JP3897416B2 - Powder aluminum alloy cylinder liner - Google Patents

Description

なお、表１中において、「隙間なく良好」とは、エンジンが稼働した状態においても、エンジンブロックからのシリンダーライナの抜け落ちがないことを意味する。また、「隙間あり」とは、鋳込みが終了した段階でシリンダーライナがエンジンブロックから抜け落ちることを、あるいはエンジン稼働時の高温下においてシリンダーライナとエンジンブロックとの界面に隙間が生じてエンジンブロックからのシリンダーライナの抜け落ちが生じることを意味する。
【００８０】
上記表１に示すような熱膨張率α_C を有するアルミ合金製シリンダーライナをアルミ高圧鋳造法によりエンジンブロック本体中に鋳込んだ後、シリンダーライナとエンジンブロックとの接触界面の結合状態およびシリンダーライナの直径方向での変形の有無を確認した。
【００８１】
なお、シリンダーライナには抜け落ち防止のための溝加工などは施さずに鋳込み実験を行なった。また、ここで、アルミ高圧鋳造法により製造したアルミ合金製エンジンブロック本体の合金組成はＡｌ−１７％Ｓｉ−３Ｃｕ−１Ｍｇ（重量％）であり、その熱膨張率α_B は、１９．５×１０^-6／℃である。ただし、ここで記載した熱膨張率の値は常温から２００℃までの平均値である。
【００８２】
表１に示すように、本願発明が規定するα_B −α_C ≧１×１０^-6／℃、かつ、α_B −α_C ≦８×１０^-6／℃といった熱膨張率の関係式を満足するシリンダーライナとエンジンブロックとの組合せ番号、Ｎｏ．１〜Ｎｏ．５においては、鋳込んだ後のシリンダーライナの外周面はエンジンブロックからの圧縮残留応力によりエンジンブロック本体によって強固に拘束されており、シリンダーライナとエンジンブロック本体との接触界面に隙間が生じることない。
【００８３】
その結果、シリンダーライナに抜け落ち防止加工を施さなくとも、エンジンブロック本体からのシリンダーライナの抜け落ちといった問題が発生していないことがわかる。
【００８４】
また、エンジンブロックからの拘束力が適正条件であるために鋳込んだ後のシリンダーライナ自身が変形することなく、シリンダーライナとして十分使用することのできる真円度を有している。したがって、シリンダーライナの薄肉化を実現することが確認できる。
【００８５】
一方、本願発明が規定するシリンダーライナとエンジンブロックとの熱膨張率に関する上記の関係式を満足しないＮｏ．６〜Ｎｏ．８においては、以下のような問題が生じることが確認される。
【００８６】
Ｎｏ．６；シリンダーライナの熱膨張率が小さすぎるために、エンジンブロックからの圧縮応力による拘束力が過剰に作用するためにシリンダーライナが変形する。
【００８７】
Ｎｏ．７；シリンダーライナの熱膨張率が大きすぎるために、エンジンブロックからの圧縮応力による拘束力が十分に作用しないために、シリンダーライナがエンジンブロックに保持されず、隙間が生じて抜け落ちる。
【００８８】
Ｎｏ．８；シリンダーライナの熱膨張率が大きすぎるために、エンジンブロックからの圧縮応力による拘束力が十分に作用しないために、シリンダーライナがエンジンブロックに保持されず、隙間が生じて抜け落ちる。
【００８９】
（実施例２）
【００９０】
【表２】

なお、表２中において、「隙間なく良好」とは、エンジンが稼働した状態においても、エンジンブロックからのシリンダーライナの抜け落ちがないことを意味する。また、「隙間あり」とは、鋳込みが終了した段階でシリンダーライナがエンジンブロックから抜け落ちることを、あるいはエンジン稼働時の高温下においてシリンダーライナとエンジンブロックとの界面に隙間が生じてエンジンブロックからのシリンダーライナの抜け落ちが生じることを意味する。
【００９１】
表２に示すようなＮｏ．１〜Ｎｏ．７に示す熱膨張率α_C を有するアルミ合金製シリンダーライナをアルミ高圧鋳造法によりエンジンブロック本体中に鋳込んだ後、シリンダーライナとエンジンブロックとの接触界面の結合状態およびシリンダーライナの直径方向での変形の有無を確認した。
【００９２】
なお、シリンダーライナには抜け落ち防止のための溝加工等は施さず鋳込み実験を行なった。また、アルミ高圧鋳造法により作製したアルミ合金製エンジンブロック本体の合金組成は、Ａｌ−１１％Ｓｉ−３Ｃｕ−０．５Ｍｇ（重量％）であり、その熱膨張率α_B は、２１×１０^-6／℃である。ただし、ここで記載した熱膨張率の値は常温から２００℃までの平均値である。
【００９３】
表２に示すように、本願発明が規定するα_B −α_C ≧１×１０^-6／℃、かつ、α_B −α_C ≦８×１０^-6／℃といった熱膨張率の関係式を満足するシリンダーライナとエンジンブロックとの組合せは、Ｎｏ．１〜Ｎｏ．６である。鋳込んだ後のシリンダーライナ外周面はエンジンブロックからの圧縮残留応力によりエンジンブロック本体によって強固に拘束されており、シリンダーライナとエンジンブロック本体との接触界面に隙間が生じることがない。
【００９４】
その結果、シリンダーライナに抜け落ち防止加工を施さなくとも、エンジンブロック本体からのシリンダーライナの抜け落ちといった問題が発生していないことがわかる。また、エンジンブロックからの拘束力が適正条件であるために、鋳込んだ後のシリンダーライナ自身が変形することなく、シリンダーライナとして十分使用できる真円度を有している。したがって、シリンダーライナとしての薄肉化が実現できることが確認できた。
【００９５】
一方、本願発明が規定するシリンダーライナとエンジンブロックとの熱膨張率に関する上記の関係式を満足しないＮｏ．６およびＮｏ．７の場合、以下のような問題が生じることが確認された。
【００９６】
Ｎｏ．６；シリンダーライナの熱膨張率が小さすぎるために、エンジンブロックからの圧縮応力による拘束力が作用するためにシリンダーライナが変形する。
【００９７】
Ｎｏ．７；シリンダーライナの熱膨張率が大きすぎるために、エンジンブロックからの圧縮応力による拘束力が十分に作用しないために、シリンダーライナがエンジンブロックに保持されず、隙間が生じて抜け落ちる。
【００９８】
（実施例３）
【００９９】
【表３】

上記表３に示すＮｏ．１〜Ｎｏ．１８のアルミ合金粉末に、必要に応じて酸化物球状粒子（平均粒径５〜１０μｍ）および固体潤滑粒子（平均粒径５〜１５μｍ）を混合したものを原料粉末とし、これを成形した後、窒素雰囲気中で加熱・焼結することでアルミ合金焼結体中に窒化アルミニウム（ＡｌＮ）を生成させ、この焼結体を熱間押出し法によりシリンダーライナを作製した。ここで、それぞれの酸化物球状粒子、固体潤滑粒子とＡｌＮおよび窒素の含有量は、焼結アルミ合金全体に対する比率を重量％で示している。また、押出し条件によりシリンダーライナの空孔率を３〜５％に調節した。
【０１００】
シリンダーライナ素材から摩耗試験用試料を作製し、溶製アルミ合金（ＪＩＳＡＣ８Ａ材）を相手材に用いて、境界潤滑条件における各焼結アルミ合金の耐摩耗性を評価した。また、油膜切れの条件下での耐焼きつき性（押しつけ荷重を増加させて焼きつき現象が発生した際の荷重を比較）を評価した。なお、チップオンディスク式摩耗試験を用いてそれぞれの特性を評価した。
【０１０１】
さらに、比較材Ｎｏ．１９として溶製アルミ合金（ＪＩＳ ＡＣ８Ａ材）を用いたシリンダーライナを作製し、試料の摺動面には硬質Ｃｒめっきを施した。さらに、比較材Ｎｏ．２０として鋳鉄材を用いた。摩耗試験後のライナ素材および相手材の摩耗量および焼きつき発生荷重の評価結果を表４に示す。
【０１０２】
【表４】

本実施例におけるシリンダーライナ用焼結アルミ合金においては、表４からわかるように、耐摩耗性に優れ、かつ相手材への攻撃性も少なく、現行の鋳鉄材や硬質Ｃｒめっき処理を施したアルミ合金と同等であることがわかる。また、耐焼きつき性についても鋳鉄材と同等であり、めっき被膜が剥離した硬質Ｃｒめっき処理材に比べて優れていることがわかる。
【０１０３】
一方、比較材Ｎｏ．１３〜Ｎｏ．１８については、以下のような問題が確認された。
【０１０４】
Ｎｏ．１３；ＡｌＮが含有されていないために、十分な耐摩耗性および相手攻撃性が得られない。
【０１０５】
Ｎｏ．１４；ＡｌＮ含有量が少ないために、十分な耐摩耗性および相手攻撃性が得られない。
【０１０６】
Ｎｏ．１５；ＡｌＮ含有量が１８％と多いためにアルミ合金の強度が低下し、加圧時に試料が欠損した。
【０１０７】
Ｎｏ．１６；潤滑粒子の含有量が６％と多いためにアルミ合金の強度が低下し、加圧時に試料が欠損した。また、熱間押出し時にシリンダーライナ表面がむしれた状態を示した。
【０１０８】
Ｎｏ．１７；硬質粒子の含有量が６％と多いために、相手材を攻撃し、耐焼きつき性が低下する。
【０１０９】
Ｎｏ．１８；硬質粒子の含有量が７％と多いために、相手材を攻撃し、耐焼きつき性が低下する。
【０１１０】
なお、Ｎｏ．１５においては、ＡｌＮの含有量が、またＮｏ．１７，１８においては、硬質粒子の含有量が本願発明が規定する適正量よりも多いために、摩擦試験片に加工する際に超硬工具の磨耗が他に比べて顕著であった。
【０１１１】
（実施例４）
上記実施例３において、シリンダーライナ素材を所定の円筒形状に加工した後、アルミ高圧鋳造法によりアルミ合金製エンジンブロックに鋳込み、各シリンダーライナについて単体耐久試験を実施した。
【０１１２】
なお、比較材Ｎｏ．１９は溶製アルミ合金（ＪＩＳ ＡＣ８Ａ材）を用いたシリンダーライナを作製し、その摺動面に耐摩耗性や耐焼きつき性を改善する目的で、硬質Ｃｒめっきを施した。また、比較材Ｎｏ．２０は、Ｆｃ鋳鉄材を用いて同形状のシリンダーライナを作製してエンジンブロックに鋳込んだ。また、ピストン材として溶製アルミ合金（ＪＩＳ ＡＣ８Ａ材）を用いており、比較材Ｎｏ．１９の場合に限り、ピストン材として溶製アルミ合金（ＪＩＳ ＡＣ８Ａ材）に加えて、シリンダーライナと摺動する外周表面にＦｅめっきを施したものも準備した。
【０１１３】
耐久試験後のシリンダーライナおよびピストンの摺動面の破損状況を観察し、摩耗や凝着（焼きつき）の有無を確認した。その結果を表５に示す。
【０１１４】
【表５】

本実施例におけるシリンダーライナ用焼結アルミ合金においては、上記表５からわかるように、シリンダーライナ自身の耐摩耗性に優れており、またピストンにＦｅめっきを施さなくても摩耗や凝着を生じることなく、相手材への攻撃性も少なく、現行の鋳鉄材と同等である。
【０１１５】
一方、比較材Ｎｏ．１３〜Ｎｏ．１９については、以下のような問題が確認された。
【０１１６】
Ｎｏ．１３；ＡｌＮが含有されていないために、十分な耐摩耗性および相手攻撃性が得られない。
【０１１７】
Ｎｏ．１４；ＡｌＮ含有量が少ないために、十分な耐摩耗性および相手攻撃性が得られない。
【０１１８】
Ｎｏ．１５；ＡｌＮ含有量が１８％と多いためにピストン側への攻撃量は増加した。
【０１１９】
Ｎｏ．１６；潤滑粒子の含有量が６％と多いためにアルミ合金の強度が低下し、耐摩耗性が若干低下した。
【０１２０】
Ｎｏ．１７；硬質粒子の含有量が６％と多いために、ピストン側への攻撃量が増加した。
【０１２１】
Ｎｏ．１８；硬質粒子の含有量が７％と多いために、ピストン側への攻撃量が増加した。
【０１２２】
Ｎｏ．１９；溶製アルミ合金ではその摺動面に硬質Ｃｒめっきを施し、かつ、ピストン側にもＦｅめっきを施さないと、摩耗や凝着といった問題が生じてライナとしては使用できない。
【０１２３】
なお、Ｎｏ．１５においては、ＡｌＮの含有量が、またＮｏ．１７，１８においては、硬質粒子の含有量が本発明が規定する適正量よりも多いために、シリンダーライナ形状に加工する際に超硬工具の摩耗が他に比べて顕著であった。
【０１２４】
以上により、本実施例における焼結アルミ合金は、硬質Ｃｒめっきなどの表面処理を施さなくとも、シリンダーライナとしての耐摩耗性・耐焼きつき性を十分に有しており、また相手のピストン側にもＦｅめっき処理を施すことなく使用できるといった経済性の面においても優れている。
【０１２５】
（実施例５）
重量基準でＳｉ；１２％、Ｆｅ；３％、Ｎｉ；３％、Ｍｇ；１％を含有するアルミ合金粉末に対してＴｉＯ₂ 粒子（平均粒径；７μｍ）を１．５％、黒鉛粉末（平均粒径；１０μｍ）を１％それぞれ添加した混合粉末を成形した後、５４０℃に制御した窒素雰囲気中で３ｈｒ加熱・保持することで焼結アルミ合金を作製し、かつ、その際に窒化反応により焼結アルミ合金全体に対して４％のＡｌＮが生成する焼結体を得た。この素材から熱間押出し法により円筒形状のシリンダーライナを作製した。
【０１２６】
このとき、押出し条件（押出し比）を制御することで、押出し後のシリンダーライナ素材の空孔率を変えて各アルミ合金の耐摩耗性および耐焼きつき性を評価した。その結果を表６に示す。
【０１２７】
【表６】

なお、耐摩耗性については上記実施例３に記載のチップオンディスク式摩耗試験により境界潤滑条件での性能を評価した。また、相手材であるディスク側には溶製アルミ合金（ＪＩＳ ＡＣ８Ａ材）を使用した。
【０１２８】
さらには、各シリンダーライナをアルミ高圧鋳造によりエンジンブロック本体に鋳込み、そのときのシリンダーライナの変形の有無を確認した。なお、比較材としてＦＣ鋳鉄を用いたシリンダーライナについても併せて評価を行なった。
【０１２９】
表６からわかるように、本願発明において規定する空孔率を有する焼結アルミ合金を用いたシリンダーライナにおいては、現行のシリンダーライナ材であるＦＣ鋳鉄材と同等の耐摩耗性および耐焼きつき性を有している。
【０１３０】
特に、空孔率が３％〜１０％の焼結アルミ合金については、それらの特性はさらに優れていることがわかる。また、エンジンブロックに鋳込んだ場合においても、エンジンブロック本体側からの拘束力により変形することなく、シリンダーライナ形状に加工した状態の真円度が確保されていることがわかる。一方、比較材においては以下のような問題が確認された。
【０１３１】
Ｎｏ．６；空孔率が１８％と大きいためにエンジンブロックに鋳込んだ際に、シリンダーライナ側に作用する圧縮応力によりシリンダーライナが変形した。
【０１３２】
Ｎｏ．７；空孔率が２２％と大きいために焼結アルミ合金の強度が低下し、摩擦試験において試料が欠損した。また、エンジンブロックに鋳込んだ際に、シリンダーライナ側に作用する圧縮応力によりシリンダーライナが変形した。
【０１３３】
（実施例６）
実施の形態において提案する窒化反応法により作製した熱間押出し後の焼結アルミ合金（合金組成；Ａｌ−１２Ｓｉ−２Ｎｉ−１Ｍｇ−２ＡｌＮ／重量％）中に生成・分散するＡｌＮ粒子の組織構造のＴＥＭ像（１８，０００倍にて撮影）を図１に示し、またＳＩＭ像を図２に示す。
【０１３４】
また、比較として同一組成の焼結アルミ合金を従来の製法、つまりＡｌＮ粒子（平均粒径２２μｍ）をアルミ合金粉末（組成；Ａｌ−１２Ｓｉ−２Ｎｉ−１Ｍｇ／重量％）に添加・混合したものを成形・焼結・熱間押出しにより作製し、このアルミ合金中に分散するＡｌＮ粒子のＳＩＭ像を図３に示す。
【０１３５】
図１および図２に示すように、本実施の形態において提案する直接窒化反応法により生成したＡｌＮは繊維状あるいは樹枝状に一方向に成長した組織構造を有していることがわかる。また、その成長方向をＡｌＮの厚みとすると、図からもわかるように、窒化反応法により生成するＡｌＮの厚みは約１μｍ程度である。
【０１３６】
一方、図３に示すように、従来製法によるＡｌＮ粒子を添加する場合、ＡｌＮは繊維状構造ではなく、単結晶構造を有しており、明らかに本発明の窒化反応法により生成したＡｌＮ粒子と異なることがわかる。
【０１３７】
（実施例７）
本実施の形態が提案する窒化反応法により作製した熱間押出し後の焼結アルミ合金の光学顕微鏡組織写真を図４に示す。合金組成はＡｌ−１２Ｓｉ−２Ｎｉ−１Ｍｇ−２ＡｌＮ／重量％）である。また、比較としてＡｌＮ粒子（平均粒径２２μｍ）をアルミ合金粉末（組成；Ａｌ−１２Ｓｉ−２Ｎｉ−１Ｍｇ／重量％）に添加して本発明材と同一組成にした焼結アルミ合金を熱間押出し法により作製した。その焼結体の組織写真を図５に示す。
【０１３８】
図４に示すように、本発明の窒化反応法により生成したＡｌＮ粒子（黒い矢印で示す部分）はマトリックスのアルミ合金素地との境に隙間がない結合界面を有していることがわかる。これに対して、図５に示す従来法（ＡｌＮ粒子を添加する方法）では、ＡｌＮ粒子（黒い矢印で示す部分）とアルミ合金素地との境に隙間（Ｇａｐと記した白い矢印で示した部分）が存在していることがわかる。
【０１３９】
（実施例８）
上記実施例６で作製した焼結アルミ合金について、チップオンディスク式摩擦試験を境界潤滑条件下で実施した後の焼結体および相手材の摺動面の損傷状況を光学顕微鏡により観察した。その結果を、図６（ａ），（ｂ）および図７（ａ），（ｂ）に示す。図６（ａ），（ｂ）は、本発明が提案する窒化反応法により作製したＡｌＮが生成分散する焼結アルミ合金であり、図７（ａ），（ｂ）は、従来法であるＡｌＮ粒子を添加して得られた焼結アルミ合金である。なお、相手材には溶製アルミ合金（ＡＤＣ１２材）を用いた。
【０１４０】
図６（ａ）に示すように、本願発明が提案する窒化反応法により作製した焼結アルミ合金の摺動面においては、軽微な擦れ跡が見られる程度で凝着・焼きつき現象は観察されない。またＡｌＮ粒子が脱落した形跡も摺動面には認められない。さらに、相手材についても、図６（ｂ）に示すように、凝着・焼きつき現象は見られず軽微な擦れ跡が存在する程度である。
【０１４１】
一方、図７（ａ）においては、焼結アルミ合金にＡｌＮ粒子の脱落した孔（Hallと記した白い矢印部分）が各所に存在しており、深い摺動傷も観察される。また相手材についても、図７（ｂ）に示すように、脱落したＡｌＮ粒子により攻撃された深い摺動傷および凝着領域（Seizure と記した白い部分）が各所に存在していることがわかる。
【０１４２】
このように本願発明が提案する窒化反応法により作製した焼結アルミ合金においては窒化アルミニウム（ＡｌＮ）とマトリックスであるアルミ合金が隙間なく、強固に結合した界面を有することで、相手材と摩擦摺動した場合においてもＡｌＮ粒子が脱落せず、優れた耐摩耗性・耐焼きつき性および相手攻撃性を有することが確認された。
【０１４３】
（実施例９）
【０１４４】
【表７】

上記表７のＮｏ．１〜Ｎｏ．１１に示す合金組成を有するアルミ合金粉末を成形した後、窒素雰囲気中で加熱・焼結することにより、アルミ合金焼結体中に窒化アルミニウム（ＡｌＮ）を生成させ、この焼結体を熱間押出し法によりシリンダーライナを製作した。空孔率は、押出し条件により３〜５％に調整した。
【０１４５】
窒化アルミニウムおよび窒素の含有量は焼結アルミ合金全体に対する比率を重量％で表示し、上記表７中に示す。なお、残部はすべてＡｌである。また、熱膨張率も併せて上記表７中に示す。
【０１４６】
シリンダーライナ素材から摩耗試験用試料を作製し、溶製アルミ合金（ＪＩＳＡＣ８Ａ材）を相手材に用いて、境界潤滑条件における各焼結アルミ合金の耐摩耗性を評価した。また、油膜切れの条件下での耐焼きつき性（押出し荷重を増加させて焼きつき現象が発生した際の荷重を比較）を評価した。なお、チップオンディスク式摩耗試験を用いてそれぞれの特性を評価した。摩耗試験後のシリンダーライナ素材および相手材の摩耗量および焼きつき発生荷重の評価結果を表８に示す。
【０１４７】
【表８】

また、アルミ高圧鋳造法により熱膨張率がα_B が２２×１０^-6／℃であるアルミ合金溶湯（組成；Ａｌ−８Ｓｉ−３Ｃｕ−０．５Ｍｇ／重量％）を用いて各シリンダーライナをエンジンブロック本体に鋳込み、その結合界面およびシリンダーライナの変形の有無を確認した。その結果を、上記表８中に示す。
【０１４８】
表７および表８に示すように、粉末アルミ合金中の窒化アルミニウムとＳｉとの合計含有量が本願発明が規定する適正範囲を満足するＮｏ．１〜Ｎｏ．９においては、その熱膨張率α_C は１４×１０^-6／℃〜２０×１０^-6／℃を満足し、かつ、優れた耐摩耗特性を有することがわかる。また、鋳込んだ後のシリンダーライナとエンジンブロック本体の界面は密着した良好な状態を示しており、シリンダーライナの変形も認められなかった。
【０１４９】
一方、比較例Ｎｏ．１０，１１においては、以下のような問題が確認された。Ｎｏ．１０；ＡｌＮとＳｉの合計含有量が２％と少ないために、十分な耐摩耗性が得られず、また両者の合計含有量は少ないために熱膨張率は２１．６×１０^-6／℃と大きい値を示した。また、シリンダーライナとエンジンブロックの熱膨張率の差が０．４×１０^-6／℃と小さいためにシリンダーライナとエンジンブロックとの界面に隙間が確認された。
【０１５０】
Ｎｏ．１１；ＡｌＮとＳｉの合計含有量が３６％と多いために熱膨張率は１３．０×１０^-6／℃と小さい値を示し、エンジンブロックとシリンダーライナの熱膨張率の差が９×１０^-6／℃と大きいために、鋳込んだ後にシリンダーライナが変形した。また、ＡｌＮとＳｉの合計含有量が３６％と多いために相手材を若干攻撃することも認められた。
【０１５１】
【発明の効果】
この発明に基づいた請求項１〜請求項１２に記載の発明によれば、シリンダーライナとエンジンブロックの熱膨張率の関係により、両者の接触界面に隙間が生じることがない。その結果、エンジンブロックからのシリンダーライナの抜け落ちを防止することが可能となる。
【図面の簡単な説明】
【図１】熱間押出し後の焼結アルミ合金中に生成・分散するＡｌＮ粒子の組織構造のＴＥＭ写真である。
【図２】熱間押出し後の焼結アルミ合金中に生成・分散するＡｌＮ粒子の組織構造のＳＩＭ写真である。
【図３】従来製法におけるＡｌＮ粒子の組織構造のＳＩＭ写真である。
【図４】窒化反応によるＡｌＮ分散焼結アルミ合金の顕微鏡写真である。
【図５】ＡｌＮ粒子添加焼結アルミ合金の顕微鏡写真である。
【図６】（ａ）および（ｂ）は、本願発明に基づく窒化反応によるＡｌＮ分散焼結アルミ合金の顕微鏡写真である。
【図７】（ａ）および（ｂ）は、従来法であるＡｌＮ粒子添加焼結アルミ合金の顕微鏡写真である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a powder aluminum alloy cylinder liner used in automobiles, motorcycles, snowmobiles, water bikes, and the like, and more specifically, when casting a cylinder liner into an engine block body by aluminum high pressure casting. The present invention relates to a suitable powder aluminum alloy for a cylinder liner.
[0002]
[Prior art]
The weight reduction of automobile parts and motorcycle parts that slide frictionally in lubricating oil can be expected to greatly improve fuel efficiency by reducing friction and driving torque, so the weight of sliding parts such as connecting rods and pistons can be reduced. Is extremely effective.
[0003]
However, if the lubricating oil is not sufficiently present at the sliding interface for some reason during operation, the aluminum part causes problems such as seizure phenomenon or adhesion. For example, the piston itself is made of an aluminum alloy, and as a counterpart cylinder liner material for internal combustion engines, the seizure phenomenon is suppressed by applying a cast aluminum alloy with a hard plating such as nickel, chromium or iron on the sliding surface. Was considered.
[0004]
However, since the heat resistance of the aluminum alloy constituting the substrate is not sufficient, it cannot be used as a liner material, and there is a problem in terms of economy.
[0005]
Therefore, in order to improve the wear resistance and heat resistance of aluminum alloys, it is possible to improve these characteristics by using a powdered aluminum alloy having a microstructure obtained by rapid solidification and to put it into practical use as a cylinder liner material. Was found. For example, according to the technology disclosed in Japanese Patent Publication No. 6-21309 and Japanese Patent Laid-Open No. 1-255641, the aluminum alloy powder having a special alloy composition can be used as a fine and nearly spherical alumina hard particle and a lubricating component. We propose a cylinder liner material for internal combustion engines that can be solidified by hot extrusion by mixing and adding graphite powder.
[0006]
In the technique disclosed in Japanese Patent Application Laid-Open No. 1-271053, a method of casting a powder aluminum alloy cylinder liner into an aluminum alloy engine block body is proposed.
[0007]
[Problems to be solved by the invention]
However, when casting such an aluminum alloy cylinder liner into an aluminum alloy engine block body by the aluminum high pressure casting method, the outer surface of the cylinder liner is welded to the engine block body in order to finish casting in a relatively short time.・ Do not combine. When the engine block is cooled to room temperature in this state, a gap is generated at the contact interface between the two due to the relationship between the coefficient of thermal expansion between the cylinder liner and the engine block. As a result, there is a problem that the cylinder liner falls out of the engine block body.
[0008]
On the other hand, in the prior art, the outer peripheral surface of the cylinder liner is subjected to drop-off prevention processing by groove processing or the like. However, this slip-off prevention process necessitates thickening of the cylinder liner, and causes problems such as an increase in the cost of the cylinder liner and an increase in the size and weight of the engine block body.
[0009]
Therefore, the object of the present invention is to prevent a gap from occurring at the interface between the cylinder liner and the engine block body even after casting the cylinder liner into the engine block body made of molten aluminum alloy, and to prevent falling off. The object is to provide a thin and lightweight powder aluminum alloy cylinder liner that can withstand actual use without requiring any processing.
[0010]
[Means for Solving the Problems]
The powder aluminum alloy cylinder liner according to claim 1 based on the present invention is a powder aluminum alloy cylinder liner cast into a molten aluminum alloy engine block. Dar The liner is formed into a cylindrical shape by a hot extrusion method, and the powdered aluminum alloy has a porosity of 1% or more and 15% or less by volume with respect to the entire aluminum alloy, and aluminum nitride is based on weight. AlN dispersion type powder aluminum alloy containing 0.5% or more and 15% or less, with the balance being aluminum. The AlN dispersion type powder aluminum alloy is formed in an aluminum alloy as a layered film of AlN in the form of fibers or dendrites. Is distributed. In addition, the coefficient of thermal expansion of the powder aluminum alloy cylinder liner is α _C The coefficient of thermal expansion of the molten aluminum alloy engine block is α _B The relationship between the two is 14 × 10 ^-6 / ℃ ≦ α _C ≦ 20 × 10 ^-6 / ° C and 1 × 10 ^-6 / ℃ ≦ α _B -Α _C ≦ 8 × 10 ^-6 Satisfies / ° C.
[0012]
Above, claims 1 According to the described invention, there is no gap at the contact interface between the cylinder liner and the engine block due to the relationship between the thermal expansion coefficients. As a result, it is possible to prevent the cylinder liner from falling off the engine block. The powder aluminum alloy of the cylinder liner is an AlN-dispersed powder aluminum alloy containing aluminum nitride in an amount of 0.5% or more and 15% or less by weight, with the balance being aluminum. Thereby, sufficient wear resistance and machinability can be obtained. In addition, the powder aluminum alloy of the above cylinder liner is a volume ratio relative to the entire aluminum alloy. 1% or more It has a porosity of 15% or less. As a result, the holes are dispersed on the sliding surface of the cylinder liner that comes into contact with the piston or the piston ring, so that the hole portion forms a concave pit with respect to the sliding surface, and the lubricating oil is held in that portion. Thus, it is possible to prevent the oil film from being cut off at the sliding interface with the piston or the like, and to realize excellent seizure resistance and wear resistance. Further, in the AlN-dispersed powder aluminum alloy, AlN is produced and dispersed in the aluminum alloy as a layered film in the form of fibers or dendrites. As a result, the AlN particles have no gap at the contact interface with the aluminum alloy substrate, and can be firmly adhered by having a structure bonded to the aluminum substrate, so that the heat resistance, wear resistance and seizure resistance of the aluminum alloy can be achieved. Can be greatly improved. As a result, even when cast into an aluminum alloy engine block body by high-pressure casting, it can be sufficiently used as a cylinder liner.
[0013]
Next, the claim 2 In the invention described in claim 1, 1 The powder aluminum alloy cylinder liner described above, wherein the powder aluminum alloy cylinder liner is cast into the molten aluminum alloy engine block by an aluminum high pressure casting method.
[0016]
Next And claims 3 In the invention described in claim 1, 1 The powder aluminum alloy cylinder liner according to claim 1, wherein the powder aluminum alloy of the cylinder liner contains 0.1% or more and 5% or less of nitrogen on a weight basis, the balance is aluminum, and the nitrogen is the aluminum This is an AlN-dispersed powder aluminum alloy having a structure bonded to the.
[0017]
As a result, it is possible to produce an appropriate amount of AlN, and as a result, it is possible to obtain a powder aluminum alloy cylinder liner excellent in heat resistance, wear resistance, seizure resistance and machinability.
[0018]
Next, the claim 4 In the invention described in claim 1, 1 The powder aluminum alloy cylinder liner described above, wherein the cylinder liner powder aluminum alloy contains 0.5% to 15% by weight of aluminum nitride and 0.05% or more of Mg by weight. An AlN-dispersed powder aluminum alloy with the balance being aluminum.
[0019]
Next, the claim 5 In the described invention, the claims 1 The powder aluminum alloy cylinder liner described above, wherein the cylinder liner powder aluminum alloy contains 0.1% to 5% by weight of nitrogen and 0.05% or more of Mg by weight. The balance is aluminum, and the nitrogen is an AlN-dispersed powder aluminum alloy having a structure bonded to aluminum. This makes it possible to reliably generate and disperse AlN in the powder aluminum alloy, which is excellent. An AlN-dispersed powder aluminum alloy can be formed.
[0020]
Next, the claim 6 In the invention described in claim 1, 1 The powder aluminum alloy cylinder liner described above, wherein the powder aluminum alloy of the cylinder liner includes aluminum nitride having a structure that grows in one direction in a fiber shape, and the growth direction is a thickness described above. Aluminum nitride has a layered particle shape of 3 μm or less.
[0021]
Thus, when the thickness is 3 μm or less, it is possible to obtain excellent slidability as compared with conventionally used AlN particles without reducing the machinability.
[0022]
Next, the claim 7 In the invention described in claim 1, 1 The powder aluminum alloy cylinder liner described above, wherein the powder aluminum alloy of the cylinder liner includes aluminum nitride, and has a bonding interface with no gap at a boundary between the aluminum nitride and aluminum which is a matrix of the aluminum alloy substrate. ing.
[0024]
And claims 8 In the described invention, the claims 1 The powder aluminum alloy cylinder liner described above, wherein the porosity is 3% or more and 10% or less in terms of volume ratio with respect to the entire aluminum alloy.
[0025]
As a result, the holes are dispersed on the sliding surface of the cylinder liner that comes into contact with the piston or the piston ring, so that the hole portion forms a concave pit with respect to the sliding surface, and the lubricating oil is held in that portion. Thus, it is possible to prevent the oil film from being cut at the sliding interface with the piston or the like, and to realize excellent seizure resistance and wear resistance.
[0026]
Next, the claim 9 In the invention described in claim 1, 1 The powder aluminum alloy cylinder liner described above, wherein the powder aluminum alloy of the cylinder liner is graphite, MoS ₂ , WS ₂ And 5% or less of at least one lubricating component selected from the group consisting of CaF on a weight basis.
[0027]
Claims 10 In the invention described in claim 1, 9 The cylinder liner made of powdered aluminum alloy according to claim 1, wherein the content of the lubricating component is 1% or more and 3% or less on a weight basis.
[0028]
Thus, graphite, MoS ₂ , WS ₂ The solid lubricating powder such as CaF is dispersed on its own lubrication performance and the sliding surface of the cylinder liner to form a concave oil sump as in the above-described holes, so that the sliding interface with the piston etc. It is possible to prevent the oil film from being cut off and to realize excellent seizure resistance and wear resistance.
[0029]
Next, the claim 11 In the invention described in claim 1, 1 The powder aluminum alloy cylinder liner according to claim 1, wherein the powder aluminum alloy of the cylinder liner contains at least one element selected from the group consisting of Si, Fe, Ni, Cr, Ti, Mn, and Zr. And the content is 25 weight% or less.
[0030]
This makes it possible to improve mechanical properties such as wear resistance, seizure resistance, strength, hardness and rigidity of the powder aluminum alloy for cylinder liners.
[0031]
Next, the claim 12 In the invention described in claim 1, 1 The powder aluminum alloy cylinder liner according to claim 1, wherein the powder aluminum alloy for the cylinder liner is TiO 2. ₂ , ZrO ₂ , SiO ₂ , MgO ₂ , Al ₂ O _Three , Cr ₂ O _Three 5% by weight or less of at least one oxide spherical particle selected from the group consisting of:
[0032]
As a result, the hard particles are dispersed in the base material of the powder aluminum alloy for the cylinder liner, like aluminum nitride and Si, and it becomes possible to improve the wear resistance and the seizure resistance.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a powder aluminum alloy cylinder liner according to the present invention will be described in detail.
[0034]
(1) Relation between thermal expansion coefficient of cylinder liner and engine block and its effect
When an aluminum alloy cylinder liner is cast into an engine block body by aluminum low pressure casting, the outer periphery of the aluminum alloy cylinder liner is in contact with the molten aluminum for a long time at a high temperature exceeding 500 ° C. Therefore, the interface between the aluminum alloy cylinder liner and the engine block body is welded and joined. As a result, a good bonding interface is obtained between the two, and there is no problem of the aluminum liner cylinder liner falling off from the engine block.
[0035]
On the other hand, when such an aluminum alloy cylinder liner is cast into an aluminum alloy engine block body by aluminum high pressure casting, the casting is completed in a relatively short time. Therefore, the outer peripheral surface of the aluminum alloy cylinder liner is not welded to the engine block body, and as a result, a good bonding interface cannot be obtained between the two. As a result, the conventional cylinder liner has a problem of falling off the engine block.
[0036]
Here, the inventors of the present application can prevent the cylinder liner from falling out of the engine block without causing a gap at the contact interface between the aluminum alloy cylinder liner and the engine block due to the relationship between the thermal expansion coefficients. Invented technology.
[0037]
In other words, when cooling the engine block body to room temperature with the cylinder liner cast into the engine block by high-pressure aluminum casting, the thermal expansion coefficient of the cylinder liner aluminum alloy is the thermal expansion coefficient of the aluminum alloy of the engine block body. When the engine block is relatively small, the engine block contracts more than the cylinder liner, and compressive residual stress acts on the joint interface between the cylinder liner and the engine block.
[0038]
Due to this residual stress, the cylinder liner is restrained by the engine block. As a result, the problem that the cylinder liner falls out of the engine block body can be avoided without causing a gap at the contact interface between the two.
[0039]
On the other hand, the engine block expands more than the cylinder liner due to heat generated when the engine is operated, and tensile thermal stress acts on the contact interface between the two. As a result, the compressive residual stress may be reduced, causing a problem of cylinder liner falling off. Further, if the compressive residual stress from the engine block is excessively large, the thin cylinder liner may not have sufficient rigidity, so that the cylinder liner may be deformed and roundness may not be obtained.
[0040]
Therefore, the present inventors considered these problems, and as a result of optimizing the correlation of the coefficient of thermal expansion between the cylinder liner and the engine block body,
α _B -Α _C ≧ 1 × 10 ^-6 / ° C and α _B -Α _C ≦ 8 × 10 ^-6 / ℃
α _B : Thermal expansion coefficient of aluminum alloy for engine block
α _C : Thermal expansion coefficient of aluminum alloy for cylinder liner
It was found that the cylinder liner can be made thinner without problems such as deformation of the cylinder liner and falling off of the cylinder liner when the engine is running only when the above conditions are satisfied.
[0041]
In other words, α _B -Α _C <1 × 10 ^-6 In the case of / ° C, the compressive stress at the contact interface between the cylinder liner and the engine block is not sufficiently large, so that sufficient restraint force from the engine block cannot be obtained on the cylinder liner, so In this case, a gap is generated at the contact interface between them, and the cylinder liner falls off.
[0042]
Α _B -Α _C > 8 × 10 ^-6 / ° C, as mentioned above, because the residual stress of compression from the engine block increases, a sufficient restraining force against the cylinder liner can be obtained, but the cylinder liner with a small wall thickness (difference between outer diameter and inner diameter) has rigidity. Therefore, when an excessive compressive stress is applied, the cylinder liner is deformed in the radial direction and the roundness cannot be obtained. Accordingly, there arises a problem that thinning of the cylinder liner is hindered.
[0043]
However, as a specific value regarding the thermal expansion coefficient of the powder aluminum alloy used for the cylinder liner at this time, α _C Is 14 × 10 ^-6 / ° C. to 20 × 10 ^-6 / ° C is desirable.
[0044]
Generally, coefficient of thermal expansion α of molten aluminum alloy used for engine block _B Is 18 × 10 ^-6 / ° C. to 22 × 10 ^-6 Since the temperature is about / ° C., the correlation between the thermal expansion coefficients of the cylinder liner and the engine block described above (1 × 10 ^-6 / ℃ ≦ α _B -Α _C ≦ 8 × 10 ^-6 / ° C), the thermal expansion coefficient α of the cylinder liner _C Is 14 × 10 ^-6 / ° C. or higher is desirable.
[0045]
As will be described later, the total content of aluminum nitride and Si having a strong correlation with wear resistance, which is one of the important properties required for cylinder liners, is preferably 5% or more. The thermal expansion coefficient of the powdered aluminum alloy is 20 × 10 ^-6 / ° C or less. Therefore, the thermal expansion coefficient α of the powdered aluminum alloy for the cylinder liner in the case where the castability with the engine block and the wear resistance of the cylinder liner are compatible. _C Is 14 × 10 ^-6 / ° C. to 20 × 10 ^-6 / ° C is desirable.
[0046]
On the other hand, the inventors of the present application need to achieve both the appropriate range of the above-mentioned thermal expansion coefficient and excellent wear resistance for the total content of aluminum nitride and Si contained in the powdered aluminum alloy constituting the cylinder liner. I found a suitable range.
[0047]
Specifically, the total content of aluminum nitride and Si contained in the powder aluminum alloy is 5% or more and 30% or less, more preferably 7% or more and 20% or less, based on the weight of the entire powder aluminum alloy. is there.
[0048]
Here, when the total content of aluminum nitride and Si is less than 5%, it becomes difficult to have the wear resistance required as a cylinder liner. On the other hand, if the total content of both exceeds 30%, the coefficient of thermal expansion α of the cylinder liner _C 14 × 10 ^-6 It becomes smaller than / ° C., and the above-mentioned problems occur.
[0049]
In particular, the total content of both is desirably 20% or less from the viewpoint of machinability, and the total content is 7% or more from the viewpoint of sliding characteristics with the piston or piston ring of the counterpart material. It is more desirable. Therefore, in the present embodiment, the total content of aluminum nitride and Si in the powdered aluminum alloy is 5% or more and 30% or less.
[0050]
(2) Features of aluminum nitride in AlN-dispersed powder aluminum alloy and its functions and effects
Since the cylinder liner slides with a mating material such as a piston or piston ring, high temperature wear resistance, seizure resistance and mating attack are required. In the powder aluminum alloy used for the cylinder liner in the present embodiment, it is thermally stable even when the temperature exceeds 500 ° C. for the purpose of improving heat resistance, wear resistance, seizure resistance and opponent attack. It has been found that by producing and dispersing aluminum nitride (AlN) in an aluminum alloy, it has excellent heat resistance and frictional sliding characteristics as compared with conventional powder aluminum alloys.
[0051]
Moreover, in the present embodiment, as in the conventional powder metallurgy technique, AlN is not mixed with the aluminum alloy powder as particles (particles) and added and dispersed in the sintered aluminum alloy, but in the aluminum alloy powder. It is characterized in that AlN is produced and dispersed in an aluminum alloy by reacting the aluminum component with nitrogen gas.
[0052]
That is, according to the conventional method, the added AlN particles have a gap at the contact interface with the aluminum alloy substrate, and the AlN particles are mechanically constrained in the substrate, so that the heat resistance is improved. The effect is small, and when friction and sliding with a mating material such as a piston or piston ring, the AlN particles fall off and become hard wear powder, causing problems such as seizure phenomenon and galling phenomenon.
[0053]
On the other hand, according to the present embodiment, as described above, AlN is produced by reacting with aluminum in the aluminum alloy powder (hereinafter referred to as direct nitriding reaction). There is no gap in the contact interface, and it has a structure bonded to the aluminum substrate, so that it is firmly adhered. As a result, the heat resistance, wear resistance and seizure resistance of the aluminum alloy are greatly improved. Therefore, the powdered aluminum alloy in the present embodiment can be sufficiently used as a cylinder liner even when cast into an aluminum alloy engine block body by high pressure casting.
[0054]
As a specific manufacturing method of the cylinder liner in the present embodiment, first, an aluminum alloy powder is die-molded by a hydraulic press, a cold isostatic press or the like to produce a green compact. AlN by nitriding reaction is generated and dispersed in the old powder grain boundary of the aluminum alloy sintered body obtained by heating and sintering the green compact in a nitrogen gas atmosphere. It is also effective to improve the strength of the sintered body by applying a hot extrusion method or a hot forging method as necessary.
[0055]
In the powdered aluminum alloy in the present embodiment obtained by such a manufacturing method, the appropriate amount of AlN generation is 0.5% or more and 15% or less on a weight basis with respect to the entire powdered aluminum alloy, and wear resistance / machining From the viewpoint of property, it is more preferably 1% or more and 7% or less. When the amount of AlN produced and dispersed is less than 0.5% by weight, sufficient heat resistance and wear resistance cannot be obtained. On the other hand, even if the AlN production dispersion amount exceeds 15%, the wear resistance is not remarkably improved. On the other hand, economical efficiency such as lower machinability, lower toughness of the sintered body, or longer time of the sintering process. Problems arise.
[0056]
In order to generate the appropriate amount of AlN, the powder aluminum alloy contains 0.1% or more and 5% or less on a weight basis as the amount of nitrogen necessary to react with the aluminum component. In other words, the inventors of the present application confirmed that when the nitrogen content is less than 0.1%, 0.5% or more of AlN cannot be generated, and when the nitrogen content exceeds 5%, AlN exceeding 15% is generated.
[0057]
As described above, the powder aluminum alloy cylinder liner according to the present embodiment contains 0.5% or more and 15% or less AlN and 0.1% or more and 5% or less nitrogen based on the weight of the entire aluminum alloy. By doing so, it has excellent heat resistance, wear resistance, seizure resistance and machinability, and can be used as a cylinder liner in a state of being cast into an aluminum alloy engine block body by aluminum high pressure casting. .
[0058]
In order to cause the nitriding reaction to proceed directly as described above to generate and disperse AlN in the powdered aluminum alloy, it is preferable to contain 0.05% or more of Mg. Mg is previously contained in the aluminum alloy powder, and has the effect of removing the aluminum oxide film covering the powder surface by a reduction reaction when the aluminum compact is heated and sintered in a nitrogen gas atmosphere. . As a result, nitrogen gas and the aluminum component in the powder can react to generate AlN. Therefore, in the powder aluminum alloy of the present embodiment, the Mg content needs to be 0.05% by weight or more. That is, when the Mg content is less than 0.05% by weight, the above-described reduction reaction by Mg does not occur sufficiently, so that there is a problem that AlN cannot be generated uniformly.
[0059]
Furthermore, as described above, AlN produced in a powdered aluminum alloy using a direct nitridation reaction is significantly different in structure from the AlN particles added by the conventional method. Specifically, in the direct nitriding reaction, AlN grows in one direction from the surface of the aluminum alloy powder in the green compact in the form of fibers or dendrites. As a result, a layered film as shown in FIGS. 1 and 2 is generated and dispersed in the aluminum alloy.
[0060]
On the other hand, in the conventional AlN particle dispersion type sintered aluminum alloy, as shown in FIG. 3, AlN particles having a single crystal are dispersed. That is, the AlN in the sintered aluminum alloy by the nitriding reaction method in the present embodiment is superior to the AlN particles used in the conventional method by having a fibrous structure as shown in FIGS. The inventors of the present application have found that they have excellent slidability.
[0061]
Moreover, when the direction of fiber growth is the thickness direction of AlN, the thickness of AlN produced by the nitriding reaction is desirably 3 μm or less, and more preferably 1 μm or less. This is because the thickness of AlN is substantially proportional to the amount of AlN produced. For example, when the amount of AlN produced is 15% by weight, the thickness of AlN is about 3 μm. The thickness of AlN produced by the reaction method is 3 μm or less. That is, when the thickness exceeds 3 μm, it means that the amount of AlN produced exceeds 15% by weight. In this case, problems such as deterioration of machinability and toughness of the sintered body occur as described above. . In particular, from the viewpoint of machinability, the thickness of AlN is more preferably 1 μm or less.
[0062]
(3) Porosity in powder aluminum alloy and its action / effect
Holes are dispersed on the sliding surface of the cylinder liner that comes into contact with the piston and piston ring, so that the hole part forms a concave pit with respect to the sliding surface, and lubricating oil is held in this part and It is possible to prevent the oil film from being cut off at the sliding interface, and to achieve excellent seizure resistance and wear resistance.
[0063]
In order to obtain such an effect, the porosity in the powdered aluminum alloy in the present embodiment is 15% or less, preferably 3% or more and 10% or less in terms of the volume ratio with respect to the entire aluminum alloy. Is preferred. When the porosity exceeds 15%, the mechanical properties of the powdered aluminum alloy deteriorate. For example, sufficient strength and rigidity as a cylinder liner cannot be obtained, and as a result, there is a problem that the cylinder liner is deformed when cast into an engine block. Therefore, in order to achieve both excellent seizure resistance, wear resistance and mechanical properties, the porosity in the powdered aluminum alloy needs to be 15% or less, and a more preferable range is 3% or more. It was found to be 10% or less.
[0064]
(4) Solid lubricating components and their functions and effects
Graphite, MoS ₂ , WS ₂ The solid lubricating powder such as CaF is dispersed on the sliding surface of its own lubricating performance and cylinder liner to form a concave oil sump at the sliding interface with the piston or the like in the same manner as the above holes. It is possible to prevent the oil film from being cut and to realize excellent seizure resistance and wear resistance. The powder aluminum alloy of the cylinder liner in the present embodiment is graphite, MoS. ₂ , WS ₂ Further, at least one or two or more kinds of lubricating components selected from CaF are contained in an amount of 5% or less, preferably 1% or more and 3% or less based on weight.
[0065]
If the content of the lubricating component exceeds 5% by weight, the bonding strength between the aluminum alloy powders constituting the aluminum alloy substrate is reduced, so that the mechanical properties required as a cylinder liner cannot be obtained sufficiently and the cylinder liner is produced. In the hot extrusion method, which is one of the above, the bonding between the aluminum alloy powders is not sufficient, so that the liner surface after extrusion is in a wrinkled state (peeled state), which causes a problem in manufacturing.
[0066]
Therefore, in order to suppress deterioration of the mechanical properties of the cylinder liner and to obtain excellent wear resistance and seizure resistance, graphite, MoS ₂ , WS ₂ In addition, at least one or two or more lubricating components selected from CaF must be contained in an amount of 5% or less, preferably 1% or more and 3% or less based on weight.
[0067]
(5) Composition and action / effect of powder aluminum alloy
In the powdered aluminum alloy in the present embodiment, each of the following effects can be obtained by containing at least one element of Si, Fe, Ni, Cr, Ti, Zr and Mn as required. Can be realized. However, in order to improve mechanical properties such as wear resistance, seizure resistance, strength, hardness, rigidity, etc. of the powdered aluminum alloy, at least one or more of the above elements are contained, and the total The content is desirably 25% or less. This is because, even if the total content of each additive element exceeds 25%, each characteristic does not remarkably improve, and the toughness of the powdered aluminum alloy decreases, and the hardness and rigidity of the aluminum alloy become too large. For this reason, there arises a problem in the manufacturing method such that hot extrusion, which is a subsequent process, becomes difficult.
[0068]
In the present embodiment, when each of the above elements is added to an aluminum alloy, an aluminum alloy powder is produced from a molten metal having a predetermined alloy composition by a rapid solidification method, and this is used as a raw material powder. That is, it is possible to produce a sintered aluminum alloy having a predetermined composition by forming a molten aluminum alloy composed of a predetermined alloy component into a powder by a spraying method (atomizing method), and molding and solidifying this aluminum alloy powder. Here, the characteristics of each element will be briefly described below.
[0069]
(I) Si
It is effective in improving the wear resistance and seizure resistance of the alloy by being dispersed in the aluminum alloy substrate. However, even if added over 25%, the characteristics are not further improved, but the toughness of the aluminum alloy is reduced, and the extruded body is created by hot extrusion due to the increased rigidity of the aluminum alloy. In particular, a high extrusion force, that is, a large-scale extrusion equipment is required, resulting in an economical problem.
[0070]
(II) Fe, Ni, Cr, Ti, Zr
These metal elements have the effect of improving the heat resistance, rigidity and hardness of the aluminum alloy by forming a fine intermetallic compound with aluminum and dispersing it in the substrate. In other words, the addition of these elements is effective since the seizure with the counterpart material during sliding is greatly suppressed by improving the heat resistance.
[0071]
Moreover, the growth of Si crystal during heating and sintering can be suppressed by finely and uniformly dispersing such a thermally stable intermetallic compound. As a result, there is an effect that the machinability of the aluminum alloy is greatly improved.
[0072]
In addition, in order to acquire such an effect, addition of Fe, Ni, Cr, Ti, and Zr is effective, and it is necessary to contain 1% or more at that time. On the other hand, when appropriate amounts of these elements are added and added, the intermetallic compound with aluminum as described above becomes coarse, which causes problems such as lowering the toughness and strength of the aluminum alloy, and producing aluminum alloy powder. In doing so, the melting point of the molten aluminum alloy rises, leading to an increase in manufacturing cost. As a result, there arises an economic problem that the price of the aluminum alloy powder is increased. Therefore, in the present embodiment, the appropriate addition amount of each element is Fe: 1-8%, Ni: 1-8%, Cr: 1-6%, Ti: 1-4%, Zr: 1-4 %It was set.
[0073]
(III) Mn
As with the above metal elements, an intermetallic compound with aluminum is formed and dispersed uniformly in the alloy substrate, thereby improving the mechanical properties of the alloy and the seizure resistance with the counterpart during sliding. There is. In order to realize these effects, it is necessary to contain 1% or more, but even if added over 5%, the characteristics are not improved, but rather the toughness of the aluminum alloy is lowered.
[0074]
(6) Hard particles
The powder aluminum alloy for the cylinder liner in the present embodiment is made of TiO as required. ₂ , ZrO ₂ , SiO ₂ , MgO ₂ , Al ₂ O _Three , Cr ₂ O _Three 5% by weight or less of at least one oxide spherical particle selected from
[0075]
The hard particles are dispersed in the powdered aluminum alloy substrate like aluminum nitride and Si, and have the effect of improving wear resistance and seizure resistance. However, the amount of hard particles added is desirably 5% or less based on the weight of the entire aluminum alloy. This is because even if hard particles are added in excess of 5%, the wear resistance and seizure resistance are not significantly improved. This is because a problem occurs.
[0076]
In addition, as a kind of hard particle, TiO ₂ , ZrO ₂ , SiO ₂ , MgO ₂ , Al ₂ O _Three , Cr ₂ O _Three Oxide particles such as are preferred. Above all, from the viewpoint of wear resistance and machinability of aluminum alloys, TiO ₂ , SiO ₂ , MgO ₂ , Al ₂ O _Three The present inventors have found that the addition of spherical oxide particles is more effective.
[0077]
【Example】
Examples of the embodiment based on the present invention will be described below with reference to the tables.
[0078]
Example 1
[0079]
[Table 1]

In Table 1, “good with no gap” means that the cylinder liner does not fall out of the engine block even when the engine is operating. In addition, “with a gap” means that the cylinder liner falls out of the engine block when casting is completed, or a gap is generated at the interface between the cylinder liner and the engine block at a high temperature during engine operation. It means that the cylinder liner falls out.
[0080]
Thermal expansion coefficient α as shown in Table 1 above _C After casting an aluminum alloy cylinder liner having an inner diameter into an engine block body by an aluminum high pressure casting method, the contact state of the contact surface between the cylinder liner and the engine block and the presence or absence of deformation in the diameter direction of the cylinder liner were confirmed.
[0081]
The cylinder liner was subjected to a casting experiment without being subjected to groove processing for preventing falling off. Here, the alloy composition of the engine block body made of aluminum alloy manufactured by the aluminum high pressure casting method is Al-17% Si-3Cu-1Mg (wt%), and its thermal expansion coefficient α _B Is 19.5 × 10 ^-6 / ° C. However, the value of the coefficient of thermal expansion described here is an average value from room temperature to 200 ° C.
[0082]
As shown in Table 1, α defined by the present invention _B -Α _C ≧ 1 × 10 ^-6 / ° C and α _B -Α _C ≦ 8 × 10 ^-6 No. of combination of cylinder liner and engine block satisfying the relational expression of thermal expansion coefficient such as / ° C. 1-No. In No. 5, the outer peripheral surface of the cylinder liner after casting is firmly restrained by the engine block body due to the compressive residual stress from the engine block, and no gap is generated at the contact interface between the cylinder liner and the engine block body. .
[0083]
As a result, it can be seen that the problem of the cylinder liner falling off from the engine block body does not occur even if the cylinder liner is not subjected to the fall prevention process.
[0084]
Further, since the restraining force from the engine block is an appropriate condition, the cylinder liner itself after casting is not deformed and has a roundness that can be sufficiently used as a cylinder liner. Therefore, it can be confirmed that the cylinder liner is thinned.
[0085]
On the other hand, No. which does not satisfy the above relational expression regarding the coefficient of thermal expansion between the cylinder liner and the engine block defined by the present invention. 6-No. In No. 8, it is confirmed that the following problems occur.
[0086]
No. 6: Since the coefficient of thermal expansion of the cylinder liner is too small, the restraining force due to the compressive stress from the engine block acts excessively, so that the cylinder liner is deformed.
[0087]
No. 7: Since the thermal expansion coefficient of the cylinder liner is too large, the restraining force due to the compressive stress from the engine block does not act sufficiently, so the cylinder liner is not held by the engine block, and a gap is generated and falls off.
[0088]
No. 8: Since the thermal expansion coefficient of the cylinder liner is too large, the restraining force due to the compressive stress from the engine block does not sufficiently act, so the cylinder liner is not held by the engine block, and a gap is generated and falls off.
[0089]
(Example 2)
[0090]
[Table 2]

In Table 2, “good with no gap” means that the cylinder liner does not fall out of the engine block even when the engine is operating. In addition, “with a gap” means that the cylinder liner falls out of the engine block when casting is completed, or a gap is generated at the interface between the cylinder liner and the engine block at a high temperature during engine operation. It means that the cylinder liner falls out.
[0091]
No. as shown in Table 2. 1-No. Thermal expansion coefficient α shown in FIG. _C After casting an aluminum alloy cylinder liner having an inner diameter into an engine block body by an aluminum high-pressure casting method, the connection state of the contact interface between the cylinder liner and the engine block and the presence or absence of deformation in the diameter direction of the cylinder liner were confirmed.
[0092]
The cylinder liner was subjected to a casting experiment without groove processing or the like for preventing falling off. The alloy composition of the aluminum alloy engine block body produced by the aluminum high pressure casting method is Al-11% Si-3Cu-0.5Mg (% by weight), and its coefficient of thermal expansion α _B Is 21 × 10 ^-6 / ° C. However, the value of the coefficient of thermal expansion described here is an average value from room temperature to 200 ° C.
[0093]
As shown in Table 2, α defined by the present invention _B -Α _C ≧ 1 × 10 ^-6 / ° C and α _B -Α _C ≦ 8 × 10 ^-6 The combination of the cylinder liner and the engine block that satisfies the relational expression of the coefficient of thermal expansion such as / ° C is No. 1-No. 6. The outer peripheral surface of the cylinder liner after casting is firmly restrained by the engine block main body due to compressive residual stress from the engine block, and no gap is generated at the contact interface between the cylinder liner and the engine block main body.
[0094]
As a result, it can be seen that the problem of the cylinder liner falling off from the engine block body does not occur even if the cylinder liner is not subjected to the fall prevention process. Further, since the restraining force from the engine block is an appropriate condition, the cylinder liner itself after casting is not deformed and has a roundness that can be sufficiently used as a cylinder liner. Therefore, it was confirmed that the thinning of the cylinder liner can be realized.
[0095]
On the other hand, No. which does not satisfy the above relational expression regarding the coefficient of thermal expansion between the cylinder liner and the engine block defined by the present invention. 6 and no. In the case of 7, it was confirmed that the following problems occur.
[0096]
No. 6: Since the coefficient of thermal expansion of the cylinder liner is too small, the restraining force due to the compressive stress from the engine block acts and the cylinder liner is deformed.
[0097]
No. 7: Since the thermal expansion coefficient of the cylinder liner is too large, the restraining force due to the compressive stress from the engine block does not sufficiently act, so the cylinder liner is not held by the engine block, and a gap is generated and falls off.
[0098]
(Example 3)
[0099]
[Table 3]

No. shown in Table 3 above. 1-No. 18 aluminum alloy powder was mixed with oxide spherical particles (average particle size 5 to 10 μm) and solid lubricant particles (average particle size 5 to 15 μm) as necessary as raw material powder, and after molding this, Aluminum nitride (AlN) was produced in the aluminum alloy sintered body by heating and sintering in a nitrogen atmosphere, and a cylinder liner was produced by hot extrusion of the sintered body. Here, the content of each spherical oxide particle, solid lubricant particle, and AlN and nitrogen indicates a ratio with respect to the entire sintered aluminum alloy in weight%. Moreover, the porosity of the cylinder liner was adjusted to 3 to 5% depending on the extrusion conditions.
[0100]
A sample for a wear test was prepared from a cylinder liner material, and a molten aluminum alloy (JISAC8A material) was used as a counterpart material to evaluate the wear resistance of each sintered aluminum alloy under boundary lubrication conditions. Also, the seizure resistance under the condition of running out of the oil film (comparing the load when the seizure phenomenon occurs by increasing the pressing load) was evaluated. Each characteristic was evaluated using a chip-on-disk wear test.
[0101]
Furthermore, the comparative material No. A cylinder liner using a molten aluminum alloy (JIS AC8A material) as 19 was produced, and the sliding surface of the sample was plated with hard Cr. Furthermore, the comparative material No. A cast iron material was used as 20. Table 4 shows the evaluation results of the wear amount and seizure load of the liner material and the mating material after the wear test.
[0102]
[Table 4]

In the sintered aluminum alloy for cylinder liners in this example, as can be seen from Table 4, aluminum is excellent in wear resistance and less aggressive to the counterpart material, and has been subjected to current cast iron material or hard Cr plating treatment. It turns out that it is equivalent to an alloy. Further, the seizure resistance is equivalent to that of the cast iron material, and it is understood that the seizure resistance is superior to that of the hard Cr plating material from which the plating film is peeled off.
[0103]
On the other hand, comparative material No. 13-No. Regarding 18, the following problems were confirmed.
[0104]
No. 13: Since AlN is not contained, sufficient wear resistance and opponent attack cannot be obtained.
[0105]
No. 14: Since the AlN content is small, sufficient wear resistance and opponent attack cannot be obtained.
[0106]
No. 15: Since the AlN content was as high as 18%, the strength of the aluminum alloy was reduced, and the sample was lost during pressurization.
[0107]
No. 16: Since the content of lubricating particles was as high as 6%, the strength of the aluminum alloy was reduced, and the sample was lost during pressurization. In addition, the cylinder liner surface was peeled off during hot extrusion.
[0108]
No. 17: Since the content of hard particles is as large as 6%, the counterpart material is attacked and seizure resistance is lowered.
[0109]
No. 18: Since the content of the hard particles is as high as 7%, the counterpart material is attacked and the seizure resistance is lowered.
[0110]
In addition, No. In No. 15, the content of AlN is no. In Nos. 17 and 18, since the hard particle content is larger than the appropriate amount specified by the present invention, the wear of the cemented carbide tool is more remarkable than the other when processing into a friction test piece.
[0111]
Example 4
In Example 3 above, after processing the cylinder liner material into a predetermined cylindrical shape, the cylinder liner material was cast into an aluminum alloy engine block by an aluminum high pressure casting method, and a single durability test was performed on each cylinder liner.
[0112]
In addition, comparative material No. No. 19 produced a cylinder liner using a molten aluminum alloy (JIS AC8A material), and hard Cr plating was applied to the sliding surface for the purpose of improving wear resistance and seizure resistance. Comparative material No. In No. 20, a cylinder liner having the same shape was produced using an Fc cast iron material and cast into an engine block. Also, a molten aluminum alloy (JIS AC8A material) is used as the piston material, and comparative material No. In the case of 19 only, in addition to a molten aluminum alloy (JIS AC8A material) as a piston material, an outer peripheral surface sliding with a cylinder liner was also provided with Fe plating.
[0113]
After the endurance test, the cylinder liner and the sliding surface of the piston were observed for damage, and the presence or absence of wear or adhesion (burn-in) was confirmed. The results are shown in Table 5.
[0114]
[Table 5]

As can be seen from Table 5 above, the sintered aluminum alloy for the cylinder liner in this example is excellent in wear resistance of the cylinder liner itself, and wear and adhesion occur even if the piston is not plated with Fe. Without attacking the counterpart material, it is equivalent to the current cast iron material.
[0115]
On the other hand, comparative material No. 13-No. The following 19 problems were confirmed.
[0116]
No. 13: Since AlN is not contained, sufficient wear resistance and opponent attack cannot be obtained.
[0117]
No. 14: Since the AlN content is small, sufficient wear resistance and opponent attack cannot be obtained.
[0118]
No. 15: Since the AlN content was as high as 18%, the amount of attack on the piston side increased.
[0119]
No. 16: Since the content of the lubricating particles was as high as 6%, the strength of the aluminum alloy was lowered and the wear resistance was slightly lowered.
[0120]
No. 17: Since the content of hard particles was as high as 6%, the amount of attack on the piston side increased.
[0121]
No. 18: Since the content of hard particles was as high as 7%, the amount of attack on the piston side increased.
[0122]
No. 19: If a molten aluminum alloy is subjected to hard Cr plating on the sliding surface and also not subjected to Fe plating on the piston side, problems such as wear and adhesion occur and it cannot be used as a liner.
[0123]
In addition, No. In No. 15, the content of AlN is no. In Nos. 17 and 18, since the hard particle content is larger than the appropriate amount specified by the present invention, the wear of the cemented carbide tool is more remarkable than the other when processing into a cylinder liner shape.
[0124]
As described above, the sintered aluminum alloy in the present example has sufficient wear resistance and seizure resistance as a cylinder liner without performing surface treatment such as hard Cr plating, and the other piston side Moreover, it is excellent also in the economical aspect that it can be used without performing Fe plating treatment.
[0125]
(Example 5)
TiO for aluminum alloy powder containing Si; 12%, Fe; 3%, Ni; 3%, Mg; 1% by weight ₂ After molding a mixed powder to which 1.5% of particles (average particle size: 7 μm) and 1% of graphite powder (average particle size: 10 μm) were added, the mixture was heated and held in a nitrogen atmosphere controlled at 540 ° C. for 3 hours. Thus, a sintered aluminum alloy was produced, and a sintered body in which 4% of AlN was generated with respect to the entire sintered aluminum alloy by a nitriding reaction was obtained. A cylindrical cylinder liner was produced from this material by hot extrusion.
[0126]
At this time, by controlling the extrusion conditions (extrusion ratio), the porosity of the cylinder liner material after extrusion was changed to evaluate the wear resistance and seizure resistance of each aluminum alloy. The results are shown in Table 6.
[0127]
[Table 6]

For wear resistance, the performance under boundary lubrication conditions was evaluated by the chip-on-disk wear test described in Example 3 above. Further, a molten aluminum alloy (JIS AC8A material) was used on the disk side which is the counterpart material.
[0128]
Furthermore, each cylinder liner was cast into the engine block body by high-pressure aluminum casting, and the presence or absence of deformation of the cylinder liner was confirmed. In addition, a cylinder liner using FC cast iron as a comparative material was also evaluated.
[0129]
As can be seen from Table 6, in the cylinder liner using the sintered aluminum alloy having the porosity defined in the present invention, wear resistance and seizure resistance equivalent to the FC cast iron material which is the current cylinder liner material. have.
[0130]
In particular, it can be seen that the properties of sintered aluminum alloys having a porosity of 3% to 10% are even better. In addition, even when cast into the engine block, it is understood that the roundness of the cylinder liner shape is ensured without being deformed by the restraining force from the engine block main body side. On the other hand, the following problems were confirmed in the comparative material.
[0131]
No. 6: Since the porosity was as high as 18%, the cylinder liner was deformed by the compressive stress acting on the cylinder liner side when cast into the engine block.
[0132]
No. 7: Since the porosity was as large as 22%, the strength of the sintered aluminum alloy was lowered, and the sample was lost in the friction test. Also, when cast into the engine block, the cylinder liner was deformed by the compressive stress acting on the cylinder liner side.
[0133]
(Example 6)
Structure of AlN particles formed and dispersed in a sintered aluminum alloy after hot extrusion (alloy composition: Al-12Si-2Ni-1Mg-2AlN / wt%) produced by the nitriding reaction method proposed in the embodiment A TEM image (taken at 18,000 times) is shown in FIG. 1, and a SIM image is shown in FIG.
[0134]
For comparison, a sintered aluminum alloy having the same composition is added to a conventional manufacturing method, that is, AlN particles (average particle size 22 μm) are added to and mixed with aluminum alloy powder (composition: Al-12Si-2Ni-1Mg / wt%). FIG. 3 shows a SIM image of AlN particles produced by molding, sintering, and hot extrusion and dispersed in the aluminum alloy.
[0135]
As shown in FIGS. 1 and 2, it can be seen that AlN produced by the direct nitridation method proposed in the present embodiment has a tissue structure that grows in one direction in the form of fibers or dendrites. If the growth direction is the thickness of AlN, as can be seen from the figure, the thickness of AlN produced by the nitriding reaction method is about 1 μm.
[0136]
On the other hand, as shown in FIG. 3, when adding AlN particles according to the conventional manufacturing method, AlN has a single crystal structure, not a fibrous structure, and apparently AlN particles produced by the nitriding reaction method of the present invention I can see that they are different.
[0137]
(Example 7)
FIG. 4 shows an optical micrograph of the sintered aluminum alloy after hot extrusion produced by the nitriding reaction method proposed by this embodiment. The alloy composition is Al-12Si-2Ni-1Mg-2AlN / wt%). For comparison, a sintered aluminum alloy having the same composition as that of the present invention by adding AlN particles (average particle size 22 μm) to an aluminum alloy powder (composition: Al-12Si-2Ni-1Mg / wt%) is hot-extruded. It was produced by the method. A structural photograph of the sintered body is shown in FIG.
[0138]
As shown in FIG. 4, it can be seen that AlN particles (parts indicated by black arrows) produced by the nitriding reaction method of the present invention have a bonded interface with no gap at the boundary with the aluminum alloy substrate of the matrix. On the other hand, in the conventional method shown in FIG. 5 (method of adding AlN particles), a gap (a portion indicated by a white arrow marked Gap) is formed at the boundary between the AlN particles (a portion indicated by a black arrow) and the aluminum alloy substrate. ) Exists.
[0139]
(Example 8)
About the sintered aluminum alloy produced in Example 6 above, the damage state of the sliding surface of the sintered body and the counterpart material after the chip-on-disk friction test was performed under boundary lubrication conditions was observed with an optical microscope. The results are shown in FIGS. 6 (a) and 6 (b) and FIGS. 7 (a) and 7 (b). FIGS. 6A and 6B are sintered aluminum alloys in which AlN produced by the nitriding reaction method proposed by the present invention is generated and dispersed. FIGS. 7A and 7B are AlNs which are conventional methods. It is a sintered aluminum alloy obtained by adding particles. A melted aluminum alloy (ADC12 material) was used as the counterpart material.
[0140]
As shown in FIG. 6 (a), no adhesion or seizure phenomenon is observed on the sliding surface of the sintered aluminum alloy produced by the nitriding reaction method proposed by the present invention to the extent that a slight rubbing trace is observed. . Also, no evidence of AlN particles dropping off is observed on the sliding surface. Further, as shown in FIG. 6 (b), the mating material does not show any adhesion / burn-in phenomenon, and there is a slight rubbing trace.
[0141]
On the other hand, in FIG. 7 (a), holes from which AlN particles have dropped (white arrow portions indicated as Hall) exist in various places in the sintered aluminum alloy, and deep sliding flaws are also observed. In addition, as shown in FIG. 7 (b), the counterpart material also shows that deep sliding flaws and adhesion regions (white portions indicated as Seizure) attacked by the dropped AlN particles exist in various places. .
[0142]
As described above, in the sintered aluminum alloy produced by the nitriding reaction method proposed by the present invention, the aluminum nitride (AlN) and the matrix aluminum alloy have a tightly bonded interface with no gap, so that the frictional sliding with the counterpart material is eliminated. Even when moved, the AlN particles did not fall off, and it was confirmed that they had excellent wear resistance, seizure resistance and opponent attack.
[0143]
Example 9
[0144]
[Table 7]

No. in Table 7 above. 1-No. After forming an aluminum alloy powder having the alloy composition shown in No. 11, aluminum nitride (AlN) is produced in the aluminum alloy sintered body by heating and sintering in a nitrogen atmosphere. A cylinder liner was manufactured by an extrusion method. The porosity was adjusted to 3 to 5% depending on the extrusion conditions.
[0145]
The contents of aluminum nitride and nitrogen are shown in Table 7 above, expressed as a percentage by weight with respect to the entire sintered aluminum alloy. The remainder is all Al. The thermal expansion coefficient is also shown in Table 7 above.
[0146]
A sample for a wear test was prepared from a cylinder liner material, and a molten aluminum alloy (JISAC8A material) was used as a counterpart material to evaluate the wear resistance of each sintered aluminum alloy under boundary lubrication conditions. In addition, the seizure resistance under the condition of running out of the oil film (comparing the load when the seizure phenomenon occurs by increasing the extrusion load) was evaluated. Each characteristic was evaluated using a chip-on-disk wear test. Table 8 shows the evaluation results of the wear amount and seizure load of the cylinder liner material and the counterpart material after the wear test.
[0147]
[Table 8]

In addition, the coefficient of thermal expansion is α _B Is 22 × 10 ^-6 Each cylinder liner was cast into an engine block body using molten aluminum alloy (composition: Al-8Si-3Cu-0.5Mg / wt%) at / ° C., and the presence or absence of deformation of the joint interface and the cylinder liner was confirmed. The results are shown in Table 8 above.
[0148]
As shown in Tables 7 and 8, No. 1 in which the total content of aluminum nitride and Si in the powdered aluminum alloy satisfies the appropriate range defined by the present invention. 1-No. 9, the coefficient of thermal expansion α _C Is 14 × 10 ^-6 / ° C. to 20 × 10 ^-6 It can be seen that / ° C. is satisfied and that the wear resistance is excellent. In addition, the interface between the cast cylinder liner and the engine block main body was in good contact with each other, and no deformation of the cylinder liner was observed.
[0149]
On the other hand, Comparative Example No. In 10 and 11, the following problems were confirmed. No. 10: Since the total content of AlN and Si is as low as 2%, sufficient wear resistance cannot be obtained, and since the total content of both is small, the coefficient of thermal expansion is 21.6 × 10 ^-6 It showed a large value of / ° C. The difference in coefficient of thermal expansion between the cylinder liner and engine block is 0.4 × 10 ^-6 Since it was as small as / ° C, a gap was observed at the interface between the cylinder liner and the engine block.
[0150]
No. 11: Since the total content of AlN and Si is as high as 36%, the coefficient of thermal expansion is 13.0 × 10 ^-6 Shows a small value of / ° C, and the difference in coefficient of thermal expansion between the engine block and cylinder liner is 9 x 10 ^-6 The cylinder liner was deformed after casting because it was as large as / ° C. Moreover, since the total content of AlN and Si was as high as 36%, it was also observed that the opponent material was attacked slightly.
[0151]
【The invention's effect】
Claims 1 to Claims based on this invention 12 According to the invention described in (1), no gap is formed at the contact interface between the two due to the relationship between the thermal expansion coefficients of the cylinder liner and the engine block. As a result, it is possible to prevent the cylinder liner from falling off the engine block.
[Brief description of the drawings]
FIG. 1 is a TEM photograph of the structure of AlN particles produced and dispersed in a sintered aluminum alloy after hot extrusion.
FIG. 2 is a SIM photograph of the structure of AlN particles produced and dispersed in a sintered aluminum alloy after hot extrusion.
FIG. 3 is a SIM photograph of the structure of AlN particles in a conventional manufacturing method.
FIG. 4 is a photomicrograph of an AlN dispersion sintered aluminum alloy by nitriding reaction.
FIG. 5 is a micrograph of an AlN particle-added sintered aluminum alloy.
FIGS. 6A and 6B are photomicrographs of an AlN dispersion sintered aluminum alloy by nitriding reaction based on the present invention.
FIGS. 7A and 7B are photomicrographs of a conventional AlN particle-added sintered aluminum alloy.

Claims (12)

A powder aluminum alloy cylinder liner cast into a molten aluminum alloy engine block,
The cylinder Zehnder liner is obtained by a cylindrical shape with hot extrusion method, the powder aluminum alloy has a porosity of 15% or more and 1% or less by volume ratio for the entire aluminum alloy, aluminum nitride 0.5% or more and 15% or less on a weight basis, the balance being an aluminum AlN-dispersed powder aluminum alloy,
The AlN-dispersed powder aluminum alloy is produced and dispersed in the aluminum alloy as a layered film of AlN in the form of fibers or dendrites,
When the thermal expansion coefficient of the powder aluminum alloy cylinder liner is α _C and the thermal expansion coefficient of the molten aluminum alloy engine block is α _B , the relationship between them is 14 × 10 ⁻⁶ / ° C. ≦ α _C ≦ 20. a × 10 ^-6 / ℃, and, 1 × satisfies _{^{10 -6 / ℃ ≦ α B -α}} C ≦ 8 × 10 -6 / ℃, powdered aluminum alloy cylinder liner according to claim 1. The powder aluminum alloy cylinder liner according to claim 1, wherein the powder aluminum alloy cylinder liner is cast into the molten aluminum alloy engine block by an aluminum high pressure casting method. The powder aluminum alloy of the cylinder liner contains 0.1% to 5% by weight of nitrogen, the balance is aluminum, and the nitrogen has a structure in which the nitrogen is combined with the aluminum. The powder aluminum alloy cylinder liner according to claim 1, wherein The cylinder liner powder aluminum alloy is an AlN-dispersed powder aluminum alloy containing 0.5 to 15% by weight of aluminum nitride, 0.05% or more of Mg by weight, and the balance being aluminum. The powder aluminum alloy cylinder liner according to claim 1 . The powder liner alloy of the cylinder liner contains 0.1% to 5% by weight of nitrogen, contains 0.05% or more of Mg by weight, and the balance is aluminum, and the nitrogen is The cylinder liner made of powder aluminum alloy according to claim 1, which is an AlN dispersion type powder aluminum alloy having a structure bonded to the aluminum. The powder aluminum alloy of the cylinder liner includes aluminum nitride having a structure grown in one direction in a fiber shape, and the aluminum nitride has a layered particle shape of 3 μm or less when the growth direction is defined as a thickness. The cylinder liner made of powdered aluminum alloy according to claim 1 . Powder aluminum alloy of the cylinder liner includes aluminum nitride, has a bonding interface is no gap at the boundary between the aluminum as the matrix aluminum this nitride and aluminum alloy base, powder aluminum alloy cylinder liner according to claim 1 . 2. The powder aluminum alloy cylinder liner according to claim 1, wherein the porosity is 3% or more and 10% or less in volume ratio with respect to the entire aluminum alloy. Powder aluminum alloy of the cylinder liner, graphite, MoS _2, WS _2, at least one or more kinds of lubricating components selected from the group consisting of CaF containing less than 5% by weight, the powder of aluminum according to claim 1 Alloy cylinder liner. The powder aluminum alloy cylinder liner according to claim 9, wherein the content of the lubricating component is 1% or more and 3% or less on a weight basis. The powder aluminum alloy of the cylinder liner contains at least one element selected from the group consisting of Si, Fe, Ni, Cr, Ti, Mn, and Zr, and the content thereof is 25% by weight or less. The powder aluminum alloy cylinder liner according to claim 1 . The powder aluminum alloy of the cylinder liner is 5% by weight of at least one oxide spherical particle selected from the group consisting of TiO ₂ , ZrO ₂ , SiO ₂ , MgO ₂ , Al ₂ O ₃ , and Cr ₂ O _3. The powder aluminum alloy cylinder liner according to claim 1, which is contained below.

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