| Valve train is one of the critical mechanisms that significantly affect the power,fuel economy and NVH performance of internal combustion engines.With the further investigation and application carried out by OEMs and suppliers,valve train has been greatly improved in aspect of lift characteristic flexibility,charge efficiency and friction reduction,which has made contributions to the promoting of engine thermal efficiency.Variable valve timing is a mainstream technology to improve the flexibility of valve train lift characteristics.Engine hydraulic or electric power was used to real time drive the intake and exhaust camshaft,in order to achieve the effect that matching the most suitable valve overlaps for different driving conditions.In 1980 s,company Alfa Romeo firstly applied variable valve timing technology to their engines.After that,the application of this technology rapidly grew in OEMs world widely for its significant reduction in fuel consumption and ease of implementation.To meet the requirement of engine application,foreign and domestic researchers have carried out a lot of investigations in aspect of design,development and control strategy of VVT mechanism,promoted the upgrading both in hardware and software of VVT systems.This research aims to optimize and improve the development process of VVT system,deeply investigated the key technologies for system forward development.Our research work takes a 3 cylinder GDI engine development project which was carried out by DFMC as a carrier,combine with previous experience,focusing on the areas of key parameters definition,dynamic simulation model construction and application and motored and ignition engine measurement.Finally the technological achievements are applied into following projects which make great contributions to development efficiency and the success rate improvement.The research work can be summarized as:1.By investigating the application and development status of VVT products,the technical advantages and limitations of each product are analyzed,and the technical maturity and feasibility of existing technical solutions are comprehensively evaluated.The development trend of VVT technology in 5-10 years is analyzed and forecasted in combination of engine advanced technology roadmap.2.Under the help of existing development tools,solutions evaluation and parameters definition are carried out.In this paper,the method of VVT adjusting angle definition,lock-pin structure and unlock parameter setting and the calculation method of internal and external leakage are discussed.Aforementioned works provides a basis reference for VVT mechanism design.3.Analyzing the working principle of VVT system,establishing the mathematical model and simulation model of VVT phaser and its related mechanism.Simulating and calculating the dynamic characteristics of the system by software AMESim then analysis the effects of parameters such as coil spring characteristics and air content to system dynamics.4.Investigate the dynamic test method of the system,set up the ignition and motored bench to measure the VVT characteristics.Compare test data with the simulation one to analyze the reasons of difference and rules,as well as draw the dynamic characteristics map base on measurement.Data obtained by dynamic test can support fast verification of VVT performance,development problem analysis and formulate the calibration strategy.5.Applying aforementioned key technical achievements to update current developing process,define working contents and outputs of each stage.Build the ideal cooperation mode that OEM dominant system matching and developing,suppliers in line with production and verification during VVT system development.This paper summarizes the necessary technical means for forward development of hydraulic driven VVT system,clarifies the development method and critical design elements.Method mentioned in this research is able to guide the development work effectively,which has a high engineering value in practical use. |
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