The principle of gear shifting in an automatic transmission (automatic transmission)
The automatic transmission automatically changes gears based on input from various sensors, such as vehicle speed, engine speed and accelerator pedal position. Here is a typical gear shift process:
1. Pulling away
* When the ignition is turned on and the brake pedal is pressed, the transmission is in Park (P) mode.
* When the gear selector is moved to the Drive (D) position, first gear is engaged.
* Pressing the gas pedal causes the car to move from first gear.
2. Shifting to a higher gear
* When vehicle speed and engine speed increase, the hydraulic control unit (HCU) receives signals from the corresponding sensors.
* The hydraulic unit opens the solenoid valves, which direct hydraulic fluid to the desired clutch pack.
* The clutch pack connects to the transmission, resulting in shifting to a higher gear.
3. Downshifting
* When the vehicle speed decreases or the brake pedal is pressed, the engine speed drops.
* The GCU receives signals from the corresponding sensors and activates another clutch package.
* This clutch pack connects to the lower gear to provide engine braking and additional power for acceleration.
4. Torque converter lock
* At higher speeds, the torque converter connecting the engine and transmission locks up.
* Locking reduces power loss and improves efficiency.
Types of automatic transmission
There are different types of automatic transmissions, including:
*Conventional torque converter automatic transmission: Uses hydraulic fluid to transfer power between the engine and transmission.
* Variable Transmission (CVT): Uses cones and a belt to smoothly change the gear ratio.
* Robotic Manual Transmission (RMT): Combines elements of both manual and automatic transmissions.
Advantages of automatic transmission
* Convenience and ease of use
* Smooth gear shifting
* Automatic engine braking
* Possibility of manual gear shifting (on some models)