JP4392084B2 - Lead wire sealing structure and gas sensor using the same - Google Patents

Description

【００１４】
また、これ以外では、
・テトラフルオロエチレン−ヘキサフルオロプロピレン共重合体（ＦＥＰ）
・ポリクロロ−トリフルオロエチレン（ＰＣＴＦＥ）
・エチレン−テトラフルオロエチレン共重合体（ＥＴＦＥ）
・クロロトリフルオロエチレン−エチレン共重合体（ＥＣＴＦＥ）
・ポリふっ化ビニリデン（ポリビニリデンフルオライド；ＰＶＤＦ）
・ポリふっ化ビニル（ポリビニルフルオライド；ＰＶＦ）
等の使用が可能である。
【００１５】
なお、本明細書において「主体」とは、最も重量含有率の高い成分を意味し、必ずしも「５０重量％以上を占める成分」を意味するものではない。
【００１６】
また、本発明のリード線が芯線を樹脂製の外被で覆った状態で複数設けられる場合は、グロメットには各リード線が個別に挿通される複数のリード線挿通孔を形成し、各リード線挿通孔に形成される前記挿通孔封着面と、これに対応するリード線の外被外面との間をそれぞれ封着樹脂層により封着することができる。すなわち、各リード線毎に個別にリード線挿通孔を設けて、各挿通孔封着面と、これに対応するリード線の外被外面との間をそれぞれ封着樹脂層で封着することにより、両者の間のシール性を一層確実なものとすることができる。
【００１７】
さらに、本発明のリード線挿通孔には座ぐり部を形成し、この座ぐり部の内面を前記挿通孔封着面に形成することができる。座ぐり部に対して封着樹脂層が充填形成されることになるので、リード線挿通孔に対する封着樹脂層の位置決めがスムーズかつ確実に行え、挿通孔封着面とリード線の外面との間のシール性を確実に形成することができる。
【００１８】
さらに本発明のグロメットの多孔質体形成部には、少なくとも表層部において樹脂含浸層を形成することができる。グロメットが、例えば多孔質金属すなわち焼結金属又は焼結金属合金等で形成される場合、その内部には多数の空隙を包含する。多孔質金属の焼結度合等によっては、グロメットの多孔質体形成部に分布する空隙がグロメットの後端面側から前端面側にかけて又は外周面側から前端面側にかけて一連の鎖状に連続して並び、外筒の外部と内部とを連通する形態で、気通路が多孔質体形成部に形成される場合がある。この気通路を通じて水等が浸入すると、電気素子が作動不良を起こしたり、作動不能になったりする恐れがある。多孔質体形成部の、少なくとも表層部において樹脂含浸層を形成することによって、この気通路を塞ぎ、水等の浸入を阻止することが可能になる。この場合、樹脂含浸層がグロメットの後端面（すなわち、外筒の開口部から露出している面）を含む形で形成すれば、又は樹脂含浸層がグロメットの外周面を含む形で形成すれば、グロメットの後端面上又は外周面上の空隙を確実に塞いで水等の浸入を効果的に阻止できる。
【００１９】
なお、樹脂含浸層を形成する含浸樹脂として、例えば熱可塑性ポリイミド（以下、ＴＰＩと略記する）樹脂を主体とするものを使用することができる。ＴＰＩ樹脂は、融点が３００℃を超える耐熱性樹脂で、成形加工性に優れている。
【００２０】
さらに本発明は、グロメットが、外筒の開口部内側に配置され、開口部内壁とグロメットの外周面とを接合する全周接合部を、グロメットの周方向に沿って形成することができる。グロメットの周方向（すなわち外筒の開口部の周方向）に沿って、例えばレーザー溶接、抵抗溶接、ろう接等により全周接合部を形成することによって、外筒の開口部内壁とグロメットの外周面との間の隙間を塞ぎ、この隙間からの水等の浸入を効果的に阻止できる。
【００２１】
一方、上記課題を解決するために、第二番目の発明に係るガスセンサは、上記電気素子が、測定対象となるガス中の被検出成分を検出するための検出素子であり、かつ上記第一番目の発明に係るリード線封止構造を用いたことを特徴とする。具体的には、該ガスセンサは、
内側に測定対象となるガス中の被検出成分を検出するための検出素子を配置し、少なくとも一端に開口部を有する外筒と、
前記検出素子と導通され、前記開口部を通って前記外筒の外側に延出されるリード線と、
前記リード線が挿通されるリード線挿通孔を有するとともに、前記開口部内側に配置されて、前記リード線と前記外筒の開口部内壁との間を封止するグロメットとを備え、
前記リード線挿通孔の内面を含む前記グロメットの全体が多孔質金属からなる多孔質体で形成された多孔質体形成部からなり、該多孔質体形成部の内で前記リード線挿通孔の内面を構成する挿通孔封着面と前記リード線の外被との間が、封着樹脂層を熱融着させて接合させた状態で封着されるとともに、
前記挿通孔封着面の表面に露出している前記多孔質体の空隙に前記封着樹脂層が充填されて、前記多孔質体形成部と封着樹脂層とは密着しており、
前記外筒の開口部内壁と前記グロメットの外周面とは、該グロメットの周方向に沿って形成された全周溶接部により接合されていることを特徴とする。
【００２２】
上記第二番目の発明によれば、例えばガスセンサが排気管等に設置される場合のように、長時間高温下に晒されたり、あるいは熱サイクルが繰返し付加されたりするような苛酷な使用環境下でも、ガスセンサはリード線の外面と外筒の開口部内壁との間のシール性を長期にわたって良好に維持することができる。上記のシール性が維持されていれば、ガスセンサへの水等の浸入が防止されるので、検出素子は作動不良や作動不能に陥ることなく機能する。したがって、検出素子からの電気的出力が安定した状態で得られるようになる。
【００２３】
【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を参照して説明する。
図１には、この発明のリード線封止構造を用いて構成された応用電子機器の一実施例として、自動車等の内燃機関から排出される排気ガス中の酸素濃度を検出する酸素センサ１を示している。この酸素センサ１はλ型酸素センサと通称されるガスセンサの代表的なもので、検出素子２（電気素子）が、筒状の主体金具３の内側に設けられた軸状の挿通孔３１内にて固定された構造を有している。そして、主体金具３の外周面に形成された取付ねじ部３ａにより、検出素子２の先端側の検出部Ｄが排気管内に位置するように取り付けられ、排気管内を流れる高温の排気ガスに晒される。なお、主体金具３には、挿通孔３１の軸線方向においてその中間部に所定幅で、かつ外周面から突出する形態で六角断面形状の鍔部３ｄが形成されている。よって、この鍔部３ｄにレンチ等の工具を嵌合させ回転させると、酸素センサ１はガスケット３ｂを介して取付ねじ部３ａにより排気管内の所定位置に取り付けられる。
【００２４】
検出素子２は方形状断面を有する長尺状のもので、図２（ａ）に示すように、それぞれ横長板状に形成された酸素濃淡電池素子２０と、酸素濃淡電池素子２０を所定の活性化温度に加熱するセラミックヒータ２２とが積層されたものとして構成されている。酸素濃淡電池素子２０は、酸素イオン伝導性を有する固体電解質により構成された素子本体層２１を有する。そ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。また、ベースとなるＺｒＯ_２にはＨｆＯ_２が含有されていてもよい。
【００２５】
一方、セラミックヒータ（以下、単にヒータともいう）２２は、高融点金属あるいは導電性セラミックで構成された抵抗発熱体パターン２３をセラミック基体中に埋設した構成を有する。具体的には、ヒータ２２は、第一絶縁層２４と、抵抗発熱体パターン２３と、第一ヒータ本体層２８及び第二ヒータ本体層２９とを備えた多層構造となっている。このうち、第一絶縁層２４は、絶縁性セラミックとしてのアルミナを主体とするアルミナ系セラミックにより、ヒータ２２の板厚方向中間位置に形成されている。また、抵抗発熱体パターン２３は、第一絶縁層２４中に埋設される形でヒータ２２の板面方向に沿って形成されている。そして、第一ヒータ本体層２８及び第二ヒータ本体層２９は、第一絶縁層２４を厚さ方向両側から挟む形で形成されるとともに、それぞれジルコニアを主成分とする酸素イオン伝導性固体電解質で構成されている。
【００２６】
酸素濃淡電池素子２０には、その長手方向における一方の端部（主体金具３の先端より突出する部分）寄りにおいてその両面に、酸素分子解離能を有した多孔質電極２５，２６が形成されている。そして、それら電極２５，２６及びそれらの間に挟まれる固体電解質部分とが検出部Ｄを形成することとなる。なお、以下の記載において、検出素子２の軸方向（長手方向）における主体金具３から突出する側を「前方側（あるいは先端側）」、これと反対側を「後方側（あるいは後端側）」として説明を行う。
【００２７】
酸素濃淡電池素子２０において、多孔質電極２５，２６には、素子本体層２１の長手方向に沿って酸素センサ１の取付基端側（後端側）に向けて延びる電極リード部２５ａ，２６ａがそれぞれ一体に形成されている。このうち、ヒータ２２と対向しない側の電極２５からの電極リード部２５ａは、その末端が電極端子部７として使用される。一方、ヒータ２２に対向する側の電極２６の電極リード部２６ａは、図２（ｃ）に示すように、素子本体層２１を厚さ方向に横切るビア２６ｂにより反対側の素子面に形成された電極端子部７と接続されている。すなわち、酸素濃淡電池素子２０は、両多孔質電極２５，２６の電極端子部７が電極２５側の板面末端に並んで形成される形となっている。上記各電極２５，２６、電極端子部７及びビア２６ｂは、Ｐｔ又はＰｔ合金など、酸素分子解離反応の触媒活性を有した金属粉末のペーストを用いてスクリーン印刷等によりパターン形成し、これを焼成することにより得られるものである。
【００２８】
一方、ヒータ２２の抵抗発熱体パターン２３に通電するためのリード部２３ａ，２３ａも、図２（ｄ）に示すように、ヒータ２２の酸素濃淡電池素子２０と対向しない側の板面末端に形成された電極端子部７，７に、それぞれビア２３ｂを介して接続されている。
【００２９】
図２（ｂ）に示すように、ヒータ２２は、第一ヒータ本体層２８側において、アルミナ系セラミックにより構成される第二絶縁層２７を介して、酸素濃淡電池素子２０の多孔質電極２６側に接合されている。そして、その接合側の多孔質電極（基準電極）２６には、電極リード部２６ａ（これも多孔質である）の一端が接続されるとともに、反対側の多孔質電極（測定電極）２５との間には、多孔質電極２６側に酸素が汲み込まれる方向に微小なポンピング電流が印加される。ここで、電極リード部２６ａは接合された酸素濃淡電池素子２０とヒータ２２との間に挟まれる形で、セラミック素子２の内部に位置し、その末端面はセラミック素子２の取付基端側の端面に露出して、ガス放出口を形成している。そして、上記ポンピングされた酸素は電極リード部２６ａを経てガス放出口から大気中に放出される。これにより、多孔質電極２６内の酸素濃度は大気よりも若干高い値に保持され、酸素基準電極として機能することとなる。一方、反対側の多孔質電極２５は排気ガスと接触する測定電極となる。
【００３０】
このような検出素子２が、図１に示すように、主体金具３に形成された挿通孔３１に挿通されるとともに、挿通孔３１の内面と検出素子２の外面との間が、ガラス（例えば結晶化亜鉛シリカほう酸系ガラス）を主体に構成される封着材層３２により封着されている。そして、検出素子２は、上記封着材層３２等により、先端の検出部Ｄが、排気管に固定される主体金具３の先端より突出した状態で該主体金具３内に固定される。主体金具３の先端部３ｈ外周には、検出素子２の突出部分を覆う金属製の二重のプロテクトカバー６ａ、６ｂがレーザー溶接あるいは抵抗溶接（例えばスポット溶接）等によって固着されている。このカバー６ａ、６ｂは、キャップ状を呈するもので、その先端や周囲に、排気管内を流れる高温の排気ガスをカバー６ａ、６ｂ内に導く開口６ｃ、６ｄが形成されている。一方、主体金具３の後端部は外筒１８の先端部内側に挿入され、その重なり部において周方向に環状に形成された結合部としての溶接部（例えばレーザー溶接部）３５により互いに気密状態で接合されている。
【００３１】
検出素子２の各電極端子部７（４極を総称する）には、第一コネクタＡ、導線８（長手状金属薄板）、さらに第二コネクタ部１３を介して、リード線１４が電気的に接続されている。そして、都合４本のリード線１４は、外筒１８の後端側に形成された開口部１８ｃの内側に嵌め込まれるグロメット５１を貫通して外部に延び、それらの先端に図示しないコネクタプラグが連結されている。さらに各リード線１４のグロメット５１より外部に延びる部分には、これらを収束して保護する保護チューブ１７が被せられている。
【００３２】
図３に、リード線封止構造５０の一例を示す。図３の実施例では、封止構造５０は、グロメット５１、全周溶接部５２及び封着樹脂層５３等より構成される。グロメット５１は、リード線１４が挿通されるリード線挿通孔５１ａが軸方向に貫通して形成されるとともに、外筒１８の開口部１８ｃの内側に嵌入されて、リード線１４と外筒１８の開口部１８ｃ内壁との間を封止（シール）する。またグロメット５１は、多孔質金属で形成された多孔質体形成部５１ｂで全体が構成されている。具体的には、多孔質体形成部５１ｂ（グロメット５１）は、焼結により製造されたステンレススチール（例えばＳＵＳ３０４）からなる。それにより、酸素センサ１が長時間高温下に晒されたり、あるいは熱サイクルを繰返し付加された場合でも、多孔質体形成部５１ｂに形成される空隙ｋが崩壊したりせず、封止構造５０はリード線１４の外面と外筒１８の開口部１８ｃ内壁との間の良好なシール性を維持できる。
【００３３】
図３（ｂ）に示すように、リード線１４は都合４本あり、それぞれのリード線１４は、芯線１４ａの外側をポリテトラフルオロエチレン（ＰＴＦＥ）樹脂チューブ製の外被１４ｂで覆った形態である。グロメット５１には、各リード線１４が個別に挿通される４個のリード線挿通孔５１ａがそれぞれ軸方向に貫通し、かつリード線挿通孔５１ａの軸直交断面において、各リード線１４の中心が単一のピッチ円Ｐ上に等間隔で配置されている。そして、各リード線挿通孔５１ａの内面と、これに対応するリード線１４の外被１４ｂ外面との間は、ＰＦＡ樹脂を主体とする封着樹脂層５３により封着されている。ここで封着樹脂層５３は、熱溶着により各リード線挿通孔５１ａの内面及びリード線１４の外被１４ｂ外面に対して接合された状態で封着される。なお、グロメット５１の各リード線挿通孔５１ａには各々座ぐり部５１ａ’が形成されており、この座ぐり部５１ａ’に対して封着樹脂層５３が充填形成されている。
【００３４】
図３（ｃ）に表された多孔質体形成部５１ｂと封着樹脂層５３との密着面において、座ぐり部５１ａ’（リード線挿通孔５１ａ）の内面に形成される多孔質金属の空隙ｋ（すなわち、多孔質体形成部５１ｂの挿通孔封着面５１０の表面に露出して形成される多孔質金属の空隙ｋ）に封着樹脂層５３が充填されることになる。つまり、封着樹脂層５３は多孔質体形成部５１ｂの挿通孔封着面５１０に対して機械的にかみ合うことから、多孔質体形成部５１ｂと封着樹脂層５３とは強く密着する。そして、座ぐり部５１ａ’（リード線挿通孔５１ａ）の内面と、リード線１４の外被１４ｂ外面との間を封着する形で、封着樹脂層５３が熱溶着により接合され、良好なシール性を有する封止構造を実現している。
【００３５】
ここで、座ぐり部５１ａ’は、図３（ｃ）に示すようにグロメット５１の後端面を起点として軸線方向の長さの略半分まで設けられている。座ぐり部５１ａ’の前端部は前方側が縮径しており、封着樹脂層５３もこの縮径部に対応して、前方側に行くほどその厚みを減少させている。その結果、封着樹脂層５３の軸線方向の長さはグロメット５１のそれよりも短く形成されている。このように、リード線挿通孔５１ａの内面の一部、つまり座ぐり部５１ａ’の軸線方向長さに相当する内面部分が挿通孔封着面５１０を形成している。ただし、多孔質体形成部５１ｂの挿通孔封着面５１０はリード線挿通孔５１ａ（座ぐり部５１ａ’）の内面のうち周方向においては全周にわたって形成されており、挿通孔封着面５１０がリード線１４の全周を囲む形で配置されている。そして、この挿通孔封着面５１０とリード線１４の外被１４ｂ外面との間が封着樹脂層５３により隙間なく封着されることになる。したがって、多孔質体形成部５１ｂの挿通孔封着面５１０をリード線１４の全周を囲む形で配置すれば、挿通孔封着面５１０とリード線１４の外被１４ｂ外面との間のシール性が一層確実になる。勿論、挿通孔封着面５１０はリード線挿通孔５１ａの内面全体を占める場合もある（例えば図７（ｂ）参照）。なお、座ぐり部５１ａ’の上記形状は、グロメット５１を金型プレスにより所期の形状に成形・焼結するときに形成すればよい。
【００３６】
なお、多孔質体形成部５１ｂを形成するステンレススチール（例えばＳＵＳ３０４）の多孔性すなわち空隙の体積率は、２５〜４５％（望ましくは３０〜４０％）、焼結粉末の平均粒子径は、１００〜２５０μｍ（望ましくは１５０〜２００μｍ）の範囲で調整するのがよい。
【００３７】
多孔質金属の焼結度合によっては、グロメット５１の多孔質体形成部５１ｂに分布する空隙ｋがグロメット５１の後端面側から前端面側にかけて又は外周面側から前端面側にかけて一連の鎖状に連続して並び、外筒１８の外部と内部とを連通する形態で、気通路Ｋが多孔質体形成部５１ｂに形成される場合がある（図３（ｃ）参照）。このような場合には、グロメット５１の多孔質体形成部５１ｂの後端面、外周面及び前端面において、それぞれの表層部に樹脂含浸層５１ｂ’を形成（含浸）すれば、この樹脂含浸層５１ｂ’が気通路Ｋを塞ぎ、水等の浸入を阻止する。
【００３８】
グロメット５１が外筒１８の開口部１８ｃ内側に挿入され、グロメット５１（又は外筒１８の開口部１８ｃ）の周方向に沿って、例えばレーザー溶接や抵抗溶接等により全周溶接部５２（全周接合部）を形成し、開口部１８ｃ内壁とグロメット５１の外周面とを接合している。その結果、外筒１８の開口部１８ｃ内壁とグロメット５１の外周面との間の隙間Ｓが塞がれ、この隙間Ｓからの水等の浸入が阻止される。
【００３９】
このような封止構造５０は、例えば次のようにして形成することができる。 まず、図４（ａ）に示すように、金型Ｍの中央部に形成された加圧室に下部パンチＬＰを挿入し、グロメット５１を形成する多孔質金属材料として、ステンレススチールの焼結粉末Ｔを金型Ｍの加圧室に充填する。充填完了後金型Ｍの加圧室に上部パンチＵＰを上方から挿入する。このとき、台座Ｂに固定された４本のピンＦＰが焼結粉末Ｔの充填層に埋設され、この固定ピンＦＰは下部パンチＬＰ及び加圧室を経て上部パンチＵＰをも貫通している。各々の固定ピンＦＰは、リード線１４を挿通するためのリード線挿通孔５１ａと、封着樹脂層５３を形成するための座ぐり部５１ａ’とに対応する形状を有している。そして上部パンチＵＰを加圧すると、多孔質のグロメット成形体５１Ａが得られるので、下部パンチＬＰを上昇させてグロメット成形体５１Ａを抜き出す。なお、加圧成形後のグロメット成形体５１Ａを多孔質体とするため、グロメット成形体５１Ａの密度が４．５〜６．５ｇ／ｃｍ^３となるように以下に述べる調整を行う。すなわち、焼結粉末Ｔの充填時に下部パンチＬＰを昇降させて粉末充填量を調整し、また加圧成形時に上部パンチＵＰのストローク量（グロメット成形体５１Ａの軸線方向寸法に該当する）を調整する。グロメット成形体５１Ａの密度が４．５ｇ／ｃｍ^３未満であると、グロメット成形体５１Ａが充分に固まらずに粉末状態のままとなる場合がある。一方、密度が６．５ｇ／ｃｍ^３を超えると、空隙ｋが充分に残存せず多孔質体が形成されない場合がある。
【００４０】
このようにして得られたグロメット成形体５１Ａは、窒素雰囲気中において、１１２０℃前後の温度で１時間程度焼成される。その結果、図４（ｂ）に示すように、４個のリード線挿通孔５１ａとその座ぐり部５１ａ’とを有し、全体が多孔質体形成部５１ｂで構成されるグロメット焼結体５１Ｂが得られる。
【００４１】
次いで、図５（ａ）に示すように、エマルジョン状態の熱可塑性ポリイミド（以下、ＴＰＩと略記する）樹脂を浸漬槽Ｔに貯留し、必要により溶媒で薄めて樹脂の含有量が２０〜４０重量％（例えば３０重量％）程度の含浸剤Ｅを調整する。浸漬槽Ｔの含浸剤Ｅに図４（ｂ）で作成したグロメット焼結体５１Ｂをどぶ漬けし、多孔質体形成部５１ｂの後端面、外周面及び前端面において、それぞれの表層部に分布する空隙ｋに含浸剤（ＴＰＩ樹脂エマルジョン）Ｅを充填する。
【００４２】
さらに、図５（ｂ）に示すように、常温で真空引きして含浸剤Ｅを多孔質体形成部５１ｂの表層部に含浸させ、２００〜４００℃（例えば３８０℃）で乾燥すると、多孔質体形成部５１ｂの表層部に樹脂含浸層５１ｂ’が形成される。その結果、空隙ｋが一連の鎖状に連続して並び、グロメット焼結体５１Ｂの両端面間又はいずれかの端面と外周面との間に形成されていた気通路Ｋが、空隙ｋへの含浸剤Ｅの充填によって塞がれる（図３（ｃ）参照）。
【００４３】
次に図６（ａ）に示すように、形成すべき封着樹脂層５３（図３）に対応するＰＦＡ樹脂チューブ５３’を用意する。そして、これらＰＦＡ樹脂チューブ５３’を各リード線１４に対し、外被１４ｂの外側に装着する。なお、本実施例では、ＰＦＡ樹脂チューブ５３’の孔内径は、リード線１４の挿通を容易として作業能率を向上させる観点から、リード線１４の外径よりも多少大きく設定されている。他方、ＰＦＡ樹脂チューブ５３’の孔内径をリード線１４の外径よりも少し小さく設定しておくこともできる。この場合は、ＰＦＡ樹脂チューブ５３’をリード線１４上の所定位置に対し、摩擦により容易に位置決めすることができる利点が生ずる。
【００４４】
さて、図５（ｂ）においてグロメット焼結体５１Ｂに埋設されていた４個の中子Ｎを、座ぐり部５１ａ’が形成された側から引き抜くと、グロメット焼結体５１Ｂには軸線方向に貫通する４個のリード線挿通孔５１ａ及び座ぐり部５１ａ’が現れる。そこで、図６（ｂ）に示すように、ＰＦＡ樹脂チューブ５３’を装着した各リード線１４を、それぞれグロメット焼結体５１Ｂのリード線挿通孔５１ａに挿入する。このとき、各ＰＦＡ樹脂チューブ５３’はリード線１４とともにリード線挿通孔５１ａの座ぐり部５１ａ’に入り込むとともに、座ぐり部５１ａ’の先端に形成された縮径部に当たって止められる。これによって、リード線１４がグロメット焼結体５１Ｂに対して位置決め装着される。なお、ＰＦＡ樹脂チューブ５３’の位置決めに際しては、リード線挿通孔５１ａの内径をリード線１４の外径よりも少し小さく設定しておくことが有利であるが、本実施例では前述の通り、リード線１４挿通の作業能率を確保するために、リード線挿通孔５１ａの内径をリード線１４の外径よりも多少大きく設定している。
【００４５】
図６（ｂ）の状態で、全体をＰＦＡ樹脂の軟化点以上に（例えば３６０℃で２０分間）加熱する。これにより図６（ｃ）に示すように、ＰＦＡ樹脂チューブ５３’は座ぐり部５１ａ’の内面すなわち挿通孔封着面５１０と、リード線１４の外被１４ｂの外面とにそれぞれ融着して封着樹脂層５３となり、グロメット５１が形成される。なお、封着樹脂層５３を形成する方法としては、ＰＦＡ樹脂チューブ５３’を用いて形成する方法以外に、次のような方法もある。すなわち、型成形又は加工成形されたリード線挿通孔５１ａ（座ぐり部５１ａ’）にＰＦＡ樹脂の粉末、溶液、エマルジョン等を充填し、上記と同様にＰＦＡ樹脂の軟化点以上に加熱する方法等も採用できる。
【００４６】
そして、図６（ｃ）に示すように、グロメット５１を外筒１８の後端側開口部１８ｃ内側に挿入し、グロメット５１の後端面と外筒１８の開口部１８ｃの後端縁とを位置合わせする。そして、その状態でグロメット５１（又は外筒１８の開口部１８ｃ）の周方向に沿って全周溶接部５２を形成し、開口部１８ｃ内壁とグロメット５１の外周面とを接合する。具体的には、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１８の開口部１８ｃの外周面に対して略水平方向に照射する。この照射位置において、グロメット５１の外周面と外筒１８の開口部１８ｃ内壁とが金属同士融着されるため、グロメット５１の外周面と外筒１８の開口部１８ｃ内壁との間に形成される隙間Ｓが塞がれる。以上のようにして封止構造５０が完成する。
【００４７】
次に、図１に戻り、検出素子２の軸線方向において、封着材層３２の少なくとも一方の側に隣接する形で（本実施例では封着材層３２の、検出部Ｄに近い端面側に隣接して）、多孔質無機物質で構成された緩衝層３８が形成されている。該緩衝層３８は、例えばタルク（滑石）等の無機物質粉末の圧粉成形体あるいは多孔質仮焼体として形成されており、封着材層３２から軸方向に突出するセラミック素子２を外側から包むように支持し、過度の曲げ応力や熱応力が検出素子２に加わるのを抑制する役割を果たす。
【００４８】
また、挿通孔３１の内面と外筒１８の内面との間には、封着材層３２の周囲を取り囲む空隙部３３が、主体金具３の一部を切り欠く形態で形成されている。上記空隙部３３は、主体金具３の挿通孔３１の周方向に形成された環状形態をなし、かつ主体金具３の肉厚方向中間部において挿通孔３１の形成方向に延びる溝部とされている（以下、溝部３３という）。なお、本実施例において溝部３３の底面３３ａは、検出素子２の軸線方向において封着材層３２の対応する端面よりも先端側に位置するものとされている。
【００４９】
この溝部（空隙部）３３は、センサ１に急激な温度変化等が加わった場合に断熱層の役割を果たし、その熱衝撃の影響が封着材層３２に及びにくくなる。また、溝部３３の外側壁部を形成する主体金具部分３ｇが、自身の変形により衝撃を吸収する緩衝部として作用しうるので、封着材層３２への影響を緩和することができる。溝部３３の底面３３ａは、検出素子２の軸線方向において、主体金具３の鍔部３ｄの後端縁３ｅよりも先端側に延びて形成されている。これにより溝部３３は、主体金具３の後端側の外筒１８が接合される肉薄部分３ｆの全長に渡るように形成されることとなる。この場合、溝部３３の底面３３ａは、検出素子２の軸線方向において溶接部３５よりも先端側に位置するものとなる。
【００５０】
以下、酸素センサ１の作動と封止構造５０の作用について説明する。
すなわち、酸素センサ１は、前述の通り主体金具３のねじ部３ａにおいて車両の排気管等に固定され、またコネクタプラグ（図示せず）を介して各リード線１４がコントローラに接続されて使用に供される。そして、その検出部Ｄが排気ガスに晒されると、酸素濃淡電池素子２０の多孔質電極２５（図２）が排気ガスと接触し、酸素濃淡電池素子２０には該排気ガス中の酸素濃度に応じた酸素濃淡電池起電力が生じる。この起電力が、電極リード部２５ａ及び２６ａを経て電極端子部７，７、さらにはリード線１４，１４を介してセンサ出力として取り出される。この種のλ型酸素センサは、排気ガス組成が理論空燃比となる近傍で濃淡電池起電力が急激に変化する特性を示すことから、空燃比検出用に広く使用されるものである。
【００５１】
ここで、酸素センサ１の、例えば自動車における取り付け位置は、エキゾーストマニホルドや車両の足周り部分に近い排気管等であり、かなりの高温となる。しかし、上記封止構造５０においては、グロメット５１の挿通孔封着面５１０を含む部分に形成される多孔質金属の空隙ｋに封着樹脂層５３が充填され、多孔質体形成部５１ｂと封着樹脂層５３とは強く密着している。これにより、長時間高温下に晒される使用環境下でも、上記封止構造５０はリード線の外面と外筒の開口部内壁との間に良好なシール性を長期にわたって維持することができる。
【００５２】
また、上記取り付け位置は、水しぶき等もかかりやすい。しかし、上記封止構造５０においては、グロメット５１の多孔質体形成部５１ｂの表層部に樹脂含浸層５１ｂ’が形成され、気通路Ｋを塞いでいる。さらに、グロメット５１（又は外筒１８の開口部１８ｃ）の周方向に沿って全周溶接部５２が形成され、グロメット５１の外周面と外筒１８の開口部１８ｃ内壁との間の隙間Ｓを塞いでいる。これらにより、水しぶき等のかかりやすい使用環境下でも、上記封止構造５０は良好な防水性能を長期にわたって維持することができる。
【００５３】
図７に、リード線封止構造の変形例を示す。図７（ａ）の封止構造６０では、図３（ａ）の全周溶接部５２に代えて、グロメット５１（又は外筒１８の開口部１８ｃ）の周方向に沿って全周ろう接部５４（全周接合部）が形成されている。具体的には、グロメット５１の軸方向の全長にわたり、その周方向に沿って全周ろう接部５４を形成し、グロメット５１の外周面と外筒１８の開口部１８ｃ内壁との間の隙間Ｓを塞いでいる。なお、図３（ａ）の実施例と共通する部分には同一符号を付して説明を省略する。
【００５４】
図７（ｂ）の封止構造７０では、グロメット５１には、多孔質体形成部５１ｂの外周面の周方向に沿って形成された全周ろう接層５１ｃを介して、非多孔質金属リング５１ｄが一体的に接合され、外筒１８の開口部１８ｃの内側に挿入されている。そして、グロメット５１（又は外筒１８の開口部１８ｃ）の周方向に沿って全周溶接部５２（全周接合部）が形成されている。具体的には、レーザー溶接等によって全周溶接部５２を形成し、グロメット５１（非多孔質金属リング５１ｄ）の外周面と外筒１８の開口部１８ｃ内壁との間の隙間Ｓを塞いでいる。なお、多孔質体形成部５１ｂの外周面と非多孔質金属リング５１ｄの内周面との間の隙間Ｓ’は、グロメット５１（多孔質体形成部５１ｂ）の軸方向の全長にわたり、その周方向に沿って形成された全周ろう接層５１ｃにより、塞がれている。
【００５５】
図７（ｂ）の封止構造７０では、さらに、グロメット５１の中央にやや大径のリード線挿通孔５１ａを形成し、ここに複数のリード線１４を一括して挿通するとともに、それら各リード線１４の各外面と、リード線挿通孔５１ａの内面（挿通孔封着面５１０を構成している）とを一体の封着樹脂層５３により封着する構成としている。なお、図３（ａ）の実施例と共通する部分には同一符号を付して説明を省略する。
【００５６】
なお、図７（ｂ）の封止構造７０において、レーザー溶接等による全周溶接部５２の形成によって、グロメット５１（非多孔質金属リング５１ｄ）の外周面と外筒１８の開口部１８ｃ内壁との間の隙間Ｓのみならず、多孔質体形成部５１ｂの外周面と非多孔質金属リング５１ｄの内周面との間の隙間Ｓ’をも塞がれる場合には、全周ろう接層５１ｃを設けなくても済む場合がある。また、図７（ｂ）の封止構造７０において、全周溶接部５２に代えて、図７（ａ）の実施例に記載された全周ろう接部５４をグロメット５１（非多孔質金属リング５１ｄ）の外周面と外筒１８の開口部１８ｃ内壁との間に形成してもよい。
【００５７】
なお、第二番目の発明は、酸素センサ以外にＨＣセンサ、ＮＯｘセンサ、ＣＯセンサ、ＣＯ_２センサ等他のガスセンサにも適用できる。さらに、第一番目の発明が適用される応用電子機器としては、これらのガスセンサの他、セラミックヒータ、グロープラグ等が挙げられる。
【００５８】
また、多孔質体として、以上に述べた多孔質金属の他、多孔質セラミック等も使用できる。さらに、金属、セラミック等の表面にこれらを溶射することによって多孔質体を構成することもできる。
【図面の簡単な説明】
【図１】 本発明に係るリード線封止構造が適用される応用電子機器の一実施例である酸素センサの一例を示す縦断面図。
【図２】 図１における検出素子の構造を示す説明図。
【図３】 リード線封止構造の一例を示す縦断面図、横断面図及び要部拡大断面模式図。
【図４】 図３のリード線封止構造の組立工程の説明図。
【図５】 図４に続く説明図。
【図６】 図５に続く説明図。
【図７】 リード線封止構造の変形例を示す縦断面図。
【符号の説明】
１ 酸素センサ（ガスセンサ；応用電子機器）
２ 検出素子（電気素子）
２０ 酸素濃淡電池素子
２２ セラミックヒータ（ヒータ）
１４ リード線
１４ａ 芯線
１４ｂ 外被
１８ 外筒
１８ｃ 開口部
５０，６０，７０ リード線封止構造
５１ グロメット
５１ａ リード線挿通孔
５１ａ’ 座ぐり部
５１ｂ 多孔質体形成部
５１ｂ’ 樹脂含浸層
５１０ 挿通孔封着面
５２ 全周溶接部（全周接合部）
５３ 封着樹脂層
５４ 全周ろう接部（全周接合部）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lead wire sealing structure that is applied to applied electronic equipment that includes electrical elements such as various gas sensors, ceramic heaters, glow plugs, and the like and is used at high temperatures. In the present invention, the electrical element is a detection element for detecting a component to be detected in a gas to be measured, such as an oxygen sensor, an HC sensor, and a NOx sensor, and the lead wire seal is provided. The present invention relates to a gas sensor using a stop structure.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as an example of applied electronic equipment, for example, an oxygen sensor that detects an oxygen concentration in exhaust gas discharged from an internal combustion engine such as an automobile is known. In such an oxygen sensor, zirconia (ZrO ₂ ) And the like, and a detection element (electric element) composed of a solid oxide or a metal oxide semiconductor is used. The detection element is arranged inside a metal outer cylinder having an opening, and its output is taken out of the outer cylinder by a lead wire connected to the detection element. A rubber grommet is inserted into the opening of the outer cylinder from which the lead wire is drawn out to prevent water and the like from entering the outer cylinder, and the lead wire penetrates the grommet to the outside of the outer cylinder. It is extended to. The space between the lead wire and the outer cylinder is sealed by the elastic force of the grommet.
[0003]
Here, the oxygen sensor has a high operating temperature of 300 ° C. or higher, and generally employs a structure in which the detection element is forcibly heated by a heater. As a result, the heat generated by the heater overlaps with the heat generated by the heater, the temperature of the outer cylinder rises, and the grommet is exposed to a considerably high temperature due to heat conduction from the outer cylinder. Therefore, in general, the grommet is made of a heat-resistant rubber such as fluorine rubber to ensure the sealing performance between the lead wire and the outer cylinder at a high temperature. Among them, as a sealing structure with further excellent sealing performance at high temperatures, a lead wire is inserted through a grommet made of polytetrafluoroethylene (PTFE) resin, and a cylindrical rubber seal member is disposed outside the grommet. A sealing structure in which the rubber seal member is compressed by crimping the tube toward the rubber seal member is also employed.
[0004]
[Problems to be solved by the invention]
However, the PTFE resin, which is a grommet material, has a considerably high coefficient of thermal expansion. Therefore, in the above conventional sealing structure, the grommet expands when exposed to a high temperature for a long time, and between the grommet and the outer cylinder. An excessive compressive force may act on the rubber seal member in a compressed state, and the rubber seal member may be damaged. Further, a strong caulking force always acts on the rubber seal member in a compressed state, and an expansion force from the grommet is also added to this state at a high temperature. From this, for example, when a heating / cooling cycle (hereinafter simply referred to as a thermal cycle) is repeatedly applied due to, for example, repeated operation of the internal combustion engine, the elasticity of the rubber seal member deteriorates and permanent deformation distortion tends to occur in the rubber seal member. In some cases, the sealing performance may be lowered.
[0005]
An object of the present invention is to provide a lead sealing structure and a gas sensor using the same, which can maintain a good sealing performance for a long period of time even when exposed to a high temperature for a long time or repeatedly subjected to a thermal cycle. Is to provide.
[0006]
[Means for solving the problems and actions / effects]
In order to solve the above problems, the lead wire sealing structure according to the first invention (hereinafter also simply referred to as a sealing structure)
on the inside In gas sensor, ceramic heater or glow plug An outer cylinder in which an electric element is arranged and having an opening at least at one end;
A lead wire that is electrically connected to the electrical element and extends to the outside of the outer cylinder through the opening;
A lead wire insertion hole through which the lead wire is inserted, and a grommet that is disposed inside the opening and seals between the lead wire and the inner wall of the opening of the outer cylinder,
The entire grommet including the inner surface of the lead wire insertion hole comprises a porous body forming portion formed of a porous body made of a porous metal, and the inner surface of the lead wire insertion hole in the porous body forming portion. Of the insertion hole sealing surface and the lead wire Jacket Between , Sealing resin layer In a state of being heat-sealed and bonded As well as being sealed
The sealing resin layer is filled in the voids of the porous body exposed on the surface of the insertion hole sealing surface. The porous body forming part and the sealing resin layer are in close contact with each other. And
The inner wall of the opening of the outer cylinder and the outer peripheral surface of the grommet are joined by an all-around weld formed along the circumferential direction of the grommet.
[0007]
According to the first aspect of the present invention, the portion including the insertion hole sealing surface of the lead wire insertion hole in the grommet into which the lead wire is inserted is composed of a porous body forming portion formed of a porous body, A space between the insertion hole sealing surface and the outer surface of the lead wire is sealed with a sealing resin layer. In other words, in the adhesion surface between the porous body forming portion and the sealing resin layer, the void of the porous body formed on the surface of the through hole sealing surface of the porous body forming portion (that is, the insertion hole sealing) The sealing resin layer is filled into the surface irregularities). Therefore, since the sealing resin layer is mechanically engaged with the insertion hole sealing surface of the porous body forming portion, the porous body forming portion and the sealing resin layer are in close contact with each other. As a result, the sealing structure is located between the outer surface of the lead wire and the inner wall of the opening of the outer cylinder, even under harsh usage environments such as exposure to high temperatures for a long time or repeated thermal cycles. In addition, good sealing performance can be maintained over a long period of time. There are cases where the entire grommet is formed of a porous body such as a porous metal, and cases where a part of the grommet (for example, only the portion including the insertion hole sealing surface) is formed of a porous body. In the latter case, when the insertion hole sealing surface of the porous body forming portion is formed over the entire circumference in the circumferential direction of the inner surface of the lead wire insertion hole, the insertion hole sealing surface surrounds the entire circumference of the lead wire. Thus, the gap between the insertion hole sealing surface and the outer surface of the lead wire is sealed without a gap by the sealing resin layer. Therefore, disposing the insertion hole sealing surface of the porous body forming portion so as to surround the entire circumference of the lead wire ensures the sealing performance between the insertion hole sealing surface and the outer surface of the lead wire. desirable.
[0008]
Furthermore, in the present invention, the porous body forming the porous body forming portion can be a porous metal. By using the porous metal, the voids do not collapse even under the above-mentioned severe use environment, and good sealing properties can be stably maintained over a long period of time. Moreover, since it is a porous metal, the heat | fever accumulate | stored in a grommet can be thermally radiated effectively, and the excessive temperature rise of an outer cylinder can be suppressed.
[0009]
In addition, as a porous metal, stainless steel manufactured by sintering, Al (aluminum), Al alloy, Cu (copper), Cu alloy, or hard chromium plating can be used. In consideration of the usage environment in which the porous metal is exposed to a high temperature for a long time or repeatedly applied with a thermal cycle, the porous metal preferably has a thermal expansion coefficient close to that of the sealing resin.
[0010]
Moreover, regarding the porous metal that forms the porous body forming portion, the average particle diameter of the sintered powder is preferably adjusted in the range of 100 to 250 μm. At this time, the surface roughness in the porous body forming portion is 40 to 100 μm R in terms of the maximum height. _y When expressed in terms of arithmetic average roughness, 5 to 15 μmR _a It can be expressed as. Maximum height R _y And arithmetic mean roughness R _a As for the cut-off value and the evaluation length, the standard value of JIS B0601 (established in 1994) is adopted. Here, the maximum height is 40 μm R _y If it is less than this, the void is too small, and the porous body forming part and the sealing resin layer may not be strongly adhered. On the other hand, the maximum height is 100μmR _y If it exceeds 1, the gap is too large, and the sealing resin layer filled in the gap may be peeled off or dropped off.
[0011]
Furthermore, the sealing resin layer of the present invention is preferably sealed in a state where it is bonded to the through hole sealing surface and the outer surface of the lead wire by heat welding. That is, when sealing is performed by forming a caulking portion on the outer cylinder using a rubber grommet as in the past, the caulking pressure is not necessarily uniformly applied around the lead wire insertion hole. Not limited to this, the sealing performance may be affected. However, if the sealing resin layer is heat sealed, a high sealing property can be obtained with certainty.
[0012]
The sealing resin layer has a certain degree of fluidity (for example, a melt viscosity of 10 by heating). ³ -10 ⁵ It is convenient to use a fluororesin of a type that can be added with a degree of poise) in order to enhance the sealing effect by heat welding. Examples of such a fluorine-based resin include those mainly composed of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (perfluoroalkoxyalkane; hereinafter abbreviated as PFA) resin. This has the general structural formula shown in Chemical Formula 1. However, (-O-Rf) is (-O-CF ₃ ), (-O-C ₂ F ₅ ) Or the like (perfluoroalkoxy group).
[0013]
[Chemical 1]

[0014]
Besides this,
・ Tetrafluoroethylene-hexafluoropropylene copolymer (FEP)
・ Polychloro-trifluoroethylene (PCTFE)
・ Ethylene-tetrafluoroethylene copolymer (ETFE)
・ Chlorotrifluoroethylene-ethylene copolymer (ECTFE)
・ Polyvinylidene fluoride (polyvinylidene fluoride; PVDF)
・ Polyvinyl fluoride (polyvinyl fluoride; PVF)
Etc. can be used.
[0015]
In the present specification, “main body” means a component having the highest weight content, and does not necessarily mean “a component occupying 50% by weight or more”.
[0016]
Further, when a plurality of lead wires of the present invention are provided in a state where the core wire is covered with a resin sheath, a plurality of lead wire insertion holes through which each lead wire is individually inserted are formed in the grommet. The insertion hole sealing surface formed in the line insertion hole and the outer surface of the outer surface of the corresponding lead wire can be sealed with a sealing resin layer. That is, by individually providing lead wire insertion holes for each lead wire, and sealing between each insertion hole sealing surface and the outer surface of the corresponding lead wire outer sheath with a sealing resin layer, respectively The sealing property between the two can be further ensured.
[0017]
Furthermore, a counterbore part can be formed in the lead wire insertion hole of this invention, and the inner surface of this counterbore part can be formed in the said insertion hole sealing surface. Since the sealing resin layer is filled and formed in the spot facing, the positioning of the sealing resin layer with respect to the lead wire insertion hole can be performed smoothly and reliably, and the insertion hole sealing surface and the outer surface of the lead wire It is possible to reliably form a sealing property between them.
[0018]
Furthermore, a resin-impregnated layer can be formed at least in the surface layer portion in the porous body forming portion of the grommet of the present invention. When the grommet is formed of, for example, a porous metal, that is, a sintered metal or a sintered metal alloy, a large number of voids are included therein. Depending on the degree of sintering of the porous metal, etc., the voids distributed in the porous body forming part of the grommet are continuously chained from the rear end surface side of the grommet to the front end surface side or from the outer peripheral surface side to the front end surface side. The air passages may be formed in the porous body forming portion in a form in which the outside and the inside of the outer cylinder communicate with each other. If water or the like enters through this air passage, the electric element may malfunction or become inoperable. By forming the resin-impregnated layer at least in the surface layer portion of the porous body forming portion, it is possible to block this air passage and prevent water and the like from entering. In this case, if the resin-impregnated layer is formed to include the rear end surface of the grommet (that is, the surface exposed from the opening of the outer cylinder), or the resin-impregnated layer includes the outer peripheral surface of the grommet. In addition, it is possible to reliably block the gap on the rear end surface or the outer peripheral surface of the grommet and effectively prevent the entry of water or the like.
[0019]
As the impregnating resin for forming the resin impregnated layer, for example, a resin mainly composed of a thermoplastic polyimide (hereinafter abbreviated as TPI) resin can be used. TPI resin is a heat-resistant resin having a melting point exceeding 300 ° C., and is excellent in molding processability.
[0020]
Further, according to the present invention, the grommet can be formed along the circumferential direction of the grommet, in which the grommet is arranged inside the opening of the outer cylinder and the inner wall of the opening and the outer peripheral surface of the grommet are joined. Along the circumferential direction of the grommet (that is, the circumferential direction of the opening of the outer cylinder), for example, by forming a circumferential joint by laser welding, resistance welding, brazing, etc., the inner wall of the opening of the outer cylinder and the outer circumference of the grommet The gap between the surfaces can be blocked, and the entry of water and the like from this gap can be effectively prevented.
[0021]
On the other hand, in order to solve the above-described problem, a gas sensor according to a second invention is such that the electrical element is a detection element for detecting a component to be detected in a gas to be measured, and the first sensor The lead wire sealing structure according to the invention is used. Specifically, the gas sensor
A detection element for detecting a component to be detected in the gas to be measured is disposed inside, and an outer cylinder having an opening at least at one end;
A lead wire that is electrically connected to the detection element and extends to the outside of the outer cylinder through the opening;
A lead wire insertion hole through which the lead wire is inserted, and a grommet that is disposed inside the opening and seals between the lead wire and the inner wall of the opening of the outer cylinder,
The entire grommet including the inner surface of the lead wire insertion hole comprises a porous body forming portion formed of a porous body made of a porous metal, and the inner surface of the lead wire insertion hole in the porous body forming portion. Of the insertion hole sealing surface and the lead wire Jacket Between , Sealing resin layer In a state of being heat-sealed and bonded As well as being sealed
The sealing resin layer is filled in the voids of the porous body exposed on the surface of the insertion hole sealing surface. The porous body forming part and the sealing resin layer are in close contact with each other. And
The inner wall of the opening of the outer cylinder and the outer peripheral surface of the grommet are joined by an all-around weld formed along the circumferential direction of the grommet.
[0022]
According to the second aspect of the present invention, for example, when a gas sensor is installed in an exhaust pipe or the like, it is exposed to a high temperature for a long time or is repeatedly applied with a heat cycle. However, the gas sensor can maintain the sealing performance between the outer surface of the lead wire and the inner wall of the opening of the outer cylinder well over a long period of time. If the sealing property is maintained, water or the like can be prevented from entering the gas sensor, so that the detection element functions without malfunction or inoperability. Therefore, the electrical output from the detection element can be obtained in a stable state.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to examples shown in the drawings.
FIG. 1 shows an oxygen sensor 1 for detecting the oxygen concentration in exhaust gas discharged from an internal combustion engine such as an automobile, as an embodiment of an applied electronic device constructed using the lead wire sealing structure of the present invention. Show. This oxygen sensor 1 is a typical gas sensor commonly called a λ-type oxygen sensor, and a detection element 2 (electric element) is placed in a shaft-like insertion hole 31 provided inside a cylindrical metal shell 3. And has a fixed structure. And the detection part D of the front end side of the detection element 2 is attached so that it may be located in an exhaust pipe with the attachment screw part 3a formed in the outer peripheral surface of the metal shell 3, and is exposed to the high temperature exhaust gas which flows through the inside of an exhaust pipe. . In addition, the metal shell 3 has a hexagonal cross-sectionally shaped flange portion 3d that has a predetermined width and protrudes from the outer peripheral surface at an intermediate portion in the axial direction of the insertion hole 31. Therefore, when a tool such as a wrench is fitted to the flange portion 3d and rotated, the oxygen sensor 1 is attached to a predetermined position in the exhaust pipe by the attachment screw portion 3a via the gasket 3b.
[0024]
The detection element 2 has an elongated shape having a rectangular cross section. As shown in FIG. 2A, each of the oxygen concentration cell element 20 and the oxygen concentration cell element 20 formed in a horizontally long plate shape has a predetermined activity. The ceramic heater 22 that is heated to the crystallization temperature is laminated. The oxygen concentration cell element 20 has an element body layer 21 made of a solid electrolyte having oxygen ion conductivity. As such a solid electrolyte, Y ₂ O ₃ ZrO in which CaO is dissolved ₂ Is representative, but other alkaline earth metal or rare earth metal oxides and ZrO ₂ A solid solution may be used. The base ZrO ₂ HfO ₂ May be contained.
[0025]
On the other hand, a ceramic heater (hereinafter also simply referred to as a heater) 22 has a configuration in which a resistance heating element pattern 23 made of a refractory metal or a conductive ceramic is embedded in a ceramic substrate. Specifically, the heater 22 has a multilayer structure including a first insulating layer 24, a resistance heating element pattern 23, a first heater body layer 28, and a second heater body layer 29. Among these, the 1st insulating layer 24 is formed in the plate | board thickness direction intermediate position of the heater 22 with the alumina-type ceramic which has as a main the alumina as an insulating ceramic. The resistance heating element pattern 23 is formed along the plate surface direction of the heater 22 so as to be embedded in the first insulating layer 24. The first heater body layer 28 and the second heater body layer 29 are formed so as to sandwich the first insulating layer 24 from both sides in the thickness direction, and are each an oxygen ion conductive solid electrolyte mainly composed of zirconia. It is configured.
[0026]
In the oxygen concentration cell element 20, porous electrodes 25 and 26 having oxygen molecule dissociation ability are formed on both sides near one end in the longitudinal direction (portion protruding from the tip of the metal shell 3). Yes. And these electrodes 25 and 26 and the solid electrolyte part pinched | interposed between them form the detection part D. FIG. In the following description, the side protruding from the metal shell 3 in the axial direction (longitudinal direction) of the detection element 2 is “front side (or front end side)”, and the opposite side is “back side (or rear end side)”. Will be described.
[0027]
In the oxygen concentration cell element 20, electrode leads 25 a and 26 a extending toward the attachment base end side (rear end side) of the oxygen sensor 1 along the longitudinal direction of the element main body layer 21 are provided on the porous electrodes 25 and 26. Each is integrally formed. Among these, the terminal end of the electrode lead portion 25 a from the electrode 25 on the side not facing the heater 22 is used as the electrode terminal portion 7. On the other hand, as shown in FIG. 2C, the electrode lead portion 26a of the electrode 26 on the side facing the heater 22 is formed on the element surface on the opposite side by a via 26b crossing the element body layer 21 in the thickness direction. It is connected to the electrode terminal portion 7. That is, the oxygen concentration cell element 20 is formed such that the electrode terminal portions 7 of the porous electrodes 25 and 26 are formed side by side at the end of the plate surface on the electrode 25 side. Each of the electrodes 25, 26, the electrode terminal portion 7 and the via 26b is formed into a pattern by screen printing or the like using a metal powder paste having catalytic activity of oxygen molecule dissociation reaction such as Pt or Pt alloy, and this is fired. It is obtained by doing.
[0028]
On the other hand, lead portions 23a and 23a for energizing the resistance heating element pattern 23 of the heater 22 are also formed at the end of the plate surface of the heater 22 on the side not facing the oxygen concentration cell element 20, as shown in FIG. The electrode terminal portions 7 and 7 are connected via vias 23b.
[0029]
As shown in FIG. 2B, the heater 22 has a porous electrode 26 side of the oxygen concentration cell element 20 through a second insulating layer 27 made of alumina ceramic on the first heater body layer 28 side. It is joined to. Then, one end of an electrode lead portion 26a (which is also porous) is connected to the porous electrode (reference electrode) 26 on the joining side, and the porous electrode (measurement electrode) 25 on the opposite side is connected to the other end. In the meantime, a minute pumping current is applied in the direction in which oxygen is pumped to the porous electrode 26 side. Here, the electrode lead part 26a is sandwiched between the joined oxygen concentration cell element 20 and the heater 22 and is located inside the ceramic element 2, and its end face is on the attachment base end side of the ceramic element 2. A gas discharge port is formed by being exposed at the end face. The pumped oxygen is released into the atmosphere from the gas outlet through the electrode lead portion 26a. As a result, the oxygen concentration in the porous electrode 26 is maintained at a value slightly higher than that of the atmosphere, and functions as an oxygen reference electrode. On the other hand, the opposite porous electrode 25 serves as a measurement electrode in contact with the exhaust gas.
[0030]
As shown in FIG. 1, such a detection element 2 is inserted into an insertion hole 31 formed in the metal shell 3, and a glass (for example, between the inner surface of the insertion hole 31 and the outer surface of the detection element 2 is used. It is sealed with a sealing material layer 32 mainly composed of crystallized zinc silica borate glass). The detection element 2 is fixed in the metal shell 3 by the sealing material layer 32 and the like in a state in which the detection portion D at the tip projects from the tip of the metal shell 3 fixed to the exhaust pipe. Double metal protective covers 6a and 6b covering the protruding portion of the detection element 2 are fixed to the outer periphery of the tip 3h of the metal shell 3 by laser welding or resistance welding (for example, spot welding). The covers 6a and 6b have a cap shape, and openings 6c and 6d for guiding the high-temperature exhaust gas flowing in the exhaust pipe into the covers 6a and 6b are formed at the tip and the periphery thereof. On the other hand, the rear end portion of the metal shell 3 is inserted inside the front end portion of the outer cylinder 18 and is airtight with each other by a welded portion (for example, a laser welded portion) 35 as a joint portion formed annularly in the circumferential direction at the overlapping portion. It is joined with.
[0031]
A lead wire 14 is electrically connected to each electrode terminal portion 7 (collectively referring to four poles) of the detection element 2 via the first connector A, the conductive wire 8 (longitudinal thin metal plate), and the second connector portion 13. It is connected. The four lead wires 14 extend outside through a grommet 51 fitted inside an opening 18c formed on the rear end side of the outer cylinder 18, and a connector plug (not shown) is connected to the tip of the lead wire 14. Has been. Further, a portion of each lead wire 14 that extends outward from the grommet 51 is covered with a protective tube 17 that converges and protects them.
[0032]
FIG. 3 shows an example of the lead wire sealing structure 50. In the embodiment of FIG. 3, the sealing structure 50 includes a grommet 51, an all-around welded portion 52, a sealing resin layer 53, and the like. The grommet 51 is formed so that a lead wire insertion hole 51 a through which the lead wire 14 is inserted penetrates in the axial direction, and is fitted inside the opening 18 c of the outer tube 18, so that the lead wire 14 and the outer tube 18 The space between the opening 18c and the inner wall is sealed (sealed). Grommet 51 is entirely composed of a porous body forming portion 51b formed of a porous metal. Specifically, the porous body forming part 51b (grommet 51) is made of stainless steel (for example, SUS304) manufactured by sintering. Thereby, even when the oxygen sensor 1 is exposed to a high temperature for a long time or repeatedly applied with a heat cycle, the gap k formed in the porous body forming portion 51b does not collapse, and the sealing structure 50 Can maintain a good sealing property between the outer surface of the lead wire 14 and the inner wall of the opening 18 c of the outer cylinder 18.
[0033]
As shown in FIG. 3 (b), there are four lead wires 14, and each lead wire 14 has a form in which the outer side of the core wire 14a is covered with a jacket 14b made of a polytetrafluoroethylene (PTFE) resin tube. is there. In the grommet 51, four lead wire insertion holes 51a through which the lead wires 14 are individually inserted penetrate the grommet 51 in the axial direction, respectively, and the center of each lead wire 14 is in the axial orthogonal section of the lead wire insertion hole 51a. They are arranged on a single pitch circle P at equal intervals. And between the inner surface of each lead wire insertion hole 51a and the outer surface 14b outer surface of the corresponding lead wire 14 is sealed with a sealing resin layer 53 mainly composed of PFA resin. Here, the sealing resin layer 53 is sealed in a state where it is bonded to the inner surface of each lead wire insertion hole 51a and the outer surface of the outer sheath 14b of the lead wire 14 by heat welding. Each lead wire insertion hole 51a of the grommet 51 is formed with a counterbore part 51a ', and a sealing resin layer 53 is filled in the counterbore part 51a'.
[0034]
In the contact surface between the porous body forming portion 51b and the sealing resin layer 53 shown in FIG. 3 (c), the void of the porous metal formed on the inner surface of the spot facing portion 51a ′ (lead wire insertion hole 51a). The sealing resin layer 53 is filled in k (that is, the void k of the porous metal formed on the surface of the insertion hole sealing surface 510 of the porous body forming portion 51b). That is, since the sealing resin layer 53 is mechanically engaged with the insertion hole sealing surface 510 of the porous body forming portion 51b, the porous body forming portion 51b and the sealing resin layer 53 are in close contact with each other. Then, the sealing resin layer 53 is bonded by heat welding so as to seal between the inner surface of the spot facing portion 51a ′ (lead wire insertion hole 51a) and the outer surface of the outer sheath 14b of the lead wire 14. A sealing structure having a sealing property is realized.
[0035]
Here, the spot facing portion 51a ′ is provided up to approximately half the length in the axial direction starting from the rear end face of the grommet 51 as shown in FIG. 3 (c). The front end portion of the spot facing portion 51a ′ has a reduced diameter on the front side, and the sealing resin layer 53 also decreases in thickness toward the front side corresponding to the reduced diameter portion. As a result, the length of the sealing resin layer 53 in the axial direction is shorter than that of the grommet 51. Thus, a part of the inner surface of the lead wire insertion hole 51a, that is, the inner surface portion corresponding to the axial length of the spot facing portion 51a ′ forms the insertion hole sealing surface 510. However, the insertion hole sealing surface 510 of the porous body forming portion 51b is formed over the entire circumference in the circumferential direction of the inner surface of the lead wire insertion hole 51a (counterbore portion 51a ′). Is arranged so as to surround the entire circumference of the lead wire 14. The space between the insertion hole sealing surface 510 and the outer surface of the outer sheath 14b of the lead wire 14 is sealed without a gap by the sealing resin layer 53. Therefore, if the insertion hole sealing surface 510 of the porous body forming portion 51b is arranged so as to surround the entire circumference of the lead wire 14, the seal between the insertion hole sealing surface 510 and the outer surface of the outer sheath 14b of the lead wire 14 is provided. Sex is more certain. Of course, the insertion hole sealing surface 510 may occupy the entire inner surface of the lead wire insertion hole 51a (see, for example, FIG. 7B). The shape of the spot facing portion 51a ′ may be formed when the grommet 51 is formed and sintered into a desired shape by a die press.
[0036]
In addition, the porosity of stainless steel (for example, SUS304) forming the porous body forming portion 51b, that is, the void volume ratio is 25 to 45% (desirably 30 to 40%), and the average particle diameter of the sintered powder is 100 It is good to adjust in the range of -250 micrometers (desirably 150-200 micrometers).
[0037]
Depending on the degree of sintering of the porous metal, the gaps k distributed in the porous body forming part 51b of the grommet 51 form a series of chains from the rear end face side to the front end face side of the grommet 51 or from the outer peripheral face side to the front end face side. The air passage K may be formed in the porous body forming portion 51b in such a form that it is continuously arranged and the outside and the inside of the outer cylinder 18 communicate with each other (see FIG. 3C). In such a case, the resin-impregnated layer 51b can be formed by forming (impregnating) the resin-impregnated layer 51b 'on each surface layer portion on the rear end surface, outer peripheral surface, and front end surface of the porous body forming portion 51b of the grommet 51. 'Blocks the air passage K and prevents water from entering.
[0038]
The grommet 51 is inserted inside the opening 18c of the outer cylinder 18, and along the circumferential direction of the grommet 51 (or the opening 18c of the outer cylinder 18), for example, an all-around welded part 52 (entire circumference) by laser welding, resistance welding or the like A joint portion) is formed, and the inner wall of the opening 18c and the outer peripheral surface of the grommet 51 are joined. As a result, the gap S between the inner wall of the opening 18c of the outer cylinder 18 and the outer peripheral surface of the grommet 51 is closed, and entry of water or the like from the gap S is prevented.
[0039]
Such a sealing structure 50 can be formed as follows, for example. First, as shown in FIG. 4A, a lower punch LP is inserted into a pressurization chamber formed at the center of the mold M, and a sintered powder of stainless steel is used as a porous metal material for forming the grommet 51. T is filled in the pressurizing chamber of the mold M. After filling is completed, the upper punch UP is inserted into the pressurizing chamber of the mold M from above. At this time, the four pins FP fixed to the pedestal B are embedded in the packed layer of the sintered powder T, and the fixed pin FP penetrates the upper punch UP through the lower punch LP and the pressurizing chamber. Each fixing pin FP has a shape corresponding to a lead wire insertion hole 51 a for inserting the lead wire 14 and a counterbore portion 51 a ′ for forming the sealing resin layer 53. When the upper punch UP is pressurized, a porous grommet molded body 51A is obtained. Therefore, the lower punch LP is raised and the grommet molded body 51A is extracted. In addition, in order to make the grommet molded body 51A after pressure molding into a porous body, the density of the grommet molded body 51A is 4.5 to 6.5 g / cm. ³ The following adjustments are made so that That is, when the sintered powder T is filled, the lower punch LP is moved up and down to adjust the powder filling amount, and the stroke amount of the upper punch UP (corresponding to the axial dimension of the grommet molded body 51A) is adjusted during pressure molding. . The density of the grommet molded body 51A is 4.5 g / cm. ³ If it is less than this, the grommet molded body 51A may not be sufficiently hardened and may remain in a powder state. On the other hand, the density is 6.5 g / cm. ³ Exceeding may cause the voids k not to remain sufficiently to form a porous body.
[0040]
The grommet molded body 51A thus obtained is fired for about 1 hour at a temperature of about 1120 ° C. in a nitrogen atmosphere. As a result, as shown in FIG. 4 (b), the grommet sintered body 51B has four lead wire insertion holes 51a and counterbore portions 51a ′, and is entirely composed of a porous body forming portion 51b. Is obtained.
[0041]
Next, as shown in FIG. 5 (a), a thermoplastic polyimide (hereinafter abbreviated as TPI) resin in an emulsion state is stored in a dipping tank T, and if necessary, the resin content is 20 to 40 wt. % Of the impregnating agent E (for example, 30% by weight) is adjusted. The grommets sintered body 51B created in FIG. 4B is immersed in the impregnating agent E in the immersion tank T, and distributed on the respective surface layer portions on the rear end surface, outer peripheral surface and front end surface of the porous body forming portion 51b. Fill the gap k with the impregnating agent (TPI resin emulsion) E.
[0042]
Furthermore, as shown in FIG. 5 (b), when the surface of the porous body forming portion 51b is impregnated with the impregnating agent E by evacuation at room temperature and dried at 200 to 400 ° C. (for example, 380 ° C.), the porous A resin-impregnated layer 51b ′ is formed on the surface layer portion of the body forming portion 51b. As a result, the gaps k are continuously arranged in a series of chains, and the air passage K formed between the both end faces of the grommet sintered body 51B or between any one end face and the outer peripheral face is formed into the gap k. It is blocked by filling with the impregnating agent E (see FIG. 3C).
[0043]
Next, as shown in FIG. 6A, a PFA resin tube 53 ′ corresponding to the sealing resin layer 53 (FIG. 3) to be formed is prepared. Then, these PFA resin tubes 53 ′ are attached to the outer sides of the jacket 14 b with respect to the lead wires 14. In this embodiment, the inner diameter of the hole of the PFA resin tube 53 ′ is set to be slightly larger than the outer diameter of the lead wire 14 from the viewpoint of facilitating insertion of the lead wire 14 and improving work efficiency. On the other hand, the hole inner diameter of the PFA resin tube 53 ′ can be set slightly smaller than the outer diameter of the lead wire 14. In this case, there is an advantage that the PFA resin tube 53 ′ can be easily positioned by friction with respect to a predetermined position on the lead wire 14.
[0044]
Now, when the four cores N embedded in the grommet sintered body 51B in FIG. 5B are pulled out from the side where the counterbore 51a ′ is formed, the grommet sintered body 51B has an axial direction. Four lead wire insertion holes 51a and counterbore portions 51a 'appear. Therefore, as shown in FIG. 6B, each lead wire 14 fitted with the PFA resin tube 53 ′ is inserted into the lead wire insertion hole 51a of the grommet sintered body 51B. At this time, each PFA resin tube 53 ′ enters the counterbore 51 a ′ of the lead wire insertion hole 51 a together with the lead wire 14, and stops by hitting the reduced diameter portion formed at the tip of the counterbore 51 a ′. Thereby, the lead wire 14 is positioned and attached to the grommet sintered body 51B. When positioning the PFA resin tube 53 ′, it is advantageous to set the inner diameter of the lead wire insertion hole 51a slightly smaller than the outer diameter of the lead wire 14, but in this embodiment, as described above, the lead In order to ensure the work efficiency of inserting the wire 14, the inner diameter of the lead wire insertion hole 51 a is set to be slightly larger than the outer diameter of the lead wire 14.
[0045]
In the state of FIG. 6B, the whole is heated to a temperature higher than the softening point of the PFA resin (for example, at 360 ° C. for 20 minutes). As a result, as shown in FIG. 6C, the PFA resin tube 53 ′ is fused to the inner surface of the spot facing portion 51a ′, that is, the insertion hole sealing surface 510 and the outer surface of the outer sheath 14b of the lead wire 14. It becomes the sealing resin layer 53 and the grommet 51 is formed. In addition to the method of forming the sealing resin layer 53 using the PFA resin tube 53 ′, there is the following method. That is, a method of filling a molded or processed molded lead wire insertion hole 51a (counterbore portion 51a ') with a powder, solution, emulsion, or the like of PFA resin and heating it to the softening point or more of the PFA resin as described above. Can also be adopted.
[0046]
Then, as shown in FIG. 6C, the grommet 51 is inserted inside the rear end side opening 18c of the outer cylinder 18, and the rear end face of the grommet 51 and the rear end edge of the opening 18c of the outer cylinder 18 are positioned. Match. Then, in this state, the entire circumference welded portion 52 is formed along the circumferential direction of the grommet 51 (or the opening 18 c of the outer cylinder 18), and the inner wall of the opening 18 c and the outer peripheral surface of the grommet 51 are joined. Specifically, a YAG (yttrium, aluminum, garnet) laser beam LB emitted from the laser light source L is applied to the outer peripheral surface of the opening 18 c of the outer cylinder 18 in a substantially horizontal direction. At this irradiation position, the outer peripheral surface of the grommet 51 and the inner wall of the opening 18c of the outer cylinder 18 are fused together, so that it is formed between the outer peripheral surface of the grommet 51 and the inner wall of the opening 18c of the outer cylinder 18. The gap S is closed. The sealing structure 50 is completed as described above.
[0047]
Next, returning to FIG. 1, in the axial direction of the detection element 2, it is adjacent to at least one side of the sealing material layer 32 (in this embodiment, the end surface side of the sealing material layer 32 close to the detection portion D). A buffer layer 38 made of a porous inorganic material is formed. The buffer layer 38 is formed, for example, as a compacted body or a porous calcined body of an inorganic substance powder such as talc (talc), and the ceramic element 2 protruding in the axial direction from the sealing material layer 32 is externally provided. It supports so that it may be wrapped, and plays the role which suppresses that excessive bending stress and thermal stress are added to the detection element 2.
[0048]
Further, a gap portion 33 surrounding the periphery of the sealing material layer 32 is formed between the inner surface of the insertion hole 31 and the inner surface of the outer cylinder 18 so as to cut out a part of the metal shell 3. The gap portion 33 has an annular shape formed in the circumferential direction of the insertion hole 31 of the metal shell 3 and is a groove portion extending in the formation direction of the insertion hole 31 in the intermediate portion in the thickness direction of the metal shell 3 ( Hereinafter, it is referred to as a groove portion 33). In the present embodiment, the bottom surface 33 a of the groove 33 is positioned on the front end side with respect to the corresponding end surface of the sealing material layer 32 in the axial direction of the detection element 2.
[0049]
The groove portion (void portion) 33 serves as a heat insulating layer when a sudden temperature change or the like is applied to the sensor 1, and the influence of the thermal shock hardly reaches the sealing material layer 32. Moreover, since the metal shell portion 3g forming the outer wall portion of the groove portion 33 can act as a buffer portion that absorbs an impact by its deformation, the influence on the sealing material layer 32 can be mitigated. The bottom surface 33 a of the groove 33 is formed so as to extend from the rear end edge 3 e of the flange 3 d of the metal shell 3 toward the front end side in the axial direction of the detection element 2. Accordingly, the groove 33 is formed so as to extend over the entire length of the thin portion 3f to which the outer cylinder 18 on the rear end side of the metal shell 3 is joined. In this case, the bottom surface 33 a of the groove portion 33 is located on the tip side of the welded portion 35 in the axial direction of the detection element 2.
[0050]
Hereinafter, the operation of the oxygen sensor 1 and the operation of the sealing structure 50 will be described.
That is, as described above, the oxygen sensor 1 is fixed to a vehicle exhaust pipe or the like at the screw portion 3a of the metal shell 3, and each lead wire 14 is connected to a controller via a connector plug (not shown) for use. Provided. When the detection part D is exposed to the exhaust gas, the porous electrode 25 (FIG. 2) of the oxygen concentration cell element 20 comes into contact with the exhaust gas, and the oxygen concentration cell element 20 has an oxygen concentration in the exhaust gas. A corresponding oxygen concentration cell electromotive force is generated. This electromotive force is taken out as a sensor output through the electrode lead portions 25a and 26a, the electrode terminal portions 7 and 7, and the lead wires 14 and 14. This type of λ-type oxygen sensor is widely used for air-fuel ratio detection because it exhibits a characteristic that the concentration cell electromotive force changes rapidly in the vicinity of the exhaust gas composition reaching the stoichiometric air-fuel ratio.
[0051]
Here, the mounting position of the oxygen sensor 1 in, for example, an automobile is an exhaust manifold or an exhaust pipe close to a leg portion of the vehicle, and the temperature is considerably high. However, in the sealing structure 50, the sealing resin layer 53 is filled in the gap k of the porous metal formed in the portion including the insertion hole sealing surface 510 of the grommet 51, so that the sealing member 50 and the porous body forming portion 51b are sealed. The adhesive resin layer 53 is in strong contact. As a result, the sealing structure 50 can maintain a good sealing property between the outer surface of the lead wire and the inner wall of the opening of the outer cylinder over a long period of time even under a usage environment exposed to a high temperature for a long time.
[0052]
Further, the mounting position is likely to be splashed. However, in the sealing structure 50, the resin impregnated layer 51 b ′ is formed on the surface layer portion of the porous body forming portion 51 b of the grommet 51 to block the air passage K. Further, an all-around welded portion 52 is formed along the circumferential direction of the grommet 51 (or the opening 18c of the outer cylinder 18), and a gap S between the outer peripheral surface of the grommet 51 and the inner wall of the opening 18c of the outer cylinder 18 is formed. It is blocking. As a result, the sealing structure 50 can maintain good waterproof performance for a long period of time even under a usage environment that is likely to be splashed.
[0053]
FIG. 7 shows a modification of the lead wire sealing structure. In the sealing structure 60 in FIG. 7A, instead of the all-around welded portion 52 in FIG. 3A, the all-around brazing joint along the circumferential direction of the grommet 51 (or the opening 18c of the outer cylinder 18). 54 (an all-around joint) is formed. Specifically, the entire brazed portion 54 is formed along the circumferential direction of the grommet 51 in the axial direction, and the gap S between the outer peripheral surface of the grommet 51 and the inner wall of the opening 18c of the outer cylinder 18 is formed. Is blocking. In addition, the same code | symbol is attached | subjected to the part which is common in the Example of Fig.3 (a), and description is abbreviate | omitted.
[0054]
In the sealing structure 70 of FIG. 7B, the grommet 51 is provided with a non-porous metal ring via an entire circumferential brazing layer 51c formed along the circumferential direction of the outer peripheral surface of the porous body forming portion 51b. 51 d is integrally joined and is inserted inside the opening 18 c of the outer cylinder 18. And the all-around welding part 52 (all-around joining part) is formed along the circumferential direction of the grommet 51 (or opening part 18c of the outer cylinder 18). Specifically, the entire circumference welded portion 52 is formed by laser welding or the like, and the gap S between the outer peripheral surface of the grommet 51 (non-porous metal ring 51d) and the inner wall of the opening 18c of the outer cylinder 18 is blocked. . The gap S ′ between the outer peripheral surface of the porous body forming portion 51b and the inner peripheral surface of the non-porous metal ring 51d extends over the entire length in the axial direction of the grommet 51 (porous body forming portion 51b). The entire circumference brazing layer 51c formed along the direction is closed.
[0055]
In the sealing structure 70 of FIG. 7B, a slightly larger diameter lead wire insertion hole 51a is further formed in the center of the grommet 51, and a plurality of lead wires 14 are collectively inserted therein, and each of the leads Each outer surface of the wire 14 and the inner surface of the lead wire insertion hole 51a (which constitutes the insertion hole sealing surface 510) are sealed by an integral sealing resin layer 53. In addition, the same code | symbol is attached | subjected to the part which is common in the Example of Fig.3 (a), and description is abbreviate | omitted.
[0056]
In addition, in the sealing structure 70 of FIG.7 (b), the outer peripheral surface of the grommet 51 (non-porous metal ring 51d) and the inner wall of the opening 18c of the outer cylinder 18 are formed by forming the all-around welded portion 52 by laser welding or the like. When not only the gap S between the gaps but also the gap S ′ between the outer peripheral face of the porous body forming portion 51b and the inner peripheral face of the non-porous metal ring 51d are blocked, In some cases, 51c may not be provided. Moreover, in the sealing structure 70 of FIG.7 (b), it replaces with the perimeter welding part 52, and the grommet 51 (non-porous metal ring) describes the perimeter brazing part 54 described in the Example of Fig.7 (a). 51d) and the inner wall of the opening 18c of the outer cylinder 18 may be formed.
[0057]
The second aspect of the invention is not only an oxygen sensor but also an HC sensor, NOx sensor, CO sensor, CO ₂ It can also be applied to other gas sensors such as sensors. Furthermore, examples of applied electronic devices to which the first invention is applied include ceramic heaters, glow plugs and the like in addition to these gas sensors.
[0058]
In addition to the porous metal described above, porous ceramics can be used as the porous body. Furthermore, a porous body can be formed by spraying these on the surface of metal, ceramic or the like.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an example of an oxygen sensor which is an embodiment of an applied electronic device to which a lead wire sealing structure according to the present invention is applied.
FIG. 2 is an explanatory diagram showing a structure of a detection element in FIG.
FIG. 3 is a longitudinal sectional view, a transverse sectional view, and an enlarged schematic sectional view of an essential part showing an example of a lead wire sealing structure.
4 is an explanatory diagram of an assembly process of the lead wire sealing structure of FIG. 3;
FIG. 5 is an explanatory diagram following FIG. 4;
FIG. 6 is an explanatory diagram following FIG. 5;
FIG. 7 is a longitudinal sectional view showing a modified example of the lead wire sealing structure.
[Explanation of symbols]
1 Oxygen sensor (gas sensor; applied electronic equipment)
2 Detection element (electric element)
20 Oxygen concentration cell element
22 Ceramic heater (heater)
14 Lead wire
14a core wire
14b jacket
18 outer cylinder
18c opening
50, 60, 70 Lead wire sealing structure
51 Grommet
51a Lead wire insertion hole
51a 'counterbore
51b Porous body forming part
51b 'resin impregnated layer
510 Insertion hole sealing surface
52 All-around weld (all-joint joint)
53 Sealing resin layer
54 All-around brazing joint (all-around joint)

Claims (7)

An electric cylinder in the gas sensor, ceramic heater or glow plug is arranged inside, and an outer cylinder having an opening at least at one end;
A lead wire that is electrically connected to the electrical element and extends to the outside of the outer cylinder through the opening;
A lead wire insertion hole through which the lead wire is inserted, and a grommet that is disposed inside the opening and seals between the lead wire and the inner wall of the opening of the outer cylinder,
The entire grommet including the inner surface of the lead wire insertion hole comprises a porous body forming portion formed of a porous body made of a porous metal, and the inner surface of the lead wire insertion hole in the porous body forming portion. between the envelope of the insertion hole sealing surface and the lead wire constituting the can, while being sealed in a state of being bonded by heat fusion sealing resin layer,
The sealing resin layer is filled in the voids of the porous body exposed on the surface of the insertion hole sealing surface, and the porous body forming portion and the sealing resin layer are in close contact with each other,
The lead wire sealing structure characterized in that the inner wall of the opening of the outer cylinder and the outer peripheral surface of the grommet are joined by an all-around weld formed along the circumferential direction of the grommet. The lead wire sealing structure according to claim 1, wherein the sealing resin layer is mainly composed of tetrafluoroethylene-perfluoroalkyl vinyl ether resin. A plurality of the lead wires are provided in a state where the core wire is covered with a resin sheath, and the plurality of lead wire insertion holes through which each lead wire is individually inserted are formed in the grommet,
And the insertion hole sealing surface formed on the lead wire insertion hole, according to claim 1 or 2 between are sealed by each of the sealing resin layer of the jacket outer surfaces of the leads corresponding thereto Lead wire sealing structure. The lead wire sealing structure according to any one of claims 1 to 3 , wherein a counterbore portion is formed in the lead wire insertion hole, and an inner surface of the counterbore portion forms the insertion hole sealing surface. . The lead wire sealing structure according to any one of claims 1 to 4 , wherein a resin-impregnated layer is formed at least in a surface layer portion of the porous body forming portion of the grommet. 6. The lead wire sealing structure according to claim 5 , wherein the resin impregnated layer is mainly composed of a thermoplastic polyimide resin. A detection element for detecting a component to be detected in the gas to be measured is disposed inside, and an outer cylinder having an opening at least at one end;
A lead wire that is electrically connected to the detection element and extends to the outside of the outer cylinder through the opening;
A lead wire insertion hole through which the lead wire is inserted, and a grommet that is disposed inside the opening and seals between the lead wire and the inner wall of the opening of the outer cylinder,
The entire grommet including the inner surface of the lead wire insertion hole comprises a porous body forming portion formed of a porous body made of a porous metal, and the inner surface of the lead wire insertion hole in the porous body forming portion. between the envelope of the insertion hole sealing surface and the lead wire constituting the can, while being sealed in a state of being bonded by heat fusion sealing resin layer,
The sealing resin layer is filled in the voids of the porous body exposed on the surface of the insertion hole sealing surface, and the porous body forming portion and the sealing resin layer are in close contact with each other,
The gas sensor according to claim 1, wherein the inner wall of the opening of the outer cylinder and the outer peripheral surface of the grommet are joined by an all-around weld formed along the circumferential direction of the grommet.

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