COMPARATIVE INVESTIGATIONS ON THE ACOUSTIC BEHAVIOR OF A PLASTIC AND A STEEL GEAR STAGE IN A LIGHT ELECTRIC VEHICLE POWERTRAIN

Gears made of plastic are often highlighted in literature as a low-noise alternative to gears made of steel. The reasons usually given are the material's lower stiffness and better damping properties. Numerous studies are comparing the acoustic behavior of steel and plastic gears. However, these studies are usually carried out on component test rigs, which cannot fully simulate the interacting conditions of various machine elements of the entire gearbox system. As part of a research project, the steel gears of the input stage of a gearbox for a small electric vehicle in the EU vehicle category L7e were replaced by plastic gears. This paper aims to compare the acoustic behavior of the transmission when using plastic and steel gears. For this purpose, run-up tests are performed at different loads and oil sump temperatures at a gearbox test rig. The excitation behavior of the transmission is objectively evaluated based on structure-borne noise tests. For this purpose, the housing vibrations are recorded using high-fidelity acceleration sensors and evaluated in conjunction with the speed signal regarding resonances, orders, and application force levels. Under the given operating conditions, replacing the steel gears with plastic gears does not lead to significant improvements in the acoustic behavior, which is discussed in detail based on the measured data.