What Is an Ignition Coil?
Ignition coils are part of the ignition system installed in gasoline engines and are transformers that provide the high voltage needed for the spark plug discharge.
In a gasoline engine, gasoline in the combustion chamber is ignited and burned by the spark plug discharge. Ignition coils supply the high-voltage electricity for the spark plugs to discharge.
Ignition coils are responsible for converting the 12-volt voltage of the lead-acid battery in the car into the high voltage needed for the spark plugs to discharge. The voltage of electricity that the ignition coils supply to the spark plugs is approximately 20,000 to 35,000 volts.
Uses of Ignition Coils
Ignition coils are used in gasoline engines in automobiles. Most gasoline engines today are reciprocating engines, which consist of three to twelve pistons moving back and forth in a cylinder, turning a single crankshaft that serves as the engine’s output shaft. Ignition coils are installed in each cylinder, along with spark plugs.
However, ignition coils are not used in diesel engine vehicles, even in automobiles. In diesel engines, diesel oil, which is used as fuel, ignites itself through compression. Therefore, neither spark plugs nor ignition coils are needed.
Principle of Ignition Coils
Ignition coils consist of an iron core, called a core, around which two wires, called primary and secondary coils, are wound around it. In addition, the parts are filled with epoxy resin between each other for insulation.
First, when the driver makes an action to start the engine when starting the car, the engine control unit called ECU turns a switch called the igniter to the ON state. When the igniter is turned on, electricity is supplied to the primary ignition coils from the 12V battery in the car.
As the current supplied by the battery flows to the primary coil of the ignition coils, a magnetic flux is generated in the core, which becomes an electromagnet. The ECU then switches the igniter to the OFF state, and when the current to the primary coil stops, the magnetic flux in the core is suddenly lost. What then occurs in the secondary coil is a phenomenon called “electromagnetic induction.”
Electromagnetic induction is a phenomenon in which a coil generates a high voltage when the magnetic flux passing through it changes. Due to the difference in the number of turns between the primary and secondary coils, a high voltage is generated in the secondary coil; the high voltage generated in the secondary coil is supplied to the spark plug, which discharges electricity, igniting the gasoline in the combustion chamber of the engine and causing it to burn.
Other Information on Ignition Coils
Ignition Coils Life Span
Ignition coils have a limited life span. Generally speaking, the recommended replacement interval is 100,000 km. If the ignition coils deteriorate or fail over their lifetime, the following phenomena will occur in the car:
- Engine rpm does not rise as expected when the accelerator pedal is depressed
- The engine is difficult to start.
- The engine speed becomes unstable when idling
- The warning light of the check engine light in the dashboard comes on
If you experience any of the above phenomena, consider replacing the ignition coils. In the case of ignition coils, it is basic to replace all cylinders at the same time.
In addition, consider replacing the spark plugs as well. Spark plugs are gradually worn out by electrical discharge. Worn spark plugs place a higher voltage demand on the ignition coils, which places a greater burden on the newly replaced ignition coils. When replacing the ignition coils, the spark plugs should also be inspected.