The principle of operation of an automatic gearbox (automatic transmission)
The automatic transmission changes gears automatically based on factors such as speed, load and throttle position. It consists of several main components:
Hydraulic transformer
* Consists of two impellers (pump and turbine) connected by hydraulic fluid.
*Transmits torque from the engine to the transmission and increases it through slippage.
Planetary gearbox
* A set of gears that are connected in different ways to create different gear ratios.
Locking mechanism
* Connects the transformer turbine to the transmission directly when torque is not required.
Hydraulic control unit (HCU)
* Electronic control unit, which receives input data from various sensors and controls the operation of the automatic transmission.
* Regulates hydraulic fluid pressure to shift gears and control the operation of the locking mechanism.
Automatic transmission operation
1. Starting the engine: When starting the engine, the GCU selects first gear.
2. Acceleration: As the accelerator pedal is pressed, the GCU increases the hydraulic fluid pressure to shift to the next gear.
3. Constant Speed: When the vehicle reaches the set speed, the GCU engages the locking mechanism to reduce slippage in the transformer and improve fuel economy.
4. Braking: When braking, the GCU can shift to lower gears to improve engine braking efficiency.
5. Stopping: When the vehicle stops, the GCU shifts to neutral.
Automatic transmission modes
Many automatic transmissions have additional modes, such as:
*Sport Mode: Shifts to higher gears at higher rpm for improved acceleration.
* Economy Mode: Shifts to lower gears at lower rpm to save fuel.
Types of automatic transmission
There are several types of automatic transmissions, including:
* Planetary automatic transmissions: The most common type using planetary gearboxes.
* Variable speed drives (CVT): Use a belt or chain to continuously change the gear ratio.
* Automatic transmission (DCT): Uses a clutch and gears like a manual transmission, but automates the gear shifting process.