| Since the beginning of the 21 st century,with the continuous development of the social economy,the number of car ownership has increased year by year,and the automobile technology has also been rapidly improved.However,the ensuing energy crisis,emissions pollution,driving safety and other issues have gradually become a serious challenge for people.The future automotive technology is bound to solve these three major problems as the premise,so the CVT came into being at the historic moment.Although the concept of infinitely variable speed has been proposed for a long time,it has only been more than a decade since the real assembly was applied to the car.However,with its excellent fuel economy,easy operation,and high transmission efficiency and low emission pollution,it gradually occupies a place in the automobile market.At present,the key technology of CVT manufacturing and R&D is monopolized by foreign companies,and domestic automobile manufacturers are still in the development stage for the production and R&D of CVT.Due to the lack of technical experience,the process of localization of CVT is not smooth,especially in the early stage of development,transmission components often encounter wear,damage and other issues.In order to break the foreign monopoly on CVT technology and promote the development of China's own brand CVT.In this paper,the structural strength of a new metal belt CVT developed by a domestic company in the testing stage is analyzed by using the finite element transient method.The main work is as follows:(1)According to the mechanism of CVT transmission,the components and working principle of the pulley group are introduced,the geometric model of metal belt transmission is established,and the corresponding relationship between the working radius,wrap angle and speed ratio of the pulley is obtained.The clamping forces of the driving pulley under various working conditions are calculated by empirical formula,and the axial displacement of the driving pulley under each working condition is deduced theoretically;(2)Finite element modeling of CVT is carried out,and complete mesh model of pulley group is obtained.Finite element modeling of interference fit position in the model is carried out.The correctness and accuracy of the finite element method are verified by comparing the simulation value of contact pressure with the theoretical value;(3)The hydraulic loading scheme of the pulley from the initial speed ratio to the target speed ratio is proposed.The influence of different oil pressure difference,oil pressure loading time,input speed and torque on the speed ratio simulation is studied.Then,according to the speed ratio debugging law,the transient simulation of the overall model of the pulley group under each actual working condition is completed;(4)Transient simulation method is used to analyze the deformation of the pulley,pointing out the difference of the deformation between the fixed pulley and the movable pulley,and studying the influence of different speed ratio and cylinder pressure on the deformation of the pulley.The deformation of the pulley will cause eccentric load,and then affect the stress of each component.(5)According to the transient stress results of the pulley group under actual working conditions,combined with stress nephogram and fatigue analysis,the strength analysis of the key components of the CVT pulley group transmission is carried out.It is pointed out that the position of the active key is the dangerous part of the stress.Finally,the structure of the pulley group is optimized.The stiffness of the pulley can be increased and the deformation of the pulley can be reduced by reinforcing.The stress of the corresponding parts can be reduced to a safe range by replacing the original single-bond scheme with three-bond matching. |
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