Specific research needs for each particular transmission type have been identified. In general, research is needed leading to more comprehensive CVT efficiency and system dynamics models and data, to facilitate comparisons of various CVTs and to aid in control system development. These are at a relatively early stage of development. Ratchet CVTs, based on variable-stroke oscillatory motion, are also being developed for automotive use. Automotive units are now being tested in prototype installations. Traction CVTs, based on traction between two or more rotating elements at a variable-location contact area, are being developed by several companies for automotive applications. Cost, weight, noise, and efficiency problems need to be solved for automotive applications. Hydrostatic CVTs, based on variable-displacement hydraulic pump/motor combinations, are at an advanced state of engineering development and are in production for off-road applications. One European car line presently uses a rubber belt CVT. Designs based on rubber belts are also expected to appear on small cars in the middle to late 1980s. The van Doorne CVT, which employs a more ยป multipiece steel belt, is expected to be used in production automobiles within two years. Belt CVTs, are now well developed technology. Successful development of a CVT promises significant fuel economy benefits, even compared with the advanced automatic transmissions due to the improved matching of engine operating regime to vehicle requirements made possible by the continuous range of transmission ratios available with a CVT. ![]() ![]() The status of conventional transmission technology is briefly examined, and the development status of continuously variable transmissions (CVTs) for automotive applications is examined in detail. This report summarizes the development status of advanced automotive transmissions and identifies areas where further research effort is needed.
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