JP3696444B2

JP3696444B2 - Gas sensor

Info

Publication number: JP3696444B2
Application number: JP22832299A
Authority: JP
Inventors: 康司松尾; 正二赤塚; 昌弘浅井; 聡石川; 勝久籔田
Original assignee: NGK Spark Plug Co Ltd
Current assignee: Niterra Co Ltd
Priority date: 1999-08-12
Filing date: 1999-08-12
Publication date: 2005-09-21
Anticipated expiration: 2019-08-12
Also published as: JP2001050928A

Description

【０００１】
【発明の属する技術分野】
この発明は、酸素センサ、ＨＣセンサ、ＮＯｘセンサなど、測定対象となるガス中の被検出成分を検出するためのガスセンサに関する。
【０００２】
【従来の技術】
従来より、上述のようなガスセンサとして、固体電解質部材の両面に電極層が形成された筒状ないし板状の検出素子を、筒状のケーシングの内側に配置した構造のものが知られている。例えばガスセンサとして代表的な酸素センサの場合、先端部が閉じた中空軸状の固体電解質部材の内外面にそれぞれ電極層が形成された酸素検出素子を、前方側が測定対象となるガスに向けられるような形で筒状のケーシング内に配し、酸素検出素子の先端外面をガスと接触させるとともに、その内面に基準ガスとしての大気を導入して、その内外面に生ずる酸素濃淡電池起電力を、ガス中の酸素濃度の検出信号として内外電極層からリード線を介して外部へ出力した構造のものが広く用いられている。また、上記のような酸素センサにおいては、リード線をケーシングから取り出すための構造として、酸素検出素子の後端部側に個別のリード線挿通孔が形成されたセラミックセパレータを配置させ、リード線挿通孔に各リード線を通すように構成されることが多い。なお、このようにセラミックセパレータを使用することにより、リード線同士の短絡の防止を図っている。
【０００３】
ところで、セラミックセパレータを使用する従来のガスセンサは、例えばセラミックセパレータの外周面に突出するフランジ部を形成し、そのセラミックセパレータをケーシング内に挿入させるとともに、そのフランジ部をケーシングの開口端面に当接させ、さらにその外側を筒状のカバー部材で覆うようにした二重構造のものが多い。このような二重構造のものでは、例えば、カバー部材に段付き部を設け、カバー部材をケーシングに対して軸方向に押圧しながら、セラミックセパレータのフランジ部をケーシング開口端部とカバー部材の段付き部との間で挟み込むことで、セラミックセパレータを保持している。また、上記二重構造にあっては、ケーシングとカバー部材との気密性を維持するため加締め等の接合手段を施す必要がある。
【０００４】
【発明が解決しようとする課題】
近年、排気ガスによる大気汚染など環境保護上の問題に対応するために、ガスセンサに対する需要も増え、それに伴う低コスト化やコンパクト化に対する要望も年々高まりつつある。そのために、ガスセンサの構造の見直しによる部品点数の削減、組立工数の削減が要求され、それと同時にセンサ自体のコンパクト化も要求されている。
【０００５】
本発明の課題は、センサ構造全体の簡素化・コンパクト化および組立工数の削減を図ることのできるガスセンサ構造を提供することにある。
【０００６】
【課題を解決するための手段及び作用・効果】
上記課題を解決するために、第一番目の発明にかかるガスセンサは、前方側が測定対象となるガスに向けられる軸状の検出素子と、前記検出素子の外側に配置される径方向において一重に構成された筒状の外筒部材と、前記検出素子よりも後方側に配置されるとともに、前記外筒部材の内側に配置され、前記検出素子からのリード線を挿通するためのリード線挿通孔が形成されるセラミックセパレータとを備え、前記セラミックセパレータには外周面から突出するセパレータ側支持部が形成される一方、一重に構成された前記外筒部材には内周面から突出する外筒側支持部が形成され、該セパレータ側支持部が該外筒側支持部に直接または他部材を介して間接的に支持されてなり、
前記外筒部材の後端開口部に嵌入されるとともに、前記セラミックセパレータの後端面に直接または他部材を介して間接的に接触するグロメットが備えられてなることを特徴とする。
【０００７】
上記本発明によれば、従来のようにケーシングの開口端面にセラミックセパレータのフランジ部を支持させるのではなく、外筒部材の任意の部位を内周面から内向きに突出して形成される外筒側支持部にセラミックセパレータの外周面から突出形成されるセパレータ側支持部を支持させることにより、セラミックセパレータを保持するにあたり、セラミックセパレータの外側を別のカバー部材を用いて覆う必要がない。すなわち、セラミックセパレータを保持するにあたり、従来必要であった二重構造を廃止して、センサの部品点数の削減、それに伴うセンサ構造の簡素化・コンパクト化が図れ、さらには低コスト化にも寄与することができる。しかも、従来必要であった二重構造を廃止できることから、ケーシングとカバー部材との気密性を維持するための加締め等の接合手段が不要となり、セラミックセパレータの保持を容易にするばかりか、組立工数の削減を図ることもでき、ひいては低コスト化にも寄与することができる。さらに、セラミックセパレータが既存品であるグロメットによりがたつきなく安定的に保持できるので、部品点数の削減を図ることができる。なお、部品点数削減の観点においては、セラミックセパレータ（のセパレータ側支持部）は外筒側支持部に対して他部材を介さず直接支持させる構造がより望ましい。
【０００８】
ここで上記発明のセパレータ側支持部の前方側支持面を、前方側に向かうほど外径が小となる傾斜面に形成し、また外筒側支持部の後方側支持面を、前方側に向かうほど内径が小となる傾斜面に形成することができる。これらの傾斜面を設けることにより、外筒部材に対してセラミックセパレータの挿入がスムーズに行える。例えばセパレータ側支持部の前方側支持面の傾斜は、セラミックセパレータのセパレータ側支持部が外筒部材の後端開口部に挿入される際の案内ガイドとなり、外筒側支持部の後方側支持面の傾斜は、セラミックセパレータの先端部が外筒側支持部の内側に挿入される際の案内ガイドとなる。
【００１０】
さらに本発明のグロメットは、液体の透過は阻止し、かつ気体の透過は許容する通気部を有することができる。フィルタ等の通気部をグロメットに設けることで、ガスセンサの中で最も高温に晒される部位である検出部から通気部をできるだけ遠ざけることができ、例えばシリコンゴム、フッ素樹脂等のフィルタ構成材に関して耐熱性を確保することができる。また、例えば自動車用の酸素センサの場合、その取り付け場所はエンジンルーム以外にも、車両の足周り部分に近い排気管等に取り付けられることも多い。このような状況においてはガスセンサは、雨中走行時や洗車時等に水滴の噴射を受けたり時には水没したりすることになる。フィルタ等の通気部をグロメットに設けることで、通気部を相対的に高位置に設けることが容易になり、水滴が侵入しにくく防水性の高い状態での外気導入を可能にする。
【００１１】
さらに本発明は、セパレータ側支持部と外筒側支持部のうちの少なくとも一方に、通気路を形成することができる。セラミックセパレータの外周面に沿うように通気路を形成すると、ガスセンサの内部において基準ガスの循環が促進されて換気性能がよくなる傾向がみられる。そこで、排気ガス等の混入が少ない状態で基準ガスを導入して、排気ガス濃度の検出が精度よく行える。
【００１２】
さらに本発明の通気路は、グロメットに設けられる通気部と連通することができる。ガスセンサの小型化により容積率が増大した場合にも、測定に必要な酸素（大気）等の基準ガスを取り入れるために通気径路の確保が容易である。
【００１３】
さらに本発明の外筒側支持部は、外筒部材の内周面から突出して、周方向に断続的に形成することができる。かかる構成をとるときには、外筒側支持部の形成加工が容易に行え、加工コストの低廉化が図れる。全周にわたり一体的にフランジ状の外筒側支持部が形成される場合に比べて、安価にかつ高精度で加工できるとともに、隣合う外筒側支持部間にできる周方向の隙間が前述の通気路を形成し、大気の通気量が増して換気性能が向上する。
【００１４】
さらに本発明は、検出素子に形成される電極層と導通し、当該検出素子の電気的出力を外部に取り出す端子金具の一端が該検出素子の後端部に係合され、その他端が前記セラミックセパレータに形成されるリード線挿通孔内にてリード線と接続されており、
前記外筒部材の後端から前記検出素子の後端までの軸線方向距離をＬ1とし、前記セパレータ側支持部の前端から前記端子金具と前記検出素子との係合部前端までの軸線方向距離をＬ2としたときに、Ｌ1＞Ｌ2の関係を満足する構成をとることができる。端子金具が検出素子の後端部に係合する以前に、セパレータ側支持部が外筒部材の後端部に挿入開始され、組立の際の基準側であるセラミックセパレータ側のズレを先に矯正し位置決めを行うこととなり、その後の組立作業がスムーズにかつ能率的に行える。
【００１５】
ここで、検出素子の内外面に電極層がそれぞれ形成され、各電極層に対応して第一及び第二の端子金具が嵌合するような場合には、軸線方向距離Ｌ2は次のようにして定められる。すなわち、Ｌ2は、セパレータ側支持部の前端から、第一又は第二端子金具のうち先に検出素子の後端との係合を開始する端子金具と検出素子との係合部前端までの軸線方向距離をいう。
【００１７】
さらに本発明の外筒部材の肉厚ｔは、０．３≦ｔ≦０．８ｍｍが望ましい。例えば自動車用の酸素センサの場合、車両の足周り部分に近い排気管等に取り付けられて路面からの石はね等による衝撃を受けても破損等を生じにくくすることができる。
【００１８】
また、上記課題を解決するために、第二番目の発明にかかるガスセンサは、
前方側が測定対象となるガスに向けられる軸状の検出素子と、
前記検出素子の外側に配置される筒状の外筒部材と、
前記検出素子よりも後方側に配置されるとともに、前記外筒部材の内側に配置され、前記検出素子からのリード線を挿通するためのリード線挿通孔が形成されるセラミックセパレータとを備え、
前記セラミックセパレータには外周面から突出するセパレータ側支持部が形成される一方、前記外筒部材には内周面から突出する外筒側支持部が形成され、該セパレータ側支持部が該外筒側支持部に直接または他部材を介して間接的に支持されるとともに、
前記検出素子に形成される電極層と導通し、当該検出素子の電気的出力を外部に取り出す端子金具の一端が該検出素子の後端部に係合され、その他端が前記セラミックセパレータに形成されるリード線挿通孔内にてリード線と接続されており、
前記外筒部材の後端から前記検出素子の後端までの軸線方向距離をＬ1とし、前記セパレータ側支持部の前端から前記端子金具と前記検出素子との係合部前端までの軸線方向距離をＬ2としたときに、Ｌ1＞Ｌ2の関係を満足することを特徴とする。
【００１９】
組立の際の基準側であるセラミックセパレータ側のズレを先に矯正し位置決めを行えば、その後の組立がスムーズであり、組み付け性が良好となって作業効率が向上する。すなわち、端子金具が検出素子の後端部に係合する以前に、セパレータ側支持部が外筒部材の後端部に挿入開始され、セラミックセパレータの位置決め及びズレの矯正が確実に行われる。この矯正され位置決めされたセラミックセパレータを基準として端子金具が検出素子の後端部に係合することとなってその後の組み付け作業が効率よく行える。
【００２０】
【発明の実施の形態】
以下、本発明の実施の形態を図面に示す実施例に基づき説明する。
図１は本発明のガスセンサの一実施例たる酸素センサの内部構造を示し、図２は要部の拡大図である。酸素センサ１（ガスセンサ）は、先端が閉じた中空軸状の酸素検出素子２（検出素子）と、酸素検出素子２の中空部２ａに挿入された発熱体３とを備える。酸素検出素子２は、酸素イオン伝導性を有する固体電解質により中空軸状に形成されている。なお、このような固体電解質としては、Ｙ_２Ｏ_３ないしＣａＯを固溶させたＺｒＯ_２が代表的なものであるが、それ以外のアルカリ土類金属ないし希土類金属の酸化物とＺｒＯ_２との固溶体を使用してもよい。さらには、ベースとなるＺｒＯ_２にはＨｆＯ_２が含有されていてもよい。そして、図２及び図３に示すように、酸素検出素子２の中空部２ａの内面には、そのほぼ全面を覆うように、例えばＰｔあるいはＰｔ合金により多孔質に形成された内部電極層２ｃが、一方その外面にはその前方部を覆うように、同じく外部電極層２ｂがそれぞれ設けられている。また、この酸素検出素子２の中間部外側には、絶縁性セラミックから形成されたインシュレータ６，７及びタルクから形成されたセラミック粉末８を介して筒状の金属製ケーシング１０が設けられている。なお、以下の説明において、酸素検出素子２の軸方向先端部に向かう側（閉じている側）を「前方側」、これと反対方向に向かう側を「後方側」と称する。
【００２１】
ケーシング１０は、酸素センサ１を排気管等の取付部に取り付けるためのねじ部９ｂを有する主体金具９と、その主体金具９の前方側開口部を覆うように取り付けられたプロテクタ１１からなる。本実施例の酸素センサ１はねじ部９ｂより前方が排気管等のエンジン内に位置し、それより後方は外部の大気中に位置して使用される。主体金具９（ケーシング１０）は、その前方側開口部から酸素検出素子２の先端側（検出部）を測定対象となる排気ガスに向けられるように突出させた状態で酸素検出素子２を保持するとともに、この開口部に形成される筒状のプロテクタ装着部９ａにキャップ状のプロテクタ１１が装着されて、酸素検出素子２の検出部を所定の空間を隔てて覆っている。プロテクタ１１には、排気ガスを透過させる複数のガス透過口１２が貫通形態で形成されている。
【００２２】
主体金具９の後方部は、絶縁体６との間にリング１５を介して加締められ、この主体金具９に筒状の金属製外筒部材１６の前端側に形成された開口部が外側から嵌合・固定されている。また、この外筒部材１６の後端側開口部はゴム等で構成されたグロメット１７を嵌入させることにより封止され、さらにこれに続いて内方（前方側）にセラミックセパレータ１８が設けられている。そして、それらセラミックセパレータ１８及びグロメット１７を貫通するように、酸素検出素子２用のリード線２０，２１及び発熱体３用のリード線１９，２２が配置されている（図５、図６参照）。
【００２３】
セラミックセパレータ１８は、ケーシング１０の後方側にケーシング１０とほぼ同軸的に設けられている。外筒部材１６は、セラミックセパレータ１８を外側から覆う状態で、ケーシング１０に対し後方外側からほぼ同軸的に連結される筒状形態をなす。グロメット１７は、セラミックセパレータ１８の後方側に位置して、外筒部材１６の後端開口部に対しその内側に弾性的に嵌入されている。
【００２４】
次に、酸素検出素子２用の一方のリード線２１は、互いに一体に形成されたコネクタ２３ａ、引出し線部２３ｂ、固定部２３ｃ及び下方押圧部２３ｄとを有する第一端子金具２３（端子金具）を経て前述の酸素検出素子２の内部電極層２ｃ（図２）と電気的に接続されている。一方、他方のリード線２０は、互いに一体に形成されたコネクタ３３ａ、引出し線部３３ｂ及び金具本体部３３ｃとを有する第二端子金具３３（端子金具）を経て、酸素検出素子２の外部電極層２ｂ（図３）と電気的に接続されている。酸素検出素子２は、その内側に配置された発熱体３で加熱することで活性化される。発熱体３は棒状のセラミックヒータであり、Ａｌ_２Ｏ_３を主とする芯材に抵抗発熱体（図示せず）を有する発熱部３ａが、＋極側及び−極側の発熱体端子部３ｂ，３ｂに接続されるリード線１９，２２（図６）を経て通電されることにより、酸素検出素子２の先端部（検出部）を加熱する。各リード線１９，２０，２１，２２は、セラミックセパレータ１８の軸線方向に貫通して設けられた４個のリード線挿通孔１８ａと、グロメット１７の軸線方向に貫通して設けられた４個のリード線挿通孔１７ａとに、各々挿通されて外部へ引き出されている。
【００２５】
なお、発熱体３に形成される発熱部３ａは、発熱体３の周方向に偏在することで、より小さな容積に発熱エネルギーが集中することになり、ヒータ通電時間の活性化時間を短縮する上で効果的である。また、発熱部３ａを発熱体３の先端部に偏在させるようにすれば、酸素検出素子２を速やかに加熱する上で有効である。つまり、発熱部３ａを発熱体３の全体に広げることもできるが、そうすると熱エネルギーが分散しやすくなるため、むしろ発熱部３ａを発熱体３の先端部に偏在させた方が局部的に発熱するために好ましい。そして、このような発熱部３ａの形成と、後述するように少なくとも発熱体３の先端部を酸素検出素子２の中空部２ａ内壁面に接触させることとの組み合わせにより、酸素センサ１の活性化時間をより短縮することができる。
【００２６】
図２及び図３に示すように、第一端子金具２３（端子金具）は、先端側に形成された下方押圧部２３ｄの内面で発熱体３の外面を押圧し、少なくとも発熱体３の先端部を酸素検出素子２の中空部２ａ内壁面に接触させる。下方押圧部２３ｄに続く固定部２３ｃの外面が酸素検出素子２の内面に嵌入することにより第一端子金具２３を軸方向に位置固定する。また引出し線部２３ｂの一端が固定部２３ｃの周方向の１ケ所に接続する形で一体化され、さらにその他端にコネクタ２３ａが一体化されている。なお、２３ｇは固定部２３ｃが発熱体端部収容穴１８ｃに入り込まないようにするための鍔である。
【００２７】
下方押圧部２３ｄは、略Ｌ字状の横断面形状を有する２個の部材を向き合わせて発熱体３の周囲を包囲する形態で形成されている。そして、発熱体３の挿入に伴い弾性的に押し広げられ、その弾性復元力、すなわち押圧力により発熱体３を径方向に押すことによって、少なくとも発熱体３の先端部を酸素検出素子２の中空部２ａ内壁面に接触させる。
【００２８】
また、固定部２３ｃは、板状金属体を円筒状に曲げ加工することにより、周方向の一部に開口を有する、軸直交断面で見て略Ｃ字状又は略馬蹄形状の形態で形成されている。固定部２３ｃの内側に挿通される発熱体３は、固定部２３ｃの開口の左右両縁部に設けられる下方押圧部２３ｄでの押圧により開口と反対側の固定部２３ｃ内周面で支持されている。そして、固定部２３ｃの外周面が酸素検出素子２の内壁面に直接嵌入することにより第一端子金具２３を軸方向に位置固定する。なお、固定部２３ｃの上方部（後方部）において、開口の左右両縁部側近傍には固定部２３ｃの周面の一部にコ字状の切れ目を設け、この切れ目が径方向内側へ折り込まれて上方押圧部２３ｅを形成している。上方押圧部２３ｅは、発熱体３の挿入時には弾性的に押し広げられて弾性復元力すなわち押圧力を生じ、発熱体３を径方向に押す。
【００２９】
ここで、発熱体３は、下方押圧部２３ｄ及び上方押圧部２３ｅにより、固定部２３ｃの開口側から開口とは反対側の径方向に押圧され、発熱部３ａ近傍において、発熱体３の中心軸線が酸素検出素子２の中空部２ａの中心軸線Ｏに対して片側に寄るように偏心（オフセット）して配置されるとともに、発熱体３はほぼ全長にわたって酸素検出素子２の中空部２ａ内壁面に接触している。
【００３０】
なお、酸素検出素子２の中空部２ａの後端開口部内側に面取２ｈを設けることにより、酸素検出素子２に欠け等の不具合を生じることなく、第一端子金具２３の嵌入がスムーズに行える。また、固定部２３ｃの外周面は、酸素検出素子２の中空部２ａの内壁面との接触により内部電極層２ｃ内面と導通するようになっている。さらに、固定部２３ｃは他部材を介して間接的に、酸素検出素子２の内面、すなわち中空部２ａ内壁面に嵌合されていてもよい。
【００３１】
一方、第二端子金具３３（端子金具）は、円筒状の金具本体部３３ｃを有するとともに、引出し線部３３ｂの一端が金具本体部３３ｃの周方向の１ケ所に接続する形で一体化され、さらにその他端にコネクタ３３ａが一体化されている。他方、その中心軸線を挟んで引出し線部３３ｂの接続点と反対側には、軸線方向のスリット３３ｅが形成されている。このような金具本体部３３ｃの内側に、酸素検出素子２の後端部がこれを弾性的に押し広げる形で内側から挿入されている。具体的には、酸素検出素子２の外周面後端部には外部側出力取出部としての導電層２ｆが、周方向に沿って帯状に形成されている。外部電極層２ｂは、例えば無電解メッキ等により、酸素検出素子２の係合フランジ部２ｓよりも前端側の要部全面を覆うものとされている。他方、導電層２ｆは、例えば金属ペーストを用いたパターン形成・焼き付けにより形成されるもので、同様に形成される軸線方向の接続パターン層２ｄを介して外部電極層２ｂと電気的に接続されている。
【００３２】
なお、金具本体部３３ｃの酸素検出素子２挿入側の開口部には、例えばその周方向に沿って外向きに開く挿入ガイド部３３ｆを形成しておけば、挿入時の引っ掛かり等が生じにくく、一層スムーズな組付けが可能となる。また、同様の目的で、酸素検出素子２の開口部外縁に面取部２ｇを形成することもできる。
【００３３】
図４は外筒部材１６を示す。円筒状の外筒部材１６の軸線方向前方側は、外径Ｄ1が相対的に大きい大径部１６ａに形成され、主体金具９（ケーシング１０）に外側から嵌合される。一方、外筒部材１６の軸線方向後方側は、外径Ｄ2が相対的に小さい小径部１６ｃに形成され、セラミックセパレータ１８がその内部に収容され、後端開口部１６ｄにはグロメット１７が嵌入される。そして、外筒部材１６の軸線方向中間部は、その両端において大径部１６ａと小径部１６ｃとに各々接続され、外径が連続的に変化する傾斜部１６ｂを形成している。また、外筒部材１６の小径部１６ｃの中間部内面において、全周にわたり内向きに一体的に突出する形態でフランジ状の外筒側支持部１６Ａが形成されている。なお、大径部１６ａと小径部１６ｃとの外径比Ｄ1／Ｄ2は、１．１〜１．５程度、例えば１．３であり、Ｄ1／Ｄ2が１．５を超えると外筒部材１６とセラミックセパレータ１８との間に後述の通気路Ｋを形成するのが困難な場合があり、一方Ｄ1／Ｄ2が１．１未満であると外筒部材１６の内部空間が狭くなって換気性能や耐熱性の点で不利になる場合がある。
【００３４】
外筒部材１６は、径方向において一重に構成されており、酸素センサ１の小型化（小径化）・軽量化に有効であるが、他方で、酸素センサ１を車両の足周り部分に近い排気管等に取り付けた場合には、路面からの石はね等による衝撃に伴う変形・破損等への対処も重要になる。そこで外筒部材１６の肉厚ｔは、全範囲にわたって、０．３≦ｔ≦０．８ｍｍ、より望ましくは０．４≦ｔ≦０．６ｍｍとし、路面からの石はね等による衝撃を受けても変形・破損等を発生しにくいようにしている。なお、肉厚ｔについて、ｔ＜０．３ｍｍになると、十分な耐衝撃性を確保できない場合があり、ｔ＞０．８ｍｍになると、グロメット１７の加締めが充分に行えない場合がある。
【００３５】
図５にセラミックセパレータ１８を示す。軸直交断面が円状に形成されるセラミックセパレータ１８には、各リード線１９，２０，２１，２２（図６）を挿通するための４個のリード線挿通孔１８ａが軸方向に貫通して形成されている。その軸線方向後端側の外周面には、全周にわたり外向きに一体的に突出する形態でフランジ状のセパレータ側支持部１８Ａが形成されている。セラミックセパレータ１８の後端面において、通気溝１８ｂが４個のリード線挿通孔１８ａと干渉しない位置に十字形態で軸線と直交する方向に形成され、後端面の外周に達した各通気溝１８ｂはそこから直角に向きを変え、セパレータ側支持部１８Ａの外周面に沿って軸線方向前方側へ延びている。また、セラミックセパレータ１８の前端面から開口する有底状の発熱体端部収容穴１８ｃが軸線方向に形成されている。なお、この発熱体端部収容穴１８ｃの内径は発熱体３の外径よりも大きく設定されている。また、発熱体端部収容穴１８ｃの底面１８ｄはセラミックセパレータ１８の軸線方向中間部に位置している。発熱体３の後端部は、セラミックセパレータ１８の軸線方向前方側から発熱体端部収容穴１８ｃに挿入され、発熱体３の後端面が収容穴１８ｃの底面１８ｄに当接することで軸線方向の位置決めがなされる。
【００３６】
図５、図２又は図４において、外筒部材１６の外筒側支持部１６Ａは、その後方側支持面１６Ａ１において、セラミックセパレータ１８のセパレータ側支持部１８Ａの前方側支持面１８Ａ１を受け止め支持している。すなわち、外筒部材１６の小径部１６ｃ内面には、セラミックセパレータ１８のセパレータ側支持部１８Ａの外径Ｄよりも小さな内径ｄを有する外筒側支持部１６Ａが内向きに突出して形成される。さらに、外筒部材１６の後端側小径部１６ｃの内面１６ｃ１はセラミックセパレータ１８のセパレータ側支持部１８Ａの外周面１８Ａ２に対して、また外筒部材１６の外筒側支持部１６Ａの内面１６Ａ２はセラミックセパレータ１８の本体部１８ｅの外周面１８ｅ１に対して、それぞれ外筒部材１６にセラミックセパレータ１８を挿入する際のガイドとして機能している。したがって、後端側小径部１６ｃの内面１６ｃ１とセパレータ側支持部１８Ａの外周面１８Ａ２との間、及び外筒側支持部１６Ａの内面１６Ａ２と本体部１８ｅの外周面１８ｅ１との間には、それぞれ径方向の隙間Ｓ1，Ｓ2が形成され、これらは前述の通気溝１８ｂとともに通気路Ｋを構成する。セラミックセパレータ１８の外周面に沿うように通気路Ｋを形成すると、酸素センサ１の内部において基準ガスである大気の循環が促進されて換気性能がよくなる傾向があり、排気ガス等の混入が少ない状態で酸素検出素子２の中空部２ａに大気を導入することができる。
【００３７】
図６はグロメット１７と通気部５３との組立状態を示す。グロメット１７には、各リード線１９，２０，２１，２２を挿通するための４個のリード線挿通孔１７ａがその内部に軸線方向に貫通して設けられている。グロメット１７の径方向中央部には中央貫通孔１７ｂが設けられ、この中央貫通孔１７ｂに通気部５３が嵌入されている。グロメット１７のリード線挿通孔１７ａ、中央貫通孔１７ｂ及び外周面１７Ａは、これら通気部５３及びリード線１９，２０，２１，２２の外面と外筒部材１６の開口部内面（小径部内面）１６ｃ１との間をシールする。通気部５３をグロメット１７に設けることで、通気部５３を相対的に高位置に設けることが容易になり、水滴が侵入しにくく防水性が高くなる。
【００３８】
通気部５３は、フィルタ５３Ａとフィルタ支持金具５３Ｂとから構成されている。フィルタ５３Ａは、軸線方向に延びる円筒状周面部５３Ａ１と、周面部５３Ａ１に対して後端部で蓋状に連接され、軸線方向に外気を導く通気端面部５３Ａ２とを有し、全体が軸方向断面にて逆Ｕ字状を呈している。そして、円筒状のフィルタ支持金具５３Ｂは、前端部に鍔部５３Ｂ２を有し、軸線方向に延びる円筒状周面部５３Ｂ１がフィルタ５３Ａの円筒状周面部５３Ａ１内部に嵌合して、フィルタ５３Ａを内側から支持し、外筒部材１６の小径部１６ｃを加締めてグロメット加締部１６Ｂを形成するときにフィルタ５３Ａの円筒状周面部５３Ａ１が破壊しないよう支えている。フィルタ５３Ａ等の通気部５３をグロメット１７に設けることで、酸素センサ１の中で最も高温に晒される部位である酸素検出素子２の検出部から通気部５３をできるだけ遠ざけることができ、フィルタ５３Ａの耐熱性に有利である。
【００３９】
フィルタ５３Ａ又はフィルタ支持金具５３Ｂには各々内外の周面に軸線方向に沿うテーパ等の傾斜を設けて嵌合を強固なものとする事ができる。フィルタ５３Ａは、図６の状態から１８０゜回転させて通気端面部５３Ａ２を底部（前端部）に位置させることもできるが、水等の侵入を防止する意味において、グロメット１７の後端面と通気端面部５３Ａ２とがほぼ面一になる図６の状態がより望ましい。また、フィルタ支持金具５３Ｂは、外筒部材１６の小径部１６ｃを加締めてグロメット加締部１６Ｂを形成したのちは抜去して、次のグロメット１７の組立用治具として使用することもできる。なお、フィルタ５３Ａは、例えばポリテトラフルオロエチレン（ＰＴＦＥ）の多孔質繊維構造体（商品名：例えばゴアテックス（ジャパンゴアテックス（株）））等により、水滴等の水を主体とする液体の透過は阻止し、かつ空気及び／又は水蒸気などの気体の透過は許容する撥水性フィルタとして構成されている。
【００４０】
上記酸素センサ１において、基準ガスとしての大気はフィルタ５３Ａの通気端面部５３Ａ２（通気部）→セラミックセパレータ１８の通気溝１８ｂ→外筒部材１６とセラミックセパレータ１８との間の径方向の隙間Ｓ1，Ｓ2（通気路Ｋ）→中空部２ａを経て酸素検出素子２の内面（内部電極層２ｃ）に導入される（図２矢印Ｒ参照）。一方、酸素検出素子２の外面（外部電極層２ｂ）にはプロテクタ１１のガス透過口１２を介して導入された排気ガスが接触し、酸素検出素子２には、その内外面の酸素濃度差に応じて酸素濃淡電池起電力が生じる。そして、この酸素濃淡電池起電力を、排気ガス中の酸素濃度の検出信号として内外電極層２ｃ，２ｂ（図２、図３）から第一及び第二端子金具２３，３３並びにリード線２１，２０を介して取り出すことにより、排気ガス中の酸素濃度を検出できる。
【００４１】
図７は、酸素センサの組立方法の一例を示す工程説明図である。まず、発熱体３が第一端子金具２３の下方押圧部２３ｄ及び上方押圧部２３ｅとで径方向に保持された状態で、第一端子金具２３に接続されたリード線２１が、セラミックセパレータ１８のリード線挿通孔１８ａとグロメット１７のリード線挿通孔１７ａとに順次挿通されて外部へ引き出される。第一端子金具２３の鍔２３ｇがセラミックセパレータ１８の前端面に接当するように配置され、かつ発熱体３の後端部が、発熱体端部収容穴１８ｃの底面１８ｄで受け止められ、軸線方向の位置決めがなされる。なお、第二端子金具３３に接続されたリード線２０も、リード線挿通孔１８ａ，１７ａに順次挿通して外部へ引き出される。一方、ケーシング１０（主体金具９）に酸素検出素子２を保持して別途組み立て、ケーシング１０（主体金具９）の後端部に対して外筒部材１６の前端部側を後方外側から嵌合させる。
【００４２】
そして、酸素検出素子２及びケーシング１０が組み込まれた外筒部材１６と、両端子金具２３，３３及び発熱体３が組み込まれたセラミックセパレータ１８とを相対的に接近させると、前方側では酸素検出素子２の中空部２ａ内壁面をガイドとして発熱体３が徐々に挿入され、後方側では外筒部材１６の後端側小径部１６ｃの内面１６ｃ１をガイドとして、セラミックセパレータ１８のセパレータ側支持部１８Ａの外周面１８Ａ２が、徐々に挿入される（図７（ａ））。ここで、「相対的に接近」とは、外筒部材１６とセラミックセパレータ１８との間で、いずれか一方を固定し他方を移動させるか、又は両者を互いに逆方向に移動させることにより、両者を接近させることを表している。
【００４３】
やがて、第二端子金具３３の金具本体部３３ｃの内側に、酸素検出素子２の後端部が金具本体部３３ｃを弾性的に押し広げる形で挿入され、次いで、酸素検出素子２の中空部２ａの後端開口部から第一端子金具２３の固定部２３ｃの外面が中空部２ａ内壁面に嵌入される。セパレータ側支持部１８Ａの前方側支持面１８Ａ１が、外筒側支持部１６Ａの後方側支持面１６Ａ１に当接したときに、外筒部材１６とセラミックセパレータ１８との相対的な接近を停止する。このとき、発熱体３の外面は上方押圧部２３ｅ及び下方押圧部２３ｄにより径方向に押圧され酸素検出素子２の中空部２ａ内壁面に発熱体３のほぼ全長が接触させられている。こののち外筒部材１６の後端開口部１６ｄから、後端側小径部１６ｃの内面１６ｃ１をガイドとして、通気部５３が組み込まれたグロメット１７の外周面１７Ａを嵌入する。セラミックセパレータ１８の後端面に既存品であるグロメット１７の前端面が当接して、セラミックセパレータ１８はがたつきなく安定的に外筒部材１６内に保持される。
【００４４】
これらの挿入位置を維持しつつ、外筒部材１６の後端部において、グロメット１７と外筒部材１６の小径部１６ｃとを加締めてグロメット加締部１６Ｂを形成し、最後に外筒部材１６の前端部において、レーザー光源Ｌから発射されるＹＡＧ（イットリウム、アルミニウム、ガーネット）レーザービームＬＢを外筒部材１６の大径部１６ａと主体金具９との重ね合わせ部に向けて略水平方向に全周にわたって照射し、レーザー溶接部１６Ｃを形成する。（図７（ｂ））。
【００４５】
図７において、外筒部材１６の後端から酸素検出素子２の後端までの軸線方向距離をＬ1とし、セパレータ側支持部１８Ａの前端（前方側支持面１８Ａ１）から第二端子金具３３と酸素検出素子２との係合部前端までの軸線方向距離をＬ2としたとき、Ｌ1＞Ｌ2の関係を満足するように構成されている。かかる構成により、外筒部材１６とセラミックセパレータ１８との相対的な接近により両者を組み付けるとき、まず外筒部材１６に対するセパレータ側支持部１８Ａの挿入が開始され（図７（ａ））、その後に第二端子金具３３に対する酸素検出素子２の挿入が始まる。
【００４６】
各部品の製造誤差が許容範囲内であっても例えば中心軸線のズレにより組み付け性が悪化したり破損を生じたりする場合がある。一般的に、組立の際の基準側であるセラミックセパレータ側のズレを先に矯正し位置決めを行えば、その後の組立がスムーズであり、組み付け性が良好となって作業効率が向上する。ここでは、セパレータ側支持部１８Ａが外筒部材１６の後端部に挿入開始され、セラミックセパレータ１８の位置決め及びズレの矯正が確実に行われる。この矯正され位置決めされたセラミックセパレータ１８を基準として第二端子金具３３に対する酸素検出素子２の挿入が始まり、その後の組み付け作業が効率よく行える。
【００４７】
ここで、セパレータ側支持部１８Ａの前端（前方側支持面１８Ａ１）から第二端子金具３３と酸素検出素子２との係合部前端までの軸線方向距離Ｌ2に関して以下の点に留意する必要がある。すなわち図７等の実施例の場合のように、酸素検出素子２の後端から第一及び第二端子金具２３，３３が組み込まれたセラミックセパレータ１８を接近させて行くと、まず第二端子金具３３の金具本体部３３ｃの内側に、酸素検出素子２の後端部が金具本体部３３ｃを弾性的に押し広げる形で挿入され、次いで、酸素検出素子２の中空部２ａの後端開口部から第一端子金具２３の固定部２３ｃの外面が中空部２ａ内壁面に嵌入されるときは、先に酸素検出素子２の後端との係合を開始する第二端子金具３３によって軸線方向距離Ｌ2が決定される。換言すれば、酸素検出素子２の後端から第一及び第二端子金具２３，３３が組み込まれたセラミックセパレータ１８を接近させて行くと、まず酸素検出素子２の中空部２ａの後端開口部から第一端子金具２３の固定部２３ｃの外面が中空部２ａ内壁面に嵌入され、次いで、第二端子金具３３の金具本体部３３ｃの内側に、酸素検出素子２の後端部が金具本体部３３ｃを弾性的に押し広げる形で挿入されるときは、先に酸素検出素子２の後端との係合を開始する第一端子金具２３によって軸線方向距離Ｌ2が決定される（図９参照）。
【００４８】
よって、Ｌ2は、セパレータ側支持部１８Ａの前端（前方側支持面１８Ａ１）から、第一又は第二端子金具２３，３３のうち先に酸素検出素子２の後端との係合を開始する端子金具と酸素検出素子２との係合部前端までの軸線方向距離をいう。なお、第一又は第二端子金具２３，３３は、酸素検出素子２の後端部に対して、直接でなく他部材を介して間接的に嵌合（係合）されていてもよい。
【００４９】
図８に、図４の外筒部材の他の実施例を示す。この実施例においては、外筒部材１６の小径部１６ｃの中間部内面において、内向きに突出する形態の外筒側断続支持部１６Ａ’（外筒側支持部）が周方向に断続的に形成されている。具体的には、小径部１６ｃの中間部内面において、複数（図では８個）の半球状突起形態の外筒側断続支持部１６Ａ’が周方向に所定間隔（図では４５゜間隔）毎に内向きに突出形成されている。突起の大きさ、形状、個数、設置間隔等は任意に設定できる。この実施例によれば、図４のように全周にわたり一体的にフランジ状の外筒側支持部１６Ａが形成される場合に比べて、安価に製造できる上に加工の際の歪も小さく抑えられる。さらに、隣合う半球状突起１６０Ａ’間にできる周方向の隙間Ｓ3が前述の径方向の隙間Ｓ1，Ｓ2と組み合わされて通気路Ｋを形成し、大気の通気量が増すとともに換気性能が向上する。なお、図８において図４と共通する部分には同一符号を付して、説明を省略する。
【００５０】
図９に、図１の酸素センサの他の実施例を示す。この実施例が図１と異なるところは主として以下の２点である。
▲１▼セラミックセパレータ１８において、全周にわたり外向きに一体的に突出するフランジ状のセパレータ側支持部１８Ａが、軸線方向後端位置の外周面に形成される状態（図１）から、軸線方向中間位置の外周面に形成される状態（図９）に変更している。
▲２▼酸素検出素子２の後端部に対する、第一又は第二端子金具２３，３３の嵌合（係合）順序に関して、まず第二端子金具３３の金具本体部３３ｃの内側に、酸素検出素子２の後端部が金具本体部３３ｃを弾性的に押し広げる形で挿入され、次いで、酸素検出素子２の中空部２ａの後端開口部から第一端子金具２３の固定部２３ｃの外面が中空部２ａ内壁面に嵌入される態様（図１：この場合は、先に酸素検出素子２の後端との係合を開始する第二端子金具３３によって軸線方向距離Ｌ2が決定される）から、まず酸素検出素子２の中空部２ａの後端開口部から第一端子金具２３の固定部２３ｃの外面が中空部２ａ内壁面に嵌入され、次いで、第二端子金具３３の金具本体部３３ｃの内側に、酸素検出素子２の後端部が金具本体部３３ｃを弾性的に押し広げる形で挿入される態様（図９：この場合は、先に酸素検出素子２の後端との係合を開始する第一端子金具２３によって軸線方向距離Ｌ2が決定される）に変更している。なお、図９において図１と共通する部分には同一符号を付して、説明を省略する。
【００５１】
図１０に、図４の外筒部材のさらに他の実施例を示す。この実施例においては、外筒側支持部１６Ａの後方側支持面１６Ａ１は、前方側に向かうほど内径が小となる傾斜面に形成されている。また、セパレータ側支持部１８Ａの前方側支持面１８Ａ１も、前方側に向かうほど外径が小となる傾斜面に形成されている。そして、外筒側支持部１６Ａの後方側支持面１６Ａ１の傾斜は、セラミックセパレータ１８の先端部が外筒側支持部１６Ａの内側に挿入される際の案内ガイドとなる（図１０（ａ）参照）。次に、セパレータ側支持部１８Ａの前方側支持面１８Ａ１の傾斜は、セラミックセパレータ１８のセパレータ側支持部１８Ａが外筒部材１６の後端開口部１６ｄに挿入される際の案内ガイドとなる（図１０（ｂ）参照）。これらの傾斜面１６Ａ１，１８Ａ１を設けることにより、外筒部材１６に対してセラミックセパレータ１８の挿入がスムーズに行える。
【００５２】
図１０（ａ）の外筒側支持部１６Ａは、外筒部材１６の小径部１６ｃの中間部内面において、全周にわたり内向きに一体的に突出するフランジ状に形成されている。一方、図１０（ｂ）の外筒側断続支持部１６Ａ’（外筒側支持部）は、図８と同様に周方向に断続的に形成されている。具体的には、小径部１６ｃの中間部内面において、複数（図では４個）の帯状突起形態の外筒側断続支持部１６Ａ’が周方向に所定間隔（図では９０゜間隔）毎に内向きに突出形成されている。突起の大きさ、形状、個数、設置間隔等は任意に設定できる。
【００５３】
図１０において、セパレータ側支持部１８Ａの前方側支持面１８Ａ１前端からセラミックセパレータ１８の前端までの軸線方向距離をＬ3とし、外筒部材１６の後端から外筒側支持部１６Ａの後方側支持面１６Ａ１前端までの軸線方向距離をＬ4としたとき、Ｌ3＞Ｌ4の関係を満足するように構成されている。かかる構成により、後方側支持面１６Ａ１，１６Ａ１’及び前方側支持面１８Ａ１の各傾斜面が案内ガイドとしての機能を充分に発揮できるようになる。なお、図１０において図４及び図８と共通する部分には同一符号を付して、説明を省略する。図１０では両傾斜面すなわち後方側支持面１６Ａ１，１６Ａ１’及び前方側支持面１８Ａ１は、ともに平面状に形成されているが曲面状等であってもよい。
【００５４】
図１１は、さらに異なる外筒部材を組み込んだ酸素センサを表している。図１１に示す外筒部材１６は、図１のものに比べて、小径部１６ｃの前半部分と中間部１６ｂとを大径部１６ａに置き換えて構成されている。すなわち、酸素検出素子２とセラミックセパレータ１８とを外方から被う大径部１６ａは、外筒部材１６の前端から外筒側支持部１６Ａに至るまで形成されている。大径部１６ａの軸線方向長さは、外筒部材１６の全長の１／２以上に及び、また酸素センサ１の全長の１／２近くを占めるようになる。その結果、外筒部材１６と酸素検出素子２又はセラミックセパレータ１８との間に形成される内部空間は、図１のものに比べて相対的に広くなる。内部空間が広くなったことで、仮に路面からの石はね等による衝撃によって外筒部材１６が変形した（ただし、衝撃による変形等に対しては、肉厚ｔに対する考慮等によって別途対策を講じている）としても、セラミックセパレータ１８の破損に至らず、両端子金具２３，３３の接触による短絡等を回避できる。また、内部空間を広くしたことで、導入大気に排気ガス等の異物が混入した場合にも、空間全体に薄められてセンサ出力への影響を小さくすることができる。なお、図１１において図１と共通する部分には同一符号を付して、説明を省略する。
【００５５】
以上説明した本発明のセンサの構造は、酸素センサ以外のガスセンサ、例えばＨＣセンサやＮＯｘセンサなどにも同様に適用することができる。また、セラミックセパレータ１８は外筒側支持部１６Ａにおいて直接でなく他部材を介して間接的に支持されていてもよい。
【図面の簡単な説明】
【図１】本発明のガスセンサの一実施例たる酸素センサの縦断面図。
【図２】図１の酸素センサの一部拡大縦断面図。
【図３】セラミックセパレータへの組み付け状態を示す分解斜視図。
【図４】外筒部材の平面図及び正面半断面図。
【図５】セラミックセパレータの平面図、底面図及び半断面図。
【図６】グロメットと通気部との組み付け状態を示す分解斜視図。
【図７】図１の酸素センサの組立方法の一例を示す工程説明図。
【図８】図４の外筒部材の他の実施例を示す平面図及び正面半断面図。
【図９】図１の酸素センサの他の実施例を示す縦断面図。
【図１０】図４の外筒部材のさらに他の実施例を示す軸直交断面図及び正面半断面図。
【図１１】さらに異なる外筒部材を組み込んだ酸素センサの縦断面図。
【符号の説明】
１酸素センサ（ガスセンサ）
２酸素検出素子（検出素子）
２ｂ外部電極層（電極層）
２ｃ内部電極層（電極層）
１０ケーシング
１６外筒部材
１６Ａ外筒側支持部
１６Ａ’ 外筒側断続支持部（外筒側支持部）
１６Ａ１後方側支持面
１６Ａ１’ 後方側支持面
１６ｄ後端開口部
１７グロメット
１８セラミックセパレータ
１８Ａセパレータ側支持部
１８Ａ１前方側支持面
１９，２０，２１，２２リード線
２３第一端子金具（端子金具）
３３第二端子金具（端子金具）
５３通気部
５３Ａフィルタ
Ｋ通気路
Ｌ1 外筒部材の後端から検出素子の後端までの軸線方向距離
Ｌ2 セパレータ側支持部の前端から端子金具と検出素子との係合部前端までの軸線方向距離
ｔ外筒部材の肉厚[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas sensor for detecting a component to be detected in a gas to be measured, such as an oxygen sensor, an HC sensor, or a NOx sensor.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a gas sensor having a structure in which a cylindrical or plate-like detection element having electrode layers formed on both surfaces of a solid electrolyte member is arranged inside a cylindrical casing is known as the above-described gas sensor. For example, in the case of a typical oxygen sensor as a gas sensor, an oxygen detection element in which an electrode layer is formed on each of the inner and outer surfaces of a hollow shaft-shaped solid electrolyte member whose tip is closed is directed toward the gas to be measured on the front side. The oxygen concentration cell electromotive force generated on the inner and outer surfaces of the oxygen sensing element is introduced into the inner and outer surfaces by introducing the atmosphere as a reference gas to the inner surface of the oxygen sensing element. As a detection signal of the oxygen concentration in the gas, one having a structure in which it is output from the inner and outer electrode layers to the outside through a lead wire is widely used. Further, in the oxygen sensor as described above, as a structure for taking out the lead wire from the casing, a ceramic separator in which an individual lead wire insertion hole is formed on the rear end side of the oxygen detection element is arranged to insert the lead wire. It is often configured to pass each lead through the hole. In addition, by using a ceramic separator in this way, a short circuit between lead wires is prevented.
[0003]
By the way, a conventional gas sensor using a ceramic separator, for example, forms a flange portion protruding on the outer peripheral surface of the ceramic separator, and inserts the ceramic separator into the casing, and makes the flange portion contact the opening end surface of the casing. In addition, there are many double structures in which the outside is covered with a cylindrical cover member. In such a double structure, for example, a stepped portion is provided on the cover member, and the flange portion of the ceramic separator is pressed between the casing opening end portion and the cover member while pressing the cover member in the axial direction against the casing. The ceramic separator is held by being sandwiched between the attached portions. Further, in the above double structure, it is necessary to apply joining means such as caulking in order to maintain the airtightness between the casing and the cover member.
[0004]
[Problems to be solved by the invention]
In recent years, in order to cope with environmental protection problems such as air pollution caused by exhaust gas, the demand for gas sensors has increased, and the demand for cost reduction and downsizing associated therewith has been increasing year by year. Therefore, it is required to reduce the number of parts and the number of assembling steps by reviewing the structure of the gas sensor, and at the same time, the sensor itself is required to be compact.
[0005]
An object of the present invention is to provide a gas sensor structure capable of simplifying and downsizing the entire sensor structure and reducing the number of assembly steps.
[0006]
[Means for solving the problems and actions / effects]
In order to solve the above-described problem, a gas sensor according to a first aspect of the present invention is arranged on the outside of the detection element having an axial detection element whose front side is directed to the gas to be measured.Single-layered in the radial directionA cylindrical outer cylinder member and a lead wire insertion hole that is disposed on the rear side of the detection element and disposed on the inner side of the outer cylinder member and for inserting a lead wire from the detection element are formed. A separator-side support projecting from the outer peripheral surface is formed on the ceramic separator,Singlely composedThe outer cylinder member is formed with an outer cylinder side support portion projecting from the inner peripheral surface, and the separator side support portion is supported directly or indirectly via the other member by the outer cylinder side support portion.Become
A grommet is provided that is inserted into the rear end opening of the outer cylinder member and directly contacts the rear end surface of the ceramic separator directly or through another member.It is characterized by that.
[0007]
According to the present invention, the outer cylinder formed by projecting an arbitrary part of the outer cylinder member inward from the inner peripheral surface, instead of supporting the flange portion of the ceramic separator on the opening end face of the casing as in the prior art. By supporting the separator-side support portion formed to protrude from the outer peripheral surface of the ceramic separator on the side support portion, it is not necessary to cover the outside of the ceramic separator with another cover member when holding the ceramic separator. In other words, the double structure, which was necessary in the past when holding the ceramic separator, can be eliminated, the number of sensor parts can be reduced, the sensor structure can be simplified and made compact, and the cost can be reduced. can do. Moreover, since the double structure that has been necessary in the past can be eliminated, there is no need for a joining means such as caulking to maintain the airtightness between the casing and the cover member, which facilitates the holding of the ceramic separator as well as the assembly. The number of man-hours can be reduced, which in turn can contribute to cost reduction.Furthermore, since the ceramic separator can be stably held without rattling by the existing grommet, the number of parts can be reduced.In view of reducing the number of parts, a structure in which the ceramic separator (the separator-side support portion) is directly supported by the outer cylinder-side support portion without any other member is more desirable.
[0008]
Here, the front support surface of the separator-side support portion of the present invention is formed into an inclined surface whose outer diameter decreases toward the front side, and the rear support surface of the outer tube side support portion faces the front side. It can be formed on an inclined surface with a smaller inner diameter. By providing these inclined surfaces, the ceramic separator can be smoothly inserted into the outer cylinder member. For example, the inclination of the front support surface of the separator-side support portion serves as a guide when the separator-side support portion of the ceramic separator is inserted into the rear end opening of the outer cylinder member, and the rear support surface of the outer cylinder-side support portion This inclination serves as a guide when the tip of the ceramic separator is inserted inside the outer cylinder side support.
[0010]
Furthermore, the grommet of the present invention can have a ventilation portion that prevents liquid from passing and allows gas to pass. By providing a ventilation part such as a filter in the grommet, it is possible to keep the ventilation part as far as possible from the detection part which is the part exposed to the highest temperature in the gas sensor. For example, heat resistance with respect to filter components such as silicon rubber and fluororesin Can be secured. For example, in the case of an oxygen sensor for an automobile, the attachment location is often attached to an exhaust pipe or the like close to a portion around the foot of the vehicle in addition to the engine room. In such a situation, the gas sensor is subjected to water droplet jetting or sometimes submerged during traveling in the rain or during a car wash. By providing a ventilation portion such as a filter in the grommet, it is easy to provide the ventilation portion at a relatively high position, and it is possible to introduce outside air in a highly waterproof state in which water droplets hardly enter.
[0011]
Furthermore, according to the present invention, an air passage can be formed in at least one of the separator side support portion and the outer cylinder side support portion. When the air passage is formed along the outer peripheral surface of the ceramic separator, the circulation of the reference gas is promoted inside the gas sensor, and the ventilation performance tends to be improved. Therefore, the exhaust gas concentration can be accurately detected by introducing the reference gas with a small amount of exhaust gas mixed therein.
[0012]
Furthermore, the ventilation path of this invention can be connected with the ventilation part provided in a grommet. Even when the volume ratio increases due to the downsizing of the gas sensor, it is easy to secure a ventilation path in order to incorporate a reference gas such as oxygen (atmosphere) necessary for measurement.
[0013]
Furthermore, the outer cylinder side support part of this invention can protrude from the internal peripheral surface of an outer cylinder member, and can be intermittently formed in the circumferential direction. When such a configuration is adopted, the outer cylinder side support portion can be easily formed and the processing cost can be reduced. Compared to the case where the flange-shaped outer cylinder side support portion is integrally formed over the entire circumference, the circumferential clearance between the adjacent outer cylinder side support portions can be processed at low cost and with high accuracy. Ventilation path is formed, and the ventilation performance is improved by increasing the air flow rate.
[0014]
Furthermore, the present invention provides an electrode layer formed on the detection element, and one end of a terminal fitting for taking out an electrical output of the detection element is engaged with the rear end of the detection element, and the other end is the ceramic. It is connected to the lead wire in the lead wire insertion hole formed in the separator,
The axial distance from the rear end of the outer cylindrical member to the rear end of the detection element is L1, and the axial distance from the front end of the separator-side support portion to the front end of the engagement portion between the terminal fitting and the detection element is When L2, L1> L2 can be satisfied. Before the terminal fitting engages the rear end of the detection element, the separator-side support part starts to be inserted into the rear end of the outer cylinder member, and the ceramic separator side, which is the reference side during assembly, is corrected first. Therefore, subsequent assembly work can be performed smoothly and efficiently.
[0015]
Here, when the electrode layers are respectively formed on the inner and outer surfaces of the detection element, and the first and second terminal fittings are fitted to correspond to each electrode layer, the axial distance L2 is as follows. Determined. That is, L2 is an axis from the front end of the separator-side support portion to the front end of the engagement portion between the terminal fitting and the detection element that starts engagement with the rear end of the detection element first of the first or second terminal fitting. It refers to the direction distance.
[0017]
Furthermore, the wall thickness t of the outer cylinder member of the present invention is preferably 0.3 ≦ t ≦ 0.8 mm. For example, in the case of an oxygen sensor for an automobile, it can be attached to an exhaust pipe or the like near the foot periphery of the vehicle and can be less likely to be damaged even when subjected to an impact from a stone splash from a road surface.
[0018]
Moreover, in order to solve the said subject, the gas sensor concerning 2nd invention is
An axial detection element whose front side is directed to the gas to be measured;
A cylindrical outer cylinder member disposed outside the detection element;
A ceramic separator that is disposed on the rear side of the detection element, is disposed on the inner side of the outer cylinder member, and has a lead wire insertion hole for inserting a lead wire from the detection element,
The ceramic separator is formed with a separator-side support that protrudes from the outer peripheral surface, while the outer cylinder member is formed with an outer cylinder-side support that protrudes from the inner peripheral surface, and the separator-side support is the outer cylinder. While being supported directly or indirectly via other members on the side support,
One end of a terminal fitting that is electrically connected to the electrode layer formed on the detection element and takes out the electrical output of the detection element is engaged with the rear end of the detection element, and the other end is formed on the ceramic separator. Connected to the lead wire in the lead wire insertion hole
The axial distance from the rear end of the outer cylindrical member to the rear end of the detection element is L1, and the axial distance from the front end of the separator-side support portion to the front end of the engagement portion between the terminal fitting and the detection element is When L2, L1> L2 is satisfied.
[0019]
If the deviation on the ceramic separator side, which is the reference side in assembling, is first corrected and positioned, the subsequent assembling is smooth, the assembling property is good, and the working efficiency is improved. That is, before the terminal fitting is engaged with the rear end portion of the detection element, the separator-side support portion is started to be inserted into the rear end portion of the outer cylinder member, and the ceramic separator is reliably positioned and the displacement is corrected. The terminal fitting engages with the rear end portion of the detection element with the corrected and positioned ceramic separator as a reference, so that the subsequent assembling work can be performed efficiently.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples shown in the drawings.
FIG. 1 shows the internal structure of an oxygen sensor as an embodiment of the gas sensor of the present invention, and FIG. 2 is an enlarged view of the main part. The oxygen sensor 1 (gas sensor) includes a hollow shaft-shaped oxygen detection element 2 (detection element) whose tip is closed, and a heating element 3 inserted into the hollow portion 2a of the oxygen detection element 2. The oxygen detection element 2 is formed in a hollow shaft shape by a solid electrolyte having oxygen ion conductivity. As such a solid electrolyte, Y₂O₃ZrO in which CaO is dissolved₂Is representative, but other alkaline earth metal or rare earth metal oxides and ZrO₂A solid solution may be used. Furthermore, the base ZrO₂HfO₂May be contained. As shown in FIGS. 2 and 3, the inner surface of the hollow portion 2a of the oxygen detecting element 2 has an internal electrode layer 2c formed porous, for example, of Pt or a Pt alloy so as to cover almost the entire surface. On the other hand, external electrode layers 2b are similarly provided on the outer surface so as to cover the front portion thereof. In addition, a cylindrical metal casing 10 is provided outside the intermediate portion of the oxygen detecting element 2 via insulators 6 and 7 made of insulating ceramic and ceramic powder 8 made of talc. In the following description, the side (closed side) toward the tip end in the axial direction of the oxygen detection element 2 is referred to as “front side”, and the side toward the opposite direction is referred to as “rear side”.
[0021]
The casing 10 includes a metal shell 9 having a threaded portion 9b for attaching the oxygen sensor 1 to an attachment portion such as an exhaust pipe, and a protector 11 attached so as to cover a front opening of the metal shell 9. The oxygen sensor 1 of the present embodiment is used in such a manner that the front side of the screw portion 9b is located in the engine such as an exhaust pipe, and the rear side thereof is located in the outside atmosphere. The metal shell 9 (casing 10) holds the oxygen detection element 2 in a state in which the front end side (detection part) of the oxygen detection element 2 is projected from the front opening so as to be directed to the exhaust gas to be measured. At the same time, a cap-like protector 11 is attached to a cylindrical protector attachment portion 9a formed in the opening, and covers the detection portion of the oxygen detection element 2 with a predetermined space therebetween. The protector 11 is formed with a plurality of gas permeation ports 12 through which exhaust gas permeates.
[0022]
A rear portion of the metal shell 9 is crimped between the insulator 6 and the insulator 6 via a ring 15, and an opening formed in the metal shell 9 on the front end side of the cylindrical metal outer cylinder member 16 is provided from the outside. Mated and fixed. Further, the rear end side opening of the outer cylinder member 16 is sealed by inserting a grommet 17 made of rubber or the like, and subsequently, a ceramic separator 18 is provided inward (front side). Yes. The lead wires 20 and 21 for the oxygen detection element 2 and the lead wires 19 and 22 for the heating element 3 are disposed so as to penetrate the ceramic separator 18 and the grommet 17 (see FIGS. 5 and 6). .
[0023]
The ceramic separator 18 is provided substantially coaxially with the casing 10 on the rear side of the casing 10. The outer cylinder member 16 has a cylindrical shape that is coaxially connected to the casing 10 from the rear outer side in a state of covering the ceramic separator 18 from the outer side. The grommet 17 is located on the rear side of the ceramic separator 18 and is elastically fitted inside the rear end opening of the outer cylinder member 16.
[0024]
Next, one lead wire 21 for the oxygen detection element 2 is a first terminal fitting 23 (terminal fitting) having a connector 23a, a lead wire portion 23b, a fixing portion 23c, and a downward pressing portion 23d that are integrally formed with each other. Then, it is electrically connected to the internal electrode layer 2c (FIG. 2) of the oxygen detecting element 2 described above. On the other hand, the other lead wire 20 passes through a second terminal fitting 33 (terminal fitting) having a connector 33a, a lead wire portion 33b, and a fitting main body portion 33c, which are integrally formed with each other, and then the external electrode layer of the oxygen detection element 2. 2b (FIG. 3) is electrically connected. The oxygen detection element 2 is activated by heating with the heating element 3 disposed inside thereof. The heating element 3 is a rod-shaped ceramic heater, Al₂O₃Lead wires 19 and 22 (FIG. 6) in which a heat generating portion 3a having a resistance heating element (not shown) in a core material mainly composed of is connected to heat generating element terminal portions 3b and 3b on the positive electrode side and the negative electrode side. By energizing through this, the tip (detection part) of the oxygen detection element 2 is heated. Each of the lead wires 19, 20, 21, 22 is provided with four lead wire insertion holes 18 a provided so as to penetrate in the axial direction of the ceramic separator 18, and four pieces provided so as to penetrate in the axial direction of the grommet 17. The lead wire insertion holes 17a are inserted through the lead wire insertion holes 17a.
[0025]
The heat generating portion 3a formed in the heat generating element 3 is unevenly distributed in the circumferential direction of the heat generating element 3, so that the heat generating energy is concentrated in a smaller volume, thereby shortening the activation time of the heater energizing time. It is effective. Further, if the heat generating portion 3a is unevenly distributed at the tip of the heat generating body 3, it is effective in rapidly heating the oxygen detecting element 2. That is, although the heat generating portion 3a can be spread over the entire heat generating body 3, heat energy is easily dispersed, so that the heat generating portion 3a is more unevenly distributed at the tip of the heat generating body 3 to generate heat locally. Therefore, it is preferable. Then, the activation time of the oxygen sensor 1 is achieved by a combination of the formation of the heat generating portion 3a and the contact of at least the tip of the heat generating element 3 with the inner wall surface of the hollow portion 2a of the oxygen detecting element 2 as described later. Can be further shortened.
[0026]
As shown in FIGS. 2 and 3, the first terminal fitting 23 (terminal fitting) presses the outer surface of the heating element 3 with the inner surface of the lower pressing portion 23 d formed on the distal end side, and at least the distal end portion of the heating element 3. Is brought into contact with the inner wall surface of the hollow portion 2 a of the oxygen detecting element 2. The outer surface of the fixing portion 23c following the downward pressing portion 23d is fitted into the inner surface of the oxygen detection element 2, thereby fixing the position of the first terminal fitting 23 in the axial direction. Further, one end of the lead wire portion 23b is integrated so as to be connected to one place in the circumferential direction of the fixed portion 23c, and the connector 23a is integrated to the other end. Reference numeral 23g denotes a hook for preventing the fixing portion 23c from entering the heating element end accommodating hole 18c.
[0027]
The downward pressing portion 23d is formed in a form that surrounds the periphery of the heating element 3 by facing two members having a substantially L-shaped cross-sectional shape. Then, the heat generating element 3 is elastically expanded as the heat generating element 3 is inserted, and the heat generating element 3 is pushed in the radial direction by the elastic restoring force, that is, the pressing force, so that at least the tip of the heat generating element 3 is hollow in the oxygen detecting element 2. The part 2a is brought into contact with the inner wall surface.
[0028]
Further, the fixing portion 23c is formed in a substantially C-shaped or substantially horseshoe-shaped form as viewed in an axial orthogonal section having an opening in a part of the circumferential direction by bending a plate-like metal body into a cylindrical shape. ing. The heating element 3 inserted inside the fixing portion 23c is supported by the inner peripheral surface of the fixing portion 23c opposite to the opening by pressing at the lower pressing portions 23d provided at both left and right edges of the opening of the fixing portion 23c. Yes. And the outer peripheral surface of the fixing | fixed part 23c fits directly in the inner wall face of the oxygen detection element 2, and the position of the 1st terminal metal fitting 23 is fixed to an axial direction. In addition, in the upper part (rear part) of the fixed part 23c, a U-shaped cut is provided in a part of the peripheral surface of the fixed part 23c near the left and right edges of the opening, and the cut is folded inward in the radial direction. Thus, an upper pressing portion 23e is formed. The upper pressing portion 23e is elastically expanded when the heating element 3 is inserted to generate an elastic restoring force, that is, a pressing force, and pushes the heating element 3 in the radial direction.
[0029]
Here, the heating element 3 is pressed in the radial direction opposite to the opening from the opening side of the fixing part 23c by the lower pressing part 23d and the upper pressing part 23e, and the central axis of the heating element 3 is near the heating part 3a. Is arranged eccentrically (offset) so as to be shifted to one side with respect to the central axis O of the hollow portion 2a of the oxygen detecting element 2, and the heating element 3 is disposed on the inner wall surface of the hollow portion 2a of the oxygen detecting element 2 over almost the entire length. In contact.
[0030]
In addition, by providing the chamfering 2h inside the rear end opening of the hollow portion 2a of the oxygen detection element 2, the first terminal fitting 23 can be smoothly inserted without causing defects such as chipping in the oxygen detection element 2. . Further, the outer peripheral surface of the fixing portion 23c is electrically connected to the inner surface of the internal electrode layer 2c by contact with the inner wall surface of the hollow portion 2a of the oxygen detecting element 2. Furthermore, the fixing portion 23c may be indirectly fitted to the inner surface of the oxygen detection element 2, that is, the inner wall surface of the hollow portion 2a via another member.
[0031]
On the other hand, the second terminal fitting 33 (terminal fitting) has a cylindrical fitting main body portion 33c and is integrated in such a manner that one end of the lead wire portion 33b is connected to one place in the circumferential direction of the fitting main body portion 33c. Further, a connector 33a is integrated with the other end. On the other hand, an axial slit 33e is formed on the side opposite to the connection point of the lead line portion 33b across the central axis. The rear end portion of the oxygen detection element 2 is inserted into the metal fitting main body portion 33c from the inside in such a manner as to elastically push it. Specifically, a conductive layer 2 f as an external output extraction portion is formed in a strip shape along the circumferential direction at the rear end portion of the outer peripheral surface of the oxygen detection element 2. The external electrode layer 2b covers the entire surface of the main part on the front end side of the engagement flange portion 2s of the oxygen detection element 2 by, for example, electroless plating. On the other hand, the conductive layer 2f is formed, for example, by pattern formation / baking using a metal paste, and is electrically connected to the external electrode layer 2b via the axially formed connection pattern layer 2d. Yes.
[0032]
In addition, if an insertion guide portion 33f that opens outward along the circumferential direction is formed in the opening portion of the metal fitting main body portion 33c on the oxygen detection element 2 insertion side, for example, a hook at the time of insertion hardly occurs, Smoother assembly becomes possible. For the same purpose, the chamfered portion 2g can be formed on the outer edge of the opening of the oxygen detecting element 2.
[0033]
FIG. 4 shows the outer cylinder member 16. The axially forward side of the cylindrical outer cylinder member 16 is formed in a large diameter portion 16a having a relatively large outer diameter D1, and is fitted to the metal shell 9 (casing 10) from the outside. On the other hand, the axially rear side of the outer cylinder member 16 is formed in a small diameter portion 16c having a relatively small outer diameter D2, a ceramic separator 18 is accommodated therein, and a grommet 17 is fitted in the rear end opening portion 16d. The And the axial direction intermediate part of the outer cylinder member 16 is each connected to the large diameter part 16a and the small diameter part 16c in the both ends, and forms the inclination part 16b from which an outer diameter changes continuously. Further, on the inner surface of the intermediate portion of the small diameter portion 16c of the outer cylinder member 16, a flange-shaped outer cylinder side support portion 16A is formed so as to protrude integrally inward over the entire circumference. The outer diameter ratio D1 / D2 between the large-diameter portion 16a and the small-diameter portion 16c is about 1.1 to 1.5, for example 1.3, and when D1 / D2 exceeds 1.5, the outer cylinder member 16 It may be difficult to form a later-described air passage K between the ceramic separator 18 and the ceramic separator 18. On the other hand, if D1 / D2 is less than 1.1, the inner space of the outer cylindrical member 16 becomes narrower and ventilation performance or It may be disadvantageous in terms of heat resistance.
[0034]
The outer cylinder member 16 is configured in a single layer in the radial direction, and is effective for reducing the size (reducing the diameter) and reducing the weight of the oxygen sensor 1. On the other hand, the oxygen sensor 1 is exhausted near the leg portion of the vehicle. When it is attached to a pipe, etc., it is also important to deal with deformation / breakage caused by impact from stone splashes from the road surface. Therefore, the wall thickness t of the outer cylinder member 16 is set to 0.3 ≦ t ≦ 0.8 mm, more preferably 0.4 ≦ t ≦ 0.6 mm over the entire range, and the impact is caused by stone splashes from the road surface. However, deformation and breakage are less likely to occur. When the thickness t is t <0.3 mm, sufficient impact resistance may not be ensured, and when t> 0.8 mm, the grommet 17 may not be sufficiently crimped.
[0035]
FIG. 5 shows the ceramic separator 18. In the ceramic separator 18 whose axial cross section is formed in a circular shape, four lead wire insertion holes 18a for inserting the lead wires 19, 20, 21, 22 (FIG. 6) penetrate in the axial direction. Is formed. A flange-like separator-side support portion 18A is formed on the outer peripheral surface on the rear end side in the axial direction so as to integrally protrude outward over the entire circumference. On the rear end surface of the ceramic separator 18, the ventilation grooves 18 b are formed in a cross shape in a direction perpendicular to the axis line at positions where they do not interfere with the four lead wire insertion holes 18 a, and each of the ventilation grooves 18 b reaching the outer periphery of the rear end surface The direction is changed to a right angle from the front, and extends axially forward along the outer peripheral surface of the separator-side support 18A. In addition, a bottomed heating element end accommodating hole 18c opened from the front end face of the ceramic separator 18 is formed in the axial direction. Note that the inner diameter of the heating element end accommodating hole 18 c is set larger than the outer diameter of the heating element 3. Further, the bottom surface 18 d of the heating element end accommodating hole 18 c is located in the axial direction intermediate portion of the ceramic separator 18. The rear end portion of the heating element 3 is inserted into the heating element end accommodation hole 18c from the front side in the axial direction of the ceramic separator 18, and the rear end surface of the heating element 3 contacts the bottom surface 18d of the accommodation hole 18c. Positioning is done.
[0036]
5, 2, or 4, the outer cylinder side support portion 16A of the outer cylinder member 16 receives and supports the front side support surface 18A1 of the separator side support portion 18A of the ceramic separator 18 on the rear side support surface 16A1. ing. That is, an outer cylinder side support portion 16A having an inner diameter d smaller than the outer diameter D of the separator side support portion 18A of the ceramic separator 18 is formed on the inner surface of the small diameter portion 16c of the outer cylinder member 16 so as to protrude inward. Further, the inner surface 16c1 of the rear end side small diameter portion 16c of the outer cylinder member 16 is opposed to the outer peripheral surface 18A2 of the separator side support portion 18A of the ceramic separator 18, and the inner surface 16A2 of the outer cylinder side support portion 16A of the outer cylinder member 16 is The outer peripheral surface 18e1 of the main body 18e of the ceramic separator 18 functions as a guide when the ceramic separator 18 is inserted into the outer cylinder member 16, respectively. Therefore, between the inner surface 16c1 of the rear end side small diameter portion 16c and the outer peripheral surface 18A2 of the separator side support portion 18A, and between the inner surface 16A2 of the outer cylinder side support portion 16A and the outer peripheral surface 18e1 of the main body portion 18e, respectively. Radial gaps S1 and S2 are formed, and these constitute the ventilation path K together with the above-described ventilation groove 18b. When the air passage K is formed along the outer peripheral surface of the ceramic separator 18, the circulation of the atmosphere, which is the reference gas, is promoted inside the oxygen sensor 1, and the ventilation performance tends to be improved. Thus, the atmosphere can be introduced into the hollow portion 2 a of the oxygen detection element 2.
[0037]
FIG. 6 shows an assembled state of the grommet 17 and the ventilation portion 53. In the grommet 17, four lead wire insertion holes 17 a for inserting the lead wires 19, 20, 21, and 22 are provided through the grommet 17 in the axial direction. A central through hole 17b is provided in the central portion in the radial direction of the grommet 17, and a ventilation portion 53 is fitted into the central through hole 17b. The lead wire insertion hole 17a, the central through hole 17b, and the outer peripheral surface 17A of the grommet 17 are formed on the outer surface of the ventilation portion 53 and the lead wires 19, 20, 21, and 22 and the inner surface of the opening (small diameter portion inner surface) 16c1 of the outer cylinder member 16. Seal between. By providing the ventilation part 53 in the grommet 17, it becomes easy to provide the ventilation part 53 at a relatively high position, and it is difficult for water droplets to enter and the waterproofness is improved.
[0038]
The ventilation part 53 includes a filter 53A and a filter support fitting 53B. The filter 53A has a cylindrical peripheral surface portion 53A1 extending in the axial direction, and a ventilation end surface portion 53A2 that is connected to the peripheral surface portion 53A1 in a lid shape at the rear end portion and guides outside air in the axial direction, and is entirely axial. The cross section has an inverted U shape. The cylindrical filter support fitting 53B has a flange portion 53B2 at the front end, the cylindrical peripheral surface portion 53B1 extending in the axial direction is fitted into the cylindrical peripheral surface portion 53A1 of the filter 53A, and the filter 53A is placed inside. The cylindrical peripheral surface portion 53A1 of the filter 53A is supported so as not to be broken when the small diameter portion 16c of the outer cylinder member 16 is swaged to form the grommet swaged portion 16B. By providing the grommet 17 with the ventilation part 53 such as the filter 53A, the ventilation part 53 can be as far away as possible from the detection part of the oxygen detection element 2 which is the part exposed to the highest temperature in the oxygen sensor 1, and the filter 53A It is advantageous for heat resistance.
[0039]
The filter 53A or the filter support metal fitting 53B can be provided with an inclination such as a taper along the axial direction on the inner and outer peripheral surfaces, respectively, so that the fitting can be strengthened. The filter 53A can be rotated 180 ° from the state shown in FIG. 6 so that the ventilation end surface portion 53A2 is positioned at the bottom (front end portion). However, in order to prevent intrusion of water or the like, the rear end surface and the ventilation end surface of the grommet 17 are used. The state of FIG. 6 where the portion 53A2 is substantially flush is more desirable. Further, the filter support fitting 53B can be used as an assembly jig for the next grommet 17 after the small diameter portion 16c of the outer cylinder member 16 is crimped to form the grommet crimping portion 16B. The filter 53A is made of, for example, polytetrafluoroethylene (PTFE) porous fiber structure (trade name: Gore-Tex (Japan Gore-Tex Co., Ltd.)), etc. Is configured as a water-repellent filter that blocks air and / or gas such as water vapor.
[0040]
In the oxygen sensor 1, the atmosphere as the reference gas is the air gap end 53 A 2 (vent) of the filter 53 A → the vent groove 18 b of the ceramic separator 18 → the radial gap S 1 between the outer cylinder member 16 and the ceramic separator 18, S2 (ventilation path K) is introduced into the inner surface (internal electrode layer 2c) of the oxygen detection element 2 through the hollow portion 2a (see arrow R in FIG. 2). On the other hand, the exhaust gas introduced through the gas permeation port 12 of the protector 11 is in contact with the outer surface (external electrode layer 2b) of the oxygen detection element 2, and the oxygen detection element 2 has an oxygen concentration difference between its inner and outer surfaces. Accordingly, an oxygen concentration cell electromotive force is generated. The oxygen concentration cell electromotive force is used as a detection signal of the oxygen concentration in the exhaust gas from the inner and outer electrode layers 2c and 2b (FIGS. 2 and 3) and the first and second terminal fittings 23 and 33 and the lead wires 21 and 20. The oxygen concentration in the exhaust gas can be detected by taking it out through.
[0041]
FIG. 7 is a process explanatory view showing an example of an assembly method of the oxygen sensor. First, in a state where the heating element 3 is held in the radial direction by the lower pressing portion 23 d and the upper pressing portion 23 e of the first terminal fitting 23, the lead wire 21 connected to the first terminal fitting 23 is connected to the ceramic separator 18. The lead wire insertion hole 18a and the lead wire insertion hole 17a of the grommet 17 are sequentially inserted and pulled out. The flange 23g of the first terminal fitting 23 is disposed so as to contact the front end surface of the ceramic separator 18, and the rear end portion of the heating element 3 is received by the bottom surface 18d of the heating element end accommodating hole 18c, and is axially Is positioned. Note that the lead wire 20 connected to the second terminal fitting 33 is also sequentially inserted into the lead wire insertion holes 18a and 17a and drawn out to the outside. On the other hand, the oxygen detection element 2 is held separately in the casing 10 (metal shell 9) and assembled separately, and the front end side of the outer cylinder member 16 is fitted from the rear outside to the rear end portion of the casing 10 (metal shell 9). .
[0042]
When the outer cylinder member 16 in which the oxygen detection element 2 and the casing 10 are incorporated and the ceramic separator 18 in which both the terminal fittings 23 and 33 and the heating element 3 are incorporated are relatively close to each other, oxygen detection is performed on the front side. The heating element 3 is gradually inserted using the inner wall surface of the hollow portion 2a of the element 2 as a guide, and on the rear side, the separator side support portion 18A of the ceramic separator 18 using the inner surface 16c1 of the rear end side small diameter portion 16c of the outer cylinder member 16 as a guide. The outer peripheral surface 18A2 is gradually inserted (FIG. 7A). Here, “relatively close” means that either one is fixed and the other is moved between the outer cylinder member 16 and the ceramic separator 18 or both are moved in opposite directions. Represents approaching.
[0043]
Eventually, the rear end portion of the oxygen detection element 2 is inserted inside the metal fitting main body portion 33c of the second terminal metal fitting 33 so as to elastically push the metal fitting main body portion 33c, and then the hollow portion 2a of the oxygen detection element 2 is obtained. The outer surface of the fixing portion 23c of the first terminal fitting 23 is fitted into the inner wall surface of the hollow portion 2a from the rear end opening. When the front side support surface 18A1 of the separator side support portion 18A comes into contact with the rear side support surface 16A1 of the outer tube side support portion 16A, the relative approach between the outer tube member 16 and the ceramic separator 18 is stopped. At this time, the outer surface of the heating element 3 is pressed in the radial direction by the upper pressing part 23e and the lower pressing part 23d, and the almost entire length of the heating element 3 is brought into contact with the inner wall surface of the hollow part 2a of the oxygen detecting element 2. Thereafter, the outer peripheral surface 17A of the grommet 17 in which the ventilation portion 53 is incorporated is fitted from the rear end opening portion 16d of the outer cylindrical member 16 with the inner surface 16c1 of the rear end side small diameter portion 16c as a guide. The front end surface of the existing grommet 17 is in contact with the rear end surface of the ceramic separator 18, and the ceramic separator 18 is stably held in the outer cylinder member 16 without rattling.
[0044]
While maintaining these insertion positions, the grommet 17 and the small diameter portion 16c of the outer cylinder member 16 are caulked at the rear end portion of the outer cylinder member 16 to form a grommet caulking portion 16B, and finally the outer cylinder member 16 The YAG (yttrium, aluminum, garnet) laser beam LB emitted from the laser light source L is entirely directed in a substantially horizontal direction toward the overlapping portion of the large-diameter portion 16a of the outer cylinder member 16 and the metal shell 9. Irradiation is performed over the circumference to form a laser weld 16C. (FIG. 7B).
[0045]
In FIG. 7, the axial distance from the rear end of the outer cylinder member 16 to the rear end of the oxygen detection element 2 is L1, and the second terminal fitting 33 and oxygen are connected from the front end (front support surface 18A1) of the separator side support portion 18A. When the distance in the axial direction to the front end of the engaging portion with the detecting element 2 is L2, the relationship L1> L2 is satisfied. With this configuration, when the outer cylinder member 16 and the ceramic separator 18 are assembled together by relative approach, first, the insertion of the separator-side support portion 18A into the outer cylinder member 16 is started (FIG. 7A), and thereafter Insertion of the oxygen detection element 2 into the second terminal fitting 33 starts.
[0046]
Even if the manufacturing error of each part is within an allowable range, for example, assemblability may deteriorate or breakage may occur due to deviation of the central axis. In general, if the deviation on the ceramic separator side, which is the reference side in assembling, is first corrected and positioned, the subsequent assembling is smooth, the assemblability is good, and the working efficiency is improved. Here, the separator-side support portion 18A is started to be inserted into the rear end portion of the outer cylinder member 16, and the positioning of the ceramic separator 18 and the correction of the displacement are reliably performed. Insertion of the oxygen detecting element 2 into the second terminal fitting 33 starts with the corrected and positioned ceramic separator 18 as a reference, and the subsequent assembling work can be performed efficiently.
[0047]
Here, it is necessary to pay attention to the following points regarding the axial distance L2 from the front end (front support surface 18A1) of the separator side support portion 18A to the front end of the engagement portion between the second terminal fitting 33 and the oxygen detection element 2. . That is, as in the case of the embodiment of FIG. 7 and the like, when the ceramic separator 18 incorporating the first and second terminal fittings 23 and 33 is approached from the rear end of the oxygen detecting element 2, first the second terminal fitting is obtained. The rear end portion of the oxygen detection element 2 is inserted inside the metal fitting body 33c of 33 in such a manner as to elastically expand the metal fitting main body portion 33c, and then from the rear end opening of the hollow portion 2a of the oxygen detection element 2. When the outer surface of the fixing portion 23c of the first terminal fitting 23 is fitted into the inner wall surface of the hollow portion 2a, the axial distance L2 is caused by the second terminal fitting 33 which starts the engagement with the rear end of the oxygen detecting element 2 first. Is determined. In other words, when the ceramic separator 18 incorporating the first and second terminal fittings 23 and 33 is approached from the rear end of the oxygen detection element 2, first, the rear end opening of the hollow portion 2a of the oxygen detection element 2 The outer surface of the fixing portion 23c of the first terminal fitting 23 is fitted into the inner wall surface of the hollow portion 2a, and then the rear end portion of the oxygen detection element 2 is located inside the fitting main body portion 33c of the second terminal fitting 33. When inserted in such a manner that 33c is elastically expanded, the axial distance L2 is determined by the first terminal fitting 23 which starts the engagement with the rear end of the oxygen detecting element 2 first (see FIG. 9). .
[0048]
Therefore, L2 is a terminal that starts engagement with the rear end of the oxygen detection element 2 first of the first or second terminal fittings 23 and 33 from the front end (front support surface 18A1) of the separator side support portion 18A. This is the axial distance to the front end of the engagement portion between the metal fitting and the oxygen detection element 2. The first or second terminal fittings 23 and 33 may be fitted (engaged) indirectly to the rear end portion of the oxygen detecting element 2 via other members instead of directly.
[0049]
FIG. 8 shows another embodiment of the outer cylinder member of FIG. In this embodiment, on the inner surface of the intermediate portion of the small diameter portion 16c of the outer cylinder member 16, an outer cylinder side intermittent support portion 16A ′ (outer cylinder side support portion) that protrudes inward is intermittently formed in the circumferential direction. Has been. Specifically, on the inner surface of the intermediate portion of the small-diameter portion 16c, a plurality (eight in the drawing) of the outer tube side intermittent support portions 16A ′ in the form of hemispherical projections are arranged at predetermined intervals (45 ° in the drawing) in the circumferential direction. Projecting inward. The size, shape, number, and installation interval of the protrusions can be arbitrarily set. According to this embodiment, as compared with the case where the flange-like outer cylinder side support portion 16A is integrally formed over the entire circumference as shown in FIG. 4, it can be manufactured at a lower cost and the distortion during processing is kept small. It is done. Further, the circumferential gap S3 formed between the adjacent hemispherical protrusions 160A ′ is combined with the aforementioned radial gaps S1 and S2 to form the air passage K, and the ventilation performance is improved as the air flow rate is increased. . In FIG. 8, parts that are the same as those in FIG.
[0050]
FIG. 9 shows another embodiment of the oxygen sensor of FIG. This embodiment differs from FIG. 1 mainly in the following two points.
(1) In the ceramic separator 18, from the state (FIG. 1) in which the flange-like separator-side support portion 18A integrally protruding outward is formed on the outer peripheral surface at the rear end position in the axial direction. It has changed to the state (FIG. 9) formed in the outer peripheral surface of an intermediate position.
(2) Regarding the fitting (engagement) sequence of the first or second terminal fittings 23 and 33 with respect to the rear end portion of the oxygen detection element 2, first, oxygen detection is performed inside the fitting body 33c of the second terminal fitting 33. The rear end portion of the element 2 is inserted so as to elastically expand the metal fitting main body portion 33c, and then the outer surface of the fixing portion 23c of the first terminal metal fitting 23 extends from the rear end opening of the hollow portion 2a of the oxygen detecting element 2. From a mode of being fitted into the inner wall surface of the hollow portion 2a (FIG. 1: in this case, the axial distance L2 is determined by the second terminal fitting 33 which starts the engagement with the rear end of the oxygen detecting element 2 first). First, the outer surface of the fixing portion 23c of the first terminal fitting 23 is fitted into the inner wall surface of the hollow portion 2a from the rear end opening of the hollow portion 2a of the oxygen detecting element 2, and then the fitting main body portion 33c of the second terminal fitting 33 is inserted. Inside, the rear end of the oxygen detection element 2 is connected to the metal fitting body 33c A mode of insertion in a form that pushes sexually (FIG. 9: In this case, the axial distance L2 is determined by the first terminal fitting 23 that starts the engagement with the rear end of the oxygen detection element 2 first) Has been changed. In FIG. 9, parts that are the same as those in FIG.
[0051]
FIG. 10 shows still another embodiment of the outer cylinder member of FIG. In this embodiment, the rear support surface 16A1 of the outer cylinder side support portion 16A is formed as an inclined surface whose inner diameter becomes smaller toward the front side. Further, the front support surface 18A1 of the separator side support portion 18A is also formed on an inclined surface whose outer diameter becomes smaller toward the front side. The inclination of the rear side support surface 16A1 of the outer cylinder side support portion 16A serves as a guide when the tip of the ceramic separator 18 is inserted inside the outer cylinder side support portion 16A (see FIG. 10A). ). Next, the inclination of the front-side support surface 18A1 of the separator-side support portion 18A serves as a guide when the separator-side support portion 18A of the ceramic separator 18 is inserted into the rear end opening 16d of the outer cylinder member 16 (FIG. 10 (b)). By providing these inclined surfaces 16A1 and 18A1, the ceramic separator 18 can be smoothly inserted into the outer cylinder member 16.
[0052]
The outer cylinder side support portion 16A of FIG. 10A is formed in a flange shape that integrally protrudes inward over the entire circumference on the inner surface of the intermediate portion of the small diameter portion 16c of the outer cylinder member 16. On the other hand, the outer cylinder side intermittent support part 16A '(outer cylinder side support part) in FIG. 10B is intermittently formed in the circumferential direction as in FIG. Specifically, on the inner surface of the intermediate portion of the small-diameter portion 16c, a plurality (four in the figure) of the outer-tube-side intermittent support portions 16A ′ in the form of belt-like protrusions are provided at predetermined intervals (90 ° intervals in the figure) in the circumferential direction. Protruding in the direction. The size, shape, number, and installation interval of the protrusions can be arbitrarily set.
[0053]
In FIG. 10, the axial distance from the front end of the front support surface 18A1 of the separator side support 18A to the front end of the ceramic separator 18 is L3, and the rear support surface of the outer cylinder side support 16A from the rear end of the outer cylinder member 16 When the axial distance to the front end of 16A1 is L4, the relationship L3> L4 is satisfied. With this configuration, the inclined surfaces of the rear support surfaces 16A1 and 16A1 'and the front support surface 18A1 can sufficiently exhibit the function as a guide. 10 that are the same as those in FIG. 4 and FIG. In FIG. 10, both the inclined surfaces, that is, the rear side support surfaces 16A1 and 16A1 'and the front side support surface 18A1 are both formed in a flat shape, but may be curved or the like.
[0054]
FIG. 11 shows an oxygen sensor incorporating a different outer cylinder member. The outer cylinder member 16 shown in FIG. 11 is configured by replacing the front half portion of the small diameter portion 16c and the intermediate portion 16b with the large diameter portion 16a, as compared with the one shown in FIG. That is, the large-diameter portion 16a that covers the oxygen detection element 2 and the ceramic separator 18 from the outside is formed from the front end of the outer cylinder member 16 to the outer cylinder side support section 16A. The length in the axial direction of the large-diameter portion 16 a extends over ½ of the entire length of the outer cylinder member 16 and occupies nearly ½ of the total length of the oxygen sensor 1. As a result, the internal space formed between the outer cylinder member 16 and the oxygen detection element 2 or the ceramic separator 18 is relatively wider than that of FIG. Due to the wide internal space, the outer cylinder member 16 is deformed by an impact caused by a stone splash from the road surface. However, the ceramic separator 18 is not damaged, and a short circuit or the like due to contact between the two terminal fittings 23 and 33 can be avoided. Further, by widening the internal space, even when foreign matter such as exhaust gas is mixed into the introduced atmosphere, the entire space can be diluted to reduce the influence on the sensor output. In FIG. 11, the same reference numerals are given to portions common to FIG. 1, and description thereof is omitted.
[0055]
The structure of the sensor of the present invention described above can be similarly applied to gas sensors other than oxygen sensors, such as HC sensors and NOx sensors. Further, the ceramic separator 18 may be supported indirectly through other members instead of directly at the outer cylinder side support portion 16A.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an oxygen sensor as an embodiment of a gas sensor of the present invention.
FIG. 2 is a partially enlarged longitudinal sectional view of the oxygen sensor of FIG.
FIG. 3 is an exploded perspective view showing an assembled state of the ceramic separator.
FIG. 4 is a plan view and a front half sectional view of an outer cylinder member.
FIG. 5 is a plan view, a bottom view, and a half cross-sectional view of a ceramic separator.
FIG. 6 is an exploded perspective view showing an assembled state of the grommet and the ventilation portion.
7 is a process explanatory view showing an example of an assembly method of the oxygen sensor of FIG. 1;
8A and 8B are a plan view and a front half sectional view showing another embodiment of the outer cylinder member of FIG.
9 is a longitudinal sectional view showing another embodiment of the oxygen sensor of FIG. 1. FIG.
10 is an axial cross-sectional view and a front half sectional view showing still another embodiment of the outer cylinder member of FIG.
FIG. 11 is a longitudinal sectional view of an oxygen sensor incorporating a different outer cylinder member.
[Explanation of symbols]
1 Oxygen sensor (gas sensor)
2 Oxygen detection element (detection element)
2b External electrode layer (electrode layer)
2c Internal electrode layer (electrode layer)
10 Casing
16 Outer cylinder member
16A outer cylinder side support
16A 'Outer cylinder side intermittent support part (outer cylinder side support part)
16A1 Rear support surface
16A1 'rear support surface
16d rear end opening
17 Grommet
18 Ceramic separator
18A Separator side support
18A1 Front support surface
19, 20, 21, 22 Lead wire
23 First terminal fitting (terminal fitting)
33 Second terminal fitting (terminal fitting)
53 Ventilation part
53A filter
K air passage
L1 Axial distance from the rear end of the outer cylinder member to the rear end of the detector
L2 Axial distance from the front end of the separator-side support part to the front end of the engaging part between the terminal fitting and detection element
t Thickness of outer cylinder member

Claims

An axial detection element whose front side is directed to the gas to be measured, a cylindrical outer cylinder member that is arranged in a radial direction outside the detection element, and a rear side of the detection element And a ceramic separator that is disposed inside the outer cylindrical member and has a lead wire insertion hole for inserting a lead wire from the detection element, the ceramic separator protruding from an outer peripheral surface. The separator-side support part is formed, while the outer cylinder member configured in a single layer is formed with an outer cylinder-side support part protruding from the inner peripheral surface, and the separator-side support part is formed on the outer cylinder-side support part. It is supported directly or indirectly through other members ,
A gas sensor comprising a grommet fitted into a rear end opening of the outer cylinder member and in contact with a rear end surface of the ceramic separator directly or indirectly through another member .

The front support surface of the separator-side support portion is formed in an inclined surface whose outer diameter decreases toward the front side, and the rear support surface of the outer cylinder side support portion has an inner diameter toward the front side. The gas sensor according to claim 1, wherein the gas sensor is formed on an inclined surface that becomes small .

The gas sensor according to claim 1, wherein the grommet has a ventilation portion that prevents liquid from being permeated and allows gas to permeate .

The gas sensor according to any one of claims 1 to 3, wherein an air passage is formed in at least one of the separator side support portion and the outer cylinder side support portion .

The gas sensor according to claim 4 , wherein the ventilation path communicates with a ventilation portion provided in the grommet.

The gas sensor according to any one of claims 1 to 5, wherein the outer cylinder side support portion protrudes from an inner circumferential surface of the outer cylinder member and is intermittently formed in a circumferential direction .

Conducted with the electrode layer is formed before Symbol detection element, one end of the terminal fitting taking out electrical output of the detector element to the outside is engaged with the rear end portion of the detection element, forming the other end to the ceramic separator Is connected to the lead wire in the lead wire insertion hole, and the axial distance from the rear end of the outer cylinder member to the rear end of the detection element is L 1, and the front end of the separator-side support portion 7. The relationship according to claim 1, wherein a relationship of L 1 > L 2 is satisfied , where L 2 is an axial distance from the terminal fitting to the front end of the engagement portion between the detection element and the engagement portion . Gas sensor.

The gas sensor according to claim 7, wherein a wall thickness t of the outer cylinder member is 0.3 ≦ t ≦ 0.8 mm .