The Secret is in a Gear-Box. Gear World. Part 2
Automatic with Positive Blocking
The more advanced automatic transmission learned to “lock” the hydraulic coupling at the higher gears and gave all the controlling functions to the electronics. The fast electronics and hydraulics were able to restore that old “steel” link in an automatic transmission inherently repeating the ancient algorithm of a simple mechanic transmission. This is the way many modern Mercedes transmission work. This was the first attempt to return to the “mechanic” algorithm.
Automatic with positive shifting
Automotive sportsmen and just “hot heads” who didn’’t want to “pull the lever” all the time demanded a more lively shifting from an automatic transmission. So there appeared automatic transmission with positive shifting. Initially – with a special sector of the lever, later – with levers and buttons on the steering wheel. In substance, it is the same automatic transmission, but with a possibility of the driver’s interference into the work of the system.
Stepless transmission (continuously variable transmission (CVT) or progressive transmission) means constantly shifting gear ratio. Pay attention to the fact that it shifts steplessly. It just means that such a scheme enables not to change the engine turn from the beginning of the acceleration to the max speed. The fist serial CVT transmissions were introduces by DAF in 1958. A dozen years ago such a technology was quite rare. But at the end of the 90s – looked like a real “burst-out”. A CVT under the cowling of Honda, Audi A6, Nissan Murano or Mercedes B-klasse is no longer a wonder.
Robotic Mechanics
With the development of the automatic transmission, the mechanics hasn’t been forgotten. There appeared a real mechanic gear-box with high-end hydro- (like in Audi A2) or electric drive (Peugeot 1007) and the “brain” automatically calculated all the algorithms and torque. The majority of robotics are slow. The only exceptions are AllShift by Mitsubishi and extra-fast SMG by BMW (M5 and M6).
DSG (now S-Tronic)
It seems quite strange why such a progressive idea has been realized only recently by the engineers of VW and Audi. DSG stands for Direct Shift Gearbox (German: Direkt Schalt Getriebе). The idea is as simple as possible: two gear-boxes and two clutches in one body. However, the double DSG works in oil like the automatic transmission. Moreover, DSG has one obvious disadvantage – it cannot “jump” over the fixed gears.
Hybrid Transmissions
The surprise sprang up in the serial Toyota Prius and Lexus RX 400h. Two types of fuel – petrol and electricity – unifying into a single stream just before the driving axle of these cars simply displaced a gear-box. There is no gear-box as there is no clutch. The only thing that remained is a simple planetary differential (redirecting the power stream like a bathroom mixer). The electronics rules the process and all the possible “skidding” is killed by a electromagnetic field.
The Secret is in a Gear-Box. Gear World. Part 1
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