JP4063996B2

JP4063996B2 - Gas sensor

Info

Publication number: JP4063996B2
Application number: JP08997299A
Authority: JP
Inventors: 儀明松原; 聡石川
Original assignee: NGK Spark Plug Co Ltd
Current assignee: NGK Spark Plug Co Ltd
Priority date: 1999-03-30
Filing date: 1999-03-30
Publication date: 2008-03-19
Anticipated expiration: 2019-03-30
Also published as: JP2000283949A

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】
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。このようなガスセンサは、該ケーシングの一部をなす主体金具の外周面に形成されたねじ部により排気管等の所定の取付部に取り付けられるとともに、主体金具の端部から突出する検出部が測定雰囲気中に保持され、被検出成分を検出する。そして、多くのガスセンサにおいては、測定雰囲気中に位置する検出部を被水や被毒から保護するために、該検出部を覆うプロテクタが設けられている。プロテクタの側壁部には気体流通孔が形成され、被測定ガスはこの気体流通孔からプロテクタ内に導かれ、検出部と接触させられる。
【０００３】
最近では、検出部の保護性能を高めるため、該プロテクタを内外２つの筒状部からなる二重構造としたものも多く使用されている。このような二重構造プロテクタにおいては、その内外の筒状部に形成される気体流通孔の形成位置に重なりが生じていると、その重なり部において水や被毒成分が検出部に直接到達する経路が形成されるので、二重構造による保護性能の向上効果が必ずしも十分に達成できない場合がある。そのため、多くの二重構造プロテクタにおいては、内側の筒状部と外側の筒状部とで気体流通孔の形成位置をずらせることで、上記のような経路が発生しないようにし、保護性能を高める工夫がなされている。
【０００４】
【発明が解決しようとする課題】
ところで、上記のような二重構造プロテクタにおいて、内外の筒状部は、気体流通孔が初期の位置関係を満足するものとなるように、周方向に位置合わせした状態で固定しなければならない。この場合、従来は、例えば２つの筒状部を底部が互いに重なるように配置するとともに、その重なり面に凹凸を形成しておき、それら凹凸の係合により位置合わせを行うようにしていたが、内外の筒状部は振動等により軸線方向に動きやすいため、組付け作業時において上記位置合わせ用の凹凸の係合が外れやすく、作業能率が極めて悪い欠点がある。また、位置合わせ後の両筒状部は、重なった底部同士を抵抗溶接により接合する形で固定されていたが、センサが高温環境で使用される場合には溶接部の劣化や振動付加により該固定が外れやすい問題がある。
【０００５】
本発明の課題は、２以上の筒状部を重ね配置した構造のプロテクタを有するとともに、それら筒状部の周方向の位置合わせが容易であり、ひいては組立て作業が容易なガスセンサを提供することにある。
【０００６】
【課題を解決するための手段及び作用・効果】
上記課題を解決するために本発明のガスセンサは、
先端部に検出部が形成された棒状又は筒状形態をなし、測定対象となるガス中の被検出成分を検出する検出素子と、前記検出部を一方の端部側から突出させた状態で、前記検出素子を覆う筒状の素子収容体と、その素子収容体の、前記検出部が突出する側の開口端部に結合されるとともに、前記被測定ガスの流通を許容した状態で該検出部を覆うプロテクタとを備え、そのプロテクタは、内外２つの筒状部、すなわち外側の第一筒状部と、その内側に軸方向に挿入される第二筒状部とを有するものとされ、かつ前記第二筒状部の外周面には、前記第一筒状部内への挿入に伴い該第一筒状部の内周面に形成された第一側係合部と係合して、前記第二筒状部を当該第一筒状部に対して周方向の所定位置に位置決め保持させる第二側係合部が形成され、
前記第一側係合部は前記第一筒状部の内周面から突出形成された係合凸部であり、前記第二側係合部は、前記第二筒状部の外周面においてその軸線方向に延び、前記係合凸部が嵌まり込んで該軸線方向に相対的にスライド移動することを許容する溝部であり、
前記素子収容体の前方側開口部には筒状のプロテクタ装着部が形成され、
前記第二筒状部は、前記第一筒状部の開口縁よりも所定距離内側に入り込むように、前記第一筒状部よりも軸線方向の長さが短く形成されており、該第一筒状部の開口側には、前記プロテクタ装着部への装着代部が所定幅で形成され、該装着代部に対し前記素子収容体の前記プロテクタ装着部を挿入し、該装着代部とプロテクタ装着部との重なり部に対し全周の環状溶接部を形成することにより取り付けられたことを特徴とする。
【０００７】
上記構成では、プロテクタの組立作業時において、内側の第二筒状部を外側の第一筒状部に挿入する際に、該第一筒状部の内周面に形成された第一側係合部と、第二筒状部の外周面に形成された第二側係合部とを互いに係合させることにより、第二筒状部が第一筒状部に対して周方向の所定位置に位置決め保持されるようにした。これにより、少なくとも２つの筒状部を重ね配置した構造のプロテクタを有するガスセンサにおいて、それら筒状部の周方向の相対的な位置決めが極めて行いやすくなり、プロテクタ組立の作業性が向上する。
【０００８】
なお、第一筒状部と第二筒状部とは、軸断面を略円形状に形成することができるが、この場合は第一側係合部と第二側係合部とは、それらの係合により両筒状部の相対回転を阻止するものとして構成することができる。これにより、略円形状軸断面を有する２つの筒状部同士の位置決め位置からの相対回転が、上記係合部の係合により阻止されるため、プロテクタの組立作業を一層容易に行うことができる。
【０００９】
上記ガスセンサにおいては、第一筒状部と第二筒状部との各側壁部に、気体の流通を許容する第一側気体流通孔及び第二側気体流通孔をそれぞれ厚さ方向に貫通する形態で形成することができる。この場合、第一側係合部と第二側係合部との係合により、それら第一側気体流通孔と第二側気体流孔とが所定の位置関係を満足するように、第一筒状部と第二筒状部とを容易に位置決め保持することが可能となる。
【００１０】
例えば、第一筒状部と第二筒状部との外壁部同士の間に所定量の隙間を形成し、第一側気体流通孔と第二側気体流孔とをそれら筒状部の周方向において互いにずれた位置関係となるように位置決めすれば、水や被毒成分がプロテクタを経て検出部に直接到達する経路が形成されにくくなり、検出部に対するプロテクタの保護性能が高められる。この場合、第一側係合部と第二側係合部とを設けることで、第一筒状部と第二筒状部とを上記位置関係を満足する形で容易に組み立てることができるようになる。
【００１１】
第一側係合部は、具体的には第一筒状部の内周面から突出形成された係合凸部とすることができ、第二側係合部は、第二筒状部の外周面においてその軸線方向に延び、係合凸部が嵌まり込んで該軸線方向に相対的にスライド移動することを許容する溝部とすることができる。この構成によれば、第二筒状部側の溝部に対し、第二筒状部側の係合凸部を嵌め入れ、その状態で該凸部を上記溝部内で相対的にスライドさせながら、第二筒状部を第一筒状部内に挿入することにより、両筒状部の位置決め組立の作業を極めて簡単に行うことができる。
【００１２】
なお、溝部は、第二筒状部の外周面においてその周方向にほぼ等角度間隔で複数形成することができる。この場合、係合凸部は、第一筒状部の内周面上の所定位置に１つ、又は該内周面の周方向において溝部の形成角度間隔の整数倍となる角度間隔で複数形成することができる。こうすれば、係合凸部を複数の溝部のいずれかに選択的に係合させることが可能となり、例えば係合凸部と溝部とを１組のみ形成する場合と比較して、その係合位置を探す手間が省けるので、組立作業の能率が一層向上する。
【００１３】
次に、本発明のガスセンサは、より具体的には、第二筒状部の側壁部は軸方向中間部に形成された段差部により開口端部側が拡径され、その拡径された開口端部を第一部分、段差部を挟んでその第一部分と反対側に位置する部分を第二部分として、溝部がその第一部分に形成される一方、第二部分において、第一筒状部と第二筒状部との間には、段差部に対応する大きさの隙間が形成されるとともに、第二筒状部には第二部分に第二側気体流通孔が、また第一筒状部の第二部分に対応する側壁部分に第一側気体流通孔がそれぞれ形成されたものとして構成することができる。該構成によれば、第二筒状部に段差部を設けることで第一筒状部と第二筒状部との間に気体流通に必要な隙間を容易に形成でき、かつ該段差部により拡径された第一部分を、位置決めに必要な溝部の形成部位として有効活用することが可能となる。
【００１４】
この場合、第二筒状部の第一部分を、第一筒状部の側壁部に対し、溝部と干渉しない位置に形成された溶接部により接合することができる。この構成によれば、両筒状部の重ね合わされた底部同士を溶接接合する従来の二重構造プロテクタの構成と比較して、溶接部の衝撃に対する耐性が増し、また高温となるプロテクタ先端位置から溶接部が離れるので、センサが高温環境で使用される場合においても溶接部に劣化や損傷が生じにくくなる。これにより、筒状部同士の位置決め結合状態が外れたりするトラブルが生じにくくなる。この場合、両筒状部の重ね合わされた底部同士にも、それらを接合する溶接部を形成すれば、筒状部間の位置決め結合強度をさらに高めることができる。
【００１５】
【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、軸状のセラミックヒータである発熱体３とを備えて構成される。酸素検出素子２は酸素イオン伝導性を有する固体電解質により構成されている。そのような固体電解質としては、Ｙ_２Ｏ_３ないしＣａＯを固溶させたＺｒＯ_２が代表的なものであるが、それ以外のアルカリ土類金属ないし希土類金属の酸化物とＺｒＯ_２との固溶体を使用してもよい。また、ベースとなるＺｒＯ_２にはＨｆＯ_２が含有されていてもよい。
【００１６】
この酸素検出素子２の中間部外側には、絶縁性セラミックから形成されたインシュレータ６，７、並びにタルクから形成されたセラミック粉末８を介して、素子収容体としての金属製のケーシング１０が設けられ、酸素検出素子２はケーシング１０と電気的に絶縁された状態でこれらを貫通している。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等を備える。また、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一対の電極層２ｂ，２ｃが設けられている。これら電極層２ｂ，２ｃはいずれも、酸素検出素子２を構成する固体電解質へ酸素を注入するための酸素分子の解離反応、及び該固体電解質から酸素を放出させるための酸素の再結合反応に対する可逆的な触媒機能（酸素解離触媒機能）を有する多孔質電極、例えばＰｔ多孔質電極として構成されている。
【００１７】
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。
【００１８】
まず、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を介してかしめられ、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の図中上端側の開口は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（リード線２０，２１の影になって見えない）が配置されている。
【００１９】
酸素検出素子２用の一方のリード線２０は、端子金具２３のコネクタ部２４及びこれに続く引出し線部２５、並びに端子金具２３の内部電極接続部２６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、別の端子金具３３のコネクタ部３４及びこれに続く引出し線部３５並びに外部電極接続部３５ｂを経て、酸素検出素子２の図示しない外側の電極層と電気的に接続されている。
【００２０】
ここで、酸素検出素子２は、排気ガス温が十分高温となっている場合には当該排気ガスで加熱されて活性化されるが、エンジン始動時など排気ガス温が低温である場合には前述の発熱体３で強制的に加熱することで活性化される。発熱体３は、通常はセラミックヒータであり、例えばアルミナを主とするセラミック棒４５の先端部に、例えば蛇行状に形成された抵抗発熱線部（図示せず）を有する発熱部４２が設けられたものである。この抵抗発熱線部は、ヒータ端子部４０から延びるリード線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）を所定の活性化温度以上に加熱する役割を果たす。
【００２１】
また、上述の発熱体３は、端子金具２３により酸素検出素子２の中空部内に保持される。この端子金具２３には、前述の内部電極接続部２６に関して発熱体３の先端側（すなわち発熱部４２に近い側）に発熱体把持部２７が形成されている。発熱体把持部２７は、発熱体３の周囲を包囲するＣ字状の横断面形状を有している。そして、発熱体３を未挿入の状態では該発熱体３の外径よりは少し小さい内径を有し、発熱体３の挿入に伴い弾性的に拡径してその摩擦力により該発熱体３を把持する。図１の構成において、この発熱体把持部２７は内部電極接続部２６の片側の１箇所にのみ設けられている。
【００２２】
内部電極接続部２６は、左右両側の縁に鋸刃状の接触部２６ａがそれぞれ複数形成された板状部分を円筒状に曲げ加工することにより、発熱体３を包囲する形態で形成されている。そして、その外周面と酸素検出素子２の中空部内壁面２ａとの間の摩擦力によって発熱体３を該中空部に対し軸線方向に位置決めする役割を果たすとともに、上記複数の接触部２６ａの各先端部において内側の電極層２ｃ（図２）と接触・導通するようになっている。
【００２３】
次に、図１に示すように、外筒部材５４は、内筒部材１４（ケーシング１０）に対し後方外側からほぼ同軸的に連結される筒状形態をなす。また、内筒部材１４の後端部には、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。そして、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かしめ部５６，５７が形成されている。
【００２４】
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／内筒連結かしめ部７５が形成されている。この外筒／内筒連結かしめ部７５により、外筒部材５４が内筒部材１４に対して結合される。
【００２５】
なお、フィルタ５３は、例えばポリテトラフルオロエチレン（以下、ＰＴＦＥという）の未焼成成形体を、ＰＴＦＥの融点よりも低い加熱温度で１軸以上の方向に延伸することにより得られる多孔質繊維構造体（商品名：例えばゴアテックス（ジャパンゴアテックス（株）））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。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。
【００２６】
次に、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、ここから突出する酸素検出素子２の先端側、すなわち検出部２ｋ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１００が装着されている。該プロテクタ１００は、有底の第一筒状部１０１と、その内側に所定の隙間を経て同心的に配置された有底の第二筒状部１０２とを有する二重構造となっている。
【００２７】
図３（ｂ）に示すように、第二筒状部１０２は、その側壁部に対し軸方向において開口端部寄りの中間位置に、テーパ面状の段差部１０２ｂが形成されている。そして、その段差部１０２ｂに関して開口側に位置する端部が、第一筒状部１０１の内径にちょうど嵌まる程度に拡径されて第一部分１０２ａを形成する一方、上記段差部１０２ｂに関してこれと反対側に位置する部分は、該第一部分１０２ａよりも径小の第二部分１０２ｃとされている。
【００２８】
また、第一筒状部１０１の側壁部には、軸線方向に並ぶ２つの長孔状の第一側気体流通孔１０３，１０３の組が周方向に略一定の角度間隔で複数形成されている。また、第二筒状部１０２の側壁部にも同様の第二側気体流通孔１０４，１０４の組が、第一側気体流通孔１０３，１０３の組と同じ角度間隔で複数形成されている。そして、第一筒状部１０１と第二筒状部１０２とは、水滴等の侵入防止のために、図３（ｃ）に示すように、第一側気体流通孔１０３，１０３と第二側気体流通孔１０４，１０４との周方向の形成位置位相が互いにずれたものとなるよう位置決めされている。
【００２９】
次に、第一筒状部１０１と第二筒状部１０２とを上記のような位置関係で位置決め配置するために、図３（ａ）に示すように、第二筒状部１０２の第一部分１０２ａには、第二側係合部としての所定幅の溝部２５０が、周方向に所定の角度間隔で、具体的には第一側気体流通孔１０３，１０３ないし第二側気体流通孔１０４，１０４の形成角度間隔の整数倍となる角度間隔で複数形成されている。この溝部２５０は、金型プレス加工等により第一部分１０２ａを溝形状に内向きに凹ませることにより、段差部１０２ｂに対応する端部側がこれに開放する形態で形成されている。なお、本実施例では、第一側気体流通孔１０３，１０３ないし第二側気体流通孔１０４，１０４の形成角度間隔を４５°、溝部２５０の形成角度間隔をその２倍の９０°としている。
【００３０】
他方、第一筒状部１０１の側壁部内面には、軸線方向において上記溝部２５０に対応する位置に第一側係合部としての係合凸部２５１が形成されている。この係合凸部２５１は、第一筒状部１０１を金型プレス加工等で内向きに凹ませることにより、溝部２５０の幅よりも少し狭幅に形成されており、上記複数の溝部２５０のいずれかと選択的に係合することにより、第一筒状部１０１と第二筒状部１０２との周方向の相対回転を阻止するとともに、第一側気体流通孔１０３，１０３と第二側気体流通孔１０４，１０４とが、周方向において互いにずれた位置関係で配列するよう、第一筒状部１０１と第二筒状部１０２とを互いに位置決めする役割を果たす。ここで、溝部２５０の形成角度間隔が、第一側気体流通孔１０３，１０３ないし第二側気体流通孔１０４，１０４の形成角度間隔の整数倍となっていることで、該係合凸部２５１がいずれの溝部２５０と係合した状態においても、上記位置決め状態が得られるようになっている。
【００３１】
第二筒状部１０２は、第一部分１０２ａにおいて、溝部２５０と干渉しない位置において周方向に所定の間隔で形成された複数の溶接部１０７（例えばスポット溶接等の抵抗溶接にて形成される）により、第一筒状部１０１の側壁部と結合されている。なお、第二筒状部１０２は、第一筒状部１０１よりも軸線方向の長さが短く形成されており、その第一部分１０２ａの開口縁が第一筒状部１０１の開口縁よりも所定距離内側に入り込む形で配置されている。これにより、第一筒状部１０１の開口側には、プロテクタ装着部９ａの装着代部１０１ａが所定幅で形成される形となっている。
【００３２】
他方、第一筒状部１０１と第二筒状部１０２との各底部は互いに密着した形態とされ、各々その中央にはガス透過口１０５，１０６が互いに連通する形で形成される。そして、図３（ｄ）に示すように、それら底部は、溶接部１５２（例えばスポット溶接等の抵抗溶接にて形成されたもの）により互いに結合されている。本実施例では、該溶接部１５２は、ガス透過口１０５，１０６の周囲を取り囲む形で複数個形成されている。なお、この溶接部１５２は省略してもよい。
【００３３】
このようなプロテクタ１００は、その装着代部１０１ａに対し主体金具９のプロテクタ装着部９ａを挿入し、装着代部１０１ａとプロテクタ装着部９ａとの重なり部に対し環状の溶接部９０を、例えばレーザー溶接等により形成することで取り付けられている。
【００３４】
なお、図６により示すプロテクタ１００の各部の寸法は、例えば以下のように設定できる（なお、括弧内は、図３に示すものの具体的な数値例である）。
Ｐ1：１０．１５〜１２．０５ｍｍ（１０．３５ｍｍ）
Ｐ2：３．７〜４．１ｍｍ（３．９ｍｍ）
Ｐ3：例えば２０ｍｍ
Ｐ4：７．５〜７．９ｍｍ（７．７ｍｍ）
【００３５】
また、図７により示す主体金具９の各部の寸法は、例えば以下のように設定できる（なお、括弧内は、図１に示すものの具体的な数値例である）。
Ｋ1：２５〜３０ｍｍ（２９．６ｍｍ）
Ｋ2：１３〜１７ｍｍ（１６．８ｍｍ）
Ｋ3：１２．５〜１３ｍｍ（１２．８６ｍｍ）
Ｋ4：８．８〜９．２ｍｍ（９ｍｍ）
Ｋ5：３．６〜４ｍｍ（３．８ｍｍ）
Ｋ6：１〜２．５ｍｍ（２ｍｍ）
Ｋ7：０．５〜１．５ｍｍ（１ｍｍ）
Ｋ8：１２〜１４ｍｍ（１３．９ｍｍ）
Ｋ9：７〜１０ｍｍ（９．６ｍｍ）
Ｋ10：７．５〜１０．５ｍｍ（１０ｍｍ）
Ｋ11：２０〜２３．６ｍｍ（２３．１ｍｍ）
Ｋ12：５〜７ｍｍ（６．５ｍｍ）
Ｋ13：２１．８〜２２．２ｍｍ（２２ｍｍ）
Ｋ14：例えばＭ１８
Ｋ15：９．３〜１１．２ｍｍ（９．５ｍｍ）
Ｋ16：７．３〜７．７ｍｍ（７．５ｍｍ）
Ｋ17：１６．３〜１６．７ｍｍ（１６．５ｍｍ）
Ｋ18：１１．４〜１１．８ｍｍ（１１．６ｍｍ）
Ｋ19：１５．８〜１６．２ｍｍ（１６ｍｍ）
【００３６】
また、図１において、センサ１の全長Ｌ1は約８４ｍｍである。また、主体金具９のガスケットＧの受け面９ｄから、プロテクタ１００の先端面までの長さＬ2は約２９ｍｍである。
【００３７】
以下、酸素センサ１の作動について説明する。
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１００のガス透過口１０５、１０６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。
【００３８】
そして、検出素子２の検出部２ｋを覆うプロテクタ１００は、第一筒状部１０１と第二筒状部１０２とを有する二重構造とされ、かつ各側壁面には、それぞれ周方向に並ぶ第一側気体流通孔１０３，１０３と第二側気体流通孔１０４，１０４とが、互いにずれた位置関係で配列している。これにより、プロテクタの外側から内側に向けて、第一筒状部１０１と第二筒状部１０２とを径方向に直接的に貫く流通経路が生じなくなるので、検出部２ｋに対する水滴や被毒成分からの保護機能が高められている。
【００３９】
他方、プロテクタ１００は、図３に示すように、第一筒状部１０１に前述の係合凸部２５１が形成され、第二筒状部１０２に溝部２５０が形成されていることで、第一側気体流通孔１０３，１０３と第二側気体流通孔１０４，１０４とを相対的に位置決めしながらの組立作業を、次のようにして極めて簡単に行うことができる。すなわち、図４に示すように、第一筒状部１０１に対し第二筒状部１０２を、その開口部から軸線方向に挿入する。この状態で、例えば第二筒状部１０２を第一筒状部１０１の内側で、係合凸部２５１が複数ある溝部２５０のいずれかに係合する位置まで回転させる。係合凸部２５１と溝部２５０とが係合状態となれば、係合凸部２５１を溝部２５０内で相対的に滑らせながら、第二筒状部１０２を、その底部が第一筒状部１０１の底に当たる位置まで押し込む。この状態で、図３に示す溶接部１０７ないし１５２を形成することで、第一筒状部１０１と第二筒状部１０２との接合を行う。このとき、第一筒状部１０１と第二筒状部１０２とは、係合凸部２５１と溝部２５０との係合により相対回転が阻止されるから、溶接作業が極めて行いやすく、また、作業に伴う第一側気体流通孔１０３，１０３と第二側気体流通孔１０４，１０４との位置ずれもほとんど生じない。
【００４０】
なお、図５（ａ）に示すように、第一筒状部１０１側の係合凸部２５１を、その周方向に沿って複数形成するようにしてもよい。他方、図５（ｂ）に示すように、係合凸部２５１と溝部２５０とを１組のみ設ける構成としてもよい。また、第一側係合部と第二側係合部とは、第一筒状部１０１と第二筒状部１０２との相対回転が阻止できるものであれば、係合凸部と溝部との組み合わせに限らず、例えば図５（ｃ）に示すように、第二筒状部１０２の第一部分１０２ａの外周面形状を多角形状とし、第一筒状部１０１側には、その軸方向中間位置にて、挿入後の第一部分１０２ａに対応する位置に、多角形状の内周面形状を有した第一側係合部１０１ｆを形成するようにしてもよい。この場合、第二筒状部１０２の第一部分１０２ａを、この第一側係合部１０１ｆに嵌め合わせることにより、第一筒状部１０１と第二筒状部１０２との相対回転が阻止されることとなる。
【００４１】
なお、プロテクタ１００は主体金具９に対し、以下の図８〜図１１に示す方法にて形成される加締め溶接構造部１５０により接合することもできる。すなわち、図８に示すように、主体金具９のプロテクタ装着部９ａを、プロテクタ１００の装着代部１０１ａに対し、該装着代部１０１ａの開口縁が金具端面に当たる位置まで挿入する。そして、図９に示すように、この状態で装着代部１０１ａの軸方向中間部を、プロテクタ装着部９ａに向けて周方向に加締めることにより、図１０に示すように加締め部８１を形成する。このとき、プロテクタ装着部９ａ側には、この加締め部８１に対応して環状の凹所が形成される場合がある。
【００４２】
次いで、図１１（ａ）に示すように、この加締め部８１に対し、周方向の溶接部８３を、例えばレーザー溶接により形成すれば、目的とする加締め溶接構造部１５０が得られる。ここで、溶接部８３の幅をｗ1、加締め部８１の幅をｗ2とした場合、接合強度確保の観点からｗ1／ｗ2は０．５以上とするのがよい（図１の例では、ｗ1は約０．７ｍｍ、ｗ2は約１ｍｍ、ｗ1／ｗ2は約０．７である）。また、図１１（ｂ）に示すように、加締めによる圧着力をプロテクタ装着部９ａ（内側部材）側に十分生じさせ、良好な圧着状態を確保するために、装着代部１０１ａ（外側部材）の厚さｔ2は１ｍｍ以下に設定するのがよい（図１の例では、ｔ2は約０．４ｍｍである）。さらに、プロテクタ装着部９ａ（内側部材）側の溶接部８３の侵入深さｄ1は、接合強度確保の観点から０．３ｍｍ以上となっているのがよい。ただし、プロテクタ装着部９ａ（内側部材）を厚さ方向に貫く形で溶接部８３が形成されると、溶接欠陥等の影響を受けて接合強度が低下する場合があるので、上記侵入深さｄ1はプロテクタ装着部９ａの厚さｔ1よりも小さくなっていることが望ましい。
【００４３】
プロテクタ１００とプロテクタ装着部９ａとの重なり部に加締め部８１を予め形成して、両者の密着を高めた状態で、ここに全周の溶接部８３を形成して接合する構造とすることで、溶接部８３における欠陥発生が効果的に防止され、接合の気密性を高めることができる。例えば、酸素センサ１が低温となったときに、凝結した水滴がプロテクタの外面に付着することがある。この場合、主体金具９とプロテクタ１００とを接合する溶接部８３に欠陥があると、その欠陥部から凝結した水滴が侵入して検出部をぬらしたり、あるいは錆等の汚れを付着させたりする場合がある。しかしながら、主体金具９とプロテクタ１００との接合構造が上記加締め溶接構造部１５０となっていることで、そのような水滴や汚れの侵入等の不具合を効果的に防止することができる。
【００４４】
なお、このような全周溶接部の形成は、従来は隙間嵌めあるいは圧入によりプロテクタ１００とプロテクタ装着部９ａとを嵌め合わせ、その状態で溶接部を形成するようにしていた。しかしながら、この方法では、プロテクタ１００とプロテクタ装着部９ａとの寸法管理、特にプロテクタ１００の内径とプロテクタ装着部９ａの外径との差に対する寸法管理を極度に厳しく行わないと良好な溶接接合状態が得られない場合があった。しかしながら、上記構成では、嵌め合わせの段階で多少径差がばらついていても、加締め部８１の形成により密着状態を確保できるので、上記のような厳しい寸法管理は不要となる。その結果、センサの製造能率及び歩留まりが向上する。
【００４５】
なお、プロテクタ１００の開口基端部に、予め周方向の縮径部を例えばプレス加工等により帯状に形成しておき、その状態でその縮径部に主体金具９側のプロテクタ装着部９ａを圧入して、その縮径部に溶接部を形成することにより両者を接合してもよい。縮径部にプロテクタ装着部９ａを圧入することにより、プロテクタ１００の開口側が裾拡がり形態になりにくくなるので、同様に溶接部への欠陥発生確率を低減することができる。
【００４６】
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】プロテクタの一例を示す平面図及び正面半断面図、Ａ−Ａ断面図及び底面図。
【図４】プロテクタの組立工程を説明する斜視図。
【図５】プロテクタの第一筒状部と第二筒状部との軸線周りの相対回転を阻止する機構のいくつかの変形例を示す説明図。
【図６】プロテクタの寸法説明図。
【図７】主体金具の寸法説明図。
【図８】プロテクタと主体金具とを、加締め溶接構造部の形成により接合する工程を説明する図。
【図９】図８に続く工程説明図。
【図１０】図９に続く工程説明図。
【図１１】図１０に続く工程説明図。
【符号の説明】
１酸素センサ（ガスセンサ）
２酸素検出素子
９主体金具
９ａプロテクタ装着部
１０ケーシング（検出素子収容体）
２５０溝部（第二側係合部）
２５１係合凸部（第二側係合部）
１００プロテクタ
１０１第一筒状部
１０２第二筒状部
１０３第一側気体流通孔
１０４第二側気体流通孔[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.
[0002]
[Prior art]
As a gas sensor as described above, a gas sensor having a structure in which a rod-like or cylindrical detection element having a detection portion for detecting a component to be detected is disposed inside a metal casing is known. Such a gas sensor is attached to a predetermined mounting portion such as an exhaust pipe by a screw portion formed on the outer peripheral surface of the metal shell forming a part of the casing, and a detection portion protruding from the end of the metal shell is measured. It is kept in the atmosphere and detects the component to be detected. In many gas sensors, a protector that covers the detection unit is provided in order to protect the detection unit located in the measurement atmosphere from being exposed to water and poisoning. A gas flow hole is formed in the side wall of the protector, and the gas to be measured is introduced into the protector from the gas flow hole and brought into contact with the detection unit.
[0003]
Recently, in order to enhance the protection performance of the detection unit, a protector having a double structure composed of two cylindrical parts inside and outside is often used. In such a double structure protector, if there is an overlap at the formation position of the gas flow hole formed in the inner and outer cylindrical portions, water and poisoning components directly reach the detection portion in the overlap portion. Since the path is formed, the effect of improving the protection performance by the double structure may not always be sufficiently achieved. For this reason, in many double structure protectors, it is possible to prevent the occurrence of the above-mentioned path by shifting the formation position of the gas flow hole between the inner cylindrical portion and the outer cylindrical portion, thereby improving the protection performance. A device to raise is made.
[0004]
[Problems to be solved by the invention]
By the way, in the above double structure protector, the inner and outer cylindrical portions must be fixed in a state of being aligned in the circumferential direction so that the gas flow holes satisfy the initial positional relationship. In this case, conventionally, for example, the two cylindrical portions are arranged so that the bottom portions overlap each other, and an unevenness is formed on the overlapping surface, and the alignment is performed by the engagement of the unevennesses. Since the inner and outer cylindrical portions easily move in the axial direction due to vibration or the like, the engagement of the positioning irregularities is easily disengaged during the assembling work, and the work efficiency is extremely poor. In addition, both cylindrical parts after alignment are fixed in such a manner that the overlapping bottom parts are joined together by resistance welding. However, when the sensor is used in a high temperature environment, the welded parts are deteriorated or vibrations are applied. There is a problem that the fixation is easy to come off.
[0005]
An object of the present invention is to provide a gas sensor that has a protector having a structure in which two or more cylindrical portions are arranged in an overlapping manner, and that the cylindrical portions can be easily aligned in the circumferential direction, and thus easy to assemble. is there.
[0006]
[Means for solving the problems and actions / effects]
In order to solve the above problems, the gas sensor of the present invention is
In a rod-like or cylindrical form in which a detection part is formed at the tip part, with a detection element for detecting a detected component in a gas to be measured, and a state in which the detection part protrudes from one end side, A cylindrical element container that covers the detection element, and the detection part that is coupled to the opening end of the element container on the side from which the detection part protrudes and allows the gas to be measured to flow A protector that covers the inner and outer two cylindrical portions, that is, an outer first cylindrical portion, and a second cylindrical portion that is inserted axially inside thereof, and The outer peripheral surface of the second cylindrical portion is engaged with the first side engaging portion formed on the inner peripheral surface of the first cylindrical portion along with the insertion into the first cylindrical portion, A second side engaging portion is formed that positions and holds the second cylindrical portion at a predetermined position in the circumferential direction with respect to the first cylindrical portion. ,
The first side engaging part is an engaging convex part protruding from the inner peripheral surface of the first cylindrical part, and the second side engaging part is formed on the outer peripheral surface of the second cylindrical part. A groove that extends in the axial direction and allows the engagement convex portion to be fitted and slide relative to the axial direction;
Above Element container A cylindrical protector mounting portion is formed in the front opening of the
The second cylindrical portion is formed to have an axial length shorter than the first cylindrical portion so as to enter a predetermined distance inside the opening edge of the first cylindrical portion. On the opening side of the cylindrical portion, a mounting margin to the protector mounting portion is formed with a predetermined width, and the mounting margin is formed with respect to the mounting margin. Element container The protector mounting portion is inserted, and an annular welded portion is formed around the overlapping portion between the mounting allowance portion and the protector mounting portion.
[0007]
In the above configuration, when the protector is assembled, the first side member formed on the inner peripheral surface of the first cylindrical portion is inserted when the inner second cylindrical portion is inserted into the outer first cylindrical portion. By engaging the joint portion and the second side engaging portion formed on the outer peripheral surface of the second cylindrical portion, the second cylindrical portion is positioned at a predetermined position in the circumferential direction with respect to the first cylindrical portion. The positioning was maintained. Thereby, in a gas sensor having a protector having a structure in which at least two cylindrical portions are arranged in an overlapping manner, the relative positioning in the circumferential direction of the cylindrical portions is extremely easy, and the workability of the protector assembly is improved.
[0008]
The first cylindrical portion and the second cylindrical portion can be formed to have a substantially circular axial cross section. In this case, the first side engaging portion and the second side engaging portion The relative rotation of both cylindrical parts can be prevented by the engagement. Thereby, since relative rotation from the positioning position of two cylindrical parts which have a substantially circular-shaped axial cross section is blocked | prevented by engagement of the said engaging part, an assembly operation | work of a protector can be performed more easily. .
[0009]
In the gas sensor, the first side gas flow hole and the second side gas flow hole that allow gas flow are respectively penetrated in the thickness direction in the side wall portions of the first cylindrical portion and the second cylindrical portion. It can be formed in the form. In this case, the first side gas flow hole and the second side gas flow hole satisfy the predetermined positional relationship by the engagement between the first side engagement part and the second side engagement part. It becomes possible to easily position and hold the cylindrical portion and the second cylindrical portion.
[0010]
For example, a predetermined amount of gap is formed between the outer wall portions of the first cylindrical portion and the second cylindrical portion, and the first side gas flow hole and the second side gas flow hole are arranged around the cylindrical portions. If positioning is performed so that the positional relationship is shifted from each other in the direction, it is difficult to form a path for water and poisoning components to reach the detection unit directly through the protector, and the protection performance of the protector against the detection unit is enhanced. In this case, by providing the first side engaging part and the second side engaging part, the first cylindrical part and the second cylindrical part can be easily assembled in a form satisfying the positional relationship. become.
[0011]
Specifically, the first side engaging portion can be an engaging convex portion that protrudes from the inner peripheral surface of the first cylindrical portion, and the second side engaging portion is the second cylindrical portion. It can be a groove that extends in the axial direction on the outer peripheral surface and allows the engaging convex portion to be fitted and slide relatively in the axial direction. According to this configuration, the engaging projection on the second cylindrical portion side is fitted into the groove portion on the second cylindrical portion side, and while the convex portion is relatively slid in the groove portion in that state, By inserting the second cylindrical part into the first cylindrical part, the positioning and assembling work of both cylindrical parts can be performed very easily.
[0012]
Note that a plurality of groove portions can be formed at substantially equal angular intervals in the circumferential direction on the outer peripheral surface of the second cylindrical portion. In this case, one or more engaging convex portions are formed at predetermined positions on the inner peripheral surface of the first cylindrical portion, or a plurality of engagement convex portions are formed at an angular interval that is an integral multiple of the groove portion forming angular interval in the circumferential direction of the inner peripheral surface. can do. In this way, it is possible to selectively engage the engagement convex portion with any of the plurality of groove portions. For example, the engagement convex portion and the groove portion are compared with the case where only one set is formed. The efficiency of assembling work is further improved because the labor for searching the position can be saved.
[0013]
Next, in the gas sensor of the present invention, more specifically, the side wall portion of the second cylindrical portion is enlarged in diameter on the opening end side by a stepped portion formed in the intermediate portion in the axial direction, and the expanded opening end. The groove portion is formed in the first portion with the first portion as the first portion and the portion located on the opposite side of the first portion across the step portion as the second portion. A gap having a size corresponding to the step portion is formed between the cylindrical portion, the second cylindrical portion has a second side gas flow hole in the second portion, and the first cylindrical portion. The first side gas flow holes can be formed on the side wall portions corresponding to the second portion. According to this configuration, by providing the step portion in the second cylindrical portion, a gap necessary for gas flow can be easily formed between the first cylindrical portion and the second cylindrical portion, and the step portion The expanded first portion can be effectively used as a groove forming portion necessary for positioning.
[0014]
In this case, the 1st part of a 2nd cylindrical part can be joined with the weld part formed in the position which does not interfere with a groove part with respect to the side wall part of a 1st cylindrical part. According to this structure, compared with the structure of the conventional double structure protector which welds and joins the overlapped bottom parts of both cylindrical parts, resistance to the impact of the welded part is increased, and from the protector tip position where the temperature becomes high. Since the welded portion is separated, even when the sensor is used in a high temperature environment, the welded portion is hardly deteriorated or damaged. Thereby, the trouble that the positioning coupling state of the cylindrical portions is removed is less likely to occur. In this case, if the welding part which joins them is formed also in the bottom parts on which both the cylindrical parts were overlapped, the positioning coupling strength between the cylindrical parts can be further increased.
[0015]
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 that is a shaft-shaped ceramic heater. The oxygen detection element 2 is composed of a solid electrolyte having oxygen ion conductivity. As such a solid electrolyte, Y ₂ O ₃ ZrO in which CaO is dissolved ₂ Is representative, but other alkaline earth metal or rare earth metal oxides and ZrO ₂ A solid solution may be used. The base ZrO ₂ HfO ₂ May be contained.
[0016]
A metal casing 10 as an element container is provided outside the intermediate portion of the oxygen detection element 2 via insulators 6 and 7 formed of insulating ceramic and ceramic powder 8 formed of talc. The oxygen detection element 2 passes through the oxygen detection element 2 while being electrically insulated from the casing 10. 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. Etc. As shown in FIG. 2, a pair of electrode layers 2b and 2c are provided on the inner and outer surfaces of the oxygen detection element 2 so as to cover almost the entire surface. These electrode layers 2b and 2c are both reversible with respect to the dissociation reaction of oxygen molecules for injecting oxygen into the solid electrolyte constituting the oxygen detecting element 2 and the recombination reaction of oxygen for releasing oxygen from the solid electrolyte. A porous electrode having a typical catalytic function (oxygen dissociation catalytic function), for example, a Pt porous electrode.
[0017]
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.
[0018]
First, the inner cylinder member 14 described above is caulked through a ring 15 between the metal shell 9 and the insulator 6 in the opening on the rear side of the metal shell 9, and an outer cylinder member 54 is further fitted to the inner cylinder member 14 from the outside. Fixed and fixed. An opening on the upper end side in the figure of the outer cylinder member 54 is sealed with a grommet (elastic seal member) 17 made of rubber or the like, and subsequently, a ceramic separator 18 is provided further inward. The lead wires 20 and 21 for the oxygen detecting element 2 and the lead wires for the heating element 3 (not visible in the shadow of the lead wires 20 and 21) are arranged so as to penetrate the ceramic separator 18 and the grommet 17. Has been.
[0019]
One lead wire 20 for the oxygen detecting element 2 passes through the connector portion 24 of the terminal fitting 23, the lead wire portion 25 that follows the connector portion 24, and the internal electrode connecting portion 26 of the terminal fitting 23, to the inside of the oxygen detecting element 2 described above. The electrode layer 2c (FIG. 2) is electrically connected. On the other hand, the other lead wire 21 is electrically connected to an outer electrode layer (not shown) of the oxygen detection element 2 through a connector portion 34 of another terminal fitting 33, a lead wire portion 35 and an external electrode connection portion 35b following the connector portion 34. It is connected.
[0020]
Here, when the exhaust gas temperature is sufficiently high, the oxygen detection element 2 is heated and activated by the exhaust gas. However, when the exhaust gas temperature is low, such as when the engine is started, the oxygen detection element 2 is activated. It is activated by forcibly heating with the heating element 3. The heating element 3 is usually a ceramic heater, and a heating part 42 having a resistance heating line part (not shown) formed in, for example, a meandering shape is provided at the tip of a ceramic rod 45 mainly made of alumina, for example. It is a thing. The resistance heating wire portion plays a role of heating the tip portion (detection portion) of the oxygen detection element 2 to a predetermined activation temperature or higher by being energized through a lead wire extending from the heater terminal portion 40.
[0021]
The heating element 3 described above is held in the hollow portion of the oxygen detection element 2 by the terminal fitting 23. In the terminal fitting 23, a heating element gripping part 27 is formed on the tip side of the heating element 3 (that is, the side close to the heating part 42) with respect to the internal electrode connection part 26 described above. The heating element gripping portion 27 has a C-shaped cross section that surrounds the periphery of the heating element 3. When the heating element 3 is not inserted, the heating element 3 has an inner diameter slightly smaller than the outer diameter of the heating element 3, and elastically expands with the insertion of the heating element 3. Hold it. In the configuration of FIG. 1, the heating element gripping portion 27 is provided only at one place on one side of the internal electrode connection portion 26.
[0022]
The internal electrode connecting portion 26 is formed in a form surrounding the heating element 3 by bending a plate-like portion in which a plurality of saw blade-like contact portions 26a are formed on both left and right edges into a cylindrical shape. . The heating element 3 is positioned in the axial direction with respect to the hollow portion by a frictional force between the outer peripheral surface and the hollow inner wall surface 2a of the oxygen detecting element 2, and each tip of the plurality of contact portions 26a. In this part, contact / conduction with the inner electrode layer 2c (FIG. 2) is achieved.
[0023]
Next, as shown in FIG. 1, the outer cylinder member 54 has a cylindrical shape that is substantially coaxially connected to the inner cylinder member 14 (casing 10) from the rear outer side. Further, at the rear end portion of the inner cylinder member 14, a stepped portion 51 is used, with the stepped portion 51 serving as the first portion 61 on the axial front side and the second portion 62 on the rearward side in the axial direction. 62 is configured to have a smaller diameter than the first portion 61, and a plurality of gas introduction holes 52 in the circumferential direction 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. 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.
[0024]
On the other hand, the outer cylinder member 54 is disposed so as to overlap the inner cylinder member 14 from the outside in the first portion 61, and a circumferential annular outer cylinder / inner cylinder connection caulking portion 75 is formed in the overlapping portion. Is formed. The outer cylinder / inner cylinder connection caulking portion 75 couples the outer cylinder member 54 to the inner cylinder member 14.
[0025]
The filter 53 is, for example, a porous fiber structure obtained by stretching an unfired molded body of polytetrafluoroethylene (hereinafter referred to as PTFE) in a uniaxial direction at a heating temperature lower than the melting point of PTFE. (Product name: Gore-Tex (Japan Gore-Tex Co., Ltd.), for example, a water-repellent filter that prevents the permeation of water such as water droplets and allows the permeation of gases such as air and / or water vapor. It is configured as. 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.
[0026]
Next, a cylindrical protector mounting portion 9a is formed at the front opening of the metal shell 9, and covers the distal end side of the oxygen detection element 2 projecting therefrom, that is, the detection portion 2k with a predetermined space therebetween. A cap-shaped protector 100 is attached. The protector 100 has a double structure including a bottomed first cylindrical portion 101 and a bottomed second cylindrical portion 102 disposed concentrically with a predetermined gap inside.
[0027]
As shown in FIG. 3B, the second cylindrical portion 102 is formed with a stepped portion 102b having a tapered surface at an intermediate position near the opening end in the axial direction with respect to the side wall portion. The end portion located on the opening side with respect to the stepped portion 102b is enlarged to the extent that it just fits the inner diameter of the first cylindrical portion 101 to form the first portion 102a, while the stepped portion 102b is opposite to this. The portion located on the side is a second portion 102c having a smaller diameter than the first portion 102a.
[0028]
In addition, a plurality of sets of two long-hole-like first gas flow holes 103, 103 arranged in the axial direction are formed in the side wall portion of the first cylindrical portion 101 at a substantially constant angular interval in the circumferential direction. . Also, a plurality of similar sets of second side gas circulation holes 104, 104 are formed in the side wall portion of the second cylindrical portion 102 at the same angular intervals as the sets of first side gas circulation holes 103, 103. And the 1st cylindrical part 101 and the 2nd cylindrical part 102 are the 1st side gas circulation holes 103 and 103 and the 2nd side, as shown in FIG.3 (c), in order to prevent intrusion of a water drop etc. Positioning is performed so that the circumferential formation position phases of the gas flow holes 104 and 104 are shifted from each other.
[0029]
Next, in order to position and arrange the first tubular portion 101 and the second tubular portion 102 in the positional relationship as described above, as shown in FIG. In 102a, a groove portion 250 having a predetermined width as a second side engaging portion is arranged at predetermined angular intervals in the circumferential direction, specifically, the first side gas circulation holes 103, 103 to the second side gas circulation holes 104, A plurality are formed at an angular interval that is an integral multiple of the forming angular interval 104. The groove portion 250 is formed in such a manner that the end portion side corresponding to the stepped portion 102b is opened to the groove portion by indenting the first portion 102a inwardly by die pressing or the like. In the present embodiment, the formation angle interval of the first gas circulation holes 103, 103 to the second gas circulation holes 104, 104 is 45 °, and the formation angle interval of the groove portions 250 is 90 °, which is twice as much.
[0030]
On the other hand, on the inner surface of the side wall portion of the first tubular portion 101, an engaging convex portion 251 as a first side engaging portion is formed at a position corresponding to the groove portion 250 in the axial direction. The engagement convex portion 251 is formed to be slightly narrower than the width of the groove portion 250 by denting the first tubular portion 101 inward by die press processing or the like. By selectively engaging either one, the relative rotation in the circumferential direction between the first cylindrical portion 101 and the second cylindrical portion 102 is prevented, and the first side gas flow holes 103 and 103 and the second side gas are prevented. It plays the role which positions the 1st cylindrical part 101 and the 2nd cylindrical part 102 mutually so that the circulation holes 104 and 104 may be arranged in the positional relationship which mutually shifted | deviated in the circumferential direction. Here, since the formation angle interval of the groove portion 250 is an integral multiple of the formation angle interval of the first side gas circulation holes 103, 103 to the second side gas circulation holes 104, 104, the engagement convex portion 251 The above positioning state can be obtained even in the state in which any of the groove portions 250 is engaged.
[0031]
The second cylindrical portion 102 is formed by a plurality of welded portions 107 (formed by resistance welding such as spot welding) formed at a predetermined interval in the circumferential direction at a position where the second cylindrical portion 102 does not interfere with the groove portion 250. The first cylindrical portion 101 is coupled to the side wall portion. The second tubular portion 102 is formed to have a shorter axial length than the first tubular portion 101, and the opening edge of the first portion 102 a is more predetermined than the opening edge of the first tubular portion 101. It is arranged so as to enter the distance inside. As a result, the mounting margin 101a of the protector mounting portion 9a is formed with a predetermined width on the opening side of the first tubular portion 101.
[0032]
On the other hand, the bottom portions of the first cylindrical portion 101 and the second cylindrical portion 102 are in close contact with each other, and the gas permeation ports 105 and 106 are formed in communication with each other at the center. And as shown in FIG.3 (d), those bottom parts are mutually couple | bonded by the welding part 152 (For example, formed by resistance welding, such as spot welding). In the present embodiment, a plurality of the welded portions 152 are formed so as to surround the gas permeation ports 105 and 106. The welded portion 152 may be omitted.
[0033]
In such a protector 100, the protector mounting portion 9a of the metal shell 9 is inserted into the mounting allowance portion 101a, and an annular welded portion 90 is attached to the overlapping portion of the mounting allowance portion 101a and the protector mounting portion 9a, for example, a laser. It is attached by forming by welding or the like.
[0034]
Note that the dimensions of each part of the protector 100 shown in FIG. 6 can be set as follows, for example (in parentheses are specific numerical examples of what is shown in FIG. 3).
P1: 10.15 to 12.05 mm (10.35 mm)
P2: 3.7 to 4.1 mm (3.9 mm)
P3: 20mm for example
P4: 7.5 to 7.9 mm (7.7 mm)
[0035]
Moreover, the dimension of each part of the metal shell 9 shown in FIG. 7 can be set as follows, for example (in parentheses are specific numerical examples of what is shown in FIG. 1).
K1: 25-30 mm (29.6 mm)
K2: 13-17mm (16.8mm)
K3: 12.5-13mm (12.86mm)
K4: 8.8 to 9.2 mm (9 mm)
K5: 3.6 to 4 mm (3.8 mm)
K6: 1 to 2.5mm (2mm)
K7: 0.5 to 1.5 mm (1 mm)
K8: 12-14mm (13.9mm)
K9: 7 to 10 mm (9.6 mm)
K10: 7.5 to 10.5 mm (10 mm)
K11: 20 to 23.6 mm (23.1 mm)
K12: 5-7mm (6.5mm)
K13: 21.8 to 22.2mm (22mm)
K14: For example, M18
K15: 9.3 to 11.2 mm (9.5 mm)
K16: 7.3 to 7.7 mm (7.5 mm)
K17: 16.3 to 16.7 mm (16.5 mm)
K18: 11.4 to 11.8mm (11.6mm)
K19: 15.8 to 16.2 mm (16 mm)
[0036]
In FIG. 1, the total length L1 of the sensor 1 is about 84 mm. The length L2 from the receiving surface 9d of the gasket G of the metal shell 9 to the tip surface of the protector 100 is about 29 mm.
[0037]
Hereinafter, the operation of the oxygen sensor 1 will be described.
In the oxygen sensor 1, the atmospheric air as the reference gas is introduced through the filter 53 of the outer cylinder member 54 as described above, while the outer surface of the oxygen detection element 2 is passed through the gas permeation ports 105 and 106 of the protector 100. The exhaust gas introduced in this manner 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 through the lead wires 21 and 20 as a detection signal of the oxygen concentration in the exhaust gas, whereby the oxygen concentration in the exhaust gas can be detected.
[0038]
And the protector 100 which covers the detection part 2k of the detection element 2 is made into the double structure which has the 1st cylindrical part 101 and the 2nd cylindrical part 102, and each side wall surface is each arranged in the circumferential direction. The first side gas circulation holes 103 and 103 and the second side gas circulation holes 104 and 104 are arranged in a positional relationship shifted from each other. Thereby, since the flow path which penetrates the 1st cylindrical part 101 and the 2nd cylindrical part 102 directly to a radial direction does not arise toward the inner side from the outer side of a protector, the water droplet with respect to the detection part 2k, or a poisoning component The protection function from is enhanced.
[0039]
On the other hand, as shown in FIG. 3, the protector 100 has the first cylindrical portion 101 formed with the above-described engaging convex portion 251 and the second cylindrical portion 102 formed with the groove portion 250. Assembling work while relatively positioning the side gas flow holes 103, 103 and the second side gas flow holes 104, 104 can be performed very easily as follows. That is, as shown in FIG. 4, the second tubular portion 102 is inserted into the first tubular portion 101 in the axial direction from the opening. In this state, for example, the second tubular portion 102 is rotated inside the first tubular portion 101 to a position where the engaging convex portion 251 is engaged with any of the plurality of groove portions 250. If the engagement convex part 251 and the groove part 250 will be in an engagement state, while the engagement convex part 251 slides relatively within the groove part 250, the bottom part of the 2nd cylindrical part 102 will be 1st cylindrical part. Push it to the position where it hits the bottom of 101. In this state, the first tubular portion 101 and the second tubular portion 102 are joined by forming the welded portions 107 to 152 shown in FIG. At this time, since the first cylindrical portion 101 and the second cylindrical portion 102 are prevented from rotating relative to each other by the engagement between the engaging convex portion 251 and the groove portion 250, the welding operation is extremely easy. The first side gas flow holes 103, 103 and the second side gas flow holes 104, 104 are hardly displaced.
[0040]
In addition, as shown to Fig.5 (a), you may make it form multiple engagement convex part 251 by the side of the 1st cylindrical part 101 along the circumferential direction. On the other hand, as shown in FIG. 5B, only one set of the engaging convex portion 251 and the groove portion 250 may be provided. In addition, the first side engaging portion and the second side engaging portion may be an engagement convex portion and a groove portion as long as relative rotation between the first cylindrical portion 101 and the second cylindrical portion 102 can be prevented. For example, as shown in FIG. 5C, the outer peripheral surface shape of the first portion 102a of the second cylindrical portion 102 is a polygonal shape, and the first cylindrical portion 101 side has an axial intermediate portion. You may make it form the 1st side engaging part 101f which has a polygonal internal peripheral surface shape in the position corresponding to the 1st part 102a after insertion in a position. In this case, relative rotation between the first cylindrical portion 101 and the second cylindrical portion 102 is prevented by fitting the first portion 102a of the second cylindrical portion 102 to the first side engaging portion 101f. It will be.
[0041]
The protector 100 can also be joined to the metal shell 9 by a caulking weld structure 150 formed by the method shown in FIGS. 8 to 11 below. That is, as shown in FIG. 8, the protector mounting portion 9a of the metal shell 9 is inserted into the mounting margin portion 101a of the protector 100 until the opening edge of the mounting margin portion 101a hits the end surface of the bracket. Then, as shown in FIG. 9, in this state, the intermediate portion in the axial direction of the mounting margin 101a is caulked in the circumferential direction toward the protector mounting portion 9a, thereby forming a crimped portion 81 as shown in FIG. To do. At this time, an annular recess may be formed on the protector mounting portion 9 a side corresponding to the caulking portion 81.
[0042]
Next, as shown in FIG. 11A, if a circumferential welded portion 83 is formed on the caulking portion 81 by, for example, laser welding, the intended caulking welded structure portion 150 is obtained. Here, when the width of the welded portion 83 is w1 and the width of the crimped portion 81 is w2, w1 / w2 is preferably 0.5 or more from the viewpoint of securing the bonding strength (in the example of FIG. 1, w1 Is about 0.7 mm, w2 is about 1 mm, and w1 / w2 is about 0.7). In addition, as shown in FIG. 11B, in order to generate a sufficient crimping force by caulking on the protector mounting portion 9a (inner member) side and to ensure a good crimping state, the mounting margin 101a (outer member). The thickness t2 is preferably set to 1 mm or less (in the example of FIG. 1, t2 is about 0.4 mm). Further, the penetration depth d1 of the welded portion 83 on the protector mounting portion 9a (inner member) side is preferably 0.3 mm or more from the viewpoint of securing the bonding strength. However, if the welded portion 83 is formed so as to penetrate the protector mounting portion 9a (inner member) in the thickness direction, the joint strength may be reduced due to the influence of a welding defect or the like. Is preferably smaller than the thickness t1 of the protector mounting portion 9a.
[0043]
A caulking portion 81 is formed in advance in the overlapping portion between the protector 100 and the protector mounting portion 9a, and a welded portion 83 of the entire circumference is formed and joined in a state where both are closely attached. The occurrence of defects in the weld 83 is effectively prevented, and the airtightness of the joint can be improved. For example, when the oxygen sensor 1 becomes low temperature, condensed water droplets may adhere to the outer surface of the protector. In this case, if there is a defect in the welded part 83 that joins the metal shell 9 and the protector 100, water droplets condensed from the defective part may invade and wet the detection part or attach dirt such as rust. There is. However, since the joining structure of the metal shell 9 and the protector 100 is the above-described caulking welded structure 150, such inconveniences as water droplets and dirt can be effectively prevented.
[0044]
It should be noted that, conventionally, the entire circumference welded portion is formed by fitting the protector 100 and the protector mounting portion 9a by gap fitting or press-fitting and forming the welded portion in that state. However, in this method, a good welded joint state can be obtained unless the dimensional control between the protector 100 and the protector mounting portion 9a, particularly the dimensional control with respect to the difference between the inner diameter of the protector 100 and the outer diameter of the protector mounting portion 9a, is not performed strictly. In some cases, it could not be obtained. However, in the above configuration, even if the diameter difference varies somewhat at the fitting stage, the tight contact state can be ensured by forming the crimped portion 81, so that the strict dimensional control as described above is not necessary. As a result, sensor manufacturing efficiency and yield are improved.
[0045]
A circumferentially reduced diameter portion is formed in advance in the base end of the opening of the protector 100 by, for example, pressing, and the protector mounting portion 9a on the metal shell 9 side is press-fitted into the reduced diameter portion in that state. And you may join both by forming a welding part in the reduced diameter part. By press-fitting the protector mounting portion 9a into the reduced diameter portion, the opening side of the protector 100 is less likely to have a flared form, and similarly, the probability of occurrence of defects in the welded portion can be reduced.
[0046]
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 a heat generating portion and an oxygen detection element in FIG. 1;
FIG. 3 is a plan view, a front half sectional view, an AA sectional view, and a bottom view showing an example of a protector.
FIG. 4 is a perspective view illustrating an assembling process of the protector.
FIGS. 5A and 5B are explanatory views showing some modified examples of a mechanism for preventing relative rotation around the axis between the first cylindrical portion and the second cylindrical portion of the protector. FIGS.
FIG. 6 is an explanatory diagram of the dimensions of the protector.
FIG. 7 is an explanatory diagram of dimensions of the metal shell.
FIG. 8 is a diagram for explaining a process of joining the protector and the metal shell by forming a caulking weld structure.
FIG. 9 is a process explanatory diagram following FIG. 8;
FIG. 10 is a process explanatory diagram following FIG. 9;
FIG. 11 is a process explanatory diagram following FIG. 10;
[Explanation of symbols]
1 Oxygen sensor (gas sensor)
2 Oxygen detection element
9 Main metal fittings
9a Protector mounting part
10 Casing (detecting element housing)
250 Groove (second side engagement part)
251 Engaging convex part (second side engaging part)
100 protector
101 1st cylindrical part
102 Second cylindrical part
103 1st side gas flow hole
104 Second side gas flow hole

Claims

In a rod-like or cylindrical form in which a detection part is formed at the tip part, with a detection element for detecting a detected component in a gas to be measured, and a state in which the detection part protrudes from one end side, A cylindrical element container that covers the detection element, and the detection part that is coupled to the opening end of the element container on the side from which the detection part protrudes and allows the gas to be measured to flow A protector that covers the inner and outer two cylindrical portions, that is, an outer first cylindrical portion, and a second cylindrical portion that is inserted axially inside thereof, and The outer peripheral surface of the second cylindrical portion is engaged with the first side engaging portion formed on the inner peripheral surface of the first cylindrical portion along with the insertion into the first cylindrical portion, A second side engaging portion is formed that positions and holds the second cylindrical portion at a predetermined position in the circumferential direction with respect to the first cylindrical portion. ,
The first side engaging part is an engaging convex part protruding from the inner peripheral surface of the first cylindrical part, and the second side engaging part is formed on the outer peripheral surface of the second cylindrical part. A groove that extends in the axial direction and allows the engagement convex portion to be fitted and slide relative to the axial direction;
A cylindrical protector mounting part is formed in the front side opening of the element container ,
The second cylindrical portion is formed to have an axial length shorter than the first cylindrical portion so as to enter a predetermined distance inside the opening edge of the first cylindrical portion. A mounting margin to the protector mounting portion is formed with a predetermined width on the opening side of the cylindrical portion, and the protector mounting portion of the element container is inserted into the mounting margin, and the mounting margin and the protector are inserted. A gas sensor, which is attached by forming an annular welded portion around the entire circumference of the overlapping portion with the mounting portion.

In each side wall portion of the first cylindrical portion and the second cylindrical portion, a first side gas flow hole and a second side gas flow hole that allow the gas flow are respectively penetrated in the thickness direction. So that the first side gas flow hole and the second side gas flow hole satisfy a predetermined positional relationship by the engagement of the first side engagement part and the second side engagement part. The gas sensor according to claim 1, wherein the first cylindrical portion and the second cylindrical portion are positioned and held.

A predetermined amount of gap is formed between the outer wall portions of the first cylindrical portion and the second cylindrical portion, and the first cylindrical portion and the second cylindrical portion, The first side gas flow hole and the second side gas flow hole are displaced from each other in the circumferential direction of the cylindrical part due to the engagement between the first side engagement part and the second side engagement part. The gas sensor according to claim 2, wherein the gas sensor is positioned so as to have a positional relationship.

A plurality of the groove portions are formed at substantially equal angular intervals in the circumferential direction on the outer peripheral surface of the second cylindrical portion, and the engagement convex portion is 1 at a predetermined position on the inner peripheral surface of the first cylindrical portion. 4. The gas sensor according to claim 1, wherein a plurality of gas sensors are formed at an angular interval that is an integral multiple of the angular interval of the groove portions in the circumferential direction of the inner peripheral surface.

The side wall portion of the second cylindrical portion is enlarged in diameter on the opening end side by a step portion formed in an axially intermediate portion, the enlarged opening end portion is a first portion, and the first portion is sandwiched by the step portion. The portion located on the opposite side as the second portion, the groove portion is formed in the first portion, while in the second portion, between the first cylindrical portion and the second cylindrical portion, A gap having a size corresponding to the stepped portion is formed, the second cylindrical portion has a second side gas flow hole in the second portion, and the second portion of the first cylindrical portion. The gas sensor according to any one of claims 1 to 4, wherein the first side gas flow holes are respectively formed in corresponding side wall portions.

The gas sensor according to claim 5, wherein the first portions of the second cylindrical portion are joined to the side wall portion of the first cylindrical portion by a weld portion formed at a position that does not interfere with the groove portion.