Analysis of Lubricating Characteristics of Rotary Compressors for Domestic Refrigerators

We investigated the lubricating characteristics between a vane and piston lubricated with an oil-refrigerant mixture. Theoretical analyses were performed using mixed elastohydrodynamic lubrication analysis theory, taking metallic contacts into account. Lubricating conditions were evaluated by comparing the theoretical results of piston dynamics based on actual surface roughness distributions measured by SEM, with the experimental results measured under practical operation. We conclude that (1) lubricating conditions between the vane and piston can be assumed to be within the mixed lubricating zone, in which the coefficient of friction changes from 0.04 to 0.08, and the contact force is almost equally supported by oil film and metallic contact; (2) the coefficient of friction decreases as the contact force increases because the ratio of pressure rise of the oil film to the decrease in clearance is much greater than that for metallic contact pressure; and (3) in mixed EHL analysis, it is important not only to measure the actual surface roughness but also to select the appropriate contact model.