Research On Fault Diagnosistic Method And System For Automatic Transmission

Since the automatic transmission (AT) has a series of advantages such as good velocity ratio transformation performance, the improvement of the comfortable and crossing ability, to ease the tiredness of driver, to reduce emission of engine and so on, it has widely used in modern automobile. AT is a complex system which including mechanical subsystem, electronic subsystem and hydraulic subsystem. Its configuration and theory is complicated, which results in difficultly to diagnose. Research on failure analysis for AT is the foundation of the analysis of system reliability and has the great significance to the product development. At the same time, it is the basis of development for OBD which has more formidable function. Through the attempt to design the automatic transmission fault diagnosis system, it has provided the method for the AT fault diagnosis by using software, which has avoid the blindness of current diagnosis for AT. With the development of diagnostic technology and further study in AT failure analysis, the real-time monitor system and expert system for fault diagnosis by using computer technology has the important practical significance to enhance the product reliability and the quality of service.The paper presented the present research situation and tendency of AT in three aspects: torque converter, planetary gear box and shifting control system. On the basis of analyzing the elementary structure and function of mechanical system and hydraulic controlled system of AT, carried out the failure analysis of AT. Then the AMESim model of AT is established and the qualitative simulation is conducted. The result of simulation validated the result of failure analysis. On the basis of failure analysis, established the fault database. Finally, the software named ATFDT for AT fault diagnosis is programmed byusing Visual Basic and Access. The main research works are focused on the following aspects:1. Failure analysis for AT. Hydraulic controlled system of AT is divided into the oil pressure supplying, regulating and flow control subsystem,the shifting control subsystem,the shifting quality control subsystem and the torque converter control subsystem according to the functions of different subsystems. The configuration and function of these four subsystems are analyzed. Then failure anaysis for hydraulic controlled system is carried out. In view of the logicality that shifting control subsystem has, the logic mathematical model and structure function for failure analsys is established. In consideration of the flaw of single failure mode analysis, multiple failure modes analysis based on RPN is proposed, which can solve the contradiction between'combination explosion'and missing of some important information of failure.2. Modeling of AT in AMESim. Study on qualitative simulation for some performance parameters of AT is carried out. Two cases on qualitative simulation when the typical part works normally and part is disabled are researched by using batch run function of AMESim. Failure analysis is validated by compared with results of simulation.3. Combination of testing method. On the basis of analyzing the commonly used testing method for AT fault detection and the function of shifting elements, obtained that reasonable logical combination of testing method can reduce judgement scope of shifting executor skid. It had the vital significance to analyzing skid of shifting element.4. Failure diagnosis software for automatic transmission is designed preliminary. Classified the AT failure according to the different Classified principle. Designed the failure diagnostic flow for AT. The software for failure diagnosis is programmed by using Visual Basic and Access.