JP2004093306A

JP2004093306A - Gas sensor

Info

Publication number: JP2004093306A
Application number: JP2002254066A
Authority: JP
Inventors: Takashi Kojima; 児島　孝志
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2002-08-30
Filing date: 2002-08-30
Publication date: 2004-03-25

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor, capable of reliably securing electrical continuity between a terminal spring and a terminal of a sensor element. <P>SOLUTION: With the terminal spring 51 in contact with the terminal, the terminal spring 51 sandwiches the sensor element 29 by adding load to the sensor element 29 in the radial direction of the gas sensor. Two or more sandwiching members 61 and 62 are provided at the outer circumference of the terminal spring 51, and a pressure spring is provided at the outer circumference of the sandwiching members 61 and 62 so as to press and fix the sandwiching members 61 and 62. The relation F1≤F2 holds between a sandwiching load F1 with respect to the sensor element 29 by the terminal spring 51 and a press load F2 to the sandwiching members by the press spring. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【技術分野】
本発明は，自動車用内燃機関の燃焼制御等に用いるガスセンサに関する。
【０００２】
【従来技術】
従来，被測定ガス中の特定ガス濃度を測定するガスセンサとして，基端側に複数の端子を有するセンサ素子を有し，上記センサ素子の端子とガスセンサ基端側から引き込んだリード線との間を電気的に接続する端子バネを有する構成が知られている。
【０００３】
【解決しようとする課題】
近年，一つのセンサ素子内に複数種のセルを設け，複数種類のガス濃度を検出する等といったガスセンサが登場した。
このようなガスセンサの場合，センサ素子の持つ端子の数も多くなり，従って端子バネの数もより多くなる。よって，多数の端子バネについて端子と確実に電気的な導通が確保できる構成のガスセンサが必要である。
【０００４】
本発明は，かかる従来の問題点に鑑みてなされたもので，端子バネとセンサ素子の端子との間でより確実に電気的な導通を確保することができるガスセンサを提供しようとするものである。
【０００５】
【課題の解決手段】
第１の発明は，基端側に複数の端子を有するセンサ素子を有し，上記端子とガスセンサ基端側から引き込んだリード線との間を電気的に接続する端子バネを有し，
上記端子バネと上記端子とが接触した状態で，上記端子バネはガスセンサ径方向への荷重を上記センサ素子に付与することで上記センサ素子を挟持し，
上記端子バネの外周に２つ以上の挟持部材を設け，更に上記挟持部材の外周に押圧バネを設けて上記挟持部材を押圧固定するよう構成したガスセンサであって，
上記端子バネによる上記センサ素子に対する挟持荷重Ｆ１と，
上記押圧バネによる上記挟持部材に対する押圧荷重Ｆ２との間には，
端子バネの挟持荷重Ｆ１≦押圧バネの押圧荷重Ｆ２
という関係が成立することを特徴とするガスセンサにある（請求項１）。
【０００６】
本発明にかかるガスセンサにおいて，端子バネによるセンサ素子の挟持荷重Ｆ１と押圧バネによる挟持部材への押圧荷重Ｆ２との間にＦ１≦Ｆ２という関係が成立する。すなわち，端子バネがセンサ素子を挟持する力以上の圧力で，押圧バネは挟持部材を押圧固定する。
このため，端子バネとセンサ素子との間での隙間の発生が防止され，両者間の電気的導通を確実に確保することができる。
仮にＦ１＞Ｆ２であったなら，端子バネとセンサ素子との間に隙間が生じやすくなり，端子バネと端子との電気的導通が確保できなくなるおそれがある。
なお，挟持荷重，押圧荷重の詳細については後述する。
【０００７】
以上，本発明によれば，端子バネとセンサ素子の端子との間でより確実に電気的な導通を確保することができるガスセンサを提供することができる。
【０００８】
【発明の実施の形態】
端子バネと押圧バネはそれぞれバネとしての性能を備え，両者によって生じる挟持荷重，押圧荷重はバネの弾性力に由来する。
一般に弾性力を測定する際は，弾性体の変形，磁気ひずみ，圧電気，振動子の固有振動数などを測定し，予め測定しておいた校正曲線と比較して，力の大きさを決定する方法を利用する。
詳細は実施例にて説明する。
【０００９】
外部からガスセンサ内部に引き込むリード線の本数の少ないガスセンサに本発明を適用することもできるが，引き込むリード線の本数の多いガスセンサについて本発明を適用するほうがより効果的である。
【００１０】
そして，リード線の本数が多いガスセンサとは，例えば，ＮＯｘやＨＣを測定するガスセンサがある。ＮＯｘやＨＣを測定するセンサ素子は複数の電気化学的セルを備えているため，これら複数の電気化学的セルに対する電圧印加や出力取り出しのために多数のリード線が必要となるためである。
【００１１】
また，リード線の本数の多いガスセンサとして，１本で複数種類のガス濃度を測定するものがある。このガスセンサも，複数種類の測定に対応した電気化学的セルを備えたセンサ素子を内蔵しているため，多数のリード線が必要となる。
なお，リード線と端子バネとの間は直接接続することもあるが，図１に示すごとく，別途接続部材を必要とすることもある。
【００１２】
また，上記押圧バネは２つ以上設けることが好ましい（請求項２）。
押圧バネの数を増やすことで押圧力を増やすことができる。また，押圧バネを複数設け，複数箇所で押圧を行うことで，挟持部材全体をバランスよく押圧することができる。
【００１３】
また，ガスセンサ軸方向に沿った平面に対し，上記端子バネと上記端子とがそれぞれ接触する接触位置を投影した点を接触点，上記押圧バネによる上記挟持部材への押圧位置を投影した点を押圧点とすると，上記接触点における上記挟持荷重Ｆ１の荷重中心の合計と，上記押圧点における上記押圧荷重Ｆ２の荷重中心は等しいことが好ましい（請求項３）。
これにより，多数の端子バネの上記接触点における上記挟持荷重の各々を等しくでき，各々の端子バネと端子との電気的導通を確実に行うことができる。
なお，具体的な荷重中心の求め方は実施例に記載した。
【００１４】
【実施例】
以下に，図面を用いて本発明の実施例について説明する。
（実施例１）
本例は，図１に示すごとく，基端側に８個の端子２９１，２９２を有するセンサ素子２９を有し，上記端子２９１，２９２とガスセンサ基端側から引き込んだリード線４１との間を電気的に接続する端子バネ５１，５２を有する。
上記端子バネ５１，５２と上記端子２９１，２９２とが接触した状態で，上記端子バネ５１，５２はガスセンサ径方向への荷重を上記センサ素子２９に付与することで上記センサ素子２９を挟持する。
また，上記端子バネ５１，５２の外周に２つの挟持部材６１，６２を設け，更に上記挟持部材６１，６２の外周に押圧バネ３１，３２を設けて上記挟持部材６１，６２を押圧固定するよう構成する。
【００１５】
そして，上記端子バネ５１，５２による上記センサ素子２９に対する挟持荷重Ｆ１と，上記押圧バネ３１，３２による上記挟持部材６１，６２に対する押圧荷重Ｆ２とはＦ１≦Ｆ２の関係を満たす。
【００１６】
以下，詳細に説明する。
本例にかかるガスセンサ１は自動車エンジンの排気管に設置し，排気ガス中の酸素濃度とＮＯｘ濃度，エンジン燃焼室の空燃比を測定する。
上記ガスセンサ１が内蔵するセンサ素子２９はセラミック板を積層して構成した積層型の素子で，素子内部に設けた被測定ガス室内の酸素濃度を測定，監視するモニタセルと，被測定ガス室内の酸素濃度を調整する酸素ポンプセルと，被測定ガス室内のＮＯｘ濃度を測定するセンサセルを有し，さらに通電により発熱するヒータが一体的に設けてある（図示略）。
上記ヒータに対する電圧印加，各セルに対する電圧印加，出力取出しはセンサ素子２９の側面に設けた端子２９１，２９２において行う。
【００１７】
そのため，本例にかかるガスセンサ１は，３つのセル及びヒータに電力を供給し，出力を取出すために，合計で８本のリード線４１が必要であり，該リード線４１と端子２９１，２９２との間を接続する接続部材４２，端子バネ５１，５２も８個必要である。
【００１８】
そして，図２，図５に示すごとく，センサ素子２９の一方の側面にある端子電極２９１，２９２は４個で，これと反対側の側面にある端子電極２９１，２９２も４個である。従って，上記端子バネ５１，５２は，センサ素子２９を一方の側面と反対側の側面とから挟むように４本づつ配置される。
なお，図１はガスセンサ１の軸方向に沿って切断した断面図であるため，見えない位置にあるリード線の記載は省略した。
【００１９】
図１に示すごとく，本例のガスセンサ１は，金属製のハウジング１０と該ハウジング１０の先端側に取り付けた二重構造の金属製の被測定ガス側カバー１０９と，基端側に取り付けた金属製の大気側カバー１１とよりなる。大気側カバー１１はハウジング１０にかしめ固定する第１カバー１１１と該第１カバー１１１の基端側に撥水フィルタ１１３を介してかしめ固定する外側カバー１１２とよりなる。
【００２０】
ハウジング１０内にセラミック製の素子側絶縁碍子２を挿通するが，素子側絶縁碍子２の側面はガスセンサ先端側を向いたテーパー面１０２を有する。また，ハウジング１０の内側面はガスセンサ基端側を向いて，上記テーパー面１０２を金属製パッキン２００を介して支承する受け面１０１を有する。
【００２１】
素子側絶縁碍子２の先端側端面に皿バネ２１を載置し，該皿バネ２１の上から押圧部材２２を被冠する。押圧部材２２は，皿バネ２１を押さえてガスセンサ軸方向に縮める押さえ板２２１と該押さえ板２２１からハウジング１０の基端側側面に沿って先端側へ伸びる脚部２２２とよりなり，ハウジング１０の基端側側面と上記脚部２２２との間を固定することで，素子側絶縁碍子２をハウジング１０に対し固定する。
【００２２】
端子バネ５１，５２の導通接触部５０２と端子２９１，２９２とが接触し（図５参照），かつ導通接触部５０２を支持部５０に向けて撓ませた状態（図７参照）で，２個の挟持部材６１，６２を用いて上記端子バネ５１，５２と上記センサ素子２９とを挟持固定する。
【００２３】
挟持部材６１，６２の外周に，ガスセンサ１の径方向内側に向かう押圧力を挟持部材６１，６２に加えるよう構成した押圧バネ３１，３２を２個設ける。
また，挟持部材６１，６２は絶縁セラミックよりなり，該挟持部材６１，６２によって，端子バネ５１，５２相互間の絶縁性を確保する大気側絶縁碍子３を形成する。
【００２４】
上記押圧バネ３１，３２について説明する。
図３に示すごとく，押圧バネ３１は本体３１０と弾性を有するバネ部３１９とよりなる。
本体３１０は挟持部材６１，６２の外周面に沿った軽く湾曲した長方形の板状で，軽量化と可撓性付与のために中央に長方形の窓部３１９を設ける。
また，本体３１０の４隅より，該本体３１０に対して略直行する方向に延設したバネ部３１９がある。バネ部３１９を設けた部分における押圧バネ３１の断面形状は，図３（ａ）に示すごとくコの字状となる。また，バネ部３１９の先端はくの字状に曲折される。
【００２５】
そして，挟持部材６１，６２に対し組付ける前のバネ部３１９の形状を図３（ａ）の実線で示した。挟持部材６１，６２に組付けることで，バネ部３１９は，図３（ａ）の破線にかかる形状となる。また，押圧バネ３１を挟持部材６１，６２に組付けた状態は図２より明らかである。このように押圧バネ３１のバネ部３１９の変形により生じるバネ力が，ガスセンサ１の径方向に挟持部材６１，６２を押圧することができる。
【００２６】
また，図４に示すごとく，押圧バネ３２は本体３２０とバネ部３２９とよりなり，該押圧バネ３２は，本体３２０から大気側カバー１１の内側面に向って延設され，先端が大気側カバー１１の内側面に対し径方向に押圧固定するためのバネ部３２１を有する。
図４（ａ）に示すごとく，押圧バネ３２は挟持部材６１，６２の外周面に沿って長尺部材を曲折して形成した断面コの字状の部材よりなる。バネ部３２９は本体部３２０に対し略直交する方向に形成され，バネ部３２９の先端はくの字状に曲折される。
【００２７】
そして，挟持部材６１，６２に対し組付ける前のバネ部３２９の形状を図４（ａ）の実線で示した。挟持部材６１，６２に組付けることで，バネ部３２９は，図４（ａ）の破線にかかる形状となる。また，押圧バネ３２を挟持部材６１，６２に組付けた状態は図２より明らかである。このように，押圧バネ３２のバネ部３２９の変形により生じるバネ力がガスセンサ１の径方向に挟持部材６１，６２を押圧することができる。
【００２８】
上記端子バネ５１，５２について説明する。
図５〜図７に示すごとく，端子バネ５１，５２は，支持部５０と該支持部５０に設け，挟持部材６１（挟持部材６２とセンサ素子２９との間にある端子バネ５１，５２であれば挟持部材６２）側に突出する固定用突部５００と，曲折部５０１において曲折して構成した導通接触部５０２とよりなる。
【００２９】
端子バネ５２の支持部５０は，図５，図６（ｂ）に示すごとく，センサ素子２９と平行に延びたストレート形状で，支持部５０の末端は上記曲折部５０１となる。また，曲折部５０１からセンサ素子２９に沿って基端側に向けて折り返した部分が導通接触部５０２となる。
【００３０】
また，端子バネ５１の支持部５０は，図５，図６（ａ）に示すごとく，基端側から順にセンサ素子２９と平行なＡ部と該Ａ部より垂直に形成したＢ部とよりなり，Ｂ部の末端が上記曲折部５０１となる。曲折部５０１からセンサ素子２９に沿って基端側に向けて折り返した部分が導通接触部５０２となる。なお，支持部５０と導通接触部５０２との間の曲折の角度θは鋭角である。
【００３１】
図６（ａ）（ｂ）に示すごとく，導通接触部５０２は第２曲折部５０５を有し，曲折部５０１と第２曲折部５０５との間が第１接触部５０３，第２曲折部５０５と導通接触部５０２の末端との間が第２接触部５０４である。また，第２曲折部５０５における曲折の角度φは鈍角である。
【００３２】
そして，端子バネ５１，５２はセンサ素子２９の端子２９１，２９２に対し，図５，図７に示すごとく接触する。端子２９１と当接するのが端子バネ５１，端子２９２と当接するのが端子バネ５２である。
そして，両者が接触する際，端子バネ５２の導通接触部５０２は，図７に示す破線５０９のようにガスセンサ径方向に撓んで変形する。端子バネ５１についても同様である。
更に，本例にかかるガスセンサ１は，合計８つの端子バネ５１，５２を備えており，これら８本の端子バネ５１，５２とガスセンサ素子２９における端子２９１，２９２の距離は一様ではないが，図７に示すような撓みが各端子バネ５１，５２と端子２９１，２９２との距離の差を吸収する。
【００３３】
次に，挟持部材６１，６２について説明する。
挟持部材６１，６２は絶縁セラミックよりなり，二つあわせることで軸方向に貫通穴を有する断面八角形の大気側絶縁碍子３となる。挟持部材６１，６２の断面は八角形を径方向で２分割した形状であり，図２にガスセンサ１の基端側から見下ろした状態の挟持部材６１，６２を示す。
【００３４】
挟持部材６１で端子バネ５１，５２と対面する面を図８に示す。また，図９（ａ）は端子バネ６１を，図９（ｂ）は端子バネ６２を収納する収納溝部６０１，６０２を設けた位置での図８の（ａ−ａ）矢視断面図及び（ｂ−ｂ）矢視断面図である。
挟持部材６１で端子バネ５１，５２と対面する面は端子バネ５１，５２を収納する収納溝部６０１，６０２を有する。各収納溝部６０１，６０２は端子バネ５１，５２の支持部５０と略同形状である。
【００３５】
挟持部材６１，６２でセンサ素子２９ごと端子バネ５１，５２を挟持する際は，端子バネ５１，５２は収納溝部６０１，６０２に収納されて，径方向へ位置ズレし難くなる。
なお，挟持部材６１，６２は同じ形状なので，図面は挟持部材６１についてのみ記載した。
【００３６】
挟持部材６１，６２と端子バネ５１，５２とを固定するよう，端子バネ５１，５２の支持部５０に挟持部材６１，６２側に突出する固定用突部５００を設ける。この固定用突部５００は，図６より明らかであるが，支持部５０を長手方向に折り曲げて形成した。
そして，図８，図９に示すごとく，上記収納溝部６０１，６０２は，上記固定用突部５００を嵌合する固定用凹部６００を有する。
【００３７】
また，図１０は挟持部材６１の外側面の平面図である。外側面は上記押圧バネ３１，３２を設けた際に該押圧バネ３１，３２の位置ズレ防止の，押圧バネ３１，３２を収納する押圧バネ用凹部６０５，６０６を有する。
６０５が押圧バネ３１を，６０６が押圧バネ３２を収納する押圧バネ用凹部である。
【００３８】
本例の端子バネ５１，５２の４本は，該端子バネ５１，５２の４本がセンサ素子２９の１つの側面に設けた４個の端子２９１，２９２と接触して，センサ素子２９を挟持する。この場合，各押圧バネ３１，３２による押圧荷重は８本全ての端子バネ５１，５２による挟持荷重の１／２で等しくなる。
従って，本例の８本全ての端子バネ５１，５２による挟持荷重は２個の押圧バネ３１，３２による押圧荷重と釣り合って等しくなる。
【００３９】
なお，図１１（ａ）に示すごとく，端子バネ５１として，導通接触部５０２の第１接触部５０３に，図１１（ｂ）に示すごとく，打ち出しにより作製した導通突出部５０５を設けることもできる。
また，上記挟持部材６１，６２の端子バネ５１，５２と対面する面を，図１２に示すように構成することもできる。この図にかかる挟持部材６１，６２において，端子バネ５１，５２は，同じ収納溝部６０７に収納される。
【００４０】
本例の作用効果について説明する。
本例にかかるガスセンサ１において，端子バネ５１，５２によるセンサ素子２９に対する挟持荷重Ｆ１と押圧バネ３１，３２による挟持部材に対する押圧荷重Ｆ２とは釣り合うか，またはＦ２のほうが大きい。
すなわち，端子バネがセンサ素子を挟持する力と等しい圧力以上でもって，押圧バネ３１，３２は挟持部材５１，５２を押圧固定することができる。このため，端子バネ５１，５２とセンサ素子２９との間での隙間の発生が防止され，両者間の電気的導通を確実に確保することができる。
【００４１】
以上，本例によれば，端子バネとセンサ素子の端子との間でより確実に電気的な導通を確保することができるガスセンサを提供することができる。
【００４２】
（実施例２）
端子バネや押圧バネによる挟持荷重Ｆ１，押圧荷重Ｆ２について説明する。
端子バネと押圧バネはそれぞれバネとしての性能を備え，両者によって生じる挟持荷重，押圧荷重はバネの弾性力に由来する。
一般に弾性力を測定する際は，弾性体の変形，磁気ひずみ，圧電気，振動子の固有振動数などを測定し，予め測定しておいた校正曲線と比較して，力を大きさを決定する方法を利用する。
【００４３】
校正曲線としては，図１３に示すごとく，バネの撓みとバネに加えた荷重との間に成立する関係を測定しておけば，未知の荷重が加わった際の撓みを測定することで，荷重の大きさを知ることができる。
なお，図１３は単純に撓みと荷重とが正比例となる関係であるが，勿論これ以外の関係を備えた端子バネや押圧バネを用いることもできる。
【００４４】
更なる具体例として，図１４に示すごとき押圧バネ３１について説明する。この押圧バネ３１の詳細形状は，実施例１の図３に記載した。
押圧バネ３１は荷重のない自由状態においてバネ部３１９が実線の位置にある。荷重Ｋ１を与えることでバネ部３１９は破線の位置に移動する。この場合，押圧バネの撓みはａ−ｂとなる。
従って，実施例１に示すごとき挟持部材に組み込む前に予め上記撓みの形成に要する荷重を測定しておくことで，挟持部材に組み込んだ後の押圧バネの形状から，押圧バネの挟持部材に対する押圧荷重が分かる。
【００４５】
また，図１５に示す端子バネ５１について説明する。この端子バネ５１の詳細形状は，実施例１の図６等に記載した。
この端子バネ５１は荷重のない自由状態での形状は実線で，荷重Ｋ２を与えることで変形した形状は破線である。この場合，端子バネ５１の撓みはｃ−ｄとなる。
従って，実施例１に示すごときセンサ素子を挟持する前に予め上記撓みの形成に要する荷重を測定しておくことで，センサ素子を挟持した後の端子バネの形状から，端子バネのセンサ素子に対する挟持荷重が分かる。
【００４６】
（実施例３）
次に，押圧バネが１個の場合と２個の場合での押圧荷重について説明する。
図１６に示す形状の挟持部材６１，６２に押圧バネ３１を設けた場合，挟持部材６１，６２を挟むために押圧バネ３１が変形しているときの寸法ｆは，挟持部材６１，６２と押圧バネ３１とが当接した当接点６１０間の距離とする。
また押圧バネ３１の自由状態，つまり図１６の状態から挟持部材６１，６２を抜いた状態での上記当接点６１１間の距離をｅとする。
実施例２で記載した図１３にかかるような撓みと荷重との関係を予め押圧バネ３１単独で評価しておくことで，ｆ−ｅの値から挟持部材６１，６２に対する押圧荷重が判明する。
【００４７】
また，２個の押圧バネ３１，３２を設ける場合を図１７に示すが，同様にｆ１−ｅ１，ｆ２−ｅ２の値から押圧荷重が判明する。ただし，２個の押圧バネ３１，３２で押しているため，両者の押圧荷重を合わせた合計が全体の押圧荷重となる。
【００４８】
（実施例４）
次に，端子バネ５１による挟持荷重について説明する。
図１８に示す形状のセンサ素子２９に端子バネ５１を設け，外周から挟持部材６１，６２を設けた場合，挟持部材６１，６２の内側面６１３間の距離ｈより，センサ素子２９の厚みｇを引いた値の１／２が端子バネ５１の変形時の寸法となる。
【００４９】
端子バネ５１が拘束を受けない自由状態での寸法を予め測定し，かつ実施例２で記載した図１３にかかるような撓みと荷重の関係を端子バネ５１単独で評価しておくことで，端子バネ５１によるセンサ素子２９に対する挟持荷重が判明する。
なお，端子バネが２種類，合計８個ある実施例１においても同様に挟持荷重を求めることができる。
【００５０】
（実施例５）
挟持荷重の荷重中心と押圧荷重の荷重中心について説明する。
実施例１にかかるガスセンサにおいて，センサ素子は断面長方形であり，長方形の長辺となる一対の側面がそれぞれ４個の端子を有する。この端子に対しそれぞれ４本の端子バネが接する。よって，センサ素子の両側を４本の端子バネが挟持する状態となる（実施例１の図２参照）。
【００５１】
図１９に示すごとく，センサ素子の一対の側面のうち一方を含む平面をＨとし，この平面Ｈの適当な位置を原点Ｏとする。この平面Ｈに対し，端子バネと端子とが接触する位置を投影した接触点が（ｘ１，ｙ１）〜（ｘ４，ｙ４），押圧バネによって挟持部材が押圧される押圧位置を投影した押圧点が（ｘｗ，ｙｘ）となる。
【００５２】
各接触点における挟持荷重をＰ１〜Ｐ４，押圧点における押圧荷重をＷとすると（ここにＰ１〜Ｐ４，Ｗはベクトルである），接触点における挟持荷重Ｆ１の荷重中心は，
ｘ軸について
Ｘｐ＝（Ｐ１・ｘ１＋Ｐ２・ｘ２＋Ｐ３・ｘ３＋Ｐ４・ｘ４）／（Ｐ１＋Ｐ２＋Ｐ３＋Ｐ４）
ｙ軸について
Ｙｐ＝（Ｐ１・ｙ１＋Ｐ２・ｙ２＋Ｐ３・ｙ３＋Ｐ４・ｙ４）／（Ｐ１＋Ｐ２＋Ｐ３＋Ｐ４）
また，押圧点における押圧荷重Ｆ２の荷重中心はｘ軸についてｘｗ，ｙ軸についてｙｗである。
また，本例において，接触点における挟持荷重と押圧点における押圧荷重の荷重中心が等しく，Ｘｐ＝ｘｗ，Ｙｐ＝ｙｗとなる。
よって，これらの関係が成立するようにｘｗ，ｘｙの押圧点を定める。
また，押圧位置は押圧バネと挟持部材とが当接した位置でもあるため，投影した押圧点から求めることができる。
【００５３】
また，図１９は押圧点が一つの場合であるが，２個の押圧バネで押圧する場合など，押圧点が２つある場合については図２０に示した。
この場合も図１９と同様で，
接触点における挟持荷重Ｆ１の荷重中心の合計は，
ｘ軸について
Ｘｐ＝（Ｐ１・ｘ１＋Ｐ２・ｘ２＋Ｐ３・ｘ３＋Ｐ４・ｘ４）／（Ｐ１＋Ｐ２＋Ｐ３＋Ｐ４）
ｙ軸について
Ｙｐ＝（Ｐ１・ｙ１＋Ｐ２・ｙ２＋Ｐ３・ｙ３＋Ｐ４・ｙ４）／（Ｐ１＋Ｐ２＋Ｐ３＋Ｐ４）
また，押圧点における押圧荷重Ｆ２の荷重中心は
ｘ軸について
Ｘｗ＝（Ｗ１・ｘｗ１＋Ｗ２・ｘｗ２）／（Ｗ１＋Ｗ２）
ｙ軸について
Ｙｗ＝（Ｗ１・ｙｗ１＋Ｗ２・ｙｗ２）／（Ｗ１＋Ｗ２）
である。
よって，接触点における挟持荷重と押圧点における押圧荷重の荷重中心が等しく，Ｘｐ＝Ｘｗ，Ｙｐ＝Ｙｗとなる。
よって，これらの関係が成立するように押圧点１，２を定める。
【図面の簡単な説明】
【図１】実施例１における，ガスセンサの軸方向の断面説明図。
【図２】実施例１における，ガスセンサの大気側カバーの内部をガスセンサ基端側から見下ろした状態を示す平面図。
【図３】実施例１における，押圧バネの断面説明図及び平面図。
【図４】実施例１における，もう一つの押圧バネの断面説明図及び平面図。
【図５】実施例１における，端子バネの平面図。
【図６】実施例１における，端子バネの側面図。
【図７】実施例１における，端子バネの撓みについての説明図。
【図８】実施例１における，挟持部材の端子バネと対面する側の平面図。
【図９】実施例１における，挟持部材の収納溝部にかかる断面説明図。
【図１０】実施例１における，挟持部材の外側面の平面図。
【図１１】実施例１における，図６とは別の端子バネであって，導通突出部を有する端子バネの説明図。
【図１２】実施例１における，図８とは別の挟持部材であって，４つの端子バネを１つの収納溝部において収納した挟持部材の端子バネと対面する側の平面図。
【図１３】実施例２における，撓みと荷重との関係を示す線図。
【図１４】実施例２における，押圧バネの撓みについての説明図。
【図１５】実施例２における，端子バネの撓みについての説明図。
【図１６】実施例３における，押圧バネを１個設けた際の押圧荷重についての説明図。
【図１７】実施例３における，押圧バネを２個設けた際の押圧荷重についての説明図。
【図１８】実施例４における，端子バネによる挟持荷重についての説明図。
【図１９】実施例５における，押圧バネによる押圧点が１箇所である場合の挟持荷重の荷重中心と押圧荷重の荷重中心の説明図。
【図２０】実施例５における，押圧バネによる押圧点が２箇所である場合の挟持荷重の荷重中心と押圧荷重の荷重中心の説明図。
【符号の説明】
１．．．ガスセンサ，
１０．．．ハウジング，
２９．．．センサ素子，
２９１，２９２．．．端子，
３１，３２．．．押圧バネ，
４１．．．リード線，
５１，５２．．．端子バネ，
５０．．．支持部，
５０１．．．曲折部，
５０２．．．導通接触部，
６１，６２．．．挟持部材，[0001]
【Technical field】
The present invention relates to a gas sensor used for controlling combustion of an internal combustion engine for a vehicle.
[0002]
[Prior art]
Conventionally, as a gas sensor for measuring a specific gas concentration in a gas to be measured, a sensor element having a plurality of terminals on a base end side is provided. A configuration having a terminal spring for electrically connecting is known.
[0003]
[Problem to be solved]
2. Description of the Related Art In recent years, gas sensors have emerged in which a plurality of types of cells are provided in one sensor element to detect a plurality of types of gas concentrations.
In the case of such a gas sensor, the number of terminals of the sensor element increases, and accordingly, the number of terminal springs also increases. Therefore, there is a need for a gas sensor having a configuration capable of reliably ensuring electrical continuity with a plurality of terminal springs.
[0004]
The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a gas sensor that can more reliably secure electrical conduction between a terminal spring and a terminal of a sensor element. .
[0005]
[Means for solving the problem]
The first invention has a sensor element having a plurality of terminals on a base end side, and has a terminal spring for electrically connecting the terminal to a lead wire drawn in from the base end side of the gas sensor.
When the terminal spring is in contact with the terminal, the terminal spring clamps the sensor element by applying a load in the gas sensor radial direction to the sensor element,
A gas sensor comprising: two or more holding members provided on an outer periphery of the terminal spring; and a pressing spring provided on an outer periphery of the holding member to press and fix the holding member.
A holding load F1 on the sensor element by the terminal spring,
Between the pressing load F2 on the holding member by the pressing spring,
Terminal spring holding load F1 ≦ Pressing spring pressing load F2
The gas sensor is characterized in that the following relationship is established (claim 1).
[0006]
In the gas sensor according to the present invention, the relationship of F1 ≦ F2 is established between the holding load F1 of the sensor element by the terminal spring and the pressing load F2 on the holding member by the pressing spring. That is, the pressing spring presses and fixes the holding member at a pressure higher than the force at which the terminal spring holds the sensor element.
For this reason, generation of a gap between the terminal spring and the sensor element is prevented, and electrical conduction between the two can be reliably ensured.
If F1> F2, a gap is likely to be formed between the terminal spring and the sensor element, and electrical conduction between the terminal spring and the terminal may not be secured.
The details of the holding load and the pressing load will be described later.
[0007]
As described above, according to the present invention, it is possible to provide a gas sensor that can more reliably ensure electrical continuity between a terminal spring and a terminal of a sensor element.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Each of the terminal spring and the pressing spring has a performance as a spring, and the holding load and the pressing load generated by the both are derived from the elastic force of the spring.
In general, when measuring elastic force, the deformation of the elastic body, magnetostriction, piezoelectricity, the natural frequency of the vibrator, etc. are measured, and the magnitude of the force is determined by comparing it with a calibration curve measured in advance. Take advantage of the method.
Details will be described in Examples.
[0009]
Although the present invention can be applied to a gas sensor having a small number of lead wires drawn into the inside of the gas sensor from the outside, it is more effective to apply the present invention to a gas sensor having a large number of lead wires drawn.
[0010]
The gas sensor having a large number of lead wires is, for example, a gas sensor that measures NOx and HC. This is because a sensor element for measuring NOx and HC has a plurality of electrochemical cells, and therefore requires a large number of lead wires for applying a voltage to the plurality of electrochemical cells and extracting output.
[0011]
Further, as a gas sensor having a large number of lead wires, there is a gas sensor that measures a plurality of types of gas concentrations with a single wire. Since this gas sensor also has a built-in sensor element having an electrochemical cell corresponding to a plurality of types of measurement, a large number of lead wires are required.
The lead wire and the terminal spring may be directly connected to each other, but may require a separate connecting member as shown in FIG.
[0012]
Further, it is preferable to provide two or more pressing springs (claim 2).
The pressing force can be increased by increasing the number of pressing springs. Further, by providing a plurality of pressing springs and performing pressing at a plurality of locations, the entire holding member can be pressed in a well-balanced manner.
[0013]
In addition, a point where a contact position where the terminal spring and the terminal contact each other is projected on a plane along the gas sensor axial direction is a contact point, and a point where a pressing position of the pressing spring against the holding member is projected is pressed. In this case, it is preferable that the total of the load centers of the holding load F1 at the contact point and the load center of the pressing load F2 at the pressing point be equal (claim 3).
Thereby, each of the pinching loads at the contact points of a large number of terminal springs can be equalized, and electrical conduction between each terminal spring and the terminal can be reliably performed.
The specific method of obtaining the center of load is described in Examples.
[0014]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Example 1)
As shown in FIG. 1, this embodiment has a sensor element 29 having eight terminals 291 and 292 on the base end side, and connects between the terminals 291 and 292 and the lead wire 41 drawn in from the gas sensor base end side. It has terminal springs 51 and 52 for electrical connection.
When the terminal springs 51 and 52 are in contact with the terminals 291 and 292, the terminal springs 51 and 52 clamp the sensor element 29 by applying a load in the gas sensor radial direction to the sensor element 29.
Further, two holding members 61 and 62 are provided on the outer periphery of the terminal springs 51 and 52, and pressing springs 31 and 32 are further provided on the outer periphery of the holding members 61 and 62 to press and fix the holding members 61 and 62. Constitute.
[0015]
The holding load F1 of the terminal springs 51 and 52 on the sensor element 29 and the pressing load F2 of the pressing springs 31 and 32 on the holding members 61 and 62 satisfy the relationship of F1 ≦ F2.
[0016]
The details are described below.
The gas sensor 1 according to the present embodiment is installed in an exhaust pipe of an automobile engine, and measures an oxygen concentration and a NOx concentration in exhaust gas and an air-fuel ratio of an engine combustion chamber.
The sensor element 29 incorporated in the gas sensor 1 is a stacked element formed by stacking ceramic plates, and a monitor cell provided inside the element for measuring and monitoring the oxygen concentration in the gas chamber to be measured and an oxygen sensor in the gas chamber to be measured. It has an oxygen pump cell for adjusting the concentration, a sensor cell for measuring the NOx concentration in the gas chamber to be measured, and a heater for generating heat when energized (not shown).
The voltage application to the heater, the voltage application to each cell, and the output extraction are performed at terminals 291 and 292 provided on the side surface of the sensor element 29.
[0017]
Therefore, the gas sensor 1 according to the present example requires a total of eight lead wires 41 in order to supply power to three cells and a heater and to take out an output, and the lead wire 41 and the terminals 291 and 292 are connected to each other. Also, eight connecting members 42 and terminal springs 51 and 52 for connecting between them are required.
[0018]
As shown in FIGS. 2 and 5, there are four terminal electrodes 291 and 292 on one side surface of the sensor element 29, and four terminal electrodes 291 and 292 on the opposite side surface. Therefore, the four terminal springs 51 and 52 are arranged so as to sandwich the sensor element 29 from one side surface and the opposite side surface.
Since FIG. 1 is a cross-sectional view cut along the axial direction of the gas sensor 1, the description of the lead wires that are not visible is omitted.
[0019]
As shown in FIG. 1, a gas sensor 1 of the present embodiment includes a metal housing 10, a double-structured metal gas-to-be-measured cover 109 mounted on the distal end side of the housing 10, and a metal mounted on a base end side. And an air-side cover 11 made of aluminum. The atmosphere-side cover 11 includes a first cover 111 that is caulked and fixed to the housing 10 and an outer cover 112 that is caulked and fixed to the base end side of the first cover 111 via a water-repellent filter 113.
[0020]
The element-side insulator 2 made of ceramic is inserted into the housing 10, and the side surface of the element-side insulator 2 has a tapered surface 102 facing the tip side of the gas sensor. The inner surface of the housing 10 has a receiving surface 101 that faces the base end side of the gas sensor and supports the tapered surface 102 via a metal packing 200.
[0021]
A disc spring 21 is placed on the tip end side of the element-side insulator 2, and a pressing member 22 is covered from above the disc spring 21. The pressing member 22 includes a pressing plate 221 that presses down the disc spring 21 and shrinks in the axial direction of the gas sensor, and a leg 222 that extends from the pressing plate 221 to the distal side along the base side surface of the housing 10. The element-side insulator 2 is fixed to the housing 10 by fixing between the end side surface and the leg portion 222.
[0022]
In a state where the conductive contact portions 502 of the terminal springs 51 and 52 are in contact with the terminals 291 and 292 (see FIG. 5) and the conductive contact portions 502 are bent toward the support portion 50 (see FIG. 7), two The terminal springs 51 and 52 and the sensor element 29 are clamped and fixed using the clamping members 61 and 62.
[0023]
Two pressing springs 31 and 32 configured to apply a pressing force toward the radial inside of the gas sensor 1 to the holding members 61 and 62 are provided on the outer periphery of the holding members 61 and 62.
The holding members 61 and 62 are made of an insulating ceramic, and the holding members 61 and 62 form the air-side insulator 3 that ensures insulation between the terminal springs 51 and 52.
[0024]
The pressing springs 31 and 32 will be described.
As shown in FIG. 3, the pressing spring 31 includes a main body 310 and a spring portion 319 having elasticity.
The main body 310 is a lightly curved rectangular plate along the outer peripheral surfaces of the holding members 61 and 62, and has a rectangular window 319 in the center for weight reduction and flexibility.
Further, there are spring portions 319 extending from four corners of the main body 310 in a direction substantially perpendicular to the main body 310. The cross-sectional shape of the pressing spring 31 at the portion where the spring portion 319 is provided has a U-shape as shown in FIG. Further, the tip of the spring portion 319 is bent in a V shape.
[0025]
The shape of the spring portion 319 before being assembled to the holding members 61 and 62 is shown by a solid line in FIG. By attaching the spring portion 319 to the holding members 61 and 62, the spring portion 319 has a shape corresponding to the broken line in FIG. The state in which the pressing spring 31 is assembled to the holding members 61 and 62 is clear from FIG. Thus, the spring force generated by the deformation of the spring portion 319 of the pressing spring 31 can press the holding members 61 and 62 in the radial direction of the gas sensor 1.
[0026]
As shown in FIG. 4, the pressing spring 32 includes a main body 320 and a spring portion 329. The pressing spring 32 extends from the main body 320 toward the inner surface of the atmosphere-side cover 11, and has a tip at the air-side cover. 11 has a spring portion 321 for radially pressing and fixing to the inner side surface.
As shown in FIG. 4A, the pressing spring 32 is formed of a member having a U-shaped cross section formed by bending a long member along the outer peripheral surfaces of the holding members 61 and 62. The spring portion 329 is formed in a direction substantially perpendicular to the main body portion 320, and the tip of the spring portion 329 is bent in a square shape.
[0027]
The shape of the spring portion 329 before being assembled to the holding members 61 and 62 is shown by a solid line in FIG. By attaching the spring portion 329 to the holding members 61 and 62, the spring portion 329 has a shape corresponding to the broken line in FIG. The state in which the pressing spring 32 is assembled to the holding members 61 and 62 is clear from FIG. Thus, the spring force generated by the deformation of the spring portion 329 of the pressing spring 32 can press the holding members 61 and 62 in the radial direction of the gas sensor 1.
[0028]
The terminal springs 51 and 52 will be described.
As shown in FIGS. 5 to 7, the terminal springs 51 and 52 are provided on the support 50 and the holding member 61 (the terminal springs 51 and 52 between the holding member 62 and the sensor element 29). For example, it includes a fixing protrusion 500 protruding toward the holding member 62) and a conductive contact portion 502 formed by bending the bent portion 501.
[0029]
As shown in FIGS. 5 and 6B, the support portion 50 of the terminal spring 52 has a straight shape extending in parallel with the sensor element 29, and the end of the support portion 50 is the bent portion 501. Further, a portion folded from the bent portion 501 toward the base end side along the sensor element 29 becomes the conductive contact portion 502.
[0030]
As shown in FIGS. 5 and 6A, the support portion 50 of the terminal spring 51 includes an A portion parallel to the sensor element 29 in order from the base end and a B portion formed perpendicularly to the A portion. , B end portion is the bent portion 501. A portion folded from the bent portion 501 toward the base end along the sensor element 29 becomes a conductive contact portion 502. The angle θ of the bend between the support portion 50 and the conductive contact portion 502 is an acute angle.
[0031]
As shown in FIGS. 6A and 6B, the conductive contact portion 502 has a second bent portion 505, and a portion between the bent portion 501 and the second bent portion 505 is a first contact portion 503 and a second bent portion 505. A second contact portion 504 is provided between the first contact portion 502 and the end of the conductive contact portion 502. The angle φ of the bend in the second bent portion 505 is an obtuse angle.
[0032]
Then, the terminal springs 51 and 52 contact the terminals 291 and 292 of the sensor element 29 as shown in FIGS. The terminal spring 51 is in contact with the terminal 291, and the terminal spring 52 is in contact with the terminal 292.
Then, when they come into contact with each other, the conductive contact portion 502 of the terminal spring 52 bends and deforms in the gas sensor radial direction as shown by a broken line 509 shown in FIG. The same applies to the terminal spring 51.
Further, the gas sensor 1 according to the present example includes a total of eight terminal springs 51 and 52, and the distance between the eight terminal springs 51 and 52 and the terminals 291 and 292 of the gas sensor element 29 is not uniform. The bending as shown in FIG. 7 absorbs the difference in the distance between the terminal springs 51 and 52 and the terminals 291 and 292.
[0033]
Next, the holding members 61 and 62 will be described.
The holding members 61 and 62 are made of insulating ceramics. By joining the two members, the air-side insulator 3 having an octagonal cross section having a through hole in the axial direction is obtained. The cross section of the holding members 61 and 62 has a shape obtained by dividing an octagon in two in the radial direction. FIG. 2 shows the holding members 61 and 62 viewed from the base end side of the gas sensor 1.
[0034]
FIG. 8 shows a surface of the holding member 61 that faces the terminal springs 51 and 52. 9A is a cross-sectional view of the terminal spring 61, and FIG. 9B is a cross-sectional view of FIG. 8A taken along a line (a-a) at a position where storage grooves 601 and 602 for storing the terminal spring 62 are provided. (bb) It is an arrow sectional view.
The surface of the holding member 61 facing the terminal springs 51 and 52 has storage grooves 601 and 602 for storing the terminal springs 51 and 52. Each of the storage grooves 601 and 602 has substantially the same shape as the support 50 of the terminal springs 51 and 52.
[0035]
When the holding members 61 and 62 hold the terminal springs 51 and 52 together with the sensor element 29, the terminal springs 51 and 52 are housed in the housing grooves 601 and 602, and are less likely to be displaced in the radial direction.
Since the holding members 61 and 62 have the same shape, the drawing describes only the holding member 61.
[0036]
In order to fix the holding members 61 and 62 and the terminal springs 51 and 52, a fixing projection 500 protruding toward the holding members 61 and 62 is provided on the support portion 50 of the terminal springs 51 and 52. As is apparent from FIG. 6, the fixing projection 500 is formed by bending the support 50 in the longitudinal direction.
As shown in FIGS. 8 and 9, the storage grooves 601 and 602 have a fixing recess 600 into which the fixing protrusion 500 is fitted.
[0037]
FIG. 10 is a plan view of the outer side surface of the holding member 61. The outer side surface has depressions 605 and 606 for the pressing springs 31 and 32 for accommodating the pressing springs 31 and 32 for preventing displacement of the pressing springs 31 and 32 when the pressing springs 31 and 32 are provided.
Reference numeral 605 denotes a pressing spring 31, and 606 denotes a pressing spring recess for housing the pressing spring 32.
[0038]
The four terminal springs 51 and 52 of the present example are in contact with the four terminals 291 and 292 provided on one side surface of the sensor element 29 so that the four terminal springs 51 and 52 sandwich the sensor element 29. I do. In this case, the pressing load by each of the pressing springs 31 and 32 is equal to １／ of the holding load by all the eight terminal springs 51 and 52.
Therefore, the holding load by all eight terminal springs 51 and 52 in this example is equal to the pressing load by the two pressing springs 31 and 32 in proportion.
[0039]
In addition, as shown in FIG. 11A, as the terminal spring 51, the first contact portion 503 of the conductive contact portion 502 may be provided with a conductive projecting portion 505 formed by stamping as shown in FIG. 11B. .
Further, the surfaces of the holding members 61, 62 facing the terminal springs 51, 52 may be configured as shown in FIG. In the holding members 61 and 62 according to this figure, the terminal springs 51 and 52 are housed in the same housing groove 607.
[0040]
The operation and effect of this example will be described.
In the gas sensor 1 according to the present example, the holding load F1 on the sensor element 29 by the terminal springs 51 and 52 and the pressing load F2 on the holding member by the pressing springs 31 and 32 are balanced or F2 is larger.
That is, the pressing springs 31 and 32 can press and fix the holding members 51 and 52 with a pressure equal to or greater than the force by which the terminal springs hold the sensor element. For this reason, generation of a gap between the terminal springs 51 and 52 and the sensor element 29 is prevented, and electrical conduction between the two can be reliably ensured.
[0041]
As described above, according to the present embodiment, it is possible to provide a gas sensor that can more reliably ensure electrical conduction between the terminal spring and the terminal of the sensor element.
[0042]
(Example 2)
The holding load F1 and the pressing load F2 by the terminal spring and the pressing spring will be described.
Each of the terminal spring and the pressing spring has a performance as a spring, and the holding load and the pressing load generated by the both are derived from the elastic force of the spring.
In general, when measuring elastic force, the deformation of an elastic body, magnetostriction, piezoelectricity, the natural frequency of a vibrator, etc. are measured, and the magnitude of the force is determined by comparing with a previously measured calibration curve. Take advantage of the method.
[0043]
As shown in FIG. 13, as a calibration curve, if a relationship between the deflection of the spring and the load applied to the spring is measured, the deflection when an unknown load is applied is measured. You can know the size of the.
Although FIG. 13 simply shows a relationship in which the deflection and the load are directly proportional, it is needless to say that a terminal spring or a pressing spring having any other relationship can be used.
[0044]
As a further specific example, a pressing spring 31 as shown in FIG. 14 will be described. The detailed shape of the pressing spring 31 is described in FIG.
When the pressing spring 31 is in a free state with no load, the spring portion 319 is at the position indicated by the solid line. By applying the load K1, the spring portion 319 moves to the position indicated by the broken line. In this case, the bending of the pressing spring is ab.
Therefore, by measuring the load required for the formation of the above-mentioned deflection in advance before assembling into the holding member as shown in Embodiment 1, the pressing force of the pressing spring against the holding member can be changed from the shape of the pressing spring after being incorporated into the holding member. You can see the load.
[0045]
Further, the terminal spring 51 shown in FIG. 15 will be described. The detailed shape of the terminal spring 51 is described in FIG.
The shape of the terminal spring 51 in the free state where there is no load is a solid line, and the shape deformed by applying the load K2 is a broken line. In this case, the bending of the terminal spring 51 is cd.
Therefore, by measuring the load required to form the above-described deflection before clamping the sensor element as shown in the first embodiment, the shape of the terminal spring after clamping the sensor element can be applied to the sensor element relative to the sensor element. You can see the pinching load.
[0046]
(Example 3)
Next, the pressing load in the case of one pressing spring and the case of two pressing springs will be described.
When the pressing spring 31 is provided on the holding members 61 and 62 having the shape shown in FIG. 16, the dimension f when the pressing spring 31 is deformed to hold the holding members 61 and 62 is equal to the dimension f of the pressing members 31 and 62. The distance between the contact points 610 with which the springs 31 are in contact.
The distance between the contact points 611 when the pressing spring 31 is in the free state, that is, when the holding members 61 and 62 are removed from the state shown in FIG.
By previously evaluating the relationship between the deflection and the load as shown in FIG. 13 described in the second embodiment with the pressing spring 31 alone, the pressing load on the holding members 61 and 62 can be determined from the value of fe.
[0047]
FIG. 17 shows a case where two pressing springs 31 and 32 are provided. Similarly, the pressing load is determined from the values of f1-e1 and f2-e2. However, since the two pressing springs 31 and 32 are pressing, the sum of the pressing loads of both is the total pressing load.
[0048]
(Example 4)
Next, the holding load by the terminal spring 51 will be described.
When the terminal spring 51 is provided on the sensor element 29 having the shape shown in FIG. 18 and the holding members 61 and 62 are provided from the outer periphery, the thickness g of the sensor element 29 is determined by the distance h between the inner side surfaces 613 of the holding members 61 and 62. One-half of the subtracted value is the dimension when the terminal spring 51 is deformed.
[0049]
By measuring in advance the dimensions of the terminal spring 51 in a free state in which the terminal spring 51 is not restrained, and evaluating the relationship between the bending and the load shown in FIG. The clamping load on the sensor element 29 by the spring 51 is determined.
It should be noted that the pinching load can be obtained in the same manner in the first embodiment in which there are two types of terminal springs and a total of eight terminal springs.
[0050]
(Example 5)
The load center of the holding load and the load center of the pressing load will be described.
In the gas sensor according to the first embodiment, the sensor element has a rectangular cross section, and a pair of side surfaces that are long sides of the rectangle each have four terminals. Four terminal springs are in contact with each of these terminals. Therefore, four terminal springs sandwich the sensor element on both sides (see FIG. 2 of the first embodiment).
[0051]
As shown in FIG. 19, a plane including one of the pair of side surfaces of the sensor element is defined as H, and an appropriate position on the plane H is defined as an origin O. The contact points that project the position where the terminal spring contacts the terminal with respect to this plane H are (x1, y1) to (x4, y4), and the pressing point that projects the pressing position at which the holding member is pressed by the pressing spring is (Xw, yx).
[0052]
Assuming that the holding load at each contact point is P1 to P4 and the pressing load at the pressing point is W (where P1 to P4, W is a vector), the center of the holding load F1 at the contact point is
Xp = (P1 · x1 + P2 · x2 + P3 · x3 + P4 · x4) / (P1 + P2 + P3 + P4) for the x axis
Yp = (P1 · y1 + P2 · y2 + P3 · y3 + P4 · y4) / (P1 + P2 + P3 + P4) for the y-axis
The center of the pressing load F2 at the pressing point is xw on the x-axis and yw on the y-axis.
Further, in this example, the load centers of the holding load at the contact point and the pressing load at the pressing point are equal, and Xp = xw and Yp = yw.
Therefore, the pressing points of xw and xy are determined so that these relationships are established.
Further, since the pressing position is also a position where the pressing spring and the holding member are in contact with each other, the pressing position can be obtained from the projected pressing point.
[0053]
FIG. 19 shows a case where there is one pressing point, but FIG. 20 shows a case where there are two pressing points, such as a case where two pressing springs are used.
This case is similar to FIG.
The sum of the load centers of the pinching load F1 at the contact point is
Xp = (P1 · x1 + P2 · x2 + P3 · x3 + P4 · x4) / (P1 + P2 + P3 + P4) for the x axis
Yp = (P1 · y1 + P2 · y2 + P3 · y3 + P4 · y4) / (P1 + P2 + P3 + P4) for the y-axis
The center of the pressing load F2 at the pressing point is Xw = (W1.xw1 + W2.xw2) / (W1 + W2) on the x axis.
Yw = (W1 · yw1 + W2 · yw2) / (W1 + W2) for the y-axis
It is.
Therefore, the load centers of the holding load at the contact point and the pressing load at the pressing point are equal, and Xp = Xw and Yp = Yw.
Therefore, the pressing points 1 and 2 are determined so that these relationships are established.
[Brief description of the drawings]
FIG. 1 is an explanatory cross-sectional view in the axial direction of a gas sensor according to a first embodiment.
FIG. 2 is a plan view showing a state in which the inside of an atmosphere-side cover of the gas sensor is viewed from a gas sensor base end side in the first embodiment;
FIGS. 3A and 3B are a sectional explanatory view and a plan view of a pressing spring according to the first embodiment. FIGS.
FIG. 4 is a cross-sectional explanatory view and a plan view of another pressing spring according to the first embodiment.
FIG. 5 is a plan view of the terminal spring according to the first embodiment.
FIG. 6 is a side view of the terminal spring according to the first embodiment.
FIG. 7 is an explanatory view of bending of a terminal spring in the first embodiment.
FIG. 8 is a plan view of the holding member facing the terminal spring in the first embodiment.
FIG. 9 is an explanatory cross-sectional view of the holding groove of the holding member according to the first embodiment.
FIG. 10 is a plan view of the outer side surface of the holding member according to the first embodiment.
FIG. 11 is an explanatory view of a terminal spring different from FIG. 6 and having a conductive protrusion in the first embodiment.
FIG. 12 is a plan view of a holding member different from FIG. 8 in the first embodiment on the side facing the terminal spring of the holding member in which four terminal springs are stored in one storage groove.
FIG. 13 is a diagram showing a relationship between deflection and load in the second embodiment.
FIG. 14 is an explanatory diagram of bending of a pressing spring according to the second embodiment.
FIG. 15 is an explanatory diagram of bending of a terminal spring in the second embodiment.
FIG. 16 is a diagram illustrating a pressing load when one pressing spring is provided in the third embodiment.
FIG. 17 is an explanatory diagram of a pressing load when two pressing springs are provided in the third embodiment.
FIG. 18 is an explanatory diagram of a holding load by a terminal spring in the fourth embodiment.
FIG. 19 is an explanatory diagram of a load center of a holding load and a load center of a pressing load in a case where the pressing point of the pressing spring is one place in the fifth embodiment.
FIG. 20 is an explanatory diagram of the load center of the holding load and the load center of the pressing load when the pressing points by the pressing spring are two places in the fifth embodiment.
[Explanation of symbols]
1. . . Gas sensor,
10. . . housing,
29. . . Sensor element,
291,292. . . Terminal,
31, 32. . . Pressing spring,
41. . . Lead,
51, 52. . . Terminal spring,
50. . . Support,
501. . . Bend,
502. . . Conductive contact,
61, 62. . . Clamping member,

Claims

A sensor element having a plurality of terminals on the base end side, and a terminal spring for electrically connecting the terminal to a lead wire drawn in from the base end side of the gas sensor;
In a state where the terminal spring is in contact with the terminal, the terminal spring clamps the sensor element by applying a load in the gas sensor radial direction to the sensor element,
A gas sensor comprising: two or more holding members provided on an outer periphery of the terminal spring; and a pressing spring provided on an outer periphery of the holding member to press and fix the holding member.
A holding load F1 on the sensor element by the terminal spring,
Between the pressing load F2 on the holding member by the pressing spring,
Terminal spring holding load F1 ≦ Pressing spring pressing load F2
A gas sensor characterized by the following relationship.

2. The gas sensor according to claim 1, wherein two or more pressing springs are provided.

3. The contact point according to claim 1 or 2, wherein a point at which a contact position at which the terminal spring contacts the terminal is projected on a plane along the gas sensor axis direction, and a pressing position of the pressing spring against the holding member. When the projected point is defined as a pressing point, the total of the load centers of the pinching load F1 at the contact point and the load center of the pressing load F2 at the pressing point are equal.