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Multi-parameter Weight and Efficiency Optimization of a Cylindrical Gear Pair without Standard Basic Rack Geometry Limitations

In recent years, growing demand for light-weight, efficient and quiet transmissions, fueled by the introduction of electric vehicles is observed. This calls for simultaneous gear optimization regarding efficiency, mass, and NVH (noise vibration harshness). Herewith gear macro-geometry was optimized for efficiency and mass using pressure and helix angles, gear width, modulus, tooth count, addendum, dedendum and root radius coefficients as variables. Optimization was carried out using NSGA-II. The optimization algorithm results have shown that a clear trade- off between weight and efficiency exists, as previously reported by other authors. Since the third axis of solution space, the transmission error, was not implemented yet the algorithm will tend to minimize addendum coefficient values so as to minimize sliding. In-turn, this will worsen the NVH (noise vibration harshness) behavior of the gear pair. Consequently, minimum transverse and axial contact ratio value constraints were implemented to ensure that the algorithm returns a solution with decent NVH behavior. On the other hand, such constraints will prevent the algorithm from finding the actual global optimum of the original objective function. This was implemented to prepare the algorithm for the future introduction of the third objective, which is the transmission error. With the current setup of constraints, the resulting gearing will always fall in the category of high contact ratio gearing.

multi-parameter optimization ; cylindrical gears ; mass ; efficiency ; genetic algorithm

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