Nissan unveils next-generation XTRONIC CVT, new 1-motor, 2-clutch FWD hybrid system, new fuel cell stack
|The new XTRONIC CVT features a sub planetary gear to enable a higher ratio coverage. Click to enlarge.|
At a technical briefing in Yokohama, Nissan Motor Co., Ltd. unveiled its new generation XTRONIC CVT (Continuously Variable Transmission) for 2.0 to 3.5-liter engine vehicles as well as a new front-wheel-drive parallel hybrid system using the one-motor, two-clutch design earlier applied in the rear-wheel drive Infiniti M35 (earlier post).
The company also released its Next Generation Fuel Cell Stack (2011 Model) for Fuel Cell Electric Vehicles (FCEV). Through improvements to the MEA (Membrane Electrode Assembly) and the separator flow path, Nissan significantly improved the power density of the stack to 2.5 times greater than its 2005 model, achieving 2.5 kW per liter—the world’s best among auto manufacturers, Nissan said.
XTRONIC CVT. The new generation XTRONIC CVT model achieves an improvement in fuel economy of up to 10% compared to previous CVTs for comparable vehicles, based on in-house measurements using US (EPA) combined mode. The new transmission features a ratio coverage of 7.0 using a sub planetary gear to switch between low and high ranges, allowing smaller pulleys to reach higher transmission ratio coverage. This raises responsiveness on startups and at low speeds while allowing lower engine rpm at high speeds, resulting in higher fuel economy. Nissan also reduced friction by 40%.
|Main technologies of the XTRONIC CVT. Click to enlarge.|
Combined with Adaptive Shift Control (which adapts shifting patterns to match each driver’s style and the road), the new generation XTRONIC CVT delivers responsive and powerful acceleration. It also helps keep the engine from revving too fast at high speeds and minimize noise. The new generation XTRONIC CVT will be introduced in North America from 2012, then globally thereafter.
By combining smaller shaft-diameter pulleys with a new and differently shaped belt, the range of ratios between the two pulleys has been expanded with only minimally increased axial distance. The resulting ratio coverage of 7.0 sets a new benchmark for CVTs for 2.0-liter-plus vehicles around the world, Nissan said.
The adoption of a more compact oil pump was achieved by reducing oil leak and reducing necessary oil pressure resulted from the interface increase between the pulleys and the belt. This, plus the use of specially formulated low viscosity oil, has reduced friction. Also approximately 60% of the component parts have been modified to reduce friction.
Adaptive Shift Control (ASC) senses each driver’s intentions through the way he or she accelerates and the choices made in handling and speed. Based on these preferences, ASC selects a gear ratio optimal to the specific conditions and the driver’s intention. ASC’s linear shift control function gives the driver a more direct sense of acceleration by coordinating engine speed (RPM) with vehicle speed as the car accelerates.
New hybrid system for FWD vehicles. Nissan’s new system incorporates one electric motor and two clutches into the new generation XTRONIC CVT and combines this with a compact lithium-ion battery and a 2.5-liter supercharged engine.
|The new hybrid system combines an efficient CVT with Nissan’s own one-motor two-clutch system; a downsized, supercharged engine; and a high-output lithium-ion battery. Click to enlarge.|
The result is a compact, versatile powertrain that does not require a specially designed body. It delivers power equivalent to a 3.5-liter engine but with much better city and highway fuel economy. Nissan plans to release a new hybrid vehicle in North America in 2013, and later in global markets.
Fuel cell stack. In addition to significantly increasing the power density, Nissan molded the supporting frame of the MEA integrally with the MEA enabled stable, single-row lamination of the Fuel Cell, thereby significantly reducing its overall size by more than half compared to conventional models.
|Click to enlarge.|
Additionally, compared with the 2005 model, both the usage of platinum and parts variation has been reduced to one quarter, thereby reducing cost of the Next Generation Fuel Cell Stack to one-sixth of the 2005 model.