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1、Unit 2 EFI System,EFI system is composed of 3 basic subsystems: Fuel, Air Induction and Electronic Control Systems. An EFI system is shown in Fig. 1-2-1 1. Electronic Control System The Engine Electronic Control System consists of various sensors, switches and actuators. The various sensors detect t
2、he intake air pressure, engine speed, oxygen density in the exhaust gas, engine coolant temperature, intake air temperature and atmospheric pressure etc, and convert the information into an electrical signal, which is sent to the ECM. Based on these signals, the ECM determines the injection volume (
3、timing) and calculates the optimum ignition timing for the current conditions. The ECM not only controls the fuel injection timing, but also the self diagnostic function which records the occurrence of a malfunction, ignition timing control, idle speed control and EGR control.,induction (发动机)进气 actu
4、ator 执行器 density 浓度 oxygen 化氧 atmospheric 大气的 determine 决定 injection 喷射 optimum 最适宜的 ignition 点火 current 当前的 diagnostic 诊断 occurrence 发生 malfunction 故障,Fig.1-2-1 A EFI System（燃油系统） 1-ignition switch 2-EFImain replay 3-vehicle speed sensor 4-terminal TE1 5.PNP switch 6-A/C compressor 7-starter 8-head
5、light switch 9-defogger switch 10-MAP sensor 11-intake air temp. sensor 12-IAC valve 13-throttle position sensor 14- engine coolant temperature sensor 15-knock sensor 16-EGR valve 17-VSV for EGR 18-distributor W/ ignition coil 19-igniter 20-battery 21-malfunction indicator lamp 22-circuit opening re
6、lay 23-fuel tank 24-fuel pump 25-fuel filter 26-fuel pressure pulsation damper 27-fuel pressure regulator 28-injector 29-main oxygen sensor 30-sub oxygen sensor,(1)The ECM controls the following functions: Optimum AirFuel Ratio The ECM receives signals from various sensors indicating changing engine
7、 operation conditions. Such as: intake manifold pressure, intake air temperature, engine coolant temperature, engine speed, throttle valve opening angle, exhaust oxygen content etc. The signals are utilized by the ECM to determine the injection duration necessary for an optimum airfuel ratio. Electr
8、onic Spark Advance (ESA) The ECM is programmed with data for optimum ignition timing under all operating conditions. Using data provided by sensors which monitor various engine functions ( RPM, engine coolant temperature, etc.), the microcomputer (ECM) triggers the spark at precisely the right insta
9、nt.,content 含量 utilize 利用 duration 持续（时间） monitor 监控 RPM = Revolution Per Minute 发动机转速 microcomputer 微电脑 trigger 触发 precisely 精确地 instant 片刻,(2)Input signal The available input signals of a vehicle include the following: 1) Airflow Sensor 2) Intake Air Temperature Sensor (IAT) 3) Throttle Position S
10、ensor 4) Camshaft Position Sensor 5) Crankshaft Position Sensor 6) Vehicle Speed Sensor 7) Oxygen Sensor 8）Engine Coolant Temperature (ECT) Sensor 9）Manifold Absolute Pressure (MAP) Sensor 10) EGR Gas Temperature Sensor 11) Knock Sensor 12) Park/Neutral Position(PNP) Switch 13) Engine Cranking Signa
11、l 14) Brake Light Switch Signal 15) Air Conditioning (A/C) Switch 16) Battery Signal,Airflow Sensor 空气流量计 Intake Air Temperature Sensor 进气温度传感器 Throttle Position Sensor 节气门位置传感器 EGR=Exhaust Gas Recirculation 废气再循环 Knock Sensor 爆震传感器 Park/Neutral Position (PNP) Switch 驻车/空挡位置开关 Cranking 起动,equip 装备 l
12、ist 列出 idle-up 怠速提升 Vacuum Solenoid Valve 真空电磁阀 fuel pump 燃油泵 injector 喷油器 igniter 点火器 pressure up 增压,(3) Output signals Vehicles are equipped with different combinations of computer-controlled components. Not all components listed below are used on every vehicle. The ECM receives input signals from
13、 sensors and switches to control the following components and sub-systems. The available input signals of a vehicle include the following: 1) A/C Idle-Up System. 2) Idle Air Control Valve (IACV) 3) EGR Vacuum Solenoid Valve ( VSV) 4) Electronic Spark Advance System. 5) EVAP Vacuum Solenoid Valve ( V
14、SV) 6) Fuel Pump 7) Injector 8) Igniter 9) Fuel pressure up VSV 10) Self-Diagnostic System. 11) Circuit Opening Relay,2. Fuel System The fuel system consists of a fuel tank, electric fuel pump, a fuel filter, fuel feed and return lines, fuel pressure regulator, the pulsation damper and injectors. Fi
15、g. 1-2-2 shows the parts of a fuel system. (1) Electric fuel pump Electric fuel pump is mounted in the fuel tank. It draws fuel from the fuel tank and sends it to the fuel rail, which distributes fuel evenly to all injectors. (2) Fuel pressure regulator The fuel pressure regulator adjusts the pressu
16、re of the fuel from the fuel line (high pressure side) to a constant pressure higher than the pressure inside the intake manifold, and excess fuel is returned to the fuel tank through the return pipe. (3) Pulsation damper The pulsation damper absorbs the slight fluctuations in fuel pressure caused by fuel injector from the injector. (4) Injectors The injectors inject a metered quantity of fuel into the intake port in accordance with signals from the ECM (Engine Control Module).,filter 滤清
