Inside Honda's new two-motor 50-mpg Accord Hybrid
The all-new 2014 Accord Hybrid employs Honda’s newi-MMD (intelligent Multi-Mode Drive) two-motor hybrid system for midsizevehicles that debuted earlier this year on the Accord Plug-in Hybrid sedan.
The Accord Hybrid has EPA fuel-economy(FE) ratings of 50/45/47 mpg city/highway/combined, which Honda claims is abest-in-class city rating for a four-door sedan. The car also boasts a drivingrange of 673 mi (1083 km).
The key difference between the plug-in (PHEV) and hybridversions—besides the presence of an onboard charging system and cord for thePHEV—is the size of the onboard battery. The Accord Plug-in Hybrid uses a6.7-kW·h lithium-ion pack, whereas the new hybrid model employs a more compact1.3-kW·h pack that is charged via the 2.0-L "Earth Dreams" Atkinson-cycle gasolineengine, regenerative braking, or a combination of the two.
Blue Energy, a subsidiary of GS Yuasa Corp., supplies its EH5 Li-ion batteryfor the Accord Hybrid and its EH19 model for the PHEV.
“The engine in the two-motor system is the same in the hybrid andthe PHEV,” Hiroo Shimada, Chief Engineer, Assistant Large Project Leader,Powertrain Design, explained to SAE Magazinesthrough an interpreter. “In the rear, the battery unit is different between thetwo. But there’s very high commonality in terms of the parts between thehybrid and the plug-in hybrid.”
Honda’s two-motor hybrid approach continuously cycles betweenthree different modes: EV drive, hybrid drive, and engine drive. (Go to http://video.sae.org/11763/ to see a Honda video illustrating how the system operates.)
Honda also has developed a new three-motor “sport hybrid” system.Read about it and the 2014 Acura RLXSport Hybrid at http://articles.sae.org/12670/; also http://books.sae.org/b-hon-014/.
The new i-MMD system
Shimada has spent 15 years on hybrid powertrain engineering atHonda, including work as Project Leader on the IMA (Integrated Motor Assist)system for the first-generation (MY2000) Insight. He also is responsible for researchthat led to development of the i-MMD hybrid system.
Shimada said he couldn’t discuss how long it took to develop thetwo-motor hybrid system, but he did share some challenges encountered duringits development.