Thermal Conductance and Torque of Thin Section Four-Point Contact Ball Bearings in Vacuum

摘要

Ball bearings for the L-SAT antenna pointing mechanism (APM) were tested in vacuum with external diameter clearance (i.e., free fit rings) and held in-situ with clamp rings. The influence of speed, temperature, internal preload, axial ring clamping force, lubricant and cage type was examined. As the inner race becomes warmer than the outer, the conductance increases linearly with the temperature difference, whereas the increase in torque is almost a square law relation. With a colder inner race, the bearing develops internal diametral clearance and thus gives low conductance and a small constant torque. Bearing torque and conductance are also shown to be dependent on axial clamping force, internal preload and lubricant quantity. Hysteresis effects of temperature on conductance and torque, and the contribution of the cage to the overall bearing torque are noted. By suitable selection of internal preload and clamping force, the design requirements for L-SAT APM bearings can be achieved.