Gear Surface Machining for Noise Suppression
Gear noise in modern automobiles is unacceptable. It has different sources, such as design parameters and manufacturing errors. Manufacturing errors, for example, can be reduced using advanced grinding operations. However, sometimes grinding operations can introduce micro-geometry deviations that cause severe noise problems.
The present thesis defines and characterizes the micro-geometry of gears, studies its noise consequences, explores some finishing-operations characteristics from the micro-geometry point of view, and uses this knowledge to optimize one of the most important grinding operations (Reishauer Grinding). Results of the proposed optimization routine are verified, and capabilities of the optimized grinding are compared to an alternative operation method (Power Honing).
The most "noisy" surface parameters were identified as undulations. Amplitude, wavelength, and main direction of undulations were considered as noise-influential. Therefore, three optimization criteria were assumed: 1) reduction of the amplitude of undulations, 2) shortening their wavelength, 3) producing surfaces with a suitable direction of the undulations.
Experimental noise investigations showed that assumptions of the optimization criteria worked out properly, since experiments showed that gear surfaces having undulations caused a significantly higher noise level. Extra noise frequencies were identified as corresponding to the wavelength of undulations. The noise level also was shown to directly correlate to undulation amplitude. Finally, theoretical modeling and simulations explained characteristic noise changes (as indicated by experiments).