Study On FAI Liquid Dosing Unit For Engines And Oxygen Sensors Applied On Motorcycle

As the global environmental problems and energy crisis are increasing more and more seriously, energy conservation and emission reduction has become increasingly urgent. Our country’s fourth vehicle emission regulation will be fully implemented and there comes with new demands for motorcycles and heavy-duty diesel vehicles. For motorcycles, EFI technology must be used to meet new emission requirements. Because of special characteristics of motorcycles, suitable closed-loop EFI technology need to be developed; for diesel engines, considering the situation of our country, Selective Catalytic Reduction(SCR) technology will become the optimum solution. However, there are still some problems with the current SCR system: foreign systems have high stability and reliability, but they are complicated and costly; and domestic products’ quality varys greatly, the dosing accuracy can’t be guaranteed.FAI liquid dosing unit is based on the electromagnetic pulse intermittent fuel injection technology. With high injecting pressure, strong fuel adaptability, precise fuel injecting calculation, simple structure and low cost,it has achieved some performances in the field of fuel injection for small gasoline engine such as motorcycle. What’s more, the dosing unit can be used to inject conductive liquid, it can be used as SCR reductant(urea solution) dosing unit in diesel engine exhaust system. It can ensure accuracy easily, simplify the system greatly and reduce the cost.During the development of EFI system, the reliable performance testing system can guarantee the quality of products, and provide guidance for product development and performance improvement. Dosing unit and oxygen sensor which are two key components of the FAI closed-loop EFI system were worked on and the stable and reliable performance testing systems were developed. For injection units, a steady flow testing system based on the U-shaped pipe flow balance method was achieved and the reliability of the fuel injecting quantity correcting T3 theory was verified. For oxygen sensors, a small generator’s emission which was controlled by ECU acted as the measuring media to achieve the oxygen sensor’s fast testing offline. On board application proved the accuracy of the test result.The injection unit’s performance of kerosene and urea was researched based on the testing system developed. The result shows that the T3 theory has a satisfactory correction on the driving voltage and temperature’s impact on the two kinds of liquids. The abnormal urea injection at high frequency and high pulse can be avoided by improving the structure. The injection unit’s feasibility of being applied on SCR metering unit was demonstrated.In addition, there may be some reliability risks for oxygen sensors which are used in the closed-loop EFI system for motorcycles. The relationship between temperature and installation position of the oxygen sensor was researched by vehicle bench experiment. A cooling pad was designed and turned out to have significantly improving effect on the oxygen sensor heated issue, it is practical meaningful.