On the Design of Precise Linear Motion Bearing Mechanism in Vacuum

本研究的目的是1)研究滑块在真空中的干摩擦特性及其对运动精度的影响；2)提出滑块机构的设计方法。在这里，其性能目标是更高的负载能力，更长的行程（米级）和更高的精度（微米级）比传统的。实验用滑块为不锈钢材质，尺寸为90x120x20（滑面为2）。宽度，长度120mm， 2排，接触压力39kPa)，由导线驱动。钢轨也是由不锈钢制成，长度为600毫米。采用三个间隙传感器和二轴激光干涉测量系统测量滑块滑动过程中的角运动和直线运动。摩擦系数通过安装在传动轴上的应变片测量。实验条件为大气压、1.3x10^<-4>和1.3x10^<-5>。气压和滑动速度可调至40 mm/s。在这些条件下，澄清了下列事项。1)摩擦系数与滑动速度的关系不大，但趋势不同。即在大气中，随着速度的增加，e系数减小，而在真空中，e系数增大。2)在真空条件下，摩擦系数均值增大，但散点减小。3)经过一些滑动循环后，摩擦系数突然增加，滑块被锁住（粘附）。运动精度不一定取决于摩擦系数。观察到一些良好的运动精度。然而，当摩擦系数分散时，精度降低。粘连发生后，精度变得极低。根据实验结果，研究了一些设计准则。

The purpose of this research is 1) to investigate the dry frictional behavior of a slider in vacuum and its effect on the motion accuracy, and 2) to propose a design procedure of a sliding mechanism. Here, t he goal of its performance is higher load capacity, longer stroke (meter order) and higher accuracy (micron meter order) than the conventional ones.The slider for experiment is made of stainless steel which dimensions are 90x120x20 (sliding face is 2. width, 120 mm length, 2 rows, contact pressure 39kPa) and was driven by a wire. The rail is also made of stainless steel and its length is 600 mm. Three gap sensors and 2-axes laser interferometry system were used to measure the slider's angular and linear motion during sliding. Frictional coefficient was measured by a strain gage attached on the driving shaft.As the experimental conditions, pressure were set as atmosphere, 1.3x10^<-4> and 1.3x10^<-5>. Pa and sliding speed was adjusted up to 40 mm/s. Under these conditions, the following was clarified.1) Coefficient of friction does not depend on sliding speed so much, however, the tendency is different. That is, in atmosphere the coefficient decrease with the speed increase, on the other hand in vacuum th e coefficient is increase.2) In vacuum, the mean value of coefficient of friction increase, however, the its scatter becomes small.3) After some cycles of slide, the coefficient of friction suddenly increase and sliders are locked.(adhesion).The motion accuracy did not necessarily depend on the coefficient of friction. Some good motion accuracy was observed. However, when the coefficient of friction scatter, the accuracy became low. After the adhesion has occurred, the accuracy became extremely low.According to the experimental results, some design guideline was studied.