JP2004286491A

JP2004286491A - Manufacturing method of temperature sensor

Info

Publication number: JP2004286491A
Application number: JP2003076555A
Authority: JP
Inventors: Takeshi Hanzawa; 剛半沢; Masahiko Nishi; 雅彦西; Masaki Iwatani; 雅樹岩谷; Takaaki Chiyousokabe; 孝昭長曽我部
Original assignee: NGK Spark Plug Co Ltd
Current assignee: Niterra Co Ltd
Priority date: 2003-03-19
Filing date: 2003-03-19
Publication date: 2004-10-14
Anticipated expiration: 2023-03-19
Also published as: JP4143450B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature sensor manufacturing method wherein a temperature sensitive element is reliably arranged at a prescribed location (target arrangement location) in a tubular metal tube having a bottom. <P>SOLUTION: An electrode wire 22 of a thermistor element 2, the temperature sensitive element, is joined to a metal core wire 7 of a sheath member 8 to prepare a temperature sensitive element assembly. The temperature sensitive element assembly is inserted from a rear-end-side opening of a second tubular part 32 having both open ends, a thermistor sintered body 21 is protruded from the tip side of the second tubular part 32 by a prescribed size, and the sheath member 8 and the second tubular part 32 are caulked and fixed. A tip part of the second tubular part 32, to which the temperature sensitive element assembly is assembled, is positioned inside a rear end part 36 of a first tubular part 31 and arranged in such a way as to create an overlapping part 37 of a prescribed size, and both tubular parts are caulked over their circumferential direction. Their overall circumferences are welded by laser. Thereby the temperature sensor 1 is acquired in which the thermistor sintered body 21 is arranged at the target arrangement location in the tubular metal tube 3 having the bottom. <P>COPYRIGHT: (C)2005,JPO&NCIPI

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焼結体や金属抵抗体等の感温部を有する感温素子を、有底筒状の金属チューブの内部に収納してなる温度センサに関する。詳細には、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感温素子を配置させて、被測定流体の温度検出を行う温度センサに関する。
【０００２】
【従来の技術】
従来より、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排気ガス流路を流れる排気ガスの温度を、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。この種の温度センサとしては、サーミスタ素子を先端側が閉塞した有底筒状の金属チューブの中に収容したものがある。より具体的には、サーミスタ素子の電極線と接続される金属芯線をシースパイプ内に絶縁保持してなるシース部材を、フランジに溶接された一部材から形成される有底筒状の金属チューブ内に挿入しつつ、サーミスタ素子を金属チューブの先端側内部に配置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１図、第２図）
【０００４】
【発明が解決しようとする課題】
ところで、このような形態の温度センサを製造するにあたっては、サーミスタ素子が接続されたシース部材を有底筒状の金属チューブ内に挿入していき、シース部材を金属チューブに所定寸法挿入させることで、金属チューブ内におけるサーミスタ素子の位置決め（換言すれば、金属チューブの先端を基準にした軸線方向における位置決め）を行っている。しかし、サーミスタ素子が接続されたシース部材を細長い有底筒状の金属チューブ内に挿入する場合には、その挿入過程において、サーミスタ素子が金属チューブの内壁面等に当たることがある。すると、その衝撃によってシース部材の金属芯線やサーミスタ素子の電極線が曲がってしまう。
【０００５】
このように上記挿入過程において金属芯線や電極線が曲がることがあると、有底筒状の金属チューブに対してシース部材を所定寸法挿入させてサーミスタ素子の位置決めを行っても、金属チューブ内におけるサーミスタ素子の狙い配置位置からずれて配置されてしまうことがある。そのために、従来の温度センサの製造方法では、同一品番の温度センサを量産した場合に、金属チューブ内のサーミスタ素子の配置位置がまちまちとなりがちで、温度検出の精度にばらつきを来たすおそれがあった。
【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、有底筒状の金属チューブ内にシース部材に接続されたサーミスタ素子等の感温素子を収納する構造の温度センサを製造するにあたって、製造容易であり、且つ感温素子を金属チューブ内の所定位置（狙い配置位置）に確実に配置させることができる温度センサ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、先端側が閉塞した筒状の金属チューブと、温度によって電気的特性が変化する感温部とこれに設けられる一対の電極線とを有し、金属チューブの内部に収納される感温素子と、金属チューブの軸線方向に沿うように配置されると共に、感温素子の電極線と接続される一対の金属芯線をシースパイプの内部に絶縁保持してなるシース部材と、を備える温度センサの製造方法であって、
金属チューブは、先端側が閉塞した有底筒状の第１筒状部と、両端が開口する筒状の第２筒状部とが軸線方向に隣接配置される形態で構成されるものとされており、
感温素子の電極線とシース部材の金属芯線とを互いに接合して感温素子組立体を作製する第１工程と、
第２筒状部の両端のいずれかの開口より感温素子組立体を挿入すると共に、第２筒状部の先端側から感温部の少なくとも一部を突き出させる形態で、第２筒状部の内部に位置するシース部材と当該第２筒状部とを固定して、感温素子組立体を第２筒状部に組み付ける第２工程と、
感温素子組立体が組み付けられた第２筒状部の先端部を、第１筒状部の後端部の内側または外側に位置させた形で重なり部を生ずるように配置し、重なり部に周方向にわたって溶接を行う第３工程と、
を備えることを特徴とする温度センサの製造方法である。
【０００８】
本発明の温度センサの製造方法では、有底筒状の金属チューブを従来のように一部材で形成せずに、複数の部材（筒状部）にて形成している。そして、複数の部材の１つである第２筒状部の両端のいずれかの開口より、感温素子が接続されるシース部材を挿入し、第２筒状部の内部に位置するシース部材と当該第２筒状部とを固定する。このとき、第２筒状部の先端側から感温部の少なくとも一部を突き出せる形態で、第２筒状部とシース部材とを固定する。そして、先端側から感温部の少なくとも一部を突き出させた状態の第２筒状部に対して、有底筒状の第１筒状部を周方向にわたって溶接して、金属チューブ内に感温素子を収納させている。
【０００９】
つまり、本発明の温度センサの製造方法によれば、第２筒状部に感温素子組立体を挿入する過程において、感温部が第２筒状部の内壁面に当たってシース部材の金属芯線や感温素子の電極線が曲がったとしても、第２筒状部の両端を開口させているので、同第２筒状部の先端側から感温部の少なくとも一部を確実に所定寸法（予定した寸法）だけ突き出させるように調整することができる。そして、先端側から感温部を所定寸法突き出させた状態の第２筒状部と有底筒状の第１筒状部とを同軸状に所定寸法（予定した寸法）だけ重ねて溶接すれば、有底筒状の金属チューブの狙い配置位置に感温素子を確実に配置させることができる。従って、金属チューブを複数の部材にて形成してなる本発明によれば、同一品番の温度センサを量産する場合にも、感温素子（感温部）を金属チューブ内の所定位置（狙い配置位置）に確実に配置させることができる。
【００１０】
また、本発明の温度センサの製造方法では、シース部材（感温素子組立体）が固定された第２筒状部の先端部に第１筒状部の後端部の内側または外側に位置する形で重なり部を生ずるように配置して溶接するようにしているので、容易に有底筒状の金属チューブを形成することができる。よって、本発明によれば、感温素子（感温部）を金属チューブ内の狙い配置位置に配置させた温度センサを製造効率良く、且つ容易に製造することができる。
【００１１】
感温素子としては、感温部としてサーミスタ焼結体を用い、このサーミスタ焼結体に電極線の一部を埋設させたサーミスタ素子や、温度によって抵抗値が変化する金属抵抗体をセラミック基板上に形成したものを感温部として用い、この金属抵抗体に電極線を接続した基板型素子等を挙げることができる。さらに、金属チューブを構成することになる第１筒状部及び第２筒状部は、十分な機械的強度及び耐熱性等を有する金属材料にて形成されていればその材質は特に限定されず、具体的にはステンレス合金やインコネル材によって形成することができる。
【００１２】
感温素子組立体が組み付けられた第２筒状部の先端部を第１筒状部の後端部の内側または外側に位置する形で重なり部を生ずるように配置するにあたっては、両者を当接させる形態で重なり部を生ずるように配置しても良いし、両者が遊嵌状態で重なり部を生ずるように配置しても良い。また、この重なり部を周方向にわたって溶接するための溶接手法は特に限定されないが、具体的な手法として、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。なお、この中でもレーザー溶接が安価な手法でありながら、良好な溶接強度を得ることができることから最も好ましい。
【００１３】
ついで、上記温度センサの製造方法であって、前記第２工程において、前記第２筒状部の先端側から前記感温素子の前記電極線と前記シース部材の前記金属芯線との接続部までを少なくとも突き出させるようにして、前記感温素子組立体を前記第２筒状部に組み付ける温度センサの製造方法とすると良い。
【００１４】
第２筒状部に感温素子が接続されたシース部材を挿入する過程においては、上述したようにシース部材の金属芯線や感温素子の電極線が曲がることがあるが、この曲がりの程度によっては、金属芯線と電極線の接続部が切り離されたりするといった不具合を招く可能性がある。そのために、感温部の一部のみを第２筒状部の先端側から突き出す形態で、第２筒状部とシース部材とを固定したのでは、感温部を金属チューブの狙い配置位置に配置させることはできるものの、感温部からの電気的出力を、電極線及び金属芯線を介して出力することができないおそれがある。
【００１５】
これに対して、本発明の温度センサの製造方法によれば、第２工程において、感温素子の電極線とシース部材の金属芯線との接続部までを少なくとも第２筒状部の先端側から突き出させた形態で、第２筒状部とシース部材とを組み付けるようにしている。これにより、シース部材（感温素子組立体）を第２筒状部に組み付けた後、第２筒状部の先端側にて、電極線と金属芯線との接続部の状態を確認することができる。従って、本発明によれば、感温素子（感温部）を金属チューブ内の狙い配置位置に配置させつつ、電気的な信頼性に優れた温度センサを、製造効率良く得ることができる。なお、本明細書において、「感温素子の電極線とシース部材の金属芯線との接続部」とは、該電極線と該金属芯線とが重なり合う（ラップする）部位を指すものである。
【００１６】
なお、上記温度センサの製造方法では、第２工程において、上記接続部に留まらず、シース部材のシースパイプの先端から突き出た金属芯線までを第２筒状部の先端側から突き出させた形態で、第２筒状部とシース部材とを組み付けると良い。このようにすれば、シース部材（感温素子組立体）を第２筒状部に組み付けた後、第２筒状部の先端側にて、電極線と金属芯線との接続部の状態を確認する以外に、電極線同士、金属芯線同士が接触して短絡を生じていないかどうかを確認することができ、より電気的な信頼性に優れた温度センサを製造することができる。
【００１７】
さらに、上記いずれかに記載の温度センサの製造方法であって、前記第２工程において、前記第２筒状部と前記シース部材との固定は、前記第２筒状部を前記シース部材の前記シースパイプの外周面に向けて加締めることにより行う温度センサの製造方法とすると良い。
【００１８】
このように、第２筒状部とシース部材とを加締め固定することにより、両者を安価な手法により強固に固定することができる。なお、第２筒状部とシース部材とを加締め固定するにあたっては、第２筒状部の周方向において２点以上で加締めることが好ましい。第２筒状部内において、シース部材を安定して固定することができるからである。また、シースパイプの外側にて行われる第２筒状部の加締めにおいて、その加締め深さが第２筒状部の肉厚以上になると、加締めを行ったときに同第２筒状部が破損する（換言すれば、加締め割れを生ずる）おそれがある。そこで、この第２筒状部の破損を抑制するために、第２筒状部の肉厚をＤ（単位：ｍｍ）、シースパイプの外周面と第２筒状部の内周面との加締め前における隙間をＳ（単位：ｍｍ）としたときに、Ｄ≧Ｓの関係を満たすように調整されていることが好ましい。
【００１９】
また、上記温度センサの製造方法において、前記第２筒状部の軸線方向における離間した少なくとも２箇所以上の位置において、前記第２筒状部を前記シース部材の前記シースパイプに向けて加締めるようにすると良い。
【００２０】
このように、第２筒状部の軸線方向の離間した少なくとも２箇所以上の位置にて、第２筒状部とシース部材との加締め固定を行うことによって、第２筒状部に対するシース部材の固定をより安定して実現することができる。なお、この軸線方向の離間した位置での各加締めについても、第２筒状部の周方向において２点以上で加締めることが好ましい。
【００２１】
さらに、上記いずれかに記載の温度センサの製造方法であって、前記第３工程において、前記第２筒状部の先端部と前記第１筒状部の後端部を遊嵌状態で前記重なり部が生ずるように配置し、前記重なり部において該第１筒状部及び該第２筒状部のうちで外側に位置する筒状部を内側に位置する筒状部に向けて周方向に加締めることで加締め部を形成して、前記加締め部に周方向の前記溶接を行うようにすると良い。
【００２２】
第２筒状部の先端部と第１筒状部の後端部とを重なり部を生ずるように配置させるにあたっては、例えば第２筒状部の先端部外側に対して第１筒状部を圧入させれば実現することが可能である。ところで、この第３工程では、有底筒状の金属チューブ内の狙い位置に感温部を配置させるために、上述したように先端側から感温部を所定寸法突き出させた第２筒状部と有底筒状の第１筒状部とを所定寸法重ね合わせる必要がある。しかし、第１筒状部と第２筒状部とを上記圧入によって所定寸法重ねるには、両筒状部に対する径寸法の管理をかなり厳しく行う必要があると共に、圧入工程に手間がかかるため好ましい態様とは言い難い側面がある。
【００２３】
これに対して、本発明の温度センサの製造方法では、まず、第２筒状部の先端部と第１筒状部の後端部を遊嵌状態で重なり部が生ずるように配置させるようにしている。このように両筒状部を遊嵌状態で重ね合わせるようにすることで、両筒状部を容易に所定寸法だけ重ねることができる。
【００２４】
そして、第２筒状部の先端部と第１筒状部の後端部を遊嵌状態で重なり部が生ずるように配置した後、この重なり部において第１筒状部及び第２筒状部のうちで外側に位置する筒状部を内側に位置する筒状部に向けて周方向に加締めることで加締め部を形成するようにしている。このような加締め部を形成することにより、遊嵌状態に重ねられた両筒状部との間の隙間を減少させて密着性を高めることができる。そして、このように両筒状部の密着性が高まった状態にある周方向に形成された加締め部に対し周方向の溶接を行うことによって、第１筒状部と第２筒状部とを確実に溶接することができる。
【００２５】
このように本発明によれば、上記加締め部を形成するようにしたので、第１筒状部及び第２筒状部に対する径寸法管理を極度に厳しく行わなくとも、両筒状部を所定寸法重ね合わせた後に確実に溶接することができ、ひいては温度センサの製造効率を高めることができる。なお、上記重なり部において第１筒状部及び第２筒状部のうちで外側に位置する筒状部を内側に位置する筒状部に向けて周方向に加締めるにあたっては、六角加締めや八角加締めといった多角加締めの方法で行っても良いし、丸加締め等の方法で行っても良い。
【００２６】
さらに、上記いずれかに記載の温度センサの製造方法であって、前記第２筒状部の外径よりも小さい内径を有する小径部と、前記小径部よりも後端側に位置すると共に、前記第２筒状部の外径以上の内径を有する前記後端部と、前記小径部と前記後端部とを繋ぐ段部とを有する前記第１筒状部を、前記第３工程に先立って形成し、前記第３工程において、前記第２筒状部の先端が前記第１筒状部の前記段部に当接するように、且つ前記第１筒状部の前記後端部の内側に前記第２筒状部の先端部を位置させた形で前記重なり部を生ずるように、該第１筒状部と該第２筒状部とを組み付ける温度センサの製造方法とすると良い。
【００２７】
本発明の温度センサでは、第１筒状部として、先端側から小径部、段部、後端部の順に形成された第１筒状部を用いるようにし、第２筒状部の外径よりも小さく内径を有する小径部と、第２筒状部の外径以上の内径を有する大径部と、それらを繋ぐ段部とを有するものを用いている。そして、この第１筒状部を第２筒状部に挿入するにあたって、第１筒状部の小径部の後端側に連結する段部の内面に第２筒状部の先端が当接するまで挿入を行い、第２筒状部に対する第１筒状部の軸線方向における位置決めを行うようにしている。
【００２８】
それより、本発明の温度センサの製造方法では、第２筒状部の先端が第１筒状部の段部の内面に当接した時点で、所定寸法（予定した寸法）の重なり部が生ずるように第１筒状部の各寸法を予め調整しておくことにより、第２筒状部３２の先端が第１筒状部３１の段部３８の内面に当接するように挿入を行うだけで、重なり部の重なり寸法を予定した値に設定することができる。その結果、感温部を第１筒状部の狙い位置により確実に配置させることが可能となる。なお、第１筒状部と第２筒状部の軸ズレを有効に防止するために、段部の内面はテーパ形状をなしていることが好ましい。
【００２９】
また、上記いずれかに記載の温度センサの製造方法であって、前記第３工程において、前記第２筒状部の先端側から突き出た前記感温部の周囲を加熱処理によって絶縁性部材となるペースト状の絶縁性ペーストにて覆った上で、前記第１筒状部と前記第２筒状部とを前記重なり部を生ずるように配置させ、第３工程を経て得られた組立体に対して加熱処理を行って、前記感温部と前記第１筒状部との間に絶縁部材を介在させるようにすると良い。
【００３０】
このようにして、第２筒状部の先端側から突き出た感温部の周囲であって、第１筒状部の内壁面との間に絶縁部材を介在させることにより、感温素子を振動から保護するができ、感温素子に熱を早く伝えて応答性を向上可能な温度センサを製造することができる。また、本発明の温度センサの製造方法によれば、第１工程の段階で感温素子組立体の感温部に絶縁性ペーストを被覆せずに、第２筒状部に感温素子組立体を組み付けた後に、その第２筒状部の先端側から突き出た感温部に絶縁性ペーストを被覆するようにしている。その結果、前記第２工程において、感温部を第２筒状部の先端側から所定寸法突き出させることが容易となり、温度センサの製造効率を高めることができる。
【００３１】
【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。また、図２は図１に示した温度センサ１の要部であるサーミスタ素子２近傍の拡大図である。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、同温度センサ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。
【００３２】
金属チューブ３は、先端側（図１における下側）が閉塞した有底筒状に形成されており、この先端側の内部にサーミスタ素子２を収納している。この金属チューブ３は、先端側が閉塞する一方で後端側が開口する有底筒状の第１筒状部３１と、両端が開口する筒状の第２筒状部３２とが、軸線方向に隣接配置される形態で構成されている。より具体的には、第２筒状部３２の先端部の外周面を取り囲むように第１筒状部３１が配置され、周方向にわたって形成される加締め部３９によって加締め固定されると共に、その加締め部３９に全周レーザー溶接されることによって一体化されている。なお、この第１筒状部３１、第２筒状部３２は、略同等の肉厚を有しており、後述するようにステンレス合金から形成されている。
【００３３】
第１筒状部３１は、サーミスタ素子２の感温部であるサーミスタ焼結体２１を内部に収納している。なお、第１筒状部３１のうちで第２筒状部３２の先端部の外側面との間で重なり部３７を生ずる部位（後端部３６）よりも先端側には、第２筒状部３２の外径よりも内径が小さく形成された小径部３３が形成されている。また、第１筒状部３１には、小径部３３と後端部３６とを繋ぐ段部３８が形成されており、この段部３８の内面に第２筒状部３２の先端を当接させることで、第２筒状部３２に対する第１筒状部３１の軸線方向における位置決めを行っている。
【００３４】
第１筒状部３１の小径部３３の内部には、感温部であるサーミスタ焼結体２１の全体が収納される。そして、この小径部３３の内部には、絶縁性部材であるセメント１０が充填されている。より具体的には、サーミスタ焼結体２１の外表面と第１筒状部３１（詳細には小径部３３）の内壁面との間にセメント１０が介在するように、小径部３３の内部にセメント１０が充填されている。このようにセメント１０が介在することで、振動等によるサーミスタ素子２の揺動が防止される。さらには、金属チューブ３（第１筒状部３１）の受熱を、セメント１０を介してサーミスタ焼結体２１に効率良く伝熱することができ、温度検出の高速応答化を図ることができる。なお、本実施の形態に使用されるセメント１０は、アルミナ粉末を主成分とする骨材と、Ｓｉを含むガラス成分とからなる。
【００３５】
一方、第２筒状部３２は、後端側がステンレス合金製のフランジ４の内側に挿通される形態で、同フランジ４に固定される。この第２筒状部３２は、内部に後述するシース部材８の先端側を配置している。なお、第２筒状部３２の軸線方向における離間した２箇所の位置（部位）には、自身の外側からシース部材８（詳細には、後述するシース部材８のシースパイプ９の外周面）に向けて加締めることによって形成された先端側加締め部３４と、後端側加締め部３５とが備えられている。この先端側加締め部３４と後端側加締め部３５によって、第２筒状部３２とシース部材８とは固定（加締め固定）されている。
【００３６】
フランジ４は、軸線方向に延びる鞘部４２と、この鞘部４２の先端側に位置し、径方向外側に向かって突出する突出部４１とを有している。突出部４１は、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。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。
【００３７】
第２筒状部３２は、自身の先端側からフランジ４の後端側より挿入され、鞘部４２の内側に圧入固定されている。そして、第２筒状部３２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が、周方向にわたってレーザー溶接されている。
【００３８】
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の内で鞘部４２の先端側段部４４の径方向外側には、筒状の継手６が気密状態で接合されている。具体的には、鞘部４２の先端側段部４４の外周面に継手６の内周面が重なり合うように、同継手６が鞘部４２の先端側段部４４に圧入され、継手６と先端側段部４４とが周方向にわたってレーザー溶接されている。
【００３９】
金属チューブ３における第２筒状部３２、フランジ４及び継手６の内部には、一対の金属芯線７をシースパイプ９内に絶縁保持してなるシース部材８が配置される。シース部材８は、上述したように第２筒状部３２に対して加締め固定されている。このシース部材８の先端側から突出する金属芯線７は、サーミスタ素子２を構成する一対のＰｔ／Ｒｈ合金製の電極線２２に互いに抵抗溶接されることで接続されている。なお、一対の電極線２２は、自身の先端部が軸断面六角形状をなすサーミスタ焼結体２１の内部に埋設されており、サーミスタ焼結体２１と同時に焼成されて形成されている。また、シース部材８は、ＳＵＳ３１０Ｓからなるシースパイプ９と、ＳＵＳ３１０Ｓからなる導電性の一対の金属芯線７と、シースパイプ９と各金属芯線７の間に充填される絶縁粉末１４（図４参照）とから形成され、金属芯線７が絶縁状態でシースパイプ９に保持された形態で構成されている。
【００４０】
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に接続されている。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。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。そして、排気ガスの温度変化に応じたサーミスタ焼結体２１からの電気的出力は、電極線２２、シース部材８の金属芯線７、リード線１２を介して図示しない外部回路（例えば、ＥＣＵ）に取り出され、排気ガスの温度検出に用いられる。
【００４１】
この排気ガスの温度を検出する温度センサ１は、最高温度で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を構成する第１筒状部３１及び第２筒状部３２、フランジ４、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。
【００４２】
温度センサ１は、以下のようにして製造される。まず、ＳＵＳ３１０Ｓ製の鋼板に深絞り加工を行って、肉厚０．３ｍｍ、内径２．７ｍｍ、外径３．３ｍｍ、全長（軸線方向における寸法）５４ｍｍをなし、両端が開口した第２筒状部３２と、肉厚０．３ｍｍ、全長（軸線方向における寸法）１３ｍｍをなす有底筒状の第１筒状部３１とを形成する。なお、第１筒状部３１については、内径２．６ｍｍ、外径３．２ｍｍの小径部３３と、内径３．４ｍｍ、外径４．０ｍｍの後端部３６と、小径部３３と後端部３６とを繋ぐテーパ形状を有する段部３８とが形成されるように加工を施した。また、別途ＳＵＳ３１０Ｓの金属体に対して冷間鍛造又は／及び切削加工を施して、第２筒状部３２を圧入固定するための内孔と、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。
【００４３】
そして、第１工程として、サーミスタ素子２の電極線２２とシース部材８の金属芯線７とを所定寸法だけラップするように重ね合わせ、互いを抵抗溶接することによって、図３に示すようなシース部材８にサーミスタ素子２が接続された感温素子組立体Ｋを作製する（サーミスタ素子２の電極線２２とシース部材８の金属芯線７とのラップした部位が、特許請求の範囲の「接続部」に相当）。図３は、感温素子組立体Ｋの外観図を示している。なお、シース部材８を構成するシースパイプ９の先端側の所定領域には、後工程において、第１筒状部３１と第２筒状部３２とを加締め固定した際に形成される加締め部３９が自身の外周面に接触しないように、径方向内側に向かって窪む凹部８１を形成している。また、このシースパイプ９は、上記凹部８１を除く部分の肉厚が０．３ｍｍ、外径が２．５ｍｍとなるように形成されている。ついで、第２筒状部３２をフランジ４の内孔に圧入固定し、第２筒状部３２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を、周方向にわたってレーザー溶接する。
【００４４】
そして、第２工程として、フランジ４にレーザー溶接された第２筒状部３２内に感温素子組立体Ｋを挿入する。このとき、感温素子組立体Ｋのサーミスタ素子２が配置される側から、第２筒状部３２の後端側の開口への挿入を開始する。そして、第２筒状部３２の先端側からサーミスタ素子２のサーミスタ焼結体２１を所定寸法Ｌ１（図５参照）だけ突き出させ、サーミスタ焼結体２１が所定寸法Ｌ１突き出た時点で、感温素子組立体Ｋの第２筒状部３２への挿入を終了する。その後、第２筒状部３２の先端側から突き出た状態にある電極線２２と金属芯線７との接続部に異常がないかどうか、さらには電極線２２同士、金属芯線７同士が接触していないかを確認する。この確認作業にて感温素子組立体Ｋに異常無しと判断されると、続いて第２筒状部３２と感温素子組立体Ｋとを固定する作業を行う。
【００４５】
第２筒状部３２と感温素子組立体Ｋとの固定については、以下の手順により行う。まず、第２筒状部３２のうちで、フランジ４よりも先端側に突き出た部位であって且つフランジ４の先端に近接した部位を、シース部材８のシースパイプ９の外周面に向けて加締める。この加締め工程は、図４（ａ）及び（ｂ）に示すように、加締め型Ｂを用いて、第２筒状部３２の外側から周方向において対向する２点を加締めるようにして行う。これにより、２つの後端側加締め部３５を形成し、シース部材８（感温素子組立体Ｋ）と第２筒状部３２とを加締め固定する。
【００４６】
ついで、後端側加締め部３５よりも軸線方向先端側に離間した部位であって且つ凹部８１よりも後端側の部位を、シース部材８のシースパイプ９の外周面に向けて加締める。この加締め工程についても、上述した加締め型Ｂを用い、第２筒状部３２の外側から周方向において対向する２点を加締めるようにした。これにより、２つの先端側加締め部３４を形成し、上記後端側加締め部３５と共にシース部材８（感温素子組立体Ｋ）と第２筒状部３２とを加締め固定する。このようにして、第２筒状部３２の先端側からサーミスタ焼結体２１を所定寸法Ｌ１だけ突き出させた形態で、感温素子組立体Ｋと第２筒状部３２とを一体的に組み付ける。感温素子組立体Ｋと第２筒状部３２が一体的に組み付けられた組付体構造の部分破断断面図を、図５に示す。
【００４７】
ここで、本実施の形態では、詳細は図示しないが、対向し合う２つの後端側加締め部３５同士を第２筒状部３２の軸線方向に直交する向きに結んだ仮想線と、対向し合う２つの先端側加締め部３４同士を上記軸線方向に直交する向きに結んだ仮想線とが、第２筒状部３２の軸線方向に沿ってみたときに直交する関係を満たすように、両加締め部３４、３５を形成している。このような直交関係を満たすように両加締め部３４、３５を形成することで、第２筒状部３２内に配置されるシース部材８をより安定して保持することができる。なお、上記仮想線については、周方向における２点の加締め部をみたときに第２筒状部３２の内周面とシースパイプ９の外周面とが点接触する場合、その点接触する箇所同士を第２筒状部３２の軸線方向に直交する向きに結ぶことで導くことができる。一方、周方向における２点の加締め部をみたときに第２筒状部３２の内周面とシースパイプ９の外周面とが面接触する場合には、その面接触する部分の中央部（中心）同士を第２筒状部３２の軸線方向に直交する向きに結ぶことで上記仮想線を導くことができる。
【００４８】
なお、本実施形態では、先端側加締め部３４および後端側加締め部３５の各加締め部を、軸線方向に沿った軸線長さが加締め幅よりも長い寸法を有するように形成している。具体的に、両加締め部３４、３５のそれぞれは、軸線長さＬ５を４．０ｍｍ、加締め幅Ｗを０．４ｍｍとなるように形成した（図４参照）。このように各加締め部の軸線長さを加締め幅よりも長い寸法を有するように形成することで、第２筒状部３２に対して細長いシース部材８を安定して固定することができる。
【００４９】
ついで、感温素子組立体Ｋを組み付けた第２筒状部３２に対して、第１筒状部３１を組み付けてサーミスタ素子２を有底筒状の金属チューブ３の内部に収納させる第３工程を行う。まず、第２筒状部３２の先端側から所定寸法Ｌ１だけ突き出たサーミスタ焼結体２１の周囲を覆うように、セメント１０となる絶縁性ペーストを塗布する。ついで、第２筒状部３２の先端側から第１筒状部３１を遊嵌状に且つ同軸状に挿入し、第１筒状部３１の後端部３６が第２筒状部３２の先端部の外側面を取り囲むように、第２筒状部３２に対して第１筒状部３１を隣接配置させる。このとき、図６に示すように、第２筒状部３２の先端部に遊嵌状態で所定寸法Ｌ２の重なり部３７を生ずるように、且つサーミスタ素子２のサーミスタ焼結体２１が絶縁性ペーストと共に第１筒状部３１の小径部３３に収納されるように、第１筒状部３１を第２筒状部３２に対して配置させる。
【００５０】
ここで、本実施の形態では、第１筒状部３１を第２筒状部３２に挿入するにあたって、第１筒状部３１の小径部３３の後端側に連結する段部３８の内面に第２筒状部３２の先端が当接するまで挿入を行うことで、第２筒状部３２に対する第１筒状部３１の軸線方向における位置決めを行っている。つまり、本実施の形態では、第１筒状部３１を第２筒状部３２に遊嵌状且つ同軸状に挿入していき、第２筒状部３２の先端が第１筒状部３１の段部３８の内面に当接した時点で、所定寸法Ｌ２の重なり部３７が生ずるように、第１筒状部３１の各寸法を予め調整しているのである。これにより、本実施の形態では、第１筒状部３１の各寸法を適宜調整し、第２筒状部３２の先端が第１筒状部３１の段部３８の内面に当接するように挿入を行うことで、第２筒状部３２に対する第１筒状部３１の軸線方向における重なり寸法（図６のＬ２に相当）を一義的に決めることができる。その結果、サーミスタ焼結体２１を第１筒状部３１の狙い位置に確実に配置させることが可能となる。
【００５１】
ついで、第１筒状部３１の後端部３６と第２筒状部３２の先端部の重なり部３７であって、シース部材８のシースパイプ９に形成した凹部８１を取り囲む部位において、外側に位置する第１筒状部３１を内側に位置する第２筒状部３２に向けて周方向に加締めて、加締め部３９を形成する。このとき、加締め部３９は、リードパイプ９の凹部８１の表面に接触しないように形成する。なお、この加締めは、八方丸加締めにて行った。このようにして形成される加締め部３９は、後述する全周レーザー溶接によるレーザー溶接部の形成部位にあたるが、この加締め部３９を形成することで、第１筒状部３１と第２筒状部３２との間の隙間量を減少させることができ、溶接強度に優れる全周レーザー溶接を行うことができる。
【００５２】
そして、図７に示すように、この重なり部３７に形成された加締め部３９に対して、レーザー光ＬＢを照射して全周レーザー溶接を行い、第１筒状部３１と第２筒状部３２とに跨るレーザー溶接部を形成して、両筒状部３１、３２を一体化する。その後、両筒状部３１、３２を一体化した組立体を加熱処理することで、絶縁性ペーストを固化させてセメント１０を得る。
【００５３】
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の製造を完了する。
【００５４】
このような温度センサ１の製造方法によれば、第２筒状部３２に感温素子組立体Ｋを挿入する過程において、サーミスタ焼結体２１が第２筒状部３２の内壁面に当たってシース部材８の金属芯線９やサーミスタ素子２の電極線２２が曲がったとしても、第２筒状部の両端を開口させているので、第２筒状部３２の先端側からサーミスタ焼結体２１を確実に予定した所定寸法Ｌ１だけ突き出させることができる。そして、上述した製造方法では、先端側からサーミスタ焼結体２１を所定寸法Ｌ１突き出させた第２筒状部３２と有底筒状の第１筒状部３１とを同軸状に所定寸法Ｌ２だけ重ねて、両筒状部３１、３２を溶接により一体化することで、有底筒状の金属チューブ３の予定した位置（狙い配置位置）にサーミスタ素子２（サーミスタ焼結体２１）を配置させた温度センサ１を得ることができる。従って、この温度センサ１の製造方法によれば、同一品番の温度センサを量産する場合にも、サーミスタ素子２（サーミスタ焼結体２１）を金属チューブ３内の所定位置（狙い配置位置）に確実に配置させることができる。
【００５５】
また、上述した温度センサ１の製造方法では、シース部材８（感温素子組立体Ｋ）が固定された第２筒状部３２の先端部に第１筒状部３１の後端部の内側が位置する形で重なり部３７を生ずるように配置して溶接しているので、容易に有底筒状の金属チューブ３を形成することができる。よって、サーミスタ素子２（サーミスタ焼結体２１）を金属チューブ３内の狙い配置位置に配置させた温度センサ１を製造効率良く、且つ容易に製造することができる。
【００５６】
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、感温素子組立体Ｋ（シース部材８）と第２筒状部３１を加締め固定するにあたっては、第２筒状部３２の外側から周方向において対向する２点を加締める形態に限らず、第２筒状部３２の外周面から周方向に等間隔で３点を加締めるようにして、先端側加締め部３４及び後端側加締め部３５を形成し、両者を加締め固定しても良い。
【００５７】
また、第１筒状部３１と第２筒状部３２の重なり部３７における溶接は、レーザー溶接を周方向にわたって行っているが、溶接はレーザーに限らずプラズマ溶接でも良い。さらに、本実施の形態では、サーミスタ焼結体２１を感温部としたサーミスタ素子２を感温素子として使用したが、温度によって抵抗値が変化する金属抵抗体をセラミック基板上に形成したものを感温部とし、この金属抵抗体に電極線を接続した基板型素子を感温素子として用いても良い。また、本実施の形態では、第２筒状部３２の先端側からサーミスタ素子２の全体を突き出させるようにしたが、サーミスタ素子２を構成するサーミスタ焼結体２１の少なくとも一部を所定寸法突き出させるようにして、温度センサを製造しても良い。
【００５８】
また、感温部をなすサーミスタ焼結体２１の形状は、軸断面において六角形状に限定されず、円形状や楕円形状であっても良い。さらに、本発明の温度センサ１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】第１筒状部と第２筒状部を軸線方向に隣接配置して構成された有底筒状の金属チューブ内に、感温素子であるサーミスタ素子を収納した温度センサの全体構造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、要部であるサーミスタ素子２近傍の拡大図である。
【図３】サーミスタ素子とシース部材とを組み付けた感温素子組立体の外観図である。
【図４】第２筒状部をシース部材のシースパイプの外周面に向けて加締める工程を模式的に示す図である。
【図５】第２筒状部の先端側から所定寸法サーミスタ素子（サーミスタ焼結体）を突き出させた状態で、感温素子組立体と第２筒状部を一体的に組み付けた構造を示す部分破断断面図である。
【図６】感温素子組立体を組み付けた第２筒状部の先端部の外側に、第１筒状部の後端側を所定寸法重なるようにして遊嵌状に配置させた状態を示す図である。
【図７】レーザーを照射して第１筒状部と第２筒状部を全周レーザー溶接する状態を模式的に示す図である。
【符号の説明】
１・・・温度センサ、２・・・サーミスタ素子、２１・・・サーミスタ焼結体、２２・・・電極線、３・・・金属キャップ、３１・・・第１筒状部、３２・・・第２筒状部、３３・・・小径部、３４・・・先端側加締め部、３５・・・後端側加締め部、３６・・・後端部、３７・・・重なり部、３８・・・段部、３９・・・加締め部、４・・・フランジ、６・・・継手、７・・・金属芯線、８・・・シース部材、９・・・シースパイプ、１０・・・セメント、１２・・・リード線、１４・・・絶縁粉末、Ｋ・・・感温素子組立体。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a temperature sensor in which a temperature-sensitive element having a temperature-sensitive portion such as a thermistor sintered body or a metal resistor made of a semiconductor such as a metal oxide is housed in a bottomed cylindrical metal tube. Specifically, a temperature sensing element is disposed in a flow passage through which a fluid to be measured (for example, exhaust gas) flows, such as in a catalytic converter or an exhaust pipe of an exhaust gas purifying device of an automobile, to detect the temperature of the fluid to be measured. It relates to a temperature sensor.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there has been known a temperature sensor that detects the temperature of exhaust gas flowing through an exhaust gas flow path such as the inside of a catalytic converter or the inside of an exhaust pipe of an exhaust gas purifying device of an automobile using a thermistor element that is a temperature-sensitive element, a so-called exhaust temperature sensor. ing. As this type of temperature sensor, there is a temperature sensor in which a thermistor element is housed in a bottomed cylindrical metal tube whose front end is closed. More specifically, a sheath member obtained by insulating and holding a metal core wire connected to the electrode wire of the thermistor element in a sheath pipe is placed in a bottomed cylindrical metal tube formed from one member welded to a flange. There is known a temperature sensor having a structure in which a thermistor element is arranged inside a distal end side of a metal tube while being inserted into a metal tube (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP 2000-266609 A (FIGS. 1 and 2)
[0004]
[Problems to be solved by the invention]
By the way, when manufacturing a temperature sensor of such a form, the sheath member to which the thermistor element is connected is inserted into a bottomed cylindrical metal tube, and the sheath member is inserted into the metal tube by a predetermined dimension. The positioning of the thermistor element in the metal tube (in other words, positioning in the axial direction with reference to the tip of the metal tube) is performed. However, when the sheath member to which the thermistor element is connected is inserted into an elongated bottomed cylindrical metal tube, the thermistor element may hit the inner wall surface or the like of the metal tube during the insertion process. Then, the metal core wire of the sheath member and the electrode wire of the thermistor element are bent by the impact.
[0005]
In this way, if the metal core wire or the electrode wire is bent in the above insertion process, even if the sheath member is inserted into the bottomed cylindrical metal tube by a predetermined size to position the thermistor element, the thermistor element is positioned inside the metal tube. The thermistor element may be displaced from the intended arrangement position. Therefore, in the conventional method of manufacturing a temperature sensor, when mass-producing temperature sensors of the same product number, the arrangement positions of the thermistor elements in the metal tube tend to be different, and there is a possibility that the accuracy of the temperature detection may vary. .
[0006]
SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and is intended to manufacture a temperature sensor having a structure in which a thermosensitive element such as a thermistor element connected to a sheath member is housed in a bottomed cylindrical metal tube. It is an object of the present invention to provide a method of manufacturing a temperature sensor which is easy to manufacture and can surely arrange a temperature-sensitive element at a predetermined position (target arrangement position) in a metal tube.
[0007]
[Means for Solving the Problems]
The solution includes a cylindrical metal tube having a closed distal end, a temperature-sensitive portion whose electrical characteristics change with temperature, and a pair of electrode wires provided in the tube. A temperature element, and a sheath member arranged along the axial direction of the metal tube and having a pair of metal core wires connected to the electrode wires of the temperature sensitive element insulated and held inside the sheath pipe. A method for manufacturing a sensor, comprising:
The metal tube is configured in such a manner that a first tubular portion having a closed bottom at the distal end and a tubular second tubular portion having both ends opened are arranged adjacent to each other in the axial direction. Yes,
A first step of bonding the electrode wire of the temperature-sensitive element and the metal core wire of the sheath member to each other to produce a temperature-sensitive element assembly;
The second tubular portion is inserted by inserting the temperature sensing element assembly through one of the openings at both ends of the second tubular portion and projecting at least a part of the temperature sensing portion from the distal end side of the second tubular portion. A second step of fixing the sheath member located inside the second cylindrical portion and the second cylindrical portion, and assembling the temperature-sensitive element assembly to the second cylindrical portion;
The distal end of the second cylindrical portion to which the temperature-sensitive element assembly is attached is arranged so as to form an overlapping portion in a form positioned inside or outside the rear end of the first cylindrical portion. A third step of welding over the circumferential direction;
A method for manufacturing a temperature sensor, comprising:
[0008]
In the method of manufacturing a temperature sensor according to the present invention, the bottomed cylindrical metal tube is formed by a plurality of members (cylindrical portions) instead of being formed by a single member as in the related art. Then, a sheath member to which the temperature sensing element is connected is inserted through one of the openings at both ends of the second tubular portion, which is one of the plurality of members, and a sheath member located inside the second tubular portion. The second cylindrical portion is fixed. At this time, the second tubular portion and the sheath member are fixed in such a manner that at least a part of the temperature sensing portion can protrude from the distal end side of the second tubular portion. Then, the first cylindrical portion having a bottomed cylindrical shape is welded in a circumferential direction to the second cylindrical portion in a state where at least a part of the temperature sensing portion is protruded from the distal end side, so that the inside of the metal tube is sensed. The temperature element is housed.
[0009]
That is, according to the temperature sensor manufacturing method of the present invention, in the process of inserting the temperature-sensitive element assembly into the second cylindrical portion, the temperature-sensitive portion hits the inner wall surface of the second cylindrical portion and the metal core wire of the sheath member or the like. Even if the electrode wire of the temperature-sensitive element is bent, since both ends of the second cylindrical portion are opened, at least a part of the temperature-sensitive portion from the distal end side of the second cylindrical portion is surely set to a predetermined size (planned). Can be adjusted so as to protrude by the same size. Then, the second cylindrical portion having the temperature-sensitive portion protruding from the distal end by a predetermined size and the first cylindrical portion having the bottomed cylindrical shape are coaxially overlapped with each other by a predetermined size (planned size) and welded. In addition, the temperature-sensitive element can be reliably arranged at a target arrangement position of the bottomed cylindrical metal tube. Therefore, according to the present invention in which the metal tube is formed of a plurality of members, even when mass-producing a temperature sensor having the same product number, the temperature-sensitive element (temperature-sensitive portion) is placed at a predetermined position (target arrangement) in the metal tube. Position).
[0010]
In the method of manufacturing a temperature sensor according to the present invention, the sheath member (the temperature-sensitive element assembly) is located at the front end of the second cylindrical portion fixed inside or outside the rear end of the first cylindrical portion. Since it is arranged and welded so as to form an overlapping portion, a bottomed cylindrical metal tube can be easily formed. Therefore, according to the present invention, it is possible to efficiently and easily manufacture a temperature sensor in which a temperature-sensitive element (temperature-sensitive portion) is disposed at a target position in a metal tube.
[0011]
As the temperature sensing element, a thermistor sintered body is used as a temperature sensing part, and a thermistor element in which a part of the electrode wire is embedded in this thermistor sintered body, or a metal resistor whose resistance value changes with temperature is mounted on a ceramic substrate. A substrate-type element in which an electrode wire is connected to the metal resistor by using the element formed as described above as a temperature sensing part can be given. Further, the first tubular portion and the second tubular portion that constitute the metal tube are not particularly limited as long as they are formed of a metal material having sufficient mechanical strength and heat resistance. Specifically, it can be formed of a stainless alloy or an Inconel material.
[0012]
When arranging the distal end of the second tubular portion to which the temperature-sensitive element assembly is attached so as to form an overlapping portion inside or outside the rear end of the first tubular portion, the two are pressed against each other. They may be arranged so as to form an overlapping portion in a contact form, or they may be arranged so as to form an overlapping portion in a loosely fitted state. The welding method for welding the overlapping portion in the circumferential direction is not particularly limited, but specific methods include laser welding, plasma welding, electron beam welding, and argon welding. Among these, laser welding is the most preferable because good welding strength can be obtained even though it is an inexpensive technique.
[0013]
Next, in the method for manufacturing a temperature sensor, in the second step, a process from a tip end side of the second cylindrical portion to a connection portion between the electrode wire of the temperature sensing element and the metal core wire of the sheath member is performed. It is preferable to use a method of manufacturing a temperature sensor in which the temperature-sensitive element assembly is assembled to the second cylindrical portion so as to at least protrude.
[0014]
In the process of inserting the sheath member to which the temperature-sensitive element is connected into the second tubular portion, the metal core wire of the sheath member and the electrode wire of the temperature-sensitive element may be bent as described above, but depending on the degree of this bend. May cause a problem that a connection portion between the metal core wire and the electrode wire is disconnected. Therefore, if the second cylindrical portion and the sheath member are fixed in such a manner that only a part of the temperature-sensitive portion protrudes from the distal end side of the second cylindrical portion, the temperature-sensitive portion is located at the target position of the metal tube. Although it can be arranged, there is a possibility that the electrical output from the temperature sensing part cannot be output via the electrode wire and the metal core wire.
[0015]
On the other hand, according to the temperature sensor manufacturing method of the present invention, in the second step, at least the connection portion between the electrode wire of the temperature sensing element and the metal core wire of the sheath member is at least from the distal end side of the second cylindrical portion. The second tubular portion and the sheath member are assembled in a protruded form. Thereby, after assembling the sheath member (temperature-sensitive element assembly) to the second tubular portion, it is possible to confirm the state of the connection portion between the electrode wire and the metal core wire at the distal end side of the second tubular portion. it can. Therefore, according to the present invention, a temperature sensor having excellent electrical reliability can be obtained with high manufacturing efficiency while arranging the temperature-sensitive element (temperature-sensitive portion) at a target position in the metal tube. In addition, in this specification, the "connection portion between the electrode wire of the temperature sensing element and the metal core wire of the sheath member" indicates a portion where the electrode wire and the metal core wire overlap (wrap).
[0016]
In the method of manufacturing the temperature sensor, in the second step, not only the connection portion but also the metal core wire protruding from the distal end of the sheath pipe of the sheath member is protruded from the distal end side of the second cylindrical portion. Preferably, the second tubular portion and the sheath member are assembled. With this configuration, after assembling the sheath member (the temperature-sensitive element assembly) to the second tubular portion, the state of the connection portion between the electrode wire and the metal core wire is checked at the distal end side of the second tubular portion. In addition to the above, it is possible to confirm whether or not the electrode wires and the metal core wires are in contact with each other to cause a short circuit, and a temperature sensor having more excellent electrical reliability can be manufactured.
[0017]
Furthermore, in the method for manufacturing a temperature sensor according to any one of the above, in the second step, the fixing of the second tubular portion and the sheath member includes the second tubular portion and the sheath member. It is preferable to use a method of manufacturing a temperature sensor by caulking toward the outer peripheral surface of the sheath pipe.
[0018]
Thus, by caulking and fixing the second tubular portion and the sheath member, both can be firmly fixed by an inexpensive method. In addition, when caulking and fixing the second tubular portion and the sheath member, it is preferable to caulk at two or more points in the circumferential direction of the second tubular portion. This is because the sheath member can be stably fixed in the second cylindrical portion. Further, in the caulking of the second cylindrical portion performed outside the sheath pipe, if the caulking depth is equal to or greater than the thickness of the second cylindrical portion, the second cylindrical portion is formed when caulking is performed. The portion may be damaged (in other words, a caulking crack may occur). Therefore, in order to suppress the breakage of the second cylindrical portion, the thickness of the second cylindrical portion is set to D (unit: mm), and the addition of the outer peripheral surface of the sheath pipe and the inner peripheral surface of the second cylindrical portion is performed. When the gap before fastening is S (unit: mm), it is preferable that the gap is adjusted so as to satisfy the relationship of D ≧ S.
[0019]
In the method of manufacturing a temperature sensor, the second tubular portion may be swaged toward the sheath pipe of the sheath member at at least two or more positions separated in the axial direction of the second tubular portion. It is good to
[0020]
In this way, by caulking and fixing the second tubular portion and the sheath member at at least two or more positions separated in the axial direction of the second tubular portion, the sheath member with respect to the second tubular portion is formed. Can be more stably realized. In addition, it is preferable that each caulking at a position separated in the axial direction be caulked at two or more points in the circumferential direction of the second cylindrical portion.
[0021]
Further, in the method for manufacturing a temperature sensor according to any one of the above, in the third step, the tip of the second tubular portion and the rear end of the first tubular portion overlap each other in a loosely fitted state. The first cylindrical portion and the second cylindrical portion of the overlapping portion are circumferentially pressed toward the inner cylindrical portion of the first cylindrical portion and the second cylindrical portion. It is preferable to form a caulked portion by tightening and to perform the welding in the circumferential direction on the caulked portion.
[0022]
In arranging the front end of the second cylindrical portion and the rear end of the first cylindrical portion so as to form an overlap portion, for example, the first cylindrical portion is disposed outside the front end of the second cylindrical portion. This can be realized by press-fitting. By the way, in the third step, in order to dispose the temperature-sensitive part at a target position in the bottomed cylindrical metal tube, as described above, the second cylindrical part having the temperature-sensitive part protruding from the distal end side by a predetermined dimension. It is necessary to overlap the bottomed first cylindrical portion with a predetermined size. However, in order to overlap the first tubular portion and the second tubular portion with each other by a predetermined size by the press-fitting, it is necessary to control the diameters of the two tubular portions quite strictly, and it takes time and effort in the press-fitting process. There are aspects that are difficult to describe.
[0023]
On the other hand, in the method of manufacturing a temperature sensor according to the present invention, first, the leading end of the second tubular portion and the rear end of the first tubular portion are arranged so that an overlapping portion is formed in a loosely fitted state. ing. In this way, by overlapping the two tubular portions in the loosely fitted state, the two tubular portions can be easily overlapped by a predetermined dimension.
[0024]
Then, after arranging the leading end of the second tubular portion and the rear end of the first tubular portion such that an overlapping portion is formed in a loosely fitted state, the first tubular portion and the second tubular portion are formed in the overlapping portion. Of these, a caulked portion is formed by caulking the outer cylindrical portion toward the inner cylindrical portion in the circumferential direction. By forming such a caulked portion, it is possible to reduce the gap between the two cylindrical portions stacked in the loosely fitted state, thereby improving the adhesion. The first cylindrical portion and the second cylindrical portion are welded in the circumferential direction to the caulked portion formed in the circumferential direction in a state where the adhesion between the two cylindrical portions is enhanced. Can be reliably welded.
[0025]
As described above, according to the present invention, since the caulked portion is formed, the two cylindrical portions can be formed in a predetermined shape without extremely strictly controlling the diameters of the first cylindrical portion and the second cylindrical portion. It is possible to reliably perform welding after the dimensions are overlapped, and thus it is possible to increase the manufacturing efficiency of the temperature sensor. When the outer cylindrical portion of the first cylindrical portion and the second cylindrical portion in the overlapping portion is circumferentially crimped toward the inner cylindrical portion, hexagonal crimping or It may be performed by a method of polygonal caulking such as octagonal caulking, or by a method such as round caulking.
[0026]
Further, in the method for manufacturing a temperature sensor according to any one of the above, a small-diameter portion having an inner diameter smaller than an outer diameter of the second cylindrical portion, and located at a rear end side than the small-diameter portion, Prior to the third step, the first cylindrical portion having the rear end portion having an inner diameter equal to or larger than the outer diameter of the second cylindrical portion and a step portion connecting the small diameter portion and the rear end portion. Forming, in the third step, the front end of the second cylindrical portion is in contact with the step portion of the first cylindrical portion, and the inside of the rear end portion of the first cylindrical portion is It is preferable to use a method of manufacturing a temperature sensor in which the first tubular portion and the second tubular portion are assembled so that the overlapping portion is formed with the tip of the second tubular portion positioned.
[0027]
In the temperature sensor of the present invention, a first cylindrical portion formed in the order of a small diameter portion, a step portion, and a rear end portion from the front end side is used as the first cylindrical portion. A small-diameter portion having a smaller inner diameter, a large-diameter portion having an inner diameter equal to or larger than the outer diameter of the second cylindrical portion, and a step portion connecting them are used. Then, when inserting the first cylindrical portion into the second cylindrical portion, until the tip of the second cylindrical portion contacts the inner surface of the step portion connected to the rear end side of the small diameter portion of the first cylindrical portion. Insertion is performed to position the first tubular portion relative to the second tubular portion in the axial direction.
[0028]
According to the temperature sensor manufacturing method of the present invention, when the tip of the second cylindrical portion comes into contact with the inner surface of the step of the first cylindrical portion, an overlapping portion having a predetermined size (planned size) is generated. By adjusting the dimensions of the first cylindrical portion in advance as described above, it is only necessary to insert the second cylindrical portion 32 so that the tip of the second cylindrical portion 32 contacts the inner surface of the step portion 38 of the first cylindrical portion 31. The overlapping dimension of the overlapping portion can be set to a predetermined value. As a result, it is possible to arrange the temperature sensing portion more reliably at the target position of the first tubular portion. It is preferable that the inner surface of the step has a tapered shape in order to effectively prevent the first cylindrical portion and the second cylindrical portion from being misaligned with each other.
[0029]
Further, in the method for manufacturing a temperature sensor according to any one of the above, in the third step, the periphery of the temperature-sensitive portion protruding from the distal end side of the second cylindrical portion becomes an insulating member by a heat treatment. After covering with a paste-like insulating paste, the first tubular portion and the second tubular portion are arranged so as to generate the overlapping portion, and the assembly obtained through the third step is It is preferable that a heat treatment is performed so that an insulating member is interposed between the temperature-sensitive portion and the first cylindrical portion.
[0030]
In this manner, by interposing the insulating member between the temperature sensing portion protruding from the distal end side of the second cylindrical portion and the inner wall surface of the first cylindrical portion, the temperature sensing element vibrates. Thus, it is possible to manufacture a temperature sensor that can be protected from heat and can quickly transmit heat to the temperature-sensitive element to improve responsiveness. Further, according to the temperature sensor manufacturing method of the present invention, the temperature-sensitive part of the temperature-sensitive element assembly is not coated with the insulating paste in the first step, and the temperature-sensitive element assembly is provided on the second cylindrical portion. After assembling, the temperature-sensitive portion protruding from the distal end side of the second cylindrical portion is coated with an insulating paste. As a result, in the second step, it is easy to make the temperature-sensitive portion protrude from the distal end side of the second cylindrical portion by a predetermined dimension, and it is possible to increase the manufacturing efficiency of the temperature sensor.
[0031]
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. FIG. 2 is an enlarged view of the vicinity of the thermistor element 2, which is a main part of the temperature sensor 1 shown in FIG. The temperature sensor 1 uses the thermistor element 2 as a temperature-sensitive element. By mounting the temperature sensor 1 on an exhaust pipe of an automobile, the thermistor element 2 is disposed in an exhaust pipe through which exhaust gas flows. It is used for detecting the temperature of exhaust gas.
[0032]
The metal tube 3 is formed in a cylindrical shape with a closed bottom end (lower side in FIG. 1), and houses the thermistor element 2 inside the front end side. In the metal tube 3, a bottomed first tubular portion 31 having a closed front end and an open rear end, and a second tubular portion 32 having both ends opened are axially adjacent to each other. It is configured to be arranged. More specifically, the first cylindrical portion 31 is disposed so as to surround the outer peripheral surface of the distal end portion of the second cylindrical portion 32, and is caulked and fixed by the caulking portion 39 formed in the circumferential direction. The crimping portion 39 is integrated by laser welding all around. The first tubular portion 31 and the second tubular portion 32 have substantially the same thickness, and are formed of a stainless alloy as described later.
[0033]
The first cylindrical portion 31 houses therein a thermistor sintered body 21 which is a temperature-sensitive portion of the thermistor element 2. In the first cylindrical portion 31, the second cylindrical portion 32 is located closer to the distal end than the portion where the overlapping portion 37 is formed between the outer surface of the distal end of the second cylindrical portion 32 (the rear end 36). A small-diameter portion 33 having an inner diameter smaller than the outer diameter of the portion 32 is formed. The first cylindrical portion 31 has a step portion 38 connecting the small diameter portion 33 and the rear end portion 36, and the tip of the second cylindrical portion 32 is brought into contact with the inner surface of the step portion 38. Thus, the positioning of the first tubular portion 31 with respect to the second tubular portion 32 in the axial direction is performed.
[0034]
Inside the small diameter portion 33 of the first cylindrical portion 31, the entire thermistor sintered body 21 which is a temperature sensing portion is housed. The inside of the small diameter portion 33 is filled with the cement 10 which is an insulating member. More specifically, the small-diameter portion 33 is provided inside the small-diameter portion 33 so that the cement 10 is interposed between the outer surface of the thermistor sintered body 21 and the inner wall surface of the first cylindrical portion 31 (specifically, the small-diameter portion 33). The cement 10 is filled. The interposition of the cement 10 prevents the thermistor element 2 from swinging due to vibration or the like. Furthermore, the heat reception of the metal tube 3 (the first cylindrical portion 31) can be efficiently transferred to the thermistor sintered body 21 via the cement 10, and a high-speed response of temperature detection can be achieved. The cement 10 used in the present embodiment is composed of an aggregate mainly composed of alumina powder and a glass component containing Si.
[0035]
On the other hand, the second cylindrical portion 32 is fixed to the flange 4 in such a manner that the rear end side is inserted into the inside of the stainless steel flange 4. The second tubular portion 32 has a distal end side of a sheath member 8 described later disposed therein. In addition, the sheath member 8 (specifically, the outer peripheral surface of the sheath pipe 9 of the sheath member 8 described later) is placed at two positions (parts) apart from each other in the axial direction of the second cylindrical portion 32 from the outside thereof. A front-side caulking portion 34 formed by caulking toward the front and a rear-side caulking portion 35 are provided. The second tubular portion 32 and the sheath member 8 are fixed (crimped and fixed) by the front-side crimping portion 34 and the rear-side crimping portion 35.
[0036]
The flange 4 has a sheath portion 42 extending in the axial direction, and a projecting portion 41 located on the distal end side of the sheath portion 42 and projecting radially outward. 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. 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.
[0037]
The second cylindrical portion 32 is inserted from the front end side of the second cylindrical portion 32 from the rear end side of the flange 4 and is press-fitted and fixed inside the sheath portion 42. A portion where the outer peripheral surface of the second cylindrical portion 32 and the inner peripheral surface of the rear end side step portion 43 of the sheath portion 42 overlap is laser-welded in the circumferential direction.
[0038]
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. 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 pressed 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 side step portion 44 is laser welded in the circumferential direction.
[0039]
A sheath member 8 formed by holding a pair of metal core wires 7 insulated in a sheath pipe 9 is disposed inside the second tubular portion 32, the flange 4, and the joint 6 in the metal tube 3. The sheath member 8 is crimped and fixed to the second tubular portion 32 as described above. The metal core wire 7 protruding from the distal end side of the sheath member 8 is connected to a pair of Pt / Rh alloy electrode wires 22 constituting the thermistor element 2 by resistance welding. The pair of electrode wires 22 are embedded in the thermistor sintered body 21 having their hexagonal cross-sections at their tips, and are formed by being fired at the same time as the thermistor sintered body 21. The sheath member 8 includes a sheath pipe 9 made of SUS310S, a pair of conductive metal core wires 7 made of SUS310S, and an insulating powder 14 filled between the sheath pipe 9 and each metal core wire 7 (see FIG. 4). And the metal core wire 7 is held in an insulated state by the sheath pipe 9.
[0040]
The metal core wire 7 protruding to the rear end side of the sheath member 8 inside the joint 6 is connected via a caulking terminal 11 to a lead wire 12 for connection to a pair of external circuits (for example, an ECU of a vehicle). 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 coating material, and is inserted through an auxiliary ring 13 made of heat-resistant rubber provided at a rear end side opening of the joint 6. The auxiliary ring 13 is fixed to the joint 6 while being round-tightly or polygonally swaged from above the joint 6 while keeping the airtightness between the two. The electric output from the thermistor sintered body 21 according to the temperature change of the exhaust gas is sent to an external circuit (not shown) (for example, an ECU) via the electrode wire 22, the metal core wire 7 of the sheath member 8, and the lead wire 12. It is taken out and used for detecting the temperature of the exhaust gas.
[0041]
Since the temperature sensor 1 for detecting the temperature of the exhaust gas is used in a high-temperature environment reaching a maximum temperature of 1000 ° C., each constituent member needs to have sufficient heat resistance. Therefore, the first tubular portion 31 and the second tubular portion 32, the flange 4, and the metal core wire 7 constituting the metal tube 3 are mainly composed of Fe, and are made of C, Si, Mn, P, S, Ni and Cr. It is formed of SUS310S which is a heat-resistant alloy to be contained. The joint 6 is formed of SUS304.
[0042]
The temperature sensor 1 is manufactured as follows. First, a SUS310S steel plate is subjected to deep drawing to form a second cylindrical member having a thickness of 0.3 mm, an inner diameter of 2.7 mm, an outer diameter of 3.3 mm, and a total length (dimension in the axial direction) of 54 mm, both ends being open. A portion 32 and a bottomed first cylindrical portion 31 having a thickness of 0.3 mm and a total length (dimension in the axial direction) of 13 mm are formed. The first cylindrical portion 31 has a small-diameter portion 33 having an inner diameter of 2.6 mm and an outer diameter of 3.2 mm, a rear end portion having an inner diameter of 3.4 mm and an outer diameter of 4.0 mm, a small-diameter portion 33 and a rear end. Processing was performed so that a stepped portion 38 having a tapered shape connecting the portion 36 was formed. Further, an inner hole for press-fitting and fixing the second tubular portion 32 by subjecting the metal body of SUS310S to cold forging and / or cutting separately, and a front end side step portion 44 and a rear end side step portion 43 A flange 4 having a sheath portion 42 having a two-stage shape and a projecting portion 41 located on the distal end side of the sheath portion 42 and protruding radially outward is formed.
[0043]
Then, as a first step, the electrode wire 22 of the thermistor element 2 and the metal core wire 7 of the sheath member 8 are overlapped with each other so as to wrap by a predetermined size, and resistance welding is performed on each other to form a sheath member as shown in FIG. A temperature-sensitive element assembly K in which the thermistor element 2 is connected to the thermoelectric element 8 (the wrapped portion of the electrode wire 22 of the thermistor element 2 and the metal core wire 7 of the sheath member 8 is referred to as a “connection part” in the claims) Equivalent). FIG. 3 is an external view of the temperature-sensitive element assembly K. In a predetermined region on the distal end side of the sheath pipe 9 constituting the sheath member 8, a crimping formed when the first tubular portion 31 and the second tubular portion 32 are crimped and fixed in a later step. A concave portion 81 is formed to be depressed inward in the radial direction so that the portion 39 does not contact the outer peripheral surface thereof. In addition, the sheath pipe 9 is formed so that the thickness except for the concave portion 81 is 0.3 mm and the outer diameter is 2.5 mm. Next, the second cylindrical portion 32 is press-fitted and fixed in the inner hole of the flange 4, and a portion where the outer peripheral surface of the second cylindrical portion 32 and the inner peripheral surface of the rear end side step portion 43 of the sheath 42 overlap each other. Laser welds across directions.
[0044]
Then, as a second step, the temperature-sensitive element assembly K is inserted into the second tubular portion 32 laser-welded to the flange 4. At this time, the insertion of the second cylindrical portion 32 into the opening on the rear end side of the temperature sensing element assembly K is started from the side where the thermistor element 2 is disposed. Then, the thermistor sintered body 21 of the thermistor element 2 is protruded from the distal end side of the second cylindrical portion 32 by a predetermined dimension L1 (see FIG. 5), and when the thermistor sintered body 21 protrudes the predetermined dimension L1, the temperature is sensed. The insertion of the element assembly K into the second tubular portion 32 ends. Thereafter, the connection between the electrode wire 22 and the metal core wire 7 protruding from the distal end side of the second tubular portion 32 is checked for any abnormality. Check if there are any. If it is determined that there is no abnormality in the temperature-sensitive element assembly K in this confirmation work, subsequently, an operation of fixing the second tubular portion 32 and the temperature-sensitive element assembly K is performed.
[0045]
The fixing of the second tubular portion 32 and the temperature-sensitive element assembly K is performed according to the following procedure. First, a portion of the second tubular portion 32 that protrudes from the distal end side of the flange 4 and is close to the distal end of the flange 4 is applied toward the outer peripheral surface of the sheath pipe 9 of the sheath member 8. Tighten. In this caulking step, as shown in FIGS. 4A and 4B, a caulking die B is used to caulk two points facing each other in the circumferential direction from the outside of the second cylindrical portion 32. Do. Thereby, two rear end side crimping portions 35 are formed, and the sheath member 8 (temperature sensing element assembly K) and the second tubular portion 32 are crimped and fixed.
[0046]
Then, a portion that is further away from the rear end side crimping portion 35 in the axial direction and closer to the rear end side than the concave portion 81 is crimped toward the outer peripheral surface of the sheath pipe 9 of the sheath member 8. Also in this caulking process, the above-described caulking die B was used to caulk two points facing each other in the circumferential direction from the outside of the second cylindrical portion 32. As a result, two front-side caulking portions 34 are formed, and the sheath member 8 (the temperature-sensitive element assembly K) and the second tubular portion 32 are caulked and fixed together with the rear-side caulking portion 35. In this manner, the temperature-sensitive element assembly K and the second cylindrical portion 32 are integrally assembled with the thermistor sintered body 21 protruding from the tip end side of the second cylindrical portion 32 by a predetermined dimension L1. . FIG. 5 shows a partially cutaway cross-sectional view of an assembled structure in which the temperature-sensitive element assembly K and the second cylindrical portion 32 are integrally assembled.
[0047]
Here, in the present embodiment, although not shown in detail, an imaginary line connecting two opposing rear end side crimping portions 35 in a direction orthogonal to the axial direction of the second cylindrical portion 32 is formed. An imaginary line connecting the two tip side caulking portions 34 to each other in a direction orthogonal to the axial direction satisfies a relationship of orthogonality when viewed along the axial direction of the second tubular portion 32. Both caulking portions 34 and 35 are formed. By forming the crimping portions 34 and 35 so as to satisfy such an orthogonal relationship, the sheath member 8 disposed in the second tubular portion 32 can be more stably held. In addition, regarding the said virtual line, when the inner peripheral surface of the 2nd cylindrical part 32 and the outer peripheral surface of the sheath pipe 9 make point contact when seeing two crimping parts in the circumferential direction, the point contact point They can be guided by connecting them to each other in a direction orthogonal to the axial direction of the second cylindrical portion 32. On the other hand, when the inner peripheral surface of the second tubular portion 32 comes into surface contact with the outer peripheral surface of the sheath pipe 9 when the two crimped portions in the circumferential direction are viewed, the central portion of the surface contact portion ( The imaginary line can be guided by connecting the (centers) to each other in a direction orthogonal to the axial direction of the second cylindrical portion 32.
[0048]
In the present embodiment, the crimping portions of the front-side crimping portion 34 and the rear-end-side crimping portion 35 are formed such that the axial length along the axial direction is longer than the crimping width. ing. Specifically, each of the caulking portions 34 and 35 was formed such that the axial length L5 was 4.0 mm and the caulking width W was 0.4 mm (see FIG. 4). In this way, by forming the axial length of each caulking portion to be longer than the caulking width, the elongated sheath member 8 can be stably fixed to the second tubular portion 32. .
[0049]
Then, a third step of assembling the first tubular portion 31 with the second tubular portion 32 to which the temperature-sensitive element assembly K has been attached and storing the thermistor element 2 in the bottomed tubular metal tube 3. I do. First, an insulating paste to be the cement 10 is applied so as to cover the periphery of the thermistor sintered body 21 protruding from the tip end side of the second cylindrical portion 32 by a predetermined dimension L1. Next, the first tubular portion 31 is loosely fitted and coaxially inserted from the distal end side of the second tubular portion 32, and the rear end portion 36 of the first tubular portion 31 is positioned at the distal end of the second tubular portion 32. The first tubular portion 31 is arranged adjacent to the second tubular portion 32 so as to surround the outer surface of the portion. At this time, as shown in FIG. 6, the overlapping portion 37 having a predetermined dimension L2 is generated in a loosely fitted state at the tip of the second cylindrical portion 32, and the thermistor sintered body 21 of the thermistor element 2 is made of an insulating paste. At the same time, the first tubular portion 31 is arranged with respect to the second tubular portion 32 so as to be stored in the small diameter portion 33 of the first tubular portion 31.
[0050]
Here, in the present embodiment, when the first cylindrical portion 31 is inserted into the second cylindrical portion 32, the inner surface of the step portion 38 connected to the rear end side of the small diameter portion 33 of the first cylindrical portion 31 is formed. By performing insertion until the tip of the second tubular portion 32 comes into contact, positioning of the first tubular portion 31 with respect to the second tubular portion 32 in the axial direction is performed. That is, in the present embodiment, the first tubular portion 31 is loosely fitted and coaxially inserted into the second tubular portion 32, and the tip of the second tubular portion 32 is inserted into the first tubular portion 31. Each dimension of the first cylindrical portion 31 is adjusted in advance so that the overlapping portion 37 having the predetermined dimension L2 occurs when the inner surface of the step portion 38 comes into contact with the inner surface. Thereby, in the present embodiment, the respective dimensions of the first tubular portion 31 are appropriately adjusted, and the second tubular portion 32 is inserted so that the tip of the second tubular portion 32 contacts the inner surface of the step portion 38 of the first tubular portion 31. By performing the above, the overlapping dimension (corresponding to L2 in FIG. 6) of the first tubular portion 31 in the axial direction with respect to the second tubular portion 32 can be uniquely determined. As a result, it is possible to reliably arrange the thermistor sintered body 21 at the target position of the first cylindrical portion 31.
[0051]
Next, in a portion surrounding the concave portion 81 formed in the sheath pipe 9 of the sheath member 8 in the overlapping portion 37 between the rear end portion 36 of the first tubular portion 31 and the distal end portion of the second tubular portion 32, The located first tubular portion 31 is swaged in the circumferential direction toward the inner second tubular portion 32 to form a swaged portion 39. At this time, the caulked portion 39 is formed so as not to contact the surface of the concave portion 81 of the lead pipe 9. This caulking was performed by Happomaru caulking. The caulked portion 39 formed in this manner corresponds to a portion where a laser welded portion is formed by full-circle laser welding, which will be described later. By forming the caulked portion 39, the first cylindrical portion 31 and the second cylindrical portion 31 are formed. It is possible to reduce the amount of the gap with the shape portion 32, and it is possible to perform full circumference laser welding with excellent welding strength.
[0052]
Then, as shown in FIG. 7, a laser beam LB is applied to the caulking portion 39 formed in the overlapping portion 37 to perform full-circle laser welding, and the first cylindrical portion 31 and the second cylindrical shape are welded. A laser weld is formed over the portion 32 to integrate the two tubular portions 31 and 32. After that, the assembly in which the two tubular portions 31 and 32 are integrated is subjected to a heat treatment to solidify the insulating paste and obtain the cement 10.
[0053]
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 manufacture of the temperature sensor 1 is completed.
[0054]
According to such a method of manufacturing the temperature sensor 1, in the process of inserting the temperature-sensitive element assembly K into the second tubular portion 32, the thermistor sintered body 21 comes into contact with the inner wall surface of the second tubular portion 32 and the sheath member Even if the metal core wire 9 of 8 and the electrode wire 22 of the thermistor element 2 are bent, since both ends of the second cylindrical portion are opened, the thermistor sintered body 21 can be securely held from the tip end side of the second cylindrical portion 32. At a predetermined dimension L1. In the above-described manufacturing method, the second cylindrical portion 32 formed by projecting the thermistor sintered body 21 by the predetermined dimension L1 from the front end side and the bottomed cylindrical first cylindrical portion 31 are coaxially formed by the predetermined size L2. The thermistor element 2 (thermistor sintered body 21) is arranged at a predetermined position (target arrangement position) of the bottomed tubular metal tube 3 by overlapping and integrating the two tubular parts 31 and 32 by welding. Temperature sensor 1 can be obtained. Therefore, according to the method of manufacturing the temperature sensor 1, even when mass-producing a temperature sensor having the same product number, the thermistor element 2 (thermistor sintered body 21) is surely placed at a predetermined position (target position) in the metal tube 3. Can be arranged.
[0055]
In the above-described method for manufacturing the temperature sensor 1, the inside of the rear end of the first tubular portion 31 is attached to the front end of the second tubular portion 32 to which the sheath member 8 (the temperature-sensitive element assembly K) is fixed. Since it is arranged and welded so as to form the overlapping portion 37, the bottomed cylindrical metal tube 3 can be easily formed. Therefore, the temperature sensor 1 in which the thermistor element 2 (thermistor sintered body 21) is arranged at a target arrangement position in the metal tube 3 can be easily and efficiently manufactured.
[0056]
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 caulking and fixing the temperature-sensitive element assembly K (sheath member 8) and the second tubular portion 31, the present invention is not limited to a mode in which two points circumferentially opposed from the outside of the second tubular portion 32 are crimped. Instead, three points are crimped at equal intervals in the circumferential direction from the outer peripheral surface of the second cylindrical portion 32 to form a front-side crimping portion 34 and a rear-side crimping portion 35, and these are crimped and fixed. You may.
[0057]
Further, the welding at the overlapping portion 37 of the first tubular portion 31 and the second tubular portion 32 is performed by laser welding in the circumferential direction, but the welding is not limited to laser but may be plasma welding. Further, in the present embodiment, the thermistor element 2 using the thermistor sintered body 21 as a temperature sensing part is used as a temperature sensing element. However, a metal resistor whose resistance value changes with temperature is formed on a ceramic substrate. A substrate-type element in which an electrode wire is connected to the metal resistor as the temperature sensing section may be used as the temperature sensing element. Further, in the present embodiment, the entire thermistor element 2 is made to protrude from the tip end side of the second cylindrical portion 32, but at least a part of the thermistor sintered body 21 constituting the thermistor element 2 is protruded by a predetermined size. Then, the temperature sensor may be manufactured.
[0058]
Further, the shape of the thermistor sintered body 21 forming the temperature sensing part is not limited to a hexagonal shape in an axial cross section, but may be a circular shape or an elliptical shape. Further, the temperature sensor 1 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 an overall view of a temperature sensor in which a thermistor element as a temperature sensing element is housed in a bottomed cylindrical metal tube configured by arranging a first cylindrical part and a second cylindrical part adjacent to each other in an axial direction. It is a fragmentary sectional view showing a structure.
FIG. 2 is an enlarged view of the vicinity of a thermistor element 2 as a main part in the temperature sensor shown in FIG.
FIG. 3 is an external view of a temperature sensing element assembly in which a thermistor element and a sheath member are assembled.
FIG. 4 is a view schematically showing a step of caulking a second cylindrical portion toward an outer peripheral surface of a sheath pipe of a sheath member.
FIG. 5 shows a structure in which a temperature-sensitive element assembly and a second cylindrical portion are integrally assembled in a state where a thermistor element (thermistor sintered body) having a predetermined dimension is protruded from a front end side of a second cylindrical portion. It is a fragmentary sectional view.
FIG. 6 shows a state in which the rear end of the first cylindrical portion is arranged in a loose fitting manner outside the front end of the second cylindrical portion to which the temperature sensing element assembly is attached so that the rear end side of the first cylindrical portion overlaps by a predetermined dimension. FIG.
FIG. 7 is a view schematically showing a state in which a first cylindrical portion and a second cylindrical portion are laser-welded by laser irradiation all around the circumference.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Temperature sensor, 2 ... Thermistor element, 21 ... Thermistor sintered body, 22 ... Electrode wire, 3 ... Metal cap, 31 ... 1st cylindrical part, 32 ... 2nd cylindrical part, 33 ... small diameter part, 34 ... tip side crimping part, 35 ... rear end side crimping part, 36 ... rear end part, 37 ... overlapping part, 38 ... stepped part, 39 ... caulked part, 4 ... flange, 6 ... joint, 7 ... metal core wire, 8 ... sheath member, 9 ... sheath pipe, 10 ... ··· Cement, 12 lead wires, 14 insulating powder, K… temperature-sensitive element assembly.

Claims

A cylindrical metal tube with a closed distal end,
A thermosensitive element having a thermosensitive part whose electrical characteristics change with temperature and a pair of electrode wires provided therein, and a thermosensitive element housed inside the metal tube,
A sheath member arranged along the axial direction of the metal tube and holding a pair of metal core wires connected to the electrode wires of the temperature sensing element insulated and held inside a sheath pipe,
A method for manufacturing a temperature sensor comprising:
The metal tube is configured in such a manner that a first cylindrical portion having a closed bottom at the distal end and a second cylindrical portion having both ends open are arranged adjacent to each other in the axial direction. And
A first step of bonding the electrode wire of the temperature-sensitive element and the metal core wire of the sheath member to each other to produce a temperature-sensitive element assembly;
Inserting the temperature-sensitive element assembly through one of the openings at both ends of the second cylindrical portion, and projecting at least a part of the temperature-sensitive portion from the distal end side of the second cylindrical portion, A second step of fixing the sheath member located inside the second tubular portion and the second tubular portion, and assembling the temperature-sensitive element assembly to the second tubular portion;
The distal end of the second cylindrical portion to which the temperature-sensitive element assembly is assembled is disposed so as to form an overlap portion in a form positioned inside or outside the rear end of the first cylindrical portion, A third step of welding the overlapping portion in the circumferential direction;
A method for manufacturing a temperature sensor, comprising:

It is a manufacturing method of the temperature sensor of Claim 1, Comprising:
In the second step, the temperature-sensing element assembly is configured to at least protrude from a distal end side of the second cylindrical portion to a connection portion between the electrode wire of the temperature-sensing element and the metal core wire of the sheath member. A method of manufacturing a temperature sensor for attaching a solid to the second cylindrical portion.

It is a manufacturing method of the temperature sensor according to claim 1 or 2,
In the second step, the temperature sensor is manufactured by fixing the second tubular portion and the sheath member by crimping the second tubular portion toward the outer peripheral surface of the sheath pipe of the sheath member. Method.

It is a manufacturing method of the temperature sensor of Claim 3, Comprising:
A method for manufacturing a temperature sensor, comprising caulking the second cylindrical portion toward the outer peripheral surface of the sheath pipe of the sheath member at at least two or more positions separated in the axial direction of the second cylindrical portion.

It is a manufacturing method of the temperature sensor as described in any one of Claims 1-4, Comprising:
In the third step, the leading end of the second tubular portion and the rear end of the first tubular portion are arranged so that the overlapping portion is generated in a loosely fitted state, and the first tubular portion is formed in the overlapping portion. Of the second cylindrical portion and the second cylindrical portion, an outer cylindrical portion is circumferentially swaged toward the inner cylindrical portion to form a swage portion, and the outer circumferential portion is formed around the swage portion. A method for manufacturing a temperature sensor for performing the above-described welding in directions.

It is a manufacturing method of the temperature sensor as described in any one of Claims 1-5, Comprising:
A small-diameter portion having an inner diameter smaller than an outer diameter of the second cylindrical portion; and a rear-end portion located at a rear end side of the small-diameter portion and having an inner diameter equal to or larger than the outer diameter of the second cylindrical portion. And forming the first cylindrical portion having a step portion connecting the small diameter portion and the rear end portion prior to the third step. In the third step, a tip of the second cylindrical portion is formed. The overlapping portion so as to abut on the step portion of the first cylindrical portion, and the tip of the second cylindrical portion is positioned inside the rear end of the first cylindrical portion. A method for manufacturing a temperature sensor, wherein the first tubular portion and the second tubular portion are assembled so as to cause the following.

It is a manufacturing method of the temperature sensor as described in any one of Claims 1-6, Comprising:
The method for manufacturing a temperature sensor, wherein the welding in the third step is laser welding.