JP2004177182A

JP2004177182A - Temperature sensor

Info

Publication number: JP2004177182A
Application number: JP2002341431A
Authority: JP
Inventors: Masaki Iwatani; 雅樹岩谷; Takaaki Chiyousokabe; 孝昭長曽我部; Takeshi Hanzawa; 剛半沢; Masahiko Nishi; 雅彦西
Original assignee: NGK Spark Plug Co Ltd
Current assignee: Niterra Co Ltd
Priority date: 2002-11-25
Filing date: 2002-11-25
Publication date: 2004-06-24
Anticipated expiration: 2022-11-25
Also published as: JP3826098B2

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable temperature sensor having both superior durability in the sensor itself and speedy responsivity even in the case where a heat sensing part is reduced in diameter or thinned in wall thickness. SOLUTION: A cylindrical metal tube 3 housing a thermistor element 2 of which the electrical characteristics change according to temperature is inserted in a flange 4. The metal tube 3 is fixed to a tip-side sheath part 43 by caulking. Since a welded part L1 between the metal tube 3 and the flange 4 is not exposed to a high-temperature environment in an exhaust gas passage in the temperature sensor 1 of this constitution, the oxidation of the welded part hardly occurs, and it is possible to improve airtightness reliability to exhaust gases. COPYRIGHT: (C)2004,JPO

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、素子が筒状金属製部材の先端側に封止されてなる温度センサであって、測温を必要とする各種の用途に用いることができ、特に自動車排気ガス浄化装置の触媒コンバータ内部及び排気管内等の、温度変化、振動等の激しい環境下の温度検出においても十分な耐久性を有する温度センサに関する。
【０００２】
【従来の技術】
従来より、図３に示すように、先端側にサーミスタ素子２０１が接続され、後端側に外部回路接続用のリード線２０２が接続される金属芯線を内包したシース部材２０３と、先端側が閉塞し、内部にサーミスタ素子２０１を収納するようにシース部材２０３に接合された金属キャップ２０４と、シース部材２０３の外周を取り囲むように配置され、先端側に延びる鞘部２０６を有するフランジ２０５とを備え、シース部材２０３と鞘部２０６をレーザー溶接により固定した構造の温度センサ２００が知られている（特許文献１参照）。この温度センサは、自動車の触媒コンバータ内部及び排気管内等の、低温から高温まで温度変化が大きく、且つ振動の激しい温度検出に使用される。
【０００３】
【特許文献１】
特開２０００−２３４９６２
【０００４】
【発明が解決しようとする課題】
特許文献１のような従来の温度センサの場合、例えば排気管に装着されたときに、フランジとシース部材との溶接部が排気ガス通路に配置されることになる。
このとき、溶接部が高温環境下に直接晒されるために同溶接部が酸化してしまい、長期間の使用によりセンサ自体の耐久性を損なうおそれがある。そのために、温度センサの信頼性を高めるべく、排気ガス通路内に配置されるレーザー溶接等の溶接部をできるだけ少なくさせた構造が望まれている。
【０００５】
本発明は、上記の従来の問題点を解決するものであり、自動車の触媒コンバータ内部、或は排気管内のように、温度変化、振動とともに激しい環境下に使用した場合でも、優れた耐久性を有し、信頼性の高い温度センサを提供することを目的とする。
【０００６】
【課題を解決する手段】
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、前記金属チューブの先端側内部に収納され、温度によって電気的特性が変化する素子と、前記金属チューブの外周面を取り囲むように配置されるフランジと、を備える温度センサであって、前記フランジは、径方向外側に突出する突出部と、該突出部の先端側に位置し、該突出部の径より径小で、前記軸線方向に延びる先端側鞘部を有し、前記金属チューブと前記先端側鞘部とが加締めにより固定されていることを特徴とする。
【０００７】
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、最高温度で１０００℃程度の高温環境下での使用に供されることがあり、この場合には、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、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。そこで、本発明では、金属チューブと先端側鞘部が加締めにより固定されている構造である。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とを固定するための溶接部が流通路内に配置されることがない。よって、長期間の使用によるセンサ自体の耐久性を損なうことなく、さらに、素子に特性変化が生じることがない、信頼性の高い温度センサとすることができる。
【０００８】
ところで、温度センサでは、先端側鞘部の肉厚及び長さは、感熱部（フランジの先端部よりサーミスタ素子側の部位）の径及び長さに対応して設定されている。これは、温度センサの応答性を向上させるために、感熱部を縮径化、或は薄肉化することがある。また、触媒コンバータ、或は排気管への取り付け時にできるだけ触媒コンバータ、或は排気管の中心部に近づけることが好ましいため、感熱部の長さをより長くすることがある。しかし、これらにより、感熱部の共振周波数が低周波側へシフトし、自動車等に使用される内燃機関の排気系の振動周波帯に近づいていく虞がある。そこで本発明では、感熱部の径或いは長さの変化に対して、フランジの先端側鞘部の肉厚或いは長さを調整することで、感熱部の共振周波数が、内燃機関の排気系の振動周波帯に近づくのを防ぐことができる。
【０００９】
なお、特許文献１の温度センサでも本発明のように、フランジの先端側に鞘部を持つ構成となっており、鞘部の肉厚、及び長さを調整することで、上記効果を得ることができるように考えられる。しかし、特許文献１の温度センサでは、鞘部の長さを長くすると、より溶接部は先端側に位置することにより、溶接部がさらに被測定ガスに晒されることになる。よって、溶接部の酸化が助長されることとなり、長期間の使用にこの温度センサを使用することは、現実的でない。また、鞘部の肉厚を単純に厚くすると、溶接部を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することが必要となり、単純なコストアップにつながる同時に良好な溶接をするための条件設定が難しくなってしまうので、現実的でない。つまり、金属チューブと先端側鞘部とが加締めにより固定される構造とすることで、優れた耐久性を有し、かつ感熱部の共振周波数が、内燃機関の排気系の振動周波帯に近づくのを防ぐことができる。
【００１０】
また、本発明の温度センサは、金属チューブと先端側鞘部とが多角加締めまたは丸加締めにより固定されているとよい。このように、金属チューブと先端側鞘部とが多角加締めまたは丸加締めにより固定されていることで、フランジと金属チューブとの密着強度に優れ、感熱部の共振周波数が内燃機関の排気系の振動周波帯に近づくのをより有効に防ぐことができる。
【００１１】
また、本発明の温度センサでは、フランジは突出部の後端側に位置し軸線方向に延びる後端側鞘部を有し、金属チューブは少なくとも後端側鞘部に圧入または加締め固定され、該金属チューブと該後端側鞘部とが周方向にわたって溶接されているとよい。
【００１２】
素子を収納する金属チューブをフランジの少なくとも後端側鞘部に圧入又は加締め固定しつつ、金属チューブと後端側鞘部とを周方向に溶接しているため、溶接強度に優れると共に、フランジと金属チューブとの密着強度に優れる。したがって、本発明の温度センサは、自動車等の振動の激しい環境下に使用した場合にも耐久性に優れ、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。
【００１３】
また、金属チューブとフランジが溶接により一体に接合されるが、この溶接は、フランジの内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（具体的には先端側鞘部）ではなく、突出部の後端側に位置する後端側鞘部において行われるものである。上記にも述べたが、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とを固定するための溶接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との溶接部が、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。よって、本発明では、金属チューブ自身がフランジの後端側鞘部に溶接固定される構造であるため、上述したように同溶接部が被測定流体に晒されることがなくなり、溶接部において生じやすい酸化を有効に防止することができると共に、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。これは金属チューブと先端側鞘部とが加締めにより固定される構造により成しえたものである。
【００１４】
金属チューブとフランジの後端側鞘部との溶接部を同後端側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後端側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る同時に良好な溶接をするための条件設定が難しくなってしまい、逆に後端側鞘部全体の肉厚を薄くすると後端側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、フランジの後端側鞘部を、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、金属チューブを後端側鞘部の後端側段部に溶接している。つまり、後端側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、後端側鞘部と金属チューブ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、後端側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。尚、後端側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。
【００１５】
尚、金属チューブとフランジとの溶接の手段は特に限定されず、レーザー溶接、プラズマ溶接、アルゴン溶接、電子ビーム溶接等を挙げることができる。
【００１６】
さらに、上述したいずれかの温度センサであって、先端側に素子が接続され、後端側に外部回路接続用のリード線が接続される金属芯線を内包したシース部材と、フランジの後端側鞘部の径方向外側に気密状態に接合されると共に、軸線方向の後方に向かって延びる筒状の継手とを備え、シース部材の先端側が金属チューブの内部に挿通されるとともに、金属チューブの後端側及びリード線の先端側が継手の内部に配置されていると良い。
【００１７】
本発明の温度センサにあっては、金属チューブ内に収納する素子と、外部回路接続用のリード線とを金属芯線を内包するシース部材を介して接続されるため、金属チューブとリード線との間に別途絶縁粉末を充填するなどの工程が不要となり、両者の電気的な絶縁が確実になされる。また、本発明では、シース部材の先端側を金属チューブの内部に挿通させた状態で、金属チューブの後端側をフランジの後端側に別途接合された継手の内部に配置させると共に、リード線の先端側を継手の内部に配置させている。そのため、素子が、金属チューブ、フランジ及び継手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一方で、上記閉空間とセンサ自身の外部とは、リード線の内部（リード線内の空隙）、継手の内部空間、シース部材の先端側外周面と金属チューブとの内周面との間の空隙とから形成される通気経路によって通気が確保されることになる。
【００１８】
したがって、本発明では、金属チューブの内面が酸化されることがあっても、外部と金属チューブの内部との通気が確保されるので、金属チューブ内の酸素濃度の低下を抑えられ、上記酸化に伴う素子の特性変化を抑制することができる。
尚、継手とフランジとの接合の手段は特に限定されず、レーザー溶接、プラズマ溶接、アルゴン溶接、電子ビーム溶接、ロー付け接合等が挙げられる。
【００１９】
また、上記構成の温度センサにあっては、後端側鞘部は、先端側に位置する先端側段部と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、金属チューブは、後端側鞘部の後端側段部に溶接されるとともに、継手は、後端側鞘部の先端側段部の外周面に周方向にわたって接合されていると良い。
【００２０】
上述したように、フランジの後端側鞘部を、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、金属チューブを後端側鞘部の後端側段部に溶接することで、後端側鞘部と金属チューブとの溶接強度を十分に確保することができる一方、後端側鞘部ひいてはフランジの機械的強度を確保することができる。さらに、本発明の温度センサにあっては、筒状の継手をフランジの先端側段部の外周面に接合している。そのため、フランジの後端側鞘部の後端側段部と金属チューブとの溶接部が、継手内部に収納されることになる。したがって、継手が、金属チューブとフランジとの溶接部に塩水や水分が付着するのを保護する役割を果たし、同溶接部が水分等の影響で腐食されるのが抑えられる。
【００２１】
ついで、他の解決手段は、先端側に温度によって電気的特性が変化する素子が接続され、後端側に外部回路接続用のリード線が接続される金属芯線を内包したシース部材と、先端側が閉塞した軸線方向に延びる筒状をなし、内部に素子に収納する形態で後端側内周がシース部材の先端側外周の周方向にわたって接合された金属キャップと、シース部材の外周面を取り囲むように配置されるフランジ部と、を備える温度センサであって、フランジは、径方向外側に突出する突出部と、該突出部の先端側に位置し、該突出部の径より径小で、軸線方向に延びる先端側鞘部を有し、前記シース部材と前記先端側鞘部とが加締めにより固定されていることを特徴とする温度センサである。
【００２２】
本発明の温度センサでは、シース部材と先端側鞘部が加締めにより固定されている構造である。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、フランジとシース部材とを固定するための溶接部が流通路内に配置されることがない。よって、シース部材自身がフランジの先端側鞘部が加締めにより固定される構造であるため、上述したように同溶接部が被測定流体に晒されることがない。よって、優れた耐久性を有し、信頼性の高い温度センサとすることができる。
【００２３】
ところで、本発明の温度センサでは、先端側鞘部の肉厚及び長さは、感熱部（フランジの先端部よりサーミスタ素子側の部位）の径及び長さに対応して設定されている。これは、温度センサの応答性を向上させるために、感熱部を縮径化、或は薄肉化することがある。また、触媒コンバータ、或は排気管への取り付け時にできるだけ触媒コンバータ、或は排気管の中心部に近づけることが好ましいため、感熱部の長さをより長くすることがある。しかし、これらにより、感熱部の共振周波数が低周波側へシフトし、自動車等に使用される内燃機関の排気系の振動周波帯に近づいていく虞がある。そこで本発明では、感熱部の径或は長さの変化に対して、フランジの先端側鞘部の肉厚或は長さを調整することで、感熱部の共振周波数が、内燃機関の排気系の振動周波帯に近づくのを防ぐことができる。
【００２４】
また、本発明の温度センサは、シース部材と先端側鞘部とが多角加締めまたは丸加締めにより固定されているとよい。このように、シース部材と先端側鞘部とが多角加締めまたは丸加締めにより固定されていることで、フランジとシース部材との密着強度に優れると共に、感熱部の共振周波数が内燃機関の排気系に近づくのを有効に防ぐことができる。
【００２５】
また、本発明の温度センサでは、フランジは突出部の後端側に位置し軸線方向に延びる後端側鞘部を有し、シース部材は少なくとも後端側鞘部に圧入または加締め固定され、該シース部材と該後端側鞘部とが周方向にわたって溶接されているとよい。
【００２６】
素子を収納するシース部材をフランジの少なくとも後端側鞘部に圧入又は加締め固定しつつ、シース部材と後端側鞘部とを周方向に溶接しているため、溶接強度に優れると共に、フランジとシース部材との密着強度に優れる。したがって、本発明の温度センサは、自動車等の振動の激しい環境下に使用した場合にも耐久性に優れ、被測定流体に対する気密の信頼性をより向上させることができる。
【００２７】
また、シース部材とフランジが溶接により一体に接合されるが、この溶接は、フランジの内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（具体的には先端側鞘部）ではなく、突出部の後端側に位置する後端側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、フランジとシース部材とを固定するための溶接部が流通路内に配置されることがない。換言すれば、フランジとシース部材との溶接部が、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。よって、本発明では、シース部材自身がフランジの後端側鞘部に溶接固定される構造であるため、上述したように同溶接部が被測定流体に晒されることがなくなり、溶接部において生じ易い酸化を有効に防止することができると共に、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。
【００２８】
シース部材とフランジの後端側鞘部との溶接部を同後端側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後端側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る同時に良好な溶接をするための条件設定が難しくなってしまい、逆に後端側鞘部全体の肉厚を薄くすると後端側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、フランジの後端側鞘部を、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、シース部材を後端側鞘部の後端側段部に溶接している。つまり、後端側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、後端側鞘部とシース部材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、後端側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。尚、後端側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】
尚、上述したいずれかの温度センサであって、シース部材とフランジの後端側鞘部との溶接は特に限定されず、レーザー溶接、プラズマ溶接、アルゴン溶接、電子ビーム溶接等を挙げることができる。
【００３０】
【発明の実施の形態】
以下、本発明の実施例により更に具体的に説明する。
実施例１（フランジの先端面に軸線方向に延びた先端側鞘部により金属チューブが覆われている温度センサ）
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の構造を示す部分破断断面図である。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】
軸線方向に延びる金属チューブ３は、鋼板の深絞り加工により先端側３１が閉塞した筒状をなしており、この先端側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。金属チューブ３の後端側３２は開放されており、この後端側３２はステンレス合金製のフランジ４の内側に挿通されている。
【００３２】
このフランジ４は、径方向外側に突出する突出部４１と、その突出部４１の先端側に位置し、該突出部の径より径小で、軸線方向に延びる先端側鞘部４３と、突出部の後端側に位置し、軸線方向に延びる後端側鞘部４２とを有している。突出部４１は、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する座面４５を有する環状に形成されており、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。
【００３３】
先端側鞘部４３は、環状に形成されており、金属チューブ３は、自身の後端側３２からフランジ４の突出部４１の先端側に挿入されて、金属チューブ３の外周面と先端側鞘部４３の内周面との重なり合う部分が、加締められている。この加締めによる固定により、図１に示すように、先端側鞘部４３に加締め固定部Ｃ１が形成され、金属チューブ３がフランジ４に対して固定される。なお、本実施例では、加締め固定部Ｃ１は八角加締めにより固定されている。
【００３４】
温度センサ１は、金属チューブ３と先端側鞘部４３が加締めにより固定されている構造であることより、温度センサ１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とを固定するための溶接部が流通路内に配置されることがない。よって、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、信頼性の高い温度センサ１とすることができる。
【００３５】
なお、金属チューブ３とフランジ４の先端側鞘部４３とを加締めにより固定し、先端側鞘部４３の肉厚及び長さを調整することで、感熱部８１の共振周波数が低周波側へシフトすることによる、自動車等に使用される内燃機関の排気系の振動周波帯に近づいていくことを防ぐことができる。また、先端側鞘部４３により、振動の支点が強化されるため、機械的強度も増加される。
【００３６】
さらに、温度センサ１は、金属チューブ３と先端側鞘部４３とが八角加締めにより固定されていることより、感熱部の共振周波数が内燃機関の排気系の振動周波帯に近づいていくことをより有効に防ぐことができる。なお、フランジ４の先端側鞘部４３と金属チューブ３とを八角加締めで固定する構造に限られず、六角以上（例えば、六角、十角など）の加締めにより固定しても良く、さらには丸加締めにより固定しても良い。
【００３７】
また、温度センサ１は、金属チューブ３と先端側鞘部４３とが多角加締めにより固定されている場合、感熱部８１からフランジ４等への熱引きの度合いを従来に比べて抑えることができる。これは、多角加締めの場合、加締め固定部Ｃ１以外については、温度センサ１の感熱部８１からフランジ４に至る伝熱経路が形成されにくいためである。よって、温度センサ１は、熱引きの度合いを従来に比べて抑えることができ、応答性の向上、温度測定精度の低下防止の効果を得ることもできる。
【００３８】
フランジ４の後端側鞘部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４６とを備える二段形状をなしている。
【００３９】
金属チューブ３は、自身の後端側３２からフランジ４の突出部４１の先端側に挿入されて、後端側鞘部４２の内側に圧入されている。そして、金属チューブ３の外周面と後端側鞘部４２の後端側段部４６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ー溶接されている。このレーザー溶接がなされることにより、図１に示すように、後端側鞘部４２の後端側段部４６と金属チューブ３とに跨る溶接部Ｌ１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。
【００４０】
このように、金属チューブ３をフランジ４の後端側鞘部４２に圧入しつつ、後端側鞘部４２の後端側段部４６にレーザー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。したがって、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より向上させることができる。なお、フランジ４の後端側鞘部４２と金属チューブ３との密着性を確保するにあたっては、後端側鞘部４２に金属チューブ３を圧入する手法に限られず、後端側鞘部４２と金属チューブ３とを径方向内側に向かって加締めても良く、さらには上記圧入と上記加締めとを併用させても良い。
【００４１】
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の内で後端側鞘部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、後端側鞘部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が後端側鞘部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ー溶接している。このレーザー溶接がなされることにより、図１に示すように、後端側鞘部４２の先端側段部４４と継手６とに跨る溶接部Ｌ２が形成される。
【００４２】
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。尚、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。
【００４３】
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。尚、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多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。
【００４４】
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。したがって、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。
【００４５】
尚、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。
【００４６】
実施例２（フランジの先端面に延設された先端側鞘部によりシース部材が覆われている温度センサ）
次に、実施例２の温度センサ１００について、図面を参照しつつ説明する。尚、実施例２の温度センサ１００は、実施例１の温度センサ１と比較して、サーミスタ素子２を収容するための部材、フランジの先端側鞘部に加締められる部材、及びフランジの後端側鞘部にレーザー溶接される部材が主に異なるものであり、その他の部分についてはほぼ同様である。従って、実施例１と異なる部分を中心に説明し、同様な部分については、説明を省略または簡略化する。
【００４７】
まず、温度センサ１００の構造を示す部分破断断面図を図２に示す。上述した実施例１の温度センサ１では、サーミスタ素子２を金属チューブ３の内側に収納すると共に、その金属チューブ３とフランジ４とのレーザー溶接及び先端側鞘部４３での加締めにより固定していた（図１参照）。これに対し、実施例２の温度センサ１００では、サーミスタ素子２を金属キャップ１４に収納し、この金属キャップ１４をシース部材８に接合した状態で、シース部材８とフランジ４とのレーザー溶接及び先端側鞘部４３での加締めにより固定している。
【００４８】
軸線方向に延びる金属キャップ１４は、自身の先端側１３１が閉塞された筒状をなしており、この先端側１３１の内部にサーミスタ素子２が収納されている。
この金属キャップ１４は、ＳＵＳ３１０Ｓ等のステンレス合金から形成されている。尚、サーミスタ素子２は、自身の電極線（Ｐｔ／Ｒｈ合金線）９を介してシース部材８の先端側から突出する金属芯線７に接続される。そして、金属キャップ１４の後端側１３２は開放されており、この後端側１３２の内周面が一対の金属芯線７を内包するシース部材８（詳細にはシース部材８の外筒）の外周面に重なり合った状態で、周方向にわたってレーザー溶接されている。これにより、金属キャップ１４がシース部材８に固定される。
【００４９】
フランジ４は、径方向外側に突出する突出部４１と、その突出部４１の先端側に位置し、該突出部の径より径小で、軸線方向に延びる先端側鞘部４３と、突出部の後端側に位置し、軸線方向に延びる後端側鞘部４２とを有している。
【００５０】
先端側鞘部４３は、上記したように環状に形成されており、シース部材８は、自身の後端側からフランジ４の突出部４１の先端側に挿入されて、シース８の外周面と先端側鞘部４３の内周面との重なり合う部分が、加締められている。この加締めによる固定により、図２に示すように、先端側鞘部４３に加締め固定部Ｃ２が形成され、シース部材８がフランジ４に対して固定される。なお、本実施例では、加締め固定部Ｃ２は八角加締めにより固定されている。
【００５１】
また、温度センサ１００は、シース部材８と先端側鞘部４３とが多角加締めにより固定されている場合、感熱部８１からフランジ４等への熱引きの度合いを従来に比べて抑えることができる。これは、多角加締めの場合、加締め固定部Ｃ２以外では、温度センサ１００の感熱部８１からフランジ４に至る伝熱経路が形成さにくいためである。よって、温度センサ１００は、熱引きの度合いを従来に比べて抑えることができ、応答性の向上、温度測定精度の低下防止の効果を得ることもできる。
【００５２】
また、温度センサ１００は、シース部材８と先端側鞘部４３が加締めにより固定されている構造であることにより、温度センサ１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４とシース部材８とを固定するための溶接部Ｌ３が流通路内に配置されることがない。優れた耐久性を有し、信頼性の高い温度センサ１００とすることができる。
【００５３】
なお、シース部材８とフランジ４の先端側鞘部４３とを加締めにより固定する構造においては、先端側鞘部４３の肉厚及び長さを調整することで、感熱部８１の共振周波数が低周波側へシフトすることによる、自動車等に使用される内燃機関の排気系の振動周波帯に近づいていくことを防ぐことができる。また、先端側鞘部４３により、振動の支点が強化されるため、機械的強度も増加される。
【００５４】
さらに、温度センサ１００は、シース部材８と先端側鞘部４３とが八角加締めにより固定されていることにより、感熱部の共振周波数が内燃機関の排気系の振動周波帯に近づいていくことより有効に防ぐことができる。
【００５５】
その上、フランジ４の後端側鞘部４２は、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４６とを備える二段形状をなしている。
【００５６】
シース部材８は、自身の後端側がフランジ４の内側に挿通された状態で、後端側鞘部４２の外周面の所定位置において径方向内側に向かって加締められ、フランジ４に対して固定されている。さらに、シース部材８の外周面と後端側鞘部４２の後端側段部４６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ー溶接されている。このレーザー溶接がなされることにより、図２に示すように、後端側鞘部４２の後端側段部４６とシース部材８（詳細にはシース部材８の外筒）とに跨る溶接部Ｌ３が形成され、シース部材８がフランジ４に対して強固に固定される。
【００５７】
このように、シース部材８をフランジ４の後端側鞘部４２に加締め固定しつつ、後端側鞘部４２の後端側段部４６にレーザー溶接を行うことにより、フランジ４とシース部材８との溶接強度に優れると共に、フランジ４とシース部材８との密着強度に優れる温度センサ１００とすることができる。したがって、自動車等の振動の激しい環境下において温度センサ１００が強い振動を受けても、シース部材８が振れ難く、シース部材８の折損等を抑制することができる。また、溶接部において生じ易い酸化を有効に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より向上させることができる。
【００５８】
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、実施形態の温度センサ１において、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１の応答性をさらに向上させることもできる。
【００５９】
さらに、実施例１の温度センサ１において、継手６が後端側鞘部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ー溶接しているのに限らず、継手６を先端側段部４４に加締め固定しつつ、継手６と先端側段部４４とを周方向にわたってレーザー溶接してもよい。それにより、継手６と先端側段部４４との溶接強度により優れると共に、継手６と先端側段部４４との密着強度により優れる温度センサ１００とすることができる。
【００６０】
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の外周面とフランジの先端側鞘部の内周面が加締められている温度センサを示す部分破断断面図である。
【図２】サーミスタ素子を収納する金属キャップを接合したシース部材の外周面とフランジの先端側鞘部の内周面が加締められている温度センサを示す部分破断断面図である。
【図３】サーミスタ素子を収納する金属キャップを接合したシース部材がフランジの鞘部において周方向にわたってレーザー溶接されている従来の温度センサを示す部分破断断面図である。
【符号の説明】
１、１００、２００・・・温度センサ、２・・・サーミスタ素子、３・・・金属チューブ、４・・・フランジ、４１・・・突出部、４２・・・後端側鞘部、４３・・・先端側鞘部、４４・・・先端側段部、４５・・・座面、４６・・・後端側段部、６・・・継手、７・・・金属芯線、８・・・シース部材、１２・・・リード線、Ｌ１、Ｌ２、Ｌ３・・・溶接部、Ｃ１、Ｃ２・・・加締め固定部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a temperature sensor including a thermistor or a metal resistor made of a semiconductor such as a metal oxide as a temperature-sensitive element. More specifically, it is a temperature sensor in which an element is sealed on the tip side of a cylindrical metal member, and can be used for various applications requiring temperature measurement. The present invention relates to a temperature sensor having sufficient durability even when detecting a temperature in a severe environment such as a temperature change and a vibration inside or inside an exhaust pipe.
[0002]
[Prior art]
Conventionally, as shown in FIG. 3, a sheath member 203 containing a metal core wire to which a thermistor element 201 is connected to a distal end side and a lead wire 202 for connecting an external circuit is connected to a rear end side, and a distal end side is closed. A metal cap 204 joined to the sheath member 203 so as to house the thermistor element 201 therein, and a flange 205 having a sheath portion 206 disposed to surround the outer periphery of the sheath member 203 and extending toward the distal end, A temperature sensor 200 having a structure in which a sheath member 203 and a sheath portion 206 are fixed by laser welding is known (see Patent Document 1). This temperature sensor is used for detecting a temperature in a catalytic converter and an exhaust pipe of an automobile which has a large temperature change from a low temperature to a high temperature and in which vibration is severe.
[0003]
[Patent Document 1]
JP-A-2000-234962
[0004]
[Problems to be solved by the invention]
In the case of a conventional temperature sensor as disclosed in Patent Document 1, for example, when the temperature sensor is mounted on an exhaust pipe, a welded portion between the flange and the sheath member is disposed in the exhaust gas passage.
At this time, since the welded portion is directly exposed to a high temperature environment, the welded portion is oxidized, and there is a possibility that the durability of the sensor itself may be impaired due to long-term use. Therefore, in order to increase the reliability of the temperature sensor, a structure in which the number of welds such as laser welding arranged in the exhaust gas passage is reduced as much as possible is desired.
[0005]
The present invention solves the above-mentioned conventional problems, and achieves excellent durability even when used in a severe environment with temperature change and vibration, such as inside a catalytic converter of an automobile or inside an exhaust pipe. It is an object of the present invention to provide a highly reliable temperature sensor.
[0006]
[Means to solve the problem]
The temperature sensor according to the present invention includes a cylindrical metal tube having a distal end closed and extending in the axial direction; an element housed inside the distal end of the metal tube, the electrical characteristics of which change with temperature; and an outer peripheral surface of the metal tube. And a flange disposed so as to surround the protrusion, wherein the flange is located on the tip side of the protrusion protruding radially outward, and has a diameter smaller than the diameter of the protrusion. And a tip side sheath portion extending in the axial direction, wherein the metal tube and the tip side sheath portion are fixed by caulking.
[0007]
When a temperature sensor is used to detect the exhaust gas temperature of an automobile, it may be used in a high-temperature environment at a maximum temperature of about 1000 ° C. In this case, not only the outer surface of the metal tube but also the inner surface may be used. Is oxidized, the oxygen concentration in the space in which the element is housed is remarkably reduced, and the characteristics of the element may be changed due to reduction of the surface of the element. This oxidation is particularly likely to occur on the outer and inner surfaces of the welded portion between the metal tube and the flange, and when the weld is formed on the tip side of the flange facing the flow passage, the weld itself is directly exposed to a high temperature environment. Because of the exposure, oxidation will be promoted. Then, in this invention, it is the structure by which the metal tube and the front end side sheath part are fixed by caulking. Thus, when the temperature sensor is mounted on the flow pipe through which the fluid to be measured flows, a welded portion for fixing the flange and the metal tube is not disposed in the flow passage. Therefore, a highly reliable temperature sensor can be provided without deteriorating the durability of the sensor itself due to long-term use and without causing a change in characteristics of the element.
[0008]
By the way, in the temperature sensor, the thickness and length of the sheath portion on the distal end side are set in accordance with the diameter and length of the heat-sensitive portion (the portion closer to the thermistor element than the distal end portion of the flange). This may reduce the diameter of the heat-sensitive part or make it thinner in order to improve the responsiveness of the temperature sensor. In addition, the length of the heat-sensitive portion may be longer because it is preferable that the heat-sensitive portion be as close to the central portion of the catalytic converter or the exhaust pipe as possible when attached to the catalytic converter or the exhaust pipe. However, due to these, the resonance frequency of the heat-sensitive part shifts to a lower frequency side, and may approach the vibration frequency band of the exhaust system of the internal combustion engine used in an automobile or the like. Therefore, in the present invention, the resonance frequency of the heat-sensitive portion is adjusted by adjusting the thickness or the length of the front end side sheath portion of the flange with respect to the change in the diameter or the length of the heat-sensitive portion, so that the vibration frequency of the exhaust system of the internal combustion engine is reduced. It can be prevented from approaching the frequency band.
[0009]
It should be noted that the temperature sensor of Patent Document 1 also has a sheath at the distal end side of the flange as in the present invention, and the above-described effects can be obtained by adjusting the thickness and length of the sheath. It is thought that it can be done. However, in the temperature sensor of Patent Literature 1, when the length of the sheath portion is increased, the welded portion is located closer to the distal end, so that the welded portion is further exposed to the gas to be measured. Therefore, oxidation of the welded portion is promoted, and it is not practical to use this temperature sensor for long-term use. In addition, if the thickness of the sheath is simply increased, it is necessary to set welding conditions higher in order to form the welded portion with sufficient welding strength, which leads to a simple cost increase and at the same time a favorable Setting the conditions for welding becomes difficult, which is not practical. That is, the structure in which the metal tube and the distal end side sheath portion are fixed by caulking has excellent durability, and the resonance frequency of the heat-sensitive portion approaches the vibration frequency band of the exhaust system of the internal combustion engine. Can be prevented.
[0010]
Further, in the temperature sensor of the present invention, the metal tube and the distal end side sheath portion are preferably fixed by polygonal caulking or round caulking. As described above, since the metal tube and the distal end side sheath portion are fixed by polygonal caulking or round caulking, the adhesion strength between the flange and the metal tube is excellent, and the resonance frequency of the heat sensitive part is reduced by the exhaust system of the internal combustion engine. Approaching the vibration frequency band can be more effectively prevented.
[0011]
Further, in the temperature sensor of the present invention, the flange has a rear end side sheath portion which is located on the rear end side of the protrusion and extends in the axial direction, and the metal tube is press-fitted or crimped and fixed to at least the rear end side sheath portion, Preferably, the metal tube and the rear end side sheath portion are welded in a circumferential direction.
[0012]
The metal tube and the rear end side sheath are welded in the circumferential direction while press-fitting or caulking and fixing the metal tube housing the element to at least the rear end side sheath of the flange. Excellent adhesion strength between metal and metal tube. Therefore, the temperature sensor according to the present invention has excellent durability even when used in an environment where the vibration is severe such as an automobile, and can improve the reliability of hermetic sealing of the fluid to be measured.
[0013]
In addition, the metal tube and the flange are integrally joined by welding. This welding is performed by a portion facing the inside of the flange, such as the exhaust gas passage, through which the fluid to be measured flows (specifically, the tip side sheath portion). ), But not at the rear end side sheath located on the rear end side of the protrusion. As described above, when the temperature sensor is mounted on the flow pipe through which the fluid to be measured flows, a welded portion for fixing the flange and the metal tube is not disposed in the flow passage. In other words, the welded portion between the flange and the metal tube is provided at a position that is not exposed to the fluid to be measured such as exhaust gas. Therefore, in the present invention, since the metal tube itself has a structure in which the metal tube itself is welded and fixed to the rear end side sheath portion of the flange, the welded portion is not exposed to the fluid to be measured as described above, and easily occurs in the welded portion. Oxidation can be effectively prevented, and the reliability of airtightness for the fluid to be measured can be improved. This is achieved by a structure in which the metal tube and the sheath on the distal end side are fixed by caulking.
[0014]
In order to form a welded portion between the metal tube and the rear end side sheath portion of the flange in a state having a sufficient welding strength in the circumferential direction of the rear end side sheath portion, the welding conditions are set to a higher value or the welding conditions are set higher. It is conceivable to perform welding by reducing the thickness of the rear end side sheath portion without changing the thickness. However, simply increasing the welding conditions leads to an increase in cost, and at the same time it becomes difficult to set conditions for good welding, and conversely, if the thickness of the entire rear end side sheath portion is reduced, the rear end side sheath portion itself becomes thin. Mechanical strength may be reduced. Therefore, in the present invention, the rear end side 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 is formed on the rear end side of the rear end side sheath portion. Welded to the step. In other words, the thickness of the portion provided for welding in the rear end side sheath portion is reduced.
As a result, the rear end side sheath portion and the metal tube can be welded satisfactorily and the welding strength of both can be ensured well, and the mechanical strength of the rear end side sheath portion and thus the flange can be ensured. Forming the rear end side of the rear end side sheath portion smaller in diameter than the front end side is easier and more desirable than forming the rear end side larger in diameter than the front end side.
[0015]
The means for welding the metal tube and the flange is not particularly limited, and examples thereof include laser welding, plasma welding, argon welding, and electron beam welding.
[0016]
Further, in any one of the above-described temperature sensors, a sheath member including a metal core wire to which an element is connected on a front end side and a lead wire for connecting an external circuit is connected on a rear end side, and a rear end side of a flange. A cylindrical joint extending radially outward from the sheath portion and extending rearward in the axial direction, the distal end side of the sheath member being inserted into the inside of the metal tube, and Preferably, the end side and the tip side of the lead wire are arranged inside the joint.
[0017]
In the temperature sensor of the present invention, since the element housed in the metal tube and the lead wire for connecting the external circuit are connected via the sheath member including the metal core wire, the metal tube and the lead wire are connected to each other. There is no need for a step of separately filling an insulating powder between them, and electrical insulation between the two is ensured. Further, in the present invention, with the distal end side of the sheath member inserted through the inside of the metal tube, the rear end side of the metal tube is disposed inside a joint separately joined to the rear end side of the flange, and the lead wire is provided. Is located inside the joint. Therefore, while the element is housed in a closed space formed by the metal tube, the flange, and the joint as a metal surrounding member, the closed space and the outside of the sensor itself are inside the lead wire (in the lead wire). ), The inner space of the joint, and the air gap formed between the outer peripheral surface on the distal end side of the sheath member and the inner peripheral surface of the metal tube, thereby ensuring ventilation.
[0018]
Therefore, in the present invention, even if the inner surface of the metal tube is oxidized, ventilation between the outside and the inside of the metal tube is ensured, so that a decrease in the oxygen concentration in the metal tube can be suppressed, and the oxidation can be prevented. The accompanying change in the characteristics of the element can be suppressed.
The means for joining the joint and the flange is not particularly limited, and examples thereof include laser welding, plasma welding, argon welding, electron beam welding, and brazing.
[0019]
Further, in the temperature sensor having the above configuration, the rear end side sheath portion includes a front end side step portion located on the front end side and a rear end side step portion having an outer diameter smaller than the front end side step portion. Formed, the metal tube is welded to the rear end side step of the rear end side sheath, and the joint is joined circumferentially to the outer peripheral surface of the front end side step of the rear end side sheath. good.
[0020]
As described above, the rear end side 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 the front end side step portion, and the metal tube is formed in the rear end side step portion of the rear end side sheath portion. By welding to the portion, the welding strength between the rear end side sheath portion and the metal tube can be sufficiently ensured, while the mechanical strength of the rear end side sheath portion and thus the flange can be ensured. Further, in the temperature sensor of the present invention, the cylindrical joint is joined to the outer peripheral surface of the step on the tip end side of the flange. Therefore, the welded portion between the rear end side step portion of the flange and the metal tube and the metal tube is housed inside the joint. Therefore, the joint serves to protect salt water or moisture from adhering to the weld between the metal tube and the flange, and the weld is suppressed from being corroded by the influence of moisture or the like.
[0021]
Another solution is a sheath member including a metal core wire to which an element whose electrical characteristics change depending on temperature is connected to the front end side and a lead wire for connecting an external circuit is connected to the rear end side; A metal cap having a closed cylindrical shape extending in the axial direction and having a rear end inner periphery joined in a circumferential direction of a distal end outer periphery of the sheath member in a form to be housed in the element inside, so as to surround an outer peripheral surface of the sheath member. And a flange portion disposed on the axis, wherein the flange is located on the tip side of the projection projecting radially outward, and is located on the tip side of the projection, and has a diameter smaller than the diameter of the projection, and has an axis line. A temperature sensor having a distal sheath portion extending in a direction, wherein the sheath member and the distal sheath portion are fixed by caulking.
[0022]
The temperature sensor of the present invention has a structure in which the sheath member and the distal end side sheath portion are fixed by caulking. Accordingly, when the temperature sensor is mounted on the flow pipe through which the fluid to be measured flows, a welded portion for fixing the flange and the sheath member is not disposed in the flow passage. Therefore, since the sheath member itself has a structure in which the distal end side sheath portion of the flange is fixed by caulking, the welded portion is not exposed to the fluid to be measured as described above. Therefore, a highly reliable temperature sensor having excellent durability can be obtained.
[0023]
By the way, in the temperature sensor of the present invention, the thickness and the length of the distal end side sheath portion are set in accordance with the diameter and the length of the heat sensitive portion (the portion closer to the thermistor element than the distal end portion of the flange). This may reduce the diameter of the heat-sensitive part or make it thinner in order to improve the responsiveness of the temperature sensor. In addition, the length of the heat-sensitive portion may be longer because it is preferable that the heat-sensitive portion be as close to the central portion of the catalytic converter or the exhaust pipe as possible when attached to the catalytic converter or the exhaust pipe. However, due to these, the resonance frequency of the heat-sensitive part shifts to a lower frequency side, and may approach the vibration frequency band of the exhaust system of the internal combustion engine used in an automobile or the like. Therefore, in the present invention, the resonance frequency of the heat-sensitive part is adjusted by adjusting the thickness or length of the sheath on the distal end side of the flange in response to a change in the diameter or the length of the heat-sensitive part. Approaching the vibration frequency band.
[0024]
Further, in the temperature sensor of the present invention, the sheath member and the distal end side sheath portion are preferably fixed by polygonal or round caulking. Since the sheath member and the distal end side sheath portion are fixed by polygonal caulking or round caulking as described above, the adhesion strength between the flange and the sheath member is excellent, and the resonance frequency of the heat-sensitive portion is reduced by the exhaust gas of the internal combustion engine. Approaching the system can be effectively prevented.
[0025]
Further, in the temperature sensor of the present invention, the flange has a rear end side sheath portion that is located on the rear end side of the protruding portion and extends in the axial direction, and the sheath member is press-fitted or crimped and fixed to at least the rear end side sheath portion, Preferably, the sheath member and the rear end side sheath portion are welded in a circumferential direction.
[0026]
Since the sheath member and the rear end side sheath portion are welded in the circumferential direction while press-fitting or caulking and fixing the sheath member for housing the element to at least the rear end side sheath portion of the flange, the welding strength is excellent and the flange It has excellent adhesion strength between the sheath member and the sheath member. Therefore, the temperature sensor of the present invention is excellent in durability even when used in an environment where the vibration is severe such as an automobile, and can further improve the reliability of airtightness against the fluid to be measured.
[0027]
In addition, the sheath member and the flange are integrally joined by welding, and this welding is performed by a portion facing the inside of the flange, such as the exhaust gas passage, through which the fluid to be measured flows (specifically, the distal end side sheath portion). ), But not at the rear end side sheath located on the rear end side of the protrusion. Accordingly, when the temperature sensor is mounted on the flow pipe through which the fluid to be measured flows, a welded portion for fixing the flange and the sheath member is not disposed in the flow passage. In other words, the welded portion between the flange and the sheath member is provided at a position that is not exposed to the fluid to be measured such as exhaust gas. Therefore, according to the present invention, since the sheath member itself is welded and fixed to the rear end side sheath portion of the flange, the welded portion is not exposed to the fluid to be measured as described above, and easily occurs in the welded portion. Oxidation can be effectively prevented, and the reliability of airtightness for the fluid to be measured can be improved.
[0028]
In order to form a welded portion between the sheath member and the rear end side sheath portion of the flange in a state having a sufficient welding strength in the circumferential direction of the rear end side sheath portion, the welding conditions are set higher or the welding conditions are set higher. It is conceivable to perform welding by reducing the thickness of the rear end side sheath portion without changing the thickness. However, simply increasing the welding conditions leads to an increase in cost, and at the same time it becomes difficult to set conditions for good welding, and conversely, if the thickness of the entire rear end side sheath portion is reduced, the rear end side sheath portion itself becomes thin. Mechanical strength may be reduced. Therefore, in the present invention, the rear end side 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 sheath member is formed on the rear end side of the rear end side sheath portion. Welded to the step. In other words, the thickness of the portion provided for welding in the rear end side sheath portion is reduced. Thereby, the rear end side sheath portion and the sheath member can be satisfactorily welded to each other, and the welding strength of both can be ensured well, and the mechanical strength of the rear end side sheath portion and thus the flange can be ensured. Forming the rear end side of the rear end side sheath portion smaller in diameter than the front end side is easier and more desirable than forming the rear end side larger in diameter than the front end side.
[0029]
In any one of the temperature sensors described above, welding of the sheath member and the rear end side sheath portion of the flange is not particularly limited, and examples thereof include laser welding, plasma welding, argon welding, and electron beam welding. .
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described more specifically with reference to Examples.
Example 1 (Temperature sensor in which a metal tube is covered with a distal end side sheath portion extending in the axial direction on a distal end surface of a flange)
A temperature sensor 1 according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a partially broken sectional view showing the structure of the temperature sensor 1 of the present invention. The temperature sensor 1 uses the 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 extending in the axial direction has a cylindrical shape whose front end 31 is closed by deep drawing of a steel plate, and the thermistor element 2 is housed inside the front end 31. The metal tube 3 is formed from a stainless alloy as described later. The cement 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 or the like during use. The rear end side 32 of the metal tube 3 is open, and this rear end side 32 is inserted through the inside of the stainless steel flange 4.
[0032]
The flange 4 has a projecting portion 41 projecting radially outward, a distal end side sheath portion 43 which is located on the distal end side of the projecting portion 41 and has a diameter smaller than the diameter of the projecting portion and extends in the axial direction, and a projecting portion. And a rear end side sheath 42 extending in the axial direction. The protruding portion 41 is formed in an annular shape having a seat surface 45 having 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 in close contact with the tapered portion of the mounting portion. This prevents the exhaust gas from leaking out of the exhaust pipe.
[0033]
The distal sheath 43 is formed in an annular shape, and the metal tube 3 is inserted from the rear end 32 of itself into the distal end of the protrusion 41 of the flange 4, and the outer peripheral surface of the metal tube 3 and the distal sheath are connected. A portion of the portion 43 overlapping with the inner peripheral surface is swaged. By this caulking fixation, as shown in FIG. 1, a caulking fixing portion C1 is formed on the distal end side sheath portion 43, and the metal tube 3 is fixed to the flange 4. In this embodiment, the caulking fixing portion C1 is fixed by octagonal caulking.
[0034]
Since the temperature sensor 1 has a structure in which the metal tube 3 and the distal end side sheath portion 43 are fixed by caulking, when the temperature sensor 1 is mounted on the flow pipe through which the fluid to be measured flows, the flange and the metal tube are connected. There is no need to arrange a welded portion for fixing in the flow passage. Therefore, oxidation that easily occurs on the inner surface of the welded portion can be effectively suppressed, and further, a change in the characteristics of the thermistor element 2 can be suppressed, and the temperature sensor 1 with high reliability can be obtained.
[0035]
The resonance frequency of the heat-sensitive part 81 is shifted to the low frequency side by fixing the metal tube 3 and the distal end side sheath 43 of the flange 4 by caulking and adjusting the thickness and length of the distal end side sheath 43. It is possible to prevent the shift from approaching the vibration frequency band of the exhaust system of an internal combustion engine used for an automobile or the like due to the shift. In addition, since the fulcrum of vibration is strengthened by the distal end side sheath portion 43, the mechanical strength is also increased.
[0036]
Further, the temperature sensor 1 detects that the resonance frequency of the heat-sensitive portion approaches the vibration frequency band of the exhaust system of the internal combustion engine because the metal tube 3 and the distal end side sheath portion 43 are fixed by octagonal caulking. It can be more effectively prevented. Note that the structure is not limited to the structure in which the distal end side sheath portion 43 of the flange 4 and the metal tube 3 are fixed by octagonal caulking, but may be fixed by hexagonal or higher (for example, hexagonal, decagonal, or the like). It may be fixed by round caulking.
[0037]
Further, when the metal tube 3 and the distal end side sheath portion 43 are fixed by polygonal caulking, the temperature sensor 1 can suppress the degree of heat removal from the heat sensitive portion 81 to the flange 4 or the like as compared with the conventional case. . This is because, in the case of polygonal caulking, a heat transfer path from the heat-sensitive part 81 of the temperature sensor 1 to the flange 4 is difficult to be formed except for the caulked fixed part C1. Therefore, the temperature sensor 1 can suppress the degree of heat removal as compared with the related art, and can also obtain the effect of improving the responsiveness and preventing the temperature measurement accuracy from lowering.
[0038]
The rear end side sheath portion 42 of the flange 4 is formed in an annular shape, and includes a front end side step portion 44 located on the front end side and a rear end side step portion 46 having an outer diameter smaller than the front end side step portion 44. It has a two-stage shape.
[0039]
The metal tube 3 is inserted from the rear end side 32 of the metal tube 3 to the front end side of the protruding portion 41 of the flange 4, and is pressed into the rear end side sheath portion 42. Then, a portion where the outer peripheral surface of the metal tube 3 and the inner peripheral surface of the rear end side step portion 46 of the rear end side sheath portion 42 overlap is laser-welded in the circumferential direction. By performing this laser welding, as shown in FIG. 1, a welded portion L 1 straddling the rear end side step 46 of the rear end side sheath 42 and the metal tube 3 is formed, and the metal tube 3 is attached to the flange 4. It is firmly fixed.
[0040]
As described above, while the metal tube 3 is pressed into the rear end side sheath portion 42 of the flange 4 and the rear end side step portion 46 of the rear end side sheath portion 42 is laser-welded, the flange 4 and the metal tube 3 are connected to each other. Temperature sensor 1 having excellent welding strength and excellent adhesion strength between the flange 4 and the metal tube 3. Therefore, even if the temperature sensor 1 receives a strong vibration in a vibrating environment such as an automobile, the metal tube 3 itself does not easily vibrate and the metal tube 3 can be prevented from being broken. Further, the reliability of airtightness against exhaust gas can be further improved. In securing the adhesion between the rear end side sheath 42 of the flange 4 and the metal tube 3, it is not limited to the method of press-fitting the metal tube 3 into the rear end side sheath 42, The metal tube 3 may be caulked radially inward, or the press-fitting and the caulking may be used in combination.
[0041]
A nut 5 having a hexagonal nut portion 51 and a screw portion 52 is rotatably fitted around the flange 4. The temperature sensor 1 is fixed by a nut 5 with the seat surface 45 of the protruding portion 41 of the flange 4 in contact with the mounting portion of the exhaust pipe. A cylindrical joint 6 is hermetically joined to a radially outer side of the distal end side step portion 44 of the rear end side sheath portion 42 in the flange 4. More specifically, the joint 6 is press-fitted into the distal step 44 of the rear sheath 42 so that the inner peripheral surface of the joint 6 overlaps the outer peripheral surface of the distal step 44 of the rear sheath 42. The joint 6 and the distal end side step portion 44 are laser-welded in the circumferential direction. By performing this laser welding, as shown in FIG. 1, a welded portion L 2 straddling the front end side step portion 44 of the rear end side sheath portion 42 and the joint 6 is formed.
[0042]
A sheath member 8 containing a pair of metal core wires 7 is arranged 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. The 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 a metal outer cylinder made of SUS310S, a pair of conductive metal core wires 7 made of SUS310S, and the like, and insulates between the outer cylinder and each metal core wire 7, And an insulating powder for holding the metal core wire 7.
[0043]
A lead wire 12 for connecting a pair of external circuits (for example, 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 caulking terminal 11. The pair of metal core wires 7 and the pair of caulking 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 contained in an auxiliary ring 13 made of heat-resistant rubber. When the auxiliary ring 13 is crimped or polygonally crimped from above the joint 6, the two rings 13 and 6 are joined to each other while maintaining airtightness.
As a result, the thermistor element 2 is housed in a closed space formed by the metal tube 3, the flange 4, and the joint 6 as a metal surrounding member. Then, the output of the thermistor element 2 is extracted from the metal core wire 7 of the sheath member 8 to an external circuit (not shown) by the lead wire 12, and the temperature of the exhaust gas is detected.
[0044]
Here, in the temperature sensor 1 according to the present embodiment, when air enters the inside of the joint 6 from outside through the space inside the lead wire 12, the atmosphere is changed to the joint 6, the metal tube 3, and the flange. Because the inside of 4 is formed in a closed space, it enters into the metal tube 3. Therefore, in the temperature sensor 1, ventilation from the inside of the lead wire 12 to the inside of the metal tube 3 is secured, and even if the metal tube 3 housing the thermistor element 2 is oxidized, the inside of the metal tube 3 is not oxidized. A decrease in the oxygen concentration can be suppressed, and a change in the characteristics of the thermistor element 2 can be suppressed.
[0045]
Since the temperature sensor 1 is used in a high-temperature environment as high as 1000 ° C., each component must 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 of SUS304.
[0046]
Example 2 (Temperature sensor in which a sheath member is covered by a distal-side sheath extending from the distal end surface of the flange)
Next, a temperature sensor 100 according to a second embodiment will be described with reference to the drawings. The temperature sensor 100 according to the second embodiment is different from the temperature sensor 1 according to the first embodiment in that a member for accommodating the thermistor element 2, a member that is crimped to the front end side sheath of the flange, and a rear end of the flange The members that are laser-welded to the side sheath are mainly different, and the other parts are almost the same. Therefore, the following description focuses on portions that are different from the first embodiment, and description of similar portions is omitted or simplified.
[0047]
First, FIG. 2 is a partially broken cross-sectional view showing the structure of the temperature sensor 100. In the temperature sensor 1 of the first embodiment described above, the thermistor element 2 is housed inside the metal tube 3, and is fixed by laser welding the metal tube 3 and the flange 4 and by caulking at the distal end side sheath portion 43. (See FIG. 1). On the other hand, in the temperature sensor 100 according to the second embodiment, the thermistor element 2 is housed in the metal cap 14, and the metal cap 14 is joined to the sheath member 8. It is fixed by caulking at the side sheath 43.
[0048]
The metal cap 14 extending in the axial direction has a cylindrical shape with its distal end 131 closed, and the thermistor element 2 is housed inside the distal end 131.
The metal cap 14 is formed from a stainless steel alloy such as SUS310S. The thermistor element 2 is connected to the metal core wire 7 protruding from the distal end side of the sheath member 8 via its own electrode wire (Pt / Rh alloy wire) 9. The rear end side 132 of the metal cap 14 is open, and the inner peripheral surface of the rear end side 132 is the outer periphery of the sheath member 8 (specifically, the outer cylinder of the sheath member 8) containing the pair of metal core wires 7. It is laser welded over the surface in the circumferential direction. Thereby, the metal cap 14 is fixed to the sheath member 8.
[0049]
The flange 4 has a protruding portion 41 protruding radially outward, a distal end side sheath portion 43 that is located on the distal end side of the protruding portion 41, has a diameter smaller than the diameter of the protruding portion, and extends in the axial direction. A rear end side sheath portion 42 which is located on the rear end side and extends in the axial direction.
[0050]
The distal sheath 43 is formed in an annular shape as described above, and the sheath member 8 is inserted into the distal end of the protrusion 41 of the flange 4 from the rear end of the sheath member 8 so that the outer peripheral surface of the sheath 8 is The portion of the side sheath 43 that overlaps the inner peripheral surface is swaged. By the crimping, as shown in FIG. 2, a crimping fixing portion C 2 is formed in the distal end side sheath portion 43, and the sheath member 8 is fixed to the flange 4. In this embodiment, the caulking fixing portion C2 is fixed by octagonal caulking.
[0051]
Further, when the sheath member 8 and the distal end side sheath portion 43 are fixed by polygonal caulking, the temperature sensor 100 can suppress the degree of heat removal from the heat-sensitive portion 81 to the flange 4 or the like as compared with the related art. . This is because in the case of polygonal caulking, a heat transfer path from the heat-sensitive part 81 of the temperature sensor 100 to the flange 4 is difficult to be formed except for the caulked fixed part C2. Therefore, the temperature sensor 100 can suppress the degree of heat removal as compared with the related art, and can also obtain the effects of improving responsiveness and preventing a decrease in temperature measurement accuracy.
[0052]
Further, since the temperature sensor 100 has a structure in which the sheath member 8 and the distal end side sheath portion 43 are fixed by caulking, when the temperature sensor 1 is mounted on the flow pipe through which the fluid to be measured flows, the flange 4 The welded portion L3 for fixing the sheath and the sheath member 8 is not disposed in the flow passage. A highly reliable temperature sensor 100 having excellent durability can be obtained.
[0053]
In the structure in which the sheath member 8 and the distal end sheath portion 43 of the flange 4 are fixed by caulking, the resonance frequency of the heat-sensitive portion 81 is reduced by adjusting the thickness and length of the distal end sheath portion 43. By shifting to the frequency side, it is possible to prevent approaching the vibration frequency band of the exhaust system of the internal combustion engine used for an automobile or the like. In addition, since the fulcrum of vibration is strengthened by the distal end side sheath portion 43, the mechanical strength is also increased.
[0054]
Further, in the temperature sensor 100, since the sheath member 8 and the distal end side sheath portion 43 are fixed by octagonal caulking, the resonance frequency of the heat sensitive portion approaches the vibration frequency band of the exhaust system of the internal combustion engine. Can be effectively prevented.
[0055]
In addition, the rear end side sheath portion 42 of the flange 4 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 46 having an outer diameter smaller than the front end side step portion 44. No.
[0056]
The sheath member 8 is caulked radially inward at a predetermined position on the outer peripheral surface of the rear end side sheath portion 42 in a state where the rear end side of the sheath member 8 is inserted inside the flange 4, and fixed to the flange 4. Have been. Further, a portion where the outer peripheral surface of the sheath member 8 and the inner peripheral surface of the rear end side step portion 46 of the rear end side sheath portion 42 overlap is laser-welded in the circumferential direction. By performing this laser welding, as shown in FIG. 2, a welded portion L 3 straddling the rear end side step 46 of the rear end side sheath 42 and the sheath member 8 (specifically, the outer cylinder of the sheath member 8). Is formed, and the sheath member 8 is firmly fixed to the flange 4.
[0057]
As described above, while the sheath member 8 is fixed by caulking to the rear end side sheath portion 42 of the flange 4 and the rear end side step portion 46 of the rear end side sheath portion 42 is laser-welded, the flange 4 and the sheath member The temperature sensor 100 is excellent in the welding strength with the flange 8 and the bonding strength between the flange 4 and the sheath member 8. Therefore, even when the temperature sensor 100 receives a strong vibration in an environment such as an automobile where the vibration is intense, the sheath member 8 hardly swings, and the breakage of the sheath member 8 can be suppressed. In addition, while oxidation that easily occurs in the welded portion can be effectively suppressed, the reliability of airtightness against exhaust gas can be further improved.
[0058]
Note that the present invention is not limited to the specific embodiments described above, but can be variously modified embodiments within the scope of the present invention depending on the purpose and application. For example, in the temperature sensor 1 of the embodiment, the responsiveness of the temperature sensor 1 can be further improved by making the thickness of the distal end portion of the metal tube 3 thinner than other portions.
[0059]
Further, in the temperature sensor 1 according to the first embodiment, the joint 6 is press-fitted into the distal end side step portion 44 of the rear end side sheath portion 42, and the joint 6 and the distal end side step portion 44 are laser-welded in the circumferential direction. Alternatively, the joint 6 and the distal end step 44 may be laser-welded in the circumferential direction while the joint 6 is fixed by caulking to the distal end step 44. Thereby, the temperature sensor 100 can be provided with more excellent welding strength between the joint 6 and the distal side step portion 44 and more excellent in the adhesion strength between the joint 6 and the distal side step portion 44.
[0060]
Further, the temperature sensor of the present invention is applicable not only to an exhaust gas 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 partially cutaway cross-sectional view showing a temperature sensor in which an outer peripheral surface of a metal tube for housing a thermistor element and an inner peripheral surface of a distal end side sheath portion of a flange are caulked.
FIG. 2 is a partially broken cross-sectional view showing a temperature sensor in which an outer peripheral surface of a sheath member to which a metal cap for accommodating a thermistor element is joined and an inner peripheral surface of a distal end side sheath portion of a flange are caulked.
FIG. 3 is a partially cutaway sectional view showing a conventional temperature sensor in which a sheath member joined to a metal cap for housing a thermistor element is laser-welded in a circumferential direction at a sheath portion of a flange.
[Explanation of symbols]
1, 100, 200: Temperature sensor, 2: Thermistor element, 3: Metal tube, 4: Flange, 41: Projection, 42: Rear end sheath, 43 ·········································································································· Sheath member, 12 ... lead wire, L1, L2, L3 ... welded part, C1, C2 ... crimped fixed part

Claims

A cylindrical metal tube having a distal end closed and extending in the axial direction, an element housed inside the metal tube, and whose electrical characteristics change depending on temperature, and a flange arranged to surround the outer peripheral surface of the metal tube. A temperature sensor comprising:
The flange has a protruding portion that protrudes radially outward, and a distal end side sheath portion that is located on the distal end side of the protruding portion, is smaller in diameter than the diameter of the protruding portion, and extends in the axial direction,
A temperature sensor, wherein the metal tube and the distal end side sheath portion are fixed by caulking.

The temperature sensor according to claim 1, wherein the metal tube and the distal end side sheath portion are fixed by polygonal caulking or round caulking.

The flange has a rear end side sheath portion that is located on the rear end side of the protruding portion and extends in the axial direction.
The metal tube is fixed to at least the rear end side sheath by press fitting or caulking,
The temperature sensor according to claim 1, wherein the metal tube and the rear end side sheath portion are welded in a circumferential direction.

The rear end side sheath portion has a two-stage shape including a front end side step portion located on the front end side and a rear end side step portion having an outer diameter smaller than the front end side step portion, and the metal tube has the rear end side sheath. The temperature sensor according to claim 3, wherein the temperature sensor is welded to the rear end step portion of the portion.

A sheath member containing a metal core wire to which the element is connected to a front end side and a lead wire for connecting an external circuit to a rear end side, and an airtight state radially outward of the rear end side sheath portion of the flange. And a cylindrical joint extending rearward in the axial direction, wherein a distal end side of the sheath member is inserted into the metal tube, and a rear end side of the metal tube is inserted into the joint. The temperature sensor according to any one of claims 1 to 4, wherein the temperature sensor is arranged, and a distal end side of the lead wire is arranged inside the joint.

The rear end side sheath portion has a two-stage shape including a front end side step portion located on the front end side and a rear end side step portion having an outer diameter smaller than the front end side step portion. The temperature sensor according to claim 5, wherein the joint is welded to the rear end side step portion of the rear end side sheath portion, and the joint is joined to an outer peripheral surface of the front end side step portion in a circumferential direction. .

A sheath member containing a metal core wire to which an element whose electrical characteristics change depending on temperature is connected to the front end side and a lead wire for connecting an external circuit is connected to the rear end side, and a cylindrical shape extending in the axial direction with the front end closed. A metal cap having a rear end inner periphery joined in a circumferential direction of a distal end outer periphery of the sheath member in a form in which the element is housed therein, and a flange disposed to surround an outer peripheral surface of the sheath member And a temperature sensor comprising:
The sheath member includes a protrusion protruding radially outward, and a distal end side sheath located at the distal end side of the protrusion and having a diameter smaller than the diameter of the protrusion and extending in the axial direction. And the front end side sheath portion is fixed by caulking.

The temperature sensor according to claim 7, wherein the sheath member and the distal end side sheath portion are fixed by polygonal caulking or round caulking.

The flange has a rear end side sheath portion that is located on the rear end side of the protruding portion and extends in the axial direction.
The sheath member is fixed at least to the rear end side sheath portion by press fitting or caulking,
The temperature sensor according to claim 7, wherein the sheath member and the rear end side sheath portion are welded in a circumferential direction.

The rear end side sheath portion has a two-stage shape including a front end side step portion located on the front end side and a rear end side step portion having an outer diameter smaller than the front end side step portion, and the sheath member includes the rear end side sheath. The temperature sensor according to claim 9, wherein the temperature sensor is welded to the rear end side step portion of the portion.