Continuously Variable Transmissions (CVTs) The reciprocating internal combustion engines which substituted the steam engines brought a problem for road (and railway) traction: they do not develop any torque at rest. Ever since, a constant obsession of engineers and inventors has been to conceive a system of mechanical drive able to progressively and continuous vary the transmission ratio, in order to allow the engine to spin always at the most favorable revs.
Countless systems have been imagined and even tested, but the "natural selection" has let survive very few of them.
Contents :
Page 1 : Principle (1/2),
Page 2 : Principle (2/2),
Page 3 : CVTs with pulleys of variable effective diameter,
Page 4 : Push belt or chain (1/2),
Page 5 : Push belt or chain (2/2),
Page 6 : Clutch and reverser,
Page 7 : Virtual discrete ratios,
Page 8 : Williams-Renault FW 15 C (1/2),
Page 9 : Williams-Renault FW 15 C (2/2),
Page 10 : The ZF Ecotronic,
Page 11 : Developments of the belt and pulleys CVTs,
Page 12 : CVT by wire and Zero inertia concept,
Page 13 : New fluid,
Page 14 : Right angle friction drive,
Page 15 : The Beier variator,
Page 16 : The Flichy-Citroën variator,
Page 17 : Toroidal and half-toroidal variators,
Page 18 : Milner CVT,
Page 19 : The GIF dual cone and ring CVT (1/2),
Page 20 : The GIF dual cone and ring CVT (2/2),
Page 21 : The Turbo-Trac variator / power splitting.
Author : François Dovat .
Pictures : LuK, ZF, Turbo-Trac, GIF, Nissan, Torotrak, Ford, GM, Napier.
Publication date : November 2004.
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