The Vibration Isolation On Engine Mounting System And Test Research Of Noise Reduction On Vehicle Interior

With the developing of automobile industry and people's requirement on the riding comfort of automobiles is increasing.Good performance of NVH is an important symbol of present-day automobiles.What is called NVH,it means Noise,Vibration,Harshness(the feeling of body for noise and vibration,or infection of body by noise and vibration).Automobile powertrian is one of most important vibration and noise source of vehicle,which affects the performance of full vehicle mostly.There are two vibration resources in automobile,one is the road surface random exciting while running;The other one is vibration of engine while working. Therefore,it's becoming a key design technology to damp and isolate vibration between powertrian and frame.In a general way,the first one has great influences on the passenger,but with the improvement of road conditions and the consummate of the mount frame system designing,the influences in this aspect are lowered to a certain degree;On the other hand,the design of modern car emphasized on loweringthe weight,adopting new-type,high-strength,light-nature materials in order to lower the mass of the whole vehicle,but it is too hard to lower the weight of engine,thus the proportion of the engine in the weight of the whole vehicle goes up.But most of the engine is four-cylinder four-stroke which are lack of balance characteristic,most of the car use integrity pattern and thin-cell-fabric body which leads to the increasing of the flexibility of the bodywork and the trend of vibration goes up,the vibration exciting of the engine on the bodywork increase comparatively.Thus the vibration exciting of the engine becomes the main vibration resourse of car.Nowadays, the furious market competition and various demands for vehicle products lead to an increasingly short product developing period of both entire car and spare parts enterprises. The old integrated developing style has evolved into more specialized one. As China's entrance in WTO, global order of automobile spare parts comes into realization. This not only promotes entire car developing, but also innovates the traditional developing way. Now besides the body design, the entire car development mainly focuses on structure integration and function matching of the car. That is to produce standard and excellent entire car system on the basis of good quality spare parts. As an important regulation, NVH releases its vital position in market competition. Vibration noise control and research are attracting serious attention now. Changes happened in entire car developing direction cause shifts in keystone of vibration noise control from spare parts and assembly domination in the past to comprehensive function matching between spare parts today.Powertrian mounting system is the most important vehicle vibration subsystem, the performance of this system decides the vibration transfer.A good powertrian mounting system can control the engine force transfer to car body preferably,not making the chassis and car body bring violent vibration and noise when working,improving the vehicle ride comfortableness and used reliability. In order to improve the performance of powertrian rubber mounting system,based on some parameter of a car which collocated MR479Q engine powertrian mounting system made in our country,using dynamic simulation software ADAMS,building a powertrian mounting system dynamic model with 6-Degree-of-Freedom (DOF). Computing and compareing the force, displacement, acceleration of three mountings of powertrian mounting system at different condition,simulating and analysising system frequency distribution,modal shape decoupling.Discussing mounting component stiffness coefficient influences the performance parameter above. Idiographic working as follows:1,In recent several tens years,people do much study on powertrian mounting system.Both the design of powertrian mounting system and the exploitation of the mounting components gain a great deal of successful experiences. In this paper, Based on a large number of references about the study of powertrian mounting system at home and abroad,the developing history of mounts is reviwed, including rubber mount and hydraulic mount.This dissertation summarizes some design principle and research result for the powertrian mount system;2,Expatiating the function of powertrian mounting system;Showing the familiar form of laying and supporting for powertrian mounting system.Expression of steady state stimulates and the transient stimulates are giving;analysing the vibrating isolation principle on powertrian mounting system;Analysing the range of powertrian rigid body frequency.3,Based on some test data of the powertrian which is researched, Look upon the engine , carriage as the rigid body ,using software PRO/E and ADAMS to build up a space dynamic model with 6-Degree-of-Freedom (DOF).Making the rotational properties(stiffness and damping) of bushing be zero,then the elasticity component can have three stiffness and damping. Using ADAMS/View and ADAMS/Vibration to simulate and analyse the model when working in stabilize state,getting the vibration responds of powertrian system when idling and high speed work. From the analysis above,the powertrian system meeting a series of design demand such as supporting and mount displacement limitation.At the same time,also simulating and analyzing the powertrian model when braking,the system meets the demand when braking.To simulate and analysis in frequency-domain,getting the modal frequency distribution,modal shape decoupling.4,Giving the math expression of the modal shape decoupling(or part decoupling), the modal frequency distribution,the modal transmission force is least,the force of supporting is least as optimition function.The design variables are nine stiffness of three mounting,taking the minimum vibration transfer rate inθx direction as the target function,computing,the result indicates the modal shape decoupling in reason,all mountings force is falling.5,Based on the simulation and analysis of powertrian mounting system,testing the sample vehicle on different condition, laying the sensor at the location above and below the mounting,collecting acceleration signal,getting the transmission ratio by computing every mounting's RMS value.The vibration isolation performance of two front mounting is better,the transmission ratio is a little higher at high speed. Analysing the noise inner which is produced by engine from solid and air,using vibration isolation, sound absorption material to reduce the noise inner 2-3dB when idling working.Enhancing the whole vehicle comfort effectively.In virtue of the software ADAMS/View to build a dynamics model,can consider many complex factors during matching process,analysising multi performance through a simple model,predigesting working enormously, quicken empolder plan.From the simulation in this paper,the mounting can meet many design requests form this design model,and getting good effect.