What is torque converter?

A torque converter is a type of fluid coupling which transfers rotating power from a prime mover, like an internal combustion engine, to a driven rotating load. It is typically used in automatic transmissions in motor vehicles, replacing a mechanical clutch.

Here's a breakdown of key aspects:

• Function: A torque converter multiplies torque when there is a substantial difference between input and output rotational speed, thus providing torque multiplication. The degree of this multiplication varies depending on the relative speeds, and it is highest at stall (when the output shaft is held stationary).

• Components: The main components of a torque converter are:

  • Impeller (Pump): Connected to the engine's crankshaft, it acts as a centrifugal pump, accelerating fluid outwards.
  • Turbine: Connected to the transmission input shaft, it receives the fluid from the impeller and rotates, driving the transmission.
  • Stator: Positioned between the turbine and impeller, the stator redirects the returning fluid flow from the turbine back to the impeller. This redirection is critical for torque multiplication. A one-way clutch allows the stator to rotate freely at higher speeds when torque multiplication is no longer needed, improving efficiency.

• Operation: The impeller spins and throws fluid against the turbine, causing it to rotate. When the turbine spins much slower than the impeller, the fluid returning from the turbine hits the stator vanes in a way that locks the stator and redirects the fluid back to the impeller at a more favorable angle, multiplying torque. As the turbine speed increases, the stator eventually unlocks and spins freely, and the torque converter acts more like a fluid coupling.

• Torque Multiplication: This is the key advantage. At stall, a torque converter can multiply engine torque by a factor of 2:1 or greater, depending on the design.

• Efficiency: Torque converters are not perfectly efficient. Some energy is lost due to fluid friction and turbulence. Lock-up converters are often used to improve efficiency at cruising speeds. A lock-up clutch mechanically connects the engine to the transmission, eliminating the fluid coupling and associated losses.

• Applications: Primarily used in vehicles with automatic transmissions, but also found in some industrial equipment and heavy machinery.