ZF debuted the AS Tronic fully automatic heavy-duty transmissions for commercial trucks in Europe last month. All transmission functions have been integrated into a single unit, eliminating the number of sources for potential problems that plague add-on technology.
The advent of more sophisticated engine electronics has sparked a trend towards more automation in the gearbox. The intent was to provide fleets with a transmission designed to handle a less skilled driving force, while delivering greater fuel efficiency, less drivetrain abuse, and better resale value.
To this end, mechanical transmissions automated with shift cylinders, valves, sensors, and other add-on technology have been employed. Since 1997, the company has been selling a 12- and 16-speed semi- automated transmission that requires a driver's command for gearshifts. That transmission has been installed in Iveco heavy-duty trucks. There is no synchronization for the main transmission gears because the engine electronics take care of the synchronization. Plus, there are no external shifting elements, which plagued other semi-automatic transmissions with reliability problems.
The new automatic ZF transmission takes that technology to the next level. The automatic shift strategy permits operation of the engine in the most economical range, with the potential of a 5% fuel economy gain. Plus, it allows the driver to keep both hands on the steering wheel. The electronic system selects the most efficient starting gear and helps relieve the driveline of peak loads. In addition, by reading both engine speed and road speed, the system allows for shifts that are 30% faster than manual shifts.
Electronic overspeed protection helps eliminate driver errors, making the drive smoother and clutch-free - all of which translates into a safer, more efficient operation. At any time, the driver can choose to drive in automatic mode or opt to shift gears manually. In either case, there is no clutching.
The ZF automatic transmission boasts a weight savings of more than 130 lb. when compared to its semi-automated predecessors. Since the driveline is relieved of peak loads, there is less clutch wear. And since the system is easy to operate and learn, attracting and training less skilled drivers is now possible.
The design features a double countershaft with an integrated splitter group, helical gears, and planetary-designed, range-change group. The shifting module, which contains the integrated transmission electronics, the valves for shifting, the shift cylinders, and the speed sensors, rests on top of the transmission, making it easily accessible.
The unit also features a display that keeps drivers informed of the operating mode as well as information on system failures.
In fact, the AS Tronic system continuously performs self-diagnosis. It recognizes malfunctions and informs drivers both visually and audibly as to whether they should stop the journey or whether the trip can be continued - and if it can, whether any restrictions are necessary.
The unit also includes ZF's Intarder, which allows constant downhill drive speeds to be controlled. That is said to extend the life of service brakes by up to 90% and helps eliminate the risk of brake overheating.
The transmission is available in two classes - the AS 2301 12-speed, for vehicles with engines that carry up to 450 hp., and the AS 2601 16-speed transmission, for engines that go as high as 550 hp.