What is a torque converter?

A torque converter is a type of fluid coupling that transfers rotating power from a prime mover, like an internal combustion engine, to a rotating driven load. It's typically used in automatic transmissions in vehicles. Unlike a simple fluid coupling, a torque converter multiplies torque when there is a substantial difference between the rotational speed of the input (engine) and the output (transmission).

Here's a breakdown of key aspects:

• Function: Its primary function is to allow the engine to spin independently of the transmission at low speeds and to provide torque multiplication when needed for acceleration or climbing hills. Think of it as a buffer and a gear ratio multiplier, combined.

• Components: A torque converter consists of three main components inside a sealed housing filled with transmission fluid:

  • Impeller: Also known as the pump, it's connected to the engine's crankshaft and driven by it. It spins and throws fluid outwards, creating a vortex.
  • Turbine: Connected to the transmission's input shaft, the turbine is driven by the fluid flow from the impeller. The force of the fluid against the turbine blades causes it to rotate, transferring power to the transmission.
  • Stator: Located between the turbine and the impeller, the stator redirects the fluid flow returning from the turbine back to the impeller. This redirection is crucial for torque multiplication. The stator has a one-way clutch that allows it to freewheel at higher speeds, preventing it from hindering the fluid flow.

• Operation:

  1. The engine spins the impeller.
  2. The impeller throws fluid towards the turbine.
  3. The fluid strikes the turbine blades, causing it to rotate and transfer power to the transmission.
  4. The fluid exiting the turbine is directed by the stator back to the impeller. At lower turbine speeds (high slip), the stator redirects the fluid in a way that effectively multiplies the torque being applied to the turbine.
  5. As the turbine speed approaches the impeller speed (low slip), the stator freewheels, acting like a simple fluid coupling.

• Torque Multiplication: The torque converter multiplies torque when the turbine is spinning significantly slower than the impeller. This happens because the stator redirects the fluid flow in a way that increases the force applied to the turbine. The amount of torque multiplication decreases as the turbine speed increases, eventually reaching a 1:1 ratio when the stator freewheels.

• Efficiency: Torque converters are not perfectly efficient. Some energy is lost due to fluid friction and turbulence. Lock-up%20Torque%20Converters are sometimes used to improve efficiency. A lock-up clutch mechanically connects the engine to the transmission, bypassing the fluid coupling and eliminating slip, at cruising speeds when torque multiplication is not needed.

• Applications: While primarily found in automotive automatic transmissions, torque converters are also used in other applications such as heavy equipment, marine propulsion, and some industrial machinery.