A New Approach to CVT Traction Drives in Automotive Applications 861351

This paper describes the operation and performance of the new Vadetec NTD-XA2 traction drive. The NTD-XA2 is based on the concept of a compound planetary where one stage is formed by variable ratio traction element and the other stage by a fixed ratio spur bevel gear set. This arrangement has the advantage that the power split between the traction element and the gear set can be controlled by the traction ratio.
The construction of the NTD-XA2 is such that it can be mounted directly on the engine crankshaft, replacing the conventional engine flywheel. Because the functions of flywheel, reverse, clutch and forward speed variation are all incorporated in one small package it allows for a great deal of freedom in the instalation configuration.
The manufacturing requirements for this drive fall well within current automotive practices. Automotive transmission fluid is used as the lubricating and traction fluid.
Computer simulation of the drive for a typical automotive application shows that the efficiency at full power is about 96% for most of the overdrive range, and remains high at part load.


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