Study On Torsional Vibration Mechanism And Attenuation Measures Of Vehicle Drivetrain With Dual-clutch-transmission

The existence of the passive clutch driven disc large inertia of the dual clutch transmission reduces the rattle threshold of the transmission,greatly improves the rattle sensitivity of the transmission,and causes the rattle noise of the gearbox gear,which is one of the main problems faced by dual-clutch transmission.The engine input torque fluctuation causes the torsional vibration of the power train,which affects the meshing motion of the loose gears of the gearbox,which is the main reason for the rattle of the gearbox gears.This paper studies the torsional vibration suppression measures of the vehicle powertrain from four aspects:theoretical research,simulation research,experimental research and parameter optimization,in order to solve the problem of gear rattle in dual-clutch transmission.The specific work is summarized as follows:(1)Based on the simplification principle of dynamic model and the equivalent principle of dynamic parameters,the power transmission system of a vehicle equipped with 7-speed dual clutch transmission is simplified into four different degrees of freedom torsional vibration models,and then the power transmission system of the vehicle is calculated based on the calculation theory of inherent characteristics and the calculation theory of parameter sensitivity respectively.Sensitivity of natural frequency,modal mode shape,moment of inertia and torsional stiffness to natural frequency and sensitivity of moment of inertia and torsional stiffness to modal mode shape.According to the natural frequency of the system,the degrees of freedom of the model in this study are determined,the mode shape of the key research order is determined according to the modal mode shape,and the most sensitive structural parameters to the torsional vibration of the transmission system are determined according to the calculation results of the parameter sensitivity.Torsional vibration of the transmission system provides a research direction.(2)In order to reduce the torsional vibration of the vehicle transmission system,four kinds of mainstream vibration damping measures are proposed to be applied to the vehicle transmission system:clutch driven disc torsional damper,dual mass flywheel,clutch micro-slip control,centrifugal pendulum vibration absorbs.Firstly,the vibration reduction mechanism of the above four vibration reduction measures is analyzed,and the nonlinear dynamic sub-model of the relevant shock absorber is established,and then integrated into the vehicle powertrain model to obtain the nonlinear dynamic model of the vehicle powertrain.After that,the vibration reduction performance of various vibration reduction measures under the gear rattle conditions was simulated and analyzed,and the vibration reduction performance was compared with the gearbox rattle threshold curve.Finally,the synergistic analysis of vibration reduction performance and transmission efficiency was carried out.It was concluded that only Bifilar type centrifugal pendulum vibration absorber with dual-mass flywheel and the dual-mass flywheel considering 10rpm and 20rpm clutch micro-slip control can meet the conclusion that the transmission has no gear rattle noise and transmission efficiency at the same time.(3)In order to verify the effectiveness of the simulation model,this paper conducts a road torsional vibration test study on a certain type of 7-speed dual clutch transmission vehicle equipped with various vibration reduction measures,and compares it with the simulation results to verify the accuracy of the simulation model.First,various types of shock absorbers were trial-produced,and the test plan was designed.Then,the road torsional vibration test of the whole vehicle was carried out to extract relevant test data.Finally,compared the angular acceleration amplitudes of the flywheel end of the engine and the input shaft of the gearbox obtained by simulation and actual measurement,combined with the colormap of the vibration acceleration of the gearbox casing and the engineer’s subjective driving evaluation,the validity of the simulation model is verified.(4)In order to further improve the vibration reduction performance of the Bifilar type centrifugal pendulum vibration absorber with single-mass flywheel,it is necessary to carry out parameter optimization analysis.Firstly,a parameter optimization model is established by determining the optimization parameters,optimization objectives and constraints.Then,based on the one-dimensional search optimization calculation method,the centrifugal pendulum structure parameter r+l and the centrifugal pendulum mass parameter m_p are optimized and calculated respectively.Finally,by comparing the before and after optimization the relationship between the angular acceleration amplitude of the input shaft of the Bifilar type centrifugal pendulum vibration absorber with single-mass flywheel and the gearbox rattle threshold proves that the optimized Bifilar type centrifugal pendulum vibration absorber with single-mass flywheel can meet the requirements of the gearbox in the entire speed range,no rattle noise requirement.