With all the excitement about a future, perhaps 2010, Chevy Volt plug-in hybrid from GM, the soon-to-be-announced full hybrids from the Global Hybrid Cooperation of General Motors, DaimlerChrysler and the BMW Group seem to be taking a backseat. Just like the plug-in hybrid, the two-mode (AKA 2-mode or dual-mode) hybrid is a significant departure from existing hybrids but the engineering effort is complete.
The 2008 Chevy Tahoe and GMC Yukon that will be introduced in 2007 will get better fuel economy thanks to electric motor operation at highway speeds. The power split hybrid approach is similar to single-mode hybrids that create two paths for applying torque to the wheels from a gasoline powered internal combustion engine and a battery powered motor. However, instead of a generator and a traction motor used in single-mode hybrids, the two-mode Electric Variable Transmission (EVT) hybrid has an electric variator that uses two 60-kW motors, one that operates in low speed range and one that operates in the high speed range..
As explained by Peter Savagian, engineering director for Hybrid Power Systems at General Motors, planetary gears split the engine power and can multiply all torque.
Clutches activate the EVT modes and fixed gear ratios. With fixed gears ratios, the motors do not have to carry engine power. The results are improved fuel consumption in real world driving with increased continuous duty operation for towing and increased speed range for high-speed driving. The same EVT will appear on GM's Saturn Vue Green Line in 2008 and a Chrysler Group SUV.
Check out the video that shows the operation of the two-mode EVT and how its design is packaged within a housing similar to a conventional transmission.
Get more information on Front-Wheel-Drive, 2-Mode Hybrid System
2-Mode Transmission System
Motors, planetary gears, fixed gears and clutches fit inside a conventional transmission housing.