CVT System Description - Clutches
Forward Clutch, Reverse Brake, Planetary Gears, and Pulleys
Forward Clutch
The forward clutch is the hydraulic-actuated clutch, and engages and disengages the planetary sun gear. When hydraulic pressure is introduced into the forward clutch drum, the forward clutch piston moves. This presses the friction discs and steel plates together, locking them so they don't slip. Power is then transmitted through the engaged clutch pack to the forward clutch hub/sun gear. Likewise, when the hydraulic pressure is bled from the clutch pack, the piston releases the friction discs and the steel plates, and they are free to slide past each other. This allows the sun gear to spin independently on the forward clutch, transmitting no power. The forward clutch is integrated at the middle of the input shaft. The forward clutch is supplied hydraulic pressure by a circuit connected to the internal hydraulic circuit.
Reverse Brake
The reverse brake is the hydraulic-actuated brake, and engages and disengages the planetary carrier with the transmission housing. When hydraulic pressure is introduced into the reverse brake piston cavity, the reverse brake piston moves. This presses the friction discs and steel plates together, locking them so the planetary carrier locks. Power from forward clutch drum and ring gear is then transmitted through the planetary pinion gears and the sun gear. Likewise, when the hydraulic pressure is bled from the reverse brake piston cavity, the piston releases the friction discs and the steel plates, and they are free to slide past each other. This allows the planetary carrier to free from the reverse brake, transmitting no power. The reverse brake is mounted in the transmission housing. The reverse brake is supplied hydraulic pressure by a circuit connected to the internal hydraulic circuit.
Planetary Gear Train
The planetary gear train is only used for switching the rotational direction of the pulley shafts in R. The planetary gear train consists of the sun gear, the planetary pinion gears, the planetary carrier, and the ring gear. The sun gear is connected to the drive pulley shaft by the splines. The planetary pinion gears are installed on the planetary carrier. The planetary carrier assembly is located on the drive pulley shaft, the carrier is mounted in the reverse brake, and the pinion gears are engaged with the sun gear. The ring gear is connected with the forward clutch drum, and engaged with the planetary pinion gears. In R, the reverse brake locks the planetary carrier, and the ring gear drives the planetary pinion gears to rotate. The pinion gears drive the sun gear in the reverse direction from the rotational direction of the input shaft. The engine power from the input shaft drives the sun gear and the drive pulley shaft via the forward clutch drum, ring gear, planetary pinion gears.
Pulleys
Both pulleys consist of a movable face and a fixed face, and the effective pulley ratio changes with engine speed. The drive pulley and the driven pulley are linked by the steel belt. To achieve a low pulley ratio, high hydraulic pressure works on the movable face of the driven pulley and reduces the effective diameter of the drive pulley, and a lower hydraulic pressure works on the movable face of the drive pulley to eliminate the steel belt slippage. To achieve a high pulley ratio, high hydraulic pressure works on the movable face of the drive pulley and reduces the effective diameter of the driven pulley, and low hydraulic pressure works on the movable face of the driven pulley to eliminate the steel belt slippage.
Transmission Cutaway View
NOTE: The illustration shows the AWD/4WD transmission; 2WD transmission does not have the transfer mechanism.
