Effect of mating form on the rigidity of linear ball bearing
The linear bearing is a kind of motion unit that can realize the linear motion of the shaft. The steel ball is used as the rolling part, and the steel ball is in the cylindrical bearing.
The body circulates around the closed channel. The shaft and the bearing reciprocate linearly in the axial direction, and can also rotate relative to each other. Shaft and bearing
Actually, the point contact of the steel ball is rolling friction during movement, which has the advantages of small moving drag force, no creeping, high motion precision, etc., but also
Shortcomings such as poor impact resistance and poor rigidity.
The plurality of steel balls inside the linear bearing roll axially on the shaft surface to provide radial support to the shaft. Due to the limitation of the steel ball circulation structure
The steel ball that supports the shaft is limited, and the smaller the bearing size, the fewer the number of columns supporting the steel ball. Linear bearing with 50 mm inner diameter is
For example, a total of 6 columns of steel balls inside the bearing provide radial support to the shaft over the entire circumference. But when the shaft is subjected to a radial uniform load in a certain direction
At the time, only 1 column or 2 columns are actually used, and up to 3 columns of steel balls are loaded. The actual working condition is that the shaft cantilever end is subjected to radial load.
Shown (F' is the concentrated load on the cantilever end of the shaft), due to the fit clearance, only the steel ball near the bearing ends is carried, the less the steel ball is carried, the more rigid
Angular contact ball bearing ball diameter change 1 μm, the clearance will be reduced by 2μm, if the measured amount of protrusion is small, it can be guaranteed by changing the ball diameter.
The clearance is within the design requirements, and the amount of protrusion required for the universal single set or the assembled bearing can be achieved by changing the ball diameter. By theory
Comparing with the actual measured amount of change in the amount of protrusion, it can be seen that the error is small, so the amount of protrusion can be finely adjusted by changing the ball diameter.
After the matching of the linear bearing and the shaft is changed from the clearance fit to the interference fit, the gap between the shaft, the steel ball and the channel is eliminated.
When a certain preload is applied between the three, the rigidity of the linear bearing is significantly improved. But for the interference between the bearing and the shaft
Volume, no specific reference materials, the general experience is that the larger the bearing size, the greater the interference. When the bearing and the shaft are interference fit, it needs to be applied
The axial load of 10 to 30 N is relatively moderate in the interference fit state. If you increase the amount of interference, there will be obvious movement crawling or even stuck.
Phenomenon, reduce bearing life; reduce the interference, it will have less impact on the improvement of bearing rigidity.
Experience has shown that the choice of interference is related to the nominal diameter of the bearing, and the optimum interference is 0. 07%.
Due to imperfect national standards, the linear bearing standards of different manufacturers are not uniform. To determine the interference between linear bearings and shafts,
Determine the inner diameter tolerance of the bearing and select the appropriate shaft tolerance.
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