Research On The Method And The Performance Of Isolation Of Torsional Vibration Of DMF-CS Based On The Vehicle Power Train

Dual mass flywheel torsional damper (DMF) can fall the low natural frequencies of the power train below the idling speed of engine and effectively isolate the torsional vibration from engine, so DMF has been developed rapidly in recent years. However, the technology of DMF was only masted in several oversea companies. Up to the present, there hasn't been mature method of DMF at home. Today, under the condition of higher fuel price and the global crisis of economy, people select a small displacement car more and more. But the torsional vibration and noise of the power train of a small displacement car is an universal phenomenon for 4-cylinder engine in line. Now, the DMF is almost foreign product and the higher price of DMF blocks its abroad application in the small displacement car. Therefore, the research on DMF (especially for a small displacement car) is very important.In the thesis, research on the mothed of DMF-CS combining in the item of exploitation of DMF in Jilin Province was based on the power train of a small displacement car(code name'QR'). On this condition, the study and simulation analysis of the DMF-CS with centrifugal pendulum-type absorber which is an up-to-date product with much more perfect performance. The thesis combine theoretical analysis, simulation, and test verification together, drew some conclusions on the mothed of DMF-CS and performance of isolation of torsional vibration for DMF-CS with centrifugal pendulum-type. Details are introduced as followings. 1. The characteristic analysis of torsional vibratioin of power train which does not only verify the effect of vibration isolation, but also offer the gist of torsional rigidity, moment of inertia parameters, is one of important taches in the processs of designing DMF. Considering the characteristics of power train of vehicle, the torsional vibration model of QR power train was built and the natural frequencies and normal modes were computed. The characteristic of torsional vibration of engine was analyzed and the critical plots of power train including CTD and DMF were drawn respectively. The result is that the number of critical resonance points is reduced from 4 to 1 in the common driving condition (4th gear), especially the harmful low resonance eliminated. At last, the influence on the natural characters of torsional vibration of power train by torsional rigidity of DMF was analyzed.2. The design method of DMF-CS was researched and the principle or means of some important parameters was summarized. The elasticity characteristic is always the keystone and nodus of the process of designing DMF-CS, so a new way was applied to educe the formula of arc spring in this thesis, avoiding the complex process by the exit way and extending the scope of the formula of arc spring. The requirement of damp character of DMF-CS was summarized, and the difficulty of design process was discussed. The topic how to ascertain the moment of inertia of the first flywheel and the second flywheel was analized. Subsequently, one set of DMF-CS with two-level elasticity characteristic was devised according to the QR power train, and the flow of exploitation of DMF-CS was summed up. After analyzing some projects of variable torsional rigidity, a new project of variable pitch arc spring with ideal elasticity characteristic was brought forward, the number of components of DMF-CS was decreased and the cost of DMF-CS was fallen by the project. The way on which the formula of arc spring is deduced and the variable pitch arc spring were directive and useful to research on DMF-CS.3. The research on DMF-CS was in underway phase at home, so there were short of the checkout way, test method and reference values of DMF-CS, and the correlative studies of the sample were explored. The method of arc spring was verified by the result of static torsional rigidity of DMF-CS. The dynamic character of DMF-CS was measured by the power in different frequencies, swing and pre-torsional angle. Further more, the variable rule of characterics of dynamic torsional rigidity and damp in medium and low frequency (0 ~ 40Hz ) was summarized, offering the gist of torsional rigidity and damp of DMF-CS. No matter what the method or conclusions of test about DMF-CS was useful of referencing to research on DMF-CS.4. Based on the researches mentioned, the DMF-CS with centrifugal pendulum-type absorber was studied. On the condition that the linking form between centrifugal pendulum-type absorbe and DMF-CS and the relative movement were analyzied, the mathematical model was built and the theory of isolation of torsional vibration was deeply researched. The differential equations were established using the theory of Lagrange, and the conclusion that the natural frequency of pendulum is proportional to the rotate speed of DMF-CS was drawn by computing the equations. Utilizing the above conclusion, the intia moment in reverse of pendulum was counteracted to the disturbing torque of engine at ignition frequency by adjusting the parameters of pendulum. Hereby, the disturbing torque of engine at ignition frequency was able to eliminate entirely in theory. For getting the more performance of the DMF-CS with centrifugal pendulum-type absorber, we further studied the isolation of torsional vibration under other disturbing torque at impormant frequencies of engine and on the condition of the pendulum being weared. Based on the virtual prototype technology, the model of QR power train which included the DMF-CS with centrifugal pendulum-type absorber was built, and simulation was done under different effect of engine. The simulation results show that DMF-CS with centrifugal pendulum-type absorber almost eliminates the disturbing torque of engine at ignition frequency and restains the disturbing torque below ignition frequency. The simulation results are agreement to theory analysis, which validates the analysis and the mothed of modeling of DMF-CS with centrifugal pendulum-type absorber.