Gear shift strategies analysis of the automatic transmission in comparison with the double clutch transmission 2006-01-2872

From the several kind of transmission available for passenger vehicles, two of then find themselves in antagonistic position in the automobile development history. In one side the conventional automatic tr ansmission, with more then 60 years of development and use which in the last years experiments a growth in its demand and a movement for its improvement aiming more comfort, less fuel consumption, and to attain the rigid impositions of exhausting gasses reduction. On the other side, the double clutch transmission is in its early development, where just a feel applications can be found on the market. But it is expected that this kind of transmission automatization can offer the advantages of the automatic transmission, without its disadvantages.

The two systems under analysis in this work have a very different way of work. The conventional automatic transmission has 3 major elements, the torque converter, the planetary gear set and the multi -disc clutches and brakes, while the double clutch transmission arises from a conventional mechanical manual transmission, but it has a singular way of gear assembly, where one clutch acts over the even-numbered gears and the other on over the odd -numbered gears. Both clutches are actuated by an electrical -hydraulic devise and the gear shifts are provided by electrical motors.

The improvement of the automatic transmission and the development of the double clutch transmission were only possible due to the progress of the mi croelectronics that allowed the implementation of more accurate control strategies, especially for the gear shift process.

This work gives emphasis in the analysis of the transmissions behavior during up shifts. First of all, it was done a detailed descrip tion of each kind of transmission system and after that a comparison between its ways of work for several areas of engine torque. To perform this comparison it was proposed a factor, called force ratio, based on the maximal or ideal tractive force that can be transmitted to the wheels and the tractive force really existent on the wheels.

The results obtained pointed out that both systems have similar dynamic behavior and comfortable gear shifts. However, the double clutch transmission used is still under development and has a potential to be improved.

The automation in the automotive industry, whether in process or in products, is a necessity due to the aggressive market competition and the legal requirements. The transmission automatization aims to provid e one more option, what can be translated in competition advantage.