Both gearboxes are electronically hydraulically controlled and this control works according to various input parameters (engine speed, speed, load, etc.), when the next gear is engaged. In addition, the control recognizes the driver's driving style and sets shift points from «sports» before «economical», without having to actuate any of the switches. The whole system is called DSP - Dynamische Schalt-Programm (dynamic shift program). In addition, when choosing a gear, the terrain is taken into account - that is, the automation selects a gear shift mode on a flat road that differs from driving on a mountain road.
Basic principles of operation
The main link of all automatic transmissions are the so-called planetary kits. They consist of a gear around which three other gears rotate. A ring with internal teeth is put on top. Each pair of these elements is connected into a set of gears and forms its own small two-speed gearbox. The genius thing about these gearboxes is the way they shift. Gear shifting is carried out by holding or releasing parts of the planetary kit. This is done without interrupting the flow of power. Holding and releasing is provided by plate clutches and hydraulically actuated plate brakes.
To obtain a multi-stage gearbox, two planetary sets are connected in series. With the correct arrangement of gears, a four- or five-speed gearbox with a reverse gear is formed. Coordination of the operation of gear sets is provided by the gearbox control.
Torque converter
The cutaway photo of the torque converter clearly shows the turbine blades and idler. The arrow points to the friction lining of the torque converter clutch, which - except when the ATF is cold - switches from high speeds to a hard transmission of power in order to prevent «clearance».
The transmission of engine power to the gearbox is carried out by means of a fluid. The engine drives a turbine in a torque converter. The fluid in the torque converter, set into rotation, by means of a vane guide located between them, can also drive a turbine wheel connected to the gearbox. There is always a difference in speed between the turbine, which rotates in accordance with the engine speed, and the turbine wheel at the gearbox input. At the beginning of the movement, it is the largest, as the speed increases, the difference in the number of revolutions between the pump turbine and the gearbox turbine decreases more and more. But in a traditional automatic transmission, there is still some «gap». In our gearboxes, the torque converter is bridged in the range of 3rd and 4th gears and in 4th and 5th, i.e. a rigid connection dominates between the engine and the automatic transmission. This allows you to reduce fuel consumption.
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