An ignition coil (also called a spark coil) is an induction coil in an automobile's ignition system which transforms the battery's 12 volts (6 volts in some older vehicles) to the thousands of volts (20 to 30 thousand volts or more) needed to create an electric spark in the spark plugs to ignite the fuel. Some coils have an internal resistor to reduce the voltage and some rely on a resistor wire or an external resistor to reduce the voltage from the car's 12 volt wiring flowing into the coil. The wire which goes from the ignition coil to the distributor and the wires which go from the distributor to each of the spark plugs are called spark plug wires or high tension leads.
This specific form of the autotransformer, together with the contact breaker and a capacitor (still referred to in automobile parlance by its old name of "condensor"), converts low voltage from a battery into the high voltage required by spark plugs in an internal combustion engine.
When the contact breaker closes, it allows a current from the battery to build up in the primary winding of the ignition coil. (The current does not flow instantly because of the inductance of the coil.) Once the current has built up to its full level, the contact breaker opens. Since it has a capacitor connected across it, the primary winding and the capacitor form a tuned circuit, and as the stored energy oscillates between the inductor formed by the coil and the capacitor, the changing magnetic field in the core of the coil induces a much larger voltage in the secondary of the coil. More modern electronic ignition systems operate on exactly the same principle, but some rely on charging the capacitor to around 400 volts rather than charging the inductance of the coil.
Use in cars
In older vehicles a single (large) coil would serve all the spark plugs via the ignition distributor. Notable exceptions are the Saab 92, and the Wartburg 353 which have one ignition coil per cylinder.
Modern ignition systems
In modern systems, the distributor is omitted and ignition is instead electronically controlled. Much smaller coils are used with one coil for each spark plug or one coil serving two spark plugs (for example two coils in a four-cylinder engine, or three coils in a six-cylinder engine). A large ignition coil puts out about 20 kV, and a small one such as from a lawn mower puts out about 15 kV. These coils may be remotely mounted or they may be placed on top of the spark plug (coil-on-plug or Direct Ignition). Where one coil serves two spark plugs (in two cylinders), it is through the "wasted spark" system. In this arrangement the coil generates two sparks per cycle to both cylinders. The fuel in the cylinder that is nearing the end of its compression stroke is ignited, whereas the spark in its companion that is nearing the end of its exhaust stroke has no effect. The wasted spark system is more reliable than a single coil system with a distributor and less expensive than coil-on-plug.
Where coils are individually applied per cylinder, they may all be contained in a single molded block with multiple high-tension terminals. This is commonly called a coil-pack.
A bad coil pack may cause a slight or not so slight misfire, bad fuel economy, loss in power, and in some rare cases loss of braking performance and power steering problems.
The disruptive discharge Tesla coil is an early predecessor of the "ignition coil" in the ignition system as was invented in 1891. Tesla also gained U.S. Patent 609,250, "Electrical Igniter for Gas Engines", on August 16, 1898. The principles of the modern ignition coil used today is based on this design. A. Atwater Kent, in 1921, patented the modern form of the ignition coil.
- Faraday's law of induction
- Ignition system
- Induction coil
- Magnetic field
- U.S. Patent 1,391,256 - Induction coil structure - Arthur Atwater Kent - 1921
- U.S. Patent 1,474,152 - Induction coil - Arthur Atwater Kent - 1923
- U.S. Patent 1,474,597 - Induction coil - Arthur Atwater Kent - 1923
- U.S. Patent 1,569,756 - Ignition coil - Arthur Atwater Kent - 1926
- U.S. Patent 1,723,908 - Ignition system - Ernst Alexanderson - 1929
- Interactive tutorial on Ignition Coils National High Magnetic Field Laboratory
Wikimedia Foundation. 2010.
Look at other dictionaries:
ignition coil — A pulse transformer which is a part of the ignition system. It receives a small amount of electrical voltage from the battery and steps up the low primary voltage and amplifies it into a big jolt of voltage of about 20,000 volts, and sends it to… … Dictionary of automotive terms
ignition coil — noun an induction coil that converts current from a battery into the high voltage current required by spark plugs • Hypernyms: ↑induction coil • Part Holonyms: ↑ignition, ↑ignition system * * * (in an automotive ignition system) a transformer… … Useful english dictionary
ignition coil — uždegimo ritė statusas T sritis Energetika apibrėžtis Vidaus degimo variklių ir kitų įrenginių baterinio uždegimo įtaisas, transformuojantis akumuliatoriaus žemosios įtampos (6 12 V) srovę į aukštosios įtampos (10 30 kV) srovę. atitikmenys: angl … Aiškinamasis šiluminės ir branduolinės technikos terminų žodynas
ignition coil — (in an automotive ignition system) a transformer consisting of two wire windings or coils in which low voltage direct current is fed through the primary winding to generate high voltage spark pulses in the secondary winding. Also called coil.… … Universalium
ignition coil — /ɪgˈnɪʃən kɔɪl/ (say ig nishuhn koyl) noun an induction coil used in an internal combustion engine for converting the battery voltage to the high tension required by the sparking plugs … Australian English dictionary
ignition coil resistor — A ballast resistor … Dictionary of automotive terms
single-spark ignition coil — In a distributorless ignition system with an odd number of cylinders, each cylinder requires its own ignition coil; distributor logic on the low voltage side performs the voltage distribution to each coil. Also see multi spark ignition coil … Dictionary of automotive terms
multi-spark ignition coil — A type of ignition coil used in static high voltage distribution, designed as a double spark or four spark coil … Dictionary of automotive terms
four-spark ignition coil — An ignition coil with two primary windings and one secondary winding … Dictionary of automotive terms
multiple-spark ignition coil — See multi spark ignition coil … Dictionary of automotive terms