Ultra Silent Gears

• Applicant: Professor Dr.-Ing. Karsten Stahl
• Subject Area: Engineering Design, Machine Elements, Product Development
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 546841893

Due to the increasing electrification of drivetrains, masking noises are constantly being reduced. As a result, transmission noises are becoming more prominent, which makes noise optimization necessary. Gear noises mainly occur in the tooth mesh due to the fluctuating tooth stiffness over the meshing, which leads to an non-uniform transmission ratio, also known as transmission error. A reduction in the excitation behavior of the gearing is usually achieved by geometric flank topology modifications compared to the involute. However, flank modifications are only effective at a certain load. In order to achieve additional noise reduction, new design strategies are required. In-equidistant or non-involute gearings have not been successful so far. Gears with adapted stiffness are promising in theory, but are difficult or impossible to produce using conventional manufacturing processes. Additive manufacturing represents a solution to enable complex freeforms through layer-by-layer construction. This makes it possible, for example, to produce a lattice structure inside the tooth, which directly influences the rigidity of a tooth, while at the same time keeping the surface simple for grinding. The aim of this research project is to optimize the component stiffness in all spatial directions based on analytical modeling of the gear noise behaviour of gears and to use the structures calculated in this way for the design of test gears. The tooth stiffness can be determined using an approach proposed by Weber/Banaschek. This approach allows for the determination of a specific stiffness over the tooth height. The defined stiffnesses then serve as a target value for the lattice structures to be developed. A calculation method for the dimensioning of such a lattice structure is to be developed as part of the project. The basic investigations of the mechanical properties will be carried out on sample components. The results of the basic investigations are to be verified using the practical example of a test gear. The primary objective of the proposed project is therefore to derive a design method for the stiffness-optimized structures produced using additive manufacturing for use in noise-optimized gearbox design. The overall aim is to show that additively manufactured complex structures in gears can generally be produced in a noise-reducing manner and represent an alternative to today's conventionally manufactured gears. The project provides a theoretical model that describes the noise reduction by changing the stiffness and an example of an additively manufactured gear that is compared with conventionally manufactured gears.

• DFG Programme: Research Grants
• International Connection: Switzerland
• Partner Organisation: Schweizerischer Nationalfonds (SNF)
• Cooperation Partner: Dr.-Ing. Hans-Jörg Dennig