A continuously variable power transmission (CVT) has a potential to present comfortable cruising, powerful acceleration, fuel economy and improvement of exhaust-gas emission as an autmotive power transmission. There have been many developments of the half-toroidal traction-drive CVT since 1980 and ceaseless improvements of the traction material, synthetic fluid and effeciency continue to be made. Recent technology of the half-toroidal CVT and fundamental issues on the effeciency and materials are introduced. A low-spin design extends the limitation of rotational speed and the stress cycle tests provide a reliable design on the maximum Hertzian pressure for large-capcity CVTs. They are now applied not only to 3-4 L passenger cars but also to commercial vehicles with a 4 ton payload for evaluating the reliabilty, weight and cost. In this paper the following results are obtained: Low-spin design provides a low-temperature rise on the tracton contact and rigid speed transmission. The fatigue index indicates that surface-originated fatigue precedes subsurface fatigue under the maximum Hertzian pressure of 2.7 GPa. A stress cyle chart permits the design of the maximum Hertzian pressure of 3 GPa for endurance of 108 cycles. The double-cavity CVT with a speed ratio range of 0.44-2.28 and capacity of 200 kW succeds in approaching a maximum effeciency of 92 per cent. The electrohydraulic servomechanism provides a quick response to the speed ratio change and equal force transmisson of four power rollers.
Half-toroidal traction-drive continuously variable power transmission
Ein stufenlos verstellbares Fahrzeuggetriebe mit halbkreisförmigen Variatorscheiben
1996
8 Seiten, 18 Bilder, 12 Quellen
Article (Journal)
English
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