平面磨床砂轮主轴—轴承系统热—结构耦合分析与试验研究

发布时间：2018-09-05 18:58

【摘要】：机床主轴系统的高精度主要受主轴轴承的预紧状态和热态特性稳定性的影响。分析机床主轴系统在工作时的温升和热变形等热特性是提高数控机床加工精度的关键,且能有效改进数控机床产品的性能。主轴系统中的轴承摩擦热是主要的内部热源,轴承摩擦发热使得主轴系统中各个部件之间出现不同的温升,而温升又引起各部件的热膨胀,进而导致主轴产生热位移。为了进一步研究机床主轴系统各部件之间温度随时间变化的规律与其自身热变形的变化特征,本文以MGK7120×6高精度卧轴矩台平面磨床为研究对象,对其砂轮主轴-轴承系统进行了温度场与热变形的仿真,并对主轴系统进行了温度测量试验以验证温度场仿真的正确性。本文主要研究工作如下:(1)基于滚动轴承热态特性理论,对轴承的摩擦起因与摩擦力矩进行了详细介绍与计算。以传热学理论为基础,对具有不同导热系数的物质之间的三种基本传热模式做了理论阐释与分析,且进一步总结了传热分析的四种分析方法。(2)基于温度场热传导与边界条件理论,对主轴-轴承系统进行了稳态和瞬态的温度场仿真计算。从稳态温度场仿真结果分析了主轴沿轴线方向上的温度分布规律,且改变主轴的转速后得到了不同转速下轴承部件的温度变化。从瞬态温度场仿真结果分析了轴承滚子与内外圈滚道温度随时间的变化规律,进一步得到了时间t=600s、1800s、3600s和4800s时的主轴沿轴线方向的温度分布曲线对比图。(3)基于Hertz弹性接触理论,对滚动轴承的应力与变形进行了计算公式的分析。根据热-结构耦合分析理论且在温度场仿真的基础上,对主轴-轴承系统进行了热-结构耦合分析。由仿真得到的结果有:轴承滚子表面热应力分布为椭圆形状,且与Hertz弹性接触应力的描述相同;建立轴承内外圈沿圆周方向的路径,得到轴承内外圈在径向、切向与轴向三个方向的热位移大小,且进一步得出了轴承内外圈在三个方向的热位移变化形状;最后建立主轴沿轴线方向的路径,得到了主轴在径向、切向与轴向三个方向的热位移与热应力的变化规律。(4)针对主轴-轴承系统温度场仿真结果,对MGK7120×6高精度卧轴矩台平面磨床砂轮主轴系统进行了温度测量试验,以此验证主轴-轴承系统温度场仿真的正确性。改变主轴转速,重复试验,得到了转速与热平衡时间两者之间的关系。
[Abstract]:The high accuracy of machine tool spindle system is mainly affected by the preload state and thermal characteristic stability of spindle bearing. The analysis of the temperature rise and thermal deformation of the spindle system is the key to improve the machining accuracy of the NC machine tool, and the performance of the CNC machine tool product can be improved effectively. The friction heat of bearing in spindle system is the main internal heat source. The friction heat of bearing causes different temperature rise among the parts of spindle system, and temperature rise causes the thermal expansion of each component, which leads to the thermal displacement of spindle. In order to further study the variation of temperature with time between parts of machine tool spindle system and the variation characteristics of its own thermal deformation, this paper takes MGK7120 脳 6 high-precision horizontal grinding machine with lying shaft moment table as the research object. The temperature field and thermal deformation of the spindle bearing system of the grinding wheel are simulated, and the temperature measurement test of the spindle system is carried out to verify the correctness of the temperature field simulation. The main work of this paper is as follows: (1) based on the theory of hot state characteristic of rolling bearing, the friction cause and friction moment of bearing are introduced and calculated in detail. Based on the theory of heat transfer, three basic heat transfer modes between materials with different thermal conductivity are theoretically explained and analyzed. Furthermore, four methods of heat transfer analysis are summarized. (2) based on the theory of heat conduction and boundary conditions of temperature field, the steady and transient temperature field simulation of spindle bearing system is carried out. Based on the simulation results of steady state temperature field, the temperature distribution of the spindle along the axis is analyzed, and the temperature change of bearing parts under different rotational speeds is obtained by changing the rotation speed of the spindle. From the simulation results of transient temperature field, the temperature variation law of bearing roller and inner and outer ring raceway with time is analyzed, and the temperature distribution curves of spindle along axis direction at time t ~ (600s) ~ 1800s ~ (36) s) and 4800s are further obtained. (3) based on Hertz's elastic contact theory, The stress and deformation of rolling bearing are analyzed. Based on the thermal-structural coupling analysis theory and temperature field simulation, the thermal-structural coupling analysis of the spindle bearing system is carried out. The results obtained from the simulation are as follows: the thermal stress distribution on the bearing roller surface is elliptical, which is the same as the description of the Hertz elastic contact stress, the path of the inner and outer ring of the bearing along the circumferential direction is established, and the radial direction of the inner and outer ring of the bearing is obtained. The magnitude of the thermal displacement in the tangential and axial directions, and the shape of the thermal displacement of the inner and outer rings of the bearing in the three directions are further obtained. Finally, the path of the spindle along the axis is established, and the radial direction of the spindle is obtained. The variation of thermal displacement and thermal stress in three directions of tangential and axial direction. (4) according to the simulation results of temperature field of spindle bearing system, the temperature measurement test of MGK7120 脳 6 high precision horizontal grinding wheel spindle system for horizontal grinding machine is carried out. The correctness of temperature field simulation of spindle bearing system is verified. The relationship between rotational speed and heat balance time is obtained by changing the spindle speed and repeating the test.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG596

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