Part 1

System Description

General Operation
The continuously variable transmission (CVT) is an electronically controlled automatic transmission with drive and driven pulleys, and a steel belt. The CVT provides non-stage speeds forward and one reverse.

Transmission
Around the outside of the flywheel is a ring gear which meshes with the starter pinion when the engine is being started. The transmission has four parallel shafts: the input shaft, the drive pulley shaft, the driven pulley shaft, and the final drive shaft. The input shaft is connected to the flywheel, which is connected to the IMA motor rotor through the drive plate. This is connected to the end of the engine crankshaft. The drive pulley shaft and driven pulley shaft consists of movable and fixed face pulleys. Both pulleys are linked by the steel belt.
The input shaft includes the sun gear and planetary gears with carrier. The drive pulley shaft includes the drive pulley and forward clutch. The driven pulley shaft includes the driven pulley, start clutch, and the secondary drive gear which is integral with the park gear. The final drive shaft is positioned between the secondary drive gear and the final driven gear. The final drive shaft includes the secondary driven gear and the final drive gear which serves to change the rotation direction, because the drive pulley shaft and driven pulley shaft rotate the same direction. When certain conditions of the planetary gears in the transmission are engaged by the forward clutch and the reverse brake, power is transmitted from the drive pulley shaft to the driven pulley shaft to provide L, S, D, and R positions.

Electronic Control
The electronic control system consists of the powertrain control module (PCM), sensors, and solenoid valves. Shifting is electronically controlled for comfortable driving under all conditions. The PCM is located in the engine compartment.

Hydraulic Control
The lower valve body assembly includes the main valve body, the secondary valve body, the CVT driven pulley pressure control valve, the CVT drive pulley pressure control valve, the CVT start clutch pressure control valve, and the inhibitor solenoid valve. These valve bodies are positioned on the lower portion of the transmission housing. The manual valve body is bolted on the intermediate housing.
The main valve body contains the start clutch shift valve, the shift inhibitor valve, the lubrication regulator valve, and cooler relief valve. The secondary valve body contains the pressure high (PH) regulator valve, the pressure high control (PHC) shift valve, the start clutch back-up valve, the clutch reducing valve, and the start clutch accumulator.
The CVT driven pulley pressure control valve contains pulley control valve A and the driven pulley control valve with the solenoid. The CVT drive pulley pressure control valve contains pulley control valve B and the drive pulley control valve with the solenoid. The CVT start clutch pressure control valve consists of the start clutch pressure control valve and the solenoid. These solenoids are controlled by the PCM. The manual valve body contains the manual valve and the reverse inhibitor valve.
The ATF pump is located on the transmission housing, and it is linked with the input shaft by the sprockets and the sprocket chain. The pulleys, forward clutch, and start clutch receive fluid from their respective feed pipes, and the reverse brake receives fluid from an internal hydraulic circuit.

Shift Control
The PCM controls the shift pulley ratio through the solenoids, while receiving input signals from the various sensors and switches located throughout the vehicle. The PCM actuates the pulley control solenoids to control pulley control valves A and B. Drive pulley pressure is regulated at pulley control valve B and applied to the drive pulley, driven pulley pressure is regulated at pulley control valve A and applied to the driven pulley, and the pulley ratio is changed to their directed ratio.

Gear Selection
The shift lever has six positions; P: PARK, R: REVERSE, N: NEUTRAL, D: DRIVE, S: SECOND, and L: LOW.





Starting is possible only in the P and N positions through the use of a slide-type, neutral-safety switch.

Automatic Transmission (A/T) Gear Position Indicator
The A/T gear position indicator in the instrument panel shows what gear has been selected without looking down at the console.

Clutches/Reverse Brake/Planetary Gear/Pulleys

Clutches/Reverse Brake
The CVT uses the hydraulic-actuated clutches and brake to engage and disengage the transmission gears. When hydraulic pressure is introduced into the clutch drum and the reverse brake piston cavity, the clutch piston and the reverse brake piston move. This presses the friction discs and steel plate together, locking them so they do not slip. Power is then transmitted through the engaged clutch pack to its hub-mounted gear, and through the engaged ring gear to the pinion gears.
Likewise, when the hydraulic pressure is bled from the clutch pack and 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 gear to spin independently on its shaft, transmitting no power.





Start Clutch
The start clutch engages/disengages the secondary drive gear, and is located at the end of the driven pulley shaft. The start clutch is supplied hydraulic pressure by its ATF feed pipe within the driven pulley shaft.

Forward Clutch
The forward clutch engages/disengages the sun gear, and is located at the end of the drive pulley shaft. The forward clutch is supplied hydraulic pressure by its ATF feed pipe within the drive pulley shaft.

Reverse Brake
The reverse brake locks the planetary carrier in the R position, and is located inside the intermediate housing around the planetary carrier. The reverse brake discs are mounted to the planetary carrier and the reverse brake plates are mounted on the intermediate 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 switch the rotational direction of the pulley shafts in the R position. The planetary gear train consists of the sun gear, planetary pinion gears, and ring gear. The sun gear is connected to the input shaft with splines. The pinion gears are mounted on the planetary carrier. The planetary carrier is located on the end of the input shaft, over the sun gear. The ring gear is located in the planetary carrier, and connected to the forward clutch drum. The sun gear inputs the engine power via the input shaft to the planetary gears, and the carrier outputs the engine power.
In the D, S, and L positions (forward range), the pinion gears do not rotate and revolve around the sun gear, so the carrier rotates. In the R position (reverse range), the reverse brake locks the planetary carrier, and the sun gear drives the pinion gears to rotate. The pinion gears rotate, but do not revolve around the sun gear. The pinion gears drive the ring gear in the opposite direction from the rotational direction of the sun gear.

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 driven 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.

Power Flow

P Position
Hydraulic pressure is not applied to the start clutch, forward clutch, and reverse brake. Power is not transmitted to the secondary drive gear. The secondary drive gear is locked by the park pawl, interlocking the park gear.

N Position
Engine power transmitted from the flywheel drives the input shaft, but hydraulic pressure is not applied to the forward clutch and reverse brake. Power is not transmitted to the drive pulley shaft. Also hydraulic pressure is not applied to the start clutch.





Forward Range; D, S, and L Positions
^ Forward clutch: engaged
^ Reverse brake: released
^ Start clutch: engaged
^ Hydraulic pressure is applied to the forward clutch and start clutch, and the sun gear drives the forward clutch.
^ The forward clutch drives the drive pulley shaft, which drives the drive pulley shaft linked by the steel belt.
^ The driven pulley shaft drives the secondary drive gear via the start clutch.
^ Power is transmitted to the secondary driven gear and final drive gear, which in turn drives the final driven gear.





Reverse Range; R position
^ Forward clutch: released
^ Reverse brake: engaged
^ Start clutch: engaged
^ Hydraulic pressure is applied to the reverse brake and the start clutch, and the planetary carrier locks with the reverse brake.
^ The sun gear drives the pinion gears to rotate, and the pinion gears drive the ring gear in the opposite direction from the rotational direction of the sun gear.
^ The ring gear drives the drive pulley shaft via the forward clutch drum, and drive pulley shaft drives the driven pulley shaft linked by the steel belt.
^ The driven pulley shaft drives the secondary drive gear via the start clutch.
^ Power is transmitted to the secondary driven gear and final drive gear, which in turn drives the final driven gear.





Electronic Control System

Electronic Control
The electronic control system consists of the powertrain control module (PCM), sensors, switches, and solenoid valves. Shifting is electronically controlled for comfortable driving under all conditions.
The PCM receives input signals from the sensors, switches, and other control units, processes data, and outputs signals for the engine control system and the CVT control system. The CVT control system includes shift control, pulley pressure control, start clutch pressure control, and reverse inhibitor control. The PCM actuates the pulley control solenoids to control pulley control valves A and B shifting transmission pulley ratios.

Electronic Controls Locations:

Pulley Pressure Control/Shift Control
To reduce belt slippage and increase belt life, the PCM calculates signals from the sensors and switches, and actuates the pulley pressure control solenoid valves to maintain optimum pulley pressure. When the pulley ratio is low (low vehicle speed), high hydraulic pressure works on the movable face of the driven pulley and reduces the effective diameter of the driven pulley, and a lower hydraulic pressure works on the movable face of the drive pulley to eliminate the steel belt slippage. When the pulley ratio is high (high vehicle speed), high hydraulic pressure works on the movable face of the drive pulley and reduces the effective diameter of the drive pulley, and a lower hydraulic pressure works on the movable face of the driven pulley to eliminate the steel belt slippage.
The PCM compares actual driving conditions with programmed driving conditions to control shifting, and it instantly determines a drive pulley ratio from various signals sent from sensors and switches. The PCM activates the CVT drive pulley pressure control valve to control pulley pressure to the pulleys. The drive pulley drives the driven pulley via a steel belt at varying ratios ranging from 2.526 to 0.421 in the D position.





Start Clutch Pressure Control
The hydraulic-controlled start clutch controls smooth starting-off and creeping in the D, S, L, and R positions like a torque converter. The PCM inputs signals from the sensors, and switches, and actuates the start clutch pressure control valve to regulate the clutch reducing pressure, and the clutch reducing pressure controls the start clutch.

PCM CVT Control System Electrical Connections:

PCM CVT Control System Inputs and Outputs (Part 1):

PCM CVT Control System Inputs and Outputs (Part 2):

PCM CVT Control System Inputs and Outputs (Part 3):

PCM CVT Control System Inputs and Outputs (Part 4):