双螺母预紧滚珠丝杠副摩擦力矩与接触刚度波动关系研究

Relation between friction torque and contact stiffness fluctuation of a double-nut preloaded ball screw mechanism

目前,滚珠丝杠副刚性的一次测量只能测得一个位置处刚度,需进行多次测量才能获得有效行程内的刚度波动情况,且每次测量需要拆卸和调整测量装置,耗时耗力。由于滚珠丝杠副摩擦力矩测量是空载扭矩,在测量行程中,螺旋升角和接触角是基本没有什么变化,同时在刚性测量中,轴向载荷的加载对螺旋升角和接触角的影响非常小,可以简单、快速获得双螺母预紧滚珠丝杠副不同位置处接触刚度值波动情况,对双螺母预紧滚珠丝杠副的滚珠进行动力学分析,建立预紧力与接触刚度的关系式,结合滚珠丝杠副预紧力与摩擦力矩平衡方程,建立关于摩擦力矩的接触刚度数学模型;使用滚珠丝杠副摩擦力矩试验台对两种不同型号的双螺母预紧滚珠丝杠副进行摩擦力矩测量;在滚珠丝杠副静刚度试验台上对以上两件滚珠丝杠副进行静刚度测量。试验结果表明:当双螺母预紧滚珠丝杠副的轴向载荷<23/2倍预紧力时,双螺母预紧滚珠丝杠副的接触刚度与摩擦力矩的1/3次方成正比;可通过测量双螺母预紧滚珠丝杠副行程内的摩擦力矩来反映不同位置处接触刚度的波动情况。

Currently,only a certain position’s rigidity of a double-nut preloaded ball screw mechanism can be measured in one rigidity measurement,several measurements are needed to get its stiffness fluctuation situation within its effective stroke,each measurement needs to install,disassemble and adjust the measuring device,it is time-consuming and laborious. As a ball screw pair’s friction torque measurement is in a no-load case,in its measurement process,helix angle and contact angle have almost no change,while the effects of axial loading on these two angles are very small in rigid measurement. Here,to acquire contact stiffness fluctuation of a double-nut preloaded ball screw mechanism simply and quickly,the ball of the mechanism firstly was dynamically analyzed,and then the relationship between preload and contact stiffness was established. Combining the equilibrium equation of preload and friction torque,the mathematical model of contact stiffness versus friction torque was established. Friction torques for two different types of double nut preload ball screw mechanisms were measured on a ball screw pair friction torque test table. Static rigidities of the two ball screw pairs were also measured on a ball screw pair static stiffness test table. The test results showed that the contact stiffness is proportional to the 1/3 power of friction torque when an axial load exerted on the ball screw pair is not larger than times of preload; contact stiffness fluctuation of a double-nut preloaded ball screw mechanism can be reflected by measuring friction torque at different positions within the mechanism’s effective stroke.