The acoustical optimisation of passenger car transmissions is an important aim in automotive industry. One of the most annoying noises in automotive transmissions is whining, a noise that occurs when gear pairs are driven under load. During the past few years, the main focus of research was on minimising the excitation by optimising the shape and surface of the gears. However a gear pair can only be perfectly designed and developed for one special load case. The criteria for the optimisation of acoustics are not always in line with the criteria for the optimising of load capacity of gears. Hence, the aspect of excitation cannot be neglected completely. This paper deals with the possibility to abate structure-borne noise caused by excitations of a tooth contact. Different design approaches for a component that is part of the structure-borne noise transmission path are analyzed and evaluated. This requires the physical basics of wave propagation in solid structures to be examined. Based on existing mechanisms, different designs were developed. They were classified into three different categories. The rings belonging to the first category all include geometrical discontinuities. The expected minimization of sound propagation is rather low but the manufacturing of the parts quite easy. In the second category elastic interlayers are included. The expected improvement by these rings is significantly higher, especially with lower frequency ranges. Resonators and vibration absorbers compose the third group. The potential of these designs is considered the most effective way to abate propagation of structure-borne noise. A problem is that these components are expensive to manufacture. To determine the different designs, FE-calculations were made. To identify the real potential of the different designs a testing transmission was developed. It was mounted on a special testing bench to be driven under specified load and speed conditions. On the surface of the gearbox housing, accelerometers were fixed to measure the level of acceleration at which the structure-borne sound is transmitted to the gearbox housing. In a further step the different design proposals will be manufactured and mounted on the testing transmission. Measurements of the housing acceleration will be used to compare the different designs to a non-optimised ring. Another future prospect will be the improvement of the FE model to pre-validate the different designs. First of all, a more realistic calculation of the excitation is required. To meet this requirement a multi-body model of the transmission was developed that will be able to simulate the parametrical, geometrical, and shock excitation occurring at the gear stage. The exciting forces calculated in the multi-body system will then be applied to a FE-model of the testing transmission to calculate the acceleration of the housing. These values can be directly compared to the data established by the accelerometers that were mounted on the gear-box housing. With these improved models it will be possible to improve the design proposals of the rings or to create new principles to abate the propagation of structure-borne noise.
Reducing propagation of structure-borne noise in transmissions
2012
13 Seiten, 14 Bilder, 1 Tabelle, 5 Quellen
Conference paper
English
Structure-borne noise in an end-of-line test of dual clutch transmissions
Automotive engineering | 2010
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