Noise And Vibration Inhibition Of A Passenger Car Under Idling Or Speeding Up Condition

With the development of modern automobile industry and the improvement of people’sliving standards, automotive NVH (Noise Vibration and Harshness) performance causes moreand more attention. People’s requirements for the car are not only just appearance, power,security, etc., but also the higher comfort demands of the vehicle. Idling condition is one ofthe most common conditions, and human body is sensitive to the riding comfort of the idlecondition. Accelerrated conditions will directly affect customers’s intuitive impression of theNVH level. Accordingly, the car’s vibration noise under idling and accelerated conditions hasan important influence on vehicle’s NVH levels.Combined with the simulation and experiment, the vibration and noise problems of apassenger car when idling and acceleration are studied. Different solutions are given to solvethe car idling vibration and acceleration noise.For idling vibration problem, the powertrain mounting system is optimized byMATLAB and ADAMS software, in which MATLAB is used to optimize mount stiffness andimprove the mount systems’ decoupling rate; and the ADAMS software is used to calculatethe static displacement of various mount mounting system.After the optimizing of the engine mount system, vehicle idling vibration is decreased,especially when the air condition is open under R shift, the vibration of the steering and theseat rail reduce25%and27%, respectively. The implementation is applied to the productioncar finally.The tests also show that, after the rear mount optimization, the steering wheel andthe seat rail vibration is worse generally. Especially when the air conditioner is off, the seatrail vibration of R shift rise36%. The scheme doesn’t be applied to production finally. Asfor the acceleration noise of third gear, after troubleshooting tests and transfer pathanalysis, it is found that the largest noise impact comes from the rear mount. NTF(NoiseTransfer Function) value up to62dB(A) at85Hz from rear mount of Z direction to the backrow passenger’s left ear, while only51dB (A) to front row. The results of acoustic modalanalysis show that the first-order acoustic modal modes is about77.3Hz. Since the frontear is in the formation of section line, while the row ear is in the position of the highervibration amplitude, that is why the front row noise at full throttle acceleration of about2500rpm is less than the rear. In order to solve this problem, the rear mount spacing block isimproved and the dynamic vibration absorber is installed to reduce acceleration roar. After the two solutions, the original value around2500rpm peak is decreased from73.6dB (A) to63.89dB (A) and peak at about2500rpm was flatten. Now the problem is solve apparently.