Characteristic Values Of Air Spring - Audi A6 242 Service Manual

Air spring parameters
Resilience/spring rate
The resilience (supporting force) F of an air
spring is determined by the effective surface
A and the excess pressure in the air
w
spring p .
i
F = p x A
i w
The effective surface A
effective diameter d .
w
In the case of a rigid structure, such as piston
and cylinder, the effective diameter
corresponds to the piston diameter.
In the case of air springs with U-bellows, the
effective diameter is determined by the
lowest point of the fold.
As the formula shows, the supporting force of
an air spring is in direct relation to the
internal pressure and the effective surface. It
is very easy to alter the supporting strength
(resilience) statically (no movement of the
bodywork) by varying the pressure in the air
spring.
The various pressures, depending on the
load, result in the relevant characteristic
curves of the springs and/or spring rates.
The spring rate alters at the same rate as the
bodywork weight, while the natural frequency
of the bodywork which determines the
handling characteristics remains constant.
The air suspension is adapted to a natural
frequency of the bodywork of 1.1 Hz.
is defined by the
w
laden
un-laden
Piston and cylinder
Supporting force
p
d
W
U-bellows
Supporting force
p
d
W
-s ± 0
Spring travel
i
242_023
i
242_025
9 bar
8 bar
7 bar
6 bar
242_078
+s
21