Automatic transmission (AT)
An automatic transmission is a type of transmission in cars that automatically changes gears based on engine speed and load. It consists of several main components:
Automatic transmission housing
* Made of aluminum alloy or cast iron.
* Contains all internal automatic transmission components.
Torque converter
* Located between the engine and gearbox.
* Serves to transmit torque from the engine to the gearbox and ensures smooth gear shifting.
* Consists of:
* Pump (driven by motor)
* Turbines (connected to the gearbox input shaft)
* Stator (located between the pump and turbine)
Planetary gearbox
* A device that provides gear ratios for various gears.
* Consists of:
* Set of gears (solar, planetary and epicyclic)
* Planetary gear holders
* Brake bands or friction discs for engaging and disengaging gears
Hydraulic system
* Consists of a pump, valves and solenoids that control the flow of pressurized fluid.
*Used to change gears by applying pressure to the brake bands or friction discs.
Electronic control unit (ECU)
* A computer that controls the operation of the automatic transmission based on:
* Engine speed
* Engine load
* Gear selector positions
* Sensors that monitor the temperature and rotation speed of the transmission
Gear shift lever
* Allows the driver to select the desired automatic transmission operating mode, for example, ‘park’, ‘reverse’, ‘neutral’, ‘drive’, etc.
Automatic transmission sensors
* Observe various automatic transmission parameters, such as:
* Rotation speed of input and output shafts
*Transmission fluid temperature
* Fluid pressure
Types of automatic transmissions
There are several types of automatic transmissions, including:
*Hydraulic automatic transmission: The most common type of automatic transmission, using a hydraulic system to change gears.
* Electronic automatic transmissions: Use electronic solenoids instead of hydraulic valves to control gear shifts.
*Continuously Variable Transmissions (CVT): Use two bevel pulleys and a belt that varies the diameter of the pulleys to provide smooth gear changes.
* Robotic Manual Transmissions (RMT): Combines a manual transmission with electro-hydraulic control for automatic gear shifting.