Reseach On Dynamic Characteristics Of Passenger Car Dual Mass Flywheel

The vehicle power train is a multi-freedom torsional vibration sytem, and its torsional vibration and nosie decrease the safety and comfortableness of a vehicle. The torsional vibration of the vechile power train originates from the fluctuation of engine rotating speed and torque. The traditional clutch damper has finite damping performance due to its space structure constraint. Dual Mass Flywheel (DMF), as a new type torsional damper, has favorable work performance, and then is widly applied into the passenger cars in overseas. However, the present status of development in this field still rest on the theory research stage in China.Based on domestic and abroad research results and development trend about DMF, the Circumferential arc spring Dual Mass Flywheel (CS-DMF) is taken for the study object in this thesis, the method of DMF is further studied, which includes rotary inertia coefficient ascertain, optimization of each torsional stiffness and elastic characteristics of Circumferential arc spring.First of all, the two undamped multi-freedom torsional vibration models of DMF under idling and driving condition are built based on the principles of vehicle power train equivalent torsional model. According to mechanical dynamics and the elastic characteristic of DMF, the design model of DMF is built, that is, the first order model and the second order model.Secondly, the relationship between rotary inertia coefficient, torsional stiffness, transmission gearbox and torsional vibration frequency is analyzed on the basis of the design model. Furthermore, a design method of rotary inertia coefficient and the first level torsional stiffness and the matching method of DMF and transmission gearbox are proposed. Afterwards, the relationship between the first level torsional stiffness and the second level torsional stiffness is derived out on the basis of the installation form of the springs so that the design method of the second level torsional stiffness is established. Moreover, the optimization principle and method of the two levels torsional stiffness under driving condition is studied. In the later, the elastic characteristics of the spring is analyzed by the discrete method, and then the calculation formula for the elastic characteristics is derived out, and also the suitable conditions of the formula is discussed. Thirdly, the design model and design method of DMF are verified by torsional vibration experiments under idling condition and static stiffness experiment. Furthermore, a CS-DMF is matched with the VM diesel engine based on this method, and then its performance is verified by dynamic simulation. The nature torsional vibration characteristics are studied by analyzing the nature torsional vibration frequencies and torsional vibration shapes.Finally, the software system of DMF design and analysis which integrates the design method of DMF and the analyzing method of nature torsional vibration characteristics of the vechile power train is developed by VC++programming language.