自动变速器automatictransmission.ppt

Automatic Transmission自动变速器 Automatic Transmission A transmission is a part of the drive train. The transmission is used to transfer the engine power to the drive wheels. It also allows the driver to choose more power (1-st gear) or more speed (4-th or 5-th gear) by changing the gear ratio. Automatic Transmission There are two basic types of automatic transmissions based on whether the vehicle is rear wheel drive or front wheel drive.?? Rear Wheel Drive Transmission ?On a rear wheel drive car, the transmission is usually mounted to the back of the engine and is located under the hump in the center of the floorboard alongside the gas pedal position.? A drive shaft connects the rear of the transmission to the final drive which is located in the rear axle and is used to send power to the rear wheels.??Power flow on this system is simple and straight forward going from the engine, through the torque converter, then through the transmission and drive shaft until it reaches the final drive where it is split and sent to the two rear wheels. Front Wheel Drive Transmission On a front wheel drive car, the transmission is usually combined with the final drive to form what is called a transaxle. The engine on a front wheel drive car is usually mounted sideways in the car with the transaxle tucked under it on the side of the engine facing the rear of the car.? Front axles are connected directly to the transaxle and provide power to the front wheels.? Automatic Transmission Transmission Components Planetary Gear Sets which are the mechanical systems that provide the various forward gear ratios as well as reverse. The Hydraulic System which uses a special transmission fluid sent under pressure by an Oil Pump through the Valve Body to control the Clutches and the Bands in order to control the planetary gear sets. Seals and Gaskets are used to keep the oil where it is supposed to be and prevent it from leaking out.? Transmission Components The Torque Converter which acts