Hybrid Modes of Operation
Hybrid Modes of Operation Description
This overview is not a comprehensive list of all aspects of the Two-Mode Hybrid vehicle. Refer to Automatic Transmission 2ML70 Electronic Component Description Electronic Component Description for information regarding transmission operation. More detailed and comprehensive information is also available through the dealer training program.
Engine Starting
This vehicle does not use a 12 V starter motor to crank the internal combustion engine. A much more powerful 300 V motor/generator located within the transmission is utilized to crank the engine. The 300 V drive motor generator can rotate the engine to operating speed (800 RPM) within just a few hundred milliseconds. The 300 V drive motor generator allows near-instant starting of the engine. Once started, engine operation may cycle between Autostop (engine off) and Autostart (engine running) for the duration of the drive trip.
Autostop
After a successful engine start, the hybrid powertrain control module may turn off the engine and operate in the Autostop mode. Some of the vehicle conditions that allow the engine to stop running and enter the Autostop mode include:
* Vehicle power mode is correct:
- The ignition switch is in the Run position after first being turned to the crank position which resulted in a successful engine start,
OR
- The ignition switch is turned to the Run position after a successful remote vehicle start request.
* Hood switch position status is Closed.
* ECM is not requesting continued engine operation for diagnostic purposes.
* Gear selector is not in the Reverse or Manual position.
* Hybrid battery state of charge is more than 20 percent.
* Hybrid battery voltage, temperature or power limits are not exceeded.
* Engine coolant temperature (ECT) is more than an acceptable limit.
* Drive motor generator temperature limits are not exceeded.
* Drive motor generator power inverter module temperature limits are not exceeded.
* No hybrid system faults exist.
A chime will sound if the drivers door is opened while in Autostop as a reminder that the engine is not in the OFF mode.
Engine OFF and AUTOSTOP modes are indicated on the tachometer display.
When the tachometer needle indicates OFF, the engine is not running and will remain Off until the ignition key is placed in the Crank position or a remote vehicle start request is received from the keyless entry transmitter.
When the tachometer needle indicates AUTOSTOP, the engine is not running but may Autostart at any time without notice.
Autostart
The Two-Mode Hybrid vehicle does not require internal combustion engine operation at all times. After a successful engine start, the hybrid powertrain control module may turn off the engine (Autostop) when not required for the current vehicle conditions. The engine will remain off while in Autostop mode, until such time that vehicle conditions require the engine to run. The near-instant starting of the engine from Autostop mode is called Autostart. Some of the vehicle conditions that may cause the hybrid powertrain control module to exit the Autostop mode and Autostart the engine include:
Important: If any of the following conditions exist while operating in Autostop, the hybrid powertrain control module may Autostart the engine without notice.
* Hood switch position status changes to Open
* ECM Request
* Gear selector is placed in the Reverse or Manual position
* Hybrid battery state of charge is too low
* Hybrid battery voltage, temperature or power limits are exceeded
* Engine coolant temperature (ECT) is too low
* Drive motor generator temperature limits are exceeded
* Drive motor generator power inverter module temperature limits are exceeded
* A hybrid system fault is observed
* Electric Launch capability has been exceeded and engine operation is required
Electric Launch/Assist
The transmission assembly contains two 300 V drive motor generator assemblies. These powerful 60 kW drive motor generators are capable of propelling the vehicle while the engine is in the Autostop mode or they may assist an already running engine. Depending upon accelerator pedal position, the vehicle may be propelled solely with the electric drive motor generators at speeds exceeding 41 km/H (26 mph) before assistance from the engine is required. The engine will Autostart when driving conditions require engine assistance. During engine running conditions, the torque provided by the drive motor generators is supplemented with the engine torque output.
Regenerative Braking
When the vehicle is coasting or braking the hybrid powertrain control module may operate the drive motor generators in an electrical generation mode. Operating as electrical generators, the drive motor generators exert a driveline load that helps to slow the vehicle. The electrical energy that the drive motor generators create is transferred by the drive motor generator power inverter module to the drive motor generator battery assembly (hybrid batteries). Constant communication between the hybrid powertrain control module and the electronic brake control module (EBCM) allows the blending of regenerative braking force with hydraulic braking force.
Enhancements to Engine Operation
While not unique to the Two-Mode hybrid vehicle, the following modes of operation benefit from expanded operational ranges. Expanded operational range is possible because the drive motor generators can be utilized to smooth driveline disturbances that would be objectionable without the intervention of the drive motor generator.
Deceleration Mode
When the driver releases the accelerator pedal, air flow into the engine is reduced. The ECM monitors the corresponding changes in the TP, the MAP, and the MAF. The ECM shuts OFF fuel completely if the deceleration is very rapid, or for long periods, such as long, closed-throttle coast-down. The fuel shuts OFF in order to prevent damage to the catalytic converters. This mode is activated more quickly and for a longer duration in the Two-Mode hybrid vehicle.
Cylinder Deactivation (Active Fuel Management)
To provide maximum fuel economy under light load driving conditions, the engine control module (ECM) will command the cylinder deactivation system ON to deactivate engine cylinders 1 and 7 on the left bank, and cylinders 4 and 6 on the right bank, switching to a V4 mode. The engine will operate on 8 cylinders, or V8 mode, during engine starting, engine idling, and medium to heavy throttle applications. This mode is activated more quickly and for a longer duration in the Two-Mode hybrid vehicle.