| The sound quality in the car has become the focus of consumer attention.Improving the sound quality of vehicles has gradually become an important means of competition for vehicle manufacturers.By investigating vehicle and transmission manufacturers,it is found that the transmission rattle noise has become one of the main problems of after-sales complaints,seriously affecting the brand image and sale.Therefore,it is of great engineering significance to study the rattle characteristics of transmission assembly and reduce the transmission rattle sensitivity to torsion vibration of transmission system by design.A rattle dynamic model on involute helical gear based on impact rebound rate is established.An experimental method is proposed for the impact of gear teeth,and the impact rebound rate and impact time of gear teeth are measured.The empirical formula of impact rebound rate and impact time including impact momentum,impact position and gear module is presented.Considering that the impact time of gear teeth is much less than the period of torsional vibration excitation,and based on the assumption that only one pair of gear teeth can impact for gear pair,an involute helical gear rattle dynamic model is established by combining the impact rebound rate,impact judgment condition and the non-impact state motion equation.It solves the uncertain problem of the stiffness and damping parameters of gear rattle and realizes the quantitative analysis of gear rattle characteristics.The analysis and experimental results are in good agreement?The performance evaluation index system of transmission assembly rattle was established.According to the propagation characteristics of rattle vibration and noise,select the key connection point between transmission and vehicle and specific noise radiation point as the evaluation point of transmission assembly rattle performance.Keep transmission running at constant average speed and average torque,and at the same time,120 seconds long torque fluctuation excitation is applied,the excitation fluctuation amplitude increases linearly from 0 N ? m to 120 N ? m within 120 seconds.The cumulative energy of rattle vibration or noise caused by torque excitation within 120 second is used as the evaluation index of the transmission rattle performance.It makes up for the lack of evaluation methods for the transmission assembly rattle performance,and provides an effective means for the comparison evaluation of the transmission assembly rattle performance,and also provides necessary target for the vehicle transmission system torsional vibration design to against the transmission rattle.A semi-empirical prediction method for transmission rattle performance is presented.By analyzing the torsional vibration of the transmission shaft system to obtain the motion response of the driving gear in each rattle gear pair,and It is used as the input of gear rattle dynamics model,then The rattle force sequences of each gear pair is analyzed.The vibration response of each bearing seat under the rattle force is calculated by using the experimental transfer function between the gear rattle point and each bearing seat.The vibration response of the bearing seat is taken as input,and the prediction of transmission rattle performance is realized by using the shell finite element and boundary element model.This method avoids many non-linear computing problems,and makes the prediction result of transmission rattle performance more than 80% consistent with the experiment.Finally,based on the above study,the rattle performance of a transmission is analyzed and evaluated,and according to the key influencing factors,the corresponding optimal control measures are given.Through the implementation of engineering,the rattle noise radiation performance of transmission housing is improved by about 17%,and the rattle vibration performance of key point is improved by about 25%... |
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