JP2004177183A

JP2004177183A - Method for manufacturing temperature sensor, and the temperature sensor

Info

Publication number: JP2004177183A
Application number: JP2002341432A
Authority: JP
Inventors: Takaaki Chiyousokabe; 孝昭長曽我部; Masaki Iwatani; 雅樹岩谷; Masahiko Nishi; 雅彦西; Takeshi Hanzawa; 剛半沢
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: JP3707018B2

Abstract

PROBLEM TO BE SOLVED: To provide a temperature sensor for appropriately performing the centering of a flange and a metal tube when forcing in both of them, avoiding the variation of a press fit load, and reducing the heat conduction from a heat sensitive section to the flange, and to provide a method for manufacturing the temperature sensor. SOLUTION: A variable diameter section 47 for reducing an inner diameter toward a press fit section 46 is formed between an insertion side end section 49 located at the tip side of an inner hole 48 of a flange 4 and the press fit section 46 in advance before the press fit process for pressing in a metal tube 3 into the flange 4. Then, in the press fit process, the rear end side of the metal tube 3 is inserted from the insertion side end section 49 of the inner hole 48 of the flange 4. In the obtained temperature sensor 1, a space is formed between the inner periphery surface of the variable diameter section 47 of the flange 4 and the outer periphery surface of the metal tube 3, so that the length from the tip of the press fit section 46 to the heat sensitive section can be extended, thus reducing heat conduction to the flange 4. 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及びその製造方法に関する。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及びその製造方法に関する。
【０００２】
【従来の技術】
従来より、排気管（流通管）に装着され、排気ガス通路（流通路）内を流れる排気ガス（被測定流体）の温度を感温素子であるサーミスタ素子によって検出する温度センサ、いわゆる排気温センサが知られている。そして、この種の温度センサとして、金属キャップと外形が等しいシース部材を準備し、サーミスタ素子を収納した金属キャップの後端部とシース部材の先端部を突き合わせ溶接した上で、シース部材をフランジの内孔内に圧入固定させた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）。
【０００３】
【特許文献１】
特開２０００−２６６６０９号公報（第６図、第７図）
【０００４】
【発明が解決しようとする課題】
しかし、特許文献１に示す温度センサの製造方法のように、フランジとシース部材とを圧入固定する場合には、両者の芯出しが重要となるが、その芯出しは容易とは言えず、シースとフランジとの芯ずれを生ずることがある。また、特許文献１のように、内径が略同一のフランジの内孔に対して、外径が略同一のシース部材の後端側を挿入して圧入固定する場合、シース部材の挿入開始当初における摩擦抵抗が大きくなりがちで、その結果圧入荷重がばらつき、圧入荷重が過大となることがある。このように、圧入荷重が過大となると、フランジに対して薄肉部材であるシース部材が座屈する等の不具合を発生してしまう。
【０００５】
一方、特許文献１に示す温度センサでは、上述したように、内径が略同一のフランジの内孔に対して、外径が略同一のシース部材の後端側を圧入固定させた構造を有している。そのために、フランジの内周面の全体にわたってシース部材の外周面が密着した状態となるため、感熱部（流通管内に配置される素子側の部位）からフランジへ熱が伝導し易い。感熱部からフランジへの熱伝導が容易になると、センサ自身の応答性の悪化、感熱部での温度測定精度の低下を招くことに繋がってしまう。
【０００６】
本発明は、上述した従来の問題点を解決するものであり、フランジと金属チューブとを圧入するにあたって、両者の芯出しを精度良く行うことができると共に、圧入荷重のばらつきを抑制することができ、また感熱部からフランジへの熱伝導が低減可能な温度センサ及びその製造方法を提供することを目的とする。
【０００７】
【課題を解決するための手段】
その解決手段は、内孔を有するフランジと、フランジの内孔内の圧入部に圧入固定されると共に、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を備える温度センサの製造方法であって、フランジの内孔の先端側に位置する挿入側端部と圧入部との間に、該圧入部に向かうほど内径が小さくなる変径部を形成し、その後、フランジの内孔の挿入側端部より金属チューブの後端側を挿入して、該金属チューブを該フランジに圧入固定する温度センサである。
【０００８】
本発明の温度センサの製造方法において注目すべきことは、金属チューブをフランジに圧入固定する圧入工程の前に、予めフランジの内孔の先端側に位置する挿入側端部と圧入部との間に、該圧入部に向かうほど内径が小さくなる変径部を形成しておくことである。そして、上記圧入工程において、フランジの内孔の挿入側端部より金属チューブの後端側を挿入することで、フランジの内孔内の変径部を通過させて圧入部に対し金属チューブを圧入固定させるのである。
【０００９】
これにより、金属チューブをフランジの内孔内の圧入部に圧入固定するにあたって、金属チューブとフランジとの軸芯合わせを精度良く行うことができる。また、フランジの内孔内への金属チューブ挿入開始当初（換言すれば、変径部通過時）における摩擦抵抗を少なくすることができ、圧入荷重がばらついて過大な荷重になるのを有効に抑制することができる。したがって、金属チューブをフランジの内孔内の圧入部に圧入固定するにあたり、金属チューブとフランジとの芯ずれや、圧入荷重の過大による金属チューブの曲がりといった不具合の発生を抑えられた信頼性の高い温度センサを製造することができる。なお、フランジの内孔の挿入側端部より金属チューブの後端側を挿入するにあたっては、フランジを固定した状態で金属チューブの後端側を挿入してもよく、逆に金属チューブを固定した状態でその後端側に対してフランジを挿入してもよい。
【００１０】
また、本発明によって製造される温度センサは、内径が一定の内孔を有するフランジに金属チューブを圧入固定させた従来の温度センサと比較し、内孔の軸線方向長さが等しい条件下において、上記変径部を有しているので圧入部先端からの感熱部（流通管内に配置される素子側の部位）の長さが長くなる。つまり、本発明によって製造される温度センサでは、フランジの変径部の内周面と金属チューブの外周面との間に空間が生じるので、圧入部先端からの感熱部の長さを長くすることができ、同感熱部からフランジへの熱伝導を低減することができる。これにより、センサ自身の応答性を従来に比して向上させることができ、温度測定精度の高い温度センサとすることができる。
【００１１】
なお、フランジの内孔内における変径部の内周面は、前記内孔の中心軸線を含む断面形状としてみた場合に、テーパ形状、Ｒ形状、或いはそれらの組み合わせ等を挙げることができるが、上述した温度センサの製造方法では、前記変径部の内周面は、テーパ形状であると良い。
【００１２】
これにより、フランジの内孔の挿入側端部より金属チューブの後端側を挿入したときに、金属チューブの後端に変径部の内周面が当接すると当該内周面のテーパ形状によるセンターリング効果で、金属チューブとフランジとの軸芯がより一致する方向に導かれる。それ故、金属チューブとフランジとの圧入固定を行うにあたり、金属チューブとフランジとの軸芯合わせをより精度良く行うことができる。このテーパ形状のフランジの軸線に対する角度（換言すれば、挿入側端部に向けての傾斜角度）は特に限定されないが、１０〜３０°、特に１０〜２５°、さらには１０〜２０°とすることが好ましい。なお、変径部の成形し易さの観点からも、変径部の内周面はテーパ形状であることが好ましい。
【００１３】
さらに、上述した温度センサの製造方法であって、フランジは、軸線方向に延びる鞘部と、該鞘部の先端側に位置し、径方向外側に向かって突出する該鞘部よりも大径の突出部とを有し、圧入部は少なくとも鞘部内に位置しており、金属チューブをフランジに圧入固定した後に、圧入部を含む形態で鞘部と金属チューブを周方向にわたって溶接すると良い。
【００１４】
本発明の温度センサの製造方法では、金属チューブとフランジとを圧入固定した後に、金属チューブとフランジとを溶接により一体に接合している。そのため、金属チューブの外周面とフランジの内孔の内周面（圧入部）との密着強度が向上すると共に、両者がより強固に固定されることになる。従って、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、気密の信頼性に優れる温度センサを製造することができる。
【００１５】
ところで、本発明の温度センサの製造方法によれば、上述したように金属チューブとフランジとを圧入固定した後に両者を溶接しているが、この溶接は、フランジの内で突出部の後端側に位置する鞘部に行うようにしている。つまり、温度センサは、排気管等に装着されて使用に供されるが、排気ガス通路内に金属体同士の溶接部が配置される場合、溶接部が高温環境下に晒されるために同溶接部が酸化してしまい、センサ自体の耐久性や排気ガス等の被測定流体に対する気密性を長期にわたって維持することができないことがある。
【００１６】
そこで、本発明の温度センサの製造方法では、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行うようにしているのである。これにより、本発明によって製造される温度センサは、被測定流体が流通する流通管（例えば排気管）に装着されても、溶接部自身が高温環境下に晒されないため、同溶接部での酸化の発生を抑えられ、センサ自身の耐久性や被測定流体の気密性を長期にわたって良好に維持することができる。なお、圧入部を含む形態で鞘部と金属チューブとを溶接する手法は特に限定されないが、レーザー溶接、プラズマ溶接、電子ビーム溶接、アルゴン溶接等を挙げることができる。
【００１７】
さらに、上述した本発明の温度センサの製造方法であって、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、圧入部は少なくとも後端側段部内に位置しており、圧入部を含む形態で鞘部の後端側段部と金属チューブを周方向にわたって溶接すると良い。
【００１８】
本発明の温度センサの製造方法では、フランジの溶接部を、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、圧入部を含む形態で鞘部の後端側段部と金属チューブとを溶接している。つまり、フランジに形成される鞘部の内で、金属チューブとの溶接に供される部分の肉厚を薄くした形状を採用している。これにより、金属チューブとフランジとの圧入固定後、圧入部を含む形態で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。尚、フランジにおいて、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。
【００１９】
さらに、上述した温度センサの製造方法であって、フランジの鞘部の後端側段部と金属チューブを周方向にわたって溶接した後、軸線方向後方に向かって延びる筒状の継手を、鞘部の先端側段部の外周面に周方向にわたって接合すると良い。このように、鞘部の後端側段部と金属チューブとの溶接後に、筒状の継手を先端側段部に接合することで、鞘部の後端側段部と金属チューブとの溶接部を、継手の内部に収納させることができる。これにより、本発明によって製造される温度センサは、継手が、金属チューブとフランジ（鞘部）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。
【００２０】
ついで、他の解決手段は、内孔を有するフランジと、フランジの内孔内の圧入部に圧入固定されると共に、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を備える温度センサであって、フランジの内孔の先端側に位置する挿入側端部と圧入部との間に、該圧入部に向かうほど内径が小さくなる変径部が形成され、フランジに金属チューブが圧入固定された状態において、変径部の内周面と金属チューブの外周面との間に空間が形成されている温度センサである。
【００２１】
本発明の温度センサにおいて注目すべきことは、フランジの内孔の先端側に位置する挿入側端部と圧入部との間に、該圧入部に向かうほど内径が小さくなる変径部を形成することである。そして、フランジに金属チューブを圧入固定した状態において、変径部の内周面と金属チューブの外周面との間に空間を形成させるのである。
【００２２】
これにより、本発明の温度センサでは、フランジの内孔内に上記変径部を形成したことにより、内径が一定の内孔を有するフランジに金属チューブを圧入固定させた従来の温度センサと比較し、内孔の軸線方向長さが等しい条件下において、圧入部先端からの感熱部の長さを長くすることができる。つまり、本発明の温度センサでは、フランジの変径部の内周面と金属チューブの外周面との間に空間を形成したので、圧入部先端からの感熱部の長さを長くすることができ、同感熱部からフランジへの熱伝導を低減することができる。これにより、センサ自身の応答性を従来に比して向上させることができ、温度測定精度の高い温度センサとすることができる。
【００２３】
【発明の実施の形態】
（実施形態）
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。
【００２４】
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はフランジ４に圧入固定されている。
【００２５】
このフランジ４は、ステンレス合金（具体的にはＳＵＳ３１０Ｓ）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、軸線方向に貫通した内孔４８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装着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が上記装着部のテーパ部に当接することで、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。
【００２６】
フランジ４の内孔４８には、少なくとも鞘部４２の後端側段部４３に対応する部分に圧入部４６が形成されており、この圧入部４６に金属チューブ３が圧入固定される。なお、本実施の形態では、圧入部４６は、フランジの内孔４８のうちで、鞘部４２の後端側段部４３に対応する部分に形成されると共に、先端側段部４４の後方側の一部分に対応する部分にまで形成されている。さらに、図２に示す図１の主要拡大図に示すように、フランジ４の内孔４８には、自身の先端側に位置する挿入側端部４９と圧入部４６との間に、圧入部４６に向かうほど内径が小さくなる変径部４７を形成している。この変径部４７の内周面は、内孔４８の中心軸線を含む断面形状としてみた場合に、テーパ形状に形成されている。なお、テーパ角度については、本実施の形態では１５°とした。この変径部４７の機能については、後述する。
【００２７】
金属チューブ３は、自身の後端側３２からフランジ４の内孔４８の挿入側端部４９より挿入されて、鞘部４２の内側に位置する圧入部４６に圧入固定されている。そして、金属チューブ３の外周面と、鞘部４２の後端側段部４３の内周面との重なり合う部分（即ち、圧入部４６）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、鞘部４２の後端側段部４３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。
【００２８】
このように、金属チューブ３をフランジ４の鞘部４２の圧入部４６に圧入しつつ、鞘部４２の後端側段部４３に圧入部４６を含む形態で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向上させることができる。
【００２９】
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、排気管の装着部にフランジ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を鞘部４２の先端側段部４４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、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。
【００３０】
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。
【００３１】
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。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り、継手６の後端側開口に備えられる耐熱ゴム製の補助リング１３に挿通される。そして、補助リング１３は、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固定される。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。
【００３２】
ここで、本実施の形態の温度センサ１では、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内にまで入り込むことになる。したがって、温度センサ１では、外部（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。
【００３３】
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。
【００３４】
ついで、上述した本実施形態の温度センサ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、圧入部４６及び変径部４７を有する内孔４８と、先端側段部４４と後端側段部４３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（図２参照）。また、鋼板の深絞り加工により先端側３１が閉塞した筒状をなす金属チューブ３を別途形成する。なお、本実施の形態では、底壁を含む金属チューブ３全体を、鋼板の深絞り加工によって形成している。
【００３５】
そして、フランジ４の内孔４８の挿入側端部４９より金属チューブ３の後端側３２を挿入して、内孔４８の圧入部４６（少なくとも後端側鞘部４４の位置に対応する圧入部４６）に対して金属チューブ３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、金属チューブ３の後端に変径部４７の内周面が当接すると当該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、上記変径部４７を内孔４８内に設けているので、フランジ４の内孔４８内への金属チューブ３挿入開始当初（換言すれば、変径部４７通過時）における摩擦抵抗を少なくすることができ、圧入荷重がばらつくのを抑制することができる。
【００３６】
そして、金属チューブ３とフランジ４とを圧入した後、フランジ４の鞘部４２の後端側段部４３と金属チューブ３とを周方向にわたってレーザー溶接する。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とを電気的に接続する。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ー溶接する。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。
【００３７】
上述した製造方法により製造した温度センサ１では、図１に示すように、フランジ４の内孔４８内に変径部４７を形成したので、内径が一定の内孔を有するフランジに金属チューブを圧入固定させた従来の温度センサと比較し、内孔の軸線方向長さが等しい条件下において、圧入部４６先端からの感熱部（流通管内に配置される素子側の部位）の長さを長くすることができる。つまり、温度センサ１では、図２に示すように、フランジ４の変径部４７の内周面と金属チューブ３の外周面との間にリング状の空間Ｓが生じるで、圧入部４６先端からの感熱部の長さを長くすることができ、同感熱部からフランジ４への熱伝導を低減することができる。これにより、センサ自身の応答性を従来に比して向上させることができ、温度測定精度の高い温度センサ１とすることができる。
【００３８】
以上において、本発明を実施の形態に即して説明したが、本発明は上述した具体的な実施形態に限定されるものではなく、その要旨を逸脱しない範囲で、適宜変更して適用できることはいうまでもない。例えば、本実施の形態の温度センサ１において、金属チューブ３のうちで、フランジ４の内孔４８内の圧入部４６に圧入固定される部分よりも先端側の肉厚を、圧入部４６に固定される部分よりも薄くすることにより、温度センサの応答性をさらに向上させることもできる。
【００３９】
また、本実施の形態の温度センサ１では、フランジ４に形成される変径部４７を、挿入側端部４９と連なるように内孔４８の最先端側に形成したが、変径部４７の形成位置はこれに限られず、挿入側端部４９と圧入部４６との間に形成されていればよい。例えば、略同一の内径を有すると共に、圧入部４６の内径よりも大きい内径を有する座ぐり部を挿入側端部４９に連なるように形成し、この座ぐり部の後端と圧入部４８の先端とを連結するように、内周面がテーパ形状をなす変径部４７を形成するようにしてもよい。さらに、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後端側が、フランジの内孔の挿入側端部より挿入されて、圧入固定された状態の温度センサを示す部分破断断面図である。
【図２】図１に示す温度センサにおいて、金属チューブとフランジとの圧入固定された状態を示す拡大断面図である。
【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、４・・・フランジ、４１・・・突出部、４２・・・鞘部、４３・・・後端側段部、４４・・・先端側段部、４６・・・圧入部、４７・・・変形部、４８・・・内孔、４９・・・挿入側端部、６・・・継手、Ｌ１、Ｌ２・・・溶接部、Ｓ・・・空間[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, and a method for manufacturing the same. More specifically, a temperature sensor for detecting the temperature of the fluid to be measured by disposing an element in a flow passage through which the fluid to be measured (for example, exhaust gas) flows, such as the inside of a catalytic converter or the inside of an exhaust pipe of an exhaust gas purification device for an automobile, It relates to the manufacturing method.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a temperature sensor mounted on an exhaust pipe (flow pipe) and detecting the temperature of an exhaust gas (fluid to be measured) flowing in an exhaust gas passage (flow path) by a thermistor element as a temperature-sensitive element, a so-called exhaust temperature sensor. It has been known. As a temperature sensor of this type, a sheath member having the same outer shape as the metal cap is prepared, and the rear end of the metal cap containing the thermistor element is butt welded to the front end of the sheath member. 2. Description of the Related Art A temperature sensor having a structure in which an inner hole is press-fitted and fixed is known (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP 2000-266609 A (FIGS. 6 and 7)
[0004]
[Problems to be solved by the invention]
However, when the flange and the sheath member are press-fitted and fixed as in the method of manufacturing the temperature sensor shown in Patent Document 1, centering of both is important, but the centering is not easy, and the sheath is not easily positioned. Misalignment between the shaft and the flange may occur. Further, as in Patent Literature 1, when the rear end side of a sheath member having substantially the same outer diameter is inserted into the inner hole of a flange having substantially the same inner diameter and press-fitted and fixed, the insertion of the sheath member at the beginning of insertion is started. The frictional resistance tends to increase, and as a result, the press-fit load varies, and the press-fit load may become excessive. As described above, when the press-fitting load is excessive, problems such as buckling of the sheath member, which is a thin member, with respect to the flange occur.
[0005]
On the other hand, the temperature sensor disclosed in Patent Document 1 has a structure in which the rear end side of a sheath member having substantially the same outer diameter is press-fitted and fixed to the inner hole of a flange having substantially the same inner diameter as described above. ing. Therefore, the outer peripheral surface of the sheath member is in close contact with the entire inner peripheral surface of the flange, so that heat is easily conducted from the heat-sensitive portion (the part on the element side arranged in the flow pipe) to the flange. If heat conduction from the heat-sensitive part to the flange becomes easy, the responsiveness of the sensor itself will be degraded and the accuracy of temperature measurement in the heat-sensitive part will be reduced.
[0006]
The present invention is to solve the above-described conventional problems, and when press-fitting a flange and a metal tube, it is possible to accurately center the two and to suppress variation in the press-fit load. It is another object of the present invention to provide a temperature sensor capable of reducing heat conduction from a heat-sensitive portion to a flange, and a method of manufacturing the same.
[0007]
[Means for Solving the Problems]
The solution is a flange having an inner hole, a press-fitted and fixed to a press-fitting portion in the inner hole of the flange, and a cylindrical metal tube extending in the axial direction whose front end side is closed, and housed inside the metal tube, A method for manufacturing a temperature sensor, comprising: an element whose electrical characteristics change according to temperature, wherein an inner diameter increases toward the press-fit portion between the press-fit portion and an insertion-side end located at the tip side of the inner hole of the flange. Is a temperature sensor that forms a variable diameter portion that reduces the diameter of the metal tube, then inserts the rear end side of the metal tube from the insertion side end of the inner hole of the flange, and press-fits and fixes the metal tube to the flange.
[0008]
It should be noted that in the method of manufacturing the temperature sensor of the present invention, before the press-fitting step of press-fitting and fixing the metal tube to the flange, a gap between the insertion-side end and the press-fitting portion, which is located at the front end side of the inner hole of the flange in advance. In addition, a variable diameter portion whose inner diameter becomes smaller toward the press fitting portion is formed in advance. Then, in the press-fitting step, by inserting the rear end side of the metal tube from the insertion side end of the inner hole of the flange, the metal tube is pressed into the press-fitted portion by passing through the variable diameter portion in the inner hole of the flange. It is fixed.
[0009]
Thus, when the metal tube is press-fitted and fixed to the press-fitting portion in the inner hole of the flange, the axial alignment of the metal tube and the flange can be accurately performed. In addition, the frictional resistance at the beginning of the insertion of the metal tube into the inner hole of the flange (in other words, when passing through the variable diameter portion) can be reduced, and the excessive load due to the variation of the press-fitting load can be effectively suppressed. can do. Therefore, in press-fitting and fixing the metal tube to the press-fitting portion in the inner hole of the flange, the occurrence of problems such as misalignment between the metal tube and the flange and bending of the metal tube due to excessive press-fitting load is suppressed and high reliability is achieved. A temperature sensor can be manufactured. When inserting the rear end side of the metal tube from the insertion side end of the inner hole of the flange, the rear end side of the metal tube may be inserted with the flange fixed, and the metal tube may be fixed. In this state, a flange may be inserted to the rear end side.
[0010]
Further, the temperature sensor manufactured according to the present invention is compared with a conventional temperature sensor in which a metal tube is press-fitted and fixed to a flange having an inner hole with a constant inner diameter, under the condition that the axial lengths of the inner holes are equal, The length of the heat-sensitive part (the part on the element side arranged in the flow pipe) from the tip of the press-fitting part becomes longer because of having the above-mentioned variable diameter part. In other words, in the temperature sensor manufactured according to the present invention, since a space is created between the inner peripheral surface of the variable diameter portion of the flange and the outer peripheral surface of the metal tube, the length of the heat-sensitive portion from the tip of the press-fit portion must be increased. Thus, heat conduction from the heat-sensitive portion to the flange can be reduced. As a result, the responsiveness of the sensor itself can be improved as compared with the related art, and a temperature sensor with high temperature measurement accuracy can be obtained.
[0011]
The inner peripheral surface of the variable diameter portion in the inner hole of the flange may have a tapered shape, an R shape, or a combination thereof when viewed as a cross-sectional shape including the central axis of the inner hole. In the above-described method for manufacturing a temperature sensor, the inner peripheral surface of the variable diameter portion may have a tapered shape.
[0012]
Due to this, when the rear end side of the metal tube is inserted from the insertion side end of the inner hole of the flange, when the inner peripheral surface of the variable diameter portion comes into contact with the rear end of the metal tube, the inner peripheral surface is tapered. By the centering effect, the metal tube and the flange are guided in a direction in which the axes of the flange and the flange coincide more. Therefore, when press-fitting and fixing the metal tube and the flange, the axis of the metal tube and the flange can be more accurately aligned. The angle of the tapered flange with respect to the axis (in other words, the inclination angle toward the insertion side end) is not particularly limited, but is 10 to 30 °, particularly 10 to 25 °, and furthermore 10 to 20 °. Is preferred. In addition, it is preferable that the inner peripheral surface of the variable diameter portion has a tapered shape also from the viewpoint of easy forming of the variable diameter portion.
[0013]
Furthermore, in the above-described method for manufacturing a temperature sensor, the flange has a sheath portion extending in the axial direction, and a flange having a diameter larger than that of the sheath portion located on the tip side of the sheath portion and protruding radially outward. It is preferable that the press-fitting portion is located at least inside the sheath portion, and the metal tube is press-fitted and fixed to the flange, and then the sheath portion and the metal tube are welded in the circumferential direction so as to include the press-fitting portion.
[0014]
In the temperature sensor manufacturing method of the present invention, after the metal tube and the flange are press-fitted and fixed, the metal tube and the flange are integrally joined by welding. Therefore, the adhesive strength between the outer peripheral surface of the metal tube and the inner peripheral surface (press-fit portion) of the inner hole of the flange is improved, and both are more firmly fixed. Therefore, it is possible to manufacture a temperature sensor that is excellent in durability even when used in an environment of severe vibration such as an automobile, and that is excellent in airtight reliability.
[0015]
By the way, according to the temperature sensor manufacturing method of the present invention, the metal tube and the flange are press-fitted and fixed to each other and then welded as described above. This welding is performed in the flange at the rear end side of the protruding portion. To the sheath located at That is, the temperature sensor is mounted on an exhaust pipe or the like for use. However, when a welded portion between metal bodies is arranged in the exhaust gas passage, the welded portion is exposed to a high-temperature environment, so the same The part may be oxidized, and it may not be possible to maintain the durability of the sensor itself and the airtightness with respect to the fluid to be measured such as exhaust gas for a long period of time.
[0016]
Therefore, according to the temperature sensor manufacturing method of the present invention, the portion of the flange that faces the flow passage through which the fluid to be measured, such as the exhaust gas passage, faces (specifically, the front end side of the protrusion) is not the flange. This is done on the sheath located on the rear end side. Accordingly, even when the temperature sensor manufactured according to the present invention is mounted on a flow pipe (for example, an exhaust pipe) through which the fluid to be measured flows, the welded part itself is not exposed to a high temperature environment. Can be suppressed, and the durability of the sensor itself and the airtightness of the fluid to be measured can be maintained satisfactorily for a long period of time. The method of welding the sheath and the metal tube in a form including the press-fit portion is not particularly limited, and examples thereof include laser welding, plasma welding, electron beam welding, and argon welding.
[0017]
Furthermore, in the above-described method for manufacturing a temperature sensor according to the present invention, the sheath portion includes a distal end step portion located on the distal end side and a rear end side step portion having an outer diameter smaller than the distal end step portion. It has a two-stage shape, and the press-fit portion is located at least in the rear-end-side step portion, and the rear-end-side step portion of the sheath portion and the metal tube are preferably welded in the circumferential direction so as to include the press-fit portion.
[0018]
In the method for manufacturing a temperature sensor according to the present invention, the welded portion of the flange is formed in a two-stage shape having a front end side step portion and a rear end side step portion having a smaller diameter than the front end side step portion, and the rear end of the sheath portion in a form including a press-fit portion. The side step and the metal tube are welded. That is, in the sheath portion formed on the flange, a shape in which the thickness of the portion provided for welding with the metal tube is reduced is adopted. With this, after press-fitting and fixing the metal tube and the flange, the sheath and the metal tube can be welded favorably in a form including the press-fit portion, and while securing the welding strength of both, the mechanical strength of the sheath and thus the flange is improved. Can also be secured. In the flange, forming the rear end side of the sheath portion smaller in diameter than the front end side is easier and more preferable than forming the rear end side larger in diameter than the front end side.
[0019]
Further, in the method for manufacturing a temperature sensor described above, a cylindrical joint extending rearward in the axial direction after welding the rear end side step portion of the flange portion of the flange and the metal tube in the circumferential direction is provided. It is good to join to the outer peripheral surface of the step part on the tip side in the circumferential direction. Thus, after welding the rear end side step of the sheath and the metal tube, by joining the cylindrical joint to the front end side step, the welding portion of the rear end side step of the sheath and the metal tube is welded. Can be stored inside the joint. Accordingly, in the temperature sensor manufactured according to the present invention, the joint serves to protect salt water or moisture from adhering to the welded portion between the metal tube and the flange (sheath portion), and the welded portion has the moisture Corrosion due to the influence is suppressed.
[0020]
Next, another solution is to provide a flange having an inner hole, a cylindrical metal tube which is press-fitted and fixed to a press-fit portion in the inner hole of the flange, and has a tip end side closed and extends in the axial direction; A temperature sensor comprising an element that is housed and whose electrical characteristics change according to temperature, between an insertion-side end located at the tip end side of the inner hole of the flange and the press-fit portion, the inner diameter increases toward the press-fit portion. This is a temperature sensor in which a space is formed between an inner peripheral surface of the variable diameter portion and an outer peripheral surface of the metal tube in a state where a variable diameter portion in which the diameter is reduced is formed and the metal tube is press-fitted and fixed to the flange.
[0021]
It should be noted that in the temperature sensor of the present invention, a variable diameter portion whose inner diameter decreases toward the press-fit portion is formed between the press-fit portion and the insertion-side end located at the tip side of the inner hole of the flange. That is. Then, in a state where the metal tube is press-fitted and fixed to the flange, a space is formed between the inner peripheral surface of the variable diameter portion and the outer peripheral surface of the metal tube.
[0022]
Thereby, in the temperature sensor of the present invention, by forming the variable diameter portion in the inner hole of the flange, the temperature sensor is compared with a conventional temperature sensor in which a metal tube is press-fitted and fixed to a flange having an inner hole having a constant inner diameter. Under the condition that the lengths of the inner holes in the axial direction are equal, the length of the heat-sensitive portion from the tip of the press-fitting portion can be increased. That is, in the temperature sensor of the present invention, since the space is formed between the inner peripheral surface of the diameter changing portion of the flange and the outer peripheral surface of the metal tube, the length of the heat-sensitive portion from the tip of the press-fit portion can be increased. In addition, heat conduction from the heat-sensitive portion to the flange can be reduced. As a result, the responsiveness of the sensor itself can be improved as compared with the related art, and a temperature sensor with high temperature measurement accuracy can be obtained.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
(Embodiment)
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.
[0024]
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 press-fitted and fixed to the flange 4.
[0025]
The flange 4 is formed of a stainless alloy (specifically, SUS310S), and has a sheath 42 extending in the axial direction, and a protruding portion located on the distal end side of the sheath 42 and protruding radially outward. 41 and an inner hole 48 penetrating 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 a distal end side, and the seating surface 45 contacts the tapered portion of the mounting portion. This prevents the exhaust gas from leaking out of 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 the front end side step portion 44. ing.
[0026]
A press-fit portion 46 is formed in the inner hole 48 of the flange 4 at least at a portion corresponding to the rear end side step portion 43 of the sheath portion 42, and the metal tube 3 is press-fitted and fixed to the press-fit portion 46. In the present embodiment, the press-fitting portion 46 is formed in a portion of the inner hole 48 of the flange corresponding to the rear end side step portion 43 of the sheath portion 42 and at the rear side of the front end side step portion 44. Is formed up to a part corresponding to a part of the. Further, as shown in the main enlarged view of FIG. 1 shown in FIG. 2, an inner hole 48 of the flange 4 has a press-fit portion 46 between an insert-side end portion 49 located at the front end side thereof and the press-fit portion 46. A variable diameter portion 47 whose inner diameter becomes smaller as going toward is formed. The inner peripheral surface of the variable diameter portion 47 is formed in a tapered shape when viewed as a cross-sectional shape including the central axis of the inner hole 48. In this embodiment, the taper angle is set to 15 °. The function of the diameter changing portion 47 will be described later.
[0027]
The metal tube 3 is inserted from the insertion side end 49 of the inner hole 48 of the flange 4 from the rear end side 32 of the metal tube 3 and is press-fitted and fixed to the press-fitting portion 46 located inside the sheath portion 42. A portion where the outer peripheral surface of the metal tube 3 and the inner peripheral surface of the rear end side step portion 43 of the sheath 42 overlap (that is, the press-fit portion 46) 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 43 of the sheath 42 and the metal tube 3 is formed, and the metal tube 3 is firmly attached to the flange 4. Fixed to.
[0028]
As described above, while the metal tube 3 is press-fitted into the press-fitting portion 46 of the sheath portion 42 of the flange 4 and the laser welding is performed in a form including the press-fitting portion 46 at the rear end side step portion 43 of the sheath portion 42, the flange 4 is formed. Temperature sensor 1 having excellent welding strength between metal tube 3 and metal tube 3 and having excellent adhesion strength between flange 4 and 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. In addition, the reliability of airtightness against exhaust gas can be improved.
[0029]
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 the nut 5 with the seating surface 45 of the projection 41 of the flange 4 abutting the mounting portion of the exhaust pipe. Further, a cylindrical joint 6 is hermetically joined to a radially outer side of the distal 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 step 44 of the sheath 42 so that the inner peripheral surface of the joint 6 overlaps the outer peripheral surface of the distal end step 44 of the sheath 42. The distal step 44 is laser-welded in the circumferential direction. By performing this laser welding, as shown in FIG. 1, a welded portion L 2 extending between the distal end side step portion 44 of the sheath portion 42 and the joint 6 is formed.
[0030]
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.
[0031]
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 the insulating tube 15. The lead wire 12 is formed by coating a conductive wire made of a stainless alloy with an insulating covering material, and is inserted through an auxiliary ring 13 made of heat-resistant rubber provided at an opening on the rear end side of the joint 6. Then, the auxiliary ring 13 is fixed to each other while maintaining the airtightness thereof by being crimped or polygonally crimped from above the joint 6. 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.
[0032]
Here, in the temperature sensor 1 according to the present embodiment, when the air enters the inside of the joint 6 from the outside via the space inside the lead wire 12, the air flows into the inside of the joint 6, the metal tube 3, and the flange 4. Is formed in the metal tube 3 because of the formation in the closed space. Therefore, in the temperature sensor 1, ventilation from the outside (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 metal tube 3 The decrease in the oxygen concentration in the thermistor element 3 can be suppressed, and the characteristic change of the thermistor element 2 can be suppressed.
[0033]
Since this temperature sensor 1 is used in a high-temperature environment of 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.
[0034]
Next, a method of manufacturing the above-described temperature sensor 1 of the present embodiment will be described. First, the metal body of SUS310S is subjected to cold forging or / and cutting, and has an inner hole 48 having a press-fit portion 46 and a diameter changing portion 47, and a front end side step portion 44 and a rear end side step portion 43. A flange 4 having a two-staged sheath portion 42 and a projecting portion 41 located on the distal end side of the sheath portion 42 and projecting radially outward is formed (see FIG. 2). Further, a metal tube 3 having a cylindrical shape whose front end 31 is closed by deep drawing of a steel plate is separately formed. In the present embodiment, the entire metal tube 3 including the bottom wall is formed by deep drawing of a steel plate.
[0035]
Then, the rear end side 32 of the metal tube 3 is inserted from the insertion side end portion 49 of the inner hole 48 of the flange 4, and the press fit portion 46 of the inner hole 48 (at least the press fit portion corresponding to the position of the rear end sheath portion 44). The metal tube 3 is press-fitted and fixed to 46). In this press-fitting step, in the present embodiment, when the inner peripheral surface of the variable diameter portion 47 comes into contact with the rear end of the metal tube 3, the centering effect of the tapered shape of the inner peripheral surface causes the metal tube 3 and the flange 4. Are guided in a direction in which the axes of the two coincide. Therefore, both can be press-fitted in a form in which the misalignment of both is suppressed. Further, since the variable diameter portion 47 is provided in the inner hole 48, the frictional resistance at the beginning of the insertion of the metal tube 3 into the inner hole 48 of the flange 4 (in other words, at the time of passing the variable diameter portion 47) is reduced. And the variation of the press-fit load can be suppressed.
[0036]
Then, after press-fitting the metal tube 3 and the flange 4, the rear end step 43 of the sheath 42 of the flange 4 and the metal tube 3 are laser-welded in the circumferential direction. Next, an assembly in which a predetermined amount of unsolidified cement 10 is filled in the metal tube 3 and the distal end of the metal core wire 7 of the sheath member 8 is connected to the electrode of the thermistor element 2, is assembled from the thermistor element 2 side. Insert inside metal tube 3. Thereafter, the cement 10 is solidified. Next, the rear end of the metal core wire 7 of the sheath member 8 is electrically connected to the lead wire 12 by using a crimping terminal 11 by a known method. Thereafter, the cylindrical joint 6 is press-fitted radially outside the distal end step 44 of the sheath 42, and the joint 6 and the distal end step 44 are laser-welded in the circumferential direction. Then, the auxiliary ring 13 and the nut 5 are appropriately assembled. Thus, the temperature sensor 1 is completed.
[0037]
In the temperature sensor 1 manufactured by the above-described manufacturing method, as shown in FIG. 1, since the variable diameter portion 47 is formed in the inner hole 48 of the flange 4, the metal tube is press-fitted into the flange having the inner hole having a constant inner diameter. Under the condition that the axial length of the inner hole is equal to that of the fixed conventional temperature sensor, the length of the heat-sensitive portion (the portion on the element side arranged in the flow pipe) from the tip of the press-fit portion 46 is increased. be able to. That is, in the temperature sensor 1, as shown in FIG. 2, a ring-shaped space S is generated between the inner peripheral surface of the diameter changing portion 47 of the flange 4 and the outer peripheral surface of the metal tube 3, The length of the heat-sensitive portion can be increased, and heat conduction from the heat-sensitive portion to the flange 4 can be reduced. As a result, the responsiveness of the sensor itself can be improved as compared with the related art, and the temperature sensor 1 with high temperature measurement accuracy can be obtained.
[0038]
In the above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the above-described specific embodiments, and may be appropriately modified and applied without departing from the gist thereof. Needless to say. For example, in the temperature sensor 1 of the present embodiment, the thickness of the metal tube 3 on the distal end side of the portion of the metal tube 3 closer to the press-fit portion 46 in the inner hole 48 of the flange 4 is fixed to the press-fit portion 46. The responsiveness of the temperature sensor can be further improved by making the portion thinner than the portion to be formed.
[0039]
Further, in the temperature sensor 1 of the present embodiment, the variable diameter portion 47 formed on the flange 4 is formed on the most distal side of the inner hole 48 so as to be continuous with the insertion side end portion 49. The formation position is not limited to this, and may be formed between the insertion-side end portion 49 and the press-fit portion 46. For example, a counterbore portion having substantially the same inner diameter and having an inner diameter larger than the inner diameter of the press-fitting portion 46 is formed so as to be continuous with the insertion side end 49, and the rear end of the counterbore portion and the tip of the press-fitting portion 48 are formed. May be formed so that the inner peripheral surface is tapered. Further, the temperature sensor of the present invention can be applied 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 a state where a rear end side of a metal tube housing a thermistor element is inserted from an insertion side end of an inner hole of a flange and is press-fitted and fixed.
FIG. 2 is an enlarged sectional view showing a state in which a metal tube and a flange are press-fitted and fixed in the temperature sensor shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Temperature sensor, 2 ... Thermistor element, 3 ... Metal tube, 4 ... Flange, 41 ... Projection part, 42 ... Sheath part, 43 ... Rear end side step part , 44: tip side step part, 46: press-fit part, 47: deformation part, 48: inner hole, 49: insertion side end part, 6: joint, L1, L2. ..Welds, S ... space

Claims

A flange having an inner hole, a cylindrical metal tube which is press-fitted and fixed to a press-fitting portion in the inner hole of the flange, and whose distal end side is closed and extends in the axial direction, and which is housed inside the metal tube, A method for manufacturing a temperature sensor comprising an element whose electrical characteristics change,
Between the insertion-side end and the press-fitting portion located on the tip side of the inner hole of the flange, a variable-diameter portion whose inner diameter decreases toward the press-fitting portion is formed, and then the inner diameter of the inner hole of the flange is formed. A method for manufacturing a temperature sensor, wherein a rear end side of the metal tube is inserted from an end of the insertion side, and the metal tube is press-fitted and fixed to the flange.

The method according to claim 1, wherein an inner peripheral surface of the variable diameter portion has a tapered shape.

The flange has a sheath portion extending in the axial direction, and a projection portion having a larger diameter than the sheath portion that is located on the distal end side of the sheath portion and protrudes radially outward. 3. The method according to claim 1, wherein the sheath and the metal tube are welded in a circumferential direction at a position including the press-fit portion after the metal tube is press-fitted and fixed to the flange at least within the sheath portion. Manufacturing method of temperature sensor.

The 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 press-fit portion is at least the rear end side. The method for manufacturing a temperature sensor according to claim 3, wherein the rear end step portion of the sheath portion and the metal tube are welded in a circumferential direction in a form including the press-fit portion.

A flange having an inner hole, a cylindrical metal tube which is press-fitted and fixed to a press-fitting portion in the inner hole of the flange, and whose distal end side is closed and extends in the axial direction, and which is housed inside the metal tube, A temperature sensor comprising an element whose electrical characteristics change,
A variable diameter portion whose inner diameter decreases toward the press-fit portion is formed between the insertion-side end portion located on the distal end side of the inner hole of the flange and the press-fit portion, and the metal tube is press-fitted and fixed to the flange. In the temperature sensor, a space is formed between an inner peripheral surface of the variable diameter portion and an outer peripheral surface of the metal tube.