A Study On VVT System Control Strategy For Motorcycle Engine

The low energy consumption and low pollution has become the aim of engine become of the demand of environment protecting and human development. The VVT technology has become one of the new technology development way. It is very big the motorcycle engine speed than automobile speed (the highest speed for general automobile engine is 6000rpm, but for motorcycle engine is 12000rpm). The demand of valve timing is very different for low and high speed and the unchangeable valve timing has become more and more disadvantages. In allusion to the structure characteristics of small-medium displacement motorcycle engine in China, a variable valve timing(VVT)system of switching cam profile was developed for the engines of SOHC valve-train with two valves. Based on the system, the control strategy of variable valve timing and lifting running-mode at different work condition was carried out. So we can mastery the key technology of variable valve timing.Based on cycle simulation, a VVT cycle simulation model was developed on JH125 motorcycle engine. The parameters was introduced particularly, include: geometry size for intake and exhaust pipe system, geometry size for cylinder part, valve lift and discharge coefficient, the model of air cleaner, carburetion model, combustion model and mechanical power loss. The reliability was validated too.Based on the VVT model, the control strategy of variable valve timing and lifting running-model was carried out at idle speed low negative load,middle negative load,low speed high negative load and high speed high negative load. It has been proved that the performance of JH125 motorcycle engine can be effectively improved by loading the new type VVT system. The control strategy can apply to switching cam profile VVT mechanism gasoline engine broadly.The cam profile was designed combining VVT mechanism. The design includes: valve timing and high valve lift confirm, valve lift design and cam lift. It is a very good way for cam design.It has been proved by test that the power performance and fuel economy at small-medium speed can be improved obviously in JH125 motorcycle engine assembled with VVT mechanism, and the good high performance can be keep too. Accordingly, the performance of engine can be improved obviously at the whole speed. The VVT system control strategy is accurate.