MAIN FUNCTIONAL REQUIREMENT: Transmit "rotational power" using fluid coupling rather than a mechanical clutch.
DESIGN PARAMETER: Hydrodynamic Drive (torque converter) - transmits power via re-circulating fluid in a closed housing.
EXPLANATION OF HOW IT WORKS/ IS USED:
The torque converter receives power from the engine.
P(in) = T(in) * w(in)
A portion of the input power is dissipated in the transmission fluid inside the chamber. The calculations for the power loss are beyond the scope of this explanation and will be referenced as P(loss).
P(loss) = f(friction, viscous effects, other effects .)
P(out) = T(out) * w(out) = P(in) P(loss) = T(in) * w(in) P(loss)
P(out) = h (m) * P(in)
h (m) = is P(out)/P(in). This is a function of fluid viscosity, fin design in the turbine and impeller units, T(out), T(in) and other variables. Torque converters run at efficiencies anywhere from 0-95% depending on w(in), w(out), and T(in) and T(out). For example, when a car is stopped at a traffic light, the engine still applies power to the input shaft, but the brakes and transmission prevent the output shaft from rotating. Since P(out) = T(out) * w(out), and w(out) equals zero, P(out) equals zero. Therefore, the efficiency equals zero.
When a car is traveling at highway speeds, the turbine is rotating nearly as fast as the impeller. Recalling that they are attached to the output shaft and the input shaft respectfully, then P(in) » P(out) and therefore efficiency is rather high.
WHERE YOU CAN FIND TORQUE CONVERTERS:
A torque converter is found directly between the engine and the transmission gear housings on cars and trucks with automatic transmission. The significance of the torque converter is that it allows the output shaft to be stopped with out stalling the engine, and without physically disconnecting the input and output shafts.
General Info | Syllabus