JP3713148B2

JP3713148B2 - Gas sensor and gas sensor manufacturing method

Info

Publication number: JP3713148B2
Application number: JP25117698A
Authority: JP
Inventors: 康司松尾; 聡石川
Original assignee: NGK Spark Plug Co Ltd
Current assignee: NGK Spark Plug Co Ltd
Priority date: 1998-09-04
Filing date: 1998-09-04
Publication date: 2005-11-02
Anticipated expiration: 2018-09-04
Also published as: JP2000081412A

Description

【０００１】
【発明の属する技術分野】
本発明は、酸素センサ、ＨＣセンサ、ＮＯ_Ｘセンサなど、測定対象となるガス中の被検出成分を検出するためのガスセンサとその製造方法とに関する。
【０００２】
【従来の技術】
従来より、上述のようなガスセンサとして、被検出成分を検出する検出部が先端に形成された棒状ないし筒状の検出素子を、金属製のケーシングの内側に配置した構造のものが知られている。このようなセンサには、図１６に示すように、検出素子あるいはそれを加熱するための発熱体からの各リード線１０８を通すためのセラミックセパレータ１０５が設けられている。例えば、ケーシングを内筒部材１００と外筒部材１０１とで構成し、セラミックセパレータ１０５を内筒部材１００内に挿入する。セラミックセパレータ１０５の後端部には外向きに張り出すフランジ部１０５ａを形成し、これを内筒部材１００の開口端面部に係止させる。そして、その外側から外筒部材１０１を被せ、その後端開口部をグロメット１０７で封止する。
【０００３】
また、セラミックセパレータ１０５のフランジ部１０５ａの前端面と、内筒部材１００の開口端面と外筒部材１０１の内面とをシールするゴム製のシール部材１０６が配置される。このシール部材１０６は、フランジ部１０５ａと内筒部材１００との間で軸線方向に圧縮され、それにより横方向にも変形して外筒部材１０１の内面と密着してこれをシールすることとなる。
【０００４】
一方、ケーシング内に外気を導くために、外筒部材１０１と内筒部材１００との間に撥水性のフィルタ１０３を配した構造のセンサもある。外気は外筒部材１０１側の貫通孔１０４からフィルタ１０３を経て内筒部材１００の貫通孔１０２を通り、内側に導かれる。このような構造のセンサの組立ては、従来次のようにして行っていた。すなわち、図１７（ａ）に示すように、内筒部材１００の外側にフィルタ１０３を装着し、次いでリング状のシール部材１０６を嵌め込んだセラミックセパレータ１０５を内筒部材１００の開口端部に挿入し、シール部材を１０６をフランジ部１０５ａと内筒部材１００の開口端縁との間で圧縮する。次いで、（ｂ）に示すように、外側から外筒部材１０１を被せ、図１６のように加締部１０９，１１０を形成して固定する。
【０００５】
【発明が解決しようとする課題】
上記構造のセンサでは、外筒部材１０１の内面とセラミックセパレータ１０５との間のシールを、シール部材１０６の軸線方向の圧縮に伴う横方向の変位のみに頼る形となっている。しかしながら、シール部材１０６の横方向の変形量は、製造条件や寸法ばらつき等により必ずしも一定しないことが多く、また、仮に一定の横変形量が確保できたとしても、外筒部材１０１の内径がばらつき等によって大きくなり過ぎるとシール性能が不足しやすくなる問題がある。また、該シール部材１０６は飛石等の衝撃を受けやすい外筒部材１０１の角部に位置しており、また高熱付加による永久歪も蓄積しやすく、長期にわたって使用するうちに、シール性を確実に維持することが困難になることもある。
【０００６】
他方、フィルタ１０３を有するセンサ構造の場合、図１７に示した従来の製法では、外筒部材１０１の内面との間のシール性を十分に確保するために、シール部材１０６を大きく弾性変形させた状態で外筒部材１０１を被せるようにしている。ところが、この方法の場合、シール部材１０６が横方向に大きく変形・突出した状態で外筒部材１０１が被せられるので、シール部材１０６の側面が外筒部材１０１の内面に強く擦られて垂れてしまうことがある。このような状態になると、シール部材１０６と外筒部材１０１との間のシール性が十分に確保できなくなる場合がある。また、シール部材１０６の垂れにより、フィルタ１０３の対応する縁がしわ寄せられたりずり下げられたりすると、フィルタ１０３が加締部１０９（図１６）から外れてしまい、水滴等のケーシング内への漏洩が生じやすくなることもある。なお、このようなフィルタ１０３に生ずる不具合は、外筒部材１０１の内側で発生するので、目視によりこれを発見することは不可能に近い。
【０００７】
本発明の課題は、ケーシングとセラミックセパレータとの間のシール性に優れ、ひいては検出素子を水等の漏れ込みから確実に保護しうる構造を有したガスセンサ及び製造方法を提供することにある。
【０００８】
【課題を解決するための手段及び作用・効果】
上記課題を解決するために本発明のガスセンサは、筒状のケーシングの内側に検出素子が配置され、ケーシングは、内筒部材と、その後端側に結合される外筒部材とを有し、その内筒部材に対し後端側開口部から内側に挿入されるとともに、周方向に形成されたフランジ部において該内筒部材の開口端面により支持され、少なくとも前記検出素子からのものを含む複数のリード線がそれぞれ挿通される複数のリード線挿通孔が軸線方向に貫通して形成されたセラミックセパレータが設けられ、セラミックセパレータのフランジ部前端面と内筒部材の開口端面と外筒部材内面とにそれぞれ接してそれらをシールするシール部材を備えるとともに、外筒部材には、内面側のシール部材との当接位置に対応して自身を周方向に沿って内向きに凹ませることにより、シール部材を横方向から圧縮する環状のシール加締部が形成されており、外筒部材の軸線を含む断面においてシール加締部は、前端がシール部材の前端よりも前方側に延出する下り勾配の斜面状、又は内向きに凹んだアール面状に形成されていることを特徴とする。
【０００９】
また、本発明のガスセンサの製造方法は、内筒部材の後端部内側にセラミックセパレータを挿入し、そのセラミックセパレータの外周面に形成されたフランジ部を内筒部材の開口端面において支持させ、その状態で内筒部材の後端部及びセラミックセパレータを外側から外筒部材にて覆うとともに、セラミックセパレータのフランジ部前端面と内筒部材の開口端面との間にシール部材を圧縮状態にて配した構造を有するガスセンサの製造方法に関する。そして、その第一は、上記本発明のガスセンサを製造するために、
フランジ部と内筒部材の開口端面との間にシール部材を位置させた状態で、該内筒部材の後端部内側にセラミックセパレータを挿入し、内筒部材の後端部及びセラミックセパレータを外側から外筒部材にて覆う外筒部材組付工程と、
外筒部材内面に形成された外筒部材側係合部をセラミックセパレータのフランジ部後端面に係合させ、それら外筒部材と内筒部材とを軸線方向に相対的に接近させることにより、フランジ部と内筒部材の開口端面との間でシール部材を圧縮し、それに伴う横方向の変位に基づき外筒部材内面に密着した状態とするシール圧縮工程と、
シール部材の圧縮状態を維持しつつ外筒部材を内筒部材に対して固定する固定工程と、
外筒部材に対し、内面側のシール部材との当接位置に対応してこれを周方向に沿って内向きに凹ませることによりシール部材を横方向から圧縮する、環状のシール加締部を形成するシール加締部形成工程と、
を有することを特徴とする。
【００１０】
上記本発明のガスセンサ及びその製造方法においては、内筒部材とシール部材との当接位置に対応して外筒部材に環状のシール加締部を形成するようにした。これにより、シール部材がそのシール加締部により横方向にも圧縮され、シール部材と外筒部材内面との間のシール性を大幅に向上させることができ、ひいては検出素子側への水等の漏洩を確実に阻止することができる。
【００１１】
次に、本発明のガスセンサの製造方法の第二は、
フランジ部と内筒部材の開口端面との間にシール部材を位置させた状態で、該内筒部材の後端部内側にセラミックセパレータを挿入するとともに、フランジ部と内筒部材の開口端面との間にてシール部材を最終的な圧縮量よりも小さい予備圧縮状態又は非圧縮状態（以下、これらを総称して圧縮準備状態という）とする圧縮準備工程と、
次いで、圧縮準備状態を維持しつつ内筒部材の後端部及びセラミックセパレータを外側から外筒部材にて覆う外筒部材組付工程と、
外筒部材内面に形成された外筒部材側係合部をセラミックセパレータのフランジ部後端面に係合させ、それら外筒部材と内筒部材とを軸線方向に相対的に接近させることにより、フランジ部と内筒部材の開口端面との間でシール部材を最終的な圧縮量に到達するまで本圧縮し、それに伴う横方向の変位により外筒部材内面に密着した状態とするシール圧縮工程と、
該シール部材の圧縮状態を維持しつつ外筒部材を内筒部材に対して固定する固定工程と、
を有することを特徴とする。
【００１２】
この方法では、セラミックセパレータのフランジ部と内筒部材の開口端面との間にシール部材を配し、これを最終的な圧縮量に到達させない圧縮状態又は非圧縮状態である圧縮準備状態（すなわち、シール部材をあまり強く圧縮しない状態）として外筒部材を被せ、次いで外筒部材と内筒部材とを軸線方向に相対的に接近させてシール部材を最終圧縮量となるように本圧縮するようにした。すなわち、外筒部材を被せる時点ではシール部材の圧縮量が少なく、横方向への突出量も小さいから、例えば外筒部材内面によりシール部材側面が強く擦られて垂れることを効果的に防止ないし抑制することができる。これにより、シール部材の垂れ等による外筒部材との間のシール性の低下を効果的に防止ないし抑制することができる。この場合、外筒部材にシール加締部を形成する本発明の製造方法の第一と組み合わせることにより、さらに良好なシール性を確保できるようになることはいうまでもない。
【００１３】
上記本発明の製造方法の第二は、ガスセンサが次の構成を有している場合、すなわち、内筒部材の後端部に気体導入孔が周方向に沿って複数形成され、その後端部の外側において気体導入孔を塞ぐように配置され、液体の透過は阻止し気体の透過は許容するフィルタが設けられ、外筒部材はフィルタを外側から覆うとともに、周方向に複数の補助気体導入孔が形成されており、それら補助気体導入孔の列を挟んでその両側に形成された環状のフィルタ加締部により、フィルタを内筒部材との間で挟み付けて保持するものとされたものである場合に適用するとさらに効果的である。その際、圧縮準備工程に先だって、内筒部材の後端部外側にフィルタを配置するフィルタ配置工程を実施するとともに、固定工程において外筒部材は、フィルタ加締部を形成することにより内筒部材に固定するようようにする。これにより、シール部材の垂れによるフィルタの対応する縁のしわ寄せやずり下がりが防止されるので、フィルタが加締部から外れる心配が少なく、水滴等のケーシング内への漏洩を生じにくくすることができる。
【００１４】
【発明の実施の形態】
以下、本発明の実施の形態を図面に示す実施例に基づき説明する。
図１は本発明のガスセンサの一実施例たる酸素センサの内部構造を示している。該酸素センサ１は、先端が閉じた中空軸状の固体電解質部材である酸素検出素子２と、発熱体３とを備える。酸素検出素子２は、ジルコニア等を主体とする酸素イオン伝導性固体電解質により中空に形成されている。また、この酸素検出素子２の外側には金属製のケーシング１０が設けられている。
【００１５】
ケーシング１０は、酸素センサ１を排気管等の取付部に取り付けるためのねじ部９ｂを有する主体金具９、その主体金具９の一方の開口部に内側が連通するように結合された内筒部材１４、該内筒部材１４とは反対側から主体金具９に取り付けられたプロテクタ１１等を備える。図２に示すように、酸素検出素子２の内面及び外面には、そのほぼ全面を覆うように、例えばＰｔあるいはＰｔ合金により多孔質に形成された一対の電極層２ｂ，２ｃが設けられている。なお、以下においては、酸素検出素子２の軸方向においてその閉じた先端部に向かう側を「前方側（あるいは先端側）」、これと反対方向に向かう側を「後方側（あるいは後端側）」として説明を行う。
【００１６】
図１に戻り、主体金具９の後方側の開口部には、前述の内筒部材１４がインシュレータ６との間にリング１５を介して加締められ、この内筒部材１４にさらに外筒部材５４が外側から嵌合・固定されている。この外筒部材５４の後方側の開口はゴム（例えばシリコンゴム）等で構成されたグロメット（弾性シール部材）１７で封止され、またこれに続いてさらに内方にセラミックセパレータ１８が設けられている。そして、それらセラミックセパレータ１８及びグロメット１７を貫通するように、酸素検出素子２用のリード線２０，２１及び発熱体３用のリード線１９，２２が配置されている。酸素検出素子２用の一方のリード線２０は、固定金具２３を経て前述の酸素検出素子２の内側の電極層２ｃ（図２）と電気的に接続されている。一方、他方のリード線２１は、別の固定金具３３を経て、酸素検出素子２の外側の電極層２ｂ（図２）と電気的に接続されている。酸素検出素子２は、その内側に配置された発熱体３で加熱することで活性化される。発熱体３は棒状のセラミックヒータであり、抵抗発熱線部（図示せず）を有する発熱部４２がリード線１９，２２（図１）を経て通電されることにより、酸素検出素子２の先端部（検出部）を加熱する。
【００１７】
次に、図３に示すように、外筒部材５４は、内筒部材１４に対し後方外側からほぼ同軸的に連結される筒状形態をなす。また、内筒部材１４は、軸線方向においてその後端寄りに形成された段付き部５１により、該段付き部５１に関して軸方向前方側を第一部分６１、同じく軸方向後方側を第二部分６２として、該第二部分６２が第一部分６１よりも径小となるように構成され、その第二部分６２には周方向の複数の気体導入孔５２が形成されている。また、第二部分６２の外側には、上記気体導入孔５２を塞ぐ筒状のフィルタ５３が配置され、さらに、そのフィルタ５３の外側が外筒部材５４により覆われている。なお、フィルタ５３は、例えばポリテトラフルオロエチレンの多孔質繊維構造体（商品名：例えばゴアテックス（ジャパンゴアテックス（株）））等により、水滴等の水を主体とする液体の透過は阻止し、かつ空気及び／又は水蒸気などの気体の透過は許容する撥水性フィルタとして構成されている。
【００１８】
一方、フィルタ５３に対応する位置において外筒部材５４の壁部には、周方向に所定の間隔で複数の補助気体導入孔５５が形成されるとともに、それら補助気体導入孔５５の列を挟んで両側に、フィルタ５３を自身と内筒部材１４の第二部分６２との間で圧着固定する環状のフィルタ加締部５６，５７が形成されている。これにより、補助気体導入孔５５からフィルタ５３を経て気体導入孔５２より、基準ガスとしての大気（外気）が内筒部材１４（ケーシング１０）内に導入されるとともに、水滴等の液体状態の水は内筒部材１４内に侵入することが阻止されるようになっている。他方、外筒部材５４は、第一部分６１において内筒部材１４に対し外側からこれに重なりを生じるように配置され、その重なり部には周方向の環状の外筒／内筒連結加締部７５が形成されている。この外筒／内筒連結加締部７５により、外筒部材５４が内筒部材１４に対して結合される。
【００１９】
図１に戻り、主体金具９の前方側開口部には筒状のプロテクタ装着部９ａが形成され、ここに、酸素検出素子２の先端側（検出部）を所定の空間を隔てて覆うようにキャップ状のプロテクタ１１が装着されている。図示はしていないが、プロテクタ１１には、排気ガスを透過させる複数のガス透過口が貫通形態で形成されている。なお、図１において、センサ１の全長Ｌ1は、例えば約９３ｍｍである。
【００２０】
上記酸素センサ１においては、前述の通り外筒部材５４のフィルタ５３を介して基準ガスとしての大気が導入される一方、酸素検出素子２の外面にはプロテクタ１１のガス透過口を介して導入された排気ガスが接触し、該酸素検出素子２には、その内外面の酸素濃度差に応じて酸素濃淡電池起電力が生じる。そして、この酸素濃淡電池起電力を、排気ガス中の酸素濃度の検出信号として電極層２ｂ，２ｃ（図２）からリード線２１，２０を介して取り出すことにより、排気ガス中の酸素濃度を検出できる。
【００２１】
次に、図３に示すように、セラミックセパレータ１８は、内筒部材１４に対し後端側開口部から内側に挿入されるとともに、自身の後端部に周方向に形成されたフランジ部１８ａにおいて内筒部材１４の開口端面により支持され、各リード線１９〜２２がそれぞれ挿通される複数のリード線挿通孔１８ｂが軸線方向に貫通して形成されている。他方、外筒部材５４の後端部は、セラミックセパレータ１８の後端面よりも突出するとともに、その突出部基端側に形成された周方向の段部５４ａにより縮径されており、前記したグロメット１７は、その縮径部５４ｂ内に配置されている。
【００２２】
また、セラミックセパレータ１８のフランジ部１８ａの前端面と内筒部材１４の開口端面と外筒部材５４の内面とにそれぞれ接する形で、それらをシールするリング状のシール部材４０が、セラミックセパレータ１８の基端部に嵌め込まれる形で配置されている。そして、外筒部材５４には、内面側のシール部材４０との当接位置に対応して自身を周方向に沿って内向きに凹ませることにより、シール部材４０を横方向から圧縮する環状のシール加締部６５が形成されている。シール部材４０をシール加締部６５により横方向に圧縮することで、該シール部材４０と外筒部材５４の内面との間の密着状態、すなわちシール性を大幅に向上させることができる。
【００２３】
具体的には、シール加締部６５は、フィルタ加締部５６，５７のうち外筒部材５４の軸線方向後方側に位置するもの、すなわち後方側フィルタ加締部５６よりも軸線方向後方側に形成されている。後方側フィルタ加締部５６を形成すると、外筒部材５４のそれよりも後方側に隣接する部分、すなわちシール部材４０に対応する部分が半径方向外向きに拡がるように変形しやすく、シール部材４０と外筒部材５４との間の密着が特に弛みやすい。そこで、該部分にシール加締部６５を形成すれば、フィルタ加締部５６を形成する場合においてもシール部材４０の密着弛みを極めて効果的に防止することができる。
【００２４】
また、外筒部材５４の軸線方向において、シール加締部６５は後方側フィルタ加締部５６に連なる形態で形成されている。このようにすることで、図１０（ａ）に示すように、シール加締部６５と後方側フィルタ加締部５６とを、共通の加締パンチの凸条部２５２の先端に形成された一連のパンチ面２５１ｃ，２５１ｂにより、容易に一括形成することができる。さらに、このように隣接する２つの加締部６５，５６を共通のパンチの凸条部２５２により一括形成すれば、一方の加締部形成に伴う被加工材（外筒部材）の浮き上がりの影響が他方の加締部に及びにくくなり、シール部材４０（図３）の弛みを一層生じにくくすることができる。
【００２５】
また、本実施例においては、外筒部材５４の軸線Ｏを含む断面において、シール加締部６５が、後方側フィルタ加締部５６の底に向けて下る斜面状に形成されている。シール加締部６５をこのような形態とすることで、シール部材４０をより効果的に横方向に圧縮することができ、シール性を一層向上させることができる。この場合、シール加締部６５は、外筒部材５４の軸線Ｏとのなす角度θが５〜３０°の範囲に調整されているのがよい。θが５°未満になるとシール部材４０の横圧縮量が小さくなり、十分なシール性向上効果が期待できなくなる場合がある。また、θが３０°を超えるとシール部材４０が過度に横圧縮されて損傷しやすくなり、却ってシール性が損なわれる場合がある。なお、上記θは、望ましくは１０〜２０°の範囲で調整するのがよい。また、シール加締部６５は、図１０（ｂ）に示すように、内向きに凹んだアール面状に形成してもよい。
【００２６】
次に、図３に戻り外筒部材５４の段部５４ａの内面とセラミックセパレータ１８（フランジ部１８ａ）の後端面外縁との間には、両者をシールする補助シール部材４１が設けられている。該補助シール部材４１は、セラミックセパレータ１８の後端面外縁に沿うリング状に形成されており、部品点数削減のため、図４及び図５に示すように、グロメット１７の外周面に一体化されている。また、セラミックセパレータ１８とグロメット１７及び補助シール部材４１との間のシール性をより良好なものとするために、セラミックセパレータ１８の後端面とフランジ部１８ａの後端面、及びグロメット１７の前端面と補助シール部材４１の前端面をそれぞれ面一として、それらを互いに密着させている。
【００２７】
内筒部材１４、外筒部材５４及びセラミックセパレータ１８の間が、２つのシール部材４０，４１によりいわば２段階にシールされているので、検出素子２側への水等の漏洩を確実に阻止することができる。また、フィルタ５３の熱影響による収縮等によりフィルタ加締部５６の気密性が損なわれ、かつシール部材４０のシール性が低下して、補助気体導入孔５５等からの水滴が漏れ込んできても、補助シール部材４１により、これがグロメット１７とセパレータ１８との間に侵入すること、ひいてはリード線挿通孔１８ｂ等を通ってさらに内側に漏れ込むことを確実に防止することができる。
【００２８】
本実施例では、補助シール部材４１は、図４に示すように、グロメット１７の外周面に鍔状形態で一体化されており、図５（ａ）に示すように、その鍔状の補助シール部材４１の外縁部はグロメット１７への接続基端側よりも厚肉に形成されている。そして図６（ａ）及び（ｂ）に示すように、外縁部に形成されたその厚肉部４１ａは、段部５４ａの内面とセラミックセパレータ１８との間で軸線方向に圧縮することによりつぶれるのでシール性能が一層向上する。なお、本実施例では厚肉部４１ａは、略円状断面としている。これにより、段部５４ａの内面とセラミックセパレータ１８との間が環状経路に沿って線接触状態でシールされるので、シール性能がさらに良好となる。ただし、厚肉部４１ａは、図５（ｄ）に示すように、矩形断面等、他の断面形状を有するものとして形成してもよい。また、シール部材４０によるシールのみで十分な場合は、補助シール部材４１を省略する構成としてもよい。
【００２９】
次に、図３に示すように、前述のリード線１９〜２２は、内筒部材１４を経て外筒部材５４の後端開口部から外側に延出するとともに、前記したグロメット１７は、外筒部材５４の後端部内側において、その開口端から軸線方向に所定距離だけ入り込んだ位置に配置されている。また、該グロメット１７よりも後方側において外筒部材５４の後端部内側には、グロメット１７から後方側に伸びるリード線１９〜２２を一体的に覆う被覆部材２４（例えばＥＰＤＭゴムで構成される）の先端側が挿入されている。ここで、複数のリード線１９〜２２は、外筒部材５４の軸線方向に伸びる加締受け部材２５を取り囲む形態で配置されている。そして、外筒部材５４には、被覆部材２４及びリード線１９〜２２を介して加締受け部材２５に向けて縮径する周方向の加締部２６，２７が、例えば軸線方向に所定の間隔で２箇所形成されている。これら加締部２６，２７において外筒部材５４の内面と被覆部材２４の外面との間がシールされている。加締受け部材２５で加圧力を受けとめることで、被覆部材２４に対し周方向に均一な加締力が付加することができる。
【００３０】
図４及び図５に示すように、加締受け部材２５は、部品点数削減のためグロメット１７の後端面から突出する形態でこれと一体化されている。また、図５（ｂ）に示すように、加締受け部材２５の外周面には、リード線１９〜２２（図３）を安定に支持するために、各リード線１９〜２２の断面に倣う内面形状を有する溝部２８が、それぞれ軸線方向に形成されている。図５（ｃ）に示すように、リード線１９〜２２は、それぞれ対応する溝部２８に収容される形で加締受け部材２５に当接する形となる。なお、グロメット１７には、リード線挿通孔１７ａが該グロメット１７の軸線Ｏを取り囲む形態で複数孔設されており、加締受け部材２５は、該グロメット１７端面のリード線挿通孔１７ａに取り囲まれた領域から突出する形で設けられている。そして、加締受け部材２５の外周面には、各リード線挿通孔１７ａの延長に対応する位置に溝部２８が形成されている。
【００３１】
図６〜図９は、センサ１の、本発明の要部に係る部分の組立工程の流れを示すものである。まず、図６（ａ）に示すように、セラミックセパレータ１８及びグロメット１７にリード線１９〜２２を挿通し、さらに固定金具２３に発熱体３を挿通・固定することにより第一アセンブリ８０（「臓物」とも称される）を作製する。なお、セラミックセパレータ１８の基端部には、シール部材４０を装着しておく。他方、図６（ｂ）に示すように、主体金具９の内側に検出素子２を配し、さらに内筒部材１４を組み付けて第二アセンブリ８１を作製する。なお、内筒部材１４の第二部分６２（後端部）には、筒状のフィルタ５３を装着しておく。このフィルタ５３は、前端縁が段付部５１に当たることで軸線方向の位置決めがなされる。
【００３２】
そして、図７に示すように、第一アセンブリ８０を第二アセンブリ８１内に挿入する。セラミックセパレータ１８は内筒部材１４内に挿入される一方、発熱体３は検出素子２の内側に挿入される。他方、セラミックセパレータ１８の基端部に嵌め込まれたシール部材４０は、フランジ部１８ａと内筒部材１４の開口端面との間に位置した状態となる。なお、固定金具２３は中空の検出素子２の内側に篏入され、内側の電極層２ｃ（図２）と接した状態で摩擦固定される。他方、固定金具３３の下端側には、検出素子２の外面と接続するための接続部６６が一体化されている。この接続部６６は、例えば筒状に形成されて検出素子２の開口端部外面に摩擦嵌合し、外側の電極層２ｂ（図２）と電気的に接続する。
【００３３】
このとき、第一アセンブリ８０の第二アセンブリ８１内への押込量を調整することにより、図８（ｂ）に示すように、フランジ部１８ａと内筒部材の開口端面との間にてシール部材４０が、図９（ｂ）に示す最終的な圧縮量よりも小さい予備圧縮状態又は非圧縮状態となる圧縮準備状態とする。具体的には、シール部材４０がフランジ部１８ａと内筒部材１４と軽く接したような状態であり、圧縮による顕著なつぶれ（すなわち横方向への変位）が生じないようにしておく。
【００３４】
続いて、図９（ａ）に示すように、上記圧縮準備状態を維持しつつ内筒部材１４の後端部（第二部分６２）及びセラミックセパレータ１８を外側から外筒部材５４にて覆う。このとき、シール部材４０は横方向へのつぶれ変形がほとんど生じていないので、外筒部材５４の内面に側面が擦られて垂れたりする心配がない。次いで、（ａ）に示すように、外筒部材５４を軸線方向に加圧する。このとき、段部５４ａの内面（外筒部材側係合部）がセラミックセパレータ１８のフランジ部１８ａの後端面と係合し、加圧により外筒部材５４と内筒部材１４とが軸線方向に相対的に接近して、フランジ部１８ａと内筒部材１４の開口端面との間でシール部材４０が圧縮される。これにより、シール部材４０は、横方向につぶれて外筒部材５４の内面と密着し、セラミックセパレータ１８との間にシール状態を形成する。他方、補助シール部材４１は、段部５４ａの内面とセラミックセパレータ１８の後端面との間で厚肉部４１ａが圧縮され、両者の間をシールする。
【００３５】
一方、リード線１９〜２２の外側に被せられている被覆部材２４は、その前端部を外筒部材５４の縮径部５４ｂ内に挿入しておく。そして、（ｂ）の加圧状態を保持しつつ、（ｄ）に示すように、加締部２６，２７，５６（及び、図示はしていないが５７：図３参照）を形成して組立が完了する。ここで、図８（ａ）に示すように、外筒部材５４は、補助気体導入孔５５の列の両側においてそれぞれフィルタ部に向けて周方向に加締めることにより、図３のフィルタ加締部５６，５７が形成される。
【００３６】
フィルタ加締部５６，５７は、図８（ｂ）に示すように、外筒部材５４の周方向に沿って配置された複数の加締パンチ２５１を用いて、該外筒部材５４を半径方向に圧縮することにより形成することができる。各加締パンチ２５１の内周面は互いに連なって外筒部材５４の外周面に対応する筒状面を形成するとともに、それぞれ外筒部材５４の外周面に対して接近・離間可能とされ、図示しないパンチ駆動部により外筒部材５４に対し一斉に接近してこれを圧縮するようになっている。
【００３７】
そして、各加締めパンチ２５１の軸方向両端縁には凸条部２５２，２５３が形成され、それぞれ外筒部材５４の外周面に押し付けられてそれぞれ弧状の凹部を形成し、これが周方向に連なることでフィルタ加締部５６，５７となる。ここで、後方側の凸条部２５２の先端には、後方側フィルタ加締部５６を形成するためのパンチ面２５１ｂと、シール加締部６５を形成するためのパンチ面２５１ｃが互いに連なった形で形成されており、加締パンチ２５１を外筒部材５４の外周面に接近させることで、後方側フィルタ加締部５６及びシール加締部６５（さらには前方側フィルタ加締部５７）が一括形成されることとなる。これら加締部５６，５７，６５の形成により、シール部材４０の圧縮状態が維持されつつ、外筒部材５４は内筒部材１４に対して固定されることとなる。
【００３８】
なお、本発明のセンサにおいては、図１１及び図１２に示すように、補助シール部材４１をグロメット１７と別体に形成することもできる。図１１では、補助シール部材４１はリード線挿通孔１７ａが形成された円板状とされ、グロメット１７とセラミックセパレータ１８との間に挟み込まれている。他方、図１２では、補助シール部材４１はグロメット１７の前端部外側に配置されるリング状に形成されている。
【００３９】
また、図１３に示すように、加締受け部材２５を、グロメット１７のリード線挿通孔１７ａよりも外側に位置する部分と異なる材質で構成することもできる。例えばグロメット１７をゴムで構成する場合、加締受け部材２５をそれよりも硬質の材料、例えばセラミック、金属あるいは硬質プラスチック等で構成することができる。これにより、加締部２６，２７を形成する際の加締め力をより確実に受けとめることができるようになる。なお、図１３では、加締受け部材２５とグロメット１７の中心部分（４つのリード線挿通孔１７ａに囲まれた部分）とが一体の芯材１２５として構成されている。この場合、芯材１２５とグロメット１７の外側部分１７ｃとを各々別体に形成しておき、後工程において芯材１２５を外側部分１７ｃの中心に挿入する形で一体化してもよいし、インサート成形等により芯材１２５と外側部分１７ｃとをはじめから一体化する形で製造してもよい。
【００４０】
また、図１４に示すように、加締受け部材２５とグロメット１７とを別体に形成してもよい。なお、図１５に示すように、被覆部材２４を外筒部材５４に対して加締止めしない構成では、当然のことながら、加締受け部材を省略することができる。
【００４１】
なお、以上説明した本発明のセンサの構造は、酸素センサ以外のガスセンサ、例えばＨＣセンサやＮＯ_Ｘセンサなどにも同様に適用できる。
【図面の簡単な説明】
【図１】本発明のガスセンサの一実施例たる酸素センサの内部構造を示す縦断面図。
【図２】図１の、発熱部及び固定金具と酸素検出素子との接触部付近を拡大して示す断面図。
【図３】図１のガスセンサの要部を示す拡大縦断面図。
【図４】加締受け部材及び補助シール部材が一体化されたグロメットの一例を示す斜視図。
【図５】図４のグロメットの正面図、平面図及び各部の拡大図。
【図６】図１のセンサの組立工程の一例を示す説明図。
【図７】図６に続く説明図。
【図８】図７に続く説明図。
【図９】図３に示すセンサ要部の組立工程の一連の流れを示す説明図。
【図１０】図３のシール加締部の近傍を拡大して示す断面図、及びシール加締部の変形例を示す断面図。
【図１１】図１のセンサの第一の変形例の要部を示す縦断面図。
【図１２】同じく第二の変形例の要部を示す縦断面図。
【図１３】同じく第三の変形例の要部を示す縦断面図。
【図１４】同じく第四の変形例の要部を示す縦断面図。
【図１５】同じく第五の変形例の要部を示す縦断面図。
【図１６】従来のセンサの要部縦断面図。
【図１７】その組立工程の問題点を説明する図。
【符号の説明】
１酸素センサ（ガスセンサ）
２酸素検出素子（検出素子）
９主体金具
１０ケーシング
１４内筒部材
１８セラミックセパレータ
１８ａフランジ部
４０シール部材
５２気体導入孔
５３フィルタ
５４外筒部材
５４ａ段部（外筒部材側係合部）
５５補助気体導入孔
５６，５７フィルタ加締部
６５シール加締部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to oxygen sensors, HC sensors, NO _X The present invention relates to a gas sensor for detecting a component to be detected in a gas to be measured, such as a sensor, and a manufacturing method thereof.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a gas sensor as described above, a gas sensor having a structure in which a rod-shaped or cylindrical detection element having a detection portion for detecting a detected component formed at the tip is arranged inside a metal casing is known. . As shown in FIG. 16, such a sensor is provided with a ceramic separator 105 for passing each lead wire 108 from a detection element or a heating element for heating the detection element. For example, the casing is composed of the inner cylinder member 100 and the outer cylinder member 101, and the ceramic separator 105 is inserted into the inner cylinder member 100. A flange portion 105 a projecting outward is formed at the rear end portion of the ceramic separator 105, and this is engaged with the open end surface portion of the inner cylinder member 100. And the outer cylinder member 101 is covered from the outer side, and the rear end opening is sealed with a grommet 107.
[0003]
Further, a rubber seal member 106 that seals the front end surface of the flange portion 105 a of the ceramic separator 105, the open end surface of the inner cylinder member 100, and the inner surface of the outer cylinder member 101 is disposed. The seal member 106 is compressed in the axial direction between the flange portion 105a and the inner cylinder member 100, thereby deforming in the lateral direction to be in close contact with the inner surface of the outer cylinder member 101 and sealing it. .
[0004]
On the other hand, there is also a sensor having a structure in which a water-repellent filter 103 is arranged between the outer cylinder member 101 and the inner cylinder member 100 in order to guide outside air into the casing. The outside air is guided from the through hole 104 on the outer cylinder member 101 side through the filter 103 to the inside through the through hole 102 of the inner cylinder member 100. The assembly of the sensor having such a structure has been conventionally performed as follows. That is, as shown in FIG. 17A, the filter 103 is attached to the outside of the inner cylinder member 100, and then the ceramic separator 105 into which the ring-shaped seal member 106 is fitted is inserted into the opening end of the inner cylinder member 100. Then, the seal member 106 is compressed between the flange portion 105 a and the opening edge of the inner cylinder member 100. Next, as shown in (b), the outer cylinder member 101 is covered from the outside, and the crimped portions 109 and 110 are formed and fixed as shown in FIG.
[0005]
[Problems to be solved by the invention]
In the sensor having the above-described structure, the seal between the inner surface of the outer cylinder member 101 and the ceramic separator 105 is relied only on the lateral displacement accompanying the compression of the seal member 106 in the axial direction. However, the amount of lateral deformation of the seal member 106 is not always constant due to manufacturing conditions, dimensional variations, and the like. Even if a certain amount of lateral deformation is ensured, the inner diameter of the outer cylinder member 101 varies. If it becomes too large due to, for example, the sealing performance tends to be insufficient. In addition, the seal member 106 is located at the corner of the outer cylinder member 101 that is susceptible to impacts such as stepping stones, and also tends to accumulate permanent distortion due to the addition of high heat. It can be difficult to maintain.
[0006]
On the other hand, in the case of the sensor structure having the filter 103, in the conventional manufacturing method shown in FIG. 17, the seal member 106 is greatly elastically deformed in order to ensure a sufficient sealing performance with the inner surface of the outer cylinder member 101. In this state, the outer cylinder member 101 is covered. However, in the case of this method, since the outer cylinder member 101 is covered with the seal member 106 being greatly deformed and protruded in the lateral direction, the side surface of the seal member 106 is strongly rubbed against the inner surface of the outer cylinder member 101 and droops. Sometimes. In such a state, the sealing performance between the seal member 106 and the outer cylinder member 101 may not be sufficiently ensured. Further, when the corresponding edge of the filter 103 is wrinkled or lowered due to the drooping of the seal member 106, the filter 103 is detached from the crimping portion 109 (FIG. 16), and leakage of water droplets or the like into the casing is caused. May be more likely to occur. In addition, since the malfunction which arises in such a filter 103 generate | occur | produces inside the outer cylinder member 101, it is almost impossible to discover this visually.
[0007]
An object of the present invention is to provide a gas sensor having a structure excellent in sealing performance between a casing and a ceramic separator, and thus capable of reliably protecting a detection element from leakage of water or the like, and a manufacturing method.
[0008]
[Means for solving the problems and actions / effects]
In order to solve the above problems, the gas sensor of the present invention has a detection element disposed inside a cylindrical casing, and the casing has an inner cylinder member and an outer cylinder member coupled to the rear end side thereof. A plurality of leads inserted into the inner cylinder member from the rear end side opening, and supported by the opening end surface of the inner cylinder member in a circumferentially formed flange portion, including at least those from the detection element A ceramic separator is provided in which a plurality of lead wire insertion holes through which wires are inserted are formed penetrating in the axial direction, respectively, on the front end surface of the flange portion of the ceramic separator, the open end surface of the inner cylinder member, and the inner surface of the outer cylinder member A seal member that seals them in contact with each other is provided, and the outer cylinder member is recessed inward along the circumferential direction corresponding to the contact position with the seal member on the inner surface side. It allows the seal member to seal crimped portion of the annular compressing the lateral direction is formed In the cross section including the axis of the outer cylinder member, the seal crimping portion is formed in a downward sloped surface shape in which the front end extends forward from the front end of the seal member, or an indented rounded surface shape. Have It is characterized by that.
[0009]
Further, in the gas sensor manufacturing method of the present invention, a ceramic separator is inserted inside the rear end portion of the inner cylinder member, and the flange portion formed on the outer peripheral surface of the ceramic separator is supported on the opening end surface of the inner cylinder member. In this state, the rear end portion of the inner cylinder member and the ceramic separator are covered with the outer cylinder member from the outside, and the seal member is disposed in a compressed state between the front end face of the flange portion of the ceramic separator and the open end face of the inner cylinder member. The present invention relates to a method for manufacturing a gas sensor having a structure. And the first is to manufacture the gas sensor of the present invention.
With the sealing member positioned between the flange portion and the opening end surface of the inner cylinder member, a ceramic separator is inserted inside the rear end portion of the inner cylinder member, and the rear end portion of the inner cylinder member and the ceramic separator are placed outside. An outer cylinder member assembling process covering with an outer cylinder member,
By engaging the outer cylinder member side engagement portion formed on the inner surface of the outer cylinder member with the rear end surface of the flange portion of the ceramic separator, the outer cylinder member and the inner cylinder member are relatively close to each other in the axial direction, thereby providing a flange. A seal compression step in which the seal member is compressed between the opening portion and the opening end surface of the inner cylinder member, and in close contact with the inner surface of the outer cylinder member based on the lateral displacement associated therewith,
A fixing step of fixing the outer cylinder member to the inner cylinder member while maintaining the compressed state of the seal member;
An annular seal crimping portion that compresses the seal member from the lateral direction by denting the outer cylinder member inward along the circumferential direction corresponding to the contact position with the seal member on the inner surface side. Forming a seal crimping portion to be formed;
It is characterized by having.
[0010]
In the gas sensor of the present invention and the manufacturing method thereof, an annular seal crimping portion is formed on the outer cylinder member corresponding to the contact position between the inner cylinder member and the seal member. As a result, the seal member is also compressed in the lateral direction by the seal caulking portion, so that the sealing performance between the seal member and the inner surface of the outer cylinder member can be greatly improved. Leakage can be reliably prevented.
[0011]
Next, the second method of manufacturing the gas sensor of the present invention is:
With the sealing member positioned between the flange portion and the opening end surface of the inner cylinder member, a ceramic separator is inserted inside the rear end portion of the inner cylinder member, and the flange portion and the opening end surface of the inner cylinder member A compression preparation step in which the seal member is in a pre-compression state or a non-compression state (hereinafter collectively referred to as a compression preparation state) smaller than the final compression amount,
Next, an outer cylinder member assembly step of covering the rear end portion of the inner cylinder member and the ceramic separator with the outer cylinder member from the outside while maintaining the compression preparation state,
By engaging the outer cylinder member side engagement portion formed on the inner surface of the outer cylinder member with the rear end surface of the flange portion of the ceramic separator, the outer cylinder member and the inner cylinder member are relatively close to each other in the axial direction, thereby providing a flange. The main compression of the seal member until the final compression amount is reached between the opening portion and the opening end surface of the inner cylinder member, and a seal compression step for bringing the seal member into close contact with the inner surface of the outer cylinder member by a lateral displacement associated therewith;
A fixing step of fixing the outer cylinder member to the inner cylinder member while maintaining the compressed state of the seal member;
It is characterized by having.
[0012]
In this method, a sealing member is disposed between the flange portion of the ceramic separator and the opening end surface of the inner cylinder member, and the compression ready state (i.e., the compressed state or the uncompressed state in which the seal member is not allowed to reach the final compression amount (i.e. The sealing member is not compressed so strongly) that the outer cylinder member is covered, and then the outer cylinder member and the inner cylinder member are relatively approached in the axial direction so that the sealing member is finally compressed to the final compression amount. did. That is, when the outer cylinder member is covered, the amount of compression of the seal member is small and the amount of protrusion in the lateral direction is also small. can do. Thereby, the fall of the sealing performance between the outer cylinder members due to the sagging of the seal member or the like can be effectively prevented or suppressed. In this case, it goes without saying that even better sealing performance can be secured by combining with the first manufacturing method of the present invention in which the seal crimping portion is formed on the outer cylinder member.
[0013]
In the second manufacturing method of the present invention, when the gas sensor has the following configuration, that is, a plurality of gas introduction holes are formed along the circumferential direction at the rear end portion of the inner cylinder member, and the rear end portion A filter is provided on the outside so as to block the gas introduction hole, and a filter that prevents the liquid from passing and allows the gas to pass therethrough is provided. The outer cylinder member covers the filter from the outside, and a plurality of auxiliary gas introduction holes are provided in the circumferential direction. The filter is sandwiched between the inner cylinder member and held by the annular filter crimping portions formed on both sides of the auxiliary gas introduction hole. It is more effective when applied to cases. At that time, prior to the compression preparation step, a filter placement step for placing the filter outside the rear end of the inner tube member is performed, and in the fixing step, the outer tube member is formed by forming a filter crimping portion, thereby forming the inner tube member. To be fixed to. As a result, wrinkles and sliding down of the corresponding edge of the filter due to the sagging of the seal member are prevented, so there is little fear that the filter will come off from the crimping portion, and leakage of water droplets or the like into the casing can be made difficult. .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples shown in the drawings.
FIG. 1 shows the internal structure of an oxygen sensor as an embodiment of the gas sensor of the present invention. The oxygen sensor 1 includes an oxygen detection element 2 that is a hollow shaft-shaped solid electrolyte member with a closed tip, and a heating element 3. The oxygen detection element 2 is formed hollow with an oxygen ion conductive solid electrolyte mainly composed of zirconia or the like. A metal casing 10 is provided outside the oxygen detection element 2.
[0015]
The casing 10 includes a metal shell 9 having a threaded portion 9b for attaching the oxygen sensor 1 to an attachment portion such as an exhaust pipe, and an inner cylinder member 14 coupled so that the inside communicates with one opening of the metal shell 9. And a protector 11 attached to the metal shell 9 from the side opposite to the inner cylinder member 14. As shown in FIG. 2, a pair of electrode layers 2b and 2c formed porous, for example, of Pt or a Pt alloy are provided on the inner and outer surfaces of the oxygen detection element 2 so as to cover almost the entire surface. . In the following, the side toward the closed tip in the axial direction of the oxygen detection element 2 is referred to as “front side (or tip side)”, and the side opposite to this is referred to as “rear side (or rear end side)”. Will be described.
[0016]
Returning to FIG. 1, the above-described inner cylinder member 14 is crimped to the opening of the metal shell 9 through the ring 15 between the insulator 6 and the outer cylinder member 54. Is fitted and fixed from the outside. An opening on the rear side of the outer cylinder member 54 is sealed with a grommet (elastic seal member) 17 made of rubber (for example, silicon rubber), and a ceramic separator 18 is further provided inward. Yes. The lead wires 20 and 21 for the oxygen detection element 2 and the lead wires 19 and 22 for the heating element 3 are disposed so as to penetrate the ceramic separator 18 and the grommet 17. One lead wire 20 for the oxygen detection element 2 is electrically connected to the inner electrode layer 2c (FIG. 2) of the oxygen detection element 2 through the fixture 23. On the other hand, the other lead wire 21 is electrically connected to the outer electrode layer 2b (FIG. 2) of the oxygen detecting element 2 through another fixing bracket 33. The oxygen detection element 2 is activated by heating with the heating element 3 disposed inside thereof. The heating element 3 is a rod-shaped ceramic heater, and a heating portion 42 having a resistance heating wire portion (not shown) is energized through lead wires 19 and 22 (FIG. 1), whereby the distal end portion of the oxygen detecting element 2 is obtained. (Detector) is heated.
[0017]
Next, as shown in FIG. 3, the outer cylinder member 54 has a cylindrical shape that is substantially coaxially connected to the inner cylinder member 14 from the rear outer side. Further, the inner cylinder member 14 has a stepped portion 51 formed near the rear end in the axial direction, and the axially forward side of the stepped portion 51 is defined as a first portion 61 and the axially rearward side is defined as a second portion 62. The second portion 62 is configured to have a smaller diameter than the first portion 61, and a plurality of circumferential gas introduction holes 52 are formed in the second portion 62. A cylindrical filter 53 that closes the gas introduction hole 52 is disposed outside the second portion 62, and the outside of the filter 53 is covered with an outer cylinder member 54. The filter 53 is made of, for example, a polytetrafluoroethylene porous fiber structure (trade name: Gore-Tex (Japan Gore-Tex Co., Ltd.)) or the like to prevent the permeation of liquid such as water droplets. In addition, it is configured as a water repellent filter that allows permeation of gas such as air and / or water vapor.
[0018]
On the other hand, a plurality of auxiliary gas introduction holes 55 are formed at predetermined intervals in the circumferential direction in the wall portion of the outer cylinder member 54 at a position corresponding to the filter 53, and the rows of these auxiliary gas introduction holes 55 are sandwiched between them. On both sides, annular filter caulking portions 56 and 57 are formed that press-fix the filter 53 between itself and the second portion 62 of the inner cylinder member 14. As a result, air (outside air) as a reference gas is introduced from the auxiliary gas introduction hole 55 through the filter 53 and from the gas introduction hole 52 into the inner cylinder member 14 (casing 10), and water in a liquid state such as water droplets. Is prevented from entering the inner cylinder member 14. On the other hand, the outer cylinder member 54 is arranged so as to overlap with the inner cylinder member 14 from the outside in the first portion 61, and a circumferential annular outer cylinder / inner cylinder coupling caulking portion 75 is formed in the overlapping portion. Is formed. The outer cylinder member 54 is coupled to the inner cylinder member 14 by the outer cylinder / inner cylinder coupling caulking portion 75.
[0019]
Returning to FIG. 1, a cylindrical protector mounting portion 9 a is formed at the front opening of the metal shell 9, and covers the distal end side (detection portion) of the oxygen detection element 2 with a predetermined space therebetween. A cap-shaped protector 11 is attached. Although not shown, the protector 11 is formed with a plurality of gas permeation ports through which exhaust gas permeates. In FIG. 1, the total length L1 of the sensor 1 is, for example, about 93 mm.
[0020]
In the oxygen sensor 1, the atmosphere as the reference gas is introduced through the filter 53 of the outer cylinder member 54 as described above, while introduced into the outer surface of the oxygen detection element 2 through the gas permeation port of the protector 11. Exhaust gas comes into contact, and oxygen concentration cell electromotive force is generated in the oxygen detection element 2 in accordance with the difference in oxygen concentration between the inner and outer surfaces. The oxygen concentration cell electromotive force is taken out from the electrode layers 2b and 2c (FIG. 2) through the lead wires 21 and 20 as a detection signal of the oxygen concentration in the exhaust gas, thereby detecting the oxygen concentration in the exhaust gas. it can.
[0021]
Next, as shown in FIG. 3, the ceramic separator 18 is inserted into the inner cylindrical member 14 from the rear end side opening portion, and at the flange portion 18 a formed in the circumferential direction at the rear end portion of the ceramic separator 18. A plurality of lead wire insertion holes 18b, which are supported by the opening end face of the inner cylinder member 14 and through which the lead wires 19 to 22 are respectively inserted, are formed so as to penetrate in the axial direction. On the other hand, the rear end portion of the outer cylinder member 54 protrudes from the rear end surface of the ceramic separator 18 and is reduced in diameter by a circumferential step portion 54a formed on the base end side of the protrusion portion. 17 is disposed in the reduced diameter portion 54b.
[0022]
A ring-shaped sealing member 40 that seals the front end surface of the flange portion 18 a of the ceramic separator 18, the open end surface of the inner cylindrical member 14, and the inner surface of the outer cylindrical member 54 is provided on the ceramic separator 18. It arrange | positions in the form fitted by the base end part. Then, the outer cylinder member 54 has an annular shape that compresses the seal member 40 from the lateral direction by denting itself inward along the circumferential direction corresponding to the contact position with the seal member 40 on the inner surface side. A seal caulking portion 65 is formed. By compressing the seal member 40 in the lateral direction by the seal caulking portion 65, the close contact state between the seal member 40 and the inner surface of the outer cylinder member 54, that is, the sealing performance can be greatly improved.
[0023]
Specifically, the seal caulking portion 65 is located on the rear side in the axial direction of the outer cylinder member 54 of the filter caulking portions 56 and 57, that is, on the rear side in the axial direction from the rear side filter caulking portion 56. Is formed. When the rear filter caulking portion 56 is formed, the portion adjacent to the rear side of the outer cylinder member 54, that is, the portion corresponding to the seal member 40 is easily deformed so as to expand outward in the radial direction. And the outer cylinder member 54 are particularly loose. Therefore, if the seal crimping portion 65 is formed in this portion, even when the filter crimping portion 56 is formed, it is possible to extremely effectively prevent the seal member 40 from loosening.
[0024]
Further, in the axial direction of the outer cylinder member 54, the seal crimping portion 65 is formed in a form continuous with the rear filter crimping portion 56. By doing in this way, as shown to Fig.10 (a), the seal | sticker crimping part 65 and the back side filter crimping part 56 are the series formed in the front-end | tip of the convex strip part 252 of a common crimping punch. The punch surfaces 251c and 251b can be easily formed collectively. Further, if the two adjacent caulking portions 65 and 56 are collectively formed by the common punch ridges 252 as described above, the influence of the lifting of the workpiece (outer cylinder member) due to the formation of one caulking portion. However, it is difficult to reach the other caulking portion, and the slackness of the seal member 40 (FIG. 3) can be further reduced.
[0025]
In the present embodiment, the seal crimping portion 65 is formed in a sloped shape that goes down toward the bottom of the rear filter crimping portion 56 in the cross section including the axis O of the outer cylinder member 54. By setting the seal crimping portion 65 in such a form, the seal member 40 can be more effectively compressed in the lateral direction, and the sealing performance can be further improved. In this case, the seal caulking portion 65 is preferably adjusted so that the angle θ formed with the axis O of the outer cylinder member 54 is in the range of 5 to 30 °. If θ is less than 5 °, the amount of lateral compression of the seal member 40 becomes small, and a sufficient sealing performance improvement effect may not be expected. On the other hand, if θ exceeds 30 °, the sealing member 40 is excessively laterally compressed and easily damaged, and the sealing performance may be impaired. The angle θ is desirably adjusted in a range of 10 to 20 °. Further, as shown in FIG. 10B, the seal crimping portion 65 may be formed in a rounded shape that is recessed inward.
[0026]
Next, referring back to FIG. 3, an auxiliary seal member 41 is provided between the inner surface of the stepped portion 54a of the outer cylinder member 54 and the outer edge of the rear end surface of the ceramic separator 18 (flange portion 18a). The auxiliary seal member 41 is formed in a ring shape along the outer edge of the rear end surface of the ceramic separator 18, and is integrated with the outer peripheral surface of the grommet 17 as shown in FIGS. 4 and 5 to reduce the number of parts. Yes. In order to improve the sealing performance between the ceramic separator 18 and the grommet 17 and the auxiliary seal member 41, the rear end surface of the ceramic separator 18, the rear end surface of the flange portion 18a, and the front end surface of the grommet 17 The front end surfaces of the auxiliary seal members 41 are flush with each other and are in close contact with each other.
[0027]
Since the space between the inner cylinder member 14, the outer cylinder member 54 and the ceramic separator 18 is sealed in two stages by the two sealing members 40 and 41, leakage of water or the like to the detection element 2 side is surely prevented. be able to. Further, even if the airtightness of the filter caulking portion 56 is impaired due to shrinkage due to the thermal effect of the filter 53 and the sealing performance of the seal member 40 is lowered, water droplets from the auxiliary gas introduction hole 55 etc. may leak. The auxiliary seal member 41 can surely prevent this from entering between the grommet 17 and the separator 18, and further leaking inward through the lead wire insertion hole 18b and the like.
[0028]
In this embodiment, the auxiliary seal member 41 is integrated with the outer peripheral surface of the grommet 17 in the form of a bowl as shown in FIG. 4, and the hook-like auxiliary seal is shown in FIG. 5 (a). The outer edge portion of the member 41 is formed to be thicker than the connection base end side to the grommet 17. 6 (a) and 6 (b), the thick portion 41a formed on the outer edge portion is crushed by being compressed in the axial direction between the inner surface of the stepped portion 54a and the ceramic separator 18. The sealing performance is further improved. In the present embodiment, the thick portion 41a has a substantially circular cross section. Thereby, since the space between the inner surface of the stepped portion 54a and the ceramic separator 18 is sealed in a line contact state along the annular path, the sealing performance is further improved. However, the thick portion 41a may be formed as having another cross-sectional shape such as a rectangular cross-section as shown in FIG. In addition, when only the sealing by the sealing member 40 is sufficient, the auxiliary sealing member 41 may be omitted.
[0029]
Next, as shown in FIG. 3, the above-described lead wires 19 to 22 extend outward from the rear end opening of the outer cylinder member 54 via the inner cylinder member 14, and the above-described grommet 17 includes the outer cylinder. Inside the rear end portion of the member 54, the member 54 is disposed at a position that enters a predetermined distance from the opening end in the axial direction. Further, a covering member 24 (for example, made of EPDM rubber) integrally covering the lead wires 19 to 22 extending rearward from the grommet 17 is provided inside the rear end portion of the outer cylinder member 54 on the rear side of the grommet 17. ) Is inserted. Here, the plurality of lead wires 19 to 22 are arranged in a form surrounding the crimping receiving member 25 extending in the axial direction of the outer cylinder member 54. The outer cylinder member 54 has circumferential crimping portions 26 and 27 that are reduced in diameter toward the crimping receiving member 25 via the covering member 24 and the lead wires 19 to 22, for example, at a predetermined interval in the axial direction. In two places. These caulking portions 26 and 27 seal between the inner surface of the outer cylinder member 54 and the outer surface of the covering member 24. By receiving the pressing force with the crimping receiving member 25, a uniform crimping force can be applied to the covering member 24 in the circumferential direction.
[0030]
As shown in FIGS. 4 and 5, the crimping receiving member 25 is integrated with the grommet 17 so as to protrude from the rear end face of the grommet 17 in order to reduce the number of parts. Further, as shown in FIG. 5B, the outer peripheral surface of the crimping receiving member 25 follows the cross section of each of the lead wires 19 to 22 in order to stably support the lead wires 19 to 22 (FIG. 3). Groove portions 28 having an inner surface shape are formed in the axial direction. As shown in FIG. 5C, the lead wires 19 to 22 are in contact with the crimping receiving member 25 while being accommodated in the corresponding groove portions 28. The grommet 17 is provided with a plurality of lead wire insertion holes 17a surrounding the axis O of the grommet 17, and the crimp receiving member 25 is surrounded by the lead wire insertion holes 17a on the end face of the grommet 17. It is provided so as to protrude from the area. And the groove part 28 is formed in the outer peripheral surface of the crimp receiving member 25 in the position corresponding to extension of each lead wire penetration hole 17a.
[0031]
6 to 9 show the flow of the assembly process of the sensor 1 according to the main part of the present invention. First, as shown in FIG. 6 (a), the lead wires 19 to 22 are inserted into the ceramic separator 18 and the grommet 17, and the heating element 3 is inserted into and fixed to the fixing bracket 23 to fix the first assembly 80 ("organ" Is also called). A seal member 40 is attached to the base end portion of the ceramic separator 18. On the other hand, as shown in FIG. 6B, the detection element 2 is arranged inside the metal shell 9, and the inner cylinder member 14 is further assembled to produce the second assembly 81. A cylindrical filter 53 is attached to the second portion 62 (rear end portion) of the inner cylinder member 14. The filter 53 is positioned in the axial direction by the front end edge of the filter 53 hitting the stepped portion 51.
[0032]
Then, as shown in FIG. 7, the first assembly 80 is inserted into the second assembly 81. The ceramic separator 18 is inserted into the inner cylinder member 14, while the heating element 3 is inserted inside the detection element 2. On the other hand, the seal member 40 fitted into the base end portion of the ceramic separator 18 is in a state positioned between the flange portion 18a and the open end surface of the inner cylinder member 14. The fixing bracket 23 is inserted inside the hollow detection element 2 and is frictionally fixed in contact with the inner electrode layer 2c (FIG. 2). On the other hand, a connecting portion 66 for connecting to the outer surface of the detection element 2 is integrated with the lower end side of the fixing bracket 33. The connecting portion 66 is formed in a cylindrical shape, for example, and is frictionally fitted to the outer surface of the opening end portion of the detection element 2 to be electrically connected to the outer electrode layer 2b (FIG. 2).
[0033]
At this time, by adjusting the pushing amount of the first assembly 80 into the second assembly 81, as shown in FIG. 8B, the seal member is provided between the flange portion 18a and the opening end surface of the inner cylinder member. Reference numeral 40 denotes a compression preparation state in which a preliminary compression state or a non-compression state is smaller than the final compression amount shown in FIG. Specifically, the seal member 40 is in a state where it is in light contact with the flange portion 18a and the inner cylinder member 14, so that significant collapse (that is, lateral displacement) due to compression does not occur.
[0034]
Subsequently, as illustrated in FIG. 9A, the outer cylinder member 54 covers the rear end portion (second portion 62) and the ceramic separator 18 from the outside while maintaining the compression preparation state. At this time, since the seal member 40 is hardly deformed in the lateral direction, there is no fear that the side surface is rubbed against the inner surface of the outer cylinder member 54 and droops. Next, as shown in (a), the outer cylinder member 54 is pressurized in the axial direction. At this time, the inner surface (outer tube member side engaging portion) of the stepped portion 54a is engaged with the rear end surface of the flange portion 18a of the ceramic separator 18, and the outer tube member 54 and the inner tube member 14 are axially moved by pressurization. The seal member 40 is compressed between the flange portion 18a and the opening end surface of the inner cylinder member 14 relatively close to each other. As a result, the seal member 40 is crushed in the lateral direction and is in close contact with the inner surface of the outer cylinder member 54, thereby forming a sealed state with the ceramic separator 18. On the other hand, in the auxiliary seal member 41, the thick portion 41a is compressed between the inner surface of the stepped portion 54a and the rear end surface of the ceramic separator 18, and seals between the two.
[0035]
On the other hand, the front end of the covering member 24 covering the outside of the lead wires 19 to 22 is inserted into the reduced diameter portion 54 b of the outer cylinder member 54. Then, while maintaining the pressurized state of (b), as shown in (d), the caulking portions 26, 27, and 56 (and 57: not shown, refer to FIG. 3) are formed and assembled. Is completed. Here, as shown in FIG. 8 (a), the outer cylinder member 54 is caulked in the circumferential direction toward the filter portion on both sides of the row of the auxiliary gas introduction holes 55, so that the filter caulking portion of FIG. 56 and 57 are formed.
[0036]
As shown in FIG. 8 (b), the filter caulking portions 56 and 57 use a plurality of caulking punches 251 arranged along the circumferential direction of the outer cylinder member 54 to cause the outer cylinder member 54 to move in the radial direction. It can be formed by compressing. The inner peripheral surfaces of the caulking punches 251 are connected to each other to form a cylindrical surface corresponding to the outer peripheral surface of the outer cylindrical member 54, and can be approached and separated from the outer peripheral surface of the outer cylindrical member 54, respectively. The outer cylinder member 54 is moved all at once by the punch driving portion that is not to be compressed.
[0037]
And the convex stripe part 252 and 253 are formed in the axial direction both ends edge of each caulking punch 251, and each presses against the outer peripheral surface of the outer cylinder member 54, respectively, forms an arc-shaped recessed part, and this continues in the circumferential direction. Thus, the filter caulking portions 56 and 57 are obtained. Here, a punch surface 251b for forming the rear filter caulking portion 56 and a punch surface 251c for forming the seal caulking portion 65 are connected to each other at the tip of the rear convex portion 252. When the caulking punch 251 is brought close to the outer peripheral surface of the outer cylinder member 54, the rear side filter caulking part 56 and the seal caulking part 65 (and the front side filter caulking part 57) are collectively collected. Will be formed. By forming these crimping portions 56, 57, and 65, the outer cylinder member 54 is fixed to the inner cylinder member 14 while maintaining the compressed state of the seal member 40.
[0038]
In the sensor of the present invention, as shown in FIGS. 11 and 12, the auxiliary seal member 41 can be formed separately from the grommet 17. In FIG. 11, the auxiliary seal member 41 is formed in a disk shape in which a lead wire insertion hole 17 a is formed, and is sandwiched between the grommet 17 and the ceramic separator 18. On the other hand, in FIG. 12, the auxiliary seal member 41 is formed in a ring shape that is disposed outside the front end portion of the grommet 17.
[0039]
Moreover, as shown in FIG. 13, the crimping receiving member 25 can also be comprised with a different material from the part located outside the lead wire penetration hole 17a of the grommet 17. As shown in FIG. For example, when the grommet 17 is made of rubber, the crimping receiving member 25 can be made of a harder material such as ceramic, metal, or hard plastic. As a result, the caulking force when forming the caulking portions 26 and 27 can be received more reliably. In FIG. 13, the caulking receiving member 25 and the central portion of the grommet 17 (the portion surrounded by the four lead wire insertion holes 17 a) are configured as an integral core member 125. In this case, the core member 125 and the outer portion 17c of the grommet 17 may be formed separately, and may be integrated by inserting the core member 125 into the center of the outer portion 17c in a later process, or insert molding. For example, the core member 125 and the outer portion 17c may be integrated from the beginning.
[0040]
Further, as shown in FIG. 14, the crimping receiving member 25 and the grommet 17 may be formed separately. As shown in FIG. 15, in the configuration in which the covering member 24 is not crimped to the outer cylinder member 54, the crimping receiving member can be omitted as a matter of course.
[0041]
The structure of the sensor of the present invention described above is a gas sensor other than an oxygen sensor, such as an HC sensor or NO. _X The same applies to sensors.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing the internal structure of an oxygen sensor as an embodiment of a gas sensor of the present invention.
2 is an enlarged cross-sectional view of the vicinity of a contact portion between the heat generating portion and the fixing bracket and the oxygen detection element in FIG.
3 is an enlarged longitudinal sectional view showing a main part of the gas sensor of FIG.
FIG. 4 is a perspective view showing an example of a grommet in which a crimping receiving member and an auxiliary seal member are integrated.
FIG. 5 is a front view, a plan view, and an enlarged view of each part of the grommet in FIG. 4;
6 is an explanatory view showing an example of an assembly process of the sensor shown in FIG. 1. FIG.
FIG. 7 is an explanatory diagram following FIG. 6;
FIG. 8 is an explanatory diagram following FIG. 7;
FIG. 9 is an explanatory diagram showing a series of flows of an assembly process of the sensor main part shown in FIG.
10 is an enlarged sectional view showing the vicinity of a seal crimping portion in FIG. 3, and a sectional view showing a modification of the seal crimping portion.
11 is a longitudinal sectional view showing a main part of a first modification of the sensor of FIG.
FIG. 12 is a longitudinal sectional view showing the main part of the second modified example.
FIG. 13 is a longitudinal sectional view showing the main part of a third modified example.
FIG. 14 is a longitudinal sectional view showing the main part of a fourth modified example.
FIG. 15 is a longitudinal sectional view showing the main part of a fifth modified example.
FIG. 16 is a longitudinal sectional view of a main part of a conventional sensor.
FIG. 17 is a view for explaining problems in the assembly process.
[Explanation of symbols]
1 Oxygen sensor (gas sensor)
2 Oxygen detection element (detection element)
9 Main metal fittings
10 Casing
14 Inner cylinder member
18 Ceramic separator
18a Flange
40 Sealing member
52 Gas introduction hole
53 Filter
54 Outer cylinder member
54a Step (outer tube member side engaging portion)
55 Auxiliary gas introduction hole
56, 57 Filter caulking section
65 Seal crimping part

Claims

A detection element is arranged inside a cylindrical casing, and the casing includes an inner cylinder member and an outer cylinder member coupled to the rear end side, and the inner cylinder member is located inside from the rear end side opening. And a plurality of lead wire insertion holes through which a plurality of lead wires including at least one from the detection element are respectively inserted in a flange portion formed in the circumferential direction and supported by the opening end surface of the inner cylinder member Is provided with a ceramic separator formed so as to penetrate in the axial direction, and a sealing member that contacts and seals the front end surface of the flange portion of the ceramic separator, the open end surface of the inner cylinder member, and the inner surface of the outer cylinder member, respectively. The outer cylinder member is recessed inwardly along the circumferential direction so as to correspond to the contact position with the seal member on the inner surface side. Member and seal crimped portion of the annular compressing the lateral direction is formed, and
In the cross section including the axis of the outer cylinder member, the seal tightening portion is formed in a downward sloped surface shape in which the front end extends forward from the front end of the seal member, or a rounded surface shape recessed inward. the gas sensor characterized in that is.

A plurality of gas introduction holes are formed along the circumferential direction at the rear end of the inner cylinder member,
The filter is disposed outside the rear end so as to block the gas introduction hole, and is provided with a filter that prevents the permeation of liquid and allows the permeation of gas.
The outer cylinder member covers the filter from the outside, and a plurality of auxiliary gas introduction holes are formed in the circumferential direction, and an annular filter crimping portion formed on both sides of the row of auxiliary gas introduction holes Thus, the filter is sandwiched and held between the inner cylinder member,
The seal caulking portion is formed on the rear side of the filter caulking portion that is located on the rear side in the axial direction of the outer cylinder member (hereinafter referred to as a rear side filter caulking portion). The gas sensor described.

The gas sensor according to claim 2, wherein the seal caulking portion is formed in a form continuous with the rear filter caulking portion in the axial direction of the outer cylinder member.

The cross-section including the axis of the outer cylinder member, the seal caulking portion is formed in a sloped shape or an indented indented inward surface toward the bottom of the rear filter caulking portion. The gas sensor described.

5. The gas sensor according to claim 4, wherein an angle formed between the slant-shaped seal caulking portion and the axis of the outer cylinder member is adjusted to a range of 5 to 30 °.

A ceramic separator is inserted inside the rear end portion of the inner cylinder member, and a flange portion formed on the outer peripheral surface of the ceramic separator is supported on the opening end surface of the inner cylinder member, and in this state, the rear end portion of the inner cylinder member And a gas sensor having a structure in which the ceramic separator is covered with an outer cylinder member from the outside, and a seal member is disposed in a compressed state between the front end face of the flange portion of the ceramic separator and the open end face of the inner cylinder member. In the method
With the sealing member positioned between the flange portion and the opening end surface of the inner cylinder member, the ceramic separator is inserted inside the rear end portion of the inner cylinder member, and the rear end portion of the inner cylinder member And an outer cylinder member assembly step for covering the ceramic separator with an outer cylinder member from the outside,
Engaging the outer cylinder member side engaging portion formed on the inner surface of the outer cylinder member with the rear end surface of the flange portion of the ceramic separator so that the outer cylinder member and the inner cylinder member are relatively close to each other in the axial direction. The seal compression step of compressing the seal member between the flange portion and the opening end surface of the inner cylinder member, and bringing the seal member into close contact with the inner surface of the outer cylinder member based on a lateral displacement associated therewith,
A fixing step of fixing the outer cylinder member to the inner cylinder member while maintaining a compressed state of the seal member;
An annular seal is added to compress the seal member from the lateral direction by denting the outer cylinder member inward along the circumferential direction corresponding to the contact position with the seal member on the inner surface side. A seal caulking portion forming step for forming a tightening portion;
A method for producing a gas sensor, comprising:

A ceramic separator is inserted inside the rear end portion of the inner cylinder member, and a flange portion formed on the outer peripheral surface of the ceramic separator is supported on the opening end surface of the inner cylinder member, and in this state, the rear end portion of the inner cylinder member And a gas sensor having a structure in which the ceramic separator is covered with an outer cylinder member from the outside, and a seal member is disposed in a compressed state between the front end face of the flange portion of the ceramic separator and the open end face of the inner cylinder member. In the method
With the sealing member positioned between the flange portion and the opening end surface of the inner cylinder member, the ceramic separator is inserted inside the rear end portion of the inner cylinder member, and the flange portion and the inner cylinder A compression preparation step in which the seal member is in a pre-compressed state or a non-compressed state smaller than the final compression amount (hereinafter collectively referred to as a compression preparation state) between the opening end surface of the member;
Next, an outer cylinder member assembly step of covering the rear end portion of the inner cylinder member and the ceramic separator with an outer cylinder member from the outside while maintaining the compression preparation state,
Engaging the outer cylinder member side engaging portion formed on the inner surface of the outer cylinder member with the rear end surface of the flange portion of the ceramic separator so that the outer cylinder member and the inner cylinder member are relatively close to each other in the axial direction. The main compression of the sealing member until the final compression amount is reached between the flange portion and the opening end surface of the inner cylinder member, and the state in close contact with the inner surface of the outer cylinder member due to a lateral displacement associated therewith Seal compression process and
A fixing step of fixing the outer cylinder member to the inner cylinder member while maintaining the compressed state of the seal member;
A method for producing a gas sensor, comprising:

An annular seal is added to compress the seal member from the lateral direction by denting the outer cylinder member inward along the circumferential direction corresponding to the contact position with the seal member on the inner surface side. The method for manufacturing a gas sensor according to claim 7, further comprising a seal crimping portion forming step for forming a tightening portion.

The gas sensor to be manufactured is
A plurality of gas introduction holes are formed along the circumferential direction at the rear end of the inner cylinder member,
The filter is disposed outside the rear end so as to block the gas introduction hole, and is provided with a filter that prevents the permeation of liquid and allows the permeation of gas.
The outer cylinder member covers the filter from the outside, and a plurality of auxiliary gas introduction holes are formed in the circumferential direction, and an annular filter crimping portion formed on both sides of the row of auxiliary gas introduction holes Thus, the filter is to be sandwiched and held between the inner cylinder member,
Prior to the compression preparation step, including a filter placement step of placing the filter outside the rear end of the inner cylinder member,
The method of manufacturing a gas sensor according to claim 6 or 8, wherein the outer cylinder member is fixed to the inner cylinder member by forming the filter caulking portion in the fixing step.