小孔节流动静压混合气体润滑球轴承的干扰力矩分析

为提高小孔节流动静压混合气体润滑球轴承的漂移精度,分析了气体干扰力矩(误差力矩)的成因,在一定假设条件下,建立了干扰力矩的数学模型;运用有限元方法,实现了该结构轴承小误差条件下气体干扰力矩的数值求解,并分析了节流孔的孔径误差、节流孔在球面上的位置度误差、球或球腔的非球形误差等几种常见误差对干扰力矩的影响规律。结果表明,节流孔尺寸误差越大、位置偏移误差越大,引起的干扰力矩越大;转子或球腔的非球形误差以及方位角变化,使转子表面切向方向存在不对称的气体分流,使支撑力不通过球心,引起干扰力矩,非球形误差越大,干扰力矩越大;干扰力矩随轴承偏心率增加而增大,同时轴承发生轴向和径向偏心时,即使无误差,也会产生干扰力矩;摩擦力矩不直接影响仪表的漂移率,只对转子的转动起阻尼作用。实验测量了静止状态下,一种开式结构的小孔节流气体润滑球轴承的干扰力矩,验证了该模型和求解方法的正确性。

Disturbing Torque Analysis of Orifice Compensated Hybrid Gas Spherical Bearing

In order to improve the drift precision of an orifice compensated hybrid gas spherical bearing,causes of gas-lubricated disturbing torques(error torques) were analyzed and a mathematic model was introduced.The solution of the disturbing torque of bearing when small errors exist was obtained by finite element method.The effects of several kinds of usual errors,including the diameter and position error of orifices,un-spherical error of both the rotor and the cavity on disturbing torque of the bearing were presented.The result shows that disturbing torques are increased with both the diameter error of orifices and their position error;un-spherical error of the rotor and the cavity,together with their directional angels,can induce asymmetry distribution of pressure,besides,un-spherical error of rotor can make the suspending force not pass through the geometry center of the rotor,which all would induce disturbing torques that increase with the errors and vary periodically with the cyclic of directional angels;disturbing torques increase linearly with the increase of eccentricity,having axial and radial eccentricity simultaneously,even there have no manufacturing errors,the bearing would still have disturbing torques;friction torque,although its numerical value is bigger,only plays a damping action on the rotor and has no direct influence to the bearing's drift.An experiment was carried out to evaluate the disturbing torque of such a bearing,which has obvious machining errors of restriction orifice,and the correctness of both the model and its solving method was testified by the result.