Initiative Tribology Design Of Gear Transmission

The current contact fatigue strength design of involute cylinder gearing is based on Hertz theory. This theory is only suitable for dry contacting, however, between two smooth surfaces, which is inconsistent with the reality of industrial gear transmission. This traditional strength design didn't fully concern lubrication conditions while the current lubrication design doesn't consider strength needs. Therefore, how to establish a new design model by combing strength design with lubrication design, and to conduct the contact strength design of involute cylinder gearing according to the model is obviously a very meaningful research topic.This paper summarized the developments of elastohydrodynamic lubrication theory, represented the main reasons to tooth face failure in gear transmissions firstly. And then, the general formula of strength design is formed based on Hertz theory, and the model of lubrication design is given based on elastohydrodynamic lubrication theory. Combining lubrication design with strength design, the tribological design model of involute cylinder gearing is established. This model considers lubrication needs when preceding strength design, and does not passively checking the minimum film thickness for tooth face after strength design. So this design method is called initiative tribological design.Based on the above model, the paper compiled numerical calculation programs and carried respectively design calculations by applying these programs under different working conditions such as loads, rotational speeds, manufacture accuracies, film thickness ratios, etc. The results indicate that under some working conditions, gear transmissions designed by lubrication needs do not fulfill strength needs; While, under other working conditions, the design results according to strength conditions do not meet lubrication needs. The results from the model of initiative tribological design can satisfy both needs, however, at the same time under any working conditions, which show that the design model given by the current paper is scientific, and the design results according to this model have higher credibility.The model of initiative tribological design in the paper is only suitable for the conditions of Newtonian fluid, smooth tooth face. In order to make the model further close to engineering realities, both the effects of surface roughness and the rheological natures of lubricating oil must be considered into the design model meanwhile. In addition, the results are still required to be verified by experiments and practices.