【Listening】

【Vocabulary & Phrases】

converter变矩器

torque converter 液力变矩器

impeller 叶轮

pump泵轮

turbine涡轮

stator定子

guide wheel导轮

Planetary gears行星齿轮机构

sun gear太阳轮

planet gear行星轮

ring gear齿圈

axle车轴、车桥

front axle前桥

rear axle后桥

pinion gear行星齿轮

beveled pinion gear斜行星齿轮

drive shaft驱动轴

propeller shaft传动轴

universal joints（U-joints）万向节

transfer case分动器

【Reading】

Power Train System

3.TorqueConverter

The key to the modern automatic transmission is thetorque converter. It takes the place of a clutch in a manual transmission tosend the power from the engine to the transmission input shaft. The torque converteroffers the advantage of multiplying the turning power provided by the engine.

It has three parts that help multiply the power: animpeller（orpump）connectedto the engine’scrankshaft, a turbine to turn the turbine shaft which is connected to thegears, and a stator（or guide wheel）between the two.

The torque converter is filled with transmissionfluid that is moved by impeller blades. When the impeller spins above a certainspeed, the turbine spins, driven by the impeller.

4.Planetary Gearing

   Planetary gearsprovide for the different gear ratios needed to move a vehicle in the desireddirection at the correct speed. A planetary gear set consists of a sun gear,planet gears, and a internal ring.

In the center ofthe planetary gear set is the sun gear. Planet gears surround the sun gear,just like the earth and other planets in our solar system. These gears aremounted and supported by the planet carrier and each gear spins on its ownseparate shaft. The planet gears are in constant mesh with the sun and ringgears. The ring gear is the outer gear of the gear set. Its has internal teethand surrounds the rest of the gear set .Its gear teeth are in constant meshwith the planet gears. The number of planet gears used in a planetary gear setvaries according to the loads the transmission is designed to face. For heavyloads ,the number of planet gears is increased to spread the work load overmore gear teeth.

The planetary gear set can provide a gear reductionor overdrive, direct drive or reverse, or a neutral position. Because the gearsin constant mesh, gear changes are made without engaging or disengaging gears,as is required in a manual transmission. Rather, clutches and bands are used toeither hold or release different members of the gear set to get the properdirection of rotation and/or gear ratio.

5.Differential

On FWD cars, the differential unit is normally partof the transaxle assembly. On RWD cars, it is part of the rear axle assembly. Locatedinside the differential case are the differential pinion shafts and gears andthe differential side gears. See Fig.5-8 The differential assembly revolveswith the ring gear. Axle side gears are splined to the rear axle or front axledrive shafts.

When an automobile is moving straight ahead, bothwheels are free to rotate. Engine power is applied to the pinion gear, whichrotates the ring gear. Beveled pinion gears are carried around by the ring gearand rotate as one unit. Each axle receives the same power, so each wheel turnsat the same speed.

When the car turns a sharp corner, only one wheelrotates freely. Torque still comes in on the pinion gear and rotates the ringgear, carrying the beveled pinions around with it. However, one axle is held stationaryand the beveled pinions are forced to rotate on their own axis and "walkaround" their gear. The other side is forced to rotate because it issubjected to the turning force of the ring gear, which is transmitted throughthe pinions.

6.Drive shaft

A drive shaft and universal joints（U-joints）connect the transmission to the rear drive axle on most rear-wheel-drivevehicles. Many four-wheel-drive vehicles also use drive shafts and universaljoints, with one drive shaft between the transfer case and rear drive axle anda second drive shaft between the transfer case and the front drive axle. Thedrive shaft is sometimes called a propeller shaft.

The drive shaft and U-joints provide a means oftransferring engine torque to drive axles. The universal joints allow the driveshaft to move up and down, to allow for suspension travel. Some drive shaftalso have a slip joints that allows the drive shaft to make minor lengthchanges as the vehicle suspension height changes.

【随堂测试】