JP2005061219A - Valve for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve for an engine, which is reduced in weight using aluminum alloy demonstrating extremely excellent low frictional property and wear resistance, and exerting fuel saving effect more excellent than a conventional steel material. <P>SOLUTION: The valve for the engine is mainly composed of the alloy which slides under the existence of lubricant, has a hard carbon membrane at the surface, and uses aluminum as a main element. The hard carbon membrane has a hydrogen atom of 30 atom % or less in the content. The lubricant used is desirable to contain one or both of a fatty acid ashless friction adjuster and an aliphatic amine ashless friction adjuster. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００３３】
【化２】

【００３４】
で表される化合物が挙げられる。これら一般式におけるＰＩＢは、ポリブテニル基を示し、高純度イソブテン又は１−ブテンとイソブテンの混合物をフッ化ホウ素系触媒又は塩化アルミニウム系触媒で重合させて得られる数平均分子量が９００〜３５００、望ましくは１０００〜２０００のポリブテンから得られる。上記数平均分子量が９００未満の場合は清浄性効果が劣り易く、３５００を超える場合は低温流動性に劣り易いため、望ましくない。
また、上記一般式におけるｎは、清浄性に優れる点から１〜５の整数、より望ましくは２〜４の整数であることがよい。更に、上記ポリブテンは、製造過程の触媒に起因して残留する微量のフッ素分や塩素分を、吸着法や十分な水洗等の適切な方法により、５０ｐｐｍ以下、より望ましくは１０ｐｐｍ以下、特に望ましくは１ｐｐｍ以下まで除去してから用いることもよい。
【００３５】
かかるポリブテニルコハク酸イミドの製造方法としては、特に限定はないが、例えば、上記ポリブテンの塩素化物又は塩素やフッ素が充分除去されたポリブテンと無水マレイン酸とを１００〜２００℃で反応させて得られるポリブテニルコハク酸を、ジエチレントリアミン、トリエチレンテトラミン、テトラエチレンペンタミン及びペンタエチレンヘキサミン等のポリアミンと反応させることにより得ることができる。
【００３６】
一方、上述したポリブテニルコハク酸イミドの誘導体としては、上記一般式（１）又は（２）で表される化合物に、ホウ素化合物や含酸素有機化合物を作用させて、残存するアミノ基及びイミノ基の一方又は双方の一部又は全部を中和したり、アミド化した、いわゆるホウ素変性又は酸変性化合物を例示できる。その中でもホウ素含有ポリブテニルコハク酸イミド、特にホウ素含有ビスポリブテニルコハク酸イミドが現時点では最も好ましいものとして挙げられる。
【００３７】
上記ホウ素化合物としては、ホウ酸、ホウ酸塩、ホウ酸エステル等が挙げられる。具体的には、上記ホウ酸として、オルトホウ酸、メタホウ酸及びテトラホウ酸などが挙げられる。また、上記ホウ酸塩としては、アンモニウム塩等、具体的には、メタホウ酸アンモニウム、四ホウ酸アンモニウム、五ホウ酸アンモニウム及び八ホウ酸アンモニウム等のホウ酸アンモニウムが好適例として挙げられる。
また、ホウ酸エステルとしては、ホウ酸と好ましくは炭素数１〜６のアルキルアルコールとのエステル、より具体的には、ホウ酸モノメチル、ホウ酸ジメチル、ホウ酸トリメチル、ホウ酸モノエチル、ホウ酸ジエチル、ホウ酸トリエチル、ホウ酸モノプロピル、ホウ酸ジプロピル、ホウ酸トリププロピル、ホウ酸モノブチル、ホウ酸ジブチル及びホウ酸トリブチル等が好適例として挙げられる。なお、ホウ素含有ポリブテニルコハク酸イミドにおけるホウ素含有量Ｂと窒素含有量Ｎとの質量比「Ｂ／Ｎ」は、通常０．１〜３であり、好ましくは、０．２〜１である。
【００３８】
また、上記含酸素有機化合物としては、具体的には、ぎ酸、酢酸、グリコール酸、プロピオン酸、乳酸、酪酸、吉草酸、カプロン酸、エナント酸、カプリル酸、ペラルゴン酸、カプリン酸、ウンデシル酸、ラウリン酸、トリデカン酸、ミリスチン酸、ペンタデカン酸、パルミチン酸、マルガリン酸、ステアリン酸、オレイン酸、ノナデカン酸及びエイコサン酸等の炭素数１〜３０のモノカルボン酸、シュウ酸、フタル酸、トリメリット酸及びピロメリット酸等の炭素数２〜３０のポリカルボン酸並びにこれらの無水物、又はエステル化合物、炭素数２〜６のアルキレンオキサイドやヒドロキシ（ポリ）オキシアルキレンカーボネート等が挙げられる。
【００３９】
なお、本発明に用いる潤滑油では、ポリブテニルコハク酸イミド及びその誘導体の一方又は双方の含有量は特に制限されないが、潤滑油全量基準で０．１〜１５％が好ましく、１．０〜１２％であることが更に好ましい。０．１％未満では清浄性効果に乏しくなることがあり、１５％を超えると含有量に見合う清浄性効果が得られにくく、抗乳化性が悪化し易い。
【００４０】
更にまた、本発明に用いる潤滑油は、次の一般式（３）
【００４１】
【化３】

【００４２】
で表されるジチオリン酸亜鉛を含有することが好適である。
上記式（３）中のＲ^４、Ｒ^５、Ｒ^６及びＲ^７は、それぞれ別個に炭素数１〜２４の炭化水素基を示す。これら炭化水素基としては、炭素数１〜２４の直鎖状又は分枝状のアルキル基、炭素数３〜２４の直鎖状又は分枝状のアルケニル基、炭素数５〜１３のシクロアルキル基又は直鎖状若しくは分枝状のアルキルシクロアルキル基、炭素数６〜１８のアリール基又は直鎖状若しくは分枝状のアルキルアリール基、炭素数７〜１９のアリールアルキル基等のいずれかであることが望ましい。また、アルキル基やアルケニル基は、第１級、第２級及び第３級のいずれであってもよい。
【００４３】
上記Ｒ^４、Ｒ^５、Ｒ^６及びＲ^７としては、具体的には、メチル基、エチル基、プロピル基、ブチル基、ペンチル基、へキシル基、ヘプチル基、オクチル基、ノニル基、デシル基、ウンデシル基、ドデシル基、トリデシル基、テトラデシル基、ペンタデシル基、ヘキサデシル基、ヘプタデシル基、オクタデシル基、ノナデシル基、イコシル基、ヘンイコシル基、ドコシル基、トリコシル基及びテトラコシル基等のアルキル基や、プロペニル基、イソプロペニル基、ブテニル基、ブタジエニル基、ペンテニル基、ヘキセニル基、ヘプテニル基、オクテニル基、ノネニル基、デセニル基、ウンデセニル基、ドデセニル基、トリデセニル基、テトラデセニル基、ペンタデセニル基、ヘキサデセニル基、ヘプタデセニル基及びオレイル基等のオクタデセニル基や、ノナデセニル基、イコセニル基、ヘンイコセニル基、ドコセニル基、トリコセニル基及びテトラコセニル基等のアルケニル基や、シクロペンチル基、シクロへキシル基及びシクロヘプチル基等のシクロアルキル基や、メチルシクロペンチル基、ジメチルシクロペンチル基、エチルシクロペンチル基、プロピルシクロペンチル基、エチルメチルシクロペンチル基、トリメチルシクロペンチル基、ジエチルシクロペンチル基、エチルジメチルシクロペンチル基、プロピルメチルシクロペンチル基、プロピルエチルシクロペンチル基、ジ−プロピルシクロペンチル基、プロピルエチルメチルシクロペンチル基、メチルシクロへキシル基、ジメチルシクロへキシル基、エチルシクロへキシル基、プロピルシクロへキシル基、エチルメチルシクロへキシル基、トリメチルシクロへキシル基、ジエチルシクロヘキシル基、エチルジメチルシクロヘキシル基、プロピルメチルシクロヘキシル基、プロピルエチルシクロヘキシル基、ジ−プロピルシクロへキシル基、プロピルエチルメチルシクロヘキシル基、メチルシクロヘプチル基、ジメチルシクロヘプチル基、エチルシクロヘプチル基、プロピルシクロヘプチル基、エチルメチルシクロヘプチル基、トリメチルシクロヘプチル基、ジエチルシクロヘプチル基、エチルジメチルシクロヘプチル基、プロピルメチルシクロヘプチル基、プロピルエチルシクロヘプチル基、ジ−プロピルシクロヘプチル基及びプロピルエチルメチルシクロヘプチル基等のアルキルシクロアルキル基や、フェニル基及びナフチル基等のアリール基や、トリル基、キシリル基、エチルフェニル基、プロピルフェニル基、エチルメチルフェニル基、トリメチルフェニル基、ブチルフェニル基、プロピルメチルフェニル基、ジエチルフェニル基、エチルジメチルフェニル基、テトラメチルフェニル基、ペンチルフェニル基、ヘキシルフェニル基、ヘプチルフェニル基、オクチルフェニル基、ノニルフェニル基、デシルフェニル基、ウンデシルフェニル基及びドデシルフェニル基等のアルキルアリール基や、ベンジル基、メチルベンジル基、ジメチルベンジル基、フェネチル基、メチルフェネチル基及びジメチルフェネチル基等のアリールアルキル基が例示できる。
なお、Ｒ^４、Ｒ^５、Ｒ^６及びＲ^７がとり得る上記炭化水素基には、考えられる全ての直鎖状構造及び分枝状構造が含まれ、また、アルケニル基の二重結合の位置、アルキル基のシクロアルキル基への結合位置、アルキル基のアリール基への結合位置、及びアリール基のアルキル基への結合位置は任意である。また、上記炭化水素基の中でも、その炭化水素基が、直鎖状又は分柱状の炭素数１〜１８のアルキル基である場合若しくは炭素数６〜１８のアリール基、又は直鎖状若しくは分枝状アルキルアリール基である場合が特に好ましい。
【００４４】
上記ジチオリン酸亜鉛の好適な具体例としては、ジイソプロピルジチオリン酸亜鉛、ジイソブチルジチオリン酸亜鉛、ジ−ｓｅｃ−ブチルジチオリン酸亜鉛、ジ−ｓｅｃ−ペンチルジチオリン酸亜鉛、ジ−ｎ−ヘキシルジチオリン酸亜鉛、ジ−ｓｅｃ−ヘキシルジチオリン酸亜鉛、ジ−オクチルジチオリン酸亜鉛、ジ−２−エチルヘキシルジチオリン酸亜鉛、ジ−ｎ−デシルジチオリン酸亜鉛、ジ−ｎ−ドデシルジチオリン酸亜鉛、ジイソトリデシルジチオリン酸亜鉛及びこれらの任意の組合せに係る混合物等が挙げられる。
【００４５】
また、上記ジチオリン酸亜鉛の含有量は、特に制限されないが、より高い摩擦低減効果を発揮させる観点から、潤滑油全量基準且つリン元素換算量で、０．１％以下であることが好ましく、また０．０６％以下であることが更に好ましく、ジチオリン酸亜鉛が含有されないことが特に好ましい。ジチオリン酸亜鉛の含有量が潤滑油全量基準且つリン元素換算量で０．１％を超えると、硬質炭素薄膜が被覆された部材と鉄基部材との摺動面における上記脂肪酸エステル系無灰摩擦調整剤や上記脂肪族アミン系無灰摩擦調整剤の優れた摩擦低減効果が阻害される可能性がある。
【００４６】
かかるジチオリン酸亜鉛の製造方法としては、従来方法を任意に採用することができ、特に制限されないが、具体的には、上記Ｒ^４、Ｒ^５、Ｒ^６及びＲ^７に対応する炭化水素基を持つアルコール又はフェノールを五酸化二リン（Ｐ_２Ｏ_５）と反応させてジチオリン酸とし、これを酸化亜鉛で中和させることにより合成することができる。なお、上記ジチオリン酸亜鉛の構造は、使用する原料アルコールによって異なることは言うまでもない。
本発明においては、上記一般式（３）に包含される２種以上のジチオリン酸亜鉛を任意の割合で混合して使用することもできる。
【００４７】
上述のように、本発明に用いる潤滑油は、硬質炭素薄膜が被覆された部材と鉄基部材との摺動面に用いた場合に、極めて優れた低摩擦特性を示すものであるが、特に内燃機関用潤滑油として必要な性能を高める目的で、金属系清浄剤、酸化防止剤、粘度指数向上剤、他の無灰摩擦調整剤、他の無灰分散剤、摩耗防止剤若しくは極圧剤、防錆剤、非イオン系界面活性剤、抗乳化剤、金属不活性化剤、消泡剤等を単独で又は複数種を組合せて配合し、必要な性能を高めることができる。
【００４８】
上記金属系清浄剤としては、潤滑油用の金属系清浄剤として通常用いられる任意の化合物が使用できる。例えば、アルカリ金属又はアルカリ土類金属のスルホネート、フェネート、サリシレートナフテネート等を単独で又は複数種を組合せて使用できる。ここで、上記アルカリ金属としてはナトリウム（Ｎａ）やカリウム（Ｋ）等、上記アルカリ土類金属としてはカルシウム（Ｃａ）やマグネシウム（Ｍｇ）等が例示できる。また、具体的な好適例としては、Ｃａ又はＭｇのスルフォネート、フェネート及びサリシレートが挙げられる。
なお、これら金属系清浄剤の全塩基価及び添加量は、要求される潤滑油の性能に応じて任意に選択できる。通常、全塩基価は、過塩素酸法で０〜５００ｍｇＫＯＨ／ｇ、望ましくは１５０〜４００ｍｇＫＯＨ／ｇであり、その添加量は潤滑油全量基準で、通常０．１〜１０％である。
【００４９】
また、上記酸化防止剤としては、潤滑油用の酸化防止剤として通常用いられる任意の化合物を使用できる。例えば、４，４’−メチレンビス（２，６−ジ−ｔｅｒｔ−ブチルフェノール）、オクタデシル−３−（３，５−ジ−ｔｅｒｔ−ブチル−４−ヒドロキシフェニル）プロピオネート等のフェノール系酸化防止剤、フェニル−α−ナフチルアミン、アルキルフェニル−α−ナフチルアミン、アルキルジフェニルアミン等のアミン系酸化防止剤、並びにこれらの任意の組合せに係る混合物等が挙げられる。また、かかる酸化防止剤の添加量は、潤滑油全量基準で、通常０．０１〜５％である。
【００５０】
更に、上記粘度指数向上剤としては、具体的には、各種メタクリル酸エステルから選ばれる１種又は２種以上のモノマーの共重合体やその水添物等のいわゆる非分散型粘度指数向上剤、及び更に窒素化合物を含む各種メタクリル酸エステルを共重合させたいわゆる分散型粘度指数向上剤等が例示できる。また、他の粘度指数向上剤の具体例としては、非分散型又は分散型エチレン−α−オレフィン共重合体（α−オレフィンとしては、例えばプロピレン、１−ブテン、１−ペンテン等）及びその水素化物、ポリイソブチレン及びその水添物、スチレン−ジエン水素化共重合体、スチレン−無水マレイン酸エステル共重合体、並びにポリアルキルスチレン等も例示できる。
これら粘度指数向上剤の分子量は、せん断安定性を考慮して選定することが必要である。具体的には、粘度指数向上剤の数平均分子量は、例えば分散型及び非分散型ポリメタクリレートでは５０００〜１００００００、好ましくは１０００００〜８０００００がよく、ポリイソブチレン又はその水素化物では８００〜５０００、エチレン−α−オレフィン共重合体又はその水素化物では８００〜３０００００、好ましくは１００００〜２０００００がよい。また、かかる粘度指数向上剤は、単独で又は複数種を任意に組合せて含有させることができるが、通常その含有量は、潤滑油全量基準で０．１〜４０．０％であることが望ましい。
【００５１】
更にまた、他の無灰摩擦調整剤としては、ホウ酸エステル、高級アルコール、脂肪族エーテル等の無灰摩擦調整剤、ジチオリン酸モリブデン、ジチオカルバミン酸モリブデン、二硫化モリブデン等の金属系摩擦調整剤等が挙げられる。
また、他の無灰分散剤としては、数平均分子量が９００〜３５００のポリブテニル基を有するポリブテニルベンジルアミン、ポリブテニルアミン、数平均分子量が９００未満のポリブテニル基を有するポリブテニルコハク酸イミド等及びそれらの誘導体等が挙げられる。
更に、上記摩耗防止剤又は極圧剤としては、ジスルフィド、硫化油脂、硫化オレフィン、炭素数２〜２０の炭化水素基を１〜３個含有するリン酸エステル、チオリン酸エステル、亜リン酸エステル、チオ亜リン酸エステル及びこれらのアミン塩等が挙げられる。
更にまた、上記防錆剤としては、アルキルベンゼンスルフォネート、ジノニルナフタレンスルフォネート、アルケニルコハク酸エステル及び多価アルコールエステル等が挙げられる。
また、上記非イオン系界面活性剤及び抗乳化剤としては、ポリオキシエチレンアルキルエーテル、ポリオキシエチレンアルキルフェニルエーテル及びポリオキシエチレンアルキルナフチルエーテル等のポリアルキレングリコール系非イオン系界面活性剤が挙げられる。
更に、上記金属不活性化剤としては、イミダゾリン、ピリミジン誘導体、チアジアゾール、ベンゾトリアゾール及びチアジアゾール等が挙げられる。
更にまた、上記消泡剤としては、シリコーン、フルオロシリコーン及びフルオロアルキルエーテル等が挙げられる。
なお、これら添加剤を本発明に用いる潤滑油に含有させる場合には、その含有量は、潤滑油全量基準で、他の摩擦調整剤、他の無灰分散剤、摩耗防止剤又は極圧剤、防錆剤、及び抗乳化剤については０．０１〜５％、金属不活性剤については０．００５〜１％、消泡剤については０．０００５〜１％の範囲から適宜選択できる。
【００５２】
【実施例】
以下、本発明を実施例及び比較例により更に詳細に説明するが、本発明はこれら実施例に限定されるものではない。
【００５３】
（実施例１）
基材であるＡｌ−Ｓｉ系合金からφ１８×２２ｍｍの試験片（円柱体）を切り出し、この試験片の表面に、ＰＶＤアーク式イオンプレーティング法により、水素原子の量が２０原子％以下であり且つ厚さ０．５μｍのＤＬＣ薄膜を成膜し、本例の摺動部試験片を製造した。なお、本例においては、添加剤を含まないベースオイル（ＰＡＯ）を潤滑油として性能評価を実施した。
【００５４】
（実施例２）
基材であるＡｌ−Ｓｉ系合金からφ１８×２２ｍｍの試験片（円柱体）を切り出し、この試験片の表面に、ＰＶＤアーク式イオンプレーティング法により、水素原子の量が０．５原子％以下であり且つ厚さ０．５μｍのＤＬＣ薄膜を成膜し、本例の摺動部試験片を製造した。なお、本例においては、添加剤を含まないベースオイル（ＰＡＯ）を潤滑油として性能評価を実施した。
【００５５】
（実施例３）
基材であるＡｌ−Ｓｉ系合金からφ１８×２２ｍｍの試験片（円柱体）を切り出し、この試験片の表面に、ＰＶＤアーク式イオンプレーティング法により、水素原子の量が０．５原子％以下であり且つ厚さ０．５μｍのＤＬＣ薄膜を成膜し、本例の摺動部試験片を製造した。なお、本例においては、ベースオイル（ＰＡＯ）にエステル系無灰摩擦調整剤を添加したものを潤滑油として性能評価を実施した。
【００５６】
（比較例１）
基材であるＡｌ−Ｓｉ系合金からφ１８×２２ｍｍの試験片（円柱体）を切り出し、この試験片の表面に、アルマイト処理を施し、本例の摺動部試験片を製造した。なお、本例においては、ベースオイル（ＰＡＯ）にエステル系無灰摩擦調整剤を添加したものを潤滑油として性能評価を実施した。
【００５７】
（比較例２）
基材であるＡｌ−Ｓｉ系合金からφ１８×２２ｍｍの試験片（円柱体）を切り出し、この試験片の表面に、クロムめっき処理を施し、本例の摺動部試験片を製造した。なお、本例においては、ベースオイル（ＰＡＯ）にエステル系無灰摩擦調整剤を添加したものを潤滑油として性能評価を実施した。
【００５８】
［性能評価］
各例の摺動部試験片を、下記の試験条件下で摩擦摩耗試験（ＳＲＶ試験）を実施して、即ち、図２に示すように、相手側試験片（円板）１１０上で摺動部試験片（円柱）１００を荷重Ｌで相手側試験片１１０に押し付けつつ矢印Ｓ、Ｔ方向に揺動させて、摩擦係数及び試験後の摩耗量を測定した。
得られた結果を表１に示す。表１中の各例の摩耗量は実施例３の摩耗量を基準値（１．０）とした相対値である。
【００５９】
（試験条件）
・摺動部試験片 ：φ１８×２２ｍｍ 円柱試験片（Ａｌ−Ｓｉ系合金）
・相手側試験片 ：φ２４×７ｍｍ 円板試験片（Ｆｅ系焼結合金）
・試験装置 ：ＳＲＶ試験装置
・周波数 ：５０Ｈｚ
・試験温度 ：８０℃
・荷重方式 ：４００Ｎ
・摺動幅 ：３ｍｍ
・試験時間 ：１５ｍｉｎ
【００６０】
【表１】

【００６１】
表１より、本発明の範囲に属する実施例１〜３は、本発明外の比較例１及び２よりも摩擦係数が小さく、試験後の摩耗量も少ないことが分かる。
また、現時点では、摩擦係数が小さく、摩耗量が少ないという観点から、実施例３が最も良好な結果をもたらすものと思われる。
【００６２】
【発明の効果】
以上説明してきたように、本発明によれば、アルミニウム合金製のバルブ表面に所定の潤滑油の存在下において極めて優れた低摩擦性や耐摩耗性を示す硬質炭素薄膜を被覆させることなどとしたため、極めて優れた低摩擦性や耐摩耗性を示し、従来の鋼材料よりも更に優れた省燃費効果を発揮し得るアルミニウム合金を用いて軽量化したエンジン用バルブを提供することができる。
【図面の簡単な説明】
【図１】エンジン用バルブの動弁機構の一例を示す断面図である。
【図２】ＳＲＶ試験の要領を示す斜視説明図である。
【符号の説明】
１ バルブ
１ａ フェース面
１ｂ ステム面
１ｃ 溝部表面
１ｄ 軸端部表面
１ｅ 先端面
１０ カム
２０ バルブリフタ
３０ ステムシール
４０ ステムガイド
５０ バルブシート
６０ 吸気ポート
７０ バルブスプリング
８０ リテーナ
９０ コッタ
１００ 摺動部試験片
１１０ 相手側試験片[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a valve for an engine, and more specifically, a hard carbon thin film such as a diamond-like carbon (DLC) thin film that exhibits extremely low friction and wear resistance in the presence of a specific lubricating oil. The present invention relates to a valve for an engine that is lightened by using an aluminum alloy.
[0002]
[Prior art]
Global environmental issues such as global warming and destruction of the ozone layer are greatly highlighted, and in particular, each country has reduced carbon dioxide (CO ₂ ), which is said to have a major impact on global warming. There is a great interest in how to determine regulatory values.
As for CO ₂ reduction, reducing the fuel consumption of automobiles is one of the major issues, and the role played by sliding materials and lubricants is significant.
[0003]
The role of the sliding material is to exhibit excellent wear resistance and a low coefficient of friction for parts where the frictional wear environment is severe among the sliding parts of the engine. For lifter shims, various hard thin film materials and roller rocker arms incorporating roller needle bearings have been developed.
In general, DLC materials are expected to be low-friction sliding materials because their coefficient of friction in air and in the absence of lubricating oil is lower than hard-wearing materials such as titanium nitride (TiN) and chromium nitride (CrN). Has been.
[0004]
In addition, as a fuel-saving measure in lubricating oil, (1) by reducing viscosity, reducing viscosity resistance in the fluid lubrication region and stirring resistance in the engine, (2) by blending optimal friction modifiers and various additives, Reduction of friction loss under the mixing and boundary lubrication region has been proposed, and as a friction modifier, many studies have been made mainly on organic molybdenum compounds such as molybdenum dithiocarbamate (MoDTC) and molybdenum dithiophosphate (MoDTP). On the sliding surfaces made of conventional steel materials, a lubricating oil blended with an organic molybdenum compound exhibiting an excellent low friction coefficient at the beginning of use has been applied, which has been effective.
Several reports have been made on the friction characteristics of such DLC materials and the performance of organic molybdenum compounds as friction modifiers (see, for example, Non-Patent Documents 1 and 2).
Furthermore, as for engine valves, various aluminum valves have been proposed for the purpose of reducing the weight of conventional iron valves (see, for example, Patent Documents 1 and 2).
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-247628 [Patent Document 2]
JP-A-11-247629 [Non-patent Document 1]
Kano et al., Proceedings of Japan Society of Tribology, May 1999, p. 11-12
[Non-Patent Document 2]
Kano et al., World Tribology Congress 2001.9, Vienna, Proceeding, p. 342
[0006]
[Problems to be solved by the invention]
However, in the above-described prior art, wear on the seat surface has been a problem. Further, the face surface has a problem of deterioration of sealability and wear due to deposit adhesion.
[0007]
The present invention has been made in view of such problems of the prior art, and the object of the present invention is to exhibit extremely low friction and wear resistance, which is superior to conventional steel materials. The object is to provide a valve for an engine that is lightened by using an aluminum alloy that exhibits a fuel-saving effect.
[0008]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present inventors have obtained a hard carbon thin film that exhibits extremely low friction and wear resistance in the presence of a predetermined lubricating oil on the surface of an aluminum alloy valve. The inventors have found that the above object can be achieved by coating, etc., and have completed the present invention.
[0009]
That is, the engine valve of the present invention slides in the presence of lubricating oil, has a hard carbon thin film on its surface, and is mostly composed of an alloy containing aluminum as a main element. The content of is 30 atomic% or less.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the engine valve of the present invention will be described in more detail. In the present specification, “%” represents mass percentage unless otherwise specified.
[0011]
As described above, the engine valve of the present invention slides in the presence of lubricating oil, has a hard carbon thin film on the surface, and is composed mostly of an alloy mainly composed of aluminum. The hydrogen atom content is 30 atomic% or less.
Here, the hard carbon thin film is an amorphous material mainly composed of a carbon element, and the bonding form between carbons consists of both a diamond structure (SP ³ bond) and a graphite bond (SP ² bond). Specific examples include an amorphous carbon thin film made of only carbon elements, a hydrogen amorphous carbon thin film containing hydrogen, and a metal amorphous carbon thin film partially containing a metal element such as titanium (Ti) or molybdenum (Mo). .
The alloy containing aluminum as a main element is a metal containing 50 atomic% or more of aluminum. Further, “the majority is constituted” means that 50 vol% or more with respect to the total volume of the valve. An alloy containing aluminum as the main element. Of course, all may be an aluminum alloy.
[0012]
An engine valve of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing an example of a valve operating mechanism of an engine valve in a cylinder head. As shown in the figure, in the valve mechanism, when the cam 10 rotates, the valve lifter 20 is pushed down while compressing the valve spring 70, and at the same time, the valve 1 is guided and pushed down by the stem guide 40 having the stem seal 30. Then, the valve 1 is separated from the valve seat 50, and the intake port 60 communicates with a combustion chamber (not shown) (the valve is opened). Thereafter, when the cam 10 further rotates, the valve 1 is pushed up together with the valve lifter 20, the retainer 80 and the cotter 90 by the repulsive force of the valve spring 70, the valve 1 comes into contact with the valve seat 50, and the intake port 60 and a combustion chamber (not shown). Is shut off (valve closed). Such valve opening and closing is performed in synchronization with the rotation of the cam 10. Here, the normal valve 1 rotates around the axis mainly due to the influence of the winding direction of the valve spring 70.
[0013]
In the engine valve of the present invention, a hard carbon thin film is coated on one or more of the face surface 1a, stem surface 1b, groove surface 1c, shaft end surface 1d, and tip surface 1e of the surface of the valve 1. It is desirable.
[0014]
The face surface 1a of the valve 1 is in contact with the seat surface of the valve seat 50 to maintain the hermeticity of a combustion chamber (not shown). However, since the sealing performance is reduced due to deposit adhesion, the hard carbon thin film is coated. Thus, deposit adhesion can be prevented by utilizing the characteristic that the hard carbon thin film is inactive.
Further, since the face surface 1a slides with respect to the seat surface of the valve seat 50 due to the vertical movement of the valve 1, etc., low friction and wear resistance can be improved by coating the hard carbon thin film. . As a result, the sealing performance of the combustion chamber is further improved, and the fuel consumption can be improved.
[0015]
Since the stem surface 1b of the valve 1 slides with respect to the stem guide 40 or the stem seal 30 attached to the stem guide 40 by the vertical movement of the valve 1 or the like, low friction is achieved by coating the hard carbon thin film. In addition, wear resistance can be improved.
Further, the groove portion surface 1c and the shaft end portion surface 1d of the bulb 1 slide with respect to the cotter 90 by the rotation or vertical movement of the bulb 1, so that low friction and resistance can be achieved by coating the hard carbon thin film. Abrasion can be improved. The groove surface 1c includes the upper and lower surfaces of the groove.
Furthermore, since the tip surface 1e of the valve 1 slides with respect to the valve lifter 20 when the valve 1 moves up and down, it is possible to improve low friction and wear resistance by covering with a hard carbon thin film. It becomes.
[0016]
In particular, the tip surface 1e and the shaft end surface 1d of the valve 1 have a problem of so-called pitching wear in which the vicinity of the material surface layer causes fatigue failure due to repeated stress. However, as described above, the hard carbon thin film should be coated. Such wear can be suppressed by reducing the weight of the valve by aluminizing the base material. Further, the entire surface of the bulb 1 may be coated with a hard carbon thin film.
The engine valve of the present invention is not limited to be incorporated only in a valve system having a structure as shown in FIG. 1, and for example, the same applies even when the valve 1 is on the exhaust port side. Further, the mechanical element which is the counterpart material of the valve 1 may be slightly changed. On the other hand, it is also mentioned as a preferred embodiment that the counterpart material sliding with the valve 1 is covered with a hard carbon thin film.
[0017]
In the present invention, the hydrogen atom content of the hard carbon thin film is preferably as low as the hydrogen atom content from the viewpoint of exerting a significant friction reducing effect, and the hydrogen atom content is 30 atom% or less. The hydrogen atom content is preferably 5 atom% or less, and more preferably, the hydrogen atom content is 0.5 atom% or less.
[0018]
As the hard carbon thin film as described above, a DLC thin film formed by one or both of the PVD method and the CVD method can be used.
The PVD method and the CVD method are not particularly limited as long as the DLC thin film can be coated in a desired arrangement, but a typical example is an arc ion plating method.
[0019]
Next, the lubricating oil used in the present invention will be described.
The lubricating oil used in the present invention is a lubricating oil that is used in combination with the engine valve of the present invention. The lubricating base oil includes a fatty acid ester-based ashless friction modifier and an aliphatic amine-based ashless friction modifier. It is preferable to contain a component of polybutenyl succinimide, a derivative of polybutenyl succinimide or zinc dithiophosphate, and any combination thereof.
Here, the lubricating base oil is not particularly limited, and any type of lubricating base oil can be used as long as it is normally used as a lubricating base oil, such as mineral oil, synthetic oil, fats and oils, and mixtures thereof. be able to.
[0020]
As mineral oil, specifically, a lubricating oil fraction obtained by subjecting crude oil to atmospheric distillation and vacuum distillation can be desolvated, solvent extraction, hydrocracking, solvent dewaxing, hydrorefining, sulfuric acid washing, clay Oils such as paraffinic or naphthenic oils or normal paraffins, etc., which are refined by appropriately combining purification treatments, etc., can be used. Solvent refining and hydrorefining treatments are generally used, but the aromatic content is further reduced. It is more preferable to use an advanced hydrocracking process that can be carried out or a GTL Wax (gas tow liquid wax) produced by isomerization.
[0021]
Specific examples of synthetic oils include poly-α-olefins (eg, 1-octene oligomers, 1-decene oligomers, ethylene-propylene oligomers), poly-α-olefin hydrides, isobutene oligomers, and isobutene oligomers. Hydride, isoparaffin, alkylbenzene, alkylnaphthalene, diester (eg, ditridecyl glutarate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, dioctyl sebacate, etc.), polyol ester (eg, trimethylolpropane caprylate, trimethylolpropane pelargol And trimethylolpropane esters such as trimethylolpropane isostearinate; pentaerythritol 2-ethylhexanoate, pentaerythritol Pentaerythritol esters such as largonate), polyoxyalkylene glycols, dialkyldiphenyl ethers and polyphenyl ethers. Among them, preferred examples include poly-α-olefins such as 1-octene oligomers and 1-decene oligomers or hydrides thereof.
[0022]
The base oil in the lubricating oil used in the present invention is a mixture of two or more kinds of mineral base oils or two or more kinds of synthetic base oils, in addition to using a mineral base oil and a synthetic base oil alone or in combination. There is no problem. Further, the mixing ratio of two or more kinds of base oils in the above mixture is not particularly limited and can be arbitrarily selected.
[0023]
The sulfur content in the lubricating base oil is not particularly limited, but is preferably 0.2% or less, more preferably 0.1% or less, and even more preferably 0.05% or less, based on the total amount of the base oil. Preferably there is. In particular, since the sulfur content of hydrorefined mineral oil or synthetic base oil is 0.005% or less, or contains substantially no sulfur content (5 ppm or less), it is preferable to use these as the base oil.
[0024]
Also, the aromatic content in the lubricating base oil is not particularly limited, but the total aromatic content is 15% or less in order to maintain a low friction characteristic for a long time as a lubricating oil for an internal combustion engine. It is preferably 10% or less, more preferably 5% or less. That is, when the total aromatic content of the lubricating base oil exceeds 15%, the oxidation stability is inferior, which is not preferable.
In addition, the total aromatic content mentioned here means the aromatic fraction content measured based on the method prescribed | regulated to ASTM, D2549.
[0025]
The kinematic viscosity of the lubricating base oil is not particularly limited, but when used as a lubricating oil for an internal combustion engine, the kinematic viscosity at 100 ° C. is preferably 2 mm ² / s or more, more preferably 3 mm ^2. / S or more. On the other hand, the kinematic viscosity at 100 ° C. is preferably 20 mm ² / s or less, more preferably 10 mm ² / s or less, and particularly preferably 8 mm ² / s or less. When the kinematic viscosity at 100 ° C. of the lubricating base oil is less than 2 mm ² / s, it is not preferable because sufficient abrasion resistance cannot be obtained and evaporation characteristics may be deteriorated. On the other hand, when the kinematic viscosity exceeds 20 mm ² / s, it is difficult to exhibit low friction performance, and low temperature performance may be deteriorated. In the present invention, a mixture of any two or more base oils selected from the above base oils can be used, and as long as the kinematic viscosity at 100 ° C. is within the above preferred range, the base oil alone Even if the kinematic viscosity is other than the above, it can be used.
[0026]
Also, the viscosity index of the lubricating base oil is not particularly limited, but is preferably 80 or more, more preferably 100 or more, particularly when used as a lubricating oil for internal combustion engines. The above is preferable. By increasing the viscosity index of the lubricating base oil, it is possible to obtain a lubricating oil for an internal combustion engine that consumes less oil and has excellent low-temperature viscosity characteristics and fuel saving performance.
[0027]
One or both of the fatty acid ester-based ashless friction modifier and the aliphatic amine-based ashless friction modifier to be used has 6 to 30 carbon atoms, preferably 8 to 24 carbon atoms, and particularly preferably 10 to 20 carbon atoms. Mention may be made of fatty acid esters having a linear or branched hydrocarbon group, fatty acid amine compounds, and any mixtures thereof. When the carbon number is outside the range of 6 to 30, there is a possibility that the friction reducing effect cannot be obtained sufficiently.
[0028]
Specific examples of the straight chain or branched hydrocarbon group having 6 to 30 carbon atoms include hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group. Group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group, heneicosyl group, docosyl group, tricosyl group, tetracosyl group, pentacosyl group, hexacosyl group, heptacosyl group, octacosyl group, nonacosyl group and triacontyl group, etc. Alkyl groups, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl, nonadecenyl, icosenyl , It can be exemplified henicosenyl group, docosenyl, tricosenyl group, tetracosenyl group, Pentakoseniru group, Hekisakoseniru group, Heputakoseniru group, Okutakoseniru group, an alkenyl group such as Nonakoseniru group and thoria container group.
The alkyl group and alkenyl group include all possible linear structures and branched structures, and the position of the double bond in the alkenyl group is arbitrary.
[0029]
Moreover, as said fatty acid ester, the ester of the fatty acid which has this C6-C30 hydrocarbon group, and aliphatic monohydric alcohol or aliphatic polyhydric alcohol etc. can be illustrated, Specifically, glycerol monooleate, Particularly preferred examples include glycerine diolate, sorbitan monooleate, and sorbitan diolate.
Examples of the aliphatic amine compound include aliphatic monoamines or their alkylene oxide adducts, aliphatic polyamines, imidazoline compounds, and derivatives thereof. Specifically, fats such as laurylamine, lauryldiethylamine, lauryldiethanolamine, dodecyldipropanolamine, palmitylamine, stearylamine, stearyltetraethylenepentamine, oleylamine, oleylpropylenediamine, oleyldiethanolamine and N-hydroxyethyloleylimidazoline Amine alkylene compounds, amine alkylene oxide adducts such as N, N-dipolyoxyalkylene-N-alkyl (or alkenyl) (carbon number 6 to 28) of these aliphatic amine compounds, carbon numbers in these aliphatic amine compounds 2 to 30 monocarboxylic acids (fatty acids, etc.) and carboxylic acids such as oxalic acid, phthalic acid, trimellitic acid, pyromellitic acid, etc. one Or amidated or neutralize part or all of both the so-called acid-modified compounds, and the like. Preferable examples include N, N-dipolyoxyethylene-N-oleylamine.
[0030]
Further, the content of one or both of the fatty acid ester-based ashless friction modifier and the aliphatic amine-based ashless friction modifier contained in the lubricating oil used in the present invention is not particularly limited, but based on the total amount of the lubricating oil, The content is preferably 0.05 to 3.0%, more preferably 0.1 to 2.0%, and particularly preferably 0.5 to 1.4%. If the content is less than 0.05%, the friction reducing effect tends to be small, and if it exceeds 3.0%, the solubility and storage stability in the lubricating oil are significantly deteriorated, and precipitates are likely to be generated. It is not preferable.
[0031]
On the other hand, as polybutenyl succinimide mentioned above, following general formula (1) and (2)
[0032]
[Chemical 1]

[0033]
[Chemical 2]

[0034]
The compound represented by these is mentioned. PIB in these general formulas represents a polybutenyl group, and the number average molecular weight obtained by polymerizing a high purity isobutene or a mixture of 1-butene and isobutene with a boron fluoride catalyst or an aluminum chloride catalyst is 900 to 3500, preferably Obtained from 1000-2000 polybutene. When the number average molecular weight is less than 900, the cleanability effect tends to be poor, and when it exceeds 3500, the low temperature fluidity tends to be poor.
Further, n in the above general formula is preferably an integer of 1 to 5, more preferably an integer of 2 to 4, from the viewpoint of excellent cleanability. Further, the polybutene is used to remove a trace amount of fluorine and chlorine remaining due to a catalyst in the production process by an appropriate method such as an adsorption method or sufficient water washing, more preferably 50 ppm or less, more preferably 10 ppm or less. It is also possible to use after removing to 1 ppm or less.
[0035]
The method for producing such polybutenyl succinimide is not particularly limited. For example, the polybutene chlorinated product or polybutene from which chlorine or fluorine has been sufficiently removed and maleic anhydride are reacted at 100 to 200 ° C. The polybutenyl succinic acid obtained can be obtained by reacting with polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine.
[0036]
On the other hand, as a derivative of the polybutenyl succinimide described above, a boron compound or an oxygen-containing organic compound is allowed to act on the compound represented by the general formula (1) or (2), thereby remaining amino groups and imino. Examples thereof include so-called boron-modified or acid-modified compounds in which part or all of one or both groups are neutralized or amidated. Among them, boron-containing polybutenyl succinimide, particularly boron-containing bispolybutenyl succinimide, is most preferred at the present time.
[0037]
Examples of the boron compound include boric acid, borates, and borate esters. Specifically, examples of the boric acid include orthoboric acid, metaboric acid, and tetraboric acid. Moreover, as said borate, ammonium borates, such as ammonium salt etc., specifically, ammonium metaborate, ammonium tetraborate, ammonium pentaborate, and ammonium octaborate, are mentioned as a suitable example.
The boric acid ester is an ester of boric acid and preferably an alkyl alcohol having 1 to 6 carbon atoms, more specifically, monomethyl borate, dimethyl borate, trimethyl borate, monoethyl borate, diethyl borate Preferable examples include triethyl borate, monopropyl borate, dipropyl borate, triplypropyl borate, monobutyl borate, dibutyl borate, and tributyl borate. In addition, the mass ratio “B / N” of the boron content B and the nitrogen content N in the boron-containing polybutenyl succinimide is usually 0.1 to 3, preferably 0.2 to 1. .
[0038]
Specific examples of the oxygen-containing organic compound include formic acid, acetic acid, glycolic acid, propionic acid, lactic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, and undecyl acid. , Lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, oleic acid, nonadecanoic acid and eicosanoic acid, etc., monocarboxylic acid having 1 to 30 carbon atoms, oxalic acid, phthalic acid, trimellit Examples thereof include polycarboxylic acids having 2 to 30 carbon atoms such as acid and pyromellitic acid and anhydrides or ester compounds thereof, alkylene oxides having 2 to 6 carbon atoms, and hydroxy (poly) oxyalkylene carbonate.
[0039]
In the lubricating oil used in the present invention, the content of one or both of polybutenyl succinimide and derivatives thereof is not particularly limited, but is preferably 0.1 to 15% based on the total amount of the lubricating oil, and is 1.0 to More preferably, it is 12%. If it is less than 0.1%, the cleaning effect may be poor, and if it exceeds 15%, it is difficult to obtain a cleaning effect corresponding to the content, and the demulsibility tends to deteriorate.
[0040]
Furthermore, the lubricating oil used in the present invention has the following general formula (3):
[0041]
[Chemical 3]

[0042]
It is preferable to contain the zinc dithiophosphate represented by these.
R ⁴ , R ⁵ , R ⁶ and R ⁷ in the above formula (3) each independently represent a hydrocarbon group having 1 to 24 carbon atoms. Examples of these hydrocarbon groups include linear or branched alkyl groups having 1 to 24 carbon atoms, linear or branched alkenyl groups having 3 to 24 carbon atoms, and cycloalkyl groups having 5 to 13 carbon atoms. Or a linear or branched alkylcycloalkyl group, an aryl group having 6 to 18 carbon atoms, a linear or branched alkylaryl group, an arylalkyl group having 7 to 19 carbon atoms, or the like. It is desirable. The alkyl group or alkenyl group may be any of primary, secondary, and tertiary.
[0043]
Specific examples of R ⁴ , R ⁵ , R ⁶ and R ⁷ include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group. Alkyl groups such as undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group, heicosyl group, docosyl group, tricosyl group and tetracosyl group, and propenyl group , Isopropenyl group, butenyl group, butadienyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, undecenyl group, dodecenyl group, tridecenyl group, tetradecenyl group, pentadecenyl group, hexadecenyl group, and heptadecenyl group Octyl such as oleyl group Cenyl group, alkenyl group such as nonadecenyl group, icocenyl group, heicosenyl group, dococenyl group, tricocenyl group and tetracocenyl group, cycloalkyl group such as cyclopentyl group, cyclohexyl group and cycloheptyl group, methylcyclopentyl group, dimethyl group Cyclopentyl group, ethylcyclopentyl group, propylcyclopentyl group, ethylmethylcyclopentyl group, trimethylcyclopentyl group, diethylcyclopentyl group, ethyldimethylcyclopentyl group, propylmethylcyclopentyl group, propylethylcyclopentyl group, di-propylcyclopentyl group, propylethylmethylcyclopentyl group , Methylcyclohexyl group, dimethylcyclohexyl group, ethylcyclohexyl group, propylcyclohexyl group, ethylmethyl Cyclohexyl group, trimethylcyclohexyl group, diethylcyclohexyl group, ethyldimethylcyclohexyl group, propylmethylcyclohexyl group, propylethylcyclohexyl group, di-propylcyclohexyl group, propylethylmethylcyclohexyl group, methylcycloheptyl group, dimethyl Cycloheptyl group, ethylcycloheptyl group, propylcycloheptyl group, ethylmethylcycloheptyl group, trimethylcycloheptyl group, diethylcycloheptyl group, ethyldimethylcycloheptyl group, propylmethylcycloheptyl group, propylethylcycloheptyl group, di- Alkyl cycloalkyl groups such as propylcycloheptyl group and propylethylmethylcycloheptyl group, aryl groups such as phenyl group and naphthyl group, and tolyl groups Xylyl group, ethylphenyl group, propylphenyl group, ethylmethylphenyl group, trimethylphenyl group, butylphenyl group, propylmethylphenyl group, diethylphenyl group, ethyldimethylphenyl group, tetramethylphenyl group, pentylphenyl group, hexylphenyl Group, heptylphenyl group, octylphenyl group, nonylphenyl group, decylphenyl group, undecylphenyl group, dodecylphenyl group and other alkylaryl groups, benzyl group, methylbenzyl group, dimethylbenzyl group, phenethyl group, methylphenethyl group And arylalkyl groups such as a dimethylphenethyl group.
The hydrocarbon group which R ⁴ , R ⁵ , R ⁶ and R ⁷ can take include all possible linear structures and branched structures, and the position of the double bond of the alkenyl group. The bonding position of the alkyl group to the cycloalkyl group, the bonding position of the alkyl group to the aryl group, and the bonding position of the aryl group to the alkyl group are arbitrary. Further, among the hydrocarbon groups, when the hydrocarbon group is a linear or branched alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms, or a linear or branched group Particularly preferred is a linear alkylaryl group.
[0044]
Preferred examples of the zinc dithiophosphate include zinc diisopropyldithiophosphate, zinc diisobutyldithiophosphate, zinc di-sec-butyldithiophosphate, zinc di-sec-pentyldithiophosphate, zinc di-n-hexyldithiophosphate, di- -Sec-hexyl dithiophosphate zinc, di-octyl dithiophosphate zinc, di-2-ethylhexyl dithiophosphate zinc, di-n-decyl dithiophosphate zinc, di-n-dodecyl dithiophosphate zinc, diisotridecyl dithiophosphate zinc and these The mixture etc. which concern on arbitrary combinations of these are mentioned.
[0045]
Further, the content of the zinc dithiophosphate is not particularly limited, but from the viewpoint of exerting a higher friction reduction effect, it is preferably 0.1% or less in terms of the total amount of lubricating oil and in terms of phosphorus element, It is more preferable that it is 0.06% or less, and it is particularly preferable that zinc dithiophosphate is not contained. When the zinc dithiophosphate content exceeds 0.1% in terms of the total amount of lubricating oil and in terms of phosphorus element, the above fatty acid ester-based ashless friction on the sliding surface between the member coated with the hard carbon thin film and the iron base member There is a possibility that the excellent friction reducing effect of the adjusting agent and the aliphatic amine-based ashless friction adjusting agent is inhibited.
[0046]
As a method for producing such zinc dithiophosphate, a conventional method can be arbitrarily adopted, and is not particularly limited. Specifically, hydrocarbon groups corresponding to the above R ⁴ , R ⁵ , R ⁶ and R ⁷ are used. It can be synthesized by reacting the alcohol or phenol possessed with diphosphorus pentoxide (P ₂ O ₅ ) to give dithiophosphoric acid and neutralizing it with zinc oxide. In addition, it cannot be overemphasized that the structure of the said zinc dithiophosphate changes with raw material alcohol to be used.
In the present invention, two or more kinds of zinc dithiophosphates included in the general formula (3) may be mixed and used at an arbitrary ratio.
[0047]
As described above, the lubricating oil used in the present invention exhibits extremely low friction characteristics when used on the sliding surface between the member coated with the hard carbon thin film and the iron base member. For the purpose of enhancing the performance required as a lubricating oil for internal combustion engines, metallic detergents, antioxidants, viscosity index improvers, other ashless friction modifiers, other ashless dispersants, antiwear or extreme pressure agents, Rust preventives, nonionic surfactants, demulsifiers, metal deactivators, antifoaming agents, and the like can be blended alone or in combination of a plurality of types to enhance the required performance.
[0048]
As said metallic detergent, the arbitrary compounds normally used as a metallic detergent for lubricating oil can be used. For example, alkali metal or alkaline earth metal sulfonates, phenates, salicylate naphthenates and the like can be used alone or in combination. Here, examples of the alkali metal include sodium (Na) and potassium (K), and examples of the alkaline earth metal include calcium (Ca) and magnesium (Mg). Specific preferred examples include Ca or Mg sulfonates, phenates and salicylates.
In addition, the total base number and addition amount of these metal detergents can be arbitrarily selected according to the required performance of the lubricating oil. Usually, the total base number is 0 to 500 mgKOH / g, preferably 150 to 400 mgKOH / g by the perchloric acid method, and the addition amount is usually 0.1 to 10% based on the total amount of the lubricating oil.
[0049]
Further, as the antioxidant, any compound usually used as an antioxidant for lubricating oil can be used. For example, phenolic antioxidants such as 4,4′-methylenebis (2,6-di-tert-butylphenol) and octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, phenyl Examples thereof include amine-based antioxidants such as -α-naphthylamine, alkylphenyl-α-naphthylamine, and alkyldiphenylamine, as well as mixtures according to any combination thereof. Moreover, the addition amount of this antioxidant is 0.01 to 5% normally on the basis of the total amount of lubricating oil.
[0050]
Furthermore, as the above viscosity index improver, specifically, a so-called non-dispersion type viscosity index improver such as a copolymer of one or more monomers selected from various methacrylic acid esters and hydrogenated products thereof, Furthermore, a so-called dispersion type viscosity index improver obtained by copolymerizing various methacrylic acid esters containing a nitrogen compound can be exemplified. Specific examples of other viscosity index improvers include non-dispersed or dispersed ethylene-α-olefin copolymers (eg, α-olefins include propylene, 1-butene, 1-pentene, etc.) and hydrogen thereof. Examples thereof include a compound, polyisobutylene and a hydrogenated product thereof, a styrene-diene hydrogenated copolymer, a styrene-maleic anhydride ester copolymer, and a polyalkylstyrene.
The molecular weight of these viscosity index improvers needs to be selected in consideration of shear stability. Specifically, the number average molecular weight of the viscosity index improver is, for example, 5,000 to 1,000,000, preferably 100,000 to 800,000 for dispersed and non-dispersed polymethacrylates, 800 to 5,000 for polyisobutylene or a hydride thereof, ethylene- In the case of an α-olefin copolymer or a hydride thereof, 800 to 300,000, preferably 10,000 to 200,000 is preferable. In addition, the viscosity index improver can be contained alone or in any combination of plural kinds, but the content is usually preferably 0.1 to 40.0% based on the total amount of the lubricating oil. .
[0051]
Furthermore, other ashless friction modifiers include ashless friction modifiers such as boric acid esters, higher alcohols, aliphatic ethers, metal friction modifiers such as molybdenum dithiophosphate, molybdenum dithiocarbamate, and molybdenum disulfide. Is mentioned.
Other ashless dispersants include polybutenylbenzylamine and polybutenylamine having a polybutenyl group having a number average molecular weight of 900 to 3500, and polybutenyl succinimide having a polybutenyl group having a number average molecular weight of less than 900. And derivatives thereof.
Furthermore, as the antiwear agent or extreme pressure agent, disulfide, sulfurized fat and oil, sulfurized olefin, phosphate ester containing 1 to 3 hydrocarbon groups having 2 to 20 carbon atoms, thiophosphate ester, phosphite ester, Examples thereof include thiophosphite esters and amine salts thereof.
Furthermore, examples of the rust preventive include alkylbenzene sulfonate, dinonyl naphthalene sulfonate, alkenyl succinate and polyhydric alcohol ester.
Examples of the nonionic surfactant and the demulsifier include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, and polyoxyethylene alkyl naphthyl ether.
Furthermore, examples of the metal deactivator include imidazoline, pyrimidine derivatives, thiadiazole, benzotriazole, and thiadiazole.
Furthermore, examples of the antifoaming agent include silicone, fluorosilicone, and fluoroalkyl ether.
When these additives are contained in the lubricating oil used in the present invention, the content is based on the total amount of the lubricating oil, other friction modifiers, other ashless dispersants, antiwear agents or extreme pressure agents, The rust inhibitor and demulsifier can be appropriately selected from the range of 0.01 to 5%, the metal deactivator is 0.005 to 1%, and the antifoaming agent is 0.0005 to 1%.
[0052]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.
[0053]
(Example 1)
A test piece (cylindrical body) of φ18 × 22 mm was cut out from an Al—Si based alloy as a base material, and the amount of hydrogen atoms was 20 atomic% or less on the surface of this test piece by PVD arc type ion plating method. A DLC thin film having a thickness of 0.5 μm was formed to produce a sliding part test piece of this example. In this example, performance evaluation was performed using a base oil (PAO) containing no additive as a lubricating oil.
[0054]
(Example 2)
A test piece (cylindrical body) of φ18 × 22 mm was cut out from an Al—Si alloy as a base material, and the amount of hydrogen atoms was 0.5 atomic% or less on the surface of this test piece by PVD arc type ion plating method. A DLC thin film having a thickness of 0.5 μm was formed, and a sliding part test piece of this example was manufactured. In this example, performance evaluation was performed using a base oil (PAO) containing no additive as a lubricating oil.
[0055]
(Example 3)
A test piece (cylindrical body) of φ18 × 22 mm was cut out from an Al—Si alloy as a base material, and the amount of hydrogen atoms was 0.5 atomic% or less on the surface of this test piece by PVD arc type ion plating method. A DLC thin film having a thickness of 0.5 μm was formed, and a sliding part test piece of this example was manufactured. In this example, performance evaluation was performed using a base oil (PAO) added with an ester-based ashless friction modifier as a lubricating oil.
[0056]
(Comparative Example 1)
A test piece (cylindrical body) of φ18 × 22 mm was cut out from an Al—Si based alloy as a base material, and an alumite treatment was applied to the surface of the test piece to produce a sliding part test piece of this example. In this example, performance evaluation was performed using a base oil (PAO) added with an ester-based ashless friction modifier as a lubricating oil.
[0057]
(Comparative Example 2)
A test piece (cylindrical body) of φ18 × 22 mm was cut out from the Al—Si based alloy as the base material, and the surface of this test piece was subjected to chromium plating to produce a sliding part test piece of this example. In this example, performance evaluation was performed using a base oil (PAO) added with an ester-based ashless friction modifier as a lubricating oil.
[0058]
[Performance evaluation]
The sliding part test piece of each example is subjected to a frictional wear test (SRV test) under the following test conditions, that is, as shown in FIG. The test piece (cylinder) 100 was swung in the directions of arrows S and T while being pressed against the counterpart test piece 110 with a load L, and the friction coefficient and the amount of wear after the test were measured.
The obtained results are shown in Table 1. The wear amount of each example in Table 1 is a relative value with the wear amount of Example 3 as a reference value (1.0).
[0059]
(Test conditions)
・ Sliding part test piece: φ18 × 22mm Cylindrical test piece (Al-Si alloy)
・ Molder specimen: φ24 × 7mm Disc specimen (Fe-based sintered alloy)
・ Test equipment: SRV test equipment ・ Frequency: 50 Hz
Test temperature: 80 ° C
・ Loading method: 400N
・ Sliding width: 3mm
・ Test time: 15 min
[0060]
[Table 1]

[0061]
From Table 1, it can be seen that Examples 1 to 3 belonging to the scope of the present invention have a smaller coefficient of friction and less wear after the test than Comparative Examples 1 and 2 outside the present invention.
Also, at the present time, Example 3 seems to give the best results from the viewpoint of a small friction coefficient and a small amount of wear.
[0062]
【The invention's effect】
As described above, according to the present invention, the surface of an aluminum alloy valve is coated with a hard carbon thin film that exhibits extremely low friction and wear resistance in the presence of a predetermined lubricating oil. Thus, it is possible to provide a valve for an engine that is reduced in weight by using an aluminum alloy that exhibits extremely low friction and wear resistance, and that can exhibit a fuel-saving effect even better than conventional steel materials.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a valve operating mechanism of an engine valve.
FIG. 2 is an explanatory perspective view showing the outline of an SRV test.
[Explanation of symbols]
1 Valve 1a Face surface 1b Stem surface 1c Groove surface 1d Shaft end surface 1e Tip surface 10 Cam 20 Valve lifter 30 Stem seal 40 Stem guide 50 Valve seat 60 Inlet port 70 Valve spring 80 Retainer 90 Cotta 100 Sliding part test piece 110 Side specimen

Claims (10)

A valve for an engine that slides in the presence of lubricating oil, has a hard carbon thin film on the surface, and is mostly composed of an alloy mainly composed of aluminum,
An engine valve characterized in that the amount of hydrogen atoms contained in the hard carbon thin film is 30 atomic% or less. The engine valve according to claim 1, wherein the hard carbon thin film is coated on at least one of a face surface, a stem surface, a groove portion, a shaft end portion, and a tip end surface of the engine valve. The engine valve according to claim 1 or 2, wherein the amount of hydrogen atoms contained in the hard carbon thin film is 5 atomic% or less. 4. The engine valve according to claim 1, wherein the amount of hydrogen atoms contained in the hard carbon thin film is 0.5 atomic% or less. 5. The engine valve according to any one of claims 1 to 4, wherein the hard carbon thin film is a diamond-like carbon thin film formed by a PVD method and / or a CVD method. The engine valve according to any one of claims 1 to 5, wherein the lubricating oil contains a fatty acid ester-based ashless friction modifier and / or an aliphatic amine-based ashless friction modifier. . The fatty acid ester-based ashless friction modifier and / or the aliphatic amine-based ashless friction modifier has a hydrocarbon group having 6 to 30 carbon atoms and is contained in an amount of 0.05 to 3.0% based on the total amount of the lubricating oil. The engine valve according to claim 6, wherein the valve is an engine valve. The engine valve according to any one of claims 1 to 7, wherein the lubricating oil contains polybutenyl succinimide and / or a derivative thereof. 9. The valve for an engine according to claim 8, wherein the polybutenyl succinimide and / or a derivative thereof is contained in an amount of 0.1 to 15% based on the total amount of lubricating oil. The said lubricating oil contains zinc dithiophosphate, The content is 0.1% or less by the amount reference | standard of lubricating oil whole quantity, and phosphorus element conversion amount, The term of any one of Claims 1-9 characterized by the above-mentioned. The engine valve described in 1.

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