Research on Discontinuity of Lubricant Film in Journal Bearings : 1st Report, Bearing Characteristics and Lubricant Film Rupture

Abstract

There have been presented various boundary conditions for the trailing edge of the lubricant film of journal bearing in the hydrodynamic lubrication theory. They are, however, not so clearly investigated physically in connection with the lubricant film rupture. In this paper, eccentricity ratio and attitude angle are measured, and, at the same time, the generation and growth of the lubricant film rupture are observed by using a transparent journal bearing bushing. The results are investigated with theoretical solutions under various boundary conditions. The shaft center is found to travel along Sommerfeld's theoretical locus in the case of a continuous lubricant film. Then, with occurrence of the lubricant film rupture, the shaft jumps rapidly to the theoretical locus defined with Reynolds' or Gumbel's boundary condition. The theoretical pressure distribution shows that the pressure becomes almost atmospheric in the discontinuous film region. From these results, the conditions of the lubricant film rupture are investigated theoretically.