Comparative characteristics and selection of speed bearings

Abstract

The characteristics of bearing supports have been considered. Improving the efficiency of mechanical processing, the quality of operation of mechanisms that use sliding bearing supports, and ensuring stable operation are always important tasks. Solving these tasks contributes to reducing labor costs, reducing operating costs, and increasing the productivity of individual operations. The following main criteria are proposed for the selection of supports: the magnitude of the loads that supports can withstand; the range of allowable shaft rotation frequencies; accuracy in maintaining the position of the axis of shaft rotation; stability of shaft rotation (possibility of autooscillations and undesirable transient processes); energy costs and economic indicators of manufacturing and operation; vibroacoustic characteristics (noise level, sound level). The study of the movement of the working body that separates the friction pairs in the bearing is based on two fundamental laws of hydrodynamic lubrication theory: the law of mass conservation and the law ofmomentumconservation.Mathematicalmodels of supports with fluid lubrication, based on the Navier-Stokes equations, were used. The requirements for bearing supports are formulated on the basis of the tasks solved by the entire mechanism. The flow parameters of the working body affect the load-bearing capacity of radial bearings, and the proposed evaluation dependencies can also be used for tapered supports. The calculation results indicate a significant influence of the flow parameters of the working body on the expansion of the areas of rarefaction and the range of their values, as well as on the reduction of the area and range of increased pressures. It has been established that with small shaft eccentricities rotating at speeds of 60–70 m/s and with a radial clearance of 80 μm, the increase in load capacity can reach 20 %. An important qualitative feature has been identified: with an increase in the Reynolds number Re*, the load capacity of the bearing increases. The greatest intensity of changes in load capacity due to the influence of flow parameters of the working body is observed at a relative eccentricity of e = 0.2–0.4. The terms in the Navier-Stokes equation that take into account the parameters of the working fluid flow can have values that are comparable to other terms, so ignoring them is not always permissible.