Bearing configuration form point average
To avoid bearing jamming, understand three typical bearing configurations:
1. The double fulcrum is fixed in one direction
This configuration allows each fulcrum to axially fix the shafting in one direction. The defect is: since both fulcrum are fixed by the bearing cover, when the shaft is heated and extended, it is bound to make the shaft bear the effect of additional load and affect the service life.
Therefore, this form is only suitable for occasions with low working temperature rise and short shaft (span L ≤ 400mm). For deep groove ball bearings, an axial clearance C shall also be reserved between the bearing outer ring and the bearing cover, taking C = 0.2 ~ 0.4 mm to compensate for the thermal elongation of the shaft. Due to the small clearance, it may not be drawn on the drawing. For angular contact bearings, the thermal compensation clearance is guaranteed by the clearance inside the bearing.
2. One fulcrum is fixed in both directions, and the other fulcrum swims
The left end is a fixed fulcrum, which bears two-way axial force; The right end is the swimming fulcrum, which only bears the radial force. When the shaft is heated and extended, it can swim axially.
For the fixed fulcrum, when the axial force is small, the deep groove ball bearing can be used, and the left and right sides of its outer ring are fixed. The upper part in the figure is fixed by the shoulder of the bearing seat hole. This structure makes the seat hole unable to be bored at one time, affecting the machining efficiency and coaxiality. When the axial force is small, the outer ring can be fixed with a circlip through the hole, as shown in the lower half of the figure. In order to bear the axial force to the right, the inner ring of the fixed fulcrum must also be fixed axially. For the swimming fulcrum, deep groove ball bearings are often used, and cylindrical roller bearings can also be used when the radial force is large, as shown in the lower part of the figure. When the deep groove ball bearing is selected, there is a large gap between the bearing outer ring and the bearing cover, so that the shaft can extend freely during thermal expansion, but the inner ring needs to be fixed axially to prevent the bearing from loosening. When the floating fulcrum adopts cylindrical roller bearing, because its inner and outer rings can move axially, the inner and outer rings should be fixed axially to avoid excessive dislocation caused by the movement of the outer ring. During design, attention shall be paid to avoid redundant or insufficient axial fixation of the inner and outer rings of the bearing.
The fixed fulcrum is symmetrically bearing arranged with two angular contact bearings, which respectively bear the axial force in the left and right directions and jointly bear the radial force. It is suitable for occasions with large axial load. In order to facilitate assembly and adjustment, the fixed fulcrum adopts the cup structure. At this time, when selecting the size of the floating fulcrum bearing, generally make the outer diameter of the bearing equal to the outer diameter of the cup, so as to facilitate the processing of the two bearing seat holes.
