Technology
The technology is referred to as "two-mode" hybrid transmission due to the ability to extend the abilities of both electrical and mechanical paths of power. The two modes of operation are:
- Input-split mode — At low speeds, the vehicle can move with either the electric motor/generators, the internal combustion engine, or both, making it a so-called full hybrid. All accessories will still remain functioning on electric power, and the engine can restart instantly if needed. In this mode, one of the motor/generators (M/G 1) acts as a generator, while the other operates as a motor (M/G 2). This mode is operational for the two continuously variable ranges (input split and compound split) of the transmission.
- Compound-split mode — At higher speeds or heavier loads, the internal combustion engine always runs, and the system uses advanced technologies like Active Fuel Management and late intake valve closing to optimize engine and fuel efficiency.
This mode begins at the point where one of the motor/generators reaches zero speed; at this point some clutches within the system engage while others disengage to alter the physical configuration of the transmission, and the velocity is Vshift. Immediately after the shift, both electric machines operate as motors and the first gear ratio is employed. At a given velocity above Vshift, the second gear ratio is employed, and M/G 2 begins to operate as a generator, while also slowing down its angular speed.
Although the transmission mechanically has only four conventional gear ratios, the electric motors allow it to function as a continuously variable transmission. This variable ratio functions in addition to the torque multiplication of the planetary gears.
A special automatic transmission (designated as a 2ML70 by General Motors) incorporates two 82 kW (110 hp peak) three phase permanent magnet motors, three planetary gear sets, and four selectively engaging friction clutches. This system amplifies the output of the electric motors similarly to the way in which a conventional transmission amplifies the torque of an internal combustion engine. It also, when required, permits transfer of more of the engine's torque to the wheels, making the transmission more efficient even without the electric motors in use. Finally, the whole system fits into the space of, and indeed appears as, a conventional Allison model 1000 automatic transmission.
A 300 volt battery pack is housed elsewhere in the vehicle to store energy.
Read more about this topic: Global Hybrid Cooperation
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