Классификация автомобильных катушек зажигания

Ignition coils are divided into open magnetic circuit coils and closed magnetic circuit coils based on the type of magnetic path.

Open Magnetic Circuit Ignition Coil

The open magnetic circuit ignition coil generally has a cylindrical structure. It is made up of several silicon steel sheets stacked together to form a rod-shaped iron core, with secondary and primary coils wound around it. The secondary coil uses 0.05-1 mm enameled wire wound around 20,000 to 30,000 turns. The primary coil, being thicker with a diameter of 0.5-1.0 mm, only has 150-300 turns. Since the primary coil is wound outside the secondary coil, the changes in magneto-motive force produced by the secondary coil are entirely identical to those of the primary coil. Both coils are wound in the same direction, with one end of the secondary coil connected to the high voltage output connector and the other end connected to the start of the primary coil and “+ “terminal on the shell. The end of the primary coil is connected to the “-” terminal on the shell and is connected to the collector of the power transistor in the ignition device, which controls the switch of the primary coil current.

Closed Magnetic Circuit Ignition Coil

The iron core of the closed magnetic circuit ignition coil is sealed, and all the magnetic flux passes through the interior of the iron core. As the magnetic conductivity of the iron core is about ten thousand times that of air, an open magnetic circuit ignition coil must have a larger magneto-motive force (ampere-turn ratio) to achieve the same magnetic flux as a closed magnetic circuit ignition coil. Therefore, a primary coil with a larger number of turns and thicker wire is required; if the primary coil has many turns and the same turn count ratio is desired, the number of turns of the secondary coil also needs to increase. Hence, miniaturization of an open magnetic circuit ignition coil is impossible. On the contrary, thanks to its small magnetic resistance, a closed magnetic circuit ignition coil effectively reduces the magneto-motive force of the coil and enables the miniaturization of the ignition coil. Nowadays, closed magnetic circuit ignition coils have become considerably miniaturized, can be integrated with the ignition device, or even combined with the spark plug. The spark plug ignites the combustible compressed gas in the cylinder. Traditional ignition coils used an open magnetic circuit, with the iron core made up of about 0.3 mm silicon steel sheets stacked together, around which the secondary and primary coils were wound. The closed magnetic circuit uses an iron core similar to “Ⅲ” shape to wind the primary coil, and then the secondary coil is wound outside. The magnetic lines of force form a closed magnetic path by the iron core. The advantage of the closed magnetic circuit ignition coil is that it has less magnetic leakage, less energy loss, and a smaller volume, so electronic ignition systems generally use closed magnetic circuit ignition coils.