The Measurement And Analysis Of Variable Cam Timing Mechanism

Energy conservation and the control of harmful emissions have become the dominant direction in the development of internal combustion engine technology. Conventionally, the valve timing and lift have been fixed in use, optimized for the standard condition and circumstances. The valve timing of engine can't be permitted variation during engine operation. So this valve drive system has certain limitations, which make engine performance in various conditions difficult to optimize. However variable valve timing(VVT) can better meet the different engine speed, load conditions and thereby improve overall engine performance for the allocation of gas is different requirements. VVT has become one of the key technologies.This dissertation investigates it on the basis of a host of reference, and combines the real situation of the subject. A comprehensive study pattern, the integration of analysis, simulation, design and production, unit test and experimental engine is applied to develop variable cam timing(VCT) system. Major research work can be summed up as follows:1. Through analysis of the whole system, a VCT mathematical model is set up, including mechanical, electrical, hydraulic and electromagnetic simulation mode. The influences of different working parameters and structure parameters of VCT are discussed by using the MATLAB/SIMULINK code with strong capability of engineering calculation and the number analysis. The effect of the systemic operational parameters and various parameters of VCT on its operation process is revealed. It can provide reliable parameter and data to the mechanical design and manufacture.2. Through analysis of the hydraulic system, the leakage of vane-type VCT mathematical model is set up. We carry out the forecasts and verifications of the influences that the various factors exert on the leakage flow. According to the study on leakage, the effect of various parameters of VCT on its operation process is revealed. It can provide reliable parameter and data to the mechanical design and manufacture.3. This dissertation analyzes the practical technology for VVT and the variable factors of VVT. The technology for VCT based on the camshaft phase shift theory is determined. Based on the simulation results and learning from foreign experience, VCT is designed. Through analysis of vane-type VCT, the sort and design are introduced about the structure such as vane, seal, lock pin and oil passage, and it is revealed that the different designs of the structure of intake and exhaust cam and the select of material. Furthermore, the design and key technique of VCT are primarily described.4. The measuring system is developed for VCT. For the problem of hydraulic pressure serving as the driving source of the VCT and the mechanism of the VCT have non-linear characteristics, the policy of PID control is suggested.Study indicates that the control arithmetic is simple in structure,good in real time capability,fast in response and preferably satisfies control request.By the testing systems, theVCT characteristics and parameters related to operation process of VCT can be analyzed. Electronic control, intelligent, integrated control and testing friendly interface is applied to the measuring system. Testing system is domestic initiative.5. Experiment study of VCT on SI engine is done. At the same time, it plays a final measuring of successful design. The results show that the new VCT can meet the requirements of engine and the measuring system can be used for performance testing of VCT.