JP3737898B2

JP3737898B2 - Gas sensor and gas sensor manufacturing method

Info

Publication number: JP3737898B2
Application number: JP37105598A
Authority: JP
Inventors: 正二赤塚; 聡石川
Original assignee: NGK Spark Plug Co Ltd
Current assignee: NGK Spark Plug Co Ltd
Priority date: 1998-12-25
Filing date: 1998-12-25
Publication date: 2006-01-25
Anticipated expiration: 2018-12-25
Also published as: JP2000193628A

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。例えば酸素センサの場合、ジルコニア等の固体電解質セラミックで構成された軸状の酸素検出素子を、先端の検出部が突出した形でケーシング内に配し、検出部が被測定ガスに触れるに伴い素子に発生するセンサ出力をリード線を介して外部に取り出す。
【０００３】
例えば、一般の多くの酸素センサにおいては、酸素検出素子を収容するケーシングの後端側（検出部と反対側）に、基準ガスとしての大気をケーシング内に導入するための気通部を有したカバー部材が組み付けられる。リード線は、カバー部材内に配置されたセラミックセパレータ内を貫通し、さらにカバー部材の後端開口部に嵌め込まれたシール用のゴムグロメットを貫いて引き出される。
【０００４】
ところで、近年は自動車産業の隆盛に伴い酸素センサに対する需要も増え、かつ価格低下に対する要望も年々強まりつつある。酸素センサをはじめとするガスセンサは、自動車用電装部品の中でも部品点数が多く、組立工程の簡略化を如何にして図るかが製造コスト削減の重要な鍵を握っている。そのためには、組立工程の自動化など生産設備側の技術改良も必要であるが、工数削減に有利なセンサ構造を工夫することも重要である。
【０００５】
【発明が解決しようとする課題】
従来、上記のような酸素センサを組み立てる際には、例えば、酸素検出素子やこれを加熱する発熱体等を筒状のケーシング内に予め組みつけておき、それらからのリード線等をセラミックセパレータのリード線挿通孔に通す。このとき、各リード線をカバー部材の後端側開口部から外側に延出した状態としておく。そして、その後の組立は、内面側にてリード線上を滑らせながらカバー部材をケーシングの後端部に取り付けた後、カバー部材にグロメットを嵌入するという、最低２段階の工程を含む形となっている。
【０００６】
しかしながら、この方式は、カバー部材のケーシングへの取り付けと、カバー部材へのグロメットの取り付けを逐次的に行うので、工数が増え能率が悪い。また、カバー部材の後端側開口部は、グロメット寸法を縮小してシール性を高めるために、縮径されていることが多いが、そこを通る複数のリード線の束の上を、グロメット嵌め込み前のカバー部材を滑らせてケーシングへ取り付ける形となる。従って、リード線の束の上をカバー部材を少しでも傾けて滑らせると、カバー部材の開口縁にてリード線の外被が削られ、絶縁不良を起こしたり、削り屑がケーシング内に残留してトラブルの原因になりやすい。
【０００７】
他方、例えばカバー部材の外側からケーシング内に導入される外気の流通経路を確保したり、あるいはリード線挿通孔の配列ピッチ円の大きさがグロメットとセラミックセパレータとの間で異なる場合に、そのピッチ円径差を吸収する等の目的で、カバー部材内に配置されるセラミックセパレータとグロメットとの間には所定量の隙間を形成することも多い。この場合、グロメットをカバー部材内に押し込むときに、該グロメットの軸線方向の位置決めが行いにくく、隙間の量を所期の値に調整するのに手間がかかるという、別の問題も発生する。
【０００８】
本発明の課題は、グロメットのカバー部材への位置決めを容易に行うことができる構造を有したガスセンサと、当該構造の採用により、カバー部材とグロメットとのセンサへの組付けを能率よく行うことができる上、カバー部材のケーシングへの取付けに際してリード線外被等を傷つけにくいガスセンサの製造方法とを提供することにある。
【０００９】
【課題を解決するための手段及び作用・効果】
上記の課題を解決するために、本発明のガスセンサの第一は、
軸状の検出素子と、その検出素子の先端に形成された検出部を突出させた状態で、該検出素子を収容する筒状のケーシングと、そのケーシングに対し軸方向後方側から連結されるとともに、後端開口部から検出素子からのリード線を外側に延出させるカバー部材と、そのカバー部材に対し後端開口部から内側に嵌め込まれ、リード線と該カバー部材の内面との間をシールするグロメットとを備え、カバー部材には、後端開口部からグロメットを軸線方向に嵌入した際に、グロメット側に形成されたグロメット側係合部と係合することにより、該カバー部材に対するグロメットの軸線方向の嵌入位置を規定するカバー側係合部が形成され、カバー側係合部は、カバー部材の後端開口縁から軸線方向に所定距離隔たった位置において、その内面から突出形成されたカバー側係合凸部であり、グロメットの軸線方向前端縁部をグロメット側係合部として、これと係合するようになっていることを特徴とする。
また、本発明の第二は、
軸状の検出素子と、その検出素子の先端に形成された検出部を突出させた状態で、該検出素子を収容する筒状のケーシングと、そのケーシングに対し軸方向後方側から連結されるとともに、後端開口部から検出素子からのリード線を外側に延出させるカバー部材と、そのカバー部材に対し後端開口部から内側に嵌め込まれ、リード線と該カバー部材の内面との間をシールするグロメットとを備え、カバー部材には、後端開口部からグロメットを軸線方向に嵌入した際に、グロメット側に形成されたグロメット側係合部と係合することにより、該カバー部材に対するグロメットの軸線方向の嵌入位置を規定するカバー側係合部が形成され、カバー部材は、ケーシングの後方側においてこれと一体的に設けられ、ケーシング内に外気を導くための第一気体導入孔が形成された第一フィルタ保持部と、その第一フィルタ保持部の外側に設けられ、ケーシング内に外気を導くための第二気体導入孔が形成された第二フィルタ保持部と、それら第一及び第二フィルタ保持部の間において第一及び第二気体導入孔を塞ぐ形態で配置され、液体の透過は阻止し気体の透過は許容するフィルタとを備えるフィルタアセンブリであり、該フィルタアセンブリの第一フィルタ保持部が、ケーシングとは別体の筒状体として該ケーシングに対し後方側から連結され、さらに、グロメットは第一フィルタ保持部の後端開口部内に嵌め込まれており、第一気体導入孔は第一フィルタ保持部の周方向に沿って所定の間隔で複数形成されるとともに、筒状の前記フィルタにより外側から塞がれており、カバー側係合部は、軸線方向中間部においてカバー部材の壁部を周方向に内向きに凹ませることにより、壁部内面側の対応する位置に形成される環状の凸部であり、第一気体導入孔の列は、その環状の凸部の稜線に沿って形成されるとともに、壁部外面側においてその環状の凸部に対応する形で環状の溝部が形成され、その溝部がフィルタを経て第一気体導入孔に向かう外気の流通空間となっていることを特徴とする。
【００１０】
上記ガスセンサの構成によれば、カバー部材にグロメットを取り付ける際に、グロメット側係合部とカバー側係合部との係合により、グロメットのカバー部材への軸線方向の位置決めを容易に行うことができる。
上記ガスセンサの第一の構成によれば、例えばカバー部材内には、複数のリード線をそれぞれ個別に挿通するためのリード線挿通孔が軸線方向に形成されたセラミックセパレータを配置することができる。この場合、カバー側係合部とグロメット側係合部との係合により、該グロメットを、自身の前端面とセラミックセパレータの後端面との間に所定量の隙間が形成される位置に容易に固定することができ、ひいてはその隙間の確保と隙間量管理とを極めて容易に行うことができる。また、グロメットの軸線方向前端縁部をグロメット側係合部として、これを上記カバー側係合凸部と係合させることにより、グロメットのカバー部材への位置決めを確実に行うことができる。
上記ガスセンサの第二の構成によれば、カバー側係合部に対応して生ずる溝部を、外気の流通空間として流用することで、フィルタを通って流れ込む基準ガスとしての外気（大気）の流通抵抗が和らげられ、第一気体導入孔から外筒内にスムーズにこれを導入できる。
【００１１】
また、本発明のガスセンサの製造方法は、上記構造の本発明のガスセンサを製造する際に、ケーシングに取付前の状態にて、ケーシングに取付前の状態にて、カバー部材に、後端開口部からグロメットを軸線方向に嵌入した際に、グロメット側に形成されたグロメット側係合部と係合することにより、該カバー部材に対するグロメットの軸線方向の嵌入位置を規定するカバー側係合部を予め形成しておき、さらに、カバー部材の後端開口部にグロメットを、カバー側係合部とグロメット側係合部とが係合させる形で嵌入・固定し、そのグロメット取付け済みのカバー部材をケーシングに取り付けることを特徴とする。
【００１２】
この方法によれば、ケーシングに取付前の状態にてグロメットをカバー部材に予め取り付けておき、そのグロメット付のカバー部材をケーシングに組み付けるようにしている。これにより、多数のガスセンサの組立を行う際に、カバー部材へのグロメットの取り付けとカバー部材のケーシングへの取り付けとを並列的に行うことができるので、組立工程を大幅に能率化することができる。また、カバー部材へグロメットを軸線方向に位置決めしつつ組み付ける作業も、前記本発明のガスセンサの構成を採用することにより、極めて能率よく行うことができる。なお、カバー部材内のリード線をグロメットに挿通した状態にしておき、該グロメットの挿通孔においてリード線上を滑らせながら、カバー部材をケーシングに取り付けるようにすることができる。これにより、リード線の束の上をカバー部材を多少傾けて滑らせても、カバー部材の開口部内縁とリード線との間にはゴム等で構成されたグロメットが介在しているので、カバー部材の開口縁にてリード線の外被が削られるトラブルが生じにくくなる。
【００１３】
なお、上記ガスセンサの第一の構成においては、カバー側係合凸部は、その軸線方向中間部においてカバー部材の壁部を内向きに凹ませることにより、その壁部内面側の対応する位置に形成される凸部とすることができる。このような凸部は、カバー部材を軸方向中間位置にて外側からプレス加工等の加工を施すことにより、容易に形成できる。また、凸部は、カバー部材の周方向に沿って連続的または断続的に形成されていてもよい。これにより、グロメットのカバー部材に対する位置決めが一層行いやすくなり、例えばグロメットがカバー部材の軸線に対して傾いて取り付けられる等の不具合も生じにくい。
他方、グロメット側係合部は、グロメットの軸線方向後端側において、その外周面から突出形成されたグロメット側凸部とすることもできる。この場合、カバー部材の後端開口端面をカバー側係合部として、これを上記グロメット側凸部と係合させることにより、グロメットのカバー部材への位置決めを確実に行うことができる。
【００１４】
また、上記ガスセンサの第一の構成では、ケーシングの後方側においてこれと一体的に設けられ、ケーシング内に外気を導くための第一気体導入孔が形成された第一フィルタ保持部と、その第一フィルタ保持部の内側又は外側に設けられ、ケーシング内に外気を導くための第二気体導入孔が形成された第二フィルタ保持部と、それら第一及び第二フィルタ保持部の間において第一及び第二気体導入孔を塞ぐ形態で配置され、液体の透過は阻止し気体の透過は許容するフィルタとを備え、第一フィルタ保持部が、ケーシングとは別体の筒状体として該ケーシングに対し後方側から連結されるものとして構成できる。
【００１５】
このような構造のガスセンサは、以下のような方法にて製造できる。まず、ケーシングに組付ける前の状態で、第一フィルタ保持部の外側にフィルタ及び第二フィルタ保持部をこの順序で配置し、その状態で加締部を形成することにより、第二フィルタ保持部及びフィルタを第一フィルタ保持部に組み付けてフィルタアセンブリとなす。このフィルタアセンブリをカバー部材として、これにグロメットを予め組み付けた状態となし、そのグロメット取付け済みのフィルタアセンブリをケーシングに取り付ける。
【００１６】
上記のセンサ構成の要旨は、フィルタを含む気通構造部をフィルタアセンブリとしてケーシングとは独立に構成し、これをケーシングに連結・一体化した構成を有する点にある。これにより、その製法上、次のような効果が達成される。
▲１▼フィルタアセンブリの組立てを、酸素検知素子などのケーシング内への組付けとは独立に行うことができるので、例えば検知素子のリード線が邪魔になったりせず、組立作業を極めて能率的に行うことができる。
▲２▼ケーシング内への部品の組付けと、フィルタアセンブリの組立てとを並行して行えるので、生産性が飛躍的に向上する。また、フィルタの組付け不良などが生じても、フィルタアセンブリの段階で不良が発見できれば、センサ完成品に該不良の影響は及ばず、部品等の無駄等が生じにくい。
【００１７】
【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。ケーシング１０は、センサ取付け用のねじ部９ｂを有する主体金具９と、これに結合された主筒１４及びプロテクタ１１等を備える。プロテクタ１１には、排気ガスを透過させる複数のガス透過口１２が貫通形態で形成されている。酸素検出素子２の外面及び中空部２ａの内面には、そのほぼ全面を覆うように図示しない電極層が形成されている。
【００１８】
主体金具９の後方側の開口部には、前述の主筒１４が絶縁体６との間にリング１５を介して加締められ、この主筒１４に筒状のフィルタアセンブリ１６（カバー部材）が外側から嵌合・固定されている。このフィルタアセンブリ１６の後端側開口部はゴム等で構成されたグロメット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（図示していない）が配置されている。
【００１９】
図２に示すように、セラミックセパレータ１８にはセパレータ側リード線挿通孔７２が形成されており、その外周面にはフランジ状のセパレータ側支持部７３が突出形成されている。酸素検出素子２用の一方のリード線２０は、互いに一体に形成されたコネクタ２３ａ、引出し線部２３ｂ、金具本体部２３ｃ及び発熱体把持部２３ｄからなる内部電極接続金具２３を経て前述の酸素検出素子２の内部電極層と電気的に接続されている。一方、他方のリード線２１は、互いに一体に形成されたコネクタ３３ａ、引出し線部３３ｂ及び金具本体部３３ｃとを有する外部電極接続金具３３を経て、酸素検出素子２の外部電極層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（図１）がリード線（図示せず）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。
【００２０】
次に、フィルタアセンブリ１６は、複数の第一気体導入孔５２が形成された第一フィルタ保持部５１を備える。その外側には第一気体導入孔５２を塞ぐ筒状のフィルタ５３と、複数の第二気体導入孔５５が形成てフィルタ５３を第一フィルタ保持部５１との間で挟み付けて保持する第二フィルタ保持部５４とが配置される。フィルタアセンブリ１６の、第一フィルタ保持部５１の後端開口縁から軸線Ｏの方向に所定距離隔たった位置には、その内面から突出する形でカバー側係合部としてのカバー側係合凸部１００が形成されている。そして、該後端開口部に嵌め込まれたグロメット１７の軸線方向前端縁部がグロメット側係合部となって、これが上記カバー側係合凸部１００と係合することにより、グロメット１７の第一フィルタ保持部５１への軸線方向の組付け位置が規定されている。
【００２１】
カバー側係合凸部１００は、その軸線方向中間部において第一フィルタ保持部５１の壁部を内向きに凹ませることにより、その壁部内面側の対応する位置に形成されるリブ状の凸部とされている。このような凸部１００は、第一フィルタ保持部５１（カバー部材）を軸方向中間位置にて外側からプレス加工等の加工を施すことにより、容易に形成できる。また、凸部１００は、第一フィルタ保持部５１の周方向に沿って連続環状に形成されているが、これにより、グロメット１７の第一フィルタ保持部５１に対する位置決めが一層行いやすくなり、例えばグロメット１７が第一フィルタ保持部５１の軸線に対して傾いて取り付けられる等の不具合も生じにくい。なお、カバー側係合凸部１００は、第一フィルタ保持部５１の周方向に沿って断続的に形成してもよい。また、カバー側係合凸部１００によりグロメット１７の軸線方向前端位置が規定されることにより、グロメット１７とセラミックセパレータ１８の後端面との間には、一定量の隙間９８が形成されている。
【００２２】
図３は、フィルタアセンブリ１６の組立状態を示している。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等で構成された撥水性フィルタであり、第二フィルタ保持部５４には、第二気体導入孔５５の列を挟んでその軸方向両側に環状のフィルタ加締部５６，５７が形成されている。第一フィルタ保持部５１は、段付き部６０により径大の第一部分６１と径小の第二部分６２とが形成され、第一気体導入孔５２は第二部分６２に形成されている。図２に示すように、第一フィルタ保持部５１は、段付き部６０においてセパレータ側支持部７３に対し金属弾性部材７４（波形座金）を介して当接配置される。また、第一部分６１と主筒１４との重なり部にはケーシング加締部７６が形成されている。さらに、第二フィルタ保持部５４の外側には、筒状の防護カバー６４が設けられている。なお、第一フィルタ保持部５１の第一部分６１の外周面には、気体導入部となる溝部６９が周方向に沿って複数形成されている。
【００２３】
図２に戻り、セラミックセパレータ１８はセパレータ側支持部７３よりも前方側が主筒１４（ケーシング１０）の内側に入り込むように配置され、各リード線２０，２１等がセパレータ側リード線挿通孔７２において軸方向に挿通される。一方、グロメット１７は、第一フィルタ保持部５１の後方側開口部に対しその内側に弾性的に嵌め込まれ、各リード線２０，２１等を挿通するためのシール側リード線挿通孔９１を有するとともに、それらリード線２０，２１等の外面と第一フィルタ保持部５１の内面との間をシールする。
【００２４】
セラミックセパレータ１８の後端面は、軸方向において第一気体導入孔５２よりも後方側に位置するとともに、グロメット１７とセラミックセパレータ１８との間には前記した隙間９８が形成されている。また、第一フィルタ保持部５１の内周面とセラミックセパレータ１８の外周面との間にも隙間９２が形成されている。そして、第一気体導入孔５２からの気体は該隙間９２内に供給され、さらにセパレータ側リード線挿通孔７２とリード線との間に形成された隙間Ｋを通ってケーシング１０内に導かれる。
【００２５】
セラミックセパレータ１８には、４つのリード線挿通孔７２が略９０°間隔で形成され、その軸線方向中央前端側には、発熱体端部収容孔１８ａが軸線方向に形成されている。発熱体端部収容孔１８ａは、各リード線挿通孔７２に対し内側から重なりを生ずるように、セラミックセパレータ１８の中央部を切り欠いた形態で形成されている。そして、図６に示すように、外部電極接続金具３３の金具本体部３３ｃの後端縁は、セラミックセパレータ１８の発熱体端部収容孔１８ａの開口側の端面において、隣接するリード線挿通孔７２間に形成された隔壁部１８ｂの端面に当接している。また、内部電極接続金具２３の金具本体部２３ｃの後端縁は、外部電極接続金具３３の金具本体部３３ｃよりも内側にて、上記隔壁部１８ｂの端面に当接している。
【００２６】
図１の酸素センサ１は、フィルタ５３を介して大気が導入される一方、酸素検出素子２の外面には排気ガスが接触する。酸素検出素子２は、その内外面の酸素濃度差に応じて生ずる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リード線２１，２０を介して出力するものである。以下、酸素センサ１の製造方法について説明する。まず、図４（ａ）に示すように、フィルタアセンブリ１６を予め組み立てておき、内側にはリード線２０，２１等を挿通しておく。なお、各リード線２０，２１は、セラミックセパレータ１８のリード線挿通孔７２に通しておき、内部電極接続金具２３及び外部電極接続金具３３を接続しておく。また、セラミックセパレータ１８の後端部外側には金属弾性部材７４を外挿する（図４（ｂ）参照）。そして、フィルタアセンブリ１６の第一フィルタ保持部５１の後端開口部内にグロメット１７を軸線方向に嵌着する。グロメット１７の前端縁は、第一フィルタ保持部５１の内周面に形成されたカバー側係合凸部１００に当たって位置決めされる。
【００２７】
続いて、そのグロメット１７を装着済みのフィルタアセンブリ１６を、グロメット１７の挿通孔９１内にてリード線２０，２１を滑らせながら、段部６０の内面がリング状の金属弾性部材７４に当たる位置まで移動させ、セラミックセパレータ１８の外側に被せる（図４（ｃ））。例えば、リード線２０，２１の束の上をフィルタアセンブリ１６を多少傾けて滑らせても、第一フィルタ保持部５１の開口部内縁とリード線２０，２１との間にはゴム製のグロメット１７が介在しているので、該開口縁にてリード線２０，２１の外被が削られる心配がない。
【００２８】
この状態で防護カバー６４及び第一フィルタ保持部５１の後端側重なり部を周方向に沿って内側のグロメットに向けて加締めることにより、グロメット加締部６７を形成する。なお、リード線２０，２１等は両金具３３，２３のコネクタ３３ａ，２３ａに接続され、セラミックセパレータ１８のセパレータ側リード線挿通孔７２を通って、グロメット１７を経て外側に延出した状態となっている。他方、酸素検出素子２は主筒１４内に予め組み付けておく。
【００２９】
そして、図５（ａ）に示すように、発熱体３を先端側から酸素検出素子２内に挿入し、フィルタアセンブリ１６の第一フィルタ保持部５１を主筒１４に被せ、セラミックセパレータ１８を酸素検出素子２の後端部に向けて軸線方向に接近させる。これにより、外部電極接続金具３３の金具本体部３３ｃと、内部電極接続金具２３の金具本体部２３ｃとが、酸素検出素子２の開口部に位置決めされた形となる。そして、その状態でセラミックセパレータ１８の前端面（図６の隔壁部１８ｂの端面）に、金具本体部３３ｃ及び２３ｃの後端縁を当接させつつ、セラミックセパレータ１８と酸素検出素子２に向けて軸線方向にさらに接近させる。図６に示すように、酸素検出素子２の後端部が金具本体部３３ｃの内側に相対的に押し込まれるとともに、金具本体部２３ｃは酸素検出素子２の内側に押し込まれる。このとき、各金具本体部３３ｃ，２３ｃの後端縁はセラミックセパレータ１８の端面に当接しているので、軸線方向の押込力による引出し線部３３ｂ，２３ｂの挫屈といった不具合を生じることなく、スムーズな組立てが可能となっている。
【００３０】
そして、図５（ｂ）において、第一フィルタ保持部５１と主筒１４とを軸線方向に加圧して金属弾性部材７４を圧縮変形させ、その状態で第一フィルタ保持部５１と主筒１４とにケーシング加締部７６を形成して両者を結合することにより組立てが終了する。
【００３１】
なお、図７に示すように、グロメット側係合部を、グロメット１７の軸線方向後端側において、その外周面から突出形成されたグロメット側凸部１０１を形成することもできる。そして、第一フィルタ保持部５１の後端開口端面をカバー側係合部として、これを上記グロメット側凸部１０１と係合させることにより、グロメット１７の第一フィルタ保持部５１への軸線方向の位置決めを行うことができる。
【００３２】
なお、図に示す実施例では、グロメット側凸部１０１はグロメット１７の周方向に沿う鍔状に形成されている。また、第二フィルタ保持部５４の後端部内周縁を内向きに突出させてグロメット押さえ部５４ａを形成し、グロメット側凸部１０１をそのグロメット押さえ部５４ａと第一フィルタ保持部５１の後端開口端面との間で挟み付けて保持する形としている。この場合、グロメット１７を第一フィルタ部５１へ嵌め込んだ後、フィルタ５３及び第二フィルタ保持部５４をこの順序で外側から被せ、加締部６７，５６，５７を形成して組付けを行う形となる。グロメット押さえ部５４ａは、第二フィルタ保持部５４を被せた際に、グロメット１７が第一フィルタ保持部５１から飛び出すことを防止する役割を果たす。また、第二フィルタ保持部５４の軸線方向前端側は、第一フィルタ保持部５１の第一部分６２にかかる位置まで延長され、加締部６６によりこれに加締止めされている。なお、防護カバーは省略されている。
【００３３】
また、図８に示す構成では、カバー側係合凸部１０２が、軸線方向中間部において第一フィルタ保持部５１（カバー部材）の壁部を周方向に内向きに凹ませることにより、壁部内面側の対応する位置に形成される環状の凸部として形成されている。第一気体導入孔５２の列は、その環状の凸部１０２の稜線に沿って形成されるとともに、壁部外面側においてその環状の凸部１０２に対応する形で環状の溝部１０２ａが形成され、その溝部がフィルタ５３を経て第一気体導入孔５２に向かう外気の流通空間となっている。この構成では、カバー側係合凸部１０２に対応して生ずる溝部１０２ａを、外気の流通空間として流用することで、フィルタ５３を通って流れ込む基準ガスとしての外気（大気）の流通抵抗が和らげられ、第一気体導入孔５２から外筒１４内にスムーズにこれを導入できる。なお、防護カバー６４の後方側開口内縁には、グロメット１７の飛び出しを防止するための飛び出し防止凸部６４ａが、例えば周方向に沿って形成されている。
【００３４】
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することができる。
【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縦断面図。
【図２】図１の酸素センサの要部を示す縦断面図。
【図３】組立状態のフィルタアセンブリの部分縦断面図。
【図４】図１の酸素センサの組立方法の一例を示す工程説明図。
【図５】図４に続く工程説明図。
【図６】図１のセラミックセパレータの作用説明図。
【図７】図１の酸素センサの変形例の要部を示す縦断面図。
【図８】同じく別の変形例の要部を示す縦断面図。
【符号の説明】
１酸素センサ
２酸素検出素子
３発熱体
１６フィルタアセンブリ（カバー部材）
１７グロメット
１８セラミックセパレータ
２０，２１リード線
１００，１０２カバー側係合凸部
１０１グロメット側係合凸部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to oxygen sensors, HC sensors, NO_XThe present invention relates to a gas sensor for detecting a component to be detected in a gas to be measured, such as a sensor.
[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. . For example, in the case of an oxygen sensor, a shaft-shaped oxygen detection element made of a solid electrolyte ceramic such as zirconia is arranged in the casing so that the detection part at the tip protrudes, and the element comes in contact with the gas to be measured. The sensor output generated in is taken out through the lead wire.
[0003]
For example, many general oxygen sensors have an air passage for introducing air as a reference gas into the casing on the rear end side (opposite to the detection portion) of the casing that houses the oxygen detection element. A cover member is assembled. The lead wire passes through a ceramic separator disposed in the cover member, and is further drawn out through a rubber grommet for sealing fitted in a rear end opening of the cover member.
[0004]
By the way, in recent years, the demand for oxygen sensors has increased with the rise of the automobile industry, and the demand for price reduction has been increasing year by year. Gas sensors such as oxygen sensors have a large number of parts among electric parts for automobiles, and how to simplify the assembly process is an important key to reducing manufacturing costs. To that end, it is necessary to improve the technology on the production equipment side, such as automation of the assembly process, but it is also important to devise a sensor structure that is advantageous for man-hour reduction.
[0005]
[Problems to be solved by the invention]
  Conventionally, when assembling the oxygen sensor as described above, for example, an oxygen detection element, a heating element for heating the oxygen detection element, and the like are assembled in advance in a cylindrical casing, and a lead wire or the like is attached to a ceramic separator. Pass through the lead wire insertion hole. At this time, each lead wire is in a state of extending outward from the rear end opening of the cover member. In the subsequent assembly, the cover member is attached to the rear end of the casing while sliding on the lead wire on the inner surface side, and then the grommet is attached to the cover member.FittingIt is a form that includes a process of at least two stages of entering.
[0006]
However, in this method, since the attachment of the cover member to the casing and the attachment of the grommet to the cover member are sequentially performed, the number of man-hours increases and the efficiency is poor. In addition, the rear end opening of the cover member is often reduced in diameter in order to reduce the grommet size and improve the sealing performance. However, the grommet fits over the bundle of lead wires that pass therethrough. The front cover member is slid and attached to the casing. Therefore, if the cover member is tilted and slid even slightly over the bundle of lead wires, the outer cover of the lead wire is scraped at the opening edge of the cover member, resulting in poor insulation or shavings remaining in the casing. It is easy to cause trouble.
[0007]
On the other hand, for example, when the flow path of outside air introduced into the casing from the outside of the cover member is secured, or when the size of the arrangement pitch circle of the lead wire insertion holes is different between the grommet and the ceramic separator, the pitch In many cases, a predetermined amount of gap is formed between the ceramic separator and the grommet disposed in the cover member for the purpose of absorbing the difference in the diameters of the circles. In this case, when the grommet is pushed into the cover member, it is difficult to position the grommet in the axial direction, and another problem arises that it takes time to adjust the amount of the gap to an intended value.
[0008]
An object of the present invention is to efficiently perform assembly of the cover member and the grommet to the sensor by adopting the gas sensor having a structure capable of easily positioning the grommet to the cover member and the structure. Another object of the present invention is to provide a method of manufacturing a gas sensor that hardly damages a lead wire jacket or the like when the cover member is attached to the casing.
[0009]
[Means for solving the problems and actions / effects]
  In order to solve the above problems, the gas sensor of the present inventionThe first of,
A shaft-shaped detection element and a cylindrical casing that accommodates the detection element in a state where the detection portion formed at the tip of the detection element is projected, and is connected to the casing from the rear side in the axial direction. A cover member for extending the lead wire from the detection element to the outside from the rear end opening, and the cover member is fitted inward from the rear end opening to seal the gap between the lead wire and the inner surface of the cover member The cover member has a grommet in the axial direction from the rear end opening.FittingWhen engaged, it engages with the grommet side engaging portion formed on the grommet side, so that the grommet in the axial direction of the grommet with respect to the cover memberFittingA cover side engagement part that defines the entry position is formed.The cover side engaging portion is a cover side engaging convex portion that protrudes from the inner surface at a position spaced apart from the opening edge of the rear end of the cover member by a predetermined distance in the axial direction, and the front end edge in the axial direction of the grommet. As a grommet side engaging part, it comes to engage with thisIt is characterized by.
The second of the present invention is
A shaft-shaped detection element and a cylindrical casing that accommodates the detection element in a state where the detection portion formed at the tip of the detection element is projected, and is connected to the casing from the rear side in the axial direction. A cover member for extending the lead wire from the detection element to the outside from the rear end opening, and the cover member is fitted inward from the rear end opening to seal the gap between the lead wire and the inner surface of the cover member The cover member is engaged with a grommet side engaging portion formed on the grommet side when the grommet is inserted in the axial direction from the rear end opening portion, so that the grommet with respect to the cover member is engaged with the cover member. A cover side engaging portion that defines an insertion position in the axial direction is formed, and the cover member is provided integrally therewith on the rear side of the casing for guiding the outside air into the casing. A first filter holding portion having one gas introduction hole, and a second filter holding portion provided outside the first filter holding portion and having a second gas introduction hole for introducing outside air into the casing; A filter assembly including a filter disposed between the first and second filter holding portions so as to block the first and second gas introduction holes, and blocking liquid permeation and allowing gas permeation. The first filter holding portion of the filter assembly is connected to the casing from the rear side as a cylindrical body separate from the casing, and the grommet is fitted in the rear end opening of the first filter holding portion, A plurality of first gas introduction holes are formed at predetermined intervals along the circumferential direction of the first filter holding portion, and are closed from the outside by the cylindrical filter, and are engaged on the cover side. Is an annular convex portion formed at a corresponding position on the inner surface side of the wall portion by denting the wall portion of the cover member inward in the circumferential direction at the intermediate portion in the axial direction, and a row of first gas introduction holes Is formed along the ridge line of the annular convex portion, and an annular groove portion is formed on the outer surface side of the wall portion in a shape corresponding to the annular convex portion, and the groove portion passes through the filter and the first gas introduction hole is formed. It is characterized by being a distribution space for outside air toward
[0010]
  According to the configuration of the gas sensor, when the grommet is attached to the cover member, the grommet can be easily positioned in the axial direction on the cover member by the engagement of the grommet side engaging portion and the cover side engaging portion. it can.
According to the first configuration of the gas sensor,For example, a ceramic separator in which lead wire insertion holes for individually inserting a plurality of lead wires are formed in the axial direction can be disposed in the cover member. In this case, the engagement of the cover side engaging portion and the grommet side engaging portion makes it easy to place the grommet at a position where a predetermined amount of gap is formed between its front end surface and the rear end surface of the ceramic separator. As a result, the clearance can be secured and the gap amount can be managed very easily.Further, the front end edge of the grommet in the axial direction is used as a grommet side engaging portion, and this is engaged with the cover side engaging convex portion, whereby the grommet can be reliably positioned on the cover member.
According to the second configuration of the gas sensor, the flow resistance of the outside air (atmosphere) as the reference gas flowing through the filter is obtained by diverting the groove formed corresponding to the cover side engaging portion as the outside air circulation space. And can be smoothly introduced into the outer cylinder from the first gas introduction hole.
[0011]
  In addition, the manufacturing method of the gas sensor of the present invention, when manufacturing the gas sensor of the present invention having the above structure, in a state before being attached to the casing,When the grommet is inserted into the cover member in the axial direction from the rear end opening in the state before being attached to the casing, the cover member is engaged with the grommet side engaging portion formed on the grommet side. A cover side engagement portion that prescribes the insertion position of the grommet in the axial direction is formed in advance, andThe grommet is engaged with the rear end opening of the cover member, and the cover side engaging portion and the grommet side engaging portion are engaged.Fit in the formThe cover member that is inserted and fixed and has the grommet attached thereto is attached to the casing.
[0012]
According to this method, the grommet is attached to the cover member in a state before being attached to the casing, and the cover member with the grommet is assembled to the casing. Thereby, when assembling a large number of gas sensors, the attachment of the grommet to the cover member and the attachment of the cover member to the casing can be performed in parallel, so that the assembly process can be greatly streamlined. . Further, the operation of assembling the grommet while positioning the grommet on the cover member in the axial direction can be performed very efficiently by employing the configuration of the gas sensor of the present invention. Note that the lead wire in the cover member can be inserted into the grommet, and the cover member can be attached to the casing while sliding on the lead wire in the insertion hole of the grommet. As a result, even if the cover member is slightly tilted and slid over the bundle of lead wires, a grommet made of rubber or the like is interposed between the inner edge of the opening of the cover member and the lead wire. The trouble that the outer jacket of the lead wire is cut off at the opening edge of the member is less likely to occur.
[0013]
  In addition,In the first configuration of the gas sensor, the cover-side engagement convex portion is formed at a corresponding position on the inner surface side of the wall portion by indenting the wall portion of the cover member inward in the axial direction intermediate portion. It can be a convex part. Such a convex part can be easily formed by performing a process such as pressing from the outside at the intermediate position in the axial direction of the cover member. Moreover, the convex part may be formed continuously or intermittently along the circumferential direction of the cover member. As a result, the grommet can be more easily positioned with respect to the cover member, and problems such as the grommet being inclined with respect to the axis of the cover member are less likely to occur.
  On the other hand, the grommet side engaging portion may be a grommet side convex portion that protrudes from the outer peripheral surface on the rear end side in the axial direction of the grommet. In this case, the rear end opening end face of the cover member is used as a cover side engaging portion, and this is engaged with the grommet side convex portion, whereby the grommet can be reliably positioned on the cover member.
[0014]
  In addition, the gas sensorIn the first configurationIs provided integrally therewith on the rear side of the casing, and has a first filter holding portion in which a first gas introduction hole for guiding outside air is formed in the casing, and inside or outside of the first filter holding portion. A second filter holding portion provided with a second gas introduction hole for guiding the outside air into the casing, and a configuration for closing the first and second gas introduction holes between the first and second filter holding portions. The first filter holding unit is connected to the casing from the rear side as a cylindrical body separate from the casing. Can be configured.
[0015]
The gas sensor having such a structure can be manufactured by the following method. First, the second filter holding part is formed by arranging the filter and the second filter holding part in this order on the outside of the first filter holding part in this order before being assembled to the casing, and forming the crimped part in that state. And a filter is assembled | attached to a 1st filter holding | maintenance part, and it is set as a filter assembly. The filter assembly is used as a cover member, and the grommet is assembled in advance to the cover member, and the filter assembly to which the grommet is already attached is attached to the casing.
[0016]
The gist of the sensor configuration described above is that the ventilation structure including the filter is configured as a filter assembly independently of the casing, and is connected to and integrated with the casing. Thereby, the following effects are achieved in the manufacturing method.
(1) Since the assembly of the filter assembly can be performed independently of the assembly of the oxygen sensing element into the casing, for example, the lead wire of the sensing element does not get in the way, and the assembly work is extremely efficient. Can be done.
(2) Since the assembly of parts into the casing and the assembly of the filter assembly can be performed in parallel, the productivity is dramatically improved. Even if a filter assembly failure or the like occurs, if a failure can be found at the filter assembly stage, the sensor will not be affected by the failure, and parts will not be wasted.
[0017]
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. The casing 10 includes a metal shell 9 having a sensor mounting screw portion 9b, a main tube 14 and a protector 11 coupled thereto. The protector 11 is formed with a plurality of gas permeation ports 12 through which exhaust gas permeates. On the outer surface of the oxygen detecting element 2 and the inner surface of the hollow portion 2a, an electrode layer (not shown) is formed so as to cover almost the entire surface.
[0018]
In the opening on the rear side of the metal shell 9, the aforementioned main cylinder 14 is crimped via a ring 15 between the insulator 6 and a tubular filter assembly 16 (cover member) is attached to the main cylinder 14. It is fitted and fixed from the outside. The opening on the rear end side of the filter assembly 16 is sealed with a grommet 17 made of rubber or the like, and a ceramic separator 18 is further provided inward. Then, lead wires 20 and 21 for the oxygen detecting element 2 and lead wires (not shown) for the heating element 3 are arranged so as to penetrate the ceramic separator 18 and the grommet 17.
[0019]
As shown in FIG. 2, a separator-side lead wire insertion hole 72 is formed in the ceramic separator 18, and a flange-like separator-side support portion 73 is formed to protrude from the outer peripheral surface thereof. One lead wire 20 for the oxygen detection element 2 passes through the internal electrode connection fitting 23 including the connector 23a, the lead wire portion 23b, the fitting main body portion 23c, and the heating element gripping portion 23d, which are integrally formed with each other. The internal electrode layer of the element 2 is electrically connected. On the other hand, the other lead wire 21 is electrically connected to the external electrode layer of the oxygen detection element 2 through the external electrode connection fitting 33 having a connector 33a, a lead wire portion 33b and a fitting main body portion 33c that are integrally formed with each other. It is connected. The oxygen detection element 2 is activated by heating with the heating element 3 disposed inside thereof. The heating element 3 is a rod-shaped ceramic heater, and a heating part 42 (FIG. 1) having a resistance heating line part (not shown) is energized through a lead wire (not shown). The tip (detector) is heated.
[0020]
Next, the filter assembly 16 includes a first filter holding part 51 in which a plurality of first gas introduction holes 52 are formed. A cylindrical filter 53 that closes the first gas introduction hole 52 and a plurality of second gas introduction holes 55 are formed on the outside thereof, and the second filter 53 is sandwiched and held between the first filter holding portion 51 and the second. A filter holding unit 54 is disposed. A cover-side engagement convex portion as a cover-side engagement portion protrudes from the inner surface of the filter assembly 16 at a position spaced a predetermined distance from the rear end opening edge of the first filter holding portion 51 in the direction of the axis O. 100 is formed. Then, the front end edge in the axial direction of the grommet 17 fitted in the rear end opening serves as a grommet side engaging portion, and this engages with the cover side engaging convex portion 100, whereby the first grommet 17 The assembly position of the filter holder 51 in the axial direction is defined.
[0021]
The cover-side engaging convex portion 100 has a rib-shaped convex portion formed at a corresponding position on the inner surface side of the wall portion by indenting the wall portion of the first filter holding portion 51 inward in the axial direction intermediate portion. It is considered to be a part. Such a convex part 100 can be easily formed by subjecting the first filter holding part 51 (cover member) to a pressing process or the like from the outside at an intermediate position in the axial direction. Moreover, although the convex part 100 is formed in the continuous annular shape along the circumferential direction of the 1st filter holding | maintenance part 51, this makes it easier to position the grommet 17 with respect to the 1st filter holding | maintenance part 51, for example, a grommet Inconveniences such as 17 being attached to the axis of the first filter holding portion 51 are not likely to occur. Note that the cover-side engagement convex portion 100 may be formed intermittently along the circumferential direction of the first filter holding portion 51. Further, by defining the axial front end position of the grommet 17 by the cover side engaging convex portion 100, a certain amount of gap 98 is formed between the grommet 17 and the rear end face of the ceramic separator 18.
[0022]
FIG. 3 shows the assembled state of the filter assembly 16. The filter 53 is a water-repellent filter made of, for example, a polytetrafluoroethylene porous fiber structure, and the second filter holding portion 54 has both sides in the axial direction sandwiching a row of second gas introduction holes 55. Annular filter caulking portions 56 and 57 are formed in the upper part. In the first filter holding part 51, a first part 61 having a large diameter and a second part 62 having a small diameter are formed by a stepped part 60, and a first gas introduction hole 52 is formed in the second part 62. As shown in FIG. 2, the first filter holding portion 51 is disposed in contact with the separator-side support portion 73 in the stepped portion 60 via a metal elastic member 74 (corrugated washer). A casing caulking portion 76 is formed at an overlapping portion between the first portion 61 and the main cylinder 14. Further, a cylindrical protective cover 64 is provided outside the second filter holding portion 54. Note that a plurality of groove portions 69 serving as gas introduction portions are formed on the outer peripheral surface of the first portion 61 of the first filter holding portion 51 along the circumferential direction.
[0023]
Returning to FIG. 2, the ceramic separator 18 is arranged so that the front side of the separator side support portion 73 enters the inside of the main cylinder 14 (casing 10), and the lead wires 20, 21, etc. are placed in the separator side lead wire insertion holes 72. It is inserted in the axial direction. On the other hand, the grommet 17 is elastically fitted inside the opening on the rear side of the first filter holding portion 51 and has a seal-side lead wire insertion hole 91 for inserting each lead wire 20, 21 and the like. The space between the outer surfaces of the lead wires 20 and 21 and the inner surface of the first filter holding portion 51 is sealed.
[0024]
The rear end surface of the ceramic separator 18 is positioned rearward of the first gas introduction hole 52 in the axial direction, and the gap 98 described above is formed between the grommet 17 and the ceramic separator 18. A gap 92 is also formed between the inner peripheral surface of the first filter holding part 51 and the outer peripheral surface of the ceramic separator 18. Then, the gas from the first gas introduction hole 52 is supplied into the gap 92 and further guided into the casing 10 through the gap K formed between the separator-side lead wire insertion hole 72 and the lead wire.
[0025]
In the ceramic separator 18, four lead wire insertion holes 72 are formed at approximately 90 ° intervals, and a heating element end accommodating hole 18a is formed in the axial direction on the front end side in the center in the axial direction. The heating element end accommodating hole 18a is formed in a form in which the central portion of the ceramic separator 18 is cut away so as to overlap each lead wire insertion hole 72 from the inside. As shown in FIG. 6, the rear end edge of the metal body 33 c of the external electrode connection metal 33 is adjacent to the lead wire insertion hole 72 on the end face of the ceramic separator 18 on the opening side of the heating element end accommodating hole 18 a. It abuts against the end face of the partition wall 18b formed therebetween. The rear end edge of the metal body part 23 c of the internal electrode connection fitting 23 is in contact with the end surface of the partition wall part 18 b on the inner side of the metal fitting body part 33 c of the external electrode connection metal part 33.
[0026]
In the oxygen sensor 1 of FIG. 1, the atmosphere is introduced through the filter 53, while the exhaust gas contacts the outer surface of the oxygen detection element 2. The oxygen detection element 2 outputs an oxygen concentration cell electromotive force generated according to the difference in oxygen concentration between the inner and outer surfaces through lead wires 21 and 20 as a detection signal of the oxygen concentration in the exhaust gas. Hereinafter, a method for manufacturing the oxygen sensor 1 will be described. First, as shown in FIG. 4A, the filter assembly 16 is assembled in advance, and lead wires 20, 21 and the like are inserted inside. The lead wires 20 and 21 are passed through the lead wire insertion holes 72 of the ceramic separator 18 to connect the internal electrode connection fitting 23 and the external electrode connection fitting 33. Further, a metal elastic member 74 is extrapolated outside the rear end portion of the ceramic separator 18 (see FIG. 4B). Then, the grommet 17 is fitted in the axial direction in the rear end opening of the first filter holding portion 51 of the filter assembly 16. The front edge of the grommet 17 is positioned by hitting the cover side engaging convex portion 100 formed on the inner peripheral surface of the first filter holding portion 51.
[0027]
Subsequently, the filter assembly 16 to which the grommet 17 is already attached is moved to a position where the inner surface of the stepped portion 60 contacts the ring-shaped metal elastic member 74 while sliding the lead wires 20 and 21 in the insertion hole 91 of the grommet 17. Move and cover the outside of the ceramic separator 18 (FIG. 4C). For example, even if the filter assembly 16 is slightly tilted and slid on the bundle of the lead wires 20 and 21, the rubber grommet 17 is provided between the opening inner edge of the first filter holding portion 51 and the lead wires 20 and 21. Therefore, there is no concern that the outer sheath of the lead wires 20 and 21 is cut off at the opening edge.
[0028]
In this state, a grommet caulking portion 67 is formed by caulking the protective cover 64 and the overlapping portion on the rear end side of the first filter holding portion 51 toward the inner grommet along the circumferential direction. The lead wires 20, 21, etc. are connected to the connectors 33 a, 23 a of both metal fittings 33, 23, pass through the separator-side lead wire insertion hole 72 of the ceramic separator 18, and extend outward through the grommet 17. ing. On the other hand, the oxygen detection element 2 is assembled in the main cylinder 14 in advance.
[0029]
Then, as shown in FIG. 5A, the heating element 3 is inserted into the oxygen detection element 2 from the tip side, the first filter holding portion 51 of the filter assembly 16 is covered on the main cylinder 14, and the ceramic separator 18 is oxygenated. It is made to approach in the axial direction toward the rear end portion of the detection element 2. Thereby, the metal fitting main body portion 33 c of the external electrode connecting metal fitting 33 and the metal fitting main body portion 23 c of the internal electrode connecting metal fitting 23 are positioned in the opening of the oxygen detection element 2. In this state, the rear end edges of the metal fitting main body portions 33c and 23c are brought into contact with the front end surface of the ceramic separator 18 (the end surface of the partition wall portion 18b in FIG. 6) while facing the ceramic separator 18 and the oxygen detection element 2. Further approach in the axial direction. As shown in FIG. 6, the rear end portion of the oxygen detection element 2 is relatively pushed into the inside of the metal fitting main body portion 33 c, and the metal fitting main body portion 23 c is pushed into the inside of the oxygen detection element 2. At this time, since the rear end edges of the respective metal fitting main body portions 33c and 23c are in contact with the end face of the ceramic separator 18, smoothness can be achieved without causing problems such as buckling of the lead wire portions 33b and 23b due to the pushing force in the axial direction. Assembly is possible.
[0030]
5 (b), the first filter holding part 51 and the main cylinder 14 are pressurized in the axial direction to compress and deform the metal elastic member 74, and in this state, the first filter holding part 51 and the main cylinder 14 are The assembly is completed by forming the casing crimping portion 76 and joining them together.
[0031]
In addition, as shown in FIG. 7, the grommet side engaging part can also form the grommet side convex part 101 which protrudes from the outer peripheral surface at the axial direction rear end side of the grommet 17. Then, the rear end opening end face of the first filter holding portion 51 is used as a cover side engaging portion, and this is engaged with the grommet side convex portion 101, whereby the grommet 17 in the axial direction to the first filter holding portion 51 is engaged. Positioning can be performed.
[0032]
In the embodiment shown in the figure, the grommet side convex portion 101 is formed in a bowl shape along the circumferential direction of the grommet 17. Further, the inner peripheral edge of the rear end of the second filter holding portion 54 protrudes inward to form a grommet pressing portion 54a, and the grommet-side convex portion 101 is opened to the rear end of the grommet pressing portion 54a and the first filter holding portion 51. The shape is sandwiched and held between the end faces. In this case, after fitting the grommet 17 into the first filter portion 51, the filter 53 and the second filter holding portion 54 are covered from the outside in this order, and the crimping portions 67, 56, 57 are formed and assembled. It becomes a shape. The grommet pressing part 54 a plays a role of preventing the grommet 17 from jumping out of the first filter holding part 51 when the second filter holding part 54 is covered. Further, the front end side in the axial direction of the second filter holding portion 54 is extended to a position on the first portion 62 of the first filter holding portion 51, and is fastened to this by a crimping portion 66. The protective cover is omitted.
[0033]
Further, in the configuration shown in FIG. 8, the cover-side engagement convex portion 102 dents the wall portion of the first filter holding portion 51 (cover member) inward in the circumferential direction at the intermediate portion in the axial direction. It is formed as an annular convex portion formed at a corresponding position on the inner surface side. The row of the first gas introduction holes 52 is formed along the ridge line of the annular convex portion 102, and an annular groove portion 102a is formed in a shape corresponding to the annular convex portion 102 on the outer side of the wall portion. The groove portion serves as a circulation space for the outside air toward the first gas introduction hole 52 through the filter 53. In this configuration, the flow resistance of the outside air (atmosphere) as the reference gas flowing through the filter 53 is reduced by diverting the groove portion 102 a generated corresponding to the cover side engaging convex portion 102 as the outside air circulation space. This can be smoothly introduced into the outer cylinder 14 from the first gas introduction hole 52. Note that, at the inner edge of the rear opening of the protective cover 64, a pop-out preventing convex portion 64a for preventing the grommet 17 from popping out is formed, for example, along the circumferential direction.
[0034]
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._XThe same applies to sensors and the like.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an oxygen sensor as an embodiment of a gas sensor of the present invention.
FIG. 2 is a longitudinal sectional view showing a main part of the oxygen sensor of FIG.
FIG. 3 is a partial longitudinal sectional view of the filter assembly in an assembled state.
4 is a process explanatory view showing an example of an assembly method of the oxygen sensor of FIG. 1; FIG.
FIG. 5 is a process explanatory diagram following FIG. 4;
6 is an operation explanatory view of the ceramic separator of FIG. 1. FIG.
7 is a longitudinal sectional view showing the main part of a modification of the oxygen sensor of FIG.
FIG. 8 is a longitudinal sectional view showing the main part of another modification.
[Explanation of symbols]
1 Oxygen sensor
2 Oxygen detection element
3 Heating elements
16 Filter assembly (cover member)
17 Grommet
18 Ceramic separator
20, 21 Lead wire
100, 102 Cover-side engagement convex part
101 Grommet side engagement convex part

Claims

An axial sensing element;
In a state where the detection portion formed at the tip of the detection element is protruded, a cylindrical casing that accommodates the detection element;
A cover member that is connected to the casing from the rear side in the axial direction and extends the lead wire from the detection element to the outside from the rear end opening, and is fitted inward from the rear end opening to the cover member A grommet that seals between the lead wire and the inner surface of the cover member,
Said cover member from said rear end opening when you type fitting the grommet in the axial direction, by engaging the grommet-side engagement portion formed on the grommet side, the axis of the grommet against the cover member A cover-side engagement portion that defines the insertion position in the direction is formed ;
The cover-side engagement portion is a cover-side engagement convex portion that is formed to protrude from the inner surface of the cover member at a predetermined distance in the axial direction from the rear end opening edge of the cover member, and the front end edge in the axial direction of the grommet A gas sensor characterized in that a part is used as the grommet side engaging part and is engaged with the grommet side engaging part .

A ceramic separator in which lead wire insertion holes for individually inserting a plurality of the lead wires are formed in the axial direction is disposed in the cover member, and the grommet includes the cover side engaging portion and the grommet. The gas sensor according to claim 1 , wherein the gas sensor is fixed at a position where a predetermined amount of gap is formed between the front end surface of the ceramic separator and the rear end surface of the ceramic separator by engagement with the side engaging portion.

The cover-side engaging convex portion is a convex portion that is formed at a corresponding position on the inner surface side of the wall portion by denting the wall portion of the cover member inward in the axially intermediate portion, and the convex portion The gas sensor according to claim 1 , wherein the gas sensor is formed continuously or intermittently along a circumferential direction of the cover member.

The cover member is provided integrally therewith on the rear side of the casing, and a first filter holding portion in which a first gas introduction hole for introducing outside air into the casing is formed;
A second filter holding portion provided outside the first filter holding portion and having a second gas introduction hole for guiding outside air into the casing;
A filter assembly including a filter disposed between the first and second filter holding portions so as to close the first and second gas introduction holes, and blocking the permeation of liquid and allowing the permeation of gas. The gas sensor according to any one of claims 1 to 3 , wherein the first filter holding portion of the filter assembly is connected to the casing from the rear side as a cylindrical body separate from the casing.

An axial sensing element;
In a state where the detection portion formed at the tip of the detection element is protruded, a cylindrical casing that accommodates the detection element;
A cover member that is connected to the casing from the rear side in the axial direction and extends the lead wire from the detection element to the outside from the rear end opening, and is fitted inward from the rear end opening to the cover member A grommet that seals between the lead wire and the inner surface of the cover member,
Said cover member from said rear end opening when you type fitting the grommet in the axial direction, by engaging the grommet-side engagement portion formed on the grommet side, the axis of the grommet against the cover member A cover-side engagement portion that defines the insertion position in the direction is formed ;
The cover member is provided integrally therewith on the rear side of the casing, and includes a first filter holding portion in which a first gas introduction hole for introducing outside air into the casing is formed, and the first filter holding portion. A second filter holding portion provided on the outside of the casing and formed with a second gas introduction hole for introducing outside air into the casing, and the first and second gases between the first and second filter holding portions. A filter assembly that is arranged in a form to close the introduction hole, and includes a filter that prevents permeation of liquid and allows permeation of gas, and wherein the first filter holding portion of the filter assembly is a cylinder separate from the casing. Connected to the casing from the rear side as a body
Further, the grommet is fitted in a rear end opening of the first filter holding part,
A plurality of the first gas introduction holes are formed at predetermined intervals along the circumferential direction of the first filter holding portion, and are closed from the outside by the cylindrical filter,
The cover side engaging portion is an annular convex portion formed at a corresponding position on the inner surface side of the wall portion by denting the wall portion of the cover member inward in the circumferential direction at an axially intermediate portion, The row of the first gas introduction holes is formed along the ridge line of the annular convex portion, and an annular groove portion is formed on the outer surface side of the wall so as to correspond to the annular convex portion. A gas sensor characterized in that it is a circulation space of outside air that goes to the first gas introduction hole through the filter .

An axial sensing element;
In a state where the detection portion formed at the tip of the detection element is protruded, a cylindrical casing that accommodates the detection element;
A cover member connected to the casing from the rear side in the axial direction, and extending a lead wire from the detection element to the outside from the rear end opening,
A gas sensor manufacturing method comprising a grommet that is fitted inward from the rear end opening to the cover member and seals between the lead wire and the inner surface of the cover member,
At before being mounted in said casing, said cover member, from said rear end opening when you type fitting the grommet in the axial direction, by engaging the grommet-side engagement portion formed on the grommet side A cover side engaging portion that prescribes a fitting position of the grommet in the axial direction with respect to the cover member is formed in advance , and further, in a state before being attached to the casing, in the rear end opening portion of the cover member. It said grommet, fitted to the input and fixed in a manner to engage the said cover-side engaging portion and the grommet-side engagement portion,
A method of manufacturing a gas sensor, comprising attaching the grommet-attached cover member to the casing.

The cover member is provided integrally therewith on the rear side of the casing, and includes a first filter holding portion in which a first gas introduction hole for introducing outside air into the casing is formed, and the first filter holding portion. A second filter holding portion provided on the outside of the casing and formed with a second gas introduction hole for introducing outside air into the casing, and the first and second gases between the first and second filter holding portions. A filter assembly that is arranged in a form that closes the introduction hole, and that includes a filter that prevents liquid from passing and allows gas to pass;
The method for manufacturing a gas sensor according to claim 6 , wherein the grommet is assembled in advance with respect to the filter assembly, and the filter assembly with the grommet attached thereto is attached to the casing.