8-ст. автоматическая коробка передач Aisin

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8-ст. автоматическая коробка передач Aisin

Оригинальный пресс-релиз на английском

Transmission

New 8-Speed Automatic:
World's first 8-speed automatic in an SUV

New automatic can transfer torques of up to 850 Nm
7th and 8th gears reduce engine speed, noise and fuel consumption

Wolfsburg/ Florence, March 2010. In all Touareg versions, a new 8-speed automatic transmission is being used - an advanced develop¬ment of the previous 6-speed automatic transmission. That makes this Volkswagen the first SUV in the world with this type of transmission. The automatic is designed for engine torques of up to 850 Newton-metres. Due to the two additional gear levels, a 20 percent larger gea¬ring spread can be attained between 1 st and 8 th gears. This accomplishes two objectives: First, thanks to this larger spread, the engines operate with even greater efficiency over all speed ranges, making them both more fuel efficient and responsive. Second, it was possible to lay out the 7 th and 8 th gears as speed-reducing gears (20 percent reduction) - fuel-saving overdrive gears.
On the transmission of the previous model, 6th gear handled this job. On the new 8-speed automatic, on the other hand, the car's top speed is reached in 6th gear. The lower engine rpms attained in this way have a positive effect on noise levels as well. If the engine speed required to reach top speed in 6th gear is considered 100 percent, this means that in 8th gear engine speed is reduced by 34 percent. An example: At 130 km/h cruising speed, the Touareg's V6 TSI only turns at about 2,200 rpm. To optimally isolate the drivetrain from vibration generated by engine torque, further improvements to the torsional damping provided by the torque converter have been made.
In the Touareg Hybrid, the 8-speed automatic - which shifts faster than the gearbox on the previous model - is coupled to a transfer case with Torsen differential. This results in a 40:60 distribution of the propulsive force between the front and rear axles. The Torsen differential is already being used in a similar form within the Volkswagen Group, but it was further refined for the Touareg to improve its weight and efficiency.
Back to the automatic: By using a low-friction transmission fluid (Auto¬matic Transmission Fluid / ATF) and a newly developed heat exchanger, additional fuel economy gains were achieved by lowering friction losses - especially in the cold running phase of the automatic transmission. The so-called plate heat exchanger has been mounted on the back of the transmission, and both coolant from the engine cooling system and ATF circulate through it. The heat exchanger serves two purposes: As soon as the ATF exceeds a predefined temperature, the heat exchanger is used to cool the oil. If there is further need to cool, an auxiliary ATF-Air heat exchanger in the front end is also activated. This assures that optimal temperatures are maintained in the automatic even under extreme conditions, which are not all that rare in an SUV.
To implement the Touareg's smoothly transitioning Stop-Start function in every driving phase, the transmission must be provided with suffi¬cient oil pressure to ensure slip-free power transfer within the gear elements. Conventional gearboxes only accomplish this once the engine has attained a specific idling speed, so that the mechanically driven transmission oil pump can build up sufficient oil pressure and oil flow. This is different on the Touareg's 8-speed automatic: Here the system is supplemented by an electrically driven pump, which is able to maintain a stable oil pressure level within the hydraulic system during the engine's stopped phase.