33
Actuation mechanism of separation clutch K0
649_070
Sub-bus high
30
Sub-bus systems
31
V606
The separation clutch actuator drives the worm gear shaft via the
shaft slip-on coupling. The worm gear is connected to the spur
gear drive of the adjusting ring. When the clutch disengages, the
adjusting ring is rotated about 120° in the direction of the arrow.
The ball cage holds three balls in position and evenly distributed
over its circumference. By rotating the adjusting ring, the balls
push the reciprocating plate against the disengagement bearing
over the ball ramps in the adjusting ring and in the reciprocating
plate. Longitudinal guides stop the reciprocating plate from
rotating.
The separation clutch otherwise functions in the same way as a
convetional frictional clutch with diaphragm spring and contact
plate.
If the actuator is deactivated in the event of a fault, or if the
maximum allowable temperature is exceeded, the separation
clutch K0 is engaged because the clutch actuating mechanism is
not self-locking. In this case, the vehicle can only run in hybrid
mode where drive is provided by both the internal combustion
engine and e-machine.
Function diagram The separation clutch actuator V606 is a brushless DC motor. It is
supplied with power through the 12-volt electrical system. Termi-
nal 30 is protected by a 30A fuse.
The engine control unit J623 instructs the actuator via a sub-bus to
control the clutch. For this purpose, the engine control unit uses
clutch control software which is ancillary to the hybrid manage-
ment system.
Temperature protection
The actuator electronics measure the temperature via an inte-
grated temperature sensor. If the temperature of the actuator
exceeds a value of 125°C, the electronics indicate the actual
temperature to the engine control unit J623.
The clutch control software thereupon activates the separation
clutch K0 as little as possible, to allow the actuator to cool down
again. If this fails and the temperature rises to a value of 135°C,
the actuator will not be activated any further until it has cooled
down to a temperature of 110°C. Once this temperature level is
reached, operation of the actuator, and hence separation clutch
K0, is again unrestricted.
Actuator diagnostics
Actuator diagnostics are provided by the engine control unit J623
(address code 01). If the vehicle is raised on a hydraulic lift and the
engine cover has been removed, the actuation of the clutch by the
actuator is distinctly audible.
Note:
Actuator diagnostics are not possible with the actuator removed.
The reason for this is that the actuator cannot be zero-calibrated
when removed. This is necessary because the actuator cannot
recall its position after a change of terminal status (terminal 15
o).
The software in the actuator electronics requires that a zero cali-
bration be performed immediately after starting (terminal 15 on).
The actuator rotates the worn gear shaft through an angle of about
300° and moves the adjusting ring up against its mechanical stop.
The actuator identifies its zero position by the resistance and
begins to open the clutch from this starting point.
When the actuator is removed, there is no resistance. After about
60turns, the fault is registered in the event of memory of the
engine control unit J623 as a "referencing error" and the actuator
is not activated any further. The actuator stops rotating. The
system is restored to full functionality by deleting the event
memory entry and after a change of terminal status.
Adaption and basic setting
The actuator has a rotor position sensor, which measures angle of
rotation and speed.
The electronics calculate the stroke of the disengagement bearing
from the angle of rotation of the actuator shaft. The electronics are
able to determine the force-distance characteristic and the clutch
pressure point from the power input, which corresponds to the
force acting on the disengagement bearing as a function of angle
of rotation and travel.
To factor in the clutch pressure point shift resulting from clutch
lining wear, the clutch control software adapts the force-distance
characteristic after the change of terminal status (terminal 15 o).
However, this takes place at ever increasing intervals over the life
of the clutch.
If the engine control unit software is updated or if the engine
control unit or the hybrid module or the separation clutch actuator
V606 is replaced, the force-distance characteristic must be repro-
grammed using the "Basic setting" guided function on the diagnos-
tic tester.
Fault diagnostics
The electronics of the separation clutch actuator V606 determine
the speed and current input of the actuator via a rotor position
sensor. An excessively high power input is indicative of an actuator
overload. Classic faults sich as open circuit and short circuit to
positive or ground are also detected. The irregularities are stored in
the event memory of the engine control unit.
Measured values
The measured value for disengagement bearing travel, which can
be read out using the diagnostic tester, is simply a theoretical
value calculated by means of actuator speed and gear ratio. This
measurement value is not an absolutely reliable guide to the actual
travel of the disengagement bearing.
Updating software
If necessary, the software of the separation clutch actuator V606
can be updated via the engine control unit J623 using an SVM
code.
Separation clutch actuator V606
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