Transaxle Description: Notes

This transaxle represents the start of a new generation of automatic transmissions. This is a continuously variable transaxle (CVT) that permits the engine to operate at its most efficient running speeds. There are no discrete gear shifts and no interruptions in the power flow during acceleration. Instead, optimum use is always made of the engine's potential to transmit its full torque to the wheels. Since this is a continuously variable transaxle, there is an infinite number of gear ratios, so that the optimum engine operating point can always be found. Like the engine, it is located transversely in the vehicle. The mechanical section of the automatic transaxle contains 2 pressure controlled variator assemblies, a high performance chain and a single planetary gear set. The variator assemblies function as pulleys. One is connected to the engine output through the converter. The other is connected to the driveline through the transaxle differential. The chain passes around the pulleys connecting the transaxle input and output. The axial distance on each pulley where the chain travels can be varied. As the axial distance on one pulley decreases (becomes narrow) the other pulley increases (becomes wider) creating the speed (gear) ratio between them. This ratio varies continuously. The chain length remains constant. The single planetary gear set is used to change the rotation of the pulley assemblies for forward or reverse driving ranges. A combined hydraulic and electronic control system (mechatronic) is used to control the transaxle function. The mechatronic is located inside the transaxle. The CVT uses a torque converter with a lock-up clutch.

Fig 1: Identifying Automatic Transmission

Courtesy of FORD MOTOR CO.