Choosing the right bearing, to guarantee the normal operation of the machine, raise the bearing service life and make full use of the carrying capacity of the bearings is large. Rolling bearing fit selection is mainly based on the nature and size of the load of bearing rings and combined bearing type, size, conditions of work, the shaft and housing materials and structures, as well as temperature and other factors to consider.
(1) the rings are spinning
When the inner or outer ring of the bearing is rotating ring, a little close coordination should be used, should match the size of its surplus under the working load is not "crawl", because once they crawl, mating surfaces will wear, slide, ring speed is higher, more serious wear. When bearing, if any rings or to not rotate the ring on the outer ring, for ease of disassembly and adjustment, use a loose tie. Due to the different temperature rise will have a different journal or shell holes in the longitudinal elongation. So when you choose to meet, to reach the bearing along axis you can move freely and eliminate support the principle of internal stress. But excessive clearance will reduce overall rigidity of the parts, vibrations, increased wear.
(2) type of load three dimensional
Bearing radial load, in accordance with the relative motion of the load and the ring can be divided into the following three types.
① partial load
Local load refers to the synthesis of the radial load acting on the bearing f, with rings of relatively static, that is, f, by a local Raceway of rings to withstand. ② circulating load cycle load refers to the synthesis of the radial load acting on the bearing f, relative rotation of races, namely f, sequence effects on the entire circumference of Raceway Bu.
③ oscillating loads
Oscillating load refers to the synthesis of the radial load acting on the bearing rings within a certain area of the swing, is subjected to a radial load f unchanged and a rotating load f. F,>F, their synthesis of the radial load f fixed relative swing within a Raceway of rings. Ring subjected to local loads should be selected more transition fit or a small gap between the tie, so that the friction torque in Raceway transposition of led rings, ring force evenly and extended bearing service life. Subjected to a cyclic load ring should be selected with interference or transition fit tighter, the size of its interference, to not make the bearing ring and shaft or housing bore surface creeping principle. Under oscillating load, which tie in with the same requirements as the circulating load or slightly loose.
(3) load size
Bearing and axle journal and shell combined with the minimum of interference depends on the size of load. When the P,/c, less than 0. 07 o'clock for the light loads when 0. 07<P,/c, ≤ 0.15 for a normal load; P,/c>0. 15 o'clock for heavy loads. Withstand the shock loads or heavy-load ring, prone to deformation, force uneven mating surfaces, causing tie loose, so you should choose a tight match, namely minimum interference should be larger. The ring under light load, you should choose a loose tie.
(4) other factors
① the effect of temperature
Bearing work, due to the effect of frictional heating and other sources of heat, temperature matched parts above the temperature of the ring. It caused by thermal expansion of the inner ring and shaft neck fits loose, patrons circle thermal expansion causes it tightened in conjunction with shell holes. Therefore, the operating temperature of the bearing is high should be combined with the selection of suitable.
② influence of rotational accuracy and speed of rotation
Load large and require a high running accuracy of the bearing, in order to eliminate the effects of elastic deformation and vibration, support of a gap should be avoided. Light load bearing on precision machine tools, in order to avoid error on precision of bearings and the shape of the shaft effect, often using gap alignment. Generally considered to be the higher the rotational speed of the bearing, coupled with tighter.
③ the conditions for mounting and dismounting bearings
Bearing installation and removal easier, should adopt more cooperation on large and extra large bearing used in heavy machinery, this is especially important. When the requirements are required for Assembly and disassembly easy and tight fit, separable, or the use of rings with taper hole, bearings with adapter sleeves and withdrawal slot. In addition, the bearing should adapt to tighter elected under the following circumstances: a size smaller than the size of bearings; hollow axle shaft neck; thin-walled shell than thick-wall Shell; Shell than steel or light alloy cast iron Shell; Shell than the parts of the whole shell.



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