C
A
B
ASf02053
Figure 2-53.--Effects of oil jetstream on a flat surface and on a curved surface.
pump is mounted on an overrunning clutch to make this
back of oil, which is wasted power. If the oil enters and
leaves a curved bucket, as in view B, the push imparted
possible. The overrunning clutch allows the secondary
to the bucket and wheel is small. However, if a curved
pump to spin faster than the primary pump when the oil
vane is used to redirect the oil leaving the bucket back
is hitting the back faces of its vanes, but locks or
into the bucket as in view C, the torque is increased.
"clutches" when the secondary pump tries to rotate
Detail views B and C act like a torque converter with a
more slowly than the primary pump. More information
pump, turbine, and stator.
is given about overrunning clutches later in this
section.
Normally, a torque converter has at least three
members. However, some have more than three
After start and during normal operation, turbine
members. Refer again to figure 2-52. This converter
(2) picks up speed and thus approaches the speed of
has five members, and each member is numbered in
pump (1). Under these conditions the total oil mass
sequence as oil passes through it; thus, (1) is the
between pump (1) and turbine (2) rotates (a low coil
primary pump, (2) is the turbine, (3) is the secondary
vortex condition as described earlier develops), and
stator, (4) is the primary stator, and (5) is the secondary
secondary pump (5) overruns.
pump. The five members are mounted on shafts and
During this time, the oil, as it leaves the trailing
hubs in such a way that each one has some degree of
edges of the turbine, is not thrown back with as great a
independent rotation. The stator elements are mounted
thrust against the vanes of stator (3). As a result, the
through overrunning clutches to a stationary hub shaft,
rotating oil mass will cause stator (3) to begin to rotate
while the secondary pump is mounted through an
(it is also mounted on an overrunning clutch). As stator
overrunning clutch to the pump shaft. If there is a
secondary turbine element, it will be mounted on the
(3) begins to rotate, the oil leaving the turbine vanes
turbine shaft.
hits the back side of the stator vanes and overruns to
move out of the oil flow path.
When the vehicle is first started or is under heavy
load (fig. 2-52), the primary pump (1) is turning at a
At the time this is happening, secondary pump (5)
relatively high speed while the turbine (2) is turning
tends to slow down as the oil no longer strikes the back
slowly. As shown by the oil flow arrow, the oil is
side of its vanes with any appreciable thrust. It
passing from the primary pump (1) to and through the
"clutches" or locks and actually helps the primary
turbine (2). As the oil leaves the turbine (2), it flows
pump impart some forward motion or driving force to
into the stators (3 and 4). Notice that these stators
the oil. Primary stator (4) remains stationary and
change the direction of the oil flow to aid the primary
changes the oil flow direction only slightly.
pump (1). However, the secondary pump (5) is between
When the turbine and primary pump reach the
the primary stator (4) and the primary pump (1). Note
"coupling stage", the torque converter acts just like a
how the vanes of the secondary pump (5) oppose the oil
fluid coupling. At this time, both stators (3) and (4) are
flow from the stators to the primary pump (1).
freewheeling, or rotating with the mass of rotating oil.
The secondary pump (5) is not needed during
Neither is contributing anything to the converter
heavy load, hard acceleration operation. To keep it
operation.
from hindering the action of the torque converter at this
The secondary pump, however, is locked to the
time, the secondary pump is allowed to overrun, or spin
primary pump, and thus helps impart the required
faster than the primary pump. This moves it out of the
path of the oil flow into the main pump. The secondary
driving force to the oil under light loads or high speeds.
2-43
