基于装配质量的滚珠丝杠进给系统热力耦合机理的理论与试验研究

Because accuracy measurement and technique assurance steps of assembly are imperfect, the performances and their preservation of the machine tools made in China are poorer than that for the foreign products, which has become the technical bottleneck of machine tool industry development in our country. This project takes the ball screw feed system as a subject investigated. By combining mutative scale straightness measurement with continuous measurement, detecting instrument of assembly error and the corresponding algorithm of errors separation are developed, the methods of evaluation and continuous description for the assembly errors of ball screw feed systems are proposed. By combining experiments with finite element thermal analysis, the method of identifying the heat sources strength is investigated to determine the friction distributions of the parts. Time variance of the thermal error and temperature distributions in the feed system is investigated. The effect of the assembly errors on the contact rigidity in screw-nut is investigated by finite element analysis. The non-linear dynamic model of feed system is established to analyze the variations of the frequency response function with the worktable position. These facts will reveal thermal mechanical coupling mechanism of ball-screw feed systems. Variations of instantaneous average friction tendency, time-frequency characteristics of friction fluctuating signal , turning driving work with the worktable position and accumulative driving work are investigated to extract the identification characteristics of screw wear, and then a comprehensive evaluation method of nonuniform pitch errors of shaft is proposed. The research results can provide a theoretical basis for accuracy control, technique and technological improvement, and ball screw selection for the feed system assembly.

由于机床装配精度检测、工艺保证措施的不完善，致使国产机床的功能及其保持性与国际水平尚有较大差距,并已成为国内机床产业发展的技术瓶颈。本项目以滚珠丝杠进给系统为研究对象，通过变尺度测量与连续检测相结结合方法，开发装配误差检测仪器和误差分离计算算法，提出进给系统装配误差的评估和连续描述方法。通过试验和有限元热分析相结合，研究进给系统热源强度的辨识方法，确定各部件的摩擦力分布，探索热误差和温度分布的时变特性；通过有限元分析，确定装配误差对丝杠螺母副接触刚度的影响，建立进给系统的非线性动力学模型，分析其频率响应函数随工作台位置的变化规律，揭示进给系统的热力耦合机理。研究进给系统的摩擦力瞬时均值及波动信号时频特征、切削驱动功随工作台位置和累计驱动功的变化，提取丝杠磨损的识别特征，提出丝杠节距误差不均匀度的综合评估方法。为滚珠丝杠进给系统的装配误差控制、工艺改进和丝杠筛选提供理论依据。

由于机床装配精度检测、工艺保证措施的不完善，致使国产机床的功能保持性与国际水平沿有较大差距，并已成为国内机床产业的瓶颈。针对这一国内机床产业的现状，本项目研究了数控机床滚珠丝杠进给系统导轨安装面直线度和平行度误差的检测方法，提出了安装面直线度和平行度误差的评估方法。基于阻容网络热传导模型，推导出网络中各节点温度与系统热载荷关系的时变表达式，提出了进给系统热源载荷辨识的算法，实现了滚珠丝杠进给系统温度场分布和热误差的预测。基于赫兹接触理论,建立角接触球轴承的热力耦合模型，探明了轴承工况变化对轴承内部接触参数、载荷分布和以及发热率的影响；建立滚珠丝杠副的拟动态接触模型，提出了滚珠丝杠副摩擦热计算方法，通过数值计算分析了丝杠转速和外载荷对滚珠丝杠副接触参数的影响，揭示了进给系统的热力耦合机理。基于赫兹接触理论，建立了进给系统接触载荷的非线性方程组，通过数值计算探明了螺母位于丝杠在不同位置时接触载荷、接触角和扭转角的分布规律，分析了联轴器平行不对中误差和丝杠轴线与导轨平行度误差对滚珠丝杠副接触特性与载荷分布的影响。通过推导丝杠螺母、直线导轨和滚动轴承的非线性恢复力函数以及丝杠轴的刚度，建立了滚珠丝杠进给系统的十四自由度动力学模型；基于将Newmark方法与Monte Carlo模拟相结合，提出了的进系统动力学方程组的数值求解算法；通过数值计算，探明了系统动力学参数及导轨装配误差对进给系统动态特性的影响，并进行了实验验证。提出了利用伺服电机力矩电流估计进给系统摩擦力的方法，通过试验检测提取了不同类型、不同工作状态的多台车床主进给系统的摩擦力均值和波动量频谱成分与丝杠螺母副的位置关系，对比分析了丝杠局部误差及磨损状态、进给方向及进给速度对摩擦力瞬时均值和波动量频谱的影响，进而提出进给系统健康状态评估的方法。本项目的研究成果为进给系统的设计与制造提供理论依据。