Optimization of transport vehicle transmission vibroacoustic characteristics

Abstract

One of the main sources of vibroacoustic emissions is the transmission of a transport vehicle. Providing a high level of fuel economy performance and an acceptable level of power-train noise and vibration (NVH) is a complex engineering task and a real professional challenge for NVH specialists. The purpose of the research is to provide the required level of vibroacoustic characteristics of the transport vehicle transmission being developed at the design stage through a feasible correction of structural characteristics. To achieve this goal requires deeper understanding the dynamic phenomena of NVH, as well as expansion of the virtual design methods. We used multiphase analytical methods that allow us to estimate operation dynamics and vibroacoustic response of the transmission. Based on application of advanced CAE methods, a structural analysis and subsequent calculation of acoustic radiation is performed using the example of an automatic transmission (AT) prototype which is being developed for a vehicle of category N. The ability to control acoustic emissions is demonstrated by adjusting the structural (modal) parameters of the transmission case. Engineering solutions (configuration modifications) are being worked out to change the structural state (Limit state design) of the AT configuration (structural optimization) to ensure an acceptable level of acoustic emissions. For the gearbox in question, the first 50 waveforms (mode shapes, wave mode)were identified in the frequency range up to 8 kHz. The analysis made it possible to conclude that the greatest contribution to the integral noise level is made by wave forms at a frequency of 950 Hz, the internal partitions of the gearbox housing; at a frequency of 1324 Hz, the side walls of the shaft part of the gearbox and at a frequency of 1439 Hz are connected oscillations of the side walls and partitions between the shaft part of the gearbox and the demultiplier. To suppress these vibrations, additional finning of the partition between the shaft part of the automatic gearbox and the demultiplier was installed, as well diagonal reinforcing ribs were introduced into the design of the automatic gearbox side walls and the distributor cap. The performed measures allowed significantly reducing the integral level of acoustic pressure.