first upper washer 29 when the lower surface of the contact portion 31 of the first upper washer 29 is brought into contact with the upper surface of the sensor substrate 11 while being brought into contact with the lower surface of the sensor substrate 11. The first fixing member 28 is fixed to the sensor substrate 11 by press-fitting into the inner peripheral portion of the insertion portion 34 of the first lower washer 30, but is opposite to the first embodiment. To After inserting the insertion portion 32 of the first upper washer 29 that constitutes the first fixing member 28 from below the first fixing hole 12 in the sensor substrate 11, the first upper washer 29 is inserted from above the first fixing hole 12. The insertion portion 34 is inserted into the first lower washer 30 constituting the fixing member 28, and the upper surface of the contact portion 31 of the first upper washer 29 is brought into contact with the lower surface of the sensor substrate 11, and the first When the lower surface of the contact portion 33 of the lower washer 30 is brought into contact with the upper surface of the sensor substrate 11, the inner peripheral portion of the insertion portion 34 of the first lower washer 30 is inserted into the insertion portion of the first upper washer 29. Even when the first fixing member 28 is fixed to the sensor substrate 11 by press-fitting the outer periphery of the sensor 32, the same effect as that of the first embodiment of the present invention is provided.
[0039]
(Embodiment 2)
Hereinafter, a second embodiment of the present invention will be described with reference to the second embodiment.
[0040]
FIG. 6 is a side sectional view of the strain sensor according to Embodiment 2 of the present invention, and FIG. 7 is an exploded perspective view showing a state before the first fixing member of the strain sensor is fixed to the sensor substrate.
[0041]
In the second embodiment of the present invention, components having the same configuration as that of the first embodiment of the present invention are denoted by the same reference numerals, and description thereof is omitted.
[0042]
6 and 7, in the strain sensor according to the second embodiment of the present invention, as shown in FIG. 7, a metal first upper washer that abuts on the upper surface of the sensor substrate 11 is provided. 29 and a first lower washer 42 made of metal, which is in contact with the lower surface of the sensor substrate 11. The first upper washer 29 includes a circular contact portion 31 that contacts the upper surface of the sensor substrate 11 and an insertion portion 32 that is inserted into the first fixing hole 12 of the sensor substrate 11. The first lower washer 42 has an upper surface in contact with the lower surface of the sensor substrate 11 and has a hole 43 extending from the upper surface to the lower surface. The insertion portion 32 of the first upper washer 29 is press-fitted into the hole 43. The first fixing member 41 including the first upper washer 29 and the first lower washer 42 is fixed to the sensor substrate 11 by being fitted. Further, like the first fixing member 41, the second fixing member 44 also includes a first upper washer 36 made of metal and a second lower washer 45 made of metal. Further, the detection member 46 also includes a metal detection unit upper washer 39 and a metal detection unit lower washer 47.
[0043]
In the second embodiment of the present invention, the insertion portion 32 is provided in the first upper washer 29 of the first fixing member 41, and the hole 43 is formed in the first lower washer 42 of the first fixing member 41. The first fixing member 41 is fixed to the sensor board 11 by press-fitting the insertion portion 32 of the first upper washer 29 into the hole 43 of the first lower washer 42. The whole of the first lower washer 42 is involved in the press-fitting with the first upper washer 29, and the thickness of the insertion portion 32 in the first upper washer 29 can be increased. As a result, The effect that the strength of the first fixing member 41 is improved can be obtained.
[0044]
In the strain sensor according to Embodiment 2 of the present invention, the first and second upper washers 29 and 36 and the detector upper washer 39 of the first and second fixing members 41 and 44 and the detecting member 46 are provided. In addition to providing an insertion portion, holes are provided in the first and second lower washers 42 and 45 and the detection portion lower washer 47 in the first and second fixing members 41 and 44 and the detection member 46, and the first and second fixing members 41 and 44 and the detection portion lower washer 47 are provided. The first and second insertion holes of the upper washer 29 and 36 and the detection unit upper washer 39 are press-fitted into holes of the first and second lower washers 42 and 45 and the detection unit lower washer 47. Although the second fixing members 41 and 44 and the detection member 46 are fixed to the sensor substrate 11, the first and second fixing members 41 and 44 and the detection member 6, the first and second lower washers 42 and 45 and the detection portion lower washer 47 are provided with insertion portions, and the first and second fixing members 41 and 44 and the first and second upper portions of the detection member 46 are provided. Holes are provided in the washers 29 and 36 and the detection portion upper washer 39, and the insertion portions of the first and second lower washers 42 and 45 and the detection portion lower washer 47 are connected to the first and second upper washers 29 and 36. Even when the first and second fixing members 41 and 44 and the detection member 46 are fixed to the sensor substrate 11 by press-fitting into holes in the detection portion upper washer 39, the above-described embodiment of the present invention can be implemented. This has the same effect as the strain sensor according to the second aspect.
[0045]
【The invention's effect】
As described above, according to the present invention, the fixing member and the detection member are configured by the upper washer and the lower washer, respectively, and the sensor substrate is sandwiched between the upper washer and the lower washer, so that the fixing member and the detection member are formed. Since the sensor is fixed to the sensor substrate, the fixing member and the detection member are fixed to the sensor substrate by the force in the vertical direction and the thickness of the sensor substrate generated by sandwiching the sensor substrate between the upper washer and the lower washer. As a result, no internal stress due to torsion is generated around the fixed hole and the detection hole in the sensor substrate, so that the stress is not always applied to the strain detecting element, and as a result, the output signal is stabilized. This has an excellent effect that a strain sensor can be provided.
[Brief description of the drawings]
FIG. 1 is a top view of a strain sensor according to Embodiment 1 of the present invention. FIG. 2 is a side sectional view of the strain sensor. FIG. 3 is a state before a first fixing member of the strain sensor is fixed to a sensor substrate. FIG. 4 is a top view of a sensor substrate in the strain sensor. FIG. 5 is a sectional side view showing a state in which the strain sensor operates. FIG. 6 is a side of the strain sensor according to Embodiment 2 of the present invention. FIG. 7 is an exploded perspective view showing a state before the first fixing member of the strain sensor is fixed to the sensor substrate. FIG. 8 is a perspective view of a conventional strain sensor. FIG. Side sectional view showing a state of being fixed to a detection member.
DESCRIPTION OF SYMBOLS 11 Sensor board 12 1st fixing hole 13 2nd fixing hole 14 Detection hole 16 1st distortion detecting element 17 2nd distortion detecting element 21 3rd distortion detecting element 23 4th distortion detecting element 28 1st Fixing member 29 First upper washer 30 First lower washer 31 Contact portion 32 Insertion portion 33 Contact portion 34 Insertion portion 35 Second fixing member 36 Second upper washer 37 Second lower washer 38 Detection Member 39 Detector upper washer 40 Detector lower washer 41 First fixing member 42 First lower washer 43 Hole 44 Second fixing member 45 Second lower washer 46 Detecting member 47 Detector lower washer

Claims

A sensor substrate provided with at least one fixing hole and a detection hole, and having at least one strain detecting element on the upper surface or the lower surface; a fixing member inserted into the fixing hole in the sensor substrate; A detection member to be inserted is provided, and the fixed member and the detection member are each configured by an upper washer and a lower washer, and the sensor substrate is sandwiched between the upper washer and the lower washer, thereby forming the fixed member and the detection member. A strain sensor fixed to a sensor substrate.

Insertion portions are provided on the upper washer and the lower washer of the fixed member and the detection member, respectively, and one of these insertion portions is provided on the sensor substrate with a gap provided between the fixed hole and the detection hole on the sensor substrate. It is fixed by inserting into the fixing hole and the detection hole, and further press-fitting one of the other insertion portions into any one of the insertion portions provided on the upper washer and the lower washer of the fixing member and the detection member. The strain sensor according to claim 1, wherein the member and the detection member are fixed to the sensor substrate.

The upper washer of the fixed member and the detection member is provided with a contact portion that comes into contact with the upper surface of the sensor substrate, and the lower washer is provided with a contact portion that comes into contact with the lower surface of the sensor substrate, and each of these contact portions has a circular shape. The strain sensor according to claim 1, wherein:

An insertion portion is provided in the upper washer of the fixed member and the detection member, a hole is provided in the lower washer of the fixed member and the detection member, and the insertion portion of the upper washer is press-fitted into the hole of the lower washer, thereby fixing the member. The strain sensor according to claim 1, wherein the member and the detection member are fixed to the sensor substrate.

An insertion portion is provided in the lower washer of the fixed member and the detection member, a hole is provided in the upper washer of the fixed member and the detection member, and the insertion portion of the lower washer is press-fitted into the hole of the upper washer, thereby fixing the member. The strain sensor according to claim 1, wherein the member and the detection member are fixed to the sensor substrate.