汽车专业英语课件与读译教程2版配套9 u5ta

1、 UNIT 5 DIESEL FUEL INJECTION TEXT A Overview of Conventional Diesel Fuel Injection and Common Rail Injection Systems PROFESSIONAL ENGLISH Conventional Diesel Fuel Injection System components Common Rail Injection Systems System components Injector operation 本次课学习内容 本次课学习目标 l掌握柴油机喷油系统的组成 l掌握主要部件的型式及

2、原理 l掌握有关的专业名词与术语 l了解翻译技巧省略 NEW WORDS particle p:tikln.微粒，颗粒微粒，颗粒 clog klgv.&n.阻塞，堵塞阻塞，堵塞 nozzle nzln.喷嘴喷嘴 trap trpn.圈套，陷阱，捕集器圈套，陷阱，捕集器 plunger plnn.柱塞，活塞柱塞，活塞 variation ?verieinn.变化，变更，变种，变调变化，变更，变种，变调 protrude prtru:dv.突出，伸入突出，伸入 solenoid sulinidn.螺线管，电磁线圈螺线管，电磁线圈铁，阀，开关铁，阀，开关 energize endaizv.供给供给能

3、量，通电，励磁能量，通电，励磁 depression diprenn.消沉，萧条；低气压，凹陷，凹坑消沉，萧条；低气压，凹陷，凹坑 stackstk n.堆堆, 一堆；一堆；v.堆叠堆叠 piezoelectric paii:zuilektrika.压电的压电的 fuel pump燃油泵燃油泵 fuel filter燃油滤清器燃油滤清器 injection pump喷油泵喷油泵 fuel line燃油管燃油管 light truck轻型货车轻型货车 inline injection pump直列式喷油泵直列式喷油泵 distributor injection pump分配式喷油泵分配式喷油泵

4、delivery valve出油阀出油阀 spray pattern喷注形状喷注形状 glow plug预热塞预热塞 intake air heater进气加热器进气加热器 precombustion chamber预燃室预燃室 fuel rail油轨油轨 pressure shoulder承压锥面，承压锥面， solenoid-type injector电磁式喷油器电磁式喷油器 piezoelectric injector压电式喷油器压电式喷油器 PHRASES AND EXPRESSIONS Conventional Fuel Injection System Typical diesel

5、 fuel injection system components include the fuel tank, fuel pump, fuel filter, injection pump, injectors, and the necessary fuel lines (Fig.5-1). Fig5-1 A conventional diesel fuel injection system Fuel Filter. Diesel fuel must be kept clean to avoid injector system trouble. Very small particles ar

6、e enough to clog injector nozzles. Diesel fuel systems typically use one or more filters to trap dirt and other deposits. Injection Pump. Due to the high compression (around 22:1) used in diesel engines, the diesel injection pump must be capable of producing high pressures. There are a number of inj

7、ection pump designs. The most commonly used automobile and light truck diesel injection pumps are classified as inline or distributor. The inline injection pump uses a separate cylinder-plunger- cam unit for each cylinder. These units are contained in a straight row in a common housing. In the distr

8、ibutor injection pump, a single double-plunger type pump serves all injector outlets. A single delivery valve is located in the rotor. Injector. There are many different injector designs, but all are a variation of two basic types-inward opening and outward opening. Diesel spray patterns will vary d

9、epending upon engine design. Glow Plug and Intake Air Heaters. To aid in igniting the compressed air-fuel mixture during cold starting, diesel engines use glow plugs and intake air heaters. The glow plug is an electrically operated device that protrudes into the precombustion chamber. On later engin

10、es, the glow plugs are turned on and off automatically. Intake air heaters warm the air as it passes through on its way to the intake manifold. The heater element is a wire mesh that is electrically heated. The computer energizes the heater element before cranking. Common Rail Injection System Newer

11、 diesel engines are equipped with common rail injection systems (Fig.5-2 and Fig.5-3). Common rail systems are direct injection (DI) systems. The injectors nozzles are placed inside the combustion chamber. The piston top has a depression where initial combustion takes place. The injector must be abl

12、e to withstand the temperature and pressure inside the cylinder and must be able to deliver a fine spray of fuel into those conditions. These systems have a high pressure fuel rail connected to individual injectors. The injectors are controlled by a computer that attempts to match injector operation

13、 to the operating conditions of the engine. Fig.5-2 Common rail (CR) system Fig.5-3 Bosch third-generation common rail system with piezoelectric injectors The injector facilitates precise control of the start of injection and injected fuel quantity as well as pre- and post-injection. Injector closed

14、 (rest state). The fuel flows through the fuel- inlet passage into the valve control chamber and to the injection-nozzle pressure shoulder. The discharge throttle is closed by the valve ball. The pressure above the valve control plunger in the valve control chamber generates a force which is greater

15、 than the opposing force which acts on the nozzle-needle pressure shoulder1. The nozzle needle thus remains closed, regardless of the rail pressure applied at the injector (see Fig.5-4). Injector opens (start of injection). When the solenoid valve is actuated by the ECU, the armature is attracted, a

16、s a result of which the valve ball opens the discharge throttle. Now more fuel flows through the discharge throttle than through the inlet throttle. This causes a drop in pressure in the valve control chamber. Now the nozzle needle is raised by the force acting on its pressure shoulder. The nozzle n

17、eedle opens and fuel is injected, see Fig.5-4. Injector closes (end of injection). When the solenoid valve is no longer supplied with power by the FCU, the valve spring forces the valve ball onto its seat. As a result, the discharge throttle is closed and the fuel pressure builds up again abruptly i

18、n the valve control chamber. The force acting on the valve control plunger and the force of the nozzle spring acting from above exceed the force on the nozzle-needle pressure shoulder acting from below. The nozzle needle closes. Pre- and post-injection (Fig.5-5). The solenoid valve is only supplied

19、with power for a brief period in order to inject small quantities of fuel. The nozzle needle is raised slightly. The fuel injector opens briefly and in the process does not open the entire opening cross-section. Injector activation. Rapidly switching solenoid valves are required in order to be able

20、to subdivide fuel injection into up to three sequences (pre-, main and post-injection). This can only be achieved with high currents of approx. 20 A and voltages of approx. 100V. This so-called booster voltage is generated with the aid of induction when the solenoid valves are supplied with power and is stored in a capacitor in the ECU. Fig.5-4 solenoid- type injector Fig.5-5 Rate-of-discharge curve Newer diesel fuel injectors rely on stacked piezoelectric crystals