Torque Converter

g. Variations in Torque Converters
While the foregoing description covers torque converters generally, some torque converters have more members (other than the impeller, turbine, and stator).
(1) Three element torque converter
The three element torque converter found on many pieces of equipment will have either a fixed or a rotating stator (reaction member).
(a) The fixed stator is mounted rigidly in the converter and will not turn.
(b) The stator that is mounted on a one-way clutch is able to turn in the same direction as the engine only (Figure 16).
(c) The overrunning clutch used in a torque converter is generally a sprag-type. The sprags are somewhat like flattened rollers (Figure 17). The inner and outer races of the overrunning clutch are smooth. A series of sprags are positioned between the inner and outer races and are held in place by two springs put into the sprag notches (Figure 17). The outer race is stationary but the inner race is splined to the stator hub and therefore will turn with the stator. During steady running, the stator is not needed and as mentioned will rotate. The sprags shown in Figure 17, have no effect on the forward rotation of the inner race. During acceleration the oil must change direction and the oil is thrown against the front faces of the stator vanes. This produces a backward thrust, or pressure on the stator vanes, which halts the stator and attempts to turn it backwards. As this happens, the sprags jam between the inner and outer races, thereby locking the inner race so that it cannot turn backward. The stator then becomes stationary so that its vanes can effectively change the direction of the oil flow.