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 43 Four- and All-Wheel Drive Four-Wheel-Drive (4WD) and All-Wheel-Drive (AWD) • Increased popularity on modern SUVs and AWD cars • Increase traction even with narrower tires • Both add initial cost and weight • 4WD vehicles have special maintenance requirements not found on 2WD vehicles Typical 4WD Vehicle Part-Time 4WD • Basically RWD with a two-speed transfer case • Axles connect/disconnect via locking hubs • The front and rear axles split engine torque • Should not be operated on dry surfaces Full-Time 4WD • All four wheels have power all of the time • Use a center or interaxle differential or viscous clutch that allows for different speeds between axles • Has a high and low speed range • No 2WD option • Does not use locking hubs AWD Systems • Do not have a separate transfer case • Use a front-wheel drive transaxle equipped with a viscous clutch, center differential, or transfer (Haldex) clutch • Operate continuously in four-wheel drive Full-Time AWD • Similar to full time 4WD systems • Not designed for heavy off-road use • Engine torque is divided according to operating conditions • Can be computer controlled • May allow the driver to lock the front and rear driveshafts Transfer Case • Delivers power to front and rear assemblies Interaxle Differentials • Driveline windup can cause handling problems • The front and rear must rotate at different speeds to eliminate windup • The interaxle differential allows for different front and rear speeds similar to a differential allowing separate left and right speeds Viscous Clutches or Couplings • Are self contained and not serviceable • Can be installed inside or outside the transaxle housing • Consist of two sets of steel plates in a drum of thick fluid • Split the engine torque according to the needs of each axle Axle Disconnects • Some vehicles use standard front hubs and a vacuum operated axle disconnect • May disconnect using an electric motor to allow smooth transitions Four-Wheel-Drive Passenger Cars • Most developed from FWD models • No separate transfer case • Not designed for off-road driving Limited-Slip and Open Differentials • Used on many 4WD passenger cars to help prevent wheel scrubbing and windup • A LSD is used to join the right and left axle shafts to the differential case • Allows traction even if one or two wheels have none • Systems with open differentials have a mode selector for lock up if needed Diagnosing 4WD and AWD Systems • Verify complaint • Inspect for mechanical and electrical faults: – – – – – – Halfshafts - Locking hubs Driveshafts and U-joints - Shift lever/linkage Mode switch - Shift motor Electromagnetic clutch vacuum lines Matching tire sizes - Transfer case Wiring and connectors fuses ...Four-Wheel -Drive (4WD) and All-Wheel- Drive (AWD) • Increased popularity on modern SUVs and AWD cars • Increase traction... computer controlled • May allow the driver to lock the front and rear driveshafts Transfer Case • Delivers power to front and rear assemblies Interaxle Differentials • Driveline windup can cause handling... transfer case • Use a front-wheel drive transaxle equipped with a viscous clutch, center differential, or transfer (Haldex) clutch • Operate continuously in four-wheel drive Full-Time AWD • Similar