An automatic transmission does not have a clutch in the traditional sense, like a manual transmission. Instead, an automatic transmission uses a torque converter or multi-plate clutch to transfer torque from the engine to the transmission.
Torque converter
* A torque converter is a fluid coupling that transfers power from the engine to the transmission through circulating fluid under pressure.
* There are three main components in a torque converter: pump, turbine and stator. The pump, driven by the engine, creates pressure in the fluid, which then drives a turbine connected to the transmission.
* The torque converter ensures smooth gear shifting without the need for a clutch. This is because the fluid in the clutch acts as a buffer between the engine and transmission, smoothing the transition between gears.
Multi-disc clutch
*Some types of automatic transmissions, such as dual-clutch transmissions (DCTs), use multi-plate clutches instead of a torque converter.
*A multi-disc clutch has multiple discs that are sandwiched between two metal plates.
* To enable a certain gear ratio, one of the disks is pressed tightly against the plate, ensuring the transmission of torque.
*Multi-plate clutches provide faster and smoother gear changes than torque converters.
How does this work
The automatic transmission uses the following components to control torque transmission:
* Gear selector: The driver selects the desired gear using the gear selector.
*Transmission Control Module (TCM): The TCM processes the signal from the gear selector and transmits commands to the automatic transmission components.
*Hydraulic solenoids: Solenoids control the flow of pressurized fluid into the automatic transmission, engaging and disengaging clutches and band brakes.
* Band Brakes: Band brakes are used to hold certain gears engaged.
*Planetary gears: Planetary gears are mechanical devices that change the gear ratio by connecting different gears.
When the driver selects a gear, the TCM sends signals to the hydraulic solenoids, which engage the appropriate clutches and band brakes. This allows the planetary gears to adjust the gear ratio, transferring torque from the engine to the transmission.