双半外圈调心球轴承预紧力和预紧量的分析计算

预紧是保证轴承刚度和旋转精度的重要途径。为了保证双半外圈双列调心球轴承的预紧效果，对其预紧力的确定和预紧量的大小进行了分析计算。目前这种双半外圈双列调心球轴承在轴承分类中还没有，它结合了成对双联向心推力球轴承和双列向心调心球轴承的优点。既能实现大角度调心，调心角度达3°，又能进行轴向预紧。通过对这类轴承的力学分析，推导了轴向预紧力与轴承支撑负载的关系公式。预紧量是通过控制两个半外圈之间的隔圈厚度进行调节的，基于弹性接触理论，推导了轴承定位隔圈磨削量大小的公式。这种轴承在国家重大科技项目LAMOST天文望远镜像场旋转轴中得到应用，内径1100mm的轴承现场安装预紧调整后实测，在任意50°范围内（旋转轴工作范围），轴系径向跳动小于0.02mm，端面跳动小于0.03mm。满足了LAMOST对像场旋转轴系刚度和旋转精度的要求。跟星实测像场旋转精度RMS值优于0.3″。

Preload and precompact analysis and calculation of two-piece outer ring self-aligning ball bearing

Preload is an effective way to ensure the bearing having the high working stiffness and accuracy. The analysis and calculation of preload and precompact of a kind of bearing is given in this paper. This bearing is a combo of double row angular contact ball bearing and double row self-aligning ball bearing. The main feature of double row contact angular bearing is that it can be preloaded during the integration. The direct result is that the working stiffness of the rotator, supported by the double row contact angular bearings, can be improved greatly. For the double row self-aligning ball bearing, just as its name states that its main feature is that it can compensate the misalignment of the shaft supporting bases. So, the main features of the combo are: preloaded to enhance stiffness and self-aligning to compensate the misalignment. We call this bearing two-piece outer ring double row self-aligning ball bearing. In order to be preloaded properly, the outer ring is consisted of two spherical inner face raceways, which form a spherical surface whose center is common to the bearing center, and a in-between spacer. Controlling the thickness of spacer is a way to control the bearing preload. The inner ring has two raceways. The steel balls, cage and inner ring can rotate freely at a certain angle. The allowable misalignment angle of this bearing is about 3 °. The relationship between preload and bearing supporting load is analysed and formulated with the help of mechanics theory. Meanwhile, based on the Hertz contact theory, the formular to determine the spacer thickness is given in this paper.This kind of bearing was adopted in China national key scientific project LAMOST telescope focal rotating axis and got perfect performance: the radial runout is less than 0.02mm and axial runout is less than 0.03mm of a φ1100mm bearing at arbitrary 50°angle（working range）. The tracking accuracy of focal rotation axis is better than 0.3″supportted by this kind of bearings.