The new General Motors 2-Mode Hybrid transmission for full-size, full-utility SUVs integrates two electromechanical power-split operating modes with four fixed gear ratios and provides fuel savings from electric assist, regenerative braking and low-speed electric vehicle operation. A combination of two power-split modes reduces the amount of mechanical power that must be converted to electricity for continuously variable transmission operation. Four fixed gear ratios further improve power transmission capacity and efficiency for especially demanding maneuvers such as full acceleration, hill climbing, and towing. This paper explains the basics of electro-mechanical power-split transmissions, input-split and compound-split modes, and the addition of fixed gear ratios to these modes to create the 2-Mode Hybrid transmission for SUVs.

The Chevrolet Volt is an electric vehicle (EV) with extended-range (ER) that is capable of operation on battery power alone, and on power generated by an on-board gasoline engine after depletion of the battery charge. For 2016, GM has developed the next generation of the Volt vehicle and "Voltec" propulsion system.Building on the experience of the first generation Volt, the second generation targeted improved all-electric range, improved charge sustaining fuel economy, and improved performance. All of this was to be accomplished while maintaining the EV character of the first generation Volt which customers clearly valued.This paper describes the next generation "Voltec" system and the realized improvements in efficiency and performance. The features of the propulsion system components, including energy storage, transaxle, electric motors and power electronics, on-board charging, and engine are described and compared with the previous generation. Next, the transaxle powerflow is discussed and operation under typical driving conditions is explained. Finally, system efficiency and performance data, based on component tests, is presented and compared with the previous generation.This system includes a battery pack with greater energy density, a new transaxle with integrated power electronics and motors, and an engine with optimized displacement, direct injection, and other advanced features.As a result of these improvements, the second generation Volt vehicle is projected to achieve a 30% increase in EV range, an 11% improvement in charge sustaining label fuel economy, and improved vehicle performance both as an electric vehicle, and in extended range mode.

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