Ignition coil
An ignition coil is used in the
The ignition coil is constructed of two sets of coils wound around an iron core. Older engines often use a single ignition coil which has its output directed to each cylinder by a distributor, a design which is still used by various small engines (such as lawnmower engines). Modern car engines often use a distributor-less system (such as coil-on-plug), whereby every cylinder has its own ignition coil.
Diesel engines use compression ignition and therefore do not have ignition coils.
Design
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An ignition coil consists of an iron core surrounded by two coils (windings) made from copper wire. The
When the
The timing of the circuit opening must be coordinated with the rotation of the engine, so that the burst of high-voltage electricity is produced at the optimal time to ignite the air/fuel mixture.
Modern
A modern single-spark system has one coil per spark plug. To prevent premature sparking at the start of the primary pulse, a
Materials
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Formerly, ignition coils were made with
The ignition coil is usually inserted into a metal can or plastic case with insulated terminals for the high voltage and low voltage connections.
History
Predecessor
Early cars used a
Early systems
Most older ignition coil systems used a single coil shared by all the spark plugs (via a
Distributorless systems
Since the 1990s, ignition systems have mostly switched to a design where the distributor is omitted and ignition is instead electronically controlled. In these distributor-less systems, multiple smaller ignition coils are used, usually in the form of one coil for each cylinder or a
The ignition coils for these can be combined into a single casing (a coil pack) and located away from the spark plugs; however it is increasingly common for coil-on-plug systems to be used, whereby the individual ignition coils are small units attached directly to the top of each spark plug. An advantage of coil-on-plug systems is that in the event of a fault, a single ignition coil can be replaced rather than unnecessarily replacing the coils for all of the other cylinders.
See also
References
- ISBN 0-8376-0333-1pg.439-440
- ISBN 0-7487-2695-0, page 167