Carbon-fiber stiffens CVT belts
The Goodyear Tire & Rubber Co., Akron, Ohio, is using carbon-fiber reinforcement to add stiffness across the width of their continuously variable transmission or CVT belts. "Threadlike strands of carbon fiber are strong, flexible, and weigh much less than steel of similar strength," says Loren Danhauer, Goodyear chief belt engineer.
A CVT system varies the working ratio of two V-shaped pulleys linked by the belt. The distance between pulley flanges fluctuates, letting the belt ride smoothly up and down the pulley, continuously changing the gear ratio and varying vehicle speed. The pulleys, part of a power-sensing drive, increase tension during acceleration and lower tension when power is reduced.
Danhauer says conventional CVT belt sidewalls glaze and char from heat buildup when the pulleys are under extreme loads. The top width of the belt then turns down and inward, creating vibrations that can quickly destroy the belt. "Carbon fiber in the rubber compound allows edge slippage without losing top width. When extreme demand subsides, the belt self-heals and again picks up the load," Danhauer explains.
Goodyear Tire & Rubber Co., goodyear.com