An ignition system is a system for igniting a fuel-air mixture. It is best known in the field of internal combustion engines but also has other applications, e. The internal combustion engine is an engine in which the Combustion of Fuel and an Oxidizer (typically air occurs in a confined space called a g. in oil-fired and gas-fired boilers. A boiler is a closed vessel in which Water or other Fluid is heated The earliest internal combustion engines used a flame, or a heated tube, for ignition but these were quickly replaced by systems using an electric spark.
Contents |
History
Magneto systems
The simplest form of spark ignition is that using a magneto. This article is about the Engine component For other uses of the term see Magneto (disambiguation. The engine spins a magnet inside a coil, and also operates a contact breaker, interrupting the current and causing the voltage to be increased sufficiently to jump a small gap. A magnet (from Greek grc μαγνήτης λίθος " Magnesian stone" is a material or object that produces a Magnetic field. A contact breaker (or "points" is a type of electrical Switch, and the term typically refers to the switching device found in the Distributor of the The spark plugs are connected directly from the magneto output. A spark plug (also very rarely nowadays in British English: a sparking plug) is an electrical device that fits into the Cylinder Magnetos are not used in modern cars, but because they generate their own electricity they are often found on piston aircraft engines and small engines such as those found in mopeds, lawnmowers, snowblowers, chainsaws, etc. Mopeds are a class of low-powered (typically under 50 cc displacement) motorized vehicle generally two or three wheeled A lawn mower or lawnmower is a machine that has one or more revolving blades to cut a Lawn at an even length where there is no battery
Magnetos were used on the small engine's ancestor, the stationary "hit or miss" engine which was used in the early twentieth century, on older gasoline or distillate farm tractors before battery starting and lighting became common, and on aircraft piston engines. A stationary engine is an engine whose framework does not move A tractor is a Vehicle specifically designed to deliver a high Tractive effort at slow speeds for the purposes of hauling a trailer or machinery used Magnetos were used in these engines because their simplicity and self-contained nature was more reliable, and because magnetos weighed less than having a battery and generator or alternator.
Aircraft engines usually have multiple magnetos to provide redundancy in the event of a failure. In Engineering, redundancy is the duplication of critical components of a system with the intention of increasing reliability of the System, usually Some older automobiles had both a magneto system and a battery actuated system (see below) running simultaneously to ensure proper ignition under all conditions with the limited performance each system provided at the time.
Switchable systems
The output of a magneto depends on the speed of the engine, and therefore starting can be problematic. This article is about the Engine component For other uses of the term see Magneto (disambiguation. Some magnetos include an impulse system, which spins the magnet quickly at the proper moment, making easier starting at slow cranking speeds. Some engines, such as aircraft but also the Ford Model T, used a system which relied on non rechargeable dry cells, (like large flashlight batteries, not what are usually thought of as automobile batteries today) to start the engine or for running at low speed; then the operator would manually switch the ignition over to magneto operation for high speed operation. The Ford Model T (colloquially known as the Tin Lizzie and also the Flivver) was an Automobile produced by Henry Ford 's Ford A dry cell is a galvanic Electrochemical cell with a pasty low-moisture Electrolyte.
In order to provide high voltage for the spark from the low voltage batteries, however, a "tickler" was used, which was essentially a larger version of the once widespread electric buzzer. A buzzer or beeper is a signalling device usually electronic typically used in Automobiles household appliances such as a Microwave oven, or With this apparatus, the direct current passes through an electromagnetic coil which pulls open a pair of contact points, interrupting the current; the magnetic field collapses, the spring-loaded points close again, the circuit is reestablished, and the cycle repeats rapidly. The rapidly collapsing magnetic field, however, induces a high voltage across the coil which can only relieve itself by arcing across the contact points; while in the case of the buzzer this is a problem as it causes the points to oxidize and/or weld together, in the case of the ignition system this becomes the source of the high voltage to operate the spark plugs.
In this mode of operation, the coil would "buzz" continuously, producing a constant train of sparks. The entire apparatus was known as the Model T spark coil (in contrast to the modern ignition coil which is only the actual coil component of the system), and long after the demise of the Model T as transportation they remained a popular self-contained source of high voltage for electrical home experimenters, appearing in articles in magazines such as Popular Mechanics and projects for school science fairs as late as the early 1960s. An ignition coil (also called a spark Coil) is an Induction coil in an Automobile 's Ignition system which transforms Popular Mechanics is an American magazine devoted to Science and Technology. A science fair is generally a competition where contestants present their Science project results in the form of a report display board and models that they have created The 1960s decade refers to the years from the beginning of 1960 to the end of 1969 In the UK these devices were commonly known as trembler coils and were popular in cars pre-1910, and also in commercial vehicles with large engines until around 1925 to ease starting.
The Model T (built into the flywheel) differed from modern implementations by not providing high voltage directly at the output; the maximum voltage produced was about 30 volts, and therefore also had to be run through the spark coil to provide high enough voltage for ignition, as described above, although the coil would not "buzz" continuously in this case, only going through one cycle per spark. A flywheel is a mechanical device with significant Moment of inertia used as a storage device for Rotational energy. In either case, the high voltage was switched to the appropriate spark plug by the timer mounted on the front of the engine, the equivalent of the modern distributor. The timing of the spark was adjustable by rotating this mechanism through a lever mounted on the steering column. Steering is the term applied to the collection of components linkages etc
Battery-operated ignition
With the universal adaptation of electrical starting for automobiles, and the concomitant availability of a large battery to provide a constant source of electricity, magneto systems were abandoned for systems which interrupted current at battery voltage, used an ignition coil (a type of autotransformer) to step the voltage up to the needs of the ignition, and a distributor to route the ensuing pulse to the correct spark plug at the correct time. An ignition coil (also called a spark Coil) is an Induction coil in an Automobile 's Ignition system which transforms An autotransformer (sometimes called autoformer) is an electrical Transformer with only one winding. A distributor is a device in the Ignition system of an Internal combustion engine that routes High voltage from the Ignition coil to the
The first reliable battery operated ignition was developed by the Dayton Engineering Laboratories Co. (Delco) and introduced in the 1910 Cadillac. This ignition was developed by Charles Kettering and was a wonder in its day. It consisted of a single coil, points (the switch), a capacitor and a distributor set up to allocate the spark from the ignition coil timed to the correct cylinder. A contact breaker (or "points" is a type of electrical Switch, and the term typically refers to the switching device found in the Distributor of the The coil was basically an autotransformer set up to step up the low (6 or 12V) voltage supply to the high ignition voltage required to jump a spark plug gap.
The points allow the coil to charge magnetically and then, when they are opened by a cam arrangement, the magnetic field collapses and a large (20KV or greater) voltage is produced. The capacitor is used to absorb the back EMF from the magnetic field in the coil to minimize point contact burning and maximize point life. The Kettering system became the primary ignition system for many years in the automotive industry due to its lower cost, higher reliability and relative simplicity. [1].
Modern ignition systems
Mechanically timed ignition
Most four-stroke engines have used a mechanically timed electrical ignition system. The heart of the system is the distributor. A distributor is a device in the Ignition system of an Internal combustion engine that routes High voltage from the Ignition coil to the The distributor contains a rotating cam running off the engine's drive, a set of breaker points, a condenser, a rotor and a distributor cap. External to the distributor is the ignition coil, the spark plugs, and wires linking the spark plugs and ignition coil to the distributor. An ignition coil (also called a spark Coil) is an Induction coil in an Automobile 's Ignition system which transforms A spark plug (also very rarely nowadays in British English: a sparking plug) is an electrical device that fits into the Cylinder An ignition coil (also called a spark Coil) is an Induction coil in an Automobile 's Ignition system which transforms
The system is powered by a lead-acid battery, which is charged by the car's electrical system using a dynamo or alternator. Lead-acid batteries, invented in 1859 by French Physicist Gaston Planté, are the oldest type of Rechargeable battery. A dynamo, originally another name for an Electrical generator, now means a generator that produces Direct current with the use of a commutator. alternator is an electromechanical device that converts mechanical energy to Alternating current electrical energy The engine operates contact breaker points, which interrupt the current to an induction coil (known as the ignition coil). An induction coil or "spark coil" ( archaically known as a Ruhmkorff coil) is a type of Disruptive discharge Coil. An ignition coil (also called a spark Coil) is an Induction coil in an Automobile 's Ignition system which transforms
The ignition coil consists of two transformer windings sharing a common magnetic core -- the primary and secondary windings. An alternating current in the primary induces alternating magnetic field in the coil's core. Because the ignition coil's secondary has far more windings than the primary, the coil is a step-up transformer which induces a much higher voltage across the secondary windings. For an ignition coil, one end of windings of both the primary and secondary are connected together. An ignition coil (also called a spark Coil) is an Induction coil in an Automobile 's Ignition system which transforms This common point is connected to the battery (usually through a current-limiting resistor). The other end of the primary is connected to the points within the distributor. The other end of the secondary is connected, via the distributor cap and rotor, to the spark plugs.
The ignition firing sequence begins with the points (or contact breaker) closed. A contact breaker (or "points" is a type of electrical Switch, and the term typically refers to the switching device found in the Distributor of the A steady charge flows from the battery, through the current-limiting resistor, through the coil primary, across the closed breaker points and finally back to the battery. This steady current produces a magnetic field within the coil's core. This magnetic field forms the energy reservoir that will be used to drive the ignition spark.
As the engine turns, so does the cam inside the distributor. A cam is a projecting part of a rotating Wheel or shaft that strikes a Lever at one or more points on its circular path A distributor is a device in the Ignition system of an Internal combustion engine that routes High voltage from the Ignition coil to the The points ride on the cam so that as the engine turns and reaches the top of the engine's compression cycle, a high point in the cam causes the breaker points to open. A cam is a projecting part of a rotating Wheel or shaft that strikes a Lever at one or more points on its circular path A cam is a projecting part of a rotating Wheel or shaft that strikes a Lever at one or more points on its circular path This breaks the primary winding's circuit and abruptly stops the current through the breaker points. Without the steady current through the points, the magnetic field generated in the coil immediately begins to quickly collapse. This rapid decay of the magnetic field induces a high voltage in the coil's secondary windings.
At the same time, current exits the coil's primary winding and begins to charge up the capacitor ("condenser") that lies across the now-open breaker points. A capacitor is a passive electrical component that can store Energy in the Electric field between a pair of conductors This capacitor and the coil’s primary windings form an oscillating LC circuit. A capacitor is a passive electrical component that can store Energy in the Electric field between a pair of conductors An LC circuit is a variety of resonant circuit or tuned circuit and consists of an Inductor, represented by the letter L and a Capacitor, represented This LC circuit produces a damped, oscillating current which bounces energy between the capacitor’s electric field and the ignition coil’s magnetic field. The oscillating current in the coil’s primary, which produces an oscillating magnetic field in the coil, extends the high voltage pulse at the output of the secondary windings. This high voltage thus continues beyond the time of the initial field collapse pulse. The oscillation continues until the circuit’s energy is consumed.
The ignition coil's secondary windings are connected to the distributor cap. A distributor is a device in the Ignition system of an Internal combustion engine that routes High voltage from the Ignition coil to the A turning rotor, located on top of the breaker cam within the distributor cap, sequentially connects the coil's secondary windings to one of the several wires leading to each cylinder's spark plug. A distributor is a device in the Ignition system of an Internal combustion engine that routes High voltage from the Ignition coil to the A cam is a projecting part of a rotating Wheel or shaft that strikes a Lever at one or more points on its circular path A distributor is a device in the Ignition system of an Internal combustion engine that routes High voltage from the Ignition coil to the A spark plug (also very rarely nowadays in British English: a sparking plug) is an electrical device that fits into the Cylinder The extremely high voltage from the coil's secondary -– often higher than 1000 volts -- causes a spark to form across the gap of the spark plug. A spark plug (also very rarely nowadays in British English: a sparking plug) is an electrical device that fits into the Cylinder This, in turn, ignites the compressed air-fuel mixture within the engine. It is the creation of this spark which consumes the energy that was originally stored in the ignition coil’s magnetic field.
High performance engines with eight or more cylinders that operate at high r. p. m. as in motor racing that demand higher rate and energy of sparks than the simple ignition circuit can provide may use either of these adaptations:
- Two complete sets of coils, breakers and condensers can be provided - one set for each half of the engine, which is typically arranged in V-8 or V-12 configuration. Although the two ignition system halves are electrically independent, they typically share a single distributor which in this case contains two breakers driven by the rotating cam, and a rotor with two isolated conducting planes for the two high voltage inputs.
- A single breaker driven by a cam and a return spring is limited in spark rate by the onset of contact bounce or float at high rpm. This limit can be overcome by substituting for the breaker a pair of breakers that are connected electrically in parallel but spaced on opposite sides of the cam so they are driven out of phase. Each breaker then switches at half the rate of a single breaker and the "dwell" time for current buildup in the coil is maximised since it is shared between the breakers.
The Lamborghini V-12 engine has both these adaptations and therefore uses two ignition coils and a single distributor that contains 4 contact breakers.
Except that more separate elements are involved, a distributor-based system is not greatly different from a magneto system. There are also advantages to this arrangement. For example, the position of the contact breaker points relative to the engine angle can be changed a small amount dynamically, allowing the ignition timing to be automatically advanced with increasing revolutions per minute (RPM) and/or increased manifold vacuum, giving better efficiency and performance. Ignition timing in an Internal combustion engine is the process of setting the time that a spark will occur in the combustion chamber (during the Power stroke) relative Manifold vacuum, or engine Vacuum in an internal combustion engine is the difference in air pressure between the engine's intake manifold and
However it is necessary to check periodically the maximum opening gap of the breaker(s), using a feeler gauge, since this mechanical adjustment affects the "dwell" time during which the coil charges, and breakers should be replaced when they have become pitted by electric arcing. This system was used almost universally until the late 1970s, when electronic ignition systems started to appear. This article is about the Decade 1970-1979 For the Year 1970 see 1970. Electronics refers to the flow of charge (moving Electrons through Nonmetal conductors (mainly Semiconductors, whereas electrical
Electronic ignition
The disadvantage of the mechanical system is the use of breaker points to interrupt the low voltage high current through the primary winding of the coil; the points are subject to mechanical wear where they ride the cam to open and shut, as well as oxidation and burning at the contact surfaces from the constant sparking. They require regular adjustment to compensate for wear, and the opening of the contact breakers, which is responsible for spark timing, is subject to mechanical variations. Ignition timing in an Internal combustion engine is the process of setting the time that a spark will occur in the combustion chamber (during the Power stroke) relative
In addition, the spark voltage is also dependent on contact effectiveness, and poor sparking can lead to lower engine efficiency. A mechanical contact breaker system cannot control an average ignition current of more than about 3 A while still giving a reasonable service life, and this may limit the power of the spark and ultimate engine speed.
Electronic ignition (EI) solves these problems. In the initial systems, points were still used but they only handled a low current which was used to control the high primary current through a solid state switching system. Soon, however, even these contact breaker points were replaced by an angular sensor of some kind - either optical, where a vaned rotor breaks a light beam, or more commonly using a Hall effect sensor, which responds to a rotating magnet mounted on a suitable shaft. In Geometry and Trigonometry, an angle (in full plane angle) is the figure formed by two rays sharing a common Endpoint, called A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument A Hall effect sensor is a Transducer that varies its output Voltage in response to changes in Magnetic field. A magnet (from Greek grc μαγνήτης λίθος " Magnesian stone" is a material or object that produces a Magnetic field. The sensor output is shaped and processed by suitable circuitry, then used to trigger a switching device such as a thyristor, which switches a large current through the coil. The thyristor is a solid-state Semiconductor device with four layers of alternating N and P-type material
The rest of the system (distributor and spark plugs) remains as for the mechanical system. The lack of moving parts compared with the mechanical system leads to greater reliability and longer service intervals. For older cars, it is usually possible to retrofit an EI system in place of the mechanical one. In some cases, a modern distributor will fit into the older engine with no other modifications.
Other innovations are currently available on various cars. In some models, rather than one central coil, there are individual coils on each spark plug. This allows the coil a longer time to accumulate a charge between sparks, and therefore a higher energy spark. A variation on this has each coil handle two plugs, on cylinders which are 360 degrees out of phase (and therefore reach TDC at the same time); in the four-cycle engine this means that one plug will be sparking during the end of the exhaust stroke while the other fires at the usual time, a so-called "wasted spark" arrangement which has no drawbacks apart from faster spark plug erosion; the paired cylinders are 1/4 and 2/3. In a Reciprocating engine, the dead center is the position of a piston in which it is farthest from or nearest to the Crankshaft. A wasted spark is when in an Ignition system in a Four-stroke cycle Internal combustion engine Spark plugs fire in pairs on both the exhaust Other systems do away with the distributor as a timing apparatus and use a magnetic crank angle sensor mounted on the crankshaft to trigger the ignition at the proper time. A crank sensor is a component used in an Internal combustion engine to monitor the position or Rotational speed of the Crankshaft.
During the 1980s, EI systems were developed alongside other improvements such as fuel injection systems. The 1980s was the decade spanning from January 1 1980 to December 31 1989. Fuel injection is a system for mixing fuel with air in an Internal combustion engine. After a while it became logical to combine the functions of fuel control and ignition into one electronic system known as an engine control unit. An engine control unit (ECU is an Electronic control unit which controls various aspects of an Internal combustion engine 's operation
Digital Electronic Ignitions
At the turn of the century digital electronic ignition modules became available for small engines on such applications as chainsaws, string-trimmers, leaf blowers, and lawn mowers. This was made possible by low cost, high speed, and small footprint microcontrollers. Digital electronic ignition modules can be designed as either capacitive discharge (CDI) or inductive discharge ignitions (IDI). Capacitor discharge ignition (CDI or thyristor ignition is a type of automotive electronic Ignition system which is widely used in Motorcycles Lawn mowers Capacitive discharge digital ignitions store charged energy for the spark in a capacitor within the module that can be released to the spark plug at virtually any time throughout the engine cycle via a control signal from the microprocessor. This allows for greater timing flexibility, and engine performance; especially when designed hand-in-hand with the engine carburetor.
Engine management
In an Engine Management System (EMS), electronics control fuel delivery, ignition timing and firing order. An engine control unit (ECU is an Electronic control unit which controls various aspects of an Internal combustion engine 's operation Ignition timing in an Internal combustion engine is the process of setting the time that a spark will occur in the combustion chamber (during the Power stroke) relative The firing order is the sequence of power delivery of each cylinder in a multi-cylinder Reciprocating engine. Primary sensors on the system are engine angle (crank or Top Dead Center (TDC) position), airflow into the engine and throttle demand position. The circuitry determines which cylinder needs fuel and how much, opens the requisite injector to deliver it, then causes a spark at the right moment to burn it. Early EMS systems used analogue computer circuit designs to accomplish this, but as embedded systems became fast enough to keep up with the changing inputs at high revolutions, digital systems started to appear. An analog computer (spelt analogue in British English is a form of Computer that uses continuous physical phenomena such as electrical mechanical An embedded system is a special-purpose Computer system designed to perform one or a few dedicated functions often with Real-time computing constraints A digital system uses discrete (discontinuous values usually but not always Symbolized Numerically (hence called "digital" to represent information for
Some designs using EMS retain the original coil, distributor and spark plugs found on cars throughout history. Other systems dispense with the distributor and coil and use special spark plugs which each contain their own coil (Direct Ignition). A distributor is a device in the Ignition system of an Internal combustion engine that routes High voltage from the Ignition coil to the This means high voltages are not routed all over the engine, but are instead created at the point at which they are needed. Such designs offer potentially much greater reliability than conventional arrangements.
Modern EMS systems usually monitor other engine parameters such as temperature and the amount of uncombined oxygen in the exhaust. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the This allows them to control the engine to minimise unburnt or partially burnt fuel and other noxious gases, leading to much cleaner and more efficient engines. Fuel efficiency, in its basic sense is the same as Thermal efficiency, meaning the efficiency of a process that converts chemical potential energy contained in a carrier
Turbine and jet engines
Turbine engines have a capacitor discharge ignition system using 1 or more igniter plugs, which are only used at startup or in case the combustor(s) flame goes out. Rocket engines have particularly demanding ignitions systems- if prompt ignition does not occur the chamber can fill with excess fuel and oxidiser and significant overpressure can occur (a 'hard start'). A hard start is a Rocketry term referring to an explosion of a rocket engine at ignition Rockets often employ pyrotechnic devices that place flames across the face of the injector plate, or, alternatively, self-igniting chemicals.
See also
- Spark plug
- Spark-ignition
- Wasted_spark
- Distributor
- Capacitor discharge ignition
- Direct Ignition (eliminates the distributor and high tension leads)
References
- Spark Timing - Ignition System
- Ignition System Repairs Guide
- [http://www.modelt.org/techarticles/model_t_ignition_system.pdf The Model T Ford Ignition System & Spark
Timing (pdf)]
A spark plug (also very rarely nowadays in British English: a sparking plug) is an electrical device that fits into the Cylinder The term spark-ignition engine is normally used to refer to Internal combustion engines where the fuel-air mixture is ignited with a spark. A wasted spark is when in an Ignition system in a Four-stroke cycle Internal combustion engine Spark plugs fire in pairs on both the exhaust A distributor is a device in the Ignition system of an Internal combustion engine that routes High voltage from the Ignition coil to the Capacitor discharge ignition (CDI or thyristor ignition is a type of automotive electronic Ignition system which is widely used in Motorcycles Lawn mowers A distributor is a device in the Ignition system of an Internal combustion engine that routes High voltage from the Ignition coil to theDapyx Software network: MP3 Explorer | Ebook Manager | Zenithic