Operating principle of an automatic transmission
An automatic transmission (AT) is a multi-speed transmission that automatically changes gears depending on speed and load. It consists of the following main components:
*Hydraulic Transformer: Connects the engine to the transmission and transmits power.
*Planetary Gear: A set of gears that provides different gear ratios.
* Valve Unit: Controls the flow of pressurized fluid to change gears.
* Solenoids: Solenoid valves that switch the valve body.
* Electronic control unit (ECU): Controls the operation of the automatic transmission based on input data from various sensors.
Operating procedure:
1. When the engine starts, the torque converter is filled with liquid under pressure.
2. When the driver moves the gear selector, the ECU sends a signal to the valve body.
3. The hydraulic unit redirects fluid under pressure to the appropriate channels in the planetary gear.
4. This causes various gears to engage or disengage, changing the gear ratio.
5. Simultaneously with gear shifting, the hydraulic transformer ensures a smooth transition between gears due to slippage.
6. As speed and load changes, the ECU analyzes sensor inputs and automatically changes gears to maintain optimal engine performance.
7. When the driver releases the accelerator pedal, the automatic transmission goes into engine deceleration or freewheel mode to save fuel.
Additional features:
*Sport Driving Mode: Allows you to shift gears at higher engine speeds for improved performance.
* Fuel Economy Mode: Shifts gears at lower engine speeds for improved fuel economy.
*Manual Mode: Allows the driver to manually shift gears, simulating a manual transmission.
* Parking Mode (P): Locks the transmission, preventing the vehicle from moving.