| Vehicle itself is a complex vibration system with mass, flexibility and damping. Torsional vibration of the engine and transmission systems is most prominent and it is the most harmful to the working performance and life of powertrain. Torsional vibration affects the ride performance of the modern high-speed car greatly and makes the crews have a feeling of uncomfortable and tired. Torsional vibration also affects the power and economic performance, as well as the trafficability characteristic, road-holding property, or even damages vehicle parts.Torsional vibration damper is an indispensable vehicle powertrain device for controling the torsional vibration. The clutch driven plate type torsional vibration damper born in the 1930s are gradually withdraw from the stage of history because of its own structural limitations, and it does not have the development potential in torsional vibration and noise control of the transmission system. The dual-mass flywheel type torsional vibration damper (DMF) is a breakthrough invention of the vehicle powertrain torsional vibration controling technology. After more than 20 years of development since 1980s, the design theory and manufacturing technology of DMF have become mature and stable, and the use has also been extended, promoting from truck of the very beginning to all kinds of the current vehicles, from single linear torsional stiffness characteristics to multi-stage non-linear elastic properties. Dual-mass flywheel torsional vibration damper has become mainstream in the middle and top grade passenger cars which have the superior technical requirements of the comfort performance. At present, this new torsional vibration damper has been extensively equipped on European vehicles. But at home, DMF has not been spread, and manufacturers have not commenced. Only some research institutions and companies developed some kinds of samples.In this paper, the DMF basic technical data requirements, which match to EA888 assembly, including overall contour size and DMF two-stage stiffness characteristic curve were given by a company. The DMF with circumferential long arc spring--EA888-DMF-CS is designed to meet the established technical requirements and match to the powertrain of a medium-sized car of Volkswagen on which is equipped EA888 engine. ADAMS-Pro/E joint dynamic analysis and simulation technology and design process are valuable and referential for the development and designing methodology of long arc spring dual-mass flywheel. Dual-mass flywheel is simplified to the torsional vibration model of 2 degrees of freedom, and then its torsional vibration is calculated. The conclusion of the calculating analysis is that natural frequency of the system is relative to distribution ratio of the moment of inertia J1 and J2 on both sides of the damper and torsional stiffness k. When J1/J2=1, the natural frequency is minimum, and it means that if the total rotation masses on both sides of the damper are equal to each other, the resonant frequency will be minimum. The reducing of the torsional stiffness k, or choosing damper with springs of low torsional stiffness, can make the natural frequency lower and avoid the resonance. The arrangement of springs is relatively easy because of the structural advantage of circumferential long arc spring dual-mass flywheel--DMF-CS. With a larger arranged radius and circumferential length for springs, the torsional stiffness can be low enough to control torsional vibration and noise capably. So DMF-CS is an excellent damper of dual-mass flywheel. The driving plate of the DMF-CS may equip some short light straight springs or centrifugal pendulum to form the compound dual-mass flywheel. It is the most representative dual-mass flywheel, so EA888-DMF-CS designed in this paper is this type.After the selection of structural type and preliminary analysis of parameters of DMF, the research of performance parameters of DMF can be done in the vehicle powertrain. Firstly, Vehicle's torsional vibration equivalent model, lumped mass-stiffness discretization model, is established under two different working condition, idle and running condition; Then, Torsional vibration of the model about the resonance is analyzed. The analysis includes two aspects, external factor--disturbance torque and internal factor--natural frequency; Next, The mathematical model is established for optimizing the DMF parameters, including design variables, the objective function, and constraints. Based on the parameters optimized theoretical foundation, the virtual prototype can be established in ADAMS, which can carry out dynamics simulation of models. Through the simulation in ADAMS, the range of optimal solutions and optimized results of DMF mass and damping parameters are obtained. The ratio range of the two masses moment of inertia is 0.6 to 1.0, which accords with preliminary calculating analysis and provides the data on the performance parameters for the next phase of design work. The study on DMF shall be not only in the clutch flywheel assembly, but also in the vehicle powertrain.With these parameters'optimized results, the structure of non-linear elastic part and other parts of the two-stage dual-mass flywheel can be designed. Firstly, nonlinear stiffness and damping characteristics of EA888-DMF-CS are analyzed, and the designing outlines of two-stage elastic characteristics against the saltation of stiffness is obtained, which can be referred for structural design; The analysis of parameters and structural design for EA888-DMF-CS, among which the design and analysis of the elastic part is most important, are key components of the paper. Before the design of elastic part, the choosing principles of mass and damping parameters have been discussed, and the overall structures of the DMF have been planned and designed in accordance with the optimizing result of ADAMS. The layout space of spring chamber of elastic part is reserved for next design. Designing and analyzing of elastic part also include its structure, spring stiffness parameters and the design of curved spring. The calculating design of the curved spring uses two different methods of calculation, and the results of estimating method are basically the same to the accurate calculation. Eventually, a 3D model of EA888-DMF-CS is built in Pro/E, and it is imported into ADAMS with MechPro software. In ADAMS, dynamics simulation can be done to verify its damping effect. The simulation results show that EA888-DMF-CS is effective for attenuating the fluctuation's amplitude of angular velocity, angular acceleration and torque delivered from crank shaft to clutch and gearbox.
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