Advanced Automotive Fault Diagnosis
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| 10.3.4 Constantly variable
transmission Figure 10.9 shows the Ford CTX (Constantly vari- able TransaXle) transmission. This kind of auto- matic transmission called a continuously variable transmission uses two pairs of cone-shaped pulleys connected by a metal belt. The key to this system is the high friction drive belt. The belt is made from high performance steel and transmits drive by thrust rather than tension. The ratio of the rota- tions, often called the gear ratio, is determined by how far the belt rides from the centres of the pul- leys. The transmission can produce an unlimited number of ratios. As the car changes speed the ratio is continuously adjusted. Cars with this sys- tem are said to use fuel more efficiently than cars with set gear ratios. Within the gearbox hydraulic control is used to move the pulleys and hence change the drive ratio. An epicyclic gear set is used to provide a reverse gear as well as a fixed ratio. 254 Advanced automotive fault diagnosis Figure 10.7 This cut-away gearbox shows the torque converter components Transmission systems 255 First gear: the line shows power flow through the two epicyclic gears. Driving the front annulus and braking the rear planet carrier gives two gear reductions Second gear: one gear reduction is achieved by driving the first annulus and braking the common sun wheel Planet Reverse-high clutch Brake applied Top gear: all gears are held stationary in relation to each other, and the complete assembly rotates to provide direct drive Reverse: braking the second planet carrier causes the rear annulus and output shaft to turn in the opposite direction Forward clutch applied Planet carrier First annulus Brake applied Forward clutch applied Sun wheel Second annulus Brake applied tải về 7.07 Mb. Chia sẻ với bạn bè của bạn:
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