Mating Tooth Surfaces Research Articles

Fundamental Research on Gear Lubrication : 4th Report, Analysis on the Formation of Oil Film and Its Dynamic Phenomena in Mating Gears

Oil film state in mating gears is considered to be quite a dynamic phenomenon, and it has become very important to analyze the dynamic performance of oil film between mating gearteeth. The hydrodynamic squeeze-effect and the tooth deflection were introduced into the lubrication theory, and the variation of oil film thickness between mating teeth was calculated. Experimentally, the variation of oil film thickness was measured by the electrical resistance method from the beginning to the ending of a tooth mating, using specially manufactured test gears which do not form a parallel resistance circuit even in mating of two pairs of teeth. The theoretical result is in good agreement with the experimental results particularly at the beginning part of mating. It is clarified that the principle of oil film formation on mating tooth surfaces can be fundamentally explained by the dynamic lubrication theory which is introduced in this paper.

Experimental Investigation of the Minimum Oil-Film Thickness in Spur Gears

As a pair of gears is loaded, the minimum oil-film thickness between the gear teeth decreases and can approach a magnitude equal to the magnitude of the surface roughness. Metal-to-metal contact then occurs between the microscopic peaks on both mating teeth surfaces. Therefore, the minimum thickness of the film separating the mating teeth surfaces may be considered as one of the criteria of capacity for a gear drive. A testing technique that was developed for measuring oil-film thickness between loaded gear teeth while running is presented in this paper. The voltage drop across a thin oil film that is required to cause an electrical discharge was used to determine the oil-film thickness. A specially designed machine containing a planetary gear train was used in these experiments. The relationships between the minimum oil-film thickness and the load transmitted by the gearing under certain conditions were determined using this method.