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With drastically reduction of engine noise, the gear rattle noise generated by the impact between neutral gears inside transmission can be much easily perceived. It is well known that the torsional mode has a direct relationship with the transmission gear rattle noise. This paper establishes a torsional model of a front wheel drive automotive drivetrain, including clutch system, transmission box and equivalent load of a full vehicle, in AMESim software. The experimental engine speed fluctuations at different gears are used to excite the torsional model. The influences of several parameters, including flywheel inertia, clutch stiffness, clutch hysteresis and drive shaft stiffness, on the 2nd order (major engine firing order for a 4-cylinder-4-stroke engine) torsional resonant frequency and the 2nd order torsional resonant peak of the transmission input shaft are analyzed by changing them alternatively.

Currently, four wheel drive (4WD) system is widely used in Sports Utility Vehicle (SUV) due to the increasing demand of fuel efficiency and dynamic performance by customers. However, propeller shaft consisting of different universal joints and tubes on 4WD vehicle easily induces low frequency bending vibration. This paper analyzes the characteristics of driveline bending vibration of a 4WD vehicle and provides control methods to reduce the low frequency vibration caused by propeller shaft bending resonances. Firstly, the driveline bending vibration model of the 4WD vehicle is established using FEA method and the natural frequencies are calculated. Secondly, the influence parameters, such as universal joint, relative length of two-piece propeller shaft, and tube diameters, on bending frequencies are analyzed by both FEA analysis and physical testing.

The paper analyzes the characteristics of driveline torsional vibration of a RWD vehicle and provides the control methods of transmission rattle noise caused by the system torsional resonances. A driveline dynamic model of the RWD vehicle is established by multi-body dynamic method. The natural frequencies and modal shapes are calculated for each gear position and torsional vibration responses are predicted by forced vibration analysis. The system sensitivity and DOE are analyzed based on the parameterized stiffness, inertia and damping. The 2nd and 3rd order modal results show that the transmission shaft possesses the maximum amplitudes and its corresponding modal frequencies vary with different gear position. The sensitivity analysis results show that the system torsional vibration is significantly reduced by reducing clutch stiffness, increasing propeller shaft stiffness, raising half shaft stiffness, increasing the input shaft inertia and increasing the clutch damping.