What are the structure and working principles of the Automobile ignition coil? (2024)

Structure

To understand the working principle of the ignition coil,we should learn aboutit* structurefirstly.

Usually, there are two groups of coils in the ignition coil, the primary coil and the secondary coil. The primary coil is wrapped with thick enamelled wire, usually around 200-500 turns with enamelled wire of 0.5-1 mm; The secondary coil is wrapped with fine enamelled wire, usually with about 15000-25000 turns of enamelled wire of about 0.1mm.

One end of the primary coil is connected with the low-voltage power supply (+) on the vehicle, and the other end is connected with the switching device (breaker). One end of the secondary coil is connected with the primary coil, and the other end is connected with the output end of the high-voltage line to output high-voltage electricity.

Working principle

When the primary coil is powered on, a strong magnetic field is generated around it with the increase of current, and the iron core stores the magnetic field energy; When the switch device disconnects the circuit of the primary coil, the magnetic field of the primary coil decays rapidly, and the secondary coil will induce a very high voltage.

The faster the magnetic field of the primary coil disappears, the greater the current at the moment of current disconnection, and the greater the turn ratio of the two coils, the higher the voltage induced by the secondary coil, which is converted from low to high voltage.

Similar to ordinary transformers, the turn ratio of the primary and secondary coils of the ignition coil is large, which turns the low-voltage electricity on the vehicle into high voltage. The difference is that it stores and discharges energy repeatedly at different frequencies according to different engine speeds, and works intermittently.

What are the structure and working principles of the Automobile ignition coil? (2)

Generally, the ignition coils used in the engine ignition system can be divided into open magnetic circuit types and closed magnetic circuit types according to the magnetic circuit.

Open magnetic circuit ignition coil

The open magnetic circuit ignition coil is generally of the tank structure. It consists of several pieces of silicon steel laminations to form a rod-shaped iron core, and the secondary coil and primary coil are respectively wound on the outside of the iron core.

The secondary coil is enamelled wire with a wire diameter of 0.05~1mm and turns of 20000~30000. The wire diameter of the primary coil is 0.5~1.0mm, which is thicker than the secondary coil, and the number of turns is only 150~300.

The primary coil is wound on the outside of the secondary coil, so the magnetic flux change generated by the secondary coil is exactly the same as the primary coil. The winding direction of the primary coil and the secondary coil are the same.

What are the structure and working principles of the Automobile ignition coil? (3)

Closed magnetic circuit ignition coil

The iron core of the closed magnetic circuit ignition coil is closed, and the magnetic flux all passes through the iron core. The magnetic conductivity of the iron core is about 10000 times that of the air. Therefore, if the open magnetic circuit ignition coil wants to obtain the same magnetic flux as the closed magnetic circuit ignition coil, its primary coil must have a large magnetomotive force (ampere-turns).

Therefore, the primary coil with more turns and a larger wire diameter must be adopted; The number of turns of the primary coil is large. If the same ratio of turns is to be obtained, the number of turns of the secondary coil will also need to be increased. Therefore, it is impossible to miniaturize the ignition coil by opening the magnetic circuit.

On the contrary, the closed magnetic circuit ignition coil, due to its small magnetic resistance, can effectively reduce the magnetomotive force of the coil and miniaturize the ignition coil.