General principle of operation
The core of the automatic transmission are the so-called planetary gear sets. They consist of a gear around which three more gears rotate. On top of all this, an annular gear with internal gearing is put on. Such units are assembled in pairs into one gear train and form their own small two-speed gearbox. The genius of these transmissions is the way they shift. Changing the gear ratio occurs only by delaying or releasing the elements of the planetary gear sets. In this way, switching takes place without interruption of force. Holding and releasing is provided by hydraulically controlled multi-disc clutches and multi-disc brakes.
To get a multi-speed gearbox, three planetary gears are connected one after the other. So there is a four-speed gearbox with reverse gear. Coordination of the gear train is provided by hydraulic control of the gearbox.
The cross section of the torque converter clearly shows the impeller and idler vanes. The arrow points to the friction lining of the clutch to connect the impeller to the engine, which - except in conditions of operation with cold ATF - shifts from higher gears to a rigid through drive to prevent slippage.
Torque converter
The transmission of engine thrust to the gearbox occurs through fluid. The motor drives the pump wheel in the torque converter. The fluid of the transformer set in rotation can now in turn drive the turbine wheel. There is always a speed difference between the pump wheel rotating at the engine speed and the turbine wheel at the gearbox input. When starting off, this difference is greatest, with an increase in speed, the rotational speeds of the pump and turbine wheels are more and more comparable. In our gearbox, the torque converter is blocked in the third and fourth gear ratio ranges, i.e. there is a rigid connection between the engine and the automatic transmission. This saves fuel.
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