JP4355082B2

JP4355082B2 - Gas sensor

Info

Publication number: JP4355082B2
Application number: JP2000047393A
Authority: JP
Inventors: 聡石川
Original assignee: NGK Spark Plug Co Ltd
Current assignee: Niterra Co Ltd
Priority date: 2000-02-24
Filing date: 2000-02-24
Publication date: 2009-10-28
Anticipated expiration: 2020-02-24
Also published as: JP2001235445A

Description

【０００１】
【発明の属する技術分野】
本発明は、排気ガス等の被測定ガスが流れる流路を形成する管に取り付けられ、基準ガスとしての大気を外部から導入して機能するガスセンサに関する。
【０００２】
【従来の技術】
従来より、混合ガス中から特定のガス成分の濃度を検出するガスセンサとして、ＨＣセンサやＮＯｘセンサ等種々のものが知られている。
この種のガスセンサの一つとして、例えば特開平９−５４０６３号公報に示される外気導入型の酸素センサがある。この酸素センサは、外気を導入する通気孔を、ガスセンサの最上部に設けられたシール部材の中央を軸方向に貫通するように形成すると共に、この通気孔を硬質の撥水性フィルタにより閉塞することにより、その通気性と防水性を保持している。
【０００３】
しかし、このような硬質フィルタを通気孔全体にわたって配置した構成では、フィルタ自体の体積が大きいことから、その通気性を十分に確保することが困難であるという問題があった。
そこで、例えば先行する特許出願（特願平１０−３７４１１７）に示された技術では、シート状の撥水性フィルタを、通気孔に嵌挿可能な筒状挿入部材の外周面と通気孔の内周面との間に挟持する態様で通気孔内に固定する構成とし、その通気性を保持している。
【０００４】
【発明が解決しようとする課題】
しかしながら、上記構成では、撥水性フィルタを筒状挿入部材に被せた状態で、通気孔に挿入する際に、通気孔の内面との間の摩擦力により撥水性フィルタが引っ張られる状態となる。このため、撥水性フィルタの材質によっては、挿入の際に撥水性フィルタが薄肉化して耐水圧が下がり、防水性能が低下してしまうという問題が懸念された。
【０００５】
本発明はこうした問題に鑑みてなされたものであり、大気を外部から導入して機能するガスセンサにおいて、通気性、防水性等に優れたガスセンサを提供することを目的とする。
【０００６】
【課題を解決するための手段及び発明の効果】
上記課題に鑑み、請求項１記載のガスセンサにおいては、ガスセンサの基準ガス空間を大気側からシールする部材であるゴムグロメットに、大気側から基準ガス空間に酸素を導入する通気経路を、通気経路の大気側開口部がゴムグロメットの上端面に開口する様に形成した上で、その外側開口部を閉塞する様にフィルタを設け、そのフィルタを、前記ゴムグロメットの上端面と、自らの下端面との間で挟持するように、押え部材を配置する様にした。
【０００７】
フィルタとしては、上記の様にシール部材と押え部材で挟持するようにしたので、フィルタとしてシート状のものを用いても、平板な形状でそのまま用いることが出来るので、一部が引っ張られて防水性が低下することが無い。
上記押え部材としては、あらゆる材質のものを用いる事が出来る。例えば、テフロン等の樹脂、フッ素ゴムなどのゴム材料、或いは、金属やセラミックスでも良い。
【０００８】
なお、樹脂を用いると押え部材の加工が容易であり、安価に出来るというメリットを有する。更に樹脂の中でもゴム等の弾性体材料を用いると、シール部材を傷つける恐れが無いというメリットを有する。但し、フィルタと接触する界面において防水性を有する必要があるので、ある程度の硬度が必要になる。特に押え部材はその厚みを厚くしすぎると、フィルタの通気面上部に形成される凹部に塵などが溜まりやすいので、ある程度の厚さ以下にする必要が有る。その場合、シール部材よりも硬いゴムを用いないと、フィルタが押え部材とシール部材の間にしっかりと挟持されなくなり、防水性が低下する恐れが有るため、押え部材側の弾性体はシール部材よりも硬度が高い弾性体で形成するのが望ましい。
【０００９】
一方、押え部材を金属やセラミックスで形成した場合には、金属やセラミックスはシール部材よりも遥かに硬度が高いので、押え部材を樹脂や弾性体で形成するよりも薄くする事が出来る。その為、フィルタの通気面上部に形成される凹部に塵などが溜まり難くなるので好ましい。また、金属やセラミックスであれば耐熱性も良好であり、通常の使用環境温度下では硬度が低下しないので、高温でも防水性を維持することが出来る。
【００１０】
押え部材の形状としては、前記シール部材の少なくとも一部を内側に収容する様に、外周縁から一方向に延びる側壁が形成された形状とする事が出来る。この様な形状とする事で、シール部材と押え部材は一体に組付ける事が出来るので、ガスセンサに組付ける前の段階で、フィルタと共に一体に組付けてからセンサに組付ける事が出来る。
【００１１】
なお、押え部材とシール部材の間にフィルタを固定した場合に、両部材が相互に自由に動くような状態でフィルタを挟持していると、両部材に逆方向の力が加わった場合に、フィルタを撚るような力が働いて、フィルタに皺が形成されたり、場合によってはフィルタが切れたりする恐れが有る。
【００１２】
そこで、シール部材と押え部材はフィルタを挟持した状態では、相互に自由に動かない様に一体に係止している事が望ましい。その為、シール部材と押え部材にはそれぞれ第１係合部と第２係合部を設けて、第１係合部と第２係合部が係合して、シール部材と押え部材が一体に係止している構造とすると良い。
【００１３】
特に押え部材はシール部材の上端面に接しているので、上端面に平行な方向での動きを止める事が出来れば、フィルタを変形するような力が掛かる事を防止できる。そこで、シール部材の上端面に凸部を形成し、押え部材にその凸部に係合するような凹部を設け、それら凸部に凹部を係合する構造とすると良い。押え部材に凸部を設け、シール部材に凹部を設けても同じように両者の動きを固定する事が出来る。なお、押え部材の厚みが薄く凹部を形成することが難しい場合には、凹部ではなく係合孔を形成して、凸部を挿通するようにしてもよい。
【００１４】
ところで、ガスセンサの検出素子には通常、外部との電気的接続を図るためにリード線が接続されている。そしてシール部材には、このリード線を挿通しつつ気密状態でシールするための挿通孔が形成されているが、前記の凸部は前記挿通孔を含んだ領域に形成することが望ましい。通常のガスセンサの場合、前記シール部材の上端面は面積が少なく、挿通孔と係止用の凸部を別々に設ける面積は無い。そこで、挿通孔を含む領域全体を凸状に突出させて、凸部の上端面にリード線挿通孔の大気側開口部が形成されるようにすれば、シール部材の上端面を効率的に利用することが出来る。更に、押え部材に前記凸部を挿通する係合孔を設けるようにすれば、係合孔はそれ自体がリード線を挿通する孔となるため合理的である。
【００１５】
なお、フィルタはそれ自体が薄く小さな小片であるため、少しの風でも飛んでしまい、取扱いに注意を要するため、製造工程上それ単体の状態である時間は出来るだけ少ないことが望ましい。その為、シール部材又は押え部材と一体にした状態で、取り扱えるようにしておくことが望ましい。そこで、フィルタに第３係合部を形成し、シール部材又は押え部材に第４係合部を形成しておくと良い。シール部材や押え部材の第４係合部にフィルタの第３係合部を係合させることで、フィルタをシール部材や押え部材などの比較的大きな部材と同時に取り扱うことが出来るので、取扱いが容易になる。それぞれの係合部は第３係合部としてフィルタに係合孔を形成し、第４係合部としてシール部材又は押え部材に凸部を形成し、それぞれを係合する形態が考えられる。この場合、前記第２係合部又は第１係合部を前記第４係合部として利用すると、別途第４係合部を設ける必要が無いので、合理的である。
【００１６】
ところで、フィルタとシール部材或いは押え部材との密着性は重要であるが、シール部材と押え部材の密着性も防水の点から考えて重要である。この防水性を向上させるために、シール部材の上端面と押え部材の下端面の接触部分はテーパ状とする事が望ましい。この接触部分をテーパ状とする事で、係合の形状が僅かにずれているような場合にも、テーパ面のどこかで防水シール面が形成されるので、防水を確実にする事が出来る。
【００１７】
【発明の実施の形態】
以下、本発明の好適な実施例を図面と共に説明する。
［第１実施例］
本実施例は、本発明のガスセンサを酸素センサとして構成したものであり、図１は、当該酸素センサの全体構成を示す断面図である。
【００１８】
同図に示すように、酸素センサ１は、ＺｒＯ₂を主成分とする固体電解質体により先端が閉じた中空軸状に形成された検出素子２、検出素子２内に配置された軸状のセラミックヒータ３、検出素子２を収容するケーシング１０等から構成されている。
【００１９】
ケーシング１０は、酸素センサ１を排気管等の取付部に固定すると共に、セラミックホルダ６，７及びセラミック粉末８を内部に収容し、検出素子２の閉じた先端部を排気管等の内部に突出させる主体金具９と、主体金具９の上部に延設され、上方から検出素子２の内面に大気を導入するための外筒１３とから構成されている。
【００２０】
また、主体金具９の上端部には、内側に延出したフランジ部９ａの先端縁により円形の上部開口部が形成されており、このフランジ部９ａがリング５を介してセラミックホルダ６，７及びセラミック粉末８を上方から固定している。そして、その上部開口部を覆う態様で外筒１３の下端開口端部が嵌合装着されている。
【００２１】
また、外筒１３の上端開口部には、ゴム製の弾性体からなり、軸方向に通気孔１５ａを有する円柱形状のシール部材１５と、シール部材１５の上端面の一部を覆うように配置されたゴム製の押え部材１６が挿入されており、シール部材１５の上端面と押え部材１６の下端面の間に撥水性フィルタ５０を挟持してシールユニット１４を構成している。シール部材１５も押え部材１６も耐熱性を確保するためにフッ素ゴムを用いているが、それぞれの硬度は異なり、シール部材１５の硬度はショア硬さで６０〜８５であり、押え部材１６の硬度は８０〜１００のものを用いる。このシール部材１５にはリード線を挿通する挿通孔が形成されており、検出素子２及びセラミックヒータ３に接続されるリード線が挿通されている。
【００２２】
そして、酸素センサ１における外筒１３の内部に形成される基準ガス空間と大気との酸素の流通は、シールユニット１４の通気経路に配置された撥水性フィルタ５０を介して行われる。更に押え部材１６の外周縁上端部では、外筒１３が折り込まれて、押え部材１６が抜け落ちない様になっている。
【００２３】
以下、シール部材１５の構造及び撥水性フィルタ５０の取付構造等について、図２に基づいて説明する。
図２に示すように、シール部材１５は円柱状であり、円板状の押え部材１６と互いに上下軸方向に突き合わされる。そして、同図（ａ）に示すように、これらシール部材１５と押え部材１６との間にシート状の撥水性フィルタ５０を介挿する態様でシールユニット１４を構成している。
【００２４】
押え部材１６には、図２（ｂ）上段に示すように、円板状の本体の中央を軸方向に貫通して外気を導入する通気孔１６ａと、この通気孔１６ａの周りに等間隔で配置され、上述したリード線２０，２１等を挿通するために同本体を軸方向に貫通する４つの挿通孔１６ｂとが形成されている。
【００２５】
また、シール部材１５は、図２（ｂ）下段に示すように、押え部材１６とほぼ同様の形状を有し、押え部材１６に設けられた通気孔１６ａに対応する位置に通気孔１５ａが、挿通孔１６ｂに対応する位置に挿通孔１５ｂが、それぞれ軸方向に貫通して形成されている。このシール部材１５の軸方向の長さは、押え部材１６のそれよりも長く形成されている。
【００２６】
尚、上記通気孔１６ａと通気孔１５ａが上述したシールユニット１４の通気経路を構成する。
撥水性フィルタ５０は、図２（ｂ）中段及び図２（ｃ）に示すように、押え部材１６及びシール部材１５の外径にほぼ等しい外径を有する円形のシート状に形成され、上記挿通孔１６ｂ及び挿通孔１５ｂに対応する位置に、挿通孔５０ａがそれぞれ形成されている。
【００２７】
この撥水性フィルタ５０は、例えばポリテトラフルオロエチレン（ＰＴＦＥ）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（例えば、商品名：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、かつ気体（空気、水蒸気等）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。また、さらに撥油コートした多孔質繊維構造体（商品名：オレオベントフィルタ（ジャパンゴアテックス（株））を用いることもできる。これを用いることにより、付着した油分が気化して内部に侵入する危険性を低下させることができる。
【００２８】
そして、シールユニット１４の組付けは、図２（ｂ）に示すように、押え部材１６、撥水性フィルタ５０、シール部材１５を、それぞれに設けられた対応する各挿通孔を突き合わせる態様で接着することにより行われる。このとき、撥水性フィルタ５０は、通気孔１６ａと通気孔１５ａとの間を通気可能に閉塞する。
【００２９】
そして、このように形成されたシールユニット１４が外筒１３の開口端部４７の内側に配置され、撥水性フィルタ５０よりも僅かに下方の位置で、外筒１３を介して径方向に加締められ、それにより外筒１３及びシール部材１５が密着し、そのシール性がより確実なものとされる。
【００３０】
上記実施例では、シール部材１５と押え部材１６の間にシート状の撥水性フィルタ５０を挟持する態様で固定するので、撥水性フィルタ５０をシール部材１５に固定する際に撥水性フィルタ５０が引っ張られることが無く、防水性を維持することが出来る。
［第２実施例］
上記第１実施例では、シール部材１５及び押え部材１６の各々の平坦な端面を対向させ、その間に撥水性フィルタ５０を配設する態様とした。しかし、この態様では、上記加締め工程においてその加締め力によるシール部材１５及び押え部材１６の軸方向の膨張によりこれらの間に抗力が生じ、場合によっては、外筒１３の開口部４７側に配置された押え部材１６が、開口部４７から脱落してしまうことが懸念される。
【００３１】
この問題を回避する為に、第１実施例では、外筒の上端部を内側に少し折り曲げることで押え部材１６の抜けを防止していた。
第２の実施例では、この様な問題を従前に回避するシールユニットの構成を示す。
【００３２】
図３（ａ）は、本実施例に係るシールユニット２１４の平面図、同図（ｂ）は、その断面Ａ−Ａに相当する部分断面図、そして、同図（ｃ）は、シールユニット２１４の組み付け工程の説明図である。尚、酸素センサの全体構成は第１実施例と同様であるため、その説明については省略する。
【００３３】
図３に示すように、押え部材２１６は、有底円筒状であり、これに内挿される円柱状のシール部材２１５との間に第１実施例と同様にシート状の撥水性フィルタ２５０を介挿してシールユニット２１４を構成している。
押え部材２１６は、図３（ｃ）上段に示すように、その上端面中央に、後述するシール部材２１５の突出部２１５ｃを嵌合させるための係止孔２１６ａが形成されている。また、この係止孔２１６ａの周りには、後述するシール部材２１５の４つの突出部２１５ｄを嵌合させるための４つの係止孔２１６ｂが、等間隔で配置される態様で形成されている。そして、上端面の周端縁からは、下方に延びる側壁が円筒状に形成されている。
【００３４】
一方、シール部材２１５は、同図下段に示すように、その外径が押え部材２１６の側壁の内径にほぼ等しく、その軸方向の長さが押え部材２１６の軸方向の長さにほぼ等しくなるように形成されている。そして、その円柱状の本体の中央を軸方向に貫通して外気を導入する通気孔２１５ａと、この通気孔２１５ａの周りに等間隔で配置され、上述したリード線２０，２１等を挿通するために同本体を軸方向に貫通する４つの挿通孔２１５ｂとが形成されている。そして、その上端面には、通気孔２１５ａの周りに同軸状に突設された筒状の突出部２１５ｃ、及び、各々の挿通孔２１５ｂの周りに同軸状に突設された筒状の突出部２１５ｄがそれぞれ形成されている。
【００３５】
そして、これらシール部材２１５、押え部材２１６、及び撥水性フィルタ２５０との組付けは、まず、撥水性フィルタ２５０に設けられ、挿通孔を兼ねた４つの係止孔２５０ａを、対応するシール部材２１５の４つの突出部２１５ｄの周りにはめ込む。この時点において、撥水性フィルタ２５０は、シール部材２１５の中央の突出部２１５ｃの位置で僅かに浮き上がった状態となっている。
【００３６】
そして、この状態からシール部材２１５を押え部材２１６に内挿嵌合させる。このとき、撥水性フィルタ２５０がシール部材２１５と押え部材２１６とにより挟持される態様で固定される。この際、撥水性フィルタ２５０は中央の係止孔２１６ａと突出部２１５ｃとの界面で引っ張られるが、突出部２１５ｃの長さ（高さ）が小さいため、撥水性フィルタ２５０の耐水圧にはほとんど影響がない。
【００３７】
本実施例の構成によれば、押え部材２１６にシール部材２１５が内挿されるので、接着剤を用いなくても全体を一体のシールユニット２１４として取り扱うことが出来る。このため、組付け時に取扱いが容易なる。また、シールユニット２１４を外筒１３を加締めて固定する場合に、押え部材２１６の側壁がシール部材２１５と外筒１３との間に挟持されるので、押え部材２１６が抜け落ちることを防止できる。また、加締め力によりシール部材２１５が垂直方向に膨らむことで、シール部材２１５の上端面と押え部材２１６の下端面との間の押圧力が増えるので、撥水性フィルタ２５０近傍のシール性が向上する。
【００３８】
また、本実施例では、検出素子２の電極に接続されたリード線２０，２１等を挿通するための複数の挿通孔２１５ｂを、シール部材２１５側に集中して設ける態様をとった。このため、上記第１実施例のように、これら複数の挿通孔を押え部材２１６及びシール部材２１５の双方にそれぞれ設けた場合のように、これら挿通孔の突き合わせの精度を考慮する必要もない。
【００３９】
さらに、撥水性フィルタ２５０の組み付けに際し、撥水性フィルタ２５０側に設けられた係止孔２５０ａをシール部材２１５側の複数の突出部２１５ｄに係合させる態様をとっている。このため、加締め工程時においても撥水性フィルタ２５０がシール部材２１５と押え部材２１６との界面においてずれる等の心配はなく、そのシール性を保持することができる。
【００４０】
なお、押え部材２１６は、金属でも良い。特に第２実施例のように、押え部材２１６の厚さを薄くする場合には、材質を金属とする事が望ましい。この場合、外筒１３からの加締めは押え部材２１６の側壁ごと加締めてもよいが、外筒１３と押え部材２１６の側壁の間の防水性は加締めによるシールだけが頼りとなるので、若干防水性が低下する恐れが有る。
【００４１】
そこで、図４（ａ）に示すようにシール部材２１５の下端（一点鎖線部）を拡径してシール部材２１５と外筒１３の間でも防水のシール面を形成する様にすると良い。
更に、図４（ｂ）の様に、押え部材２１６の側壁の下端部からシール部材２１５の下端の拡径部に亘って外筒１３を加締めることで、更に確実にシール性を確保することが出来る（一点鎖線部参照）。
【００４２】
なお、押え部材２１６を殆ど変形しない硬質の樹脂又はセラミックスで形成した場合には、外筒１３と同時に側壁を加締める事が出来ないので、その場合には、図４（ｃ）の様にシール部材２１５の拡径部において、外筒１３を加締めるようにする（一点鎖線部参照）。但し、この場合には、押え部材２１６がシール部材２１５に強固に固定されないと抜け落ちる恐れが有るので、外筒１３の上端部（点線部）を内側に折り曲げて押え部材２１６が抜け落ちない様にすることが望ましい。
【００４３】
以上、本発明の実施例について説明したが、本発明の実施の形態は、上記実施例に何ら限定されることなく、本発明の技術的範囲に属する限り種々の形態をとり得ることはいうまでもない。
例えば、上記第２実施例の構成において、押え部材２１６、撥水性フィルタ２５０、及びシール部材２１５の密着性をより確実なものとするために、図５に示すような構成を採用することもできる。
【００４４】
すなわち、図５に示す構成では、押え部材３１６とシール部材３１５の上下軸方向に互いに直接又はフィルタを介して当接する接触面３１６ａ，３１５ａを、テーパ形状に形成している。
このように、両シール部材３１６，３１５の接触面をテーパ状に形成することで、押え部材３１６及びシール部材３１５による撥水性フィルタ３５０への押しつけ面積を増加させることができ、それにより、撥水性フィルタ３５０のより堅固な組付けを図ることができる。
【図面の簡単な説明】
【図１】本発明の実施例に係る酸素センサの全体構成を示す断面図である。
【図２】本発明の第１実施例に係るシールユニットの構成を示す説明図である。
【図３】本発明の第２実施例に係るシールユニットの構成を示す説明図である。
【図４】第２実施例の変形例に係るシールユニットの構成を示す部分断面図である。
【図５】第２実施例の変形例に係るシールユニットの構成を示す部分断面図である。
【符号の説明】
１・・・酸素センサ、２・・・検出素子、９・・・主体金具、
１３・・・外筒、１４，２１４・・・シールユニット、
１５，２１５，３１５・・・シール部材、
１６，２１６，３１６・・・押え部材、１５ａ，１６ａ・・・通気孔、
１５ｂ，１６ｂ・・・挿通孔、２０，２１・・・リード線、
５０，２５０，３５０・・・撥水性フィルタ、
５０ａ，２５０ａ・・・挿通孔、２１５ａ・・・通気孔、
２１５ｂ・・・挿通孔、２１５ｃ・・・突出部、２１５ｄ・・・突出部、
２１６ａ・・・係止孔、２１６ｂ・・・係止孔、
３１５ａ，３１６ａ・・・接触面[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas sensor that is attached to a pipe that forms a flow path through which a gas to be measured such as exhaust gas flows, and functions by introducing atmospheric air as a reference gas from the outside.
[0002]
[Prior art]
Conventionally, various sensors such as an HC sensor and a NOx sensor are known as gas sensors for detecting the concentration of a specific gas component from a mixed gas.
As one of this type of gas sensor, for example, there is an outside air introduction type oxygen sensor disclosed in Japanese Patent Laid-Open No. 9-54063. In this oxygen sensor, a vent hole for introducing outside air is formed so as to penetrate the center of a seal member provided at the uppermost portion of the gas sensor in the axial direction, and the vent hole is closed with a hard water repellent filter. Therefore, it retains its breathability and waterproofness.
[0003]
However, in the configuration in which such a hard filter is arranged over the entire ventilation hole, there is a problem that it is difficult to sufficiently ensure the air permeability because the volume of the filter itself is large.
Therefore, for example, in the technology disclosed in the prior patent application (Japanese Patent Application No. 10-374117), an outer peripheral surface of a cylindrical insertion member that can be inserted into a vent hole and an inner periphery of the vent hole. It is set as the structure fixed in a ventilation hole in the aspect pinched between surfaces, and the air permeability is hold | maintained.
[0004]
[Problems to be solved by the invention]
However, in the above configuration, when the water-repellent filter is covered with the cylindrical insertion member, the water-repellent filter is pulled by a frictional force with the inner surface of the vent hole when the filter is inserted into the vent hole. For this reason, depending on the material of the water-repellent filter, there is a concern that the water-repellent filter is thinned at the time of insertion, the water pressure resistance is lowered, and the waterproof performance is lowered.
[0005]
The present invention has been made in view of these problems, and an object of the present invention is to provide a gas sensor that functions by introducing air from the outside and is excellent in air permeability and waterproofness.
[0006]
[Means for Solving the Problems and Effects of the Invention]
In view of the above problems, in the gas sensor according to claim 1, the rubber grommet, which is a member for sealing the reference gas space of the gas sensor from the atmosphere side, has a ventilation path for introducing oxygen from the atmosphere side to the reference gas space. A side opening is formed so as to open to the upper end surface of the rubber grommet, and a filter is provided so as to close the outer opening, and the filter is placed between the upper end surface of the rubber grommet and its lower end surface. The presser member is arranged so as to be clamped .
[0007]
Since the filter is sandwiched between the sealing member and the holding member as described above, even if a sheet-like filter is used, it can be used as it is in a flat shape, so that it is partially pulled and waterproof. There is no decline in performance.
As the pressing member, any material can be used. For example, a resin such as Teflon, a rubber material such as fluorine rubber, or a metal or ceramic may be used.
[0008]
Note that the use of resin has the advantage that the pressing member can be easily processed and can be made inexpensive. Furthermore, when an elastic material such as rubber is used among the resins, there is an advantage that there is no fear of damaging the seal member. However, since it is necessary to have waterproofness at the interface that contacts the filter, a certain degree of hardness is required. In particular, if the thickness of the holding member is too thick, dust or the like tends to accumulate in the recess formed in the upper part of the ventilation surface of the filter, so it is necessary to make the thickness below a certain level. In that case, when not used harder rubber than the sealing member, the filter is no longer firmly held between the pressing member and the seal member, since the possibility that waterproof is lowered there, the elastic body of the pressing member side from the sealing member Also, it is desirable to form an elastic body having high hardness.
[0009]
On the other hand, when the pressing member is formed of metal or ceramic, the metal or ceramic is much harder than the sealing member, and therefore, the pressing member can be made thinner than that formed of resin or elastic body. Therefore, it is preferable because dust or the like hardly accumulates in the recess formed in the upper part of the ventilation surface of the filter. Moreover, if it is a metal and ceramics, heat resistance is also favorable, and since hardness does not fall under normal use environmental temperature, waterproofness can be maintained even at high temperature.
[0010]
The shape of the pressing member can be a shape in which a side wall extending in one direction from the outer peripheral edge is formed so that at least a part of the sealing member is accommodated inside. By adopting such a shape, the seal member and the presser member can be assembled together, so that they can be assembled together with the filter and then assembled to the sensor at a stage before being assembled to the gas sensor.
[0011]
In addition, when the filter is fixed between the holding member and the seal member, when the filter is sandwiched in a state in which both members move freely with respect to each other, when a reverse force is applied to both members, A force that twists the filter works, and there is a risk that wrinkles may be formed on the filter or the filter may be cut off in some cases.
[0012]
Therefore, it is desirable that the seal member and the presser member are integrally locked so as not to move freely in a state where the filter is sandwiched . Therefore, the seal member and the presser member are provided with the first engagement portion and the second engagement portion, respectively, and the first engagement portion and the second engagement portion are engaged, so that the seal member and the presser member are integrated. It is preferable to have a structure that is locked to.
[0013]
In particular, since the pressing member is in contact with the upper end surface of the seal member, if the movement in the direction parallel to the upper end surface can be stopped, it is possible to prevent a force that deforms the filter from being applied. Therefore, it is preferable that a convex portion is formed on the upper end surface of the seal member, a concave portion that engages with the convex portion is provided on the holding member, and the concave portion is engaged with the convex portion. Even if the pressing member is provided with a convex portion and the sealing member is provided with a concave portion, the movement of both can be fixed in the same manner. In addition, when the thickness of the pressing member is thin and it is difficult to form the concave portion, an engaging hole may be formed instead of the concave portion, and the convex portion may be inserted.
[0014]
Incidentally, a lead wire is usually connected to the detection element of the gas sensor for electrical connection with the outside. The seal member is formed with an insertion hole for sealing in an airtight state while inserting the lead wire, and the convex portion is preferably formed in a region including the insertion hole. In the case of a normal gas sensor, the upper end surface of the seal member has a small area, and there is no area for separately providing the insertion hole and the locking projection. Therefore, by projecting the entire region including the insertion hole in a convex shape so that the atmosphere side opening of the lead wire insertion hole is formed on the upper end surface of the projection, the upper end surface of the seal member is efficiently used. I can do it. Furthermore, if an engagement hole for inserting the convex portion is provided in the holding member, the engagement hole itself is a hole for inserting the lead wire, which is reasonable.
[0015]
Since the filter itself is a thin and small piece, it can fly even with a small amount of wind, and care must be taken in handling. Therefore, it is desirable that the time in a single state in the manufacturing process be as short as possible. For this reason, it is desirable that the seal member or the pressing member can be handled in an integrated state. Therefore, it is preferable to form a third engagement portion on the filter and form a fourth engagement portion on the seal member or the pressing member. By engaging the third engagement portion of the filter with the fourth engagement portion of the seal member or the presser member, the filter can be handled simultaneously with a relatively large member such as the seal member or the presser member. become. Each engaging portion may be formed as an engagement hole in the filter as the third engaging portion, and a convex portion may be formed in the seal member or the pressing member as the fourth engaging portion, and the respective engaging portions may be engaged. In this case, if the second engaging portion or the first engaging portion is used as the fourth engaging portion, there is no need to separately provide a fourth engaging portion, which is reasonable.
[0016]
Incidentally, the adhesion between the filter and the seal member or the pressing member is important, but the adhesion between the sealing member and the pressing member is also important from the viewpoint of waterproofing. In order to improve this waterproof property, it is desirable that the contact portion between the upper end surface of the seal member and the lower end surface of the pressing member be tapered. By making this contact portion tapered, even when the engagement shape is slightly shifted, a waterproof seal surface is formed somewhere on the tapered surface, so that waterproofing can be ensured. .
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below with reference to the drawings.
[First embodiment]
In this embodiment, the gas sensor of the present invention is configured as an oxygen sensor, and FIG. 1 is a cross-sectional view showing the overall configuration of the oxygen sensor.
[0018]
As shown in the figure, the oxygen sensor 1 includes a detection element 2 formed in a hollow shaft shape whose end is closed by a solid electrolyte body mainly composed of ZrO ₂ , and a shaft-shaped ceramic disposed in the detection element 2. The heater 3 and the casing 10 that accommodates the detection element 2 are configured.
[0019]
The casing 10 fixes the oxygen sensor 1 to an attachment portion such as an exhaust pipe, accommodates the ceramic holders 6 and 7 and the ceramic powder 8 therein, and projects the closed end of the detection element 2 into the exhaust pipe or the like. The metal shell 9 is made to extend, and the outer tube 13 is provided on the upper surface of the metal shell 9 to introduce the air into the inner surface of the detection element 2 from above.
[0020]
A circular upper opening is formed at the upper end of the metal shell 9 by the leading edge of the flange portion 9 a extending inward. The flange portion 9 a is connected to the ceramic holders 6, 7 and the ring 5 via the ring 5. The ceramic powder 8 is fixed from above. And the lower end opening edge part of the outer cylinder 13 is fittingly mounted in the aspect which covers the upper opening part.
[0021]
Also, the upper end opening of the outer cylinder 13 is made of a rubber elastic body and is arranged so as to cover a cylindrical seal member 15 having a vent hole 15a in the axial direction and a part of the upper end surface of the seal member 15. A rubber pressing member 16 is inserted, and a water repellent filter 50 is sandwiched between the upper end surface of the sealing member 15 and the lower end surface of the pressing member 16 to constitute the sealing unit 14. Both the sealing member 15 and the pressing member 16 use fluororubber to ensure heat resistance, but the hardness of each is different, and the hardness of the sealing member 15 is 60 to 85 in Shore hardness, and the hardness of the pressing member 16 80 to 100 are used. The seal member 15 is formed with an insertion hole through which a lead wire is inserted, and a lead wire connected to the detection element 2 and the ceramic heater 3 is inserted therethrough.
[0022]
Then, oxygen flows between the reference gas space formed in the outer cylinder 13 of the oxygen sensor 1 and the atmosphere through the water repellent filter 50 disposed in the ventilation path of the seal unit 14. Further, the outer cylinder 13 is folded at the upper end of the outer peripheral edge of the presser member 16 so that the presser member 16 does not fall off.
[0023]
Hereinafter, the structure of the seal member 15 and the mounting structure of the water repellent filter 50 will be described with reference to FIG.
As shown in FIG. 2, the seal member 15 has a columnar shape and abuts against the disc-shaped presser member 16 in the vertical axis direction. As shown in FIG. 5A, the seal unit 14 is configured in such a manner that a sheet-like water-repellent filter 50 is interposed between the seal member 15 and the pressing member 16.
[0024]
As shown in the upper part of FIG. 2 (b), the holding member 16 has a vent hole 16a that passes through the center of the disk-shaped main body in the axial direction and introduces outside air, and is equidistant around the vent hole 16a. Four insertion holes 16b that are arranged and penetrate the main body in the axial direction are formed in order to insert the above-described lead wires 20, 21 and the like.
[0025]
The seal member 15, as shown in FIG. 2 (b) lower, has almost the same shape as the pressing member 16, the vent holes 15a at positions corresponding to the vent hole 16a provided in the pressing member 16 is, Insertion holes 15b are respectively formed in the positions corresponding to the insertion holes 16b so as to penetrate in the axial direction. The axial length of the seal member 15 is longer than that of the pressing member 16.
[0026]
The vent hole 16a and the vent hole 15a constitute the vent path of the seal unit 14 described above.
The water-repellent filter 50 is formed in a circular sheet shape having outer diameters substantially equal to the outer diameters of the pressing member 16 and the seal member 15 as shown in the middle part of FIG. 2B and FIG. Insertion holes 50a are respectively formed at positions corresponding to the holes 16b and the insertion holes 15b.
[0027]
The water-repellent filter 50 is made of, for example, a porous fiber structure (for example, a polytetrafluoroethylene (PTFE) green body) that is obtained by stretching in a uniaxial direction at a heating temperature lower than the melting point of PTFE. , Product name: Gore-Tex (Japan Gore-Tex Co., Ltd.) is configured as a water-repellent filter that prevents the permeation of water, such as water droplets, and allows the permeation of gas (air, water vapor, etc.) Has been. Further, a porous fiber structure (trade name: Oleovent filter (Japan Gore-Tex Co., Ltd.)) further coated with an oil repellent can be used. Risk can be reduced.
[0028]
As shown in FIG. 2B, the seal unit 14 is assembled by adhering the presser member 16, the water repellent filter 50, and the seal member 15 in such a manner as to abut each corresponding insertion hole provided therein. Is done. At this time, the water repellent filter 50 closes between the vent hole 16a and the vent hole 15a so as to allow ventilation.
[0029]
The seal unit 14 thus formed is arranged inside the opening end 47 of the outer cylinder 13 and is caulked in the radial direction via the outer cylinder 13 at a position slightly below the water-repellent filter 50. As a result, the outer cylinder 13 and the seal member 15 are brought into close contact with each other, and the sealing performance is further ensured.
[0030]
In the above embodiment, since the fixing in a manner sandwiching the sheet-shaped water-repellent filter 50 between the seal member 15 and the pressing member 16, the water repellant filter 50 when fixing the water-repellent filter 50 to the seal member 15 pulling It can be kept waterproof.
[Second Embodiment]
In the first embodiment, the flat end surfaces of the seal member 15 and the pressing member 16 are opposed to each other, and the water-repellent filter 50 is disposed therebetween. However, in this aspect, a drag force is generated between the sealing member 15 and the presser member 16 in the axial direction due to the caulking force in the caulking step, and depending on the case, on the opening 47 side of the outer cylinder 13. There is a concern that the arranged presser member 16 may fall out of the opening 47.
[0031]
In order to avoid this problem, in the first embodiment, the presser member 16 is prevented from coming off by slightly bending the upper end portion of the outer cylinder inward.
The second embodiment shows a configuration of a seal unit that avoids such a problem in the past.
[0032]
3A is a plan view of the seal unit 214 according to the present embodiment, FIG. 3B is a partial cross-sectional view corresponding to the cross section AA, and FIG. 3C is the seal unit 214. It is explanatory drawing of this assembly | attachment process. The overall configuration of the oxygen sensor is the same as that of the first embodiment, and a description thereof will be omitted.
[0033]
As shown in FIG. 3, the presser member 216 has a bottomed cylindrical shape, and a sheet-like water repellent filter 250 is interposed between the presser member 216 and a columnar seal member 215 inserted therein. The seal unit 214 is configured by being inserted.
As shown in the upper part of FIG. 3 (c), the holding member 216 is formed with a locking hole 216a for fitting a protruding portion 215c of a seal member 215 described later at the center of the upper end surface. Further, around the locking hole 216a, four locking holes 216b for fitting four projecting portions 215d of a seal member 215 described later are formed in a manner arranged at equal intervals. And from the peripheral edge of an upper end surface, the side wall extended below is formed in the cylindrical shape.
[0034]
On the other hand, the outer diameter of the seal member 215 is substantially equal to the inner diameter of the side wall of the presser member 216, and the axial length thereof is substantially equal to the axial length of the presser member 216, as shown in the lower part of FIG. It is formed as follows. Then, a vent hole 215a that penetrates the center of the cylindrical main body in the axial direction and introduces outside air is disposed at equal intervals around the vent hole 215a, and the lead wires 20, 21 and the like described above are inserted therethrough. Are formed with four insertion holes 215b penetrating the main body in the axial direction. Further, on the upper end surface, a cylindrical projection 215c that is coaxially projected around the vent hole 215a, and a cylindrical projection that is coaxially projected around each insertion hole 215b. 215d is formed respectively.
[0035]
Then, the seal member 215, the pressing member 216, and the water repellent filter 250 are assembled with the four locking holes 250a provided in the water repellent filter 250, which also serve as insertion holes, and the corresponding seal members 215. Are fitted around the four protrusions 215d. At this point, the water-repellent filter 250 is slightly lifted at the position of the central protrusion 215c of the seal member 215.
[0036]
Then, from this state, the seal member 215 is inserted and fitted into the presser member 216. At this time, the water repellent filter 250 is fixed in such a manner that it is sandwiched between the seal member 215 and the pressing member 216. At this time, the water repellent filter 250 is pulled at the interface between the central locking hole 216a and the protruding portion 215c. However, since the length (height) of the protruding portion 215c is small, the water repellent filter 250 has almost no water pressure resistance. There is no effect.
[0037]
According to the configuration of the present embodiment, since the seal member 215 is inserted into the presser member 216, the whole can be handled as the integrated seal unit 214 without using an adhesive. For this reason, handling becomes easy at the time of assembly. Further, when the seal unit 214 is fixed by crimping the outer cylinder 13, the side wall of the pressing member 216 is sandwiched between the sealing member 215 and the outer cylinder 13, so that the pressing member 216 can be prevented from falling off. Further, since the sealing member 215 swells in the vertical direction due to the caulking force, the pressing force between the upper end surface of the sealing member 215 and the lower end surface of the pressing member 216 increases, so that the sealing performance in the vicinity of the water repellent filter 250 is improved. To do.
[0038]
In the present embodiment, a plurality of insertion holes 215 b for inserting the lead wires 20, 21 etc. connected to the electrodes of the detection element 2 are concentrated on the seal member 215 side. For this reason, it is not necessary to consider the accuracy of butting of these insertion holes as in the case of providing the plurality of insertion holes in both the pressing member 216 and the seal member 215 as in the first embodiment.
[0039]
Further, when the water repellent filter 250 is assembled, the locking holes 250a provided on the water repellent filter 250 side are engaged with the plurality of protrusions 215d on the seal member 215 side. For this reason, there is no fear that the water-repellent filter 250 is displaced at the interface between the sealing member 215 and the pressing member 216 even during the caulking step, and the sealing performance can be maintained.
[0040]
The pressing member 216 may be a metal. In particular, when the thickness of the presser member 216 is reduced as in the second embodiment, the material is preferably a metal. In this case, the caulking from the outer cylinder 13 may be caulked together with the side wall of the presser member 216, but the waterproofness between the outer cylinder 13 and the side wall of the presser member 216 depends only on the seal by caulking. There is a risk that the waterproofness is slightly lowered.
[0041]
Therefore, as shown in FIG. 4A, the lower end (one-dot chain line portion) of the seal member 215 may be enlarged to form a waterproof seal surface between the seal member 215 and the outer cylinder 13.
Further, as shown in FIG. 4B, the outer cylinder 13 is crimped from the lower end portion of the side wall of the pressing member 216 to the enlarged diameter portion of the lower end of the sealing member 215, thereby further ensuring the sealing performance. (Refer to the alternate long and short dash line).
[0042]
If the presser member 216 is formed of a hard resin or ceramic that hardly deforms, the side wall cannot be crimped simultaneously with the outer cylinder 13, and in that case, a seal as shown in FIG. The outer cylinder 13 is caulked in the enlarged diameter portion of the member 215 (see the chain line portion). However, in this case, there is a possibility that the presser member 216 will come off unless it is firmly fixed to the seal member 215. Therefore, the upper end portion (dotted line portion) of the outer cylinder 13 is bent inward so that the presser member 216 does not fall off. It is desirable.
[0043]
As mentioned above, although the Example of this invention was described, it cannot be overemphasized that embodiment of this invention can take various forms, as long as it belongs to the technical scope of this invention, without being limited to the said Example at all. Nor.
For example, in the configuration of the second embodiment, a configuration as shown in FIG. 5 can be adopted in order to make the adhesion of the pressing member 216, the water repellent filter 250, and the seal member 215 more reliable. .
[0044]
That is, in the configuration shown in FIG. 5, the contact surfaces 316a and 315a that are in contact with each other in the vertical axis direction of the pressing member 316 and the seal member 315 directly or through the filter are formed in a tapered shape.
Thus, by forming the contact surfaces of both seal members 316 and 315 in a tapered shape, the pressing area of the pressing member 316 and the sealing member 315 against the water-repellent filter 350 can be increased, and thereby the water-repellent property is increased. The filter 350 can be more firmly assembled.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an overall configuration of an oxygen sensor according to an embodiment of the present invention.
FIG. 2 is an explanatory view showing a configuration of a seal unit according to the first embodiment of the present invention.
FIG. 3 is an explanatory view showing a configuration of a seal unit according to a second embodiment of the present invention.
FIG. 4 is a partial cross-sectional view showing a configuration of a seal unit according to a modification of the second embodiment.
FIG. 5 is a partial cross-sectional view showing a configuration of a seal unit according to a modification of the second embodiment.
[Explanation of symbols]
1 ... oxygen sensor, 2 ... sensing element, 9 ... metal shell,
13 ... outer cylinder 14, 214 ... seal unit,
15, 215, 315... Sealing member,
16, 216, 316 ... holding member, 15a, 16a ... vent hole,
15b, 16b ... insertion hole, 20, 21 ... lead wire,
50, 250, 350 ... water-repellent filter,
50a, 250a ... insertion hole, 215a ... vent hole,
215b ... insertion hole, 215c ... projection, 215d ... projection,
216a ... locking hole, 216b ... locking hole,
315a, 316a ... contact surface

Claims

A sensing element ;
A metal shell for holding the detection element;
An outer cylinder forming a reference gas space isolated from the atmosphere on the upper end side of the detection element;
A sealing member made of an elastic body that forms the reference gas space together with the outer cylinder;
A gas sensor comprising:
At least one ventilation path is formed in the sealing member,
The atmosphere side opening of the ventilation path is open to the upper end surface of the seal member,
A filter is provided so as to cover the atmosphere side opening,
The filter is sandwiched between the seal member and a pressing member provided to cover at least part of the upper end surface of the filter;
A gas sensor.

The pressing member is made of resin;
The gas sensor according to claim 1.

The pressing member is formed of an elastic body;
The gas sensor according to claim 1.

The pressing member is made of rubber;
The gas sensor according to claim 3.

The presser member has a higher hardness than the seal member;
The gas sensor according to claim 3.

The pressing member is made of metal;
The gas sensor according to claim 1.

The pressing member is made of ceramics;
The gas sensor according to claim 1.

The pressing member is formed with a side wall extending in one direction from the outer peripheral edge so as to accommodate at least a part of the sealing member inside,
A gas sensor according to any one of claims 1 to 7.

The seal member has a first engagement portion,
The pressing member has a second engaging portion,
The first engaging portion and the second engaging portion are engaged, and the presser member is locked to the seal member;
A gas sensor according to any one of claims 1 to 8.

The first engaging portion is a convex portion formed on the upper end surface of the seal member,
The second engaging portion is a concave portion that engages with the convex portion formed on the pressing member;
The gas sensor according to claim 9.

The first engaging portion is a convex portion formed on the upper end surface of the seal member,
The second engaging portion is an engaging hole for inserting the convex portion formed in the pressing member;
The gas sensor according to claim 9.

A lead wire is connected to the detection element,
The seal member has an insertion hole through which the lead wire is inserted,
The protrusion is formed in a region including the insertion hole;
The gas sensor according to claim 10 or 11, wherein:

The filter has a third engagement portion,
The seal member or the pressing member has a fourth engaging portion,
The third engaging portion and the fourth engaging portion are engaged, and the filter is locked to the seal member or the presser member;
The gas sensor according to claim 1, wherein:

The third engagement portion is an engagement hole provided in the filter,
The fourth engaging portion is a convex portion formed on the seal member or the pressing member;
The gas sensor according to claim 13.

The fourth engaging portion is the first engaging portion or the second engaging portion;
The gas sensor according to claim 13 or 14, characterized in that:

Each of the upper end surface of the seal member and the lower end surface of the presser member is formed in a tapered shape,
The gas sensor according to any one of claims 8 to 15, wherein: