Torque Converter: Notes

The torque converter is a three element unit containing a single plate lock up clutch. The lock up clutch can be controlled and engaged in any gear 1 to 6. The clutch is applied by removing transmission fluid pressure from one side of the plate. The torque converter transmits and multiplies torque. The torque converter is a three-element device:

• Impeller assembly.
• Turbine assembly.
• Reactor assembly

The standard torque converter components operate as follows:

• The impeller, which is driven by the engine, imparts a circular flow to the transmission fluid in the converter.
• This transmission fluid strikes the turbine wheel, which causes the flow to change its direction.
• The transmission fluid flows out of the turbine wheel close to the hub and strikes the stator, where its direction is changed again to a direction suitable for re-entering the impeller.
• The change in direction at the stator generates a torque reaction that increases the torque reaching the turbine.
• The ratio between turbine and impeller torque is referred to as torque multiplication or conversion.
• The greater the difference in speeds of rotation at the impeller and turbine, the greater the increase in torque; The maximum increase is obtained when the turbine wheel is stationary. As turbine wheel speed increases, the amount of torque multiplication gradually drops.
• When the turbine wheel is rotating at about 85% of the impeller speed, torque conversion reverts to 1, that is to say torque at the turbine wheel is no higher than the torque at the impeller.
• The stator, which is prevented from rotating backwards by a freewheel and the shaft in the transmission housing, runs freely in the transmission fluid flow and overruns the freewheel. From this point on, the converter acts only as a fluid coupling. During the torque conversion process, the stator ceases to rotate and bears against the housing by the freewheel.

Fig 1: Identifying Torque Converter Components

Courtesy of JAGUAR CARS, INC.