Hybrid Transmission: Notes

The Hybrid transmission contains two electric drive motor with generator assemblies, 3 planetary gear sets, and 4 wet-plate clutches. The hybrid transmission can operate in either two electronically variable transmission (EVT) modes or one of four fixed gear ratios. The two permanent magnet electric motors are packaged within the transmission which is installed longitudinally in the vehicle. Three high voltage A/C cables, connected to each of the two motors, attach to transmission housing and are routed via rigid conduit around the transmission then transition to flexible cable at the attachment to the drive motor generator control module (DMGCM) Transmission fluid is used for hydraulic control and transmission component and motor cooling. An auxiliary oil pump is mounted externally to the transmission and provides oil pressure during engine-off Auto-Stop operation.

Fig 1: Drive Motor with Generator Assemblies

Courtesy of GENERAL MOTORS CORP.

Two permanent magnet electric motors mounted inside the transmission enable engine cranking, transmission reverse, and two EVT modes of operation. The front, or motor 1 and the rear, or motor 2 each provide 60kW peak power. Both are actively cooled via transmission fluid and are encased in steel housings to facilitate transmission assembly. The front motor is used to start the engine and also react torque from the rear motor. The rear motor propels the vehicle when operating in full-electric mode with the engine off or in reverse. Motor speeds are controlled and monitored by position sensors internal to the motor housings. The drive motor generator position sensor is monitored by the motor control module (MCM). The MCM monitors the angular position, speed and direction of the drive motor generator based upon the signals of the resolver-type position sensor. The position sensor (or resolver) contains a drive coil, two driven coils and an irregular shaped metallic rotor. The metallic rotor is mechanically attached to the shaft of the drive motor generator. At ignition ON, the MCM outputs a 5 volt ac, 10 kHz excitation signal to the drive coil. The drive coil excitation signal creates a magnetic field surrounding the two driven coils and the irregular shaped rotor. The MCM then monitors the two driven coil circuits for a return signal. The position of the irregular shaped metallic rotor causes the magnetically-induced return signals of the driven coils to vary in size and shape. A comparison of the two driven coils signals allows the MCM to determine the exact angle, speed and direction of the drive motor generator. For more information on the drive motor function and system interaction refer to Drive Motor Generator Control Module Description and Operation and Drive Motor Battery System Description .

Fig 2: Control Solenoid (W/Body and TCM) Valve Assembly

Courtesy of GENERAL MOTORS CORP.

The control solenoid (w/body and TCM) valve assembly contains the following components:

• Transmission control module (TCM)
• Clutch pressure control solenoids (Clutch PC Sol)
• Shift solenoids (SS)
• Line pressure control solenoid (Line PC Sol)
• Transmission fluid temperature sensor (TFT Sensor)
• TCM temperature sensor
• Power-up temperature sensor (not used)
• Transmission fluid pressure switches (TFP Sw)

These components are not serviced separately. The control solenoid (w/body and TCM) valve assembly utilizes a lead-frame system to connect these components electrically to the TCM. No wires are used for these components. The control solenoid (w/body and TCM) valve assembly bolts directly to the lower and upper valve body assemblies inside the transmission. The control solenoid (w/body and TCM) valve assembly connects to the engine harness 16-way connector via a pass-thru sleeve.