Research And Development Of The Malfunction Simulator For Gasoline Engine Oxygen Sensor

Stage III emission statute will be carried out since July 1 st, 2007 throughout the country. On-Board diagnostics (OBD) system test is the core and one of technical difficulties of the implementation of Stage III. OBD system monitors the emission-related components and control subsystems when the automobile engine is running. Once the malfunctions of some components or subsystems may bring about emissions exceeding the limits of standard, Malfunction Indicator Light (MIL) will be activated, Power Control Module (PCM) will store the information of malfunction in memory and record the diagnostic trouble code (DTC) at the same time. The DTC could be taken out from PCM by means of scanning equipment, by which the maintenance man could judge the character and position of malfunction rapidly and precisely, and make repairs to the vehicle.The diagnosis of oxygen sensor is one of the important functions of OBD. This paper develops a suit of malfunction simulator for oxygen sensor, which can be used in the function approved test of OBD system or the development of OBD system. The device could simulate the different malfunction aimed at the sensor's signal, taking the excursion of upper or downmost limit and the response delay as examples. Therefore, this development is of great significance to the smooth implementation of Stage III emission statute nationwide.The paper make researches on the OBD system's diagnosis strategy, introduces the monitor principles of engine misfire, oxygen sensor, catalytic converter and other assistant systems. The paper still elaborates on the configuration and working principles of different oxygen sensors, and analyses the reasons of malfunction about the oxygen sensor (ZrO₂), which provides some grounds for the development of the equipment.The malfunction simulator is connected in the middle of ECU and oxygen sensor. The signal of sensor doesn't input ECU, but inputs the simulator directly. The simulator collects the oxygen sensor's signal through the employment of A/D switching module, and then the signal is disposed. Lastly the simulator uses the A/D switching module output the disposed single to ECU. Simultaneously a suit of control software is designed to control the malfunction style and extent, which could monitor the simulating signal through the computer and supply a convenient operation environment.The emission is analyzed with the help of test results of engines by simulator. Besides, the function of equipment is tested and verified through using the device on vehicle. Finally, we apply a patent of invention according to the simulator.