Air spring systems gain more and more popularity in the
automotive industry and with the ever growing demand for comfort
nowadays they are almost inevitable. Some significant advantages
over conventional steel springs are appealing for commercial
vehicles as well as for the modern passenger vehicles in the luxury
class. Current production air spring systems exist in combination
with hydraulic shock absorbers (integrated or resolved). An
alternative is to use the medium air not only as a spring but also
as a damper: a so-called air spring air damper.
Air spring air dampers are force elements which could be a great
step for the chassis technology due to their functionality
(frequency selectivity, load levelling, load independent vibration
behaviour, load dependent damping). Some of their design which
avoid dynamic seals by the using of rubber bellows contribute to
a better ride comfort.
This paper is about a simulation model for the air spring air
damper (LFD from its German name Lüftfederdämpfer) combined with a
rubber bellow model. First of all it presents the working
properties of the LFD, summarises the state of the art of
simulation models for air spring air damper and gives some insight
into the physics of such systems and their sensitivity to some
parameters. Then it deals with rubber bellow and its behaviour under
dynamic excitation. For this purpose, a phenomenological rubber
bellow model is presented and validated with measurement. The
combined model is calibrated based on an existing air spring air
damper hardware, validated with measurements and integrated into a
quarter car model for ride comfort simulation. At the end the
simulation results are discussed to decide whether or not this
should be taken in account for ride comfort simulation.
