汽车专业外语04ppt课件.ppt
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1、,Engine Ignition System and Starting System 发动机点火和启动系统,Unit 4,Passage A,Whats its function?,To supply a spark across the spark plug electrode at the correct time under all operating conditions,Passage A,Ignition System 点火系统,Passage A,Ignition System 点火系统,Passage A,Three functions of the ignition sys
2、tem,To convert low voltage direct current (DC) to high voltage pulses To direct the high voltage pulses to each spark plug to ignite the air fuel mixture To properly time the high voltage pulses for efficient engine operation,Passage A,Ignition System 点火系统,Passage A,Two types of ignition system,Conv
3、entional ignition system (CI) Electronic ignition system (EI) or Direct ignition system (DI),Passage A,Conventional ignition system (CI) 传统点火系统,Passage A,Two basic electrical circuits: Primary (Low voltage) circuit Secondary (High voltage) circuit,Primary (Low voltage) circuit includes: Battery, Ign
4、ition switch, Resistance wire, Coil primary winding, Distributor contact point, and Connecting wire,Secondary (High voltage) circuit includes: Coil secondary winding, Distributor cap, Distributor rotor, Spark plugs and Spark plug wires,Passage A,Conventional ignition system (CI) 传统点火系统,Passage A,Bat
5、tery,Source of electrical energy for the ignition system Is it the only source of electrical energy?,After the engine is started, current is supplied by the alternator or the alternator and battery working together.,http:/.au/Membership/BenefitsofMembership/tabid/62/Default.aspx,Passage A,Convention
6、al ignition system (CI) 传统点火系统,Passage A,Ignition switch,Open and close the circuit between the electrical energy source and the other ignition components Four positions: OFF (LOCK) ACCESSORY ON START,http:/ A,Conventional ignition system (CI) 传统点火系统,Passage A,Ignition coil,The voltage developed by
7、battery or alternator is not high enough Step up, or transform, the low voltage to the 35 kV or more required for ignition,http:/ A,Conventional ignition system (CI) 传统点火系统,Passage A,Distributor,Three jobs: Open and close a low voltage circuit between the source of electrical energy and the ignition
8、 coil by intermittent surges developed by it Time the surges, which is accomplished with centrifugal or vacuum advance mechanism Direct the high voltage to spark plug through wires or ignition cables,http:/ A,Conventional ignition system (CI) 传统点火系统,Passage A,Spark plug,Located in engines combustion
9、 chamber Has an air gap that current is forced to jump As the current jumps across the air gap, a spark is developed,http:/www.hobbydirect.co.uk/spark-plugcmr7h-146-p.asp,http:/ A,Electronic ignition system (EI) 电子点火系统,Passage A,Appeared in early 1990s Called the distributorless ignition system, or
10、direct ignition system Provides a high voltage spark at spark plug without many of secondary system parts Requires an engine control computer to control the primary current and develop the secondary current Crankshaft / Camshaft timing sensor is needed to send a signal to the computer regarding engi
11、ne speed and crankshaft / camshaft position,Passage A,Comparison,Passage A,CI system: Switching on and off the primary voltage is done with a set of breaker points. These points are set inside the distributor and rode on a cam on the distributor shaft. EI system: The points are replaced with a contr
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