Repair manual

14
292_016
System components
Shock absorber
Construction:
A twin-tube gas-filled shock absorber with
continuous electrical control is used (ccontin-
uous damping control =CDC shock absorber).
The main damping valve 3 in the piston 1 is
mechanically pre-tensioned by a spring 4. A
solenoid 5 is situated above the valve, and the
connecting cable is routed to the outside
through the hollow piston rod.
Function:
For general information on the function of a
twin-tube gas-filled shock absorber, see
SSP 242.
The damping force is determined to a consid-
erable extent by the flow resistance of the
valves. The greater the flow resistance for the
oil flowing through the valves, the higher the
damping force.
Basic method of operation using bump as an example (= bump absorption):
The entire piston unit 1 is moved downwards
inside the cylinder tube 2 at speed v.
The oil pressure in the chamber below the
main damping valve 3 increases.
Current flows to the solenoid 5. The magnetic
force F
M
counteracts the spring force F
F
and
partially raises it.
If the sum of the magnetic force and the oil
pressure force (F
M
+F
P
) exceeds the spring
force F
F
, the resulting force F
R
opens the
valve. The amount of magnetic force can be
regulated by adjusting the amount of electri-
cal current. The higher the electrical current,
the lower the flow resistance and thus the
damping force.
Info: The highest damping force is achieved when the solenoid is not electrically actuated.
For the lowest damping force, the solenoid must be receiving a current of approx.
1800 mA.
In emergency running mode, the solenoid is not electrically actuated. In this way, the
damping force is set to maximum, ensuring a dynamically stable driving condition.