舶用エンジンのクロスへッド軸受の潤滑特性

摘要

The crosshead bearings in large two-stroke diesel engines operate under severe lubrication conditions, because the bearings oscillate within a small angle at a low speed and are subject to a high specific load. Crosshead bearings have several axial oil-grooves on the loaded surface to promote oil film exchange with bearing oscillation. However, because the development of a thick oil film by hydrodynamic action is impaired by these oil grooves, the bearings become prone to damage by seizure and fatigue cracking. This manuscript describes the lubrication characteristics of the crosshead bearings. A decrease in the clearance ratio is generally effective at enhancing the squeeze action on the entirety of the bearing pads. However, this degrades the formation of an adequate wedge film and reduces the load carrying capacity. Incorporating oil-grooves with tapered geometry and an externally pressurized lubrication system promotes a thicker oil film, achieving a significant enhancement of the load carrying capacity. The aluminum-tin bearing coated with a tin-copper overlay improves running-in properties, enhancing the load carrying capacity.%大型2ストロークディーゼル機関のクロスへッ ド軸受（図1)は，高い荷重が常に下向きに作用す ることと小さい揺動運動しか行わないという特徴 が重なるため油膜が薄く,焼損，破損を起こしや すい滑り軸受である.近年の大型機関では高 効率化と排ガス規制への対応が強く求められてお り正味平均有効圧力の上昇とコンパクト化が進ん でいる.その結果，クロスヘッド軸受の潤滑状態 がー段と苛酷化する傾向にあり負荷能力の向上が 課題になっている.著者らはクロスヘッド軸 受の潤滑状態を模擬した軸受試験機を用いて油膜 厚さの計測と負荷限界試験を実施してきた.ここ では本試験機で得られた実験結果を中心に，ク口 スへッド軸受の潤滑特性および負荷能力の向上策 について解説する.