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The New TelligentSr Shift From Mercedes-Benz
Published June 05, 1997 by Verlag Des Verein Deutscher Ingenieure GmbH in Germany
The EPS Electronic-Pneumatic Shift system, which has been fitted by Mercedes-Benz as standard in the heavy-range trucks since 1986, has been substantially further developed for the introduction of the Actros. By coupling this gearshift system to the CAN communication bus used in the new vehicle generation and by optimizing the operating philosophy with a modified shift lever, Mercedes has been able to provide a wider range of functions and a significant increase in customer utility. This new system is available under the name Telligent® Shift.
One new feature that is of major benefit to the driver is the Telligent Selection, which is activated simply by moving the lever forward or back. In this mode, the electronic system determines the appropriate target gear on the basis of vehicle speed, load condition, accelerator pedal position, engine torque and vehicle acceleration, so that after changing gear the engine will be running at the optimal speed for the driving situation. This new target gear selection system enhances driver convenience and relaxation, and at the same time ensures that the gear change will always bring the engine into the most economical part of its characteristic map. In this way, the Telligent® Shift makes a significant contribution to ensuring an economical driving style.
In addition to the Telligent Selection mode, the driver can still force driver-selected gear changes with defined steps between gears. This Driver Selection mode is activated by simultaneously moving the main lever and pressing the function button (to shift up ro down by one gear). A half-gear rocker switch is also fitted to the shift lever to provide a simple method of shifting up or down by one half-gear; in this case, not only is the splitter group shifted, as before, but the main gears can also be automatically shifted if necessary. By fully integrating the splitter group in the shift program, the specified engine speed range can be more efficiently utilized.
Even before the clutch is activated, a gear can be preselected both in Telligent Selection mode (optimal gear) and Driver Selection mode (driver-defined gear). This preselection facility even applies to shifting from standstill to the driveaway gear, which can be particularly easily selected for 2 s and 4 s by preselection. The preselected starting gear remains stored for 10 s (or for 2 minutes if the handbrake is on) and can be corrected with the shift lever while in memory.
The recurrent demand of drivers for shorter traction interruption times has been taken into account in the Telligent® shift; the previous strict time sequence of activating the shift lever and clutch pedal and then starting the gear change has been replaced by a degree of overlapping.
Also, the shift lever's intermediate position, which signals the completion of the gear change, is now confirmed in advance, so that the driver can engage the clutch at an earlier stage. The Telligent® Shift also supports rapid forward/reverse changes for rocking the vehicle out of off-road mire or snow drifts. With these features and the Telligent Selection mode, which even takes account of vehicle slowing due to clutch release when determining the optimal target gear, the prospect of efficient application even in heavy-duty use on the construction site can be envisaged.
Careful analysis of the known problems of EPS, combined with wide-ranging field experience, has enabled Mercedes to eliminate previous weak point from the new version, thereby considerably enhancing reliability. In addition, a comprehensive emergency driving concept has been implemented, so that in the unlikely event that a fault occurs, in particular due to full utilization of redundant systems, the vehicle can still be driven, possibly with certain functional limitations. Systematic cost reduction of all components has ensured that the Telligent® Shift does not add to the price of manual transmission