ABSTRACT The present production General Motors 2-Mode Hybrid system for full-size SUVs and pickup trucks integrates truck utility functions with a full hybrid system. The 2-mode hybrid system incorporates two electro-mechanical power-split operating modes with four fixed-gear ratios. The combination provides fuel savings from electric assist, regenerative braking and low-speed electric vehicle operation. The combination of two power-split modes reduces the amount of mechanical power that is converted to electric power for continuously variable transmission operation, meeting the utility required for SUVs and trucks. This paper describes how fuel economy functionality was blended with full-size truck utility functions. Truck functions described include: Manual Range Select, Cruise Control, 4WD-Low and continuous high load operation. INTRODUCTION The 2-Mode Hybrid system was originally designed for GM's Full-Size Truck family which includes the Tahoe SUV, as well as the Silverado pickup truck. The center of the 2-mode system is an EVT (Electrically Variable Transmission), which uses a pair of electric motors to choose nearly any ratio through the transmission. Though mechanically very different from the conventional Continuously Variable Transmission (CVT), the EVT allows ratio slewing like a CVT. Utilizing the electric motors in the transmission also allows hybrid functions such as: electric vehicle (EV) operation, electricassist, regenerative braking, as well as engine starting. The 2- Mode Hybrid transmission is also an automatic transmission with conventional hydraulically-applied wet-plate clutches to allow automatic shifting among two continuously variable modes and four fixed gears. The system has a total of six mechanical configurations: EVT mode 1, EVT mode 2, and fixed gears 1, 2, 3, and 4. This combination is integrated into a package similar in size to a conventional automatic transmission, with added cables leading to electronic control modules and a high-voltage battery. Considerable effort was expended in the 2-Mode system to develop class-leading fuel economy, while also maintaining the truck utility functions expected from a full-size SUV. Functions developed for fuel economy had to be balanced with those required for truck utility capabilities without sacrificing key vehicle characteristics. The general specifications of the Tahoe 2-mode hybrid system are given in Table 1. <table 1 here> INTRODUCTION TO THE 2-MODE HYBRID SYSTEM An EVT uses electric motors to control its speed ratio, enabling a continuous choice of transmission ratios. The input, output, and electric motors are connected to planetary gearing. In a set of planetary gears, the speed of a planet carrier is the weighted average of the speeds of its sun gear Truck Utility & Functionality in the GM 2-Mode Hybrid2010-01-0826 Published 04/12/2010 Goro Tamai GM Powertrain Shannon Reeves General Motors LLC Timothy H. Grewe GM Powertrain Copyright © 2010 SAE International SAE Int. J. Engines | Volume 3 | Issue 1 620Downloaded from SAE International by Brought to you by the University of Texas Libraries, Sunday, August 05, 2018and its ring gear. In a given EVT mode, the speed of the transmission output is a weighted average of the speeds of the engine and each of the electric motors, as determined by the planetary gearing. Therefore, a vehicle equipped with an EVT can be driven by the electric motor with the engine at zero speed (transmission ratio of zero), or the engine can be spinning while connected to the output with the vehicle at zero speed (transmission ratio of infinity), or anywhere in between. EVT MODE AND FIXED GEAR RANGE-SHIFT KINEMATICS The 2-Mode Hybrid transmission cross-section is shown in Figure 1. A schematic representation of this cross-section is shown in Figure 2. This schematic can be represented as a lever diagram as shown in Figure 3. This lever diagram can be further simplified for kinematic visualizations by com