摩托车电控汽油机点火系统干扰和抑制研究.doc

合肥工业大学本科毕业论文 PAGE PAGE I 摘 要 大阳CG125汽油机的单片机控制系统是准确控制汽油机点火时刻、节气门开度等的关键部件。然而，点火系统在火花跳火时刻向外的强电磁干扰对单片机控制系统的可靠工作造成了严重威胁。本文研究了造成这些影响的干扰源的特性，并针对该特性提出了一系列措施以保证单片机控制系统的可靠工作。 本文详细分析了点火系统的干扰源特性，并以高压线为例分析计算了由于断电器断开瞬间高压线上电流的脉动变化所产生的电磁辐射，计算出了不同频段所对应的远场和近场距离。基于远场和近场的不同特点计算出在不同的场点至源点的距离r和不同的方位角θ所对应的电场强度和磁场强度，并绘制出其变化曲线。 对于点火系统而言，电磁干扰信号传输耦合的途径主要有传导和辐射两种方式。传导耦合又可分为电导性耦合、电感性耦合和电容性耦合。针对电　导性耦合，本文中采用光电耦合器、单片机和点火系统独立供电、点火系统初级电路、次级电路、单片机电路等单独设置地线，并在一点接地的方法来抑制和消除电导性耦合干扰；针对电容耦合和电感耦合干扰，在电路设计上采取点火信号驱动电路和单片机电路分开设计布线，并在电路板上采取隔离的措施。针对点火系统对外的电磁辐射耦合干扰，本文中采用盒状铁屏蔽壳将火花塞和高压线屏蔽起来，屏蔽壳接地的方法，此方法可同时起到电场屏蔽和磁场屏蔽的作用。 采取上述屏蔽措施后，经实验证明，单片机控制系统在点火系统点火时 刻能够正常工作。 关键词：汽油机，单片机，点火系统，抗干扰 合肥工业大学毕业论文 PAGE PAGE IV ABSTRACT Gasoline CG125 Dayang microcontroller control system is a key component to accurately control the ignition times, throttle opening and so on. However, it will creat strong electromagnetic interference to control system while the ignition system spark is flashing,which will take a serious threat to the reliable 　work. In this paper,the characteristics of the interference source is talked and a series of approach to ensure a reliable single-chip control system work are refered to. In this paper, a detailed analysis on the characteristics of the interference source from the ignition system is done, and analysis of electromagnetic radiation generated by the high voltage pulse current at the moment when the broken appliance disconnect is also include in the study by taking the high-tension line as an example. And then,the corresponding far-field and near-field distance is calculated. Based on far-field and near-field to calculate the the electric field strength and magnetic field strength in different position r and the azimuth angle 　θ corresponding to, and to map out its plans. For the ignition system, the mainly two ways of electromagnetic interference signal transmission are conduction and radiation. Conduction can be divided into conductive coupling, inductive coupling and capacitive coupling. F