JP4210165B2

JP4210165B2 - Electrical contact member with excellent arc resistance

Info

Publication number: JP4210165B2
Application number: JP2003183009A
Authority: JP
Inventors: 雅夫水野; 隆志宮本; 政洋柳川
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 2003-06-26
Filing date: 2003-06-26
Publication date: 2009-01-14
Anticipated expiration: 2023-06-26
Also published as: JP2005019230A

Description

【０００１】
【発明の属する技術分野】
本発明は、スイッチやリレー、あるいはコネクタなどに電気接点として用いられて好適な、耐アーク性に優れる電気接点部材に関するものである。
【０００２】
【従来の技術】
従来から、電気接点材料として、Ｃｕ合金、Ａｇ合金、Ｗ合金、Ｎｉ合金、Ｐｄ合金などが使用されている。このような材料でなる電気接点部材に供せられる電圧としては、例えば自動車用電源では、これまで１２〜１４Ｖ程度が一般的であったが、より高電圧化しようという動きが始まっている。しかし、このような高電圧化を図ろうとする際、例えば４０Ｖ程度まで電圧を高めると電気接点を開くとき（コネクタを外すとき）にアーク放電が発生するという事態が生じている。アークが発生すると接点が損傷することがあり、電気接点部材にとっては大きな問題となる。
【０００３】
そこで、アークの発生を抑えるために、雄コネクタに一対の永久磁石を設け、磁石による磁界によってアークの軌跡を引き伸ばしてアーク継続時間を短縮し、端子の溶損を低減するようにした方法が提案されている（非特許文献１参照）。また、ＳＦ₆ガスなど熱伝導性が良好なガスを封入し、アークが点弧しないようにした方法も提案されている（非特許文献２参照）。
【０００４】
【非特許文献１】
「自動車用４２Ｖ電源システム対応コネクタ」，フジクラ技報，株式会社フジクラ，２００１年１０月発行第１０１号，ｐ．６６−７０
【非特許文献２】
Ｄ＆Ｍ，２００２年６月，Ｎｏ．５７３，ｐ．９２
【０００５】
【発明が解決しようとする課題】
しかし、安価で小型の部品に対してはコストやサイズの点で前述のような方法の採用が難しいことから、前記永久磁石などのような補助部品や前記ＳＦ₆ガスなどのような特別な雰囲気を必要としなくてすむような、耐アーク性に優れる電気接点部材の開発が要請されている。また、接点が摺動する摺動接点でも微小アークの発生に伴う損傷が問題となっており、耐アーク性に優れる電気接点部材の開発が求められている。
【０００６】
本発明はこのような事情に鑑みてなされたものであり、本発明の目的は、耐アーク性に優れる電気接点部材を提供することにある。
【０００７】
【課題を解決するための手段】
前記目的を達成するために、本願発明は次のように構成されている。請求項１の発明は、素材がＣｕ合金、Ｃｕ合金の表面にめっきを施したもの又はＣｕ合金に異種合金をクラッドしたものからなり、表面粗さ計により、接点部表面における線分長さ０．８ｍｍ部分の表面の粗さプロファイルを測定し、その測定結果から求められる、最大突起頂点高さとの突起頂点高さの差が０〜３μｍの範囲に存在する突起数の全突起数に対する割合を示す突起積算度数が、３０〜６０％の範囲内を満足することを特徴とする耐アーク性に優れる電気接点部材である。
【０００８】
請求項２の発明は、請求項１記載の耐アーク性に優れる電気接点部材において、Ｃｕ合金表面の前記めっきが、Ｎｉめっき又はＳｎめっきであることを特徴とするものである。
【００１０】
【発明の実施の形態】
本発明者らは、金属表面の評価方法として、スイッチやリレーの電気接点として用いられる電気接点部材（電気接点対）の耐アーク性の良否を評価しうる方法（耐アーク性評価方法）を確立し、この方法を基に本発明に係る耐アーク性に優れる電気接点部材を得たものである。まず、本発明者らは、Ｃｕ合金製電気接点部材についてアーク発生の難易度合いを調査し、同一組成のものであってもアークの発生し難さは接点部の表面性状によって大きく異なることを見出した。そこで、アーク発生の難易度合いと対応関係を持つ表面性状を調べるため、接点部が種々の表面粗さを有するＣｕ合金製電気接点部材について、表面の粗さプロファイル（表面凹凸の形状）を測定して算術平均粗さＲａ（ＪＩＳＢ０６０１−２００１）を測定した。しかしながら、アーク発生の難易度合いと算術平均粗さＲａとの対応関係（相関）は得られなかった。同様に、ＪＩＳＢ０６０１−２００１で規定される突起の最大高さＲｚと凹凸の平均間隔ＲＳｍとについても、アーク発生の難易度合いとの対応関係は得られなかった。
【００１１】
そこで、さらに考察研究した結果、電気接点部材ではその接点部同士の表面突起先端が接触し接触点を形成して通電が生じること、また、閉じられていた接点部を開くときには接点部表面の突起が微小溶融して劣化することを見出した。さらに、この微小溶融によって突起先端に酸化物を生じ、多数回の接点部の開閉を繰り返すと、ついにはこの酸化物が起点となってアークが発生するようになることを見出した。
【００１２】
このように接点部同士の接触には接点部の表面突起が関与するため、耐アーク性を評価できるようにするには接点部の表面凹部ではなく表面突起の特徴だけを抽出する必要がある。そして、接点部同士の接触に最も密接に係わるものは、電気接点部材接点部において接触に実際に関与する突起の数であることが判明した。そこで、さらにこの評価方法について研究した。
【００１３】
その結果、電気接点部材について、その接点部における一定長さ部分にて表面の粗さプロファイルを測定し、最大突起頂点高さとの突起頂点高さの差が０〜３μｍの範囲に存在する突起数の全突起数に対する割合である突起積算度数（評価値）Ｃ_０−３を算出し、この突起積算度数Ｃ_０−３が３０〜６０％の範囲内を満足するか否かによって耐アーク性の良否を評価できることがわかった。
【００１４】
この評価方法を詳しく説明する。まず、電気接点部材接点部の一定長さＬ（０．８ｍｍ）の線分部分の表面の粗さプロファイル（表面凹凸の形状）を表面粗さ計で測定する。次に、突起頂点を抽出する。抽出は粗さ曲線上における各極大をとる点を突起頂点とする。そして、線分上の一端に定めた基準点から線分に沿って抽出した各突起頂点位置をｈｉとする。ここで、ｉは各突起につけた番号（１〜ｎ）を表す。次に、水平基準線から計測した各突起頂点高さをＡ（ｈｉ）とする。その中の最大突起頂点高さＡ（ｈｍａｘ）を抽出する。ｍａｘは最大突起頂点位置の番号である。しかる後、全ての突起について、最大突起頂点高さＡ（ｈｍａｘ）と各突起頂点高さをＡ（ｈｉ）との差Ｂ（ｈｉ）を、Ｂ（ｈｉ）＝Ａ（ｈｍａｘ）−Ａ（ｈｉ）により算出する。
【００１５】
次いで、最大突起頂点高さＡ（ｈｍａｘ）との高さの差が０〜３μｍの範囲にある突起の数を総計し（０≦Ｂ（ｈｉ）≦３μｍ）、しかる後、この突起数の全突起数に対する割合である突起積算度数Ｃ_０−３（％）を算出する。そして、この突起積算度数Ｃ_０−３が３０〜６０％の範囲内を満足する場合に、その電気接点部材はアークが発生し難く耐アーク性に優れていることをつきとめ、耐アーク性の良否を評価できる方法を確立したものである。
【００１６】
この評価方法は、素材がＣｕ合金、Ｃｕ合金の表面にめっきを施したもの又はＣｕ合金に異種合金をクラッドしたものからなる電気接点部材に有効であり、この方法を基に、本発明に係る耐アーク性に優れる電気接点部材を得たものである。なお、めっきを施したＣｕ合金としては、ＮｉめっきＣｕ合金、ＳｎめっきＣｕ合金が挙げられる。Ｃｕ合金に異種合金をクラッドしたものとしては、純銅、黄銅又は青銅にＡｇ合金をクラッドしたものが挙げられる。
【００１７】
本発明による電気接点部材が耐アーク性に優れる理由について説明する。本発明による電気接点部材では、突起高さの差Ｂ（ｈｉ）が０〜３μｍの範囲にある突起数の全突起数に対する割合を表す突起積算度数Ｃ_０−３を３０〜６０％の範囲内を満足するように規定して、接点部における通電を生じる接触点の数を増大させたものであるから、アーク発生までの接点開閉回数を延ばして耐アーク性に優れたものとなる。この場合、突起積算度数Ｃ_０−３が３０％を下回ると通電を生じる接触点の個数が少なくて、接点部を開くときに突起が微小溶融して突起先端が酸化することで電気抵抗が増加し、比較的短期間でアークが発生しやすい状態となってしまう。突起積算度数Ｃ_０−３は、より好ましくは、突起積算度数Ｃ_０−３が５０〜６０％の範囲内を満足するものがよい。
【００１８】
なお、発明者らは、突起高さの差Ｂ（ｈｉ）が０〜１μｍの範囲にある突起数の全突起数に対する割合を表す突起積算度数Ｃ_０−１による評価も行ってみた。しかし、この突起積算度数Ｃ_０−１だけでは耐アーク性との相関は得られなかった。このことは、本発明で規定する突起高さの差Ｂ（ｈｉ）が３μｍ以下程度のものまでが耐アーク性との相関に影響していることを示すものであると考えられる。また、突起高さの差Ｂ（ｈｉ）が３μｍ超える突起数の全突起数に対する割合が多い電気接点部材は、接点接触に際し、対極と接触しない突起が多いので（突起が対極と接触しないので）耐アーク性にはそれ程影響を与えず、その結果、耐アーク性との相関がとれないものと考えられる。
【００１９】
次に、本発明による電気接点部材の製造方法について説明する。従来の電気接点部材では、供される電圧が１２Ｖ程度と低く、アークの発生が問題となっていなかったため、表面性状がそれほど厳密には制御されておらず、部材表面は圧延加工のまま、あるいは研削加工のまま、あるいはプレス加工のままの状態であった。そのため、従来の電気接点部材では、表面性状は前記突起積算度数Ｃ_0-3で評価した場合には数％〜２０数％程度であり、それまでとは違って例えば４０Ｖ程度の高電圧を供せられた場合には、アークが発生するという事態が生じていたのである。
【００２０】
これに対して本発明による電気接点部材は、圧延加工あるいは研削加工の後、部材表面について、さらにコンパウンド研磨、バフ研磨又は電解研磨による研磨を行ったり、あるいは、鏡面加工したプレス板を用いてプレス加工を行ったりなどすることにより、突起積算度数Ｃ_0-3を本発明範囲に制御して作製することができる。これにより、４０Ｖ程度の高電圧を供した場合にも耐アーク性に優れている。
【００２１】
なお、前述の通り、算術平均粗さＲａだけではアークの発生との相関は見られないが、算術平均粗さＲａを著しく小さくすることができれば、アークの発生を抑制するにあたって、より一層好ましいものとなると考えられる。例えば、算術平均粗さＲａで１μｍ以下となれば、本発明で規定する突起積算度数Ｃ_0-3の範囲を多少はずれていても良好な耐アーク性を得られる可能性がある。もちろん、突起積算度数Ｃ_0-3を本発明範囲とした上で算術平均粗さＲａを１μｍ以下とすれば、一層良好な耐アーク性が得られると考えられる。しかしながら、算術平均粗さＲａ：１μｍ以下を達成することは通常の研磨法では困難であり、イオンエッチング等の特別な方法を採用する必要があるため、コスト面などから、現状では実現は難しいと考えられる。
【００２２】
【実施例】
次に、金属表面の評価方法としての耐アーク性評価方法の有効性を確認した試験結果について説明する。なお、この試験ではアークを発生しやすくするため、素材として、試験１ではＣｕ合金に代えてタフピッチ銅（純銅）、試験２ではタフピッチ銅の表面にＮｉめっきを施したもの、また、試験３ではタフピッチ銅の表面にＮｉめっきを施したもの、タフピッチ銅の表面にＳｎめっきを施したものを使用した。
【００２３】
［試験１］：まず、試験１について説明する。研削加工により外径３ｍｍ、長さ１０ｍｍのタフピッチ銅からなる円柱体を所定個数作製した。そして、試料１として、研削加工によって円柱体の一方の端面にＲ２０の丸みを有する円弧状面を形成し、これを試料１とした。試料２として、１μｍのダイヤモンド砥粒を用いたバフ研磨によって円柱体の一方の端面にＲ２０の丸みを有する円弧状面を形成し、これを試料２とした。試料３として、研削加工により円柱体の一方の端面にＲ２０の丸みを有する円弧状面を形成し、この円弧状面を５０％リン酸溶液、電流１Ａの条件で１０秒間電解研磨し、これを試料３とした。また、試料４として、鏡面加工したステンレス板に押し付けてプレス加工することによって、円柱体の一方の端面にＲ２０の丸みを有する円弧状面を形成し、これを試料４とした。さらに、試料５として、研削加工により円柱体の一方の端面にＲ２０の丸みを有する円弧状面を形成し、この円弧状面を＃１５００番のサンドペーパーにより研磨し、これを試料５とした。
【００２４】
前記試料１〜５について、小坂研究所製の表面粗さ計ＳＥ３５００を用いて、接点部（円弧状面）表面における線分長さ０．８ｍｍ部分の表面の粗さプロファイル（表面凹凸の形状）を測定した。その表面の粗さプロファイルから、各試料１〜５について、最大突起頂点高さＡ（ｈｍａｘ）と各突起頂点高さＡ（ｈｉ）との差Ｂ（ｈｉ）が０〜３μｍの範囲にある突起数の全突起数に対する割合を表す突起積算度数Ｃ_0-3を求めた。また、前記差Ｂ（ｈｉ）が０〜１μｍの範囲にある突起数の全突起数に対する割合を表す突起積算度数Ｃ_0-1、及び、前記差Ｂ（ｈｉ）が３μｍ超５μｍ以下の範囲にある突起数の全突起数に対する割合を表す突起積算度数Ｃ_3-5についても求めた。算出したこれらの突起積算度数を表１に示す。さらに、比較のために、各試料１〜５について、表面粗さに関するＪＩＳＢ０６０１−２００１に規定する算術平均荒さＲａ、最大高さＲｚ、凹凸の平均間隔（平均長さ）ＲＳｍを測定した。これらの測定値を表１に示す。
【００２５】
図１及び図２は耐アーク性評価試験の説明図である。各試料１〜５毎に、一対の試料の円弧状面同士を突合せ、この試料間に直流電源１から負荷抵抗２を介して４２Ｖ、３Ａの電流を流した。そして、速度５０ｍｍ／ｓの速度で接点部を開離し、アーク発生の有無を確認しながら接点部の開閉を繰り返して、アークが発生するまでの接点開離回数を測定した。試験結果を表１、図３及び図４に示す。
【００２６】
【表１】

【００２７】
表１からわかるように、アークが発生するまでの接点開離回数は、試料２が最も多く、次いで試料４、試料３、試料１、試料５の順で減少し、試料５が最も少なかった。このうち、試料１、試料５については耐アーク性が悪かった。そして、図３からわかるように、突起積算度数Ｃ_0-3によって耐アーク性の良否を正しく評価できることが確認できた。他の突起積算度数Ｃ_0-1、あるいは突起積算度数Ｃ_3-5は、耐アーク性を評価する評価値として不適切であった。また、図４からわかるように、算術平均荒さＲａ、最大高さＲｚ及び凹凸の平均間隔ＲＳｍについても、耐アーク性評価値として不適切であった。
【００２８】
［試験２］：次に、試験２について説明する。この試験では素材としてタフピッチ銅表面にＮｉめっきを施したものを使用した。
【００２９】
まず、研削加工により外径３ｍｍ、長さ１０ｍｍのタフピッチ銅からなる円柱体を所定個数作製した。そして、試料１として、１μｍの砥粒によるコンパウンド研磨を行って円柱体の一方の端面にＲ２０の丸みを有する円弧状面を形成し、しかる後、電解めっきを行って試料表面に厚み１μｍのＮｉめっきを施し、これを試料１とした。試料２として、１μｍのダイヤモンド砥粒を用いたバフ研磨によって円柱体の一方の端面にＲ２０の丸みを有する円弧状面を形成し、しかる後、電解めっきを行って試料表面に厚み１μｍのＮｉめっきを施し、これを試料２とした。また、試料３として、鏡面加工したステンレス板に押し付けてプレス加工することによって、円柱体の一方の端面にＲ２０の丸みを有する円弧状面を形成し、しかる後、電解めっきを行って試料表面に厚み１μｍのＮｉめっきを施し、これを試料３とした。さらに、試料４として、研削加工により円柱体の一方の端面にＲ２０の丸みを有する円弧状面を形成し、この円弧状面を＃１５００番のサンドペーパーにより研磨し、しかる後、電解めっきを行って試料表面に厚み１μｍのＮｉめっきを施し、これを試料４とした。
【００３０】
前記試料１〜４について、試験１と同様にして、突起積算度数Ｃ_0-3、Ｃ_0-1及びＣ_3-5を求めた。算出したこれらの突起積算度数を表３に示す。また、比較のために、各試料１〜４について、算術平均荒さＲａ、最大高さＲｚ及び凹凸の平均間隔ＲＳｍを測定した。これらの測定値を表３に示す。
【００３１】
そして、各試料１〜４について、試験１と同様にして、一対の試料の円弧状面同士を突合せ、この試料間に直流２２０Ｖ、０．５Ａの電流を流し、速度５０ｍｍ／ｓの速度で接点部を開離し、アーク発生の有無を確認しながら接点部の開閉を繰り返して、アークが発生するまでの接点開離回数を測定した。試験結果を表２及び図５に示す。
【００３２】
【表２】

【００３３】
表２からわかるように、アークが発生するまでの接点開離回数は、試料２が最も多く、次いで試料３、試料１、試料４の順で減少し、試料４が最も少なかった。このうち、試料４については耐アーク性が悪かった。そして、図５からわかるように、耐アーク性の良否は、突起積算度数Ｃ_0-3によって正しく評価できることが確認できた。他の突起積算度数Ｃ_0-1、あるいは突起積算度数Ｃ_3-5は、耐アーク性を評価する評価値として不適切であった。また、算術平均荒さＲａ、最大高さＲｚ及び凹凸の平均間隔ＲＳｍについても、耐アーク性評価値として不適切であった。
【００３４】
［試験３］：次に、試験３について説明する。この試験では素材としてタフピッチ銅表面にＮｉめっきに代えてＳｎめっきを施したものを使用した。
【００３５】
まず、研削加工により外径３ｍｍ、長さ１０ｍｍのタフピッチ銅からなる円柱体を所定個数作製した。そして、試料１として、１μｍの砥粒によるコンパウンド研磨を行って円柱体の一方の端面にＲ２０の丸みを有する円弧状面を形成し、しかる後、電解めっきを行って試料表面に厚み１μｍのＳｎめっきを施し、これを試料１とした。試料２として、１μｍのダイヤモンド砥粒を用いたバフ研磨によって円柱体の一方の端面にＲ２０の丸みを有する円弧状面を形成し、しかる後、電解めっきを行って試料表面に厚み１μｍのＳｎめっきを施し、これを試料２とした。また、試料３として、鏡面加工したステンレス板に押し付けてプレス加工することによって、円柱体の一方の端面にＲ２０の丸みを有する円弧状面を形成し、しかる後、電解めっきを行って試料表面に厚み１μｍのＳｎめっきを施し、これを試料３とした。さらに、試料４として、研削加工により円柱体の一方の端面にＲ２０の丸みを有する円弧状面を形成し、この円弧状面を＃１５００番のサンドペーパーにより研磨し、しかる後、電解めっきを行って試料表面に厚み１μｍのＳｎめっきを施し、これを試料４とした。
【００３６】
前記試料１〜４について、試験１と同様にして、突起積算度数Ｃ_0-3、Ｃ_0-1及びＣ_3-5を求めた。算出したこれらの突起積算度数を表３に示す。また、比較のために、各試料１〜４について、算術平均荒さＲａ、最大高さＲｚ及び凹凸の平均間隔ＲＳｍを測定した。これらの測定値を表３に示す。
【００３７】
そして、各試料１〜４について、試験１と同様にして、一対の試料の円弧状面同士を突合せ、この試料間に直流４２Ｖ、５Ａの電流を流し、速度５０ｍｍ／ｓの速度で接点部を開離し、アーク発生の有無を確認しながら接点部の開閉を繰り返して、アークが発生するまでの接点開離回数を測定した。試験結果を表３及び図６に示す。
【００３８】
【表３】

【００３９】
表３からわかるように、アークが発生するまでの接点開離回数は、試料２が最も多く、次いで試料３、試料１、試料４の順で減少し、試料４が最も少なかった。このうち、試料４については耐アーク性が悪かった。そして、図６からわかるように、耐アーク性の良否は、最大突起頂点高さＡ（ｈｍａｘ）と各突起頂点高さＡ（ｈｉ）との差Ｂ（ｈｉ）が０〜３μｍの範囲にある突起数の全突起数に対する割合を表す突起積算度数Ｃ_0-3によって正しく評価できることが確認できた。差Ｂ（ｈｉ）が０〜１μｍの範囲にある突起数に関する突起積算度数Ｃ_0-1、あるいは、差Ｂ（ｈｉ）が３μｍ超５μｍの範囲にある突起数に関する突起積算度数Ｃ_3-5は、耐アーク性を評価する評価値として不適切であった。また、算術平均荒さＲａ、最大高さＲｚ及び凹凸の平均間隔ＲＳｍについても、耐アーク性評価値として不適切であった。
【００４０】
次に、本発明に係る耐アーク性に優れる電気接点部材の実施例について説明する。実施例１〜１１では、それぞれ、表４に示す組成のＣｕ合金材（実施例１，２は純銅）を用いて研削加工により外径３ｍｍ、長さ１０ｍｍの円柱体を作製し、次いで１μｍの砥粒によるコンパウンド研磨を行って円柱体の一方の端面にＲ２０の丸みを有する円弧状面を形成して、電気接点部材とした。なお、研磨時間などを変化させて表面性状を適宜変化させた。また、比較のため、比較例１〜１３の電気接点部材を作製した。比較例１〜１３では、それぞれ、表５に示す組成のＣｕ合金材（比較例１は純銅）を用いて研削加工により外径３ｍｍ、長さ１０ｍｍの円柱体を作製し、次いで研削加工によって円柱体の一方の端面にＲ２０の丸みを有する円弧状面を形成して、電気接点部材とした。
【００４１】
実施例１〜１１及び比較例１〜１３の電気接点部材について、小坂研究所製の表面粗さ計ＳＥ３５００を用いて、接点部（円弧状面）表面における線分長さ０．８ｍｍ部分の表面の粗さプロファイルを測定した。その表面の粗さプロファイルから、突起積算度数Ｃ_0-3を求めた。算出した各突起積算度数Ｃ_0-3を表４に示す。
【００４２】
そして、実施例１〜１１及び比較例１〜１３について、それぞれ、一対の電気接点部材の円弧状面同士を突合せ、この電気接点部材間に直流４２Ｖ、３Ａの電流を流した。そして、速度５０ｍｍ／ｓの速度で接点部を開離し、アーク発生の有無を確認しながら接点部の開閉を繰り返して、アークが発生するまでの接点開離回数を測定した。試験結果を表４及び図７に示す。
【００４３】
【表４】

【００４４】
表４からわかるように、突起積算度数Ｃ_0-3の値が本発明の規定範囲から外れる比較例１〜１３は、アークが発生するまでの接点開離回数が４００回を下回っており、耐アーク性が劣るものであった。これに対して、実施例１〜１１は、４００回以上の接点開離回数が得られており、比較例と同一組成であっても耐アーク性に優れたものとなっている。
【００４５】
【発明の効果】
以上述べたように、本発明によれば、簡易な表面加工法を用いて得られる耐アーク性に優れる電気接点部材を提供することができ、スイッチやリレー、あるいはコネクタなどの小型部品において電気接点部材の耐アーク性の向上と低コスト化に寄与することができる。
【図面の簡単な説明】
【図１】耐アーク性評価試験の説明図である。
【図２】耐アーク性評価試験の説明図である。
【図３】評価試験１におけるアーク発生までの接点開離回数と突起積算度数Ｃ_0-1，Ｃ_0-3，Ｃ_3-5との関係を示すグラフである。
【図４】評価試験１におけるアーク発生までの接点開離回数と接点部表面状態Ｒａ，Ｒｚ，ＲＳｍとの関係を示すグラフである。
【図５】評価試験２におけるアーク発生までの接点開離回数と突起積算度数Ｃ_0-1，Ｃ_0-3，Ｃ_3-5との関係を示すグラフである。
【図６】評価試験３におけるアーク発生までの接点開離回数と突起積算度数Ｃ_0-1，Ｃ_0-3，Ｃ_3-5との関係を示すグラフである。
【図７】本発明に係る耐アーク性に優れる電気接点部材の実施例及び比較例におけるアーク発生までの接点開離回数と突起積算度数Ｃ_0-3との関係を示すグラフである。
【符号の説明】
１…直流電源２…負荷抵抗[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrical contact member excellent in arc resistance, which is suitable for use as an electrical contact in a switch, a relay, or a connector.
[0002]
[Prior art]
Conventionally, Cu alloys, Ag alloys, W alloys, Ni alloys, Pd alloys, and the like have been used as electrical contact materials. As a voltage applied to the electrical contact member made of such a material, for example, in a power source for automobiles, about 12 to 14 V has been generally used so far, but a movement to increase the voltage has started. However, when attempting to increase the voltage, for example, if the voltage is increased to about 40 V, an arc discharge occurs when the electrical contact is opened (when the connector is removed). When an arc occurs, the contact may be damaged, which is a serious problem for the electrical contact member.
[0003]
Therefore, in order to suppress the occurrence of arc, a method has been proposed in which a pair of permanent magnets is provided on the male connector, and the arc trajectory is extended by the magnetic field generated by the magnets to shorten the arc duration and reduce the melting damage of the terminals. (See Non-Patent Document 1). In addition, a method has been proposed in which a gas having good thermal conductivity such as SF ₆ gas is enclosed so that the arc does not start (see Non-Patent Document 2).
[0004]
[Non-Patent Document 1]
“Connector for 42V power supply system for automobiles”, Fujikura Technical Report, Fujikura Co., Ltd., October 2001, No. 101, p. 66-70
[Non-Patent Document 2]
D & M, June 2002, no. 573, p. 92
[0005]
[Problems to be solved by the invention]
However, since it is difficult to adopt the above-described method for cheap and small parts in terms of cost and size, a special atmosphere such as auxiliary parts such as the permanent magnet and SF ₆ gas is used. There is a demand for the development of electrical contact members with excellent arc resistance that do not need to be required. In addition, damage caused by the occurrence of a small arc is a problem even in a sliding contact where the contact slides, and the development of an electric contact member having excellent arc resistance is required.
[0006]
This invention is made | formed in view of such a situation, and the objective of this invention is providing the electrical contact member excellent in arc resistance.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is configured as follows. The invention according to claim 1, made from those materials clad with Cu alloy, those plated on the surface of the Cu alloy or Cu alloy to a heterologous alloy, the surface roughness meter, the line segment length in the contact area surface 0 the roughness profile is measured in .8mm portion of the surface is determined from the measurement result, the difference of the projection apex height between the maximum projection apex height the ratio of the total number of protrusions projecting number present in the range of 0~3μm It is an electrical contact member excellent in arc resistance, characterized in that the projection integration frequency shown is in the range of 30 to 60 %.
[0008]
According to a second aspect of the present invention, in the electrical contact member excellent in arc resistance according to the first aspect, the plating on the surface of the Cu alloy is Ni plating or Sn plating.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
As an evaluation method of the metal surface, the present inventors established a method (an arc resistance evaluation method) capable of evaluating the arc resistance of an electrical contact member (electrical contact pair) used as an electrical contact of a switch or a relay. The electric contact member having excellent arc resistance according to the present invention is obtained based on this method. First, the present inventors investigated the difficulty of arc generation for Cu alloy electrical contact members, and found that the difficulty of arc generation varies greatly depending on the surface properties of the contact portion even if they have the same composition. It was. Therefore, in order to investigate the surface properties that have a corresponding relationship with the degree of difficulty of arc generation, the surface roughness profile (surface unevenness shape) was measured for electrical contact members made of Cu alloy with various contact surface roughness. The arithmetic average roughness Ra (JIS B0601-2001) was measured. However, the correspondence (correlation) between the degree of difficulty of arc generation and the arithmetic average roughness Ra was not obtained. Similarly, a correspondence relationship between the maximum height Rz of the protrusions defined in JIS B0601-2001 and the average interval RSm of the projections and depressions with the degree of difficulty of arc generation was not obtained.
[0011]
Therefore, as a result of further investigation and research, in the electrical contact member, the tips of the surface protrusions of the contact portions contact each other to form a contact point and energize, and when the closed contact portion is opened, the protrusion on the surface of the contact portion Was found to deteriorate due to minute melting. Furthermore, it has been found that, by this minute melting, an oxide is generated at the tip of the projection, and when the contact portion is repeatedly opened and closed many times, an arc is generated starting from this oxide.
[0012]
As described above, since the surface protrusions of the contact portions are involved in the contact between the contact portions, it is necessary to extract only the characteristics of the surface protrusions, not the surface recesses of the contact portions, so that the arc resistance can be evaluated. It has been found that the most closely related contact between the contact portions is the number of protrusions actually involved in the contact in the electrical contact member contact portion. Therefore, this evaluation method was further studied.
[0013]
As a result, for the electrical contact member, the surface roughness profile was measured at a certain length in the contact portion, and the number of projections present in the range of 0 to 3 μm in the difference between the projection vertex height and the maximum projection vertex height. The projection integrated frequency (evaluation value) C _0-3 , which is a ratio to the total number of projections, is calculated, and the arc resistance depends on whether or not the projection integrated frequency C _0-3 satisfies the range of 30 to 60 %. It turned out that pass / fail can be evaluated.
[0014]
This evaluation method will be described in detail. First, the surface roughness profile (surface irregularity shape) of the line segment portion of a certain length L ( 0.8 mm ) of the electrical contact member contact portion is measured with a surface roughness meter. Next, the projection vertex is extracted. In the extraction, a point having each maximum on the roughness curve is set as a projection vertex. Then, each projection vertex position extracted along the line segment from the reference point defined at one end on the line segment is defined as hi. Here, i represents the number (1-n) given to each protrusion. Next, let A (hi) be the height of each protrusion vertex measured from the horizontal reference line. Among them, the maximum protrusion vertex height A (hmax) is extracted. max is the number of the maximum protrusion vertex position. Thereafter, for all the protrusions, the difference B (hi) between the maximum protrusion apex height A (hmax) and each protrusion apex height A (hi) is expressed as B (hi) = A (hmax) −A (hi ).
[0015]
Next, the number of protrusions whose height difference from the maximum protrusion apex height A (hmax) is in the range of 0 to 3 μm is totaled (0 ≦ B (hi) ≦ 3 μm). A projection integration frequency C _0-3 (%), which is a ratio to the number of projections, is calculated. And when this protrusion integration frequency C _0-3 satisfies the range of 30 to 60 %, the electrical contact member finds that the arc hardly occurs and has excellent arc resistance. Is established.
[0016]
This evaluation method is effective for an electrical contact member made of a Cu alloy, a Cu alloy surface plated, or a Cu alloy clad with a dissimilar alloy, and based on this method, the present invention relates to An electrical contact member having excellent arc resistance is obtained. Examples of the plated Cu alloy include Ni plated Cu alloy and Sn plated Cu alloy. As what clad a dissimilar alloy to Cu alloy, what clad Ag alloy to pure copper, brass, or bronze is mentioned.
[0017]
The reason why the electrical contact member according to the present invention is excellent in arc resistance will be described. In the electrical contact member according to the present invention, the projection integration frequency C _0-3 representing the ratio of the number of projections having a projection height difference B (hi) in the range of 0 to 3 μm to the total number of projections is in the range of 30 to 60 %. Since the number of contact points that cause energization at the contact portion is increased, the number of contact opening and closing times until the occurrence of an arc is increased, and the arc resistance is excellent. In this case, if the protrusion integration frequency C _0-3 is less than 30%, the number of contact points that cause energization is small, and when the contact portion is opened, the protrusion is slightly melted and the tip of the protrusion is oxidized to increase the electrical resistance. However, arcs are likely to occur in a relatively short period of time. Projection integration degree _{C 0-3,} more preferably, it is intended that the protrusions integrated power _{C 0-3} satisfies the range of 60% 50.
[0018]
In addition, the inventors also performed an evaluation based on the protrusion integration frequency C _0-1 that represents the ratio of the number of protrusions having a protrusion height difference B (hi) in the range of 0 to 1 μm to the total number of protrusions. However, a correlation with arc resistance was not obtained with only the protrusion integration frequency C _0-1 . This is considered to indicate that even when the difference in protrusion height B (hi) defined in the present invention is about 3 μm or less, the correlation with the arc resistance is affected . In addition, there are many protrusions that do not come into contact with the counter electrode when the contact point contacts the electric contact member having a large ratio of the number of protrusions with a protrusion height difference B (hi) exceeding 3 μm with respect to the total number of protrusions (because the protrusion does not contact the counter electrode). It is considered that the arc resistance is not affected so much, and as a result, it cannot be correlated with the arc resistance.
[0019]
Next, the manufacturing method of the electrical contact member by this invention is demonstrated. In the conventional electrical contact member, the supplied voltage is as low as about 12 V, and the occurrence of arcing has not been a problem, so the surface properties are not so strictly controlled, and the surface of the member remains rolled, or It was in the state of grinding or pressing. Therefore, in the conventional electrical contact member, the surface property is about several percent to about several tens percent when evaluated by the projection integration frequency C _0-3 , and a high voltage of, for example, about 40 V is provided. When it was done, there was a situation where an arc occurred.
[0020]
On the other hand, the electrical contact member according to the present invention is subjected to pressing by using a press plate that is further polished by compound polishing, buffing or electrolytic polishing after mirroring or rolling after rolling or grinding. By performing processing or the like, the protrusion integration frequency C _0-3 can be controlled within the range of the present invention. Thereby, even when a high voltage of about 40 V is provided, the arc resistance is excellent.
[0021]
As described above, the arithmetic average roughness Ra alone does not correlate with the occurrence of arc, but if the arithmetic average roughness Ra can be significantly reduced, it is more preferable for suppressing the occurrence of arc. It is thought that it becomes. For example, when the arithmetic average roughness Ra is 1 μm or less, there is a possibility that good arc resistance can be obtained even if the range of the protrusion integration frequency C _0-3 specified in the present invention is slightly deviated. Of course, it is considered that if the arithmetic average roughness Ra is set to 1 μm or less with the projection integration frequency C _0-3 within the range of the present invention, even better arc resistance can be obtained. However, it is difficult to achieve an arithmetic average roughness Ra of 1 μm or less by a normal polishing method, and it is necessary to employ a special method such as ion etching, so that it is difficult to realize at present due to cost and the like. Conceivable.
[0022]
【Example】
Next, the test results for confirming the effectiveness of the arc resistance evaluation method as the metal surface evaluation method will be described. In this test, in order to make it easy to generate an arc, as a raw material, the tough pitch copper (pure copper) is used instead of the Cu alloy in the test 1, the surface of the tough pitch copper is Ni-plated in the test 2, and in the test 3, A tough pitch copper surface with Ni plating and a tough pitch copper surface with Sn plating were used.
[0023]
[Test 1]: Test 1 will be described first. A predetermined number of cylindrical bodies made of tough pitch copper having an outer diameter of 3 mm and a length of 10 mm were produced by grinding. Then, as Sample 1, an arcuate surface having R20 roundness was formed on one end surface of the cylindrical body by grinding, and this was used as Sample 1. As sample 2, an arcuate surface having R20 roundness was formed on one end surface of the cylindrical body by buffing using 1 μm diamond abrasive grains, and this was used as sample 2. As sample 3, an arcuate surface having R20 roundness is formed on one end surface of the cylindrical body by grinding, and this arcuate surface is electropolished for 10 seconds under the condition of 50% phosphoric acid solution and current 1A. Sample 3 was obtained. Further, as sample 4, an arcuate surface having R20 roundness was formed on one end surface of the cylindrical body by pressing against a mirror-finished stainless steel plate, and this was used as sample 4. Further, as Sample 5, an arc-shaped surface having R20 roundness was formed on one end face of the cylindrical body by grinding, and this arc-shaped surface was polished with # 1500 sandpaper.
[0024]
About the samples 1-5, using the surface roughness meter SE3500 manufactured by Kosaka Laboratory, the surface roughness profile (surface irregularity shape) of the line segment length of 0.8 mm on the contact portion (arc-shaped surface) surface Was measured. From the roughness profile of the surface, for each sample 1-5, the protrusion B has a difference B (hi) between the maximum protrusion apex height A (hmax) and each protrusion apex height A (hi) in the range of 0 to 3 μm. The projection integration frequency C _0-3 representing the ratio of the number to the total number of projections was determined. Further, the projection integration frequency C _0-1 representing the ratio of the number of projections in the range where the difference B (hi) is in the range of ₀ to 1 μm to the total number of projections, and the difference B (hi) is in the range of more than 3 μm to 5 μm or less. The projection integration frequency C _3-5 representing the ratio of the number of projections to the total number of projections was also determined. These calculated protrusion integration frequencies are shown in Table 1. Furthermore, for comparison, for each of the samples 1 to 5, the arithmetic average roughness Ra, the maximum height Rz, and the average interval (average length) RSm as defined in JIS B0601-2001 concerning the surface roughness were measured. These measured values are shown in Table 1.
[0025]
1 and 2 are explanatory diagrams of an arc resistance evaluation test. For each sample 1-5, the arcuate surfaces of a pair of samples were butted together, and currents of 42 V and 3 A were passed from the DC power source 1 through the load resistor 2 between the samples. Then, the contact part was opened at a speed of 50 mm / s, and the contact part was repeatedly opened and closed while confirming whether or not the arc was generated, and the number of contact breaks until the arc was generated was measured. The test results are shown in Table 1, FIG. 3 and FIG.
[0026]
[Table 1]

[0027]
As can be seen from Table 1, the number of contact breaks until the arc was generated was the largest in sample 2, then decreased in the order of sample 4, sample 3, sample 1, and sample 5, and sample 5 was the least. Of these, Sample 1 and Sample 5 had poor arc resistance. As can be seen from FIG. 3, it was confirmed that the quality of arc resistance could be correctly evaluated by the protrusion integration frequency C _0-3 . Other projection integration frequency C _0-1 or projection integration frequency C _3-5 was inappropriate as an evaluation value for evaluating arc resistance. Further, as can be seen from FIG. 4, the arithmetic average roughness Ra, the maximum height Rz, and the average interval RSm of the irregularities were also inappropriate as the arc resistance evaluation value.
[0028]
[Test 2]: Next, Test 2 will be described. In this test, a tough pitch copper surface subjected to Ni plating was used as a material.
[0029]
First, a predetermined number of cylindrical bodies made of tough pitch copper having an outer diameter of 3 mm and a length of 10 mm were produced by grinding. Then, as sample 1, compound polishing with 1 μm abrasive grains is performed to form an arc-shaped surface having R20 roundness on one end surface of the cylindrical body, and then electrolytic plating is performed to form a 1 μm thick Ni on the sample surface. Plating was performed and this was designated as Sample 1. As sample 2, a circular arc surface having R20 roundness is formed on one end face of the cylindrical body by buffing using 1 μm diamond abrasive grains, and then electrolytic plating is performed to deposit 1 μm thick Ni on the sample surface. This was designated Sample 2. Also, as sample 3, by pressing against a mirror-finished stainless steel plate, a circular arc surface having R20 roundness is formed on one end surface of the cylindrical body, and thereafter, electrolytic plating is performed on the sample surface. Ni plating with a thickness of 1 μm was applied, and this was used as Sample 3. Further, as sample 4, an arc-shaped surface having R20 roundness is formed on one end surface of the cylindrical body by grinding, and this arc-shaped surface is polished with # 1500 sandpaper, and then electrolytic plating is performed. Then, Ni plating with a thickness of 1 μm was applied to the sample surface, and this was designated as Sample 4.
[0030]
For Samples 1 to 4, as in Test 1, the protrusion integration frequencies C _0-3 , C _0-1 and C _3-5 were determined. Table 3 shows the calculated cumulative projection frequencies. For comparison, the arithmetic average roughness Ra, the maximum height Rz, and the average interval RSm of the unevenness were measured for each of the samples 1 to 4. These measured values are shown in Table 3.
[0031]
For each of the samples 1 to 4, the arcuate surfaces of the pair of samples were butted together in the same manner as in test 1, and a current of DC 220 V and 0.5 A was passed between the samples, and the contacts were made at a speed of 50 mm / s. The contact part was opened and closed, and the contact part was repeatedly opened and closed while confirming the occurrence of an arc, and the number of contact breaks until the arc was generated was measured. The test results are shown in Table 2 and FIG.
[0032]
[Table 2]

[0033]
As can be seen from Table 2, the number of contact breaks until the arc was generated was the largest in sample 2, then decreased in the order of sample 3, sample 1, and sample 4, and the smallest in sample 4. Of these, Sample 4 had poor arc resistance. As can be seen from FIG. 5, it was confirmed that the quality of arc resistance can be correctly evaluated by the projection integration frequency C _0-3 . Other projection integration frequency C _0-1 or projection integration frequency C _3-5 was inappropriate as an evaluation value for evaluating arc resistance. Further, the arithmetic average roughness Ra, the maximum height Rz, and the average interval RSm of the irregularities were also inappropriate as the arc resistance evaluation value.
[0034]
[Test 3]: Next, Test 3 will be described. In this test, the tough pitch copper surface was subjected to Sn plating instead of Ni plating.
[0035]
First, a predetermined number of cylindrical bodies made of tough pitch copper having an outer diameter of 3 mm and a length of 10 mm were produced by grinding. Then, as sample 1, compound polishing with 1 μm abrasive grains is performed to form an arc-shaped surface having R20 roundness on one end surface of the cylindrical body, and then electrolytic plating is performed to form Sn on the sample surface with a thickness of 1 μm. Plating was performed and this was designated as Sample 1. As sample 2, a circular arc surface having R20 roundness is formed on one end face of the cylindrical body by buffing using 1 μm diamond abrasive grains, and then electrolytic plating is performed to form Sn plating with a thickness of 1 μm on the sample surface. This was designated Sample 2. Also, as sample 3, by pressing against a mirror-finished stainless steel plate, a circular arc surface having R20 roundness is formed on one end surface of the cylindrical body, and thereafter, electrolytic plating is performed on the sample surface. Sn plating with a thickness of 1 μm was applied, and this was used as Sample 3. Further, as sample 4, an arc-shaped surface having R20 roundness is formed on one end surface of the cylindrical body by grinding, and this arc-shaped surface is polished with # 1500 sandpaper, and then electrolytic plating is performed. Then, Sn plating with a thickness of 1 μm was applied to the sample surface, and this was designated as Sample 4.
[0036]
For Samples 1 to 4, as in Test 1, the protrusion integration frequencies C _0-3 , C _0-1 and C _3-5 were determined. Table 3 shows the calculated cumulative projection frequencies. For comparison, the arithmetic average roughness Ra, the maximum height Rz, and the average interval RSm of the unevenness were measured for each of the samples 1 to 4. These measured values are shown in Table 3.
[0037]
For each of the samples 1 to 4, the arc-shaped surfaces of the pair of samples were butted together in the same manner as in test 1, and a direct current of 42 V and 5 A was passed between the samples, and the contact portion was moved at a speed of 50 mm / s. The contact was repeatedly opened and closed while confirming whether or not arcing occurred, and the number of times the contact was opened until arcing was measured. The test results are shown in Table 3 and FIG.
[0038]
[Table 3]

[0039]
As can be seen from Table 3, the number of contact breaks until the arc was generated was the largest in Sample 2, then decreased in the order of Sample 3, Sample 1, and Sample 4, and the smallest in Sample 4. Of these, Sample 4 had poor arc resistance. As can be seen from FIG. 6, whether the arc resistance is good or not is such that the difference B (hi) between the maximum protrusion apex height A (hmax) and each protrusion apex height A (hi) is in the range of 0 to 3 μm. It was confirmed that the evaluation can be correctly performed by the protrusion integration frequency C _0-3 representing the ratio of the number of protrusions to the total number of protrusions. The projection integration frequency C _{0-1 for} the number of projections having a difference B (hi) in the range of 0 to 1 μm, or the projection integration frequency C _3-5 for the number of projections having a difference B (hi) in the range of more than 3 μm to 5 μm is It was inappropriate as an evaluation value for evaluating arc resistance. Further, the arithmetic average roughness Ra, the maximum height Rz, and the average interval RSm of the irregularities were also inappropriate as the arc resistance evaluation value.
[0040]
Next, examples of the electrical contact member excellent in arc resistance according to the present invention will be described. In Examples 1 to 11, a cylindrical body having an outer diameter of 3 mm and a length of 10 mm was prepared by grinding using a Cu alloy material having the composition shown in Table 4 (Examples 1 and 2 are pure copper), and then 1 μm in length. Compound polishing with abrasive grains was performed to form an arc-shaped surface having R20 roundness on one end surface of the cylindrical body, thereby obtaining an electric contact member. Note that the surface properties were appropriately changed by changing the polishing time and the like. Moreover, the electrical contact member of Comparative Examples 1-13 was produced for the comparison. In Comparative Examples 1 to 13, a cylindrical body having an outer diameter of 3 mm and a length of 10 mm was prepared by grinding using a Cu alloy material having the composition shown in Table 5 (Comparative Example 1 is pure copper), and then cylindrical by grinding. An arcuate surface having a roundness of R20 was formed on one end surface of the body to obtain an electrical contact member.
[0041]
About the electrical contact member of Examples 1-11 and Comparative Examples 1-13, the surface of the line segment length 0.8mm part in a contact part (arc-shaped surface) surface using surface roughness meter SE3500 made from Kosaka Laboratory. The roughness profile of was measured. The projection integration frequency C _0-3 was determined from the roughness profile of the surface. Table 4 shows the calculated projection integration frequencies C _0-3 .
[0042]
And about Examples 1-11 and Comparative Examples 1-13, respectively, the arc-shaped surface of a pair of electrical contact member was faced | matched, and the electric current of direct current | flow 42V and 3A was sent between this electrical contact member. Then, the contact part was opened at a speed of 50 mm / s, and the contact part was repeatedly opened and closed while confirming whether or not the arc was generated, and the number of contact breaks until the arc was generated was measured. The test results are shown in Table 4 and FIG.
[0043]
[Table 4]

[0044]
As can be seen from Table 4, in Comparative Examples 1 to 13 where the value of the protrusion integration frequency C _0-3 deviates from the specified range of the present invention, the number of contact breaks until the arc is generated is less than 400 times, The arc property was inferior. On the other hand, in Examples 1 to 11, the contact opening number of 400 times or more was obtained, and even with the same composition as the comparative example, the arc resistance was excellent.
[0045]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an electric contact member having excellent arc resistance obtained by using a simple surface processing method, and an electric contact in a small part such as a switch, a relay, or a connector. This can contribute to improvement of arc resistance of the member and cost reduction.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an arc resistance evaluation test.
FIG. 2 is an explanatory diagram of an arc resistance evaluation test.
FIG. 3 is a graph showing the relationship between the number of contact breaks until arc occurrence in evaluation test 1 and the protrusion integration frequency C _0-1 , C _0-3 , C _3-5 .
FIG. 4 is a graph showing the relationship between the number of contact breaks until the occurrence of an arc in evaluation test 1 and the contact portion surface states Ra, Rz, RSm.
FIG. 5 is a graph showing the relationship between the number of contact breaks until the occurrence of an arc in the evaluation test 2 and the projection integration frequency C _0-1 , C _0-3 , C _3-5 .
FIG. 6 is a graph showing the relationship between the number of contact breaks until the occurrence of an arc in evaluation test 3 and the protrusion integration frequencies C _0-1 , C _0-3 , C _3-5 .
FIG. 7 is a graph showing the relationship between the number of contact breaks until arc generation and the protrusion integration frequency C _0-3 in the examples and comparative examples of the electric contact member excellent in arc resistance according to the present invention.
[Explanation of symbols]
1 ... DC power supply 2 ... Load resistance

Claims

The material is a Cu alloy, a Cu alloy surface plated or a Cu alloy clad with a dissimilar alloy, and a surface roughness meter is used to measure the surface roughness of the 0.8 mm line segment on the contact surface. The height profile is measured, and the projection integration frequency indicating the ratio of the number of projections existing in the range of 0 to 3 μm in the projection vertex height difference from the maximum projection vertex height, which is obtained from the measurement result , is 30 An electric contact member excellent in arc resistance, characterized by satisfying a range of ˜60 %.

The electrical contact member excellent in arc resistance according to claim 1, wherein the plating on the surface of the Cu alloy is Ni plating or Sn plating.