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Cvt Lubrication: the Effect of Lubricants on the Frictional Characteristics of the Belt-Pulley Interface
Published May 13, 1997 by Coordinating European Council in Belgium
Interest in continuously variable transmissions (CVT) has grown dramatically in the past several years as automobile builders in Europe, Japan and North America rush to take advantage of the fuel economy benefits possible with these devices. This relatively explosive growth of CVTs is illustrated by the fact that in the fifteen years preceding 1995 a total of about one million push belt CVT transmissions had been manufactured; current predictions are that in 1997, or latest 1998, CVT production will reach the rate of one million a year.
Production vehicles equipped with steel push-belt continuously variable transmissions have been marketed for over 10 years. It was not until recently however, when fully integrated electronic control systems became available that the full potential of these transmissions for reduction of fuel consumption could be realized. Total electronic control of the vehicle drivetrain, engine and transmission, allows the vehicle to operate at the most fuel efficient engine speed and transmission reduction ratio over 90% of the time the vehicle is being driven. Reported increases in fuel economy over conventional automatic transmissions are in the range of 5 to 20% depending on the driving cycle and reference used. Another factor which contributes to the increased interest in CVTs, are the significant improvements in drivability and passenger comfort gained through electronic control and transmission re-design.
The key to the push-belt CVT is the metal link belt developed by Van Doorne's Transmissie b.v. (VDT). The construction of the VDT belt is shown. All commercial push-belt transmissions use this design. The heart of the CVT is the variator system composed of the steel push belt and the two pulleys in which it runs. A drawing of a CVT transmission is included