JP4190126B2 - Lead wire sealing structure, manufacturing method thereof, and gas sensor using lead wire sealing structure - Google Patents

Description

【００１５】
さらに本発明では、筒状部の外周面のうち、少なくともグロメットの側方部の内周面にて覆われる部分に面荒らし処理を施すことができる。これによって側方部の内周面が、筒状部の外周面に面荒らしによって形成された粗面部の凹凸に食い込みやすくなり、そのアンカー効果により融着強度を向上させてシール性を向上させることができる。また上記補助層が側方部の内周面と筒状部の外周面との間に形成される場合には、補助層が両面の凹凸に入り込みやすくなり、グロメットの側方部の内周面と筒状部の外周面とのシール性がさらに強固になる。なお、筒状部表面の面荒らし処理としては、ショットブラストのほか、ねじ切り、ローレット、スプライン、セレーション等も採用できる。
【００１６】
さらに本発明の筒状部の端部には、グロメットの少なくとも側方部を外側から覆う形で保護カバーが配置されていてもよい。側方部の外周面を覆う保護カバーにより外部からの衝撃による側方部の損傷が防止できるとともに、グロメットが高温下に晒された際の側方部の径方向外側への熱膨張を保護カバーにより抑制することで、グロメットの側方部と筒状部の外周面との間に隙間が生じにくく、安定したシール性が確保される。
【００１７】
ここで、保護カバーには、少なくとも保護カバーの内周面と側方部の外周面とを圧着するグロメット加締め部を形成することができる。グロメット加締め部の形成により側方部の内周面と筒状部の外周面との間のシール性がより一層安定し、かつこのシール性が長期にわたって維持できる。
【００１８】
また、筒状部の軸線方向において開口部に向かう側を後方側として、保護カバーの前端部が、グロメットの側方部の縁よりも前方側に位置し、前端部において保護カバーの内周面が筒状部の外周面に対し前方加締め部によって圧着されることにより、グロメットの側方部を保護する保護カバーの固定を確実なものとすることができる。
【００１９】
さらに本発明のリード線は芯線と、その芯線の外側を覆う外被とを有し、グロメットのリード線挿通孔の内周面と外被の外周面とが直接又は他部材を介して間接的に熱融着させることができる。これによって、グロメットの側方部を筒状部の外周面に対して熱融着させてシール性を確保するときに、グロメットのリード線挿通孔内面とリード線の外被の外周面との間のシール性、すなわちリード線周りのシール性をも同時に確保することが可能となる。つまり、１回の加熱・冷却操作でグロメットの側方部の内周面と筒状部の外周面との間のシール性確保と、グロメットのリード線挿通孔内面とリード線の外被の外周面との間のシール性確保とが同時に達成される。
【００２０】
なお、グロメットのリード線挿通孔の内周面とリード線の外被の外周面との間に、例えばＰＦＡ樹脂を主体とする封着樹脂層を介在させ、この封着樹脂層をリード線挿通孔の内周面及びリード線の外被の外周面に対し熱融着させることができる。このように構成すれば、封着樹脂層がリード線挿通孔の内周面の凹凸に食い込んでそのアンカー効果により、融着強度が向上してリード線周りのシール性が強固となる。
【００２１】
そして、グロメットとリード線の外被とは同材質の耐熱性樹脂（例えばＰＴＦＥ樹脂を主体とする耐熱性樹脂）で構成することができる。グロメット本体部とリード線の外被とが同じ材質であれば、上記した軟化が略同時に進行し、かつ両者は一体となった形態で熱融着されるので、グロメット本体部のリード線挿通孔の内周面とリード線の外被の外周面との間のシール性、すなわちリード線周りのシール性は強固となる。
【００２２】
そして本発明にいう耐熱性樹脂として、フッ素系樹脂又はポリイミド（以下、ＰＩと略記する）樹脂を主体とするものが好適に使用される。このような耐熱樹脂製グロメットを所定温度（例えば軟化温度以上）に加熱すれば、これらの樹脂にある程度の流動性（例えば、溶融粘度にて１０^３〜１０^５ポアズ程度）が付加されて側方部の内周面の凹凸が筒状部の外周面の凹凸に食い込みやすくなる。それより、アンカー効果が高められて、筒状部の外周面に対してグロメットの側方部の内周面を隙間なく止め付ける（熱融着）ことができる。また、グロメットを構成するこれらの樹脂は耐熱性にも優れ、その融点は、例えば上記酸素センサ使用時におけるグロメットの上昇温度よりも高いので、グロメットによる筒状部の開口部のシール性を高温下においても長期にわたって維持できる。
【００２３】
なお、グロメットを構成する耐熱性樹脂として、次のようなフッ素系樹脂を例示できる。
・ポリテトラフルオロエチレン（ＰＴＦＥ）
・テトラフルオロエチレン−パーフルオロアルキルビニルエーテル共重合体（パーフルオロアルコキシアルカン；ＰＦＡ）
・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）
【００２４】
これらの中でもＰＴＦＥ樹脂は、「テフロン」（デユポン社商標）等の商品名でも知られ、融点３２７℃、連続使用温度２６０℃以上と、フッ素系樹脂の中でもとりわけ耐熱性に優れ、化学的に安定であるので、本発明のグロメットを構成する耐熱性樹脂として好適に使用できる。
【００２５】
次に、上記第二の課題を解決するために第二番目の発明に係るリード線封止構造の製造方法は、
前記グロメットの前記本体部となるべき本体成形部と、同じく前記側方部となるべき側方成形部とが一体連結されたグロメット成形体を前記耐熱性樹脂により形成し、
該グロメット成形体の前記本体成形部には、前記リード線を挿通する一方、前記側方成形部の内側には、前記開口部側の端部外周面に前記補助層が形成された前記筒状部を当該端部側から挿入して組立体を構成し、
該組立体を前記耐熱性樹脂の軟化温度以上に加熱し、その後冷却することにより、前記側方成形部を前記筒状部の外周面に対して前記補助層を介して間接的に熱融着させることを特徴とする。
【００２６】
上記第二番目の発明に係るリード線封止構造の製造方法によれば、グロメットの本体部が筒状部の開口部を少なくとも外側から塞ぐとともに、その側方部が筒状部の外周面を覆うことによって、筒状部の開口部を封止して、良好なシール性を有するリード線封止構造が容易に得られる。なお、１回の加熱・冷却操作で、２カ所の熱融着（すなわち、グロメットの側方部の筒状部の外周面への熱融着と、グロメットの本体部とリード線の外被との熱融着）が同時に完成できる場合がある。この場合には、２カ所のシール性確保（すなわち、グロメットの側方部の内周面と筒状部の外周面との間のシール性確保と、グロメットの本体部のリード線挿通孔内周面とリード線の外被の外周面との間のシール性確保）が同時に達成されるので製造コストを低く抑えることができる。
【００２７】
そして、本発明方法は、組立体を構成するグロメット成形体の外側に、少なくとも側方成形部の外周面を覆う保護カバーを被せてから、側方成形部を加熱により径方向に熱膨張させ、その後冷却することにより、側方成形部を筒状部の外周面に対して補助層を介して間接的に熱融着させることができる。側方成形部の径方向の外方側と内方側への熱膨張によって、筒状部の外周面と保護カバーの内周面との間が封着される。そして、側方成形部の外方側への熱膨張は、保護カバーでせき止められるため、冷却過程において反転して内方側に作用（収縮作用）し、その結果、側方部の内周面と筒状部の外周面とは隙間なく密着（熱融着）することができる。
【００２８】
さて、前提となるリード線封止構造として、
筒状部の端に形成された開口部が、該筒状部よりも大なる熱膨張率を有するグロメットにより封止され、かつリード線が前記筒状部の内方側から前記グロメットを貫いて外部に延出する構造を有するとともに、
前記グロメットが、前記開口部に対応して配置されるとともに、前記リード線の挿通孔が形成された本体部と、該本体部に一体化されるとともに、該開口部の縁を経て前記筒状部の外周面側に回り込んでこれに接する側方部とを有する場合がある。
【００２９】
上記のようなリード線封止構造によれば、本体部と側方部とを有するグロメットを用いて、筒状部の開口部を少なくとも外側から上記本体部にて塞ぐとともに、筒状部の外周面を上記側方部にて覆うことによって、開口部に対してグロメットをキャップ状に被冠させている。これにより、筒状部の開口部はグロメットの本体部と側方部とによって全体として包み込まれるように封止されている。そして、グロメットは筒状部よりも熱膨張率が大きい材質で構成されるため、熱収縮の際に側方部の内周面が筒状部の外周面に対して外側から充分に密着させて封止することができる。
【００３０】
そして、筒状部の端部にグロメットの少なくとも側方部を外側から覆う形で保護カバーが配置され、保護カバーに形成された周方向のグロメット加締め部において、グロメットの側方部が保護カバーと筒状部との間で挟圧されることにより、これら保護カバーと筒状部との間を封着することができる。グロメット加締め部を形成することにより、グロメットが熱収縮する際の側方部の内周面と筒状部の外周面との密着がさらに確実になる。
【００３１】
また、上記第一の課題を解決するために第三番目の発明に係るガスセンサは、上記リード線封止構造を有し、かつ前記リード線は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に導通していることを特徴とする。
【００３２】
上記第三番目の発明に係るガスセンサによれば、既に第一発明において述べた如く、グロメットの側方部の内周面と筒状部の外周面との間に隙間が生じにくく、安定したシール性が確保できるリード線封止構造を有している。とりわけガスセンサが自動車用として使用される場合には、その取り付け場所が車両の足回り部分に近い排気管等であるため、雨中走行時や洗車時等に水滴を浴びることがあるが、上記リード線封止構造を有することにより、筒状部内への水滴の浸入を防止できる。したがって、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ことができ、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。
【００３３】
【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。
【００３４】
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。
【００３５】
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。
【００３６】
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。
【００３７】
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。
【００３８】
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。
【００３９】
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２６には、電極リード部２６ａの一端が接続されるとともに、反対側の多孔質電極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。
【００４０】
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の後端部はステンレススチール等の金属製外筒１８（筒状部）の前端部１８Ａ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。
【００４１】
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の後端に形成された開口部１８ｃに対してキャップ状に被冠されてこれを封止するグロメット５１を貫通して外筒１８の外側に延び、それらの後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。
【００４２】
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、補助層５２及び保護カバー５３等より構成される。グロメット５１は、本体部５１Ａと環状に形成された側方部５１Ｂ（以下、環状部５１Ｂという）とを有し、全体としてキャップ状を呈する。グロメット５１の本体部５１Ａは、リード線１４が挿通されるリード線挿通孔５１ａを軸方向に貫通した形態で有し、外筒１８の開口部１８ｃと同心状に設けられている。側方部５１Ｂは、本体部５１Ａと一体的に連結され、その内周面が外筒１８の後端部１８Ｃ外周面に接している。一方、外筒１８は上記前端部１８Ａと、前端部１８Ａの後方に位置する中間部１８Ｂと、後端に開口部１８ｃを有する後端部１８Ｃと、中間部１８Ｂと後端部１８Ｃとを連結する縮径部１８Ｄとを有し、全体として細長い筒状を呈する。後端部１８Ｃは、中間部１８Ｂよりも小径に形成され、その外周面がグロメット５１の環状部５１Ｂの内周面に接しつつグロメット５１の軸線方向に挿入されている。
【００４３】
そして、グロメット５１の本体部５１Ａが外筒１８の開口部１８ｃを少なくとも外側から塞ぐとともに、環状部５１Ｂの内周面が外筒１８の後端部１８Ｃの外周面と接することによって、グロメット５１が開口部１８ｃに対してキャップ状に被冠されて開口部１８ｃを封止している。
【００４４】
グロメット５１の本体部５１Ａと環状部５１Ｂとは、外筒１８の後端部１８Ｃの外側において一体的に連結されており、かつ、ＰＴＦＥ樹脂を用いた加圧成形によって一体構成されている。ＰＴＦＥ樹脂は、融点３２７℃でフッ素系樹脂の中でも耐熱性が良好で、化学的にも安定であるといった優れた物性を備えており、加熱によりある程度の流動性を付加できる。
【００４５】
外筒１８は、自身の後端部１８Ｃ外周面がグロメット５１の環状部５１Ｂの内周面と接しながら、グロメット５１と中心軸線同士が略一致する形態で挿入されて、外筒１８の後端部１８Ｃ内周面の内側には広い内部空間１８１（空間部）が形成されている。この内部空間１８１には、検出素子２の各電極端子部７とリード線１４とを接続するために、既に述べた第一コネクタＡ、導線８、第二コネクタ部１３等が収容され、これらの組立用又は配置用のスペースとして利用される。なお、組立時のグロメット５１の環状部５１Ｂの内径と外筒１８の後端部１８Ｃの外径とのはめ合いが締まりばめで行われる場合に、外筒１８の後端部１８Ｃ外周面が環状部５１Ｂの内周面にスムーズに挿入されるように、外筒１８の外周面後端にその周方向に沿ってアール状（曲面状）又はテーパ状（平面状）の面取り１８ｅを設けている。
【００４６】
そして、このように外筒１８が挿入されたグロメット５１を軟化温度以上に加熱すれば、ＰＴＦＥ樹脂に流動性が付加されて環状部５１Ｂの内周表面部分の凹凸が外筒１８の外周表面部分の凹凸に食い込みやすくなり、アンカー効果が高められて、加熱後に冷却されることで外筒１８に対してグロメット５１の環状部５１Ｂを熱融着させることができる。そして、ＰＴＦＥ樹脂（グロメット５１）はステンレススチール（外筒１８）よりも熱膨張率が大きいので、グロメット５１の環状部５１Ｂは、加熱後の冷却時の熱収縮の際外筒１８との熱膨張率の差により外筒１８の外周面を隙間なく覆い、環状部５１Ｂの内周面と外筒１８の外周面との接触部において、安定したシール性が確保される。さらに、グロメット５１をＰＴＦＥ樹脂で構成しているので、その熱融着によってグロメット５１の環状部５１Ｂ内周面と外筒１８の外周面との密着性が確保され、外筒１８の開口部１８ｃを容易に封止することができる。なお熱収縮の際グロメット５１には、外筒１８との熱膨張率の差に基づき外筒１８の外周面を加圧するように、詳しくは外筒１８の外周面を径方向内側に加圧するように作用する収縮力（締付力）が発生する場合がある。この収縮力によっても、環状部５１Ｂの内周面と外筒１８の外周面との接触部において、一層安定したシール性が確保される。
【００４７】
次に図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の本体部５１Ａ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、リード線外被１４Ｂはグロメット５１と同材質のＰＴＦＥ樹脂で構成されている。
【００４８】
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外面とは熱融着されている。グロメット本体部５１Ａとリード線外被１４ＢとについてはがともにＰＴＦＥ樹脂製なので、グロメット５１を所定温度（例えば軟化温度以上）に加熱した後冷却すると、軟化が両者略同時に進行し、かつ両者は熱融着され、グロメット本体部５１Ａのリード線挿通孔５１ａ内面とリード線１４の外被１４Ｂ外面との間のシール性が強固となる。
【００４９】
外筒１８の後端部１８Ｃ外周面のうちグロメット５１の環状部５１Ｂの内周面に覆われる部分の表面にショットブラストによる面荒らし処理を施し、粗面部１８ｄ（面荒らし部）を形成している。これによって環状部５１Ｂの内周面が外筒１８の外周面の粗面部１８ｄの凹凸に食い込みやすくなり、そのアンカー効果により熱融着による融着強度を向上させている。
【００５０】
なお、上記アンカー効果を高めるためにはこれらの面荒らし処理によって、外筒１８の粗面部１８ｄの表面粗さが最大高さＲ_ｙで１５μｍＲ_ｙ以上（基準長さと評価長さとはいずれもＪＩＳ Ｂ０６０１−1994の標準値を採用）とするのが好ましい。
【００５１】
外筒１８の粗面部１８ｄにはＰＦＡ樹脂の補助層５２がコーティングされている。この補助層５２は、環状部５１Ｂ（樹脂製）と外筒１８（金属製）とで材質を異にするときでも、補助層５２が環状部５１Ｂの内周面の凹凸と外筒１８の粗面部１８ｄの凹凸との間に形成される微小な隙間を埋めるように入り込んで両者の馴染みが良くなり、アンカー効果が発揮され、熱融着による融着強度が向上する。このとき、ＰＦＡ樹脂はＰＴＦＥ樹脂よりも軟化しやすく流動性もよいので、グロメット５１の環状部５１Ｂの内周表面の凹凸及び外筒１８の外周表面の凹凸に入り込みやすくアンカー効果が大きくなると予測される。
【００５２】
グロメット５１の外側には、グロメット５１の本体部５１Ａの後端面の一部と環状部５１Ｂの外周面とを覆い、全体としてキャップ状を呈する保護カバー５３が被せられている。そして、保護カバー５３の後端寄りには、保護カバー５３の内周面と環状部５１Ｂの外周面とを圧着する、断面円環状のグロメット加締め部５３ａを保護カバー５３の周方向に沿って全周にわたり連続的に形成している。また、保護カバー５３の前端部がさらに前方に延びて外筒１８の中間部１８Ｂ外周面を覆うとともに、グロメット加締め部５３ａの前方側において、保護カバー５３の内周面と外筒１８の中間部１８Ｂ外周面とを圧着する、断面円環状の外筒加締め部５３ｂ（前方加締め部）を保護カバー５３の周方向に沿って全周にわたり連続的に形成している。
【００５３】
グロメット５１の環状部５１Ｂの外周面と外筒１８の中間部１８Ｂの外周面とを覆う保護カバー５３を設けることにより、外部からの衝撃による環状部５１Ｂの損傷が防止されるとともに、環状部５１Ｂが高温下に晒された際に径方向外側へ向かって熱膨張するのを抑制している。そして、グロメット加締め部５３ａの形成によりグロメット５１の環状部５１Ｂの内周面と外筒１８の後端部１８Ｃの外周面との間のシール性が向上し、かつこのシール性が長期にわたって維持できる。また、外筒加締め部５３ｂを形成することにより、保護カバー５３の固定を確実なものにすることができる。
【００５４】
なお、グロメット加締め部５３ａと外筒加締め部５３ｂとはともに断面円環状に形成したが、断面多角形状に形成してもよい。断面円環状の場合には、保護カバー５３と環状部５１Ｂ又は外筒１８との接触面が円筒状面になるのでシール性（気密性）に優れており、断面多角形状の場合には、保護カバー５３と環状部５１Ｂ又は外筒１８との接触面が角筒状面になるので接触面でのズレ（相対回転）が生じにくい利点がある。したがって、両者の長所を活かすため、グロメット加締め部５３ａと外筒加締め部５３ｂとで断面円環状と断面多角形状とを組み合わせて使用してもよい。また、両加締め部５３ａ，５３ｂは周方向に沿って断続的に形成することもできるが、保護カバー５３の固定を確実にするため、全周にわたり形成するのが望ましい。
【００５５】
このような封止構造５０は、例えば次のような製造工程によって形成することができる。
＜成形工程＞
まず、グロメット５１は、ＰＴＦＥ樹脂粉末Ｔの加圧一体成形により形成される。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を構成する樹脂として、ＰＴＦＥ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ＰＴＦＥ粉末Ｔの充填層を貫通し、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に対応する形状を有している。
【００５６】
そして上部パンチＵＰを加圧すると、図４（ｂ）に示すように、全体がＰＴＦＥ樹脂で構成され、キャップ状形態のグロメット成形体５１１が得られる。このグロメット成形体５１１は、４個のリード線挿通孔５１ａを有する本体成形部５１１Ａと、その本体成形部５１１Ａと一体的に形成される環状成形部５１１Ｂ（側方成形部）とから構成されている。
【００５７】
＜外筒挿入工程＞
次いで、図５（ａ）に示すように、グロメット成形体５１１の環状成形部５１１Ｂの内周面と外筒１８の後端部１８Ｃ外周面とを接触させながら、外筒１８をグロメット成形体５１１に中心軸線同士が略一致するようにして挿入する。このとき、外筒１８の後端部１８Ｃ外周面には、ショットブラストによる面荒らし処理を施し粗面部１８ｄを形成するとともに、この粗面部１８ｄにＰＦＡ樹脂の補助層５２がコーティングされている。また、加熱後の常温での締め代を確保するために、図５（ａ）におけるグロメット成形体５１１の環状成形部５１１Ｂの内径と外筒１８の後端部１８Ｃの外径とのはめ合いを締まりばめで行う場合がある。そこで、外筒１８の外周面後端にその周方向に沿ってアール状（曲面状）又はテーパ状（平面状）の面取り１８ｅを設け、外筒１８の後端部１８Ｃ外周面が環状成形部５１１Ｂの内周面にスムーズに挿入されるようにしている。
【００５８】
＜リード線挿通工程＞
さらに、図５（ｂ）に示すように、グロメット成形体５１１の本体成形部５１１Ａに形成された４個のリード線挿通孔５１ａに、芯線１４Ａの外側をＰＴＦＥ樹脂チューブ製の外被１４Ｂで覆った形態の４本のリード線１４をそれぞれ軸方向に挿通する。これにより、グロメット成形体５１１に外筒１８とリード線１４とが組み合わされて組立体６００となる。なお、外筒１８の後端部１８Ｃ内周面の内側には内部空間１８１が形成されている。
【００５９】
＜保護カバー被覆及び加締め工程＞
次に、図６（ａ）に示すように、グロメット成形体５１１に対してキャップ状形態の保護カバー５３を軸線方向後方外側から被せる。そして、保護カバー５３の後端寄りに、断面円環状のグロメット加締め部５３ａを保護カバー５３の周方向に沿って形成し、保護カバー５３の内周面と環状部５１Ｂの外周面とを圧着する。また、グロメット加締め部５３ａの前方側において、断面円環状の外筒加締め部５３ｂを保護カバー５３の周方向に沿って形成し、保護カバー５３の内周面と外筒１８の中間部１８Ｂ外周面とを圧着する。以上により、組立体６００に保護カバー５３が被せられるとともに保護カバー５３には加締め部５３ａ，５３ｂが形成され、加締め組立体６５０ができあがる。
【００６０】
＜熱融着工程＞
以上のようにして組み立てられた加締め組立体６５０を、加熱炉においてＰＴＦＥ樹脂の軟化温度以上（例えば３４０〜３５０℃）に所定時間（例えば２〜３時間）加熱し、その後徐冷すると、封止構造５０が完成する。これによって、図６（ｂ）に示すように、グロメット成形体５１１はＰＴＦＥ粉末Ｔが軟化して焼結しグロメット５１となる。このとき、補助層５２のＰＦＡ樹脂はＰＴＦＥ樹脂よりも軟化しやすく流動性もよいので、環状部５１Ｂの内周面の凹凸と外筒１８の粗面部１８ｄの凹凸との間に形成される微小な隙間を埋めるように入り込んで両者の馴染みを良くし、アンカー効果を発揮する。さらに、ＰＴＦＥ樹脂はステンレススチールよりも熱膨張率が大きいので、グロメット５１の環状部５１Ｂは、熱収縮の際熱膨張率の差により外筒１８の外周面を隙間なく覆い、環状部５１Ｂの内周面と外筒１８の外周面との接触部（熱融着部）において、安定したシール性が確保される。なお、この収縮作用によってグロメット５１の環状部５１Ｂは外筒１８に対して締まりばめ状態となる場合もある。また、グロメット５１の本体部５１Ａとリード線１４の外被１４ＢとがともにＰＴＦＥ樹脂製なので、熱融着により両者は一体となっている。
【００６１】
この熱融着工程における挙動をさらに詳細に示したのが、図１４である。図１４（ａ）の加締め組立体６５０において、環状成形部５１１Ｂの内周面と外筒１８の外周面（又は補助層５２のコーティング外面）との間には、外筒１８の環状成形部５１１Ｂへの挿入に伴い径方向の隙間ｔ1（以下、内側の隙間という）が形成される。一方、環状成形部５１１Ｂの外周面と保護カバー５３の内周面との間には、保護カバー５３による組立体６００の被覆及びグロメット加締め部５３ａの形成に伴う径方向の隙間ｔ2（以下、外側の隙間という）が形成されている。なお、外筒挿入工程において、環状成形部５１１Ｂの内径と外筒１８の後端部１８Ｃの外径とのはめ合いを締まりばめ（圧入）で行う場合は、内側の隙間ｔ1は０となる。ただし、内外の隙間ｔ1，ｔ2には、それぞれ粗面部１８ｄに代表されるような表面上の凹凸の山と谷の間の空間等も含まれるものとする。
【００６２】
加熱炉におけるＰＴＦＥ樹脂の軟化温度以上への加熱によって、グロメット成形体５１１は軟化して焼結し、図１４（ｂ）に示すグロメット５１となる。このときグロメット５１の環状部５１Ｂは、熱膨張により上記隙間ｔ1，ｔ2を埋めて外筒１８の外周面と保護カバー５３の内周面との間を封着（熱融着）する。しかも、外側の隙間ｔ2を埋めてさらに外側へ熱膨張しようとする環状部５１Ｂは、保護カバー５３でせき止められるため内側の隙間ｔ1を埋めるように作用する。したがって、環状部５１Ｂの内側へ向かう上記膨張力と、補助層５２の介在とが、環状部５１Ｂの熱融着に相乗的に作用して、内側の隙間ｔ1は、面荒らしによる粗面部１８ｄ等の表面の凹凸を含めて確実に埋められ、環状部５１Ｂの内周面と外筒１８の外周面とは隙間なく密着する。
【００６３】
その後の冷却によっても、グロメット５１と外筒１８との熱膨張率の差により、環状成形部５１Ｂの内周面と外筒１８の外周面との間には隙間は発生せず、図１４（ｃ）に示すように両面が密着した状態を維持する。なお、環状部５１Ｂの外周面と保護カバー５３の内周面との間には、グロメット５１の熱収縮に伴う径方向の隙間ｔ2’が再び形成される場合があるが、この隙間ｔ2’は酸素センサ１の気密性とは関係しないので、加締め組立体６５０から保護カバー５３が外れたりしない限り問題とはならない。
【００６４】
例えば、グロメット加締め部５３ａの形成によって内側の隙間ｔ1を充分小さくできれば、外筒挿入工程において、環状成形部５１１Ｂの内径と外筒１８の後端部１８Ｃの外径とのはめ合いを締まりばめ（圧入）で行わなくても済む場合がある。また例えば、保護カバー５３による組立体６００の被覆によって外側の隙間ｔ2を充分小さくできれば、グロメット加締め部５３ａの形成を省略できる場合がある。このように、グロメットに用いる材料（材質）の選定、グロメットの形状及び外筒とのはめ合い等の工夫により、総熱膨張代ｔと内外の隙間ｔ1，ｔ2とを適切に管理すれば、製造工程を簡略化することができる。
【００６５】
以上の製造工程において、図５（ａ）の＜外筒挿入工程＞と、図５（ｂ）の＜リード線挿通工程＞とは順序を入れ替えても差し支えない。また、＜保護カバー被覆工程＞は、＜外筒挿入工程＞及び＜リード線挿通工程＞の少なくとも一方よりも先行して実施することができる。なお、図４（ｂ）において、グロメット成形体５１１の４個のリード線挿通孔５１ａは、型成形時に固定ピンＦＰを貫通させておく以外に、型成形後にドリル等によって穴開けしてもよい。
【００６６】
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、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。
【００６７】
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。
【００６８】
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。
【００６９】
図７〜図１３に、図３のリード線封止構造及び図４〜図６の製造工程の変形例を示す。まず第一変形例について、図７にその封止構造を、図８及び図９にその製造工程の変更部分をそれぞれ示す。図７のリード線封止構造６０では、図３のグロメット５１の形状を次のように変更している。すなわち、グロメット５１の本体部５１Ａが軸方向前方側に延長され、外筒１８の開口部１８ｃ内に深く入り込んでいる。さらに、外筒１８の後端部１８Ｃがグロメット５１の軸線方向に挿入されると、外筒１８の後端部１８Ｃ内周面とグロメット５１の本体部５１Ａ外周面との間には、内部空間１８１に代わって環状の隙間１８２が形成される。この環状の隙間１８２は、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が繰返し付加されたりしてグロメット本体部５１Ａが熱膨張したときの膨張代として機能する。また、グロメット５１の本体部５１Ａが外筒１８の開口部１８ｃ内に深く入り込んでいるので、リード線挿通孔５１ａを長く設けることができ、リード線１４同士の短絡や絡みつき等をより確実に防止できる。図７（ａ）では、リード線挿通孔５１ａを第二コネクタ部１３の収納スペースとしても利用した場合を例示している。なお、図３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。
【００７０】
図７のリード線封止構造６０を得るため、図４及び図５の製造工程を図８及び図９の如く変更している。図４（ａ）における金型Ｍの加圧室の形状を図８（ａ）の如く変更すると、図８（ｂ）に示すように本体成形部５１１Ａが軸方向に延長された形状のグロメット成形体５１１が得られる。グロメット成形体５１１の環状成形部５１１Ｂの内周面と密着させながら、外筒１８の後端部１８Ｃ外周面をグロメット成形体５１１の軸線方向後方側に挿入すると、外筒１８の後端部１８Ｃ内周面とグロメット成形体５１１の本体成形部５１１Ａ外周面との間に環状の隙間１８２が形成される。なお、以後の組立は図６と同様に行う（図９参照）。
【００７１】
次に第二変形例について、図１０にその封止構造を、図１１にその製造工程の変更部分をそれぞれ示す。図１０のリード線封止構造７０では、図３のグロメット５１の形状を次のように変更している。すなわち、グロメット５１の本体部５１Ａが軸方向前方側に延長され、本体部５１Ａの一部が外筒１８の開口部１８ｃに入り込んでいる。したがって、外筒１８の後端部１８Ｃがグロメット５１の軸線方向に挿入されると、外筒１８の後端部１８Ｃ内周面とグロメット５１の本体部５１Ａ外周面との間には、内部空間１８１に代わって環状の隙間１８２が形成される。図１０の環状の隙間１８２も図７と同様に、グロメット本体部５１Ａが熱膨張したときの膨張代として機能する。なお、図３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。
【００７２】
図１０のリード線封止構造７０を得るため、図５の製造工程を図１１の如く変更している。図４で得られたグロメット成形体５１１の環状成形部５１１Ｂは、図１１（ａ１）に示すように、その本体成形部５１１Ａと環状成形部５１１Ｂとの連結部を中心として外側方向へ略１８０度にわたってラッパ状に開くように曲げ（折り返し）加工される。その結果、図１１（ａ２）に示すように本体成形部５１１Ａが軸方向に延長された形状のグロメット成形体５１１が得られる。グロメット成形体５１１の環状成形部５１１Ｂの内周面と密着させながら、外筒１８の後端部１８Ｃ外周面をグロメット成形体５１１の軸線方向後方側に挿入すると、外筒１８の後端部１８Ｃ内周面とグロメット成形体５１１の本体成形部５１１Ａ外周面との間に環状の隙間１８２（図１０参照）が形成される。なお、以後の組立は図５（ｂ）及び図６と同様に行う。
【００７３】
さらに第三変形例について、図１２にその封止構造を、図１３にその製造工程の変更部分をそれぞれ示す。図１２のリード線封止構造８０では、図３のグロメット５１の形状を次のように変更している。すなわち、グロメット５１の本体部５１Ａが軸方向前方側に延長され、本体部５１Ａの一部が外筒１８の開口部１８に入り込んでいる。したがって、外筒１８の後端部１８Ｃがグロメット５１の軸線方向に挿入されると、外筒１８の後端部１８Ｃ内周面とグロメット５１の本体部５１Ａ外周面との間には、内部空間１８１に代わって環状の隙間１８２が形成される。図１２の環状の隙間１８２も図１０と同様に、グロメット本体部５１Ａが熱膨張したときの膨張代として機能する。ただし、図１２における環状の隙間１８２の径方向寸法（外筒１８の後端部１８Ｃ内周面とグロメット５１の本体部５１Ａ外周面との間の距離）は図１０よりも小に形成されている。なお、図３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。
【００７４】
図１２のリード線封止構造８０を得るため、図５の製造工程を図１３の如く変更している。図１３（ａ）に示すように、図４で得られたグロメット成形体５１１の環状成形部５１１Ｂの内周面と密着させながら、外筒１８の後端部１８Ｃ外周面をグロメット成形体５１１の軸線方向後方側に挿入するとき、外筒１８の後端がグロメット成形体５１１の本体成形部５１１Ａの前方側端面よりもさらに後方側に至る迄挿入する（図１３（ｂ））。すなわち、外筒１８の後端はグロメット成形体５１１の本体成形部５１１Ａに刺さり込むまで挿入される。そして、組立後の加熱・徐冷の際、外筒１８（ステンレススチール）とグロメット成形体５１１（ＰＴＦＥ樹脂）との熱膨張率の差に応じて、外筒１８の後端部１８Ｃ内周面とグロメット５１の本体部５１Ａ外周面との間に環状の隙間１８２（図１２参照）が形成される。なお、以後の組立は図６と同様に行う。
【００７５】
以上の各実施例において、側方部５１Ｂは円環状を呈する環状部として形成したが、外筒１８の外形に対応して角筒状、楕円筒状等他の形状であってもよい。
【００７６】
なお、第四番目の発明は、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、第一番目ないし第三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。
【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半断面図及び横断面図。
【図４】図３のリード線封止構造の製造工程の説明図。
【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第一変形例を示す縦半断面図。
【図８】図７のリード線封止構造の製造工程の説明図。
【図９】図８に続く説明図。
【図１０】リード線封止構造の第二変形例を示す縦半断面図。
【図１１】図１０のリード線封止構造の製造工程の説明図。
【図１２】リード線封止構造の第三変形例を示す縦半断面図。
【図１３】図１２のリード線封止構造の製造工程の説明図。
【図１４】図６（ｂ）における熱融着工程の詳細説明図。
【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（筒状部）
１８１ 内部空間（空間部）
１８２ 隙間
１８ｃ 開口部
１８ｄ 粗面部（面荒らし部）
５０，６０，７０，８０ リード線封止構造
５１ グロメット
５１ａ リード線挿通孔
５１Ａ 本体部
５１Ｂ 環状部（側方部）
５２ 補助層
５３ 保護カバー
５３ａ グロメット加締め部
５３ｂ 外筒加締め部（前方加締め部）
５１１ グロメット成形体
５１１Ａ 本体成形部
５１１Ｂ 環状成形部（側方成形部）
６００ 組立体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lead wire sealing structure applied to applied electronic devices used at high temperatures, such as various gas sensors, ceramic heaters, glow plugs, and the like, and a manufacturing method thereof. Further, according to the present invention, for example, an oxygen sensor, an HC sensor, a NOx sensor, etc., a lead wire is connected to a detection element for detecting a detected component in a gas to be measured, and the lead wire is sealed. The present invention relates to a gas sensor using a 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 (ZrO₂) 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 disposed inside a metal cylindrical portion having an opening, and an output thereof is taken out of the cylindrical portion by a lead wire connected to the detection element. A rubber grommet is fitted inside the opening of the cylindrical portion from which the lead wire is drawn out to prevent water and the like from entering the cylindrical portion, and the lead wire is a lead formed on the grommet. It extends through the line insertion hole to the outside of the cylindrical portion. The space between the lead wire and the cylindrical portion is sealed (sealed) by the elastic force of the grommet.
[Problems to be solved by the invention]
[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, heat from the engine and exhaust gas overlaps with heat generated by the heater, and the temperature of the cylindrical portion rises, and the grommet is exposed to a high temperature (for example, around 200 ° C.) due to heat conduction from the cylindrical portion. For this reason, when rubber grommets are exposed to a high temperature for a long time, the rubber grommets may cause thermal degradation, which may reduce the sealing performance.
[0004]
Therefore, it has been considered that the grommet is constituted by using a heat-resistant resin such as a fluorine resin instead of rubber. However, the sealing structure itself still follows the conventional method of arranging grommets inside the opening of the cylindrical portion. For this reason, when the grommet is cooled from a high temperature state, heat shrinkage occurs inside the opening of the cylindrical portion, and a gap is formed between the outer peripheral surface of the grommet and the inner peripheral surface of the opening of the cylindrical portion. There is a concern that the sealing performance of the resin becomes insufficient.
[0005]
  The first problem of the present invention is heat resistancesexWhen constructing a resin grommet, there is no gap between the grommet and the tubular part during heat shrinkage, and the grommet is securely sealed to the tubular part by thermal fusion of the grommet. Another object of the present invention is to provide a lead wire sealing structure capable of ensuring sealing performance and a gas sensor using the same. In addition, the second problem of the present invention is heat resistance.sexTo provide a manufacturing method capable of easily realizing a lead wire sealing structure having the above-described sealing property by heat fusion using a resin grommet molded body.is there.
[0006]
[Means for solving the problems and actions / effects]
In order to solve the above-mentioned problems, the present inventors have conceived that at least a part of the grommet is arranged on the outer surface side of the cylindrical portion so that the thermal shrinkage of the grommet occurs on the outer surface side of the cylindrical portion, and the following As a result, the present invention has been completed.
[0007]
  That is, in order to solve the first problem, the lead wire sealing structure according to the first invention (hereinafter also simply referred to as a sealing structure)
  Consists of heat-resistant resin mainly composed of PTFE resin, which is fluorine resinBy grommetThe opening formed at the end of the cylindrical partThe lead wire is sealed and has a structure extending through the grommet from the inner side of the cylindrical portion and extending to the outside.
  GrommetIsThe lead wire is disposed in correspondence with the opening.Lead wire insertion holeAnd a side part that is integrated with the main body part and arranged in a form that wraps around the outer peripheral surface side of the cylindrical part through the edge of the opening part,
  Of the grommetInner peripheral surface of the side portionWhenThe outer peripheral surface of the cylindrical partIs an auxiliary layer formed mainly of PFA resin, which is a fluorine-based resin that is softer and has better fluidity than PTFE resin.It is characterized in that it is indirectly heat-sealed through the.
[0008]
According to the lead wire sealing structure according to the first aspect of the invention, the side portion (the inner peripheral surface of the side portion) of the heat-resistant resin grommet is heat-sealed to the outer peripheral surface of the cylindrical portion. The heat shrinkage of the grommet occurs toward the outer peripheral surface side of the cylindrical portion. As a result, a gap is not easily formed between the inner peripheral surface of the grommet's side part and the outer peripheral surface of the cylindrical part during heat shrinkage, and this heat-sealing ensures stable sealing with the heat-resistant resin grommet. can do.
[0009]
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”. In addition, in this specification, “thermal fusion” means “to soften and harden the grommet by heating and cooling and seal it to the outer peripheral surface of the cylindrical portion” and “outside of the grommet and the lead wire”. It may mean “to soften and harden the substrate by heating / cooling to join the two”.
[0010]
As the heat resistant resin constituting the grommet of the present invention, one having a softening temperature of 200 ° C. or higher can be used. Here, as the softening temperature, the Vicat softening temperature measured according to JIS K7206 is used.
[0011]
Furthermore, in this invention, an auxiliary | assistant layer can be formed between the internal peripheral surface of the side part of a grommet, and the outer peripheral surface of a cylindrical part. For example, when both are made of different materials, such as when the grommet is made of resin and the cylindrical portion is made of metal, it may be difficult for both to be in close contact. Even in such a case, the auxiliary layer penetrates so as to at least partially fill a minute gap formed between the unevenness of the inner peripheral surface of the side part of the grommet and the unevenness of the outer peripheral surface of the cylindrical part. The familiarity of both can be improved by the anchor effect, and the sealing strength can be improved by improving the fusion strength between the inner peripheral surface of the side part of the grommet and the outer peripheral surface of the cylindrical part. The auxiliary layer is formed by resin, metal coating, plating, thermal spraying, etc. on the outer peripheral surface of the cylindrical part or the inner peripheral surface of the side part, as well as the inner peripheral surface of the side part and the cylinder. You may insert between the outer peripheral surfaces of a shape part.
[0012]
The auxiliary layer is formed mainly of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (perfluoroalkoxyalkane; hereinafter abbreviated as PFA) resin or a polytetrafluoroethylene (hereinafter abbreviated as PTFE) resin. Can do. Since these resins used for the auxiliary layer have excellent heat resistance and have a melting point comparable to the resin constituting the grommet, for example, the auxiliary layer does not soften even when the oxygen sensor is used, and the inner side of the grommet The sealing performance between the peripheral surface and the outer peripheral surface of the cylindrical portion can be maintained over a long period of time even at high temperatures.
[0013]
In addition, since PFA resin melts more easily than PTFE resin and has good fluidity, it is considered that the anchor effect is large because it easily enters the unevenness of the inner peripheral surface of the grommet and / or the outer peripheral surface of the cylindrical portion. . The PFA resin has a general structural formula shown in Chemical Formula 1. However, (-O-Rf) is (-O-CF₃), (-O-C₂F₅) Or the like (perfluoroalkoxy group).
[0014]
[Chemical 1]

[0015]
Furthermore, in the present invention, surface roughening treatment can be performed on at least a portion of the outer peripheral surface of the cylindrical portion that is covered with the inner peripheral surface of the side portion of the grommet. As a result, the inner peripheral surface of the side portion can easily bite into the irregularities of the rough surface portion formed by surface roughening on the outer peripheral surface of the cylindrical portion, and the anchoring effect improves the sealing strength by improving the fusion strength. Can do. Further, when the auxiliary layer is formed between the inner peripheral surface of the side portion and the outer peripheral surface of the cylindrical portion, the auxiliary layer easily enters the unevenness on both sides, and the inner peripheral surface of the side portion of the grommet. And the outer peripheral surface of the cylindrical portion are further improved in sealing performance. In addition to shot blasting, thread cutting, knurling, spline, serration, etc. can be employed as the surface roughening treatment on the surface of the cylindrical portion.
[0016]
Furthermore, the protective cover may be arrange | positioned in the form which covers the at least side part of a grommet from the outer side at the edge part of the cylindrical part of this invention. The protective cover that covers the outer peripheral surface of the side part prevents damage to the side part due to external impact and protects the thermal expansion of the side part radially outward when the grommet is exposed to high temperatures. By suppressing by this, it is hard to produce a clearance gap between the side part of a grommet, and the outer peripheral surface of a cylindrical part, and the stable sealing performance is ensured.
[0017]
Here, the protective cover can be formed with a grommet caulking portion that crimps at least the inner peripheral surface of the protective cover and the outer peripheral surface of the side portion. By forming the grommet crimped portion, the sealing property between the inner peripheral surface of the side portion and the outer peripheral surface of the cylindrical portion is further stabilized, and this sealing property can be maintained for a long time.
[0018]
Also, the side toward the opening in the axial direction of the cylindrical portion is the rear side, and the front end of the protective cover is located on the front side of the side edge of the grommet, and the inner peripheral surface of the protective cover at the front end Is crimped to the outer peripheral surface of the cylindrical portion by the front caulking portion, thereby securing the protective cover that protects the side portion of the grommet.
[0019]
Furthermore, the lead wire of the present invention has a core wire and a jacket covering the outside of the core wire, and the inner peripheral surface of the lead wire insertion hole of the grommet and the outer peripheral surface of the jacket are directly or indirectly through other members. Can be heat-sealed. As a result, when the side part of the grommet is heat-sealed to the outer peripheral surface of the tubular part to ensure sealing performance, the inner surface of the lead wire insertion hole inner surface of the grommet and the outer peripheral surface of the outer cover of the lead wire It is possible to simultaneously secure the sealing performance around the lead wire. That is, the sealing performance between the inner peripheral surface of the side part of the grommet and the outer peripheral surface of the tubular part is ensured by one heating / cooling operation, and the inner surface of the lead wire insertion hole inner surface of the grommet and the outer periphery of the outer cover of the lead wire The sealing performance between the surfaces can be achieved at the same time.
[0020]
A sealing resin layer mainly composed of PFA resin, for example, is interposed between the inner peripheral surface of the grommet lead wire insertion hole and the outer peripheral surface of the lead wire jacket, and this sealing resin layer is inserted into the lead wire. It can be heat-sealed to the inner peripheral surface of the hole and the outer peripheral surface of the outer jacket of the lead wire. If comprised in this way, a sealing resin layer will dig into the unevenness | corrugation of the internal peripheral surface of a lead wire penetration hole, and the fusion | bonding strength improves by the anchor effect, and the sealing performance around a lead wire becomes strong.
[0021]
The grommet and the outer jacket of the lead wire can be made of the same material heat resistant resin (for example, a heat resistant resin mainly composed of PTFE resin). If the grommet body and the lead wire jacket are made of the same material, the above-mentioned softening proceeds almost simultaneously, and both are heat-sealed in an integrated form, so the lead wire insertion hole in the grommet body The sealing property between the inner peripheral surface of the lead wire and the outer peripheral surface of the outer sheath of the lead wire, that is, the sealing property around the lead wire becomes strong.
[0022]
And as a heat resistant resin said to this invention, what mainly has a fluorine resin or a polyimide (it abbreviates as PI below) resin is used suitably. If such a heat-resistant resin grommet is heated to a predetermined temperature (for example, a softening temperature or higher), the resin has a certain degree of fluidity (for example, a melt viscosity of 10³-10⁵As a result, the unevenness on the inner peripheral surface of the side portion is likely to bite into the unevenness on the outer peripheral surface of the cylindrical portion. As a result, the anchor effect is enhanced, and the inner peripheral surface of the side portion of the grommet can be fastened to the outer peripheral surface of the tubular portion without any gap (thermal fusion). In addition, these resins constituting the grommet are excellent in heat resistance, and their melting point is higher than, for example, the rising temperature of the grommet when the oxygen sensor is used. Can be maintained over a long period of time.
[0023]
In addition, as a heat resistant resin which comprises a grommet, the following fluororesins can be illustrated.
・ Polytetrafluoroethylene (PTFE)
・ Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (perfluoroalkoxyalkane; PFA)
・ 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)
[0024]
Among these, PTFE resin is also known by trade names such as “Teflon” (trademark of Deyupon Co., Ltd.), and has a melting point of 327 ° C. and a continuous use temperature of 260 ° C. or more. Therefore, it can be suitably used as a heat resistant resin constituting the grommet of the present invention.
[0025]
  Next, in order to solve the second problem, the manufacturing method of the lead wire sealing structure according to the second invention,
  A grommet molded body in which a main body molding portion to be the main body portion of the grommet and a side molding portion to be the side portion are integrally connected is formed of the heat resistant resin,
  In the main body molding portion of the grommet molded bodyIsWhile inserting the lead wire, inside the side molding partThe cylindrical portion in which the auxiliary layer is formed on the outer peripheral surface of the end portion on the opening side from the end portion side.Insert to configure the assembly,
  The assembly is heated above the softening temperature of the heat-resistant resin and then cooled, so that the side molded portion is placed on the outer peripheral surface of the cylindrical portion.Indirectly through the auxiliary layerIt is characterized by heat fusion.
[0026]
According to the manufacturing method of the lead wire sealing structure according to the second aspect of the invention, the main body portion of the grommet closes the opening of the cylindrical portion from at least the outside, and the side portion thereof covers the outer peripheral surface of the cylindrical portion. By covering, the opening of the cylindrical portion is sealed, and a lead wire sealing structure having good sealing properties can be easily obtained. It should be noted that in one heating / cooling operation, heat fusion at two locations (that is, heat fusion to the outer peripheral surface of the cylindrical portion of the side portion of the grommet, and the outer portion of the grommet main body and lead wire) May be completed at the same time. In this case, the sealing performance at two locations is ensured (that is, the sealing performance between the inner peripheral surface of the side portion of the grommet and the outer peripheral surface of the cylindrical portion, and the inner periphery of the lead wire insertion hole of the main body portion of the grommet) Since the sealing performance between the surface and the outer peripheral surface of the outer sheath of the lead wire is achieved at the same time, the manufacturing cost can be kept low.
[0027]
  And the method of the present invention comprises:Configure the assemblyCover the outside of the grommet molded body with a protective cover that covers at least the outer peripheral surface of the side molded part.AfterThe lateral molded part is thermally expanded in the radial direction by heating, and then cooled, whereby the lateral molded part is formed on the outer peripheral surface of the cylindrical part.As opposed to indirectly through the auxiliary layerIt can be heat-sealed. The space between the outer peripheral surface of the cylindrical portion and the inner peripheral surface of the protective cover is sealed by thermal expansion toward the radially outer side and the inner side of the side molded portion. And since the thermal expansion to the outer side of the side molding part is blocked by the protective cover, it reverses in the cooling process and acts on the inner side (contraction action). As a result, the inner peripheral surface of the side part And the outer peripheral surface of the tubular portion can be closely adhered (heat-sealed) without any gap.
[0028]
  Now,PremiseLead wire sealing structureAs,
  An opening formed at the end of the cylindrical portion is sealed with a grommet having a thermal expansion coefficient larger than that of the cylindrical portion, and a lead wire penetrates the grommet from the inner side of the cylindrical portion. It has a structure that extends to the outside,
  The grommet is disposed corresponding to the opening, and is integrated with the main body portion in which the insertion hole for the lead wire is formed, and the tubular shape through the edge of the opening portion. And a side part that wraps around and contacts the outer peripheral surface side of the partSometimes.
[0029]
  the abovelikeAccording to the lead wire sealing structure, the grommet having the main body portion and the side portion is used to block the opening portion of the cylindrical portion from at least the outer side with the main body portion, and the outer peripheral surface of the cylindrical portion is the above side. The grommet is crowned in a cap shape with respect to the opening by covering with the side. Thereby, the opening part of a cylindrical part is sealed so that it may be enclosed as a whole by the main-body part and side part of a grommet. Since the grommet is made of a material having a larger coefficient of thermal expansion than that of the cylindrical portion, the inner peripheral surface of the side portion is sufficiently brought into close contact with the outer peripheral surface of the cylindrical portion from the outside during heat shrinkage. It can be sealed.
[0030]
A protective cover is disposed at the end of the tubular portion so as to cover at least the side portion of the grommet from the outside. Between the protective cover and the tubular portion can be sealed. By forming the grommet crimping portion, the close contact between the inner peripheral surface of the side portion and the outer peripheral surface of the cylindrical portion when the grommet is thermally contracted is further ensured.
[0031]
  Also, aboveFirst challengeTo solveThirdA gas sensor according to the invention has the lead wire sealing structure, and the lead wire is electrically connected to a detection element for detecting a component to be detected in a gas to be measured.
[0032]
  the aboveThirdAccording to the gas sensor of the present invention, it has already beenFirst inventionAs described in, a lead wire sealing structure is provided in which a gap is hardly generated between the inner peripheral surface of the side portion of the grommet and the outer peripheral surface of the cylindrical portion, and a stable sealing property can be secured. In particular, when the gas sensor is used for automobiles, the mounting location is an exhaust pipe or the like close to the undercarriage of the vehicle, so water drops may occur during running in the rain or during car washing. By having the sealing structure, it is possible to prevent water droplets from entering the cylindrical portion. Therefore, the detection element can function without causing malfunction or inoperability, and an electrical output from the detection element can be obtained in a stable state.
[0033]
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.
[0034]
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, Y₂O₃ZrO in which CaO is dissolved₂Is representative, but other alkaline earth metal or rare earth metal oxides and ZrO₂A solid solution may be used. The base ZrO₂HfO₂May be contained.
[0035]
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.
[0036]
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.
[0037]
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.
[0038]
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.
[0039]
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 the electrode lead portion 26a is connected to the porous electrode 26 on the joining side, and oxygen is pumped into the porous electrode 26 side between the porous electrode 25 on the opposite side. A very small pumping current is applied to the. 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.
[0040]
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. On the outer periphery of the front end portion 3h of the metal shell 3, metal protective covers 6a and 6b that cover the protruding portion of the detection element 2 are fixed by laser welding or the like. 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 18A of a metal outer cylinder 18 (cylindrical portion) such as stainless steel, and welded as a coupling portion formed annularly in the circumferential direction at the overlapping portion. The parts (for example, laser welding parts) 35 are joined together in an airtight state.
[0041]
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 pass through a grommet 51 which is covered with a cap shape and seals the opening 18 c formed at the rear end of the outer cylinder 18, and is outside the outer cylinder 18. A connector plug (not shown) is connected to the rear end of the connector plug. 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.
[0042]
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 auxiliary layer 52, a protective cover 53, and the like. The grommet 51 has a main body 51A and a side part 51B formed in an annular shape (hereinafter referred to as an annular part 51B), and has a cap shape as a whole. The main body 51 </ b> A of the grommet 51 has a form that penetrates the lead wire insertion hole 51 a through which the lead wire 14 is inserted in the axial direction, and is provided concentrically with the opening 18 c of the outer cylinder 18. The side portion 51B is integrally connected to the main body portion 51A, and the inner peripheral surface thereof is in contact with the outer peripheral surface of the rear end portion 18C of the outer cylinder 18. On the other hand, the outer cylinder 18 connects the front end portion 18A, the intermediate portion 18B located behind the front end portion 18A, the rear end portion 18C having an opening 18c at the rear end, and the intermediate portion 18B and the rear end portion 18C. It has a reduced diameter portion 18D, and has an elongated cylindrical shape as a whole. The rear end portion 18C is formed with a smaller diameter than the intermediate portion 18B, and the outer peripheral surface thereof is inserted in the axial direction of the grommet 51 while being in contact with the inner peripheral surface of the annular portion 51B of the grommet 51.
[0043]
The main body 51A of the grommet 51 closes the opening 18c of the outer cylinder 18 from at least the outside, and the inner peripheral surface of the annular portion 51B is in contact with the outer peripheral surface of the rear end portion 18C of the outer cylinder 18, whereby the grommet 51 The opening 18c is covered with a cap so as to seal the opening 18c.
[0044]
The main body portion 51A and the annular portion 51B of the grommet 51 are integrally connected to the outside of the rear end portion 18C of the outer cylinder 18 and are integrally configured by pressure molding using PTFE resin. PTFE resin has a melting point of 327 ° C. and has excellent physical properties such as good heat resistance and chemical stability among fluorine-based resins, and can add some fluidity by heating.
[0045]
The outer cylinder 18 is inserted such that the outer peripheral surface of the rear end portion 18 </ b> C thereof is in contact with the inner peripheral surface of the annular portion 51 </ b> B of the grommet 51, and the grommet 51 and the central axis are substantially aligned with each other. A wide internal space 181 (space portion) is formed inside the inner peripheral surface of the portion 18C. In this internal space 181, the first connector A, the conductive wire 8, the second connector portion 13 and the like already described are accommodated in order to connect each electrode terminal portion 7 of the detection element 2 and the lead wire 14. Used as a space for assembly or placement. When the fitting between the inner diameter of the annular portion 51B of the grommet 51 and the outer diameter of the rear end portion 18C of the outer cylinder 18 is performed by an interference fit, the outer peripheral surface of the rear end portion 18C of the outer cylinder 18 is annular. A rounded (curved) or tapered (planar) chamfer 18e is provided along the circumferential direction at the rear end of the outer peripheral surface of the outer cylinder 18 so as to be smoothly inserted into the inner peripheral surface of the portion 51B. .
[0046]
And if the grommet 51 in which the outer cylinder 18 is inserted in this way is heated to the softening temperature or higher, the fluidity is added to the PTFE resin, and the irregularities on the inner peripheral surface portion of the annular portion 51B become the outer peripheral surface portion of the outer cylinder 18. The annular portion 51B of the grommet 51 can be heat-sealed to the outer cylinder 18 by being easy to bite into the unevenness of the material, enhancing the anchor effect, and cooling after heating. Since PTFE resin (grommet 51) has a larger coefficient of thermal expansion than stainless steel (outer cylinder 18), the annular portion 51B of the grommet 51 is thermally expanded with the outer cylinder 18 during thermal contraction during cooling after heating. Due to the difference in rate, the outer peripheral surface of the outer cylinder 18 is covered without a gap, and a stable sealing property is ensured at the contact portion between the inner peripheral surface of the annular portion 51B and the outer peripheral surface of the outer cylinder 18. In addition, since the grommet 51 is made of PTFE resin, the heat-sealing ensures adhesion between the inner peripheral surface of the annular portion 51B of the grommet 51 and the outer peripheral surface of the outer cylinder 18, and the opening 18c of the outer cylinder 18 is secured. Can be easily sealed. It should be noted that the grommet 51 is pressed against the outer peripheral surface of the outer cylinder 18 based on the difference in coefficient of thermal expansion with the outer cylinder 18 in detail, and more specifically, the outer peripheral surface of the outer cylinder 18 is pressed radially inward. There may be a contraction force (clamping force) that acts on the surface. This contracting force also ensures a more stable sealing performance at the contact portion between the inner peripheral surface of the annular portion 51B and the outer peripheral surface of the outer cylinder 18.
[0047]
Next, as shown in FIG. 3B, 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 PTFE resin tube. In the main body 51A of the grommet 51, four lead wire insertion holes 51a through which the lead wires 14 are individually inserted respectively penetrate in the axial direction, and each lead wire in the cross section orthogonal to the lead wire insertion hole 51a. The centers of 14 are arranged at equal intervals on a single pitch circle P. The lead wire jacket 14 </ b> B is made of PTFE resin made of the same material as the grommet 51.
[0048]
The inner surface of each lead wire insertion hole 51a and the outer surface of the outer sheath 14B of the lead wire 14 corresponding thereto are heat-sealed. Since both the grommet main body 51A and the lead wire jacket 14B are made of PTFE resin, when the grommet 51 is heated to a predetermined temperature (for example, the softening temperature or higher) and then cooled, the softening proceeds almost simultaneously, and both are heated. The sealing performance between the inner surface of the lead wire insertion hole 51a of the grommet body 51A and the outer surface of the outer sheath 14B of the lead wire 14 is strengthened.
[0049]
Surface roughening by shot blasting is performed on the surface of the outer peripheral surface of the rear end portion 18C of the outer cylinder 18 that is covered with the inner peripheral surface of the annular portion 51B of the grommet 51 to form a rough surface portion 18d (surface roughening portion). Yes. As a result, the inner peripheral surface of the annular portion 51B can easily bite into the irregularities of the rough surface portion 18d of the outer peripheral surface of the outer cylinder 18, and the anchoring effect improves the fusion strength by heat fusion.
[0050]
In order to enhance the anchor effect, the surface roughness of the rough surface portion 18d of the outer cylinder 18 is increased to the maximum height R by these surface roughening treatments._y15μmR_yIt is preferable to use the above (the standard length and the evaluation length are both JIS B0601-1994 standard values).
[0051]
The rough surface portion 18d of the outer cylinder 18 is coated with an auxiliary layer 52 of PFA resin. Even when the material of the auxiliary layer 52 is different between the annular portion 51B (made of resin) and the outer cylinder 18 (made of metal), the auxiliary layer 52 is not rough on the inner peripheral surface of the annular portion 51B and the rough surface of the outer cylinder 18. The small gap formed between the concave and convex portions of the surface portion 18d is filled to improve the familiarity between them, the anchor effect is exhibited, and the fusion strength by heat fusion is improved. At this time, since the PFA resin is softer and has better fluidity than the PTFE resin, it is predicted that the anchoring effect is likely to easily enter the unevenness on the inner peripheral surface of the annular portion 51B of the grommet 51 and the unevenness on the outer peripheral surface of the outer cylinder 18. The
[0052]
On the outside of the grommet 51, a protective cover 53 that covers a part of the rear end surface of the main body 51A of the grommet 51 and the outer peripheral surface of the annular portion 51B and has a cap shape as a whole is covered. Further, near the rear end of the protective cover 53, a grommet crimped portion 53 a having an annular cross section that presses the inner peripheral surface of the protective cover 53 and the outer peripheral surface of the annular portion 51 </ b> B along the circumferential direction of the protective cover 53. It is formed continuously over the entire circumference. Further, the front end portion of the protective cover 53 extends further forward to cover the outer peripheral surface of the intermediate portion 18B of the outer cylinder 18, and at the front side of the grommet crimping portion 53a, the intermediate portion between the inner peripheral surface of the protective cover 53 and the outer cylinder 18 is provided. An outer cylinder crimping portion 53b (front crimping portion) having an annular cross-section, which crimps the outer peripheral surface of the portion 18B, is continuously formed over the entire circumference along the circumferential direction of the protective cover 53.
[0053]
By providing the protective cover 53 that covers the outer peripheral surface of the annular portion 51B of the grommet 51 and the outer peripheral surface of the intermediate portion 18B of the outer cylinder 18, the annular portion 51B is prevented from being damaged by an external impact, and the annular portion 51B. Prevents thermal expansion toward the outside in the radial direction when exposed to high temperatures. The formation of the grommet crimping portion 53a improves the sealing performance between the inner peripheral surface of the annular portion 51B of the grommet 51 and the outer peripheral surface of the rear end portion 18C of the outer cylinder 18, and this sealing performance is maintained for a long time. it can. Further, the protective cover 53 can be securely fixed by forming the outer cylinder crimping portion 53b.
[0054]
The grommet crimping portion 53a and the outer cylinder crimping portion 53b are both formed in an annular cross section, but may be formed in a polygonal cross section. In the case of a circular cross section, the contact surface between the protective cover 53 and the annular portion 51B or the outer cylinder 18 is a cylindrical surface, so that the sealing performance (airtightness) is excellent. Since the contact surface between the cover 53 and the annular portion 51B or the outer cylinder 18 is a rectangular tube surface, there is an advantage that displacement (relative rotation) on the contact surface is unlikely to occur. Therefore, in order to take advantage of both advantages, the grommet caulking portion 53a and the outer cylinder caulking portion 53b may be used in combination with a circular cross section and a polygonal cross section. Moreover, although both the crimping parts 53a and 53b can also be intermittently formed along the circumferential direction, in order to secure fixation of the protective cover 53, it is desirable to form over the perimeter.
[0055]
Such a sealing structure 50 can be formed by the following manufacturing process, for example.
<Molding process>
First, the grommet 51 is formed by pressure integral molding of the PTFE resin powder T. As shown in FIG. 4A, the lower punch LP is inserted into the pressurizing chamber formed in the center of the mold M, and PTFE powder T is used as the resin constituting the grommet 51 to pressurize the mold M. To fill. 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 pass through the filling layer of the PTFE powder T, and the fixed pin FP passes through the lower punch LP and the pressurizing chamber and also passes through the upper punch UP. Each fixing pin FP has a shape corresponding to the lead wire insertion hole 51 a for inserting the lead wire 14.
[0056]
Then, when the upper punch UP is pressurized, as shown in FIG. 4B, the whole is made of PTFE resin, and a cap-shaped grommet molded body 511 is obtained. The grommet molded body 511 includes a main body molded portion 511A having four lead wire insertion holes 51a and an annular molded portion 511B (side molded portion) formed integrally with the main body molded portion 511A. Yes.
[0057]
<Outer cylinder insertion process>
Next, as shown in FIG. 5A, the outer cylinder 18 is grommet molded body 511 while the inner peripheral surface of the annular molded portion 511 </ b> B of the grommet molded body 511 is brought into contact with the outer peripheral surface of the rear end portion 18 </ b> C of the outer cylinder 18. Are inserted so that the central axes substantially coincide with each other. At this time, a rough surface portion 18d is formed on the outer peripheral surface of the rear end portion 18C of the outer cylinder 18 by shot blasting, and the rough surface portion 18d is coated with an auxiliary layer 52 of PFA resin. Further, in order to secure the allowance at normal temperature after heating, the inner diameter of the annular molded portion 511B of the grommet molded body 511 and the outer diameter of the rear end portion 18C of the outer cylinder 18 in FIG. May be done with an interference fit. Therefore, a rounded (curved surface) or tapered (planar) chamfer 18e is provided along the circumferential direction at the rear end of the outer peripheral surface of the outer cylinder 18, and the outer peripheral surface of the rear end portion 18C of the outer cylinder 18 is an annular molded portion. It is inserted smoothly into the inner peripheral surface of 511B.
[0058]
<Lead wire insertion process>
Further, as shown in FIG. 5 (b), the outside of the core wire 14A is covered with a jacket 14B made of PTFE resin tube in the four lead wire insertion holes 51a formed in the main body molding portion 511A of the grommet molded body 511. The four lead wires 14 having the above-described configuration are respectively inserted in the axial direction. Thereby, the outer cylinder 18 and the lead wire 14 are combined with the grommet molded body 511 to form an assembly 600. An internal space 181 is formed inside the inner peripheral surface of the rear end portion 18C of the outer cylinder 18.
[0059]
<Protective cover coating and caulking process>
Next, as shown to Fig.6 (a), the protective cover 53 of a cap shape is covered with respect to the grommet molded object 511 from an axial direction back outer side. Then, near the rear end of the protective cover 53, a grommet crimped portion 53a having an annular cross section is formed along the circumferential direction of the protective cover 53, and the inner peripheral surface of the protective cover 53 and the outer peripheral surface of the annular portion 51B are crimped together. To do. In addition, on the front side of the grommet crimping portion 53a, an outer cylinder crimping portion 53b having an annular cross section is formed along the circumferential direction of the protective cover 53, and the inner peripheral surface 18B of the protective cover 53 and the outer cylinder 18 are formed. Crimp the outer peripheral surface. As described above, the protective cover 53 is placed on the assembly 600, and the crimping portions 53a and 53b are formed on the protective cover 53, whereby the crimping assembly 650 is completed.
[0060]
<Heat fusion process>
The caulking assembly 650 assembled as described above is heated in a heating furnace to a temperature higher than the softening temperature of PTFE resin (for example, 340 to 350 ° C.) for a predetermined time (for example, 2 to 3 hours) and then gradually cooled. The stop structure 50 is completed. Thereby, as shown in FIG. 6B, the PTFE powder T is softened and sintered in the grommet molded body 511 to become a grommet 51. At this time, since the PFA resin of the auxiliary layer 52 is softer and has better fluidity than the PTFE resin, a minute amount formed between the unevenness of the inner peripheral surface of the annular portion 51B and the unevenness of the rough surface portion 18d of the outer cylinder 18 is formed. It fills in the gaps to improve the familiarity of both, and demonstrates the anchor effect. Further, since PTFE resin has a higher coefficient of thermal expansion than stainless steel, the annular portion 51B of the grommet 51 covers the outer peripheral surface of the outer cylinder 18 without a gap due to the difference in thermal expansion coefficient during thermal contraction, and the inner portion of the annular portion 51B. Stable sealing performance is ensured at the contact portion (heat-sealed portion) between the peripheral surface and the outer peripheral surface of the outer cylinder 18. In addition, the annular portion 51B of the grommet 51 may be in an interference fit state with respect to the outer cylinder 18 by this contraction action. Further, since the main body 51A of the grommet 51 and the outer sheath 14B of the lead wire 14 are both made of PTFE resin, they are integrated by heat fusion.
[0061]
FIG. 14 shows the behavior in the heat fusion process in more detail. In the caulking assembly 650 of FIG. 14A, the annular molded portion of the outer cylinder 18 is disposed between the inner peripheral surface of the annular molded portion 511B and the outer peripheral surface of the outer cylinder 18 (or the coating outer surface of the auxiliary layer 52). A radial gap t1 (hereinafter referred to as an inner gap) is formed with the insertion into 511B. On the other hand, between the outer peripheral surface of the annular molded portion 511B and the inner peripheral surface of the protective cover 53, a radial gap t2 (hereinafter, referred to as covering of the assembly 600 by the protective cover 53 and formation of the grommet crimped portion 53a). An outer gap) is formed. When the fitting between the inner diameter of the annular molded portion 511B and the outer diameter of the rear end portion 18C of the outer cylinder 18 is performed by interference fitting (press-fit) in the outer cylinder insertion step, the inner clearance t1 is zero. . However, it is assumed that the inner and outer gaps t1, t2 include a space between the uneven peaks and valleys on the surface as represented by the rough surface portion 18d.
[0062]
By heating the PTFE resin to a temperature higher than the softening temperature of the PTFE resin in the heating furnace, the grommet molded body 511 is softened and sintered to become a grommet 51 shown in FIG. At this time, the annular portion 51 </ b> B of the grommet 51 fills the gaps t <b> 1 and t <b> 2 by thermal expansion and seals (thermally seals) the outer peripheral surface of the outer cylinder 18 and the inner peripheral surface of the protective cover 53. In addition, the annular portion 51B that fills the outer gap t2 and tries to thermally expand further outward is blocked by the protective cover 53 and acts to fill the inner gap t1. Therefore, the expansion force toward the inside of the annular portion 51B and the interposition of the auxiliary layer 52 act synergistically on the thermal fusion of the annular portion 51B, so that the inner gap t1 is a rough surface portion 18d caused by surface roughening or the like. The inner surface of the annular portion 51B and the outer surface of the outer cylinder 18 are in close contact with each other without any gaps.
[0063]
Even with subsequent cooling, a gap does not occur between the inner peripheral surface of the annular molded portion 51B and the outer peripheral surface of the outer cylinder 18 due to the difference in thermal expansion coefficient between the grommet 51 and the outer cylinder 18, and FIG. As shown in c), the both surfaces are kept in close contact. Note that a radial gap t2 ′ accompanying the thermal contraction of the grommet 51 may be formed again between the outer peripheral surface of the annular portion 51B and the inner peripheral surface of the protective cover 53. Since it does not relate to the airtightness of the oxygen sensor 1, there is no problem unless the protective cover 53 is detached from the crimping assembly 650.
[0064]
For example, if the inner gap t1 can be made sufficiently small by forming the grommet crimped portion 53a, the fit between the inner diameter of the annular molded portion 511B and the outer diameter of the rear end portion 18C of the outer tube 18 can be tightened in the outer tube insertion step. (Press-fit) may not be necessary. Further, for example, if the outer gap t2 can be made sufficiently small by covering the assembly 600 with the protective cover 53, the formation of the grommet crimped portion 53a may be omitted. Thus, if the total thermal expansion allowance t and the inner and outer gaps t1 and t2 are appropriately managed by selecting the material (material) used for the grommet, fitting the grommet shape, and fitting with the outer cylinder, etc., manufacturing is possible. The process can be simplified.
[0065]
In the above manufacturing process, the order of the <outer cylinder insertion process> in FIG. 5 (a) and the <lead wire insertion process> in FIG. 5 (b) may be interchanged. The <protective cover covering step> can be performed prior to at least one of the <outer cylinder inserting step> and the <lead wire inserting step>. In FIG. 4B, the four lead wire insertion holes 51a of the grommet molded body 511 may be drilled with a drill or the like after the molding, in addition to the fixed pin FP being penetrated during the molding. .
[0066]
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 supports the ceramic element 2 protruding in the axial direction from the layer 32 so as to wrap from the outside, and plays a role of suppressing application of excessive bending stress or thermal stress to the detection element 2.
[0067]
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 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.
[0068]
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.
[0069]
7 to 13 show a modified example of the lead wire sealing structure of FIG. 3 and the manufacturing process of FIGS. 4 to 6. First, as for the first modification, FIG. 7 shows the sealing structure, and FIGS. 8 and 9 show the changed parts of the manufacturing process. In the lead wire sealing structure 60 of FIG. 7, the shape of the grommet 51 of FIG. 3 is changed as follows. That is, the main body 51 </ b> A of the grommet 51 is extended forward in the axial direction and penetrates deeply into the opening 18 c of the outer cylinder 18. Further, when the rear end portion 18C of the outer cylinder 18 is inserted in the axial direction of the grommet 51, there is an internal space between the inner peripheral surface of the rear end portion 18C of the outer cylinder 18 and the outer peripheral surface of the main body portion 51A of the grommet 51. Instead of 181, an annular gap 182 is formed. The annular gap 182 functions as an expansion margin when the oxygen sensor 1 is exposed to high temperature for a long time or a thermal cycle is repeatedly applied and the grommet body 51A thermally expands. Further, since the main body 51A of the grommet 51 penetrates deeply into the opening 18c of the outer cylinder 18, the lead wire insertion hole 51a can be provided long, and the lead wires 14 can be more reliably prevented from being short-circuited or entangled. it can. FIG. 7A illustrates a case where the lead wire insertion hole 51 a is also used as a storage space for the second connector portion 13. In addition, the same code | symbol is attached | subjected to the part which is common in the Example of FIG. 3, and description is abbreviate | omitted.
[0070]
In order to obtain the lead wire sealing structure 60 of FIG. 7, the manufacturing process of FIGS. 4 and 5 is changed as shown in FIGS. When the shape of the pressurizing chamber of the mold M in FIG. 4A is changed as shown in FIG. 8A, the grommet molding in which the main body molding portion 511A is extended in the axial direction as shown in FIG. 8B. A body 511 is obtained. When the outer peripheral surface of the rear end portion 18C of the outer cylinder 18 is inserted into the rear side in the axial direction of the grommet molded body 511 while being in close contact with the inner peripheral surface of the annular molded portion 511B of the grommet molded body 511, the rear end portion 18C of the outer cylinder 18 is inserted. An annular gap 182 is formed between the inner peripheral surface and the outer peripheral surface of the main body molding portion 511A of the grommet molded body 511. The subsequent assembly is performed in the same manner as in FIG. 6 (see FIG. 9).
[0071]
Next, about the 2nd modification, the sealing structure is shown in FIG. 10, and the change part of the manufacturing process is shown in FIG. 11, respectively. In the lead wire sealing structure 70 of FIG. 10, the shape of the grommet 51 of FIG. 3 is changed as follows. That is, the main body 51 </ b> A of the grommet 51 is extended forward in the axial direction, and a part of the main body 51 </ b> A enters the opening 18 c of the outer cylinder 18. Therefore, when the rear end portion 18C of the outer cylinder 18 is inserted in the axial direction of the grommet 51, an inner space is formed between the inner peripheral surface of the rear end portion 18C of the outer cylinder 18 and the outer peripheral surface of the main body 51A of the grommet 51. Instead of 181, an annular gap 182 is formed. The annular gap 182 in FIG. 10 also functions as an expansion allowance when the grommet body 51A thermally expands, as in FIG. In addition, the same code | symbol is attached | subjected to the part which is common in the Example of FIG. 3, and description is abbreviate | omitted.
[0072]
In order to obtain the lead wire sealing structure 70 of FIG. 10, the manufacturing process of FIG. 5 is changed as shown in FIG. As shown in FIG. 11 (a1), the annular molded portion 511B of the grommet molded body 511 obtained in FIG. 4 is approximately 180 degrees outward from the connection portion between the main body molded portion 511A and the annular molded portion 511B. It is bent (turned back) so as to open like a trumpet. As a result, as shown in FIG. 11 (a2), a grommet molded body 511 having a shape in which the main body molded portion 511A is extended in the axial direction is obtained. When the outer peripheral surface of the rear end portion 18C of the outer cylinder 18 is inserted into the rear side in the axial direction of the grommet molded body 511 while being in close contact with the inner peripheral surface of the annular molded portion 511B of the grommet molded body 511, the rear end portion 18C of the outer cylinder 18 is inserted. An annular gap 182 (see FIG. 10) is formed between the inner peripheral surface and the outer peripheral surface of the main body molding portion 511A of the grommet molded body 511. The subsequent assembly is performed in the same manner as in FIGS.
[0073]
Furthermore, about a 3rd modification, the sealing structure is shown in FIG. 12, and the change part of the manufacturing process is shown in FIG. 13, respectively. In the lead wire sealing structure 80 of FIG. 12, the shape of the grommet 51 of FIG. 3 is changed as follows. That is, the main body 51 </ b> A of the grommet 51 is extended to the front side in the axial direction, and a part of the main body 51 </ b> A enters the opening 18 of the outer cylinder 18. Therefore, when the rear end portion 18C of the outer cylinder 18 is inserted in the axial direction of the grommet 51, an inner space is formed between the inner peripheral surface of the rear end portion 18C of the outer cylinder 18 and the outer peripheral surface of the main body 51A of the grommet 51. Instead of 181, an annular gap 182 is formed. Similarly to FIG. 10, the annular gap 182 in FIG. 12 also functions as an expansion allowance when the grommet body 51A is thermally expanded. However, the radial dimension of the annular gap 182 in FIG. 12 (the distance between the inner peripheral surface of the rear end portion 18C of the outer cylinder 18 and the outer peripheral surface of the main body 51A of the grommet 51) is formed smaller than that in FIG. Yes. In addition, the same code | symbol is attached | subjected to the part which is common in the Example of FIG. 3, and description is abbreviate | omitted.
[0074]
In order to obtain the lead wire sealing structure 80 of FIG. 12, the manufacturing process of FIG. 5 is changed as shown in FIG. As shown in FIG. 13A, the outer peripheral surface of the rear end portion 18C of the outer cylinder 18 is brought into contact with the inner peripheral surface of the annular molded portion 511B of the grommet molded body 511 obtained in FIG. When inserted on the rear side in the axial direction, the outer cylinder 18 is inserted until the rear end of the outer cylinder 18 is further on the rear side than the front end surface of the main body molding portion 511A of the grommet molded body 511 (FIG. 13B). That is, the rear end of the outer cylinder 18 is inserted until it is inserted into the main body molding portion 511A of the grommet molded body 511. Then, during heating / slow cooling after assembly, the inner peripheral surface of the rear end portion 18C of the outer cylinder 18 according to the difference in thermal expansion coefficient between the outer cylinder 18 (stainless steel) and the grommet molded body 511 (PTFE resin). And an annular gap 182 (see FIG. 12) is formed between the outer peripheral surface of the grommet 51 and the main body 51A. The subsequent assembly is performed in the same manner as in FIG.
[0075]
In each of the embodiments described above, the side portion 51B is formed as an annular portion having an annular shape, but may have other shapes such as a rectangular tube shape or an elliptic tube shape corresponding to the outer shape of the outer tube 18.
[0076]
The fourth invention is an HC sensor, a NOx sensor, a CO sensor, a CO sensor in addition to the oxygen sensor.₂It can also be applied to other gas sensors such as sensors. Furthermore, examples of applied electronic devices to which the first to third inventions are applied include ceramic heaters, glow plugs and the like in addition to these gas sensors.
[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 the structure of the detection element in FIG.
FIG. 3 is a longitudinal half sectional view and a transverse sectional view showing an example of a lead wire sealing structure.
4 is an explanatory diagram of a manufacturing 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 half sectional view showing a first modified example of the lead wire sealing structure.
8 is an explanatory diagram of a manufacturing process of the lead wire sealing structure of FIG. 7;
FIG. 9 is an explanatory diagram following FIG. 8;
FIG. 10 is a longitudinal half sectional view showing a second modification of the lead wire sealing structure.
11 is an explanatory diagram of a manufacturing process of the lead wire sealing structure of FIG. 10;
FIG. 12 is a longitudinal half sectional view showing a third modification of the lead wire sealing structure.
13 is an explanatory diagram of a manufacturing process of the lead wire sealing structure of FIG. 12;
FIG. 14 is a detailed explanatory view of the heat fusion process in FIG.
[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 (cylindrical part)
181 Internal space (space part)
182 Clearance
18c opening
18d Rough surface part (surface roughening part)
50, 60, 70, 80 Lead wire sealing structure
51 Grommet
51a Lead wire insertion hole
51A body
51B Annular part (side part)
52 Auxiliary layer
53 Protective cover
53a Grommet caulking part
53b Outer cylinder crimping part (front crimping part)
511 Grommet molded body
511A body molding part
511B annular molded part (side molded part)
600 assembly

Claims (11)

The opening formed at the end of the cylindrical portion is sealed with a grommet composed of a heat-resistant resin mainly composed of PTFE resin, which is a fluorine-based resin , and the lead wire extends from the inner side of the cylindrical portion. Having a structure extending through the grommet and extending outside,
The grommet is disposed corresponding to the opening, and is integrated with a main body portion in which a lead wire insertion hole for inserting the lead wire is formed, and an edge of the opening portion. And a side portion arranged in a manner to wrap around the outer peripheral surface side of the cylindrical portion,
The inner peripheral surface of the side portion of the grommet and the outer peripheral surface of the cylindrical portion are interposed via an auxiliary layer mainly made of PFA resin, which is a fluorine-based resin that is softer and more fluid than PTFE resin. Lead wire sealing structure characterized by being indirectly heat-sealed.   The lead wire sealing structure according to claim 1, wherein the heat-resistant resin constituting the grommet is one having a softening temperature of 200 ° C or higher. 3. The lead wire sealing structure according to claim 1, wherein a surface roughening treatment is applied to at least a portion of the outer peripheral surface of the cylindrical portion that is covered with an inner peripheral surface of the side portion of the grommet. An end of the tubular portion, the lead wire sealing structure according to to the protective cover so as to cover from outside claims 1 are disposed any one of the three at least the side sections of the grommet. The lead wire sealing structure according to claim 4, wherein the protective cover is formed with a grommet caulking portion that crimps at least the inner peripheral surface of the protective cover and the outer peripheral surface of the side portion. The front end portion of the protective cover is located on the front side of the edge of the side portion of the grommet, with the side toward the opening in the axial direction of the cylindrical portion as the rear side, and the protection is provided at the front end portion. The lead wire sealing structure according to claim 4 or 5, wherein the inner peripheral surface of the cover is pressure-bonded to the outer peripheral surface of the cylindrical portion by a front crimping portion. The lead wire has a core wire and a jacket covering the outside of the core wire, and the inner peripheral surface of the lead wire insertion hole of the grommet and the outer peripheral surface of the jacket are directly or indirectly through other members. lead sealing structure according to any one of claims 1 and is thermally fused 6. The lead wire sealing structure according to claim 7, wherein the grommet and the jacket are made of a heat-resistant resin made of the same material. A method of manufacturing a lead sealing structure according to any one of claims 1 to 8,
A grommet molded body in which a main body molding portion to be the main body portion of the grommet and a side molding portion to be the side portion are integrally connected is formed of the heat resistant resin,
The The main body molding portion of the grommet moldings, while inserting the lead wire on the inside of the side molding section, the cylindrical which the auxiliary layer is formed on the end portion outer peripheral surface of the opening side Part is inserted from the end side to constitute an assembly,
The The assembly is heated to above the softening temperature of the heat-resistant resin, followed by cooling, indirectly heat fusion through said auxiliary layer against the side molding part to the outer peripheral surface of the tubular portion A method for producing a lead wire sealing structure, wherein: Outside of the grommet molded body constituting the assembly, after covered with a protective cover covering at least the outer peripheral surface of the side molding section, it is thermally expanded radially by the heat the side molding part, then cooled it allows manufacturing method of lead sealing structure according to the lateral shaping section to claim 9 for indirectly thermally fused through the auxiliary layer against the outer peripheral surface of the cylindrical portion to be. It has a lead wire sealing structure according to any one of claims 1 to 8, and said lead wires are electrically connected to the detection device for detecting a test substance in the measurement object gas A gas sensor.

Images