Abstract
As a core component of the motorized spindle, the dynamic stiffness of the angular contact ball bearing directly affects the dynamic characteristics of machinery. A modified quasistatic model of the ball bearing is established considering the influences of thermal deformation, centrifugal deformation, and elastohydrodynamic lubrication (EHL). Then, the film stiffness model considering spin motion is constructed. On this basis, the composite stiffness model of the ball bearing is proposed, and the effects of different factors on dynamic characteristic parameters are investigated. The results show that different factors have different effects on the dynamic parameters. With the increase in preload, the contact stiffness and composite stiffness increase. Considering EHL, the radial contact stiffness and composite stiffness increase while the axial and angular contact stiffness and composite stiffness decrease. Considering the thermal effect and centrifugal effect, the radial contact stiffness and composite stiffness increase while the axial and angular contact stiffness and composite stiffness decrease. The film stiffness and composite stiffness increase with the consideration of the spinning motion.
Highlights
E dynamic characteristic parameters of the bearing are important indexes to evaluate the performance of the bearing and the factors to be considered in bearing design
According to the above calculations of the centrifugal deformation, thermal deformation, and assembly deformation, the radial bearing deformation ur and axial deformation ua of the bearing can be obtained. e axial deformation ua is shown by equation (7), and the radial deformation is shown by the following equation: ur δ1 + δ2 + δ3
The contact equivalent curvature radius between the roller and the outer ring is larger, which results in the larger film stiffness of the outer ring than that of the inner ring. is conclusion is consistent with the result of Reference [20], which verifies the correctness of the film stiffness model
Summary
With the development of science and technology, the level of modern manufacturing technology and CNC processing technology has been improved sharply. e motorized spindle is the kernel component of machine tools. e bearing is the support component of the motorized spindle, and its performance directly affects the processing precision and efficiency of the motorized spindle and the whole machine tool. e stiffness of the bearing has an important influence on the dynamic performance of the rotor-bearing system and directly affects the machining precision [1]. Guo et al [9] presented the EHL model with spin motion and calculated the dynamic characteristics of the angular contact ball bearing. Considering the centrifugal deformation, thermal deformation, and EHL, the modified quasistatic mechanical model of the angular contact ball bearing is put forward. Where ah and as are the thermal expansion coefficients of bearing housing and the shaft, respectively, lh and ls are the effective contact lengths between the housing hole and the outer ring and between the shaft and the inner ring, respectively, and ΔTh and ΔTs are the temperature rise of the housing and the shaft, respectively. According to equations (3)–(7), the temperature rise of each component of the angular contact ball bearing is measured and calculated to obtain the thermal deformation of the inner and outer rings and rolling elements. According to the above calculations of the centrifugal deformation, thermal deformation, and assembly deformation, the radial bearing deformation ur and axial deformation ua of the bearing can be obtained. e axial deformation ua is shown by equation (7), and the radial deformation is shown by the following equation: ur δ1 + δ2 + δ3
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