Study On Application Of On-board Diagnostic System

The vehicles'emission already is the major sources of pollution. Now more and more countries began to improve the environmental quality through controlling the emissions of vehicles .The main goal to install OBD system on vehicle is to control the emissions during the whole life of the vehicle. Now in China most of large auto companies are Sino-foreign equity joint venture, and the engine control system companies also are European or American joint venture enterprise or foreign-funded enterprise. So in short term, it is the main way to introduce the OBD technology. And for the implementation of the regulation, it seems very important to study the application of the OBD for the used vehicle. The OBD system was researched in this thesis. The main word includes below aspects:(1) Study the technology of OBD system, focus on study the monitoring strategy of catalyst, Oxygen sensor, misfire and EGR system, and the requirements about communication protocol and fault codes and Malfunction indicate light(MIL);(2) Study on application of OBD;(3) Study the management of in-use vehicle with OBD.Through the study of experiences and data of European's and American from the application, the following conclusions were gotten in the thesis:(1) Along with the finding and solving of the problems of OBD during its application, the function of OBD was improved step by step;(2) There is no relativity about emission results between the vehicles failed to pass dual idling emission test and the vehicles which has malfunctions of OBD system; (3) The total emission decreased through the way to monitor the malfunction by OBD and maintenance on time is much than through testing the tailpipe emission of vehicles in I/M (Inspect/Maintenance);(4) OBD system really ignores some high emission vehicles, but this condition is still better than tailpipe emission test in I/M;(5) OBD system, it can offer the forecast maintenance, it is to say before one malfunction makes the tailpipe emission become bad, the vehicle was maintained. And we can't get this advantage in previous I/M;(6) It should be decreased to acceptable degree of OBD self-faults when the OBD test becomes the enforcement item in in-use vehicle test;(7) Because OBD test take more short time and less cost than tailpipe emission test, so there is exist a trend to replace the tailpipe test.Study the regulation frames of Euro and America, and the implement procedures, introduce the methods of OBD test of Euro and America.Analyze the reason that the technology of OBD is still not very well at present. It is not the best time to replace the tailpipe emission test with OBD test for in-use vehicle annual check at present.Give the suggestion: It can try out OBD test for in-use vehicle annual check, at the beginning, it can be test the OBD system and tailpipe emission both. When gets some data, then decide how to do next step.Give the methods of OBD test.The research results of this thesis has been taken into the report'Policy study on phase III\IV of auto emission in Beijing'. The suggestions and conclusions of this thesis were introduced in the emission regulation step by step. The contents and conclusions also were adopted into'Criterion of Management and Technology about OBD system'drafted out by our institute, which is a task given by State Environmental Protection Administration of China .