Figure 7-16.Torque converter in fluid coupling stage.
engine torque through the converter has begun. If the
counterclockwise spinning oil was allowed to continue
to the section of the pump member, the oil would strike
the blades of the pump in a direction that would hinder
its rotation and cancel any gains obtained in torque. To
prevent this, a stator assembly is added (fig, 7- 17).
The stator is located between the pump and the
turbine and is mounted on a one way or roller clutch
which allows it to rotate clockwise but not
Figure 7-17.Stator assembly.
counterclockwise. The purpose of the stator is to redirect
the oil returning from the turbine and change its
direction of rotation back to that of the pump member.
The energy of the oil is then used to assist the engine in
turning the pump. This increases the force of the oil,
driving the turbine, and as a result, multiplying the
torque. The force of the oil flowing from the turbine to
the blades of the stator tends to rotate the stator
counterclockwise, but the one way roller clutch prevents
this from happening.
With the engine operating at full throttle, the
transmission in gear, and the vehicle standing still, the
torque converter is capable of multiplying engine torque
by approximately 2:1. As turbine and vehicle speed
increase, the direction of the oil leaving the turbine
changes (fig. 7-18). The oil flows against the rear side
of the stator vanes in a clockwise direction. Since the
stator is now impeding the smooth flow of oil, its roller
clutch automatically releases, and the stator revolves
freely on its shaft. Once the stator becomes inactive,
there is no further multiplication of engine torque within
the converter. At this point, the converter is merely
acting as a fluid coupling as both the converter pump
and the turbine are turning at the same speed or at a 1:1
Figure 7-18.Torque converter in torque multiplication stage.