Optimization of gear macro-geometry for reducing gear whine noise in agricultural tractor transmission

Agricultural tractors generate various noise sources, such as the engine, transmission, and hydraulic systems. In particular, tractors generate considerable transmission gear whine noises during operation, and such noises need to be reduced for the driver's comfort. The gear whine noise level is related to peak-to-peak static transmission errors (PPSTEs), and the PPSTE can be minimized through the gear macro-geometry optimization method. Here, we optimized the gear macro-geometry of a 75-kW agricultural tractor transmission through a genetic algorithm (non-dominated sorting genetic algorithm III; NSGA-III) to minimize PPSTEs. The two gear pairs were optimized to maintain the gear mesh efficiency at similar levels and to minimize the PPSTE to less than 25 % of the existing gear specifications. To determine the improvement in noise, the noise levels were evaluated and compared using a 3-axis dynamometer tester. The overall noise level in the transmission operating range was found to reduce by 3.1 dBA, and all the noise levels of the gear harmonic components were reduced effectively.