Inductive discharge ignition systems were developed in the 19th century as a means to ignite the air–fuel mixture in the

combustion chamber A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process. Interna ...

internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combus ...

s. The first versions were

low tension coil A low tension coil is an electrical device used to create a spark across the points of an ignitor on early 1900s gasoline engines, generally flywheel engines, hit and miss engines, and other engines of that era. In modern electronic terms, a low te ...

s, then low-tension and in turn high-tension

magneto A magneto is an electrical generator that uses permanent magnets to produce periodic pulses of alternating current. Unlike a dynamo, a magneto does not contain a commutator to produce direct current. It is categorized as a form of alternator, ...

s, which were offered as a more effective alternative to the older-design

hot-tube ignitor A hot-tube ignitor was an early device that fit onto the cylinder head of an internal-combustion engine, used to ignite the compressed fuel/air mixture by means of a flame heating part of the tube red-hot. A hot-tube ignitor consisted of a metal o ...

s that had been utilized earlier on

hot tube engine The hot tube engine is a primitive and long-obsolete type of combustion engine, not to be confused with the hot-bulb engine. The timing of a hot tube engine is controlled by means of varying the length of the hot-tube ignitor, that does the job t ...

s. With the advent of small

stationary engine A stationary engine is an engine whose framework does not move. They are used to drive immobile equipment, such as pumps, generators, mills or factory machinery, or cable cars. The term usually refers to large immobile reciprocating engines, pr ...

s; and with the development of the

automobile A car or automobile is a motor vehicle with Wheel, wheels. Most definitions of ''cars'' say that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, pe ...

, engine-driven

tractors A tractor is an engineering vehicle specifically designed to deliver a high tractive effort (or torque) at slow speeds, for the purposes of hauling a trailer or machinery such as that used in agriculture, mining or construction. Most common ...

, and engine-driven

truck A truck or lorry is a motor vehicle designed to transport cargo, carry specialized payloads, or perform other utilitarian work. Trucks vary greatly in size, power, and configuration, but the vast majority feature body-on-frame construction ...

s; first the magneto and later the distributor-type systems were utilized as part of an efficient and reliable engine ignition system on commercially available motorized equipment. These systems were in widespread use on all cars and trucks through the 1960s. Manufacturers such as Ford, General Motors, Chrysler, Citroen, Mercedes, John Deere, International Harvester, and many others incorporated them into their products. The inductive discharge system is still extensively used today.

Faraday's law

The inductive-discharge ignition system operates according to the rules of

electromagnetism In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions of a ...

described by

Faraday's Law of Induction Faraday's law of induction (briefly, Faraday's law) is a basic law of electromagnetism predicting how a magnetic field will interact with an electric circuit to produce an electromotive force (emf)—a phenomenon known as electromagnetic inducti ...

which states that the

induction Induction, Inducible or Inductive may refer to: Biology and medicine * Labor induction (birth/pregnancy) * Induction chemotherapy, in medicine * Induced stem cells, stem cells derived from somatic, reproductive, pluripotent or other cell t ...

electromotive force In electromagnetism and electronics, electromotive force (also electromotance, abbreviated emf, denoted \mathcal or ) is an energy transfer to an electric circuit per unit of electric charge, measured in volts. Devices called electrical ''transd ...

(emf) in any

closed circuit Closed circuit can refer to: *Closed-circuit television *Closed-circuit radio *Rebreather – breathing sets * ''Closed Circuit'' (1978 film), a 1978 Italian film * ''Closed Circuit'' (2013 film), a 2013 British thriller film *An electric circuit ...

is equal to the

time Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, to ...

rate of change of the

magnetic flux In physics, specifically electromagnetism, the magnetic flux through a surface is the surface integral of the normal component of the magnetic field B over that surface. It is usually denoted or . The SI unit of magnetic flux is the weber ( ...

through the circuit. In other words, the emf generated is proportional to the rate of change of the magnetic flux. More simply stated, an

electric field An electric field (sometimes E-field) is the physical field that surrounds electrically charged particles and exerts force on all other charged particles in the field, either attracting or repelling them. It also refers to the physical field fo ...

is induced in any system in which a

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

is changing with time. The change could be changes in direction of

force In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a p ...

or strength. The effects described by this law are those by which generators,

motors An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power g ...

alternators An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature.Gord ...

, and

transformer A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...

s function. There are two main concepts to be taken from Faraday's Law that apply to the design of inductive discharge ignitions. One is that moving a

wire Overhead power cabling. The conductor consists of seven strands of steel (centre, high tensile strength), surrounded by four outer layers of aluminium (high conductivity). Sample diameter 40 mm A wire is a flexible strand of metal. Wire is c ...

through a magnetic field will induce an

electric Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by ...

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...

and

current Currents, Current or The Current may refer to: Science and technology * Current (fluid), the flow of a liquid or a gas ** Air current, a flow of air ** Ocean current, a current in the ocean *** Rip current, a kind of water current ** Current (stre ...

in the wire, aka electromagnetic induction. The second is that current moving in a wire will induce a magnetic field around the wire.

Magnetos

A magneto is one of the

electromechanical In engineering, electromechanics combines processes and procedures drawn from electrical engineering and mechanical engineering. Electromechanics focuses on the interaction of electrical and mechanical systems as a whole and how the two systems ...

devices invented for the purpose of

ignition Ignition may refer to: Science and technology * Firelighting, the human act of creating a fire for warmth, cooking and other uses * Combustion, an exothermic chemical reaction between a fuel and an oxidant * Fusion ignition, the point at which a ...

with

gasoline Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic co ...

s. A magneto at its most basic is a simple

magnet A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, ...

that moves next to a wire, or sometimes a wire moves next to a magnet. As they move in relation to each other, the changes in direction of

magnetic force In physics (specifically in electromagnetism) the Lorentz force (or electromagnetic force) is the combination of electric and magnetic force on a point charge due to electromagnetic fields. A particle of charge moving with a velocity in an elect ...

induce an electric current in the wire. Usually the wire (called a primary wire) is very long, and looped around an

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...

magnetic core A magnetic core is a piece of magnetic material with a high magnetic permeability used to confine and guide magnetic fields in electrical, electromechanical and magnetic devices such as electromagnets, transformers, electric motors, generators, in ...

that more or less channels the magnetic field through the loop of wire. As the current flows, the wire loops develop their own magnetic field, which takes a certain amount of energy to form. The magnetic field is a type of

potential energy In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors. Common types of potential energy include the gravitational potentia ...

. There is usually some sort of device that opens and closes the circuit called a

contact breaker A contact breaker (or "points") is a type of electrical switch, found in the ignition systems of spark-ignition internal combustion engines. The switch is automatically operated by a cam driven by the engine. The timing of operation of the switch ...

, points or an

ignitor Ignitor is the Italian name for a planned tokamak device, developed by ENEA. , the device has not been constructed. Started in 1977 by Prof. Bruno Coppi at MIT, Ignitor based on the 1970s Alcator machine at MIT which pioneered the high magnetic ...

. As the points or ignitor open, the current ceases flowing, and the magnetic field collapses. The energy stored in the magnetic field is released in the form of increased electric voltage in the wire. This voltage jumps across the gap of either the ignitor or a

spark plug A spark plug (sometimes, in British English, a sparking plug, and, colloquially, a plug) is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air ...

located in the

and ignites the air–fuel mixture to do

work Work may refer to: * Work (human activity), intentional activity people perform to support themselves, others, or the community ** Manual labour, physical work done by humans ** House work, housework, or homemaking ** Working animal, an animal t ...

. Some magnetos have a second coil of wire located next to the first, called a secondary coil. This coil is usually much longer than the primary loop, accomplished by many more loops around the magnetic core. As the magnetic field is built, it induces a current in the secondary coil as well. When the contact breaker opens the circuit, the magnetic field collapses, causing a high electric voltage in the primary and secondary coils. However, due to the greater number of turns of the secondary coil, the voltage is much higher, causing a larger spark at the ignitor or spark plug, meaning more assured ignition. Due to their reliability, magnetos are used as ignition systems on

aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines ...

. They are also used on

machinery A machine is a physical system using power to apply forces and control movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to natural biological macromolecule ...

that do not have a separate electric supply or

battery Battery most often refers to: * Electric battery, a device that provides electrical power * Battery (crime), a crime involving unlawful physical contact Battery may also refer to: Energy source *Automotive battery, a device to provide power t ...

. They are also used on drag race cars because they offer a

weight In science and engineering, the weight of an object is the force acting on the object due to gravity. Some standard textbooks define weight as a Euclidean vector, vector quantity, the gravitational force acting on the object. Others define weigh ...

advantage over systems that utilize a

distributor A distributor is an enclosed rotating switch used in spark-ignition internal combustion engines that have mechanically timed ignition. The distributor's main function is to route high voltage current from the ignition coil to the spark plugs ...

and battery.

Distributor ignition systems

As ignition technology developed, engineers realized that a functional ignition system could be designed that dispensed with the magnets altogether. By applying a current to a primary wire loop wrapped around an iron magnetic core, a magnetic field would be generated in the primary loop without the magnets. This magnetic field would induce a current in an adjacent longer secondary loop of wire. By opening the circuit in the primary loop, the collapsing magnetic field would cause a voltage to be induced in the secondary loop. This high voltage was carried or "distributed" by a

to each of the multiple spark plugs in a gasoline car or truck engine. The most familiar version of this kind of system was invented by

Charles F. Kettering Charles Franklin Kettering (August 29, 1876 – November 25, 1958) sometimes known as Charles Fredrick Kettering was an American inventor, engineer, businessman, and the holder of 186 patents. For the list of patents issued to Kettering, see, Le ...

in about 1909 and was known by some as the

Delco ignition system The Delco ignition system, also known as the Kettering ignition system, points and condenser ignition or breaker point ignition, is a type of inductive discharge ignition system invented by Charles F. Kettering. It was first sold commercially on ...

. Later

patent application A patent application is a request pending at a patent office for the grant of a patent for an invention described in the patent specification and a set of one or more claims stated in a formal document, including necessary official forms and re ...

s to the

US Patent Office The United States Patent and Trademark Office (USPTO) is an agency in the U.S. Department of Commerce that serves as the national patent office and trademark registration authority for the United States. The USPTO's headquarters are in Alexan ...

make reference to the "

Kettering ignition system The Delco ignition system, also known as the Kettering ignition system, points and condenser ignition or breaker point ignition, is a type of inductive discharge ignition system invented by Charles F. Kettering. It was first sold commercially on t ...

". This type of ignition system was used on automobiles, trucks,

lawn mowers A lawn mower (also known as a mower, grass cutter or lawnmower) is a device utilizing one or more revolving blades (or a reel) to cut a grass surface to an even height. The height of the cut grass may be fixed by the design of the mower, but g ...

, tractors,

chainsaws A chainsaw (or chain saw) is a portable gasoline-, electric-, or battery-powered saw that cuts with a set of teeth attached to a rotating chain driven along a guide bar. It is used in activities such as tree felling, limbing, bucking, pruning, ...

, and other gasoline-powered machinery with great success for many decades until the development of

capacitive-discharge ignition Capacitor discharge ignition (CDI) or thyristor ignition is a type of automotive electronic ignition system which is widely used in outboard motors, motorcycles, lawn mowers, chainsaws, small engines, turbine-powered aircraft, and some cars. It w ...

systems.

References

External links

* https://www.google.com/patents/US1037491 Charles F. Kettering 15 September 1909/3 September 1912 "Ignition Apparatus for Explosion-Motors" no capacitor, no points, separate coils * https://www.google.com/patents/US1037492 Charles F. Kettering 2 November 1910/3 September 1912 "Ignition System" distributor with capacitor 46 (not points) * https://www.google.com/patents/US1223180 Charles F. Kettering 11 August 1911/17 April 1917 "Ignition System" points, no capacitor, ignition switch to avoid draining the battery * https://www.google.com/patents/US3327165 John A. Hawthorne 1964/1967 comments about Kettering ignition system: "Practical efforts to improve or supplant this system have failed, and it has remained virtually unchanged through the years. However, the present trend toward higher performance automobile engines threatens to render this tried and true system obsolete. The principal limitation of the Kettering system is, as typically applied, the inability to develop adequate levels of spark plug gap energy without sacrificing longevity of the ignition points or the transformer coil. The inherent inefficiency of the system is particularly apparent at higher engine speeds." {{DEFAULTSORT:Inductive Discharge Ignition Ignition systems Gasoline engines