1990-09-01

Dynamic Characteristics of Speed Ratio Control of the Halt Toroidal CVT for Passenger Cars 901761

This paper describes the results of an investigation into the controllability of a traction-drive type half toroidal CVT, built with traction-drive elements. One feature of this CVT is that it provides better power transmission efficiency at its rolling contact points than other traction-drive CVTs developed previously. Another feature is that ratio changes can be effected with only a slight power input. A third feature is that it does not require any special hydraulic system to engage the contact points of rolling elements because it is designed to generate engaging force spontaneously in proportion to the torque input.
The first half of the paper presents an analysis of the shifting mechanism. The characteristics of ratio changes effected by slight displacements of the power rollers were analyzed theoretically. A simplified CVT model was then examined experimentally and found to provide good response characteristics.
The second half of the paper deals with an experiment carried out with a CVT-equipped car. The aim of this experiment was to confirm whether the same quick response could be obtained with an actual vehicle as with the simplified model. Measurements made of the downshifting response during sudden braking showed that fast enough response was obtained to ensure sufficient reliability.

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