JP4209575B2

JP4209575B2 - piston ring

Info

Publication number: JP4209575B2
Application number: JP2000082320A
Authority: JP
Inventors: 英司一杉; 圭一金光
Original assignee: Nippon Piston Ring Co Ltd
Current assignee: Nippon Piston Ring Co Ltd
Priority date: 2000-03-23
Filing date: 2000-03-23
Publication date: 2009-01-14
Anticipated expiration: 2020-03-23
Also published as: JP2001271928A

Description

【０００１】
【産業上の利用分野】
本発明はピストンリングに関し、特にローポイントピストンリングに関する。
【０００２】
【従来の技術】
従来のピストンリングの面圧分布としては、図７に示す等面圧分布、図８に示す楕円面圧分布、図９に示す桃型分布（合口高面圧分布）、図１０に示すりんご型分布などが知られている。
【０００３】
図７に示される等面圧分布は、全周に亘り均一に面圧が分布している。中高回転型４サイクルエンジンでは使用時のリング摩耗によって、合口部の面圧の低下が生じるため、低回転型エンジンやコンプレッサ等のリングに用いられる。
【０００４】
図８に示される楕円面圧分布は、合口付近とその反対側位置（１８０°位置）の面圧のみが高くなるよう面圧が分布している。この分布は、合口部から９０°位置と２７０°位置の２箇所で面圧が高くなるよう分布させても良い。
【０００５】
図９に示される桃型分布（合口高圧分布）は、合口部における面圧が他の部分の面圧と比較して高くなる面圧分布である。自動車を始めとする各種高回転型のエンジンのリングに用いられている。
【０００６】
図１０に示されるりんご型分布は、合口部における面圧が他の部分の面圧と比較して低くなる面圧分布である。特に、合口部における面圧の変化率は０であり、合口部付近において面圧はなだらかに変化する。そして、合口部付近の両端側では、他の部分と比較して面圧が高くなっている。りんご型分布のピストンリングは、２サイクルエンジンや、合口部よりスカッフィングの発生しやすい大型の舶用リングに用いられる。
【０００７】
【発明が解決しようとする課題】
上述した等面圧分布等のピストンリングでは、シリンダとピストンリングの温度差による熱膨張量の差や、ピストンリングの内周側と外周側の温度差による熱応力等により、ピストンリングのリングカーブの曲率が小さくなり、合口部付近が高面圧となる。
【０００８】
特に、高Ｐｍａｘディーゼルエンジンのトップリングとして用いた場合では、極めて過酷な運転条件にあるため、合口部のブローバイガスの吹き抜けによって合口部付近が極端に加熱される。このため、ピストンリングの内周側と外周側の温度差による熱応力が極端に大きくなると共に、合口部付近の周方向への熱膨張が大きくなるため、合口部付近での曲率が極端に小さくなり、筒内圧力作用時以外の行程では、図１１に示すように、ピストンリング４０の合口部４２の周辺位置であるα部とβ部の中間位置においてシリンダボア４５に対する当たり抜けが発生する。一方で、このような状態で筒内圧力が作用した場合は、ピストンリング背部に作用する筒内圧力によってピストンリングがシリンダボア４５に押しつけられ、ピストンリングの摺動面がシリンダボア４５に追従する。これにより、図１１に示すα部とβ部付近の面圧が高くなる。ここで、α部は特に、点接触状態でシリンダボアに押しつけられるため、非常に高い接触圧力となる。
【０００９】
また、こうして、合口部におけるピストンリング外周部の面圧が高くなり、摩耗が増大することにより、ピストンリングの耐摩擦性を向上させる目的でピストンリング外周面に被覆したＰＶＤ被膜のクラック・剥離の原因となり、合口端部に向かって極端に摩耗が増加していく摩耗形状となる。ここで、特に外周面にクロムめっきを施したピストンリングの場合は、摩耗量が極端に多くなり、シリンダ呼び径の治具に耐久運転後のピストンリングを挿入した場合、合口部が当たり抜けして漏光してしまう程になる。
【００１０】
従って、高Ｐｍａｘディーゼルエンジンに対しては、耐摩耗性の高いＣｒ−Ｎ系のＰＶＤコーティングを施したピストンリングを使用することになる。しかし、ＰＶＤコーティングを施したトップリングについては、合口部近傍のＰＶＤ被膜のクラック・剥離等の問題が数多く発生しているという問題がある。
【００１１】
そこで本発明は、合口部付近における面圧を低減し、実働時の合口部周辺における当たり抜けを防止するとともに、合口部付近における摩耗の少ない高Ｐｍａｘディーゼルエンジン用ピストンリングを提供することを目的とする。
【００１２】
【課題を解決するための手段】
上記目的を達成するために、本発明は、略円形状をなし、シリンダに対し摺動する外周摺動面３と、ピストンに対向する内周面４と、該略円形状を半径方向に分断する１つの合口部２とを備え、該内周面側４において、該合口部２の端面を始端とする所定の周長部分に亘り、該内周面４の一部をなす切欠部４ａが形成されており、該所定周長部分以外の部分の半径方向の厚さは一定であり、該所定周長部分における半径方向の厚さが、該所定周長部分以外の部分の半径方向の厚さａ₁に比較して小さくなっているピストンリングであって、該切欠部４ａは該合口部２端面に向かって徐々に該外周摺動面３に近づく円弧面状をなし、該合口部２端面における半径方向厚さが、該所定周長部分以外の部分における半径方向の厚さａ₁の０．６乃至０．８倍であり、該所定周長部分は該外周摺動面４の中心軸Ｏ₁で規定される中心角３０°乃至５０°の範囲に亘り形成されているピストンリングを提供している。
【００１３】
また、略円形状をなし、シリンダに対し摺動する外周摺動面１３と、ピストンに対向する内周面１４と、該略円形状を半径方向に分断する１つの合口部１２とを備え、該内周面１４側において、該合口部１２の端面を始端とする所定の周長部分に亘り、該内周面１４の一部をなす切欠部１４ａ、１４ｂ、……が形成されており、該所定周長部分以外の部分の半径方向の厚さは一定であり、該切欠部形成部分における半径方向の厚さが、該所定周長部分以外の部分の半径方向の厚さａ₁に比較して小さくなっているピストンリングであって、該切欠部１４ａ、１４ｂ、……は該内周面１４側に略等間隔に複数箇所形成されて、該所定周長部分の内周面１４が交互に連続する凹凸状をなし、該所定周長部分は該外周摺動面の中心軸で規定される中心角２０°乃至４０°の範囲に亘り形成されているピストンリングを提供している。
【００１４】
更に、略円形状をなし、シリンダに対し摺動する外周摺動面２３と、ピストンに対向する内周面２４と、該略円形状を半径方向に分断する１つの合口部２２とを備え、該内周面２４側において、該合口部２２の端面から所定距離離れた位置を中心点として、所定の周長部分に亘り対称に該内周面２４の一部をなす切欠部２４ａが形成されており、該所定周長部分における半径方向の厚さが、該所定周長部分以外の部分の半径方向の厚さａ₁に比較して小さくなっているピストンリングであって、該切欠部２４ａの所定周長部分は外周摺動面に略平行な直線状又は曲面状をなし、該中心点は、合口端面を始点として中心角２０°乃至４０°の範囲に位置しているピストンリングを提供している。
【００１５】
これらのピストンリングは、スチール母材に窒化処理を施してその後該外周摺動面３、１３、２３にＰＶＤ膜を形成するのが好ましい。
【００１６】
【発明の実施の形態】
本発明の第１の実施の形態によるピストンリングについて図１に基づき説明する。図１に示すピストンリング１は、略円形状をなし、図示せぬシリンダに対し摺動する外周面（外周摺動面）３と、図示せぬピストンに対向する内周面４と、略円形状を半径方向に分断する１つの合口部２とを有し、呼び径の半分はＲ ₁ である。
【００１７】
外周面３と内周面４との距離（ピストンリング半径方向の厚さ寸法）がａ ₁ であるが、内周面４側において、合口部２の端面を始端とする所定の周長部分に亘り（図１のＡ乃至Ｂに亘り）、内周面４の一部をなす切欠部４ａが形成されており、該所定周長部分における半径方向の厚さが、所定周長部分以外の部分の半径方向の厚さに比較して小さく形成されている。
【００１８】
具体的には、切欠部４ａは合口部２の端面に向かって徐々に外周面３に近づく円弧面Ａ−Ｂをなしている。Ｂにおけるリング半径方向の厚さはａ ₁ であるが、合口部２の端面上に存在するＡに向かってリング半径方向の厚さが徐々に減少し、Ａでは０．６乃至０．８ａ ₁ となる。０．６ａ ₁ 未満では半径方向曲げ剛性低減幅が大きすぎ、また、削除体積が大きいので合口近傍の曲率変化が大きく漏光が過大となってしまうが、実機運転による温度上昇時でも合口端部付近の面圧が十分でなくなる。０．８ａ ₁ を越えると、半径方向曲げ剛性低減幅が十分でなく、また削減体積が小さいので、漏光エリアが過小で、実機運転による温度上昇時では合口端部の面圧が高くなり本リングの効果を発揮できない。そのため、０．６乃至０．８ａ ₁ とする必要がある。
【００１９】
円弧面Ａ−Ｂは、本実施の形態では、ピストンリング１の外周面の中心軸Ｏ ₁ に平行で、この中心軸Ｏ ₁ から合口部２方向へｂ＝３ｍｍ乃至５ｍｍ離れた軸Ｏ ₂ を中心とし、半径Ｒ ₂ ＝Ｒ ₁ −０．６ａ ₁ −ｂの円周面の一部をなす。また、円弧面Ａ−Ｂは、合口面を始点とし、外周面３の中心軸Ｏ ₁ で規定される中心角３０°乃至５０°（本実施の形態では３０°）の範囲に亘り形成されている。ここで、中心角が３０°未満では半径方向曲げ剛性低減幅が十分でなく、機関運転時に面圧上昇が発生する。一方、中心角が５０°を越えると、合口端部の面圧が機関運転時であっても十分に上昇しないので潤滑油消費量に対し問題となる。
【００２０】
このピストンリング１によると、合口部付近の曲げ剛性を減少させることができ、合口端部の面圧が均一断面形状のピストンリングよりも小さくなることから、機関運転時には局所的摩耗、ＰＶＤ皮膜のクラック、剥離等に対して優位となる。尚、図面には示さないが、図に示された合口面に対向するもう一方の合口面からも、同様の切欠部４ａが形成される。
【００２１】
本発明の第２の実施の形態によるピストンリングについて図２に基づき説明する。図２に示すピストンリング１０は、略円形状をなし、図示せぬシリンダに対し摺動する外周面（外周摺動面）１３と、図示せぬピストンに対向する内周面１４と、略円形状を半径方向に分断する１つの合口部１２とを有する。
【００２２】
内周面１４側において、合口部１２の端面を始端とする中心角２０°乃至４０°の周長部分に亘り、内周面１４の一部をなす切欠部１４ａ、１４ｂ……が形成されており、切欠部形成部分における半径方向の厚さが、合口面を始点とする中心角２０°乃至４０°の周長部分以外の部分の半径方向の厚さａ ₁ に比較して小さくなっている。この実施の形態の場合、中心角が２０°未満では合口近傍の曲率変化が小さく曲げ剛性低減幅が小さいので、実機運転による温度上昇時は合口端部の面圧が高くなってしまう。４０°を超えると、合口近傍の曲率変化が大きく、曲げ剛性低減の幅も大きくなりすぎるので、温度上昇時に十分な面圧が発生しにくくなる。
【００２３】
切欠部１４ａ、１４ｂ、……は内周面１４側に略等間隔に複数箇所形成されて、所定周長部分の内周面が交互に連続する凹凸状をなしている。尚、図面には示さないが、図に示された合口面に対向するもう一方の合口面からも、同様の切欠部が形成される。
【００２４】
本発明の第３の実施の形態によるピストンリングについて図３に基づき説明する。図３に示すピストンリング２０は、略円形状をなし、図示せぬシリンダに対し摺動する外周面（外周摺動面）２３と、図示せぬピストンに対向する内周面２４と、略円形状を半径方向に分断する１つの合口部２２とを有する。
【００２５】
内周面２４側において、合口部２２の端面から中心角２０°乃至４０°離れた位置を中心点として、中心角２０°の周長部分に亘り対称に内周面２４の一部をなす切欠部２４ａが形成されており、当該切欠部２４ａ形成部分における半径方向の厚さが、当該切欠部２４ａ形成部分以外の部分の半径方向の厚さａ ₁ に比較して小さくなっている。切欠部２４ａの所定周長部分は外周摺動面に略平行な直線状又は曲面状をなしている。尚、図面には示さないが、図に示された合口面に対向するもう一方の合口面から中心角２０°乃至４０°の範囲にも、同様の切欠部が形成される。この中心角２０°乃至４０°の範囲に限定する理由は図２に示した実施の形態と同様の理由に基づくものである。
【００２６】
図４に示す面圧分布測定装置によって本発明の第１の実施の形態によるピストンリングの面圧分布と従来例のピストンリングの面圧分布とを測定し、比較した。尚、測定に際しては、各リングの軸方向厚さや外周面形状、半径方向厚さａ ₁ が同一のものを用いた。
【００２７】
図４は、測定装置の左半分を示しており、シリンダ１０２、１０３は、シリンダホルダ１０１に支持され、シリンダ１０３の外周面の一部に凹部１０３ａが形成されて最薄部となる。テストピースであるピストンリングを、ピストン１０５のリング溝１０５ａに装着し、ピストンリングの外周面をシリンダ１０３の内周面に当接させる。すると、シリンダ１０３の最薄部にはピストンリングからの面圧が作用し、歪みが生じることとなる。よって、凹部１０３ａの底部に歪みゲージ１０４を貼りつけ、歪みゲージ１０４をストレインアンプ１０７に接続し、ペンレコーダ１０８に歪みの値を記録することによって、歪み値を面圧として測定した。また、ピストンリング溝１０５ａ付近と、ピストンリングに対向する位置にあるシリンダ１０３の内周面付近に、Ｊ型熱電対１０９を備え、高速打点計１１０に接続することで、温度を計測した。更に、ピストンリングを保持するピストン１０５の上側に、ヒーター１０６を取付けて、ピストンリングを加熱する一方で、シリンダ１０３の外周側には冷却水を接触させてシリンダ１０３の冷却を行い、ピストン１０５からシリンダ１０３まで実機運転時に近い温度勾配を分布させた。
【００２８】
図５、６は、縦軸が面圧、横軸が合口部からの周方向角度を示す。また、黒丸は常温時（リング・ライナともに２０℃）、白丸は実働時（ピストン２５０℃、ライナ１２０℃）の実験結果を示す。従来例の等面圧のピストンリングでは、図５に白丸で示すように熱負荷の作用が働くと、合口端部付近の面圧が極端に上昇した。そして、合口端部付近においてピストンリングがシリンダに強く押しつけられるのに伴い、５°乃至２０°の範囲において、当たり抜けが生じた。
【００２９】
これに対して本発明の第１の実施の形態によるピストンリング１では、図６から明らかなように、黒丸で示す常温時の外周面３のシリンダ１０３に対する面圧の分布は、合口部２からその近傍に亘ってゼロであり、合口部２端面を始点として該中心角１５°の範囲に亘り当たり抜けが生じている。また、中心角が大きくなる方向へ向かって、ゼロから急激に上昇した後に最大値を取り、その後なだらかに減少した後に略一定値となり、面圧が略一定値となり始める位置は、合口部１２端面を始点として中心角が略８０°の位置である。また、合口部１２端面を始点として該中心角１５°の位置における面圧の変化率が不連続となっている。
【００３０】
しかし、実働時とほぼ同様の熱負荷を与えた時には、白丸に示されるように、合口端部近傍における面圧が上昇し、合口端部近傍における当たり抜けは見られなくなった。また従来のピストンリングと比して、合口端部の急激な面圧上昇が見られない。従って、これに伴い、合口端部２の周辺における当たり抜けが生じなくなっている。なお、この実験結果より、実働時の合口部におけるブローバイガスの吹き抜けによる加熱を考慮しても、合口部における面圧の極端な上昇は見られないことがわかる。
【００３１】
本実施の形態では単にピストンリング合口部の内周側に切欠部を形成することのみを説明したが、このような加工を、スチールに窒化処理を施してその後摺動面にＰＶＤ被膜を形成したピストンリングに対して行うことにより、更に顕著な効果を得ることができる。ＰＶＤ被膜と窒化膜の持つ圧縮応力を利用して合口付近のリング曲率をより大きくすることができるからである。
【００３２】
尚、本実験においては常温時における合口部近辺以外の部分の面圧が約１．５ｋｇｆ／ｃｍ ² 程度のピストンリングを試作し、実験を行ったが、この数値はその用途に応じて様々に設定しうることは言うまでもない。
【００３３】
本発明によるピストンリングは上述した実施の形態に限定されず、特許請求の範囲に記載した範囲で種々の変形や改良が可能である。例えば、本実施の形態では常温時に合口端部にて当たり抜けが生じるよう構成したが、合口端部の面圧が他の部分に比して極端に小さくなっていれば、当たり抜けが生じないよう構成しても良い。
【００３４】
【発明の効果】
本発明のピストンリングによれば、合口端部の高面圧を抑制するために、合口部近傍のピストンリング半径方向の厚さ寸法ａ ₁ を小さくし、曲げ剛性を減少させている。これにより、合口端部の面圧を均一断面形状のピストンリングよりも低減することができる。従って、実動時において合口部における極端な面圧の上昇を抑えることができ、合口部の極端な摩耗を防止すると同時に、特にピストンリング外周面にＰＶＤ被膜を施した場合には、膜のクラック、剥離等の障害を阻止することができる。更に、請求項１記載のピストンリングによると、ピストンリングの半径方向厚さが緩やかに減少しているので、曲げ剛性の変化も緩やかな減少となり、応力集中を回避することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態によるピストンリングの合口部近傍の形状を示す平面図。
【図２】本発明の第２の実施の形態によるピストンリングの合口部近傍の形状を示す平面図。
【図３】本発明の第３の実施の形態によるピストンリングの合口部近傍の形状を示す平面図。
【図４】本発明の実施の形態によるピストンリングの面圧分布と従来例のピストンリングの面圧分布との測定に用いた面圧分布測定装置を示す断面図。
【図５】従来のピストンリングの面圧分布を示す折線図。
【図６】本発明の第１の実施の形態によるピストンリングの面圧分布を示す折線図。
【図７】等面圧分布の面圧分布を示す図。
【図８】楕円面圧分布の面圧分布を示す図。
【図９】桃型分布（合口高圧分布）の面圧分布を示す図。
【図１０】りんご型分布の面圧分布を示す図。
【図１１】従来のピストンリングの機関動作中の合口部付近の形状を示す図。
【符号の説明】
１、１０、２０、３０ピストンリング
２、１２、２２合口部
３、１３、２３外周面
４、１４、２４内周面
４ａ、１４ａ、１４ｂ、２４ａ、切欠部[0001]
[Industrial application fields]
The present invention relates to a piston ring, and more particularly to a low point piston ring.
[0002]
[Prior art]
As the surface pressure distribution of the conventional piston ring, the isosurface pressure distribution shown in FIG. 7 , the elliptic surface pressure distribution shown in FIG. 8 , the peach type distribution (abutment high surface pressure distribution) shown in FIG. 9 , and the apple type shown in FIG. Distribution etc. are known.
[0003]
In the isosurface pressure distribution shown in FIG. 7 , the surface pressure is uniformly distributed over the entire circumference. In a medium and high rotation type four-cycle engine, the ring pressure during use decreases the surface pressure of the joint portion, so it is used for rings such as low rotation type engines and compressors.
[0004]
In the elliptical surface pressure distribution shown in FIG. 8 , the surface pressure is distributed so that only the surface pressure in the vicinity of the joint and the opposite side position (180 ° position) is increased. This distribution may be distributed so that the surface pressure becomes high at two positions of 90 ° position and 270 ° position from the joint portion.
[0005]
The peach-shaped distribution (abutment high pressure distribution) shown in FIG. 9 is a surface pressure distribution in which the contact pressure at the joint is higher than the contact pressure at other portions. It is used for rings of various high-speed engines such as automobiles.
[0006]
The apple-type distribution shown in FIG. 10 is a surface pressure distribution in which the surface pressure at the abutment portion is lower than the surface pressure at other portions. In particular, the rate of change of the surface pressure at the joint portion is 0, and the surface pressure changes gently in the vicinity of the joint portion. And the surface pressure is high compared with other parts at both ends near the joint part. Piston rings with an apple-type distribution are used for two-cycle engines and large marine rings that are more likely to scuff from the abutment.
[0007]
[Problems to be solved by the invention]
In the piston ring with the isosurface pressure distribution described above, the ring curve of the piston ring is caused by the difference in thermal expansion due to the temperature difference between the cylinder and the piston ring or the thermal stress due to the temperature difference between the inner and outer circumferences of the piston ring. The curvature becomes smaller, and the vicinity of the joint becomes high surface pressure.
[0008]
In particular, when used as a top ring of a high Pmax diesel engine, since it is under extremely severe operating conditions, the vicinity of the abutment portion is heated extremely by blow-by gas blow-through of the abutment portion. For this reason, the thermal stress due to the temperature difference between the inner and outer circumferences of the piston ring becomes extremely large, and the thermal expansion in the circumferential direction near the joint portion becomes large, so the curvature near the joint portion is extremely small. Thus, in a stroke other than the time of in-cylinder pressure action, as shown in FIG. 11 , a contact with the cylinder bore 45 occurs at an intermediate position between the α portion and the β portion, which are the peripheral positions of the joint portion 42 of the piston ring 40. On the other hand, when the in-cylinder pressure acts in such a state, the piston ring is pressed against the cylinder bore 45 by the in-cylinder pressure acting on the back of the piston ring, and the sliding surface of the piston ring follows the cylinder bore 45. As a result, the surface pressure in the vicinity of the α and β portions shown in FIG. 11 is increased. Here, the α portion is particularly pressed against the cylinder bore in a point contact state, and therefore has a very high contact pressure.
[0009]
In addition, the surface pressure of the outer peripheral portion of the piston ring at the abutment portion increases and wear increases, so that the PVD coating coated on the outer peripheral surface of the piston ring is cracked and peeled for the purpose of improving the friction resistance of the piston ring. This causes a wear shape in which wear increases extremely toward the end of the joint. Here, especially in the case of a piston ring with chrome plating on the outer peripheral surface, the amount of wear is extremely large, and when the piston ring after endurance operation is inserted into a jig with a cylinder nominal diameter, the abutment part will hit and come off. The light will leak.
[0010]
Therefore, for a high Pmax diesel engine, a piston ring with a highly wear-resistant Cr—N PVD coating is used. However, the top ring to which the PVD coating is applied has a problem that many problems such as cracking and peeling of the PVD coating near the joint portion have occurred.
[0011]
Therefore, the present invention has an object to provide a piston ring for a high Pmax diesel engine that reduces the surface pressure in the vicinity of the abutment portion, prevents the hitting in the vicinity of the abutment portion during actual operation, and has less wear in the vicinity of the abutment portion. To do.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has a substantially circular shape, and an outer peripheral sliding surface 3 that slides on a cylinder, an inner peripheral surface 4 that faces the piston, and the substantially circular shape is divided in the radial direction. A notch portion 4a forming a part of the inner peripheral surface 4 over a predetermined peripheral length portion starting from the end surface of the joint portion 2 on the inner peripheral surface side 4. The radial thickness of the portion other than the predetermined circumferential length portion is constant, and the radial thickness of the predetermined circumferential length portion is the radial thickness of the portion other than the predetermined circumferential length portion. It is a piston ring that is smaller than a ₁ , and the cutout portion 4 a has an arcuate surface shape that gradually approaches the outer peripheral sliding surface 3 toward the end surface of the joint portion 2. The radial thickness at the end face is 0.6 to 0 of the radial thickness a ₁ at a portion other than the predetermined circumferential length portion. The predetermined circumferential length portion provides a piston ring formed over a central angle range of 30 ° to 50 ° defined by the central axis O ₁ of the outer peripheral sliding surface 4.
[0013]
Further, it has a substantially circular shape, and includes an outer peripheral sliding surface 13 that slides relative to the cylinder, an inner peripheral surface 14 that faces the piston, and one abutment portion 12 that divides the substantially circular shape in the radial direction, On the inner peripheral surface 14 side, notches 14a, 14b,... Forming part of the inner peripheral surface 14 are formed over a predetermined peripheral length portion starting from the end surface of the joint portion 12. The thickness in the radial direction of the portion other than the predetermined circumferential length portion is constant, and the radial thickness in the notch forming portion is compared with the radial thickness a ₁ of the portion other than the predetermined circumferential length portion. The notch portions 14a, 14b,... Are formed at a plurality of positions at substantially equal intervals on the inner peripheral surface 14 side, and the inner peripheral surface 14 of the predetermined peripheral length portion is formed. Convex and concave portions that are alternately continuous, and the predetermined circumferential length portion is defined by the central axis of the outer peripheral sliding surface. It provides a piston ring which is formed over a range of angular 20 ° to 40 °.
[0014]
Furthermore, it has a substantially circular shape, and includes an outer peripheral sliding surface 23 that slides relative to the cylinder, an inner peripheral surface 24 that faces the piston, and one abutment portion 22 that divides the substantially circular shape in the radial direction, On the inner peripheral surface 24 side, a notch 24a that forms a part of the inner peripheral surface 24 is formed symmetrically over a predetermined peripheral portion with a position that is a predetermined distance away from the end surface of the joint portion 22 as a center point. A piston ring in which a radial thickness in the predetermined circumferential length portion is smaller than a radial thickness a ₁ in a portion other than the predetermined circumferential length portion, and the notch portion 24a The predetermined circumferential length portion is formed in a straight line shape or a curved surface shape substantially parallel to the outer peripheral sliding surface, and the center point provides a piston ring located in a range of a central angle of 20 ° to 40 ° starting from the abutment end surface. is doing.
[0015]
These piston rings are preferably formed by nitriding a steel base material and then forming a PVD film on the outer peripheral sliding surfaces 3, 13 and 23.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
A piston ring according to a first embodiment of the present invention will be described with reference to FIG. A piston ring 1 shown in FIG. 1 has a substantially circular shape, an outer peripheral surface (outer peripheral sliding surface) 3 that slides on a cylinder (not shown), an inner peripheral surface 4 that faces the piston (not shown), and a substantially circular shape. It has one abutment part 2 that divides the shape in the radial direction, and half of the nominal diameter is R ₁ .
[0017]
The distance between the outer peripheral surface 3 and the inner peripheral surface 4 (thickness dimension in the piston ring radial direction) is a ₁ , but on the inner peripheral surface 4 side, a predetermined peripheral length portion starting from the end surface of the joint portion 2 is used. A notch 4a that forms a part of the inner peripheral surface 4 is formed (over A to B in FIG. 1), and the radial thickness of the predetermined peripheral length portion is a portion other than the predetermined peripheral length portion. It is formed smaller than the thickness in the radial direction.
[0018]
Specifically, the cutout portion 4 a forms an arc surface AB that gradually approaches the outer peripheral surface 3 toward the end surface of the joint portion 2. The thickness in the ring radial direction at B is a ₁ , but the thickness in the ring radial direction gradually decreases toward A existing on the end face of the joint portion 2, and in A, 0.6 to 0.8 a ₁ It becomes. If it is less than 0.6a ₁ , the radial bending rigidity reduction width is too large, and the volume of deletion is large, so the change in curvature near the joint is large and light leakage becomes excessive, but even near the end of the joint even when the temperature rises due to actual operation. The surface pressure is not enough. Exceeds 0.8a _1, the radial flexural rigidity reduction width is not sufficient, and because reducing the volume is small, too small is light leakage area, the ring increases the surface pressure of the abutment end portion than at the temperature rise due to actual operation The effect of can not be demonstrated. Therefore, it is necessary to set to 0.6 to 0.8a ₁ .
[0019]
In the present embodiment, the arc surface AB is parallel to the central axis O ₁ of the outer peripheral surface of the piston ring 1, and an axis O ₂ that is b = 3 mm to 5 mm away from the central axis O _{1 in the} direction of the joint portion 2. The center is a part of the circumferential surface with a radius R ₂ = R ₁ −0.6a ₁ −b. Further, the arc surface AB is formed over a range of a central angle of 30 ° to 50 ° (30 ° in the present embodiment) defined by the central axis O ₁ of the outer peripheral surface 3 starting from the abutment surface. Yes. Here, if the central angle is less than 30 °, the radial bending rigidity reduction width is not sufficient, and the surface pressure rises during engine operation. On the other hand, if the central angle exceeds 50 °, the surface pressure at the abutment end does not increase sufficiently even during engine operation, which causes a problem with respect to the amount of lubricant consumed.
[0020]
According to this piston ring 1, the bending rigidity in the vicinity of the joint portion can be reduced, and the surface pressure at the joint end portion becomes smaller than that of the piston ring having a uniform cross-sectional shape. It is superior to cracks, peeling, etc. Although not shown in the drawing, a similar notch 4a is formed also from the other abutment surface facing the abutment surface shown in the drawing.
[0021]
A piston ring according to a second embodiment of the present invention will be described with reference to FIG. The piston ring 10 shown in FIG. 2 has a substantially circular shape, an outer peripheral surface (outer peripheral sliding surface) 13 that slides against a cylinder (not shown), an inner peripheral surface 14 that faces the piston (not shown), and a substantially circular shape. And one abutting portion 12 that divides the shape in the radial direction.
[0022]
On the inner peripheral surface 14 side, notches 14 a, 14 b... Forming part of the inner peripheral surface 14 are formed over a peripheral portion having a central angle of 20 ° to 40 ° starting from the end surface of the joint portion 12. In addition, the radial thickness in the notch forming portion is smaller than the radial thickness a ₁ of the portion other than the circumferential portion having a central angle of 20 ° to 40 ° starting from the joint surface . . In the case of this embodiment, when the center angle is less than 20 °, the change in curvature near the joint is small and the bending rigidity reduction width is small, so the surface pressure at the joint end becomes high when the temperature rises due to actual machine operation. If it exceeds 40 °, the curvature change in the vicinity of the abutment is large, and the width of bending rigidity reduction is too large, so that it is difficult to generate sufficient surface pressure when the temperature rises.
[0023]
The notches 14a, 14b,... Are formed at a plurality of locations at substantially equal intervals on the inner peripheral surface 14 side, and have an uneven shape in which the inner peripheral surfaces of the predetermined peripheral length portions are alternately continuous. Although not shown in the drawings, a similar notch is formed also from the other abutment surface facing the abutment surface shown in the drawing.
[0024]
A piston ring according to a third embodiment of the present invention will be described with reference to FIG. The piston ring 20 shown in FIG. 3 has a substantially circular shape, an outer peripheral surface (outer peripheral sliding surface) 23 that slides against a cylinder (not shown), an inner peripheral surface 24 that faces the piston (not shown), and a substantially circular shape. And one abutment portion 22 that divides the shape in the radial direction.
[0025]
On the inner peripheral surface 24 side, a notch that forms a part of the inner peripheral surface 24 symmetrically over the peripheral portion of the central angle 20 °, with the center point being a position 20 ° to 40 ° away from the end face of the joint portion 22 part 24a is formed, the thickness in the radial direction of the cutout portion 24a forming portion is smaller as compared with the radial thickness of a ₁ part other than the cutout portion 24a formed part. The predetermined circumferential length portion of the notch 24a has a linear shape or a curved surface shape substantially parallel to the outer peripheral sliding surface. Although not shown in the drawing, a similar notch is also formed in the range of a central angle of 20 ° to 40 ° from the other abutment surface facing the abutment surface shown in the drawing. The reason why the central angle is limited to the range of 20 ° to 40 ° is based on the same reason as that of the embodiment shown in FIG.
[0026]
The surface pressure distribution of the piston ring according to the first embodiment of the present invention and the surface pressure distribution of the piston ring of the conventional example were measured and compared using the surface pressure distribution measuring apparatus shown in FIG. In the measurement, the rings having the same axial thickness, outer peripheral surface shape, and radial thickness a ₁ were used.
[0027]
FIG. 4 shows the left half of the measuring apparatus. The cylinders 102 and 103 are supported by the cylinder holder 101, and a recess 103a is formed in a part of the outer peripheral surface of the cylinder 103 to become the thinnest part. A piston ring, which is a test piece, is mounted in the ring groove 105 a of the piston 105, and the outer peripheral surface of the piston ring is brought into contact with the inner peripheral surface of the cylinder 103. Then, the surface pressure from the piston ring acts on the thinnest part of the cylinder 103, and distortion occurs. Therefore, the strain gauge 104 was attached to the bottom of the recess 103a, the strain gauge 104 was connected to the strain amplifier 107, and the strain value was recorded on the pen recorder 108, thereby measuring the strain value as the surface pressure. Further, a temperature was measured by providing a J-type thermocouple 109 in the vicinity of the piston ring groove 105a and in the vicinity of the inner peripheral surface of the cylinder 103 at a position facing the piston ring, and connecting it to the high-speed dot meter 110. Further, a heater 106 is attached to the upper side of the piston 105 that holds the piston ring to heat the piston ring, while cooling water is brought into contact with the outer peripheral side of the cylinder 103 to cool the cylinder 103. A temperature gradient close to that during actual operation was distributed to the cylinder 103.
[0028]
5 and 6, the vertical axis represents the surface pressure, and the horizontal axis represents the circumferential angle from the joint portion. The black circles show the experimental results at normal temperature (both the ring and the liner are 20 ° C.), and the white circles show the actual operations (piston 250 ° C., liner 120 ° C.). In the piston ring of the same surface pressure of the conventional example, when the effect of the heat load is applied as shown by the white circle in FIG. 5, the surface pressure near the end of the joint is extremely increased. Then, as the piston ring was strongly pressed against the cylinder in the vicinity of the abutment end, hitting occurred in the range of 5 ° to 20 °.
[0029]
On the other hand, in the piston ring 1 according to the first embodiment of the present invention, as is clear from FIG. 6, the distribution of the surface pressure with respect to the cylinder 103 of the outer peripheral surface 3 at room temperature indicated by a black circle is It is zero over the vicinity, and the hit | omission part has arisen over the range of this central angle 15 degree | times from the end surface of the abutment part 2 as a starting point. In addition, the position where the center angle takes a maximum value after suddenly rising from zero toward the direction in which the central angle increases, then becomes a substantially constant value after gradually decreasing, and the surface pressure starts to become substantially constant is the end face of the abutment portion 12 Is the position where the central angle is approximately 80 °. Further, the change rate of the surface pressure at the position of the central angle of 15 ° starting from the end face of the joint portion 12 is discontinuous.
[0030]
However, when a heat load almost the same as that in actual operation was applied, the surface pressure in the vicinity of the abutment end increased as shown by the white circle, and no contact omission near the abutment end was observed. In addition, as compared with the conventional piston ring, a sudden increase in surface pressure at the end of the joint is not observed. Accordingly, in accordance with this, there is no longer any hit in the vicinity of the joint end 2. Note that, from this experimental result, it is understood that an extreme increase in the surface pressure at the abutment portion is not observed even when heating due to blow-by gas blown through at the abutment portion during actual operation is taken into consideration.
[0031]
In the present embodiment, only the formation of the notch portion on the inner peripheral side of the piston ring joint portion has been described, but such processing is performed by nitriding the steel and then forming the PVD coating on the sliding surface. By performing the operation on the piston ring, a more remarkable effect can be obtained. This is because the ring curvature near the joint can be increased by using the compressive stress of the PVD film and the nitride film.
[0032]
The surface pressure in the portion other than the vicinity of the abutment portion at the normal temperature in the present experiment a prototype about 1.5 kgf / cm ² about the piston rings have been experimented, this number-like depending on the application s It goes without saying that it can be set to.
[0033]
The piston ring according to the present invention is not limited to the above-described embodiment, and various modifications and improvements can be made within the scope described in the claims. For example, in this embodiment, it is configured such that a hit occurs at the abutment end at normal temperature. However, if the surface pressure at the abutment end is extremely small compared to other parts, the abutment does not occur. You may comprise as follows.
[0034]
【The invention's effect】
According to the piston ring of the present invention, in order to suppress the high surface pressure abutment end, to reduce the thickness dimension a ₁ of the piston ring radially in the vicinity of abutment part, thereby reducing the bending stiffness. Thereby, the surface pressure of an abutment edge part can be reduced rather than the piston ring of uniform cross-sectional shape. Therefore, during actual operation, it is possible to suppress an increase in the extreme surface pressure at the abutment portion, to prevent extreme wear of the abutment portion, and at the same time, particularly when a PVD coating is applied to the outer peripheral surface of the piston ring, the film cracks. It is possible to prevent troubles such as peeling. Further, according to the piston ring of the first aspect, since the radial thickness of the piston ring is gradually decreased, the bending rigidity is also gradually decreased, and stress concentration can be avoided.
[Brief description of the drawings]
FIG. 1 is a plan view showing a shape in the vicinity of a joint portion of a piston ring according to a first embodiment of the present invention.
FIG. 2 is a plan view showing a shape in the vicinity of a joint portion of a piston ring according to a second embodiment of the present invention.
FIG. 3 is a plan view showing a shape in the vicinity of a joint portion of a piston ring according to a third embodiment of the present invention.
FIG. 4 is a cross-sectional view showing a surface pressure distribution measuring apparatus used for measuring a surface pressure distribution of a piston ring and a surface pressure distribution of a conventional piston ring according to an embodiment of the present invention.
FIG. 5 is a broken line diagram showing a surface pressure distribution of a conventional piston ring.
FIG. 6 is a broken line diagram showing a surface pressure distribution of the piston ring according to the first embodiment of the present invention.
FIG. 7 is a diagram showing a surface pressure distribution of an isosurface pressure distribution.
FIG. 8 is a diagram showing a surface pressure distribution of an elliptic surface pressure distribution.
FIG. 9 is a diagram showing a surface pressure distribution of a peach type distribution (abutment high pressure distribution).
FIG. 10 is a diagram showing a surface pressure distribution of an apple-type distribution.
FIG. 11 is a view showing a shape of a conventional piston ring in the vicinity of a joint portion during engine operation.
[Explanation of symbols]
1,10,20,30 piston rings 2,12, 22 Go mouth 3,13, 23 outer peripheral surface 4, 14, 24 inner circumferential surface 4a, 14a, 14b, 24a, notch

Claims

An outer peripheral sliding surface that slides with respect to the cylinder, an inner peripheral surface that faces the piston, and one abutment that divides the substantially circular shape in the radial direction;
On the inner peripheral surface side, a notch portion forming a part of the inner peripheral surface is formed over a predetermined peripheral length portion starting from the end surface of the joint portion, and a portion other than the predetermined peripheral length portion is formed. A piston ring in which a radial thickness is constant and a radial thickness in the predetermined circumferential length portion is smaller than a radial thickness in a portion other than the predetermined circumferential length portion. ,
The notch has an arcuate surface shape that gradually approaches the outer peripheral sliding surface toward the end surface of the joint portion,
The radial thickness at the end face of the joint portion is 0.6 to 0.8 times the radial thickness at a portion other than the predetermined circumferential length portion,
The piston ring is characterized in that the predetermined circumferential length portion is formed over a central angle range of 30 ° to 50 ° defined by the central axis of the outer peripheral sliding surface.

An outer peripheral sliding surface that slides with respect to the cylinder, an inner peripheral surface that faces the piston, and one abutment that divides the substantially circular shape in the radial direction;
On the inner peripheral surface side, a notch portion forming a part of the inner peripheral surface is formed over a predetermined peripheral length portion starting from the end surface of the joint portion, and a portion other than the predetermined peripheral length portion is formed. A piston ring in which a radial thickness is constant and a radial thickness in the notch forming portion is smaller than a radial thickness in a portion other than the predetermined circumferential length portion. ,
The notch is formed at a plurality of substantially equal intervals on the inner peripheral surface side, and has an uneven shape in which the inner peripheral surface of the predetermined peripheral length portion is alternately continuous,
The piston ring is characterized in that the predetermined circumferential length portion is formed over a central angle range of 20 ° to 40 ° defined by the central axis of the outer peripheral sliding surface.

An outer peripheral sliding surface that slides with respect to the cylinder, an inner peripheral surface that faces the piston, and one abutment that divides the substantially circular shape in the radial direction;
On the inner peripheral surface side, there is formed a notch that forms a part of the inner peripheral surface symmetrically over a predetermined peripheral length portion, with a center point at a position away from the end surface of the joint portion, A piston ring in which a radial thickness in a predetermined circumferential length portion is smaller than a radial thickness of a portion other than the predetermined circumferential length portion,
The predetermined circumferential length portion of the notch has a straight or curved surface substantially parallel to the outer peripheral sliding surface, and the center point is located in a range of a central angle of 20 ° to 40 ° starting from the abutment end surface. Piston ring characterized by

4. The piston ring according to claim 1, wherein the steel base material is subjected to nitriding treatment, and then a PVD film is formed on the outer peripheral sliding surface .