曲轴不同平衡率对曲轴强度与振动特性的影响  

Study on the influence of the crankshaft’s different balance rates upon its strength and vibration

作　　者：毕玉华[1] 罗力 张磊[1] 王鹏[1] 姚国仲[1] 申立中[1] 代云辉 BI Yu-hua;LUO Li;ZHANG Lei;WANG Peng;YAO Guo-zhong;SHEN Li-zhong;DAI Yun-hui(Yunnan Key Laboratory of Internal Combustion Engine,Kunming University of Science and Technology,Kunming 650500;Kunming Yunnei Power Co.,Ltd.,Kunming,650217)

机构地区：[1]昆明理工大学云南省内燃机重点实验室,云南昆明650500 [2]昆明云内动力股份有限公司,云南昆明650217

出　　处：《机械设计》2020年第8期11-20,共10页Journal of Machine Design

基　　金：国家自然科学基金资助项目(51765025);云南省科技强省资助项目(2015AA024)。

摘　　要：曲轴不同平衡方案不仅直接影响整机振动与噪声,还影响曲轴的轻量化设计。研究不同平衡率方案曲轴对发动机振动与曲轴强度的影响,优化设计曲轴,对降低整机振动与提高可靠性具有重要意义。以非道路高压共轨四缸柴油机为研究对象,系统分析了不同平衡率与不同平衡块结构的4个曲轴方案的平衡性;通过曲轴模态试验与机体模态仿真,验证了曲轴和机体有限元模型的准确性;基于柔性多体动力学理论,建立了整机多体动力学仿真模型,研究了曲轴不同平衡率对额定转速工况下曲轴强度与振动特性的影响。研究结果表明:随着平衡率增加,曲轴各圆角处最大应力值增大,曲轴圆角疲劳安全系数降低;最大应力值为284.1 MPa,最小安全系数为1.7,均出现在四平衡块100%平衡率曲柄销圆角处。随着平衡率增加,油底壳关注点的不同谐次下振动加速度峰值减小,机体上各关注点的振动速度级降低,汽缸盖罩在低频段下振动速度级降低。随着平衡率增加,各倍频程下机体振动速度级降低,倍频程中心频率为500 Hz,汽缸盖罩和油底壳振动速度级增大。Different balancing schemes of the crankshaft not only directly affect the whole machine’s vibration and noise,but also affect its lightweight design.It is of great significance to explore the influence of different balance rates for improving the engine’s vibration and strength,optimizing its design,and ensuring a higher standard of reliability.This article focuses on the nonroad four-cylinder high-pressure common-rail diesel engine.The balance of four crankshaft schemes with different balance rates and different balance weight structures is analyzed systematically.Both the crankshaft‘s modal test and its block’s modal simulation are conducted to verify that the finite-element models of both the crankshaft and its block are accurate.Based on the theory of flexible multi-body dynamics,the whole machine’s multi-body dynamic simulation model is worked out.The influence of the crankshaft’s different balance rates upon its strength and vibration under the conditions of rated power is explored.The results show that the maximum stress at each fillet increases and the factor safety decreases as the balance rate rises.The maximum stress is 284.1 MPa and the minimum safety factor is 1.7,both of which occur at the fillet of the crank pin with four counterweights and the balance rate of 100%.With the ever-growing balance rate,the peak of vibration acceleration at different harmonic orders of points of the oil sump decreases,the velocity level of points of the block decreases,and the velocity level of the cylinder head cover decreases at the low frequency.In addition,with the ever-growing balance rate,the velocity level of the block decreases at each octave;the velocity level of both the cylinder head cover and the oil sump increases when the center frequency of the octave is 500 Hz.

关 键 词：柴油机 平衡率 疲劳强度 振动特性 

分 类 号：TK422[动力工程及工程热物理—动力机械及工程]