Research On Engine Control Unit Of A Diesel Engine With Common Rail Fuel System

With the increasingly stringent emissions regulations and common-rail technology widely used, ?Homogeneous, Compression ignition, Low-temperature combustion?, as the basic characteristics of a new generation of combustion technology, has also been in-depth studied and applied. Electronic control technology is an effective way to implementation of combustion theory, and is an important component of new generation of clean, efficient and intelligent engine technology. This paper reviews the development trends of diesel engine electronic control technology and electronic design automation (EDA) technology features. Aiming at characters and control demands of HPCR (High Pressure Common-rail) technique and new generation combustion technique, ECU?s (Engine Control Unit) development is completed by adopting bran-new Electronic technology, and lastly optimizing experiment research on newly developed HPCR fuel injection system is carried out with the successfully developed ECU.A new generation of combustion theory demands fuel injection control system with flexible fuel injection modulation model, precise control of injection timing and oil quality and other parameters, which makes control systems in the development of a large number of digital logic circuits. Therefore, with 32-bit microprocessor MCF5233 and CPLD (Complex Programmable Logic Device) as the core framework, the ECU is designed, which can achieve time tasks, algorithm tasks, and digital logic tasks to concurrently process. For improving response speed-rate of injector electromagnetism valve, an innovative type of digital modulation booster module, based on CPLD, is brought forward, which substitutes IC of making PWM (Pulse Width Modulation) signal and the circuits of compensating inclined-wave in traditional booster module, and predigested structure of the module. At the same time, based on CPLD the logic synthesis of injector, drive signals of high-low voltage are completed, which realize high-low voltage time-sharing control to injectors. Relative to the older generation natural gas ECU (Patent Number: 02125326.9), the ECU is more suitable for next-generation combustion technology and common-rail technology development?s needs.Based on MCF5233-eTPU module, the instantaneous speed algorithm is designed by using crank-speed signal, thinks to which design of timing control for PCV (Pressure Control Valve) and injector is developed, and flexible timing control can be achieved. The internal and external reference point method was developed , which solves the stability of the system timing control, and further improves the timing accuracy. Injection parameters is defined by using an structure array, and using only one interrupt service, multistage injection control is achieved to improve the working efficiency of the CPU. With the help of eTPU-qom function, fuel control system meets these requirements of flexibly modulating of injection mode, and freely switching between different modes. In addition, based on reliability design theory, the all-round reliability design for the ECU is completed, and some of the fault diagnosis units are designed, which further strengthen reliability of ECU.From software engineering point of view in this paper, the life cycle model of embedded real-time system is built. Using object-oriented technology and CODARTS (Concurrent Design Approach for Real-Time System), the ECU system software is developed to ensure ECU systems to be real-time and transplantable and expansible at the same time. For making object-oriented technology and CODARTS to be better compatible, a method is brought forward, which makes the object standard of COBRA (Concurrent Object Based Real-time Analysis) to be carried through the whole process of object-oriented requirement analysis of software system. Meanwhile, in order to meet the fuel injection system development?s needs, a platform for human-computer interaction is built.Based on electronically controlled fuel injection system bench from FRANCE EFS INC, with self-developed ECU as the core, an experimental calibration platform for common-rail electronically controlled fuel system is set up. On this platform, all functions of ECU are verified while booster module and driver circuit of injector is optimized. In view of excessive configuration parameters in booster circuit, and higher request of ECU for boost-voltage characteristics of the recovery response, based on Pspice circuit simulation software, the structural parameters of the booster module is optimized. The results shows that the biggest booster module conversion efficiency can reach more than 90%, and the ECU's experiments showed that the biggest boost-voltage fluctuation don?t exceed 10%, and the renewing-time only was 1.3ms, which met these needs of ECU within engine operating range.Aiming at the question about inconsistencies of injector drive channels, effect of power circuit and discharge circuit on injection character is researched as a focus of experiment. According to the analysis of the experimental results, the introduction of a fixed value resistance into each loop, weakening the various driven channel impedance inconsistencies, improves the consistency of injector drive channels, which results in the driver channel RSD (relative standard deviation) down to 3.8%, from 11.9% before optimization in jet fuel of 40mg~50mg. In the end, research on character of newly developed common-rail fuel injection system is completed by using ECU in practical experiment, and the 135Ti diesel is modified by using the new electronic control fuel system that has passed all tests. Practice has proved that ECU developed in this work reached anticipated target and had good application prospects.