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1、P82Unit Eighttext Engine Ignition System All gasoline engines require some form of ignition systemThe purpose of this system is to。supply to the spark plugs，within the engine combustion chambers，highvoltage surgesFurthermore，the ignition system must provide these surges or sparks to the correct cyli
2、nder 0f the engine at the proper time in its operating cycle for most efficient combustionThe result of these sparks，of course，is ignition of the airfuel mixture within each 0f the combustion chambers. Modern ignition systems operate from a batteryConventional systems consist of the battery,ignition
3、 coil，distributor, condenser, ignition switch，spark plugs，resistor and necessary low and high tension wiring The battery is the heat of the total electrical systemIn regard to the primary circuit ,itsfunction is to supply voltage and current flow to the primary windings of the ignition coilin order
4、to produce an electromagnet The primary side of the ignition coil connects in series between the resistor and the breakerpoints The function of this coil when current passes through it is to create a very strongp83electromagnetic field. In other words, the coil becomes an electromagnet with N and S
5、poles .Themagnetic field from this coil, in turn, induces a voltage in the secondary windings that is necessaryto cause an arc at the spark plug gap. The secondary ignition circuit not only transforms the 6 or 12 volts of the battery to a voltagehigh enough to cause an arc at the spark plug but also
6、 delivers this high-voltage surge to the sparkplugs. The automotive battery supplies either 6 or 12 volts to the primary coil windings. But thevoltage necessary to jump across the spark plug air gap and ignite the air-fuel mixture can rangefrom 5 000 to 25 000 volts or more, depending upon the engin
7、es operating condition at any giventime. The ignition distributor has several functions. It opens and closes the primary ignition circuit.It distributes the high tension current to the respective cylinders of the engine. It also has amechanism that controls the point at which the breaker points open
8、, thereby advancing or retardingthe spark in accordance with engine requirements. The distributor cap and rotor receive the high-voltage surge from the secondary coil windingsthrough a high-tension wire. This surge enters the distributor cap through its center terminal, knownas the coil tower to spa
9、rk plug electrodes formed into the rim of the cap. The rotor itself mounts on the upper distributor shaft and rotates with it. As a result, the rotorelectrode moves from one cap spark plug electrode to another, following the specific firing order ofthe engine. The purpose of the ignition condenser i
10、s to reduce arcing at the breaker points, and prolongtheir life. Most automotive condensers are formed from two thin foil strips, separated by severallayers of insulation. The insulating material is known as a dielectric and is usually paper or anysimilar nonconductive material. The spark plug provi
11、des the gap in the combustion chamber across which the high-tensionelectrical spark jumps to ignite the combustion charge. The purpose of the ignition switch is to connect and disconnect the ignition system from thebattery, so the engine can be started and stopped as desired. With the ignition switc
12、h ON, and ignition distributor contacts closed; current will flow fromthe battery, through the primary winding of the ignition coil, to the distributor contact (breaker)points, to the ground connection and back to the battery. The current flowing through the primary winding of the ignition coil prod
13、uces a magneticfield in the coil, When the distributor contact points open (break), the magnetic field collapse andthe movement of the magnetic field induces current in the secondary winding. Since there are manymore turns of wire in the secondary winding than there are in the primary winding, the v
14、oltage isincreased up to 20 000V. The distributor then directs this high voltage to the proper spark plug, where it jumps to thegap. The heat of the spark ignites the air-fuel mixture in the combustion chamber. The burning fuelexpands and forces the piston down. Downward motion of the piston, in tur
15、n, rotates thecrankshaft. The ignition coil is a pulse transfomer designed to step up primary voltage (received fromP84electromagnetic field. In other words, the coil becomes an electromagnet with N and S poles .Themagnetic field from this coil, in turn, induces a voltage in the secondary windings that is necessaryto cause an arc at the spark plug gap. The secondary ignition circuit not only transforms the 6 or 12 volts of the battery to a voltagehigh enough to cause an arc at the spark plug but also delivers this high-voltage surge to the sparkplugs. The automotive battery supplies e
