xcel
06-17-2006, 03:15 PM
The two-mode system evolved from GM’s Allison heavy-duty hybrid drive … (http://www.sae.org/automag/techbriefs/06-2006/1-114-6-20.pdf)
Lindsay Brooke - SAE Online - June 2006
http://www.cleanmpg.com/photos/data/501/GM_DUAL_MODE1.jpg
In presenting the first public look inside its new two-mode hybrid drive system, the hybrid-development consortium of General Motors, DaimlerChrysler, and BMW revealed technologies that it claims make the system more capable and efficient than current hybrid systems.
At the recent Vienna Motor Symposium, executives from the Global Hybrid Cooperation, as the alliance is
called, said the two-mode system adds a pair of clutches and two planetary gearsets to the base electrically variable transmission (EVT). The existence of the clutches had been a closely guarded secret until the Vienna event.
The system enters production on the 2008 Chevrolet Tahoe, Dodge Durango, and GMC Yukon. The consortium members are planning other applications in rear-wheel-drive trucks and luxury cars as
well as configurations for front- and allwheel-drive use.
The two-mode system evolved from GM’s Allison heavy-duty hybrid drive currently used in 436 transit buses in the U.S. and Canada as well as from GM’s EV-1 electric car program of the 1990s. As with current full hybrids, the twomode system gives electric-only operation at low speeds; electric power-boost under acceleration; idle stop; and regenerative braking. But its additional clutches and gearsets provide a key feature the current one-mode hybrids lack: four fixed gear ratios overlaid on the EVT.
http://www.cleanmpg.com/photos/data/501/Large_Size_GM_DUAL_MODE_Cutaway.jpg
The gearing creates a mechanical power path that is 20% more efficient at higher speeds when the vehicle is operating on engine power under sustained load, said Larry Nitz, GM’s hybrid engineering director and a consortium executive.
“While the one-mode EVTs do a very nice job in the city, they are somewhat challenged on the highway because they depend on maintaining an electrical power path to transmit most of the system’s power,” he said.
One-mode hybrid drives, such as those used by Toyota and Ford, employ a single planetary gearset with the EVT to split input torque for driving the wheels or charging the battery. The design has been proven in small to mid-size vehicles carrying light loads.
But for larger vehicles with greater payload and towing ratings, the electric power flow needed for sustained-load operation requires larger, heavier electric motors.
The consortium’s design provides a compound-split EVT mode (operating range) as well as the input split, said Andreas Truckenbrodt, Executive Director of DCX’s hybrid program and the consortium’s executive director. The arrangement “allows smaller, less costly electric machines,” he said.
The design can engage a combination of EVT modes and gear ratios depending on speed and load. Mode 1 propels the vehicle from launch to second gear. Mode 2 takes it from second gear to overdrive 4th. Shifts between the two modes are synchronous, with the driving feel similar to that of a traditional stepped automatic transmission.
Nitz gave an example of two-mode operation in a full-size truck. “You will launch in the electric-variable mode (mode 1), then very quickly pick up the mechanical first-gear ratio,” he said. “The mechanical ratio puts the power to the ground. You’ll go back into mode 1 for a little bit before going to second-gear ratio.
You’ll go into mode 2 before going into third-gear ratio, then back into mode 2 on the way to fourth-gear ratio.”
What happens when you’re cruising down the highway and approach a hill?
“It will smoothly go from maybe mode 2 to fourth gear, then fourth gear to third gear,” said Nitz. “And you’ll pull that hill in third gear most of the time. The e-motors can boost, but you’re really pushing
most of the power through mechanically. Fixed gears are happy-they’re right there hooked to the ground.”
The two-mode is expected to achieve 25% better fuel efficiency in composite city-highway driving compared with nonhybrid versions, said Wolfgang Epple, Vice President of hybrid development at
BMW and a consortium director. Engine cylinder deactivation on the GM and DCX full-size hybrids is expected to factor in the greater overall powertrain efficiency.
The two-mode will be assembled at GM’s Baltimore transmission plant, which has the capacity for 360,000 units per year. It will be calibrated to match each company’s array of engines and unique brand character, Epple explained.
While Toyota continues with a onemode system, it has added a two-speed reduction gearset to the new L110 transmission used in the Lexus GS450h and LS600h L rear-drive luxury cars. This improves
torque multiplication and also allows the electric motors to be slightly reduced in size, said Dave Hermance, Executive Engineer at Toyota’s U.S. technical center.
At a recent media symposium, Hermance indicated that Toyota is looking at increasing the number of reduction gear ratios for future applications.
Lindsay Brooke - SAE Online - June 2006
http://www.cleanmpg.com/photos/data/501/GM_DUAL_MODE1.jpg
In presenting the first public look inside its new two-mode hybrid drive system, the hybrid-development consortium of General Motors, DaimlerChrysler, and BMW revealed technologies that it claims make the system more capable and efficient than current hybrid systems.
At the recent Vienna Motor Symposium, executives from the Global Hybrid Cooperation, as the alliance is
called, said the two-mode system adds a pair of clutches and two planetary gearsets to the base electrically variable transmission (EVT). The existence of the clutches had been a closely guarded secret until the Vienna event.
The system enters production on the 2008 Chevrolet Tahoe, Dodge Durango, and GMC Yukon. The consortium members are planning other applications in rear-wheel-drive trucks and luxury cars as
well as configurations for front- and allwheel-drive use.
The two-mode system evolved from GM’s Allison heavy-duty hybrid drive currently used in 436 transit buses in the U.S. and Canada as well as from GM’s EV-1 electric car program of the 1990s. As with current full hybrids, the twomode system gives electric-only operation at low speeds; electric power-boost under acceleration; idle stop; and regenerative braking. But its additional clutches and gearsets provide a key feature the current one-mode hybrids lack: four fixed gear ratios overlaid on the EVT.
http://www.cleanmpg.com/photos/data/501/Large_Size_GM_DUAL_MODE_Cutaway.jpg
The gearing creates a mechanical power path that is 20% more efficient at higher speeds when the vehicle is operating on engine power under sustained load, said Larry Nitz, GM’s hybrid engineering director and a consortium executive.
“While the one-mode EVTs do a very nice job in the city, they are somewhat challenged on the highway because they depend on maintaining an electrical power path to transmit most of the system’s power,” he said.
One-mode hybrid drives, such as those used by Toyota and Ford, employ a single planetary gearset with the EVT to split input torque for driving the wheels or charging the battery. The design has been proven in small to mid-size vehicles carrying light loads.
But for larger vehicles with greater payload and towing ratings, the electric power flow needed for sustained-load operation requires larger, heavier electric motors.
The consortium’s design provides a compound-split EVT mode (operating range) as well as the input split, said Andreas Truckenbrodt, Executive Director of DCX’s hybrid program and the consortium’s executive director. The arrangement “allows smaller, less costly electric machines,” he said.
The design can engage a combination of EVT modes and gear ratios depending on speed and load. Mode 1 propels the vehicle from launch to second gear. Mode 2 takes it from second gear to overdrive 4th. Shifts between the two modes are synchronous, with the driving feel similar to that of a traditional stepped automatic transmission.
Nitz gave an example of two-mode operation in a full-size truck. “You will launch in the electric-variable mode (mode 1), then very quickly pick up the mechanical first-gear ratio,” he said. “The mechanical ratio puts the power to the ground. You’ll go back into mode 1 for a little bit before going to second-gear ratio.
You’ll go into mode 2 before going into third-gear ratio, then back into mode 2 on the way to fourth-gear ratio.”
What happens when you’re cruising down the highway and approach a hill?
“It will smoothly go from maybe mode 2 to fourth gear, then fourth gear to third gear,” said Nitz. “And you’ll pull that hill in third gear most of the time. The e-motors can boost, but you’re really pushing
most of the power through mechanically. Fixed gears are happy-they’re right there hooked to the ground.”
The two-mode is expected to achieve 25% better fuel efficiency in composite city-highway driving compared with nonhybrid versions, said Wolfgang Epple, Vice President of hybrid development at
BMW and a consortium director. Engine cylinder deactivation on the GM and DCX full-size hybrids is expected to factor in the greater overall powertrain efficiency.
The two-mode will be assembled at GM’s Baltimore transmission plant, which has the capacity for 360,000 units per year. It will be calibrated to match each company’s array of engines and unique brand character, Epple explained.
While Toyota continues with a onemode system, it has added a two-speed reduction gearset to the new L110 transmission used in the Lexus GS450h and LS600h L rear-drive luxury cars. This improves
torque multiplication and also allows the electric motors to be slightly reduced in size, said Dave Hermance, Executive Engineer at Toyota’s U.S. technical center.
At a recent media symposium, Hermance indicated that Toyota is looking at increasing the number of reduction gear ratios for future applications.