精密机床主轴导热通道高效集中散热机制研究

Bearings and built-in motor are the main heat sources of the spindle. As the demands for precision machine tool is increasing, reducing the impacts of inner heat sources on the manufacturing accuracy becomes more and more important. The efficiency of traditional cooling methods is low. And the heat of cooling fluids could be absorbed by the spindle house and other parts. In this project, conducting paths were used to transfer the heat generated by the inner heat sources to outside of the spindle system for cooling intensively by reference to the centralized cooling idea in microelectronics field. By using the new method, the impacts of heat sources on the temperature rise of the spindle and machining accuracy were minimized..Firstly, the temperature fields and heat rising of the bearings in the front and end of the spindle system and built-in motor were investigated. Secondly, conducting paths were built according to the temperature gradient and non-uniform temperature field. The inner heat would be transferred through the conducting path to outside of spindle system. In order to improve the heat transfer efficiency, the size and number of the paths were studied. To avoid the heat transferring from the inner wall of paths to bearing block and spindle house, the filled material with high heat conductivity was coated with thermal insulation material. The layout of paths was optimized based on the non-uniform temperature field of the bearings and built-in motor to intensify the heat dissipation and guarantee that the spindle temperature in both radial and axial direction was equalized with the room temperature. Finally, a testing apparatus was built up to verify the feasibility and effectiveness of transferring heat trough the conducting paths and then implementing centralized cooling for the precision spindle.

机械主轴轴承发热或电主轴电机发热是精密机床内部主要热源，随着机床精度要求的提高，减小机床内部热源的影响显得愈加重要。传统的散热方式效率低，并且热量还会被主轴壳体及安装部件吸收。本项目借鉴微电子领域集中散热的思路，提出利用导热通道将主轴内部热源发热量高效传导到主轴外再进行集中冷却的新思路，以减小主轴内部热源对主轴精度及各部件温升的影响。.研究主轴轴承及内置电机轴向、周向温度场分布和温升特性，根据温度场分布不同以及热源温度与室温间的温度梯度，构建导热通道将热量高效传导至主轴系统外，研究导热通道尺寸、数量对散热效率的影响规律。为避免通道内热量传递至轴承座和壳体上，在填充的高导材料外增加绝热涂层。以散热强度最大化为目标，根据主轴前后端轴承和电机轴向与周向温场的不同，确定合理的导热通道布局，以达到主轴系统轴向和周向温升与室温的平衡。搭建实验台，验证项目所提导热通道高效集中散热方案的可行性。

随着机床向高速、高精方向发展，机床热问题越来越受到科学家和工程师的关注。主轴是精密机床内部的主要热源，而主轴轴承和主轴内置电机发热是导致主轴温度升高并产生热误差的根本原因。为减小机床主轴发热对机床精度的影响，工程上往往采用强制冷却的方式，如在主轴系统外部增加螺旋水道并通有冷却液。然而，这种传统的散热方式效率低，并且热量还会被主轴壳体及安装部件吸收。..本项目借鉴微电子领域集中散热的思路，提出利用导热通道将主轴内部热源发热量高效传导到主轴外再进行集中冷却的新思路，以减小主轴内部热源对主轴精度及各部件温升的影响。项目以主轴轴承为研究对象，建立了二维导热模型，沿径向方向构建导热通道，并填充高导材料，为了避免通道内热量沿周向传递至轴承座和壳体上，在填充的高导材料外增加绝热涂层。利用解析法分析了导热通道尺寸、数量以及填充材料体积占比对二维导热模型散热效率的影响规律，确定了最优的导热通道布局方法。借助有限元方法对散热效果进行仿真，结果表明：与传统冷却方法相比，利用导热通道进行高效集中散热，最高可使主轴轴承平均温度降低约20%。