Study On Electronic Control System Of High Pressure Common Rail Diesel Engine

With the increasingly strict emission regulation and the development of diesel engine electronic control technology, as a high flexible fuel injection system,the high pressure common rail (CR) injection system has become a trend of the diesel engines technology for its remarkable advantages. Research on hardware and software design of electronic control system for CR diesel engines is very important for improving independent development ability of domestic automobile industry.Based on the control principle of electronic control system, a total design scheme of the electronic control system for CR diesel engines has been made out. The hardware of electronic control unit (ECU) for CR engines is designed and developed. Motorola's MC9S12DP512 micro controller unit is used as the electronic control unit. The sensors and actuators are also selected.On the basis of the electronic control theory, the stable control strategy of injection quantity, injection timing and rail pressure have been designed after designing of system's control project. The injection quantity and the injection timing are controlled on the basis of the MAP, and the rail pressure is mainly controlled by using PID of closed loop. Finally, the whole control system adopts the control strategy based on the injection quantity. According to various conditions of the diesel engine, detailed control strategy achieves the steady rail pressure, precise injection quantity and injection timing, as well as the performance of rapid starting and stable running.According to the idea of hierarchical and modular design, the development of controlled software is divided into six functional modules, including initialization module, signal acquiring module, logic control module, driver module, serial communication module and monitor module. All above modules are independent, but interrelated to each other, and they can achieve the control objects of electronic control system together.The test of ECU has been carried out and the results show that the basal functions of ECU are achieved. It can acquire signals from sensors,communicate with PC and drive actuators. Then the ECU has been installed on the fuel injection pump test bed and the elementary bench experiment is made. The experiment results show that basic control of fuel injection can be achieved, and the rail pressure control is achieved by using PID of closed loop.