Gearbox

Automatic gearboxes are those who carries out the shifting gears without the intervention of the driver of the car. The decision of the gear shift lever is taken by the computer of the electronic control of the gearbox, on the basis of the information from the sensors position on the accelerator pedal and the speed of the car.

Automatic transmission is composed of three components:

- The torque converter is the subassembly which transmits the engine when the gearbox, by means of a fluid. In the case where hidrotransformatorul is unlocked, the movement of the originating from the engine is not transmitted directly mechanical but hydraulic, between the engine and the gearbox because there is no mechanical connection.

The torque converter, is composed of four main components:

- pump

- the turbine

- stator

- the clutch assembly locking

- The Gear-Shift Planetary Drive With the clutches and brakes multidisc types. The achievement of a gear in an automatic transmission is done by means of several mechanisms planetary gears. Engage or the formation of the gear is performed using the clutches and brakes multidisc types. These are designed to engage the two elements to turn at the same speed (clutch) or to block an element to zero speed (brake).

- The electro-hydraulic command and control which constitute the "brain" the functioning of the automatic gearbox.

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Automatic transmission 4HP20

The automatic gearbox 4HP20 has 4 reports of transmission (gearbox) and sends a maximum torque of 330 Nm. Has in component 2 Planetary mechanisms simple, a hidrotrasformator (torque converter lockable), 2 clutches, 3 disc brakes and an electro-hydraulic unit. Hidrotrasformatorul (the torque converter) is provided with a clutch controlled by a valve with electrical control unit. Usually, in gears 2, 3 and 4, depending on the operating mode, the transmission computer command to lock the hidrotrasformatorului to eliminate the losses stack.

The hydraulic circuit is equipped with a cooling radiator. Oil, due to the fact that it is taking the discs clutches and brakes, at the request of intense, it may become very much, reaching to temperatures above 100°C. Under these conditions the transmission computer controls an electrical valve that opens the cooling circuit and allow oil to pass through the radiator.