Ignition Coils: The Power Behind the Spark
If you have ever wondered how a petrol engine produces a spark at the right time to ignite the air-fuel mixture, you may have heard of a device called an ignition coil. But what exactly is an ignition coil, and how does it work? In this article, we will explore the basic principles and functions of ignition coils, and how they have evolved over time.
What is an ignition coil?
An ignition coil is a device that transforms the low voltage from the battery to the high voltage required to operate the spark plugs. The spark plugs then use this burst of high-voltage electricity to create a spark that ignites the air-fuel mixture in the combustion chamber. Without ignition coils, petrol engines would not be able to run efficiently or reliably.
An ignition coil consists of two sets of coils (windings) made from copper wire, wrapped around an iron core. The primary winding has relatively few turns of thick wire, while the secondary winding has thousands of turns of thin wire. The primary winding is connected to the battery and a switch (such as a contact breaker or a transistor), while the secondary winding is connected to the spark plugs.
How does an ignition coil work?
An ignition coil works by using the principles of electromagnetism. When an electric current flows through a coil of wire, it creates a magnetic field around the coil. The magnetic field stores energy that can be converted back into electricity when the current is switched off.
When the switch is closed, current flows through the primary winding and creates a magnetic field around the core. This magnetic field also induces a small voltage in the secondary winding, but it is not enough to produce a spark. This current flow lasts for a short period of time (a few milliseconds) to build up energy in the coil.
When the switch is opened, the current flow in the primary winding stops abruptly, and the magnetic field collapses rapidly. This causes a large voltage spike in the secondary winding, which can reach up to 40 kV (depending on the design of the coil). This high-voltage electricity travels through the spark plug wires and reaches the spark plugs, where it jumps across a small gap and creates a spark that ignites the air-fuel mixture.
The timing of opening and closing the switch must be synchronized with the rotation of the engine, so that each spark plug receives a high-voltage pulse at the optimal time to ignite its corresponding cylinder. This is achieved by using various devices such as distributors, sensors, or electronic control units.
How have ignition coils evolved over time?
The first coil-based ignition system was developed by Charles Kettering in 1910/1911 for mass-produced petrol cars. It used a single ignition coil that produced a high voltage for all cylinders, and distributed it through a rotor arm and a series of contacts in a distributor assembly. This system was simple and reliable, but had some drawbacks such as uneven wear of contacts, voltage losses, and interference with radio signals.
In the 1970s and 1980s, electronic ignition systems started to replace mechanical ones, using transistors or capacitors instead of contact breakers to switch the current in the primary winding. This improved the accuracy and efficiency of ignition timing, reduced maintenance costs, and increased performance and fuel economy.
In modern petrol engines, distributor-based systems have been largely replaced by distributorless systems (such as coil-on-plug), where each cylinder has its own dedicated ignition coil. This eliminates the need for spark plug wires and distributors, reduces voltage losses and emissions, and allows for more precise control of ignition timing and duration.
Conclusion
Ignition coils are essential components of petrol engines that convert low voltage from the battery to high voltage for the spark plugs. They work by using electromagnetism to create and store energy in a magnetic field, and release it as a high-voltage pulse when needed. Ignition coils have evolved from single-coil systems with distributors to multiple-coil systems without distributors, improving the performance and reliability of petrol engines.