Study on starved HEL for developing lubrication method of rolling bearing with minute amount of lubricant

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Regression formulae which give central film thickness, minimum film thickness and both inlet meniscus and side meniscus lengths as a function of inlet film thickness are derived by a numerical analysis incorporating Elrod algorithm, respectively. A ratio of the minimum film thickness to central film thickness becomes uniform value as starvation state proceeds.A measurement apparatus for starved film thickness with interferometry has been developed to verify the derived formulae and to investigate effect of sequential ball passing on the starved EHL film thickness, which appears in practical ball bearings. That effect is investigated by measuring the reduction of the each starved EHL film thickness of the three sequentially arranged balls in the same circumferencial track on a glass disk with interferometry. Initial inlet film thickness with uniform distribution is generated by a roller which is placed in front of the first ball. This lubricant film on the glass disk passes through the conjunction between ball and disk and, then, partially re-flows an same inlet of the ball by adhering its ball surface. Therefore, central film thickness is controlled with sum of the film thickness on the glass disk and half of the film thickness on the ball surface flowing in its inlet. Central film thickness by solving simultaneously this relationship, the derived formulae and Hamrock-Dowson formula for central film thickness agrees with interferometry measurement result with errors less than 10%. In addition, the predicted reduction in film thickness by sequentially passing also agrees with measurement result.Influence of side band of lubricant on the meniscus length appears if the inlet film thickness is approximately equal to central film thickness in a fully flooded condition. In this case, the side meniscus length becomes to considerably differ from calculating result. However, this difference has merely influence on the central film thickness.