The preload is divided into radial preload method and axial preload method, as described below.
1. Radial preload radial top tight method is mostly used in the radial load bearing tapered bore, the typical example is the double row precision cylindrical roller bearings, this bearing nut adjustment relative to the taper journal shaft to the position of the inner circle have the right amount of expansion and radial negative clearance, this method is used for machine tool spindle and the jet engine.
2. Axial preload method can be divided into position preload and constant pressure preload two kinds. Positioning pretension to adjust the size of the bushing or gasket, to get the right preload; by measurement or control starting friction torque to adjust the right of pretension; can also be used directly to pre-tuned preload paired double bearing preload the purpose at this time generally do not need re-adjusted, short, all the axial preload bearing, the use of its relative position will certainly not change. The constant pressure preload the bearing with spiral springs, disc springs to get the appropriate pretension. Preload spring rigid - like than the bearing rigidity is much smaller, so the constant pressure preload the bearings relative position of use varies, but preloading remains largely unchanged. Position preload and constant pressure preload as follows:
(1) is equal to the preload amount, location preload on the effect of bearing stiffness increase greater positioning pretension, rigid change of bearing load is much less.
(2) Positioning preload in use, due to the shaft and bearing temperature difference caused by the axial length, inner and outer rings, the temperature difference caused by radial expansion, as well as the displacement caused by the load, will preload the amount of change; constant pressure preload in use, preload changes is negligible.



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