供油条件对线接触热混合润滑性能的影响

Effects of Oil Supply Conditions on Thermal Mixed Lubrication Performance of Line Contact

为提高齿轮、圆柱滚子轴承等线接触副零件的润滑性能,有必要研究供油条件对其混合润滑特性的影响。基于平均流量模型,建立考虑供油条件的线接触非牛顿热混合润滑模型。将入口供油量作为控制乏油程度的参数,同时考虑膜厚比(最小膜厚与粗糙度的比值)与粗糙峰接触载荷比(粗糙峰接触载荷与总载荷的比值)来判断润滑状态,研究供油量、速度、接触副材料和环境黏度对混合润滑性能的影响。结果表明:随着供油量的增加,膜厚比增加,粗糙峰接触载荷比减小,最小膜厚与中心膜厚逐渐增大,平均摩擦因数逐渐减小,油膜最高温度逐渐增加,但最终都趋于稳定值;对于3种不同接触副(钢-钢、钢-Si_(3)N_(4)和Si_(3)N_(4)-Si_(3)N_(4)),钢-钢接触副的总压力与油膜温度最低,Si_(3)N_(4)-Si_(3)N_(4)接触副的总压力与油膜温度最高;在充分供油时,Si_(3)N_(4)-Si_(3)N_(4)接触副油膜厚度略高,膜厚比最高,粗糙峰接触载荷比最低;在乏油条件下,钢-钢接触副油膜厚度略高,膜厚比最高,粗糙峰接触载荷比最低;随着速度或环境黏度的增加,油膜厚度增加,总压力基本不变,粗糙峰压力减小,膜厚比增大,载荷比减小。与充分供油相比,乏油条件下的混合润滑性能较差。

To improve the lubrication performance of line contact pairs such as gears and cylindrical roller bearings,it is necessary to investigate the effects of oil-supply conditions on their mixed lubrication characteristics.Based on the average flow model,a line contact non-Newtonian thermal mixed lubrication model was established by considering oil supply conditions.Taking the inlet oil supply quantity as the parameter to control the degree of starvation,and by simultaneously considering the film thickness ratio(the ratio of minimum film thickness to roughness)and the rough peak contact load ratio(the ratio of rough peak contact load to total load)to judge the lubrication state,the effects of oil supply quantity,velocity,contact pair materials and ambient viscosity on mixed lubrication performance were studied.The results show that,with the increase of oil supply quantity,the film thickness ratio increases,the asperity contact load ratio decreases,the minimum and central film thickness increase gradually,the average friction coefficient decreases,and the maximum film temperature increases gradually.However,they tend to a stable value finally.For three different contact pairs(steel-steel,steel-Si_(3)N_(4) and Si_(3)N_(4)-Si_(3)N_(4)),the total pressure and oil film temperature of steel-steel contact pair are the lowest,and the total pressure and oil film temperature of Si_(3)N_(4)-Si_(3)N_(4) contact pair are the highest.Under the fully flooded condition,the film thickness of Si_(3)N_(4)-Si_(3)N_(4) contact pair is higher slightly,the film thickness ratio is the highest,and the asperity contact load ratio is the lowest.Under the starved condition,the film thickness of the steel-steel contact pair is thicker slightly,the film thickness ratio is the highest,and the asperity contact load ratio is the lowest.With the increase of velocity or ambient viscosity,the film thickness increases,the total pressure remains unchanged,the asperity pressure decreases,the film thickness ratio increases and the asperity contact load ratio decreases.Different from fully flooded condition,the mixed lubrication performance is poor under the starved condition.