Simulation Analysis of Electromagnetic Compatibility in Vehicle Ignition Control System

Abstract

The ignition control system is the critical Electromagnetic interference source in automobile, and the transient voltage in primary circuit loop attacks the accumulator and interferes with the ECU or other electronic devices by power cord, and simultaneously the high frequency spark noise caused by spark plug may produce radiated noise which affects the electromagnetic environment inside and outside the automobile. Lots of vehicle manufactory are faced with the problem that the EMI testing value exceeds the threshold value. It is an urgent need to research the ignition system electromagnetic compatibility and seek the ignition system EMI suppressing method for enhancing the vehicle EMC. The objective of this study is to analyze the ignition system EMI formation mechanism and its effect for electromagnetism environment inside the vehicle, then taking effective suppressing measures to optimize ignition system EMC design. This paper simulates the ignition primary circuit transient current and voltage in EMC simulating software by analysing the working principle of gasoline engine ignition system and the formation mechanism of ignition system EMI. This study establishes secondary coil circuit loop spark plug discharge modle, the high voltage wire is equivalent to antenna, the electric field EMI distribution inside vehicle has been worked out, and then it researched the electromagnetic environmental effect of high-voltage wire position, length, working frequency and load impedance. The radiated electric field distribution is acquired by establishing vehicle body, antenna model in the Simulation Analysis. The longer length the high-voltage wire is, the stronger the radiated noise is. The height of wire from ground has little effect on electric field intensity, working frequency is higher and the radiated noise is stronger. These studies provide judgement basis for the optimization of electronic equipment installation position. This paper analyses the reason of ignition system EMI and electromagnetic environmental effect, and gives suggestion for susceptive electronic equipment installation. An important limitation of the current study is our study can’t include all ignition system problems, and some problems need to be discussed further; more convenient vehicle body modeling methods and spark plug noise suppressing methods need to be researched further. It is a new study of analysing ignition system EMI, establishing math model and analysing the effect of susceptivity equipment for electromagnetic environment. At present, most of car manufactories mainly focus on electromagnetic noise testing, so the simulating researching of ignition system disturbance characteristic can improve automobile overall EMC design. The research result indicates: making use of damp high-voltage wire, resistance type spark plug and shielding method for ignition coil and high-voltage wire can reduce radialization disturbance, but sometimes various suppressing measures will be taken.