JP4269726B2 - Sliding member, crankshaft, and variable compression ratio engine - Google Patents

Description

【００５０】
（実施例および比較例）
実施例１〜３および比較例１〜６は、潤滑油に自動車用エンジンオイル５Ｗ−３０ＳＪを用いた。実施例５は、潤滑油に自動車用エンジンオイル０Ｗ−２０（モリブデンジチオカーバメート入り）を用いた。
【００５１】
各実施例は、いずれもφ４４．８ｍｍの内円筒表面に凹部微細形状を形成した（比較例は形成していない）。凹部微細形状は、マスクブラスト処理により形成した。すなわち、光リソグラフィ技術を利用し、樹脂製マスクに凹部微細形状を形成し、その樹脂マスクを円筒表面に貼り付けた後、平均粒径２０μｍのアルミナ砥粒を、投射ノズルからワ−クまでの距離を１００ｍｍとし、投射流量１００ｇ／ｍｉｎ、投射圧０．４ＭＰａの条件下で投射し、凹部微細形状を得た。その後、凹部微細形状周辺に形成されたエッジ部の盛り上がりを粒径９μｍのテープラップフィルムにより除去し所望の形状を得た。
【００５２】
その後、ＤＬＣ膜の形成を行った。ＤＬＣ膜は、炭素をターゲットとしたマグネトロンスパッタリング法により、基材表面に硬質炭素皮膜をコーティングしたものである。スパッタリングの際のガスにはアルゴンを用いた。成膜時の試料温度は約２５０℃とした。
【００５３】
なお、この方法では、凹部内にもＤＬＣ膜が形成され得るが、凹部内についてはＤＬＣ膜は形成されてもされなくてもよい。しかしＤＬＣ膜が凹部内にも形成される場合には、形成されたＤＬＣ膜によって凹部内が埋まってしまわないようにする必要がある。
【００５４】
なお、実施例（実施例についてはＤＬＣ膜形成後）の凹部微細形状深さは、いずれのサンプルにおいても１μｍ、面積率は５％とした。
【００５５】
図７は、実施例および比較例の凹部パターンを示す図面である。
【００５６】
実施例１は、図７（ａ）に示すように、開口部の直径がφ１２０μｍのディンプルを、中央部において最大深さが３μｍ、端部において０．３μｍとなるように形成した。
【００５７】
その後、テープラップ加工を施しディンプル周辺のエッジを除去した後、炭素をターゲットとしたマグネトロンスパッタリング法により、この基材表面に硬質炭素皮膜をコーティングした。スパッタリングの際のガスにはアルゴンを用いた。成膜時の試料温度は約２５０℃とした。
【００５８】
ＤＬＣ膜形成後の摺動面の表面粗さを測定したところ仕上げ加工無しで皮膜表面の粗さはＲａ０．０３μｍであった。またＤＬＣ膜の厚さは予め試料の一部をマスクしておき、ＤＬＣ膜が付着した部分とそうでない部分との段差を表面粗さ計で計測することにより求めた結果、０．６μｍであった。
【００５９】
ＤＬＣ膜中の水素量の定量は二次イオン質量分析法（ＳＩＭＳ）によった。表面から深さ約２０ｎｍを掘り取り平均の水素量を求めた結果、０．３原子％であった。
【００６０】
比較例１は、実施例１と同様に、開口部の直径がφ１２０μｍのディンプルパターンとして（図７（ａ）参照）、その深さは実施例１と異なり、中央部から端部まで３μｍとなるように形成した。ＤＬＣ膜は実施例１と同様の手法、手順で形成した。ＤＬＣ膜の厚さも同様に０．６μｍであった。
【００６１】
実施例２は、図７（ｂ）に示すように、幅８０μｍ、長さ×３２０μｍの矩形状の凹部を、中央部での最大深さが３μｍ、端部において０．３μｍとなるように形成した。ＤＬＣ膜は実施例１と同様の手法、手順で形成した。ＤＬＣ膜の厚さも同様に０．６μｍであった。
【００６２】
比較例２は、実施例２と同様に、幅８０μｍ、長さ×３２０μｍの矩形状パターンとして（図７（ｂ）参照）、その深さは実施例２と異なり、中央部から端部まで３μｍとなるように形成した。ＤＬＣ膜は実施例１と同様の手法、手順で形成した。ＤＬＣ膜の厚さも同様に０．６μｍであった。
【００６３】
実施例３は、図７（ｂ）に示すように、幅８０μｍ、長さ×３２０μｍの矩形状パターンの凹部を、中央部での最大深さが２μｍ、端部での深さが０．３μｍとなるように形成した。
【００６４】
ＤＬＣ膜は、炭素ターゲットを用いたマグネトロンスパッタリングにより、サンプル基材の表面にコーティングしたものである。また、このスパッタリングにおいては、ターゲット上に二酸化チタン（ＴｉＯ₂）のプレートを置き、同時にスパッタリングを行うことによりＴｉおよびＯがＤＬＣ膜中に入るようにした。スパッタリングの際のガスにはアルゴンを用いた。
【００６５】
またＤＬＣ膜の厚さは予め試料の一部をマスクしておき、硬質炭素皮膜が付着した部分とそうでない部分との段差を表面粗さ計で計測することにより求めた結果、０．７μｍであった。
【００６６】
ＤＬＣ膜中の各元素の存在比の定量はオージェ電子分光法によった。実際に行ったオージェ電子分光法は、まず、分析装置内で試料表面を一定時間Ａｒガスでエッチングし、次に分析装置から取り出してエッチングされた部分の深さを求めた。これを総エッチング時間に対し直線的に割り付けてエッチングレートを求めた。求められたエッチングレートは１分あたり３．８ｎｍであった。
【００６７】
次にこのエッチングレートをもとに一定の深さを掘り取るための時間を逆算し、試料をその時間だけ掘り取ってはオージェ電子分光により組成を分析する操作を所定の回数だけこれを繰り返し、各元素の深さ方向の分布（デプスプロファイル）を求めた。試料表面から５ｎｍの地点から５ｎｍごとに５０ｎｍの深さまで１０点の測定を行い、その平均を以って「表面層の各元素の存在比」とみなした。この分析の結果、膜中にＴｉが７原子％、酸素は２４原子％存在していた。
【００６８】
比較例３は、図７（ａ）に示すように、開口部の直径がφ１２０μｍのディンプル形状の凹部を、深さが中央部から端部まで３μｍとなるように形成した。なお、ＤＬＣ膜は形成していない。
【００６９】
比較例４は、図７（ｃ）に示すように（すなわち凹部を形成していない）、全面を表面粗さＲａが０．０１μｍ以下になるように、テープラップ加工を施し、鏡面に近い状態に仕上げた。
【００７０】
その後、プラズマＣＶＤ法によってＤＬＣ膜を成膜した。炭素源にはベンゼンを用いた。試料温度は２００℃とした。
【００７１】
膜中の水素量の定量は二次イオン質量分析法（ＳＩＭＳ）によった。表面から深さ約２０ｎｍを掘り取り平均の水素量を求めた結果４０原子％であった。
【００７２】
比較例５は、図７（ｃ）に示すように（すなわち凹部を形成していない）、全面を表面粗さＲａが０．０１μｍ以下になるように、テープラップ加工を施し、鏡面に近い状態に仕上げた。
【００７３】
その後、ＤＬＣ膜の形成を行った。ＤＬＣ膜は、炭素をターゲットとしたマグネトロンスパッタリング法により、この基材表面に硬質炭素皮膜をコーティングしたものである。スパッタリングの際のガスにはアルゴンを用いた。水素量を求めた結果０．３原子％であった。
【００７４】
比較例６は、図７（ｃ）に示すように（すなわち凹部を形成していない）、全面を表面粗さＲａが０．０１μｍ以下になるように、テープラップ加工を施し、鏡面に近い状態に仕上げた。なお、ＤＬＣ膜は形成していない。
【００７５】
実施例４は、幅８０μｍ、長さ×１６０μｍの矩形状の凹部を、中央部での最大深さが３μｍ、端部において０．３μｍとなるように形成した。ＤＬＣ膜は実施例１と同様の手法、手順で形成した。ＤＬＣ膜の厚さも同様に０．６μｍであった。
【００７６】
実施例５は、幅８０μｍ、長さ×１６０μｍの矩形状の凹部を、中央部での最大深さが３μｍ、端部において０．３μｍとなるように形成した。ＤＬＣ膜は、炭素ターゲットを用いたマグネトロンスパッタリングにより、サンプル基材の表面にコーティングしたものである。また、このスパッタリングにおいては、ターゲット上にＭｏのプレートを置き、同時にスパッタリングを行うことによりＭｏがＤＬＣ膜中に入るようにした。スパッタリングの際のガスにはアルゴンを用いた。
【００７７】
またＤＬＣ膜の厚さは予め試料の一部をマスクしておき、硬質炭素皮膜が付着した部分とそうでない部分との段差を表面粗さ計で計測することにより求めた結果、０．７μｍであった。
【００７８】
比較例７は、炭素ターゲットを用いたマグネトロンスパッタリングにより、サンプル基材の表面にＤＬＣ膜を形成した。また、このスパッタリングにおいては、ターゲット上に二酸化チタン（ＴｉＯ₂）のプレートを置き、同時にスパッタリングを行うことによりＴｉおよびＯがＤＬＣ膜中に入るようにした。Ｔｉの添加量は１原子％となるようにした。スパッタリングの際のガスにはアルゴンを用いた。
【００７９】
また、ＤＬＣ膜の厚さは予め試料の一部をマスクしておき、硬質炭素皮膜が付着した部分とそうでない部分との段差を表面粗さ計で計測することにより求めた結果、０．７μｍであった。また、凹部は形成していない。
【００８０】
比較例８は、比較例７と同様の手法により、Ｔｉ含有量が２５原子％となるように調整した。
【００８１】
比較例９は、実施例１と同様の手法を用いて、直径φ５０μｍのディンプル状の凹部を、中央部での最大深さが３μｍ、端部においても３μｍとなるように形成した。ＤＬＣ膜は、炭素ターゲットを用いたマグネトロンスパッタリングにより、サンプル基材の表面にコーティングしたものである。スパッタリングの際のガスにはアルゴンと水素の混合ガスを使用し、膜中の水素量を１２原子％となるように調整した。
【００８２】
これら実施例および比較例における望小解析結果を表１および表２に示す。なお、この表１におけるトルクは比較例６を１として比較した値である。
【００８３】
【表１】

【００８４】
【表２】

【００８５】
まず、実施例１〜３と比較例３〜６の結果から、摺動面に凹部を形成するとともに摺動面そのものをＤＬＣ膜とすることで、低いトルクで回転可能となっており、この結果からＤＬＣ膜を摺動面とすることで摩擦係数が低くなっていることがわかる。そして、実施例１と比較例１、および実施例２と比較例２の結果から、それぞれ、同じようにＤＬＣ膜を形成した場合においては、凹部を中心部ほど深く、端部ほど浅くしたもの、すなわち、油膜厚さ分布に応じた凹部を形成したものが、いっそう低いトルクで回転可能となっており、摩擦係数が低くなっていることがわかる。
【００８６】
また、実施例３の結果からは、モリブデンジチオカーバメート入りの潤滑油を用いた場合に、Ｔｉ（原子％（表中はａｔ％と記載））入りのＤＬＣとしたことで、いっそう低いトルクで回転可能となっており、摩擦係数が低くなっていることがわかる。
【００８７】
同様に、実施例５の結果からもＭｏ入りのＤＬＣとしたことで、低いトルクで回転可能となっており、摩擦係数が低くなっていることがわかる。
【００８８】
そして、比較例７および８の結果から、Ｔｉ入りのＤＣＬ膜を設けたとしてもその含有量が少ない場合（比較例７）、および多い場合（比較例８）には、いずれも、金属含有量が適切なはに無いではないため、実施例３および５よりトルクが高くなっていて、摩擦係数の低減効果が少ないことがわかる。
【００８９】
また、比較例９の結果からＤＬＣ膜を摺動面として凹部を設けた場合でも、ＤＬＣ膜中の水素が１２原子％と多い場合には、摩擦係数の低減効果が低いことがわかる。これはまた、比較例４および９の結果と各実施例の結果と合わせれば、水素量は少なければすくなうほどよく、比較例４および９の傾向から水素含有量が１０原子％以下にすることが好ましいことがわかる。
【００９０】
以上説明したように本発明の実施の形態および実施例によれば、クランクシャフト１の摺動面５において、油膜厚さの分布と同じく、中央が深く、端部の方が浅くなるように微細な凹部４を形成し、摺動面にＤＬＣ膜を形成したので、フリクション低減効果を発現するとともに、軸受け３端部での磨耗や焼き付きなどの損傷を抑制するという優れた効果をもたらす。
【００９１】
凹部４の深さを、油膜厚Ｚをｈ、凹部深さをｔとして、その比をｈ／ｔが０．２〜２となるようにしたことで、さまざまな油膜厚さに対応して、より広い作動条件でフリクション低減効果を発現するとともに、軸受け３端部での磨耗や焼き付きなどの損傷を抑制することができる。
【００９２】
さらに、摺動面５のベースの凹凸が凸面の最大高さが１μｍ以下となるようにし、凹部４の最大深さを０．５μｍ〜２０μｍとすることで、金属接触を抑制し、耐磨耗性や耐焼き付き性が向上する。
【００９３】
そして、このクランクシャフト１を内燃機関に用いることにより、クランクシャフト１端部で発生する磨耗や焼き付きを抑制し、微細形状付与なしに比べて、摩擦係数を低下できるという優れた機能が発現される。
【００９４】
すなわち、クランクシャフト１は、シリンダ内を往復動するピストンを有する内燃機関において、ピストンはピストンピンを介してアッパリンクと連結され、アッパリンクはＵＬ間接続ピンを介してロアリンクと揺動可能に連結され、クランクピンに回転可能に装着されたロアリンクと、コントロールリンクとはＬＣ間接続ピンを介して揺動可能に連結され、コントロールリンクのロアリンクとは連結されない接続点の位置を運転条件に応じて変更することにより機関圧縮比を可変制御するリンク機構を構成する。
【００９５】
このリンク機構により、通常のレシプロエンジンに比べてクランクシャフト１に対する入力が増加した場合にも、焼き付き性や磨耗が改善され、さらに摩擦係数が低減することにより摩擦損失を低減できるという優れた効果がもたらされる。
【００９６】
（第２の実施の形態）
第２の実施の形態は、前述した第１の実施の形態の摺動部材を用いた可変圧縮比エンジンである。
【００９７】
図８は可変圧縮比エンジンのクランクシャフト部分とエンジンシリンダ内部の概略断面図である。
【００９８】
この可変圧縮比エンジンは、シリンダ１０１内を往復動するピストン１０２に、ピストンピン１０３を介して第１コンロット１０４と接続されており、この第１コンロッド１０４がコンロッド間接続ピン１０５によって第２コンロッド１０６と揺動可能に接続されている。第２コンロッド１０６は、クランクシャフト１とクランクピン１０７によって回転可能に装着されている。そして第２コンロッド１０６は、さらに、コントロールロッド１０８とコントロールロッド接続ピン１０９により揺動可能に接続され、コントロールロッド１０８の第２コンロッド１０６と接続されていない側の接続部１１０は、このコントロールロッド１０８を移動させて機関圧縮比を可変制御する制御機構（不図示）に接続されている。
【００９９】
このように構成された可変圧縮比エンジンは、コントロールロッド１０８を移動させて、第２コンロッド１０６をクランクピン１０７を中心にして回転させることで、実質的にコンロッド長（クランクピンからピストンピンまでの長さＬ）を変えてピストン１０２のストロークを変化させ、機関圧縮比を変更できるようにしている。
【０１００】
このような第１コンロッド１０４と第２コンロッド１０６の接続部であるコンロッド間接続ピン１０５の部分、第２コンロッド１０６とクランクシャフト１の接続部であるクランクピン１０７の部分、および第２コンロッド１０６とコントロールロッド１０８の接続部であるコントロールロッド接続ピン１０９の部分は、いずれも摺動部であり、この摺動部に本発明を適用した摺動部材、すなわち、摺動面に摺動方向と直交する方向の中心から端部方向へ、深さ分布が油膜厚さ分布に応じて変化する微細な凹部を形成し、かつ凸部の表面にＤＬＣを形成したものである。凹部は、油膜厚さをｈとし、凹部の深さをｔとした場合に、その比ｈ／ｔが０．２〜３となることが好ましい。さらに摺動面は、ベース面の凹凸の最大高さが１μｍ以下、凹部の最大深さが０．５〜２０μｍであることが好ましい。
【０１０１】
これにより、通常のレシプロエンジンに比べて、接続部が多くなっているために、クランクシャフトに加わる力が大きくなる可変圧縮比エンジンにおいても、クランクシャフトのクランクピン部分のほか、その他の摺動部において摩擦係数を小さくすることが可能となり、摺動部における耐焼き付き性や耐磨耗性を改善することができ、エンジンの効率を良くすることが可能となる。
【０１０２】
なお、本第２の実施の形態においては、各ロッドが接続されている摺動部すべてに第１の実施の形態による摺動部材を用いたが、これに変えてクランクシャフトのみを本発明による摺動部材としてもよい。これは、可変圧縮比エンジンにおいては、上記のとおり接続部が多くなっているために、クランクシャフトに加わる力が通常のエンジンと比較して大きくなるため、このクランクシャフトのクランクピン部分の摩擦係数を下げるだけでも効率改善効果が期待できるためである。
【図面の簡単な説明】
【図１】 クランクシャフトの軸受け接触部における油膜厚さ分布を説明するための説明図であり、（ａ）はクランクシャフトの一例を示す平面図、（ｂ）は軸受け接触部における油膜厚さ分布示すグラフである。
【図２】 摺動面における表面荒さを説明するための説明図であり、（ａ）はクランクシャフトと軸受け接触部の断面図、（ｂ）は接触部における摺動面の平面図である。
【図３】 摺動面における凹部の深さ分布の一例を示すグラフである。
【図４】 摺動面の構造を示す図面である。
【図５】 内接２円筒を説明するための説明図である。
【図６】 フリクションマップの一例を示す図面である。
【図７】 微細な凹部パターンを示す図面である。
【図８】 可変圧縮比エンジンのクランクシャフト部分とエンジンシリンダ内部の概略断面図である。
【符号の説明】
１ クランクシャフト
２ 接触部
３ 軸受け
４ 凹部
１０ 外円筒
１１ 鋼製円筒
１２ アルミメタル
２０ 内円筒
１０１ シリンダ
１０２ ピストン
１０３ ピストンピン
１０４ 第１コンロッド
１０５ コンロッド間接続ピン
１０６ 第２コンロッド
１０７ クランクピン
１０８ コントロールロッド
１０９ コントロールロッド接続ピン[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sliding member, a crankshaft using the sliding member, and a variable compression ratio engine using the sliding member.
[0002]
[Prior art]
Conventionally, in order to reduce the friction in the sliding member, it has been performed to form fine depressions, concave surfaces, grooves and the like on the sliding surface of the sliding member.
[0003]
The conventional technology for forming such depressions, concave surfaces, grooves, etc. in the sliding member is to form the sliding surface with respect to the sliding direction in order to reduce the friction of the piston / bore that performs reciprocating sliding. There is one in which a fine recess having a changed depth is formed (see Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-235852
[Problems to be solved by the invention]
However, the conventional sliding member, such as a crankshaft, has a uniform recess, dent, and groove depth with respect to the fine shape in the direction perpendicular to the sliding direction under the sliding condition of rotational movement. There has been a problem that optimization according to the oil film thickness distribution in the section and the oil film holding ability has not been achieved, and the function of low friction is not necessarily fully exhibited. Especially in crankshafts, bending of the shaft occurs, and there is a place where the oil film is thin at the end of the metal material that supports it, and only by forming unevenness with uniform depth, the effect of reducing friction is limited. In addition, there is a problem that damage such as wear and seizure at the bearing end is concerned.
[0006]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a sliding member having a large friction reduction effect and excellent seizure resistance in a sliding member that rotates. Another object is to provide an engine system in which the frictional resistance in the rotating portion is reduced by using the sliding member with reduced friction.
[0007]
[Means for Solving the Problems]
The present invention for solving the above-mentioned problems is in contact with the inner peripheral surface of the outer cylinder, is in contact with the inner peripheral surface via an oil film containing molybdenum thiocarbamate, and is relatively in the circumferential direction. The hard carbon film that is the outer peripheral surface of the rotating inner cylinder and serving as the sliding surface, and the depth distribution from the center of the direction orthogonal to the sliding direction to the end direction is closer to the center. The hard carbon film has a hydrogen atom content of 0.3 atomic% or less, and contains at least 4 to 20 atomic% of metal on the surface thereof. It is a hard carbon film sliding member characterized by these.
[0008]
Moreover, the present invention for solving the above-mentioned problems is a crankshaft of an internal combustion engine using the sliding member.
[0009]
Further, in the present invention for solving the above problems, a first conrot is connected to a piston that reciprocates in a cylinder via a piston pin, and the first conrod can be swung with a second conrod by a connecting pin between connecting rods. The second connecting rod is rotatably mounted by a crankshaft and a crankpin, and the second connecting rod can be swung by a control rod and a control rod connecting pin for changing the rotational position around the crankpin. In a variable compression ratio engine connected to a control mechanism for changing the stroke of the piston by moving the control rod to a connection portion of the control rod that is not connected to the second connecting rod, In the crankpin portion of the crankshaft Variable compression ratio engine characterized by using a serial sliding member.
[0010]
【The invention's effect】
According to the sliding member of the present invention, the sliding surface is made of a hard carbon film, and the depth distribution varies depending on the oil film thickness distribution from the center of the direction perpendicular to the sliding direction to the end direction. Since the changed concave portion is provided, the friction coefficient of the sliding surface can be lowered, the effect of reducing friction is increased, and seizure resistance can be improved.
[0011]
Further, according to the crankshaft of the present invention, it is possible to suppress wear and seizure generated at the end of the crankshaft and reduce the friction coefficient.
[0012]
Furthermore, according to the variable compression ratio engine of the present invention, the seizure property and wear are improved, and the friction loss can be reduced by further reducing the friction coefficient.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0014]
(First embodiment)
First, a crankshaft receiver that is one of the members to which the present invention is applied will be briefly described as an embodiment.
[0015]
FIG. 1 is an explanatory view for explaining the oil film thickness distribution in the bearing contact portion of the crankshaft, FIG. 1 (a) is a plan view showing an example of the crankshaft, and FIG. 1 (b) is in the bearing contact portion. It is a graph which shows oil film thickness distribution.
[0016]
As shown in the drawing, the oil film thickness of the sliding surface of the contact portion 2 (portion in the circle shown) with the bearing of the crankshaft 1 is smaller at the end portion T than at the central portion S.
[0017]
In the first embodiment, in the contact portion 2 of the crankshaft 1, that is, the sliding surface in contact with the bearing, the depth distribution is from the center in the direction perpendicular to the sliding direction to the end portion. A fine concave portion that changes according to the oil film thickness distribution is formed, and further, a hard carbon film is formed on the surface of the convex portion with respect to the bag, that is, the portion that actually becomes the sliding surface 5 It is a thing.
[0018]
Specifically, a diamond-like carbon (DLC) film 6 (see FIG. 4) is used as the hard carbon film.
[0019]
A DLC film (Diamond-Like Carbon Films) is a name given in the sense of a hard carbon film such as diamond. This DLC film usually has a Vickers hardness of Hv 2000 to 4000 and an electric resistance of 10 ⁶ to 10 ¹² Ω · cm, and has properties such as translucency in the infrared region and high refractive index. The crystal structure is amorphous.
[0020]
The characteristics of this DLC film are that it can be coated at a large area, at a low temperature (possible if it is about 150 ° C. or higher), and the obtained film has a very small coefficient of friction. The reason why the DLC film is smooth is considered to have an amorphous structure and no crystal grain boundary.
[0021]
The thickness of the DLC film provided to be the sliding surface is preferably 0.5 to 10 μm. This is because if the thickness is less than 0.5 μm, the adhesion strength between the sliding member itself (usually a metal member) and the DLC film is insufficient, and a part of the DLC film may be peeled off. This is not preferable. On the other hand, if the thickness exceeds 10 μm, the residual stress in the DLC film increases, and there is a possibility of partial peeling in the same manner, which is not preferable.
[0022]
In this DLC film, it is preferable that the hydrogen atoms be 10 atoms or 1% or less.
[0023]
The DLC film has many bonds that are not bonded to the carbon atoms in the DLC film due to the disorder of the structure. In oil, oil molecules are adsorbed based on these bonds, and the friction coefficient decreases. It is considered. However, when a large amount of hydrogen is present in the process environment as in CVD, the hydrogen bonds to the dangling bonds and terminates, making it difficult for oil molecules to be adsorbed, which reduces the coefficient of friction in the lubricating oil. It seems to be difficult. For this reason, it is preferable that the number of hydrogen atoms in the DLC film is 10 atomic% or less and the smaller it is.
[0024]
Furthermore, it is preferable that at least the surface of the sliding surface made of the DLC film contains metal. For this purpose, a metal element is added to the DLC film. As a result, the extreme pressure additive in the lubricating oil is easily adsorbed on the surface and the reaction product is easily formed on the surface, and a hard carbon film sliding member having low friction in the lubricating oil can be obtained.
[0025]
For example, mineral oil and synthetic oil used for engine oil and the like for the purpose of saving fuel are used as base oil, molybdenum dithiocarbamate is 50 to 1000 ppm (mass ratio) in terms of molybdenum, and zinc dithiophosphate is 0.01 in terms of phosphorus. Addition of molybdenum dithiocarbamate and zinc dithiophosphate added as extreme pressure additives to the lubricating oil in hard carbon coatings that do not contain metal and oxygen elements on the surface in lubricating oil containing ~ 0.2% by mass The agent film is not formed, and the friction coefficient becomes higher than that of the steel sliding member that does not form the carbon film, but by including a metal element and an oxygen element on its surface, It is presumed that the extreme pressure additive tends to form a film on the surface, thereby reducing the friction coefficient.
[0026]
As the metal used here, any metal that is industrially used and can be contained in the DLC film can be used. Specifically, for example, at least one metal element selected from Group 2b, 3, 4, 5a, 6a, 7a and Group 8 of the Periodic Table of Elements is 4 to 20 atomic%, especially Ti, Mo, W, Nb, Fe, and the like are widely used industrially, and thus are easy to handle and can provide excellent effects.
[0027]
The amount of the metal to be contained is preferably 4 to 20 atomic% of the metal element. This is because when the amount of the metal element in the surface layer of the DLC film is less than 4 atomic%, the extreme pressure additive is difficult to adhere and the friction becomes high, while when it exceeds 20 atomic%, the bonding state between carbons of the hard carbon film changes. This is because the friction coefficient is increased again because the properties of the film change.
[0028]
Thus, when a metal is contained, it is more preferable to contain oxygen with a metal. It is presumed that by adding metal and oxygen at the same time so that the metal is included in the DLC film surface, the extreme pressure additive can easily form a film on the surface by the cooperative action of the metal and oxygen. Thus, the friction coefficient can be further reduced.
[0029]
The oxygen content is not particularly limited, but it is preferably 6 to 30 atomic%. This is because when the amount of oxygen in the surface layer of the DLC film is less than 6%, the cooperative action with the metal is low and the extreme pressure additive does not adhere, so that the effect of adding oxygen is small. On the other hand, if it exceeds 30 atomic%, the bonding state between carbons of the hard carbon film changes, and the properties of the film change. In addition, the content of the metal when oxygen is contained is the same as the content of the metal alone.
[0030]
2A and 2B are explanatory views for explaining the surface roughness on the sliding surface. FIG. 2A is a cross-sectional view of the crankshaft 1 and the bearing contact portion 2, and FIG. It is a top view of a surface. FIG. 3 is a graph showing an example of the depth distribution of the recesses on the sliding surface.
[0031]
As shown in FIG. 2A, the contact portion 2 that receives the oil film of the crankshaft 1 is provided with a bearing 3 so as to surround the contact portion 2.
[0032]
As shown in FIG. 2B, a recess 4 is formed on the sliding surface 5 of the contact portion 2.
[0033]
The recess 4 is formed such that the depth distribution changes in accordance with the oil film thickness distribution from the center in the direction y perpendicular to the sliding direction x to the end direction. Therefore, as shown in FIG. 3, the depth is deeper at the center and shallower toward the end.
[0034]
The depth of the recess is preferably 0.2 to 2 when the oil film thickness is h, the depth of the recess 4 is t, and the ratio is h / t. For example, when the maximum height of the convex and concave portions on the base surface of the sliding surface 5 is 1 μm or less (the lower limit value is 0, but actually becomes the accuracy limit of the processing machine), It is preferable that the maximum depth of the recess 4 is 0.5 μm to 20 μm.
[0035]
By setting h / t to 0.2 to 2 in this way, a friction reducing effect is exhibited under a wider operating condition, and damage such as wear and seizure at the end of the bearing 3 is suppressed. Since the oil film thickness changes depending on the operating conditions, it is possible to achieve both wear resistance and seizure resistance effects while expressing the effect of reducing friction under a wider range of operating conditions. This is not preferable because it may not be possible to cope with changes in the oil film thickness due to operating conditions.
[0036]
In particular, the crankshaft is operated with a combination of a soft metal such as aluminum metal and a hard metal such as steel. In such a state, the maximum height of the convex portion of the base surface is 1 μm or less, and the concave portion 4 By setting the maximum depth to 0.5 μm to 20 μm, solid contact is suppressed, and wear resistance and seizure resistance are improved. When the maximum height of the convex part exceeds 1 μm and when the maximum depth of the concave part 4 exceeds 20 μm, the wear resistance and seizure resistance are lowered, which is not preferable. In addition, when the maximum depth of the recess 4 is less than 0.5 μm, the effect of reducing friction cannot be obtained sufficiently.
[0037]
Moreover, the length of the opening part of the recessed part 4 shall be 15-500 micrometers on average. If the length of the opening of the recess 4 is less than 15 μm, the oil film retention performance deteriorates, and solid contact occurs, which is not preferable. On the other hand, if it exceeds 500 μm, the opening becomes too wide, the inflow of oil into the recess increases, the load capacity decreases, solid contact occurs, and seizure resistance decreases, which is not preferable.
[0038]
In this way, by setting the average length of the opening of the recess 4 to 15 to 500 μm, not only the above-described reduction of the friction coefficient, suppression of seizure resistance, wear resistance, etc., but also the fine shape An increase in vibration due to the application can be suppressed.
[0039]
Various shapes such as a rectangle and a circle are conceivable as the shape of the recess 4. For example, as shown in FIG. 4A, a circular recess 4 is formed on the sliding surface 5 made of the DLC film 6, and the sliding surface 5 made of the DLC film 6 as shown in FIG. 4B. A form in which a groove-like recess 4 is formed on the surface, and a form in which a rectangular recess 4 is formed on the sliding surface 5 made of the DLC film 6 as shown in FIG.
[0040]
(Example)
Next, on the basis of the embodiment configured as described above, experiments were conducted in which sliding members having various concave shapes were actually manufactured to obtain a friction coefficient.
[0041]
FIG. 5 is an explanatory diagram for explaining the inscribed two cylinders used in this embodiment.
[0042]
As the sliding member used in the experiment, an inscribed two cylinder composed of an outer cylinder 10 and an inner cylinder 20 was used as shown in FIG. The outer cylinder 10 is obtained by press-fitting an aluminum metal 12 having an inner diameter of 45 mm into a steel cylinder 11 having an outer diameter of φ60. On the other hand, the inner cylinder 20 is a quenching and tempering material of steel (SCM435H steel) having an outer diameter of φ44.8 mm, and finished to Ra of 0.01 μm or less. Both the inner cylinder 20 and the outer cylinder 10 have a width of 10 mm.
[0043]
An AC servomotor (not shown) is attached to each of the inner cylinder 20 and the outer cylinder 10 so that the rotation can be controlled independently. Then, by immersing the inner cylinder 20 and the outer cylinder 10 in the oil bath, an oil film was formed between the inner cylinder 20 and the outer cylinder 10.
[0044]
In the experiment, when the radial load is 500 kg, the oil temperature is 80 ° C., the relative sliding speed is 0.2 to 12 m / s, the average speed is changed from −2 to 2 m / s, and the rotational torque is measured by the torque sensor attached to the inner cylindrical shaft. Then, the tangential force was calculated, and the coefficient of friction was obtained by dividing by the radial load. The average speed is (u1 + u2) / 2 when the inner cylinder speed is u1 and the outer cylinder speed u2. Similarly, the relative sliding speed is (u1-u2).
[0045]
The measured coefficient of friction was organized as a friction map with the vertical axis representing relative sliding speed and the horizontal axis representing average speed. Based on these friction maps, we performed a small-scale analysis of the friction coefficient.
[0046]
FIG. 6 is an example of a friction map. As shown in the figure, the friction map is such that the vertical axis represents relative sliding speed and the horizontal axis represents average speed, and the friction coefficient is arranged on the map as a contour map. From this map, it can be seen what friction coefficient distribution is in the contact portion 2 on the inner cylindrical surface. In FIG. 6, 123 pieces of data are collected.
[0047]
The coefficient of friction was analyzed as a rotational torque. The desired analysis was calculated by the following formula.
[0048]
Small hope analysis [0049]
[Expression 1]

[0050]
(Examples and Comparative Examples)
In Examples 1 to 3 and Comparative Examples 1 to 6, automobile engine oil 5W-30SJ was used as the lubricating oil. In Example 5, automotive engine oil 0W-20 (containing molybdenum dithiocarbamate) was used as the lubricating oil.
[0051]
In each of the examples, a concave fine shape was formed on the inner cylindrical surface of φ44.8 mm (comparative example was not formed). The concave fine shape was formed by mask blasting. That is, using a photolithographic technique, a concave fine shape is formed on a resin mask, the resin mask is affixed to the cylindrical surface, and alumina abrasive grains having an average particle diameter of 20 μm are then applied from the projection nozzle to the workpiece. The distance was set to 100 mm, and projection was performed under the conditions of a projection flow rate of 100 g / min and a projection pressure of 0.4 MPa to obtain a fine concave portion. Thereafter, the bulge of the edge portion formed around the concave fine shape was removed with a tape wrap film having a particle size of 9 μm to obtain a desired shape.
[0052]
Thereafter, a DLC film was formed. The DLC film is obtained by coating the base material surface with a hard carbon film by a magnetron sputtering method using carbon as a target. Argon was used as the gas during sputtering. The sample temperature during film formation was about 250 ° C.
[0053]
In this method, the DLC film can also be formed in the recess, but the DLC film may or may not be formed in the recess. However, when the DLC film is also formed in the recess, it is necessary to prevent the recess from being filled with the formed DLC film.
[0054]
In addition, the recess fine shape depth of the example (after the DLC film formation in the example) was 1 μm and the area ratio was 5% in any sample.
[0055]
FIG. 7 is a drawing showing a recess pattern of an example and a comparative example.
[0056]
In Example 1, as shown in FIG. 7A, a dimple having an opening with a diameter of 120 μm was formed so that the maximum depth was 3 μm at the center and 0.3 μm at the end.
[0057]
Thereafter, tape lapping was performed to remove edges around the dimples, and then a hard carbon film was coated on the surface of the substrate by a magnetron sputtering method using carbon as a target. Argon was used as the gas during sputtering. The sample temperature during film formation was about 250 ° C.
[0058]
When the surface roughness of the sliding surface after the DLC film was formed was measured, the roughness of the coating surface was Ra 0.03 μm without finishing. The thickness of the DLC film was 0.6 μm as a result of obtaining a step difference between the portion where the DLC film was adhered and the portion where the DLC film was adhered and measuring it with a surface roughness meter. It was.
[0059]
The amount of hydrogen in the DLC film was determined by secondary ion mass spectrometry (SIMS). As a result of digging a depth of about 20 nm from the surface and determining the average amount of hydrogen, it was 0.3 atomic%.
[0060]
Similar to Example 1, Comparative Example 1 is a dimple pattern with an opening having a diameter of 120 μm (see FIG. 7A), and its depth is 3 μm from the center to the end, unlike Example 1. Formed as follows. The DLC film was formed by the same method and procedure as in Example 1. Similarly, the thickness of the DLC film was 0.6 μm.
[0061]
In Example 2, as shown in FIG. 7B, a rectangular recess having a width of 80 μm and a length of 320 μm is formed so that the maximum depth at the center is 3 μm and the end is 0.3 μm. did. The DLC film was formed by the same method and procedure as in Example 1. Similarly, the thickness of the DLC film was 0.6 μm.
[0062]
Similar to Example 2, Comparative Example 2 is a rectangular pattern having a width of 80 μm and a length of 320 μm (see FIG. 7B), and the depth is 3 μm from the center to the end, unlike Example 2. It formed so that it might become. The DLC film was formed by the same method and procedure as in Example 1. Similarly, the thickness of the DLC film was 0.6 μm.
[0063]
In Example 3, as shown in FIG. 7B, a rectangular pattern with a width of 80 μm and a length of 320 μm has a maximum depth of 2 μm at the center and a depth of 0.3 μm at the end. It formed so that it might become.
[0064]
The DLC film is formed by coating the surface of the sample base material by magnetron sputtering using a carbon target. Further, in this sputtering, a titanium dioxide (TiO ₂ ) plate was placed on the target, and at the same time, sputtering was performed so that Ti and O entered the DLC film. Argon was used as the gas during sputtering.
[0065]
The thickness of the DLC film was obtained by masking a part of the sample in advance and measuring the step between the portion with the hard carbon film attached and the portion with no hard carbon film with a surface roughness meter. there were.
[0066]
The abundance ratio of each element in the DLC film was determined by Auger electron spectroscopy. In the actual Auger electron spectroscopy, first, the surface of the sample was etched with Ar gas for a certain period of time in the analyzer, and then the depth of the etched portion was obtained by taking out from the analyzer. This was assigned linearly with respect to the total etching time to obtain the etching rate. The obtained etching rate was 3.8 nm per minute.
[0067]
Next, the time for digging a certain depth based on this etching rate is calculated back, and the operation of digging the sample for that time and analyzing the composition by Auger electron spectroscopy is repeated a predetermined number of times, The distribution (depth profile) of each element in the depth direction was determined. Ten points were measured from a point 5 nm from the sample surface to a depth of 50 nm every 5 nm, and the average was regarded as the “abundance ratio of each element in the surface layer”. As a result of this analysis, 7 atomic% Ti and 24 atomic% oxygen were present in the film.
[0068]
In Comparative Example 3, as shown in FIG. 7A, a dimple-shaped recess having an opening with a diameter of 120 μm was formed so as to have a depth of 3 μm from the center to the end. A DLC film is not formed.
[0069]
In Comparative Example 4, as shown in FIG. 7C (that is, no recess is formed), the entire surface is tape-wrapped so that the surface roughness Ra is 0.01 μm or less, and is close to a mirror surface. Finished.
[0070]
Thereafter, a DLC film was formed by plasma CVD. Benzene was used as the carbon source. The sample temperature was 200 ° C.
[0071]
The amount of hydrogen in the membrane was determined by secondary ion mass spectrometry (SIMS). A depth of about 20 nm was dug from the surface and the average amount of hydrogen was determined to be 40 atomic%.
[0072]
In Comparative Example 5, as shown in FIG. 7C (that is, no recess is formed), the entire surface is tape-wrapped so that the surface roughness Ra is 0.01 μm or less, and is close to a mirror surface. Finished.
[0073]
Thereafter, a DLC film was formed. The DLC film is obtained by coating a hard carbon film on the surface of the base material by magnetron sputtering using carbon as a target. Argon was used as the gas during sputtering. As a result of obtaining the amount of hydrogen, it was 0.3 atomic%.
[0074]
In Comparative Example 6, as shown in FIG. 7C (that is, no recess is formed), the entire surface is tape-wrapped so that the surface roughness Ra is 0.01 μm or less, and is close to a mirror surface. Finished. A DLC film is not formed.
[0075]
In Example 4, a rectangular recess having a width of 80 μm and a length of 160 μm was formed such that the maximum depth at the center was 3 μm and the end was 0.3 μm. The DLC film was formed by the same method and procedure as in Example 1. Similarly, the thickness of the DLC film was 0.6 μm.
[0076]
In Example 5, a rectangular recess having a width of 80 μm and a length of 160 μm was formed such that the maximum depth at the center was 3 μm and the end was 0.3 μm. The DLC film is formed by coating the surface of the sample base material by magnetron sputtering using a carbon target. Further, in this sputtering, a Mo plate was placed on the target, and sputtering was performed at the same time so that Mo entered the DLC film. Argon was used as the gas during sputtering.
[0077]
The thickness of the DLC film was obtained by masking a part of the sample in advance and measuring the step between the portion with the hard carbon film attached and the portion with no hard carbon film with a surface roughness meter. there were.
[0078]
In Comparative Example 7, a DLC film was formed on the surface of the sample substrate by magnetron sputtering using a carbon target. Further, in this sputtering, a titanium dioxide (TiO ₂ ) plate was placed on the target, and at the same time, sputtering was performed so that Ti and O entered the DLC film. The amount of Ti added was 1 atomic%. Argon was used as the gas during sputtering.
[0079]
Further, the thickness of the DLC film was determined by measuring a step difference between a portion where the hard carbon film was adhered and a portion where the hard carbon film was adhered with a surface roughness meter in advance by masking a part of the sample. Met. Moreover, the recessed part is not formed.
[0080]
Comparative Example 8 was adjusted by the same method as Comparative Example 7 so that the Ti content was 25 atomic%.
[0081]
In Comparative Example 9, a dimple-like recess having a diameter of 50 μm was formed using the same method as in Example 1 so that the maximum depth at the center was 3 μm and the end was 3 μm. The DLC film is formed by coating the surface of the sample base material by magnetron sputtering using a carbon target. A mixed gas of argon and hydrogen was used as a gas during sputtering, and the amount of hydrogen in the film was adjusted to 12 atomic%.
[0082]
Tables 1 and 2 show the results of the desired analysis in these examples and comparative examples. The torque in Table 1 is a value compared with Comparative Example 6 as 1.
[0083]
[Table 1]

[0084]
[Table 2]

[0085]
First, from the results of Examples 1 to 3 and Comparative Examples 3 to 6, it was possible to rotate with a low torque by forming a recess on the sliding surface and using the sliding surface itself as a DLC film. It can be seen that the friction coefficient is lowered by using the DLC film as the sliding surface. And, from the results of Example 1 and Comparative Example 1, and Example 2 and Comparative Example 2, respectively, when the DLC film was formed in the same manner, the concave portion was deeper at the center and shallower at the end, That is, it can be seen that the concave portion corresponding to the oil film thickness distribution can be rotated with a lower torque and the friction coefficient is low.
[0086]
Further, from the results of Example 3, when using a lubricating oil containing molybdenum dithiocarbamate, the DLC containing Ti (atomic% (shown as at% in the table)) was used, so that rotation with a lower torque was achieved. It can be seen that the coefficient of friction is low.
[0087]
Similarly, from the results of Example 5, it can be seen that the use of DLC with Mo enables rotation with a low torque and a low friction coefficient.
[0088]
From the results of Comparative Examples 7 and 8, even when a Ti-containing DCL film was provided, the content was low when the content was low (Comparative Example 7) and when the content was high (Comparative Example 8). Is not appropriate, the torque is higher than in Examples 3 and 5, and it can be seen that the effect of reducing the friction coefficient is small.
[0089]
Further, it can be seen from the results of Comparative Example 9 that even when the concave portion is provided with the DLC film as a sliding surface, the effect of reducing the friction coefficient is low when hydrogen in the DLC film is as large as 12 atomic%. In addition, when the results of Comparative Examples 4 and 9 are combined with the results of each Example, the smaller the amount of hydrogen, the better. The hydrogen content should be 10 atomic% or less from the tendency of Comparative Examples 4 and 9. Is preferable.
[0090]
As described above, according to the embodiments and examples of the present invention, the sliding surface 5 of the crankshaft 1 is fine so that the center is deep and the end is shallow, as with the oil film thickness distribution. Since the concave portion 4 is formed and the DLC film is formed on the sliding surface, a friction reducing effect is exhibited and an excellent effect of suppressing damage such as wear and seizure at the end of the bearing 3 is brought about.
[0091]
By setting the depth of the recess 4 to h, the oil film thickness Z as h, and the recess depth as t, and the ratio of h / t is 0.2 to 2, corresponding to various oil film thicknesses, A friction reducing effect is exhibited under a wider operating condition, and damage such as wear and seizure at the end of the bearing 3 can be suppressed.
[0092]
Further, the unevenness of the base of the sliding surface 5 is set so that the maximum height of the convex surface is 1 μm or less, and the maximum depth of the concave portion 4 is 0.5 μm to 20 μm, thereby suppressing metal contact and wear resistance. And seizure resistance are improved.
[0093]
By using this crankshaft 1 for an internal combustion engine, the wear and seizure generated at the end of the crankshaft 1 is suppressed, and an excellent function of reducing the coefficient of friction is achieved compared to the case where no fine shape is imparted. .
[0094]
That is, the crankshaft 1 is an internal combustion engine having a piston that reciprocates in a cylinder. The piston is connected to the upper link via a piston pin, and the upper link can swing with the lower link via a UL connection pin. The lower link, which is connected and rotatably mounted on the crank pin, and the control link are connected so as to be swingable via the LC connection pin, and the position of the connection point that is not connected to the lower link of the control link is determined as an operating condition. A link mechanism that variably controls the engine compression ratio is configured by changing according to the above.
[0095]
With this link mechanism, even when the input to the crankshaft 1 is increased compared to a normal reciprocating engine, the seizure and wear are improved, and the friction loss is reduced by reducing the friction coefficient. Brought about.
[0096]
(Second Embodiment)
The second embodiment is a variable compression ratio engine using the sliding member of the first embodiment described above.
[0097]
FIG. 8 is a schematic cross-sectional view of the crankshaft portion of the variable compression ratio engine and the inside of the engine cylinder.
[0098]
The variable compression ratio engine is connected to a piston 102 that reciprocates in a cylinder 101 via a piston pin 103 and a first connecting rod 104, and the first connecting rod 104 is connected to a second connecting rod 106 by an connecting rod connecting pin 105. And is swingably connected. The second connecting rod 106 is rotatably mounted by the crankshaft 1 and the crankpin 107. The second connecting rod 106 is further swingably connected by a control rod 108 and a control rod connecting pin 109, and the connecting portion 110 of the control rod 108 that is not connected to the second connecting rod 106 is connected to the control rod 108. Is connected to a control mechanism (not shown) that variably controls the engine compression ratio.
[0099]
In the variable compression ratio engine configured as described above, the control rod 108 is moved and the second connecting rod 106 is rotated around the crankpin 107, so that the length of the connecting rod is substantially reduced (from the crankpin to the piston pin). The length L) is changed to change the stroke of the piston 102 so that the engine compression ratio can be changed.
[0100]
The connecting rod connecting pin 105 portion which is the connecting portion between the first connecting rod 104 and the second connecting rod 106, the crank pin 107 portion which is the connecting portion between the second connecting rod 106 and the crankshaft 1, and the second connecting rod 106 The part of the control rod connecting pin 109 which is the connecting part of the control rod 108 is a sliding part, and the sliding member to which the present invention is applied to this sliding part, that is, the sliding surface is orthogonal to the sliding direction. In the direction from the center to the end direction, a fine concave portion whose depth distribution changes according to the oil film thickness distribution is formed, and DLC is formed on the surface of the convex portion. The recess preferably has a ratio h / t of 0.2 to 3 when the oil film thickness is h and the depth of the recess is t. Further, the sliding surface preferably has a maximum height of irregularities of the base surface of 1 μm or less and a maximum depth of the recesses of 0.5 to 20 μm.
[0101]
As a result, the number of connecting parts is larger than that of a normal reciprocating engine, so even in a variable compression ratio engine where the force applied to the crankshaft is large, in addition to the crankpin part of the crankshaft, other sliding parts Thus, it is possible to reduce the friction coefficient, improve seizure resistance and wear resistance at the sliding portion, and improve engine efficiency.
[0102]
In the second embodiment, the sliding members according to the first embodiment are used for all the sliding portions to which the rods are connected. Instead, only the crankshaft is used according to the present invention. A sliding member may be used. This is because, in a variable compression ratio engine, since the number of connections is increased as described above, the force applied to the crankshaft is larger than that in a normal engine. This is because an efficiency improvement effect can be expected simply by lowering the value.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram for explaining the oil film thickness distribution at a bearing contact portion of a crankshaft, (a) is a plan view showing an example of a crankshaft, and (b) is an oil film thickness distribution at a bearing contact portion. It is a graph to show.
2A and 2B are explanatory views for explaining surface roughness on a sliding surface, in which FIG. 2A is a cross-sectional view of a crankshaft and a bearing contact portion, and FIG. 2B is a plan view of the sliding surface at the contact portion;
FIG. 3 is a graph showing an example of a depth distribution of a concave portion on a sliding surface.
FIG. 4 is a drawing showing a structure of a sliding surface.
FIG. 5 is an explanatory diagram for explaining an inscribed two cylinder.
FIG. 6 is a drawing showing an example of a friction map.
FIG. 7 is a drawing showing a fine recess pattern.
FIG. 8 is a schematic cross-sectional view of a crankshaft portion and an engine cylinder inside a variable compression ratio engine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Crankshaft 2 Contact part 3 Bearing 4 Recess 10 Outer cylinder 11 Steel cylinder 12 Aluminum metal 20 Inner cylinder 101 Cylinder 102 Piston 103 Piston pin 104 First connecting rod 105 Connecting rod connecting pin 106 Second connecting rod 107 Crank pin 108 Control rod 109 Control rod connection pin

Claims (4)

Abutting the inner circumferential surface of the outer cylinder, contacting the inner circumferential surface via an oil film containing molybdenum thiocarbamate, and the outer circumferential surface of the inner cylinder rotating relative to the circumferential direction. A hard carbon film as a moving surface;
Provided on the sliding surface, from the center in the direction perpendicular to the sliding direction to the end direction, the depth distribution is deeper toward the center, and has a plurality of recesses shallower toward the end,
The hard carbon film sliding member, wherein the hard carbon film has a hydrogen atom content of 0.3 atomic% or less and contains at least 4 to 20 atomic% of metal on the surface thereof. The sliding surface, the 1μm or less the maximum height of the irregularities of the flat portion, claim 1 Symbol mounting sliding member of maximum depth of the recess, characterized in that a 0.5 to 20 [mu] m. A crankshaft for an internal combustion engine, wherein the sliding member according to claim 1 or 2 is used. A first conrot is connected to a piston that reciprocates in the cylinder via a piston pin, the first connecting rod is swingably connected to a second connecting rod by a connecting pin between connecting rods, and the second connecting rod is connected to a crankshaft and a crank. The second connecting rod is rotatably mounted by a pin, and the second connecting rod is swingably connected by a control rod for changing a rotational position around the crank pin and a control rod connecting pin, and the second connecting rod of the control rod In a variable compression ratio engine to which a control mechanism for changing the stroke of the piston is moved by moving the control rod to a connection part on the side not connected,
3. A variable compression ratio engine, wherein the sliding member according to claim 1 is used at least in the crank pin portion of the crank shaft.

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