Tài liệu học tập cơ bản khái quát về động cơ và các bộ phận trên ô tô phiên bản tiếng anh. Tài liệu này nhằm giúp chúng ta tiếp cận được cấu tạo chức năng của các bộ phận của xe. Với tài liệu này giúp các bạn sinh viên ngành cơ khí ô tô tiếp cận được những kiến thức cơ bản về ô tô và đồng thời nâng cao kiến thức tiếng anh. Bộ tài liệu này được soạn thảo bởi trường đào tạo và huấn luyện nghề ở Canada.
Chapter 19 Charging Systems Charging Systems • Primary purpose is to recharge battery • Changes mechanical energy into electrical energy • Voltage is induced into a wire as it passes through a magnetic field • The voltage has positive and negative pulses AC Generator Construction • Rotor assembly • Rotating magnetic field • – 6.5 amps pass through coil • One pole piece assumes north and other south polarity Slip Rings and Brushes • Regulated current supplied to rotor coil via slip rings and brushes Stator • Most AC generators use three stator windings Stator (cont’d) • Each stator conductor produces a single phase of AC current • The phases are staggered 120º apart Diodes with cooling fins Rear driveshaft bearing AC Generator Operation • Produce alternating current • The AC must be converted, or rectified, into direct current, DC • The AC passes through diodes Diodes DC Rectification • Using six diodes allows for full-wave rectification • Two diodes for each stator winding • One diode is positive, the other negative • The wye winding has a central neutral junction Preliminary Checks • Safety Precautions – Disconnect negative terminal – Avoid contact with generator output terminal – Only apply pressure to front of generator housing when applying belt tension – Observe correct polarity of battery cables – Keep carbon pile tester off at all times – Use caution around moving parts Charging Indicators • Indicator (charge) lamp – Operates on the principle of opposing voltages • Meters – Voltmeter or ammeter display on dash • Electronic voltage monitor – Is used to monitor voltage and control a lamp or warning message Inspection • Inspect the battery • Check wiring and connections • Inspect alternator mountings for loose or missing bolts • Check condition of the drive belt • Ensure proper pulley alignment PCM-Controlled Systems • Check DTCs • Monitor voltage with scan tool • PCM monitors battery current, voltage, and temperature • May adjust idle speed to increase charging rate Noise Diagnosis • • • • Noise can be mechanical or electrical Some electrical noise is normal Belts and bearings can produce noise Check mounting, wiring, cooling and A/C hoses and lines for misrouting • Generator pulley should spin freely with belt removed Regulator Tests • Excessive charging most likely caused by voltage regulator • Can also cause no output • Some systems can bypass regulator for fullfield tests • Always follow manufacturer’s procedures Voltage Output Test • Measure battery open circuit voltage • Run engine at fast idle (1500 rpm) • No load voltage should be about volts higher than open circuit voltage • If low, increase speed to 2000 rpm and turn on accessories • Voltage should be about 0.5 volts above open circuit voltage Current Output Test • Run engine around 2500 rpm • Adjust carbon pile to maximum current output • Should be within 10 amps of rated output AC Leakage Test • Connect DMM in series to charging output terminal with engine off • Should be no more than 0.5 mA reading Circuit and Ground Resistance • Check voltage drop of charging output connection and ground circuit • Test between battery positive and generator output terminal • Test between battery negative and generator case • Test under at least 20 amps output .. .Charging Systems • Primary purpose is to recharge battery • Changes mechanical energy into electrical... alignment PCM-Controlled Systems • Check DTCs • Monitor voltage with scan tool • PCM monitors battery current, voltage, and temperature • May adjust idle speed to increase charging rate Noise Diagnosis... freely with belt removed Regulator Tests • Excessive charging most likely caused by voltage regulator • Can also cause no output • Some systems can bypass regulator for fullfield tests • Always