In a CVT, which components are used to change the drive ratio?

In a CVT, which components are used to change the drive ratio?

• A. Fixed gears
• B. Hydraulic pistons
• C. Torsional couplings
• D. Belt and variable-width pulleys

Answer: (D)

CVTs change drive ratio by altering the size of the pulleys the power belt runs between. The belt transmits torque between two pulleys, and each pulley’s effective diameter can be changed so that the belt rides at different radii. When one pulley becomes smaller and the other larger, the belt moves to new contact points, producing a continuous range of gear ratios rather than fixed steps. This combination—belt plus pulleys with variable widths—is what creates and controls the changing drive ratio. Hydraulics or pistons may act to move the pulley halves in some designs, but the actual variation in ratio comes from the belt engaged with pulleys whose effective diameters are adjusted. Fixed gears would not allow ratio changes, and torsional couplings mainly dampen vibrations rather than set the gear ratio.

CVTs change drive ratio by altering the size of the pulleys the power belt runs between. The belt transmits torque between two pulleys, and each pulley’s effective diameter can be changed so that the belt rides at different radii. When one pulley becomes smaller and the other larger, the belt moves to new contact points, producing a continuous range of gear ratios rather than fixed steps. This combination—belt plus pulleys with variable widths—is what creates and controls the changing drive ratio. Hydraulics or pistons may act to move the pulley halves in some designs, but the actual variation in ratio comes from the belt engaged with pulleys whose effective diameters are adjusted. Fixed gears would not allow ratio changes, and torsional couplings mainly dampen vibrations rather than set the gear ratio.