Ignition coils are divided into open and closed magnetic types according to the magnetic circuit.

Open magnetic circuit type ignition coil

Open magnetic circuit type ignition coils are generally can-like structures. It is composed of several pieces of silicon steel laminated rod core, the secondary coil and the primary coil are wound on the outside of the core. The secondary coil has a wire diameter of 0. 05 to 1 mm enameled wire, and the number of turns is 2 to 30 thousand. The primary coil has a wire diameter of 0.5 to 1.0 mm, which is thicker than the secondary coil and has only 150 to 300 turns. The primary coil is wound on the outside of the secondary coil, so the secondary coil produces the same magnetic flux change as the primary coil. The winding direction of the primary coil and the secondary coil is the same. The beginning of the secondary coil is connected to the high voltage output connector, and the end of the secondary coil is connected to the beginning of the primary coil and is connected to the “+” connector of the housing. The end of the primary coil is connected to the housing. The "one" is connected to the column and connected to the collector of the power transistor in the igniter. The igniter controls the on-off of the primary coil current.

Closed magnetic circuit type ignition coil

The magnetic core of the closed magnetic circuit ignition coil is closed, and the magnetic flux passes through the core. The magnetic permeability of the core is approximately 10,000 times that of air. Therefore, the open magnetic circuit ignition coil must be the same as the closed magnetic circuit ignition coil. For magnetic fluxes, the primary coil must not have a large magnetomotive force (Amps). Therefore, it is necessary to use a primary coil with a larger number of turns and a larger wire diameter; the number of turns of the primary coil is large. If the number of turns of the secondary coil is to be obtained, the number of turns of the secondary coil also needs to be increased. Therefore, the open circuit is fired. The miniaturization of coils is impossible. On the contrary, closed magnetic circuit ignition coils, due to the small magnetic resistance, can effectively reduce the magnetomotive force of the coils and miniaturize the ignition coils. At present, the closed magnetic circuit ignition coil has been very compact, can be combined with the igniter, and even integrated with the spark plug. The spark plug ignites flammable compressed gas in the cylinder. The traditional ignition coil is an open magnetic type. Its iron core is made up of 0.3mm silicon steel sheets, and the secondary and primary coils are wound around the iron core. Closed-magnetic type uses the core of the shape of III around the primary coil, and then the secondary coil around the outside, the magnetic flux from the core to form a closed magnetic circuit. Closed-magnetic ignition coils have the advantages of low leakage flux, small energy loss, and small size. Therefore, closed-magnetic ignition coils are commonly used in electronic ignition systems.