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IDROCONVERT TRANSMISSION
351
Fig. 569 - Operating diagram of release mechanism.
1. Impeller•• 2. Stalor. - 3. Turbine. - 4. Torque converter output shalt.• 5. Bell housing. - 6. Disc type spring. - 7. Partiatlsfng valve.•
8. Pressure plate. - 9. Driven plate. - 10. Snap ring.
disc spring and cause the pressure plate to move
back. However. the subsequent clutch engagement
will
be slightly retarded as, in order to pass from
chamber
C
to
0
I
the oil must overcome the resist-
ance of the valve which is lifted
in
the process -
the pressure plate is pushed rapidly towards the
driven plate
by
a spring and oil pressure acting
from
B whilst
the oil is simultaneously compressed
within chamber C and forced through into chamber
D to give a gradual engagement.
It
should also be noted that the driven plate is
compressed between bell housing and pressure
plate.
At the moment of engagement the driven
plate is subjected to an elastic deformation which
facilitates separation during subsequent disengage-
ment to avoid sticking.
On the other hand, the engagement phase must
adjust itseU to the speed of bell housing/pressure
plate assembly (turbine speed) and that of the
driven plate (gearbox input speed) as it
is
these
factors which determine its duration.
In fact, so far we have been dealing with static
pressures only whereas, to obtain a clear under-
standing
or
the system, one must also consider the
dynamic pressures at work within the system.
Under certain conditions, bell housing/pressure
plate on the one hand, and driven plate on the
other, rotate at different speeds acting as separate
turbines.
Consequently, the dynamic pressures
generated during rotat:on must be added to the
static pressures.
Such dynamic pressures are directly propor-
tional to the rotational speeds, and oil transfer
from chamber C to chamber D and vice-versa is
governed by the pressure differential between them.
From this it may easily be inferred that the pres-
sure-plate-to-driven-plate approach speed varies
according to whether the dynamic pressures prevail
over the static pressures and vice-versa.
This adjustment in the speed of engagement oc-
curs quite automatically thanks to careful dimen-
sioning of the components. Its purpose is to give
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