Ignition principle of automobile engine

The working process of the mechanical ignition system is that the crankshaft drives the distributor shaft to rotate, and the cam on the distributor shaft rotates, so that the primary contact of the ignition coil is turned on and off, resulting in high voltage electricity.

This kind of ignition high voltage electricity is sent to the spark plugs of each cylinder in turn through the ignition head on the distributor shaft according to the working requirements of the engine, and the spark plugs emit electric sparks to ignite the gas in the combustion chamber.

The distributor housing can be manually rotated to adjust the basic ignition advance angle (that is, the ignition advance angle at idle speed), and there is also a vacuum advance device to provide different advance angles according to the change of the vacuum degree of the intake pipe.

Second, electronic ignition.

Electronic ignition system is completely different from mechanical ignition system. It has an electronic control device for ignition, which contains the ignition control MAP required by the engine under various working conditions.

The working state of the engine is judged by a series of sensors such as engine speed sensor, intake pipe vacuum sensor (engine load sensor), throttle position sensor and crankshaft position sensor.

Find out the ignition advance angle required by the engine in this working state on the diagram and ignite according to this requirement.

Then, according to the knock sensor signal, the above ignition requirements are corrected to make the engine work at the best ignition time.

Electronic ignition system can also be divided into closed-loop control and open-loop control: the electronic control system with knock sensor that can correct the ignition advance angle in time according to whether the engine knocks is called closed-loop control system;

Without the knock sensor, the ignition advance control is only controlled according to the program set in the electronic control unit, which is called an open-loop control system.

Extended data:

Engine ignition spark should have enough energy.

When the engine is working normally, only 1~5mJ spark energy is needed because the compressed temperature of the mixture is close to its auto-ignition temperature. However, when the mixture is too rich or too lean, when the engine starts, idles or the throttle valve opens sharply, higher spark energy is needed.

With the improvement of modern engine economy and exhaust purification requirements, it is urgent to improve spark energy. Therefore, in order to ensure reliable ignition.

A high-energy electronic ignition system should generally have a spark energy of 80 ~1000 mj, and the spark energy should be higher than1000 mj when starting.

Reference source: Baidu Encyclopedia-Automobile Ignition System