Transmission options
In this comprehensive review of technology, ZF's Group Vice President for Product Development concludes that the future belongs to automated manual, continuously variable, and six-speed automatic and manual transmissions with increased capacities.
Just a few years ago, driveline configurations in passenger cars easily could be categorized into two groups: "standard" drive, with a longitudinal, inline engine/transmission unit in the front of the vehicle powering the rear wheels, or front-wheel drive, with a transverse engine/transmission in front. Other driveline configurations, such as rear engine with rear-wheel drive, were special cases. Transmission choices were either manual or automatic with four or five speeds.
More recently, the diversification and broadening of the passenger-car market has led to new driveline configurations and transmissions. In addition, the ever-growing commitment to fuel consumption and emissions reductions, as well as better performance and comfort, require new transmission solutions.
Manual transmissions now have as many as six gears, with automation being implemented in the areas of clutch and gearshift actuation. Automated gear selection, either by lever or steering-wheel buttons, as well as a fully automatic mode, is now possible via shift-by-wire control systems. While automatic transmissions for North American vehicles normally have four speeds, many European and Asian cars have five speeds—and the introduction of six speeds is nearing. For vehicles with low to moderate torque output, a continuously variable transmission (CVT) is an option. CVT development is now focused on greater power-transmission capability to enable the technology's use in mid-range vehicles. Toroidal transmissions are making news for vehicles with even higher-torque eight- and twelve-cylinder engines.
Dr.-Ing. Gerhard Wagner, ZF Group Vice President for Product Development, and his colleagues have examined the implications for the various transmission systems and, based on future demands of the passenger car market, have outlined the range of transmission options for various driveline configurations and made recommendations for preferred transmission applications.
