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First, the way to improve the rigidity of the shaft support can be summarized as follows:
(1) Select a bearing with high rigidity;
(2) Using bearing application technology to improve the support rigidity;
(3) Appropriate adjustment of the host structure parameters to improve the support rigidity.
Second, the key to selecting a bearing from the point of view of bearing rigidity is
(1) The rigidity of the roller bearing is higher than that of the ball bearing;
(2) Bearings with large dimensions are stiffer than bearings with smaller dimensions, even for bearings of the same diameter and larger width, which are stiffer than the width;
(3) The number of rolling elements and the number of bearings and the number of columns are large, and the rigidity is good;
(4) The bearing with adjustable clearance is beneficial to improve the bearing rigidity.
(5) If necessary, bearings without inner ring, without outer ring or without inner and outer rings can be used to reduce deformation and increase the number of rolling bodies.
Third, the application technology to improve the rigidity of the shaft support The application technology to improve the rigidity of the shaft support is very important, as follows:
(1) Requirements for the mating surface of the bearing The lower the surface roughness of the bearing mounting portion on the shaft and the seat hole, the better the shape and positional accuracy, and the higher the support rigidity. Applying a surface strengthening treatment to the above surface is advantageous for improving rigidity. The use of a high-hardness stopper with a very low roughness, with a certain degree of interference in a lubricated state, multiple times to gently press in and exit the seat hole, is also beneficial to improve the support rigidity, if necessary, the collar can be similarly treated with a snap ring .
(2) The bearing pre-tightening method is used to improve the bearing rigidity. For the ball bearing or the tapered roller bearing, the axial pre-tightening method can be adopted, and for the short cylindrical roller bearing, the radial pre-tightening method can be adopted, which can significantly improve the rigidity of the shaft bearing. At this time, the bearing clearance is eliminated or a small negative clearance is obtained. However, under the condition that the rotation speed is not too high and the temperature rise is not large, it is better to adjust to a small negative clearance state. When preloading is applied, it is necessary to continuously measure the deformation. Note that in the low value stage of deformation, the deformation is nonlinear with the increase of the preloading load; in the high value stage, the deformation is linear with the increase of the load. Once the deformation-load has a linear relationship, the pre-tensioning load is stopped immediately, and a constant stiffness is obtained. Thereafter, there is a fixed relationship between the axial stiffness and the radial stiffness of the bearing, independent of the applied load. The above-mentioned deformation amount can be measured by, for example, abutting the dial gauge against an appropriate end portion of the bearing end face or the shaft, and observing the change of the reading with the preload load. The pre-tightening method has its disadvantages, such as increasing the friction torque of the bearing, increasing the temperature rise, shortening the life, etc., so it is necessary to comprehensively consider the trade-offs and gain the appropriate pre-tightening amount.
(3) Bearing arrangement The configuration of the bearing has a great influence on the bearing rigidity. Generally speaking, for the ball thrust bearing and the roller bearing of the centripetal thrust type, it is preferable to adopt the large end face of the outer ring when the pair is used (ie, the pressure thereof). The arrangement of the pressure cones formed by the wires outwards is such that the bearing has a large ability to resist the overturning moment, and the amount of preload that is adjusted when the temperature changes is less changed.
(4) Multi-bearing support mode Two or more bearings are used as radial support for each fulcrum under the conditions of axial position, which can improve the support rigidity. For example, in the recent spindle parts of machine tools, a plurality of sets of radial thrust bearings mounted axially preloaded as shaft supports of the same fulcrum are widely used.