Ignition system in car

Ignition device

The gasoline engine ignites the mixture of gasoline and air by the high voltage ignition system. In this ignition system, spark discharge is caused by applying high voltage equal to or higher than several thousand volt in the gap between electrodes of the ignition plug, and the spark energy causes ignition and explosion of the fuel-air mixture sent into the cylinder.

For ignition devices, the magnet ignition method using electromotive force of its own generator as the energy source for generating high voltage for ignition or the battery ignition method using battery voltage as ignition energy may be used. Most small-sized gasoline engines use the magnet ignition method.

Spark plug

The spark plug emits sparks in the gap between electrodes by high voltage generated in
the ignition coil to ignite the compressed fuel-air mixture and cause combustion. As the spark plug is exposed to high temperature and high pressure gas due to high voltage equal to or higher than 1,000 V during engine rotation, it needs to have excellent heat resistance, insulation and so on.

As shown in the drawing, the spark plug consists of main parts including the plug, the
insulator, and the electrodes. The electrodes are divided into the central electrode and the L-shaped earth electrode, and sparks are emitted into the appropriate gap provided between the two electrodes.

In general, a resistor plug, which has excellent radio wave noise prevention effect in any
frequency ranging from low to high, is used