A New Precise Temperature Controlling Method for Machine Tool Structures

近年来，人们对机床的加工精度提出了更高的要求。但在加工过程中要保持较高的精度是非常困难的。加工误差的原因之一是机床的热变形，特别是非稳态条件下的热变形，进而将两个热源视为机床非稳态热变形的原因。它们如下：(1)内热源：如轴承、电机等。(2)外热源：车间内的温度变化和车间墙体和其他机床的热辐射。在本研究中，提出了两种新的方法来防止在非稳态条件下由内热源和外热源引起的热变形。在第一种方法中，采用强制冷却的方法来带走内热源…产生的热更多的资源通过结构。这种冷却是在结构周围局部进行的，冷却液的温度不是在20^ﾟC保持恒定，而是根据内部产热而变化。这种控制方法已应用于可被认为具有内热源的主轴结构。在第二种方法中，结构的外表面被隔热，以减小外部热源变化的影响。在这种隔热方法中，在结构的外表面贴上两层隔热材料，并在它们之间流动温控空气。将这种隔热方法应用于某机床立柱，得到以下结论：(1)采用这种内冷方法控制的气缸温升或热变形很小，时间常数很短。(2)在这种隔热方法中，如果内冷完全带走内源产生的热量，结构的温度将保持在20ﾟ℃不变。较少

In recent years, a high machining accuracy have been demanded from machine tools. But it is very difficult to keep a high accuracy during machining. One of the causes for the machining errors is the thermal deformation of machine tools, especially, the thermal deformation in unsteady-state conditions.Then, two heat sources are considered as the cause of thermal deformations of machine tool in unsteady-state conditions. They are as follows :(1) Inner heat sources : Such as bearings, motors and so on. The heat generation in them varies with the variation of the spindle speed.(2) Outer heat sources : The room temperature variation in a machine shop and thermal radiation from the walls of the machine shop and the other machine.In this study, two new methods are thought out to prevent the thermal deformation in unsteady-state conditions caused by the inner heat sources and outer heat sources.In the first method, forced cooling is adopted to take away the heat generated at the inner heat sou … More rce which passes through the structure. This cooling is carried out locally around the structure and the temperature of the coolant is not kept constant at 20 ^ﾟC, but varied according to the inner heat generation. This controlling method has been applied to a main spindle structure which may be considered to have a inner heat source. A hollow cylinder is considered as the model of the structure which supports a main spindle through bearings at which heat is generated.In the second method, the outer surface of the structure is thermally isolated to have little influence of the variable outer heat sources. In this isolating method, two sheets of thermal insulator are attached on the outer surface of the structure and the temperature controlled air is flowed between them. This isolating method has been applied to a column of a machine tool.In this study, the following conclusions are obtained.(1) The temperature rise or the thermal deformation of this cylinder controlled with this inner cooling method is very small and the time constant is very short.(2) In this isolating method, the temperature of the structure will be kept constant at 20^ﾟC if the heat caused by inner source is perfectly taken away by the inner cooling. Less