With the development of automobile gasoline engines in the direction of high speed, high compression ratio, high power, low fuel consumption and low emissions, the traditional ignition device has been unable to meet the requirements of use. The core components of the ignition device are the ignition coil and the switching device. By increasing the energy of the ignition coil, the spark plug can generate a spark with sufficient energy. This is the basic condition for the ignition device to adapt to the operation of modern engines.
The ignition coil is divided into two types: open magnetic type and closed magnetic type according to the magnetic circuit. The traditional ignition coil is an open-magnet type. The core is stacked with silicon steel sheets of about 0.3 mm, and the core is wound with secondary and primary coils. The closed magnetic type uses an iron core shaped like III to wind the primary coil, and the secondary coil is wound outside. The magnetic field lines form a closed magnetic circuit with the iron core. The advantages of closed magnetic ignition coil are less magnetic leakage, small energy loss, and small volume. Therefore, electronic ignition systems generally use closed magnetic ignition coils.
The reason that the ignition coil can change the low-voltage electricity on the car to high voltage is because it has the same form as the ordinary transformer. The primary coil has a larger turn ratio than the secondary coil. However, the ignition coil works differently from ordinary transformers. The operating frequency of ordinary transformers is fixed at 50Hz, also known as power frequency transformers. The ignition coils work in pulse form and can be regarded as pulse transformers. The rotation speed repeatedly stores and releases energy at different frequencies.
When the primary coil is powered on, a strong magnetic field is generated around the current as the current increases, and the iron core stores the magnetic field energy; when the switching device disconnects the primary coil circuit, the magnetic field of the primary coil rapidly decays, and the secondary coil High voltages can be induced. The faster the magnetic field of the primary coil disappears, the larger the current at the moment of current disconnection, and the larger the turns ratio of the two coils, the higher the voltage induced by the secondary coil.