Research On Vibration Problem And Performance Optimization For Transmission Shaft Of Heavy Truck

It has been found in the present process of production that many vehicles'vibrations are caused by unbalance of transmission shaft. During the vehicle design, designers closely concern the vibrations of transmission shaft, and hope to acquire the quantitative relationship about vibrations between transmission shaft and vehicle.In this paper, in conjunction with FAW Group Corporation R&D Center-related research carried out, the FAW vehicle vibrations are conducted in-depth explorations. The content of this paper is the basis of vibration theory, and dual-axis of heavy vehicles'vibrations and their transmission shaft's optimal matching are studied. The corresponding vibration in the vehicle modeling, dynamics analysis of rear axle shaft, transmission shaft's optimal matching and fault vehicle's optimal matching the four aspects carried out with a certain depth of exploration and study, and obtained some useful conclusions.1. Improvement of the Vehicle Vibrant ModelIt is very important for us to establish reasonable vehicle vibrant model, while vehicle vibration is considered. The main relevant research method of the vehicle vibrant model both in China and abroad is taking terrain displacement signal as the input signal of multi-degree of freedom vehicle model, which needs to build complex terrain model and tire model,but it is very difficult to build them till now.Accelerometer has the advantage of small volume and high precision, and it is convenient to use as engineering survey, so it is frequently used to analyze the vibration problem of vehicle. The traditional vehicle vibrant model is improved by the method of coordinate transform, by which the acceleration signal of the front axle and rear drive axle is used as the model input signal. Because of the input signal which is measured after being filtered by tires and bears tire enveloping properties, it will be more authentic and practical. Approximate equivalent and coordinate transform are firstly used to resolving the transplantation difficulty about the input signal of automobile dependent suspension optimization model. Two types of problems are discussed: 1) the input signal is changed by changing with suspension stiffness in the suspension optimization model; 2) the input signal is changed by changing with sprung mass during sprung mass randomly varied in certain extent. Without losing the accuracy of the input signal, the model can be used into not only the suspension optimization model, but also all kinds of deforming vehicles'calculation models which have identical suspension and different sprung mass. Thus, the improved vibration model is more practical in engineering. Compared with the traditional automobile dependent suspension optimization model,not only the input signal is convenient to attain, but also the input signal is changed by changing with suspension stiffness. Thus, the comparison between simulation and test shows that not only the calculation accuracy of model is improved, but also the model is more practical in engineering.2. Kinematics Characteristics of Rear-axle Transmission ShaftA new method of space analytic geometry is presented, by which the kinematics characteristics of single cross universal joint is analyzed and the dynamic model of the rotate speed, the angular acceleration and the torque about driven shaft are built. This method is clear, uncomplicated and lucid, which offers a more convenient way to analyze mechanism's kinematics characteristic so that it is suitable for project designs. By means of resolving the vehicle abnormal vibration, it can prove that the model in this paper is correct, and it draws the conclusion about the main reason for abnormal vibration induce by the angle ? between drive shaft and driven shaft. The driven shaft's periodicity on rotate speed, angle acceleration and torque find by matlab simulation, which breadth increasing with angle? . So it provides theory for reasonable disposal and reliability analysis on transmission shaft.A method of vector analysis is presented, which is used to building the rear-axle flouncing model. This method is clear, uncomplicated and lucid. Through comparing with the traditional diagram of transmission shaft, the result of the rear-axle flouncing model is accurate, and it can completely replace the traditional diagram of transmission shaft. The Matlab software is used to making the simulation and the variation curve of transmission shaft's length and angle is gained during rear axle flouncing, which will provide theoretic reference for the disposal of the transmission shaft, and which is more practical in engineering.On the basis of the rear-axle flouncing, the kinematics emulational characteristics of the transmission shaft are done on the different pavement. The conclusion can be drawn as follow: 1) Root mean square will increase with increasing of transmission shaft initial angle, 5 ~ 7°in the angle between the root mean square value of the trend slowing down;2)For the influence of root mean square value,transmission shaft initial angle changes more rapidly than amplitude of pavement., thus affecting the acceleration root mean square value change in the major factor in transmission shaft initial angle. So it provides theoretical basis for the design of transmission shaft.3. Research on Transmission Shaft's Optimal MatchingFirstly,the transmission shaft's centrifugal force is analyzed, and the vehicle vibration model including the transmission shaft's centrifugal force is built.Secondly,multiple parameters of the transmission shaft are analyzed and researched on the basis of the improved vibration model by means of orthogonal test,which will provide the theoretical basis for the reasonable matching of the transmission shaft's parameters.Thirdly,It can be drawn from the orthogonal test that assembly errors and ratio of rear axle are important factors for influencing test index from vibration level's point of view, and that errors , ratio of rear axle and carrying-capacity of saddle are important factors for influencing test index from comfort performance's point of view.4. Research on Fault Vehicle's Optimal MatchingOn the basis of genetic algorithm, optimization analysis of the fault vehicle's suspension has been done, and it will provide the reference for optimal matching of suspension. By optimal matching of the fault vehicle's suspension, it can be drawn the conclusion that suspension stiffness is so large that vehicle vibration aggravates. With fixed suspension stiffness of the fault vehicle, by optimal matching of saddle's carrying-capacity, it can decrease the fault vehicle's vibration. By means of orthogonal test, It can be found that carrying-capacity of saddle is fluctuant and important factors for influencing the fault vehicle's vibration. The original design carrying-capacity of saddle is 10 tons, but its corresponding root mean square is too large from curve, so design value is unreasonable. It is a suggestion that the design carrying-capacity of saddle should be 11 tons.With fixed suspension stiffness of the fault vehicle, by optimal matching of ratio of rear axle and distance of towing attachment, it can decrease the fault vehicle's vibration. By means of orthogonal test, multiple parameters of the transmission shaft are analyzed and researched, which will provide some solutions and methods for the improvement vibration level of the fault vehicle. Through the vehicle road test, it verifies the correctness of the simulation results, and the improved vehicle vibrates perfectly.