Alfa Romeo MiTo

ALFA TCT operating principles - Mechanical part

FPT engineers have designed solutions to allow continuous motion transmission using the C633 manual gearbox. Firstly, the main shaft of the Alfa TCT consists of two mutually coaxial shafts, called outer main shaft and inner main shaft. The junction area houses an axial bearing allowing reciprocal rotation. Both shafts are made of steel. The inner main shaft has a grooved profile for splining 3rd and 5th speed drive gears, while the outer main shaft is made in one piece.

Section view:

Fig. 7

1. 3rd speed drive gear

2. outer main shaft (coupled to clutch K2 – even gears)

3. inner shaft odd gear clutch grooved profile bearing

5. inner main shaft (coupled to clutch K1 – odd gears)

6. outer main shaft even gear clutch grooved profile

7. clutch rod bushing

8. outer main shaft bearing

9. roller cage

10. inner main shaft roller cage

11. inner main shaft hole for introducing odd gear clutch rod

The need for two main shafts derives from the fact that two pairs of gears must be meshed to allow continuous motion gearbox. Therefore, two clutches are needed to obtain this without causing mechanical damage, one for odd gears (called K1) and one for even gears (called K2). While travelling, one of the two clutches is closed to transmit motion from one only pair of gears and the other clutch is open to prevent gearbox using the other gear pair. While shifting either up or down, both clutches work in tandem: one closes when the other one opens, and vice versa.

• The even drive gears (2nd, 4th and 6th) are obtained on the outer shaft (coupled to clutch K2), along with the groove for splining the even gear clutch.

• The odd driven gears (1st, 3rd, 5th, reverse) are splined on the inner main shaft (connected to the clutch K1), along with the grooved profile for splining the odd gear clutch.

- 16 - Alfa TCT