JP2004198363A

JP2004198363A - Gas sensor

Info

Publication number: JP2004198363A
Application number: JP2002370189A
Authority: JP
Inventors: Kazuya Nakagawa; 和也中川
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2002-12-20
Filing date: 2002-12-20
Publication date: 2004-07-15
Anticipated expiration: 2022-12-20
Also published as: JP3894116B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor having such a structure that the peripheral temperature of a thermally weak water repellent filter or elastic seal member is hard to become high. <P>SOLUTION: The gas sensor 1 has a housing 10, an insulator 12 on an element side, a gas sensor element 19, a cover 11 on a side of a gas to be measured, an insulator 13 on an atmospheric side and a cover 2 on the atmospheric side. The cover 2 on the atmospheric side has a caulked/fixed elastic seal member 17 on its base end side, introducing holes 210 and 220 for introducing the atmosphere into the cover 2 on the atmospheric side and the water repellent filter 23 covering these holes. A heat conduction inhibiting member 3 is arranged between the end surface 121 on the base end side of the insulator 12 on the element side and the end surface 131 on the leading end side of the insulator 13 on the atmospheric side. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【技術分野】
本発明は，自動車エンジンの排気管等に取り付けて熱い高温の排気ガス中にさらされて特定ガス濃度を測定するガスセンサに関する。
【０００２】
【従来技術】
自動車の排気管に取り付けて空燃比制御に利用するガスセンサが知られている。
このガスセンサ９は，図７に示すごとく，被測定ガス中の特定ガス濃度を検出するガスセンサ素子１９と該ガスセンサ素子１９を素子側絶縁碍子１２を介して挿通配置する筒型のハウジング１０と，上記ガスセンサ素子１９の先端側を覆うように上記ハウジング１０の先端側に固定する被測定ガス側カバー１１と，上記ガスセンサ素子１９の基端側を覆うように上記ハウジング１０の基端側に固定する大気側カバー２とを有する。
【０００３】
図７に示すごとく，上記大気側カバー２は，先端側がガスセンサ１の外部に露出し，ハウジング１０の基端側側面１００に溶接固定するメインカバー部材２１と，該メインカバー部材２１の基端側に筒型の撥水フィルタ２３を介してかしめ固定したフィルタカバー部材２２とよりなる。
【０００４】
上記ガスセンサ９において，大気側カバー２の基端側の内側面に弾性シール部材１７をかしめ固定し，該弾性シール部材１７において大気側カバー２の基端側がシールされる。また，上記ガスセンサ素子１９に接続した出力取り出し用及び／または電力印加用リード線１６は上記弾性シール部材１７を経由してガスセンサ外部へと延設され，上記リード線１６は上記弾性シール部材１７に設けた挿通穴１７０に対しシール固定される。
【０００５】
【特許文献１】
特開２００１−３４３３５５号公報
【０００６】
【解決しようとする課題】
ところで，ガスセンサ９を自動車の排気管に取り付けた際は，図７に示すごとく，ハウジング１０の先端側で破線Ｌより下側が熱い排気ガスに熱せられ，ハウジング１０は高温となる。ハウジング１０に挿通配置される素子側絶縁碍子１２も同様に高温となり，ここから大気側絶縁碍子１３を経て，熱がガスセンサ９の基端側に到達する。
【０００７】
そして，図７に示すごとく，筒型の撥水フィルタ２３を設けた部分においてメインカバー部材２１は外部に露出せず，筒型の撥水フィルタ２３とフィルタカバー部材２２で覆われているため熱がこもりやすい。
また，弾性シール部材１７をかしめ固定した部分もメインカバー部材２１が外部に露出せず，フィルタカバー部材２２により覆われており，ここも熱がこもりやすい。
【０００８】
ところで，弾性シール部材１７は熱に強くない。そして耐熱限界付近では変形したり，弾性率が変わってしまう。弾性シール部材１７は大気側カバー２に対しかしめ固定されており，弾性シール部材１７が変形したり，弾性率が変わって，かしめ固定された部分に隙間が生じ，そこでシール性が低下するおそれがある。また，リード線１６は弾性シール部材１７によって保持されているため，リード線１６の位置ずれや脱落発生のおそれもある。
【０００９】
また，撥水フィルタ２３は一般に多孔質の樹脂材料よりなるため，弾性シール部材１７と同様に熱で変形したり弾性率が変わり，かしめ固定された部分でゆるんでしまうおそれがある。さらに，多孔質の撥水フィルタ２３は，熱によって気孔が溶けて変形し，塞がって，通気性が悪化するおそれがある。
【００１０】
撥水フィルタ２３は，ガスセンサ９の大気側カバー２の内部に大気を導入する導入穴２１０，２２０を覆うように設け，該導入穴２１０，２２０からの水分浸入を防止するために設けてあるため，大気を通す通気性が必要である。
撥水フィルタ２３の通気性が低下した際は大気の導入が困難となり，ガスセンサ１内部が酸欠状態となってガス濃度測定に支障が生じるおそれがある。
【００１１】
本発明は，かかる従来の問題点に鑑みてなされたもので，熱に弱い撥水フィルタや弾性シール部材の周辺温度が高くなり難い構造のガスセンサを提供しようとするものである。
【００１２】
【課題の解決手段】
本発明は，筒型のハウジングと，該ハウジング内に挿通配置した素子側絶縁碍子と，該素子側絶縁碍子内に挿通配置したガスセンサ素子と，該ガスセンサ素子の先端側を覆うように上記ハウジングの先端側に固定する筒型の被測定ガス側カバーと，上記ガスセンサ素子の基端側を覆うように上記素子側絶縁碍子の基端側に配置する大気側絶縁碍子と，上記ハウジングの基端側に固定する筒型の大気側カバーとを有し，
上記大気側カバーの基端側は，該基端側をシールするためにかしめ固定した弾性シール部材を有し，また上記大気側カバーの基端側は，該大気側カバーの内部に大気を導入する導入穴を有し，該導入穴を覆う筒型の撥水フィルタを有するガスセンサにおいて，
上記素子側絶縁碍子の基端側端面と上記大気側絶縁碍子の先端側端面との間に熱伝導阻害部材を配置することを特徴とするガスセンサにある（請求項１）。
【００１３】
本発明にかかるガスセンサでは，素子側絶縁碍子と大気側絶縁碍子との間に熱伝導阻害部材をおいて，両者間での熱のやりとりを阻害する。これにより熱に弱い撥水フィルタや弾性シール部材などを設けたガスセンサ基端側の温度上昇を防止することができる。
【００１４】
以上，本発明によれば，熱に弱い撥水フィルタや弾性シール部材の周辺温度が高くなり難い構造のガスセンサを提供することができる。
【００１５】
【発明の実施の形態】
本発明にかかるガスセンサは，被測定ガス中の酸素濃度やＮＯｘ濃度，ＣＯ濃度，ＨＣ濃度などを測定する各種のガスセンサに対し適用することができる。また，自動車エンジン等の内燃機関の排気系に設置して，燃焼制御に利用する空燃比センサとして用いることができる。
また，ガスセンサ素子も積層型，コップ型，いずれを採用したガスセンサについても，本発明を適用することができる。
なお，ガスセンサの詳細構成は実施例で説明するが，本発明は実施例の構成にとどまらず，多くのガスセンサにおいて適用することができる。
【００１６】
本発明にかかるガスセンサにおいて，撥水フィルタは，大気側カバーに設けた導入穴から内部に水が侵入することを防ぐために設ける。テトラフルオロエチレンなどの各種樹脂材料よりなる多孔質材料で構成することが一般的である。
【００１７】
本発明にかかる熱伝導阻害部材とは，素子側絶縁碍子から大気側絶縁碍子への熱の流れを妨げることができれば，どのような構造，材質の部材を用いてもよい。
たとえば，大気側絶縁碍子よりも熱伝導率の小さな材料からなる部材を熱伝導阻害部材として使用することができる。一般に，素子側絶縁碍子は緻密でガスを通さないセラミックで構成するため，多孔質で気孔の多いポーラスなセラミックを熱伝導阻害部材として用いることができる。
【００１８】
また，接触面積を小さくすると熱伝導の阻害効果が高くなるため，素子側絶縁碍子と大気側絶縁碍子とが直接接触する際の接触面積よりも，更に小さな接触面積で大気側絶縁碍子や素子側絶縁碍子に接触できる形状の部材を熱伝導阻害部材として用いることができる。
さらに，素子側絶縁碍子や大気側絶縁碍子と線接触または点接触するような部材を熱伝導阻害部材として用いることができる。
【００１９】
具体的な熱伝導阻害部材として，たとえばハニカム構造を有する部材を用いることが好ましい（請求項２）。ハニカム構造の熱伝導阻害部材は，図２に示すごとく，素子側絶縁碍子や大気側絶縁碍子と向きあう面に貫通する穴を多数有し，従ってこのような熱伝導阻害部材は，素子側絶縁碍子や大気側絶縁碍子との接触面積が小さくなるため，熱伝導の阻害効果が高くなる。
また，上記素子側絶縁碍子の基端側端面及び上記大気側絶縁碍子の先端側端面に当接する当接面が凹凸面よりなる部材を用いることが好ましい（請求項３）。こちらの熱伝導阻害部材も，素子側絶縁碍子や大気側絶縁碍子との接触面積が小さくなるため，熱伝導の阻害効果が高くなる。
【００２０】
また，上記熱伝導阻害部材は，上記熱伝導阻害部材は，ガスセンサの先端側と基端側を結ぶ軸方向と平行方向に復元力が生じる弾性体よりなることが好ましい（請求項４）。
これにより，弾性体の復元力で素子側絶縁碍子を押圧し，確実にハウジング内の所定の位置に押圧固定することができる。
なお，軸方向とは，ガスセンサの先端側と基端側とを結ぶ，略筒型のガスセンサにおける中心軸と平行な方向である。
【００２１】
また，上記弾性体を大気側絶縁碍子よりも熱伝導率の小さな材料から構成することができる。また，上記弾性体における素子側絶縁碍子や大気側絶縁碍子と当接する当接面を，より小さな接触面積で大気側絶縁碍子や素子側絶縁碍子に対し接触するような形状で構成することが好ましい。
なお，上記弾性体としては各種のバネ部材，皿バネや板バネなどを用いることができる。
また，上記熱伝導阻害部材として，弾性体以外で大気側絶縁碍子や素子側絶縁碍子との間に挟んで用いる部材を用いることができる（図４参照）。
また，熱伝導阻害部材を２つ以上設けることもできる。
【００２２】
【実施例】
以下に，図面を用いて本発明の実施例について説明する。
（実施例１）
本例にかかるガスセンサ１は，図１に示すごとく，筒型のハウジング１０と，該ハウジング１０内に挿通配置した素子側絶縁碍子１２と，該素子側絶縁碍子１２内に挿通配置したガスセンサ素子１９と，該ガスセンサ素子１９の先端側を覆うように上記ハウジング１０の先端側に固定する筒型の被測定ガス側カバー１１と，上記ガスセンサ素子１９の基端側を覆うように上記素子側絶縁碍子１２の基端側に配置する大気側絶縁碍子１３と，上記ハウジング１０の基端側に固定する筒型の大気側カバー２とを有する。
【００２３】
上記大気側カバー２の基端側は，該基端側をシールするためにかしめ固定した弾性シール部材１７を有し，また上記大気側カバー２の基端側は，該大気側カバー２の内部に大気を導入する導入穴２１０，２２０を有し，該導入穴２１０，２２０を覆う筒型の撥水フィルタ２３を有する。
そして，上記素子側絶縁碍子１２の基端側端面１２１と上記大気側絶縁碍子１３の先端側端面１３１との間に熱伝導阻害部材３を配置する。
【００２４】
以下，詳細に説明する。
本例にかかるガスセンサ１は，自動車エンジンに接続した排気管の壁面に取り付けて，自動車エンジンの空燃比を測定して空燃比制御に使用する（図示略）。このときガスセンサ１は，ハウジング１０の側面に設けた径方向に突出する胴部１０１の先端側端面１０２を排気管の外壁面に向けて取り付ける。また，先端側端面１０２に対して上記排気管に対してシール固定できるようにバネ部１０３を設けてある。
【００２５】
そして，図１に記載した破線Ｌより下側が，ガスセンサ１による空燃比測定時に排気ガスで加熱される領域である。破線Ｌより上側は大気雰囲気である。したがって，破線Ｌからガスセンサ１の基端側に向かうに従って，ガスセンサ１の温度が低下する。なお，図１等では図面の上側をガスセンサの基端側，下方を先端側とした。
【００２６】
上記ハウジング１０の先端側に，二重構成の被測定ガス側カバー１１を設け，該カバー１１の内部に排気ガスを導入する導入穴が側面に設ける。また，被測定ガス側カバー１１の内部でガスセンサ素子１９の先端側が露出する。
上記ガスセンサ素子１９は，素子側絶縁碍子１２を介してハウジング１０内部に固定する。素子側絶縁碍子１２とハウジング１０との間，素子側絶縁碍子１２とガスセンサ素子１９との間はそれぞれシール固定して，ガスの流通が生じないようにする。
【００２７】
上記素子側絶縁碍子１２の基端側端面１２１に熱伝導阻害部材３を介して大気側絶縁碍子１３を載置する。大気側絶縁碍子１３は内部が空洞１３０で，そこにガスセンサ素子１９の基端側を収納する。また，上記空洞１３０と大気側絶縁碍子１３の基端側の端面との間を連絡する連絡穴１３９がある。
【００２８】
また，上記熱伝導阻害部材３は，図２に示すごとく，素子側絶縁碍子１２の基端側端面１２１や大気側絶縁碍子１３の先端側端面１３１と当接する当接面３０９に対し開口した貫通穴３０８を多数備えたハニカム構造の環状板で，素子側及び大気側絶縁碍子１２，１３を構成するセラミックより気孔率が高く熱伝導率が低いセラミックよりなる。なお，両絶縁碍子１２，１３及び熱伝導阻害部材３は共にアルミナセラミックである。
【００２９】
上記ガスセンサ素子１９と電気的に接続して，外部に素子１９の出力を取り出したり，または外部から素子１９に電力を供給する端子１９１がある。この端子１９１は上記連絡穴１３９を通じて，大気側絶縁碍子１３の外部で大気側カバー２の内部に突出する。この突出した箇所において，連結部材１９２を介して上記端子１９１はリード線１６に電気的に接続される。
上記リード線１６は，大気側カバー２の基端側をシールする弾性シール部材１７に設けた挿通穴１７０を通じてガスセンサ１の外部へと引き出して，外部に設けた測定装置や電源などと接続する。
【００３０】
また，大気側カバー２は，ハウジング１０の基端側側面に固定したメインカバー部材２１と該メインカバー部材２１の基端側の外部に撥水フィルタ２３をフィルタカバー部材２２を用いて固定する。
すなわち，メインカバー部材２１において大気導入用の導入穴２１０を設けた部分の外方に筒型の撥水フィルタ２３を配置し，撥水フィルタ２３の外側に同じく筒型のフィルタカバー部材２２を配置する。なお，フィルタカバー部材２２でも撥水フィルタ２３と対面する位置に大気導入用の導入穴２２０を有する。そして，フィルタカバー部材２２の外側から力を加えて，撥水フィルタ２３ごとメインカバー部材２１に対しかしめ固定する。
なお，メインカバー部材２１は先端側が径大で，基端側が径細である。撥水フィルタ２３やフィルタカバー部材２２は径細の部分に設ける。
【００３１】
また，大気側絶縁碍子１３の基端側端面１３２とメインカバー部材２１の径大及び径細の切替部における内側面との間に皿バネ１５を載置する。この皿バネ１５はガスセンサ１の軸方向への復元力を持つ。
【００３２】
そして，素子側絶縁碍子１２はハウジング１０の内側面に突出形成されたテーパ面１０５に載置し，大気側絶縁碍子１３は素子側絶縁碍子１２の基端側端面１２１に熱伝導阻害部材３を介して載置する。皿バネ１５は大気側絶縁碍子１３の基端側端面１３２と大気側カバー２との間に位置して，図１の基端側から先端側に向かう軸方向の押圧力を大気側絶縁碍子１３及び素子側絶縁碍子１２に与えて，大気側絶縁碍子１３と素子側絶縁碍子１２と熱伝導阻害部材３のそれぞれの間，また素子側絶縁碍子１２とハウジング１０のテーパー面１０５との間を密着固定する。
【００３３】
本例の作用効果について説明する。
本例では，素子側絶縁碍子１２と大気側絶縁碍子１３との間に熱伝導阻害部材３をおいて，両者間での熱のやりとりを阻害する。これにより撥水フィルタ２３や弾性シール部材１７などを設けたガスセンサ１の基端側の温度上昇を防止することができる。
以上，本例によれば，熱に弱い撥水フィルタ２３や弾性シール部材１７の周辺温度が高くなり難い構造のガスセンサを提供することができる。
【００３４】
また，本例のガスセンサ１は，自動車で使用する空燃比センサを想定したが，空燃比センサ以外であっても使用環境でハウジング１０が加熱される構成のガスセンサについて本例の構成は有効である。
【００３５】
また，図３に示すごとき，基端側端面１２１や先端側端面１３１と当接する当接面３０９を凹凸面としたセラミックの環状板よりなる熱伝導阻害部材３を用いることもできる。
また，図示は略したが，単なる環状板で熱伝導率が小さな材料から構成した部材を熱伝導阻害部材として用いることができる。また，この場合の熱伝導阻害部材の熱伝導率は，大気側絶縁碍子や素子側絶縁碍子よりも小さい。
【００３６】
（実施例２）
本例は，図４〜図６に示すごとく，ガスセンサ１の先端側と基端側を結ぶ軸方向と平行方向に復元力が生じる弾性体４１及び該弾性体４１に被せ，該弾性体４１を素子側絶縁碍子１２の基端側端面１２１に固定するキャップ部材４２を備える構成について説明する。
【００３７】
本例のガスセンサ１は，実施例１と同様に，筒型のハウジング１０と，該ハウジング１０内に挿通配置した素子側絶縁碍子１２と，該素子側絶縁碍子１２内に挿通配置したガスセンサ素子１９と，該ガスセンサ素子１９の先端側を覆うように上記ハウジング１０の先端側に固定する筒型の被測定ガス側カバーと，上記ガスセンサ素子１９の基端側を覆うように上記素子側絶縁碍子１２の基端側に熱伝導阻害部材を介して配置する大気側絶縁碍子１３と，上記ハウジング１０の基端側に固定する筒型の大気側カバー２とを有する。
【００３８】
本例にかかるガスセンサ１は，図４，図５に示すごとき，皿バネよりなる弾性体４１と該弾性体４１を基端側端面１２１に固定するキャップ部材４２を有する。
上記弾性体４１である皿バネは金属の環状板からなり，図５（ｂ）に示す断面説明図にあるように側面からみた形が波状で，図面の上下方向から押圧することで，図５（ｂ）において図面上下方向への復元力が生じる。
また，上記キャップ４２は，図６に示すごとく，弾性体４１である皿バネの外径とほぼ同じ内径を備え，先端側が開口した筒状部材である。弾性体４１を基端側から押える押え板４２１と，該押え板４２１からハウジング１０の側面に沿って伸びる側面部４２２とよりなる。上記押え板４２１は表面に二箇所の突部４２３が設けてある。
【００３９】
そして，素子側絶縁碍子１２の基端側端面１２１に弾性体４１を載置して，復元力が生じるようにキャップ４２で軸方向に押圧しつつ側面部４２２をハウジング１０の基端側に差込み，側面部４２２において溶接固定する。
この押圧によって弾性体４１にかかる皿バネは平べったくつぶされ，素子側絶縁碍子１２の基端側端面４２１やキャップ部材４２の押え板４２１とは全面当接状態となるが（図４参照），大気側絶縁碍子１３の先端側端面１３１と押え板４２１との間は，突部４２３においてのみ接触する。
【００４０】
これにより，ハウジング１０からの熱は素子側絶縁碍子１２に伝導し，さらにそこから大気側絶縁碍子１３に伝わるが，素子側絶縁碍子１２と弾性体４１，キャップ部材４２との間は接触面積も広く，熱もよく伝わるが，キャップ部材４２と大気側絶縁碍子１３との間は突部４２３においてのみ接触する状態にあるため，熱が伝わりにくい。
すなわち，キャップ部材４２が熱伝導阻害部材として機能するため，本例にかかるガスセンサ１でも，基端側にある撥水フィルタや弾性シール部材（図示略）の加熱を防止することができる。
そのほか詳細な構成や作用効果は実施例１と同様である。
【図面の簡単な説明】
【図１】実施例１における，ガスセンサの軸方向全体断面図。
【図２】実施例１における，ハニカムよりなる熱伝導阻害部材の平面図及び断面図。
【図３】実施例１における，当接面が凹凸面となる熱伝導阻害部材の平面図及び断面図。
【図４】実施例２における，皿バネとキャップ部材を大気側と素子側絶縁碍子との間に設けたガスセンサの軸方向断面説明図。
【図５】実施例２における，皿バネの平面図及び断面図。
【図６】実施例２における，皿バネにかぶせるキャップ部材の平面図及び断面図。
【図７】従来例にかかる，ガスセンサの軸方向全体断面図。
【符号の説明】
１．．．ガスセンサ，
１０．．．ハウジング，
１２．．．大気側絶縁碍子，
１３．．．素子側絶縁碍子，
３．．．熱伝導阻害部材，[0001]
【Technical field】
The present invention relates to a gas sensor attached to an exhaust pipe or the like of an automobile engine and exposed to hot and high-temperature exhaust gas to measure a specific gas concentration.
[0002]
[Prior art]
2. Description of the Related Art A gas sensor that is attached to an exhaust pipe of an automobile and used for air-fuel ratio control is known.
As shown in FIG. 7, the gas sensor 9 includes a gas sensor element 19 for detecting a specific gas concentration in the gas to be measured, a cylindrical housing 10 through which the gas sensor element 19 is inserted via an element-side insulator 12, and The measured gas side cover 11 fixed to the distal end of the housing 10 so as to cover the distal end of the gas sensor element 19, and the atmosphere fixed to the proximal end of the housing 10 so as to cover the proximal end of the gas sensor element 19. And a side cover 2.
[0003]
As shown in FIG. 7, the atmosphere-side cover 2 includes a main cover member 21 whose distal end is exposed to the outside of the gas sensor 1 and is welded and fixed to a base side surface 100 of the housing 10. And a filter cover member 22 which is caulked and fixed via a cylindrical water-repellent filter 23.
[0004]
In the gas sensor 9, an elastic seal member 17 is caulked and fixed to the inner surface on the base end side of the atmosphere-side cover 2, and the base end side of the atmosphere-side cover 2 is sealed with the elastic seal member 17. A lead 16 for output and / or power application connected to the gas sensor element 19 extends to the outside of the gas sensor via the elastic seal member 17, and the lead 16 is connected to the elastic seal member 17. It is sealed and fixed to the insertion hole 170 provided.
[0005]
[Patent Document 1]
JP 2001-343355 A
[Problem to be solved]
By the way, when the gas sensor 9 is attached to the exhaust pipe of an automobile, as shown in FIG. 7, the lower end of the housing 10 below the broken line L is heated by the hot exhaust gas, and the temperature of the housing 10 becomes high. Similarly, the temperature of the element-side insulator 12 inserted into the housing 10 becomes high, and the heat reaches the base end of the gas sensor 9 via the atmosphere-side insulator 13.
[0007]
As shown in FIG. 7, the main cover member 21 is not exposed to the outside at the portion where the cylindrical water-repellent filter 23 is provided, and is covered with the cylindrical water-repellent filter 23 and the filter cover member 22. It is easy to be muffled.
In addition, the portion where the elastic seal member 17 is fixed by caulking is also covered with the filter cover member 22 without exposing the main cover member 21 to the outside.
[0008]
Incidentally, the elastic seal member 17 is not strong against heat. And near the heat resistance limit, it deforms and its elastic modulus changes. The elastic seal member 17 is caulked and fixed to the atmosphere side cover 2, and the elastic seal member 17 is deformed or its elastic modulus is changed, so that a gap is formed in the caulked and fixed portion, and the sealing performance may be reduced there. There is. Further, since the lead 16 is held by the elastic seal member 17, there is a possibility that the lead 16 may be displaced or fall off.
[0009]
Further, since the water-repellent filter 23 is generally made of a porous resin material, it may be deformed by heat or have a changed elastic modulus as in the case of the elastic seal member 17, and may be loosened at the portion fixed by caulking. Furthermore, the pores of the porous water-repellent filter 23 may be melted and deformed by heat, and may be blocked, thereby deteriorating air permeability.
[0010]
The water-repellent filter 23 is provided so as to cover the introduction holes 210 and 220 for introducing the atmosphere into the inside of the atmosphere-side cover 2 of the gas sensor 9, and is provided to prevent moisture from entering through the introduction holes 210 and 220. ， Ventilation through the atmosphere is required.
When the air permeability of the water-repellent filter 23 is reduced, it is difficult to introduce the air, and the inside of the gas sensor 1 may be in an oxygen-deficient state, which may hinder the gas concentration measurement.
[0011]
The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a gas sensor having a structure in which the temperature around a water-repellent filter or an elastic seal member that is weak to heat is hardly increased.
[0012]
[Means for solving the problem]
The present invention relates to a cylindrical housing, an element-side insulator inserted and arranged in the housing, a gas sensor element inserted and arranged in the element-side insulator, and a housing for covering the distal end of the gas sensor element. A cylindrical gas-side cover to be measured fixed to the distal end, an atmosphere-side insulator disposed on the proximal end of the element-side insulator so as to cover the proximal end of the gas sensor element, and a proximal end of the housing. A cylindrical atmospheric side cover fixed to the
The base end side of the atmosphere side cover has an elastic seal member fixed by caulking to seal the base end side, and the base end side of the atmosphere side cover introduces air into the inside of the atmosphere side cover. A gas sensor having a cylindrical water-repellent filter having an introduction hole to cover and covering the introduction hole,
The gas sensor according to claim 1, wherein a heat conduction inhibiting member is disposed between a base end surface of the element-side insulator and a front end surface of the atmosphere-side insulator.
[0013]
In the gas sensor according to the present invention, a heat conduction inhibiting member is provided between the element-side insulator and the atmosphere-side insulator to prevent the exchange of heat between the two. Thus, it is possible to prevent a temperature rise on the base end side of the gas sensor provided with a water-repellent filter, an elastic seal member, and the like that are weak to heat.
[0014]
As described above, according to the present invention, it is possible to provide a gas sensor having a structure in which the temperature around the water-repellent filter and the elastic seal member that is weak to heat is not easily increased.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
The gas sensor according to the present invention can be applied to various gas sensors for measuring the oxygen concentration, NOx concentration, CO concentration, HC concentration, and the like in the gas to be measured. Further, it can be installed in an exhaust system of an internal combustion engine such as an automobile engine and used as an air-fuel ratio sensor used for combustion control.
Further, the present invention can be applied to a gas sensor employing any of a stacked type and a cup type gas sensor element.
Although the detailed configuration of the gas sensor will be described in the embodiment, the present invention is not limited to the configuration of the embodiment, and can be applied to many gas sensors.
[0016]
In the gas sensor according to the present invention, the water-repellent filter is provided to prevent water from entering the inside through the introduction hole provided in the atmosphere-side cover. It is common to use a porous material made of various resin materials such as tetrafluoroethylene.
[0017]
The heat conduction inhibiting member according to the present invention may be any member having any structure and material as long as it can prevent the flow of heat from the element-side insulator to the atmosphere-side insulator.
For example, a member made of a material having a lower thermal conductivity than the air-side insulator can be used as the heat conduction inhibiting member. In general, since the element-side insulator is made of a dense and gas-impermeable ceramic, a porous ceramic having many pores can be used as a heat conduction inhibiting member.
[0018]
In addition, since the effect of inhibiting heat conduction increases when the contact area is reduced, the air-side insulator and the element-side insulator have a smaller contact area than the direct contact area between the element-side insulator and the air-side insulator. A member having a shape capable of contacting the insulator can be used as the heat conduction inhibiting member.
Furthermore, a member that makes line contact or point contact with the element-side insulator or the atmosphere-side insulator can be used as the heat conduction inhibiting member.
[0019]
It is preferable to use, for example, a member having a honeycomb structure as a specific heat conduction inhibiting member (claim 2). As shown in FIG. 2, the heat conduction inhibiting member having a honeycomb structure has a large number of holes that penetrate the surface facing the element-side insulator and the air-side insulator. Since the contact area with the insulator or the insulator on the atmosphere side is reduced, the effect of inhibiting heat conduction is increased.
In addition, it is preferable to use a member whose contact surface that comes into contact with the proximal end surface of the element-side insulator and the distal end surface of the atmosphere-side insulator is formed of an uneven surface. The heat conduction inhibiting member also has a small contact area with the element-side insulator and the air-side insulator, so that the effect of inhibiting heat conduction increases.
[0020]
Preferably, the heat conduction inhibiting member is formed of an elastic body that generates a restoring force in a direction parallel to an axial direction connecting a distal end side and a base end side of the gas sensor.
Thus, the element-side insulator is pressed by the restoring force of the elastic body, and can be reliably pressed and fixed at a predetermined position in the housing.
The axial direction is a direction that connects the distal end side and the proximal end side of the gas sensor and is parallel to the central axis of the substantially cylindrical gas sensor.
[0021]
Further, the elastic body can be made of a material having a lower thermal conductivity than the air-side insulator. In addition, it is preferable that the contact surface of the elastic body, which is in contact with the element-side insulator or the air-side insulator, has a smaller contact area so as to contact the air-side insulator or the element-side insulator. .
Note that various spring members, disc springs, leaf springs, and the like can be used as the elastic body.
In addition, as the heat conduction inhibiting member, a member other than an elastic body used between the air-side insulator and the element-side insulator can be used (see FIG. 4).
Further, two or more heat conduction inhibiting members may be provided.
[0022]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Example 1)
As shown in FIG. 1, a gas sensor 1 according to the present embodiment has a cylindrical housing 10, an element-side insulator 12 inserted through the housing 10, and a gas sensor element 19 inserted through the element-side insulator 12. A cylindrical gas-to-be-measured cover 11 fixed to the distal end of the housing 10 so as to cover the distal end of the gas sensor element 19; and the element-side insulator so as to cover the proximal end of the gas sensor element 19. The housing has an atmosphere-side insulator 13 arranged on the base end side of the housing 12 and a cylindrical atmosphere-side cover 2 fixed to the base end side of the housing 10.
[0023]
The base end of the atmosphere-side cover 2 has an elastic seal member 17 fixed by caulking to seal the base end, and the base end of the atmosphere-side cover 2 has And a cylindrical water-repellent filter 23 that covers the introduction holes 210 and 220.
Then, the heat conduction inhibiting member 3 is arranged between the base end surface 121 of the element-side insulator 12 and the front end surface 131 of the atmosphere-side insulator 13.
[0024]
The details are described below.
The gas sensor 1 according to the present embodiment is mounted on the wall of an exhaust pipe connected to an automobile engine, measures the air-fuel ratio of the automobile engine, and is used for air-fuel ratio control (not shown). At this time, the gas sensor 1 is mounted with the front end surface 102 of the body portion 101 provided on the side surface of the housing 10 and protruding in the radial direction facing the outer wall surface of the exhaust pipe. Further, a spring portion 103 is provided on the front end side end surface 102 so that it can be sealed and fixed to the exhaust pipe.
[0025]
The area below the broken line L shown in FIG. 1 is an area heated by the exhaust gas when the air-fuel ratio is measured by the gas sensor 1. Above the broken line L is the air atmosphere. Accordingly, the temperature of the gas sensor 1 decreases from the broken line L toward the base end of the gas sensor 1. In FIG. 1 and the like, the upper side of the drawing is the base end side of the gas sensor, and the lower side is the front end side.
[0026]
A double-sided gas-to-be-measured cover 11 is provided on the tip side of the housing 10, and an introduction hole for introducing exhaust gas into the inside of the cover 11 is provided on the side surface. Further, the tip side of the gas sensor element 19 is exposed inside the measured gas side cover 11.
The gas sensor element 19 is fixed inside the housing 10 via the element-side insulator 12. Seals are fixed between the element-side insulator 12 and the housing 10 and between the element-side insulator 12 and the gas sensor element 19 so that gas does not flow.
[0027]
The air-side insulator 13 is placed on the base end surface 121 of the element-side insulator 12 via the heat conduction inhibiting member 3. The atmosphere-side insulator 13 has a cavity 130 therein and accommodates the base end side of the gas sensor element 19 therein. In addition, there is a communication hole 139 that communicates between the cavity 130 and the end face on the proximal end side of the air-side insulator 13.
[0028]
Further, as shown in FIG. 2, the heat conduction inhibiting member 3 has a through hole opened to a contact surface 309 which is in contact with the proximal end surface 121 of the element-side insulator 12 and the distal end surface 131 of the air-side insulator 13. This is an annular plate having a honeycomb structure having a large number of holes 308 and made of a ceramic having a higher porosity and a lower thermal conductivity than the ceramics constituting the element-side and atmosphere-side insulators 12 and 13. The insulators 12, 13 and the heat conduction inhibiting member 3 are both made of alumina ceramic.
[0029]
There is a terminal 191 that is electrically connected to the gas sensor element 19 and externally extracts the output of the element 19 or supplies power to the element 19 from outside. The terminal 191 protrudes into the atmosphere-side cover 2 outside the atmosphere-side insulator 13 through the communication hole 139. At the protruding portion, the terminal 191 is electrically connected to the lead wire 16 via the connecting member 192.
The lead wire 16 is drawn out of the gas sensor 1 through an insertion hole 170 provided in an elastic seal member 17 that seals the base end side of the atmosphere-side cover 2, and is connected to a measuring device, a power supply, and the like provided outside.
[0030]
The atmosphere side cover 2 has a main cover member 21 fixed to the base end side surface of the housing 10 and a water repellent filter 23 fixed to the outside of the base end side of the main cover member 21 using a filter cover member 22.
That is, the cylindrical water-repellent filter 23 is disposed outside the portion of the main cover member 21 where the introduction hole 210 for introducing air is provided, and the cylindrical filter cover member 22 is also disposed outside the water-repellent filter 23. I do. The filter cover member 22 also has an introduction hole 220 for introducing air into the air at a position facing the water-repellent filter 23. Then, a force is applied from the outside of the filter cover member 22 to fix the entire water repellent filter 23 to the main cover member 21 by caulking.
The main cover member 21 has a large diameter at the distal end and a small diameter at the proximal end. The water-repellent filter 23 and the filter cover member 22 are provided in a small diameter portion.
[0031]
Further, the disc spring 15 is placed between the base end surface 132 of the air-side insulator 13 and the inner surface of the large-diameter and small-diameter switching portion of the main cover member 21. The disc spring 15 has a restoring force in the axial direction of the gas sensor 1.
[0032]
The element-side insulator 12 is mounted on a tapered surface 105 protruding from the inner surface of the housing 10, and the air-side insulator 13 is provided with the heat conduction inhibiting member 3 on the base end surface 121 of the element-side insulator 12. Placed via. The disc spring 15 is located between the base end surface 132 of the air-side insulator 13 and the air-side cover 2 and applies an axial pressing force from the base end to the front end in FIG. And applied to the element-side insulator 12 to closely contact each other between the atmosphere-side insulator 13, the element-side insulator 12, and the heat conduction inhibiting member 3, and between the element-side insulator 12 and the tapered surface 105 of the housing 10. Fix it.
[0033]
The operation and effect of this example will be described.
In this example, a heat conduction inhibiting member 3 is provided between the element-side insulator 12 and the atmosphere-side insulator 13 to prevent heat exchange between the two. Thereby, it is possible to prevent a temperature rise on the base end side of the gas sensor 1 provided with the water repellent filter 23, the elastic seal member 17, and the like.
As described above, according to this example, it is possible to provide a gas sensor having a structure in which the temperature around the water-repellent filter 23 and the elastic seal member 17 that is weak to heat is unlikely to increase.
[0034]
Further, the gas sensor 1 of the present embodiment is assumed to be an air-fuel ratio sensor used in an automobile. However, the configuration of the present embodiment is effective for a gas sensor having a configuration in which the housing 10 is heated in a use environment even if it is other than the air-fuel ratio sensor. .
[0035]
Further, as shown in FIG. 3, a heat conduction inhibiting member 3 made of a ceramic annular plate having an abutting surface 309 in contact with the proximal end surface 121 or the distal end surface 131 may be used.
Further, although not shown, a member made of a material having a small thermal conductivity with a simple annular plate can be used as the heat conduction inhibiting member. In this case, the thermal conductivity of the heat conduction inhibiting member is smaller than that of the air-side insulator and the element-side insulator.
[0036]
(Example 2)
In this example, as shown in FIGS. 4 to 6, an elastic body 41 which generates a restoring force in a direction parallel to an axial direction connecting the distal end side and the base end side of the gas sensor 1 and the elastic body 41 are covered with the elastic body 41. A configuration including a cap member 42 fixed to the base end surface 121 of the element-side insulator 12 will be described.
[0037]
As in the first embodiment, the gas sensor 1 of this embodiment includes a cylindrical housing 10, an element-side insulator 12 inserted through the housing 10, and a gas sensor element 19 inserted through the element-side insulator 12. A cylindrical cover for measuring a gas to be measured, which is fixed to the distal end of the housing 10 so as to cover the distal end of the gas sensor element 19; and the insulator 12 to cover the proximal end of the gas sensor element 19. An air-side insulator 13 is disposed on the base end side of the housing 10 via a heat conduction inhibiting member, and a cylindrical air-side cover 2 is fixed to the base end side of the housing 10.
[0038]
As shown in FIGS. 4 and 5, the gas sensor 1 according to the present embodiment includes an elastic body 41 formed of a disc spring and a cap member 42 for fixing the elastic body 41 to the base end surface 121.
The disc spring, which is the elastic body 41, is made of a metal annular plate, and has a wavy shape as viewed from the side as shown in the cross-sectional explanatory view shown in FIG. In (b), a restoring force is generated in the vertical direction in the drawing.
As shown in FIG. 6, the cap 42 is a tubular member having an inner diameter substantially equal to the outer diameter of the disc spring serving as the elastic body 41 and having an open end. A pressing plate 421 presses the elastic body 41 from the base end side, and a side surface portion 422 extending from the pressing plate 421 along the side surface of the housing 10. The pressing plate 421 has two projections 423 on the surface.
[0039]
Then, the elastic body 41 is placed on the base end surface 121 of the element-side insulator 12, and the side portion 422 is inserted into the base end side of the housing 10 while being pressed in the axial direction by the cap 42 so as to generate a restoring force. , And is fixed by welding at the side surface portion 422.
Due to this pressing, the disc spring applied to the elastic body 41 is flattened and brought into contact with the base end surface 421 of the element-side insulator 12 and the pressing plate 421 of the cap member 42 (see FIG. 4). ), The contact between the front end surface 131 of the air-side insulator 13 and the holding plate 421 is made only at the protrusion 423.
[0040]
As a result, heat from the housing 10 is conducted to the element-side insulator 12 and further transmitted to the atmosphere-side insulator 13, but the contact area between the element-side insulator 12 and the elastic body 41 and the cap member 42 is also small. Although the heat is widely transmitted well, heat is hardly transmitted because the cap member 42 and the air-side insulator 13 are in contact only with the protrusion 423.
That is, since the cap member 42 functions as a heat conduction inhibiting member, even the gas sensor 1 according to the present embodiment can prevent the water-repellent filter and the elastic seal member (not shown) at the base end from being heated.
The other detailed configurations and operational effects are the same as those of the first embodiment.
[Brief description of the drawings]
FIG. 1 is an overall sectional view in the axial direction of a gas sensor according to a first embodiment.
FIGS. 2A and 2B are a plan view and a cross-sectional view of a heat conduction inhibiting member made of a honeycomb according to the first embodiment.
FIGS. 3A and 3B are a plan view and a cross-sectional view of a heat conduction inhibiting member in which a contact surface is an uneven surface according to the first embodiment.
FIG. 4 is an axial sectional explanatory view of a gas sensor according to a second embodiment in which a disc spring and a cap member are provided between an atmosphere side and an element-side insulator;
5A and 5B are a plan view and a cross-sectional view of a disc spring according to the second embodiment.
FIGS. 6A and 6B are a plan view and a cross-sectional view of a cap member over a disc spring according to a second embodiment.
FIG. 7 is an overall sectional view in the axial direction of a gas sensor according to a conventional example.
[Explanation of symbols]
1. . . Gas sensor,
10. . . housing,
12. . . Air side insulator,
13. . . Element side insulator,
3. . . Heat conduction inhibitor,

Claims

筒型のハウジングと，該ハウジング内に挿通配置した素子側絶縁碍子と，該素子側絶縁碍子内に挿通配置したガスセンサ素子と，該ガスセンサ素子の先端側を覆うように上記ハウジングの先端側に固定する筒型の被測定ガス側カバーと，上記ガスセンサ素子の基端側を覆うように上記素子側絶縁碍子の基端側に配置する大気側絶縁碍子と，上記ハウジングの基端側に固定する筒型の大気側カバーとを有し，
上記大気側カバーの基端側は，該基端側をシールするためにかしめ固定した弾性シール部材を有し，また上記大気側カバーの基端側は，該大気側カバーの内部に大気を導入する導入穴を有し，該導入穴を覆う筒型の撥水フィルタを有するガスセンサにおいて，
上記素子側絶縁碍子の基端側端面と上記大気側絶縁碍子の先端側端面との間に熱伝導阻害部材を配置することを特徴とするガスセンサ。A cylindrical housing, an element-side insulator inserted through the housing, a gas sensor element inserted through the element-side insulator, and fixed to the tip end of the housing so as to cover the tip end of the gas sensor element. A cylindrical cover to be measured, an air-side insulator disposed at the base end of the element-side insulator so as to cover the base end of the gas sensor element, and a cylinder fixed to the base end of the housing. With a mold-type atmosphere-side cover,
The base end side of the atmosphere side cover has an elastic seal member fixed by caulking to seal the base end side, and the base end side of the atmosphere side cover introduces air into the inside of the atmosphere side cover. A gas sensor having a cylindrical water-repellent filter having an introduction hole to cover and covering the introduction hole,
A gas sensor, wherein a heat conduction inhibiting member is disposed between a base end surface of the element-side insulator and a front end surface of the atmosphere-side insulator.

請求項１において，上記熱伝導阻害部材は，ハニカム構造を有することを特徴とするガスセンサ。2. The gas sensor according to claim 1, wherein the heat conduction inhibiting member has a honeycomb structure.

請求項１において，上記熱伝導阻害部材は，上記素子側絶縁碍子の基端側端面及び上記大気側絶縁碍子の先端側端面に当接する当接面が凹凸面よりなることを特徴とするガスセンサ。2. The gas sensor according to claim 1, wherein the heat conduction inhibiting member has an uneven surface in contact with a base end surface of the element-side insulator and a front end surface of the atmosphere-side insulator.

請求項１において，上記熱伝導阻害部材は，ガスセンサの先端側と基端側とを結ぶ軸方向と平行方向に復元力が生じる弾性体よりなることを特徴とするガスセンサ。2. The gas sensor according to claim 1, wherein the heat conduction inhibiting member is made of an elastic body that generates a restoring force in a direction parallel to an axial direction connecting a distal end side and a base end side of the gas sensor.