Function and working principle of automobile ignition system

The function of the automobile ignition system: When the gasoline engine is working, the combustion of the mixture is controlled by the ignition of the spark plug. The function of the ignition system is to provide high-voltage electricity with enough energy to the spark plug at a suitable time according to the working state and sequence of the engine, so that sparks can be generated between its electrodes, ensuring that the mixture can be ignited and the engine can do work.

Working principle: When the engine is working, the ECU determines the optimal ignition advance angle and power-on time according to the signals received from various sensors and relevant programs and data stored in the memory, and sends instructions to the igniter accordingly. The igniter controls the on-off of the primary circuit of the ignition coil according to the instruction.

When the circuit is connected, current flows through the primary circuit in the ignition coil, which stores ignition energy in the form of magnetic field. When the primary circuit is cut off, a high induced electromotive force (15 ~ 20kV) is generated in the secondary coil, which is sent to the spark plug of the working cylinder through the distributor or directly. ?

Extended data:

The ignition system shall be ignited according to the working sequence of the engine. Ignition must be carried out at the most favorable moment.

Because the mixture burns in the cylinder for a certain period of time, the mixture should not be ignited at the top dead center of the compression stroke, but should be properly advanced, so that when the piston reaches the top dead center, the mixture has been fully burned, so that the engine can obtain more power. Ignition time is generally expressed by ignition advance angle, that is, the angle of crankshaft rotation during a period from spark to piston reaching top dead center.

If the ignition is too late, the ignition will start only when the piston reaches the top dead center. The combustion of the mixture is mainly completed during the downward movement of the piston, that is, the combustion process is carried out under the condition of increasing the volume, which increases the contact area between the hot gas and the cylinder wall, thus reducing the heat converted into effective work, reducing the highest combustion pressure in the cylinder, leading to overheating of the engine and power decline.

References:

Baidu encyclopedia-automobile ignition system