Gear System Description - General Operation
General Description
The Electric Continuously Variable Transmission (e-CVT) is an electronically controlled transmission. The e-CVT provides stepless forward speeds and reverse. The e-CVT allows the vehicle to be driven under electric power, engine power, or combination of both power sources. Both power sources transmit power through the gears inside the transmission.
Transmission
The e-CVT assembly contains four parallel shafts, gears, the over drive clutch, the traction motor, and the generator motor. The input shaft is connected to the flywheel, which is connected to the engine crankshaft through the drive plate. Also, the input shaft is connected to the over drive clutch. When the input shaft is joined with the over drive gear by engaging the over drive clutch, engine power is transmitted through the input shaft, to the over drive gear and the countershaft, then to the final driven gear of the differential to provide drive. The motor shaft is connected to the traction motor, traction motor power is transmitted through the motor shaft, to the motor shaft gear and the countershaft, then to the final driven gear of the differential to provide drive. The generator shaft is connected to the generator motor. To charge the high voltage battery by generator motor, engine power is transmitted through the input shaft and generator shaft.
Electronic Control
The electronic control system consists of the powertrain control module (PCM), sensors, shift solenoid valves, and switches. The e-CVT seamlessly shifts between three drive modes; EV drive mode, HV drive mode, and engine drive mode. The PCM determines the drive mode based on the information sent from each sensor and control unit.
Hydraulic Control
The valve body assembly includes the regulator valve body and the shift valve body. They are installed to the flywheel housing. The regulator valve body contains ATF pumps A and B. ATF pump A is driven by the engine. ATF pump B is driven by the differential. These pumps supply hydraulic pressure to the hydraulic circuit. Transmission fluid pressure sensor is mounted on the outside of the transmission housing. Shift solenoid valves A and B are mounted on the outside of the flywheel housing. The PCM actuates the shift solenoid valves to control hydraulic pressure and engaging the over drive clutch.
Gear Selection
The SBW (Shift By Wire) system is a system that performs the shift operations of the driver electrically instead of using control cables. The SBW shifter has four positions/modes; P: PARK, R: REVERSE, N: NEUTRAL, and D: DRIVE.
| Position | Description |
|---|---|
| P: PARK | Front wheels locked; the parking brake pawl engaged with the parking gear on the motor shaft. Over drive clutch is released. Traction motor does not rotate. |
| R: REVERSE | Traction motor rotates in reverse direction. The motor shaft drives the countershaft in reverse rotation. |
| N: NEUTRAL | Over drive clutch is released. Traction motor does not rotate. |
| D: DRIVE | General driving; D position/mode has three driving modes; EV drive mode, HV drive mode, and engine drive mode. |
Shift Position Indicator
The shift position indicator in the gauge control module shows which shift position/mode has been selected without looking down at the console.
Over Drive Clutch
The over drive clutch is the hydraulic-actuated clutch, and is located at the end of the input shaft. The e-CVT applies hydraulic pressure to the over drive clutch to engage or disengage the over drive gear. When hydraulic pressure is introduced into the clutch drum, the clutch piston moves and presses the steel plates and the clutch discs. Power is then transmitted through the engaged clutch pack to its hub-mounted gear. Likewise, when the hydraulic pressure is bled from the clutch drum, the piston releases the steel plates and the clutch discs. Then the steel plates rotate with the clutch drum, and the clutch discs rotate with hub-mounted gear. The clutch discs are released from the steel plates. This allows the clutch disc to spin independently, transmitting no power.
Gear Operation
Gears on the input shaft:
- The input shaft gear is integral with the input shaft, and transmits the input shaft rotation to the generator shaft.
- The over drive gear is engaged/disengaged with the input shaft by the over drive clutch.
Gears on the motor shaft:
- The motor shaft gear is integral with the motor shaft, and transmits the traction motor rotation to the countershaft.
- The parking gear is splined with the motor shaft, and rotates with the motor shaft.
Gears on the generator shaft:
The generator shaft gear is integral with the generator shaft, and transmits the input shaft rotation to the generator motor.
Gears on the countershaft:
- The countershaft gear is integral with the countershaft, and transmits the motor shaft gear or over drive gear rotation to the final drive gear.
- The final drive gear is splined with the countershaft, and rotates with the countershaft.
Gears on the transfer assembly:
- The transfer driven gear is splined with the transfer hypoid drive gear/shaft assembly, and rotates with the transfer hypoid drive gear/shaft assembly.
- The transfer hypoid drive gear is integral with the hypoid drive shaft, and transmits the hypoid drive shaft rotation to the transfer hypoid driven gear.
- The transfer hypoid driven gear rotates the companion flange.
Transmission Cutaway View