Gear shifting in the automatic transmission occurs by blocking individual elements of the planetary mechanism, which is carried out as a result of the hydraulic effect of the friction clutch. The clutch in the automatic transmission is carried out using a torque converter.
An automatic gearbox (automatic transmission) is designed to change the speed of the transmission shaft depending on the current driving conditions of the car without the direct participation of the driver. In modern cars, hydromechanical automatic transmissions are mainly used. The main structural units of the automatic transmission are the torque converter, planetary gearbox, friction clutch and overtaking clutch. The coordination of the automatic transmission is carried out using an electro-hydraulic control unit.
Torque converter
The torque converter as part of the automatic transmission acts as a clutch in manual transmissions, ensuring the transmission of torque when the car starts to move. Structurally, the torque converter consists of three impeller wheels - one stationary (stator) and two rotating ones. The first rotating wheel (pump) is attached to the flywheel of the crankshaft and transmits torque from the engine. The flow of hydraulic fluid is directed by the impeller to the stator, after which it causes the second wheel (turbine) to rotate, transmitting torque to the transmission shaft.
Planetary reductor
The planetary gear in the automatic transmission design is used to transmit torque and change its value depending on driving conditions. The planetary gearbox differs from other types in its more compact dimensions, as well as the absence of jerks during gear shifting.
The planetary transmission of an automatic transmission consists of a sun gear, satellites, a carrier and an epicycle. Torque is transmitted from the sun gear to the satellites moving along the inner teeth of the epicycle. Further, the transmission of torque is carried out to the casing of the satellites (carrier), connected to the output shaft of the gearbox. Gear shifting is carried out by locking the individual elements of the planetary gearbox.
Friction clutches
The friction clutch is designed to create a hydraulic control effect on the elements of the planetary gearbox, blocking them depending on the required transmission shaft speed. The clutch consists of a drum and an internal hub, in the space between which there is a pack of friction discs, the movement of which is carried out depending on the position of the hydraulic piston.
Overtaking clutch
The overrunning clutch ensures that the torque is transmitted in the desired direction and prevents the shaft from turning in the opposite direction. Structurally, it consists of an external disk, an external disk and rollers. As the centrifugal force increases, the rollers are pressed against the peripheral surface of the outer disc, providing mechanical transmission of torque.
