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1、1附 录附录 A 英文文献与中文参考译文A1Fuel injection systemsA1.1 General informationFuel injection systems have been used on vehicles for many years. The earliest ones were purely mechanical. As technology advanced, electronic fuel injection systems became more popular. Early mechanical and electronic fuel injectio
2、n systems did not use feedback controls. As emissions became more of a concern, feedback controls were adapted to both types of fuel injection systems. Both mechanical and electronic fuel injection systems can be found on gasoline engines.A1.2 Multi-port fuel injectionsThis is the most common type o
3、f fuel injection system found today. Regardless of the manufacturer, they all function in the same basic way. On these systems an equal amount of fuel is delivered to each cylinder.These systems all use sensors which transmit operating conditions to the computer. Information from these sensors is pr
4、ocessed by the computer which then determines the proper air/fuel mixture. This signal is sent to the fuel injectors which open and inject fuel into their ports. The longer the injector is held open, the richer the fuel mixture will be. Most fuel injection systems need the following information to o
5、perate 2properly.Temperature sensors-this includes both air and coolant temperature. The computer determine how rich or lean the mixture should be. The colder the temperature, the richer the mixture.Throttle position sensors or switches-the computer uses this information to determine the position of
6、 the throttle valve(s). Some vehicles use sensors which relay the exact position of the throttle valve(s) at all times. Others use switches which only relay closed and wide-open throttle positions (some may also use a mid-throttle switch). These switches and sensors help determine engine load.Airflo
7、w sensors-these sensors also help the computer determine engine load by indicating the amount of air entering the engine. There are several different types of airflow sensors, but in the end, they all do the same job.Manifold pressure sensors-if a vehicle is not equipped with an airflow sensor, it u
8、ses a manifold pressure sensor to determine engine load (Note that some vehicles with an airflow sensor may also have a manifold pressure sensor. This is used as a fail-safe if the airflow sensor fails). As engine load increases, so does intake manifold air pressure.Engine speed and position sensors
9、-engine speed/position sensors can be referenced form the crankshaft, camshaft or both. In addition to helping determine engine load, these sensors also tell the computer 3when the injectors should be fired.These systems operate at a relatively high pressure(usually at least 30 psi). To control the
10、fuel pressure, a fuel pressure regulator is used. As engine load increases, more fuel pressure is needed. This is due to the richer mixture (more fuel needed) and to overcome the increased air pressure in the ports. Any unused fuel is diverted back to the fuel tank using a return line.A2. Ignition s
11、ystemThere are many different types of ignition systems. Most of these systems can be placed into one of three distinct groups: the conventional breaker point type ignition systems (in use since the early 1900s); the electronic ignition systems (popular since the mid 70s); and the distributorless ig
12、nition system (introduced in the mid 80s).The automotive ignition system has two basic functions: it must control the spark and timing of the spark plug firing to match varying engine requirements, and it must increase battery voltage to a point where it will overcome the resistance offered by the s
13、park plug gap and fire the plug.A2.1How does the ignition system workAn automotive ignition system is divided into two electrical circuitsthe primary and secondary circuits. The primary circuit carries low voltage. This circuit operates only on battery current and is 4controlled by the breaker point
14、s and the ignition switch. The secondary circuit consists of the secondary windings in the coil, the high tension lead between the distributor and the coil (commonly called the coil wire) on external coil distributors, the distributor cap, the distributor rotor ,the spark plug leads and the spark pl
15、ugs.The distributor is the controlling element of the system. It switches the primary current on and off and distributes the current to the proper spark plug each time a spark is needed. The distributor is a stationary housing surrounding a rotating shaft. The shaft is driven at one-half engine spee
16、d by the engines camshaft through the distributor drive gears. A cam near the top of the distributor shaft has one lobe for each cylinder of the engine. The cam operates the contact points, which are mounted on a plate within the distributor housing.A rotor is attached to the top of the distributor shaft. When the distributor cap is in place, a spring-loaded piece of metal in the center of the cap makes contact with a metal strip on top of the rotor. The outer end of the rotor passes very c
