Study On Ratio Control For Metal V-belt Continuously Variable Transmission

As the ideal transmission equipment for automotive, continuously variable trans- mission has wide progress and market space. Compared with automatic transmission (AT), CVT has advantages of good performance, more simple structure, achieving continuously variable speed. Therefore, CVT is more and more valued by people and developing rapidly. Research on CVT proceeded in main automotive enterprises of the world. Studying on metal V-belt continuously variable transmission is the most common, also the technology about it is the most mature.Studying on CVT is mainly focused on transmission control, as an important part of transmission control system about CVT, ratio control is the key point to control the engine working at the best operating point.Transmission mechanics of CVT is analyzed firstly in the paper, and the force of second actuator is determined. Secondly, the model of hydraulic system is established base on discussing electro-hydraulic control system, then the effect of hydraulic control system on the changing rate of speed ratio in CVT is analyzed. Then matching between CVT and engine is studied, control strategy is raised base on the studying. Finally, the emphasis is on ratio control, from the aspects of determine of target ratio with different driving cycle, the effect of the changing rate of speed ratio on performance of automotive, design of ratio controller etc.. The simulation model of CVT transmission system is created using the software named AMESim after theoretical analysis, related performance index of Ratio control in different driving cycle is analyzed intuitively by this model and then to verified the theoretical analysis.The traditional ratio control algorithm is improved aiming at problem of powertrain response lag in practical application. And a new algorithm named time delay algorithm is put forward. The problem for deviation of the engine operation from the optimal operation line has been improved, and the fuel economy of automotive has been improved at the same time.Studying on ratio control for CVT comprehensively in this paper, and the control algorithm is improved, it is believed that it has greater value in practical application.