Operating principle of a hydromechanical automatic transmission (automatic transmission)
Hydromechanical automatic transmission consists of the following main components:
* Torque converter
* Planetary gearbox
* Hydraulic control unit
* Friction clutches and brake bands
Job:
1. Torque converter:
* The input shaft, driven by the engine, transmits torque to the torque converter.
* The torque converter consists of a turbine, pump and stator filled with transmission fluid (ATF).
* The pump (connected to the input shaft) rotates, accelerating the ATF fluid.
* ATF is directed to a turbine (connected to the output shaft), which transmits torque to the planetary gearbox.
* The stator (located between the pump and turbine) changes the direction of ATF flow, increasing torque and speed of rotation of the secondary shaft.
2. Planetary gearbox:
* The planetary gearbox consists of a set of gears, including the sun gear, planetary gears and carrier.
* Clutches and brake bands mesh with various gears, changing the transmission ratio.
3. Hydraulic control unit:
* The hydraulic control unit receives signals from sensors, throttle sensor, speed sensor and other components.
* It uses these signals to determine the correct gearing and control the ATF pressure that is supplied to the clutches and brake bands.
4. Friction clutches and brake bands:
* Clutches use ATF pressure to engage various gears to transmit torque.
*Brake bands use ATF pressure to hold the gears stationary.
Gear shift:
When the car accelerates or decelerates, the automatic transmission control system reads signals from sensors and determines whether a gear change is necessary.
*Upshift: The hydraulic control unit reduces the ATF pressure on the clutch of the current gear while increasing the pressure on the clutch of the higher gear. This results in a gradual upshift.
* Downshift: The hydraulic control unit performs the opposite operation, reducing the pressure on the higher gear and increasing the pressure on the current gear, resulting in a quick downshift.
Peculiarities:
* Hydromechanical automatic transmissions provide smooth gear shifting.
* They handle high torques better than other types of automatic transmissions.
*They are relatively easy to maintain.
Flaws:
*Hydromechanical automatic transmissions are less efficient than other types of automatic transmissions due to energy loss in the torque converter.
*They can be bulky and heavy.