Study On Optimum Of Vehicle Powertrain Mounting System For CA7106 Car

With the development of vehicle industry, vehicle' s speed becoming more higher and it' s weight becoming more light, lead to vibration is increasing greatly, but people' s request about comfort performance is becoming more and more higher. Uneven road, imbalance force and moment that produced by engine when it is running are the main exciting vibration sources. Engine is one of the most important vibration sources of vehicle. If vibration produced by engine has not been got a good control, it can cause vehicle frame and other parts to produce abnormal vibration and noise, influence the performance of vehicle such as it' s ride comfort, controllability and stability, make the passenger to feel tired and discomfortable, even damage vehicle' s parts and shorten it' s service life.When choosing the suited engine mounts, vehicle' s vibration and noise will be decreased obviously. Therefore, the engine mounting system' s design suffered extensive attention. Engine mounts contain three primarily functions: support, limiting position, isolating vibration. On the one hand, vibration isolation function need a softer mount; on the other hand, in consideration of limited space , to avoid collide with other parts and too much displacement when vehicle starting and stopping, support and limiting position function need a more rigid mount to fix engine position. Powertrain rigid modal frequency range should avoid engine ignition frequency, road excited frequency , and other part' s natural frequencies. Engine mounts also should be produced easily and service life should long enough. A excellent design mount system must accord with all these request. How to successfully design a set of optimum mounts that vibration spreaded from engine to frame can be availably isolated has become an important task of the vehicle design. In this paper, based on a lot of references about mount, vibration isolation of engine mounting system has been studied deeply. The engine mounting system is a complex multi-freedom degrees vibration system, it need to consider the natural characteristics of three axes directions and three rotary directions. The paper regard the mount as a spring which has three stiffness along three main elasticity axles and regard the vehicle frame as a rigid body, established a six freedom degrees vibration model, deduced out the solution of vibration equation in detail , analyzed the characteristics of inertia matrix and stiffness matrix , investigated the influence reason of dynamic performance caused by mount parameters.By investigating the mass spring vibration system, known when outside excitation frequency coincide with the system natural frequency, the system will resonance and enhanced vibration. If want to get a ideal isolating vibration effect, the ratio of excitation frequency tonatural frequency must be higher than 2^1/2 according to the isolating vibration diagram. As for engine mounting system, the most important excitation is firing pulse. Therefore, must adjust the mountsparameters that the engine mount system natural frequencies is 1/(2^1/2)times lower than firing frequency.Generally, vibration coupling exist in modal vibration mode of engine mounting system. The coupling degree have relation with the coordinates of mass center, the position of main inertial axis, the direction and position of excitation, the stiffness and position of engine mounts. On one hand, vibration coupling extend the range of frequency which will cause resonance, increase the difficulty of vibration isolation.0n the other hand ,when excition input in one freedom degree, it also lead to vibration on the coupling freedom degree. Therefore, must minimize the degree of vibration coupling. Since excition mainly comes from uneven road, imbalance force and moment produced by engine, it should mimimize vertical and roll vibration mode coupling as far as possible.Based on the research of stroke center theory, elastic center theory , torque axis theory and modal energy decoupling theory, the paper studied the method how to build engine mount system model with ADAMS software, and how to optimize mount parameters with iSIGHT software.The advantages of modal energy decoupling are: (1) decoupling design on the original coordinate system; (2) only need to analyze rigid body modal parameters without knowing the engine type and engine layout, so it has widely applicability; (3) decoupling index range between (0,100%), it can keep a very good numerical stability when optimizing.The paper measured the weight, position of mass center and inertia parameters of CA4GA1 powertrain. Built a dynamic model using the obtained inertia parameters. In the iSIGHT software, calling ADAMS to solve the modal parameters of the dynamic model and MatLab to treat with data. Adopted multiple island genetic algorithm as global searching algorithm and sequential quadratic programming as local searching algorithm, since it is a multi-peaks optimum problem.In this paper, applying ADAMS and iSIGHT software optimized CA4GA1 powertrain mount stiffness based on modal energy decoupling theory, which provide basis for engine mount matching design, shorten the period of design cycles.Engine mount decoupling design optimum method which had been investigated in this paper, building model is very easy and quickly, need no complex programming, has higher reliability and stability.