磁电机点火性能的分析与测试

Analysis and Test of IgnitionPer formance of Magneto Dynamo

点火电压是借磁电机在无负荷不同转速上所测得的电压,此电压与外界条件无关,是反映磁电机本身性能的一个重要参数;在进行磁电机的实验或检验时,无断火现象并不能说其点火性能达到了标准,还要视其火花能量而定,一般无触点磁电机的火花能量在10mJ左右,持续时间在50～100μs范围内;点火提前角随转速变化的关系应能使发动机在其运行的整个速度范围内输出最大力矩,也即油汽混合体燃烧爆发时气缸活塞始终还在最佳位置,现在无触点电子点火磁电机具备提前角随转速增加而增大的功能;磁电机在运行中产生断火现象其原因很多,根本原因是二次电压达不到击穿介质的数值,某些速度点上储能电容上的能量不足,另外也与断火、空气的温度,及受到放电极针表面氧化程度的影响。

Ignition voltage is measured at different rotation speed of the magneto dynamo with no load. The value of the voltage, which has no connection with the ambient conditions, is a very important parameter denoting the performance of the magneo dynamo itself. If there is no ignition breaks occure when the magneto dynamo is tested or inspected,it does not mean that the ignition performance would meet the requirements of the standard. Its performance should further depend on the spark energy. Generally the spark energy released by the breakerless magneto dynamo is around 10 mJ and its duration is within 50 to 100μs. The variation of the ignition advance angle with the rotation speed should allow the engine to produce the maximum torque i. e. the piston is always kept on the optimum position when the air-fuel mixture starts to burn. At present the breakerless electronic ignition magneto dynamo has a function which permits the advance angle to increase with the raise of the rotation speed. Many reasons can cause the magneto dynamo to generate the ignition break phenomenon. The essential reason is that the secondary voltage can not reach the value puncturing the medium and the capacity of the energy reserving capacitor is not sufficient at some speed points. In addition,the ignition break phenomenon is also influenced by the factors such as air temprature and the oxidation of the discharging poler needle surface.