Investigation of the forced structure-borne noise transfer through the gear body of powder metallurgical spur gears for the speed-related design of the noise emission of high-speed transmissions

• Applicant: Professor Dr.-Ing. Christian Brecher
• Subject Area: Engineering Design, Machine Elements, Product Development
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 450663051

The increasing requirements on noise emission from powertrain systems are determined by the awareness of surrounding noise, the legal noise limits and the rising expectations of noise quality. In electric mobility, the rising power density of the electric motor leads to a combination of high-speed electric motors and reduction transmissions. Due to the higher drive speeds, the resonance frequencies of the gears in the transmission are excited throughout the entire human hearing range. Alternative materials can realize the optimization of the noise behavior. Due to the near-net-shape and resource-efficient production of the green part by pressing, powder metallurgically produced gears offer the potential to modify the gear body in terms of geometry and density without additional manufacturing steps. Thus, density- and geometry-dependent damping and insulation mechanisms can be integrated into the gear body at cost-neutral conditions and the structure-borne noise transfer behavior of the gears can be significantly improved.Previous research results show, depending on the density of the gear body, that the structure-borne noise emission of the first tooth meshing order can be reduced by approx. ΔLp = 5 dB in the experimental running test. The maximum structure-borne noise emission at the bearing points results from the natural frequency of the individual gear and dominates the noise emission of the gear set in the test rig.The overall objective of the research project is to optimize the structure-borne noise transfer by means of a method for designing the gear body of powder-metallurgical spur gears in consideration of insulation and damping mechanisms. In order to achieve this objective, a method for the analysis and design of the insulation and damping mechanisms in the gear body will be developed. On the other hand, a test rig for the measurement of the structure-borne sound transfer through the gear body because of a forced excitation under load is to be designed and constructed. In order to validate the design method, the optimized gear body variants with the highest potential are investigated in a running test up to a maximum speed of n_max = 30000 rpm. The result of the project is a novel method for NVH-oriented optimization of the design of powder metallurgical spur gears by a specific, locally variable density and gear body geometry based on a speed-related design.

• DFG Programme: Research Grants