JP4170740B2

JP4170740B2 - Temperature sensor manufacturing method and temperature sensor

Info

Publication number: JP4170740B2
Application number: JP2002341430A
Authority: JP
Inventors: 剛半沢; 雅彦西; 雅樹岩谷; 孝昭長曽我部
Original assignee: NGK Spark Plug Co Ltd
Current assignee: Niterra Co Ltd
Priority date: 2002-11-25
Filing date: 2002-11-25
Publication date: 2008-10-22
Anticipated expiration: 2022-11-25
Also published as: JP2004177181A

Description

【０００１】
【発明の属する技術分野】
本発明は、金属酸化物などの半導体からなるサーミスタや金属抵抗体等を感温素子として備える温度センサに関する。更に詳しくは、自動車の排気ガス浄化装置の触媒コンバータ内部や排気管内等といった被測定流体（例えば、排気ガス）が流通する流通路内に素子を配置し、被測定流体の温度検出を行う温度センサに関する。
【０００２】
【従来の技術】
従来より、感温素子であるサーミスタ素子を収納し、軸線方向に延びる金属チューブ（金属ケース）と、該金属チューブを挿入するための貫通孔（貫通穴）を有し、金属チューブの外周面を取り囲むように配置されたフランジ（取付ナット）とを備え、該フランジが金属チューブに圧入固定されるとともに、溶接される構造の温度センサが知られている（例えば、特許文献１参照）。このような温度センサは、排気ガス流通路内を流れる排気ガスの温度を感温素子によって検出するための排気温センサとして用いられている。
【０００３】
【特許文献１】
特開平５−３４０８２２号公報
【０００４】
【発明が解決しようとする課題】
温度センサでは、薄肉部材である金属チューブと厚肉部材であるフランジとを圧入により固定する。しかし、従来の温度センサでは、金属チューブ略全体の外径とフランジの貫通孔の内径とが略同一であるため、圧入長さ（金属チューブ外周面とフランジ貫通孔内周面との当接部であって、軸線方向における長さ）が長い。そのため、金属チューブにフランジを圧入する際に、金属チューブが座屈する等の問題があった。
【０００５】
本発明は、上述した従来の問題点を解決するものであり、金属チューブにフランジを圧入する際に、金属チューブの変形を防止することができる温度センサの製造方法及び温度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】
上記課題を解決するためになされた本発明の温度センサの製造方法は、先端側が閉塞した軸線方向に延びる筒状の金属チューブと、金属チューブの内部に収納され、温度によって電気的特性が変化する素子と、金属チューブを挿入するための貫通孔を有し、金属チューブの外周面を取り囲むように配置されたフランジと、を備える温度センサの製造方法において、外径が貫通孔の最小内径よりも大径の金属チューブ後端部と、金属チューブ後端部の先端側に位置し、貫通孔の最小内径よりも小径の金属チューブ本体部と、を有した金属チューブを、該金属チューブの先端側からフランジを挿入し、貫通孔全体にわたって金属チューブが配置された後、金属チューブ本体部の外周面と貫通孔の内周面との間に空間が形成されるように、金属チューブ後端部にフランジを圧入固定することを特徴とする。
【０００７】
本発明の温度センサの製造方法では、金属チューブをフランジの貫通孔の最小内径よりも小径の金属チューブ本体部側からフランジに挿入して、金属チューブ後端部とフランジとを圧入固定している。従って、フランジに金属チューブを挿入し易い。また、金属チューブにフランジを圧入する際に、金属チューブのうち実際に圧入に寄与する部分は、フランジの貫通孔の最小内径よりも大径である金属チューブ後端部のみである。これにより、圧入長さを短くすることができ、座屈等の金属チューブの変形を抑えることができる。更に、圧入長さが短いことから、従来よりも圧入荷重を低減することができ、金属チューブの変形を更に抑えることができる。
【０００８】
また、本発明の温度センサの製造方法では、フランジの貫通孔は、内径が略一定の先端側貫通孔と、先端側貫通孔の後端側に位置し、後端側ほど内径が大きい形状の後端側貫通孔と、からなり、後端側貫通孔側から金属チューブ後端部を圧入することを特徴とする。
【０００９】
本発明の温度センサの製造方法では、後端側ほど内径が大きい形状を有した後端側貫通孔側から金属チューブ後端部を圧入している。従って、圧入荷重を低減することができ、金属チューブの変形を更に抑えることができる。ここで、後端側貫通孔の形状は、圧入のし易さを考慮すると、テーパ形状やアール形状であることが好ましい。また、後端側貫通孔の最大内径は、金属チューブ後端部の外径よりも大きいことが好ましい。
【００１０】
また、本発明の温度センサの製造方法では、軸線方向において、金属チューブ後端部と先端側貫通孔との圧入長さ（金属チューブ後端部の外周面と先端側貫通孔の内周面との当接面であって、軸線方向における長さ）は、先端側貫通孔の長さよりも小さい。これにより、圧入長さが短くなり、圧入荷重を更に低減することができる。
【００１１】
また、本発明の温度センサの製造方法では、フランジは、軸線方向に延びる鞘部と、鞘部の先端側に位置し、径方向外側に向かって突出する突出部と、を有し、金属チューブ後端部は鞘部に圧入固定される。
【００１２】
温度センサでは、フランジと金属チューブ後端部とが圧入された圧入部を介して、フランジに熱が伝導する熱引きの問題がある。この熱引きが顕著になると、応答性の悪化、温度測定精度の低下を招くことになる。本発明の製造方法により得られる温度センサでは、フランジと金属チューブ後端部とが圧入固定により一体とされるが、この圧入固定は、フランジのうちで排気ガス通路等の被測定流体が流通する流通路内に臨む部分（具体的には突出部の先端側）ではなく、突出部の後端側に位置する鞘部において行われるものである。これにより、温度センサを被測定流体が流通する流通管に装着したときに、フランジと金属チューブ後端部との圧入部が流通路内に配置されることがない。換言すれば、フランジと金属チューブ後端部との圧入部が、排気ガス等の被測定流体に晒されない位置に設けられる。その結果、流通路内において、感熱部（温度センサであって、自動車の排気管内等に配置されるサーミスタ側の部位）から圧入部を介してフランジに至る伝熱経路が形成されることはなく、感熱部からフランジ等への熱引きの度合いを従来に比して抑えられ、センサ自身の応答性の向上、温度測定精度の低下防止の効果が得られる。
【００１３】
また、本発明の温度センサの製造方法では、金属チューブ後端部は、鞘部であって先端側貫通孔が形成されている領域に、周方向にわたって溶接される。
【００１４】
温度センサを自動車の排気ガス温度を検出するために使用した場合、２００〜１０００℃程度の高温環境下での使用に供されるが故に、金属チューブの外面はもとより内面が酸化されて、素子が収納される空間内の酸素濃度が著しく低下し、素子の表面が還元される等の理由で同素子に特性変化が生じることがある。そして、この酸化は特に金属チューブ後端部とフランジとの溶接部分の外面及び内面において生じ易く、この溶接部が流通路内に臨むフランジの先端側に形成される場合は、溶接部自身が高温環境下に直接晒されることになるので、酸化が助長されることになる。これに対し、本発明の製造方法により得られる温度センサでは、金属チューブ後端部とフランジとの溶接を、フランジの内で流通路内に臨む先端側の突出部ではなく、突出部の後端側に位置する鞘部に行っており、溶接部での酸化の発生が抑えられ、耐久性に優れた温度センサとすることができる。更に、金属チューブ自身がフランジの鞘部に溶接される構造であるため、上述したように溶接部が被測定流体に晒されることがなくなり、被測定流体に対する気密の信頼性を向上させることができる。
【００１５】
また、上記課題を解決するためになされた本発明の温度センサは、先端側が閉塞した軸線方向に延びる筒状の金属チューブと、金属チューブの内部に収納され、温度によって電気的特性が変化する素子と、金属チューブを挿入するための貫通孔を有し、金属チューブの外周面を取り囲むように配置されたフランジと、を備える温度センサにおいて、金属チューブは、その外径が貫通孔の最小内径よりも大径の金属チューブ後端部と、金属チューブ後端部の先端側に位置し、貫通孔の最小内径よりも小径の金属チューブ本体部と、を有し、貫通孔全体にわたって金属チューブが配置されてなり、軸線方向において、金属チューブ後端部と貫通孔との圧入長さが貫通孔の長さよりも小さくなるように、且つ金属チューブ本体部の外周面と貫通孔の内周面との間に空間が形成されるように、金属チューブ後端部がフランジに圧入固定されていることを特徴とする。
【００１６】
本発明の温度センサでは、金属チューブが、その外径がフランジの貫通孔の最小内径よりも大径の金属チューブ後端部と、該金属チューブ後端部の先端側に位置し、貫通孔の最小内径よりも小径の金属チューブ本体部とを有している。そして、軸線方向における金属チューブ後端部と貫通孔との圧入長さが、貫通孔の長さよりも小さくなるように、金属チューブ後端部がフランジに圧入固定されている構造となっている。これにより、金属チューブにフランジを圧入する際に、金属チューブのうち実際に圧入に寄与する部分は、フランジの貫通孔の最小内径よりも大径の金属チューブ後端部のみである。従って、圧入長さを短くすることができ、座屈等の金属チューブの変形を抑えることができる。また、圧入長さが短いことから、従来よりも圧入荷重を低減することができ、金属チューブの変形を更に抑えることができる。
【００１７】
また、温度センサでは、応答性向上のために、サーミスタが収納される金属チューブ本体部の外径を小径化することが行われている。従来の温度センサでは、金属チューブの小径化に伴い金属チューブ全体が小径化し、そのために、圧入工程時等に金属チューブの取り扱い性が低下することがあった。また、金属チューブの小径化に合わせて、新たなフランジを用意しなければならず、コストアップとなる。これに対し、本発明の温度センサでは、フランジが圧入される金属チューブ後端部の外径はそのままで、金属チューブ本体部の外径のみを変更すれば良い。従って、フランジの圧入作業性の低下を抑えることができる。また、金属チューブ本体部が小径化される毎に、新たなフランジを用意する必要もなく、低コスト化を実現することができる。
【００１８】
更に、温度センサでは、フランジと金属チューブ後端部とが圧入された圧入部を介して、フランジに熱が伝導する熱引きの問題がある。この熱引きが顕著になると、応答性の悪化、温度測定精度の低下を招くことになる。本発明の温度センサでは、軸線方向における金属チューブ後端部と貫通孔との圧入長さが、貫通孔の長さよりも小さくなるように、金属チューブ後端部がフランジに圧入固定されている構造となっている。従って、従来の温度センサに比べて、圧入長さが短いため、感熱部（温度センサであって、自動車の排気管内等に配置されるサーミスタ側の部位）からフランジへの熱引きを低減することができ、応答性の向上、温度測定精度の低下防止の効果が得られる。
【００１９】
また、金属チューブの径方向において、金属チューブ本体部の外周面と貫通孔の内周面との間に空間が形成されるように、金属チューブ後端部がフランジに圧入固定されている。このような構造にすることで、感熱部からフランジに至る伝熱経路を長くすることができ、感熱部に最も近いフランジの先端部からの熱引きが低減され、更に応答性を向上させることができる。
【００２０】
また、本発明の温度センサでは、フランジの貫通孔が、内径が略一定の先端側貫通孔と、先端側貫通孔の後端側に位置し、後端側ほど内径が大きい形状の後端側貫通孔と、からなり、前記金属チューブ後端部の外径は上記先端側貫通孔の内径よりも大径である。
【００２１】
本発明の温度センサでは、フランジの貫通孔のうち、後端側貫通孔が後端側ほど内径の大きい形状となっている。従って、フランジを金属チューブ後端部に圧入固定する際、後端側貫通孔から先端側貫通孔に向けて、金属チューブを先端側から挿入すれば、圧入荷重を更に低減することができ、座屈等の金属チューブの変形を抑えることができる。
【００２２】
また、フランジの後端部貫通孔が後端側ほど内径の大きい形状であるから、圧入長さが短くなると共に、後端部貫通孔の内周面と金属チューブ後端部の外周面との間に空間が形成される。これにより、熱引きを更に低減することができ、応答性の向上、温度測定精度の低下防止の効果が得られる。
【００２３】
また、本発明の温度センサでは、フランジは、軸線方向に延びる鞘部と、鞘部の先端側に位置し、径方向外側に向かって突出する突出部と、を有し、金属チューブ後端部は、鞘部に圧入固定されている。
【００２４】
本発明の温度センサでは、フランジと金属チューブ後端部とが圧入固定により一体とされるが、この圧入固定は、フランジのうちで排気ガス通路等の被測定流体が流通する流通路内に臨む部分（具体的には突出部の先端側）ではなく、突出部の後端側に位置する鞘部において行われるものである。これにより、温度センサを被測定流体が流通する流通管に装着したときに、フランジと金属チューブ後端部との圧入部が流通路内に配置されることがない。換言すれば、フランジと金属チューブ後端部との圧入部が、排気ガス等の被測定流体に晒されない位置に設けられる。その結果、流通路内において、感熱部（温度センサであって、自動車の排気管内等に配置されるサーミスタ側の部位）から圧入部を介してフランジに至る伝熱経路が形成されることはなく、感熱部からフランジ等への熱引きの度合いを従来に比して抑えられ、センサ自身の応答性の向上、温度測定精度の低下防止の効果が得られる。
【００２５】
また、本発明の温度センサでは、金属チューブ後端部は、鞘部であって先端側貫通孔が形成されている領域に、周方向にわたって溶接されている。
【００２６】
温度センサを自動車の排気ガス温度を検出するために使用した場合、２００〜１０００℃程度の高温環境下での使用に供されるが故に、金属チューブの外面はもとより内面が酸化されて、素子が収納される空間内の酸素濃度が著しく低下し、素子の表面が還元される等の理由で同素子に特性変化が生じることがある。そして、この酸化は特に金属チューブ後端部とフランジとの溶接部分の外面及び内面において生じ易く、この溶接部が流通路内に臨むフランジの先端側に形成される場合は、溶接部自身が高温環境下に直接晒されることになるので、酸化が助長されることになる。これに対し、本発明の温度センサでは、金属チューブ後端部とフランジとの溶接を、フランジの内で流通路内に臨む先端側の突出部ではなく、突出部の後端側に位置する鞘部に行っており、溶接部での酸化の発生が抑えられ、耐久性に優れた温度センサとすることができる。更に、金属チューブ自身がフランジの鞘部に溶接される構造であるため、上述したように溶接部が被測定流体に晒されることがなくなり、被測定流体に対する気密の信頼性を向上させることができる。
【００２７】
なお、本発明の温度センサでは、フランジを構成する鞘部は、先端側に位置する先端側段部と該先端側段部よりも小さい外径を有する後端側段部とを備える二段形状をなし、金属チューブ後端部は、鞘部の後端側段部に溶接されていると良い。
【００２８】
金属チューブ後端部とフランジの鞘部との溶接部を同鞘部の周方向にわたって十分な溶接強度を有する状態で形成するには、溶接条件を高めに設定したり、溶接条件を変更せずに鞘部の肉厚を薄肉化して溶接を行うことが考えられる。しかし、単純に溶接条件を高めるとコストアップに繋がり、逆に鞘部全体の肉厚を薄くすると鞘部自身の機械的強度が低下するおそれがある。そこで、本発明では、フランジの鞘部を、先端側段部とそれよりも小径の後端側段部の二段形状に形成し、金属チューブ後端部を鞘部の後端側段部に溶接している。つまり、鞘部の内で溶接に供される部分の肉厚が薄くなる形状としている。それにより、鞘部と金属チューブ後端部との溶接を良好に行え両者の溶接強度を良好に確保しつつ、鞘部ひいてはフランジの機械的強度についても確保することができる。なお、鞘部の後端側を先端側よりも小径に形成することは、後端側を先端側よりも大径に形成するのに比して加工の面から容易であり望ましい。
【００２９】
また、本発明では、金属チューブ後端部とフランジの鞘部との溶接は、特に限定されず、例えば、レーザ溶接、プラズマ溶接（例えば、アルゴン溶接等）、電子ビーム溶接等を挙げることができる。溶接強度の確保とコスト面との兼ね合いを考慮すると、レーザ溶接、或いは、アルゴン溶接が好ましい。
【００３０】
【発明の実施の形態】
本発明の実施の形態である温度センサ１について、図面を参照しつつ説明する。図１は、本発明の温度センサ１の構造を示す断面図である。また、図２は、図１の温度センサ１のフランジ４周辺部を拡大して示す部分断面図である。この温度センサ１は、サーミスタ素子２を感温素子として用いたものであり、同センサ１を自動車の排気管に装着することにより、サーミスタ素子２を排気ガスが流れる排気管内に配置させて、排気ガスの温度検出に使用するものである。
【００３１】
金属チューブ３は、鋼板の深絞り加工により先端側３１が閉塞した軸線方向に延びる筒状形状をなしており、その先端側３１の内部にサーミスタ素子２が収納されている。この金属チューブ３は、後述するフランジ４の先端側貫通孔４７の内径よりも大径の金属チューブ後端部３３と、この金属チューブ後端部３３の先端側に位置し、フランジの先端側貫通孔４７の内径よりも小径の金属チューブ本体部３４とを有している。なお、金属チューブ後端部３３と金属チューブ本体部３４との間には、テーパ形状の金属チューブ変径部が形成されている。また、金属チューブ３は、後述するようにステンレス合金から形成されている。そして、金属チューブ３の内部であってサーミスタ素子２の周囲には、セメント１０が充填されており、これにより使用時の振動等によるサーミスタ素子２の揺動が防止される。また、金属チューブ３の内部であってサーミスタ素子２の先端側には、酸化ニッケル製のペレット１４が配置されている。このペレット１４は、万一、金属チューブ３の内部の酸素濃度が低下したときに、そのペレット１４から酸素を放出させて酸素濃度の低下を抑えるためのものである。更に、金属チューブ３の後端側３２は開放されており、金属チューブ後端部３３はステンレス合金製のフランジ４の貫通孔４６に挿通されている。
【００３２】
フランジ４は、ステンレス合金により形成されており、軸線方向に延びる鞘部４２と、この鞘部４２の先端側に位置し、径方向外側に向かって突出する突出部４１とを有している。突出部４１は、鞘部４２よりも大きな外径を有している。更に、突出部４１は、環状に形成されると共に、先端側に図示しない排気管の取付部のテーパ部に対応したテーパ形状を有しており、この座面４５が上記取付部のテーパ部に密着することで、排気ガスが排気管外部へ漏出するのを防止するようになっている。また、鞘部４２は環状に形成される一方、先端側に位置する先端側段部４４と先端側段部４４よりも小さい外径を有する後端側段部４３とを備える二段形状をなしている。更に、フランジ４は、軸線方向に貫通した貫通孔４６を有しており、この貫通孔４６に金属チューブ３が挿入される。この貫通孔４６は、内径が略一定の先端側貫通孔４７と、先端側貫通孔４７の後端側に位置し、後端側ほど内径が大きいテーパ形状の後端側貫通孔４８とからなっている。また、後端側貫通孔４８の最大内径は、金属チューブ後端部３３の外径よりも大径となっている。
【００３３】
金属チューブ３は、自身の先端側３１からフランジ４の後端側貫通孔４８に挿入され、金属チューブ後端部３３の外周面と、鞘部４２の後端側段部４３に対応する領域に位置する先端側貫通孔４７の内周面とが、圧入固定されている。そして、金属チューブ後端部３３の外周面と先端側貫通孔４７の内周面との重なり合う部分が、周方向にわたってレーザ溶接されている。このレーザ溶接がなされることにより、図１に示すように、鞘部４２の後端側段部４３と金属チューブ後端部３３とに跨る溶接部Ｗ１が形成され、金属チューブ３がフランジ４に対して強固に固定される。なお、軸線方向において、金属チューブ後端部と先端側貫通孔４７の圧入長さは、先端側貫通孔４７の長さよりも小さくなっている。また、フランジの先端側において、金属チューブ本体部３４の外周面と先端側貫通孔４７の内周面との間には、空間が形成されている。
【００３４】
このように、金属チューブ後端部３３をフランジ４の鞘部４２に圧入しつつ、鞘部４２の後端側段部４３にレーザ溶接を行うことによって、フランジ４と金属チューブ３との溶接強度に優れると共に、フランジ４と金属チューブ３との密着強度に優れる温度センサ１とすることができる。従って、自動車等の振動の激しい環境下において温度センサ１が強い振動を受けても、金属チューブ３自体が振れ難く、金属チューブ３の折損等を抑制することができる。また、排気ガスに対する気密の信頼性を向上させることができる。
【００３５】
フランジ４の周囲には、六角ナット部５１及びネジ部５２を有するナット５が回動自在に嵌挿されている。温度センサ１は、排気管の取付部にフランジ４の突出部４１の座面４５を当接させ、ナット５により固定される。また、フランジ４のうちで鞘部４２の先端側段部４４の径方向外側には、筒状の継手６が気密状態で接合されている。具体的には、鞘部４２の先端側段部４４の外周面に継手６の内周面が重なり合うように、同継手６が鞘部４２の先端側段部４４に圧入され、継手６と先端側段部４４とを周方向にわたってレーザ溶接している。このレーザ溶接がなされることにより、図１に示すように、鞘部４２の先端側段部４４と金属チューブ３とに跨る溶接部Ｗ２が形成される。
【００３６】
金属チューブ３、フランジ４及び継手６の内部には、一対の金属芯線７を内包するシース部材８が配置される。金属チューブ３の内部においてシース部材８の先端側から突出する金属芯線７には、サーミスタ素子２がＰｔ／Ｒｈ合金線９を介して接続される。この合金線９は、サーミスタ素子２と同時に焼成されるものである。合金線９及び金属芯線７は互いに抵抗溶接される。なお、シース部材８は、詳細は図示しないが、ＳＵＳ３１０Ｓからなる金属製の外筒と、ＳＵＳ３１０Ｓ等からなる導電性の一対の金属芯線７と、外筒と各金属芯線７の間を絶縁し、金属芯線７を保持する絶縁粉末とから構成される。
【００３７】
継手６の内部にてシース部材８の後端側へ突き出す金属芯線７は、加締め端子１１を介して一対の外部回路（例えば車両のＥＣＵ等）接続用のリード線１２が接続される。なお、一対の金属芯線７及び一対の加締め端子１１は絶縁チューブ１５により互いに絶縁される。リード線１２は、ステンレス合金製の導線を絶縁性の被覆材にて被覆したものである。これらリード線１２は、耐熱ゴム製の補助リング１３に内包される。補助リング１３が継手６の上から丸加締め或いは六角加締めされることにより、両者１３、６が気密性を保ちながら互いに接合される。これにより、サーミスタ素子２が、金属チューブ３、フランジ４及び継手６を金属包囲部材として形成される閉空間に収容されることになる。そして、サーミスタ素子２の出力は、シース部材８の金属芯線７からリード線１２により、図示しない外部回路に取り出され、排気ガスの温度が検出される。
【００３８】
ここで、本実施の形態の温度センサ１にあっては、外部からリード線１２の内側の空隙を介して大気が継手６の内部に入り込むと、その大気は、継手６、金属チューブ３及びフランジ４の内部が閉空間に形成される関係上、金属チューブ３内まで入り込むことになる。従って、温度センサ１では、リード線１２の内部から金属チューブ３内までの通気が確保されることになり、サーミスタ素子２を収納する金属チューブ３が酸化した場合にも、同金属チューブ３内の酸素濃度の低下が抑えられ、サーミスタ素子２の特性変化を抑制することができる。
【００３９】
なお、この温度センサ１は１０００℃にも達する高温環境下で使用されるため、各々の構成部材は十分な耐熱性を有している必要がある。そのため、金属チューブ３、フランジ４及び金属芯線７は、Ｆｅを主成分とし、Ｃ、Ｓｉ、Ｍｎ、Ｐ、Ｓ、Ｎｉ及びＣｒを含有する耐熱合金であるＳＵＳ３１０Ｓにより形成されている。また、継手６は、ＳＵＳ３０４に形成されている。
【００４０】
続いて、上述した本実施の形態の温度センサ１の製造方法について説明する。まず、ＳＵＳ３１０Ｓの金属体に対して冷間鍛造又は／及び切削加工を施し、先端側貫通孔４７及び後端側貫通孔４８からなる貫通孔４６と、先端側段部４４と後端側段部４６とを有する二段形状をなす鞘部４２と、この鞘部４２の先端側に位置し、径方向外側に向かって突出する突出部４１とを有するフランジ４を形成する。なお、フランジ４の後端側貫通孔４８は、フランジ４の形成と同時に形成されても良く、フランジ４を冷間鍛造した後、切削加工することで形成しても良い。また、別途平らなＳＵＳ３１０Ｓ鋼板を準備し、この鋼板をダイス型の所定位置にセットした上で、ポンチを用いて深絞り加工することで金属チューブ３全体を形成する。この深絞り加工により、先端側３１が閉塞した筒状をなし、上述の金属チューブ本体部、金属チューブ変径部、金属チューブ後端部を有した金属チューブ３が形成される。
【００４１】
次に、金属チューブ３とフランジ４とを圧入固定する。具体的には、金属チューブ３を、自身の先端側３１からフランジ４の後端側貫通孔４８に挿入する。そして、金属チューブ後端部３３の外周面と、鞘部４２の後端側段部４３に対応する領域に位置する先端側貫通孔４７の内周面とを、圧入固定する。この圧入工程時において、本実施の形態では、フランジ４の後端側貫通孔４８の内周面に金属チューブ後端部３３先端側外周面が当接すると、後端側貫通孔４８内周面のテーパ形状によるセンターリング効果で、金属チューブ３とフランジ４との軸芯が一致する方向に導かれる。そのため、両者の芯ずれを抑制した形で、両者の圧入を行うことができる。また、上記後端側貫通孔４８内周面がテーパ形状であるため、フランジ４の貫通孔４６内への金属チューブ後端部３３圧入開始当初における摩擦抵抗を少なくすることができ、圧入荷重を低減することができる。従って、座屈等の金属チューブの変形を抑えることができる。また、金属チューブ３にはテーパ形状の金属チューブ変径部が形成されているので、テーパ形状を有した後端側貫通孔４８と相まって、更に圧入荷重が低減され、金属チューブの変形を更に抑えることができる。
【００４２】
そして、金属チューブ３とフランジ４とを圧入した後、金属チューブ後端部３３の外周面と先端側貫通孔４７の内周面との重なり合う部分を、周方向にわたってレーザ溶接する。ついで、金属チューブ３内に所定量の未固化状態のセメント１０と、ペレット１４とを充填し、シース部材８の金属芯線７の先端部とサーミスタ素子２の電極とを接続した組立体を、サーミスタ素子２側から該金属チューブ３の内部に挿入する。その後、セメント１０を固化させる。ついで、公知の手法により、加締め端子１１を用いてシース部材８の金属芯線７の後端部とリード線１２とを接続する。その後、筒状の継手６を、鞘部４２の先端側段部４４の径方向外側に圧入して、継手６と先端側段部４４を周方向にわたってレーザ溶接する。そして、補助リング１３やナット５等を適宜組み付ける。このようにして、温度センサ１が完成する。
【００４３】
以上に説明したように、本実施の形態の温度センサ１は、フランジ４の先端側貫通孔４７の最小内径よりも小径の金属チューブ本体部３３側からフランジ４に挿入して、金属チューブ後端部３３とフランジ４とを圧入固定している。従って、フランジ４に金属チューブ３を挿入し易い。また、軸線方向における金属チューブ後端部３３と先端側貫通孔４７との圧入長さが、先端側貫通孔４７の長さよりも小さくなるように、金属チューブ後端部３３がフランジ４に圧入固定されるので、圧入長さを短くすることができ、座屈等の金属チューブの変形を抑えることができる。更に、フランジの貫通孔のうち、後端側貫通孔４８が後端側ほど内径の大きいテーパ形状となっているので、圧入荷重を低減することができ、座屈等の金属チューブの変形を更に抑えることができる。
【００４４】
また、本実施の形態の温度センサ１は、従来に比べて圧入長さが短いため、感熱部からフランジへの熱引きを低減することができ、応答性の向上、温度測定精度の低下防止の効果が得られる。更に、フランジ４の後端部貫通孔４８がテーパ形状であるので、後端部貫通孔４８の内周面と金属チューブ後端部３３の外周面との間に空間が形成されると共に、金属チューブ本体部３３の外周面と先端側貫通孔４７の内周面との間にも空間が形成されている。このため、フランジからの熱引きが更に低減され、更なる応答性の向上、温度測定精度の低下を抑制できる。
【００４５】
更に、本実施の形態の温度センサ１は、金属チューブ３とフランジ４とがレーザ溶接により一体に接合されるが、レーザ溶接により形成される溶接部Ｗ１は、フランジ４のうちで排気管内に臨む先端側の突出部４１ではなく、後端側に位置する鞘部４２に形成される。これにより、排気管内において、温度センサ１の感熱部（フランジ４の座面よりもサーミスタ素子２側の部位）から溶接部を介してフランジ４に至る伝熱経路が形成されず、感熱部からフランジ４等への熱引きの度合いを従来に比して抑えることができる。その結果、応答性向上、温度測定精度の低下防止の効果を得ることができると共に、継手６の温度上昇を抑えて補助リング１３の信頼性を維持することができる。
【００４６】
また、金属チューブ３とフランジ４との溶接部Ｗ１が排気管内に晒されないことから、溶接部の内面にて生じ易い酸化を有効に抑制することができ、ひいてはサーミスタ素子２が特性変化することを抑制することができる一方、排気ガスに対する気密の信頼性を向上させることができる。
【００４７】
更に、金属チューブ３全体が、ＳＵＳ３１０Ｓ鋼板の深絞り加工により形成されている。従って、金属チューブ３の先端部に酸化しやすい溶接部を有しないため、耐久性、信頼性に優れた温度センサ１とすることができる。
【００４８】
なお、本発明においては、上述した具体的な実施形態に限られず、目的、用途に応じて本発明の範囲内で種々変更した実施形態とすることができる。
例えば、金属チューブ３の先端部の厚さを他の部分よりも薄くすることにより、温度センサの応答性を更に向上させることもできる。さらに、フランジ４の突出部４１よりも先端側に、同突出部４１よりも外径が小径の外径を有し、金属チューブ本体部３４あるいはシース部材８の外径よりも大径の内径を有する筒状部を一体に形成し、この筒状部の外周面を径方向内側に加締めることで、筒状部と金属チューブ本体部３４あるいはシース部材８とを加締め固定してもよい。これにより、金属チューブ本体部３４あるいはシース部材８の折損がより一層起こり難い耐震性に優れた温度センサとすることができる。また、本発明の温度センサは、排気温センサのみならず、被測定流体として水や油等の液体が流れる流通路に取り付けられる温度センサにも適用可能である。
【図面の簡単な説明】
【図１】サーミスタ素子を収納する金属チューブがフランジの鞘部に圧入され、この鞘部において周方向にわたってレーザ溶接されている温度センサを示す断面図である。
【図２】図１の温度センサのフランジ周辺部を拡大して示す部分断面図である。
【符号の説明】
１・・・温度センサ、２・・・サーミスタ素子、３・・・金属チューブ、３３・・・金属チューブ後端部、３４・・・金属チューブ本体部、４・・・フランジ、４１・・・突出部、４２・・・鞘部、４３・・・後端側段部、４４・・・先端側段部、６・・・継手、７・・・金属芯線、８・・・シース部材、１２・・・リード線、Ｗ１、Ｗ２・・・溶接部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a temperature sensor including a thermistor made of a semiconductor such as a metal oxide, a metal resistor, or the like as a temperature sensitive element. More specifically, a temperature sensor that detects the temperature of the fluid to be measured by disposing an element in a flow path through which the fluid to be measured (for example, exhaust gas) flows, such as in a catalytic converter or an exhaust pipe of an exhaust gas purification device of an automobile. About.
[0002]
[Prior art]
Conventionally, it has a thermistor element, which is a temperature sensitive element, and has a metal tube (metal case) extending in the axial direction and a through hole (through hole) for inserting the metal tube. 2. Description of the Related Art A temperature sensor is known that includes a flange (mounting nut) disposed so as to surround the flange, and the flange is press-fitted and fixed to a metal tube and is welded (see, for example, Patent Document 1). Such a temperature sensor is used as an exhaust temperature sensor for detecting the temperature of exhaust gas flowing in the exhaust gas flow passage by a temperature sensing element.
[0003]
[Patent Document 1]
JP-A-5-340822
[0004]
[Problems to be solved by the invention]
In the temperature sensor, a metal tube that is a thin member and a flange that is a thick member are fixed by press-fitting. However, in the conventional temperature sensor, the outer diameter of the entire metal tube and the inner diameter of the through hole of the flange are substantially the same, so the press-fitted length (the contact portion between the outer peripheral surface of the metal tube and the inner peripheral surface of the flange through hole) (The length in the axial direction) is long. Therefore, there has been a problem that the metal tube buckles when the flange is press-fitted into the metal tube.
[0005]
The present invention solves the above-described conventional problems, and provides a temperature sensor manufacturing method and a temperature sensor that can prevent deformation of a metal tube when a flange is press-fitted into the metal tube. Objective.
[0006]
[Means for Solving the Problems]
The temperature sensor manufacturing method of the present invention, which has been made to solve the above problems, is a cylindrical metal tube extending in the axial direction with the tip side closed, and is housed inside the metal tube, and its electrical characteristics change depending on the temperature. In a manufacturing method of a temperature sensor comprising an element and a flange having a through hole for inserting a metal tube and disposed so as to surround an outer peripheral surface of the metal tube, the outer diameter is smaller than the minimum inner diameter of the through hole. A metal tube having a rear end portion of a large-diameter metal tube and a metal tube main body portion having a diameter smaller than the minimum inner diameter of the through-hole located on the front end side of the metal tube rear end portion is connected to the front end side of the metal tube. Insert the flange from After the metal tube is arranged over the entire through hole, a space is formed between the outer peripheral surface of the metal tube main body and the inner peripheral surface of the through hole. A flange is press-fitted and fixed to the rear end of the metal tube.
[0007]
In the temperature sensor manufacturing method of the present invention, the metal tube is inserted into the flange from the metal tube main body side smaller than the minimum inner diameter of the through hole of the flange, and the metal tube rear end portion and the flange are press-fitted and fixed. . Therefore, it is easy to insert the metal tube into the flange. Further, when the flange is press-fitted into the metal tube, the portion of the metal tube that actually contributes to the press-fitting is only the rear end portion of the metal tube having a diameter larger than the minimum inner diameter of the through hole of the flange. Thereby, the press-fitting length can be shortened, and deformation of the metal tube such as buckling can be suppressed. Furthermore, since the press-fitting length is short, the press-fitting load can be reduced as compared with the conventional case, and the deformation of the metal tube can be further suppressed.
[0008]
In the temperature sensor manufacturing method of the present invention, the through hole of the flange is positioned at the front end side through hole having a substantially constant inner diameter and the rear end side of the front end side through hole, and the inner diameter increases toward the rear end side. A rear end side through hole, and the metal tube rear end portion is press-fitted from the rear end side through hole side.
[0009]
In the temperature sensor manufacturing method of the present invention, the rear end portion of the metal tube is press-fitted from the rear end side through-hole side having a shape having a larger inner diameter toward the rear end side. Therefore, the press-fit load can be reduced and the deformation of the metal tube can be further suppressed. Here, the shape of the rear end side through-hole is preferably a tapered shape or a rounded shape in consideration of ease of press-fitting. The maximum inner diameter of the rear end side through hole is preferably larger than the outer diameter of the rear end portion of the metal tube.
[0010]
In the temperature sensor manufacturing method of the present invention, in the axial direction, the press-fitting length of the rear end portion of the metal tube and the front end side through hole (the outer peripheral surface of the rear end portion of the metal tube and the inner peripheral surface of the front end side through hole) (Length in the axial direction) is smaller than the length of the front end side through hole. Thereby, the press-fitting length is shortened and the press-fitting load can be further reduced.
[0011]
Further, in the temperature sensor manufacturing method of the present invention, the flange has a sheath portion extending in the axial direction, and a projecting portion located on the distal end side of the sheath portion and projecting radially outward, and a metal tube The rear end is press-fitted and fixed to the sheath.
[0012]
In the temperature sensor, there is a problem of heat pulling in which heat is conducted to the flange through a press-fit portion in which the flange and the rear end portion of the metal tube are press-fitted. When this heat pulling becomes significant, the responsiveness deteriorates and the temperature measurement accuracy decreases. In the temperature sensor obtained by the manufacturing method of the present invention, the flange and the rear end of the metal tube are integrated by press fitting, and this press fitting fixes the fluid to be measured such as an exhaust gas passage in the flange. This is performed not at the portion facing the flow passage (specifically, at the front end side of the protruding portion) but at the sheath portion positioned on the rear end side of the protruding portion. Thereby, when the temperature sensor is attached to the flow pipe through which the fluid to be measured flows, the press-fitted portion between the flange and the rear end portion of the metal tube is not disposed in the flow passage. In other words, the press-fitting portion between the flange and the rear end portion of the metal tube is provided at a position where it is not exposed to the fluid to be measured such as exhaust gas. As a result, no heat transfer path is formed in the flow path from the heat-sensitive part (a temperature sensor, a part on the thermistor side disposed in the exhaust pipe of an automobile, etc.) to the flange through the press-fit part. The degree of heat pulling from the heat sensitive part to the flange or the like can be suppressed as compared with the conventional case, and the effect of improving the responsiveness of the sensor itself and preventing the temperature measurement accuracy from being lowered can be obtained.
[0013]
Moreover, in the manufacturing method of the temperature sensor of this invention, a metal tube rear-end part is welded over the circumferential direction to the area | region in which it is a sheath part and the front end side through-hole is formed.
[0014]
When the temperature sensor is used to detect the exhaust gas temperature of an automobile, it is used in a high-temperature environment of about 200 to 1000 ° C., so that not only the outer surface of the metal tube but also the inner surface is oxidized, and the element is A characteristic change may occur in the element because the oxygen concentration in the space to be stored is significantly reduced and the surface of the element is reduced. This oxidation is likely to occur particularly on the outer surface and the inner surface of the welded portion between the rear end portion of the metal tube and the flange. When this welded portion is formed on the front end side of the flange facing the flow passage, the welded portion itself is hot. Oxidation is promoted because it is directly exposed to the environment. On the other hand, in the temperature sensor obtained by the manufacturing method of the present invention, the rear end of the protruding portion is not the protruding portion on the front end side facing the flow path in the flange, but the welding of the rear end portion of the metal tube and the flange. This is performed on the sheath located on the side, and generation of oxidation at the welded portion is suppressed, and a temperature sensor having excellent durability can be obtained. Further, since the metal tube itself is welded to the sheath portion of the flange, the welded portion is not exposed to the fluid to be measured as described above, and the airtight reliability with respect to the fluid to be measured can be improved. .
[0015]
Further, the temperature sensor of the present invention made to solve the above-mentioned problems is an element that has a cylindrical metal tube that extends in the axial direction with the tip side closed, and an element that is housed inside the metal tube and whose electrical characteristics change depending on the temperature. And a flange having a through-hole for inserting the metal tube and disposed so as to surround the outer peripheral surface of the metal tube, the outer diameter of the metal tube is smaller than the minimum inner diameter of the through-hole. Also has a large-diameter metal tube rear end, and a metal tube main body portion located on the front end side of the metal tube rear end, and having a diameter smaller than the minimum inner diameter of the through-hole, A metal tube is arranged over the entire through hole, In the axial direction, the press-fitting length between the rear end portion of the metal tube and the through hole is smaller than the length of the through hole. And so that a space is formed between the outer peripheral surface of the metal tube main body and the inner peripheral surface of the through hole, The rear end portion of the metal tube is press-fitted and fixed to the flange.
[0016]
In the temperature sensor of the present invention, the metal tube is positioned at the rear end portion of the metal tube whose outer diameter is larger than the minimum inner diameter of the through hole of the flange, and at the front end side of the rear end portion of the metal tube. A metal tube main body having a diameter smaller than the minimum inner diameter. The metal tube rear end portion is press-fitted and fixed to the flange so that the press-fitting length between the metal tube rear end portion and the through hole in the axial direction is smaller than the length of the through hole. Thus, when the flange is press-fitted into the metal tube, the portion of the metal tube that actually contributes to the press-fitting is only the rear end portion of the metal tube having a diameter larger than the minimum inner diameter of the through hole of the flange. Therefore, the press-fitting length can be shortened, and deformation of the metal tube such as buckling can be suppressed. Further, since the press-fitting length is short, the press-fitting load can be reduced as compared with the conventional case, and the deformation of the metal tube can be further suppressed.
[0017]
In the temperature sensor, the outer diameter of the metal tube main body in which the thermistor is housed is reduced in order to improve the response. In the conventional temperature sensor, as the diameter of the metal tube is reduced, the entire diameter of the metal tube is reduced. For this reason, the handleability of the metal tube may be reduced during the press-fitting process. In addition, a new flange must be prepared as the diameter of the metal tube is reduced, resulting in an increase in cost. On the other hand, in the temperature sensor of the present invention, the outer diameter of the rear end portion of the metal tube into which the flange is press-fitted remains unchanged, and only the outer diameter of the metal tube main body portion needs to be changed. Accordingly, it is possible to suppress a decrease in the press-fitting workability of the flange. Further, it is not necessary to prepare a new flange every time the diameter of the metal tube main body is reduced, and cost reduction can be realized.
[0018]
Furthermore, in the temperature sensor, there is a problem of heat pulling in which heat is conducted to the flange through a press-fit portion in which the flange and the rear end portion of the metal tube are press-fitted. When this heat pulling becomes significant, the responsiveness deteriorates and the temperature measurement accuracy decreases. In the temperature sensor of the present invention, the metal tube rear end portion is press-fitted and fixed to the flange so that the press-fitting length between the metal tube rear end portion and the through hole in the axial direction is smaller than the length of the through hole. It has become. Therefore, since the press-fitting length is shorter than that of the conventional temperature sensor, heat extraction from the heat-sensitive part (the temperature sensor, which is the thermistor side portion disposed in the exhaust pipe of the automobile) to the flange is reduced. Thus, the effect of improving the responsiveness and preventing the temperature measurement accuracy from being lowered can be obtained.
[0019]
Also, in the radial direction of the metal tube, Outer surface and through hole The rear end of the metal tube is press-fitted and fixed to the flange so that a space is formed between the inner peripheral surface of Has been. By adopting such a structure, it is possible to lengthen the heat transfer path from the heat sensitive part to the flange, reduce the heat drawn from the front end of the flange closest to the heat sensitive part, and further improve the responsiveness. it can.
[0020]
In the temperature sensor of the present invention, the through hole of the flange is positioned at the front end side through hole having a substantially constant inner diameter and the rear end side of the shape having a larger inner diameter toward the rear end side. And the outer diameter of the rear end portion of the metal tube is larger than the inner diameter of the front end side through hole.
[0021]
In the temperature sensor of the present invention, among the through holes of the flange, the rear end side through hole has a shape with a larger inner diameter toward the rear end side. Therefore, when the flange is press-fitted and fixed to the rear end of the metal tube, if the metal tube is inserted from the front end side toward the front end side through hole from the rear end side through hole, the press-fitting load can be further reduced. Deformation of the metal tube such as bending can be suppressed.
[0022]
In addition, since the rear end through hole of the flange has a shape with a larger inner diameter toward the rear end, the press-fitting length is shortened, and the inner peripheral surface of the rear end through hole and the outer peripheral surface of the metal tube rear end are A space is formed between them. As a result, heat sinking can be further reduced, and an effect of improving responsiveness and preventing a decrease in temperature measurement accuracy can be obtained.
[0023]
Further, in the temperature sensor of the present invention, the flange has a sheath portion extending in the axial direction, and a projecting portion located on the distal end side of the sheath portion and projecting radially outward, and the rear end portion of the metal tube Is press-fitted and fixed to the sheath.
[0024]
In the temperature sensor of the present invention, the flange and the rear end portion of the metal tube are integrated by press-fitting, and this press-fitting is faced in a flow passage in the flange through which a fluid to be measured such as an exhaust gas passage flows. It is performed not on the part (specifically, on the front end side of the protrusion) but on the sheath located on the rear end side of the protrusion. Thereby, when the temperature sensor is attached to the flow pipe through which the fluid to be measured flows, the press-fitted portion between the flange and the rear end portion of the metal tube is not disposed in the flow passage. In other words, the press-fitting portion between the flange and the rear end portion of the metal tube is provided at a position where it is not exposed to the fluid to be measured such as exhaust gas. As a result, no heat transfer path is formed in the flow path from the heat-sensitive part (a temperature sensor, a part on the thermistor side disposed in the exhaust pipe of an automobile, etc.) to the flange through the press-fit part. The degree of heat pulling from the heat sensitive part to the flange or the like can be suppressed as compared with the conventional case, and the effect of improving the responsiveness of the sensor itself and preventing the temperature measurement accuracy from being lowered can be obtained.
[0025]
Moreover, in the temperature sensor of this invention, the metal tube rear-end part is welded over the area | region where it is a sheath part and the front end side through-hole is formed in the circumferential direction.
[0026]
When the temperature sensor is used to detect the exhaust gas temperature of an automobile, it is used in a high-temperature environment of about 200 to 1000 ° C., so that not only the outer surface of the metal tube but also the inner surface is oxidized, and the element is A characteristic change may occur in the element because the oxygen concentration in the space to be stored is significantly reduced and the surface of the element is reduced. This oxidation is likely to occur particularly on the outer surface and the inner surface of the welded portion between the rear end portion of the metal tube and the flange. When this welded portion is formed on the front end side of the flange facing the flow passage, the welded portion itself is hot. Oxidation is promoted because it is directly exposed to the environment. On the other hand, in the temperature sensor according to the present invention, the sheath between the rear end portion of the metal tube and the flange is positioned on the rear end side of the projecting portion instead of the projecting portion on the front end side facing the flow passage in the flange. Therefore, the occurrence of oxidation at the welded portion is suppressed, and a temperature sensor having excellent durability can be obtained. Further, since the metal tube itself is welded to the sheath portion of the flange, the welded portion is not exposed to the fluid to be measured as described above, and the airtight reliability with respect to the fluid to be measured can be improved. .
[0027]
In the temperature sensor of the present invention, the sheath part constituting the flange has a two-stage shape including a front end side step part located on the front end side and a rear end side step part having an outer diameter smaller than that of the front end side step part. The rear end portion of the metal tube is preferably welded to the rear end side step portion of the sheath portion.
[0028]
To form the welded portion between the rear end of the metal tube and the sheath portion of the flange with sufficient welding strength over the circumferential direction of the sheath portion, the welding conditions are not set high or the welding conditions are not changed. It is conceivable to perform welding by reducing the thickness of the sheath part. However, simply increasing the welding conditions leads to an increase in cost, and conversely, if the thickness of the entire sheath is reduced, the mechanical strength of the sheath itself may be reduced. Therefore, in the present invention, the sheath portion of the flange is formed in a two-stage shape of the front end side step portion and the rear end side step portion having a smaller diameter than that, and the metal tube rear end portion is formed on the rear end side step portion of the sheath portion. Welding. That is, it is set as the shape where the thickness of the part used for welding within a sheath part becomes thin. Thereby, welding with a sheath part and a metal tube rear-end part can be performed favorably, and also the mechanical strength of a sheath part and a flange can also be ensured, ensuring both welding strength favorable. In addition, forming the rear end side of the sheath portion with a smaller diameter than the front end side is easier and desirable from the viewpoint of processing than forming the rear end side with a larger diameter than the front end side.
[0029]
In the present invention, the welding of the rear end portion of the metal tube and the sheath portion of the flange is not particularly limited, and examples thereof include laser welding, plasma welding (for example, argon welding), and electron beam welding. . In consideration of the balance between securing the welding strength and cost, laser welding or argon welding is preferable.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
A temperature sensor 1 according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of a temperature sensor 1 of the present invention. FIG. 2 is an enlarged partial sectional view showing the periphery of the flange 4 of the temperature sensor 1 of FIG. This temperature sensor 1 uses a thermistor element 2 as a temperature-sensitive element. By mounting the sensor 1 on an exhaust pipe of an automobile, the thermistor element 2 is disposed in an exhaust pipe through which exhaust gas flows, and the exhaust gas is exhausted. It is used for gas temperature detection.
[0031]
The metal tube 3 has a cylindrical shape extending in the axial direction in which the distal end side 31 is closed by deep drawing of a steel plate, and the thermistor element 2 is accommodated inside the distal end side 31. The metal tube 3 is positioned on the distal end side of the metal tube rear end portion 33 having a diameter larger than the inner diameter of the distal end side through hole 47 of the flange 4 to be described later, and on the front end side of the flange. A metal tube main body 34 having a diameter smaller than the inner diameter of the hole 47 is provided. A tapered metal tube diameter changing portion is formed between the metal tube rear end portion 33 and the metal tube main body portion 34. Moreover, the metal tube 3 is formed from the stainless alloy so that it may mention later. The cement tube 10 is filled inside the metal tube 3 and around the thermistor element 2, thereby preventing the thermistor element 2 from swinging due to vibration during use. Further, a nickel oxide pellet 14 is disposed inside the metal tube 3 and on the tip side of the thermistor element 2. The pellet 14 is intended to suppress a decrease in oxygen concentration by releasing oxygen from the pellet 14 in the unlikely event that the oxygen concentration inside the metal tube 3 decreases. Further, the rear end side 32 of the metal tube 3 is opened, and the rear end portion 33 of the metal tube is inserted through the through hole 46 of the flange 4 made of stainless alloy.
[0032]
The flange 4 is formed of a stainless alloy, and includes a sheath portion 42 that extends in the axial direction, and a projecting portion 41 that is located on the distal end side of the sheath portion 42 and projects outward in the radial direction. The protrusion 41 has a larger outer diameter than the sheath 42. Further, the projecting portion 41 is formed in an annular shape and has a tapered shape corresponding to a tapered portion of a mounting portion of an exhaust pipe (not shown) on the distal end side, and the seat surface 45 is formed on the tapered portion of the mounting portion. By closely contacting, the exhaust gas is prevented from leaking outside the exhaust pipe. The sheath portion 42 is formed in a ring shape, and has a two-stage shape including a front end side step portion 44 located on the front end side and a rear end side step portion 43 having an outer diameter smaller than that of the front end side step portion 44. ing. Further, the flange 4 has a through hole 46 penetrating in the axial direction, and the metal tube 3 is inserted into the through hole 46. The through hole 46 includes a front end side through hole 47 having a substantially constant inner diameter, and a tapered rear end side through hole 48 located on the rear end side of the front end side through hole 47 and having a larger inner diameter toward the rear end side. ing. Further, the maximum inner diameter of the rear end side through hole 48 is larger than the outer diameter of the metal tube rear end portion 33.
[0033]
The metal tube 3 is inserted into the rear end side through hole 48 of the flange 4 from the front end side 31 of the metal tube 3, and in the region corresponding to the outer peripheral surface of the metal tube rear end portion 33 and the rear end stepped portion 43 of the sheath portion 42. The inner peripheral surface of the distal end side through-hole 47 is press-fitted and fixed. And the part which the outer peripheral surface of the metal tube rear-end part 33 and the inner peripheral surface of the front end side through-hole 47 overlap is laser-welded over the circumferential direction. By performing this laser welding, as shown in FIG. 1, a welded portion W <b> 1 straddling the rear end side step portion 43 of the sheath portion 42 and the metal tube rear end portion 33 is formed, and the metal tube 3 is attached to the flange 4. On the other hand, it is firmly fixed. In the axial direction, the press-fitting length of the rear end portion of the metal tube and the front end side through hole 47 is smaller than the length of the front end side through hole 47. In addition, a space is formed between the outer peripheral surface of the metal tube main body 34 and the inner peripheral surface of the front end side through hole 47 on the front end side of the flange.
[0034]
Thus, the welding strength between the flange 4 and the metal tube 3 is achieved by performing laser welding on the rear end side step portion 43 of the sheath portion 42 while pressing the metal tube rear end portion 33 into the sheath portion 42 of the flange 4. In addition, the temperature sensor 1 having excellent adhesion strength between the flange 4 and the metal tube 3 can be obtained. Therefore, even if the temperature sensor 1 is subjected to strong vibration in an environment where the vibration is intense such as an automobile, the metal tube 3 itself is difficult to shake, and breakage of the metal tube 3 can be suppressed. In addition, the reliability of the airtightness with respect to the exhaust gas can be improved.
[0035]
A nut 5 having a hexagonal nut portion 51 and a screw portion 52 is rotatably fitted around the flange 4. In the temperature sensor 1, the seat surface 45 of the projecting portion 41 of the flange 4 is brought into contact with the attachment portion of the exhaust pipe and is fixed by the nut 5. In addition, a tubular joint 6 is joined in an airtight state on the radially outer side of the front end side step portion 44 of the sheath portion 42 in the flange 4. Specifically, the joint 6 is press-fitted into the distal end side step portion 44 of the sheath portion 42 such that the inner peripheral surface of the joint 6 overlaps the outer peripheral surface of the distal end side step portion 44 of the sheath portion 42, and the joint 6 and the distal end The side stepped portion 44 is laser welded in the circumferential direction. By performing this laser welding, as shown in FIG. 1, a welded portion W <b> 2 straddling the distal end side stepped portion 44 of the sheath portion 42 and the metal tube 3 is formed.
[0036]
A sheath member 8 that includes a pair of metal core wires 7 is disposed inside the metal tube 3, the flange 4, and the joint 6. The thermistor element 2 is connected via a Pt / Rh alloy wire 9 to a metal core wire 7 protruding from the distal end side of the sheath member 8 inside the metal tube 3. This alloy wire 9 is fired simultaneously with the thermistor element 2. The alloy wire 9 and the metal core wire 7 are resistance-welded to each other. Although not shown in detail, the sheath member 8 insulates between a metal outer cylinder made of SUS310S, a pair of conductive metal core wires 7 made of SUS310S, and the like, and between the outer cylinder and each metal core wire 7. And an insulating powder for holding the metal core wire 7.
[0037]
A lead wire 12 for connecting a pair of external circuits (e.g., an ECU of a vehicle) is connected to a metal core wire 7 protruding to the rear end side of the sheath member 8 inside the joint 6 via a crimping terminal 11. The pair of metal core wires 7 and the pair of crimp terminals 11 are insulated from each other by an insulating tube 15. The lead wire 12 is obtained by coating a conductive wire made of a stainless alloy with an insulating coating material. These lead wires 12 are enclosed in an auxiliary ring 13 made of heat-resistant rubber. When the auxiliary ring 13 is round-clamped or hexagonally-clamped from above the joint 6, both the members 13 and 6 are joined to each other while maintaining airtightness. Thereby, the thermistor element 2 is accommodated in the closed space formed by using the metal tube 3, the flange 4 and the joint 6 as a metal surrounding member. The output of the thermistor element 2 is taken out from the metal core wire 7 of the sheath member 8 to the external circuit (not shown) through the lead wire 12, and the temperature of the exhaust gas is detected.
[0038]
Here, in the temperature sensor 1 of the present embodiment, when the atmosphere enters the inside of the joint 6 from the outside through the gap inside the lead wire 12, the atmosphere is connected to the joint 6, the metal tube 3, and the flange. Since the inside of 4 is formed in the closed space, the metal tube 3 enters. Therefore, in the temperature sensor 1, ventilation from the inside of the lead wire 12 to the inside of the metal tube 3 is ensured, and even if the metal tube 3 that houses the thermistor element 2 is oxidized, The decrease in oxygen concentration can be suppressed, and the change in characteristics of the thermistor element 2 can be suppressed.
[0039]
Since the temperature sensor 1 is used in a high temperature environment as high as 1000 ° C., each component member needs to have sufficient heat resistance. Therefore, the metal tube 3, the flange 4 and the metal core wire 7 are formed of SUS310S which is a heat-resistant alloy containing Fe as a main component and containing C, Si, Mn, P, S, Ni and Cr. The joint 6 is formed on SUS304.
[0040]
Then, the manufacturing method of the temperature sensor 1 of this Embodiment mentioned above is demonstrated. First, a cold forging or / and cutting process is performed on the metal body of SUS310S, a through hole 46 including a front end side through hole 47 and a rear end side through hole 48, a front end side stepped portion 44, and a rear end side stepped portion. A flange 4 is formed having a two-stage sheath portion 42 having 46 and a projecting portion 41 located on the distal end side of the sheath portion 42 and projecting radially outward. The rear end side through-hole 48 of the flange 4 may be formed simultaneously with the formation of the flange 4 or may be formed by performing a cutting process after cold-forging the flange 4. Further, a separate flat SUS310S steel plate is prepared, this steel plate is set at a predetermined position of a die mold, and then deep drawn using a punch to form the entire metal tube 3. By this deep drawing, a metal tube 3 having a cylindrical shape with the front end side 31 closed and having the above-described metal tube main body portion, metal tube diameter changing portion, and metal tube rear end portion is formed.
[0041]
Next, the metal tube 3 and the flange 4 are press-fitted and fixed. Specifically, the metal tube 3 is inserted into the rear end side through hole 48 of the flange 4 from its front end side 31. Then, the outer peripheral surface of the metal tube rear end portion 33 and the inner peripheral surface of the front end side through hole 47 located in the region corresponding to the rear end step portion 43 of the sheath portion 42 are press-fitted and fixed. At the time of this press-fitting process, in this embodiment, when the outer peripheral surface of the distal end side of the metal tube rear end portion 33 comes into contact with the inner peripheral surface of the rear end side through hole 48 of the flange 4, the inner peripheral surface of the rear end side through hole 48 By the centering effect due to the taper shape, the metal tube 3 and the flange 4 are guided in the direction in which the axial centers coincide. Therefore, it is possible to perform press-fitting of both in a form that suppresses misalignment of both. Further, since the inner peripheral surface of the rear end side through hole 48 is tapered, the friction resistance at the beginning of press-fitting of the metal tube rear end portion 33 into the through hole 46 of the flange 4 can be reduced, and the press-fitting load can be reduced. Can be reduced. Therefore, deformation of the metal tube such as buckling can be suppressed. In addition, since the metal tube 3 is formed with a tapered metal tube diameter changing portion, coupled with the taper-shaped rear end side through hole 48, the press-fitting load is further reduced, and the deformation of the metal tube is further suppressed. be able to.
[0042]
Then, after press-fitting the metal tube 3 and the flange 4, the overlapping portion between the outer peripheral surface of the metal tube rear end portion 33 and the inner peripheral surface of the front end side through hole 47 is laser welded in the circumferential direction. Next, an assembly in which a predetermined amount of unsolidified cement 10 and pellets 14 are filled in the metal tube 3 and the tip of the metal core wire 7 of the sheath member 8 and the electrode of the thermistor element 2 are connected is connected to the thermistor. The metal tube 3 is inserted from the element 2 side. Thereafter, the cement 10 is solidified. Next, the rear end portion of the metal core wire 7 of the sheath member 8 and the lead wire 12 are connected using a crimping terminal 11 by a known method. Thereafter, the tubular joint 6 is press-fitted radially outward of the distal end side step portion 44 of the sheath portion 42, and the joint 6 and the distal end side step portion 44 are laser welded in the circumferential direction. Then, the auxiliary ring 13 and the nut 5 are assembled as appropriate. In this way, the temperature sensor 1 is completed.
[0043]
As described above, the temperature sensor 1 of the present embodiment is inserted into the flange 4 from the metal tube main body 33 side having a diameter smaller than the minimum inner diameter of the front end side through-hole 47 of the flange 4, and the rear end of the metal tube The portion 33 and the flange 4 are press-fitted and fixed. Therefore, it is easy to insert the metal tube 3 into the flange 4. Further, the metal tube rear end portion 33 is press-fitted and fixed to the flange 4 such that the press-fitting length between the metal tube rear end portion 33 and the front end side through hole 47 in the axial direction is smaller than the length of the front end side through hole 47. Therefore, the press-fitting length can be shortened, and deformation of the metal tube such as buckling can be suppressed. Further, among the through holes of the flange, the rear end side through hole 48 has a tapered shape with a larger inner diameter toward the rear end side, so that the press-fitting load can be reduced, and the deformation of the metal tube such as buckling can be further reduced. Can be suppressed.
[0044]
Further, the temperature sensor 1 of the present embodiment has a shorter press-fitting length as compared with the conventional one, so that heat sinking from the heat sensitive part to the flange can be reduced, improving responsiveness and preventing deterioration in temperature measurement accuracy. An effect is obtained. Furthermore, since the rear end portion through hole 48 of the flange 4 is tapered, a space is formed between the inner peripheral surface of the rear end portion through hole 48 and the outer peripheral surface of the metal tube rear end portion 33, and the metal A space is also formed between the outer peripheral surface of the tube main body portion 33 and the inner peripheral surface of the distal end side through hole 47. For this reason, the heat drawn from the flange is further reduced, and further improvement in responsiveness and reduction in temperature measurement accuracy can be suppressed.
[0045]
Furthermore, in the temperature sensor 1 of the present embodiment, the metal tube 3 and the flange 4 are integrally joined by laser welding, but the welded portion W1 formed by laser welding faces the exhaust pipe in the flange 4. It is formed in the sheath part 42 located in the rear end side instead of the protrusion part 41 at the front end side. Thus, in the exhaust pipe, a heat transfer path from the heat sensitive part of the temperature sensor 1 (a part closer to the thermistor element 2 than the seating surface of the flange 4) to the flange 4 through the welded part is not formed, and the heat sensitive part is connected to the flange. The degree of heat pulling to 4 etc. can be suppressed as compared with the conventional case. As a result, it is possible to obtain an effect of improving responsiveness and preventing a decrease in temperature measurement accuracy, and it is possible to suppress the temperature increase of the joint 6 and maintain the reliability of the auxiliary ring 13.
[0046]
In addition, since the welded portion W1 between the metal tube 3 and the flange 4 is not exposed to the exhaust pipe, oxidation that tends to occur on the inner surface of the welded portion can be effectively suppressed, and as a result, the thermistor element 2 changes its characteristics. On the other hand, it is possible to improve the airtight reliability against the exhaust gas.
[0047]
Furthermore, the entire metal tube 3 is formed by deep drawing of a SUS310S steel plate. Therefore, since the welded portion that is easily oxidized is not provided at the distal end portion of the metal tube 3, the temperature sensor 1 having excellent durability and reliability can be obtained.
[0048]
The present invention is not limited to the specific embodiments described above, and various modifications can be made within the scope of the present invention depending on the purpose and application.
For example, the responsiveness of the temperature sensor can be further improved by making the thickness of the tip of the metal tube 3 thinner than the other portions. Further, the outer diameter of the flange 4 is smaller than the outer diameter of the metal tube main body 34 or the sheath member 8, and the inner diameter is larger than the outer diameter of the metal tube main body 34 or the sheath member 8. The cylindrical portion may be integrally formed, and the cylindrical portion and the metal tube main body 34 or the sheath member 8 may be crimped and fixed by caulking the outer peripheral surface of the cylindrical portion radially inward. Thereby, it can be set as the temperature sensor excellent in earthquake resistance in which breakage of the metal tube main-body part 34 or the sheath member 8 does not occur much more easily. The temperature sensor of the present invention can be applied not only to an exhaust temperature sensor but also to a temperature sensor attached to a flow passage through which a liquid such as water or oil flows as a fluid to be measured.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a temperature sensor in which a metal tube containing a thermistor element is press-fitted into a sheath portion of a flange and laser-welded in the sheath portion in the circumferential direction.
2 is a partial cross-sectional view showing an enlarged peripheral portion of a flange of the temperature sensor of FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Temperature sensor, 2 ... Thermistor element, 3 ... Metal tube, 33 ... Metal tube rear end part, 34 ... Metal tube main-body part, 4 ... Flange, 41 ... Projection part, 42 ... sheath part, 43 ... rear end side step part, 44 ... tip side step part, 6 ... joint, 7 ... metal core wire, 8 ... sheath member, 12 ... Lead wires, W1, W2 ... welded parts

Claims

A cylindrical metal tube extending in the axial direction with the tip side closed, and an element housed in the metal tube, the electrical characteristics of which vary with temperature,
A flange having a through-hole for inserting the metal tube and disposed so as to surround the outer peripheral surface of the metal tube;
In a method for manufacturing a temperature sensor comprising:
A metal tube rear end having an outer diameter larger than the minimum inner diameter of the through-hole, and a metal tube main body having a diameter smaller than the minimum inner diameter of the through-hole, located on the distal end side of the metal tube rear end; Is inserted into the flange from the distal end side of the metal tube, and the metal tube is disposed over the entire through hole, and then the outer peripheral surface of the metal tube main body and the inner peripheral surface of the through hole A method of manufacturing a temperature sensor, wherein the flange is press-fitted and fixed to the rear end portion of the metal tube so that a space is formed between them .

The through hole of the flange is composed of a front end side through hole having a substantially constant inner diameter, and a rear end side through hole located on the rear end side of the front end side through hole and having a larger inner diameter toward the rear end side, The temperature sensor manufacturing method according to claim 1, wherein the metal tube rear end portion is press-fitted from the rear end side through hole side.

3. The method of manufacturing a temperature sensor according to claim 2, wherein in the axial direction, a press-fitting length between the rear end portion of the metal tube and the front end side through hole is smaller than a length of the front end side through hole. .

The flange has a sheath portion extending in the axial direction, and a projecting portion located on the distal end side of the sheath portion and projecting radially outward, and the rear end portion of the metal tube is located on the sheath portion. 4. The method of manufacturing a temperature sensor according to claim 1, wherein the temperature sensor is press-fitted and fixed.

The method for manufacturing a temperature sensor according to claim 4, wherein the rear end portion of the metal tube is welded in a circumferential direction to a region of the sheath portion where the front end side through hole is formed.

A cylindrical metal tube extending in the axial direction with the tip side closed, and an element housed in the metal tube, the electrical characteristics of which vary with temperature,
A flange having a through-hole for inserting the metal tube and disposed so as to surround the outer peripheral surface of the metal tube;
In a temperature sensor comprising:
The metal tube is located on the rear end of the metal tube having an outer diameter larger than the minimum inner diameter of the through hole and on the tip side of the rear end of the metal tube, and has a smaller diameter than the minimum inner diameter of the through hole. A metal tube main body,
The metal tube is arranged over the entire through-hole, and the press-fitting length between the rear end portion of the metal tube and the through-hole is smaller than the length of the through-hole in the axial direction, and the metal A temperature sensor, wherein the rear end portion of the metal tube is press-fitted and fixed to the flange so that a space is formed between the outer peripheral surface of the tube main body and the inner peripheral surface of the through hole .

The through hole of the flange is composed of a front end side through hole having a substantially constant inner diameter, and a rear end side through hole located on the rear end side of the front end side through hole and having a larger inner diameter toward the rear end side, The temperature sensor according to claim 6, wherein an outer diameter of the rear end portion of the metal tube is larger than an inner diameter of the distal end side through hole.

The flange has a sheath portion extending in the axial direction, and a projecting portion located on the distal end side of the sheath portion and projecting radially outward, and the rear end portion of the metal tube is located on the sheath portion. The temperature sensor according to claim 6 or 7, wherein the temperature sensor is press-fitted and fixed.

The temperature sensor according to claim 8, wherein the rear end portion of the metal tube is welded in a circumferential direction to a region of the sheath portion where the front end side through hole is formed.