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1、UNIT 5 Automotive Ignition System,Part I Technical and Practical Reading,Passage A Conventional Ignition System,The purpose of the ignition system is to create a spark that will ignite the fuel-air mixture in the cylinder of an engine. The ignition system has two tasks to perform.,First, it must cre
2、ate a voltage high enough (20,000+) to jump across the gap of a spark plug, thus creating a spark strong enough to ignite the air-fuel mixture for combustion. Second, it must control the timing of the spark, so it occurs at the exact right time and send it to the correct cylinder. See figure 5-1.,Fi
3、gure 5-1 Ignition System,Currently, there are two distinct types of ignition systems: the conventional ignition (CI) system and the electronic ignition (EI) system. The ignition system is divided into two sections, the primary circuit (low-voltage circuit) and the secondary circuit (high-voltage cir
4、cuit).,The primary circuit consists of the battery, ignition switch, coil primary winding, distributor contact point, and connecting wiring. The secondary circuit consists of ignition coil secondary windings, distributor cap, distributor rotor, spark plugs and spark plug wires. See figure 5-2.,Figur
5、e 5-2,Distributor,The distributor, see figure 5-3, is the nerve center of the ignition system. It contains a rotating cam, a set of breaker points, a condenser, a rotor and a distributor cap.,The distributor has two tasks to perform. First, it is responsible for triggering the ignition coil to gener
6、ate a spark at the precise instant. Second, the distributor is responsible for directing that spark to the proper cylinder.,Figure 5-3,Ignition Coil,External to the distributor is the ignition coil. It is nothing more than an electrical transformer. It contains both primary and secondary winding cir
7、cuits. The coil primary winding contains 100 to 150 turns of copper wire. The primary circuit wire goes into the coil through the positive terminal, loops around the primary windings, then exits through the negative terminal.,The coil secondary winding circuit contains 15,000 to 30,000 turns of fine
8、 copper wire, which also must be insulated from each other. The secondary windings sit inside the loops of the primary windings. To further increase the coils magnetic field the windings are wrapped around a soft iron core.,The ignition coil is the heart of the ignition system. As current flows thro
9、ugh the coil a strong magnetic field is built up. When the current is shut off, the collapse of this magnetic field to the secondary windings induces a high voltage which is released through the large center terminal. This voltage is then directed to the spark plugs through the distributor. See figu
10、re 5-4.,Figure 5-4 Ignition Coil,Spark Plug,The ignition systems sole job is to serve the spark plug. It must provide sufficient voltage to jump the gap at the tip of the spark plug and do it at the exact right time, reliably in the order of thousands of times per minute for each spark plug in the e
11、ngine. The modern spark plug is designed to last many thousands of miles before it requires replacement. See figure 5-5.,Figure 5-5,Ignition Wires,Ignition wires are designed to handle 20,000 to more than 50,000 volts. The job of the spark plug wires is to get enormous power to the spark plug withou
12、t leaking out. Spark plug wires have to endure the heat of a running engine as well as the extreme changes in the weather. Spark plug wires are routed around the engine very carefully. Plastic clips are often used to keep the wires separated so that they do not touch together. See figure 5-6.,Figure
13、 5-6 Spark Plug Wire,Spark plug wires go from the distributor cap to the spark plugs in a very specific order. This is called the “firing order” and is part of the engine design. Each spark plug must only fire at the end of the compression stroke. Each cylinder has a compression stroke at a differen
14、t time, so it is important for the individual spark plug wire to be routed to the correct cylinder. See figure 5-7.,Figure 5-7 Firing Order,New Words,spark sp:k n. 火花 gap gp n. 间隙，裂口 conventional knvennl a. 普通的，常见的，传统的 secondary sekndri a. 次要的，次级的 distributor distribjut n. 分电器 condenser kndens n. 冷却
15、器，电容器 transformer trnsf:m n. 变压器 terminal t:minl n. 终点，末端 current krnt n. 电流,collapse klps v. 倒塌，崩溃，瓦解 induce indju:s v. 引诱，招致 enormous in:ms a. 巨大的，庞大的 endure indju vt. 耐久，忍耐，容忍 clip klip n. 夹子，别针，回形针 individual 7individjul a. 个别的，单个的,Phrases and Expressions,ignition system 点火系统 be divided into 被分成
16、，被分为 primary circuit 初级电路，一次电路 secondary circuit 次级电路，二次电路 ignition switch 点火开关 ignition coil primary winding 点火线圈初级绕组 distributor contact point (breaker point) 分电器触点 connecting wiring 连接线 external to 在之外的,ignition coil secondary winding 点火线圈次级绕组 distributor cap 分电器盖 distributor rotor 分电器转子 spark plug wire 火花塞线 primary circuit 初级电路 magnetic field 磁场 high voltage 高电压 center terminal 中央线柱 firing order 点火次
