1、 附 录 1 Differential and Rear Axles The differential is part of the rear-axle-housing assembly, which includes the differential, rear axles, wheels, and bearings. If the car were to be driven in a straight line without having to make turns, then no differential would be necessary. However, when the c
2、ar rounds a turn, the outer wheel must travel farther than the inner wheel. The differential permits the two rear wheels to rotate different amounts when the car goes around a turn, while still delivering power to both rear wheels. The rear axles are attached to the wheels and have bevel side gears
3、on their inner ends. The differential case is assembled on the left axle but can rotate on a bearing independently of the axle.The differential case supports the differential-pinion gear on a shaft, and this gear meshes with the two bevel gears. The ring gear is attached to the differential case so
4、that the case rotates with the ring gear when the later is driven by the drive pinion.The driving power enters the differential through the drive pinion on the end of the propeller shaft. The drive pinion is meshed with a large ring gear so that the ring gear revolves with the pinion. Attached to th
5、e ring gear (through the differential case) is a differential-pinion shaft on which are assembled two differential-pinion gears. Each rear car wheel has a separate axle, and there are two side gears splined to the inner ends of the two wheel axles. The two differential-pinion gears mesh with these t
6、wo side gears. When the car is on a straight road, the two differential-pinion gears do not rotate on the pinion shaft, but they do exert pressure on the two side gears so that the side gears turn at the same speed as the ring gear, causing both rear wheels to turn at the same speed, also.The differ
7、ential case is supported in the carrier by two tapered-roller side bearings. This assembly can be adjusted from side to side to provide the proper backlash between the ring gear and pinion and the required side bearing preload. This adjustment is achieved by threaded bearing adjusters on some units
8、and the placement of selective shims and spacers on others. The differential case is supported in the carrier by two tapered-roller side bearings. This assembly can be adjusted from side to side to provide the proper backlash between the ring gear and pinion and the required side bearing preload. Th
9、is adjustment is achieved by threaded bearing adjusters on some units and the placement of selective shims and spacers on others. Transaxle final drive gears provide the means for transmitting transmission output torque to the differential section of the transaxle. The differential section of the tr
10、ansaxle has the same components as the differential gears in a RWD axle and basically operate in the same way. The power flow in transversely mounted power trains is in line with the wheels and therefore the differential unit does not need to turn the power 90 degrees. When the car rounds a curve, t
11、he outer wheel must turn faster than the inner wheel. To permit this, the two pinion gears rotate on their pinion shaft, transmitting more turning movement to the outer side gear than to the inner side gear. Thus, the side gear on the outer-wheel axle turns more rapidly than the side gear on the inn
12、er-wheel axle. This permits the outer wheel to turn more rapidly while the car is rounding the curve.There are two basic types of axle: dead axles and live axle. The dead axle does not rotate； the wheel rotates on it. A common example is the axle on a horse- drawn wagon. Live axles are attached to t
13、he wheel so that both the wheel and the axle rotate together. Live axles are classified according to the manner in which they are supported: semi-floating, three-quarter-floating, and full-floating. Propeller Shaft and Universal Joint The propeller shaft is a drive shaft to carry the power from the
14、transmission to the rear-wheel axles. It connects the transmission main, shaft carries through the propeller shaft to the differential at the rear axles. Rotary motion of the transmission main shaft carries through the propeller shaft to the differential, causing the rear wheels to rotate. The prope
15、ller-shaft design must take two facts into consideration. First, the engine and transmission are more or less rigidly attached to the car frame. Second, the rear-axle housing (with wheels and differential) is attached to the frame by springs. As the rear wheels encounter irregularities in the road,
16、the springs compress or expand. This changes the angle of drive and the distance between the transmission and the differential, and the propeller shaft may take care of these two changes. That is to say, as the rear axle housing, with differential and wheels, moves up and down, the angel between the
17、 transmission output shaft changes. The reason the propeller shaft shortens as the angel increases is that the rear axle and differential move in a shorter arc than the propeller shaft. The center point of the axle-housing arc is the rear-spring or control-arm attachment to the frame. In order that
18、the propeller shaft may take care of these two changes, it must incorporate two separate types of device. There must be one or more universal joints to permit variations in the angel of drive. There must also be a slip joint that permits the effective length of the propeller shaft to change. The pro
19、peller shaft may be solid or hollow, protected by an outer tube or exposed. Some applications include bearings at or near the propeller shaft center to support the shaft. The two-section propeller is supported by a center bearing and coupled together by universal joints. A universal joint is essenti
20、ally a double- hinged joint consisting of two Y-shaped yokes, one on the driving shaft and the other on the driven shaft, and across-shaped member called the spider. The four arms of the spider, known as trunnions, are assembled into bearings in the ends of the two shaft yokes. The driving shaft cau
21、ses the spider to rotate, and the other two trunnions of the spider cause the driven shaft to rotate. When the two shafts are at an angel to each other, the bearings in the yokes permit the yokes to swing around on the trunnions with each revolution. A variety of universal joints have been used on a
22、uto mobiles, but the types now in most common use are the spider and two-yoke, the constant-velocity, and the ball-and-trunnion joints. A slip joint consists of outside splines on one shaft and matching internal splines in the mating hollow shaft, the splines cause the two shafts to rotate together but permit the two to move endwise with each other. This accommodates any effective change of length of the propeller shaft as the rear axles move toward or away from the car frame.
