For these studies a 1700 kg (3750 lb) vehicle with an energy storage flywheel was specified. The results of preliminary design studies conducted under contract to NASA for DOE on four CVT concepts for use in advanced electric vehicles are discussed. The arrangement and function of several CVT concepts are cited along with their current developmental status. CVT concepts which are potentially suitable for application with electric and hybrid vehicles are discussed. « lessĪ brief historical account of the evolution of continuously variable transmissions (CVT) for automotive use is given. The system comprises: a clutch for transmitting torque of the engine to the transmission first means for shifting the spool of the line pressure control valve in dependence on operating conditions of the engine so as to provide a line pressure an engine speed sensor for producing an engine speed signal dependent on speed of the engine second means responsive to the engine speed signal for producing an engine torque signal dependent on output torque of the engine third means for producing a clutch torque signal dependent on the transmitting of the torque of the clutch detecting means for detecting engaging conditions of the clutch and for producing a clutch slipping signal when the clutch slips and producing a clutch engaging signal when the clutch is engaged selector means responsive to the clutch slipping signal for applying the clutch torque signal to the first means and responsive to the clutch engaging signal for applying the engine torque signal to the first means, whereby the line pressure is controlled in accordance with the engaging conditions of the clutch. This patent describes a control system for a continuously variable transmission for transmitting the power of an internal combustion engine to driving wheels of a motor vehicle, having a drive pulley including a hydraulically shiftable disc and a first hydraulic cylinder for shifting the disc, a driven pulley including a hydraulically shiftable disc and a second hydraulic cylinder for operating the disc, a belt engaged with both pulleys, a transmission ratio control valve having ports and a spool, a line pressure control valve having ports and a spool, a first hydraulic circuit having a pump for supplying oil to the more » first and second cylinders through the line pressure control valve and the transmission ratio control valve. 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 » 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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