柴油机曲轴减重孔对曲轴动态特性的影响

发布时间：2018-05-28 17:47

本文选题：曲轴 + 减重孔　；参考：《中北大学》2016年硕士论文

【摘要】：曲轴是发动机中结构最复杂、承受载荷最大、成本极高的核心零件,它的质量直接影响着柴油机的整体性能。曲轴在工作中承受着来自活塞连杆传递的周期性变化的扭矩作用,会产生扭转强迫振动,当外界激励频率和曲轴的自振频率接近或者相同时,就会发生共振现象。共振会使曲轴动力特性突变,扭振幅度剧增,加大曲轴承受的附加应力,产生噪音,加速曲轴齿轮的磨损,影响气门定时和供油提前角,严重影响发动机的耐久性能。曲轴减重孔的增设,可以减轻曲轴重量,降低过渡圆角处的应力集中,改善曲轴模态及连杆负荷。研究减重孔对曲轴特性的影响规律,对曲轴结构的改进与优化具有重要意义。本文以东风CY4102BZQ型号车用柴油机曲轴为研究对象进行了以下研究工作:(1)根据曲轴的实际尺寸参数,用Solidworks软件建立曲轴及轴瓦和轴承座的三维实体模型,将模型导入到workbench中,研究单元类型和尺寸对网格质量和网格收敛性的影响,设置适当的单元类型和单元尺寸,得到曲轴的有限元模型;(2)分别对不同尺寸减重孔的曲轴进行曲轴自由模态分析和约束模态分析,得到曲轴模态随减重孔尺寸的变化规律;(3)分析曲轴载荷,对曲轴施加适当的边界条件,对不同尺寸减重孔的曲轴进行强度分析和刚度分析,得到不同减重孔尺寸对曲轴应力和刚度的影响规律。通过对曲轴减重孔的研究,综合对比各模型的模态、强度和刚度,选取25mm来设定曲轴减重孔直径,实现曲轴减重4.65%。
[Abstract]:Crankshaft is the core part of engine with the most complex structure, maximum load and high cost. Its quality directly affects the overall performance of diesel engine. The crankshaft is subjected to the periodic variation of torque from the piston and connecting rod in the work, which will produce torsional forced vibration. When the external excitation frequency and the natural vibration frequency of the crankshaft are close to or the same, resonance will occur. Resonance will cause sudden change of crankshaft dynamic characteristics, increase the amplitude of torsional vibration, increase the additional stress of crankshaft, produce noise, accelerate the wear of crankshaft gear, affect valve timing and fuel supply advance angle, and seriously affect the durability of engine. The addition of weight loss holes in the crankshaft can reduce the weight of the crankshaft, reduce the stress concentration at the transition corner, and improve the crankshaft mode and the connecting rod load. It is of great significance to study the influence of weight loss holes on the characteristics of crankshaft and to improve and optimize the structure of crankshaft. This paper takes the crankshaft of Dongfeng CY4102BZQ diesel engine as the research object. (1) according to the actual size parameters of the crankshaft, the 3D solid model of crankshaft, bearing bush and bearing seat is established by Solidworks software, and the model is imported into workbench. To study the effect of cell type and size on mesh quality and mesh convergence, set appropriate cell types and cell sizes, The finite element model of crankshaft is obtained. The free mode analysis and constrained modal analysis of crankshaft with different sizes of weight reducing holes are carried out, and the crankshaft load is analyzed according to the variation of crankshaft mode with the size of weight reducing hole. By applying proper boundary conditions to the crankshaft, the strength and stiffness of the crankshaft with different sizes of weight reducing holes are analyzed, and the influence of the different size of the reducing hole on the stress and stiffness of the crankshaft is obtained. Through the study of the weight loss hole of the crankshaft, the mode, strength and stiffness of each model are compared synthetically, and the diameter of the weight loss hole of the crankshaft is set by selecting 25mm to realize the weight loss of the crankshaft 4.65.
【学位授予单位】：中北大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U464.172

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