Gear Production
Issue link: http://gear.epubxp.com/i/262216
March 2014—25 nine-speed can reduce fuel consumption by as much as 16 percent compared with the six-speed. One of the challenges that ZF took on in developing this new transmission is that of space. While it is comparatively easier to accommodate more gears in a longitudinal confguration, in a traverse design, there is less room to package the transmission, especially when you've upped the number from six to nine. Also realize that most cars that deploy transversely oriented transmissions are small to midsize, so there is a set space constraint. Given that about 75 percent of all cars have a traverse setup, this is a great opportunity for ZF. So the company capitalized on the opportunity while paying keen attention to constraints. Realize also that in the segment of the market in which the transmission was developed to be deployed, there is considerable price sensitivity, so it had to engineer the product with that in mind, too. It created the nine-speed with four simple gear sets, six shift elements, and two dog clutches, each with two multidisc clutches and two multidisc brakes. The total spread is 9.81. The setup features two planetary gear sets on top of each other; consequently, there are never more than three gear sets in a row. There are two series in the nine-speed range, and the torque spread is from 200 to 480 kNm. Another way that ZF saved space was to install the electronic control unit (ECU) on the upper side of the transmission housing rather than with the reduced-size hydraulic control unit. The sensors within the transmission providing vehicle-side signals are connected to the ECU via its male plug. ZF engineers found that it was necessary to develop and produce the ECU for the nine-speed, the frst time the company has done it. While there is likely to be an increase in the number of gears going forward, a more likely scenario is the use of hybrid technology to improve overall fuel effciency. ZF has cleverly protected the nine-speed's future integrity for integration with hybrid components. What's more, the transmission also lends itself for use in all-wheel-drive setups. While the ZF Gray Court, S.C., manufacturing plant was opened in July 2013 for transmission production, demand for eight- and nine-speed transmissions has grown so signifcantly that the automotive supplier is already expanding it for more capacity. 0314_MMS_Gear_GaryFeature2.indd 25 2/13/2014 2:46:51 PM