What is the principle of an automatic transmission?
3 Answers
The principle of an automatic transmission consists of a torque converter, planetary gears, a hydraulic torque variation system, and a hydraulic control system, achieving speed and torque variation through hydraulic power transmission and gear combinations. Below is an introduction to the torque converter in an automatic transmission: 1. Torque Converter: The torque converter is the most distinctive component of an AT, composed of a pump wheel, turbine, and guide wheel, directly inputting engine power and transmitting torque while also serving a clutch function. 2. Pump Wheel and Turbine: If liquid is used instead of air as the medium for transmitting kinetic energy, the pump wheel will drive the turbine to rotate via the liquid. By adding a guide wheel between the pump wheel and turbine, a speed difference between them can be achieved through reaction forces, enabling speed and torque variation.
The principle of automatic transmissions is quite interesting. Let me explain it from a technical perspective. It replaces the clutch with a component called a torque converter, which transfers engine power through fluid. The planetary gear set is the core, where several gears work together inside a housing, changing gear ratios during shifts. The electronic control unit continuously monitors vehicle speed, throttle position, and engine RPM, then uses a hydraulic system to automatically engage clutch plates and determine whether to shift to high, medium, or low gear. This allows the car to accelerate smoothly without manual operation. It’s especially convenient in urban traffic jams—the engine doesn’t need to rev frequently, and fuel consumption is better controlled. Modern cars often use CVT or dual-clutch versions, which significantly improve efficiency. For daily driving, remember to change the transmission fluid on time to avoid overheating and component damage.
I've been driving automatic transmission cars for years, and the principle is not hard to understand. It operates via a hydraulic system where the engine drives an oil pump, and hydraulic fluid transmits power to the planetary gear set. The control module automatically selects gears based on sensor data—for example, upshifting at higher speeds to save fuel or downshifting when you floor the accelerator to boost power. The entire process requires no manual intervention, making driving smoother. This design significantly eases driving, especially on long trips or mountainous roads, by eliminating clutch concerns. However, it's important to note that aged or leaking hydraulic fluid can affect shift smoothness. Regular maintenance extends its lifespan, ensuring both reliability and comfort.
