The Clamping Force Control And Simulation Analysis Of Hydraulic Control System About Metal-belt Type CVT

The metal pushing V-belt type continuously variable transmission (CVT) has the advantages of simple and compact structure, excellent performance and easy operation, Which is an ideal transmission form for economical automobiles. It can realize the optimum matching between the engine and the vehicle, so it can improve the vehicle’s fuel economy and dynamic performance, and lower air pollution.But, the ability to save fuel of the present vehicles which are equipped with CVT has not been very well. The main reason is that the drive efficiency for CVT is low. The clamping force control is the determining factor on the drive efficiency of CVT. While the clamping force being too small, slip will appear between belt and pulleys, the engine output torque would not be transmitted reliably, and the interface of the pulleys and the metal would have serious wear. While the clamping force being too big, the load of the metal belt will be big, and the interaction force of internal components is become bigger. It would not only raise unnecessary friction losses, but also reduce the life of the metal belt. The clamping force is provided by hydraulic control system, excessive clamping force needs large system pressure which is provided by hydraulic control system. It would directly lead to increase the energy consumption of the engine, and reduce the fuel economy. Therefore, in order to effectively improve CVT transmission efficiency, the target clamping force is made reasonable by driving demand, and the control system make the clamping force being the best condition.This paper based on the current universal clamping force control method of CVT, Through the bench test to get the critical clamping force, clarified the method of how to get the critical clamping force within speed ratio is dynamic changing and the other load is changing,at the same time, Introduced correction factor to correct critical clamping force caused by the change of the temperature and using fuzzy algorithm to make certain the safety factor in various conditions, so get the target clamping force of the Metal V-belt. The experimental show that the fuzzy calculating method can reduce the object clamping force and guarantee no sliding. The target clamping can also improve the efficiency.The paper is based on the natural science foundation of Hunan Province-The digital valve of the CVT electro-hydraulic module design and experimental study.