Automatic 4 - Power Flow
In this case, a Ravigneaux-set with two sun wheels, two planet wheel sets, a hollow wheel ring, one simple planetary set, four multiple-disc clutches, two rib brakes and a freewheel result in an automatic gearbox with
five-speeds, which are designed with freely selectable gear ratios, which are automatically selected by electronics and magnetic valves. Together with the torque converter this
arrangement corresponds to a six-speed manual gear-box.
How it works
the torque is transferred from the input shaft through a corresponding multiple-disc clutch to the smaller hollow shaft and the bigger sun wheel.Because the accompanying planet wheel carrier is locked by the freewheel against run-back, the torque is then transferred through the
other planet wheels to the hollow-wheel-ring. Because the sun wheel of the rear planet set is also
locked by a suitable rib brake, the planet wheels roll on the sun wheel. Thus the way through the planet wheel carrier to the output shaft is
The larger hollow shaft, together with the smaller front sun wheel is now fixed by the left rib brake. The planet wheel
carrier is thereby moved in the direction not locked by the freewheel. The smaller planet wheels mesh with the larger planet wheels
and these with the sun wheel.They provide for a higher gear ratio. The rest remains as in the first gear.
The rear planet set now is locked by the opening of the right rib brake and the simultaneous closing of the right multiple-disc clutch and runs as a unit without gear reduction. The front part stays the same as in the
The front planet set is now also locked by the opening of the left rib brake and the closing of two multiple-disc clutches. Again no gear reduction takes place. The 4th gear is the direct gear for this automatic gear-box.
To reach a reduction of the gear ratio lower than 1, the left sun wheel is held by the left rib brake. At the same time the torque of the input shaft
is transferred by the corresponding multiple-disc clutch to the innermost shaft. This re-appears in the rear, in the planet wheel carrier. The rear planet
wheels mesh with the front planet wheels. These mesh themselves with the now static sun wheel and drive the hollow-wheel-ringat the, up to now, highest RPMs in comparison to the engine speed. In the rear everything remains as in the 4th gear.
The freewheel lock is used for the second time after its deployment in the 1st gear. The input shaft connects with the larger hollow shaft and with it to the small front sun wheel. The planet wheels provide for a reversal of the rotary direction. The
rest remains as in the first gear. 09/08