Caused by bearing preloaded and preload stiffness analysis

When ZhuanPei machine tool spindle bearings, generally to be exerted on the spindle bearing preload, its purpose is to improve the bearing rotating accuracy, can increase the stiffness of shaft, shaft vibration and noise control, and to prevent the sliding roller. The bearing pre-tightening and pre-tightening methods, when bearing preloaded on stiffness of the shaft have what change? 崋 bearing in the network (for short ） Based on the knowledge of bearing preload, and make detailed introduction. A, what is the bearing pre-tightening? Refers to the installation of bearings, bearing preload, trying to exert some pressure force between outer ring, rolling body and the contacts inside and outside the circle produce certain initial deformation, in the compression state. Second, the bearing pre-tightening methods have? Bearing pre-tightening methods are divided into two kinds: locate preloaded and constant pressure preload. 1, positioning refers to the combination of bearing preloaded positioning preload axial position, in use process will not change the preload method, the various methods are as follows: ( 1) Will be adjusted in advance for the preloaded, width of the poor or the combination of the axial clearance of bearing after fastening. With the method. ( 2) Using the adjusted the size of the baffle or gasket, so that inflicts on bearing pre-tightening methods. ( As shown in figure 1) Figure 1 ( 3) The fastening of the axial clearance can be adjusted screw, nut. In this case, to obtain the appropriate pre-tightening force, to adjust while starting friction torque measurement. However, this approach is difficult to control the preloaded and bearing likely tilt, so for high accuracy requirement of machine tool spindle is not recommended. 2 is a constant pressure and constant pressure preload preload by cylindrical spring, butterfly spring on bearing pre-tightening methods appropriately. Even if in the process of using bearing a change in the relative position, preloaded quantity can keep constant. Usually used in the high-speed rotating angular contact bearings pairing. ( As shown in figure 2) Figure 2, 3, 1 changes the stiffness of bearing preload, positioning preloaded and axial stiffness as shown in figure 3, after combination bearing inner ring axial fastening, bearing bearing A and B respectively have the delta delta aoB and aoA displacement, eliminate the clearance between the inner ring of the delta ao. This state was preloaded Fao. On the preloaded bearing as shown in the axial load, the bearing stiffness, the corresponding relations between load and displacement of preloaded map, as shown in figure 4, Fa: external axial load, the FaA: bearing A bear axial load, FaB: bearing B bear axial load, the delta A: the position of the composite bearing, the delta aA: bearing A displacement, the delta aB: bearing the displacement of B. In figure 3, figure 42, and the axial stiffness constant pressure preload preload spring stiffness compared with the bearing stiffness is usually very small, so the spring displacement of the straight line approximately parallel to the horizontal axis. Therefore, rigidity and constant pressure preload in advance on the axial pre-tightening force of the Fao single bearing stiffness is roughly equal. Four, summarizes different bearing pre-tightening methods to the change of the stiffness of preloaded with location and constant pressure preload. In from the same amount of bearing preloaded cases, positioning preload is more effective to increase the bearing stiffness, namely when positioning preload caused by load displacement is smaller. But positioning is expected, in the process of operation, caused by the difference in temperature between shaft and bearing axial expansion amount of different, both inside and outside temperature difference caused by the radial difference of thermal expansion and rotation effect in the centrifugal force on the roller, the prestressing quantity change. And in the case of constant pressure preload, due to shaft extension spring load change is very small, so you can ignore the change of preloaded. So generally to improve the stiffness, suitable for positioning preload suits when high speed rotating with constant pressure preload.