マイクログループ軸受の混合潤滑モデル（第2報）: 自動車エンジン用コンロッド大端部軸受への適用芦原克宏

摘要

近年，自動車エンジン用のすべり軸受はますまrnす苛酷な運転条件下で使用されることが多くなっrnてきている．代表的な事例として，高出力化に対rn応する高回転・高荷重，低燃費を目的とした低粘rn度潤滑，アイドリングストップ機能やハイブリッrnド方式の採用により増加するエンジンの停止・始rn動時のスターブ潤滑などが挙げられる．このようrnな苛酷な運転条件下では，油膜厚さが表面粗さよrnり薄くなり，軸と軸受表面の一部が接触する混合rn潤滑状態となりやすく，その結果異常摩耗や焼付rnき・疲労といった損傷の危険性が高まることが懸rn念される．%Recently, in designing of plain bearings for automotive engines, it is necessary to establish the mixed lubrication model considering asperity contact between bearing and journal surfaces. A numerical calculation model under mixed lubrication conditions for microgrooved bearings, which was formulated in the previous paper, can easily predict contact pressures and real contact areas between bearing and journal surfaces. Then, in this paper, the model is applied to predict the performance of engine bearings. From the numerical results, it was found that when the engine is started under low speed conditions, relatively wide area of real contact will occur, but friction loss is not significant because of low shearing velocity. It was also found that when the engine is operated under high speed conditions, real contact area is limited to relatively narrow range, but friction loss increases because of high shearing velocity. Moreover, under both low and high rotational speed conditions, severe contact will occur near the bearing edge from the bearing angles of 50 degrees to 110 degrees.