Research On Transmission Vibration And Noise Based Rigid-flexible Coupling Model

Transmission is one of the major automobile noise and vibration sources. Studying the dynamic response characteristics and radiated noise characteristics by the transmission of noise and vibration prediction model not only can better understand the mechanism of transmission of noise and vibration, but also can reduce the development costs and development cycle of the transmission. The rigid-flexible coupling model of transmission is established using multi-body dynamics software, the transmission whistle and rattle features are analyzed, and noise radiation characteristics of the transmission is discussed too. It is important for low vibration and low noise design of transmission during the development stage. The main conclusions are as follows:(1) Establish rigid-flexible coupling model of transmission. Based on the basic design theory of transmission, a transmission containing only two stalls is designed. The rigid-flexible coupling multi-body dynamics model of transmission is built, which takes the connection between the parts, gear time-varying stiffness and damping characteristics, backlash, bearing stiffness and damping characteristics, engine speed fluctuations, load incentives and box flexible features into consideration. Model analysis is carried out on the transmission box and the entire transmission system measured. Simulation and experimental results show that the maximum error is less than 3% and 7% respectively, which proves the model is accurate.(2) Study whistle and rattle characteristics of transmission systematically. The value of rattle time history that is greater than or equal to 1 can produce rattle, the value of rattle time history that is less than 1 can’t produce rattle. The effects of various factors on rattle strength are studied. For avoiding rattle, speed fluctuation and the gear ratio, the moment of inertia and backlash of no passing power gear should be reduced as much as possible, while the damping coefficient between the gear and the shaft should be as large as possible. It can been found from analysis that the whistle produced under two conditions, one is the gear time-varying stiffness, the second is the gear bearing transmission power. With the input speed and load torque increasing, the whistle increases too. Especially when gear meshing frequency is in close to box inherent frequency, the noise will increase greatly. However, the whistle decreases with the increasing of coincidence degree, and the modulus and pressure angle is almost inversely proportional to coincidence degree, while the helix angle and tooth width is almost proportional to coincidence degree.(3) Research on the transmission radiated noise characteristic. The transmission radiated noise characteristic under single speed and increasing speed conditions is studied using modal acoustic transfer vector(MATV) method, the results show that the gear mesh frequency, the shaft frequency modulation due to speed fluctuation have enormous influence on the resonance frequency of transmission noise. Experiments are carried out under the condition of the increasing speed, and the results show that there are an obvious resonance band and the order components of the loading gear.