What is Ignition System?
An ignition system generates a spark or heats an electrode to a high temperature to ignite a fuel-air mixture in spark ignition internal combustion engines, oil-fired and gas-fired boilers, rocket engines, etc.
The broadest application for spark ignition IC engines is in gasoline road vehicles such as car and motorcycles.
Compression-ignition Diesel engines ignite the fuel-air mixture using the heat of compression and do not need a spark. They usually have glow plugs that preheat the combustion chamber to allow it to start in cold weather. Other engines may use a flame or heated tube for ignition. While this was common on very early engines, it is rare now.
The first electric spark ignition was probably Alessandro Volta’s toy electric pistol from the 1780s. Siegfried Marcus patented his “Electrical igniting device for gas engines” on 7 October 1884.
Types of Ignition System
This are the types of Ignition system:
- Conventional Ignition System.
- Distributorless Ignition Systems.
- Electronic Ignition Systems.
1. Conventional Ignition System.
A vehicle ignition system is divided into two electrical circuits, the primary and the secondary.
The primary circuit carries low voltage. This circuit operates on battery power only and is controlled by the breakpoints and the ignition switch. When the ignition key is switched on, a low voltage current flows from the battery through the primary windings of the ignition coil, through the breakpoints and back to the battery. This flow of current causes a magnetic field to form around the coil.
The secondary circuit consists of the secondary windings in the coil, the high voltage line between the manifold and the coil (commonly referred to as coil wire) on external coil manifolds, the distributor cap, the distributor rotor, the spark plug leads, and the spark plugs.
As the engine rotates, the distributor shaft cam rotates until the high point of the cam causes the breakpoints to suddenly separate. Immediately when the points are open (disconnected), the flow of current through the primary windings of the ignition coil stops. This causes the magnetic field around the coil to collapse.
The capacitor absorbs the energy and prevents an arc between the points each time it is opened. This capacitor also helps with the rapid breakdown of the magnetic field.
2. Distributor less Ignition Systems
Distributor less ignition systems are based on a vehicle’s internal computer rather than a distributor. You have multiple ignition coils, either one coil per two spark plugs or one coil per spark plug.
The vehicle’s computer system uses engine sensors to regulate the electronic control module and instruct the ignition coils to ignite the spark plugs.
Very different from conventional and electronic – coils sit directly on the spark plugs, no spark plug cables, and the system is electronic.
The second type of ignition system is distributorless ignition. The spark plugs are fired directly from the coils. The spark plug control is controlled by an ignition module and the engine computer. The distributorless ignition system may have one coil per cylinder or one coil for each pair of cylinders.
There are several advantages of not having a dealer:
- No timing adjustments.
- No distributor cap and no rotor.
- No moving parts to wear.
- No distributor to accumulate moisture and cause start-up problems.
- No distributor for driving, which results in less motor resistance.
3. What is Electronic Ignition System?
Electronic ignition system is the type of ignition system that uses electronic circuit, usually by transistors controlled by sensors to generate electronic pulses which in turn generate. Better spark that can even burn the lean mixture and provide better economy & lower emission.
In an internal combustion engine, combustion is a continuous cycle and occurs thousands of times in a minute, so an effective and accurate ignition source is required. The idea of spark ignition came from an electric toy gun that used an electric spark to ignite a mixture of hydrogen and air to shoot a cork.
The need for higher mileage reduced emissions and greater reliability has led to the development of the electronic ignition system.
This system still has a distributor, but the breaker points have been replaced with a pickup coil, and there’s an electronic ignition control module.
Parts of the Electronic Ignition System
The parts of the Electronic ignition system are:
- Ignition Switch
- Electronic Ignition Module
- Ignition Coil
- Spark Plug
A rechargeable lead-acid battery is used to provide electrical energy for ignition in the cylinder. This battery is charged by a dynamo powered by the engine.
2. Ignition switch
One end of the battery is grounded and the other end (positive pole) is connected to the primary winding of the ignition coil via the ignition switch. This switch (key) is used to switch the ignition system on and off.
3. Electronic control module
The electronics module detects the signal generated by the pickup coil and stops the flow of current from the primary circuit. The timer circuit in the ignition module is switched on and the current flows back into the circuit when the voltage is not generated.
Contact breakpoints of the battery ignition system are replaced by an anchor. When the armature tooth comes in front of the pick-up coil, a voltage signal is generated. The electronics module detects the signal generated by the pickup coil and stops the flow of current from the primary circuit.
5. Ignition coil
The ignition coil is the source of the ignition energy. Its function is to increase the low voltage to high voltage to induce an electric spark in the spark plug.
An ignition coil consists of a magnetic soft iron core and two insulated conductive coils, known as the primary and secondary windings. The primary winding consists of 200 to 300 turns, both ends being connected to the external terminals.
The secondary winding consists of 21,000 turns with one end connected to the high voltage wire leading to the distributor and the other end connected to the primary coil.
A distributor is provided in order to distribute the ignition pulses to individual spark plugs in the correct order in relation to the ignition order.
It consists of the rotor in the middle and the metal electrode on the circumference. These metal electrodes are directly connected to the spark plugs and are also known as the ignition harness.
The secondary winding of the ignition coil is connected to the rotor of this distributor, which is driven by the camshaft. As the rotor rotates, it passes the high voltage current to the ignition harness, which then fed those high voltage currents to the spark plugs.
7. Spark plugs
It is the output part of the entire ignition system that is responsible for generating sparks in the engine cylinder.
It consists of 2 electrodes, one of which is attached to the live high voltage wires and the other is earthed. The potential difference between these electrodes ionizes the gap between them and thus a spark is generated which ignites the combustible mixture.