连杆小头摩擦副间隙形状对活塞销润滑及冲击特性的影响

Influence of Clearance Shape of Small Head Friction Pair of Connecting Rod on Lubrication and Impact Characteristics of Piston Pins

为改善柴油机全浮式活塞销与连杆小头间的润滑与冲击特性,基于弹流润滑理论和粗糙峰接触理论,采用测试与仿真分析方法,运用AVL Power Unit建立活塞连杆组柔性多体动力学模型,研究不同抛物型线和三角型线方案连杆小头衬套对连杆小头轴承润滑与活塞销冲击特性的影响。结果表明:在润滑与冲击特性方面,效果最好的是抛物型线衬套,而三角型线衬套由于平均间隙较大,不能形成有效的润滑,润滑与冲击特性相对较差,其中抛物型线相比直线型线最小油膜厚度最小值平均增加了0.104μm,峰值油膜压力最大值平均降低了8.29 MPa,峰值油膜压力平均值平均增加了7.62 MPa,峰值粗糙接触压力最大值平均降低了77.19 MPa。综合连杆小头轴承润滑与活塞销冲击特性,采用最大径向切削量为12μm的抛物型线衬套是最优的连杆小头衬套型线方案,对连杆小头轴承润滑与活塞销的冲击性能改善较大,其中最小油膜厚度的最小值增加了0.170μm,峰值油膜压力最大值减小了8.28 MPa,峰值粗糙接触压力最大值降低了119.49 MPa,进气冲程前期和排气冲程后期活塞销加速运动阶段相对于连杆小头的纵向加速度峰值分别减小了0.33 mm/s~2和0.24 mm/s~2。

In order to improve the lubrication and impact characteristics between the full floating piston pin and the small head of connecting rod of diesel engine,a flexible multi-body dynamics model of piston and connecting rod group was established by AVL Power Unit based on the elastohydrodynamic lubrication theory and rough peak contact theory.Considering the influence of small head bushing of connecting rod with different parabolic profile and triangular profile scheme,lubrication and piston pin impact characteristics of connecting rod small head bearing was studied.Results show that the parabolic bushing has the best lubrication and impact characteristics,while the triangle bushing can not form effective lubrication due to the large average clearance,and the lubrication and impact characteristics are relatively poor.The minimum oil film thickness of the parabolic bushing is 0.104 μm higher than that of the linear bushing.The maximum peak oil film pressure decreased by 8.29 MPa on average,the average peak oil film pressure increased by 7.62 MPa,and the maximum peak rough contact pressure decreased by 77.19MPa on average.Considering the characteristics of small head bearing lubrication and piston pin impact,parabolic bushing with the maximum radial cutting of 12 μm is the best small head bushing profile scheme of connecting rod.The impact performance of small head bearing lubrication and piston pin impact of connecting rod is improved greatly,and the minimum oil film thickness increases by 0.170 μm.The maximum value of peak oil film pressure and peak rough contact pressure decreases by 8.28 MPa and 119.49 MPa respectively.The peak value of longitudinal acceleration of piston pin relative to the small head of connecting rod in the early intake stroke and late exhaust stroke decreases by 0.33 mm/s~2 and 0.24 mm/s~2 respectively.