JP3890495B2 - Sliding part for internal combustion engine and internal combustion engine using the same - Google Patents

Description

【００５６】
このような表面粗さを備えたシリンダーボアとピストンスカートにおいて、荷重を受ける摺動面間に形成される潤滑油膜は、ピストンの往復動によって起こるクリアランスに潤滑油を巻き込む流量と、荷重に起因する圧力によってその隙間から漏れ出る流量とのバランスによって決定される。この実施例において、運転される頻度が高く、摩擦損失が燃料消費量に影響する割合が大きい上記運転条件である２０００ｒｐｍ、１／４負荷の運転条件では、完全平滑面で考えれば、油膜厚さｈ＝８μｍのとき、そのバランスが得られる。そのとき、隙間から漏れ出ようとする油は、摺動する２つの面の表面形状によって形成される空間を流れ、流動抵抗が小さい部分からより多く流れる。また、その流れは層流なので、潤滑油の流量は隙間の３乗に比例する。よって、流動方向に連続した隙間の広い空間があると、流動抵抗が大きく低下する。この実施例においては、ｂ＜Ｌなので、溝と溝とが２面間にあっても連結されることが確率的に非常に小さいので、隙間の大きな空間が摺動方向に対して連続する可能性がほとんどなく、隙間から漏れ出ようとする油は、溝２１に沿って接触部位外に漏れ出るか、シリンダーボアの溝と溝の間のベース面２０と、ピストンスカートの溝と溝の間のベース面２０との間の比較的狭い流路を必ず通過する必要がある。これは、従来のクロスハッチ状の表面形状に比較すると、隙間から漏れ出ようとする油の流動抵抗を大きくする効果がある。このことによって、全体の凹凸は大きくても、摺動面間の最接近距離が小さくならず、粗さ先端の流体せん断力を大きくすることなく、凹部分の流体せん断力が小さくなるので摩擦損失を減らすことができる。
【００５７】
この実施例の場合も、実施例1と同様に説明される。すなわち、ｂ＜Ｌの条件の場合、溝に沿って漏れ出す潤滑油は、溝の間隔に較べて十分に大きいため、油の流れの多くは隙間分布の狭い部分を通過するので、潤滑油の流れの流動抵抗の合計は、隙間分布を図１０のように２次元形状と考えて、その形状に直交した層流圧力流れに対する抵抗で近似できる。この流動抵抗を粗さ形状に対して計算し、完全平滑面で考えて油膜厚さｈ＝８μｍのときの流動抵抗と同じになる２面間の接近状態を求めた。溝と溝の間のベース面の粗さ形状を３次元的にランダムと考えれば、その流動抵抗は平滑な場合で近似できるので平滑とした。この２面間の近接状態がその運転条件での２面の摺動状態に対応する。
【００５８】
また、その時のせん断摺動による摩擦損失は、油膜厚さの逆数の面積分に比例すると近似できる。ここで、溝と溝の間のベース面の粗さ形状は油膜厚さの逆数への影響が大きく、無視することはできない。よって、油膜厚さの逆数の合計は、溝と溝の間のベース面のランダムな粗さ形状と微細溝形状を合成した形状に対して計算した。粗さ形状を変化させ、そのときの合成粗さの高さの累積分布の例を図４に示し、計算データを整理したパラメータを示す。
【００５９】
溝の間のベース面の粗さ高さ相当の値をｒ、溝の深さに相当する値をＨ、溝の面積割合の相当値をＣとおいた。これらのパラメータで整理し、摩擦損失に相当する油膜厚さの逆数の面積分値Ｔと流動抵抗の等しい完全平滑面でのＴの値をＴsmoothとして、その比の計算結果を図５〜７に示す。
【００６０】
図５には、溝の深さに相当する値Ｈ／ｈに対して、ｒ／ｈの値およびの値をパラメータとして整理した結果を示す。ｒが小さい場合、Ｈが大きいほどＴは小さくなるが、ｒが大きい場合、逆の傾向となる。
【００６１】
図６には、溝の面積割合の相当値Ｃに対して、ｒ／hの値およびＨ／ｈの値をパラメータとして整理した結果を示す。この場合もｒが小さい場合、Ｃが大きいほどＴは小さくなるが、ｒが大きい場合は逆の傾向となる。
【００６２】
図７には、溝の間のベース面の粗さ高さ相当の値ｒ／ｈに対して、Ｃの値をパラメータとして整理した結果を示す。ｒ／ｈがある値以上大きいと急激にＴの値は大きくなり、Ｃの値が大きいほど、小さなｒ／ｈでＴは急激に大きくなる。
【００６３】
以上により、この実施例の表面粗さ形状によって、摩擦損失が減少するのは、以下の理由であることがわかる。
【００６４】
流動抵抗が隙間の３乗に逆比例するので、大きな凹部が存在しても、潤滑油の流れが必ず狭い部分を通過するような形状とし、その流動抵抗を大きくすることによって、平滑面と同等の流動抵抗を得るための部品表面の最接近距離があまり小さくならない。しかし、溝の存在は流動抵抗を必ず小さくするので、最接近距離は平滑面の場合より必ず接近する。一方、溝の存在はせん断率（隙間の逆数と相対速度の積）の小さな部分の面積を広くする。よって、結果として最接近距離が小さくなった部分のせん断率が大きくなった分より、溝の存在によるせん断率の小さな部分の面積を広くする効果が上回って、全体の摩擦損失が低下する。よって、溝の間のベース面の粗さ高さが大きいと、溝の存在による流動抵抗を小さくし、最接近距離を小さくする影響が溝の存在によるせん断率の小さな部分の面積を広くする効果を上回って、逆に溝の存在によって摩擦が大きくなる。摩擦は隙間に逆比例するので、ｒが油膜厚さｈに近くなると、摩擦増大の影響が大きくなることがわかる。つまり、２面の表面形状で形成される２部品間の隙間形状の、隙間から漏れる流れの方向に対する圧力勾配に対する流動抵抗が２つの面が完全平滑面で形成される隙間形状での流動抵抗と等しい状態のときに、２部品間の隙間の逆数を面積分した値が、その完全平滑面で形成される隙間形状での値よりも小さいときに摩擦損失が低減することがわかる。
【００６５】
よって、それぞれ２面の溝のまわりの平滑面の凹凸の最大高さの合計が油膜厚さよりも小さいときに、ｂ＜Ｌの形状であれば、溝の面積が大きく深いほど摩擦損失が低減する。また、それぞれ２面の溝のまわりの平滑面の凹凸の最大高さの合計が油膜厚さよりも小さいときに、ｂ＜Ｌの形状であれば、２面の表面形状で形成される２部品間の隙間形状の、隙間から漏れる流れの方向に対する圧力勾配に対する流動抵抗が、２つの面が完全平滑面で形成される隙間形状での流動抵抗と等しい状態のときに２部品間の隙間の逆数を面積分した値がその完全平滑面で形成される隙間形状での値よりも小さくなるということである。
【００６６】
当該実施例では、２面の溝のまわりのベース面における凹凸の最大高さの合計が１．５μｍであり、油膜厚さ８μｍよりも小さいため、摩擦を小さくすることができる。原理から明きらかなように、溝の大きさの関係は、ここで示したものだけでなく、ｂをピストンスカートの溝の幅としても効果があることがわかる。つまり、それぞれ２面の溝のまわりのベース面の凹凸の最大高さの合計が油膜厚さよりも小さい時に、ｂ＜Ｌの形状であることが本発明の効果が得られる条件であり、本発明の特徴である。
【００６７】
また、溝の幅が流体潤滑油膜が発生している範囲より大きければ、上記原理を考えれば、その効果がなくなることは自明である。また、溝の深さは必要以上に深くても摩擦は低減せず、あまりに溝の中の容積が大きいと潤滑油の圧縮性の影響が現れ、部品表面の最接近距離が小さくなる場合も考えられる。
【００６８】
また、以上の作用効果の原理から、いかなる摺動部位でも、相対運動する２つの面間が流体である潤滑剤で潤滑され、その部品間の潤滑油の流れが層流であり、ある荷重を支えつつ摺動する２つの部品の表面形状に関しては、上記構成とすることにより、上記実施例で示した作用効果が得られることが明らかである。
【００６９】
また、この実施例のように、一方の部品、ここではピストンスカートの硬度が、もう一方の部品、ここではシリンダーボアの硬度よりも小さい場合、直接接触があると、摩耗によってピストンスカート側の表面が削り取られる。このとき、この実施例のように、硬い方の窪みの直径をｂとして、ｂ＜Ｌの関係を持たせることで、小さなｂであっても摩耗によって溝がなくなるようなことが少なく、Ｌが小さく設定できるので、ピストンスカート側の溝割合を大きく設定してもこの関係が崩れることがなく、柔らかい側の溝の幅を大きくすることによって溝自体が摩耗によってなくなる時間を長くすることができ、摩擦低減効果を長期間維持することができる。さらに、運転初期のなじみ効果を期待すれば、当初、ピストンスカート側の溝と溝の間のベース面の凹凸の最大高さが油膜厚さよりも大きくても、なじみ終了後に油膜厚さよりも小さくなれば、当該実施例と同等の効果が得られる。
【００７０】
さらに、例えば自動車用内燃機関のピストン摺動面であれば、その相対摺動速度は機関の最高回転時に２０ｍ／ｓを超え得る。このような条件の時には、摺動摩擦発熱に基づく温度上昇による粘度低下に起因して、油膜厚さが小さくなり、部品に作用する慣性力などによる部品の弾性変形などによって、直接接触の頻度が高くなる。また、他の機構であっても、このような高速摺動時に例えば異物の混入などによって部品間の直接接触が発生すれば、その摺動速度が高いために、局部的な冷却作用があることが部品の耐焼き付き性を確保するために有効である。この実施例のように溝状の凹部を形成することで、溝の中に所定の体積の潤滑油が存在できるので、冷却効果が期待できる。また、混入した異物を溝内に捕捉して、部品間の直接接触を低減することもできる。また、往復摺動しているので、摺動が停止する上下死点においては、流体潤滑油膜の形成能力が低下し、油膜厚さが小さくなり直接接触の発生が多くなる。このとき、上記のような溝状の凹部が摺動面に存在することによって、局部的冷却、境界膜の破断面への潤滑剤の連続した供給が可能となり、耐摩耗性、耐スカッフ性も向上させることができる。
【００７１】
上記作用効果は、他の摺動部位、例えば、内燃機関のシリンダーボアとピストンリングの摺動面に対しても、油膜厚さの値に対して同様の関係で表面形状を形成すれば、同様の効果が得られる。
【００７２】
さらに、内燃機関を前記自動車用のものと限定すれば、その常用運転条件において、摺動速度が比較的大きいので、摩擦損失寄与度が大きいストローク中央部のタイミングの油膜厚さは、ピストンスカートが８μｍ程度、ピストンリングが１μｍ程度となる。よって、例えば以下の表面形状とすることによって、摩擦損失を低減することができる。
【００７３】
すなわち、シリンダーボアについては、上記同様の素材および加工方法により、最大高さｔ（Ｒｙ）：０．５μｍの平滑なベース面２０上に、深さ３〜５μｍ、幅１０〜３０μｍ（平均値ｂ＝２０μｍ）、ピッチ６０〜１００μｍ（平均値：８０μｍ）、溝間の最小距離の平均値Ｌ'が６０μｍの溝２１を形成する。
【００７４】
ピストンスカートについては、上記同様に深さ１０〜１５μｍ（平均値：１３μｍ）、幅５０〜８０μｍ（平均値：６０μｍ）、ピッチ１１０〜１８０μｍ（平均値：１５０μｍ）、溝間の最小距離の平均値Ｌが９０μｍの溝２１を形成する。
【００７５】
ピストンリングにはクロムめっきが施され、その表面硬度は１０００Ｈｖ程度であり、ピストンリングについては、ホーニング加工により研磨を施ことによって、非常に微細で交差状の研磨溝からなる平均粗さＲａ：０．０３μｍ、最大高さＲｙ：０．５μｍという平滑な平面とした。
【００７６】
ピストンリングとシリンダーボア間の油膜厚さが１．０μｍであることと、ピストンリングには溝はないものの、溝と溝の間隔を無限大とみれば、ｂ＜Ｌの関係が成り立ち、ピストンリングとシリンダーボア間の摺動接触幅が０．５ｍｍ程度であり、シリンダーボアの溝幅ｂに溝と溝の間隔Ｌ’を加えたｂ＋Ｌ’より接触幅ａが十分大きいことから、シリンダーボア−ピストンリング間でも、シリンダーボア−ピストンスカート間と同様に摩擦損失が低減できる。このように、シリンダーボア−ピストンリング間でｂ＋Ｌ’＜ａの関係、シリンダーボア−ピストンスカート間でｂ（ボア）＜Ｌ（スカート）が成り立っているので、長期にわたって摩擦損失低減効果を持続させることができる。
【図面の簡単な説明】
【図１】（ａ） 軸受メタルおよびクランクシャフトの形状及び構造を示す横断面図でる。
（ｂ） 図１（ａ）に示した軸受メタルを収納した軸受ボックスを示す斜視図である。
（ｃ） 図１（ａ）における線Ｃ−Ｃについての水平断面図である。
【図２】（ａ），（ｂ）および（ｃ）は本発明に係わる摺動部品としてクランクシャフトおよび軸受メタル（アルミ合金製、Ｈｖ１００）の摺動表面の微細形状を示すそれぞれ斜視図、平面図および断面図である。
【図３】図２に示した表面形状を２次元形状と見なした該略図である。
【図４】粗さ高さの累積分布を示すグラフである。
【図５】凹部の深さに相当する値Ｈ／ｈと摩擦損失の関係を示すグラフである。
【図６】凹部の面積割合の相当値Ｃと摩擦損失の関係を示すグラフである。
【図７】ベース部の粗さ高さ相当の値ｒ／ｈと摩擦損失の関係を示すグラフである。
【図８】内燃機関におけるシリンダーボアとピストンリングとピストンスカートを示す概略図である
【図９】（a）（ｂ）および（ｃ）は本発明に係わる摺動部品としてシリンダーボアおよびピストンスカートの摺動表面の微細形状を示すそれぞれ斜視図、平面図および断面図である。
【図１０】図９に示した表面形状を２次元形状と見なした該略図である。
【図１１】従来のクランクシャフトの摺動面形状を示すグラフである。
【図１２】従来のピストンスカートの表面形状を示す概略図である。
【図１３】（ａ）および（ｂ）は従来のシリンダーボア内面の表面形状を示す概略図である。
【符号の説明】
１０，２０ ベース面
１１ 窪み
２１ 溝
３１ 軸受メタル
３２ クランク
３５ シリンダーボア
３６ ピストンリング
３７ ピストンスカート[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a friction reduction technology based on a fine shape formed on a sliding surface of a machine part. For example, a sliding part for a reciprocating internal combustion engine that can reduce friction loss of a reciprocating internal combustion engine for an automobile. It relates to a surface roughness structure.
[0002]
[Prior art]
As a sliding part of a reciprocating internal combustion engine, for example, as a surface shape of a bearing metal that supports a crankshaft, Japanese Patent Laid-Open No. 2000-504089 has a lubricating surface having a predetermined depth and area on a sliding surface. As shown in FIG. 11, for example, the sliding surface of the crankshaft, which is a counterpart component of such a bearing metal, is disclosed, and a deep valley portion on a fine uneven surface is continuous over a wide range. The above-mentioned floating pocket exists on the surface of the bearing metal, and the seizure resistance at the time of insufficient lubrication or high rotation and high load is improved by the effect of the oil reservoir.
[0003]
Further, for example, as shown in FIG. 12, the sliding surface of the piston skirt is processed so that the ten-point average roughness Rz is 20 μm or more by a method such as turning or roller rolling. However, the oil sump also has a part that remains, and the effect of the oil sump also improves the seizure resistance during insufficient lubrication and high rotation and load. Yes. Further, the sliding surface of the cylinder bore which is the mating part is processed into a cross-hatch shape as shown in FIGS. 13A and 13B, for example, and has a wide range where a rough valley of the unevenness is deep. It is continuous.
[0004]
[Problems to be solved by the invention]
However, in the surface roughness structure of the sliding parts as described above, the thickness of the lubricating oil film formed between the sliding surfaces receiving the load is caught in the gap between the parts due to relative motion. It is determined by the balance between the flow rate of the lubricating oil and the flow rate of the lubricating oil leaking from the gap due to the pressure caused by the load. At this time, the oil that is about to leak from the gap flows through the space formed by the surface shapes of the two surfaces to be repaired, and flows more from the portion where the flow resistance is small. Further, since the flow is a laminar flow, the flow rate is proportional to the third power of the gap. Therefore, if there is a space having a wide gap continuously in the flow direction, the flow resistance is greatly reduced.
[0005]
Here, when sliding in a combination as described above, the oil reservoir dent formed in the bearing metal or piston skirt is where the deep valleys on the sliding surface of the crankshaft or cylinder bore are continuous over a wide range. The oil that has a high probability of connecting the parts and tries to leak from the gap selectively flows through the large area of the continuous gap, so that the flow resistance is reduced, thereby reducing the oil film thickness, There is a problem that the shearing force increases and the friction loss increases, and solving such a problem has been a problem in improving the efficiency of the internal combustion engine by reducing the friction between the sliding surfaces.
[0006]
OBJECT OF THE INVENTION
The present invention has been made by paying attention to the above-mentioned problems in the sliding parts for conventional reciprocating internal combustion engines, and can prevent a decrease in the flow resistance of the lubricating oil flowing between the sliding surfaces of the two parts. Another object of the present invention is to provide a sliding component for a reciprocating internal combustion engine that can secure the oil film thickness of the lubricating oil and reduce the friction loss, thereby improving the efficiency of the internal combustion engine.
[0007]
[Means for Solving the Problems]
  A sliding component for an internal combustion engine according to claim 1 of the present invention has a surface roughness structure on a sliding surface of two components which are relatively moved in the internal combustion engine and are lubricated with lubricating oil in a laminar flow state between the sliding surfaces. And when both sliding surfaces have a dimple-like depression surrounded by the base surface on the base surface having the unevenness of the maximum height t, and both sliding surfaces are made completely smooth. The closest approach distance between the sliding surfaces when the inflow amount of the lubricating oil due to the relative movement to the gap formed between the two parts and the outflow amount of the lubricating oil due to the pressure generated between the two parts is balanced as h. When defined, h is greater than t, at least one of the average depths of the recesses on each sliding surface is greater than h, and the maximum diameter of the recesses on both sliding surfaces is within the range where the lubricating oil film is formed The average value of the maximum diameter of the depressions on one sliding surface is d, and the other sliding It is characterized in that d <L, where L is the average value of the minimum distances between the recesses on the surface, and this configuration in the sliding part for an internal combustion engine solves the above-described conventional problems. As a means to do.
[0008]
  As an embodiment of the sliding component according to claim 1 of the present invention, in the sliding component according to claim 2, the maximum diameter of the recess in the sliding surface having the higher surface hardness of both sliding surfaces. And d <L, where d is the average value of the minimum distance between the depressions on the sliding surface with the lower surface hardness, and the embodiment is as follows. The sliding component according to the present invention is configured such that D> d, where D is the average value of the maximum diameter of the recesses on the sliding surface with the lower surface hardness of both sliding surfaces. In the sliding component, the base surface of the sliding surface with the lower surface hardness has a maximum height of the unevenness of the base surface of the sliding surface with the higher surface hardness of both sliding surfaces smaller than h. The maximum height of the projections and depressions is greater than h.
[0009]
  Further, in the sliding component according to claim 5, the component having a higher surface hardness of the sliding surface is a crankshaft, and the component having a lower surface hardness is a bearing metal that supports the crankshaft. At this time, as described in claim 6, both parts are those of an internal combustion engine for automobiles, and the maximum height of the unevenness of the base surface on the crankshaft sliding surface is 1 μm or less. The average depth can be 1 to 50 μm, the average depth of the depressions on the bearing metal sliding surface can be 1 to 50 μm, and the average value of the maximum diameters can be 1 mm or less. The sliding part according to claim 7 is characterized in that the part having the higher surface hardness of the sliding surface is a cylinder bore, and the part having the lower surface hardness is a piston skirt. When both parts are those of an internal combustion engine for an automobile as described in claim 8, the maximum height of the unevenness of the base surface on the sliding surface of the cylinder bore is 1 μm or less, and the average depth of the recess is 1 to 50 μm The average depth of the depressions on the sliding surface of the piston skirt can be 1 to 50 μm and the average value of the maximum diameter thereof can be 1 mm or less. In the sliding component according to claim 9, the surface hardness of the sliding surface is The higher part is a piston ring, and the lower part of the surface hardness is a cylinder bore. At this time, both parts are used in an automobile. The maximum height of the unevenness of the base surface on the piston ring sliding surface is 1 μm or less, the average depth of the recess is 1 to 50 μm, the average depth of the recess on the cylinder bore sliding surface is 1 to 50 μm, The average value of the maximum diameter can be 1 mm or less. Further, in the sliding component according to claim 11, the component having the higher surface hardness of the sliding surface is the cylinder bore, and the component having the lower surface hardness is the piston ring. As described in claim 12, when both parts are those of an internal combustion engine for an automobile, the maximum height of the unevenness of the base surface on the cylinder bore sliding surface is 1 μm or less, and the average depth of the depression is 1 to 50 μm, the average depth of the depressions on the sliding surface of the piston ring can be 1 to 50 μm, and the average value of the maximum diameter can be 1 mm or less.
[0010]
  A sliding part for an internal combustion engine according to claim 13 of the present invention relates to a surface roughness structure on the sliding surfaces of a cylinder bore, a piston skirt and a piston ring of the internal combustion engine, and the sliding surface of the cylinder bore. Has a recess with a depth of 1 to 50 μm and an average value d of maximum diameter of 50 μm or less, surrounded by a base surface having irregularities with a maximum height of 1 μm or less, and the cylinder bore The sliding surface of the piston skirt that slidably contacts is surrounded by a base surface having irregularities with a maximum height of 5 μm or less, surrounded by the base surface, the depth is 1 to 50 μm, and the average maximum diameter is 1 mm or less. The sliding surface of the piston ring that has a recess and is in sliding contact with the cylinder bore is surrounded by a base surface having irregularities with a maximum height of 1 μm or less, and the depth is 1 to 50 μm. When the average value of the maximum diameters is 50 μm or less and the average value of the minimum distance between the pits of the piston skirt is L1, and the average value of the minimum distance between the pits of the piston ring is L2, d <L1 and A feature is that d <L2.
[0011]
  Further, the sliding component for an internal combustion engine according to claim 14 of the present invention is a surface roughness on the sliding surfaces of two components which are relatively moved in the internal combustion engine and are lubricated with lubricating oil in a laminar flow state between the sliding surfaces. In relation to the height structure, both sliding surfaces have a plurality of grooves that form an angle of 45 ° or more with the sliding direction on the base surface having irregularities with maximum heights t1 and t2 (μm), respectively, without intersecting each other. H / t1 and H / t2 are larger than 1 where the maximum depth of the grooves on both sliding surfaces is H (μm), and the maximum width of the grooves is the contact length in the sliding direction in which the lubricating oil film is formed. When the average value of the maximum width of the grooves on one sliding surface is b (μm) and the average value of the minimum distance between the grooves on the other sliding surface is L (μm), b < As an embodiment of the surface roughness structure of the sliding part according to the claim, the structure of In the sliding parts concerned, when both sliding surfaces are completely smooth surfaces, the amount of lubricating oil inflow due to relative movement into the gap formed between the two parts and the amount of lubricating oil due to the pressure generated between the two parts When the closest approach distance between the sliding surfaces when the amount of outflow is balanced is defined as h, the t1 and t2 are configured to be smaller than h. Similarly, in the sliding component according to claim 16, The average value of the maximum width of the groove on the sliding surface with the higher surface hardness of both sliding surfaces is b, and the average value of the minimum distance between the grooves on the sliding surface with the lower surface hardness is L. In the sliding component according to claim 17, the average value of the maximum width of the grooves on the sliding surface having the lower surface hardness of both sliding surfaces is represented by B. When B> b, the sliding part according to claim 18 is used. Information, better part of the high surface hardness of the sliding surface is a cylinder bore, toward the surface of the component low hardness is configured is a piston skirt. In the sliding part according to claim 19, both parts are those of an internal combustion engine for an automobile, the unevenness of the base surface on the sliding surface of the cylinder bore and the piston skirt is set to 1 μm or less in the maximum roughness indication Ry, and the cylinder The average depth of the groove in the bore is 1 to 50 μm, the average value of the minimum distance between the grooves is 100 μm or less, the average depth of the groove in the piston skirt is 5 to 50 μm, and the average value of the minimum distance between the grooves is 1 mm. It can be as follows.
[0012]
  Furthermore, as an embodiment, in the sliding part according to claim 20, when the sliding surface of the piston skirt and piston ring and the cylinder bore is assumed to be a completely smooth surface, the relative to the gap formed between the parts. The closest distance between the sliding surfaces when the inflow of lubricating oil due to movement balances the outflow of lubricating oil due to the pressure generated between the parts is h, and the piston skirt at the center of the piston vertical stroke The smaller value of h on the two sliding surfaces of the cylinder bore and piston ring and cylinder bore is set to h0, the average value of the maximum width of the groove in the cylinder bore is b, and the average value of the minimum distance between the grooves is When L ′ is the average value of the minimum distance between the grooves in the cylinder bore and L is the contact width in the sliding direction of the piston ring and the cylinder bore, The sliding part according to claim 21, wherein the maximum height of the irregularities on the base surface of the ston skirt, piston ring and cylinder bore is not more than h0, and b> L, b + L ′ <a. The base surface of the sliding surface of the skirt, piston ring and cylinder bore has irregularities with a maximum height of 1 μm or less, the average value b of the maximum width of the groove in the cylinder bore is 1 to 50 μm, and the average depth of the groove is 1 to 10 μm, the average value L ′ of the minimum distance between the grooves is 100 μm or less, the average value B of the maximum groove width in the piston skirt is 50 μm or more, the average depth of the grooves is 5 to 50 μm, and the minimum distance between the grooves An average value L is 50 μm or more and 1 mm or less, and this configuration in the surface roughness structure of a sliding component for an internal combustion engine is used to solve the conventional problems described above. It is characterized as a means.
[0013]
  An internal combustion engine according to the present invention is characterized in that the above-described sliding component of the present invention is used.
[0014]
【The invention's effect】
  According to the sliding component for an internal combustion engine according to the present invention, a dimple-like depression or an angle of 45 ° or more with the sliding direction is formed on the base surface having the above-described configuration, in particular, where both sliding surfaces have a maximum height t. When the two sliding surfaces are completely smooth surfaces, the closest distance between the sliding surfaces is defined as h when the inflow and outflow amounts of lubricant to the gap between the two parts are balanced. In this case, h is larger than t, and one or both of the average depths of the depressions on each sliding surface are larger than h, or the maximum diameter of the depressions on both sliding surfaces is formed on the lubricating oil film. Less than the shortest span of the range, the maximum groove depth on both sliding surfaces is greater than t, and the maximum groove width on both sliding surfaces is the contact length in the sliding direction in which the lubricating oil film is formed Or the average value of the maximum width of the groove on one sliding surface on the other sliding surface By making it smaller than the average value of the minimum distance between the grooves, the depressions and grooves that function as an oil reservoir formed on one sliding surface are connected via the depressions and grooves on the other sliding surface. The flow resistance is reduced, the required lubricating oil film thickness can be ensured, and sliding parts for internal combustion engines such as bearing metal and crankshaft, piston skirt and cylinder bore In addition, the friction loss between the piston ring and the cylinder bore can be reduced, and the engine output efficiency can be increased.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described based on examples.
[0016]
Example 1
First, an example in which the surface roughness structure in the sliding component according to the present invention is applied to the sliding surfaces of the bearing metal and the crankshaft of the internal combustion engine for automobiles will be described. Note that the internal combustion engine here was one having a displacement of about 2000 cc and a maximum rotational speed of about 6000 rpm.
[0017]
  FIG. 1 shows the shape of the bearing metal and the crankshaft. FIG. 1 (a) is a cross-sectional view of the bearing metal and the crankshaft, and FIG. 1 (b) is a bearing box containing the bearing metal. A perspective view and FIG.1 (c) are horizontal sectional views about line CC of FIG.1 (a). The bearing metal 31 is a pair of half-cylindrical cylinders, and supports the crankshaft 32 from above and below. The axial length S1 shown in FIG. 1C is the circumferential length. It is shorter than S2 and has the shortest span of the sliding surface in this embodiment.
[0018]
Since the lubricating oil is sufficiently supplied between the sliding surfaces of the bearing metal 31 and the crankshaft 32 and the relative rotational motion is always generated, the fluid lubricating oil film f is formed. In this case, under normal operating conditions that are frequently used, in this embodiment, the frequency of operation is high, and under the operating conditions of 2000 rpm, 1/4 load, which is a condition in which the friction loss has a large influence on the fuel consumption, the oil film thickness Becomes 2 μm.
[0019]
The crankshaft 32 is made of steel and is adjusted to a hardness of about Hv500 by heat treatment or the like. By applying this material to polishing using a wrapping tape, an average consisting of extremely fine and intersecting polishing grooves is formed. An extremely smooth base surface 10 having a roughness Ra: 0.08 μm and a maximum height (t) Ry: 0.5 μm was formed.
[0020]
Next, this smooth base surface 10 was irradiated with a pulsed laser beam using a YAG laser device, thereby forming independent fine dimple-like depressions 11 as shown in FIG. In this embodiment, the depression 11 has a substantially spherical shape, and the depth k of the depression 11_{1 ~ N}Is 3 to 5 μm, the average value is 4 μm (k = 4 μm), and the diameter d of the recess 11_{1 ~ N}Is 10-30 μm, the average value is 20 μm (d = 20 μm), and the area ratio of the recess 11 is 30-80%.
[0021]
On the other hand, the bearing metal 31 forms a base surface 10 having irregularities with a maximum height t (Ry) of 1.0 μm by broaching (or boring), and a pulsed laser beam is applied to the base surface 10. The same depression 11 was formed by irradiation. Depth k of this depression 11_{1 ~ N}Is 3 to 10 μm, the average value is 7 μm (k = 7 μm), and the diameter d of the recess 11_{1 ~ N}Is 50 to 80 μm, the average value is 60 μm (d = 60 μm), and the pitch P of the recesses 11_{1 ~ N}Was 110 to 180 μm and an average of 150 μm (the average value L of the minimum distance between the recesses L = 30 μm).
[0022]
In a crankshaft and bearing metal having such a surface roughness, the thickness of the lubricating oil film formed between the sliding surfaces receiving the load depends on the flow rate of the lubricating oil involved in the clearance caused by the crank rotation and the load. It is determined by the balance with the flow rate leaking from the gap due to the resulting pressure. In this embodiment, under the above operating conditions in which the ratio of the friction loss affecting the fuel consumption is large, the balance is obtained when the oil film thickness is h = 2 μm, considering a completely smooth surface. At that time, the oil that is about to leak from the gap flows through the space formed by the surface shapes of the two sliding surfaces, and flows more from the portion where the flow resistance is small. Further, since the flow is laminar, the flow rate of the lubricating oil is proportional to the third power of the gap. Therefore, if there is a wide space with a continuous gap in the flow direction, the flow resistance is greatly reduced. In this embodiment, the average value d of the maximum diameter of the recess 11 on the crankshaft sliding surface is 20 μm, while the average value L of the minimum distance between the recesses 11 on the bearing metal sliding surface is 30 μm (d <L). Therefore, it is probable that the depressions are very much less likely to be connected, so there is almost no possibility that a space with a large gap will continue in any direction. It is necessary to pass through a relatively narrow flow path between the base surface 10 around the crankshaft recess 11 and the base surface 10 around the bearing metal recess 11, and the oil leaking from the gap Increases flow resistance. As a result, even if the overall unevenness is large, the closest approach distance between the sliding surfaces is not reduced, and the fluid shear force of the concave portion is reduced without increasing the fluid shear force at the tip of the roughness. Friction loss can be reduced.
[0023]
Next, this effect is examined quantitatively.
[0024]
As in this embodiment, when the condition of d <L is satisfied, the flow of lubricating oil always passes through a narrow portion of the gap distribution, so that the total flow resistance is a two-dimensional shape as shown in FIG. Therefore, it can be approximated by resistance to laminar pressure flow perpendicular to the unevenness. This flow resistance was calculated with respect to the roughness shape, and an approaching state between the two surfaces, which was the same as the flow resistance when the oil film thickness h = 2 μm, was obtained in consideration of a completely smooth surface. If the roughness shape of the base surface between the depressions is considered to be three-dimensionally random, the flow resistance can be approximated in a smooth case, and thus smooth. The proximity state between the two surfaces corresponds to the sliding state of the two surfaces under the operating conditions.
[0025]
Further, the friction loss due to shear sliding at that time can be approximated to be proportional to the area of the reciprocal of the oil film thickness. Here, the influence of the roughness shape of the base surface between the depressions on the reciprocal of the oil film thickness is large and cannot be ignored. Therefore, the sum of the reciprocal of the oil film thickness was calculated with respect to a shape obtained by synthesizing the random roughness shape of the base surface between the depressions and the dimple shape of the depressions. FIG. 4 shows an example (Abbott's load curve) of the cumulative distribution of the height of the combined roughness at the time when the roughness shape is changed, and shows parameters in which the calculation data is arranged.
[0026]
A value corresponding to the roughness height of the base surface between the recesses was set as r, a value corresponding to the depth of the recess was set as H, and an equivalent value of the area ratio of the recess was set as C. Organized with these parameters, the area value T of the reciprocal of the oil film thickness corresponding to the friction loss and the T value on a perfectly smooth surface with the same flow resistance are taken as Tsmooth, and the calculation results of the ratios are shown in FIGS. Show.
[0027]
FIG. 5 shows the result of arranging the value of r / h and the value thereof as parameters with respect to the value H / h corresponding to the depth of the depression. When r is small, T is smaller as H is larger. However, when r is large, the tendency is reversed.
[0028]
FIG. 6 shows the result of arranging the values of r / h and H / h as parameters with respect to the equivalent value C of the area ratio of the depressions. In this case as well, when r is small, T decreases as C increases, but when r is large, the reverse trend occurs.
[0029]
  FIG. 7 shows the result of arranging the C value as a parameter with respect to the value r / h corresponding to the roughness height of the base surface between the depressions. When r / h is larger than a certain value, the value of T increases rapidly, and as the value of C increases, T increases rapidly with a smaller r / h.
[0030]
From this examination, it is understood that the friction loss is reduced by the surface roughness shape according to the present invention for the following reason.
[0031]
Since the flow resistance is inversely proportional to the third power of the gap, even if there is a large depression, the flow of the lubricating oil always passes through a narrow part, and the flow resistance is increased so that the flow resistance equivalent to that of a smooth surface is obtained. The closest distance between the sliding surfaces to obtain is not so small. However, since the presence of the depression necessarily reduces the flow resistance, the closest distance is always closer than in the case of a smooth surface. On the other hand, the presence of the recess widens the area of the small shear rate (product of the reciprocal of the gap and the relative speed). Accordingly, as a result, the effect of widening the area of the portion having a small shear rate due to the presence of the depression exceeds the amount by which the shear rate of the portion where the closest approach distance is reduced is increased, and the overall friction loss is reduced. Therefore, if the roughness height of the base surface between the recesses is large, the flow resistance due to the presence of the recesses is reduced, and the effect of reducing the closest approach distance is to increase the area of the portion with a small shear rate due to the presence of the recesses. On the contrary, the friction increases due to the presence of the depression. Since friction is inversely proportional to the gap, it can be seen that the effect of increased friction increases as r approaches the oil film thickness h. That is, the flow resistance with respect to the pressure gradient with respect to the direction of the flow leaking from the gap in the gap shape between the two parts formed by the surface shape of the two surfaces is the flow resistance in the gap shape in which the two surfaces are formed as completely smooth surfaces. It can be seen that the friction loss is reduced when the value obtained by dividing the reciprocal of the gap between the two parts by area is smaller than the value in the gap shape formed by the completely smooth surface in the same state.
[0032]
Therefore, when the sum of the maximum heights of the unevenness of the smooth surface around the two depressions is smaller than the oil film thickness, if d <L, the friction loss decreases as the depression area increases and becomes deeper. . Further, when the sum of the maximum heights of the unevenness of the smooth surface around the depressions on each of the two surfaces is smaller than the oil film thickness, if the shape of d <L, the distance between the two parts formed with the surface shape of the two surfaces When the flow resistance with respect to the pressure gradient with respect to the direction of the flow leaking from the gap is equal to the flow resistance in the gap shape formed by two completely smooth surfaces, the reciprocal of the gap between the two parts is That is, the value for the area is smaller than the value for the gap shape formed by the completely smooth surface.
[0033]
In this example, the sum of the maximum heights of the irregularities on the base surface around the depressions on the two surfaces is 1.5 μm, which is smaller than the oil film thickness, so that the friction can be reduced. As is clear from the principle, the relationship between the sizes of the recesses is not limited to that shown here, and it can be seen that d (= 20 μm) is effective even when the diameter of the recess on the bearing side is used. In other words, when the sum of the maximum heights of the unevenness of the base surface around each of the two depressions is smaller than the oil film thickness, it is a condition for obtaining the effect of the present invention that the shape of d <L. It is the feature.
[0034]
If the size of the recess is large and larger than the range where the fluid lubricating oil film is generated, it is obvious that the effect is lost in view of the above principle. Further, even if the depth of the dent is deeper than necessary, the friction is not reduced. If the volume of the dent is too large, the influence of the compressibility of the lubricating oil appears, and the closest distance on the part surface may be reduced.
[0035]
In addition, from the above principle of action and effect, any sliding part is lubricated with a lubricant that is a fluid between the two surfaces that move relative to each other, and the flow of lubricating oil between the components is laminar, and a certain load is applied. With respect to the surface shapes of the two parts that slide while being supported, it is apparent that the effects described in the above embodiments can be obtained by adopting the above configuration. In this embodiment, the two depressions are formed as independent dimples having a substantially spherical shape by irradiating a laser beam. However, even in the irregular shape as shown in FIG. In principle, it is clear that the same effect can be obtained as long as it is.
[0036]
Also, as in this embodiment, when the hardness of one part, here the bearing metal, is smaller than the hardness of the other part, here the crankshaft, if there is direct contact, the surface on the bearing metal side will be worn by wear. Scraped off. At this time, as in this embodiment, by setting the diameter of the hard dent as d and having a relationship of d <L, even if d is small, the dent is less likely to disappear due to wear. Since it can be set small, this relationship will not be lost even if the dent ratio on the bearing side is set large, and by increasing the diameter of the dent on the low hardness side, the time that the dent itself disappears due to wear can be lengthened. The friction reducing effect can be maintained for a long time. Furthermore, if the familiarity effect at the initial stage of operation is expected, even if the maximum height of the irregularities on the base surface around the bearing metal recess is larger than the initial oil film thickness, The same effects as in the embodiment can be obtained.
[0037]
Further, for example, in the case of a crank bearing or piston sliding surface of an automobile internal combustion engine, the relative sliding speed can exceed 20 m / s at the maximum engine speed. Under such conditions, the oil film thickness decreases due to the decrease in viscosity due to temperature rise based on sliding frictional heat generation, and the frequency of direct contact increases due to elastic deformation of the component due to inertial force acting on the component. Become. Also, in other mechanisms, if direct contact between components occurs due to, for example, foreign matter mixed during such high-speed sliding, the sliding speed is high, so there is a local cooling effect. This is effective for ensuring the seizure resistance of the steel. By forming a dimple-like depression as in this embodiment, a certain amount of lubricating oil can be present in the depression, so that a cooling effect can be expected. In addition, it is possible to reduce the direct contact between the components by capturing the mixed foreign matter in the recess.
[0038]
In particular, for the case where the oil film thickness is reduced as compared with the normal operating condition, such as a crank bearing of an internal combustion engine for automobiles under a high temperature condition of high rotation, for example, the substantial viscosity due to the cooling effect described above. It is also effective in improving wear resistance by improving the resistance.
[0039]
Further, if limited to the crank bearing of an internal combustion engine for automobiles, the oil film thickness with respect to normal operating conditions does not deviate so much from the value shown in this embodiment, so the numerical value of the shape shown in this embodiment A common effect can be obtained.
[0040]
(Example 2)
The above-described effects can be obtained in the same manner in other sliding members and other sliding portions. For example, as shown in FIG. 8, the surface shapes of the cylinder bore 35 and the piston ring 36 of the internal combustion engine and the sliding surfaces of the cylinder bore 35 and the piston skirt 37 are similar to the oil film thickness value. If this is formed, the same effect can be obtained. Further, since the piston slides back and forth with respect to the cylinder, the fluid lubricating oil film forming ability is reduced at the top and bottom dead center where the sliding stops, the oil film thickness is reduced, and the occurrence of direct contact is increased. At this time, the presence of the dimple-like depression as described above on the sliding surface enables local cooling and continuous supply of lubricant to the fracture surface of the boundary film, and also provides wear resistance and scuff resistance. Can be improved.
[0041]
Further, if the internal combustion engine is limited to the one for the automobile, the sliding speed is relatively large under the normal operating conditions, so the oil film thickness at the timing of the stroke center portion where the friction loss contribution is large is the piston skirt. About 8 μm and the piston ring is about 1 μm. Therefore, for example, the friction loss can be reduced by using the following surface shape. In addition, if it is limited to those for automobiles, the oil film thickness under normal operating conditions does not deviate so much from the value shown here, so a common effect can be obtained by setting the above-mentioned numerical surface shape. .
[0042]
That is, the cylinder bore is made of cast iron, and is made to a hardness of about Hv300 by heat treatment, etc., the piston skirt is made of aluminum alloy, about Hv150, the piston ring is chrome plated, and the surface hardness is about Hv1000. is there.
[0043]
First, the cylinder bore is polished by a honing process, and a smooth flat surface (base surface) having an average roughness Ra: 0.13 μm and a maximum height Ry (t): 1 μm composed of very fine intersecting polishing grooves. It was. Next, a YAG laser device is used to irradiate this plane with a pulsed laser beam, thereby obtaining an average value of 20 μm (d = 20 μm) at a depth of 3 to 5 μm, a diameter of 10 to 30 μm, and a pitch of 60 to 100 μm. A dimple-like depression having a substantially spherical shape of 80 μm (average value L = 30 μm of the minimum distance between the depressions) was formed.
[0044]
With respect to the piston ring, the same YAG laser is irradiated to a plane (base surface) having an average roughness Ra: 0.13 μm and a maximum height Ry (t): 1 μm made of similar intersecting polishing grooves by the same processing. Thus, a dimple-like depression having a substantially spherical shape with a depth of 3 to 5 μm, a diameter of 10 to 30 μm, an average value of 20 μm (d = 20 μm), and an area ratio of 30 to 80% was formed.
[0045]
Further, with respect to the piston skirt, the above smooth surface (base surface) is formed by grinding, and then the smooth surface is irradiated with a pulsed YAG laser to obtain an average value of 13 μm at a depth of 10 to 15 μm and a diameter of 50 μm. Recesses having an average value of 60 μm at ˜80 μm and an average value of 150 μm at a pitch of 110 to 180 μm (average value L = 30 μm of the minimum distance between the recesses) were similarly formed.
[0046]
In the above, the relationship of d (ring) <L (bore) is established between the cylinder bore and the piston ring, and the relationship of d (bore) <L (skirt) is established between the cylinder bore and the piston skirt. Can be reduced.
[0047]
Moreover, friction loss can be reduced by setting it as the following surface shapes, and also the following effects are acquired.
[0048]
That is, by using the same material and the same processing method as described above, each of the cylinder bores, the piston rings, and the piston skirt sliding surfaces having the same size are formed, and the average value L1 of the minimum distance between the recesses in the piston skirt is The pitch of the recesses in the piston ring was 60 to 100 μm, the average value was 80 μm, and the average value L2 of the minimum distance between the recesses was 30 μm. That is, the feature is that d (bore) <L1 (skirt) and d (bore) <L2 (ring), and the diameter of the recess of the cylinder bore is smaller than the other recesses.
[0049]
The cylinder bore has a relatively large oil film thickness because the sliding speed is relatively high when the ring and skirt slide along the stroke center of the cylinder bore. Therefore, wear is difficult to occur. Therefore, even if the depression of the cylinder bore is formed small, it is unlikely that the cylinder bore disappears due to wear. Therefore, since the depression of the cylinder bore can be made small, the ratio of the depression on the ring and skirt can be increased while maintaining the relationship of d (bore) <L1 (skirt) and d (bore) <L2 (ring). Even if the depressions on the ring and skirt become small due to wear, the effect of reducing friction loss can be maintained for a long time.
[0050]
(Example 3)
An example in which the surface roughness structure of the sliding component according to the present invention is applied to the sliding surfaces of a piston skirt and a cylinder bore of an internal combustion engine for an automobile will be described. Here, an internal combustion engine having a displacement of about 2000 cc and a maximum rotation speed of about 6000 rpm will be described.
[0051]
The piston skirt slides at a high speed with respect to the cylinder bore, and the stroke direction is reversed at the top dead center and the bottom dead center. In the vicinity of this reverse position, the sliding parts of each other are instantaneously exposed to boundary lubrication, but the friction loss contribution is large in the central part of the stroke. Since a high speed relative motion is always generated, a fluid lubricating oil film is formed. Under normal operating conditions that are frequently used, in this embodiment, the frequency of driving is high, and the operating conditions in which friction loss contributes to the fuel consumption are large. The oil film thickness at the center of the stroke with a large stroke is about 8 μm between the piston skirt and the cylinder bore, and about 1 μm between the piston ring and the cylinder bore.
[0052]
Here, on the cylinder bore surface, as shown in FIG. 9, a fine groove 21 perpendicular to the sliding direction is formed on a smooth base surface 20 having a maximum unevenness height t (Ry) of 0.5 μm. Has been. The depth H ′ of the groove 21_{1 ~ N}Is 3-5 μm, the average value H ′ is 4 μm, its width b_{1 ~ N}Is 10 to 30 μm, the average value b is 20 μm, and the pitch P ′ of the grooves 21_{1 ~ N} Is 50 to 100 μm, the average value P ′ is 80 μm, the average value L ′ of the minimum distance between the grooves is 60 μm, and the area ratio of the grooves 21 is 10 to 60%.
[0053]
On the other hand, grooves 21 that are orthogonal to the sliding direction are also formed on the surface of the piston skirt, and the base surface 20 between these grooves has a maximum height t (Ry) of irregularities of 1.0 μm. It has become a smooth surface. The groove 21 has a depth H_{1 ~ N}
Is 10 to 15 μm, the average value H is 13 μm, and its width B_{1 ~ N}Is 50 to 80 μm, the average value B is 60 μm, the pitch P is 110 to 180 μm, the average value P is 150 μm, and the average value L of the minimum distance between the grooves is 90 μm.
[0054]
The cylinder bore is made of cast iron, adjusted to a hardness of about Hv300 by heat treatment or the like, and the piston skirt is made of an aluminum alloy and has a hardness of about Hv150. The cylinder bore is polished by a honing process, so that it has an extremely smooth base surface with an average roughness Ra: 0.03 μm and a maximum height t (Ry): 0.5 μm consisting of extremely fine and intersecting polishing grooves. After forming 20, the base surface 20 was irradiated with a YAG laser, thereby forming grooves 21 having the above-mentioned dimensions that do not intersect with other grooves at the above-mentioned intervals. For the piston skirt, the base surface 2 having the above-described irregularities (maximum height t = 1.0 micron) is formed by grinding, and the groove 21 having the above-mentioned dimensions and intervals is formed by turning the surface. It was formed so as not to cross the groove. Table 1 summarizes the dimensions of the grooves 21 formed in the sliding surfaces of the cylinder bore and the piston skirt in this way.
[0055]
[Table 1]

[0056]
In the cylinder bore and piston skirt having such a surface roughness, the lubricating oil film formed between the sliding surfaces that receive the load is caused by the flow rate of the lubricating oil in the clearance caused by the reciprocating motion of the piston and the load. It is determined by the balance with the flow rate leaking from the gap due to the pressure. In this embodiment, the oil film thickness is considered to be a perfectly smooth surface under the operation conditions of 2000 rpm and ¼ load, which are the above-described operation conditions where the frequency of operation is high and the friction loss affects the fuel consumption is large. The balance is obtained when h = 8 μm. At that time, the oil that is about to leak from the gap flows through the space formed by the surface shapes of the two sliding surfaces, and flows more from the portion where the flow resistance is small. Further, since the flow is laminar, the flow rate of the lubricating oil is proportional to the third power of the gap. Therefore, if there is a wide space with a continuous gap in the flow direction, the flow resistance is greatly reduced. In this embodiment, since b <L, it is probable that the groove and the groove are connected even if they are between the two surfaces, so there is a possibility that a space with a large gap is continuous in the sliding direction. Almost no oil that leaks out of the gap leaks out of the contact area along the groove 21, or the base surface 20 between the groove of the cylinder bore and the base between the groove of the piston skirt. It must pass through a relatively narrow flow path between the surface 20. This has the effect of increasing the flow resistance of the oil that is about to leak out from the gap as compared to the conventional cross-hatch surface shape. As a result, even if the overall unevenness is large, the closest approach distance between the sliding surfaces is not reduced, and the fluid shear force of the concave portion is reduced without increasing the fluid shear force at the tip of the roughness. Can be reduced.
[0057]
This embodiment will be described in the same manner as in the first embodiment. That is, in the case of b <L, the lubricating oil leaking along the groove is sufficiently larger than the groove interval, so that most of the oil flow passes through a narrow gap distribution portion. The total flow resistance of the flow can be approximated by the resistance to the laminar pressure flow orthogonal to the shape, assuming that the gap distribution is a two-dimensional shape as shown in FIG. This flow resistance was calculated with respect to the roughness shape, and the approaching state between the two surfaces, which was the same as the flow resistance when the oil film thickness was h = 8 μm, was obtained by considering a completely smooth surface. If the roughness shape of the base surface between the grooves is considered to be three-dimensionally random, the flow resistance can be approximated in a smooth case, so that it is smooth. The proximity state between the two surfaces corresponds to the sliding state of the two surfaces under the operating conditions.
[0058]
Further, the friction loss due to shear sliding at that time can be approximated to be proportional to the area of the reciprocal of the oil film thickness. Here, the roughness shape of the base surface between the grooves has a great influence on the reciprocal of the oil film thickness and cannot be ignored. Therefore, the sum of the reciprocal number of the oil film thickness was calculated with respect to the shape obtained by synthesizing the random roughness shape and the fine groove shape of the base surface between the grooves. FIG. 4 shows an example of the cumulative distribution of the height of the combined roughness at the time when the roughness shape is changed, and shows parameters obtained by arranging the calculation data.
[0059]
A value corresponding to the roughness height of the base surface between the grooves was set as r, a value corresponding to the depth of the groove was set as H, and an equivalent value of the area ratio of the grooves was set as C. Organized with these parameters, the area value T of the reciprocal of the oil film thickness corresponding to the friction loss and the T value on a perfectly smooth surface with the same flow resistance are taken as Tsmooth, and the calculation results of the ratios are shown in FIGS. Show.
[0060]
FIG. 5 shows the result of arranging the value of r / h and the value thereof as parameters with respect to the value H / h corresponding to the depth of the groove. When r is small, T is smaller as H is larger. However, when r is large, the tendency is reversed.
[0061]
FIG. 6 shows the result of arranging the values of r / h and H / h as parameters with respect to the equivalent value C of the groove area ratio. In this case as well, when r is small, T decreases as C increases, but when r is large, the reverse trend occurs.
[0062]
  FIG. 7 shows the result of arranging the C value as a parameter with respect to the value r / h corresponding to the roughness height of the base surface between the grooves. When r / h is larger than a certain value, the value of T increases rapidly, and as the value of C increases, T increases rapidly with a smaller r / h.
[0063]
From the above, it is understood that the friction loss is reduced by the surface roughness shape of this example for the following reason.
[0064]
Since the flow resistance is inversely proportional to the third power of the gap, even if there is a large recess, the shape is such that the flow of lubricating oil always passes through a narrow part, and by increasing its flow resistance, it is equivalent to a smooth surface The closest approach distance of the part surface to obtain the flow resistance is not so small. However, since the presence of the groove necessarily reduces the flow resistance, the closest distance is always closer than in the case of a smooth surface. On the other hand, the presence of the groove widens the area of the portion having a small shear rate (product of the reciprocal of the gap and the relative speed). Therefore, as a result, the effect of widening the area of the portion having a small shear rate due to the presence of the groove exceeds the effect of increasing the shear rate of the portion where the closest approach distance is reduced, and the overall friction loss is reduced. Therefore, when the roughness height of the base surface between the grooves is large, the flow resistance due to the presence of the grooves is reduced, and the effect of reducing the closest distance is the effect of widening the area of the portion with a small shear rate due to the presence of the grooves. In contrast, the presence of grooves increases the friction. Since friction is inversely proportional to the gap, it can be seen that the effect of increased friction increases as r approaches the oil film thickness h. That is, the flow resistance with respect to the pressure gradient with respect to the direction of the flow leaking from the gap in the gap shape between the two parts formed by the surface shape of the two surfaces is the flow resistance in the gap shape in which the two surfaces are formed as completely smooth surfaces. It can be seen that the friction loss is reduced when the value obtained by dividing the reciprocal of the gap between the two parts by area is smaller than the value in the gap shape formed by the completely smooth surface in the same state.
[0065]
Therefore, when the sum of the maximum heights of the smooth surface irregularities around the two grooves is smaller than the oil film thickness, the friction loss is reduced as the groove area is larger and deeper if the shape of b <L. . In addition, when the sum of the maximum heights of the unevenness of the smooth surface around the grooves on each of the two surfaces is smaller than the oil film thickness, if the shape of b <L, between the two parts formed with the surface shape of the two surfaces When the flow resistance with respect to the pressure gradient with respect to the direction of the flow leaking from the gap is equal to the flow resistance in the gap shape formed by two completely smooth surfaces, the reciprocal of the gap between the two parts is That is, the value for the area is smaller than the value for the gap shape formed by the completely smooth surface.
[0066]
In this embodiment, the sum of the maximum heights of the irregularities on the base surface around the two grooves is 1.5 μm, which is smaller than the oil film thickness of 8 μm, so that the friction can be reduced. As is apparent from the principle, the relationship between the groove sizes is not limited to that shown here, but it can be seen that b is effective even if b is the groove width of the piston skirt. That is, when the sum of the maximum heights of the unevenness of the base surface around each of the two grooves is smaller than the oil film thickness, it is a condition for obtaining the effect of the present invention that the shape of b <L. It is the feature.
[0067]
If the width of the groove is larger than the range where the fluid lubricating oil film is generated, it is obvious that the effect is lost in view of the above principle. In addition, even if the groove depth is deeper than necessary, the friction is not reduced, and if the volume in the groove is too large, the effect of compressibility of the lubricating oil will appear and the closest distance on the part surface may be reduced. It is done.
[0068]
In addition, from the above principle of action and effect, any sliding part is lubricated with a lubricant that is a fluid between the two surfaces that move relative to each other, and the flow of lubricating oil between the components is laminar, and a certain load is applied. With respect to the surface shapes of the two parts that slide while being supported, it is apparent that the effects described in the above embodiments can be obtained by adopting the above configuration.
[0069]
Also, as in this embodiment, when the hardness of one part, here the piston skirt, is smaller than the hardness of the other part, here the cylinder bore, if there is direct contact, the surface on the piston skirt side will wear due to wear. Is scraped off. At this time, as in this embodiment, assuming that the diameter of the hard recess is b, and b <L, the groove is not lost due to wear even with a small b. Since it can be set small, this relationship does not collapse even if the groove ratio on the piston skirt side is set large, and by increasing the width of the groove on the soft side, it is possible to lengthen the time that the groove itself disappears due to wear, The effect of reducing friction can be maintained for a long time. In addition, if the conforming effect at the initial stage of operation is expected, even if the maximum height of the unevenness of the base surface between the grooves on the piston skirt side is larger than the oil film thickness, it can be smaller than the oil film thickness after the familiarization is completed. In this case, the same effect as that of the embodiment can be obtained.
[0070]
Further, for example, in the case of a piston sliding surface of an automobile internal combustion engine, the relative sliding speed can exceed 20 m / s at the maximum engine speed. Under such conditions, the oil film thickness decreases due to the decrease in viscosity due to temperature rise based on sliding frictional heat generation, and the frequency of direct contact increases due to elastic deformation of the component due to inertial force acting on the component. Become. In addition, even with other mechanisms, if direct contact between parts occurs due to, for example, foreign matter mixed during such high-speed sliding, the sliding speed is high, so there is a local cooling effect. Is effective to ensure the seizure resistance of the parts. By forming a groove-like recess as in this embodiment, a predetermined volume of lubricating oil can be present in the groove, so that a cooling effect can be expected. Moreover, the foreign matter mixed in can be captured in the groove, and direct contact between components can be reduced. In addition, since the sliding is reciprocating, at the top and bottom dead center where the sliding stops, the formation capability of the fluid lubricating oil film is reduced, the oil film thickness is reduced, and the occurrence of direct contact is increased. At this time, the presence of the groove-shaped recess as described above on the sliding surface enables local cooling and continuous supply of the lubricant to the fracture surface of the boundary film, and also provides wear resistance and scuff resistance. Can be improved.
[0071]
The above effect is the same as long as the surface shape is formed in the same relationship with respect to the value of the oil film thickness for other sliding parts, for example, the sliding surfaces of the cylinder bore and the piston ring of the internal combustion engine. The effect is obtained.
[0072]
Further, if the internal combustion engine is limited to the one for the automobile, the sliding speed is relatively large under the normal operating conditions, so the oil film thickness at the timing of the stroke center portion where the friction loss contribution is large is the piston skirt. About 8 μm and the piston ring is about 1 μm. Therefore, for example, the friction loss can be reduced by using the following surface shape.
[0073]
That is, with respect to the cylinder bore, by using the same material and processing method as described above, a depth of 3 to 5 μm and a width of 10 to 30 μm (average value b) on a smooth base surface 20 having a maximum height t (Ry): 0.5 μm. = 20 μm), a groove 21 having a pitch of 60 to 100 μm (average value: 80 μm) and an average value L ′ of the minimum distance between the grooves of 60 μm is formed.
[0074]
For the piston skirt, the depth is 10 to 15 μm (average value: 13 μm), the width is 50 to 80 μm (average value: 60 μm), the pitch is 110 to 180 μm (average value: 150 μm), and the average value of the minimum distance between the grooves is the same as above. A groove 21 having L of 90 μm is formed.
[0075]
The piston ring is chrome-plated and has a surface hardness of about 1000 Hv. The piston ring is polished by a honing process to obtain an average roughness Ra: 0 consisting of very fine and intersecting polishing grooves. A smooth flat surface of 0.03 μm and maximum height Ry: 0.5 μm.
[0076]
If the oil film thickness between the piston ring and the cylinder bore is 1.0 μm, and there is no groove in the piston ring, the relationship of b <L is established if the distance between the grooves is infinite. The cylinder bore-piston has a sliding contact width of approximately 0.5 mm between the cylinder bore and the cylinder bore, and the contact width a is sufficiently larger than b + L ′, which is obtained by adding the groove width b of the cylinder bore to the groove width L ′. The friction loss can be reduced between the rings as well as between the cylinder bore and the piston skirt. As described above, the relationship of b + L ′ <a is established between the cylinder bore and the piston ring, and b (bore) <L (skirt) is established between the cylinder bore and the piston skirt. Can do.
[Brief description of the drawings]
FIG. 1 (a) is a cross-sectional view showing the shape and structure of a bearing metal and a crankshaft.
(B) It is a perspective view which shows the bearing box which accommodated the bearing metal shown to Fig.1 (a).
(C) It is a horizontal sectional view about line CC in Drawing 1 (a).
FIGS. 2 (a), (b) and (c) are a perspective view and a plan view showing the fine shapes of the sliding surfaces of a crankshaft and a bearing metal (aluminum alloy, Hv100) as sliding parts according to the present invention, respectively. It is a figure and sectional drawing.
FIG. 3 is a schematic diagram in which the surface shape shown in FIG. 2 is regarded as a two-dimensional shape.
FIG. 4 is a graph showing a cumulative distribution of roughness height.
FIG. 5 is a graph showing the relationship between the value H / h corresponding to the depth of the recess and the friction loss.
FIG. 6 is a graph showing the relationship between the equivalent value C of the area ratio of the recesses and the friction loss.
FIG. 7 is a graph showing a relationship between a value r / h corresponding to a roughness height of a base portion and friction loss.
FIG. 8 is a schematic view showing a cylinder bore, a piston ring, and a piston skirt in an internal combustion engine.
FIGS. 9A, 9B, and 9C are a perspective view, a plan view, and a cross-sectional view, respectively, showing fine shapes of sliding surfaces of a cylinder bore and a piston skirt as sliding parts according to the present invention.
10 is a schematic view in which the surface shape shown in FIG. 9 is regarded as a two-dimensional shape.
FIG. 11 is a graph showing the shape of a sliding surface of a conventional crankshaft.
FIG. 12 is a schematic view showing the surface shape of a conventional piston skirt.
FIGS. 13A and 13B are schematic views showing the surface shape of the inner surface of a conventional cylinder bore. FIGS.
[Explanation of symbols]
10,20 Base surface
11 depression
21 groove
31 Bearing metal
32 cranks
35 cylinder bore
36 piston ring
37 piston skirt

Claims (22)

  The surface roughness structure of the sliding surfaces of two parts which are relatively moved in an internal combustion engine and are lubricated with lubricating oil in a laminar flow state between the sliding surfaces, and both sliding surfaces have an unevenness with a maximum height t. The base surface has dimple-like depressions all surrounded by the base surface, and when both sliding surfaces are completely smooth surfaces, the lubricating oil by relative movement to the gap formed between the two parts When h is defined as the closest approach distance between sliding surfaces when the inflow amount and the outflow amount of lubricating oil due to pressure generated between two parts are balanced, h is greater than t, and each sliding surface At least one of the average depths of the recesses is greater than h, the maximum diameter of the recesses on both sliding surfaces is less than or equal to the shortest span in the range where the lubricating oil film is formed, and the maximum of the recesses on one sliding surface When the average value of the diameter is d and the average value of the minimum distance between the depressions of the other sliding surface is L, <Sliding part, which is a L.   The average value of the maximum diameter of the recesses on the sliding surface with the higher surface hardness of both sliding surfaces is d, and the average value of the minimum distance between the recesses on the sliding surface with the lower surface hardness is L. 2. The sliding component according to claim 1, wherein d <L.   3. The D according to claim 1, wherein D> d, where D is an average value of the maximum diameter of the depressions on the sliding surface having the lower surface hardness of both sliding surfaces. Sliding parts.   The maximum height of the unevenness of the base surface on the sliding surface with the higher surface hardness of both sliding surfaces is smaller than h, and the maximum height of the unevenness of the base surface on the sliding surface with the lower surface hardness is The sliding component according to any one of claims 1 to 3, wherein the sliding component is larger than h.   5. The component having a higher surface hardness of the sliding surface is a crankshaft, and the component having a lower surface hardness is a bearing metal that supports the crankshaft. Sliding parts as described in   Both parts are of an internal combustion engine for automobiles, the maximum height of the unevenness of the base surface on the crankshaft sliding surface is 1 μm or less, the average depth of the recesses is 1 to 50 μm, and the recesses on the bearing metal sliding surface The sliding part according to claim 5, wherein the average depth is 1 to 50 μm and the average value of the maximum diameter is 1 mm or less.   5. The sliding part according to claim 1, wherein the part having the higher surface hardness of the sliding surface is a cylinder bore, and the part having the lower surface hardness is a piston skirt. .   Both parts are of an internal combustion engine for automobiles, the maximum height of the unevenness of the base surface on the cylinder bore sliding surface is 1 μm or less, the average depth of the recess is 1 to 50 μm, and the recess on the piston skirt sliding surface The sliding part according to claim 7, wherein the average depth is 1 to 50 μm and the average value of the maximum diameter is 1 mm or less.   5. The sliding component according to claim 1, wherein the component having a higher surface hardness of the sliding surface is a piston ring, and the component having a lower surface hardness is a cylinder bore. .   Both parts are of an internal combustion engine for automobiles, the maximum height of the unevenness of the base surface on the piston ring sliding surface is 1 μm or less, the average depth of the recess is 1 to 50 μm, and the recess on the cylinder bore sliding surface The sliding part according to claim 9, wherein the average depth is 1 to 50 μm and the average value of the maximum diameter is 1 mm or less.   5. The sliding part according to claim 1, wherein the part having a higher surface hardness of the sliding surface is a cylinder bore, and the part having a lower surface hardness is a piston ring. .   Both parts are of an internal combustion engine for automobiles, the maximum height of the unevenness of the base surface on the cylinder bore sliding surface is 1 μm or less, the average depth of the recess is 1 to 50 μm, and the recess on the piston ring sliding surface The sliding part according to claim 11, wherein the average depth is 1 to 50 μm and the average value of the maximum diameter is 1 mm or less.   This is a surface roughness structure on the sliding surfaces of the cylinder bore, piston skirt and piston ring of an internal combustion engine. The sliding surface of the cylinder bore goes around the base surface with an unevenness with a maximum height of 1 μm or less. And has a depression with a depth of 1 to 50 μm and an average value d of the maximum diameter of 50 μm or less, and the sliding surface of the piston skirt that is in sliding contact with the cylinder bore has irregularities with a maximum height of 5 μm or less. The base surface is surrounded by the base surface and has a depth of 1 to 50 μm and an average value of the maximum diameter of 1 mm or less. The sliding surface of the piston ring that is in sliding contact with the cylinder bore has a maximum height. A base surface having a ruggedness of 1 μm or less is surrounded by the base surface, and has a depth of 1 to 50 μm and an average maximum diameter of 50 μm or less. A sliding component characterized in that d <L1 and d <L2 where L1 is an average value of the minimum distance between the recesses and L2 is an average value of the minimum distance between the recesses of the piston ring.   In the internal combustion engine, the surface roughness structure of the sliding surfaces of the two parts which are relatively moved and are lubricated with lubricating oil between the sliding surfaces in a laminar flow state, both sliding surfaces having maximum heights t1, t2 respectively. The base surface with (μm) irregularities has a plurality of grooves that make an angle of 45 ° or more with the sliding direction without intersecting each other, and the maximum depth of the grooves on both sliding surfaces is H (μm) H / t1, H / t2 is greater than 1, the maximum width of the groove is equal to or less than the contact length in the sliding direction in which the lubricating oil film is formed, and the average value of the maximum width of the groove on one sliding surface Is a sliding component, wherein b <L, where b (μm) is L and the average value of the minimum distance between grooves on the other sliding surface is L (μm).   When both sliding surfaces are perfectly smooth surfaces, the amount of lubricating oil inflow due to relative movement in the gap formed between the two parts and the amount of lubricating oil outflow due to pressure generated between the two parts are balanced. The surface roughness structure of a sliding part according to claim 14, wherein when the closest distance between the sliding surfaces is defined as h, the t1 and t2 are smaller than h.   The average value of the maximum width of the groove on the sliding surface with the higher surface hardness of both sliding surfaces is b, and the average value of the minimum distance between the grooves on the sliding surface with the lower surface hardness is L. 16. The sliding component according to claim 14, wherein b <L.   17. The structure according to claim 15, wherein B> b, where B is an average value of the maximum groove widths on the sliding surface having the lower surface hardness of both sliding surfaces. Sliding parts.   18. The sliding component according to claim 15, wherein the component having a higher surface hardness of the sliding surface is a cylinder bore, and the component having a lower surface hardness is a piston skirt. .   Both parts are of an internal combustion engine for automobiles, the unevenness of the base surface on the sliding surface of the cylinder bore and the piston skirt is 1 μm or less in the maximum roughness indication Ry, and the average depth of the groove in the cylinder bore is 1 to The average value of the minimum distance between the grooves is 50 μm, the average value of the minimum distance between the grooves is 100 μm or less, the average depth of the grooves in the piston skirt is 5 to 50 μm, and the average value of the minimum distance between the grooves is 1 mm or less. 18. The sliding part according to 18.   Lubrication due to the inflow of lubricating oil by the relative movement to the gap formed between the parts and the pressure generated between the parts, assuming that the sliding surface of the piston skirt and piston ring and the cylinder bore is a perfectly smooth surface. Let h be the closest distance between the sliding surfaces when the oil outflow is balanced, and h on the two sliding surfaces of the piston skirt and cylinder bore and piston ring and cylinder bore at the center of the piston vertical stroke. The smaller value of h is defined as h0, the average value of the maximum groove width in the cylinder bore is b, the average value of the minimum distance between the grooves is L ', and the average value of the minimum distance between the grooves in the cylinder bore is L. When the contact width in the sliding direction of the piston ring and the cylinder bore is a, the piston skirt, piston ring and cylinder bore The sliding part according to any one of claims 16 to 19, wherein the maximum height of the unevenness of the surface is h0 or less and b> L, b + L '<a.   The base surfaces of the piston skirt, piston ring, and cylinder bore sliding surface have irregularities with a maximum height of 1 μm or less, the average value b of the maximum groove width in the cylinder bore is 1 to 50 μm, and the average depth of the groove Is 1 to 10 μm, the average value L ′ of the minimum distance between the grooves is 100 μm or less, the average value B of the maximum groove width in the piston skirt is 50 μm or more, the average groove depth is 5 to 50 μm, and the minimum distance between the grooves 21. The sliding component according to claim 20, wherein an average value L of is not less than 50 μm and not more than 1 mm.   An internal combustion engine using the sliding component according to any one of claims 1 to 4.

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